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Technical peer review
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Overview
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Peer reviews are distinct from management reviews, which are conducted by management representatives rather than by colleagues and for management and control purposes rather than for technical evaluation. This is especially true of line managers of the author or other participants in the review. A policy of encouraging management to stay out of peer reviews encourages the peer review team to concentrate on the product being reviewed and not on the people or personalities involved.
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Technical peer review
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Overview
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They are also distinct from software audit reviews, which are conducted by personnel external to the project, to evaluate compliance with specifications, standards, contractual agreements, or other criteria. A software peer review is a type of technical peer review. The IEEE defines formal structures, roles, and processes for software peer reviews.
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Technical peer review
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Roles of participants
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Moderator Responsible for conducting the technical peer review process and collecting inspection data. The moderator plays a key role in all stages of the process except rework and is typically required to perform several duties during a technical peer review in addition to inspectors' tasks.Inspectors Responsible for finding defects in work product from a general point of view, as well as defects that affect their area of expertise.Author Provides information about work product during all stages of process. The author is responsible for correcting all major defects and any minor and trivial defects that cost and schedule permit, as well as performing the duties of an inspector.Reader Guides team through work product during the technical peer review meeting. The reader reads or paraphrases work product in detail and also may perform the duties of an inspector.Recorder Accurately records each defect found during inspection meeting on the Inspection Defect List, and may also perform the duties of an inspector.
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Technical peer review
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Vested interest of reviewers
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There are two philosophies about the vested interest of the inspectors in the product under review. On one hand, project personnel who have a vested interest in the work product under review have the most knowledge of the product and are motivated to find and fix defects. On the other hand, personnel from outside the project who do not have a vested interest in the work product bring objectivity and a fresh viewpoint to the technical peer review team. Each inspector is invited to disclose vested interests to the rest of the technical peer review panel so the moderator can exercise sound judgement in evaluating the inspector's inputs.
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Cloud storage gateway
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Cloud storage gateway
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A cloud storage gateway is a hybrid cloud storage device, implemented in hardware or software, which resides at the customer premises and translates cloud storage APIs such as SOAP or REST to block-based storage protocols such as iSCSI or Fibre Channel or file-based interfaces such as NFS or SMB.According to a 2011 report by Gartner Group, cloud gateways were expected to increase the use of cloud storage by lowering monthly charges and eliminating the concern of data security.
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Cloud storage gateway
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Technology
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Features Modern applications (aka "cloud native applications") use network attached storage by means of REST and SOAP with hypertext transfer protocol on the protocol layer. The related storage is provided from arrays that offer these as object storage. Classic applications use network attached storage by means of Network File System NFS, iSCSI or Server Message Block SMB. To make use of all the advantages of object storage, existing applications need to be rewritten and new applications must be object storage aware, which is not the case by default. This problem is addressed by cloud storage gateways. They offer object storage via classic native storage protocols like Network File System NFS or Server Message Block SMB (and a very few offer iSCSI as well). As a rule of thumb, classic applications with cloud native object storage can now be used with cloud storage gateways.
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Cloud storage gateway
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Technology
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Functionality In enterprise infrastructures NFS is mainly used by Linux systems whereas Windows systems are using SMB. Object storage needs data in form of objects rather than files. For all cloud storage gateways it is mandatory to cache the incoming files and destage them to object storage on a later step. The time of destaging is subject to the gateway and a policy engine allows functions like pinning = bind specific files to the cache and destage them only for mirroring purpose content based destaging = move only files with specific characteristics to object storage e.g. all MP3 files multi-cloud mirroring = mirror all files to two different object stores Least Recently use = fill the local cache to maximum, move all files to object storage and delete files in cache on a LRU algorithm encrypt prior of destage = files are encrypted on the cloud storage gateway and destaged to object storage in an encrypted form compress and/or deduplication prior of destage = files are deduplicated and/or compressed prior of destaging backup data in a native backup formatCombinations of these functions are usual. Default sorting schematics spanning the retrieval interface generally rely on zero-fault content processing, which carries the obvious requirement that two or more of the above functions are synchronized.
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Cloud storage gateway
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Technology
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Extensions Nearly all object storage gateways support Amazon S3 protocol as a quasi-standard. Some offer as well Microsoft Azure Blob, Google Storage, or Openstack SWIFT. Most gateways support public cloud storage e.g. from Amazon or Microsoft as an object store and Dropbox as a file drive store, there are as well a lot of vendors that support private cloud storage as well – including off and on prem storage.
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Cloud storage gateway
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Technology
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Deployment methods There are multiple variants to deploy such gateways – and some vendors support as well different variants as of their product line: bare metal hardware appliance software appliance supporting different hypervisors software on top of an operating system – aka FUSE basedSoftware appliances as well as FUSE-based gateways can be installed on public cloud infrastructures.
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Cloud storage gateway
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Advantages
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Cloud storage gateways avoid the need to change existing applications by providing a standard interface.
Additionally, IT users are used to existing protocols – like SMB or NFS. They can make use of cloud storage with the advantage of still using their existing infrastructures (including e.g. Active Directory, LDAP integration, file share functions etc.).
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Cloud storage gateway
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Advantages
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While cloud storage gateways initially covered a niche only, they got more attraction as of multi-cloud technologies. As an example: It is possible to run a cloud storage gateway in form of a software appliance on top of a public or private cloud infrastructure by offering docker volume drivers that enable containers for automatic provisioning of storage used by these containers in a consistent form. They are using the hypervisors disks as a cache only, but destage data on least recently used algorithm to the underlying cloud storage.
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Cloud storage gateway
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Advantages
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The de facto standard for object storage is Amazon S3 – it had the most popularity and capacity installed on object storage. But every object storage vendor can (and most of them do) offer Amazon S3 storage – even there is no real "standard" S3 API: Every vendor is a little bit different in implementing S3 API (as seen from the different cloud storage gateway vendors supporting the "specific" APIs of the different object storage vendors). Since 2018, an increasing number of cloud storage gateways hide this complexity by offering S3 on northbound (as of networking technologies, southbound relates to the storage used by a gateway, whereas northbound is the storage provided by the gateway). As such, one may utilize a richer S3 implementation on northbound than the southbound supports.
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Cloud storage gateway
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Disadvantages
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By using cloud storage gateways the complexity to use object storage is hidden, but that also hides some of the advantages of object storage: the ability of horizontal scaling ability to add high efficient metadata to the data content to use extended WORM and archiving capabilities of object storageAs applications change to cloud-aware applications (aka called cloud native applications), cloud storage gateways will change from multiprotocol gateways to multi-cloud gateways, providing access to multiple cloud providers as well as multiple southbound protocols and act as relays between different clouds.
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Cloud storage gateway
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Market
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As of 2020 the cloud storage gateway market was valued at over USD 2 billion and was predicted to reach USD 11 billion by 2026, based on a report by the market research firm Mordor intelligence.
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Alphabet Synthesis Machine
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Alphabet Synthesis Machine
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The Alphabet Synthesis Machine (2002) is a work of interactive art which makes use of genetic algorithms to "evolve" a set of glyphs similar in appearance to a real-world alphabet. Users create initial glyphs and the program takes over. As the creators of the project put it, their goal was "to bring about the specific feeling of semi-sense one experiences when one recognizes—- but cannot read—- the unfamiliar writing of another culture." The project was developed by Golan Levin, a new-media artist, in collaboration with Cassidy Curtis and Jonathan Feinberg.
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Silicon on insulator
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Silicon on insulator
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In semiconductor manufacturing, silicon on insulator (SOI) technology is fabrication of silicon semiconductor devices in a layered silicon–insulator–silicon substrate, to reduce parasitic capacitance within the device, thereby improving performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator, typically silicon dioxide or sapphire (these types of devices are called silicon on sapphire, or SOS). The choice of insulator depends largely on intended application, with sapphire being used for high-performance radio frequency (RF) and radiation-sensitive applications, and silicon dioxide for diminished short-channel effects in other microelectronics devices. The insulating layer and topmost silicon layer also vary widely with application.
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Silicon on insulator
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Industry need
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SOI technology is one of several manufacturing strategies to allow the continued miniaturization of microelectronic devices, colloquially referred to as "extending Moore's Law" (or "More Moore", abbreviated "MM"). Reported benefits of SOI relative to conventional silicon (bulk CMOS) processing include: Lower parasitic capacitance due to isolation from the bulk silicon, which improves power consumption at matched performance Resistance to latchup due to complete isolation of the n- and p-well structures Higher performance at equivalent VDD. Can work at low VDD's Reduced temperature dependency due to no doping Better yield due to high density, better wafer utilization Reduced antenna issues No body or well taps are needed Lower leakage currents due to isolation thus higher power efficiency Inherently radiation hardened (resistant to soft errors), reducing the need for redundancyFrom a manufacturing perspective, SOI substrates are compatible with most conventional fabrication processes. In general, an SOI-based process may be implemented without special equipment or significant retooling of an existing factory. Among challenges unique to SOI are novel metrology requirements to account for the buried oxide layer and concerns about differential stress in the topmost silicon layer. The threshold voltage of the transistor depends on the history of operation and applied voltage to it, thus making modeling harder.
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Silicon on insulator
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Industry need
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The primary barrier to SOI implementation is the drastic increase in substrate cost, which contributes an estimated 10–15% increase to total manufacturing costs.
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Silicon on insulator
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SOI transistors
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An SOI MOSFET is a metal–oxide–semiconductor field-effect transistor (MOSFET) device in which a semiconductor layer such as silicon or germanium is formed on an insulator layer which may be a buried oxide (BOX) layer formed in a semiconductor substrate. SOI MOSFET devices are adapted for use by the computer industry. The buried oxide layer can be used in SRAM designs. There are two types of SOI devices: PDSOI (partially depleted SOI) and FDSOI (fully depleted SOI) MOSFETs. For an n-type PDSOI MOSFET the sandwiched n-type film between the gate oxide (GOX) and buried oxide (BOX) is large, so the depletion region can't cover the whole n region. So to some extent PDSOI behaves like bulk MOSFET. Obviously there are some advantages over the bulk MOSFETs. The film is very thin in FDSOI devices so that the depletion region covers the whole channel region. In FDSOI the front gate (GOX) supports fewer depletion charges than the bulk so an increase in inversion charges occurs resulting in higher switching speeds. The limitation of the depletion charge by the BOX induces a suppression of the depletion capacitance and therefore a substantial reduction of the subthreshold swing allowing FD SOI MOSFETs to work at lower gate bias resulting in lower power operation. The subthreshold swing can reach the minimum theoretical value for MOSFET at 300K, which is 60mV/decade. This ideal value was first demonstrated using numerical simulation. Other drawbacks in bulk MOSFETs, like threshold voltage roll off, etc. are reduced in FDSOI since the source and drain electric fields can't interfere due to the BOX. The main problem in PDSOI is the "floating body effect (FBE)" since the film is not connected to any of the supplies.
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Silicon on insulator
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Manufacture of SOI wafers
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SiO2-based SOI wafers can be produced by several methods: SIMOX - Separation by IMplantation of OXygen – uses an oxygen ion beam implantation process followed by high temperature annealing to create a buried SiO2 layer.
Wafer bonding – the insulating layer is formed by directly bonding oxidized silicon with a second substrate. The majority of the second substrate is subsequently removed, the remnants forming the topmost Si layer.
One prominent example of a wafer bonding process is the Smart Cut method developed by the French firm Soitec which uses ion implantation followed by controlled exfoliation to determine the thickness of the uppermost silicon layer.
NanoCleave is a technology developed by Silicon Genesis Corporation that separates the silicon via stress at the interface of silicon and silicon-germanium alloy.
ELTRAN is a technology developed by Canon which is based on porous silicon and water cut.
Seed methods - wherein the topmost Si layer is grown directly on the insulator. Seed methods require some sort of template for homoepitaxy, which may be achieved by chemical treatment of the insulator, an appropriately oriented crystalline insulator, or vias through the insulator from the underlying substrate.An exhaustive review of these various manufacturing processes may be found in reference
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Silicon on insulator
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Use in the microelectronics industry
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IBM began to use SOI in the high-end RS64-IV "Istar" PowerPC-AS microprocessor in 2000. Other examples of microprocessors built on SOI technology include AMD's 130 nm, 90 nm, 65 nm, 45 nm and 32 nm single, dual, quad, six and eight core processors since 2001. Freescale adopted SOI in their PowerPC 7455 CPU in late 2001, currently Freescale is shipping SOI products in 180 nm, 130 nm, 90 nm and 45 nm lines. The 90 nm PowerPC- and Power ISA-based processors used in the Xbox 360, PlayStation 3, and Wii use SOI technology as well. Competitive offerings from Intel however continue to use conventional bulk CMOS technology for each process node, instead focusing on other venues such as HKMG and tri-gate transistors to improve transistor performance. In January 2005, Intel researchers reported on an experimental single-chip silicon rib waveguide Raman laser built using SOI.As for the traditional foundries, on July 2006 TSMC claimed no customer wanted SOI, but Chartered Semiconductor devoted a whole fab to SOI.
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Silicon on insulator
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Use in high-performance radio frequency (RF) applications
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In 1990, Peregrine Semiconductor began development of an SOI process technology utilizing a standard 0.5 μm CMOS node and an enhanced sapphire substrate. Its patented silicon on sapphire (SOS) process is widely used in high-performance RF applications. The intrinsic benefits of the insulating sapphire substrate allow for high isolation, high linearity and electro-static discharge (ESD) tolerance. Multiple other companies have also applied SOI technology to successful RF applications in smartphones and cellular radios.
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Silicon on insulator
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Use in photonics
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SOI wafers are widely used in silicon photonics. The crystalline silicon layer on insulator can be used to fabricate optical waveguides and other optical devices, either passive or active (e.g. through suitable implantations). The buried insulator enables propagation of infrared light in the silicon layer on the basis of total internal reflection. The top surface of the waveguides can be either left uncovered and exposed to air (e.g. for sensing applications), or covered with a cladding, typically made of silica
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Silicon on insulator
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Disadvantages
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The major disadvantage of SOI technology when compared to conventional semiconductor industry is increased cost of manufacturing. As of 2012 only IBM and AMD used SOI as basis for high-performance processors and the other manufacturers (Intel, TSMC, Global Foundries etc.) used conventional silicon wafers to build their CMOS chips.
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Silicon on insulator
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SOI market
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As of 2020 the market utilizing the SOI process was projected to grow up by ~15% for the next 5 years according to Market Research Future group.
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Neuropeptide S
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Neuropeptide S
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Neuropeptide S (NPS) is a neuropeptide found in human and mammalian brain, mainly produced by neurons in the amygdala and between Barrington's nucleus and the locus coeruleus, although NPS-responsive neurons extend projections into many other brain areas. NPS binds specifically to a G protein-coupled receptor, NPSR. Animal studies show that NPS suppresses anxiety and appetite, induces wakefulness and hyperactivity, including hyper-sexuality, and plays a significant role in the extinction of conditioned fear. It has also been shown to significantly enhance dopamine activity in the mesolimbic pathway, and inhibits motility and increases permeability in neurocrine fashion acting through NO in the myenteric plexus in rats and humans.
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Neuropeptide S
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Synthetic ligands
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The non-peptide NPS receptor antagonist SHA-68 blocks the effects of NPS in animals and is anxiogenic. Several peptide derived NPS agonists and antagonists have also been developed.
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Neuropeptide S
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Peptide sequence
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Below are the sequences of mature neuropeptide S in several representative species in which it is expressed: According to Pfam's HMM logo, there is a conserved "KR" cleave site immediately N-terminal to the C-terminal mature peptide.
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VSTa
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VSTa
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Valencia's Simple Tasker (VSTa) is an operating system with a microkernel architecture, with all device drivers and file systems residing in userspace mode. It mostly complies with the Portable Operating System Interface (POSIX), except where such compliance interferes with extensibility and modularity. It is conceptually inspired by QNX and Plan 9 from Bell Labs. Written by Andy Valencia, and released under a GNU General Public License (GPL). As of 2020, the licensing for VSTa is Copyleft.
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VSTa
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VSTa
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It was originally written to run on Intel 80386 hardware, and then was ported to several different platforms, e.g., Motorola 68030 based Amigas.
VSTa is no longer developed. A fork, named Flexible Microkernel Infrastructure/Operating System (FMI/OS), did not make a release.
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VSTa
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User interface
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The default graphical user interface provided as a tar-ball with the system was ManaGeR (MGR).
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Shaala Darpan
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Shaala Darpan
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Shala Darpan is an ICT Programme of Ministry of Human Resource Development, Government of India that to provide mobile access to parents of students of Government and Government aided schools. This information can only be obtained about the students of government schools. The implementation of Shala Darpan Portal is with the Rajasthan Government Education Department.
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Shaala Darpan
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Facilities available on Rajasthan Shala Darpan portal
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School search process Process to view school report Procedure for viewing student's report Procedure for viewing staff report Scheme Search Process Know Your School NICSD ID Process to know the staff details Staff login Transfer schedule
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Chief networking officer
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Chief networking officer
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The chief networking officer (CNO) is a business networking position in a company or organization. The term refers less commonly to a technical executive position in the computer industry.
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Chief networking officer
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Business networking
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In the business networking context, a chief networking officer manages the social capital of a company. The CNO connects people and businesses within the company, with other companies, and with consumers. The CNO's mission is to facilitate know-how transfer and information flow, fostering innovation, safeguarding diversity, and facilitating profit growth. Chief networking officers are responsible for creation and cultivation of new communities and acquisition of pre-existing communities. Other definitions, such as one by the Wharton Global Business Forum in India, include managing outreach, communication and logistics, usually in partnership with the chief operating officer."As the CNO position builds on soft skills culturally common to women, it can advance women’s careers in areas such as public policy and large-scale business development. Although the position has been around since 2004, there is an ongoing academic debate related to the issue of CNOs—or even the need for CNOs— in modern business.
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Chief networking officer
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Responsibilities
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A Chief Networking Officer (CNO) is the corporate business networks portfolio manager. The Chief Networking Officer centrally manages the business networks' environment. Their responsibility is to solve conflicts in ways that serve mutual best interests. The CNO is a direct contact, although not primary, and should be able to assume the management of any partnership with any stakeholders during primary network manager absence. This professional maps out and organizes all resources available inside the network, i.e., contacts, experiences, success stories, knowledge, competences and business opportunities. They set up long-term partnerships with mutually beneficial gains with each stakeholder inside all business networks.
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Chief networking officer
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Responsibilities
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The CNO is concerned with the self-development of each member of the internal network, and qualifying them to reach their goals. The CNO can only directly impact the employees network. All others are outside their direct control. The CNO achieves recognition of peers from various networks, creating interdependence among all parties. The CNO is the business networks' portfolio strategist, acting as coach and trainer during implementation of related projects during transition from existing and traditional model towards a virtual agile global networking enterprise. To successfully implement this project, the CNO must have cooperation from all departments.
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Chief networking officer
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Responsibilities
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The CNO position requires negotiation experience, knowledge of the company, and knowledge of the marketplace plus an understanding of coaching methodology is useful.
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Chief networking officer
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Computer networking
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In computer networking, the chief networking officer is "responsible for network strategy, advanced network product development, and translation to line products of future networking and distributed computing technologies."
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Fare strike
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Fare strike
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A fare strike is a direct action in which people in a city with a public transit system carry out mass fare evasion as a method of protest. Jumping turnstiles, boarding buses through the back or very quickly through the front, and leaving doors open in subway stations are some tactics used. In some cases, transit operators obstruct the fare box to prevent anyone from paying. Often, fare strikes are used to protest against fare hikes and service cuts, but they can also organize solidarity between riders and drivers.
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Fare strike
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History
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The first historical mention of a fare strike in the United States was in 1944 in Cleveland, Ohio when "streetcar workers threatened to refuse to collect fares in order to win a pay increase." The action was effective because "the City Council gave in before they actually used the tactic." These kinds of "social strikes," collective acts of refusal where workers continue to provide services (in this case, transit) but do not collect any money, have occurred in France and parts of Latin America.
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Fare strike
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History
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In 1969, Italy's "Hot Autumn" was sparked at FIAT's Mirafiori plant in Turin and spilled past the factory gates as workers coordinated movements using other forms of the social strike: FIAT workers refused to pay for the trams and buses and went into stores to demand reductions in prices, backed only by showing their factory ID badges. Others squatted houses and collectively refused to pay utility bills. These kinds of struggles spread throughout Italy until the end of the 1970s.
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Fare strike
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History
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Another type of social strike occurred during the 1970 postal strike in the United States when "letter carriers promised to deliver welfare checks even while on strike." In 2004, much like in the 1944 example in Cleveland, the Chicago group Midwest Unrest was able to organize a fare strike that forced the Chicago Transit Authority to back down on service cuts and fare increases. In 2005, at least 5,000 riders participated in the first ever fare strike in Vancouver, British Columbia, Canada.In San Francisco, in 2005, "Despite heavy police presence at major bus transfer points, at least a couple thousand passengers rode the buses for free in San Francisco on Thursday, September 1st - the opening day of a fare strike in North America's most bus-intensive city." Two of the main groups involved in organizing this were Muni Social Strike and Muni Fare Strike. Other community groups also participated, including the Chinese Progressive Association and "the one major extension of the strike, through the participation of the day laborers' organization in organizing among Spanish-speaking immigrants" working class in San Francisco's Mission District, where the strike was most successful.
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Fare strike
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History
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In the United Kingdom, there were fare strikes against First Great Western in January 2007 and January 2008.In Montreal, striking students in 2005 often used the subway as a means of transportation during demonstrations. As a group, the demonstration would enter the subway without paying, usually while chanting "Métro populaire."In New York City, Occupy Wall Street activists chained and taped open service gates and turnstiles to the subway system to protest "escalating service cuts, fare hikes, racist policing, assaults on transit workers' working conditions and livelihoods — and the profiteering of the super-rich by way of a system they've rigged in their favor" on March 28, 2012.In Grand Rapids, in 2016, a coalition of community activists boarded numerous city buses and refused to pay; part of a "Day of Action" against the Interurban Transit Partnership (ITP), which culminated in a sit-in aimed at disrupting the scheduled ITP board meeting later that same day. The activists were protesting the board's refusal to negotiate a contract settlement with the workers of Amalgamated Transit Union Local 836, violations of those workers' First Amendment rights, a 16% fare hike, and a raise given to CEO, Peter Varga, while these perceived attacks on workers and riders were taking place. This was the first fare strike in Michigan history.
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Double-sided painting
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Double-sided painting
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A double-sided painting is a canvas which has a painting on either side. Historically, artists would often paint on both sides out of need of material. The subject matter of the two paintings was sometimes, although not normally, related.
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Stizolobate synthase
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Stizolobate synthase
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In enzymology, a stizolobate synthase (EC 1.13.11.29) is an enzyme that catalyzes the chemical reaction 3,4-dihydroxy-L-phenylalanine + O2 ⇌ 4-(L-alanin-3-yl)-2-hydroxy-cis,cis-muconate 6-semialdehydeThus, the two substrates of this enzyme are 3,4-dihydroxy-L-phenylalanine and O2, whereas its product is 4-(L-alanin-3-yl)-2-hydroxy-cis,cis-muconate 6-semialdehyde.
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Stizolobate synthase
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Stizolobate synthase
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This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O2 as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O2. The systematic name of this enzyme class is 3,4-dihydroxy-L-phenylalanine:oxygen 4,5-oxidoreductase (recyclizing). This enzyme participates in tyrosine metabolism. It employs one cofactor, zinc.
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Cyclohexanetetrol
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Cyclohexanetetrol
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A cyclohexanetetrol is a chemical compound consisting of a cyclohexane molecule with four hydroxyl groups (–OH) replacing four of the twelve hydrogen atoms. It is therefore a cyclitol (cyclic polyol). Its generic formula is C6H12O4 or C6H8(OH)4.Some cyclohexanetetrols have biologically important roles in some organisms.
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Cyclohexanetetrol
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Isomers
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There are several cyclohexanetetrol isomers that differ on the position of the hydroxyl groups along the ring, and on their orientation relative to the mean plane of the ring.
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Cyclohexanetetrol
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Isomers
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The isomers with each hydroxyl on a distinct carbon are: 1,2,3,4-Cyclohexanetetrol or ortho- (10 isomers, including 4 enantiomer pairs) 1,2,3,5-Cyclohexanetetrol or meta- (8 isomers, including 2 enantiomer pairs) 1,2,4,5-Cyclohexanetetrol or para- (7 isomers, including 2 enantiomer pairs) Possible isomers with two geminal hydroxyls (on the same carbon) are 1,1,2,3-Cyclohexanetetrol (4 isomers); hydrate of 2,3-dihydroxy-cyclohexanone 1,1,2,4-Cyclohexanetetrol (4 isomers); hydrate of 2,4-dihydroxy-cyclohexanone 1,1,3,4-Cyclohexanetetrol (4 isomers); hydrate of 3,4-dihydroxy-cyclohexanonePossible isomers with two pairs of geminal hydroxyls: 1,1,2,2-Cyclohexanetetrol (1 isomer); twofold hydrate of 1,2-cyclohexanedione 1,1,3,3-Cyclohexanetetrol (1 isomer); twofold hydrate of 1,3-cyclohexanedione 1,1,4,4-Cyclohexanetetrol (1 isomer); twofold hydrate of 1,4-cyclohexanedione
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Cyclohexanetetrol
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Preparation
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The synthesis of cyclohexanetetrols can be achieved by, among other methods: reduction or hydrogenation of (1) cyclohexenetetrols, (2) tri-hydroxycyclohexanones, (3) pentahydroxycyclohexanones, (4) hydroxylated aromatic hydrocarbons, or (5) hydroxylated quinones; the (6) hydrogenolysis of dibromocyclohexanetetrols; the (7) hydration of diepoxycyclohexanes; and the hydroxylation of (8) cyclohexadienes or (9) cyclohexenediols.
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Equipossibility
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Equipossibility
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Equipossibility is a philosophical concept in possibility theory that is a precursor to the notion of equiprobability in probability theory. It is used to distinguish what can occur in a probability experiment. For example, it is the difference between viewing the possible results of rolling a six sided dice as {1,2,3,4,5,6} rather than {6, not 6}. The former (equipossible) set contains equally possible alternatives, while the latter does not because there are five times as many alternatives inherent in 'not 6' as in 6. This is true even if the die is biased so that 6 and 'not 6' are equally likely to occur (equiprobability).
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Equipossibility
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Equipossibility
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The Principle of Indifference of Laplace states that equipossible alternatives may be accorded equal probabilities if nothing more is known about the underlying probability distribution. However, it is a matter of contention whether the concept of equipossibility, also called equispecificity (from equispecific), can truly be distinguished from the concept of equiprobability.
In Bayesian inference, one definition of equipossibility is "a transformation group which leaves invariant one's state of knowledge". Equiprobability is then defined by normalizing the Haar measure of this symmetry group. This is known as the principle of transformation groups.
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Kinetic width
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Kinetic width
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A kinetic width data structure is a kinetic data structure which maintains the width of a set of moving points. In 2D, the width of a point set is the minimum distance between two parallel lines that contain the point set in the strip between them. For the two dimensional case, the kinetic data structure for kinetic convex hull can be used to construct a kinetic data structure for the width of a point set that is responsive, compact and efficient.
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Kinetic width
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2D case
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Consider the parallel lines which contain the point set in the strip between them and are of minimal distance apart. One of the lines must contain an edge ab of the convex hull, and the other line must go through a point c of the convex hull such that (a,c) and (b,c) are antipodal pairs. ab and c are referred to as an antipodal edge-vertex pair.
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Kinetic width
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2D case
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Consider the dual of the point set. The points dualize to lines and the convex hull of the points dualizes to the upper and lower envelope of the set of lines. The vertices of the upper convex hull dualize to segments on the upper envelope. The vertices of the lower convex hull dualize to segments on the lower envelope. The range of slopes of the supporting lines of a point on the hull dualize to the x-interval of segment that point dualizes to. When viewed in this dualized fashion the antipodal pairs, are pairs of segments, one from the upper envelope, one from the lower, with overlapping x ranges. Now, the upper and lower envelopes can be viewed as two different x-ordered lists of non overlapping intervals. If these two lists are merged, the antipodal pairs are the overlaps in the merged list. If a pair ab and c is an antipodal edge-vertex pair, then the x-interval for a and b must both intersect the x-interval for c. This means that the common endpoint of the x intervals for a and b must lie within the x-interval for c.
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Kinetic width
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2D case
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The endpoints of both of the sets of x-intervals can be maintained in a kinetic sorted list. When points swap, the list of antipodal edge-point pairs are updated appropriately. The upper and lower envelopes can be maintained using the standard data structure for kinetic convex hull. The minimum distance between edge-point pairs can be maintained with a kinetic tournament. Thus, using kinetic convex hull to maintain the upper and lower envelopes, a kinetic sorted list on these intervals to maintain the antipodal edge-vertex pairs, and a kinetic tournament to maintain the pair of minimum distance apart, the diameter of a moving point set can be maintained.
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Kinetic width
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2D case
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This data structure is responsive, compact and efficient. The data structure uses O(n) space because the kinetic convex hull, sorted list, and tournament data structures all use O(n) space. In all of the data structures, events, inserts, and deletes can be handled in log 2n) time, so the data structure are responsive, requiring log 2n) per event. The data structure is efficient because the total number of events is O(n2+ϵ) for all ϵ>0 and the width of a point set can change Ω(n2) times, even if the points are moving linearly. This data structure is not local because one point may be in many antipodal edge-vertex pairs, and thus appear many times in the kinetic tournament.
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Kinetic width
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2D case
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The existence of a local kinetic data structure for width is open.
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Kinetic width
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Higher Dimensions
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Efficiently maintaining the kinetic width of a point set in dimensions higher than 2 is an open problem. Efficient kinetic convex hull in dimensions higher than 2 is also an open problem.
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Phospholipase A
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Phospholipase A
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Phospholipase A can refer to: Phospholipase A1 Phospholipase A2 Outer membrane phospholipase A1An enzyme that displays both phospholipase A1 and phospholipase A2 activities is called a Phospholipase B (see main article on phospholipases).
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Secondary chromosome
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Secondary chromosome
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Chromids, formerly (and less specifically) secondary chromosomes, are a class of bacterial replicons (replicating DNA molecules). These replicons are called "chromids" because they have characteristic features of both chromosomes and plasmids. Early on, it was thought that all core genes could be found on the main chromosome of the bacteria. However, in 1989 a replicon (now known as a chromid) was discovered containing core genes outside of the main chromosome. These core genes make the chromid indispensable to the organism. Chromids are large replicons, although not as large as the main chromosome. However, chromids are almost always larger than a plasmid (or megaplasmid). Chromids also share many genomic signatures of the chromosome, including their GC-content and their codon usage bias. On the other hand, chromids do not share the replication systems of chromosomes. Instead, they use the replication system of plasmids. Chromids are present in 10% of bacteria species sequenced by 2009.Bacterial genomes divided between a main chromosome and one or more chromids (and / or megaplasmids) are said to be divided or multipartite genomes. The vast majority of chromid-encoding bacteria only have a single chromid, although 9% have more than one (compared with 12% of megaplasmid-encoding bacteria containing multiple megaplasmids). The genus Azospirillum contains three species which have up to five chromids, the most chromids known in a single species to date. Chromids also appear to be more common in bacteria which have a symbiotic or pathogenic relationship with eukaryotes and with organisms with high tolerance to abiotic stressors.Chromids were discovered in 1989, in a species of Alphaproteobacteria known as Rhodobacter sphaeroides. However, the formalization of the concept of a "chromid" as an independent type of replicon only came about in 2010. Several classifications further distinguish between chromids depending on conditions of their essentiality, their replication system, and more. The two hypotheses for the origins of chromids are the "plasmid" and "schism" hypotheses. According to the plasmid hypothesis, chromids originate from plasmids which have acquired core genes over evolutionary time and so stabilized in their respective lineages. According to the schism hypothesis, chromids as well as the main chromosome originate from a schism of a larger, earlier chromosome. The plasmid hypothesis is presently widely accepted, although there may be rare cases where large replicons originate from a chromosomal schism. One finding holds that chromids originated 45 times across bacterial phylogenies and were lost twice.
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Secondary chromosome
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Discovery and classification
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Discovery Early in the era of bacterial genomics, the genomes of bacteria were thought to have a relatively simple architecture. All known bacteria had circular chromosomes containing all the crucial genes. Some bacteria had additional replicons known as plasmids, and plasmids were characteristically small, circular, and dispensable (meaning that they only encoded non-essential genes). As more bacteria and their genomes were studied, many alternative forms of bacterial genomic architecture began to be discovered. Linear chromosomes and linear plasmids were discovered in a number of species. Soon after, bacteria with several large replicons were discovered, leading to the view that bacteria, just like eukaryotes, can have a genome made up of more than one chromosome. The first example of this was Rhodobacter sphaeroides in 1989, but additional discoveries quickly followed with Brucella melitensis in 1993, Burkholderia cepacia complex in 1994, Rhizobium meliloti in 1995, Bacillus thuringiensis in 1996, and now about 10% of bacterial species are known to have large replicons that are separate from the main chromosome.
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Secondary chromosome
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Discovery and classification
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Definition With the onset of these discoveries, several approaches in classifying different components of multipartite genomes were proposed. Various terms have been used to describe large replicons other than the main chromosome, including simply designating them as additional chromosomes, or "minichromosomes", "megaplasmids", or "secondary chromosomes". Criteria used to distinguish between these replicons typically revolve around features such as size and the presence of core genes. In 2010, the classification of these genomic elements as chromids was proposed. Previous terms, such as "secondary chromosome", are considered inadequate upon the observation that these replicons contain the replication systems of plasmids and so are a fundamentally different class of replicons than chromosomes. The original definition of a 'chromid' involves meeting three criteria: While this definition is robust, the authors who proposed it did so with the expectation that some exceptions would be found that would blur the lines between chromids and other replicons. This expectation existed because of the general tendency for evolutionary lineages to produce ambiguous systems, which has resulted in the more well-known issues in formulating a widely-encompassing species definition.Since the classification of chromids, other replicons have been discovered which share some features of chromids but have been categorized separately. One example is the designated "rrn-plasmid" found in a clade within the bacterial genus Aureimonas. The rrn-plasmid contains the rrn (rRNA) operon (hence its name), and the rrn operon cannot be found on the main chromosome. The main chromosome is therefore termed as an "rrn-lacking chromosome" or RLC, and so the clade of bacteria within Aureimonas which possess the rrn-plasmid is also termed the "RLC clade". Members of the RLC clade have nine replicons, of which the main chromosome is the largest and the rrn-plasmid is the smallest at only 9.4kb. The rrn-plasmid also has a high copy number in RLC bacteria. While this very small size and copy number resembles plasmids moreso than it does chromids, the rrn-plasmid still ahs the only copies of the genes in the rrn operon and for tRNA(Ile). This distinctive collection of features led the scientists discovering this replicon to simply classify it as an rrn-plasmid, which is thought of as a separate classification than a "plasmid" or "chromid".
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Secondary chromosome
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Discovery and classification
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Additional proposed classifications Beyond classifying certain replicons as chromids, a number of scientists have proposed further distinguishing between different types of chromids. One classification distinguishes between primary and secondary chromids. Primary chromids are defined as chromids containing core genes that are always essential for the survival of the bacterium under all conditions. Secondary chromids are defined as chromids essential for survival in the native conditions of the bacterium, but may be non-essential in certain "safe" conditions such as a laboratory environment. Secondary chromids may also have more recent evolutionary origins and may retain some more plasmid-like features as compared with primary chromids. An example of a proposed primary chromid is "chromosome II" of Paracoccus denitrificans PD1222.
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Secondary chromosome
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Characteristics
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Size and copy number In a bacterial genome, the main chromosome will always be the largest replicon, followed by the chromid and then the plasmid. One exception to this trend is known in Deinococcus deserti VCD115, where both plasmids are larger than the chromid.Chromids vary considerably in size between organisms. In the bacterial genus Vibrio, the main chromosome varies between 3.0–3.3 Mb whereas the chromid varies between 0.8–2.4 Mb in size. A replicon in a strain of Buchnera, which encodes some core genes, is only 7.8kb. While the presence of core genes may lead to the classification of this replicon as a chromid, this replicon may also be excluded on certain definitions. Some approaches only categorize certain replicons as chromids if they meet a threshold size of 350kb. It has also been observed that chromids tend to have a low copy number in the cell, as with chromosomes and megaplasmids. On average, chromids are twice as large as megaplasmids (and so the emergence of a chromid from a megaplasmid is associated with a sizable gene accumulation in the aftermath of the conversion). One of the largest chromids is the one in Burkholderia pseudomallei, which exceeds 3.1 million nucleotides in size, i.e. 3.1 megabases or 3.1 Mb.
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Secondary chromosome
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Characteristics
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Genomic features Chromids more frequently have a lower G + C content compared with the main chromosome, although the strength of this association is not very strong. A chromid will also typically have a G + C content within 1% of that of the main chromosome, reflecting its nearing the base composition equilibrium of the main chromosome after having stably existed within a bacterial lineage for a necessary period of time. Chromids also resemble the main chromosome in their codon usage bias. One analysis found that chromids had a median 0.34% difference in GC content with the main chromosome, compared with values of 1.9% for megaplasmids and 2.8% for plasmids.Chromids have at least one core gene absent from the main chromosome. (Main chromosomes contain the bulk of the core genes of a bacterium, whereas plasmids contain no core genes.) For example, the chromid in Vibrio cholerae contains genes for the ribosomal subunits L20 and L35. While most chromids have a disproportionately smaller number of essential genes compared to the main chromosome, such as rRNA genes or the genes in the rRNA operon, some may have many more essential genes and may even be considered "equal partners" with the chromosome. In general, chromids also see an enrichment of genes involved in the processes of transport, metabolism, transcription, regulatory functions, signal transduction, and motility-related functions. Proteins located on chromids are involved in processes which can interact with proteins encoded on the main chromosome. Chromids also have more transposase genes than chromosomes, but less than megaplasmids.
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Secondary chromosome
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Characteristics
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Phylogenetic distribution The presence of core genes makes the chromid essential to the survival of the bacterium. The same core genes will be found on the chromids within a genus but not necessarily between genera. All chromids of a genus may additionally share a large number of conserved but non-essential genes which help define the phenotype of the genus (and the emergence of chromids appears to be the primary evolutionary force in the formation of chromid-encoding bacterial genera, as has been suggested in the case of Vibrio). In contrast, bacterial chromosomes may universally or near-universally share hundreds of conserved core genes. Plasmids contain no core genes, and unlike chromids, plasmids of different species within a bacterial genus (or even just different isolates within the same species) share few genes. This is partly due to the common transfer of gain and loss of plasmids and their transfer between bacteria through conjugation (a form of horizontal gene transfer), while chromids are passed on through cell divisions (vertically) with no evidence of chromids moving through horizontal gene transfer. It has been observed that the chromid in at least one bacterial species could be eliminated without making the bacterium inviable, however, the bacterium did become auxotrophic indicating a severe fitness compromise associated with the loss of the chromid.Due to their stable presence within a bacterial genus, chromids also have a feature of being phylogenetically restricted to specific genera. Examples of genera of bacteria with chromids include Deinococcus, Leptospira, Cyanothece (a type of cyanobacteria), and an enrichment of genera of the Pseudomonadota. Overall, bacterial genome sequencing indicates that roughly 10% of bacterial species have a chromid. It has also been found that there is a bias towards co-occurrence of a chromid and a megaplasmid in the same organism. Chromids also appear more frequently in phylogenies than do megaplasmids (in approximately twice as many species), despite megaplasmids being the putative evolutionary source for chromids. This may result in the tendency of organisms to lose their megaplasmids over time, compared with the inherently greater evolutionary stability of chromids.
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Secondary chromosome
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Characteristics
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Replication Chromids share features of the replication of both chromosomes and chromids. For one, chromids use the replication system of plasmids. While plasmids do not replicate in coordination with the main chromosome or the cell cycle, chromids do and only replicate once per cell cycle. In the bacterial genus Vibrio, replication of the main chromosome begins before replication of the chromid. The chromid is smaller than the chromosome, and so takes a shorter amount of time to finish replication. For this reason, replication of the chromid is delayed to coordinate replication termination between the chromosome and chromid. Earlier replication of the chromosome compared with the chromid has also been observed in Ensifer meliloti. Bacteria also rely on different replication factors to start replication between the chromosome and the chromid. Replication of the chromosome is initiated upon stimulation of the expression of the protein DnaA, whereas expression of chromid replication requires DnaA but also depends on RctB. This is similar to F1 and P plasmids which also depend on DnaA but still have their replication controlled by other proteins (specifically RepA and RepE). Segregation of the chromid follows different patterns between different genera of bacteria, although it typically takes place after the segregation of the main chromosome.So far, chromids are known to replicate with one of two types of systems: either with the repABC system or with iterons.
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Secondary chromosome
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Characteristics
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Evolutionary flexibility Several studies indicate that chromids are less conserved and evolve more rapidly than do chromosomes in bacteria. In a study of many species of the genus Vibrio, it was found that the main, large chromosome had a consistent size range of 3–3.3 Mb, whereas the secondary chromosome flexibly ranged from 0.8–2.4 Mb. This considerable variation indicates a greater degree of structural flexibility. Bacteria of the genus Agrobacterium and another genera can have three or more chromids, and these multiple chromids in several strains commonly undergo large-scale rearrangements which can involve the translocation of one sizable portion of one chromid into another. Genes located on chromids are also more prone to evolve and display less purifying selection. Since common species definition for prokaryotes are based on DNA sequence or average nucleotide identity, the greater evolvability of the chromid may result in organisms with chromids having a greater tendency to speciate.
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Secondary chromosome
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Origins
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"Schism" and "plasmid" hypotheses Several suggestions have been put forwards to explain the origins of chromids. The two main hypotheses are the "schism hypothesis" and the "plasmid hypothesis". According to the schism hypothesis, two separate bacterial chromosomes may arise through the splitting of one larger chromosome, resulting in a main and a secondary chromosome (or a chromid). However, due to the plasmid-type maintenance and replication systems in chromids as well as the uneven distribution of core genes between the main chromosome and the chromid, the plasmid hypothesis suggesting that chromids evolved from megaplasmids which acquired core genes is widely accepted. Once megaplasmids acquire core genes from the main chromosome, combined with the simultaneous loss of those core genes from the main chromosome, the plasmid becomes a stable and required element of the bacterial genome. (Megaplasmids may also acquire duplicate copies of core genes from the main chromosome. The existence of the duplicate core gene may degenerate on the main chromosome, leading to its sole presence on the newly formed chromid. In this case, the chromid is formed through a neutral transition.) This event also stabilizes the other genes located on the new chromid, which may result in a characteristic phenotype for the new lineage. These core genes can transfer to a megaplasmid through several means. One is homologous recombination between the main chromosome and the plasmid. It is also possible that an existing chromid could recombine with a plasmid to gain its replication system. Once a chromid appears in a lineage, it is stable over long evolutionary periods. Several bacteria genera have chromids which are characteristic to each genus. Whereas the chromids found in a single genus may universally share a large number of genes, there are no genes universally found across the chromids of different genera.Plasmids are almost always if not always the source for the origins of chromids, but at least two bacterial strains may have their large replicons derive from the schism of a larger chromosome. In these exceptional cases, the term "secondary chromosome" may be retained to describe them and so, in this sense, differentiate them from "chromids". Identifying a replicon as a "secondary chromosome" may be done on the basis of conserved synteny and random distribution of core genes with the main chromosome.
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Secondary chromosome
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Origins
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Proposed adaptive causes The question of the origins of chromids is tied to the question of why they evolved. One possibility is that chromids are a "frozen accident", where they simply happened to evolve by chance and for no particular reason and so, for this reason alone, are present in the lineage descendant from the organism in which they emerged. In this scenario, core genes end up on the chromid by chance, but the chance fixation of core genes on the secondary replicon through neutral transitions leads to its essentiality to the organism. However, chromids may also bring some advantages which helps the bacterium compete in its environment. It has been observed that bacteria with chromids are capable of growing faster in culture, and also contain fairly more sizable genomes. Chromid-encoding bacteria have a genome with an average size of 5.73 ± 1.66 Mb, whereas bacteria which do not encode chromids have an average genome size of 3.38 ± 1.81 Mb. For this reason, some have concluded that the placement of a number of genes on the chromid instead of the main chromosome allows for genome expansion without compromising replication speed and efficiency. On the other hand, two thirds of bacterial genomes over 6 Mb are not multipartite and only three of the fifty largest genomes are multipartite, and so a larger genome has not yet been causally demonstrated as a reason for the evolutionary origins of a chromid. Chromids can also be frequently found on fast-growing bacteria, suggesting their contribution to replication and division speed, although here too several analyses have raised difficulties with this suggestion as a driving evolutionary force for the emergence of chromids. Instead, it is more likely that genome expansion and faster replication speed may be involved in the maintenance of chromids in lineages but not a causal explanation for their emergence. Chromids may also allow for coordinated expression of niche-specific genes. Random though rare emergence of chromids which happen to have the necessary genes to confer an advantageous lifestyle in a given environment may play an important role in stabilizing that chromid in the organism and leading to a new lineage defined by the presence of the now crucial replicon.
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Name resolution
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Name resolution
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Name resolution can refer to any process that further identifies an object or entity from an associated, not-necessarily-unique alphanumeric name: In computer systems, it refers to the retrieval of the underlying numeric values corresponding to computer hostnames, account user names, group names, and other named entities; In programming languages, it refers to the resolution of the tokens within program expressions to the intended program components In semantics and text extraction, it refers to the determination of the specific person, actor, or object a particular use of a name refers to.
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HP Client Automation Software
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HP Client Automation Software
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Radia Client Automation software is an end-user device (PC and mobile device) lifecycle management tool for automating routine client-management tasks such as operating system deployments and upgrades, patch management, application software deployment, application use monitoring, security, compliance, and remote system management.In February 2013, Hewlett-Packard (HP) and Persistent Systems, Inc. agreed to an exclusive license for Persistent to access the HP Client Automation technology. Persistent is now developing the Radia Client Automation product line, based on the original HP Client Automation products. HP is also selling the Radia Client Automation products from Persistent.
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HP Client Automation Software
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History
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Radia Client Automation has been called various names in its life-cycle: HP OpenView Configuration Management software, Radia Enterprise Desktop Manager (EDM), and HP Client Automation Software.
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HP Client Automation Software
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History
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1992 - Novadigm launches Enterprise Desktop Manager (EDM) 1997 - Novadigm launches Radia 2004 - HP acquires Novadigm September 2004 - Version 4.0 Radia released April 2007 - Version 5.0 HP OpenView Configuration Management released October 2007 - Version 5.1 HP Configuration Management released July 2008 - Version 7.20 HP Client Automation released May 2009 - Version 7.50 HP Client Automation released Dec 2009 - Version 7.80 HP Client Automation released June 2010 – Version 7.90 HP Client Automation released Feb 2011 - Version 8.10 HP Client Automation released Jan 2013 - Version 9.00 HP Client Automation released Feb 2013 - Persistent Systems Ltd. enters into a strategic agreement with Hewlett-Packard (HP) to license its HP Client Automation (HPCA) software.
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HP Client Automation Software
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History
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June 2013 - Persistent Systems delivers on HPCA licensing agreement, launches Radia Client Automation at HP® Discover 2013
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HP Client Automation Software
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Key Features
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Radia Client Automation software can manage hundreds of thousands of client devices. It can be used to manage Microsoft Windows, Mac OS X and Linux desktops and laptops, mobile devices and tablets running iOS, Android and Windows 8 Series Mobile operating System, HP thin clients, and Windows and Linux servers.Radia Client Automation uses a desired state management model where IT defines how it wants devices to look through a series of policies, while agents on client devices proactively synchronize and manage to that defined state. This model results in higher levels of compliance while at the same time significantly reducing the amount of effort needed to manage the environment. It is especially effective for notebook or laptop PCs because infrequent and lower-bandwidth connections can limit the effectiveness of task-based models that are commonly found across the industry.The major features in the 9.00 release are: Mobile device (iOS, Android and Windows) support Management over the Internet Windows 8 support End-to-end IPv6 support Patch management for Adobe and Java software Target-wise role-based access control
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Chlorpyrifos
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Chlorpyrifos
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Chlorpyrifos (CPS), also known as Chlorpyrifos ethyl, is an organophosphate pesticide that has been used on crops, animals, and buildings, and in other settings, to kill several pests, including insects and worms. It acts on the nervous systems of insects by inhibiting the acetylcholinesterase enzyme. Chlorpyrifos was patented in 1966 by Dow Chemical Company.Chlorpyrifos is considered moderately hazardous to humans (Class II) by the World Health Organization based on acute toxicity information dating to 1999. Exposure surpassing recommended levels has been linked to neurological effects, persistent developmental disorders, and autoimmune disorders. Exposure during pregnancy may harm the mental development of children.In the United Kingdom, the use of chlorpyrifos was banned as of 1 April 2016 (with one minor exception).
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Chlorpyrifos
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Chlorpyrifos
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As of 2020, chlorpyrifos and chlorpyrifos-methyl were banned throughout the European Union, where they may no longer be used.
The EU also applied to have chlorpyrifos listed as a persistent organic pollutant under the Stockholm Convention on Persistent Organic Pollutants.
As of August 18, 2021, the U.S. Environmental Protection Agency (EPA) announced a ban on the use of chlorpyrifos on food crops in the United States. Most home uses of chlorpyrifos had already been banned in the U.S. and Canada since 2001.
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Chlorpyrifos
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Chlorpyrifos
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It is banned in several other countries and jurisdictions as well. The Chlorpyrifos ban on food crops is the result of a 1999 lawsuit filed by NRDC to force the EPA to take action on the riskiest pesticides, as well as five additional successful court orders obtained by Earthjustice to force the EPA to take action on a 2007 petition to ban Chlorpyrifos filed by NRDC and the Pesticide Action Network of North America (PANNA).
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Chlorpyrifos
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Synthesis
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The industrial synthesis of chlorpyrifos (3) is made by reacting 3,5,6-trichloro-2-pyridinol (TCPy) (1) with O,O-diethyl phosphorochloridothioate (2):
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Chlorpyrifos
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Uses
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Chlorpyrifos was used in about 100 countries around the world to control insects in agricultural, residential, and commercial settings. Its use in residential applications is restricted in multiple countries. According to Dow, chlorpyrifos is registered for use in nearly 100 countries and is annually applied to approximately 8.5 million crop acres. The crops with the most usefulness include cotton, corn, almonds, and fruit trees, including oranges, bananas, and apples.Chlorpyrifos was first registered for use in the United States in 1965 for the control of foliage and soil-born insects. The chemical became widely used in residential settings, on golf course turf, as a structural termite control agent, and in agriculture. Most residential use of chlorpyrifos has been phased out in the United States; however, agricultural use remains common.EPA estimated that, between 1987 and 1998, about 21 million pounds of chlorpyrifos were used annually in the US. In 2001, chlorpyrifos ranked 15th among pesticides used in the United States, with an estimated 8 to 11 million pounds applied. In 2007, it ranked 14th among pesticide ingredients used in agriculture in the United States.
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Chlorpyrifos
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Uses
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Application Chlorpyrifos is normally supplied as a 23.5% or 50% liquid concentrate. The recommended concentration for direct-spray pin point application is 0.5% and for wide area application a 0.03–0.12% mix is recommended (US).
Kinetics Chlorpyrifos enters the insect through several routes. Simon et al. 1998 report that insects encounter the active ingredient in their food plants and eat it. They also find it to enter through the digestive system, skin and membranes of the respiratory system.
Mechanism of action Like other organophosphate pesticides chlorpyrifos acts by acetylcholinesterase inhibition.
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Chlorpyrifos
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Human toxicity
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Chlorpyrifos exposure may lead to acute toxicity at higher doses. Persistent health effects follow acute poisoning or from long-term exposure to low doses, and developmental effects appear in fetuses and children even at very small doses.
Acute health effects For acute effects, the World Health Organization classifies chlorpyrifos as Class II: moderately hazardous. The oral LD50 in experimental animals is 32 to 1000 mg/kg. The dermal LD50 in rats is greater than 2000 mg/kg and 1000 to 2000 mg/kg in rabbits. The 4-hour inhalation of LC50 for chlorpyrifos in rats is greater than 200 mg/m3.
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Chlorpyrifos
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Human toxicity
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Symptoms of acute exposure Acute poisoning results mainly from interference with the acetylcholine neurotransmission pathway, leading to a range of neuromuscular symptoms. Relatively mild poisoning can result in eye-watering, increased saliva and sweating, nausea, and headache. Intermediate exposure may lead to muscle spasms or weakness, vomiting, or diarrhea, and impaired vision. Symptoms of severe poisoning include seizures, unconsciousness, paralysis, and suffocation from lung failure.Children are more likely to experience muscle weakness rather than twitching; excessive saliva rather than sweat or tears; seizures; and sleepiness or coma.
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Chlorpyrifos
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Human toxicity
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Frequency of acute exposure Acute poisoning is probably most common in agricultural areas in Asia, where many small farmers are affected. Poisoning may be due to occupational or accidental exposure or intentional self-harm. Precise numbers of chlorpyrifos poisonings globally are not available. Pesticides are used in an estimated 200,000+ suicides annually with tens of thousands due to chlorpyrifos. Organophosphates are thought to constitute two-thirds of ingested pesticides in rural Asia. Chlorpyrifos is among the commonly used pesticides used for self-harm.In the US, the number of incidents of chlorpyrifos exposure reported to the US National Pesticide Information Center shrank sharply from over 200 in the year 2000 to less than 50 in 2003, following the residential ban.
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Chlorpyrifos
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Human toxicity
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Treatment Poisoning is treated with atropine and simultaneously with oximes such as pralidoxime. Atropine blocks acetylcholine from binding with muscarinic receptors, which reduces the pesticide's impact. However, atropine does not affect acetylcholine at nicotinic receptors and thus is a partial treatment. Pralidoxime is intended to reactivate acetylcholinesterase, but the benefit of oxime treatment is questioned. A randomized controlled trial (RCT) supported the use of higher doses of pralidoxime rather than lower doses. A subsequent double-blind RCT, that treated patients who self-poisoned, found no benefit of pralidoxime, including specifically in chlorpyrifos patients.
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Chlorpyrifos
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Human toxicity
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Tourist deaths Chlorpyrifos poisoning was described by New Zealand scientists as the likely cause of death of several tourists in Chiang Mai, Thailand who developed myocarditis in 2011. Thai investigators came to no conclusion on the subject, but maintain that chlorpyrifos was not responsible and that the deaths were not linked.
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Chlorpyrifos
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Human toxicity
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Long term Development Epidemiological and experimental animal studies suggest that infants and children are more susceptible than adults to the effects of low-dose exposure. Chlorpyrifos has been suggested to have negative impacts on cognitive functions in the developing brain. The young have a decreased capacity to detoxify chlorpyrifos and its metabolites. It is suggested that adolescents differ from adults in the metabolism of these compounds due to the maturation of organs in adolescents. This results in disruption in nervous system developmental processes, as observed in animal experiments. There are several studies observed in animals that show that chlorpyrifos alters the expression of essential genes that assist in the development of the brain.Human studies: In multiple epidemiological studies, chlorpyrifos exposure during gestation or childhood has been linked with lower birth weight and neurological changes such as slower motor development and attention problems. Children with prenatal exposure to chlorpyrifos have been shown to have lower IQs. They have also been shown to have a higher chance of developing autism, attention deficit problems, and developmental disorders. A cohort of 7-year-old children was studied for neurological damage from prenatal exposure to chlorpyrifos. The study determined that the exposed children had deficits in working memory and full scale intelligence quotient (IQ). In a study on groups of Chinese infants, those exposed to chlorpyrifos showed significant decreases in motor functions such as reflexes, locomotion, and grasping at 9 months compared to those not exposed. Exposure to organophosphate pesticides in general has been increasingly associated with changes in children's cognitive, behavioral and motor performance. Infant girls were shown to be more susceptible to harmful effects from organophosphate insecticides than infant boys.Animal experiments: In experiments with rats, early, short-term low-dose exposure to chlorpyrifos resulted in lasting neurological changes, with larger effects on emotional processing and cognition than on motor skills. Such rats exhibited behaviors consistent with depression and reduced anxiety. In rats, low-level exposure during development has its greatest neurotoxic effects during the period in which sex differences in the brain develop. Exposure leads to reductions or reversals of normal gender differences. Exposure to low levels of chlorpyrifos early in rat life or as adults also affects metabolism and body weight. These rats show increased body weight as well as changes in liver function and chemical indicators similar to prediabetes, likely associated with changes to the cyclic AMP system. Moreover, experiments with zebrafish showed significant detriments to survivability, reproductive processes, and motor function. Varying doses created a 30%–100% mortality rate of embryos after 90 days. Embryos were shown to have decreased mitosis, resulting in mortality or developmental dysfunctions. In the experiments where embryos did survive, spinal lordosis and lower motor functions were observed. The same study showed that chlorpyrifos had more severe morphological deformities and mortality in embryos than diazinon, another commonly used organophosphate insecticide.
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Chlorpyrifos
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Human toxicity
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Adulthood Adults may develop lingering health effects following acute exposure or repeated low-dose exposure. Among agricultural workers, chlorpyrifos has been associated with slightly increased risk of wheeze, a whistling sound while breathing due to obstruction of the airways.Among 50 farm pesticides studied, chlorpyrifos was associated with higher risks of lung cancer among frequent pesticide applicators than among infrequent or non-users. Pesticide applicators as a whole were found to have a 50% lower cancer risk than the general public, likely due to their nearly 50% lower smoking rate. However, chlorpyrifos applicators had a 15% lower cancer risk than the general public, which the study suggests indicates a link between chlorpyrifos application and lung cancer.Twelve people who had been exposed to chlorpyrifos were studied over periods of 1 to 4.5 years. They were found to have a heightened immune responses to common allergens and increased antibiotic sensitivities, elevated CD26 cells, and a higher rate of autoimmunity, compared with control groups. Autoantibodies were directed toward smooth muscle, parietal cell, brush border, thyroid gland, myelin, and the subjects also had more anti-nuclear antibodies.
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Chlorpyrifos
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Chlorpyrifos methyl
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The Dow Chemical Company also developed Chlorpyrifos methyl in 1966, which had a lower acute toxicity (WHO class III), but this appears to be no longer in commercial use. The molecule is similar to Chlorpyrifos ethyl, but with a O,O dimethyl chain. Proposed applications included vector control.
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Chlorpyrifos
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Mechanisms of toxicity
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Acetylcholine neurotransmission Primarily, chlorpyrifos and other organophosphate pesticides interfere with signaling from the neurotransmitter acetylcholine. One chlorpyrifos metabolite, chlorpyrifos-oxon, binds permanently to the enzyme acetylcholinesterase, preventing this enzyme from deactivating acetylcholine in the synapse. By irreversibly inhibiting acetylcholinesterase, chlorpyrifos leads to a build-up of acetylcholine between neurons and a stronger, longer-lasting signal to the next neuron. Only when new molecules of acetylcholinesterase have been synthesized can normal function return. Acute symptoms of chlorpyrifos poisoning only occur when more than 70% of acetylcholinesterase molecules are inhibited. This mechanism is well established for acute chlorpyrifos poisoning and also some lower-dose health impacts. It is also the primary insecticidal mechanism.
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Chlorpyrifos
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Mechanisms of toxicity
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Non-cholinesterase mechanisms Chlorpyrifos may affect other neurotransmitters, enzymes and cell signaling pathways, potentially at doses below those that substantially inhibit acetylcholinesterase. The extent of and mechanisms for these effects remain to be fully characterized. Laboratory experiments in rats and cell cultures suggest that exposure to low doses of chlorpyrifos may alter serotonin signaling and increase rat symptoms of depression; change the expression or activity of several serine hydrolase enzymes, including neuropathy target esterase and several endocannabinoid enzymes; affect components of the cyclic AMP system; and influence other chemical pathways.
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Chlorpyrifos
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Mechanisms of toxicity
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Paraoxonase activity The enzyme paraoxonase 1 (PON1) detoxifies chlorpyrifos oxon, the more toxic metabolite of chlorpyrifos, via hydrolysis. In laboratory animals, additional PON1 protects against chlorpyrifos toxicity while individuals that do not produce PON1 are particularly susceptible. In humans, studies about the effect of PON1 activity on the toxicity of chlorpyrifos and other organophosphates are mixed, with modest yet inconclusive evidence that higher levels of PON1 activity may protect against chlorpyrifos exposure in adults; PON1 activity may be most likely to offer protection from low-level chronic doses. Human populations have genetic variation in the sequence of PON1 and its promoter region that may influence the effectiveness of PON1 at detoxifying chlorpyrifos oxon and the amount of PON1 available to do so. Some evidence indicates that children born to women with low PON1 may be particularly susceptible to chlorpyrifos exposure. Further, infants produce low levels of PON1 until six months to several years after birth, likely increasing the risk from chlorpyrifos exposure early in life.
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Chlorpyrifos
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Mechanisms of toxicity
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Combined exposures Several studies have examined the effects of combined exposure to chlorpyrifos and other chemical agents, and these combined exposures can result in different effects during development. Female rats exposed first to dexamethasone, a treatment for premature labor, for three days in utero and then to low levels of chlorpyrifos for four days after birth experienced additional damage to the acetylcholine system upstream of the synapse that was not observed with either exposure alone. In both male and female rats, combined exposures to dexamethasone and chlorpyrifos decreased serotonin turnover in the synapse, for female rats with a greater-than-additive result. Rats that were co-exposed to dexamethasone and chlorpyrifos also exhibited complex behavioral differences from exposure to either chemical alone, including lessening or reversing normal sex differences in behavior. In the lab, in rats and neural cells co-exposed to both nicotine and chlorpyrifos, nicotine appears to protect against chlorpyrifos acetylcholinesterase inhibition and reduce its effects on neurodevelopment. In at least one study, nicotine appeared to enhance chlorpyrifos detoxification.
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Chlorpyrifos
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Human exposure
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In 2011, EPA estimated that, in the general US population, people consume 0.009 micrograms of chlorpyrifos per kilogram of their body weight per day directly from food residue. Children are estimated to consume a greater quantity of chlorpyrifos per unit of body weight from food residue, with toddlers the highest at 0.025 micrograms of chlorpyrifos per kilogram of their body weight per day. People may also ingest chlorpyrifos from drinking water or from residue in food handling establishments. The EPA's acceptable daily dose is 0.3 micrograms/kg/day. However, as of 2016, EPA scientists had not been able to find any level of exposure to the pesticide that was safe. The EPA 2016 report states in part "... this assessment indicates that dietary risks from food alone are of concern ..." The report also states that previous published risk assessments for "chlorpyrifos may not provide a sufficiently health protective human health risk assessment given the potential for neurodevelopmental outcomes."Humans can be exposed to chlorpyrifos by way of ingestion (e.g., residue on treated produce, drinking water), inhalation (especially of indoor air), or absorption (i.e., through the skin). However, compared to other organophosphates, chlorpyrifos degrades relatively quickly once released into the environment. According to the National Institutes of Health, the half-life for chlorpyrifos (i.e., the period of time that it takes for the active amount of the chemical to decrease by 50%) "can typically range from 33–56 days for soil incorporated applications and 7–15 days for surface applications"; in water, the half-life is about 25 days, and in the air, the half-life can range from four to ten days.Children of agricultural workers are more likely to come into contact with chlorpyrifos. A study done in an agricultural community in Washington State showed that children who lived in closer proximity to farmlands had higher levels of chlorpyrifos residues from house dust. Chlorpyrifos residues were also found on work boots and children's hands, showing that agricultural families could take home these residues from their jobs. Urban and suburban children get most of their chlorpyrifos exposure from fruits and vegetables. A study done in North Carolina on children's exposure showed that chlorpyrifos was detected in 50% of the food, dust, and air samples in both their homes and daycare, with the main route of exposure being through ingestion. Certain other populations with higher likely exposure to chlorpyrifos, such as people who apply pesticides, work on farms, or live in agricultural communities, have been measured in the US to excrete TCPy in their urine at levels that are 5 to 10 times greater than levels in the general population.As of 2016, chlorpyrifos was the most used conventional insecticide in the US and was used in over 40 states; the top five states (in total pounds applied) are California, North Dakota, Minnesota, Iowa, and Texas. It was used on over 50 crops, with the top five crops (in total pounds applied) being soybeans, corn, alfalfa, oranges, and almonds. Additionally, crops with 30% or more of the crop treated (compared to total acres grown) include apples, asparagus, walnuts, table grapes, cherries, cauliflower, broccoli, and onions.Air monitoring studies conducted by the California Air Resources Board (CARB) documented chlorpyrifos in the air of California communities. Analyses indicate that children living in areas of high chlorpyrifos use are often exposed to levels that exceed EPA dosages. A study done in Washington state using passive air samplers showed that households who lived less than 250 meters from a fruit tree field had higher levels of chlorpyrifos concentrations in the air than households that were further away. Advocacy groups monitored air samples in Washington and Lindsay, California, in 2006 with comparable results. Grower and pesticide industry groups argued that the air levels documented in these studies are not high enough to cause significant exposure or adverse effects. A follow-up biomonitoring study in Lindsay also showed that people there display above-normal chlorpyrifos levels.
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Chlorpyrifos
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Effects on wildlife
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Aquatic life Among freshwater aquatic organisms, crustaceans and insects appear to be more sensitive to acute exposure than fish. Aquatic insects and animals appear to absorb chlorpyrifos directly from water rather than ingesting it with their diet or through sediment exposure.Concentrated chlorpyrifos released into rivers killed insects, shrimp and fish. In Britain, the rivers Roding (1985), Ouse (2001), Wey (2002 & 2003), and Kennet (2013) all experienced insect, shrimp, or fish kills as a result of small releases of concentrated chlorpyrifos. The July 2013 release along the River Kennet poisoned insect life and shrimp along 15 km of the river, likely from a half a cup of concentrated chlorpyrifos washed down a drain.
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Chlorpyrifos
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Effects on wildlife
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Bees Acute exposure to chlorpyrifos can be toxic to bees, with an oral LD50 of 360 ng/bee and a contact LD50 of 70 ng/bee. Guidelines for Washington state recommend that chlorpyrifos products should not be applied to flowering plants such as fruit trees within 4–6 days of blossoming to prevent bees from directly contacting the residue.Risk assessments have primarily considered acute exposure, but more recently researchers have begun to investigate the effects of chronic, low-level exposure through residue in pollen and components of bee hives. A review of US studies, several European countries, Brazil and India found chlorpyrifos in nearly 15% of hive pollen samples and just over 20% of honey samples. Because of its high toxicity and prevalence in pollen and honey, bees are considered to have higher risk from chlorpyrifos exposure via their diet than from many other pesticides.When exposed in the laboratory to chlorpyrifos at levels roughly estimated from measurements in hives, bee larvae experienced 60% mortality over 6 days, compared with 15% mortality in controls. Adult bees exposed to sub-lethal effects of chlorpyrifos (0.46 ng/bee) exhibited altered behaviors: less walking; more grooming, particularly of the head; more difficulty righting themselves; and unusual abdominal spasms. Chlorpyrifos oxon appears to particularly inhibit acetylcholinesterase in bee gut tissue as opposed to head tissue. Other organophosphate pesticides impaired bee learning and memory of smells in the laboratory.
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Chlorpyrifos
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Regulation
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International law Chlorpyrifos is not regulated under international law or treaty. Organizations such as PANNA and the NRDC state that chlorpyrifos meets the four criteria (persistence, bioaccumulation, long-range transport, and toxicity) in Annex D of the Stockholm Convention on Persistent Organic Pollutants and should be restricted. In 2021, the European Union submitted a proposal to list chlorpyrifos in Annex A to the Stockholm Convention.
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