title
stringlengths 1
149
⌀ | section
stringlengths 1
1.9k
⌀ | text
stringlengths 13
73.5k
|
|---|---|---|
Trioxide
|
Trioxide
|
A trioxide is a compound with three oxygen atoms. For metals with the M2O3 formula there are several common structures. Al2O3, Cr2O3, Fe2O3, and V2O3 adopt the corundum structure. Many rare earth oxides adopt the "A-type rare earth structure" which is hexagonal. Several others plus indium oxide adopt the "C-type rare earth structure", also called "bixbyite", which is cubic and related to the fluorite structure.
|
Trioxide
|
List of trioxides
|
MO3 Carbon trioxide, CO3 Chromium trioxide, CrO3 Molybdenum trioxide, MoO3 Rhenium trioxide, ReO3 Selenium trioxide, SeO3 Sulfur trioxide, SO3 Tellurium trioxide, TeO3 Tungsten trioxide, WO3 Uranium trioxide, UO3 Xenon trioxide, XeO3 M2O3 Antimony trioxide, Sb2O3 Arsenic trioxide, As2O3 Bismuth(III) oxide, Bi2O3 Boron trioxide, B2O3 Cobalt(III) oxide, Co2O3 Dichlorine trioxide, Cl2O3 Dinitrogen trioxide, N2O3 Gadolinium oxide, Gd2O3 Gallium(III) oxide, Ga2O3 Gold trioxide, Au2O3 Indium(III) oxide, In2O3 Iron(III) oxide, Fe2O3 Manganese(III) oxide, Mn2O3 Nickel(III) oxide, Ni2O3 Phosphorus trioxide, P4O6 (named before the true formula known) Thallium(III) oxide, Tl2O3 Terbium(III) oxide, Tb2O3 Trioxidane, H2O3 Vanadium trioxide, V2O3 Ytterbium(III) oxide, Yb2O3 Yttrium(III) oxide, Y2O3 Other trioxides Mineral trioxide aggregate Sulfur trioxide pyridine complex, SO3(py)
|
Tungsten dichloride dioxide
|
Tungsten dichloride dioxide
|
Tungsten dichloride dioxide, or Tungstyl chloride is the chemical compound with the formula WO2Cl2. It is a yellow-colored solid. It is used as a precursor to other tungsten compounds. Like other tungsten halides, WO2Cl2 is sensitive to moisture, undergoing hydrolysis.
|
Tungsten dichloride dioxide
|
Preparation
|
WO2Cl2 is prepared by ligand redistribution reaction from tungsten trioxide and tungsten hexachloride: 2 WO3 + WCl6 → 3 WO2Cl2Using a two-zone tube furnace, a vacuum-sealed tube containing these solids is heated to 350 °C. The yellow product sublimes to the cooler end of the reaction tube. No redox occurs in this process. An alternative route highlights the oxophilicity of tungsten: WCl6 + 2 ((CH3)3Si)2O → 3 WO2Cl2 + 4 (CH3)3SiClThis reaction, like the preceding one, proceeds via the intermediacy of WOCl4.
|
Tungsten dichloride dioxide
|
Structure
|
Gaseous tungsten dichloride dioxide is a monomer. Solid tungsten dichloride dioxide is a polymer consisting of distorted octahedral W centres. The polymer is characterized by two short W-O distances, typical for a multiple W-O bond, and two long W-O distances more typical of a single or dative W-O bond.
|
Tungsten dichloride dioxide
|
Related oxy halides
|
Tungsten forms a number of oxyhalides including WOCl4, WOCl3, WOCl2. The corresponding bromides (WOBr4, WOBr3, WOBr2) are also known as is WO2I2.
|
Tungsten dichloride dioxide
|
Reactions
|
WO2Cl2 is a Lewis acid, forming soluble adducts of the type WO2Cl2L2, where L is a donor ligand such as bipyridine and dimethoxyethane. Such complexes often cannot be prepared by depolymerization of the inorganic solid, but are generated in situ from WOCl4.
|
Twenty Thousand Hertz
|
Twenty Thousand Hertz
|
Twenty Thousand Hertz is a podcast about "the world’s most recognizable and interesting sounds". Episodes are published every other Wednesday.
|
Twenty Thousand Hertz
|
Overview
|
The show's title refers to highest frequency that can be perceived within the human hearing range (without hearing loss). It grew out of host Dallas Taylor's admiration for the podcast 99% Invisible and a desire to hear more stories like the ones they produced about audio design. The show is hosted and produced by Dallas Taylor and the writer of the episode, with help from Sam Schneble.
|
Twenty Thousand Hertz
|
Overview
|
Though the audio production company Defacto Sound, which is owned by Taylor, is the production headquarters for Twenty Thousand Hertz, he has said that the podcast is not intended as content marketing. Instead of focusing on the industry of sound design exclusively, episodes focus on a variety of topics related to sound. The podcast has covered topics such as the THX Deep Note, misophonia, the Voyager Golden Record, the Shure SM7 microphone, ASMR, and advertising jingles.
|
Twenty Thousand Hertz
|
Overview
|
"Theater of the Mind", a crossover episode with the podcast Imaginary Worlds, was produced in 2018. The episode explored the history of radio dramas. Episodes of Twenty Thousand Hertz have also been featured on the Radiotopia productions 99% Invisible and The Allusionist.In May 2020, host Dallas Taylor delivered a TED Talk, "What silence can teach you about sound." The talk discussed John Cage's composition 4'33", a topic which had previously been explored in an episode of Twenty Thousand Hertz. In August 2020, the podcast joined the TED podcast network, but left due to unexplained reasons. In October 2020, host Dallas Taylor was featured in "Sound and Silence," an episode of the TED Radio Hour, drawn from his TED Talk.Following a Twenty Thousand Hertz episode about audio deepfakes, host Dallas Taylor was featured in a September 2020 segment of NPR's Here & Now, discussing the topic. Taylor was featured in a November 2020 episode of the Popular Science podcast The Weirdest Thing I Learned This Week, discussing the use of animals noises in sound design.
|
Twenty Thousand Hertz
|
Reception
|
The podcast was featured in Esquire magazine's list of "The 63 Best Podcasts You Can Listen To In 2020," as well as Discover Pods "The 71 Best Podcasts of 2020."In 2017, OZY listed Twenty Thousand Hertz as one of "4 Podcasts that'll Make You Wish Your Commute Were Longer."Doug Fabrizio of KUER-FM says the show "challenges listeners to refine their sense of hearing." In a review for 34th Street Magazine, reviewer Caylen David writes, "Twenty Thousand Hertz presents the stories of iconic sound designs in a creative way that keeps listeners wanting more. Give it a listen—you might find that the journey to create pop culture's greatest sounds is more interesting than the finished product."The show's "I'm Lovin' It" episode was chosen as one of Spotify's "Best Podcast Episodes of 2021." Awards
|
Matrix (biology)
|
Matrix (biology)
|
In biology, matrix (PL: matrices) is the material (or tissue) in between a eukaryotic organism's cells.
The structure of connective tissues is an extracellular matrix. Fingernails and toenails grow from matrices. It is found in various connective tissues. It serves as a jelly-like structure instead of cytoplasm in connective tissue.
|
Matrix (biology)
|
Tissue matrices
|
Extracellular matrix (ECM) The main ingredients of the extracellular matrix are glycoproteins secreted by the cells. The most abundant glycoprotein in the ECM of most animal cells is collagen, which forms strong fibers outside the cells. In fact, collagen accounts for about 40% of the total protein in the human body. The collagen fibers are embedded in a network woven from proteoglycans. A proteoglycan molecule consists of a small core protein with many carbohydrate chains covalently attached, so that it may be up to 95% carbohydrate. Large proteoglycan complexes can form when hundreds of proteoglycans become noncovalently attached to a single long polysaccharide molecule. Some cells are attached to the ECM by still other ECM glycoproteins such as fibronectin. Fibronectin and other ECM proteins bind to cell surface receptor proteins called integrins that are built into the plasma membrane. Integrins span the membrane and bind on the cytoplasmic side to associated proteins attached to microfilaments of the cytoskeleton. The name integrin is based on the word integrate, integrins are in a position to transmit signals between the ECM and the cytoskeleton and thus to integrate changes occurring outside and inside the cell. Current research on fibronectin, other ECM molecules, and integrins is revealing the influential role of the ECM in the lives of cells. By communicating with a cell through integrins, the ECM can regulate a cell's behavior. For example, some cells in a developing embryo migrate along specific pathways by matching the orientation of their microfilaments to the "grain" of fibers in the ECM. Researchers are also learning that the ECM around a cell can influence the activity of genes in the nucleus. Information about the ECM probably reaches the nucleus by a combination of mechanical and chemical signaling pathways. Mechanical signaling involves fibronectin, integrins, and microfilaments of the cytoskeleton. Changes in the cytoskeleton may in turn trigger chemical signaling pathways inside the cell, leading to changes in the set of proteins being made by the cell and therefore changes in the cells function. In this way, the ECM of a particular tissue may help coordinate the behavior of all the cells within that tissue. Direct connections between cells also function in this coordination.
|
Matrix (biology)
|
Tissue matrices
|
Bone matrix Bone is a form of connective tissue found in the body, composed largely of hardened hydroxyapatite-containing collagen. In larger mammals, it is arranged in osteon regions. Bone matrix allows mineral salts such as calcium to be stored and provides protection for internal organs and support for locomotion.
Cartilage matrix Cartilage is another form of connective tissue found in the body, providing a smooth surface for joints and a mechanism for growth of bones during development.
|
Matrix (biology)
|
Subcellular matrices
|
Mitochondrial matrix In the mitochondrion, the matrix contains soluble enzymes that catalyze the oxidation of pyruvate and other small organic molecules.
Nuclear matrix In the cell nucleus the matrix is the insoluble fraction that remains after extracting the solubled DNA.
Golgi matrix The Golgi matrix is a protein scaffold around the Golgi apparatus made up of Golgins, GRASP's and miscellaneous other proteins on the cytoplasmic side of the Golgi apparatus involved in keeping its shape and membrane stacking.
|
Matrix (biology)
|
Matrix (medium)
|
A matrix is also a medium in which bacteria are grown (cultured). For instance, a Petri dish of agar may be the matrix for culturing a sample swabbed from a patient's throat.
|
Volume Table of Contents
|
Volume Table of Contents
|
In the IBM System/360 storage architecture, the Volume Table of Contents (VTOC), is a data structure that provides a way of locating the data sets that reside on a particular DASD volume. With the exception of the IBM Z compatible disk layout in Linux on Z, it is the functional equivalent of the MS/PC DOS File Allocation Table (FAT), the NTFS Master File Table (MFT), and an inode table in a file system for a Unix-like system. The VTOC is not used to contain any IPLTEXT and does not have any role in the IPL process, therefore does not have any data used by or functionally equivalent to the MBR. It lists the names of each data set on the volume as well as size, location, and permissions. Additionally, it contains an entry for every area of contiguous free space on the volume. The third record on the first track of the first cylinder of any DASD (e.g., disk) volume is known as the volume label and must contain a pointer to the location of the VTOC. The location of the VTOC may be specified when the volume is initialized. For performance reasons it may be located as close to the center of the volume as possible, since it is referenced frequently. A VTOC is added to a DASD volume when it is initialized using the Device Support Facilities program, ICKDSF, in current systems.
|
Volume Table of Contents
|
Volume Table of Contents
|
When in OS/360 and successors allocates a data set, it generally searches the catalog to determine the volumes on which it resides. When a program opens a Direct Access Storage Device (DASD) dataset, the OPEN routine searches the VTOC index (VTOCIX) if there is one, or directly searches the VTOC if there is no VTOCIX.
|
Volume Table of Contents
|
Data Set Control Block types
|
The VTOC consists of a sequence of 140-byte records known as Data Set Control Blocks (DSCBs). There are ten types of DSCB.
|
Volume Table of Contents
|
Data Set Control Block types
|
The VTOC must reside within the first 64K tracks on the volume, and The first DSCB in the VTOC is always a format 4 DSCB which describes the VTOC itself and attributes of the DASD volume on which this VTOC resides. The second DSCB is always a format 5 DSCB which describes free space within the VTOC. Normally, the rest of the VTOC will contain format 0 DSCBs, which are empty entries, and format 1 or format 3 DSCBs, which describe the extents of data sets, giving their start address and end address of up to 16 such extents on disk. The initial part of a data set is described by a format 1 DSCB. If necessary, format 3 DSCBs are used to describe further extents of the data set. When a data set is deleted, its format 1 DSCB is overwritten to become a format 0 DSCB, and the format 3 DSCB, if one exists, is similarly deleted.
|
Volume Table of Contents
|
Data Set Control Block types
|
Originally, a VTOC search was a sequential scan of the DSCBs, stopping when the correct format 1 DSCB was found or the end of the VTOC was reached. As DASD volumes became larger, VTOC search became a bottleneck and so a VTOC index was added.
Format 1 DSCB This VTOC entry describes a dataset and defines its first three extents. This is the format of the DSCB from OS/360 Release 21.7 in 1973, prior to changes for Y2K.
|
(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate
|
(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate
|
(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP or HMB-PP) is an intermediate of the MEP pathway (non-mevalonate pathway) of isoprenoid biosynthesis. The enzyme HMB-PP synthase (GcpE, IspG) catalyzes the conversion of 2-C-methyl-D-erythritol 2,4-cyclodiphosphate (MEcPP) into HMB-PP. HMB-PP is then converted further to isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) by HMB-PP reductase (LytB, IspH).
|
(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate
|
(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate
|
HMB-PP is an essential metabolite in most pathogenic bacteria including Mycobacterium tuberculosis as well as in malaria parasites, but is absent from the human host.HMB-PP is the physiological activator ("phosphoantigen") for human Vγ9/Vδ2 T cells, the major γδ T cell population in peripheral blood. With a bioactivity of 0.1 nM it is 10,000-10,000,000 times more potent than any other natural compound, such as IPP or alkyl amines. HMB-PP functions in this capacity by binding the B30.2 domain of BTN3A1.
|
BFSP1
|
BFSP1
|
BFSP1 is a gene that encodes the protein filensin ("beaded filament structural protein 1") in humans.More than 99% of the vertebrate ocular lens is made up of terminally differentiated lens fiber cells. Two lens-specific intermediate filament proteins, phakinin (also known as CP49) and the protein product of this gene, filensin (or CP115), are expressed only after fiber cell differentiation has begun. Both proteins are found in a structurally unique cytoskeletal element that is referred to as the beaded filament (BF).The two BFSP proteins are put into a "type VI" of intermediate filament (IF) classification. Unlike other IFs that form unbranched links, the two proteins form a network of filaments together with CRYAA.
|
Campimeter
|
Campimeter
|
The campimeter is an instrument for examining the visual field. Campimeters have been in clinical use since the mid-nineteenth century. Initially, examination of the visual field was concerned only with the outer limits, or 'perimeter' of the visual field, hence the term 'perimetry', which tends to be used inter-changeably with 'campimetry'.
|
Lower crustal flow
|
Lower crustal flow
|
In geodynamics lower crustal flow is the mainly lateral movement of material within the lower part of the continental crust by a ductile flow mechanism. It is thought to be an important process during both continental collision and continental break-up.
|
Lower crustal flow
|
Rheology
|
The tendency of the lower crust to flow is controlled by its rheology. Ductile flow in the lower crust is assumed to be controlled by the deformation of quartz and/or plagioclase feldspar as its composition is thought to be granodioritic to dioritic. With normal thickness continental crust and a normal geothermal gradient, the lower crust, below the brittle–ductile transition zone, exhibits ductile flow behaviour under geological strain rates. Factors that can vary this behaviour include: water content, thickness, heat flow and strain-rate.
|
Lower crustal flow
|
Collisional belts
|
In some areas of continental collision, the lower part of the thickened crust that results is interpreted to flow laterally, such as in the Tibetan plateau, and the Altiplano in the Bolivian Andes.
|
Base-promoted epoxide isomerization
|
Base-promoted epoxide isomerization
|
Base-promoted epoxide isomerization is the conversion of alkyl epoxides to ring-opened products through the action of strong base. Isomerizations of this type are most often used to synthesize allylic alcohols, although other products are possible.
|
Base-promoted epoxide isomerization
|
Introduction
|
In the presence of lithium or aluminum amide bases, epoxides may open to give the corresponding allylic alcohols. Removal of a proton adjacent to the epoxide, elimination, and neutralization of the resulting alkoxide lead to synthetically useful allylic alcohol products. In reactions of chiral, non-racemic epoxides, the configuration of the allylic alcohol product matches that of the epoxide substrate at the carbon whose C–O bond does not break (the starred carbon below). Besides β-elimination some other reactions are possible, as metalation of the epoxide ring can take place competitively. Vinylogous eliminations are possible when the epoxide substrate is substituted with vinyl or dienyl groups. Unconstrained systems tend to form trans double bonds, as significant non-bonding interactions are avoided in the transition state for the formation of trans products (see equation (2) below). The strongly basic conditions required for most isomerizations of this type represent the reaction's primary disadvantage.
|
Base-promoted epoxide isomerization
|
Mechanism and stereochemistry
|
Prevailing mechanism Isomerization of epoxides to allylic alcohols under strongly basic conditions proceeds by a β-elimination process. A model has been advanced that invokes an initial complex between the lithium amide base and epoxide. Concerted C–O bond cleavage and deprotonation proceeds via a syn transition state to give an allylic alkoxide, which is protonated upon workup. Deprotonation typically occurs at the exist in the transition state for cis double bond formation.
|
Base-promoted epoxide isomerization
|
Mechanism and stereochemistry
|
(2) Other processes may take place competitively under basic conditions, particularly when β-elimination is slow or not possible. These pathways likely begin with lithiation of a carbon in the epoxide ring, followed by α-elimination to afford a carbene intermediate. 1,2-hydrogen migration leads to ketones, while intramolecular C–H insertion affords cyclic alcohols with the formation of a new carbon-carbon bond.(3) In many cases when hexamethylphosphoramide (HMPA) is used as an additive with lithium amide bases, selectivity for the formation of allylic alcohols increases. These reactions are believed to proceed through E2 elimination.
|
Base-promoted epoxide isomerization
|
Mechanism and stereochemistry
|
Stereoselective variants Chiral amide bases may be used in catalytic amounts to isomerize meso epoxides to chiral allylic alcohols with high enantioselectivity.
(4)
|
Base-promoted epoxide isomerization
|
Scope and limitations
|
Terminal epoxides suffer from the limitation that competitive nucleophilic addition of the base to the unsubstituted epoxide carbon may take place. Non-nucleophilic, sterically hindered bases have been used to isomerize terminal epoxides successfully, however.(5) Acyclic disubstituted epoxides undergo deprotonation at the least substituted site (unless a conjugated double bond can be formed; see equation (9) below) with high selectivity for trans double bonds.
|
Base-promoted epoxide isomerization
|
Scope and limitations
|
(6) Five- and six-membered rings containing epoxides afford allylic alcohols upon treatment with amide bases; however, reactions of medium-ring epoxides may be complicated by competitive transannular C–H insertion or ketone formation.
(7) Trisubstituted epoxides do not easily undergo metalation in the ring. As a result, allylic alcohols are formed from these substrates without competitive carbenoid transformations. The use of bulky aluminum amide bases facilitates elimination at the substituent cis to hydrogen, which occurs from the less sterically hindered epoxide-base complex.
(8) Suitably substituted unsaturated epoxides may undergo vinylogous elimination, which leads to conjugated allylic alcohols. Substituted vinyl epoxides undergo 1,4-elimination in some but not all cases; however, epoxides with β unsaturation eliminate cleanly to give conjugated allylic alcohols.
(9)
|
Base-promoted epoxide isomerization
|
Experimental conditions and procedure
|
Typical conditions Lithium amides are usually prepared in the laboratory through the addition of a titrated solution of n-butyllithium in hexanes to a solution of the amine in ether. Dry glassware and inert atmosphere are required for these reactions. Alternatively, lithium amides may be prepared by the direct action of lithium on the corresponding amine. Typical temperatures for isomerization reactions employing lithium amides are between 0 °C and reflux (ether/hexane solvent mixtures derived from the synthesis of the lithium amide are usually used directly for isomerization reactions). An excess of the base is employed to account for impurities that consume base and reaction of the base with the ether solvent. Care should be taken when HMPA is added to lithium amide reactions, as it is a known animal carcinogen.
|
Base-promoted epoxide isomerization
|
Experimental conditions and procedure
|
Organolithium reagents may also be used; however, lower temperatures are required to avoid decomposition of the base. These reactions are most often run in hexanes.
Aluminum amides, which are bulkier and sometimes more selective than lithium amides, are prepared from the corresponding lithium amides and diethylaluminum chloride. Reactions are usually carried out at 0 °C in an inert atmosphere, with benzene as the solvent.
Example procedure (10) A benzene solution of 1 eq of diethylaluminum chloride was added dropwise at 0° to a solution of 1 eq of lithium 2,2,6,6-tetramethylpiperidide prepared in the usual fashion in benzene. The resulting slurry was stirred for 30 minutes and used immediately.
|
Base-promoted epoxide isomerization
|
Experimental conditions and procedure
|
To a stirred mixture of 0.004 mol of diethylaluminum 2,2,6,6-tetramethylpiperidide in 10 mL of benzene at 0 °C was added dropwise over 5 minutes a solution of 0.18 g (0.001 mol) of epoxide in 3 mL of benzene. The mixture was stirred at 0 °C until analysis indicated the absence of starting material. The reaction was quenched by the addition of ice-cold 1 N hydrochloric acid. The organic layer was separated, and the aqueous layer was extracted with ether. The organic layers were combined, washed with brine, dried, and concentrated. The residue was purified by preparative TLC (Rf 0.22 in 1:2 ether–hexane) to give 99% of (E)-2-cyclododecenol: IR (neat) 3330–3370, 1465, 1450, 970 cm−1; NMR (CCl4) δ 3.73–4.20 (1, m), 4.97–5.82 (2, m); mass spectrum (m/z) 182 (16), 164 (13), 139 (32), 125 (46), and 98 (100).
|
Diffraction standard
|
Diffraction standard
|
In crystallography, a diffraction standard, or calibration crystal, is a crystal used to calibrate an X-ray spectrometer to an absolute X-ray energy scale. Quartz or silicon crystals are typically used. There are also reports of crystals of silver behenate or silver stearate having been used for this purpose.
|
SMK- Composite Bridge System
|
SMK- Composite Bridge System
|
In dentistry, SMK, short for System kompozytowy most (in Polish) ("Composite Bridge System"), is an adhesive restorative prosthodontic technique, developed in Poland during the 1990s. Using the SMK method, a prosthetic tooth is constructed and fitted without damage to the neighbouring teeth.
|
SMK- Composite Bridge System
|
Description of method
|
In the SMK method, the dentist models and shapes a tooth from composite materials and fits it in the interdental gap to be filled. In some cases a porcelain veneer is then placed on the new tooth to give it a more natural look. The tooth is attached to the neighbouring teeth also with composite materials. In 2011 over 1000 SMK treatments were performed, mostly on the lateral incisors.
|
SMK- Composite Bridge System
|
Description of method
|
The main advantage of this method is that there is no grinding of neighbouring teeth, so that the neighbouring teeth are not damaged. This means that the patient can at any time revert to their natural teeth. This method can also be used in situations where other techniques are not applicable: for example, if there is not enough bone and implants cannot be inserted, or the grinding and damaging of neighbouring teeth for a normal dental bridge is not accepted by the patient, or the cost of alternative treatments is too high for the patient. The dentist makes the tooth in the surgery (a dental technician is not needed), and the treatment is completed in approximately two hours.
|
SMK- Composite Bridge System
|
History
|
In 1992, the first SMK treatment was performed in the Orthodontic Department of the Pomeranian Medical School in Szczecin, Poland, by C. Turostowski. At the beginning it was treated as a temporary solution. However, after seven years, due to continuing research the SMK method became increasingly used as a permanent option. In June 1999, Turostowski completed his Ph.D., "SMK – composite bridge of own construction applied in the rebuilding of lateral incisors".
|
SMK- Composite Bridge System
|
History
|
Initially, SMK treatment was applied with orthodontic patients with missing lateral incisors. Later, it was applied to patients with other missing teeth, especially premolars. In some cases SMK was used together with veneers so as to give it a more cosmetic and natural look. Shortly afterwards SMK was introduced for use not only with orthodontics patients but also with other dental patients. In 2003 many dental courses for dentists and dental workshops at medical schools and orthodontics departments were organised around Poland.
|
SMK- Composite Bridge System
|
History
|
Different variations of the SMK method have been developed.
|
DLL3
|
DLL3
|
Delta-like 3 (Drosophila), also known as DLL3, is a protein which in humans is encoded by the DLL3 gene. Two transcript variants encoding distinct isoforms have been identified for this gene.
|
DLL3
|
Function
|
This gene encodes a member of the delta protein ligand family. This family functions as Notch ligands that are characterized by a DSL domain, EGF repeats, and a transmembrane domain. Expression of DLL3 is highest in fetal brain. It plays a key role in somitogenesis within the Paraxial mesoderm.
|
DLL3
|
Clinical significance
|
Mutations in this gene cause the autosomal recessive genetic disorder Jarcho-Levin syndrome. Expression of the gene occurs in Neuroendocrine tumors, which has been targeted as a potential pathway for treatment.An experimental drug, rovalpituzumab tesirine, targets DLL3 as a possible treatment for lung cancer.
|
Renoise
|
Renoise
|
Renoise is a digital audio workstation (DAW) based upon the heritage and development of tracker software. Its primary use is the composition of music using sound samples, soft synths, and effects plug-ins. It is also able to interface with MIDI and OSC equipment. The main difference between Renoise and other music software is the characteristic vertical timeline sequencer used by tracking software.
|
Renoise
|
History
|
Renoise was originally based on the code of another tracker called NoiseTrekker, made by Juan Antonio Arguelles Rius (Arguru). The then unnamed Renoise project was initiated by Eduard Müller (Taktik) and Zvonko Tesic (Phazze) during December 2000. The development team planned to take tracking software into a new standard of quality, enabling tracking scene composers to make audio of the same quality as other existing professional packages, while still keeping the proven interface that originated with Soundtracker in 1987. Version 1.0 was released in June 2002. Over the years the development team has grown to distribute the tasks of testing, administrative, support and web duties among several people.
|
Renoise
|
Features
|
Renoise currently runs under recent versions of Windows (DirectSound or ASIO), Mac OS X (Core Audio) and Linux (ALSA or JACK).
Renoise has full MIDI and MIDI sync support, VST 3 plugin support, ASIO multi I/O cards support, integrated sampler and sample editor, internal real-time DSP effects with unlimited number of effects per track, master and send tracks, full automation of all commands, Hi-Fi wav/aiff rendering (up to 32-bit, 192 kHz), Rewire support, etc.
|
Renoise
|
Features
|
Supported sample formats WAV, AIFF, FLAC, Ogg, MP3, CAF Supported effects standards VSTi, AU, LADSPA, DSSI Renoise also features a Signal Follower and cross-track routing. The Signal Follower analyzes the audio output of a track and automates user-specified parameters based on the values it generates. Cross-track routing sends the automation of any Meta Device to any track. Computer Music magazine considered the combination of these two features to "open up some incredibly powerful control possibilities", and demonstrated how the signal triggered by a drum loop could control the filter cutoff frequency on a bass sound.Renoise includes an arranging tool called the "pattern matrix", full cross-track modulation routing, built-in effects including a signal-follower metadevice that allows sidechain functionality, automatic softsynth-to-sample instrument rendering, and improved MIDI mapping.
|
Renoise
|
Versions
|
Renoise is available as either a demo or a commercial version. The demo version excludes rendering to .WAV, ASIO support in Windows (DirectSound only) and a few other features. Also, the demo version has nag screens. The commercial version includes high quality WAV rendering (up to 32 bit 192 kHz) and ASIO support.
|
Renoise
|
Development
|
With the introduction of Lua scripting in version 2.6, users can expand Renoise. They are encouraged to share their work on the centralized Renoise Tools web page.
XRNS file format The XRNS file format is native to Renoise. It is based on the XML standard, and so is readable in any text editor. The XML-based file format makes it possible for anyone to develop 3rd party applications and other systems in order to manipulate file content.
3rd party tools A project for creating PHP scripts utilities for needed advanced edit tasks has been set up at SourceForge: XRNS-PHP project.
|
Renoise
|
Development
|
In August 2007, a functional XRNS2MIDI script was published by Renoise team member Bantai. It enables Renoise users, via an external frontend, to convert native songs into regular MIDI files (.mid) and thus exporting their work for use in conventional piano-roll sequencers such as Cubase or Reason.Since version 2.6, it is possible to extend Renoise capabilities by writing plugins in the Lua programming language. A specific tools mini site has been created to showcase these. Almost any aspect of the program, except realtime audio data mangling, can be scripted using the native Renoise Lua API.
|
OSBPL9
|
OSBPL9
|
Oxysterol binding protein-like 9 is a protein that in humans is encoded by the OSBPL9 gene.This gene encodes a member of the oxysterol-binding protein (OSBP) family, a group of intracellular lipid receptors. Most members contain an N-terminal pleckstrin homology domain and a highly conserved C-terminal OSBP-like sterol-binding domain, although some members contain only the sterol-binding domain. This family member functions as a cholesterol transfer protein that regulates Golgi structure and function. Multiple transcript variants, most of which encode distinct isoforms, have been identified. Related pseudogenes have been identified on chromosomes 3, 11 and 12.
|
OSBPL9
|
Model organisms
|
Model organisms have been used in the study of OSBPL9 function. A conditional knockout mouse line, called Osbpl9tm1a(KOMP)Wtsi was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists — at the Wellcome Trust Sanger Institute.Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty four tests were carried out on homozygous mutant adult mice, however no significant abnormalities were observed.
|
KronoScope
|
KronoScope
|
KronoScope is a peer-reviewed academic journal dedicated to the interdisciplinary study of time, both in the humanities and in the sciences. It is published biannually under the imprint of Brill Publishers on behalf of the International Society for the Study of Time. It is indexed in Sociological Abstracts.
|
Phosphate permease
|
Phosphate permease
|
Phosphate permeases are membrane transport proteins that facilitate the diffusion of phosphate into and out of a cell or organelle. Some of these families include: TC# 2.A.1.4 - Organophosphate:Pi Antiporter (OPA) Family, (i.e., Pho-84 of Neurospora crassa; TC# 2.A.1.9.2) TC# 2.A.20 - Inorganic Phosphate Transporter (PiT) Family TC# 2.A.47.2 - Phosphate porters of the Divalent Anion:Na+ Symporter (DASS) Family, includes Pho87/90/91 TC# 2.A.58 - Phosphate:Na+ Symporter (PNaS) Family TC# 2.A.94 - Phosphate Permease (Pho1) Family
|
Bustle
|
Bustle
|
A bustle is a padded undergarment used to add fullness, or support the drapery, at the back of women's dresses in the mid-to-late 19th century. Bustles are worn under the skirt in the back, just below the waist, to keep the skirt from dragging. Heavy fabric tended to pull the back of a skirt down and flatten it. As a result a woman's petticoated skirt would lose its shape during everyday wear (from merely sitting down or moving about).
|
Bustle
|
History
|
In the early stages of the fashion for the bustle, the fullness to the back of the skirts was carried quite low and often fanned out to create a train. The transition from the voluminous crinoline-enhanced skirts of the 1850s and 1860s can be seen in the loops and gathers of fabric and trimmings worn during this period. The bustle later evolved into a much more pronounced humped shape on the back of the skirt immediately below the waist, with the fabric of the skirts falling quite sharply to the floor, changing the shape of the silhouette.
|
Bustle
|
History
|
Transition from crinoline (1867–1872) As the fashion for crinolines wore on, their shape changed. Instead of the large bell-like silhouette previously in vogue, they began to flatten out at the front and sides, creating more fullness at the back of the skirts. One type of crinoline, the crinolette, created a shape very similar to the one produced by a bustle. Crinolettes were more restrictive than traditional crinolines, as the flat front and bulk created around the posterior made sitting down more difficult for the wearer. The excess skirt fabric created by this alteration in shape was looped around to the back, again creating increased fullness.
|
Bustle
|
History
|
Early bustle (1869–1876) The bustle later developed into a feature of fashion on its own after the overskirt of the late 1860s was draped up toward the back and some kind of support was needed for the new draped shape. Fullness of some sort was still considered necessary to make the waist look smaller and the bustle eventually replaced the crinoline completely. The bustle was worn in different shapes for most of the 1870s and 1880s, with a short period of non-bustled, flat-backed dresses from 1878 to 1882.
|
Bustle
|
History
|
Late bustle (1881–1889) The bustle reappeared in late 1881, and was exaggerated to become a major fashion feature in the mid and late 1880s, in 1885 reaching preposterous proportions to modern eyes, as used in the play Arms and the Man by George Bernard Shaw. The fashion for large bustles ended in 1889.
|
Bustle
|
History
|
1889–1913 The bustle then survived into the 1890s and early 20th century, as a skirt support was still needed and the stylish shape dictated a curve in the back of the skirt to balance the curve of the bust in front. The bustle had completely disappeared by 1905, as the long corset of the early 20th century was now successful in shaping the body to protrude behind.
|
Bustle
|
History
|
Contemporary fashion Bustles and bustle gowns are rarely worn in contemporary society. Notable exceptions occur in the realm of haute couture, bridal fashion, steampunk fashion and Lolita fashion. Bustles are employed as part of period costuming in film and theatre: an example would be the 1992 film Bram Stoker's Dracula, for which costume designer Eiko Ishioka won an Academy Award. The film features several extravagant bustle gowns created for female leads Winona Ryder and Sadie Frost.
|
Bustle
|
Other usage
|
Bustle was also the term used for an additional external space at the rear of a tank's turret used for storing extra equipment, a notable usage being the added box at the rear of the turret on the Sherman Firefly variant. Its positioning on the vehicle resembling the similar placement of the bustle as used on the dress item.In sailboat design, a bustle stern refers to any kind of stern that has a large "bustle" or blister at the waterline below the stern to prevent the stern from squatting when getting underway, or to a similar shape produced by the IOR measuring system in the late '70, '80 and early '90s.The term bustleback was used to describe cars styled with an additional rear protrusion that were produced in the early 1980s, such as the Cadillac Bustleback Seville.
|
American Warmblood
|
American Warmblood
|
The American Warmblood is a horse of warmblood type, intended primarily for the traditional sport horse disciplines of dressage, show jumping, eventing and combined driving.
|
American Warmblood
|
Characteristics
|
The American Warmblood is usually between 15 and 17 hands (60 and 68 inches, 152 and 173 cm) high and may come in any color, though the solid colors are the most common. Horses of nearly all bloodlines are eligible for registration as American Warmbloods, as long as they are of a sport horse or warmblood type, and are able to meet the appropriate studbook selection or performance criteria.
|
American Warmblood
|
Characteristics
|
The emphasis is on the quality of each individual horse, for both registration and breeding approval. While the ideal horse for registration is already a warmblood type, there are no breed restrictions for American Warmbloods. Horses which are 100% hot or cold blooded are not typical, but can be registered if they are able to meet the registry's performance standards (this would include draft horses, Arabians, and Thoroughbreds). Gaited horse breeds (like the Tennessee Walker, Missouri Fox Trotter, or Icelandic horses) are also non-typical, though if they are able to perform walk-trot-canter in the appropriate levels of the accepted disciplines, they too can be eligible for registration.
|
American Warmblood
|
Characteristics
|
Horses which fail to meet or have yet to meet these performance criteria may still be issued recording papers, but are not considered registered American Warmbloods until they satisfy performance or inspection standards.Breeding stock must be approved for breeding through studbook inspection, which requires mares and stallions to meet even more stringent inspection and/or performance criteria.
|
American Warmblood
|
Breed history
|
There are two registries in the United States which recognize American Warmbloods - the American Warmblood Society & Sporthorse Registry and the American Warmblood Registry, both of which are recognized by the World Breeding Federation for Sport Horses (WBFSH).
|
American Warmblood
|
Breed history
|
The American Warmblood is more of a "type" than a "breed". Like most of the European warmbloods, the American Warmblood has an "open" book. There is more emphasis on producing quality sport horses, rather than the preservation of any particular bloodlines, which allows for much diversity in the bloodlines of American Warmbloods.The American Warmblood has been influenced by the European warmbloods, the Thoroughbred and the Arabian, as well as some draft horse breeds.
|
American Warmblood
|
Breed history
|
Both registries have also begun sport pony books, creating similar performance registries for North American ponies.
|
History of the Theory of Numbers
|
History of the Theory of Numbers
|
History of the Theory of Numbers is a three-volume work by Leonard Eugene Dickson summarizing work in number theory up to about 1920. The style is unusual in that Dickson mostly just lists results by various authors, with little further discussion. The central topic of quadratic reciprocity and higher reciprocity laws is barely mentioned; this was apparently going to be the topic of a fourth volume that was never written (Fenster 1999).
|
History of the Theory of Numbers
|
Volumes
|
Volume 1 - Divisibility and Primality - 486 pages Volume 2 - Diophantine Analysis - 803 pages Volume 3 - Quadratic and Higher Forms - 313 pages
|
.cym
|
.cym
|
.cym is a GeoTLD reserved for eventual assignment to the Cayman Islands. The primary top-level domain used by the Cayman Islands is .ky. The Islands already have the international three letter code, CYM. ICANN plans to increase the number of generic top-level domains, and it is through this process that a .cym top-level domain might be awarded. The Cayman Islands were previously in competition with Wales over use of the top-level domain. A campaign named "dot.CYM", not overly supported at government level, sought to have the .cym suffix for websites concerning Wales (Welsh: Cymru), the Welsh language (Welsh: Cymraeg) and Welsh culture. However, .cym was eventually assigned to the Cayman Islands because ICANN's policy states that new applications for 3-letter domains will not be accepted if they match existing ISO 3-letter codes. Wales was eventually granted the domain .cymru.
|
.cym
|
.cymru and .wales
|
In June 2012, ICANN opened the process of applications for new top level domains. Nominet, who own the .uk TLD, applied to ICANN for both .cymru and .wales.
|
Parachute tower
|
Parachute tower
|
A parachute tower is a tower used for parachute training, often by members of a military paratroop unit. A mixture of tower heights are used at different stages of training. Trainees typically begin on towers around 35 feet (11 m) in height in fall-arrest harnesses before progressing onto parachute descents from towers that can be in excess of 250 feet (76 m). The use of towers allows trainees to practice their landing technique before jumping from an aircraft.
|
Parachute tower
|
Use
|
Parachute towers are used to train people, particularly military paratroopers, in parachute jump technique. Towers are typically divided into low towers of approximately 35 feet (11 m) and high towers of around 100–200 feet (30–61 m) or higher. The shorter towers are used by trainees jumping in harnesses with a fall-restraint cable to simulate the exit from an aircraft and safe landing technique.Trainees then pass onto the high tower jumps with parachutes. The high tower typically has one or more arms at the top from which the trainee is winched up into the air and released to descend by parachute. The parachutes used are specific variants developed for training and were originally modified commercial systems, though the US military later developed the Type J-I parachute specifically for high tower jumps.The high tower allows trainees to practice the "body landing" (or parachute landing fall) technique, which is essential to avoid injuries such as broken legs or ankles. The high tower can also be used to carry out "shock harness drills", intended to simulate the initial shock of a parachute canopy opening. The trainee is hauled up into the air and dropped to free fall approximately 15 feet (4.6 m) before being brought to a complete stop. After high tower training is passed troops proceed onto aircraft jumps from an altitude of approximately 1,250 feet (380 m). In the United States Army during the Second World War, five jumps from aircraft were sufficient to complete the course; the British Army required trainees to undertake an additional two jumps from tethered balloons prior to jumping from aircraft.
|
Parachute tower
|
Military history
|
The first parachute tower in the United States was a 115-foot-tall (35 m) tower in Ocean County, New Jersey, built by Stanley Switlik and first used by Amelia Earhart on 2 June 1935. The 262-foot (80 m) Parachute Jump ride at the 1939 New York World's Fair (later moved to Coney Island) was a parachute tower, though the United States Army parachute training centre at Fort Benning had only 34-foot (10 m) towers until 1941. Major William Lee of the United States Army, in charge of the training of the first 48-man platoon of US paratroopers, saw the Parachute Jump ride and constructed a similar tower at Fort Benning. Three further towers were later erected. Each stood 254 feet (77 m) high and had four arms—each of which could hoist a single paratrooper—that spanned 134 feet (41 m).The Polish Army used the Parachute Tower Katowice for training. The tower was used as a vantage point on 4 September 1939 during the defence of the town from the German invasion. The story of its defence by Polish boy and girl scouts has been described as a "heroic myth". Some of the Polish Army escaped to the United Kingdom after the fall of Poland and was based at Largo House, Scotland. Here they constructed a parachute tower, the first to be built in the British Empire, which was used to train the 1st Independent Parachute Brigade. The British military later constructed their own parachute tower (with capacity for two paratroopers) at RAF Ringway, which was moved to RAF Abingdon in 1950.The USSR had a large number of parachute training towers, with 559 in operation by 1939. Japan had at least four in operation during the Second World War. The Turkish Aeronautical Association constructed two parachute towers in İzmir and Ankara between 1935 and 1937 based on a Russian tower in use at Gorky Park. Rhodesia also had a parachute tower at New Sarum Air Force Base.
|
Parachute tower
|
Fairground rides
|
As well as the original Parachute Jump at the 1939 World's Fair, there have been several other fairground rides based on a similar premise. The Pair-O-Chutes ride operated at Chicago's Riverview Park but was demolished in 1968. Parachute towers, known as "Parachute Drops" were developed by Intamin for the Six Flags theme parks. The Texas Chute Out operated at Six Flags Over Texas from 1976 to 2012; Great Gasp operated at Six Flags Over Georgia from 1976 to 2005 and Sky Chuter was at Six Flags Over Mid-America from 1978 to 1982. Sky Chuter was relocated to Six Flags Great Adventure, where it reopened in 1983 as Parachuter's Perch, and as of 2019, it is still operational under the name "Parachute Training Center". Intamin also produced a "Parachute Drop" for Knott's Berry Farm in California in the late 1970s, which was named "Sky Jump". The parachute jump portion of the tower was removed but its observation tower remains in operation. Tokyo Dome City Attractions, Japan, has an Intamin parachute drop ride named Sky Flower.
|
Klein paradox
|
Klein paradox
|
In 1929, physicist Oskar Klein obtained a surprising result by applying the Dirac equation to the familiar problem of electron scattering from a potential barrier. In nonrelativistic quantum mechanics, electron tunneling into a barrier is observed, with exponential damping. However, Klein's result showed that if the potential is at least of the order of the electron mass, Ve∼mc2 , the barrier is nearly transparent. Moreover, as the potential approaches infinity, the reflection diminishes and the electron is always transmitted.
|
Klein paradox
|
Klein paradox
|
The immediate application of the paradox was to Rutherford's proton–electron model for neutral particles within the nucleus, before the discovery of the neutron. The paradox presented a quantum mechanical objection to the notion of an electron confined within a nucleus. This clear and precise paradox suggested that an electron could not be confined within a nucleus by any potential well. The meaning of this paradox was intensely debated at the time.
|
Klein paradox
|
Massless particles
|
Consider a massless relativistic particle approaching a potential step of height V0 with energy E0<V0e and momentum p The particle's wave function, ψ , follows the time-independent Dirac equation: (σxp+V)ψ=E0ψ,V={0,x<0V0,x>0 And σx is the Pauli matrix: σx=(0110) Assuming the particle is propagating from the left, we obtain two solutions — one before the step, in region (1) and one under the potential, in region (2): ψ1=Aeipx(11)+A′e−ipx(−11),p=E0 ψ2=Beikx(11),|k|=V0−E0 where the coefficients A, A′ and B are complex numbers.
|
Klein paradox
|
Massless particles
|
Both the incoming and transmitted wave functions are associated with positive group velocity (Blue lines in Fig.1), whereas the reflected wave function is associated with negative group velocity. (Green lines in Fig.1) We now want to calculate the transmission and reflection coefficients, T,R.
They are derived from the probability amplitude currents.
The definition of the probability current associated with the Dirac equation is: Ji=ψi†σxψi,i=1,2 In this case: J1=2[|A|2−|A′|2],J2=2|B|2 The transmission and reflection coefficients are: R=|A′|2|A|2,T=|B|2|A|2 Continuity of the wave function at x=0 , yields: |A|2=|B|2 |A′|2=0 And so the transmission coefficient is 1 and there is no reflection.
|
Klein paradox
|
Massless particles
|
One interpretation of the paradox is that a potential step cannot reverse the direction of the group velocity of a massless relativistic particle. This explanation best suits the single particle solution cited above. Other, more complex interpretations are suggested in literature, in the context of quantum field theory where the unrestrained tunnelling is shown to occur due to the existence of particle–antiparticle pairs at the potential.
|
Klein paradox
|
Massive case
|
For the massive case, the calculations are similar to the above.
The results are as surprising as in the massless case. The transmission coefficient is always larger than zero, and approaches 1 as the potential step goes to infinity.
The Klein zone If the energy of the particle is in the range mc2<E<Ve−mc2 , then partial reflection rather than total reflection will result.
|
Klein paradox
|
Massive case
|
Resolutions for the massive case While the traditional resolution uses particle–anti-particle pair production in the context of quantum field theory (Hansen 1981), a simpler resolution exists that substitutes physical pair production for the scattering of negative energy solutions under the barrier (Alhaidari 2009). This strategy was also applied to obtain analytic solutions to the Dirac equation for an infinite square well.
|
Klein paradox
|
Other cases
|
These results were expanded to higher dimensions, and to other types of potentials, such as a linear step, a square barrier, a smooth potential, etc.
Many experiments in electron transport in graphene rely on the Klein paradox for massless particles.
|
Abacha (food)
|
Abacha (food)
|
Abacha (listen) is a type of food originating with the Igbos in south eastern Nigeria.
|
Abacha (food)
|
Ingredients
|
Dried shredded cassava Ugba or ukpaka Palm oil Powdered potash Fish (spiced cooked) Ponmo (cooked and sliced) Onion (sliced) Garden eggs (diced) Garden egg leaves (chopped) Salt and dry pepper Crayfish Seasoning cubes Calabash nutmeg Ogiri Fresh utazi leaves Boiling water
|
Dunkirk Formation
|
Dunkirk Formation
|
The Dunkirk Formation is a geologic formation in New York. It preserves fossils dating back to the Devonian period.
|
Hematocrit
|
Hematocrit
|
The hematocrit () (Ht or HCT), also known by several other names, is the volume percentage (vol%) of red blood cells (RBCs) in blood, measured as part of a blood test. The measurement depends on the number and size of red blood cells. It is normally 40.7–50.3% for males and 36.1–44.3% for females. It is a part of a person's complete blood count results, along with hemoglobin concentration, white blood cell count and platelet count.
|
Hematocrit
|
Hematocrit
|
Because the purpose of red blood cells is to transfer oxygen from the lungs to body tissues, a blood sample's hematocrit—the red blood cell volume percentage—can become a point of reference of its capability of delivering oxygen. Hematocrit levels that are too high or too low can indicate a blood disorder, dehydration, or other medical conditions. An abnormally low hematocrit may suggest anemia, a decrease in the total amount of red blood cells, while an abnormally high hematocrit is called polycythemia. Both are potentially life-threatening disorders.
|
Hematocrit
|
Names
|
There are other names for the hematocrit, such as packed cell volume (PCV), volume of packed red cells (VPRC), or erythrocyte volume fraction (EVF). The term hematocrit (or haematocrit in British English) comes from the Ancient Greek words haima (αἷμα, "blood") and kritēs (κριτής, "judge"), and hematocrit means "to separate blood". It was coined in 1891 by Swedish physiologist Magnus Blix as haematokrit, modeled after lactokrit.
|
Hematocrit
|
Measurement methods
|
With modern lab equipment, the hematocrit can be calculated by an automated analyzer or directly measured, depending on the analyzer manufacturer. Calculated hematocrit is determined by multiplying the red cell count by the mean cell volume. The hematocrit is slightly more accurate, as the PCV includes small amounts of blood plasma trapped between the red cells. An estimated hematocrit as a percentage may be derived by tripling the hemoglobin concentration in g/dL and dropping the units.The packed cell volume (PCV) can be determined by centrifuging EDTA-treated or heparinized blood in a capillary tube (also known as a microhematocrit tube) at 10,000 RPM for five minutes. This separates the blood into layers. The volume of packed red blood cells divided by the total volume of the blood sample gives the PCV. Since a tube is used, this can be calculated by measuring the lengths of the layers.Another way of measuring hematocrit levels is by optical methods such as spectrophotometry. Through differential spectrophotometry, the differences in optical densities of a blood sample flowing through small-bore glass tubes at isosbestic wavelengths for deoxyhemoglobin and oxyhemoglobin and the product of the luminal diameter and hematocrit create a linear relationship that is used to measure hematocrit levels.Other than potential bruising at the puncture site, and/or dizziness, there are no complications associated with this test.While known hematocrit levels are used in detecting conditions, it may fail at times due to hematocrit being the measure of concentration of red blood cells through volume in a blood sample. It does not account for the mass of the red blood cells, and thus the changes in mass can alter a hematocrit level or go undetected while affecting a subject's condition. Additionally, there have been cases in which the blood for testing was inadvertently drawn proximal to an intravenous line that was infusing packed red cells or fluids. In these situations, the hemoglobin level in the blood sample will not be the true level for the patient because the sample will contain a large amount of the infused material rather than what is diluted into the circulating whole blood. That is, if packed red cells are being supplied, the sample will contain a large amount of those cells and the hematocrit will be artificially very high.
|
Hematocrit
|
Levels
|
Hematocrit can vary from the determining factors of the number of red blood cells. These factors can be from the age and sex of the subject. Typically, a higher hematocrit level signifies the blood sample's ability to transport oxygen, which has led to reports that an "optimal hematocrit level" may exist. Optimal hematocrit levels have been studied through combinations of assays on blood sample's hematocrit itself, viscosity, and hemoglobin level.Hematocrit levels also serve as an indicator of health conditions. Thus, tests on hematocrit levels are often carried out in the process of diagnosis of such conditions, and may be conducted prior to surgery. Additionally, the health conditions associated with certain hematocrit levels are the same as ones associated with certain hemoglobin levels. As blood flows from the arterioles into the capillaries, a change in pressure occurs. In order to maintain pressure, the capillaries branch off to a web of vessels that carry blood into the venules. Through this process blood undergoes micro-circulation. In micro-circulation, the Fåhræus effect will take place, resulting in a large change in hematocrit. As blood flows through the arterioles, red cells will act a feed hematocrit (Hf), while in the capillaries, a tube hematocrit (Ht) occurs. In tube hematocrit, plasma fills most of the vessel while the red cells travel through in somewhat of a single file line. From this stage, blood will enter the venules increasing in hematocrit, in other words the discharge hematocrit (Hd).In large vessels with low hematocrit, viscosity dramatically drops and red cells take in a lot of energy. While in smaller vessels at the micro-circulation scale, viscosity is very high. With the increase in shear stress at the wall, a lot of energy is used to move cells.
|
Hematocrit
|
Shear rate relations
|
Relationships between hematocrit, viscosity, and shear rate are important factors to put into consideration. Since blood is non-Newtonian, the viscosity of the blood is in relation to the hematocrit, and as a function of shear rate. This is important when it comes to determining shear force, since a lower hematocrit level indicates that there is a need for more force to push the red blood cells through the system. This is because shear rate is defined as the rate to which adjacent layers of fluid move in respect to each other. Plasma is a more viscous material than typically red blood cells, since they are able to adjust their size to the radius of a tube; the shear rate is purely dependent on the amount of red blood cells being forced in a vessel.
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.