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Metric temporal logic
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Syntax
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The full metric temporal logic is defined similarly to linear temporal logic, where a set of non-negative real number is added to temporal modal operators U and S. Formally, MTL is built up from: a finite set of propositional variables AP, the logical operators ¬ and ∨, and the temporal modal operator UI (pronounced "φ until in I ψ."), with I an interval of non-negative numbers.
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Metric temporal logic
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Syntax
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the temporal modal operator SI (pronounced "φ since in I ψ."), with I as above.When the subscript is omitted, it is implicitly equal to [0,∞) Note that the next operator N is not considered to be a part of MTL syntax. It will instead be defined from other operators.
Past and Future The past fragment of metric temporal logic, denoted as past-MTL is defined as the restriction of the full metric temporal logic without the until operator. Similarly, the future fragment of metric temporal logic, denoted as future-MTL is defined as the restriction of the full metric temporal logic without the since operator.
Depending on the authors, MTL is either defined as the future fragment of MTL, in which case full-MTL is called MTL+Past. Or MTL is defined as full-MTL.
In order to avoid ambiguity, this article uses the names full-MTL, past-MTL and future-MTL. When the statements holds for the three logic, MTL will simply be used.
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Metric temporal logic
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Model
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Let T⊆R+ intuitively represent a set of points in time. Let γ:T→A a function which associates a letter to each moment t∈T . A model of a MTL formula is such a function γ . Usually, γ is either a timed word or a signal. In those cases, T is either a discrete subset or an interval containing 0.
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Metric temporal logic
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Semantics
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Let T and γ as above and let t∈T some fixed time. We are now going to explain what it means that a MTL formula ϕ holds at time t which is denoted γ,t⊨ϕ Let I⊆R+ and ϕ,ψ∈MTL . We first consider the formula ϕUIψ . We say that γ,t⊨ϕUIψ if and only if there exists some time t′∈I+t such that: γ,t′⊨ψ and for each t″∈T with t<t″<t′ , γ,t″⊨ϕ .We now consider the formula ϕSIψ (pronounced " ϕ since in I ψ .") We say that γ,t⊨ϕSIψ if and only if there exists some time t′∈I−t such that: γ,t′⊨ψ and for each t″∈T with t′<t″<t , γ,t″⊨ϕ .The definitions of γ,t⊨ϕ for the values of ϕ not considered above is similar as the definition in the LTL case.
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Metric temporal logic
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Operators defined from basic MTL operators
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Some formulas are so often used that a new operator is introduced for them. These operators are usually not considered to belong to the definition of MTL, but are syntactic sugar which denote more complex MTL formula. We first consider operators which also exists in LTL. In this section, we fix ϕ,ψ MTL formulas and I⊆R+ Operators similar to the ones of LTL Release and Back to We denote by ϕRIψ (pronounced " ϕ release in I , ψ ") the formula ¬ϕUI¬ψ . This formula holds at time t if either: there is some time t′∈t+I such that ϕ holds, and ψ hold in the interval (t,t′)∩(t+I) at each time t′∈t+I , ϕ holds.The name "release" come from the LTL case, where this formula simply means that ϕ should always hold, unless ψ releases it.
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Metric temporal logic
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Operators defined from basic MTL operators
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The past counterpart of release is denote by ϕBIψ (pronounced " ϕ back to in I , ψ ") and is equal to the formula ¬ϕSI¬ψ Finally and Eventually We denote by ◊Iϕ or FIϕ (pronounced "Finally in I , ϕ ", or "Eventually in I , ϕ ") the formula ⊤UIϕ . Intuitively, this formula holds at time t if there is some time t′∈t+I such that ϕ holds.
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Metric temporal logic
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Operators defined from basic MTL operators
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We denote by ◻Iϕ or GIϕ (pronounced "Globally in I , ϕ ",) the formula ¬◊I¬ϕ . Intuitively, this formula holds at time t if for all time t′∈t+I , ϕ holds.
We denote by ◻←Iϕ and ◊←Iϕ the formula similar to ◻Iϕ and ◊Iϕ where U is replaced by S . Both formula has intuitively the same meaning, but when we consider the past instead of the future.
Next and previous This case is slightly different from the previous ones, because the intuitive meaning of the "Next" and "Previously" formulas differs depending on the kind of function γ considered.
We denote by ◯Iϕ or NIϕ (pronounced "Next in I , ϕ ") the formula ⊥UIϕ . Similarly, we denote by ⊖Iϕ (pronounced "Previously in I , ϕ ) the formula ⊥SIϕ . The following discussion about the Next operator also holds for the Previously operator, by reversing the past and the future.
When this formula is evaluated over a timed word γ:T→A , this formula means that both: at the next time in the domain of definition T , the formula ϕ will holds.
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Metric temporal logic
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Operators defined from basic MTL operators
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furthermore, the distance between this next time and the current time belong to the interval I In particular, this next time holds, thus the current time is not the end of the word.When this formula is evaluated over a signal γ , the notion of next time does not makes sense. Instead, "next" means "immediately after". More precisely γ,t⊨∘ϕ means: I contains an interval of the form (0,ϵ) and for each t′∈(t,t+ϵ) , γ,t′⊨ϕ Other operators We now consider operators which are not similar to any standard LTL operators.
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Metric temporal logic
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Operators defined from basic MTL operators
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Fall and Rise We denote by ↑ϕ (pronounced "rise ϕ "), a formula which holds when ϕ becomes true. More precisely, either ϕ did not hold in the immediate past, and holds at this time, or it does not hold and it holds in the immediate future. Formally ↑ϕ is defined as (ϕ∧(¬ϕS⊤))∨(¬ϕ∧(ϕU⊤)) .Over timed words, this formula always hold. Indeed ϕU⊤ and ¬ϕS⊤ always hold. Thus the formula is equivalent to ϕ∨¬ϕ , hence is true.
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Metric temporal logic
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Operators defined from basic MTL operators
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By symmetry, we denote by ↓ϕ (pronounced "Fall ϕ ), a formula which holds when ϕ becomes false. Thus, it is defined as (¬ϕ∧(ϕS⊤))∧(ϕ∧(¬ϕU⊤)) History and Prophecy We now introduce the prophecy operator, denoted by ▹ . We denote by ▹Iϕ the formula ¬ϕUIϕ . This formula asserts that there exists a first moment in the future such that ϕ holds, and the time to wait for this first moment belongs to I We now consider this formula over timed words and over signals. We consider timed words first. Assume that =∣ a,b∣′ where ∣ and ∣′ represents either open or closed bounds. Let γ a timed word and t in its domain of definition. Over timed words, the formula γ,t⊨▹Iϕ holds if and only if γ,t⊨◻]0,b[∖I¬ϕ∧◊Iϕ also holds. That is, this formula simply assert that, in the future, until the interval t+I is met, ϕ should not hold. Furthermore, ϕ should hold sometime in the interval t+I . Indeed, given any time t″∈t+I such that γ,t″⊨ϕ hold, there exists only a finite number of time t′∈t+I with t′<t″ and γ,t′⊨ϕ . Thus, there exists necessarily a smaller such t″ Let us now consider signal. The equivalence mentioned above does not hold anymore over signal. This is due to the fact that, using the variables introduced above, there may exists an infinite number of correct values for t′ , due to the fact that the domain of definition of a signal is continuous. Thus, the formula ▹Iϕ also ensures that the first interval in which ϕ holds is closed on the left.
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Metric temporal logic
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Operators defined from basic MTL operators
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By temporal symmetry, we define the history operator, denoted by ◃ . We define ◃Iϕ as ¬ϕSIϕ . This formula asserts that there exists a last moment in the past such that ϕ held. And the time since this first moment belongs to I Non-strict operator The semantic of operators until and since introduced do not consider the current time. That is, in order for ϕ1U¯ϕ2 to holds at some time t , neither ϕ1 nor ϕ2 has to hold at time t . This is not always wanted, for example in the sentence "there is no bug until the system is turned-off", it may actually be wanted that there are no bug at current time. Thus, we introduce another until operator, called non-strict until, denoted by U¯ , which consider the current time.
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Metric temporal logic
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Operators defined from basic MTL operators
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We denote by ϕ1U¯Iϕ2 and ϕ1S¯Iϕ2 either: the formulas ϕ2∨(ϕ1∧(ϕ1UIϕ2)) and ϕ2∨(ϕ1∧(ϕ1SIϕ2)) if 0∈I , and the formulas ϕ1∧(ϕ1UIϕ2) and ϕ1∧(ϕ1SIϕ2) otherwise.For any of the operators O introduced above, we denote O¯ the formula in which non-strict untils and sinces are used. For example ◊¯p is an abbreviation for ⊤U¯p Strict operator can not be defined using non-strict operator. That is, there is no formula equivalent to ◯Ip which uses only non-strict operator. This formula is defined as ⊥UIp . This formula can never hold at a time t if it is required that ⊥ holds at time t
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Metric temporal logic
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Example
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We now give examples of MTL formulas. Some more example can be found on article of fragments of MITL, such as metric interval temporal logic.
◻(p⟹◊{1}q) states that each letter p is followed exactly one time unit later by a letter q .◻(p⟹¬◊{1}p) states that no two successive occurrences of p can occur at exactly one time unit from each other.
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Metric temporal logic
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Comparison with LTL
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A standard (untimed) infinite word w=a0,a1,…, is a function from N to A . We can consider such a word using the set of time T=N and the function γ(i)=ai . In this case, for ϕ an arbitrary LTL formula, w,i⊨ϕ if and only if γ,i⊨ϕ , where ϕ is considered as a MTL formula with non-strict operator and [0,∞) subscript. In this sense, MTL is an extension of LTL.For this reason, a formula using only non-strict operator with [0,∞) subscript is called an LTL formula. This is because the
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Metric temporal logic
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Algorithmic complexity
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The satisfiability of ECL over signals is EXPSPACE-complete.
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Metric temporal logic
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Fragments of MTL
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We now consider some fragments of MTL.
MITL An important subset of MTL is the Metric Interval Temporal Logic (MITL). This is defined similarly to MTL, with the restriction that the sets I , used in U and S , are intervals which are not singletons, and whose bounds are natural numbers or infinity.
Some other subsets of MITL are defined in the article MITL.
Future Fragments Future-MTL was already introduced above. Both over timed-words and over signals, it is less expressive than Full-MTL: 3 .
Event-Clock Temporal Logic The fragment Event-Clock Temporal Logic of MTL, denoted EventClockTL or ECL, allows only the following operators: the boolean operators, and, or, not the untimed until and since operators.
The timed prophecy and history operators.Over signals, ECL is as expressive as MITL and as MITL0. The equivalence between the two last logics is explained in the article MITL0. We sketch the equivalence of those logics with ECL.
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Metric temporal logic
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Fragments of MTL
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If I is not a singleton and ϕ is a MITL formula, ▹Iϕ is defined as a MITL formula. If I={i} is a singleton, then ▹Iϕ is equivalent to ◻]0,i[¬ϕ∧◊]0,i]ϕ which is a MITL-formula. Reciprocally, for ψ an ECL-formula, and I an interval whose lower bound is 0, ◻Iψ is equivalent to the ECL-formula ¬▹I¬ψ The satisfiability of ECL over signals is PSPACE-complete.
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Metric temporal logic
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Fragments of MTL
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Positive normal form A MTL-formula in positive normal form is defined almost as any MTL formula, with the two following change: the operators Release and Back are introduced in the logical language and are not considered anymore to be notations for some other formulas.
negations can only be applied to letters.Any MTL formula is equivalent to formula in normal form. This can be shown by an easy induction on formulas. For example, the formula ¬(ϕUSψ) is equivalent to the formula (¬ϕ)RS(¬ψ) . Similarly, conjunctions and disjunctions can be considered using De Morgan's laws.
Strictly speaking, the set of formulas in positive normal form is not a fragment of MTL.
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Interactive television (narrative technique)
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Interactive television (narrative technique)
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Interactive television or interactive TV, sometimes also called pseudo-interactive television to distinguish it from technologically enabled interactive television, is a term used to refer to television programs in which it is pretended that the characters and the viewing audience can interact, while in actuality they cannot. This narrative technique is often used in children's television. It is a simulated form of audience participation. When employed, characters will often break the fourth wall and ask the viewers to give them advice or the solution to a problem. Characters typically provide a short period of time for the viewers to react, and then proceed as though the viewers have given them the correct answer.
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Interactive television (narrative technique)
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Examples and history
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Winky Dink and You Airing 1953 to 1957, the Winky Dink and You program was perhaps the first interactive TV show. The central gimmick of the show, praised by Microsoft mogul Bill Gates as "the first interactive TV show", was the use of a "magic drawing screen"—a piece of vinyl plastic that stuck to the television screen via static electricity. A kit containing the screen and various Winky Dink crayons could be purchased for 50 cents. At a climactic scene in every Winky Dink short film, Winky would arrive on a scene that contained a connect-the-dots picture that could be navigated only with the help of viewers. Winky Dink then would prompt the children at home to complete the picture, and the finished result would help him continue the story. Examples included drawing a bridge to cross a river, using an axe to chop down a tree, or creating a cage to trap a dangerous lion. Another use of the interactive screen was to decode messages. An image would be displayed, showing only the vertical lines of the letters of the secret message. Viewers would then quickly trace onto their magic screen, and a second image would display the horizontal lines, completing the text. A final use of the screen was to create the outline of a character with whom Jack Barry would have a conversation. It would seem meaningless to viewers without the screen, further encouraging its purchase.
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Interactive television (narrative technique)
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Examples and history
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Blue's Clues Premiering in 1996, Blue's Clues was perhaps the most influential interactive TV show. It used pauses that were "long enough to give the youngest time to think, short enough for the oldest not to get bored". The length of the pauses, which was estimated from formative research, gave children enough time to process the information and solve the problem. After pausing, child voice-overs provided the answers so that they were given to children who had not come up with the solution and helped encourage viewer participation. Researcher Alisha M. Crawley and her colleagues stated that although earlier programs sometimes invited overt audience participation, Blue's Clues was "unique in making overt involvement a systematic research-based design element". In 2004, Daniel Anderson said that Blue's Clues "raised the bar" for educational television; he and Variety reported that audience participation became an important part of other educational preschool TV programs such as Dora the Explorer and Sesame Street.
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CNMa
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CNMa
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CNMamide (CNMa) is a cyclic neuropeptide identified by computational analysis of Drosophila melanogaster protein sequences and named after its C-terminal ending motif. A gene encoding CNMa was found in most arthropods and comparison among the precursor sequences of several representative species revealed high conservation, particularly in the region of the predicted mature peptide. Two conserved cysteine residues enveloping four amino acids form a disulfide bond and were shown to be important for binding of the peptide to its receptor. Expression of CNMa was confirmed in the larval and adult brain of D. melanogaster but the function of the peptide has not been elucidated yet.
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CNMa
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Sequences
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CNMa is cleaved from a larger protein to form a mature peptide at two flanking dibasic (K or R) cleavage sites. The sequences of the final peptides are: DROME: Gln-Tyr-Met-Ser-Pro-Cys-His-Phe-Lys-Ile-Cys-Asn-Met-amide APIME: Thr-Met-Ile-Ser-Tyr-Met-Thr-Leu-Cys-His-Phe-Lys-Ile-Cys-Asn-Met-amide DAPPU: Asp-Ser-Tyr-Leu-Ser-Met-Cys-His-Phe-Lys-Leu-Cys-Asn-Leu-amide The overall sequence motif, in ProSite format, is [LPM]-C-[HI]-F-K-[IL]-C-N-[ML]-G-[RK](2). Some species encode two forms of CNMa via alternative splicing.
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CNMa
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Receptor
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The receptor for CNMa (CG33696) is a G protein-coupled receptor. Phylogenetic analysis identified two separate clades of CNMaRs in arthropod species, but many taxa retain only one. Existence of two paralogous CNMaRs suggests that CNMaR has additional ligands in some insect species. This assumption is also supported by absence of the gene for CNMa in the genome of Lepidopteran species (such as Bombyx mori and Danaus plexippus) that retain the CNMaR.
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Passive smoking
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Passive smoking
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Passive smoking is the inhalation of tobacco smoke, commonly called secondhand smoke (SHS) or environmental tobacco smoke (ETS), by persons other than the active smoker. It occurs when tobacco smoke diffuses into the surrounding atmosphere as an aerosol pollutant, which leads to its inhalation by nearby bystanders within the same environment. Exposure to secondhand tobacco smoke causes many of the same diseases caused by active tobacco smoking, although to a lower prevalence due to the reduced concentration of smoke that enters the airway. The health risks of secondhand smoke are a matter of scientific consensus, and have been a major motivation for smoke-free laws in workplaces and indoor venues, including restaurants, bars and night clubs, as well as some open public spaces.Concerns around secondhand smoke have played a central role in the debate over the harms and regulation of tobacco products. Since the early 1970s, the tobacco industry has viewed public concern over secondhand smoke as a serious threat to its business interests. Harm to bystanders was perceived as a motivator for stricter regulation of tobacco products. Despite the industry's awareness of the harms of secondhand smoke as early as the 1980s, the tobacco industry coordinated a scientific controversy with the purpose of stopping regulation of their products.: 1242
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Passive smoking
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Terminology
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As of 2003, "secondhand smoke" was the term most used to refer to other people's smoke in the English-language media. Other terms used include "environmental tobacco smoke", while "involuntary smoking" and "passive smoking" are used to refer to exposure to secondhand smoke. The term "environmental tobacco smoke" can be traced back to a 1974 industry-sponsored meeting held in Bermuda, while the term "passive smoking" was first used in the title of a scientific paper in 1970. The Surgeon General of the United States prefers to use the phrase "secondhand smoke" rather than "environmental tobacco smoke", stating that "The descriptor 'secondhand' captures the involuntary nature of the exposure, while 'environmental' does not.": 9 Most researchers consider the term "passive smoking" to be synonymous with "secondhand smoke". In contrast, a 2011 commentary in Environmental Health Perspectives argued that research into "thirdhand smoke" renders it inappropriate to refer to passive smoking with the term "secondhand smoke", which the authors stated constitutes a pars pro toto.The term "sidestream smoke" is sometimes used to refer to smoke which goes into the air directly from a burning cigarette, cigar, or pipe, while "mainstream smoke" refers to smoke that a smoker exhales.
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Passive smoking
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Effects
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Secondhand smoke causes many of the same diseases as direct smoking, including cardiovascular diseases, lung cancer, and respiratory diseases. These include: Cancer: General: overall increased risk; reviewing the evidence accumulated on a worldwide basis, the International Agency for Research on Cancer concluded in 2004 that "Involuntary smoking (exposure to secondhand or 'environmental' tobacco smoke) is carcinogenic to humans." The Centers for Disease Control and Prevention reports that about 70 chemicals present in secondhand smoke are carcinogenic.
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Passive smoking
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Effects
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Lung cancer: Passive smoking is a risk factor for lung cancer. In the United States, secondhand smoke is estimated to cause more than 7,000 deaths from lung cancer a year among non-smokers. A quarter of all cases occur in people who have never smoked.
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Passive smoking
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Effects
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Breast cancer: The California Environmental Protection Agency concluded in 2005 that passive smoking increases the risk of breast cancer in younger, primarily premenopausal females by 70% and the US Surgeon General has concluded that the evidence is "suggestive", but still insufficient to assert such a causal relationship. In contrast, the International Agency for Research on Cancer concluded in 2004 that there was "no support for a causal relation between involuntary exposure to tobacco smoke and breast cancer in never-smokers." A 2015 meta-analysis found that the evidence that passive smoking moderately increased the risk of breast cancer had become "more substantial than a few years ago".
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Passive smoking
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Effects
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Cervical cancer: A 2015 overview of systematic reviews found that exposure to secondhand smoke increased the risk of cervical cancer.
Bladder cancer: A 2016 systematic review and meta-analysis found that secondhand smoke exposure was associated with a significant increase in the risk of bladder cancer.
Circulatory system: risk of heart disease and reduced heart rate variability.Epidemiological studies have shown that both active and passive cigarette smoking increase the risk of atherosclerosis.
Passive smoking is strongly associated with an increased risk of stroke, and this increased risk is disproportionately high at low levels of exposure.
Lung problems: Risk of asthma Risk of chronic obstructive pulmonary disease (COPD) According to a 2015 review, passive smoking may increase the risk of tuberculosis infection and accelerate the progression of the disease, but the evidence remains weak.
The majority of studies on the association between secondhand smoke exposure and sinusitis have found a significant association between the two.
Cognitive impairment and dementia: Exposure to secondhand smoke may increase the risk of cognitive impairment and dementia in adults 50 and over. Children exposed to secondhand smoke show reduced vocabulary and reasoning skills when compared with non-exposed children as well as more general cognitive and intellectual deficits.
Mental health: Exposure to secondhand smoke is associated with an increased risk of depressive symptoms.
During pregnancy: Miscarriage: a 2014 meta-analysis found that maternal secondhand smoke exposure increased the risk of miscarriage by 11%.
Low birth weight, part B, ch. 3.
Premature birth, part B, ch. 3 (Evidence of the causal link is described only as "suggestive" by the US Surgeon General in his 2006 report.) Laws limiting smoking decrease premature births.
Stillbirth and congenital malformations in children Recent studies comparing females exposed to secondhand smoke and non-exposed females, demonstrate that females exposed while pregnant have higher risks of delivering a child with congenital abnormalities, longer lengths, smaller head circumferences, and neural tube defects.
General: Worsening of asthma, allergies, and other conditions. A 2014 systematic review and meta-analysis found that passive smoking was associated with a slightly increased risk of allergic diseases among children and adolescents; the evidence for an association was weaker for adults.
Type 2 diabetes. It remains unclear whether the association between passive smoking and diabetes is causal.
Risk of carrying Neisseria meningitidis or Streptococcus pneumoniae.
A possible increased risk of periodontitis.
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Passive smoking
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Effects
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Overall increased risk of death in both adults, where it was estimated to kill 53,000 nonsmokers per year in the U.S in 1991, and in children. The World Health Organization states that passive smoking causes about 600,000 deaths a year, and about 1% of the global burden of disease. As of 2017, passive smoking causes about 900,000 deaths a year, which is about 1/8 of all deaths caused by smoking.
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Passive smoking
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Effects
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Skin conditions: A 2016 systematic review and meta-analysis found that passive smoking was associated with a higher rate of atopic dermatitis.
Risk to children Sudden infant death syndrome (SIDS). In his 2006 report, the US Surgeon General concludes: "The evidence is sufficient to infer a causal relationship between exposure to secondhand smoke and sudden infant death syndrome." Secondhand smoking has been estimated to be associated with 430 SIDS deaths in the United States annually.
Asthma. Secondhand smoke exposure is also associated with an almost doubled risk of hospitalization for asthma exacerbation among children with asthma.
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Passive smoking
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Effects
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Lung infections, also including more severe illness with bronchiolitis and bronchitis, and worse outcome, as well as increased risk of developing tuberculosis if exposed to a carrier. In the United States, it is estimated that secondhand smoke has been associated with between 150,000 and 300,000 lower respiratory tract infections in infants and children under 18 months of age, resulting in between 7,500 and 15,000 hospitalizations each year.
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Passive smoking
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Effects
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Impaired respiratory function and slowed lung growth Allergies Maternal passive smoking increases the risk of non-syndromic orofacial clefts by 50% among their children.
Learning difficulties, developmental delays, executive function problems, and neurobehavioral effects. Animal models suggest a role for nicotine and carbon monoxide in neurocognitive problems.
An increase in tooth decay (as well as related salivary biomarkers) has been associated with passive smoking in children.
Increased risk of middle ear infections.
Invasive meningococcal disease.
Anesthesia complications and some negative surgical outcomes.
Sleep disordered breathing: Most studies have found a significant association between passive smoking and sleep disordered breathing in children, but further studies are needed to determine whether this association is causal.
Adverse effects on the cardiovascular system of children.
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Passive smoking
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Evidence
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Epidemiological studies show that non-smokers exposed to secondhand smoke are at risk for many of the health problems associated with direct smoking.
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Passive smoking
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Evidence
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In 1992, a review estimated that secondhand smoke exposure was responsible for 35,000 to 40,000 deaths per year in the United States in the early 1980s. The absolute risk increase of heart disease due to ETS was 2.2%, while the attributable risk percent was 23%. A 1997 meta-analysis found that secondhand smoke exposure increased the risk of heart disease by a quarter, and two 1999 meta-analyses reached similar conclusions.Evidence shows that inhaled sidestream smoke, the main component of secondhand smoke, is about four times more toxic than mainstream smoke. This fact has been known to the tobacco industry since the 1980s, though it kept its findings secret. Some scientists believe that the risk of passive smoking, in particular the risk of developing coronary heart diseases, may have been substantially underestimated.In 1997, a meta-analysis on the relationship between secondhand smoke exposure and lung cancer concluded that such exposure caused lung cancer. The increase in risk was estimated to be 24% among non-smokers who lived with a smoker. In 2000, Copas and Shi reported that there was clear evidence of publication bias in the studies included in this meta-analysis. They further concluded that after correcting for publication bias, and assuming that 40% of all studies are unpublished, this increased risk decreased from 24% to 15%. This conclusion has been challenged on the basis that the assumption that 40% of all studies are unpublished was "extreme".: 1269 In 2006, Takagi et al. reanalyzed the data from this meta-analysis to account for publication bias and estimated that the relative risk of lung cancer among those exposed to secondhand smoke was 1.19, slightly lower than the original estimate. A 2000 meta-analysis found a relative risk of 1.48 for lung cancer among men exposed to secondhand smoke, and a relative risk of 1.16 among those exposed to it at work. Another meta-analysis confirmed the finding of an increased risk of lung cancer among women with spousal exposure to secondhand smoke the following year. It found a relative risk of lung cancer of 1.29 for women exposed to secondhand smoke from their spouses. A 2014 meta-analysis noted that "the association between exposure to secondhand smoke and lung cancer risk is well established."A minority of epidemiologists have found it hard to understand how secondhand smoke, which is more diluted than actively inhaled smoke, could have an effect that is such a large fraction of the added risk of coronary heart disease among active smokers. One proposed explanation is that secondhand smoke is not simply a diluted version of "mainstream" smoke, but has a different composition with more toxic substances per gram of total particulate matter. Passive smoking appears to be capable of precipitating the acute manifestations of cardio-vascular diseases (atherothrombosis) and may also have a negative impact on the outcome of patients who have acute coronary syndromes.In 2004, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) reviewed all significant published evidence related to tobacco smoking and cancer. It concluded: These meta-analyses show that there is a statistically significant and consistent association between lung cancer risk in spouses of smokers and exposure to second-hand tobacco smoke from the spouse who smokes. The excess risk is of the order of 20% for women and 30% for men and remains after controlling for some potential sources of bias and confounding.
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Passive smoking
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Evidence
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Subsequent meta-analyses have confirmed these findings.The National Asthma Council of Australia cites studies showing that secondhand smoke is probably the most important indoor pollutant, especially around young children: Smoking by either parent, particularly by the mother, increases the risk of asthma in children.
The outlook for early childhood asthma is less favourable in smoking households.
Children with asthma who are exposed to smoking in the home generally have more severe disease.
Many adults with asthma identify ETS as a trigger for their symptoms.
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Passive smoking
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Evidence
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Doctor-diagnosed asthma is more common among non-smoking adults exposed to ETS than those not exposed. Among people with asthma, higher ETS exposure is associated with a greater risk of severe attacks.In France, exposure to secondhand smoke has been estimated to cause between 3,000 and 5,000 premature deaths per year, with the larger figure cited by Prime Minister Dominique de Villepin during his announcement of a nationwide smoke-free law: "That makes more than 13 deaths a day. It is an unacceptable reality in our country in terms of public health."There is good observational evidence that smoke-free legislation reduces the number of hospital admissions for heart disease.
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Passive smoking
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Evidence
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Exposure and risk levels The International Agency for Research on Cancer of the World Health Organization concluded in 2004 that there was sufficient evidence that secondhand smoke caused cancer in humans. Those who work in environments where smoke is not regulated are at higher risk. Workers particularly at risk of exposure include those in installation repair and maintenance, construction and extraction, and transportation.Much research has come from studies of nonsmokers who are married to a smoker. The US Surgeon General, in his 2006 report, estimated that living or working in a place where smoking is permitted increases the non-smokers' risk of developing heart disease by 25–30% and lung cancer by 20–30%.Similarly, children who are exposed to environmental tobacco smoke are shown to experience a range of adverse effects and a higher risk of becoming smokers later in life. The WHO has identified reduction of exposure to environmental tobacco smoke as key element for actions to encourage healthy child development.The US Centers for Disease Control and Prevention monitors the extent of and trends in exposure to environmental tobacco smoke by measuring serum cotinine in national health surveys. The prevalence of secondhand smoke exposure among U.S. nonsmokers declined from 87.5% in 1988 to 25.2% in 2014. However, nearly half of blacks and the poor were exposed in 2014.
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Passive smoking
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Evidence
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Interventions to reduce environmental tobacco smoke A systematic review compared smoking control programmes and their effects on smoke exposure in children. The review distinguishes between community-based, ill-child and healthy-child settings and the most common types of interventions were counselling or brief advice during clinical visits. The review did not find superior outcomes for any intervention, and the authors caution that evidence from adult settings may not generalise well to children.
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Passive smoking
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Evidence
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Biomarkers Environmental tobacco smoke can be evaluated either by directly measuring tobacco smoke pollutants found in the air or by using biomarkers, an indirect measure of exposure. Carbon monoxide monitored through breath, nicotine, cotinine, thiocyanates, and proteins are the most specific biological markers of tobacco smoke exposure. Biochemical tests are a much more reliable biomarker of secondhand smoke exposure than surveys. Certain groups of people are reluctant to disclose their smoking status and exposure to tobacco smoke, especially pregnant women and parents of young children. This is due to their smoking being socially unacceptable. Also, it may be difficult for individuals to recall their exposure to tobacco smoke.A 2007 study in the Addictive Behaviors journal found a positive correlation between secondhand tobacco smoke exposure and concentrations of nicotine and/or biomarkers of nicotine in the body. Significant biological levels of nicotine from secondhand smoke exposure were equivalent to nicotine levels from active smoking and levels that are associated with behaviour changes due to nicotine consumption.
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Passive smoking
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Evidence
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Cotinine Cotinine, the metabolite of nicotine, is a biomarker of secondhand smoke exposure. Typically, cotinine is measured in the blood, saliva, and urine. Hair analysis has recently become a new, noninvasive measurement technique. Cotinine accumulates in hair during hair growth, which results in a measure of long-term, cumulative exposure to tobacco smoke. Urinary cotinine levels have been a reliable biomarker of tobacco exposure and have been used as a reference in many epidemiological studies. However, cotinine levels found in the urine reflect exposure only over the preceding 48 hours. Cotinine levels of the skin, such as the hair and nails, reflect tobacco exposure over the previous three months and are a more reliable biomarker.
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Passive smoking
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Evidence
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Carbon monoxide (CO) Carbon monoxide monitored via breath is also a reliable biomarker of secondhand smoke exposure as well as tobacco use. With high sensitivity and specificity, it not only provides an accurate measure, but the test is also non-invasive, highly reproducible, and low in cost. Breath CO monitoring measures the concentration of CO in an exhalation in parts per million, and this can be directly correlated to the blood CO concentration (carboxyhemoglobin). Breath CO monitors can also be used by emergency services to identify patients who are suspected of having CO poisoning.
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Passive smoking
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Pathophysiology
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A 2004 study by the International Agency for Research on Cancer of the World Health Organization concluded that non-smokers are exposed to the same carcinogens as active smokers. Sidestream smoke contains more than 4,000 chemicals, including 69 known carcinogens. Of special concern are polynuclear aromatic hydrocarbons, tobacco-specific N-nitrosamines, and aromatic amines, such as 4-aminobiphenyl, all known to be highly carcinogenic. Mainstream smoke, sidestream smoke, and secondhand smoke contain largely the same components, however the concentration varies depending on type of smoke. Several well-established carcinogens have been shown by the tobacco companies' own research to be present at higher concentrations in sidestream smoke than in mainstream smoke.Secondhand smoke has been shown to produce more particulate-matter (PM) pollution than an idling low-emission diesel engine. In an experiment conducted by the Italian National Cancer Institute, three cigarettes were left smoldering, one after the other, in a 60 m3 garage with a limited air exchange. The cigarettes produced PM pollution exceeding outdoor limits, as well as PM concentrations up to 10-fold that of the idling engine.Secondhand tobacco smoke exposure has immediate and substantial effects on blood and blood vessels in a way that increases the risk of a heart attack, particularly in people already at risk. Exposure to tobacco smoke for 30 minutes significantly reduces coronary flow velocity reserve in healthy nonsmokers. Secondhand smoke is also associated with impaired vasodilation among adult nonsmokers. Secondhand smoke exposure also affects platelet function, vascular endothelium, and myocardial exercise tolerance at levels commonly found in the workplace.Pulmonary emphysema can be induced in rats through acute exposure to sidestream tobacco smoke (30 cigarettes per day) over a period of 45 days. Degranulation of mast cells contributing to lung damage has also been observed.The term "third-hand smoke" was recently coined to identify the residual tobacco smoke contamination that remains after the cigarette is extinguished and secondhand smoke has cleared from the air. Preliminary research suggests that by-products of third-hand smoke may pose a health risk, though the magnitude of risk, if any, remains unknown. In October 2011, it was reported that Christus St. Frances Cabrini Hospital in Alexandria, Louisiana, would seek to eliminate third-hand smoke beginning in July 2012, and that employees whose clothing smelled of smoke would not be allowed to work. This prohibition was enacted because third-hand smoke poses a special danger for the developing brains of infants and small children.In 2008, there were more than 161,000 deaths attributed to lung cancer in the United States. Of these deaths, an estimated 10% to 15% were caused by factors other than first-hand smoking; equivalent to 16,000 to 24,000 deaths annually. Slightly more than half of the lung cancer deaths caused by factors other than first-hand smoking were found in nonsmokers. Lung cancer in non-smokers may well be considered one of the most common cancer mortalities in the United States. Clinical epidemiology of lung cancer has linked the primary factors closely tied to lung cancer in non-smokers as exposure to secondhand tobacco smoke, carcinogens including radon, and other indoor air pollutants.
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Passive smoking
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Opinion of public health authorities
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There is widespread scientific consensus that exposure to secondhand smoke is harmful. The link between passive smoking and health risks is accepted by every major medical and scientific organisation, including: World Health Organization U.S. National Institutes of Health Centers for Disease Control United States Surgeon General U.S. National Cancer Institute United States Environmental Protection Agency California Environmental Protection Agency American Heart Association, American Lung Association, and American Cancer Society American Medical Association American Academy of Pediatrics Australian National Health and Medical Research Council United Kingdom Scientific Committee on Tobacco and Health
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Passive smoking
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Public opinion
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Recent major surveys conducted by the U.S. National Cancer Institute and Centers for Disease Control have found widespread public awareness that secondhand smoke is harmful. In both 1992 and 2000 surveys, more than 80% of respondents agreed with the statement that secondhand smoke was harmful. A 2001 study found that 95% of adults agreed that secondhand smoke was harmful to children, and 96% considered tobacco-industry claims that secondhand smoke was not harmful to be untruthful.A 2007 Gallup poll found that 56% of respondents felt that secondhand smoke was "very harmful", a number that has held relatively steady since 1997. Another 29% believe that secondhand smoke is "somewhat harmful"; 10% answered "not too harmful", while 5% said "not at all harmful".
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Passive smoking
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Controversy over harm
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As part of its attempt to prevent or delay tighter regulation of smoking, the tobacco industry funded a number of scientific studies and, where the results cast doubt on the risks associated with secondhand smoke, sought wide publicity for those results. The industry also funded libertarian and conservative think tanks, such as the Cato Institute in the United States and the Institute of Public Affairs in Australia which criticised both scientific research on passive smoking and policy proposals to restrict smoking. New Scientist and the European Journal of Public Health have identified these industry-wide coordinated activities as one of the earliest expressions of corporate denialism. Further, they state that the disinformation spread by the tobacco industry has created a tobacco denialism movement, sharing many characteristics of other forms of denialism, such as HIV-AIDS denialism.
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Passive smoking
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Controversy over harm
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Industry-funded studies and critiques Enstrom and Kabat A 2003 study by James Enstrom and Geoffrey Kabat, published in the British Medical Journal, argued that the harms of passive smoking had been overstated. Their analysis reported no statistically significant relationship between passive smoking and lung cancer, coronary heart disease (CHD), or chronic obstructive pulmonary disease, though the accompanying editorial noted that "they may overemphasise the negative nature of their findings." This paper was widely promoted by the tobacco industry as evidence that the harms of passive smoking were unproven. The American Cancer Society (ACS), whose database Enstrom and Kabat used to compile their data, criticized the paper as "neither reliable nor independent", stating that scientists at the ACS had repeatedly pointed out serious flaws in Enstrom and Kabat's methodology prior to publication. Notably, the study had failed to identify a comparison group of "unexposed" persons.Enstrom's ties to the tobacco industry also drew scrutiny; in a 1997 letter to Philip Morris, Enstrom requested a "substantial research commitment... in order for me to effectively compete against the large mountain of epidemiologic data and opinions that already exist regarding the health effects of ETS and active smoking." In a US racketeering lawsuit against tobacco companies, the Enstrom and Kabat paper was cited by the US District Court as "a prime example of how nine tobacco companies engaged in criminal racketeering and fraud to hide the dangers of tobacco smoke." The Court found that the study had been funded and managed by the Center for Indoor Air Research, a tobacco industry front group tasked with "offsetting" damaging studies on passive smoking, as well as by Philip Morris who stated that Enstrom's work was "clearly litigation-oriented". A 2005 paper in Tobacco Control argued that the disclosure section in the Enstrom and Kabat BMJ paper, although it met the journal's requirements, "does not reveal the full extent of the relationship the authors had with the tobacco industry."In 2006, Enstrom and Kabat published a meta-analysis of studies regarding passive smoking and coronary heart disease in which they reported a very weak association between passive smoking and heart disease mortality. They concluded that exposure to secondhand smoke increased the risk of death from CHD by only 5%, although this analysis has been criticized for including two previous industry-funded studies that suffered from widespread exposure misclassification.
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Passive smoking
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Controversy over harm
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Gori Gio Batta Gori, a tobacco industry spokesman and consultant and an expert on risk utility and scientific research, wrote in the libertarian Cato Institute's magazine Regulation that "...of the 75 published studies of ETS and lung cancer, some 70% did not report statistically significant differences of risk and are moot. Roughly 17% claim an increased risk and 13% imply a reduction of risk." Milloy Steven Milloy, the "junk science" commentator for Fox News and a former Philip Morris consultant, claimed that "of the 19 studies" on passive smoking "only 8— slightly more than 42%— reported statistically significant increases in heart disease incidence."Another component of criticism cited by Milloy focused on relative risk and epidemiological practices in studies of passive smoking. Milloy, who has a master's degree from the Johns Hopkins School of Hygiene and Public Health, argued that studies yielding relative risks of less than 2 were meaningless junk science. This approach to epidemiological analysis was criticized in the American Journal of Public Health: A major component of the industry attack was the mounting of a campaign to establish a "bar" for "sound science" that could not be fully met by most individual investigations, leaving studies that did not meet the criteria to be dismissed as "junk science." The tobacco industry and affiliated scientists also put forward a set of "Good Epidemiology Practices" which would have the practical effect of obscuring the link between secondhand smoke and lung cancer; the privately stated goal of these standards was to "impede adverse legislation". However, this effort was largely abandoned when it became clear that no independent epidemiological organization would agree to the standards proposed by Philip Morris et al.
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Passive smoking
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Controversy over harm
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Levois and Layard In 1995, Levois and Layard, both tobacco industry consultants, published two analyses in the journal Regulatory Toxicology and Pharmacology regarding the association between spousal exposure to secondhand smoke and heart disease. Both of these papers reported no association between secondhand smoke and heart disease. These analyses have been criticized for failing to distinguish between current and former smokers, despite the fact that former smokers, unlike current ones, are not at a significantly increased risk of heart disease.
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Passive smoking
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Controversy over harm
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World Health Organization controversy A 1998 study by the International Agency for Research on Cancer (IARC) on environmental tobacco smoke (ETS) found "weak evidence of a dose–response relationship between risk of lung cancer and exposure to spousal and workplace ETS."In March 1998, before the study was published, reports appeared in the media alleging that the IARC and the World Health Organization (WHO) were suppressing information. The reports, appearing in the British Sunday Telegraph and The Economist, among other sources, alleged that the WHO withheld from publication of its own report that supposedly failed to prove an association between passive smoking and a number of other diseases (lung cancer in particular).
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Passive smoking
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Controversy over harm
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In response, the WHO issued a press release stating that the results of the study had been "completely misrepresented" in the popular press and were in fact very much in line with similar studies demonstrating the harms of passive smoking. The study was published in the Journal of the National Cancer Institute in October of the same year, and concluded the authors found "no association between childhood exposure to ETS and lung cancer risk" but "did find weak evidence of a dose–response relationship between risk of lung cancer and exposure to spousal and workplace ETS." An accompanying editorial summarized: When all the evidence, including the important new data reported in this issue of the Journal, is assessed, the inescapable scientific conclusion is that ETS is a low-level lung carcinogen.
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Passive smoking
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Controversy over harm
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With the release of formerly classified tobacco industry documents through the Tobacco Master Settlement Agreement, it was found (by Elisa Ong and Stanton Glantz) that the controversy over the WHO's alleged suppression of data had been engineered by Philip Morris, British American Tobacco, and other tobacco companies in an effort to discredit scientific findings which would harm their business interests. A WHO inquiry, conducted after the release of the tobacco-industry documents, found that this controversy was generated by the tobacco industry as part of its larger campaign to cut the WHO's budget, distort the results of scientific studies on passive smoking, and discredit the WHO as an institution. This campaign was carried out using a network of ostensibly independent front organizations and international and scientific experts with hidden financial ties to the industry.
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Passive smoking
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Controversy over harm
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EPA lawsuit In 1993, the United States Environmental Protection Agency (EPA) issued a report estimating that 3,000 lung cancer related deaths in the United States were caused by passive smoking annually.Philip Morris, R.J. Reynolds Tobacco Company, and groups representing growers, distributors and marketers of tobacco took legal action, claiming that the EPA had manipulated this study and ignored accepted scientific and statistical practices.
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Passive smoking
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Controversy over harm
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The United States District Court for the Middle District of North Carolina ruled in favor of the tobacco industry in 1998, finding that the EPA had failed to follow proper scientific and epidemiologic practices and had "cherry picked" evidence to support conclusions which they had committed to in advance. The court stated in part, "EPA publicly committed to a conclusion before research had begun…adjusted established procedure and scientific norms to validate the Agency's public conclusion... In conducting the ETS Risk Assessment, disregarded information and made findings on selective information; did not disseminate significant epidemiologic information; deviated from its Risk Assessment Guidelines; failed to disclose important findings and reasoning…" In 2002, the EPA successfully appealed this decision to the United States Court of Appeals for the Fourth Circuit. The EPA's appeal was upheld on the preliminary grounds that their report had no regulatory weight, and the earlier finding was vacated.In 1998, the U.S. Department of Health and Human Services, through the publication by its National Toxicology Program of the 9th Report on Carcinogens, listed environmental tobacco smoke among the known carcinogens, observing of the EPA assessment that "The individual studies were carefully summarized and evaluated." Tobacco-industry funding of research The tobacco industry's role in funding scientific research on secondhand smoke has been controversial. A review of published studies found that tobacco-industry affiliation was strongly correlated with findings exonerating secondhand smoke; researchers affiliated with the tobacco industry were 88 times more likely than independent researchers to conclude that secondhand smoke was not harmful. In a specific example which came to light with the release of tobacco-industry documents, Philip Morris executives successfully encouraged an author to revise his industry-funded review article to downplay the role of secondhand smoke in sudden infant death syndrome. The 2006 U.S. Surgeon General's report criticized the tobacco industry's role in the scientific debate: The industry has funded or carried out research that has been judged to be biased, supported scientists to generate letters to editors that criticized research publications, attempted to undermine the findings of key studies, assisted in establishing a scientific society with a journal, and attempted to sustain controversy even as the scientific community reached consensus.
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Passive smoking
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Controversy over harm
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This strategy was outlined at an international meeting of tobacco companies in 1988, at which Philip Morris proposed to set up a team of scientists, organized by company lawyers, to "carry out work on ETS to keep the controversy alive." All scientific research was subject to oversight and "filtering" by tobacco-industry lawyers: Philip Morris then expect the group of scientists to operate within the confines of decisions taken by PM scientists to determine the general direction of research, which apparently would then be 'filtered' by lawyers to eliminate areas of sensitivity.
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Passive smoking
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Controversy over harm
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Philip Morris reported that it was putting "...vast amounts of funding into these projects... in attempting to coordinate and pay so many scientists on an international basis to keep the ETS controversy alive." Tobacco industry response Measures to tackle secondhand smoke pose a serious economic threat to the tobacco industry, having broadened the definition of smoking beyond a personal habit to something with a social impact. In a confidential 1978 report, the tobacco industry described increasing public concerns about secondhand smoke as "the most dangerous development to the viability of the tobacco industry that has yet occurred." In United States of America v. Philip Morris et al., the District Court for the District of Columbia found that the tobacco industry "... recognized from the mid-1970s forward that the health effects of passive smoking posed a profound threat to industry viability and cigarette profits," and that the industry responded with "efforts to undermine and discredit the scientific consensus that ETS causes disease."Accordingly, the tobacco industry have developed several strategies to minimise the impact on their business: The industry has sought to position the secondhand smoke debate as essentially concerned with civil liberties and smokers' rights rather than with health, by funding groups such as FOREST.
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Passive smoking
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Controversy over harm
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Funding bias in research; in all reviews of the effects of secondhand smoke on health published between 1980 and 1995, the only factor associated with concluding that secondhand smoke is not harmful was whether an author was affiliated with the tobacco industry. However, not all studies that failed to find evidence of harm were by industry-affiliated authors.
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Passive smoking
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Controversy over harm
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Delaying and discrediting legitimate research (see for an example of how the industry attempted to discredit Takeshi Hirayama's landmark study, and for an example of how it attempted to delay and discredit a major Australian report on passive smoking) Promoting "good epidemiology" and attacking so-called junk science (a term popularised by industry lobbyist Steven Milloy): attacking the methodology behind research showing health risks as flawed and attempting to promote sound science. Ong & Glantz (2001) cite an internal Phillip Morris memo giving evidence of this as company policy.
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Passive smoking
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Controversy over harm
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Creation of outlets for favourable research. In 1989, the tobacco industry established the International Society of the Built Environment, which published the peer-reviewed journal Indoor and Built Environment. This journal did not require conflict-of-interest disclosures from its authors. With documents made available through the Master Settlement, it was found that the executive board of the society and the editorial board of the journal were dominated by paid tobacco-industry consultants. The journal published a large amount of material on passive smoking, much of which was "industry-positive".Citing the tobacco industry's production of biased research and efforts to undermine scientific findings, the 2006 U.S. Surgeon General's report concluded that the industry had "attempted to sustain controversy even as the scientific community reached consensus... industry documents indicate that the tobacco industry has engaged in widespread activities... that have gone beyond the bounds of accepted scientific practice." The U.S. District Court, in U.S.A. v. Philip Morris et al., found that "...despite their internal acknowledgment of the hazards of secondhand smoke, Defendants have fraudulently denied that ETS causes disease." Position of major tobacco companies The positions of major tobacco companies on the issue of secondhand smoke is somewhat varied. In general, tobacco companies have continued to focus on questioning the methodology of studies showing that secondhand smoke is harmful. Some (such as British American Tobacco and Philip Morris) acknowledge the medical consensus that secondhand smoke carries health risks, while others continue to assert that the evidence is inconclusive. Several tobacco companies advocate the creation of smoke-free areas within public buildings as an alternative to comprehensive smoke-free laws.
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Passive smoking
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Controversy over harm
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US racketeering lawsuit against tobacco companies On September 22, 1999, the U.S. Department of Justice filed a racketeering lawsuit against Philip Morris and other major cigarette manufacturers. Almost 7 years later, on August 17, 2006, U.S. District Court Judge Gladys Kessler found that the Government had proven its case and that the tobacco company defendants had violated the Racketeer Influenced Corrupt Organizations Act (RICO). In particular, Judge Kessler found that PM and other tobacco companies had: conspired to minimize, distort and confuse the public about the health hazards of smoking; publicly denied, while internally acknowledging, that secondhand tobacco smoke is harmful to nonsmokers, and destroyed documents relevant to litigation.The ruling found that tobacco companies undertook joint efforts to undermine and discredit the scientific consensus that secondhand smoke causes disease, notably by controlling research findings via paid consultants. The ruling also concluded that tobacco companies were fraudulently continuing to deny the health effects of ETS exposure.On May 22, 2009, a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit unanimously upheld the lower court's 2006 ruling.
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Passive smoking
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Smoke-free laws
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As a consequence of the health risks associated with secondhand smoke, many national and local governments have outlawed smoking in indoor public places, including restaurants, cafés, and nightclubs, as well as some outdoor open areas. Ireland was the first country in the world to institute a comprehensive national ban on smoking in all indoor workplaces on 29 March 2004. Since then, many others have followed suit. The countries which have ratified the WHO Framework Convention on Tobacco Control (FCTC) have a legal obligation to implement effective legislation "for protection from exposure to tobacco smoke in indoor workplaces, public transport, indoor public places and, as appropriate, other public places." (Article 8 of the FCTC) The parties to the FCTC have further adopted Guidelines on the Protection from Exposure to secondhand Smoke which state that "effective measures to provide protection from exposure to tobacco smoke ... require the total elimination of smoking and tobacco smoke in a particular space or environment in order to create a 100% smoke-free environment."Opinion polls have shown considerable support for smoke-free laws. In June 2007, a survey of 15 countries found 80% approval for such laws. A survey in France, reputedly a nation of smokers, showed 70% support.
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Passive smoking
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Smoke-free laws
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Effects Smoking bans by governments result in decreased harm from secondhand smoke, including less admissions for acute coronary syndrome. In the first 18 months after the town of Pueblo, Colorado, enacted a smoke-free law in 2003, hospital admissions for heart attacks dropped 27%. Admissions in neighbouring towns without smoke-free laws showed no change, and the decline in heart attacks in Pueblo was attributed to the resulting reduction in secondhand smoke exposure. A 2004 smoking ban instituted in Massachusetts workplaces decreased workers' secondhand smoke exposure from 8% of workers in 2003 to 5.4% of workers in 2010. A 2016 review also found that bans and policy changes in specific locations such as hospitals or universities can lead to reduced smoking rates. In prison settings bans might lead to reduced mortality and to lower exposure to secondhand smoke.In 2001, a systematic review for the Guide to Community Preventive Services acknowledged strong evidence of the effectiveness of smoke-free policies and restrictions in reducing expose to secondhand smoke. A follow-up to this review, identified the evidence on which the effectiveness of smoking bans reduced the prevalence of tobacco use. Articles published until 2005, were examined to further support this evidence. The examined studies provided sufficient evidence that smoke-free policies reduce tobacco use among workers when implemented in worksites or by communities.While a number of studies funded by the tobacco industry have claimed a negative economic impact from smoke-free laws, no independently funded research has shown any such impact. A 2003 review reported that independently funded, methodologically sound research consistently found either no economic impact or a positive impact from smoke-free laws.Air nicotine levels were measured in Guatemalan bars and restaurants before and after an implemented smoke-free law in 2009. Nicotine concentrations significantly decreased in both the bars and restaurants measured. Also, the employees' support for a smoke-free workplace substantially increased in the post-implementation survey compared to pre-implementation survey.
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Passive smoking
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Smoke-free laws
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Public opinion Recent surveys taken by the Society for Research on Nicotine and Tobacco demonstrate supportive attitudes of the public, towards smoke-free policies in outdoor areas. A vast majority of the public supports restricting smoking in various outdoor settings. The respondents' support for the policies were for varying reasons such as litter control, establishing positive smoke-free role models for youth, reducing youth opportunities to smoke, and avoiding exposure to secondhand smoke.
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Passive smoking
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Smoke-free laws
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Alternative forms Alternatives to smoke-free laws have also been proposed as a means of harm reduction, particularly in bars and restaurants. For example, critics of smoke-free laws cite studies suggesting ventilation as a means of reducing tobacco smoke pollutants and improving air quality. Ventilation has also been heavily promoted by the tobacco industry as an alternative to outright bans, via a network of ostensibly independent experts with often undisclosed ties to the industry. However, not all critics have connections to the industry.
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Passive smoking
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Smoke-free laws
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The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) officially concluded in 2005 that while completely isolated smoking rooms do eliminate the risk to nearby non-smoking areas, smoking bans are the only means of eliminating health risks associated with indoor exposure. They further concluded that no system of dilution or cleaning was effective at eliminating risk. The U.S. Surgeon General and the European Commission Joint Research Centre have reached similar conclusions. The implementation guidelines for the WHO Framework Convention on Tobacco Control states that engineering approaches, such as ventilation, are ineffective and do not protect against secondhand smoke exposure. However, this does not necessarily mean that such measures are useless in reducing harm, only that they fall short of the goal of reducing exposure completely to zero.
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Passive smoking
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Smoke-free laws
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Others have suggested a system of tradable smoking pollution permits, similar to the cap-and-trade pollution permits systems used by the United States Environmental Protection Agency in recent decades to curb other types of pollution. This would guarantee that a portion of bars/restaurants in a jurisdiction will be smoke-free, while leaving the decision to the market.
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Passive smoking
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In animals
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Multiple studies have been conducted to determine the carcinogenicity of environmental tobacco smoke to animals. These studies typically fall under the categories of simulated environmental tobacco smoke, administering condensates of sidestream smoke, or observational studies of cancer among pets.
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Passive smoking
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In animals
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To simulate environmental tobacco smoke, scientists expose animals to sidestream smoke, that which emanates from the cigarette's burning cone and through its paper, or a combination of mainstream and sidestream smoke. The IARC monographs conclude that mice with prolonged exposure to simulated environmental tobacco smoke, that is six hours a day, five days a week, for five months with a subsequent four-month interval before dissection, will have significantly higher incidence and multiplicity of lung tumors than with control groups.
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Passive smoking
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In animals
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The IARC monographs concluded that sidestream smoke condensates had a significantly higher carcinogenic effect on mice than did mainstream smoke condensates.
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Passive smoking
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In animals
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Observational studies Secondhand smoke is popularly recognised as a risk factor for cancer in pets. A study conducted by the Tufts University School of Veterinary Medicine and the University of Massachusetts Amherst linked the occurrence of feline oral cancer to exposure to environmental tobacco smoke through an overexpression of the p53 gene. Another study conducted at the same universities concluded that cats living with a smoker were more likely to get feline lymphoma; the risk increased with the duration of exposure to secondhand smoke and the number of smokers in the household. A study by Colorado State University researchers, looking at cases of canine lung cancer, was generally inconclusive, though the authors reported a weak relation for lung cancer in dogs exposed to environmental tobacco smoke. The number of smokers within the home, the number of packs smoked in the home per day, and the amount of time that the dog spent within the home had no effect on the dog's risk for lung cancer.
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Heun's method
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Heun's method
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In mathematics and computational science, Heun's method may refer to the improved or modified Euler's method (that is, the explicit trapezoidal rule), or a similar two-stage Runge–Kutta method. It is named after Karl Heun and is a numerical procedure for solving ordinary differential equations (ODEs) with a given initial value. Both variants can be seen as extensions of the Euler method into two-stage second-order Runge–Kutta methods.
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Heun's method
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Heun's method
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The procedure for calculating the numerical solution to the initial value problem: y′(t)=f(t,y(t)),y(t0)=y0, by way of Heun's method, is to first calculate the intermediate value y~i+1 and then the final approximation yi+1 at the next integration point.
y~i+1=yi+hf(ti,yi) yi+1=yi+h2[f(ti,yi)+f(ti+1,y~i+1)], where h is the step size and ti+1=ti+h
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Heun's method
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Description
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Euler's method is used as the foundation for Heun's method. Euler's method uses the line tangent to the function at the beginning of the interval as an estimate of the slope of the function over the interval, assuming that if the step size is small, the error will be small. However, even when extremely small step sizes are used, over a large number of steps the error starts to accumulate and the estimate diverges from the actual functional value.
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Heun's method
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Description
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Where the solution curve is concave up, its tangent line will underestimate the vertical coordinate of the next point and vice versa for a concave down solution. The ideal prediction line would hit the curve at its next predicted point. In reality, there is no way to know whether the solution is concave-up or concave-down, and hence if the next predicted point will overestimate or underestimate its vertical value. The concavity of the curve cannot be guaranteed to remain consistent either and the prediction may overestimate and underestimate at different points in the domain of the solution.
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Heun's method
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Description
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Heun's Method addresses this problem by considering the interval spanned by the tangent line segment as a whole. Taking a concave-up example, the left tangent prediction line underestimates the slope of the curve for the entire width of the interval from the current point to the next predicted point. If the tangent line at the right end point is considered (which can be estimated using Euler's Method), it has the opposite problem.
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Heun's method
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Description
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The points along the tangent line of the left end point have vertical coordinates which all underestimate those that lie on the solution curve, including the right end point of the interval under consideration. The solution is to make the slope greater by some amount. Heun's Method considers the tangent lines to the solution curve at both ends of the interval, one which overestimates, and one which underestimates the ideal vertical coordinates. A prediction line must be constructed based on the right end point tangent's slope alone, approximated using Euler's Method. If this slope is passed through the left end point of the interval, the result is evidently too steep to be used as an ideal prediction line and overestimates the ideal point. Therefore, the ideal point lies approximately halfway between the erroneous overestimation and underestimation, the average of the two slopes.
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Heun's method
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Description
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Euler's Method is used to roughly estimate the coordinates of the next point in the solution, and with this knowledge, the original estimate is re-predicted or corrected. Assuming that the quantity f(x,y) on the right hand side of the equation can be thought of as the slope of the solution sought at any point (x,y) , this can be combined with the Euler estimate of the next point to give the slope of the tangent line at the right end-point. Next the average of both slopes is used to find the corrected coordinates of the right end interval.
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Heun's method
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Derivation
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Slope left =f(xi,yi) Slope right =f(xi+h,yi+hf(xi,yi)) Slope ideal Slope left Slope right ) Using the principle that the slope of a line equates to the rise/run, the coordinates at the end of the interval can be found using the following formula: Slope ideal =Δyh Slope ideal ) xi+1=xi+h , yi+1=yi+Δy Slope ideal Slope left Slope right ) yi+1=yi+h2(f(xi,yi)+f(xi+h,yi+hf(xi,yi))) The accuracy of the Euler method improves only linearly with the step size is decreased, whereas the Heun Method improves accuracy quadratically . The scheme can be compared with the implicit trapezoidal method, but with f(ti+1,yi+1) replaced by f(ti+1,y~i+1) in order to make it explicit. y~i+1 is the result of one step of Euler's method on the same initial value problem. So, Heun's method is a predictor-corrector method with forward Euler's method as predictor and trapezoidal method as corrector.
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Heun's method
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Runge–Kutta method
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The improved Euler's method is a two-stage Runge–Kutta method, and can be written using the Butcher tableau (after John C. Butcher): The other method referred to as Heun's method (also known as Ralston's method) has the Butcher tableau: This method minimizes the truncation error.
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Emphasis (typography)
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Emphasis (typography)
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In typography, emphasis is the strengthening of words in a text with a font in a different style from the rest of the text, to highlight them. It is the equivalent of prosody stress in speech.
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Emphasis (typography)
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Methods and use
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The most common methods in Western typography fall under the general technique of emphasis through a change or modification of font: italics, boldface and SMALL CAPS.
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Emphasis (typography)
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Methods and use
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A means of emphasis that does not have much effect on blackness is the use of italics, where the text is written in a script style, or oblique, where the vertical orientation of each letter of the text is slanted to the left or right. With one or the other of these techniques (usually only one is available for any typeface), words can be highlighted without making them stand out much from the rest of the text (inconspicuous stressing). This is used for marking passages that have a different context, such as book titles, words from foreign languages, or internal dialogue.
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Emphasis (typography)
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Methods and use
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By contrast, a bold font weight makes letters of a text thicker than the surrounding text. Bold strongly stands out from regular text, and is often used to highlight keywords important to the text's content. For example, printed dictionaries often use boldface for their keywords, and the names of entries can conventionally be marked in bold.Small capitals (THUS) are also used for emphasis, especially for the first line of a section, sometimes accompanied by or instead of a drop cap, or for personal names as in bibliographies.
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Emphasis (typography)
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If the text body is typeset in a serif typeface, it is also possible to highlight words by setting them in a sans serif face. This practice is often considered archaic in Latin script, and on computers is complicated since fonts are no longer issued by foundries with a standard baseline, so switching font may distort line spacing. It is still possible using some font super families, which come with matching serif and sans-serif variants, though these are not generally supplied with modern computers as system fonts. In Japanese typography, due to the reduced legibility of heavier Minchō type, the practice remains common.
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Emphasis (typography)
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Methods and use
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Of these methods, italics, small capitals and capitalization are oldest, with bold type and sans-serif typefaces not arriving until the nineteenth century.
Capitalization The house styles of many publishers in the United States use all caps text for: chapter and section headings; newspaper headlines; publication titles; warning messages; and words of important meaning.Capitalization is used much less frequently by British publishers, and usually only for book titles.
All-uppercase letters are a common substitute form of emphasis where the medium lacks support for boldface, such as old typewriters, plain-text email, SMS and other text-messaging systems.
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Emphasis (typography)
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Socially, the use of all-caps text in Roman languages has become an indicator of shouting when quoting speech. It was also often used in the past by American lawyers to flag important points in a legal text. Coinciding with the era of typewriter use, the practice became unnecessary with the advent of computerized text formatting, although it is still found on occasion in documents created by older lawyers.
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Emphasis (typography)
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Letter-spacing Another means of emphasis is to increase the spacing between the letters, rather than making them darker, but still achieving a distinction in blackness. This results in an effect reverse to boldface: the emphasized text becomes lighter than its environment. This is often used in blackletter typesetting and typewriter manuscripts, but by no means restricted to those situations.This letter-spacing is referred to as sperren in German, which could be translated as "spacing out": in typesetting with letters of lead, the spacing would be achieved by inserting additional non-printing slices of metal between the types, usually about an eighth of an em wide. On typewriters a full space was used between the letters of an emphasized word and also one before and one after the word.
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Emphasis (typography)
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Methods and use
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For black letter type boldface was not feasible, since the letters were very dark in their standard format, and on (most) typewriters only a single type was available. Although letter-spacing was common, sometimes different typefaces (e.g. Schwabacher inside Fraktur), underlining or colored, usually red ink were used instead.
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Emphasis (typography)
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Methods and use
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Since blackletter type remained in use in German speaking parts of Europe much longer than anywhere else, the custom of letter-spacing is sometimes seen as specific to German, although it has been used with other languages, including English. Especially in German, however, this kind of emphasis may also be used within modern type, e.g. where italics already serve another semantic purpose (as in linguistics) and where no further means of emphasis (e.g. small caps) are easily available or feasible. Its professional use today is very limited in German. This use of spacing is also traditionally found in Polish.German orthographic (or rather typographic) rules require that the mandatory blackletter ligatures are retained. That means, ſt, ch, ck, and tz are still stuck together just as the letter ß, whereas optional, additional ligatures like ff and ſi are broken up with a (small) space in between. Other writing systems did not develop such sophisticated rules since spacing was so uncommon therein.
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Emphasis (typography)
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In Cyrillic typography, it also used to be common to emphasize words using letter-spaced type. This practice for Cyrillic has become obsolete with the availability of Cyrillic italic and small capital fonts.
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Emphasis (typography)
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Methods and use
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Underlining Professional Western typesetting usually does not employ lines under letters for emphasis within running text. In proofreading, underlining (or underscoring) is a convention that says "set this text in italic type", traditionally used on manuscript or typescript as an instruction to the printer. Its use to add emphasis in modern documents is a deprecated practice. In web pages, hyperlinks are often displayed with underlines – to identify them as such rather than to emphasize them. Underlining is also used for secondary emphasis, i.e. marks added to a printed text by the reader.
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Overlining In Arabic, it is traditional to emphasize text by drawing a line over the letters. This is seen in the Quran, where the word at which Sujud Tilawa is performed is overlined.
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Emphasis (typography)
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Punctuation marks Sometimes quotation marks are used for emphasis. However, this clashes with the general understanding of how the marks are properly used, particularly scare quotes, and can leave the reader with a different impression than intended.In Chinese, emphasis in body text is supposed to be indicated by using an "emphasis mark" (着重號／着重号), which is a dot placed under each character to be emphasized. This is still taught in schools but in practice it is not usually done, probably due to the difficulty of doing this using most computer software. Consequently, methods used for emphasis in Western text are often used instead, even though they are considered inappropriate for Chinese (for example, the use of underlining or setting text in oblique type).
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Emphasis (typography)
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In Japanese texts, when katakana would be inappropriate, emphasis is indicated by "emphasis dots" (圏点 or 傍点) placed above the kanji and any accompanying furigana in horizontal writing and to the right in vertical writing. Japanese also has an "emphasis line" (傍線) used in a similar manner, but less frequently.
In Korean texts, a dot is placed above each Hangul syllable block or Hanja to be emphasized.In Armenian the շեշտ (šešt) sign ( ՛ ) is used.
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Emphasis (typography)
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On websites and other Internet services, as with typewriters, rich text is not always available. Asterisks are sometimes used for emphasis (as in "That was *really* bad"). Less commonly, underscores may be used, resembling underlining ("That was _really_ bad"). Periods can be used between words (as in "That. was. really. bad.") to emphasize whole sentences, mimicking when somebody slows down their speech for impact. In some cases, the engine behind the text area being parsed will render the text and the asterisks in bold automatically after the text is submitted. Markdown is a common formalization of this concept.
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Emphasis (typography)
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Color Colors are important for emphasizing. Important words in a text may be colored differently from others. For example, many dictionaries use a different color for headwords, and some religious texts color the words of deities red, commonly referred to as rubric. In Ethiopic script, red is used analogously to italics in Latin text.Post-print emphasis added by a reader is often done with highlighters which add a bright background color to usual black-on-white text.
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Emphasis (typography)
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Design
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There are many designs. With both italics and boldface, the emphasis is correctly achieved by swapping into a different font of the same family; for example by replacing body text in Arial with its bold or italic style. Professional typographic systems, including most modern computers, would therefore not simply tilt letters to the right to achieve italics (that is instead referred to as slanting or oblique), print them twice or darker for boldface, or scale majuscules to the height of middle-chamber minuscules (like x and o) for small-caps, but instead use entirely different typefaces that achieve the effect. The letter 'w', for example, looks quite different in italic compared to upright.
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Emphasis (typography)
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Design
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As a result, typefaces therefore have to be supplied at least fourfold (with computer systems, usually as four font files): as regular, bold, italic, and bold italic to provide for all combinations. Professional typefaces sometimes offer even more variations for popular fonts, with varying degrees of blackness. Only if such fonts are not available should the effect of italic or boldface be imitated by algorithmically altering the original font.
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Emphasis (typography)
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Design
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The modern Latin-alphabet system of fonts appearing in two standard weights, with the styles being regular (or "Roman"), italic, bold and bold italic is a relatively recent development, dating to the early twentieth century. Modern "Roman" type was developed around the 1470s, while italic type was developed around 1500 and was commonly used for emphasis by the early 17th century. Bold type did not arrive until the nineteenth century, and at first fonts did not have matching bold weights; instead a generic bold, sometimes a Clarendon or other kind of slab-serif, would be swapped in. In some books printed before bold type existed, emphasis could be shown by switching to blackletter. Some font families intended for professional use in documents such as business reports may also make the bold-style numbers take up the same width as the regular (non-bold) numbers, so a bold-style total lines up below the digits of the sum in regular style.
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