There are known knowns
"There are known knowns" is a phrase from a response United States Secretary of Defense Donald Rumsfeld gave to a question at a U. S. Department of Defense news briefing on February 12, 2002 about the lack of evidence linking the government of Iraq with the supply of weapons of mass destruction to terrorist groups. Rumsfeld stated: Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns. We know there are known unknowns, but there are unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones; the statement became the subject of much commentary, including a documentary by Academy Award–winning film director Errol Morris. Rumsfeld's statement brought much fame and public attention to the concepts of known knowns, known unknowns, unknown unknowns, but national security and intelligence professionals have long used an analysis technique referred to as the Johari window.
The idea of unknown unknowns was created in 1955 by two American psychologists, Joseph Luft and Harrington Ingham in their development of the Johari window. They used it as a technique to help people better understand their relationship with themselves as well as others; the term was commonly used inside NASA. Rumsfeld himself cited NASA administrator William Graham in his memoir. Kirk Borne, an astrophysicist, employed as a data scientist at NASA Goddard Space Flight Center at the time, noted in an April 2013 TED talk that he had used the phrase "unknown unknowns" in a talk to personnel at the Homeland Security Transition Planning Office a few days prior to Rumsfeld's remarks, speculated that the term may have percolated up to Rumsfeld and other high-ranking officials in the defense department; the terms "known unknowns" and "unknown unknowns" are used in project management and strategic planning circles. Known unknowns refers to "risks you are aware of, such as cancelled flights...."Unknown unknowns are risks that come from situations that are so unexpected that they would not be considered.
"For example, prior to the invention of the personal computer, manufacturers of typewriters didn't foresee the risks to their business". Contemporary usage is consistent with the earliest known usages. For example, the term was used in evidence given to the British Columbia Royal Commission of Inquiry into Uranium Mining in 1979: Site conditions always pose unknowns, or uncertainties, which may become known during construction or operation to the detriment of the facility and lead to damage of the environment or endanger public health and safety; the risk posed by unknowns is somewhat dependent on the nature of the unknown relative to past experience. This has led me classify unknowns into one of the following two types: 1. Known unknowns, which can be reasonably anticipated but not quantified based on past experience as exemplified by case histories. Unknown unknowns, which pose a greater risk because they cannot be anticipated based on past experience or investigation. -- Known unknowns result from phenomena which are recognized.
On the other hand, unknown unknowns are phenomena which cannot be expected because there has been no prior experience or theoretical basis for expecting the phenomena. The term appeared in a 1982 New Yorker article on the aerospace industry, which cites the example of metal fatigue, the cause of crashes in de Havilland Comet airliners in the 1950s. While the remarks led to some ridicule towards the Bush administration in general and Rumsfeld in particular, the consensus regarding it has shifted over the years, it now enjoys some level of respect. For example, Rumsfeld's defenders have included Canadian columnist Mark Steyn, who called it "in fact a brilliant distillation of quite a complex matter", Australian economist and blogger John Quiggin, who wrote, "Although the language may be tortured, the basic point is both valid and important."Psychoanalytic philosopher Slavoj Žižek says that beyond these three categories there is a fourth, the unknown known, that which we intentionally refuse to acknowledge that we know: "If Rumsfeld thinks that the main dangers in the confrontation with Iraq were the'unknown unknowns', that is, the threats from Saddam whose nature we cannot suspect the Abu Ghraib scandal shows that the main dangers lie in the "unknown knowns"—the disavowed beliefs and obscene practices we pretend not to know about though they form the background of our public values."German sociologists Daase and Kessler agree with a basic point of Rumsfeld in stating that the cognitive frame for political practice may be determined by the relationship between what we know, what we do not know, what we cannot know, but Rumsfeld left out what we do not like to know.
The event has been used in multiple books to discuss risk assessment. Rumsfeld named his autobiography Known and Unknown: A Memoir. In an "Author's Note" at the start of the book, he expressly acknowledged the source of his memoir's title and mentioned a few examples of his statement's prominence, including this Wikipedia article; the Unknown Known is the title of Errol Morris's 2013 biographical documentary about Rumsfeld. The term "known unknowns" has been applied to the ident
Bisphenol A is an organic synthetic compound with the chemical formula 2C2 belonging to the group of diphenylmethane derivatives and bisphenols, with two hydroxyphenyl groups. It is a colorless solid, soluble in organic solvents, but poorly soluble in water. BPA is a starting material for the synthesis of plastics certain polycarbonates and epoxy resins, as well as some polysulfones and certain niche materials. BPA-based plastic is clear and tough, is made into a variety of common consumer goods, such as plastic bottles including water bottles, sports equipment, CDs, DVDs. Epoxy resins containing BPA are used to line water pipes, as coatings on the inside of many food and beverage cans and in making thermal paper such as that used in sales receipts. In 2015, an estimated 4 million tonnes of BPA chemical were produced for manufacturing polycarbonate plastic, making it one of the highest volume of chemicals produced worldwide. BPA is a xenoestrogen, exhibiting estrogen-mimicking, hormone-like properties that raise concern about its suitability in some consumer products and food containers.
Since 2008, several governments have investigated its safety, which prompted some retailers to withdraw polycarbonate products. The U. S. Food and Drug Administration has ended its authorization of the use of BPA in baby bottles and infant formula packaging, based on market abandonment, not safety; the European Union and Canada have banned BPA use in baby bottles. World production capacity of BPA was 1 million tons in the 1980s, more than 2.2 million tons in 2009. It is a high production volume chemical; this compound is synthesized by the condensation of acetone with two equivalents of phenol. The reaction is catalyzed by a strong acid, such as hydrochloric acid or a sulfonated polystyrene resin. Industrially, a large excess of phenol is used to ensure full condensation. In 2003, U. S. consumption was 856,000 tons, 72% of which used to make polycarbonate plastic and 21% going into epoxy resins. In the U. S. less than 5% of the BPA produced is used in food contact applications, but remains in the canned food industry and printing applications such as sales receipts.
Bisphenol A and phosgene react to give polycarbonate. The reaction is conducted under biphasic conditions, it is a precursor in production of major classes of resins the vinyl ester resins. This application begins with alkylation of BPA with epichlorohydrin. BPA is a versatile building block. Nitration give dinitrobisphenol A. Bromination gives tetrabromobisphenol A, which exhibits fire retardant properties. BPA is used in the synthesis of polysulfones and some Polyether ether ketones, it is an antioxidant in some plasticizers, as a polymerization inhibitor in PVC. Several drug candidates have been developed from bisphenol A, including Ralaniten, #Ralaniten acetate, EPI-001. In the U. S. plastic packaging is split into seven broad classes for recycling purposes by a Plastic identification code. As of 2014 there are no BPA labeling requirements for plastics in the U. S. "In general, plastics that are marked with Resin Identification Codes 1, 2, 4, 5, 6 are unlikely to contain BPA. Some, but not all, plastics that are marked with the Resin Identification Code 7 may be made with BPA."
Type 7 is the catch-all "other" class, some type 7 plastics, such as polycarbonate and epoxy resins, are made from bisphenol A monomer. Type 3 may contain bisphenol A as an antioxidant in "flexible PVC" softened by plasticizers, but not rigid PVC such as pipe and siding. Bisphenol A was discovered in 1891 by Russian chemist Aleksandr Dianin. In 1934 workers at I. G. Farbenindustrie reported the coupling of epichlorohydrin. Over the following decade and resins derived from similar materials were described by workers at the companies of DeTrey Freres in Switzerland and DeVoe and Raynolds in the US; this early work underpinned the development of epoxy resins, which in turn motivated production of BPA. The utilization of BPA further expanded with discoveries at Bayer and General Electric on polycarbonate plastics; these plastics first appeared in 1958, being produced by Mobay and General Electric, Bayer. In terms of the endocrine disruption controversy, the British biochemist Edward Charles Dodds tested BPA as an artificial estrogen in the early 1930s.
He found BPA to be 1 / 37,000 as effective as estradiol. Dodds developed a structurally similar compound, diethylstilbestrol, used as a synthetic estrogen drug in women and animals until it was banned due to its risk of causing cancer. BPA was never used as a drug. BPA's ability to mimic the effects of natural estrogen derive from the similarity of phenol groups on both BPA and estradiol, which enable this synthetic molecule to trigger estrogenic pathways in the body. Phenol-containing molecules similar to BPA are known to exert weak estrogenic activities, thus it is considered an endocrine disrupter and estrogenic chemical. Xenoestrogens is another category the chemical BPA fits under because of its capability to interrupt the network that regulates the signals which control the reproductive development in humans and animals. BPA has been found to bind to both of the nuclear estrogen receptors
Fluorosurfactants are synthetic organofluorine chemical compounds that have multiple fluorine atoms. They can be fluorocarbon-based; as surfactants, they are more effective at lowering the surface tension of water than comparable hydrocarbon surfactants. They have a fluorinated "tail" and a hydrophilic "head." Some human-made fluorosurfactants, such as PFOS and PFOA, are persistent organic pollutants and are detected in humans and wildlife. Fluorosurfactants can lower the surface tension of water down to a value half of what is attainable by using hydrocarbon surfactants; this ability is due to the lipophobic nature of fluorocarbons, as fluorosurfactants tend to concentrate at the liquid-air interface. They are not as susceptible to the London dispersion force, a factor contributing to lipophilicity, because the electronegativity of fluorine reduces the polarizability of the surfactants' fluorinated molecular surface. Therefore, the attractive interactions resulting from the "fleeting dipoles" are reduced, in comparison to hydrocarbon surfactants.
Fluorosurfactants are more stable and fit for harsh conditions than hydrocarbon surfactants because of the stability of the carbon–fluorine bond. Perfluorinated surfactants persist in the environment for that reason. Fluorosurfactants play a key economic role for companies such as DuPont, 3M, W. L. Gore & Associates because they are used in emulsion polymerization to produce fluoropolymers. Fluorosurfactants have two main markets: a $1 billion annual market for use in stain repellents, a $100 million annual market for use in polishes and coatings. Fluorosurfactants such as perfluorooctanesulfonic acid, perfluorooctanoic acid, perfluorononanoic acid have caught the attention of regulatory agencies because of their persistence and widespread occurrence in the blood of general populations and wildlife. In 2009 PFASs were listed as persistent organic pollutants under the Stockholm Convention, due to their ubiquitous, persistent and toxic nature, their production has been regulated or phased out by manufacturers, such as 3M, DuPont and Miteni in the USA, Europe.
Some manufacturers have now replaced PFOS and PFOA with short-chain PFASs, such as perfluorohexanoic acid, perfluorobutanesulfonic acid and perfluorobutane sulfonate. Shorter fluorosurfactants may be less prone to accumulating in mammals. In 2017, the ABC's current affairs programme Four Corners reported that the storage and use of firefighting foams containing perfluorinated surfactants at Australian Defence Force facilities around Australia had contaminated nearby water resources. Certain PFAS chemicals are no longer manufactured in the United States as a result of phase outs including the PFOA Stewardship Program, in which eight major chemical manufacturers agreed to eliminate the use of PFOA and PFOA-related chemicals in their products and as emissions from their facilities. Although PFOA and PFOS are no longer manufactured in the United States, they are still produced internationally and can be imported into the United States in consumer goods such as carpet and apparel, textiles and packaging, coatings and plastics.
There are an estimated 26,000 PFAS-contaminated sites across the United States, six million Americans are believed to be impacted by PFAS-contaminated drinking water. Launched in 2017, the Michigan PFAS Action Response Team is the first multi-agency action team of its kind in the nation. Agencies representing health and other branches of state government have joined together to investigate sources and locations of PFAS contamination in the state, take action to protect people’s drinking water, keep the public informed. Groundwater is tested at locations throughout the state by various parties to ensure safety, compliance with regulations, to proactively detect and remedy potential problems. In 2010, the Michigan Department of Environmental Quality discovered levels of Per- and Polyfluoroalkyl Substances in groundwater monitoring wells at the former Wurtsmith Air Force Base; as additional information became available from other national testing, Michigan expanded its investigations into other locations where PFAS compounds were used.
In 2018, the MDEQ's Remediation and Redevelopment Division established cleanup criteria for groundwater used as drinking water of 70 ppt of perfluorooctanoic acid and perfluorooctanesulfonic acid, individually or combined. The RRD staff are responsible for implementing these criteria as part of their ongoing efforts to clean-up sites of environmental contamination; the RRD staff are the lead investigators at most of the PFAS sites on the MPART website and conduct interim response activities, such as coordinating bottled water or filter installations with local health departments at sites under investigation or with known PFAS concerns. Most of the groundwater sampling at PFAS sites under RRD’s lead is conducted by contractors familiar with PFAS sampling techniques; the RRD has a Geologic Services Unit, with staff who install monitoring wells and are well versed with PFAS sampling techniques. The MDEQ has been conducting environmental clean-up of regulated contaminants for decades. Due to the evolving nature of PFAS regulations as new science becomes available, the RRD is evaluating the need for regular PFAS sampling at Superfund sites and is including an evaluation of PFAS sampling needs as part of a Baseline Environmental Assessment review.
Earlier this year, the RRD purchased lab equipment that will allow the MDEQ E
Antony John Williams
Antony John Williams is a British chemist and expert in the fields of both nuclear magnetic resonance spectroscopy and cheminformatics at the United States Environmental Protection Agency. He is the founder of the ChemSpider website, purchased by the Royal Society of Chemistry in May 2009, he is a science blogger, one of the hosts of the SciMobileApps wiki, a community-based wiki for Scientific Mobile Apps and an author. Antony Williams was born in St Asaph, June 1964 to Ernest Edward Williams, owner of a building contracting firm, Eirlys Elizabeth Williams, he has Rae. He grew up in a small village near Caerwys. Williams attended Primary School in both Holywell and Nannerch until 1975. From the age of eleven, he attended Alun School where he received A-levels in mathematics and chemistry. Williams earned his Bachelor of Science in chemistry from the University of Liverpool, in 1985, writing an undergraduate dissertation on "Spectroscopic Studies of Vitamin E Related Systems" where he applied both electron paramagnetic resonance and Nuclear magnetic resonance spectroscopy to the study of molecules similar in structure to Vitamin E. Williams earned his Ph.
D. in chemistry, funded by Royal Dutch Shell, from Royal Holloway, University of London in 1988 and wrote a thesis entitled "High pressure NMR and relaxation studies of alkyl chain systems". He won the Bourne Medal from the University of London for this work and developed a unifying theory for modeling NMR relaxation data to examine the molecular motions of alkyl chains, he used the Cobalt-59 NMR chemical shift for cobalt hexacyanide as both a temperature and pressure probe. During his PhD he developed an interest in personal computers and wrote software programs to fit NMR relaxation data. Williams continued his work in spectroscopy at the National Research Council using EPR spectroscopy to perform single-crystal studies of organometallics compounds. In 1991, Williams joined Ottawa University as their NMR Facility Manager, he continued his personal interests in multinuclear NMR to perform 2D-NMR experiments examining Selenium exchange in mixed-halogen systems. He performed Silicon-29 and Tellurium-125 NMR studies.
In 1992 Williams left Canada for Rochester, NY to work for the Eastman Kodak Company as their NMR Technology Leader. At Kodak he used his previous experience in studying alkyl chain related systems to study micelles, he was involved in the early adoption of Liquid Chromatography-NMR into the company and in the development of an Open Access laboratory for chemists to use roboticized analytical instrumentation to generate data. At Kodak he was part of a three-member team that developed a web-based Laboratory information management system system called WIMS, the Web-based Information Management System and it was the first web-based LIMS system in the world to manage chemical structures and spectral data, he was granted two patents while at Kodak,In 1997 he started work for a Canadian start-up company, Advanced Chemistry Development as their senior product manager. He was responsible for managing all spectroscopy, structure drawing and IUPAC nomenclature, products. While in that role the analytical data management software was expanded to include support for mass spectrometry, infrared spectroscopy, UV-Vis spectroscopy and other forms of analytical sciences.
His research interests at that time include the development of algorithms for NMR prediction and development of software approaches to Computer Assisted structure Elucidation, so-called CASE systems. The CASE tools have been used for the purpose of structure revision whereby algorithms have been demonstrated to outperform human interpretation of spectral data. While at ACD/Labs Williams was involved in a number of industry firsts including producing a chemical dictionary on a Palm Computer and Pocket PC, working with Gary E. Martin and other colleagues to develop new NMR processing techniques using covariance-based approaches, the introduction of fuzzy-logic based approaches to computer-assisted structure elucidation and 4) Approaches for automated structure verification. While at the company he initiated a hobby project to link together chemistry databases on the web; this project was called ChemSpider. ChemSpider was formally announced at the Chicago ACS meeting in March 2007 with a database containing over 10 million compounds sourced from PubChem.
In 2007 when he left ACD/Labs he was the Chief Science Officer. He became an independent consultant working with a number of software companies in the cheminformatics domain, such as SimBioSys, with research organizations to support their cheminformatics efforts. In parallel he continued to develop the ChemSpider platform with a small group of like-minded individuals interested in the development of web-based systems to serve chemists The site is a crowdsourced community for chemistry with chemists depositing their structure collections, spectral data and molecular properties. Williams is focused on educating the community as to the issues of data quality associated with internet chemistry databases. In May 2009 the Royal Society of Chemistry announced. Williams joined RSC as their Vice President of Strategic Development for ChemSpider. In May 2015 he joined the United States Environmental Protection Agency to work on the development of websites delivering public access to EPA data and tools for mass spectrometry.
Williams has contributed to the world of "Mobile Chemistry" by contributing to the development of ChemMobi, an iPhone app for accessing millions of chemical compounds and associated data. Williams is an advocate for Open Notebook Science and is a judge for the Open Notebook Science Challenge, he worked with Jean-Claude Bradley to deliver a
United States Environmental Protection Agency
The Environmental Protection Agency is an independent agency of the United States federal government for environmental protection. President Richard Nixon proposed the establishment of EPA on July 9, 1970 and it began operation on December 2, 1970, after Nixon signed an executive order; the order establishing the EPA was ratified by committee hearings in the Senate. The agency is led by its Administrator, appointed by the President and approved by Congress; the current Administrator is former Deputy Administrator Andrew R. Wheeler, acting administrator since July 2018; the EPA is not a Cabinet department, but the Administrator is given cabinet rank. The EPA has its headquarters in Washington, D. C. regional offices for each of the agency's ten regions, 27 laboratories. The agency conducts environmental assessment and education, it has the responsibility of maintaining and enforcing national standards under a variety of environmental laws, in consultation with state and local governments. It delegates some permitting and enforcement responsibility to U.
S. states and the federally recognized tribes. EPA enforcement powers include fines and other measures; the agency works with industries and all levels of government in a wide variety of voluntary pollution prevention programs and energy conservation efforts. In 2018, the agency had 14,172 full-time employees. More than half of EPA's employees are engineers and environmental protection specialists; the Environmental Protection Agency can only act under statutes, which are the authority of laws passed by Congress. Congress must approve the statute and they have the power to authorize or prohibit certain actions, which the EPA has to implement and enforce. Appropriations statutes authorize how much money the agency can spend each year to carry out the approved statutes; the Environmental Protection Agency has the power to issue regulations. A regulation is a standard or rule written by the agency to interpret the statute, apply it in situations and enforce it. Congress allows the EPA to write regulations in order to solve a problem, but the agency must include a rationale of why the regulations need to be implemented.
The regulations can be challenged by the Courts, where the regulation is confirmed. Many public health and environmental groups advocate for the agency and believe that it is creating a better world. Other critics believe that the agency commits government overreach by adding unnecessary regulations on business and property owners. Beginning in the late 1950s and through the 1960s, Congress reacted to increasing public concern about the impact that human activity could have on the environment. Senator James E. Murray introduced a bill, the Resources and Conservation Act of 1959, in the 86th Congress; the 1962 publication of Silent Spring by Rachel Carson alerted the public about the detrimental effects on the environment of the indiscriminate use of pesticides. In the years following, similar bills were introduced and hearings were held to discuss the state of the environment and Congress's potential responses. In 1968, a joint House–Senate colloquium was convened by the chairmen of the Senate Committee on Interior and Insular Affairs, Senator Henry M. Jackson, the House Committee on Science and Astronautics, Representative George P. Miller, to discuss the need for and means of implementing a national environmental policy.
In the colloquium, some members of Congress expressed a continuing concern over federal agency actions affecting the environment. The National Environmental Policy Act of 1969 was modeled on the Resources and Conservation Act of 1959. RCA would have established a Council on Environmental Quality in the office of the President, declared a national environmental policy, required the preparation of an annual environmental report. President Nixon signed NEPA into law on January 1, 1970; the law created the Council on Environmental Quality in the Executive Office of the President. NEPA required that a detailed statement of environmental impacts be prepared for all major federal actions affecting the environment; the "detailed statement" would be referred to as an environmental impact statement. On July 9, 1970, Nixon proposed an executive reorganization that consolidated many environmental responsibilities of the federal government under one agency, a new Environmental Protection Agency; this proposal included merging antipollution programs from a number of departments, such as the combination of pesticide programs from the United States Department of Agriculture, Department of Interior, U.
S. Department of Interior. After conducting hearings during that summer, the House and Senate approved the proposal; the EPA was created 90 days before it had to operate, opened its doors on December 2, 1970. The agency's first Administrator, William Ruckelshaus, took the oath of office on December 4, 1970. In its first year, the EPA had 5,800 employees. At its start, the EPA was a technical assistance agency that set goals and standards. Soon, new acts and amendments passed by Congress gave the agency its regulatory authority. EPA staff recall that in the early days there was "an enormous sense of purpose and excitement" and the expectation that "there was this agency, going to do something about a problem, on the minds of a lot of people in this country," leading to tens of thousands of resumes from those eager to participate in the mighty effort to clean up America's environment; when EPA first began operation, members of the private sector felt that the environ
Environmental science is an interdisciplinary academic field that integrates physical and information sciences to the study of the environment, the solution of environmental problems. Environmental science emerged from the fields of natural history and medicine during the Enlightenment. Today it provides an integrated and interdisciplinary approach to the study of environmental systems. Related areas of study include environmental engineering. Environmental studies incorporates more of the social sciences for understanding human relationships and policies towards the environment. Environmental engineering focuses on design and technology for improving environmental quality in every aspect. Environmental scientists work on subjects like the understanding of earth processes, evaluating alternative energy systems, pollution control and mitigation, natural resource management, the effects of global climate change. Environmental issues always include an interaction of physical and biological processes.
Environmental scientists bring a systems approach to the analysis of environmental problems. Key elements of an effective environmental scientist include the ability to relate space, time relationships as well as quantitative analysis. Environmental science came alive as a substantive, active field of scientific investigation in the 1960s and 1970s driven by the need for a multi-disciplinary approach to analyze complex environmental problems, the arrival of substantive environmental laws requiring specific environmental protocols of investigation and the growing public awareness of a need for action in addressing environmental problems. Events that spurred this development included the publication of Rachel Carson's landmark environmental book Silent Spring along with major environmental issues becoming public, such as the 1969 Santa Barbara oil spill, the Cuyahoga River of Cleveland, Ohio, "catching fire", helped increase the visibility of environmental issues and create this new field of study.
In common usage, "environmental science" and "ecology" are used interchangeably, but technically, ecology refers only to the study of organisms and their interactions with each other and their environment. Ecology could be considered a subset of environmental science, which could involve purely chemical or public health issues ecologists would be unlikely to study. In practice, there is considerable overlap between the work of ecologists and other environmental scientists; the National Center for Education Statistics in the United States defines an academic program in environmental science as follows: A program that focuses on the application of biological and physical principles to the study of the physical environment and the solution of environmental problems, including subjects such as abating or controlling environmental pollution and degradation. Includes instruction in biology, physics, climatology and mathematical modeling. Atmospheric sciences focus on the Earth's atmosphere, with an emphasis upon its interrelation to other systems.
Atmospheric sciences can include studies of meteorology, greenhouse gas phenomena, atmospheric dispersion modeling of airborne contaminants, sound propagation phenomena related to noise pollution, light pollution. Taking the example of the global warming phenomena, physicists create computer models of atmospheric circulation and infra-red radiation transmission, chemists examine the inventory of atmospheric chemicals and their reactions, biologists analyze the plant and animal contributions to carbon dioxide fluxes, specialists such as meteorologists and oceanographers add additional breadth in understanding the atmospheric dynamics. Ecology is the study of the interactions between their environment. Ecologists might investigate the relationship between a population of organisms and some physical characteristic of their environment, such as concentration of a chemical. For example, an interdisciplinary analysis of an ecological system, being impacted by one or more stressors might include several related environmental science fields.
In an estuarine setting where a proposed industrial development could impact certain species by water and air pollution, biologists would describe the flora and fauna, chemists would analyze the transport of water pollutants to the marsh, physicists would calculate air pollution emissions and geologists would assist in understanding the marsh soils and bay muds. Environmental chemistry is the study of chemical alterations in the environment. Principal areas of study include water pollution; the topics of analysis include chemical degradation in the environment, multi-phase transport of chemicals, chemical effects upon biota. As an example study, consider the case of a leaking solvent tank which has entered the habitat soil of an endangered species of amphibian; as a method to resolve or understand the extent of soil contamination and subsurface transport of solvent, a computer model would be implemented. Chemists would characterize the molecular bonding of the solvent to the specific soil type, biologists would study the impacts upon soil arthr
International Standard Serial Number
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is helpful in distinguishing between serials with the same title. ISSN are used in ordering, interlibrary loans, other practices in connection with serial literature; the ISSN system was first drafted as an International Organization for Standardization international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard; when a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in electronic media; the ISSN system refers to these types as electronic ISSN, respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is assigned a linking ISSN the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.
The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits; the last code digit, which may be 0-9 or an X, is a check digit. Formally, the general form of the ISSN code can be expressed as follows: NNNN-NNNC where N is in the set, a digit character, C is in; the ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, C=5. To calculate the check digit, the following algorithm may be used: Calculate the sum of the first seven digits of the ISSN multiplied by its position in the number, counting from the right—that is, 8, 7, 6, 5, 4, 3, 2, respectively: 0 ⋅ 8 + 3 ⋅ 7 + 7 ⋅ 6 + 8 ⋅ 5 + 5 ⋅ 4 + 9 ⋅ 3 + 5 ⋅ 2 = 0 + 21 + 42 + 40 + 20 + 27 + 10 = 160 The modulus 11 of this sum is calculated. For calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, counting from the right.
The modulus 11 of the sum must be 0. There is an online ISSN checker. ISSN codes are assigned by a network of ISSN National Centres located at national libraries and coordinated by the ISSN International Centre based in Paris; the International Centre is an intergovernmental organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, the ISDS Register otherwise known as the ISSN Register. At the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept. An ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an anonymous identifier associated with a serial title, containing no information as to the publisher or its location. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change. Since the ISSN applies to an entire serial a new identifier, the Serial Item and Contribution Identifier, was built on top of it to allow references to specific volumes, articles, or other identifiable components.
Separate ISSNs are needed for serials in different media. Thus, the print and electronic media versions of a serial need separate ISSNs. A CD-ROM version and a web version of a serial require different ISSNs since two different media are involved. However, the same ISSN can be used for different file formats of the same online serial; this "media-oriented identification" of serials made sense in the 1970s. In the 1990s and onward, with personal computers, better screens, the Web, it makes sense to consider only content, independent of media; this "content-oriented identification" of serials was a repressed demand during a decade, but no ISSN update or initiative occurred. A natural extension for ISSN, the unique-identification of the articles in the serials, was the main demand application. An alternative serials' contents model arrived with the indecs Content Model and its application, the digital object identifier, as ISSN-independent initiative, consolidated in the 2000s. Only in 2007, ISSN-L was defined in the