The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating. However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry.
Measurement of the ratios of naturally occurring stable isotopes (isotope analysis) plays an important role in isotope geochemistry, but stable isotopes (mostly carbon, nitrogen, oxygen and sulfur) are also finding uses in ecological and biological studies. Other workers have used oxygen isotope ratios to reconstruct historical atmospheric temperatures, making them important tools for paleoclimatology.
These isotope systems for lighter elements that exhibit more than one primordial isotope for each element, have been under investigation for many years in order to study processes of isotope fractionation in natural systems. The long history of study of these elements is in part because the proportions of stable isotopes in these light and volatile elements is relatively easy to measure. However, recent advances in isotope ratio mass spectrometry (i.e. multiple-collector inductively coupled plasma mass spectrometry) now enable the measurement of isotope ratios in heavier stable elements, such as iron, copper, zinc, molybdenum, etc.
The variations in oxygen and hydrogen isotope ratios have applications in hydrology since most samples will lie between two extremes, ocean water and Arctic/Antarctic snow. Given a sample of water from an aquifer, and a sufficiently sensitive tool to measure the variation in the isotopic ratio of hydrogen in the sample, it is possible to infer the source, be it ocean water seeping into the aquifer or precipitation seeping into the aquifer, and even to estimate the proportions from each source. Stable isotopes of water are also used in partitioning water sources for plant transpiration and groundwater recharge.
Another application is in paleotemperature measurement for paleoclimatology. For example, one technique is based on the variation in isotopic fractionation of oxygen by biological systems with temperature. Species of Foraminifera incorporate oxygen as calcium carbonate in their shells. The ratio of the oxygen isotopes oxygen-16 and oxygen-18 incorporated into the calcium carbonate varies with temperature and the oxygen isotopic composition of the water. This oxygen remains "fixed" in the calcium carbonate when the forminifera dies, falls to the sea bed, and its shell becomes part of the sediment. It is possible to select standard species of forminifera from sections through the sediment column, and by mapping the variation in oxygen isotopic ratio, deduce the temperature that the Forminifera encountered during life if changes in the oxygen isotopic composition of the water can be constrained.
In ecology, carbon and nitrogen isotope ratios are widely used to determine the broad diets of many free-ranging animals. They have been used to determine the broad diets of seabirds, and to identify the geographical areas where individuals spend the breeding and non-breeding season. Numerous ecological studies have also used isotope analyses to understand migration, food-web structure, diet, and resource use in sea turtles. Determining diets of aquatic animals using stable isotopes has been particularly common, as direct observations are difficult, they also enable researchers to measure how human interactions with wildlife, such as fishing, may alter natural diets.
In forensic science, research suggests that the variation in certain isotope ratios in drugs derived from plant sources (cannabis, cocaine) can be used to determine the drug's continent of origin.
Chondrite meteorites are classified using the oxygen isotope ratios. In addition, an unusual signature of carbon-13 confirms the non-terrestrial origin for organic compounds found in carbonaceous chondrites, as in the Murchison meteorite.
Caldey Island (Welsh:Ynys Bŷr) is a small island 0.6 miles (1 km) off the coast near Tenby in Pembrokeshire, Wales. With a recorded history going back over 1,500 years, it is one of the holy islands of Britain. A number of traditions inherited from Celtic times are observed by the Cistercian monks of Caldey Abbey, the owners of the island.The island's population consists of about 40 permanent residents and a varying number of Cistercian monks, known as Trappists. The monks' predecessors migrated there from Belgium in the early 20th century, taking over from Anglican Benedictines who had bought the island in 1906 and built the extant monastery and abbey but later got into financial difficulties. Today, the monks of Caldey Abbey rely on tourism and making perfumes and chocolate.
The usual access to the island is by small boat from Tenby, 2 1⁄2 miles (4 km) to the north. In the spring and summer, visitors are ferried to Caldey, not only to visit the sacred sanctuary but also to view the island's rich wildlife. Following a rat eradication programme, red squirrels were introduced in 2016. Alongside rare breed sheep and cattle, the island has a diverse bird and plant life.Carbon dioxide in Earth's atmosphere
Carbon dioxide (CO2) is an important trace gas in Earth's atmosphere. It is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere. Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis. Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds. CO2 absorbs and emits infrared radiation at wavelengths of 4.26 µm (asymmetric stretching vibrational mode) and 14.99 µm (bending vibrational mode) and consequently is a greenhouse gas that plays a vital role in regulating Earth's surface temperature through the greenhouse effect.Concentrations of CO2 in the atmosphere were as high as 4,000 parts per million (ppm) during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years. Estimates based on reconstructed temperature records suggests that the amount of CO2 during the last 420 million years ago was with ~2000 ppm highest during the Devonian (∼400 Myrs ago) and Triassic (220–200 Myrs ago), with a few maximum estimates ranging up to ∼3,700±1,600 ppm (215 Myrs ago). Global annual mean CO2 concentration has increased by more than 45% since the start of the Industrial Revolution, from 280 ppm during the 10,000 years up to the mid-18th century to 410 ppm as of mid-2018. The present concentration is the highest in the last 800,000 and possibly even the last 20 million years. The increase has been caused by human activities, particularly the burning of fossil fuels and deforestation. This increase of CO2 and other long-lived greenhouse gases in Earth's atmosphere has produced the current episode of global warming. About 30–40% of the CO2 released by humans into the atmosphere dissolves into oceans, rivers and lakes, which has produced ocean acidification.Elementar
Elementar is a German multinational manufacturer of elemental analyzers and isotope ratio mass spectrometers for the analysis of non-metallic elements like carbon, nitrogen, sulphur, hydrogen, oxygen or chlorine. The company emerged from Heraeus, a multinational German engineering company that produced analytical instrumentation. Elemental analyzers and isotope ratio mass spectrometers are used in the fields of analytical and environmental chemistry to measure the elemental and isotopic composition of diverse materials like chemicals, pharmaceuticals, fuels, food, water, plants, soil or waste.Ethyl butyrate
Ethyl butyrate, also known as ethyl butanoate, or butyric ether, is an ester with the chemical formula CH3CH2CH2COOCH2CH3. It is soluble in propylene glycol, paraffin oil, and kerosene. It has a fruity odor, similar to pineapple and is a key ingredient used as a flavor enhancer in processed orange juices. It also occurs naturally in many fruits, albeit at lower concentrations.Glossary of physics
This glossary of physics is a list of definitions of terms and concepts relevant to physics, its sub-disciplines, and related fields, including mechanics, materials science, nuclear physics, particle physics, and thermodynamics.
For more inclusive glossaries concerning related fields of science and technology, see Glossary of chemistry terms, Glossary of astronomy, Glossary of areas of mathematics, and Glossary of engineering.History and culture of substituted amphetamines
Amphetamine and methamphetamine are pharmaceutical drugs used to treat a variety of conditions; when used recreationally, they are colloquially known as "speed." Amphetamine was first synthesized in 1887 in Germany by Romanian chemist Lazăr Edeleanu, who named it phenylisopropylamine. Around the same time, Japanese organic chemist Nagai Nagayoshi isolated ephedrine from the Ephedra sinica plant and later developed a method for ephedrine synthesis. Methamphetamine was synthesized from ephedrine in 1893 by Nagayoshi. Neither drug had a pharmacological use until 1934, when Smith, Kline and French began selling amphetamine as an inhaler under the trade name Benzedrine for congestion.During World War II, amphetamine and methamphetamine were used extensively by Allied and Axis forces for their stimulant and performance-enhancing effects. As the addictive properties of the drugs became known, governments began to place strict controls on the sale of the drugs. During the early 1970s in the United States, amphetamine became a schedule II controlled substance under the Controlled Substances Act. Despite strict government controls, amphetamine and methamphetamine have been used (legally or illegally) by individuals from a variety of backgrounds for a variety of purposes.Due to the large underground market for these drugs, they are often illegally synthesized by clandestine chemists, trafficked, and sold on the black market. Based on drug and drug precursor seizures, illicit amphetamine production and trafficking is much less prevalent than that of methamphetamine.Hydrogen isotope biogeochemistry
Hydrogen isotope biogeochemistry is the scientific study of biological, geological, and chemical processes in the environment using the distribution and relative abundance of hydrogen isotopes. There are two stable isotopes of hydrogen, protium 1H and deuterium 2H, which vary in relative abundance on the order of hundreds of permil. The ratio between these two species can be considered the hydrogen isotopic fingerprint of a substance. Understanding isotopic fingerprints and the sources of fractionation that lead to variation between them can be applied to address a diverse array of questions ranging from ecology and hydrology to geochemistry and paleoclimate reconstructions. Since specialized techniques are required to measure natural hydrogen isotope abundance ratios, the field of hydrogen isotope biogeochemistry provides uniquely specialized tools to more traditional fields like ecology and geochemistry.Isotopic signature
An isotopic signature (also isotopic fingerprint) is a ratio of non-radiogenic 'stable isotopes', stable radiogenic isotopes, or unstable radioactive isotopes of particular elements in an investigated material. The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry against an isotopic reference material. This process is called isotope analysis.Phellodon
Phellodon is a genus of tooth fungi in the family Bankeraceae. Species have small- to medium-sized fruitbodies with white spines on the underside from which spores are released. All Phellodon have a short stalk or stipe, and so the genus falls into the group known as "stipitate hydnoid fungi". The tough and leathery flesh usually has a pleasant, fragrant odor, and develops a cork-like texture when dry. Neighboring fruitbodies can fuse together, sometimes producing large mats of joined caps. Phellodon species produce a white spore print, while the individual spores are roughly spherical to ellipsoid in shape, with spiny surfaces.
The genus, with about 20 described species, has a distribution that includes to Asia, Europe, North America, South America, Australia, and New Zealand. About half of the species are found in the southeastern United States, including three species added to the genus in 2013–14. Several Phellodon species were placed on a preliminary Red List of threatened British fungi because of a general decline of the genus in Europe. Species grow in a symbiotic mycorrhizal association with trees from the families Fagaceae (beeches and oaks) and Pinaceae (pines). Accurate DNA-based methods have been developed to determine the presence of Phellodon species in the soil, even in the extended absence of visible fruitbodies. Although Phellodon fruitbodies are considered inedible due to their fibrous flesh, the type species, P. niger, is used in mushroom dyeing.Phellodon niger
Phellodon niger, commonly known as the black tooth, is a species of tooth fungus in the family Bankeraceae, and the type species of the genus Phellodon. It was originally described by Elias Magnus Fries in 1815 as a species of Hydnum. Petter Karsten included it as one of the original three species when he circumscribed Phellodon in 1881. The fungus is found in Europe and North America, although molecular studies suggest that the North American populations represent a similar but genetically distinct species.Reference materials for stable isotope analysis
Isotopic reference materials are compounds (solids, liquids, gasses) with well-defined isotopic compositions and are the ultimate sources of accuracy in mass spectrometric measurements of isotope ratios. Isotopic references are used because mass spectrometers are highly fractionating. As a result, the isotopic ratio that the instrument measures can be very different from that in the sample's measurement. Moreover, the degree of instrument fractionation changes during measurement, often on a timescale shorter than the measurement's duration, and can depend on the characteristics of the sample itself. By measuring a material of known isotopic composition, fractionation within the mass spectrometer can be removed during post-measurement data processing. Without isotope references, measurements by mass spectrometry would be much less accurate and could not be used in comparisons across different analytical facilities. Due to their critical role in measuring isotope ratios, and in part, due to historical legacy, isotopic reference materials define the scales on which isotope ratios are reported in the peer-reviewed scientific literature.
Isotope reference materials are generated, maintained, and sold by the International Atomic Energy Agency (IAEA), the National Institute of Standards and Technology (NIST), the United States Geologic Survey (USGS), the Institute for Reference Materials and Measurements (IRMM), and a variety of universities and scientific supply companies. Each of the major stable isotope systems (hydrogen, carbon, oxygen, nitrogen, and sulfur) has a wide variety of references encompassing distinct molecular structures. For example, nitrogen isotope reference materials include N-bearing molecules such ammonia (NH3), atmospheric dinitrogen (N2), and nitrate (NO3−). Isotopic abundances are commonly reported using the δ notation, which is the ratio of two isotopes (R) in a sample relative to the same ratio in a reference material, often reported in per mille (‰) (equation below). Reference material span a wide range of isotopic compositions, including enrichments (positive δ) and depletions (negative δ). While the δ values of references are widely available, estimates of the absolute isotope ratios (R) in these materials are seldom reported. This article aggregates the δ and R values of common and non-traditional stable isotope reference materials.
SIRA may refer to:
Stable Isotope Ratio Analysis
Section 115 Reform Act of 2006Stable nuclide
Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes.
The 80 elements with one or more stable isotopes comprise a total of 253 nuclides that have not been known to decay using current equipment (see list at the end of this article). Of these elements, 26 have only one stable isotope; they are thus termed monoisotopic. The rest have more than one stable isotope. Tin has ten stable isotopes, the largest number of isotopes known for an element.