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In 1997, several Georgian soldiers suffered radiation poisoning and burns. They were eventually traced back to training sources left abandoned, forgotten, and unlabeled after the dissolution of the Soviet Union. One was a caesium-137 pellet in a pocket of a shared jacket that released about 130,000 times the level of background radiation at 1 meter distance. | 1 | Fission Products + Nuclear Fission |
Trace concentrations of unstable isotopes of some mononuclidic elements are found in natural samples. For example, beryllium-10 (Be), with a half-life of 1.4 million years, is produced by cosmic rays in the Earth's upper atmosphere; iodine-129 (I), with a half-life of 15.7 million years, is produced by various cosmogenic and nuclear mechanisms; caesium-137 (Cs), with a half-life of 30 years, is generated by nuclear fission. Such isotopes are used in a variety of analytical and forensic applications. | 0 | Isotopes |
In archaeological studies, stable isotope ratios have been used to track diet within the time span formation of analyzed tissues (10–15 years for bone collagen and intra-annual periods for tooth enamel bioapatite) from individuals; "recipes" of foodstuffs (ceramic vessel residues); locations of cultivation and types of plants grown (chemical extractions from sediments); and migration of individuals (dental material). | 0 | Isotopes |
Nitrogen isotopes indicate the trophic level position of organisms (reflective of the time the tissue samples were taken). There is a larger enrichment component with δN because its retention is higher than that of N. This can be seen by analyzing the waste of organisms. Cattle urine has shown that there is a depletion of N relative to the diet. As organisms eat each other, the N isotopes are transferred to the predators. Thus, organisms higher in the trophic pyramid have accumulated higher levels of N ( and higher δN values) relative to their prey and others before them in the food web. Numerous studies on marine ecosystems have shown that on average there is a 3.2‰ enrichment of N vs. diet between different trophic level species in ecosystems. In the Baltic sea, Hansson et al. (1997) found that when analyzing a variety of creatures (such as particulate organic matter (phytoplankton), zooplankton, mysids, sprat, smelt and herring,) there was an apparent fractionation of 2.4‰ between consumers and their apparent prey.
In addition to trophic positioning of organisms, δN values have become commonly used in distinguishing between land derived and natural sources of nutrients. As water travels from septic tanks to aquifers, the nitrogen rich water is delivered into coastal areas. Waste-water nitrate has higher concentrations of N than the nitrate that is found in natural soils in near shore zones. For bacteria, it is more convenient for them to uptake N as opposed to N because it is a lighter element and easier to metabolize. Thus, due to bacteria's preference when performing biogeochemical processes such as denitrification and volatilization of ammonia, N is removed from the water at a faster rate than N, resulting in more N entering the aquifer. N is roughly 10-20‰ as opposed to the natural N values of 2-8‰. The inorganic nitrogen that is emitted from septic tanks and other human-derived sewage is usually in the form of . Once the nitrogen enters the estuaries via groundwater, it is thought that because there is more N entering, that there will also be more N in the inorganic nitrogen pool delivered and that it is picked up more by producers taking up N. Even though N is easier to take up, because there is much more N, there will still be higher amounts assimilated than normal. These levels of δN can be examined in creatures that live in the area and are non migratory (such as macrophytes, clams and even some fish). This method of identifying high levels of nitrogen input is becoming a more and more popular method in attempting to monitor nutrient input into estuaries and coastal ecosystems. Environmental managers have become more and more concerned about measuring anthropogenic nutrient inputs into estuaries because excess in nutrients can lead to eutrophication and hypoxic events, eliminating organisms from an area entirely. | 0 | Isotopes |
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number greatly affects nuclear properties, but its effect on chemical properties is negligible for most elements. Even for the lightest elements, whose ratio of neutron number to atomic number varies the most between isotopes, it usually has only a small effect although it matters in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to affect biology strongly). The term isotopes (originally also isotopic elements, now sometimes isotopic nuclides) is intended to imply comparison (like synonyms or isomers). For example, the nuclides , , are isotopes (nuclides with the same atomic number but different mass numbers), but , , are isobars (nuclides with the same mass number). However, isotope is the older term and so is better known than nuclide and is still sometimes used in contexts in which nuclide might be more appropriate, such as nuclear technology and nuclear medicine. | 0 | Isotopes |
NAIL-MS (short for nucleic acid isotope labeling coupled mass spectrometry) is a technique based on mass spectrometry used for the investigation of nucleic acids and its modifications. It enables a variety of experiment designs to study the underlying mechanism of RNA biology in vivo. For example, the dynamic behaviour of nucleic acids in living cells, especially of RNA modifications, can be followed in more detail. | 0 | Isotopes |
A compound tagged by replacing specific atoms with the corresponding isotopes can facilitate the following mass spectrometry methods:
# Metabolic flux analysis (MFA)
# Stable isotopically labeled internal standards for quantitative analysis | 0 | Isotopes |
Fission chain reactions occur because of interactions between neutrons and fissile isotopes (such as U). The chain reaction requires both the release of neutrons from fissile isotopes undergoing nuclear fission and the subsequent absorption of some of these neutrons in fissile isotopes. When an atom undergoes nuclear fission, a few neutrons (the exact number depends on uncontrollable and unmeasurable factors; the expected number depends on several factors, usually between 2.5 and 3.0) are ejected from the reaction. These free neutrons will then interact with the surrounding medium, and if more fissile fuel is present, some may be absorbed and cause more fissions. Thus, the cycle repeats to give a reaction that is self-sustaining.
Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur. Nuclear weapons, on the other hand, are specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction will lead to an explosive energy release. | 1 | Fission Products + Nuclear Fission |
During the Cold War, the governments of the U.S., the USSR, Great Britain, and China attempted to educate their citizens about surviving a nuclear attack by providing procedures on minimizing short-term exposure to fallout. This effort commonly became known as Civil Defense.
Fallout protection is almost exclusively concerned with protection from radiation. Radiation from a fallout is encountered in the forms of alpha, beta, and gamma radiation, and as ordinary clothing affords protection from alpha and beta radiation, most fallout protection measures deal with reducing exposure to gamma radiation. For the purposes of radiation shielding, many materials have a characteristic halving thickness: the thickness of a layer of a material sufficient to reduce gamma radiation exposure by 50%. Halving thicknesses of common materials include: 1 cm (0.4 inch) of lead, 6 cm (2.4 inches) of concrete, 9 cm (3.6 inches) of packed earth or 150 m (500 ft) of air. When multiple thicknesses are built, the shielding multiplies. A practical fallout shield is ten halving-thicknesses of a given material, such as 90 cm (36 inches) of packed earth, which reduces gamma ray exposure by approximately 1024 times (2). A shelter built with these materials for the purposes of fallout protection is known as a fallout shelter. | 1 | Fission Products + Nuclear Fission |
The Global Meteoric Water Line (GMWL) describes the global annual average relationship between hydrogen and oxygen isotope (oxygen-18 and deuterium) ratios in natural meteoric waters. The GMWL was first developed in 1961 by Harmon Craig, and has subsequently been widely used to track water masses in environmental geochemistry and hydrogeology. | 0 | Isotopes |
Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a fission product produced per fission.
Yield can be broken down by:
# Individual isotope
# Chemical element spanning several isotopes of different mass number but same atomic number.
# Nuclei of a given mass number regardless of atomic number. Known as "chain yield" because it represents a decay chain of beta decay.
Isotope and element yields will change as the fission products undergo beta decay, while chain yields do not change after completion of neutron emission by a few neutron-rich initial fission products (delayed neutrons), with half-life measured in seconds.
A few isotopes can be produced directly by fission, but not by beta decay because the would-be precursor with atomic number one greater is stable and does not decay. Chain yields do not account for these "shadowed" isotopes; however, they have very low yields (less than a millionth as much as common fission products) because they are far less neutron-rich than the original heavy nuclei.
Yield is usually stated as percentage per fission, so that the total yield percentages sum to 200%. Less often, it is stated as percentage of all fission products, so that the percentages sum to 100%. Ternary fission, about 0.2–0.4% of fissions, also produces a third light nucleus such as helium-4 (90%) or tritium (7%). | 1 | Fission Products + Nuclear Fission |
In the event of a large-scale nuclear exchange, the effects would be drastic on the environment as well as directly to the human population. Within direct blast zones everything would be vaporized and destroyed. Cities damaged but not completely destroyed would lose their water system due to the loss of power and supply lines rupturing. Within the local nuclear fallout pattern suburban areas' water supplies would become extremely contaminated. At this point stored water would be the only safe water to use. All surface water within the fallout would be contaminated by falling fission products.
Within the first few months of the nuclear exchange the nuclear fallout will continue to develop and detriment the environment. Dust, smoke, and radioactive particles will fall hundreds of kilometers downwind of the explosion point and pollute surface water supplies. Iodine-131 would be the dominant fission product within the first few weeks, and in the months following the dominant fission product would be strontium-90. These fission products would remain in the fallout dust, resulting in rivers, lakes, sediments, and soils being contaminated with the fallout.
Rural areas' water supplies would be slightly less polluted by fission particles in intermediate and long-term fallout than cities and suburban areas. Without additional contamination, the lakes, reservoirs, rivers, and runoff would be gradually less contaminated as water continued to flow through its system.
Groundwater supplies such as aquifers would however remain unpolluted initially in the event of a nuclear fallout. Over time the groundwater could become contaminated with fallout particles, and would remain contaminated for over 10 years after a nuclear engagement. It would take hundreds or thousands of years for an aquifer to become completely pure. Groundwater would still be safer than surface water supplies and would need to be consumed in smaller doses. Long term, cesium-137 and strontium-90 would be the major radionuclides affecting the fresh water supplies.
The dangers of nuclear fallout do not stop at increased risks of cancer and radiation sickness, but also include the presence of radionuclides in human organs from food. A fallout event would leave fission particles in the soil for animals to consume, followed by humans. Radioactively contaminated milk, meat, fish, vegetables, grains and other food would all be dangerous because of fallout.
From 1945 to 1967 the U.S. conducted hundreds of nuclear weapon tests. Atmospheric testing took place over the US mainland during this time and as a consequence scientists have been able to study the effect of nuclear fallout on the environment. Detonations conducted near the surface of the earth irradiated thousands of tons of soil. Of the material drawn into the atmosphere, portions of radioactive material will be carried by low altitude winds and deposited in surrounding areas as radioactive dust. The material intercepted by high altitude winds will continue to travel. When a radiation cloud at high altitude is exposed to rainfall, the radioactive fallout will contaminate the downwind area below.
Agricultural fields and plants will absorb the contaminated material and animals will consume the radioactive material. As a result, the nuclear fallout may cause livestock to become ill or die, and if consumed the radioactive material will be passed on to humans.
The damage to other living organism as a result to nuclear fallout depends on the species. Mammals particularly are extremely sensitive to nuclear radiation, followed by birds, plants, fish, reptiles, crustaceans, insects, moss, lichen, algae, bacteria, mollusks, and viruses.
Climatologist Alan Robock and atmospheric and oceanic sciences professor Brian Toon created a model of a hypothetical small-scale nuclear war that would have approximately 100 weapons used. In this scenario, the fires would create enough soot into the atmosphere to block sunlight, lowering global temperatures by more than one degree Celsius. The result would have the potential of creating widespread food insecurity (nuclear famine). Precipitation across the globe would be disrupted as a result. If enough soot was introduced in the upper atmosphere the planet's ozone layer could potentially be depleted, affecting plant growth and human health.
Radiation from the fallout would linger in soil, plants, and food chains for years. Marine food chains are more vulnerable to the nuclear fallout and the effects of soot in the atmosphere.
Fallout radionuclides' detriment in the human food chain is apparent in the lichen-caribou-eskimo studies in Alaska. The primary effect on humans observed was thyroid dysfunction. The result of a nuclear fallout is incredibly detrimental to human survival and the biosphere. Fallout alters the quality of our atmosphere, soil, and water and causes species to go extinct. | 1 | Fission Products + Nuclear Fission |
The Chernobyl accident released a large amount of caesium isotopes which were dispersed over a wide area. Cs is an isotope which is of long-term concern as it remains in the top layers of soil. Plants with shallow root systems tend to absorb it for many years. Hence grass and mushrooms can carry a considerable amount of Cs, which can be transferred to humans through the food chain.
One of the best countermeasures in dairy farming against Cs is to mix up the soil by deeply ploughing the soil. This has the effect of putting the Cs out of reach of the shallow roots of the grass, hence the level of radioactivity in the grass will be lowered. Also the removal of top few centimeters of soil and its burial in a shallow trench will reduce the dose to humans and animals as the gamma rays from Cs will be attenuated by their passage through the soil. The deeper and more remote the trench is, the better the degree of protection.
Fertilizers containing potassium can be used to dilute cesium and limit its uptake by plants.
In livestock farming, another countermeasure against Cs is to feed to animals prussian blue. This compound acts as an ion-exchanger. The cyanide is so tightly bonded to the iron that it is safe for a human to consume several grams of prussian blue per day. The prussian blue reduces the biological half-life (different from the nuclear half-life) of the caesium. The physical or nuclear half-life of Cs is about 30 years. Caesium in humans normally has a biological half-life of between one and four months. An added advantage of the prussian blue is that the caesium which is stripped from the animal in the droppings is in a form which is not available to plants. Hence it prevents the caesium from being recycled. The form of prussian blue required for the treatment of animals, including humans is a special grade. Attempts to use the pigment grade used in paints have not been successful. | 1 | Fission Products + Nuclear Fission |
For fission of uranium-235, the predominant radioactive fission products include isotopes of iodine, caesium, strontium, xenon and barium. The threat becomes smaller with the passage of time. Locations where radiation fields once posed immediate mortal threats, such as much of the Chernobyl Nuclear Power Plant on day one of the accident and the ground zero sites of U.S. atomic bombings in Japan (6 hours after detonation) are now relatively safe because the radioactivity has decreased to a low level.
Many of the fission products decay through very short-lived isotopes to form stable isotopes, but a considerable number of the radioisotopes have half-lives longer than a day.
The radioactivity in the fission product mixture is initially mostly caused by short lived isotopes such as I and Ba; after about four months Ce, Zr/Nb and Sr take the largest share, while after about two or three years the largest share is taken by Ce/Pr, Ru/Rh and Pm. Later Sr and Cs are the main radioisotopes, being succeeded by Tc. In the case of a release of radioactivity from a power reactor or used fuel, only some elements are released; as a result, the isotopic signature of the radioactivity is very different from an open air nuclear detonation, where all the fission products are dispersed. | 1 | Fission Products + Nuclear Fission |
Xe has not been detected in Venus's atmosphere. Xe has an upper limit of 10 parts per billion by volume. The absence of data on the abundance of Xe precludes us from evaluating if the abundance of Xe is close to solar values or if there is Xe paradox on Venus. The lack also prevents us from checking if the isotopic composition has been mass dependently fractionated, as in the case of Earth and Mars. | 0 | Isotopes |
On Mars, Xe isotopes in the present atmosphere are mass fractionated relative to their primordial composition from in situ measurement of the Curiosity Rover at Gale Crater, Mars. Paleo-atmospheric Xe trapped in the Martian regolith breccia NWA 11220 is mass-dependently fractionated relative to solar Xe by ~16.2‰. The extent of fractionation is comparable for Mars and Earth, which may be compelling evidence that hydrodynamic escape also occurred in the Mars history. The regolith breccia NWA7084 and the >4 Ga orthopyroxene ALH84001 Martian meteorites trap ancient Martian atmospheric gases with little if any Xe isotopic fractionation relative to modern Martian atmospheric Xe. Alternative models for Mars consider that the isotopic fractionation and escape of Mars atmospheric Xe occurred very early in the planet's history and ceased around a few hundred million years after planetary formation rather than continuing during its evolutionary history | 0 | Isotopes |
The compounds used as isotopic references have a relatively complex history. The broad evolution of reference materials for the hydrogen, carbon, oxygen, and sulfur stable isotope systems are shown in Figure 1. Materials with red text define the primary reference commonly reported in scientific publications and materials with blue text are those available commercially. The hydrogen, carbon, and oxygen isotope scales are defined with two anchoring reference materials. For hydrogen the modern scale is defined by VSMOW2 and SLAP2, and is reported relative to VSMOW. For carbon the scale is defined by either NBS-19 or IAEA-603 depending on the age of the lab, as well as LSVEC, and is reported relative to VPDB. Oxygen isotope ratios can be reported relative to either the VSMOW or VPDB scales. The isotopic scales for sulfur and nitrogen are both defined for only a single anchoring reference material. For sulfur the scale is defined by IAEA-S-1 and is reported relative to VCDT, while for nitrogen the scale is both defined by and reported relative to AIR. | 0 | Isotopes |
The stable isotope composition of amino acids refers to the abundance of heavy and light non-radioactive isotopes of carbon (C and C), nitrogen (N and N), and other elements within these molecules. Amino acids are the building blocks of proteins. They are synthesized from alpha-keto acid precursors that are in turn intermediates of several different pathways in central metabolism. Carbon skeletons from these diverse sources are further modified before transamination, the addition of an amino group that completes amino acid biosynthesis. Bonds to heavy isotopes are stronger than bonds to light isotopes, making reactions involving heavier isotopes proceed slightly slower in most cases. This phenomenon, known as a kinetic isotope effect, gives rise to isotopic differences between reactants and products that can be detected using isotope ratio mass spectrometry. Amino acids are synthesized via a variety of pathways with reactions containing different, unknown isotope effects. Because of this, the C content of amino acid carbon skeletons varies considerably between the amino acids. There is also an isotope effect associated with transamination, which is apparent from the abundance of N in some amino acids.
Because of these properties, amino acid isotopes record useful information about the organisms that produce them. Variations in metabolism between different taxonomical groups give rise to characteristic patterns of C enrichment in their amino acids. This allows the sources of carbon in food webs to be identified. The isotope effect associated with transamination also makes amino acid nitrogen isotopes a useful tool to study the structure of food webs. Repeated transamination by consumers results in a predictable increase in the abundance of N as amino acids are transferred up food chains. Together, these application, among others in ecology, demonstrate the utility of stable isotopes as tracers of environmental processes that are difficult to measure directly. | 0 | Isotopes |
Cadmium is a strong neutron poison and in fact control rods are often made out of cadmium, making the accumulation of cadmium in fuel of particular concern for the maintenance of stable neutron economy. Cadmium is also a chemically poisonous heavy metal, but given the number of neutron absorptions required for transmutation, it is not a high priority target for deliberate transmutation. | 1 | Fission Products + Nuclear Fission |
In April 2011, elevated levels of caesium-137 were also being found in the environment after the Fukushima Daiichi nuclear disasters in Japan. In July 2011, meat from 11 cows shipped to Tokyo from Fukushima Prefecture was found to have 1,530 to 3,200 becquerels per kilogram of Cs, considerably exceeding the Japanese legal limit of 500 becquerels per kilogram at that time. In March 2013, a fish caught near the plant had a record 740,000 becquerels per kilogram of radioactive caesium, above the 100 becquerels per kilogram government limit. A 2013 paper in Scientific Reports found that for a forest site 50 km from the stricken plant, Cs concentrations were high in leaf litter, fungi and detritivores, but low in herbivores. By the end of 2014, "Fukushima-derived radiocaesium had spread into the whole western North Pacific Ocean", transported by the North Pacific current from Japan to the Gulf of Alaska. It has been measured in the surface layer down to 200 meters and south of the current area down to 400 meters.
Cesium-137 is reported to be the major health concern in Fukushima. A number of techniques are being considered that will be able to strip out 80% to 95% of the caesium from contaminated soil and other materials efficiently and without destroying the organic material in the soil. These include hydrothermal blasting. The caesium precipitated with ferric ferrocyanide (Prussian blue) would be the only waste requiring special burial sites. The aim is to get annual exposure from the contaminated environment down to 1 mSv above background. The most contaminated area where radiation doses are greater than 50 mSv/year must remain off limits, but some areas that are currently less than 5 mSv/year may be decontaminated, allowing 22,000 residents to return. | 1 | Fission Products + Nuclear Fission |
For isotopes of elements like carbon and sulfur, the difference in kinetic parameters is too small, and the measurement precision too low, to measure an isotope effect by directly comparing the rates of the monoisotopic and rare isotope substrates. Instead, the two are mixed together using the natural abundance of stable isotopes in molecules. The enzyme is exposed to both isotopes simultaneously and its preference for the light isotope is analyzed by collecting the product of the reaction and measuring its isotope composition. For example, if an enzyme removes a carbon from a molecule by turning it into carbon dioxide, that carbon dioxide product can be collected and measured on an Isotope Ratio Mass Spectrometer for its carbon isotope composition. If the carbon dioxide has less C than the substrate mixture, the enzyme has preferentially reacted with the substrate that has a C at the site that is decarboxylated. In this way, internal competition experiments are also position-specific. If only the CO is measured, then only the isotope effect on the site of decarboxylation is recorded. | 0 | Isotopes |
An isotope of an element contains the same number of protons, but a different number of neutrons, giving it a different mass number than the element found on the periodic table. Isotopes with a large variation in nucleon number will decay into more stable nuclei, and are known as radionuclides or radioisotopes.
The field of nuclear medicine uses radioisotopes to diagnose and treat patients. The radiation and particles emitted by these radioisotopes can be used to weaken or destroy target cells, for example in the case of cancer. For diagnosis, a radioactive dose is given to a patient and its activity can be tracked to study the functionality of a target organ. The tracers used within this process are generally short-lived isotopes.
Diagnostic radiopharmaceuticals are used to examine organ functionality, blood flow, bone growth and other diagnostic procedures. Radioisotopes needed for this procedure must emit gamma radiation with a high energy and short half-life, in order for it to escape the body and decay quickly. There is currently a trend to use cyclotron-produced isotopes as they are becoming more widely available.
Positron emission tomography (PET) is an imaging technique, using radioisotopes also most often produced with a cyclotron. They are injected into the patient, accumulating in the target tissue, and decays through positron emission. The positron annihilates with an electron nearby which results in the emission to two gamma rays (photons) in opposite directions. A PET camera detects these rays and can determine quantitative information about the target tissue.
Therapeutic radiopharmaceuticals are used to destroy or weaken malfunctioning cells, using a radioisotope localised to a specific organ. This process is called radionuclide therapy (RNT), and uses heavy proton radioisotopes (located on the North-West area of the nuclide chart) that decay through beta or alpha emission. | 0 | Isotopes |
The PRoduction of high purity Isotopes by mass Separation for Medical APplication (PRISMAP) is the European medical radionuclide programme, with the goal to provide a sustainable source of high-purity radioisotopes for medicine. The programme brings together 23 beneficiaries from 13 countries, to create a single entry point for the medical isotope user community. The MEDICIS facility provides mass separation of isotopes, which can then be transported to nearby research facilities hosting external researchers to limit long haul transport of the samples. | 0 | Isotopes |
udQM could be possibly formed during a supernova core collapse from conversion of superheavy nuclei. In this environment there is a high density of electrons and electron neutrinos present. The udQM would then end up in neutron stars. udQM nuclides may be detectable in cosmic rays.
A star containing a large proportion of udQM is called a ud quark star (or udQS). Heavy neutron stars may convert into this star type. Whether they do may be verified by detecting binary compact stellar collisions via gravitational waves. | 0 | Isotopes |
Differences in the abundance of isotopes among natural samples are extremely small (almost always below 0.1% or 1 per mille). Nevertheless, these very small differences can record meaningful geological processes. To compare these tiny but meaningful differences, isotope abundances in natural materials are often reported relative to isotope abundances in designated standards, with the delta (δ) notation. The absolute values of Xe isotopes are normalized to atmospheric Xe. Define where i = 124, 126, 128, 129, 131, 132, 134, 136. | 0 | Isotopes |
NAIL-MS is used to study RNA modification mechanisms. Therefore, cells in culture are first fed with stable isotope labeled nutrients and the cells incorporate these into their biomolecules. After purification of the nucleic acids, most often RNA, analysis is done by mass spectrometry. Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of ions. Pairs of chemically identical nucleosides of different stable-isotope composition can be differentiated in a mass spectrometer due to their mass difference. Unlabeled nucleosides can therefore be distinguished from their stable isotope labeled isotopologues. For most NAIL-MS approaches it is crucial that the labeled nucleosides are more than 2 Da heavier than the unlabeled ones. This is because 1.1% of naturally occurring carbon atoms are C isotopes. In the case of nucleosides this leads to a mass increase of 1 Da in ~10% of the nucleosides. This signal would disturb the final evaluation of the measurement.
NAIL-MS can be used to investigate RNA modification dynamics by changing the labeled nutrients of the corresponding growth medium during the experiment. Furthermore, cell populations can be compared directly with each other without effects of purification bias. Furthermore, it can be used for the production of biosynthetic isotopologues of most nucleosides which are needed for quantification by mass spectrometry and even for the discovery of yet unknown RNA modifications. | 0 | Isotopes |
A variety of different instruments can be used to perform position-specific isotope analysis, and each have distinct advantages and drawbacks. Many of them require comparison the sample of interest to a standard of known isotopic composition; fractionation within the instrument and variation of instrumental conditions over time can affect accuracy of individual measurements if not standardized. | 0 | Isotopes |
Isotopes are distinct nuclear species (or nuclides) of the same chemical element. They have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), but differ in nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have similar chemical properties, they have different atomic masses and physical properties.
The term isotope is derived from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by Scottish doctor and writer Margaret Todd in a 1913 suggestion to the British chemist Frederick Soddy, who popularized the term.
The number of protons within the atoms nucleus is called its atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of nucleons (both protons and neutrons) in the nucleus is the atoms mass number, and each isotope of a given element has a different mass number.
For example, carbon-12, carbon-13, and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons so that the neutron numbers of these isotopes are 6, 7, and 8 respectively. | 0 | Isotopes |
Iodine-131 is used for unsealed source radiotherapy in nuclear medicine to treat several conditions. It can also be detected by gamma cameras for diagnostic imaging, however it is rarely administered for diagnostic purposes only, imaging will normally be done following a therapeutic dose. Use of the I as iodide salt exploits the mechanism of absorption of iodine by the normal cells of the thyroid gland. | 1 | Fission Products + Nuclear Fission |
Doubly labeled water is water in which both the hydrogen and the oxygen have been partly or completely replaced (i.e. labeled) with an uncommon isotope of these elements for tracing purposes.
In practice, for both practical and safety reasons, almost all recent applications of the "doubly labeled water" method use water labeled with heavy but non-radioactive forms of each element (deuterium and oxygen-18). In theory, radioactive heavy isotopes of the elements could be used for such labeling; this was the case in many early applications of the method.
In particular, doubly labeled water (DLW) can be used for a method to measure the average daily metabolic rate of an organism over a period of time (often also called the Field metabolic rate, or FMR, in non-human animals). This is done by administering a dose of DLW, then measuring the elimination rates of deuterium and oxygen-18 in the subject over time (through regular sampling of heavy isotope concentrations in body water, by sampling saliva, urine, or blood). At least two samples are required: an initial sample (after the isotopes have reached equilibrium in the body), and a second sample some time later. The time between these samples depends on the size of the animal. In small animals, the period may be as short as 24 hours; in larger animals (such as adult humans), the period may be as long as 14 days.
The method was invented in the 1950s by Nathan Lifson and colleagues at the University of Minnesota. However, its use was restricted to small animals until the 1980s because of the high cost of the oxygen-18 isotope. Advances in mass spectrometry during the 1970s and early 1980s reduced the amount of isotope required, which made it feasible to apply the method to larger animals, including humans. The first application to humans was in 1982, by Dale Schoeller, over 25 years after the method was initially discovered. A complete summary of the technique is provided in a book by British biologist John Speakman. | 0 | Isotopes |
Reference materials are compounds which are carefully calibrated against the primary reference or a calibration material. These compounds allow for isotopic analysis of materials differing in chemical or isotopic composition from the compounds defining the isotopic scales on which measurements are reported. In general these are the materials most researchers mean when they say "reference materials". An example of a reference material is USGS-34, a KNO salt with a δN of -1.8‰ vs. AIR. In this case the reference material has a mutually agreed upon value of δN when measured relative to the primary reference of atmospheric N (Böhlke et al., 2003). USGS-34 is useful because it allows researchers to directly measure the N/N of NO in natural samples against the standard and report observations relative to N without having to first convert the sample to N gas. | 0 | Isotopes |
All biologically active elements exist in a number of different isotopic forms, of which two or more are stable. For example, most carbon is present as C, with approximately 1% being C. The ratio of the two isotopes may be altered by biological and geophysical processes, and these differences can be utilized in a number of ways by ecologists.
The main elements used in isotope ecology are carbon, nitrogen, oxygen, hydrogen and sulfur, but also include silicon, iron, and strontium. | 0 | Isotopes |
Site specific isotope enrichments of NO is measured in the environment to help disentangle microbial sources and sinks in the environment. Different isotopologues of N2O absorb light at different wavelengths. Laser spectroscopy converts these differences as it scans across wavelengths to measure the abundance of N-N-O vs. N-N-O, a distinction that is impossible on other instruments. These measurements have achieved very high precision, down to 0.2 per mille. | 0 | Isotopes |