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Anthropometry is defined as the scientific study of the human body measurements and proportions. These studies are generally used by clinicians and pathologists for adequate assessments of the growth and development of the fetus at any specific point of gestational maturity. Fetal height, fetal weight, head circumferen...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
range can be specified like 90 to 100 grams. This number of variations applies to all other anthropometric measurements. Often, the scientific world cover up their ignorance by stating that the rate of growth of particular human fetus depends on its intrinsic growth potential and environment provided by the normal moth...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
in Calcutta between 1977 and 1987 under the supervision of K.L.Mukherjee, a stalwart in the field of medical biochemistry in Institute of Post Graduate Medical Education and Research. The researchers divided the fetuses into 6 groups consisting of A, B, C, D, E and F with a difference of 4 weeks of gestation period amo...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
lung is known to expand and contract in the last phase of development. Both the weight of the right and left lungs are normally assessed at different periods of gestation and is expressed as a function of the total body weight. An irregular graph was observed by K.L.Mukherjee and his group instead of the standard norma...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
organ. After the 10th week of gestation, the kidney grows at a much rapid rate than the adrenal glands. Hence with an increase in gestational time, i.e. by the 12th week of gestation, both the kidneys and adrenal glands measure the same. Post 12 weeks the kidneys measure more than the adrenal glands. However, the Adren...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
gram of body weight. This decline was however not maintained uniformly. == Growth of the Human fetal ovaries == A steep decline in the ovarian weight in the early gestational period was observed though it was not a uniformly maintained decline. With increase in the gestational time, progressive weight of the ovaries wa...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
Conclusion == Growth and development throughout the fetal life are two most important factors which determine the growth rate of each individual and their specific organs. This process of maturation and development of the organs are observed in postnatal life also. With an increase in gestational time, the fetal organs...	{ "page_id": 51115674, "title": "Anthropometric measurement of the developing fetus" }
Micro heat exchangers, Micro-scale heat exchangers, or microstructured heat exchangers are heat exchangers in which (at least one) fluid flows in lateral confinements with typical dimensions below 1 mm. The most typical such confinement are microchannels, which are channels with a hydraulic diameter below 1 mm. Microch...	{ "page_id": 6157978, "title": "Micro heat exchanger" }
classical investigations of single channel heat transfer to more applied investigations in parallel micro-channel and micro scale plate fin heat exchangers. Recent work in the field has focused on the potential of two-phase flows at the micro-scale. == Classification == Just like "conventional" or "macro scale" heat ex...	{ "page_id": 6157978, "title": "Micro heat exchanger" }
The spin Nernst effect is a phenomenon of spin current generation caused by the thermal flow of electrons or magnons in condensed matter. Under a thermal drive such as temperature gradient or chemical potential gradient, spin-up and spin-down carriers can flow perpendicularly to the thermal current and towards opposite...	{ "page_id": 55965344, "title": "Spin Nernst Effect" }
Data augmentation is a statistical technique which allows maximum likelihood estimation from incomplete data. Data augmentation has important applications in Bayesian analysis, and the technique is widely used in machine learning to reduce overfitting when training machine learning models, achieved by training models o...	{ "page_id": 51443362, "title": "Data augmentation" }
performance. The evolution of this practice has introduced a broad spectrum of techniques, including geometric transformations, color space adjustments, and noise injection. === Geometric Transformations === Geometric transformations alter the spatial properties of images to simulate different perspectives, orientation...	{ "page_id": 51443362, "title": "Data augmentation" }
- Zanini, et al. noted that it is possible to use a generative adversarial network (in particular, a DCGAN) to perform style transfer in order to generate synthetic electromyographic signals that corresponded to those exhibited by sufferers of Parkinson's Disease. The approaches are also important in electroencephalogr...	{ "page_id": 51443362, "title": "Data augmentation" }
focus on the field of deep learning, more specifically on the ability of generative models to create artificial data which is then introduced during the classification model training process. In 2018, Luo et al. observed that useful EEG signal data could be generated by Conditional Wasserstein Generative Adversarial Ne...	{ "page_id": 51443362, "title": "Data augmentation" }
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of void space accessible from the...	{ "page_id": 19461794, "title": "Porosity" }
is the total or bulk volume of material, including the solid and void components. Both the mathematical symbols ϕ {\displaystyle \phi } and n {\displaystyle n} are used to denote porosity. Porosity is a fraction between 0 and 1, typically ranging from less than 0.005 for solid granite to more than 0.5 for peat and clay...	{ "page_id": 19461794, "title": "Porosity" }
form may be used: ϕ = 1 − ρ bulk ρ particle {\displaystyle \phi =1-{\frac {\rho _{\text{bulk}}}{\rho _{\text{particle}}}}} A mean normal particle density can be taken as approximately 2.65 g/cm3 (silica, siliceous sediments or aggregates), or 2.70 g/cm3 (calcite, carbonate sediments or aggregates), although a better es...	{ "page_id": 19461794, "title": "Porosity" }
the pores (where all water flow takes place), drastically reducing porosity and hydraulic conductivity, while only being a small fraction of the total volume of the material. For tables of common porosity values for earth materials, see the "further reading" section in the Hydrogeology article. === Porosity of rocks ==...	{ "page_id": 19461794, "title": "Porosity" }
harkens back to the relative force required to pull a tillage implement through the clayey soil at field moisture content as compared to sand. Porosity of subsurface soil is lower than in surface soil due to compaction by gravity. Porosity of 0.20 is considered normal for unsorted gravel size material at depths below t...	{ "page_id": 19461794, "title": "Porosity" }
porosity) Refers to the fraction of the total volume in which fluid flow is effectively taking place and includes catenary and dead-end (as these pores cannot be flushed, but they can cause fluid movement by release of pressure like gas expansion) pores and excludes closed pores (or non-connected cavities). This is ver...	{ "page_id": 19461794, "title": "Porosity" }
less than visual porosity, by an amount that depends on the constriction of holes. == Die casting porosity == Casting porosity is a consequence of one or more of the following: gasification of contaminants at molten-metal temperatures; shrinkage that takes place as molten metal solidifies; and unexpected or uncontrolle...	{ "page_id": 19461794, "title": "Porosity" }
non-mercury intrusion techniques have been developed due to toxicological concerns, and the fact that mercury tends to form amalgams with several metals and alloys). Gas expansion method. A sample of known bulk volume is enclosed in a container of known volume. It is connected to another container with a known volume w...	{ "page_id": 19461794, "title": "Porosity" }
magnetic resonance – (NMR cryoporometry) or measuring the amplitude of neutron scattering from the imbibed crystalline or liquid phases – (ND cryoporometry). == See also == Void ratio Petroleum geology Poromechanics Bulk density Particle density (packed density) Packing density Void (composites) Coherent diffraction im...	{ "page_id": 19461794, "title": "Porosity" }
The molecular formula C7H5ClO3 (molar mass: 172.56 g/mol) may refer to: meta-Chloroperoxybenzoic acid Chlorosalicylic acid	{ "page_id": 24376996, "title": "C7H5ClO3" }
Staged reforming is a thermochemical process to convert organic material or bio waste such as wood, dung or hay into combustible gases containing methane, carbon monoxide and hydrogen. The single-stage reforming of bio materials results in high dust and tar yields in the produced gas restricting its use, hence the use ...	{ "page_id": 19986090, "title": "Staged reforming" }
Antitranspirants are compounds applied to the leaves of plants to reduce transpiration. They are used on Christmas trees, on cut flowers, on newly transplanted shrubs, and in other applications to preserve and protect plants from drying out too quickly. They have also been used to protect leaves from salt burn and fung...	{ "page_id": 718507, "title": "Antitranspirant" }
Transition state analogs (transition state analogues), are chemical compounds with a chemical structure that resembles the transition state of a substrate molecule in an enzyme-catalyzed chemical reaction. Enzymes interact with a substrate by means of strain or distortions, moving the substrate towards the transition s...	{ "page_id": 8124077, "title": "Transition state analog" }
more common natural substrate. Kinetic isotope effect values are a ratio of the turnover number and include all steps of the reaction. Intrinsic kinetic isotope values stem from the difference in the bond vibrational environment of an atom in the reactants at ground state to the environment of the atom's transition sta...	{ "page_id": 8124077, "title": "Transition state analog" }
carbon (see in the diagram in this section), the transition state structure can be defined by early or late dissociation stage. Based on the finding of different transition state structures, Schramm and coworkers designed two transition state analogues mimicking the early and late dissociative transition state. The ear...	{ "page_id": 8124077, "title": "Transition state analog" }
== References ==	{ "page_id": 8124077, "title": "Transition state analog" }
This is a list of contributors to the mathematical background for general relativity. For ease of readability, the contributions (in brackets) are unlinked but can be found in the contributors' article. == B == Luigi Bianchi (Bianchi identities, Bianchi groups, differential geometry) == C == Élie Cartan (curvature comp...	{ "page_id": 2422456, "title": "Contributors to the mathematical background for general relativity" }
Glomalin is a hypothetical glycoprotein produced abundantly on hyphae and spores of arbuscular mycorrhizal (AM) fungi in soil and in roots. Glomalin was proposed in 1996 by Sara F. Wright, a scientist at the USDA Agricultural Research Service, but it was not isolated and described yet. The name comes from Glomerales, a...	{ "page_id": 2881211, "title": "Glomalin" }
using that method. == Description == Based on her extraction, Wright thinks the "glomalin molecule is a clump of small glycoproteins with iron and other ions attached... glomalin contains from 1 to 9% tightly bound iron.... We've seen glomalin on the outside of hyphae, and we believe this is how the hyphae seal themsel...	{ "page_id": 2881211, "title": "Glomalin" }
30 percent of the soil carbon where mycorrhizal fungi is present. The highest levels of GRSP were found in volcanic soils of Hawaii and Japan. Concentrations of glomalin in soil were correlated with the primary productivity of an ecosystem. A strong correlation has been found between GRSP and soil aggregate water stabi...	{ "page_id": 2881211, "title": "Glomalin" }
Hydrogen isotope biogeochemistry (HIBGC) is the scientific study of biological, geological, and chemical processes in the environment using the distribution and relative abundance of hydrogen isotopes. Hydrogen has two stable isotopes, protium 1H and deuterium 2H, which vary in relative abundance on the order of hundre...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
component. The work of Luis Walter Alvarez and Robert Cornog first isolated 3H and reversed Rutherford's incorrect notion. Alvarez reasoned that tritium was radioactive, but did not measure the half-life, though calculations at the time suggested >10 years. At the end of World War II, physical chemist Willard Libby det...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
position-specific isotope compositions and comprehending biosynthetic pathways. Tritium is also used in NMR, as it is the only nucleus more sensitive than 1H, generating very large signals. However, tritium's radioactivity discouraged many studies of 3H-NMR. While tritium's radioactivity discourages use in spectroscopy...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
relationship between rainwater's hydrogen and oxygen isotope ratios. The linear correlation between the two heavy isotopes occurs worldwide and is called the global meteoric water line. By the late 1960s, the focus of hydrogen isotopes shifted away from water and toward organic molecules. Plants use water to form bioma...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
possible to look at smaller samples with more precision. Hydrogen isotope applications quickly emerged in petroleum geochemistry by measuring oil, paleoclimatology by observing lipid biomarkers, and ecology by constructing trophic dynamics. Advances are underway in the clumped-isotope composition of methane after devel...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
as isotope ratio 2R or fractional abundance 2F defined as: R 2 = H 2 H 1 {\displaystyle {\ce {^2R\ =\ {\frac {^2H}{^1H}}}}} and F 2 = H 2 H 1 + H 2 {\displaystyle {\ce {^{2}F\ =\ {\frac {^{2}H}{{^{1}H}+{^{2}H}}}}}} where xH is amount of isotope xH. Fractional abundance is equivalent to mole fraction, and yields atom pe...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
do not vary greatly from one another the α value is often very close to unity. A related measure called epsilon (ε) is often used which is given simply by: ϵ A / B = α A / B − 1 {\displaystyle \epsilon _{A/B}=\alpha _{A/B}-1} These values are often very close to zero, and are reported as per mill values by multiplying ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
( R std ) [ ( δ A − δ B ) / 2 ] 2 {\displaystyle \delta _{\text{error}}=(R_{\text{std}})[(\delta _{A}-\delta _{B})/2]^{2}} This error is quite small for nearly all mixing of naturally occurring isotope values, even for hydrogen which can have quite large natural variations in δ values. The estimation is usually avoided...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
the reactant and product in a chemical reaction. This is known as the kinetic isotope effect (KIE). A classic example of KIE is the DHR difference in the equilibrium between H2O and H2 which can have an α value of as much as 3–4. === Isotope ratio as tracer for fingerprint === In many areas of study the origin of a che...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
Bang nucleosynthesis (BBN). As protons and neutrons combined, helium-4 was produced with a deuterium intermediate. Alpha reactions with 4He produce many of the larger elements that dominate today's Solar System. However, before the universe cooled, high-energy photons destroyed any deuterium, preventing larger element ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
the same state, collections of bosons behave very differently than fermions at colder temperatures. As bosons are cooled and relaxed to the lowest energy state, phenomena like superfluidity and superconductivity occur. === Kinetic and equilibrium isotope effects === Isotopes differ by number of neutrons, which directly...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
form, where k is the spring constant and h is the Planck constant. E n = ℏ k μ ( n + 1 2 ) . {\displaystyle E_{n}=\hbar {\sqrt {k \over \mu }}\left(n+{1 \over 2}\right).} The effects of this energy distribution manifest in the kinetic isotope effect (KIE) and the equilibrium isotope effect. In a reversible reaction, un...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
if they represent exchange with water or mineral hydrogen near by. Research in this area is still inconclusive in regards to rates of exchange, but it is generally understood that hydrogen exchange complicates the preservation of information in isotope studies. ==== Rapid exchange ==== Hydrogen atoms easily separate fr...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
hydrogen. This is due to the increasing stability of associated carbocations. Primary carbocations are considered too unstable to exist and have never been isolated in an FT-ICR spectrometer. On the other hand, tertiary carbocations are relatively stable and are often intermediates in organic chemistry reactions. This ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
of water, non-polar molecules like oils and lipids, have gaseous counterparts enriched with deuterium relative to the liquid. This is thought to be associated with the polarity from hydrogen bonding in water that does not interfere in long-chain hydrocarbons. == Observed variations in isotope abundance == Due to physic...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
the range of 0‰ to −10‰. The estimates of δD for different parts of the ocean across the world are shown on the map. ==== Ice caps ==== Typical δDs for ice sheets in the polar regions range from around −400‰ to −300‰ (‰SMOW). Ice caps' δDs are affected by distance from open ocean, latitude, atmospheric circulation, and...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
of around −30 ~ −150‰ in the northern hemisphere and −30~+30‰ over land areas of the southern hemisphere. In North America, the δD of average monthly precipitation across regions is lower in January (ranging up to around −300‰ in Canada) than in July (up to around −190‰). The overall mean precipitation is determined by...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
algae ==== The factors affecting δD of algal lipids are: δD of water, algal species (up to 160%), lipid type (up to 170%), salinity (+0.9±0.2% per PSU), growth rate (0 ~ −30% per day) and temperature (−2 ~ −8% per °C). In a study by Zhang et al. (2009), the δDs of fatty acids in Thalassiosira pseudonana chemostat cultu...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
that Xw = 1. The isotopic fractionation between lipids and methane (αl/m) is 0.94 for fatty acids and 0.79 for isoprenoid lipids. The isotopic fractionation between lipids and water (αl/w) is 0.95 for fatty acids and 0.85 for isoprenoid lipids. For plants and algae, the isotopic fractionation between lipids and methane...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
phosphates and interconversion between fructose-6-phosphate and glucose-6-phosphate. These cellular processes promote the exchange between organic H and H2O within the plant tissues leading to around 158‰ of D-enrichment of those exchanged sites. The δD of C3 plants such as sugar beet, orange and grape ranges from −132...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
proteins. The average δD for Chironomid and fish protein was estimated to be in the range of −128‰ to +203‰. Most hydrogen in heterotrophic tissues comes from water not from diet sources, but the proportion coming from water varies. In general, hydrogen from water is transferred to NADPH and then taken up to the tissue...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
than acetogenic (n-alkyl) lipids with more negative δDs. ‡ Enrichment relative to water === Geosphere === ==== Oil ==== Source: Oil samples from northeast Japan: from −130‰ to around −110‰ with higher maturity. Oil samples from Portiguar Basin: −90‰ (lancustrine environment), −120‰ to –135‰ (marine-evaporitic environme...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
significant external forces are applied under constant temperature and pressure. The following is an empirically determined equation for estimating the D/H fractionation factor: 1000 In αkaolinite-water = −2.2 × 106 × T−2 − 7.7. The δDs vs. ‰SMOW for hydrogen minerals found in mantle, metamorphic rock, shales, marine c...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
~8 × 10−4 respectively. The DHRs of Uranus and Neptune are larger than that of protosolar reservoir by a factor of ~3 due to their deuterium-rich icy cores. The DHRs for comets are much larger than the values for the planets in the Solar System with δD of around 1000‰. The HICs in the galaxy and the Solar System are sh...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
offline preparation procedure is very time-consuming and complicated. It also requires a large sample (several 100 mg). Thus, online preparation based on combustion/reduction coupled with the subsequent continuous flow-IRMS (CF-IRMS) system has been more often used nowadays. Chromium reduction or high temperature conve...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
liquid sample recently can also be measured in TC/EA-IRMS system by adapting an autosampler for liquids. The drawback of TC/EA is the relatively big sample size (~ mg), which is smaller than offline combustion/reduction but larger than GC/pyrolysis. It cannot separate different compounds as GC/pyrolysis does and thus o...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
GC/pyrolysis method for HIC measurement is that it can separate different compounds in the samples. It requires the smallest sample size (typically ~200 ng) relative to other methods and has a high precision of 1~5 ‰. But this method is relatively slow and limited to the samples which can be applied in GC system. === L...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
be measured. And coexisting organic compounds (i.e. ethanol) could interfere with the optical light absorption features of water, resulting in cross-contamination. === SNIF-NMR === 2H-Site-specific Natural Isotope Fractionation-Nuclear Magnetic Resonance (2H-SNIF-NMR) is a type of NMR specialized in measuring the 2H co...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
and Forensics") When measuring sugar compounds, a timesaving strategy is to convert them into ethanol through fermentation because 2H-SNIF NMR for ethanol is well established. Several studies have proved that hydrogen isotopes on the methyl and methylene position of the resulting ethanol is not affected by either ferme...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
and analyzing isotopologues of an intact organic molecule of interest rather than its products of pyrolysis or conversion. However, it does not work for natural abundance hydrogen isotopes because conventional mass spectrometers do not have enough mass-resolving power to measure the 13C/D isotopologues of intact organi...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
type of instruments includes high cost, and standardization difficulty. Also, studying site-specific isotopes with mass spectrometry is less straightforward and needs more constraints than the SNIF-NMR method, and can only distinguish isotopologues but not isotopomers. == Hydrologic cycle == === Isotope fractionation i...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
ε l − v = − 2.0667 − 0.4156 × 1000 T ( K ) + 1.137 × 10 6 T ( K ) 2 {\displaystyle ^{18}\varepsilon _{l-v}=-2.0667-0.4156\times {1000 \over T(K)}+1.137\times {10^{6} \over T(K)^{2}}} (‰) The amount of liquid-vapor equilibrium fractionation for hydrogen isotopes is about 8x that of oxygen isotopes at Earth surface tempe...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
isotope ratio in the remaining water vapor after some condensation, f is the fraction of water vapor remaining in the air, and α is the liquid-vapor equilibrium fractionation factor (α=1+ε). The isotopic composition of the resulting precipitation (Rp) can be derived from the composition of the remaining vapor: R p / R ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
a different slope and intercept from the GMWL, due to differences in humidity and evaporation intensity at different places. Hydrogen and oxygen isotopes in water thus serve as an excellent tracer of the hydrological cycle both globally and locally. === Water isotopes and climate === Based on the processes that fractio...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
process; (2) A small amount of rainfall is more likely to be influenced by evaporation and exchange with surrounding moisture, which tend to make it more isotopically enriched. At low latitudes, the amount effect for δ18O is around −1.6‰/100mm precipitation increase at island stations, and −2.0‰/100mm at continental st...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
generally be treated as a two-endmember mixing problem, a base-flow endmember (mainly ground water recharge) and an overland-flow endmember (mainly storm events). The isotope data suggest that the long-term integrated base-flow endmember is more important in most rivers, even during peak flows in summer. Systematic riv...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
stable isotope-temperature correlation caused by the history of the air masses from which the snow formed. Ice cores in Greenland and Antarctica can be thousands of meters thick and record snow isotopic composition of the past few glacial-interglacial cycles. Ice cores can be dated by layer counting on the top and ice ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
interglacials, suggesting a role of greenhouse gases in regulating global climate; (3) Antarctic air temperature and greenhouse gas concentration changes precede global ice volume and Greenland air temperature changes during glacial terminations, and greenhouse gases may be an amplifier of insolation forcing during gla...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
not exchangeable on experimental timescales. By this criterion, lipids are a much better subject for hydrogen isotope studies than sugars or amino acids. The net fractionation between source water and lipids is denoted εl/w: ϵ l / w = R l R w − 1 = δ D l + 1 δ D w + 1 − 1 {\displaystyle \epsilon _{l/w}={\frac {R_{l}}{R...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
complicate the cellulose δD proxy. Despite these complications, tree ring δD have been used for paleoclimate reconstructions of the past few millennia. For example, a tree ring cellulose δD records from pine trees in the White Mountains, California shows a 50‰ depletion from 6800 year ago to present. The cooling trend ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
state enrichment of leaf water, εeq is the temperature-dependent equilibrium fractionation between liquid water and vapor, εk is the KIE from diffusion between leaf internal air space and the atmosphere, ΔDv is the leaf/air disequilibrium, ea is atmospheric vapor pressure, and ei is internal leaf vapor pressure. Δ D e ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
pathways. While leaf water is the main source of hydrogen in leaf biomolecules, relatively depleted hydrogen from acetate or NADPH is often added during biosynthesis, and contributes to the HIC of the final molecule. Secondary hydrogen exchange reactions, meaning hydrogenation and dehydrogenation reactions outside of t...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
proxy for reconstructing ancient environments, it is important to be aware of the biases inherent in the sedimentary record. Leaf matter incorporated into sediment is largely deposited in the autumn, so seasonal variations in leaf waxes must be considered accordingly. Furthermore, sediments average leaf waxes over lots...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
that constrain the isotopic composition of sea water. The most notable reconstruction that alkenone δD values are applied to is the salinity of ancient oceans. Both the δDs of sea water and the fractionations associated with hyptophyte biochemistry (εbio) are fairly well understood, so alkenones can be readily used to ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
ancient topography in the Great Basin. The hydrogen and oxygen isotopes of hydrous silicate minerals have since then been used to reconstruct topographic histories in mountain ranges across the world, including the North American Cordillera, the Rocky Mountains, the Himalayas, the European Alps, and Southern Alps in Ne...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
from both inheritance of source material and water as well as fractionations during hydrocarbon generation and subsequent alteration by processes such as isotopic exchange or biodegradation. When interpreting HIC data of sedimentary organic matter one must take all the processes that might have an isotope effect into c...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
have been shown to correlate with paleolatitude. Source correlation. Marine and lacustrine environments are characterized by distinctly different δD values. Many studies have tried to relate measured δD with source types. For methane, D concentration and clumped isotopes is particularly diagnostic of sources. Possible ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
differences in organic composition can also reflect in primary signal. Isotopic exchange, H loss and H addition: This can involve mixing water-derived D with the primary signal. Generation of bitumen, oil and gas: There's a fractionation between the product and kerogen. Research on the Australian basins showed that δD ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
over geologic timescales. The complex composition and chemistry of kerogen complicates the results. Nevertheless, most research on HIC of kerogen show D enrichment with increasing maturity. Type II kerogen (marine derived) from New Albany Shale is reported to have δD rise from −120‰ to −70‰ as vitrinite reflectance inc...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
to −90‰, and a butane δD of −118‰ to −85‰. However, some recent studies show that opposite patterns could also exist, meaning δDmethane > δDethane > δDpropane. This phenomenon is often called 'isotopic reversal' or 'isotopic rollover'. The isotopic order could also be partly reversed, like δDmethane > δDethane < δDprop...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
where the organism lives and substrate concentration also affect isotopic composition: rumen methanogenesis, which occurs in a more closed system and with higher partial pressures of hydrogen, exhibits a greater fractionation (−300 to −400‰) than wetland methanogenesis (−250 to −170‰). Recent advances in analytical che...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
resulting in depletion of 13C and 2H in the products and enrichment in the residual reactants due to KIEs. Yongchun Tang and his colleagues modeled this process based on laboratory-calibrated kinetics data and found that the frequency factor ratio for D/H is 1.07. Moreover, oil is also affected by isotope fractionation...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
be representative of oil as they are the major components. Schimmelmann et al. confirmed that alkane fractions have almost the same DHRs as whole oils. Depending on source material type and maturity, δD of n-alkanes can vary from −100‰ to −180‰. A common phenomenon of various oil and matured rock derived n-alkanes is a...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
to even carbon numbered alkanes is also found in some subset of samples and the reason is unclear at this point. This odd-even effect is also observed in immature clastic sediments. === Ecohydrology === Ecohydrology is concerned with the interaction between ecosystems and water cycling, from measuring the small scale d...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
forests do not just take up water from their roots but acquire a significant proportion of water via stomatal uptake on leaves. Plant water can be used to characterize other plant physiological processes that affect the water cycle; for example, leaf water is widely used for modeling transpiration and water-use efficie...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
carb − ϵ diff ) ( ϵ carb − Δ C 13 ) {\displaystyle {\ce {WUE}}={\frac {(1-\phi )p_{{\ce {CO2}}}}{1.6(\epsilon _{{\ce {carb}}}-\epsilon _{{\ce {diff}}})}}(\epsilon _{{\ce {carb}}}-\Delta {\ce {^{13}C}})} , where Δ 13 C = δ 13 C atm − δ 13 C plant 1 + δ 13 C atm {\displaystyle {\ce {\Delta^{13}C\ =\ {\frac {\delta^{13}C_...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
is technically hard to do, and the resolution seems to be too poor to track small altitudinal changes. 2H is most useful in tracking movement of species between areas with large continental water variation, since species movement can be complicated by the similarity of local water δD between places. For example, source...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
its prey plant is more 2H-enriched than their organic material. Going up trophic levels from prey (plant) to predator (caterpillar) results in an isotopic enrichment. This same trend of enrichment is seen in many other animals - carnivores, omnivores, and herbivores - and seems to follow 15N relative abundances. Carniv...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
more saline waters affect growth rate, the rate of hydrogen exchange, and evaporation rate. All of these factors influence lipid δD upon hydrogen being incorporated into biomass. In coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica, alkenone δD has been found to correlate strongly to organism growth rate div...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
occurred in oil reservoirs in China, and studies on pure cultures of n-alkane degrading organisms have shown a chain-length dependence on the amount of hydrogen isotope fractionation during degradation. Additional studies have also shown hydrogen isotope effects in the degradation of methyl tert-butyl ether and toluene...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
==== Foods, flavorings and scents are often sold with the guarantee that chemical additives come from natural sources. This claim becomes hard to test when the chemical compound has a known structure and is readily synthesized in a lab. Authentication of claims about the origins of these chemicals has made good use of ...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
with measurements of other isotope ratios. In an early study on the stable isotope compositions of tropicamide, hydrocortisone, quinine and tryptophan; carbon, nitrogen, oxygen and hydrogen stable isotopes were analyzed by EA-IRMS; clear distinctions were able to be made between manufacturers and even batches of the dr...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
different sources or production mechanisms. The same combination of stable isotopes with the addition of δ18O was applied to heroin and associated packaging and could successfully distinguish between different samples. Analysis using deuterium NMR was also able to shed light on the origin and processing of both cocaine...	{ "page_id": 50525886, "title": "Hydrogen isotope biogeochemistry" }
The Aza-Wittig reaction or is a chemical reaction of a carbonyl group with an aza-ylide, also known as an iminophosphorane (R3P=NR'). Aza-Wittig reactions are most commonly used to convert aldehydes and ketones to the corresponding imines. The conversion has also been practiced in an intramolecular sense, which is comm...	{ "page_id": 77002430, "title": "Aza-Wittig reaction" }
A Hughes–Ingold symbol describes various details of the reaction mechanism and overall result of a chemical reaction. For example, an SN2 reaction is a substitution reaction ("S") by a nucleophilic process ("N") that is bimolecular ("2" molecular entities involved) in its rate-determining step. By contrast, an E2 react...	{ "page_id": 62256831, "title": "Hughes–Ingold symbol" }
Michael Escott Ruse (21 June 1940 – 1 November 2024) was a British-born Canadian philosopher of science who specialised in the philosophy of biology and worked on the relationship between science and religion, the creation–evolution controversy, and the demarcation problem within science. Ruse began his career teaching...	{ "page_id": 1439425, "title": "Michael Ruse" }

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