Sentences with phrase «isotope ratio for»

The team then compared the oxygen isotope ratio for each year's wet season from 1990 to 2010 with a cyclone activity index of the average accumulated energy expended, based on factors such as number of cyclones, cyclone strength, size and time on storm track.

The study by Andersen and his colleagues is the first to use the uranium isotope ratio for the examination of igneous rock and apply it to the recycling process in deep Earth.

«And the diagnostic clue is that all of the isotope ratios for neon, argon, krypton, xenon, nitrogen, what have you, look as if they have suffered an escape process in which the lightest isotope escaped preferentially relative to the heavier ones» — a process called fractionation.

To date, we have a full complement of analyses for about three years of growth for one tusk from the Taimir Peninsula of Siberia (the Jarkov mammoth; ca. 20,300 rybp) and growth increment and tusk apatite carbon and oxygen isotope ratios for two to three years of growth from two tusks from Wrangel Island (4,400 and 4,120 year bp).

To date, we have a full complement of analyses for about three years of growth for one tusk from the Taimir Peninsula of Siberia (the Jarkov mammoth; ca. 20,300 rybp) and growth increment and tusk apatite carbon and oxygen isotope ratios for two to three years of growth from two tusks from Wrangel Island (4,400 and 4,120 year bp).

Because the different isotope ratios for the two kinds of plants propagate through the food chain, it is possible determine if the principal diet of a human or other animal consists primarily of C3 plants or C4 plants by measuring the isotopic signature of their collagen and other tissues.

Not exact matches

Gas - source isotope ratio mass spectrometers are a special breed of a class of instruments — mass spectrometers — that are used in many different areas of science, from physics to biomedical science, for the separation of atoms and molecules of different charges and molecular weights.

In some ways, a California company seems an odd choice for an upstate New York scientist who was determined to put down roots, but with a 90 % market share of gas - source isotope ratio mass spectrometers, applying to Thermo Finnigan was pretty much a no - brainer for someone with Burdett's experience, and it worked out.

They also found that the strontium isotope ratio is a sensitive tracer for selenium contamination, one of the major pollutants of mountaintop mining.

Two recent models for the formation of the Moon, one that allows exchange through a silicate atmosphere (top), and another that creates a more thoroughly mixed sphere of a supercritical fluid (bottom), lead to different predictions for potassium isotope ratios in lunar and terrestrial rocks (right).

He realized that the skewed oxygen isotope ratios could be explained if the rock had been exposed to martian air or water for a long period.

The researchers suspected that the ants provide D. major with nutrients in return for shelter To test this idea, they looked at the ratios of different isotopes of carbon and nitrogen in the plant's tissues.

Although scientists know that the tools for reconstructing past climates at polar latitudes are far from perfect, he says, pinning down the relationship between isotope ratios and temperature is essential.

So Hallis and her colleagues went looking for vestiges of the early Earth that might preserve the original hydrogen isotope ratio of the planet.

The ratio between quantities of different isotopes provides the data for an equation that calculates the age.

Later, additional investigation using carbon isotope ratio testing revealed a foreign, prohibited substance as the likely source for the positive test.

Isotope ratios (the ratio of carbon - 13 to carbon - 12, for example) are different in human foods than in the wild plants and animals that black bears naturally eat in Yosemite, partly due to the large amounts of meat and corn - based foods in our diets.

By applying uranium - thorium dating to the corals and measuring ratios of oxygen isotopes in their skeletons, her lab reconstructed ocean temperatures for much of the last 7000 years.

For this work, conducted at the University of Bristol including Morten Andersen (now Earth Science, ETH Zurich) along with researchers from the Durham (UK), Wyoming and Rhode Island (US), used the «fingerprint» carried in the ratio of the two uranium isotopes.

For example, based on the isotope ratios they detected in cow rumen, they calculated that this methane formed at 400 degrees Celsius — impossible, as cow stomachs are typically about 40 C.

The results also have an important consequence for rock compositions — notably the ratios of certain isotopes, Natland says.

Back at their Georgia Tech lab, they analyzed the stalagmites for the ratio of oxygen isotopes contained in samples of calcium carbonate, the material from which the stalagmites were formed.

The most convincing evidence for this, says Jouzel, comes from isotope ratios; ice that has frozen in site has a higher proportion of water molecules containing the heavy form of oxygen, oxygen - 18, than that of ice that has been transported over long distances by weather systems.

As a result, «a wide range of proportions of available prey items» could account for the lions» isotope ratios, including «many or no people, even during the period before they became maneaters».

He notes that the amount of ruthenium - 106 that the French team estimates was emitted — between 1 gram and 4 grams — matches the 30 grams of cerium - 144 required for SOX, given that spent fuel contains the two isotopes in a ratio of about one to 14.

MPI - DING reference glasses for in situ microanalysis: New reference values for element concentrations and isotope ratios

It measures the ratios of several different isotopes that are important for understanding the long - term history of the atmosphere.

«Laser ablation isotope ratio mass spectrometry for enhanced sensitivity and spatial resolution in stable isotope analysis.»

It is most difficult to envision plausible nuclear events that can account for the peculiarities of these abundances, particularly the strange isotope ratios of mercury.

«Scientists use the ratio of the various sulfur isotopes as their strongest evidence for atmospheric oxygen.»

The granite in these bags is destined for isotope ratio measurement at Lawrence Livermore National Laboratory's Center for Accelerator Mass Spectrometry (CAMS...

For instance, radiocarbon dating determines the age of biological remains based on the ratio between the carbon isotopes (atoms of the same element with different numbers of neutrons) carbon - 12 and carbon - 14 it holds - this proportion changes as radioactive carbon - 14 breaks down while stable carbon - 12 does not.

Qualitatively, the slow ventilation is consistent with very saline and very cold deep waters reconstructed for the last glacial maximum (Adkins et al., 2002), as well as low glacial stable carbon isotope ratios (13C / 12C) in the deep South Atlantic.

Another option is to test fossil teeth for the ratio of stable isotopes present for a given element, such as the ratio of carbon C12 to C13.

The Center for Accelerator Mass Spectrometry uses unique and state - of - the - art instrumentation to perform ultrasensitive isotope ratio measurements and ion beam analysis

Trapped gases within the rock may be extracted and analyzed for their isotope ratios to determine where they originated.

Different places in the solar system have different ratios for isotopes.

Scientists are looking for the ratio of those two isotopes in a sample.

This is because plants have a preference for the lighter isotopes (12C vs. 13C); thus they have lower 13C / 12C ratios.

For example check out the paper of Frapier (2005) describing the testing of a method for identifying tropical cyclone events using isotope ratios in the cores of stalagmitFor example check out the paper of Frapier (2005) describing the testing of a method for identifying tropical cyclone events using isotope ratios in the cores of stalagmitfor identifying tropical cyclone events using isotope ratios in the cores of stalagmites.

Now, Hubertus Fischer of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, and colleagues have measured carbon isotope ratios in methane from the whole of the last glacial - interglacial transition (between 20,000 and 10,000 years before present) by analysing ice - cores.

As for the alleged irrefutable evidence that people caused the last century's CO2 increase, the «smoking gun» invoked by one of my critics, Dr. Michael Mann, and his fellow fearmongers at realclimate.com, the claim is based on the idea that the normal ratio of heavy to light carbon — that is, the carbon - 13 isotope to the lighter carbon - 12 isotope, is roughly 1 to 90 in the atmosphere, but in plants there's a 2 percent lower C13 / C12 ratio.

The team examined the neodymium and strontium isotope ratios of the sediments and compared them to the known values for the various geological terranes on land.

As Pat notes, several different isotope ratios lead to the conclusion that humans are largely responsible for the increase.

The group now wants to determine the ratio of nitrogen - 14 and nitrogen - 15 isotopes for individual sources of nitric oxides, including lightning, biomass burning, bacterial «fixing» of nitrogen, and fossil fuel burning.

For decades, scientists studying climate change have measured the oxygen isotope ratio in tree - ring cellulose to determine the ambient temperature and relative humidity of past climates.

The group highlighted the added value of measuring paired coral strontium / calcium ratios (Sr / Ca) and oxygen isotope ratios (δ18O), two key proxies for sea surface temperature that are often referred to as paleothermometers (δ18O also reflects sea surface salinity).

Thus even if more C4 plants are grown, that changes the amounts of 12CO2 which is absorbed vs. 13CO2, but as long as the O2 levels show that the biosphere is a net sink for CO2 (whatever the type), more 12CO2 leaves the atmosphere than 13CO2, compared to the atmospheric isotope ratio.

The net result is that the 14C intake by the oceans is much faster for 14C (despite the slower intake speed) than for 12C or 13C, as the total 14C in the atmosphere will go down until about the same ratio as for the other isotopes, that is 1:1, then a new equilibrium for 14C is reached.

Stable carbon isotope ratios from tree rings record changes in the internal concentration of carbon dioxide and, in the northern Boreal zone, are regarded as a proxy for photosynthetic rate, and therefore summer sunshine.