Knowledge of the evolution of atmospheric carbon dioxide concentrations throughout the Earth's history is important for a
reconstruction of the links between climate and radiative forcing of the Earth's surface temperatures. Although atmospheric
carbon dioxide concentrations in the early Cenozoic era (about 60Myr ago) are widely believed to have been higher than at present,
there is disagreement regarding the exact carbon dioxide levels, the timing of the decline and the mechanisms that are most
important for the control of CO2 concentrations over geological timescales. Here we use the boron-isotope ratios of ancient
planktonic foraminifer shells to estimate the pH of surface-layer sea water throughout the past 60 million years, which can be used
to reconstruct atmospheric CO2 concentrations. We estimate CO2 concentrations of more than 2,000 p.p.m. for the late Palaeocene
and earliest Eocene periods (from about 60 to 52 Myr ago), and ®nd an erratic decline between 55 and 40 Myr ago that may have
been caused by reduced CO2 outgassing from ocean ridges, volcanoes and metamorphic belts and increased carbon burial. Since
the early Miocene (about 24Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more
stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately
15 and 3 Myr ago.

Atmospheric carbon dioxide concentrations over the past 60 million years

Amino acid side chains play fundamental roles in stabilising protein structures and in catalysing enzymatic reactions. These fields are increasingly investigated by infrared spectroscopy at the molecular level. To help the interpretation of the spectra, a review of the infrared absorption of amino acid side chains in H(2)O and 2H(2)O is given. The spectral region of 2600-900cm(-1) is covered.

The infrared absorption of amino acid side chains.

The Commission’s Subcommittee for the Isotopic Composition of the Elements has carried out its biennial review of isotopic compositions, as determined by mass spectrometry and other relevant methods. This involves a critical evaluation of the published literature, element by element, and forms the basis of the Table of Isotopic Compositions of the Elements as Determined by Mass Spectrometry presented here. New guidelines have been used to arrive at the uncertainties on the isotopic abundances and there are numerous changes to the table since it was last published in 1991. Atomic Weights calculated from this table are consistent with Ar(E) values listed in the Table of Standard Atomic Weights 1997.

Isotopic compositions of the elements 1997

Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols

The Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) completed its last update of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2009. That update involved a critical evaluation of the published literature and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The repre- sentative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element A r (E) and its uncertainty U(A r (E)) recommended by CIAAW in 2007.

/pdf/isotopic-compositions-of-the-elements-2009-iupac-technical-3tevgc6uxw.pdf

Isotopic compositions of the elements 2009 (IUPAC Technical Report)

The single-stage separation factors for boron isotopes between an ion-exchange resin and an external solution were determined, using an ion-exchange breakthrough operation. The lighter isotope boron-10 was considerably enriched in the anion-exchange resin phase. The separation factor was very much influenced by the boric acid concentration in the external solution, but not as much influenced by the kind of the anion exchange resin used and operation temperature. The separation factor increased with a decrease in the boric acid concentration of external solution from 1.008 (0.501 mol/l) to 1.016 (0.010 mol/l). The value of the separation factors obtained experimentally were compared with those estimated on the basis of the theory of the two-phase distribution of isotopes.

Fundamental studies on the ion-exchange separation of boron isotopes

Coordination structures for uranyl carboxylate complexes in aqueous solution studied by IR and carbon-13 NMR spectra

Boron isotopic compositions of some boron minerals

Variational transition‐state theory rate constants for the H+H2 reaction and its isotopic analogs at very low temperatures have been calculated using the LSTH potential surface. The Wigner threshold law is found to hold quantitatively below 1 K and to within 34% on average at 5 K. The transition‐state theory rate constants are found to be consistent with the requirements of the Wigner threshold law provided that a tunneling probability having the correct threshold behavior is used in calculating the transmission coefficient. Using these calculated rate constants, decay rates of H and D atoms in solid H2, D2, and HD were estimated and compared with experiment. The good agreement found suggests that these decays occur through quantum mechanical tunneling exchange reactions.

Makoto Okamoto

Papers

Fundamental studies on the ion-exchange separation of boron isotopes

Coordination structures for uranyl carboxylate complexes in aqueous solution studied by IR and carbon-13 NMR spectra

Boron isotopic compositions of some boron minerals

The rate constants for the H+H2 reaction and its isotopic analogs at low temperatures: Wigner threshold law behavior

Boron isotopic composition of fumarolic condensates from some volcanoes in Japanese island arcs