Diffusion of isotopes in the annual layers of ice sheets

Abstract The annual layering in the Greenland and Antarctic ice sheets revealed by the b 0 record becomes less distinct with depth because of self-diffusion. However, the calculated diffusion rates are loo slow to explain die observations. It is suggested that the presence of veins of liquid water increases the effective diffusion constant by a factor of about 20.

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Diffusion of isotopes in the annual layers of ice sheets

Journal of Glaciology ◽

10.3189/s0022143000001982 ◽

1998 ◽

Vol 44 (148) ◽

pp. 467-468

Author(s):

J. F. Nye

Keyword(s):

Liquid Water ◽

Effective Diffusion ◽

Diffusion Constant ◽

Ice Sheets ◽

Self Diffusion ◽

Diffusion Rates ◽

Antarctic Ice Sheets

AbstractThe annual layering in the Greenland and Antarctic ice sheets revealed by the b 0 record becomes less distinct with depth because of self-diffusion. However, the calculated diffusion rates are loo slow to explain die observations. It is suggested that the presence of veins of liquid water increases the effective diffusion constant by a factor of about 20.

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Water and Deuterium Oxide Permeability through Aquaporin 1: MD Predictions and Experimental Verification

The Journal of General Physiology ◽

10.1085/jgp.200709810 ◽

2007 ◽

Vol 130 (1) ◽

pp. 111-116 ◽

Cited By ~ 31

Author(s):

Artem B. Mamonov ◽

Rob D. Coalson ◽

Mark L. Zeidel ◽

John C. Mathai

Keyword(s):

Deuterium Oxide ◽

Diffusion Constant ◽

Structural Data ◽

Md Simulations ◽

Water Model ◽

Aquaporin 1 ◽

Self Diffusion ◽

Osmotic Permeability ◽

Protein Channels ◽

And Diffusion

Determining the mechanisms of flux through protein channels requires a combination of structural data, permeability measurement, and molecular dynamics (MD) simulations. To further clarify the mechanism of flux through aquaporin 1 (AQP1), osmotic pf (cm3/s/pore) and diffusion pd (cm3/s/pore) permeability coefficients per pore of H2O and D2O in AQP1 were calculated using MD simulations. We then compared the simulation results with experimental measurements of the osmotic AQP1 permeabilities of H2O and D2O. In this manner we evaluated the ability of MD simulations to predict actual flux results. For the MD simulations, the force field parameters of the D2O model were reparameterized from the TIP3P water model to reproduce the experimentally observed difference in the bulk self diffusion constants of H2O vs. D2O. Two MD systems (one for each solvent) were constructed, each containing explicit palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) phospholipid molecules, solvent, and AQP1. It was found that the calculated value of pf for D2O is ∼15% smaller than for H2O. Bovine AQP1 was reconstituted into palmitoyl-oleoyl-phosphatidylcholine (POPC) liposomes, and it was found that the measured macroscopic osmotic permeability coefficient Pf (cm/s) of D2O is ∼21% lower than for H2O. The combined computational and experimental results suggest that deuterium oxide permeability through AQP1 is similar to that of water. The slightly lower observed osmotic permeability of D2O compared to H2O in AQP1 is most likely due to the lower self diffusion constant of D2O.

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A Possible Change in Mass Balance of Greenland and Antarctic Ice Sheets in the Coming Century

Journal of Climate ◽

10.1175/1520-0442(1996)009<2124:apcimb>2.0.co;2 ◽

1996 ◽

Vol 9 (9) ◽

pp. 2124-2135 ◽

Cited By ~ 100

Author(s):

Atsumu Ohmura ◽

Martin Wild ◽

Lennart Bengtsson

Keyword(s):

Mass Balance ◽

Ice Sheets ◽

Antarctic Ice Sheets

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Concluding remarks

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1977.0115 ◽

1977 ◽

Vol 280 (972) ◽

pp. 373-374

Keyword(s):

Lake Sediments ◽

Ice Sheets ◽

The Arctic ◽

Peat Bogs ◽

British Isles ◽

Field Of Study ◽

Great Range ◽

Scientific Disciplines ◽

History Of ◽

Antarctic Ice Sheets

The conclusion of this two day meeting finds us with a very great deal on which we may congratulate ourselves. In the first place there is the extremely large attendance, embracing scientists of all ages, and graced and illuminated by the attendance of many overseas colleagues of experience and distinction. In the second place we have the great range of scientific disciplines that are now applied to our field of study, many now extremely sophisticated, and the corresponding extension of Quaternary Studies into fields of evidence not hitherto exploited. In the early days of palynology of laminated lake sediments one could write of deciphering the ‘annals of the lakes’, but beginning by reading the record of lakes, peat bogs, coastal, fluviatile, glacial and periglacial geology, we have progressed to translating the long and detailed records of the deep oceans, and now the encapsulated history of the Arctic and Antarctic ice sheets. We have been introduced to the marvellous potential of the great CLIMAP Project, and all [biologists in the British Isles at least will now have to consider whether their hypotheses of past biotic history satisfy the new principle that we can all see emerging as ‘McIntyre’s Gate’.

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Silver Self-Diffusion in Al2O3/QE22 Magnesium Alloy Matrix Composite

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.283-286.155 ◽

2009 ◽

Vol 283-286 ◽

pp. 155-160

Author(s):

Ivo Stloukal ◽

Jiří Čermák

Keyword(s):

Magnesium Alloy ◽

Temperature Dependence ◽

Temperature Interval ◽

Matrix Composite ◽

Diffusion Coefficients ◽

Volume Diffusion ◽

Effective Diffusion ◽

Measured Temperature ◽

Alloy Matrix ◽

Self Diffusion

Self-diffusion of 110mAg has been investigated in fiber reinforced QE22 magnesium alloy matrix composite. Short Saffil fibers (97% -Al2O3 + 3% SiO2) were used as reinforcement. The diffusion measurements were carried out in the temperature interval 648 – 728 K by serial sectioning method. The volume diffusion coefficients Dv (alloy without reinforcement) and the effective diffusion coefficients Deff (alloy with reinforcement) were obtained by analysis of the penetration curves. The silver diffusion coefficient in the interface boundary matrix/Saffil Di was also estimated. The temperature dependence of volume diffusion coefficients Dv was compared with previous data measured using 65Zn in the same alloy and with literature data for Zn impurity diffusion in Mg single crystal. It was observed, that the temperature dependence of both Deff and Di was significantly non-linear in the measured temperature interval. This behavior supports previous observations with zinc diffusion in the same alloy.

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Airborne infection in a fully air-conditioned hospital: III. Transport of gaseous and airborne particulate material along ventilated passageways

Journal of Hygiene ◽

10.1017/s0022172400047057 ◽

1975 ◽

Vol 75 (1) ◽

pp. 45-56 ◽

Cited By ~ 5

Author(s):

O. M. Lidwell

Keyword(s):

Mathematical Model ◽

Flow Velocity ◽

Effective Diffusion ◽

Diffusion Constant ◽

Particulate Material ◽

Airborne Particulate ◽

Airborne Infection ◽

Directional Flow ◽

A Value

SUMMARYA mathematical model is described for the transport of gaseous or airborne particulate material between rooms along ventilated passageways.Experimental observations in three hospitals lead to a value of about 0.06m.2/sec. for the effective diffusion constant in air without any systematic directional flow. The ‘constant’ appears to increase if there is any directional flow along the passage, reaching about 0.12 m.2/sec. at a flow velocity of 0.04 m./sec.Together with previously published methods the present formulae make it possible to calculate the expected average amounts of gaseous or particulate material that will be transported from room to room in ventilated buildings in which the ventilation and exchange airflows can be calculated.The actual amounts transported in occupied buildings, however, vary greatly from time to time.

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