14,691 research outputs found
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Nitrogen cycling and bacterial production
I. Bacterial abundance and production in Nueces and Guadalupe Estuaries, Texas -- II. Ammonium regeneration and utilization in Nueces Estuary, Texas -- III. Comparison of benthic ammonium flux with ammonium regeneration in the water column of Nueces and Guadalupe Estuaries, Texas -- IV. Denitrification in Nueces and Guadalupe Estuaries, Texas -- V. Ammonium regeneration and utilization in Guadalupe Estuary, Texas.Marine Scienc
The mean shape of transition and first-passage paths
We calculate the mean shape of transition paths and first-passage paths based
on the one-dimensional Fokker-Planck equation in an arbitrary free energy
landscape including a general inhomogeneous diffusivity profile. The transition
path ensemble is the collection of all paths that do not revisit the start
position and that terminate when first reaching the final position .
In contrast, a first-passage path can revisit but not cross its start position
before it terminates at . Our theoretical framework employs the
forward and backward Fokker-Planck equations as well as first-passage, passage,
last-passage and transition-path time distributions, for which we derive the
defining integral equations. We show that the mean time at which the transition
path ensemble visits an intermediate position is equivalent to the mean
first-passage time of reaching the starting position from without
ever visiting . The mean shape of first-passage paths is related to the
mean shape of transition paths by a constant time shift. Since for large
barrier height the mean first-passage time scales exponentially in
while the mean transition path time scales linearly inversely in , the time
shift between first-passage and transition path shapes is substantial. We
present explicit examples of transition path shapes for linear and harmonic
potentials and illustrate our findings by trajectories generated from Brownian
dynamics simulations
Effects of Government Programs on Corn, Soybeans, and Wheat Production in the U.S.
Agricultural Finance, Farm Management, Production Economics,
U.S. WHEAT STORAGE CONTROL UNDER JOINT CRITERIA OF MEAN BENEFITS AND PRICE VARIATION
A method based on stochastic dynamic programming is developed to derive efficiency frontiers for the trade-off between the long-run average social benefits and price variation. The method is used to quantify the importance of price variation per se as a criterion in U.S. wheat storage policy. The results suggest that a single criterion of maximum expected social benefits, calculated by the traditional surplus measures, is satisfactory because price variation is incidentally reduced enough that further reductions can be attained only a considerable opportunity cost.Crop Production/Industries,
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Hypoxia-inducible factor: role in cell survival in superoxide dismutase overexpressing mice after neonatal hypoxia-ischemia.
BackgroundSixty percent of infants with severe neonatal hypoxic-ischemic encephalopathy die, while most survivors have permanent disabilities. Treatment for neonatal hypoxic-ischemic encephalopathy is limited to therapeutic hypothermia, but it does not offer complete protection. Here, we investigated whether hypoxia-inducible factor (HIF) promotes cell survival and suggested neuroprotective strategies.PurposeHIF-1α-deficient mice have increased brain injury after neonatal hypoxia-ischemia (HI), and the role of HIF-2α in HI is not well characterized. Copper-zinc superoxide dismutase (SOD)1 overexpression is not beneficial in neonatal HI. The expression of HIF-1α and HIF-2α was measured in SOD1 overexpressing mice and compared to wild-type littermates to see if alteration in expression explains this lack of benefit.MethodsOn postnatal day 9, C57Bl/6 mice were subjected to HI, and protein expression was measured by western blotting in the ipsilateral cortex of wild-type and SOD1 overexpressing mice to quantify HIF-1α and HIF-2α. Spectrin expression was also measured to characterize the mechanism of cell death.ResultsHIF-1α protein expression did not significantly change after HI injury in the SOD1-overexpressing or wild-type mouse cortex. However, HIF-2α protein expression increased 30 minutes after HI injury in the wild-type and SOD1-overexpressing mouse cortex and decreased to baseline value at 24 hours after HI injury. Spectrin 145/150 expression did not significantly change after HI injury in the SOD1- overexpressing or wild-type mouse cortex. However, spectrin 120 expression increased in both wild-type and SOD1-overexpressing mouse at 4 hours after HI, which decreased by 24 hours, indicating a greater role of apoptotic cell death.ConclusionHIF-1α and HIF-2α may promote cell survival in neonatal HI in a cell-specific and regional fashion. Our findings suggest that early HIF-2α upregulation precedes apoptotic cell death and limits necrotic cell death. However, the influence of SOD was not clarified; it remains an intriguing factor in neonatal HI
Possible f-wave superconductivity in SrRuO?
Until recently it has been believed that the superconductivity in
SrRuO is described by p-wave pairing. However, both the recent specific
heat and the magnetic penetration depth measurements on the purest single
crystals of SrRuO appear to be explained more consistently in terms of
f-wave superconductivity. In order to further this hypothesis, we study
theoretically the thermodynamics and thermal conductivity of f-wave
superconductors in a planar magnetic field. We find the simple expressions for
these quantities when and , which should be
readily accessible experimentally.Comment: 6 pages, 2 figure
Effect of nuclear interactions of neutral kaons on CP asymmetry measurements
We examine the effect of the difference in nuclear interactions of
and mesons on the measurement of CP asymmetry for experiments at
colliders - charm and -meson factories. We find that this effect on
CP asymmetry can be as large as 0.3%, and therefore sufficiently significant in
interpreting measurements of CP asymmetry when neutral kaons are present in the
final state.Comment: accepted to PR
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