18,502 research outputs found
Stem-root flow effect on soil–atmosphere interactions and uncertainty assessments
Abstract. Soil water can rapidly enter deeper layers via vertical redistribution of soil water through the stem–root flow mechanism. This study develops the stem–root flow parameterization scheme and coupled this scheme with the Simplified Simple Biosphere model (SSiB) to analyze its effects on land–atmospheric interactions. The SSiB model was tested in a single column mode using the Lien Hua Chih (LHC) measurements conducted in Taiwan and HAPEX-Mobilhy (HAPEX) measurements in France. The results show that stem–root flow generally caused a decrease in the moisture content at the top soil layer and moistened the deeper soil layers. Such soil moisture redistribution results in significant changes in heat flux exchange between land and atmosphere. In the humid environment at LHC, the stem–root flow effect on transpiration was minimal, and the main influence on energy flux was through reduced soil evaporation that led to higher soil temperature and greater sensible heat flux. In the Mediterranean environment of HAPEX, the stem–root flow significantly affected plant transpiration and soil evaporation, as well as associated changes in canopy and soil temperatures. However, the effect on transpiration could either be positive or negative depending on the relative changes in the moisture content of the top soil vs. deeper soil layers due to stem–root flow and soil moisture diffusion processes
First-principles and model simulation of all-optical spin reversal
All-optical spin switching is a potential trailblazer for information storage
and communication at an unprecedented fast rate and free of magnetic fields.
However, the current wisdom is largely based on semiempirical models of
effective magnetic fields and heat pulses, so it is difficult to provide
high-speed design protocols for actual devices. Here, we carry out a massively
parallel first-principles and model calculation for thirteen spin systems and
magnetic layers, free of any effective field, to establish a simpler and
alternative paradigm of laser-induced ultrafast spin reversal and to point out
a path to a full-integrated photospintronic device. It is the interplay of the
optical selection rule and sublattice spin orderings that underlines seemingly
irreconcilable helicity-dependent/independent switchings. Using realistic
experimental parameters, we predict that strong ferrimagnets, in particular,
Laves phase C15 rare-earth alloys, meet the telecommunication energy
requirement of 10 fJ, thus allowing a cost-effective subpicosecond laser to
switch spin in the GHz region.Comment: 23 pages, 6 figures and one tabl
DLC2 modulates angiogenic responses in vascular endothelial cells by regulating cell attachment and migration.
Deleted in liver cancer 1 (DLC1) is a RhoGTPase activation protein-containing tumor suppressor that associates with various types of cancer. Although DLC2 shares a similar domain structure with that of DLC1, the function of DLC2 is not well characterized. Here, we describe the expression and ablation of DLC2 in mice using a reporter-knockout approach. DLC2 is expressed in several tissues and in endothelial cells (ECs) of blood vessels. Although ECs and blood vessels show no histological abnormalities and mice appear overall healthy, DLC2-mutant mice display enhanced angiogenic responses induced by matrigel and by tumor cells. Silencing of DLC2 in human ECs has reduced cell attachment, increased migration, and tube formation. These changes are rescued by silencing of RhoA, suggesting that the process is RhoA pathway dependent. These results indicate that DLC2 is not required for mouse development and normal vessel formation, but may protect mouse from unwanted angiogenesis induced by, for example, tumor cells
Triaxially deformed relativistic point-coupling model for hypernuclei: a quantitative analysis of hyperon impurity effect on nuclear collective properties
The impurity effect of hyperon on atomic nuclei has received a renewed
interest in nuclear physics since the first experimental observation of
appreciable reduction of transition strength in low-lying states of
hypernucleus Li. Many more data on low-lying states of
hypernuclei will be measured soon for -shell nuclei, providing good
opportunities to study the impurity effect on nuclear low-energy
excitations. We carry out a quantitative analysis of hyperon impurity
effect on the low-lying states of -shell nuclei at the beyond-mean-field
level based on a relativistic point-coupling energy density functional (EDF),
considering that the hyperon is injected into the lowest
positive-parity () and negative-parity () states. We
adopt a triaxially deformed relativistic mean-field (RMF) approach for
hypernuclei and calculate the binding energies of hypernuclei as well
as the potential energy surfaces (PESs) in deformation plane.
We also calculate the PESs for the hypernuclei with good quantum
numbers using a microscopic particle rotor model (PRM) with the same
relativistic EDF. The triaxially deformed RMF approach is further applied in
order to determine the parameters of a five-dimensional collective Hamiltonian
(5DCH) for the collective excitations of triaxially deformed core nuclei.
Taking Mg and Si as examples, we analyse
the impurity effects of and on the low-lying states of
the core nuclei...Comment: 15 pages with 18 figures and 1 table (version to be published in
Physical Review C
Theory for transport through a single magnetic molecule: Endohedral N@C60
We consider transport through a single N@C60 molecule, weakly coupled to
metallic leads. Employing a density-matrix formalism we derive rate equations
for the occupation probabilities of many-particle states of the molecule. We
calculate the current-voltage characteristics and the differential conductance
for N@C60 in a break junction. Our results reveal Coulomb-blockade behavior as
well as a fine structure of the Coulomb-blockade peaks due to the exchange
coupling of the C60 spin to the spin of the encapsulated nitrogen atom.Comment: 5 pages, 4 figures, v2: version as publishe
Parametrical modeling and design optimization of blood plasma separation device with microchannel mechanism
This paper presents an analysis of biofluid behavior in a T-shaped microchannel device and a design optimization for improved biofluid performance in terms of particle liquid separation. The biofluid is modeled with single phase shear rate non-Newtonian flow with blood property. The separation of red blood cell from plasma is evident based on biofluid distribution in the microchannels against various relevant effects and findings, including Zweifach-Fung bifurcation law, Fahraeus effect, Fahraeus-Lindqvist effect and cell free phenomenon. The modeling with the initial device shows that this T-microchannel device can separate red blood cell from plasma but the separation efficiency among different bifurcations varies largely. In accordance with the imbalanced performance, a design optimization is conducted. This includes implementing a series of simulations to investigate the effect of the lengths of the main and branch channels to biofluid behavior and searching an improved design with optimal separation performance. It is found that changing relative lengths of branch channels is effective to both uniformity of flow rate ratio among bifurcations and reduction of difference of the flow velocities between the branch channels, whereas extending the length of the main channel from bifurcation region is only effective for uniformity of flow rate ratio
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