1,231 research outputs found
Stability and flow fields structure for interfacial dynamics with interfacial mass flux
We analyze from a far field the evolution of an interface that separates
ideal incompressible fluids of different densities and has an interfacial mass
flux. We develop and apply the general matrix method to rigorously solve the
boundary value problem involving the governing equations in the fluid bulk and
the boundary conditions at the interface and at the outside boundaries of the
domain. We find the fundamental solutions for the linearized system of
equations, and analyze the interplay of interface stability with flow fields
structure, by directly linking rigorous mathematical attributes to physical
observables. New mechanisms are identified of the interface stabilization and
destabilization. We find that interfacial dynamics is stable when it conserves
the fluxes of mass, momentum and energy. The stabilization is due to inertial
effects causing small oscillations of the interface velocity. In the classic
Landau dynamics, the postulate of perfect constancy of the interface velocity
leads to the development of the Landau-Darrieus instability. This
destabilization is also associated with the imbalance of the perturbed energy
at the interface, in full consistency with the classic results. We identify
extreme sensitivity of the interface dynamics to the interfacial boundary
conditions, including formal properties of fundamental solutions and
qualitative and quantitative properties of the flow fields. This provides new
opportunities for studies, diagnostics, and control of multiphase flows in a
broad range of processes in nature and technology
Two-Triplet-Dimer Excitation Spectra in the Shastry-Sutherland Model for SrCu_2(BO_3)_2
By using the perturbation expansion up to the fifth order, we study the
two-triplet-dimer excitation spectra in the Shastry-Sutherland model, where the
localized nature of a triplet-dimer, the propagation of a triplet-dimer pair by
the correlated hopping and the long-range interactions between triplet-dimers
play an essential role. It is found that the dispersion relations for
first-neighbor triplet-dimer pair excitations with S=1 and p-type symmetry
qualitatively explain the second-lowest branch observed in the neutron
inelastic scattering experiment. It is also predicted that the second-lowest
branch consists of two components, p_x- and p_y-states, with slightly different
excitation energies. The origin of the singlet mode at 3.7meV observed in the
Raman scattering experiment is also discussed.Comment: 5 pages, 3 figure
Livestock Producer’s Nutrient Management Planner Guidebook: A Waste Management Planning Guide for Pacific Island Livestock Producers
This Livestock Producer’s Nutrient Management Planner provides you, the livestock producer, with help in developing an animal waste management plan for your farm. The plan will be unique to each individual farm due to differences in the types of animals you raise, where your farm is located, and how you manage your operation. This workbook is designed to provide the basics on laws and regulations, the concept of nutrient flow through your farm, a series of worksheets to establish the status of your operation, and a guide to developing your farm’s nutrient management plan
Exchange interactions and magnetic properties of the layered vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9
We have performed ab-initio calculations of exchange couplings in the layered
vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9. The uniform susceptibility of the
Heisenberg model with these exchange couplings is then calculated by quantum
Monte Carlo method; it agrees well with the experimental measurements. Based on
our results we naturally explain the unusual magnetic properties of these
materials, especially the huge difference in spin gap between CaV2O5 and
MgV2O5, the unusual long range order in CaV3O7 and the "plaquette resonating
valence bond (RVB)" spin gap in CaV4O9
First-principles study on the intermediate compounds of LiBH
We report the results of the first-principles calculation on the intermediate
compounds of LiBH. The stability of LiBH and LiBH has been examined with the ultrasoft pseudopotential method based on
the density functional theory. Theoretical prediction has suggested that
monoclinic LiBH is the most stable among the candidate
materials. We propose the following hydriding/dehydriding process of LiBH
via this intermediate compound : LiBHLiBH LiH HLiH B H. The hydrogen content and enthalpy of the first
reaction are estimated to be 10 mass% and 56 kJ/mol H, respectively, and
those of the second reaction are 4 mass% and 125 kJ/mol H. They are in good
agreement with experimental results of the thermal desorption spectra of
LiBH. Our calculation has predicted that the bending modes for the
-phonon frequencies of monoclinic LiBH are lower than
that of LiBH, while stretching modes are higher. These results are very
useful for the experimental search and identification of possible intermediate
compounds.Comment: 7 pages, 5 figures, submitted to PR
Localization properties of a one-dimensional tight-binding model with non-random long-range inter-site interactions
We perform both analytical and numerical studies of the one-dimensional
tight-binding Hamiltonian with stochastic uncorrelated on-site energies and
non-fluctuating long-range hopping integrals . It was argued recently [A.
Rodriguez at al., J. Phys. A: Math. Gen. 33, L161 (2000)] that this model
reveals a localization-delocalization transition with respect to the disorder
magnitude provided . The transition occurs at one of the band edges (the upper
one for and the lower one for). The states at the other band edge are always
localized, which hints on the existence of a single mobility edge. We analyze
the mobility edge and show that, although the number of delocalized states
tends to infinity, they form a set of null measure in the thermodynamic limit,
i.e. the mobility edge tends to the band edge. The critical magnitude of
disorder for the band edge states is computed versus the interaction exponent
by making use of the conjecture on the universality of the normalized
participation number distribution at transition.Comment: 7 pages, 6 postscript figures, uses revtex
Microstructural characterization of AISI 431 martensitic stainless steel laser-deposited coatings
High cooling rates during laser cladding of stainless steels may alter the microstructure and phase constitution of the claddings and consequently change their functional properties. In this research, solidification structures and solid state phase transformation products in single and multi layer AISI 431 martensitic stainless steel coatings deposited by laser cladding at different processing speeds are investigated by optical microscopy, Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), orientation imaging microscopy (OIM), ternary phase diagram, Schaeffler and TTT diagrams. The results of this study show how partitionless solidification and higher solidification rates alter the microstructure and phase constitution of martensitic stainless steel laser deposited coatings. In addition, it is shown that while different cladding speeds have no effect on austenite–martensite orientation relationship in the coatings, increasing the cladding speed has resulted in a reduction of hardness in deposited coatings which is in contrast to the common idea about obtaining higher hardness values at higher cladding speeds.
Regulation of Apoptosis in Myeloid Cells by Interferon Consensus Sequence–Binding Protein
Mice with a null mutation of the gene encoding interferon consensus sequence–binding protein (ICSBP) develop a disease with marked expansion of granulocytes and macrophages that frequently progresses to a fatal blast crisis, thus resembling human chronic myelogenous leukemia (CML). One important feature of CML is decreased responsiveness of myeloid cells to apoptotic stimuli. Here we show that myeloid cells from mice deficient in ICSBP exhibit reduced spontaneous apoptosis and a significant decrease in sensitivity to apoptosis induced by DNA damage. In contrast, apoptosis in thymocytes from ICSBP-deficient mice is unaffected. We also show that overexpression of ICSBP in the human U937 monocytic cell line enhances the rate of spontaneous apoptosis and the sensitivity to apoptosis induced by etoposide, lipopolysaccharide plus ATP, or rapamycin. Programmed cell death induced by etoposide was specifically blocked by peptides inhibitory for the caspase-1 or caspase-3 subfamilies of caspases. Studies of proapoptotic genes showed that cells overexpressing ICSBP have enhanced expression of caspase-3 precursor protein. In addition, analyses of antiapoptotic genes showed that overexpression of ICSBP results in decreased expression of Bcl-XL. These data suggest that ICSBP modulates survival of myeloid cells by regulating expression of apoptosis-related genes
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