5,585 research outputs found
Epitaxial Growth of an n-type Ferromagnetic Semiconductor CdCr2Se4 on GaAs(001) and GaP(001)
We report the epitaxial growth of CdCr2Se4, an n-type ferromagnetic
semiconductor, on both GaAs and GaP(001) substrates, and describe the
structural, magnetic and electronic properties. Magnetometry data confirm
ferromagnetic order with a Curie temperature of 130 K, as in the bulk material.
The magnetization exhibits hysteretic behavior with significant remanence, and
an in-plane easy axis with a coercive field of ~125 Oe. Temperature dependent
transport data show that the films are semiconducting in character and n-type
as grown, with room temperature carrier concentrations of n ~ 1 x 10^18 cm-3.Comment: 12 pages, 3 figure
The Effect of Spinner-body Gap on the Pressures Available for Cooling in the NACA E-type Cowling
Flight-wind restrictions procedure, Atlas/ Centaur AC-6 through AC-15
Prelaunch calculation of wind profile effect using axial load and bending moments for Atlas and Centaur launch vehicle
Earth-like sand fluxes on Mars
Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving—implying large sand fluxes—or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar
Magnetic Properties of Epitaxial and Polycrystalline Fe/Si Multilayers
Fe/Si multilayers with antiferromagnetic interlayer coupling have been grown
via ion-beam sputtering on both glass and single-crystal substrates. High-angle
x-ray diffraction measurements show that both sets of films have narrow Fe
peaks, implying a large crystallite size and crystalline iron silicide spacer
layers. Low-angle x-ray diffraction measurements show that films grown on glass
have rougher interfaces than those grown on single-crystal substrates. The
multilayers grown on glass have a larger remanent magnetization than the
multilayers grown on single-crystal substrates. The observation of
magnetocrystalline anisotropy in hysteresis loops and peaks in x-ray
diffraction demonstrates that the films grown on MgO and Ge are epitaxial. The
smaller remanent magnetization in Fe/Si multilayers with better layering
suggests that the remanence is not an intrinsic property.Comment: 9 pages, RevTex, 4 figures available by fax. Send email to
[email protected] for more info. Submitted to '95 MMM proceeding
Implicit solvation using the superposition approximation (IS-SPA): extension to polar solutes in chloroform
Efficient, accurate, and adaptable implicit solvent models remain a significant challenge in the field of molecular simulation. A recent implicit solvent model, IS-SPA, based on approximating the mean solvent force using the superposition approximation, provides a platform to achieve these goals. IS-SPA was originally developed to handle non-polar solutes in the TIP3P water model but can be extended to accurately treat polar solutes in other polar solvents. In this manuscript, we demonstrate how to adapt IS-SPA to include the treatment of solvent orientation and long ranged electrostatics in a solvent of chloroform. The orientation of chloroform is approximated as that of an ideal dipole aligned in a mean electrostatic field. The solvent–solute force is then considered as an averaged radially symmetric Lennard-Jones component and a multipole expansion of the electrostatic component through the octupole term. Parameters for the model include atom-based solvent density and mean electric field functions that are fit from explicit solvent simulations of independent atoms or molecules. Using these parameters, IS-SPA accounts for asymmetry of charge solvation and reproduces the explicit solvent potential of mean force of dimerization of two oppositely charged Lennard-Jones spheres with high fidelity. Additionally, the model more accurately captures the effect of explicit solvent on the monomer and dimer configurations of alanine dipeptide in chloroform than a generalized Born or constant density dielectric model. The current version of the algorithm is expected to outperform explicit solvent simulations for aggregation of small peptides at concentrations below 150 mM, well above the typical experimental concentrations for these materials.Chemistr
Force, Static Longitudinal Stability, and Control Characteristics of a 1/16-scale Model of the Bell XS-1 Transonic Research Airplane at High Mach Numbers
Implicit Solvation Using the Superposition Approximation (IS-SPA): Extension to Polar Solutes in Chloroform
Efficient, accurate, and adaptable implicit solvent models remain a
significant challenge in the field of molecular simulation. A recent implicit
solvent model, IS-SPA, based on approximating the mean solvent force using the
superposition approximation, provides a platform to achieve these goals. IS-SPA
was originally developed to handle non-polar solutes in the TIP3P water model
but can be extended to accurately treat polar solutes in other polar solvents.
In this manuscript, we demonstrate how to adapt IS-SPA to include the treatment
of solvent orientation and long ranged electrostatics in a solvent of
chloroform. The orientation of chloroform is approximated as that of an ideal
dipole aligned in a mean electrostatic field. The solvent--solute force is then
considered as an averaged radially symmetric Lennard-Jones component and a
multipole expansion of the electrostatic component through the octupole term.
Parameters for the model include atom-based solvent density and mean electric
field functions that are fit from explicit solvent simulations of independent
atoms or molecules. Using these parameters, IS-SPA accounts for asymmetry of
charge solvation and reproduces the explicit solvent potential of mean force of
dimerization of two oppositely charged Lennard-Jones spheres with high
fidelity. Additionally, the model more accurately captures the effect of
explicit solvent on the monomer and dimer configurations of alanine dipeptide
in chloroform than a generalized Born or constant density dielectric model. The
current version of the algorithm is expected to outperform explicit solvent
simulations for aggregation of small peptides at concentrations below 150 mM,
well above the typical experimental concentrations for these materials
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