4,025 research outputs found
A PARAMETRIC INVESTIGATION OF THE LUNAR-ORBIT-RENDEZVOUS SCHEME
Lunar orbit rendezvous scheme - mission analysi
A Two-Impulse Plan for Performing Rendezvous on a Once-A-Day Basis
An investigation of a two-impulse plan for performing rendezvous on a once-a-day basis with a near-earth satellite station indicates that launch into rendezvous from slightly less than maximum satellite latitude is an unusually favorable circumstance in that no appreciable expense in mass ratio is incurred. In addition, it was found for the two-impulse maneuver employed in this study that the optimum angular travel of the ferry vehicle to rendezvous was considerably less than the 1800 transfer which is optimum for the two-impulse in-plane launch
Isohemagglutinins of Graft Origin after ABO-Unmatched Liver Transplantation
THE increasing success of liver transplantation in recent years has provided an experimental model to study and document the hepatic synthesis of many plasma proteins.12345 The normal hepatobiliary tract has not been regarded as a major source of antibody,6,7 aside from the enteric IgA secreted from plasma into the biliary tree.8 Liver transplantation affords the opportunity to study the production of antibody to red cells. Recipient ABO incompatibility to the donor (a mismatched transplant, e.g., a group A liver transplanted into a group B recipient), although not absolutely contraindicated in liver transplantation, is avoided when possible. However, ABO-unmatched transplants (defined. © 1984, Massachusetts Medical Society. All rights reserved
Direct conversion of rheological compliance measurements into storage and loss moduli
We remove the need for Laplace/inverse-Laplace transformations of
experimental data, by presenting a direct and straightforward mathematical
procedure for obtaining frequency-dependent storage and loss moduli
( and respectively), from time-dependent experimental
measurements. The procedure is applicable to ordinary rheological creep
(stress-step) measurements, as well as all microrheological techniques, whether
they access a Brownian mean-square displacement, or a forced compliance. Data
can be substituted directly into our simple formula, thus eliminating
traditional fitting and smoothing procedures that disguise relevant
experimental noise.Comment: 4 page
Beating patterns of filaments in viscoelastic fluids
Many swimming microorganisms, such as bacteria and sperm, use flexible
flagella to move through viscoelastic media in their natural environments. In
this paper we address the effects a viscoelastic fluid has on the motion and
beating patterns of elastic filaments. We treat both a passive filament which
is actuated at one end, and an active filament with bending forces arising from
internal motors distributed along its length. We describe how viscoelasticity
modifies the hydrodynamic forces exerted on the filaments, and how these
modified forces affect the beating patterns. We show how high viscosity of
purely viscous or viscoelastic solutions can lead to the experimentally
observed beating patterns of sperm flagella, in which motion is concentrated at
the distal end of the flagella
Frontotemporal Dementia and Parkinsonism Linked to Chromosome 17: A New Group of Tauopathies
Frontotemporal dementia is a neurological disorder characterised by personality changes, deterioration of memory and executive functions as well as stereotypical behaviour. Sometimes a Parkinsonian syndrome is prominent. Several cases of frontotemporal dementia are hereditary and recently families have been identified where the disease is linked to chromosome 17q21-22. Although, there is clinical and neuropathological variability among and within families, they all consistently present a symptomathology that has led investigators to name the disease "Frontotemporal Dementia and Parkinsonism linked to chromosome 17." Neuropathologically, these patients present with atrophy of frontal and temporal cortex as well as of basal ganglia and substantia nigra. In the majority of cases these features are accompanied by neuronal loss, gliosis and microtubule-associated protein tau deposits which can be present in both neurones and glial cells. The distribution, structural and biochemical characteristics of the tau deposits differentiate them from those present in Alzheimer's disease, corticobasal degeneration, progressive supranuclear palsy and Pick's disease. No beta-amyloid deposits are present. The clinical and neuropathological features of the disease in these families suggest that Frontotemporal Dementia and Parkinsonism linked to chromosome 17 is a distinct disorder. The presence of abundant tau deposits in the majority of these families define this disorder as a new tauopathy
Multiscale Particle-Continuum Simulations of Hypersonic Flow over a Planetary Probe
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76410/1/AIAA-37319-396.pd
Collision statistics in sheared inelastic hard spheres
The dynamics of sheared inelastic-hard-sphere systems are studied using
non-equilibrium molecular dynamics simulations and direct simulation Monte
Carlo. In the molecular dynamics simulations Lees-Edwards boundary conditions
are used to impose the shear. The dimensions of the simulation box are chosen
to ensure that the systems are homogeneous and that the shear is applied
uniformly. Various system properties are monitored, including the one-particle
velocity distribution, granular temperature, stress tensor, collision rates,
and time between collisions. The one-particle velocity distribution is found to
agree reasonably well with an anisotropic Gaussian distribution, with only a
slight overpopulation of the high velocity tails. The velocity distribution is
strongly anisotropic, especially at lower densities and lower values of the
coefficient of restitution, with the largest variance in the direction of
shear. The density dependence of the compressibility factor of the sheared
inelastic hard sphere system is quite similar to that of elastic hard sphere
fluids. As the systems become more inelastic, the glancing collisions begin to
dominate more direct, head-on collisions. Examination of the distribution of
the time between collisions indicates that the collisions experienced by the
particles are strongly correlated in the highly inelastic systems. A comparison
of the simulation data is made with DSMC simulation of the Enskog equation.
Results of the kinetic model of Montanero et al. {[}Montanero et al., J. Fluid
Mech. 389, 391 (1999){]} based on the Enskog equation are also included. In
general, good agreement is found for high density, weakly inelastic systems.Comment: 10 figures, 1 table, 27 page
Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion
Non-equilibrium molecular dynamics simulations were performed to study the
thermodynamic, structural, and dynamical properties of the single-component
Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems
are known to be strongly correlating, i.e., have strong correlations between
equilibrium thermal fluctuations of virial and potential energy. Such systems
have good isomorphs, i.e., curves in the thermodynamic phase diagram along
which structural, dynamical, and some thermodynamic quantities are invariant
when expressed in reduced units. The SLLOD equations of motion were used to
simulate Couette shear flows of the two systems. We show analytically that
these equations are isomorph invariant provided the reduced strain rate is
fixed along the isomorph. Since isomorph invariance is generally only
approximate, a range of shear rates were simulated to test for the predicted
invariance, covering both the linear and non-linear regimes. For both systems,
when represented in reduced units the radial distribution function and the
intermediate scattering function collapse for state points that are isomorphic.
The strain-rate dependence of the viscosity, which exhibits shear thinning, is
also invariant along an isomorph. Our results extend the isomorph concept to
the state-state non-equilibrium situation of a shear flow, in which the phase
diagram is three dimensional because the shear rate defines the third
dimension
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