134,002 research outputs found
Many-body dipole-induced dipole model for electrorheological fluids
Theoretical investigations on electrorheological (ER) fluids usually rely on
computer simulations. An initial approach for these studies would be the
point-dipole (PD) approximation, which is known to err considerably when the
particles approach and finally touch due to many-body and multipolar
interactions. Thus various work attempted to go beyond the PD model. Being
beyond the PD model, previous attempts have been restricted to either
local-field effects only or multipolar effects only, but not both. For
instance, we recently proposed a dipole-induced-dipole (DID) model which is
shown to be both more accurate than the PD model and easy to use. This work is
necessary because the many-body (local-field) effect is included to put forth
the many-body DID model. The results show that the multipolar interactions can
indeed be dominant over the dipole interaction, while the local-field effect
may yield an important correction.Comment: RevTeX, 3 eps figure
Dielectric behavior of oblate spheroidal particles: Application to erythrocytes suspensions
We have investigated the effect of particle shape on the eletrorotation (ER)
spectrum of living cells suspensions. In particular, we consider coated oblate
spheroidal particles and present a theoretical study of ER based on the
spectral representation theory. Analytic expressions for the characteristic
frequency as well as the dispersion strength can be obtained, thus simplifying
the fitting of experimental data on oblate spheroidal cells that abound in the
literature. From the theoretical analysis, we find that the cell shape, coating
as well as material parameters can change the ER spectrum. We demonstrate good
agreement between our theoretical predictions and experimental data on human
erthrocytes suspensions.Comment: RevTex; 5 eps figure
Nonlinear ac responses of electro-magnetorheological fluids
We apply a Langevin model to investigate the nonlinear ac responses of
electro-magnetorheological (ERMR) fluids under the application of two crossed
dc magnetic (z axis) and electric (x axis) fields and a probing ac sinusoidal
magnetic field. We focus on the influence of the magnetic fields which can
yield nonlinear behaviors inside the system due to the particles with a
permanent magnetic dipole moment.
Based on a perturbation approach, we extract the harmonics of the magnetic
field and orientational magnetization analytically. To this end, we find that
the harmonics are sensitive to the degree of anisotropy of the structure as
well as the field frequency. Thus, it is possible to real-time monitor the
structure transformation of ERMR fluids by detecting the nonlinear ac
responses.Comment: 21 pages, 4 figure
Identification of a Sjogren\u27s syndrome susceptibility locus at OAS1 that influences isoform switching, protein expression, and responsiveness to type I interferons
Catalysts for electrochemical generation of oxygen
An effort was made to study the effects of cation and anion additions on oxygen evolution kinetics on platinum and the inhibitive or catalytic nature of the additions. The kinetics and mechanism of oxygen evolution on planitum metal in hydrofluoric and sulfuric acids, including the effects of foreign anions, were examined. The LEED-Auger-thin layer electrochemical system was developed for the examination of electrocatalytic surfaces. Samples for electrocatalytic LEED-Auger studies were prepared and examined
Evidence of Counter-Streaming Ions near the Inner Pole of the HERMeS Hall Thruster
NASA is continuing the development of a 12.5-kW Hall thruster system to support a phased exploration concept to expand human presence to cis-lunar space and eventually to Mars. The development team is transitioning knowledge gained from the testing of the government-built Technology Development Unit (TDU) to the contractor-built Engineering Test Unit (ETU). A new laser-induced fluorescence diagnostic was developed to obtain data for validating the Hall thruster models and for comparing the behavior of the ETU and TDU. Analysis of TDU LIF data obtained during initial deployment of the diagnostics revealed evidence of two streams of ions moving in opposite directions near the inner front pole. These two streams of ions were found to intersect the downstream surface of the front pole at large oblique angles. This data points to a possible explanation for why the erosion rate of polished pole covers were observed to decrease over the course of several hundred hours of thruster operation
Unification of Gravitation, Gauge Field and Dark Energy
This paper is composed of two correlated topics: 1. unification of
gravitation with gauge fields; 2. the coupling between the daor field and other
fields and the origin of dark energy. After introducing the concept of ``daor
field" and discussing the daor geometry, we indicate that the complex daor
field has two kinds of symmetry transformations. Hence the gravitation and
SU(1,3) gauge field are unified under the framework of the complex connection.
We propose a first-order nonlinear coupling equation of the daor field, which
includes the coupling between the daor field and SU(1,3) gauge field and the
coupling between the daor field and the curvature, and from which Einstein's
gravitational equation can be deduced. The cosmological observations imply that
dark energy cannot be zero, and which will dominate the doom of our Universe.
The real part of the daor field self-coupling equation can be regarded as
Einstein's equation endowed with the cosmological constant. It shows that dark
energy originates from the self-coupling of the space-time curvature, and the
energy-momentum tensor is proportional to the square of coupling constant
\lambda. The dark energy density given by our scenario is in agreement with
astronomical observations. Furthermore, the Newtonian gravitational constant G
and the coupling constant \epsilon of gauge field satisfy G=
\lambda^{2}\epsilon^{2}.Comment: 24 pages, revised version; references added; typos correcte
Fibroblast growth factor receptor 2 (FGFR2) is required for meibomian gland homeostasis in the adult mouse
- …