15,153 research outputs found
Nanomechanical detection of the spin Hall effect
The spin Hall effect creates a spin current in response to a charge current
in a material that has strong spin-orbit coupling. The size of the spin Hall
effect in many materials is disputed, requiring independent measurements of the
effect. We develop a novel mechanical method to measure the size of the spin
Hall effect, relying on the equivalence between spin and angular momentum. The
spin current carries angular momentum, so the flow of angular momentum will
result in a mechanical torque on the material. We determine the size and
geometry of this torque and demonstrate that it can be measured using a
nanomechanical device. Our results show that measurement of the spin Hall
effect in this manner is possible and also opens possibilities for actuating
nanomechanical systems with spin currents.Comment: 5 pages + 2 pages supplementary material, 4 figures tota
Comment on "Cherenkov Radiation by Neutrinos in a Supernova Core"
Mohanty and Samal have shown that the magnetic-moment interaction with
nucleons contributes significantly to the photon dispersion relation in a
supernova core, and with an opposite sign relative to the usual plasma effect.
Because of a numerical error they overestimated the magnetic-moment term by two
orders of magnitude, but it is still of the same order as the plasma effect. It
appears that the Cherenkov processes gamma+nu -> nu and nu -> nu+gamma remain
forbidden, but a final verdict depends on a more detailed investigation of the
dynamical magnetic susceptibility of a hot nuclear medium.Comment: 2 pages, REVTEX. Submitted as a Comment to PR
Elliptic flow of thermal dileptons as a probe of QCD matter
We study the variation of elliptic flow of thermal dileptons with transverse
momentum and invariant mass of the pairs for Pb+Pb collisions at
= 2.76 TeV. The dilepton productions from quark gluon plasma
(QGP) and hot hadrons have been considered including the spectral change of
light vector mesons in the thermal bath. The space time evolution has been
carried out within the frame work of 2+1 dimensional ideal hydrodynamics with
lattice+hadron resonance gas equation of state. We find that a judicious
selection of invariant mass(M) and transverse momentum (p_T) windows can be
used to extract the collective properties of quark matter, hadronic matter and
also get a distinct signature of medium effects on vector mesons. Our results
indicate a reduction of elliptic flow (v_2) for M beyond phi mass, which if
observed experimentally would give the measure of v_2 of the partonic phase.Comment: To appear in Phys. Rev. C (Rapid Comm.
Physical Properties of Young Brown Dwarfs and Very Low-Mass Stars Inferred from High-Resolution Model Spectra
By comparing near-infrared spectra with atmosphere models, we infer the
effective temperature, surface gravity, projected rotational velocity, and
radial velocity for 21 very-low-mass stars and brown dwarfs. The unique sample
consists of two sequences in spectral type from M6-M9, one of 5-10 Myr objects
and one of >1 Gyr field objects. A third sequence is comprised of only ~M6
objects with ages ranging from 1 Gyr. Spectra were obtained in the J
band at medium (R~2,000) and high (R~20,000) resolutions with NIRSPEC on the
Keck II telescope. Synthetic spectra were generated from atmospheric structures
calculated with the PHOENIX model atmosphere code. Using multi-dimensional
least-squares fitting and Monte Carlo routines we determine the best-fit model
parameters for each observed spectrum and note which spectral regions provide
consistent results. We identify successes in the reproduction of observed
features by atmospheric models, including pressure-broadened KI lines, and
investigate deficiencies in the models, particularly missing FeH opacity, that
will need to be addressed in order to extend our analysis to cooler objects.
The precision that can be obtained for each parameter using medium- and high-
resolution near-infrared spectra is estimated and the implications for future
studies of very low mass stars and brown dwarfs are discussed.Comment: Accepted to the Astrophysical Journal Supplement Serie
Acceptance Dependence of Fluctuation in Particle Multiplicity
The effect of limiting the acceptance in rapidity on event-by-event
multiplicity fluctuations in nucleus-nucleus collisions has been investigated.
Our analysis shows that the multiplicity fluctuations decrease when the
rapidity acceptance is decreased. We explain this trend by assuming that the
probability distribution of the particles in the smaller acceptance window
follows binomial distribution. Following a simple statistical analysis we
conclude that the event-by-event multiplicity fluctuations for full acceptance
are likely to be larger than those observed in the experiments, since the
experiments usually have detectors with limited acceptance. We discuss the
application of our model to simulated data generated using VENUS, a widely used
event generator in heavy-ion collisions. We also discuss the results from our
calculations in presence of dynamical fluctuations and possible observation of
these in the actual data.Comment: To appear in Int. J. Mod. Phys.
Field Effect Transistor Nanosensor for Breast Cancer Diagnostics
Silicon nanochannel field effect transistor (FET) biosensors are one of the most promising technologies in the development of highly sensitive and label-free analyte detection for cancer diagnostics. With their exceptional electrical properties and small dimensions, silicon nanochannels are ideally suited for extraordinarily high sensitivity. In fact, the high surface-to-volume ratios of these systems make single molecule detection possible. Further, FET biosensors offer the benefits of high speed, low cost, and high yield manufacturing, without sacrificing the sensitivity typical for traditional optical methods in diagnostics. Top down manufacturing methods leverage advantages in Complementary Metal Oxide Semiconductor (CMOS) technologies, making richly multiplexed sensor arrays a reality. Here, we discuss the fabrication and use of silicon nanochannel FET devices as biosensors for breast cancer diagnosis and monitoring
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