9,921 research outputs found
On the Antenna Beam Shape Reconstruction Using Planet Transit
The calibration of the in-flight antenna beam shape and possible
beamdegradation is one of the most crucial tasks for the upcoming Planck
mission. We examine several effects which could significantly influence the
in-flight main beam calibration using planet transit: the problems of the
variability of the Jupiter's flux, the antenna temperature and passing of the
planets through the main beam. We estimate these effects on the antenna beam
shape calibration and calculate the limits on the main beam and far sidelobe
measurements, using observations of Jupiter and Saturn. We also discuss
possible effects of degradation of the mirror surfaces and specify
corresponding parameters which can help us to determine these effects.Comment: 10 pages, 8 figure
Quasi-local energy and the choice of reference
A quasi-local energy for Einstein's general relativity is defined by the
value of the preferred boundary term in the covariant Hamiltonian formalism.
The boundary term depends upon a choice of reference and a time-like
displacement vector field (which can be associated with an observer) on the
boundary of the region. Here we analyze the spherical symmetric cases. For the
obvious analytic choice of reference based on the metric components, we find
that this technique gives the same quasi-local energy values using several
standard coordinate systems and yet can give different values in some other
coordinate systems. For the homogeneous-isotropic cosmologies, the energy can
be non-positive, and one case which is actually flat space has a negative
energy. As an alternative, we introduce a way to determine the choice of both
the reference and displacement by extremizing the energy. This procedure gives
the same value for the energy in different coordinate systems for the
Schwarzschild space, and a non-negative value for the cosmological models, with
zero energy for the dynamic cosmology which is actually Minkowski space. The
timelike displacement vector comes out to be the dual mean curvature vector of
the two-boundary.Comment: 21 pages; revised version to appear in CQ
Phase-sensitive quantum effects in Andreev conductance of the SNS system of metals with macroscopic phase breaking length
The dissipative component of electron transport through the doubly connected
SNS Andreev interferometer indium (S)-aluminium (N)-indium (S) has been
studied. Within helium temperature range, the conductance of the individual
sections of the interferometer exhibits phase-sensitive oscillations of
quantum-interference nature. In the non-domain (normal) state of indium
narrowing adjacent to NS interface, the nonresonance oscillations have been
observed, with the period inversely proportional to the area of the
interferometer orifice. In the domain intermediate state of the narrowing, the
magneto-temperature resistive oscillations appeared, with the period determined
by the coherence length in the magnetic field equal to the critical one. The
oscillating component of resonance form has been observed in the conductance of
the macroscopic N-aluminium part of the system. The phase of the oscillations
appears to be shifted by compared to that of nonresonance oscillations.
We offer an explanation in terms of the contribution into Josephson current
from the coherent quasiparticles with energies of order of the Thouless energy.
The behavior of dissipative transport with temperature has been studied in a
clean normal metal in the vicinity of a single point NS contact.Comment: 9 pages, 7 figures, to be published in Low Temp. Phys., v. 29, No.
12, 200
Using Clinical Decision Support to Maintain Medication and Problem Lists: A Pilot Study to Yield Higher Patient Safety
To Investigate Whether Clinical Decision Support that Automates the Matching of Ordered Drugs to Problems (Clinical Diagnoses) on the Problem List Can Enhance the Maintenance of Both Medication and Problem Lists in the Electronic Medical Record, We Designed a Clinical Decision Support System to Match Ordered Drugs on the Medication List and Ongoing Problems on the Problem List. We Evaluated the Capability and Performance of This Clinical Decision Support System in Medication-Problem Matching using Physician Expert Chart Audits to Match Ordered Drugs to Ongoing Clinical Problems. a Clinical Decision Support System Was Shown to Be Useful in Improving Medication-Problem Matches in 140 Randomly Selected Audited Patient Encounters in Three Inpatient Units. Enhanced Maintenance of Both the Medication and Problem Lists Can Permit the Exploitation of Advanced Decision Support Strategies that Yield Higher Patient Safety. © 2008 IEEE
Spin injection from perpendicular magnetized ferromagnetic -MnGa into (Al,Ga)As heterostructures
Electrical spin injection from ferromagnetic -MnGa into an (Al,Ga)As
p-i-n light emitting diode (LED) is demonstrated. The -MnGa layers show
strong perpendicular magnetocrystalline anisotropy, enabling detection of spin
injection at remanence without an applied magnetic field. The bias and
temperature dependence of the spin injection are found to be qualitatively
similar to Fe-based spin LED devices. A Hanle effect is observed and
demonstrates complete depolarization of spins in the semiconductor in a
transverse magnetic field.Comment: 4 pages, 3 figure
Hitting Time of Quantum Walks with Perturbation
The hitting time is the required minimum time for a Markov chain-based walk
(classical or quantum) to reach a target state in the state space. We
investigate the effect of the perturbation on the hitting time of a quantum
walk. We obtain an upper bound for the perturbed quantum walk hitting time by
applying Szegedy's work and the perturbation bounds with Weyl's perturbation
theorem on classical matrix. Based on the definition of quantum hitting time
given in MNRS algorithm, we further compute the delayed perturbed hitting time
(DPHT) and delayed perturbed quantum hitting time (DPQHT). We show that the
upper bound for DPQHT is actually greater than the difference between the
square root of the upper bound for a perturbed random walk and the square root
of the lower bound for a random walk.Comment: 9 page
Optimal Choices of Reference for a Quasi-local Energy: Spherically Symmetric Spacetimes
For a given timelike displacement vector the covariant Hamiltonian
quasi-local energy expression requires a proper choice of reference spacetime.
We propose a program for determining the reference by embedding a neighborhood
of the two-sphere boundary in the dynamic spacetime into a Minkowski reference,
so that the two sphere is embedded isometrically, and then extremizing the
energy to determine the embedding variables. Applying this idea to
Schwarzschild spacetime, we found that for each given future timelike
displacement vector our program gives a unique energy value. The static
observer measures the maximal energy. Applied to the
Friedmann-Lemaitre-Robertson-Walker spacetime, we find that the maximum energy
value is nonnegative; the associated displacement vector is the unit dual mean
curvature vector, and the expansion of the two-sphere boundary matches that of
its reference image. For these spherically symmetric cases the reference
determined by our program is equivalent to isometrically matching the geometry
at the two-sphere boundary and taking the displacement vector to be orthogonal
to the spacelike constant coordinate time hypersurface, like the timelike
Killing vector of the Minkowski reference.Comment: 12 page
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