131,658 research outputs found
A process yields large quantities of pure ribosome subunits
Development of process for in-vitro protein synthesis from living cells followed by dissociation of ribosomes into subunits is discussed. Process depends on dialysis or use of chelating agents. Operation of process and advantages over previous methods are outlined
Gaussian Effective Potential and the Coleman's normal-ordering Prescription : the Functional Integral Formalism
For a class of system, the potential of whose Bosonic Hamiltonian has a
Fourier representation in the sense of tempered distributions, we calculate the
Gaussian effective potential within the framework of functional integral
formalism. We show that the Coleman's normal-ordering prescription can be
formally generalized to the functional integral formalism.Comment: 6 pages, revtex; With derivation details and an example added. To
appear in J. Phys.
Generation of Entangled Photon Holes using Quantum Interference
In addition to photon pairs entangled in polarization or other variables,
quantum mechanics also allows optical beams that are entangled through the
absence of the photons themselves. These correlated absences, or ``entangled
photon holes'', can lead to counter-intuitive nonlocal effects analogous to
those of the more familiar entangled photon pairs. Here we report an
experimental observation of photon holes generated using quantum interference
effects to suppress the probability that two photons in a weak laser pulse will
separate at an optical beam splitter.Comment: 4 pages, color figures, submitted to Phys. Rev.
Thermalized Displaced Squeezed Thermal States
In the coordinate representation of thermofield dynamics, we investigate the
thermalized displaced squeezed thermal state which involves two temperatures
successively. We give the wavefunction and the matrix element of the density
operator at any time, and accordingly calculate some quantities related to the
position, momentum and particle number operator, special cases of which are
consistent with the results in the literature. The two temperatures have
diffenent correlations with the squeeze and coherence components. Moreover,
different from the properties of the position and momentum, the average value
and variance of the particle number operator as well as the second-order
correlation function are time-independent.Comment: 7 pages, no figures, Revtex fil
Delocalized, non-SUSY -branes, tachyon condensation and tachyon matter
We construct non-supersymmetric -brane solutions of type II supergravities
in arbitrary dimensions () delocalized in one of the spatial transverse
directions. By a Wick rotation we convert these solutions into Euclidean
-branes delocalized in the transverse time-like direction. The former
solutions in nicely interpolate between the -dimensional non-BPS
D-branes and the -dimensional BPS D-branes very similar to the picture of
tachyon condensation for the tachyonic kink solution on the non-BPS D-branes.
On the other hand the latter solutions interpolate between the
-dimensional non-BPS D-branes and the tachyon matter supergravity
configuration very similar to the picture of rolling tachyon on the non-BPS
D-branes.Comment: 15 pages, typos correcte
Closed-form Absorption Probability of Certain D=5 and D=4 Black Holes and Leading-Order Cross-Section of Generic Extremal p-branes
We obtain the closed-form absorption probabilities for minimally-coupled
massless scalars propagating in the background of D=5 single-charge and D=4
two-charge black holes. These are the only two examples of extremal black holes
with non-vanishing absorption probabilities that can be solved in closed form
for arbitrary incident frequencies. In both cases, the absorption probability
vanishes when the frequency is below a certain threshold, and we discuss the
connection between this phenomenon and the behaviour of geodesics in these
black hole backgrounds. We also obtain leading-order absorption cross-sections
for generic extremal p-branes, and show that the expression for the
cross-section as a function of frequency coincides with the leading-order
dependence of the entropy on the temperature in the corresponding near-extremal
p-branes.Comment: Latex (3 times), 20 page
Orbits and origins of the young stars in the central parsec of the galaxy
We present new proper motions from the 10 m Keck telescopes for a puzzling population of massive, young stars located within a parsec of the supermassive black hole at the Galactic Center. Our proper motion measurements have uncertainties of only 0.07 mas yr^(â1) (3 km s^(â1) ), which is âł7 times better than previous proper motion measurements for these stars, and enables us to measure accelerations as low as 0.2 mas yr^(â2) (7 km s^(â1) yr^(â1) ). These measurements, along with stellar line-of-sight velocities from the literature, constrain the true orbit of each individual star and allow us to directly test the hypothesis that the massive stars reside in two stellar disks as has been previously proposed. Analysis of the stellar orbits reveals only one disk of young stars using a method that is capable of detecting disks containing at least 7 stars. The detected disk contains 50% (38 of 73) of the young stars, is inclined by ~115° from the plane of the sky, and is oriented at a position angle of âŒ100° East of North. The on-disk and off-disk populations have similar K-band luminosity functions and radial distributions that decrease at larger radii as â r^(â2). The disk has an out-of-the-disk velocity dispersion of 28±6 km s^(â1) , which corresponds to a half-opening angle of 7°±2° , and several candidate disk members have eccentricities greater than 0.2. Our findings suggest that the young stars may have formed in situ but in a more complex geometry than a simple thin circular disk
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