64,114 research outputs found
Thermal conductivity and dielectric constant of silicate materials
Report on the thermal conductivity and dielectric constant of nonmetallic materials evaluates the mechanisms of heat transfer in evacuated silicate powders and establishes the complex dielectric constant of these materials. Experimental measurements and results are related to postulated lunar surface materials
New technique for determination of cross-power spectral density with damped oscillators
New cross-power spectral density computation technique has been developed, as well as a technique for discrimination between periodic and random signals. This development is applicable to analysis of any stationary random process, and can be used in the aerospace and transportation fields
Thermal conductivity and dielectric constant of silicate materials, 1 April 1965 - 31 August 1966
Heat transfer, and dielectric constants measurements in evacuated silicate powder
Impedance-matched cavity quantum memory
We consider an atomic frequency comb based quantum memory inside an
asymmetric optical cavity. In this configuration it is possible to absorb the
input light completely in a system with an effective optical depth of one,
provided that the absorption per cavity round trip exactly matches the
transmission of the coupling mirror ("impedance matching"). We show that the
impedance matching results in a readout efficiency only limited by irreversible
atomic dephasing, whose effect can be made very small in systems with large
inhomogeneous broadening. Our proposal opens up an attractive route towards
quantum memories with close to unit efficiency.Comment: 4 pages, 2 figure
Explicit Representations for the T-Matrix on Unphysical Energy Sheets and Resonances in Two- and Three-Body Systems
We discuss the structure of the two- and three-body T-matrices, scattering
matrices, and resolvents continued to the unphysical energy sheets. Our
conclusions arise due to the representations that have been found for
analytically continued momentum-space kernels of the T-operators. These
representations are explicitly written only in terms of the physical-sheet
kernels of the T-matrix itself. One of advantages of the representations in the
three-body case is that they show which portions of the physical-sheet
three-body scattering matrix are ``responsible'' for the resonances associated
with a particular unphysical sheet. A resonance appears to be the energy where
the correspondingly truncated scattering matrix (taken on the physical sheet)
has eigenvalue zero. We also mention applications of this approach to some
specific three-body systems, based on the Faddeev differential equations.Comment: Based on a lecture given at the International Workshop ``Critical
Stability of Few-Body Quantum Systems'' (Dresden, October 17--22, 2005
Mapping a star with transits: orbit precession effects in the Kepler-13 system
Kepler-13b (KOI-13.01) is a most intriguing exoplanet system due to the rapid
precession rate, exhibiting several exotic phenomena. We analyzed
Short Cadence data up to Quarter 14, with a total time-span of 928 days, to
reveal changes in transit duration, depth, asymmetry, and identify the possible
signals of stellar rotation and low-level activity. We investigated long-term
variations of transit light curves, testing for duration, peak depth and
asymmetry. We also performed cluster analysis on quarters. We computed
the autocorrelation function of the out-of-transit light variations. Transit
duration, peak depth, and asymmetry evolve slowly, due to the slowly drifting
transit path through the stellar disk. The detected transit shapes will map the
stellar surface on the time scale of decades. We found a very significant
clustering pattern with 3-orbit period. Its source is very probably the
rotating stellar surface, in the 5:3 spin-orbit resonance reported in a
previous study. The autocorrelation function of the out-of-transit light
variations, filtered to 25.4 hours and harmonics, shows slow variations and a
peak around 300--360 day period, which could be related to the activity cycle
of the host star.Comment: 7 pages, 7 figures, accepted in MNRA
The Contribution of Late-type/Irregulars to the Faint Galaxy Counts from HST Medium Deep Survey Images
We present a complete morphologically classified sample of 144 faint field
galaxies from the HST Medium Deep Survey with 20.0 < I <22.0 mag. We compare
the global properties of the ellipticals, early and late-type spirals, and find
a non-negligible fraction (13/144) of compact blue [(V-I) < 1.0 mag] systems
with -profiles. We give the differential galaxy number counts for
ellipticals and early-type spirals independently, and find that the data are
consistent with no-evolution predictions based on conventional flat Schechter
luminosity functions (LF's) and a standard cosmology.
Conversely, late-type/Irregulars show a steeply rising differential number
count with slope . No-evolution
models based on the Loveday et al. (1992) and Marzke et al. (1994b) {\it local}
luminosity functions under-predict the late-type/Irregular counts by 1.0 and
0.5 dex, respectively, at I = 21.75 mag. Examination of the Irregulars alone
shows that % appear inert and the remainder have multiple cores. If
the inert galaxies represent a non-evolving late-type population, then a
Loveday-like LF () is ruled out for these types, and a LF
with a steep faint-end () is suggested. If multiple core
structure indicates recent star-formation, then the observed excess of faint
blue field galaxies is likely due to {\it evolutionary} processes acting on a
{\it steep} field LF for late-type/Irregulars. The evolutionary mechanism is
unclear, but 60% of the multiple-core Irregulars show close companions. To
reconcile a Marzke-like LF with the faint redshift surveys, this evolution must
be preferentially occurring in the brightest late-type galaxies with z > 0.5 at
I = 21.75 mag.Comment: 29 pages, 1 catalog and 10 figures. The figures and catalog can be
found at http://www.phys.unsw.edu.au/~spd/bib.htm
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