49,565 research outputs found
Detector Efficiency Limits on Quantum Improvement
Although the National Institute of Standards and Technology has measured the
intrinsic quantum efficiency of Si and InGaAs APD materials to be above 98 % by
building an efficient compound detector, commercially available devices have
efficiencies ranging between 15 % and 75 %. This means bandwidth, dark current,
cost, and other factors are more important than quantum efficiency for existing
applications. This paper systematically examines the generic detection process,
lays out the considerations needed for designing detectors for non-classical
applications, and identifies the ultimate physical limits on quantum
efficiency.Comment: LaTeX, 7 pages, 3 figure
Characterizations of Student's t-distribution via regressions of order statistics
Utilizing regression properties of order statistics, we characterize a family
of distributions introduced by Akhundov, Balakrishnan, and Nevzorov (2004),
that includes the t-distribution with two degrees of freedom as one of its
members. Then we extend this characterization result to t-distribution with
more than two degrees of freedom.Comment: To appear in "Statistics
Modification of the Brink-Axel Hypothesis for High Temperature Nuclear Weak Interactions
We present shell model calculations of electron capture strength
distributions in A=28 nuclei and computations of the corresponding capture
rates in supernova core conditions. We find that in these nuclei the Brink-Axel
hypothesis for the distribution of Gamow-Teller strength fails at low and
moderate initial excitation energy, but may be a valid tool at high excitation.
The redistribution of GT strength at high initial excitation may affect capture
rates during collapse. If these trends which we have found in lighter nuclei
also apply for the heavier nuclei which provide the principal channels for
neutronization during stellar collapse, then there could be two implications
for supernova core electron capture physics. First, a modified Brink-Axel
hypothesis could be a valid approximation for use in collapse codes. Second,
the electron capture strength may be moved down significantly in transition
energy, which would likely have the effect of increasing the overall electron
capture rate during stellar collapse.Comment: 15 pages, 19 figure
Neutrino Pair Emission from Hot Nuclei During Stellar Collapse
We present shell-model calculations showing that residual interaction-induced
configuration mixing enhances the rate of neutral current de-excitation of
thermally excited nuclei into neutrino-antineutrino pairs. Though our
calculations reinforce the conclusions of previous studies that this process is
the dominant source of neutrino pairs near the onset of neutrino trapping
during stellar collapse, our shell-model result has the effect of increasing
the energy of these pairs, possibly altering their role in entropy transport in
supernovae.Comment: 9 pages, 8 figure
Convergence and Divergence of Themes in Successful Psychotherapy: An Assimilation Analysis
Theme convergence is the linking of seemingly unrelated problem domains as they advance through assimilation stages-a developmental sequence of cognitive and affective changes through which problematic content is hypothesized to pass during successful psychotherapy. Theme divergence is the contradiction or conflict of solutions to different problems, so that progress in one domain leads to stagnation or regression in another domain. An intensive qualitative method called assimilation analysis was used to examine theme convergence and divergence in a successful psychodynamic psychotherapy with a 20–yr–old female patient. Because specific problems often fail to progress monotonically, even in successful psychotherapy cases, it is suggested that clients\u27 problems cannot be resolved in isolation; instead, they may influence each other toward resolution or stagnation in complex and unpredictable ways
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Potent Attractant for Root-Knot Nematodes in Exudates from Seedling Root Tips of Two Host Species.
Root-knot nematodes (RKN; Meloidogyne spp.) can parasitize over 2,000 plant species and are generally considered to be the most agriculturally damaging group of plant-parasitic nematodes worldwide. Infective juveniles (J2) are non-feeding and must locate and invade a host before their reserves are depleted. However, what attracts J2 to appropriate root entry sites is not known. An aim of this research is to identify semiochemicals that attract RKN to roots. J2 of the three RKN species tested are highly attracted to root tips of both tomato and Medicago truncatula. For both hosts, mutants defective in ethylene signaling were found to be more attractive than those of wild type. We determined that cell-free exudates collected from tomato and M. truncatula seedling root tips were highly attractive to M. javanica J2. Using a pluronic gel-based microassay to monitor chemical fractionation, we determined that for both plant species the active component fractionated similarly and had a mass of ~400 based on size-exclusion chromatography. This characterization is a first step toward identification of a potent and specific attractant from host roots that attracts RKN. Such a compound is potentially a valuable tool for developing novel and safe control strategies
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