99 research outputs found
Measurements of Scintillation Efficiency and Pulse-Shape for Low Energy Recoils in Liquid Xenon
Results of observations of low energy nuclear and electron recoil events in
liquid xenon scintillator detectors are given. The relative scintillation
efficiency for nuclear recoils is 0.22 +/- 0.01 in the recoil energy range 40
keV - 70 keV. Under the assumption of a single dominant decay component to the
scintillation pulse-shape the log-normal mean parameter T0 of the maximum
likelihood estimator of the decay time constant for 6 keV < Eee < 30 keV
nuclear recoil events is equal to 21.0 ns +/- 0.5 ns. It is observed that for
electron recoils T0 rises slowly with energy, having a value ~ 30 ns at Eee ~
15 keV. Electron and nuclear recoil pulse-shapes are found to be well fitted by
single exponential functions although some evidence is found for a double
exponential form for the nuclear recoil pulse-shape.Comment: 11 pages, including 5 encapsulated postscript figure
The BCS-Bose Crossover Theory
We contrast {\it four} distinct versions of the BCS-Bose statistical
crossover theory according to the form assumed for the electron-number equation
that accompanies the BCS gap equation. The four versions correspond to
explicitly accounting for two-hole-(2h) as well as two-electron-(2e) Cooper
pairs (CPs), or both in equal proportions, or only either kind. This follows
from a recent generalization of the Bose-Einstein condensation (GBEC)
statistical theory that includes not boson-boson interactions but rather 2e-
and also (without loss of generality) 2h-CPs interacting with unpaired
electrons and holes in a single-band model that is easily converted into a
two-band model. The GBEC theory is essentially an extension of the
Friedberg-T.D. Lee 1989 BEC theory of superconductors that excludes 2h-CPs. It
can thus recover, when the numbers of 2h- and 2e-CPs in both BE-condensed and
noncondensed states are separately equal, the BCS gap equation for all
temperatures and couplings as well as the zero-temperature BCS
(rigorous-upper-bound) condensation energy for all couplings. But ignoring
either 2h- {\it or} 2e-CPs it can do neither. In particular, only {\it half}
the BCS condensation energy is obtained in the two crossover versions ignoring
either kind of CPs. We show how critical temperatures from the original
BCS-Bose crossover theory in 2D require unphysically large couplings for the
Cooper/BCS model interaction to differ significantly from the s of
ordinary BCS theory (where the number equation is substituted by the assumption
that the chemical potential equals the Fermi energy).Comment: thirteen pages including two figures. Physica C (in press, 2007
Exciton swapping in a twisted graphene bilayer as a solid-state realization of a two-brane model
It is shown that exciton swapping between two graphene sheets may occur under
specific conditions. A magnetically tunable optical filter is described to
demonstrate this new effect. Mathematically, it is shown that two turbostratic
graphene layers can be described as a "noncommutative" two-sheeted
(2+1)-spacetime thanks to a formalism previously introduced for the study of
braneworlds in high energy physics. The Hamiltonian of the model contains a
coupling term connecting the two layers which is similar to the coupling
existing between two braneworlds at a quantum level. In the present case, this
term is related to a K-K' intervalley coupling. In addition, the experimental
observation of this effect could be a way to assess the relevance of some
theoretical concepts of the braneworld hypothesis.Comment: 15 pages, 3 figures, final version published in European Physical
Journal
E-retailing ethics in Egypt and its effect on customer repurchase intention
The theoretical understanding of online shopping behaviour has received much attention. Less focus has been given to the formation of the ethical issues that result from online shopper interactions with e-retailers. The vast majority of earlier research on this area is conceptual in nature and limited in scope by focusing on consumers’ privacy issues. Therefore, the purpose of this paper is to propose a theoretical model explaining what factors contribute to online retailing ethics and its effect on customer repurchase intention. The data were analysed using variance-based structural equation modelling, employing partial least squares regression. Findings indicate that the five factors of the online retailing ethics (security, privacy, non- deception, fulfilment/reliability, and corporate social responsibility) are strongly predictive of online consumers’ repurchase intention. The results offer important implications for e-retailers and are likely to stimulate further research in the area of e-ethics from the consumers’ perspective
Quantum Mechanical Co-Adsorption Modelling of Real Electrically Controlled Semiconductor Gas Sensors
CMOS-compatible nanoscale gas-sensor based on field effect
The integration of a solid state gas sensor of the metal oxide sensor type into CMOS technology still is a challenge because of the high temperatures during metal oxide annealing and sensor operation that do not comply with silicon device stability. In the presence of an external electric field sensor sensitivity can be controlled through a change of the Fermi energy level and consequently it is possible to reduce the operation temperature. Based in this effect, a novel field effect gas sensor was developed resembling a reversed insulated gate field effect transistor (IGFET) with the thickness of gas sensing layer in the range of the Debye length (L-D). Under these conditions the controlling electrical field reaches the sensitive surface and a modulation of the Fermi energy level occurs, producing an effective control of gas sensitivity and sensor response. In this paper several aspects are treated, like technological fabrication process, complete sensor characterization by means of an electrical model and sensor response measurements. Other effects as base-line drift effects and layer thickness implications also are studied
CMOS-compatible field effect nanoscale gas-sensor: Operation and annealing models
Complete modelling of electrically controlled nanoscale gas sensors with Poisson, Wolkenstein, Fokker-Planck and continuity is presented. Based on a plausible Drift explanation we developed suitable models for sensitivity control and operational modes. An onset for CMOS-complying annealing procedures is given
"Relationship Between Pumping-Test and Slug-Test Parameters: Scale Effect or Artifact?" by J.J. Butler Jr. and J.M. Healey
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