360 research outputs found
Low-temperature electrical discharge through solid xenon
The uniform self-sustained electrical discharge through solid xenon has been realized and studied. The
multiplication of electrons proceeds in the noble gas above the xenon crystal interface whereas a positive
feedback is realized at the account of multiple exciton formation by excess electrons drifted through the
crystal: molecular excitons emit VUV photons which knocked out secondary electrons from photosensitive
cathode. The discharge was stimulated by short electrical spark along the sample axes. The discharge electrical
properties as well as the spectra of solid xenon electroluminescence in UV and visible have been studied.
Electric discharge in solid xenon was proved to be an effective source of UV radiation and a convenient tool
to study the processes involving excitons and electrons in solid xenon at high pressures
A comparison principle for functions of a uniformly random subspace
This note demonstrates that it is possible to bound the expectation of an
arbitrary norm of a random matrix drawn from the Stiefel manifold in terms of
the expected norm of a standard Gaussian matrix with the same dimensions. A
related comparison holds for any convex function of a random matrix drawn from
the Stiefel manifold. For certain norms, a reversed inequality is also valid.Comment: 8 page
Теоретические аспекты создания виртуального практикума по морфологическим дисциплинам
The theoretical analysis of issues related to designing a virtual morphological workshop, showed the necessity to set some principles for its development. In this work the structural organization of the virtual laboratory and five principles of software development are described.Теоретическое рассмотрение вопросов, связанных с проектированием виртуального морфологического практикума, показало целесообразность выделения ряда принципов его разработки. В настоящей работе рассмотрена структурная организация виртуальной лаборатории и описан ряд принципов программной разработки
Алгоритмы количественного анализа изображений в информационном окружении морфологического исследования
It's necessary to make an effective performance of research work in the conditions of a modern science research automation. This aspect is not realized as full as it need in the Russian medical high schools. Most actual questions of medical education process are introduction and active use of these research automation tools. To solve this problem it is necessary to design some new principles and algorithms of working with them.В условиях современной науки автоматизация проводимых исследований является необходимым условием эффективного выполнения исследовательской работы. В российских медицинских вузах данный аспект реализуется не в полной мере. Актуальным вопросом медицинского образования является внедрение и активное использование новых инструментов автоматизации исследования, для чего необходима разработка принципов и алгоритмов работы с ними
Новые методы ведения лабораторного практикума
Medico-biological laboratories in Russian institutes of higher medical education do not support effectively the educational process. Development of universal criteria and requirements to modeling of a virtual medico-biological laboratory is significant for medical education. The purpose of the article is to develop principal approaches to realization of the model in a virtual medico-biological laboratory.Образовательный потенциал медико-биологических лабораторий российских медицинских вузов не реализуется в полной мере. Актуальным вопросом медицинского образования является дополнение и замена проводимых лабораторных экспериментов виртуальными практикумами, для чего необходима разработка принципиальных подходов к моделированию виртуальной медико-биологической лаборатории
Electron Scattering From High-Momentum Neutrons in Deuterium
We report results from an experiment measuring the semi-inclusive reaction
where the proton is moving at a large angle relative to the
momentum transfer. If we assume that the proton was a spectator to the reaction
taking place on the neutron in deuterium, the initial state of that neutron can
be inferred. This method, known as spectator tagging, can be used to study
electron scattering from high-momentum (off-shell) neutrons in deuterium. The
data were taken with a 5.765 GeV electron beam on a deuterium target in
Jefferson Laboratory's Hall B, using the CLAS detector. A reduced cross section
was extracted for different values of final-state missing mass ,
backward proton momentum and momentum transfer . The data
are compared to a simple PWIA spectator model. A strong enhancement in the data
observed at transverse kinematics is not reproduced by the PWIA model. This
enhancement can likely be associated with the contribution of final state
interactions (FSI) that were not incorporated into the model. A ``bound neutron
structure function'' was extracted as a function of and
the scaling variable at extreme backward kinematics, where effects of
FSI appear to be smaller. For MeV/c, where the neutron is far
off-shell, the model overestimates the value of in the region of
between 0.25 and 0.6. A modification of the bound neutron structure
function is one of possible effects that can cause the observed deviation.Comment: 33 pages RevTeX, 9 figures, to be submitted to Phys. Rev. C. Fixed 1
Referenc
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
tex
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
First measurement of direct photoproduction on the proton
We report on the results of the first measurement of exclusive
meson photoproduction on protons for GeV and GeV. Data were collected with the CLAS detector at the Thomas
Jefferson National Accelerator Facility. The resonance was detected via its
decay in the channel by performing a partial wave analysis of the
reaction . Clear evidence of the meson
was found in the interference between and waves at GeV. The -wave differential cross section integrated in the mass range of
the was found to be a factor of 50 smaller than the cross section
for the meson. This is the first time the meson has been
measured in a photoproduction experiment
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
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