935 research outputs found
Optical phonon scattering and theory of magneto-polarons in a quantum cascade laser in a strong magnetic field
We report a theoretical study of the carrier relaxation in a quantum cascade
laser (QCL) subjected to a strong magnetic field. Both the alloy (GaInAs)
disorder effects and the Frohlich interaction are taken into account when the
electron energy differences are tuned to the longitudinal optical (LO) phonon
energy. In the weak electron-phonon coupling regime, a Fermi's golden rule
computation of LO phonon scattering rates shows a very fast non-radiative
relaxation channel for the alloy broadened Landau levels (LL's). In the strong
electron-phonon coupling regime, we use a magneto-polaron formalism and compute
the electron survival probabilities in the upper LL's with including increasing
numbers of LO phonon modes for a large number of alloy disorder configurations.
Our results predict a nonexponential decay of the upper level population once
electrons are injected in this state.Comment: 10 pages, 23 figure
Diffractive gauge bosons production beyond QCD factorisation
We discuss single diffractive gauge bosons ()
production in proton-proton collisions at different (LHC and RHIC) energies
within the color dipole approach. The calculations are performed for gauge
bosons produced at forward rapidities. The diffractive cross section is
predicted as function of fractional momentum and invariant mass of the lepton
pair. We found a dramatic breakdown of the diffractive QCD factorisation caused
by an interplay of hard and soft interactions. Data from the CDF experiment on
diffractive production of and are well explained in a parameter free
way.Comment: 28 pages, 10 figures; a clarification of absorptive corrections has
been added, typos corrected; the published versio
Large Rapidity Gap Processes in Proton-Nucleus Collisions
The cross sections for a variety of channels of proton-nucleus interaction
associated with large gaps in rapidity are calculated within the Glauber-Gribov
theory. We found inelastic shadowing corrections to be dramatically enhanced
for such events. We employ the light-cone dipole formalism which allows to
calculate the inelastic corrections to all orders of the multiple interaction.
Although Gribov corrections are known to make nuclear matter more transparent,
we demonstrate that in some instances they lead to an opaqueness. Numerical
calculations are performed for the energies of the HERA-B experiment, and the
RHIC-LHC colliders.Comment: 19 page
Клинический случай поражения молнией
Atmospheric electricity damage as a result of lightning strike is a relatively rare condition in intensive care medicine, however it can be accompanied by high mortality and serious complications in the majority of survived patients.The objective was to demonstrate a clinical case of lightning injury and discussion of diagnostic and treatment aspects in this condition.Materials and Methods. 18-yr old patient was delivered to hospital after lightning strike. She lost consciousness, there was no breathing for a short time, and the witnesses provided artificial respiration and external cardiac compressions. On admission, the signs of shock were present in parallel with dopamine infusion, the skin was pale-grey and cold, with traces of thermal damage according to the type of contact with metal of various localization on the neck, scalp, front surface of the chest and abdominal wall, in the groin, on the left foot. The patient was hospitalized to ICU, therapeutic and diagnostic measures were started. We revealed decompensated lactic acidosis, biochemical signs of myocardial and muscle damage. The infusion therapy, analgesics, antibiotics, proton pump inhibitors, anticoagulants were administered. During the therapy in the first 6 hours, the signs of shock were attenuated, in 4 days, the patient was transferred to traumatological department in a stable state. After the transfer from the ICU, hearing decline as well as pain and sensory disturbances in the left foot are persisting.Conclusion. An integrated approach is required in the diagnosis, treatment, and rehabilitation of patients with lightning injury.Поражение атмосферным электричеством в результате удара молнии – состояние, достаточно редко встречающееся в реанимационной практике; вместе с тем, оно сопровождается высокой смертностью и серьезными осложнениями у значительной части выживших пациентов.Цель – демонстрация клинического наблюдения поражения атмосферным электричеством и обсуждение аспектов диагностики и лечения данной патологии.Материалы и методы. Пациентка 18 лет доставлена в стационар после поражения молнией на берегу. Отмечалась потеря сознания, кратковременно отсутствовало дыхание, свидетели происшествия проводили искусственное дыхание и наружный массаж сердца. При поступлении – признаки шока на фоне инфузии допамина, кожный покров бледно-серый, холодный, следы термического повреждения по типу соприкосновения с металлом различной локализации на шее, волосистой части головы, передней поверхности грудной клетки, брюшной стенке, в паховой области, на левой стопе. Госпитализирована в ОРИТ, начат комплекс мер диагностики и интенсивной терапии. Выявлены декомпенсированный метаболический ацидоз, биохимические признаки повреждения миокарда и мышечной ткани. Назначены инфузионная терапия, анальгетики, антибиотики, блокаторы протонной помпы, антикоагулянты. На фоне проводимого лечения в первые 6 часов явления шока купированы, через 4 суток в стабильном состоянии переведена в травматологическое отделение. После перевода из ОРИТ сохраняются нарушения слуха, боль и нарушения чувствительности в левой стопе.Заключение. Необходим комплексный подход в диагностике, лечении, реабилитации пациентов с поражением атмосферным электричеством
Gluon Shadowing in DIS off Nuclei
Within a light-cone quantum-chromodynamics dipole formalism based on the
Green function technique, we study nuclear shadowing in deep-inelastic
scattering at small Bjorken xB < 0.01. Such a formalism incorporates naturally
color transparency and coherence length effects. Calculations of the nuclear
shadowing for the \bar{q}q Fock component of the photon are based on an exact
numerical solution of the evolution equation for the Green function, using a
realistic form of the dipole cross section and nuclear density function. Such
an exact numerical solution is unavoidable for xB > 0.0001, when a variation of
the transverse size of the \bar{q}q Fock component must be taken into account.
The eikonal approximation, used so far in most other models, can be applied
only at high energies, when xB < 0.0001 and the transverse size of the \bar{q}q
Fock component is "frozen" during propagation through the nuclear matter. At xB
< 0.01 we find quite a large contribution of gluon suppression to nuclear
shadowing, as a shadowing correction for the higher Fock states containing
gluons. Numerical results for nuclear shadowing are compared with the available
data from the E665 and NMC collaborations. Nuclear shadowing is also predicted
at very small xB corresponding to LHC kinematical range. Finally the model
predictions are compared and discussed with the results obtained from other
models.Comment: 29 pages including 7 figures; Fig.7 modified, some references and
corresponding discussion adde
Stimulated emission of radiation using spin-population inversion in metals: a spin-laser
Arrays of 10 nm-diameter point contacts of exchange-coupled
spin-majority/spin-minority ferromagnetic metals, integrated into
infrared-terahertz range photon resonators, are fabricated and measured
electrically and optically. Giant, threshold-type electronic excitations under
high-current pumping of the devices are observed as abrupt but reversible steps
in device resistance, in many cases in access of 100%, which correlate with
optical emission from the devices. The results are interpreted as due to
stimulated spin-flip electron-photon relaxation in the system.Comment: 5 page
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