Double-exciton component of the cyclotron spin-flip mode in a quantum Hall ferromagnet

We report on the calculation of the cyclotron spin-flip excitation (CSFE) in a spin-polarized quantum Hall system at unit filling. This mode has a double-exciton component which contributes to the CSFE correlation energy but can not be found by means of a mean field approach. The result is compared with available experimental data.Comment: 9 pages, 2 figure

Magnetophonon resonance in photoluminescence excitation spectra of magnetoexcitons in GaAs/Al0.3Ga0.7As superlattice

Strong increase in the intensity of the peaks of excited magneto-exciton (ME) states in the photoluminescence excitation (PLE) spectra recorded for the ground heavy-hole magneto-excitons (of the 1sHH type) has been found in a GaAs/AlGaAs superlattice in strong magnetic field B applied normal to the sample layers. While varying B the intensities of the PLE peaks have been measured as functions of energy separation $\Delta E$ between excited ME peaks and the ground state of the system. The resonance profiles have been found to have maxima at $\Delta E_{\rm max}$ close to the energy of the GaAs LO-phonon. However, the value of $\Delta E_{\rm max}$ depends on quantum numbers of the excited ME state. The revealed very low quantum efficiency of the investigated sample allows us to ascribe the observed resonance to the enhancement of the non-radiative magneto-exciton relaxation rate arising due to LO-phonon emission. The presented theoretical model, being in a good agreement with experimental observations, provides a method to extract 1sHH magneto-exciton ``in-plane" dispersion from the dependence of $\Delta E_{\rm max}$ on the excited ME state quantum numbers.Comment: 9 pages, 6 figure

Особенности инфузионной терапии при бариатрических операциях

The objective: to determine principles of intraoperative infusion therapy in patients with morbid obesity under the control of volemic status.Methods: a prospective randomized study was conducted in 60 patients with BMI of 45.57 (40.01; 48.65) kg/m2 who underwent laparoscopic gastric resection under combined anesthesia based on low-flow desflurane inhalation in combination with prolonged epidural analgesia with ropivacaine. Patients were allowed to consume 200 ml of clear liquid 3 hours before the surgery, and solid foods 6 hours before surgery. Patients were divided into 2 groups (n = 30) depending on the composition of infusion therapy: colloids (gelatin solution) were used in Group 1 with balanced crystalloids in a ratio of 1:1-1.5, balanced crystalloid solutions were used in Group 2. The following parameters were studied: hemodynamics, water sector distribution index (IRVS), hemoglobin, hematocrit, potassium ions, sodium, creatinine, lactate, and CBS. A PLR test was performed intraoperatively.Results. It was revealed that the patients had an uneven distribution between water sectors with shortage of fluid in the intravascular bed, as evidenced by a positive PLR test, as well as low IRVS. When conducting targeted infusion therapy in Group 1, a smaller volume of infusion solutions was used, however, that made it possible to achieve stabilization of hemodynamic parameters due to redistribution of water sectors, which was also evidenced by changes in laboratory parameters.Conclusion. Obese patients have intravascular fluid deficiency due to uneven distribution between water sectors. The inclusion of a colloidal plasma substitute to the infusion therapy contributes to the elimination of hypovolemia and reduces the volume of transfused media.Цель: под контролем волемического статуса определить принципы проведения интраоперационной инфузионной терапии у больных морбидным ожирением.Методы: проспективное рандомизированное исследование 60 больных с индексом массы тела 45,57 (40,01; 48,65) кг/м2, которым проведена лапароскопическая резекция желудка в условиях сочетанной анестезии на основе низкопоточной ингаляции десфлурана в комбинации с продленной эпидуральной анальгезией ропивакаина. Больным разрешалось употребление 200 мл прозрачной жидкости за 3 ч, а твердой ‒ за 6 ч до операции. Пациенты делились на две группы (n = 30) в зависимости от состава инфузионной терапии: в 1-й группе использовали коллоиды (раствор желатина) со сбалансированными кристаллоидами в соотношении 1:1‒1,5, во 2-й группе ‒ сбалансированные кристаллоидные растворы. Исследовали показатели гемодинамики, индекс распределения водного сектора (ИРВС), гемоглобина, гематокрита, ионов калия, натрия, креатинина, лактата, кислотно-основного состояния. Интраоперационно проводился PLR-тест.Результаты. Выявлено, что у больных имелось неравномерное распределение жидкости между водными секторами с дефицитом ее во внутрисосудистом русле, о чем свидетельствовал положительный PLR-тест, а также низкий ИРВС. При проведении целенаправленной инфузионной терапии в 1-й группе был использован меньший объем инфузионных растворов, однако это позволило добиться стабилизации гемодинамических показателей за счет перераспределения жидкости между водными секторами, о чем также свидетельствовали изменения лабораторных показателей.Заключение. У больных ожирением имеется внутрисосудистый дефицит жидкости за счет неравномерного распределения между водными секторами. Включение в состав инфузионной терапии коллоидного плазмозаменителя способствует ликвидации гиповолемии и сокращает объем переливаемых сред

Diffusion-induced vortex filament instability in 3-dimensional excitable media

We studied the stability of linear vortex filaments in 3-dimensional (3D) excitable media, using both analytical and numerical methods. We found an intrinsic 3D instability of vortex filaments that is diffusion-induced, and is due to the slower diffusion of the inhibitor. This instability can result either in a single helical filament or in chaotic scroll breakup, depending on the specific kinetic model. When the 2-dimensional dynamics were in the chaotic regime, filament instability occurred via on-off intermittency, a failure of chaos synchronization in the third dimension.Comment: 5 pages, 5 figures, to appear in PRL (September, 1999

Thermal properties and structure of cast carbon-containing invar and superinvar alloys after two-stage annealing

The effect of carbon content on thermal properties of cast superinvar alloys subjected to two-stage annealing is studied. It is shown that carbon improves the casting properties of the alloys but raises the temperature coefficient of linear expansion (CTLE). Two-stage high-temperature annealing makes it possible to remove carbon from the solid solution and to transfer it into graphite, which is accompanied by decrease in the CTLE. © 2013 Springer Science+Business Media New York

Isospin dependence of relative yields of K+K^+ and K0K^0 mesons at 1.528 AGeV

Results on $K^+$ and $K^0$ meson production in $^{96}_{44}$Ru + $^{96}_{44}$Ru and $^{96}_{40}$Zr + $^{96}_{40}$Zr collisions at a beam kinetic energy of 1.528$A$ GeV, measured with the FOPI detector at GSI-Darmstadt, are investigated as a possible probe of isospin effects in high density nuclear matter. The measured double ratio ($K^+/K^0$)$_{Ru}$/($K^+/K^0$)$_{Zr}$ is compared to the predictions of a thermal model and a Relativistic Mean Field transport model using two different collision scenarios and under different assumptions on the stiffness of the symmetry energy. We find a good agreement with the thermal model prediction and the assumption of a soft symmetry energy for infinite nuclear matter while more realistic transport simulations of the collisions show a similar agreement with the data but also exhibit a reduced sensitivity to the symmetry term.Comment: 5 pages, 3 figures. accepted for publication in Phys. Rev.

First analysis of anisotropic flow with Lee--Yang zeroes

We report on the first analysis of directed and elliptic flow with the new method of Lee--Yang zeroes. Experimental data are presented for Ru+Ru reactions at 1.69 AGeV measured with the FOPI detector at SIS/GSI. The results obtained with several methods, based on the event-plane reconstruction, on Lee--Yang zeroes, and on multi-particle cumulants (up to 5th order) applied for the first time at SIS energies, are compared. They show conclusive evidence that azimuthal correlations between nucleons and composite particles at this energy are largely dominated by anisotropic flow.Comment: 5 pages, 3 figures, submitted to Phys. Rev. C Rapid Co

Strange meson production in Al+Al collisions at 1.9A GeV

The production of K$^+$, K$^-$ and $\varphi$(1020) mesons is studied in Al+Al collisions at a beam energy of 1.9A GeV which is close or below the production threshold in NN reactions. Inverse slopes, anisotropy parameters, and total emission yields of K$^{\pm}$ mesons are obtained. A comparison of the ratio of kinetic energy distributions of K$^-$ and K$^+$ mesons to the HSD transport model calculations suggests that the inclusion of the in-medium modifications of kaon properties is necessary to reproduce the ratio. The inverse slope and total yield of $\phi$ mesons are deduced. The contribution to K$^-$ production from $\phi$ meson decays is found to be [17 $\pm$ 3 (stat) $^{+2}_{-7}$ (syst)] %. The results are in line with previous K$^{\pm}$ and $\phi$ data obtained for different colliding systems at similar incident beam energies.Comment: 16 pages, 11 figure

Direct comparison of phase-space distributions of K- and K+ mesons in heavy-ion collisions at SIS energies - evidence for in-medium modifications of kaons ?

The ratio of K- to K+ meson yields has been measured in the systems RuRu at 1.69 A GeV, Ru+Zr at 1.69 A GeV, and Ni+Ni at 1.93 A GeV incident beam kinetic energy. The yield ratio is observed to vary across the measured phase space. Relativistic transport-model calculations indicate that the data are best understood if in-medium modifications of the kaons are taken into account.Comment: 14 pages including 3 figure