Q(2) dependence of nuclear transparency for exclusive rho(0) production

Exclusive coherent and incoherent electroproduction of the rho(0) meson from H-1 and N-14 targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q(2)). The ratio of N-14 to H-1 cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q(2) is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency

Nuclear Attenuation of high energy two-hadron system in the string model

Nuclear attenuation of the two-hadron system is considered in the string model. The two-scale model and its improved version with two different choices of constituent formation time and sets of parameters obtained earlier for the single hadron attenuation, are used to describe available experimental data for the $z$-dependence of subleading hadron, whereas satisfactory agreement with the experimental data has been observed. A model prediction for $\nu$-dependence of the nuclear attenuation of the two-hadron system is also presented.Comment: 8 page

Application of the Two-Scale Model to the HERMES Data on Nuclear Attenuation

The Two-Scale Model and its improved version were used to perform the fit to the HERMES data for $\nu$ (the virtual photon energy) and z (the fraction of $\nu$ carried by hadron) dependencies of nuclear multiplicity ratios for $\pi^+$ and $\pi^-$ mesons electro-produced on two nuclear targets ($^{14}$N and $^{84}$Kr). The quantitative criterium $\chi ^2$ was used for the first time to analyse the results of the model fit to the nuclear multiplicity ratios data. The two-parameter's fit gives satisfactory agreement with the HERMES data. Best values of the parameters were then used to calculate the $\nu$- and $z$ - dependencies of nuclear attenuation for $\pi^0$, K$^+$, K$^-$ and $\bar{p}$ produced on $^{84}$Kr target, and also make a predictions for $\nu$, z and the Q$^2$ (the photon virtuality) - dependencies of nuclear attenuation data for those identified hadrons and nuclea, that will be published by HERMES

Evidence for quark-hadron duality in the proton spin asymmetry A(1)

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A(1). Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q(2) between 1.2 and 12 GeV2 and values of W-2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A(1) in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q(2) above 1.6 GeV2

Клапансохраняющие операции на аортальном клапане и восходящей аорте при радикальной коррекции врожденных и приобретенных пороков сердца. Непосредственные результаты

This paper presents the immediate outcomes of valve-sparing operations on the aortic valve and ascending aorta in radical correction of congenital and acquired heart disease. Materials and methods. The study enrolled 50 patients with aortic insufficiency who were operated upon at Shumakov National Medical Research Center of Transplantology and Artificial Organs from 2011 to 2019. The mean age was 48 ± 16 years, 64% of them were men (n = 32). The study included patients with tricuspid (n = 36, 72%) and bicuspid (n = 14, 28%) aortic valves. Aortic valve reimplantation was performed in 32 (64%) patients, aortic root remodeling - in 1 (2%). 17 (34%) patients had no aortic root reconstruction or remodeling. Aortic valve reimplantation was done in 4 (8%) cases in combination with coronary artery bypass grafting, and in 4 (8%) with mitral and tricuspid valve repair. Results. Thirty-day mortality was 0%. In 1 case (2%), a permanent pacemaker was installed due to complete atrioventricular block. There were no neurological and coronary events, and cases of endocarditis. In all patients (100%), aortic valve insufficiency after surgical correction did not exceed grade 1 according to echocardiographic follow-up examination. On aortic valve mean and peak gradients were 8 ± 6 and 15 ± 7 mm Hg, respectively. Findings. Type I and II valve-sparing reconstructive surgery (for bicuspid and tricuspid aortic valves) is an excellent alternative to prosthetic repair with great postoperative outcomes, low valve-associated complications and low mortality. В данной статье представлены непосредственные результаты клапансохраняющих операций на аортальном клапане и восходящей аорте при радикальной коррекции врожденных и приобретенных пороков сердца. Материалы и методы. В исследование вошли 50 пациентов с аортальной недостаточностью, оперированных в нашем центре с 2011-го по 2019 г. Средний возраст составил 48 ± 16 лет, 64% мужчины (n = 32). В исследование вошли пациенты с трехстворчатым (n = 36; 72%) и двустворчатым (n = 14; 28%) аортальным клапаном. Реимплантация аортального клапана выполнена у 32 (64%) пациентов, ремоделирование корня аорты - у 1 (2%). Без реконструкции и ремоделирования корня аорты - 17 (34%) пациентов. В сочетании с коронарным шунтированием - 4 (8%), с пластикой митрального и трикуспидального клапанов - 4 (8%). Результаты. Летальных случаев за период в 30 дней не наблюдали. В 1 случае (2%) в связи с полной атриовентрикулярной блокадой был установлен постоянный электрокардиостимулятор. Неврологических и коронарных событий, а также случаев возникновения эндокардита не наблюдали. У всех пациентов (100%) недостаточность на аортальном клапане после хирургической коррекции по данным эхокардиографического исследования не превышала 1-й степени. На аортальном клапане средний и пиковый градиент составили 8 ± 6 и 15 ± 7 мм рт. ст. соответственно. Выводы. Реконструктивная хирургия с сохранением нативных створок I и II типа, как двустворчатых, так и трехстворчатых аортальных клапанов является прекрасной альтернативой протезированию с отличными послеоперационными результатами, с низкими клапанассоциированными осложнениями и низкой смертностью