On a Possibility to Determine the Sign of the Polarized Gluon Distribution

We investigate the possibility to draw conclusions on the sign of the spin-dependent gluon distribution, $\Delta G(x, Q^2)$, from existing polarized DIS data. The spin-dependent parton distributions $\Delta u_v, \Delta d_v, \Delta {\bar u}, \Delta {\bar d}, \Delta {s}$, and $\Delta G$ are constructed in the framework of a phenomenological procedure taking into account some assumptions on signs of valence and sea parton distributions motivated by 't Hooft's mechanism of quark-quark interaction induced by instantons. The axial gluon anomaly and data on integral quark contributions to the proton spin, $\Delta \tilde u, \Delta \tilde d$, and $\Delta \tilde s$, are also taken into account. Predictions for the $x$- and $Q^2$-dependencies of the polarized proton and neutron structure functions, $g_1^p$ and $g_1^n$, are compared to experimental data. It is shown that the neutron structure function, $g_1^n$, is especially sensitive to the sign of $\Delta G(x, Q^2)$. The results of our analysis supports the conclusion that this sign should be positive.Comment: 14 pages, latex, 12 figure

Jet Energy Density in Hadron-Hadron Collisions at High Energies

The average particle multiplicity density dN/deta is the dynamical quantity which reflects some regularities of particle production in low-pT range. The quantity is an important ingredient of z-scaling. Experimental results on charged particle density are available for pp, pA and AA collisions while experimental properties of the jet density are still an open question. The goal of this work is to find the variable which will reflect the main features of the jet production in low transverse energy range and play the role of the scale factor for the scaling function psi(z) and variable z in data z-presentation. The appropriate candidate is the variable we called "scaled jet energy density". Scaled jet energy density is the probability to have a jet with defined ET in defined xT and pseudorapidity regions. The PYTHIA6.2 Monte Carlo generator is used for calculation of scaled jet energy density in proton-proton collisions over a high energy range (sqrt s = 200-14000 GeV) and at eta = 0. The properties of the new variable are discussed and sensitivity to "physical scenarios" applied in the standard Monte Carlo generator is noted. The results of scaled jet energy density at LHC energies are presented and compared with predictions based on z-scaling.Comment: 11 pages, LaTeX, 8 figures, Presented at the XVII International Baldin Seminar on High Energy Physics Problems "Relativistic Nuclear Physics & Quantum Chromodynamics", Dubna, Russia, September 27 - October 2, 200

Permafrost hydrology in changing climatic conditions: seasonal variability of stable isotope composition in rivers in discontinuous permafrost

Role of changing climatic conditions on permafrost degradation and hydrology was investigated in the transition zone between the tundra and forest ecotones at the boundary of continuous and discontinuous permafrost of the lower Yenisei River. Three watersheds of various sizes were chosen to represent the characteristics of the regional landscape conditions. Samples of river flow, precipitation, snow cover, and permafrost ground ice were collected over the watersheds to determine isotopic composition of potential sources of water in a river flow over a two year period. Increases in air temperature over the last forty years have resulted in permafrost degradation and a decrease in the seasonal frost which is evident from soil temperature measurements, permafrost and active-layer monitoring, and analysis of satellite imagery. The lowering of the permafrost table has led to an increased storage capacity of permafrost affected soils and a higher contribution of ground water to river discharge during winter months. A progressive decrease in the thickness of the layer of seasonal freezing allows more water storage and pathways for water during the winter low period making winter discharge dependent on the timing and amount of late summer precipitation. There is a substantial seasonal variability of stable isotopic composition of river flow. Spring flooding corresponds to the isotopic composition of snow cover prior to the snowmelt. Isotopic composition of river flow during the summer period follows the variability of precipitation in smaller creeks, while the water flow of larger watersheds is influenced by the secondary evaporation of water temporarily stored in thermokarst lakes and bogs. Late summer precipitation determines the isotopic composition of texture ice within the active layer in tundra landscapes and the seasonal freezing layer in forested landscapes as well as the composition of the water flow during winter months

Качественная и количественная оценка ликвородинамики

Disorders of cerebrospinal fluid (CSF) secretion, dynamics and absorption are common in different illnesses and injuries of the central nervous system (CNS). Nowadays magnetic-resonance tomography (MRI) is the leading research method of CSF dynamics. There are some MRI techniques for both qualitative and quantitative evaluation of CSF dynamic. The assessment of CSF movement is needed to define treatment strategy for patients with different types of hydrocephalus. In this review we have summarized the information about physic basement, area of application of modern MRI techniques. The main attention was paid to modern views on hydrocephalus pathogenesis, pathological CSF flow dynamics in CNS disorders and traumatic brain injury.Нарушения продукции, тока и резорбции спинномозговой жидкости (СМЖ) встречаются при многих заболеваниях и повреждениях нервной системы. В настоящее время магнитно-резонансная томография (МРТ) является ведущим методом исследования ликовородинамики. На сегодняшний день известно несколько методик исследования, которые позволяют оценить качественные и количественные параметры движения спинномозговой жидкости. Оценка ликвородинамики необходима для определения правильной тактики лечения пациентов с различными видами гидроцефалии. В обзоре литературы приведены физические основы, области применения современных МРТ-методов изучения ликвородинамики. Особое внимание уделено современным взглядам на патогенез гидроцефалии, особенностям тока ликвора при различных заболеваниях центральной нервной системы и черепно-мозговой травме

Tungstate Based Ceramics Obtained By Spark Plasma Sintering Method – Possible Material for Consolidation of Radioactive Wastes’ Components

The Spark Plasma Sintering method was used to produce high-density ceramics from tungstates SrWO4 and NaNd(WO4)2 with scheelite structure. These compounds are proposed as possible matrices for the consolidation of radwaste components. Powder samples were obtained by coprecipitation method and studied by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). After sintering, the samples retained their phase identity (scheelite structure). The total duration of sintering was ∼ 13-15 min, the relative density was reached ∼ 92, 99%. Keywords: Tungstates, RW, Spark Plasma Sintering, high density, microstructur

The Gross--Llewellyn Smith Sum Rule in the Analytic Approach to Perturbative QCD

We apply analytic perturbation theory to the Gross--Llewellyn Smith sum rule. We study the $Q^2$ evolution and the renormalization scheme dependence of the analytic three-loop QCD correction to this sum rule, and demonstrate that the results are practically renormalization scheme independent and lead to rather different $Q^2$ evolution than the standard perturbative correction possesses.Comment: 17 pages, 9 eps figures, REVTe

Радиохирургическое лечение пациента с разрывом артериовенозной мальформации, расположенной в функционально значимой зоне

Arteriovenous malformations (AVMs) of the brain are quite rare vascular pathologies, but they are life-threatening, due to the risk of intracerebral hemorrhage. Stereotactic radiosurgical treatment of patients with cerebral AVM is performed in cases where surgical removal is impossible or embolization with a stable occlusive effect cannot be performed. Currently, for the diagnosis of AVM, magnetic resonance imaging (MRI) is increasingly used because of its noninvasiveness and minimal risks. When a malformation is located in a functionally significant area, then a non-invasive technique is used to assess its interposition and mapping - functional magnetic resonance imaging.We have presented the experience of radiosurgical treatment of a 43-year-old male patient with a ruptured AVM located in the left temporal lobe, near Wernicke’s area. The patient underwent stereotactic radiosurgical treatment with Elekta Leksell Gamma Knife Perfection device, taking into account the location of the AVM in a functionally significant area, preoperative mapping was performed. After two years, according to MR angiography, the arterial component in the projection of the irradiated AVM was not visualized, which was confirmed by the data of cerebral angiography. Thus, a clinical example has demonstrated the high efficiency of MRI in the diagnosis and assessment of the results of the performed stereotactic radiosurgical treatment of AVMs. Артериовенозные мальформации (АВМ) головного мозга — достаточно редкие сосудистые патологии, однако являются опасными для жизни в связи с риском развития внутримозгового кровоизлияния. Стереотаксическое радиохирургическое лечение пациентов с АВМ головного мозга применяют в тех случаях, когда удаление хирургическим способом не возможно или не может быть проведена эмболизация с устойчивым окклюзионным эффектом. В настоящее время для диагностики АВМ все чаще используют магнитно-резонансную томографию (МРТ) из-за ее неинвазивности и минимальных рисков. При расположении мальформации в функционально значимой зоне для оценки ее взаиморасположения и картирования применяют неинвазивную методику — функциональную МРТ.Нами представлен опыт радиохирургического лечения пациента 43 лет с разрывом АВМ, расположенной в левой височной доле, вблизи зоны Вернике. Больному было проведено стереотаксическое радиохирургическое лечение на аппарате “Elekta Leksell Gamma Knife Perfection”, с учетом расположения АВМ в функционально значимой зоне, выполнили предоперационное картирование. По прошествии двух лет по данным МР-ангиографии артериальный компонент в проекции облученной АВМ не визуализировался, что подтверждалось данными церебральной ангиографии. Таким образом, на клиническом примере продемонстрирована высокая эффективность МРТ в диагностике и оценке результатов проведенного стереотаксического радиохирургического лечения АВМ.

Photon Physics in Heavy Ion Collisions at the LHC

Various pion and photon production mechanisms in high-energy nuclear collisions at RHIC and LHC are discussed. Comparison with RHIC data is done whenever possible. The prospect of using electromagnetic probes to characterize quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One figure added in chapter 5 (comparison with PHENIX data). Some figures and correponding text corrected in chapter 6 (off-chemical equilibrium thermal photon rates). Some figures modified in chapter 7 (off-chemical equilibrium photon rates) and comparison with PHENIX data adde