MORPHOLOGICAL ALTERATIONS OF THE CEPHALIC VEIN WALL AS A PAT OF A NATIVE RTERIOVENOUS FISTULA FOR CHRONIC HEMODIALYSIS

The creation of an internal arterio-venous fistula according to Brescia and Cimino (1966) changes the functional conditions of cephalic vein and radial artery. Arterial blood enters under high pressure the cephalic vein and turbulent blood flow appears. The pathomorphology of the cephalic vein incorporated in the internal native arterio-venous fistula (NAVF) for chronic hemodialysis was studied. Single portions of the vein were surgically removed from 16 patients aged from 20 to 60 years with failed NAVF and then excised because of repeated NAVF creation (group one) and from 3 patients where the vein was removed during the primary NAVF creation (group two). Light and transmission electron microscopy was used. In the first group, the intima and media of the cephalic vein was much ticker than that of the veins of the patients of the second and control group. The increased thickness of the venous intima was accompanied by an augmented number of smooth muscles cells and appearance of new layers while that of the media was followed by structural changes of its elastic network. These alterations depend on the duration of NAVF functioning

Multi-particle Production and Thermalization in High-Energy QCD

We argue that multi-particle production in high energy hadron and nuclear collisions can be considered as proceeding through the production of gluons in the background classical field. In this approach we derive the gluon spectrum immediately after the collision and find that at high energies it is parametrically enhanced by ln(1/x) with respect to the quasi-classical result (x is the Bjorken variable). We show that the produced gluon spectrum becomes thermal (in three dimensions) with an effective temperature determined by the saturation momentum Qs, T= c Qs/2pi during the time ~1/T; we estimate c=sqrt{2pi}/2 ~ 1.2. Although this result by itself does not imply that the gluon spectrum will remain thermal at later times, it has an interesting applications to heavy ion collisions. In particular, we discuss the possibility of Bose-Einstein condensation of the produced gluon pairs and estimate the viscosity of the produced gluon system.Comment: 25 pages, 4 figures; typos fixed; discussions expanded; we added a new section IV in which we argue that at high energies the production mechanism discussed in the paper is parametrically enhanced by ln(1/x) with respect to the quasi-classical resul

Pair production by boost-invariant fields in comoving coordinates

We derive the pair-production probability in a constant electric field in Rindler coordinates in a quasi-classical approximation. Our result is different from the pair-production probability in an inertial frame (Schwinger formula). In particular, it exhibits non-trivial dependence on rapidity and deviation from Gaussian behavior at small transverse momenta. Our results can be important for analysis of particle production in heavy-ion collisions.Comment: 12 pages, 2 figures. Discussion added and typos fixe

REGULARITIES OF THE VASCULARIZATION OF HUMAN ARTERIAL VESSELS

No abstrac

Damping of electromagnetic waves due to electron-positron pair production

The problem of the backreaction during the process of electron-positron pair production by a circularly polarized electromagnetic wave propagating in a plasma is investigated. A model based on the relativistic Boltzmann-Vlasov equation with a source term corresponding to the Schwinger formula for the pair creation rate is used. The damping of the wave, the nonlinear up-shift of its frequency due to the plasma density increase and the effect of the damping on the wave polarization and on the background plasma acceleration are investigated as a function of the wave amplitude.Comment: 11 pages, 5 figures; revtex

Time-of-arrival distribution for arbitrary potentials and Wigner's time-energy uncertainty relation

A realization of the concept of "crossing state" invoked, but not implemented, by Wigner, allows to advance in two important aspects of the time of arrival in quantum mechanics: (i) For free motion, we find that the limitations described by Aharonov et al. in Phys. Rev. A 57, 4130 (1998) for the time-of-arrival uncertainty at low energies for certain mesurement models are in fact already present in the intrinsic time-of-arrival distribution of Kijowski; (ii) We have also found a covariant generalization of this distribution for arbitrary potentials and positions.Comment: 4 pages, revtex, 2 eps figures include

The Quantum Vlasov Equation and its Markov Limit

The adiabatic particle number in mean field theory obeys a quantum Vlasov equation which is nonlocal in time. For weak, slowly varying electric fields this particle number can be identified with the single particle distribution function in phase space, and its time rate of change is the appropriate effective source term for the Boltzmann-Vlasov equation. By analyzing the evolution of the particle number we exhibit the time structure of the particle creation process in a constant electric field, and derive the local form of the source term due to pair creation. In order to capture the secular Schwinger creation rate, the source term requires an asymptotic expansion which is uniform in time, and whose longitudinal momentum dependence can be approximated by a delta function only on long time scales. The local Vlasov source term amounts to a kind of Markov limit of field theory, where information about quantum phase correlations in the created pairs is ignored and a reversible Hamiltonian evolution is replaced by an irreversible kinetic one. This replacement has a precise counterpart in the density matrix description, where it corresponds to disregarding the rapidly varying off-diagonal terms in the adiabatic number basis and treating the more slowly varying diagonal elements as the probabilities of creating pairs in a stochastic process. A numerical comparison between the quantum and local kinetic approaches to the dynamical backreaction problem shows remarkably good agreement, even in quite strong electric fields, over a large range of times.Comment: 49 pages, RevTex/LaTeX2e, 8 .eps figures included in 404KB .gz file (~3MB total uncompressed). Replacement added \tightenpages command to reduce from 67 to 49 p

Semiempirical Shell Model Masses with Magic Number Z = 126 for Superheavy Elements

A semiempirical shell model mass equation applicable to superheavy elements up to Z = 126 is presented and shown to have a high predictive power. The equation is applied to the recently discovered superheavy nuclei Z = 118, A = 293 and Z = 114, A = 289 and their decay products.Comment: 7 pages, including 2 figures and 2 table

Quantum Magnetic Algebra and Magnetic Curvature

The symplectic geometry of the phase space associated with a charged particle is determined by the addition of the Faraday 2-form to the standard structure on the Euclidean phase space. In this paper we describe the corresponding algebra of Weyl-symmetrized functions in coordinate and momentum operators satisfying nonlinear commutation relations. The multiplication in this algebra generates an associative product of functions on the phase space. This product is given by an integral kernel whose phase is the symplectic area of a groupoid-consistent membrane. A symplectic phase space connection with non-trivial curvature is extracted from the magnetic reflections associated with the Stratonovich quantizer. Zero and constant curvature cases are considered as examples. The quantization with both static and time dependent electromagnetic fields is obtained. The expansion of the product by the deformation parameter, written in the covariant form, is compared with the known deformation quantization formulas.Comment: 23 page

Пространственное динамометрирование рабочих органов почвообрабатывающих орудий

Improvement of agricultural tools is impossible without experimental proof and assessments of demand setup while operation. Tools of agricultural machines usually have an asymmetrical geometric shape and are exposed to the spatial system without resultant force. In comparison with the known devices, the proposed scheme for spatial dynamometry has a number of advantages related to the accuracy of the measurement and the possibility of a complete determination of all components of the spatial power characteristics. During operation the dynamometer is installed instead of any usual agricultural tool. The dynamometer records the force in the strain-measuring segment at various operating modes of the agricultural tool. A block diagram of the strain-measuring segments connection with the electronic media provides the definition of the main vector parameters and the principal moment of the external force loading of agricultural machines tools. The strain-measuring segments are rigidly fixed concerning a skeleton of the soil-cultivating implement. For convenience of the subsequent processing of results of measurement all tensometric links are located parallel to the corresponding coordinate axis.The proposed algorithm for processing the results of measuring the stress of strain-measuring segment makes it possible to determine the point grid reference of the dynamic screw axis with the surface of the tool. The latter is a necessary circumstance in the analysis of the dynamics of the movement of the agricultural aggregate and, in particular, when considering of the dynamical stability of an aggregate while performing technological operations.Совершенствование почвообрабатывающих орудий невозможно без экспериментальных проверок и оценок реальных нагрузок при эксплуатации. Рабочие органы почвообрабатывающих орудий как правило имеют несимметричную геометрическую форму и подвергаются действию пространственной системы сил, которая не имеет равнодействующей силы. Предложено устройство для пространственного динамометрирования, которое обладает рядом преимуществ, связанных с точностью измерения и возможностью полного определения всех компонентов пространственных силовых характеристик. В процессе работы динамометрический рабочий орган устанавливают вместо обычного на любое почвообрабатывающее орудие. Записывают усилие в тензометрических звеньях при различных режимах работы. Установили, что блок-схема соединения тензометрических звеньев с электронными носителями обеспечивает определение параметров главного вектора и главного момента внешнего силового нагружения рабочих органов почвообрабатывающих орудий. Отметили, что тензометрические звенья жестко закреплены относительно остова почвообрабатывающего орудия. Для удобства последующей обработки результатов измерения все тензометрические звенья располагают параллельно соответствующим осям координат. Выявили, что предложенный алгоритм обработки результатов измерения усилий тензометрических звеньев позволяет определять координаты точек пересечения оси динамического винта с поверхностью рабочего органа, что важно при анализе динамики движения почвообрабатывающего агрегата и, в частности, для обеспечения устойчивости движения агрегата при выполнении технологических операций