The Behavior of the Slope of Elastic Nucleon Scattering at Small Transfer Momenta and Recent Ua4 Data

Theoretical predictions for the behavior of the slope of the nucleon-nucleon scattering and another parameters of the differential cross sections in the framework of the dynamic model are compared with the recent UA4 data at small transfer momenta and at the centre-of-mass energy of 541 GeV. The predictions at superhigh energies are considered.Comment: 6 pages, 1 fig.-fig.ps, LATEX., JINR E2-93-43

Supercritical Pomeron and eikonal representation of the diffraction scattering amplitude

The intercept of the supercritical Pomeron is examined with the use of different forms of the scattering amplitudes of the bare Pomeron. The one-to-one correspondence between the eikonal phase and the ratio of the elastic and total cross section is shown. Based on new experimental data of the CDF Collaboration, the intercept and power of the logarithmic growth of the bare and total Pomeron amplitude are analyzed. It is shown that as a result of the eikonalization procedure, the bare QCD Pomeron becomes compatible with experiment.Comment: LaTex text of the article + 1 Fig.1 in LaTex for

Radiation Damage Studies of Silicon Photomultipliers

We report on the measurement of the radiation hardness of silicon photomultipliers (SiPMs) manufactured by Fondazione Bruno Kessler in Italy (1 mm$^2$ and 6.2 mm$^2$), Center of Perspective Technology and Apparatus in Russia (1 mm$^2$ and 4.4 mm$^2$), and Hamamatsu Corporation in Japan (1 mm$^2$). The SiPMs were irradiated using a beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences of up to $3 \times 10^{10}$ protons per cm$^2$ with the SiPMs at operating voltage. Leakage currents were read continuously during the irradiation. The delivery of the protons was paused periodically to record scope traces in response to calibrated light pulses to monitor the gains, photon detection efficiencies, and dark counts of the SiPMs. The leakage current and dark noise are found to increase with fluence. Te leakage current is found to be proportional to the mean square deviation of the noise distribution, indicating the dark counts are due to increased random individual pixel activation, while SiPMs remain fully functional as photon detectors. The SiPMs are found to anneal at room temperature with a reduction in the leakage current by a factor of 2 in about 100 days.Comment: 35 pages, 25 figure

Seiberg Duality is an Exceptional Mutation

The low energy gauge theory living on D-branes probing a del Pezzo singularity of a non-compact Calabi-Yau manifold is not unique. In fact there is a large equivalence class of such gauge theories related by Seiberg duality. As a step toward characterizing this class, we show that Seiberg duality can be defined consistently as an admissible mutation of a strongly exceptional collection of coherent sheaves.Comment: 32 pages, 4 figures; v2 refs added, "orbifold point" discussion refined; v3 version to appear in JHEP, discussion of torsion sheaves improve

Exceptional Collections and del Pezzo Gauge Theories

Stacks of D3-branes placed at the tip of a cone over a del Pezzo surface provide a way of geometrically engineering a small but rich class of gauge/gravity dualities. We develop tools for understanding the resulting quiver gauge theories using exceptional collections. We prove two important results for a general quiver gauge theory: 1) we show the ordering of the nodes can be determined up to cyclic permutation and 2) we derive a simple formula for the ranks of the gauge groups (at the conformal point) in terms of the numbers of bifundamentals. We also provide a detailed analysis of four node quivers, examining when precisely mutations of the exceptional collection are related to Seiberg duality.Comment: 26 pages, 1 figure; v2 footnote 2 amended; v3 ref adde

The daily cloud-to-ground lightning flash density in the contiguous united states and Finland

A method is developed to quantify thunderstorm intensity according to cloud-to-ground lightning flashes (hereafter ground flashes) determined by a lightning-location sensor network. The method is based on the ground flash density ND per thunderstorm day (ground flashes per square kilometer per thunderstorm day) calculated on 20 km × 20 km fixed squares. Because the square size roughly corresponds to the area covered by a typical thunderstorm, the flash density for one square defines a unit thunderstorm for the purposes of this study. This method is tested with ground flash data obtained from two nationwide lightning-location systems: the National Lightning Detection Network (NLDN) in the contiguous United States and the portion of the Nordic Lightning Information System (NORDLIS) in Finland. The distribution of daily ground flash density ND is computed for all of Finland and four 800 000 km2 regions in the United States (identified as western, central, eastern, and Florida). Although Finland and all four U.S. regions have median values of ND of 0.01- 0.03 flashes per square kilometer per thunderstorm day-indicating that most thunderstorms produce relatively few ground flashes regardless of geographical region-the most intense 1% of the storms (as measured by the 99th percentiles of the ND distributions within each region) show much larger differences among regions. For example, the most intense 1% of the ND distributions is 1.3 flashes per square kilometer per thunderstorm day in the central U.S. region, but only 0.2 flashes per square kilometer per thunderstorm day in Finland. The spatial distribution of the most intense 1% of the ND distributions illustrates that the most intense thunderstorm days occur in the central United States and upper Midwest, which differs from the maximaof the average annual flash density NA and the number of thunderstorm days TD, bothof which occur in Florida and along the coast of the Gulf of Mexico. This method for using ND to quantify thunderstorm intensity is applicable to any region as long as the detection efficiency of the lightning-location network is high enough or known. This method can also be employed in operational forecasting to provide a quantitative measure of the lightning intensity of thunderstorms relative to climatology. © 2011 American Meteorological Society

Математическая оценка гемолиза канального центробежного насоса

The objective of this work is to conduct research on a mathematical model to assess hemolytic characteristics in a channel centrifugal blood pump developed by us with 2000–3400 rpm impeller speed range and 100–250 mmHg pressure drop in different parts of the pump flow path. Hemolysis index was measured at 1 to 10 L/min flow rate. The result was an estimate of the average magnitude of the shear stress (SS), taking into account the distribution in the pump, which ranged from 40 to 60 Pa. The most critical areas of the pump in terms of blood injury were evaluated. The maximum SSs were determined: 456 Pa in the impeller wheel zone and 533.3 Pa in the adjacent area of the body, with an exposure time of 0.0115 s and 0.0821 s respectively. In these zones, maximum hemolysis index values were 0.0420 and 0.0744 respectively. Based on the data obtained, these zones were optimized in terms of minimizing hemolysis.Целью работы является проведение исследований на математической модели по оценке гемолитических характеристик в разработанном нами канальном центробежном насосе в диапазоне скоростей рабочего колеса 2000–3400 об/мин и перепадом давления 100–250 мм рт. cт. в разных отделах проточного тракта насоса. Расчетный индекс гемолиза проведен при скоростях потока от 1 до 10 л/мин. Результатом работы явилась оценка среднего значения касательного напряжения (КН) с учетом распределения в насосе, которое составило от 40 до 60 Па. Были проведены оценки наиболее критичных с точки зрения травмы крови зон насоса. В результате расчетов определены максимальные КН в зоне РК 456 Па и прилежащей зоне корпуса 533,3 Па, при соответствующем времени экспозиции 0,0115 и 0,0821 с. В этих зонах наблюдаются максимальные значения ИГ 0,0420 и 0,0744. На основании полученных данных была проведена оптимизация данных зон с точки зрения минимизации гемолиза