Turbulent Thermalization

We study, analytically and with lattice simulations, the decay of coherent field oscillations and the subsequent thermalization of the resulting stochastic classical wave-field. The problem of reheating of the Universe after inflation constitutes our prime motivation and application of the results. We identify three different stages of these processes. During the initial stage of ``parametric resonance'', only a small fraction of the initial inflaton energy is transferred to fluctuations in the physically relevant case of sufficiently large couplings. A major fraction is transfered in the prompt regime of driven turbulence. The subsequent long stage of thermalization classifies as free turbulence. During the turbulent stages, the evolution of particle distribution functions is self-similar. We show that wave kinetic theory successfully describes the late stages of our lattice calculation. Our analytical results are general and give estimates of reheating time and temperature in terms of coupling constants and initial inflaton amplitude.Comment: 27 pages, 13 figure

Dynamics of tachyonic preheating after hybrid inflation

We study the instability of a scalar field at the end of hybrid inflation, using both analytical techniques and numerical simulations. We improve previous studies by taking the inflaton field fully into account, and show that the range of unstable modes depends sensitively on the velocity of the inflaton field, and thereby on the Hubble rate, at the end of inflation. If topological defects are formed, their number density is determined by the shortest unstable wavelength. Finally, we show that the oscillations of the inflaton field amplify the inhomogeneities in the energy density, leading to local symmetry restoration and faster thermalization. We believe this explains why tachyonic preheating is so effective in transferring energy away from the inflaton zero mode.Comment: 12 pages, 10 figures, REVTeX. Minor changes, some references added. To appear in PR

The surface detector array of the Telescope Array experiment

The Telescope Array (TA) experiment, located in the western desert of Utah,USA, is designed for observation of extensive air showers from extremely high energy cosmic rays. The experiment has a surface detector array surrounded by three fluorescence detectors to enable simultaneous detection of shower particles at ground level and fluorescence photons along the shower track. The TA surface detectors and fluorescence detectors started full hybrid observation in March, 2008. In this article we describe the design and technical features of the TA surface detector.Comment: 32 pages, 17 figure

New air fluorescence detectors employed in the Telescope Array experiment

Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment involves a surface detector (SD) array and three fluorescence detector (FD) stations. FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies and species. The detectors employed at one of the three FD stations were relocated from the High Resolution Fly's Eye experiment. At the other two stations, newly designed detectors were constructed for the TA experiment. An FD consists of a primary mirror and a camera equipped with photomultiplier tubes. To obtain the EAS parameters with high accuracies, understanding the FD optical characteristics is important. In this paper, we report the characteristics and installation of new FDs and the performances of the FD components. The results of the monitored mirror reflectance during the observation time are also described in this report.Comment: 44 pages, 23 figures, submitted to NIM-

PDX-модель высокодифференцированной нейроэндокринной опухоли поджелудочной железы на иммунодефицитных мышах линии Balb/c Nude

Background: Orthotopic patient-derived xenografts (PDX) in immunodeficient mice are recognized as the most adequate neoplastic model due to their ability to maintain primary tumor properties after implantation. They can be used to study anti-neoplastic effects of pharmacological substances in vivo and to investigate characteristics and mechanisms of carcinogenesis. Results of preclinical studies of pharmacological substances obtained with PDX models are virtually no different from those of subsequent clinical trials. Aim: To develop an orthotopic PDX model of a highly differentiated human pancreatic neuroendocrine tumor (pNET) by implanting a fragment of the patient's tumor into the pancreas of immunodeficient mice. Materials and methods: A tumor fragment was obtained from a patient with a highly differentiated pNET G2 and liver metastasis. Fifteen (15) male immunodeficient Balb/c Nude mice with a mass of 22-24 grams were used to establish the orthotopic PDX model of human well-differentiated pNET. A fragment of primary pNET was orthotopically transplanted into the pancreas of 10 animals. A fragment of the metastatic lesion was transplanted into the liver of 5 animals. The animals were followed for up to 45 days. In vivo monitoring of the tumor growth was performed with a magnetic resonance imaging (MRI) system (ClinScan, Bruker BioSpin, Rheinstetten, Germany). At the end of the experiment, animals were euthanized and autopsies were performed, with routine histopathological examination and immunohistochemical study with antibodies to human chromogranin A, synaptophysin, and the marker of proliferative activity (Ki-67) of both original donor tumor and orthotopic pancreatic and liver xenografts. Results: Obvious changes in the mice condition were noticed at 30 days after surgery. They manifested as an increase in abdominal distension, swelling, and cyanosis in the projection of the pancreas. MRI showed a homogeneous neoplasm in the pancreas. At autopsy, the engraftment rate was 73% of all study animals, with yellow masses with even contours and a volume of about 100 cm3 present within the yellow-pink pancreatic tissues. The morphological assessment showed histological similarity between the original patient's tumor and patient-derived xenografts, which were identified as highly differentiated G2 pNETs. At immunohistochemical assessment, the patient's primary and metastatic tumor tissue specimens expressed anti-chromogranin A (full-blown cytoplasmic reaction) and anti-synaptophysin (mild cytoplasmic reaction) antibodies. Ki-67 was positive in 5.2% of the cells. An immunohistochemical study of the orthotopic tumor fragments and heterotopic tumor fragments showed moderate cytoplasmic staining with antibodies to chromogranin A and synaptophysin. The rate of Ki-67 in the orthotopic pNET model and metastatic model does not exceed 5% and 8%, respectively. Conclusion: Engraftment of tumor material after transplantation of human pancreatic cancer was observed in 73% of the cases, which should be considered a good first passage implantation result. The morphological studies confirmed that the orthotopic PDX was a well-differentiated pNET, histologically corresponding to the donor tumor. The model created in the experiment mirrors the histological characteristics of the donor tumor and can be used in preclinical studies of new treatments for well-differentiated pNETs, including those of antitumor activity of new pharmacological substances.Актуальность. Ортотопические ксенограф-ты человеческих опухолей (patient-derived xenograft - PDX) на иммунодефицитных мышах признаны наиболее адекватной моделью опухолевого процесса благодаря способности сохранять после имплантации первоначальные свойства опухоли. Они могут применяться для изучения противоопухолевого действия фармакологических субстанций in vivo, а также исследования особенностей и механизмов канцерогенеза. Результаты доклинических исследований фармакологических субстанций, полученные на PDX-моделях, практически не разнятся с последующими клиническими испытаниями. Цель - создание ортотопической PDX-модели высокодифференцированной нейроэндокринной опухоли (НЭО) поджелудочной железы (ПЖ) человека путем имплантации фрагмента опухоли пациента в ПЖ иммунодефицитных мышей. Материал и методы. Фрагмент опухоли был взят от пациента с диагнозом высокодифференцированной НЭО ПЖ, G2 с метастазом в печени. Для создания ортотопической PDX-модели НЭО ПЖ человека было использовано 15 самцов иммунодефицитных мышей линии Balb/c Nude массой 22-24 г. Фрагмент первичной НЭО ПЖ был трансплантирован в ПЖ 10 животным. Фрагмент метастаза НЭО в печени был имплантирован в печень 5 мышей. Наблюдение за животными проводили в течение 45 суток. Прижизненное наблюдение за ростом опухоли выполнялось с использованием визуализации на магнитно-резонансном томографе ClinScan. По окончании эксперимента осуществляли эвтаназию и некропсию. Проводили стандартное гистологическое и иммуногистохимическое исследование с антителами к хромогранину А, синаптофизину, маркеру пролиферативной активности (Ki-67) человеческой опухоли донора и ортотопических ксенографтов в ПЖ и печени мышей. Результаты. Видимые изменения в состоянии мышей были замечены спустя 30 дней после операции. Они выражались в увеличении живота, его припухлости и синюшности в проекции ПЖ. Магнитно-резонансная томография показала однородное новообразование в области ПЖ. При некропсии всех исследованных мышей отмечалось приживление опухолевого материала в 73% случаев, при этом в ПЖ желто-розового цвета были обнаружены опухоли желтоватого цвета с четкими контурами объемом около 100 мм3. При морфологическом анализе опухоли донора и реципиентов были гистологически схожи и идентифицированы как высокодифференцированная НЭО ПЖ, G2. При иммуногистохимическом исследовании первичная и метастатическая опухоли пациента экспрессировали антитела к хромограни-ну А (резко выраженная цитоплазматическая реакция) и синаптофизину (слабо выраженная цитоплазматическая реакция). Ki-67 был позитивен в 5,2% клеток. При иммуногистохимическом исследовании модели первичной опухоли и модели метастатической опухоли была выявлена умеренно выраженная цитоплазматическая окраска с антителами к хромогранину А и синаптофизину. Ki-67 в модели первичной НЭО ПЖ не превышал 5%, а в модели метастаза в печени достигал 8%. Заключение. В результате трансплантации опухоли ПЖ человека отмечалось приживление опухолевого материала в 73% случаев, что следует признать хорошим результатом имплантации для первого пассажа. Согласно результатам морфологических исследований, ортотопический ксенографт, полученный от пациента, является высокодифференцированной НЭО ПЖ, G2, то есть гистологически соответствует опухоли пациента-донора. Полученная в нашем эксперименте модель повторяет гистологические особенности донорской опухоли и может найти свое применение в доклинических исследованиях новых методов лечения высокодифференцированных НЭО ПЖ, в том числе в исследованиях противоопухолевой активности новых фармакологических субстанций

Gain monitoring of telescope array photomultiplier cameras for the first 4 years of operation

The stability of the gain of the photomultiplier (PMT) camera for the Fluorescence Detector (FD) of the Telescope Array experiment was monitored using an 241Am loaded scintillator pulsers (YAP) and a diffused xenon flasher (TXF) for a selected set of 35 PMT-readout channels. From the monitoring of YAP pulses over four years of FD operation, we found slow monotonic drifts of PMT gains at a rate of -1.7???+1.7%/year. An average of the PMT gains over the 35 channels stayed nearly constant with a rate of change measured at -0.01??0.31(stat)??0.21(sys)%/year. No systematic decrease of the PMT gain caused by the night sky background was observed. Monitoring by the TXF also tracked the PMT gain drift of the YAP at 0.88??0.14(stat)%/year.close0

The energy spectrum of Telescope Array's Middle Drum detector and the direct comparison to the High Resolution Fly's Eye experiment

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Energy spectrum of ultra-high energy cosmic rays observed with the Telescope Array using a hybrid technique

We measure the spectrum of cosmic rays with energies greater than 10(18.2) eV with the fluorescence detectors (FDs) and the surface detectors (SDs) of the Telescope Array Experiment using the data taken in our first 2.3-year observation from May 27, 2008 to September 7, 2010. A hybrid air shower reconstruction technique is employed to improve accuracies in determination of arrival directions and primary energies of cosmic rays using both FD and SD data. The energy spectrum presented here is in agreement with our previously published spectra and the HiRes results. (C) 2014 Elsevier B.V. All rights reserved.close