Континуальный подход в теории взаимодействия заряженных частиц с твердым телом

In this paper, the main radiative processes, for the first time, are considered within the framework of continuum physics, where the motion of charged particles occurs in a continuous resisting medium.Within the analysis, new characteristics of the interaction of ions with matter are introduced. The proposed formalism also uses some results of modern corpuscular theory. It allows giving a physically clear space-time description of the processes and phenomena analyzed in this paper. Further in this paper, the authors have estimated, with a high degree of accuracy, the ranges of ions in various materials; constructed their energy loss profiles; determined the mean free path and mean free time of the charged particles in matter, and proposed the formalism for analyzing the radiative change in the physical properties of solids. For the first time, the physical nature of the main characteristic of the radiation resistance of materials, i.e., the threshold displacement energy, has been studied in detail, and the formula for its calculation has been derived by the authors. В настоящей работе основные радиационные процессы впервые рассмотрены в рамках континуальной физики, когда движение заряженных частиц происходит в сплошной среде с сопротивлением. При этом вводятся новые характеристики взаимодействия ионов с веществом. В предлагаемом формализме также используются некоторые результаты современной корпускулярной теории. Это позволило использовать физически ясное пространственно-временное описание рассматриваемых процессов и явлений. С высокой степенью точности произведены оценки пробегов ионов в различных материалах, построены профили потерь энергии, рассчитаны длины и времена свободного пробега заряженных частиц в веществе, предложен формализм анализа радиационного изменения физических свойств твердых тел. Впервые детально исследована физическая природа главной характеристики радиационной стойкости материалов – пороговой энергии смещения и получена формула для ее определения

Формирование сложных радиационных дефектов в облучаемых материалах

The principles of formation of the complex vacancy defects (V-clusters), their ensembles and patterns of formation of superlattices of the V-clusters are determined. The inclusion of the drift component of the elementary defects into the field of elastic stresses of the V-cluster in the analysis allowed describing its genesis and development adequately. The mechanisms of motion of the V-clusters in the material are described in detail, considering their interaction with each other. The authors have developed the original physical and mathematical formalism within which it has become possible to describe the order-disorder phase transition when an ensemble of clusters chaotically distributed in the irradiated solid transforms into an ordered coherent superlattice. The critical point of the phase transition and the parameters of the defect lattice itself are determined. They are confirmed by the experimental results. The ordering process in this system is understood as the motion of the undamped wave of order parameter through the material, while other configuration states of the V-cluster ensemble constitute rapidly damping fluctuations. The article also shows the mechanism of linking the symmetry of the V-cluster superlattice to the symmetry of the initial crystal.Установлены принципы образования сложных вакансионных дефектов (V-кластеров), их ансамблей и закономерности формирования сверхрешеток V-кластеров. Учет дрейфовой составляющей элементарных дефектов в поле упругих напряжений V-кластера позволил адекватно описать его зарождение и развитие. Детально описаны механизмы движения V-кластеров в материале с учетом их взаимодействия друг с другом. Предложен оригинальный физико-математический формализм, в рамках которого оказалось возможным описать фазовый переход беспорядок–порядок, когда ансамбль хаотически распределенных в облучаемом твердом теле V-кластеров переходит в упорядоченное когерентное состояние – сверхрешетку. Строго определена критическая точка фазового перехода и параметры самой решетки дефектов, которые подтверждаются результатами эксперимента. Процесс упорядочения в данной системе представляется движением по материалу незатухающей волны параметра порядка, в то время как другие конфигурационные варианты состояния ансамбля V-кластеров являются быстрозатухающими флуктуациями. Показан механизм связи симметрии сверхрешетки V-кластеров и симметрии исходного кристалла

Formation of complex radiation defects in irradiated materials

Установлены принципы образования сложных вакансионных дефектов (V-кластеров), их ансамблей и закономерности формирования сверхрешеток V-кластеров. Учет дрейфовой составляющей элементарных дефектов в поле упругих напряжений V-кластера позволил адекватно описать его зарождение и развитие. Детально описаны механизмы движения V-кластеров в материале с учетом их взаимодействия друг с другом. Предложен оригинальный физико-математический формализм, в рамках которого оказалось возможным описать фазовый переход беспорядок–порядок, когда ансамбль хаотически распределенных в облучаемом твердом теле V-кластеров переходит в упорядоченное когерентное состояние – сверхрешетку. Строго определена критическая точка фазового перехода и параметры самой решетки дефектов, которые подтверждаются результатами эксперимента. Процесс упорядочения в данной системе представляется движением по материалу незатухающей волны параметра порядка, в то время как другие конфигурационные варианты состояния ансамбля V-кластеров являются быстрозатухающими флуктуациями. Показан механизм связи симметрии сверхрешетки V-кластеров и симметрии исходного кристалла. The principles of formation of the complex vacancy defects (V-clusters), their ensembles and patterns of formation of superlattices of the V-clusters are determined. The inclusion of the drift component of the elementary defects into the field of elastic stresses of the V-cluster in the analysis allowed describing its genesis and development adequately. The mechanisms of motion of the V-clusters in the material are described in detail, considering their interaction with each other. The authors have developed the original physical and mathematical formalism within which it has become possible to describe the order-disorder phase transition when an ensemble of clusters chaotically distributed in the irradiated solid transforms into an ordered coherent superlattice. The critical point of the phase transition and the parameters of the defect lattice itself are determined. They are confirmed by the experimental results. The ordering process in this system is understood as the motion of the undamped wave of order parameter through the material, while other configuration states of the V-cluster ensemble constitute rapidly damping fluctuations. The article also shows the mechanism of linking the symmetry of the V-cluster superlattice to the symmetry of the initial crystal

Diagnosis of IgG4 - related ophthalmic disease in a group of patients with various lesions of the eye and orbits

Purpose of the study. To provide demographic, clinical, laboratory, ultrasound, radiological, morphological/ immunomorphological phenotype of IgG4-related ophthalmic diseases, which allowsmaking a differential diagnosis with granulomatous, autoimmune, inflammatory, endocrine and hematologic diseases affecting the eye and orbits. Materials and methods. From 2004 to 2016 108 (78.2%) of the 138 patients were diagnosed with non-tumoral lesions of eye and orbits. In 48 patients (35%) at admission and 5 patients in the follow were diagnosed IgG4-related ophthalmic disease. In the analysis of 82 (f-44, m-38) patients with IgG4-related disease, localization of lesions in orbit observed in 53 (f-36, m-17) and it was the most frequent involvement in patients with IgG4-related disease (64.5%). Only 7 patients had isolated IgG4-related ophthalmic disease, whereas 46 patients (87%) had involvement of 2-7 locations, as a manifestation of IgG4-related systemic disease.During the examination, the average age of patients with IgG4-related ophthalmic disease was 47.5 years (19-73 years). Median time to diagnosis was 52.8 months before 2004 and 36 months 2004-2016. Results. We noted the predominance of females in the ratio 2: 1 inthe group of patients with IgG4-related ophthalmic disease. Edema of the eyelids, nasal congestion (55-60%), tumor-like formations of the upper eyelids and increased lacrimation prevailed at the onset of the disease, whereas such functional impairment like limited mobility and pain in eyeballs, exophthalmos, ptosis and diplopia appeared later at 15-38% with a loss visual acuity in one case. Bilateral lesion (86%), mainly affecting the lacrimal glands (93.5%), infiltration of the extraocular muscles (83.5%) and retrobulbar tissue with a thickening of the optic nerve in one third of patients were the main localizations IgG4-related ophthalmic disease. Clinical symptoms were accompanied by the appearance of moderate inflammatory activity (38%), increased levels IgG (44%), IgG4(88%) and IgE (61%). Indicators of autoimmune disorders observed in 6-22% of patients, most often in patients with simultaneous involvement of the salivary glands. Significant lymphoplasmacytic infiltration (94%) with a ratio of plasma cells (IgG4/IgG) secreting IgG4> 40% (90%) with fibrosis formation (94%) and follicle formation (71%) with a moderate amount of eosinophils (34%) were the major morphological / immunomorphological manifestations of IgG4-related ophthalmic disease. Signs of vasculitis and obliterative phlebitis were found in a small amount of patients. Conclusion. Determination of elevated levels of IgG-4 / IgE in patients with edema, pseudotumor of the eyelid, sinusitis and increase of the palpebral lobe of the lacrimal gland suggests the presence of IgG4-related ophthalmic disease. Minimally invasive incisional biopsy of lacrimal glands and salivary glands followed by morphological / immunomorphological research is needed for the correct diagnosis. Diagnostic orbitotomy in ophthalmic hospitals in such cases is inexpedient, since it leads to the development of dry eye. Massive lymphoplasmacytic infiltration with IgG4 / IgG ratio more than 40%, advanced fibrosis in biopsiesof the orbits tissue or salivary glands when combined lesions are required for the making the diagnosis of IgG4-related ophthalmic disease

Temperature-ramped 129Xe spin-exchange optical pumping

We describe temperature-ramped spin-exchange optical pumping (TR-SEOP) in an automated high-throughput batch-mode 129Xe hyperpolarizer utilizing three key temperature regimes: (i) “hot”where the 129Xe hyperpolarization rate is maximal, (ii) “warm”-where the 129Xe hyperpolarization approaches unity, and (iii) “cool” where hyperpolarized 129Xe gas is transferred into a Tedlar bag with low Rb content (<5 ng per ∼1 L dose) suitable for human imaging applications. Unlike with the conventional approach of batch-mode SEOP, here all three temperature regimes may be operated under continuous high-power (170 W) laser irradiation, and hyperpolarized 129Xe gas is delivered without the need for a cryocollection step. The variable-temperature approach increased the SEOP rate by more than 2-fold compared to the constant-temperature polarization rate (e.g., giving effective values for the exponential buildup constant γSEOP of 62.5 ± 3.7 × 10−3 min−1 vs 29.9 ± 1.2 × 10−3 min−1) while achieving nearly the same maximum %PXe value (88.0 ± 0.8% vs 90.1% ± 0.8%, for a 500 Torr (67 kPa) Xe cell loadingcorresponding to nuclear magnetic resonance/magnetic resonance imaging (NMR/MRI) enhancements of ∼3.1 × 105 and ∼2.32 × 108 at the relevant fields for clinical imaging and HP 129Xe production of 3 T and 4 mT, respectively); moreover, the intercycle “dead” time was also significantly decreased. The higher-throughput TR-SEOP approach can be implemented without sacrificing the level of 129Xe hyperpolarization or the experimental stability for automation-making this approach beneficial for improving the overall 129Xe production rate in clinical settings

МАГНЕТОСОПРОТИВЛЕНИЕ ОБЛУЧЕННЫХ ПРОТОНАМИ НИТЕВИДНЫХ КРИСТАЛЛОВ Si0,97Ge0,03

Whiskers are a new material that is characterized by high structural perfection, chemical resistance and strength which reaches the theoretically possible limit for crystals of small transverse dimensions. The test whiskers were synthesized by the method of chemical transport reactions in a closed bromide system using gold as the initiator of growth. The crystals were irradiated by protons with an energy of 6 MeV and doses of 5 · 1013, 1015 and 1 · 1017 p+/cm2 at 40 °C in a U−120 cyclotron. The effects of proton irradiation and high magnetic fields on the magnetoresistance of Si1−xGex (x = 0,03) whiskers in the 4,2—300 K temperature range has been studied. A slight decrease in the electrical resistance of the crystals in the 4,2—40 K temperature range during irradiation with small proton doses and a significant increase in their resistance in the entire investigated temperature range for a dose of 1·1017 p+/cm2 have been found. The ionization energy of the impurity atoms in different magnetic fields has been calculated. It has been revealed that the energy level of the impurity depends on the magnetic field but slightly which in turn indicates a independence of the concentration of holes on the magnetic field. It has been shown that a significant magnetoresistance at all studied temperatures was due to the magnetic field−caused decrease in the mobility of free charge carriers (holes). It has been found that the concentration of holes depends on magnetic field but a little. Conclusion has been made about a negligible expansion of the band gap in magnetic fields of up to 8 T. Нитевидные кристаллы — это новый материал, который характеризуется высоким структурным совершенством, химической стойкостью, прочностью, которая для кристаллов небольших поперечных размеров достигает теоретически возможного предела. Исследованные нитевидные кристаллы получены методом химических транспортных реакций в закрытой бромидной системе с использованием золота в качестве инициатора роста. Кристаллы облучали протонами с энергией 6 МэВ и дозами 5 · 1013, 1015 и 1 · 1017 р+/см−2 при 40 °С на циклотроне У−120. Изучено влияние протонного облучения и сильных магнитных полей на магнетосопротивление нитевидных кристаллов Si1−xGex (х = 0,03) в интервале температур 4,2—300 К. Обнаружено незначительное уменьшение электрического сопротивления кристаллов в температурной области 4,2—40 К в процессе облучения малыми дозами протонов и существенное увеличение сопротивления во всей исследуемой температурной области при облучении дозой 1 · 1017 р+/см2. Рассчитана энергия ионизации примесных атомов в разных магнитных полях. Установлено, что энергия примесного уровня практически не зависит от магнитного поля, что, в свою очередь, говорит о независимости концентрации дырок от магнитного поля. Показано, что существенное магнетосопротивление при всех исследованных температурах связано с магнитополевым уменьшением подвижности свободных носителей заряда (дырок). Установлено, что концентрация дырок практически не зависит от магнитного поля. Сделан вывод, что расширение запрещенной зоны в магнитных полях до 8 Тл незначительно.

ВЛИЯНИЕ ПОГОДНЫХ УСЛОВИЙ НА ИЗМЕНЧИВОСТЬ ХАРАКТЕРИСТИК БИОХИМИЧЕСКОГО СОСТАВА ПЛОДОВ ИНТРОДУЦИРОВАННЫХ СОРТОВ OXYCOCCUS MACROCARPUS (AIT.) PERS. В УСЛОВИЯХ БЕЛАРУСИ

The article presents the results of a comparative study of the variability of the biochemical composition of the fruits of six cultivars introduced in Belarus: Oxycoccus macrocarpus (Ait.) Pers. – Stevens, Bain Favorit, Hiliston, Holistar Red, Stankovic and WSU 108 during contrast moistening seasons. It has been established that the least pronounced intersectional differences are characterized by the parameters of accumulation in the fruits of dry substances, ascorbic and hydroxycinnamic acids, as well as the total amount of antoniated pigments and bioflavonoids in general, while of most significance are the sugar-dependent concentration and the content of soluble sugars, pectins, leucoanthocyanins and flavonols. It is shown that in the taxonomic series of large-fruited cranberries the Stankovich cultivar was characterized by the greatest resistance of the biochemical composition of the fruits to weather factors, while the lowest cultivar was Bain Favorit and especially Hiliston. Приведены результаты сравнительного исследования изменчивости биохимического состава плодов 6 новых интродуцированных в Беларуси сортов: Oxycoccus macrocarpus (Аit.) Рers. – Stevens, Bain Favorit, Hiliston, Holistar Red, Stankovich и WSU 108 в контрастные по режиму увлажнения сезоны. Установлено, что наименее выраженными межсезонными различиями характеризовались параметры накопления в плодах сухих веществ, аскорбиновой и гидроксикоричных кислот, а также общее количество антоциановых пигментов и биофлавоноидов в целом, тогда как наиболее значительными – показатель сахарокислотного индекса и содержание в них растворимых сахаров, пектиновых веществ, лейкоантоцианов и флавонолов. Показано, что в таксономическом ряду клюквы крупноплодной наибольшей устойчивостью биохимического состава плодов к погодным факторам характеризовался сорт Stankovich, тогда как наименьшей – сорта Bain Favorit и особенно Hiliston.

Incremental grouping of image elements in vision

One important task for the visual system is to group image elements that belong to an object and to segregate them from other objects and the background. We here present an incremental grouping theory (IGT) that addresses the role of object-based attention in perceptual grouping at a psychological level and, at the same time, outlines the mechanisms for grouping at the neurophysiological level. The IGT proposes that there are two processes for perceptual grouping. The first process is base grouping and relies on neurons that are tuned to feature conjunctions. Base grouping is fast and occurs in parallel across the visual scene, but not all possible feature conjunctions can be coded as base groupings. If there are no neurons tuned to the relevant feature conjunctions, a second process called incremental grouping comes into play. Incremental grouping is a time-consuming and capacity-limited process that requires the gradual spread of enhanced neuronal activity across the representation of an object in the visual cortex. The spread of enhanced neuronal activity corresponds to the labeling of image elements with object-based attention