Continuous and discrete models of cooperation in complex bacterial colonies

We study the effect of discreteness on various models for patterning in bacterial colonies. In a bacterial colony with branching pattern, there are discrete entities - bacteria - which are only two orders of magnitude smaller than the elements of the macroscopic pattern. We present two types of models. The first is the Communicating Walkers model, a hybrid model composed of both continuous fields and discrete entities - walkers, which are coarse-graining of the bacteria. Models of the second type are systems of reaction diffusion equations, where the branching of the pattern is due to non-constant diffusion coefficient of the bacterial field. The diffusion coefficient represents the effect of self-generated lubrication fluid on the bacterial movement. We implement the discreteness of the biological system by introducing a cutoff in the growth term at low bacterial densities. We demonstrate that the cutoff does not improve the models in any way. Its only effect is to decrease the effective surface tension of the front, making it more sensitive to anisotropy. We compare the models by introducing food chemotaxis and repulsive chemotactic signaling into the models. We find that the growth dynamics of the Communication Walkers model and the growth dynamics of the Non-Linear diffusion model are affected in the same manner. From such similarities and from the insensitivity of the Communication Walkers model to implicit anisotropy we conclude that the increased discreteness, introduced be the coarse-graining of the walkers, is small enough to be neglected.Comment: 16 pages, 10 figures in 13 gif files, to be published in proceeding of CMDS

EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary

The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6° cgmLat) and Longyearbyen (75.2° cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5° cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. <br><br> During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 <I>R<sub>E</sub></I> mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H<sup>+</sup> and O<sup>+</sup> ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. <br><br> The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2° during ~5 min. The beginning of the poleward motion of the PCB was associated with an intensification of the downward FAC at the boundary. We suggest that the downward FAC sheet at the PCB is the high-altitude counterpart of the Earthward flowing FAC produced in the vicinity of the magnetotail neutral line by the Hall effect (Sonnerup, 1979) during a short-lived reconnection pulse

MANAGEMENT DECISION-MAKING AND RISK MANAGEMENT IN THE DIGITAL ECONOMY

This article reviews the aspects of management decision-making in the digital economy and as a consequence the possibility of timely and qualitative response to emerging risks in the process of management decision-making. This issue is considered from the position of influence on management decision-making both internal and external factors of the operation of the company has been considered. Therefore, the topic under consideration is relevant, since the issue of digitalization with a large coverage extends in all areas and spheres of our life and as a result should cover more the possibility of improving the quality of management decision-making, but is it so

Medical and sociological problems of cryptorchism

The problem of cryptorchidism is still of great medical and sociological importance. Normally, at the birth of a full-term boy, the testicles should be in the scrotum. One of the most common malformations is cryptorchidism. It occurs in 30% of newborns, 2-4% of boys aged 1 year, and 1.8-2% - up to 15 years. In adults, the incidence of cryptorchidism reaches 0.18-8%. Over the last 15 years, there has been a tendency to increase the number of cases of this malformation, but the reasons for this have not yet been established

A reaction-diffusion model for the growth of avascular tumor

A nutrient-limited model for avascular cancer growth including cell proliferation, motility and death is presented. The model qualitatively reproduces commonly observed morphologies for primary tumors, and the simulated patterns are characterized by its gyration radius, total number of cancer cells, and number of cells on tumor periphery. These very distinct morphological patterns follow Gompertz growth curves, but exhibit different scaling laws for their surfaces. Also, the simulated tumors incorporate a spatial structure composed of a central necrotic core, an inner rim of quiescent cells and a narrow outer shell of proliferating cells in agreement with biological data. Finally, our results indicate that the competition for nutrients among normal and cancer cells may be a determinant factor in generating papillary tumor morphology.Comment: 9 pages, 6 figures, to appear in PR

Противоопухолевая эффективность контактной лучевой терапии в комбинации с фотосенсибилизатором хлоринового ряда в эксперименте

Authors have studied the antitumor efficacy of contact radiation therapy (CRT) in combination with a chlorin-based photosensitizer (PS) in an experiment on laboratory animals with transplanted tumors. The experimental study was performed in 50 white outbred rats weighing 250±50 g. Subcutaneously transplanted Pliss lymphosarcoma (PLS) and alveolar liver cancer RS1 (RS1) were used as tumor models. Chlorinbased PS photolon (RUE «Belmedpreparaty», Republic Belarus) was injected intravenously at a dose of 2.5 mg/kg. The radiation sessions were carried out 2.5–4 hours (depending on the tumor model) after the administration of the PS using the device «microSelectron HDR V3 Digital» («Nucletron», Netherlands) with a 192-Ir radiation source in single focal doses 5 and 10 Gy. All laboratory animals (for PLS and RS1) were subdivided into 5 groups of 5 animals each: intact control, CRT 5 Gy, CRT 10 Gy, PS + CRT 5 Gy, PS + CRT 10 Gy. For the PLS tumor model – on the 14th day from the beginning of the experiment Vav. in groups were 26.31±5.81; 22.45±6.97; 18.99±4.86; 10.75±5.18 and 28.06±2.85 cm3, respectively (p˂0.05). The coefficients of tumor growth inhibition in the experimental groups were 14.67%, 27.82%, 59.14% and 6.65%, respectively. The frequency of complete tumor regressions 60 days after the start of the experiment was 0%, 20%, 20%, 60%, and 20%, respectively. On RS1 tumor model – on the 14th day from the beginning of the experiment Vav. in groups were 4.48±1.03; 0.80±0.21; 0.29±0.09; 0.19±0.07 and 0.32±0.08 cm3, respectively (p=0.009). The coefficients of tumor growth inhibition in the experimental groups were 82.14%, 93.53%, 95.76% and 92.86%, respectively. The frequency of complete tumor regressions 60 days after the start of the experiment was 0%, 0%, 20%, 0%, and 0%, respectively. Systemic administration of chlorin-based PS before the CRT session increases the antitumor efficacy of radiation therapy in animals with transplantable tumors of different histological structure and growth patterns. The data obtained indicate that further studies of the radiosensitizing properties of PS are promising.Авторами изучена противоопухолевая эффективность контактной лучевой терапии (КЛТ) в комбинации с фотосенсибилизатором (ФС) хлоринового ряда в эксперименте на лабораторных животных с перевивными опухолями. Работа выполнена на 50 лабораторных животных (белые беспородные крысы) с массой тела 250±50 г. В качестве опухолевых моделей использовали лимфосаркому Плисса (ЛСП) и альвеолярный рак печени РС (РС1), перевитые подкожно. ФС хлоринового ряда фотолон (РУП «Белмедпрепараты», Беларусь) вводился внутривенно капельно в дозе 2,5 мг/кг массы тела. Сеанс КЛТ проводили через 2,5 – 4 ч (в зависимости от опухолевой модели) после введения ФС с использованием аппарата «microSelectron HDR V3 Digital» («Nucletron», Нидерланды) с источником излучения 192–Ir в разовых очаговых дозах (РОД) 5 и 10 Гр. Все лабораторные животные, как в подгруппе с ЛСП, так и в подгруппе с РС1, были разделены на 5 групп по 5 особей в каждой: интактный контроль, КЛТ РОД 5 Гр, КЛТ РОД 10 Гр, ФС + КЛТ РОД 5Гр, ФС + КЛТ РОД 10 Гр. На модели ЛСП на 14–е сутки от начала воздействий средний объем опухоли (Vср ) в группах составил 26,31±5,81; 22,45±6,97; 18,99±4,86; 10,75±5,18 и 28,06±2,85 см3, соответственно (р˂0,05). Коэффициент торможения роста опухоли (ТРО) в опытных группах составил 14,67%; 27,82%; 59,14% и - 6,65%, соответственно. Частота полных регрессий опухолей через 60 суток после начала эксперимента составила 0%, 20%, 20%, 60% и 20%, соответственно. На модели РС1 на 14–е сутки от начала воздействий Vср . в группах составил 4,48±1,03; 0,80±0,21; 0,29±0,09; 0,19±0,07 и 0,32±0,08 см3, соответственно (р=0,009). Коэффициент ТРО в опытных группах составил 82,14%; 93,53%; 95,76% и 92,86%, соответственно. Частота полных регрессий опухолей через 60 суток после начала эксперимента составила 0%, 0%, 20%, 0% и 0%, соответственно. Результаты исследования показали, что введение ФС хлоринового ряда перед сеансом КЛТ увеличивает противоопухолевую эффективность лучевой терапии у животных с различными по гистологической структуре и характеру роста перевивными опухолями. Полученные данные свидетельствуют о перспективности дальнейших исследований радиосенсибилизирующих свойств ФС

Light Element Evolution and Cosmic Ray Energetics

Using cosmic-ray energetics as a discriminator, we investigate evolutionary models of LiBeB. We employ a Monte Carlo code which incorporates the delayed mixing into the ISM both of the synthesized Fe, due to its incorporation into high velocity dust grains, and of the cosmic-ray produced LiBeB, due to the transport of the cosmic rays. We normalize the LiBeB production to the integral energy imparted to cosmic rays per supernova. Models in which the cosmic rays are accelerated mainly out of the average ISM significantly under predict the measured Be abundance of the early Galaxy, the increase in [O/Fe] with decreasing [Fe/H] notwithstanding. We suggest that this increase could be due to the delayed mixing of the Fe. But, if the cosmic-ray metals are accelerated out of supernova ejecta enriched superbubbles, the measured Be abundances are consistent with a cosmic-ray acceleration efficiency that is in very good agreement with the current epoch data. We also find that neither the above cosmic-ray origin models nor a model employing low energy cosmic rays originating from the supernovae of only very massive progenitors can account for the $^6$Li data at values of [Fe/H] below $-$2.Comment: latex 19 pages, 2 tables, 10 eps figures, uses aastex.cls natbib.sty Submitted to the Astrophysical Journa

Оценка эффективности оперативного лечения больных с хронической критической ишемией нижних конечностей в стадии трофических осложнений

Relevance. Chronic critical ischemia of the lower extremities (CCILE) in the stage of trophic complications is the final stage of diseases of the arteries of the lower extremities, leading to disability of patients and having a poor prognosis in terms of preservation of the lower extremities and mortality.Aim of study. Objective assessment of the efficacy of lower limb revascularization in trophic disorders.Material and methods. The analysis of treatment of 52 patients with stage IV CCILE (according to the classification of R. Fontaine and A.V. Pokrovsky) was carried out. Of these, 42 patients underwent three-phase scintigraphy combined with X-ray computed angiography on a hybrid apparatus. After the operation, this study was conducted in 37 patients.Results. Out of 52 patients, surgery for revascularization of the lower extremities was performed in 37 patients, 15 were not operated on. Out of 37 operated patients, improvement of blood circulation occurred in 32 (86.5%). Circulatory decompensation was observed in 5 patients (9.7%). Among non-operated patients, improvement of blood circulation occurred in 9 patients (17.3%), no effect or decompensation — in 5 (9.7%). Subjective improvement in the condition and decrease in the degree of ischemia corresponded to the improvement of microcirculation according to the data of three-phase scintigraphy.Conclusion.1. Revascularization of the lower extremities in patients with trophic disorders is an effective method of treating this pathology. Therefore, all patients with chronic ischemia threatening limb loss should be considered as candidates for revascularization.2. If the leg arteries or short occlusive or stenotic lesions of the main arteries are affected, such patients should be discussed together with specialists in endovascular surgery for endovascular treatment or joint intervention.3. Hybrid radiation method (three-phase scintigraphy and single-photon emission computed tomography, combined with X-ray computed angiography) is an objective method that reflects the state of peripheral circulation and microcirculation, and allows you to objectively assess the effectiveness of the treatment.Актуальность. Хроническая критическая ишемия нижних конечностей (ХКИНК) в стадии трофических осложнений представляет собой конечную стадию заболеваний артерий нижних конечностей, приводящую к инвалидизации больных и имеющую неблагоприятный прогноз по показателям сохранения нижних конечностей и летальности.Цель исследования. Объективная оценка эффективности реваскуляризации нижних конечностей при трофических расстройствах.Материал и методы. Проведен анализ лечения 52 больных ХКИНК IV стадии (по классификации R. Fontaine и А.В. Покровского). Из них 42 пациентам выполнена трехфазная сцинтиграфия, совмещенная с рентгеновской компьютерной ангиографией на гибридном аппарате. После операции данное исследование проведено 37 пациентам.Результаты. Из 52 пациентов операция по реваскуляризации нижних конечностей выполнена 37 пациентам, не оперированы 15. Из 37 оперированных улучшение кровообращения произошло у 32 (86,5%). Декомпенсация кровообращения отмечена у 5 пациентов (9,7%). Среди неоперированных пациентов улучшение кровообращения произошло у 9 пациентов (17,3%), отсутствие эффекта или декомпенсация — у 5 (9,7%). Субъективное улучшение состояния и снижение степени ишемии соответствовали улучшению микроциркуляции по данным трехфазной сцинтиграфии.Выводы.1. Реваскуляризация нижних конечностей у пациентов с трофическими нарушениями является эффективным методом лечения данной патологии. Поэтому все пациенты с хронической ишемией, угрожающей потерей конечности, должны быть рассмотрены как кандидаты для реваскуляризации.2. При поражении артерий голени или коротких окклюдирующих или стенотических поражениях магистральных артерий такие пациенты должны быть обсуждены совместно со специалистами по рентгенэндоваскулярной хирургии на предмет эндоваскулярного лечения или выполнения вмешательства совместно.3. Гибридный лучевой метод (трехфазная сцинтиграфия и однофотонная эмиссионная компьютерная томография, совмещенная с рентгеновской компьютерной ангиографией) является объективным методом, отображающим состояние периферического кровообращения и микроциркуляции, и позволяет объективно оценить эффективность проведенного лечения