Active particles with chirality: Application to pedestrian flows

We analyse pattern formation in systems of active particles with right/left asymmetry of the interaction forces in the context of pedestrian dynamics. To describe the inter-particle interactions we use the standard social force model and supplement it with the new type of force, reflecting the chirality of pedestrians. We perform numerical simulations of two pedestrian flows moving in opposite directions in a long corridor. We observe phase transition from disordered motion to multi-lane motion and quantify it in terms of the order parameter. Also we observe a phase transition from the multi-lane to two-lane motion, which occurs with varying number density of pedestrians and strength of the chirality force. We perform a qualitative analysis to predict the critical density of this transition and its dependence on the chirality. The results of our analysis agree fairly well with the simulation data. Our findings may find applications in urbanistic and transport problems

A model of ballistic aggregation and fragmentation

A simple model of ballistic aggregation and fragmentation is proposed. The model is characterized by two energy thresholds, Eagg and Efrag, which demarcate different types of impacts: If the kinetic energy of the relative motion of a colliding pair is smaller than Eagg or larger than Efrag, particles respectively merge or break; otherwise they rebound. We assume that particles are formed from monomers which cannot split any further and that in a collision-induced fragmentation the larger particle splits into two fragments. We start from the Boltzmann equation for the mass-velocity distribution function and derive Smoluchowski-like equations for concentrations of particles of different mass. We analyze these equations analytically, solve them numerically and perform Monte Carlo simulations. When aggregation and fragmentation energy thresholds do not depend on the masses of the colliding particles, the model becomes analytically tractable. In this case we show the emergence of the two types of behavior: the regime of unlimited cluster growth arises when fragmentation is (relatively) weak and the relaxation towards a steady state occurs when fragmentation prevails. In a model with mass-dependent Eagg and Efrag the evolution with a cross-over from one of the regimes to another has been detected

RELATIONSHIPS BETWEEN GLANDULAR AND LYMPHOID TISSUES IN HUMAN TONGUE AND PHARYNGEAL WALLS IN POSTNATAL ONTOGENESIS

The article aims for description of glandular/lymphoid interactions within digestive tract over the postnatal ontogenesis which is of special importance for clinical immunology. We have examined lingual salivary glands obtained from 299 autopsies, using macroscopic and histological techniques. Their age ranged from newborns to senile individuals; both males and females were included. The biological material was sampled at the local pathology departments at the Moscow Bureau for Forensic and Medical Expertise, according to approval by Russian federal law (No. 323, art. 47, 4180-1, 355н). The cases with pathological changes of digestive system revealed upon autopsies were excluded from evaluation. The transverse tissue sections were stained with H&E and picro fuchsin by van Gieson technique.The minor salivary lingual and pharyngeal glands, being located in the depth of tongue and pharyngeal walls, perform an important endocrine function, i.e they participate in oral immunity responses. A lot of publications concerns regenerative changes of oral mucosa caused by secretory IgA which plays a main role in regulation of local immunity. The article describes important age-dependent changes of both lingual and pharyngeal minor salivary glands. Typical scarcity of the glands in childhood may be caused by the uniform nutrition at this age, whereas decreased secretory IgA production, is generally leading to development of common inflammatory events in the oropharyngeal area. With increasing age, the glandular apertures become wider and more numerous, thus leading to increased local immunity in oral cavity and oropharynx. Sufficient involutional changes are observed in old and senile age cohorts, accompanied by diminished secretory IgA production, and, respectively, by decreased indexes of local and humoral immunity. These results are entirely reflecting topographical interrelations between the glands and lymphoid cells, and appropriate data are quite important for clinical immunology

The laser technologies of targeted opening of blood-brain barrier for drug brain delivery

Here we show the photodynamic treatmen

Ретикулярные тромбоциты – новый фактор риска атеротромбоза?

In this review we described the properties of reticulated platelets (RP) and showed how variations of their content might influence platelet activity, efficacy of antiplatelet drugs and the rate of thrombotic events in patients with cardiovascular diseases. RP represent a minor platelet fraction containing residual RNA from megakaryocytes. Platelets have no nucleus and do not synthesize RNA de novo, and RNA of megakaryocytic origin is destroyed during their circulation. That is why only recently produced “young” platelets contain RNA. In healthy donors RP are identified by staining with the RNA specific fluorescent dyes by flow cytofluorimetry or using standard protocols in modern flow haematological analyzers. RP content in blood reflects the level of thrombocytopoesis in the bone marrow. RP on average amounted from 3 to 10% of all platelets in the circulation depending on the method applied for their determination. RP absolute amount and/or their percentage is changed in haematological diseases associated with the alterations of megakaryocyte productive properties. RT measurements in patients with cardiovascular diseases have shown that their content is increased in acute coronary syndrome patients. RP are larger and functionally more active in comparison with not reticulated forms. They more frequently incorporate into the platelet aggregates and contain more intracellular granules. Increase of RT content in the circulation correlates with the increase of the average size and functional activity in the whole platelet population. High RP content in patients with cardiovascular diseases reduces antiaggregative effects of aspirin and P2Y12 APD receptor antagonists and increases the risk of atherothrombotic events.В обзоре рассмотрены свойства ретикулярных тромбоцитов (РТ) и показано, как как вариации их содержания могут влиять на активность тромбоцитов, действие антитромбоцитарных препаратов и частоту тромбозов у больных сердечно-сосудистыми заболеваниями (ССЗ). РТ представляют собой минорную фракцию тромбоцитов, содержащих остаточную РНК из мегакариоцитов. Тромбоциты не имеют ядра и не синтезируют РНК de novo, а РНК мегакариоцитарного происхождения разрушается в процессе их циркуляции в кровотоке. В связи с этим РНК содержит только недавно образовавшиеся, «молодые» тромбоциты. РТ определяют по окраске РНК специфическими флуоресцентными красителями с помощью проточной цитофлуориметрии или используя стандартные протоколы в современных проточных гематологических анализаторах. Содержание в крови РТ отражает уровень тромбоцитопоэза в костном мозге. У здоровых лиц, в зависимости от способа определения, РТ составляют в среднем от 3 до 10% всех циркулирующих тромбоцитов. Абсолютное количество и/или процентное содержание РТ изменяется при гематологических патологиях, ассоциированных с изменениями продуктивных свойств мегакариоцитов. Измерения РТ у больных с ССЗ показали, что их содержание повышено у больных с острым коронарным синдромом. РТ крупнее и функционально более активны, чем неретикулярные формы. Они чаще включаются в состав агрегатов и содержат больше внутриклеточных гранул. Увеличение количества РТ в кровотоке коррелирует с увеличением среднего размера и функциональной активности в общей популяции тромбоцитов. Повышенное содержание РТ у больных с ССЗ снижает антиагрегационное действие аспирина и антагонистов P2Y12 рецепторов АДФ и увеличивает риск атеротромботических событий