Structural and entropic insights into the nature of the random-close-packing limit

Disordered packings of equal sized spheres cannot be generated above the limiting density (fraction of volume occupied by the spheres) of ??0.64 without introducing some partial crystallization. The nature of this “random-close-packing” limit (RCP) is investigated by using both geometrical and statistical mechanics tools applied to a large set of experiments and numerical simulations of equal-sized sphere packings. The study of the Delaunay simplexes decomposition reveals that the fraction of “quasiperfect tetrahedra” grows with the density up to a saturation fraction of ?30% reached at the RCP limit. At this limit the fraction of aggregate “polytetrahedral” structures (made of quasiperfect tetrahedra which share a common triangular face) reaches it maximal extension involving all the spheres. Above the RCP limit the polytetrahedral structure gets rapidly disassembled. The entropy of the disordered packings, calculated from the study of the local volume fluctuations, decreases uniformly and vanishes at the (extrapolated) limit ?K?0.66. Before such limit, and precisely in the range of densities between 0.646 and 0.66, a phase separated mixture of disordered and crystalline phases is observed

Structure characterization of hard sphere packings in amorphous and crystalline states

The channel size distribution in hard sphere systems, based on the local neighbor correlation of four particle positions, is investigated for all volume fractions up to jamming. For each particle, all three particle combinations of neighbors define channels, which are relevant for the concept of caging. The analysis of the channel size distribution is shown to be very useful in distinguishing between gaseous, liquid, partially and fully crystallized, and glassy (random) jammed states. A common microstructural feature of four coplanar particles is observed in crystalline and glassy jammed states, suggesting the presence of "hidden" two-dimensional order in three-dimensional random close packings.Comment: 5 pages, 5 figure

A Tiling Approach to Counting Inherent Structures in Hard Potential Systems

The number of distinguishable inherent structures of a liquid is the key component to understanding the thermodynamics of glass formers. In the case of hard potential systems such as hard discs, spheres and ellipsoids, an inherent structure corresponds to a collectively jammed configuration. This work develops a tiling based approach to counting inherent structures that constructs packings by combining sets of elementary locally jammed structures but eliminates those final packings that either, do not tile space, or are not collectively jammed, through the use of tile incompatibility rules. The resulting theory contains a number of geometric quantities, such as the number of growth sites on a tile and the number of tile compatibilities that provide insight into the number of inherent structures in certain limits. We also show that these geometric quantities become quite simple in a system of highly confined hard discs.Comment: 12 pages, 2 figures. Accepted for Publication : Journal of Non-Crystalline Solid

Structural transitions in granular packs: statistical mechanics and statistical geometry investigations

We investigate equal spheres packings generated from several experiments and from a large number of different numerical simulations. The structural organization of these disordered packings is studied in terms of the network of common neighbours. This geometrical analysis reveals sharp changes in the network's clustering occurring at the packing fractions (fraction of volume occupied by the spheres respect to the total volume, $\rho$) corresponding to the so called Random Loose Packing limit (RLP, $\rho \sim 0.555$) and Random Close Packing limit (RCP, $\rho \sim 0.645$). At these packing fractions we also observe abrupt changes in the fluctuations of the portion of free volume around each sphere. We analyze such fluctuations by means of a statistical mechanics approach and we show that these anomalies are associated to sharp variations in a generalized thermodynamical variable which is the analogous for these a-thermal systems to the specific heat in thermal systems.Comment: 7 pages, 6 figure

A Probabilistic Description of the Configurational Entropy of Mixing

This work presents a formalism to calculate the configurational entropy of mixing based on the identification of non-interacting atomic complexes in the mixture and the calculation of their respective probabilities, instead of computing the number of atomic configurations in a lattice. The methodology is applied in order to develop a general analytical expression for the configurational entropy of mixing of interstitial solutions. The expression is valid for any interstitial concentration, is suitable for the treatment of interstitial short-range order (SRO) and can be applied to tetrahedral or octahedral interstitial solutions in any crystal lattice. The effect of the SRO of H on the structural properties of the Nb-H and bcc Zr-H solid solutions is studied using an accurate description of the configurational entropy. The methodology can also be applied to systems with no translational symmetry, such as liquids and amorphous materials. An expression for the configurational entropy of a granular system composed by equal sized hard spheres is deduced

Changes in the expression of HLA-DR on lymphocyte subpopulations of spouses having children with sporadic congenital heart defects without chromosomal diseases, under the influence of female’s autoserum

This study is aimed to investigate the effect of female autoserum on the HLA-DR expression in various subpopulations of lymphocytes obtained from spouses with children with sporadic congenital heart defects without chromosomal diseases. 78 married couples with children with congenital heart disease were included in the study group. The control group was formed from 35 married couples with healthy children. The immune response in a mixed culture of lymphocytes of spouses was evaluated by an increased HLA-DR expression in a mixed culture in relation to spontaneous cultures of lymphocytes. Primary staining of female and male lymphocytes by monoclonal antibodies to CD45 conjugated with various fluorescent dyes (PC-5 and PC-7) was performed to assess the immune response of female lymphocytes to male ones and vice versa. The activating effect of female autoserum on all subpopulations of female lymphocytes simultaneously occurred significantly less frequently in the study group compared to the control. The control group was characterized by the domination of the positive effect of female autoserum on HLA-DR expression for all subpopulations of female lymphocyte. For all female lymphocytes having HLA-DR molecule on its membrane, the blocking effect of female autoserum in the study group was significantly more expressed in relation to the control group. Thus, the effect of female autoserum is manifested in relation to the HLA-DR expression on its own lymphocytes, but not on the lymphocytes of the spouse

К вопросу комплексной оценке здоровья детей, оперированных по поводу врожденных пороков сердца

Aim. To find out the problems in children health in long-time postoperative period after cardiosurgery using the comprehensive method for creating rehabilitation program.Methods. A prospective investigation of group of children was done before (n = 88) and in a year (n = 115), in 2 years (n = 90) and in 3 years (n = 58) after the surgical correction of congenital heart defects on the base of Kuzbass cardiological center. The anamnesis, clinical and hemodynamic aspects were studied as well as the postoperative period, residual problems after the correction, social status of the family and the comprehensive assessment was done in the both groups.Results. Before the correction the most part of children had low and very low levels of physical functioning, but there was a positive dynamic right after the surgery: the most part of children had high and middle levels (13% and 44% in a year), while the amount of children with low and very low data were reduced. Nevertheless, in 3 years after the surgery the amount of children with low and very low data was increased while the hemodynamic became better. Such tendency was mentioned with all aspects of the health.Conclusion. Despite of hemodynamic normalization the quality of life with all aspects still suffers. It predicts dangers in development and quality of life in general.Цель. Выявление отклонений в состоянии здоровья детей в отдаленном послеоперационном периоде, перенесших кардиохирургическое вмешательство по поводу врожденных пороков сердца с применением комплексного подхода для определения возникновения возможных рисков развития.Материалы и методы. Нами было проведено проспективное исследование группы детей до (n = 88) и через 1 (n = 115), 2 (n = 90) и 3 года (n = 58) после оперативного вмешательства по поводу врожденных пороков сердца на базе Кузбасского кардиологического центра. В обеих группа изучались анамнез, клинико-гемодинамические особенности, течение послеоперационного периода, остаточные явления после коррекции порока на момент выписки из стационара, оценивался социальный статус родителей, а также проводилась комплексная оценка здоровья.Результаты. До кардиохирургического вмешательства большинство детей имели низкое и очень низкое физическое функционирование, однако непосредственно после операции отмечалась положительная динамика: большая часть детей имели высокое и среднее физическое функционирование (13% и 44% соответственно через 1 год), в то время как количество детей с низкими и очень низкими показателями физического статуса уменьшалось. Тем не менее, на 3 году жизни после операции растет количество детей с низким функционированием и уменьшается высокое и среднее, что происходит на фоне нормализации гемодинамики. Подобная тенденция отмечается в отношении всех компонентов здоровья, включая психоэмоциональный и нейрокогнитивный статус.Заключение. Несмотря на исчезновение гемодинамических нарушений, качество здоровья, включая все аспекты – физическое, эмоциональное, социальное и умственное функционирование, продолжает страдать, что прогнозирует значительные риски и снижение качества жизни в целом

ОСОБЕННОСТИ ДИАГНОСТИКИ И ЛЕЧЕНИЯ ТЯЖЕЛОЙ АОРТАЛЬНОЙ НЕДОСТАТОЧНОСТИ У ПОДРОСТКА 14 ЛЕТ НА ФОНЕ ДИСПЛАЗИИ СОЕДИНИТЕЛЬНОЙ ТКАНИ (КЛИНИЧЕСКИЙ СЛУЧАЙ)

Medical records of a patient presented with severe aortic and mitral regurgitation and connective tissue dysplasia were reviewed. Clinical, laboratory and instrumental findings were collected at baseline and after the surgery. Long-term outcomes, including quality of life, were estimated.Проведен анализ медицинской документации пациента детского возраста с выраженной недостаточностью аортального и митрального клапанов на фоне синдрома недифференцированной дисплазии соединительной ткани. Изучалась динамика клинических, лабораторных показателей, результатов инструментальных исследований до и после оперативного лечения, а также отдаленные результаты, включая оценку качества жизни

Combined Molecular Algorithms for the Generation, Equilibration and Topological Analysis of Entangled Polymers: Methodology and Performance

We review the methodology, algorithmic implementation and performance characteristics of a hierarchical modeling scheme for the generation, equilibration and topological analysis of polymer systems at various levels of molecular description: from atomistic polyethylene samples to random packings of freely-jointed chains of tangent hard spheres of uniform size. Our analysis focuses on hitherto less discussed algorithmic details of the implementation of both, the Monte Carlo (MC) procedure for the system generation and equilibration, and a postprocessing step, where we identify the underlying topological structure of the simulated systems in the form of primitive paths. In order to demonstrate our arguments, we study how molecular length and packing density (volume fraction) affect the performance of the MC scheme built around chain-connectivity altering moves. In parallel, we quantify the effect of finite system size, of polydispersity, and of the definition of the number of entanglements (and related entanglement molecular weight) on the results about the primitive path network. Along these lines we approve main concepts which had been previously proposed in the literature