Tailoring the flow of soft glasses by soft additives

We examine the vitrification and melting of asymmetric star polymers mixtures by combining rheological measurements with mode coupling theory. We identify two types of glassy states, a {\it single} glass, in which the small component is fluid in the glassy matrix of the big one and a {\it double} glass, in which both components are vitrified. Addition of small star polymers leads to melting of {\it both} glasses and the melting curve has a non-monotonic dependence on the star-star size ratio. The phenomenon opens new ways for externally steering the rheological behavior of soft matter systems.Comment: 4 pages, 4 figures, accepted in Phys. Rev. Let

Topological effects in ring polymers: A computer simulation study

Unconcatenated, unknotted polymer rings in the melt are subject to strong interactions with neighboring chains due to the presence of topological constraints. We study this by computer simulation using the bond-fluctuation algorithm for chains with up to N=512 statistical segments at a volume fraction \Phi=0.5 and show that rings in the melt are more compact than gaussian chains. A careful finite size analysis of the average ring size R \propto N^{\nu} yields an exponent \nu \approx 0.39 \pm 0.03 in agreement with a Flory-like argument for the topologica interactions. We show (using the same algorithm) that the dynamics of molten rings is similar to that of linear chains of the same mass, confirming recent experimental findings. The diffusion constant varies effectively as D_{N} \propto N^{-1.22(3) and is slightly higher than that of corresponding linear chains. For the ring sizes considered (up to 256 statistical segments) we find only one characteristic time scale \tau_{ee} \propto N^{2.0(2); this is shown by the collapse of several mean-square displacements and correlation functions onto corresponding master curves. Because of the shrunken state of the chain, this scaling is not compatible with simple Rouse motion. It applies for all sizes of ring studied and no sign of a crossover to any entangled regime is found.Comment: 20 Pages,11 eps figures, Late

Ісак Мазепа: перші кроки у великій політиці

Досліджується становлення світоглядних позицій та формування політичних поглядів І. Мазепи.Исследуется становление мировоззренческих позиций и формирование политических взглядов И. Мазепы.Formation world outlook positions and formation of political views of I. Mazepa is investigated

Імунологічні аспекти діагностики та лікування постгістеректомічного синдрому

В статье представлены данные клинико-иммунологического, вегетологического, психологического статуса 80 женщин, страдающих постгистерэктомическими расстройствами с целью поиска оптимальных подходов к терапии. Установлено, что постгистерэктомический синдром сопровождается различными изменениями нейровегетативной регуляции, коррелирующими с гормонально-иммунологическими нарушениями. Стабильные положительные клинико-иммунологические сдвиги у пациенток с постгистерэктомическим синдромом показали высокую эффективность включения иммунокорригирующих препаратов для оптимизации терапевтических мероприятий в борьбе с указанной патологией.Basing on clinical, immunological, vegetologycal investigations in 80 women with posthysterectomy disorders with the purpose of search of optimum pathogenetic approaches to therapy. It has been found that a posthysterectomy syndrome is accompanied by the different changes neyrovegetatic regulationand also psychoemotional disorders. New important hormonal and immunological aspects of pathogenesis were determinated. Stable positive clinical and immunological changes at patients with a postgysterektomy syndrome showed high effect of including of immunological correction for the complex of treatment of patients with this pathology

Self-diffusion in binary blends of cyclic and linear polymers

A lattice model is used to estimate the self-diffusivity of entangled cyclic and linear polymers in blends of varying compositions. To interpret simulation results, we suggest a minimal model based on the physical idea that constraints imposed on a cyclic polymer by infiltrating linear chains have to be released, before it can diffuse beyond a radius of gyration. Both, the simulation, and recently reported experimental data on entangled DNA solutions support the simple model over a wide range of blend compositions, concentrations, and molecular weights.Comment: 10 pages, 2 figure

Polydisperse star polymer solutions

We analyze the effect of polydispersity in the arm number on the effective interactions, structural correlations and the phase behavior of star polymers in a good solvent. The effective interaction potential between two star polymers with different arm numbers is derived using scaling theory. The resulting expression is tested against monomer-resolved molecular dynamics simulations. We find that the theoretical pair potential is in agreement with the simulation data in a much wider polydispersity range than other proposed potentials. We then use this pair potential as an input in a many-body theory to investigate polydispersity effects on the structural correlations and the phase diagram of dense star polymer solutions. In particular we find that a polydispersity of 10%, which is typical in experimental samples, does not significantly alter previous findings for the phase diagram of monodisperse solutions.Comment: 14 pages, 7 figure