Self-Consistent-Field Study of Adsorption and Desorption Kinetics of Polyethylene Melts on Graphite and Comparison with Atomistic Simulations

A method is formulated, based on combining self-consistent field theory with dynamically corrected transition state theory, for estimating the rates of adsorption and desorption of end-constrained chains (e.g. by crosslinks or entanglements) from a polymer melt onto a solid substrate. This approach is tested on a polyethylene/graphite system, where the whole methodology is parametrized by atomistically detailed molecular simulations. For short-chain melts, which can still be addressed by molecular dynamics simulations with reasonable computational resources, the self-consistent field approach gives predictions of the adsorption and desorption rate constants which are gratifyingly close to molecular dynamics estimates.Comment: 18 pages, 10 figure

Equation of State Based Slip Spring Model for Entangled Polymer Dynamics

A mesoscopic, mixed particle- and field-based Brownian dynamics methodology for the simulation of entangled polymer melts has been developed. Polymeric beads consist of several Kuhn segments, and their motion is dictated by the Helmholtz energy of the sample, which is a sum of the entropic elasticity of chain strands between beads, slip springs, and nonbonded interactions. The entanglement effect is introduced by the slip springs, which are springs connecting either nonsuccessive beads on the same chain or beads on different polymer chains. The terminal positions of slip springs are altered during the simulation through a kinetic Monte Carlo hopping scheme, with rate-controlled creation/destruction processes for the slip springs at chain ends. The rate constants are consistent with the free energy function employed and satisfy microscopic reversibility at equilibrium. The free energy of nonbonded interactions is derived from an appropriate equation of state, and it is computed as a functional of the local density by passing an orthogonal grid through the simulation box; accounting for it is necessary for reproducing the correct compressibility of the polymeric material. Parameters invoked by the mesoscopic model are derived from experimental volumetric and viscosity data or from atomistic molecular dynamics simulations, establishing a "bottom-up" predictive framework for conducting slip spring simulations of polymeric systems of specific chemistry. The mesoscopic simulation methodology is implemented for the case of cis-1,4-polyisoprene, whose structure, dynamics, thermodynamics, and linear rheology in the melt state are quantitatively predicted and validated without a posteriori fitting the results to experimental measurements.Comment: 80 pages, 17 figure

Allelic polymorphism of Ovar-DRB1 exon2 gene and parasite resistance in two dairy sheep breeds

The Ovar-DRB1 gene locus is one of the most polymorphic genes of the Major Histocompatibility Complex (Ovar-MHC) and holds a functional role to antigen presentation. The aim of this study was: a) to describe the Ovar-DRB1 locus variability in two dairy Greek sheep breeds and b) to investigate associations between this variability with resistance to gastrointestinal parasitosis. Blood and faecal samples were collected from 231 and 201 animals of Arta and Kalarrytiko breeds, respectively. The identification of alleles was performed using the sequence–base method. Faecal egg counting (FEC) of the gastrointestinal parasites and measures of blood plasma pepsinogen levels were performed in order to evaluate parasitological parameters. From this study in the overall examined animals, thirty-nine Ovar-DRB1 alleles were identified, among them, ten new alleles, reported for the first time in the literature. In Arta breed a total of twenty-four alleles were found. Among the detected alleles, ten were breed specific and five were new. Regarding the Kalarrytiko breed, twenty-nine alleles were found, fifteen of them were unique and nine were new. The studied breeds differed in their allelic profile, with only 12 common from the total of 134 different recorded genotypes. A higher number of animals with high parasitic load and high plasma pepsinogen values were found in Kalarrytiko. Associations between Ovar-DRB1 alleles with FEC values were found with certain heterozygous genotypes to present significantly reduced FEC values. The large number of detected alleles with low frequencies and the fact that the majority of animals were heterozygous, make hard to find strong association

Ankylosing Spondylitis in a 33- years old man with Hypermobility Joints

Background: Ankylosing spondylitis, is a chronic inflammatory autoimmune disease that mainly affects spine joints. It can cause severe, chronic pain, spine fusion and chronic disability. Ehlers-Danlos syndrome is a rare heterogenous group of hereditary connective tissue disorders which are characterized by skin hyperextensibility, joint hypermobility and tissue fragility.Case report: A 33-year old man was admitted to the Rheumatology Department of 251 Airforce General Hospital in order to decide on his capability to serve his duty as an aircraftsman at Hellenic Airforce. He was diagnosed with ankylosing spondylitis twelve years ago. On physical examination joint hypermobility and skin hyperextensibility were observed and after further investigation, he was diagnosed with hypermobility type of Ehlers Danlos Syndrome. Laboratory investigation was normal. MRI radiologic investigation revealed bony sclerosis of the left sacroiliac joint and bone marrow oedema on right sacroiliac joint. No extraskeletal manifestations were detected. The patient was informed about both conditions and he was given medical advice about their proper management. Conclusion: Rare diseases sometimes manifest as atypical inflammatory arthritis syndromes. Careful medical history, thorough physical examination and use of diagnostic criteria are useful in such patients for disease identification and treatment

STRIDE REGULATION AT THE APPROACH PHASE OF LONG JUMP IN VISUALLY IMPAIRED (F13) ATHLETES

The present work studied whether visually impaired (VI) class F13 long jumpers showed at the approach run the same pattern of variability in footfall placement across trials as their non-VI counterparts. The long jump finalists (men and women), of the IBSA 2009 European Athletics Championship were recorded. VI long jumpers demonstrated an initial ascending variability followed by a descending one suggesting some type of regulation. This control emerged on the 5th and 4th stride prior to take-off and at a mean distance of 8.8±1.9m and 8.3±2.6m from the take-off board for men and women respectively. TBD variability reached a maximum value of 30.0±18.9cm and 25.2± 14.4cm and was finally reduced to 7.73cm (± 6.65cm) and 8.2± 2.6cm for males and females respectively. The striding pattern observed was similar to that reported in the literature for non-VI athletes

Association of dietary soy with expression of various pro-inflammatory genes in porcine phagocytes

Soybean and whey are two common protein sources used in piglet feeding; however, their effects on pro-inflammatory responses remain unclear. The present study investigated the expression of various genes implicated in the activation/deactivation of porcine phagocytes post-weaning. Eighteen piglets were divided into two groups based on the main protein source of their diet; soybean (SB) or whey proteins (WP). Blood phagocytes were isolated at 72 days of age. Expression of urokinase plasminogen activator (u-PA), u-PA receptor (u-PAR), plasminogen activator inhibitors 1 and 2, intercellular adhesion molecule 1 (ICAM-1), inducible NO synthase (iNOS), cyclo-oxygenase-2 and interleukin-10 (IL-10) in activated monocytes and neutrophils (except IL-10) was determined by quantitative PCR. Expression of u-PAR, ICAM-1 and iNOS were lower  in both cell types obtained from SB-fed piglets compared to WP-fed piglets. In conclusion, a SB-based diet, compared with a WP diet, is associated with reduced expression of crucial pro-inflammatory genes in porcine phagocytes