Shear flow induced isotropic to nematic transition in a suspension of active filaments

We study the effects of externally applied shear flow on a model of suspensions of motors and filaments, via the equations of active hydrodynamics [PRL {\bf 89} (2002) 058101; {\bf 92} (2004) 118101]. In the absence of shear, the orientationally ordered phase of {\it both} polar and apolar active particles is always unstable at zero-wavenumber. An imposed steady shear large enough to overcome the active stresses stabilises both apolar and moving polar phases. Our work is relevant to {\it in vitro} studies of active filaments, the reorientation of endothelial cells subject to shear flow and shear-induced motility of attached cells.Comment: 8 pages, 4 figures submitted to Europhysics Letter

Surgical implications of magnetic resonance-enhanced dura

Journal ArticleTHE PURPOSE OF this study was to assess tissue changes responsible for dural enhancement on magnetic resonance imaging (MRI) and its clinical implications. A prospective surgical, histopathological, and MRI study was performed in 7 3 patients with various types of disease, including meningiomas (n = 29), craniofacial tumors with possible direct intracranial extension (n = 2 1), gliomas and brain metastasis in close proximity to the dura mater (n = 9), and a variety of nonneoplastic processes (n = 1 4). Contrast-enhanced MRI was obtained within 5 days before surgery and in some cases within 3 days after surgery as well. Histopathological examination of the dural specimens was performed in all 59 patients with neoplasia and in selected patients with nonneoplastic processes. Dural invasion was noted in 1 8 of 29 meningiomas, 1 5 of 21 craniofacial neoplasms, 3 of 5 gliomas, and 3 of 4 brain metastases. In these patients invasion was focal and in direct continuity with the tumors. MRI disclosed that dura invaded by the tumor had a break in the continuity of enhancement, or that there was no discernible enhancement. Association between patterns of dural enhancement and tumor invasion of dura was statistically significant (P < 0.001) . The thickened-enhanced portion of the dura represented reactive changes. Postoperative enhancement was seen as early as 24 hours after surgery and as shown histologically to be associated with vasodilation and reactive changes. Conclusions from this study are: 1) dural enhancement is a nonspecific reaction and may be seen in association with many pathological conditions; 2) a fairly uniform "enhanced dura" adjacent to a tumor correlated with a dural inflammatory reaction, whereas discontinuous enhancing dura indicated dural invasion; 3) a few false-negative cases of dural invasion (one extracranial and four intracranial neoplasms) underscore that there are some limitations of contrast-enhanced MRI in predicting dural invasion by adjacent neoplasms

Impact and flexural properties of hybrid jute/HTPET fibre reinforced epoxy composites

In this study, hybridizing jute with high tenacity polyethylene terephthalate (HTPET) fibres has been proposed. Different hybrid jute/HTPET fibre reinforced epoxy composite samples have been fabricated with different weight ratios of HTPET, and subjected to charpy impact and three-point bending test. The results show that increasing the content of HTPET fibres in the composites will considerably improve their energy absorption capabilities and structural integrity after impact and bending test. However, hybrid composites with HTPET show lower flexural stress and bending modulus than pure jute composites

Characterization method of formability properties of zinc alloy coating on a metal substrate

The present invention relates to a method for the characterisation of formability properties of a zinc alloy coating on a metal substrate and a metal substrate comprising a zinc alloy coating. The method for the characterisation of formability properties of a zinc alloy coating on a metal substrate, the zinc alloy coating containing one or more alloying elements selected from the group consisting of Mg, Al, Ni each with a content of at least 0.3 weight % and at most 10 weight %, optionally one or more additional elements selected from the group consisting of Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, or Bi, wherein the content by weight of each additional element in the metallic coating is less than 0.3 weight %, inevitable impurities, the remainder being zinc, the zinc alloy coating having a microstructure comprising a primary zinc phase and binary eutectic and/or ternary eutectic phases, wherein Electron Backscatter Diffraction (EBSD) is used to determine a crystallographic orientation-dependent strain hardening exponent (n) of the zinc alloy coating microstructure

Epidemiology of Shigella-Associated diarrhea in Gorgan, north of Iran

Objective : Shigella is an important etiological agent for diarrhea and especially dysentery. Shigellosis is an intestinal infection that is a major public health problem in many developing countries. The aim of this study was to evaluate the prevalence of Shigella and its various species in diarrheal samples in Gorgan located in the north of Iran. Materials and Methods: Between January-December 2005, the epidemiology of Shigella- associated diarrhea was studied among 634 patients in Gorgan. The diarrheal samples accompanied with a questionnaire, which contained the demographic and main symptoms of the patients, were transported to the laboratory and inoculated in different culture media. Colonies suspected to be of Shigella were detected using differential biochemical tests and subsequently, the serotype of Shigella was defined using antisera. Results : Shigella was isolated from 56/634 diarrheal samples) (8.8%) of which S. sonnei was the predominant species (55%). Occurrence of Schigella was highest in the 2-5 years′ age group (70.9%) and highest in summer (73.2%) with the most frequent clinical manifestation being abdominal pain (67.8%). The prevalence of Shigella in males and females was 8 and 9.8% respectively, but this difference was not statistically significant. Conclusion: It has been shown that Shigella sonnei is the most common Shigella serogroup among 2-5 year-old children in Gorgan. It is therefore suggested that hygienic training be given to childcare attendants and the children themselves

Nematic and Polar order in Active Filament Solutions

Using a microscopic model of interacting polar biofilaments and motor proteins, we characterize the phase diagram of both homogeneous and inhomogeneous states in terms of experimental parameters. The polarity of motor clusters is key in determining the organization of the filaments in homogeneous isotropic, polarized and nematic states, while motor-induced bundling yields spatially inhomogeneous structures.Comment: 4 pages. 3 figure