Effects of Water Saturation and Low Temperature Coupling on the Mechanical Behavior of Carbon and E-Glass Epoxy Laminates

An experimentally based study has been conducted to quantify the effects of coupled water saturation and low temperatures on the quasi-static and dynamic mechanical behavior of E-Glass and Carbon Epoxy laminates. The relative performance of the materials as a function of water saturation and decreasing temperature was characterized through detailed experiments, specifically in-plane (tensile/compressive) and shear material properties, static and dynamic Mode-I fracture, and impact/flexure after impact strength. In the investigation temperatures from Room Temperature (20°C) down to arctic seawater and extreme ocean depth conditions (-2°C) were evaluated. The materials utilized in the study, Carbon/Epoxy and E-glass/Epoxy, are chosen due to their primary interest to the underwater vehicle and marine industry communities. The results of the quasi-static and dynamic material experiments show that all properties are affected by both water saturation and decreasing temperature, although the trends are specific to the property under consideration

Low Temperature Effects on the Mechanical, Fracture, and Dynamic Behavior of Carbon and E-glass Epoxy Laminates

An experimental investigation through which the effects of low temperatures on the mechanical, fracture, impact, and dynamic properties of carbon- and E-glass-epoxy composite materials has been conducted. The objective of the study is to quantify the influence of temperatures from 20 °C down to −2 °C on the in-plane (tensile/compressive) and shear material properties, static and dynamic Mode-I fracture characteristics, impact/residual strength, and the storage and loss moduli for the materials considered. The low end of the temperature range considered in the study is associated with Arctic seawater as well as conditions found at extreme ocean depths (2 °C–4 °C). In the investigation, both carbon/epoxy and E-glass/epoxy laminates are evaluated as these materials are of keen interest to the marine and undersea vehicle community. The mechanical characterization of the laminates consists of controlled tension, compression, and short beam shear testing. The Mode-I fracture performance is quantified under both quasi-static and highly dynamic loading rates with additional flexure after impact strength characterization conducted through the use of a drop tower facility. Finally, dynamic mechanical analysis (DMA) testing has been completed on each material to measure the storage and loss moduli of the carbon fiber- and E-glass fiber reinforced composites. The findings of the study show that nearly all characteristics of the mechanical performance of the laminates are both material and temperature dependent

The development and characterisation of a bacterial artificial chromosome library for Fragaria vesca

<p>Abstract</p> <p>Background</p> <p>The cultivated strawberry <it>Fragaria ×ananassa </it>is one of the most economically-important soft-fruit species. Few structural genomic resources have been reported for <it>Fragaria </it>and there exists an urgent need for the development of physical mapping resources for the genus. The first stage in the development of a physical map for <it>Fragaria </it>is the construction and characterisation of a high molecular weight bacterial artificial chromosome (BAC) library.</p> <p>Methods</p> <p>A BAC library, consisting of 18,432 clones was constructed from <it>Fragaria vesca </it>f. <it>semperflorens </it>accession 'Ali Baba'. BAC DNA from individual library clones was pooled to create a PCR-based screening assay for the library, whereby individual clones could be identified with just 34 PCR reactions. These pools were used to screen the BAC library and anchor individual clones to the diploid <it>Fragaria </it>reference map (FV×FN).</p> <p>Findings</p> <p>Clones from the BAC library developed contained an average insert size of 85 kb, representing over seven genome equivalents. The pools and superpools developed were used to identify a set of BAC clones containing 70 molecular markers previously mapped to the diploid <it>Fragaria </it>FV×FN reference map. The number of positive colonies identified for each marker suggests the library represents between 4× and 10× coverage of the diploid <it>Fragaria </it>genome, which is in accordance with the estimate of library coverage based on average insert size.</p> <p>Conclusion</p> <p>This BAC library will be used for the construction of a physical map for <it>F. vesca </it>and the superpools will permit physical anchoring of molecular markers using PCR.</p

Analysis of Saharan dust intrusions into the Carpathian Basin (Central Europe) over the period of 1979–2011

Aeolian dust particles and dust storms play substantial role in climatic and other environmental processes of the Earth system. The largest and most important dust source areas are situated in the Sahara, from where several hundred thousand tons of mineral dust is emitted each year and transported towards the European continent. Here we show that 130 Saharan dust events (SDEs) reached the atmosphere of the Carpathian Basin from 1979 to 2011 by using the NASA's daily TOMS Aerosol Index data, satellite images and backward trajectory calculations of NOAA HYSPLIT model. Monthly trends of dust events demonstrate that the main period of dust transportation is in the spring, with a secondary maximum in the summer (in July and August). This seasonal distribution match well the seasonality of Saharan dust emissions. However synoptic meteorological conditions govern primarily the occurrence of long-range dust transport towards Central Europe. Based on their different meteorological backgrounds (geopotential field, wind vector and meridional flow), SDEs were classified into three main types. By using composite mean maps of synoptic situations and backward trajectories, the possible source areas have also been identified for the different types of events. Finally, we provide a short discussion on how the African mineral dust could contribute to the local aeolian sedimentation of the Carpathian Basin during the Plio-Pleistocene

Dark Matter and Fundamental Physics with the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a project for a next-generation observatory for very high energy (GeV-TeV) ground-based gamma-ray astronomy, currently in its design phase, and foreseen to be operative a few years from now. Several tens of telescopes of 2-3 different sizes, distributed over a large area, will allow for a sensitivity about a factor 10 better than current instruments such as H.E.S.S, MAGIC and VERITAS, an energy coverage from a few tens of GeV to several tens of TeV, and a field of view of up to 10 deg. In the following study, we investigate the prospects for CTA to study several science questions that influence our current knowledge of fundamental physics. Based on conservative assumptions for the performance of the different CTA telescope configurations, we employ a Monte Carlo based approach to evaluate the prospects for detection. First, we discuss CTA prospects for cold dark matter searches, following different observational strategies: in dwarf satellite galaxies of the Milky Way, in the region close to the Galactic Centre, and in clusters of galaxies. The possible search for spatial signatures, facilitated by the larger field of view of CTA, is also discussed. Next we consider searches for axion-like particles which, besides being possible candidates for dark matter may also explain the unexpectedly low absorption by extragalactic background light of gamma rays from very distant blazars. Simulated light-curves of flaring sources are also used to determine the sensitivity to violations of Lorentz Invariance by detection of the possible delay between the arrival times of photons at different energies. Finally, we mention searches for other exotic physics with CTA.Comment: (31 pages, Accepted for publication in Astroparticle Physics

Basolateral Sorting of Syntaxin 4 Is Dependent on Its N-terminal Domain and the AP1B Clathrin Adaptor, and Required for the Epithelial Cell Polarity

Generation of epithelial cell polarity requires mechanisms to sort plasma membrane proteins to the apical and basolateral domains. Sorting involves incorporation into specific vesicular carriers and subsequent fusion to the correct target membranes mediated by specific SNARE proteins. In polarized epithelial cells, the SNARE protein syntaxin 4 localizes exclusively to the basolateral plasma membrane and plays an important role in basolateral trafficking pathways. However, the mechanism of basolateral targeting of syntaxin 4 itself has remained poorly understood. Here we show that newly synthesized syntaxin 4 is directly targeted to the basolateral plasma membrane in polarized Madin-Darby canine kidney (MDCK) cells. Basolateral targeting depends on a signal that is centered around residues 24–29 in the N-terminal domain of syntaxin 4. Furthermore, basolateral targeting of syntaxin 4 is dependent on the epithelial cell-specific clathrin adaptor AP1B. Disruption of the basolateral targeting signal of syntaxin 4 leads to non-polarized delivery to both the apical and basolateral surface, as well as partial intercellular retention in the trans-Golgi network. Importantly, disruption of the basolateral targeting signal of syntaxin 4 leads to the inability of MDCK cells to establish a polarized morphology which suggests that restriction of syntaxin 4 to the basolateral domain is required for epithelial cell polarity

Beta2-Microglobulin Amyloid Fibrils Are Nanoparticles That Disrupt Lysosomal Membrane Protein Trafficking and Inhibit Protein Degradation by Lysosomes.

Fragmentation of amyloid fibrils produces fibrils that are reduced in length but have an otherwise unchanged molecular architecture. The resultant nanoscale fibril particles inhibit the cellular reduction of the tetrazolium dye 3-(4,5-dimethylthi-azol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), a substrate commonly used to measure cell viability, to a greater extent than unfragmented fibrils. Here we show that the internalization of β2-microglobulin (β2m) amyloid fibrils is dependent on fibril length, with fragmented fibrils being more efficiently internalized by cells. Correspondingly, inhibiting the internalization of fragmented β2m fibrils rescued cellular MTT reduction. Incubation of cells with fragmented β2m fibrils did not, however, cause cell death. Instead, fragmented β2m fibrils accumulate in lysosomes, alter the trafficking of lysosomal membrane proteins, and inhibit the degradation of a model protein substrate by lysosomes. These findings suggest that nanoscale fibrils formed early during amyloid assembly reactions or by the fragmentation of longer fibrils could play a role in amyloid disease by disrupting protein degradation by lysosomes and trafficking in the endolysosomal pathway