Effect of packing on void morphology in resin transfer molded E‐glass/epoxy composites

Effects of applying a packing pressure on void content, void morphology, and void spatial distribution were investigated for resin transfer molding (RTM) E‐glass/epoxy composites. Packing pressures of zero and 570 kPa were respectively applied to center‐gated composites containing 17.5% randomly oriented, E‐glass fiber preform. Radial samples of these disk‐shaped composites were utilized to evaluate voidage via microscopic image analysis. Two adjacent surfaces were cut from each molded disk in order to evaluate void presence from both through‐the‐thickness and planar views. The packed composite was found to contain almost 92% less void content than the unpacked composite. While void fractions of 2.2 and 2.6% were measured, respectively, from the through‐the‐thickness and planar surfaces of the unpacked composite, only 0.2% void content was observed in the packed composite from both surfaces. Digital images obtained from through‐the‐thickness surface showed that average void size dropped from 59.3 μm in the unpacked composite to 31.7 μm in the packed composite. A similar reduction in average void size from 66.7 to 41.1 μm was observed from the planar surfaces. Circular voids were found to experience higher removal rates at 99%, followed by cylindrical and elliptical voids at 83 and 81%, respectively; while irregular voids show slightly lower void removal rates at 67%. Void proximity to fiber bundles was also observed to affect void reduction as voids located inside fiber tows experience lower void reduction rates. Along the radial direction of the molded disks, removal of voids with different proximities to fibers seems to depend on their arrangement at the end of the filling stage. These findings are believed to ascertain packing as an effective void removal method for RTM and similar liquid composite molding processes. POLYM. COMPOS., 26:614–627, 2005. © 2005 Society of Plastics Engineers     

Calculation of Detonation Properties of Gaseous Explosives Using Generalized Reduced Gradient Nonlinear Optimization

In this paper, a study on the development of a numerical modeling of the detonation of C H N O‐based gaseous explosives is presented. In accordance with the numerical model, a FORTRAN computer code named GasPX has been developed to compute both the detonation point and the detonation properties on the basis of Chapman–Jouguet (C‐J) theory. The determination of the detonation properties in GasPX is performed in chemical equilibrium and steady‐state conditions. GasPX has two improvements over other thermodynamic equilibrium codes, which predict steady‐state detonation properties of gaseous explosives. First, GasPX employs a nonlinear optimization code based on Generalized Reduced Gradient (GRG) algorithm to compute the equilibrium composition of the detonation products. This optimization code provides a higher level of robustness of the solutions and global optimum determination efficiency. Second, GasPX can calculate the solid carbon formation in the products for gaseous explosives with high carbon content. Detonation properties such as detonation pressure, detonation temperature, detonation energy, mole fractions of species at the detonation point, etc. have been calculated by GasPX for many gaseous explosives. The comparison between the results from this study and those of CEA code by NASA and the experimental studies in the literature are in good agreement.     

Heat evolution of high-volume fly ash concrete

In this paper, the results of a laboratory investigation conducted with heat evolution of high-volume fly ash (HVFA) concrete are presented. Heat evolution of concrete was studied by measuring the temperature increase in concrete under adiabatic curing condition. Characteristic of heat evolution of fly ash concrete was found to be strongly dependent on the replacement level of fly ash and dosage of superplasticizer used to maintain workability. It was also found that using fly ash as cement replacement resulted in a reduction on the maximum temperature rise. Increasing the replacement level of fly ash caused lower temperature rise in concrete. Superplasticizer caused a delay in peak temperature rise time; this is taken as an indicator that high-dosage superplasticizer used in concrete caused retardation in hydration of cement. Concretes having similar ingredients showed similar peak temperature rise whether they are superplasticized or not.     

An alpha-mercaptoacrylic acid derivative is a selective nonpeptide cell-permeable calpain inhibitor and is neuroprotective

Overactivation of calcium-activated neutral protease (calpain) has been implicated in the pathophysiology of several degenerative conditions, including stroke, myocardial ischemia, neuromuscular degeneration, and cataract formation. Alpha-mercaptoacrylate derivatives (exemplified by PD150606), with potent and selective inhibitory actions against calpain, have been identified. PD150606 exhibits the following characteristics: (i) Ki values for mu- and m-calpains of 0.21 microM and 0.37 microM, respectively, (ii) high specificity for calpains relative to other proteases, (iii) uncompetitive inhibition with respect to substrate, and (iv) it does not shield calpain against inactivation by the active-site inhibitor trans-(epoxysuccinyl)-L-leucyl-amido-3-methylbutane, suggesting a nonactive site action for PD150606. The recombinant calcium-binding domain from each of the large or small subunits of mu-calpain was found to interact with PD150606. In low micromolar range, PD15O6O6 inhibited calpain activity in two intact cell systems. The neuroprotective effects of this class of compound were also demonstrated by the ability of PD150606 to attenuate hypoxic/hypoglycemic injury to cerebrocortical neurons in culture and excitotoxic injury to Purkinje cells in cerebellar slices.     

XRF and Raman Characterization of Antimonite

Abstract

Two type Antimonite (stibnite) ore samples were analyzed by polarized energy dispersive X-ray fluorescence (PEDXRF) spectrometry and by confocal Raman spectrometry (CRS) in this study. The samples were collected from two different localities (?zmir-Ödemi? and Bursa-Uluda? zones from Turkey) according to the sampling methods. The first locality hosted within the metamorphic basement and the second locality hosted within the felsic intrusive rock units. The goal of this paper is to compare two different stibnite samples from various regions through PEDXRF and CRS with the optical characteristic features under the ore microscope. Ore microscopy studies reveal that the ?zmir-Ödemi? stibnite is associated mainly with calcite and the Bursa-Uluda? stibnite is associated with celestite and quartz as gangue minerals. Two different colored species were observed in the stibnite of the studied samples. Ore microscopy results, CRS with the PEDXRF results show that the stibnites from the two different localities have different mineral associations, different chemical compositions, and different physical properties.     

A genetic animal model of human neocortical heterotopia associated with seizures

Malformations of the human neocortex are commonly associated with developmental delays, mental retardation, and epilepsy. This study describes a novel neurologically mutant rat exhibiting a forebrain anomaly resembling the human neuronal migration disorder of double cortex. This mutant displays a telencephalic internal structural heterotopia (tish) that is inherited in an autosomal recessive manner. The bilateral heterotopia is prominent below the frontal and parietal neocortices but is rarely observed in temporal neocortex. Neurons in the heterotopia exhibit neocortical-like morphologies and send typical projections to subcortical sites; however, characteristic lamination and radial orientation are disturbed in the heterotopia. The period of neurogenesis during which cells in the heterotopia are generated is the same as in the normotopic neocortex; however, the cells in the heterotopia exhibit a "rim-to-core" neurogenetic pattern rather than the characteristic "inside-out" pattern observed in normotopic neocortex. Similar to the human syndrome of double cortex, some of the animals with the tish phenotype exhibit spontaneous recurrent electrographic and behavioral seizures. The tish rat is a unique neurological mutant that shares several features with a human cortical malformation associated with epilepsy. On the basis of its regional connectivity, histological composition, and period of neurogenesis, the heterotopic region in the tish rat is neocortical in nature. This neurological mutant represents a novel model system for investigating mechanisms of aberrant neocortical development and is likely to provide insights into the cellular and molecular events contributing to seizure development in dysplastic neocortex.     

High‐Potential Metalless Nanocarbon Foam Supercapacitors Operating in Aqueous Electrolyte

Light‐weight graphite foam decorated with carbon nanotubes (dia. 20–50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g^?1, 22.85 and 12.58 Wh kg^?1, 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4–0.45 g cm^?3) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices.     

A practical privacy-preserving targeted advertising scheme for IPTV users

In this work, we present a privacy-preserving scheme for targeted advertising via the Internet Protocol TV (IPTV). The scheme uses a communication model involving a collection of subscribers, a content provider (IPTV), advertisers and a semi-trusted server. To target potential customers, the advertiser can utilize not only demographic information of subscribers, but also their watching habits. The latter includes watching history, preferences for IPTV content and watching rate, which are periodically (e.g., weekly) published on a semi-trusted server (e.g., cloud server) along with anonymized demographics. Since the published data may leak sensitive information about subscribers, it is safeguarded using cryptographic techniques in addition to the anonymization of demographics. The techniques used by the advertiser, which can be manifested in its queries to the server, are considered (trade) secrets and therefore are protected as well. The server is oblivious to the published data and the queries of the advertiser as well as its own responses to these queries. Only a legitimate advertiser, endorsed with so-called trapdoors by the IPTV, can query the cloud server and access the query results. Even when some background information about users is available, query responses do not leak sensitive information about the IPTV users. The performance of the proposed scheme is evaluated with experiments, which show that the scheme is practical. The algorithms demonstrate both weak and strong scaling property and take advantage of high level of parallelism. The scheme can also be applied as a recommendation system.     

The relation between preset distinguishing sequences and synchronizing sequences

We study the relation between synchronizing sequences and preset distinguishing sequences which are some special sequences used in finite state machine based testing. We show that the problems related to preset distinguishing sequences can be converted into related problems of synchronizing sequences. Using the results existing in the literature for synchronizing sequences, we offer several reflections of these results for preset distinguishing sequences. Although computing a preset distinguishing sequence is PSPACE-hard , we do identify a class of machines for which computing a preset distinguishing sequence can be performed in polynomial time and argue that this class is practically relevant. We also present an experimental study to compare the performance of exponential brute-force and polynomial heuristic algorithms to compute a preset distinguishing sequence.