On the phase composition of polymethylsiloxane derived ceramics

The pyrolysis products of polymethylsiloxanes (PMS) have been studied in order to characterize their phase composition from the viewpoint of equilibrium thermodynamics. Dilatometry measurements and redox analyses with PbO have been conducted and the results analysed and compared with respect to the second law of thermodynamics. In agreement with equilibrium thermodynamics, which shows that there is no ternary compound in the Si–O–C system, the experimental results imply that the pyrolysis residue is an amorphous or nanocrystalline composite consisting of a SiO2-phase matrix with embedded SiC and C particles. These findings seem to contradict the accepted scientific opinion of ternary silicon-oxycarbide phases.     

Observations of the outer radiation belt with REM and comparisonswith models

Radiation environment monitors (REMs) on-board the STRV-1b spacecraft in geostationary transfer orbit (GTO) and externally on Mir have returned valuable results over the last few years. STRV data show the great variability of the electron radiation belt and a stable proton belt feature. In this paper, a detailed assessment is made of the flux values derived from the REM on STRV and particularly how they compare with the AE-8 and CRRESELE electron radiation-belt models. To compare with CRRESELE, the activity index Ap₁₅ is used and the behavior of this index as a parameter is assessed. GOES data are used to aid this assessment     

EFFECTS OF SURFACE HYDRATION AND APPLICATION METHOD ON THE BOND STRENGTH OF SELF-ETCHING ADHESIVES TO DENTIN

The effect of application methods and dentin hydration on the bond strength of three self-etching adhesives (SEA) were evaluated; 195 extracted bovine incisors were used. The buccal surface was ground in order to expose the dentin, which remained 2-mm minimum thickness, measured by a thickness meter through an opening on the lingual surface. Adper Single Bond 2? was used for the control group. The SEA were applied following two modes of application: passive or active and two hydration states of the dentin surface—dry and wet. After light-curing, composite buildups were made using Grandio? composite. The specimens were sectioned and tested with a microtensile bond strength test. The application method and the hydration state resulted in statistical differences (p = 0.000) making the values of active application for μTBS to dentin higher than passive application. The wet surfaces showed higher μTBS to dentin ratios than dry surfaces. There were no statistical differences in μTBS among the SEA tested but there were differences regarding to control group.     

Parallel programming inPanda

Distributed systems are an alternative to shared-memory multiprocessors for the execution of parallel applications.Panda is a run-time system that provides architectural support for efficient parallel and distributed programming. It supplies fast user-level threads and a means for transparent and coordinated sharing of objects across a homogeneous network. The paper motivates the major architectural choices that guided our design. The problem of sharing data in a distributed environment is discussed, and the performance of the mechanisms provided by thePanda prototype implementation is assessed.     

Acceleration of ungapped extension in Mercury BLAST

The amount of biosequence data being produced each year is growing exponentially. Extracting useful information from this massive amount of data efficiently is becoming an increasingly difficult task. There are many available software tools that molecular biologists use for comparing genomic data. This paper focuses on accelerating the most widely used such tool, BLAST. Mercury BLAST takes a streaming approach to the BLAST computation by offloading the performance-critical sections to specialized hardware. This hardware is then used in combination with the processor of the host system to deliver BLAST results in a fraction of the time of the general-purpose processor alone.This paper presents the design of the ungapped extension stage of Mercury BLAST. The architecture of the ungapped extension stage is described along with the context of this stage within the Mercury BLAST system. The design is compact and runs at 100 MHz on available FPGAs, making it an effective and powerful component for accelerating biosequence comparisons. The performance of this stage is 25× that of the standard software distribution, yielding close to 50× performance improvement on the complete BLAST application. The sensitivity is essentially equivalent to that of the standard distribution.     

Surface Chemical Study of Sheet Molded Composite (SMC) as Related to Adhesion

Surfaces of commercial sheet molded composite (SMC) materials have been characterized by X-ray photoelectron spectroscopy (XPS) before and after various surface treatments. Surface treatments included cleaning with methylene chloride, abrasion using methylene chloride and a Scotch Brite ® abrasive pad, and application of an isocyanate primer. The pretreated SMC materials were bonded using a polyurethane adhesive. Bonded coupons were tested under a variety of conditions using the lap shear technique. Lap shear test results for specimens bonded following the abrasion and primer pretreatment indicated a favorable fracture force and mode of failure. Surface analysis studies were used to characterize the pretreated and failed surfaces.     

Biosequence Similarity Search on the <Emphasis Type="BoldItalic">Mercury</Emphasis> System

Biosequence similarity search is an important application in modern molecular biology. Search algorithms aim to identify sets of sequences whose extensional similarity suggests a common evolutionary origin or function. The most widely used similarity search tool for biosequences is BLAST, a program designed to compare query sequences to a database. Here, we present the design of BLASTN, the version of BLAST that searches DNA sequences, on the Mercury system, an architecture that supports high-volume, high-throughput data movement off a data store and into reconfigurable hardware. An important component of application deployment on the Mercury system is the functional decomposition of the application onto both the reconfigurable hardware and the traditional processor. Both the Mercury BLASTN application design and its performance analysis are described.     

Rainbow trout cytochrome P450s: purification, molecular aspects, metabolic activity, induction and role in environmental monitoring

Cytochromes P450 (P450s or CYPs) constitute a superfamily of heme-thiolate proteins that play important roles in oxidative metabolism of endogenous and exogenous compounds. This review provides some limited history but addresses mainly the research progress on the cytochrome P450s in rainbow trout (Oncorhynchus mykiss), their purification, structures at the primary level, role in metabolism, responses to chemicals and environmental pollutants, application to biomonitoring and the effect of various factors on their expression or activities. Information obtained to date suggests that the rainbow trout P450 systems are as complex as those seen in mammals. Fourteen P450s have been purified from liver or trunk kidney to relatively high specific content. cDNAs belonging to seven different P450 families have been documented from trout liver, kidney and ovary. Two CYP1A genes, nine cDNAs containing open reading frames, and a cDNA fragment were entered into GenBank. Among them, CYP2K1, CYP2K3, CYP2K4, CYP2M1, CYP3A27 and CYP4T1 are the most recently described forms. CYP2K1, CYP2M1 and CYP4T1 represent newly identified P450 subfamilies first described in the rainbow trout. In many cases, the cloned rainbow trout P450s have subsequently been expressed in heterologous expressions systems such as COS-7 cells, yeast and baculovirus infected insect cells. Some of the overexpressed P450 isoforms have been partially characterized. Potential future research directions are discussed.     

Proteoid Dynamers with Tunable Properties

A range of doubly dynamic proteoid biodynamers based on the polycondensation of various categories of amino acid hydrazides with a di‐ aldehyde have been generated through formation of two types of reversible CN bonds (imine and acylhydrazone). Their structures and properties (rates of polymerization and dynamic character) have been characterized by NMR, small‐angle neutron scattering, dynamic light scattering, and cryo‐transmission‐electron microscopy. Three types of structures (nanorods, globular nano‐objects, oligomers) are obtained at different rates after polycondensation. Competitive polymerization shows that electrostatic effects markedly influence polymerizations when two oppositely charged monomers are used, and an exchange experiment demonstrates the preferential incorporation of a specific monomer in the biodynamer chain. Taken together, all our results show that the side chains of the amino acid hydrazides have a strong influence on the rates of polymerization, structures, and dynamic properties of the resulting biodynamers. The present study provides a basis for the rational design and synthesis of various types of well‐ordered structures and adaptive materials, offering great potential for utilization in the field of biomaterials science.