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191.
Parisa Pour Shahid Saeed Abadi Chia-Ken Leong D.D.L. Chung 《Journal of Electronic Materials》2009,38(1):175-192
Finite element modeling is conducted to understand the factors that govern the performance of thermal interface pastes of
controlled thickness between copper surfaces of controlled roughness. Carbon black paste is lower in thickness than metal
particle paste, so it shows better performance. The performance of both pastes is more influenced by the paste-copper interfacial
conductance than by the paste thermal conductivity. The effects of pressure, paste thickness, and copper surface roughness
on performance are mainly due to the change in fractional filling of the valleys in the copper surface topography. Reasonable
agreement is found between modeling and experimental results. 相似文献
192.
193.
Bioremediation of toxic nonmetal and metalloid oxyanions is of great interest. In this study, among 148 bacterial isolates from two types of polluted water, strain STG-83 showed maximum oxyanion reduction and resistance ability. Sequencing of the 16S rDNA gene of STG-83 showed that the strain is closely related to Bacillus pumilus and morphological and biochemical tests confirmed the result. The strain was nitrate negative, but it could reduce half of tellurite in solution containing 1-mM concentration and completely reduced selenite and selenate in solutions containing 1-mM concentrations. Both reduction to elemental form and volatilization occurred in case of all oxyanions tested, according to hydride generation atomic absorption spectroscopy and proton induced X-ray emission analytical methods. The strain was able to tolerate remarkably high concentrations of selenite (640 mM), selenate (320 mM), and tellurite (1250 microM); and tolerance to tellurite increased in presence of selenite and selenate. Biochemical tests and zymogram of extracted culture solutions on gel electrophoresis showed that the strain was nitrate negative and therefore nitrate did not interfere with reduction of other oxyanions. Thus, the strain opens up good opportunities for the bioremediation of polluted waters in natural environment, since nitrate usually inhibits or decelerates reduction of the mentioned toxic oxyanions. 相似文献
194.
An attempt was made to isolate bacterial strains capable of biologically removing tungstate (WO42−) and perrhenate (ReO4−). Thirty-eight water samples were collected from various areas of Anzali lagoon, Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum biosorption capacity of WO42− and ReO4−. It was tentatively identified as Bacillus sp. according to morphological and biochemical properties and named strain GT-83. WO42− and ReO4− uptake by Bacillus sp. GT-83 involved both inactive and active phenomena. The amount of WO42− (initial concentration 184 mg/l) removed from aqueous solution after 16 h by inactive and active phenomena was 26 and 194.5 μg/mg protein, respectively. The strain also removed ReO4− inactively (23 μg/mg protein). Bacillus sp. GT-83 tolerated high MIC of the oxyanions. The order of toxicity of the oxyanions to the bacterium was WO42− > ReO4− in solid media. The effects of increasing metal concentrations on the growth rate were determined in order to obtain precise patterns of resistance in liquid cultures. From the results of the oxyanions toxicity, inhibitory concentrations in solid media were higher than those in liquid media. Oxyanions biosorption was determined during the course of growth. Bacillus sp. GT-83 was capable of removing WO42− and ReO4− during the active growth cycle with a sorption capacity of 194.5 μg WO42−/mg protein and 137.1 μg ReO4−/mg protein. In view of the results of oxyanions accumulation experiments, it was concluded that Bacillus sp. GT-83 was not only tolerant to oxyanions, but it also bound considerable amounts of WO42− and ReO4− from the growth medium. The binding of tungsten and rhenium on the cell wall of Bacillus sp. GT-83 was confirmed with micro-PIXE. 相似文献
195.
Aerosols are considered major players in climate change and represent health hazards. Dicarboxylic acids are among a major class of components that form secondary organic atmospheric aerosols. To understand the atmospheric transformation of these compounds, kinetic studies on the ozonolysis and the photoinduced ozonolysis (lambda > or = 250 nm) of aqueous solutions of seven (C2-C9) dicarboxylic acids, which have been identified in atmospheric aerosols, were performed using Fourier transform infrared and ultraviolet-visible spectroscopy. The measured apparent rate constants for dicarboxylic acids in 0.1 mol L(-1) aqueous solutions at 298 +/- 2 K are as follows: oxalic, (2.7 +/- 0.1) x 10(-2); malonic, (5.5 +/- 0.1); succinic, (6.7 +/- 0.4) x 10(-4); glutaric, (1.3 +/- 0.2) x 10(-3); adipic, (1.7 +/- 0.1) x 10(-3); pimelic, (4.4 +/- 0.1) x 10(-3); and pinic, (2.5 +/- 0.1) x 10(-2) (L mol(-1) s(-1)). An empirical equation is provided to estimate the ozonolysis rate constant of dicarboxylic acids containing more than three carbon atoms for which no experimental data exists. A mechanism for malonic acid ozonolysis, which explains its fast ozonolysis rate constant, is also suggested. The implications of our results to atmospheric chemistry indicate that ozonolysis and photoinduced ozonolysis are not significant removal pathways for dicarboxylic acids. 相似文献
196.
Mercury is a key toxic environmental pollutant, and its speciation affects its bioavailability. BrO radicals have been identified as key oxidants during mercury depletion events observed in Arctic and sub-Arctic regions. We report the first experimental product study of BrO-initiated oxidation of elemental mercury at atmospheric pressure of ca. 0.987 bar and T= 296+/-2 K. We used chemical ionization and electron impact mass spectrometry, gas chromatography coupled to a mass spectrometer, a MALDI-TOF mass spectrometer, a cold vapor atomic fluorescence spectrometer, and high-resolution transmission electron microscopy coupled to energy dispersive spectrometry. BrO radicals were formed using visible and UV photolysis of Br2 and CH2Br2 in the presence of ozone. We have analyzed the products in the gas phase, on suspended aerosols and on wall deposits, and identified HgBr, HgBrO/HgOBr, and HgO as reaction products. Mercury aerosols with a characteristic width of ca. 0.2 microm were observed as products. We herein discuss the implications of our results to the chemistry of atmospheric mercury and its potential implications in the biogeochemical cycling of mercury. 相似文献
197.
Parisa Moazzen Mohammad Reza Toroghinejad Fathallah Karimzadeh Jef Vleugels Hamed Ravash 《粉末冶金学》2013,56(5):405-416
ABSTRACTEquiatomic FeCoCrNi (Zr0) and non-equiatomic FeCoCrNiZr0.4 (Zr0.4) high-entropy alloys (HEAs) were synthesised by mechanical alloying and spark plasma sintering. XRD analysis verified the formation of FCC and BCC solid solution phases in both alloys after 30?h of ball milling. While the SPS FeCoCrNi alloy contains both FCC and BCC solid solution phases, the FeCoCrNiZr0.4 presents an FCC solid solution. The thermodynamic analysis showed that FeCoCrNiZr0.4 is more stable with respect to the FeCoCrNi alloy. The phase stability of FeCoCrNiZr0.4 was revealed up to ~800°C. The shear strength and hardness of the FeCoCrNi HEA improved with Zr addition. Failure analysis of the shear punch tested samples revealed a ductile fracture with dimple structure for FeCoCrNi and a brittle fracture with a smooth featureless surface for FeCoCrNiZr0.4. 相似文献
198.
Shan‐Yu Fung Hong Yang Parisa Sadatmousavi Yuebiao Sheng Tewodros Mamo Reyhaneh Nazarian P. Chen 《Advanced functional materials》2011,21(13):2456-2464
Molecular self‐assembly has emerged as the “bottom‐up” engineering route to fabricate functional supramolecules for diverse applications. The design of molecular building units becomes critical in determining the structure, properties, and function of the resulting assemblies. Here, a de novo design principle of amino acid pairing (AAP) to generate new classes of self‐assembling peptides (SAPs) is presented. In this study, the AAP focuses on hydrogen bonding, and ionic and hydrophobic interactions among amino acid pairs. With solely hydrogen bond pairs, SAPs can be constructed with only two amino acids. With all three AAP strategies (hydrogen bonds, ionic and hydrophobic pairs), a short novel SAP is constructed. This peptide can self‐assemble into β‐sheet‐rich nanofibers with a relatively low “critical aggregation concentration (CAC)” of ~10 μM . It also shows the ability to stabilize and deliver the hydrophobic anticancer agent ellipticine in aqueous solution. The peptide‐drug complexes/co‐assemblies exhibit anticancer activity against human lung carcinoma cells A549 and breast cancer cells MCF‐7, and have good dilution stability. The presented AAP design provides a new strategy to fabricate functional supramolecules with potential applications in nanomedicine. 相似文献
199.
Poulain AJ Garcia E Amyot M Campbell PG Raofie F Ariya PA 《Environmental science & technology》2007,41(6):1883-1888
It is well-established that atmospheric deposition transports Hg to Arctic regions, but the postdepositional dynamics of Hg that can alter its impact on Arctic food chains are less understood. Through a series of in situ experiments, we investigated the redox transformations of Hg in coastal and inland aquatic systems. During spring and summer, Hg reduction in streams and pond waters decreased across a 4-fold increase in salinity. This alteration of Hg reduction due to chloride was counterbalanced by the presence of particles, which favored the conversion of oxidized Hg to its elemental form. In saline waters, biogenic organic materials, produced by algae, were able to promote oxidation of Hg(O) even under dark conditions. Overall these results point to the vulnerability of marine/ coastal Arctic systems to Hg, compared to inland systems, with oxidation processes enhancing Hg residence times and thus increasing its potential to enter the food chain. 相似文献
200.
This paper deals with the dynamic output feedback stabilization problem of deterministic finite automata (DFA).The static form of this problem is defined and so... 相似文献