A stochastic process-based server consolidation approach for dynamic workloads in cloud data centers

The Journal of Supercomputing - With the development of information technology, there is a need for computational works everywhere and every time. Thus, people should be able to carry out their...     

Polymerization initiation by N-p-tolylglycine: Free-radical reactions studied by pulse and steady-state radiolysis

The extensive use of N-p-tolylglycine (NTG) and analogous compounds in adhesive bonding technologies requires a better understanding of their role in initiating free-radical polymerization. The fast oxidation and reduction reactions of NTG proceed via the formation of various free radicals and radical cation and anion intermediates. These intermediates were identified and their reactivity with oxygen, to produce the corresponding peroxyl radicals, was measured. Hydroxyl radicals (?H) were used to initiate oxidation reactions of NTG, while the reduction reactions were initiated with hydrated electrons (e). OH radicals react with NTG predominately by addition to the aromatic ring followed by OHÞ elimination to produce NTG⁺· radical cations. In the presence of oxygen, the OH–NTG^? adduct also reacts with oxygen to produce peroxyl radicals. The reaction of NTG with e forms the radical anion, which subsequently protonates on the aromatic ring to produce cyclohexadienyl radicals, or undergoes an amine elimination to yield an acetic acid free radical and 4-methylaniline. Hydroperoxyl radicals (HO) abstract hydrogen from the α position of NTG to form the corresponding alkyl free radical. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Innovative preparation of bacterial cellulose/silver nanocomposite hydrogels: In situ green synthesis,characterization, and antibacterial properties

In this study, an innovative in situ green strategy was applied to prepare bacterial cellulose/silver nanocomposites using green tea as a substrate for the fermentation of Acetobacter xylinum bacteria and a reducing agent for the in situ synthesis of silver nanoparticles. The samples were analyzed by different characterization tests including field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), UV–vis spectroscopy, atomic absorption spectroscopy, and ATR. The results indicated the excellent antibacterial activities with 100% bacterial reduction percentage and inhibition zones of 2.6 and 2.8 cm against S. aureus and E. coli, respectively. Moreover, water absorption percentage and vertical wicking measurements supported the hydrogel properties of the prepared bio-cellulose/silver nanocomposites. Finding of this research suggested the potential of the proposed green route for preparing antibacterial BC which can be regarded as a candidate for future wound healing applications.     

Moderate concentration of citric acid for the formation of LaMnO3 and LaCoO3 nano-perovskites

Stoichiometric LaMnO3 and LaCoO3 nanoparticles were synthesized via calcination of a dried solution, containing molar ratio of La(NO3)3·6H2O/[Mn(NO3)2·4H2O or Co(NO3)2·6H2O]=1 and citric acid as disper...     

Allele frequency distribution for D11S1304, D11S1998, and D11S934 and metabolic syndrome in TLGS

Different variant frequencies may lead to different frequencies of the same variants in individuals with drugs resistance and disease susceptibility at the population level. In this study, the allele frequency of three STRs loci including D11S1304, D11S1998, and D11S934 was analyzed on a representative sample of 563 individuals from the capital city of Tehran. The sample included four different ethnic groups. In this sample, 130 individuals were affected with metabolic syndrome (Mets). Calculated parameters on the whole sample were: allele frequency, polymorphic information content values, observed and expected heterozygosity, discrimination power, matching probability, power of discrimination, power of exclusion, and paternity index. For all markers, no significant deviation from Hardy–Weinberg equilibrium was found in observed allele frequencies except D11S1998. There were no significant differences in the allele frequencies in short, medium and long alleles between the metabolic affected subjects and controls. The most significant findings of this study report allele frequency of some STRs on chromosome 11 for the first time in Iran and the observed differences between subjects affected with Mets as opposed to subjects in the control group.     

The extraordinary stability imparted to silver monolayers by chloride

While single crystal surfaces facilitate the majority of surface studies, only a handful of these materials are stable under ambient conditions and at extreme temperatures. Therefore, there is a continued interest in the development of robust and ordered surfaces that can be studied under realistic conditions. Electrochemical scanning tunneling microscopy (EC-STM) revealed that in a chloride-free electrolyte, Ag forms an ordered monolayer on Au(1 1 1) with a structure that could be atomically resolved. However, upon removal from the cell, these chloride-free Ag monolayers were subject to degradation by air and high temperatures. Interestingly, if the Ag layer was formed in the presence of chloride, the resulting AgCl_x layer was stable both in air and at high temperatures. X-ray photoelectron spectroscopy was used to characterize the system and ambient-, low temperature-, and EC-STM revealed that even after exposure to extreme temperatures, the AgCl_x layer remained intact. Density functional theory (DFT) indicated that the equilibrium coverage of Cl on the Ag monolayer was ∼0.5 ML, and that the barrier for surface reorganization of the overlayer was low. It is proposed that this facile mobility of the overlayer imparts a protective property that allows the AgCl_x layer to withstand extreme temperatures and attack by oxygen.     

Investigating the microstructure and composition of cold gas-dynamic spray (CGDS) Ti powder deposited on Al 6063 substrate

The compositional variation, morphology and microstructure of cold gas-dynamic spray are of great importance for its proper application. This study investigates titanium powder deposition on an Al 6063 substrate using light optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composition was examined using energy dispersive X-ray spectroscopy (EDX), X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF SIMS). Optical and electron microscopy revealed heavily deformed Ti powder particles penetrating 10 to 30 μm into the Al substrate. Examination using TEM did not reveal any evidence of second phases at the interface suggesting a sharp transition between the two metals. The presence of nanocrystals and grain refinement of both the coating and the substrate suggest the formation of a partial hetero-epitaxy condition near the interface. EDX results from a dedicated high-resolution scanning transmission electron microscope showed a sharp compositional change with a maximum inter-diffusion region of about 5 nm. Bonding of the coating to the substrate is therefore thought to be achieved by the particle/substrate interlocking and direct metal to metal bonding. However, it is most likely that the refine crystalline structure near the interface will be beneficial to the adhesion of the coating. XPS and ToF SIMS provided evidence of nitrogen pick-up during the spray process in the form of N and TiN even when utilizing Helium as the gas carrier. The presence of TiN suggests reaction of the Ti with the entrained air during spraying which explains the occurrence of flashing jet outside the nozzle. Investigation of the material properties using nanoindentation showed reasonably consistent hardness and elastic modulus values throughout the titanium coating and at the transition region. The hardness was slightly higher than typical commercially available bulk Ti.     

Numerical Investigation of Nanofluid Laminar Convective Heat Transfer through a Circular Tube

Laminar-flow convective heat transfer of nanofluid in a circular tube with constant wall temperature boundary condition is investigated numerically. A dispersion model is used to account for the presence of nanoparticles. Numerical predictions are in agreement with experimental results obtained in our laboratory for different particles in different sizes. Results clearly show that addition of nanoparticles to base liquid produces considerable enhancement of heat transfer. Heat transfer coefficients increase with nanoparticle concentration. Decreasing nanoparticles size at a specific concentration increases heat transfer coefficients.