Sliding wear behavior of plasma nitrided Austenitic Stainless Steel Type AISI 316LN in the temperature range from 25 to 400 degrees C at 10(-4) bar

There is a research knowledge gap for the dry wear data of nitride treated Stainless Steel in high temperature and high vacuum environment. In order to fill this gap, plasma nitriding was done on austenitic Stainless Steel type AISI 316LN (316LN SS) and dry sliding wear tests have been conducted at 25 degrees C, 200 degrees C and 400 degrees C in high vacuum of 1.6 x 10(-4) bar. The two different slider material (316LN SS and Colmonoy) and two different sliding speeds (0.0576 m/s and 0.167 m/s) have been used. The tribological parameters such as friction coefficient, wear mechanism and volume of metal loss have been evaluated. Scanning Electron Microscopy (SEM) was used to study the surface morphology of the worn pins and rings. Electronic balancing machine was used to record the mass of metal loss during wear tests. The 2D optical profilometer was used to measure the depth of the wear track. The Plasma Nitride treated 316LN SS rings (PN rings) exhibit excellent wear resistance against 316LN SS pin and Colmonoy pin at all temperatures. However, PN ring vs. Colmonoy pin Pair shows better wear resistance than PN ring vs. 316LN SS pin Pair at higher temperature. (C) 2012 Elsevier B.V. All rights reserved.

Criticality guided energy aware speculation for speculative multithreaded processors

Unending quest for performance improvement coupled with the advancements in integrated circuit technology have led to the development of new architectural paradigm. Speculative multithreaded architecture (SpMT) philosophy relies on aggressive speculative execution for improved performance. However, aggressive speculative execution comes with a mixed flavor of improving performance, when successful, and adversely affecting the energy consumption (and performance) because of useless computation in the event of mis-speculation. Dynamic instruction criticality information can be usefully applied to control and guide such an aggressive speculative execution. In this paper, we present a model of micro-execution for SpMT architecture that we have developed to determine the dynamic instruction criticality. We have also developed two novel techniques utilizing the criticality information namely delaying the non-critical loads and the criticality based thread-prediction for reducing useless computations and energy consumption. Experimental results showing break-up of critical instructions and effectiveness of proposed techniques in reducing energy consumption are presented in the context of multiscalar processor that implements SpMT architecture. Our experiments show 17.7% and 11.6% reduction in dynamic energy for criticality based thread prediction and criticality based delayed load scheme respectively while the improvement in dynamic energy delay product is 13.9% and 5.5%, respectively. (c) 2012 Published by Elsevier B.V.

Nanoindentation as a probe for mechanically-induced molecular migration in layered organic donor-acceptor complexes

Nanoindentation and scratch experiments on 1:1 donor-acceptor complexes, 1 and 2, of 1,2,4,5-tetracyanobenzene with pyrene and phenanthrene, respectively, reveal long-range molecular layer gliding and large interaction anisotropy. Due to the layered arrangements in these crystals, these experiments that apply stress in particular directions result in the breaking of interlayer interactions, thus allowing molecular sheets to glide over one another with ease. Complex 1 has a layered crystal packing wherein the layers are 68° skew under the (002) face and the interlayer space is stabilized by van der Waals interactions. Upon indenting this surface with a Berkovich tip, pile-up of material was observed on just one side of the indenter due to the close angular alignment of the layers with the half angle of the indenter tip (65.35°). The interfacial differences in the elastic modulus (21 ) and hardness (16 ) demonstrate the anisotropic nature of crystal packing. In 2, the molecular stacks are arranged in a staggered manner; there is no layer arrangement, and the interlayer stabilization involves C-H�N hydrogen bonds and ��� interactions. This results in a higher modulus (20 ) for (020) as compared to (001), although the anisotropy in hardness is minimal (4 ). The anisotropy within a face was analyzed using AFM image scans and the coefficient of friction of four orthogonal nanoscratches on the cleavage planes of 1 and 2. A higher friction coefficient was obtained for 2 as compared to 1 even in the cleavage direction due to the presence of hydrogen bonds in the interlayer region making the tip movement more hindered. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Geometrically non-linear dynamics of composite four-bar mechanisms

This work intends to demonstrate the importance of a geometrically nonlinear cross-sectional analysis of certain composite beam-based four-bar mechanisms in predicting system dynamic characteristics. All component bars of the mechanism are made of fiber reinforced laminates and have thin rectangular cross-sections. They could, in general, be pre-twisted and/or possess initial curvature, either by design or by defect. They are linked to each other by means of revolute joints. We restrict ourselves to linear materials with small strains within each elastic body (beam). Each component of the mechanism is modeled as a beam based on geometrically non-linear 3-D elasticity theory. The component problems are thus split into 2-D analyses of reference beam cross-sections and non-linear 1-D analyses along the three beam reference curves. For the thin rectangular cross-sections considered here, the 2-D cross-sectional non-linearity is also overwhelming. This can be perceived from the fact that such sections constitute a limiting case between thin-walled open and closed sections, thus inviting the non-linear phenomena observed in both. The strong elastic couplings of anisotropic composite laminates complicate the model further. However, a powerful mathematical tool called the Variational Asymptotic Method (VAM) not only enables such a dimensional reduction, but also provides asymptotically correct analytical solutions to the non-linear cross-sectional analysis. Such closed-form solutions are used here in conjunction with numerical techniques for the rest of the problem to predict multi-body dynamic responses more quickly and accurately than would otherwise be possible. The analysis methodology can be viewed as a three-step procedure: First, the cross-sectional properties of each bar of the mechanism is determined analytically based on an asymptotic procedure, starting from Classical Laminated Shell Theory (CLST) and taking advantage of its thin strip geometry. Second, the dynamic response of the non-linear, flexible four-bar mechanism is simulated by treating each bar as a 1-D beam, discretized using finite elements, and employing energy-preserving and -decaying time integration schemes for unconditional stability. Finally, local 3-D deformations and stresses in the entire system are recovered, based on the 1-D responses predicted in the previous step. With the model, tools and procedure in place, we identify and investigate a few four-bar mechanism problems where the cross-sectional non-linearities are significant in predicting better and critical system dynamic characteristics. This is carried out by varying stacking sequences (i.e. the arrangement of ply orientations within a laminate) and material properties, and speculating on the dominating diagonal and coupling terms in the closed-form non-linear beam stiffness matrix. A numerical example is presented which illustrates the importance of 2-D cross-sectional non-linearities and the behavior of the system is also observed by using commercial software (I-DEAS + NASTRAN + ADAMS). (C) 2012 Elsevier Ltd. All rights reserved.

Total synthesis of (+)-phomopsolide B

An enantiospecific total synthesis of polyhydroxy delta-pyrone natural product phomopsolide B is accomplished. The main feature of the synthesis is the installation of the required E-olefin by Horner-Emmons-Wordsworth reaction and the formation of the lactone involving Still-Gennari olefination followed by lactonization. (C) 2012 Elsevier Ltd. All rights reserved.

Direct ultrafast laser written C-band waveguide amplifier in Er-doped chalcogenide glass

This paper reports the fabrication and characterization of an ultrafast laser written Er-doped chalcogenide glass buried waveguide amplifier; Er-doped GeGaS glass has been synthesized by the vacuum sealed melt quenching technique. Waveguides have been fabricated inside the 4 mm long sample by direct ultrafast laser writing. The total passive fiber-to-fiber insertion loss is 2.58 +/- 0.02 dB at 1600 nm, including a propagation loss of 1.6 +/- 0.3 dB. Active characterization shows a relative gain of 2.524 +/- 0.002 dB/cm and 1.359 +/- 0.005 dB/cm at 1541 nm and 1550 nm respectively, for a pump power of 500 mW at a wavelength of 980 nm. (C) 2012 Optical Society of America

Synthesis, characterization and pharmacological study of 4,5-dihydropyrazolines carrying pyrimidine moiety

A series of 5-bromo-2-(3,5-diaryl-4,5-dihydro-1H-Pyrazol-1-yl)pyrimidine were prepared under conventional heating as well as microwave reaction condition. The newly synthesized compounds were characterized on the basis of elemental, spectral and single crystal X-ray studies. These new compounds were screened for their antioxidant, anti-inflammatory and analgesic activities. Some of these compounds exhibited potent biological activities compared to the standard drug. (C) 2012 Elsevier Masson SAS. All rights reserved.

Polymorphs and hydrates of Etoricoxib, a selective COX-2 inhibitor

The crystal structures of two polymorphs and two polymorphic hemihydrates of Etoricoxib are reported. Etoricoxib is a non-steroidal anti-inflammatory drug (NSAID) that is a selective inhibitor of COX-2. It is used in the treatment of various types of inflammation, pain and fever. Clas et al. have reported four polymorphs (labeled I through IV) and two solvates (hemi-and sesquihydrate) of the API in US patent 6,441,002 (Clas et al, US patent 6,441,002, 2002). However, no crystal structures have been reported for any of these forms. A comparison was made between the PXRD patterns reported in patent `002 and the powder spectra simulated from single crystal data. The two polymorphs characterized here correspond to form I and form IV of the patent. Form II of the patent could not be obtained by us with a variety of experimental conditions. Form III of the patent corresponds to hemihydrate II of this study. Form III is therefore not a polymorph of form I and form IV. What we have termed hemihydrate I in this study is obtained under a wide variety of conditions and it is also the only hemihydrate reported as such in the patent. Because the Etoricoxib molecule contains no conventional hydrogen bond donors, there cannot be any strong hydrogen bonds in the crystal structures of forms I and IV. The packing is accordingly characterized by weak hydrogen bonds of the C-H center dot center dot center dot O=S and C-H center dot center dot center dot N type. Thermal data were collected for form I, form IV and hemihydrate I to shed some light on relative stabilities. PXRD diffractograms show the transformation of form IV to form I at elevated temperature, indicating that form I is more stable than form IV. However, this transformation occurs only in samples of form IV that contain some form I; it does not occur in pure form IV. The formation of the two hemihydrates could follow from the known tendency of an acceptor-rich molecule to crystallize as a hydrate.

Discovery of novel glitazones incorporated with phenylalanine and tyrosine: Synthesis, antidiabetic activity and structure-activity relationships

We report a series of new glitazones incorporated with phenylalanine and tyrosine. All the compounds were tested for their in vitro glucose uptake activity using rat-hemidiaphragm, both in presence and absence of insulin. Six of the most active compounds from the in vitro screening were taken forward for their in vivo triglyceride and glucose lowering activity against dexamethazone induced hyperlipidemia and insulin resistance in Wistar rats. The liver samples of rats that received the most active compounds, 23 and 24, in the in vivo studies, were subjected to histopathological examination to assess their short term hepatotoxicity. The investigations on the in vitro glucose uptake, in vivo triglyceride and glucose lowering activity are described here along with the quantitative structure-activity relationships. (C) 2012 Elsevier Inc. All rights reserved.

Novel low-temperature growth of SnO2 nanowires and their gas-sensing properties

A simple thermal evaporation method is presented for the growth of crystalline SnO2 nanowires at a low substrate temperature of 450 degrees C via an gold-assisted vapor-liquid-solid mechanism. The as-grown nanowires were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, and were also tested for methanol vapor sensing. Transmission electron microscopy studies revealed the single-crystalline nature of the each nanowire. The fabricated sensor shows good response to methanol vapor at an operating temperature of 450 degrees C. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

High-temperature, high-pressure granulites (retrogressed eclogites) in the central region of the Lewisian, NW Scotland: Crustal-scale subduction in the Neoarchaean

Eclogites and associated high-pressure (HP) rocks in collisional and accretionary orogenic belts preserve a record of subduction and exhumation, and provide a key constraint on the tectonic evolution of the continents. Most eclogites that formed at high pressures but low temperatures at > 10-11 kbar and 450-650 degrees C can be interpreted as a result of subduction of cold oceanic lithosphere. A new class of high-temperature (HT) eclogites that formed above 900 degrees C and at 14 to 30 kbar occurs in the deep continental crust, but their geodynamic significance and processes of formation are poorly understood. Here we show that Neoarchaean mafic-ultramafic complexes in the central granulite facies region of the Lewisian in NW Scotland contain HP/HT garnet-bearing granulites (retrogressed eclogites), gabbros, Iherzolites, and websterites, and that the HP granulites have garnets that contain inclusions of omphacite. From thermodynamic modeling and compositional isopleths we calculate that peak eclogite-facies metamorphism took place at 24-22 kbar and 1060-1040 degrees C. The geochemical signature of one (G-21) of the samples shows a strong depletion of Eu indicating magma fractionation at a crustal level. The Sm-Nd isochron ages of HP phases record different cooling ages of ca. 2480 and 2330 Ma. We suggest that the layered mafic-ultramafic complexes, which may have formed in an oceanic environment, were subducted to eclogite depths, and exhumed as HP garnet-bearing orogenic peridotites. The layered complexes were engulfed by widespread orthogneisses of tonalite-trondhjemite-granodiorite (TTG) composition with granulite facies assemblages. We propose two possible tectonic models: (1) the fact that the relicts of eclogitic complexes are so widespread in the Scourian can be taken as evidence that a >90 km x 40 km-size slab of continental crust containing mafic-ultramafic complexes was subducted to at least 70 km depth in the late Archaean. During exhumation the gneiss protoliths were retrogressed to granulite facies assemblages, but the mafic-ultramafic rocks resisted retrogression. (2) The layered complexes of mafic and ultramafic rocks were subducted to eclogite-facies depths and during exhumation under crustal conditions they were intruded by the orthogneiss protoliths (TTG) that were metamorphosed in the granulite facies. Apart from poorly defined UHP metamorphic rocks in Norway, the retrogressed eclogites in the central granulite/retrogressed eclogite facies Lewisian region, NW Scotland have the highest crustal pressures so far reported for Archaean rocks, and demonstrate that lithospheric subduction was transporting crustal rocks to HP depths in the Neoarchaean. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Modeling of agglomeration inside a droplet with nanosuspensions in an acoustic field

This short communication reports results of particle agglomeration details of an acoustically levitated nanosilica droplet. The droplet undergoes thermo-physical and morphological changes under external heating load (convective or radiative) forming different solid structures due to particle agglomeration. We report an agglomeration model based on population balance approach coupled with species and energy conservation equations in the liquid phase and compare it with the experimentally observed structure formations using high speed photography. The analysis is able to predict similar spherical bowl shaped morphologies as observed experimentally using scanning electron microscopy and laser induced fluorescence. (C) 2012 Elsevier Ltd. All rights reserved.

Interaction between a notch and cylindrical voids in aluminum single crystals: Experimental observations and numerical simulations

A combined 3D finite element simulation and experimental study of interaction between a notch and cylindrical voids ahead of it in single edge notch (tension) aluminum single crystal specimens is undertaken in this work. Two lattice orientations are considered in which the notch front is parallel to the crystallographic 10 (1) over bar] direction. The flat surface of the notch coincides with the (010) plane in one orientation and with the (1 (1) over bar1) plane in the other. Three equally spaced cylindrical voids are placed directly ahead of the notch tip. The predicted load-displacement curves, slip traces, lattice rotation and void growth from the finite element analysis are found to be in good agreement with the experimental observations for both the orientations. Finite element results show considerable through-thickness variation in both hydrostatic stress and equivalent plastic slip which, however, depends additionally on the lattice orientation. The through-thickness variation in the above quantities affects the void growth rate and causes it to differ from the center-plane to the free surface of the specimen. (c) 2012 Elsevier Ltd. All rights reserved.

Time variant reliability model updating in instrumented dynamical systems based on Girsanov's transformation

The problem of updating the reliability of instrumented structures based on measured response under random dynamic loading is considered. A solution strategy within the framework of Monte Carlo simulation based dynamic state estimation method and Girsanov's transformation for variance reduction is developed. For linear Gaussian state space models, the solution is developed based on continuous version of the Kalman filter, while, for non-linear and (or) non-Gaussian state space models, bootstrap particle filters are adopted. The controls to implement the Girsanov transformation are developed by solving a constrained non-linear optimization problem. Numerical illustrations include studies on a multi degree of freedom linear system and non-linear systems with geometric and (or) hereditary non-linearities and non-stationary random excitations.

Superparamagnetic behaviour and T-1, T-2 relaxivity of ZnFe2O4 nanoparticles for magnetic resonance imaging

In the present study, ZnFe2O4 nanoparticles were synthesized by the chemical co-precipitation followed by calcinations at 473 and 673K for 4h. Particle sizes obtained were 4 and 6nm for the calcination temperatures of 473 and 673K, respectively. To study the origin of system's low temperature spin dynamic behaviour, temperature dependence of susceptibility was investigated as a function of particle size and frequency. Slight increase in the grain size from 4nm at 473K to 6nm at 673K has led to a peak shift of temperature dependence of susceptibility measured at a constant frequency of 400Hz. Temperature dependence of at different frequencies also resulted in peak shift. Relaxation time dependence of peak temperature obeys a power law, which provides the fitting parameters within the range of superparamagnetic nature of the particles. Further, dependence of relaxation time and peak temperature obeys VogelFulcher law rather than NeelBrown equation demonstrating that the particles follow the behaviour of superparamagnetism of slightly interacting system. Spinlattice, T-1 and spinspin, T-2 relaxivity of proton of the water molecule in the presence of chitosan-coated superparamagnetic ZnFe2O4 nanoparticle yields the values of 0.002 and 0.360s(1)perppm.