Structural,electrical and optical properties of metal complexes of NNS donor ligand

The temperature dependence of electrical conductivity, optical property and crystal structure (PXRD) of [Ni(Hdammthiol)(CH₃COO)] (1), [Co(Hdammthiol)(CH₃COO)]·H₂O (2) and [Cu(Hdammthiol)(CH₃COO)]·H₂O (3) [where H₂dammthiol is the thiol form of the ligand diacetylmonoxime morpholine N-thiohydrazone (Hdammth)] complexes were investigated. The crystal structures of samples at room temperature were examined by using powder X-ray diffraction (PXRD). The results showed that all the complexes belong to the monoclinic system. Hot probe measurement indicated that these complexes had an n-type electrical conductivity. Optical absorption studies in the wavelength range 190–1100 nm at room temperature showed that the optical band gap E_gd of complexes 1–3 is 2.75 eV, 2.37 eV and 1.58 eV, respectively.     

Pseudodynamic systems approach based on a quadratic approximation of update equations for diffuse optical tomography

We explore a pseudodynamic form of the quadratic parameter update equation for diffuse optical tomographic reconstruction from noisy data. A few explicit and implicit strategies for obtaining the parameter updates via a semianalytical integration of the pseudodynamic equations are proposed. Despite the ill-posedness of the inverse problem associated with diffuse optical tomography, adoption of the quadratic update scheme combined with the pseudotime integration appears not only to yield higher convergence, but also a muted sensitivity to the regularization parameters, which include the pseudotime step size for integration. These observations are validated through reconstructions with both numerically generated and experimentally acquired data.     

Negative and positive persistent photoconductance in graphene

Persistent photoconductance, a prolonged light-induced conducting behavior that lasts several hundred seconds, has been observed in semiconductors. Here we report persistent negative photoconductance and consecutive prominent persistent positive photoconductance in graphene. Unusually large yields of negative PC (34%) and positive PC (1652%) and remarkably long negative transient response time (several hours) were observed. Such high yields were reduced in multilayer graphene and were quenched under vacuum conditions. Two-dimensional metallic graphene strongly interacts with environment and/or substrate, causing this phenomenon, which is markedly different from that in three-dimensional semiconductors and nanoparticles.     

Biodiesel production in a semiarid environment: a life cycle assessment approach

While the use of biodiesel appears to be a promising alternative to petroleum fuel, the replacement of fossil fuel by biofuel may not bring about the intended climate cooling because of the increased soil N2O emissions due to N-fertilizer applications. Using a life cycle assessment approach, we assessed the influence of soil nitrous oxide (N2O) emissions on the life cycle global warming potential of the production and combustion of biodiesel from canola oil produced in a semiarid climate. Utilizing locally measured soil N2O emissions, rather than the Intergovernmental Panel on Climate Change (IPCC) default values, decreased greenhouse gas (GHG) emissions from the production and combustion of 1 GJ biodiesel from 63 to 37 carbon dioxide equivalents (CO2-e)/GJ. GHG were 1.1 to 2.1 times lower than those from petroleum or petroleum-based diesel depending on which soil N2O emission factors were included in the analysis. The advantages of utilizing biodiesel rapidly declined when blended with petroleum diesel. Mitigation strategies that decrease emissions from the production and application of N fertilizers may further decrease the life cycle GHG emissions in the production and combustion of biodiesel.     

Development of a Novel Cast 6351 Al-Al4SiC4 In Situ Composite

In this research work 6351 Al-Al₄SiC₄ composite has been developed through stir casting route with incorporation of fine TiC powder in 6351 Al melt. During stir casting, round shaped Al₄SiC₄ particles were generated as TiC reacted with molten aluminum. These Al₄SiC₄ particles were found to be acting as nucleation sites for primary α (causing grain refinement) along with engulfment effects promoting particle distribution without clustering. Furthermore, as the volume fraction of Al₄SiC₄ particles increased, the proportion of dendritic region decreased (more equiaxed grains appeared) and the overall grain size of the matrix decreased. This resulted in an improved strength and ductility of the composite. Equations were developed with a reasonable accuracy correlating the strength with microstructural parameters. An excellent combination of strength (UTS = 215 MPa) and ductility (%Elongation = 10) was obtained for 6351 Al-7 vol.% Al₄SiC₄ composite as compared to base cast 6351 Al alloy (UTS = 121 MPa, %Elongation = 3).     

Vectorized 3D microstructure for finite element simulations

Microstructure based forming models using statistically representative microstructural input provide the most accurate predictions for early localization and failure during complex forming operations. However, the sheer size and complexity of the three dimensional (3D) microstructural data from real materials makes it hard to implement that data in current finite element models. In this report, a technique to create a vectorized 3D microstructure suitable for input into finite element codes is developed and applied to represent the distribution of particles of different phases found in continuous cast (CC) AA5754 sheets, which tend to have heterogeneous particle distributions with particles of several phases in different shapes and sizes (from 0.2 μm to 10 μm) and distributed at random, in stringers and along the “centerline”. The technique consists of a 3D reconstruction of the true microstructure by performing serial sections and conversion of the 3D raster image to the vector image. A 3D mesh is generated automatically using Unigraphics and Hypermesh from real particle field measurements, which can be imported to any FE code. The vectorized microstructure is validated by comparison with the reconstructed images of particle distribution data.     

Effect of bauxite addition on densification and mullitization behaviour of West Bengal clay

The effect of bauxite addition on the densification and mullitization of reaction sintered bauxite-clay mixture had been studied in the temperature range 1400–1500°C. The maximum bulk density (2·89 g/cc) and minimum apparent porosity (0·58%) was achieved by addition of 50 wt% bauxite. The impurities present in bauxite and clay formed liquid phase which helped in particle diffusion to aid densification. The X-ray diffraction of sample fired at 1500°C showed cristoballite phase gradually disappearing and at the same time mullite and α-Al₂O₃ phase appearing at a higher level of bauxite addition. The in situ nascent alumina formed was reactive that facilitated the formation of secondary mullite by solution precipitation mechanism. The presence of bauxite also changed the morphology of the mullite particles. Two types of mullite were distinctly observed in the SEM photographs: elongated primary mullite and equiaxed secondary mullite.     

Synthesis of nanocrystalline yttria doped ceria powder by urea-formaldehyde polymer gel auto-combustion process

Nanocrystalline yttria doped ceria powder has been prepared by auto-combustion of a transparent gel formed by heating an aqueous acidic solution containing methylol urea, urea, cerium(III) nitrate and yttrium(III) nitrate. The TGA and DSC studies showed the combustion reaction of the gel initiated at 225 °C and completed within a short period of time. XRD spectrum of the combustion product reveals the formation of phase pure cubic yttria doped ceria during the combustion process. Loose agglomerate of yttria doped ceria particle obtained by the combustion reaction could be easily deagglomerated by planetary ball milling and the powder obtained contains particles in the size range of 0.05-3.3 μm with D₅₀ value of 0.13 μm. The powder particles are aggregate of nanocrystallites with a wide size range of 14-105 nm. Pellets prepared by pressing the yttria doped ceria powder sintered to 95.2% TD at 1400 °C.     

Bis-cationic heteroaromatics as macrofilaricides: synthesis of bis-amidine and bis-guanylhydrazone derivatives of substituted imidazo[1,2-a]pyridines

A series of guanylhydrazone, amidine, and hydrazone derivatives of 2-phenylimidazo[1,2-a]pyridine have been prepared and evaluated for macrofilarial activity against Acanthocheilonema viteae and Brugia pahangi in jirds. Compounds with 4',6-bis-substitution by cyclic guanylhydrazone groups show activity. 4',6-Bis-amidines show some activity but are more toxic; 4'- or 6-monosubstituted compounds are inactive. 2,6-Bis-substituted compounds lacking the phenyl ring are inactive. 4',6-Bis-substituted compounds having additional double bonds inserted between the heterocyclic ring and the phenyl ring or between the substituent and the ring system show reduced activity.