Preparation and characterization of chemically deposited lead sulphide thin films

A chemical method for the deposition of PbS thin films has been developed using appropriate amounts of lead acetate, thioacetamide and triethanolamine. The thickness of the films are in the range 0.3 to 1 m. The films are polycrystalline and p-type. The dependence of the film thickness as a function of the bath parameters has also been studied and explained on the basis of ion-ion condensation theory.     

Coke formation during simultaneous hydrocracking of bitumen and hydrogenation of coal

Conventional catalysts are rapidly fouled with coke deposits when they are used to hydrocrack residual oils. The work reported here was part of an investigation on the removal of coke-forming compounds from residual oils prior to their contact with catalysts. Semianthracite coal particles have been added to a reaction mixture of hydrogen and Athabasca bitumen at 13.9 MPa and 723 K, to provide a large surface area on which coke could deposit. Agglomeration of coal particles occurred during hydrogenation in the absence of bitumen, but did not occur when bitumen, coal, and hydrogen were all present together in the reaction system. A solid mass of coke formed when bitumen was hydrocracked in the absence of coal particles, but did not form when the bitumen was present with coal and hydrogen. These observations illustrate one of the advantages of processing bitumen and coal simultaneously. The solid particles from hydrocracking experiments, coal hydrogenation experiments, and experiments on coal carbonization were examined petrographically. It was found that coke formed from Athabasca bitumen has a different microstructure from that formed from semi-anthracite coal. On the basis of these studies it was concluded that semi-anthracite coal was converted to coke similar to that normally made from low-volatile bituminous coal. Simultaneously coke formed from the bitumen was deposited on the exterior of the particles.     

Role of energy transfer,defect, and lattice dimension in photophysical characteristics of AWO4:Nd3+ (A=Ca,Sr and Ba)

The fact that the scheelite based compounds are of high technological importance in the area of scintillator and optoelectronics, makes their detailed photophysical study relevant not only for fundamental material science but also in tailoring their optical properties for advanced applications. With this view, we have carried out a very systematic study on near infra-red (NIR) emitting Nd³⁺ doped CaWO₄, SrWO₄, and BaWO₄ compounds. Light emitting efficiency in AWO4:Nd³⁺ is governed strongly by radiative/nonradiative properties, host-dopant energy transfer (HDET) efficiency and defect density. We have used photoluminescence, positron annihilation, and photoacoustic (PA) spectroscopy to study the factors effecting light emission. These scheelites are known to exhibit self activated luminescence in visible region due to charge transfer within the tungstate group and wavelength maxima exhibited red shift as we move from Ca→Sr→Ba. This can provide a new strategy to achieve spectral tunability in AWO₄ scheelite by changing A²⁺ ionic radius. The fractional intensity in the green region is least in the case of SrWO₄ samples suggesting that the oxygen vacancy density is minimal in case of SrWO₄ which is well-supported by the positron annihilation lifetime spectroscopy (PALS). Based on our studies, we found that the HDET was highly efficient in CaWO₄:Nd³⁺ and minimal in BaWO₄:Nd³⁺ which get's reflected in photoluminescence intensity. Emission lifetimes are shorter in CaWO₄ and highest in SrWO₄ host which are in sync with positron annihilation lifetime values. Based on our results of PALS, it was found that CaWO₄:Nd³⁺ has the highest concentration of defects i.e. cation vacancies; so larger is the probability of nonradiative signals and hence higher PA intensity from it.     

Degenerate Quantum Gases in Microgravity

Clouds of ultra-cold atoms and especially Bose–Einstein condensates (BEC) provide a source for coherent matter-waves in numerous earth bound experiments. Analogous to optical interferometry, matter-wave interferometers can be used for precision measurements allowing for a sensitivity orders of magnitude above their optical counterparts. However, in some respects the presence of gravitational forces in the lab limits experimental possibilities. In this article, we report about a compact and robust experiment generating Bose–Einstein condensates in the drop tower facility in Bremen, Germany. We also present the progress of building the succeeding experiment in which a two species atom interferometer will be implemented to test the weak equivalence principle with quantum matter.     

Validation of fully implicit method for simulation of flows with interfaces using primitive variables

This paper describes applications of the fully implicit procedure for computing flow of two immiscible fluids. Six problems in two and three dimensions are solved to highlight effects of grid size, pressure smoothing, TVD convection scheme and geometric and fluid dynamic evaluations of surface tension force. Free surface and cavity flows are considered in which effect of sloshing, interface merger and splitting as well as splashing are included. Wherever possible, present solutions are compared with results of previous experiments and/or numerical computations. Computational details such as grid size, time step, under-relaxation factors, mass/volume conservation are reported.     

Generative model based robotic grasp pose prediction with limited dataset

Applied Intelligence - In the present investigation, we propose an architecture which we name as Generative Inception Neural Network (GI-NNet), capable of predicting antipodal robotic grasps...     

Effect of Zn Doping on Structural and Magnetic Properties of Ba4Ni2−x Zn x Fe36O60 Hexaferrites

Polycrystalline Ba₄Ni_2?x Zn _x Fe₃₆O₆₀ (0.0 ≤x ≤ 1.4) hexagonal ferrite samples have been prepared by conventional solid-state reaction method. Structural and magnetic properties of the prepared samples were then analyzed by the X-ray diffraction technique and with superconducting quantum interface device (SQUID) magnetometer, respectively. Variations of lattice parameters, density, and porosity with Zn content were measured. Magnetic properties such as complex permeability, relative quality factor, loss factor, and saturation magnetization have been investigated as a function of Zn content. The study revealed that Zn content has a significant effect on structural and magnetic properties of the Ba₄Ni₂Fe₃₆ O ₆₀ hexaferrites.     

Synthesis and Characterization of Novel Surfactants: Combination Products of Fatty Acids,Hydroxycarboxylic Acids and Alcohols

The reaction of hydroxycarboxylic acids, such as citric, malic and tartaric species with an excess of fatty acid chlorides produces the corresponding O-acylated hydroxycarboxylic anhydrides in one step and in a near quantitative yield. These molecules are excellent electrophiles which react readily with a variety of nucleophiles including alcohols, diols and polyols. Their reaction with triethylene glycol and triethylene glycol monomethyl ether leads to two series of novel anionic surfactants, which are unsymmetrical gemini surfactants. The determination of their properties (CMC, foaming, HLB) revealed that these molecules are—depending on the chain length of the fatty acid—excellent emulsifiers, and that they also display interesting antimicrobial activity. These novel functional surfactants are of interest for applications in food and personal care products and for the formulation of pharmaceuticals.     

In vitro and in vivo release of cefuroxime axetil from bioactive glass as an implantable delivery system in experimental osteomyelitis

The aim of this study was to evaluate the characterisation, in vitro and in vivo biocompatibility and antimicrobial activity of bioactive glass (BG) impregnated with an antibiotic. The BG was prepared by normal glass melting procedures as a controlled release device to treat experimental osteomyelitis. The study design was for prospective in vivo experimental study. Two sets of porous bioactive glass ceramic blocks (9 mm × 4 mm × 4 mm and 20 mm × 9 mm × 9 mm) were fabricated using bioactive glass powder and subsequently antibiotic cefuroxime axetil (CFA) (55 and 125 mg on an average) was impregnated in these two sets of blocks, respectively. Osteomyelitis was produced in the right tibia of the rabbits according to the model of Norden. After thorough in vitro characterization of the porous blocks [including X-ray diffraction (XRD), Fourier-transformed infra-red spectroscopy (FTIR), thorough chemical analysis by inductively coupled plasma-atomic emission spectra (ICP-AES) and field-emission scanning electron microscopy (FESEM)] and in vitro elution of the said drug, in vivo test was carried out with rabbit species split into two groups: (a) animals treated with CFA impregnated bioactive glass and (b) parenteral [intra muscular (IM)] administration of CFA. Histological, radiological and drug concentration in bone and serum (measured by HPLC) in both groups were carried out. HPLC technique was used for determination of concentration both in vitro and in vivo. Fabricated porous struts showed amorphous microstructure without formation of any crystallite. The elution of said drug was stopped after 6 days in vitro. Histological studies at 3 and 6 weeks revealed formation of well-developed lamellar bone and havarsian canal. Radiological evaluation pointed out disappearance of sequestrum and existence of newly formed bony specules. Concentration of cefuroxime axetil in bone and serum showed highest value on day 21 which reduced marginally by day 42 and these values were higher than minimum inhibitory concentration (MIC) against Staphylococcus aureus (known pathogen for chronic osteomyelitis). It could be concluded that the biodegradable antibiotic carrier system developed in this study proved to be an effective therapeutic approach toward an experimental model of osteomyelitis. Based particularly on the in vivo results of the study, this cefuroxime axetil incorporated bioactive glass blocks can be successfully used in clinical cases of osteomyelitis in veterinary as well as human orthopaedic surgery.