Rhodium‐Catalyzed Enantioselective Conjugate Addition of Arylboronic Acids to Dihydronitronaphthalenes

A highly enantioselective (up to 91% ee) rhodium‐catalyzed asymmetric addition of arylboronic acids has been achieved leading to the challenging dihydro‐3‐nitronaphthalenes using one equivalent of phosphoramidite ligand to rhodium catalyst. A concise formal asymmetric synthesis of the dopamine D1 agonist, dihydrexidine was accomplished using the method.     

Interfacial properties of metallized alumina ceramics

An alumina ceramic material (purity-96%) was metallized by the conventional molybdenum-manganese (Mo-Mn) process in which an alumina substrate was coated with Mo-Mn paste and subsequently heat treated at 1400 °C for 10 min. During the entire process a moist H₂ and N₂ gas mixture (dew point-20 °C) with 3:1 ratio was passed continuously through the furnace. X-ray diffraction analysis of the metallized alumina substrate identified only molybdenum phase at the surface of the metallizing layer. The microstructural observations of the metallized alumina substrate were made by scanning electron microscopy. Energy dispersive X-ray analysis showed the elemental compositions along the cross-sectional region of the metallized alumina substrate. The adhesion of the metallic coatings on the alumina substrates was evaluated qualitatively by a scratch testing technique and quantitatively by an adhesion tester. Nanohardness measurements showed gradual change in the nanohardness values across the metallized alumina substrate.     

Development of iron oxide and titania treated fly ash based ceramic and its bioactivity

The increasing accumulation of fly ash from thermal power plants poses a major problem to the environment. The present work reflects the novel utilization of this profusely available industrial waste in the form of an antibacterial hard ceramic material by treating fly ash with ferric oxide (Fe₂O₃) and titania (TiO₂) during sintering process at 1600 °C. The developed material shows more than 90% bacterial reduction against both Gram-positive and Gram-negative bacteria. The mechanism of their antibacterial action was studied by transmission electron microscopy (TEM) image analysis of the bacterial cross-section. The developed ceramic material acquires hardness due to the enhancement of the natural mullite content in the matrix. The mullite content and the crystallinity of mullite have shown their increasing trend with increasing concentration of the metal oxide during sintering process. A maximum of ~ 37% increase in mullite was obtained for 7% w/w Fe₂O₃ and TiO₂. Metal oxide lowered the activation energy of the reaction and enhanced the reaction rate of alumina (Al₂O₃)–silica (SiO₂) to form mullite which increases the hardness. The study highlights novel utilization of fly ash as a hard ceramic antibacterial product (bioceramics) for both structural and hygiene applications in an eco-friendly way.     

Different hierarchical nanostructured carbons as counter electrodes for CdS quantum dot solar cells

CdS quantum dot sensitized solar cells based on TiO(2) photoanode and nanostructured carbon as well as Pt as counter electrodes using iodide/triiodide and polysulfide electrolytes were fabricated to improve the efficiency and reduce the cost of solar cells. Compared with conventional Pt (η = 1.05%) and CMK-3 (η = 0.67%) counter electrodes, hollow core-mesoporous shell carbon (HCMSC) counter electrode using polysulfide electrolyte exhibits much larger incident photon to current conversion efficiency (IPCE = 27%), photocurrent density (J(sc) = 4.31 mA.cm(-2)) and power conversion efficiency (η = 1.08%), which is basically due to superb structural characters of HCMSC such as large specific surface area, high mesoporous volume, and 3D interconnected well-developed hierarchical porosity network, which facilitate fast mass transfer with less resistance and enable HCMSC to have highly enhanced catalytic activity toward the reduction of electrolyte shuttle.     

Realization of thermally durable close-packed 2D gold nanoparticle arrays using self-assembly and plasma etching

Realization of thermally and chemically durable, ordered gold nanostructures using bottom-up self-assembly techniques are essential for applications in a wide range of areas including catalysis, energy generation, and sensing. Herein, we describe a modular process for realizing uniform arrays of gold nanoparticles, with interparticle spacings of 2?nm and above, by using RF plasma etching to remove ligands from self-assembled arrays of ligand-coated gold nanoparticles. Both nanoscale imaging and macroscale spectroscopic characterization techniques were used to determine the optimal conditions for plasma etching, namely RF power, operating pressure, duration of treatment, and type of gas. We then studied the effect of nanoparticle size, interparticle spacing, and type of substrate on the thermal durability of plasma-treated and untreated nanoparticle arrays. Plasma-treated arrays showed enhanced chemical and thermal durability, on account of the removal of ligands. To illustrate the application potential of the developed process, robust SERS (surface-enhanced Raman scattering) substrates were formed using plasma-treated arrays of silver-coated gold nanoparticles that had a silicon wafer or photopaper as the underlying support. The measured value of the average SERS enhancement factor (2?×?10(5)) was quantitatively reproducible on both silicon and paper substrates. The silicon substrates gave quantitatively reproducible results even after thermal annealing. The paper-based SERS substrate was also used to swab and detect probe molecules deposited on a solid surface.     

Enhanced fluorescence and time resolved fluorescence properties of p-terphenyl crystal grown by selective self seeded vertical Bridgman technique

The fluorescence and fluorescence decay time of a modified Bridgman grown p-terphenyl single crystals have been studied. The fluorescence spectra of selective self seeded vertical Bridgman technique (SSVBT) grown p-terphenyl single crystals exhibit intense peak at 372 nm and a hump at 388 nm. Fluorescence lifetime measured by Time Correlated Single Photon Counting (TCSPC) method for p-terphenyl crystal showed a very short fluorescence decay time (τ) of 3.3 ns.     

Analysis of π-mode Stopband in an Asymmetric Millimeter-Wave Helical Slow-Wave Structure

A simple closed form formula for the estimation of π-mode stopband in an azimuthally asymmetric helical slow-wave structure (SWS) was developed following coupled-mode analysis of multiple reflections of the degenerate space-harmonic modes from the support rod discontinuities. The method incorporates the effects of circuit loss, and accrues the accuracy of 3D electromagnetic analysis by allowing the use of dispersion characteristics obtainable from any standard electromagnetic modeling. The formula is simple and amenable to easy computation, even using a scientific calculator, and without resorting to exhaustive and time-intensive numerical computation, and at the same time, without sacrificing the accuracy in results. The analysis was benchmarked against published results and excellent agreement observed. The analysis was further used for demonstrating the stopband phenomenon for a typical millimeter-wave helical slow-wave structure. Compared to low frequency structures, the stopband phenomenon for a millimeter-wave structure was found to be more pronounced, and an interesting inference was drawn as to how asymmetry induced stopband might be made to advantage in combating π-mode instabilities in a millimeter-wave traveling-wave tube.     

Prospects of microwave processing: An overview

Microwave processing has been emerging as an innovative sintering method for many traditional ceramics, advanced ceramics, specialty ceramics and ceramic composites as well as polymer and polymer composites. Development of functionally gradient materials, joining, melting, fibre drawing, reaction synthesis of ceramics, synthesis of ceramic powder, phosphor materials, whiskers, microtubes and nanotubes, sintering of zinc oxide varistors, glazing of coating surface and coating development have been performed using microwave heating. In addition, microwave energy is being explored for the sintering of metal powders also. Ceramic and metal nanopowders have been sintered in microwave. Furthermore, initiatives have been taken to process the amorphous materials (e.g. glass) by microwave heating. Besides this, an attempt has been made to study the heating behaviour of materials in the electric and magnetic fields at microwave frequencies. The research is now focused on the use of microwave processing for industrial applications.     

Selection of Superior Tillage and Fertilizer Practices Based on Rainfall and Soil Moisture Effects on Pearl Millet Yield under Semiarid Inceptisols

Based on seven field experiments of pearl millet with nine treatment combinations of tillage and fertilizer nutrients conducted during 2000–2006 in a semiarid inceptisol at Agra, an assessment is made in this paper about sustainability of treatments using rainfall received during the crop growing period and available soil moisture at sowing, 20, 40, and 60?days after sowing (DAS) and harvest. Three practices, each of tillage: conventional tillage+mechanical weed control, low tillage+mechanical weed control, and low tillage+mechanical weed control+herbicide; and fertilizer application of 60?kg?N [farm?yard?manure?(FYM)]+40?kg?P/ha, 30?kg?N (FYM)+30?kg?N (urea)+40?kg?P/ha and 60?kg?N (urea)+40?kg?P/ha were tested in the same site over seven years. The F-test indicated significant soil moisture differences on different DAS and also between different tillage treatments. Significant yield differences were found among treatments of tillage and fertilizer and their interaction in all seasons, except 2001 and 2002. Treatment-wise correlation of yield with monthly rainfall received in June–September and available soil moisture on different DAS indicated that September rainfall had a negative and significant correlation with yield attained by tillage and fertilizer treatments. The soil moisture at 20 DAS had a negative and significant correlation with yield under all treatments except conventional tillage+mechanical weed control. The soil moisture at 60 DAS and harvest had a positive and significant correlation with yield attained under different tillage and fertilizer treatments. Regression models of yield were calibrated for tillage and fertilizer treatments through monthly rainfall during July–September and soil moisture on different DAS. The predictability of yield improved significantly by inclusion of both rainfall and soil moisture variables in the models compared to either of the two groups of variables. Ranks were assigned to tillage and fertilizer treatments for yield attained in individual years and mean yield, prediction error, and sustainable yield index over years. The study indicated that conventional tillage+mechanical weed control among tillage together with 30?kg?N (FYM)+30?kg?N (urea)+40?kg?P/ha was superior with a minimum rank sum compared to other treatments. The treatment gave a maximum sustainable yield of 1,683?kg/ha with a net return of Rs 5,670?ha, benefit–cost ratio of 1.16, and sustainable yield index of 47.2% under semiarid inceptisols of Agra.     

Electrospun self‐assembled nanofiber yarns

A technique for making self‐assembled electrospun (E‐spun) nanofiber yarns from poly(acrylonitrile) in a single step is described. The process involved formation of the nanofiber yarn directly within the electrospinning zone and its removal before it can reach the counter‐electrode. The yarn is presumably formed due to splitting of the main jet into numerous nanojets and their reassembly into a single entity midway between the two electrodes. The process was found to occur at a particular field strength, which varied considerably with the concentration of the polymer dope. The gross morphology of yarns and the alignment of nanofibers in the yarn were evaluated by scanning electron microscopy (SEM). The rationale behind the formation of the yarn like structure has been explained. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008