Selective oxidation of alcohols by combinatorial catalysis

High-throughput synthesis and screening of polyoxometalate (POM) and supported-metal libraries have been developed for the selective aerobic oxidation of alcohols to the corresponding aldehydes/ketones in the liquid phase. Libraries consisting of 96 catalysts were prepared in multi-well reactors and screened for catalytic activity using TLC, GC and NMR detection methods. Promising hits identified in the high-throughput primary screens were successfully scaled up and optimized in conventional laboratory test units. Isolated yields confirm high selectivities of more than 90% with quantitative conversions. Substrates tested include primary and secondary alcohols. Specific results will be presented for hydroxymethyl-substituted heterocycles and bicyclo-octanols.     

Neodymium triflate modified nafion composite membrane for reduced alcohol permeability in direct alcohol fuel cell

This paper reports an experimental study on the modification of nafion membrane with neodymium triflate, Nd(SO₃CF₃)₃, a rare earth triflate. The triflate ion resembles nafion in structure and has high lewis acidity, high coordination number, hygroscopic nature and thermal stability. These properties make the neodymium triflate (NdTfO) suitable to improve the performance of NdTfO/nafion membranes in direct alcohol fuel cell by reducing fuel permeability without compromising other properties. The NdTfO/nafion membranes reduced alcohol permeability by nearly 48%. The proton conductivity of 1% NdTfO/nafion was increased by at least 24% as compared to pure cast nafion membrane. The mechanical strength of 1% NdTfO/nafion was higher than that of pure cast nafion. The composite membrane was thermally and chemically stable and has potential for use in direct alcohol fuel cells. A DMFC was developed and its performance was evaluated using the composite membrane, which showed encouraging results.     

Porous composites of hydroxyapatite‐filled poly[ethylene‐co‐(vinyl acetate)] for tissue engineering

A novel porous composite of hydroxyapatite/poly[ethylene‐co‐vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X‐ray microcomputed tomography (µCT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X‐ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non‐cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3‐(4,5‐dimethylthiazol)‐2‐yl]‐2,5‐diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. Copyright © 2010 Society of Chemical Industry     

Attenuation of ultrasonic waves in V, Nb and Ta at low temperatures

Variation of ultrasonic attenuation and velocities with temperature have been evaluated in the temperature range 5-50 K due to electron-phonon interaction mechanism in transition metals vanadium, niobium and tantalum for longitudinal and shear waves. For this evaluation, we have also computed the second order elastic constants using Morse potential. Behaviour of acoustical phonons in these bcc metals is different from other normal metals, intermetallics, semimetallics and alloys. Some characteristic features of these materials connected to ultrasonic parameters are discussed.     

Impact of Inspected Buffers on Production Parameters of Construction Processes

This paper examines the production implications of quality control inspections conducted on the buffer between processes in a construction project by modeling the linkage between these processes. Inspection of partially completed work at the end of one activity but before the beginning of work by the next activity is fairly common. Work that is deemed to be of sufficient quality is then made available for the next activity. Work that is deemed insufficient requires rework, typically by the trade appropriate to the activity that fed into the buffer, to bring the work into compliance. This has implications for workload management for that trade, of course, as well as for the reliability of work flow to the successor or downstream processes. While such situations are common in all construction sectors, an example from the residential construction sector was examined via a simulation model augmented by field data collected from residential construction projects. The impacts of the work flow into the predecessor process, the inspection pass rate, and resource availability were examined. The inspection pass rate was found to dramatically affect the reliability of work flow, unless resources are unlimited. Furthermore, the inspection pass rate was found to be functionally related to the production parameters of the process.     

Boson Inverse Operators and a New Family of Two-photon Annihilation Operators

Abstract

We introduce the inverse of the Hermitian operator (ââ ^?) and express the Boson inverse operators â ^?1 and â ^??1 in terms of the operators â, â ^? and (ââ ^?)^?1. We show that these Boson inverse operators may be realized by Susskind-Glogower phase operators. In this way, we find a new two-photon annihilation operator and denote it as â ²(ââ ^?)^?1. We show that the eigenstates of this operator have interesting non-classical properties. We find that the eigenstates of the operators (ââ ^?)^?1 â ², â(ââ ^?)^?1 â and â ²(ââ ^?)^?1 have many similar properties and thus they constitute a family of two-photon annihilation operators.     

Convective heat transfer enhancement techniques of heat exchanger tubes: a review

Heat exchangers are widely used in almost all industrial activities. Turbulent promoters used in heat exchanger tubes are an effective way of enhancing the performance. This paper summarises various investigations using twisted tapes, wire coil ribs, baffles, and swirl flow generators. The main objective of this paper is to review various studies, in which different obstacle roughness elements are used to enhance the rate of heat transfer in the heat exchanger tubes. It has been found that a lot of experimental and analytical studies reported in the literature. On the basis of correlations developed by various investigators an attempt has been made to compare the thermal hydraulic performance of obstacles in heat exchanger tubes. In this work, a comparative study is also carried out to select the best obstacle roughness shapes for higher heat transfer rate and low pressure drop losses.