Granular dynamics simulations of the effect of grain size dispersity on uniaxially compacted powder blends

We investigate, via granular dynamics simulations, the influence of particle size dispersity on the packing characteristics of uniaxially compacted pharmaceutical blends. We employ reduced models of representative pharmaceutical excipient blends comprised of one, two, four and six components of different size, where the grain size in each component is distinct. We investigate the particle dynamics and reorganization during the compaction phase after the blend has been poured into a tablet die. For small strains, we demonstrate the packing fraction of the powder blends to scale linearly with the axial strain. We do not observe any significant variation in the stress response of the blend with particle size dispersity at small strains, but the mixtures with greater particle size dispersity remain compactible up to higher strains than the less polydisperse mixtures.     

An impression of coffee carbohydrates

Coffee is one of the most popular beverages in the world. It is consumed for its refreshing and stimulating properties. Carbohydrates are the major constituents of coffee beans and serve various functions like binding of aroma, stabilization of foam, formation of sedimentation, and increased viscosity of the extract. The principal low molecular weight carbohydrate is sucrose and no evidence of other simple oligosaccharides has been found. Polysaccharide fraction from green coffee is dominated by arabinogalactan, galactomannan, and cellulose. The polysaccharide content is reduced during roasting due to degradation to low molecular weight carbohydrates (viz., mono and oligosaccharide) and become more extractable. Various methods that can be employed to extract the carbohydrate from roasted coffee are sequential extraction, acid hydroloysis, hot water extraction, enzymatic extraction etc. Carbohydrates from coffee can be quantitatively determined by liquid chromatography, high performance anion exchange chromatography, size exclusion chromatography, and high performance liquid chromatography. Besides improving the organoleptic quality of the coffee beverage, carbohydrates also possess various biological activities such as lowering colon cancer risk. Besides their sheer mass, a variety of evidences testify to the important contribution that the polysaccharide content makes to the character of the final brew. Although a number of chemical and enzymatic methods have been devised to isolate and quantify the carbohydrates of R&G coffee, till date hot water extraction is the only method which can be accepted as a most feasible process and hence, there is wide scope of further research for the efficient and economically viable technology for extraction of carbohydrates from coffee.     

Prevalence of tuberculosis in Kishtwar Tehsil of Jammu region in Jammu and Kashmir State

A study of prevalence of tuberculosis in Kishtwar tehsil of Jammu region was conducted from June 1991 to May 1992. A total of one thousand two hundred ninety-eight rural as well as urban population suffering from various types of lung diseases was studied for prevalence of tuberculosis and a sizeable number (98) of patients were found to be positive of various types of tuberculosis, viz, pulmonary tuberculosis, tuberculous pleural effusion and miliary tuberculosis. Of the population studied 7.55% were found to be positive for tuberculosis and among them 88.76% patients were anaemic and the commonest type of anaemia was normocytic normochromic and normocytic hypochromic. The ESR was raised in almost of all the patients. Of the population, 80.61% were seen to be positive on skiagram chest and 58.16% were found to be positive on other diagnostic tests like Mantoux's tests, sputum for acid-fast bacilli, etc. Mantoux's test was positive in 27.55% cases and sputum was positive in 30.61% cases. All the cases studied were subjected to special investigations. The changes in parameters are consistent with the diagnosis of tuberculosis. Large family size, poverty, excessive smoking, illiteracy, etc, are the major contributing factors.     

Biochemical removal of nitrogen from tannery wastewater: performance and stability of a full‐scale plant

This paper describes the performance of a full‐scale common effluent plant treating tannery wastewater, based on a single‐sludge nitrification/denitrification process, with the objective of investigating the reasons for its instability. The plant was monitored over a 1.5‐year period; operational parameters were evaluated daily and their impact on process rates assessed together with the characteristics of the wastewater sampled at different points in the treatment scheme. The results showed that instability problems and a periodic failure of nitrification/denitrification occurred due to a series of reasons, often persisting simultaneously and having an additive synergetic effect. Factors whose magnitude would be insufficient to affect the performance of a plant treating domestic wastewater, eg; small deviations from the optimal pH in nitrification or denitrification basins, a temperature decrease to 17 °C or an increase of the influent nitrogen content, caused the plant's efficiency to drop from 100% to 40% in some periods. To ensure stable performance, the dilution rate, D, along with the sludge retention time were shown to be key parameters for the control of the process. Maintaining values of D considerably lower than critical theoretical values calculated from the specific growth rate of nitrifiers at a given temperature and sludge recycle ratio may prevent problems in the plant's performance, particularly when high fluctuations of the concentration of inflow solids make calculation of the sludge age uncertain and proper sludge management difficult. Copyright © 2004 Society of Chemical Industry     

Solution to the problem of low order harmonic resonance from HVDCconverters

A severe form of the low-order harmonic resonance problem was identified in a HVDC/AC system. Solutions to the problem were sought by HVDC control means and were achieved by a proper design of the voltage-dependent current order limiter (VDCOL), the current regulator, and the timing pulse generator. Supplementary control loops were also introduced, resulting in a satisfactory performance as compared to that obtained with the use of an uncharacteristic harmonic filter on the AC side. Robustness of all the options has been demonstrated through recovery performance of the DC link in response to three-phase five-cycle faults on both rectifier and inverter commutating buses     

A scheduling strategy in the manufacture of printed circuit boards (PCBs) using Surface Mount Technology (SMT)

A scheduling strategy for a company that manufacturers printed circuit boards is presented. This firm makes on an average over 70 different ceramic boards in a month to customer specification using Surface Mount Technology. These hybrid circuit boards are made to order. Therefore, the objective in the scheduling strategy is to minimize the number of tardy jobs and minimize the makespan.     

Lot sizing in cellular manufacturing systems

Cellular manufacturing systems are found to be very productive compared to the discrete lot manufacturing systems. New techniques are required for planning and scheduling jobs in this type of systems. A technique for lot sizing in cellular manufacturing systems has been presented in this paper. The manufacturing system considered consists of two stages the primary and secondary. The cell is considered to be in the secondary stage and is composed of four machines. An example problem has been solved using the computer software developed.     

Basis for detection of stenosis using venous administration of microbubbles during myocardial contrast echocardiography: bolus or continuous infusion?

Recent studies have shown that the lactating mammary gland is able to utilize plasma-derived dipeptides for milk protein synthesis. However, it was not clear whether the peptides were hydrolysed followed by uptake of the constituent amino acids or were taken up intact. In view of this, we have designed experiments to investigate (a) whether the lactating rat mammary gland is capable of transporting hydrolysis-resistant dipeptides and (b) whether or not mammary cells are able to hydrolyse peptides, including glutathione, extracellularly. The uptake of the hydrolysis-resistant dipeptides D-[3H]Phe-L-Gln and D-[3H]Phe-L-Glu by the perfused rat mammary gland was low. Concomitant addition of L-Leu-L-Ala (50 mM) had no effect on the clearance of either labelled dipeptide suggesting that the small, albeit significant, uptake of the dipeptides is not via a high affinity peptide transporter (PepT1/PepT2). All anionic dipeptides tested (L-Glu-L-Ala, L-Asp-L-Ala, L-Ala-L-Asp, L-Asp-Gly, Gly-L-Asp and Gly-L-Glu) with the exception of D-Phe-L-Glu were able to trans-accelerate the efflux of labelled D-aspartate from preloaded rat mammary tissue (explants and perfused mammary gland). It appears that these peptides were being hydrolysed extracellularly followed by the uptake of free anionic amino acids via the mammary tissue high affinity, Na+-dependent anionic amino acid carrier operating in the exchange mode. Glutathione was able to trans-accelerate D-aspartate efflux from lactating rat mammary tissue in a fashion which was sensitive to the peptidase inhibitor acivicin. This suggests that gamma-glutamyltranspeptidase hydrolyses glutathione to produce L-glutamate which is subsequently transported via the high-affinity anionic amino acid carrier. Hydrolysis of peptides followed by uptake of the constituent amino acids may provide an important source of amino acids for milk protein synthesis.     

Spike leakage of thin Si PIN limiters

Thin PIN diode limiters (10 μm or less) are used to protect sensitive microwave components from fast-risetime microwave pulses having energies exceeding 1 to 10 μJ. This paper analyzes and experimentally confirms the performance of these PIN limiters. It is shown that spike leakage is a transit-time effect that is controlled by the mobility of the carriers. A p-type background I-region should yield less spike leakage energy for a given thickness. It is proposed that the hysteresis effect observed when limiters are operated under cw conditions is due to space charge effects and stored charges remaining after the reverse-biased half cycle. Detailed agreement between the measured and calculated device voltage waveforms requires accurate modeling of the circuit parasitics because of the high rate-of-change currents arising from avalanching