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Articles by R. Singh
Total Records ( 11 ) for R. Singh
  R. Singh , P.D. Lee , Trevor C. Lindley , R.J. Dashwood , Emilie Ferrie and T. Imwinkelried
  Titanium foams produced via the space-holder method are used for spinal fusion devices since their combination of an open-cell structure and bone-like mechanical properties promises potentially excellent bone ingrowth. Earlier studies have indicated that the size of the pores and interconnects must be greater than 100 μm for effective bone ingrowth and vascularization. Hence, the quantification of the pore and interconnect size is required for efficient scaffold design. In this study, microcomputed tomography (μCT) was used to obtain the three-dimensional (3D) structure of Ti foams with three levels of porosity (51%, 65% and 78%). Novel algorithms were then applied to quantify both the pore and interconnect size of Ti foams as a function of porosity. All foams possessed a modal pore and interconnect size in excess of 300 μm, satisfying the requirement of being greater than 100 μm. The pore and interconnect size also dominates the flow properties or permeability of open-cell structures. Therefore, the μCT data was also used to generate a mesh for computational fluid dynamics analysis to predict the permeability. The calculated permeability (117–163 × 10−12 m2 depending on direction) for the Ti foams with 65% porosity was first validated against experimental measurements (98–163 × 10−12 m2) and then compared to prior authors’ measurements in healthy cancellous bovine bone (233–465 × 10−12 m2). The close match among all the permeability values proves the suitability of the material for biomedical skeletal-implant applications.
  V. Rakesh , R. Singh and P.C. Joshi
  A number of experiments were conducted to study the impact of updating model basic fields by satellite data (Quick Scatterometer (QSCAT) surface winds and Atmospheric Infrared Sounder (AIRS) temperature and humidity profiles) on long-range simulation during the Indian summer monsoon 2006. The Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model version5 (MM5) and its four dimensional data assimilation (FDDA) technique was used for the numerical simulations. The spatial distribution and temporal variation in model simulated basic meteorological parameters and rainfall were verified against the observed fields from National Center for Environmental Prediction (NCEP) analysis and Tropical Rainfall Measuring Mission (TRMM), respectively. The overall analysis of the results from QSCAT surface wind assimilation as compared to control simulation (CNT; without the satellite data assimilation) suggest that a better representation of a single level wind field during model integration fail to make significant improvement in the model simulation both in the basic meteorological parameters and rainfall. The assimilation of temperature and humidity profiles from the AIRS during model integration significantly improved the rainfall prediction during monsoon period. It is found that the improvement in rainfall prediction is attributed to improved thermodynamics structure due to AIRS profile assimilation and the degree of improvement is more in temperature prediction as compared to humidity prediction. It is also found that the prediction over the regions, such as south west part of India and foothills of Himalaya, where a complex orography exists, is not significantly benefited from satellite data assimilation which highlights the need of improvement in the model in addition to a better representation of atmospheric state.
  A. E. Ghaly , F. Alkoaik , A. Snow and R. Singh
  An effective thermophilic composting bioreactor, in which a homogenous distribution of temperature was maintained at 63-65°C by the addition of a bioavailable carbon and low mixing, was developed. The bioreactor operated on a mixture of tomato plant residues-wood shavings-municipal solid waste compost infected with tobacco mosaic virus (TMV). The initial C: N ratio and moisture content of the compost mixture were adjusted to 30:1 and 60%, respectively. The composting process was successful in destroying the tobacco mosaic virus. The results showed that the ability of the untreated virus (inoculum) to infect tobacco plants (150 LL L-1) was much higher than its ability to infect tomato plants (22 LL L-1). The TMV completely lost its ability to infect the leaves of susceptible hosts (tobacco and tomato plants) after 96 hrs of controlled thermophilic (63-65 °C) composting (or 126 h from the start of the composting process). Semilog plots of the ratio of the infection ability of the surviving virus to that of the initial inoculum (as measured by the number of local lesions) were developed. The decimal reduction time (the time necessary to reduce the infection ability of TMV by 1-log or 90%) was found to be 62.4 and 109.7 hrs for tobacco and tomato plants, respectively. The relatively short time required for complete inactivation of TMV in this study was achieved as a result of the extension of the thermophilic stage and maintaining a constant high temperature with a uniform temperature distribution by the continuous addition of the proper amount of bioavailable carbon (used cooking oil) and low mixing.
  R. Singh , V. Kapoor and V. Kumar
  The present study deals with the standardization of different cultural conditions for extracellular α-amylase production by thermophilic Streptomyces sp. MSC702 in submerged fermentation (SmF). The appropriate incubation period (48 h), temperature (50°C) and pH (7.0) were determined. The effects of derived and natural carbon sources, inorganic and organic nitrogen sources were also examined. Maximum α-amylase production i.e., 435.71 and 373.89 U mL-1 were achieved by employing derived (D-inositol) and natural (rice bran) carbon sources, respectively. Among the tested nitrogen sources, ammonium sulphate and peptone were found the best inorganic and organic sources, respectively. The C:N ratio found to be the optimum was 1:1. The highest α-amylase activity (807.64 U mL-1) was obtained by utilizing rice bran and wheat bran in 1:2 ratio as the substrate with supplements of D-inositol (1% w/v), ammonium sulphate (0.5% w/v) and peptone (1% w/v). By using the optimized cultural conditions with further characterization, this α-amylase may be utilized in wide spread applications like detergent, saccharification and pharmaceutical industry.
  R. Singh , A. T. Hattersley and L. W. Harries
 

Aims  Mitochondrial depletion in pancreatic beta cells is known to reduce glucose stimulated insulin secretion. We aimed to determine whether the offspring of patients with early onset Type 2 diabetes had reduced peripheral blood mitochondrial content relative to control subjects and whether this could lead to a predisposition to type 2 diabetes in later life.

Methods  We measured the levels of mitochondria relative to a single copy genomic target by real time polymerase chain reaction in a series of peripheral blood samples taken from the offspring of Caucasian patients with Type 2 diabetes and matched controls. Measures of insulin sensitivity and beta cell function were also taken.

Results  In contrast with previous studies, mitochondrial DNA content was not decreased in the offspring of patients with Type 2 diabetes relative to matched controls in our cohort. Conversely, we noted a small proliferation in mitochondrial numbers in our case subjects. In agreement with these findings, no correlations with either insulin sensitivity or beta cell function were noted.

Conclusions  Our results indicate that reduced mitochondrial DNA content in peripheral blood is not a risk factor for the development of Type 2 diabetes in the offspring of patients with early onset Type 2 diabetes.

  R. Singh and M. Press
  Aims  To determine the factors responsible for poor glycaemic control in diabetes and whether any such factors are associated with likely improvement in glycaemic control.

Methods  A prospective cohort study of 130 diabetic patients with poor glycaemic control (HbA1c ≥ 10.0%) with 1-year follow-up in a teaching hospital Diabetes Clinic. Changes in HbA1c were measured after 1 year.

Results  Poor glycaemic control was attributed to one of 15 possible causes. Those cases due to recent diagnosis of diabetes, inadequate treatment with diet, oral glucose-lowering agents or insulin, exacerbation of co-existent medical problems, recent stressful life-events and missed clinic appointments were all associated with significant improvement in HbA1c at 12 months. Patients with low mood or alcohol excess, inadequate blood glucose monitoring, poor exercise/sedentary lifestyle, refusal to take tablets or underdosing and refusal to take insulin at all or to increase the dose were all associated with continuing poor glycaemic control at 12 months. The patients were divided almost equally between the two groups.

Conclusions  In patients with poor glycaemic control, it is possible by simple features identified at clinic to predict which individuals are likely to show improvement in control and which will not. These findings have not been reported previously and suggest that about half of individuals with poor control will improve within our current diabetes clinic practice. Additional strategies will be required to address those individuals who are not likely to respond.

  M.R. Siddiqui , A. Tariq , K.D. Reddy , P.S. Negi , J. Yadav , A. Bhatnagar , M. Chaudhary and R. Singh
  A simple and sensitive assay method was developed for simultaneous determination of cefepime and sulbactam sodium in Supime (a fixed dose combined formulation of cefepime and sulbactam manufactured by Venus Remedies limited, India) with UV detection at 230 nm. Chromatographic separation of two drugs was achieved on a Hypersil ODS C-18 column using a binary mixture of acetonitrile and tetrabutyl ammonium hydroxide as a mobile phase adjusted to pH 5.0 with orthophosphoric acid in ratio 20:80 v/v ratio. The developed liquid chromatographic method offers good linearity, accuracy and precision over the concentration range of 125-750 ppm for cefepime and 62.5-375 ppm for sulbactam sodium. This method was successfully applied for the quality control of formulated products and plasma samples containing Cefepime and sulbactam. Since, Supime, a fixed dose combination of cefepime and sulbactam is a research product of Venus Remedies limited the literature lacks any method of analysis for such combination, the main motive behind this experiment was to develop and validate a method which could be used for the quality control of cefepime and sulbactam in combined dosage form.
  R. Singh , K. Khanna , K.N. Wadhwani , R.S. Joshi and A.M. Patel
  Increase in feed prices in recent years has stimulated renewed interest in the area of feed restriction and simultaneously the birds have to provide space for feeding, watering and normal movements for their optimum growth and production. Thus, a great emphasis has been laid on feeding system, which employs the use of quantitative or qualitative feed restriction. During growing phase 468 White Leghorn (WLH) birds from random bred control population housed on deep litter housing system were exposed to three feeding regimes viz. T1 (ad lib.), T2 (Skip-two-days a week) and T3 (75% of ad lib.) on three different stocking densities viz. S1 (2.5 ft2/bird; 20 birds/pen), S2(2.0 ft2/bird; 25 birds/pen) and S3 (1.5 ft2/bird; 33 birds/pen) to form nine combinations of feed regimes and stocking density. Between 20 to 32 weeks of age, T1, T2 and T3 birds gained 31.76, 45.19 and 70.82 percent of body weight. The T1xS3 birds were heavier (1904.5±39.9 g) than other groups at the end of laying phase. The maximum feed consumed by T1 group (117.91±4.17 g) followed by T3 (116.61±3.80g) and T2 group (108.28±3.61 g), which differed significantly. T1xS3 birds consumed daily about 102 g feed and was significantly lower from other interaction groups. The birds kept under T3xS1 treatment gave maximum hen day egg production (64.36±6.78%) followed by T1xS2 (63.83±0.28%) and T1xS1 (61.71±4.84%). Hen housed egg production followed almost the same pattern with hen day egg production. Skip-two-days a week and 1.5-ft2/ bird treatment (T2xS3) produced eggs of 54.52 ±1.24 g weights, which were acceptable in market. It appears that skip-two-days fed birds reared on the density of 1.5 ft2/bird to be the most promising interaction group with respect to lower feed consumption during the laying period without any significant adverse effect on hen housed egg production. It appears that skip-two-days fed birds reared at the density of 1.5 ft2/bird to be the most promising interaction group with respect to lower feed consumption during the laying period.
  R. Singh , S.A. Dar and P. Sharma
  Herbs are largely unexplored source of drug repository. Medicinal plants have great potential for providing novel drug leads with novel mechanism of action. The present study describes the antibacterial activity, phytochemical profile and toxicological evaluation of Urtica dioica. U. dioica leaves were subjected to solvent extraction by hexane, ethyl acetate, chloroform, methanol and water. All the extracts were tested for antibacterial activity against five clinical isolates of Gram positive and Gram negative bacteria by disc diffusion method. Hexane extract showed good antibacterial activity against all the five bacterial strains, hence it was further purified using silica column chromatography and Minimum Inhibitory Concentration (MIC) of the semi purified fraction-B (FB) of hexane extract was determined by serial tube dilution method. FB showed MIC value of 31.25, 250, 7.81, 31.25 and 125 μg mL-1 against Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Klebsiella pneumoniae and Shigella flexneri, respectively. FB was subjected to GC-MS analysis in search of potent antibacterial compound(s). Neophytadiene (26.97%) butyl tetradecyl ester (9.53%), Dibutyl phthalate (7.45%), Bis (2-ethyl hexyl) maleate (8.80%) and 1,2-benzenedicarboxylic acid (9.89%) were the major constituents which may be responsible for the antibacterial activity of FB of U. dioica. Sub-acute oral toxicity of FB was carried out in wistar rats at doses of 100, 200, 400 and 800 mg kg-1 Body Weight (b.wt.) to assess index of safety. FB showed MIC value as low as 7.81 μg mL-1 against Salmonella typhi, exhibiting that a promising antibacterial agent is present in this fraction. Hematological and biochemical parameters showed that the FB was safe at tested concentrations. Hence further purification of FB is required to obtained potential antibacterial compound.
  Dileep K. Panda , R. Singh , D. K. Kundu , H. Chakraborty and A. Kumar
  Assessment of soil organic C (SOC) stocks is important for monitoring the effect of land use change in the C cycle and for formulation of C sequestration strategies in the context of global climate change. Discrepancies among the recent global SOC estimates by different researchers underscore the importance of precise estimation of the uncertainty associated with the SOC stocks. A method was recently proposed to estimate the SOC storage uncertainty using the Taylor series of approximations. Here we show that the accuracy of SOC storage uncertainty can be improved by incorporating the covariance among the input variables. Measurement of input variables from independent samples or use of an incomplete model leads to either over- or underestimation of the SOC storage uncertainty. The application of the method to an experimental data set indicated that ignoring covariance would lead to a substantial overestimate of the uncertainty.
  S. K. Chaudhari , R. Singh and D. K. Kundu
  In most soil testing laboratories, textural analysis is performed by the pipette method (PM) or by hydrometer. Objectives of this study were (i) to evaluate simplified methods that can be used for soils of various textures, and (ii) to modify a rapid method for reliable and accurate textural analysis of saline and alkaline soils. One hundred soils were collected from different agro-ecological regions of India. Coefficients of variation for sand, silt, and clay of soil samples by the rapid method varied across a range of 0 to 5% with a mean value <3% for all soils. Absolute differences between the PM and the rapid method for sand, silt, and clay fractions ranged from –1.8 to 1.7, –1.8 to 5.3, and –2.9 to 1.8%, with averages across the sites of –0.04, 2.92, and –6.52%, respectively. Among various methods, regression analysis between the rapid and pipette methods produced the highest coefficient of determination (r2) values of 0.9989, 0.9927, and 0.9930 for sand, silt, and clay fractions, respectively. A rapid method with modified sodium hexametaphosphate concentrations and soil shaking periods produced mean, standard error, and standard deviation values very close to the PM, with r2 values >0.99 with small intercepts <0.5, <0.3, and <0.7 for saline, saline–alkaline, and alkaline soils, respectively. The rapid method with proposed modifications provides the most accurate and fast estimation of texture for saline–alkaline soils.
 
 
 
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