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P K Sarkar

Publications and source records attributed to P K Sarkar.

At least 19 recordsLinked to original sources
PubMed2006

Thick target neutron dose evaluation for 19F+Al system.

Measured angular distribution of neutron dose from 110 MeV (19)F projectiles bombarding a thick aluminium target is reported. The measurements are carried out with a commercially available rem meter at 0 degrees, 30 degrees, 60 degrees and 90 degrees. The experimental results are compared with calculated dose from different empirical formulations proposed by earlier workers as well as with calculated dose from theoretically estimated energy distributions from the nuclear reaction model code EMPIRE-2.18.

Algorithms↗
PubMed2006

Determination of dose-build-up thickness for absorbed dose measurement in high energy electron-photon radiation at electron storage rings.

Radiation field during accidental electron beam loss near electron storage rings comprises of high-energy electrons and bremsstrahlung photons. Due to high-energy nature of the radiation, the absorbed dose is expected to build up with depth of the body of an exposed worker and hence absorbed dose measurements in 30 cm water/tissue equivalent phantom is essential. Carrying out the measurements with in such phantoms is not practically feasible for routine applications and hence the use of an equivalent solid material around the dosemeters would be convenient. Monte Carlo calculations have been carried out in order to determine the dose-build-up thickness required in copper and lead, corresponding to the maximum absorbed within 30 cm depth of water in such radiation fields. Equivalent build-up thickness calculated for a case was verified by measurement using an ion chamber detector. The results are found to be in agreement within +/-20%.

Aluminum↗
PubMed2005

Single dose parecoxib significantly improves ventilatory function in early extubation coronary artery bypass surgery: a prospective randomized double blind placebo controlled trial.

BACKGROUND: Parecoxib, a cyclo oxygenase-2 inhibiting non-steroidal anti-inflammatory drug, has been widely used for postoperative analgesia. Our aim was to quantify the benefit of a single dose after coronary artery bypass grafting. METHODS: The investigation was carried out as a randomized double blind placebo controlled study. A single i.v. dose of parecoxib 40 mg or placebo was given at closure of sternotomy. No opioid other than morphine was given in the first 24 postoperative hours. Pain was assessed using both a Visual Analogue Score (1-10), and the amount of morphine used via a morphine patient controlled analgesia pump. Creatinine clearance was measured before and after operation from 24 h urine collections. After a global announcement by Pfizer that paracoxib was 'contraindicated in patients with ischaemic heart disease' further recruitment was suspended and the collected data from 40 patients were analysed. RESULTS: Twenty-one patients received parecoxib and 19 received placebo. Amongst those who received parecoxib, there was a highly significant sparing of rescue medication before tracheal extubation (P=0.004) compared with placebo, and an overall 35% morphine sparing effect during the first 6 h post extubation after correction for the variability in extubation time (P=0.037). Respiration, as measured by arterial carbon dioxide tension at the time of extubation, was significantly better in the parecoxib group (P=0.045). Significantly more furosemide was given for postoperative oliguria in those patients who received parecoxib (P=0.036). After correcting for differences in diuretic usage and fluid balance, parecoxib was associated with a significant increase in plasma creatinine (P=0.041). CONCLUSION: A single dose of parecoxib has a significant opioid sparing effect in the first 6 h after coronary artery bypass grafting which resulted in significantly improved ventilation with mild elevation of plasma creatinine within normal limits.

Adult↗
PubMed2005

In vitro thyroid hormone rapidly modulates protein phosphorylation in cerebrocortical synaptosomes from adult rat brain.

Thyroid hormones induced rapid changes in phosphorylation in a membrane-containing lysate of synaptosomes purified from adult rat cerebral cortex. The in vitro addition of 3,5,3'-L-triiodothyronine or L-thyroxine strongly influenced incorporation of label from [gamma-32P]-ATP into proteins in a cerebrocortical synaptosomal lysate. Incubation with 3,5,3'-L-triiodothyronine or L-thyroxine had strong biphasic dose-dependent effects on the phosphorylation of 38+/-1, 53+/-1, 62+/-1, and 113+/-1 kDa proteins (which we termed alpha, beta, gamma, and delta, respectively) and several others. Although we observed differing levels of phosphorylation among the four proteins, doses of 3,5,3'-L-triiodothyronine or L-thyroxine ranging from 1 to 30 nM caused significant dose-dependent stimulation of the phosphorylation of all of them, an effect which occurred within three minutes. In each case, the enhancement of phosphorylation diminished with higher concentrations (100 nM-1 microM) of 3,5,3'-L-triiodothyronine. In contrast, incubations with similar doses of 3,3',5'-L-triiodothyronine (reverse L-triiodothyronine) were without significant effect, indicating a specificity for 3,5,3'-L-triiodothyronine and L-thyroxine. Western blots of synaptosomal lysates incubated with 3,5,3'-L-triiodothyronine (1 nM-1 microM) demonstrated phosphorylation at the serine residues of a 112 kDa protein (matching delta) and phosphorylation at tyrosyl residues of a distinct 95 kDa protein. These data support the contention that thyroid hormones have a variety of rapid nongenomic pathways for regulation of protein phosphorylation in mature mammalian brain.

Animals↗
PubMed2005

Dose build up correction for radiation monitors in high-energy bremsstrahlung photon radiation fields.

Conventional radiation monitors have been found to underestimate the personal dose equivalent in the high-energy bremsstrahlung photon radiation fields encountered near electron storage rings. Depth-dose measurements in a water phantom were carried out with a radiation survey meter in the bremsstrahlung photon radiation fields from a 450 MeV electron storage ring to find out the magnitude of the underestimation. Dose equivalent indicated by the survey meter was found to build up with increase in thickness of water placed in front of the meter up to certain depth and then reduce with further increase in thickness. A dose equivalent build up factor was estimated from the measurements. An absorbed dose build up factor in a water phantom was also estimated from calculations performed using the Monte Carlo codes, EGS-4 and EGSnrc. The calculations are found to be in very good agreement with the measurements. The studies indicate inadequacy of commercially available radiation monitors for radiation monitoring within shielded enclosures and in streaming high-energy photon radiation fields from electron storage rings, and the need for proper correction for use in such radiation fields.

Algorithms↗
PubMed2005

Monte Carlo simulations to estimate the background spectrum in a shielded NaI(Tl) gamma-spectrometric system.

The paper describes a Monte Carlo simulation technique to estimate the background gamma-radiation for a low-level counting setup with NaI(Tl) detector inside an iron shield box. With monoenergetic gamma-sources ranging from 300 to 2000 keV at intervals of 100 keV we have got a matrix of transmitted flux data calculated using a general purpose Monte Carlo code. The intrinsic efficiency of the detector is also calculated. This matrix of data is folded with the measured spectrum outside the setup to estimate the observed spectrum in the NaI(Tl) detector. We have studied various combinations of splitting and Russian roulette to arrive at an optimal combination based on the figure of merit of the Monte Carlo results. The observed discrepancy between the measured and calculated spectra is mainly due to porosity of the iron shield box.

Journal Article↗
PubMed2005

Arrangement of high-energy neutron irradiation field and shielding experiment using 4 m concrete at KENS.

An irradiation field of high-energy neutrons produced in the forward direction from a thick tungsten target bombarded by 500 MeV protons was arranged at the KENS spallation neutron source facility. In this facility, shielding experiment was performed with an ordinary concrete shield of 4 m thickness assembled in the irradiation room, 2.5 m downstream from the target centre. Activation detectors of bismuth, aluminium, indium and gold were inserted into eight slots inside the shield and attenuations of neutron reaction rates were obtained by measurements of gamma-rays from the activation detectors. A MARS14 Monte Carlo simulation was also performed down to thermal energy, and comparisons between the calculations and measurements show agreements within a factor of 3. This neutron field is useful for studies of shielding, activation and radiation damage of materials for high-energy neutrons, and experimental data are useful to check the accuracies of the transmission and activation calculation codes.

Computer Simulation↗
PubMed2005

Balanced nitrogen economy as a flexible strategy on yield stabilizing and quality of aquatic food crops in wetland ecosystem.

In wetland ecosystem, nitrogen along with other elements and its management is most imperative for the production of so many aquatic food, non-food and beneficial medicinal plants and for the improvement of soil and water characteristics. With great significant importance of INM (integrated nutrient management) as sources, emphasizing on management on nitrogen as a key element and its divergence, a case study was undertaken on such aquatic food crops (starch and protein-rich, most popular and remunerative) in the farmers' field of low-lying 'Tal' situation of New Alluvial Zone of Indian subtropics. The study was designed in factorial randomized block design, where, three important aquatic food crops (water chestnut (Trapa bispinosa Roxb.), makhana (Euryale ferox Salisb.) and water lily (Nymphaea spp.) as major factor and eleven combinations of organic and inorganic sources of nutrients as sub-factor was considered in the experiment. It revealed from the results that the production of fresh kernels or nuts of water chestnut (8.57 t ha(-1)), matured nut yield of makhana (3.06 t ha(-1)) and flower stalks of water-lily as vegetables (6.38 t ha(-1)) including its nutritional quality (starch, protein, sugar and minerals) was remarkably influenced with the application of both organic (neem oilcake @ 0.2 t ha(-1)) and inorganic sources (NPK @ 30:20:20 kg ha(-1) along with spraying of NPK @ 0.5% each over crop canopy at 20 days interval after transplanting) than the other INM combinations applied to the crops. Among the crops, highest WCYE (water chestnut yield equivalence) exhibited in makhana due to its high price of popped-form in the country, which is being exported to other countries at now. Sole application of both (organic and inorganic sources) with lower range did not produce any significant outcome from the study and exhibited lower value for all the crops. Besides production of food crops, INM also greatly influenced the soil and water characterization and it was favourably reflected in this study. The physico-chemical characteristics of soil (textural class, pH, organic carbon, organic matter, ammoniacal nitrogen, nitrate nitrogen, available nitrogen, phosphorus and potassium) are most important and contributed a significant improvement due to cultivation of these aquatic crops. Analysis of such wet bodies represented the water characteristics (pH, BOD, COD, CO3-, HCO3-, NO3-N, SO4-S and Cl-) were most responsive, adaptable and quite favourable for the cultivation of these crops in this vast waste unused wetlands for the mankind without any environmental degradation.

Biomass↗
PubMed2004

Radial artery as a conduit for coronary artery bypass graft.

Since its resurgence in the 1990s, some 30 years after its abandonment as an alternative conduit, the radial artery has rapidly gained popularity. This article describes the application of this conduit in coronary grafting and details the controversies surrounding its use. A historical account as well as technical aspects such as operative technique are also discussed.

Bioprosthesis↗
PubMed2002

Diversity and functionality of Bacillus and related genera isolated from spontaneously fermented soybeans (Indian Kinema) and locust beans (African Soumbala).

A total of 126 isolates of Bacillus and related genera from indigenous, spontaneously fermented soybeans (Kinema) and locust beans (Soumbala) were characterized with the purpose of defining interspecific, as well as intraspecific relationships among the components of their microflora. B. subtilis was the dominant species, and species diversity was more pronounced in Soumbala than in Kinema. While from Kinema, six species were isolated (B. subtilis, B. licheniformis, B. cereus, B. circulans, B. thuringiensis and B. sphaericus), in Soumbala, the species found were B. subtilis, B. thuringiensis, B. licheniformis, B. cereu, B. badius, Paenibacillus alvei, B. firmus, P. larvae, Brevibacillus laterosporus, B. megaterium, B. mycoides and B. sphaericus. Genomic diversity in the isolates of B. subtilis was investigated by random amplified polymorphic DNA (RAPD) analysis using the polymerase chain reaction (PCR). The RAPD-PCR fingerprint analysis showed a high level of diversity. With more than 90% similarity, all 52 RAPD subdivisions were source and continent-wise homogeneous. Profiles of carbon source fermentation also showed a wide but corresponding phenotypic diversity, largely corresponding with RAPD subdivisions. The various strains were tested for several criteria for functionality in soybean fermentation, viz. protein degradation, pH increase, and development of desirable stickiness caused by viscous exopolymers. Profiles of functionality, based upon estimations of pH, free amino nitrogen and stickiness were associated with genotypic and phenotypic profiles. Notwithstanding the heterogenous fermentation results for some genotypic profiles, a ranking of RAPD groups is possible and can be useful in the further selection and study of B. subtilis strains.

Bacillus↗
PubMed2002

Enhanced frequency of micronuclei in individuals exposed to arsenic through drinking water in West Bengal, India.

In West Bengal, India arsenic in ground water has been found to be above the maximum permissible limit in seven districts covering an area of 37,493km2. In the present study, evaluation of the micronuclei (MN) formation in oral mucosa cells, urothelial cells and peripheral blood lymphocytes was carried out in the symptomatic individuals exposed to arsenic through drinking water. Forty five individuals with cutaneous signs of arsenicism from four affected districts (368.11 microg/l of As in drinking water) were considered as the exposed group and 21 healthy individuals with no symptoms of arsenic poisoning and residing in two unaffected districts (5.49 microg/l of As) were considered as controls. The exposed and control groups had similar age distribution and socioeconomic status. Standardised questionnaires were utilised and medical examination was conducted to ascertain exposure history, sociodemographic characteristics, diet, health, medication, addiction and chief symptoms in the study participants. Arsenic exposure was confirmed by measuring the arsenic content in the drinking water, nails, hair and urine samples from the volunteers. Arsenic contents in the urine, nail and hair in the exposed group were 24.45 microg/l, 12.58 and 6.97 microg/g, respectively which were significantly high in comparison to corresponding control group values of 4.88 microg/l, 0.51 and 0.34 microg/g, respectively. Exposed individuals showed a statistically significant increase in the frequency of MN in oral mucosa, urothelial cells and lymphocytes (5.15, 5.74 and 6.39/1000 cells, respectively) when compared with the controls (0.77, 0.56 and 0.53/1000 cells, respectively). Thus, the above results indicate that the symptomatic individuals exposed to arsenic through drinking water in this region have significant cytogenetic damage.

Adolescent↗
PubMed2002

SSP2, a sporulation-specific gene necessary for outer spore wall assembly in the yeast Saccharomyces cerevisiae.

Sporulation in yeast consists of two highly coordinated processes. First, a diploid cell that is heterozygous at the mating-type locus undergoes meiosis, in which one round of DNA replication is followed by two rounds of nuclear division. Second, the meiotic products are packaged into spore cells that remain within the mother cell. A large number of genes are induced specifically during sporulation, and their products carry out different sporulation-specific events. Expression of these sporulation-specific genes is controlled by several regulators which function at different stages of the sporulation program, resulting in a cascade of gene expression following induction of meiosis. Here we describe one sporulation-specific gene, SSP2, which is induced midway through meiosis. Ssp2 shows significant homology to the predicted product of a hypothetical ORF in Candida albicans. Homozygous mutant ssp2 diploid cells fail to sporulate. In the mutant background, meiotic recombination and nuclear divisions remain normal; however, viability declines rapidly. Following meiosis, ssp2 cells form the prospore membrane, but fail to form the outer layer of the spore wall. The Ssp2 protein localizes to the spore wall after meiosis II. In addition, the ssp2 defect is also associated with delayed and reduced expression of late sporulation-specific genes. Our results suggest that SSP2 function is required after meiosis II and during spore wall formation.

Cell Wall↗
PubMed2002

Moisture sorption characteristics of dudh churpi, a traditional milk product in India.

The sorption isotherms of dudh churpi, a shelf-stable traditional milk product in India, determined at 15, 25, 35 and 45 degrees C, were typical type II sigmoidal according to the BDDT (Brunauer-Deming-Deming-Teller) classification. Nine equations, namely Bradley, Henderson, Iglesias and Chirife, Khun, Mizrahi, GAB (Guggenheim-Anderson-de Boer), modified Mizrahi, Oswin and Caurie were fitted to the sorption data. Caurie's equation was found to be suited best to predict equilibrium moisture content of dudh churpi. Monolayer value, density of sorbed water, number of monolayers and area of adsorbent decreased with the increase in temperature.

Adsorption↗
PubMed2001

Splenectomy and splenic slice grafting in the management of thalassemia.

Over the last decade and a half, we performed a splenectomy along with slice grafting of the spleen in 170 (beta28 and Ebeta 142) transfusion-dependent, high-risk thalassemic patients. Of these, 17 were selected for study of the fate of the grafts and their immune status before and after operation. The procedure had equally good advantages of splenectomy and immunoconservation as partial splenectomy, partial splenic embolization, or partial splenic dearterialization, if not better, but none of the disadvantages of the other procedures.

Child↗
PubMed2001

Hypothyroidism in the developing rat brain is associated with marked oxidative stress and aberrant intraneuronal accumulation of neurofilaments.

The effects of hypothyroidism on parameters of oxidative stress and on intraneuronal distribution of neurofilaments have been investigated in the developing rat brain. Progressive hypothyroidism during the first 4 weeks of postnatal development led to an increase in superoxide dismutase and catalase activity, decline in the level of glutathione and mitochondrial cytochrome c oxidase activity and increase in the level of .OH radical along with enhanced protein carbonylation and lipid peroxidation. Immunocytochemical staining of cryostat sections of normal and hypothyroid cerebella from 25 day postnatal rats with anti neurofilament (NF) light chain (L) antibody showed aberrant accumulation of neurofilaments in the perikaryon of the hypothyroid Purkinje neurons in contrast to relatively uniform distribution in the controls. The morphological and biochemical alterations in the neurons of the developing hypothyroid brain are comparable to those seen in several neurodegenerative diseases.

Animals↗