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排序方式: 共有102条查询结果,搜索用时 31 毫秒
51.
H. C. Manjunatha 《X射线光谱测定》2013,42(6):508-523
The beta‐induced bremsstrahlung spectra produced by 113 pure beta nuclides in teeth enamel and dentin are computed. The computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth‐dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The computed bremsstrahlung spectrum is used in the evaluation of bremsstrahlung dose in teeth enamel and dentin. The evaluated Beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The beta bremsstrahlung dose decreases with the increase of distance. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
52.
H.C. Manjunatha 《Isotopes in environmental and health studies》2014,50(4):555-564
In the natural uranium-238 decay series, pure beta isotopes such as 234Th, 234Pa, 214Pb, 214Bi, 210Pb and 210Bi are released. The few lead isotopes such as 211Pb, 212Pb, 213Pb and 215Pb are good beta emitters. In certain nuclear reactions of reactor these isotopes are released. These beta isotopes have maximum beta energies, which induce the bremsstrahlung radiation. The bremsstrahlung component of these beta isotopes has been traditionally ignored in dosimetry calculations. The shapes of bremsstrahlung spectra are a basic ingredient in the understanding and quantification of beta-ray dosimetry. The bremsstrahlung spectra produced by these high-energy isotopes such as 234Th, 234Pa, 214Pb, 214Bi, 210Pb, 210Bi, 211Pb, 212Pb, 213Pb and 215Pb in bone, muscle and teeth are studied, and the computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth–dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The evaluated beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The efficiency, intensity and dose rate of bremsstrahlung induced by beta isotopes of natural uranium-238 decay series and beta-emitting lead isotopes in human tissues such as brain, breast, heart, kidney, liver, muscle, pancreas and bone have also been studied in the present investigation. The values of bremsstrahlung dosimetric parameters are low for pancreas, but they are high for bone. For all studied tissues these parameters are high for 234Pa, but low for 210Pb. 相似文献
53.
Hanumanthrayappa Manjunatha Doddahalli Hanumantharayudu Nagaraju Gurukar Shivappa Suresh Thimmappa Venkatarangaiah Venkatesha 《Electroanalysis》2009,21(20):2198-2206
The properties of graphite electrode (Gr) modified with poly(diallyl dimethyl ammonium chloride) (PDDA) for the detection of uric acid (UA) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA) have been investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The polymer modified graphite electrode was prepared by a very simple method just by immersing the graphite electrode in PDDA solution for 20 minutes. The PDDA/Gr modified electrode displayed excellent electrocatalytic activity towards the oxidation of UA, DA and AA compared to that at the bare graphite electrode. The electrochemical oxidation signals of UA, DA and AA are well resolved into three distinct peaks with peak potential separations of 220 mV, 168 mV and 387 mV between AA‐DA, DA‐UA and AA‐UA respectively in cyclic voltammetry studies and the corresponding peak potential separations are 230 mV, 130 mV and 354 mV respectively in differential pulse voltammetry. The lowest detection limits obtained for UA, DA and AA were 1×10?7 M, 2×10?7 M and 800×10?9 M respectively. The PDDA/Gr electrode efficiently eliminated the interference of DA and a high concentration of AA in the determination of UA with good selectivity, sensitivity and reproducibility. The modified electrode was also successfully applied for simultaneous determination of UA, DA and AA in their ternary mixture. 相似文献
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The kinetics and mechanism of sodium N-chloro-p-toluenesulfonamide oxidative decolorization of ethyl orange (EO) in aqueous perchloric acid have been studied at 303 K in the presence of rhodium(III) chloride as catalyst. The reaction exhibits first-order dependence on [EO]o and a fractional-order dependence on [CAT]o, [H+] and [RhIII]. The dielectric effect is positive. The stoichiometry of the reaction was found to be 1:1, and the oxidation products of EO were identified as N-(4-diethylamino-phenyl)-hydroxylamine and 4-nitroso-benzenesulfonic acid. The rhodium(III)-catalyzed reaction is about fourfold faster than the uncatalyzed reaction. The proposed mechanism and derived rate law are in agreement with the observed kinetic results. 相似文献
57.
Manjunatha Pattabi 《Pramana》2002,58(5-6):1141-1145
Aging, which manifests itself as an irreversible increase in electrical resistance in island metal films is of considerable
interest from both academic as well as applications point of view. Aging is attributed to various causes, oxidation of islands
and mobility of islands followed by coalescence (mobility coalescence) being the main contenders. The effect of parameters
like substrate temperature, substrate cleaning, residual gases in the vacuum chamber, ultrasonic vibration of the substrate,
suggest that the mobility coalescence is responsible for the aging in island metal films. Electron microscopy studies show
evidence for mobility of islands at high substrate temperatures. The comparison of aging data of island silver films deposited
on glass substrates in ultra high vacuum and high vacuum suggests that the oxidation of islands, as being responsible for
aging in these films, can be ruled out. Further, under certain conditions of deposition, island silver films exhibit a dramatic
and drastic fall in electrical resistance, marking the insulator-metal transition. This interesting transition observed in
a conservative system — after the stoppage of deposition of the film — is a clear evidence for mobility coalescence of islands
even at room temperature. The sudden fall in resistance is preceded by fluctuations in resistance with time and the fluctuations
are attributed to the making and breaking of the percolation path in the film. 相似文献
58.
Arora P Venkataswamy MM Baena A Bricard G Li Q Veerapen N Ndonye R Park JJ Lee JH Seo KC Howell AR Chang YT Illarionov PA Besra GS Chung SK Porcelli SA 《Journal of the American Chemical Society》2011,133(14):5198-5201
Structural variants of α-galactosylceramide (αGC) that activate invariant natural killer T cells (iNKT cells) are being developed as potential immunomodulatory agents for a variety of applications. Identification of specific forms of these glycolipids that bias responses to favor production of proinflammatory vs anti-inflammatory cytokines is central to current efforts, but this goal has been hampered by the lack of in vitro screening assays that reliably predict the in vivo biological activity of these compounds. Here we describe a fluorescence-based assay to identify functionally distinct αGC analogues. Our assay is based on recent findings showing that presentation of glycolipid antigens by CD1d molecules localized to plasma membrane detergent-resistant microdomains (lipid rafts) is correlated with induction of interferon-γ secretion and Th1-biased cytokine responses. Using an assay that measures lipid raft residency of CD1d molecules loaded with αGC, we screened a library of ~200 synthetic αGC analogues and identified 19 agonists with potential Th1-biasing activity. Analysis of a subset of these novel candidate Th1 type agonists in vivo in mice confirmed their ability to induce systemic cytokine responses consistent with a Th1 type bias. These results demonstrate the predictive value of this novel in vitro assay for assessing the in vivo functionality of glycolipid agonists and provide the basis for a relatively simple high-throughput assay for identification and functional classification of iNKT cell activating glycolipids. 相似文献
59.
H. C. Manjunatha 《辐射效应与固体损伤》2013,168(5):385-398
The effective atomic numbers (Z eff) and electron density (N el) of some hormones such as testosterone, methandienone, estradiol and rogesterone for total and partial photon interactions have been computed in the wide energy region 1 keV–100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. The computed Z eff and N el are compared with the values generated by XMuDat program. The computer tomography (CT) numbers and kerma values relative to air are also calculated and the computed data of CT numbers in the low-energy region help in visualizing the image of the biological samples and to obtain precise accuracy in treating the inhomogenity of them in medical radiology. In view of dosimetric interest, the photon absorbed dose rates of some commonly used gamma sources (Na-21, Cs-137, Mn-52, Co-60 and Na-22) are also estimated. 相似文献
60.
Physics of Particles and Nuclei Letters - We have studied the competition between different decay modes such as binary, ternary, cluster radioactivity and alpha decay. The competition between... 相似文献