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991.
Naveen?KumarEmail author V. K.?Tripathi B. K.?Sawhney 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(1):63-68
A fast rising flattop high power laser pulse, with Gaussian intensity
distribution along its wavefront, causes single and double ionizations of
the gas through which it propagates. The foot of the pulse causes single
ionization of the gas and creates a sharp radial density profile resulting
in strong defocusing of the front part of the pulse. After a little while,
single state ionization saturates, creating a flat density profile in the
axial region and weakening the divergence of the pulse. As the intensity of
the pulse rises further, second state ionization occurs, causing strong
defocusing of the beam. Later in time when the second state ionization
saturates, the relativistic mass nonlinearity together with the electron
cavitation tends to focus the pulse. 相似文献
992.
Yum HN Hemmer PR Heifetz A Shen JT Lee JK Tripathi R Shahriar MS 《Optics letters》2005,30(22):3012-3014
We demonstrate an efficient coherent holographic beam combiner (CHBC) that uses angle multiplexing of gratings in a thick polymeric substrate. Our experimental results compare well with the theoretical model based on the coupled-wave theory of multiwave mixing in a passive medium. A CHBC of this type may prove useful in producing a high-power laser by combining amplified beams produced by splitting a master oscillator. Furthermore, the ability to angle multiplex a large number of beams enables a CHBC to be used in multiple-beam interferometry applications as a high-precision surface sensor. 相似文献
993.
Poonam?VashisthaEmail author Karuna?Ghawana K.?N.?Tripathi 《Optical and Quantum Electronics》2005,37(5):469-474
We report here a comparative study of K-resin films in different solvents. A comparison of the waveguide parameters (refractive index, propagation losses, birefringence) in different solvents was done. The losses were found to be lower than 2 dB/cm for all solvents. Least losses observed were 0.62 dB/cm in the films dissolved in toluene. The birefringence was found to be in the range of 1 to 3 × 10−4. K-resin can be used successfully in fabrication of photonic devices. 相似文献
994.
ZnS:Gd, ZnS: Cu, Gd and ZnS: Mn, Gd phosphors have been prepared by firing the samples in argon atmosphere. Spectral distributions
in these phosphors are discussed with appropriate mechanism. ZnS:Cu, Gd and ZnS:Mn, Gd are found to be examples of multiple
band phosphors. Enhancement and quenching of the emission band intensities of all these phosphors have been studied inpel emission. It is observed that Gd3+ ions play an important role in transferring their excitation energy to other centres. The voltage and frequency variation
ofel brightness are in agreement with collision excitation mechanism in Schottky barrier at the metal semiconductor interface.
Studies in phosphorescence and thermoluminescence of these phosphors have also been carried out. It is observed that trap-depth
changes slowly with temperature and dopant concentration. The values of trapping parameters have been evaluated. The irregular
variation of the life-time of electrons in the traps. with temperature shows the existence of retrapping in these phosphors. 相似文献
995.
996.
Madhava B. Mallia Anupam Mathur Rohit Sharma Chandan Kumar H. D. Sarma Sharmila Banerjee Ashutosh Dash 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(3):1203-1210
Conventional 99mTc-radiopharmaceuticals for the detection of tumor hypoxia generally possess a single nitroimidazole moiety. Herein, we report the synthesis and evaluation of a 99mTc-complex with three-nitroimidazole moieties in an attempt to improve hypoxic cell detection. Isocyanide derivative of metronidazole (MetroNC) was synthesized and subsequently radiolabeled with [99mTc(CO)3(H2O)3]+ precursor complex, wherein the three labile water molecules were replaced with MetroNC ligand to form a pseudo-octahedral [99mTc(CO)3(MetroNC)3]+ complex. Analysis of corresponding Re(CO)3-analog prepared in macroscopic scale confirmed the formation of expected complex. Cyclic voltammetric studies of [Re(CO)3(MetroNC)3]+ complex showed no significant change in single-electron reduction potential (SERP) of MetroNC ligand (??0.96 V) upon forming the [Re(CO)3(MetroNC)3]+ complex (??0.90 V). In vitro studies in Chinese hamster ovary (CHO) cells showed three-fold preferential accumulation of [99mTc(CO)3(MetroNC)3]+ complex in hypoxic cells over normoxic cells. Biodistribution studies of [99mTc(CO)3(MetroNC)3]+ complex in Swiss mice bearing fibrosarcoma tumor showed tumor uptake and steady retention till 60 min post injection. Present study constitutes a novel design approach towards development of a 99mTc-radiopharmaceutical for hypoxia imaging application, which could be extended to other potential nitroimidazole ligands. 相似文献
997.
Rizwan Shariff Lawrence H. Pacquette Ashutosh K. Mittal Rajesh Girdhar 《Analytical letters》2018,51(11):1774-1788
Inductively coupled plasma–mass spectrometric determination of iron and phosphorus in three vegetable oils (soybean, coconut, and sunflower) was validated for the intermediate precision, trueness, linearity, and quantitation limit. The overall precision (n?=?5) for the analytes, which were above the method’s practical limit of quantification, were less than 2% relative standard deviation and the same as the laboratory control, NIST-SRM-1849a. Trueness was demonstrated with spike recoveries of the analytes in all vegetable oils at limit of quantification-level spiking. Although good linearity (regression coefficient greater than 0.9990) obtained, the recovery of phosphorus (156–189%) was high, possibly due to oil matrix enhancement, compared to the recovery of iron (91–106%). For soybean oil, sunflower oil, coconut oil, and medium chain triglycerides, the concentrations (mg/kg) of iron were in the range of 0.10–1.47, 0.09–1.51, 0.20–0.35, and 0.09–0.13, respectively. Similarly, phosphorus concentrations (mg/kg) were in the range of 0.77–124.56, 0.49–125.57, 0.52–9.72, and 0.85–11.90, respectively. The study achieved considerably low instrument-based practical limits of quantification for iron (0.005?mg/kg) and phosphorus (0.05?mg/kg), which are fivefold lower than the AOAC Official Method 2015.06. The high instrument sensitivity and selectivity of the method allow the determination of trace levels of iron and phosphorus in vegetable oils with good precision and trueness. 相似文献
998.
D. N. Tripathi D. K. Rai 《Journal of Quantitative Spectroscopy & Radiative Transfer》1970,10(12):1329-1334
Electron-impact ionization cross-sections of alkali-metal atoms and noble-gas atoms have been calculated using Gryzinski's, Vriens' and Burgess' formulae. The kinetic energy of the bound electron has been estimated by using Slater's rule. Comparisons have been made with experimental results. 相似文献
999.
First measurements of the composition dependence of the time-dependent nucleation rate are presented. Nucleation rates of the stoichiometric crystalline phase, Na2O · 2CaO · 3SiO2, from quenched glasses made with different SiO2 concentrations were determined as a function of temperature and glass composition. A strong compositional dependence of the nucleation rates and a weak dependence for the induction times were observed. Using measured values of the liquidus temperatures and growth velocities as a function of glass composition, these data are shown to be consistent with predictions from the classical theory of nucleation, assuming a composition-dependent interfacial energy. 相似文献
1000.
Ramachandra S. Hosmane Benjamin B. Lim Upali Siriwardane Narayan S. Hosmane 《Journal of chemical crystallography》1991,21(3):353-356
The title compound (IV) was isolated as a by-product during the course of purification of 4-nitroimidazol-5-(N-methyl)hydrazide (II) by silica gel flash chromatography, employing chloroform-acetone (4:1) as the eluting solvent. The crystals are monoclinic, space groupP21/c,a=7.425(1),b=13.615(2),c=10.359(2) Å,=97.66(1)°,d
caled=1.44 g cm–3, (MoK)=1.06 mm–1,T=298 K. The number of unique reflections=2401, reflections withI3 (I)=1773;R=0.051,R
w
=0.061. The bond distances inIV are: N-N, 1.419(3); N-C(=0), 1.359(3); N(H)-C(CH3), 1.457(3); N(C)-C(CH3), 1.501(3); N=C, 1.316(3); C=C, 1.368(3), N-C(=N), 1.353(3); N-C(=C), 1.367(2) Å. 相似文献