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71.
M. L. Shah R. C. Das P. K. Mandal D. R. Rathod Vas Dev K. G. Manohar B. M. Suri 《Pramana》2010,75(6):1141-1144
We report the measurement of photoexcitation cross-sections of three first-step uranium transitions (0 → 16900.38 cm −1, 0 → 17361.89 cm −1 and 620 → 17361.89 cm −1) using saturation method. These measurements were performed on a resonance ionization mass spectrometry (RIMS) set-up consisting
of Nd:YAG-pumped dye lasers, a reflectron time-of-flight mass spectrometer and high-temperature atomic vapour source. The
uranium vapours were excited and photoionized by two-colour, three-photon photoionization scheme using Nd:YAG-pumped dye laser
system. The resultant photoion signal was monitored as a function of dye laser fluence used for first step excitation to measure
the excitation cross-section values. A new approach was adopted to overcome the large uncertainties associated with such measurements.
With this approach the cross-section of transitions whose value is already reported in the literature was measured as a bench
mark. By normalizing the measured value to the reported value, a scaling factor was derived. This scaling factor was used
to scale up the cross-section values of other transitions measured by this method. 相似文献
72.
Vas Dev M. L. Shah A. K. Pulhani B. M. Suri 《Applied physics. B, Lasers and optics》2005,80(4-5):587-594
A U–Ne hollow cathode discharge tube is used as a source of uranium atomic vapors as well as a photoelectron/photoion detector
for carrying out two-color three-photon photoionization spectroscopy of uranium. Using the uranium excitation transition 0
cm−1 (5L
6
0
) → 16 900.38 cm−1 (7M7) at 591.5-nm laser wavelength as a first step transition and scanning the wavelength of a second laser from 558 to 568 nm,
high-lying odd-parity atomic levels of uranium are studied in the energy region 34 500–34 813 cm−1. All the expected 21 odd-parity atomic levels identified by various researchers in this region are observed in a single spectrum,
demonstrating the high sensitivity achieved therein. In addition to this, we have identified eight autoionization resonances
of uranium starting from its odd-parity atomic level at 33 801.06 cm−1 pumped by two-photon excitation. Four out of these eight autoionization resonances are observed for the first time. 相似文献
73.
John Hershberger Subhash Suri 《Journal of Algorithms in Cognition, Informatics and Logic》1996,21(3):453-475
We achieve anO(log n) amortized time bound per operation for the off-line version of the dynamic convex hull problem in the plane. In this problem, a sequence ofninsert,delete, andqueryinstructions are to be processed, where each insert instruction adds a new point to the set, each delete instruction removes an existing point, and each query requests a standard convex hull search. We process the entire sequence in totalO(n log n) time andO(n) space. Alternatively, we can preprocess a sequence ofninsertions and deletions inO(n log n) time and space, then answer queries in history inO(log n) time apiece (a query in history means a query comes with a time parametert, and it must be answered with respect to the convex hull present at timet). The same bounds also hold for the off-line maintenance of several related structures, such as the maximal vectors, the intersection of half-planes, and the kernel of a polygon. Achieving anO(log n) per-operation time bound for theon-lineversions of these problems is a longstanding open problem in computational geometry. 相似文献
74.
Epitaxial La1−x
Pb
x
MnO3 (LPMO) thin films, grown on (100) SrTiO3 substrates by laser ablation technique at different temperatures between 600 and 850°C, have been characterized for electrical
and magnetic properties. The temperature dependence of resistivity showed that the metal-insulator transition temperature
(T
MI) decreases with increasing substrate temperature, which has been attributed to decrease in Pb content in the filsm. The YBa2Cu3O
x
/La1−x
MnO3 heterostructures, exhibiting both superconductivity and ferromagnetism, have been fabricated. 相似文献
75.
Pathania Preeti Sharma Arunima Kumar Binod Rishi Praveen Raman Suri C. 《Mikrochimica acta》2017,184(5):1499-1508
Microchimica Acta - The authors report on an aptamer-based method for the detection of S. Typhimurium. The aptamers were identified by using a modified cell-based SELEX method (cell-SELEX) by... 相似文献
76.
Puri S Handa G Kalsotra AK Gupta VK Shawl AS Suri OP Qazi GN 《Journal of chromatographic science》2006,44(4):177-180
St. John's Wort (Hypericum perforatum), a perennial flowering plant, has been used medicinally for thousands of years and has most recently been identified as an effective treatment for mild to moderate depression and neuralgic disorders. This work presents a procedure for the isolation of naphthodianthrones from St. John's Wort by an accelerated extraction and separation of marker compounds by preparative high-performance liquid chromatography (HPLC) with photodiode array detection. The accelerated extraction method minimizes the extraction time and increases the yield, and the marker compounds obtained by preparative HPLC are of 98% purity. The compounds are characterized by liquid chromatography-mass spectrometry (electrospray ionization) and NMR spectra. 相似文献
77.
Antonyraj Arockiasamy Randall M. German Paul Wang Mark F. Horstemeyer Pavan Suri S. J. Park 《Journal of Thermal Analysis and Calorimetry》2010,100(1):361-366
Differential scanning calorimetry (DSC) is a powerful technique that measures the heat evolution from a sample under a controlled
condition and studies the phase transformation, precipitation, and dissolution activities. In this work, we investigated the
influence of admixed silicon and silicon carbide and the effect of different atmospheres on the heat flow properties and microstructure
of atomized Al6061 powder using DSC and scanning electron microscopy. The DSC analysis revealed the addition of silicon considerably
decreased the temperature of first endothermic peaks. With an increase in silicon content the enthalpy for the first endothermic
peak increased, whereas the second endothermic peak decreased. An endothermic peak, indicating the formation of AlN, was observed
for powders without the silicon addition, but was noticeably absent in the case of alloys with Si addition. The SiC addition
has no influence on changing the enthalpy of the systems we investigated. The reason for this behavior is analyzed and presented
in this article. 相似文献
78.
Molar excess volumes of mixing VE for binary mixtures of furfuryl alcohol with the aromatic hydrocarbons benzene, toluene, ethylbenzene, and o-, m-, and p-xylene were determined for the entire composition range at 25°C. VE was negative for the mixtures containing benzene, toluene and pxylene but positive for mixtures containing ethylbenzene and o- and m-xylene. The results are discussed in terms of specific interaction present in the binary mixture and are compared with those previously reported for tetrahydrofuran, fur an or furfural binary mixtures with aromatic hydrocarbons. 相似文献
79.
Calorimetric studies of the ferromagnetic Curie temperature Tc, and the crystallization kinetics of the metallic glass Fe78B9Si13 have been performed in an attempt to elucidate the possibility of reversible relaxation processes near Tc and the crystallization mechanisms taking place. From the change of Tc with heating rate and on annealing it appears that ageing irreversibly increases the Curie temperature. Crystallization is thermally activated following an Arrhenius behaviour and proceeds in two stages, the best fit to the experimental data for each stage of crystallization has been obtained by use of a Johnson-Mehl-Avrami-Erofe'ev equation. The effective activation energy and the kinetic exponent are respectively E = (4.7 ± 0.1) eV, n = 2.0 ± 0.2 for the first and E = (4.5 ± 0.1) eV, n = 4.0 ± 0.2 for the second stage of crystallization. From these results it appears that the mechanisms of crystallization are quite different in both stages. 相似文献
80.
Perturbative calculation of the cross section in double ionization by
high-energy Compton scattering
Z. Kaliman K. Pisk T. Surić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):369-372
In this paper we investigate double ionization in high-energy Compton scattering from the He-atom including both the shake-off
mechanism and a perturbative correction to that mechanism.
The correction is calculated in second-order perturbation theory and includes Coulomb electron-electron interaction in addition
to the correlation in the ground state of the He-atom. Our calculations for the ratio of double to single cross section cover
the range from 30 to 300 keV of impact photon energy and explain the slow convergence of the ratio towards the asymptotic
value. 相似文献