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71.
Thirty-four novel hybrid lupeol derivatives (4-18) were prepared and evaluated for antimalarial activity in vitro against Plasmodium falciparum. Three compounds (13d, 16a and 17a) have shown antimalarial activity at lower dose (10 microg mL(-1)) than lupeol. 相似文献
72.
R. Srinivasan Puri Denise Morrey Andrew J. Bell John F. Durodola Evgenii B. Rudnyi Jan G Korvink 《Applied Mathematical Modelling》2009
A reduced order model is developed for low frequency, undamped, fully coupled structural–acoustic analysis of interior cavities backed by flexible structural systems. The reduced order model is obtained by applying a projection of the coupled system matrices, from a higher dimensional to a lower dimensional subspace, whilst preserving essential properties of the coupled system. The basis vectors for projection are computed efficiently using the Arnoldi algorithm, which generates an orthogonal basis for the Krylov Subspace containing moments of the original system. The key idea of constructing a reduced order model via Krylov Subspaces is to remove the uncontrollable, unobservable and weakly controllable, observable parts without affecting the transfer function of the coupled system. Three computational test cases are analyzed, and the computational gains and the accuracy compared with the direct inversion method in ANSYS. 相似文献
73.
Puri SC Handa G Bhat BA Dhar KL Spiteller M Qazi GN 《Journal of chromatographic science》2006,44(5):239-243
High-performance liquid chromatography (HPLC) with diode array detection interfaced to electrospray ionization (ESI) mass spectrometry (MS) is applied to identify the two epimers of a novel and minor constituent, podophyllotoxin-4-O-(D)-6-acetylglucopyraniside from high-altitude Podophyllum hexandrum for the first time. This is done by matching the structural information from the tandem MS data with the reported lignan markers. The results show that LC-MS-MS is the method of choice for fast detection and detailed chemical analysis of mixtures in the crude extracts of Podophyllum. The method can be employed in the absence of reference standards for the markers and is particularly useful in view of the scarcity of these rare chemical standards. 相似文献
74.
Cascade Mi (i = 1–5) subshell X‐ray emission at incident photon energies across the Lj (j = 1–3) subshell absorption edges of 66Dy 下载免费PDF全文
Rajnish Kaur Anil Kumar Mateusz Czyzycki Alessandro Migliori Andreas G. Karydas Sanjiv Puri 《X射线光谱测定》2018,47(4):294-304
The total M shell and the Mk (k = ξ, αβ, γ, m) X‐ray production cross sections for 66Dy have been measured at incident photon energies across its Lj (j = 1–3) subshell absorption edge energies, ranging 7.8–9.2 keV. This study aims to investigate the evolution of the probability for cascade decay of Lj subshell vacancies as the tunable incident energy ionizes progressively different 66Dy Lj subshells. The experimental X‐ray production cross sections have been compared with theoretical ones calculated using the nonrelativistic Hartree–Fock–Slater (HFS) model‐based photoionization cross sections; three sets of the X‐ray emission rates, fluorescence and Coster–Kronig yield based on the nonrelativistic Hartree–Slater (NRHS) model, Dirac–Hartree–Slater (DHS) model and Dirac–Fock (DF) model; the Lj (j = 1–3) subshell to the Mi (i = 1–5) subshell vacancy transfer probabilities evaluated in the present work. Presently measured total M shell and the Mαβ X‐ray production cross sections are found to be significantly lower than the theoretical ones evaluated using physical parameters based on the relativistic Dirac–Fock/Dirac–Hartree–Slater model calculations, whereas a much better agreement is observed with respect to the NRHS model‐based calculations; however, the measured X‐ray production cross sections are still systematically lower than the NRHS values. 相似文献
75.
A new method involving pre-concentration on modified silica fiber is described for the speciation of chromium(III) [Cr(III)] and chromium(VI) [Cr(VI)] in aqueous media. This method is based on the different chelating behavior of Cr(III) and Cr(VI) with morpholine-4-carbodithioate (MDTC). Both complexes are extracted on silica fiber modified by sol-gel technology by using 3-aminopropyltriethoxysilane (APS) as a precursor. All extracted samples are directly injected into an high-performance liquid chromatography injector for the simultaneous determination of Cr(III) and Cr(VI). Cr(VI) forms two different complexes, and Cr(III) forms a single complex with MDTC. Therefore, the concentration of Cr(VI) is determined directly from the peak area obtained at 5.4 min; whereas, the assay of Cr(III) is based on subtracting the peak area of Cr(VI) from the total peak area obtained at 4.3 min. Under the optimized conditions, the limits of detection for Cr(III) and Cr(VI) are found to be 0.7 ng/mL and 0.2 ng/mL, respectively. 相似文献
76.
A. P. Singh W. R. Kalsi A. K. Tewari S. K. Puri B. Basu A. S. Sarpal 《Chromatographia》2001,54(7-8):537-540
Summary A procedure has been standarized for the determination of p-dioxan (1,4-dioxan) in benzene feedstock in the range of 1 to
100 ppm by capillary GC. The GC conditions such as oven temperature, length of the column etc were optimized to achieve better
resolution of p-dioxan from hydrocarbons. The standard addition method of quantitation, was used to determine the amount of
p-dioxan and was found to give better results than those obtained by external standardization. Prior to analysis the identity
of the p-dioxan peak was established by GC-MS. The proposed method has been applied for the monitoring of p-dioxan in high
purity benzene feedstock produced by the Udex extraction process in the refinery. The data were used for optimization of plant
conditions for the production of high purity benzene feedstock. By using this method, the p-dioxan content down to 0.5 ppm
can be determined in the benzene feedstock. 相似文献
77.
Let
be an estimator obtained by integrating a kernel type density estimator based on a random sample of size n from a (smooth) distribution function F. Sufficient conditions are given for the central limit theorem to hold for the target statistic
where {Un} is a sequence of U-statistics. 相似文献
78.
J. W. Eslick Jr H. N. Pham C. Radu A. Puri 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(3):553-562
In this paper, we revisit the problem of quantum entanglement in an
oscillating macroscopic mirror previously studied by Marshall et al. consisting
of a modified Michelson interferometer where one of the mirrors is free to
oscillate about its center of mass. A photon incident upon the oscillating
mirror becomes entangled with the mirror, driving the mirror into a
superposition of quantum states. Once the photon and mirror decouple, the
mirror returns to its initial state. The purpose of our investigations was
to optimize the parameter regime, taking into consideration the current
state of technology and the demands imposed by the need to maintain a stable
environment in the presence of thermal noise. Optimization should not demand
ultra-low temperatures and this is reflected in our results. Our results also
show that if the separation between states is maintained at 10-14 m, the mirror size is reduced, making it easier to induce superposition in
the mirror. The critical nature of mirror reflectivity and its connection to
cavity decay rate was also revealed by our investigations. The results
obtained through our investigations could be useful in quantum error
correction, where decoherence negatively affects the results of computations
performed by quantum computers. Finally, we note that we are only concerned
with an isolated system, where no losses to the external environment occur
and any decoherence that occurs within the system remains internal to the
system; that is, any mention of decoherence refers specifically to
recoverable decoherence. 相似文献
79.
A simple dielectric theory of electron energy losses in a thin metal overlayer is extended to include multiple losses. This theory is then compared with recent experimental data by Backes and Ibach. These comparisons reveal several inadequacies in the basic model, especially with regard to the shape and parameter dependence of the quasi-elastic peak. 相似文献
80.
Manoj K. Sharma Rajeev K. Puri Raj K. Gupta 《Zeitschrift für Physik A Hadrons and Nuclei》1997,359(2):141-144
We present an analytical formula for calculating the fusion barriers and fusion cross-sections. This is based on Skyrme energy density formalism and the Proximity force theorem. Comparisons with experimental data are also presented. 相似文献