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21.
S. Kunze R. Hohmann H. -J. Kluge J. Lantzsch L. Monz J. Stenner K. Stratmann K. Wendt K. Zimmer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,27(2):111-114
Lifetimes of Rydberg states of the triplet-series 5s ns 3 S 1 withn = 19–23, 35 and 5s nd 3 D 3 withn = 18–20, 23–28 in the spectrum of neutral strontium have been determined. Observation of the exponential decay after excitation by a pulsed laser in a fast atomic beam and subsequent state-selective field ionization was employed. The lifetimes of the states of the3 S 1-series show the expectedn*3 dependence on the effective principal quantum number, while the3 D 3-series is disturbed by configuration mixing. Furthermore, state re-populations induced by black-body radiation have been observed. 相似文献
22.
Stability and convergence of the spectral Lagrange-Galerkin method for mixed periodic/non-periodic convection-dominated diffusion problems 总被引:1,自引:0,他引:1
We present a convergence analysis of the spectral Lagrange-Galerkinmethod for mixed periodic/non-periodic convection-diffusionproblems. The scheme is unconditionally stable, independentof the diffusion coefficient, even in the case when numericalquadrature is used. The theoretical predictions are illustratedby a series of numerical experiments. For the periodic case,our results present a significant improvement on those givenby Süli & Ware (1991) SIAM J. Numer.Anal.28, 423-445). 相似文献
23.
K. Zimmer J. Stenner H. -J. Kluge J. Lantzsch L. Monz E. W. Otten G. Passler R. Schwalbach M. Schwarz H. Stevens K. Wendt G. Herrmann S. Nieß N. Trautmann K. Walter B. A. Bushaw 《Applied physics. B, Lasers and optics》1994,59(2):117-121
A new, fast technique for trace analysis of the radioactive isotopes89Sr and90Sr in environmental samples has been developed. Conventional mass separation is combined with resonance ionization spectroscopy in collinear geometry, which provides high selectivity and sensitivity. In addition, a chemical separation procedure for sample preparation has been developed. The described technique was used to determine the90Sr content in 870 m3 air samples collected near Munich during and shortly after the Chernobyl reactor accident in April 1986. The content of90Sr was measured to be 1.4 mBq per m3, corresponding to 1.6 × 109 atoms of90Sr per sample. This value is in good agreement with the results of radiochemical measurements.This publication comprises part of the Dissertations of J. Stenner and K. Zimmer 相似文献
24.
Large sample tests of significance for the location parameter, the scale parameter, and quantiles for a location-scale family of distributions based on a few optimally chosen sample quantiles are considered. 相似文献
25.
Testosterone has been known to play an important role in the development of the postpubertal male voice for many centuries. In fact, the prevention of pubertal development of the voice by castrating young male singers was a well-known practice, especially in Italy beginning in the sixteenth century. The “castrati” were well known for their clear, high-pitched voices. Because of the resulting small larynx and vocal folds, castrati apparently produced a distinctive resonance as well as the high pitch, which cannot be matched even by the counter tenors of today. Busy voice labs occasionally see males with sex hormone deficiencies secondary to chromosomal or gonadal problems. This is a presentation of an unusual patient who was a trained tenor singer and was found to have hypogonadism on a premarital health examination. Administration of replacement testosterone resulted in significant vocal register and voice quality changes. 相似文献
26.
A. S. Lodhi MD. Rashiduzzaman Khan 《Journal of Radioanalytical and Nuclear Chemistry》1979,49(1):89-94
A number of samples of whole blood, and urine from diabetic and non-diabetic persons have been analyzed for their trace elemental
contents using the proton-induced X-ray emission. The elemental contents of the diabetic and non-diabetic samples are compared. 相似文献
27.
Randomizing the Unfolded State of Peptides (and Proteins) by Nearest Neighbor Interactions between Unlike Residues 下载免费PDF全文
Dr. Siobhan E. Toal Nina Kubatova Dr. Christian Richter Verena Linhard Prof. Dr. Harald Schwalbe Prof. Reinhard Schweitzer‐Stenner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5173-5192
To explore the influence of nearest neighbors on conformational biases in unfolded peptides, we combined vibrational and 2D NMR spectroscopy to obtain the conformational distributions of selected “GxyG” host–guest peptides in aqueous solution: GDyG, GSyG, GxLG, GxVG, where x/y=A, K, L, V. Large changes of conformational propensities were observed due to nearest‐neighbor interactions, at variance with the isolated pair hypothesis. We found that protonated aspartic acid and serine lose their above‐the‐average preference for turn‐like structures in favor of polyproline II (pPII) populations in the presence of neighbors with bulky side chains. Such residues also decrease the above‐the‐average pPII preference of alanine. These observations suggest that the underlying mechanism involves a disruption of the hydration shell. Thermodynamic analysis of 3J(HN,Hα) (T) data for each x,y residue reveals that modest changes in the conformational ensemble masks larger changes of enthalpy and entropy governing the pPII?β equilibrium indicating a significant residue dependent temperature dependence of the peptides’ conformational ensembles. These results suggest that nearest‐neighbor interactions between unlike residues act as conformational randomizers close to the enthalpy–entropy compensation temperature, eliminating intrinsic biases in favor of largely balanced pPII/β dominated ensembles at physiological temperatures. 相似文献
28.
Yata Praveen Kumar C. Shobha Devi N. Deepika Nazar MD Gabra Nishant Jain A. Srishailam Kotha Laxma Reddy S. Satyanarayana 《Transition Metal Chemistry》2013,38(8):811-819
A new ligand, (2-ethoxy-6-(1H imadazo[4,5-f][1,10]phenanthroline-2-yl)phenol) (HEPIP) and its three Co(III) complexes [Co(phen)2(HEPIP)](ClO4)3 (1), [Co(bpy)2(HEPIP)](ClO4)3 (2) and [Co(dmb)2(HEPIP)](ClO4)3 (3) have been synthesized and characterized. All three Co(III) complexes exhibited antitumor activity against four human tumor cell lines. The interaction of these complexes with calf thymus DNA was studied by absorption and emission spectroscopy, viscosity measurements and DNA cleavage assays. The DNA-binding constants of complexes 1, 2 and 3 were determined as 6.13 × 105, 4.46 × 105 and 3.72 × 105 M?1, respectively. The complexes appear to interact with DNA through intercalation. Studies on the mechanism of photocleavage indicated that both superoxide anion radical and singlet oxygen may play an important role. 相似文献
29.
MD. Akhtaruzzaman Masaaki Tomura Kazuko Takahashi Jun-Ichi Nishida 《Supramolecular chemistry》2013,25(4):239-243
Hydrogen-bonding networks of π-extended 4,4′-bipyridines, 2,5-di(4-pyridyl)thiophene (1), 2,5-di(4-pyridyl)furan (2) and 1,4-di(4-pyridyl)benzene (3) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CA) have been investigated. The dipyridyl compounds afforded complexes 4 [(dication of 1)·(monoanion of CA)2], 5 [(dication of 2)·(dianion of CA)·(MeOH)] and 6 [(3)·(dication of 3)·(dianion of CA)·(H2O)6] with CA. X-ray structure analyses revealed the formation of unusual molecular tape and sheet structures involving N–H ?O, O–H ?O, C–H ?O and N–H ?N hydrogen bonds, where the aromatic spacer groups play an important role in constructing the unique crystal structures. 相似文献
30.
Nilay K. Pramanik Ramsankar Haldar Utpal K. Niyogi MD. Sarwar Alam 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):296-307
The non-isothermal crystallization kinetics was studied by differential scanning calorimetric analysis on nylon 66 and e-beam irradiated nylon 66 at different cooling rates. The Modified Avrami equation, the Ozawa equation and the Combined Avrami-Ozawa equation were applied to study the kinetics of non-isothermal crystallization of nylon 66. The crystallization behavior of pristine nylon 66 polymer was compared with that of e-beam irradiated nylon 66 and observed that the kinetics of non-isothermal crystallization of nylon66 was affected largely upon e-beam irradiation. E-beam irradiation not only decreased the crystallization temperature of nylon 66, but influenced the mechanism of nucleation and crystal growth and reduced the overall crystallization rate of nylon 66 also. The crystallization activation energy calculated by the Kissinger method for irradiated nylon 66 was lower than that of pristine nylon 66. 相似文献