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排序方式: 共有162条查询结果,搜索用时 15 毫秒
41.
42.
Résumé La méthode L. C. A. O. améliorée est utilisée pour étudier la structure électronique des molécules de vinylacétylène, de divinylacétylène et de butatriène, réduites à leur système . Les énergies des premières transitions N V sont en excellent accord avec l'expérience. Une relation entre l'indice de liaison mobile et la distance interatomique, pour des liaisons reliant des atomes hybridés l'un en sp et l'autre en sp
2, est proposée.
The improved LCAO theory is used to study the electronic structure of vinylacetylene, divinylacetylene and butatriene molecules, reduced at their system. The first N V transition energies are in excellent agreement with experiment. A relation between mobile bond order and bond distance, for bonds between sp and sp 2 hybridized atoms, is proposed.
Zusammenfassung Die elektronische Struktur der auf ihr -System reduzierten Moleküle Vinylacetylen, Divinylacetylen und Butatrien wird mit Hilfe der verbesserten LCAO-Methode untersucht. Die berechneten Energien der ersten N V-übergÄnge stimmen mit dem Experiment ausgezeichnet überein. Eine Beziehung zwischen Bindungsabstand und -Bindungsindex für Bindungen zwischen sp- und sp 2-hybridisierten Atomen wird vorgeschlagen.相似文献
43.
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
44.
Pell AJ Kervern G Emsley L Deschamps M Massiot D Grandinetti PJ Pintacuda G 《The Journal of chemical physics》2011,134(2):024117
We explain how and under which conditions it is possible to obtain an efficient inversion of an entire sideband family of several hundred kHz using low-power, sideband-selective adiabatic pulses, and we illustrate with some experimental results how this framework opens new avenues in solid-state NMR for manipulating spin systems with wide spinning-sideband (SSB) manifolds. This is achieved through the definition of the criteria of phase and amplitude modulation for designing an adiabatic inversion pulse for rotating solids. In turn, this is based on a framework for representing the Hamiltonian of the spin system in an NMR experiment under magic angle spinning (MAS). Following earlier ideas from Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], the so-called "jolting frame" is used, which is the interaction frame of the anisotropic interaction giving rise to the SSB manifold. In the jolting frame, the shift modulation affecting the nuclear spin is removed, while the Hamiltonian corresponding to the RF field is frequency modulated and acquires a spinning-sideband pattern, specific for each crystallite orientation. 相似文献
45.
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
46.
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
47.
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
48.
Chaos and multiple periods are presented for the harmonically excited unsymmetrical spring and damping system with clearance. This paper demonstrates the non-linear behaviour of the motion through simulation and experiment. Intensive care and caution are taken in the experiments to observe the chaos and the multiple periods properly. The focus in this paper is mainly on the change of the bilinear spring stiffness ratio as a prime factor by which chaotic motions occur from quasi-periodic motion. Other investigations and effects on motion are also discussed for the changing of the extent of clearance. The investigations are based on frequency response curves. To understand the dynamics of the non-linearity of this model, all possible data processing and displaying techniques are taken into account. To observe the overall phenomena of this bilinear system, the resonance curves and the bifurcation diagrams are taken thoroughly for a wide frequency region. 相似文献
49.
MK Bhide RM Kadam MD Sastry Ajay Singh Shashwati Sen Manmeet Kaur DK Aswal SK Gupta VC Sahni 《Pramana》2002,58(5-6):799-802
Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for
polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave
absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime. 相似文献
50.
Analysis of Voice and Quantitative Measurement of Glottal Gap After Thyroplasty Type I in the Treatment of Unilateral Vocal Paralysis 总被引:2,自引:0,他引:2
Thyroplasty type I is one of several surgical treatments in which improving the voice of unilateral vocal fold paralysis is the ultimate objective. The goal of the surgery is the medialization of the paralyzed vocal fold. The purpose of this study is to evaluate the effectiveness of thyroplasty type I through acoustical analysis, aerodynamic measures, and quantitative videostroboscopic measurements. We report on 20 patients with unilateral vocal cord paralysis who underwent thyroplasty type I. We performed preoperative and postoperative video image analysis (normalized glottal gap area) and computer-assisted voice analysis (fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, mean phonation time, mean flow rate, mean subglottic pressure) in all patients. The glottal gap was significantly reduced after thyroplasty type I. Postoperative voice quality was characterized by an improved pitch and amplitude pertubation (jitter and shimmer), phonation time (mean phonation time), and subglottic pressure (mean subglottic pressure). Thyroplasty type I is an effective method for regaining glottal closure and vocal function. 相似文献