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991.
992.
V. S. Gorelik A. A. Esakov A. N. Morozov P. P. Sverbil’ S. D. Tyves 《Journal of Russian Laser Research》2008,29(1):71-89
We developed a method for detecting traces of foreign components in water and analyzing the microstructure of water. The method
is based on studies of the characteristics of secondary emission arising in aqueous media under excitation by radiation of
ultraviolet lasers and light emitting diodes. A new type of cuvette (capillary cuvettes) for studying the secondary emission
in molecular media was elaborated. The cuvettes enable the study of aqueous solutions at small concentrations of the components;
they enable one to recognize the type of molecular compound present in aqueous media, in view of the photoluminescence spectra. 相似文献
993.
Aram A. Sahakyan Sergei K. Nikoghosyan Hrant N. Yeritsyan 《Central European Journal of Physics》2008,6(4):797-801
The influence of irradiation by electrons with an energy of 8 MeV, at dose intervals between 1013 and 2×1018el/cm2, on the properties of impurity doped, high-temperature superconductor YBa2Cu3−x
M
x
O
y
(M = Fe, Ni; x=0; x=0:01) ceramics has been studied.
It has been established that, as the irradiation dose is increased, the onset temperature of the transition to the superconducting
state (T
c
on
), and the intergranular weak link coupling temperature between granules (T
m
J
), exhibit an oscillation around their initial values of approximately about 1–1.5 K. This oscillation indicates that the
process of radiation defect formation in HTSC occurs in multiple stages. It was also found that the critical current (J
c
)decreases with an increase of the irradiation dose, and exhibits a local minimum at a dose of 8×1016el/cm2coinciding with minima for T
c
on
and T
m
J
at this dose. It was found that the introduction of Fe atoms to the ceramic decreases T
m
J
, while introducing Ni atoms decreases both T
c
on
and T
m
J
; it is suggested that this is a result of Ni substitution of Cu both in Cu2 plane sites and Cu1 chain sites. The introduction
of Ni causes a large change in the intergranular critical current density, J
c
. A critical irradiation dose is obtained (2×1018)after which all HTSC parameters strongly decrease, i. e. the superconductivity of HTSC is destroyed.
相似文献
994.
Oxidation of Aromatic Amines to Quinones by Iodic Acid under Microwave Irradiation in the Presence of Montmorillonite K10 and Silica Gel 总被引:1,自引:0,他引:1
Mohammed M.?HashemiEmail author Maryam?Akhbari 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1561-1563
Summary. A variety of aromatic amines are oxidized to their corresponding quinones in excellent yields by supported iodic acid under microwave irradiation and solvent free conditions. 相似文献
995.
996.
Klokkenburg M Lutz M Spek AL van der Maas JH van Walree CA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3544-3554
The synthesis, structure, and electronic properties of a series of cross-conjugated p-phenylenevinylidene oligomers with one to four double bonds are reported. The X-ray crystal structure of the compound with two double bonds reveals a nonplanar conformation with torsion angles about the C(phenylene)-C(vinylidene) and C(phenyl)-C(vinylidene) formal single bonds of 39.5(2) degrees and 30.5(2) degrees, respectively. Admixture of quinoid character in the ground state is observed. Infrared and Raman spectroscopy do not provide a clear picture of the degree of electron delocalization in the series, since the C=C stretching mode does not adequately reflect the C=C bond order and has a local nature. In contrast, electronic spectra and electrochemical data, as well as AM1 and PPP/SCF calculations, reveal that the cross-conjugated compounds basically behave as linearly pi-conjugated systems in the sense that molecular orbitals are delocalized over the entire structure and systematically change in energy. The electronic interaction between the repeating units is, however, not very strong, which has the consequence that spatial extension of the molecular orbitals does not lead to a red shift of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) electronic transition. This is related to the feature that the modest narrowing of the HOMO-LUMO gap with the chain length is accompanied by a relatively large reduction of electron repulsion. This finding implies that care should be taken in the use of electronic spectra for the evaluation of conjugation phenomena. 相似文献
997.
Marciniec B. Kozak M. Wachowski L. Ogrodowczyk M. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):473-485
The effect of ionising radiation (15-100 kGy) on the physico-chemical properties of 6 steroid derivatives in solid state (Hydrocortisone,
Hydrocortisone acetate, Prednisolone, Prednisolone acetate, Dexamethasone and Fludrocortisone acetate) was studied by differential
scanning calorimetry (DSC), differential thermal analysis (DTA), scanning electron microscopy (SEM), UV spectrophotometry,
high-performance liquid chromatography (HPLC), X-ray powder diffraction and polarimetry. DSC and DTA results revealed that
the irradiated compounds undergo phase transitions at lower temperatures, show lower melting points and lower enthalpy of
the melting process their non-irradiated analogues. The results of HPLC measurements proved a loss in the active substance
content after irradiation ranging from 0.5 to 2.88%. No significant effect of irradiation was detected by the UV spectrophotometry
or polarimetry in the course of the UV spectrum, absorbancy or optical rotation, as well as in the SEM photographs and X-ray
patterns. For some compounds studied a correlation was found between the irradiation dose and the shifts in DSC curves and
the loss of content determined by the HPLC method. Similar, but not so much pronounced relations were established in or earlier
studies of the derivatives of nitroimidazole and 1,4-dihydropyridine. In general the results have shown relatively high radiochemical
stability of the compounds studied and have proved that the DSC method is a sensitive detector of irradiation-caused changes
in drugs in solid phase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
998.
An experimental study on the enhancement of soft X-ray emission from a pinch plasma has been carried out by using a rotating plasma for pre-ionization. The rotating plasma is produced by a pulsed J×B cross-field discharge between coaxial electrodes, and subjected to a pinch discharge. Under an optimized discharge condition, it has been observed that UV emission of 251.6 nm (Ar III) soft X-ray intensity increases with increasing applied axial magnetic field B. At 400 G, the X-ray intensity is enhanced by a factor of 3 compared to that without the rotating plasma. It is considered that this result is due to the improved characteristics of the pre-ionization rotating plasma, which influences the uniformity and stability of subsequent pinch plasma. 相似文献
999.
本文用紫外吸收光谱、荧光光谱、磷光光谱、电子自旋共振光谱对九种水溶性硫杂蒽酮类光引发剂的光学行为进行了研究,计算了摩尔消光系数、荧光量子产率、磷光量子产率,同时测定了溶剂效应对紫外、荧光光谱的影响,并对引发剂结构与光学化学性能之间的关系做了一定的探讨。 相似文献
1000.
利用紫外-可见、近红外及中红外光声光谱对钕配合物的激发态能级状况、驰豫过程,荧光性质进行探讨,并深入研究了钕离子和配体对彼此光声谱峰移动和峰强度的影响。 相似文献