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71.
Ultrashort optical pulse generation using a fiber FM laser is presented and analyzed in detail. Fiber FM laser operation is realized using a fiber ring with an internal phase modulator and an erbium-doped fiber amplifier. To compress FM laser pulses, an external dispersive single-mode fiber is employed. Furthermore, by external intensity modulation, the pulse background is removed. The background ratio of the generated ultrashort pulse is calculated and compared with the experimental results. The experimental results show an output optical pulse width of 1.77 ps and a spectral bandwidth of 0.5 THz. 相似文献
72.
Dowding JM Dosani T Kumar A Seal S Self WT 《Chemical communications (Cambridge, England)》2012,48(40):4896-4898
In this study we have obtained evidence that cerium oxide nanoparticles (CeO(2) NPs) are able to scavenge nitric oxide radical. Surprisingly, this activity is present in CeO(2) NPs with a lower level of cerium in the 3+ state (CeO(2) NPs with low 3+/4+ ratio and therefore a reduced number of oxygen vacancies), in contrast to the superoxide scavenging properties which are correlated with an increased level of cerium in the 3+ state (CeO(2) NPs with high 3+/4+ ratio and therefore an increased number of oxygen vacancies). 相似文献
73.
AC-conductivity measurements of BaZr0.90Al0.10O3−δ (where δ describes the number of oxygen ion vacancies per unit cell) in wet and dry N2 have been carried out over the temperature range from 400 to 900 °C. Both atmospheres showed the usual Arrhenius behavior
of BaZr0.90Al0.10O2.95. The proton transport number,t
H, was also determined from the conductivity measurements of BaZr0.90Al0.10O2.95 in wet and dry N2 and takes up values of 0.97 and 0.78 in the temperature range 400 – 900 °C, respectively. 相似文献
74.
Ahmed S. A. Youssef Kamal A. Kandeel Fouli A. Fouli Wael S. I. Abou‐Elmagd 《Heteroatom Chemistry》2005,16(1):6-11
2‐Amino‐3‐cyano‐4,5,6,7‐tetrahydrobenzo[b]thiophene 1a or 2‐amino‐3‐cyano‐4,7‐di‐ phenyl‐5‐methyl‐4H‐pyrano[2,3‐c]pyrazole 2a reacted with phenylisocyanate in dry pyridine to give 2‐(3‐phenylureido)‐3‐cyanobenzo[b]thiophene 1b or 2‐disubstituted amino‐3‐cyanopyranopyrazole 2b derivative. However, when 1a and 2a were refluxed with carbon disulfide in 10% ethanolic sodium hydroxide solution, they afforded the thieno[2,3‐d]pyrimidin‐2,4‐dithione derivative 5 in the former case, 2,4‐dicyano‐1,3‐bis(dithio carboxamino)cyclobuta‐1,3‐ diene 6 and pyrazolopyranopyrido[2,3‐d]pyrimidin‐ 2,4‐dithione derivative 7 in the latter one. Treatment of 2a with thiourea in refluxing ethanol in the presence of potassium carbonate gave 2,2′‐dithiobispyrimidine derivative 9 (major) in addition to pyranopyrazole derivative 10 and 2,2′‐dithiobis ethoxypyrimidine derivative 11 in minor amounts. The structures of all products were evidenced by microanalytical and spectral data. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:6–11, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20070 相似文献
75.
Walid K. Abou Salem 《Annales Henri Poincare》2007,8(3):569-596
The quasi-static evolution of steady states far from equilibrium is investigated from the point of view of quantum statistical mechanics. As a concrete example of a thermodynamic system,
a two-level quantum dot coupled to several reservoirs of free fermions at different temperatures is considered. A novel adiabatic theorem for unbounded
and nonnormal generators of evolution is proven and applied to study the quasi-static evolution of the nonequilibrium steady
state (NESS) of the coupled system.
Submitted: April 23, 2006. Accepted: October 4, 2006. 相似文献
76.
N. Abdelmohsen H. H. A. Labib A. H. Abou El Ela S. N. Elsayed 《Applied Physics A: Materials Science & Processing》1989,48(3):251-253
Measurements of the electrical conductivity, thermelectric power and thermal conductivity of an AgTlTe2 semiconductor in the solid and liquid states were carried out in a wide range of temperatures. In the liquid state the data analyzed in terms of a model developed for the density of states and electrical transport in solid amorphous semiconductors. Positive thermoelectric power suggests a large predominance of holes in electrical transport. 相似文献
77.
The complexes of N-(2-hydroxy-1-naphthalidene)anthranilic acid abbreviated (H2NA) with some trivalent rare earth elements (Pr, Nd, Sm, Gd, Dy, Er and Yb) were prepared. The complexes were characterized by chemical and thermal analysis, ir and conductimetric methods. Two types of ionic complexes; Ln(HNA)2OH·2H2O with Dy, Er and Yb, and Ln(HNA)2OH with Pr, Nd, Sm and Gd were isolated. Coordination of the ligand with metal-ions occurs through the carboxy group and the nitrogen atom. The acid dissociation constants K1 and K2 of H2NA and the overall stability constants β1 and β2 of some lanthanide complexes in 75% (v/v) dioxan-water solutions were determined by the potentiometric method. 相似文献
78.
Manal F. Abou Taleb Samia E. Abdel-Aal Nabil A. El-Kelesh El-Sayed A. Hegazy 《European Polymer Journal》2007,43(2):468-477
Adsorption and controlled release of Chlortetracycline HCl to and from multifunctional polymeric materials (HEMA/MAA) hydrogels were investigated. P(HEMA/MAA) hydrogels were synthesized by gamma radiation-induced copolymerization of 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA) in aqueous solution. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion into the glassy polymer were discussed. Drug, Chlortetracycline HCl containing hydrogels, with different drug concentration to polymer ratios, was loaded by direct adsorption method. The influence of MAA content in the gel on the adsorption capacities of hydrogel was studied. Chlortetracycline HCl adsorption capacity of hydrogels was found to increase from 8 to 138 mg Chlortetracycline HCl per gram dry gel with increasing amount of MAA in the gel system and drug concentration. The effect of pH on the releasing behavior of Chlortetracycline HCl from gel matrix was investigated. In vitro drug release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and MAA content of hydrogel. 相似文献
79.
80.
The TG, DTG and DTA curves of curcumin(I) have been recorded in static air and inert dynamic argon atmosphere over the range between ambient temperature and 600°–700°C using a Netzsch thermal analyser STA 429. Careful examination of these curves reveals appreciable differences in the behaviour of I under either atmospheres, which are easily recognized by comparing the profiles of their thermal curves, particularly in the melting point, thermalL stability of intermediates, percent weight loss and exothermicity of the chemical processes. Gaschromatographic analysis of volatile pyrolysates trapped during thermal analysis indicates the formation of (CH3)2CO, CH3COH and C6H5OCH2COOH (phenyl oxyacetic acid). However, in static air CO2 and H2O were identified as well. X-ray diffractometry reveals the formation of amorphous carbon as a final product in argon and a mixture of amorphous carbon and graphite in air. It seems that the relatively high mass of argon plays an important role in the reactions and stability of intermediates. In either atmospheres curcumin is thermally stable up to 249°C withm.p. of 176.4°–177.5°C. The unique shape of the DTA curve of I could be used forits identification. 相似文献