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131.
Bould J Dörfler U Rath NP Barton L Kilner CA Londesborough MG Ormsby DL Kennedy JD 《Dalton transactions (Cambridge, England : 2003)》2006,(31):3752-3765
In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1 in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe2)-nido-B10H12] 2 (30%), but also the two two-cluster species [6,9-(SMe2)2-arachno-B10H11-1-(6-nido-B10H13)] 3 (20%) and [1,6-(nido-B10H13)2] 6 (ca. 0.5%) and the two three-cluster species [6,9-(SMe2)2-arachno-B10H10-1,5-(6-nido-B10H13)2] 4 (5%), characterized crystallographically, and [6,9-(SMe2)2-arachno-B10H10-1,3-(6-nido-B10H13)2] 5 (<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe2)-nido-B10H12] 2 is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe2)2-arachno-B10H12] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre--linked two-cluster compounds as starting substrates, two-cluster [5-(SMe2)-4-(2-nido-B10H13)-nido-B10H11] 7 (0.6%) has been isolated from the reaction of SMe2 with [1,5-(nido-B10H13)2], other identified products being compound 1 (39%) and compound 3 (10.5%). 相似文献
132.
This work presents a fast method for the simultaneous separation and determination of glimepiride, glibenclamide, and two related substances by RP LC. The separation was performed on a Chromolith Performance (RP-18e, 100 mm x 4.6 mm) column. As mobile phase, a mixture of phosphate buffer pH 3, 7.4 mM, and ACN (55:45 v/v) was used. Column oven temperature was set to 30 degrees C. The total chromatographic run time was 80 s. This was achieved using a flow program from 5 to 9.9 mL/min. Precisions of the interday and the intraday assay for both retention times and peak areas for the four analyzed compounds were less than 1.2%. The method showed good linearity and recovery. The short analysis time makes the method very valuable for quality control and stability testing of drugs and their pharmaceutical preparations. 相似文献
133.
The Cauchy-Born rule has been applied in the Quasicontinuum method to derive continuum material properties based on underlying atomistic model in a physically consistent way. In this short work, the procedure is demonstrated, where the resulted materials constants are compared with experimental data found in literature. Moreover, the condition for applying the Cauchy-Born rule is discussed, with an intuitive explanation for why it can be only applied to crystalline materials with perfect structure. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
134.
135.
Dietzel D Ritter C Mönninghoff T Fuchs H Schirmeisen A Schwarz UD 《Physical review letters》2008,101(12):125505
One of the most fundamental questions in tribology concerns the area dependence of friction at the nanoscale. Here, experiments are presented where the frictional resistance of nanoparticles is measured by pushing them with the tip of an atomic force microscope. We find two coexisting frictional states: While some particles show finite friction increasing linearly with the interface areas of up to 310 000 nm(2), other particles assume a state of frictionless sliding. The results further suggest a link between the degree of surface contamination and the occurrence of this duality. 相似文献
136.
We demonstrate a passively mode-locked femtosecond Yb:KLu(WO(4))(2) thin-disk laser oscillator. Chirped-pulse operation in the positive dispersion regime as well as solitary operation have been realized, and the laser performance of both configurations are compared. In the solitary mode-locking regime the output power exceeds 25 W in a diffraction-limited beam, and pulse durations as short as 440 fs at a 34.7 MHz repetition rate have been generated. For the first time we present a chirped-pulse operation of a thin-disk oscillator that yields a maximum average output power of 9.5 W with a Fourier limit of 450 fs. 相似文献
137.
Alexander Horn Ilja Mingareev Alexander Werth Martin Kachel Udo Brenk 《Applied Physics A: Materials Science & Processing》2008,93(1):165-169
Lead-free piezoelectric ceramics Bi0.5(Na1-x-yKxAgy)0.5TiO3 [BNKAT(x/y)] have been synthesized by the mixed oxide method. The effects of the amount of K+ and Ag+ on the electrical properties were examined. X-ray diffraction patterns indicate that K+ and Ag+ ions partially substitute for the Na+ ions in Bi0.5Na0.5TiO3 and form a solid solution during sintering. At room temperature, the ceramics exhibit good performances with piezoelectric
constant d33=189 pC/N, electromechanical coupling factor kp=35.0%, remanent polarization Pr=39.5 μC/cm2, and coercive field Ec=3.3 kV/mm, respectively. The curves of the dielectric constant εr and loss tangent tan δ versus temperature show that the transition temperature from ferroelectric to anti-ferroelectric phase
decreases with increasing the K+ content for the compositions researched. The dependencies of kp and polarization versus electric (P–E) hysteresis loops on temperature reveal that the depolarization temperature Td of BNKAT(0.15/0.015) ceramics, which have good piezoelectric properties (d33=134 pC/N, kp=32.5%) and strong ferroelectricity (Pr=39.5 μC/cm2, Ec=4.1 kV/mm) at room temperature, is above 160 °C.
PACS 77.22.-d; 77.65.Bn; 77.80.Bh; 77.80.Dj; 77.84.Dy 相似文献
138.
139.
Sellner B Zifferer G Kornherr A Krois D Brinker UH 《The journal of physical chemistry. B》2008,112(3):710-714
Force-field-based atomistic simulations of host-guest supramolecular complexes between beta-cyclodextrin and several aziadamantane derivatives have been analyzed with respect to relative orientation and interaction energies, explicitly considering solvent (water) molecules. For each case, the calculations revealed two stable orientations of the guest within the host that are different in interaction energy. Fluctuation of and correlation between characteristic properties were analyzed. Among other things, it turned out that orientation angle and inclusion depth are clearly correlated. In addition, for the unsubstituted aziadamantane, the enthalpy of complex formation was calculated and compared to experimental results. 相似文献
140.