Stabilization of γ‘ phase in Bi<Subscript>4</Subscript>V<Subscript>2-x</Subscript>Fe<Subscript>x</Subscript><Superscript>II</Superscript>O<Subscript>11-1.5x</Subscript> series

Summary This work reports the room-temperature stabilization of the Bi₄V_2-xFe_x^IIO_11-1.5x γ ‘ phase, a promising ionic conductive material that finds application in solid oxide fuel cell and oxygen sensor devices. The Fe(II) cation proved to be a better stabilizer than Fe(III), which was previously used, since a lower substitution degree of V⁵⁺ is needed for the former. Powder X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry were used in these experiments.     

Trennung,Identifizierung und Bestimmung von Bactericiden auf der Basis von halogenierten Aromaten mittels Gas-Chromatographie

The separation of a mixture of 22 bactericides has been achieved by gas chromatography on columns with silicone rubber W-982 as stationary phase with temperatures between 100° and 300°C. The unchanged compounds as well as their silylation products have been used. The latter are more conveniently used especially for the quantitative determination. To be able to calculate the retention indices after Kovats gas chromatography has been performed isothermally at 180°C for the more volatile compounds and at 250°C for all other bactericides.The retention indices obtained under these conditions are tabulated together with the limits of detection.     

Redox,transmetalation, and stacking properties of tetrathiafulvalene-2,3,6,7-tetrathiolate bridged tin,nickel, and palladium compounds

Here we report that capping the molecule TTFtt (TTFtt = tetrathiafulvalene-2,3,6,7-tetrathiolate) with dialkyl tin groups enables the isolation of a stable series of redox congeners and facile transmetalation to Ni and Pd. TTFtt has been proposed as an attractive building block for molecular materials for two decades as it combines the redox chemistry of TTF and dithiolene units. TTFttH₄, however, is inherently unstable and the incorporation of TTFtt units into complexes or materials typically proceeds through the in situ generation of the tetraanion TTFtt⁴⁻. Capping of TTFtt⁴⁻ with Bu₂Sn²⁺ units dramatically improves the stability of the TTFtt moiety and furthermore enables the isolation of a redox series where the TTF core carries the formal charges of 0, +1, and +2. All of these redox congeners show efficient and clean transmetalation to Ni and Pd resulting in an analogous series of bimetallic complexes capped by 1,2-bis(diphenylphosphino)ethane (dppe) ligands. Furthermore, by using the same transmetalation method, we synthesized analogous palladium complexes capped by 1,1′-bis(diphenylphosphino)ferrocene (dppf) which had been previously reported. All of these species have been thoroughly characterized through a systematic survey of chemical and electronic properties by techniques including cyclic voltammetry (CV), ultraviolet-visible-near infrared spectroscopy (UV-vis-NIR), electron paramagnetic resonance spectroscopy (EPR), nuclear magnetic resonance spectroscopy (NMR) and X-ray diffraction (XRD). These detailed synthetic and spectroscopic studies highlight important differences between the transmetalation strategy presented here and previously reported synthetic methods for the installation of TTFtt. In addition, the utility of this stabilization strategy can be illustrated by the observation of unusual TTF radical–radical packing in the solid state and dimerization in the solution state. Theoretical calculations based on variational 2-electron reduced density matrix methods have been used to investigate these unusual interactions and illustrate fundamentally different levels of covalency and overlap depending on the orientations of the TTF cores. Taken together, this work demonstrates that tin-capped TTFtt units are ideal reagents for the installation of redox-tunable TTFtt ligands enabling the generation of entirely new geometric and electronic structures.

Capping TTFtt enables facile transmetalation in three different oxidation states.     

2-Amino-4-bromobutanoic Acid

(2S)- and (2R)-2-Amino-4-bromobutanoic acid were prepared starting from N-Boc-glutamic acid α tert-butyl ester. The double tert-butyl protection was necessary to prevent a partial racemisation during Barton’s radical decarboxylation used to transform the γ-carboxylic group into a bromide. This bromide reacted with different nitrogen, oxygen and sulphur nucleophiles to give nonnatural amino acids characterised by basic or heterocyclic side chains. The title compound was also used to prepare a conformationally constrained peptidomimetic.     

Steric hindrance-controlled Pd(0)-catalyzed coupling-cyclization of 2,3-allenamides and organic iodides. An efficient synthesis of iminolactones and gamma-hydroxy-gamma-lactams

Under the catalysis of 1 mol % Pd(PPh3)4, the reaction of 4,4-disubstituted 2,3-allenamides and organic iodides in toluene afforded iminolactones stereospecifically in >90% yields using K2CO3 (2 equiv)-5 mol % TBAB as the base. A similar reaction with 4-monosubstituted 2,3-allenamides afforded gamma-hydroxy-gamma-lactams in relatively lower yields. The N/O-attack selectivity may be determined by the steric effect at the 4-position of 2,3-allenamides.     

Experimental and theoretical study of the infrared spectra of BrHI- and BrDI-

Gas phase vibrational spectra of BrHI- and BrDI- have been measured from 6 to 17 microm (590-1666 cm(-1)) using tunable infrared radiation from the free electron laser for infrared experiments in order to characterize the strong hydrogen bond in these species. BrHI-.Ar and BrDI-.Ar complexes were produced and mass selected, and the depletion of their signal due to vibrational predissociation was monitored as a function of photon energy. Additionally, BrHI- and BrDI- were dissociated into HBr (DBr) and I- via resonant infrared multiphoton dissociation. The spectra show numerous transitions, which had not been observed by previous matrix studies. New ab initio calculations of the potential-energy surface and the dipole moment are presented and are used in variational ro-vibrational calculations to assign the spectral features. These calculations highlight the importance of basis set in the simulation of heavy atoms such as iodine. Further, they demonstrate extensive mode mixing between the bend and the H-atom stretch modes in BrHI- and BrDI- due to Fermi resonances. These interactions result in major deviations from simple harmonic estimates of the vibrational energies. As a result of this new analysis, previous matrix-isolation spectra assignments are reevaluated.     

基于 uClinux的usb主设备模块实现

介绍了从原理到软件编程,USB主设备模块的实现.拓展性地把USB主设备模块建立在嵌入式微处理器上,抛开了PC;在USB主设备上使用uClinux嵌入式操作系统,符合OTG技术和嵌入式设备的发展趋向.因此,项目具有积极的经济意义和先进性.     

我国女性服饰流变中的性别权力关系探析

中国女性服饰的演变大致经历了四个时期，每一次演变过程都昭显出特定时期独特的两性权力关系，由此也可以窥知中国女性寻求个性解放的尝试及艰难历程。     

Lightning activity on the central Tibetan Plateau and its response to convective available potential energy

Lightning flash activities on the central Tibetan Plateau have been studied by using the satellite-based Lightning Imaging Sensor(LIS)database from January 1998 to July 2002.The lightning activity shows a clear diurnal variation on the central Plateau.The peak lightning activity appears at about 17:00 which is 3 h earlier than that in Jingxhou,Hubei in the same latitude belt nearby,indicating that the lightning activity is a sensitive indicator of solar heating on the Plateau.The lightning discharge is weaker on the Plateau than Jingzhou.Hubei and other low-altitude continental regions because of the lower convective available potential energy(CAPE)on the Plateau.The CAPE on the Plateau is 12 times lower than that in Jingzhou,Hubei,and 20 times lower than that in the sea-level region,such as Guangzhou and Florida.However,the sensitivity of lightning activity to CAPE changes on the Plateau is up to 30 times more sensitive than other prominent low-altitude regions.     

Inorganic chemical composition and source signature of PM2.5 in Beijing during ACE-Asia period

Aerosol samples for PM2.5 were collected in Beijing for 38 consecutive days from March to April 2001 using an IMPROVE Sampler. Concentrations of 20 elements in PM2.5 were determined using a PIXE method. Results show that the average mineral dust concentration of PM2.5 was 14.6 Ilg/m3 during the observation period. On the sand-dust event days of March 21 and April 10, dust PM2.5 mass concentrations were 62.4 and 54.1 μg/m^3, respectively.These demonstrate that fine particle pollution by dust event in Beijing was very severe. The enrichment factors of S and Cu reached minimums on the dusty days and were high on the non-dusty days. It is considered that enrichment factors of elements in PM2.5, which are associated with human activities, can probably provide an effective method to distinguish local sources from external sources of dust. Factor analysis on the chemical composition in PM2.5 shows that sources of crustal matters, anthropogenic emission, and oil combustion contributed to PM2.5 levels in air in the springtime of 2001 in Beijing.