An Efficient Approach to Chiral Ferrocene‐Based Secondary Alcohols via Asymmetric Hydrogenation of Ferrocenyl Ketones

P‐Phos‐ruthenium‐DPEN precatalysts have been found to be efficient for the asymmetric hydrogenation of various ferrocenyl ketones. The use of (R)‐xylyl‐P‐PhosRuCl₂(R,R)‐DPEN generated chiral ferrocenylethanol in 99.3% e.e. with >99% conversion in a 150‐g scale.     

A Convenient Synthesis of 2,2′,6,6′‐Tetramethoxy‐ 4,4′‐bis(dicyclohexylphosphino)‐3,3′‐bipyridine (Cy‐P‐Phos): Application in Rh‐Catalyzed Asymmetric Hydrogenation of α‐(Acylamino)acrylates

The first example of the synthesis of an axially chiral bis(aryldicyclohexylphosphine) dioxide via catalytic hydrogenation of the optically resolved parent bis(aryldiphenylphosphine) dioxide was reported. The procedure for the synthesis of Cy‐P‐Phos ( 4d ) has thus successfully avoided the need for an otherwise lengthy synthetic route owing to the π‐excessive nature of one of the aryl groups in the latter. The use of Cy‐P‐Phos in the Rh(I)‐catalyzed asymmetric hydrogenation of the derivatives of methyl (Z)‐2‐acetamidocinnamate gave significantly higher rates of reaction as compared to the use of the previously reported optimal ligand Xyl‐P‐Phos ( 4c ) whilst the level of enantioselectivity was essentially maintained.     

MBE-grown ZnSSe thin films on ITO substrates for liquid-crystal light valve applications

The MBE growth of ZnSSe alloy thin films on ITO substrates using ZnS and Se sources was studied and various structural and opto-electronic properties of the as-grown thin films were characterised. The XRD rocking curves resulting from these films indicate that the as-grown polycrystalline ZnSSe thin films have a preferred orientation along (1 1 1) direction. The evaluated crystal sizes as deduced from the FWHM of the XRD layer peaks were found to show a strong growth temperature dependence with the optimised temperature at about 290°C. TEM measurements done on these thin films also indicate a similar growth temperature dependence. The TEM cross-sectional micrograph of the sample grown at the optimised temperature shows a well-defined columnar structure whose nucleation seems to be highly correlated with the ITO grains. UV responsivity as high as 0.01 A/W and more than three orders of magnitude in rejection power for wavelengths longer than 450 nm have been achieved. It was also found that the sample grown at the optimised temperature has the lowest resistivity of 4.3×10¹¹ Ω cm, which provides a good match with that of a liquid-crystal layer. These results indicate that MBE-grown ZnSSe thin film is a promising candidate as the photoconductive material of liquid-crystal light valves for UV imaging applications.     

Halogenated La1.6Sr.04CuO4 catalysts active for ethane selective oxidation to ethene

The catalytic performances and characterization of the catalysts La_1.6Sr_0.4CuO_3.852, La_1.6Sr_0.4CuO_3.857F_0.143, and La_1.6Sr_0.4 CuO_3.856Cl_0.126 have been investigated for the oxidative dehydrogenation of ethane (ODE) to ethene. X‐ray diffraction results indicated that the three catalysts have a single‐phase tetragonal K₂NiF₄-type structure. The incorporation of fluoride or chloride ions in the La_1.6Sr_0.4CuO_4-δ lattice can significantly enhance C₂H₆ conversion and C₂H₄ selectivity. We observed 83.2% C₂H₆ conversion, 76.7% C₂H₄ selectivity, and 63.8% C₂H₄ yield over La_1.6Sr_0.4CuO_3.857F_0.143> and 79.6% C₂H₆ conversion, 74.6% C₂H₄ selectivity, and 59.4% C₂H₄ yield over La_1.6Sr_0.4CuO_3.856Cl_0.126 under the reaction conditions of C₂H₆/O₂/N₂ molar ratio 2/1/3.7, temperature 660°C, and space velocity 6000 ml h^-1 g^-1. With the rise in space velocity, C₂H₆ conversion decreased, whereas C₂H₄ selectivity increased. Life studies showed that the two catalysts were durable within 60 h of on‐stream ODE reaction. Based on the results of X‐ray photoelectron spectroscopy, O₂ temperature-programmed desorption, and C₂H₆ and C₂H₆/O₂/N₂ (2/1/3.7 molar ratio) pulse studies, we conclude that (i) the inclusion of halide ions in the La_1.6Sr_0.4CuO_4δ lattice could promote lattice oxygen mobility, and (ii) the O^- species accommodated in oxygen vacancies and desorbed below 600°C favor ethane complete oxidation whereas the lattice oxygen species desorbed in the 600–700°C range are active for ethane selective oxidation to ethene. By regulating the oxygen vacancy density and Cu³/Cu ratio in the K₂NiF₄-type halo-oxide catalyst, one can generate a durable catalyst with good performance for the ODE reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the surgical treatment of refractory epilepsy in tuberous sclerosis complex

Using the pig as a model, it was shown that stimulation of the distal nerve ending of the pudendal nerve leads to the isolated stimulation of the external anal sphincter muscle. No difference in pressure response was noted after application of between 0.5 and 1.5 mA unilateral or bilateral stimulation. Major advantages observed using between 1.5 and 2.5 mA bilateral stimulation; with a stimulation between 2.0 and 2.5 mA the pressure response was twice as high compared to unilateral stimulation. Continuous stimulation of the striated anal sphincter muscle leads to fatigue, reaching 50% fatigue after a median time between 40-90 s. In cyclic stimulation (alternation every 15 s, duration 20 min) a fatigue reaction was also seen. The peak pressure decreased after 20 min for a median of 11%, the final pressure was lowered in 15% following a logarithmic curve pattern. The experimental application of variable impulse ranges also caused pressure differences. Increasing the impulse range from 200 to 450 microseconds (peak pressure) vs. 400 microseconds (final pressure) resulted in a statistically significant pressure increase. Therefore, it was proven that selective stimulation of the external anal sphincter muscle can lead to a transient pressure increase, which possibly improves fecal continence.     

Strong Fluctuation Theory for Scattering, Attenuation, and Transmission of Microwaves through Snowfall

The strong fluctuation theory is applied to the study of the atmospheric snowfall which is modeled as a layer of random discretescatterers edium. As functions of size distribution, fractional volume, and radius of scatterers, we illustrate the relationship between the reflectivity factor and precipitation rate, the attenuation of the centimeter and millimeter waves, and the line-of-sight transmission of coherent and incoherent wave components. The theoretical results are shown to match favorably with experimental data.     

Effect of interstitial cystitis on drug absorption from urinary bladder

Borna disease (BD) is a virus-induced immunopathologic disease of the central nervous system in a variety of species from birds to primates and probably in humans. Severe inflammatory reactions lead to tissue destruction and finally to cortical brain atrophy. After experimental infection of the rat, intraparenchymal CD8+ T cells, MHC class I Ags on Borna disease virus (BDV)-infected neurons, and numerous nerve cell lesions were present. Treatment of BDV-infected rats with the mAb OX-8 directed against CD8+ cells inhibited the immunopathologic reactions and reduced MHC class I Ag expression. Neuronal lesions were minimal and no loss of brain substance could be observed. Because BDV has no acute cytopathic effects, we provide evidence that the presence of CD8+ T cells within the brain parenchyma and the expression of MHC class I Ags on neurons play a major role for immunopathologic brain tissue destruction and virus-infected neurons in vivo can be destroyed by T cell-mediated cytotoxicity.     

Gas chromatograph/isotope dilution mass spectrometric analysis of airborne benzo

A critical evaluation has been made of the gas chromatography/isotope dilution mass spectrometry (GC/IDMS) analysis of airborne benzo[a]pyrene (B[a]p) using 2H-(deuterium, D) and 13C-labeled benzo[a]pyrene and a low resolution mass spectrometer. Laboratory quality control and field samples were used to determine the suitability of these two isotopically labeled B[a]p as surrogates for GC/IDMS B[a]p analysis. With method spike QC samples, recovery of the B[a]p was compared with the recoveries of D- and 13C-labeled B[a]p to validate the assumption that these two isotopically labeled B[a]p analogs could be used as method surrogates for IDMS B[a]p analyses. Two collocated Anderson Hi-Vol samplers were used to carry out a field study in which total B[a]p loadings from one sampler were correlated to the second sampler, before and after correcting the total B[a]p loadings against the recovery of the D- and 13C-labeled B[a]p. It is shown that a low-resolution mass spectrometer can be used in GC/IDMS B[a]p analysis to achieve results of high precision and accuracy. Depending on data quality objectives, D-labeled B[a]p could be used for IDMS B[a]p analysis, but is not recommended.