ACAT inhibitors derived from hetero-Diels-Alder cycloadducts of thioaldehydes

Acyl-CoA:cholesterol acyltransferase (ACAT) is the enzyme largely responsible for intracellular cholesterol esterification. A systemic inhibitor of ACAT is believed to be able to slow or even reverse the atherosclerotic process. Towards that goal, a series of cyclic sulfides, derived from the hetero-Diels-Alder reaction of thioaldehydes with 1,3-dienes, and bearing carboxamide substituents, were prepared and evaluated for in vitro (in several tissues and species) and ex vivo ACAT inhibition. Minor changes in subsequent structure were found to have a significant effect in optimization of the biological activity of this series of compounds.     

Heat and Moisture Transfer in Wet Sand Exposed to Solar Radiation—Models and Experiments Concerning Buried Objects

One promising method of locating buried objects, such as land mines, is to use optical systems for detecting contrasts in surface temperature. With enhanced knowledge about the interacting physical processes behind these temperature contrasts, it is possible to improve detection precision. In such a context, moisture movement in the soil and moisture evaporation from the surface have been found to be of particular interest. This study was based on indoor experiments on wet and dry sand exposed to radiation from a solar panel. Simulations of heat and moisture transfer conducted with a one-dimensional model are also presented for the experiments. The calculations were successful in accurately predicting surface temperatures for both wet and dry sand, making it possible to predict surface temperatures under different conditions. These findings will contribute to increasing the probability of successful detection of buried objects under real conditions using optical methods.     

The response of the adult and ATD heads to impacts onto a rigid surface

Given the high incidence of TBI, head injury has been studied extensively using both cadavers and anthropomorphic test devices (ATDs). However, few studies have benchmarked the response of ATD heads against human data. Hence, the objective of this study is to investigate the response of adult and ATD heads in impact, and to compare adult Hybrid III head responses to the adult head responses.     

Pulmonary vein stenosis after catheter ablation of atrial fibrillation

BACKGROUND: This report describes the complication of pulmonary vein stenosis with resultant severe pulmonary hypertension that developed in 2 patients after successful catheter ablation of chronic atrial fibrillation. METHODS AND RESULTS: Three months after successful catheter ablation of atrial fibrillation, both patients developed progressive dyspnea and pulmonary hypertension. Both were found to have severe stenosis of all 4 pulmonary veins near the junction with the left atrium. Balloon dilation of the stenotic pulmonary veins was performed in these patients, with improvement in dyspnea and pulmonary hypertension. CONCLUSIONS: The complication of pulmonary vein stenosis is potentially life-threatening, and the application of radiofrequency current within the pulmonary veins with standard catheter technology should be avoided. This complication can be treated with balloon dilation, although the long-term course is unknown.     

Freestanding, Micromachined, Multimode Silicon Optical Waveguides at lambda = 1.3 mum for Microelectromechanical Systems Technology

Freestanding, multimode optical channel waveguides formed by micromachining silicon are demonstrated. Fabrication utilizes standard microelectromechanical systems (MEMS) technology. Losses in the 0.57-0.80-dB/cm range are measured for channel waveguides with an air-silicon-air structure, whereas losses in the 1.12-1.52-dB/cm range are measured for channel waveguides with a SiO(2)-silicon-SiO(2) structure. Freestanding channel waveguides, along with optical fibers and other MEMS structures, can readily be mounted on a silicon MEMS platform to provide optimal alignment for maximizing optical coupling, and they are thus expected to be useful in devices that involve light and MEMS structures.     

Closure to discussion of “Performance evaluation ofsteel-conduit-enclosed power systems”

The authors of “Performance evaluation of steel-conduit-enclosed power systems” (see ibid., vol. 35, no. 3, p. 515-23, 1999) respond to the comments on the original paper. They argue that the intention of their paper is that the users should use the proper value of overcurrent device rating as it will be dictated by the application     

The origin of the support effect in supported metal oxide catalysts: in situ infrared and kinetic studies during methanol oxidation

The strong influence of the oxide support upon the turn-over frequency (TOF) of methanol oxidation over supported metal oxide catalysts has been well documented in recent years. However, the mechanistic origins (adsorption equilibrium of methanol to methoxy species, rate-determining methoxy surface decomposition, or product desorption equilibrium) of this interesting phenomenon are not completely understood. In order to obtain additional insight, the steady-state surface concentrations of adsorbed methoxy intermediates on monolayer catalysts (8 V atoms nm⁻²) of V₂O₅/(TiO₂, CeO₂, Al₂O₃ and ZrO₂) have been quantified with in situ transmission infrared spectroscopy/mass spectrometry. Calculations of the adsorption equilibrium constant, K_ads, show a six times increase for vanadia on oxide supports of Al < Ti < Zr < Ce, whereas the methoxy surface decomposition rate constant, k_rds (rds = rate-determining step), shows a 22 times increase in value over these same catalysts. Thus, changes in both the adsorption equilibrium and the methoxy decomposition properties of supported metal oxide catalysts appear to be responsible for the support effect, although the methoxy decomposition is clearly the reaction step that is more sensitive to the specific metal oxide support. More fundamentally, the support effect appears to correlate with the electronegativity of the support cation, which is proposed to have influence upon the rate of methoxy decomposition through hydride abstraction and on the steady-state equilibrium adsorption capacity of methanol to surface methoxy intermediates through the basicity of the bridging V–O–support bond (the adsorption site).     

In situ IR,Raman, and UV-Vis DRS spectroscopy of supported vanadium oxide catalysts during methanol oxidation

The application of in situ Raman, IR, and UV-Vis DRS spectroscopies during steady-state methanol oxidation has demonstrated that the molecular structures of surface vanadium oxide species supported on metal oxides are very sensitive to the coordination and H-bonding effects of adsorbed methoxy surface species. Specifically, a decrease in the intensity of spectral bands associated with the fully oxidized surface (V⁵⁺) vanadia active phase occurred in all three studied spectroscopies during methanol oxidation. The terminal V = O (∼1030 cm⁻¹) and bridging V–O–V (∼900–940 cm⁻¹) vibrational bands also shifted toward lower frequency, while the in situ UV-Vis DRS spectra exhibited shifts in the surface V⁵⁺ LMCT band (>25,000 cm⁻¹) to higher edge energies. The magnitude of these distortions correlates with the concentration of adsorbed methoxy intermediates and is most severe at lower temperatures and higher methanol partial pressures, where the surface methoxy concentrations are greatest. Conversely, spectral changes caused by actual reductions in surface vanadia (V⁵⁺) species to reduced phases (V³⁺/V⁴⁺) would have been more severe at higher temperatures. Moreover, the catalyst (vanadia/silica) exhibiting the greatest shift in UV-Vis DRS edge energy did not exhibit any bands from reduced V³⁺/V⁴⁺ phases in the d–d transition region (10,000–30,000 cm⁻¹), even though d–d transitions were detected in vanadia/alumina and vanadia/zirconia catalysts. Therefore, V⁵⁺ spectral signals are generally not representative of the percent vanadia reduction during the methanol oxidation redox cycle, although estimates made from the high temperature, low methoxy surface coverage IR spectra suggest that the catalyst surfaces remain mostly oxidized during steady-state methanol oxidation (15–25% vanadia reduction). Finally, adsorbed surface methoxy intermediate species were easily detected with in situ IR spectroscopy during methanol oxidation in the C–H stretching region (2800–3000 cm⁻¹) for all studied catalysts, the vibrations occurring at different frequencies depending on the specific metal oxide upon which they chemisorb. However, methoxy bands were only found in a few cases using in situ Raman spectroscopy due to the sensitivity of the Raman scattering cross-sections to the specific substrate onto which the surface methoxy species are adsorbed. This revised version was published online in August 2006 with corrections to the Cover Date.