Infrared spectroscopy via substrate-integrated hollow waveguides: a powerful tool in catalysis research.

Substrate-integrated hollow waveguides (iHWG) represent an innovative generation of photon conduits, which can simultaneously serve as highly miniaturized gas cells with low sample volume. In this communication, we introduce a novel concept for analyzing the performance of catalysts via infrared gas phase analysis based on iHWGs. Due to rapid gas exchange and sample transient times within the iHWG, compositional changes of a continuous gas stream after interaction with a catalyst assembly can be monitored with high time resolution.

GeSn/Ge multiquantum well photodetectors on Si substrates.

Vertical incidence GeSn/Ge multiquantum well (MQW) pin photodetectors on Si substrates were fabricated with a Sn concentration of 7%. The epitaxial structure was grown with a special low temperature molecular beam epitaxy process. The Ge barrier in the GeSn/Ge MQW was kept constant at 10 nm. The well width was varied between 6 and 12 nm. The GeSn/Ge MQW structures were grown pseudomorphically with the in-plane lattice constant of the Ge virtual substrate. The absorption edge shifts to longer wavelengths with thicker QWs in agreement with expectations from smaller quantization energies for the thicker QWs.

Activation of molecular oxygen and the nature of the active oxygen species for CO oxidation on oxide supported Au catalysts.

Although highly dispersed Au catalysts with Au nanoparticles (NPs) of a few nanometers in diameter are well-known for their high catalytic activity for several oxidation and reduction reactions already at rather low temperatures for almost 30 years, central aspects of the reaction mechanism are still unresolved. While most studies focused on the active site, the active Au species, and the effect of the support material, the most crucial step during oxidation reactions, the activation of molecular oxygen and the nature of the resulting active oxygen species (Oact), received more attention just recently. This is topic of this Account, which focuses on the formation, location, and nature of the Oact species present on metal oxide supported Au catalysts under typical reaction conditions, at room temperature and above. It is mainly based on quantitative temporal analysis of products (TAP) reactor measurements, which different from most spectroscopic techniques are able to detect and quantify these species even at the extremely low concentrations present under realistic reaction conditions. Different types of pulse experiments were performed, during which the highly dispersed, realistic powder catalysts are exposed to very low amounts of reactants, CO and/or O2, in order to form and reactively remove Oact species and gain information on their formation, nature, and the active site for Oact formation. Our investigations have shown that the active oxygen species for CO oxidation on Au/TiO2 for reaction at 80 °C and higher is a highly stable atomic species, which at 80 °C is formed only at the perimeter of the Au-oxide interface and whose reactive removal by CO is activated, but not its formation. From these findings, it is concluded that surface lattice oxygen represents the Oact species for the CO oxidation. Accordingly, the CO oxidation proceeds via a Au-assisted Mars-van Krevelen mechanism, during which surface lattice oxygen close to the Au NPs is removed by reaction with CO, resulting in a partially reduced TiO2 surface, which is subsequently reoxidized by O2. We demonstrate that this is the dominant reaction pathway for Au catalysts based on reducible metal oxides in general, at typical reaction temperatures, while for less active Au catalysts based on nonreducible metal oxides, this reaction pathway is not possible and the remaining activity must arise from another pathway, most probably a Au-only mechanism. At lower reaction temperature, reactive removal of Oact becomes increasingly inhibited, leading to a change in the dominant reaction pathway.

Design and characterization of a temporal analysis of products reactor.

We describe an improved temporal analysis of products (TAP) reactor design whose main new features in comparison to the recent TAP-2 design of Gleaves et al. [Appl. Catal. A 160, 55 (1997)] are the use of a turbomolecular pump, piezoelectrically driven pulse valves, and a newly designed, differentially pumped gate valve. The gate valve allows fast and simple changes between high pressure operation, in which in situ catalyst treatment can be performed, and the analytic mode with a direct line-of-sight connection to the analysis chamber and the mass spectrometer. The heating system and pulse valves are located outside the vacuum chamber, resulting in a system that is easy to operate and modify. The high stability and reproducibility of the pulse intensity allows for direct, quantitative evaluation of single-pulse and multipulse experiments. The performance of the system is demonstrated using the CO oxidation over a Au/TiO(2) catalyst as test reaction.

Recent changes in JCAH standards affecting the accreditation of psychiatric facilities.

During the past five years, the Accreditation Manual for Hospitals (AMH) has undergone two separate but not entirely unrelated revisions: the incorporation of psychiatric and substance abuse standards, a step that allowed all hospital-based psychiatric services to be surveyed through the AMH and that had implications for both psychiatric and nonpsychiatric patients, and the rewriting of the standards in the medical staff chapter, which relates to staff composition and organization, staff responsibilities, and medical staff quality assurance activities. The author discusses some of the forces behind the revisions, the specific changes resulting from each revision process, and the rationale for the changes.

Assessment of the impact of medical devices on the quality of care.

Medical technology and medical devices play major roles in the diagnosis and treatment of patients in health care facilities. A facility should use a rational process to reach the decision to acquire a new piece of technology; this process should recognize the importance of both the machine and the user in modern technology. Moreover, each health care facility should assure that a newly acquired technological advance does not pose safety hazards to patients; that the device, when used in the clinical situation, produces the desired results reliably and consistently with its intended purpose; that there are appropriate means of identifying performance defects or opportunities for greater use of the existing device; and that the end of the device's useful life is anticipated so that quality does not decrease and dangers to patients do not increase due to equipment obsolescence. Successfully applying QA principles, consistent with each phase in the life of medical technological devices, should ensure equipment of high quality and thus benefit a health care facility and its patients.

Quantitative Evaluation of Photoresist Patterns in the 1 - microm Range.

During exposure of photoresist layers the light distribution inside the resist is essentially determined by three factors: the incident light pattern generated by the exposure system at the resist surface; the absorption of light by the photoresist; and the reflected waves at the interfaces between layers. Due to standing wave effects, regions of different light intensity are created inside the resist, leading to steplike edge contours of the photoresist after development. The shape of photoresist patterns can be calculated.