Investigation of NO Adsorption and NO/O2 Co-adsorption on NOx-Storage-Components by DRIFT-Spectroscopy

NO adsorption and NO/O₂ co-adsorption on CeO₂ at different temperatures was studied by DRIFT-Spectroscopy. The results indicate that this oxide plays an important role in storing NO _x . FTIR studies show that NO adsorption is dominated by the formation of nitrite species. Furthermore, cis- and trans hyponitrite species are detected. Co-adsorption of NO/O₂ leads to the formation of nitrates. The experimental data show that the formation of nitrates is a consecutive reaction: adsorption of NO to form nitrite species (NO₂ ^–), followed by an oxidation to form nitrate species (NO₃ ^–).     

Investigation of NO adsorption and NO/O2 co-adsorption on NO x -storage-components by DRIFT-spectroscopy

Topics in Catalysis - NO adsorption and NO/O2 co-adsorption on CeO2 at different temperatures was studied by DRIFT-Spectroscopy. The results indicate that this oxide plays an important role in...     

A multimedia speech learning system for the hearing impaired

The lack (or limited amount) of audio feedback for many persons with hearing disabilities greatly reduces the quality of speech development and use. Current methodologies for the teaching speech techniques are relatively primitive, and generally require the active participation of a therapist. This makes essential practice difficult, time consuming, and expensive for the student. However, using multimedia technology, it is possible to amplify the efforts of the teachers and students for improving the quality of speech. This paper presents a multimedia visualization system that augments the limited hearing capabilities of hearing impaired persons using visual and tactile feedback approaches and provides alternate representations of sound for increasing speech capabilities and reduced learning time. The proposed system has the capability of not only decreasing the learning time for many persons, but can also be adopted for teaching young children correct speech patterns through the use of speech learning games based on the system.     

A comparison of the biological properties of of androst-5-en-3β-ol,a series of (20R)-n-alkylpregn-5-en-3β-ols and 21-isopentylcholesterol with those of cholesterol

The Δ⁵-sterol, androst-5-en-3β-ol, which has no side chain at C-17, did not permit molting of the insectHeliothis zea, growth of either the protozoanTetrahymena pyriformis, or the yeastSaccharomyces cerevisiae adapted to anaerobic conditions, nor was the sterol esterified by a mammalian microsomal ACAT preparation. However, the sterol did form a liposome with egg lecithin and, when fed to mice, did inhibit hepatic cholesterol synthesis. 21-Isopentylcholesterol also formed a liposome but neither supported the growth of the yeast nor was metabolized by the protozoan. When sterols, 20(R)-n-alkylpregn-5-en-3β-ols, with side chains of varying lengths were added to the medium of the protozoan, maximal esterification with fatty acids occurred with the 20(R)-n-pentyl derivative, and maximal inhibition of tetrahymanol formation occurred with then-butyl,n-pentyl andn-hexyl derivatives. In all of the assays, cholesterol showed a positive response, either permitting molting or growth, being metabolized, inhibiting sterol or tetrahymanol synthesis, or forming a liposome.     

Identification of Phase Inversion on Sieve Trays

The fundamental differences in hydrodynamics of the froth and spray regime account for the ongoing interest in search for the point of phase inversion. This short communication presents a new approach for identification of phase inversion on sieve trays in terms of an image-based measurement technique. Image analysis of entrained droplets reveals a distinct increase in Sauter mean diameter and droplet frequency during phase inversion. Further measurement methods like pressure drop, gravimetric analysis of entrained liquid, froth height assessment and photographic observation of the flow regime serve as a reference value and complement the discussion. A flow map based on the experimental data comprises each regime and shows a good agreement with phase inversion correlations from literature.     

EPR Studies of V‐ATPase with Spin‐Labeled Inhibitors DCC and Archazolid: Interaction Dynamics with Proton Translocating Subunit c

Vacuolar‐type H⁺‐ATPases (V‐ATPases) have gained recent attention as highly promising anticancer drug targets, and therefore detailed structural analyses and studies of inhibitor interactions are very important research objectives. Spin labeling of the V‐ATPase holoenzyme from the tobacco hornworm Manduca sexta and V‐ATPase in isolated yeast (Saccharomyces cerevisiae) vacuoles was accomplished by two novel methods involving the covalent binding of a (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) derivative of N,N′‐dicyclohexylcarbodiimide (DCC) to the essential glutamate residue in the active site and the noncovalent interaction of a radical analogue of the highly potent inhibitor archazolid, a natural product from myxobacteria. Both complexes were evaluated in detail by electron paramagnetic resonance (EPR) spectroscopic studies and double electron–electron resonance (DEER) measurements, revealing insight into the inhibitor binding mode, dynamics, and stoichiometry as well as into the structure of the central functional subunit c of these medicinally important hetero‐multimeric proton‐translocating proteins. This study also demonstrates the usefulness of natural product derived spin labels as tools in medicinal chemistry.     

Substitution of Two Active‐Site Residues Alters C9‐Hydroxylation in a Class II Diterpene Synthase

Diterpenes form a vast and diverse class of natural products of both ecological and economic importance. Class II diterpene synthase (diTPS) enzymes control the committed biosynthetic reactions underlying diterpene chemical diversity. Homology modelling with site‐directed mutagenesis identified two active‐site residues in the horehound (Marrubium vulgare) class II diTPS peregrinol diphosphate synthase (MvCPS1); residue substitutions abolished the unique MvCPS1‐catalysed water‐capture reaction at C9 and redirected enzyme activity toward formation of an alternative product, halima‐5(10),13‐dienyl diphosphate. These findings contributed new insight into the steric interactions that govern diTPS‐catalysed regiospecific oxygenation reactions and highlight the feasibility of diTPS engineering to provide a broader spectrum of bioactive diterpene natural products.     

SSL: A Theory of How People Learn to Select Strategies.

The assumption that people possess a repertoire of strategies to solve the inference problems they face has been raised repeatedly. However, a computational model specifying how people select strategies from their repertoire is still lacking. The proposed strategy selection learning (SSL) theory predicts a strategy selection process on the basis of reinforcement learning. The theory assumes that individuals develop subjective expectations for the strategies they have and select strategies proportional to their expectations, which are then updated on the basis of subsequent experience. The learning assumption was supported in 4 experimental studies. Participants substantially improved their inferences through feedback. In all 4 studies, the best-performing strategy from the participants' repertoires most accurately predicted the inferences after sufficient learning opportunities. When testing SSL against 3 models representing extensions of SSL and against an exemplar model assuming a memory-based inference process, the authors found that SSL predicted the inferences most accurately. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Engineer RNA-Protein Nanowires as Light-Responsive Biomaterials

RNA molecules have emerged as increasingly attractive biomaterials with important applications such as RNA interference (RNAi) for cancer treatment and mRNA vaccines against infectious diseases. However, it remains challenging to engineer RNA biomaterials with sophisticated functions such as non-covalent light-switching ability. Herein, light-responsive RNA-protein nanowires are engineered to have such functions. It first demonstrates that the high affinity of RNA aptamer enables the formation of long RNA-protein nanowires through designing a dimeric RNA aptamer and an engineered green fluorescence protein (GFP) that contains two TAT-derived peptides at N- and C- termini. GFP is then replaced with an optogenetic protein pair system, LOV2 (light–oxygen–voltage) protein and its binding partner ZDK (Z subunit of protein A), to confer blue light-controlled photo-switching ability. The light-responsive nanowires are long (>500 nm) in the dark, but small (20–30 nm) when exposed to light. Importantly, the co-assembly of this RNA-protein hybrid biomaterial does not rely on the photochemistry commonly used for light-responsive biomaterials, such as bond formation, cleavage, and isomerization, and is thus reversible. These RNA-protein structures can serve as a new class of light-controlled biocompatible frameworks for incorporating versatile elements such as RNA, DNA, and enzymes.