Catalytic reaction between adsorbed oxygen and hydrogen on Rh(111)

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On some aspects of the noise propagation from supersonic aircraft

The noise problem associated with an aircraft flying at supersonic speeds is shown to depend primarily on the shock wave pattern formed by the aircraft. The noise intensity received by a ground observer from a supersonic aircraft flying at high as well as low altitudes, is shown to be high although it is of a transient nature. Continues

Beyond peer observation of teaching

OBJECTIVE To summarize the evidence on effectiveness of translational diabetes prevention programs, based on promoting lifestyle change to prevent type 2 diabetes in real-world settings and to examine whether adherence to international guideline recommendations is associated with effectiveness. RESEARCH DESIGN AND METHODS Bibliographic databases were searched up to July 2012. Included studies had a follow-up of ≥12 months and outcomes comparing change in body composition, glycemic control, or progression to diabetes. Lifestyle interventions aimed to translate evidence from previous efficacy trials of diabetes prevention into real-world intervention programs. Data were combined using random-effects meta-analysis and meta-regression considering the relationship between intervention effectiveness and adherence to guidelines. RESULTS Twenty-five studies met the inclusion criteria. The primary meta-analysis included 22 studies (24 study groups) with outcome data for weight loss at 12 months. The pooled result of the direct pairwise meta-analysis shows that lifestyle interventions resulted in a mean weight loss of 2.12 kg (95% CI -2.61 to -1.63; I(2) = 91.4%). Adherence to guidelines was significantly associated with a greater weight loss (an increase of 0.3 kg per point increase on a 12-point guideline-adherence scale). CONCLUSIONS Evidence suggests that pragmatic diabetes prevention programs are effective. Effectiveness varies substantially between programs but can be improved by maximizing guideline adherence. However, more research is needed to establish optimal strategies for maximizing both cost-effectiveness and longer-term maintenance of weight loss and diabetes prevention effects

Factors Dictating Carbene Formation at (PNP)Ir

The mechanistic subtleties involved with the interaction of an amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers have been investigated using density functional theory. Our analysis has revealed the factors dictating reaction direction toward either an iridium-supported carbene or a vinyl ether adduct. The (PNP)Ir structure will allow carbene formation only from accessible carbons α to the ethereal oxygen, such that d electron back-donation from the metal to the carbene ligand is possible. Should these conditions be unavailable, the main competing pathway to form vinyl ether can occur, but only if the (PNP)Ir framework does not sterically interfere with the reacting ether. In situations where steric hindrance prevents unimpeded access to both pathways, the reaction may progress to the initial C−H activation but no further. Our mechanistic analysis is density functional independent and whenever possible confirmed experimentally by trapping intermediate species experimentally. We have also highlighted an interesting systematic error present in the DFT analysis of reactions where steric environment alters considerably within a reaction

Photocatalytic antimicrobial activity of thin surface films of TiO2, CuO and TiO2 /CuO dual layers on Escherichia coli and bacteriophage T4

TiO2 coated surfaces are increasingly studied for their ability to inactivate microorganisms. The activity of glass coated with thin films of TiO2, CuO and hybrid CuO/TiO2 prepared by atmospheric Chemical Vapour Deposition (Ap-CVD) and TiO2 prepared by a sol-gel process was investigated using the inactivation of bacteriophage T4 as a model for inactivation of viruses. The chemical oxidising activity was also determined by measuring stearic acid oxidation. The results showed that the rate of inactivation of bacteriophage T4 increased with increasing chemical oxidising activity with the maximum rate obtained on highly active sol-gel preparations. However these were delicate and easily damaged unlike the Ap-CVD coatings. Inactivation rates were highest on CuO and CuO/TiO2 which had the lowest chemical oxidising activities. The inactivation of T4 was higher than that of Escherichia coli on low activity surfaces. The combination of photocatalysis and toxicity of copper acted synergistically to inactivate bacteriophage T4 and retained some selfcleaning activity. The presence of phosphate ions slowed inactivation but NaCl had no effect. The results show that TiO2/CuO coated surfaces are highly antiviral and may have applications in the food and healthcare industries

A First Principles Theory of Nuclear Magnetic Resonance J-Coupling in solid-state systems

A method to calculate NMR J-coupling constants from first principles in extended systems is presented. It is based on density functional theory and is formulated within a planewave-pseudopotential framework. The all-electron properties are recovered using the projector augmented wave approach. The method is validated by comparison with existing quantum chemical calculations of solution-state systems and with experimental data. The approach has been applied to verify measured J-coupling in a silicophosphate structure, Si5O(PO4)6Comment: 9 page

Energy-Efficient Algorithms

We initiate the systematic study of the energy complexity of algorithms (in addition to time and space complexity) based on Landauer's Principle in physics, which gives a lower bound on the amount of energy a system must dissipate if it destroys information. We propose energy-aware variations of three standard models of computation: circuit RAM, word RAM, and transdichotomous RAM. On top of these models, we build familiar high-level primitives such as control logic, memory allocation, and garbage collection with zero energy complexity and only constant-factor overheads in space and time complexity, enabling simple expression of energy-efficient algorithms. We analyze several classic algorithms in our models and develop low-energy variations: comparison sort, insertion sort, counting sort, breadth-first search, Bellman-Ford, Floyd-Warshall, matrix all-pairs shortest paths, AVL trees, binary heaps, and dynamic arrays. We explore the time/space/energy trade-off and develop several general techniques for analyzing algorithms and reducing their energy complexity. These results lay a theoretical foundation for a new field of semi-reversible computing and provide a new framework for the investigation of algorithms.Comment: 40 pages, 8 pdf figures, full version of work published in ITCS 201

Subsonic aerodynamic and flutter characteristics of several wings calculated by the SOUSSA P1.1 panel method

The SOUSSA (steady, oscillatory, and unsteady subsonic and supersonic aerodynamics) program is the computational implementation of a general potential flow analysis (by the Green's function method) that can generate pressure distributions on complete aircraft having arbitrary shapes, motions and deformations. Some applications of the initial release version of this program to several wings in steady and oscillatory motion, including flutter are presented. The results are validated by comparisons with other calculations and experiments. Experiences in using the program as well as some recent improvements are described