Running unstructured grid‐based CFD solvers on modern graphics hardware

Techniques used to implement an unstructured grid solver on modern graphics hardware are described. The three‐dimensional Euler equations for inviscid, compressible flow are considered. Effective memory bandwidth is improved by reducing total global memory access and overlapping redundant computation, as well as using an appropriate numbering scheme and data layout. The applicability of per‐block shared memory is also considered. The performance of the solver is demonstrated on two benchmark cases: a NACA0012 wing and a missile. For a variety of mesh sizes, an average speed‐up factor of roughly 9.5 × is observed over the equivalent parallelized OpenMP code running on a quad‐core CPU, and roughly 33 × over the equivalent code running in serial. Copyright © 2010 John Wiley & Sons, Ltd.     

NMR Study of Insect Adipokinetic Hormones

Mem-CC (pGlu-Leu-Asn-Tyr-Ser-Pro-Asp-Trp-NH₂), Tem-HrTH (pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-NH₂) and Del-CC (pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-GIy-Asn-NH₂) are adipokinetic hormones, isolated from the corpora cardiaca of different insect species. These hormones regulate energy metabolism during flight and so are intimately involved in an insect's mobility. In an attempt to measure the solution conformations of these peptides, their ₁H nmr spectra have been recorded in dimethylsulfoxide solution. the N7 analogue, [N7]-Mem-CC (pGlu-Leu-Asn-Tyr-Ser-Pro-Asn-Trp-NH₂) has also been studied. the solution dynamics of Tem-HrTH has been simulated in dmso and in a water droplet. These results have been correlated with measured coupling constants. the molecule was found to have a (β-turn at proline with asparagine (N7), which is postulated to be involved in receptor binding and/or activation, projecting outward from the turn.     

Synthesis of oligothiophene-bridged bisporphyrins and study of the linkage dependence of the electronic coupling

A set of twelve porphyrin dimers has been prepared to give information on how the type of connectivity between a porphyrin core and a bridge can influence the interporphyrin electronic interaction. The new porphyrin systems are substituted directly at the meso position with an oligothiophene chain tethered either with a single C-C sigma bond, a trans ethylenyl group, or a acetylenyl group. The compounds are easily obtained by palladium-catalyzed cross-coupling reactions (Stille, Heck, and Sonogashira) between 5-iodo-10,15,20-(3,5-ditert-butylphenyl)porphyrin and the appropriate oligothiophene derivative. This synthetic approach is straightforward and very effective for preparing oligothiophene-based prophyrin systems. The absorption spectra and the fluorescence properties of the dimers demonstrated the crucial importance of the characteristics of the chemical bond used to connect the bridge to the porphyrin unit. The magnitude of the electronic communication can thus be significantly modulated by altering the type of bond connectivity used to link the chromophore to the bridge. The present work shows that an oligothiophene spacer is a viable class of linker for connecting porphyrins, and that a quaterthiophene appended with ethynyl linkages affords a high electronic interaction over a distance as large as 28 A. A detailed computational study of these dimers has clarified the conditions needed for a conjugated system to behave as a molecular wire. These conditions are full planarity of the molecule and proper energy matching between the frontier orbitals of the bridge and the porphyrin. Intermolecular energy transfer in asymmetrical dyads composed of a zinc porphyrin and a freebase porphyrin has been studied by fluorescence spectroscopy. In all systems, this process is more than 98% efficient, and its rate constant decreases steadily in the order 4ZH > 1ZH > 3ZH approximately 2ZH. Thus, the largest rate (kEnT = 1.2 x 10(11) s-1) was found in the dyad linked with bisethynyl quaterthiophene, which represents the longest bridge within the series. These results clearly demonstrate that strong communication and also efficient photoinduced processes can be promoted over a large distance if the electronic structure of the molecular connector is appropriately chosen.     

Why do food analysts need quality assurance?

 Most sophisticated products require testing for compliance with specifications and safety regulations before release into many markets, and trade in many simpler commodities and products also requires supporting technical information. Test documentation has become an essential element in this trade. Food intended for human consumption certainly falls into the "sophisticated products" category. Lack of acceptance of laboratory test data across national borders may be a significant barrier to trade. In order to avoid such barriers and unnecessary duplication of laboratory tests, mutual recognition of laboratory results should be regarded as an important means of facilitating international trade in food products. It is difficult to envisage recognition of test data across borders without internationally agreed criteria for assessing the competence of testing. These criteria should, as a minimum, require that a laboratory involved in the analysis of foods operates a suitable quality system. The laboratory must create a quality system appropriate to the type, range and volume of work performed. It is necessary for the elements of this system to be documented in a quality manual which is available for use by the laboratory personnel. The quality manual must be kept up-to-date by a person or persons having responsibility for quality assurance within the laboratory. This paper describes and discusses the elements of a quality system in a food laboratory, including suitable quality assurance measures, the use of validated analytical methods and participation in proficiency testing schemes. Received: 24 February 1996 Accepted: 13 March 1996     

Balayage and Convergence of Rational Interpolants

We investigate the following problem: For which open simply connected domains do there exist interpolation schemes (a set of interpolation points) such that for any analytic function defined in the domain the corresponding interpolating polynomials converge to the function when the degree of the polynomials tends to infinity? We also study similar problems for rational interpolants. These problems are connected to the balayage (sweeping out) problems of measures.     

Self‐Assembled Cyclic d,l‐α‐Peptides as Generic Conformational Inhibitors of the α‐Synuclein Aggregation and Toxicity: In Vitro and Mechanistic Studies

Many peptides and proteins with large sequences and structural differences self‐assemble into disease‐causing amyloids that share very similar biochemical and biophysical characteristics, which may contribute to their cross‐interaction. Here, we demonstrate how the self‐assembled, cyclic d,l ‐α‐peptide CP‐2 , which has similar structural and functional properties to those of amyloids, acts as a generic inhibitor of the Parkinson′s disease associated α‐synuclein (α‐syn) aggregation to toxic oligomers by an ?off‐pathway“ mechanism. We show that CP‐2 interacts with the N‐terminal and the non‐amyloid‐β component region of α‐syn, which are responsible for α‐syn′s membrane intercalation and self‐assembly, thus changing the overall conformation of α‐syn. CP‐2 also remodels α‐syn fibrils to nontoxic amorphous species and permeates cells through endosomes/lysosomes to reduce the accumulation and toxicity of intracellular α‐syn in neuronal cells overexpressing α‐syn. Our studies suggest that targeting the common structural conformation of amyloids may be a promising approach for developing new therapeutics for amyloidogenic diseases.