Integral equation formulation for buoyancy-driven convection problems

An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations.     

Some hydrogen atom abstraction reactions of CF2H and CFH2 radicals,and the C?H bond dissociation energy in CF2H2

By photolyzing (CF₂H)₂CO and (CFH₂)₂CO the hydrogen atom abstraction reactions of CF₂H radicals with (CF₂H)₂CO, H₂, D₂, CH₄, C₂H₆, n? C₄H₁₀ and iso? C₄H₁₀, and the reactions of CFH₂ radicals with (CFH₂)₂CO and n? C₄H₁₀, have been studied. Arrhenius parameters for these reactions are compared with related systems. From a knowledge of the activation energies for the forward and reverse reactions a value of the bond dissociation energy, D(CF₂H? H) = 97.4 ± 1.3 kcal mole^?1 at a mean temperature of 543°K is obtained. This value is subject to much uncertainty due to possible compensation effects in the Arrhenius parameters. These effects are discussed for this and the other reactions, and the data suggest that D(CF₂H? H) is approximately 100 kcal mole^?1, and that D(CFH₂? H) is very similar. Other literature data tend to confirm these approximate values.     

GC‐FID determination and pharmacokinetic studies of oleanolic acid in human serum

Analytical interest of OA determination in human serum has increased owing to the increasing interest in pharmaceutical research by pharmaceutical properties. A simple, specific, precise and accurate GC method with flame ionization detector (FID) developed and validated for the determination of oleanolic acid (OA) in human serum (HS). To an aliquot of HS, internal standard was added and a combination of liquid–liquid extraction with a mixture of diethyl ether‐isopropyl alcohol, filtration and consecutive GC resulted in separation and quantification of OA. The organic phase was analyzed using a GC system equipped with a 30 × 0.25 mm i.d. Rtx‐65TG capillary column and FID detection. Total chromatographic time was 10 min and no interfering peaks from endogenous components in blank serum were observed. The OA/internal standard peak area ratio was linearly fitted to the OA concentration (r = 0.992) over the range 10–1500 ng/mL. The mean serum extraction recovery of OA was 96.7 ± 1.0% and the lower limit of quantification based on 5 mL of serum was 10.7 ng/mL. The intra‐day coefficient of variation ranged from 1.3 to 3.6% and inter‐day varied from 1.4 to 4.5%. The developed method was used to study the pharmacokinetics of OA after oral administration in humans. The assay was simple, sensitive, precise and accurate for the use in the study of the mechanisms of absorption and distribution of OA in humans. Copyright © 2015 John Wiley & Sons, Ltd.     

CRDOCK: An Ultrafast Multipurpose Protein-Ligand Docking Tool

An ultrafast docking and virtual screening program, CRDOCK, is presented that contains (1) a search engine that can use a variety of sampling methods and an initial energy evaluation function, (2) several energy minimization algorithms for fine tuning the binding poses, and (3) different scoring functions. This modularity ensures the easy configuration of custom-made protocols that can be optimized depending on the problem in hand. CRDOCK employs a precomputed library of ligand conformations that are initially generated from one-dimensional SMILES strings. Testing CRDOCK on two widely used benchmarks, the ASTEX diverse set and the Directory of Useful Decoys, yielded a success rate of ～75% in pose prediction and an average AUC of 0.66. A typical ligand can be docked, on average, in just ～13 s. Extension to a representative group of pharmacologically relevant G protein-coupled receptors that have been recently cocrystallized with some selective ligands allowed us to demonstrate the utility of this tool and also highlight some current limitations. CRDOCK is now included within VSDMIP, our integrated platform for drug discovery.     

Radar characterization of summer thunderstorms in the western Po Valley

Summary Data taken by aC-band conventional weather radar during 1979, 1980 and 1981 summer campaigns conducted in the western Po Valley, have been analysed in comparison with surface reports of hailfalls, indicating the location, time and estimated losses for each event. The aim of this paper is to determine the signature of thunder-storms on radar data,vs. the presence or absence of hail on the ground. Hail percentages of occurrence greater than 75% of all cases are experienced when reflectivity values of 55 dBZ are detected above 8000m. Detection criteria of this kind are easy to implement in real-time surveillance systems and can be used to elaborate short-time warnings.

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Riassunto Si presenta un'analisi di dati rilevati con un radar meteorologico tradizionale in bandaC durante campagne di osservazioni condotte nella parte occidentale della Valle Padana nelle estati 1979, 1980 e 1981. I dati a terra sono costituiti dallo segnalazioni di grandinate che specificano la località, l'ora e la stima dei danni arrecati alle colture agricole. S'intende con questo lavoro determinare criteri di discriminazione fra le caratte-ristiche dei segnali radar provenienti da eventi temporaleschi per cui sia stata segnalata grandine, rispetto ai casi di assenza di grandine. Percentuali di eventi grandinigeni maggiori del 75% sono state riscontrate quando valori di riflettività di almeno 55 dBZ sono stati rilevati sopra gli 8000 m di quota. Criteri di discriminazione di questo tipo sono di semplice implementazione in sistemi di sorveglianza in tempo reale e possono essere usati per elaborare messaggi di allarme a breve periodo.

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Резюме Проводится анализ данных, полученных при метеорологических радарных исследованиях в зонеC в период летних кампаний 1979, 1980 и 1981 г.г. в западной части долины По. Полученные данные сопоставляются с наземными сообщениями о выпадании града, отмечая месторасположение, время и расчетные потори для каждого события. Цель этой статьи— определить сигнатуру для гроз по радарным данным в зависимости от наличия или отсутствия града на земле. Вероятность вышадания града превышает 75% в том случае, когда детектируется величина отражательной способности ∼55 dBZ выше 8000 м. Критерии определения такого типа легко использовать в системах наблюдения в реальном времени и могут служить для предупреждения за короткий промежуток времени.

     

Permanently oriented antibody immobilization for digoxin determination with a flow-through fluoroimmunosensor

This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples.     

The photolysis of pentafluoroacetone

The photolysis of pentafluoroacetone has been investigated in the 3130 Å region, from room temperature to 360°C. The Φ_CO varies from 0.7 to 0.9 over this range, and the decomposition is represented by CF₂HCOCF₃ → CF₂H + CO + CF₃. The disproportionation/combination ratio for CF₃ and CF₂H (→ CF₃H + CF₂) radicals is found to be 0.09. Arrhenius parameters for hydrogen atom abstraction from the ketone are log₁₀A = 12.7 (units are mole^?1 cc sec^?1) and E = 14.3 kcal mole^?1 for CF₂H, and log₁₀A = 12.1 and E = 11.8, for CF₃ radicals. At low pressures HF elimination reactions are observed from the vibrationally excited fluoroethanes, C₂F₅H* and C₂F₄H₂*, formed in the system. A rough estimate of the activation energy for the process C₂F₅H → C₂F₄ + HF of 60–65 kcal mole^?1 is made.