Dynamic multiscaling in two-dimensional fluid turbulence

We obtain, by extensive direct numerical simulations, time-dependent and equal-time structure functions for the vorticity, in both quasi-Lagrangian and Eulerian frames, for the direct-cascade regime in two-dimensional fluid turbulence with air-drag-induced friction. We show that different ways of extracting time scales from these time-dependent structure functions lead to different dynamic-multiscaling exponents, which are related to equal-time multiscaling exponents by different classes of bridge relations; for a representative value of the friction we verify that, given our error bars, these bridge relations hold.     

Interactions of Nile Blue with Micelles, Reverse Micelles and a Genomic DNA

In this contribution we report studies on the nature of binding of a small ligand/drug Nile blue (NB) with sodium dodecyl sulfate (SDS) micelles, bis-(2-ethylehexyl) sulfosuccinate (AOT)/isooctane reverse micelles (RM) and a genomic DNA extracted from Salmon sperm. With detailed steady state and picosecond resolved optical spectroscopic techniques, we examined the fluorescence quenching of the ligand upon complexation with the SDS monomers and DNA. Polarization analyzed picosecond-resolved fluorescence measurements reveal geometrical restriction on the probe in SDS micelles, AOT-RM and DNA. Steady state and time resolved studies on the probe in nanocages of AOT RM with various degrees of hydration (w₀) reveal the existence of NB as two distinct species namely, neutral and cationic. This study confirms that the emission of NB in aqueous micelles and DNA solution is due to the cationic form of the drug. Our experiments clearly identified non-specific electrostatic and intercalative modes of interaction of the probe with the DNA at lower and higher DNA concentrations respectively. The nature of binding of NB in presence of the DNA and SDS micelles reveals that the binding affinity of the probe is higher with the micelles than with the DNA. The complex rigidity of NB with DNA and its fluorescence quenching with DNA elucidate a strong recognition mechanism between NB and DNA.     

Bethe-Salpeter equations forq $$\bar q$$ andqqq systems in the instantaneous approximation

We consider a model for elastic scattering and inelastic diffractive production at high energy, which is inspired by Quantum Chromodynamics. The pomeron arises in our model from gluon exchange between quark constituents. The color-neutrality of each hadron implies strong cancellations among the gluon exchanges. Hence our model is “subtractive”, in contrast to the old “additive” quark model. The subtractive model provides a natural explanation for the large cross section which is observed for diffractive dissociation. We show that multiple gluon exchange contributes significantly, alongside two gluon exchange, in building the pomeron.     

On further application of r as a metric for validation of QSAR models

Validation is a crucial aspect for quantitative structure–activity relationship (QSAR) model development. External validation is considered, in general, as the most conclusive proof of predictive capacity of a QSAR model. In the absence of truly external data set, external validation is usually performed on test set compounds, which are members of the original data set but not used in model development exercise. In the case of small data sets, QSAR researchers experience problem in model development due to the fact that the developed models may be less reliable on account of the small number of training set compounds and such models may also show poor external predictability because the models may not have captured all necessary features required for the particular structure–activity relationships. The present paper attempts to show that ‘true r_(LOO)’ statistic calculated based on the model derived from the undivided data set with application of variable selection strategy at each cycle of leave‐one‐out (LOO) validation may reflect external validation characteristics of the developed model thus obviating the requirement of splitting of the data set into training and test sets. This approach may be helpful in the case of small data sets as it uses all available data for model development and validation thus making the resulting model more reliable. Copyright © 2009 John Wiley & Sons, Ltd.     

Bioavailability studies of oral dosage forms containing levodopa and carbidopa using column-switching chromatography followed by electrochemical detection

A reliable multi-dimensional column chromatographic method employing amperometric detection using a carbon fibre microelectrode procedure was used for monitoring the plasma profiles and to evaluate the pharmacokinetics and bioavailability of levodopa (L-dopa) and carbidopa (C-dopa), after ingestion of oral formulations containing these drugs. The peak currents obtained for the different analytes were directly proportional to the analyte over the concentration range 0.02-4 micrograms ml-1. Using this method, the minimum detectable concentration was estimated to be 5 and 8 ng ml-1 for L-dopa and C-dopa, respectively. Recovery studies ranged from 93.83 to 89.76%, with a relative standard deviation of less than 7%. The study was carried out in two separate weeks on five healthy non-patient fasted male/female volunteers in the age range 20-37 years and weighing between 60 kg and 78 kg. The pharmacokinetic profile of two controlled-release products containing both L-dopa and C-dopa (Sinemet CR3 and CR4) was compared on the one hand and Sinemet conventional tablets on the other. The pharmacokinetic parameters, peak concentration (Cmax), the time taken to obtain this level (Tmax), elimination half-time T1/2, elimination rate constant (Kel), plasma level ratio, fluctuation index (FI) and the area under the time-concentration curve (AUC0-8), were investigated for each individual formulation. A comparison of the uptake of L-dopa from the conventional formulation showed that L-dopa entered the plasma and achieved peak levels higher than that of the controlled release formulations. However, it showed a much higher fluctuation index and the plasma concentrations were more stable with the controlled release formulations. The data also indicated a very low accumulation of both levodopa and carbidopa following repeated administration of the drugs, which was consistent with their relatively short half-lives (less than 2 h). In contrast, the half-life for the metabolite 3-orthomethyl dopa (3-OMD) is in the order of 13 h. As a result, there was an extensive accumulation of 3-OMD and its levels were significantly higher than those of levodopa or carbidopa upon repeated administration. Urine recoveries of the three analytes over one 8 h dosing interval showed that the majority of the excreted levodopa and carbidopa was recovered during the first 4 h, and there is proportionally greater excretion of the carbidopa dose than the levodopa dose.     

Natural Small Molecules in Gastrointestinal Tract and Associated Cancers: Molecular Insights and Targeted Therapies

Gastric cancer is one of the most common cancers of the gastrointestinal tract. Although surgery is the primary treatment, serious maladies that dissipate to other parts of the body may require chemotherapy. As there is no effective procedure to treat stomach cancer, natural small molecules are a current focus of research interest for the development of better therapeutics. Chemotherapy is usually used as a last resort for people with advanced stomach cancer. Anti-colon cancer chemotherapy has become increasingly effective due to drug resistance and sensitivity across a wide spectrum of drugs. Naturally-occurring substances have been widely acknowledged as an important project for discovering innovative medications, and many therapeutic pharmaceuticals are made from natural small molecules. Although the beneficial effects of natural products are as yet unknown, emerging data suggest that several natural small molecules could suppress the progression of stomach cancer. Therefore, the underlying mechanism of natural small molecules for pathways that are directly involved in the pathogenesis of cancerous diseases is reviewed in this article. Chemotherapy and molecularly-targeted drugs can provide hope to colon cancer patients. New discoveries could help in the fight against cancer, and future stomach cancer therapies will probably include molecularly formulated drugs.     

Halogen-containing tetrametallic aluminium alkoxides

New halogen-containing tetrametallic aluminium alkoxides of formula [Al{(mu-OEt)2AlMeCl}3] ( 2-cis; 2-trans), and [Al{(mu-OEt)2AlBr2}3] ( 4), have been synthesized by combining Al(OEt)3 and Me2AlCl (for 2) or EtAlBr2 (for 4). They were fully characterized by (1H, 27Al) NMR, IR, mp, elemental analysis, and single-crystal X-ray diffractometry. The chloride analogue of 4, [Al{(mu-OEt)2AlCl2}3] ( 3), prepared previously using a different route, was also prepared here by combining Al(OEt)3 and EtAlCl2.     

Dispersion and reactivity of copper catalysts supported on Al2O3-ZrO2

A series of CuO/Al(2)O(3)-ZrO(2) catalysts with Cu loadings varying from 1.0 to 20 wt % were prepared and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of CO(2) and NH(3), electron spin resonance (ESR), and Brunauer-Emmett-Teller surface area measurements. The dispersion and metal area of copper were determined by the N(2)O decomposition method. XRD results suggest that the copper oxide is present in a highly dispersed amorphous state at copper loadings < 10 wt % and as a crystalline CuO phase at higher Cu loadings. ESR results suggest the presence of two types of copper species on the Al(2)O(3)-ZrO(2) support. TPR results suggest well-dispersed copper oxide species at low Cu loadings and crystalline copper oxide species at high Cu loadings. Well-dispersed copper oxide species were reduced more easily than large copper oxide species by H(2). The results of CO(2) TPD suggest that the basicity of the catalysts was found to increase with an increase of copper loading up to 5.0 wt % and decreases with a further increase of copper loading. The results of NH(3) TPD suggest that the acidity of the catalysts was found to decrease with an increase of copper loading up to 5.0 wt % and increases with a further increase of copper loading. The catalytic properties were evaluated for the vapor-phase dehydrogenation of cyclohexanol to cyclohexanone and correlated with the results of CO(2) TPD measurements and the dispersion of Cu on the Al(2)O(3)-ZrO(2) support.     

Temperature-dependent solvation dynamics of water in sodium bis(2-ethylhexyl)sulfosuccinate/isooctane reverse micelles

In this paper, for the first time, we report a detailed study of the temperature-dependent solvation dynamics of a probe fluorophore, coumarin-500, in AOT/isooctane reverse micelles (RMs) with varying degrees of hydration (w0) of 5, 10, and 20 at four different temperatures, 293, 313, 328, and 343 K. The average solvation time constant becomes faster with the increase in w0 values at a particular temperature. The solvation dynamics of a RM with a fixed w0 value also becomes faster with the increase in temperature. The observed temperature-induced faster solvation dynamics is associated with a transition of bound- to free-type water molecules, and the corresponding activation energy value for the w0 = 5 system has been found to be 3.4 kcal mol-1, whereas for the latter two systems, it is approximately 5 kcal mol-1. Dynamic light scattering measurements indicate an insignificant change in size with temperature for RMs with w0 = 5 and 10, whereas for a w0 = 20 system, the hydrodynamic diameter increases with temperature. Time-resolved fluorescence anisotropy studies reveal a decrease in the rotational restriction on the probe with increasing temperature for all systems. Wobbling-in-cone analysis of the anisotropy data also supports this finding.