Turbulent transport in tokamak plasmas with rotational shear

Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E×B shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcations in the E×B shear. The critical temperature gradient for the onset of turbulence increases with flow shear at low flow shears; at higher flow shears, the dependence of heat flux on temperature gradient becomes less stiff. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity.     

Novel mesogenic asymmetric diacylhydrazines: synthesis,mesomorphic behaviour and X‐ray study

The synthesis and liquid crystalline properties of a new series of diacylhydrazine derivatives (2a–g) are reported. All compounds of series 2 exhibit a smectic C (SmC) phase. The first homologues (2a, 2b) display a monotropic SmC mesophase, whereas the highest homologues (2c–g) exhibit an enantiotropic SmC phase. The liquid crystalline properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X‐ray measurements.     

Novel amides and Schiff's bases derived from 1,3,4-oxadiazole derivatives: synthesis and mesomorphic behaviour

The synthesis and liquid crystalline properties of novel achiral amides (Ia–g, IIa–g and IVa,b), achiral Schiff's bases (IIIa–g and Va–g), chiral amides (VI, VII) and chiral Schiff's bases (VIII–XI) incorporating a 1,3,4-oxadiazole ring are reported. All amides of the series I and II display an enantiotropic smectic A phase. The amide IVa,b did not show mesomorphic properties. Amides of the series Ia–g and IIa–g contain a flexible n-tetradecylthio chain, the other terminal substituent is an n-alkoxy chain and n-alkyl chain, respectively (n?=?4–10) and the 1,3,4-oxadiazole is in the terminal rigid core. Amides Ia–g have broader mesomorphic range and higher thermal stability than the corresponding amides IIa–g. Amides IVa,d contain the 1,3,4-oxadiazole ring in the centre of the rigid core and two flexible alkoxy chains as flexible terminal substituents. Thus, the mesomorphic properties are favoured if 1,3,4-oxadiazole is shifted to a terminal position of the rigid core. Schiff's bases IIIa–g display an enantiotropic dimorphism smectic C–smectic A. Schiff's bases IIIa–g have a broader mesomorphic range than the analogous amides Ia–g. Schiff's bases Va–g exhibit a dimorphism smectic A–nematic, and in contrast to this the analogous amide IVa,b did not show mesomorphism. The chiral amides VI and VII and chiral Schiff's bases X and XI did not show mesomorphic properties and only the chiral Schiff's bases VIII and IX display a chiral smectic C phase in a short mesomorphic range. A density functional theory theoretical study at the B3LYP/6–311++G(d,p) level was performed in order to analyse the structural features that must be related with the mesomorphic behaviour of the reported compounds.     

Top-down analysis of 30–80 kDa proteins by electron transfer dissociation time-of-flight mass spectrometry

Electron transfer dissociation (ETD)-based top-down mass spectrometry (MS) is the method of choice for in-depth structure characterization of large peptides, small- and medium-sized proteins, and non-covalent protein complexes. Here, we describe the performance of this approach for structural analysis of intact proteins as large as the 80 kDa serotransferrin. Current time-of-flight (TOF) MS technologies ensure adequate resolution and mass accuracy to simultaneously analyze intact 30–80 kDa protein ions and the complex mixture of their ETD product ions. Here, we show that ETD TOF MS is efficient and may provide extensive sequence information for unfolded and highly charged (around 1 charge/kDa) proteins of ～30 kDa and structural motifs embedded in larger proteins. Sequence regions protected by disulfide bonds within intact non-reduced proteins oftentimes remain uncharacterized due to the low efficiency of their fragmentation by ETD. For serotransferrin, reduction of S–S bonds leads to significantly varied ETD fragmentation pattern with higher sequence coverage of N- and C-terminal regions, providing a complementary structural information to top-down analysis of its oxidized form.

Positive numerical solution for a nonarbitrage liquidity model using nonstandard finite difference schemes

In this article, we construct a numerical method based on a nonstandard finite difference scheme to solve numerically a nonarbitrage liquidity model with observable parameters for derivatives. This nonlinear model considers that the parameters involved are observable from order book data. The proposed numerical method use a exact difference scheme in the linear convection‐reaction term, and the spatial derivative is approximated using a nonstandard finite difference scheme. It is shown that the proposed numerical scheme preserves the positivity as well as stability and consistence. To illustrate the accuracy of the method, the numerical results are compared with those produced by other methods. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 210‐221, 2014     

Mathematical analysis of a population model with an age–weight structured two-stage life history: asymptotic behavior of solutions

In this paper, we propose a model for the dynamics of a physiologically structured population of individuals whose life cycle is divided into two stages: the first stage is structured by the weight, while the second one is structured by the age, the exit from the first stage occurring when a threshold weight is attained. The model originates in a complex one dealing with a fish population and covers a large class of situations encompassing two-stage life histories with a different structuring variable for each state, one of its key features being that the maturation process is determined in terms of a weight threshold to be reached by individuals in the first stage. Mathematically, the model is based on the classical Lotka–MacKendrick linear model, which is reduced to a delayed renewal equation including a constant delay that can be viewed as the time spent by individuals in the first stage to reach the weight threshold. The influence of the growth rate and the maturation threshold on the long-term behavior of solutions is analyzed using Laplace transform methods.     

Development and validation of a high-performance thin-layer chromatographic method, with densitometry, for quantitative analysis of ketorolac tromethamine in human plasma

Ketorolac tromethamine is a potent nonsteroidal anti-inflammatory drug that is widely used in the treatment of moderate to severe pain. A new method was developed and validated for quantifying ketorolac (the free acid of the tromethamine salt) in human plasma by high-performance thin-layer chromatography. The stationary phase was silica gel 60, and the composition of the mobile phase was n-butanol-chloroform-acetic acid-ammonium hydroxide-water (9 + 3 + 5 + 1 + 2, v/v). The densitometric analysis of ketorolac was performed at 323 nm. The method was validated for precision (repeatability and reproducibility), accuracy, and sensitivity. Repeatability was 10.11% [coefficient of variation (CV)] and reproducibility was 12.18% (CV) as the maximum variation. Accuracy was determined at 3 different concentration levels, and results were within +/-15% of the predetermined range. Data were fitted by a linear mathematical function (linear regression). The calibration graph was linear in the range of 200-2000 ng/mL. Average recovery was 73.67%. The method proved to be accurate, precise, and sensitive for the ketorolac tromethamine quantification.     

Asymmetric nucleophilic monofluorobenzylation of carbonyl compounds: synthesis of enantiopure vic-fluorohydrins and α-fluorobenzylketones

Asymmetric nucleophilic monofluoroalkylation of a broad range of aldehydes with an α-fluoro-γ-sulfinylbenzyl carbanion takes place with complete control of the facial selectivity at the carbanion and good to high anti-diastereoselectivity to give easily separable mixtures of two optically pure 1,2-fluorohydrin derivatives (up to 24:1 anti/syn). Separation and removal of the p-tolylsulfinyl group with tBuLi provides enantiomerically pure anti-1,2-disubstituted-1,2-fluorohydrins, whereas α-fluorobenzylketones can be obtained by desulfinylation of the mixture followed by pyridinium chlorochromate oxidation (one-pot process).     

Thermal,tensile and rheological properties of linear low density polyethylene (LLDPE) irradiated by gamma-ray in different atmospheres

The aim of this paper is to investigate structural changes of linear low density polyethylene (LLDPE) modified by ionizing radiation (gamma rays) in different atmospheres. The gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical–chemical and mechanical properties. Gamma irradiation originates free radicals which can induce chain scission or recombination, providing its annihilation, branching or crosslinking. This polymer was irradiated with gamma source of ⁶⁰Co at doses of 5, 10, 20, 50 or 100 kGy at a dose rate of 5 kGy/h. The changes in molecular structure of LLDPE, after gamma irradiations were evaluated using thermogravimetric analyzer (TGA) and tensile machine and oscillatory rheology. The results showed the variations of the properties depending on the dose at each atmosphere.