The evolution model of the rayleigh-taylor instability development

The turbulent mixing (TM) of different DT-fuel areas (cold with hot) and of DT-fuel with ablator is one of the deciding factors, determining the neutron yield from compressing laser fusion, and, more generally, inertial confinement fusion (ICF) targets. A lower than predicted neutron yield gained in experiments is not studied comprehensively, but can be caused by the mixing processes. A study of mixing in the ICF problem is complicated by density gradients, spherical convergence, compression, etc., so we suppose the fundamental understanding of the mixing processes must be acquired first in the problem of classical Rayleigh-Taylor (RT) instability in plain geometry. In our work we present results, obtained by the supercomputer numerical modeling of RT-induced TM processes with different initial conditions in 2D and 3D geometries conditions on a high-resolution meshes. For analysis of the modeling results we use an evolutionary model of singular perturbation development, including linear and non-linear stages. This theoretical approach allows us to obtain highly detailed view of the mixing zone evolution along with possibility to trace the initial conditions influence on the mixing late stages.     

On the computational utility of posynomial geometric programming solution methods

Ten codes or code variants were used to solve the five equivalent posynomial GP problem formulations. Four of these codes were general NLP codes; six were specialized GP codes. A total of forty-two test problems was solved with up to twenty randomly generated starting points per problem. The convex primal formulation is shown to be intrinsically easiest to solve. The general purpose GRG code called OPT appears to be the most efficient code for GP problem solution. The reputed superiority of the specialized GP codes GGP and GPKTC appears to be largely due to the fact that these codes solve the convex primal formulation. The dual approaches are only likely to be competitive for small degree of difficulty, tightly constrained problems.     

Four-level orthogonal array design as a chemometric approach to the optimization of polarographic reaction system for phosphorus determination

It is the purpose of the present work to provide information on the four-level orthogonal array design and data analysis for the optimization of analytical procedures. In the theoretical part, the construction and characteristics of the OA(16)(4(5)) matrix is described in detail, followed by the data analysis strategy, in which the significance of the different factors is quantitatively evaluated by an analysis of variance (ANOVA) method including per cent contribution, and the difference among four levels for each factor is determined by Duncan's multiple F test. Furthermore, a third-order polynomial model representing response surface is established to estimate the effects for the factors with significant influences. In the application part, the proposed four-level orthogonal array design and data analysis method were applied to optimize polarographic reaction system for phosphorus determination. By conducting 16 preplanned experiments that span the maximum working range of the system, the best experimental conditions for achieving the largest response can be obtained. The expected value for each experimental trial calculated by the third-order regression equation established is in good agreement with the corresponding experimental value. To confirm the validity of the optimization procedure, additional experiments using the recommended conditions were performed. The results demonstrate that satisfactory results can be acquired. Therefore, the proposed four-level orthogonal array design as a chemometric approach to optimize the polarographic reaction system for phosphorus determination is rather efficient and effective.     

Determination of 19-norandrosterone in human urine by isotope dilution gas chromatography-high resolution mass spectrometry

An accurate and precise method for the determination of total 19-norandrosterone (19-NA), a major metabolite of nandrolone, in human urine was developed based on isotope dilution gas chromatography-high resolution mass spectrometry (ID GC-HRMS). The 19-NA glucuronide, together with deuterated 19-NA (d₄-19-NA) (as the internal standard, IS), was subjected to enzymatic hydrolysis using β-glucuronidase, followed by solid phase extraction (XtractT, mixed-mode column) and liquid–liquid extraction cleanup. The native and deuterated analogues of 19-NA were then derivatised to the corresponding bis(trimethylsilyl) derivatives using N-methyl-N-trimethylsilyltrifluoroacteamide (MSTFA):NH₄I:Dithiothretitol (1,000:2:3 w/w). Identification was achieved under selected ion monitoring of the respective trimethylsilyl derivatives at ion masses m/z 405.26450 and 420.28800 for 19-NA and m/z 409.28920 and 424.31270 for d₄-19-NA within the specific time windows (±1% of the relative retention time to the calibration standard). A linear calibration curve (r ² > 0.9995) was obtained based on seven calibration points (five replicates at each level) in the range 0.05–10 ng/g. The detection limit for 19-NA was found to be 4 pg/g. The method has been applied for the determination of 19-NA by fortifying 19-NA glucuronide at three concentrations (0.2, 2.1 and 7.2 ng/g) in blank urine samples with excellent accuracy and reproducibility. To circumvent the iterative process of exacting matching, a single-point calibration procedure was adopted, where the acceptance criteria for the isotopic ratio in the sample (RF _s) and calibration blends (RF _c) was set close to unity (0.95–1.05). This method was successfully applied in a pilot inter-comparison study, with results in good agreement with the fortified value and other participants’ results (relative standard deviation, RSD < 2.0%) with an expanded relative uncertainty (coverage factor of 2 at 95% confidence level) of 4.7%. It was found in our determination that the main contributors to the uncertainty budget originated from the measurements of the purity of the reference material and the response factor of the calibration standard.     

Comparison of four microwave digestion methods for the determination of selenium in fish tissue by using hydride generation atomic absorption spectrometry

Four microwave digestion methods of fish tissue for selenium determination by hydride generation atomic absorption spectrometry were compared, in which potassium hexacyanoferrate(III) was chosen as a masking agent for eliminating matrix interferences. The results showed that the methods employing HNO(3)/H(2)O(2), HNO(3)/K(2)S(2)O(8)/H(2)O(2) and HNO(3)/H(3)PO(4)/H(2)O(2) digestion media were unreliable. However, the decomposition using the digestion media of HNO(3)/H(2)SO(4)/H(2)O(2) enabled adequate digestion of fish tissue and retention of selenium in a state amenable for determination. Therefore, the digestion procedures with HNO(3)/H(2)SO(4)/H(2)O(2) media are proposed for the determination of selenium in fish tissue by hydride generation atomic absorption spectrometry. The recoveries of the spiked samples investigated ranged from 90 to 102%. The result obtained from analyzing the NIES CRM No. 6 mussel was in good agreement with the reference value (reference value: 1.5 mug/g; found: 1.45 +/- 0.05 mug/g). The limit of detection for selenium was 0.03 mug/g dry mass for a 100 mg sample. The contents of selenium in local fish species investigated ranged from 0.49 to 2.90 mug/g, and the relative standard deviation for the determination of selenium was less than 8%.     

The structure, Raman spectra, and force fields of methylbromosilanes CH3SiClnBr3−n (n = 0, 1, 2)

The laser-excited Raman spectra of liquid CH₃SiCl_nBr_3?n (n = 0, 1, 2) were studied. Quantumchemical calculations of these substances with geometry optimization were performed to determine their harmonic force fields and vibrational frequencies. The calculations were made using the HF/6-31G* and HF/6-311++G** approximations and density functional theory at the B3LYP/6-31G* and B3LYP/6-311++G** levels. An interpretation of the spectra was suggested and the calculated force fields were discussed in comparison with the data on related compounds.     

Molecular interfacial engineering of adhesion between polyfluorene and indium–tin oxide

A self-assembly monolayer (SAM) selected from alkyl- and phenyl-silanes was inserted between polyfluorene (PFO) and indium–tin oxide (ITO). The relative changes in adhesion energy of PFO/SAM/ITO were semi-quantitatively measured. These relative changes are calculated by dividing the gains in adhesion energy by the adhesion energy of PFO/ITO with no SAM. The values for five alkyl-silanes with varying chain lengths are in the range of 1.0±0.2 to 1.8±0.5, and those for five selected phenyl-silanes are 1.8±0.5 to 4.1±1.1. Phenyl-silanes with a unit larger than that of benzene, together with appropriate tail-group functionality, give the best enhancement in adhesion. PACS 61.30.Hn; 61.82.Pv; 62.20.-x; 68.35.-p; 68.35.Np