Formation of nickel coatings by electrochemical deposition under X-ray irradiation

The influence of X-ray irradiation on the formation of nickel electroplating coatings is studied. The regularities of the nickel electrocrystallization kinetics under X-ray irradiation of different wavelengths, such as the increase in the deposition rate and metal output by the current, are revealed. The features of the structuring of the nickel electroplating coatings under irradiation are revealed. The influence of X-ray irradiation on microhardness, microdeformations, and dislocation structure is estimated. An increase in microhardness and a decrease in microdeformations of nickel coatings with the growth of the radiation energy are established.     

Stereoselective synthesis of alpha-C-Substituted 1,4-dideoxy-1,4-imino-D-galactitols. Toward original UDP-Galf mimics via cross-metathesis

[reaction: see text] Various alpha-C-substituted 1,4-dideoxy-1,4-imino-d-galactitols were prepared efficiently from 1-O-acetyl-2,3,5,6-tetra-O-benzyl-d-glucofuranose by a four-step sequence involving as the key step the highly syn-selective TMSOTf-catalyzed addition of silylated nucleophiles to a glycofuranosylamine. Cross-metathesis of the alpha-C-allylated iminogalactofuranose derivative with an original uridin-5'-yl vinylphosphonate led to novel UDP-galactofuranose mimics. Such compounds are of interest as potential inhibitors of the mycobacterial galactan biosynthesis pathway.     

Characterisation of ethoxylated fatty chains of anionic surfactants and determination of residual ethoxylated fatty alcohols

Bachus et al. [1] recently described a new derivatisation method using 2-furoyl chloride for the characterisation of mixtures of polyethoxylated alcohols and their corresponding sulfates. This paper deals with the control of the derivatisation steps; hydrolysis and extraction conditions were optimised. The method is extended to the characterisation of alkyl sulfosuccinates, alkyl sulfoacetates and alkyl phosphates and to the analysis of residual polyethoxylated alcohols in surfactants. Extraction of non-ionic compounds using solid-phase extraction cartridges was performed before derivatisation. Residual amounts of alcohol were determined in five commercial anionic surfactants. Moreover, direct derivatisation without preliminary SPE in the same anionic surfactants proved to be efficient for dry samples.     

Molar absorptivities of 2,4-D, cymoxanil, fenpropidin, isoproturon and pyrimethanil in aqueous solution in the near-UV

The absorption spectra of five pesticides, namely 2,4-dichloro-phenoxy acetic acid (2,4-D), cymoxanil, fenpropidin, isoproturon and pyrimethanil, have been measured in aqueous solution using a set-up consisting of two parallel absorption cells coupled to a CCD detector. The absolute values of their molar absorptivity coefficients epsilon were determined in the wavelength-range 240-344 nm with a deuterium-lamp at room temperature (298+/-2 K). Using the Beer-Lambert law, values of epsilon were also determined at 253.7 nm with a Hg-Lamp: epsilon = 145+/-14 for 2,4-D, epsilon = 7940+/-920 for cymoxanil, epsilon = 196+/-14 for fenpropidin, epsilon = 7330+/-880 for isoproturon, epsilon = 13200+/-1400 for pyrimethanil (in units of M(-1) cm(-1)). The quoted errors correspond to 2 sigma obtained from the least square fit analysis and the estimated systematic error of 5% due to the uncertainties in aqueous concentrations. For all the studied compounds, the absorbances measured were lower than 2.3 and did not exhibit any deviation from the Beer-Lambert's law. Our experimental data are discussed and compared to UV spectra of similar molecules when such data were available in the literature. Based on their UV spectra and the calculated fractions of these pesticides in the aqueous phase, their direct photolysis under sunlight environment could occur, except may be for fenpropidin, either in water surfaces or in aqueous droplets contained in the atmospheric clouds.     

TD-DFT investigation of the UV spectra of pyranone derivatives

The UV absorption spectra of more than 80 substituted coumarins and chromones have been investigated with the PCM-TD-DFT theoretical scheme using three hybrid functionals (O3LYP, B3LYP, and PBE0) and taking into account methanol or ethanol solvation effects. For most of the studied derivatives, there are at least two allowed excited states presenting a strong oscillator strength in the UV region. The first allowed excitation is associated to a HOMO-LUMO transition whereas the second corresponds to a transition from the HOMO-1 to the LUMO. Both involve a charge transfer from the benzenic cycle to the pyranone moiety. Statistically treating the PBE0 results allows a prediction of the lambda(max) with small standard deviations: in methanol, 6 nm (0.07 eV) for the first excitation (lambda(max)(1)) and 5 nm (0.08 eV) for the second one (lambda(max)(2)), whereas in ethanol 6 nm (0.08 eV) for (lambda(max)(1)) and 6 nm (0.13 eV) for (lambda(max)(2)).     

Cooper instability of nonlocal spin polarons in the CuO2 plane of high-temperature superconductors

JETP Letters - The energy structure of nonlocal spin polarons has been obtained for the real structure of the CuO2 plane of cuprate superconductors in the ensemble of such Fermi quasiparticles. A...     

Accurate standard‐based quantification of X‐ray fluorescence data using metal‐contaminated plant tissue

Quantitative X‐ray fluorescence (XRF) measurements have been conducted on naturally lead‐contaminated samples. The calibration procedure using the ratio of fluorescence to Compton scattered radiation was investigated using Monte Carlo simulation. Experimental results with low‐energy photons (14 keV) and simulations show a very good linearity of the fluorescence to Compton ratio as a function of metal concentration. Lead (Pb), iron (Fe) and zinc (Zn) are measured in samples of Phaseolus vulgaris (bean seeds) that have been grown using a nutritive solution with different Pb dopings. Naturally contaminated samples are thus obtained. The calibration must be done for fixed conditions of X‐ray energy and scattering angle, while X‐ray beam intensity and detector to sample distance can change from one sample to another. Simulation allows to evaluate the matrix effect on the calibration curve, and shows that linearity is preserved even in the presence of other heavy elements in the fluorescence spectrum. However, calibration must be done using samples with similar matrix as it affects the slope of the curve. Copyright © 2010 John Wiley & Sons, Ltd.     

Properties of the heavy-fermion spectrum in the canted phase of antiferromagnetic intermetallides

We study the effect of the magnetic-field-induced canting of magnetic sublattices on the energy structure of heavy fermion quasiparticles in intermetallides with antiferromagnetic-type ordering. We work in the framework of an effective Hamiltonian of the periodic Anderson model in the regime of strong electron correlations. With the virtual transfers into high-energy double states taken into account, this Hamiltonian involves exchange interactions between spin moments of the f ions and the s-f-exchange coupling between the two subsystems. For a noncollinear problem geometry, we introduce a unitary transformation that allows reducing an eighth-order equation for the spectrum of heavy fermions to two fourth-order equations. We show that the quasimomentum dependence of the heavy-fermion energy changes qualitatively under the transition from the antiferromagnetic phase to a phase with a considerable canting angle emerging in an external magnetic field.     

Assessing induced folding of an intrinsically disordered protein by site-directed spin-labeling electron paramagnetic resonance spectroscopy

We used site-directed spin-labeling electron paramagnetic resonance (EPR) spectroscopy to study the induced folding of the intrinsically disordered C-terminal domain of measles virus nucleoprotein (N(TAIL)). Four single-site N(TAIL) mutants (S407C, S488C, L496C, and V517C), located in three conserved regions, were prepared and labeled with a nitroxide paramagnetic probe. We could monitor the gain of rigidity that N(TAIL) undergoes in the presence of either the secondary structure stabilizer 2,2,2-trifluoroethanol (TFE) or one of its physiological partners, namely, the C-terminal domain (XD) of the viral phosphoprotein. The mobility of the spin label grafted at positions 488, 496, and 517 was significantly reduced upon addition of XD, contrary to that of the spin label bound to position 407, which was unaffected. Furthermore, the EPR spectra of spin-labeled S488C and L496C bound to XD in the presence of 30% sucrose are indicative of the formation of an alpha-helix in the proximity of the spin labels. Such an alpha-helix had been already identified by previous biochemical and structural studies. Using TFE we unveiled a previously undetected structural propensity within the N-terminal region of N(TAIL) and showed that its C-terminal region "resists" gaining structure even at high TFE concentrations. Finally, we for the first time showed the reversibility of the induced folding process that N(TAIL) undergoes in the presence of XD. These results highlight the suitability of site-directed spin-labeling EPR spectroscopy to identify protein regions involved in binding and folding events, while providing insights at the residue level.     

Malmquist indexes with quasi-fixed inputs: an application to school districts in Québec

We present a space and time allocation problem that arises in assembly halls producing large building blocks (namely, a shipyard which assembles prefabricated keel elements). The building blocks are very large, and, once a block is placed in the hall, it cannot be moved until all assembly operations on this block are complete. Each block must be processed during a predetermined time window. The objective is to maximize the number of building blocks produced in the hall.