Thermopower calculation for anisotropic normal metals

The thermopower of the divalent normal metals has been calculated in a single OPW approximation, using pseudopotential form factors and a realistic phonon spectra. The calculation emphases the contribution of the phonon drag term. The results are compared with experiments and a simple interpretation is suggested for the evolution of the thermopower anisotropy in the series Be, Mg, Zn and Cd.     

Comparison of various analytical techniques for homogeneity test of candidate standard reference materials

Three different analytical techniques: INAA, X-ray fluorescence and atomic absorption spectrometry were used at the JRC Ispra to test the total homogeneity of four candidate botanic reference materials supplied by NBS. Without adopting complex statistical formalities a “degree of inhomogeneity” was estimated in each sample for the elements considered in the test. The operating procedures and the results obtained are presented and discussed.     

X-Ray spectrographic determination of tantalum in niobium by electron excitation

An X-ray method is proposed for the determination of tantalum in niobium by direct electron excitation. The optimum excitation conditions for greatest sensitivity are given. The limit of detection for a counting time of 400 sec was found to be 20 p.p.m. The relative standard deviation in the 0.4–5% concentration range was ±2%.     

NMR analysis of surfaces and interfaces in 2-nm CdSe

Solid-state NMR analysis on wurtzite 2-nm hexadecylamine-capped CdSe nanocrystals (CdSe-HDA) provides evidence of discrete nanoparticle reconstruction within the Se sublattice of the nanomaterial. The cadmium and selenium atoms are probed with (1)H-(113)Cd and (1)H-(77)Se cross-polarization magic angle spinning (MAS) experiments, which demonstrate five ordered selenium sites in the nanoparticle that can be assigned to contributions arising from different surface sites and a selenium site one layer down from the surface. Intriguingly, in these materials both HDA and thiophenol are observed to selectively bind to specific sites on the nanoparticle surface. 2D heteronuclear chemical shift correlation (HETCOR) experiments provide evidence for thiophenol selectively binding at surface vacancies. Analysis of the NMR provides a model of a 2-nm CdSe-HDA molecular surface.     

An exact algorithm for side-chain placement in protein design

Computational protein design aims at constructing novel or improved functions on the structure of a given protein backbone and has important applications in the pharmaceutical and biotechnical industry. The underlying combinatorial side-chain placement (SCP) problem consists of choosing a SCP for each residue position such that the resulting overall energy is minimum. The choice of the side-chain then also determines the amino acid for this position. Many algorithms for this NP{\mathcal{NP}}-hard problem have been proposed in the context of homology modeling, which, however, reach their limits when faced with large protein design instances. In this paper, we propose a new exact method for the SCP problem that works well even for large instance sizes as they appear in protein design. Our main contribution is a dedicated branch-and-bound algorithm that combines tight upper and lower bounds resulting from a novel Lagrangian relaxation approach for SCP. Our experimental results show that our method outperforms alternative state-of-the-art exact approaches and makes it possible to optimally solve large protein design instances routinely.     

Detecting outlying samples in a parallel factor analysis model

To explore multi-way data, different methods have been proposed. Here, we study the popular PARAFAC (Parallel factor analysis) model, which expresses multi-way data in a more compact way, without ignoring the underlying complex structure. To estimate the score and loading matrices, an alternating least squares procedure is typically used. It is however well known that least squares techniques suffer from outlying observations, making the models useless when outliers are present in the data. In this paper, we present a robust PARAFAC method. Essentially, it searches for an outlier-free subset of the data, on which we can then perform the classical PARAFAC algorithm. An outlier map is constructed to identify outliers. Simulations and examples show the robustness of our approach.     

Decarboxylation oxydante des acides carboxyliques aliphatiques par un systeme cuivre(i)/oxygene.

A new oxidative decarboxylation reaction converts carboxylic acids 1 or 2 (Z = OH) to the corresponding carbonyl compounds 3, in the presence of oxygen and catalytic amounts of copper(I)probably via transient copper(III) carboxylates.     

4f–3d exchange coupling in Gd/X/Co (X=Pt, Cr) multilayers

We have studied the interlayer exchange coupling between Gd and Co through Pt and Cr spacers in a series of multilayers. Magnetization curves have been analyzed with a model, taking into account bilinear and biquadratic interlayer exchange couplings between Gd and Co. The interlayer exchange coupling constants have been determined as a function of the Pt or Cr spacer layer thickness.     

Comparison of liquid-liquid extraction with headspace methods for the characterization of volatile fractions of commercial hydrolats from typically Mediterranean species

Chemical composition of volatile fractions of nine commercial hydrolats and corresponding essential oils obtained using an industrial process were studied. The hydrolat volatile fractions were reported for the first time. A comparative study of those obtained, on the one hand, by liquid-liquid extraction (LLE) and, on the other hand, using five solid-phase microextraction (SPME) fibers and also purge-and-trap-automatic thermal desorption (P&T-ATD) was conducted with analysis performed by GC and GC/MS. The use of various techniques has resulted in a change of chromatographic profile of the hydrolat volatile fractions. Quantitative differences were established between chemical compositions of headspace and those obtained by a conventional method (LLE). Statistical analyses were carried out to summarize the results.