Sur les surfaces lisses de ℙ4

Sans résuméEspace projectif sur un corps algébriquement clos de caractéristique zéro     

Automatic analysis of multiplex ligation-dependent probe amplification products (exemplified by a commercial kit for prenatal aneuploidy detection)

For use in routine prenatal diagnostics, we developed software and methods for automatic aneuploidy detection based on a commercial multiplex ligation-dependent probe amplification (MLPA) kit. Software and methods ensure a reliable, objective, and fast workflow, and may be applied to other types of MLPA kits. Following CE of MLPA amplification products, the software automatically identified the peak area for each probe, normalized it in relation to the neighboring peak areas of the test sample, computed the ratio relative to a reference created from normal samples, and compensated the ratio for a side effect of the normalization procedure that scaled all chromosomally normal DNA peak areas slightly up or down depending on the kind of aneuploidy present. For the chromosomes 13, 18, 21, X, and Y, probe reliability weighted mean ratio values and corresponding SDs were calculated, and the significance for being outside a reference interval around ratio 1.0 was tested. p < or = 1% suggested aneuploidy and 1 < p < or = 5% suggested potential aneuploidy. Individual peaks, where the normalized area was situated more than 4 SD from the corresponding reference, suggested possible partial deletion or gain. Sample quality was automatically assessed. Control probes were not required. Having used the software and methods for two years, we conclude that a reliable, objective, and fast workflow is obtained.     

The charge delocalised beta,beta-carotene dication--preparation, structure elucidation by NMR and reactions with nucleophiles

The reaction between beta,beta-carotene and BF3-etherates has been investigated, leading to structural elucidation of the blue product, formed in appropriate organic solvents, as a symmetrical charge delocalised dication (lambda(max) 985 nm at room temperature in CHCl3) with considerable stability. The reaction, monitored by EPR studies at -25 degrees C, occurred via free radical intermediates. A C40H56BF3 intermediate was captured by EIMS. The detailed structure of the dication was established by COSY, HSQC, HMBC and 1D and 2D ROESY NMR techniques (600 MHz, CDCl3, -20 degrees C) leading to complete assignments of 1H and 13C chemical shifts and 3J(H,H) coupling constants. The effects of the two delocalised charges on chemical shift (charge distribution) and bond distance (3J(H,H)) were considered. The results are consistent with charge delocalisation mainly in the C-5-C-9 and C-5'-C-9' regions and with bond inversion to retro shifted double bonds in the central C-13-C-13' region. A convention for denoting the charge delocalisation and bond types is presented. The experimental results are discussed relative to previous theoretical calculations of the beta,beta-carotene dication structure. (All-E) and (15-Z)-beta,beta-carotene provided the same dication. The NIR spectra and stability of dications prepared in the same manner from the related carotenes 20,20'-dinor-beta,beta-carotene, heptapreno-beta,beta-carotene and nonapreno-beta,beta-carotene were examined for comparison. Reactions of the beta,beta-carotene dication with selected nucleophiles provided products including isocryptoxanthin, isocarotene and mutatochrome with H2O as nucleophile, and isocryptoxanthin methyl ether, 8-methoxy-7,8-dihydro-beta,beta-carotene and isocarotene with CH3ONa as nucleophile. The formation of these products is rationalised from the structure assigned to the dication.     

Individual strings of conducting carbon cones and discs in a polymer matrix: Electric field‐induced alignment and their use as a strain sensor

We demonstrate micromechanical strain sensors with integrated readout based on carbon nanocones and discs (CNCs) which are aligned into a string‐like formation using an alternating electric field and studied by AC impedance spectroscopy and electromechanical methods. The CNC particles are first dispersed into a polymer matrix with a particle fraction of 0.1 vol %. This value is well below the percolation threshold (～ 2 vol %), which suppresses particle aggregation and facilitates transparency allowing the use of an UV‐curable polymer. Alignment was carried out with a 1 kHz, 4 kV/cm electric field and is a consequence of dielectrophoretic effect. It develops in minutes and makes the initially insulating, nonaligned material conductive. This is followed by UV curing of the polymer matrix, which renders a solid state device. The stretching of the aligned strings in the cured polymer leads to a reversible piezoresistive effect, and a gauge factor of about 50 is observed. This is in a sharp contrast to CNC films with particle fraction above percolation threshold (13 vol %), which are conductive but not sensitive to stretching. The strings are Ohmic in nature and moreover show higher DC conductivity (22–500 S/m) compared to identically prepared carbon black strings (1–22 S/m). © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Nucleophilic reactions of charge delocalised carotenoid mono- and dications

In the present study insight was gained on the larger complexity of cationic mixtures of diaryl (phi,phi-carotene, isorenieratene) and aliphatic (psi,psi-carotene, lycopene) carotenes, prepared by reaction with BF3-etherate, compared with beta,beta-carotene. Chemical reactions of the mono- and dications prepared in situ from the allylic carotenols beta,beta-caroten-4-ol (isocryptoxanthin) and beta,beta-carotene-4,4'-diol (isozeaxanthin), and from isorenieratene and lycopene were investigated using selected O, N and S nucleophiles; water, methanol, azide and thioacetate. In total 22, including 18 new, neutral carotenoid products were isolated and identified by VIS, MS and NMR (in part) spectroscopy. Their structures were compatible with the structures of the cationic intermediates. The formal addition of hydride to the various dications, required to rationalise minor reaction products, is discussed in terms of more likely hydrogen radical or proton transfer in cationic reactions. Extensive E/Z isomerisation was observed for all quenching products. The potential use of carotenoid cations for the synthesis of 4,(4')-substituted beta,beta-carotenes and 7-oxabicyclo[2,2,1]heptane derivatives is discussed.     

Gas diffusion in zeolite beds: PFG NMR evidence for different tortuosity factors in the Knudsen and bulk regimes

We present molecular dynamics simulations in the micro-canonical ensemble of a Lennard-Jones model of nitrogen confined in realistic models for saccharose-based carbons developed in our previous work. We calculate the velocity autocorrelation function and mean-squared displacement, and the self-diffusivities from the latter. We observe that the self-diffusivity increases with temperature and exhibits a maximum with loading or adsorbate density. To the best of our knowledge, a maximum in self-diffusivities has not been observed in molecular dynamics simulations of fluids confined in slit pores.Received: 1 January 2003, Published online: 30 October 2003PACS: 61.43.Gt Powders, porous materials - 68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation - 82.75.Fq Synthesis, structure determination, structure modeling     

Gas diffusion in zeolite beds: PFG NMR evidence for different tortuosity factors in the Knudsen and bulk regimes

Self-diffusion of ethane in beds of zeolite NaX is studied using Pulsed Field Gradient (PFG) NMR. The ethane diffusivities were measured for displacements, which are orders of magnitude larger than the size of individual crystals. These diffusivities were compared with those, calculated using simple gas kinetic theory. The results of the comparison indicate that for the same bed of NaX crystals the apparent tortuosity factor in the Knudsen regime ( i.e. when molecule-solid collisions dominate) is significantly larger than that in the bulk regime ( i.e. when molecule-molecule collisions dominate). This finding is attributed to the more pronounced geometrical trapping by the pore structure of the zeolite bed in the Knudsen than in the bulk regime.     

External quality assurance of test requesting and test interpretation

The ultimate product of the clinical laboratory is not a number, but an advice. To what quality standards should this advice live up to? In external quality assurance for primary health care in Norway, case histories are mailed together with the analytical quality control material. The analytical result of the control material is used in the case history. The feedback reports discuss clinical guidelines as well as the influence of analytical variation on clinical decision-making.