Leek odor analysis by gas chromatography and identification of the most active substance for the leek moth,Acrolepiopsis assectella

When crushed, the leek,Allium porrum emits propyl propanethiosulfinate. The unstable thiosulfinate decomposes during GC analysis in numerous compounds, except on very short columns. The propyl propanethiosulfmate is the most attractive substance for the leek moth,Acrolepiopsis assectella. This thiosulfinate is not active onPlutella xylostella orPlodia interpunctella and seems to be repulsive onEphestia kuehniella.     

Skin optics

Quantitative dosimetry in the treatment of skin disorders with (laser) light requires information on propagation of light in the skin related to the optical properties of the individual skin layers. This involves the solution of the integro-differential equation of radiative transfer in a model representing skin geometry, as well as experimental methods to determine the optical properties of each skin layer. These activities are unified under the name skin optics. This paper first reviews the current status of tissue optics, distinguishing between the cases of: dominant absorption, dominant scattering, and scattering about equal to absorption. Then, previously published data as well as some current unpublished data on (human) stratum corneum, epidermis and dermis, have been collected and/or (re)analyzed in terms of absorption coefficient, scattering coefficient, and anisotropy factor of scattering. The results are that the individual skin layers show strongly forward scattering (anisotropy factors between 0.7 and 0.9). The absorption and scattering data show that for all wavelengths considered scattering is much more important than absorption. Under such circumstances, solutions to the transport equation for a multilayer skin model and finite beam laser irradiation are currently not yet available. Hence, any quantitative dosimetry for skin treated with (laser) light is currently lacking.     

High index microlenses for GaAlAs laser-fibre coupling

The best compromise between coupling efficiency, accuracy of positioning and reproducibility has been obtained for a high index hemispherical lens melted on the tip of an intermediate fibre between the GaAlAs laser and the transmission fibre. The letter describes the lens fabrication technique and gives various experimental results of coupling efficiencies and mechanical tolerances.     

Confrontation Vurpillot-Gibson: Recension du Livre de Monde Visuel du Jeune Enfant par Elaine Vurpillot.

Reviews the book, The Visual World of the Child by Elaine Vurpillot (1972). By reading this work in which Vurpillot approaches, by the genetic method, the problem of the perceptive conduits of identification and differentiation, it is difficult to envision a confrontation between this new approach and that of Eleanor Gibson (1969). It is done from a point of view of comparison which the work of Vurpillot will be analyzed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sur l'existence de phases ternaires hydrogenees BeP2−xHy

The phosphidation of beryllium in the presence of traces of hydrogen leads to non stoichiometric ternary phases BeP_2?xH_y. The stoichiometric diphosphide BeP₂ cannot be obtained. The hydrogenated phases are black and non hygroscopic. The structural study with X rays diffraction, neutrons diffraction, electronic microdiffraction, as well as the crystallographic data from single crystal, provide evidence for a quadratic cell with $\text{a}\text{= 7,08}\text{A}\text{?}$ & $\text{c}\text{= 30,12}\text{A}\text{?}$. The stacking is diamond type when considering all the atoms : Be, P and H.     

Evaluation of the termination mode in the radical polymerization of 2,2,2‐trifluoroethyl α‐fluoroacrylate

The mode of termination of 2,2,2‐trifluoroethyl α‐fluoroacrylate (FATRIFE) in radical polymerization was studied, and only termination by recombination occurred, which led to telechelic macromolecular structures. The radical polymerization in acetonitrile was carried out to synthesize oligomers with a low number average degree of polymerization ( )_cum (about 20), using tert‐butylcyclohexyl peroxydicarbonate (TBCPC) as initiator at 75 °C. The initial [TBCPC]₀/[FATRIFE]₀ molar ratio was monitored to evaluate its influence on the ( )_cum of α‐fluoroacrylic oligomers. The ¹H NMR analysis of the polymers showed that the ( )_cum values obtained were higher than 40, in spite of a high C₀ value. To explain these results, the mode of termination was evaluated using the following kinetic law: . The development of kinetic relationships allowed us to calculate the ratio k_prt/k_i·k_p as about 17–30 mol s l^?1, and to confirm that primary radical termination (PRT) was in competition with bimolecular macromolecular termination (BMT). © 2002 Society of Chemical Industry     

Cellulase EGZ of Erwinia chrysanthemi: structural organization and importance of His98 and Glu133 residues for catalysis

Biochemical, genetic and primary sequence analyses of the Erwiniachrysanthemi endoglucanase EGZ allowed us to identify two functionaldomains and to locate their boundaries. The catalytic domainextends from residue 1 to 288, while a domain required for EGZto bind to microcrystalline cellulose lies from residues 324to 385. Each domain was found capable of functioning in theabsence of the other. A region rich in Pro, Thr and Ser residueslinks both domains and appeared to be susceptible to proteolyticattack. Based upon predictions derived from a method developedto compare sequences sharing a low level of similarity, e.g.hydrophobic cluster analysis (HCA), we analysed the importanceof either residue His98 or Glul33 in EGZ catalytic activity.Two EGZ-derived proteins were engineered in which either His98or Glul33 amino acid was converted to an Ala residue. Characterizationof the purified proteins showed that no enzymatic activity couldbe detected, by using carboxymethylcellulose (CMC) or paranitrophenyl-cellobioside(pNPC) as substrates, while both mutated proteins retained thecapacity to bind to microcrystalline cellulose. These studies,which to date constitute the first experimental testing of HCA-derivedpredictions, allowed us to identify two particular amino acidsinvolved in cellulolytic activity. By taking into account datafrom chemical modification studies of other cellulases, we speculatethat the His98 residue is involved in the folding of the catalyticdomain while the Glul33 residue intervenes directly in the ß,1–4 glycosidic bond cleavage.     

Hydrogenolysis of n-Hexadecane on iron and its inhibition by carbon monoxide

The hydrogenolysis of normal hexadecane was studied over iron at 325° and 355°C. As expected with iron catalysts, the main product was methane, but the selectivities for intermediate alkanes were moderately large, probably due to the length of the carbon chain. Furthermore, gas chromatography—mass spectrometry analysis of the heavier products indicated the presence of alkylbenzenes, alkenes and branched alkanes which accounted for about 20 mole % of the C₉–C₁₃ hydrocarbons. When 5.7 mole % of carbon monoxide was added to the feed, hydrogenolysis reactions were inhibited and products similar to those in the Fischer—Tropsch synthesis were found. Therefore, CO acts like a poison for the hydrogenolysis of hydrocarbons.