Effect of Scanning Beam Profile to Fabricate Fused Fiber Tapers by CO2 Laser Irradiation Method

Beam uniformity is a crucial building block of CO2 experiments aimed at fusing and stretching optical fibers in a lossless manner. When the irradiation beam is expanded through a galvanometer mirror, ways to achieve beam uniformity are investigated.     

Access a divers dichalcogenophenylenes metallocenes (M = Ti, Zr, Hf). Premier exemple d'un ditellurophenylene-zirconocene

Elementary sulfur and selenium combine (in boiling heptane) with [(tBuCp)₂-Zr(C₆H₄R)₂] (Cp = η⁵-C₅H₄; R = OCH₃) to give the corresponding dichalcogenophenylenezirconocene. With tellurium, the reaction proceeds only at lower temperature (in boiling hexane), affording the first ditellurophenylenezirconocene. As no metallacycle was obtained with the Cp ligand or when the metal is Hf, complexes of the general type [(RCp)₂MSe₂C₆H₄-o] (M = Ti, Zr, Hf; R = H, t-Bu, (CH₃)₅) have been synthesized by allowing metallocene dichlorides to react with potassium benzenediselenolate, prepared by cleaving [(t-BuCp)₂ZrSe₂C₆H₄-o] with t-BuOK.     

Thermodynamic Properties of CTAB in Aqueous Solutions of Neutral Polymers at 25°C

Interactions of polyethylene glycols (PEGs) and polypropylene glycols (PPOs) in aqueous solutions of hexadecyltrimethylammonium bromide (CTAB) were investigated through thermodynamic properties at 25°C. The densities and heat capacities of the solutions were measured with a vibrating tube densimeter and a Picker flow microcalorimeter, respectively. The variations in the apparent molar volumes and heat capacities of both solutes, calculated from the densities and heat capacities of the solutions, are unusually large in the vicinity of the CMC, reflecting the existence of very strong interactions between CTAB and PPOs. With the more hydrophilic polymers, PEGs, the apparent properties of CTAB are less affected by the presence of the polymer, indicating that PEGs interact only weakly with CTAB. This revised version was published online in August 2006 with corrections to the Cover Date.     

QCD corrections to the Drell-Yan mechanism and the pion structure function

We compute the differential cross section dσ/dQ² dy for lepton pair production up to first order in the strong coupling constant α_s. We show that, in the region where the theory applies and where the statistical accuracy of the experiments is good, the ratio of the QCD correction to the Drell-Yan cross section is approximately constant, and that its magnitude is in good agreement with the results of the CERN-NA3 experiment. We thus show that, within the framework of this first-order calculation, the shape of the pion structure function extracted from dilepton production in πp collisions is approximately correct. We also comment on the average transverse momentum of the dilepton due to gluon or quark recoil.     

QCD versus recent experimental data on lepton pair production at accelerator energies

New and precise experimental results on Drell-Yan pair production at accelerator energies are now available, both in π^? andp-nucleus interactions. These data are analyzed within the QCD framework including soft gluon resummation. It is shown that a quantitative agreement of the theory with experimental data can be reasonably managed. In particular, the soft gluon resummation is shown to build up nicely the so-calledK-factor. The pion formfactor is deduced from experimental data, but is rather sensitive to the nuclear structure functions we use. Definite nuclear structure functions are needed.