Cationic polymerization of acenaphthylene and methyl acenaphthylenes

Cationic polymerization of acenaphthylene was studied both by experimental methods and theoretical calculations. Very pure acenaphthylene was obtained by double sublimation and its polymerization kinetics were studied with SnCl₄ as initiator. Reactivity ratios were determined for methyl-1, methyl-3 and methyl-5 acenaphthylenes, while values of stabilization energies, (ΔE)^s_r, have been calculated. There is good agreement between the trends of the two sets of values. In the case of acenaphthylene, the comparison of results obtained by Hückel's and by Pople's methods has shown the contribution of ring strain to the reactivity of acenaphthylenic monomers.     

Numerical optimization of a new robotized glass blowing process

To answer an increasing need for glass product manufacturing in both small and medium series, the first glass-blower robot was recently developed. In the face of this new technology, which particularly interests crystal glass-makers, expertise remains the main decision-making element which intervenes in the choices of the design and implementation of these new processes. Finite element models of this new blowing process were developed. After the analysis of the process and of these stages, an initial sensibility study allowed us to find the essential parameters for the success of the operation. With the results of these sensitivity analyses, an optimizer was developed to adjust virtually the forming process of a linear cylindrical vase by determining the optimal forming parameters. A second optimization allowed us to determine the initial shape of the parison, an essential parameter in the successful forming of a convex cylindrical vase. Finally, the numerical tools were validated during trial campaigns carried out in crystal glass-makers.Symbols A ^s _i normalized functions n ^s _i - C ₁ constraint equation - E ( p _i ) error function - ep _s ^* vase thickness obtained by finite element models - prescribed designers vase thickness - glass distribution calculated in a point m after disturbing - glass distribution obtained in a point m - G first derivative of the penalization function _j ( p) - H second derivative of the penalization function _j ( p) - I identity matrix - J Jacobian matrix of the error function E ( p _i ) - M number of comparison points - m point of the vase - N ^s number of parameters - n ^s _i standardized functions of N ^s variations - P _{s 1} pressure of free blowing - p ^s _i ith parameter p ^s - T _init initial temperature after reheating - t _{f 2} time of vertical creep - t _m time of first shaping - t _{s 1} time of free blowing - ₁ angle of tilted creep - Levenberg–Marquardt parameter - ₁ positive scalar - _j ( p) penalization function     

A possible “direct initiation” of cationic polymerization of isobutylene by boron trichloride in methylene chloride

Summary Initiation of the cationic polymerization of isobutylene by BCl₃ requires a cocatalyst in most cases. However, we found conditions (=-30°C, CH₂Cl₂ as solvent, BCl₃ 0.0l m) where a direct initiation by BCl₃ (i.e. with no cocatalyst) is possible. We showed that in such conditions HCl is not a cocatalyst and that H₂O content is too low to explain the results (high vacuum and highly purified reactants and solvent).The conversion increases linearly with tine increasing concentration of BCl₃.A mechanism is proposed.     

Evaluation of analytical methods for the determination of free formaldehyde on textile substrate

Release of formaldehyde from durable press-treated fabrics is a problem for human health and safety because formaldehyde is suspected to be carcinogenic. The accuracy of the standard test method for the free formaldehyde determination, Japan Law 112, depends on the formaldehyde content of the sample. The detection of low formaldehyde contents is particularly important in fields, like children clothing, so the application of high-performance liquid chromatography was evaluated. The results obtained by the standard test method, Japan Law 112, where UV/Vis spectrometer was used, were compared with the results obtained by HPLC method in which separation was performed on an RP C18 column with water–methanol as a mobile phase. It was shown that the detection limit and limit of quantification were improved using the HPLC method.     

Production of HIV-1 by human B cells infected in vitro: characterization of an EBV genome-negative B cell line chronically synthetizing a low level of HIV-1 after infection

Human immunodeficiency virus type 1 (HIV-1) has tropism for helper T lymphocytes and cells of the monocyte/ macrophage lineages. HIV-1 can also infect other cell types, including B cells. We show here that 10% of fresh circulating B cells from HIV-1-seronegative donors (i) express the CD4 receptor and CCR5 and CXCR4, two recently described coreceptors for HIV-1 and (ii) are permissive to HIV-1 with de novo proviral DNA integration following ex vivo infection by either SI (syncytium-inducing) or NSI (non-syncytium-inducing) isolates. To get further information on the interaction between HIV and B cells, the susceptibility of several EBV-positive or -negative B cell lines to infection by SI and NSI isolates was checked. Following infection of an EBV- CD4+ CXCR4+ CCR5- B cell line (DG75) by an SI HIV-1 isolate, we obtained a cell line which chronically produced low-level infectious HIV-1 for 2 years (HIV-DG75). Immunocytochemical data, combined with in situ PCR data, established that HIV-DG75 cells consist of at least three populations uninfected cells, infected virus-producing cells, and infected but nonproducing cells. Moreover, HIV-DG75 cells which express p24 antigen do not go into apoptosis, contrary to T lymphocytes. We infer from these results that B cells could constitute a reservoir of infectious virus in infected patients.     

Behaviour of shot peening combined with WC-Co HVOF coating under complex fretting wear and fretting fatigue loading conditions

This study investigated the fretting and fretting fatigue performance of tungsten carbide-cobalt (WC-Co) HVOF spray coating systems. Fretting wear and fretting fatigue tests of specimens with shot peening and WC-Co coatings on 30NiCrMo substrates were also performed. The WC-Co coating presents very good wear resistance by decreasing the energy wear coefficient (α) under fretting conditions by more than 9 times. The tested coating reduces crack nucleation under both fretting and fretting fatigue situations. Finally the crack arrest conditions are evaluated by the combined fretting and fretting fatigue investigation. It is shown and explained how and why this combined surface treatment (i.e., shot peening and WC-Co) presents a very good compromise against wear and cracking fretting damage.     

Study of step-growth polymerizations using epoxy-carboxy reaction

Summary Due to its importance in the fields of block-polycondensation and chemical modification, we carried out a study of the epoxy-carboxy reaction on models (3-phenoxy-1,2-epoxy propane and dodecanoic acid) in the bulk; this reaction was catalyzed either by a tertiary amine (N,N-dimethyldodecylamine) or a chromium chelate (chromium diisopropylsalicylate). Whatever the catalytic system we observed an isomerization of the hydroxy-ester (secondary-primary alcohol) plus transesterification reactions when the catalyst was an amine. The contribution of transesterification reactions is limited when the catalyst is a chromium derivative.