The Influence of C60 Powders On Cultured Human Leukocytes

In order to check its possible acute toxicity, C₆₀ was incorporated into living human phagocytes. It was observed that C₆₀ has no influence on the survival of human leukocytes.     

Macromolecular engineering of polylactones and polylactides

Summary Aluminum alkoxides carrying functional alkoxy groups are effective initiators for the-caprolactone polymerization in toluene and tetrahydrofuran. The coordination-insertion type of polymerization is living and yields exclusively linear polyesters of a predictable molecular weight with a narrow molecular weight distribution within the period of time required for the total monomer conversion. The functional group associated to the active alkoxy group of the initiator is selectively attached to one chain-end, and the second end-group is systematically a hydroxyl function resulting from the hydrolysis of the living growing site. Asymmetric telechelic polyesters are thus obtained in a perfectly controlled way, including macromonomers. Beside (meth)acrylic double bond, the functional end-group derived from the initiator can be, for instance, an unsaturation, a halogen and a tert-amine. Coupling the asymmetric telechelic polymer via the OH end-group (or the precursor Al alkoxide end-group) is a direct way to the related symmetric telechelic of a twofold increased molecular weight.The authors are indebted to IRSIA for a fellowship to one of them (Ph. Dubois) and to the Services de la Programmation de la Politique Scientifique for financial support. NMR spectra were recorded at the CREMAN facility of the University of Liège which has been funded by a grant from the Fonds National de la Recherche Scientifique. The helpful assistance of Dr. Warin has been very much appreciated. They are very greatful to G. Broze (Colgate Palmolive) who initiated this research.     

Isotypic analysis of Plasmodium falciparum-specific antibodies and their relation to protection in Madagascar

We previously reported that antibodies to the central repeat (DDEHVEEPTVA) of Pf155/RESA, a major Plasmodium falciparum antigen, were negatively related to antimalarial protection. We measured levels of isotype antibodies to this epitope and to P. falciparum in 76 Madagascan subjects. Immunoglobulin G (IgG) and isotype antibodies specific for P. falciparum had similar levels in individuals who were considered protected and those who were not (as determined during a longitudinal follow-up). The levels of IgG1 antibodies to (DDEHVEEPTVA)3 were higher in nonprotected subjects. The levels of total IgG and of other isotype antibodies had a similar tendency to be higher in nonprotected than in protected individuals.     

Surgical treatment of acute dissection of the ascending aorta (20 years experience)

PURPOSE: In 1977, the use of gelatine-resorcine-formaline (GRF) biological glue during surgery of acute type A aortic dissection was proposed. The present study retrospectively analyses the late results obtained with this adjunct in an experience extending over a 20-year period. PATIENTS AND METHODS: From January 1977 to July 1997, 193 patients (139 males and 54 females) aged from 15 to 79 years (mean age: 53 +/- 14 years) underwent an emergency operation for type A aortic dissection in our institution. All patients suffering from acute type A dissection and 162 (84%) were operated on within 48 hours after the onset of symptoms. Twenty-eight patients (15.2%) had Marfan's syndrome. In all patients the ascending aorta was replaced and the aortic stumps were reinforced with the GRF glue. In 43 patients (22.2%), the aortic valve was replaced either independently (5 cases-2.5%) or by means of a composite graft (35 cases-19.5%). Recently three patients underwent a complete replacement of the ascending aorta and coronary reimplantation with preservation of the native aortic valve. Because of the location of the intimal tear, the aortic replacement was extended to the transverse arch in 58 patients (30%). RESULTS: Hospital mortality amounted to 21% (40 patients) (22.8% in patients with arch replacement and 20.3% in patients without arch replacement) (ns). The survivors were surveyed from 2 months to 20 years post-operatively (cumulative follow-up: 856 pt/years, mean follow-up: 85 +/- 66 months). During this period of time, 23 patients (15%) had to be reoperated on for a total of 29 procedures. Six of those patients (26%) died at reoperation. At univariate analysis, presence of Marfan's syndrome (P < 0.05) and absence of arch replacement (P < 0.02) were determinant risk factors for reoperation. Emergency (P < 0.01) and thoraco-abdominal replacement (P < 0.04) were determinant risk-factors of death at reoperation. The actuarial freedom from reoperation (Kaplan-Meier, CI: 95%) was: 96.5% (90.9-98.2), 87.6% (79.8-92.7), 80.9% (70.8-88.1), 66.4% (51.1-78.9) at one, 5, 10 and 15 years, respectively. A total of 36 patients (27.7%) died during follow-up. Presence of Marfan's syndrome (P < 0.01), reoperation (P < 0.02), stroke (P < 0.05), cardiac failure (P < 0.05) were determinant risk factors of late mortality. The actuarial late survival rate (Kaplan-Meier. CI: 95%), including hospital mortality, was: 71.5% (64.3-77.8), 66% (58.3-73), 56.4% (47.7-64.7), 46.3% (36.4-56.5) at one, 5, 10 and 15 years. CONCLUSION: The GRF glue has proved to be extremely useful during initial emergency surgery for acute type A dissection, making the procedure much easier and safer. Through this operative improvement, the use of the GRF glue seems to have a beneficial influence on the late results which, however, depend mainly on the patient's basic condition.     

Interfacial adhesion in polyethylene–kaolin composites: Improvement by maleic anhydride-grafted polyethylene

Polyethylene–kaolin composites were investigated with a special emphasis on the control of the interfacial adhesion. Both matrix and filler were modified for this purpose. A stearic acid and maleic anhydride-grafted polyethylene were used as potential interfacial agents and the efficiency of aminosilane-surface-treated kaolin was considered. Tensile strength, elongation, impact strength, and melt index were currently measured in relation to the processing conditions. Enhanced interfacial filler-polymer adhesion progressively results in an decreased melt index. This has been clearly shown by comparing the effect of two polymeric additives to the polymer matrix, i.e., a maleic anhydride-grafted HDPE (MAGPE) and an unmodified HDPE of a similar melt index. Compared to low molecular weight additives, such as stearic acid and aminosilane, MAGPE has proved to be a very efficient additive in improving the impact resistance of HDPE–kaolin composites even at low contents. © 1995 John Wiley & Sons, Inc.     

A simulator for MIMD performance prediction: application to the S-1 MkIIa multiprocessor

We describe a MIMD multiprocessor simulator and application of that simulator to a multiprocessor of current interest, the S-1 MkIIa. The simulator runs on the CRAY-1 and is designed so that computational physics benchmarks are actually run and produce results. Simulator output from this run is fed into a second level (hardware) simulator which calculates the behavior of the multiprocessor. The simulator can simulate multiprocessors whose basic architecture is that of a few, large processors with or without data caches, sharing global memory through an interconnection switch. The simulator is applied to the investigation of the behavior of four problems on the S-1: The benchmark physics code SIMPLE, a conjugate gradient linear algebra problem, a simple Monte-Carlo problem, and a new method for neutron transport calculations.     

Electrical properties of electrochemically prepared thin polytetrahydrofuran films I: Characterization under A.C. conditions

The electrical characteristics of platinum-polytetrahydrofuran (poly-THF)- gold capacitors were studied under a.c. conditions at temperatures between 173 and 353 K and at frequencies between 10² and 10⁶ Hz. When the temperature T is 300 K the capacitance C and the loss tangent tan δ are constant in the frequency range 10²-10⁵ Hz; when ? is greater than 10⁵ Hz the capacitance decreases slightly and the loss tangent increases rapidly from 2 x 10^?2 to 0.17. In the range 10⁴?5x 10³ Hz the imaginary part ε″ of the dielectric constant has two loss peaks which are related to phase changes: one at 243 K corresponding to the glass transition point T_g(U) of the crystalline phase of the poly-THF (itself a semicrystalline polymer) and one at 203 K corresponding to the glass transition point T_g(L) of the amorphous phase. When T is greater than 319 K the loss tangent increases rapidly at very low frequencies $\text{(10}{}^2\text{Hz}\text{<?<10}{}^3\text{Hz}\text{)}$; 319 K corresponds to the melting point T_αC of the crystalline phase.The average dielectric constant is 3.8, a value which is of the same order of magnitude as that of bulk poly-THF. The activation energy of the dielectric is 0.002 eV in the temperature range 173–250 K and is 0.03 eV at higher temperatures. The conduction mechanism for the capacitors studied in this work is of the hopping variety, as shown by the variations of the conductance G with T and ?; G is proportional to $\text{T}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}$ at a given frequency, and G is ?ⁿ dependent where n is 0.85 at low frequencies and low temperatures and where n is 2 at high frequencies regardless of the temperature.