Cryogenic opened cavity sapphire resonator for ultra-stable oscillator

A new high-Q sapphire whispering gallery mode resonator is proposed to achieve ultra-high frequency stability. It is proposed to use the sapphire resonator without metallic walls to suppress spurious modes perturbating the main resonance. Providing the azimuthal order of the chosen whispering gallery mode is sufficiently high, Q-factors better than 2/spl times/10/sup 8/ have been observed, which turn out to be sufficient to reach a high frequency stability. A first oscillator prototype operating at 12 GHz shows a relative frequency instability of 3/spl times/10/sup -14/.     

Epileptic seizures, epilepsy and risk factors. Experiences with an investigation in Martinique. Epimart Group

Dextrans of mean molecular weight 70 kDa (dextran-70) have had clinical use as anti-thrombotics in man. A major part of the anti-thrombotic action is mediated via inhibition of platelet function. Greatorex (1975, 1977) treated thromboembolic colic in horses with infusions of dextran-70 and reported a 90% recovery rate, but this treatment is nonetheless rarely used. We have used an in vitro method to examine the effect of dextran-70 on equine platelet suspensions, in the hope that understanding the mechanism of action of dextran-70 might lead to the development of alternative therapeutic agents. The effects of dextran-70 on equine platelets occurred immediately in vitro with an initial activation and shape change. Subsequent assessment of aggregation revealed a dose-dependent specific inhibition of platelet-activating factor (PAF)-induced aggregation, significant in rate of aggregation at dextran-70 concentrations >40 g/l (P<0.05) and in extent of aggregation at dextran-70 concentrations >50 g/l (P<0.05). Pre-incubation with 60 g/l dextran-70 significantly inhibited the rate and extent of aggregation in response to PAF (1 nmol/l) (P<0.001 and P = 0.003, respectively) but this was not dependent on the duration of pre-incubation (from 0 to 150 min). No effects were seen when the agonist was adenosine 5'-diphosphate (200 nmol/l), collagen (10 mg/l), 5-hydroxytryptamine (100 micromol/l) or U44069 (600 nmol/l) (all P>0.1). Analysis of PAF concentration-aggregation curves after pre-incubation with 60 g/l dextran-70 indicated significant noncompetitive inhibition by dextran-70 (P<0.001 for rate and extent of aggregation). The ability of dextran-70 to inhibit responses of equine platelets to PAF is probably an important component of its beneficial effect as an anti-thrombotic in colic cases.     

Persistence and prevalence of pathogenic and extended-spectrum beta-lactamase-producing Escherichia coli in municipal wastewater treatment plant receiving slaughterhouse wastewater

We compared the prevalence of pathogenic and extended-spectrum beta-lactamase (ESBL) – producing Escherichia coli in effluents of a municipal wastewater treatment plant (WWTP) receiving wastewater from a slaughterhouse. A total of 1248 isolates were screened for the presence of virulence genes associated with enterohemorrhagic E. coli (EHEC) (stx₁, stx₂, and eae) and extraintestinal pathogenic E. coli (ExPEC) (sfa/focDE, kpsMT K1, hlyA, papEF, afa/draBC, clbN, f17A and cnf). The prevalence of atypical enteropathogenic E. coli (EPEC) was 0.7%, 0.2% and 0.5% in city wastewater, slaughterhouse wastewater and in the treated effluent, respectively. One stx_1a and stx_2b-positive E. coli isolate was detected in city wastewater. The prevalence of ExPEC was significantly higher in city wastewater (8.4%), compared to slaughterhouse wastewater (1.2%). Treatment in the WWTP did not significantly impact the prevalence of ExPEC in the outlet effluent (5.0%) compared to city wastewater. Moreover, the most potentially pathogenic ExPEC were isolated from city wastewater and from the treated effluent. ESBL-producing E. coli was also mainly detected in city wastewater (1.7%), compared to slaughterhouse wastewater (0.2%), and treated effluent (0.2%). One ESBL-producing E. coli, isolated from city wastewater, was eae-β1 positive. These results showed that pathogenic and/or ESBL-producing E. coli were mainly detected in human wastewater, and at a lesser extend in animal wastewater. Treatment failed to eliminate these strains which were discharged into the river, and then these strains could be transmitted to animals and humans via the environment.     

In situ high temperature and high pressure exafs studies of Pt/Al2O3 Catalysts. Part II: Carbon removal

EXAFS has been used to follow in situ the structural evolution of a Pt/Al₂O₃ catalyst during removal of carbon by hydrogenation, after reduction and carbon deposition. After reduction at 350 °C, the total hydrogen pressure was raised to 3 atm. and n-heptane was injected over the sample. EXAFS measurements at the Pt edge were carried out with simultaneous on-line EXAFS analysis of the spectra. After observing the rapid formation of a carbon-platinum bond which is unmodified with time, we stopped the heptane flow, raised the temperature to 450 °C, and maintained hydrogen flow at 3 atm. The disappearance of the platinum-carbon bond during heat treatment in hydrogen was monitored via on-line analysis. No sintering of the metal particles was observed. EXAFS is thus proven to be an efficient tool to study not just structural changes of a catalyst during a hydrocarbon reaction [1], but also to use it as a technique to study other catalytic phenomena as well.     

Influence of platinum on ceria sulfation

The influence of platinum on ceria sulfation has been studied using thermogravimetry and infrared spectroscopy. The same types of sulfate species — surface and bulk-like species — are evidenced with or without Pt. Pt does not modify the thermal stability of both types of sulfate. It favors sulfate formation on low-surface-area CeO₂ samples. The reducibility of sulfate by H₂ is promoted by Pt irrespective of the types of sulfate formed on ceria. H₂S, which is formed by H₂ reduction of sulfate, partly remains on the catalyst. It is adsorbed not only on the oxide but also on Pt. Sulfur poisoning of Pt has been shown by IR study of CO adsorption.     

Mass screening programs for breast cancer in France. Comparative evaluation

OBJECTIVE: The purpose of this work was to comparatively assess the results of mass screening programs for breast cancer implemented in six French departments in 1986, within the scope of the National Fund for Health Prevention, Education and Information of the National Health Insurance Office of Salaried Workers. MATERIAL AND METHODS: The data collected by the screening centres were analyzed by ten assessment teams that were independent from the program promotion staff, all using the same evaluation form. A complementary population study performed in eight French districts then, allowed assessing the frequency of self-referred screening (mammography performed out of program). RESULTS: The rate of participation in screening programs, in relation to the invited population, ranged from 21 to 48%, according to the district (36% in average). This low participation was probably related to the extent of self-referred screening. In fact, 19 to 40% of women, according to the district, had previously had a screening mammographic coverage: rate was around 68% in women aged 50 to 69 years. Positive findings with mammography ranged from 4.5 to 15.8% (10.1% in average), while intervention rates ranged from 0.7 to 1.6% and detection rates from 3.8 to 6.2%. The ratio between benign tumors and cancers ranged from 0.7 to 2.1 according to the district. In order to enlighten the judgement on French results, we propose a comparison with the international standards in force. CONCLUSION: The various experiences with breast cancer screening in France show that this screening is technically feasible on the basis of existing medical structures. However, some criteria are still below the expected values, especially if compared with international standards. This result is probably accounted for by the high rate self-referred screening before age 40 in France. In these conditions, the question is whether extending breast cancer screening programs in France is an appropriate course of action.     

Studies on the mechanisms involved in antigen-evoked pleural inflammation in rats: contribution of IgE and complement

Immunoglobulin E (IgE) has been shown to play a critical role in the allergic late-phase reaction, which is marked by intense leukocyte infiltration and edema. In this study we assessed the allergic pleural inflammation triggered by intrapleural (i.pl.) challenge in sensitized rats. We examined pleural effluent from actively sensitized rats following anti-IgE monoclonal antibody (mAb) (MARE-1) provocation for protein exudation, neutrophil as well as eosinophil accumulation. Inflammatory changes triggered by antigen after passive sensitization with IgE mAb was also assessed for comparison. Total serum level of IgE was found to be about threefold increased 7-8 days post-active sensitization, remaining augmented for at least 30 days. Increased levels of peritoneal leukocyte-bound IgE and serum IgE with specificity to ovalbumin were also detected. Nevertheless, the anti-IgE challenge in 14-day actively sensitized was shown to be a weak stimulus of neutrophil and eosinophil accumulation, despite being able to cause intense protein extravasation. Similarly, antigen challenge of IgE-passively sensitized rats caused protein leakage that was comparable to that induced by anti-IgE mAb in actively sensitized rats but led to a much lower neutrophil/eosinophil infiltration. Also, blockade of complement with recombinant human soluble C receptor-1 (sCR1) treatment prevented actively sensitized rats from reacting to antigen with neutrophil and eosinophil recruitment without modifying protein extravasation. These data suggest that IgE and complement-mediated mechanisms probably account for the exudation and leukocyte infiltration that is characteristic of the pleural inflammatory response observed in actively sensitized rats.