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We investigated an outbreak of 396 Salmonella enterica serotype I 4,5,12:i:- infections to determine the source. After 7 weeks of extensive hypothesis-generation interviews, no refined hypothesis was formed. Nevertheless, a case-control study was initiated. Subsequently, an iterative hypothesis-generation approach used by a single interviewing team identified brand A not-ready-to-eat frozen pot pies as a likely vehicle. The case-control study, modified to assess this new hypothesis, along with product testing indicated that the turkey variety of pot pies was responsible. Review of product labels identified inconsistent language regarding preparation, and the cooking instructions included undefined microwave wattage categories. Surveys found that most patients did not follow the product's cooking instructions and did not know their oven's wattage. The manufacturer voluntarily recalled pot pies and improved the product's cooking instructions. This investigation highlights the value of careful hypothesis-generation and the risks posed by frozen not-ready-to-eat microwavable foods.
The inhomogeneous sheath that surrounds a probe immersed in a weakly collisional magnetized plasma is investigated from the microscopic point of view, in the case when the probe is cylindrical and parallel to the magnetic field. Arbitrary surface effects of the probe (such as absorption, reflexion and emission of particles) are taken into account. The sheath is described with a model based on the solution of a boundary-value problem for the self-consistent Boltzmann—Maxwell—Poisson equation. The spatial variation of the magnetic field is discussed. Typical results of numerical computations concerning the structure of the sheath and the currents collected by the probe are given and discussed.
Two incidents involving internal exposure by inhalation of transuranic compounds are presented herein. The results of the measurements of urinary and faecal excretions of the two individuals involved do not concur with the values predicted by the ICRP models that should be applied by default, according to the circumstances of the incidents and the chemical form of the products involved: oxide in the first case and nitrate in the second. These cases are remarkable in the similarity of their biokinetic behaviour even though they occurred in different situations and involved different chemical compounds. Both situations provide an illustration of the management of internal contamination events. The precautions to be taken and the questions that the physician should ask himself in the estimation of the internal dose are listed as follows: What type of examinations should be prescribed and at what frequency? What analysis results should be used in assessing the dose? How can the effect of the Ca-DTPA treatment be assessed? How long is it necessary to perform radiotoxicological exams before assessing the dose? What should be done if the ICRP model corresponding to the initial circumstances does not fit the measurement data? Finally, our selected hypotheses, used to explain specific biokinetic behaviour and to estimate its intake in both cases, are detailed. These incidental contaminations suggest that further studies should be carried out to develop a new model for inhalation of transuranic compounds that would follow neither the S nor the M absorption type of the respiratory tract model of ICRP publication 66.
Le service de santé au travail du CEA/CADARACHE est un service médical de site chargé de la surveillance radiologique de l’exposition interne de l’ensemble du personnel travaillant sur le centre de Cadarache. Dans son activité spécifique de surveillance du risque radiologique prédomine la gestion des expositions aux transuraniens (plutonium et américium), avec environ 400 salariés concernés. Nous avons mis en place depuis 2002 une surveillance systématique de ce risque d’exposition par des analyses radiotoxicologiques des selles. Nous présentons ici notre retour d’expérience sur les trois premières années.
Le service de santé au travail du CEA/CADARACHE est un service médical de site
chargé de la surveillance radiologique de l'exposition interne de l'ensemble du
personnel travaillant sur le centre de Cadarache. Dans notre activité spécifique de
surveillance du risque radiologique prédomine la gestion des expositions aux
actinides, plutonium et américium principalement, avec environ 600 agents
concernés. Nous présentons les protocoles de prise en charge des incidents de
contamination que nous avons élaborés et mis en place en 1996 ainsi que le retour
d'expérience sur plus de 1 500 évènements gérés jusqu'à fin 2002.
In this article, we present a laboratory astrophysics experiment
on radiative shocks and its interpretation using simple modelization.
The experiment is performed with a 100-J laser (pulse duration of about
0.5 ns) which irradiates a 1-mm3 xenon gas-filled cell.
Descriptions of both the experiment and the associated diagnostics
are given. The apparition of a radiation precursor in the unshocked
material is evidenced from interferometry diagrams. A model
including self-similar solutions and numerical ones is derived
and fairly good agreements are obtained between the theoretical
and the experimental results.
A computational approach to the prediction of jet mixing noise
described. It is based
on Lighthill's analogy, used together with a semi-deterministic modelling
(SDM), where only the large-scale coherent motion is evaluated. The features
are briefly illustrated in the case of shear layers, showing that suitable
of the mean flow and of the large-scale fluctuations are obtained. Aerodynamic
calculations of two cold fully expanded plane jets at Mach numbers 0.50
and 1.33 are
then carried out. The numerical implementation of Lighthill's analogy
different integral formulations are compared for the two jets. It is shown
expressed in a space–time conjugate (κ, ω)-plane is particularly
convenient and allows
a simple geometrical interpretation of the computations. Acoustic results
with this formulation are compared to relevant experimental data. It is
that the radiation of subsonic jets cannot be explained only by the contribution
of the turbulent coherent motion. In this case, directivity effects are
recovered but the
acoustic spectra are too narrow and limited to the low-frequency range.
at Mach number 1.33, especially in the forward quadrant, results are satisfactory,
showing that coherent structures indeed provide the main source of supersonic
The different possible geometries for intersubband transitions in microcavities are discussed. A consequence of the selection rule governing intersubband transition is the vanishing interaction with the electromagnetic field inside a usual vertical cavity. The geometry of vertical planar cavities which has been used extensively with interband transitions is therefore useless in the case of intersubband transitions. Different solutions are reviewed to overcome this problem. The breakdown of the selection rule in a vertical cavity is first discussed. This can be done with the use of vertical quantum wells, or thanks to intracavity diffraction gratings. Second, the use of in plane cavities is discussed. Two solutions are here envisaged: Whispering gallery modes in microdisk cavities, and efficient etched air/GaAs Bragg mirrors. Concerning the latter attractive solution, the losses by diffraction into the substrate are evaluated theoretically and experimentally. The solution of the Maxwell equations by a finite element method in this three dimensional system shows the great importance of diffraction. These results are confirmed by waveguided Fourier transform spectroscopy. To overcome this difficulty, we propose the use of lower refractive index substrates, such as oxidized AlAs.
Circumstellar envelopes of young and evolved stars are responsible for many important phenomena concerning the exchange of matter, angular momentum, energy and maybe magnetic field between the core structure of stars and the interstellar medium. In particular, it is through them that matter enriched in heavy elements flows from evolved stars towards the interstellar gas, submitted to complex ordinary chemistry or photochemistry and condensation into solid particles.