The role of the Roper resonance in n p --> d (pi pi)

In this work, a model for the n p --> d (pi pi) reaction is developed. It is shown that the structure of the deuteron momentum spectra for a neutron beam momentum of 1.46 GeV can be explained as a consequence of the interplay of two mechanisms involving the excitation of the N^*(1440) resonance and its subsequent decay into N (pi pi)^{T=0}_{S-wave} and Delta pi respectively. The relevance of the present analysis for the study of the Roper excitation and decay properties, as well as for the interpretation of other two-pion production experiments is discussed.Comment: 13 pages, 6 ps figure

The Extension and Shape of the Collecting Zones of the Galactic Cosmic Rays from Helium to Iron

Hundreds of millions of cosmic-ray trajectories, from helium to iron, have been simulated in the Galactic disk in order to calculate the mean distance of cosmic-ray sources from Earth. The dominant parameter affecting the distance is the Galactic magnetic field, which makes cosmic-ray trajectories about 3 orders of magnitudes longer than the physical distance from the source to Earth. The calculations indicate that cosmic-ray sources powering the local flux around Earth are mainly disseminated along the regular magnetic field lines of the Galaxy. The spatial distribution of the sources form characteristic figures in the disk volume, which we define as the collecting regions of cosmic rays. Assuming cosmic-ray sources to be uniformly distributed in the disk of the Milky Way, at the arbitrary energy of 1 TeV amu-1 the typical length and width of these regions are 29.9 and 0.53 kpc for helium and 20.0 and 0.27 kpc for iron. The mean physical distance of the cosmic-ray sources from Earth turns out to be 3.5 kpc for helium and 1.6 kpc for iron

Prise en charge actuelle de l’hypertension artérielle

International audienceHypertension is a common health problem with serious consequences for individuals and a heavy attributable burden for populations. Reducing this burden requires preventive actions at the population level and early diagnosis at the individual level, followed by proactive interventions with proven benefits. Given the variability of blood pressure measurement, diagnosis is established only after repeated measurements under standardized conditions, if possible outside the clinic. Lifestyle changes can modestly reduce blood pressure; their impact is significant if they can be achieved on a large scale. Hypertension treatment requires a rational pharmacological approach, which can reach the target blood pressure within less than 6 months and three pharmacological classes at most in more than 80% of cases. Specialized consultation is required in the remaining 20% to detect secondary hypertensions, to optimize drug therapy and to discuss, in a minority of cases, non-pharmacological treatments. Recommendations are written by experts who select, interpret, and extrapolate the results of clinical research. As a consequence, they are sometimes unsuitable for primary care practice and frequently inconsistent across guidelines. Efforts are currently made to produce less disputable and more usable guidelines.L’hypertension artérielle (HTA) est un problème de santé fréquent dont les conséquences peuvent être graves pour les individus et sont très lourdes pour la population. La réduction de ce fardeau repose sur la prévention à l’échelle de la population et sur le diagnostic précoce à l’échelle des individus, suivis par la mise en œuvre proactive d’interventions dont le bénéfice est démontré. Compte tenu de la variabilité de la mesure de pression artérielle (PA), le diagnostic n’est établi qu’à l’issue de mesures répétées dans des conditions standardisées, si possible en dehors de la consultation. Les mesures hygiéno-diététiques permettent de réduire la PA de façon modeste, leur impact est significatif si elles peuvent être appliquées à grande échelle. La prise en charge des hypertendus repose essentiellement sur une escalade pharmacologique raisonnée et rapide, qui permet d’atteindre les objectifs de PA en moins de six mois avec trois classes pharmacologiques au plus dans plus de 80 % des cas. Une prise en charge spécialisée est requise dans les 20 % restant, pour chercher une cause d’hypertension secondaire, optimiser le traitement pharmacologique et discuter, dans une minorité de cas, de traitements non pharmacologiques. Les recommandations sont rédigées par des experts qui s’appuient sur la sélection, l’interprétation et l’extrapolation de résultats de la recherche clinique. Il en résulte des recommandations parfois inadaptées à la pratique courante et fréquemment contradictoires d’un guide de bonnes pratiques à l’autre. Des réflexions sont en cours pour proposer des guides moins discutables et plus directement applicables

Multi-pion production in the d d -> alpha X reaction

A simple model, based on two parallel and independent N N -> d pi processes, has recently been proposed for two-pion production in the d d -> alpha X reaction. It reproduces all observed features, including the sharp peak structure in momentum distributions (the ABC effect) and the strong oscillations in the deuteron vector and tensor analyzing powers. This model is now extended to describe also four-pion production with the same basic mechanism, but with two n p -> d pi pi processes as input. The calculations of the high missing mass spectra are within about 30% of the experimental data for beam energies in the range 1.9 < T_d < 2.4 GeV.Comment: 7 pages, LaTeX2e, 2 PS figures, submitted to Phys. Lett.

Aldosterone-producing adenoma and other surgically correctable forms of primary aldosteronism

Surgically correctable forms of primary aldosteronism are characterized by unilateral aldosterone hypersecretion and renin suppression, associated with varying degrees of hypertension and hypokalemia. Unilateral aldosterone hypersecretion is caused by an aldosterone-producing adenoma (also known as Conn's adenoma and aldosteronoma), primary unilateral adrenal hyperplasia and rare cases of aldosterone-producing adrenocortical carcinoma. In these forms, unilateral adrenalectomy can cure aldosterone excess and hypokalemia, but not necessarily hypertension. The prevalence of primary aldosteronism in the general population is not known. Its prevalence in referred hypertensive populations is estimated to be between 6 and 13%, of which 1.5 to 5% have an aldosterone-producing adenoma or primary unilateral adrenal hyperplasia. Taking into account referral biases, the prevalence of surgically correctable primary aldosteronism is probably less than 1.5% in the hypertensive population and less than 0.3% in the general adult population. Surgically correctable primary aldosteronism is sought in patients with hypokalemic, severe or resistant forms of hypertension. Recent recommendations suggest screening for primary aldosteronism using the aldosterone to renin ratio. Patients with a raised ratio then undergo confirmatory suppression tests. The differential diagnosis of hypokalemic hypertension with low renin includes mineralocorticoid excess, with the mineralocorticoid being cortisol or 11-deoxycorticosterone, apparent mineralocorticoid excess, pseudo-hypermineralocorticoidism in Liddle syndrome or exposure to glycyrrhizic acid. Once the diagnosis is confirmed, adrenal computed tomography is performed for all patients. If surgery is considered, taking into consideration the clinical context and the desire of the patient, adrenal vein sampling is performed to detect whether or not aldosterone hypersecretion is unilateral. Laparoscopic surgery for unilateral aldosterone hypersecretion is associated with a morbidity of about 8%, with most complications being minor. It generally results in the normalization of aldosterone secretion and kalemia, and in a large decrease in blood pressure, but normotension without treatment is only achieved in half of all cases. Normotension following adrenalectomy is more frequent in young patients with recent hypertension than in patients with long-standing hypertension or a family history of hypertension