Mesure de l'énergie des ions lourds par la méthode des protons projetés

Un dispositif destiné à la mesure de l'énergie des faisceaux d'ions lourds de 3 à 6 MeV/ uma a été construit. Le principe de la méthode est de mesurer l'énergie des protons projetés à zéro degré par collision élastique des ions incidents avec les noyaux d'hydrogène d'une cible de formvar. L'incertitude calculée sur l'énergie ainsi mesurée pour les ions lourds est de + 0,45 %. Des mesures faites sur des faisceaux de 19F et 40Ca d'énergie bien connue, accélérés par un Tandem MP, ont montré un écart maximum de 0,3 % entre les énergies réelles et mesurées. Le dispositif permet de contrôler ou calibrer des méthodes plus lourdes de détermination de l'énergie des ions lourds : déviation magnétique, temps de vol. Il se prête particulièrement bien à la mesure des pertes d'énergie d'ions lourds dans des ralentisseurs solides

Ion-beam mixing induced by atomic and cluster bombardment in the electronic stopping-power regime

Single crystals of magnesium oxide containing nanoprecipitates of sodium were bombarded with swift ions (∼GeV-Pb, U) or cluster beams (∼20 MeV-C60) to study the phase change induced by electronic processes at high stopping power (≳10 keV/nm). The sodium precipitates and the defect creation were characterized by optical absorption and transmission electron microscopy. The ion or cluster bombardment leads to an evolution of the Na precipitate concentration but the size distribution remains unchanged. The decrease in Na metallic concentration is attributed to mixing effects at the interfaces between Na clusters and MgO. In addition, optical-absorption measurements show a broadening of the absorption band associated with electron plasma oscillations in Na clusters. This effect is due to a decrease of the electron mean free path, which could be induced by defect creation in the metal. All these results show an influence of high electronic stopping power in materials known to be very resistant to irradiation with weak ionizing projectiles. The dependence of these effects on electronic stopping power and on various solid-state parameters is discussed

HEAVY ION SECONDARY BEAMS

The possibility of producing secondary beams of radioactive nuclei is an interesting application of medium and high energy heavy ion beams. After a first attempt at CERN (1) , two experiments have been performed at GANIL, using 44 MeV/u 40Ar (2) and 65 MeV/u 180 projectiles. This paper recalls the results of the Ar experiment, and presents new data obtained with the 180 beam

INVESTIGATION OF THE TRANSMISSION AND STOPPING OF LIGHT IONS PASSING THROUGH A PLASMA TARGET

Transmission and energy losses of 2 MeV/u Carbon and Sulphur beams passing through a plasma target, have been extensively investigated. A hydrogen plasma ignited by an electrical discharge was coupled to the Orsay Tandem beam accelerator. Fluctuations in beam transmission have been observed and attributed to a magnetic focusing effect generated during the plasma evolution. Energy loss measurements were performed on the basis of time of flight techniques and indicate an enhanced stopping power of the plasma relative to its cold matter equivalent

Tuberculosis in HIV-infected children in Europe, Thailand and Brazil: paediatric TB-HIV EuroCoord study

SETTING: Centres participating in the Paediatric European Network for Treatment of AIDS (PENTA), including Thailand and Brazil. OBJECTIVE: To describe the incidence, presentation, treatment and treatment outcomes of tuberculosis (TB) in human immunodeficiency virus (HIV) infected children. DESIGN: Observational study of TB diagnosed in HIV-infected children in 2011–2013. RESULTS: Of 4265 children aged <16 years, 127 (3%) were diagnosed with TB: 6 (5%) in Western Europe, 80 (63%) in Eastern Europe, 27 (21%) in Thailand and 14 (11%) in Brazil, with estimated TB incidence rates of respectively 239, 982, 1633 and 2551 per 100 000 person-years (py). The majority (94%) had acquired HIV perinatally. The median age at TB diagnosis was 6.8 years (interquartile range 3.0–11.5). Over half (52%) had advanced/severe World Health Organization stage immunodeficiency; 67 (53%) were not on antiretroviral therapy (ART) at TB diagnosis. Preventive anti-tuberculosis treatment was given to 23% (n = 23) of 102 children diagnosed with HIV before TB. Eleven children had unfavourable TB outcomes: 4 died, 5 did not complete treatment, 1 had recurrent TB and 1 had an unknown outcome. In univariable analysis, previous diagnosis of acquired immune-deficiency syndrome, not being virologically suppressed on ART at TB diagnosis and region (Brazil) were significantly associated with unfavourable TB outcomes. CONCLUSION: Most TB cases were from countries with high TB prevalence. The majority (91%) had favourable outcomes. Universal ART and TB prophylaxis may reduce missed opportunities for TB prevention

The Production of Z′Z' Associated With Photons or Jets as a Probe of New Gauge Boson Couplings

We examine the production of a new $Z'$ gauge boson in association with photons or jets at future hadron supercolliders as a probe of its couplings to fermions. Associated jet production is found to be rather insensitive to these couplings and suffers from large uncertainties as well as substantial backgrounds. On the other hand, the ratio of rates for associated photon $Z'$ production to that of conventional $Z'$ production has a rather clean signature (once appropriate cuts are made), and is found to be quite sensitive to the choice of extended electroweak model, while being simultaneously insensitive to structure function uncertainties and QCD corrections. Rates at both the SSC and LHC are significant for $Z'$ masses in the 1 TeV range.Comment: 14pp, 6 figs(not included), LaTex, ANL-HEP-PR-92-5

An integrative approach to decipher the chemical antagonism between the competing endophytes paraconiothyrium variabile and Bacillus subtilis

An integrative approach combining traditional natural products chemistry, molecular networking, and mass spectrometry imaging has been undertaken to decipher the molecular dialogue between the fungus Paraconiothyrium variabile and the bacterium Bacillus subtilis, which were isolated as endophytes from the conifer Cephalotaxus harringtonia and are characterized by a strong and mutual antibiosis. From this study, we highlight that bacterial surfactins and a fungal tetronic acid are involved in such competition and that the fungus is able to hydrolyze surfactins to fight against the bacterial partner