Search

Nowadays, it is possible to accelerate bunches of particles in the interaction of ultrahigh intensity (UHI) laser pulses with matter. Electrons, protons, ions, and high-energy photon beams can be produced in experiments and reach kinetic energies close to hundreds of megaelectronvolts for protons and gigaelectronvolts for electrons and for the associated Bremsstrahlung photons. At these energies, these beams can induce a large variety of nuclear reactions, which can be detected and studied using $\gamma $ -ray spectroscopy techniques. At standard accelerator facilities, scintillator detectors are commonly used to perform prompt $\gamma $ -ray spectrometry studies. However, during laser–matter interactions, high fluxes of X-rays (mostly soft) are generated, which lead to instantaneous huge energy deposits (~1 $\mu \text{J}$) in these scintillators. Depending on the laser characteristics (energy and pulse duration), the detector recovery time after these X-ray flashes can reach several milliseconds, which makes any prompt or “in beam” measurement impossible. The origin of this long-duration signal is investigated in the case of a LaBr3 crystal coupled to different photodetectors. While it was impossible using standard photomultiplier tubes to detect $\gamma $ -ray emissions before a few milliseconds after a laser shot, we could, using a hybrid photodiode, resolve single $\gamma $ -ray emission a few tens of microseconds after the laser shot. Furthermore, we have also shown that the LaBr3 scintillator presents an unexpected long-lived light emission (afterglow). Directions are suggested for future studies in order to minimize the effects of this afterglow emission. [ABSTRACT FROM AUTHOR]

The nuclear g factor and quadrupole moment ( Q s ) have been measured for the low-lying isomeric 1 + state of 34 Al, using the β -detected nuclear magnetic resonance ( β -NMR) and quadrupole resonance ( β -NQR) methods. Spin-polarized 34 Al isotopes were produced in a one-neutron pickup reaction induced by a 36 S beam on a 9 Be target at a kinetic energy of 77.5 MeV/nucleon, and were collected with the LISE fragment separator at GANIL. The measured g factor ( | g | in a range of 1.757 ± 0.014 ) and quadrupole moment ( | Q s | = 38 ( 5 ) mb) are in good agreement with shell-model calculations using effective interactions. The similarity between the g factor of 34 m Al and that of 32 Al confirms a dominant neutron 2 p 1 h configuration π ( d 5 / 2 ) − 1 ⊗ ν ( d 3 / 2 ) − 1 ( f 7 / 2 ) 2 of 34 m Al. In addition, the enhanced quadrupole moment of 34 m Al relative to that of 32 Al suggests that the neutron 1 p 1 h excitation across the N = 20 shell gap introduces extra nucleon–nucleon correlation and deformation. [ABSTRACT FROM AUTHOR]

The fission of a variety of actinides was induced by fusion and transfer reactions between a 238 U beam and 12 C nuclei, in the active target MAYA. The performance of MAYA was studied, as well as its capability to reconstruct the fission-fragment trajectories. Furthermore, a full characterization of the different transfer reactions was achieved, and the populated excitation-energy distributions were investigated as a function of the kinetic energy in the entrance channel. The ratio between transfer- and fusion-induced fission cross-sections was also determined, in order to investigate the competition between both reaction types and its evolution with the incident energy. The experimental results will be discussed with a view to forthcoming radioactive-ion beam facilities, and next-generation active-target setups. [ABSTRACT FROM AUTHOR]

Lipoxin A4 (LXA4 ) has been shown to bind to the leucocyte formyl peptide receptor (FPR) homologue, FPRL1, without triggering the biological activities induced by other FPRL1 agonists. We investigated the direct effect of LXA4 as well as the effect on agonist-induced biological responses using transfected HL-60 cells expressing FPR, FPRL1 or FPRL2. LXA4 neither induced an intracellular rise in calcium in these transfectants nor affected the response induced by the peptide Trp–Lys–Tyr–Met–Val–Met (WKYMVM), an agonist that activates cells through FPRL1 and -2. Both agonists induced Erk-2 activation; however, the eicosanoid-induced activity was independent of FPRL1 and FPRL2. Moreover, LXA4 was unable to trigger neutrophil upregulation of complement receptor 3 and respiratory burst, and it had no effect on the responses induced by triggering with WKYMVM. We conclude that LXA4 is unable to affect the WKYMVM-induced signalling through FPRL1 and suggest that it acts through a receptor different from FPRL1. [ABSTRACT FROM AUTHOR]

Study Objective: To determine the potential role of seasonality in hospitalizations for cryptogenic and noncryptogenic hemoptysis in the French population.Design: Retrospective analysis of hospital discharge data from a National Register.Setting: All 29 French university hospitals, between July 1, 1994, and June 30, 1997.Patients: Two thousand six hundred seventy-seven and 3,672 adult hospitalizations for cryptogenic and other hemoptysis, respectively.Measurements: Cumulative monthly averages were determined, expressed as the percentage above or below the average monthly value during the entire study period.Results: The distribution of cumulative monthly hospitalizations for cryptogenic hemoptysis peaked in March (32% above the average) and was lowest in summer (30% below the average; p < 0.001). Hospitalizations for noncryptogenic hemoptysis followed a similar seasonal pattern (p < 0. 001). In the 16- to 34-year-old individuals, cryptogenic hemoptysis, compared with noncryptogenic hemoptysis, showed a higher incidence with a larger seasonal amplitude (p < 0.001).Conclusions: A better understanding of the fundamental pathophysiologic mechanisms underlying this respiratory and hemorrhagic condition may be helpful in developing preventive measures, especially in patients with a risk of recurrence. [ABSTRACT FROM AUTHOR]