Protons accelerated in the target normal sheath acceleration regime by a femtosecond laser

Advanced targets based on thin films of graphene oxide covered by metallic layers have been irradiated at high laser intensity (∼1019 W/cm2) with 40 fs laser pulses to investigate the forward ion acceleration in the target normal sheath acceleration regime. A time-of-flight technique was employed with silicon-carbide detectors and ion collectors as fast on-line plasma diagnostics. At the optimized conditions of the laser focus position with respect to the target surface was measured the maximum proton energy using Au metallic films. A maximum proton energy of 2.85 MeV was measured using the Au metallization of 200 nm. The presence of graphene oxide facilitates the electron crossing of the foil minimizing the electron scattering and increasing the electric field driving the ion acceleration. The effect of plasma electron density control using the graphene oxide is presented and discussed

Comparison between Dry-Land and Swimming Priming on 50 m Crawl Performance in Well-Trained Adolescent Swimmers

The purpose of the study was to investigate the effect of dry-land priming (DLP) versus swimming priming (SP) on the 50 m crawl performance of well-trained adolescent swimmers. Thirteen adolescent swimmers were randomly assigned to perform either a DLP or SP 24 h prior to a 50 m sprint crawl time-trial. Baseline measurements included a 50 m sprint crawl time-trial as a control (C) condition, the evaluation of body composition, countermovement jump (CMJ), isometric peak torque (IPT), and rate of torque development (RTD). Rating of perceived exertion (RPE) was obtained following the DLP and SP programs. Both DLP and SP significantly decreased the 50 m crawl time-trial, by −2.51 ± 2.43% and −2.59 ± 1.89% (p < 0.01), respectively, compared with the C time-trial. RPE was not different between DLP and SP (p = 0.919). CMJ performance remained unchanged after DLP and SP programs compared with the C trial (p > 0.05). The percentage decrease in the 50 m crawl after DLP was significantly correlated with the percentage decrease in the 50 m crawl following SP (r = 0.720, p = 0.006). CMJ power, lean body mass, IPT, and RTD were significantly correlated with 50 m crawl performance. These results suggest that both DLP and SP strategies, when applied 24 h prior to a 50 m crawl time-trial, may enhance performance in well-trained adolescent swimmers. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Recreational Soccer, Body Composition and Cardiometabolic Health: A Training-Intervention Study in Healthy Adolescents

Recreational soccer (RS) is widely used for adolescents as a physical activity method. However, its impact on physical fitness, body composition and metabolic health in adolescents has not been extensively examined yet. The purpose of the present study was to examine the contribution of changes in body fatness and aerobic capacity to modifications in circulating blood lipids profile, following 8-weeks of RS in healthy youth. Fifty-three healthy male adolescents were separated in three groups: one performed RS (3 times x 60 min/week); the other two were served as control groups [soccer-specific training (SST) one and inactive one]. Physical fitness, body composition and blood lipids and glucose responses were evaluated before and after 8-weeks of exercise intervention. Post-intervention body weight and body fat percentage (BF%) were lowered, while physical fitness was improved (p < 0.05) in SST group only. High density lipoprotein cholesterol (HDL-C) was higher (n2 =.378) and total cholesterol (TC)/HDL-C ratio was lower (n2 =.195) in the SST group relative to RS and inactive groups (p < 0.05). In conclusion, although RS may improve aerobic capacity, relative to inactive control group, it does not influence body fatness and cardiometabolic health in adolescents. Consequently, RS may not secure health benefit during the crucial transition period from adolescence to adulthood

Resonant absorption effects induced by polarized laser ligth irradiating thin foils in the tnsa regime of ion acceleration

Thin foilswere irradiated by short pulsed lasers at intensities of 1016-19 W/cm2 in order to produce non-equilibrium plasmas and ion acceleration from the target-normal-sheath-acceleration (TNSA) regime. Ion acceleration in forward direction was measured by SiC detectors and ion collectors used in the time-of-flight configuration. Laser irradiations were employed using p-polarized light at different incidence angles with respect to the target surface and at different focal distances from the target surface. Measurements demonstrate that resonant absorption effects, due to the plasmawave excitations, enhance the plasma temperature and the ion acceleration with respect to those performed without to use of p-polarized light. Dependences of the ion flux characteristics on the laser energy, wavelength, focal distance and incidence angle will be reported and discussed