Anticorrelation between Ion Acceleration and Nonlinear Coherent Structures from Laser-Underdense Plasma Interaction

In laser-plasma experiments, we observed that ion acceleration from the Coulomb explosion of the plasma channel bored by the laser, is prevented when multiple plasma instabilities such as filamentation and hosing, and nonlinear coherent structures (vortices/post-solitons) appear in the wake of an ultrashort laser pulse. The tailoring of the longitudinal plasma density ramp allows us to control the onset of these insabilities. We deduced that the laser pulse is depleted into these structures in our conditions, when a plasma at about 10% of the critical density exhibits a gradient on the order of 250 {\mu}m (gaussian fit), thus hindering the acceleration. A promising experimental setup with a long pulse is demonstrated enabling the excitation of an isolated coherent structure for polarimetric measurements and, in further perspectives, parametric studies of ion plasma acceleration efficiency.Comment: 4 pages, 5 figure

Short Intense Laser Pulse Collapse in Near-Critical Plasma

It is observed that the interaction of an intense ultra-short laser pulse with an overdense gas jet results in the pulse collapse and the deposition of a significant part of energy in a small and well localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. A collisionless plasma expansion over 150 microns at a sub-relativistic velocity (~c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionization of the gas associated to the hot electron current. Numerical simulations in good agreement with the observations suggest the acceleration in the collapse region of relativistic electrons, along with the excitation of a sizeable magnetic dipole that sustains the electron current over several picoseconds. Perspectives of ion beam generation at high repetition rate directly from gas jets are discussed

Inhaled CO2 Concentration While Wearing Face Masks: A Pilot Study Using Capnography

Background: Face masks are recommended based on the assumption that they protect against SARS-CoV-2 transmission, however studies on their potential side effects are still lacking. We aimed to evaluate the inhaled air carbon dioxide (CO2) concentration, when wearing masks. Methods: We measured end-tidal CO2 using professional side-stream capnography, with water-removing tubing, (1) without masks, (2) wearing a surgical mask, and (3) wearing a FFP2 respirator (for 5 minutes each while seated after 10 minutes of rest), in 146 healthy volunteers aged 10 to 90 years, from the general population of Ferrara, Italy. The inhaled air CO2 concentration was computed as: ([mask volume × end-tidal CO2] + [tidal volume − mask volume] × ambient air CO2)/tidal volume. Results: With surgical masks, the mean CO2 concentration was 7091 ± 2491 ppm in children, 4835 ± 869 in adults, and 4379 ± 978 in the elderly. With FFP2 respirators, this concentration was 13 665 ± 3655 in children, 8502 ± 1859 in adults, and 9027 ± 1882 in the elderly. The proportion showing a CO2 concentration higher than the 5000 ppm (8-hour average) acceptable threshold for workers was 41.1% with surgical masks, and 99.3% with FFP2 respirators. Adjusting for age, gender, BMI, and smoking, the inhaled air CO2 concentration significantly increased with increasing respiratory rate (mean 10 837 ±3712 ppm among participants ⩾18 breaths/minute, with FFP2 respirators), and among the minors. Conclusion: If these results are confirmed, the current guidelines on mask-wearing should be reevaluated

Semi-basements used as dwellings: hygienic considerations and analysis of the regulations.

Current housing shortage in Italy is forcing a growing number of individuals to use as living environment spaces that were originally devoted to other purposes. Among such spaces, semi-basements hold a particular relevance because of their specific characteristics and their effects on human health. The authors analyse the relatively scarce legislation about this topic at both national and regional level. The local Building Codes of the ten most populous cities of Italy are reviewed, assessing whether the use of semi-basements as living spaces is allowed and, if so, which restrictions and requirements are imposed. The authors conclude that, on one hand, further research is strongly needed to estimate the amount of exposed population and their health risk, on the other the existing legislation on the topic is often discretionary and deeply unhomogeneous across the country

Ion acceleration in underdense plasmas by ultra-short laser pulses

We report on the ion acceleration mechanisms that occur during the interaction of an intense and ultrashort laser pulse ( λ > μ I 2 1018 W cm−2 m2) with an underdense helium plasma produced from an ionized gas jet target. In this unexplored regime, where the laser pulse duration is comparable to the inverse of the electron plasma frequency ωpe, reproducible non-thermal ion bunches have been measured in the radial direction. The two He ion charge states present energy distributions with cutoff energies between 150 and 200 keV, and a striking energy gap around 50 keV appearing consistently for all the shots in a given density range. Fully electromagnetic particle-in-cell simulations explain the experimental behaviors. The acceleration results from a combination of target normal sheath acceleration and Coulomb explosion of a filament formed around the laser pulse propagation axi

Brunel-Dominated Proton Acceleration with a Few-Cycle Laser Pulse

International audienceExperimental measurements of backward accelerated protons are presented. The beam is produced when an ultrashort (5 fs) laser pulse, delivered by a kHz laser system, with a high temporal contrast (10 8), interacts with a thick solid target. Under these conditions, proton cutoff energy dependence with laser parameters, such as pulse energy, polarization (from p to s), and pulse duration (from 5 to 500 fs), is studied. Theoretical model and two-dimensional particle-in-cell simulations, in good agreement with a large set of experimental results, indicate that proton acceleration is directly driven by Brunel electrons, in contrast to conventional target normal sheath acceleration that relies on electron thermal pressure

Antifibrotic treatment response and prognostic predictors in patients with idiopathic pulmonary fibrosis and exposed to occupational dust

BACKGROUND: Idiopathic Pulmonary Fibrosis (IPF) is an aggressive interstitial lung disease with an unpredictable course. Occupational dust exposure may contribute to IPF onset, but its impact on antifibrotic treatment and disease prognosis is still unknown. We evaluated clinical characteristics, respiratory function and prognostic predictors at diagnosis and at 12 month treatment of pirfenidone or nintedanib in IPF patients according to occupational dust exposure. METHODS: A total of 115 IPF patients were recruited. At diagnosis, we collected demographic, clinical characteristics, occupational history. Pulmonary function tests were performed and two prognostic indices [Gender, Age, Physiology (GAP) and Composite Physiologic Index (CPI)] calculated, both at diagnosis and after the 12 month treatment. The date of long-term oxygen therapy (LTOT) initiation was recorded during the entire follow-up (mean = 37.85, range 12-60 months). RESULTS: At baseline, patients exposed to occupational dust [≥ 10 years (n = 62)] showed a lower percentage of graduates (19.3% vs 54.7%; p = 0.04) and a higher percentage of asbestos exposure (46.8% vs 18.9%; p 0.002) than patients not exposed [< 10 years (n = 53)]. Both at diagnosis and after 12 months of antifibrotics, no significant differences for respiratory function and prognostic predictors were found. The multivariate analysis confirmed that occupational dust exposure did not affect neither FVC and DLCO after 12 month therapy nor the timing of LTOT initiation. CONCLUSION: Occupational dust exposure lasting 10 years or more does not seem to influence the therapeutic effects of antifibrotics and the prognostic predictors in patients with IPF

Tobacco vs. electronic cigarettes: absence of harm reduction after six years of follow-up

OBJECTIVE: Information on the long-term safety of electronic cigarettes (e-cig) is still limited. We report the results after six years of follow-up of the first observational study assessing e-cig long-term effectiveness and safety. PATIENTS AND METHODS: Participants were adults who smoked ≥1 tobacco cigarette/day (tobacco smokers); or used any type of e-cig inhaling ≥50 puffs weekly (e-cig users); or used both (dual users). Participants were contacted directly or by phone and/or internet interviews. Hospital discharge abstract data and carbon monoxide level tests were also used. RESULTS: Data were available for 228 e-cig users (all ex-smokers), 469 tobacco smokers, 215 dual users. A possibly smoking-related disease (PSRD) was recorded in 90 subjects (9.9%); 11 deceased (1.2%). No differences were observed across groups in PSRD rates, with minor changes in self-reported health. Among e-cig users, 64.0% remained tobacco abstinent. Dual users and tobacco smokers did not significantly differ in the rate of cessation of tobacco (38.6% vs. 33.9%, respectively) and all products (23.7% vs. 26.4%). A comparable decrease in daily cigarettes was also observed. 39.5% of the sample switched at least once (tobacco smokers: 15.1%; dual users: 83.3%). CONCLUSIONS: After six years, no evidence of harm reduction was found among e-cig or dual users. The complete switch to e-cig might support tobacco quitters remain abstinent, but the use of e-cig in addition to tobacco did not improve smoking cessation or reduction

Persistence of magnetic field driven by relativistic electrons in a plasma

The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media. These processes are relevant over a wide range of conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion in stars. The disparate temporal and spatial scales where each operates can be reconciled by scaling parameters that enable to recreate astrophysical conditions in the laboratory. Here we unveil a new mechanism by which the flow of ultra-energetic particles can strongly magnetize the boundary between the plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro Tesla in astrophysical conditions). The physics is observed from the first time-resolved large scale magnetic field measurements obtained in a laser wakefield accelerator. Particle-in-cell simulations capturing the global plasma and field dynamics over the full plasma length confirm the experimental measurements. These results open new paths for the exploration and modelling of ultra high energy particle driven magnetic field generation in the laboratory

Severe Acute Respiratory Syndrome Coronavirus 2 Lethality Did not Change over Time in Two Italian Provinces

This retrospective cohort study included all the subjects diagnosed with severe acute respiratory syndrome coronavirus 2 infection (n=2493) in 2 Italian provinces. Two hundred fifty-eight persons died, after a median of 14.0\ub111.0 days. Adjusting for age, gender, and main comorbidities, the 6528-day case-fatality rate did not decrease from March to April 2020 (adjusted hazard ratio, 0.93; P=.6)