STUDIO DEL COMPORTAMENTO DI METALLI REFRATTARI AD ELEVATI STRAIN-RATE E TEMPERATURE

L’introduzione di acceleratori di particelle ad elevata energia, come il Large Hardon Collider (LHC) realizzato al CERN, ha richiesto lo sviluppo di metodi avanzati per predire il comportamento di particolari dispositivi che possono essere soggetti all’impatto con il fascio di particelle, e che, quindi, sono progettati per operare in un ambiente estremamente radioattivo e fortemente sollecitato da un punto di vista termo-strutturale. I materiali coinvolti devono soddisfare una serie di requisiti, quali: elevata resistenza, buona duttilità alle alte velocità di deformazione ed elevata stabilità alle alte temperature, oltre ad una buona resistenza alla corrosione e agli ambienti radioattivi. Ne deriva che i metalli refrattari e le loro leghe risultano essere degli ottimi canditati e lo studio del loro comportamento meccanico deve essere effettuato in un ampio intervallo di velocità di deformazione e di temperature

Efficacy of Cannabidiol for Delta-9-Tetrahydrocannabinol-Induced Psychotic Symptoms, Schizophrenia, and Cannabis Use Disorders: A Narrative Review

Although cannabis’ major psychoactive component, ∆-9-tetrahydrocannabinol (THC), has been linked to both earlier onset and poorer outcomes of psychotic disorders, Cannabidiol (CBD) seems to have different pharmacological mechanisms and potential therapeutic properties. However, no clinical study has investigated CBD for the treatment of co-occurring psychotic and cannabis use disorders so far, even though its utility seems grounded in a plausible biological basis. The aim of this work is thus to provide an overview of available clinical studies evaluating the efficacy of CBD for psychotic symptoms induced by THC, schizophrenia, and cannabis use disorders. After searching for relevant studies in PubMed, Cochrane Library, and ClinicalTrials.gov, we included 10 clinical studies. Available evidence suggests that CBD may attenuate both psychotic-like symptoms induced by THC in healthy volunteers and positive symptoms in individuals with schizophrenia. In addition, preliminary data on the efficacy of CBD for cannabis use disorders show mixed findings. Evidence from ongoing clinical studies will provide insight into the possible role of CBD for treating psychotic and cannabis use disorders

Clinical trajectories of individuals with severe mental illness continuing and discontinuing long-acting antipsychotics: a one-year mirror-image analysis from the STAR Network Depot study

Evidence on long-acting antipsychotics (LAIs) in unselected populations with severe mental illness is scant. In this mirror-image study, we compared multiple clinical outcomes 1 year before and after a first LAI prescription in adults with severe mental illness, describing clinical trajectories of LAI continuers and discontinuers. We compared LAI continuers and discontinuers through Mann–Whitney U test, Kaplan–Meier survival curves, regression for interval-censored data, and a maximum-likelihood mixed-model with individual random-effect and time as predictor. Of the 261 participants analyzed, 71.3% had schizophrenia-spectrum disorders, and 29.5% discontinued the LAI before 1 year. At baseline, LAI discontinuers had a shorter illness duration, lower attitude and adherence scores. The mirror-image analysis showed reduced hospital admissions only for LAI continuers. Over time, continuers spent less days hospitalized, but had more adverse events and more antipsychotics prescribed, with higher overall doses. In conclusion, this study shows that LAIs might be beneficial in unselected patient populations, provided that adherence is maintained. LAI continuers spent less time hospitalized, but received more antipsychotics and suffered from more cumulative adverse events over time. Therefore, the choice of initiating and maintaining a LAI should be carefully weighed on a case-by-case basis

Laser system generating 250-mJ bunches of 5-GHz repetition rate, 12-ps pulses.

We report on a high-energy solid-state laser based on a master-oscillator power-amplifier system seeded by a 5-GHz repetition-rate mode-locked oscillator, aimed at the excitation of the dynamic Casimir effect by optically modulating a microwave resonator. Solid-state amplifiers provide up to 250 mJ at 1064 nm in a 500-ns (macro-)pulse envelope containing 12-ps (micro-)pulses, with a macro/micropulse format and energy resembling that of near-infrared free-electron lasers. Efficient second-harmonic conversion allowed synchronous pumping of an optical parametric oscillator, obtaining up to 40 mJ in the range 750-850 nm

Pre-Discharge Predictors of 1-Year Rehospitalization in Adolescents and Young Adults with Severe Mental Disorders: A Retrospective Cohort Study

BACKGROUND AND OBJECTIVES: Readmissions of youths hospitalized for a severe mental disorder are common events and bear a remarkable human, social, and economic burden. The current study aimed at evaluating predictors of 1-year rehospitalization in a sample of adolescents and young adults with severe mental disorders. MATERIALS AND METHODS: Data for ≤25-year-old inpatients with a severe mental disorder and consecutively admitted between 1 January 2016 and 30 June 2019 were collected. Subjects were retrospectively assessed over a follow-up period of one year after the index discharge to track readmissions—i.e., the primary outcome variable. Standard descriptive statistics were used. The association between variables and 1-year rehospitalization was estimated using the univariate Cox proportional hazards regression model. We then carried out a multivariable Cox regression model, also estimating the covariate-adjusted survivor function. Hazard ratios (HRs) with related 95% confidence intervals (95% CIs) were provided. RESULTS: The final sample included 125 individuals. The multivariable Cox regression model estimated that co-occurring substance use disorders (HR = 2.14; 95% CI: 1.08 to 4.26; p = 0.029) and being admitted for a suicide attempt (HR = 2.49; 95% CI: 1.13 to 5.49; p = 0.024) were both significant predictors of 1-year rehospitalization. CONCLUSIONS: Our study showed that comorbid substance use disorders and being admitted for a suicide attempt were predictors of early readmission in youths with severe mental disorders. Although their generalizability is limited, our findings could contribute to improve the quality of young patients’ mental health care by identifying vulnerable subjects who may benefit from tailored interventions to prevent rehospitalizations

Thermostructural characterization and structural elastic property optimization of novel high luminosity LHC collimation materials at CERN

The CERN Large Hadron Collider is currently being upgraded to operate at a stored beam energy of 680 MJ through the High Luminosity upgrade. The LHC performance is dependent on the functionality of beam collimation systems, essential for safe beam cleaning and machine protection. A dedicated beam experiment at the CERN High Radiation to Materials facility is created under the HRMT-23 experimental campaign. This experiment investigates the behavior of three collimation jaws having novel composite absorbers made of copper diamond, molybdenum carbide graphite, and carbon fiber carbon, experiencing accidental scenarios involving the direct beam impact on the material. Material characterization is imperative for the design, execution, and analysis of such experiments. This paper presents new data and analysis of the thermostructural characteristics of some of the absorber materials commissioned within CERN facilities. In turn, characterized elastic properties are optimized through the development and implementation of a mixed numerical-experimental optimization technique.peer-reviewe

Preliminary assessment of beam impact consequences on LHC Collimators

The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, the robustness of the collimators plays an important role. An accident, which causes the proton beam to hit a collimator, might result in severe beam-induced damage and, in some cases, replacement of the collimator, with consequent downtime for the machine. In this paper, several case studies representing different realistic beam impact scenarios are shown. A preliminary analysis of the thermal response of tertiary collimators to beam impact is presented, from which the most critical cases can be identified. Such work will also help to give an initial insight on the operational constraints of the LHC by taking into account all relevant collimator damage limits.peer-reviewe

behaviour of advanced materials impacted by high energy particle beams

Beam Intercepting Devices (BID) are designed to operate in a harsh radioactive environment and are highly loaded from a thermo-structural point of view. Moreover, modern particle accelerators, storing unprecedented energy, may be exposed to severe accidental events triggered by direct beam impacts. In this context, impulse has been given to the development of novel materials for advanced thermal management with high thermal shock resistance like metal-diamond and metal-graphite composites on top of refractory metals such as molybdenum, tungsten and copper alloys. This paper presents the results of a first-of-its-kind experiment which exploited 440 GeV proton beams at different intensities to impact samples of the aforementioned materials. Effects of thermally induced shockwaves were acquired via high speed acquisition system including strain gauges, laser Doppler vibrometer and high speed camera. Preliminary information of beam induced damages on materials were also collected. State-of-the-art hydrodynamic codes (like Autodyn®), relying on complex material models including equation of state (EOS), strength and failure models, have been used for the simulation of the experiment. Preliminary results confirm the effectiveness and reliability of these numerical methods when material constitutive models are completely available (W and Cu alloys). For novel composite materials a reverse engineering approach will be used to build appropriate constitutive models, thus allowing a realistic representation of these complex phenomena. These results are of paramount importance for understanding and predicting the response of novel advanced composites to beam impacts in modern particle accelerators

Preliminary comparison of the response of LHC tertiary collimators to proton and ion beam impacts

The CERN Large Hadron Collider is designed to bring into collision protons as well as heavy ions. Accidents involving impacts on collimators can happen for both species. The interaction of lead ions with matter differs to that of protons, thus making this scenario a new interesting case to study as it can result in different damage aspects on the collimator. This paper will present a preliminary comparison of the response of collimators to proton and ion beam impacts.peer-reviewe

Preliminary thermo-mechanical analysis of angular beam impact on LHC collimators

The correct functioning of the LHC Collimation System is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, accident scenarios must be well studied in order to assess their effect on the robustness of the collimators. One of the most probable accident scenarios identified is an asynchronous beam dump coupled with slight angular misalignment errors of the collimator installation at the beam-line. Previous work presented a preliminary thermal evaluation of the extent of beam-induced damage for such scenarios, where it was shown that in some cases, a tilt of the jaw could actually serve to mitigate the effect of an asynchronous dump on the collimators. This paper will further analyze the response of tertiary collimators in presence of such angular jaw alignments. Such work will also help to start identifying optimal operational conditions.peer-reviewe