Longitudinal phase space manipulation in energy recovering linac-driven free-electron lasers

Energy recovering an electron beam after it has participated in a free-electron laser (FEL) interaction can be quite challenging because of the substantial FEL-induced energy spread and the energy anti-damping that occurs during deceleration. In the Jefferson Lab infrared FEL driver-accelerator, such an energy recovery scheme was implemented by properly matching the longitudinal phase space throughout the recirculation transport by employing the so-called energy compression scheme. In the present paper,after presenting a single-particle dynamics approach of the method used to energy-recover the electron beam, we report on experimental validation of the method obtained by measurements of the so-called "compression efficiency" and "momentum compaction" lattice transfer maps at different locations in the recirculation transport line. We also compare these measurements with numerical tracking simulations.Comment: 31 pages, 13 figures, submitted to Phys. Rev. Special Topics A&

Evaluating the Open and Engaged Components of Acceptance and Commitment Therapy in an Online Self-Guided Website: Results From a Pilot Trial

Online acceptance and commitment therapy (ACT) is promising for treating a range of psychological problems. Component research can further clarify which components are needed for optimal outcomes in what contexts. Online platforms provide a highly controlled format for such research. In this pilot trial, 55 adults were randomized to: ACT-Open (i.e., acceptance, defusion components), ACT-Engaged (i.e., values, committed action), or ACT-Combined (i.e., acceptance, defusion, values, committed action). Each condition was 12 sessions over six weeks, with assessments at baseline, posttreatment, and four-week follow-up. ACT-Open, ACT-Engaged, and ACT-Combined all significantly improved from pre- to post-treatment on mental health, psychosocial functioning, and components of psychological flexibility. Compared to ACT-Combined, ACT-Open improved less on psychosocial functioning at posttreatment, and ACT-Engaged worsened on functioning at follow-up. The platform was acceptable with high satisfaction ratings. Results support the feasibility of conducting online ACT component research, which will be tested in a fully powered non-inferiority trial

Potential application of hydrogen in traumatic and surgical brain injury, stroke and neonatal hypoxia-ischemia

This article summarized findings of current preclinical studies that implemented hydrogen administration, either in the gas or liquid form, as treatment application for neurological disorders including traumatic brain injury (TBI), surgically induced brain injury (SBI), stroke, and neonatal hypoxic-ischemic brain insult (HI). Most reviewed studies demonstrated neuroprotective effects of hydrogen administration. Even though anti-oxidative potentials have been reported in several studies, further neuroprotective mechanisms of hydrogen therapy remain to be elucidated. Hydrogen may serve as an adjunct treatment for neurological disorders

An Open Trial of Group Acceptance and Commitment Therapy (ACT) With an Adjunctive Mobile App for Generalized Anxiety Disorder (GAD)

Generalized anxiety disorder (GAD) is a common and debilitating condition. Effective treatments exist, but they are time-and resource-intensive. This study tested the initial efficacy and acceptability of a novel treatment protocol designed to increase efficiency: acceptance and commitment therapy (ACT) taught in groups and through an adjunctive mobile app. Participants were 21 individuals with GAD who received six weeks of 2-hour group ACT sessions as well as access to an adjunctive ACT mobile app. Significant improvements occurred in worry, anxiety, social functioning, and depression as well as relevant processes (psychological inflexibility, anxiety-related cognitive fusion). In-the-moment improvements were also observed in symptoms and ACT processes immediately after completing mobile app sessions. Treatment was perceived as credible and acceptable overall. However, rates of reliable and clinically significant change were low, and app usage did not correlate with change in worry. Overall, this study suggests that an efficient, brief ACT group intervention combined with a mobile app may lead to improvements in GAD but may not be sufficient for clinically significant change. A detailed overview of the treatment is included, and guidance for clinicians interested in implementing this protocol is discussed

Beam-Breakup Instability Theory for Energy Recovery Linacs

Here we will derive the general theory of the beam-breakup instability in recirculating linear accelerators, in which the bunches do not have to be at the same RF phase during each recirculation turn. This is important for the description of energy recovery linacs (ERLs) where bunches are recirculated at a decelerating phase of the RF wave and for other recirculator arrangements where different RF phases are of an advantage. Furthermore it can be used for the analysis of phase errors of recirculated bunches. It is shown how the threshold current for a given linac can be computed and a remarkable agreement with tracking data is demonstrated. The general formulas are then analyzed for several analytically solvable cases, which show: (a) Why different higher order modes (HOM) in one cavity do not couple so that the most dangerous modes can be considered individually. (b) How different HOM frequencies have to be in order to consider them separately. (c) That no optics can cause the HOMs of two cavities to cancel. (d) How an optics can avoid the addition of the instabilities of two cavities. (e) How a HOM in a multiple-turn recirculator interferes with itself. Furthermore, a simple method to compute the orbit deviations produced by cavity misalignments has also been introduced. It is shown that the BBU instability always occurs before the orbit excursion becomes very large.Comment: 12 pages, 6 figure

Thomson and Compton scattering with an intense laser pulse

Our paper concerns the scattering of intense laser radiation on free electrons and it is focused on the relation between nonlinear Compton and nonlinear Thomson scattering. The analysis is performed for a laser field modeled by an ideal pulse with a finite duration, a fixed direction of propagation and indefinitely extended in the plane perpendicular to it. We derive the classical limit of the quantum spectral and angular distribution of the emitted radiation, for an arbitrary polarization of the laser pulse. We also rederive our result directly, in the framework of classical electrodynamics, obtaining, at the same time, the distribution for the emitted radiation with a well defined polarization. The results reduce to those established by Krafft et al. [Phys. Rev. E 72, 056502 (2005)] in the particular case of linear polarization of the pulse, orthogonal to the initial electron momentum. Conditions in which the differences between classical and quantum results are visible are discussed and illustrated by graphs

The influence of the Great Recession on perinatal health—an ecological study on the trend changes and regional differences in Portugal

Background: Few studies examine the relationship between socioeconomic factors and trends in mortality in high-income European countries. Due to the lack of regional-level data, most recent studies on social inequality in Portugal do not investigate regional differences. This study analyses time trends and regional disparities in the evolution of perinatal mortality (PMR) and infant mortality (IMR) associated with demographic and socioeconomic indicators following Portugal's 2008 economic and financial crisis. Methods: Associations were assessed using generalised linear models. A Poisson joinpoint regression model was applied to identify relevant PMR and IMR changes between 2000 and 2018. Country regional disparities were analysed using Mixed Effect Multilevel models. Findings: IMR and PMR significantly decreased in the pre-crisis period but not in the post-crisis period. The significant differences between regions in IMR and PMR in 2000 were followed by a different evolution of regional IMR after 2008. PMR and IMR were not significantly associated with socioeconomic indicators. A significant positive association with maternal age at first birth was identified. Interpretation: Results confirm the influence of the crisis on PMR and IMR trends in Portugal, taking into account recurring associations between macroeconomic cycles, variations in mortality trends, macroeconomic volatility, and stagnation of IMR and PMR. Regional inequalities confirm the internal variability of the crisis influence and persistent spatial inequalities affecting IMR patterns. Funding: FCT, under the Institute of Public Health of the University of Porto (ISPUP)– EPIUnit ( UIDB/04750/2020) and ITR ( LA/P/0064/2020), Maastricht University's external PhD programme under the Care and Public Health Research Institute ( CAPHRI), and the RECAP preterm project (grant agreement no 733280). © 2023 The Author(s)FCT, under the Institute of Public Health of the University of Porto (ISPUP)–EPIUnit (UIDB/04750/2020) and ITR (LA/P/0064/2020), Maastricht University's external PhD programme under the Care and Public Health Research Institute (CAPHRI), and the RECAP preterm project (grant agreement no 733280)

Interventions to improve immigrant health. A scoping review.

Background: Disparities in health between immigrants and their host populations have been described across countries and continents. Hence, interventions for improving health targeting general populations are not necessarily effective for immigrants. Aims: To conduct a systematic search of the literature evaluating health interventions for immigrants; to map the characteristics of identified studies including range of interventions, immigrant populations and their host countries, clinical areas targeted and reported evaluations, challenges and limitations of the interventions identified. Following the results, to develop recommendations for research in the field. Methods: A scoping review approach was chosen to provide an overview of the type, extent and quantity of research available. Studies were included if they empirically evaluated health interventions targeting immigrants and/or their descendants, included a control group, and were published in English (PubMed and Embase from 1990 to 2015). Results: Most of the 83 studies included were conducted in the USA, encompassed few immigrant groups and used a randomized controlled trial (RCT) or cluster RCT design. Most interventions addressed chronic and non-communicable diseases and attendance at cancer screening services, used individual targeted approaches, targeted adult women and recruited participants from health centres. Outcome measures were often subjective, with the exception of interventions for cardiovascular risk and diabetes. Generally, authors claimed that interventions were beneficial, despite a number of reported limitations. Conclusions: Recommendations for enhancing interventions to improve immigrant health are provided to help researchers, funders and health care commissioners when deciding upon the scope, nature and design of future research in this area