Analysis of enhanced-performance fibre Brillouin ring laser for Brillouin sensing applications

In this work, we present an enhanced design for a Brillouin ring laser (BRL), which employs a double resonant cavity (DRC) with short fiber length, paired with a heterodyne-based wavelength-locking system, to be employed as a pump-probe source for Brillouin sensing. The enhanced source is compared to traditional long-cavity pump-probe source, showing a significantly lower relative intensity noise (~-145 dB/Hz in the whole 0\u2013800 MHz range), a narrow linewidth (10 kHz), and large tunability features, resulting in an effective pump-probe source in BOTDA systems, with an excellent pump-probe frequency stability (~200 Hz), which is uncommon for fiber lasers. The enhanced source showed an improved signal-to-noise ratio (SNR) of about 22 dB with respect to standard BRL schemes, resulting in an improved temperature/strain resolution in BOTDA applications up to 5.5 dB, with respect to previous high-noise BRL designs

Strain Transfer in Surface-Bonded Optical Fiber Sensors

Fiber optic sensors represent one of the most promising technologies for the monitoring of various engineering structures. A major challenge in the field is to analyze and predict the strain transfer to the fiber core reliably. Many authors developed analytical models of a coated optical fiber, assuming null strain at the ends of the bonding length. However, this configuration only partially reflects real experimental setups in which the cable structure can be more complex and the strains do not drastically reduce to zero. In this study, a novel strain transfer model for surface-bonded sensing cables with multilayered structure was developed. The analytical model was validated both experimentally and numerically, considering two surface-mounted cable prototypes with three different bonding lengths and five load cases. The results demonstrated the capability of the model to predict the strain profile and, differently from the available strain transfer models, that the strain values at the extremities of the bonded fiber length are not null

Photoproduction of electron-positron pairs in bent single crystals

The process of photoproduction of electron-positron pairs in bent single crystals is considered in this paper. In particular, it is shown that the probability of the process for gamma-quanta with energies from 100 GeV on is significantly higher than the one in an amorphous medium. A possible scenario for the experimental validation of the process is discussed and the positive features of the photoproduction in bent crystals compared to straight ones are underlined from the point of view of possible applications.Comment: 13 pages, 6 figure

Adolescent drug use escalation and de-escalation: a 3-year follow-up study [Abstract]

This study aims to assess adolescents drug use with a longitudinal perspective in order to identify factors interacting with drug use onset and course. Supported by the Swiss Federal Office of Public Health, the study was initiated in 1999 with a follow-up in 2001 and 2002. The first objective was to measure risk factors for substance use initiation. The second objective was to analyse the co-variation of substance use with environmental, social, relational, medical and psychological factors. A total of 102 adolescents, aged 14-19 years, were recruited for the study in the French-speaking part of Switzerland. Results clearly show that substance use is not a disorder per se in adolescence, but that it is part of a multidimensional complex of problems that some adolescents may encounter: increase and decrease in substance use is paralleled with an increase or decrease in the other areas. This implies that prevention of substance use should not be focused mainly on substances but should consider the adolescent's environment and significant life area

A Model-Assisted Probability of Detection Framework for Optical Fiber Sensors

Optical fiber sensors (OFSs) represent an efficient sensing solution in various structural health monitoring (SHM) applications. However, a well-defined methodology is still missing to quantify their damage detection performance, preventing their certification and full deployment in SHM. In a recent study, the authors proposed an experimental methodology to qualify distributed OFSs using the concept of probability of detection (POD). Nevertheless, POD curves require considerable testing, which is often not feasible. This study takes a step forward, presenting a model-assisted POD (MAPOD) approach for the first time applied to distributed OFSs (DOFSs). The new MAPOD framework applied to DOFSs is validated through previous experimental results, considering the mode I delamination monitoring of a double-cantilever beam (DCB) specimen under quasi-static loading conditions. The results show how strain transfer, loading conditions, human factors, interrogator resolution, and noise can alter the damage detection capabilities of DOFSs. This MAPOD approach represents a tool to study the effects of varying environmental and operational conditions on SHM systems based on DOFSs and for the design optimization of the monitoring system

No efficacy of transcranial direct current stimulation on chronic migraine with medication overuse : a double blind, randomised clinical trial

Background: Transcranial direct current stimulation was suggested to provide beneficial effects in chronic migraine, a condition often associated with medication overuse for which no long-term therapy is available. Methods: We conducted a randomised controlled trial to assess long-term efficacy of transcranial direct current stimulation. Adults diagnosed with chronic migraine and medication overuse were assigned to receive in a 1:1:1 ratio anodal, cathodal, or sham transcranial direct current stimulation daily for five consecutive days, along with standardised drug withdrawal protocol. Primary outcome was 50% reduction of days of headache per month at 12 months. Co-secondary outcomes were 50% reduction of days of headache per month at 6 months, reduction of analgesic intake per month, and change in disability and quality of life, catastrophising, depression, state and trait anxiety, dependence attitude and allodynia intensity. Patients were not allowed to take any migraine prophylaxis drug for the entire study period. Results: We randomly allocated 135 patients to anodal (44), cathodal (45), and sham (46) transcranial direct current stimulation. At 6 and 12 months, the percentage of reduction of days of headache and number of analgesics per month ranged between 48.5% and 64.7%, without differences between transcranial direct current stimulation (cathodal, anodal, or the results obtained from the two arms of treatment, anodal plus cathodal) and sham. Catastrophising attitude significantly reduced at 12 months in all groups. There was no difference for the other secondary outcomes. Conclusions: Transcranial direct current stimulation did not influence the short and long-term course of chronic migraine with medication overuse after acute drug withdrawal. Behavioral and educational measures and support for patients' pain management could provide long-term improvement and low relapse rate. Trial registration number NCT04228809

A multidisciplinary approach to study the reproductive biology of wild prawns

This work aims to provide deeper knowledge on reproductive biology of P. kerathurus in a multidisciplinary way. Upon 789 examined females, 285 were found inseminated. The logistic equation enabled to estimate the size at first maturity at 30.7 mm CL for female. The Gono-Somatic Index (GSI) showed a pronounced seasonality, ranged from 0.80 ± 0.34 to 11.24 ± 5.72. Histological analysis highlighted five stages of ovarian development. Gonadal fatty acids analysis performed with gas chromatograph evidenced a pronounced seasonal variation; total lipids varied from 1.7% dry weight (dw) in Winter, to 7.2% dw in Summer. For the first time, a chemometric approach (Principal Component Analysis) was applied to relate GSI with total lipid content and fatty acid composition of gonads. The first two components (PC1 and PC2) showed that seasonality explained about 84% of the variability of all data set. In particular, in the period February-May, lipids were characterized by high PUFAs content, that were probably utilized during embryogenesis as energy source and as constituent of the cell membranes. During the summer season, gonads accumulated saturated FAs, that will be used during embryogenesis and early larval stages, while in the cold season total lipids decreased drastically and the gonad reached a quiescent state

Adalimumab efficacy in enteropathic spondyloarthritis: A 12-mo observational multidisciplinary study

AIM To report adalimumab (Ada) efficacy on articulargastrointestinal disease and health-related quality of life (HRQoL) in patients with enteropathic spondyloarthritis (ES). METHODS A cohort of 52 patients with ES was evaluated in the departments of gastroenterology and internal medicine. At baseline, all patients underwent assessment by an integrated gastro-rheumatologic evaluation of articular and gastrointestinal activity, as well patient reported outcomes (PROs) of the HRQoL questionnaires. After this integrated evaluation and following a specific working flowchart, the Ada anti-tumor necrosis factor (TNF)-inhibitor was assigned to a cohort of 30 patients and its clinical efficacy was evaluated at baseline and after 6-mo and 12-mo treatment by the following tests: (1) Ankylosing Spondylitis Disease Activity Score- C-Reactive Protein (ASDAS-CRP); Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Metrology Index (BASMI) for articular activity; (2) Inflammatory Bowel Disease Questionnaire (IBDQ), Crohn's Disease Activity Index (CDAI) and partial Mayo (pMayo) score for gastrointestinal symptoms and activity; and (3) Health Assessment Questionnaire (HAQ), Patient Global Assessment (PGA) and Short Form-36 health survey (SF-36) questionnaires for PROs of the HRQoL. RESULTS Integrated evaluation and management of the patients affected by ES, carried out simultaneously by a gastroenterologist and a rheumatologist, allowed clinicians to choose the optimal therapeutic strategy. In a cohort of 30 ES patients affected by active articular and gastrointestinal disease, or axial active articular inflammation, Ada led to fast and sustained improvement of both articular and gastrointestinal disease activities. In fact, all the clinimetric evaluation tests exploring articular or gastrointestinal activity, as well as all the HRQoL scores, showed a significant improvement having been achieved at the earliest (6-mo) assessment. This important clinical improvement was maintained at the 12-mo follow-up. Importantly, global and gastrointestinal quality of life significantly correlated with articular disease activity, providing evidence to support that the integrated evaluation is the best option to manage patients with ES. CONCLUSION Ada treatment, upon multidisciplinary (gastrorheumatologic) evaluation, significantly improves both articular and gastrointestinal inflammation, thereby improving the HRQoL in patients affected by ES