393 research outputs found

    Optimised pulse duration for the laser cleaning of oil gilding

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    The laser cleaning problem of gold leaf gilded surfaces was investigated here. Preliminary irradiation tests carried out on pure gold leaf standards evidenced the crucial importance of the laser pulse duration for avoiding serious damages. Optimised pulse duration providing good cleaning results with negligible side effects was then selected and successfully used in the restoration of three Renaissance masterpieces

    The S0_0(0) structure in highly compressed hydrogen and the orientational transition

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    A calculation of the rotational S0_0(0) frequencies in high pressure solid para-hydrogen is performed. Convergence of the perturbative series at high density is demonstrated by the calculation of second and third order terms. The results of the theory are compared with the available experimental data to derive the density behaviour of structural parameters. In particular, a strong increase of the value of the lattice constant ratio c/ac/a and of the internuclear distance is determined. Also a decrease of the anisotropic intermolecular potential is observed which is attributed to charge transfer effects. The structural parameters determined at the phase transition may be used to calculate quantum properties of the rotationally ordered phase.Comment: accepted Europhysics Letter

    Preliminary results of the Italian neutron experimental station INES at ISIS: Archaeometric applications

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    The INES project was sponsored by the CNR Neutron Spectroscopy Advisory Committee, stressing the importance of realizing an Italian Neutron Experimental Station (INES) at the world most powerful pulsed neutron source (ISIS, Rutherford Appleton Laboratory, UK) and evidencing the strategic value that such a test station would assume in the field of applied sciences like, for example, chemistry, material science, Earth science, crystallography, and last, but not least, in the field of science applied to the study of cultural-heritage artifacts

    On the Iteration Complexity of Hypergradient Computation

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    We study a general class of bilevel problems, consisting in the minimization of an upper-level objective which depends on the solution to a parametric fixed-point equation. Important instances arising in machine learning include hyperparameter optimization, meta-learning, and certain graph and recurrent neural networks. Typically the gradient of the upper-level objective (hypergradient) is hard or even impossible to compute exactly, which has raised the interest in approximation methods. We investigate some popular approaches to compute the hypergradient, based on reverse mode iterative differentiation and approximate implicit differentiation. Under the hypothesis that the fixed point equation is defined by a contraction mapping, we present a unified analysis which allows for the first time to quantitatively compare these methods, providing explicit bounds for their iteration complexity. This analysis suggests a hierarchy in terms of computational efficiency among the above methods, with approximate implicit differentiation based on conjugate gradient performing best. We present an extensive experimental comparison among the methods which confirm the theoretical findings

    Preliminary results of the Italian neutron experimental station INES at ISIS: Archaeometric applications

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    The INES project was sponsored by the CNR Neutron Spectroscopy Advisory Committee, stressing the importance of realizing an Italian Neutron Experimental Station (INES) at the world most powerful pulsed neutron source (ISIS, Rutherford Appleton Laboratory, UK) and evidencing the strategic value that such a test station would assume in the field of applied sciences like, for example, chemistry, material science, Earth science, crystallography, and last, but not least, in the field of science applied to the study of cultural-heritage artifacts

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

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    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 moderate 500-m treadmill walk for estimating peak oxygen uptake in men with NYHA class I-II heart failure and reduced left ventricular ejection fraction

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    Background: Maximal cardiopulmonary exercise testing (CPX) is the gold-standard for cardiorespiratory fitness assessment in chronic heart failure (CHF) patients. However, high costs, required medical supervision, and safety concerns make maximal exercise testing impractical for evaluating mobility-impaired adults. Thus, several submaximal walking protocols have been developed and currently used to estimate peak oxygen consumption (VO(2)peak)in CHF patients. However, these tests have to be performed at close to maximum exercise intensity. The aim of this study was to examine the validity of a 500-m treadmill-walking test carried out at moderate intensity for estimating VO(2)peak in community-dwelling adult and elderly patients with CHF and reduced left ventricular ejection fraction (HFrEF).Methods: Forty-three clinically stable men with HFrEF (age 67.7 +/- 9.2 years, and left ventricular ejection fraction, LVEF 38% +/- 6%) underwent exercise testing during an outpatient cardiac rehabilitation/secondary prevention program. Each patients completed a CPX, and a moderate and self-paced (11-13/20 on the Borg scale) 500-m treadmill-walking test. Age, weight, height, walk time, and heart rate during the 500-m test were entered into prediction equations previously validated for VO(2)peak estimation from a 1000-m walking test in patients with cardiovascular disease and preserved LVEF.Results: Directly measured and estimated VO(2)peak values were not different (21.6 +/- 4.9 vs 21.7 +/- 4.6 mL/kg/min). The comparison between measured and estimated VO(2)peak values yielded a correlation of R = 0.97 (SEE = 0.7 mL/kg/min, P < 0.0001). The slope and the intercept coincided with the line of identity (Passing and Bablock analysis, P = 0.50). Residuals were normally distributed, and the examination of the Bland-Altman analysis do not show systematic or proportional error.Conclusions: A moderate and self-regulated 500-m treadmill-walking test is a valid tool for VO(2)peak estimation in patients with HFrEF. These findings may have practical implications in the context of transitioning from clinically based programs to fitness facilities or self-guided exercise programs in adults and elderly men with HFrEF

    Dependency-like behaviors and pain coping styles in subjects with chronic migraine and medication overuse : Results from a 1-year follow-up study

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    Background: Even after successful detoxification, 20-40% of subjects presenting chronic migraine with symptomatic medication overuse (CMwMO) relapse into medication overuse within one year. In this restrospective analysis on subjects referred to our center for detoxification, we investigated whether personality traits, dependency-like behaviors and pain coping styles predicted those who relapsed into medication overuse within the 12\ua0months following the detoxification and those who did not.Methods: 63 patients with CMwMO were assessed for personality traits, mood and anxiety, pain coping styles and dependency-like behaviors prior-to and one year after a detoxification program.Results: Of the 42 subjects who attended 1-year follow-up interviews, 11 relapsed into medication overuse despite a temporary benefit from detoxification and did not show clinical or psychological improvement, instead reporting increased anxiety and unmodified perpetuation of severe dependency-like behaviors. In contrast, subjects who did not relapse into medication overuse had clinical improvements that generalized to untreated domains, including decreased depressive symptoms and dependency-like behaviors, although showing unmodified low internal control over pain.Conclusions: Subjects who did not fall into medication overuse throughout the 12\ua0months following the detoxification showed improved clinical, affective and dependence-related outcomes, but not pain coping strategies. Conversely, subjects who relapsed within one year into CMwMO continued to experience significant disability, pain intensity, and dependency-like behaviors. We believe that the persistence of maladaptive pain coping strategies and residual symptomatology increase the risk for recurrent relapses, against which pharmacological interventions are only partially effective. Further studies investigating predictors of relapse are needed to inform multi-disciplinary interventions for CMwMO

    Mapping assessments instruments for headache disorders against the icf biopsychosocial model of health and disability

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    Headache disorders have a strong impact on sufferers’ lives. However, the “content” of assessment instruments addressing concepts, such as disability and quality of life (QoL), has not comprehensively been addressed. We searched SCOPUS for research papers in which outcome measures were used in adult populations of patients with migraine, tension-type headache (TTH), and cluster headache (CH). The content of single instruments was then mapped against the International Classification of Functioning, Disability, and Health. A total of 150 papers and 26 instruments were included: 15 addressed disability or impact, two addressed work-related difficulties, and nine addressed QoL. Few instruments were commonly used across the conditions and covered domains of functioning were impact on daily life activities, homework, school, and work-related tasks, leisure time, informal and family relations, pain, emotional difficulties, energy level, and impulse control. Most of the research is based on instruments that were developed for migraine, which is critical for CH, and the impact of headache disorders on work-related activities is poorly acknowledged. Further research is needed to expand the scope of headaches impact on daily life activities, and on environmental factors relevant to headache disorders to raise knowledge on the less represented areas, e.g., TTH impact

    Neutron Tomography at INES: First experimental results

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    A neutron tomography apparatus has been designed and installed at the Italian neutron experimental station (INES) at ISIS (UK). The instrument has a double aim: an additional opportunity for the INES users and a “bench test” for an instrument component that will be proposed for installation on some of the new neutron scattering instruments of Target Station 2 (TS2) of ISIS. Here, we present the first experimental results achieved with this apparatus
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