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

A calculation of the rotational S$_0$(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 $c/a$ 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

Turmoil over the crisis: innovation capabilities and firm exit

This work investigates the relationship between the characteristics and survival probabilities of firms, distinguishing between “involuntary” firm exit and exit by merger and acquisition (M&A). More in detail, we study how, and to what extent, innovation capabilities, as proxied by patents and trademarks, are able to shape, together with standard performance variables, the observed dynamics at the firm level. By using comprehensive data on Italian firms from business registers, we separate the administrative procedures leading to “involuntary” exit from those ending up with an event of M&A. We find that while higher productivity is associated with a lower probability of “involuntary” exit, productivity increases the chances of being the target for M&A. As far as intellectual property instruments are concerned, they tend to reduce the probability of both “involuntary” exit and M&A. However, the relative importance of the two instruments differs according to the exit route: patents are more relevant than trademarks in preventing “involuntary” exit, while the opposite is true for M&A. Plain English Summary We investigate firm’s exit after a crisis. Overall innovation plays a positive role, but the relative importance of IP depends on the exit route: patents are more relevant than trademarks against “involuntary” exit, while the opposite is true for M&A. We resort to the virtual universe of Italian limited liability firms from manufacturing, trade, and service to investigate the determinants of firm survival over the period 2010–2014. We scrutinize detailed administrative data on significant events occurring to firms to distinguish between events leading to involuntary exit and to M&A. In addition to the evidence on innovation, our results show that higher productivity decreases the probability of “involuntary” exit, yet productivity increases the chances of being the target for M&A. Taken together, these findings warn against a simplistic perspective on exit: the role of innovation and firm characteristics heavily depends on the exit route

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

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

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

Turbulence underneath the big calm? The micro-evidence behind Italian productivity dynamics

Italy ranked last in terms of manufacturing productivity growth according to OECD estimates over the last decade, with a flat, if not declining, trend. In this work we investigate the underlying firm-level dynamics of enterprises on the basis of a database developed by the Italian Statistical Office (ISTAT) covering the period 1989–2004 and containing information on more than 100,000 firms. Over this period not only have the indicators of the central tendency of the distribution of labor productivity not significantly changed, but also the whole sectoral distributions have remained relatively stable over time, with their support at least not shrinking, or even possibly widening, over time. This is even more surprising if one takes into consideration the “Euro” shock that occurred during the period investigated. On the contrary, we observe that inter-decile differences in productivity have been increasing. Further, heterogeneous firms’ characteristics (i.e. export activity and innovation) seem to have contributed to boosting such intra-industry differences. Given such wide heterogeneities we resort to quantile regressions to identify the impact of a set of regressors at different levels of the conditional distribution of labor productivity. One phenomenon that we observe is what we call a tendency toward “neo-dualism” involving the co-existence of a small group of dynamic firms with a bigger ensemble of much less technologically progressive ones

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

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

Group Meritocratic Fairness in Linear Contextual Bandits

We study the linear contextual bandit problem where an agent has to select one candidate from a pool and each candidate belongs to a sensitive group. In this setting, candidates⧠rewards may not be directly comparable between groups, for example when the agent is an employer hiring candidates from different ethnic groups and some groups have a lower reward due to discriminatory bias and/or social injustice. We propose a notion of fairness that states that the agent* policy is fair when it selects a candidate with highest relative rank, which measures how good the reward is when compared to candidates from the same group. This is a very strong notion of fairness, since the relative rank is not directly observed by the agent and depends on the underlying reward model and on the distribution of rewards. Thus we study the problem of learning a policy which approximates a fair policy under the condition that the contexts are independent between groups and the distribution of rewards of each group is absolutely continuous. In particular, we design a greedy policy which at each round constructs a ridge regression estimate from the observed context-reward pairs, and then computes an estimate of the relative rank of each candidate using the empirical cumulative distribution function. We prove that, despite its simplicity and the lack of an initial exploration phase, the greedy policy achieves, up to log factors and with high probability, a fair pseudo-regret of order √dT after T rounds, where d is the dimension of the context vectors. The policy also satisfies demographic parity at each round when averaged over all possible information available before the selection. Finally, we use simulated settings and experiments on the US census data to show that our policy achieves sub-linear fair pseudo-regret also in practice

Global burden of headache disorders in children and adolescents 2007–2017

Headache disorders are prevalent and disabling conditions impacting on people of all ages, including children and adolescents with substantial impact on their school activities and leisure time. Our study aims to report specific information on headaches in children and adolescents based on the Global Burden of Disease (GBD) study, that provides estimates for incidence, prevalence, fatal and non-fatal outcomes. We relied on 2007 and 2017 GBD estimates for prevalence and Years Lived with Disability (YLDs) at the global level and in WHO regions. The results show that, migraine and tension-type headache (TTH) together account for 37.5% of all-cause prevalence and for 7% of all-cause YLDs. Over the past decade, prevalence rates showed a mild increase of TTH in all ages and of migraine alone for adolescents. The YLDs increased among females of all ages with some regional differences that might be connected to the unequal availability of effective acute and prophylactic treatments across world regions. GBD data support the need to promote public health policies and strategies including diagnosis, pharmacological and non-pharmacological treatments that are expected to help reduce the disability and burden associated to migraine and TTH among children and adolescents

Non-pharmacological approaches to headaches: Non-invasive neuromodulation, nutraceuticals, and behavioral approaches

Significant side effects or drug interactions can make pharmacological management of headache disorders very difficult. Non-conventional and non-pharmacological treatments are be-coming increasingly used to overcome these issues. In particular, non-invasive neuromodulation, nutraceuticals, and behavioral approaches are well tolerated and indicated for specific patient categories such as adolescents and pregnant women. This paper aims to present the main approaches reported in the literature in the management of headache disorders. We therefore reviewed the available literature published between 2010 and 2020 and performed a narrative presentation for each of the three categories (non-invasive neuromodulation, nutraceuticals, and behavioral therapies). Regarding non-invasive neuromodulation, we selected transcranial magnetic stimulation, supraor-bital nerve stimulation, transcranial direct current stimulation, non-invasive vagal nerve stimulation, and caloric vestibular stimulation. For nutraceuticals, we selected Feverfew, Butterbur, Riboflavin, Magnesium, and Coenzyme Q10. Finally, for behavioral approaches, we selected biofeedback, cognitive behavioral therapy, relaxation techniques, mindfulness-based therapy, and acceptance and commitment therapy. These approaches are increasingly seen as a valid treatment option in headache management, especially for patients with medication overuse or contraindications to drug treatment. However, further investigations are needed to consider the effectiveness of these approaches also with respect to the long-term effects