Linear theory of wave generation by a moving bottom

The computation of long wave propagation through the ocean obviously depends on the initial condition. When the waves are generated by a moving bottom, a traditional approach consists in translating the ``frozen'' sea bed deformation to the free surface and propagating it. The present study shows the differences between the classical approach (passive generation) and the active generation where the bottom motion is included. The analytical solutions presented here exhibit some of the drawbacks of passive generation. The linearized solutions seem to be sufficient to consider the generation of water waves by a moving bottom.Comment: 9 pages, 2 figure

Localized Dissipation in Fermionic Quantum Wires

Localized dissipation in many-body quantum systems represents an emergent focal point of non-equilibrium physics. In recent experiments, localized particle losses were realized in ultracold atomic gases, thus opening up new avenues for investigating the interplay between many-body and non-equilibrium effects. The main focus of this work is the theoretical study of collective phenomena in one-dimensional systems of interacting spinless fermions subject to a localized loss. This model constitutes a non-equilibrium counterpart of the paradigmatic Kane-Fisher potential barrier problem. In particular, strong interaction effects emerge due to the gapless nature of the system. We show that the loss and transport properties of the quantum wire in the presence of a localized loss are drastically modified by interactions as a result of the interplay between coherent and incoherent processes. In experiments with localized losses, a manifestation of the quantum Zeno effect is encountered, which can be described exhaustively in terms of local, microscopic physics. In contrast, we demonstrate that the interplay of gapless quantum fluctuations and particle interactions with the localized dissipation leads to an instance of the quantum Zeno effect of genuine many-body nature. After the localized losses are switched on, a non-equilibrium steady state emerges in the quantum wire. We derive exact results for the properties of this steady state in the non-interacting limit and formulate a theoretical description of the depletion processes by introducing the momentum-dependent loss probability of modes. Remarkably, we find that coherence properties of the initial state persist, leading to the formation of Friedel oscillations near the loss site. The presence of interactions between the fermions modifies the dynamics in the wire and leads to an energy-dependent renormalization of loss processes. We find that the loss probability is strongly renormalized for modes with an energy close to the Fermi energy, leading to the suppression of losses at the Fermi level. In the case of repulsive interactions, the suppression of losses is accompanied by the loss site becoming completely opaque, which establishes a fluctuation-induced quantum Zeno effect. For attractive interactions, instead, the localized loss becomes fully transparent to particles at the Fermi level, resulting accordingly in the suppression of losses as a fluctuation-induced transparency. The strong modifications of the loss properties are reflected in observables such as the momentum distribution in the wire, exhibiting an increased occupation at the Fermi momentum. In addition, we study the influence of self-thermalization effects on the renormalization of the effective dissipation strength. Here, we identify regimes where the generation of an effective temperature is sufficiently weak to achieve significant renormalization. Furthermore, the microscopic quantum Zeno effect affects the spectral properties of the non-Hermitian Hamiltonian associated with a localized loss for a lattice model. Here, a sharp reorganization of the spectrum is encountered at a critical dissipation strength, causing a characteristic signature in the response properties of the wire. We investigate the interplay of interactions in the wire and localized dissipation within three complementary approaches. In a microscopic real-space renormalization group analysis the physical mechanisms behind the modified depletion properties are particularly transparent. Within a dynamical Hartree-Fock approximation the resulting effects on observables such as the momentum distribution in the non-equilibrium steady states can be studied. Finally, an effective Luttinger liquid description demonstrates the universality of the findings and enables the investigation of mode-coupling effects

COVID-19 Incidence and Vaccine Effectiveness in University Staff, 1 March 2020–2 April 2022

Background: University workers undergo intense social interactions due to the frequent contact with students and colleagues and lectures in crowdy conditions. The aim of our study was to assess the incidence of COVID-19 infection and vaccine effectiveness in a cohort of workers of the University of Trieste from 1 March 2020 (start of the pandemic) through 2 April 2022. Methods: The University of Trieste implemented a number of public health policies to contain the spread of SARS-CoV-2 on the campus, including prompt contact tracing, the enhanced ventilation of all premises, fomites disinfection and the mandatory use of face masks indoors. In compliance with the surveillance protocol of the local public health department, university personnel were tested for SARS-CoV-2 by polymerase chain reaction (PCR) on a nasopharyngeal swab on demand, in the event of symptoms consistent with COVID-19 or for contact tracing, following close contact with a confirmed COVID-19 case. The incidence rates of SARS-CoV-2 infections were estimated as the number of cases by the number of person-days (p-d) at risk. The multivariable Cox proportional hazard regression model was employed to investigate the risk of primary COVID-19 infection, adjusting for a number of potential confounders and expressing the risk as the adjusted hazard ratio (aHR) with a 95% confidence interval (95% CI). Results: The incidence of SARS-CoV-2 infection among the university staff was lower than that of healthcare workers (HCWs) of the same area. Compared to unvaccinated colleagues (6.55 × 10,000 p-d), the raw incidence of SARS-CoV-2 infection was higher among university workers immunized with one (7.22 × 10,000 p-d) or two (7.48 × 10,000 p-d) doses of the COVID-19 vaccine, decreasing in those receiving the booster (1.98 × 1000 p-d). The risk of infection increased only in postgraduate medical trainees (aHR = 2.16; 95% CI: 1.04; 4.48), though this was limited to the Omicron transmission period. After the implementation of the national vaccination campaign against COVID-19, workers immunized with the booster were less likely than unvaccinated workers to be infected by SARS-CoV-2 both before (aHR = 0.10; 95% CI: 0.06; 0.16) and after (aHR = 0.37; 95% CI: 0.27; 0.52) the Omicron transmission period. The vaccine effectiveness of the booster was 90% (=(1−0.10) × 100) before versus 63% (=(1−0.37) × 100) during the Omicron wave, without a significant difference between homologous (three doses of m-RNA vaccines) and heterologous (first two doses of Vaxzevria followed by a third dose of m-RNA vaccine) immunization. Conclusions: The incidence of SARS-CoV-2 infection in the university staff was lower than that of HCWs of ASUGI, likely because the testing-on-demand schedule inevitably missed asymptomatic infections. Therefore, the observed significantly protective effect of the booster dose in university personnel referred to symptomatic SARS-CoV-2 infections. The infection prevention and control policies implemented by the University of Trieste managed to equalize the biological risk between the administrative and teaching staff

Video display operator complaints: A 10-year follow-up of visual fatigue and refractive disorders

Visual fatigue and discomfort are very common complaints for video display operators (VDTs). The aim of our study was to study work-related visual symptoms in relation to refractive disorders and psychosocial factors in 3054 public employees by way of follow-ups for 10 years with periodic medical examinations with eye evaluation in the period 2000-2009. Factors related to visual fatigue were evaluated in the follow-up using generalized equation estimation. Visual fatigue was very common in VDT operators (64.03%). During the follow-up, no relationship between visual fatigue and age, sex, seniority of work, visual acuity and refractory disorders was found. Visual fatigue was significantly associated with anxiety perception in a dose-related matter (odds ratio (OR) 7.40, confidence interval (CI) 95% 1.77-31.3), psychosocial factors (OR 1.03, CI 95% 1.01-1.07), use of lenses (OR 1.34, CI 95% 1.09-1.64) and time of VDT usage (OR 1.27, CI 95% 1.04-1.53). This study confirmed that visual fatigue is common in VDT users and is related to anxiety perception, time of VDT usage, use of lenses and stress. No relationship was found between visual fatigue and refractory disorders or visual acuit

A Galerkin boundary element method for high frequency scattering by convex polygons

In this paper we consider the problem of time-harmonic acoustic scattering in two dimensions by convex polygons. Standard boundary or finite element methods for acoustic scattering problems have a computational cost that grows at least linearly as a function of the frequency of the incident wave. Here we present a novel Galerkin boundary element method, which uses an approximation space consisting of the products of plane waves with piecewise polynomials supported on a graded mesh, with smaller elements closer to the corners of the polygon. We prove that the best approximation from the approximation space requires a number of degrees of freedom to achieve a prescribed level of accuracy that grows only logarithmically as a function of the frequency. Numerical results demonstrate the same logarithmic dependence on the frequency for the Galerkin method solution. Our boundary element method is a discretization of a well-known second kind combined-layer-potential integral equation. We provide a proof that this equation and its adjoint are well-posed and equivalent to the boundary value problem in a Sobolev space setting for general Lipschitz domains

Successioni di polinomi di tipo binomiale e operatori delta

In questa tesi riportiamo le definizioni ed i risultati principali relativi alla corrispondenza tra le successioni di polinomi di tipo binomiale (particolari basi dello spazio dei polinomi a coefficienti reali) e gli operatori delta, cioè operatori lineari sullo spazio dei polinomi che commutano con gli operatori di traslazione e il cui nucleo è costituito dai polinomi costanti. Nel capitolo 1 richiamiamo i concetti fondamentali sull'algebra delle serie formali e definiamo l'algebra degli operatori lineari invarianti per traslazione, dimostrando in particolare l'isomorfismo tra queste algebre. Nel capitolo 2, dopo aver dimostrato l'unicità della successione di base relativa ad un operatore delta, ricaviamo come esempio le successioni di base di tre operatori delta, che useremo durante tutto il capitolo: l'operatore derivata, l'operatore di differenza in avanti e l'operatore di differenza all'indietro. Arriviamo quindi a dimostrare un importante risultato, il Primo Teorema di Sviluppo, in cui facciamo vedere come le potenze di un operatore delta siano una base per l'algebra degli operatori invarianti per traslazione. Introducendo poi le successioni di Sheffer, possiamo dimostrare anche il Secondo Teorema di Sviluppo in cui esplicitiamo l'azione di un operatore invariante per traslazione su un polinomio, tramite un operatore delta fissato e una sua successione di Sheffer. Nell'ultima parte della tesi presentiamo i formalismi e alcune semplici operazioni del calcolo umbrale, che useremo per determinare le cosiddette costanti di connessione, ovvero le costanti che definiscono lo sviluppo di una successione binomiale in funzione di un'altra successione binomiale usata come base dello spazio dei polinomi

Molnupiravir, Nirmatrelvir/Ritonavir, or Sotrovimab for High-Risk COVID-19 Patients Infected by the Omicron Variant: Hospitalization, Mortality, and Time until Negative Swab Test in Real Life

Background. Several drugs which are easy to administer in outpatient settings have been authorized and endorsed for high-risk COVID-19 patients with mild–moderate disease to prevent hospital admission and death, complementing COVID-19 vaccines. However, the evidence on the efficacy of COVID-19 antivirals during the Omicron wave is scanty or conflicting. Methods. This retrospective controlled study investigated the efficacy of Molnupiravir or Nirmatrelvir/Ritonavir (Paxlovid®) or Sotrovimab against standard of care (controls) on three different endpoints among 386 high-risk COVID-19 outpatients: hospital admission at 30 days; death at 30 days; and time between COVID-19 diagnosis and first negative swab test result. Multinomial logistic regression was employed to investigate the determinants of hospitalization due to COVID-19-associated pneumonia, whereas time to first negative swab test result was investigated by means of multinomial logistic analysis as well as Cox regression analysis. Results. Only 11 patients (overall rate of 2.8%) developed severe COVID-19-associated pneumonia requiring admission to hospital: 8 controls (7.2%); 2 patients on Nirmatrelvir/Ritonavir (2.0%); and 1 on Sotrovimab (1.8%). No patient on Molnupiravir was institutionalized. Compared to controls, hospitalization was less likely for patients on Nirmatrelvir/Ritonavir (aOR = 0.16; 95% CI: 0.03; 0.89) or Molnupiravir (omitted estimate); drug efficacy was 84% for Nirmatrelvir/Ritonavir against 100% for Molnupiravir. Only two patients died of COVID-19 (rate of 0.5%), both were controls, one (aged 96 years) was unvaccinated and the other (aged 72 years) had adequate vaccination status. At Cox regression analysis, the negativization rate was significantly higher in patients treated with both antivirals—Nirmatrelvir/Ritonavir (aHR = 1.68; 95% CI: 1.25; 2.26) and Molnupiravir (aHR = 1.45; 95% CI: 1.08; 1.94). However, COVID-19 vaccination with three (aHR = 2.03; 95% CI: 1.51; 2.73) or four (aHR = 2.48; 95% CI: 1.32; 4.68) doses had a stronger effect size on viral clearance. In contrast, the negativization rate reduced significantly in patients who were immune-depressed (aHR = 0.70; 95% CI: 0.52; 0.93) or those with a Charlson index ≥ 3 (aHR = 0.63; 0.41; 0.95) or those who had started the respective treatment course 3+ days after COVID-19 diagnosis (aOR = 0.56; 95% CI: 0.38; 0.82). Likewise, at internal analysis (excluding patients on standard of care), patients on Molnupiravir (aHR = 1.74; 95% CI: 1.21; 2.50) or Nirmatrelvir/Ritonavir (aHR = 1.96; 95% CI: 1.32; 2.93) were more likely to turn negative earlier than those on Sotrovimab (reference category). Nonetheless, three (aHR = 1.91; 95% CI: 1.33; 2.74) or four (aHR = 2.20; 95% CI: 1.06; 4.59) doses of COVID-19 vaccine were again associated with a faster negativization rate. Only 64.7% of patients were immunized with 3+ doses of COVID-19 vaccines in the present study. Again, the negativization rate was significantly lower if treatment started 3+ days after COVID-19 diagnosis (aHR = 0.54; 95% CI: 0.32; 0.92). Conclusions. Molnupiravir, Nirmatrelvir/Ritonavir, and Sotrovimab were all effective in preventing hospital admission and/or mortality attributable to COVID-19. However, hospitalizations also decreased with higher number of doses of COVID-19 vaccines. Although they are effective against severe disease and mortality, the prescription of antivirals should be carefully scrutinized by double opinion, not only to contain health care costs but also to reduce the risk of generating resistant SARS-CoV-2 strains. Only 64.7% of patients were in fact immunized with 3+ doses of COVID-19 vaccines in the present study. High-risk patients should prioritize COVID-19 vaccination, which is a more cost-effective approach than antivirals against severe SARS-CoV-2 pneumonia. Likewise, although both antivirals, especially Nirmatrelvir/Ritonavir, were more likely than standard of care and Sotrovimab to reduce viral shedding time (VST) in high-risk SARS-CoV-2 patients, vaccination had an independent and stronger effect on viral clearance. However, the effect of antivirals or COVID-19 vaccination on VST should be considered a secondary benefit. Indeed, recommending Nirmatrelvir/Ritonavir in order to control VST in high-risk COVID-19 patients is rather questionable since other cheap, large spectrum and harmless nasal disinfectants such as hypertonic saline solutions are available on the market with proven efficacy in containing VST

Introduzione al concetto di frazione: una proposta di didattica inclusiva con Mathematica

La scuola è costantemente in fase di aggiornamento; lo fa attraverso riforme e leggi, ma soprattutto attraverso la disponibilità degli insegnanti a rivedere e attualizzare i metodi di insegnamento. Negli ultimi anni, forse più velocemente che nel passato, la scuola ha sentito il bisogno di introdurre nuove tecnologie per avvicinarsi alla quotidianità degli studenti e per permettere a ognuno di accedere al sapere pur con modalità e tempistiche differenti. Nelle classi di oggi sono presenti alunni con disabilità e alunni con disturbi dell'apprendimento: all'insegnante è lasciato il compito di riuscire ad includere tutti, spiegando all'intera classe la lezione, anche attraverso l'ausilio di strumenti hardware e software. Questo lavoro di tesi si è concentrato sulla creazione di un pacchetto software, utilizzabile da insegnanti e studenti, per la didattica delle frazioni. Nel primo capitolo di questa tesi si esplorano le modalità dell'insegnamento in classe e si analizzano le difficoltà che gli studenti, con o senza bisogni educativi speciali, incontrano nel consolidare il concetto di frazione nella scuola secondaria di primo grado. Si cercano altresì motivazioni all'uso in classe di software didattici. Per completezza sull'argomento, nel secondo capitolo è riportata la teoria della costruzione degli insiemi dei numeri naturali, dei numeri interi e dei numeri razionali, dedicato agli insegnanti solamente. Nel terzo capitolo viene presentato il pacchetto software “Cake” realizzato nell'ambiente “Mathematica”: vuole essere un esempio di come le tecnologie possano aiutare la didattica scolastica, includendo tutti gli alunni senza ridimensionare gli obiettivi didattici. Nel quarto capitolo sono presentati i risultati di tre casi studio, come supporto alla scelta di introdurre tecnologie informatiche nella didattica. Il quinto e ultimo capitolo tira le conclusioni di questo lavoro di tesi e ne indica alcuni possibili sviluppi ed impieghi futuri