Spin-boson dynamics: A unified approach from weak to strong coupling

We present a novel approximation scheme to describe the influence of a harmonic bath on the dynamics of a two-level particle over almost the whole regime of temperatures and coupling to the environment, for a wide class of bath spectral densities. Starting from the exact path-integral solution for the two-level system density matrix, effective intra-blip correlations are fully included, while inter-blip and blip-sojourn interactions are considered up to first order. In the proper regimes, an excellent agreement with conventional perturbative approaches and ab-initio path-integral results is found.Comment: 6 pages, 4 figures (enlarged figures and minor changes to the text

Spin-boson dynamics beyond conventional perturbation theories

A novel approximation scheme is proposed to describe the dynamics of the spin-boson problem. Being nonperturbative in the coupling strength nor in the tunneling frequency, it gives reliable results over a wide regime of temperatures and coupling strength to the thermal environment for a large class of bath spectral densities. We use a path-integral approach and start from the exact solution for the two-level system population difference in the form of a generalized master equation (GME). Then, we approximate inter-blip and blip-sojourns interactions up to linear order, while retaining all intra-blip correlations to find the kernels entering the GME in analytical form. Our approximation scheme, which we call Weakly-Interacting Blip Approximation (WIBA), fully agrees with conventional perturbative approximations in the tunneling matrix element (Non-Interacting Blip Approximation) or in the system-bath coupling strength.Comment: 15 pages, 14 figure

Mobile Emergency, an Emergency Support System for Hospitals in Mobile Devices: Pilot Study

BACKGROUND: Hospitals are vulnerable to natural disasters, man-made disasters, and mass causalities events. Within a short time, hospitals must provide care to large numbers of casualties in any damaged infrastructure, despite great personnel risk, inadequate communications, and limited resources. Communications are one of the most common challenges and drawbacks during in-hospital emergencies. Emergency difficulties in communicating with personnel and other agencies are mentioned in literature. At the moment of emergency inception and in the earliest emergency phases, the data regarding the true nature of the incidents are often inaccurate. The real needs and conditions are not yet clear, hospital personnel are neither efficiently coordinated nor informed on the real available resources. Information and communication technology solutions in health care turned out to have a great positive impact both on daily working practice and situations. OBJECTIVE: The objective of this paper was to find a solution that addresses the aspects of communicating among medical personnel, formalizing the modalities and protocols and the information to guide the medical personnel during emergency conditions with a support of a Central Station (command center) to cope with emergency management and best practice network to produce and distribute intelligent content made available in the mobile devices of the medical personnel. The aim was to reduce the time needed to react and to cope with emergency organization, while facilitating communications. METHODS: The solution has been realized by formalizing the scenarios, extracting, and identifying the requirements by using formal methods based on unified modeling language (UML). The system and was developed using mobile programming under iOS Apple and PHP: Hypertext Preprocessor My Structured Query Language (PHP MySQL). Formal questionnaires and time sheets were used for testing and validation, and a control group was used in order to estimate the reduction of time needed to cope with emergency cases. First, we have tested the usability and the functionalities of the solution proposed, then a real trial was performed to assess the reduction in communication time and the efficiency of the solution with respect to a case without Mobile Emergency tools. RESULTS: The solution was based on the development of a mobile emergency application and corresponding server device to cope with emergencies and facilitate all the related activities and communications, such as marking the position, contacting people, and recovering the exits information. The solution has been successfully tested within the Careggi Hospital, the largest medical infrastructure in Florence and Tuscany area in Italy, thus demonstrating the validity of the identified modalities, procedures, and the reduction in the time needed to cope with the emergency conditions. The trial was not registered as the test was conducted in realistic but simulated emergency conditions. CONCLUSIONS: By analyzing the requirements for developing a mobile app, and specifically the functionalities, codes, and design of the Mobile Emergency app, we have revealed the real advantages of using mobile emergency solutions compared to other more traditional solutions to effectively handle emergency situations in hospital settings

Perianal Crohn's disease and hidradenitis suppurativa: a possible common immunological scenario

Crohn's disease (CD) and Hidradenitis suppurativa (HS) are both chronic inflammatory diseases. The pathogenesis of these diseases is multifactorial, due to the interaction of genetic and environmental factors leading to a deregulated local immune response where T lymphocytes play a major role. To the best of our knowledge, no previous study has clarified whether the pathogenetic mechanism of perianal CD and HS is the same. We therefore analyzed the cellular expression pattern and the cytokine repertoire in three patients suffering from both perianal CD and HS

Primary carcinoid tumour of the common bile duct

Background Carcinoid tumours of the extrahepatic biliary tree are exceedingly rare. We report a case of primary carcinoid tumour arising in the distal portion of the common bile duct. Case outline A 30-year-old man was admitted with watery diarrhoea and symptoms of biliary obstruction. Abdominal ultrasound scan showed a normal gallbladder without stones, mild dilatation of the intra- and extrahepatic biliary tree and a 2 cm solid lesion in the head of pancreas compressing the distal common bile duct. Computed tomography confirmed these findings and showed that the tumour was hypervascular. Gastrointestinal hormone screening showed an increase in plasma serotonin. The patient underwent a standard pylorus-preserving proximal pancreatoduodenectomy (PPPD). Results Pathological examination showed a neuroendocrine tumour (carcinoid) of the distal bile duct. The postoperative plasma serotonin decreased to normal levels. One year later the patient is well without evidence of disease. Discussion Primary carcinoid tumours of the extrahepatic biliary tree are rare, accounting for 0.2–2% of all digestive carcinoids. This is the fifth report of a tumour arising from the distal common bile duct. Surgical treatment for neoplasms of the distal common bile duct can be problematic because of the site of the lesion and the difficulty in differentiating them from periampullary neoplasms lesions. Pancreatoduodenectomy (PD) is therefore the treatment of choice

Un elemento di valutazione della qualità della didattica universitaria

For many years, Italian Universities have been committed to to collecting "assessment questionnaires" of the courses from their students. It is not fully clear how to manage these questionnaires, though. In the present work, we propose a method to single out significant information from the wide amount of issues raised by the students. With this work, we aim at improving the services offered by Universities. Human resources dedicated to the evaluation of teaching are definitely scarse, if not absent. Thus, we believe that coordination committees must focus on the most critical issues, rather than dispersing information.In this work, we show how an almost automatic method allows to single out a very limited fraction (about 7% in the case of our Faculty of Sciences at Sapienza University in Rome) of really critical courses. Our political objective is to give a clear and objective answer to the students' request of improving those courses. With this approach we do not consider the students' opinions as absolute. We rather aim at respecting their implicit request of verification of their opinions.Our approach also suggests some improvements in the formulation of the questions raised in the questionnaires, so as to reduce ambiguity and obtain a more accurate statistical treatment. In the example presented here, a very high appreciation of our courses emerges if we focus on the average values. However, a punctual control of opinions for a fraction of courses is indispensable. Technically, we use the so called trimming method to single out the problematic courses. This method, used in a variety of fields, helps to control for carelessness of some students who may not take the questionnaires seriously. In our case, for each course and for each question, we delete 50% of the questionnaires, namely those corresponding to 25% of the most positive and 25% of the most negative. Still, our analysis leads to very stable results, if we focus onthe most critical courses, which is the main objective of this work.Da molti anni le Università italiane hanno l'obbligo di somministrare questionari sul gradimento degli insegnamenti. Non è chiaro tuttavia come utilizzare questi questionari. In questo lavoro si propone un metodo per selezionare l'enorme informazione contenuta nei suggerimenti di studentesse e studenti. L'unico obiettivo che appare utile è migliorare i servizi offerti dall'Università. Le risorse di personale a disposizione di coloro che coordinano le attività didattiche sono inadeguate ed a volta risibili. Pertanto sembra necessario concentrare l'attenzione degli organi di coordinamento sulle maggiori ciriticità. Nel nostro lavoro dimostriamo che un metodo quasi automatico permette di isolare una porzione molto limitata (il 7% circa nel caso della Facoltà di Scienze della Sapienza) di insegnamenti drammaticamente critici. L'obiettivo politico è rispondere, con chiarezza, nella massima trasparenza, alla domanda che viene da studentesse e studenti di migliorare quei particolari insegnamenti. Non si postula un'attestazione di sacralità alle opinioni espresse, ma si vuole praticare e diffondere il rispetto assoluto della richiesta di verifica, implicita in tali opinioni. Il nostro approccio suggerisce anche in che modo sarebbe utile modificare leggermente la formulazione delle domande per rendere l'analisi statistica ancora più accurata. Nel complesso, per la realtà studiata in questo lavoro emerge un gradimento molto alto, se si guarda soltanto a valori medi. Tuttavia esiste una porzione di insegnamenti per i quali l'azione di verifica puntuale delle affermazioni contenute nei questionari appare utile e doverosa.Tecnicamente, l'uso del cosiddetto "trimming method" appare particolarmente efficace per la selezione degli insegnamenti problematici. In sostanza si tratta di un metodo, molto adoperato in situazioni molto diverse, per ripulire il campione statistico dalla possibile presenza, in questo caso, di questionari che potrebbero essere stati compilati con scarsa attenzione. Nel nostro caso, per ogni insegnamento, e per ogni singola domanda posta nei questionari, eliminiamo il 50% dei questionari. Più esattamente, un 25% è composto dalle valutazioni più favorevoli e un 25% è composto dalle valutazioni più sfavorevoli. La nostra analisi mostra una grande stabilità dei risultati se si mantiene l'obiettivo della ricerca degli insegnamenti più critici

Loss and revival of phase coherence in a Bose-Einstein condensate moving through an optical lattice

We investigate the phase coherence of a trapped Bose-Einstein condensate that undergoes a dynamical superfluid-insulator transition in the presence of a one-dimensional optical lattice. We study the evolution of the condensate after a sudden displacement of the harmonic trapping potential by solving the Gross-Pitaevskii equation, and comparing the results with the prediction of two effective 1D models. We show that, owing to the 3D nature of the system, the breakdown of the superfluid current above a critical displacement is not associated to a sharp transition, but there exists a range of displacements for which the condensate can recover a certain degree of coherence. We also discuss the implications on the interference pattern after the ballistic expansion as measured in recent experiments at LENS.Comment: 7 pages, 9 figure