Signal modeling of high-purity Ge detectors with a small read-out electrode and application to neutrinoless double beta decay search in Ge-76

The GERDA experiment searches for the neutrinoless double beta decay of Ge-76 using high-purity germanium detectors enriched in Ge-76. The analysis of the signal time structure provides a powerful tool to identify neutrinoless double beta decay events and to discriminate them from gamma-ray induced backgrounds. Enhanced pulse shape discrimination capabilities of "Broad Energy Germanium" detectors with a small read-out electrode have been recently reported. This paper describes the full simulation of the response of such a detector, including the Monte Carlo modeling of radiation interaction and subsequent signal shape calculation. A pulse shape discrimination method based on the ratio between the maximum current signal amplitude and the event energy applied to the simulated data shows quantitative agreement with the experimental data acquired with calibration sources. The simulation has been used to study the survival probabilities of the decays which occur inside the detector volume and are difficult to assess experimentally. Such internal decay events are produced by the cosmogenic radio-isotopes Ge-68 and Co-60 and the neutrinoless double beta decay of Ge-76. Fixing the experimental acceptance of the double escape peak of the 2.614 MeV photon to 90%, the estimated survival probabilities at Qbb = 2.039 MeV are (86+-3)% for Ge-76 neutrinoless double beta decays, (4.5+-0.3)% for the Ge-68 daughter Ga-68, and (0.9+0.4-0.2)% for Co-60 decays.Comment: 27 pages, 17 figures. v2: fixed typos and references. Submitted to JINS

Etude des mécanismes impliqués dans le développement d'une insuffisance mitrale fonctionnelle lors de Cardiopathie dilatée

Introduction : Le développement d'une insuffisance mitrale fonctionnelle sévère est un facteur de mauvais pronostic dans l'évolution de toute cardiopathie dilatée (CD). Cette insuffisance est la conséquence d'une modification de la géométrie du myocarde aboutissant à une perte de coaptation des feuillets mitraux. Si on se base sur la littérature, les deux mécanismes principalement incriminés sont le remodelage ventriculaire (VG) et la dilatation de l'oreillette gauche(OG).Néanmoins, l'importance relative de chacun de ces mécanismes n'est que mal connu. A l'ère du développement de nouvelles approches thérapeutiques percutanées, il nous a semblé intéressant d'étudier plus en détail les facteurs morphologiques associés à la présence d'une insuffisance mitrale fonctionnelle significative dans la CD d'origine ischémique ou non ischémique, dans le but de mieux cibler les interventions thérapeutiques en fonction du mécanisme de la valvulopathie. Méthode : Sur la base des archives du laboratoire d'échocardiographie du CHUV, les patients répondant à la définition échocardiographique de la CD, soit un volume télédiastolique du ventricule gauche > 75cc/m2 et une fraction d'éjection inférieure à 45% ont été rétrospectivement identifiés. Seuls les examens échocardiographiques de bonnes qualités ont été inclus dans l'analyse. Les paramètres cliniques de bases ainsi que les mesures échocardiographiques incluant les volumes du ventricule et de l'oreillette gauches, ainsi que la mesure quantitiative de l'orifice régurgitant de l'insuffisance mitrale (ERO) ont été recueillis pour tous les patients. Le diagnostic d'insuffisance mitrale fonctionnelle sévère était retenu en présence d'un ERO>20 mm2. Les caractéristiques de base des patients ont été comparés en fonction du type de CD (ischémique vs non-ischémique) et les paramètres échocardiographiques significativement corrélés à la présence d'une insuffisance mitrale sévère ont été déterminés dans chacun des deux groupes par régression linéaire. Résultats : 852 patients remplissant les critères d'inclusion ont été identifiés, desquels 100 patients consécutifs avec CD ischémique et 100 patients consécutifs avec CD non-ischémique ont été retenus pour analyse. La prévalence d'une IM sévère était similaire dans les deux groupes, de 25% et 24% respectivement (p=ns). Par rapport aux CD ischémiques, les patients atteints de CD non-ischémiques étaient moins âgés (61±16 vs 68±12 ans, p<0.01) et étaient moins fréquemment de sexe masculin (67% vs 90%, p<0.001). Parmi les caractéristique échocardiographiques, les patients avec CD non- ischémiques présentaient un volume ventriculaire diastolique (125±46 vs 115±32 ml/m2, p=0.05) et systolique (166±83 vs147±58, p=0.05) plus important tandis que la fraction d'éjection (29±9% vs 31±8%, p=ns) et le volume de l'oreillette gauche (95±45 vs 89±33, p=ns) étaient comparables. En analyse multivariée, les facteurs indépendamment associés à l'IM sévère étaient le volume de l'OG (coeff -0.001 ; 95%-CI 0.0004/0.002 ; p<0.01) et l'épaisseur de la paroi postérieure (coeff -0.29 ; 95%- CI -0.49/-0.1 ; p<0.01) dans la CD non ischémique, et l'aire de tenting de la valve (coeff 0.03 ; 95%-CI 0.002/0.06 ; p<0.05) dans la CD ischémique. Conclusion : Cette analyse rétrospective monocentrique indique une prévalence élevée d'IM sévère associée à la CD tant ischémique que non-ischémique. Bien qu'une dilatation sévère du VG et de l'OG soient retrouvée dans les deux types de CD, l'IM sévère corrèle le plus significativement avec la dilatation de l'OG dans la CD non-ischémique, suggérant une importance particulière de la dilatation de l'anneau. A l'inverse, c'est l'aire de tenting de la valve qui apparaît le plus significativement corrélé à l'IM sévère dans la CD ischémique, faisant supposer un rôle plus important du remodelage - local ou global - du ventricule gauche. La force de ces corrélations est toutefois peu importante dans cette population non-sélectionnée et ne permet que de générer des hypothèses. Leur relevance clinique reste donc incertaine

Spectrum of the gauge Ising model in three dimensions

We present a high precision Monte Carlo study of the spectrum of the Ising gauge theory in three dimensions in the confining phase. Using state of the art Monte Carlo techniques we are able to accurately determine up to three masses in a single channel. We compare our results with the SU(2) spectrum and with the prediction of the Isgur-Paton model. Our data strongly support the conjecture that the glueball spectrum is described by some type of flux tube model. We also compare the spectrum with some recent results for the correlation length in the 3d spin Ising model. This analysis sheds light on some nontrivial features of the duality transformation.Comment: Talk given at LATTICE9

TL1A/DR3 axis involvement in the inflammatory cytokine network during pulmonary sarcoidosis

BACKGROUND: TNF-like ligand 1A (TL1A), a recently recognized member of the TNF superfamily, and its death domain receptor 3 (DR3), firstly identified for their relevant role in T lymphocyte homeostasis, are now well-known mediators of several immune-inflammatory diseases, ranging from rheumatoid arthritis to inflammatory bowel diseases to psoriasis, whereas no data are available on their involvement in sarcoidosis, a multisystemic granulomatous disease where a deregulated T helper (Th)1/Th17 response takes place. METHODS: In this study, by flow cytometry, real-time PCR, confocal microscopy and immunohistochemistry analyses, TL1A and DR3 were investigated in the pulmonary cells and the peripheral blood of 43 patients affected by sarcoidosis in different phases of the disease (29 patients with active sarcoidosis, 14 with the inactive form) and in 8 control subjects. RESULTS: Our results demonstrated a significant higher expression, both at protein and mRNA levels, of TL1A and DR3 in pulmonary T cells and alveolar macrophages of patients with active sarcoidosis as compared to patients with the inactive form of the disease and to controls. In patients with sarcoidosis TL1A was strongly more expressed in the lung than the blood, i.e., at the site of the involved organ. Additionally, zymography assays showed that TL1A is able to increase the production of matrix metalloproteinase 9 by sarcoid alveolar macrophages characterized, in patients with the active form of the disease, by reduced mRNA levels of the tissue inhibitor of metalloproteinase (TIMP)-1. CONCLUSIONS: These data suggest that TL1A/DR3 interactions are part of the extended and complex immune-inflammatory network that characterizes sarcoidosis during its active phase and may contribute to the pathogenesis and to the progression of the disease

About the parabolic relation existing between the skewness and the kurtosis in time series of experimental data

In this work we investigate the origin of the parabolic relation between skewness and kurtosis often encountered in the analysis of experimental time-series. We argue that the numerical values of the coefficients of the curve may provide informations about the specific physics of the system studied, whereas the analytical curve per se is a fairly general consequence of a few constraints expected to hold for most systems.Comment: To appear in Physica Script

Self-reported gait unsteadiness in mildly impaired neurological patients: an objective assessment through statistical gait analysis

Background Self-reported gait unsteadiness is often a problem in neurological patients without any clinical evidence of ataxia, because it leads to reduced activity and limitations in function. However, in the literature there are only a few papers that address this disorder. The aim of this study is to identify objectively subclinical abnormal gait strategies in these patients. Methods Eleven patients affected by self-reported unsteadiness during gait (4 TBI and 7 MS) and ten healthy subjects underwent gait analysis while walking back and forth on a 15-m long corridor. Time-distance parameters, ankle sagittal motion, and muscular activity during gait were acquired by a wearable gait analysis system (Step32, DemItalia, Italy) on a high number of successive strides in the same walk and statistically processed. Both self-selected gait speed and high speed were tested under relatively unconstrained conditions. Non-parametric statistical analysis (Mann-Whitney, Wilcoxon tests) was carried out on the means of the data of the two examined groups. Results The main findings, with data adjusted for velocity of progression, show that increased double support and reduced velocity of progression are the main parameters to discriminate patients with self-reported unsteadiness from healthy controls. Muscular intervals of activation showed a significant increase in the activity duration of the Rectus Femoris and Tibialis Anterior in patients with respect to the control group at high speed. Conclusions Patients with a subjective sensation of instability, not clinically documented, walk with altered strategies, especially at high gait speed. This is thought to depend on the mechanisms of postural control and coordination. The gait anomalies detected might explain the symptoms reported by the patients and allow for a more focused treatment design. The wearable gait analysis system used for long distance statistical walking assessment was able to detect subtle differences in functional performance monitoring, otherwise not detectable by common clinical examination

Statistical methods applied to the search of sterile neutrinos

The frequentist statistical methods applied to search for short-baseline neutrino oscillations induced by a sterile neutrino with mass at the eV scale are reviewed and compared. The comparison is performed under limit setting and signal discovery scenarios, considering both when an oscillation would enhance the neutrino interaction rate in the detector and when it would reduce it. The sensitivity of the experiments and the confidence regions extracted for specific data sets change considerably according to which test statistic is used and the assumptions on its probability distribution. A standardized analysis approach based on the most general kind of hypothesis test is proposed

Comprehensive measurement of pp-chain solar neutrinos

About 99 per cent of solar energy is produced through sequences of nuclear reactions that convert hydrogen into helium, starting from the fusion of two protons (the pp chain). The neutrinos emitted by five of these reactions represent a unique probe of the Sun's internal working and, at the same time, offer an intense natural neutrino beam for fundamental physics. Here we report a complete study of the pp chain. We measure the neutrino–electron elastic-scattering rates for neutrinos produced by four reactions of the chain: the initial proton–proton fusion, the electron-capture decay of beryllium-7, the three-body proton–electron–proton (pep) fusion, here measured with the highest precision so far achieved, and the boron-8 beta decay, measured with the lowest energy threshold. We also set a limit on the neutrino flux produced by the 3 He–proton fusion (hep). These measurements provide a direct determination of the relative intensity of the two primary terminations of the pp chain (pp-I and pp-II) and an indication that the temperature profile in the Sun is more compatible with solar models that assume high surface metallicity. We also determine the survival probability of solar electron neutrinos at different energies, thus probing simultaneously and with high precision the neutrino flavour-conversion paradigm, both in vacuum and in matter-dominated regimes