13,026 research outputs found
LArGe: Background suppression using liquid argon (LAr) scintillation for 0 decay search with enriched germanium (Ge) detectors
Measurements with a bare p-type high purity germanium diode (HPGe) submerged
in a 19 kg liquid argon (LAr) scintillation detector at MPIK Heidelberg are
reported. The liquid argon--germanium system (LArGe) is operated as a 4
anti-Compton spectrometer to suppress backgrounds in the HPGe. This R&D is
carried out in the framework of the GERDA experiment which searches for
0 decays with HPGe detectors enriched in Ge. The goal of
this work is to develop a novel method to discriminate backgrounds in
0 search which would ultimately allow to investigate the
effective neutrino mass free of background events down to the inverse mass
hierarchy scale. Other applications in low-background counting are expected.Comment: 3 pages, 6 figures, conference proceedings of the 10th Topical
Seminar on Innovative Particle and Radiation Detectors (IPRD06) 1 - 5 October
2006 Siena, Ital
Reconstruction of -attractor supergravity models of inflation
In this paper, we apply reconstruction techniques to recover the potential
parameters for a particular class of single-field models, the
-attractor (supergravity) models of inflation. This also allows to
derive the inflaton vacuum expectation value at horizon crossing. We show how
to use this value as one of the input variables to constrain the
postaccelerated inflationary phase. We assume that the tensor-to-scalar ratio
is of the order of , a level reachable by the expected
sensitivity of the next-generation CMB experiments.Comment: 10 pages, LaTeX, some typos correcte
Technical quality assessment of an optoelectronic system for movement analysis
The Optoelectronic Systems (OS) are largely used in gait analysis to evaluate the motor performances of healthy subjects and patients. The accuracy of marker trajectories reconstruction depends on several aspects: the number of cameras, the dimension and position
of the calibration volume, and the chosen calibration procedure. In this paper we propose a methodology to evaluate the eects of the mentioned sources of error on the reconstruction of marker trajectories. The novel contribution of the present work consists in the dimension of the tested calibration volumes, which is comparable with the ones normally used in gait analysis; in addition, to simulate trajectories during clinical gait analysis, we provide non-default
paths for markers as inputs. Several calibration procedures are implemented and the same trial is processed with each calibration le, also considering dierent cameras congurations.
The RMSEs between the measured trajectories and the optimal ones are calculated for each comparison. To investigate the signicant dierences between the computed indices, an ANOVA analysis is implemented. The RMSE is sensible to the variations of the considered calibration volume and the camera congurations and it is always inferior to 43 mm
Recurring patterns of atrial fibrillation in surface ECG predict restoration of sinus rhythm by catheter ablation
Background Non-invasive tools to help identify patients likely to benefit from catheter ablation (CA) of atrial fibrillation (AF) would facilitate personalised treatment planning. Aim To investigate atrial waveform organisation through recurrence plot indices (RPI) and their ability to predict CA outcome. Methods One minute 12-lead ECG was recorded before CA from 62 patients with AF (32 paroxysmal AF; 45 men; age 57±10 years). Organisation of atrial waveforms from i) TQ intervals in V1 and ii) QRST suppressed continuous AF waveforms (CAFW), were quantified using RPI: percentage recurrence (PR), percentage determinism (PD), entropy of recurrence (ER). Ability to predict acute (terminating vs. non-terminating AF), 3-month and 6-month postoperative outcome (AF vs. AF free) were assessed. Results RPI either by TQ or CAFW analysis did not change significantly with acute outcome. Patients arrhythmia-free at 6-month follow-up had higher organisation in TQ intervals by PD (
Effects of recreational scuba diving on Mediterranean fishes: evidence of involuntary feeding?
Despite a large body of literature assessing the impacts of recreational scuba diving on marine habitats, little attention has been paid to the potentially harmful effects this has on fishes. The aim of this study was the assessment of the immediate response of different fish species to divers’ activities. A decrease of fishes’ natural diffidence towards divers is shown, probably due to an enhanced availability of their prey as a result of divers’ contacts with the substrate
Exploring copepod distribution patterns at three nested spatial scales in a spring system. Habitat partitioning and potential for hydrological bioindication
In groundwater-fed springs, habitat characteristics are primarily determined by a complex combination of geomorphic features
and physico-chemical parameters, while species assemblages are even more intricate. Springs host species either inhabiting the spring
mouth, or colonizing spring habitats from the surface or from the aquifers which feed the springs. Groundwater species living in springs
have been claimed as good candidates for identifying dual aquifer flowpaths or changes in groundwater pathways before reaching the
spring outlets. However, the reliability of spring species as hydrological biotracers has not been widely investigated so far. Our study
was aimed at analysing a large karstic spring system at three nested spatial scales in order: i) to assess, at whole spring system scale,
the presence of a groundwater divide separating two aquifers feeding two spring units within a single spring system, by combining
isotope analyses, physico-chemistry, and copepod distribution patterns; ii) to test, at vertical spring system scale, the effectiveness of
copepods in discriminating surface and subsurface habitat patches within the complex mosaic spring environment; iii) to explore, at
local spring unit level, the relative role of hydrochemistry and sediment texture as describers of copepod distribution among microhabitats.
The results obtained demonstrated the presence of a hierarchical spatial structure, interestingly reflected in significant differences
in assemblage compositions. Copepod assemblages differed between the two contiguous spring units, which were clearly characterized
by their hydrochemistry and by significant differences in the groundwater flowpaths and recharge areas, as derived by the isotope
analyses. The biological results suggested that stygobiotic species seem to be related to the origin of groundwater, suggesting their potential
role as hydrological biotracers. At vertical scale, assemblage composition in surface and subsurface habitats was significantly
different, both between spring units and among microhabitats, supporting strong habitat preferences of copepod species. At the smaller
local scale, the response to habitat patchiness of subsurface copepod assemblages resulted in distribution patterns primarily defined
by sediment texture, while the sensitivity to differences in hydrochemistry was negligible
A comparison between methods of analytical continuation for bosonic functions
In this article we perform a critical assessment of different known methods
for the analytical continuation of bosonic functions, namely the maximum
entropy method, the non-negative least-square method, the non-negative Tikhonov
method, the Pad\'e approximant method, and a stochastic sampling method. Three
functions of different shape are investigated, corresponding to three
physically relevant scenarios. They include a simple two-pole model function
and two flavours of the non-interacting Hubbard model on a square lattice, i.e.
a single-orbital metallic system and a two-orbitals insulating system. The
effect of numerical noise in the input data on the analytical continuation is
discussed in detail. Overall, the stochastic method by Mishchenko et al. [Phys.
Rev. B \textbf{62}, 6317 (2000)] is shown to be the most reliable tool for
input data whose numerical precision is not known. For high precision input
data, this approach is slightly outperformed by the Pad\'e approximant method,
which combines a good resolution power with a good numerical stability.
Although none of the methods retrieves all features in the spectra in the
presence of noise, our analysis provides a useful guideline for obtaining
reliable information of the spectral function in cases of practical interest.Comment: 13 pages, 9 figure
Electron correlations in MnGaAs as seen by resonant electron spectroscopy and dynamical mean field theory
After two decades from the discovery of ferromagnetism in Mn-doped GaAs, its
origin is still debated, and many doubts are related to the electronic
structure. Here we report an experimental and theoretical study of the valence
electron spectrum of Mn-doped GaAs. The experimental data are obtained through
the differences between off- and on-resonance photo-emission data. The
theoretical spectrum is calculated by means of a combination of
density-functional theory in the local density approximation and dynamical
mean-field theory (LDA+DMFT), using exact diagonalisation as impurity solver.
Theory is found to accurately reproduce measured data, and illustrates the
importance of correlation effects. Our results demonstrate that the Mn states
extend over a broad range of energy, including the top of the valence band, and
that no impurity band splits off from the valence band edge, while the induced
holes seem located primarily around the Mn impurity.Comment: 5 pages, 4 figure
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