Search results for "ESOL"

Defect-related visible luminescence of silica nanoparticles

2013

The high photon emissivity in the visible spectral range is one of the most relevant phenomena emerging from the reduction of silica down to nanoscale; hence it is promising for the development of optical nanotechnologies (down converter, probes, display). It is well accepted that the origin of this luminescence is related to the high specific surface (~100 m2/g) that favors the formation of optically active defects at the nanosilica surface. With the aim to clarify the role of specific luminescent defects, here we report a detailed study of spectral and decay features by time-resolved photoluminescence spectra under a visible-UV tunable laser excitation. Our study is carried out on differe…

Vibrational properties of the surface-nonbridging oxygen in silica nanoparticles

2008

By studying the site-selective luminescence spectra of oxidized silica nanoparticles we identify the electronic and the vibrational lines associated with the surface nonbridging oxygen, $\ensuremath{\equiv}{\text{Si-O}}^{\ifmmode\bullet\else\textbullet\fi{}}$. This defect emits a zero-phonon line inhomogeneously distributed around 2.0 eV with full width at half maximum of 0.04 eV, weakly coupled with the local ${\text{Si-O}}^{\ifmmode\bullet\else\textbullet\fi{}}$ stretching mode whose frequency is measured to be $920\text{ }{\text{cm}}^{\ensuremath{-}1}$. These findings are different from those of the well-characterized defect in the bulk silica thus evidencing structural peculiarities of …

Time Resolved Photoluminescence Associated with Non Bridging Oxygen Hole Centers in Irradiated Silica

2007

The Large Area Detector onboard the eXTP mission

2018

The eXTP (enhanced X-ray Timing and Polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS) and China National Space Administration (CNSA) currently performing an extended phase A study and proposed for a launch by 2025 in a low-earth orbit. The eXTP scientific payload envisages a suite of instruments (Spectroscopy Focusing Array, Polarimetry Focusing Array, Large Area Detector and Wide Field Monitor) offering unprecedented simultaneous wide-band X-ray spectral, timing and polarimetry sensitivity. A large European consortium is contributing to the eXTP study and it is expected to provide key hardware elements, including a Large Area Detector (LAD). The LAD instrumen…

Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water

2016

Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a sub-nanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO2 and amorphous fully oxidized SiO2, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescen…

Baseline design of the filters for the LAD detector on board LOFT

2014

The Large Observatory for X-ray Timing (LOFT) was one of the M3 missions selected for the phase A study in the ESA's Cosmic Vision program. LOFT is designed to perform high-time-resolution X-ray observations of black holes and neutron stars. The main instrument on the LOFT payload is the Large Area Detector (LAD), a collimated experiment with a nominal effective area of ~10 m 2 @ 8 keV, and a spectral resolution of ~240 eV in the energy band 2-30 keV. These performances are achieved covering a large collecting area with more than 2000 large-area Silicon Drift Detectors (SDDs) each one coupled to a collimator based on lead-glass micro-channel plates. In order to reduce the thermal load onto …

The Cryogenic AntiCoincidence detector for ATHENA: the progress towards the final pixel design

2014

“The Hot and Energetic Universe” is the scientific theme approved by the ESA SPC for a Large mission to be flown in the next ESA slot (2028th) timeframe. ATHENA is a space mission proposal tailored on this scientific theme. It will be the first X-ray mission able to perform the so-called “Integral field spectroscopy”, by coupling a high-resolution spectrometer, the X-ray Integral Field Unit (X-IFU), to a high performance optics so providing detailed images of its field of view (5’ in diameter) with an angular resolution of 5” and fine energy-spectra (2.5eV@E<7keV). The X-IFU is a kilo-pixel array based on TES (Transition Edge Sensor) microcalorimeters providing high resolution spectroscopy …

Locally Supported Wavelets on Manifolds with Applications to the 2D Sphere

1999

Abstract In this paper we present a construction principle for locally supported wavelets on manifolds once a multiresolution analysis is given. The wavelets provide a stable (or unconditional) basis for a scale of Sobolev spaces H s , 0 ≤ s ≤ s . We examine a fast wavelet transform with almost optimal complexity. For the two-dimensional sphere we construct a multiresolution analysis generated by continuous splines that are bilinear with respect to some special spherical grid. In our approach the poles are not exceptional points concerning the approximation power or the stability of the wavelet basis. Finally we present some numerical applications to singularity detection and the analysis o…

Conflict management in groups that work in two different communication contexts: Face-to-face and computer-mediated communication

2002

The aim of this study is to test the differences in quality and frequency of conflict management behavior as a function of the interaction between task and communication medium, and practice time in continuing groups that work over two different media: computer mediated communication (CMC) and face to face communication (FTF). Conflict management behavior is studied through observed behavior and categorized by experts. Two conflict management behavior categories are differentiated: positive and negative conflict management behavior. A laboratory experiment was carried out comparing 12 groups of 4 members each, working over two communication media (6 groups FTF and 6 groups over CMC). Group…

Romantic relationships in intra-ethnic and inter-ethnic adolescent couples in Germany: The role of attachment to parents, self-esteem, and conflict r…

2010

We investigated romantic relationships in a sample of 380 adolescents who formed 190 heterosexual couples (mean age: females 17 years; males 18 years): 173 intra-ethnic (German) couples and 17 inter-ethnic couples. Factor analyses revealed two types of love experiences: (a) experiences of attraction and a passionate focus on the partner (passionate love) and (b) experiences of affiliation (companionate love). No differences were found between intra-ethnic and inter-ethnic couples in romantic experiences, self-esteem, and conflict resolution skills. Adolescents in intra-ethnic couples had more close relations with parents than adolescents in inter-ethnic couples. Actor—Partner Interdependen…