Search results for " Spectroscopy"

Determination of absolute internal conversion coefficients using the SAGE spectrometer

2016

A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for …

Deep traps in InGaN/GaN single quantum well structures grown with and without InGaN underlayers

2020

The electrical properties and deep trap spectra were compared for near-UV GaN/InGaN quantum well (QW) structures grown on free-standing GaN substrates. The structures differed by the presence or absence of a thin (110 nm) InGaN layer inserted between the high temperature GaN buffer and the QW region. Capacitance-voltage profiling with monochromatic illumination showed that in the InGaN underlayer (UL), the density of deep traps with optical threshold near 1.5 eV was much higher than in the QW and higher than for structures without InGaN. Irradiation with 5 MeV electrons strongly increased the concentration of these 1.5 eV traps in the QWs, with the increase more pronounced for samples witho…

Theoretical study of the molecular bases that control photochemical processes with biological and nanotechnological interest

2013

El trabajo desarrollado en la tesis doctoral que lleva por título "Theoretical study of the molecular bases that control photochemical processes with biological and nanotechnological interest" se enmarca en las líneas de investigación del grupo QCEXVAL (Quantum Chemistry of the Excited State University of Valencia), que nació en el seno del departamento de Química Física de la Universitat de València en 1993. Se han abordado temas de interés metodológico, biológico y nanotecnológico. La primera parte de la tesis trata el estudio del método químico-cuántico RASPT2 (Multiconfigurational second-order Perturbation Theory Restricted Active Space) donde se ha calibrado esta metolodogía para siste…

Design and development of a continuous wave functional near infrared spectroscopy system

2014

Functional Near InfraRed Spectroscopy uses light sources and optical detectors for human brain monitoring. In this paper, a portable, low cost, battery-operated, multi-channel, continuous wave fNIRS embedded system, hosting up to 64 LED sources and 128 Silicon PhotoMultiplier optical detectors, is reported on. The designed system is based on a scalable architecture, in which each probe consists of 8 modular and flexible stands, able to host 4 bi-color LEDs as light sources, 16 silicon photomultipliers as photodetectors and a temperature sensor. The hardware structure allows to easily set up several relevant parameters: the timing of the LEDs, the optical power emitted by the LEDs; the acqui…

Design of a Multichannel Continuous Wave fNIRS System implemented with SiPM

2013

Development of a CW-fNIRS System for brain monitoring

2014

Progettazione e realizzazione di un sistema Continuous Wave fNIRS basato su tecnologia SiPM

2014

Progettazione e realizzazione di un sistema Continuous Wave fNIRS basato su tecnologia SiPM

Optical techniques represent a suitable tool for in vivo and non-invasive diagnosis of human brain and tissues. Functional Near InfraRed Spectroscopy (fNIRS) is revealing as an emerging neuroimaging technology, since it is safe, relatively inexpensive and little cumbersome. fNIRS relies on the measurement of the oxygen concentration in the blood by means of light beams impinging on the tissues under test. Haemoglobin concentration variations (oxygenated/deoxygenated) can provide very important information on brain activity and allow to discriminate the main brain area involved during tests. Herein, we present the design and development of an innovative solution for a portable continuous wav…

Embedded-atom calculations of Auger and x-ray photoemission shifts for metallic elements

1982

Change in self-consistent-field energy density-functional calculations are reported for Auger and core-level binding-energy shifts in sp-bonded metals. The basic model, atom in jellium vacancy, gives good agreement with experiment, especially in the Auger case. The chemical and relaxation contributions to the shifts are discussed, and the extra-atomic response is analyzed in detail, both in position and energy space. The adequacy of the "excited-atom" approach to the energy shifts is discussed. Peer reviewed

Mapping a-priori defined plant associations using remotely sensed vegetation characteristics

2014

Abstract Incorporation of a priori defined plant associations into remote sensing products is a major challenge that has only recently been confronted by the remote sensing community. We present an approach to map the spatial distribution of such associations by using plant indicator values (IVs) for salinity, moisture and nutrients as an intermediate between spectral reflectance and association occurrences. For a 12 km 2 study site in the Netherlands, the relations between observed IVs at local vegetation plots and visible and near-infrared (VNIR) and short-wave infrared (SWIR) airborne reflectance data were modelled using Gaussian Process Regression (GPR) (R 2 0.73, 0.64 and 0.76 for sali…