14,180 research outputs found
Thermal stability of Cr/Sc multilayers for the soft x-ray range
No full textS.285-291Cr/Sc multilayer mirrors were designed for grazing (30 and 60 degrees) and normal incidence reflection at about 3.16 nm (N/K line) wavelength. The multilayer coatings have been grown on Si-substrates using ion-assisted sputtering deposition. X-ray scattering of CuK radiation and transmission electron microscopy were used for the characterization of the multilayer interface quality. The reflective properties of the Cr/Sc multilayers were measured with synchrotron radiation at different angles of incidence. Reflectivity values between R = 15 % for near normal incidence ( = 5°) and R = 29.6 % or = 60° were measured. Multilayer mirrors with periods less than 1.9 nm have amorphous Cr and Sc layers. The transition from amorphous to crystalline Cr and Sc layers takes place for multilayer periods of more than 3.1 nm and results in interface roughness development The annealing effect in short-period Cr/Sc multilayers was studied in the temperature range from 50°C to 500°C by X- ray scattering and transmission electron microscopy. Structural and phase transformations and the corresponding changes of the optical properties are presented and discussed
High-performance Cr/Sc multilayers for the soft X-ray range
No full textS.172-176Results of soft x-ray reflection measurements of Cr/Sc multilayer mirrors close to the Sc absorption edge at 3.11 nm are presented. Improvements in the deposition technology and the adjustment of the multilayer period with an accuracy of better than 0.01 nm to this absorption edge enabled a step forward towards soft x- ray mirrors with an adequate reflectance that allow the realization of normal incidence optical components in the water window. In particular, reflectivity measurements performed at the PTB reflectometer at BESSY II in Berlin revealed a reflectivity of R = 14.8% at an incidence angle of diameter = 1.5° and R = 15.0% at diameter = 5°. Simulation results show that the interface widths between the Cr and Sc nanolayers are less than 0.4 nm. The annealing effect in short-period Cr/Sc multilayers was studied in the temperature range from 50°C to 500°C by X-ray scattering and transmission electron microscopy. Structural and phase transformatio ns and the corresponding changes of the optical properties are presented and dis cussed
Estudo do cristal líquido 4,4' -Di (n) - Alcoxibenzilazina (n = 5,11) por microscopia ótica, calorimetria diferencial e difração de raios-x
Get PDFDissertaçao (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Curso de Pós-Graduação em Físico-Química
Determinação de arranjos moleculares em cristais líquidos nemáticos utilizando defração de raio-x
Get PDFDissertaçao (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Curso de Pós-Graduação em Físico-Química
Validação de equações antropométricas e de impedância bioelétrica para a estimativa da composição corporal em idosos
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Desportos. Programa de Pós-Graduação em Educação Física.O aumento da população de idosos tem desencadeado a necessidade de aprofundamento nas questões que abrangem o envelhecimento. Neste contexto, a análise das alterações morfológicas com a idade tem sido amplamente discutida. Evidências apontam que são poucas as informações sobre métodos válidos para a estimativa da composição corporal em idosos no Brasil. Desse modo, o objetivo deste estudo foi analisar a validade cruzada de equações antropométricas e de impedância bioelétrica (IB) para a estimativa da gordura corporal (%G) e da massa livre de gordura (MLG) em uma amostra de idosos do Município de Florianópolis-SC, tendo como medida-critério a Absortometria de Radiológica de Dupla Energia (DEXA). Foram avaliados 180 idosos (60 homens e 120 mulheres) com idade entre 60 e 81 anos, selecionados de forma aleatória sistemática, pertencentes a quatro Grupos de Terceira Idade, por meio de uma entrevista realizada por telefone. As variáveis de estatura, massa corporal, perímetros corporais, espessura de dobras cutâneas, reactância e resistência foram mensuradas pelo período da manhã, junto ao Centro de Desportos da Universidade Federal de Santa Catarina. As medidas da DEXA foram realizadas no período da tarde no Centro de Diagnóstico por Imagem em Florianópolis-SC. Foi analisada a validade cruzada de 20 equações antropométricas e 8 equações de IB. Para as equações que estimam a densidade corporal, utilizaram-se a equação de Siri (1961) e a equação adaptada por Deurenberg et al., (1989) para conversão em %G. As análises foram realizadas no pacote estatístico SPSS versão 11.5, adotando-se um nível de significância de 5%. Os critérios de validação cruzada sugeridos por Lohman (1992) e a análise gráfica das dispersões em relação à média, por meio do método proposto por Bland e Altman (1986), foram utilizados. O grupo avaliado apresentou um índice de massa corporal entre 18,4kg/m2 e 39,3kg/m2. O %G médio foi de 23,1% (DP=5,8) nos homens e 37,3% (DP=6,9) nas mulheres, com uma variação entre 6% a 51,4%. As diferenças entre as estimativas das equações de conversão da densidade corporal em %G não foram significativas (p<0,05). As equações antropométricas generalizadas desenvolvidas por Tran e Weltman (1988) e Deurenberg et al., (1991) mostraram-se válidas para a estimativa do %G de homens idosos, apresentando um erro padrão de estimativa (EPE) entre 3,2% e 3,5% e uma correlação significativa r= 0,78 e r= 0,74, respectivamente, com a medida critério. Em relação ao grupo de mulheres idosas, foram válidas as equações antropométricas generalizadas de Durnin e Womersley (1974), Tran e Weltman (1988) e a equação específica de Gonçalves (2004). As mesmas apresentaram um EPE entre 3,26% e 3,50% , com um erro constante entre - 1,2% e 1,9%. Para a estimativa da MLG, as equações de Kyle et al., (2001), Dey et al., (2003) e Sun et al., (2003) não diferem estatisticamente da medida da DEXA em homens, tendo um erro constante entre - 0,7kg e 2,5kg. Já para mulheres, as equações de Kyle et al., (2001) e Dey et al., (2003) mostraram-se válidas (EC entre 0,3kg e 2,7kg). Em relação à análise das categorias de índice de massa corporal (IMC), as equações de Tran e Weltman (1988) e Durnin & Womersley (1974) superestimam o %G em homens com IMC<25kg/m2. O mesmo aconteceu com a equação de Gonçalves (2004) em mulheres idosas, demonstrando que nesses grupos específicos de idosos essas equação não são válidas para a estimativa do %G. As equações de IB válidas não foram influenciadas pelas categorias de IMC. Com isso, as equações validadas no presente estudo podem ser utilizadas na população de idosos nacionais
High Resolution X-Ray Spectroscopy with Compound Semiconductor Detectors and Digital Pulse Processing Systems
Get PDFThe advent of semiconductor detectors has revolutionized the broad field of X-ray
spectroscopy. Semiconductor detectors, originally developed for particle physics, are now
widely used for X-ray spectroscopy in a large variety of fields, as X-ray fluorescence
analysis, X-ray astronomy and diagnostic medicine. The success of semiconductor detectors
is due to several unique properties that are not available with other types of detectors: the
excellent energy resolution, the high detection efficiency and the possibility of development
of compact detection systems. Among the semiconductors, silicon (Si) detectors are the key
detectors in the soft X-ray band (< 15 keV). Si-PIN diode detectors and silicon drift detectors
(SDDs), with moderate cooling by means of small Peltier cells, show excellent spectroscopic
performance and good detection efficiency below 15 keV. Germanium (Ge) detectors are
unsurpassed for high resolution spectroscopy in the hard X-ray energy band (>15 keV) and
will continue to be the choice for laboratory-based high performance spectrometers.
However, there has been a continuing desire for ambient temperature and compact
detectors with the portability and convenience of a scintillator but with a significant
improvement in resolution. To this end, numerous high-Z and wide band gap compound
semiconductors have been exploited. Among the compound semiconductors, cadmium
telluride (CdTe) and cadmium zinc telluride (CdZnTe) are very appealing for hard X-ray
detectors and are widely used for the development of spectrometer prototypes for medical
and astrophysical applications.
Beside the detector, the readout electronics also plays a key role in the development of high
resolution spectrometers. Recently, many research groups have been involved in the design
and development of high resolution spectrometers based on semiconductor detectors and
on digital pulse processing (DPP) techniques. Due to their lower dead time, higher stability
and flexibility, digital systems, based on directly digitizing and processing of detector
signals (preamplifier output signals), have recently been favored over analog electronics
ensuring high performance in both low and high counting rate environments.
In this chapter, we review the research activities of our group in the development of high
throughput and high resolution X-ray spectrometers based on compound semiconductor
detectors and DPP systems. First, we briefly describe the physical properties and the signal
formation in semiconductor detectors for X-ray spectroscopy. Second, we introduce the
main properties and critical issues of a X-ray detection system, highlighting the
characteristics of both analog and digital approaches. Finally, we report on the spectroscopic
performance of a high resolution spectrometer based on a CdTe detector and a custom DPP
system. As an application, direct measurements of mammographic X-ray spectra by using
the digital CdTe detection system are also presented
SC author and illustrator Kate Salley Palmer signing book
No full textPhotograph of SC author and illustrator Kate Salley Palmer signing boo
Book signing by SC author and illustrator Kate Salley Palmer
No full textPhotograph of Book signing by SC author and illustrator Kate Salley Palme
Chemical bonding effects in Sc compounds studied using X ray absorption and X ray photoelectron spectroscopies
No full textAdvances on understanding the nature of the chemical bonding and electron correlation effects during the X ray absorption process in ionic covalent metal complexes has been achieved for most of the transition elements, except for scandium, due to the lack of a systematic series of spectroscopic reference spectra and the shortage of standard crystallographic data on scandium compounds. To close the gap, the chemical bonding effects in eight Sc compounds are studied using X ray absorption spectroscopy XAS at Sc K and L2,3 absorption edges and X ray photoelectron spectroscopy XPS . Indeed, the fine structure of the XAS Sc K edge reflects the chemical sp3 like bond formed between scandium and the ligand while the L2,3 edge and the pre edge features of the K edge provide a direct insight into the crystal field parameters at the Sc site in the coordination compound. The XPS data provide the information on binding energies of the core electrons involved in the electron transitions caused by the absorption of high energy X rays. XAS and XPS complement each other by accessing the information on Sc structure on bulk and the surface. Herein, comprehensive information on the electronic structure of well known crystalline materials based on Sc is given with spectroscopic fingerprints X ray data. This will help to predict the formation of chemical bonds in the unknown components via the systematic evaluation of the available spectroscopic fingerprint
Chemical bonding effects in Sc compounds studied using X-ray absorption and X-ray photoelectron spectroscopies
Get PDFAdvances on understanding the nature of the chemical bonding and electron correlation effects during the X-ray absorption process in ionic–covalent metal complexes has been achieved for most of the transition elements, except for scandium, due to the lack of a systematic series of spectroscopic reference spectra and the shortage of standard crystallographic data on scandium compounds. To close the gap, the chemical bonding effects in eight Sc compounds are studied using X-ray absorption spectroscopy (XAS) at Sc K and L2,3 absorption edges and X-ray photoelectron spectroscopy (XPS). Indeed, the fine structure of the XAS Sc K edge reflects the chemical sp3-like bond formed between scandium and the ligand while the L2,3 edge and the pre-edge features of the K-edge provide a direct insight into the crystal field parameters at the Sc site in the coordination compound. The XPS data provide the information on binding energies of the core electrons involved in the electron transitions caused by the absorption of high energy X-rays. XAS and XPS complement each other by accessing the information on Sc structure on bulk and the surface. Herein, comprehensive information on the electronic structure of well-known crystalline materials based on Sc is given with spectroscopic fingerprints X-ray data. This will help to predict the formation of chemical bonds in the unknown components via the systematic evaluation of the available spectroscopic fingerprints
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