Linear and nonlinear optical properties of Si nanocrystals in SiO2 deposited by plasma-enhanced chemical-vapor deposition

Linear and nonlinear optical properties of silicon suboxide SiOx films deposited by plasma-enhanced chemical-vapor deposition have been studied for different Si excesses up to 24¿at.¿%. The layers have been fully characterized with respect to their atomic composition and the structure of the Si precipitates. Linear refractive index and extinction coefficient have been determined in the whole visible range, enabling to estimate the optical bandgap as a function of the Si nanocrystal size. Nonlinear optical properties have been evaluated by the z-scan technique for two different excitations: at 0.80¿eV in the nanosecond regime and at 1.50¿eV in the femtosecond regime. Under nanosecond excitation conditions, the nonlinear process is ruled by thermal effects, showing large values of both nonlinear refractive index (n2 ~ ¿10¿8¿cm2/W) and nonlinear absorption coefficient (ß ~ 10¿6¿cm/W). Under femtosecond excitation conditions, a smaller nonlinear refractive index is found (n2 ~ 10¿12¿cm2/W), typical of nonlinearities arising from electronic response. The contribution per nanocrystal to the electronic third-order nonlinear susceptibility increases as the size of the Si nanoparticles is reduced, due to the appearance of electronic transitions between discrete levels induced by quantum confinement.

Structural and optical properties of dilute InAsN grown by molecular beam epitaxy

We perform a structural and optical characterization of InAs1¿xNx epilayers grown by molecular beam epitaxy on InAs substrates x 2.2% . High-resolution x-ray diffraction HRXRD is used to obtain information about the crystal quality and the strain state of the samples and to determine the N content of the films. The composition of two of the samples investigated is also obtained with time-of-flight secondary ion mass spectroscopy ToF-SIMS measurements. The combined analysis of the HRXRD and ToF-SIMS data suggests that the lattice parameter of InAsN might significantly deviate from Vegard"s law. Raman scattering and far-infrared reflectivity measurements have been carried out to investigate the incorporation of N into the InAsN alloy. N-related local vibrational modes are detected in the samples with higher N content. The origin of the observed features is discussed. We study the compositional dependence of the room-temperature band gap energy of the InAsN alloy. For this purpose, photoluminescence and optical absorption measurements are presented. The results are analyzed in terms of the band-anticrossing BAC model. We find that the room-temperature coupling parameter for InAsN within the BAC model is CNM=2.0 0.1 eV.

Descriptive epidemiology of Cornelia de Lange syndrome in Europe.

Cornelia de Lange syndrome (CdLS) is a multiple congenital anomaly/mental retardation syndrome consisting of characteristic dysmorphic features, microcephaly, hypertrichosis, upper limb defects, growth retardation, developmental delay, and a variety of associated malformations. We present a population-based epidemiological study of the classical form of CdLS. The data were extracted from the database of European Surveillance of Congenital Anomalies (EUROCAT) database, a European network of birth defect registries which follow a standard methodology. Based on 23 years of epidemiologic monitoring (8,558,346 births in the 1980-2002 period), we found the prevalence of the classical form of CdLS to be 1.24/100,000 births or 1:81,000 births and estimated the overall CdLS prevalence at 1.6-2.2/100,000. Live born children accounted for 91.5% (97/106) of cases, fetal deaths 2.8% (3/106), and terminations of pregnancy following prenatal diagnosis 5.7% (6/106). The most frequent associated congenital malformations were limb defects (73.1%), congenital heart defects (45.6%), central nervous system malformations (40.2%), and cleft palate (21.7%). In the last 11 years, as much as 68% of cases with major malformations were not detected by routine prenatal US. Live born infants with CdLS have a high first week survival (91.4%). All patients were sporadic. Maternal and paternal age did not seem to be risk factors for CdLS. Almost 70% of patients, born after the 37th week of gestation, weighed <or=2,500 g. Low birth weight correlated with a more severe phenotype. Severe limb anomalies were significantly more often present in males.

Edict de création en tiltre d'office formé de cent conseillers et secrétaires ordinaires de la chambre du Roy... [D'octobre 1613.]

[Acte royal. 1613-10-00]

Er-Coupled Si Nanocluster Waveguide

Rib-loaded waveguides containing Er3+-coupled Si nanoclusters (Si-nc) have been produced to observe optical gain at 1535 nm. The presence ofSi-nc strongly improves the efficiency ofEr 3+ excitation but may introduce optical loss mechanisms, such as Mie scattering and confined carrier absorption. Losses strongly affect the possibility of obtaining positive optical gain. Si-nc-related losses have been minimized to 1 dB/cm by lowering the annealing time ofthe Er3+-doped silicon-rich oxide deposited by reactive magnetron cosputtering. Photoluminescence (PL) and lifetime measurements show that all Er3+ ions are optically active while those that can be excited at high pump rates via Si-nc are only a small percentage. Er3+ absorption cross section is found comparable to that ofEr 3+ in SiO 2.However, dependence on the effective refractive index has been found. In pump-probe measurements, it is shown how the detrimental role ofconfined carrier absorption can be attenuated by reducing the annealing time. A maximum signal enhancement ofabout 1.34 at 1535 nm was measured.

Measurement and simulation of anisotropy in the Infrared and Raman spectra of beta-FeSi2 single crystals

In this paper we show that the orthorhombic phase of FeSi2 (stable at room temperature) displays a sizable anisotropy in the infrared spectra, with minor effects in the Raman data too. This fact is not trivial at all, since the crystal structure corresponds to a moderate distortion of the fluorite symmetry. Our analysis is carried out on small single crystals grown by flux transport, through polarization-resolved far-infrared reflectivity and Raman measurements. Their interpretation has been obtained by means of the simulated spectra with tight-binding molecular dynamics.

[Illustrations de Brevis ac dilucida Burgundiae superioris... item brevis ad modum totius Galliae descriptio per eudem] / [Non identifié] ; Gilbert Cousin, aut. du texte

Comprend : [Planche entre les p. 48-49. Deux planches. Représentation du côté ouest et du côté est d'une ville. Habitations burgondes.] [Cote : BNF C214317] ; [Planche dépliante entre les p. 48-49. Partie gauche de la planche représentant le côté est d'une ville. Habitations burgondes.] [Cote : BNF C94455]

Severe neurologic manifestations from cervical spine instability in spondylo-megaepiphyseal-metaphyseal dysplasia.

Spondylo-megaepiphyseal-metaphyseal dysplasia (SMMD; OMIM 613330) is a dysostosis/dysplasia caused by recessive mutations in the homeobox-containing gene, NKX3-2 (formerly known as BAPX1). Because of the rarity of the condition, its diagnostic features and natural course are not well known. We describe clinical and radiographic findings in six patients (five of which with homozygous mutations in the NKX3-2 gene) and highlight the unusual and severe changes in the cervical spine and the neurologic complications. In individuals with SMMD, the trunk and the neck are short, while the limbs, fingers and toes are disproportionately long. Radiographs show a severe ossification delay of the vertebral bodies with sagittal and coronal clefts, missing ossification of the pubic bones, large round "balloon-like" epiphyses of the long bones, and presence of multiple pseudoepiphyses at all metacarpals and phalanges. Reduced or absent ossification of the cervical vertebrae leads to cervical instability with anterior or posterior kinking of the cervical spine (swan neck-like deformity, kyknodysostosis). As a result of the cervical spine instability or deformation, five of six patients in our series suffered cervical cord injury that manifested clinically as limb spasticity. Although the number of individuals observed is small, the high incidence of cervical spine deformation in SMMD is unique among skeletal dysplasias. Early diagnosis of SMMD by recognition of the radiographic pattern might prevent of the neurologic complications via prophylactic cervical spine stabilization. © 2012 Wiley Periodicals, Inc.

[Illustrations de Description et charte de la Terre Saincte] / [Non identifié] ; Guillaume Postel, aut. du texte

Comprend : [Carte en regard de la p.3. Carte de la Terre Sainte] [Cote : BNF C121998] ; [Carte en regard du folio E5v °. Carte de l'Arabie] [Cote : BNF C121999] ; [Carte en regard du folio F5r °. Carte des côtes de la Méditéranée] [Cote : BNF C122000] ; [Carte en regard du folio G5v °. Carte de la Terre Sainte] [Cote : BNF C122001] ; [Dernière carte du volume p.108. Carte de la Terre Sainte] [Cote : BNF C122002]

Permeâmetro de carga decrescente associado a programa computacional para a determinação da condutividade hidráulica do solo saturado

A condutividade hidráulica do solo saturado (Kθs) é uma propriedade com grande variabilidade, o que exige a utilização de um número maior de determinações para que sua descrição possa ser feita adequadamente pela função densidade de probabilidade normal. Consequentemente, há aumento de trabalho e de tempo para a obtenção dos resultados, principalmente se as determinações forem feitas com equipamentos de pouca praticidade. A construção de equipamentos de maior praticidade e o desenvolvimento de ferramentas computacionais podem tornar o processo de análise mais rápido e preciso. Com esse objetivo, foi construído um permeâmetro de carga decrescente e desenvolvido um software para a aquisição de dados. As medidas de Kθs obtidas com esses equipamentos, em amostras de um Argissolo, mostraram menor variabilidade, avaliada pelo coeficiente de variação, o que resultou em maior precisão das determinações. Além disso, o tempo de análise foi reduzido em 30 %.

Identifying the socioeconomic determinants of crime in Spanish provinces

In this paper we study, having as theoretical reference the economic model of crime (Becker, 1968; Ehrlich, 1973), which are the socioeconomic and demographic determinants of crime in Spain paying attention on the role of provincial peculiarities. We estimate a crime equation using a panel dataset of Spanish provinces (NUTS3) for the period 1993 to 1999 employing the GMMsystem estimator. Empirical results suggest that lagged crime rate and clear-up rate are correlated to all typologies of crime rate considered. Property crimes are better explained by socioeconomic variables (GDP per capita, GDP growth rate and percentage of population with high school and university degree), while demographic factors reveal important and significant influences, in particular for crimes against the person. These results are obtained using an instrumental variable approach that takes advantage of the dynamic properties of our dataset to control for both measurement errors in crime data and joint endogeneity of the explanatory variables