Raman investigation of structural photoinduced irreversible changes of Ga10Ge25S65 chalcogenide glasses

The influence of time exposure, when exposed to above band gap light (3,52 eV) and annealing, on Ga10Ge25S65 glasses has been studied through their effects on the structure and optical properties. To evaluate the photostructural change infrared and Raman spectra for bulk Ga10Ge25S65 glasses have been measured before and after exposure. The Raman spectra are interpreted in terms of models in which the Ge atoms are fourfold coordinated and the S atoms are two fold coordinated. The observed changes in the spectral region of (S-S) stretching vibration (470-490 cm (-1)) is a direct evidence for the occurrence of important structural changes in local bonding configuration caused by optical irradiation. It is shown that the dominant photostrucural changes are chain formation tendency of the chalcogenide atoms under the laser irradiation rather than rings.

Gluon mass generation in the PT-BFM scheme

In this article we study the general structure and special properties of the Schwinger-Dyson equation for the gluon propagator constructed with the pinch technique, together with the question of how to obtain infrared finite solutions, associated with the generation of an effective gluon mass. Exploiting the known all-order correspondence between the pinch technique and the background field method, we demonstrate that, contrary to the standard formulation, the non-perturbative gluon self-energy is transverse order-by-order in the dressed loop expansion, and separately for gluonic and ghost contributions. We next present a comprehensive review of several subtle issues relevant to the search of infrared finite solutions, paying particular attention to the role of the seagull graph in enforcing transversality, the necessity of introducing massless poles in the three-gluon vertex, and the incorporation of the correct renormalization group properties. In addition, we present a method for regulating the seagull-type contributions based on dimensional regularization; its applicability depends crucially on the asymptotic behavior of the solutions in the deep ultraviolet, and in particular on the anomalous dimension of the dynamically generated gluon mass. A linearized version of the truncated Schwinger-Dyson equation is derived, using a vertex that satisfies the required Ward identity and contains massless poles belonging to different Lorentz structures. The resulting integral equation is then solved numerically, the infrared and ultraviolet properties of the obtained solutions are examined in detail, and the allowed range for the effective gluon mass is determined. Various open questions and possible connections with different approaches in the literature are discussed. © SISSA 2006.

Analyzing dynamical gluon mass generation

We study the necessary conditions for obtaining infrared finite solutions from the Schwinger-Dyson equation governing the dynamics of the gluon propagator. The equation in question is set up in the Feynman gauge of the background field method, thus capturing a number of desirable features. Most notably, and in contradistinction to the standard formulation, the gluon self-energy is transverse order-by-order in the dressed loop expansion, and separately for gluonic and ghost contributions. Various subtle field-theoretic issues, such as renormalization group invariance and regularization of quadratic divergences, are briefly addressed. The infrared and ultraviolet properties of the obtained solutions are examined in detail, and the allowed range for the effective gluon mass is presented.

Fabricação e caracterização de filmes finos de perileno: arquitetura molecular e aplicações sensoriais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise químico-farmacêutica de preparações injetáveis de celftriaxona sódica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Interação entre as substâncias húmicas de sedimentos e metais potencialmente tóxicos: um estudo na Bacia Hidrográfica do Turvo/Grande

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudos de pré-formulação e formulação de Vismia guianensis (Aubl.) Choisy

A obtenção e a avaliação da formulação fitoterápica foi traçada através de parâmetros de controle de qualidade realizando-se a caracterização físico-química da matéria-prima vegetal desidratada e triturada, do seu derivado (extrato liofilizado da tintura hidroalcóolica) e da formulação semi-sólida fitoterápica antimicrobiana contendo a tintura das folhas de Vismia guianensis (Aubl) Choisy. Para tais caracterizações utilizaram-se os parâmetros específicos para as drogas vegetais contidos na Farmacopéia Brasileira 4. Ed., a análise térmica: termogravimetria, análise térmica diferencial e calorimetria exploratória diferencial e a espectroscopia na região do infravermelho e do ultravioleta. A avaliação da atividade antimicrobiana pelo método de difusão em disco em meio sólido identificou a sensibilidade de S. aureus (ATCC 25923) ao extrato seco da tintura dissolvido em DMSO, nas concentrações de 500, 250, 125 e 62,5 mg/mL. A CLAE traçou o perfil de composição das sub-frações A e B provenientes da fração acetato de etila da tintura e evidenciou o alcance máximo de absorção em 290 nm para a fração acetato de etila semelhante ao alcance máximo da emodia, sendo essa então utilizada como padrão de referência e marcador externo. A validação do método foi realizada através da espectrofotometria no ultravioleta, demonstrando ser um método seletivo, linear, repetitivo e robusto. A análise térmica evidenciou possíveis incompatibilidades existentes entre a mistura binária do extrato liofilizado da tintura com a hidroxietilcelulose e o propilenoglicol; obtendo-se então um gel com características não homogêneas devido à precipitação de proteínas, ocorrida pela interação polifenol-protéina. A avaliação da estabilidade preliminar da formulação permaneceu dentro dos parâmetros, apresentando resultados dentro dos limites aceitáveis para os testes de centrifugação, estresse térmico e características organolépticas.

Estudo químico e biológico de plantas da família Eriocaulaceae

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese, caracterização estrutural, espectroscópica e análise do potencial fotocatalítico do aluminato de cobalto e potencial catalítico na preparação do biodiesel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Raman and polarized infrared spectra of pyridine-2-thione

Polarized i.r. spectra of oriented polycrystals and the i.r. and Raman spectra of polycrystalline samples of pyridine-2-thione have been obtained. The Raman spectra of a solution of pyridine-2-thione has also been measured and the polarization of many lines determined. The i.r. spectra of S-methyl and N-deuterated compounds have also been investigated. A complete assignment of all the observed peaks has been possible. The results are correlated with the assignments available for related systems.

Restricted rotation dynamics and far-infrared spectra of liquid water governed by elastic interactions

A semi-phenomenological model describing wideband dielectric and far-infrared spectra of liquid water was proposed recently by the same authors [J. Mol. Struct. 606 (2002) 9], where a small dipole-moment component changing harmonically with time determines a weak absorption band (termed here the R-band) centred at the wavenumber v similar to 200 cm(-1). In the present work, a rough molecular theory of the R-band based on the concept of elastic interactions is given. Stretching and bending of hydrogen bonds cause restricted rotation (RR) of a polar water molecule in terms of a dimer comprising the H- bonded molecules. Analytical expression for the RR frequency nu(str) is derived as a function of the RR amplitude, geometrical parameters and force constants. The density g(nu(str)) of frequency distribution is shown to be centred in the R-band. The spectrum of the dipolar auto-correlation function calculated for this structural-dynamical model is found. A composite model comprising two intermolecular potentials is proposed, which yields for water a good description of the experimental wideband (from 0 to 1000 cm(- 1)) spectra of complex permittivity and of absorption coefficient. The presented interpretation of these spectra is based on a concept that water presents a two-component solution, with components differing by the types of molecular rotation. (C) 2003 Elsevier B.V. All rights reserved.

Interpreting the near-infrared spectra of the 'golden standard' Type Ia supernova 2005cf

We present nine near-infrared (NIR) spectra of supernova (SN) 2005cf at epochs from -10 to +42d with respect to B-band maximum, complementing the existing excellent data sets available for this prototypical Type Ia SN at other wavelengths. The spectra show a time evolution and spectral features characteristic of normal Type Ia SNe, as illustrated by a comparison with SNe 1999ee, 2002bo and 2003du. The broad-band spectral energy distribution (SED) of SN 2005cf is studied in combined ultraviolet (UV), optical and NIR spectra at five epochs between ~8d before and ~10d after maximum light. We also present synthetic spectra of the hydrodynamic explosion model W7, which reproduce the key properties of SN 2005cf not only at UV-optical as previously reported, but also at NIR wavelengths. From the radiative-transfer calculations we infer that fluorescence is the driving mechanism that shapes the SED of SNe Ia. In particular, the NIR part of the spectrum is almost devoid of absorption features, and instead dominated by fluorescent emission of both iron-group material and intermediate-mass elements at pre-maximum epochs, and pure iron-group material after maximum light. A single P-Cygni feature of Mgii at early epochs and a series of relatively unblended Coii lines at late phases allow us to constrain the regions of the ejecta in which the respective elements are abundant. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Structural refinement, growth mechanism, infrared/Raman spectroscopies and photoluminescence properties of PbMoO4 crystals

Lead molybdate (PbMoO4) crystals were synthesized by the co-precipitation method at room temperature and then processed in a conventional hydrothermal (CH) system at low temperature (70 °C for different times). These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, micro-Raman (MR) and Fourier transformed infrared (FT-IR) spectroscopies. Field emission scanning electron microscopy images were employed to observe the shape and monitor the crystal growth process. The optical properties were investigated by ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) measurements. XRD patterns and MR spectra indicate that these crystals have a scheelite-type tetragonal structure. Rietveld refinement data possibilities the evaluation of distortions in the tetrahedral [MoO 4] clusters. MR and FT-IR spectra exhibited a high mode ν1(Ag) ascribed to symmetric stretching vibrations as well as a large absorption band with two modes ν3(Eu and Au) related to anti-symmetric stretching vibrations in [MoO 4] clusters. Growth mechanisms were proposed to explain the stages involved for the formation of octahedron-like PbMoO4 crystals. UV-Vis absorption spectra indicate a reduction in optical band gap with an increase in the CH processing time. PL properties of PbMoO4 crystals have been elucidated using a model based on distortions of tetrahedral [MoO4] clusters due to medium-range intrinsic defects and intermediary energy levels (deep and shallow holes) within the band gap. © 2012 Elsevier Ltd. All rights reserved.

Optical absorption, infrared, Raman and EPR spectral studies on natural Iowaite mineral

Natural iowaite, magnesium–ferric oxychloride mineral having light green color originating from Australia has been characterized by EPR, optical, IR, and Raman spectroscopy. The optical spectrum exhibits a number of electronic bands due to both Fe(III) and Mn(II) ions in iowaite. From EPR studies, the g values are calculated for Fe(III) and g and A values for Mn(II). EPR and optical absorption studies confirm that Fe(III) and Mn(II) are in distorted octahedral geometry. The bands that appear both in NIR and Raman spectra are due to the overtones and combinations of water and carbonate molecules. Thus EPR, optical, and Raman spectroscopy have proven most useful for the study of the chemistry of natural iowaite and chemical changes in the mineral.

Molecular structure of Mg-Al, Mn-Al and Zn-Al halotrichites : an infrared spectroscopic study

Near infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to halotrichites of the formula MgAl2(SO4)4∙22H2O, MnAl2(SO4)4∙22H2O and ZnAl2(SO4)4∙22H2O. Comparison of the halotrichites in different spectral regions has shown that the incorporation of a divalent transition metal into the halotrichite structure causes a shift in OH stretching band positions to lower wavenumbers. Therefore, an increase in hydrogen bonded water is observed for divalent cations with a larger molecular mass. XRD has confirmed the formation of halotrichite for all three samples and characteristic peaks of halotrichite have been identified at 18.5 and 24.5° 2θ, along with a group of six peaks between 5 and 15° 2θ. It has been observed that Mg-Al and Mn-Al halotrichite are very similar in structure, while Zn-Al showed several differences particularly in the NIR spectra. This work has shown that halotrichite structures can be synthesised and characterised by infrared and NIR spectroscopy.