Spectroscopic Studies

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Spectroscopic studies of Ti3+ ions speciation inside MgAl2O4 spinels

Spectroscopic studies of Ti3+ ions speciation inside MgAl2O4 spinels

trivalent titanium in an unique site which consists of a Ti 3+ in the Al 3+ octahedral site of the spinel structure (B site). To explain this apparent inconsistency between our EPR observations and the results of previous studies we will consider first the spinel structure and second the possible unusual position of some atoms in the crystal structure. First, as previously mentioned, only one- eighth of the tetrahedral and one-half of the octahedral sites in the spinel structure are occupied respectively by Mg 2+ or Al 3+ ions. When heated, some Al 3+ and Mg 2+ ions may change their sites, giving rise to a more random distribution of the cations. The fraction of Al 3+ ions in the Mg 2+ sublattice is usually denoted by i and it was demonstrated by nuclear magnetic resonance (NMR) and infrared absorption that i takes values from 0.1 to 0.6 in synthetic MgAl 2 O 4 spinels [14].
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Vanadium haloperoxidases: from the discovery 30 years ago to X-Ray crystallographic and V K-edge absorption spectroscopic studies

Vanadium haloperoxidases: from the discovery 30 years ago to X-Ray crystallographic and V K-edge absorption spectroscopic studies

effective biomimetic catalyst for VHPOs, also providing an explanation for the differences in chloro- and bromo-peroxidases [147]. Much progress has also been obtained by classical biochemical studies, X-ray crystallography and spectroscopic analyses of the global and fine local structures of the native and peroxo-intermediate forms of the enzymes. The resolution of a protein crystal-structure of a VHPO specific for iodide oxidation [56] has recently allowed further exploring the molecular origin of halide selectivity, which still remains an intriguing question. Indeed the halide specificity in VHPO is related to many interacting factors, such as the amino acid composition of the active site and the fine electronic environment of the vanadate pocket. This latter study also showed that the 2 nd coordination sphere of the peroxo intermediate appears to play an equally important role. In order to decipher the complete catalytic mechanisms of VHPOs and their contrasting reactivity towards different halides, it is important to pursue and enhance the combination of approaches, undertaking protein crystallographic studies in parallel to fine local structure analyses by XAS and EXAFS, on the different VHPO available and specific site-directed mutants that show modified biochemical kinetics. For instance, the fine tuning of the VO 4 moiety during the catalytic cycle should be
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Structure, infrared and Raman spectroscopic studies of newly synthetic AII(SbV0.50FeIII0.50)(PO4)2 (A = Ba, Sr, Pb) phosphates with yavapaiite structure

Structure, infrared and Raman spectroscopic studies of newly synthetic AII(SbV0.50FeIII0.50)(PO4)2 (A = Ba, Sr, Pb) phosphates with yavapaiite structure

Sorbonne Universités, UPMC Univ Paris 06, France Abstract The synthesis and structural study of three new A II (Sb V 0.5 Fe III 0.5 )(PO 4 ) 2 (A = Ba, Sr, Pb,) phosphates belonging to the A-Sb-Fe-P-O system were reported here for the first time. Structures of [Ba], [Sr] and [Pb] compounds, obtained by solid state reaction in air atmosphere, were determined at room temperature from X-ray powder diffraction using the Rietveld method. Ba II (Sb V 0.5 Fe III 0.5 )(PO 4 ) 2 [Ba] features the yavapaiite-type structure, with space group C2/m, Z = 2 and a = 8.1568(4) Å; b= 5.1996(3) Å c= 7.8290(4) Å; β = 94.53(1)°. A II (Sb V 0.5 Fe III 0.5 )(PO 4 ) 2 (A = Sr, Pb) compounds have a distorted yavapaiite structure with space group C2/c, Z = 4 and a = 16.5215(2) Å; b = 5.1891(1) Å c = 8.0489(1) Å; β = 115.70(1)° for [Sr]; a = 16.6925(2) Å; b = 5.1832(1) Å c = 8.1215(1) Å; β = 115.03(1)° for [Pb]. Raman and Infrared spectroscopic study was used to obtain further structural information about the nature of bonding in selected compositions.
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Joint optical and near-infrared spectroscopic studies of stars with X-shooter : an insight into carbon stars

Joint optical and near-infrared spectroscopic studies of stars with X-shooter : an insight into carbon stars

In the modelling of luminous cool stellar populations, two important sources of uncertainties (other than the incompleteness of spectral libraries) are the funda- mental parameters assig[r]

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Spectroscopic studies on nanocomposites obtained by functionalization of carbon nanotubes with conducting polymers

Spectroscopic studies on nanocomposites obtained by functionalization of carbon nanotubes with conducting polymers

potential ranges (-200; +700) and (-800; +800) mV vs. SCE, respectively at a sweep rate of 100 mV s -1 . The de-doping of the PANI-ES film was achieved with NH 4 OH. Electrochemical measurements were carried out using a potentiostat / galvanostat type Princeton Applied Research (PAR), model 173, a PAR pulse generator, model 175 and a Philips-type X-Y recorder. SERS studies were performed in a backscattering geometry, under laser excitation wavelengths 1064 and 676.4 nm, using a RFS 100 FT Raman Bruker spectrophotometer and a Jobin Yvon T64000 Raman spectrophotometer, respectively. FTIR spectra were acquired with a Bruker IFS 28 spectrophotometer.
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Synthesis, characterization, spectroscopic studies and antimicrobial activity of three new Schiff bases derived from Heterocyclic moiety

Synthesis, characterization, spectroscopic studies and antimicrobial activity of three new Schiff bases derived from Heterocyclic moiety

[14] F.A. Carey, R.C. Atkins, Organic Chemistry, fifth ed., McGraw-Hill, New York, 2003 . [15] S.M. Abdallah, G.G. Mohamed, M. Zayed, M.S.A. El-Ela, Spectroscopic study of molecular structures of novel Schiff base derived from o-phthaldehyde and 2- aminophenol and its coordination compounds together with their biological activity, Spectrochim Acta Part A Mol. Biomol. Spectrosc. 73 (5) (2009) 833e840 .

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Laser Spectroscopic Studies of the E 1£+ State of the MgO Molecule

Laser Spectroscopic Studies of the E 1£+ State of the MgO Molecule

the order of only ~0.2 cm -1 . On the other hand, such small admixtures might cause only small perturbations to the E 1 Σ + (v′) vibrational energies (as observed) if the e ω′ values for the E and H states are similar (which is likely). This is a very speculative idea, but ab initio or “model” theoretical studies could confirm or deny its feasibility. We currently favor this explanation. [The “H 1 Σ + ” (secondary minimum) state, of course, is not Franck-Condon accessible from the

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Spectroscopic studies and molecular modeling for understanding the interactions between cholesterol and cyclodextrins

Spectroscopic studies and molecular modeling for understanding the interactions between cholesterol and cyclodextrins

NMR studies on Rameb are difficult because it is not a single pure compound, but rather a mixture of randomly methylated molecules of - CD (38). Only partial proton attributions could be done by comparison to the spectrum obtained with the well characterized Dimeb. The presence of cholesterol is related to an upfield shift of 2- OMe (+0.02 ppm) which seems to suggest its involvement in the interactions while no shift appeared for 6-OMe (Fig. 4C). Concerning the protons of the inner cavity, 5-H shifted downfield in the presence of cholesterol (-0.02 ppm). Data on 3-H were inconclusive. So, based on these data, only limited conclusions can be made on the involvement of the CD protons. On the ROESY spectrum (Fig 5C), correlation spots between a couple of protons of cholesterol and 2-OMe but also 6-OMe can be seen confirming the implication of the latter one in the interactions. From the two types of NMR experiments, it is possible to assume the interactions of cholesterol with the methyl groups of Rameb. Despite the difficulty to assign the methine protons of the CD after complexation, the interactions shown in Fig. 5C probably involve CD protons such as 3-H or 5-H.
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Spectroscopic constraints for low-mass asteroseismic targets

Spectroscopic constraints for low-mass asteroseismic targets

asteroseismic targets Thierry Morel Abstract A full exploitation of the observations provided by the CoRoT and Kepler missions depends on our ability to complement these data with accurate effective temperatures and chemical abundances. We review in this contribution the major efforts that have been undertaken to characterise late-type, seismic targets based on spectra gathered as part of the ground-based, follow-up campaigns. A specific feature of the spectroscopic studies of these stars is that the gravity can be advanta- geously fixed to the more accurate value derived from the pulsation spectrum. We describe the impact that such an approach has on the estimation of T eff and [Fe/H]. The relevance of red-giant seismic targets for studies of internal mixing processes and stellar populations in our Galaxy is also briefly discussed.
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Spectroscopic variability and magnetic fields of HgMn stars

Spectroscopic variability and magnetic fields of HgMn stars

2 Spectroscopic variability as a general characteristics of HgMn stars As a result of our extensive spectroscopic studies in the last years, we could establish that chemical inhomogeneities are widespread among B7–B9 HgMn primaries of spectro- scopic binaries and that previous failures to detect them were largely related to a small number of repeated observa- tions of the same targets and traditional focus on the sharp- lined stars, for which the spectrum variations are much harder to detect. High-quality spectra of a representative sample of HgMn stars were obtained with UVES (Ultra- violet and Visual Echelle Spectrograph) at the VLT and the Fiberfed Extended Range Optical Spectrograph (FEROS) at the ESO 2.2-m telescope within the framework of our ESO programs aimed at a careful study of line profile variations of various elements. In Fig. 1 we present numerous exam- ples of the variability of various spectral lines belonging to different elements in HgMn stars.
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Accurate spectroscopic parameters of WASP planet host stars

Accurate spectroscopic parameters of WASP planet host stars

is present which could affect the IRFM T eff . Table 5 gives the v mic , v mac and v sin i. The mass and radius for each star are obtained from the T eff , log g, and [Fe/H], based on the Torres et al. (2010) calibration. How- ever, it should be noted that these masses and radii are only given as an example, and that stellar evolutionary models may give different results based on the same spectroscopic parameters.

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Bipolar Jets Produced By A Spectroscopic Binary

Bipolar Jets Produced By A Spectroscopic Binary

3. JET PROPERTIES DERIVED FROM [OI]λ 6300 AND Hα It is now generally accepted that the forbidden emission lines (FELs) of T Tauri stars (TTSs) are an important diagnos- tic for their outflows close to the star on scales of 20-40 AU (Hirth et al. 1997; Hartigan et al. 1995; Eislöffel et al. 2000). The most important line for these studies is the [OI]λ 6300 line, which is usually the strongest FEL in TTSs in the opti- cal and therefore most easily observable. For KH 15D, the rather small measured out of eclipse W λ ([OI]λ 6300)=0.4-

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Detecting cervical dysplasia with quantitative spectroscopic imaging

Detecting cervical dysplasia with quantitative spectroscopic imaging

Figure 6.1 shows spectroscopy parameters measured from HSIL and non-HSIL sites (determined by pathology) in the transformation zones of the LEEP patients. The medians of the [r]

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Sensing ruthenium tetroxide Emissions : a spectroscopic study

Sensing ruthenium tetroxide Emissions : a spectroscopic study

Diagnostic tool of nuclear core degradation state Online quantification of released fission gas.. Improve the evaluation of environmental releases[r]

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spectroscopic characterization of el-oued sand dunes

spectroscopic characterization of el-oued sand dunes

The results found by researchers in countries like Libya, Egypt and Tunisia have shown the presence of mutual properties among earth's crust minerals. [1] those properties are of a significant correspondence to the geographical location. Quartz has a wide range of applications, and is considered a corner stone of many industries, for instance, building materials, thermal rocks, anti-humidity rocks and clean energy equipment. The marked quality transformation in building materials in both Egypt and Tunisia was essentially due to the studies on natural resources (generally) and quartz (specifically) utilization. Quartz is also a crucial component in electronics industry.
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Deriving biomedical diagnostics from NMR spectroscopic data

Deriving biomedical diagnostics from NMR spectroscopic data

/ La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. For the publisher’[r]

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The 2015 edition of the GEISA spectroscopic database

The 2015 edition of the GEISA spectroscopic database

Part of the GEISA-2015 methane update is based on the latest global fits of line-by-line assignments (for both line positions and line intensities). The global analysis up to the Tetradecad region [132] was used for 12 CH 4 , while a global fit up to the Octad region [133] was used for 13 CH 4 . The line list was generated by computing semi-empirical upper state energy levels. These levels are calculated from averages over several transitions sharing the same upper state; all line positions are then recomputed using these upper states. This method is the same as the one used for the HITRAN- 2012 methane update described in Ref. [134]. Since this last paper, some problems, however, have been detected especially concerning some hot band lines like those of the Octad–Dyad and Octad– Pentad regions. As a consequence, in the case of 12 CH 4 , the calculated lines of Octad–Dyad resulting from these global fits are discarded in the present GEISA update, while Octad–Pentad lines are included with an intensity cut-off limited to 10 -26 cm -1 /molecule cm -2 . Moreover, after a careful validation process based on a method described in Armante et al. [22] (this issue), it appeared that the new spectroscopic parameters of the Octad–GS lines for 12 CH 4 and 13 CH 4, and the Dyad–GS lines for 13 CH 4, were less precise than the previous ones in GEISA-2011 [11]; these have, consequently, been retained in GEISA-2015.
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Spectroscopic investigation of arc over an ice surface

Spectroscopic investigation of arc over an ice surface

e) Rotational temperatures were calculated versus current variation during discharge propagation over an ice surface using DC-, DC+ and AC applied voltages. It was observed that for diff[r]

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Active spectroscopic diagnostics for ITER utilizing neutral beams

Active spectroscopic diagnostics for ITER utilizing neutral beams

Figure 6 summarizes the signal to noise for the thermal ash density measurements, which can be achieved with beam energy of 125 keV, as a function of integration tim[r]

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Spectroscopic and photometric variability of the O9.5Vp star HD93521

Spectroscopic and photometric variability of the O9.5Vp star HD93521

Key words. Stars: early-type – Stars: individual: HD 93521 – Stars: oscillations – Stars: variables: other – Stars: fundamental param- eters 1. Introduction Time resolved spectroscopy of O-type stars has shown that absorption line profile variability at the level of a few per cent is a common feature (e.g. Fullerton et al. 1996). Various mech- anisms, including magnetic fields, stochastic structures at the base of the wind and non-radial pulsations have been proposed to explain this variability. Despite their rather subtle signature, the diagnostic potential of these phenomena is considerable. Especially in the case of non-radial pulsations, the emerging discipline of asteroseismology offers the possibility to gain insight into the interiors of early-type stars. However, to charac- terize the nature of the phenomenon requires a rather long and well sampled time series of spectra with a high resolution and a high S/N (see e.g. Aerts et al. 2004 for the case of the β Cephei variable ν Eri). Up to now, such detailed studies have therefore been restricted to a few, rather bright and well-known O-stars such as ζ Pup (Baade et al. 1991) and ζ Oph (Kambe et al. 1997). In this context, the high Galactic latitude O-star HD 93521 (l II = 183.14 ◦ , b II = 62.15 ◦ ) is an extremely interesting target.
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