79 research outputs found
Theoretical model of infrared spectra of hydrogen bonds in molecular crystals of 2-thiopheneacetic acid: Fermi resonance and Davdov coupling effects.
A general quantum theoretical approach of the Ï…X-H IR lineshape of cyclic dimers of moderately H-bonded species in the crystalline phase is proposed. In this model, the adiabatic approximation is performed for each separate H-bond bridge species of the dimer, a strong non-adiabatic correction is introduced into the model via the resonant exchange between the fast mode excited states of the two moieties, the intrinsic anharmonicity of the low-frequency mode through a Morse potential, direct and indirect damping, and a selection rule breaking mechanism for forbidden transitions in IR. The present model reduces satisfactorily to many models in the literature dealing with more special situation. It has been applied to the cyclic dimers of 2-thiopheneacetic acid (2-TAA) and his deuterated derivative in the crystalline phase. It correctly fit the experimental line shape of the hydrogenated compound and predicts satisfactorily the evolution in the line shapes with isotopic substitution. Numerical calculations show that mixing of all these effects allows one to reproduce satisfactorily the main features of the experimental IR line shapes of hydrogenated and deuterated 2-TAA crystals and is expected to confirm the importance of the Fermi resonances and Davydov coupling in reproducing the experimental spectr
Theoretical modeling of hydrogen bond infrared spectra in molecular crystals of 2-thiopheneacetic acid : Fermi resonance and Davydov coupling effects
A quantum theoretical approach, within the adiabatic approximation and taking into account a strong non-adiabatic correction via the resonant exchange between the fast mode excited states of the two moieties of the dimer. The intrinsic anharmonicity of the low-frequency mode through a Morse potential, direct and indirect damping, and a selection rule breaking mechanism for forbidden transitions, is applied to reproduce the Ï…X-H IR line shape of cyclic dimers of moderately H-bonded species in the crystalline phase. The results are used to gain an insight into the experimental spectral line shapes obtained by the transmission method. This approach fits satisfactorily the experimental line shape of 2-thiopheneacetic acid and predicts their evolution with isotopic substitution. Numerical calculations show that mixing of all these effects allows one to reproduce the main features of the experimental IR line shapes
Investigating the structural, morphological, dielectric and electric properties of the multiferroic (La0.8Ca0.2)0.9Bi0.1FeO3 material
The (La0.8Ca0.2)0.9Bi0.1FeO3 (LCBFO) compound has been synthesized by the sol-gel method and characterized
by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Raman spectroscopy and electrical impedance
spectrometry. XRD results revealed that (La0.8Ca0.2)0.9Bi0.1FeO3 crystals are orthorhombic, belonging to the
Pnma space group. The SEM measurements showed that the sample presents a large distribution of nano-grains
connected to each other. The relaxation process and the electrical conductivity are awarded to the same type of
charge carriers characterized by similar values of the activation energy determined from loss factor tangent
tg δ( ), the imaginary part of the permittivity and from the Modulus spectrum. The ac-conductivity was analysed
to examine the conduction mechanism, using the Jonscher’s universal power-law given by: = +σ ω σ Aω( )ac dc s.
Based on the parameter s behavior, the conductivity was studied according to the NSPT model (non-overlapping
small polaron tunneling).publishe
Oil quality and aroma composition of 'Chemlali' olive trees (Olea europaea L.) under three irrigation regimes
The present work focused on the chemical composition of monovarietal virgin olive oil from the cultivar Chemlali cultivated in the South of Tunisia: sub-arid zone under three different irrigation regimes: stressed, moderate and well irrigation treatment with the restitution of 50, 75 and 100% of crop evapotranspiration (ETc), respectively. Quality characteristics (acidity and peroxide value) and chemical data (antioxidant compound, fatty acids volatile compounds and oxidative stability) were studied in addition to the pomological characteristic of olive fruit. Results show that there were significant differences observed in oil composition according to the irrigation regime applied. Total phenols, bitterness intensity and LOX products content showed the highest values for low irrigation regime, whereas polyunsaturated fatty acid and oxidative susceptibility values had highest values for olive oil from well irrigated trees. Analytic characteristic of fruits showed the highest values of pulp/stone ratios from olive trees irrigated by the highest amount of wate
Computer-Assisted Classification Patterns in Autoimmune Diagnostics: The AIDA Project
Antinuclear antibodies (ANAs) are significant biomarkers in the diagnosis of autoimmune diseases in humans, done by mean of
Indirect ImmunoFluorescence (IIF)method, and performed by analyzing patterns and fluorescence intensity. This paper introduces
the AIDA Project (autoimmunity: diagnosis assisted by computer) developed in the framework of an Italy-Tunisia cross-border
cooperation and its preliminary results. A database of interpreted IIF images is being collected through the exchange of images
and double reporting and a Gold Standard database, containing around 1000 double reported images, has been settled. The Gold
Standard database is used for optimization of aCAD(Computer AidedDetection) solution and for the assessment of its added value,
in order to be applied along with an Immunologist as a second Reader in detection of autoantibodies. This CAD system is able to
identify on IIF images the fluorescence intensity and the fluorescence pattern. Preliminary results show that CAD, used as second
Reader, appeared to perform better than Junior Immunologists and hence may significantly improve their efficacy; compared with
two Junior Immunologists, the CAD system showed higher Intensity Accuracy (85,5% versus 66,0% and 66,0%), higher Patterns
Accuracy (79,3% versus 48,0% and 66,2%), and higher Mean Class Accuracy (79,4% versus 56,7% and 64.2%)
Preliminary results of the project A.I.D.A. (Auto Immunity: Diagnosis Assisted by computer)
In this paper, are presented the preliminary results of the A.I.D.A. (Auto Immunity: Diagnosis
Assisted by computer) project which is developed in the frame of the cross-border cooperation Italy-Tunisia.
According to the main objectives of this project, a database of interpreted Indirect ImmunoFluorescence (IIF)
images on HEp 2 cells is being collected thanks to the contribution of Italian and Tunisian experts involved in
routine diagnosis of autoimmune diseases. Through exchanging images and double reporting; a Gold Standard
database, containing around 1000 double reported IIF images with different patterns including negative tests,
has been settled. This Gold Standard database has been used for optimization of a computing solution (CADComputer
Aided Detection) and for assessment of its added value in order to be used along with an
immunologist as a second reader in detection of auto antibodies for autoimmune disease diagnosis. From the
preliminary results obtained, the CAD appeared more powerful than junior immunologists used as second
readers and may significantly improve their efficacy
Structural and Magnetic Characterizations of Ruddlesden–Popper Family (Ca2-xNdxMnO4) Compound Synthesized by Ceramic Route
International audienc
Specific features of structural, magnetic, Raman and Mössbauer: Properties of La 0.57 Nd 0.10 Sr 0.18 Ag 0.15 FeO 3 ferrite nanoparticules
This article reports on a detailed study of the structural, spectroscopic and magnetic properties of La 0.57 Nd 0.10 Sr 0.18 Ag 0.15 FeO 3 (LNSAFO) ferrite nanoparticles, which were prepared using the solid state tech- nique. The Rietveld analysis of the powder X-ray diffractograms indicated that the material crystalizes in an orthorhombic structure, Pnma space group. Scanning electron microscopy (SEM) measurements showed that all particles have almost spherical shapes, and are characterized by a distribution of rela- tively narrow particle sizes. The average diameter of the particles was estimated within the 25–45 nm range by three different methods (SEM, and from the XRD data using the Debye-Scherer and Williamson–Hall models).The elemental composition of the synthesized material has been investigated by energy dis- persive spectroscopy (EDS), which confirmed the presence of all expected elements in stoichiometries matching those of the precursor oxides of the synthesized perovskite. Raman spectroscopy measure- ments revealed that the studied sample had a considerable degree of crystallinity, in agreement with the X-ray diffraction data. Finally, the magnetic properties of the studied compound have been investi- gated by studying the variation of the magnetization as a function of temperature in both the ZFC (zero field cooled) and FC (field cooled) modes. A blocking temperature ( T B ) of around 100 K was observed
Uracil-DNA glycosylase is not implicated in the choice of the DNA repair pathway during B-cell class switch recombination
International audienc
- …