Search results for "Dynamic properties"
showing 10 items of 11 documents
Irradiation effects on the OH-related infrared absorption band in synthetic wet silica.
2007
The effects of b-irradiation on the OH-related infrared (IR) absorption band in synthetic wet silica samples have been investigated by Fourier transform infrared spectroscopy. Depending on the accumulated doses, b-irradiation affects different zones of the IR composite band at about 3670 cm 1 , assigned to the OH stretching modes of silanol groups. These modifications are independent of the original OH content. The results are discussed considering possible radiation-induced changes of the silanol bonding configuration and of the glass network. These are monitored by revealing the IR band a 2260 cm 1 , which is related to the distribution of Si–O–Si bond angle. We have identified the existence of…
Roton-roton crossover in strongly correlated dipolar Bose-nonstnon condensates
2011
We study the pair correlations and excitations of a dipolar Bose gas layer. The anisotropy of the dipole-dipole interaction allows us to tune the strength of pair correlations from strong to weak perpendicular and weak to strong parallel to the layer by increasing the perpendicular trap frequency. This change is accompanied by a roton-roton crossover in the spectrum of collective excitations, from a roton caused by the head-to-tail attraction of dipoles to a roton caused by the side-by-side repulsion, while there is no roton excitation for intermediate trap frequencies. We discuss the nature of these two kinds of rotons and the relation to instabilities of dipolar Bose gases. In both regime…
EPR on Radiation-Induced Defects in SiO2
2014
Continuous-wave electron paramagnetic resonance (EPR) spectroscopy has been the technique of choice for the studies of radiation-induced defects in silica (SiO2) for 60 years, and has recently been expanded to include more sophisticated techniques such as high-frequency EPR, pulse electron nuclear double resonance (ENDOR), and pulse electron spin echo envelope modulation (ESEEM) spectroscopy. Structural models of radiation-induced defects obtained from single-crystal EPR analyses of crystalline SiO2 (alfa-quartz) are often applicable to their respective analogues in amorphous silica (a-SiO2), although significant differences are common.
Polystyrene nanoparticles in the presence of (ethylene oxide)13(propylene oxide)30(ethylene oxide)13, N,N-dimethyloctylamine-N-oxide and their mixtur…
2008
Polystyrene nanoparticles were synthesized by emulsion polymerization of styrene. They were functionalized using the conventional surfactant N,N-dimethyloctylamine-N-oxide (ODAO), the tri-block copolymer (ethylene oxide)13(propylene oxide)30(ethylene oxide)13 (L64) and their mixtures. To this purpose, dynamic light scattering and calorimetric experiments were carried out and provided information consistent to each other. The L64 adsorption is Langmuir-type in the copolymer dilute regime and generates complex structures at larger concentrations. In the region where ODAO is in the unimeric state, the adsorption process is cooperative leading to hemi-micelle formation at the polystyrene nanopa…
The solubilisation behaviour of some dichloroalkanes in aqueous solutions of PEO-PPO-PEO triblock copolymers: a dynamic light scattering, fluorescenc…
2006
The aggregation behaviour of PEO-PPO-PEO triblock copolymers in water and in water + chlorinated additive mixtures was studied by means of fluorescence spectroscopy, dynamic light scattering (DLS), and small-angle neutron scattering (SANS). The copolymers were chosen such as to investigate the effects of molecular architecture (L35 and 10R5) and molecular weight by keeping constant the hydrophilic/hydrophobic balance (F88 and F108). 1,2-Dichloroethane was used as a prototype of water basins contaminants. The hydrodynamic radius of the block copolymer aggregates (R(h,M)) and the intensity ratio of pyrene of the first and the third vibrational band (I(1)/I(3)) were determined as a function of…
Liquid structure and dynamics in the choline acetate:urea 1:2 deep eutectic solvent
2021
We report on the thermodynamic, structural, and dynamic properties of a recently proposed deep eutectic solvent, formed by choline acetate (ChAc) and urea (U) at the stoichiometric ratio 1:2, hereinafter indicated as ChAc:U. Although the crystalline phase melts at 36-38 degrees C depending on the heating rate, ChAc:U can be easily supercooled at sub-ambient conditions, thus maintaining at the liquid state, with a glass-liquid transition at about -50 degrees C. Synchrotron high energy x-ray scattering experiments provide the experimental data for supporting a reverse Monte Carlo analysis to extract structural information at the atomistic level. This exploration of the liquid structure of ChA…
Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechani…
2012
[EN] This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PLA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PLA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystalli…
Calorimetric and Volumetric Investigations of the Effect of the Hydrophobicity of the Surfactant on the Binding between (Ethylene oxide)13-(propylene…
2004
The enthalpy and the volume of transfer (DeltaY(t)) of the unassociated (ethylene oxide)(13)-(propylene oxide)(30)-(ethylene oxide)(13) (L64) from water to the aqueous sodium alkanoate solutions as functions of the surfactant concentrations (m(S)) were determined at 298 K. The surfactants studied are sodium hexanoate, sodium heptanoate, sodium octanoate, sodium undecanoate, and sodium dodecanoate. As a general feature, for the short alkyl chain surfactants, DeltaY(t) describes an S-shaped curve in the range of m(S) analyzed whereas for the more hydrophobic surfactants the DeltaY(t) vs m(S) trends exhibit maxima which appear at ms values very close to the critical micellar concentration in w…
Development of a High Irradiance LED Configuration for Small Field of View Motion Estimation of Fertilizer Particles
2015
International audience; Better characterization of the fertilizer spreading process, especially the fertilizer pattern distribution on the ground, requires an accurate measurement of individual particle properties and dynamics. Both 2D and 3D high speed imaging techniques have been developed for this purpose. To maximize the accuracy of the predictions, a specific illumination level is required. This paper describes the development of a high irradiance LED system for high speed motion estimation of fertilizer particles. A spectral sensitivity factor was used to select the optimal LED in relation to the used camera from a range of commercially available high power LEDs. A multiple objective …
Protein dynamics: conformational disorder, vibrational coupling and anharmonicity in deoxy-hemoglobin and myoglobin.
1993
In this work we study the temperature dependence of the Soret band lineshape of deoxymyoglobin and deoxyhemoglobin, in the range 300-20 K. To fit the measured spectra we use an approach originally proposed by Champion and coworkers (Srajer et al. 1986; Srajer and Champion 1991). The band profile is modelled as a Voigt function that accounts for the coupling with low frequency vibrational modes, whereas the coupling with high frequency modes is responsible for the vibronic structure of the spectra. Moreover, owing to the position of the iron atom out of the mean heme plane, inhomogeneous broadening brings about a non-Gaussian distribution of 0-0 electronic transition frequencies. The reporte…