Search results for "Instrument"
showing 10 items of 5652 documents
Molecular structures and vibrations of m-methylaniline in the S0 and S1 states studied by laser induced fluorescence spectroscopy and ab initio calcu…
2000
Abstract The UV fluorescence excitation and dispersed fluorescence spectra of a jet-cooled m-methylaniline have been obtained for the S1←S0 transition, in which some of the bands have been observed for the first time. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes. It was found that the spectra exhibit an important feature which is the internal rotation of the methyl group in the electronic ground and excited states. Ab initio calculations at MP2/6-31G* and CIS/6-31G* show that the optimized structure of m-methylaniline in the ground state is not planar with the amino group having sp3 hybridation-like character due to the existence…
Micro-Raman spectroscopic characterization of a CR-39 detector.
2013
Characterization by micro-Raman spectroscopy of polymeric materials used as nuclear track detectors reveals physico-chemical and morphological information on the material's molecular structure. In this work, the nuclear track detector poly(allyl diglycol carbonate), or Columbia Resin .39 (CR-39), was characterized according to the fluence of alpha particles produced by a 226Ra source and chemical etching time. Therefore, damage of the CR-39 chemical structure due to the alpha-particle interaction with the detector was analyzed at the molecular level. It was observed that the ionization and molecular excitation of the CR-39 after the irradiation process entail cleavage of chemical bonds and…
Influence of functionalization on interaction and drug release from α,β-polyaspartylhydrazide derivatives to a biomembrane model: evaluation by diffe…
2004
Abstract A comparative study on the ability of various polymers to interact with a biomembrane model was carried out by differential scanning calorimetry (DSC). The investigated samples were a water soluble polymer, the α,β-polyaspartylhydrazide (PAHy) and its derivatives containing polyethylene glycol (PEG2000) (sample PAHy–PEG2000), or hexadecylamine (C16) (sample PAHy–C16) or both compounds (sample PAHy–PEG2000–C16). Some samples are able to arrange themselves as micellar structures and to interact potentially with the membrane surface so as to favor the release of the drug near the target membrane and consequently to improve drug adsorption processes. First, the interaction of all polym…
Ejection of molecules from WO3 under ion bombardment: the role of the crystal structure
1992
Abstract Emission of molecular ions from WO 3 and Na x WO 3 was studied by SIMS. It was found that the phenomenon of ejection of molecules had not arisen from specific WO bond lengths and strengths in tungsten trioxide.
Measurement of cloud point temperature in polymer solutions.
2013
A temperature-controlled turbidity measurement apparatus for the characterization of polymer solutions has been instrumented and set up. The main features are the coupled temperature-light transmittance measurement and the accurate temperature control, achieved by means of peltier cells. The apparatus allows to measure cloud point temperatures by adopting different cooling protocols: low rate for quasi-equilibrium measurements and high rate for detect kinetic effects. A ternary polymeric solution was adopted as case study system showing that cooling rate affects the measured cloud point temperature.
Optical planar Bragg grating sensor for real-time detection of benzene, toluene and xylene in solvent vapour
2012
Abstract We report on an optical planar Bragg grating sensor functionalized by a comparatively simple method to detect substances such as benzene, toluene and xylene (BTX). The functionalization is performed by allyl substituted γ -cyclodextrin derivatives which are immobilized on the sensor surface by dip coating. Our results prove the capability of this functionalized sensor system to detect lowest concentrations of BTX in solvent vapour in real-time with a sensitivity of 3±0.4 pm/100 ppm for benzene, 8±1 pm/100 ppm for toluene and 32±1 pm/100 ppm for m-xylene. Taking into account the spectral resolution and repeatability of the interrogation system this corresponds to a minimum concentra…
Calorimetric investigation of the complex formation between surfactants and α-, β- and γ-cyclodextrins
1992
Abstract A calorimetric technique has been used to study complex formation between α-, β- and γ-cyclodextrins (αCD, βCD and γCD) and some surfactants (sodium dodecylsulphate (SDS), hexadecyl trimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl) phenoxypoly(oxyethyleneglycol) (Triton X-100)). The experimental data indicate that some complexes (SDS-αCD, SDS-βCD and CTAB-αCD) are very stable and allow direct determination of their stoichiometry and molar enthalpy of complex formation. Those for other complexes closely fit a model based on an equilibrium reaction between surfactant, cyclodextrin and a single complex. According to the model, data analysis allows determination of the …
The catalytic-thermometric determination of molybdenum in steels based on the hydrogen peroxide-iodide indicator reaction
1990
Abstract The Mo VI -catalysed hydrogen peroxide-iodide reaction has been optimised for thermometry in an HCl medium using the initial slope method. The substitution of sodium perborate by H 2 O 2 and the conversion of the reaction to a process showing a Landolt effect are considered and discussed. The linear range extended from 0.2 μg Mo VI ml −1 to 1.2 μg Mo VI ml −1 with a detection limit of 0.06 μg Mo VI ml −1 . Interferences were also studied. The optimised procedure was applied to the evaluation of molybdenum in steels after extraction with α-benzoinoxime in chloroform.
A new method for the study of antiparallel ferroelectric domains
1992
Abstract Beam-coupling topography is a non-destructive holographic technique for spatially resolved recording of hysteresis loops and for imaging of domains. Its basic principle is interference of rays diffracted from a holographic grating with collinear, transmitted ones. Full domain contrast and noise suppression is achieved by appropriate control of intensity and phase of the interfering beams. The method is applied to antiparallel a-domains in (Sr0.61Ba0.39)Nb2O6:Ce.
Biochemistry and cell biology of silica formation in sponges
2003
The main inorganic material forming the skeletal elements in Demospongiae as well as in Hexactinellida, the spicules, is amorphous silica. The spicules occur in the cytoplasm and the extracellular space and also in the nucleus (as silicate crystals) of some sponge cells; the function in the latter compartment is unknown. Recent evidence shows that the formation of spicules is mediated by the enzyme silicatein. The cDNA as well as the gene encoding this enzyme was cloned from Suberites domuncula. The recombinant silicatein catalyzes the syn- thesis of amorphous silicate using tetraethoxysilane as substrate. The enzyme is dependent on ferric iron. Silicatein also has proteolytic (cathepsin-li…