Algorithm for preliminary evaluation of the correlation time of local dynamics in some polymeric materials

A method for preliminary evaluation of the correlation time of local dynamics of the polymeric chains, using the experimental nuclear magnetic resonance spin-lattice relaxation data, is proposed. The algorithm is based on the model of the passage of a particle over a potential energy barrier. This method was utilized for some molten polymers and concentrated polymeric solutions.     

Rheological Behavior of Some Aqueous Gels of Carbopol with Pharmaceutical Applications

The concentration and temperature dependence of the viscosity is observed for some aqueous dispersions of Carbopol. The experimental data are analyzed with the power model, and reveal non-Newtonian behavior （shear thinning） of the samples.     

ESR and XRD investigation of effects induced by gamma radiation on PVA-TiO2 membranes

The effects of gamma radiation on the local structure of PVA membranes containing TiO₂ were investigated by ESR and XRD methods. An intense ESR signal is observed after irradiation at 16 KGy dose. This signal appears only for irradiated samples and it is associated with the breaking of the polymeric chain, followed by local reorganization of the polymeric segments and the apparition of the unpaired electrons and free radicals. The intensity of the signal decreases with the concentration of TiO₂, indicating a shielding effect of the dopand. That the modification of local order of the polymeric chains has been modified after irradiation is confirmed by XRD method.     

Observation of Hydration--Drying Effect on Clotrimazole--Carbopol System

The possibility to use the polyacrylic acid （carbopol） as polymeric matrix for the clotrimazole is analysed. The hydration-drying effect on the polymeric matrix is observed by Raman spectroscopy. Similar observations are obtained on the clotrimazole included in the polymeric matrix. No modifications of the properties of the clotrimazole and of the polymeric matrix are observed under the repeated action of water.     

Preliminary spectroscopic investigation of some PVA membranes gamma irradiated

The UV-VIS absorption property and the structural modification of PVA membranes gamma irradiated were investigated by XRD, UV-VIS and Raman spectroscopies. The increase of UV absorbance is observed after irradiation. This behavior is correlated with the scission effect and local ordering of the polymeric chain induced by irradiation. These effects were probed by XRD and Raman spectroscopy.     

ESR study of some Cu(II)-oxazepam complexes

The CuL₂X₂ (L = 7-chlor-l,3-dihydro-3-hydroxi-5-phenyl-2H-l,4-benzodiazepin-2-one, also known as oxazepam, X = Cl, Br) complexes were prepared and investigated by ESR (electron spin resonance) method. Powder ESR spectra of CuL₂X₂ compounds at room temperature show the presence of monomeric species having an axial symmetry with a small rhombic distortion. In case of compounds with Cl there is a superposition of two nonequivalent mononuclear species, one with ad_{x² - y²} d_{x^2 - y^2 } ground state and another with ad_z² d_{z^2 } ground state. In pyridine (Py) and dimethylformamide (DMF) solutions the monomeric species prevail. Two different monomeric species, one with pseudotetrahedral (T_d) and the other with elongated tetrahedral-octahedral symmetry, were evidenced in DMF solutions adsorbed on NaY zeolite. In Py-DMF solutions two monomeric species were also identified. Dimeric species appear in DMF and Py solutions adsorbed on NaY zeolite through the coordination of two Cu(II) ions at the same keto-oxygen from one oxazepam molecule.     

NMR Study of the Phase Transitions in Some Derivatives of Cholesterol and B-Nor Cholesterol

In this paper we analyze by broad line NMR spectroscopy method, the influence of modifying the cholesterol skeleton upon mesomorphic properties and characteristics (phase transition points, mesomorphic ranges, etc.) in some derivatives of cholesterol. From our studies regarding the phase transition points by NMR spectroscopy method, we can assert that derivatives of the B-nor cholesterol have the same behavior as derivatives of the cholesterol.     

Calibration of NaI(TI) spectrometer for radiocesium volume-samples. Some results from Transylvania region

A four-channel NP-424 type gamma analyzer coupled with a large NaI(Tl) scintillator was calibrated using a¹³⁷Cs point source. The volume-samples were plexiglas cylindrical boxes (D=76mm, H=40mm) directly placed on the NaI(Tl) detector. Measurements for 64 indoor positions at full-662 keV-peak were made. Sample selfabsorbtion was determined considering a linear attenuation for gamma rays and measuring the absorption factor for maximum thickness of the volume sample (h0=40mm). The obtained results for two types of environmental samples (soil and milk-powder) are compared with the data acquired from other Romanian laboratories, in the frame of the Environmental Radioactivity Action (ERA) which standardized such types of measurements. The same samples were measured with a calibrated GeLi detector (INAN-Louvain la Neuve) and the results were in good agreement with our measurements. Using this NaI(Tl) calibrated spectrometer some radiocesium deposits (56 localities) from Transylvanian region were measured. The results show that a large deposit exists in the direction NE-SW in connection with the radioactive cloud passing. For Alba region were measured more than 40 kBq/m² of cesium deposit.     

Preliminary spectroscopic investigation of tacrolimus TiO2 system

The effect of air and UV exposure on the tacrolimus was observed by Raman and UV VIS spectroscopy. For moderate time exposure the chemical structure of tacrolimus is not affected. The absorption property of tacrolimus was enhanced by addition of TiO₂.