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Biomedical subjects

I Pavel

Publications and source records attributed to I Pavel.

At least 19 recordsLinked to original sources
PubMed2004

Raman, SERS and theoretical studies of papaverine hydrochloride and its neutral species.

Density functional theory (DFT) calculations and an experimental vibrational characterization of papaverine hydrochloride were performed. The computed structural parameters agree very well with the experimental values of the related crystal structure. The pH dependent Raman and SERS spectra of papaverine hydrochloride were recorded and discussed with the assistance of our theoretical results (harmonical vibrational wavenumbers, Raman scattering activities, total electron density and Natural Population Analysis of the molecule) and the SERS surface selection rules. Two different adsorption geometries were found for the corresponding evidenced species of papaverine, protonated and neutral, respectively.

Electrochemistry↗
PubMed2003

Theoretical and pH dependent surface enhanced Raman spectroscopy study on caffeine.

The surface enhanced Raman spectroscopy (SERS) spectrum of caffeine is recorded on a silver colloid at different pH values. It is discussed on the basis of the SERS "surface selection rules" in order to characterize its vibrational behavior on such a biological artificial model. To improve the previous assignments in the Raman spectrum and for a reliable, detailed analysis of SERS spectra, density functional theory calculations (structural parameters, harmonic vibrational wavenumbers, total electron density, and natural population analysis of the molecule) are performed for the anhydrous form of caffeine and the results are discussed. The predicted geometry and vibrational Raman spectra are in good agreement with the experimental data. The flat orientation of the mainly chemisorbed caffeine attached through the pi electrons and the lone pair of nonmethylated N atoms of the imidazole ring are proposed to occur at neutral and basic pH values. At acid pH values caffeine is probably adsorbed on the Ag surface through one or both oxygen atoms, more probably through the O atom of the conjugated carbonyl group with an end-on orientation. However, the changes in the overall SERS spectral pattern seem to indicate the electromagnetic mechanism as being the dominant one.

Caffeine↗
PubMed2003

Fourier-transform Raman and infrared spectroscopic analysis of 2-nitro-tetraphenylporphyrin and metallo-2-nitro-tetraphenylporphyrins.

The Fourier-transform Raman (FT-Raman) and infrared (FT-IR) spectra of 2-nitro-tetraphenylporphyrin (2-NO(2)-TPP), nickel-2-nitro-tetraphenylporphyrin (Ni-2-NO(2)-TPP), zinc-2-nitro-tetraphenylporphyrin (Zn-2-NO(2)-TPP) and copper-2-nitro-tetraphenylporphyrin (Cu-2-NO(2)-TPP) were acquired for the first time and carefully assigned and discussed. The effects of a beta-NO(2) group and the influence of the central metal on the molecular symmetry and vibrational spectra of the porphyrin macrocycle were also examined. The bands at 1323-1339, 1516-1526 and 961-971 cm(-1) were attributed to the symmetric and asymmetric stretching vibration of the NO(2) group and to the stretching vibration of the C(beta)-N bond, respectively, which connects the NO(2) group with the beta-carbon of the porphyrin macrocycle. These bands can act as a marker to distinguish beta-NO(2) TPPs from other beta-substituent TPPs. Cu-2-NO(2)-TPP has a C(4nu) molecular symmetry, which is different from those of Ni-2-NO(2)-TPP and Zn-2-NO(2)-TPP, i.e. D(4h).

Organometallic Compounds↗
PubMed1977

[Shunt between Disse spaces and biliary canaliculi and its pathology].

The existence and permeability of communications between Disse spaces and biliary canaliculi has been finally accepted, in spite of the socalled obstacle of the water-tight junctions. The explanation of pigmented bile secretion by filtration and reabsorption has become plausible. Whilst other subtances excreted by the bile after having been filtered at the level of the sinusoidal wall need to enter the hepatic cell to be synthesised, stocked or to take up their final shape, the bile pigments, cell debris, cross the hepatic lobule through the shunt between the Disse space and the bile canaliculi, without passing through the liver cell. These facts require us today to reconsider the physiopathology of some liver disorders, especially those accompanied by jaundice.

Bile↗
PubMed1976

[Dynamic epidemiology of diabetes mellitus (author's transl)].

Epidemiology as practiced to day has become outmoded. The authors propose a dynamic epidemiology, that is one applied throughout the country and which is in a stak of continuous development. This implies ascertainment of the major causes of diabetes : heredity and environment. Thus conceived, dynamic epidemiology can hope to tackle prevention in the prediabetic stage of a widespread chronic disease. A description is given of the method of application and a test of effectiveness.

Diabetes Mellitus↗
PubMed1975

[Intrahepatic cholestasis].

Intrahepatic cholestasis has become a very important aspect of liver disease. The author, in the light of electron microscopy and the theory of filtration-reabsorption of bile secretion proposes that the disease may be explained by obstructions situated at various levels of the inter-cellular spaces of the liver. This obstruction is functional at first, but is maintained by a duodeno-hepatic inhibitory reflex, the existence of which has been demonstrated by the author. In the light of facts and documents presented here, one may see that from Monneret until now, various authors have come very close to the true mechanism of this type of jaundice, each discovering some aspect of the truth.

Cholestasis↗