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M Vasilescu

Publications and source records attributed to M Vasilescu.

At least 19 recordsLinked to original sources
PubMed2001

Aggregation numbers and microstructure characterization of self-assembled aggregates of poly(ethylene oxide) surfactants and related block-copolymers, studied by spectroscopic methods.

This review presents typical examples of micellar size measurements and structural characterization of self-assembled systems as determined with spectroscopic methods, selected from our representative results accumulated in recent years of systematic studies. The choice of examples has aimed at emphasizing the potentiality of the methods used in the study of poly(ethylene oxide) (PEO) surfactants. By using the time-resolved fluorescence quenching method aggregation numbers have been determined for direct and reverse micelles as well as for micelle-like clusters formed in (bio)polymer-surfactant solutions. By using specific spectral parameters of a variety of properly chosen molecular probes [fluorescence, UV-VIS and electron spin resonance (ESR) spin probes], problems such as hydration degree and profile of the PEO chains, local viscosity, ordering and packing of surfactant chains have been addressed. The intention was to correlate results obtained from different spectroscopic methods and to refer all polarity data to a common scale, such as Kosower's polarity factor.

Journal Article↗
PubMed1997

A Comparison between Hydrophobically End-Capped Poly(ethylene oxide) with Ether and Urethane Bonds

Two models of HEUR (hydrophobically modified ethylene oxide urethane) associative polymers (AP) are compared. The two polymers are polyethyleneoxides simply end-capped with dodecyl groups, one through an ether bond H25C12-O-(CH2CH2O)304-C12H25 (AP14, Mw = 13,700) and the other through an urethane bond H25C12-NHCOO-(CH2CH2O)304-CONH-C12H25 (AP14NCO, Mw is about the same as for AP14). The results indicate that this subtle difference in polymer architecture dramatically influences the initial association and the clouding of the polymer in water, so that AP14NCO starts to aggregate earlier but has a higher clouding temperature. However, at more elevated polymer contents (above 2-3 wt%) the differences in solution behavior and transport dynamics between the two polymers seems less significant. These conclusions are drawn through fluorescence, dynamic light scattering, NMR self-diffusion, turbidimetry, and viscosity measurements. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1996

Modification of molecular properties of some dyes in sodium dodecyl sulphate (SDS) micellar aqueous solution.

The influence of SDS upon the molecular properties of proflavine (3,6-diaminoacridine), acridine yellow (2,7-dimethyl-3,6-diaminoacridine) and methylene blue (3,7-bis-dimethylamino-phenothiazine) was studied comparatively to their properties in that of aqueous media. The absorption and emission spectra of the three dyes in SDS aqueous solution (1-100 mmol/l) were recorded. The spectroscopic data also allowed the evaluation of the critical micellization concentration (CMC), acidity constants in fundamental (pk(a)) and excited (pK(*)(a)) states, and lifetimes of excited singlet states.

Journal Article↗
PubMed1993

Trophic and enzymatic adaptation of the intestine to biliopancreatic bypass in the rat.

Biliopancreatic bypass (BPB), the exclusion of a duodenojejunal loop from the digestive continuity, has been proposed as a bariatric procedure for treatment of morbid obesity. The present study in rats investigated the effect of this surgical procedure on the mucosae of the ileum directly anastomosed to the stomach, and of the jejunum irrigated only by biliopancreatic secretions. The proximal part of the ileum adapted by two-fold increases in its mucosal mass, total protein and RNA content; DNA content was four-fold higher than in sham-operated animals. There was a correlated increase of mucosal enzyme content, except for lactase. In the distal ileal mucosae, a slight, transient augmentation of mucosal mass, protein, DNA and RNA content was observed which tended to compensate for the shortening of the functional gut. No morphological changes were found in the excluded loop, probably because of an endoluminal stimulation by biliopancreatic secretions. Thus, in BPB, biliopancreatic secretions seem to exert trophic effects on the intestinal mucosa, but they are less potent than the endoluminal nutrition that restores the oral-aboral mucosal gradient.

Adaptation, Physiological↗
PubMedDate not supplied

[Pleuropulmonary diffusion in some subdiaphragmatic suppurations].

Two cases are presented of subphrenic suppurations (right perinephretic phlegmon and suppurated hepatic hydatic cyst), that developed fistulae in the lung and the pleura. The evolutive modalities are discussed the diagnostic difficulties and the corresponding therapeutic attitudes.

Adult↗
PubMedDate not supplied

[The physicochemical characterization and therapeutic evaluation of Cicatrol].

Cicatrol ointment with the formula: argentic sulphamethoxydiasine 1 g, bentonite hydrogel 12.5% for 100 g is manufactured at the Microproduction Laboratory of the Faculty of Pharmacy of Iaşi. The one-year physicochemical determinations of the aspect, colour, homogeneity, pH, rheological behaviour and relative viscosity, content in argentic sulphamethoxydiasine as well as "in vitro" antimicrobial activity of Cicatrol showed a good stability and gel properties enabling an uniform and long-term contact with the wound. The clinical investigations carried out until now in patients with burns, varicose ulcers, trophic shank ulcers, superficial phlebitis with atonic ulcerations or wounds with multiple sites revealed its remarkable therapeutic value. As compared to other similar products, Cicatrol by its aseptic properties favours the scarring of any type of wound, a normal skin, without keloid scars being obtained, it also being well tolerated.

Burns↗