1,720,974 research outputs found
Contributo alla conoscenza della flora briologica del Trentino: il Bosco Welsperg (Parco Naturale Paneveggio-Pale di S. Martino), con una nota sulla Radula visianica C. Massal.
No full text
Sucrose intake: Increase in non-stressed rats and reduction in chronically stressed rats are both prevented by the gamma-hydroxybutyrate (GHB) analogue, GET73
No full textIt has been previously shown that the gamma-hydroxybutyrate analogue N-(4-trifluoromethylbenzyl)-4-methoxybutanamide (GET73) inhibits consumption and reinforcing effect of palatable food, in rats, at doses that have no detrimental effect on open-field behaviour. Here we show that GET73 is also able to prevent both the development of preference for a sucrose solution in non-stressed rats, and the reduction of preference for a sucrose solution induced by the daily exposure to continuously varied mildly stressful situations.Adult male Wistar Kyoto rats (180-190g) were subjected to chronic unpredictable mild stress. Other rats of the same sex and strain were used to study the development of preference for a sucrose solution.Daily exposure to continuously varied mildly stressful situations produced a reduction of sucrose solution intake that started the 3rd week, and such reduction became highly significant during the 5th week. Treatment with GET73 (10 mg kg(-1), 50 mg kg(-1) or 100 mg kg(-1) once daily per os) produced a more evident reduction of sucrose solution intake during the 2nd and 3rd week, but during the 4th and 5th weeks the intake dose-dependently increased to values that, for the dose of 100 mg kg(-1), were not significantly different from those of non-stressed, vehicle-treated rats. In the same range of doses GET73 dose-dependently prevented the development of preference for a sucrose solution in non-stressed rats.The present data indicate that rats treated with GET73 do not develop the "depression-like" condition produced by the daily exposure, for several weeks, to continuously and unpredictably varied stressful situations in a valid (face, predictive, and construct validity) "depression" model. Moreover, GET73 prevents the development of preference for a sucrose solution in non-stressed rats. Concurrently, present and previous data suggest that GET73 "stabilize" the behaviour of rats, either preventing the development of a "depression-like" condition in a continuously stressful environment, or the rewarding effect of alcohol, sucrose, and palatable food. (C) 2008 Elsevier Ltd. All rights reserved
Trasport of oxygen facilitated by peroxo[N, N'-ethylene bis-(salicylideneiminato)dimethylformamide-cobalt(III)] embedded in liquid membranes immobilized by photografting onto cellulose
No full textA novel method to prepare liquid membranes, suitable to obtain facilitated transport of oxygen, incorporating the title complex (I) or the same without dimethylformamide (II), is reported. These membranes were obtained by photochemical grafting an epoxy-diacrylate copolymer onto cellulose in the presence of (I) or (II) together with dimethylformamide. Sorption isotherms of oxygen into deoxygenated membranes were obtained by Langmuir plots at 343-373 K. By these isotherms the molar ratio (0.5) between sorbed oxygen and cobalt in the membrane corresponding to saturation was evaluated, and constants K (bar-1) of heterogeneous equilibrium involving (I) and (II) were obtained as a function of temperature. From K values, a mean enthalpy change of -84 kJ mol-1 and entropy change of -220 J mol-1 K-1 were calculated. This latter reflects the high order in binuclear dioxygen complex formation. Permeability coefficients of oxygen and nitrogen from air through the photosynthetic membranes at 343 K were measured. These values show an efficient O2/N2 separation, with a very advantageous ratio (50) between their fluxes
Transport of oxygen facilitated by peroxo-bis [N, N′-ethylene bis-(salicylideneiminato)-dimethylformamide-cobalt (III)] embedded in liquid membranes immobilized by photografting onto cellulose
No full textA novel method to prepare liquid membranes, suitable to obtain facilitated transport of oxygen, incorporating the title complex (I) or the same without dimethylformamide (II), is reported. These membranes were obtained by photochemically grafting an epoxy-diacrylate copolymer onto cellulose in the presence of (I) or (II) together with dimethylformamide. Sorption isotherms of oxygen into deoxygenated membranes were obtained by Langmuir plots at 343-373 K. By these isotherms the molar ratio (0.5) between sorbed oxygen and cobalt in the membrane corresponding to saturation was evaluated, and constants K (bar-1) of heterogeneous equilibrium (Equation (2) in the text) involving (I) and (II) were obtained as a function of temperature. From K values, a mean enthalpy change of - 84 ± 1 kJ mol-1 and entropy change of -220 ± 3 J mol-1 K-1 were calculated. This latter reflects the high order in binuclear dioxygen complex formation. Permeability coefficients of oxygen and nitrogen from air through the photosynthetic membranes at 343 K (4.60 × 10-5 and 9.23 × 10-7 cm2 s-1 bar-1, respectively) were measured: These values show, within a certain range of pressure drop of air, an efficient O2/N2 separation, with a very advantageous ratio (50) between their fluxes. © 1987
Immobilization of reagents and catalysts by photochemical grafting onto polymers
No full textThe possibility of immobilizing reagents and catalysts by photochemical grafting of their composites with an epoxy-diacrylate resin has been investigated. Two model systems have been examined: (i) the catalytic decomposition of aqueous sodium hypochlorite by cobalt peroxide, with oxygen production; (ii) the reaction of alkali metals with alcohols. For case (i) the catalyst was embedded, in the form of a mixture with 90% of zeolite 13X, into the photografted polymer matrix; while for case (ii) the alkali metal reagent, supported onto 90% of zeolite 13X, was incorporated into the microporous membrane. Kinetics of reaction (i) were studied in standard conditions (1.0 M NaOCl; 1.0 M NaCl; 0.25 M NaOH) between 288.2 to 318.2 K, and the relation between pseudp-first order kinetic constants and amount of catalyst incorporated into the membrane determined. Isotope effects for reaction (ii), relative to H2, D2, HD production, were measured with mixtures of deuterated and non-deuterated CH3OH(D), C2H5OH(D), n-C3H7OH(D), and i-C3H7OH(D) at 25 °C, as a function of volume percent of non-deuterated alkanols in the liquid phase. For reaction (i) reactivity was found to be substantially the same in the membrane reactor as in ordinary chemical conditions: loss of catalytic activity did not exceed 15%. For reaction (ii) isotope effects, the origin of which is discussed, fully coincided with those measured in the absence of the polymer matrix
A simple device for quality control of polymer films, using measurements of permeation and diffusion coefficients
No full textA simple device for the rapid determination of transport characteristics of vapors, gases or gaseous mixtures through polymer films has been constructed. This device may be useful either for routine quality control or for precise research work. It consists of two coupled permeation cells: the difference between the permeation rates of a tested specimen with respect to a standard film is measured and the resulting signal interpreted in terms of diffusion and permeation coefficients. The two coupled cells are of a differential type: the gas permeating through the film is collected by a flowing stream of an inert gas and carried to the analytical system (gas-chromatographic determinations have been used in this study). Such a system allows high pressure measurements without imposing mechanical stresses on the film and determination of transport coefficients of any gaseous mixture. A theoretical analysis of the transient signal in terms of transport parameters is reported together with some experimental results on commercial polycaprolactam films
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Paracetamol revisited
No full textParacetamol (recommended international nonproprietary name) (acetaminophen) was synthesized in 1878 by Morse (Morse HN: 1878.) and first used clinically by von Mering in 1887. But it was quickly discarded in favour of phenacetin. “Rediscovered” in 1948, following the studies of Brodie and Axelrod (Brodie BB 1948.) and marketed in the 1950s in the United States as an analgesic replacement for phenacetin, “condemned” for its nephrotoxicity. Unfounded concerns about paracetamol safety delayed its widespread acceptance until the 1970s. From then on, paracetamol is one of the most popular and widely used drugs in the world for the treatment of pain and fever; probably the most commonly prescribed medicine in children.
Paracetamol occupies a unique position among analgesic drugs, both for the type of pain relieved and for the side effects. So, for example, it is almost unanimously considered to be ineffective in inflammatory pain (unlike NSAIDs), as well as in intense pain or that arising from smooth muscle spasm in hollow viscera (unlike opiates); and it has no depressant effect on respiration (unlike opiates) and does not produce gastrointestinal damage or untoward cardiorenal effects (unlike NSAIDs).
The peculiarity of effects and side effects of paracetamol should have suggested a peculiar mechanism of action for this drug. On the contrary, and curiously, surprising efforts have repeatedly been made in order to demonstrate that paracetamol shares the mechanism(s) of action of NSAIDs.
Paracetamol would act as a pro-drug, the active metabolite (AM404) being formed in the brain through the conjugation of the de-acetylated derivative of paracetamol (p-aminophenol) with arachidonic acid, by the action of fatty acid amide hydrolase (FAAH)
- …
