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  • 1
    ISSN: 0020-1693
    Keywords: Anchored complexes ; Copper complexes ; Thiourea-functionalized xerogels
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 13 (1957), S. 415-416 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Riassunto L'autore descrive un nuovo metodo per l'osservazione di substrati biologici radioattivati, basato sull'impiego della camera a diffusione. Questo strumento presenta notevoli vantaggi su quelli sinora impiegati in radiobiologia, perchè permette di osservare ad occhio nudo, fotografare ed identificare le caratteristiche di qualsiasi tipo di particelle ionizzanti, indipendentemente dalla loro energia. La camera a diffusione è particolarmente indicata per lo studio delle radiazioni ionizzanti di bassa energia. I risultati ottenuti dall'autore durante le osservazioni su organi animali e vegetali, su liquidi e minerali, sono stati assai soddisfacenti.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 401-404 
    ISSN: 0392-6737
    Keywords: Biological effects of radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Nonbilayer structures, as lysophospholipid micelles, can be produced in membranes by gamma irradiation. Interesting information on the gamma-ray effect on the lysophospholipid organization can be obtained by spin-label techniques. Variations of the TEMPO partition are appreciable, particularly in the range of the lipid thermotropic transition, even from relatively low doses. With increasing dose this transition becomes more and more complex and wider, according to the previous thermodinamic analysis.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 99-99 
    ISSN: 0392-6737
    Keywords: Biological effects of radiations ; Radiation damage and other structural irradiation effects ; Errata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 663-676 
    ISSN: 0392-6737
    Keywords: Biological effects of radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Viene presentato un modello semplificato, costituito da una dispersione in acqua di lisofosfolipide, per lo studio dei danni da radiazioni gamma su membrane lipidiche. Tecniche EPR e DSC sono state utilizzate per l'analisi della transizione, dalla struttura lamellare a quella micellare, subita da ciascun campione all'aumentare della temperatura. Le caratteristiche delle due strutture vengono discusse sulla base dei risultati ottenuti. Vengono evidenziate modificazioni, apprezzabili e permanenti, prodotte dalle radiazioni gamma fin da dosi molto inferiori a quelle necessarie per avere danni altrettanto evidenti nelle membrane lipidiche precedentemente studiate. La complessa transizione termotropica sembra coinvolgere un numero di molecole lisofosfolipidiche tanto minore quanto più alta è la dose assorbita.
    Abstract: Резюме Используя технику EPR и DSC, исследуется упрощенная модель для описания повреждений в липидных мембранах, индуцированная гамма-лучами. Молель включает дисперию воды и претерпевает переход из ламинарной в мицеллярную структуру при повышении температуры. Обсуждаются характеристики этих двух структур на основе EPR результатов. Обнаружены заметхые и перманентные изменения при дозах, значительно меньших, чем дозы при которых ранее изучались явные радиационные повреждения в липидных мембранах. Комплексный термотропный перешод, возникающий при облучении образцов, повидимомы. связан с числом лисофосфолидных молекул, которое уменьщается при увеличении досы.
    Notes: Summary A simplified model of gamma-ray-induced damage in lipid membranes has been studied with EPR and DSC techniques. The model consists of a water dispersion of a lysophospholipid and undergoes a transition from lamellar to micellar structure as temperature rises. The characteristics of these two structures are discussed on the ground of EPR results. Appreciable and permanent modifications are evident starting at doses very much lower than those causing clear damage effects in lipid membranes previously studied. The complex thermotropic transition taking birth in irradiated specimens seems to concern a number of lysophospholipid molecules that becomes smaller as the dose increases.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 15 (1993), S. 1451-1463 
    ISSN: 0392-6737
    Keywords: Biological effects of radiations ; Radiation damage and other structural irradiation effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The lipid composition of multi-lamellar vesicles of 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine exposed to137Cs γ-rays depends on the absorbed dose. In fact,31P and1H NMR analysis shows that four new molecular species are formed during the irradiation:a) 1-palmitoyl-sn-glycero-3-phosphorylcholine,b) 2-palmitoyl-sn-glycero-3-phosphorylcholine,c) glycerophosphorylcholine andd) free palmitic acid. Neglecting the speciesc), that is present only at high dose and in very small amount, the behaviour of molar fractionvs. dose is sublinear fora) andb), while ford) it is almost linear over all the dose range examined. The molecular and structural damage consequences onto the multi-lamellar vesicles, evidentiated by spin-labelling and DSC techniques, are discussed. It is clearly shown in particular, that the behaviour of the main transition does not depend on the concentration of the lysolecithins, but rather on that of the free palmitic acid, the role of which had previously been entirely neglected.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 237-249 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Degradation mechanisms have been investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 109 rads, respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation have been identified. All the composite materials evaluated have shown high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum yields for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane have been identified as the main byproducts of irradiation, along with unexpectedly high levels of CO and CO2. Initial G values for methane relative to hydrogen formation are higher in the presence of isopropylidene linkages, which occur in bisphenol-A based resins.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 2323-2332 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The use of coal conversion by-products as raw materials in the synthesis of thermosetting polyesters has been investigated. Heavy tar residues were oxidized by gaseous oxygen in an alkaline medium, yielding a complex mixture of benzenecarboxylic acids and smaller amounts of aliphatic carboxylic acids. The mixture was polymerized by condensation with tetraethylene glycol “bottoms,” a by-product of the synthesis of ethylene glycol. The resultant polyesters were cured by reacting them with epoxy resins in the presence of basic catalysts. Molded sheets and laminates were fabricated and tested. Tensile strength was found to increase with increasing curing time and with increasing concentration of epoxy crosslinking agent. Glass-reinforced composites fabricated by the autoclave process showed an increase in flexural and shear strength with decreasing autoclave pressure.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 509-521 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a study aimed at the development of a polymeric material stable to the space radiation environment, the synthesis and properties of two new perfluoroaromatic polysiloxanes have been investigated. Di(pentafluorophenyl)diethoxysilane and pentafluorophenyltriethoxysilane have been prepared via Grignard synthesis from pentafluorobromobenzene and tetraethoxysilane. By hydrolytic polymerization of these intermediates, polydi(pentafluorophenyl)siloxane and polypentafluorophenylsilsesquioxane have been synthesized. The effect of ultraviolet and low-energy proton (solar wind) irradiation in high vacuum has been determined in a space-environment-simulation facility. These polymers possess excellent resistance to low-energy proton irradiation but are less stable to ultraviolet irradiation. It is suggested that the enhanced polarization of the carbon-silicon bond due to the strong inductive effect of the pentafluorophenyl groups is responsible for the relatively low ultraviolet and thermal stability of the perfluoroaromatic polysiloxanes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 8 (1970), S. 335-349 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a study aimed at process optimization of caprolactam polymerization, particular reference has been paid to the competing role of water in caprolactam hydrolysis and endgroup polycondensation. The dependence of the apparent equilibrium constant for polycondensation on water concentration indicated that there is a strong effect of the medium on the activities of the reacting species which can not be neglected in a kinetic study of the polycondensation reaction. The effect of a variation of the medium was taken into account by using a polycondensation rate constant which included a function of the water present at any given time. With the aid of analog computer curve-fitting techniques, good agreement with second-order kinetics was found. The validity of a second-order mechanism was confirmed in a kinetic study of the chain amide linkage hydrolysis. The hydrolysis of caprolactam follows substantially different kinetics, where the generation of carboxyl groups reduces the activation energy of the reaction, which follows predominantly a third-order mechanism.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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