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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 380 (1996), S. 16-17 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Recent correspondents have drawn attention of the problems of Spanish scientists and the uncertain future. This is a sad paradox : between 1982 and 1992, "the rise in scientific production in Spain has been disproportionately greater than in the rest of the world" (F. J. Ayala, Politica ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 751-756 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymerizations of 2-vinyl-1,3-dioxane (1a), 5,5-bis(hydroxymethyl)-2-vinyl-1,3-dioxane (1b), and 5,5-dimethyl-2-vinyl-1,3-dioxane (1c) with acrylonitrile (AN) and α-chloroacrylonitrile (CPAN) in N,N-dimethylformamide (DMF) were investigated. For the AN(M1)/1a (M2), AN(M1)/1b (M2), and AN (M1)/1c (M2) pairs, the copolymerization parameters r1 are 5,2, 3,7, and 3,9, respectively. For the CPAN (M1)/1a (M2), CPAN (M1)/1b (M2), and CPAN (M1)/1c (M2) pairs, the r1 values are 7,95, 7,80, and 8,90, respectively. In all cases the r2 value is approximately zero. A clearly different influence of the monomer feed composition on the copolymerization rate is observed when the reaction takes place in the absence of solvent compared with that made in DMF. The explanation is related with the existence of associations between acrylonitrile or x-acrylonitrile and the vinyl-dioxane compound.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 757-764 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymerizations of 2-vinyl-l,3-dioxane (1a), 5,5-bis(hydroxymethyl)-2-vinyl-1,3-dioxane (1b), and 5,5-dimethyl-2-vinyl-1,3-dioxane (1c) with maleic anhydride (MA) and N-vinyl-2-pyrrolidone (NVP) were investigated. Copolymerization of the cyclic acetals 1 with MA yielded copolymers with perfectly alternating sequences independent of the initial monomer feed composition. Terpolymerization of 1a, MA, and styrene, also despite of monomer composition, yielded terpolymers with a molar composition of 50% in MA which confirms the participation of transfer complexes in these copolymerizations. The composition of the 1/NVP copolymers (mole fraction) F1(NVP) ≈ 0,6-0,8 also varied little with the feed. The copolymerization rates passed through a maximum when the monomer mixture contained a mole fraction f1 (NVP) of ca. 0,7.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 1219-1227 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The initial rate of the polymerization of methyl acrylate photoinitiated by 4-dimethylamino-4′-isopropylbenzophenone (2) varies linearly with monomer concentration and the square-root of light intensity. For small absorbances, the initial polymerization rate, Rp, varies linearly with the square-root of the photoinitiator concentration. For high absorbance values, Rp is independent of the photoinitiator concentration in a well-stirred system and decreases as the photoinitiator concentration increases in an unstirred system. This marked differences between the polymerization kinetics in well-stirred and unstirred systems is discussed. The ratio of the propagation rate constant and the square-root of the termination rate constant, kp/kt1/2, and the quantum yield of photoinitiation were determined and related to the results previously obtained in a study on the photoreactivity of 2.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 93 (1981), S. 159-173 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Oxydation von neuen durch anionische Copolymerization aus Acrolein hergestellten Vinylacetalpolymeren wird beschrieben. 3,3-Diethoxypropen wurde als Modell verwendet und die Abbauprodukte seiner Oxydation identifiziert. Es wurde festgestellt, daß die Oxidation der Modellsubstanz zu den gleichen Abbauprodukten führt. Die Geschwindigkeit des Sauerstoffverbrauchs wurde bei allen Reaktionen volumetrisch bestimmt.Ein Mechanismus für die Oxidationsreaktion gemäß den isolierten Abbauprodukten wird vorgeschlagen.
    Notes: A study on the oxidation of new vinyl-acetal polymers obtained by anionic copolymerization of acrolein is described. Identification studies were carried out on the oxidation products of 3,3-diethoxy-propene as model compound. The products of the oxidation of the unsaturated acetal polymers were found to be identical to the products from the oxidation of the model compound. Rates of oxygen consumption by the model compound and by the polymers were measured by a volumetric method.A mechanism has been proposed taking into account the products isolated and identified and the nature of the oxidation process.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 73 (1978), S. 25-33 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Reaktion zwischen Acroleindiäthylacetal und Radikalen sowie das Verhalten dieses Acetals bei der radikalischen Copolymerisation mit ungesättigten Monomeren wurde untersucht. Auf Grund der Ergebnisse wird ein Mechanismus vorgechlagen, der die Abstraktion eines H-Atoms von einem dem Sauerstoff benachbarten C-Atom durch ein Radikal beinhaltet. Copolymerisationsversuche des Acetals mit verschiedenen Monomeren waren nur mit Acrylnitril und Maleinsäureanhydrid erfolgreich. Die bemerkenswert einheitliche Zusammensetzung des Acetal-Maleinsäreanhydrid-Copolymeren zeigt, daß die Reaktion über einen Donor-Akzeptor-Komplex verläft.
    Notes: The reaction between acroleindiethylacetal (3.3-diethoxypropene) and free radicals and the behaviour of this acetal in the free radical copolymerization with unsaturated monomers has been investigated. The decomposition of benzoyl peroxide and tert.-butyl peroxide in acroleindiethylacetal has been studied in the liquid phase. On the basis of the obtained products a mechanism is proposed which involves the abstraction of a hydrogen atom by a primary radical from a carbon atom which is adjacent to oxygen. We also tried to copolymerize the acetal with several conventional comonomers but copolymers were only obtained when acrylonitrile and maleic anhydride were used. The remarkably uniform composition of the copolymers from the acetal and maleic anhydride is explained through a donor-acceptor complex between the two monomers.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 561-567 
    ISSN: 1042-7147
    Keywords: Photoreduction ; Polymerization Photoinitiator ; Radical efficiency ; Substituted dimethylanilines ; Dimethylaminobenzophenones ; 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
    Notes: A key component in light-induced radical polymerization is the photoinitiator which produces free radicals through a photochemical reaction. In the first part of this paper, a short analysis of the different steps that take place in the light-induced radical polymerization using bimolecular photoinitiating systems is made. In the second part, the obtained results in the polymerization of acrylic monomers using conjugated and nonconjugated aminobenzophenones as photoinitiators are shown. A summary of the photochemical behavior of these photoinitiators together with several aspects related to the polymerization kinetics are described. The nature and efficiency of the produced radicals are studied as well as the reactivity of the radicals generated from the substituted dimethylanilines-camphorquinone photoinitiation systems. Important mechanistic differences were found in the photochemical behavior and radical efficiency for the families of photoinitiators studied.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 142 (1986), S. 123-135 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurden lineare p-dimethylaminobenzoylierte Polystyrole hergestellt. Zwei Wege sind dabei verfolgt worden: Einer durch Bildung von Polystyrollithium und der andere durch Polystyrolamidbildung. Mit dem ersten Weg, Poly-p-iodstyrol → Poly-p-lithiumstyrol und Reaktionen des Polylithiumstyrols mit Methyl-4-N,N-dimethylaminobenzoat, wurde immer ein vernetztes Polymeres erhalten, das Hydroxygruppen, und in einigen Fällen  -  in Gegenwart eines Überschusses von Methyl-4-N,N-dimethylaminobenzoat und niedrigen Temperaturen  -  auch Dimethylaminobenzoylgruppen enthielt. Der zweite Weg, Polystyrolamidbildung und nachfolgende Reaktion dieser linear funktionellen Polystyrole mit POCl3 und Dimethylanilin, führte zu einem linearen p-dimethylaminobenzoylierten Polystyrol.Ausgehend von Cumol unter Anwendung derselben Prozedur wie für Polystyrol beschrieben, wurden N-Phenyl-p-isopropylbenzamid und 4-Isopropyl-4′-N-N-dimethylaminobenzophenon als Modellverbindungen erhalten. Beide Modellverbindungen und die funktionellen Polystyrole wurden mit IR, UV, 1H-NMR und Massenspektroskopie sowie Molekulargewichtsbestimmungen charakterisiert. Aus Polystyrolamid wurden auch Polystyrolester und Polystyrolsäure erhalten.
    Notes: Linear p-dimethylaminobenzoylated polystyrenes have been synthesized. Two routes, one of them by polystyrene lithiation and the other one by polystyrene-amide formation, have been followed. With the first route, poly-p-iodostyrene → poly-p-lithio-styrene and reaction of lithiated polystyrene with methyl-4-N,N-dimethyl-aminobenzoate, a crosslinked polymer was always obtained which contained hydroxylic groups and in some cases, in the presence of an excess of methyl-4-N,N-dimethylaminobenzoate and low temperatures, dimethylaminobenzoyl groups. The second route, polystyrene-amide formation and subsequent reaction of this linear functionalized polystyrene with POCl3 and dimethyl-aniline, yielded a linear p-dimethylaminobenzoylated polystyrene. Starting with cumene and following the same procedure described for the polystyrene, the model compounds N-phenyl-p-isopropylbenzamide and 4-isopropyl-4′-N,N-dimethylaminobenzophenone were also obtained. Both model compounds and functionalized polystyrenes were characterized by IR, UV, 1H-NMR and mass spectroscopy as well as molecular weight determinations. From polystyrene-amide, polystyrene-ester and polystyrene-acid were also obtained.
    Additional Material: 1 Ill.
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  • 9
    Publication Date: 2019
    Description: An actual event that happened in the Roncal valley (Spain) is investigated and the results are compared between models with and without snowmelt. A distributed rainfall model is generated with the specific data recorded by the rain gauges of the catchment during the episode. To describe the process of water routing in the hydrological cycle of the basin, a model is used based on combinations of parallel linear reservoirs (PLR model), distribution by the basin, and tip-out into its drainage network configured using a digital terrain model (DTM). This PLR model allows simulation of the different actual reservoirs of the basin, including the snow and the contribution due to its melting which, in the model, depends on the temperature. The PLR model also allows for a water budget of the episode where, in addition to the effective rainfall contribution, the water that comes from the thaw is taken into account. The PLR model also allows determination of the amount of water that exists in the basin before and after the episode, data of great interest. When comparing the simulations with and without taking into account the thawing process, it is evident that the intervention of the snow reservoir has been decisive in causing a flood to occur.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 10
    Publication Date: 2014-12-11
    Description: The use of wireless networks has experienced exponential growth due to the improvements in terms of battery life and low consumption of the devices. However, it is compulsory to conduct previous radio propagation analysis when deploying a wireless sensor network. These studies are necessary to perform an estimation of the range coverage, in order to optimize the distance between devices in an actual network deployment. In this work, the radio channel characterization for ISM 2.4 GHz Wireless Sensor Networks (WSNs) in an inhomogeneous vegetation environment has been analyzed. This analysis allows designing environment monitoring tools based on ZigBee and WiFi where WSN and smartphones cooperate, providing rich and customized monitoring information to users in a friendly manner. The impact of topology as well as morphology of the environment is assessed by means of an in-house developed 3D Ray Launching code, to emulate the realistic operation in the framework of the scenario. Experimental results gathered from a measurement campaign conducted by deploying a ZigBee Wireless Sensor Network, are analyzed and compared with simulations in this paper. The scenario where this network is intended to operate is a combination of buildings and diverse vegetation species. To gain insight in the effects of radio propagation, a simplified vegetation model has been developed, considering the material parameters and simplified geometry embedded in the simulation scenario. An initial location-based application has been implemented in a real scenario, to test the functionality within a context aware scenario. The use of deterministic tools can aid to know the impact of the topological influence in the deployment of the optimal Wireless Sensor Network in terms of capacity, coverage and energy consumption, making the use of these systems attractive for multiple applications in inhomogeneous vegetation environments.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by MDPI Publishing
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