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  • GEOPHYSICS  (12)
  • Chemistry  (11)
  • METEOROLOGY AND CLIMATOLOGY  (3)
  • Lepidoptera
  • Meteorology and Climatology
  • 1995-1999
  • 1990-1994  (26)
  • 1990  (26)
Collection
Keywords
Publisher
Years
  • 1995-1999
  • 1990-1994  (26)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Melanin-concentrating hormone: A structural and conformational study based on synthesis, biological activity, high-field nmr, and molecular modeling techniques (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 609-622 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH -  in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290314
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  • 2
    Electronic Resource
    Electronic Resource
    Grafting of 2-(dimethylamino)ethyl methacrylate on linear low density polyethylene in the melt (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 1-22 
    Details
    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: Das Pfropfen von 2-(Dimethylamino)ethyl methacrylat (DMAEMA) auf lineares Polyethylen niedriger Dichte (LLDPE) in der Schmelze wurde mittels Messungen des Monomerumsatzes, des Pfropfgrades und der Pfropfeffizienz untersucht. Die Ergebnisse zeigen, daß das Pfropfen von DMAEMA auf LLDPE bereits bei niedrigen Temperaturen von etwa 90°C in der Schmelze durchgeführt werden kann, obwohl der Schmelzpunkt von LLDPE bei etwa 120°C liegt. Wenn die Pfropfreaktion bei zu hohen oder zu niedrigen Temperaturen durchgeführt wird, kann nur ein sehr niedriger Pfropfgrad beobachtet werden. Hohe Reaktionstemperaturen begünstigen die Polymervernetzung, was sich im Absinken des Schmelzindex bemerkbar macht. Die meisten Pfropfvorgänge werden während der Anfangsphase der Reaktion (unter den vorliegenden Bedingungen während der ersten 3 min) beobachtet. Eine Verlängerung der Reaktionsdauer über diesen Zeitraum hinaus führt zu verstärkter Vernetzung und erhöhter Produktion des Homopolymeren, was die Effizienz des Prozesses verringert. Organische Peroxide sind über einen weiten Halbwertszeitenbereich effektive Initiatoren der Pfropfreaktion, während Azoinitiatoren keine Pfropfung bewirken.
    Notes: Grafting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) on linear low density polyethylene (LLDPE) in the melt has been studied through measurements of monomer conversion, the degree of grafting and the grafting efficiency. Results show that the grafting of DMAEMA on LLDPE can be carried out in the melt at temperatures as low as 90°C even though the melting point of the LLDPE is as high as 120°C. When the grafting reaction is carried out at too low or too high temperature, a low degree of grafting is observed. High reaction temperature favoured crosslinking of the polymer as indicated by decreasing melt flow index. Most of the grafts were obtained during the early period of the reaction (before 3 min under the reaction conditions used). Further increase in reaction time increased crosslinking and also produced more homopolymer, thus decreasing the grafting efficiency. Organic peroxides are effective initiators for the grafting reaction over a broad range of half-lives while azo initiators do not produce grafting.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810101
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  • 3
    Electronic Resource
    Electronic Resource
    Basic functionalization of molten linear low-density polyethylene with 2-(dimethylamino)ethyl methacrylate in an intermeshing corotating twin-screw extruder (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1299-1313 
    Details
    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: Functionalization of molten linear low-density polyethylene (LLDPE) with 2-(dimethylamino)ethyl methacrylate (DMAEMA) was studied in an intermeshing co-rotating twin-screw extruder using a peroxide initiator. The influence of monomer concentration, initiator concentration, reaction temperature, the screw speed, and the mean reaction residence time on the grafting reaction was investigated in order to determine the reaction conditions necessary to obtain a controlled degree of grafting, DG, while minimizing homopolymerization and crosslinking. Relatively high grafting levels can be obtained without excessive polyethylene crosslinking by using high monomer concentrations, wm, with low initiator concentrations, wI. DG increased with increasing monomer concentration when wm exceeded a certain value. Processing temperatures between 130 and 160°C are optimal to achieve high grafting efficiency, GE. Too high a processing temperature resulted in both low DG and GE. An optimal reaction residence time of about 5 min was found for wm = 23 wt % and wI = 0.56 wt % to obtain relatively high DG and GE. The melt flow index of the reaction product, MFI, increased with increasing wm at constant wI. This suggests that the DMAEMA monomer has the ability to suppress crosslinking of the LLDPE chains. The ability of the DMAEMA monomer to compete for initiator and polymer radicals and reduce LLDPE crosslinking was further demonstrated by the study of sequential addition of monomer and initiator along the extruder. The competition among the three reactions (i.e., the desired grafting, homopolymerization, and crosslinking) is discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410537
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  • 4
    Electronic Resource
    Electronic Resource
    The metabolism of trimipramine in the rat (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 793-806 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies on the metabolism of the tricyclic antidepressant trimipramine, 5-(3-dimethylamino-2-methylpropyl)-10, 11-dihydro-5H-dibenz[b, f] azepine, in the rat are described. Many metabolites of trimipramine (TMP) were isolated from rat urine after enzymatic hydrolysis and their structures were identified by a gas chromatographic/mass spectrometric method, before and after appropriate chemical derivatization. Besides unchanged TMP, 20 metabolites were characterized (underivatized, and after acetylation), of which 12 had undergone alicyclic (C10 or C11) oxidation. This is a hitherto unreported metabolic pathway for TMP in the rat.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191303
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  • 5
    Electronic Resource
    Electronic Resource
    Mass spectrometric assay for determination of pancuronium and vecuronium in biological fluids utilizing the moving belt introduction system (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 69-74 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An assay for the determination of the neuromuscular blocking agents pancuronium bromide and vecuronium bromide in plasma or urine has been developed. This method is based on syringe application of sample extracts to the moving belt surface and single metastable transition monitoring of the elimination of acetic acid from the ion of m/z 543 during chemical ionization. The analysis shows good linearity over three orders of magnitude and is capable of analyzing for the compounds below the 5 ng ml-1 level. The assay has been used in preliminary pharmacokinetic studies of the biological fluids of surgical patients. The utility of the method for simultaneous determination of the deacetylated metabolites of these two drugs has also been investigated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200190204
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  • 6
    Electronic Resource
    Electronic Resource
    In situ reactive compatibilization in polymer blends: Effects of functional group concentrations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 655-678 
    Details
    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: Polystyrene (PS) and polyethylene (PE), along with their reactive counterparts, i.e., polystyrene having oxazoline reactive groups (OPS) and polyethylene with carboxylic acid groups (CPE), were melt blended in a Rheomix mixer. These blends were prepared by mixing these polymers in various proportions under a variety of conditions. In an alternate procedure the OPS, CPE graft polymer (OPS-g-CPE) was prepared by melt blending these two polymers beforehand, and subsequently this grafted polymer was used as a compatibilizer for PS-PE blends. The effects of the addition of OPS and CPE, on the one hand, and OPS-g-CPE, on the other hand, on the compatibility of PS-PE blends were investigated. The morphology of these blends was examined with a scanning electron microscope (SEM) and related to their tensile properties. The PS-PE blends are found to have the typical coarse morphology of incompatible blends and poor tensile properties while their reactive counterparts, OPS-CPE blends, have fine grain microstructure and show improved tensile strength throughout the range and improved elongation in the PE-rich blends. Relatively low concentrations of the reactive pair, oxazoline and carboxylic acid, are shown to be necessary to produce improved compatibility. The preblended graft copolymer OPS-g-CPE imparts compatibility to PS-PE blends also but not as effectively. This suggests that the addition of OPS and CPE during melt mixing of PS and PE forms OPS-g-CPE polymer at the interface and that these ingredients act as “in situ reactive compatibilizers” which improve physical properties.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070390316
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  • 7
    Electronic Resource
    Electronic Resource
    Functionalization of polyethylenes and their use in reactive blending (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2285-2300 
    Details
    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 grafting of maleic anhydride (MAn) to low density polyethylenes (PEs) dissolved in 1,2-dichlorobenzene (DCB) has been studied. Grafting was successful at temperatures of about 160°C both in air without initiator and under nitrogen with the radical initiator 2,5-di(t-butylperoxy)-2,5-dimethyl-3-hexyne (LPO). The presence of succinic anhydride grafts was shown by FTIR spectroscopy of the product; 1H-NMR spectroscopy indicates that the grafts consist of single succinic anhydride units. The graft content was determined by nonaqueous titration, and the extent of crosslinking inferred from the melt flow rates (MFR) of the products. The effects of concentration of initiator, MAn, and PE on the graft content were determined; the influence of PE structure, reaction time, and temperature was also studied. Melt blending of the grafted PE with polystyrene containing oxazoline functional groups (OPS) was investigated using a Rheomix mixer. The interpolymer reaction which occurs during blending was studied by means of FTIR, and the morphology of the blends by scanning electron microscopy (SEM). Information was also gained from the change in torque viscosity during the blending process.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410931
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  • 8
    Electronic Resource
    Electronic Resource
    The structure and dynamics of FeH(DMPE)2(BH4), FeH(DEPE)2(BH4) and FeH(DPrPE)2(BH4): Iron complexes containing monodentate borohydride ligands (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 4 (1990), S. 543-549 
    Details
    ISSN: 0268-2605
    Keywords: Borohydride ; iron phosphine ; organoiron ; NMR spectroscopy ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: FeH(DMPE)2(BH4) [DMPE = 1,2-bis(dimethylphosphino)ethane] is a stable, diamagnetic complex which can be synthesized readily by borohydride reduction of FeH(DMPE)2Cl or by treatment of Fe(DMPE)2H2 with borane. The complex contains an unsupported B—H—Fe hydrogen bridge. Analogous complexes with bulkier ligands, FeH(DEPE)2(BH4), [DEPE = 1,2-bis(diethylphosphino)ethane] and FeH(DPrPE)2(BH4) [DPrPE = 1,2-bis(di-n-propylphosphino)ethane], are less stable. In all complexes, in solution the borohydride ligand undergoes rapid internal motion, with all four boron-bound hydrogens interchanging environments. The barriers for BH4 reorientation (measured by NMR spectroscopy) are in the sequence FeH(DMPE)2(BH)4 〉 FeH(DEPE)2(BH)4 〉 FeH(DPrPE)2(BH4).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590040516
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  • 9
    Electronic Resource
    Electronic Resource
    Mass spectrometry of various neuromuscular blocking agents (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 25 (1990), S. 131-134 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210250211
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and properties of bis(dialkylphosphino)ethane iron dihydrides (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 4 (1990), S. 551-556 
    Details
    ISSN: 0268-2605
    Keywords: Metal hydride ; iron phosphine ; organoiron ; NMR spectroscopy ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses and properties of the iron bisphosphinoethane complexes FeH2(PP)2 and FeHCl(PP)2[PP=R2PCH2CH2CH2PR2, where R=Me (PP=DMPE), Et(PP=DEPE), and n-Pr (PP=DprPE)] are reported. The complexes can be formed by reduction of the corresponding dichlorides FeCl2(PP)2 with lithium aluminium hydride in THF solution provided that ethanol or more acidic reagents are not employed during the reaction work-up. The dihydrides are notably basic compounds and can be protonated reversibly by alcohols.The dihydrides exist as equilibrating mixtures of cis and trans isomers in solution. The cis isomers of each of the dihydrides are fluxional on the NMR timescale and NMR studies indicate that the interconversion of cis isomers does not necessarily proceed via the trans isomer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590040517
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