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  • Chemistry  (8)
  • Aerospace Medicine
  • 2005-2009
  • 2000-2004
  • 1995-1999  (9)
  • 1980-1984
  • 1935-1939
  • 1996  (9)
Collection
Keywords
Publisher
Years
  • 2005-2009
  • 2000-2004
  • 1995-1999  (9)
  • 1980-1984
  • 1935-1939
Year
  • 1
    Electronic Resource
    Electronic Resource
    Conformational restriction of Tyr and Phe side chains in opioid peptides: Information about preferred and bioactive side-chain topology (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 1-12 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The side chain of Tyr and Phe was fixed into the gauche (-) or gauche (+) conformation by using the Tic or Htc structures, and into the trans conformation by using an aminobenzazepine-type (Aba) structure. When incorporated into dermorphin or deltorphin II, the Tic and Htc analogues all showed a large decrease in both μ and δ affinities and activities. Fixation of Phe3 in the trans rotamer resulted in a large increase in δ affinity in the dermorphin analogue, whereas in the [Aba3-Gly4] deltorphin II analogue, good δ affinity is maintained despite the removal of the Glu side chain. Whereas several authors propose a gauche (-) preferred conformation for the Phe3 side chain, these results suggest a trans conformation at the δ receptor. The use of these conformationally constrained residues for evaluating the preferred solution conformation in the flexible N-terminal tripeptide Tyr-D-Ala-Phe is illustrated. The 1H-nmr parameters - chemical shift, temperature dependence, and nuclear Overhauser effects to the D-Ala2 methyl protons in the different analogues - provide direct evidence to confirm the proposed sandwich conformation in the native peptides. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    A facile synthesis of polyamides from aromatic diisocyanates and dicarboxylic acid catalyzed by Lewis acids (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 897-903 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aromatic polyamides were prepared by an AlCl3 or HCl-catalyzed polymerization of toluene diisocyanate or methylenebis(phenyl isocyanate) with adipic acid at low temperatures (≤100°C) in a short reaction time (3-4 h). The intrinsic viscosity of the polymers was approximately 1.1 dL/g as determined at 25°C with m-cresol as solvent, indicating that the polyamides obtained by this method have relatively high molecular weights. The polymers exhibit high glass transition temperatures and good thermal stability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1996.030171208
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Poly(organo phosphazene) nanoparticles surface modified with poly(ethylene oxide) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 52 (1996), S. 89-95 
    Details
    ISSN: 0006-3592
    Keywords: poly(organo phosphazenes) ; nanoparticles ; poly(ethylene oxide) ; biodegradable materials ; surface modification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of biodegradable derivatives of poly(organo phosphazenes) for the preparation of nanoparticles and their surface modification with the novel poly(ethylene oxide) derivative of poly(organo phosphazene) has been assessed using a range of in vitro characterization methods. The nanoparticles were produced by the precipitation solvent evaporation method from the derivative co-substituted with phenylalanine and glycine ethyl ester side groups. A reduction in particle size to less than 200 nm was achieved by an increase in pH of the preparation medium. The formation (and colloidal stability) of these nanoparticles seems to be controlled by two opposite effects: attractive hydrophobic interactions between phenylalanine ester groups and electrostatic repulsions arising from the carboxyl groups formed due to (partial) hydrolysis of the ester bond(s) at the high pH of the preparation medium. The poly[(glycine ethyl ester)phosphazene] derivative containing 5000-Da poly(ethylene oxide) as 5% of the side groups was used for the surface modification of nanoparticles. Adsorbed onto the particles, the polymer produced a thick coating layer of approximately 35 nm. The coated nanoparticles exhibited reduced surface negative potential and improved colloidal stability toward electrolyte-induced flocculation, relative to the uncoated system. However, the steric stabilization provided was less effective than that of a Poloxamine 908 coating. This difference in effectiveness of the steric stabilization might indicate that, although both the stabilizing polymers possess a 5000-Da poly(ethylene oxide) moiety, there is a difference in the arrangements of these poly(ethylene oxide) chains at the particle surface. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and properties of poly(1-alkyl-3-methylene-2-pyrrolidone)s (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 3123-3133 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of α-methylene-N-alkyl-2-pyrrolidone monomers with varying length of the alkyl chain from C1 to C8 were synthesised. The monomers were subjected to free radical polymerisation to yield a range of polymers each with a different balance in hydrophobic/hydrophilic properties originating from the pyrrolidone moiety and the N-alkyl chain. The equilibrium water content of polymers crosslinked with ethylene dimethacrylate were found to decrease with increasing alkyl chain length. The glass transition temperatures of the polymers are reported ranging from 98°C to -5°C on going from the methyl to the octyl derivative. The thermal degradation of the polymers was studied using thermogravimetric analysis and pyrolysis gas chromatography-mass spectroscopy. The polymers were found to degrade at ca. 400°C predominantly via an unzipping mechanism. Pyrolysis at 450°C results in five products.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021971006
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  • 5
    Electronic Resource
    Electronic Resource
    Crystallization behavior and mechanical properties of a nylon-6, -6/6, and -12 terpolyamide (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 2237-2245 
    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: Composition, tacticity, and processing history can affect the morphology of semicrystalline polymers. Although homopolyamides are a family of polymers well known for semicrystalline character, through copolymerization or multicomponent copolymerization significant changes in materials' crystalline and thermal properties can occur. Due to chain irregularities introduced by terpolymerization, differential scanning calorimetry shows RDG 114T, a commercial polyamide of nylon-6, -6/6, and 12, to have an atypically low Tm and exhibit interesting recrystallization behavior. Specifically, the polyamide is wholly amorphous upon cooling from the melt, and since its Tg is about 20°C (due to the presence of plasticizers), chain ordering is found to occur over time at room temperature. Since the polyamide's morphology is time-dependent, the tensile properties of the polymer are also found to vary with ambient aging. For instance, Young's moduli for an amorphous and 7-day room temperature-annealed sample are 1.3×102 and 2.8×102 MPa, respectively. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Surface Analysis by SNMS: Femtosecond Laser Postionization of Sputtered and Laser Desorbed Atoms (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 363-370 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The photoionization efficiency of secondary neutral atoms from metal surfaces has been investigated by very intense (∽1014 W cm-2) and short-pulsed (∽200 fs) 248 nm laser radiation. Surface erosion of the samples was performed by Ar+ ion sputtering and by laser desorption (LD) from an N2 gas laser. Five polycrystalline samples (Al, Cu, Zr, In and Au) have been analyzed with respect to their ionization efficiency and LD yields. In order to estimate the desorption yield, we determined the useful yield of our time-of-flight (ToF) mass spectrometer by ion sputtering, followed by laser postionization with 193 nm radiation from an ArF excimer laser. The applied femtosecond pulse, high-intensity 248 nm laser radiation has been found to be an excellent source of non-selective photoionization. For each material in this study a large fraction of doubly ionized atoms was observed; the measurements on Au have also shown triply ionized atoms. For some spectra, the number of doubly ionized atoms was even higher than for singly ionized atoms. We have estimated that the useful yields for LD are significantly higher than the values observed in ion sputtering.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Ein auf einem Steroid basierender Cryptand für HalogenidionenDiese Arbeit wurde von Materials Ireland gefördert. Wir danken Peter Ashton (University of Birmingham) für die Massenspektren und Freedom Chemical Diamalt GmbH für Cholsäure. (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 108 (1996), S. 1410-1413 
    Details
    ISSN: 0044-8249
    Keywords: Molekulare Erkennung ; Steroide ; Supramolekulare Chemie ; Wirt-Gast-Chemie ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19961081208
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  • 8
    Electronic Resource
    Electronic Resource
    A Steroid-Based Cryptand for Halide AnionsFinancial support for this work was provided by Materials Ireland. We are grateful to Peter Ashton (University of Birmingham) for mass spectra, and to Freedom Chemical Diamalt GmbH for generous gifts of cholic acid. (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 35 (1996), S. 1312-1315 
    Details
    ISSN: 0570-0833
    Keywords: host-guest chemistry ; molecular recognition ; steroids ; supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199613121
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  • 9
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    Ground Reaction Forces During Locomotion in Simulated Microgravity (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Significant losses in bone density and mineral, primarily in the lower extremities have been reported following exposure to weightlessness. Recent investigations suggest that mechanical influences such as bone deformation and strain rate may be critically important in stimulating new bone formation. It was hypothesized that velocity, cadence and harness design would significantly affect lower limb impact forces during treadmill exercise in simulated zero gravity (0G). A ground-based hypogravity simulator was used to investigate which factors affect limb loading during tethered treadmill exercise. A fractional factorial design was used and 12 subjects were studied. The results showed that running on active and passive treadmills in the simulator with a tethering force close to the maximum comfortable level produced similar magnitudes for the peak ground reaction force. It was also found that these maximum forces were significantly lower than those obtained during overground trials, even when the speeds of locomotion in the simulator were 66 % greater than those in 1 G. Cadence had no effect on any of the response variables. The maximum rate of force application (DFDT-Max) was similar for overground running and exercise in simulated 0G, provided that the "weightless subjects ran on a motorized treadmill. These findings have implications for the use of treadmill exercise as a countermeasure for hypokinetic osteoporosis. As the relationship between mechanical factors and osteogenesis becomes better understood, results from human experiments in 0G simulators will help to design in-flight exercise programs that are more closely targeted to generate appropriate mechanical stimuli.
    Keywords: Aerospace Medicine
    Type: Aviation, Space and Environmental Medicine; 67; 3
    Format: text
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    NASA TECHNICAL REPORTS
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