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  • 1990-1994  (1)
  • 1985-1989  (9)
  • 1
    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: This work describes the formation of discrete micelles (⋍ 0.1 μm) from ABA poly(oxyethylene-b-isoprene-b-oxyethylene) block copolymers in water. An efficient labeling of the micelles by polymerization of [14C]-styrene within the hydrophobic core is also described. These micellar nanoparticles are being considered as promising materials for controlled release and/or site-specific drug delivery systems. In experimental animals the micelles remained in circulation with a half-life in excess of 50 h. Our results demonstrate the advantages of using block copolymers for the preparation of “perfect” biocompatible surfaces such as are required for well-tolerated, long-circulating particulate drug carriers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1741-0444
    Keywords: Dip-coated electroenzymic glucose transducer ; In vitroperformance ; Optimisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The details of construction and the performance characteristics of a dipcoated electroenzymic glucose transducer comprising an H2O2 electrode coated with a layer of glucose oxidase encapsulated in cellulose acetate and overlaid with a layer of polyurethane are presented. The steady-state current increases when the glucose oxidase and cellulose acetate concentrations of the dip-coating solutions are increased, but high cellulose acetate concentrations yield thick and mechanically unstable membranes. A compromise between current yield and mechanical stability can, however, be achieved by employing glucose oxidase and cellulose acetate concentrations of 200 mg ml−1 and 2–5 g 100 ml−1, respectively. A polyurethane concentration of 6 g 100ml−1 is optimal both in terms of the current yield and the linearity of response. The relationship between steady-state current and D-glucose concentration is approximately linear over the concentration range 0·5 to 11·5 mm, and if correction is made for deviations from linearity at higher glucose concentrations, concentrations in excess of 20 mM can readily be quantified. The steady-state current is pH and temperature dependent, but the dependencies are relatively small in the physiological range. The mean rate of decrease of the glucose current during long-term operation of the optimised transducer is 0·83 per cent of the initial current per hour at 37°C. The hydrated electrodes perform satisfactorily after storage for more than two weeks at room temperature. the transducers have a mean response time [t 90%] of 50 s or less.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract A class of completely solvable gauge field equations is investigated. These equations are shown to be closely analogous to the four-dimensional self-duality equations. A similar geometrical interpretation is exhibited, and a generalisation of the ADHM construction is shown to provide solutions.
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  • 5
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We analyse further the algebraic structure of dependent fermions, namely ones interrelated by the vertex operator construction. They are associated with special sorts of lattice systems which are introduced and discussed. The explicit evaluation of the relevant cocycles leads to the result that the operator product expansion of the fermions is related in a precise way to one or another of the division algebras given by complex numbers, quaternions or octonions. The latter case is seen to be realised in the light cone formalism of superstring theory.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract New representations of affine Lie algebras are constructed using symplectic bosons of the sort that occur naturally in the BRST treatment of fermionic string theories. These representations are shown to have analogous properties to the current algebra representations in terms of free fermion fields, though they do not act in a positive space. In particular, the condition for the Sugawara construction of the Virasoro algebra to equal the free one is the existence of a superalgebra with a quadratic Casimir operator, paralleling the symmetric space theorem for fermionic field constructions. Both results are seen to be particular cases of a more general super-symmetric space theorem, which arises from considering an affinisation of the superalgebras. These algebras are realised in terms of free fermions and symplectic bosons and lead to a super-Sugawara construction of the Virasoro algebra. The conditions for this to equal a Virasoro algebra obtained from the free fields are provided by the super-symmetric space theorem.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract A vertex operator construction is given for the level one representations of the affine Kac-Moody algebras associated with non-simply-laced finite-dimensional Lie algebras, using free boson and interacting fermion fields. The fermion fields are constructed explicitly and a detailed discussion is given of the theory of the cocycles necessary for this and other vertex operator constructions. The construction is related in detail to the folding of Dynkin diagrams and a generalisation of it yields Freudenthal's magic square.
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  • 8
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract It is shown that a method previously given for constructing representations of the Virasoro algebra out of representations of affine Kac-Moody algebras yields the full discrete series of highest weight irreducible representations of the Virasoro algebra. The corresponding method for the super-Virasoro algebras (i.e. the Neveu-Schwarz and Ramond algebras) is described in detail and shown to yield the full discrete series of irreducible highest weight representations.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The isolation of silver-resistant, silver-accumulating bacteria is reported. Following the screening of a number of environmental sources, silver-resistant Enterobacteriaceae were isolated from both sewage and photographic processing effluent. The level of resistance to silver and other heavy metals was determined for a selection of these isolates and, together with preliminary accumulation data derived from batch culture studies, one isolate, a strain of Citrobacter intermedius, was selected for further examination. The effect of silver concentration on batch culture growth of this organism was also investigated.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Accumulation of silver is reported for growing and non-growing populations of Citrobacter intermedius B6. In non-growing cultures a maximum uptake of 4.35% (w/w) was observed at an initial silver concentration of 2111.2 μmol Ag+ l-1. In contrast the maximum uptake of silver by growing bacteria was 2.81% (w/w) at an effective concentration of silver of 217.8 μmol·l-1. Silver accumulation rates in both resting (460 μmol Ag+ g-1 per hour) and continuously grown (41 μmol Ag+ g-1 per hour) bacteria are higher than previously reported. Cell fractionation and electron microscopy of continuously grown bacteria indicated that accumulation of silver was associated with the cell envelope, in the form of dense deposits of macromolecular proportions. This observation discounts simple surface adsorption as the process of accumulation in growing cultures.
    Type of Medium: Electronic Resource
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