ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 109-122 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Left-handed double-helical Z-RNA has been studied using the ribohexanucleotide pentaphosphate r(CpGpCpGpCpG). One-dimensional proton nmr experiments were used to probe the structural details of the left-handed helix in concentrated sodium perchlorate solution. In 1M NaClO4 the RNA adopts the normal A-form double helix, and in 6M NaClO4 it is nearly all in the Z form. In 4M NaClO4 it exists as nearly equal parts of A form and Z form. Resonances corresponding to both A and Z form appear in the nmr spectrum, indicating that the duplex exchanges slowly between forms. Spin-spin coupling constants between protons in the ribose rings were used to determine the sugar-pucker conformations of the individual nucleotides. Quantitative nuclear Overhauser experiments were used to determine proton-proton distances within the nucleoside, and from these distances values for the glycosidic torsion angle were determined. The results show that the cytidines adopt C2′,-endo sugar puckers (S type) with pseudo-rotation phase values (P) of ∼ 165°. The bases are in the anti conformation, with χ values of ∼ - 140°. The internal guanosines adopt C3′,-endo sugar puckers (N type) with P ∼ 18°, while the 3′-terminal guanosine ribose exists in an equilibrium between S- and N-type conformations. All three guanosine bases adopt the syn conformation, with χ ∼ 70°. The results indicate that the solution structure of Z-RNA is very similar to that of Z-DNA.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to prevent enzymatic degradation of β-casomorphin-5 (1) and morphiceptin, reduced peptide bonds were incorporated at the 2-3 and 3-4 bonds, respectively. The analogues were synthesized by a combination of solid phase methodology and reductive alkylation of resin-bound peptide amines with Boc-amino acid aldehydes (Boc: tert-butyloxycarbonyl) in the presence of NaBH3CN. During reversed phase high pressure liquid chromatography purification, peak shape distortions could be observed. Epimerization was excluded, based on gas chromatography/mass spectroscopy analysis, which indicated acceptable levels of racemization (〈3%) in the crude product. Instead, the phenomena could be attributed to slow cis/ trans isomerizations originating from the Xxx-Pro bonds in the sequence. The presence of different conformational isomers was also established by 1H-nmr spectroscopy in DMSO-d6. All analogues showed high stability in blood plasma, enhanced binding affinity for the μ receptor, and very low binding to the δ receptor. While the Phe3Ψ(CH2-N) Pro4 analogues (3) and (5) displayed agonist activity, the Pro2Ψ(CH2-NH) Phe3 modified analogue (2) showed antagonist activity comparable to D-Phe-Cys-Tyr-D -Trp-Arg-Thr-Pen-Thr-NH2.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 189 (1991), S. 195-205 
    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: 2-Hydroxyethyl-methacrylat wurde durch Initiierung mit γ-Strahlung in Masse mit zwei verschiedenen tetrafunktionellen Monomeren (Ethylenglycol-dimethacrylat und 1,2-Bis(acryloxymethyl)-tetramethyldisiloxan) und einem hexafunktionellen Monomeren (1,1,1-Trimethylolpropan-trimethacrylat) als Vernetzungsmittel copolymerisiert. Die erhaltenen Xerogele wurden anschließend mit Wasser bis zum Erreichen der Gleichgewichtsquellung behandelt. Um die drei Vernetzungsmittel vergleichen zu können, wurde unter Berücksichtigung von Molmasse und Funktionalität der Xerogele die theoretische Konzentration an Vernetzungsstellen zwischen 0,032 und 0,644 mol/l variiert. Die relative Hydrophobie der drei Vernetzungsmittel hat einen ausschlaggebenden Einfluß sowohl auf die Gleichgewichtsquellung als auch auf den Elastizitätsmodul der gequollenen Gele. Der Gehalt an nicht-einfrierbarem Wasser in mit 1,1,1-Trimethylol-propan-trimethacrylat vernetzten Gelen wurde anhand von DSC-Untersuchungen analysiert. Das Verhältnis von nicht-einfrierbarem zum Gesamtgehalt an Wasser in den Gelen nimmt mit steigender Vernetzungsdichte zu.
    Notes: By means of γ-irradiation 2-hydroxyethyl methacrylate has been copolymerized in bulk with two different tetrafunctional monomers, ethylene glycol dimethacrylate and 1,3-bis(acryloxymethyl) tetramethyl disiloxane and with a hexafunctional monomer, 1,1,1-trimethylolpropane trimethacrylate. The resultant xerogels were subsequently swollen to equilibrium in water. In order to allow a comparison among the three crosslinkers, their molar masses and funtionalities were taken into account, the theoretical crosslink concentrations being varied from 0.032 to 0.644 mol dm-3. The relative hydrophobicity of the three crosslinkers was found to have a significant effect on both the equilibrium swelling and elastic modulus of the swollen gels. Non-freezing water in several gels crosslinked with 1,1,1-trimethylolpropane trimethacrylate was analysed by differential scanning calorimetry (DSC). The proportion of non-freezing water in the gel relative to the overall water content was found to increase with increasing crosslink density.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 905-913 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ab initio molecular orbital calculations have been performed on the transition state for the addition of methyl radical to twelve vinyl monomers using the SV 3-21G basis set. A linear relationship has been found between the calculated energies of activation and previously calculated energies of reaction. This supports the assumption of an Evans-Polanyi type rule in previous work which attempted to correlate reactivity with calculated energies of reaction. The activation energies obtained for methyl addition to butadiene and styrene were calculated to be negative. This is caused by errors introduced by a number of sources, viz. basis set superposition error, spin contamination and zero point energy. These errors are discussed. Previous authors have reported reasonable agreement between calculated activation energies at SV3-21G and experimental values for methyl addition to ethylene, this work suggests that this agreement was coincidental and results from the fortuitous cancellation of errors. The nature of the transition state for these radical addition reactions is discussed and the limitations of the SV3-21G basis set are highlighted. The theoretical prediction of activation energies for radical addition reactions would require much larger calculations, beyond the computational means of most research laboratories.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 2183-2198 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The miscibility in binary blends of ferroelectric copolymers of vinylidene fluoride (VF2) and trifluoroethylene ( F3E) has been investigated over the full range of blend compositions for three different random copolymers containing 52, 65, or 73 mol % VF2. We found these copolymers miscible in the melt with each other but not with the parent homopolymer, PVF2. In thin solid films we demonstrated, for all blend compositions, the very rare phenomenon of isomorphic cocrystallization in both the ferroelectric and paraelectric phases of the 52 + 65 and the 65 + 73 mol % VF2 copolymers. However, the blend having the largest compositional difference (52 + 73 mol % VF2) was found to consist of two separate ferroelectric and paraelectric phases. These results demonstrate the very close chemical and structural similarities required for coexistence of two different macromolecules within a single crystalline lattice. Moreover, they allow us to probe the compositional limits for such similarity in both the ferroelectric and the paraelectric lattices. Phase diagrams of these blends have been constructed and are discussed. The Curie transition is shown to be an exceptionally sensitive probe of compatibility in the ferroelectric phase.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 1 (1990), S. 345-349 
    ISSN: 1042-7147
    Keywords: Graft copolymers ; Macromolecular homing devices ; Colloidal drug carriers ; bone marrow targeting ; 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 series of novel graft (comb) copolymers composed of a hydrophobic backbone and hydrophilic side chain grafts are described for the in vivo targeting of colloidal carriers. The new copolymers, when coated on nanometer size particles (nanospheres, nanocapsules), substantially reduce the capture of the particles by the reticuloendothelial system (RES) and show potential for targeting to the bone marrow.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 153-162 
    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: Low-dielectric constant (∊r) polymers, such as polytetrafluoroethylene (PTFE), are an important component of advanced electronic products that transit data, since it is this physical property that largely determines a device's performance. For instance, the dielectric constant determines overall signal speed and proximity in that one circuit line can be placed to another, i.e., wiring density, while maintaining desired electrical characteristics. However, due to PTFE's inertness and intractability, significant challenges exist in the successful application of the polymer as an insulation material. One specific example is the lack of available methods to uniformly and controllably generate fine, high-density features in the neat fluoropolymer. Recently, it was reported that excellent structuring characteristics of PTFE can be achieved by sensitizing the fluoropolymer to excimer laser radiation using small quantities of an aromatic polyimide. An important physical property of the sensitization agent, in addition to interacting strongly with the laser's emitted energy, is suitable thermal stability due to PTFE's high-temperature processing requirements. Using multiple analysis techniques, the thermal decomposition behavior of PTFE, polyimide sensitizer, and resulting polymer blend have been evaluated. It was determined that the onset of decomposition for all systems is near or greater than 500°C. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 1039-1046 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study reports the effects of Simplex bone cement powder (BC) on the proliferation and production of bone resorbing factors in vitro by human adherent monocytes/macrophages. Adherent peripheral blood cells were isolated from seven healthy individuals and exposed to a dispersion of BC powder (1 mg/mL), phytohemagglutinin (PHA, 40 μg/mL), or medium alone at different periods of cell incubation (days 0-2, 0-7, 5-7, or 10-12). Cell proliferation was quantified by incorporation of 3H-thymidine uptake. Culture supernatants were evaluated for levels of interleukin 1-like activity (IL-1) by murine thymocyte proliferation assay, prostaglandin E2 (PGE2) by radioimmunoassay, lysosomal enzyme activity (N-acetyl-β-D-glucosaminidase and β-glucuronidase) using fluorometry, and collagen and casein degrading activity using radioactive substrates. Human adherent peripheral blood cells showed a proliferative response to PHA that coincided with cell maturation; BC did not inhibit PHA-induced cell proliferation of either adherent or nonadherent blood cells, indicating the non-toxic nature of these particles at the concentrations tested. BC stimulated increased release of the lysosomal enzyme N-acetyl-β-D-glucosaminidase; the levels of PGE2, IL-1, collagenase, and caseinase were unchanged. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 17 (1991), S. 439-447 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: High-performance adhesive bonds require clean, microscopically rough adherend surfaces that are compatible with the adhesive or primer. Such surface allow wetting by the polymer and a complete filling of the pores of ‘nooks and crannies’. The resulting mechanical bonds supplement or supplant the chemical bonds present. For durability in aggressive environments, aluminum bonds that are exposed to high humidity also require hydration-resistant oxide surfaces. Such hydration resistance is inherent in some surfaces, e.g. phosphoric acid-anodized surfaces, and can be high temperatures, such bonds require oxide-free surfaces when exposed to temperatures above 300°C. These surfaces can be formed by plasma spraying a metallic powder coating onto the titanium alloy. Although preparation of high-quality surfaces and bonds is achieved readily in the laboratory, occasional failures are observed in the manufacturing environment owing to, for example, contamination, pH or temperature variations. These processing problems can prevent wetting of the surface or can destroy the microrough morphology. A basic understanding of the mechanisms involved in the production of appropriate surfaces and their resulting adhesive bonds and in their degradation is critical to the evaluation of the failures and their remedy.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 460-466 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The cathodic deposition of yttrium on iron and steel surfaces is known to improve the bond strength of joints treated in such a manner. This work explores the effect of large and small heterogeneities on the spatial distribution of the deposited species. Two systems are investigated: 98% iron with micrometre-scale inclusions, and a micro-hardness indentation on gold-coated iron. In the former case yttrium is identified (by XPS and SAM) to have been deposited in two concentration regimes: close to the inclusion (the cathodic area) the concentration is higher than elsewhere, and also contains iron produced by back-deposition. At the identation the iron substrate is exposed at the corners to provide the prerequisite anodic site, cathodic deposition of yttrium is then observed both within the identation and on the undamaged gold surface at a lower concentration. The provision of spatially resolved analytical information by SAM, time-of-flight SIMS and imaging XPS enables the interrelationship of microstructural features and extent of cathodic deposition to be readily appreciated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...