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  • Chemistry  (94)
  • 1990-1994  (94)
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  • 1990  (94)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 829-845 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This article describes the histological and ultrastructural appearance of the interface created in the implantation bed, between bone tissue and implants made of dense sintered hydroxyapatite (HA). Biopsies from dog subjects included: (a) loaded permucosal dental implants for tooth substitution, (b) subperiosteally placed implants for alveolar bone correction, (c) endosseously placed dental root implants to retain ridge form following extraction. The light and electron microscopical results show extensive bone apposition on the osseous sides of the implant surfaces. There is an intimate, direct bone contact without any visible interruption. The bone is of normal lamellar type and continuously connected with the trabecular bone. Bone has grown into the finest surface irregularities of the implant. Collagen fibers of the calcified bone matrix are observed within a distance less than 500 Å from the implant surface. The thin (20-100 Å) electron dense layer at the bone-implant interface resembled the lamina limitans of organic bone matrix, also seen at the inner walls of the osteocytes lacunes. Deposition of bone gives rise to a biologically stable bone-implant interface, without disturbance of the physiological bone turnover. This is seen as very favorable for desired long term fixation of implant to bone.
    Additional Material: 17 Ill.
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  • 2
    ISSN: 0749-1581
    Keywords: 2D NMR ; Oplopanonyl acetate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oplopanonyl acetate was isolated from Chamaecyparis pisifera. Its structure and stereochemical features were established using NMR techniques.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(ester-imide)s with a regular sequence of aliphatic spacers and aromatic imide mesogens were prepared in two ways. Either aliphatic α,ω-diacids were condensed with an acetylated diphenol derived from 4-hydroxyphthalic acid and 4-aminophenol, or aliphatic α,ω-diacid dichlorides were condensed with the silylated diphenol. The resulting poly(ester-imide)s were characterized by elemental analyses, viscosity measurements, microscopy under polarized light, DSC- and WAXS measurements. All poly(ester-imide)s are crystalline materials with a layered supermolecular structure in the solid state. Above the melting point a nematic mesophase exists over a broad temperature range. A pronounced odd-even effect was found for the temperature of isotropization, but not for the melting points.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 181-185 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The abuse of nortestosterone in sport is an important problem in doping-control analysis. In order to detect the main urinary metabolite of nortestosterone, norandrosterone (NA), sensitive and specific methodology is necessary. In this context the use of a low-cost mass spectrometric detector such as the Finnigan MAT ion-trap detector (ITD) was studied. The electron ionization (EI) and positive-ion chemical ionization (PICI) mass spectra of the methoxime-trimethylsilyi, trimethylsilyl-enol trimethylsilyl ether and pentafluoropropionic ester derivatives of NA are described. The limits of detection of these derivatives are compared with those obtained by the Hewlett-Packard mass selective detector (MSD), another low-cost mass spectrometric detector and operating only in the EI mode. For the derivatives of the reference standard of NA the ITD has in the EI mode the same limit of detection, in the range of 0.5 to 1 ng injected on the column, as the MSD. However, under these conditions the ITD provides more spectrometric information, because it gives full scan data. Moreover, with the same or even improved limits of detection the ITD can operate in the PICI mode. On the other hand, for the analysis of NA isolated from urine samples, the performance of the MSD was better than that of the ITD. The ion trapping technique is probably limited when the chemical background is high.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 163-176 
    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: Hydroxytelequelic oligoesters of molecular weight (Mn) between 500 and 3000 were prepared from dimethylterephthalate (DMT) and 2-methyl-2-propyl-1,3-propanediol (MPPD) by ester interchange polycondensation. They were modified by reaction of their end hydroxyl groups with N-(4-chlorocarbonylphenyl) maleimide and N-(4-chlorocarbonylphenyl) nadimide. Spectroscopic (NMR), chromatographic (GPC), and calorimetric (DSC) analyses demonstrated that MPPD oligoterephthalates are less reactive than previously used glycols (diethylene glycol, DEG) and only nadimide-modified oligomers could be readily synthesized. Attempts to introduce maleimide groups at the chain ends led to crosslinked materials. Furthermore, some relationships between molecular weight and properties (Tg, thermal stability, etc.) could be outlined. The oligomers, unmodified and modified, proved to be essentially amorphous.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of a series of ring-C monoaromatic tricyclic terpanes from a Tasmanian tasmanite sediment were measured. Their fragments are interpreted to include the aromatic ring-C and the side-chain, shifting by 14 u from one homologue to the next. Suggestions about the fragmentation pattern are made and compared with those for tricyclic terpanes with similar structures.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 1-4 
    ISSN: 0749-1581
    Keywords: Internal reference ; 13C chemical shift measurement ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of the nominal value of the chemical shift of the solvent to calibrate the spectrometer in 13C NMR spectroscopy was found to introduce errors due to the effect which the solute has on the solvent. In addition, hexamethyldisiloxane (HM) is proposed as an internal standard; owing to its high boiling point it is easier to manipulate than tetramethylsilane (TMS) and it is therefore possible to prepare solutions of known concentrations. In order to convert the data obtained with this standard to the TMS scale, the chemical shift of HM was determined in 16 solvents using cyclohexane as external standard in a spherical cell (5% w/w concentration of HM) as a function of the solvent factor g2. Comparing these results with a similar plot obtained previously for TMS by other workers, it is possible to convert one type of data to the other by a simple linear expression.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 11 (1990), S. 471-476 
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple bead model is proposed for the antibody molecule immunoglobulin IgG1. The partial flexibility of the hinge is represented by a quadratic potential associated to the angles between arms. Conformational and hydrodynamic properties are calculated using Monte Carlo (rigid-body) and Brownian dynamics simulations. Comparison of experimental and calculated values for some overall properties allows the assignment of dimensions and other model parameters. The Brownian dynamics technique is used next to simulate a rotational correlation function that is comparable with the decay of fluorescence emission anisotropy. This is done with varying flexibility at the hinge. The longest relaxation time shows a threefold decrease when going from the rigid Y-shaped conformation to the completely flexible case. The calculations are in good agreement with the decay times observed for IgG1. A flexibility analysis of the latter indicates that a variability of ±55° (standard deviation) in the angle between the Fab arms.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Endorphin has been studies iin SDS micelles by one- and two-dimensional nmr spectroscopy (1D and 2D nmr), and to explore the influence of peptide length and composition on the polypeptide structure, the investigation was extended to a number of fragments. The nmr results are compared with those obtained from CD experiments and discussed in terms of a secondary structure that involves the central region of β-endorphin.
    Additional Material: 11 Ill.
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