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  • Chemistry  (1,889)
  • Chemical Engineering  (260)
  • Inorganic Chemistry
  • 1970-1974  (1,889)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    A cooperative molecular weight distribution test (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 269-282 
    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 development of gel permeation chromatography (GPC) has provided a convenient tool for the rapid determination of molecular weight distribution. The question has arisen as to the suitability of the method for specification purposes. The present work, suggested by the Naval Air Systems Command, represents an attempt to assess the precision of the method through a series of tests carried out by a number of laboratories using identical procedures on the same samples. Ten laboratories agreed to take part. Naval Ordnance Station, Indian Head, worked out standard conditions for operation of the chromatograph, for calibration of the columns, and for analysis of the GPC curves. Two samples of polystyrene were used by the various organizations for calibration of their instruments. Number-average molecular weight, heterogeneity index, and cumulative molecular weight distribution curves were determined on four samples of carboxyl-terminated polybutadiene (CTPB) and two samples of hydroxyl-terminated polybutadiene (HTPB), all unidentified except by letter code. All laboratories used identical directions for setting up CTPB and HTPB calibration curves which were based on curves determined from vapor-pressure osmometer molecular weights and GPC count numbers of fractionated material. Variation among the different laboratories was 0.15 in heterogeneity index, and a maximum of 1200 in molecular weight provided one aberrant set of values was eliminated. The six samples had heterogeneity indices from 1.15 to 1.54, while molecular weight varied from approximately 3000 to 6000. The average coefficient of variation of the molecular weight values was 6.2 ± 0.7%, which is quite acceptable. Variation in heterogeneity index was too great for specification purposes when considered among the different laboratories, but may be sufficiently good when measured by any one laboratory.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070170121
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  • 2
    Electronic Resource
    Electronic Resource
    Structural components of alginic acid. II. The crystalline structure of poly-α-L-guluronic acid. Results of X-ray diffraction and polarized infrared studies (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1879-1887 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A structural investigation of the marine algal polysaccharide poly-α-L-guluronic acid is described. The molecular chains consist of 1 → 4 diaxially linked L-guluronic acid residues in the 1C chair conformation and are stabilized in a twofold helix conformation by an intra-molecular O(2)H … O(6)D hydrogen-bond. The X-ray fiber diffraction photograph has been indexed to an orthorhombic unit cell in which a = 8.6 Å, b (fiber axis) = 8.7 Å, c = 10.7 Å.A structure corresponding to the space group P212121 is proposed, in which all intermolecular hydrogen bonds interact with water molecules and in which all oxygen atoms except for the inaccessible bridge oxygens are involed. The relationship between the shape and structure of the polyguluronic acid molecule and its biological function is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120814
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  • 3
    Electronic Resource
    Electronic Resource
    Structural components of alginic acid. I. The crystalline structure of poly-β-D-mannuronic acid. Results of X-ray diffraction and polarized infrared studies (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1865-1878 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Structure determination of the naturally occuring marine algal polysaccharide poly-β-D-mannuronic acid is described. The structure consists of 1e → 4e linked D-mannuronic acid chains with the monosaccharide units in the C1 chair conformation. The X-ray fiber diffraction photograph obtained from bundles of fibers prepared from Fucus vesiculosus has been indexed to an orthorhombic unit cell in which a =7.6 Å, b (fiber axis) = 10.4 Å, c = 8.6 Å, the unit cell containing two disaccharide chain segments with space group P212121.A sheet-like structure involving one intra-chain, one intra-sheet, and one inter-sheet hydrogen bond per monosaccharide is proposed. Features of the chain-packing arrangement are compared with mannan.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120813
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  • 4
    Electronic Resource
    Electronic Resource
    Hollow fiber membrane oxygenator (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 135-148 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hollow fibers have been produced and evaluated for use as membrane oxygenators in an artificial heart device. Gas permeable capillaries now commercially available are unsuitable for this use because of: (1) low percent open cross-sectional area, (2) large internal diameter, and (3) high cost. A number of polymers were initially selected for evaluation because of their reported high gas permeabilities. Those selected include a number of rubbers of various compositions, certain poly-α-olefins and an experimental thermoplastic silicone rubber copolymer. These materials were first evaluated as flat membranes (films) for their gas permeabilities and also for ease of preparation in hollow fiber form. Hollow fibers were prepared from the most promising of those studied, poly-4-methylpentene-1 and the thermoplastic polydimethylsiloxane copolymer. Fibers, ranging in the size from 30 to 300 μ ID, were spun with open cross-sectional areas of 40-65%. Oxygen and carbon dioxide permeabilities measured on these fibers were compared to that of SilasticDow Corning medical grade poly (dimethylsiloxane). rubber membranes. These permeabilities range from 1/20 that of Silastic rubber for unmodified poly-4-methylpentene-1 to 2/3 for the thermoplastic silicone copolymer. Modification of poly-4-methylpentene-1 has made it possible to increase it's permeability by tenfold, while still maintaining physical properties necessary to spin and fabricate this material.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050214
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  • 5
    Electronic Resource
    Electronic Resource
    A new absorbable suture (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 43-58 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although satisfactory nonabsorbable sutures made from a variety of synthetic and natural materials have been available for a number of years, since ancient times only collagenous absorbable sutures have found general acceptance. While adequate, catgut and the more recently developed regenerated collagens have inherent disadvantages common to many complex natural substances, particularly variability in composition and properties.A new synthetic absorbable suture has been developed from polyglycolic acid .This material was chosen after testing a wide variety of polymers for the appropriate absorbability behavior in animals and for the required physical and mechanical properties. Polyglycolic acid suitable for this use was most conveniently prepared by the ring opening melt polymerization of glycolide. Development of a reliable process for this commercially unavailable monomer led to the discovery of the existence of two glycolide polymorphs one of which exhibits erratic polymerization behavior after exposure to trace amounts of moisture.Polyglycolic acid was converted into fiber by melt extrusion, stretching, and heat setting. Braided sutures prepared from these fibers exhibit high strength, excellent handling properties, minimal tissue reactivity, and a similar but more reproducible absorption rate than catgut. Clinical studies with these sutures are in progress.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050207
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  • 6
    Electronic Resource
    Electronic Resource
    Mass spectra of the substituted quinuclidines (1970)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1970), S. 1023-1029 
    Details
    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 the quinuclidine-2 (and -3)-ones and other functional derivatives of quinuclidine as well as 2-azaquinuclidine and benzoquinuclidine have been investigated. The fragmentation through the open form of the molecular ion and the applicability of Bredt's rule to amine fragmentation of the bridgehead nitrogen bicyclic systems are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210030805
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  • 7
    Electronic Resource
    Electronic Resource
    Crystalline structures of poly-D-mannuronic and poly-L-guluronic acids (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 9 (1971), S. 311-316 
    Details
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.110090411
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  • 8
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance and optical spectroscopic studies of block copolymers of polypeptides. I. Block copoly[(benzyl-L-glulamate)n: (benzyl-L-aspartate)m] (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2555-2568 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a study of A-B type block copolymers of γ benzyl-L-gultamate and β-benzyl-L-aspartate use has been made of the observations: (1) that for poly aspartate esters the chemical shifts of the α-CH and NH resonances are sensitive to the helix sense, (2) that in both helical and random coil conformations the same resonances of poly-γ-benzyl-L-glutamate are well separated from those of poly aspartates. Since the sense of poly-β-benzyl-L-aspartate is very sensitive to the inclusion of γ-benzyl-L-glutamate residues, the degree of overlap between the blocks can be studied by monitoring the helix sense of the aspartate. The ability of the NMR method to make separate observation of the two blocks removes the necessity of relying on an overall ORD parameter such as b0. The copolymers studied include those having lefthanded, righthanded, and mixed-sense aspartate, corresponding to differing degrees of overlap.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360101215
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  • 9
    Electronic Resource
    Electronic Resource
    Physico-chemical description of a condensed form of DNA (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 443-459 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When exposed to a low pH, in various ionic strength conditions and in sufficiently dilute solutions, DNA undergoes a transition, revealed by an increase in optical density. A careful analysis shows that, associated with this transition, there is an effective decrease in absorbance, overcompensated by an increase in scattering. The conditions for the new transition can be summarized conveniently by a graph in a pH-Na+ molarity diagram. If the pH of a DNA solution is progressively lowered at constant Na+ concentration, one finds first the melting transition (I), and at lower pH values, the new transition (II). If the same experiment is performed on pre-denatured DNA, only transition II will be found. If native DNA is brought directly to the low pH conditions, without allowing it to denature irreversibly at intermediate pH values, transition II is reversible (with a small hysteresis effect). DNA, initially native, neutralized after prolonged exposures to the low pH, recovers the buoyant density value of native DNA, along with the absorption and scattering properties of the native state. The experiments are consistent with the interpretation that a new state exists in which DNA, still double stranded, assumes a very compact shape (of the order of 1500 Å in diameter for T2 DNA), with a hyperchromicity value of 10-14% above the native value. Nearly monodisperse suspensions of DNA molecule in this apparent state may be obtained only at very low concentrations (∼0.25 μg/ml). At 1 μg DNA/ml aggregation is noticeable. The possible connection with the condition of intraphage DNA is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110210
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  • 10
    Electronic Resource
    Electronic Resource
    Optical properties and base pairing of E. coil 5S RNA (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1031-1039 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ultraviolet absorption, optical rotatory dispersion, circular dichroism, and infrared absorption spectra of renatured 5S RNA have been measured at pH 7.0 in 0.1M NaCl at 25° and used to obtain four independent estimates of the number of base pairs. These four estimations are in reaonable agreement and average values of 28 ± 4 G.C and 13 ± 4 A.U. base pairs.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110508
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