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  • Chemistry  (296)
  • Chemical Engineering  (35)
  • Cell & Developmental Biology  (34)
  • Wiley-Blackwell  (330)
  • 1975-1979  (330)
  • 1977  (330)
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  • Wiley-Blackwell  (330)
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  • 1975-1979  (330)
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  • 1
    Electronic Resource
    Electronic Resource
    Vibrational modes of A-DNA, B-DNA, and A-RNA backbones: An application of a green-function refinement procedure (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2491-2506 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Normal vibrational analysis was carried out for DNA molecules in both A and B conformations as well as for A-RNA. A simplified backbone model was examined and expanded to include the backbone phosphate-group and the ribose ring. We applied the new force-constant refinement procedure discussed in the preceeding paper [Van Zandt, L. L., Lu, K.-C. & Prohofsky, E. W. (1977) Biopolymers, 16, 2481-90] to fit some observed frequencies in the Raman spectra for all three nucleic acids with the same set of force constants. The results indicate that the observed frequency shift can be attributed to the conformational change solely. We ignored the second-order differences in force constants for the different geometries. The agreement between the observed and calculated frequencies derived from the final refined set of force constants is good and apparently justifies this assumption. Two modes previously assigned to the symmetric diester O-P-O stretch and the symmetric dioxy O‥P‥O stretch are actually fitted. They are mainly backbone phosphate-group modes. The refined ribose-ring force-constants were transferred to the calculation of the vibrational spectrum of tetrahydrofuran. The overall agreement is again good. We discuss these calculations and the resulting normal modes. We also discuss the application of the Green-function refinement scheme and several strategies adopted to bias the convergence of the procedure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360161112
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  • 2
    Electronic Resource
    Electronic Resource
    Helix coil transitions of d (A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n; evaluation of parameters governing DNA stability (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1115-1137 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermally induced helix-coil transitions of three A-T DNAs, d(A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n, were studied. Experimental transition curves of the DNAs were analyzed using the loop entropy model of DNA melting. The calculation of the melting curve of d(A-A-T)n·d(A-T-T)n is presented using the integral equation formalism of Goel and Montroll. The aim of this work was to evaluate thermodynamic parameters which govern DNA stability and to test the theoretical model employed in the analysis. Our results show (1) an excellent over-all agreement between theory and experiment, (2) a loop entropy exponent k = 1.55 ± 0.05 provided the best fit to all the polymer transition curves, (3) the evaluated stacking free energies reflect the relative stability of the DNAs, and (4) the stacking energies of the ApA·TpT dimer evaluated from d(A)n·d(T)n and d(A-A-T)n·d(A-T-T)n differ. The last result is consistent with different conformations for the dimer in these two polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160512
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanics of the syrinx in Gallus gallus. II. Electromyographic studies of Ad Libitum vocalizations (1977)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 152 (1977), S. 1-19 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Records of electrical activity in the tracheal muscles of domestic chickens were obtained for a variety of ad libitum vocalizations. Primary attention was given to an analysis of events during the most complex call, crowing.Three pairs of muscles, Mm. tracheohyoideus, tracheolateralis, and sternotrachealis, can affect the configuration of a chicken's syrinx. The firing patterns of the three muscle pairs are related to their different abilities to affect the tension of the syringeal membranes. The influence of M. tracheohyoideus is most indirect and imprecise, and its role the least clearly defined. It appears to adjust the position of the trachea so that the syrinx is isolated from unpredictable and/or undesirable consequences of nuchal position and tracheal elasticity, and also helps draw the glottis caudad, thereby deepening the pharyngeal chamber. The other two muscles interact to control the tension of the vocal membranes. M. sternotrachealis relaxes the membranes by drawing the drum of the trachea caudad, or, via the syringeal ligament, by rotating the pessulus cranioventrad, or both. M. tracheolateralis tenses the membranes and/or prevents caudal movement of the origin of M. sternotrachealis, a necessity if the syringeal ligament is to rotate the pessulus.Vocalization depends on both syringeal configuration and appropriate air flow. Hence, tracheal muscles, syrinx, air sacs, and ventilatory muscles cooperate to form a vocal system. Cooperation elicits a surprising degree of redundancy. At least one call, a high pitched wail, may be produced by two very different techniques.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051520102
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  • 4
    Electronic Resource
    Electronic Resource
    Branching and molecular weight distribution of polyethylene SRM 1476 (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 2833-2845 
    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: A method of determining the distribution of branching in a polymer is developed employing limiting viscosity numbers (intrinsic viscosity), gel permeation chromatography (GPC), and absolute molecular weight determinations of fractions of the whole polymer. A molecular weight calibration of the GPC column set is first determined empolying these fractions. From the limiting viscosity number measurements of these fractions and their molecular weight distribution determined from the GPC chromatogram, the viscosity-molecular weight relationship is determined by a nonlinear least-squares fitting procedure. For the same molecular weight, the limiting viscosity number of the branched polymer is less than the limiting viscosity number of the linear polymer. From the ratio of the two, the number of branches per unit molecular weight of the branched polymer is calculated. The method was applied to SRM 1476, the standard reference branched polyethylene issued by the National Bureau of Standards. The branching density for the constituents of SRM 1476 rise from zero at molecular weights less than 10,000 to about 6 to 8×10-5 at molecular weights of 50,000 and above. The branching of SRM 1476 was also determined by the method of Drott and Mendelson, giving a result in fair agreement with the above method.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070211019
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure drop, gas hold-up, and oxygen transfer in tower systems (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 247-265 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pressure drop, gas hold-up, and oxygen transfer were investigated in a sieve tray column, a column with Koch motionless mixers, and a bubble column. The oxygen transfer experiments were conducted using cocurrent flow of gas and liquid under steady-state conditions with oxygen transfer from the gas to the liquid phase. The oxygen transfer rates and efficiencies of the sieve tray column and the column with Koch mixers were found to be superior to those of the conventional bubble column. Gas hold-up was also greater when sieve trays or Koch mixers were inserted in the tower. The pressure drop was found to be primarily due to the liquid head in all three columns.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260190208
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  • 6
    Electronic Resource
    Electronic Resource
    Oxygen transfer and axial dispersion in an aeration tower containing static mixers (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 493-505 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxygen transfer from gas to liquid under steady-state cocurrent flow conditions was modeled using the dispersion model, and the oxygen transfer coefficients were estimated from available data for a column with Koch motionless mixers. The dispersion in the column was estimated for several different gas and liquid flow rates using steady-state tracer experiments. The estimated oxygen transfer coefficients were compared with those estimated using complete mixing and plug flow models. The results indicate that the dispersion model is the most appropriate model for estimating the mass transfer coefficient from the available data.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260190405
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  • 7
    Electronic Resource
    Electronic Resource
    Inhibitoren der Korrosion 20(1)-Über die zeitliche Abhängigkeit der analytischen Zusammensetzung der Korrosionsprodukte des Eisens von der Menge an verbrauchtem Sauerstoff (1977)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 28 (1977), S. 478-480 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Analytical composition of the corrosion products of iron as a function of time and of the oxygen consumedUsing a modified standard method of analysis it is possible to analyze mixtures containing Fe0, Fe2+ and Fe3+. This method is used to study corrosion systems catalyzed by chlorides. According to the results obtained the amount of Fe2+ is approx constant at pH 7, irrespective of the oxygen quantityt consumed, Fe0 being oxidized to give Fe2+ and the latter being oxidized, at a comparable rate, to give Fe3+. At pH 3, however, Fe2+ is obtained almost exclusively, and beyond pH Fe3+ becomes predominating.
    Notes: Mit einer modifizierten Analysenmethode ist es möglich, Gemische mit Fe0, Fe2+ und Fe3+ zu analysieren. Diese Methode wird zur Untersuchung von Systemen mit chloridkatalysierter Korrosion benutzt. Nach den Ergebnissen ist die Fe2+-Menge bei Ph 7 unabhängig von der verbrauchten Sauerstoffmenge annähernd konstant, da Fe0 zu Fe2+ und dieses weiter zu Fe3+ oxidiert wird. Die Geschwindigkeiten dieser Reaktionen sind vergleichbar. Bei pH 3 erhält man nur Fe2 und ab pH 4 wird Fe3+ vorherrschen.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19770280705
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  • 8
    Electronic Resource
    Electronic Resource
    A new procedure for refining force constants in normal coordinate calculations on large molecules (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2481-2490 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We develop a force-constant refinement procedure which we believe capable of being used in problems of large molecules and biopolymers. The procedure is based on a Green-function expression which relates changes in frequency to changes in force constants. The method does not require that assignments be made before refinment (although they may be). An expansion of this expression gives rise to a set of linear algebraic equations for the force-constant corrections, rather than an equation involving residuals to minimize. The resulting calculations are considerably simpler. This approximate is iterated to find the final refined force-constants. We discuss several methods of improving the convergence of the procedure which take into account the experimental information which may be available. Of particular interest is a scheme to select the force constants to be refined by imposing a criterion for selecting those which will fit the experimental data with the smallest changes of the force constants from their expected values. We discuss some limitations which occur for all methods of refinement applied to large molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360161111
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  • 9
    Electronic Resource
    Electronic Resource
    Antioxidants and stabilizers. LXVI. Oxidation and photooxidation of methyl- and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionates. quenching of singlet oxygenPart LXV: L. Taimr and J. Pospíšil, this journal 52 (1976) 31. (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 65 (1977), S. 197-210 
    Details
    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: Die Cyclohexadienonhydroperoxide IIIb und IIIc entstehen durch methylenblau-sensibilisierte Photooxidation von Methyl-(IB) und Octadecylester (Ic) der 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionsäure. Die Reaktion verläuft über den Singulett-Sauerstoff. Es wurde die photochemische Stabilität der beiden Hydroperoxide in Anwesenheit und Abwesenheit des Sensibilisators verfolgt. Beide Hydroperoxide spalten sich thermisch unter Bildung der Ausgangsphenole Ib bzw. Ic. Die verbindung IV, die einen wirksamen Quencher (Löscher) von Singulett-Sauerstoff darstellt, entsteht durch die Oxidation von Ib mittels Bleidioxid. Sie nähert sich in ihrer Wirkung dem β-Karotin. Die Verbindung IV ist gegen weitere Oxidation im neutralen Milieu beständig. E wurden die Umwand-lungen von Ib und Ic im Hinblick auf die Prozesse, die während der Alterung von stabilisierten Polyolefinen verlaufen, verfolgt.
    Notes: Photooxidation of the methyl ester (Ib) and octadecyl ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid (Ic) sensitized with methylene blue gives rise to cyclohexadienone hydroperoxides IIIb or IIIc. The reaction proceeds via singlet oxygen. The photochemical stability of both hydroperoxides was examined in the presence and absence of sensitizer. The thermal decomposition of both hydroperoxides leads to the respective starting phenols Ib or Ic. Oxidation of Ib with lead dioxide yields IV, an effective quencher of singlet oxygen, the effect of which approaches that of β-carotene. In a neutral medium Iv is stable against oxidation. The transformations are investigated with respect to the system of processes occurring in the aging of stabilized polyolefins.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1977.050650114
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  • 10
    Electronic Resource
    Electronic Resource
    Glass bead-filled polypropylene part I: Rheological and mechanical propertiesPresented in part at the 34th ANTEC Soc. Plastics Eng., April 26-29, 1976, Atlantic City, N. J. (1977)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 657-665 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Five glass bead-filled polypropylene composites were rheologically characterized at 240°C using two rotational rheometers to obtain low shear-rate data and a capillary rheometer to obtain high shear-rate data. Both steady and dynamic properties were measured at low shear rates. Each composite was also injection molded into tensile and flexural test bars for a mechanical properties profile at 25°C. The tensile modulus was determined from a simple extensional deformation whereas the flexural modulus was determined from a three-point-bend test.The relative shear viscosity and relative loss modulus are different nonlinear functions of the volume fraction of beads at a constant shear rate, while the relative storage modulus appears to be a linear function of bead fraction. The relative viscosity decreases with increasing shear rate and the zero shear-rate data are in very good agreement with the Guth-Gold equation.The relative tensile modulus and relative flexural modulus are each linear functions of bead fraction over the entire range of filler concentration, 0-29 vol percent. From these data it is concluded that a simple correspondence between slow viscous flow and small strain elasticity does not exist for these composites.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760170902
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