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  • Artikel  (350)
  • Physics  (220)
  • Analytical Chemistry and Spectroscopy  (130)
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  • 1
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The Philips PW 1450/00 or /10 automatic hardware-programmed X-ray spectrometer, when used in conjunction with the PW 1466 60 position sample loader, permits measurement of both standard and unknown using the same channel only when the ratio mode is selected. Further, a standard must be measured for every unknown. An electronic modification is described which overcomes both of these restrictions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 13-18 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The theoretical relationships between fluorescence intensity and concentration have been used for the calculation of correction constants of the Lachance--Traill and Rasberry--Heinrich equation for systems of solutions. The constants have also been calculated by means of the multivariate least--squares method. Those two alternatives have been tested on systems of Cu--Fe--Zn and Cu--Fe--Zn--Pb in 3.5% aqueous nitric acid and compared with the simple two-variable linear relationship between fluorescence intensity and concentration. The multivariate least--squares alternative gives for the Lachance--Traill method very accurate results (average relative deviation does not exceed 0.18%). In a theoretical discussion, the relationship between optimum sample concentration and solvent correction (enhancement) constant is shown. The optimum conditions for a background reading are also calculated.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 77-80 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The X-ray K absorption edges of Co in some 1,10 phenanthroline-based complexes of cobalt have been recorded. The results have been discussed qualitatively in terms of the effective nuclear charge on the central metal atom and the nature of the ligand.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 95-95 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 96-100 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The use of the multiple linear regression program for the derivation of influence coefficients destroys the data bank in the Philips PW 1450/10 spectrometer computer and interrupts analysis. Consideration of the basis of α-coefficients as applied to relatively dilute solutions leads to methods of avoiding the use of this program. Linear regression involving a single independent variable and simple algebraic expressions can be used to derive the coefficients. The requirements for converting α-coefficients applicable to one solvent for use in a different solvent are described.
    Zusätzliches Material: 2 Tab.
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  • 6
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Fifty pairs of window/non-window glasses, the samples in each pair being matched in refractive index to the fourth decimal place, have been analysed using energy-dispersive X-ray fluorescence spectrometry. The spectra, from 200μg fragments, were compared using a computer based multi-dimensional data processing system. Forty-three pairs of glasses were readily discriminated and forty-nine pairs showed significant differences at about the 5% level. The spectral data for the 100 glass samples were then examined graphically for trends in the elemental levels between the window and non-window glasses. This led to the construction of two linear combinations, namely the peak area ratio (to calcium) of iron with that of magnesium and the peak area of arsenic with refractive index. When plotted against each other these linear combinations and a selection rule allowed 95% of the glasses to be correctly classified.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 134-137 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Beschreibung / Inhaltsverzeichnis: A method for quantitative microprobe analyses of geological samples (silicates and carbonates) is described. In the case of silicates for total analysis the need is to detect simultaneously more than 10 chemical main- and minor-constituents. For this purpose two experimental possibilities are available: (a) automatic control of the crystal scanners (sequence control); (b) combination WDS/EDS (wavelength-dispersive and energy-dispersive system). These two possibilities are discussed. Technical notes of the equipment and the analytical method are described in detail. High analytical precision can be obtained.
    Notizen: Es wird eine quantitative Analysenmethode für geologische Proben (Silikate and Karbonate) mittels Röntgenmikrosonde beschrieben. Im Falle von Silikaten sind fur eine Totalanalyse mehr als 10 chemische Elemente simultan zu erfassen (Haupt-und Nebenelemente). Zwei experimentelle Moglichkeiten sind realisierbar: (a) Automatischer Sequenzbetrieb mittels Kristallspekrometern; (b) Kombination WDS/EDS (wellenlangendispersives und energiedispersives System). Diese beiden Möglichkeiten werden diskutiert. Technische Angaben und apparativer Aufwand werden beschrieben. Es wird dargelegt, auf welche Weise eine hohe analytische Genauigkeit erreicht werden kann.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 143-145 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The spectral photon distribution from X-ray tubes operated at constant potential is compared to the distribution resulting from self rectification circuits. Kramers' equation is modified by calculating the average values of the photon flux during one period of voltage fluctuation and the results are used to transform Gilfrich and Birks' experimental tube spectra to those expected from a half-wave rectification circuit. The effect of using both constant potential and sine wave potential, as well as constant potential with overlaid sine wave ripple, is discussed. Results are shown by using experimental data from Ag-Au-Cu alloys and ‘no standard’ methods (data evaluation without reference specimens).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 153-153 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 163-169 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The qualitative and quantitative composition of technical aluminium phosphide was studied employing X-ray electron spectrometry, X-ray fluorescence analysis and X-ray diffractometry as well as gravimetric and gas volumetric methods. In addition to aluminium phosphide, AIN (8%), Al(1%) and Al(OH)3 (10%) were found. Al(OH)3 is produced by the reaction of AlP with H2O. Models describing this reaction in humid air and allowing for quantitative analysis are presented.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 146-149 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Theory and experimental results from X-ray fluorescence analysis without standards are presented. The composition of an unknown specimen is calculated from its count rates without the use of standard specimens. A fast algorithm employing linear approximation techniques uses these normalized count rates as start values for the concentrations and delivers final results usually after the second or third iteration. Accuracy is typically around 10% relative and can be improved by system calibration with standards of arbitrary composition.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 150-152 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The construction of a demountable X-Ray tube with focal spot scanning intended for operation as an X-ray source in scanning X-ray microscopes is described.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 206-211 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Multielement thin film standards are made by mixing a solution of different elements and a radioactive tracer (24Na) with the water soluble polymer mehtylcellulose. A film is produced by spreading the liquid mixture evenly on glass plates and letting it dry. Standards of the desired size and shape are punched out. The concentrations of the elements are calculated from the tracer activity. Ten sets of standards containing the elements Na, Mg, Al, Si, P, S, Cl, K, Cs, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ag, Cd, Sn, Sb, Ba and Pb in different groupings have been prepared. Homogeneity and accuracy oof the standards are extensively discussed. The accuracy is also estimated by the alalysis of the standards using several techniques. The precision of the analysis factors derived from the standards is better than 1-2%, while the accuracy for the elements Al, Cl, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Sb, Ba and Pb is found to be better than 5%.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 110-118 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The ways in which the usefulness of the electron probe X-ray microanalyser is extended by computer control and the demands imposed on the computer operating system by a general purpose electron probe are discussed. Three main modes of operation are identified and a flexible operating system to meet the main requirements for these modes is described. Examples of the use of the system are given with particular emphasis on two applications which could not be tackled easily with a manually operated system: composition surveys over large areas of the sample and digital mapping techniques.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 126-133 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A detailed study of energy-dispersive X-ray spectra is undertaken. Considerable attention is given to a method for a systematic and accurate description of the K and L spectra; a digital correction for the peak profile is evaluated. The following second order effects and spectral artefacts are investigated: radiative Auger transitions, spectral background components, Raman scattering of X-rays, silicon escape, fluorescence of the detector materials, and sum peaks.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 138-142 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Small amounts of particulate matter electrochemically extrated from super-alloys were accurately analysed by X-ray fluorescence spectrometry with pure element bulk standards. The extracts are less than a few hundred micrograms per square centimeter and are not homogeneous. They are approximated by a thin film on a filter substrate. The penetration of the particulates into the membrane filter on which they are mounted is negligible and no absorption correction for the filter is required. The spectral distribution of the X-ray source used in the calculation was obtained from Kramer's formula with self-absorption correction for the continuum and from measurements of the characteristic line. The intensity-concentration algorithm is based on the fundamental parameter method; the calculation is simplified because no matrix correction is required if the relative intensities are less than or equal to 0.04. The method gives excellent results in chemical analyses.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980) 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 159-162 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The emission intensities of K X-rays from a number of activation products have been calculated from the known absolute γ intensities, K capture data and internal conversion coefficients of the radionuclides and the fluorescence yields of the daughter products. The calculated X-ray intensities of a few isotopes are compared with those experimentally reported. The X-ray spectrometry of activation products could usefully supplement the γ-ray spectrometry in the instrumental neutron activation analysis and in such cases the data presented here will be of value.
    Zusätzliches Material: 3 Tab.
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  • 19
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 184-188 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The paper reviews recent developments in energy-dispersive X-ray detectors and attempts to assess their relevance to industrial process control requirements.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1125-1136 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Dielectric relaxation of polyacrylonitrile (PAN) samples, in which the presence of an amorphous phase is evidenced by x-ray diffraction, has been studied over the temperature range 30-150°C and frequency range 102-105 Hz. These data as well as those reported by other authors, reveal several points useful to the understanding of the dielectric relaxations of PAN in relation to its structure. A glass transition in PAN is evidenced by at least two of the four data sets investigated; the third shows combined effect of two relaxations, whereas the fourth clearly shows a relaxation process different from the glass transition. The glass-transition behavior of the dielectric relaxation data is confirmed by Williams-Landel-Ferry theory and a recent theory of Phillips, both of which lead to consistent conclusions.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1175-1186 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The flexibility of some polyimide chains has been studied theoretically as a function of the chemical structure of the repeat unit. It has been shown that the thermodynamic flexibility can be varied over a wide range by the choice of the unit structure. For three polyimides, as an example, the flexibility of cyclochain structures approximates that for free rotation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1237-1242 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Electron microscopy reveals a high-temperature morphological transition in a styrene-butadiene-styrene block copolymer of 7000 polystyrene block molecular weight and 43,000 polybutadiene block molecular weight (7S-43B-7S). Samples quenched in liquid nitrogen from temperatures above 150°C show no structure, whereas those quenched from temperatures below 140°C clearly show a multiphase structure. We previously reported that the 7S-43B-7S polymer exhibits a relatively sharp melt rheological transition in the temperature region between 140 and 150°C from highly viscoelastic and nonlinear viscous behavior to linear viscous behavior with insignificant elasticity. The dynamic viscoelastic properties are measured at different strain amplitudes in this study, and the results show that the melt rheological transition behavior is not influenced by the strain amplitude. This study clearly shows that the melt rheological transition in the 7S-43B-7S results from a morphological transition from a multiphase structure below about 140°C to a single-phase structure above about 150°C.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1103-1124 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A model of simple molecule sorption in polymers is proposed which embraces both the glassy and rubbery regions, and incorporates the successful dual-mode model below the glass-transition temperature. Hole filling is shown to be an important sorption mechanism both above and below Tg, although saturation effects do not occur in the rubbery polymer. The model interprets the “dual-mode” Langmuir and Henry's law parameters at the molecular level, and a simple statistical mechanical analysis allows estimation of the parameter values, as well as specifying certain interrelationships between the parameters. Applications of the model to gas solubility data in five polymers are considered [polyethylene (PE), poly(ethylene terephthalate) (PET), polystyrene (PS), polymethacrylate (PMA), poly(vinyl acetate) (PVAc)] and semiquantitative agreement is obtained for PE, PET, and to a lesser extent, PS. For PMA and PVAc, the agreement is qualitative only.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 24
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Wide-angle x-ray relaxation studies were performed on films of low- and high-density polyethylene (PE). The samples were rapidly stretched by a pneumatic stretcher and held at a fixed length. The rate of crystal reorientation was monitored by measuring diffracted intensity changes using a count-rate meter with output displayed on a storage oscilloscope as well as a digital counter-timer. Experiments were completed at several temperatures and activation energies comparable to those reported for the α1 relaxation in PE were obtained.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 5-7 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The problem of estimating the chemical composition of small particles of a phase in a matrix of another occurs in a number of fields. The introduction of electron beam microanalytical techniques has made it possible to analyse a volume of 10μm3. In spite of this advancement the chemical composition of the particles themselves is difficult to determine. This difficulty arises from uncertainty as to the full containment of the analysed volume by the particle being analysed. In this paper a statistical approach to establish the chemical composition of the particles themselves has been proposed. This approach is particularly useful when the particles and the matrix have a common element. Two examples are given, one with components of known compositions and another with a component of an unknown composition.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 19-24 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A method is presented for determining the relative amounts of Nb and Ge in thin films of approximately 1 μm thickness which have been deposited onto polycrystalline substrates. Quantitative X-ray fluorescence is employed using an energy-dispersive solid state detector and multichannel analyzer system. The principal problem encountered is one of calibrating the observed Ge/Nb intensity ratios in terms of atomic composition. We have used solution standards for comparison with the spectrum of selected dissolved films. The absolute compositions in the region of 25 atomic percent Ge are believed accurate to ±1 atomic percent absolute.
    Zusätzliches Material: 3 Ill.
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  • 27
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 32-35 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A set of most probable Kβ/Kα values estimated on the basis of all available experimental data is presented.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980) 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 40-47 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: We present results of X-ray fluorescence measurements on the Shroud of Turin. Quantitative estimates are given for the observed trace quantities of calcium, iron and strontium, and detection limits are established for other elements of potential interest. The calcium and strontium appear as uniform background distributions. Iron traces are observed in all of the data spectra but their local concentrations vary. Comparisons between image and off-image areas reveal no differences, within the precision limits of the data, that would indicate the presence of pigments or dyes containing high-C elements. In ‘blood’ stain regions the measurements show significantly higher concentrations of iron. However, the data do not allow a unique identification of the stain's origin. Quantitative comparisons are made between the shroud results and similar measurements on whole blood and Fe2O3 stains.
    Zusätzliches Material: 9 Ill.
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  • 30
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 52-56 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: In X-ray fluorescence analysis the concept of radiometric diameter, d, is often introduced in considerations of the fluorescent intensity from a particulate sample. It represents the mean geometric path of the X-rays through one particle and is usually simply taken to be equal to the volume-to-area ratio of the particle. The effective radiometric path is, however, itself dependent on geometry and absorption effects. Rigorous calculations of the fluorescent intensity from a particle in the π and π/2 geometries were carried out to evaluate the errors involved. It appears that, for π geometry, the discrepancy between these exact results and the intensity calculated via the use of d does not exceed 5.2%. For the π/2 geometry, the errors are much larger and can amount to 50% in realistic cases of X-ray fluorescence analysis. These conclusions are also applicable to monolayers. The effective radiometric diameter approaches d only when absorption effects become negligible, but is smaller in other cases.
    Zusätzliches Material: 6 Ill.
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  • 31
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 25-27 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A non-linear rise in intensity of copper Kα1 and Kα2 X-ray lines has been observed from certain areas of the polycrystalline copper target of a microfocus tube operated at tube currents between 0.1 and 0.5 mA and a tube potential of 13 kV. Under the same conditions the intensity rise of the bremsstrahlung is found to be linear. A functional relationship between total count and tube current has been obtained.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 39-39 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 33
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 60-65 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Methods are considered for optimizing a conventional Bragg--Brentano X-ray powder diffractometer for the identification of crystalline phases in airborne particulates deposited on membrane filters. The instrumental parameters investigated include detector stepping increment and scan range, Kβ filtration, and the incident beam divergence slit width. Sample-related factors such as substrate material (cellulose ester, polycarbonate and polytetrafluoroethylene), off-axis displacement of the sample and X-ray induced specimen degradation were also studied. Scan times for sample deposits of several hundred μcm-2 are in the vicinity of 24 h with an 800 W tube. These times may be reduced substantially by one or more of the following modifications: rotating anode or synchrotron radiation source, energy-dispersive diffractometry, and Bragg--Brentano diffractometry with a position-sensitive gas detector.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 34
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 70-76 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A method has been investigated which allows calculations from the X-ray fluorescence spectra of the absorption coefficients at any energy for any sample, without any additional measurement. Use is made of the ratio of the characteristic X-ray signals from a Zr wire positioned in front of the sample and from a Pd foil placed behind the sample, both in a fixed geometry. From the experimentally measured absorption coefficient at the Pd L energy (2.9 keV), the coefficients for higher energies are calculated. By the use of an iterative computer routine in which corrections for the enhancement of the Pd foil by the sample are also included, an accuracy of 2% or better on the absorption coefficient determination can be reached for homogenous samples in one measurement. Grain-size and heterogeneity effects induce inaccuracies on the absorption coefficient determinations which might well reach 20% for particulate samples like intermediate thickness deposits of geological materials. This approach thus has the same limitations as the classical transmission method for such heterogeneous samples.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 90-94 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: In charged particle induced X-ray emission studies, the characteristic X-rays are superimposed on a continuous background of electromagnetic radiation. This background is a significant source of uncertainty when charged particle induced X-ray emission is used for analytical purposes. It is demonstrated that the angular distribution of secondary electron bremsstrahlung exhibits significant structure and may be exploited to improve the detection limits attainable with this method. For low-energy continuum X-rays, good agreement is obtained with predictions of the relativistic retardation model. Deviations at higher photon energies are attributed to Compton scattered γ-rays. Finally, suggestions are made regarding optimum energy and angle selections for direct application of particle induced X-ray emission as an analytical technique, especially when biological samples are investigated.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 101-109 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A computer control system for an electron probe microanalyser has been designed using CORAL-66, a high level compiler language, for the control program and CAMAC modules for the instrument interface. The consequences of the choices made in the design are discussed. The performance of the system was measured by comparing the results from carrying out typical operations by hand and by computer control. The results showed an improvement in precision for general operation and analysis, a reduction in the time for analysis and an improvement in operator performance from using the control system.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 37
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 123-125 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A simple equation relating the intensity of characteristic X-ray lines to their respective weight fractions has been obtained for a thick sample excited by an isotopic source. It follows from the equation that a single intense line in a standard sample suffices to generate calibration constants over a wide range of elements. Validity of this aproach has been demonstrated by the analysis of a standard soil sample using only the Fe Kα line for calibration. A procedure for correction of peak overlaps has been given using the Kβ/Kα ratios, modified by the matrix effects. The method is very useful for the analysis of soil samples and can be conveniently applied to other matrices.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 57-59 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: To obtain intense linear polarized monochromatic X-rays a single crystal where Bragg reflection occurs at an angle 2θ=90° is used. A number of suitable crystal materials is listed which fulfil the requirements of the Bragg equation for the wavelengths of standard X-ray tubes and the angular condition. As the first result of a new construction a detection limit of 1 ng Ca was determined using a Cr anode and a Ta single crystal (002) plane as polarizer.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 39
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 66-69 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: This paper shows the employment of five X-ray methods for the investigation of a thickness range of 1 Å to 0.1 mm. The well known techniques (X-ray fluorescence and scanning electron microscopy) are treated, a new method (energy-dispersive X-ray diffraction) is discussed and X-ray photoelectron spectroscopy measurements are essentially improved by a new evaluation method. Low energy electron induced X-ray spectrometry is mentioned. As far as significance of the measured thicknesses is concerned, the range of 10--50 nm deserves special attention.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980) 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 41
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 195-197 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A first approximation indicates that fundamental alpha coefficients for a given analyte vary as a function of the ratio of their respective atomic number raised to a power. This simple rule applies mainly at the limits (i.e., when the weight fraction of analytei, wi is of the order of 0.0 or 1.0) in cases of absorption and weak enhancement. The relation thus provides a means of generating coefficients for the system i-k from experimental data obtained on system i-j and a means of verifying experimental alphas, since arrays of coefficients must show a high degree of concordance.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 42
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 48-51 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The operation of a computer system for producing on-line chemical analyses from a three-spectrometer JEOL JXA-5A electron microprobe is briefly discussed. A new method for acquiring the X-ray data by integrating the area under the peak is discussed in greater detail. The increased reliability of the results from this new method are illustrated by considering the effect of focus error on the measured count rates.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 43
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 28-31 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A non-destructive method for the determination of platinum in reforming catalysts and doped Venezuelan laterites employing a radionuclide, 8mCi of 109Cd, and a PDP-11/05 processor is presented. The total variation for 100s of fluorescent time is about 3% for a 10% Pt-reforming catalyst. The total variation can be reduced to less than 1% by increasing the fluorescent time so that about 80 000 counts or greater are accumulated. The platinum was determined using the Lα and Lβ lines of platinum, as well as their sum. The different types of variation for each of these measuring parameters is given. Finally, both the calculated and measured values for the prepared calibration standards and the doped Venezuelan laterites were in excellent agreement.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 36-37 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A new system for on-line X-ray topography is described, in which relative motions of separate assemblies are completely eliminated. The main elements of the system are a low-power raster-type X-ray source with a transmission target and a multi-capillary collimator. It takes about 2.5-3 min to produce a topograph of silicon single-crystal (20 × 20 × 0.3mm) when the radiation source power is only 10W.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 81-89 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Optimized multilayer X-ray spectrometry, using lead myristate and lead stearate analyzers (2d values of 80 and 100 Å) has been applied to the measurement of the O--Kα and the C--Kα spectral bands from CO and CO2 in the gas and solid phases. The LII, III spectra were also measured for argon in the gas and solid states under similar conditions in order to identify and to minimize any non-molecular components in the CO and CO2 spectra. These molecular orbital data have been related to those obtained with X-ray and ultraviolet photoelectron spectroscopy and grating X-ray spectroscopy. The consistency of the results of these complementary measurements is excellent. The ionization energies for the C and O 1s levels have been determined to be 295.4 and 542.0 eV for CO and 296.8 and 540.3 eV for CO2. The MO data have also been compared with that predicted from the symmetry, strength and binding energy of the molecular orbital spectral components as calculated using the currently available computational models, CNDO/2, MINDO/3, MNDO, extended Hückel and ab initio. The molecular orbital calculated results for these organic compounds, CO and CO2, are not in as good agreement with the experimental data as previously demonstrated for molecular orbital spectra measured for C--Kα and the LII, III bands of Cl, S and P for both organic and inorganic compounds.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 46
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980) 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 47
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 1-1 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 48
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 8-12 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Carefully polished samples of five austenitic stainless steels have been examined by reflected light microscopy and analysed, using a Link Systems model 290 KX energy-dispersive spectrometer attached to a Cambridge Instrument Company Geoscan microprobe. At least ten different spots within apparently homogeneous areas of each sample were analysed. While the means of these analyses agree well with the published values, three of the samples have an inhomogeneous distribution of their major elements. Precipitates within the samples are mainly MnCr2O4 and MnS, both with much substitution of the Mn by other elements. Other precipitates are rich in P or Nb. While such blocks are probably sufficiently homogeneous for use as bulk standards, great care should be exercised if they are to be used as microprobe standards. A small excess of silicon was found in most analyses. This is believed to be due to fluorescent excitation of silicon in the detector. Analyses of pure metals suggest that a correction of 0.12 wt % silicon should be applied.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 49
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Using the effective wavelength concept, it is derived theoretically that the reciprocal of the analyte-line intensity is linearly correlated with the reciprocal of the weight fraction of the analyte. This linear relationship is substantiated experimentally in some liquid and fusion product samples. Two ways of application of the relationship in X-ray fluorescence analysis and their advantages are also described. It is emphasized that if the relationship is used the construction of calibration curves is not required.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 154-158 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A procedure is presented for constructing calibration curves of X-ray fluorescence activity versus analyte concentration for finite multicomponent media. The composition must be known for all components other than the low-concentration analyte. If these compositions are not known, the system's mass absorption coefficient must be measured. The analyte must be present in low enough concentration so that it does not contribute significantly to the total mass absorption coefficient. The calibration curve for a multicomponent system is constructed numerically from data on analyte activity versus secondary component composition in binary systems (analyte plus one secondary component). Thus calibration curves for any system containing the analyte and n secondary components are constructed from data on the n corresponding binary systems. The method is found to reproduce measured activities of uranium solutions with an accuracy of 5-7%.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 51
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 170-175 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Beschreibung / Inhaltsverzeichnis: Hybrid X-ray fluorescence analysis is a method of determining the quantitative composition using one single standard specimen together with fundamental parameter calculations. The unknown concentrations are calculated from a set of differential expressions representing changes of the count rate as a function of changes in the composition. In the case of linear hybrid methods, this function is approximated by a linear equation. The paper is based upon the linear hybrid model introduced by Kramer, Ebel and Tschismarov. This linear model is modified for improved determination of low concentrations. In addition, a quadratic model is developed and theoretical values are compared to experimental results.
    Notizen: Das Konzept der hybriden Röntgenfluoreszenzanalytk ermöglicht die quantitative Bestimmlung einer Probenzusammensetzung mit Hilfe einzigen Standardpprobe und der Kenntnis von theoretischen Zusammenhängen im Sinne der fundamentalen Parameterrechnung. Die gesuchten Konzentrationen werden aus einem Differentialausdruck berechnet, der die Zählratenänderungen als Funktion von Konzentrationsänderungen beschreibt. Im Fall des Linermodells wird diese Funktion liner approximiert, im quadratischen Modell durch eine Funktion zweiter Ordnung. Die vorliegende Arbeit geht von dem Linearmodell aus, das von Kramer, Ebel und Tschismarov vorgestellt wurde und ergänzt es zur verbesserten Bestimmbarkeit kleiner Konzentrationen. Die Ergebnisse der Theoretischen Gegenöberstellung von linerarem und quadratischem Modell werden mit experimentellen Ergebnissen belegt.
    Zusätzliches Material: 5 Ill.
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  • 52
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 189-194 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Space resolved X-ray spectroscopy with a curved crystal X-ray spectrometer for an extended source such as the Tokamak is discussed. Limits of resolution caused by instrumental broadening are shown, using various entrance apertures. Ion density distribution may be obtained by measurement of intensity variation along spectral lines. In order to obtain ion temperature distribution about the central plasma line in the Tokamak, a novel method is proposed. In this method reflection in the curved crystal takes place through the double reflection process. This is possible as practically no instrumental broadening is caused when using this method, while it reflects the radiation in a strictly space resolved mode.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 53
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 9 (1980), S. 198-205 
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The use of an automated, software-controlled X-ray fluorescence spectrometer (Phillips AXS System)for analysis of geologic materials gives rapid, precise results. Fluorescence intensities are corrected for background and peak overlap and for mass absorption, and ratioed to a standard rock analyzed at frequent intervals. Major element determinations show precision and accuracy in the 0.5-3% range and are based on calibration with a wide variety of international reference rocks. Determinations for major elements are done on specially fused rock powders. Precision and accuracy for trace elements are generally in the 1-5% range. Calibration is also by use of reference rocks but the determinations are done directly on pressed rock powders.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1383-1391 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A novel planar ↔ nonplanar visual thermochromic conformational transition of polydiacetylene molecules in poor solvents is reported. The conformational transition is associated with both a color change (blue or red ↔ yellow) and a change in the state; the yellow solution (liquid) transforms to a blue or red gel (solid). The color transition occurs within a narrow range of temperature and has a large associated hysteresis. The enthalpy of the conformational transition is 29 kJ/mole of repeat unit. Fourier-transform infrared studies show that molecules acquire a planar conformation in red or blue gels by formation of intramolecular H bonds between the adjacent substituent groups. Virtually all H bonds break (a nonplanar conformation) when the gels turn into yellow solutions.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1393-1401 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Copolymerization reaction of hexafluoroisobutylene (HFIB) and vinylidene fluoride (VF2) was studied using X-band electron spin resonance (ESR) by applying a photo-in situ method. Owing to the toxicity of HFIB monomer, the flow ESR method could not be directly applied without extensive modification. The observed ESR signal with 21-line hyperfine structure was assigned to the copolymer radical with head-to-head configuration. Although the HFIB monomer radical possesses the same hyperfine pattern, the ambiguity has been removed by using CF3 as an initiator radical. Owing to the high steady-state concentration of the observed copolymer radical with head-to-head configuration as well as the nature of the static photo-in situ ESR method, we believe the actual molecular configuration for HFIB/VF2 copolymer must be head-to-tail. The observed hyperfine constant for AβF = 1.74 mT suggests that the geometry for HFIB/VF2 copolymer radicals with both head-to-head or head-to-tail configurations is possibly similar to that of (CF3)3C· radical. The small value for AβH indicates steric hindrance to rotation about the Cα—Cβ bond, and this is also supported by the experimental results of nonalteration in linewidth during the temperature dependence study from -40 to about 90°C. Attempts to measure directly the monomer reactivities have been unsuccessful owing to the fact that not all the possible radicals were detected, but nevertheless the relative reactivities of VF2 and HFIB could be estimated. The relative reactivities of VF2 and HFIB monomers and the steric hindrance effect indicate that the conformation of the copolymer is head-to-tail; this has been further confirmed by infrared analysis.
    Zusätzliches Material: 4 Ill.
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  • 56
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1439-1453 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Using combined results of isothermal viscosity measurements and cross-polarized light microscopy on four polyisocyanate/solvent systems, the following were demonstrated: (a) an anisotropic phase appears, associated with a shoulder in the viscosity curve, at a concentration v2* lower than the peak viscosity at v2p; (b) the inversion from anisotropic inclusions in an isotropic matrix to isotropic inclusions in an anisotropic matrix, occurs at concentrations v20 〉 v2p and (c) the attainment of a single phase, microscopically anisotropic, occurs at v20 〉 v2p; where the viscosity is decreasing but has not yet reached its minimum. When the experiments were repeated with changes in temperature, the following were observed: (a) within each single phase the viscosity drops with increased temperature; (b) in the biphasic range, the total viscosity η0 remains about constant in the concentration range 20 ≤ 2p and increases with temperature in the range v20 〉 v2p; (c) in the interval v 20 〉 v2p of the biphasic range, at constant temperature an increase in concentration decreases η0, and at constant concentration, a decrease in temperature lowers η0. Qualitative explanations of the observations are proposed.
    Zusätzliches Material: 9 Ill.
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  • 57
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1497-1512 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The small-angle x-ray scattering (SAXS) pattern from a cesium salt of a 6.1 mole % ethylenemethacrylic acid (E-MAA) copolymer is shown to become azimuthally dependent on sample elongation. SAXS was measured using the Oak Ridge National Laboratory (ORNL) spectrometer with pinhole collimation and a two-dimensional position-sensitive detector. The sample was quenched prior to deformation to avoid crystallization of the ethylene unit which would complicate the interpretation of scattering. The observed SAXS patterns are interpreted in terms of several proposed models for the structure of ionomers. A model in which ionic aggregates are arranged on a paracrystalline lattice is found to be largely in disagreement with the results for undeformed and deformed samples. Spherical and lamellar models incorporating local structure around a central ionic core are capable of predicting the observed SAXS for the undeformed sample. A model of ellipsoidal deformation of the spherical shell-core model fails to predict the correct azimuthal dependence of scattering. However, a deformation scheme involving rotation of the lamellar model is more satisfactory.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1573-1585 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The theoretical relations between 13C NMR line intensities and monad, dyad, and triad populations are given. In some cases only approximations are possible. The relations between monads and dyads also between dyads and triads are given. Some necessary relations between line intensities are given which provide a basis for making corrections for differing Overhauser enhancements. Included in the discussion are three lines which have not previously been discussed.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1599-1607 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The stepwise growth and emergence of spherulitic structures as isolated entities from lyotropic solutions of polybenzylglutamate liquid crystals is described. Spherulites that form ringed internal structures indicative of a cholesteric organization of macromolecules have large optical rotatory powers. The sense of the rotation is solvent dependent. The morphology of the spherulite is distorted in the presence of a magnetic field. The pitch of the cumulative twist of “onion-shell” molecular layers was measured as a function of field strength and found to follow the theoretical form shown previously to hold for continuous-phase polypeptide liquid crystals.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1633-1641 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Results from a number of theories for the concentration dependence of the mutual diffusion coefficient in dilute polymer solutions are examined, and clarifications are made as to what forms of the equations for these theories should be used in comparisons with experimental diffusivity data. An evaluation of the available theories for the concentration dependence of the diffusivity under theta conditions is carried out using experimental diffusivity data taken using sharp fractions of polystyrene. It is concluded that the Pyun - Fixman theory appears to provide the most promising method for estimating the concentration dependence of the mutual diffusion coefficient in dilute polymer solutions at the present time.
    Zusätzliches Material: 3 Ill.
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  • 61
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1655-1657 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1665-1669 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1737-1745 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effects of elevated pressure on the morphology and crystallization kinetics of cis-polyisoprenes containing 2-2.5% trans units have been determined. Lamellar growth rates of both α and β crystals are enhanced by elevated pressure. The degree of enhancement of α-crystal rates is much greater resulting in an effective suppression of β growth. Differences in lamellar growth rates between these polymers and cis-polyisoprene result from different preexponent values. Hedritic or axialitic growth, presumably due to low-molecular-weight fractions, is observed in shish-kebabs present in strained films. The high-pressure hexagonal phase cannot be grown in these polymers.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1717-1735 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Using the concept of a point dipole lattice, it is shown that the internal field of induced dipoles can be calculated for crystals comprised of simple chain molecules. The only structure which must be taken into account accurately is that of the chain molecule itself. From the calculations, reliable values of the polarizability tensor of the CH2 unit are deduced from the birefringence of the paraffin crystal. In addition, it is shown that birefringence measurements provide a method for demonstrating the consistency of polarizability data so that no detailed structural information is needed. For the CH2 unit, it is found by both methods that α∥ - α⊥ = - 0.63 with respect to the chain direction [the units of polarizability α are 10-24 cm3 (cgs)]. The most probable anisotropies for the bond polarizabilities are α∥CH - α⊥CH = 0.30, α∥CC - α⊥CC = - 0.62.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1801-1809 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Differences in fiber structure between cotton and cuprammonium rayon are studied by a refined broad-line proton NMR analysis of samples swollen with deuterated dimethyl sulfoxide, which has no effect on the spectra but enhances differences in molecular mobility between crystalline and noncrystalline regions. The spectra obtained are decomposed into four components: broad, medium, narrow, and extremely narrow. These components are identified as contributions, respectively, from crystalline and rigid noncrystalline (frozen glassy) material, a noncrystalline glassy component exhibiting local segmental motion, a noncrystalline rubbery component exhibiting liquidlike molecular motion, and protons included in DMSO-d6 as an impurity. The mass fraction of the narrow component in cotton was about 0.01, whereas it was as high as 0.18 in cuprammonium rayon. It is concluded that even in the swollen state, native cellulose is devoid of a liquidlike mobile component, but regenerated cellulose contains a considerable amount of a noncrystalline component involving liquidlike segmental motion of molecules.
    Zusätzliches Material: 5 Ill.
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  • 66
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1791-1800 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Molecular aggregation of poly(4,4′-diphenyl ether-5,5′-bibenzimidazole)(PBI) in solution has been studied by high resolution proton NMR. PBI and model compounds have been synthesized, purified, and characterized. Proton resonances in the NMR spectrum of PBI are assigned by comparison with the proton resonances of the model compounds. Spectra are studied by total line-shape analysis, assuming each absorption curve to be Lorentzian. For PBI in N,N-dimethylacetamide (DMAc), the resonance due to the proton of a hydroxyl group formed by proton exchange between the imino group of PBI and the carbonyl group of DMAc is observed. The activation energy for the proton exchange, obtained from Arrhenius plots of the temperature dependence of the chemical shifts of the hydroxyl proton and the imino proton, was found to increase in the order corresponding to dissociation energy of the N—H···O=C hydrogen bond. The chemical shifts in the NMR spectra of PBI-DMAc solutions on the addition of LiCl are strongly dependent on the polymer-salt ratio; and thereby the coordination position of LiCl to PBI is tentatively identified, assuming a pseudocontact LiCl-induced shift. The dependence of the chemical shifts of protons in PBI on the dielectric constant of the solvent is demonstrated by using polar solvents of varying dielectric constant, such as N-methylpyrrolidone, dimethylsulfoxide, and formic acid. The viscosity of the PBI-DMAc solutions is reported at various temperatures and concentrations of LiCl. The results from viscometry are explicable in terms of the NMR observations.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1837-1846 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Torsional creep and creep recovery measurements have been made on a 56% polymer weight solution of an extremely high molecular weight polystyrene (M = 4.4 × 107) in tri-m-tolyl phosphate and on the polymer itself after recovery both from relatively dilute and more concentrated solution in benzene by freeze drying. Although viscoelastic steady state was not achievable, an anomalously shorter rubbery plateau in the response of the bulk polymer relative to its solution was indicated. On the basis of the assumed presence of physical entanglements of the threadlike molecules, which determine the length and height of the rubbery plateau, it was predicted and confirmed that the undiluted polystyrene recovered from dilute solution would have the highest and shortest creep compliance plateau.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1931-1943 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Fourier-transform (FT) infrared spectroscopy has been applied to the study the hydrothermal degradation of various coupling agents on E-glass fibers. The coupling agents studied include γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and cyclohexyltrimethoxysilane. The amount of coupling agents on E-fibers was measured as a function of immersion time in water at 80°C. Structural changes were also followed by obtaining FT-IR difference spectra of the coupling agent on the glass fiber surface. Silanes desorb quite differently depending on the organofunctional groups. The resistance to desorption is strongly influenced by the organization of the silane interphase as well as the solubility of the silane in water.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 69
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1811-1820 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Analytical expressions are derived which relate the degree of orientation caused by a biaxial nonorthogonal pseudoaffine deformation to the conditions and parameters of drawing. They contain relations previously given by Kuhn et al. and Sasaguri et al. as special cases and can be evaluated in a way which allows a proper analysis of experimental data. The plastic and elastic components of the deformation can be estimated on the basis of these equations. The equations are useful for analysis of biaxial drawing, including technical drawing of polymer films and of the phenomenon of “bowing.”
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1821-1836 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The solution behavior of metal sulfonate-containing ionomers has been investigated in various mixed solvent systems. Ionomers, such as lightly sulfonated polystyrene (sodium salt) and sulfonated ethylene-propylene-diene terpolymer (metal salts) are generally insoluble in typical hydrocarbon solvents, but readily dissolve when small amounts of alcohols or other polar cosolvents are present. At relatively low polymer concentration these ionomers display unusually high thickening behavior in nonpolar solvents when compared with nonionic polymers because of association of the metal sulfonate groups. The addition of modest levels of polar cosolvent markedly decreases the solution viscosity and gives rise to viscosity-temperature relationships different from those of conventional polymer solutions. For example, such solutions can display vicosities which increase, are relatively constant, or display maxima or minima over broad temperature ranges. These observations are interpreted as arising from a temperature-dependent preferential interaction of the cosolvent with the sulfonate groups. While these ionomers can be regarded as polyelectrolytes of low charge density, they do not display the typical “polyelectrolyte” behavior often observed in aqueous solutions. This anomalous behavior is attributed to the fact that the metal sulfonate groups are largely un-ionized in solvents of low dielectric constant. Therefore, the solution behavior is dominated by ion pair interactions rather than free ions.
    Zusätzliches Material: 12 Ill.
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  • 71
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1853-1858 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1863-1878 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Three crystal modifications of poly(3,3-dimethyloxacyclobutane) [—CH2C(CH3)2CH2O—]n were found and their structures were analyzed by x-ray diffraction. Modification I is obtained only under tension and disappears on relaxing the tension. From the fiber period of 4.83 Å, the molecular structure seems to be planar zigzag. In modification II, two chains in T3GT3Ḡ conformation pass through a monoclinic cell with parameters a = 8.93 Å, b = 7.48 Å, c (fiber axis) = 8.35 Å, β = 97.9°, and the space group P21/c-C52h. In modification III, two (T2G2)2 chains pass through an orthorhombic cell with parameters a = 15.60 Å, b = 5.74 Å, c (fiber axis) = 6.51 Å, and the space group, C2221-D52. Molecular conformations of the three crystal modifications correspond to those of polyoxacyclobutane.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 73
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1919-1929 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Wide-angle and small-angle x-ray diffraction patterns of 11 poly(N-(10-n-alkyloxycarbonyl-n-decyl)maleimides) (PEMI) (including only even members of the series) have been obtained on unoriented samples. They show major maxima at two diffraction angles. The one at the larger angles is due to the interaction of neighboring n-alkyl side-chains. The smaller one (which shows second and third orders of diffraction in higher members of the series, n = 14 to n = 22, where n is the number of methylene groups in the external n-alkyl sequence in the side chain) is related to the distance between lamellar planes formed by the main chains. In all cases, the measured layer separation di is higher than the structural unit length L of the side-chain in the most extended conformation, and lower than the length corresponding to two side-chains. On the basis of the experimental results reported here, a model is proposed for the packing of these comblike polymers in the solid state. The mode of packing is also supported by infrared spectra in the 720 cm-1 region for the —CH2— rocking mode of vibration of the n-alkyl side-chain.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 74
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1955-1961 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A high resolution carbon-13 NMR study of an ethylene-butene copolymer has yielded a spectrum whose resonances could be assigned to isolated ethyl branches, 1,3-diethyl branching as well as 1,2-diethyl branches resulting from head-to-head butene polymerization. All these structures are present in the same sample. An examination of all the published spectra of low-density (branched) polyethylenes has revealed many examples of heretofore unassigned resonances which can be associated with this latter type of diethyl branching in these polymers. Spin-lattice relaxation times have been determined, when feasible, for the carbon atoms in each of the three branched structures.
    Zusätzliches Material: 3 Ill.
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  • 75
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1979-1992 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The craze velocity was determined for poly(chlorotrifluoroethylene) (PCTFE) in CH4 and for PCTFE, polystyrene, and poly(methyl methacrylate) in N2. It was found that for temperatures near the boiling point the velocity and number of crazes depended on the relative pressure given by P exp[-(Qv/R) (TB-1 - T-1)], where P is the pressure, Qv is the heat of vaporization, and TB is the boiling point. The craze velocity was related to the coverage of the adsorbed gas. For coverages corresponding to a few monolayers the logarithm of the velocity was proportional to the relative pressure. As the temperature increases from TB, the creep rate decreases because gas desorbs with increasing temperature; the creep rate attains a minimum value at a temperature where the general process of thermally activated deformation becomes dominant.
    Zusätzliches Material: 13 Ill.
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  • 76
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2263-2270 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Model networks were prepared by selective crosslinking through vinyl groups occurring as either chain ends or as side-groups on a poly(dimethylsiloxane) backbone. Iodometric titrations were used to determine the number of unreacted groups, thereby providing detailed information on the completeness of the reactions and the structure of the resulting networks. The end-linking reaction of the vinyl-terminated chains was generally found to be at least 95% complete. In the case of very high junction functionality, however, the extent of reaction was significantly lower, presumably because of steric interferences in the vicinity of the junctions, as was concluded in a previous investigation. Lower extents of reaction were also found in the case of vinyl groups located along the chains, probably because such groups are constrained by two chain sequences instead of one. The equilibrium elastomeric properties of both types of networks were interpreted using the structural information thus obtained and were found to be in good agreement with previous experimental results. They are also in satisfactory agreement with theory, without introduction of the highly questionable assumption of large contributions from interchain entanglements.
    Zusätzliches Material: 1 Ill.
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  • 77
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2303-2305 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2369-2377 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A general equation for light scattering in multicomponent solutions is derived and applied to some important systems. The equation is compared with one published earlier by Casassa and Eisenberg [Adv. Protein Chem., 19, 287 (1964)], and the difference between them is explained.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2391-2400 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Surface and interfacial activities of A(B)2 star-shaped block copolymers, where B is a polyoxirane block and A a polydiene or polyvinyl block, have been measured at 20°C. The surface tension of organic solvents is only slightly lowered by these copolymers, whereas a significant surface activity is noted in water. Interfacial tensions are dependent on both the nature of the organic solvent (aliphatic or aromatic hydrocarbons) and the molecular parameters of the copolymers; 50% polyoxirane seems to be the composition of maximum surface activity. The role played by the molecular architecture [A-B or A(B)2] of the copolymers is demonstrated. The same limiting interfacial tension is obtained on increasing the concentration of diblock [A-B] or star-shaped block [A(B)2] copolymer. The limiting value is, however, attained at significantly lower concentration with the star-shaped copolymers. Their ability to fill the interface is accordingly higher.
    Zusätzliches Material: 2 Ill.
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  • 80
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2415-2416 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2421-2423 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2155-2168 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An experimental method using monochromatized synchrotron radiation for a wide-angle x-ray scattering study of polymers during phase transition and deformation is described. Results obtained on low-density and high-density polyethylenes and on polypropylene are given. Melting processes could be studied conveniently by making exposures during a temperature scan; a few seconds were found sufficient to obtain a diffraction spectrum. This way relatively fast crystallization processes and the structural change accompanying stress relaxation could be followed easily. The crystalline-amorphous ratio was found to decrease continuously much below the melting temperature measured dilatometrically and by DSC, implying that in the αc-relaxation transition region of polyethylene and polypropylene a structural change takes place. At the initial state of crystallization the 040 reflection in polypropylene was found to be stronger than the 110 one, while after crystallization has been completed this ratio was inverted. Equatorial spectra made after rapid uniaxial stretching of polypropylene sheet were found to exhibit a slight time dependence demonstrating that orientation went on after stretching had been stopped.
    Zusätzliches Material: 14 Ill.
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  • 83
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1643-1650 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Changes in density and in the corresponding degree of crystallinity with radiation dose are studied experimentally for γ-irradiated polytetrafluoroethylene (PTFE) in the dose range from 1 X 103 to 1 X 109 R. The relation between the amorphous fraction and the radiation dose is derived from a quantitative analysis of cold crystallization by scission of polymer backbone chains. The characteristic radiation dose, at which one break occurs on the average per initial molecule, is estimated as about 3 X 104 R on the basis of a derived kinetic equation. The theoretical relation is modified by considering microvoids produced in the irradiated samples. The radii of microvoids in the form of spheres are evaluated as about 0.2 nm, and are also related to cage spheres relevant to the chain scission process. Good agreement between the modified theoretical relation and experimental data is attained over the entire range of radiation dose.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1663-1664 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 85
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1673-1683 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Light scattering and viscometric studies have been carried out on dilute solutions of a polybenzimidazole in N,N-dimethylacetamide. The data, which span the molecular weight range 2.9 ≦ 10-4Mw ≦ 23.3, and the temperature range 290 ≦ T/K ≦343, yield the dependence of the mean-square radius of gyration 〈s2〉LS, the second virial coefficient A2, and the intrinsic viscosity [η] on molecular weight Mw and temperature. The unperturbed mean-square radius 〈s20〉LS was calculated using experimental values of 〈s2〉LS and A2. It was found that excluded volume effects on 〈s2〉LS are very small. The unperturbed hydrodynamic chain dimension 〈s20〉η was estimated by considering draining effects. A small value of the draining parameter was obtained. Analysis of the temperature dependence of A2 and [eta;] leads to the conclusion that this system approaches a lower theta temperature with increasing temperature. The steric factor σ = 〈s20〉/〈s20〉f, based on the value of 〈s20〉f calculated for the polymer chain with free rotation, is nearly unity. Most of these properties can be interpreted in terms of long rotational units within the main chain.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1879-1890 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Fluorescence polarization was used to measure segmental orientation in stretched polyisoprene networks. Stress and orientation of chemically bonded fluorescent labels were simultaneously recorded during stretching. Two deviations from the classical theory of rubber elasticity were observed: (i) an extra orientation of dry networks, which was interpreted by assuming the existence of weak nematiclike interactions between segments, and (ii) a saturation of orientation at high elongation which could be due to local conformational changes.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1907-1917 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The measurement of the sedimentation velocity coefficient of narrow distribution linear, four-arm and six-arm star and comb polystyrenes in a theta solvent permits the experimental determination of h, i.e., the ratio of the translational friction coefficients of the branched polymer to that of its linear homolog. A comparison of experimental h/g1/2 values with theoretical predictions can then be made. It was observed that the equivalent hydrodynamic radii derived from sedimentation and intrinsic viscosity measurements are identical within experimental error.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1945-1954 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: X-ray diffraction, thermally stimulated depolarization, and piezoelectric and pyroelectric current measurements have been carried out on biaxially oriented polyvinylidene fluoride film, corona-poled both negatively and positively, at elevated temperature. Larger piezoelectric and pyroelectric coefficients are obtained at lower values of the poling field, when corona charging takes place at elevated temperature rather than room temperature. Negative charging is more effective than positive. The polarization mechanism is dipole alignment, and a conversion of Form-II crystallites to Form I. The large space-charge injected by the corona, and trapped in the material, acts through creation of high internal fields, and shows little, if any, piezoelectric and pyroelectric effects of its own.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2015-2025 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In a previous paper, the extents of reaction of various functional groups in different acrylic copolymer melamine-formaldehyde crosslinked formulations were measured by infrared spectroscopy. From these data and a statistical model, various network structure parameters could be calculated. One of these, effective crosslink density, was found to correlate well with film solvent resistance. In this paper the effects of the addition of strong acid catalysts on cure chemistry and network structure are determined. Both solvent-based and water-based formulations have been studied. In the solvent-based formulations studied, the addition of acid catalysts greatly enhanced the crosslinking reactions at low temperatures and dramatically lowered the cure temperature. Acid catalysts also lowered the cure temperature of a water-based formulation based on a high (180°C) cure temperature melamine. In contrast, the addition of acid catalysts had a negligible effect on the cure chemistry of a water-based formulation crosslinked with a low (130°C) cure temperature melamine. For this case the rate limiting process was found to be the rate of removal of neutralizing amine from the film. Cure temperatures in this system could only be lowered by replacing the amine used with a more volatile amine.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2055-2067 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In deriving a constitutive equation from a molecular model of polymers in concentrated solutions and melts, Doi and Edwards used a mathematical approximation, the “independent alignment approximation,” which has recently been shown to produce significant error in the particular case of stress relaxation following a double-step strain in opposite direction. In the present paper, in order to examine the approximation in general cases, we derive a new constitutive equation without using the independent alignment approximation. The new equation is a nonlinear integro-differential equation and is solved numerically for several cases, i.e., steady shear and elongational flows, and the transient flows after the start of shear and elongation. It is found that, in the cases examined here, the new constitutive equation gives nearly the same results as the old one: the rheological functions calculated from the two theories differ no more than 30%. This substantiates the expectation that the independent alignment approximation does not produce drastic error as long as the flow direction is not reversed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2227-2241 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Heat capacities Cp of a polydiacetylene-bis(toluene sulfonate) single crystal and its monomer have been measured in the temperature range from 3 to 300 K. The temperature dependence of Cp for both monomer and polymer crystals differs from that for monoatomic solids. By applying a chain lattice model for a polymer crystal, the temperature dependence of the heat capacity can be described assuming a phonon density of states given by bending and stretching modes of the polymer backbone. With a combination of one-dimensional and three-dimensional elastic continuum approximations, the heat capacity has been calculated and a good fit to the data has been obtained. A small peak in Cp was detected at 161 K for the monomer and at 198 K for the polymer. This may be ascribed to a lower-temperature phase transition in the polydiacetylene crystals evidenced by previous x-ray and spectroscopic measurements.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2257-2261 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: There has been a growing interest in compatible blends in which one of the polymers is crystallizable. At appropriate compositions some of this polymer will crystallize, the remainder forms a compatible blend with the other polymer component; attempts have been made to relate melting point depression of the crystalline component to diluent effects, i.e., polymer/polymer interactions. Melting point is also a function of lamella thickness, the determination of which is very difficult in such systems. It is assumed in this type of study that the melting point of a crystal in an incompatible matrix will be unchanged. In an attempt to test this assumption we have determined the melting behavior of isothermally grown, single crystals of polyethylen (from the same preparation) embedded in a variety of incompatible matrices. The matrices used were polybutadiene, polystyrene, and polyphenylene oxide. This work shows that polymer single crystals embedded in an incompatible polymer matrix can show apparent melting point depressions of up to 5°. This size of depression represents a significant part of that reported for compatible systems.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2277-2286 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The C-13 NMR spectra of partly crystalline poly(phenylacetylene) (PPA) in CDCl3 CCl4 are rather well resolved and the peaks can be matched with those of 1, 3,5-triphenylbenzene. A different, less-well-resolved C-13 spectrum is characteristic of a disordered PPA obtained by heating. We conclude that crystalline PPA has the chain conformation of a cis-cis-oid helix. This interpretation is consistent with the proton NMR spectra and is supported by the fluorescence spectra, which can display two bands, one concluded to be characteristic of the cis-cis-oid conformation, the other of chain conjugation in the disordered polymer. Phase equilibria of PPA in the presence of chloroform were determined and are represented as those of the quasiternary mixture cis-cis-oid helix, disordered polymer, and chloroform.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2299-2301 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2313-2322 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The lateral thermal motion of atoms in an inextensible polymer chain would cause a shortening along the chain direction. This effect could explain the observed negative thermal expansivity α along the chain direction of a polymer crystal. Using this idea, the expansivity α is calculated for a lattice of parallel linear chains. A value of -1.3 × 10-5 K is obtained for chains with a carbon backbone, in good agreement with data for polyethylene.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2323-2336 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The mathematical solution of the following problem is given. Simultaneously with diffusion-controlled mixing of two phases (e.g., gel formation), a third substance diffuses from one of the two pure phases into the other and through the inhomogeneous mixing phase which expands at a rate proportional to the square root of the time. The phases may change their volumes.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2347-2367 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Replicas and thin-section electron microscopic studies were made of fractions of linear polyethylene covering the molecular weight range 2.78 × 104 to 6.0 × 106 for a variety of crystallizing conditions. Lamellar crystallites were found under all circumstances; and the supermolecular structure, or crystalline morphology, is in agreement with that previously reported from an analysis of the small-angle light-scattering patterns of the same samples under similar crystallization conditions. Details of the crystalline microstructure are also described, which range from truncated hollow pyramids which degenerate as the molecular weight or the undercooling are increased. From these results, it is possible to describe the mechanism of formation of polyethylene spherulites.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2401-2413 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The considerable potential of high resolution time-resolved spectroscopic data for copolymer systems in elucidation of the intramolecular photophysical processes which occur in polymer systems is illustrated. Such information can not be gleaned solely from studies of homopolymers. Kinetic data and time resolved fluorescence spectra of copolymers of 1-vinylnaphthalene and methyl methacrylate indicate that conventional kinetic schemes are inappropriate for the discription of excimer formation in 1-vinylnaphthalene polymers. Evidence is presented for the presence of an emitting species in addition to the expected monomeric and excimeric forms. The nature of this third species is discussed and photophysical kinetic schemes are proposed to describe intramolecular excimer formation in such systems. Kinetic data have been derived for the principle deactivation pathways through investigation of the observed fluorescence decays upon the intrachain concentration of aromatic species.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 71-82 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: In light of novel and problematic diffraction patterns arising through the thermoreversible gelation of isotactic polystyrene, the conformational possibilities were examined with particular reference to other conformational works published recently on this polymer. The specific objective was to ascertain whether highly extended, helical backbone geometries such as are required by the new x-ray patterns are possible or not with a purely isotactic arrangement of side groups. The first realization was that the recently announced low-energy, near-trans conformations are not relevant to the present issue as they do not provide the required extended geometry. Further, specific sampling of the conformational energy map revealed that the required high chain extension may be energetically feasible, contrary to traditional conceptions and to recent conformational calculations elsewhere. The divergences as regards the latter were traced to the specific choice of nonbonded atomic radii - all within generally accepted limits - which accordingly has a crucial effect even to the extent whether specific conformation types are forbidden or energetically stable. The implications this has for conformational analysis in general are being pointed out. While the novel crystal structure has not been solved, the present study at least eliminates the previously believed categoric objections to it being associated with isotactic chains and, beyond this, opens up new perspectives as regards conformational possibilities in polyolefins. The more general problems concerning the nature and origin of the gelation phenomenon nevertheless remain.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 111-120 
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Normal coordinate calculations have been performed for poly(vinylidene chloride) employing a TXTX′ conformational model (X and X′ denote torsional angles of equal value but opposite sign). A valence force field previously determined from the model compounds 2,2-dichloropropane and 2,2-dichlorobutane was directly transferred to the chain conformation of the polymer. The results are in excellent agreement with the observed vibrational spectra and we have been able to satisfactorily assign all the major normal modes.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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