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  • 1
    Electronic Resource
    Electronic Resource
    Configurational entropy of polyethylene and other linear polymers (1966)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 869-880 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The configurational entropy of the polyethylene chain at the melting points calculated in two ways. In both calculations, tetrahedral angles and discrete trans and gauche arrangements of all bonds are assumed, and trans bonds are assumed more stable than gauche by energy U1. First, calculations are made on chains of up to N = 18 bonds, disallowing all configurations having overlapping atoms, and the result is extrapolated to large N. Second, a calculation is made directly for long chains, with overlaps excluded only over every short chain segment. The results are in almost exact agreement, suggesting that the second method can be safely used with other molecules. The calculated configurational entropy is in line with that suggested by the entropy of fusion, assuming the chains to acquire a configurational freedom in the melt which approaches that of independent chains.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1966.160040604
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  • 2
    Electronic Resource
    Electronic Resource
    Equation of state and the thermodynamic properties of liquid polymers: Application of the Hirai-Eyring modelPresented at Symposium on Thermodynamic Properties of Bulk Polymers, National Bureau of Standards, Gaithersburg, Md., March 10-12, 1969. (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1337-1360 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that the Hirai-Eyring model for the liquid state is capable of accurately describing the p, V, T behavior of liquid polymers in the temperature range over which measurements are now made, and below. Once the parameter choices necessary to accomplish the fit are made for a particular polymer, the excess thermodynamic functions (differences in properties, liquid less solid) are determined by the same parameters. Above the glass transition temperature Tg the volume, excess enthalpy, and square of the excess entropy are predicted by the model to be essentially linear with temperature, in agreement with experiment. Below Tg, these functions do not remain linear (as is usually assumed in extrapolating the equilibrium behavior to low temperatures), but instead they rapidly approach zero in a continuous way as the temperature is lowered. These remarks apply to glass-forming materials composed of small molecules, as well as to polymers. The “paradox” raised by Kauzmann is thus resolved, and the Gibbs-DiMarzio second-order transition appears to be unnecessary.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080807
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  • 3
    Electronic Resource
    Electronic Resource
    Viscoelastic properties of branched polyethylene melts (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 455-465 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic mechanical properties of branched polyethylenes in the molten state were determined in the frequency range 10-3-10 radians/sec. The materials tested have remarkably similar rheological properties even though they vary greatly in molecular weight and molecular weight distribution. The similarity in properties is attributed to the influence of long chain branching on the relaxation spectra. A mechanistic argument is proposed to relate the observed behavior to molecular entanglement coupling. The concept of entanglement coupling involving long-chain branching leads to the expectation that the quasi-Newtonian and non-Newtonian viscosities of branched polymers may be either greater or less than those of linear polymers of the same species, which have comparable molecular weights. This is borne out by experiment.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080311
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  • 4
    Electronic Resource
    Electronic Resource
    Capillary gas chromatography/mass spectrometry of cholesteryl esters with negative ammonia chemical ionization (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 131-140 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of both synthetic and naturally occurring (human plasma) cholesteryl esters have been examined by capillary gas chromatography/mass spectrometry (GC/MS). A magnetic sector mass spectrometer was used and a variety of ionization modes were assessed with a view to obtaining structural information on intact cholesteryl esters. By employing ammonia as reagent gas, with negative ion scanning, spectra were produced from which the nature of steryl and fatty acyl moieties could be readily deduced. Analyses were performed at an ion source temperature of 300°C in order to maintain the integrity of the gas chromatographic profile. The technique described is of general use for the GC/MS analysis of steryl esters, particularly in conjunction with magnetic sector instruments.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200140307
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  • 5
    Electronic Resource
    Electronic Resource
    The determination of sequence information in homologously related proteins by mass spectrometry (1974)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 269-273 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An azurin, a small respiratory copper protein from the bacterium Pseudomonas fluorescens biotype G, has been studied by mass spectrometry to determine sequence information. The study of homologously related proteins by mass spectiometry is particularly attractive, since the correct nature of major parts of the deduced sequences can be confirmed by comparison with the sequences of the protein from related organisms. An oxidized tryptohan residue has been identified amongst the products from a cyanogen bromide digest of this wild type azurin. In the same digest, a product is also found to arise from cleavage of the peptide chain at the C-terminal side of the same tryptophan residue. These results are rationalized.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200010411
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  • 6
    Electronic Resource
    Electronic Resource
    High-performance liquid chromatography/mass spectrometry with thermospray lonization of free ecdysteroids (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 477-481 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: High-performance liquid chromatography/mass spectrometry (HPLC/MS) with thermospray ionization has been applied to the analysis of free ecdysteroids (polyhydroxylated steroids that serve as arthropod moulting hormones). Of a range of analytical conditions that were tested, optimum results were obtained by the use of re versed-phase HPLC using a methanol + water mixture containing 0.1 M ammonium acetate. The positive-ion spectra of ecdysteroids showed pseudo-molecular ions, [M + H]+, and fragment ions corresponding to the sequential losses of hydroxyl groups. The [M + H - H2O]+ and [M + H - H2O]+ ions were the most abundant for all the compounds tested. Ecdysteroids bearing a C-20 hydroxyl group (e.g. 20-hydroxyecdysone) showed ions characteristic of cleavage of the side-chain from the steroid nucleus. This mode of fragmentation was much less obvious in the case of ecdysteroids lacking C-20 hydroxylation (e.g. ecdysone). Full-scan mass spectra were readily obtained from 1 μg of free ecdysteroids, while a limit of detection of 5 ng (signal-to-noise ratio 3) was attained in the selected-ion monitoring mode. The application of HPLC/MS to the study of ecdysteroids in biological materials is demonstrated by the analysis of extracts of newly laid eggs of the desert locust (Schistocerca gregaria) and pupae of the cotton leafworm (Spodoptera litoralis).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070615
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  • 7
    Electronic Resource
    Electronic Resource
    Detection of nucleotide bases in ancient seeds using gas chromatography/mass spectrometry and gas chromatography/mass spectrometry/mass spectrometry (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 503-508 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Nucleic acid extracts from 1400-year-old radish seeds recovered from excavations at Qasr Ibrim, Upper Egypt, have been analysed by gas chromatography/mass spectrometry and gas chromatography/mass spectrometry/mass spectrometry. tert-Butyldimethyisilyl derivatives of the purine and pyrimidine bases were prepared, after treatment of the nucleic acid extracts with concentrated formic acid. Under electron ionization these derivatives yield prominent [M-57]+ ions that were found to be of value for use in analyses employing selected-ion monitoring and product-ion studies. These two techniques were used in the sensitive and selective detection of nucieotide bases in crude extracts of ancient seeds. The results obtained were supported by complementary analyses of hydrolysates of ancient nucleic acids and authentic bases by means of retention time and spectral comparisons. This work demonstrates for the first time that mass spectrometry can be used in the direct chemical examination of nucleotide bases in ancient materials. This analytical approach is currently being used to address questions regarding the possible chemical (diagenetic) changes occurring in the nucleic acids of ancient biological material.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080702
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  • 8
    Electronic Resource
    Electronic Resource
    A novel inexpensive device for the electrochemical generation of metallic emitters for field desorption (1977)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 4 (1977), S. 52-54 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Details for the construction of a novel, inexpensive device for the electrochemical generation of metallic emitters for field desorption mass spectrometry are described. Use of the device for the generation of cobalt and nickel emitters is demonstrated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200040107
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  • 9
    Electronic Resource
    Electronic Resource
    Metastable ions arising from pseudomolecular [M — H]- ions produced by fast-atom bombardment negative-ion mass spectrometry of ecdysteroids (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 352-355 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Metastable ions arising from pseudomolecular [M — H]- ions produced by fast-atom bombardment negative-ion mass spectrometry of a range of free ecdysteroids, ecdysteroid conjugates and polar metabolites were investigated by means of linked scanning at constant B/E. Free ecdysteroids displayed daughter-ion spectra which allow 20-hydroxyecdysteroids and ecdysteroids lacking C-20 hydroxylation to be readily distinguished. The ejection of acetic acid from acetylated ecdysteroids was also readily detectable. Characteristic metastable-ion decomposition of ecdysteroid acids was not observed, presumably as a result of charge localization. High-mass daughter ions were also lacking in the case of phosphate conjugates.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290031010
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  • 10
    Electronic Resource
    Electronic Resource
    Application of electrospray ionization mass spectrometry with maximum-entropy analysis to allelic ‘fingerprinting’ of major urinary proteins (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 882-886 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mixtures of a specific group of proteins, the major urinary proteins (MUPs), believed to have a role in odorant binding, have been analysed by electrospray ionization mass spectrometry. The data obtained from conventional transformed electrospray data confirm that the molecular weights of the protein mixtures, deduced from published sequences, lie in the molecular weight range 18600 to 19 000 Da. Application of maximum-entropy analysis to the raw electrospray data has confirmed a heterogeneity in MUP composition, consistent with allelic similarities (and differences) between the different mouse strains. This work demonstrates the use of maximum entropy in the assessment of protein content and in the subsequent resolution enhancement of naturally occurring protein mixtures containing components of closely similar molecular mass.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071005
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