ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Thermodynamics of isothermal vitrification by chemical reactions in a liquid (1992)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 14 (1992), S. 763-766 
    Details
    ISSN: 0392-6737
    Keywords: Glass transitions ; Calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report here first observations of the decrease in heat capacity during isothermal vitrification of a thermosetting polymer. A new experimental method has been developed for this study which allows simultaneous measurements of both the heat capacity and the enthalpy released as chemical reactions occur in quasi-isothermal conditions. During the curing the heat capacity of a thermoset first increases slightly, undergoes an abrupt decrease in a narrow range of time and thereafter slowly decreases. The abrupt decrease represents the irreversible transition of the liquid to a vitreous solid which is equivalent to the reversible glass transition appearing in a supercooled liquid when the temperature is lowered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451722
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Simultaneous dielectric spectroscopy and calorimetry of the dynamics during a macromolecules growth (1996)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 1443-1448 
    Details
    ISSN: 0392-6737
    Keywords: Glass transitions ; Calorimetry ; Dielectric loss and relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A method and an instrument has been developed for measuring almost simultaneously and continuously in time three different quantities: i) the heat evolved during the course of exothermic reactions, ii) the heat capacity and iii) the dielectric spectra of a liquid or solid sample. By using this instrument, we have studied the decrease in the d.c. conductivity and the increase in the relaxation time as molecules in an isothermally kept liquid chemically react to produce, irreversibly, a macromolecular structure until the liquid vitrifies and becomes rigid. The number of covalent bonds formed in the structure,n, has been calculated and the dielectric relaxation time, τ, is related ton. This τ increases progressively more rapidly withn, and decreases, of course, on increasing the temperature. A compensation between these two effects determines the dynamic behaviour observed during rate heating. The effect of temperature is found to predominate. Such observations have been made possible by means of the new instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02453785
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A calorimeter for the electrolytic cell and other open systems (1996)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 1333-1346 
    Details
    ISSN: 0392-6737
    Keywords: Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods) ; Calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We present here a calorimetric method and the construction details of a differential calorimeter useful for studying the reactions in an electrolytic cell and more generally slow chemico-physical processes occurring in thermodynamically open systems. The method allows measurements of the heat balance of the cell, from which the enthalpy change of the process under investigation can be calculated. The theoretical description of the calorimetric cell and the results of several studies planned to describe the performances of the instrument up to the boiling point of the electrolytic solution are reported. The features of this calorimeter fulfil most of the requirements of ≪col fusion≫ experiments, where the heat production is the fundamental and controversial aspect. By controlling both the heat and the matter exchanged, the calorimeter can be utilised also to study bioenergetic processes,e.g. fermentation, microbial metabolism and biodegradation, and liquid phase chemical reactions, involving gases as reactants and/or products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02453267
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Time-dependent heat capacity of water-lysozyme solution (1992)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 14 (1992), S. 199-205 
    Details
    ISSN: 0392-6737
    Keywords: Heat capacities of liquids ; Biomechanics, biorheology, biological fluid dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report here the first observation of the time-dependent heat capacity of water-lysozyme solution. The observed increase of heat capacity in time occurs independently of the lysozyme concentration and thepH value of the solvent. The time necessary to attain the heat capacity equilibrium value and the amplitude of the effect are not well reproducible; the former tends to increase with temperature, while the amplitude decreases and practically disappears about 35°C. Evolution of a spatial order of the proteins in water and/or of water molecules interacting with the proteins is considered as a possible explanation for the results. The phenomenon promises to be an important tool to study the role of water in biological organization and activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457352
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The temperature and polymerization effects on the relaxation time and conductivity, and the evolution of the localized motions (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 6957-6965 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: To examine the manner in which molecular dynamics of a polymerizing liquid (stoichiometric amounts of 4,4′-diaminodicyclohexylamine and diglycidyl ether of bisphenol-A) evolves during thermal cycling from its (molecular) vitreous state to its fully polymerized vitreous state, calorimetry, and dielectric spectrometry were performed simultaneously in real time. The half-width of the relaxation spectrum of the liquid was relatively narrow and became narrower on heating. This was followed by an increase in the characteristic relaxation time and the spectrum became broader as polymerization occurred and reached completion. The dc conductivity initially increased and then decreased. The faster dynamics of the Johari–Goldstein relaxation in the fully polymerized state evolved as polymerization reached completion and the temperature increased. The dielectric polarization associated with this relaxation had a broad spectrum, whose half-width increased with decrease in the temperature. Its relaxation rate followed the Arrhenius equation with an activation energy of 63.4 kJ/mol. The temperature dependence of the faster relaxation did not change with the change in the overall configurational entropy of the liquid, a feature that substantiates the dynamic heterogeneity theories for the structure of the liquid and for the origin of the relaxation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311623
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Heat capacity change on isothermal vitrification during a macromolecule's growth
    Amsterdam : Elsevier
    Physica A: Statistical Mechanics and its Applications 201 (1993), S. 95-100 
    Details
    ISSN: 0378-4371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-4371(93)90404-R
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Calorimetric effects of intergranular water in ice (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4987-4990 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The heat capacity, Cp, of microcrystalline and large or single crystal ice was measured from 270 to 272.6 K and the effect of the heat input (required before measuring the increase in temperature) on the measured Cp investigated. The measured Cp of microcrystalline solids was much higher than that of large and single crystal solids and increased further with increase in the heat input. At 271.16 K, the measured Cp was independent of the heat input, but for higher temperatures, it increased nonlinearly with the heat input. These effects are caused by the increase in the volume fraction of intergranular water in impurity free ice with increase in both its temperature and the heat input. A significant fraction of the heat used for Cp measurement is consumed in melting ice at grain junctions which does not raise the temperature. Thus, the measured Cp appears to be much greater than the true value. Quantitative analysis of the data yielded results which agree reasonably well with the prediction of a theory given in J. Chem. Phys. 100, 4548 (1994). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469548
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Water↔ice transformation in micron-size droplets in emulsions (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3115-3120 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: To investigate the crystallization and melting behaviors of micron-size droplets in a water-emulsion, the heat capacity, Cp, has been studied by adiabatic calorimetry over the 233–273 K range. Water droplets in the emulsions began to crystallize at ca. 243 K, but the crystallization rate was slow. This was caused partly by the relatively slow coalescence of crystallized and uncrystallized droplets at that temperature, in a highly nonNewtonian viscous media of the emulsion. Crystallization occurred rapidly on heating and remained incomplete even when it occurred at 260 K. Thus a substantial amount of water droplets coexisted with ice droplets in the emulsion. The onset of crystallization shifted to lower T and the number of water droplets in the emulsion at a given T decreased as the droplets grew on thermally cycling the emulsion. Cp of emulsion increased progressively more rapidly as 273 K was approached, which is attributable to premelting of the ice droplets beginning at 260 K. Analysis of the Cp data showed that interaction between the droplets and the surfactant in the emulsion changes on crystallization. This is attributable to the decrease in the entropy at the surfactant–water interface. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479592
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Reversal in the dielectric relaxation time during polymerization: Thermal energy compensation on macromolecular growth (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 10599-10605 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The increase in the dielectric relaxation time τ0 and in the number of covalent bonds n formed during polymerization of an equimolar mixture of cyclohexylamine and a diepoxide have been studies in real time, in two experiments: (i) under isothermal conditions when the dielectric spectrum monotonically shifts to the low-frequency side and the configuration entropy decreases and (ii) on heating the polymerizing liquid at a fixed rate when the spectrum initially shifts to the low-frequency side, reverses direction at a certain temperature, and shifts towards the high-frequency side. This reversal in τ0 occurs when an increase in thermal energy begins to dominate the effects of increase in n. Consequences of the two competitive effects on the measured dielectric behavior have been discussed and relations between the change in configurational entropy, and τ0 of the ultimately formed linear chain polymer, are discussed. It is shown mathematically that for a fixed τ0 and a configurational entropy, there are an infinite number of combinations of temperature and n, some of which may be explored by altering the temperature–time profile during the macromolecular growth. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478991
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Time domain reflection methods for dielectric measurements to 10 GHz (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 793-802 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Total reflection methods and instrumentation for their use are described for measurements of dielectric permittivity and loss at frequencies to 10 GHz or more. Several cell designs are shown, together with analyses of their performance. Procedures are given for correcting effects of wave propagation in the cells and residual reflections in the cells by bilinear analysis with calibrations using dielectrics of known permittivity. Representative results are presented for highly polar liquids, dilute solutions of polar molecules in nonpolar solvents, electrolyte solutions, and ionic glasses with appreciable ohmic conduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343499
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...