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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 26 (1997), S. 477-483 
    ISSN: 1432-1017
    Keywords: Key words Photosynthesis ; Electron transfer ; Fission ; Double excited states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A new mechanism for the primary photoinduced charge separation in photosynthesis is proposed. It involves as a real intermediate between the excited special pair state P* and the primary charge separated state P+ HL – a trip-trip-singlet BT BL T, which consists of a triplet on the dimer P and a further triplet on the monomer BL. Both combine to a singlet. The electron transfer is caused by spin exchange couplings. The transient spectrum of the short lived intermediate, formerly taken as evidence for the charge transfer state P+ BL –, is reinterpreted as a transient excitation of this trip-trip singlet.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 3424-3431 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 1633-1637 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3948-3957 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Energy is supplied to the solvent or solute molecules via resonantly absorbed infrared photons. The long wavelength tail of the S1 absorption band of a probe molecule is monitored on a picosecond time scale. This technique is used to study energy transfer from the solvent to the probe molecule and vice versa. Exciting a vibrational mode of the probe molecules, the energy is rapidly redistributed via intramolecular processes followed by an intermolecular dissipation to the solvent with time constants of ∼10 ps. Intermolecular energy transfer from the solvent to the probe molecules is observed within (approximately-less-than)5 ps, independent of the solvent.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0014-5793
    Keywords: Archaebacterium ; Co-methyl-5-hydroxybenzimidazolylcobamide ; Methane biosynthesis Methanol ; Methanosarcina barkeri ; Vitamin B"1"2-factor III
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Optics Communications 39 (1981), S. 375-378 
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 34 (1972), S. 393-412 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Two mathematical models of pulmonary single breath gas washout (one analytic, one numerical) are developed and their predictions compared with experimental data on human subjects. Weibel's 23 generation symmetric anatomical model is used as a guide to bronchial tree geometry. Experimental plots of nitrogen concentration versus volume expired, dead space versus breath holding time, and dead space versus tidal volume are compared with plots predicted by the models. Agreement is good. A plot of nitrogen concentration in the airways as predicted by the numerical model at different times during inhalation and exhalation of a single breath of oxygen is shown. Model predictions for changes in dead space with changes in washout gas and expiratory flow rate are discussed. Use of the analytic model for obtaining average values of the path length from mouth to alveoli in a given subject is discussed. To the extent of their agreement with experiment, the models provide a sound physical basis for the correlation of airway structure and function.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 23 (1981), S. 1057-1065 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Whole cells of the methanogen Methanosarcina barkeri were immobilized in an alginate network which was crosslinked with Ca2+ ions. The rates of methanol conversion to methane of entrapped cells were found to be in the same range as the corresponding rates of free cells. Furthermore, immobilized cells were active for a longer period than free cells. The particle size of the spherical alginate beads (1.2 mm-3.7 mm φ) and thus diffusion had no obvious influence on the turnover of methanol. The half-value period for methanol conversion activity determined in a buffer medium was approximately 4 days at 37°C for entrapped cells. The apparent Km value Km′ for such cells was nearly 140mM and the Vmax value was about 1.2 μmol methanol/min/mg entrapped protein. Therefore the high rates of methanol degradation measured, e.g., 0.5 μmol methanol/min/mg entrapped protein, indicated that the immobilization technique preserved the cellular functions of this methanogenic bacterium.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 1 (1959), S. 127-127 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 12 (1984), S. 385-405 
    ISSN: 1573-9686
    Keywords: Convective exchange length ; Diffusion ; Mass transfer resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A theoretical model of high-frequency ventilation (HFV) is presented based on the physical convective exchange process that occurs due to the irreversibility of gas velocity profiles in oscillatory flow through the bronchial airways. Mass transport during the convective exchange process can be characterized by a convective exchange length, $$\bar L_E $$ , which depends only on the irreversibility of bronchial velocity profiles and can be measured by the experimental technique of photographic flow visualization in bronchial tree models. Using the exchange length and the molecular diffusivity, a simple model of overall bronchial mass transfer is developed. The model allows a prediction of the mean gas concentration profiles along the airways, the site of maximum mass transfer resistance, and overall flow rate of the gas of interest in or out of the lung as functions of the parameters of HFV. The results predicted by the model agree with the limited experimental data available for animals and humans. For normal unassisted ventilation, total bronchial cross-sectional area around the 15th Weibel bronchial generation is predicted to be the single most important parameter in controlling the total gas transport rate along the airways. For the breathing of room air, values of the respiratory quotient around 0.78 are predicted, which are insensitive to VT and f. The model represents a fruitful combination of fluid mechanical theory and experiment with physiologic data to yield new and deeper insight into the operation of the human respiratory system during HFV and normal breathing.
    Type of Medium: Electronic Resource
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