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Reaction volume of water formation detected by time resolved photoacoustics: photoinduced proton transfer between o-nitrobenzaldehyde and hydroxyls in water
No full textThe structural volume changes accompanying light-induced proton transfer reactions in aqueous solutions of o-nitrobenzaldehyde have been investigated using time-resolved photoacoustics. The solvation of the newly formed ions is accopanied by a contraction of the medium of about −5.2 ± 0.2 ml/mol. At a pH above 9.5, the formation of water molecules leads to an expansion of 24.5 ± 0.4 ml/mol. The apparent rate constant for the protonation of hydroxyls is k = (4.9 ± 0.4) X 1010 M− s−. This is the first direct time-resolved measurement of the extent of the structual volume changes accompanying water formation
GERMINATION OF S. CEREVISIAE ASCOSPORES WITHOUT TREHALOSE MOBILIZATION AS REVEALED BY IN VIVO 13C-NMR”
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Perossidazione lipidica di membrane microsomiali da epatoma di Morris 3924A: parametri d'ordine e proprietà dinamiche determinati tramite decadimento di anisotropia di fluorescenza.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A model to account for firing behaviour of neurons stimulated by rectangular and sinusoidal currents
No full textIn biological systems the information is coded in terms of the interval between successive action potentials. Nerve and sensory cells are able to transform an external stimulus into a train of action potentials. The sequence of produced action potentials is, in some way, related to the action, but little is known about the mechanisms responsible for this coding process. A way to study these mechanisms is to apply different, known stimuli to the nerve cell and to observe the resulting electrical activity of the cell. Much emphasis, in particular, has been placed on the use of cyclic stimuli which are a natural mean of exciting a system whose parameters vary periodically. This paper is concerned with the responses of Helix pomatia neurons stimulated with rectangular and sinusoidal currents with the aim to verify a mathematical model able to describe adaptation in discharge frequency that has been demonstrated in Helix neurons
Transport coefficients in a nonlinear series membrane array
No full textDespite its many noticeable successes, several limitations of the linear thermodynamic description of membrane transport, as proposed by Kedem and Katchalsky, have been encountered. These arise as a consequence both of the various experimental non linear force-flow relationships found to date and of some intrinsic limits of the linear treatment. Suggestions intended to overcome the mentioned difficulties have been made by Patlak et al. and by Kedem and Katchalsky, utilizing series membrane arrays. Series arrays are particularly interesting as they approximate the structure of the epithelia and allow a correlation between the experimentally accessible global phenomenological coefficients of the array and the intrinsic characteristics of the single membranes. Some of these correlations will be analyzed in the following emphasizing the problems they pose in experiments
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