Elements in the history of the Periodic Table.
Discovery of the Periodic Table was rendered possible only after four decisive prerequisites had been achieved. These were (i) the abandonment of the metaphysical and occult notions of elements that typified the alchemical era; (ii) the adoption of a modern and workable definition of an element; (iii) the development of analytical chemical techniques for the isolation of the elements and determination of their properties; and (iv) the devising of a means of associating each element with a characteristic natural number. The Periodic Table made its appearance on cue almost as soon as these preconditions had been fulfilled.
Classification in psychiatry: the move towards ICD-11 and DSM-V
Purpose of review The intrinsic limitations of the current major diagnostic classifications have become increasingly apparent. Several constraints these diagnostic systems impose on clinical practice and research have led to a widespread perception that psychiatry must move beyond the nosologic model embodied in contemporary classifications. Thus, the present review covers the ongoing debate on key conceptual issues that may be relevant for the development of ICD-11 and DSM-V. Recent findings The concepts of validity and utility, as applied to diagnostic classifications, received closer attention recently and attempts were made to better define and contrast them. Against such background, issues like conciliating the multiple purposes of diagnosis, choosing taxonomic strategies and determining the boundaries between and within (subtypes and specifiers) diagnostic categories and thresholds can be properly examined. Recent findings from genetics and neuroscience have added complexity to the already intricate field of mental disorders, raising high hopes of breakthroughs in pathophysiology. This bet on pathophysiology inscribes itself in the perennial debate about the nature of mental disorders and their defining (fundamental) level, which of course has critical implications for the future of psychiatry. Summary Despite considerable scientific advances achieved recently, the challenges faced by psychiatry have only been increasing in complexity. In the present state of affairs, conceptual closure and reductionism possibly represent the most serious risks to be avoided. The review ends by suggesting that methodological pluralism is a necessary condition for building a better psychiatric nosology.
New method for analysis of enzymatic reactions: Thermolysin-catalyzed synthesis of aspartame precursor
Aspartame is an artificial sweetener which is 200 times sweeter than sucrose. A precursor of aspartame, N-(benzyloxycarbonyl)-l-aspartyl-l-phenylalanine methyl ester (Z-APM) was synthesized and hydrolyzed with thermolysin in an aqueous monophasic system. Graphical plotting methods and/or nonlinear regression have been used to analyze enzymatic reactions because of the nonlinearity of enzymatic rate equations. There are, however, problems: the former require accurate measurement of the initial reaction rate and the latter gives no analytical information. The authors proposed a method to solve the nonlinear enzymatic rate equations with respect to the concentration of a product with the Taylor expansion, especially for the reversible Theorell-Chance mechanism (Murakami, Y., Hirata, M., and Hirata, A., J. Ferment. Bioeng., 82, 246–252, 1996). This solution, however, is complex for practical use. In this paper, a simpler solution to explain the thermolysin-catalyzed synthesis of Z-APM is obtained. New methods to determine the kinetic parameters, especially for the reversible Theorell-Chance mechanism, based on the approximated solution are proposed. The results calculated using the obtained kinetic parameters can satisfactorily explain the experimental results, which demonstrates the effectiveness of the proposed analysis. We must know the relation between the concentrations of substrates and a product, and accurately evaluate of the result obtained using Taylor expansion when we determine the kinetic parameters using our newly developed methods. The methods to determine the kinetic parameters of the reversible Theorell-Chance mechanism described in this paper is, however, expected to be applied to general enzymatic reactions.