The Systems Approach in an Information Society: A Reconsideration

An information society is one in which informational (or interactional) as opposed to material entities represent the dominant form of social and economic transaction. This paper argues that in such an information-rich environment, the conventional view of the systems approach may no longer be relevant, and may in fact be a serious barrier to the development and implementation of creative management technologies. We present an alternative perspective on the systems approach that emphasizes the primacy of informational concepts as opposed to the primacy of matter/energy concepts. This alternative focuses on interactions, on the logic of change, on circular causality, and on multiple concepts of time. There are important implications for organizational design, managerial control and information systems.     

Reactive properties of trans-dichlorooxirane in relation to the contrasting carcinogenicities of vinyl chloride and trans-dichloroethylen

Our objective in this work is to gain insight into the contrasting carcinogenic activities of vinyl chloride (definitely carcinogenic) and trans-dichloroethylene (apparently inactive). The initial metabolic step for each molecule is believed to be epoxidation of the double bond, and there is evidence indicating that for vinyl chloride, this epoxide (chlorooxirane) is its ultimate (direct-acting) carcinogenic form. This article presents the findings of a computational study of the reactive properties of trans-dichlorooxirane (the epoxide of trans-dichloroethylene). An ab initio SCF -MO procedure was used to determine the energy requirements for stretching the C? O and C? Cl bonds (S_N1 reactivity) and to study the epoxide's S_N2 interactions with ammonia, taken as a model nucleophile. The starting points were the oxygen- and chlorine-protonated forms of the epoxide. The structure of the system was reoptimized at each step along the various reaction pathways. The results of this work are compared to an analogous earlier study of the reactive properties of chlorooxirane. The chlorineprotonated C? Cl bonds are found to have much lower energy barriers to stretching than do the oxygen-protonated C? O bonds. In the S_N2 processes, intermediate complexes are formed with ammonia by both the oxygen- and the chlorine-protonated epoxides; the latter complexes are the more stable. Based on our results, we propose two mechanisms (one S_N1 and the other S_N2) whereby trans-dichlorooxirane can interact with N₇ of guanine to produce an adduct analogous to one formed by chlorooxirane, which has been found to be the primary in vivo DNA alkylation product of vinyl chloride and to which has been attributed the carcinogenicity of the latter. Overall, trans-dichlorooxirane is found to be chemically more reactive than chlorooxirane; this may help to account for the much lesser carcinogenic and mutagenic activities of trans-dichloroethylene, since the epoxide may be reacting with other cellular nucleophiles before it reaches the key site(s) at which the carcinogenic or mutagenic interaction would occur. We also offer some speculations concerning other possible factors related to the differing carcinogenicities of vinyl chloride and trans-dichloroethylene, such as ease of epoxide formation and the likelihood of oxygen protonation.     

Effets de substituant sur la fréquence hydroxyle de phenols associés à des hydrocarbures benzéniques par liaison d'hydrogene

The electronic effects of X substituents in aromatic molecules XC₆H₅, XC₆H₄Me and XC₆H₄OMe are studied by measurements of the bonded OH frequencies of phenol-π-base complexes. A judicious choice of the experimental conditions (solvent, π-base concentration, phenol acidity, temperature) permits the following substituents to be studied: Me, Et, CH(Me)₂, OMe, OEt, OC₆H₅, NHMe, N(Me)₂, N(Et)₂, NHC₆H₅, C₆H₅, CHCH₂, CCH, CCMe, SMe, SC₆H₅, F, Cl, Br and I.Halogenated benzenes, benzotrichloride and benzotrifluoride were found to act solely as π-bases. Electronic effects are accurately measured by means of the linear combination ?₁σ₁ + ?_R?°_R. The ratio ?_R/?₁ shows that inductive and mesomeric effects are of the same importance. This ratio may be considered as an argument in favour of the symmetric configuration of the complex. Electronic effects are found to be additive in disubstituted benzenes.     

Cutting planes for integer programs with general integer variables

We investigate the use of cutting planes for integer programs with general integer variables. We show how cutting planes arising from knapsack inequalities can be generated and lifted as in the case of 0–1 variables. We also explore the use of Gomory's mixed-integer cuts. We address both theoretical and computational issues and show how to embed these cutting planes in a branch-and-bound framework. We compare results obtained by using our cut generation routines in two existing systems with a commercially available branch-and-bound code on a range of test problems arising from practical applications. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.Corresponding author.This research was partly performed when the author was affiliated with CORE, Université Catholique de Louvain.     

Infrared energy levels and intensities of carbon dioxide—II

Energy levels and rotational constants are provided for all carbon dioxide infrared absorption transitions of significance for terrestrial atmospheric transmission. Constants have been recalculated using new FTS measurements in the 4.3 μm region at elevated temperature, new FTS measurements in the 15, 5, and 2 μm regions, precise laser measurements around 10 μm, and high resolution grating spectrometer measurements of isotopically enriched samples. Band centers, band strengths, and coriolis coupling constants are given for some 560 bands.