Fermi-energy scaling of the metal-insulator transition temperature in quasi-one-dimensional systems

Several physical properties of four quasi-one-dimensional organic conductors are compared. Assuming that the intermolecular spacing along the conducting stacks and the magnitude of the susceptibility serve as indicators of the degree of electronic overlap, the data indicate that an increase in this overlap enhances the stability of the insulating ground state of these systems. As a result, the metal—insulator transition temperature is found to scale roughly linearly with an effective Fermi energy.     

Computer automation of soil dynamics research

The rapid development of computer technology in the past few years, combined with the accompanying reduction of costs, has resulted in the availability of a very powerful tool to researchers. A real-time multiprogramming digital computer system has been in use at the National Tillage Machinery Laboratory for 8 years. This system supports about 90% of the Laboratory's data acquisition, analysis, storage, and display requirements. The computer has had considerable impact on the productivity of the research program at the National Tillage Machinery Laboratory.     

Mechanistic elucidation of intramolecular aminoalkene hydroamination catalyzed by a tethered bis(ureate) complex: evidence for proton-assisted C-N bond formation at zirconium

A broad mechanistic investigation regarding hydroamination reactions catalyzed by a tethered bis(ureate) zirconium species, [ureate(2-)]Zr(NMe(2))(2)(HNMe(2)), is described. The cyclization of both primary and secondary aminoalkene substrates gives similar kinetic profiles, with zero-order dependence on substrate concentration up to ～60-75% conversion, followed by first-order dependence for the remainder of the reaction. The addition of 2-methylpiperidine changes the observed substrate dependence to first order throughout the reaction, but does not act as a competitive inhibitor. The reactions are first order in precatalyst up to loadings of ～0.15 M, indicating that a well-defined, mononuclear catalytic species is operative. Several model complexes have been structurally characterized, including dimeric imido and amido species, and evaluated for catalytic performance. These results indicate that imido species need not be invoked as catalytically relevant intermediates, and that the mono(amido) complex [ureate(2-)]Zr(NMe(2))(Cl)(HNMe(2)) is much less active than its bis(amido) counterpart. Structural evidence suggests that this is due to differences in coordination geometry between the mono- and bis(amido) complexes, and that an equatorial amido ligand is required for efficient catalytic turnover. On the basis of the determination of kinetic isotope effects and stoichiometric reactivity, the catalytic turnover-limiting step is proposed to be a concerted C-H, C-N bond-forming process with a highly ordered, unimolecular transition state (ΔS(?) = -21 ± 1 eu). In addition to this key bond-forming step, the catalytic cycle involves an on-cycle pre-equilibrium between six- and seven-coordinate intermediates, leading to the observed switch from zero- to first-order kinetics.     

QUANTITATIVE METHODS FOR DECISION SUPPORT IN THE ICELANDIC FISHING INDUSTRY

Abstract Modern fisheries already collect vast amount of data, for example, through ERP systems and electronic log‐books. It is however well known that the data are rarely used for improving operational decision making. By converting this data into useable information, decision making in the fishing industry could be improved. This paper attempts to show that quantitative methods can be of use in many aspects of decision making in the fishing industry. The paper proposes a hierarchically structured decision support process based on two different optimization models for supporting the long‐ and short‐term decision making in fisheries. For long‐term planning the paper proposes a linear optimization model that describes the entire operation of a vertically integrated seafood company. For short‐term decision making the paper proposes a mixed integer linear optimization model to assist in organizing vessel trips and deciding catch location with regard to raw material quality and yield obtained in processing.