Centrosymmetric lie algebras and boost-dilations

We define the Lie algebrac(n) of centrosymmetric matrices. It generates a noncompact and nonsemisimple local Lie group with the unusual property that expc(n) c(n). The group contains an invariant subgroup of Lorentz boost/ dilation transformations. Forn even, these form a subgroup of the conformal group of the Lorentzian metric with signature (– + – + – +).     

Identification of archaeal proteins that affect the exosome function in vitro

Background  

The archaeal exosome is formed by a hexameric RNase PH ring and three RNA binding subunits and has been shown to bind and degrade RNA in vitro. Despite extensive studies on the eukaryotic exosome and on the proteins interacting with this complex, little information is yet available on the identification and function of archaeal exosome regulatory factors.     

A dynamic edge covering and scheduling problem: complexity results and approximation algorithms

We consider a new dynamic edge covering and scheduling problem that focuses on assigning resources to nodes in a network to minimize the amount of time required to process all edges in it. Resources need to be co-located at the endpoints of an edge for it to be processed and, therefore, this problem contains both edge covering and scheduling decisions. These new problems have motivating applications in traffic systems and military intelligence operations. We provide complexity results for the dynamic edge covering and scheduling problem over different types of networks. We then show that existing approximation algorithms for parallel machine scheduling problems can be leveraged to provide approximation algorithms for this new class of problems over certain types of networks.     

An algorithm for calculating atomic D states with explicitly correlated gaussian functions

An algorithm for the variational calculation of atomic D states employing n-electron explicitly correlated gaussians is developed and implemented. The algorithm includes formulas for the first derivatives of the hamiltonian and overlap matrix elements determined with respect to the gaussian nonlinear exponential parameters. The derivatives are used to form the energy gradient which is employed in the variational energy minimization. The algorithm is tested in the calculations of the two lowest D states of the lithium and beryllium atoms. For the lowest D state of Li the present result is lower than the best previously reported result.     

Probabilistic value pricing

In this paper we consider the class of probabilistic value pricing mechanisms for cost allocation problems, which are related to probabilistic values for finite games with transferable utility. We characterize probabilistic value pricing axiomatically, as well as several related pricing mechanisms, including semivalue pricing (symmetric pricing without cost sharing), quasivalue pricing (cost sharing pricing without symmetry), and weighted Shapley value pricing. We also describe a class of problems in which (symmetric) Shapley value pricing coincides with Aumann-Shapley pricing, and a class of problems for which every quasivalue pricing mechanism is supportable.     

Fluorodienes. V. Copolymerization of 1,1,4,4-tetrafluoro-1,3-butadiene with oxygen and nitric oxide

1,1,4,4-Tetrafluoro-1,3-butadiene reacts with oxygen to form a polyperoxide containing 1.0–1.1 peroxide groups for each diene unit. This polymer behaves like a typical peroxide. It explodes violently when heated to 120°C. or when subjected to shock, and it initiates polymerization of vinyl monomers at temperatures of 90°C. or higher. The tetrafluorobutadiene also copolymerizes with nitric oxide to give a highly crosslinked polymer containing three molecules of diene for each two molecules of nitric oxide.     

Polymers containing polyhedral borane rings I. Condensation polymers

The preparation and properties of a unique new class of polymers containing polyhedral borane cages as part of the backbone polymer chain are described. The synthesis of polyamides, polyesters, polyureas, and polyurethanes proceeds from suitably chosen B₁₀ and B₁₂ polyhedral borane dicarbonyls, diols, and diisocyanates by typical condensation polymer techniques. Each complementary monomer may be a borane compound, but more often higher molecular weight products are provided when one monomer is a conventional organic reagent such as an aromatic diisocyanate. The polyamides prepared from 1, 12-B₁₂H₁₀(CO)₂ and organic diamines were crystalline and soluble, but molecular weight were limited because the amidation reaction was reversible and/or the amide linkage could be split by nucleophilic attack by some solvents. The polyurethanes prepared from Na₂B₁₂H₁₀(OH)₂ and aromatic diisocyanates were high molecular weight and relatively more stable. Clear, colorless, tough films were prepared. These polymers were soluble in many polar solvents and exhibited typical polyelectrolyte behavior.     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.