The proper assignment of metal ions in X-ray structures of proteins is not always easy, but in many cases this knowledge can be important, e.g. for an understanding of enzyme mechanism. In this publication, the bond-valence approach is assessed critically. A simplified version, the calcium bond-valence sum (CBVS), is proposed for the convenient analysis of the geometric environment of potential...

We present two methods for determining the sentiment expressed by a movie review. The semantic orientation of a review can be positive, negative, or neutral. We examine the effect of valence shifters on classifying the reviews. We examine three types of valence shifters: negations, intensifiers and diminishers. Negations are used to reverse the semantic polarity of a particular term, while inte...

SiIV Introduction A substantial fraction of the Ly clouds may be due to gas in small halos corresponding to dwarf galaxies or their progenitors. At low redshifts, for example, van Gorkom et al (1996) have identified a dwarf galaxy fainter than the SMC associated with a Ly cloud detected in the spectrum of Mrk 335. Many of the recent studies of the relationship between Ly clouds and galaxies hav...

We present an algorithm that is a new combination of the direct inversion in the iterative subspace ~DIIS! and the generalized valence bond ~GVB! methods. The proposed algorithm is based on applying the DIIS directly to the orbitals updated via the GVB scheme as opposed to the conventional approach of applying DIIS to a series of composite Fock matrices ~CFMs!. The new method results in GVB con...

This paper explores the large-S route to quantum disorder in the Heisenberg antiferromagnet on the pyrochlore lattice and its homologues in lower dimensions. It is shown that zero-point fluctuations of spins shape up a valencebond solid at low temperatures for one two-dimensional lattice and a liquid with very short-range valence-bond correlations for another. A one-dimensional model demonstrat...