We find zero-free regions in the complex plane at large |q| for the multivariate Tutte polynomial (also known in statistical mechanics as the Potts-model partition function) ZG(q,w) of a graph G with general complex edge weights w = {we}. This generalizes a result of Sokal [22] that applied only within the complex antiferromagnetic regime |1+we| ≤ 1. Our proof uses the polymer-gas representatio...

Let G be a finite group. We show that the Bass Nil-groups NKn(RG), n ∈ Z, are generated from the p-subgroups of G by induction, certain twistings maps depending on elements in the centralizers of the psubgroups, and the Verschiebung homomorphisms. As a consequence, the groups NKn(RG) are generated by induction from elementary subgroups. For NK0(ZG) we get an improved estimate of the torsion exp...

Fairness of non-repudiation is naturally expressed as a liveness specification. We formalize this idea by using the process algebra CSP to analyze the well-known Zhou-Gollmann protocol. We here model and verify a variant of the ZG protocol that includes a deadline (timestamp) for completion of the protocol, after which an agent can no longer initiate the recovery protocol with the TTP to get ho...

'FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, member of Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein, The Netherlands ^Institut fur Energieforschung Plasmaphysik, Forschungszentrum Jiilich Gmbh, Association EURATOM-FZJ, member of Trilateral Euregio Cluster, 52425 Jiilich, Germany ^ Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon 0X14 3DB...

In this note we investigate the hypercentral units in integral group rings ZG, where G is not necessarily torsion. One of the main results obtained is the following (Theorem 3.5): if the set of torsion elements of G is a subgroup T of G and if Z2(U) is not contained in CU (T ), then T is either an Abelian group of exponent 4 or a Q∗ group. This extends our earlier result on torsion group rings.

A method was established for the simultaneous determination of germanium and tin in one run by ion chromatography. Using a selected eluent, Ge and Sn were separated on a bifunctional ion-exchange column, followed by a postcolumn chromogenic reaction and spectrophotometric detection at 520 nm. The whole procedure was completed within 5 min with high sensitivity and selectivity at the low-/zg/1 l...

Robert van Liere Centrum voor Wiskunde en Informatica P.O. Box 94079, 1090 GB Amsterdam The Netherlands E-mail: [email protected] Jurriaan D. Mulder Centrum voor Wiskunde en Informatica P.O. Box 94079, 1090 GB Amsterdam The Netherlands E-mail: [email protected] Jarke J. van Wijk Netherlands Energy Research Foundation ECN P.O. Box 1, 1755 ZG Petten The Netherlands Centrum voor Wiskunde en Informatica P...

Let k be an algebraically closed field of characteristic 2. We prove that the restricted nilpotent commuting variety C, that is the set of pairs of (n× n)-matrices (A,B) such that A2 = B2 = [A,B] = 0, is equidimensional. C can be identified with the ‘variety of n-dimensional modules’ for Z/2Z×Z/2Z, or equivalently, for k[X,Y ]/(X2, Y 2). On the other hand, we provide an example showing that the...

Kees van Oers1,2,3), Gerdien de Jong4), Arie J. van Noordwijk2), B. Kempenaers1) & Pieter J. Drent2) (1 Max-Planck Institute for Ornithology, Department of Behavioural Ecology and Evolutionary Genetics, PO Box 1564, D-82319 Starnberg (Seewiesen), Germany; 2 Netherlands Institute of Ecology (NIOO-KNAW), Department of Animal Population Biology, PO Box 40, 6666 ZG, Heteren, The Netherlands; 4 Evol...

Gas-particle interactions above a Dutch heathland: I. Surface exchange fluxes of NH3, SO2, HNO3 and HCl E. Nemitz, M. A. Sutton, G. P. Wyers, and P. A. C. Jongejan Atmospheric Sciences, Centre for Ecology and Hydrology (CEH), Edinburgh Research Station, Bush Estate, Penicuik, Midlothian, EH26 0QB, Scotland Energy Research Centre of the Netherlands (ECN), Postbus 1, 1755 Petten ZG, The Netherlan...