range area in primates. Nature, Lond. 259: 459-462. Müller, K. H. 1996. Emigration of a masked titi monkey (Callicebus personatus) from an established group, and the foundation of a new group. Neotrop. Primates 4(1): 19-21.

Support for strong electronic mail security is widely available yet only few communicants appear to make use of these features. Apparently, the operational overhead of security outweighs its perceived benefits. Towards increasing the benefits versus overhead ratio we follow an approach that considers security and usability tradeoffs from the outset. We separate key exchange from binding keys to identities. The best effort key exchange and key maintainance scheme that we devise operates transparently for the user. We also describe complementary visualization and interaction techniques that communicate the security state of sent and received mail to users in a non-intrusive fashion. Towards a practical assessment of the overheads of binding keys to identities, we conducted a quantitative analysis of users’ mail behavior of which we present the results. We argue that for individual non-commercial users, out-of-band verification of keys could be more economical than building trust in public key certificates issued by third parties.

In this restless volume on teaching to read and write in the early grades of school, Barbara Taylor and David Pearson have brought together a mix of chapters that describe and take stock of successful ventures in teach-ing reading well, especially in unlikely places. They lead with their own multifaceted study of schools in low-income communities where reform efforts prospered, presenting variable after variable and connections among them. Three other large-scale studies of teaching practices, assessment, and schools follow. Then six case studies focus on schools, highlighting specific features that led to changes for the better. In turn, four case studies focus on teachers, offering details from their perspec-tives. The book concludes with two syntheses, one a broad array of characteristics that have emerged from research on effective schools and accomplished teach-ers for promoting good reading. The other synthesis, though, expresses doubts, troubles, and frustrations that weigh on the research in this book and in the field of literacy education, especially in these times of ac-countability to standards. The lead-off study was carried out at the Center for the Improvement of Early Reading Achievement (CIERA) by

Abstract not found

In this paper, we derive an asymptotic error expansion for the eigenvalue approximations by the lowest order Raviart-Thomas mixed finite element method for the general second order elliptic eigenvalue problems. Extrapolation based on such an expansion is applied to improve the accuracy of the eigenvalue approximations. Furthermore, we also prove the superclose property between the finite element projection with the finite element approximation of the eigenvalue problems by mixed finite element methods. In order to prove the full order of the eigenvalue extrapolation, we first propose “ the auxiliary equation method”. The result of this paper provides a general procedure to produce an asymptotic expansions for eigenvalue approximations by mixed finite elements.

In the first of two papers on Magma, a new system for computational algebra, we present the Magma language, outline the design principles and theoretical background, and indicate its scope and use. Particular attention is given to the constructors for structures, maps, and sets.

interactions between local coherence and choice of referring expressions; it argues that differences in coherence correspond in part to the inference demands made by different types of referring expressions, given a particular attentional state. It demonstrates that the attentional state properties modeled

The action of turbulence on a passive convected scalar field (e.g. temperature) or vector field (e.g. the magnetic field in an electrically conducting fluid) is reviewed, with particular attention paid to anomalous effects that can arise through the influence of Coriolis forces in a rotating system

In the feature subset selection problem, a learning algorithm is faced with the problem of selecting a relevant subset of features upon which to focus its attention, while ignoring the rest. To achieve the best possible performance with a particular learning algorithm on a particular training set

The study of computational agents capable of rational behaviour has received a great deal of attention in recent years. Theoretical formalizations of such agents and their implementations have proceeded in parallel with little or no connection between them. This paper explores a particular