Bialgebra deformations and algebras of trees

Let A denote a bialgebra over a field k and let A sub t = A((t)) denote the ring of formal power series with coefficients in A. Assume that A is also isomorphic to a free, associative algebra over k. A simple construction is given which makes A sub t a bialgebra deformation of A. In typical applications, A sub t is neither commutative nor cocommutative. In the terminology of Drinfeld, (1987), A sub t is a quantum group. This construction yields quantum groups associated with families of trees

The electronic structure of liquid water within density functional theory

In the last decade, computational studies of liquid water have mostly concentrated on ground state properties. However recent spectroscopic measurements have been used to infer the structure of water, and the interpretation of optical and x-ray spectra requires accurate theoretical models of excited electronic states, not only of the ground state. To this end, we investigate the electronic properties of water at ambient conditions using ab initio density functional theory within the generalized gradient approximation (DFT/GGA), focussing on the unoccupied subspace of Kohn-Sham eigenstates. We generate long (250 ps) classical trajectories for large supercells, up to 256 molecules, from which uncorrelated configurations of water molecules are extracted for use in DFT/GGA calculations of the electronic structure. We find that the density of occupied states of this molecular liquid is well described with 32 molecule supercells using a single k-point (k = 0) to approximate integration over the first Brillouin zone. However, the description of the density of unoccupied states (u-EDOS) is sensitive to finite size effects. Small, 32 molecule supercell calculations, using Gamma-the point approximation, yield a spuriously isolated state above the Fermi level. Nevertheless, the more accurate u-EDOS of large, 256 molecule supercells may be reproduced using smaller supercells and increased k-point sampling. This indicates that the electronic structure of molecular liquids like water is relatively insensitive to the long-range disorder in the molecular structure. These results have important implications for efficiently increasing the accuracy of spectral calculations for water and other molecular liquids.Comment: 12 pages, 11 figures (low quality) Submitted to JChemPhy

The Role of Risk: Mentoring Experiences and Outcomes for Youth with Varying Risk Profiles

This report presents results from the nation's first large-scale study to examine how youth's levels and sources of risk may influence their mentoring relationships and the benefits they derive from participating in mentoring programs. More and more, mentoring programs are being asked to serve young people who are considered "higher risk." And while mentoring has a strong research base generally, until now relatively little has been known about programs' capacities to serve and produce benefits for these youth.Funded by the Bill & Melinda Gates Foundation, the study involved more than 1,300 youth, drawn from seven programs serving young people in Washington State. Oversight and support for the project were provided by Washington State Mentors. The study looked closely at the backgrounds of participating youth and their mentors, the mentoring relationships that formed, the program supports that were offered, and the benefits youth received -- and examined how these varied for youth with differing profiles (i.e., levels and types) of risk."The Role of Risk" describes the study's methods and findings and considers their implications for practitioners and funders. Overall, the study's results suggest that mentoring programs can benefit youth with a broad range of backgrounds and characteristics. The findings also highlight the importance of youth risk in shaping match experiences, and suggest that programs should do more to tailor training and support based on the specific risks youth face

Book Reviews

Reviews of : Wansink, B. Marketing Nutrition: Soy, Functional foods, Biotechnology and Obesity Urbana and Chicago: University of Illinois Press, 2005; Motzafi-Haller, P. (ed.) Women in Agriculture in the Middle East Aldershot, England: Ashgate Publishing, 2005Teaching/Communication/Extension/Profession,

Revitalization of an Emergency Department

No abstract available

The Role of Risk: Mentoring Experiences and Outcomes for Youth with Varying Risk Profiles (Executive Summary)

This summary highlights key findings and implications from the nation's first large-scale study to examine how youth's levels and sources of risk may influence their mentoring relationships and the benefits they derive from participating in mentoring programs. More and more, mentoring programs are being asked to serve young people who are considered "higher risk." And while mentoring has a strong research base generally, until now relatively little has been known about programs' capacities to serve and produce benefits for these youth.Funded by the Bill & Melinda Gates Foundation, the study involved more than 1,300 youth, drawn from seven programs serving young people in Washington State. Oversight and support for the project were provided by Washington State Mentors. The study looked closely at the backgrounds of participating youth and their mentors, the mentoring relationships that formed, the program supports that were offered, and the benefits youth received -- and examined how these varied for youth with differing profiles (i.e., levels and types) of risk."The Role of Risk" executive summary describes the study's methods and findings and considers their implications for practitioners and funders. Overall, the study's results suggest that mentoring programs can benefit youth with a broad range of backgrounds and characteristics. The findings also highlight the importance of youth risk in shaping match experiences, and suggest that programs should do more to tailor training and support based on the specific risks youth face

Pseudo-Deterministic Streaming

A pseudo-deterministic algorithm is a (randomized) algorithm which, when run multiple times on the same input, with high probability outputs the same result on all executions. Classic streaming algorithms, such as those for finding heavy hitters, approximate counting, ?_2 approximation, finding a nonzero entry in a vector (for turnstile algorithms) are not pseudo-deterministic. For example, in the instance of finding a nonzero entry in a vector, for any known low-space algorithm A, there exists a stream x so that running A twice on x (using different randomness) would with high probability result in two different entries as the output. In this work, we study whether it is inherent that these algorithms output different values on different executions. That is, we ask whether these problems have low-memory pseudo-deterministic algorithms. For instance, we show that there is no low-memory pseudo-deterministic algorithm for finding a nonzero entry in a vector (given in a turnstile fashion), and also that there is no low-dimensional pseudo-deterministic sketching algorithm for ?_2 norm estimation. We also exhibit problems which do have low memory pseudo-deterministic algorithms but no low memory deterministic algorithm, such as outputting a nonzero row of a matrix, or outputting a basis for the row-span of a matrix. We also investigate multi-pseudo-deterministic algorithms: algorithms which with high probability output one of a few options. We show the first lower bounds for such algorithms. This implies that there are streaming problems such that every low space algorithm for the problem must have inputs where there are many valid outputs, all with a significant probability of being outputted

MalStone: Towards A Benchmark for Analytics on Large Data Clouds

Developing data mining algorithms that are suitable for cloud computing platforms is currently an active area of research, as is developing cloud computing platforms appropriate for data mining. Currently, the most common benchmark for cloud computing is the Terasort (and related) benchmarks. Although the Terasort Benchmark is quite useful, it was not designed for data mining per se. In this paper, we introduce a benchmark called MalStone that is specifically designed to measure the performance of cloud computing middleware that supports the type of data intensive computing common when building data mining models. We also introduce MalGen, which is a utility for generating data on clouds that can be used with MalStone

Flavour-Changing Neutral Currents and Leptophobic Z' Gauge Bosons

Leptophobic Z' gauge bosons can appear in models with an E_6 gauge symmetry. We show that flavour-changing neutral currents can be generated in some of these models due to the mixing of the ordinary d_R, s_R and b_R quark fields with the exotic h_R. Because the Z' does not couple to charged leptons, the constraints on the flavour-changing couplings U^{Z'}_{db} and U^{Z'}_{sb} are relatively weak. Indeed, B_q--Bbar_q mixing (q=d,s) can be dominated by Z' exchange, which will affect CP-violating rate asymmetries in B decays. Rare hadronic B decays can also be affected, while decays involving charged leptons will be unchanged.Comment: 11 pages, LaTeX, no figure