2,903 research outputs found
'Sitting alone in the staffroom contemplating my futureā : communities of practice, legitimate peripheral participation and student teachersā experiences of problematic school placements as guests
The author wishes to thank Professor Douglas Weir for his encouragement and support in the preparation of this paper.Peer reviewedPostprin
Space and biotechnology: An industry profile
The results of a study conducted by the Center for Space and Advanced Technology (CSAT) for NASA-JSC are presented. The objectives were to determine the interests and attitudes of the U.S. biotechnology industry toward space biotechnology and to prepare a concise review of the current activities of the biotechnology industry. In order to accomplish these objectives, two primary actions were taken. First, a questionnaire was designed, reviewed, and distributed to U.S. biotechnology companies. Second, reviews of the various biotechnology fields were prepared in several aspects of the industry. For each review, leading figures in the field were asked to prepare a brief review pointing out key trends and current industry technical problems. The result is a readable narrative of the biotechnology industry which will provide space scientists and engineers valuable clues as to where the space environment can be explored to advance the U.S. biotechnology industry
Magnetic susceptibility of a CuO2 plane in the La2CuO4 system: I. RPA treatment of the Dzyaloshinskii-Moriya Interactions
Motivated by recent experiments on undoped La2CuO4, which found pronounced
temperature-dependent anisotropies in the low-field magnetic susceptibility, we
have investigated a two-dimensional square lattice of S=1/2 spins that interact
via Heisenberg exchange plus the symmetric and anti-symmetric
Dzyaloshinskii-Moriya anisotropies. We describe the transition to a state with
long-ranged order, and find the spin-wave excitations, with a mean-field
theory, linear spin-wave analysis, and using Tyablikov's RPA decoupling scheme.
We find the different components of the susceptibility within all of these
approximations, both below and above the N'eel temperature, and obtain evidence
of strong quantum fluctuations and spin-wave interactions in a broad
temperature region near the transition.Comment: 20 pages, 2 column format, 22 figure
Milky Way Mass and Potential Recovery Using Tidal Streams in a Realistic Halo
We present a new method for determining the Galactic gravitational potential
based on forward modeling of tidal stellar streams. We use this method to test
the performance of smooth and static analytic potentials in representing
realistic dark matter halos, which have substructure and are continually
evolving by accretion. Our FAST-FORWARD method uses a Markov Chain Monte Carlo
algorithm to compare, in 6D phase space, an "observed" stream to models created
in trial analytic potentials. We analyze a large sample of streams evolved in
the Via Lactea II (VL2) simulation, which represents a realistic Galactic halo
potential. The recovered potential parameters are in agreement with the best
fit to the global, present-day VL2 potential. However, merely assuming an
analytic potential limits the dark matter halo mass measurement to an accuracy
of 5 to 20%, depending on the choice of analytic parametrization. Collectively,
mass estimates using streams from our sample reach this fundamental limit, but
individually they can be highly biased. Individual streams can both under- and
overestimate the mass, and the bias is progressively worse for those with
smaller perigalacticons, motivating the search for tidal streams at
galactocentric distances larger than 70 kpc. We estimate that the assumption of
a static and smooth dark matter potential in modeling of the GD-1 and Pal5-like
streams introduces an error of up to 50% in the Milky Way mass estimates.Comment: 12 pages, 6 figures, submitted to ApJ; more information on our stream
sample and a movie of the potential recovery method used can be found at
http://www.astro.yale.edu/abonaca/research/potential_recovery.htm
A Study of Student Teachersā Experiences of Belonging on Teaching Practice
Non peer reviewedPostprin
The Skn7 Response Regulator of \u3ci\u3eSaccharomyces cerevisiae\u3c/i\u3e Interacts with Hsf1 In Vivo and Is Required for the Induction of Heat Shock Genes by Oxidative Stress
The Skn7 response regulator has previously been shown to play a role in the induction of stress-responsive genes in yeast, e.g., in the induction of the thioredoxin gene in response to hydrogen peroxide. The yeast Heat Shock Factor, Hsf1, is central to the induction of another set of stress-inducible genes, namely the heat shock genes. These two regulatory trans-activators, Hsf1 and Skn7, share certain structural homologies, particularly in their DNA-binding domains and the presence of adjacent regions of coiled-coil structure, which are known to mediate proteināprotein interactions. Here, we provide evidence that Hsf1 and Skn7 interact in vitro and in vivo and we show that Skn7 can bind to the same regulatory sequences as Hsf1, namely heat shock elements. Furthermore, we demonstrate that a strain deleted for the SKN7 gene and containing a temperature-sensitive mutation in Hsf1 is hypersensitive to oxidative stress. Our data suggest that Skn7 and Hsf1 cooperate to achieve maximal induction of heat shock genes in response specifically to oxidative stress. We further show that, like Hsf1, Skn7 can interact with itself and is localized to the nucleus under normal growth conditions as well as during oxidative stress
- ā¦