879 research outputs found
A Laboratory Investigation of Supersonic Clumpy Flows: Experimental Design and Theoretical Analysis
We present a design for high energy density laboratory experiments studying
the interaction of hypersonic shocks with a large number of inhomogeneities.
These ``clumpy'' flows are relevant to a wide variety of astrophysical
environments including the evolution of molecular clouds, outflows from young
stars, Planetary Nebulae and Active Galactic Nuclei. The experiment consists of
a strong shock (driven by a pulsed power machine or a high intensity laser)
impinging on a region of randomly placed plastic rods. We discuss the goals of
the specific design and how they are met by specific choices of target
components. An adaptive mesh refinement hydrodynamic code is used to analyze
the design and establish a predictive baseline for the experiments. The
simulations confirm the effectiveness of the design in terms of articulating
the differences between shocks propagating through smooth and clumpy
environments. In particular, we find significant differences between the shock
propagation speeds in a clumpy medium compared to a smooth one with the same
average density. The simulation results are of general interest for foams in
both inertial confinement fusion and laboratory astrophysics studies. Our
results highlight the danger of using average properties of inhomogeneous
astrophysical environments when comparing timescales for critical processes
such as shock crossing and gravitational collapse times.Comment: 7 pages, 6 figures. Submitted to the Astrophysical Journal. For
additional information, including simulation animations and the pdf and ps
files of the paper with embedded high-quality images, see
http://pas.rochester.edu/~wm
Developing a Model Curriculum for a University Course in Health Impact Assessment in the United States
As Health Impact Assessment (HIA) become increasingly common in the U.S. there is growing demand for instruction beyond sho1i courses and online training. As of October 2013, there are graduate level courses that include instruction on HIA in at least 17 universities in the U.S., including 4 courses that focus explicitly on HIA. Instructors of these four courses collaborated to develop a model curriculum for teaching HIA that draws on a framework for experiential learning and on a theoretical model of curriculum formulation. This article includes an in-depth analysis of these courses and presents a model curriculum for HIA instruction during an academic quaiier or semester course in a University. This model curriculum may help faculty develop a graduate level HIA course at their institution, as well as inform public health and community design professionals interested in building capacity to conduct HIAs, and students considering taking an HIA course. International instructors could also learn from the U.S. experience, and apply the model curriculum to their setting and educational structure.This work was supported in part by the Johns Hopkins Bloomberg School of Public Health
Faculty Innovation Fund
A Subsumption Agent for Collaborative Free Improvisation
This paper discusses the design and evaluation of an artificial agent for collaborative musical free improvisation. The agent provides a means to investigate the underpinnings of improvisational interaction. In connection with this general goal, the system is also used here to explore the implementation of a collaborative musical agent using a specific robotics architecture, Subsumption. The architecture of the system is explained, and its evaluation in an empirical study with expert improvisors is discussed. A follow-up study using a second iteration of the system is also presented. The system design and connected studies bring together Subsumption robotics, ecological psychology, and musical improvisation, and contribute to an empirical grounding of an ecological theory of improvisation
Synchronizing Sequencing Software to a Live Drummer
Copyright 2013 Massachusetts Institute of Technology. MIT allows authors to archive published versions of their articles after an embargo period. The article is available at
Frequent germ-line succinate dehydrogenase subunit D gene mutations in patients with apparently sporadic parasympathetic paraganglioma
Frequent germ-line succinate dehydrogenase subunit D gene mutations in patients with apparently sporadic parasympathetic paraganglioma
Thomson scattering from a shock front
We have obtained a Thomson scattering spectrum in the collective regime by scattering a probe beam from a shock front, in an experiment conducted at the Omega laser at the Laboratory for Laser Energetics. The probe beam was created by frequency converting a beamline at Omega to a 2âns2ns pulse of 0.263âÎŒm0.263ÎŒm light, focused with a dedicated optical focusing system. The diagnostic system included collecting optics, spectrometer, and streak camera, with a scattering angle of 101°. The target included a primary shock tube, a 20-ÎŒm20-ÎŒm-thick beryllium drive disk, 0.3-ÎŒm0.3-ÎŒm-thick polyimide windows mounted on a secondary tube, and a gas fill tube. Detected acoustic waves propagated parallel to the target axis. Ten laser beams irradiated the beryllium disk with 0.351âÎŒm0.351ÎŒm light at 5Ă1014âW/cm25Ă1014Wâcm2 for 1âns1ns starting at toto, driving a strong shock through argon gas at Ïo = 1âmg/ccÏo=1mgâcc. The 200âJ200J probe beam fired at t = 19ânst=19ns for 2âns2ns, and at t = 20.1ânst=20.1ns a 0.3âns0.3ns signal was detected. We attribute this signal to scattering from the shocked argon, before the density increased above critical due to radiative collapse.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87893/2/10E504_1.pd
Frequent germ-line succinate dehydrogenase subunit D gene mutations in patients with apparently sporadic parasympathetic paraganglioma
PURPOSE: Recently, familial paraganglioma (PGL) was shown to be caused
bymutations in the gene encoding succinate dehydrogenase subunit D (SDHD).
However, the prevalence of SDHD mutations in apparently sporadic PGL is
unknown. We studied the frequency and spectrum of germ-line and somatic
SDHD mutations in patients with parasympathetic PGL. EXPERIMENTAL DESIGH:
We studied 57 unselected patients who developed parasympathetic PGLs (n =
105 tumors) and who were treated between 1987 and 1999 at the Erasmus MC
(Rotterdam, the Netherlands). Thirty-eight (67%) of these patients (n = 51
tumors) lacked a family history of parasympathetic PGL. We used
conformation-dependent gel electrophoresis and sequence determination
analysis of germ-line and tumor DNA to identify SDHD mutations. We
compared the clinical and molecular characteristics of sporadic and
hereditary PGLs. RESULTS: Three different SDHD germ-line mutations were
identified in 32 of the 57 (56%) patients. These included 19 of 19 (100%)
patients with familial PGL and also 13 of 38 (34%) patients with
apparently sporadic PGL. All three mutations were characterized as
missense mutations (D92Y, L95P, and L139P) in highly conserved regions of
the SDHD gene and were not observed in 200 control alleles. No somatic
mutations were found. CONCLUSIONS: Germ-line mutations of the SDHD gene
are present in a significant number of patients with apparently sporadic
parasympathetic PGL. Somatic SDHD mutations do not play a significant role
in the sporadic form of this tumor. Genetic testing for SDHD germ-line
mutations should be considered for every patient presenting with this
tumor, even if a personal or family history of PGL is absent, to allow
appropriate clinical management
Ire1α-Regulated Rate of mRNA Translation is Required for Acquisition of Identity and Polarity in Upper Layer Cortical Neurons
Evolutionary expansion of the neocortex is associated with the increase in upper layer neurons. Here, we present Inositol-Requiring Enzyme 1α, Ire1α, as an essential determinant of upper layer fate, neuronal polarization and cortical lamination. We demonstrate a non-canonical function of Ire1α in the regulation of global translation rates in the developing neocortex through its dynamic interaction with the ribosome and regulation of eIF4A1 and eEF-2 expression. Inactivation of Ire1α engenders lower protein synthesis rates associated with stalled ribosomes and decreased number of translation start sites. We show unique sensitivity of upper layer fate to translation rates. Whereas eEF-2 is required for cortical lamination, eIF4A1 regulates acquisition of upper layer fate downstream of Ire1α in a mechanism of translational control dependent on 5âUTR-embedded structural elements in fate determinant genes. Our data unveil developmental regulation of ribosome dynamics as post-transcriptional mechanisms orchestrating neuronal diversity establishment and assembly of cortical layers
Corrections to the Electroweak Effective Action at Finite Temperature
We calculate contributions to the finite temperature effective action for the
electroweak phase transition (EWPT) at \O(g^4), {\it i.e.} at second order in
(g^2 T/\M) and all orders in (g^2 T^2/\M^2). This requires plasma-mass
corrections in the calculation of the effective potential, inclusion of the
``lollipop'' diagram, and an estimate of derivative corrections. We find the
EWPT remains too weakly first-order to drive baryogenesis. We calculate some
one loop kinetic energy corrections using both functional and diagrammatic
methods; these may be important for saddlepoint configurations such as the
bounce or sphaleron.Comment: LaTeX, 6 figures available by email, CALT-68-1795, HUTP-92-A027,
EFI-92-2
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