707 research outputs found
Optical control of coherent interactions between quantum dot electron spins
Coherent interactions between spins in quantum dots are a key requirement for
quantum gates. We have performed pump-probe experiments in which pulsed lasers
emitting at different photon energies manipulate two distinct subsets of
electron spins within an inhomogeneous InGaAs quantum dot ensemble. The spin
dynamics are monitored through their precession about an external magnetic
field. These measurements demonstrate spin precession phase shifts and
modulations of the magnitude of one subset of oriented spins after optical
orientation of the second subset. The observations are consistent with results
from a model using a Heisenberg-like interaction with microeV-strength.Comment: 5 pages, 4 figure
The 10 Meter South Pole Telescope
The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset
Gregorian telescope with a 966-pixel, multi-color, millimeter-wave, bolometer
camera. It is located at the Amundsen-Scott South Pole station in Antarctica.
The design of the SPT emphasizes careful control of spillover and scattering,
to minimize noise and false signals due to ground pickup. The key initial
project is a large-area survey at wavelengths of 3, 2 and 1.3 mm, to detect
clusters of galaxies via the Sunyaev-Zeldovich effect and to measure the
small-scale angular power spectrum of the cosmic microwave background (CMB).
The data will be used to characterize the primordial matter power spectrum and
to place constraints on the equation of state of dark energy. A
second-generation camera will measure the polarization of the CMB, potentially
leading to constraints on the neutrino mass and the energy scale of inflation.Comment: 47 pages, 14 figures, updated to match version to be published in
PASP 123 903 (May, 2011
Hereditary Hemorrhagic Telangiectasia: Success of the Osler Calendar for Documentation of Treatment and Course of Disease
Hereditary hemorrhagic telangiectasia (HHT; Rendu-Osler-Weber syndrome) affects the capillary and larger vessels, leading to arteriovenous shunts. Epistaxis is the main symptom impairing quality of life. The aim of the Osler Calendar is to offer information about the extent of the systemic disease and the current state of treatment. A care plan with information on the rare disease and self-treatment of epistaxis was created. Organ examinations and ongoing treatments were recorded. A questionnaire documents the treatment success, including patient satisfaction, frequency of hemorrhage and hemoglobin levels. The patients using the Osler Calendar for at least one year (n = 54) were surveyed. Eighty-five percent of patients (n = 46) used the calendar to gain information about HHT. Seventy-two percent (n = 39) used the Osler Calendar for instructions on the self-treatment of nosebleeds. The calendar increased patients’ understanding for the need for organ screenings from 48% (n = 26) to 81% (n = 44). Seventy-nine percent (n = 43) of patients confirmed that the Osler Calendar documented their therapeutic process either well or very well. Fifty-two percent (n = 28) saw an improvement in the therapeutic process due to the documentation. The Osler Calendar records the individual intensity of the disease and facilitates the communication between attending physicians. It is a tool for specialists to review treatment strategies. Furthermore, the calendar enhances patients’ comprehension of their condition
Toward a first-principles integrated simulation of tokamak edge plasmas
Performance of the ITER is anticipated to be highly sensitive to the edge plasma condition. The edge pedestal in ITER needs to be predicted from an integrated simulation of the necessary first-principles, multi-scale physics codes. The mission of the SciDAC Fusion Simulation Project (FSP) Prototype Center for Plasma Edge Simulation (CPES) is to deliver such a code integration framework by (1) building new kinetic codes XGC0 and XGC1, which can simulate the edge pedestal buildup; (2) using and improving the existing MHD codes ELITE, M3D-OMP, M3D-MPP and NIMROD, for study of large-scale edge instabilities called Edge Localized Modes (ELMs); and (3) integrating the codes into a framework using cutting-edge computer science technology. Collaborative effort among physics, computer science, and applied mathematics within CPES has created the first working version of the End-to-end Framework for Fusion Integrated Simulation (EFFIS), which can be used to study the pedestal-ELM cycles
The South Pole Telescope
A new 10 meter diameter telescope is being constructed for deployment at the
NSF South Pole research station. The telescope is designed for conducting
large-area millimeter and sub-millimeter wave surveys of faint, low contrast
emission, as required to map primary and secondary anisotropies in the cosmic
microwave background. To achieve the required sensitivity and resolution, the
telescope design employs an off-axis primary with a 10m diameter clear
aperture. The full aperture and the associated optics will have a combined
surface accuracy of better than 20 microns rms to allow precision operation in
the submillimeter atmospheric windows. The telescope will be surrounded with a
large reflecting ground screen to reduce sensitivity to thermal emission from
the ground and local interference. The optics of the telescope will support a
square degree field of view at 2mm wavelength and will feed a new 1000-element
micro-lithographed planar bolometric array with superconducting transition-edge
sensors and frequency-multiplexed readouts. The first key project will be to
conduct a survey over approximately 4000 degrees for galaxy clusters using the
Sunyaev-Zel'dovich Effect. This survey should find many thousands of clusters
with a mass selection criteria that is remarkably uniform with redshift. Armed
with redshifts obtained from optical and infrared follow-up observations, it is
expected that the survey will enable significant constraints to be placed on
the equation of state of the dark energy.Comment: Written prior to SPIE conference, June 21-25, 2004. 19 pages, 13
figures. Also available (with higher resolution figures) at
http://spt.uchicago.edu
Indication for the disappearance of reactor electron antineutrinos in the Double Chooz experiment
The Double Chooz Experiment presents an indication of reactor electron
antineutrino disappearance consistent with neutrino oscillations. A ratio of
0.944 0.016 (stat) 0.040 (syst) observed to predicted events was
obtained in 101 days of running at the Chooz Nuclear Power Plant in France,
with two 4.25 GW reactors. The results were obtained from a single 10
m fiducial volume detector located 1050 m from the two reactor cores. The
reactor antineutrino flux prediction used the Bugey4 measurement as an anchor
point. The deficit can be interpreted as an indication of a non-zero value of
the still unmeasured neutrino mixing parameter \sang. Analyzing both the rate
of the prompt positrons and their energy spectrum we find \sang = 0.086
0.041 (stat) 0.030 (syst), or, at 90% CL, 0.015 \sang 0.16.Comment: 7 pages, 4 figures, (new version after PRL referee's comments
A Theoretical Analysis of How Segmentation of Dynamic Visualizations Optimizes Students' Learning
This article reviews studies investigating segmentation of dynamic visualizations (i.e., showing dynamic visualizations in pieces with pauses in between) and discusses two not mutually exclusive processes that might underlie the effectiveness of segmentation. First, cognitive activities needed for dealing with the transience of dynamic visualizations impose extraneous cognitive load, which may hinder learning. Segmentation may reduce the negative effect of this load by dividing animations into smaller units of information and providing pauses between segments that give students time for the necessary cognitive activities after each of those units of information. Second, event segmentation theory states that people mentally segment dynamic visualizations during perception (i.e., divide the information shown in pieces). Segmentation of dynamic visualisation could cue relevant segments to students, which may aid them in perceiving the structure underlying the process or procedure shown
Identification of a novel zinc metalloprotease through a global analysis of clostridium difficile extracellular proteins
Clostridium difficile is a major cause of infectious diarrhea worldwide. Although the cell surface proteins are recognized to be important in clostridial pathogenesis, biological functions of only a few are known. Also, apart from the toxins, proteins exported by C. difficile into the extracellular milieu have been poorly studied. In order to identify novel extracellular factors of C. difficile, we analyzed bacterial culture supernatants prepared from clinical isolates, 630 and R20291, using liquid chromatography-tandem mass spectrometry. The majority of the proteins identified were non-canonical extracellular proteins. These could be largely classified into proteins associated to the cell wall (including CWPs and extracellular hydrolases), transporters and flagellar proteins. Seven unknown hypothetical proteins were also identified. One of these proteins, CD630_28300, shared sequence similarity with the anthrax lethal factor, a known zinc metallopeptidase. We demonstrated that CD630_28300 (named Zmp1) binds zinc and is able to cleave fibronectin and fibrinogen in vitro in a zinc-dependent manner. Using site-directed mutagenesis, we identified residues important in zinc binding and enzymatic activity. Furthermore, we demonstrated that Zmp1 destabilizes the fibronectin network produced by human fibroblasts. Thus, by analyzing the exoproteome of C. difficile, we identified a novel extracellular metalloprotease that may be important in key steps of clostridial pathogenesis
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