2,946 research outputs found
Low-distortion slow light using two absorption resonances
We consider group delay and broadening using two strongly absorbing and
widely spaced resonances. We derive relations which show that very large pulse
bandwidths coupled with large group delays and small broadening can be
achieved. Unlike single resonance systems, the dispersive broadening dominates
the absorptive broadening which leads to a dramatic increase in the possible
group delay. We show that the double resonance systems are excellent candidates
for realizing all-optical delay lines. We report on an experiment which
achieved up to 50 pulse delays with 40% broadening.Comment: 4 pages 4 figure
Hands-On Universe: A Global Program for Education and Public Outreach in Astronomy
Hands-On Universe (HOU) is an educational program that enables students to
investigate the Universe while applying tools and concepts from science, math,
and technology. Using the Internet, HOU participants around the world request
observations from an automated telescope, download images from a large image
archive, and analyze them with the aid of user-friendly image processing
software. This program is developing now in many countries, including the USA,
France, Germany, Sweden, Japan, Australia, and others. A network of telescopes
has been established among these countries, many of them remotely operated, as
shown in the accompanying demo. Using this feature, students in the classroom
are able to make night observations during the day, using a telescope placed in
another country. An archive of images taken on large telescopes is also
accessible, as well as resources for teachers. Students are also dealing with
real research projects, e.g. the search for asteroids, which resulted in the
discovery of a Kuiper Belt object by high-school students. Not only Hands-On
Universe gives the general public an access to professional astronomy, but it
is also a more general tool to demonstrate the use of a complex automated
system, the techniques of data processing and automation. Last but not least,
through the use of telescopes located in many countries over the globe, a form
of powerful and genuine cooperation between teachers and children from various
countries is promoted, with a clear educational goal.Comment: 4 pages, 1 figure, to appear in the proceedings of the ADASS X
conference, Boston, October 2000, ASP conf. pro
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The Reduction of C14 Labeled Carbon Dioxide and Fatty Acids With Lithium Aluminum Hydride
Line Arrester Application on a 110 kV High Alpine Overhead Line to reduce Lightning-Caused Outages
This contribution discusses a project, which aims to increase the reliability in an existing
110 kV overhead transmission network by taking measures addressing lightning and
grounding issues. Due to the fault statistic in the past, a single overhead line was identified as
a main reason for the lightning-caused outages in the area. In this work a number of
possibilities for the reduction of lightning-caused outages are discussed and the measures
taken in the network are described. All considerations took the special geographical situation
of 2300 meter above sea level, the grounding resistance of up to 1200 Ohm and the local
lightning activity of more than 6 lightning strikes per km² and year into account (4 to 5 times
higher than in other Austrian regions).
An analytical process was carried out to evaluate relevant parameters and to develop a
concept of practical measures. Within these evaluations, the footing resistance, the
effectiveness of the shielding angle of the shielding wires and the line arrester locations were
analyzed. A multiplicity of numerical calculations were performed to assess the application of
surge arresters regarding the insulation coordination for the system. To improve the line
performance and to decrease the line outage rate, a number of practical measures were applied
to the 110 kV line. In the past, the double three phase systems of the 110 kV overhead line
was constructional converted into one active single three phase system with two additional
earth wires. According to the numerical results, 18 surge arresters have been installed in a line
section of 9 towers, located in a high alpine part and in an area of high lightning activity.
Three years of field experiences have shown that the theoretical investigations and the
practical measures led to a significant decrease of lightning caused outages.
In the year 2007 a new project was started to evaluate a reconstruction of the line into the
original double three phase system. New numerical calculation routines were made to apply
line arresters at this important 110 kV system in an Austrian extreme mountain region. Based
on this results, a new application of line arresters and the constructional change of the system
is planned
Characteristics of a New Carbonaceous Chondrite, Metal-Rich-Lithology Found in the Carbonaceous Chondrite Breccia Aguas Zarcas
The Aguas Zarcas meteorite fell in Costa Rica on 23 April 2019 at 21:07 local time, with a total mass of about 27 kg. Hundreds of fusion-crusted stones ranging from 0.1 to 1868 g were recovered (The Meteoritical Bulletin). The meteorite was classified as a CM chondrite, but some lithlogies show a different texture to that of CM. In this study, we investigated the petrography, mineral-ogy, chemistry, and isotopic composition of an unusual Metal-rich-lithology from this fresh fall
Transients of the Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity
We report observations of the dynamics of electromagnetically induced transparency (EIT) in a Λ system when the ground states are Stark shifted. Interactions of this type exhibit large optical nonlinearities called Kerr nonlinearities, and have numerous applications. The EIT Kerr nonlinearity is relatively slow, which is a limiting factor that may make many potential applications impossible. Using rubidium atoms, we observe the dynamics of the EIT Kerr nonlinearity using a Mach-Zehnder interferometer to measure phase modulation of the EIT fields resulting from a pulsed signal beam Stark shifting the ground state energy levels. The rise times and transients agree well with theory
Electromagnetically Induced Transparency Line Shapes for Large Probe Fields and Optically Thick Media
We calculate the line shape and linewidths for electromagnetically induced transparency (EIT) in optically thick, Doppler broadened media (buffer gasses are also considered). In generalizing the definition of the EIT linewidth to optically thick media, we find two different linewidth definitions apply depending on whether the experiment is pulsed or continuous wave (cw). Using the cw definition for the EIT line shape we derive analytic expressions describing the linewidth as a function of optical depth. We also review the EIT line shapes in optically thin media and provide physical arguments for how the line shapes change as a function of various parameters
Measuring Health Care Costs of Individuals with Employer-Sponsored Health Insurance in the U.S.: A Comparison of Survey and Claims Data
As the core nationally representative health expenditure survey in the United States, the Medical Expenditure Panel Survey (MEPS) is increasingly being used by statistical agencies to track expenditures by disease. However, while MEPS provides a wealth of data, its small sample size precludes examination of spending on all but the most prevalent health conditions. To overcome this issue, statistical agencies have turned to other public data sources, such as Medicare and Medicaid claims data, when available. No comparable publicly available data exist for those with employer-sponsored insurance. While large proprietary claims databases may be an option, the relative accuracy of their spending estimates is not known. This study compared MEPS and MarketScan estimates of annual per person health care spending on individuals with employer-sponsored insurance coverage. Both total spending and the distribution of annual per person spending differed across the two data sources, with MEPS estimates 10 percent lower on average than estimates from MarketScan. These differences appeared to be a function of both underrepresentation of high expenditure cases and underestimation across the remaining distribution of spending.
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