1,983 research outputs found
Corrections to the Born-oppenheimer Approximation, Part II
Adiabatic corrections to long-range Born- Oppenheimer potential
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
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
The Cusp Conditions for Molecular Wave Functions
Cusp conditions to describe behavior of wave function at singularities of Coulomb potential corresponding to coalescence of two or more particles - diatomic molecule
Time-dependent wave-packet approach for fusion reactions of halo nuclei
The fusion reaction of a halo nucleus 11Be on 208Pb is described by a
three-body direct reaction model. A time-dependent wave packet approach is
applied to a three-body reaction problem. The wave packet approach enables us
to obtain scattering solutions without considering the three-body scattering
boundary conditions. The time evolution of the wave packet also helps us to
obtain intuitive understanding of the reaction dynamics. The calculations
indicate a decrease of the fusion probability by the presence of the halo
neutron.Comment: 7 pages, 3 figures, use espcrc1.sty, Talk at the International
Symposium on "Physics of Unstable Nuclei (ISPUN02)", Halong Bay, Vietnam,
November 20-25, 200
Kinematic Orbits and the Structure of the Internal Space for Systems of Five or More Bodies
The internal space for a molecule, atom, or other n-body system can be
conveniently parameterised by 3n-9 kinematic angles and three kinematic
invariants. For a fixed set of kinematic invariants, the kinematic angles
parameterise a subspace, called a kinematic orbit, of the n-body internal
space. Building on an earlier analysis of the three- and four-body problems, we
derive the form of these kinematic orbits (that is, their topology) for the
general n-body problem. The case n=5 is studied in detail, along with the
previously studied cases n=3,4.Comment: 38 pages, submitted to J. Phys.
Recommended from our members
Phase I trial of procarbazine as a 5-day continuous infusion in children with central nervous system tumors.
Seven children with previously treated brain tumors were enrolled in a phase I trial of 5-day continuous-infusion procarbazine at 360, 480, and 638 mg/m2/day. Vitamin B6 levels were monitored. Myelosuppression was moderate though occasionally delayed, and nausea and vomiting were mild. At the highest dose level, a patient experienced severe psychosis that persisted for several weeks. From that dose-limiting toxicity and the degree of myelosuppression, the recommended dose for phase II trials in children is the same as for adults, 450 mg/m2/day
SINMAP 2.0 - A Stability Index Approach to Terrain Stability Hazard Mapping, User\u27s Manual
SINMAP 2.0 (Stability Index MAPping) is an ArcGIS 9.0 plug-in that implements the computation and mapping of a slope stability index based upon geographic information, primarily digital elevation data. This report describes the theoretical basis for the calculation of the stability index, describes the implementation, presents several case studies and describes use of the accompanying software. SINMAP has its theoretical basis in the infinite plane slope stability model with wetness (pore pressures) obtained from a topographically based steady state model of hydrology. Digital elevation model (DEM) methods are used to obtain the necessary input information (slope and specific catchment area). Parameters are allowed to be uncertain following uniform distributions between specified limits. These may be adjusted (and calibrated) for geographic ccalibration regionsd based upon soil, vegetation or geologic data. The methodology includes an interactive visual calibration that adjusts parameters while referring to observed landslides. The calibration involves adjustment of parameters so that the stability map ccapturesd a high proportion of observed landslides in regions with low stability index, while minimizing the extent of low stability regions and consequent alienation of terrain to regions where landslides have not been observed. This calibration is done while simultaneously referring to the stability index map, a specific catchment area and slope plot (of landslide and non landslide points) where lines distinguish the zones categorized into the different stability classes and a table giving summary statistics. The current implementation of SINMAP 2.0 is a plug-in to the ArcGIS ArcMap geographic information system (GIS) from Environmental Systems Research Institute, Inc. (ESRI). This utilizes ArcMap for its standard GIS functionality such as the input and organization of data and the presentation and output of results. SINMAP is grid based, requiring ArcGIS version 9.0 or higher
When the Diagnosis is a Victim of the Circumstances
Introduction: Haemoptysis is a common symptom which can sometimes mimic gastrointestinal bleeding.
Case description: We describe the case of a 31-year-old man who presented to the emergency department after an episode of sudden nausea and presumed massive haematemesis. The situation was interpreted as gastrointestinal bleeding but clinical evolution and greater attention to the anamnesis resulted in a diagnosis of pulmonary tuberculosis and the provision of appropriate care.
Discussion: This report emphasizes the difficulty of differentiating between haemoptysis and haematemesis and the importance of a careful anamnesis and attention to all clinical circumstances for an accurate diagnosis.
Learning points: Haematemesis and haemoptysis are not always distinguished from each other when a patient's history is being collected.Despite being a rare manifestation of tuberculosis, in the correct epidemiological context, haemoptysis should raise the suspicion of pulmonary tuberculosis.The clinical setting and the need for immediate care should not limit clinical investigation or the differential diagnosis.info:eu-repo/semantics/publishedVersio
Aging is associated with an earlier arrival of reflected waves without a distal shift in reflection sites
Background-Despite pronounced increases in central pulse wave velocity (PWV) with aging, reflected wave transit time (RWTT), traditionally defined as the timing of the inflection point (T-INF) in the central pressure waveform, does not appreciably decrease, leading to the controversial proposition of a "distal-shift" of reflection sites. T-INF, however, is exceptionally prone to measurement error and is also affected by ejection pattern and not only by wave reflection. We assessed whether RWTT, assessed by advanced pressure-flow analysis, demonstrates the expected decline with aging. Methods and Results-We studied a sample of unselected adults without cardiovascular disease (n=48; median age 48 years) and a clinical population of older adults with suspected/established cardiovascular disease (n=164; 61 years). We measured central pressure and flow with carotid tonometry and phase-contrast MRI, respectively. We assessed RWTT using wave-separation analysis (RWTTWSA) and partially distributed tube-load (TL) modeling (RWTTTL). Consistent with previous reports, T-INF did not appreciably decrease with age despite pronounced increases in PWV in both populations. However, aging was associated with pronounced decreases in RWTTWSA (general population -15.0 ms/decade, P<0.001; clinical population -9.07 ms/decade, P=0.003) and RWTTTL (general -15.8 ms/decade, P<0.001; clinical -11.8 ms/decade, P<0.001). There was no evidence of an increased effective reflecting distance by either method. TINF was shown to reliably represent RWTT only under highly unrealistic assumptions about input impedance. Conclusions-RWTT declines with age in parallel with increased PWV, with earlier effects of wave reflections and without a distal shift in reflecting sites. These findings have important implications for our understanding of the role of wave reflections with aging
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