415 research outputs found
Guidance, flight mechanics and trajectory optimization. Volume 14 - Entry guidance equations
Entry guidance equations, reference trajectories, and guidance system mechanizatio
Guidance, flight mechanics and trajectory optimization. Volume 1 - Coordinate systems and time measure
Coordinate measuring system for flight control, and trajectory optimizatio
Numerical modelling of Auriga's Wheel - a new ring galaxy
We model the formation of Auriga's Wheel - a recently discovered collisional
ring galaxy. Auriga's Wheel has a number of interesting features including a
bridge of stars linking the neighbouring elliptical to the ring galaxy, and
evidence for components of expansion and rotation within the ring. Using
N-body/SPH modelling, we study collisions between an elliptical galaxy and a
late-type disk galaxy. A near direct collision, with a mildy inclined disk, is
found to reasonably reproduce the general system morphology ~50 Myr following
the collision. The collision must have a relatively low velocity (initially
~150 km s^{-1}) in order to form the observed bridge, and simultaneously match
the galaxies separation. Our best-match model suggests the total disk galaxy is
~5 times more massive than the elliptical. We find that the velocity of
expansion of the ring is sensitive to the mass of the elliptical, while
insensitive to the encounter velocity. We evolve our simulation beyond the
current epoch to study the future destiny of the galaxy pair. In our model, the
nucleus moves further away from the plane of the ring in the direction of the
stellar bridge. The nucleus eventually merges with the elliptical galaxy ~100
Myr after the present time. The ring continues to expand for ~200 Myr before
collapsing back. The low initial relative velocity of the two galaxies will
eventually result in a complete merger.Comment: Accepted to MNRAS, March 9th, 2012. 17 pages, 16 figures, no table
Mass models from high-resolution HI data of the dwarf galaxy NGC 1560
We present HI observations performed at the GMRT of the nearby dwarf galaxy
NGC 1560. This Sd galaxy is well-known for a distinct "wiggle" in its rotation
curve. Our new observations have twice the resolution of the previously
published HI data. We derived the rotation curve by taking projection effects
into account, and we verified the derived kinematics by creating model
datacubes. This new rotation curve is similar to the previously published one:
we confirm the presence of a clear wiggle. The main differences are in the
innermost ~100 arcsec of the rotation curve, where we find slightly (<~ 5 km/s)
higher velocities. Mass modelling of the rotation curve results in good fits
using the core-dominated Burkert halo (which however does not reproduce the
wiggle), bad fits using the a Navarro, Frenk & White halo, and good fits using
MOND (Modified Newtonian Dynamics), which also reproduces the wiggle.Comment: Accepted for publication in MNRAS. 11 pages, 13 figures.
High-resolution version available at
http://users.ugent.be/~ggianfra/1560_final.pd
Estimation of airway obstruction using oximeter plethysmograph waveform data
BACKGROUND: Validated measures to assess the severity of airway obstruction in patients with obstructive airway disease are limited. Changes in the pulse oximeter plethysmograph waveform represent fluctuations in arterial flow. Analysis of these fluctuations might be useful clinically if they represent physiologic perturbations resulting from airway obstruction. We tested the hypothesis that the severity of airway obstruction could be estimated using plethysmograph waveform data. METHODS: Using a closed airway circuit with adjustable inspiratory and expiratory pressure relief valves, airway obstruction was induced in a prospective convenience sample of 31 healthy adult subjects. Maximal change in airway pressure at the mouthpiece was used as a surrogate measure of the degree of obstruction applied. Plethysmograph waveform data and mouthpiece airway pressure were acquired for 60 seconds at increasing levels of inspiratory and expiratory obstruction. At each level of applied obstruction, mean values for maximal change in waveform area under the curve and height as well as maximal change in mouth pressure were calculated for sequential 7.5 second intervals. Correlations of these waveform variables with mouth pressure values were then performed to determine if the magnitude of changes in these variables indicates the severity of airway obstruction. RESULTS: There were significant relationships between maximal change in area under the curve (P < .0001) or height (P < 0.0001) and mouth pressure. CONCLUSION: The findings suggest that mathematic interpretation of plethysmograph waveform data may estimate the severity of airway obstruction and be of clinical utility in objective assessment of patients with obstructive airway diseases
Precision medicine and public health: New challenges for effective and sustainable health
The development of high-throughput omics technologies represents an unmissable opportunity for evidence-based prevention of adverse effects on human health. However, the applicability and access to multi-omics tests are limited. In Italy, this is due to the rapid increase of knowledge and the high levels of skill and economic investment initially necessary. The fields of human genetics and public health have highlighted the relevance of an implementation strategy at a national level in Italy, including integration in sanitary regulations and governance instruments. In this review, the emerging field of public health genomics is discussed, including the polygenic scores approach, epigenetic modulation, nutrigenomics, and microbiomes implications. Moreover, the Italian state of implementation is presented. The omics sciences have important implications for the prevention of both communicable and noncommunicable diseases, especially because they can be used to assess the health status during the whole course of life. An effective population health gain is possible if omics tools are implemented for each person after a preliminary assessment of effectiveness in the medium to long term
Operations of and Future Plans for the Pierre Auger Observatory
Technical reports on operations and features of the Pierre Auger Observatory,
including ongoing and planned enhancements and the status of the future
northern hemisphere portion of the Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand events above 10^18 eV observed by the fluorescence detector of the
Pierre Auger Observatory in coincidence with at least one surface detector
station are selected for the analysis. The average shower maximum was found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
Search for non-relativistic Magnetic Monopoles with IceCube
The IceCube Neutrino Observatory is a large Cherenkov detector instrumenting
of Antarctic ice. The detector can be used to search for
signatures of particle physics beyond the Standard Model. Here, we describe the
search for non-relativistic, magnetic monopoles as remnants of the GUT (Grand
Unified Theory) era shortly after the Big Bang. These monopoles may catalyze
the decay of nucleons via the Rubakov-Callan effect with a cross section
suggested to be in the range of to
. In IceCube, the Cherenkov light from nucleon decays
along the monopole trajectory would produce a characteristic hit pattern. This
paper presents the results of an analysis of first data taken from May 2011
until May 2012 with a dedicated slow-particle trigger for DeepCore, a
subdetector of IceCube. A second analysis provides better sensitivity for the
brightest non-relativistic monopoles using data taken from May 2009 until May
2010. In both analyses no monopole signal was observed. For catalysis cross
sections of the flux of non-relativistic
GUT monopoles is constrained up to a level of at a 90% confidence level,
which is three orders of magnitude below the Parker bound. The limits assume a
dominant decay of the proton into a positron and a neutral pion. These results
improve the current best experimental limits by one to two orders of magnitude,
for a wide range of assumed speeds and catalysis cross sections.Comment: 20 pages, 20 figure
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