2,252 research outputs found
On algebraic construction of certain integrable and super-integrable systems
We propose a new construction of two-dimensional natural bi-Hamiltonian
systems associated with a very simple Lie algebra. The presented construction
allows us to distinguish three families of super-integrable monomial potentials
for which one additional first integral is quadratic, and the second one can be
of arbitrarily high degree with respect to the momenta. Many integrable systems
with additional integrals of degree greater than two in momenta are given.
Moreover, an example of a super-integrable system with first integrals of
degree two, four and six in the momenta is found.Comment: 37 page
Potential of thermal analysis in preparation and characterization of solid catalysis
Supported catalysts contain often only small amounts of active component(s) which renders their characterization difficult, particularly because they usually contain a substantial amount of water. Thermal analysis (TA) coupled with mass spectrometry (MS) offers an interesting potential for characterizing such material, various steps of catalyst preparation as well as crucial properties of fresh and used catalysts can be investigated. Some examples illustrating the versatility of TA-MS in catalysis research, such as solid-state reactions occurring upon exposure of the precursors or catalysts to reducing, oxidizing or inert atmosphere, are presented in this study. The combined use of TA and MS allows in many cases a much more detailed interpretation of the observed phenomena than could be achieved by one of these methods alon
Role and distribution of different Ba-containing phases in supported Pt-Ba NSR catalysts
Pt-Ba/MeO (where MeO=Al2O3, CeO2, SiO2 and ZrO2) NO x storage-reduction catalysts with Ba-loading varying from 0wt.% to 28wt.% were investigated concerning stability of Ba phases and NO x storage-reduction efficiency. For Pt-Ba/Al2O3 three different Ba-containing phases with different thermal stability are distinguished based on their interaction with the support. The relative concentration of these phases varies with the Ba-loading and NO x storage tests indicated that the BaCO3 phase decomposing between 400°C and 800°C (LT-BaCO3) is the most efficient Ba containing phase for NO x storage. Similar investigations of Pt-Ba catalysts supported on CeO2, SiO2 and ZrO2 showed that the relative amount of LT-BaCO3 phase depends also on the support material. NO x storage measurements confirmed a correlation between the concentration of LT-BaCO3 and NO x storage efficiency. Basicity and textural properties of the support are identified as crucial parameters for efficient NO x storage catalyst
Bound and unbound substructures in Galaxy-scale Dark Matter haloes
We analyse the coarse-grained phase-space structure of the six Galaxy-scale
dark matter haloes of the Aquarius Project using a state-of-the-art 6D
substructure finder. Within r_50, we find that about 35% of the mass is in
identifiable substructures, predominantly tidal streams, but including about
14% in self-bound subhaloes. The slope of the differential substructure mass
function is close to -2, which should be compared to around -1.9 for the
population of self-bound subhaloes. Near r_50 about 60% of the mass is in
substructures, with about 30% in self-bound subhaloes. The inner 35 kpc of the
highest resolution simulation has only 0.5% of its mass in self-bound
subhaloes, but 3.3% in detected substructure, again primarily tidal streams.
The densest tidal streams near the solar position have a 3-D mass density about
1% of the local mean, and populate the high velocity tail of the velocity
distribution.Comment: Submitted to MNRAS on 12/10/2010, 11 pages, 10 figure
Planets Around the K-Giants BD+20 274 and HD 219415
We present the discovery of planet-mass companions to two giant stars by the
ongoing Penn State- Toru\'n Planet Search (PTPS) conducted with the 9.2 m
Hobby-Eberly Telescope. The less massive of these stars, K5-giant BD+20 274,
has a 4.2 MJ minimum mass planet orbiting the star at a 578-day period and a
more distant, likely stellar-mass companion. The best currently available model
of the planet orbiting the K0-giant HD 219415 points to a Jupiter-mass
companion in a 5.7-year, eccentric orbit around the star, making it the longest
period planet yet detected by our survey. This planet has an amplitude of
\sim18 m/s, comparable to the median radial velocity (RV) "jitter", typical of
giant stars.Comment: 5 figures, 13 pages, accepted by the Astrophysical Journal. arXiv
admin note: substantial text overlap with arXiv:1110.164
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Food System Transformation: Integrating a Political-Economy and Social-Ecological Approach to Regime Shifts.
Sustainably achieving the goal of global food security is one of the greatest challenges of the 21st century. The current food system is failing to meet the needs of people, and at the same time, is having far-reaching impacts on the environment and undermining human well-being in other important ways. It is increasingly apparent that a deep transformation in the way we produce and consume food is needed in order to ensure a more just and sustainable future. This paper uses the concept of regime shifts to understand key drivers and innovations underlying past disruptions in the food system and to explore how they may help us think about desirable future changes and how we might leverage them. We combine two perspectives on regime shifts-one derived from natural sciences and the other from social sciences-to propose an interpretation of food regimes that draws on innovation theory. We use this conceptualization to discuss three examples of innovations that we argue helped enable critical regime shifts in the global food system in the past: the Haber-Bosch process of nitrogen fixation, the rise of the supermarket, and the call for more transparency in the food system to reconnect consumers with their food. This paper concludes with an exploration of why this combination of conceptual understandings is important across the Global North/ Global South divide, and proposes a new sustainability regime where transformative change is spearheaded by a variety of social-ecological innovations
Three red giants with substellar-mass companions
We present three giant stars from the ongoing Penn State-Toru\'n Planet
Search with the Hobby-Eberly Telescope, which exhibit radial velocity
variations that point to a presence of planetary --mass companions around them.
BD+49 828 is a K0 giant with a = minimum mass companion in
AU (d),
orbit. HD 95127, a log/=,
, K0 giant has a = minimum mass companion in
AU (d), orbit.
Finally, HD 216536, is a K0 giant with a minimum mass companion in
AU (d),
orbit. Both, HD 95127 b and HD 216536 b in their
compact orbits, are very close to the engulfment zone and hence prone to
ingestion in the near future. BD+49 828 b is among the longest period planets
detected with the radial velocity technique until now and it will remain
unaffected by stellar evolution up to a very late stage of its host. We discuss
general properties of planetary systems around evolved stars and planet
survivability using existing data on exoplanets in more detail.Comment: 47 pages, 11 figures. Accepted by Ap
TAPAS IV. TYC 3667-1280-1 b - the most massive red giant star hosting a warm Jupiter
We present the latest result of the TAPAS project that is devoted to intense
monitoring of planetary candidates that are identified within the
PennState-Toru\'n planet search.
We aim to detect planetary systems around evolved stars to be able to build
sound statistics on the frequency and intrinsic nature of these systems, and to
deliver in-depth studies of selected planetary systems with evidence of
star-planet interaction processes.
The paper is based on precise radial velocity measurements: 13 epochs
collected over 1920 days with the Hobby-Eberly Telescope and its
High-Resolution Spectrograph, and 22 epochs of ultra-precise HARPS-N data
collected over 961 days.
We present a warm-Jupiter (, 0.4)
companion with an orbital period of 26.468 days in a circular () orbit
around a giant evolved (, ) star
with . This is the most massive and oldest star
found to be hosting a close-in giant planet. Its proximity to its host
() means that the planet has a probability of
transits; this calls for photometric follow-up study.
This massive warm Jupiter with a near circular orbit around an evolved
massive star can help set constraints on general migration mechanisms for warm
Jupiters and, given its high equilibrium temperature, can help test energy
deposition models in hot Jupiters.Comment: 5 pages, 3 figures, accepted by A&
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