5,000 research outputs found
Blue Dots Team Transits Working Group Review
Transiting planet systems offer an unique opportunity to observationally
constrain proposed models of the interiors (radius, composition) and
atmospheres (chemistry, dynamics) of extrasolar planets. The spectacular
successes of ground-based transit surveys (more than 60 transiting systems
known to-date) and the host of multi-wavelength, spectro-photometric follow-up
studies, carried out in particular by HST and Spitzer, have paved the way to
the next generation of transit search projects, which are currently ongoing
(CoRoT, Kepler), or planned. The possibility of detecting and characterizing
transiting Earth-sized planets in the habitable zone of their parent stars
appears tantalizingly close. In this contribution we briefly review the power
of the transit technique for characterization of extrasolar planets, summarize
the state of the art of both ground-based and space-borne transit search
programs, and illustrate how the science of planetary transits fits within the
Blue Dots perspective.Comment: 9 pages, 3 figures, to be published in the proceedings (ASP Conf.
Ser.) of the "Pathways Towards Habitable Planets" conference, held in
Barcelona (14-18 Sep 2009
Multicomponent dynamical systems: SRB measures and phase transitions
We discuss a notion of phase transitions in multicomponent systems and
clarify relations between deterministic chaotic and stochastic models of this
type of systems. Connections between various definitions of SRB measures are
considered as well.Comment: 13 pages, LaTeX 2
Precision measurement of the half-life and the decay branches of 62Ga
In an experiment performed at the Accelerator Laboratory of the University of
Jyvaskyla, the beta-decay half-life of 62Ga has been studied with high
precision using the IGISOL technique. A half-life of T1/2 = 116.09(17)ms was
measured. Using beta-gamma coincidences, the gamma intensity of the 954keV
transition and an upper limit of the beta-decay feeding of the 0+_2 state have
been extracted. The present experimental results are compared to previous
measurements and their impact on our understanding of the weak interaction is
discussed.Comment: 7 pages, 7 figures, submitted to EPJ
First direct observation of two protons in the decay of Fe with a TPC
The decay of the ground-state two-proton emitter 45Fe was studied with a
time-projection chamber and the emission of two protons was unambiguously
identified. The total decay energy and the half-life measured in this work
agree with the results from previous experiments. The present result
constitutes the first direct observation of the individual protons in the
two-proton decay of a long-lived ground-state emitter. In parallel, we
identified for the first time directly two-proton emission from 43Cr, a known
beta-delayed two-proton emitter. The technique developped in the present work
opens the way to a detailed study of the mechanism of ground-state as well as
beta-delayed two-proton radioactivity.Comment: 4 pages, 5 figure
The Discovery of a Giant H-alpha Filament in NGC 7213
The nearby Seyfert galaxy NGC 7213 has been imaged in H-alpha and HI with the
CTIO 1.5 m telescope and with the Australia Telescope Compact Array (ATCA),
respectively. Optically NGC 7213 looks undisturbed and relatively featureless
but the continuum-subtracted H-alpha image shows a 19 kpc long filament located
approximately 18.6 kpc from the nucleus. The H-alpha filament could be neutral
gas photo-ionized by the active nucleus, as has been suggested for the Seyfert
galaxy NGC 5252, or shock-ionized by a jet interacting with the surrounding HI,
as has been suggested for the radio galaxy PKS 2240-41. The HI map reveals NGC
7213 to be a highly disturbed system suggesting a past merging event.Comment: 14 pages including 4 figures and 1 table. Figures 1-4 are in jpeg
format; Better quality images can be retrieved in postscript format at
ftp://charon.nmsu.edu/pub/shameed/ ; Accepted for publication in ApJ Letter
Ochratoxin A-induced cytotoxicity in liver (HepG2) cells: Impact of serum concentration, dietary antioxidants and glutathione-modulating compounds
Abbrevations: BSO, buthionine sulfoximine; CAT, catechin; DMSO, dimethyl sulfoxide; DTNB, dithio-bis-nitrobenzoic acid; EGCG, epigallocatechin gallate; FCS, foetal calf serum; GSH, glutathione; IARC, international agency for research on cancer; NAC, N-acetylcysteine; NO, nitric oxide; NR, neutral red; OATP, organic anion-transporting polypeptide; OTA, ochratoxin A; PBS, phosphate buffered saline; QUE, quercetin; ROS, reactive oxygen species; ROSAC, rosmarinic acid; RPMI, roswell park memorial institute; α-TOC, α-tocopherol; α-TOC-P, α-tocopherol phosphat
Chaotic Cascades with Kolmogorov 1941 Scaling
We define a (chaotic) deterministic variant of random multiplicative cascade
models of turbulence. It preserves the hierarchical tree structure, thanks to
the addition of infinitesimal noise. The zero-noise limit can be handled by
Perron-Frobenius theory, just as the zero-diffusivity limit for the fast dynamo
problem. Random multiplicative models do not possess Kolmogorov 1941 (K41)
scaling because of a large-deviations effect. Our numerical studies indicate
that deterministic multiplicative models can be chaotic and still have exact
K41 scaling. A mechanism is suggested for avoiding large deviations, which is
present in maps with a neutrally unstable fixed point.Comment: 14 pages, plain LaTex, 6 figures available upon request as hard copy
(no local report #
Ruelle-Perron-Frobenius spectrum for Anosov maps
We extend a number of results from one dimensional dynamics based on spectral
properties of the Ruelle-Perron-Frobenius transfer operator to Anosov
diffeomorphisms on compact manifolds. This allows to develop a direct operator
approach to study ergodic properties of these maps. In particular, we show that
it is possible to define Banach spaces on which the transfer operator is
quasicompact. (Information on the existence of an SRB measure, its smoothness
properties and statistical properties readily follow from such a result.) In
dimension we show that the transfer operator associated to smooth random
perturbations of the map is close, in a proper sense, to the unperturbed
transfer operator. This allows to obtain easily very strong spectral stability
results, which in turn imply spectral stability results for smooth
deterministic perturbations as well. Finally, we are able to implement an Ulam
type finite rank approximation scheme thus reducing the study of the spectral
properties of the transfer operator to a finite dimensional problem.Comment: 58 pages, LaTe
The non-self-adjointness of the radial momentum operator in n dimensions
The non self-adjointness of the radial momentum operator has been noted
before by several authors, but the various proofs are incorrect. We give a
rigorous proof that the -dimensional radial momentum operator is not self-
adjoint and has no self-adjoint extensions. The main idea of the proof is to
show that this operator is unitarily equivalent to the momentum operator on
which is not self-adjoint and has no self-adjoint
extensions.Comment: Some text and a reference adde
Older social housing tenantsâ experiences of rehousing programs: a systematic scoping review
This review examines the experiences of older social housing tenants who move home through rehousing schemes. These can be either elective, in the case of downsizing or rightsizing, or nonelective in the case of urban regeneration where, typically, houses are demolished and new ones built. Searches of both peer-reviewed and gray literature were carried out using appropriate databases. After screening, two peer-reviewed papers and eight gray literature reports were included in the review. Although limited, the evidence presented here provides some important guidance for providers of social housing. Organizations that provide social housing for older adults should involve older people in decision making in the conception, planning, and delivery of rehousing programs. Particular attention should be given to maintaining social connections in new homes and communities to avoid a serious loss of community involvement and the resulting increased levels of loneliness. The lack of published evidence highlighted by this review, particularly from academia, indicates that greater efforts from researchers and funders should be made to conduct studies that will give social housing providers the evidence they need to improve rehousing programs for older tenants
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