1,206 research outputs found
Preliminary vegetation map of the Espenberg Peninsula, Alaska, based on an Earth Resources Technology Satellite image
There are no author-identified significant results in this report
Effects of Quasi-Static Aberrations in Faint Companion Searches
We present the first results obtained at CFHT with the TRIDENT infrared
camera, dedicated to the detection of faint companions close to bright nearby
stars. The camera's main feature is the acquisition of three simultaneous
images in three wavelengths (simultaneous differential imaging) across the
methane absorption bandhead at 1.6 micron, that enables a precise subtraction
of the primary star PSF while keeping the companion signal. The main limitation
is non-common path aberrations between the three optical paths that slightly
decorrelate the PSFs. Two types of PSF calibrations are combined with the
differential simultaneous imaging technique to further attenuate the PSF:
reference star subtraction and instrument rotation to smooth aberrations. It is
shown that a faint companion with a DeltaH of 10 magnitudes would be detected
at 0.5 arcsec from the primary.Comment: 12 pages, 10 figures, to appear in Astronomy with High Contrast
Imaging, EAS Publications Serie
Airboat Use and Disturbance of Floating Mat Fen Wetlands in Interior Alaska, U.S.A.
The use of airboats is expanding in Alaska, particularly in the interior. This study describes the nature, magnitude, and distribution of disturbance caused by airboat trails over floating mat fen wetlands in the Tanana Flats near Fairbanks, Alaska. Airphoto interpretation showed over 300 km of airboat trails by 1995, with a 15% expansion of the trail system since 1989. Field sampling was done at 30 trail and adjacent control sites along this trail system to assess changes in hydrology, soils, and vegetation. Water velocities in the trails at two-thirds of the sites were at least an order of magnitude greater than velocities of less than 1.5 cm/sec in the control areas. On average, 30 cm of the 0.5-0.75 m thick floating mat has been removed or eroded by airboat traffic at the sampling locations. Nearly all emergent floating mat vegetation has been destroyed (5% cover remaining on average) so that the trails resemble a highly visible open water stream channel 2-3 m wide through the floating mats. Although the recovery and regrowth potential of floating mats in trails is high, recovery is unlikely in trails with continuing use.En Alaska, l'utilisation des hydroglisseurs est à la hausse, surtout à l'intérieur des terres. Cette étude décrit la nature, l'amplitude et la distribution des perturbations causées par le sillage des hydroglisseurs sur les zones humides de vasiÚres à mattes flottantes situées dans les plaines marécageuses de Tanana prÚs de Fairbanks (en Alaska). L'interprétation de photos a montré que, en 1995, les sillages d'hydroglisseurs s'étendaient sur plus de 300 km, ce qui correspond à une augmentation de 15 p. cent du réseau depuis 1989. On a procédé à un échantillonnage sur le terrain à 30 emplacements de sillages et aires témoins adjacentes le long du réseau en vue d'évaluer les changements dans l'hydrologie, les sols et la végétation. Dans deux tiers des emplacements, la vitesse de l'eau dans les sillages était d'au moins un ordre de grandeur supérieure aux vitesses de moins de 1,5 cm/sec dans les zones témoins. Aux endroits d'échantillonnage, 30 cm en moyenne de la matte flottante épaisse de 0,5 à 0,75 m a été enlevée ou érodée par la circulation de l'hydroglisseur. Presque toute la végétation de la matte flottante émergée a été détruite (il reste en moyenne 5 p. cent du couvert) de sorte que les sillages sont trÚs visibles et forment un chenal d'eau ouverte de 2 à 3 m de large à travers les mattes flottantes. Bien que le potentiel de recouvrement et de repousse des mattes flottantes dans les sillages soit élevé, il est peu probable que ce recouvrement ait lieu dans les sillages qui sont utilisés de façon continue
Quelle rĂ©gulation pour lâarrĂȘt dâun protocole de recherche clinique de thĂ©rapie gĂ©nique somatique ? Ătat des lieux auprĂšs des cliniciens-chercheurs europĂ©ens
Depuis 2002, le dĂ©bat sur les risques associĂ©s Ă la thĂ©rapie gĂ©nique est initiĂ© suite Ă lâannonce
que deux enfants inclus dans un essai thérapeutique impliquant une thérapie génique ont
développé des effets indésirables important. En Janvier 2005, le débat sur les risques reprit suite
Ă lâinterruption du protocole sur les enfants bulle du Pr Fischer Ă lâhĂŽpital Necker de Paris. Nous
avons donc étudié le processus impliqué ainsi que la réflexion éthique associée aux décisions
dâarrĂȘt de protocole de recherche. Notre travail a Ă©tĂ© menĂ© par une Ă©quipe pluridisciplinaire
combinant chercheurs en santé, généticiens et éthiciens. Nous avons étudié la participation des
chercheurs, des patients, des institutions officielles, des comitĂ©s dâĂ©thique ainsi que des
associations de patients dans le processus de dĂ©cision dâinterruption dâun protocole de recherche.Nous avons Ă©galement analysĂ© les critĂšres jugĂ©s les plus pertinents dans lâarrĂȘt dâun protocole
de recherche. Enfin nous avons analysé le point de vue des personnes directement impliquées
dans la thĂ©rapie gĂ©nique au moyen dâun questionnaire. Toutes les personnes contactĂ©es ont
présenté un poster de recherche au congrÚs de la Société Européenne de Thérapie Génique. 62
personnes dâautant dâĂ©quipes de recherche diffĂ©rentes, de 17 pays, sur les 350 contactĂ©s ont
rĂ©pondu. Selon eux, la dĂ©cision dâarrĂȘt dâun protocole de recherche doit ĂȘtre prise suite Ă une
consultation des chercheurs, des patients, du ministĂšre de tutelle, dâune agence nationale de
rĂ©gulation ou dâun comitĂ© dâĂ©thique ; la lĂ©gitimitĂ© Ă©tant accordĂ©e Ă des dĂ©cisions prises en
commun par les chercheurs, les patients et les comitĂ©s dâĂ©thique. Les incidents sĂ©rieux et de façon
plus surprenante, les incidents moins graves sont jugés comme étant des critÚres suffisants pour
interrompre un essai. Nous avons fini par analyser les conséquences éthiques, telles que balance
bĂ©nĂ©fice/risque, processus de rĂ©gulation ou responsabilitĂ©, de ces critĂšres sur lâarrĂȘt dâun protocole
de recherche.In 2002, the debate on the risks of gene therapy was initiated following the annoucement that two
children included in a clinical trial developed serious adverse effects. In January 2005, the debate
was reignited following the interruption of the âbubble kids protocolâ at the HĂŽpital Necker in Paris.
We have thus investigated the ethical stakes involved in decisions to stop protocols. This work was
carried out by a multidisciplinary team combining ethics researchers and geneticists. We studied
the specific participation of researchers, patients, official institution, ethics committees and patient
associations in the processes that can lead to an interruption of trial.We also analysed the criterion
judged most relevant for halting a trial. Finally, we analyzed the perspective of the actors implicated
directly in the provision of gene therapy, by means of a questionnaire. All the individuals contacted
had presented a scientific poster at the European Society of Gene Therapy. 62 out of 350 persons,
from 17 countries, responded to our questionnaire. According to these respondants, decisions to stop
a trial should be taken after consultation with researchers, patients, the ministry, national agencies
or ethics committees. Legitimacy was accorded to joint decision-making by researchers, patients and
committees. Serious incidents, and surprisingly less serious incidents, clearly emerge as criterion for
stopping a trial. We conclude by analyzing the ethical consequences, such as risk/benefit ratios,
regulatory processes and responsibility, associated with these criterions and decisions to stop a trial
Hamiltonian of a spinning test-particle in curved spacetime
Using a Legendre transformation, we compute the unconstrained Hamiltonian of
a spinning test-particle in a curved spacetime at linear order in the particle
spin. The equations of motion of this unconstrained Hamiltonian coincide with
the Mathisson-Papapetrou-Pirani equations. We then use the formalism of Dirac
brackets to derive the constrained Hamiltonian and the corresponding
phase-space algebra in the Newton-Wigner spin supplementary condition (SSC),
suitably generalized to curved spacetime, and find that the phase-space algebra
(q,p,S) is canonical at linear order in the particle spin. We provide explicit
expressions for this Hamiltonian in a spherically symmetric spacetime, both in
isotropic and spherical coordinates, and in the Kerr spacetime in
Boyer-Lindquist coordinates. Furthermore, we find that our Hamiltonian, when
expanded in Post-Newtonian (PN) orders, agrees with the Arnowitt-Deser-Misner
(ADM) canonical Hamiltonian computed in PN theory in the test-particle limit.
Notably, we recover the known spin-orbit couplings through 2.5PN order and the
spin-spin couplings of type S_Kerr S (and S_Kerr^2) through 3PN order, S_Kerr
being the spin of the Kerr spacetime. Our method allows one to compute the PN
Hamiltonian at any order, in the test-particle limit and at linear order in the
particle spin. As an application we compute it at 3.5PN order.Comment: Corrected typo in the ADM Hamiltonian at 3.5 PN order (eq. 6.20
The Globular Cluster System in the Inner Region of M87
1057 globular cluster candidates have been identified in a WFPC2 image of the
inner region of M87. The Globular Cluster Luminosity Function (GCLF) can be
well fit by a Gaussian profile with a mean value of m_V^0=23.67 +/- 0.07 mag
and sigma=1.39 +/- 0.06 mag (compared to m_V^0=23.74 mag and sigma=1.44 mag
from an earlier study using the same data by Whitmore it et al. 1995). The GCLF
in five radial bins is found to be statistically the same at all points,
showing no clear evidence of dynamical destruction processes based on the
luminosity function (LF), in contradiction to the claim by Gnedin (1997).
Similarly, there is no obvious correlation between the half light radius of the
clusters and the galactocentric distance. The core radius of the globular
cluster density distribution is R_c=56'', considerably larger than the core of
the stellar component (R_c=6.8''). The mean color of the cluster candidates is
V-I=1.09 mag which corresponds to an average metallicity of Fe/H = -0.74 dex.
The color distribution is bimodal everywhere, with a blue peak at V-I=0.95 mag
and a red peak at V-I=1.20 mag. The red population is only 0.1 magnitude bluer
than the underlying galaxy, indicating that these clusters formed late in the
metal enrichment history of the galaxy and were possibly created in a burst of
star/cluster formation 3-6 Gyr after the blue population. We also find that
both the red and the blue cluster distributions have a more elliptical shape
(Hubble type E3.5) than the nearly spherical galaxy. The average half light
radius of the clusters is ~2.5 pc which is comparable to the 3 pc average
effective radius of the Milky Way clusters, though the red candidates are ~20%
smaller than the blue ones.Comment: 40 pages, 17 figures, 4 tables, latex, accepted for publication in
the Ap
Cosmic Ray Spectra in Nambu-Goldstone Dark Matter Models
We discuss the cosmic ray spectra in annihilating/decaying Nambu-Goldstone
dark matter models. The recent observed positron/electron excesses at PAMELA
and Fermi experiments are well fitted by the dark matter with a mass of 3TeV
for the annihilating model, while with a mass of 6 TeV for the decaying model.
We also show that the Nambu-Goldstone dark matter models predict a distinctive
gamma-ray spectrum in a certain parameter space.Comment: 16 pages, 4 figure
Investigating the Influence of High-Speed Gantry Rotation in Cardiac CT on Motion Artifacts in Aortic Stenosis Patients Not Premedicated with ÎČ-Blockers: The FAST-CCT Randomized Trial Protocol.
Coronary CT angiography (CCTA) is increasingly used as a non-invasive tool to assess coronary artery disease (CAD). However, CCTA is subject to motion artifacts, potentially limiting its clinical utility. Despite faster (0.35 and 0.28 s/rot) gantry rotation times, low (60-65 bpm) heartbeat is recommended, and the use of ÎČ-blockers is often needed. Technological advancements have resulted in the development of faster rotation speeds (0.23 s/rot). However, their added value in patients not premedicated with ÎČ-blockers remains unclear. This prospective single-center, two-arm, randomized, controlled trial aims to assess the influence of fast rotation on coronary motion artifacts, diagnostic accuracy of CCTA for CAD, and patient safety.
We will randomize a total of 142 patients aged â„ 50 scheduled for an aortic stenosis work-up to receive CCTA with either a fast (0.23) or standard (0.28 s/rot) gantry speed.
rate of CCTAs with coronary motion artifacts hindering interpretation.
assessable coronary segments rate, diagnostic accuracy against invasive coronary angiography (ICA), motion artifact magnitude per segment, contrast-to-noise ratio (CNR), and patient ionizing radiation dose. The local ethics committee has approved the protocol. Potential significance: FAST-CCT may improve motion artifact reduction and diagnosis quality, thus eliminating the need for rate control and ÎČ-blocker administration.
gov identifier: NCT05709652
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