837 research outputs found
Return of the Volcano: PHENIX Azimuthal Correlations 62.4 GeV Au+Au
As in previous analyses at sqrt(s_NN) 200 GeV, correlations in azimuthal
angles between inclusive charge particles at intermediate transverse momentum
(p_T = 1.0-4.0) GeV/c are studied at sqrt(s_NN) 62.4 GeV. The jet correlations
reveal similar modification as in 200 GeV. Specifically large modification,
including the "volcano" or "cone" structure, persists in the awayside
correlation.Comment: POSTER Proceedings for Quark Matter 2005 Conference in Hungarian
Journal Acta Phys Hun
Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius
We present the results of a survey for stellar and substellar companions to 82 young stars in the nearby OB association Upper Scorpius. This survey used nonredundant aperture mask interferometry to achieve typical contrast
limits of ΔK ~5-6 at the diffraction limit, revealing 12 new binary companions that lay below the detection limits
of traditional high-resolution imaging; we also summarize a complementary snapshot imaging survey that discovered
seven directly resolved companions. The overall frequency of binary companions (~35 +5 -4% at separations of
6-435 AU) appears to be equivalent to field stars of similar mass, but companions could be more common among
lower mass stars than for the field. The companion mass function has statistically significant differences compared to several suggested mass functions for the field, and we suggest an alternate lognormal parameterization of the mass function. Our survey limits encompass the entire brown dwarf mass range, but we only detected a single companion that might be a brown dwarf; this deficit resembles the so-called brown dwarf desert that has been observed by radial velocity planet searches. Finally, our survey’s deep detection limits extend into the top of the planetary mass function, reaching 8-12 MJup for half of our sample. We have not identified any planetary companions at high confidence (≳99.5%), but we have identified four candidate companions at lower confidence (≳97.5%) that merit additional follow-up to confirm or disprove their existence
The Role of Multiplicity in Disk Evolution and Planet Formation
The past decade has seen a revolution in our understanding of protoplanetary
disk evolution and planet formation in single star systems. However, the
majority of solar-type stars form in binary systems, so the impact of binary
companions on protoplanetary disks is an important element in our understanding
of planet formation. We have compiled a combined multiplicity/disk census of
Taurus-Auriga, plus a restricted sample of close binaries in other regions, in
order to explore the role of multiplicity in disk evolution. Our results imply
that the tidal influence of a close (<40 AU) binary companion significantly
hastens the process of protoplanetary disk dispersal, as ~2/3 of all close
binaries promptly disperse their disks within <1 Myr after formation. However,
prompt disk dispersal only occurs for a small fraction of wide binaries and
single stars, with ~80%-90% retaining their disks for at least ~2--3 Myr (but
rarely for more than ~5 Myr). Our new constraints on the disk clearing
timescale have significant implications for giant planet formation; most single
stars have 3--5 Myr within which to form giant planets, whereas most close
binary systems would have to form giant planets within <1 Myr. If core
accretion is the primary mode for giant planet formation, then gas giants in
close binaries should be rare. Conversely, since almost all single stars have a
similar period of time within which to form gas giants, their relative rarity
in RV surveys indicates either that the giant planet formation timescale is
very well-matched to the disk dispersal timescale or that features beyond the
disk lifetime set the likelihood of giant planet formation.Comment: Accepted to ApJ; 15 pages, 3 figures, 3 tables in emulateapj forma
Beyond knowledge and skills: the use of a Delphi study to develop a technology-mediated teaching strategy
Background: While there is evidence to suggest that teaching practices in clinical education should include activities that more accurately reflect the real world, many educators base their teaching on transmission models that encourage the rote learning of knowledge and technical skills. Technology-mediated instruction may facilitate the development of professional attributes that go beyond “having” knowledge and skills, but there is limited evidence for how to integrate technology into these innovative teaching approaches.
Methods: This study used a modified Delphi method to help identify the professional attributes of capable practitioners, the approaches to teaching that may facilitate the development of these attributes, and finally, how technology could be integrated with those teaching strategies in order to develop capable practitioners. Open-ended questions were used to gather data from three different expert panels, and results were thematically analysed.
Results: Clinical educators should not view knowledge, skills and attitudes as a set of products of learning, but rather as a set of attributes that are developed during a learning process. Participants highlighted the importance of continuing personal and professional development that emphasised the role of values and emotional response to the clinical context. To develop these attributes, clinical educators should use teaching activities that are learner-centred, interactive, integrated, reflective and that promote engagement. When technology-mediated teaching activities are considered, they should promote the discussion of clinical encounters, facilitate the sharing of resources and experiences, encourage reflection on the learning process and be used to access content outside the classroom. In addition, educational outcomes must drive the integration of technology into teaching practice, rather than the features of the technology.
Conclusions: There is a need for a cultural change in clinical education, in which those involved with the professional training of healthcare professionals perceive teaching as more than the transmission of knowledge and technical skills. Process-oriented teaching practices that integrate technology as part of a carefully designed curriculum may have the potential to facilitate the development of capable healthcare graduates who are able to navigate the complexity of health systems and patient management in ways that go beyond the application of knowledge and skills.National Research FoundationWeb of Scienc
The Palomar Kernel Phase Experiment: Testing Kernel Phase Interferometry for Ground-based Astronomical Observations
At present, the principal limitation on the resolution and contrast of
astronomical imaging instruments comes from aberrations in the optical path,
which may be imposed by the Earth's turbulent atmosphere or by variations in
the alignment and shape of the telescope optics. These errors can be corrected
physically, with active and adaptive optics, and in post-processing of the
resulting image. A recently-developed adaptive optics post-processing
technique, called kernel phase interferometry, uses linear combinations of
phases that are self-calibrating with respect to small errors, with the goal of
constructing observables that are robust against the residual optical
aberrations in otherwise well-corrected imaging systems. Here we present a
direct comparison between kernel phase and the more established competing
techniques, aperture masking interferometry, point spread function (PSF)
fitting and bispectral analysis. We resolve the alpha Ophiuchi binary system
near periastron, using the Palomar 200-Inch Telescope. This is the first case
in which kernel phase has been used with a full aperture to resolve a system
close to the diffraction limit with ground-based extreme adaptive optics
observations. Excellent agreement in astrometric quantities is found between
kernel phase and masking, and kernel phase significantly outperforms PSF
fitting and bispectral analysis, demonstrating its viability as an alternative
to conventional non-redundant masking under appropriate conditions.Comment: Accepted to MNRA
On-sky speckle nulling demonstration at small angular separation with SCExAO
This paper presents the first on-sky demonstration of speckle nulling, which
was achieved at the Subaru Telescope in the context of the Subaru Coronagraphic
Extreme Adaptive Optics (SCExAO) Project. Despite the absence of a high-order
high-bandwidth closed-loop AO system, observations conducted with SCExAO show
that even in poor-to-moderate observing conditions, speckle nulling can be used
to suppress static and slow speckles even in the presence of a brighter dynamic
speckle halo, suggesting that more advanced high-contrast imaging algorithms
developed in the laboratory can be applied to ground-based systems.Comment: 5 figures, accepted for publication by PAS
Conceptual Design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) for the Subaru Telescope
Recent developments in high-contrast imaging techniques now make possible
both imaging and spectroscopy of planets around nearby stars. We present the
conceptual design of the Coronagraphic High Angular Resolution Imaging
Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph
(IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide
spectral information for 140x140 spatial elements over a 1.75 arcsecs x 1.75
arcsecs field of view (FOV). CHARIS will operate in the near infrared (lambda =
0.9 - 2.5 microns) and provide a spectral resolution of R = 14, 33, and 65 in
three separate observing modes. Taking advantage of the adaptive optics systems
and advanced coronagraphs (AO188 and SCExAO) on the Subaru telescope, CHARIS
will provide sufficient contrast to obtain spectra of young self-luminous
Jupiter-mass exoplanets. CHARIS is in the early design phases and is projected
to have first light by the end of 2015. We report here on the current
conceptual design of CHARIS and the design challenges
Direct Detection of the Brown Dwarf GJ 802B with Adaptive Optics Masking Interferometry
We have used the Palomar 200" Adaptive Optics (AO) system to directly detect
the astrometric brown dwarf GJ 802B reported by Pravdo et al. 2005. This
observation is achieved with a novel combination of aperture masking
interferometry and AO. The dynamical masses are 0.1750.021 M and
0.0640.032 M for the primary and secondary respectively. The
inferred absolute H band magnitude of GJ 802B is M=12.8 resulting in a
model-dependent T of 1850 50K and mass range of
0.057--0.074 M.Comment: 4 Pages, 5 figures, emulateapj format, submitted to ApJ
The Optical Design of CHARIS: An Exoplanet IFS for the Subaru Telescope
High-contrast imaging techniques now make possible both imaging and
spectroscopy of planets around nearby stars. We present the optical design for
the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a
lenslet-based, cryogenic integral field spectrograph (IFS) for imaging
exoplanets on the Subaru telescope. The IFS will provide spectral information
for 138x138 spatial elements over a 2.07 arcsec x 2.07 arcsec field of view
(FOV). CHARIS will operate in the near infrared (lambda = 1.15 - 2.5 microns)
and will feature two spectral resolution modes of R = 18 (low-res mode) and R =
73 (high-res mode). Taking advantage of the Subaru telescope adaptive optics
systems and coronagraphs (AO188 and SCExAO), CHARIS will provide sufficient
contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets.
CHARIS will undergo CDR in October 2013 and is projected to have first light by
the end of 2015. We report here on the current optical design of CHARIS and its
unique innovations.Comment: 15 page
Precision Masses of the low-mass binary system GJ 623
We have used Aperture Masking Interferometry and Adaptive Optics (AO) at the
Palomar 200'' to obtain precise mass measurements of the binary M dwarf GJ 623.
AO observations spread over 3 years combined with a decade of radial velocity
measurements constrain all orbital parameters of the GJ 623 binary system
accurately enough to critically challenge the models. The dynamical masses
measured are m_{1}=0.371\pm0.015 M_{\sun} (4%) and m_{2}=0.115\pm0.0023
M_{\sun} (2%) for the primary and the secondary respectively. Models are not
consistent with color and mass, requiring very low metallicities.Comment: 7 pages, 5 figures. Accepted for Ap
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