1,007 research outputs found
Extrasolar planets and brown dwarfs around A-F type stars V. A planetary system found with HARPS around the F6IV-V star HD 60532
Aims: In the frame of the search for extrasolar planets and brown dwarfs
around early-type stars, we present the results obtained for the F-type
main-sequence star HD 60532 (F6V) with HARPS.
Methods: Using 147 spectra obtained with HARPS at La Silla on a time baseline
of two years, we study the radial velocities of this star.
Results: HD 60532 radial velocities are periodically variable, and the
variations have a Keplerian origin. This star is surrounded by a planetary
system of two planets with minimum masses of 1 and 2.5 Mjup and orbital
separations of 0.76 and 1.58 AU respectively. We also detect high-frequency,
low-amplitude (10 m/s peak-to-peak) pulsations. Dynamical studies of the system
point toward a possible 3:1 mean-motion resonance which should be confirmed
within the next decade.Comment: 7 pages, 11 figures, accepted for publication in A&
Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?
(abridged) In the frame of the search for extrasolar planets and brown dwarfs
around early-type main-sequence stars, we present the results obtained on the
early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the
spectra. Our dedicated radial-velocity measurement method was used to monitor
the star's radial velocities over five years. We also use complementary, high
angular resolution and high-contrast images taken with PUEO at CFHT. We show
that Theta Cygni radial velocities are quasi-periodically variable, with a
~150-day period. These variations are not due to the ~0.35-Msun stellar
companion that we detected in imaging at more than 46 AU from the star. The
absence of correlation between the bisector velocity span variations and the
radial velocity variations for this 7 km/s vsini star, as well as other
criteria indicate that the observed radial velocity variations are not due to
stellar spots. The observed amplitude of the bisector velocity span variations
also seems to rule out stellar pulsations. However, we observe a peak in the
bisector velocity span periodogram at the same period as the one found in the
radial velocity periodogram, which indicates a probable link between these
radial velocity variations and the low amplitude lineshape variations which are
of stellar origin. Long-period variations are not expected from this type of
star to our knowledge. If a stellar origin (hence of new type) was to be
confirmed for these long-period radial velocity variations, this would have
several consequences on the search for planets around main-sequence stars, both
in terms of observational strategy and data analysis. An alternative
explanation for these variable radial velocities is the presence of at least
one planet of a few Jupiter masses orbiting at less than 1 AU. (abridged)Comment: 9 pages, accepted in A
Understanding the impact of diet and nutrition on symptoms of Tourette Syndrome: A Scoping Review
This document is the accepted manuscript version. The final, definitive version of this paper has been published in Journal of Child Health Care, December 2017, published by SAGE Publishing, doi:https://doi.org/10.1177/1367493517748373.Anecdotal reports frequently suggest some dietary involvement in the maintenance of tics in children with Tourette syndrome (TS). This scoping review aimed to (1) understand the possible influence of diet as a trigger of tics and (2) map out the existing studies documenting dietary interventions in children with TS. Current evidence suggests no single diet to benefit individuals with TS. However, reports from parents of children with TS suggest that certain allergens in food may exacerbate tic-related symptoms. For example, an increase in tics has been related to the consumption of caffeine and refined sugar. Moreover, oligoantigenic diets and sugar-free diets have been identified as significantly reducing tics. More research is urgently needed to develop more accurate guidance for parents and children with TS, as many have reported using dietary and nutritional supplements, despite the lack of evidence detailing any benefits, side effects and recommended doses.Peer reviewedFinal Accepted Versio
Radial Velocities with CRIRES: Pushing precision down to 5-10 m/s
With the advent of high-resolution infrared spectrographs, Radial Velocity
(RV) searches enter into a new domain. As of today, the most important
technical question to address is which wavelength reference is the most
suitable for high-precision RV measurements.
In this work we explore the usage of atmospheric absorption features. We make
use of CRIRES data on two programs and three different targets. We re-analyze
the data of the TW Hya campaign, reaching a dispersion of about 6 m/s on the RV
standard in a time scale of roughly 1 week. We confirm the presence of a
low-amplitude RV signal on TW Hya itself, roughly 3 times smaller than the one
reported at visible wavelengths. We present RV measurements of Gl 86 as well,
showing that our approach is capable of detecting the signal induced by a
planet and correctly quantifying it.
Our data show that CRIRES is capable of reaching a RV precision of less than
10 m/s in a time-scale of one week. The limitations of this particular approach
are discussed, and the limiting factors on RV precision in the IR in a general
way. The implications of this work on the design of future dedicated IR
spectrographs are addressed as well.Comment: 9 pages, accepted for publication in A&
Impact of perioperative chemotherapy on survival in patients with advanced primary urethral cancer: results of the international collaboration on primary urethral carcinoma
This is the first series that suggests a prognostic benefit of neoadjuvant treatment in a consecutive series of patients who underwent perioperative chemotherapy plus surgery for advanced primary urethral carcinoma. Further studies should yield a better understanding of how perioperative chemotherapy exerts a positive effect on survival in order to selectively advocate its use in advanced primary urethral carcinom
Magnetism, FeS colloids, and Origins of Life
A number of features of living systems: reversible interactions and weak
bonds underlying motor-dynamics; gel-sol transitions; cellular connected
fractal organization; asymmetry in interactions and organization; quantum
coherent phenomena; to name some, can have a natural accounting via
interactions, which we therefore seek to incorporate by expanding the horizons
of `chemistry-only' approaches to the origins of life. It is suggested that the
magnetic 'face' of the minerals from the inorganic world, recognized to have
played a pivotal role in initiating Life, may throw light on some of these
issues. A magnetic environment in the form of rocks in the Hadean Ocean could
have enabled the accretion and therefore an ordered confinement of
super-paramagnetic colloids within a structured phase. A moderate H-field can
help magnetic nano-particles to not only overcome thermal fluctuations but also
harness them. Such controlled dynamics brings in the possibility of accessing
quantum effects, which together with frustrations in magnetic ordering and
hysteresis (a natural mechanism for a primitive memory) could throw light on
the birth of biological information which, as Abel argues, requires a
combination of order and complexity. This scenario gains strength from
observations of scale-free framboidal forms of the greigite mineral, with a
magnetic basis of assembly. And greigite's metabolic potential plays a key role
in the mound scenario of Russell and coworkers-an expansion of which is
suggested for including magnetism.Comment: 42 pages, 5 figures, to be published in A.R. Memorial volume, Ed
Krishnaswami Alladi, Springer 201
Coherent Phonons in Carbon Nanotubes and Graphene
We review recent studies of coherent phonons (CPs) corresponding to the
radial breathing mode (RBM) and G-mode in single-wall carbon nanotubes (SWCNTs)
and graphene. Because of the bandgap-diameter relationship, RBM-CPs cause
bandgap oscillations in SWCNTs, modulating interband transitions at terahertz
frequencies. Interband resonances enhance CP signals, allowing for chirality
determination. Using pulse shaping, one can selectively excite
speci!c-chirality SWCNTs within an ensemble. G-mode CPs exhibit
temperature-dependent dephasing via interaction with RBM phonons. Our
microscopic theory derives a driven oscillator equation with a
density-dependent driving term, which correctly predicts CP trends within and
between (2n+m) families. We also find that the diameter can initially increase
or decrease. Finally, we theoretically study the radial breathing like mode in
graphene nanoribbons. For excitation near the absorption edge, the driving term
is much larger for zigzag nanoribbons. We also explain how the armchair
nanoribbon width changes in response to laser excitation.Comment: 48 pages, 41 figure
No Earlier Than 9:45 A.M. A Qualitative Study of Adolescents' Experiences of Later School Start Times in Aotearoa New Zealand
OBJECTIVES:
Many teenagers suffer chronic sleep loss, which could potentially be mitigated by later school start times to accommodate the natural shift in their circadian timekeeping system favoring later bedtimes. This study explored experiences of senior students from a school in Aotearoa New Zealand with later school start times.
METHOD:
Semi-structured interviews were conducted with 14 students, purposively sampled for equivalent numbers starting later every day (9:45 A.M.), or on just one weekday (10:00 A.M.). Transcripts were analyzed using reflexive thematic analysis.
RESULTS:
Four themes were identified that addressed the impact of later starts on sleep struggles, daily functioning, student autonomy, and routines and scheduling. Most perceived later starts as positively influencing their sleep quality, concentration, productivity, and personal well-being. The importance of autonomy over their learning, and impact of different start times on students' schedules was also emphasized. Major disadvantages were lack of free classes and potentially later finish times.
CONCLUSIONS:
The experiences of later school start times for these adolescents were largely positive across a variety of life domains. Findings support the need for sleep health to be considered within school's health education and policy to address the unmet health concerns of chronic sleep loss in teens.fals
3D structure and formation of hydrothermal vent complexes at the Paleocene-Eocene transition, the Møre Basin, mid-Norwegian margin
Acknowledgments We thank Statoil for providing us with the PL251 (Tulipan) geophysical and geologic reports for well 6302/6- 1. We thank NORSAR for the free academic use of the SeisRox software during the modeling procedures and to Schlumberger for the free academic use of Petrel 2015. Spectral decomposition was carried out using FFA Geoteric software at the University of Aberdeen. FFA are thanked for donation of the software license to the University of Aberdeen. The authors further acknowledge the support from the Research Council of Norway through its Center of Excellence funding scheme, project 223272 (CEED), and from the MIMES project (grant no. 244155). We also gratefully acknowledge the support by the Faculty of Mathematics and Natural Sciences of the University of Oslo to TS. Clayton Grove and Craig Magee are thanked for their many insightful comments and suggestions that helped improve the paper substantially.Peer reviewedPublisher PD
Nanocavities for Molecular Optomechanics: their fundamental description and application
Vibrational Raman scattering─a process where light exchanges energy with a molecular vibration through inelastic scattering─is most fundamentally described in a quantum framework where both light and vibration are quantized. When the Raman scatterer is embedded inside a plasmonic nanocavity, as in some sufficiently controlled implementations of surface-enhanced Raman scattering (SERS), the coupled system realizes an optomechanical cavity where coherent and parametrically amplified light–vibration interaction becomes a resource for vibrational state engineering and nanoscale nonlinear optics. The purpose of this Perspective is to clarify the connection between the languages and parameters used in the fields of molecular cavity optomechanics (McOM) versus its conventional, “macroscopic” counterpart and to summarize the main results achieved so far in McOM and the most pressing experimental and theoretical challenges. We aim to make the theoretical framework of molecular cavity optomechanics practically usable for the SERS and nanoplasmonics community at large. While quality factors (Q) and mode volumes (V) essentially describe the performance of a nanocavity in enhancing light-matter interaction, we point to the light-cavity coupling efficiencies (η) and optomechanical cooperativities (
) as the key parameters for molecular optomechanics. As an illustration of the significance of these quantities, we investigate the feasibility of observing optomechanically induced transparency with a molecular vibration─a measurement that would allow for a direct estimate of the optomechanical cooperativity
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