1,807 research outputs found
Nutrition for master athletes: From challenges to optimisation strategies
Master athletes are genuine examples of successful ageing thanks to their capacity of maintaining a high level of sports performance during their entire life. Within the last decade many studies have focused on the evolution of performance in many sports with ageing, as well as on the training modalities to reach such performance. On the contrary, there is a paucity of data on the nutritional habits of master athletes and the question of whether they need to adapt their nutrition to the ageing process remains unsolved. This is within this context of the optimisation of nutrition for master athletes that this review stands. The aim is to identify the potential nutritional challenges encountered by master athletes and how to handle them through adapted nutritional strategies. Given the lack of data specific to master athletes, studies including master athletes are considered as a priority, though we also make inferences based on nutrition for young adults and perturbations induced by ageing in non-athletic populations. The first part of this opinion paper tackles the first challenge faced by master athletes which is the gradual reduction in energy intake with ageing. The second challenge is the anabolic resistance and the need for increased protein intake. The third nutritional challenge we present is the episodes of metabolic crisis master athletes may face throughout life. Finally, we gather the main nutritional recommendations for master athletes and suggest the next stage of research. © 2019 ACAPS
Nutrition for master athletes: is there a need for specific recommendations?
Master athletes are often considered exemplars of successful aging, thanks to their capacity to maintain a high sports performance during their entire life. A high training capacity, regular participation in sporting competitions, and delayed alterations in body composition and physiological capacities have been listed among the main factors contributing to impressive master athletes’ performances. However, there is a paucity of data on the metabolism and dietary habits of master athletes, and the question of whether they need to adapt their nutrition to the aging process remains open. Herein, the authors presented a contemporary overview of themetabolic challenges associated with aging, including the risk of low energy availability, anabolic resistance, and periods of metabolic crisis due to forced immobilization. After assembling scientific evidence to show that master athletes must adapt their dietary intake, the authors proposed a summary of nutritional recommendations for master athletes and suggested the next stage of research
Larval culture of the calico scallop, Argopecten gibbus
Mature calico scallops, Argopecten gibbus, collected from the grounds off Cape Kennedy, Florida, were induced to spawn in the laboratory. Fertilized eggs were reared to postlarvae in sea water of 23° C ± 2.0° C at a salinity of 35 %o. The external morphology of eggs and developing larval stages are described
Low temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers
We report on a detailed analysis of the superconducting properties of
boron-doped silicon films grown along the 001 direction by Gas Immersion Laser
Doping. The doping concentration cB has been varied up to approx. 10 at.% by
increasing the number of laser shots to 500. No superconductivity could be
observed down to 40mK for doping level below 2.5 at.%. The critical temperature
Tc then increased steeply to reach 0.6K for cB = 8 at%. No hysteresis was found
for the transitions in magnetic field, which is characteristic of a type II
superconductor. The corresponding upper critical field Hc2(0) was on the order
of 1000 G, much smaller than the value previously reported by Bustarret et al.
in Nature (London) 444, 465 (2006).Comment: 4 pages including 4 figures, submitted to PRB-Rapid Communicatio
DISCOVERY OF A LOW-LUMINOSITY, TIGHT SUBSTELLAR BINARY AT THE T/Y TRANSITION
We have discovered that the brown dwarf WISEJ014656.66+423410.0 is a close
binary (0.08750.0021 arcsec, 0.93 AU) from Keck laser
guide star adaptive optics imaging. Our photometry for this system reveals that
both components are less luminous than those in any known substellar binary.
Combining a new integrated-light spectrum (T9p) and resolved YJH-band
photometry from Keck allows us to perform spectral decomposition and assign
component types of T9 and Y0. Many of the unusual features in the spectrum
might be explained by high surface gravity: Y-band peak broadened to the blue;
J-band peak broadened to the red; H-band peak shifted slightly to the red; and
red Y-J colors. Interestingly, the very low component luminosities imply that
the T9 primary is unexpectedly cold ( = 34545 K assuming an
age of 10 Gyr), making it 100 K cooler than any other late-T dwarf and
comparable to Y dwarfs. One intriguing explanation for this apparent
discrepancy is that the J- and H-band spectral features that trigger the
transition from T to Y spectral types are highly gravity-dependent. This can be
tested directly in the very near future by orbit monitoring. We constrain the
orbital period to be 10 yr by combining evolutionary model-based mass
estimates for the components (1221 , 1 at 10
Gyr) with a statistical constraint on the semimajor axis (1.3 AU).
Such a period is shorter than any other known T/Y transition binary, meaning
that WISEJ0146+4234AB will likely yield a dynamical mass within the next few
years.Comment: Accepted to ApJ (2015 Feb 14); 24 pages, 4 figures, 5 table
The Young L Dwarf 2MASS J11193254-1137466 Is a Planetary-mass Binary
We have discovered that the extremely red, low-gravity L7 dwarf 2MASS
J11193254-1137466 is a 0.14" (3.6 AU) binary using Keck laser guide star
adaptive optics imaging. 2MASS J11193254-1137466 has previously been identified
as a likely member of the TW Hydrae Association (TWA). Using our updated
photometric distance and proper motion, a kinematic analysis based on the
BANYAN II model gives an 82% probability of TWA membership. At TWA's 103
Myr age and using hot-start evolutionary models, 2MASS J11193254-1137466AB is a
pair of brown dwarfs, making it the
lowest-mass binary discovered to date. We estimate an orbital period of
years. One component is marginally brighter in band but
fainter in band, making this a probable flux-reversal binary, the first
discovered with such a young age. We also imaged the spectrally similar TWA L7
dwarf WISEA J114724.10-204021.3 with Keck and found no sign of binarity. Our
evolutionary model-derived estimate for WISEA J114724.10-204021.3
is 230 K higher than for 2MASS J11193254-1137466AB, at odds with their
spectral similarity. This discrepancy suggests that WISEA J114724.10-204021.3
may actually be a tight binary with masses and temperatures very similar to
2MASS J11193254-1137466AB, or further supporting the idea that near-infrared
spectra of young ultracool dwarfs are shaped by factors other than temperature
and gravity. 2MASS J11193254-1137466AB will be an essential benchmark for
testing evolutionary and atmospheric models in the young planetary-mass regime.Comment: Accepted to ApJ Letters. 8 pages, 3 figures, 2 table
ADAPTIVE OPTICS IMAGING OF VHS 1256-1257: A LOW MASS COMPANION TO A BROWN DWARF BINARY SYSTEM
Recently, Gauza et al. (2015) reported the discovery of a companion to the
late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion's absolute
photometry suggests its mass and atmosphere are similar to the HR 8799 planets.
However, as a wide companion to a late-type star, it is more accessible to
spectroscopic characterization. We discovered that the primary of this system
is an equal-magnitude binary. For an age Myr the A and B components
each have a mass of , and the b component
has a mass of , making VHS 1256-1257 only the third brown
dwarf triple system. There exists some tension between the spectrophotometric
distance of pc and the parallax distance of pc. At
12.7 pc VHS1256-1257 A and B would be the faintest known M7.5 objects, and are
even faint outliers among M8 types. If the larger spectrophotmetric distance is
more accurate than the parallax, then the mass of each component increases. In
particular, the mass of the b component increases well above the deuterium
burning limit to and the mass of each binary
component increases to . At 17.1 pc, the UVW
kinematics of the system are consistent with membership in the AB~Dor moving
group. The architecture of the system resembles a hierarchical stellar multiple
suggesting it formed via an extension of the star-formation process to low
masses. Continued astrometric monitoring will resolve this distance uncertainty
and will provide dynamical masses for a new benchmark system.Comment: Accepted to ApJ
Rotational Velocities of Individual Components in Very Low Mass Binaries
We present rotational velocities for individual components of 11 very low mass (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics system. We find that the observed sources tend to be rapid rotators (v sin i > 10 km s^(–1)), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest v sin i, LP 349–25B and HD 130948C, are rotating at ~30% of their break-up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary systems, all with orbital semimajor axes ≾3.5 AU, have component v sin i values that differ by greater than 3σ. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have implications for binary star formation and evolution. We also investigate possible dynamical evolution in the triple system HD 130948A–BC. The close binary brown dwarfs B and C have significantly different v sin i values. We demonstrate that components B and C could have been torqued into misalignment by the primary star, A, via orbital precession. Such a scenario can also be applied to another triple system in our sample, GJ 569A–Bab. Interactions such as these may play an important role in the dynamical evolution of VLM binaries. Finally, we note that two of the binaries with large differences in component v sin i, LP 349–25AB and 2MASS 0746+20AB, are also known radio sources
The Mass-Luminosity Relation in the L/T Transition:Individual Dynamical Masses for the New J-Band Flux Reversal Binary SDSSJ105213.51+442255.7AB
We have discovered that SDSSJ105213.51+442255.7 (T0.51.0) is a binary in
Keck laser guide star adaptive optics imaging, displaying a large J-to-K-band
flux reversal (J = -0.450.09 mag, K = 0.520.05 mag).
We determine a total dynamical mass from Keck orbital monitoring (885
) and a mass ratio by measuring the photocenter orbit from
CFHT/WIRCam absolute astrometry ( = 0.780.07). Combining these
provides the first individual dynamical masses for any field L or T dwarfs,
493 for the L6.51.5 primary and 393
for the T1.51.0 secondary. Such a low mass ratio for a nearly equal
luminosity binary implies a shallow massluminosity relation over the L/T
transition (log/log). This
provides the first observational support that cloud dispersal plays a
significant role in the luminosity evolution of substellar objects. Fully
cloudy models fail our coevality test for this binary, giving ages for the two
components that disagree by 0.2 dex (2.0). In contrast, our observed
masses and luminosities can be reproduced at a single age by "hybrid"
evolutionary tracks where a smooth change from a cloudy to cloudless
photosphere around 1300 K causes slowing of luminosity evolution. Remarkably,
such models also match our observed JHK flux ratios and colors well. Overall,
it seems that the distinguishing features SDSSJ1052+4422AB, like a J-band flux
reversal and high-amplitude variability, are normal for a field L/T binary
caught during the process of cloud dispersal, given that the age
(1.11 Gyr) and surface gravity (log = 5.05.2) of
SDSSJ1052+4422AB are typical for field ultracool dwarfs.Comment: Accepted to ApJ; 33 pages, 8 figures, 5 table
Mapping the Shores of the Brown Dwarf Desert III: Young Moving Groups
We present the results of an aperture masking interferometry survey for
substellar companions around 67 members of the young (~8-200Myr) nearby
(~5-86pc) AB Doradus, Beta Pictoris, Hercules-Lyra, TW Hya, and
Tucana-Horologium stellar associations. Observations were made at near infrared
wavelengths between 1.2-3.8 microns using the adaptive optics facilities of the
Keck II, VLT UT4, and Palomar Hale Telescopes. Typical contrast ratios of
~100-200 were achieved at angular separations between ~40-320mas, with our
survey being 100% complete for companions with masses below 0.25\msolar across
this range. We report the discovery of a \msolar companion to
HIP14807, as well as the detections and orbits of previously known stellar
companions to HD16760, HD113449, and HD160934. We show that the companion to
HD16760 is in a face-on orbit, resulting in an upward revision of its mass from
\mjupiter to \msolar. No substellar
companions were detected around any of our sample members, despite our ability
to detect companions with masses below 80\mjupiter for 50 of our targets: of
these, our sensitivity extended down to 40\mjupiter around 30 targets, with a
subset of 22 subject to the still more stringent limit of 20\mjupiter. A
statistical analysis of our non-detection of substellar companions allows us to
place constraints on their frequency around ~0.2-1.5\msolar stars. In
particular, considering companion mass distributions that have been proposed in
the literature, we obtain an upper limit estimate of ~9-11% for the frequency
of 20-80\mjupiter companions between 3-30AU at 95% confidence, assuming that
their semimajor axes are distributed according to in this range.Comment: Accepted by Ap
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