318 research outputs found
The influence of expertise on brain activation of the action observation network during anticipation of tennis and volleyball serves
In many daily activities, and especially in sport, it is necessary to predict the effects of others' actions in order to initiate appropriate responses. Recently, researchers have suggested that the action-observation network (AON) including the cerebellum plays an essential role during such anticipation, particularly in sport expert performers. In the present study, we examined the influence of task-specific expertise on the AON by investigating differences between two expert groups trained in different sports while anticipating action effects. Altogether, 15 tennis and 16 volleyball experts anticipated the direction of observed tennis and volleyball serves while undergoing functional magnetic resonance imaging (fMRI). The expert group in each sport acted as novice controls in the other sport with which they had only little experience. When contrasting anticipation in both expertise conditions with the corresponding untrained sport, a stronger activation of AON areas (SPL, SMA), and particularly of cerebellar structures, was observed. Furthermore, the neural activation within the cerebellum and the SPL was linearly correlated with participant's anticipation performance, irrespective of the specific expertise. For the SPL, this relationship also holds when an expert performs a domain-specific anticipation task. Notably, the stronger activation of the cerebellum as well as of the SMA and the SPL in the expertise conditions suggests that experts rely on their more fine-tuned perceptual-motor representations that have improved during years of training when anticipating the effects of others' actions in their preferred sport. The association of activation within the SPL and the cerebellum with the task achievement suggests that these areas are the predominant brain sites involved in fast motor predictions. The SPL reflects the processing of domain-specific contextual information and the cerebellum the usage of a predictive internal model to solve the anticipation task. © 2014 Balser, Lorey, Pilgramm, Naumann, Kindermann, Stark, Zentgraf, Williams and Munzert
Multi-frequency GMRT Observations of the HII regions S 201, S 206, and S 209 : Galactic Temperature Gradient
We present radio continuum images of three Galactic HII regions, S 201, S
206, and S 209 near 232, 327, and 610 MHz using the Giant Meterwave Radio
Telescope (GMRT). The GMRT has a mix of short and long baselines, therefore,
even though the data have high spatial resolution, the maps are still sensitive
to diffuse extended emission. We find that all three HII regions have bright
cores surrounded by diffuse envelopes. We use the high resolution afforded by
the data to estimate the electron temperatures and emission measures of the
compact cores of these HII regions. Our estimates of electron temperatures are
consistent with a linear increase of electron temperature with Galacto-centric
distance for distances up to 18 kpc (the distance to the most distant HII
region in our sample).Comment: Accepted for publication in Astronomy & Astrophysics, 13 figures, 6
pages, Late
Wide-Field Infrared Imaging Polarimetry of the NGC 6334 Region: A Nest of Infrared Reflection Nebulae
We report the detection of eighteen infrared reflection nebulae (IRNe) in the
, , & linear polarimetric observations of the NGC 6334 massive
star-formation complex, of which 16 IRNe are new discoveries. Our images cover
180 square arcminutes, one of the widest near-infrared polarization data
in star-formation regions so far. These IRNe are most likely associated with
embedded young OB stars at different evolutionary phases, showing a variety of
sizes, morphologies, and polarization properties, which can be divided into
four categories. We argue the different nebula characteristics to be a possible
evolutionary sequence of circumstellar structures around young massive stars.Comment: 4 pages, 1 figur
Effects of thermohaline instability and rotation-induced mixing on the evolution of light elements in the Galaxy : D, 3He and 4He
Recent studies of low- and intermediate-mass stars show that the evolution of
the chemical elements in these stars is very different from that proposed by
standard stellar models. Rotation-induced mixing modifies the internal chemical
structure of main sequence stars, although its signatures are revealed only
later in the evolution when the first dredge-up occurs. Thermohaline mixing is
likely the dominating process that governs the photospheric composition of
low-mass red giant branch stars and has been shown to drastically reduce the
net 3He production in these stars. The predictions of these new stellar models
need to be tested against galaxy evolution. In particular, the resulting
evolution of the light elements D, 3He and 4He should be compared with their
primordial values inferred from the Wilkinson Microwave Anisotropy Probe data
and with the abundances derived from observations of different Galactic
regions. We study the effects of thermohaline mixing and rotation-induced
mixing on the evolution of the light elements in the Milky Way. We compute
Galactic evolutionary models including new yields from stellar models computed
with thermohaline instability and rotation-induced mixing. We discuss the
effects of these important physical processes acting in stars on the evolution
of the light elements D, 3He, and 4He in the Galaxy. Galactic chemical
evolution models computed with stellar yields including thermohaline mixing and
rotation fit better observations of 3He and 4He in the Galaxy than models
computed with standard stellar yields. The inclusion of thermohaline mixing in
stellar models provides a solution to the long-standing "3He problem" on a
Galactic scale. Stellar models including rotation-induced mixing and
thermohaline instability reproduce also the observations of D and 4He.Comment: 12 pages, 9 figures, accepted for publication in A&
On the S-matrix renormalization in effective theories
This is the 5-th paper in the series devoted to explicit formulating of the
rules needed to manage an effective field theory of strong interactions in
S-matrix sector. We discuss the principles of constructing the meaningful
perturbation series and formulate two basic ones: uniformity and summability.
Relying on these principles one obtains the bootstrap conditions which restrict
the allowed values of the physical (observable) parameters appearing in the
extended perturbation scheme built for a given localizable effective theory.
The renormalization prescriptions needed to fix the finite parts of
counterterms in such a scheme can be divided into two subsets: minimal --
needed to fix the S-matrix, and non-minimal -- for eventual calculation of
Green functions; in this paper we consider only the minimal one. In particular,
it is shown that in theories with the amplitudes which asymptotic behavior is
governed by known Regge intercepts, the system of independent renormalization
conditions only contains those fixing the counterterm vertices with
lines, while other prescriptions are determined by self-consistency
requirements. Moreover, the prescriptions for cannot be taken
arbitrary: an infinite number of bootstrap conditions should be respected. The
concept of localizability, introduced and explained in this article, is closely
connected with the notion of resonance in the framework of perturbative QFT. We
discuss this point and, finally, compare the corner stones of our approach with
the philosophy known as ``analytic S-matrix''.Comment: 28 pages, 10 Postscript figures, REVTeX4, submitted to Phys. Rev.
Thermohaline instability and rotation-induced mixing. I - Low- and intermediate-mass solar metallicity stars up to the end of the AGB
(abridged) Numerous spectroscopic observations provide compelling evidence
for non-canonical processes that modify the surface abundances of low- and
intermediate-mass stars beyond the predictions of standard stellar theory. We
study the effects of thermohaline instability and rotation-induced mixing in
the 1-4 Msun range at solar metallicity. We present evolutionary models by
considering both thermohaline and rotation-induced mixing in stellar interior.
We discuss the effects of these processes on the chemical properties of stars
from the zero age main sequence up to the end of the second dredge-up on the
early-AGB for intermediate-mass stars and up to the AGB tip for low-mass stars.
Model predictions are compared to observational data for
lithium,12C/13C,[N/C],[Na/Fe],16O/17O, and 16O/18O in Galactic open clusters
and in field stars with well-defined evolutionary status,as well as in
planetary nebulae. Thermohaline mixing simultaneously accounts for the observed
behaviour of 12C/13C,[N/C], and lithium in low-mass stars that are more
luminous than the RGB bump, and its efficiency is increasing with decreasing
initial stellar mass. On the TP-AGB,thermohaline mixing leads to lithium
production, although the 7Li yields remain negative. Although the 3He stellar
yields are much reduced thanks to this process, we find that solar-metallicity,
low-mass stars remain net 3He producers. Rotation-induced mixing is found to
change the stellar structure so that in the mass range between \sim 1.5 and 2.2
Msun the thermohaline instability occurs earlier on the red giant branch than
in non-rotating models. Finally rotation accounts for the observed star-to-star
abundance variations at a given evolutionary status, and is necessary to
explain the features of CN-processed material in intermediate-mass stars.Comment: 18 pages, 22 figures, accepted for publication in A&
The massive expanding molecular torus in the planetary nebula NGC 6302
We measure the mass and kinematics of the massive molecular torus in the
planetary nebula NGC 6302. The nebula is the proto-typical butterfly nebula.
The origin of the wing-like morphology is disputed: determining the mass-loss
history of the confining torus is an important step in understanding the
formation of this structure. We performed submillimeter observations with JCMT
and the SMA interferometer. The continuum emission as well as the J=2-1 and 3-2
transitions of 12CO and 13CO are analysed at arcsecond resolution. The CO
emission indicates a mass of the torus of ~ 2Msun +/- 1Msun. The 12CO and 13CO
emission matches the dark lane seen in absorption in the Halpha image of the
object. The CO torus is expanding with a velocity of ~ 8 km/s, centred at
Vlsr=-31.5 km/s. The size and expansion velocity of the torus indicates that
the torus was ejected from ~ 7500 yr to 2900 yr ago, with a mass-loss rate of
5x10^{-4}Msun/yr. We also see a ballistic component in the CO images with a
velocity gradient of 140 km/s/pc.
The derived mass-loss history of the torus favours binary interaction as the
cause of the ejection of the torus. We predict the existence of a companion
with an orbital period P < 1 month.Comment: 13 pages, 10 figures, accepted for publication in A&
The Center Conjecture for spherical buildings of types F4 and E6
We prove that a convex subcomplex of a spherical building of type F4 or E6 is
a subbuilding or the automorphisms of the subcomplex fix a point on it. Our
approach is differential-geometric and based on the theory of metric spaces
with curvature bounded above. We use these techniques also to give another
proof of the same result for the spherical buildings of classical type.Comment: 34 pages. An intrinsic version of the results has been added. Proof
of the Center Conjecture for spherical buildings of classical types added.
More material on Coxeter complexe
Herschel Observations of the W43 "mini-starburst"
Aims: To explore the infrared and radio properties of one of the closest
Galactic starburst regions. Methods: Images obtained with the Herschel Space
Observatory at wavelengths of 70, 160, 250, 350, and 500 microns using the PACS
and SPIRE arrays are analyzed and compared with radio continuum VLA data and 8
micron images from the Spitzer Space Telescope. The morphology of the
far-infrared emission is combined with radial velocity measurements of
millimeter and centimeter wavelength transitions to identify features likely to
be associated with the W43 complex. Results: The W43 star-forming complex is
resolved into a dense cluster of protostars, infrared dark clouds, and ridges
of warm dust heated by massive stars. The 4 brightest compact sources with L >
1.5 x 10^4 Lsun embedded within the Z-shaped ridge of bright dust emission in
W43 remain single at 4" (0.1 pc) resolution. These objects, likely to be
massive protostars or compact clusters in early stages of evolution are
embedded in clumps with masses of 10^3 to 10^4 Msun, but contribute only 2% to
the 3.6 x 10^6 Lsun far-IR luminosity of W43 measured in a 16 by 16 pc box. The
total mass of gas derived from the far-IR dust emission inside this region is
~10^6 Msun. Cometary dust clouds, compact 6 cm radio sources, and warm dust
mark the locations of older populations of massive stars. Energy release has
created a cavity blowing-out below the Galactic plane. Compression of molecular
gas in the plane by the older HII region near G30.684-0.260 and the bipolar
structure of the resulting younger W43 HII region may have triggered the
current mini-star burst.Comment: 5 pages, 3 figures, accepted for A&A Special Issu
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