1,228 research outputs found
Dualization of non-Abelian BF model
We show that dualization of BF models to Stueckelberg-like massive gauge
theories allows a non-Abelian extension. We obtain local Lagrangians which are
straightforward extensions of the Abelian results.Comment: 6 pages, ReVTeX, no figures, to be publ. on Phys.Lett.
Sport and History: Continuity and Change. Local Stories to Explain Global History
A collection of quality papers selected from those presented at the 2021 joint Congress of the European Committee of Sports History (CESH) and the International Society for the History of Physical Education and Sport (ISHPES) in Lisbon, Portugal, has been gathered to bring an array of contemporary perspectives on sports history
The influence of the allometric scale on the relationship between running economy and biomechanical variables in distance runners
Studies have demonstrated the need for the use of parameters that diminish the effect of body mass, for intra and inter group comparison, in individuals with different masses in order to provide a different analysis on the behaviour of the relation between running economy (RE) and biomechanical variables (BVs). The allometric scale is represented by a regression equation that indicates the behaviour of a physiological variable in relation to the variable mass (RE=a.xb), where x is body mass in (kg) and the dimensionless coefficient a is characteristic of the species analysed, and the dimensionless exponent b determines the percentage of mass to be associated with the physiological variable. The influence of the allometric scale (b=-1; -0.75; -0.73; -0.67) on the relationship between RE and BVs - stride length (SL), relative stride length (RSL), stride rate (SR), stride time (ST), support time (SUPT) and balance time (BALT) - at 12 km.h-1, was analysed in nine elite runners. Factorial analysis and Pearson's Correlation Coefficient test (r) with P<0.05 were used. A decrease in the explanation power of the RE was observed, with the use of the allometric exponent, due to the BVs, as well as a reduction of the correlation coefficients between SL versus RE, ST versus RE and SR versus RE. The BALT presented a higher correlation where b=-0.75. The RSL and SUPT presented non-significant correlations. The variables SL, ST, SR and BALT were the most effective predictors of the RE, Where: b=-1, the allometric scale was most efficient to predict the running performance
The Super Lithium-Rich Red Giant Rapid Rotator G0928+73.2600: A Case for Planet Accretion?
We present the discovery of a super lithium-rich K giant star, G0928+73.2600.
This red giant (T_eff = 4885 K and log g = 2.65) is a fast rotator with a
projected rotational velocity of 8.4 km/s and an unusually high lithium
abundance of A(Li) = 3.30 dex. Although the lack of a measured parallax
precludes knowing the exact evolutionary phase, an isochrone-derived estimate
of its luminosity places the star on the Hertzsprung-Russell diagram in a
location that is not consistent with either the red bump on the first ascent of
the red giant branch or with the second ascent on the asymptotic giant branch,
the two evolutionary stages where lithium-rich giant stars tend to cluster.
Thus, even among the already unusual group of lithium-rich giant stars,
G0928+73.2600 is peculiar. Using 12C/13C as a tracer for mixing---more mixing
leads to lower 12C/13C---we find 12C/13C = 28, which is near the expected value
for standard first dredge-up mixing. We can therefore conclude that "extra"
deep mixing has not occurred. Regardless of the ambiguity of the evolutionary
stage, the extremely large lithium abundance and the rotational velocity of
this star are unusual, and we speculate that G0928+73.2600 has been enriched in
both lithium and angular momentum from a sub-stellar companion.Comment: 5 pages, 4 figures, Accepted by ApJ Letter
Large scale in vivo recording of sensory neuron activity with GCaMP6
Greater emphasis on the study of intact cellular networks in their physiological environment has led to rapid advances in intravital imaging of the central nervous system (CNS), while the peripheral system remains largely unexplored. To assess large networks of sensory neurons, we selectively label primary afferents with GCaMP6s in male and female C57bl/6 mice and visualize their functional responses to peripheral stimulation in vivo. We show that we are able to monitor the activity of hundreds of sensory neurons simultaneously, with sufficient sensitivity to detect, in most cases, single action potentials with a typical rise time of around 200 ms, and an exponential decay with a time constant of approximately 700 ms. With this technique we are able to characterize the responses of large populations of sensory neurons to innocuous and noxious mechanical and thermal stimuli under normal and inflammatory conditions. We demonstrate that the majority of primary afferents are polymodal with between 50–80% of thermally sensitive DRG neurons responding also to noxious mechanical stimulation. We also specifically assess the small population of peripheral cold neurons and demonstrate significant sensitization to cooling after a model of sterile and persistent inflammation, with significantly increased sensitivity already at decreases of 5°C when compared to uninflamed responses. This not only reveals interesting new insights into the (patho)physiology of the peripheral nervous system but also demonstrates the sensitivity of this imaging technique to physiological changes in primary afferents
Lithium-rich giants in the Galactic thick disk
Context: Lithium is a fragile element, which is easily destroyed in the
stellar interior. The existence of lithium-rich giants still represents a
challenge for stellar evolution models. Aims: We have collected a large
database of high-resolution stellar spectra of 824 candidate thick-disk giants
having 2\,MASS photometry and proper motions measured by the Southern
Proper-Motion Program (SPM). In order to investigate the nature of Li-rich
giants, we searched this database for giants presenting a strong Li\,I
resonance line. Methods: We performed a chemical abundance analysis on the
selected stars with the MOOG code along with proper ATLAS-9 model atmospheres.
The iron content and atmospheric parameters were fixed by using the equivalent
width of a sample of Fe lines. We also derive abundances for C, N, and O and
measure or derive lower limits on the C/C isotopic ratios, which
is a sensible diagnostic of the stars evolutionary status. Results: We detected
five stars with a lithium abundance higher than 1.5, i.e. Li-rich according to
the current definition. One of them (SPM-313132) has A(Li)3.3 and, because
of this, belongs to the group of the rare super Li-rich giants. Its kinematics
makes it a likely thin-disk member and its atmospheric parameters are
compatible with it being a 4\,M star either on the red giant branch
(RGB) or the early asymptotic giant branch. This object is the first super
Li-rich giant detected at this phase. The other four are likely low-mass
thick-disk stars evolved past the RGB luminosity bump, as determined from their
metallicities and atmospheric parameters. The most evolved of them lies close
to the RGB-tip. It has A(Li)2.7 and a low C/C isotopic ratio,
close to the cool bottom processing predictions.Comment: 11 pages, 7 tables, 7 figures. Accepted for publication in A&
The tidal effects on the lithium abundance of binary systems with giant component
We analise the behavior of lithium abundance as a function of effective
temperature, projected rotational velocity, orbital period and eccentricity for
a sample of 68 binary systems with giant component and orbital period ranging
from about 10 to 6400 days. For these binary systems the Li abundances show a
gradual decrease with temperature, paralleling the well established result for
single giants. We have also observed a dependence of lithium content on
rotation. Binary systems with moderate to high rotation present also moderate
to high Li content. This study shows also that synchronized binary systems with
giant component seems to retain more of their original lithium than the
unsynchronized systems. For orbital periods lower than 100 to 250 days,
typically the period of synchronization for this kind of binary systems,
lithium depleted stars seems to be unusual. The suggestion is made that there
is an 'inhibited zone' in which synchronized binary systems with giant
component having lithium abundance lower than a threshold level should be
unusual.Comment: 6 pages, 3 Postscript figures, uses: aa.cls, psfig.st
Can an aversive, extinction-resistant memory trigger impairments in walking adaptability? An experimental study using adult rats
Cognitive demands can influence the adaptation of walking, a crucial skill to maintain body stability and prevent falls. Whilst previous research has shown emotional load tunes goal-directed movements, little attention has been given to this finding. This study sought to assess the effects of suffering an extinction-resistant memory on skilled walking performance in adult rats, as an indicator of walking adaptability. Thus, 36 Wistar rats were divided in a two-part experiment. In the first part (n = 16), the aversive, extinction-resistance memory paradigm was established using a fear-conditioning chamber. In the second, rats (n = 20) were assessed in a neutral room using the ladder rung walking test before and tree days after inducing an extinction-resistance memory. In addition, the elevated plus-maze test was used to control the influence of the anxiety-like status on gait adaptability. Our results revealed the shock group exhibited worse walking adaptability (lower skilled walking score), when compared to the sham group. Moreover, the immobility time in the ladder rung walking test was similar to the controls, suggesting that gait adaptability performance was not a consequence of the fear generalization. No anxiety-like behavior was observed in the plus maze test. Finally, correlation coefficients also showed the skilled walking performance score was positively correlated with the number of gait cycles and trial time in the ladder rung walking test and the total crossings in the plus maze. Overall, these preliminary findings provide evidence to hypothesize an aversive, extinction-resistant experience might change the emotional load, affecting the ability to adapt walking
Population Synthesis of Common Envelope Mergers: I. Giant Stars with Stellar or Substellar Companions
Using a population synthesis technique, we have calculated detailed models of
the present-day field population of objects that have resulted from the merger
of a giant primary and a main-sequence or brown dwarf secondary during
common-envelope evolution. We used a grid of 116 stellar and 32 low-mass/brown
dwarf models, a crude model of the merger process, and followed the angular
momentum evolution of the binary orbit and the primary's rotation prior to
merger, as well as the merged object's rotation after the merger. We find that
present-day merged objects that are observable as giant stars or core-helium
burning stars in our model population constitute between 0.24% and 0.33% of the
initial population of ZAMS binaries, depending upon the input parameters
chosen. The median projected rotational velocity of these merged objects is ~16
km/sec, an order of magnitude higher than the median projected rotational
velocity in a model population of normal single stars calculated using the same
stellar models and initial mass function. The masses of the merged objects are
typically less than ~2 solar masses, with a median mass of 1.28 solar masses,
which is slightly more than, but not significantly different from, their normal
single star counterparts. The luminosities in our merged object population
range from ~10-100 solar luminosities, with a strong peak in the luminosity
distribution at ~60 solar luminosities, since the majority of the merged
objects (57%) lie on the horizontal branch at the present epoch. The results of
our population synthesis study are discussed in terms of possible observational
counterparts either directly involving the high rotational velocity of the
merger product or indirectly, via the effect of rotation on envelope abundances
and on the amount and distribution of circumstellar matter.Comment: 16 pages, 12 figures, accepted for publication in the Astrophysical
Journa
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