5,280 research outputs found
Planetary nebulae in M32 and the bulge of M31: Line intensities and oxygen abundances
We present spectroscopy of planetary nebulae in M32 and in the bulge of M31
that we obtained with the MOS spectrograph at the Canada-France-Hawaii
Telescope. Our sample includes 30 planetary nebulae in M31 and 9 planetary
nebulae in M32. We also observed one H II region in the disk of M31. We
detected [O III]4363 in 18 of the planetary nebulae, 4 in M32 and 14
in the bulge of M31. We use our line intensities to derive electron
temperatures and oxygen abundances for the planetary nebulae.Comment: 17 pages, 12 figures, accepted by Astronomy & Astrophysics Supplement
Serie
Polarization in the Lagoon nebula
A V-band polarimetric survey of stars associated with the Lagoon nebula was conducted. The data were combined with existing photometric and spectroscopic observations in order to investigate the alignment of magnetic field lines with identifiable symmetry axes and to evaluate the nature of dust in the immediate vicinity. Although stars are not in general highly polarized, electric vectors align with the minor axis of the Lagoon nebula, perpendicular to the major axis of the spatial distribution of massive stars. The observations indicate that the collapse of the molecular cloud progenitor was inhibited along directions perpendicular to magnetic field lines. Considering the low polarization efficiency and the high ratio of total to selective extinction, smaller grains of intranebular dust appear to have been destroyed
Are aerobic fitness and repeated sprint ability linked to fatigue in professional soccer match-play? A pilot study
This investigation examined the association between aerobic fitness and repeated sprint ability and match-related fatigue in 9 professional outfield soccer players. Aerobic fitness using maximal aerobic speed (MAS) was determined via a continuous progressive incremental running test conducted on a motorised treadmill. A repeated sprint ability test (6 successive 6 s sprints separated by 20 s passive recovery) was performed on a non-motorised treadmill to determine mean and best sprint times and a percentage decrement score (%PD). A total of 114 observations of physical performance derived using computerised time motion analyses were collected from 33 matches. Correlations between fitness test and match-play measures were examined for 1) accumulated fatigue: percentage difference between halves for total distance covered per minute, distance run at high-intensities (HIR, actions for 1s duration, >19.1 km/h) per minute, mean recovery time between high-intensity runs, and percentage difference between the distance covered in HIR in the first 5- and 15-minute periods versus the final 5- and 15-minute periods respectively in normal time; and for 2) transient fatigue: percentage difference between the distance covered in HIR in a peak 5-minute period and the subsequent 5-minute period and for the latter compared to the mean for all other 5-minute periods. No significant relationships were observed between MAS and fatigue scores (magnitude of associations: trivial to large). For mean and best sprint times and %PD, the only reported significant correlation (r=0.77, magnitude of association: very large, p<0.05) was between %PD and the % difference across halves for mean recovery time between high-intensity runs (magnitude of other associations: small to large). Criterion measures from tests of aerobic fitness and repeated sprint ability might not accurately depict a player’s capacity to resist fatigue during professional soccer competition
Squad management, injury and match performance in a professional soccer team over a Championship-winning season
Squad management, injury and physical, tactical and technical match performance were investigated in a professional soccer team across five consecutive league seasons (2008–2013, 190 league games) with specific focus on a championship-winning season (2010/11). For each player, match participation and time-loss injuries were recorded, the latter prospectively diagnosed by the team's physician. Defending and attacking tactical and technical performance indicators investigated included ball possession and possession in opponents' half, passes, forward passes, completed passes and forward passes, crosses and completed crosses, goal attempts and goal attempts on target, successful final third entries, free-kicks and 50/50 duels won/lost. Physical performance measures included total distance and distance covered at high-speeds (≥19.1 km/h). Results showed that during the 2010/11 season, squad utilisation was lowest potentially owing to the observed lower match injury occurrence and working days lost to injury thereby increasing player availability. In 2010/11, the team won both its highest number of points and conceded its lowest number of goals especially over the second half of this season. The team also won its highest number of games directly via a goal from a substitute and scored and conceded a goal first on the highest and lowest number of occasions, respectively. While multivariate analysis of variance (MANOVA) detected a significant difference in some attacking and defensive performance indicators across the five seasons, these were generally not distinguishing factors in 2010/11. Similarly, univariate ANOVAs showed a significant difference in running distances covered across seasons, but the trend was for less activity in 2010/11
Vector Area Theorem mapping in crystals and polarization stability of SIT-solitons
The stability of polarization, areas, and number of self-induced transparency
(SIT)-solitons at the output from the LaF_3:Pr^{3+} crystal is theoretically
studied versus the polarization direction and the area of the input linearly
polarized laser pulse. For this purpose the Vector Area Theorem is rederived
and two-dimensional Vector Area Theorem map is obtained. The map is governed by
the crystal symmetry and takes into account directions of the dipole matrix
element vectors of the different site subgroups of optically excited ions. The
Vector Area Theorem mapping of the time evolution of the laser pulse allows one
to highlight soliton polarization properties.Comment: 3 pages, 3 figures; v2: minor corrected labels in Fig. 3 and its
cuptur
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