4,358 research outputs found
The Shape of LITTLE THINGS Dwarf Galaxies DDO 46 and DDO 168: Understanding the stellar and gas kinematics
We present the stellar and gas kinematics of DDO 46 and DDO 168 from the
LITTLE THINGS survey and determine their respective Vmax/sigma_z,0 values. We
used the KPNO's 4-meter telescope with the Echelle spectrograph as a long-slit
spectrograph. We acquired spectra of DDO 168 along four position angles by
placing the slit over the morphological major and minor axes and two
intermediate position angles. However, due to poor weather conditions during
our observing run for DDO 46, we were able to extract only one useful data
point from the morphological major axis. We determined a central stellar
velocity dispersion perpendicular to the disk, sigma_z,0, of 13.5+/-8 km/s for
DDO 46 and of 10.7+/-2.9 km/s for DDO 168. We then derived the
maximum rotation speed in both galaxies using the LITTLE THINGS HI data. We
separated bulk motions from non-circular motions using a double Gaussian
decomposition technique and applied a tilted-ring model to the bulk velocity
field. We corrected the observed HI rotation speeds for asymmetric drift and
found a maximum velocity, Vmax, of 77.4 +/- 3.7 and 67.4 +/- 4.0 km/s for DDO
46 and DDO 168, respectively. Thus, we derived a kinematic measure,
Vmax/sigma_z,0, of 5.7 +/- 0.6 for DDO 46 and 6.3 +/- 0.3 for DDO 168.
Comparing these values to ones determined for spiral galaxies, we find that DDO
46 and DDO 168 have Vmax/sigma_z,0 values indicative of thin disks, which is in
contrast to minor-to-major axis ratio studies
Influence of Pacing Strategy on Oxygen Uptake During Treadmill Middle-Distance Running
The oxygen uptake (V·O2) attained during a constant speed 800-m pace trial on a treadmill is less than the maximal V·O2 (V·O2max) in male middle-distance runners with a high V·O2max (i.e., > 65 ml · kg-1 · min-1). We therefore investigated whether the V·O2 attained was influenced by the pacing strategy adopted. Eight male middle-distance runners (age 25.8 ± 3.3 years; height 1.78 ± 0.10 m; mass 67.8 ± 4.7 kg) with a personal best 800-m time of 112.0 ± 3.3 s volunteered to participate. Subjects undertook a speed ramped progressive test to determine V·O2max and three 800-m pace runs to exhaustion all in a randomised order. The three 800-m pace runs included constant speed, acceleration, and race simulation runs. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest V·O2 during the progressive test (i.e., V·O2max) and the highest V·O2 during the 800-m pace runs (i.e., V·O2peak) were compared. For the eight runners, V·O2max was 67.2 ± 4.3 ml · kg-1 · min-1. V·O2peak was 60.1 ± 5.1 ml · kg-1 · min-1, 61.1 ± 5.2 ml · kg-1 · min-1, and 62.2 ± 4.9 ml · kg-1 · min-1, yielding values of 89.3 ± 2.4 %, 90.8 ± 2.8 %, and 92.5 ± 3.1 % V·O2max for the constant speed, acceleration and race simulation runs, respectively. Across runs, repeated measures ANOVA revealed a significant effect (p = 0.048). Trend analysis identified a significant linear trend (p = 0.025) with the % V·O2max attained being higher for the acceleration run than the constant speed run, and higher still for the race simulation run. These results demonstrate that in middle-distance runners a) pacing strategy influences the V·O2 attained, with a race simulation run elevating the V·O2 attained compared with other pacing strategies, and b) regardless of pacing strategy the V·O2 attained in an 800-m pace run on a treadmill is less than V·O2max
A pyrene-appended spiropyran for selective photo-switchable binding of Zn(II): UV-visible and fluorescence spectroscopy studies of binding and non-covalent attachment to graphene, graphene oxide and carbon nanotubes
PublishedArticleSynthesis of photo-switchable, Zn2+ sensitive hybrid materials was achieved by facile non-covalent functionalization of graphene, graphene oxide and carbon nanotubes with a pyrene-appended spiropyran. Solution phase binding studies, using UV–visible and fluorescence spectroscopy, indicated that the pyrene-spiropyran dyad was highly selective for Zn2+ over a range of potentially competitive cations and that binding occurred with 1:1 stoichiometry and a binding constant of K=1.4×104 mol−1 dm3 at 295 K. Zn2+ binding was promoted by UV irradiation or in darkness and reversed upon irradiation with visible light.Engineering & Physical Sciences Research Council (EPSRC
Ponderomotive effects in multiphoton pair production
The Dirac-Heisenberg-Wigner formalism is employed to investigate
electron-positron pair production in cylindrically symmetric but otherwise
spatially inhomogeneous, oscillating electric fields. The oscillation
frequencies are hereby tuned to obtain multiphoton pair production in the
nonperturbative threshold regime. An effective mass as well as a
trajectory-based semi-classical analysis are introduced in order to interpret
the numerical results for the distribution functions as well as for the
particle yields and spectra. The results, including the asymptotic particle
spectra, display clear signatures of ponderomotive forces.Comment: 9 pages, 3 Tables, 3 Figure
Influence of Pacing Strategy on Oxygen Uptake During Treadmill Middle-Distance Running
The oxygen uptake (V·O2) attained during a constant speed 800-m pace trial on a treadmill is less than the maximal V·O2 (V·O2max) in male middle-distance runners with a high V·O2max (i.e., > 65 ml · kg-1 · min-1). We therefore investigated whether the V·O2 attained was influenced by the pacing strategy adopted. Eight male middle-distance runners (age 25.8 ± 3.3 years; height 1.78 ± 0.10 m; mass 67.8 ± 4.7 kg) with a personal best 800-m time of 112.0 ± 3.3 s volunteered to participate. Subjects undertook a speed ramped progressive test to determine V·O2max and three 800-m pace runs to exhaustion all in a randomised order. The three 800-m pace runs included constant speed, acceleration, and race simulation runs. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest V·O2 during the progressive test (i.e., V·O2max) and the highest V·O2 during the 800-m pace runs (i.e., V·O2peak) were compared. For the eight runners, V·O2max was 67.2 ± 4.3 ml · kg-1 · min-1. V·O2peak was 60.1 ± 5.1 ml · kg-1 · min-1, 61.1 ± 5.2 ml · kg-1 · min-1, and 62.2 ± 4.9 ml · kg-1 · min-1, yielding values of 89.3 ± 2.4 %, 90.8 ± 2.8 %, and 92.5 ± 3.1 % V·O2max for the constant speed, acceleration and race simulation runs, respectively. Across runs, repeated measures ANOVA revealed a significant effect (p = 0.048). Trend analysis identified a significant linear trend (p = 0.025) with the % V·O2max attained being higher for the acceleration run than the constant speed run, and higher still for the race simulation run. These results demonstrate that in middle-distance runners a) pacing strategy influences the V·O2 attained, with a race simulation run elevating the V·O2 attained compared with other pacing strategies, and b) regardless of pacing strategy the V·O2 attained in an 800-m pace run on a treadmill is less than V·O2max
VO2 Attained During Treadmill Running: The Influence of a Specialist (400-m or 800-m) Event
Purpose: Previously it has been observed that, in well-trained 800-m athletes, VO(2)max is not attained during middle-distance running events on a treadmill, even when a race-type pacing strategy is adopted. Therefore, the authors investigated whether specialization in a particular running distance (400-m or 800-m) influences the VO(2) attained during running on a treadmill. Methods: Six 400-m and six 800-m running specialists participated in the study. A 400-m trial and a progressive test to determine VO(2)max were completed in a counterbalanced order. Oxygen uptakes attained during the 400-m trial were compared to examine the influence of specialist event. Results: A VO(2) plateau was observed in all participants for the progressive test, demonstrating the attainment of VO(2)max. The VO(2)max values were 56.2 +/- 4.7 and 69.3 +/- 4.5 mL . kg(-1) min(-1) for the 400-m- and 800-m-event specialists, respectively (P = .0003). Durations for the 400-m trial were 55.1 +/- 4.2 s and 55.8 +/- 2.3 s for the 400-m- and 800-m-event specialists, respectively. The VO(2) responses achieved were 93.1% +/- 2.0% and 85.7% +/- 3.0% VO(2)max for the 400-m- and 800-m-event specialists, respectively (P = .001). Conclusions: These results demonstrate that specialist running events do appear to influence the percentage of VO(2)max achieved in the 400-m trial, with the 800-m specialists attaining a lower percentage of VO(2)max than the 400-m specialists. The 400-m specialists appear to compensate for a lower VO(2)max by attaining a higher percentage VO(2)max during a 400-m trial
Influence of test duration on oxygen uptake attained during treadmill running
Previous investigations have revealed that in well-trained middle-distance runners, oxygen uptake (VO2) does not attain maximal values (VO2max) in exhaustive treadmill trials where the VO2 demand exceeds VO2max. To date, this shortfall in the VO2 attained has been demonstrated in trials as short as 2 min in duration. In this study, we investigated whether a reduction in exhaustive test duration influences the VO2 attained during running on a treadmill. Six middle-distance runners participated in the study, completing an exhaustive 400 m and 800 m trial. These trials, together with a progressive test to determine VO2max, were completed in a counterbalanced order. Oxygen uptakes attained during the 400 m and 800 m trials were compared to examine the influence of exhaustive test duration. A plateau in VO2 was observed in all participants for the progressive test, demonstrating the attainment of VO2max. The mean speed, duration, and resulting distance in the constant-speed exhaustive trials were 25.8 km h(-1) (s=1.2), 55.8 s (s=2.3), and 400.2 m (s=20.2) for the 400 m trial, and 24.3 km h(-1) (s=0.8), 108.4 s (s=21.2), and 730.1 m (s=129.1) for the 800 m trial, respectively. A paired-samples t-test revealed a significantly different (P=0.018)%VO2max was attained for the 400 m (85.7%, s=3.0) and 800 m (89.1%, s=5.0) trials. In conclusion, VO2 did not reach VO2max during the exhaustive constant-speed 400 m and 800 m trials, but the test duration does influence the%VO2max achieved. Specifically, the VO2 attained becomes progressively further below VO2max as trial duration is reduced, such that 89% and 86% VO2max is achieved in exhaustive 800 m and 400 m constant-speed trials, respectively
Digital afx: digital dressing and affective shifts in Sin City and 300
In Sin City (Robert Rodriguez, 2005) and 300 (Zack Snyder, 2006) extensive
post-production work has created stylised colour palettes, manipulated areas
of the image, and added or subtracted elements. Framing a discussion around
the terms ‘affect’ and ‘emotion’, this paper argues that the digital technologies used in Sin City and 300 modify conventional interactions between
representational and aesthetic dimensions. Brian Massumi suggests affective
imagery can operate through two modes of engagement. One mode is
embedded in a meaning system, linked to a speci?c emotion. The second
is understood as an intensi?cation whereby a viewer reacts but that reaction is
not yet gathered into an alignment with meaning. The term ‘digital afx’
is used to describe manipulations that produce imagery allowing these two
modes of engagement to coexist. Digital afx are present when two competing
aesthetic strategies remain equally visible within sequences of images. As a
consequence the afx mingle with and shift the content of representation
Fermions, Skyrmions and the 3-Sphere
This paper investigates a background charge one Skyrme field chirally coupled
to light fermions on the 3-sphere. The Dirac equation for the system commutes
with a generalised angular momentum or grand spin. It can be solved explicitly
for a Skyrme configuration given by the hedgehog form. The energy spectrum and
degeneracies are derived for all values of the grand spin. Solutions for
non-zero grand spin are each characterised by a set of four polynomials. The
paper also discusses the energy of the Dirac sea using zeta function
regularization.Comment: 19 pages, 2 figure
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