2,487 research outputs found
Physical activity barriers in the workplace : an exploration of factors contributing to non-participation in a UK workplace physical activity intervention
Purpose– The purpose of this paper is to explore factors contributing to non-participation in a workplace physical activity (PA) intervention in a large UK call centre.
Design/methodology/approach – In total, 16 inactive individuals (nine male/seven female), aged 27±9 years, who had not taken part in the intervention were interviewed to explore their perceptions of PA, the intervention and factors which contributed to their non-participation. Transcripts were analysed using thematic analysis.
Findings – Six superordinate themes were identified: self-efficacy for exercise; attitudes towards PA; lack of time and energy; facilities and the physical environment; response to the PA programme and PA culture. Barriers occurred at multiple levels of influence, and support the use of ecological or multilevel models to help guide future programme design/delivery.
Research limitations/implications – The 16 participants were not selected to be representative of the workplace gender or structure. Future intentions relating to PA participation were not considered and participants may have withheld negative opinions about the workplace or intervention despite use of an external researcher.
Practical implications – In this group of employees education about the importance of PA for young adults and providing opportunities to gain social benefits from PA would increase perceived benefits and reduce perceived costs of PA. Workplace cultural norms with respect to PA must also be addressed to create a shift in PA participation.
Originality/value – Employees’ reasons for non-participation in workplace interventions remain poorly understood and infrequently studied. The study considers a relatively under-studied population of employed young adults, providing practical recommendations for future interventions
Dust-to-Gas Ratio and Metallicity in Dwarf Galaxies
We examine the dust-to-gas ratio as a function of metallicity for dwarf
galaxies [dwarf irregular galaxies (dIrrs) and blue compact dwarf galaxies
(BCDGs)]. Using a one-zone model and adopting the instantaneous recycling
approximation, we prepare a set of basic equations which describes processes of
dust formation and destruction in a galaxy. Four terms are included for the
processes: dust formation from heavy elements ejected by stellar mass loss,
dust destruction in supernova remnants, dust destruction in star-forming
regions, and accretion of heavy elements onto preexisting dust grains. Solving
the equations, we compare the result with observational data of nearby dIrrs
and BCDGs. The solution is consistent with the data within the reasonable
ranges of model parameters constrained by the previous examinations. This means
that the model is successful in understanding the dust amount of nearby
galaxies. We also show that the accretion rate of heavy element onto
preexisting dust grains is less effective than the condensation of heavy
elements in dwarf galaxies.Comment: 14 pages LaTeX, 4 figures, to appear in Ap
Cold Dust in Kepler's Supernova Remnant
The timescales to replenish dust from the cool, dense winds of Asymptotic
Giant Branch stars are believed to be greater than the timescales for dust
destruction. In high redshift galaxies, this problem is further compounded as
the stars take longer than the age of the Universe to evolve into the dust
production stages. To explain these discrepancies, dust formation in supernovae
(SNe) is required to be an important process but until very recently dust in
supernova remnants has only been detected in very small quantities. We present
the first submillimeter observations of cold dust in Kepler's supernova remnant
(SNR) using SCUBA. A two component dust temperature model is required to fit
the Spectral Energy Distribution (SED) with K and K. The total mass of dust implied for Kepler is -
1000 times greater than previous estimates. Thus SNe, or their progenitors may
be important dust formation sites.Comment: 12 pages, 2 figures, accepted to ApJL, corrected proof
Inclined Surface Locomotion Strategies for Spherical Tensegrity Robots
This paper presents a new teleoperated spherical tensegrity robot capable of
performing locomotion on steep inclined surfaces. With a novel control scheme
centered around the simultaneous actuation of multiple cables, the robot
demonstrates robust climbing on inclined surfaces in hardware experiments and
speeds significantly faster than previous spherical tensegrity models. This
robot is an improvement over other iterations in the TT-series and the first
tensegrity to achieve reliable locomotion on inclined surfaces of up to
24\degree. We analyze locomotion in simulation and hardware under single and
multi-cable actuation, and introduce two novel multi-cable actuation policies,
suited for steep incline climbing and speed, respectively. We propose
compelling justifications for the increased dynamic ability of the robot and
motivate development of optimization algorithms able to take advantage of the
robot's increased control authority.Comment: 6 pages, 11 figures, IROS 201
New Observations of the Interstellar Medium in the Lyman Break Galaxy MS 1512-cB58
We present the results of a detailed study of the interstellar medium of MS
1512-cB58, an L* Lyman break galaxy at z = 2.7276, based on new spectral
observations obtained with the Echelle Spectrograph and Imager on the Keck II
telescope at 58 km/s resolution. We focus in particular on the chemical
abundances and kinematics of the interstellar gas and our main findings are as
follows. Even at this relatively early epoch, the ISM of this galaxy is already
highly enriched in elements released by Type II supernovae; the abundances of
O, Mg, Si, P, and S are all about 2/5 of their solar values. In contrast, N and
the Fe-peak elements Mn, Fe, and Ni are underabundant by a factor of about 3.
Based on current ideas of stellar nucleosynthesis, these results can be
understood if most of the metal enrichment in cB58 has taken place within the
last 300 million years, the timescale for the release of N from intermediate
mass stars. cB58 appears to be an example of a galaxy in the process of
converting its gas into stars on a few dynamical timescales; quite possibly we
are witnessing the formation of a galactic bulge or an elliptical galaxy. The
energetic star formation activity has stirred the interstellar medium to high
velocities of up to 1000 km/s. The net effect is a bulk outflow of the ISM at a
speed of 255 km/s and at a rate which exceeds the star formation rate. It is
unclear whether this gas will be lost or retained by the galaxy. We point out
that the chemical and kinematic properties of cB58 are markedly different from
those of most damped Lyman alpha systems at the same redshift.Comment: 38 pages, LaTeX, 9 Postscript Figures. Accepted for publication in
the Astrophysical Journal. Sections 3.3 and 5.3 expanded, and two additional
figures included, following referee's repor
The Rest-Frame Optical Spectrum of MS 1512-cB58
Moderate resolution, near-IR spectroscopy of MS1512-cB58 is presented,
obtained during commissioning of the the Near IR Spectrometer (NIRSPEC) on the
Keck II telescope. The strong lensing of this z=2.72 galaxy by the foreground
cluster MS1512+36 makes it the best candidate for detailed study of the
rest-frame optical properties of Lyman Break Galaxies.
A redshift of z=2.7290+/-0.0007 is inferred from the emission lines, in
contrast to the z=2.7233 calculated from UV observations of interstellar
absorption lines. Using the Balmer line ratios, we find an extinction of
E(B-V)=0.27. Using the line strengths, we infer an SFR=620+/-18 Msun/yr
(H_0=75, q_0=0.1, Lambda =0), a factor of 2 higher than that measured from
narrow-band imaging observations of the galaxy, but a factor of almost 4 lower
than the SFR inferred from the UV continuum luminosity. The width of the Balmer
lines yields a mass of M_vir=1.2x10^10 Msun. We find that the oxygen abundance
is 1/3 solar, in good agreement with other estimates of the metallicity.
However, we infer a high nitrogen abundance, which may argue for the presence
of an older stellar population.Comment: 14 pages, including 3 figures. Accepted for publication in ApJ
Letter
The Mass-Metallicity Relation at z~2
We use a sample of 87 rest-frame UV-selected star-forming galaxies with mean
spectroscopic redshift z=2.26 to study the correlation between metallicity and
stellar mass at high redshift. Using stellar masses determined from SED fitting
to 0.3-8 micron photometry, we divide the sample into six bins in stellar mass,
and construct six composite H-alpha+[NII] spectra from all of the objects in
each bin. We estimate the mean oxygen abundance in each bin from the
[NII]/H-alpha ratio, and find a monotonic increase in metallicity with
increasing stellar mass, from 12+log(O/H) =
2.7e9 Msun to 12+log(O/H) = 8.6 for galaxies with = 1e11 Msun. We use
the empirical relation between star formation rate density and gas density to
estimate the gas fractions of the galaxies, finding an increase in gas fraction
with decreasing stellar mass. These gas fractions combined with the observed
metallicities allow the estimation of the effective yield y_eff as a function
of stellar mass; in constrast to observations in the local universe which show
a decrease in y_eff with decreasing baryonic mass, we find a slight increase.
Such a variation of metallicity with gas fraction is best fit by a model with
supersolar yield and an outflow rate ~4 times higher than the star formation
rate. We conclude that the mass-metallicity relation at high redshift is driven
by the increase in metallicity as the gas fraction decreases through star
formation, and is likely modulated by metal loss from strong outflows in
galaxies of all masses. There is no evidence for preferential loss of metals
from low mass galaxies as has been suggested in the local universe. [Abridged]Comment: 18 pages, 9 figures, 2 tables; accepted for publication in Ap
Abundances in the Neutral Interstellar Medium of I Zw 18 from FUSE Observations
We report on new FUSE far-UV spectroscopy of the most metal-poor blue compact
dwarf galaxy I Zw 18. The new data represent an improvement over previous FUSE
spectra by a factor of 1.7 in the signal-to-noise. Together with a larger
spectral coverage (917-1188 angstroms), this allows us to characterize
absorption lines in the interstellar medium with unprecedented accuracy. The
kinematics averaged over the large sampled region shows no clear evidence of
gas inflows or outflows. The H I absorption is interstellar with a column
density of 2.2 (+0.6,-0.5} * 10^21 cm^(-2). A conservative 3 sigma upper limit
of 5.25 * 10^(14) cm^(-2) is derived for the column density of diffuse H_2.
From a simultaneous fitting of metal absorption lines in the interstellar
medium, we infer the following abundances: [Fe/H] = -1.76 +/- 0.12, [O/H] =
-2.06 +/- 0.28, [Si/H] = -2.09 +/- 0.12, [Ar/H] = -2.27 +/- 0.13, and [N/H] =
-2.88 +/- 0.11. This is in general several times lower than in the H II
regions. The only exception is iron, whose abundance is the same. The abundance
pattern of the interstellar medium suggests ancient star-formation activity
with an age of at least a Gyr that enriched the H I phase. Around 470 SNe Ia
are required to produce the iron content. A more recent episode that started 10
to several 100 Myr ago is responsible for the additional enrichment of
alpha-elements and nitrogen in the H II regions.Comment: 48 pages including 3 tables (Latex) and 7 figures (postscript).
Accepted for publication in the Astrophysical Journa
The Merging System Am 2049-691
Spectroscopic and photometric observations of the peculiar object AM 2049-691
are presented here. Its systemic velocity is V(GSR) = (10956 +-30) km/s, and
the derived distance (H(0) = 75 km/s/Mpc) results 146 Mpc. A bridge is observed
between two very distinct nuclei whose separation is about 10 kpc, as well as
two tails that emerge from the extremes SW and NE of the main body and extend
up to 41 and 58 kpc respectively. The spectral characteristics of the all
observed zones are typical of H II regions of low excitation. The internal
reddening is quit high, particularly in the NE nucleus. All the derived
equivalent widths of the H(alpha)+[N II] lines indicate enhanced star formation
compared with isolated galaxies, specially in the NE nucleus; the equivalent
width corresponding to the integrated spectrum reflects starburst activity in
the whole object, and is compatible with a merger of two disk galaxies. All the
observed characteristics of AM 2049-691 indicate it is a merger, where a
overabundance of nitrogen is detected in one of the nuclei, which has the most
evolved population and would be the most massive one. The detected total IR
emission is not very high. The integrated total color B - V corresponds to a
Sc-Scd galaxy and its average integrated population is about F7 type.
Indicative B - V colors of the nuclei, corrected for internal absorption, are
in agreement with the spectroscopic results. The central radial velocity
dispersions at the nuclei suggest that the most massive galaxy would be the
progenitor of the SW component. The observed radial velocity curve shows the
presence of two subsystems, each one associated with a different nucleus.Comment: 5 pages, 4 figure
Uniqueness of reconstruction and an inversion procedure for thermoacoustic and photoacoustic tomography
The paper contains a simple approach to reconstruction in Thermoacoustic and
Photoacoustic Tomography. The technique works for any geometry of point
detectors placement and for variable sound speed satisfying a non-trapping
condition. A uniqueness of reconstruction result is also obtained
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