461 research outputs found
How Smokers Became Outlaws: An Application Of The Stakeholder Salience Model To A Social Problem
Smoking bans have gone from being essentially non-existent to being the norm over the course of the last 50 years. When some of these authors started teaching, it was the norm to smoke in the classroom, in hospitals, on airplanes, in prison and in the office. Times have changed—smoking is no longer allowed in these locations in the United States. In this paper, an overview of the history of smoking advocacy, the impacts of smoke-free legislation on different stakeholders, and changes in public perceptions of smoking are provided. Mitchell and Agle’s 1997 Stakeholder Salience Model are used to illustrate the changes over time in stakeholder status for both smokers and nonsmokers. The Mitchell Model could have been useful to predict the change in status that the two stakeholder groups experienced and the authors suggest that management should note the emergence of urgent stakeholders in the future, as they may gain salience in other matters that can impact company wealth. Firms have to be aware of both their customers’ needs (smokers) as well as other social movements that may affect the use of their product, such as nonsmoking legislation. This is the first paper to apply stakeholder salience, including the concepts of urgency, power, and legitimacy, to the changing fortunes of smokers. It looks at how smoking and smokers have gone from the norm in U.S. society to outlaw status
N-terminal lipid modification is required for the stable accumulation of CyanoQ in Synechocystis sp. PCC 6803
© 2016 Juneau et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The CyanoQ protein has been demonstrated to be a component of cyanobacterial Photosystem II (PS II), but there exist a number of outstanding questions concerning its physical association with the complex. CyanoQ is a lipoprotein; upon cleavage of its transit peptide by Signal Peptidase II, which targets delivery of the mature protein to the thylakoid lumenal space, the N-terminal cysteinyl residue is lipid-modified. This modification appears to tether this otherwise soluble component to the thylakoid membrane. To probe the functional significance of the lipid anchor, mutants of the CyanoQ protein have been generated in Synechocystis sp. PCC 6803 to eliminate the N-terminal cysteinyl residue, preventing lipid modification. Substitution of the N-terminal cysteinyl residue with serine (Q-C22S) resulted in a decrease in the amount of detectable CyanoQ protein to 17% that of the wild-type protein. Moreover, the physical properties of the accumulated Q-C22S protein were consistent with altered processing of the CyanoQ precursor. The Q-C22S protein was shifted to a higher apparent molecular mass and partitioned in the hydrophobic phase in TX-114 phase-partitioning experiments. These results suggest that the hydrophobic N-terminal 22 amino acids were not properly cleaved by a signal peptidase. Substitution of the entire CyanoQ transit peptide with the transit peptide of the soluble lumenal protein PsbO yielded the Q-SS mutant and resulted in no detectable accumulation of the modified CyanoQ protein. Finally, the CyanoQ protein was present at normal amounts in the PS II mutant strains ΔpsbB and ΔpsbO, indicating that an association with PS II was not a prerequisite for stable CyanoQ accumulation. Together these results indicate that CyanoQ accumulation in Synechocystis sp. PCC 6803 depends on the presence of the N-terminal lipid anchor, but not on the association of CyanoQ with the PS II complex
GOODS-: identification of the individual galaxies responsible for the 80-290m cosmic infrared background
We propose a new method of pushing to its faintest detection
limits using universal trends in the redshift evolution of the far infrared
over 24m colours in the well-sampled GOODS-North field. An extension to
other fields with less multi-wavelength information is presented. This method
is applied here to raise the contribution of individually detected
sources to the cosmic infrared background (CIRB) by a factor 5 close to its
peak at 250m and more than 3 in the 350m and 500m bands. We
produce realistic mock images of the deep PACS and SPIRE images of
the GOODS-North field from the GOODS- Key Program and use them to
quantify the confusion noise at the position of individual sources, i.e.,
estimate a "local confusion noise". Two methods are used to identify sources
with reliable photometric accuracy extracted using 24m prior positions.
The clean index (CI), previously defined but validated here with simulations,
which measures the presence of bright 24m neighbours and the photometric
accuracy index (PAI) directly extracted from the mock images. After
correction for completeness, thanks to our mock images, individually
detected sources make up as much as 54% and 60% of the CIRB in the PACS bands
down to 1.1 mJy at 100m and 2.2 mJy at 160m and 55, 33, and 13% of
the CIRB in the SPIRE bands down to 2.5, 5, and 9 mJy at 250m, 350m,
and 500m, respectively. The latter depths improve the detection limits of
by factors of 5 at 250m, and 3 at 350m and 500m as
compared to the standard confusion limit. Interestingly, the dominant
contributors to the CIRB in all bands appear to be distant siblings
of the Milky Way (0.96 for 300m) with a stellar mass
of 910M.Comment: 22 pages, 16 figures. Accepted for publication by Astronomy and
Astrophysic
Universal heat conduction in the iron-arsenide superconductor KFe2As2 : Evidence of a d-wave state
The thermal conductivity of the iron-arsenide superconductor KFe2As2 was
measured down to 50 mK for a heat current parallel and perpendicular to the
tetragonal c-axis. A residual linear term (RLT) at T=0 is observed for both
current directions, confirming the presence of nodes in the superconducting
gap. Our value of the RLT in the plane is equal to that reported by Dong et al.
[Phys. Rev. Lett. 104, 087005 (2010)] for a sample whose residual resistivity
was ten times larger. This independence of the RLT on impurity scattering is
the signature of universal heat transport, a property of superconducting states
with symmetry-imposed line nodes. This argues against an s-wave state with
accidental nodes. It favors instead a d-wave state, an assignment consistent
with five additional properties: the magnitude of the critical scattering rate
for suppressing Tc to zero; the magnitude of the RLT, and its dependence on
current direction and on magnetic field; the temperature dependence of the
thermal conductivity.Comment: To appear in Physical Review Letter
Lyman-Alpha Escape from Low-Mass, Compact, High-Redshift Galaxies
We investigate the effects of stellar populations and sizes on Ly
escape in 27 spectroscopically confirmed and 35 photometric Lyman-Alpha
Emitters (LAEs) at z 2.65 in seven fields of the Bo\"otes region of
the NOAO Deep Wide-Field Survey. We use deep /WFC3 imaging to supplement
ground-based observations and infer key galaxy properties. Compared to typical
star-forming galaxies (SFGs) at similar redshifts, the LAEs are less massive
(), younger (ages 1
Gyr), smaller ( 1 kpc), less dust-attenuated (E(BV) 0.26
mag), but have comparable star-formation-rates (SFRs ). Some of the LAEs in the sample may be very young galaxies
having low nebular metallicities ()
and/or high ionization parameters (). Motivated by
previous studies, we examine the effects of the concentration of star formation
and gravitational potential on Ly escape, by computing
star-formation-rate surface density, and specific
star-formation-rate surface density, . For a given
, the Ly escape fraction is higher for LAEs with
lower stellar masses. LAEs have higher on average compared
to SFGs. Our results suggest that compact star formation in a low gravitational
potential yields conditions amenable to the escape of Ly photons. These
results have important implications for the physics of Ly radiative
transfer and for the type of galaxies that may contribute significantly to
cosmic reionization.Comment: 36 pages, 15 figures; Accepted for publication in The Astronomical
Journa
The mass-metallicity relation at z~0.7
The ISM metallicity and the stellar mass are examined in a sample of 66
galaxies at 0.4<z<1, selected from the Gemini Deep Deep Survey (GDDS) and the
Canada-France Redshift Survey (CFRS). We observe a mass-metallicity relation
similar to that seen in z~0.1 SDSS galaxies, but displaced towards higher
masses and/or lower metallicities. Using this sample, and a small sample of
z~2.3 LBGs, a redshift dependent mass-metallicity relation is proposed which
describes the observed results.Comment: To appear in the proceedings of the conference "The Spectral Energy
Distribution of Gas-Rich Galaxies", eds. C.C. Popescu & R.J. Tuffs
(Heidelberg, October 2004
The Redshift One LDSS-3 Emission line Survey (ROLES) II: Survey method and z~1 mass-dependent star-formation rate density
Motivated by suggestions of 'cosmic downsizing', in which the dominant
contribution to the cosmic star formation rate density (SFRD) proceeds from
higher to lower mass galaxies with increasing cosmic time, we describe the
design and implementation of the Redshift One LDSS3 Emission line Survey
(ROLES). ROLES is a K-selected (22.5 < K_AB < 24.0) survey for dwarf galaxies
[8.5<log(M*/Msun)< 9.5] at 0.89 < z < 1.15 drawn from two extremely deep fields
(GOODS-S and MS1054-FIRES). Using the [OII]3727 emission line, we obtain
redshifts and star-formation rates (SFRs) for star-forming galaxies down to a
limit of ~0.3 Msun/yr. We present the [OII] luminosity function measured in
ROLES and find a faint end slope of alpha_faint ~ -1.5, similar to that
measured at z~0.1 in the SDSS. By combining ROLES with higher mass surveys, we
measure the SFRD as a function of stellar mass using [OII] (with and without
various empirical corrections), and using SED-fitting to obtain the SFR from
the rest-frame UV luminosity for galaxies with spectroscopic redshifts. Our
best estimate of the corrected [OII]-SFRD and UV SFRD both independently show
that the SFRD evolves equally for galaxies of all masses between z~1 and z~0.1.
The exact evolution in normalisation depends on the indicator used, with the
[OII]-based estimate showing a change of a factor of ~2.6 and the UV-based a
factor of ~6. We discuss possible reasons for the discrepancy in normalisation
between the indicators, but note that the magnitude of this uncertainty is
comparable to the discrepancy between indicators seen in other z~1 works. Our
result that the shape of the SFRD as a function of stellar mass (and hence the
mass range of galaxies dominating the SFRD) does not evolve between z~1 and
z~0.1 is robust to the choice of indicator. [abridged]Comment: Resubmitted to MNRAS following first referee report. 20 pages, 16
figures. High resolution version available at
http://astro.uwaterloo.ca/~dgilbank/papers/roles2.pd
From d-wave to s-wave pairing in the iron-pnictide superconductor (Ba,K)Fe2As2
The nature of the pairing state in iron-based superconductors is the subject
of much debate. Here we argue that in one material, the stoichiometric iron
pnictide KFe2As2, there is overwhelming evidence for a d-wave pairing state,
characterized by symmetry-imposed vertical line nodes in the superconducting
gap. This evidence is reviewed, with a focus on thermal conductivity and the
strong impact of impurity scattering on the critical temperature Tc. We then
compare KFe2As2 to Ba0.6K0.4Fe2As2, obtained by Ba substitution, where the
pairing symmetry is s-wave and the Tc is ten times higher. The transition from
d-wave to s-wave within the same crystal structure provides a rare opportunity
to investigate the connection between band structure and pairing mechanism. We
also compare KFe2As2 to the nodal iron-based superconductor LaFePO, for which
the pairing symmetry is probably not d-wave, but more likely s-wave with
accidental line nodes
Observational constraints on the physics behind the evolution of AGN since z ~ 1
We explore the evolution with redshift of the rest-frame colours and space
densities of AGN hosts (relative to normal galaxies) to shed light on the
dominant mechanism that triggers accretion onto supermassive black holes as a
function of cosmic time. Data from serendipitous wide-area XMM surveys of the
SDSS footprint (XMM/SDSS, Needles in the Haystack survey) are combined with
Chandra deep observations in the AEGIS, GOODS-North and GOODS-South to compile
uniformly selected samples of moderate luminosity X-ray AGN [L_X(2-10keV) =
1e41-1e44erg/s] at redshifts 0.1, 0.3 and 0.8. It is found that the fraction of
AGN hosted by red versus blue galaxies does not change with redshift. Also, the
X-ray luminosity density associated with either red or blue AGN hosts remains
nearly constant since z=0.8. X-ray AGN represent a roughly fixed fraction of
the space density of galaxies of given optical luminosity at all redshifts
probed by our samples. In contrast the fraction of X-ray AGN among galaxies of
a given stellar mass decreases with decreasing redshift. These findings suggest
that the same process or combination of processes for fueling supermassive
black holes are in operation in the last 5 Gyrs of cosmic time. The data are
consistent with a picture in which the drop of the accretion power during that
period (1dex since z=0.8) is related to the decline of the space density of
available AGN hosts, as a result of the evolution of the specific
star-formation rate of the overall galaxy population. Scenarios which attribute
the evolution of moderate luminosity AGN since z \approx 1 to changes in the
suppermassive black hole accretion mode are not favored by our results.Comment: MNRAS accepted, 15 pages, 10 figure
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