3,747 research outputs found
Beyond the Brim of the Hat: Kinematics of Globular Clusters out to Large Radius in the Sombrero Galaxy
We have obtained radial velocity measurements for 51 new globular clusters
around the Sombrero galaxy. These measurements were obtained using
spectroscopic observations from the AAOmega spectrograph on the
Anglo-Australian Telescope and the Hydra spectrograph at WIYN. Combined with
our own past measurements and velocity measurements obtained from the
literature we have constructed a large database of radial velocities that
contains a total of 360 confirmed globular clusters. Previous studies' analyses
of the kinematics and mass profile of the Sombrero globular cluster system have
been constrained to the inner ~9' (~24 kpc or ~5 effective radii), but our new
measurements have increased the radial coverage of the data, allowing us to
determine the kinematic properties of M104 out to ~15' (~41 kpc or ~9 effective
radii). We use our set of radial velocities to study the GC system kinematics
and to determine the mass profile and V-band mass-to-light profile of the
galaxy. We find that the V-band mass-to-light ratio increases from 4.5 at the
center to a value of 20.9 at 41 kpc (~9 effective radii or 15'), which implies
that the dark matter halo extends to the edge of our available data set. We
compare our mass profile at 20 kpc (~4 effective radii or ~7.4') to the mass
computed from x-ray data and find good agreement. We also use our data to look
for rotation in the globular cluster system as a whole, as well as in the red
and blue subpopulations. We find no evidence for significant rotation in any of
these samples.Comment: Accepted for publication in the Astronomical Journal; 23 pages, 14
figures, and 2 table
Zn-induced spin dynamics in overdoped LaSrCuZnO
Spin fluctuations and the local spin susceptibility in isovalently
Zn-substituted LaSrCuZnO (,
) are measured via inelastic neutron scattering techniques. As
Zn is substituted onto the Cu-sites, an anomalous enhancement of
the local spin susceptibility appears due to the
emergence of a commensurate antiferromagnetic excitation centered at wave
vector \textbf{Q} that coexists with the known incommensurate
SDW excitations at \textbf{Q}.
Our results support a picture of Zn-induced antiferromagnetic (AF) fluctuations
appearing through a local staggered polarization of Cu-spins, and the
simultaneous suppression of T as AF fluctuations are slowed in proximity to
Zn-impurities suggests the continued importance of high energy AF fluctuations
at the far overdoped edge of superconductivity in the cuprates.Comment: 10 pages, 8 figure
Rigid Quantum Monte Carlo Simulations of Condensed Molecular Matter: Water Clusters in the n=2 ―˃ 8 Range
The numerical advantage of quantum Monte Carlo simulations of rigid bodies relative to the flexible simulations is investigated for some simple systems. The results show that if high frequency modes in molecular condensed matter are predominantly in the ground state, the convergence of path integral simulations becomes nonuniform. Rigid body quantum parallel tempering simulations are necessary to accurately capture thermodynamic phenomena in the temperature range where the dynamics are influenced by intermolecular degrees of freedom; the stereographic projection path integral adapted for quantum simulations of asymmetric tops is a significantly more efficient strategy compared with Cartesian coordinate simulations for molecular condensed matter under these conditions. The reweighted random series approach for stereographic path integral Monte Carlo is refined and implemented for the quantum simulation of water clusters treated as an assembly of rigid asymmetric tops
Landscape-scale responses of birds to agri-environment management: a test of the English Environmental Stewardship scheme
1. Agri-environment schemes (AES) are used extensively across Europe to address biodiversity declines in farmland. In England, Environmental Stewardship (ES) was introduced in 2005 to address the shortcomings of previous schemes, but as for schemes in other countries, assessments to date have revealed little evidence for national-scale biodiversity benefits.
2. Here, we assess the efficacy of ES in driving changes in national farmland bird populations over the period 2002–2010, using BTO/JNCC/RSPB Breeding Bird Survey data. We tested for associations between ES management options, grouped into categories reflecting intended biological effects (e.g. stubble), and species’ population growth rates, wherever benefits of management might be expected to occur.
3. We found strong evidence for positive effects of management that provides winter food resources (i.e. ES stubble and wild bird seed [WBS] crops) on population growth rates across multiple granivorous species, at three landscape scales. The results for management aiming to provide breeding season benefits (i.e. grassland, field margin and boundary [hedge, ditch] management) showed mixed patterns of positive and negative associations.
4. The results for stubble and WBS provide the first evidence for landscape-scale responses of biodiversity to AES management. The negative relationships identified may also show the importance of management context driving unforeseen predation or competition effects.
5. Synthesis and Applications. This study demonstrates that agri-environment scheme management has the potential to have national-scale effects on avian population growth rates, although our results suggest that some components of the scheme have had little effect on bird populations. Therefore, whilst this study provides the first proof-of-concept for broad-and-shallow scheme impacts on biodiversity, our results underline the importance of targeting towards population-limiting factors, here winter food resources. A combination of low uptake of key in-field options that provide winter seed and a failure to cover the late-winter period effectively explains the lack of national population responses. Such issues need to be addressed before schemes like Environmental Stewardship will achieve their goals. This study shows the value of feedback from monitoring for informing scheme design, through identifying problems and testing solutions
A generalised abundance index for seasonal invertebrates
At a time of climate change and major loss of biodiversity, it is important to have efficient tools for monitoring populations. In this context, animal abundance indices play an important role. In producing indices for invertebrates, it is important to account for variation in counts within seasons. Two new methods for describing seasonal variation in invertebrate counts have recently been proposed; one is nonparametric, using generalized additive models, and the other is parametric, based on stopover models. We present a novel generalized abundance index which encompasses both parametric and nonparametric approaches. It is extremely efficient to compute this index due to the use of concentrated likelihood techniques. This has particular relevance for the analysis of data from long-term extensive monitoring schemes with records for many species and sites, for which existing modeling techniques can be prohibitively time consuming. Performance of the index is demonstrated by several applications to UK Butterfly Monitoring Scheme data. We demonstrate the potential for new insights into both phenology and spatial variation in seasonal patterns from parametric modeling and the incorporation of covariate dependence,
which is relevant for both monitoring and conservation. Associated R code is available on the journal website
Dynamic models for longitudinal butterfly data
There has been recent interest in devising stochastic models for seasonal insects, which
respond rapidly to climate change. Fitted to count data, these models are used to construct
indices of abundance, which guide conservation and management. We build upon Dennis et
al. (2014, under review) to produce dynamic models, which provide succinct descriptions of
data from all years simultaneously. They produce estimates of key life-history parameters
such as annual productivity and survival.
Analyses for univoltine species, with only one generation each year, extend to bivoltine
species, with two annual broods. In the latter case we estimate the productivities of each
generation separately, and also devise extended indices which indicate the contributions
made from different generations.
We demonstrate the performance of the models using count data for UK butterfly species,
and compare with current procedures which use generalized additive models. We may incor-
orate relevant covariates within the model, and illustrate using northing and measures of
temperature. Consistent patterns are demonstrated for multiple species. This generates a
variety of hypotheses for further investigation, which have the potential to illuminate features
of butterfly phenology and demography which are at present poorly understood
Stakeholder Theory and Marketing: Moving from a Firm-Centric to a Societal Perspective
This essay is inspired by the ideas and research examined in the special section on “Stakeholder Marketing” of the Journal of Public Policy & Marketing in 2010. The authors argue that stakeholder marketing is slowly coalescing with the broader thinking that has occurred in the stakeholder management and ethics literature streams during the past quarter century. However, the predominant view of stakeholders that many marketers advocate is still primarily pragmatic and company centric. The position advanced herein is that stronger forms of stakeholder marketing that reflect more normative, macro/societal, and network-focused orientations are necessary. The authors briefly explain and justify these characteristics in the context of the growing “prosociety” and “proenvironment” perspectives—orientations that are also in keeping with the public policy focus of this journal. Under the “hard form” of stakeholder theory, which the authors endorse, marketing managers must realize that serving stakeholders sometimes requires sacrificing maximum profits to mitigate outcomes that would inflict major damage on other stakeholders, especially society
Neurophysiology
Contains reports on seven research projects.National Institutes of Health (Grant 5 RO1 EY01149-02)Bell Telephone Laboratories, Inc. (Grant)National Institutes of Health (Grant 1 TO1 EY00090-01
Ethanol Induced Disordering of Pancreatic Acinar Cell Endoplasmic Reticulum: An ER Stress/Defective Unfolded Protein Response Model.
Background & aimsHeavy alcohol drinking is associated with pancreatitis, whereas moderate intake lowers the risk. Mice fed ethanol long term show no pancreas damage unless adaptive/protective responses mediating proteostasis are disrupted. Pancreatic acini synthesize digestive enzymes (largely serine hydrolases) in the endoplasmic reticulum (ER), where perturbations (eg, alcohol consumption) activate adaptive unfolded protein responses orchestrated by spliced X-box binding protein 1 (XBP1). Here, we examined ethanol-induced early structural changes in pancreatic ER proteins.MethodsWild-type and Xbp1+/- mice were fed control and ethanol diets, then tissues were homogenized and fractionated. ER proteins were labeled with a cysteine-reactive probe, isotope-coded affinity tag to obtain a novel pancreatic redox ER proteome. Specific labeling of active serine hydrolases in ER with fluorophosphonate desthiobiotin also was characterized proteomically. Protein structural perturbation by redox changes was evaluated further in molecular dynamic simulations.ResultsEthanol feeding and Xbp1 genetic inhibition altered ER redox balance and destabilized key proteins. Proteomic data and molecular dynamic simulations of Carboxyl ester lipase (Cel), a unique serine hydrolase active within ER, showed an uncoupled disulfide bond involving Cel Cys266, Cel dimerization, ER retention, and complex formation in ethanol-fed, XBP1-deficient mice.ConclusionsResults documented in ethanol-fed mice lacking sufficient spliced XBP1 illustrate consequences of ER stress extended by preventing unfolded protein response from fully restoring pancreatic acinar cell proteostasis during ethanol-induced redox challenge. In this model, orderly protein folding and transport to the secretory pathway were disrupted, and abundant molecules including Cel with perturbed structures were retained in ER, promoting ER stress-related pancreas pathology
Network analysis of the social and demographic influences on name choice within the UK (1838-2016)
<div><p>Chosen names reflect changes in societal values, personal tastes and cultural diversity. Vogues in name usage can be easily shown on a case by case basis, by plotting the rise and fall in their popularity over time. However, individual name choices are not made in isolation and trends in naming are better understood as group-level phenomena. Here we use network analysis to examine onomastic (name) datasets in order to explore the influences on name choices within the UK over the last 170 years. Using a large representative sample of approximately 22 million forenames from England and Wales given between 1838 and 2014, along with a complete population sample of births registered between 1996 and 2016, we demonstrate how trends in name usage can be visualised as network graphs. By exploring the structure of these graphs various patterns of name use become apparent, a consequence of external social forces, such as migration, operating in concert with internal mechanisms of change. In general, we show that the topology of network graphs can reveal naming vogues, and that naming vogues in part reflect social and demographic changes. Many name choices are consistent with a self-correcting feedback loop, whereby rarer names become common because there are virtues perceived in their rarity, yet with these perceived virtues lost upon increasing commonality. Towards the present day, we can speculate that the comparatively greater range of media, freedom of movement, and ability to maintain globally-distributed social networks increases the number of possible names, but also ensures they may more quickly be perceived as commonplace. Consequently, contemporary naming vogues are relatively short-lived with many name choices appearing a balance struck between recognisability and rarity. The data are available in multiple forms including via an easy-to-use web interface at <a href="http://demos.flourish.studio/namehistory" target="_blank">http://demos.flourish.studio/namehistory</a>.</p></div
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