6,273 research outputs found
The G Dwarf Problem Exists in Other Galaxies
Stellar population models with abundance distributions determined from the
analytic Simple model of chemical evolution fail to match observations of the
nuclei of bulge-dominated galaxies in three respects. First, the spectral
energy distribution in the mid-ultraviolet range 2000 < lam < 2400 exceeds
observation by ~ 0.6 mag. Most of that excess is due to metal-poor main
sequence stars. Second, the models do not reproduce metal-sensitive optical
absorption features that arise mainly from red giant stars. Third, the strength
of a Ca II index sensitive to hot stars does not jibe with the predicted number
of A-type horizontal branch stars. The number of metal poor stars in galaxies
is at least a factor of two less than predicted by the Simple model, exactly
similar to the ``G Dwarf problem'' in the solar cylinder. Observations at
larger radii in local group galaxies indicate that the paucity of metal poor
stars applies globally, rather than only in the nuclei. Because of the
dominance of metal rich stars, primordial galaxies will have a plentiful dust
supply early in their star formation history, and thus will probably have weak
Lyman-alpha emission, as is apparently observed. We confirm that early-type
galaxies cannot have been formed exclusively from mergers of small all-stellar
subsystems, a result already established by dynamical simulations. The
constraint of peaked abundance distributions will limit future chemical
evolution models. It will also make age estimates for the stellar populations
in early type galaxies and bulges more secure.Comment: 14 pages, LaTeX includes 3 postscript figures. Uses AAS LaTeX v 4.0
and times.sty. Accepted for publication in the Astronomical Journal.
Postscript available at http://shemesh.gsfc.nasa.gov/~dorman/Ben.htm
Making meat collectivities : entanglements of geneticisation, integration and contestation in livestock breeding
To explore some of the contours of this meat ‘supply chain integration’ - ‘the phrase of the moment’ according to Farmers Weekly - this chapter draws on research conducted as part of a project exploring the effects of the emergence of particular types of genetic knowledge-practice in beef cattle and sheep breeding in the UK and their entanglement with ‘traditional’ ways of knowing and valuing livestock. The research is interested in the production and circulation of genetic knowledge-practices in agriculture, in examining how such knowledge-practices become established and gain legitimacy, how they become tangled up with visual and other traditional knowledge-practices, and in the effects of genetic knowledge-practices on how cattle and sheep are bred and managed and on human-nonhuman animal relationships in livestock farming. The research has increasingly led us to explore the process of ‘geneticisation’ beyond the farm gate, to look at how the establishment of particular genetic truths or ways of rendering ‘life itself’ (Franklin, 2000) are entangled with processes of restructuring and differentiation within UK food systems
Strategies for Systemic Change:Youth Community Organizing to Disruptthe School-to-Prison Nexus
The school disciplinary landscape across the United States changed significantly through the enactment of policies that criminalize students’ behaviors during the 1990s and 2000s. Schools began to involve the police and criminal legal system in school disciplinary issues that used to be handled by school administrators. This shift led youth of Color1 to increasingly come into contact with the juvenile legal system through school suspensions, expulsions, and referrals to alternative schools—what we characterize as the school-toprison nexus.
Conceptualizing the school-to-prison pipeline as a nexus, or interlocking system of power over youth, allows us to understand how the criminalization of youth is a systemic problem that demands structural change and interventions across multiple levels of analysis and settings, including local schools, school districts, police departments, and state policies. Although important research has documented the ways that Black and Latino youth are referred to the juvenile legal system through punitive school policies, there has been less attention to the actions youth are taking to critique and dismantle these policies. Youth community organizing (YCO) against the school-to-prison nexus represents an arena of youth activism that deserves further attention and analysis. In this chapter, we define YCO as groups that create spaces for young people to think critically about their everyday social conditions, identify root causes of social problems, and build political power and voice to create policy solutions and change in their communities (Ginwright, Noguera, & Cammarota, 2006; Kirshner, 2015; Watts, Griffith, & Abdul- Adil, 1999)
Measuring player perceptions of advertising in online games
An experiment with 100 participants aged 18-24 was conducted to measure the effects of advertising in an online role-playing computer game on perceived interactivity and other aspects of gameplay experience. Results from a post-test questionnaire revealed insight into players\u27 attitudes toward advertising in video game environments, and reflected varying levels of advertising awareness and recall, message recognition, and factors in purchasing habits. Results suggested that while advertising in online games can sometimes trigger high advertising awareness rates, it can also reduce a game\u27s perceived sense of realism and genuinely annoy players if not appropriately coordinated with the game environment. Whereas previous research has suggested that players usually accept in-game advertising when placed relevantly, this study shows the opposite can occur when advertisers make little or no effort to contextualize their ads within the game world. Results revealed negative attitudes toward in-game advertising from participants who played a version of the game featuring ads, yet females and non-gamers were more accepting of in-game advertising and more often perceived it as interactive than did males and avid gamers. Practical implications and suggestions for further research are discussed
A fast algorithm for calculation of Thêo1
Thêo1 is a frequency stability statistic that is similar to the Allan variance but can provide stability estimates at longer averaging factors and with higher confidence. However, the calculation of Thêo1 is significantly slower than that of the Allan variance, particularly for large data sets, due to a worse computational complexity. A faster algorithm for calculating the "all- τ " version of Thêo1 is developed by identifying certain repeated sums and removing them with a recurrence relation. The new algorithm has a reduced computational complexity, which is equal to that of the Allan variance. Computation time is reduced by orders of magnitude for many data sets. The new, faster algorithm does introduce an error due to accumulated floating-point errors in very large data sets. The error can be compensated for by increasing the numerical precision used at critical steps. The new algorithm can also be used to increase the speed of ThêoBr and ThêoH that are more sophisticated statistics derived from Thêo1
POLYAMINE MODULATION IN ALCOHOLISM: EXAMINATION USING A NOVEL SCREENING PROCEDURE DESIGNED TO PREDICT ANTI-RELAPSE AND NEUROPROTECTIVE EFFICACY
Alcohol dependence is a major public health concern. Despite the FDA’s approval of multiple anti-relapse drugs, relapse rates remain unacceptably high. Furthermore, cognitive deficits among chronic drinkers are evident and are suggested to contribute to relapse risk. Current evidence suggests that several critical features of alcoholism and alcohol-associated neurodegeneration are mechanistically linked to glutamatergic actions; specifically, they appear positively affected by glutamatergic inhibition, particularly inhibition via polyamine modulation of a subpopulation of n-methyl-d-aspartate receptors. The current project was designed to evaluate the performance of two putative polyamine modulators (JR-220 and CP-101,606) in a variety of screens designed to identify the potential to reduce withdrawal severity, neurotoxicity and relapse risk. Screens included a complex organotypic screen designed to assess neuroprotective potential (Experiment 1), a simple behavioral screen designed to assess withdrawal severity (Experiment 2) as well as several more complex behavioral screens designed to examine cue-conditioning during withdrawal (Experiment 3), relapse behavior (Experiment 4), stress-associated consumption (Experiment 5) and binge-like consumption (Experiment 6). An additional open field experiment (Experiment 7) was conducted in order to address interpretational issues concerning activity in Experiments 2-6. Finally, as a first step in moving beyond simple screening, we expanded our binge screen to adhere more closely to an established, validated model of binge consumption (Experiment 8). While some interpretational issues were noted, taken together, the results from these experiments provide strong evidence for both drugs as potential pharmacotherapies for alcoholism and further implicate polyamines and NR2B subunits as critical mechanisms in ETOH consumption and withdrawal
Examining the role of structural dynamics in the assembly and function of the multidrug efflux pump AcrAB-TolC
Membrane efflux pumps are a leading cause of increasing multidrug resistant bacterial infections, which pose a significant threat to global human health. Understanding the mechanisms that underpin their function is critical for the development of inhibitors targeting these systems, with the aim being to ‘revive’ the activities of pre-existing antibiotics known to suffer bacterial resistance. AcrAB-TolC is a membrane spanning, tripartite multidrug efflux pump native to Escherichia coli and prototypical of homologous systems across other ESKAPE bacteria. The work in this thesis investigates the role of structural dynamics in the function, assembly, and inhibition of AcrAB-TolC, with a focus on the membrane fusion protein (MFP) AcrA, to reveal critical information on how these efflux systems work, which could be essential for developing novel methods of inhibition to combat multidrug resistance. Throughout this work, structural mass spectrometry (MS) techniques such as hydrogen deuterium exchange mass spectrometry (HDX-MS) and native MS were used alongside a range of complementary biophysical/biochemical techniques to investigate AcrAB-TolC.This work reveals that AcrA lipidation promotes the propensity of AcrA to form oligomers, whereas a non-lipidated, water soluble AcrA construct (AcrAS) is still monomeric. Moreover, HDX-MS showed AcrAS exhibits increased backbone structural dynamics at pH 6.0 compared to pH 7.4, yet this was largely tempered by the presence of magnesium. In the periplasm, the pH can often be ∼1.7 pH units lower than in the cytosol, and there is a significantly higher concentration of magnesium ions (7.56 times). This suggests a regulatory role of magnesium to help AcrA function within the periplasmic environment. To expand the investigations on AcrAS further, a soluble pseudo-dimer construct (AcrASD) was used to infer biological information on the AcrA functional dimer. It was found the pseudo-dimer has unique structural dynamics compared to AcrA, with extensive protection in the α-helices and in regions of the αβ-barrel and MP domains. Furthermore, whilst AcrAS and AcrASD appeared to bind peptidoglycan similarly, AcrASD had a higher propensity to form higher order complexes with AcrB. This suggests dimerization may help prime the AcrA protomers for interactions with its binding partners.Traditionally, efflux pumps inhibitors (EPIs) have been targeted against AcrB, but none have made it past clinical trials, often due to toxicity issues. This has led to a switch in focus for the next generation of EPIs, with AcrA becoming a promising target. In this work, HDX-MS and native MS were used in combination with molecular dynamics (MD) simulations, to investigate the effect of a recently identified EPI, NSC 60339, on the structural dynamics of AcrAS. The data showed NSC 60339 likely binds to AcrA in a cleft bridging the lipoyl and αβ-barrel domains, stabilising these areas as well as the MP domain which usually exhibits intrinsic disorder; NSC 60339 inhibition of AcrASD presented the same. This work proposes the first mechanism of action regarding an AcrA inhibitor and reveals a promising new way to target the AcrAB-TolC complex.Due to the hydrophobic nature of membrane proteins, a suitable membrane mimetic is required for in vitro investigations. As the AcrAB-TolC multidrug efflux pump spans the entire Gram-negative cell envelope and are therefore membrane proteins, studying them in lipid environments rather than detergents is essential as they provide a more representative environment. In this work, HDX-MS was used to show MBX-3756 stabilises the hydrophobic trap of AcrB in membrane scaffold protein (MSP) nanodiscs. Furthermore, a novel SMALP-liposome-SMALP assay was utilised to show that previously designed AcrB antimicrobial peptides did not make the AcrB trimer, purified in styrene maleic acid lipid particles (SMALPs), dissociate into monomers. Lastly, assembly of the AcrAB-TolC complex was probed using two different pull-down assays and native polyacrylamide gel electrophoresis (PAGE), however the heterogeneity and hydrophobicity of SMALPs complicated these investigations, combined with the slow energetics of this assembly in vitro.<br/
GOING VALUE AND RATE VALUATION
From the mere circumstance that a controversy has been long kept on foot, and remains still undecided, we may presume that there is some ambiguity in the expression, and that the disputants affix different ideas to the terms employed ...... Although David Hume was not here concerning himself with twentieth century utility regulation, his observation finds appropriate employment as a preface to a present day study of the problem of going value. The problem is an open one-temptingly open. Years of contention, an impressive array of publications by economists, attorneys, and engineers, and hundreds of opinions of courts and commissions have served only to invite more contention, more publications, and more opinions. And one suspects that the situation is a product not so much of the inherent complexity of going value itself as of the failure of those concerned to define carefully their terms and to proceed logically from a common point of departure. Terms moulded by the exigencies of argument and reasoning marshalled to sustain preconceived conclusions do not conduce to the happy silencing of controversy. The problem of going value is one in a hierarchy of problems ; it will not be solved without painstaking analysis of the going value concept in the light of the requirements of the relationship between the public service industry and the public, and of the demands made upon public utility valuation as a phase of the process of rate control which must subserve those ends
Closing the California Clean Energy Divide: Reducing Electric Bills in Affordable Multifamily Rental Housing with Solar+storage
This economic analysis indicates that pairing solar PV with battery storage systems can deliver significant electricity bill savings for California affordable housing residents and property owners.Battery storage is emerging as an effective new strategy for reducing electricity costs for affordable multifamily rental housing in California. Battery storage systems not only provide economic returns today, they can also preserve the value of solar in an evolving policy and regulatory environment. Because batteries empower owners of solar photovoltaic (PV) systems to take control of the energy they produce and when they consume it, storage can deliver deeper cost reductions that can be shared among affordable housing owners, developers, and tenants.California has installed numerous integrated solar and battery storage projects; however, few have served lowincome tenants or owners of affordable rental housing. This disparity is due to many factors, including a lack of information about the economics of these systems in multifamily housing. To provide that needed information, Clean Energy Group, California Housing Partnership, and Center for Sustainable Energy, with analytical support from Geli, are embarking on a series of reports on solar and storage in California affordable multifamily rental housing.This first report examines the utility bill impacts of adding battery storage to stand-alone solar in affordable rental housing facilities in California's three investor-owned utility service territories, each with different rate structures. It is the first such report ever completed on these technologies in this sector in California.The report reaches several key conclusions:Under current utility rate tariffs, the combination of solar and storage technologies could virtually eliminate electric bills for many owners of affordable housing properties. Unlike stand-alone solar, which reduces energy consumption expenses but does little to offset demand related charges, a properly sized solar and battery storage system can eliminate nearly all electricity expenses, resulting in an annual electric utility bill of less than a few hundred dollars in some cases.It makes good economic sense today for solar and battery storage to be installed in affordable multifamily rental housing in California. The addition of battery storage to solar improves the economics of each property analyzed across all utility territories, reducing project payback by over three years in some cases.The addition of storage technologies has the potential to nearly double stand-alone solar electricity bill savings at about a third of the cost of solar. For example, the addition of a 385,000 solar installation increased savings from 27,900, an 85 percent increase in savings for only a 29 percent increase in cost
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