4,287 research outputs found
Recommended from our members
The effects of equitability policies on the ZEV market: Evidence from Californiaâs Clean Vehicle Rebate Project
Californiaâs Clean Vehicle Rebate Program (CVRP) is the largest zero-emissions vehicle (ZEV) incentive program in the United States. This policy brief summarizes how changes to the CVRP incentive structure may have affected California's ZEV market
Evolution of virulence in opportunistic pathogens: generalism, plasticity, and control
Standard virulence evolution theory assumes that virulence factors are maintained because they aid parasitic exploitation, increasing growth within and/or transmission between hosts. An increasing number of studies now demonstrate that many opportunistic pathogens (OPs) do not conform to these assumptions, with virulence factors maintained instead because of advantages in non-parasitic contexts. Here we review virulence evolution theory in the context of OPs and highlight the importance of incorporating environments outside a focal virulence site. We illustrate that virulence selection is constrained by correlations between these external and focal settings and pinpoint drivers of key environmental correlations, with a focus on generalist strategies and phenotypic plasticity. We end with a summary of key theoretical and empirical challenges to be met for a fuller understanding of OPs
Extending the CRESST-II commissioning run limits to lower masses
Motivated by the recent interest in light WIMPs of mass ~O(10 GeV), an
extension of the elastic, spin-independent WIMP-nucleon cross-section limits
resulting from the CRESST-II commissioning run (2007) are presented.
Previously, these data were used to set cross-section limits from 1000 GeV down
to ~17 GeV, using tungsten recoils, in 47.9 kg-days of exposure of calcium
tungstate. Here, the overlap of the oxygen and calcium bands with the
acceptance region of the commissioning run data set is reconstructed using
previously published quenching factors. The resulting elastic WIMP cross
section limits, accounting for the additional exposure of oxygen and calcium,
are presented down to 5 GeV.Comment: 4 pages, 4 figure
âWe Are The Gap: Understanding the Inclusion of Immigrants in Moroccan Left-Wing Politicsâ
This project seeks to understand to what extent immigrants are included in left-wing politics in Morocco. In 2011, King Mohammed VI named Morocco an executive constitutional monarchy. One can argue that this means Morocco is moving in the direction of democracy, but is democracy what left-wing political parties are truly advocating for? And if they are, does the left include marginalized people it advocates for? Particularly, how are immigrants fighting for their own rights in Morocco, and to what extent are Moroccan left-wing political parties centering and uplifting the voices of immigrants, if at all
Recommended from our members
Finding the edge: Net-shape surface sculpting during cold spray deposition
This thesis provides an overview of how a successful method for structuring cold spray deposition was developed, allowing the creation of defined surfaces from a previously uncontrolled deposition profile.
When considering both additive and traditional manufacturing techniques, there remains a gap in the market for a high build rate, low-cost manufacturing system, capable of building net shape structures with good material properties from a range of difficult to work with engineering materials. A cold spray system had the potential to meet these requirements, and to provide additional benefits from being a solid-state fusion process, but the technique lacked the structural control capabilities required.
The aim of this body of work was to develop methods for controlling the shape of depositing material, allowing the creation of three-dimensional structures, and determining an approach which would allow the creation of flexible manufacturing platform. A limited number of attempts had been previously made to control the deposition shape. These methods met with limited success, did not offer real control over the shape of the deposit during operation, and presented issues of accuracy, reliability, and repeatability.
In this work, a series of concepts for shaping the deposition of the material were tested for the creation of flat vertical surfaces. Copper was used as the deposition powder as it readily deposits with cold spray under easily manageable conditions. The samples were investigated for shape conformity, surface roughness, porosity and build height, using optical microscopy and a white light interferometer. Successful shaping was delivered using masks, wide flow impeding backstops and thinner flow separating tools, provided the non-adhering powder had sufficient room to be cleared from the deposition zone. The thinner tool was further developed, as it allowed better positioning in smaller spaces for future systems.
Computational fluid dynamics models were created to assist with the understanding of some inconsistencies in deposit quality. The results of these simulations showed minimal alteration to the particle trajectory was caused by the alteration of gas dynamics from the introduction of obstacles.
The developed thin tool deposition concept was then successfully tested for robustness with deposition of further materials, and with the inclusion of laser irradiation of the substrate. It was demonstrated that the density, deposition efficiency and build heights are comparable with those expected from typical cold spray/supersonic laser deposition deposits. Following this, a range of building block structures were created, to further advance the shaping capabilities of the system, and demonstrate the freedom of deposition profile. Flat surfaces, thin walls, corners, curves, rings and overhangs were all shown to build efficiently without further complication.
It is concluded that it is both possible to control the shape of the depositing material during cold spray, and possible to do so without adversely affecting the deposit characteristics that give cold spray manufacturing its specific advantages over other manufacturing methods.
The next steps for this process are to create a more flexible system, automating the placement of the shaping tool and using a 5 or 6 axis bed and nozzle positioning setup. Further to that, precise control over the powder dosage, and the development of a known parameter space for select materials would progress the system to an additive capable platform
Recommended from our members
Carbon Pricing and the Transition from Voluntary to Mandatory Markets
The current national and global call for a coordinated and meaningful response to climate change concerns is certain to shift the United States from several regional and voluntary carbon markets today to a global compulsory market in the near future. In addition to the clear environmental benefits, this changing landscape will result in groups of carbon market "winners" and "losers" â some market segments will gain favor and market share while others will lose economic opportunity. The competitive disadvantage for traditional energy in a carbon-priced world will be a catalyst for market-driven innovations in renewable energy, and sustainable development. There are many opportunities where Austin and Texas stand to gain as larger carbon pricing components are realized. This primer looks to explore the political, economic, and design considerations that will affect the development of the carbon market.IC2 Institut
Education Policy and mental weakness:a response to a mental health crisis
Educationalists have been concerned with the labelling and treatment of children with mental health difficulties in the education system in England for some time (Timimi 2002; Rose 2005; Jull 2008, Cole 2015). These concerns have centred on the role of policy in âotheringâ such students as deviant learners. The unprecedented number of children suffering from mental illnesses, has forced policymakers to address childrenâs mental health difficulties. This has involved the identification of a sub-set of the school population experiencing âless-severeâ mental health issues, to be addressed through a suite of policy interventions delivered by whole-school approaches, but targeted towards children situated as mentally âweakâ. Drawing upon a Foucauldian theory of governmentality that addresses childrenâs behavioural motivations (Rose 1989; Millar and Rose 1990; Foucault 2001; 2008; Popkewitz 2012) an in-depth analysis of a number of educational policy initiatives related to mental health, is conducted, that it is argued are fundamentally flawed. This analysis is followed by a discussion of the performative culture of High Stakes Testing in contributing to childrenâs mental health difficulties. Here it is argued that a narrative of mental weakness serves to justify a neoliberal rationality towards the treatment of children for whom the performative logic assumed to motivate all learners, fails
The coevolution of toxin and antitoxin genes drives the dynamics of bacterial addiction complexes and intragenomic conflict
Bacterial genomes commonly contain âaddictionâ gene complexes that code for both a toxin and a corresponding antitoxin. As long as both genes are expressed, cells carrying the complex can remain healthy. However, loss of the complex (including segregational loss in daughter cells) can entail death of the cell. We develop a theoretical model to explore a number of evolutionary puzzles posed by toxinâantitoxin (TA) population biology. We first extend earlier results demonstrating that TA complexes can spread on plasmids, as an adaptation to plasmid competition in spatially structured environments, and highlight the role of kin selection. We then considered the emergence of TA complexes on plasmids from previously unlinked toxin and antitoxin genes. We find that one of these traits must offer at least initially a direct advantage in some but not all environments encountered by the evolving plasmid population. Finally, our study predicts non-transitive ârock-paper-scissorsâ dynamics to be a feature of intragenomic conflict mediated by TA complexes. Intragenomic conflict could be sufficient to select deleterious genes on chromosomes and helps to explain the previously perplexing observation that many TA genes are found on bacterial chromosomes
Synergy and Group Size in Microbial Cooperation
Microbes produce many molecules that are important for their growth and development, and the consumption of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Though the production of these public goods molecules has been studied intensely, little is known of how the benefits accrued and costs incurred depend on the quantity of public good molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density with a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether or not and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an âevolutionary trapâ which can stymie the establishment and maintenance of cooperation. By allowing density dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results for experimental design
- âŠ