387 research outputs found
p-adic quotient sets
No full textFor A ⊆ N, the question of when R(A) = {a/a0
: a, a0 ∈
A} is dense in the positive real numbers R+ has been examined by
many authors over the years. In contrast, the p-adic setting is largely
unexplored. We investigate conditions under which R(A) is dense in
the p-adic numbers. Techniques from elementary, algebraic, and analytic
number theory are employed in this endeavor. We also pose many open
questions that should be of general interest
Narrative threads: ethnographic tourism, Romani tourist tales, and fiber art
No full textThis thesis examines the need for the ethnographer to process their own emotions and experiences as part of the ethnographic experience. Specifically, it argues for the credibility of artistic expression resulting from fieldwork.
Drawing on the author’s experience during the 2012 inaugural "Romani Music, Culture, and Human Rights" study abroad program at the University of Pittsburgh, this thesis offers an analysis of five works of fiber art. Originally perceived by the author as separate from the thesis writing process, they became an integral part of thesis once they were recognized as the non-verbal processing of the my emotional response to events abroad and, therefore, essential components of the research process.
I argue that emotional processing is an integral part of writing an ethnography, for as the ethnographer works through their experiences, their understanding of the events changes, and this in turn impacts the ways in which the ethnographic is perceived and analyzed
Drop-Seq Laboratory Protocol v1
No full text We have continued to optimize this protocol since doing the experiments in the Macosko et al. Cell paper. What we are sharing here is our current, optimized protocol. As a result, this protocol will not precisely match the methods section of the paper, which is a description of the experiments done in the paper. Please feel free to use these optimizations without author consideration - just acknowledge “helpful advice from Evan Macosko, Melissa Goldman and Steve McCarroll”, and please also include the URL and version number of the protocol in your methods section. This protocol also includes hints, suggestions and images that we could not fit into the the methods section of the paper. </p
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Disentangling the rhizosphere community through stable isotope informed genome-resolved metagenomics and assembled metatranscriptomes
No full textThe functioning, health, and productivity of soil is intimately tied to the complex network of interactions in the rhizosphere. Because of this, the rhizosphere has been rigorously studied for over a century, but due to technical limitations many aspects of soil biology have been overlooked. In order to better understand rhizosphere functioning, my work has focused on the less explored organisms and interactions in microbial communities, this includes unculturable bacteria along with viruses and eukaryotes. Only by considering soil biology more holistically can we better understand the functioning of this enigmatic yet critical ecosystem. Knowledge about these interactions could direct how we think about plant-microbe relationships, soil carbon stabilization and the roles of understudied organisms in biogeochemical cycling.The transformation of plant photosynthate into soil organic carbon and its recycling to CO2 by soil microorganisms is one of the central components of the terrestrial carbon cycle. There are currently large knowledge gaps related to which soil-associated microorganisms take up plant carbon in the rhizosphere and the fate of that carbon. Additionally, understanding about obligate symbionts such as members of the Candidate Phyla Radiation (CPR) in soil is severely limited, both from the perspective of their genomic potential and their interactions with the greater soil community. We conducted an experiment in which common wild oats (Avena fatua) were grown in a 13CO2 atmosphere and the rhizosphere and non-rhizosphere soil was sampled for genomic analyses. Density gradient centrifugation of DNA extracted from soil samples enabled distinction of microbes that did and did not incorporate the 13C into their DNA. A 1.45-Mbp genome of a Saccharibacteria (TM7) was identified and, despite the microbial complexity of rhizosphere soil, curated to completion. The genome lacks many biosynthetic pathways, including genes required to synthesize DNA de novo. Rather, it acquires externally derived nucleic acids for DNA and RNA synthesis. Given this, we conclude that rhizosphere-associated Saccharibacteria recycle DNA from bacteria that live off plant exudates and/or phage that acquired 13C because they preyed upon these bacteria and/or directly from the labeled plant DNA. Isotopic labeling indicates that the population was replicating during the 6-week period of plant growth. Interestingly, the genome is ~ 30% larger than other complete Saccharibacteria genomes from non-soil environments, largely due to more genes for complex carbon utilization and amino acid metabolism. Given the ability to degrade cellulose, hemicellulose, pectin, starch, and 1,3-β-glucan, we predict that this Saccharibacteria generates energy by fermentation of soil necromass and plant root exudates to acetate and lactate. The genome also encodes a linear electron transport chain featuring a terminal oxidase, suggesting that this Saccharibacteria may respire aerobically. The genome encodes a hydrolase that could breakdown salicylic acid, a plant defense signaling molecule, and genes to interconvert a variety of isoprenoids, including the plant hormone zeatin. We propose that isotopically labeled CO2 is incorporated into plant-derived carbon and then into the DNA of rhizosphere organisms capable of nucleotide synthesis, and the nucleotides are recycled into Saccharibacterial genomes. We collected paired rhizosphere and non-rhizosphere soil at six and nine weeks of plant growth and extracted DNA that was separated by density gradient centrifugation. The separate fractions were sequenced, assembled, and binned to generate 55 unique microbial genomes that were >70% complete. Evidence for close interaction between bacteria, micro-eukaryotes and plant roots includes the ability to modulate plant signaling hormones, abundant plant pathogenicity factors and production of cyanide and insecticidal toxins. We reconstructed eukaryotic 18S rRNA sequences and identified micro-eukaryotic bacterivores and fungi in the rhizosphere soil. In addition, we reconstructed two complete genomes for phage that were among the most highly 13C-enriched entities in our study. CRISPR locus targeting connected a phage to a Burkholderiales host predicted to be a plant pathogen and a possible plant growth promoting Catenulispora may serve as the host for another phage. Thus, 13C could be tracked from the atmosphere into plant roots, soil and through the rhizosphere food web. Viruses impact nearly all organisms on Earth, with ripples of influence in agriculture, health and biogeochemical processes. We previously investigated DNA phage, however, very little is known about RNA viruses in an environmental context, and even less is known about their diversity and ecology in the most complex microbial system, soil. Here, we assembled 48 individual metatranscriptomes from four habitats within a soil sampled over a 22-day time series: rhizosphere alone, detritosphere alone, a combination of the two, and unamended soil (four time points and three biological replicates per time point). We resolved the RNA viral community, uncovering a high diversity of viral sequences. We also investigated possible host organisms by analyzing metatranscriptome marker gene content. Based on viral phylogeny, much of the diversity was Narnaviridae that parasitize fungi or Leviviridae that infect Proteobacteria. Both host and viral communities appear to be highly dynamic, and rapidly diverged depending on experimental conditions. The viral communities were structured based on the presence of litter, while putative hosts appeared to be impacted by both the presence of litter and roots. A clear time signature from Leviviridae and their hosts indicated that viruses were replicating. With this time-resolved analysis, we show that RNA viruses are diverse, abundant and active in soil. Their replication causes host cell death, mobilizing carbon in a process that represents a largely overlooked component of carbon cycling in soil.By combining state of the art techniques, stable isotope probing, genome-resolved metagenomics and assembled metatranscriptomics, we advanced knowledge about the interplay between understudied players in the rhizosphere and provided some clues for the fate of plant derived carbon in the soil microbial ecosystem. The use of genome resolved metagenomics is the only current way to determine the lifestyle of uncultured microbes. Complete genomes are still difficult to reconstruct however, they contain extensive of information, both regarding the presence and the absence of capabilities. Stable isotope probing allowed us to follow plant fixed carbon into the microbial community and in several cases across multiple trophic levels. This study demonstrates the power of stable isotope-informed genome-resolved metagenomics to resolve aspects of the complex rhizosphere food web. The approach will find broad application for study of other soils and different ecosystems
Spontaneous music : the first generation British free improvisers
No full textThe British free improvisation scene originated in London and Sheffield during the
mid 1960s. In groups such as AMM, the Spontaneous Music Ensemble and Joseph
Holbrooke, a distinctive and ambitious musicality developed that still occupies most
of its protagonists forty years later.
Marked stylistic contrasts developed within the genre, notably the `atomistic' and
`laminar' methods of interaction. Nonetheless, a consistency of principle and practice
was also apparent that defined British free improvisation as unique. In some respects
the genre resembled its German, Dutch and American counterparts, and also the jazz
and classical avant-gardes that had inspired them. Both conceptually and practically,
however, clear differences remained.
The British free improvisers refined a method and an aesthetic of musical creativity,
which suggested an intimate perspective and a detailed analysis of that which we
accept as `music'. Its techniques and results were unconventional, but remained
consistent with music's defining concepts and experiences. As such, British free
improvisation suggested a more inclusive model of musicality than is common, and
implied a broad critique of the cultural values that define `music' at all. Though the
free improvisers themselves did not explicitly state the connection, their work may be
viewed in the context of Deconstruction: the post-structuralist analytical strategy
associated with philosopher Jacques Derrida.
British free improvisation culminated from innovations within the twentieth century
avant-garde. Referencing styles such as atonality and free jazz, it challenged the
aesthetic, technical and hierarchical standards of Western tradition in a form that was
striking and extreme, but also of logical development and focus. Free improvisation
owed explicit debt to a variety of other musics; its most singular achievement
however, was the redefinition of `rhythm' by which it disguised this fact.
The music of the first generation British free improvisers is reliant upon precise
conceptual and practical execution. But though this has enabled the genre to be
musically innovative, in the long term it has also become a logical problem. With
British free improvisation as its subject, the scrutiny of Deconstruction reveals
significant discrepancies between what `free improvisation' implies and what it
actually represents
An Experiential Pedagogy for Sustainability Ethics
No full textabstract: This project is developing and testing a new approach to teaching engineering and science students that leverages their interest in experiment and experience. Unlike a traditional liberal arts pedagogy involving reading about ethics, discussing the readings, and writing new analyses, this pedagogy uses games to position students in a series of potentially adversarial relationships that force them to confront some of the salient problems of sustainability, including environmental externalities, the Tragedy of the Commons, weak vs. strong sustainability and intra-generational equity. Recent tests allow students at different universities to play the games simultaneously using information communication technologies (ICT). In each game, students must ask themselves the questions related to moral cognition , "What are my obligations to my fellow students?” and moral conation, “What am I willing to risk in my own sense of well-being to meet these obligations?" We hypothesize that this approach will result in students that are actively engaged in learning exercises, and result in an improved ability to identify ethical problems, pose potential solutions, and participate in group deliberations with regard to moral problems
Rent - seeking trade policy : a time series approach
No full textUsing a time-series approach, the author analyzes the relationship between the extent of rent-seeking trade policy and both political and economic variables. For rent-seeking trade policy, the indicator he uses is the number of foreign-trade regulations passed each year for the benefit of a single firm or industry. The author uses data from Uruguay for 1925-83. Uruguay, which experienced an impressive economic decline, is an outstanding example of a rent-seeking society. After being a wealthy economy in midcentury, it suffered almost complete stagnation, which led to social and policital disintegration by the end of the 1960s. Three decades of restrictive regulations on foreign trade had created a nearly closed economy by the end of the 1960s. It was worth analyzing whether policymakers'great receptiveness to demands for protection could account for Uruguay's decline. Over the period 1925-83, the author finds almost 4,000 laws, decrees, and administrative resolutions that create, maintain, or modify a foreign-trade regulation for the benefit of a single firm or industry. About half of them explicitly identify the petitioner - usually a firm or guild. Since the size of the Uruguayan economy changed over the period studied, the author scales the annual number of regulations by output or exports to measure the extent of rent-seeking trade policy. The author shows that the extent of rent-seeking trade policy increased with discretionary policies and under dictatorship. (In the period studied, there were two stages of democracy - until 1932 and from 1943-72 - and two stages of dictatorship.) He also shows that rent-seeking trade restrictions increased under import-substitution strategies and, more unexpectedly, under active export promotion. This suggests that discretionary power leads to wasteful distribution, whether it is used to support inward- or outward-oriented policies. Finally, the author analyzes the correlation between innovations in the trade policy indicator and innovations in the growth rates of output and exports, with a lag of up to 20 years. Surprisingly, he finds a positive correlation with output growth rates after two or three years. But the correlation becomes negative some years later, particularly in the case of exports. The short-run positive impact on growth rates, together with the surprisingly long time lag before the negative impact, may account for policymakers'receptiveness to demands for protection.Trade Policy,Achieving Shared Growth,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Environmental Economics&Policies
The dual role of employee non-compete agreements: knowledge-protection and mobility limitation
No full textHuman capital, or the knowledge, skills, and abilities of employees, can be a powerful driver of firm performance, yet the mobility of human capital raises questions over how to protect it. Employee non-compete agreements, which limit an employee’s ability to start or join a rival firm, have received recent attention, but prior research has focused on the role of non-competes as individual mobility restrictions and questioned the ethics of such agreements. This three-paper dissertation considers whether employee non-compete agreements can be ethically or economically good for firms by exploring three distinct contexts: (1) regardless of state policy, when, how and for whom should firms use non-competes; (2) when a state chooses not to enforce out-of-state employee non-competes; and (3) when a state strengthens enforcement of employee non-competes. In “The Case for Ethical Non-Compete Agreements: Executives versus Sandwich-makers,” I assert that the espoused ethical tension of non-competes over questions of property rights is due to concerns over power, autonomy, and fairness. I suggest an ethical employee non-compete agreement exists when appropriate consideration to these attributes has been made during the negotiations between the firm and employee. I then apply the resource-based view of the firm to conceptualize employee non-compete agreements as isolating mechanisms that insulate firm human capital from rivals. In “Opening the Labor Market Doors: Firm Performance Following California’s Refusal to Enforce Out-of-State Employee Non-Compete Agreements,” I exploit a quasi-natural experiment of a California Supreme Court decision, and find that this decision dramatically increased the performance of in-state firms. Moreover, this relationship was influenced by both local labor market and firm-specific resource factors. Finally, in “Don’t Mess with My Texans: Firm Performance in the Wake of Texas’ Increased Enforcement of Employee Non-Competes,” I find that firm performance can also be increased by strengthened enforcement of employee non-competes. While I find no support for labor market factors in altering this relationship, the effect of firm-specific resource factors persists. This dissertation therefore bridges both strategic management and business ethics literature. Read together, the essays demonstrate the ability of employee non-competes to enable firms to ethically create and sustain human capital-based competitive advantages.Ph.D.Includes bibliographical referencesby Lauren Elizabeth Aydinliyi
Bifurcations and strange attractors in a climate related system
No full textThe author investigates a 6-dimensional dynamical system truncated from the mathematical model of atmosphere/climate evolution. Estimation of the location of the global attractor, bifurcation behavior (via Poincaré section maps), and Lyapunov exponents are obtained. This is a very detailed dynamical analysis and simulation.Validerad; 2005; 20070212 (evan)</p
Cyclopropenylidenes as Strong Carbene Anchoring Groups on Au Surfaces
No full textThe creation of stable molecular monolayers on metallic surfaces is a fundamental challenge of surface chemistry. N-Heterocyclic carbenes (NHCs) were recently shown to form self-assembled monolayers that are significantly more stable than the traditional thiols on Au system. Here we theoretically and experimentally demonstrate that the smallest cyclic carbene, cyclopropenylidene, binds even more strongly than NHCs to Au surfaces without altering the surface structure. We deposit bis(diisopropylamino)cyclopropenylidene (BAC) on Au(111) using the molecular adduct BAC-CO2 as a precursor and determine the structure, geometry, and behavior of the surface-bound molecules through high-resolution X-ray photoelectron spectroscopy, atomic force microscopy, and scanning tunneling microscopy. Our experiments are supported by density functional theory calculations of the molecular binding energy of BAC on Au(111) and its electronic structure. Our work is the first demonstration of surface modification with a stable carbene other than NHC; more broadly, it drives further exploration of various carbenes on metal surfaces
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