667 research outputs found
Some remarks on the geometry of the Standard Map
We define and compute hyperbolic coordinates and associated foliations which
provide a new way to describe the geometry of the standard map. We also
identify a uniformly hyperbolic region and a complementary 'critical' region
containing a smooth curve of tangencies between certain canonical 'stable'
foliations.Comment: 25 pages, 11 figure
Translation and "the truth of solipsism"
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2001.Includes bibliographical references (leaves 128-129).All the things that drive me as an artist are about the same question. It is a question that may be asked in different ways. I want to know how I am already a part of the world. I want to know if when I look at the world it is the same thing others see. I want to discover why it is not possible for me to experience the world the way it is prior to my seeing it. The way I have approached answering these questions has been to find ways of accompanying events that already take place in the world. The following is an expression of these experiences.by Benjamin A. Luzzatto.S.M
Urban society and the English Revolution : the archaeology of the new Jerusalem
The English Revolution has long been a defining subject of English historiography, with a large and varied literature that reflects continuing engagement with the central themes of civil conflict, and deep-rooted social, political and religious change. By contrast, this period has failed to catch the imagination of archaeologists. This research seeks to understand the world of the English Revolution through its material expression in English towns. Identifying the material expressions of the period is central to developing an archaeological understanding of the period. The clearest material expressions are found, in the fortifications that were built to protect towns, the destruction that was wrought on towns and in the reconstruction of the material world of English towns. Towns, like any other artefact, have their meanings. These meanings are multivalent and ever shifting, defined by the interaction of their material fabric and those who experience it. As these meanings change over time, they can be traced through the structures and artefacts of the town, and through the myths and legends that accrete on them. Understanding the interactions of material, myth and memory allows archaeologists to understand the true meaning of the urban built environment to generate a deeper and more nuanced understanding of the nature of the English urban culture of the period. Towns were fundamental to the English imagination as much as they were economically, politically or socially important. The English Revolution sits at the heart of the accepted conception of historical archaeology, but has been curiously neglected by historical archaeologists. The cultural conflict of this period embodies the themes that are central to historical archaeology, and nowhere is this more apparent than in urban culture.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Statistical Consequences of Devroye Inequality for Processes. Applications to a Class of Non-Uniformly Hyperbolic Dynamical Systems
In this paper, we apply Devroye inequality to study various statistical
estimators and fluctuations of observables for processes. Most of these
observables are suggested by dynamical systems. These applications concern the
co-variance function, the integrated periodogram, the correlation dimension,
the kernel density estimator, the speed of convergence of empirical measure,
the shadowing property and the almost-sure central limit theorem. We proved in
\cite{CCS} that Devroye inequality holds for a class of non-uniformly
hyperbolic dynamical systems introduced in \cite{young}. In the second appendix
we prove that, if the decay of correlations holds with a common rate for all
pairs of functions, then it holds uniformly in the function spaces. In the last
appendix we prove that for the subclass of one-dimensional systems studied in
\cite{young} the density of the absolutely continuous invariant measure belongs
to a Besov space.Comment: 33 pages; companion of the paper math.DS/0412166; corrected version;
to appear in Nonlinearit
Invariant manifolds and equilibrium states for non-uniformly hyperbolic horseshoes
In this paper we consider horseshoes containing an orbit of homoclinic
tangency accumulated by periodic points. We prove a version of the Invariant
Manifolds Theorem, construct finite Markov partitions and use them to prove the
existence and uniqueness of equilibrium states associated to H\"older
continuous potentials.Comment: 33 pages, 6 figure
Patients with paroxysmal nocturnal hemoglobinuria have a high frequency of peripheral-blood T cells expressing activating isoforms of inhibiting superfamily receptors
Patients with paroxysmal nocturnal hemoglobinuria (PNH) have a large clonal population of blood cells deriving from hematopoietic stem cells (HSCs) deficient in glycosylphosphatidylinositol (GPI)-anchored surface molecules. A current model postulates that PNH arises through negative selection against normal HSCs exerted by autoreactive T cells, whereas PNH HSCs escape damage. We have investigated the inhibitory receptor superfamily (IRS) system in 13 patients with PNH. We found a slight increase in the proportion of T cells expressing IRS. In contrast to what applies to healthy donors, the engagement of IRS molecules on T cells from patients with PNH elicited a powerful cytolytic activity in a redirected killing assay, indicating that these IRSs belong to the activating type. This was confirmed by clonal analysis: 50% of IRS+ T-cell clones in patients with PNH were of the activating type, while only 5% were of the activating type in healthy donors. Moreover, the ligation of IRS induces (1) production of tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) and (2) brisk cytolytic activity against cells bearing appropriate IRS counter-ligands. In addition, these IRS+ T cells show natural killer (NK)-like cytolytic activity to which GPI- cells were less sensitive than GPI+ cells. Thus, T cells with NK-like features, expressing the activating isoforms of IRS, may include effector cells involved in the pathogenesis of PNH
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Molecular and Microbial Microenvironments in Chronically Diseased Lungs Associated with Cystic Fibrosis.
To visualize the personalized distributions of pathogens and chemical environments, including microbial metabolites, pharmaceuticals, and their metabolic products, within and between human lungs afflicted with cystic fibrosis (CF), we generated three-dimensional (3D) microbiome and metabolome maps of six explanted lungs from three cystic fibrosis patients. These 3D spatial maps revealed that the chemical environments differ between patients and within the lungs of each patient. Although the microbial ecosystems of the patients were defined by the dominant pathogen, their chemical diversity was not. Additionally, the chemical diversity between locales in the lungs of the same individual sometimes exceeded interindividual variation. Thus, the chemistry and microbiome of the explanted lungs appear to be not only personalized but also regiospecific. Previously undescribed analogs of microbial quinolones and antibiotic metabolites were also detected. Furthermore, mapping the chemical and microbial distributions allowed visualization of microbial community interactions, such as increased production of quorum sensing quinolones in locations where Pseudomonas was in contact with Staphylococcus and Granulicatella, consistent with in vitro observations of bacteria isolated from these patients. Visualization of microbe-metabolite associations within a host organ in early-stage CF disease in animal models will help elucidate the complex interplay between the presence of a given microbial structure, antibiotics, metabolism of antibiotics, microbial virulence factors, and host responses.IMPORTANCE Microbial infections are now recognized to be polymicrobial and personalized in nature. Comprehensive analysis and understanding of the factors underlying the polymicrobial and personalized nature of infections remain limited, especially in the context of the host. By visualizing microbiomes and metabolomes of diseased human lungs, we reveal how different the chemical environments are between hosts that are dominated by the same pathogen and how community interactions shape the chemical environment or vice versa. We highlight that three-dimensional organ mapping methods represent hypothesis-building tools that allow us to design mechanistic studies aimed at addressing microbial responses to other microbes, the host, and pharmaceutical drugs
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