10,758 research outputs found

    Feedback computability on Cantor space

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    We introduce the notion of feedback computable functions from 2ω2^\omega to 2ω2^\omega, extending feedback Turing computation in analogy with the standard notion of computability for functions from 2ω2^\omega to 2ω2^\omega. We then show that the feedback computable functions are precisely the effectively Borel functions. With this as motivation we define the notion of a feedback computable function on a structure, independent of any coding of the structure as a real. We show that this notion is absolute, and as an example characterize those functions that are computable from a Gandy ordinal with some finite subset distinguished

    An Evaluation of Size-Resolved Cloud Microphysics Scheme Numerics for Use with Radar Observations. Part I: Collision-Coalescence

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    This study evaluates some available schemes designed to solve the stochastic collection equation (SCE) for collision-coalescence of hydrometeors using a size-resolved (bin) microphysics approach, and documents their numerical properties within the framework of a box model. Comparing three widely used SCE schemes, we find that all converge to almost identical solutions at sufficiently fine mass grids. However, one scheme converges far slower than the other two and shows pronounced numerical diffusion at the large-drop tail of the size distribution. One of the remaining two schemes is recommended on the basis that it is well-converged on a relatively coarse mass grid, stable for large time steps, strictly mass-conservative, and computationally efficient. To examine the effects of SCE scheme choice on simulating clouds and precipitation, two of the three schemes are compared in large-eddy simulations of a drizzling stratocumulus field. A forward simulator that produces Doppler spectra from the large-eddy simulation results is used to compare the model output directly with radar observations. The scheme with pronounced numerical diffusion predicts excessively large mean Doppler velocities and overly broad and negatively skewed spectra compared with observations, consistent with numerical diffusion demonstrated in the box model. Statistics obtained using the recommended scheme are closer to observations, but notable differences remain, indicating that factors other than SCE scheme accuracy are limiting simulation fidelity

    New Climate Economics: Methodological Choices and Recommendations

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    Projections of future impacts, benefits and costs of climate mitigation and adaptation policies are based on both detailed empirical research, and modelling choices and assumptions that frame the analysis. For instance, assumptions about the expected growth of population and incomes drive the projections of greenhouse gas emissions. Assumptions about the pace and nature of innovation, the economy-environment-society interactions and the relative value of future versus current resources affect the estimates of the long-run benefits or costs of climate policies. Assumptions about future population health in the business-as-usual scenario affect the estimates of the health benefits or harms of climate change mitigation and adaptation policies. Further, estimates and assumptions regarding climate variability affect the benefits of adaptation measures to tackle potential increases in climate-related extreme events. Also, methodological choices about the treatment of disparate, incommensurable impacts are often decisive for policy decisions. This document presents a series of what we refer to as critical issues for climate mitigation and adaptation policy analysis, involving overarching choices that affect multiple areas of expert analysis, and in particular the socio-economic assessments of climate policies. The following pages identify key issues for a comprehensive and realistic economic analysis of climate policies, present a few major options for answering those issues, and recommend a preferred course of action or option for analysts to consider (akin to what some refer to as "new economic thinking"). The issue of risk and uncertainty has been addressed in a separate supporting guidance document, due to its overriding importance and specific inter-disciplinary profile (available on the website of the MCA4climate initiative: www.mca4climate.info). In addition, some practical implementation aspects of the issues discussed below have been provided in Annex 1 at the end of this document. Some of the topics addressed here may be more amenable to qualitative than to quantitative analysis; potential examples include the valuation of non-market "goods" such as human health and environmental protection, and the goal of intergenerational equity. It is nonetheless important to understand the implications of both quantitative and qualitative approaches to these issues, since both approaches are often raised in the discussion of climate policy. The guiding principles underpinning the overall MCA4climate approach

    Unique transcriptomic landscapes identified in idiopathic spontaneous and infection related preterm births compared to normal term births.

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    Preterm birth (PTB) is leading contributor to infant death in the United States and globally, yet the underlying mechanistic causes are not well understood. Histopathological studies of preterm birth suggest advanced villous maturity may have a role in idiopathic spontaneous preterm birth (isPTB). To better understand pathological and molecular basis of isPTB, we compared placental villous transcriptomes from carefully phenotyped cohorts of PTB due to infection or isPTB between 28-36 weeks gestation and healthy term placentas. Transcriptomic analyses revealed a unique expression signature for isPTB distinct from the age-matched controls that were delivered prematurely due to infection. This signature included the upregulation of three IGF binding proteins (IGFBP1, IGFBP2, and IGFBP6), supporting a role for aberrant IGF signaling in isPTB. However, within the isPTB expression signature, we detected secondary signature of inflammatory markers including TNC, C3, CFH, and C1R, which have been associated with placental maturity. In contrast, the expression signature of the gestational age-matched infected samples included upregulation of proliferative genes along with cell cycling and mitosis pathways. Together, these data suggest an isPTB molecular signature of placental hypermaturity, likely contributing to the premature activation of inflammatory pathways associated with birth and providing a molecular basis for idiopathic spontaneous birth
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