146 research outputs found
Basal melt rates beneath Whillans Ice Stream, West Antarctica
This is the published version, also available here: http://dx.doi.org/10.3189/002214310793146241.Basal water lubricates and enables the fast flow of the West Antarctic ice streams which exist under low gravitational driving stress. Identification of sources and rates of basal meltwater production can provide insight into the dynamics of ice streams and the subglacial hydrology, which remain insufficiently described by glaciological theory. Combining measurements and analytic modeling, we identify two regions where basal meltwater is produced beneath Whillans Ice Stream, West Antarctica. Downstream of the onset of shear crevasses, strong basal melt (20–50 mm a−1) is concentrated beneath the relatively narrow shear margins. Farther upstream, melt rates are consistently 3–7 mm a−1 across the width of the ice stream. We show that the transition in melt-rate patterns is coincident with the onset of shear margin crevassing and streaming flow and related to the development of significant lateral shear resistance, which reorganizes the resistive stress regime and induces a concentration of basal resistance adjacent to the shear margin. Finally, we discuss how downstream freeze-on in the ice-stream center coupled with melt beneath the shear margin might result in a slowing but widening ice stream
EVALUACIÓN DE RESULTADOS QUIRÚRGICOS DESDE LA PERSPECTIVA DEL PACIENTE
RESUMENMedir la calidad de vida relacionada a salud y los sÃntomas de los pacientes es un problema difÃcil. Las medición de los problemas de salud mediante escalas o cuestionarios se ha desarrollado para crear los Instrumentos de Evaluación desde la Perspectiva del Paciente o PRO's por su nombre en inglés: Patient-reported outcomes. Los PROs evalúan la calidad de vida en forma genérica o especÃfica en un continuo, entregando instrumentos que pueden evaluar la gravedad de una enfermedad o el impacto de una intervención desde la perspectiva del paciente en frecuentes escenarios clÃnicos. El objetivo de la presente revisión es entregar a clÃnicos e investigadores una introducción hacia los PROs y resumir sus principales propiedades.SUMMARYQuantifying health-related quality of life and specific patient symptoms it is a difficult problem. Health measurement scales has developed to include rigorous techniques to develop patient-reported outcome measures (PROs). PROs assess objectively the QoL in a continuum, providing instruments to measure the severity of a given disease or the impact of a therapeutic intervention from patient perspective in different clinical problems. The following review aims to introduce the PROs to clinicians and researchers and summarize its main properties
Homothetic perfect fluid space-times
A brief summary of results on homotheties in General Relativity is given,
including general information about space-times admitting an r-parameter group
of homothetic transformations for r>2, as well as some specific results on
perfect fluids. Attention is then focussed on inhomogeneous models, in
particular on those with a homothetic group (acting multiply
transitively) and . A classification of all possible Lie algebra
structures along with (local) coordinate expressions for the metric and
homothetic vectors is then provided (irrespectively of the matter content), and
some new perfect fluid solutions are given and briefly discussed.Comment: 27 pages, Latex file, Submitted to Class. Quantum Gra
A Note on Computations of D-brane Superpotential
We develop some computational methods for the integrals over the 3-chains on
the compact Calabi-Yau 3-folds that plays a prominent role in the analysis of
the topological B-model in the context of the open mirror symmetry. We discuss
such 3-chain integrals in two approaches. In the first approach, we provide a
systematic algorithm to obtain the inhomogeneous Picard-Fuchs equations. In the
second approach, we discuss the analytic continuation of the period integral to
compute the 3-chain integral directly. The latter direct integration method is
applicable for both on-shell and off-shell formalisms.Comment: 61 pages, 5 figures; v2: typos corrected, minor changes, references
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Methods of synthesizing qualitative research studies for health technology assessment
OBJECTIVES Synthesizing qualitative research is an important means of ensuring the needs, preferences, and experiences of patients are taken into account by service providers and policy makers, but the range of methods available can appear confusing. This study presents the methods for synthesizing qualitative research most used in health research to-date and, specifically those with a potential role in health technology assessment. METHODS To identify reviews conducted using the eight main methods for synthesizing qualitative studies, nine electronic databases were searched using key terms including meta-ethnography and synthesis. A summary table groups the identified reviews by their use of the eight methods, highlighting the methods used most generally and specifically in relation to health technology assessment topics. RESULTS Although there is debate about how best to identify and quality appraise qualitative research for synthesis, 107 reviews were identified using one of the eight main methods. Four methods (meta-ethnography, meta-study, meta-summary, and thematic synthesis) have been most widely used and have a role within health technology assessment. Meta-ethnography is the leading method for synthesizing qualitative health research. Thematic synthesis is also useful for integrating qualitative and quantitative findings. Four other methods (critical interpretive synthesis, grounded theory synthesis, meta-interpretation, and cross-case analysis) have been under-used in health research and their potential in health technology assessments is currently under-developed. CONCLUSIONS Synthesizing individual qualitative studies has becoming increasingly common in recent years. Although this is still an emerging research discipline such an approach is one means of promoting the patient-centeredness of health technology assessments
Generalized Toda Theory from Six Dimensions and the Conifold
Recently, a physical derivation of the Alday-Gaiotto-Tachikawa correspondence
has been put forward. A crucial role is played by the complex Chern-Simons
theory arising in the 3d-3d correspondence, whose boundary modes lead to Toda
theory on a Riemann surface. We explore several features of this derivation and
subsequently argue that it can be extended to a generalization of the AGT
correspondence. The latter involves codimension two defects in six dimensions
that wrap the Riemann surface. We use a purely geometrical description of these
defects and find that the generalized AGT setup can be modeled in a pole region
using generalized conifolds. Furthermore, we argue that the ordinary conifold
clarifies several features of the derivation of the original AGT
correspondence.Comment: 27+2 pages, 3 figure
Reviews and syntheses: The promise of big diverse soil data, moving current practices towards future potential
In the age of big data, soil data are more available and richer than ever, but – outside of a few large soil survey resources – they remain largely unusable for informing soil management and understanding Earth system processes beyond the original study.
Data science has promised a fully reusable research pipeline where data from past studies are used to contextualize new findings and reanalyzed for new insight.
Yet synthesis projects encounter challenges at all steps of the data reuse pipeline, including unavailable data, labor-intensive transcription of datasets, incomplete metadata, and a lack of communication between collaborators.
Here, using insights from a diversity of soil, data, and climate scientists, we summarize current practices in soil data synthesis across all stages of database creation: availability, input, harmonization, curation, and publication.
We then suggest new soil-focused semantic tools to improve existing data pipelines, such as ontologies, vocabulary lists, and community practices.
Our goal is to provide the soil data community with an overview of current practices in soil data and where we need to go to fully leverage big data to solve soil problems in the next century
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