3,185 research outputs found

    Theory of Drop Formation

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    We consider the motion of an axisymmetric column of Navier-Stokes fluid with a free surface. Due to surface tension, the thickness of the fluid neck goes to zero in finite time. After the singularity, the fluid consists of two halves, which constitute a unique continuation of the Navier-Stokes equation through the singular point. We calculate the asymptotic solutions of the Navier-Stokes equation, both before and after the singularity. The solutions have scaling form, characterized by universal exponents as well as universal scaling functions, which we compute without adjustable parameters

    Interests, Norms, and Support for the Provision of Global Public Goods: The Case of Climate Cooperation

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    Mitigating climate change requires countries to provide a global public good. This means that the domestic cleavages underlying mass attitudes toward international climate policy are a central determinant of its provision. We argue that the industry-specific costs of emission abatement and internalized social norms help explain support for climate policy. To evaluate our predictions we develop novel measures of industry-specific interests by cross-referencing individuals? sectors of employment and objective industry-level pollution data and employ- ing quasi-behavioral measures of social norms in combination with both correlational and conjoint-experimental data. We find that individuals working in pollutive industries are 7 percentage points less likely to support climate cooperation than individuals employed in cleaner sectors. Our results also suggest that reciprocal and altruistic individuals are about 10 percentage points more supportive of global climate policy. These findings indicate that both interests and norms function as complementary explanations that improve our under- standing of individual policy preferences

    Ultrafast Dynamics of Vibrational Symmetry Breaking in a Charge-ordered Nickelate

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    The ability to probe symmetry breaking transitions on their natural time scales is one of the key challenges in nonequilibrium physics. Stripe ordering represents an intriguing type of broken symmetry, where complex interactions result in atomic-scale lines of charge and spin density. Although phonon anomalies and periodic distortions attest the importance of electron-phonon coupling in the formation of stripe phases, a direct time-domain view of vibrational symmetry breaking is lacking. We report experiments that track the transient multi-THz response of the model stripe compound La1.75_{1.75}Sr0.25_{0.25}NiO4_{4}, yielding novel insight into its electronic and structural dynamics following an ultrafast optical quench. We find that although electronic carriers are immediately delocalized, the crystal symmetry remains initially frozen - as witnessed by time-delayed suppression of zone-folded Ni-O bending modes acting as a fingerprint of lattice symmetry. Longitudinal and transverse vibrations react with different speeds, indicating a strong directionality and an important role of polar interactions. The hidden complexity of electronic and structural coupling during stripe melting and formation, captured here within a single terahertz spectrum, opens new paths to understanding symmetry breaking dynamics in solids.Comment: 21 pages, 4 figures; updated version with journal re

    WUDAPT: Facilitating advanced urban canopy modeling for weather, climate and air quality applications

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    Environmental issues and impacts to society will be exacerbated with increased population, diminishing resources and the prospects for extreme weather events and climate changes. Current community-based models available for weather, climate and air quaity applications are powerful state-of-science modeling systems, which, with careful considerations, can be employed to address the impact of these issues fo urban areas. Given the complex and high degree of spatial inhomogeneity of the underlying surface area we will review mesh size, appropriate multi-scale science and morphological descriptions and their data requirements including unique city specific gridded morphology and material composition for their forecasting and climate applications. For this presentation, we discuss, describe and show examples from an ongoing but preliminary prototypic collaborative effort, whose design bases is to provide the experience and recommendations toward extending the scope of the National Urban Database and Access Portal Tools (NUDAPT) to worldwide coverage (WUDAPT). WUDAPT would thus provide requisite gridded data for urban applications of advanced forecast and climate models throughout the world. Strategically, the prototypic efforts will be designed to provide proven protocols for the facilitaton of the data gathering and processing based on available remote sensing and ground-based sampling. Tactically, we employ an iterative approach first obtaining coarse gridded Local Climate Zone (LCZ) classification derived from available Web-based products such as Google-Earth, and Landsat satellite magery. Further sub-class discretization of LCZs and the application of GeoWiki technology facilitates further refinements and ground truthing to yield the desired gridded building morphological distribution parameters and their material composition. Local experts would be encouraged to become involved to ensure factors unique to their area in the world would be incorporated. Finally, given that model applications may require data with different grid resolution we present an outline that employs the new and powerful Multiple Resolution Analyses scheme that can address this need within the scope of WUDAPT

    Studies for a Photon Collider at the ILC

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    One option at the International Linear Collider is to convert the electron beams into high energy photon beams by Compton scattering a few millimetres in front of the interaction region. Selected physics channels for this option have been analysed and technical issues have been studied. So far no showstoppers for this option have been found.Comment: V2: Minor changes, accepted by NI

    Teleology and Realism in Leibniz's Philosophy of Science

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    This paper argues for an interpretation of Leibniz’s claim that physics requires both mechanical and teleological principles as a view regarding the interpretation of physical theories. Granting that Leibniz’s fundamental ontology remains non-physical, or mentalistic, it argues that teleological principles nevertheless ground a realist commitment about mechanical descriptions of phenomena. The empirical results of the new sciences, according to Leibniz, have genuine truth conditions: there is a fact of the matter about the regularities observed in experience. Taking this stance, however, requires bringing non-empirical reasons to bear upon mechanical causal claims. This paper first evaluates extant interpretations of Leibniz’s thesis that there are two realms in physics as describing parallel, self-sufficient sets of laws. It then examines Leibniz’s use of teleological principles to interpret scientific results in the context of his interventions in debates in seventeenth-century kinematic theory, and in the teaching of Copernicanism. Leibniz’s use of the principle of continuity and the principle of simplicity, for instance, reveal an underlying commitment to the truth-aptness, or approximate truth-aptness, of the new natural sciences. The paper concludes with a brief remark on the relation between metaphysics, theology, and physics in Leibniz

    Stardust Interstellar Preliminary Examination (ISPE)

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    In January 2006 the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, C omet 81P/Wild2, and a collector dedicated to the capture and return o f contemporary interstellar dust. Both collectors were approximately 0.1m(exp 2) in area and were composed of aerogel tiles (85% of the co llecting area) and aluminum foils. The Stardust Interstellar Dust Col lector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m(exp 2-) day during two periods before the co metary encounter. The Stardust Interstellar Preliminary Examination ( ISPE) is a three-year effort to characterize the collection using no ndestructive techniques. The ISPE consists of six interdependent proj ects: (1) Candidate identification through automated digital microsco py and a massively distributed, calibrated search (2) Candidate extr action and photodocumentation (3) Characterization of candidates thro ugh synchrotronbased FourierTranform Infrared Spectroscopy (FTIR), S canning XRay Fluoresence Microscopy (SXRF), and Scanning Transmission Xray Microscopy (STXM) (4) Search for and analysis of craters in f oils through FESEM scanning, Auger Spectroscopy and synchrotronbased Photoemission Electron Microscopy (PEEM) (5) Modeling of interstell ar dust transport in the solar system (6) Laboratory simulations of h ypervelocity dust impacts into the collecting medi

    Parenting-Related Stress, Parental Distress, and Youth Health-Related Quality of Life in Families of Youth with Spina Bifida: Parenting Behaviors As Mediators

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    Research has shown that youth with spina bifida (SB) have poorer psychosocial outcomes, including health-related quality of life (HRQOL), compared to typically developing youth. Demographic and illness-severity factors that may affect HRQOL have been identified, but modifiable factors affecting HRQOL have not yet been identified in this population. Potential modifiable factors include parent factors. In fact, in other pediatric populations, parent factors have been found to impact HRQOL above and beyond illness-severity. This impact may be especially salient for youth with SB, as these youth are more socially isolated and depend on parents for both medical and non-medical caregiving needs. The current study proposes that increases in three parent factors (parent distress, parenting stress, and SB-specific parenting stress) lead to less adaptive parenting behaviors, which, in turn, affect youth HRQOL. The present study addresses gaps in the literature by utilizing a longitudinal, multi-method, and multi-informant research design

    Estimating Residual Error by Repeated Measurements

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    Repeated measurements can be used to estimate the residual error of a measurement process. Residual error, defined as the error remaining after all known sources of error have been accounted for, is what causes differences in the measurement outcome when everything about the measurement process is seemingly identical. Four estimators for the amount of residual error are suggested. These estimators are functions of the outcomes from m repeated measurements on each of n items. Assuming a normal distribution for the residual error, two of the estimators are unbiased estimators for the standard deviation of the residual error, and the third is the maximum likelihood estimator for the standard deviation of the residual error. The fourth is not an estimator for standard deviation, but rather it uses the distance between measurement order statistics as an indicator of the amount of residual error. The efficiencies of the first two estimators and the bias of the maximum likelihood estimator are evaluated. Computations use standard statistical methods and are included in appendices.This work, motivated by the study of machines used to measure the modulus of elasticity of dimension lumber, has been used to assess the performance of this machinery. An example using data from more than 10 years ago and some recent data show that the residual error then was about double that of today for well-tuned, high-speed production-line machinery

    Wake up, wake up! It's me! It's my life! patient narratives on person-centeredness in the integrated care context: a qualitative study

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    Person-centered care emphasizes a holistic, humanistic approach that puts patients first, at the center of medical care. Person-centeredness is also considered a core element of integrated care. Yet typologies of integrated care mainly describe how patients fit within integrated services, rather than how services fit into the patient's world. Patient-centeredness has been commonly defined through physician's behaviors aimed at delivering patient-centered care. Yet, it is unclear how 'person-centeredness' is realized in integrated care through the patient voice. We aimed to explore patient narratives of person-centeredness in the integrated care context
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