5,583 research outputs found

    Diversity and Petrogenesis of Rhyolites from an Intra-oceanic Arc: Evidence from IODP Site U1437, Izu Bonin Rear-arc and Surrounding Area

    Get PDF
    Magmas from the Izu Bonin rear-arc show a geochemical signature (medium- to high-K and light rare-earth element [LREE] enriched) that resembles the average composition of the continental crust. I investigate that continent-like signature by examining a suite of rear-arc-derived mafic to felsic tephras from International Ocean Discovery Program (IODP) Site U1437, which was drilled as part of IODP Expedition 350. Volcaniclastic glasses from Site U1437 comprise a compositional series from basalt to rhyolite, aged 1.1-4.4 Ma. Site U1437 tephras record the timespan when the Izu-Bonin arc began rifting and provide a well-dated record of changing magmatic compositions through the transition into arc rifting. Considered with context provided by a comprehensive recontextualization of published analyses ofrocks, magmatic compositions are shown to vary in coherent chronological and spatial trends and can be classified into three series: LREE-depleted volcanic front series; flat pattern REE rift-related series; and LREE-enriched rear-arc seamount chain-type (RASC-type) series which includes Site U1437 glasses. Each series has a distinctive characteristic basalt type whose trace element and radiogenic isotope chemistry matches rhyolite type from the same region. Geochemical modeling shows that fractional crystallization is a viable mechanism to generate2and oxygen isotope systematics show that some degree of open-system processes are involved in rhyolite petrogenesis; however there is no evidence for large-scale melting of pre-existing crustal sources. The \u3e12.9 Ma crustal sources inferred to exist within the rear-arc region cannot be the source for rear-arc rhyolites because of differing La/Yb and ɛHf signatures. Thus, I favor a model where fractional crystallization is the differentiation mechanism involved in the generation of intraoceanic arc rhyolites in this region

    Assessment of different urban traffic control strategy impacts on vehicle emissions

    Get PDF
    This paper investigates the influence of traffic signal control strategy on vehicle emissions, vehicle journey time and total throughput flow within a single isolated four-armed junction. Two pre-timed signal plans are considered, one with two-stages involving permissive-only opposing turns and the other with four-stages which has no conflicting traffic. Additionally, the increase in efficiency by utilising actuated signal timing where green time is re-optimised as flow values vary is investigated. A microscopic traffic simulation model is used to model flows and AIRE (Analysis of Instantaneous Road Emissions) microscopic emissions model is utilised to out- put emission levels from the flow data. A simple junction model shows that the two-stage signal plan is more efficient in both emis- sions and journey time. However, as the level of opposed turning vehicles and conflicting movement increases, the two-stage model moves to being the inferior signal plan choice and the four-stage plan outputs fewer emissions than the two-stage plan. A real-world example of a four-armed junction has been used in this study and from the traffic survey data and existing junction layout; it is rec- ommended that a two-stage plan is used as it produces lower amounts of emissions and shorter journey times compared to a four-stage plan. The results also show that nitrogen oxides (NOx) are the most sensitive to changes in flow followed by carbon dioxide (CO2), Black Carbon and then particulate matter (PM10)

    Drifting diffusion on a circle as continuous limit of a multiurn Ehrenfest model

    Full text link
    We study the continuous limit of a multibox Erhenfest urn model proposed before by the authors. The evolution of the resulting continuous system is governed by a differential equation, which describes a diffusion process on a circle with a nonzero drifting velocity. The short time behavior of this diffusion process is obtained directly by solving the equation, while the long time behavior is derived using the Poisson summation formula. They reproduce the previous results in the large MM (number of boxes) limit. We also discuss the connection between this diffusion equation and the Schro¨\ddot{\rm o}dinger equation of some quantum mechanical problems.Comment: 4 pages prevtex4 file, 1 eps figur

    Contact of Single Asperities with Varying Adhesion: Comparing Continuum Mechanics to Atomistic Simulations

    Full text link
    Atomistic simulations are used to test the equations of continuum contact mechanics in nanometer scale contacts. Nominally spherical tips, made by bending crystals or cutting crystalline or amorphous solids, are pressed into a flat, elastic substrate. The normal displacement, contact radius, stress distribution, friction and lateral stiffness are examined as a function of load and adhesion. The atomic scale roughness present on any tip made of discrete atoms is shown to have profound effects on the results. Contact areas, local stresses, and the work of adhesion change by factors of two to four, and the friction and lateral stiffness vary by orders of magnitude. The microscopic factors responsible for these changes are discussed. The results are also used to test methods for analyzing experimental data with continuum theory to determine information, such as contact area, that can not be measured directly in nanometer scale contacts. Even when the data appear to be fit by continuum theory, extracted quantities can differ substantially from their true values

    Reward, punishment, and prosocial behavior: Recent developments and implications

    Get PDF
    Reward and punishment change the payoff structures of social interactions and therefore can potentially play a role in promoting prosocial behavior. Yet, there are boundary conditions for them to be effective. We review recent work that addresses the conditions under which rewards and punishment can enhance prosocial behavior, the proximate and ultimate mechanisms for individuals’ rewarding and punishing decisions, and the reputational and behavioral consequences of reward and punishment under noise. The reviewed evidence points to the importance of more field research on how reward and punishment can promote prosocial behavior in real-world settings. We also highlight the need to integrate different methodologies to better examine the effects of reward and punishment on prosocial behavior

    Statistics of Lyapunov exponent in one-dimensional layered systems

    Full text link
    Localization of acoustic waves in a one dimensional water duct containing many randomly distributed air filled blocks is studied. Both the Lyapunov exponent and its variance are computed. Their statistical properties are also explored extensively. The results reveal that in this system the single parameter scaling is generally inadequate no matter whether the frequency we consider is located in a pass band or in a band gap. This contradicts the earlier observations in an optical case. We compare the results with two optical cases and give a possible explanation of the origin of the different behaviors.Comment: 6 pages revtex file, 6 eps figure

    Bayesian linear mixed models with polygenic effects

    Get PDF
    We considered Bayesian estimation of polygenic effects, in particular heritability in relation to a class of linear mixed models implemented in R. Our approach is applicable to both family-based and population-based studies in human genetics with which a genetic relationship matrix can be derived either from family structure or genome-wide data. Using a simulated and a real data, we demonstrate our implementation of the models in the generic statistical software systems JAGS and Stan as well as several R packages. In doing so, we have not only provided facilities in R linking standalone programs such as GCTA and other packages in R but also addressed some technical issues in the analysis. Our experience with a host of general and special software systems will facilitate investigation into more complex models for both human and nonhuman genetics

    Coupling of Light and Mechanics in a Photonic Crystal Waveguide

    Get PDF
    Observations of thermally driven transverse vibration of a photonic crystal waveguide (PCW) are reported. The PCW consists of two parallel nanobeams with a 240 nm vacuum gap between the beams. Models are developed and validated for the transduction of beam motion to phase and amplitude modulation of a weak optical probe propagating in a guided mode (GM) of the PCW for probe frequencies far from and near to the dielectric band edge. Since our PCW has been designed for near-field atom trapping, this research provides a foundation for evaluating possible deleterious effects of thermal motion on optical atomic traps near the surfaces of PCWs. Longer term goals are to achieve strong atom-mediated links between individual phonons of vibration and single photons propagating in the GMs of the PCW, thereby enabling opto-mechanics at the quantum level with atoms, photons, and phonons. The experiments and models reported here provide a basis for assessing such goals, including sensing mechanical motion at the Standard Quantum Limit (SQL).Comment: 13 pages, 13 figure

    Determination of the field-effect mobility and the density of states of a Thin-Film Transistor*

    Get PDF
    In this project we determined some basic parameters for characterizing an organic thin-film transistor (OTFT) one week after fabrication and compared them with the parameters right after fabrication, in particular the transfer characteristics, the charge carrier mobility (also known as the field-effect mobility), the activation energy, and the density of states (DOS). The material which our OTFT was made of is pentacene, a widely used organic compound in OTFT fabrication.2014/201
    • …
    corecore