5,733 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
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
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
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 (number of boxes) limit. We also discuss
the connection between this diffusion equation and the Schrdinger
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
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
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
Bayesian linear mixed models with polygenic effects
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
Statistics of Lyapunov exponent in one-dimensional layered systems
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
Determination of the field-effect mobility and the density of states of a Thin-Film Transistor*
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
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