7,973 research outputs found

    Evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu1āˆ’x_{1-x}Gdx_{x}O

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    Raman scattering studies as functions of temperature, magnetic field, and Gd-substitution are used to investigate the evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu1āˆ’x_{1-x}Gdx_{x}O. These studies reveal a greater richness of phase behavior than have been previously observed using transport measurements: a spin-fluctuation-dominated paramagnetic (PM) phase regime for T >> Tāˆ—^{*} >> TC_{C}, a two-phase regime for T << Tāˆ—^{*} in which magnetic polarons develop and coexist with a remnant of the PM phase, and an inhomogeneous ferromagnetic phase regime for T << TC_{C}

    An Experimental Study of Effects of Step Roughness in Skimming Flows on Stepped Chutes

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    On a spillway chute, a stepped design increases the rate of energy dissipation on the chute itself and reduces the size of a downstream energy dissipator. Up to date, the effects of step roughness on the flow properties remain unknown despite the practical relevance to damaged concrete steps, rock chutes and gabions weirs. New measurements were conducted in a large-size laboratory facility with two step conditions (smooth and rough) and three types of step roughness. Detailed air-water flow properties were measured systematically for several flow rates. The results showed faster flow motion on rough step chutes. Although the finding is counter-intuitive, it is linked with the location of the inception point of free-surface aeration being located further downstream than for a smooth stepped chute for an identical flow rate. In the aerated flow region, the velocities on rough-step chutes were larger than those of smooth chute flows for a given flow rate and dimensionless location from the inception point of free-surface aeration both at step edges and between step edges. The results suggest that design guidelines for smooth (concrete) stepped spillway may not be suitable to rough stepped chutes including gabion stepped weirs, and older stepped chutes with damaged steps

    How to teach fully illiterate adults to read.

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    About 750 million adults (15%) worldwide lack any literacy skills, most because they lack adequate learning opportunities (UNESCO, 2016). In this chapter, we discuss how to teach to read to such people. We first examine scientific evidence suggesting that literacy acquisition does not radically differ as a function of age of acquisition. We then discuss the data relevant for designing effective methods aimed at teaching literacy to fully illiterate adults. We argue that the available adult data confirm those relative to teaching methods and learning processes that have been gathered on literacy acquisition by children. On the basis of those works we propose principles that should underlie any method aiming at rapidly developing basic literacy skills. Lastly, we present evidence (Kolinsky, Leite, Carvalho, Franco, & Morais, submitted) suggesting that implementing these principles does indeed allow teaching illiterate adults to decode words and pseudo-words in a very short period of time

    Fluctuation induced hopping and spin polaron transport

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    We study the motion of free magnetic polarons in a paramagnetic background of fluctuating local moments. The polaron can tunnel only to nearby regions of local moments when these fluctuate into alignment. We propose this fluctuation induced hopping as a new transport mechanism for the spin polaron. We calculate the diffusion constant for fluctuation induced hopping from the rate at which local moments fluctuate into alignment. The electrical resistivity is then obtained via the Einstein relation. We suggest that the proposed transport mechanism is relevant in the high temperature phase of the Mn pyrochlore colossal magneto resistance compounds and Europium hexaboride.Comment: 8 pages, 3 figure

    The urban wage growth premium: sorting or learning?

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    This paper is concerned with the urban wage premium and addresses two central issues about which the field has not yet reached a consensus: first, the extent to which sorting of high ability individuals into urban areas explains the urban wage premium and second, whether workers receive this wage premium immediately, or through faster wage growth over time. Using a large panel of worker-level data from Britain, we first demonstrate the existence of an urban premium for wage levels, which increases in city size. We next provide evidence of a city size premium on wage growth, but show that this effect is driven purely by the increase in wage that occurs in the first year that a worker moves to a larger location. Controlling for sorting on the basis of unobservables we find no evidence of an urban wage growth premium. Experience in cities does have some impact on wage growth, however. Specifically, we show that workers who have at some point worked in a city experience faster wage growth than those who have never worked in a city
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