Development of speech fluency over a short period of time: effects of pedagogic intervention

This study investigates the effects of a short-term pedagogic intervention on the development of L2 fluency among learners studying English for Academic purposes (EAP) at a university in the UK. It also examines the interaction between the development of fluency, and complexity and accuracy. Through a pre-test, post-test design, data were collected over a period of four weeks from learners performing monologic tasks. While the Control Group (CG) focused on developing general speaking and listening skills, the Experimental Group (EG) received awareness-raising activities and fluency strategy training in addition to general speaking and listening practice i.e following the syllabus. The data, coded in terms of a range of measures of fluency, accuracy and complexity, were subjected to repeated measures MANOVA, t-tests and correlations. The results indicate that after the intervention, while some fluency gains were achieved by the CG, the EG produced statistically more fluent language demonstrating a faster speech and articulation rate, longer runs and higher phonation time ratios. The significant correlations obtained between measures of accuracy and learners’ pauses in the CG suggest that pausing opportunities may have been linked to accuracy. The findings of the study have significant implications for L2 pedagogy, highlighting the effective impact of instruction on the development of fluency.

Long-lived excited-state dynamics of i-motif structures probed by time-resolved infrared spectroscopy

UV-generated excited states of cytosine (C) nucleobases are precursors to mutagenic photoproduct formation. The i-motif formed from C-rich sequences is known to exhibit high yields of long-lived excited states following UV absorption. Here the excited states of several i-motif structures have been characterized following 267 nm laser excitation using time-resolved infrared spectroscopy (TRIR). All structures possess a long-lived excited state of ~300 ps and notably in some cases decays greater than 1 ns are observed. These unusually long-lived lifetimes are attributed to the interdigitated DNA structure which prevents direct base stacking overlap.

Picosecond Dynamics of the Prototropic Reactions of 7-Hydroxyflavylium Photoacids Anchored at an Anionic Micellar Surface

Three water-insoluble, micelle-anchored flavylium salts, 7-hydroxy-3-octyl-flavylium chloride, 4`-hexyl-7-hydroxyflavylium chloride, and 6-hexyl-7-hydroxy-4-methyl-flavylium chloride, have been employed to probe excited-state prototropic reactions in micellar sodium dodecyl sulfate (SDS). In SDS micelles, the fluorescence decays of these three flavylium salts are tetraexponential functions in the pH range from 1.0 to 4.6 at temperatures from 293 to 318 K. The four components of the decays are assigned to Four kinetically coupled excited species in the micelle: specifically, promptly deprotonable (AH(+)*) and nonpromptly deprotonable (AH(h)(+)*) orientations of the acid in the micelle. the base-proton geminate pair (A*center dot center dot center dot H(+)), and the free conjugate base (A*). The initial prompt deprotonation to form the germinate pair occurs at essentially the same rate (k(d) similar to 6-7 x 10(10) s(-1)) for all three photoacids. Recombination of the germinate pair is similar to 3-fold faster than the rate of proton escape from the pair (k(rec) similar to 3 x 10(10) s(-1) and k(diss) similar to 1 x 10(10) s(-1)), corresponding to an intrinsic recombination efficiency of the pair of similar to 75%. Finally, the reprotonation of the short-lived free A* (200-350 ps, depending oil the photoacid) has two components, only one of which depends oil the proton concentration in the intermicellar aqueous phase. Ultrafast transfer of the proton to water and substantial compartmentalization of the photogenerated proton at the micelle surface Oil the picosecond time scale strongly suggest preferential transfer of the proton to preformed hydrogen-bonded water bridges between the photoacid and the anionic headgroups. This localizes the proton in the vicinity of the excited base much more efficiently than ill bulk water, resulting ill the predominance of geminate re reprotonation at the micelle surface.

Temperature Dynamics Investigation At Small And Shallow Lakes Using Hydrodynamic Model

A three-dimensional time-dependent hydrodynamic and heat transport model of Lake Binaba, a shallow and small dam reservoir in Ghana, emphasizing the simulation of dynamics and thermal structure has been developed. Most numerical studies of temperature dynamics in reservoirs are based on one- or two-dimensional models. These models are not applicable for reservoirs characterized with complex flow pattern and unsteady heat exchange between the atmosphere and water surface. Continuity, momentum and temperature transport equations have been solved. Proper assignment of boundary conditions, especially surface heat fluxes, has been found crucial in simulating the lake’s hydrothermal dynamics. This model is based on the Reynolds Average Navier-Stokes equations, using a Boussinesq approach, with a standard k − ε turbulence closure to solve the flow field. The thermal model includes a heat source term, which takes into account the short wave radiation and also heat convection at the free surface, which is function of air temperatures, wind velocity and stability conditions of atmospheric boundary layer over the water surface. The governing equations of the model have been solved by OpenFOAM; an open source, freely available CFD toolbox. As its core, OpenFOAM has a set of efficient C++ modules that are used to build solvers. It uses collocated, polyhedral numerics that can be applied on unstructured meshes and can be easily extended to run in parallel. A new solver has been developed to solve the hydrothermal model of lake. The simulated temperature was compared against a 15 days field data set. Simulated and measured temperature profiles in the probe locations show reasonable agreement. The model might be able to compute total heat storage of water bodies to estimate evaporation from water surface.

Forecasting multivariate time series under present-value-model short- and long-run co-movement restrictions

It is well known that cointegration between the level of two variables (e.g. prices and dividends) is a necessary condition to assess the empirical validity of a present-value model (PVM) linking them. The work on cointegration,namelyon long-run co-movements, has been so prevalent that it is often over-looked that another necessary condition for the PVM to hold is that the forecast error entailed by the model is orthogonal to the past. This amounts to investigate whether short-run co-movememts steming from common cyclical feature restrictions are also present in such a system. In this paper we test for the presence of such co-movement on long- and short-term interest rates and on price and dividend for the U.S. economy. We focuss on the potential improvement in forecasting accuracies when imposing those two types of restrictions coming from economic theory.

Otimização de alavancagem e gestão de risco em estratégias long-short

Alavancagem em hedge funds tem preocupado investidores e estudiosos nos últimos anos. Exemplos recentes de estratégias desse tipo se mostraram vantajosos em períodos de pouca incerteza na economia, porém desastrosos em épocas de crise. No campo das finanças quantitativas, tem-se procurado encontrar o nível de alavancagem que otimize o retorno de um investimento dado o risco que se corre. Na literatura, os estudos têm se mostrado mais qualitativos do que quantitativos e pouco se tem usado de métodos computacionais para encontrar uma solução. Uma forma de avaliar se alguma estratégia de alavancagem aufere ganhos superiores do que outra é definir uma função objetivo que relacione risco e retorno para cada estratégia, encontrar as restrições do problema e resolvê-lo numericamente por meio de simulações de Monte Carlo. A presente dissertação adotou esta abordagem para tratar o investimento em uma estratégia long-short em um fundo de investimento de ações em diferentes cenários: diferentes formas de alavancagem, dinâmicas de preço das ações e níveis de correlação entre esses preços. Foram feitas simulações da dinâmica do capital investido em função das mudanças dos preços das ações ao longo do tempo. Considerou-se alguns critérios de garantia de crédito, assim como a possibilidade de compra e venda de ações durante o período de investimento e o perfil de risco do investidor. Finalmente, estudou-se a distribuição do retorno do investimento para diferentes níveis de alavancagem e foi possível quantificar qual desses níveis é mais vantajoso para a estratégia de investimento dadas as restrições de risco.

Forecasting multivariate time series under present-value-model short- and long-run co-movement restrictions

Using a sequence of nested multivariate models that are VAR-based, we discuss different layers of restrictions imposed by present-value models (PVM hereafter) on the VAR in levels for series that are subject to present-value restrictions. Our focus is novel - we are interested in the short-run restrictions entailed by PVMs (Vahid and Engle, 1993, 1997) and their implications for forecasting. Using a well-known database, kept by Robert Shiller, we implement a forecasting competition that imposes different layers of PVM restrictions. Our exhaustive investigation of several different multivariate models reveals that better forecasts can be achieved when restrictions are applied to the unrestricted VAR. Moreover, imposing short-run restrictions produces forecast winners 70% of the time for the target variables of PVMs and 63.33% of the time when all variables in the system are considered.

Short Lyapunov time: a method for identifying confined chaos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

CHARGED PARTICLE DYNAMICS IN TIME DEPENDENT MAGNETIC FIELDS

In this work we study the behavior of charged particles immersed in a peculiar configuration of magnetic fields, which has a main constant field B(0) and a superimposed, transversal perturbation field B(1) sin(omega(p)t), with B(1) << B(0). By taking Cartesian coordinates and placing B(0) along the z axis and B(1) sin (omega(p)t) on the x axis, an analytical solution for y(t) may be obtained by solving an integrodifferential equation. Besides, the solution z(t) also exhibits a very interesting dynamics, and the entire system is conditioned by resonances between the particle orbit frequencies and the frequency of the magnetic transversal perturbation, omega(p). In this work we also discuss numerical simulations for the related particle trajectories, as well as potential applications in the context of separation phenomena.

Coordinate and time-dependent diffusion dynamics in protein folding

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Noncommutative fluid dynamics in the Snyder space-time

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Scaling dynamics for a particle in a time-dependent potential well

Some dynamical properties for a classical particle confined in an infinitely deep box of potential containing a periodically oscillating square well are studied. The dynamics of the system is described by using a two-dimensional non-linear area-preserving map for the variables energy and time. The phase space is mixed and the chaotic sea is described using scaling arguments. Scaling exponents are obtained as a function of all the control parameters, extending the previous results obtained in the literature. (c) 2012 Elsevier B.V. All rights reserved.

Recurrence of particles in static and time varying oval billiards

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

CRITICAL EXPONENTS and SCALING PROPERTIES FOR THE CHAOTIC DYNAMICS of A PARTICLE IN A TIME-DEPENDENT POTENTIAL BARRIER

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dynamics in discrete phase spaces and time interval operators

The von Neumann-Liouville time evolution equation is represented in a discrete quantum phase space. The mapped Liouville operator and the corresponding Wigner function are explicitly written for the problem of a magnetic moment interacting with a magnetic field and the precessing solution is found. The propagator is also discussed and a time interval operator, associated to a unitary operator which shifts the energy levels in the Zeeman spectrum, is introduced. This operator is associated to the particular dynamical process and is not the continuous parameter describing the time evolution. The pair of unitary operators which shifts the time and energy is shown to obey the Weyl-Schwinger algebra. (C) 1999 Elsevier B.V. B.V. All rights reserved.