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Electron–acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron a

Persistence of embedded eigenvalues

We consider conditions under which an embedded eigenvalue of a self-adjoint operator remains embedded under small perturbations. In the case of a simple eigenvalue embedded in continuous spectrum of multiplicity m

The interaction between cyanobacteria and zooplankton in a more eutrophic world

As blooms of cyanobacteria expand and intensify in freshwater systems globally, there is increasing interest in their ecological effects. In addition to being public health hazards, cyanobacteria have long been considered a poor quality food for key zooplankton grazers that link phytoplankton to higher trophic levels. While past laboratory studies have found negative effects of nutritional constra

Infinitely many solutions of a symmetric semilinear elliptic equation on an unbounded domain

We study a semilinear elliptic equation of the form−Δu+u=f(x,u),u∈H^1_0(Ω),wheref is continuous, odd in u and satisfies some (subcritical) growth conditions. The domain Ω⊂R^N is supposed to be an unbounded domain (N≥3). We introduce a class of domains, called strongly asymptotically contractive, and show that for such domains Ω, the equation has infinitely many solutions.

New social movements, the use of ICTs, and their social impact

The following work is an analysis of new social movements and the use of new technologies from the perspective of political philosophy. It stems from the results obtained in the dissertation "New Social Movements and the Use of ICTs: Case Studies," presented at the Universidad Complutense de Madrid as part of the Communication, Social Change and Development program. While it is true that these mov

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

The late Ediacaran–mid Cambrian occurrence s of phosphorites in the wes-tern Mediterranean region (West Gondwana) and southern Sweden (north -west Baltica) are related to the poleward drift of West Gondwana and thenorthern drift of Baltica. As a result, these regions crossed subtropical andtemperate palaeolatitudes of the Southern Hemisphere, in which oceanicupwelling and high organic productivity

Perturbations of embedded eigenvalues for the planar bilaplacian

Operators on unbounded domains may acquire eigenvalues that are embedded in the essential spectrum. Determining the fate of these embedded eigenvalues under small perturbations of the underlying operator is a challenging task, and the persistence properties of such eigenvalues are linked intimately to the multiplicity of the essential spectrum. In this paper, we consider the planar bilaplacian wit

Existence and exponential decay of solutions to a quasilinear thermoelastic plate system

We consider a quasilinear PDE system which models nonlinear vibrations of a thermoelastic plate defined on a bounded domain in R^n, n ≤ 3. Existence of finite energy solutions describing the dynamics of a nonlinear thermoelastic plate is established. In addition asymptotic long time behavior of weak solutions is discussed. It is shown that finite energy solutions decay exponentially to zero with t

Perturbations of embedded eigenvalues for the bilaplacian on a cylinder

Perturbation problems for operators with embedded eigenvalues are generally challenging since the embedded eigenvalues cannot be separated from the rest of the spectrum. In this paper we study a perturbation problem for embedded eigenvalues for the bilaplacian with an added potential, when the underlying domain is a cylinder. We show that the set of nearby potentials, for which a simple embedded e

Reinforcement learning for visual object detection

One of the most widely used strategies for visual object detection is based on exhaustive spatial hypothesis search. While methods like sliding windows have been successful and effective for many years, they are still brute-force, independent of the image content and the visual category being searched. In this paper we present principled sequential models that accumulate evidence collected at a sm