Giant electrocaloric effect around Tc_c

We use molecular dynamics with a first-principles-based shell model potential to study the electrocaloric effect (ECE) in lithium niobate, LiNbO$_3$, and find a giant electrocaloric effect along a line passing through the ferroelectric transition. With applied electric field, a line of maximum ECE passes through the zero field ferroelectric transition, continuing along a Widom line at high temperatures with increasing field, and along the instability that leads to homogeneous ferroelectric switching below $T_c$ with an applied field antiparallel to the spontaneous polarization. This line is defined as the minimum in the inverse capacitance under applied electric field. We investigate the effects of pressure, temperature and applied electric field on the ECE. The behavior we observe in LiNbO$_3$ should generally apply to ferroelectrics; we therefore suggest that the operating temperature for refrigeration and energy scavenging applications should be above the ferroelectric transition region to obtain large electrocaloric response. We find a relationship among $T_c$, the Widom line and homogeneous switching that should be universal among ferroelectrics, relaxors, multiferroics, and the same behavior should be found under applied magnetic fields in ferromagnets.Comment: 5 page

Does price matter? Overseas students In UK higher education

This paper explores the determinants of the choice of UK universities by overseas undergraduate applicants. We use data on overseas applicants in Business Studies and Engineering from 2002 to 2007, to 97 UK universities. Estimating using a Hausman-Taylor model to control for the possible correlation between our explanatory variables and unobservable university level effects, we find that the fees charged may influence the application decision of some students, but that any relationship between levels of fees and applications is nonlinear. The quality of education provided is positively and significantly related to the number of applications. Proximity to London and the existing popularity of a university among home applicants, are also significant predictors of university applications

Patent Value and Citations: Creative Destruction or Strategic Disruption?

Prior work suggests that more valuable patents are cited more and this view has become standard in the empirical innovation literature. Using an NPE-derived dataset with patent-specific revenues we find that the relationship of citations to value in fact forms an inverted-U, with fewer citations at the high end of value than in the middle. Since the value of patents is concentrated in those at the high end, this is a challenge to both the empirical literature and the intuition behind it. We attempt to explain this relationship with a simple model of innovation, allowing for both productive and strategic patents. We find evidence of greater use of strategic patents where it would be most expected: among corporations, in fields of rapid development, in more recent patents and where divisional and continuation applications are employed. These findings have important implications for our basic understanding of growth, innovation, and intellectual property policy

Towards the Intersection Theory on Hurwitz Spaces

Moduli spaces of algebraic curves and closely related to them Hurwitz spaces, that is, spaces of meromorphic functions on the curves, arise naturally in numerous problems of algebraic geometry and mathematical physics, especially in relationship with the string theory and Gromov--Witten invariants. In particular, the classical Hurwitz problem about enumeration of topologically distinct ramified coverings of the sphere with prescribed ramification type reduces to the study of geometry and topology of these spaces. The cohomology rings of such spaces are complicated even in the simplest cases of rational curves and functions. However, the cohomology classes that are the most important from the point of view of applications (namely, the classes Poincar\'e dual to the strata of functions with given singularities) can be expressed in terms of relatively simple ``basic'' classes (which are, in a sense, tautological). The aim of the present paper is to identify these basic classes, to describe relations among them, and to find expressions for the strata in terms of these classes. Our approach is based on R. Thom's theory of universal polynomials of singularities, which has been extended to the case of multisingularities by the first author. Although the general Hurwitz problem still remains open, our approach allows one to achieve a significant progress in its solution, as well as in the understanding of the geometry and topology of Hurwitz spaces.Comment: 29 pages, AMSTe

A Stochastic Team Formation Approach for Collaborative Mobile Crowdsourcing

Mobile Crowdsourcing (MCS) is the generalized act of outsourcing sensing tasks, traditionally performed by employees or contractors, to a large group of smart-phone users by means of an open call. With the increasing complexity of the crowdsourcing applications, requesters find it essential to harness the power of collaboration among the workers by forming teams of skilled workers satisfying their complex tasks' requirements. This type of MCS is called Collaborative MCS (CMCS). Previous CMCS approaches have mainly focused only on the aspect of team skills maximization. Other team formation studies on social networks (SNs) have only focused on social relationship maximization. In this paper, we present a hybrid approach where requesters are able to hire a team that, not only has the required expertise, but also is socially connected and can accomplish tasks collaboratively. Because team formation in CMCS is proven to be NP-hard, we develop a stochastic algorithm that exploit workers knowledge about their SN neighbors and asks a designated leader to recruit a suitable team. The proposed algorithm is inspired from the optimal stopping strategies and uses the odds-algorithm to compute its output. Experimental results show that, compared to the benchmark exponential optimal solution, the proposed approach reduces computation time and produces reasonable performance results.Comment: This paper is accepted for publication in 2019 31st International Conference on Microelectronics (ICM

Entanglement, randomness and chaos

Entanglement is not only the most intriguing feature of quantum mechanics, but also a key resource in quantum information science. The entanglement content of random pure quantum states is almost maximal; such states find applications in various quantum information protocols. The preparation of a random state or, equivalently, the implementation of a random unitary operator, requires a number of elementary one- and two-qubit gates that is exponential in the number n_q of qubits, thus becoming rapidly unfeasible when increasing n_q. On the other hand, pseudo-random states approximating to the desired accuracy the entanglement properties of true random states may be generated efficiently, that is, polynomially in n_q. In particular, quantum chaotic maps are efficient generators of multipartite entanglement among the qubits, close to that expected for random states. This review discusses several aspects of the relationship between entanglement, randomness and chaos. In particular, I will focus on the following items: (i) the robustness of the entanglement generated by quantum chaotic maps when taking into account the unavoidable noise sources affecting a quantum computer; (ii) the detection of the entanglement of high-dimensional (mixtures of) random states, an issue also related to the question of the emergence of classicality in coarse grained quantum chaotic dynamics; (iii) the decoherence induced by the coupling of a system to a chaotic environment, that is, by the entanglement established between the system and the environment.Comment: Review paper, 40 pages, 7 figures, added reference

THE EFFECT OF HEALTH IT INVESTMENTS ON REGIONAL HEALTH CARE COSTS

This paper analyzes the relationship between health IT investments and regional health care costs. We focus on the regional level effects, which take into account externalities that arise from patient mobility. We find that the relationship between health IT and costs are stronger at a regional level than hospital level, confirming the presence of externality of health IT investments. This finding has important implications: it suggests that hospital level analysis underestimates the benefits of health IT investments and can lead to suboptimal investment decision from the society´s point of view. We also find that cost reduction impacts of health IT investment are higher over the long term. We present evidence that advanced IT applications that enable within hospital communication are more beneficial in more urban areas. Higher software integration among the adopting hospitals further decreases the health care costs in the area by enabling electronic medical record sharing. In addition, we show that not all hospitals have to make same level of IT investment to obtain optimal reductions in health care costs. Instead, having some leading hospitals in health IT investments can be more beneficial

El impacto de la mensajería instantánea en los estudiantes en forma de estrés y ansiedad para el aprendizaje: análisis empírico

La relación entre educación y TIC es especialmente dinámica en el siglo XXI, sobre todo a raíz de la aparición y popularización de las aplicaciones telefónicas móviles, encabezadas por la mensajería instantánea (WhatsApp o BlackBerry Messenger). La difusión de estas aplicaciones entre los estudiantes puede generar conductas adictivas o causantes de estrés. Ello puede afectar al aprendizaje. En este estudio se pretende detectar si existe adicción a estas aplicaciones, y averiguar si provocan estrés o ansiedad en los jóvenes. Tras la encuesta realizada a 247 jóvenes, se concluye que el uso de estas aplicaciones produce estrés y ansiedad por la necesidad de recibir respuesta inmediata a los mensajes. También se observa cierto grado de adicción a estas aplicaciones.The relationship between education and ICT is particularly dynamic in the XXI century, especially following the emergence and popularization of mobile phone applications, led by instant messaging (WhatsApp or BlackBerry Messenger). The spread of these applications can generate among students addictive or stressors behaviors. This can affect learning. This study aims to determine if there is addiction to these applications, and find out if they cause stress or anxiety in young people. After the survey of 247 young people, it is concluded that the use of these applications creates stress and anxiety about the need for immediate response to messages. Degree of addiction is also observed for these applications