Pricing and Bundling Electronic Information Goods: Field Evidence

Dramatic increases in the capabilities and decreases in the costs of computers and communication networks have fomented revolutionary thoughts in the scholarly publishing community. In one dimension, traditional pricing schemes and product packages are being modified or replaced. We designed and undertook a large-scale field experiment in pricing and bundling for electronic access to scholarly journals: PEAK. We provided Internet-based delivery of content from 1200 Elsevier Science journals to users at multiple campuses and commercial facilities. Our primary research objective was to generate rich empirical evidence on user behavior when faced with various bundling schemes and price structures. In this article we report initial results. We found that although there is a steep initial learning curve, decision-makers rapidly comprehended our innovative pricing schemes. We also found that our novel and flexible "generalized subscription" was successful at balancing paid usage with easy access to a larger body of content than was previously available to participating institutions. Finally, we found that both monetary and non-monetary user costs have a significant impact on the demand for electronic access.

Estructura factorial y consistencia interna de la Escala de Severidad de Fatiga en población colombiana con enfermedades crónicas

El presente estudio de corte psicométrico, tuvo como objetivo analizar la estructura factorial y la consistencia interna versión en español del cuestionario Fatigue Severity Scale (FSS) en población colombiana de enfermos crónicos. Para ello se aplicó el cuestionario a 52 enfermos crónicos de la ciudad de Villavicencio. El análisis factorial denota tres factores: el factor 1 denominado como afectación física, el factor 2 denominado afectación social y finalmente el factor 3 denominado afectación motivacional de la fatiga, que explican el 76,324% de la varianza total acumulada, y un alfa de Cronbach de 870. Los resultados muestran una alta confiabilidad y concordancia en la estructura factorial con la versión original, lo que implica adecuada validez de la prueba en población colombiana de enfermos crónicos.The present study has a psychometric design, with the objective of analyzing the factorial structure and the internal consistency for the Spanish version of the Fatigue Severity Scale (FSS) Questionnaire for Colombian population with chronic disease. Was applied the questionnaire to 52 people with chronic disease in Villavicencio city. The factorial Analysis indicates three factors: Factor 1 named physical affectation, Factor 2 named social affectation and Factor 3 named motivational affectation of the fatigue, where they explain the 76.324% of the total cumulative variance with .870 of Cronbach's Alpha. The results present a high reliability and concordance for the factorial structure with the original version which indicates an adequate validity of the test for Colombian population with chronic disease. © Servicio de Publicaciones - Universidad de Murcia

A class of surfaces with planar lines of curvature

En este articulo estudiamos superficies parametrizadas por líneas de curvatura. Obtenemos una caracterización de una clase de superficies con líneas de curvatura planas, esta caracterización depende de ciertas funciones holomorfas. Presentamos una clase de superficies con dos familias de líneas de curvatura planas, esta clase incluye las superficies de Dupin. También damos algunos ejemplos explícitos.In this paper we study surfaces parameterized by lines of curvature. We obtain a characterization of a class of surfaces with planar lines of curvature, this characterization depend on certain holomorphic function. We present a class of surfaces with two family of planar lines of curvature, this class of surfaces includes the Dupin surfaces. Also, we give explicit examples

Finite-size corrections to scaling of the magnetization distribution in the two-dimensional XY-model at zero temperature

The zero-temperature, classical $XY$-model on an $L \times L$ square-lattice is studied by exploring the distribution $\Phi_L(y)$ of its centered and normalized magnetization $y$ in the large $L$ limit. An integral representation of the cumulant generating function, known from earlier works, is used for the numerical evaluation of $\Phi_L(y)$, and the limit distribution $\Phi_{L \rightarrow \infty} (y) = \Phi_0(y)$ is obtained with high precision. The two leading finite-size corrections $\Phi_L (y) -\Phi_0 (y) \approx a_1(L)\, \Phi_1(y) + a_2(L)\,\Phi_2(y)$ are also extracted both from numerics and from analytic calculations. We find that the amplitude $a_1(L)$ scales as $\ln(L/L_0) /L^2$ and the shape correction function $\Phi_1 (y)$ can be expressed through the low-order derivatives of the limit distribution, $\Phi_1 (y) = [\,y\, \Phi_0 (y) + \Phi'_0 (y)\,]'$. The second finite-size correction has an amplitude $a_2(L)\propto 1/L^2$ and one finds that $a_2\,\Phi_2(y) \ll a_1 \,\Phi_1(y)$ already for small system size ($L> 10$). We illustrate the feasibility of observing the calculated finite-size corrections by performing simulations of the $XY$-model at low temperatures, including $T = 0$

Physical Wigner functions

In spite of their potential usefulness, the characterizations of Wigner functions for Bose and Fermi statistics given by O'Connell and Wigner himself almost thirty years ago has drawn little attention. With an eye towards applications in quantum chemistry, we revisit and reformulate them in a more convenient way.Comment: Latex, 10 page

Hierarchical Spatial Organization of Geographical Networks

In this work we propose the use of a hirarchical extension of the polygonality index as a means to characterize and model geographical networks: each node is associated with the spatial position of the nodes, while the edges of the network are defined by progressive connectivity adjacencies. Through the analysis of such networks, while relating its topological and geometrical properties, it is possible to obtain important indications about the development dynamics of the networks under analysis. The potential of the methodology is illustrated with respect to synthetic geographical networks.Comment: 3 page, 3 figures. A wokring manuscript: suggestions welcome

A methodology for the derivation of unloaded abdominal aortic aneurysm geometry with experimental validation

In this work, we present a novel method for the derivation of the unloaded geometry of an abdominal aortic aneurysm (AAA) from a pressurized geometry in turn obtained by 3D reconstruction of computed tomography (CT) images. The approach was experimentally validated with an aneurysm phantom loaded with gauge pressures of 80, 120, and 140mm Hg. The unloaded phantom geometries estimated from these pressurized states were compared to the actual unloaded phantom geometry, resulting in mean nodal surface distances of up to 3.9% of the maximum aneurysm diameter. An in-silico verification was also performed using a patient-specific AAA mesh, resulting in maximum nodal surface distances of 8 lm after running the algorithm for eight iterations. The methodology was then applied to 12 patient-specific AAA for which their corresponding unloaded geometries were generated in 5-8 iterations. The wall mechanics resulting from finite element analysis of the pressurized (CT image-based) and unloaded geometries were compared to quantify the relative importance of using an unloaded geometry for AAA biomechanics. The pressurized AAA models underestimate peak wall stress (quantified by the first principal stress component) on average by 15% compared to the unloaded AAA models. The validation and application of the method, readily compatible with any finite element solver, underscores the importance of generating the unloaded AAA volume mesh prior to using wall stress as a biomechanical marker for rupture risk assessment