Compact set of invariants characterizing graph states of up to eight qubits

The set of entanglement measures proposed by Hein, Eisert, and Briegel for n-qubit graph states [Phys. Rev. A 69, 062311 (2004)] fails to distinguish between inequivalent classes under local Clifford operations if n > 6. On the other hand, the set of invariants proposed by van den Nest, Dehaene, and De Moor (VDD) [Phys. Rev. A 72, 014307 (2005)] distinguishes between inequivalent classes, but contains too many invariants (more than 2 10^{36} for n=7) to be practical. Here we solve the problem of deciding which entanglement class a graph state of n < 9 qubits belongs to by calculating some of the state's intrinsic properties. We show that four invariants related to those proposed by VDD are enough for distinguishing between all inequivalent classes with n < 9 qubits.Comment: REVTeX4, 9 pages, 1 figur

Double acid etching treatment of dental implants for enhanced biological properties

Background: The topographical features on the surface of dental implants have been considered as a critical parameter for enhancing the osseointegration of implants. In this work, we proposed a surface obtained by a combination of shot blasting and double acid etching. The double acid etching was hypothesized to increase the submicron topography and hence further stimulate the biological properties of the titanium implant. Methods: The topographical features (surface roughness and real surface area), wettability and surface chemical composition were analyzed. Results: The results showed that the proposed method produced a dual roughness, mainly composed of randomly distributed peaks and valleys with a superimposed nanoroughness, and hence with an increased specific surface area. Despite the fact that the proposed method does not introduce significant chemical changes, this treatment combination slightly increased the amount of titanium available on the surface, reducing potential surface contaminants. Furthermore, the surface showed increased contact angle values demonstrating an enhanced hydrophobicity on the surface. The biological behavior of the implants was then assessed by culturing osteoblast-like cells on the surface, showing enhanced osteoblast adhesion, proliferation and differentiation on the novel surface. Conclusions: Based on these results, the described surface with dual roughness obtained by double acid etching may be a novel route to obtain key features on the surface to enhance the osseointegration of the implant. Our approach is a simple method to obtain a dual roughness that mimics the bone structure modified by osteoclasts and increases surface area, which enhances osseointegration of dental implants.Peer ReviewedPostprint (author's final draft

On the global hydration kinetics of tricalcium silicate cement

We reconsider a number of measurements for the overall hydration kinetics of tricalcium silicate pastes having an initial water to cement weight ratio close to 0.5. We find that the time dependent ratio of hydrated and unhydrated silica mole numbers can be well characterized by two power-laws in time, $x/(1-x)\sim (t/t_x)^\psi$. For early times $t < t_x$ we find an `accelerated' hydration ($\psi = 5/2$) and for later times $t > t_x$ a `deaccelerated' behavior ($\psi = 1/2$). The crossover time is estimated as $t_x \approx 16 hours$. We interpret these results in terms of a global second order rate equation indicating that (a) hydrates catalyse the hydration process for $t<t_x$, (b) they inhibit further hydration for $t > t_x$ and (c) the value of the associated second order rate constant is of magnitude 6x10^{-7} - 7x10^{-6} liter mol^{-1} s^{-1}. We argue, by considering the hydration process actually being furnished as a diffusion limited precipitation that the exponents $\psi = 5/2$ and $\psi = 1/2$ directly indicate a preferentially `plate' like hydrate microstructure. This is essentially in agreement with experimental observations of cellular hydrate microstructures for this class of materials.Comment: RevTeX macros, 6 pages, 4 postscript figure

Percepciones de profesores y alumnos de E.S.O sobre la disciplina en el aula

La manera cómo perciben y representan los problemas de disciplina profesores y alumnos es una de las claves que explica lo que es en realidad y cómo se vive la disciplina en el aula. Nuestro estudio se propone analizar las discordancias entre las percepciones declaradas por profesores y alumnos sobre cuáles son y cómo se tratan los conflictos de disciplina en el aula. Con este propósito se han recogido datos de una muestra de 1.389 estudiantes y sus 170 docentes de E.S.O. sobre sus respectivas percepciones acerca del tema. Los resultados ponen de manifiesto diferencias significativas, aunque moderadas, en la percepción de comportamientos castigados. Pero dichas diferencias se acentúan al considerar el tipo de intervención realizada por los profesoresThe way discipline problems are perceived and represented by teachers and students is, probably, one of the main cues to explain what classroom discipline is and how it is felt by them. This study focuses on the discrepancies in the perceptions of both teachers and students about which are the main behavioural problems in the classroom and how teachers cope with them. With that aim, data has been collected from a sample of 1,389 students and 170 teachers, from E.S.O. level (secondary obligatory education: ages 12 to 16). A questionnaire has been administrated to asses their perceptions about the topic. Results show significant differences, although of moderate intensity, in the behaviours that are perceived to be punished. But these differences become quite intense when considering the kind of response provided by teacher

Effects of the PowerPoint methodology on content learning

Purpose: This study focuses on whether the use of PowerPoint technology as the main resource to convey information has an effect on students' learning compared with classes taught without this technology. Design/methodology/approach: The sample consisted of 205 psychology students, divided into four groups, who were taught an ordinary Educational Psychology lesson. In two of these groups, a PowerPoint presentation (19 slides) was used to deliver the contents, while in the other two the same contents were delivered by the professors with the only aid of the blackboard. After the lesson, students' learning was assessed by means of a questionnaire consisting of ten multiple-choice items. Findings: Results showed significant differences (p < 0.000), with the scores of the groups without PowerPoint an average of 19% higher than the groups with PowerPoint. Originality/value: The use of technology can have a very positive influence on learning, provided that its use fits the circumstances inherent in learning Objeto: Este estudio se centra en los efectos del PowerPoint como medio principal de transmisión de contenidos en el aprendizaje del alumnado, comparándolos con el aprendizaje obtenido a partir de clases en las que no se usa esta tecnología.Diseño/metodología/enfoque: Se utilizó una muestra de 205 estudiantes de Psicología, repartidos en cuatro grupos, tomando como situación de aprendizaje una de las clases ordinarias de la materia de Psicología de la Educación. En dos de estos grupos se utilizó una presentación de 19 diapositivas PowerPoint para presentar los contenidos, mientras que en los otros dos grupos estos mismos contenidos fueron presentados por los profesores, con la única ayuda de la pizarra. Después de la clase, los asistentes fueron evaluados mediante un cuestionario de diez preguntas de elección múltiple. Resultados: Los resultados mostraron diferencias significativa (p < .000), siendo las puntuaciones medias de los grupos sin PowerPoint un 19% superiores a las de los grupos que recibieron la clase con esta tecnología. Originalidad/valor añadido: El uso de la tecnología puede tener una influencia muy positiva en el aprendizaje; siempre que su uso se ajuste a las circunstancias inherentes del mism

Ion Release from Dental Implants, Prosthetic Abutments and Crowns under Physiological and Acidic Conditions

Ion release from dental implants and prosthetic restoration can affect osteointegration and implant viability over a long period of time. Therefore, the aim of this study was to study the ion release from implants and crowns, with and without intermediate anodized abutments, in two different media, simulating clinical conditions. The implants, intermediate prosthetic abutments and Cr&ndash;Co crowns were divided into two groups depending on the media: Hanks&rsquo; solution and 1% lactic acid, simulating body fluids and microbiologically conditioned fluids, respectively. The study followed the ISO 10271:2011 and 10993-15:2000 standards modified to simulate the replacement of fluids in the oral environment. The ions&rsquo; release was measured by inductively coupled plasma mass spectroscopy (ICP-EOS), and only aluminum, chromium, cobalt, titanium and vanadium were identified. Ion concentration was higher in lactic acid than in Hanks&rsquo; solution at all time points (p &lt; 0.05). Only vanadium showed a very low ion release in lactic acid, with no statistically significant differences from the ion release in Hanks&rsquo; solution (p = 0.524). Both anodized abutments and the immersion medium influenced the release of ions and affected the corrosion of these structures. The presence of an intermediate anodized abutment also affected ion release, as the level of ions was lower in groups with this component

Percepciones de profesores y alumnos de E.S.O sobre la disciplina en el aula

La manera cómo perciben y representan los problemas de disciplina profesores y alumnos es una de las claves que explica lo que es en realidad y cómo se vive la disciplina en el aula. Nuestro estudio se propone analizar las discordancias entre las percepciones declaradas por profesores y alumnos sobre cuáles son y cómo se tratan los conflictos de disciplina en el aula. Con este propósito se han recogido datos de una muestra de 1.389 estudiantes y sus 170 docentes de E.S.O. sobre sus respectivas percepciones acerca del tema. Los resultados ponen de manifiesto diferencias significativas, aunque moderadas, en la percepción de comportamientos castigados. Pero dichas diferencias se acentúan al considerar el tipo de intervención realizada por los profesoresThe way discipline problems are perceived and represented by teachers and students is, probably, one of the main cues to explain what classroom discipline is and how it is felt by them. This study focuses on the discrepancies in the perceptions of both teachers and students about which are the main behavioural problems in the classroom and how teachers cope with them. With that aim, data has been collected from a sample of 1,389 students and 170 teachers, from E.S.O. level (secondary obligatory education: ages 12 to 16). A questionnaire has been administrated to asses their perceptions about the topic. Results show significant differences, although of moderate intensity, in the behaviours that are perceived to be punished. But these differences become quite intense when considering the kind of response provided by teacher

Effects of the PowerPoint methodology on content learning

Purpose: This study focuses on whether the use of PowerPoint technology as the main resource to convey information has an effect on students' learning compared with classes taught without this technology. Design/methodology/approach: The sample consisted of 205 psychology students, divided into four groups, who were taught an ordinary Educational Psychology lesson. In two of these groups, a PowerPoint presentation (19 slides) was used to deliver the contents, while in the other two the same contents were delivered by the professors with the only aid of the blackboard. After the lesson, students' learning was assessed by means of a questionnaire consisting of ten multiple-choice items. Findings: Results showed significant differences (p < 0.000), with the scores of the groups without PowerPoint an average of 19% higher than the groups with PowerPoint. Originality/value: The use of technology can have a very positive influence on learning, provided that its use fits the circumstances inherent in learning Objeto: Este estudio se centra en los efectos del PowerPoint como medio principal de transmisión de contenidos en el aprendizaje del alumnado, comparándolos con el aprendizaje obtenido a partir de clases en las que no se usa esta tecnología.Diseño/metodología/enfoque: Se utilizó una muestra de 205 estudiantes de Psicología, repartidos en cuatro grupos, tomando como situación de aprendizaje una de las clases ordinarias de la materia de Psicología de la Educación. En dos de estos grupos se utilizó una presentación de 19 diapositivas PowerPoint para presentar los contenidos, mientras que en los otros dos grupos estos mismos contenidos fueron presentados por los profesores, con la única ayuda de la pizarra. Después de la clase, los asistentes fueron evaluados mediante un cuestionario de diez preguntas de elección múltiple. Resultados: Los resultados mostraron diferencias significativa (p < .000), siendo las puntuaciones medias de los grupos sin PowerPoint un 19% superiores a las de los grupos que recibieron la clase con esta tecnología. Originalidad/valor añadido: El uso de la tecnología puede tener una influencia muy positiva en el aprendizaje; siempre que su uso se ajuste a las circunstancias inherentes del mism