Escalado de actuadores piezoléctricos: comparación con los tradicionales y otras nuevas tecnologías

[EN] Miniaturization is not a logical trend in actuator systems. Unlike actuators, sensors intrinsically perform more efficiently upon miniaturization. This is a logical consequence of the exchange of energy in the transduction process when applying sensors: measurement ideally should not influence the system being measured, thus the minimum exchange of energy is necessary and this intrinsically leads to miniaturization. In actuators, a transduction process is likewise established but the aim is to impose a mechanical state on a system. It is of particular interest not having this state influenced by perturbations, thus there are strong requirements on power delivered by the actuator. In view of current trends towards miniaturization, it is worth inquiring how the performance of piezoelectric actuators is affected by reducing their size. We are not concerned here with the domain of micro-actuators, i.e. actuators with sizes in the micrometer range. The analysis in this paper focuses on studying how four useful parameters for describing the performance of actuators are influenced by miniaturization: resonance frequency, force density, response time (bandwidth), stroke and energy density per cycle. In so doing, the analysis is restricted to non resonant piezoelectric actuators, i.e. stack, multimorph and inchworm actuators, but reference to other piezoelectric, emerging and traditional actuators is included for comparison.[ES] La miniaturización de los dispositivos actuadores no es una tendenca lógica de su naturaleza de operación. Al contrario que los actuadores, los sensores si presentan esta tendencia a la miniaturización fundamentada en la naturaleza de su operación: dado que en el proceso de medida el intercambio energético debe ser mínimo para no afectar el proceso de medida, cuanto menor sea el sensor menor será también su efecto sobre la medición. En el caso de los actuadores el objetivo es el opuesto, se pretende imponer el estado mecánico de un sistema y que este estado no sea perturbado por agentes externos de forma que los requisitos sobre la potencia del actuador son estrictos. En vista de la tendencia actual a la miniaturización de las aplicaciones, conviene preguntarse como se ven afectadas las características de operación de los actuadores cuando son miniaturizados. El análisis presentado en este trabajo se centra en determinar como evolucionan las características principales de los actuadores (frecuencia de resonancia, densidad de fuerza, tiempo de respuesta, máximo desplazamiento y densidad de energía por ciclo) al ser miniaturizados. El análisis se restringe a actuadores piezoelectricos no resonantes, en concreto multicapa, multimorfos y cíclicos, pero se ponen en contexto con otros actuadores piezoeléctricos, con otras tecnologías emergentes y con tecnologías tradicionales.Peer reviewe

Annual variation in the levels of transcripts of sex-specific genes in the mantle of the common mussel, Mytilus edulis

Mytilus species are used as sentinels for the assessment of environmental health but sex or stage in the reproduction cycle is rarely considered even though both parameters are likely to influence responses to pollution. We have validated the use of a qPCR assay for sex identification and related the levels of transcripts to the reproductive cycle. A temporal study of mantle of Mytilus edulis found transcripts of male-specific vitelline coat lysin (VCL) and female-specific vitelline envelope receptor for lysin (VERL) could identify sex over a complete year. The levels of VCL/VERL were proportional to the numbers of sperm/ova and are indicative of the stage of the reproductive cycle. Maximal levels of VCL and VERL were found in February 2009 declining to minima between July - August before increasing and re-attaining a peak in February 2010. Water temperature may influence these transitions since they coincide with minimal water temperature in February and maximal temperature in August. An identical pattern of variation was found for a cryptic female-specific transcript (H5) but a very different pattern was observed for oestrogen receptor 2 (ER2). ER2 varied in a sex-specific way with male > female for most of the cycle, with a female maxima in July and a male maxima in December. Using artificially spawned animals, the transcripts for VCL, VERL and H5 were shown to be present in gametes and thus their disappearance from mantle is indicative of spawning. VCL and VERL are present at equivalent levels in February and July-August but during gametogenesis (August to January) and spawning (March to June) VCL is present at lower relative amounts than VERL. This may indicate sex-specific control mechanisms for these processes and highlight a potential pressure point leading to reduced reproductive output if environmental factors cause asynchrony to gamete maturation or release

Parasites in Paraguay: An Analysis of the Presentation and Management of Intestinal Parasites by Short-Term Medical Mission Volunteers in Paraguay

Introduction. International medical aid in the form of short-term medical missions (STTMs) receives more than $250 million in annual donations. Needs assessments prior to the STTM and outcomes analysis for improvement are often lacking. Objective. Describe the patient population attended to during a one-week STTM in Paraguay, South America, while examining “parasites” as a presenting concern, as a diagnosis by the providers, and the prescription of antiparasitic treatment. This analysis identified variance in intestinal parasite presentation and management by age, gender, and location. The administration frequency of antiparasitic medication was considered as prophylactic versus disease-treatment based. Methods. This study was a chart review of de-identified clinic records from a temporary primary care clinic in the Capital District, Paraguay, in June, 2011. Results. Thirty percent of patients presented with “parasites,” most prevalent among females and adults (p = 0.0520 and p = 0.0730, respectively). Forty-six percent of patients were diagnosed with “parasites” and 51% were prescribed antiparasitic medication. Females more frequently received antiparasitic medication (p = 0.0660). Seventy-eight percent of patients were indicated for prophylactic antiparasitic administration; only 48% received medication. Eighty-eight percent of patients indicated for antiparasitic administration (either prophylactically or by diagnosis) received medication. Conclusion. Antiparasitic medication prescription tended toward treating newly diagnosed clinical disease, as opposed to broad prophylactic administration of antiparasitic medication to at-risk populations. Future STMMs should focus on an approach to the prevention, treatment, and eradication of intestinal parasites via education, improved sanitation, and longitudinal presence in conjunction with local medical infrastructure

Finite flavour groups of fermions

We present an overview of the theory of finite groups, with regard to their application as flavour symmetries in particle physics. In a general part, we discuss useful theorems concerning group structure, conjugacy classes, representations and character tables. In a specialized part, we attempt to give a fairly comprehensive review of finite subgroups of SO(3) and SU(3), in which we apply and illustrate the general theory. Moreover, we also provide a concise description of the symmetric and alternating groups and comment on the relationship between finite subgroups of U(3) and finite subgroups of SU(3). Though in this review we give a detailed description of a wide range of finite groups, the main focus is on the methods which allow the exploration of their different aspects.Comment: 89 pages, 6 figures, some references added, rearrangement of part of the material, section on SU(3) subgroups substantially extended, some minor revisions. Version for publication in J. Phys. A. Table 12 corrected to match eq.(256), table 14 and eq.(314) corrected to match the 2-dimensional irreps defined on p.6

The nuclear receptors of Biomphalaria glabrata and Lottia gigantea: Implications for developing new model organisms

© 2015 Kaur et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedNuclear receptors (NRs) are transcription regulators involved in an array of diverse physiological functions including key roles in endocrine and metabolic function. The aim of this study was to identify nuclear receptors in the fully sequenced genome of the gastropod snail, Biomphalaria glabrata, intermediate host for Schistosoma mansoni and compare these to known vertebrate NRs, with a view to assessing the snail's potential as a invertebrate model organism for endocrine function, both as a prospective new test organism and to elucidate the fundamental genetic and mechanistic causes of disease. For comparative purposes, the genome of a second gastropod, the owl limpet, Lottia gigantea was also investigated for nuclear receptors. Thirty-nine and thirty-three putative NRs were identified from the B. glabrata and L. gigantea genomes respectively, based on the presence of a conserved DNA-binding domain and/or ligand-binding domain. Nuclear receptor transcript expression was confirmed and sequences were subjected to a comparative phylogenetic analysis, which demonstrated that these molluscs have representatives of all the major NR subfamilies (1-6). Many of the identified NRs are conserved between vertebrates and invertebrates, however differences exist, most notably, the absence of receptors of Group 3C, which includes some of the vertebrate endocrine hormone targets. The mollusc genomes also contain NR homologues that are present in insects and nematodes but not in vertebrates, such as Group 1J (HR48/DAF12/HR96). The identification of many shared receptors between humans and molluscs indicates the potential for molluscs as model organisms; however the absence of several steroid hormone receptors indicates snail endocrine systems are fundamentally different.The National Centre for the Replacement, Refinement and Reduction of Animals in Research, Grant Ref:G0900802 to CSJ, LRN, SJ & EJR [www.nc3rs.org.uk]

The Evolution of Bat Vestibular Systems in the Face of Potential Antagonistic Selection Pressures for Flight and Echolocation

PMCID: PMC3634842This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Principles of Catholic Social Teaching, Critical Pedagogy, and the Theory of Intersectionality: An Integrated Framework to Examine the Roles of Social Status in the Formation of Catholic Teachers

This article discusses the relevance of an analytic framework that integrates principles of Catholic social teaching, critical pedagogy, and the theory of intersectionality to explain attitudes toward marginalized youth held by Catholic students preparing to become teachers. The framework emerges from five years of action research data collected in Foundations of American Education classes in a teacher education program of a Mid-Atlantic Catholic Liberal Arts University. The authors propose new directions for research on Catholic schools and suggest that the gaps between espoused values and practices in Catholic schools as identified by researchers over the last decade might be more readily redressed in teacher education programs in Catholic universities and colleges where the cycle of elitism may be recognized, taught, and transformed in the very formation of future teachers. Résumé Principes de la doctrine sociale catholique, pédagogie critique et théorie de l’intersectionalité : cadre intégré permettant l’examen des rôles du statut social dans la formation des enseignants catholiques Cet article traite de la pertinence d’un cadre analytique intégrant les principes de la doctrine sociale catholique, la pédagogie critique et la théorie de l’intersectionalité pour expliquer les attitudes vis-à-vis des jeunes marginalisés adoptées par les étudiants catholiques qui se préparent à devenir enseignant. Ce cadre est le fruit de cinq années de données de recherche action recueillies auprès des Fondations des cours d’éducation américaine dans le programme de formation des professeurs de l’université Mid-Atlantic Catholic Liberal Arts. Les auteurs proposent de nouvelles pistes de recherche sur les écoles catholiques et suggèrent que le fossé existant entres les valeurs et pratiques embrassées par les écoles catholiques, telles qu’elles ont été identifiées par les chercheurs au cours de la dernière décennie, peut être plus facilement comblé dans les programmes de formation des professeurs des universités et établissement supérieurs catholiques, où le cycle de l’élitisme est susceptible d’être reconnu, enseigné et transformé dans la formation même reçue par les futurs enseignants. Resumen Principios de la doctrina social católica, la pedagogía crítica y la teoría de interseccionalidad: un marco integrado para examinar los roles del estatus social en la formación de los profesores católicos Este artículo discute la relevancia de un marco analítico que integra los principios de las enseñanzas católicas, la crítica pedagógica y la teoría de interseccionalidad para explicar actitudes hacia los jóvenes marginados mostradas por estudiantes católicos que se preparan para ser profesores. El marco emerge tras cinco años de recopilación de información bajo investigación-acción en clases de Foundations of American Education, en un programa de educación de profesores de una universidad de artes liberales católica del Atlántico Medio. El autor propone nuevas direcciones para la investigación en escuelas católicas y sugiere que las distancias entre los valores abrazados y las prácticas de las escuelas católicas, tal y como investigadores han identificado en la última década, podrían redirigirse más fácilmente en programas de formación del profesorado en universidades y escuelas universitarias católicas en las que el ciclo del elitismo puede reconocerse, enseñarse y transformarse en la misma formación de futuros profesores

Structural health monitoring of inland navigation infrastructure

The inland navigation system in the U.S. is a civil infrastructure network that relies on the performance of a vast array of infrastructure assets scattered across the nation to function successfully. The system is critical to the U.S. economy, allowing the transportation of billions of dollars in goods annually. The primary infrastructure assets of the inland navigation system are locks and dams, which are structures that allow vessels to traverse inland waterways. Of all the components of locks and dams, the gates are the weak links and are the primary cause of closures and downtime on the inland navigation system. The closure of a lock and dam can have significant impacts to the economy, because traffic will be unable to move on the river and goods will remain stalled on the waterways. Inspection of lock and dam gates is expensive, generally requiring the complete closure of the site, and occurs relatively infrequently. Thus, lock gates are generally maintained in a reactive, manner, meaning they are operated until something breaks, at which time a portion of the inland navigation system is shut down for emergency repairs. The research presented herein addresses the difficulty in inspection of lock gates by developing a structural health monitoring (SHM) system that can be used by the stakeholders of inland navigation infrastructure to obtain the necessary information to assess the integrity and condition of their structures continuously. While SHM is being increasingly implemented on civil infrastructure, such as framed buildings and bridges, research into the application of SHM on navigation infrastructure is lacking. To accomplish the goal of developing an SHM system for navigation infrastructure, this research focuses on development of methods for the detection and assessment of several critical problems common to lock and dam gates, with emphasis given to the most common gates used in the U.S.; miter gates and Tainter gates. The layout of this dissertation is as follows: first, a general overview of inland navigation is given that explores the importance of locks and dams to the global economy. Then, design and behavior of miter and Tainter gates are discussed in detail. As an initial step to the development of a structural health monitoring system, numerical models are created of lock gates to obtain detailed information on the behavior of the structures both with and without the presence of damage. A discussion of best practices for numerical models of lock gates is provided with the models of two specific lock gates used as examples. Next, the methods developed for this dissertation to detect and assess the identified critical issues of lock gates are discussed. The first method discussed is the use of Principal Component Analysis combined with a novel strain gage data processing technique to detect boundary condition degradation of miter gates. The developed method addresses environmental variation frequently present in strain gage data and is validated by utilizing data from an in-service miter gate combined with results of a numerical model. Next, a discussion is given on the development of a non-contact, vision-based method to monitor the tension in a component of miter gates known as diagonals. The method utilizes optical-flow to track the displacement of a vibrating diagonal, from which the frequency is obtained and the tension found using Euler-Bernoulli beam theory. Partial submersion of the diagonals and the non-prismatic nature of the components are challenges that are addressed, and the method is validated with experimental and field data. Finally, the methods utilized to detect uneven hoisting of a Tainter gate are discussed. This method relies on a multi-faceted approach to show definitively that uneven hoisting is occurring on an operating Tainter gate. This approach is performed first by comparing strain gage data to numerical model results. Then data collected from inclinometers on the gate are inspected for the presence of uneven hoisting. Finally, indirect measurements of the tension in hoisting cables using vibration measurements taken during gate operation is used to show that an operating Tainter gate is hoisting unevenly. All three approaches are shown to be sensitive to the presence of uneven hoisting. The research presented herein addresses critical issues with inland navigation infrastructure. The method developed in this dissertation will be leveraged to provide the owners and operators of lock gate with the necessary information to extend the useful life of this critical infrastructure. More importantly, a structural health monitoring system of inland navigation infrastructure will aid in ensuring the continued operability of the inland navigation system, allowing river-borne traffic to continue to get goods to market