Host resistance does not explain variation in incidence of male-killing bacteria in Drosophila bifasciata

Background Selfish genetic elements that distort the sex ratio are found widely. Notwithstanding the number of records of sex ratio distorters, their incidence is poorly understood. Two factors can prevent a sex ratio distorter from invading: inability of the sex ratio distorter to function (failure of mechanism or transmission), and lack of drive if they do function (inappropriate ecology for invasion). There has been no test to date on factors causing variation in the incidence of sex ratio distorting cytoplasmic bacteria. We therefore examined whether absence of the male-killing Wolbachia infection in D. bifasciata in Hokkaido island of Japan, in contrast to the presence of infection on the proximal island of Honshu, was associated with failure of the infection to function properly on the Hokkaido genetic background. Results The male-killer both transmitted and functioned well following introgression to each of 24 independent isofemale inbred lines carrying Hokkaido genetic backgrounds. This was maintained even under stringent conditions of temperature. We therefore reject the hypothesis that absence of infection is due to its inability to kill males and transmit on the Hokkaido genetic background. Further trap data indicates that D. bifasciata may occur at different densities in Hokkaido and Honshu populations, giving some credence to the idea that ecological differentiation could be important. Conclusions The absence of the infection from the Hokkaido population is not caused by failure of the male-killer to function on the Hokkaido genetic background

Nonlinear phononic crystals based on chains of disks alternating with toroidal structures

We study experimentally the acoustic response of a load-bearing, phononic crystal composed of alternating steel disks, and polytetrafluoroethylene o-rings under precompression. The crystal allows for axial, rocking, and shear-polarized wavemodes when excited by a broad-band signal applied off-axis. Finite element analysis is employed to determine the system’s wave modes. The nonlinear interaction between disks and o-rings supports a dynamic response that is tunable with variations in static precompression, leading to controllable frequency shifts in a large band gap. A modal analysis reveals that four of the six principal wave modes are susceptible to external precompression while two modes are not

The Guidebook, the Friend, and the Room: Visitor Experience in a Historic House

In this paper, we describe an electronic guidebook prototype and report on a study of its use in a historic house. Supported by mechanisms in the guidebook, visitors constructed experiences that had a high degree of interaction with three entities: the guidebook, their companions, and the house and its contents. For example, we found that most visitors played audio descriptions played through speakers (rather than using headphones or reading textual descriptions) to facilitate communication with their companions

A new method of alpha ray measurement using a Quadrupole Mass Spectrometer

We propose a new method of alpha($\alpha$)-ray measurement that detects helium atoms with a Quadrupole Mass Spectrometer(QMS). A demonstration is undertaken with a plastic-covered $^{241}$Am $\alpha$-emitting source to detect $\alpha$-rays stopped in the capsule. We successfully detect helium atoms that diffuse out of the capsule by accumulating them for one to 20 hours in a closed chamber. The detected amount is found to be proportional to the accumulation time. Our method is applicable to probe $\alpha$-emitting radioactivity in bulk material.Comment: 8 pages, 6 figure

Bio-inspired swing leg control for spring-mass robots running on ground with unexpected height disturbance

We proposed three swing leg control policies for spring-mass running robots, inspired by experimental data from our recent collaborative work on ground running birds. Previous investigations suggest that animals may prioritize injury avoidance and/or efficiency as their objective function during running rather than maintaining limit-cycle stability. Therefore, in this study we targeted structural capacity (maximum leg force to avoid damage) and efficiency as the main goals for our control policies, since these objective functions are crucial to reduce motor size and structure weight. Each proposed policy controls the leg angle as a function of time during flight phase such that its objective function during the subsequent stance phase is regulated. The three objective functions that are regulated in the control policies are (i) the leg peak force, (ii) the axial impulse, and (iii) the leg actuator work. It should be noted that each control policy regulates one single objective function. Surprisingly, all three swing leg control policies result in nearly identical subsequent stance phase dynamics. This implies that the implementation of any of the proposed control policies would satisfy both goals (damage avoidance and efficiency) at once. Furthermore, all three control policies require a surprisingly simple leg angle adjustment: leg retraction with constant angular acceleration

High reliability sheathed, beryllia insulated, tungsten-rhenium alloy thermocouple assemblies; their fabrication and EMF stability

Tantalum sheathed, BeO insulated, W-3% Re/W-25% Re thermocouple assemblies were fabricated and their emf drift determined during 2059 hours of exposure at 2073 K in a gaseous helium environment. The sheathed thermocouple assemblies were constructed from aged thermoelements, specially heat-treated BeO insulators, and specially cleaned and etched tantalum sheaths. Their thermal emf drifts ranged from the equivalent of only -0.3 to -0.8 K drift per 1000 hours of exposure at 2073 K. No evidence of any gross chemical attack or degradation of the component materials was found. The emf drift and material behavior of some unsheathed, BeO insulated, W-3% Re/W-25% Re thermocouples at 2250 and 2400 K were also determined. Unsheathed thermocouples tested in an argon environment at 2250 K for 1100 hours and at 2400 K for 307 hours exhibited changes in thermal emf that typically ranged from the equivalent of a few degrees K to as much as +11 K. Post-test examinations of these thermocouples revealed some undesirable material degradation and interaction which included erosion of the BeO insulators and contamination of the thermoelements by tantalum from the tantalum blackbody enclosure in which the thermocouples were contained

THE ENVIROMENTAL IMPACT ON VOLUNTEER SOILDERS IN THE MEXICAN AMERICAN WAR

The Mexican-American War is largely overshadowed by historians of the War of 1812 and the Civil War. This conflict demands an in-depth examination as a unique historical event. Scholars of the Mexican-American War have largely limited their approach to underscore how social and political relations, among American military and political elite, shaped the conflict as a causeway to the American Civil War. To better understand the Mexican-American war it is necessary to understand it through the experiences of those volunteer solders living during this conflict. In addition, understanding the role the environment played in shaping the social and political relations between Volunteers and regular soldiers, as well as their own understanding of national duty, is essential to recognize this conflict as more than simply a forerunner to the American Civil War. Thus, I examined primary journals, notes, letters as well as secondary historiographies to examine the relationship between environmental impact and Volunteer solders. This paper explores the ways shifting social and geographical environments, throughout the war, sparked conflicts between Volunteers and the regular forces, as well as the Volunteers’ conflicting ideas about national duty. The relation between the environment and the Volunteer’s action is clear in this paper and as such should be expanded upon in further research

THE SUPERINTENDENT’S FEED: AN ANALYSIS OF SUPERINTENDENTS’ ENGAGEMENT IN POLITICAL DISCOURSE ON TWITTER

The modern school superintendent fulfills a unique role in the American public education system. He or she is structurally empowered as the de facto head of the local educational system, thereby granted with a certain amount of trust and authority regarding educational issues. At the same time, the superintendent is, in most cases, an employee of a politically appointed school board. This construction creates a dynamic wherein the superintendent is both the leader of a highly structured, bureaucratic system, while at the same time an employee of a largely lay, often elected, group of citizens. The position of the superintendent is highly informed by the role conceptualizations first posited by Callahan (1966). Callahan argued that there are four distinct normative roles that superintendents must fill: scholarly educational leader, business executive, educational statesman, and applied social scientist. In this study, I pay special attention to the role of educational statesman, which is alternatively referred to as political strategist by later scholars (Björk & Gurley, 2005; Brunner, Grogan, & Björk, 2002). I have examined the role of political strategist as it has manifest on the social media platform Twitter. Twitter use has become a common practice among educational leaders for a variety of reasons, including the development of professional learning networks, communicating with stakeholders, and even engaging in policy discussions (Roth, 2016; Sauers & Richardson, 2015). To date, the intersection of social media use and political engagement by superintendents has been overlooked within the field, but the practice is common and has significant importance for the discipline. I employed a two-phase analysis to explore this topic. First, I have utilized discourse analysis to better understand the constructive nature of the talk and text provided by superintendents on Twitter. The second phase of analysis employs a modified photo-elicitation methodology, wherein a subset of superintendents (7) were interviewed in a semi-structured format prompted by instances of their own political tweeting. Findings from this study indicate that superintendents are using Twitter to discuss macro-political topics and employ sophisticated strategies in order to both project the image they want to be seen and to protect themselves from the political ramifications that might accompany such discourse. I believe that these findings have importance in the way superintendents engage with their community stakeholders and indicate that there should be more attention paid to an evolving nature of communication for the position

A construção discursiva do superintendente política no Twitter

The modern school superintendent fulfills a unique role in the U.S. public education system. He or she is structurally empowered as the de facto head of the local educational system, thereby granted with a certain amount of trust and authority regarding educational issues. At the same time, the superintendent is, in most cases, an employee of a politically appointed school board. While norms have traditionally encouraged superintendents to use caution with respect to political discourse (Boyd, 1974), social media has created a new platform upon which they can reach a broad range of stakeholders regarding many issues, including politics. This study seeks to better understand the emerging practice of political discourse by superintendents on Twitter. Employing discursive psychology principles (Potter Wetherell, 1992), I will analyze the political tweets of superintendents and position current practices in relation to established role conceptualizations of the position. Findings include that superintendents utilize Twitter as a tool to establish their positions as political insiders and as advocates for students.El director de la escuela moderna desempeña un papel único en el sistema de educación pública de Estados Unidos. Él o ella está facultado estructuralmente como jefe de hecho, el sistema de educación local, así concedida con una cierta cantidad de confianza y autoridad en temas educativos. Al mismo tiempo, el superintendente suele ser un empleado de una junta escolar de designación política. Aunque las normas que tradicionalmente han animado a los superintendentes tener precaución con respecto a la expresión política (Boyd, 1974), las redes sociales han creado una nueva plataforma en la que pueden lograr una amplia gama de partes interesadas sobre muchos temas, incluyendo la política. Este estudio busca entender mejor la práctica que emerge del discurso político de los supervisores en Twitter. El empleo de principios de la psicología discursiva (Potter y Wetherell, 1992) analizan los tweets políticos de superintendentes y posicionarei prácticas actuales con respecto a la conceptualización de los roles establecidos de la posición. Los resultados incluyen los superintendentes utilizan Twitter como una herramienta para establecer sus posiciones como actores políticos y promotores de los estudiantes.O superintendente escolar moderno cumpre um papel único no sistema de educação pública dos EUA. Ele ou ela é estruturalmente habilitada como chefe de fato do sistema educacional local, concedido assim com uma certa quantidade de confiança e autoridade em relação a questões educacionais. Ao mesmo tempo, o superintendente é geralmente um empregado de um conselho escolar politicamente nomeado. Embora as normas tenham tradicionalmente encorajado os superintendentes a usarem de cautela em relação ao discurso político (Boyd, 1974), as mídias sociais criaram uma nova plataforma sobre a qual eles podem alcançar uma ampla gama de interessados em muitos assuntos, incluindo a política. Este estudo busca compreender melhor a prática emergente do discurso político dos superintendentes no Twitter. Empregando princípios de psicologia discursiva (Potter Wetherell, 1992), analisarei os tweets políticos dos superintendentes e posicionarei as práticas atuais em relação às conceitualizações de papéis estabelecidas da posição. Os resultados incluem que os superintendentes utilizam o Twitter como uma ferramenta para estabelecer suas posições como insiders políticos e como advogados para os alunos