The drive system of the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope

The MAGIC telescope is an imaging atmospheric Cherenkov telescope, designed to observe very high energy gamma-rays while achieving a low energy threshold. One of the key science goals is fast follow-up of the enigmatic and short lived gamma-ray bursts. The drive system for the telescope has to meet two basic demands: (1) During normal observations, the 72-ton telescope has to be positioned accurately, and has to track a given sky position with high precision at a typical rotational speed in the order of one revolution per day. (2) For successfully observing GRB prompt emission and afterglows, it has to be powerful enough to position to an arbitrary point on the sky within a few ten seconds and commence normal tracking immediately thereafter. To meet these requirements, the implementation and realization of the drive system relies strongly on standard industry components to ensure robustness and reliability. In this paper, we describe the mechanical setup, the drive control and the calibration of the pointing, as well as present measurements of the accuracy of the system. We show that the drive system is mechanically able to operate the motors with an accuracy even better than the feedback values from the axes. In the context of future projects, envisaging telescope arrays comprising about 100 individual instruments, the robustness and scalability of the concept is emphasized.Comment: 15 pages, 12 (10) figures, submitted to Astroparticle Physics, a high resolution version of the paper (particularly fig. 1) is available at http://publications.mppmu.mpg.de/2008/MPP-2008-101/FullText.pd

The outstanding opportunities, but persistent challenges, of dual language education

ArticleAs highlighted in the Cambio Center's November 2015 e-brief, dual language (DL) education programs are growing exponentially in the United States. (See the latest report from the Department of Education.) By some accounts, these programs -- especially two-way immersion models that integrate students from two different language backgrounds and use both languages in the classroom -- are the "astounding" answer to desegregating our schools, preparing children for a transnational world, and developing smarter thinkers. However, scholars like Nelson Flores remind us that the politics of language education and history of racism in U.S. schools make it very difficult to realize the "rich promise" of DL education for all students, especially those from minoritized groups. This e-brief will review research that documents the outstanding opportunities that DL programs provide, as well as introduce some of their persistent challenges.Includes bibliographical references

What is dual language education?

ArticleRecently, the U.S. Congress made a bipartisan request for a national commission to study the state of language education in the United States. After an era of declining availability of foreign language education for the general public and fewer bilingual programs for children from immigrant families, this kind of request may mark an important shift in thinking about the importance of multilingualism and related education initiatives. This changing discourse is coming not only from our leaders, but also from local policymakers and community members. From Delaware to North Carolina to Utah, there has been exponential growth of dual language (DL) education programs since the 1990s. But what exactly are dual language programs? And what are the promises and possibilities of this unique model of education? This Cambio eBrief will focus on defining DL programs and who they serve, and a subsequent brief will focus on the promises and possibilities of dual language education.Who do dual language persons serve? -- Commonly used terms for students in dual language programs -- How do dual language programs work? -- References.Includes bibliographical references

Waterborne Diseases: Linking Public Health and Watershed Data

This paper presents Massachusetts as a case study for linking public health data of waterborne diseases with sources of drinking water, potential recreational exposures, as well as hydrologic, climatic, and land use data. Information of reported illnesses from known waterborne pathogens will be synthesized and the relationship of confirmed illnesses will be compared with available hydrologic data. The goal is to develop a pathogen vulnerability index for Massachusetts waters to improve estimates of exposure to pathogens given watershed conditions

Work and Quantum Phase Transitions: Is there Quantum Latency?

We study the physics of quantum phase transitions from the perspective of non-equilibrium thermodynamics. For first order quantum phase transitions, we find that the average work done per quench in crossing the critical point is discontinuous. This leads us to introduce the quantum latent work in analogy with the classical latent heat of first order classical phase transitions. For second order quantum phase transitions the irreversible work is closely related to the fidelity susceptibility for weak sudden quenches of the system Hamiltonian. We demonstrate our ideas with numerical simulations of first, second, and infinite order phase transitions in various spin chain models.Comment: accepted in PR

PYRAMIR: Calibration and operation of a pyramid near-infrared wavefront sensor

The concept of pyramid wavefront sensors (PWFS) has been around about a decade by now. However, there is still a great lack of characterizing measurements that allow the best operation of such a system under real life conditions at an astronomical telescope. In this article we, therefore, investigate the behavior and robustness of the pyramid infrared wavefront sensor PYRAMIR mounted at the 3.5 m telescope at the Calar Alto Observatory under the influence of different error sources both intrinsic to the sensor, and arising in the preceding optical system. The intrinsic errors include diffraction effects on the pyramid edges and detector read out noise. The external imperfections consist of a Gaussian profile in the intensity distribution in the pupil plane during calibration, the effect of an optically resolved reference source, and noncommon-path aberrations. We investigated the effect of three differently sized reference sources on the calibration of the PWFS. For the noncommon-path aberrations the quality of the response of the system is quantified in terms of modal cross talk and aliasing. We investigate the special behavior of the system regarding tip-tilt control. From our measurements we derive the method to optimize the calibration procedure and the setup of a PWFS adaptive optics (AO) system. We also calculate the total wavefront error arising from aliasing, modal cross talk, measurement error, and fitting error in order to optimize the number of calibrated modes for on-sky operations. These measurements result in a prediction of on-sky performance for various conditions

Reexamining Citizenship: Best Practices of St. Louis Spanish Immersion Schools

Presentation made at Latinos in the Heartland (8th : 2010 : St. Louis, Mo.) and published in the annual conference proceedings.When introducing the concepts of citizenship in our schools, how an American citizen looks, speaks, and thinks is often presented in assumptions and stereotypes. As the demographics of the nation have shifted, these stereotypes sometimes remain the same and the new reality ignored. How can and should we teach our young children about citizenship? How are language immersion schools in particular developing global citizens? According to National Migration information, (Terrazas and Batalova 2008) in 2007, 22.9 percent of school-age children had at least one immigrant parent, 47.5 percent of which reported their background to be Hispanic or Latino. In this paper, we discuss two educational opportunities in the St. Louis area that build on the strengths of the Hispanic/Latino community and its primary language of Spanish. Casa de Niños is a preschool program built on the Montessori philosophy that primarily serves children through age 5. The St. Louis Language Immersion Schools, a nonprofit organization (http://sllis. org), is dedicated to supporting the development of a network of charter schools in the area. They are set to open a Spanish immersion school for K-1st grade in August 2009 and will be using the Primary Years International Baccalaureate program in order to promote "international mindedness" in their students (http://www.ibo.org). Specifically, SLLIS' mission is "to position all children for success in local and global economies through holistic, intellectually inspiring language immersion programs," in essence, to create global citizens. The central vision of these language immersion schools, then, is to provide both the opportunity to learn in another language and about other cultures and languages. This presentation will explain how these educational organizations work to develop language and citizenship capacities. In particular, we will explain in detail the planned service-learning community research project all SLLIS students will complete by the end of fifth grade. We will also provide best practices for addressing issues of culture and language in immersion settings designed for young children. Finally, we will discuss with the group the challenges and opportunities of designing these sorts of programs in areas of new immigration, such as many towns and small cities across the Midwest