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

Personality and Cognitive Ability as Predictors of Job Search and Separation Among Employed Managers

Traditional models and research on employee job search and separation focus on situationally-specific variables, those that change with time or between particular employment situations. More enduring individual characteristics, such as personality and cognitive ability, may create predispositions that affect search and separation in consistent ways across different situations. The research reported here extends traditional turnover models by incorporating two enduring individual characteristics – personality and cognitive ability – into the search and separation process. This extended model is then tested on a sample of executives. Cognitive ability as well as the personality dimensions of agreeableness, neuroticism and openness to experience related positively to job search. The effects of cognitive ability and the personality dimensions of agreeableness and openness to experience on job search were partially mediated by the array of situational factors, while the effect of neuroticism on job search was fully mediated. The relationship between extraversion and job search became significant in the presence of situational factors, suggesting a suppressor effect. With regard to separation, a similar suppressor effect was found for extraversion. Implications for future research and practice are discussed

Effects of Personality, Cognitive Ability, and Fit on Job Search and Separation Among Employed Managers

The present study attempted to provide a constructive replication and extension of a study on managerial job search completed by Bretz, Boudreau, and Judge (1994). Beyond examining the same variables as Bretz et al. (1994), the effects of personality, cognitive ability, challenge and hindrance related job stress, and fit on job search and turnover also were examined. Data were collected from a 1995 survey of employed U.S. managers and a 1996 follow-up survey of respondents. Results based on a sample of 1,886 managers generally replicated the Bretz et al. results. Furthermore, hindrance related stress, cognitive ability, extraversion, openness to experience, and agreeableness were associated with search and/or separation

A study of environmental characterization of conventional and advanced aluminum alloys for selection and design. Phase 2: The breaking load test method

A technique is demonstrated for accelerated stress corrosion testing of high strength aluminum alloys. The method offers better precision and shorter exposure times than traditional pass fail procedures. The approach uses data from tension tests performed on replicate groups of smooth specimens after various lengths of exposure to static stress. The breaking strength measures degradation in the test specimen load carrying ability due to the environmental attack. Analysis of breaking load data by extreme value statistics enables the calculation of survival probabilities and a statistically defined threshold stress applicable to the specific test conditions. A fracture mechanics model is given which quantifies depth of attack in the stress corroded specimen by an effective flaw size calculated from the breaking stress and the material strength and fracture toughness properties. Comparisons are made with experimental results from three tempers of 7075 alloy plate tested by the breaking load method and by traditional tests of statistically loaded smooth tension bars and conventional precracked specimens

Simultaneous Inference in General Parametric Models

Simultaneous inference is a common problem in many areas of application. If multiple null hypotheses are tested simultaneously, the probability of rejecting erroneously at least one of them increases beyond the pre-specified significance level. Simultaneous inference procedures have to be used which adjust for multiplicity and thus control the overall type I error rate. In this paper we describe simultaneous inference procedures in general parametric models, where the experimental questions are specified through a linear combination of elemental model parameters. The framework described here is quite general and extends the canonical theory of multiple comparison procedures in ANOVA models to linear regression problems, generalized linear models, linear mixed effects models, the Cox model, robust linear models, etc. Several examples using a variety of different statistical models illustrate the breadth of the results. For the analyses we use the R add-on package multcomp, which provides a convenient interface to the general approach adopted here

MWL observations of VHE blazars in 2006

In 2006 the MAGIC telescope observed the well known very high energy (VHE, > 80 GeV) blazars Mrk 421 and Mrk 501 in the course of multi-wavelength campaigns, comprising measurements in the optical, X-ray and VHE regime. MAGIC performed additional snapshot observations on Mrk 421 around the MWL campaigns and detected the source each night with high significance, establishing once more flux variability on nightly scales for this object. For certain nights, the integral flux exceeded the one of Crab significantly, whereas the truly simultaneous observations have been conducted in a rather low flux state. The MAGIC observations contemporaneous to XMM-Newton revealed clear intra-night variability. No significant correlation between the spectral index and the flux could be found for the nine days of observations. The VHE observations of Mrk 501 have been conducted during one of the lowest flux states ever measured by MAGIC for this object. The VHE and optical light curves do not show significant variability, whereas the flux in X-rays increased by about 50 %. In this contribution, the results of the MAGIC observations will be presented in detail.Comment: Contribution to the 31st ICRC, Lodz, Poland, July 200

Homeschoolers and the Mebane Public Library: a case study

This research describes the results of a study of homeschool administrators (i.e., parents) in Alamance County and Orange County, North Carolina and their use of the Mebane Public Library. A survey was conducted to determine if the programming and library collections available to homeschooling parents meet their curriculum needs. As this alternative form of education has gained popularity, many public libraries have seen an increase in the number of homeschoolers that use their facilities. Among the suggestions made by librarians experienced in this area are programming opportunities for homeschoolers as well as a well-rounded collection consisting of a variety of formats. Homeschoolers using the Mebane Public Library feel that enough programming is offered to meet their curriculum needs despite the fact that their attendance of these programs is very low. Suggestions for future programming were made. In general, homeschooling parents find that the Mebane Public Library's collection meets their needs, with additional materials available elsewhere in the systems as well as through Interlibrary Loan

Presence of Treponema denticola and Porphyromonas gingivalis in Children Correlated with Periodontal Disease of Their Parents

Considerable evidence exists suggesting that periodontal disease is due to the overgrowth of a finite number of specific bacteria such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Treponema denticola, Bacteroides forsythus, and Prevotella intermedia, among others. Three of these organisms-P. gingivalis, T. denticola, and B. forsythus—can be easily detected in plaque samples by the hydrolysis of the synthetic trypsin substrate benzoyl-DL-arginine-naphthylamide (BANA). The aim of the present study was to determine if a relationship could be found between the presence of either these organisms or periodontitis in the parent and the presence of BANA-positive species in the child. Thirty-four mothers or fathers and 34 children were examined for plaque scores, papillary bleeding scores, and the presence of P. gingivalis and T. denticola in four subgingival or marginal gingival plaque samples as assayed by the BANA test or specific polyclonal antibodies using an ELISA. Children whose parents were colonized by BANA-positive bacteria were 9.8 times more likely to be colonized by these BANA-positive species. Children whose parents had clinical evidence of periodontitis were 12 times more likely to be colonized by these BANA-positive species. These data are compatible with the hypothesis that children may acquire the BANA-positive species from their parents, especially if the parent has periodontitis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68201/2/10.1177_00220345940730100801.pd