740 research outputs found

    The VST telescope control software in the ESO VLT environment

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    The VST (VLT Survey Telescope) is a 2.6 m Alt-Az telescope to be installed at Mount Paranal in Chile, in the European Southern Observatory (ESO) site. The VST is a wide-field imaging facility planned to supply databases for the ESO Very Large Telescope (VLT) science and carry out stand-alone observations in the UV to I spectral range. This paper will focus mainly on control software aspects, describing the VST software architecture in the context of the whole ESO VLT control concept. The general architecture and the main components of the control software will be described.Comment: 3 pages, 2 figures, ICALEPCS 2001 Conference, PSN#THAP05

    Integration of the VIMOS control system

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    The VIRMOS consortium of French and Italian Institutes (PI: O. Le Fevre, co-PI: G. Vettolani) is manufacturing two wide field imaging multi-object spectrographs for the European Southern Observatory Very Large Telescope (VLT), with emphasis on the ability to carry over spectroscopic surveys of large numbers of sources: the VIsible Multi-Object Spectrograph, VIMOS, and the Near InfraRed Multi-Object Spectrograph, NIRMOS. There are 52 motors to be controlled in parallel in the spectrograph, making VIMOS a complex machine to be handled. This paper will focus on the description of the control system, designed in the ESO VLT standard control concepts, and on some integration issues and problem solving strategies.Comment: 3 pages, 3 figures, ICALEPCS 2001 Conference, PSN#TUBT00

    The Use of Efficient Market Hypothesis: Beyond SOX

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    This Article focuses on the regulatory use of finance theory, particularly the efficient market hypothesis ( EMH ), in two areas where securities pricing is at issue: shareholder appraisal cases and the use of employer stock in benefit plans. Regarding shareholder appraisal cases, the Article finds that the Delaware courts seem to implicitly respect the principles of EMH when ascertaining the fair value of stock, but recognize that markets cannot operate efficiently if information is withheld. Regarding employer stock in benefit plans, it concentrates on the explicit adoption of EMH by the Department of Labor to exempt directed trustees from traditional duties of inquiry regarding the prudence of investment directions

    The Use of Efficient Market Hypothesis: Beyond SOX

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    This Article focuses on the regulatory use of finance theory, particularly the efficient market hypothesis ( EMH ), in two areas where securities pricing is at issue: shareholder appraisal cases and the use of employer stock in benefit plans. Regarding shareholder appraisal cases, the Article finds that the Delaware courts seem to implicitly respect the principles of EMH when ascertaining the fair value of stock, but recognize that markets cannot operate efficiently if information is withheld. Regarding employer stock in benefit plans, it concentrates on the explicit adoption of EMH by the Department of Labor to exempt directed trustees from traditional duties of inquiry regarding the prudence of investment directions

    A Neural Tool for Ground-Based Telescope Tracking control

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    Neural Network models (NN) have emerged as important components for applications of adaptive control theories. Their basic generalization capability, based on acquired knowledge, together with execution rapidity and correlation ability between input stimula, are basic attributes to consider NN as an extremely powerful tool for on-line control of complex systems. By a control system point of view, not only accuracy and speed, but also, in some cases, a high level of adaptation capability is required in order to match all working phases of the whole system during its lifetime. This is particularly remarkable for a new generation ground-based telescope control system. Infact, strong changes in terms of system speed and instantaneous position error tolerance are necessary, especially in case of trajectory disturb induced by wind shake. The classical control scheme adopted in such a system is based on the Proportional Integral (PI) filter, already applied and implemented on a large amount of new generation telescopes, considered as a standard in this technological environment. In this paper we introduce the concept of a new approach, the Neural Variable Structure Proportional Integral, (NVSPI), related to the implementation of a standard Multi Layer Perceptron (MLP) network in new generation ground-based Alt-Az telescope control systems. Its main purpose is to improve adaptive capability of the Variable Structure Proportional Integral model, (VSPI), an already innovative control scheme recently introduced by authors [1], based on a modified version of classical PI control model, in terms of flexibility and accuracy of the dynamic response range also in presence of wind noise effects. The realization of a powerful well tested and validated telescope model simulation system allowed the possibility to directly compare performances of the two control schemes on simulated tracking trajectories, revealing extremely encouraging results in terms of NVSPI control robustness and reliability

    Ground-based telescope pointing and tracking optimization using a neural controller

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    Neural network models (NN) have emerged as important components for applications of adaptive control theories. Their basic generalization capability, based on acquired knowledge, together with execution rapidity and correlation ability between input stimula, are basic attributes to consider NN as an extremely powerful tool for on-line control of complex systems. By a control system point of view, not only accuracy and speed, but also, in some cases, a high level of adaptation capability is required in order to match all working phases of the whole system during its lifetime. This is particularly remarkable for a new generation ground-based telescope control system. Infact, strong changes in terms of system speed and instantaneous position error tolerance are necessary, especially in case of trajectory disturb induced by wind shake. The classical control scheme adopted in such a system is based on the proportional integral (PI) filter, already applied and implemented on a large amount of new generation telescopes, considered as a standard in this technological environment. In this paper we introduce the concept of a new approach, the neural variable structure proportional integral, (NVSPI), related to the implementation of a standard multi layer perceptron network in new generation ground-based Alt-Az telescope control systems. Its main purpose is to improve adaptive capability of the Variable structure proportional integral model, an already innovative control scheme recently introduced by authors [Proc SPIE (1997)], based on a modified version of classical PI control model, in terms of flexibility and accuracy of the dynamic response range also in presence of wind noise effects. The realization of a powerful well tested and validated telescope model simulation system allowed the possibility to directly compare performances of the two control schemes on simulated tracking trajectories, revealing extremely encouraging results in terms of NVSPI control robustness and reliability. © 2003 Elsevier Science Ltd. All rights reserved

    SDHA Germline Mutations in SDH-Deficient GISTs: A Current Update

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    Loss of function of the succinate dehydrogenase complex characterizes 20-40% of all KIT/PDGFRA-negative GIST. Approximately half of SDH-deficient GIST patients lack SDHx mutations and are caused by a hypermethylation of the SDHC promoter, which causes the repression of SDHC transcription and depletion of SDHC protein levels through a mechanism described as epimutation. The remaining 50% of SDH-deficient GISTs have mutations in one of the SDH subunits and SDHA mutations are the most common (30%), with consequent loss of SDHA and SDHB protein expression immunohistochemically. SDHB, SDHC, and SDHD mutations in GIST occur in only 20-30% of cases and most of these SDH mutations are germline. More recently, germline mutations in SDHA have also been described in several patients with loss of function of the SDH complex. SDHA-mutant patients usually carry two mutational events at the SDHA locus, either the loss of the wild type allele or a second somatic event in compound heterozygosis. This review provides an overview of all data in the literature regarding SDHA-mutated GIST, especially focusing on the prevalence of germline mutations in SDH-deficient GIST populations who harbor SDHA somatic mutations, and offers a view towards understanding the importance of genetic counselling for SDHA-variant carriers and relatives

    The active optics software for the VST telescope

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    The VST (VLT Survey Telescope) active optics software must basically provide the analysis of the image coming from the wavefront sensor (a 10x10 subpupils Shack Hartmann device) and the calculation of primary mirror forces and secondary mirror displacements to correct the aberrations of the optical system, instrinsic or originated for thermal and gravity reasons. After the telescope commissioning the VST will be operated by ESO. In this framework, INAF-OAC staff was committed to design and realize the software in a VLT-compliant way. This will smoothen the integration, operation and maintenance of the telescope in the Paranal observatory

    The Economic Impact of Backdating of Executive Stock Options

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    This Article discusses the economic impact of legal, tax, disclosure, and incentive issues arising from the revelation of dating games with regard to executive option grant dates. It provides an estimate of the value loss incurred by shareholders of firms implicated in backdating and compares it to the potential gain that executives might have obtained through backdating. Using a sample of firms that have already been implicated in backdating, we find that the revelation of backdating results in an average loss to shareholders of about 7%. This translates to about 400millionperfirm.Bycontrast,weestimatethattheaveragepotentialgainfrombackdatingtoallexecutivesinthesefirmsisabout400 million per firm. By contrast, we estimate that the average potential gain from backdating to all executives in these firms is about 500,000 per firm annually. We suggest some remedies not only for backdating, but also for other dubious practices such as springloading
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