1,354,254 research outputs found
Spectroscopic performances of a very large area silicon drift detector
No full textSilicon drift detectors (SDD) are known to reach extreme performances in spectroscopy applications but these devices have small active area (few cm(2) at most). We are involved in the development of very-large active area SDDs (53 cm(2)) dedicated to tracking with high position resolution in a very-high particle multiplicity environment. Here we present preliminary experimental results on X-ray spectra measured with front-end electronics optimized for energy resolution. (c) 2006 Elsevier B.V. All rights reserved
The X-Ray Spectroscopic Performance of a Very Large Area Silicon Drift Detector
No full textSilicon drift detectors (SDDs), due to their collection electrode geometry, have excellent noise performance and are well suited for low-energy X-ray spectroscopy applications. On the other hand these detectors, when dedicated to low energy X-ray spectroscopy, have a small sensitive area (from few square millimeters up to one square centimeter) to reduce the leakage current and its impact on the energy resolution. Because of this limitation they are rarely used in applications where large sensitive surfaces are required. We present the characterization of the spectroscopic performance of a very large sensitive area SDD (about 53 cm(2)) that has been realized in the frame of the LHC-ALICE experiment. We studied the energy resolution of the detector analyzing its dependence on both biasing conditions and temperature to evaluate the contribution of the different noise sources exploiting their relation with the shaping time. The experimental results obtained with (241)Am and (55)Fe sources show that the goal of a high energy resolution combined with large sensitive areas can be achieved
Electric performance of the ALICE Silicon Drift Detector irradiated with 1 GeV electrons
No full textThe final version of the ALICE Silicon Drift Detector was irradiated with 1 GeV electrons at the LINAC of the Synchrotron 'Elettra' in Trieste. The electron fluence was equivalent to the total particle fluence expected during 10 years of ALICE operation as far as the bulk damage is concerned. The anode current, the voltage distribution on the integrated divider, and the operation of the MOS injectors were tested. The detector was found to be sufficiently radiation hard for the ALICE experiment
Device simulation of the ALICE silicon drift detector
No full textLarge-area linear silicon drift detectors will equip the third and fourth layers of the inner tracking system of the ALICE experiment. During the R&D phase of this sensor, an extensive work of simulation has been carried out in order, first, to determine, and, subsequently, to refine its design. In this paper we present this work giving a detailed description of the characteristics of each building block. (c) 2006 Elsevier Ltd. All rights reserved
Controllability on Infinite-Dimensional Manifolds: A Chow-Rashevsky Theorem
No full textOne of the fundamental problems in control theory is that of controllability, the question of whether one can drive the system from one point to another with a given class of controls. A classical result in geometric control theory of finite-dimensional (nonlinear) systems is Chow–Rashevsky theorem that gives a sufficient condition for controllability on any connected manifold of finite dimension. In other words, the classical Chow–Rashevsky theorem, which is in fact a primary theorem in subriemannian geometry, gives a global connectivity property of a subriemannian manifold. In this paper, following the unified approach of Kriegl and Michor (The Convenient Setting of Global Analysis, Mathematical Surveys and Monographs, vol. 53, Am. Math. Soc., Providence, 1997) for a treatment of global analysis on a class of locally convex spaces known as convenient, we give a generalization of Chow–Rashevsky theorem for control systems in regular connected manifolds modelled on convenient (infinite-dimensional) locally convex spaces which are not necessarily normable. To indicate an application of our approach to the infinite-dimensional geometric control problems, we conclude the paper with a novel controllability result on the group of orientation-preserving diffeomorphisms of the unit circle
Intellectual pursuits of Nicolas Rashevsky: the queer duck of biology
No full textWho was Nicolas Rashevsky? To answer that question, this book draws on Rashevsky’s unexplored personal archival papers and shares interviews with his family, students and friends, as well as discussions with biologists and mathematical biologists, to flesh out and complete the picture. “Most modern-day biologists have never heard of Rashevsky. Why?” In what constitutes the first detailed biography of theoretical physicist Nicolas Rashevsky (1899-1972), spanning key aspects of his long scientific career, the book captures Rashevsky’s ways of thinking about the place mathematical biology should have in biology and his personal struggle for the acceptance of his views. It brings to light the tension between mathematicians, theoretical physicists and biologists when it comes to the introduction of physico-mathematical tools into biology. Rashevsky’s successes and failures in his efforts to establish mathematical biology as a subfield of biology provide an important test case for understanding the role of theory (in particular mathematics) in understanding the natural world. With the biological sciences moving towards new vistas of inter- and multi-disciplinary collaborations and research programs, the book will appeal to a wide readership ranging from historians, sociologists, and ethnographers of American science and culture to students and general readers with an interest in the history of the life sciences, mathematical biology and the social construction of science
Organismic Supercategories and Qualitative Dynamics of Systems
No full textThe representation of biological systems by means of organismic supercategories, developed in previous papers, is further discussed. The different approaches to relational biology, developed by Rashevsky, Rosen and by Baianu and Marinescu, are compared with Qualitative Dynamics of Systems which was initiated by Henri Poincaré (1881). On the basis of this comparison some concrete results concerning dynamics of genetic system, development, fertilization, regeneration, analogies, and oncogenesis are derived
Organismic Supercategories: I. Proposals for a General Unified Theory of Systems- Classical, Quantum, and Complex Biological Systems.\ud \ud \ud
No full textThe representation of physical and complex biological systems in terms of organismic supercategories was introduced in 1968 by Baianu and Marinescu in the attached paper which was published in the Bulletin of Mathematical Biophysics, edited by Nicolas Rashevsky. The different approaches to relational biology, developed by Rashevsky, Rosen and by Baianu et al.(1968,1969,1973,1974,1987,2004)were later discussed. \ud
The present paper is an attempt to outline an abstract unitary theory of systems. In the introduction some of the previous abstract representations of systems are discussed. Also a possible connection of abstract representations of systems with a general theory of measure is proposed. Then follow some necessary definitions and authors' proposals for an axiomatic theory of systems. Finally some concrete examples are analyzed in the light of the proposed theory.\ud
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An abstract representation of biological systems from the standpoint of the theory of supercategories is presented. The relevance of such representations forG-relational biologies is suggested. In section A the basic concepts of our representation, that is class, system, supercategory and measure are introduced. Section B is concerned with the mathematical representation starting with some axioms and principles which are natural extensions of the current abstract representations in biology. Likewise, some extensions of the principle of adequate design are introduced in section C. Two theorems which present the connection between categories and supercategories are proved. Two other theorems concerning the dynamical behavior of biological and biophysical systems are derived on the basis of the previous considerations. Section D is devoted to a general study of oscillatory behavior in enzymic systems, some general quantitative relations being derived from our representation. Finally, the relevance of these results for a quantum theoretic approach to biology is discussed.\ud
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http://www.springerlink.com/content/141l35843506596h
Organismic Supercategories: III. Qualitative Dynamics of Systems
No full textThe representation of biological systems by means of organismic supercategories, developed in previous papers, is further discussed. The different approaches to relational biology, developed by Rashevsky, Rosen and by Baianu and Marinescu, are compared with Qualitative Dynamics of Systems which was initiated by Henri Poincaré (1881). On the basis of this comparison some concrete results concerning dynamics of genetic system, development, fertilization, regeneration, analogies, and oncogenesis are derived
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