127 research outputs found
A Compact Gas Cerenkov Detector with Novel Optics
We discuss the design and performance of a threshold Cerenkov counter for
identification of charged hadrons. The radiator is pressurized gas, which is
contained in thin-walled cylindrical modules. A mirror system of novel design
transports Cerenkov photons to photomultiplier tubes. This system is compact,
contains relatively little material, and has a large fraction of active volume.
A prototype of a module designed for the proposed CLEO III detector has been
studied using cosmic rays. Results from these studies show good agreement with
a detailed Monte Carlo simulation of the module and indicate that it should
achieve separation of pions and kaons at the 2.5-3.0sigma level in the momentum
range 0.8-2.8 GeV/c. We predict performance for specific physics analyses using
a GEANT-based simulation package.Comment: Submitted to NIM. 23 pages, 11 postscript figures. Postscript file is
also available at http://w4.lns.cornell.edu/public/CLNS/199
Hopping motion of lattice gases through nonsymmetric potentials under strong bias conditions
The hopping motion of lattice gases through potentials without
mirror-reflection symmetry is investigated under various bias conditions. The
model of 2 particles on a ring with 4 sites is solved explicitly; the resulting
current in a sawtooth potential is discussed. The current of lattice gases in
extended systems consisting of periodic repetitions of segments with sawtooth
potentials is studied for different concentrations and values of the bias.
Rectification effects are observed, similar to the single-particle case. A
mean-field approximation for the current in the case of strong bias acting
against the highest barriers in the system is made and compared with numerical
simulations. The particle-vacancy symmetry of the model is discussed.Comment: 8 pages (incl. 6 eps figures); RevTeX 3.
The Self Model and the Conception of Biological Identity in Immunology
The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for sixty years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity
Quantum Dimensional Zeeman Effect in the Magneto-optical Absorption Spectrum for Quantum Dot - Impurity Center Systems
Magneto-optical properties of the quantum dot - impurity center (QD-IC)
systems synthesized in a transparent dielectric matrix are considered. For the
QD one-electron state description the parabolic model of the confinement
potential is used. Within the framework of zero-range potential model and the
effective mass approach, the light impurity absorption coefficient for the case
of transversal polarization with respect to the applied magnetic field
direction, with consideration of the QD size dispersion, has been analytically
calculated. It is shown that for the case of transversal polarization the light
impurity absorption spectrum is characterized by the quantum dimensional Zeeman
effect.Comment: 18 pages, 1 figure, PDF fil
Search for the Decay
We have searched for the decay of the tau lepton into seven charged particles
and zero or one pi0. The data used in the search were collected with the CLEO
II detector at the Cornell Electron Storage Ring (CESR) and correspond to an
integrated luminosity of 4.61 fb^(-1). No evidence for a signal is found.
Assuming all the charged particles are pions, we set an upper limit on the
branching fraction, B(tau- -> 4pi- 3pi+ (pi0) nu_tau) < 2.4 x 10^(-6) at the
90% confidence level. This limit represents a significant improvement over the
previous limit.Comment: 9 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Toward a theory of restraint
Consumption largely remains a black box in the population, environment, and global change debates. The dominant perspective takes insatiability as axiomatic and assumes that reduced consumption will only happen through scarcity or the impositions of external authority. Yet humans often exhibit resource limiting behavior that is not the result of external controls nor is it altruistic or aberrant. This article develops the concept of restraint as an evolutionarily and culturally significant behavior, yet one that in modern times has been relegated to a regressive, if not trivial, status. The article defines restraint, hypothesizes its historical and evolutionary roots, lays out the conditions under which it can occur, and develops a theoretical parallel to cooperation in international relations theory.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43491/1/11111_2005_Article_BF02208422.pd
Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology
notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations
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