876 research outputs found
Explicit Resolution of an Integrable c(4,3) Open String Theory
We study the two-matrix model which represents the sum over closed and open
random surfaces coupled to an Ising Model. The boundary conditions are
characterized by the fact that the Ising spins sitting at the vertices of the
boundaries are all in the same state. We obtain the string equation and discuss
the results. (No change in physics, only some misprints are corrected)Comment: 10 pages, phyzzx, ULB-TH-02/9
Influence of amino acids on the formation of mutagenic/carcinogenic heterocydic amines in a model system
Mixtures of creatinine, glucose and various single amino acids were heated at 180°C for 10 min in an aqueous model system. The heated mixtures all showed mutagenic activity, ranging from 80 to 2400 TA98 revertant colonies/μmol creatinine with metabolic activation. Testing of HPLC fractions for mutagenic activity showed each mixture to contain several mutagenic components, some of which corresponded to known heterocyclic amines and others to unknown compounds. The presence of 2-amino-3-methyl-imidazo[4,5-f]quinoxaline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline in most of the samples was established using HPLC with photodiode array detection and liquid chromatography/mass spectrometry with electrospray interface and single ion monitoring. In addition, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 3-amino-1,4-di-methyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole and the co-mutagenic compounds 9H-pyrido[3,4-bindole and 1-methyl-9H-pyrido[3,4-b]indole were detected in some sample
Chaotic itinerancy, temporal segmentation and spatio-temporal combinatorial codes
We study a deterministic dynamics with two time scales in a continuous state
attractor network. To the usual (fast) relaxation dynamics towards point
attractors (``patterns'') we add a slow coupling dynamics that makes the
visited patterns to loose stability leading to an itinerant behavior in the
form of punctuated equilibria. One finds that the transition frequency matrix
between patterns shows non-trivial statistical properties in the chaotic
itinerant regime. We show that mixture input patterns can be temporally
segmented by the itinerant dynamics. The viability of a combinatorial
spatio-temporal neural code is also demonstrated
Characterization of Core Optics in Gravitational-Wave Detectors: Case Study of KAGRA Sapphire Mirrors
We report the characterization of superlow-loss optics used in the second-generation gravitational-wave detectors currently in operation. The sapphire test-mass mirrors in the KAGRA detector are introduced as an example, but the techniques here are common to all detectors. In this work, we discuss mainly the surface topography obtained by interferometric techniques and the optical properties obtained with special setups
Barrett-Crane model from a Boulatov-Ooguri field theory over a homogeneous space
Boulatov and Ooguri have generalized the matrix models of 2d quantum gravity
to 3d and 4d, in the form of field theories over group manifolds. We show that
the Barrett-Crane quantum gravity model arises naturally from a theory of this
type, but restricted to the homogeneous space S^3=SO(4)/SO(3), as a term in its
Feynman expansion. From such a perspective, 4d quantum spacetime emerges as a
Feynman graph, in the manner of the 2d matrix models. This formalism provides a
precise meaning to the ``sum over triangulations'', which is presumably
necessary for a physical interpretation of a spin foam model as a theory of
gravity. In addition, this formalism leads us to introduce a natural
alternative model, which might have relevance for quantum gravity.Comment: 16 Pages (RevTeX), 4 eps figures. Minor revisions in the definition
of the mode
Procedure for the fine delay adjustment of the CMS tracker
One of the crucial aspects of the commissioning of the CMS silicon tracker will be the absolute timing adjustment of each module, to accommodate both delays introduced by the hardware configuration and effects due to the time of flight of particles. The objective is to be optimally synchronized with the bunch-crossing to maximize the efficiency while minimizing the number of remnant hits from the adjacent bunch-crossings. In the present note, a procedure to reach that goal is studied. Monte Carlo studies as well as the analysis of data from the commissioning of the detector are used to assess the time needed and the resolution that can be achieved. Critical aspects are discussed, and results from the first implementation are presented
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