363 research outputs found
Partial mirror symmetry, lattice presentations and algebraic monoids
This is the second in a series of papers that develops the theory of
reflection monoids, motivated by the theory of reflection groups. Reflection
monoids were first introduced in arXiv:0812.2789. In this paper we study their
presentations as abstract monoids. Along the way we also find general
presentations for certain join-semilattices (as monoids under join) which we
interpret for two special classes of examples: the face lattices of convex
polytopes and the geometric lattices, particularly the intersection lattices of
hyperplane arrangements. Another spin-off is a general presentation for the
Renner monoid of an algebraic monoid, which we illustrate in the special case
of the "classical" algebraic monoids.Comment: 41 page
The Southern Extension and Reactivations of the Clarendon-Linden Fault System
Gas seeps located near Pike, New York, on the inferred location of the central fault of the Clarendon-Linden Fault System (CLF), were initiated during, or slightly after, the Saguenay earthquake, 1988. Analyses of the gas show that the gas seeps have a Devonian shale source, and a nearby well suggests that the source may be as deep as 330 m. Thus, CLF fractures extending to depths possibly as great as 300+ m were probably opened as a local response to the Saguenay event, allowing the gas to be vented. Published data show that the CLF extends from Lake Ontario to slightly south of Pike. Previously, there were insufficient data available to enable investigators to determine if the fault system continued farther south. Our soil gas survey and analyses of well logs indicate the CLF continues south into Allegany County, which borders the state of Pennsylvania. Closely-spaced wells suggest that the central fault of the CLF is probably a series of step faults, even in units above the Silurian evaporite section, although a monocline cannot be ruled out. Growth-fault geometries of the CLF suggest that the CLF experienced motion during the Taconic and Acadian orogenies. Isopach maps, coupled with the proposed southward extrapolation of the CLF, suggest that in Late Devonian times the CLF motion history recorded the passage of the Appalachian foreland basin axis across the CLF.Des dĂ©gagements gazeux survenus prĂšs de Pike (Ătat de New York), Ă l'emplacement supposĂ© de la faille centrale du rĂ©seau de Clarendon-Linden (RCL), se sont produits pendant ou aussitĂŽt aprĂšs le sĂ©isme de 1988, au Saguenay. Les analyses du gaz dĂ©montrent que les fuites proviennent d'une source de shale dĂ©vonien aussi profonde que 330 m. Les fractures du RCL, atteignant plus de 300 m de profondeur, se sont vraisemblablement ouvertes en rĂ©ponse au sĂ©isme du Saguenay, permettant ainsi au gaz de se dĂ©gager. Les donnĂ©es publiĂ©es montrent que le RCL s'Ă©tend du lac Ontario jusqu'au sud de Pike, mais on n'a pu dĂ©terminer jusqu'Ă maintenant si le rĂ©seau se poursuit plus au sud. Les levĂ©s sur la dĂ©tection de gaz dans le sol et les analyses de donnĂ©es des puits indiquent que le RCL se poursuit dans le comtĂ© d'Allegany, qui borde la Pennsylvanie. Ă partir d'indices tirĂ©s de puits trĂšs rapprochĂ©s, on croit que la faille centrale du rĂ©seau consiste probablement en une sĂ©rie de failles en gradin, mĂȘme dans les unitĂ©s au-dessus de la section d'Ă©vaporite du Silurien, bien qu'un monoclinal ne puisse ĂȘtre rejetĂ©. La gĂ©omĂ©trie de la croissance des failles montre que le RCL s'est dĂ©placĂ© au cours des orogĂ©nies laconique et acadienne. Les cartes d'isopaques, ainsi que la trajectoire prĂ©sumĂ©e vers le sud du RCL, indique le RCL a enregistrĂ© le passage de l'axe de l'avant-bassin appalachien au cours du DĂ©vonien supĂ©rieur.Das Entweichen von Gas in der NĂ he von Pike, New York, an der Stelle, die man fur den zentralen Bruch des Clarendon-Linden Verwerfungssystems halt (CLV), hat I988, wĂ hrend oder kurz nach dem Erdbeben von Saguenay begonnen. Analysen des Gases zeigen, daB das entwichene Gas aus einer Tonschieferquelle des Devon stammt, und ein nahegelegener Brunnen IaRt vermuten, daB die Quelle 330 m tief sein konnte. So haben sich wohl CLV-BrĂčche, die mĂŽglicherweise bis zu 300+ m tief sind, als lokale Reaktion auf das Saguenay-Ereignis geĂŽffnet und haben so das Gas freigelassen. Die veroffentlichten Daten zeigen, daB das CLV sich vom Ontario-See bis etwas sĂčdlich von Pike ausdehnt. Zuvor waren nicht genĂčgend Daten verfĂčgbar, mit denen die Forscher bestimmen konnten, ob das Verwerfungssystem sich weiter sĂčdlich ausdehnte. Aus Erhebungen Ăčber Erdgas und Untersuchungen von Angaben aus Brunnen ergibt sich, daB das CLV sich bis in die Grafschaft Allegany fortsetzt, die an Pennsylvanien grenzt. Dicht aufeinanderfolgende Brunnen lassen darauf schlieBen, daB der zentrale Bruch des CLV wahrscheinlich aus einer SĂ©rie von abgestuften Verwerfungen besteht, selbst in Einheiten oberhalb des Evaporationsabschnittes aus dem Silur, wenn auch ein Monoklinal nicht ausgeschlossen werden kann. Die Wachstumsgeometrie der Bruche des CLV legt nahe, daB das CLV sich wĂ hrend der takonischen und akadischen OrogenĂšse bewegt hat. Isopach-Karten sowie die mutmaBliche SĂčdwartsbewegung des CLV zeigen, daB die Bewegungsgeschichte des CLV im spĂ ten Devon den Durchzug der Appalachen-Vorlandbeckenachse durch das CLV aufgezeichent hat
PRODUCTS OF IDEMPOTENT ENDOMORPHISMS OF RELATIVELY FREE ALGEBRAS WITH WEAK EXCHANGE PROPERTIES
Estimating Subjective Probabilities
Subjective probabilities play a role in many economic decisions. There is a large theoretical literature on the elicitation of subjective probabilities, and an equally large empirical literature. However, there is a gulf between the two. The theoretical literature proposes a range of procedures that can be used to recover subjective probabilities, but stresses the need to make strong auxiliary assumptions or "calibrating adjustments" to elicited reports in order to recover the latent probability. With some notable exceptions, the empirical literature seems intent on either making those strong assumptions or ignoring the need for calibration. We illustrate how the joint estimation of risk attitudes and subjective probabilities using structural maximum likelihood methods can provide the calibration adjustments that theory calls for. This allows the observer to make inferences about the latent subjective probability, calibrating for virtually any well-specified model of choice under uncertainty. We demonstrate our procedures with experiments in which we elicit subjective probabilities. We calibrate the estimates of subjective beliefs assuming that choices are made consistently with expected utility theory or rank-dependent utility theory. Inferred subjective probabilities are significantly different when calibrated according to either theory, thus showing the importance of undertaking such exercises. Our findings also have implications for the interpretation of probabilities inferred from prediction markets.
Automatic Recognition of Light Microscope Pollen Images
This paper is a progress report on a project aimed at the realization of a low-cost, automatic, trainable system "AutoStage" for recognition and counting of pollen. Previous work on image feature selection and classification has been extended by design and integration of an XY stage to allow slides to be scanned, an auto focus system, and segmentation software. The results of a series of classification tests are reported, and verified by comparison with classification performance by expert palynologists. A number of technical issues are addressed, including pollen slide preparation and slide sampling protocols
Inferring Beliefs as Subjectively Uncertain Probabilities
We propose a method for estimating subjective beliefs, viewed as a subjective probability distribution. The key insight is to characterize beliefs as a parameter to be estimated from observed choices in a well-defined experimental task, and to estimate that parameter as a random coefficient. The experimental task consists of a series of standard lottery choices in which the subject is assumed to use conventional risk attitudes to select one lottery or the other, and then a series of betting choices in which the subject is presented with a range of bookies offering odds on the outcome of some event that the subject has a belief over. Knowledge of the risk attitudes of subjects conditions the inferences about subjective beliefs. Maximum simulated likelihood methods are used to estimate a structural model in which subjects employ subjective beliefs to make bets. We present evidence that some subjective probabilities are indeed best characterized as probability distributions with non-zero variance.
ANTI-NMDA ENCEPHALITIS IN THE ACUTE SETTING
Background: Encephalitis associated with antibodies targeted against the N-methyl-D-aspartate (NMDA) receptor is
increasingly recognised as a major cause of an acute presentation of organic psychosis. Misdiagnosis and subsequent inappropriate
referral to psychiatric services is common and avoidable. This review focuses on addressing this issue in the acute setting.
Methods: The authors present a review of existing literature relating to the pathophysiology and presentation of anti-NMDA
receptor encephalitis, prior to proposing a management pathway avoiding delays to treatment incurred through misdiagnosis or
inappropriate referral.
Conclusions: Acute care physicians should have a low threshold for suspecting anti-NMDA receptor encephalitis in any patient
presenting with acute psychosis in the context of non-specific coryzal and constitutional symptoms in whom infective causes have
been excluded. The presence of pleocytosis and reduced protein in routine CSF analysis should further raise suspicion, and samples
should be sent for immunohistochemical testing. Availability and efficiency of this testing is currently suboptimal
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