We present an algorithm for improving the accuracy of algorithms for learning binary concepts. The improvement is achieved by combining a large number of hypotheses, each of which is generated by training the given learning algorithm on a different set of examples. Our algorithm is based on ideas presented by Schapire in his paper "The strength of weak learnability", and represents an improvement over his results. The analysis of our algorithm provides general upper bounds on the resources required for learning in Valiant's polynomial PAC learning framework, which are the best general upper bounds known today. We show that the number of hypotheses that are combined by our algorithm is the smallest number possible. Other outcomes of our analysis are results regarding the representational power of threshold circuits, the relation between learnability and compression, and a method for parallelizing PAC learning algorithms. We provide extensions of our algorithms to cases in which the conc...

the underlying causes require very different types of investigation and, if missed, can have serious sequelae for the patient, a rational approach based on the understanding of the causes of hypopyon uveitis is imperative. In this review, hypopyon uveitis is considered in the context of the associated ocular

Vertically acquired paediatric HIV infection: the challenges of providing comprehensive packages of care in resource-limited settings

Abstract. A macular hole is a full-thickness defect of retinal tissue involving the anatomic fovea, thereby affecting central visual acuity. Macular holes have been associated with myriad ocular conditions and originally were described in the setting of trauma. The pathogenesis of idiopathic, age-related macular holes remains unclear despite a litany of theories. Recently, Gass has described an updated biomicroscopic classification of macular holes and postulated that tangential vitreous traction may play a role. Cellular components surrounding the rim of macular holes may also contribute tangential traction forces and elevate the rim. Pseudomacular holes may be mistaken for macular hole lesions, despite careful clinical examination. Careful biomicroscopic examination with a contact lens and use of the Watzke and laser aiming beam tests help to ensure accurate diagnosis. Newer imaging technology, such as optical coherence tomography, helps distinguish true macular holes from pseudoholes and may provide additional insight into the pathogenesis of this condition. Surgical management with or without pharmacosurgical adjuncts can improve vision in select cases. The most common surgical complication is progressive lens opacification in phakic patients. (Surv Ophthalmol 42:393–416, 1998. © 1998 by Elsevier Science Inc. All rights reserved.) Key words. lamellar macular hole • macular hole • macular pseudohole • vitrectomy •

The literature on interference in the Stroop Color-Word Task, covering over 50 years and some 400 studies, is organized and reviewed. In so doing, a set ofl 8 reliable empirical findings is isolated that must be captured by any successful theory of the Stroop effect. Existing theoretical positions

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This paper presents a simple unsupervised learning algorithm for classifying reviews as recommended (thumbs up) or not recommended (thumbs down). The classification of a review is predicted by the average semantic orientation of the phrases in the review that contain adjectives or adverbs

for the modeling and simulation of genetic regulatory networks will be indispensable. This paper reviews formalisms that have been employed in mathematical biology and bioinformatics to describe genetic regulatory systems, in particular directed graphs, Bayesian networks, Boolean networks and their generalizations

An ad-hoc mobile network is a collection of mobile nodes that are dynamically and arbitrarily located in such a manner that the interconnections between nodes are capable of changing on a continual basis. In order to facilitate communication within the network, a routing protocol is used to discover routes between nodes. The primary goal of such an ad-hoc network routing protocol is correct and efficient route establishment between a pair of nodes so that messages may be delivered in a timely manner. Route construction should be done with a minimum of overhead and bandwidth consumption. This paper examines routing protocols for ad-hoc networks and evaluates these protocols based on a given set of parameters. The paper provides an overview of eight different protocols by presenting their characteristics and functionality, and then provides a comparison and discussion of their respective merits and drawbacks.

-choice behavior (d = 0.33) and self-reported interest (d = 0.31). Tangible rewards tended to be more detrimental for children than college students, and verbal rewards tended to be less enhancing for children than college students. The authors review 4 previous meta-analyses of this literature and detail how