Milagrito, a large, covered water-Cherenkov detector, was the world's first air-showerparticle detector sensitive to cosmic gamma rays below 1 TeV. It served as a prototype for the Milagro detector and operated from February 1997 to May 1998. This paper gives a description of Milagrito, a summary of the operating experience, and early results that demonstrate the capabilities of this technique. : 95.55.Ka, 29.40.Ka, 95.85.Pw
PACS
ABSTRACT.Purpose: The aim of this study was to assess the feasibility of a visual acuity (VA) test using the Lea Symbols 15-line folding distance chart and its diagnostic validity in detecting VA deficiency in preschool children. Methods: A group of 149 children aged 38-54 months underwent VA examination performed with the Lea 15-line folding optotype at a distance of 3 metres, according to a test protocol described in the Methods section. After the VA test, a complete ophthalmological examination, including cycloplegic retinoscopy, a cover test and examination of the anterior and posterior segments, was performed on each child in order to detect any VA-threatening ocular abnormality. The Lea Symbols test's sensitivity, specificity, positive and negative likelihood ratios (LR +, LR )) and the receiver operating characteristic (ROC) curve were calculated by means of standard procedures using each VA level of the chart from 0.1 to 1 (1-0 logMAR) as a cut-off point. Results: The Lea Symbols test could be successfully used in 95.9% of the population. The most useful cut-off points for screening preschool children were found to be 0.8 (LR + 5.73, LR ) 0.05) or 0.63 (LR + 11.7, LR ) 0.23).
Conclusion:The Lea Symbols test proved to be clinically useful in detecting VA deficiency in preschool children. The choice between the two best performing cut-off levels should be made according to the expected cost-effectiveness of the screening programme.
SUMMARY In 40 eyes of 20 esotropic subjects in which a 'Fadenoperation' was performed on the medial recti we measured the resistance to ocular rotation in adduction before and after the operation. The difference between the two sets of force measurements demonstrates that the Fadenoperation on medial recti produces a mechanical restriction to adduction which can explain the effect of the surgical procedure on the strabismic deviation.In 1974 Ctppers described the well known surgical procedure which he named 'Fadenoperation'.' The effect of the operation was at first attributed solely to the reduction of the tangential component of the muscle force produced by the posterior fixation.'2 Later it was pointed out3 that several different mechanisms could interact and concur to produce the surgical effect:(1) the reduction of the rotational component of the force generated by the muscle;(2) the exclusion from activity of a contingent of the muscle fibres; (3) a stretching of the muscle owing to the fact that the scleral fixation increases the distance between the origin and the true insertion of the muscle if the true insertion remains in its original position; (4) a slack in the muscle fibres posterior to the fixation suture which occurs when the tightening of the suture is made while the muscle is stretched to provide adequate exposure4;(5) a mechanical restriction to ocular rotation in the field of action of the operated muscle"6 produced by the connective tissue structures, which endeavour to maintain the physiological course of the muscle,3 or by a 'reverse leash' mechanism.7 All these hypothetical effects were derived from a theoretical analysis of the new mechanical situation Correspondence to G P Paliaga, MD, Centro per lo Strabismo, Via Masia 97,
This paper describes the results of a beam test using the Engineering Model of the GLAST Large Area Telescope, which w as installed in a beam of positrons, hadrons and tagged photons at SLAC. The performance of the four subsystems, Anti Coincidence Detector, Silicon Tracker, Calorimeter and Data Acquisition will be described.
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