Crowding impairs the perception of form in peripheral vision. It is likely to be a key limiting factor of form vision in patients without central vision. Crowding has been extensively studied in normally sighted individuals, typically with a stimulus duration of a few hundred milliseconds to avoid eye movements. These restricted testing conditions do not reflect the natural behavior of a patient with central field loss. Could unlimited stimulus duration and unrestricted eye movements change the properties of crowding in any fundamental way? We studied letter identification in the peripheral vision of normally sighted observers in three conditions: (i) a fixation condition with a brief stimulus presentation of 250 ms, (ii) another fixation condition but with an unlimited viewing time, and (iii) an unrestricted eye movement condition with an artificial central scotoma and an unlimited viewing time. In all conditions, contrast thresholds were measured as a function of target-to-flanker spacing, from which we estimated the spatial extent of crowding in terms of critical spacing. We found that presentation duration beyond 250 ms had little effect on critical spacing with stable gaze. With unrestricted eye movements and a simulated central scotoma, we found a large variability in critical spacing across observers, but more importantly, the variability in critical spacing was well correlated with the variability in target eccentricity. Our results assure that the large body of findings on crowding made with briefly presented stimuli remains relevant to conditions where viewing time is unconstrained. Our results further suggest that impaired oculomotor control associated with central vision loss can confound peripheral form vision beyond the limits imposed by crowding.

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Quadriceps tendon rupture is an uncommon injury; the incidence of simultaneous bilateral quadriceps tendon rupture is extremely rare. Two distinct categories-individuals older than 50 years and between 27 and 54 years-have been described. Bilateral quadriceps tendon rupture is more common in patients older than 50 years and is thought to be the result of tendon weakening due to obesity and arteriosclerosis-induced fibrotic changes, or previous injury.In younger individuals, bilateral simultaneous quadriceps rupture is less frequent and has been associated with anabolic steroid use, but more frequently with underlying comorbid medical conditions such as chronic renal failure, hyperparathyroidism, endocrine disorder, gout, diabetes and obesity, which predispose the patients to tendon rupture. Our case report is unique because we report the simultaneous bilateral quadriceps tendon rupture following minor trauma in an otherwise healthy 43-year-old man with no predisposing comorbidity.

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The hydroamination of various substituted vinyl arenes with benzenesulfonamide was explored using an NHC-amidate-alkoxide palladium catalyst in conjunction with p-TsOH. Utilizing halide-substituted and electron-rich vinyl arenes, this methodology selectively furnished the cross-coupled hydroamination products in moderate to excellent yields in a Markovnikov fashion while greatly reducing undesired acid-catalyzed homocoupling of the vinyl arenes. Electron-rich vinyl arenes typically required milder conditions than electron-poor ones. While most effective for para-substituted substrates, the catalyst system also furnished the desired products from ortho- and meta-substituted vinyl arenes with high chemoselectivities.