622 research outputs found

    Training the brain to overcome the effect of aging on the human eye

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    Presbyopia, from the Greek for aging eye, is, like death and taxes, inevitable. Presbyopia causes near vision to degrade with age, affecting virtually everyone over the age of 50. Presbyopia has multiple negative effects on the quality of vision and the quality of life, due to limitations on daily activities – in particular, reading. In addition presbyopia results in reduced near visual acuity, reduced contrast sensitivity, and slower processing speed. Currently available solutions, such as optical corrections, are not ideal for all daily activities. Here we show that perceptual learning (repeated practice on a demanding visual task) results in improved visual performance in presbyopes, enabling them to overcome and/or delay some of the disabilities imposed by the aging eye. This improvement was achieved without changing the optical characteristics of the eye. The results suggest that the aging brain retains enough plasticity to overcome the natural biological deterioration with age

    Universality in the three-dimensional random bond quantum Heisenberg antiferromagnet

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    The three-dimensional quenched random bond diluted (J1J2)(J_1-J_2) quantum Heisenberg antiferromagnet is studied on a simple-cubic lattice. Using extensive stochastic series expansion quantum Monte Carlo simulations, we perform very long runs for L×L×LL \times L \times L lattice up to L=48L=48. By employing standard finite-size scaling method, the numerical values of the N\'eel temperature are determined with high precision as a function of the coupling ratio r=J2/J1r=J_2/J_1. Based on the estimated critical exponents, we find that the critical behavior of the considered model belongs to the pure classical 3D3D O(3)O(3) Heisenberg universality class.Comment: 8 pages, 7 figure

    The spatial range of peripheral collinear facilitation

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    Contrast detection thresholds for a central Gabor patch (target) can be modulated by the presence of co-oriented and collinear high contrast Gabors flankers. In foveal vision collinear facilitation can be observed for target-to-flankers relative distances beyond two times the wavelength (λ) of the Gabor's carrier, while for shorter relative distances (<2λ) there is suppression. These modulatory influences seem to disappear after 12λ. In this study, we measured contrast detection thresholds for different spatial frequencies (1, 4 and 6 cpd) and target-to-flankers relative distances ranging from 6 to 16λ, but with collinear configurations presented in near periphery at 4° of eccentricity. Results showed that in near periphery collinear facilitation extends beyond 12λ for the higher spatial frequencies tested (4 and 6 cpd), while it decays already at 10λ for the lowest spatial frequency used (i.e., 1 cpd). In addition, we found that increasing the spatial frequency the peak of collinear facilitation shifts towards larger target-to-flankers relative distances (expressed as multiples of the stimulus wavelength), an effect never reported neither for near peripheral nor for central vision. The results suggest that the peak and the spatial extent of collinear facilitation in near periphery depend on the spatial frequency of the stimuli used

    Effect of different defoliants and application times on the yield and quality components of cotton in semi-arid conditions

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    This study was conducted to determine the effect of different defoliants (Dropp ultra&#174; (DU): thidiazuron+diuron and Roundup (RU): glyphosate) and application times [60, 75 and 90 days after flowering (DAF)] on cotton. The research was carried out at the Harran University, Faculty of Agriculture Research and Application Center in 2001 and 2002 using cotton variety cv. Stoneville-453. Experiments were arranged as split plot design with three replications. Defoliations were at the main plots and application times at the subplots. Experimental plots were consisted of six rows, 10 m in length, interrow was 0.70 m and intra-row spacing was 0.20 m. The results of the study indicated that the application of DU defoliant at 60 days after flowering reduced seed cotton yield, number of bolls, boll weight and lint index. With this, seed cotton yield, number of bolls, boll weight and lint index increased with delayed defoliation time in both years. Also, there were no statistically significant differences between the treatments in terms of ginning outturn, fiber length, fiber strength and fiber fineness. It was also found that the application of 2000 cc ha-1 RU was not enough as a dose to affect leaf defoliation and other investigated components

    Reducing Crowding by Weakening Inhibitory Lateral Interactions in the Periphery with Perceptual Learning

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    We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at an early level of central visual processing, could be weakened by perceptual learning and whether learning transferred to an untrained, higher-level lateral masking known as crowding. The trained task was contrast detection of a Gabor target presented in the near periphery (4°) in the presence of co-oriented and co-aligned high contrast Gabor flankers, which featured different target-to-flankers separations along the vertical axis that varied from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at target-to-flankers distances (2λ - 4λ and 8λ, respectively) that were larger than those found in the fovea. Training reduces suppression but does not increase facilitation. Most importantly, we found that learning reduces crowding and improves contrast sensitivity, but has no effect on visual acuity (VA). These results suggest a different pattern of connectivity in the periphery with respect to the fovea as well as a different modulation of this connectivity via perceptual learning that not only reduces low-level lateral masking but also reduces crowding. These results have important implications for the rehabilitation of low-vision patients who must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation, which normal sighted subjects perform in the fovea

    CT in differential diagnosis of benign and malignant pleural disease

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    Background. CT plays a valuable role in assessment of patients with a wide variety of diseases of the pleura, and pulmonologists should be aware of the significance of different CT findings for the differential diagnosis of benign and malignant pleural diseases. Methods. 155 patients with pleural disease who had undergone CT scans of the lungs and thorax before treatment were enrolled. We retrospectively reviewed CT findings in 146 patients with proven pleural disease. Results. Fifty-nine of the cases were malignant, 87 of them had benign pleural diseases. CT findings that were helpful in distinguishing malignant from benign pleural disease were: 1) pleural nodularity; 2) rind; 3) mediastinal pleural involvement; and 4) pleural thickening greater than 1 cm. The sensitivities and specificities were 37%/97%, 22%/97%, 31%/85%, 35%/87%, respectively. CT findings differentiating malignant pleural mesothelioma from metastatic pleural disease were identified. Findings for malignant mesothelioma were as follows: 1) involvement of interlobar fissure (sensitivity 30%, specificity 92%), 2) pleural thickening greater than 1 cm (sensitivity 60%, specificity 77%). Whereas, findings for metastatic pleural disease were mediastinal/hilar lymph node enlargement and lung parenchymal involvement (P<.05). Conclusion. CT is helpful in the differential diagnosis of pleural diseases, particularly in differentiating malignant from benign conditions and metastatic pleural disease from malignant mesothelioma

    Evaluation of the Steelex M600H coagulometer prothrombin time-international normalized ratio assay with Steelex test reagents

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    Introduction: The aim of the present study was to validate prothrombin time (PT) international nor-malized ratio (INR) results obtained using Steelex test reagents and a Steelex coagulometer (Steelex Scientific Instrument Company, Beijing, China), in comparison with use of a well-established standard test employing Pacific Hemostasis reagents (Fisher Diagnostics, Middletown, VA, USA) and Teco Coatron A4 coagulometer (Teco Medical Instruments GmbH, Neufahrn, Germany). Materials and methods: Between- and within-day coefficients of variation (CVs) of both assays were calculated using control samples provided by the test manufacturers. Samples from 90 subjects were collected and INR values were determined in a double-blind parallel manner employing both systems. Results: The within-day coefficients of variation (CVs) in INR estimates ranged from 2.6% (INR = 1.12) to 3.1% (INR = 2.51) for the Steelex system and from 2.1% (INR = 1.09) to 1.8% (INR = 2.8) for the Pacific test; the between-day values ran from 3.4% (INR = 1.16) to 7.9% (INR = 2.64) and from 3.3% (INR = 1.1) to 2.3% (INR = 2.7), respectively. Passing-Bablok fit of the of the Steelex and Pacific methods yielded the equation: Steelex INR = 0.85 (0.79-0.91) × Pacific INR + 0.12 (-0.02-0.21), whereas the CUSUM linearity P value was <0.01. The mean bias as determined by the Bland-Altman test was -0.156 (-0.912-0.600). Conclusion: The results obtained using Steelex reagents and the M600H coagulometer are not equivalent to those obtained using Pacific Hemostasis reagents and a Teco Coatron A4 coagulome-ter, at least in the therapeutic range

    Building productive relationships with young people with SEBD in transition: the role of identity

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    This article reports a study of the experiences of school leavers with social, emotional and behavioural difficulties (SEBD), which identified supportive relationships as key elements in young people demonstrating resilience through this transitional period. Almost all the young people involved in the study had access to potential helpers, but few managed to establish productive relationships with them. Analysis of interviews, conducted over a 15 month period with a group of 15 school leavers, their parents and those who worked with them, suggested that barriers and facilitators to relationship development existed at two levels: institutional and individual. This article focuses on the individual level, in which identity processes appear to play a key role. These processes are used to explain why some school leavers built productive relationships and thrived, whilst many failed to do so, and struggled. These findings have implications for policy, practice and theory
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