Effect of lutein and antioxidant dietary supplementation on contrast sensitivity in age-related macular disease:A randomized controlled trial

Objective: The aim of the study is to determine the effect of lutein combined with vitamin and mineral supplementation on contrast sensitivity in people with age-related macular disease (ARMD). Design: A prospective, 9-month, double-masked randomized controlled trial. Setting: Aston University, Birmingham, UK and a UK optometric clinical practice. Subjects: Age-related maculopathy (ARM) and atrophic age-related macular degeneration (AMD) participants were randomized (using a random number generator) to either placebo (n = 10) or active (n=15) groups. Three of the placebo group and two of the active group dropped out. Interventions: The active group supplemented daily with 6 mg lutein combined with vitamins and minerals. The outcome measure was contrast sensitivity (CS) measured using the Pelli-Robson chart, for which the study had 80% power at the 5% significance level to detect a change of 0.3log units. Results: The CS score increased by 0.07 ± 0.07 and decreased by 0.02 ± 0.18 log units for the placebo and active groups, respectively. The difference between these values is not statistically significant (z = 0.903, P = 0.376). Conclusion: The results suggest that 6 mg of lutein supplementation in combination with other antioxidants is not beneficial for this group. Further work is required to establish optimum dosage levels.

Contrast masking in strabismic amblyopia: attenuation, noise, interocular suppression and binocular summation

To investigate amblyopic contrast vision at threshold and above we performed pedestal-masking (contrastdiscrimination) experiments with a group of eight strabismic amblyopes using horizontal sinusoidal gratings (mainly 3 c/deg) in monocular, binocular and dichoptic configurations balanced across eye (i.e. five conditions). With some exceptions in some observers, the four main results were as follows. (1) For the monocular and dichoptic conditions, sensitivity was less in the amblyopic eye than in the good eye at all mask contrasts. (2) Binocular and monocular dipper functions superimposed in the good eye. (3) Monocular masking functions had a normal dipper shape in the good eye, but facilitation was diminished in the amblyopic eye. (4) A less consistent result was normal facilitation in dichoptic masking when testing the good eye, but a loss of this when testing the amblyopic eye. This pattern of amblyopic results was replicated in a normal observer by placing a neutral density filter in front of one eye. The two-stage model of binocular contrast gain control [Meese, T.S., Georgeson, M.A. & Baker, D.H. (2006). Binocular contrast vision at and above threshold. Journal of Vision 6, 1224--1243.] was `lesioned' in several ways to assess the form of the amblyopic deficit. The most successful model involves attenuation of signal and an increase in noise in the amblyopic eye, and intact stages of interocular suppression and binocular summation. This implies a behavioural influence from monocular noise in the amblyopic visual system as well as in normal observers with an ND filter over one eye.

The effect of lutein and antioxidant dietary supplementation on contrast sensitivity in age-related macular disease

There is interest in the use of nutritional supplementation as a prevention and treatment strategy for age-related macular disease as later stages of the condition are the leading cause of visual disability in the developed World .

Social media in emergency management:Twitter as a tool for communicating risks to the public

One of the main challenges of emergency management lies in communicating risks to the public. On some occasions, risk communicators might seek to increase awareness over emerging risks, while on others the aim might be to avoid escalation of public reactions. Social media accounts offer an opportunity to rapidly distribute critical information and in doing so to mitigate the impact of emergencies by influencing public reactions. This article draws on theories of risk and emergency communication in order to consider the impact of Twitter as a tool for communicating risks to the public. We analyse 10,020 Twitter messages posted by the official accounts of UK local government authorities (councils) in the context of two major emergencies: the heavy snow of December 2010 and the riots of August 2011. Twitter was used in a variety of ways to communicate and manage associated risks including messages to provide official updates, encourage protective behaviour, increase awareness and guide public attention to mitigating actions. We discuss the importance of social media as means of increasing confidence in emergency management institutions.

Contrast and lustre:a model that accounts for eleven different forms of contrast discrimination in binocular vision

Our goal here is a more complete understanding of how information about luminance contrast is encoded and used by the binocular visual system. In two-interval forced-choice experiments we assessed observers' ability to discriminate changes in contrast that could be an increase or decrease of contrast in one or both eyes, or an increase in one eye coupled with a decrease in the other (termed IncDec). The base or pedestal contrasts were either in-phase or out-of-phase in the two eyes. The opposed changes in the IncDec condition did not cancel each other out, implying that along with binocular summation, information is also available from mechanisms that do not sum the two eyes' inputs. These might be monocular mechanisms. With a binocular pedestal, monocular increments of contrast were much easier to see than monocular decrements. These findings suggest that there are separate binocular (B) and monocular (L,R) channels, but only the largest of the three responses, max(L,B,R), is available to perception and decision. Results from contrast discrimination and contrast matching tasks were described very accurately by this model. Stimuli, data, and model responses can all be visualized in a common binocular contrast space, allowing a more direct comparison between models and data. Some results with out-of-phase pedestals were not accounted for by the max model of contrast coding, but were well explained by an extended model in which gratings of opposite polarity create the sensation of lustre. Observers can discriminate changes in lustre alongside changes in contrast.

Binocular summation of contrast remains intact in strabismic amblyopia

PURPOSE. Strabismic amblyopia is typically associated with several visual deficits, including loss of contrast sensitivity in the amblyopic eye and abnormal binocular vision. Binocular summation ratios (BSRs) are usually assessed by comparing contrast sensitivity for binocular stimuli (sens BIN) with that measured in the good eye alone (sensGOOD), giving BSR = sensBIN/sensGOOD. This calculation provides an operational index of clinical binocular function, but does not assess whether neuronal mechanisms for binocular summation of contrast remain intact. This study was conducted to investigate this question. METHODS. Horizontal sine-wave gratings were used as stimuli (3 or 9 cyc/deg; 200 ms), and the conventional method of assessment (above) was compared with one in which the contrast in the amblyopic eye was adjusted (normalized) to equate monocular sensitivities. RESULTS. In nine strabismic amblyopes (mean age, 32 years), the results confirmed that the BSR was close to unity when the conventional method was used (little or no binocular advantage), but increased to approximately √2 or higher when the normalization method was used. The results were similar to those for normal control subjects (n = 3; mean age, 38 years) and were consistent with the physiological summation of contrast between the eyes. When the normal observers performed the experiments with a neutral-density (ND) filter in front of one eye, their performance was similar to that of the amblyopes in both methods of assessment. CONCLUSIONS. The results indicate that strabismic amblyopes have mechanisms for binocular summation of contrast and that the amblyopic deficits of binocularity can be simulated with an ND filter. The implications of these results for best clinical practice are discussed. Copyright © Association for Research in Vision and Ophthalmology.

Interocular suppression and contrast gain control in human vision

The human visual system combines contrast information from the two eyes to produce a single cyclopean representation of the external world. This task requires both summation of congruent images and inhibition of incongruent images across the eyes. These processes were explored psychophysically using narrowband sinusoidal grating stimuli. Initial experiments focussed on binocular interactions within a single detecting mechanism, using contrast discrimination and contrast matching tasks. Consistent with previous findings, dichoptic presentation produced greater masking than monocular or binocular presentation. Four computational models were compared, two of which performed well on all data sets. Suppression between mechanisms was then investigated, using orthogonal and oblique stimuli. Two distinct suppressive pathways were identified, corresponding to monocular and dichoptic presentation. Both pathways impact prior to binocular summation of signals, and differ in their strengths, tuning, and response to adaptation, consistent with recent single-cell findings in cat. Strikingly, the magnitude of dichoptic masking was found to be spatiotemporally scale invariant, whereas monocular masking was dependent on stimulus speed. Interocular suppression was further explored using a novel manipulation, whereby stimuli were presented in dichoptic antiphase. Consistent with the predictions of a computational model, this produced weaker masking than in-phase presentation. This allowed the bandwidths of suppression to be measured without the complicating factor of additive combination of mask and test. Finally, contrast vision in strabismic amblyopia was investigated. Although amblyopes are generally believed to have impaired binocular vision, binocular summation was shown to be intact when stimuli were normalized for interocular sensitivity differences. An alternative account of amblyopia was developed, in which signals in the affected eye are subject to attenuation and additive noise prior to binocular combination.

The social construction of sleep and work in the British print news media

This article presents a sociological study of sleep issues in the British print news media, with particular focus on the relationship between sleep, work and the changing demands of ‘flexible capitalism’. Drawing on over 1000 newspaper articles from 1984 to 2005, we explore how and why sleep is framed or constructed in terms of continuity and change (in British working life and work cultures) and, equally, viewed as a neglected component of our social lives which is too easily sacrificed to the demands of the 24/7 society, long hours culture and the struggle to create a harmonious work-life balance. This is particularly the case for certain British work cultures in which sleep has conflicting and contrasting associations. Finally, we reflect on the broader class-based discourses and debates that arise from certain workers having their sleep patterns increasingly scrutinized and regulated, and the role of the media in any ensuing sleep/work ‘crisis’.

Distinct contrast response functions in striate and extra-striate regions of visual cortex revealed with magnetoencephalography (MEG)

Objective: To spatially and temporally characterise the cortical contrast response function to pattern onset stimuli in humans. Methods: Magnetoencephalography (MEG) was used to investigate the human cortical contrast response function to pattern onset stimuli with high temporal and spatial resolution. A beamformer source reconstruction approach was used to spatially localise and identify the time courses of activity at various visual cortical loci. Results: Consistent with the findings of previous studies, MEG beamformer analysis revealed two simultaneous generators of the pattern onset evoked response. These generators arose from anatomically discrete locations in striate and extra-striate visual cortex. Furthermore, these loci demonstrated notably distinct contrast response functions, with striate cortex increasing approximately linearly with contrast, whilst extra-striate visual cortex followed a saturating function. Conclusions: The generators that underlie the pattern onset visual evoked response arise from two distinct regions in striate and extra-striate visual cortex. Significance: The spatially, temporally and functionally distinct mechanisms of contrast processing within the visual cortex may account for the disparate results observed across earlier studies and assist in elucidating causal mechanisms of aberrant contrast processing in neurological disorders. © 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Differential impact of posterior lesions in the left and right hemisphere on visual category learning and generalization to contrast reversal

Hemispheric differences in the learning and generalization of pattern categories were explored in two experiments involving sixteen patients with unilateral posterior, cerebral lesions in the left (LH) or right (RH) hemisphere. In each experiment participants were first trained to criterion in a supervised learning paradigm to categorize a set of patterns that either consisted of simple geometric forms (Experiment 1) or unfamiliar grey-level images (Experiment 2). They were then tested for their ability to generalize acquired categorical knowledge to contrast-reversed versions of the learning patterns. The results showed that RH lesions impeded category learning of unfamiliar grey-level images more severely than LH lesions, whereas this relationship appeared reversed for categories defined by simple geometric forms. With regard to generalization to contrast reversal, categorization performance of LH and RH patients was unaffected in the case of simple geometric forms. However, generalization to of contrast-reversed grey-level images distinctly deteriorated for patients with LH lesions relative to those with RH lesions, with the latter (but not the former) being consistently unable to identify the pattern manipulation. These findings suggest a differential use of contrast information in the representation of pattern categories in the two hemispheres. Such specialization appears in line with previous distinctions between a predominantly lefthemispheric, abstract-analytical and a righthemispheric, specific-holistic representation of object categories, and their prediction of a mandatory representation of contrast polarity in the RH. Some implications for the well-established dissociation of visual disorders for the recognition of faces and letters are discussed.

Growth, sporulation and spore properties of bacillus stearothemophilus produced in chemically defined media

The nutritional requirements for the vegetative growth of B. stearothermophilus strains NCIB 8919, NCTC lO,OO3 (wild) were found to be DL-methionine, biotin, nicotinic acid, thiamin, glucose and mineral salts. Strains NCIB 8920 required in addition L-tryptophan. B. stearothermophilus NCTC lO,OO3 (mutant) grew in a medium containing only glucose and mineral salts. Separate chemically defined media for the growth of Bacillus stearothermophilus strains NCIB 8919, 8920, NCTC lO,OO3 (wild) and NCTC lO,OO3 (mutant) were developed. Optimally aerated culture of B. stearothermonhilus NCTC lO,OO3(mutant) required 1.0 x 10-4 M. Mn2+ and 2.4 x 10-3 M. glutamic acid for optimal sporulation. Specific nutrient depletion of growth affected percentage sporulation. Spore suspensions of B. stearothermophilus NCTC 10,003 (mutant) were prepared from media in which sulphate (SO4-), nitrogen (N-),phosphate (Po4-), carbon (C-), magnesium-carbon simultaneously (Ng-C-) depleted growth. The heat resistance, dormancy and chemistry of these spores varied considerably. B. stearothermophilus NCTC 10,003 10,00310,00(mutant) spores prepared from carbon depleted cultures containing high and low concentrations of calcium, iron or manganese showed variations in heat resistance,dormancy and chemical composition. Progressive increase in the concentration of medium calciumfrom 1.0 X 10-5  M to 1.4 X 10-4 M. progressively increased theheat resistance of B. stearothermophilus NCTC 10,003 (mutant) spores prepared from nitrogen depleted cultures (N-). The thermodynamic functions for germination rate, magnesium and manganese release of N- and SO4- spores were within the range expected of enzymic reactions. The thermodynamic functions for the breaking of dormancy in SO4- spores and that for the release of D.P.A. were identical. Sublethal heating of SO4- spores (96.5°C and below) induced dormancy in these spores, whereas heating above 96.5°C gave rise to heat activation. Pooled results of the chemical analyses of all spore types studied showed that the concentration of D.P.A. and calcium were positively related to heat resistance whereas magnesium concentration and Mg/Ca molar ratio were inversely proportional to heat resistance.

The effect of intraocular scattered light on the contrast sensitivity function

Intraocular light scatter is high in certain subject groups eg the elderly, due to increased optical media turbidity, which scatters and attenuates light travelling towards the retina. This causes reduced retinal contrast especially in the presence of glare light. Such subjects have depressed Contrast Sensitivity Functions (CSF). Currently available clinical tests do not effectively reflect this visual disability. Intraocular light scatter may be quantified by measuring the CSF with and without glare light and calculating Light Scatter Factors (LSF). To record the CSF on clinically available equipment (Nicolet CS2000), several psychophysical measurement techniques were investigated, and the 60 sec Method of Increasing Contrast was selected as the most appropriate. It was hypothesised that intraocular light scatter due to particles of different dimensions could be identified by glare sources at wide (30°) and narrow (3.5°) angles. CSFs andLSFs were determined for: (i) Subjects in young, intermediate and old age groups. (ii) Subjects during recovery from large amounts of induced corneal oedema. (iii) A clinical sample of contact lens (CL) wearers with a group of matched controls. The CSF was attenuated at all measured spatial frequencies with the intermediate and old group compared to the young group. High LSF values were found only in the old group (over 60 years). It was concluded that CSF attenuation in the intermediate group was due to reduced pupil size, media absorption and/or neural factors. In the old group, the additional factor was high intraocular light scatter levels of lenticular origin. The rate of reduction of the LSF for the 3.5° glare angle was steeper than that for the 30° angle, following induced corneal oedema. This supported the hypothesis, as it was anticipated that epithelial oedema would recover more rapidly than stromal oedema. CSFs and LSFs were markedly abnormal in the CL wearers. The analytical details and the value of these investigative techniques in contact lens research are discussed.

Real-time detection, tracking, and monitoring of automatically discovered events in social media

We introduce ReDites, a system for realtime event detection, tracking, monitoring and visualisation. It is designed to assist Information Analysts in understanding and exploring complex events as they unfold in the world. Events are automatically detected from the Twitter stream. Then those that are categorised as being security-relevant are tracked, geolocated, summarised and visualised for the end-user. Furthermore, the system tracks changes in emotions over events, signalling possible flashpoints or abatement. We demonstrate the capabilities of ReDites using an extended use case from the September 2013 Westgate shooting incident. Through an evaluation of system latencies, we also show that enriched events are made available for users to explore within seconds of that event occurring.

Harnessing linked knowledge sources for topic classification in social media

Topic classification (TC) of short text messages offers an effective and fast way to reveal events happening around the world ranging from those related to Disaster (e.g. Sandy hurricane) to those related to Violence (e.g. Egypt revolution). Previous approaches to TC have mostly focused on exploiting individual knowledge sources (KS) (e.g. DBpedia or Freebase) without considering the graph structures that surround concepts present in KSs when detecting the topics of Tweets. In this paper we introduce a novel approach for harnessing such graph structures from multiple linked KSs, by: (i) building a conceptual representation of the KSs, (ii) leveraging contextual information about concepts by exploiting semantic concept graphs, and (iii) providing a principled way for the combination of KSs. Experiments evaluating our TC classifier in the context of Violence detection (VD) and Emergency Responses (ER) show promising results that significantly outperform various baseline models including an approach using a single KS without linked data and an approach using only Tweets. Copyright 2013 ACM.