African peasants on the move: turmoil between global dynamics, migration and food insecurity

This issue presents some of the publications resulting from the research project “African societies facing global dynamics: Turbulences between external intervention, migration, and food insecurity” [Dynamics]1. The underlying idea was to investigate contemporary global dynamics faced by African societies, how they interact with internal processes of change and these societies’ responses to these pressures. The contributions address the key issues raised in the Dynamics research project in different ways. They focus on an analysis of migration (internal as well as international), agricultural transformation and food (in)security in different societies and locations. They also explore the links between them and their interrelations with global dynamics. The work was based on case studies conducted in Guinea-Bissau, São Tomé and Príncipe (STP), Cape Verde and Senegal. An additional contribution from Mozambique was also included as it addressed the central issues of the project. Although this research project in itself can only address a few aspects of this complex set of interactions and highlight some of the key issues at play in specific case studies, the project is part of a long-term investigation about the dynamics of change in African agrarian societies which contemplates a wider range of issues.info:eu-repo/semantics/publishedVersio

Offline digital – digital offline: The potential of offline digitised information for the production, distribution and appropriation of human knowledge

The lifeworlds of large parts of the human population have undergone profound transformations through the expansion of the internet. Yet great parts of the world are still totally or partially offline. Cheap smartphones, tablets and (off-grid) electricity reach ever more of these populations. Scientists’ fascination with the internet – where money, investments, business models, communication, political control, as well as their lifeworlds converge - has largely obscured the potential of offline digitised information for the storage and distribution of information and the appropriation of knowledge. The profound changes of the socialisation of human knowledge through the revolutions in the transmission media have influenced how societies produce, distribute, receive and appropriate information. The expansion of access to digitised information revolutionises horizontal and vertical transmission. The differences are manifold: physical requirements are reduced – a whole library fits into a pocket; digital information is much cheaper to acquire; logistic chains through which books or journals are produced, shipped, distributed and stored are as unnecessary as are libraries. The actual access to information is also vastly different – the electronic search function and the offline Wikipedia may serve as examples. This suggests a rethinking of the “digital divide” which is no longer synonymous with internet access. Is there rather a frontier zone where different forms of access overlap? What are the distribution and market mechanisms for offline digital information? To what uses can digitised information be put offline? How will the new availability of ever cheaper technology affect knowledge production and appropriation?info:eu-repo/semantics/publishedVersio

Saudações em África - Além do aperto de mão: Um ensaio sobre os rituais de saudação e despedida como prática de comunicação em sociedades agrárias da África Subsaariana

In African Agrarian Societies greeting and leave-taking rituals are an essential part of the communication processes that constitute these societies as collective entities. Through elaborate forms of greeting and leave-taking people initiate and end communication and interaction processes within a framework of collective identities and cultures. Intricate greeting rituals allow to deal with all forms of encounters, with living people as well as with the spirits of the deceased. Greeting rituals are acquired through lengthy periods of learning. Their mastery is the sign of being an adult and competent member of society. External actors from different cultures often seem to be unaware of the subtleties of these greeting rituals. They ignore them at a cost. This essay provides some insights into the inner workings of African societies concerning the framing of most of their internal and external communication processes that are as vital for their lifeworlds as they are for their interaction with external actors from different spheres. Analysing the societies in a comprehensive manner as self-organising entities within an ethnic matrix clearly shows the limits of reducing greeting rituals to mere speech acts between individuals and proves that some of the fundamental assumptions of modern communication theories are not valid for African Agrarian Societies.info:eu-repo/semantics/publishedVersio

Contrast sensitivity and night driving in older people: Quantifying the relationship between visual acuity, contrast sensitivity, and hazard detection distance in a night-time driving simulator

Purpose: (i) To assess how well contrast sensitivity (CS) predicts night-time hazard detection distance (one key component of night driving ability), in normally sighted older drivers, relative to a conventional measure of high contrast visual acuity (VA); (ii) To evaluate whether CS can be accurately quantified within a night driving simulator. Methods: Participants were fifteen (five female) ophthalmologically healthy adults, aged 55 to 81 years. CS was measured in a driving simulator using Landolt Cs, presented under static or dynamic driving conditions, and with or without glare. In the dynamic driving condition, the participant was asked to simultaneously maintain a (virtual) speed of 60 km/h on a country road. In the (dynamic) with glare condition, two calibrated LED arrays, moved by cable robots, simulated the trajectories and luminance characteristics of the (low beam) headlights of an approaching car. For comparison, CS was also measured clinically (with & without glare) using a Optovist I instrument (Vistec Inc., Olching/FRG). Visual acuity (VA) thresholds were also assessed at high and low contrast using the Freiburg Visual Acuity Test (FrACT) under photopic conditions. As a measure of driving performance, median hazard detection distance (MHDD) was computed, in meters, across three kinds of simulated obstacles of varying contrast. Results: CS and low contrast VA were both significantly associated with driving performance (both P < 0.01), whereas conventional high contrast acuity was not (P = 0.10). There was good correlation (P < 0.01) between CS measured in the driving simulator and a conventional clinical instrument (Optovist). As expected, CS was shown to decrease in the presence of glare, in dynamic driving conditions, and as a function of age (all P < 0.01). Conclusions: CS and low contrast VA predict night-time hazard detection ability in a manner that conventional high contrast VA does not. Either may therefore provide a useful metric for assessing fitness to drive at night, particularly in older individuals. CS measurements can be made within a driving simulator, and the data are in good agreement with conventional clinical methods (Optovist I)

Does intraocular straylight predict night driving visual performance? Correlations between straylight levels and contrast sensitivity, halo size, and hazard recognition distance with and without glare

Purpose: To evaluate the relationship between intraocular straylight perception and: (i) contrast sensitivity (CS), (ii) halo size, and (iii) hazard recognition distance, in the presence and absence of glare. Subjects and methods: Participants were 15 (5 female) ophthalmologically healthy adults, aged 54.6–80.6 (median: 67.2) years. Intraocular straylight (log s) was measured using a straylight meter (C-Quant; Oculus GmbH, Wetzlar, Germany). CS with glare was measured clinically using the Optovist I device (Vistec Inc., Olching, Germany) and also within a driving simulator using Landolt Cs. These were presented under both static or dynamic viewing conditions, and either with or without glare. Hazard detection distance was measured for simulated obstacles of varying contrast. For this, the participant was required to maintain a speed of 60 km/h within a custom-built nighttime driving simulator. Glare was simulated by LED arrays, moved by cable robots to mimic an oncoming car’s headlights. Halo size (“halometry”) was measured by moving Landolt Cs outward originating from the center of a static glare source. The outcome measure from “halometry” was the radius of the halo (angular extent, in degrees visual angle). Results: The correlation between intraocular straylight perception, log s, and hazard recognition distance under glare was poor for the low contrast obstacles (leading/subdominant eye: r = 0.27/r = 0.34). Conversely, log CS measured with glare strongly predicted hazard recognition distances under glare. This was true both when log CS was measured using a clinical device (Optovist I: r = 0.93) and within the driving simulator, under static (r = 0.69) and dynamic (r = 0.61) conditions, and also with “halometry” (r = 0.70). Glare reduced log CS and hazard recognition distance for almost all visual function parameters. Conclusion: Intraocular straylight was a poor predictor of visual function and driving performance within this experiment. Conversely, CS was a strong predictor of both hazard recognition and halo extent. The presence of glare and motion lead to a degradation of CS in a driving simulator. Future studies are necessary to evaluate the effectiveness of all above-mentioned vision-related parameters for predicting fitness to drive under real-life conditions

Specification of progression in glaucomatous visual field loss, applying locally condensed stimulus arrangements

The goal of this work was to (i) determine patterns of progression in glaucomatous visual field loss, (ii) compare the detection rate of progression between locally condensed stimulus arrangements and conventional 6° × 6° grid, and (iii) assess the individual frequency distribution of test locations exhibiting a local event (i.e., an abrupt local deterioration of differential luminance sensitivity (DLS) by more than -10dB between any two examinations). The visual function of 41 glaucomatous eyes of 41 patients (16 females, 25 males, 37 to 75 years old) was examined with automated static perimetry (Tuebingen Computer Campimeter or Octopus 101-Perimeter). Stimuli were added to locally enhance the spatial resolution in suspicious regions of the visual field. The minimum follow-up was four subsequent sessions with a minimum of 2-month (median 6-month) intervals between each session. Progression was identified using a modified pointwise linear regression (PLR) method and a modified Katz criterion. The presence of events was assessed in all progressive visual fields. Eleven eyes (27%) showed progression over the study period (median 2.5 years, range 1.3–8.6 years). Six (55%) of these had combined progression in depth and size and five eyes (45%) progressed in depth only. Progression in size conformed always to the nerve fiber course. Seven out of 11 (64%) of the progressive scotomata detected by spatially condensed grids would have been missed by the conventional 6° × 6° grid. At least one event occurred in 64% of all progressive eyes. Five of 11 (46%) progressive eyes showed a cluster of events. The most common pattern of progression in glaucomatous visual fields is combined progression in depth and size of an existing scotoma. Applying individually condensed test grids remarkably enhances the detection rate of glaucomatous visual field deterioration (at the expense of an increased examination time) compared to conventional stimulus arrangements

A mathematical description of nerve fiber bundle trajectories and their variability in the human retina

AbstractWe developed a mathematical model wherein retinal nerve fiber trajectories can be described and the corresponding inter-subject variability analyzed. The model was based on traced nerve fiber bundle trajectories extracted from 55 fundus photographs of 55 human subjects. The model resembled the typical retinal nerve fiber layer course within 20° eccentricity. Depending on the location of the visual field test point, the standard deviation of the calculated corresponding angular location at the optic nerve head circumference ranged from less than 1° to 18°, with an average of 8.8°

Mycophenolic acid in the treatment of birdshot chorioretinopathy: long-term follow-up

Aim: To assess the long-term efficacy and tolerability of both derivatives of mycophenolic acid, mycophenolate mofetil (MMF) and mycophenolate sodium (MPS), in the therapy of patients with birdshot chorioretinopathy (BSCR). Methods: Retrospective analysis of 24 patients (48 eyes) with BSCR, treated with MMF or MPS with a follow-up of at least 1 year. The main outcome measures included control of inflammation, steroid-sparing potential and side effects. Secondary outcome measure was the development of retinal function during the therapy measured by best-corrected visual acuity (BCVA), visual field and/or electroretinography (ERG). Results: Twelve patients (50%) were treated with MMF and 12 patients (50%) with MPS. Control of intraocular inflammation, defined as complete lack of clinical and angiographic signs of inflammatory activity, was achieved in 16 of 24 patients (67%). The angiographic signs of activity were significantly reduced during the follow-up (p0.05). In 20 out of 21 patients (95%) who received systemic corticosteroids, the corticosteroids could be tapered to a daily dose of ≤10 mg (rate 0.26/patient-year). Drug-related side effects occurred in 12 patients (50%, rate 0.16/patient-year). In four patients (17%), a therapy switch from MMF to MPS was undertaken due to gastrointestinal discomfort. Conclusions: Derivatives of mycophenolic acid are effective and safe drugs for the treatment of BSCR. In cases with gastrointestinal side effects, a therapy switch from MMF to MPS should be considered