Evaluating the quality of AVHRR Pathfinder NDVI data for the African continent using SPOT-4 Vegetation data

2006 ◽  
Vol 106 (1) ◽  
pp. 87-102 ◽  
Author(s):  
Rasmus Fensholt ◽  
Thomas Theis Nielsen ◽  
Simon Stisen
Keyword(s):  
African Continent

Elasmobranch exploitation in Africa

1998 ◽  
Vol 49 (7) ◽  
pp. 573 ◽  
Author(s):  
M. Kroese ◽  
W. H. H. Sauer
Keyword(s):  
Commercial Fisheries ◽  
African Continent ◽  
Conservative Estimate ◽  
Artisanal Fishery ◽  
Limited Data ◽  
Subsistence Fisheries ◽  
By Catch ◽  
The Impact ◽  
Existing Data

The impact of fisheries on elasmobranchs in Africa is not well documented. Available data suggest that there are no large shark fishing nations (> 10000 t year-1), reported landings for 1994 being around 39 000 t. This value is believed to be a underestimate, because of a lack of data on catches and landings from the various different fishing methods and the large number of nations fishing in African waters. Existing data are mostly linked to industrial fisheries, although the artisanal sector could be responsible for substantial catches. Landed by-catch and discard rates of elasmobranchs are unknown for most commercial fisheries targeting teleosts. Limited data sources allowed only crude estimates of catch. The artisanal fishery is calculated to land a minimum of 20 000 t of sharks, whereas the industrial trawl sector is likely to catch 23 000 t. A conservative estimate for the African continent and the surrounding islands is ~95 000 t. The quality of catch-and-effort data for both commercial and subsistence fisheries on the African continent needs to be improved, and the by-catch issue should be investigated through trained onboard observers.

Spatial reconstruction of semi-quantitative precipitation fields over Africa during the nineteenth century from documentary evidence and gauge data

2012 ◽  
Vol 78 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Sharon E. Nicholson ◽  
Douglas Klotter ◽  
Amin K. Dezfuli
Keyword(s):  
Nineteenth Century ◽  
Rain Gauge ◽  
African Continent ◽  
Documentary Evidence ◽  
Proxy Data ◽  
Data Set ◽  
Spatial Reconstruction ◽  
Geographical Regions ◽  
Gauge Data

AbstractThe article presents a newly created precipitation data set for the African continent and describes the methodology used in its creation. It is based on a combination of proxy data and rain gauge records. The data set is semi-quantitative, with a “wetness” index of − 3 to + 3 to describe the quality of the rainy season. It covers the period AD 1801 to 1900 and includes data for 90 geographical regions of the continent. The results underscore a multi-decadal period of aridity early in the nineteenth century.

scholarly journals A New 60-year 1940/1999 Monthly-Gridded Rainfall Data Set for Africa

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 387 ◽  
Author(s):  
Claudine Dieulin ◽  
Gil Mahé ◽  
Jean-Emmanuel Paturel ◽  
Soundouss Ejjiyar ◽  
Yves Tramblay ◽  
...  
Keyword(s):  
Hydrological Modeling ◽  
Statistical Tests ◽  
Rain Gauge ◽  
Climatic Research Unit ◽  
Rainfall Regime ◽  
Western Coast ◽  
African Continent ◽  
Data Set ◽  
Long Time

The African continent has a very low density of rain gauge stations, and long time-seriesfor recent years are often limited and poorly available. In the context of global change, it is veryimportant to be able to characterize the spatio-temporal variability of past rainfall, on the basis ofdatasets issued from observations, to correctly validate simulations. The quality of the rainfall datais for instance of very high importance to improve the efficiency of the hydrological modeling,through calibration/validation experiments.The HydroSciences Montpellier Laboratory (HSM) has a long experience in collecting andmanaging hydro-climatological data. Thus, HSM had initiated a program to elaborate a referencedataset, in order to build monthly rainfall grids over the African continent, over a period of 60 years(1940/1999). The large quantity of data collected (about 7,000 measurement points were used in thisproject) allowed for interpolation using only observed data, with no statistical use of a referenceperiod. Compared to other databases that are used to build the grids of the Global HistoricalClimatology Network (GHCN) or the Climatic Research Unit of University of East Anglia, UK (CRU),the number of available observational stations (a was significantly much higher, including the end ofthe century when the number of measurement stations dropped dramatically, everywhere.Inverse distance weighed (IDW) was the chosen method to build the 720 monthly grids and amean annual grid, from rain gauges. The mean annual grid was compared to the CRU grid. The gridswere significantly different in many places, especially in North Africa, Sahel, the horn of Africa, andthe South Western coast of Africa, with HSM_SIEREM data (database HydroSciencesMontpellier_Système d’Information Environnementales pour les Ressources en Eau et leurModélisation) being closer to the observed rain gauge values. The quality of the grids computed waschecked, following two approaches—cross-validation of the two interpolation methods, ordinarykriging and inverse distance weighting, which gave a comparable reliability, with regards to theobserved data, long time-series analysis, and analysis of long-term signals over the continent,compared to previous studies. The statistical tests, computed on the observed and gridded data,detected a rupture in the rainfall regime around 1979/1980, on the scale of the whole continent; thiswas congruent with the results in the literature. At the monthly time-scale, the most widely observedsignal over the period of 1940/1999, was a significant decrease of the austral rainy season betweenMarch and May, which has not earlier been well-documented. Thus, this would lead to a furtherdetailed climatological study from this HSM_SIEREM database.

scholarly journals Tracking and predicting the African COVID-19 pandemic

2020 ◽  
Author(s):  
Paddy Ssentongo ◽  
Claudio Fronterre ◽  
Andrew Geronimo ◽  
Steven J. Greybush ◽  
Pamela K. Mbabazi ◽  
...  
Keyword(s):  
Human Development Index ◽  
Control Strategies ◽  
Specific Humidity ◽  
African Continent ◽  
Short Term ◽  
Social Interventions ◽  
Lagged Effects ◽  
Reported Data ◽  
Country Specific

The ongoing coronavirus disease 2019 (COVID-19) pandemic is heterogeneous throughout Africa and threatening millions of lives. Surveillance and short-term modeling forecasts are critical to provide timely information for decisions on control strategies. We use a model that explains the evolution of the COVID-19 pandemic over time in the entire African continent, parameterized by socioeconomic and geoeconomic variations and the lagged effects of social policy and meteorological history. We observed the effect of the human development index, containment policies, testing capacity, specific humidity, temperature and landlocked status of countries on the local within-country and external between-country transmission. One week forecasts of case numbers from the model were driven by the quality of the reported data. Seeking equitable behavioral and social interventions, balanced with coordinated country-specific strategies in infection suppression, should be a continental priority to control the COVID-19 pandemic in Africa.

Electoral Rulings and Public Trust in African Courts and Elections

2021 ◽  
Vol 53 (2) ◽  
pp. 257-290
Author(s):  
Nicholas Kerr ◽  
Michael Wahman
Keyword(s):  
Public Opinion ◽  
Survey Data ◽  
Political Institutions ◽  
Public Trust ◽  
Public Perceptions ◽  
Parliamentary Election ◽  
African Continent ◽  
Parliamentary Elections ◽  
Distribution Of Power

On the African continent, where elections are often surrounded by accusations of fraud and manipulation, legal avenues for challenging elections may enhance election integrity and trust in political institutions. Court rulings on electoral petitions have consequences for the distribution of power, but how do they shape public opinion? We theorize and study the way in which court rulings in relation to parliamentary election petitions shape public perceptions of election and judicial legitimacy. Using survey data from the 2016 Zambian election, our results suggest that opposition voters rate quality of elections lower when courts nullify elections. However, judicial legitimacy seems unaffected even for voters in constituencies where the courts have shown independence vis a vis the executive and nulli' fied parliamentary elections won by the governing party.

scholarly journals Looking through the African lenses: a critical exploration of the CSR activities of Chinese International Construction Companies (CICCs) in Africa

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Oluwasegun Oluwaseyi Seriki
Keyword(s):  
Business Processes ◽  
African Continent ◽  
Construction Sector ◽  
Construction Companies ◽  
International Construction ◽  
Employee Welfare ◽  
Chinese Rhetoric ◽  
Csr Strategy ◽  
Corporate Social

AbstractThe importance of Chinese International Construction Companies (CICCs) within the construction sector in Africa can no longer be ignored, as these firms hold a considerable amount of market share within the African continent. The construction industry is of high importance to African economic renaissance, and Corporate Social Responsibility (CSR) is becoming a key issue in business processes on the developing continent. Narratives around the implementation of CSR within construction in African economies have been largely one-sided, viewed from foreign perspectives and outsider anecdotes, without engaging locals in evaluating these initiatives. As a result, this paper explores CSR as a critical component of the continued penetration and dominance of Chinese contractors in the highly competitive African construction markets. The paper adopts a quantitative survey to explore the areas of implementation of CSR by CICCs, how they line up against current local and international counterparts and the future of these firms in Africa using CSR as a metric. Residents of Africa’s largest economy, Nigeria, who have Chinese-led projects ongoing in their communities, were surveyed for the study, and the findings used to propose solutions for future CSR policy-making in local African communities where Chinese contractors carry out business. The study found that in terms of CSR strategy implementation, CICCs were ranked highly on quality of construction and respect for local laws and customs, but ranked low in perception of employee welfare and environmental protection. The study highlighted that African governments taking responsible leadership by formulating a CSR policy for all international contractors might stem the tide of increasing anti-Chinese rhetoric within the construction sector on the African continent.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

Lithography below 100 nm

1983 ◽  
Vol 41 ◽  
pp. 96-99
Author(s):  
L. D. Jackel
Keyword(s):  
Spatial Distribution ◽  
Electron Beam ◽  
Electron Scattering ◽  
Electron Beam Lithography ◽  
Substrate Material ◽  
Local Electron ◽  
Electron Dose ◽  
Positive Resist ◽  
Exposure Process

Most production electron beam lithography systems can pattern minimum features a few tenths of a micron across. Linewidth in these systems is usually limited by the quality of the exposing beam and by electron scattering in the resist and substrate. By using a smaller spot along with exposure techniques that minimize scattering and its effects, laboratory e-beam lithography systems can now make features hundredths of a micron wide on standard substrate material. This talk will outline sane of these high- resolution e-beam lithography techniques.We first consider parameters of the exposure process that limit resolution in organic resists. For concreteness suppose that we have a “positive” resist in which exposing electrons break bonds in the resist molecules thus increasing the exposed resist's solubility in a developer. Ihe attainable resolution is obviously limited by the overall width of the exposing beam, but the spatial distribution of the beam intensity, the beam “profile” , also contributes to the resolution. Depending on the local electron dose, more or less resist bonds are broken resulting in slower or faster dissolution in the developer.

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