Unravelling biodiversity, evolution and threats to conservation in the Sahara-Sahel.

Science.gov (United States)

Brito, José C; Godinho, Raquel; Martínez-Freiría, Fernando; Pleguezuelos, Juan M; Rebelo, Hugo; Santos, Xavier; Vale, Cândida G; Velo-Antón, Guillermo; Boratyński, Zbyszek; Carvalho, Sílvia B; Ferreira, Sónia; Gonçalves, Duarte V; Silva, Teresa L; Tarroso, Pedro; Campos, João C; Leite, João V; Nogueira, Joana; Alvares, Francisco; Sillero, Neftalí; Sow, Andack S; Fahd, Soumia; Crochet, Pierre-André; Carranza, Salvador

2014-02-01

Deserts and arid regions are generally perceived as bare and rather homogeneous areas of low diversity. The Sahara is the largest warm desert in the world and together with the arid Sahel displays high topographical and climatic heterogeneity, and has experienced recent and strong climatic oscillations that have greatly shifted biodiversity distribution and community composition. The large size, remoteness and long-term political instability of the Sahara-Sahel, have limited knowledge on its biodiversity. However, over the last decade, there have been an increasing number of published scientific studies based on modern geomatic and molecular tools, and broad sampling of taxa of these regions. This review tracks trends in knowledge about biodiversity patterns, processes and threats across the Sahara-Sahel, and anticipates needs for biodiversity research and conservation. Recent studies are changing completely the perception of regional biodiversity patterns. Instead of relatively low species diversity with distribution covering most of the region, studies now suggest a high rate of endemism and larger number of species, with much narrower and fragmented ranges, frequently limited to micro-hotspots of biodiversity. Molecular-based studies are also unravelling cryptic diversity associated with mountains, which together with recent distribution atlases, allows identifying integrative biogeographic patterns in biodiversity distribution. Mapping of multivariate environmental variation (at 1 km × 1 km resolution) of the region illustrates main biogeographical features of the Sahara-Sahel and supports recently hypothesised dispersal corridors and refugia. Micro-scale water-features present mostly in mountains have been associated with local biodiversity hotspots. However, the distribution of available data on vertebrates highlights current knowledge gaps that still apply to a large proportion of the Sahara-Sahel. Current research is providing insights into key

The Logistics Of The War In The Sahel

OpenAIRE

Busch, Gary K

2013-01-01

There are both positive and negative aspects of waging a counter-insurgency war in the Sahel. The impediments are easy to see. The terrain of the Sahel does not lend itself to conventional warfare. There are broad expanses of sand and dunes, broken up by small villages and, occasionally, a town or city. There are no petrol stations, wells, repair shops, water stores, food stocks or fuel reserves in most of the region. Trucks and buses, as well as conventional armour, are difficult to transpor...

Life on the edge: vulnerability in the Sahel

Energy Technology Data Exchange (ETDEWEB)

Rubin, Vanessa [Africa Hunger Advisor, Care International UK (United Kingdom)

2007-07-15

Locusts, drought, crops crumbling into dust: in 2005, the Sahel was hit by a catastrophic food crisis. Eight million people were affected. Two years on, drought has eased in this arid strip south of the Sahara, but its people still live in the grip of extreme vulnerability. Their condition is a crisis in itself and a near-guarantee of more humanitarian disasters in the region, whatever the force or frequency of future shocks. Aid donors need to recognise this vulnerability as the root cause of the Sahel's rolling crises.

Characterization of Heat Waves in the Sahel and associated mechanisms

Science.gov (United States)

Oueslati, Boutheina; Pohl, Benjamin; Moron, Vincent; Rome, Sandra

2016-04-01

Large efforts are made to investigate the heat waves (HW) in developed countries because of their devastating impacts on society, economy and environment. This interest increased after the intense event over Europe during summer 2003. However, HWs are still understudied over developing countries. This is particularly true in West Africa, and especially in the Sahel, where temperatures recurrently reach critical values, such as during the 2010 HW event. Understanding the Sahelian HWs and associated health risks constitute the main objective of ACASIS, a 4-year project funded by the French Agence Nationale de la Recherche. Our work contributes to this project and aims at characterizing the Sahelian HWs and understanding the mechanisms associated with such extreme events. There is no universal definition of a HW event, since it is highly dependent on the sector (human health, agriculture, transport...) and region of interest. In our case, a HW is defined when the heat index of the day and of the night exceeds the 90th percentile for at least 3 consecutive days (Rome et al. 2016, in preparation). This index combines temperature and relative humidity in order to determine the human-perceived equivalent temperature (definition adapted from Steadman, 1979). Intrinsic properties of Sahelian HW are analyzed from the Global Summary of the Day (GSOD) synoptic observations and ERA-interim reanalyses over 1979-2014 during boreal spring seasons (April-May-June), the warmest period of the year in the Central Sahel. ERA-interim captures well the observed interannual variability and seasonal cycle at the regional scale, as well as the 1979-2014 increasing linear trend of springtime HW occurrences in the Sahel. Reanalyses, however, overestimate the duration, spatial extent of HW, and underestimate their intensity. For both GSOD and ERA-interim, we show that, over the last three decades, Sahelian HWs tend to become more frequent, last longer, cover larger areas and reach higher

Water for a Thirsty Sahel

International Nuclear Information System (INIS)

Quevenco, Rodolfo

2013-01-01

In 2012, the IAEA launched a large scale, four-year, technical cooperation project to promote the integrated management and development of shared groundwater resources in the Sahel region. The project supports the use of isotope techniques in hydrological studies to map underground water, and to identify and understand the root causes of the main threats to the five transboundary aquifers. Isotope hydrology techniques can also provide useful information about the quality and availability of water hidden underground, and can be used to investigate the impact of climate change on water resources

Ground-and satellite-based evidence of the biophysical mechanisms behind the greening Sahel

DEFF Research Database (Denmark)

Brandt, Martin Stefan; Mbow, Cheikh; Diouf, Abdoul A.

2015-01-01

After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness...... over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass...... remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987-2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass...

Ground- and satellite-based evidence of the biophysical mechanisms behind the greening Sahel.

Science.gov (United States)

Brandt, Martin; Mbow, Cheikh; Diouf, Abdoul A; Verger, Aleixandre; Samimi, Cyrus; Fensholt, Rasmus

2015-04-01

After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987-2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass of woody species, herb biomass, and woody species abundance in different ecosystems located in the Sahel zone of Senegal. We found that the positive trend observed in satellite vegetation time series (+36%) is caused by an increment of in situ measured biomass (+34%), which is highly controlled by precipitation (+40%). Whereas herb biomass shows large inter-annual fluctuations rather than a clear trend, leaf biomass of woody species has doubled within 27 years (+103%). This increase in woody biomass did not reflect on biodiversity with 11 of 16 woody species declining in abundance over the period. We conclude that the observed greening in the Senegalese Sahel is primarily related to an increasing tree cover that caused satellite-driven vegetation indices to increase with rainfall reversal. © 2014 John Wiley & Sons Ltd.

Using Relative Humidity Forecasts to Manage Meningitis in the Sahel

Science.gov (United States)

Pandya, R. E.; Adams-Forgor, A.; Akweogno, P.; Awine, T.; Dalaba, M.; Dukic, V.; Dumont, A.; Hayden, M.; Hodgson, A.; Hopson, T. M.; Hugonnet, S.; Yoksas, T. C.

2012-12-01

Meningitis epidemics in the Sahel occur quasi-regularly and with devastating impact. In 2008, for example, eighty-eight thousand people contracted meningitis and over five thousand died. Until very recently, the protection provided by the only available vaccine was so limited and short-lived that the only practical strategy for vaccination was reactive: waiting until an epidemic occurred in the region and then vaccinating in that region to prevent the epidemic's further growth. Even with that strategy, there were still times when demand outpaced available vaccine. While a new vaccine has recently been developed that is effective and inexpensive enough to be used more broadly and proactively, it is only effective against the strain of bacteria that causes the most common kind of bacterial meningitis. As a result, there will likely be continued need for reactive vaccination strategies. It is widely known that meningitis epidemics in the Sahel occur only in the dry season. Our project investigated this relationship, and several independent lines of evidence demonstrate a robust relationship between the onset of the rainy season, as marked by weekly average relative humidity above 40%, and the end of meningitis epidemics. These lines of evidence include statistical analysis of two years of weekly meningitis and weather data across the Sahel, cross-correlation of ten years of meningitis and weather data in the Upper East region of northern Ghana, and high-resolution weather simulations of past meningitis seasons to interpolate available weather data. We also adapted two techniques that have been successfully used in public health studies: generalized additive models, which have been used to relate air quality and health, and a linearized version of the compartmental epidemics model that has been used to understand MRSA. Based on these multiple lines of evidence, average weekly relative humidity forecast two weeks in advance appears consistently and strongly related to

Developing a Shuffled Complex-Self Adaptive Hybrid Evolution (SC-SAHEL) Framework for Water Resources Management and Water-Energy System Optimization

Science.gov (United States)

Rahnamay Naeini, M.; Sadegh, M.; AghaKouchak, A.; Hsu, K. L.; Sorooshian, S.; Yang, T.

2017-12-01

Meta-Heuristic optimization algorithms have gained a great deal of attention in a wide variety of fields. Simplicity and flexibility of these algorithms, along with their robustness, make them attractive tools for solving optimization problems. Different optimization methods, however, hold algorithm-specific strengths and limitations. Performance of each individual algorithm obeys the "No-Free-Lunch" theorem, which means a single algorithm cannot consistently outperform all possible optimization problems over a variety of problems. From users' perspective, it is a tedious process to compare, validate, and select the best-performing algorithm for a specific problem or a set of test cases. In this study, we introduce a new hybrid optimization framework, entitled Shuffled Complex-Self Adaptive Hybrid EvoLution (SC-SAHEL), which combines the strengths of different evolutionary algorithms (EAs) in a parallel computing scheme, and allows users to select the most suitable algorithm tailored to the problem at hand. The concept of SC-SAHEL is to execute different EAs as separate parallel search cores, and let all participating EAs to compete during the course of the search. The newly developed SC-SAHEL algorithm is designed to automatically select, the best performing algorithm for the given optimization problem. This algorithm is rigorously effective in finding the global optimum for several strenuous benchmark test functions, and computationally efficient as compared to individual EAs. We benchmark the proposed SC-SAHEL algorithm over 29 conceptual test functions, and two real-world case studies - one hydropower reservoir model and one hydrological model (SAC-SMA). Results show that the proposed framework outperforms individual EAs in an absolute majority of the test problems, and can provide competitive results to the fittest EA algorithm with more comprehensive information during the search. The proposed framework is also flexible for merging additional EAs, boundary

The Logistics Of The War In The Sahel

Directory of Open Access Journals (Sweden)

Gary K Busch

2013-06-01

Full Text Available There are both positive and negative aspects of waging a counter-insurgency war in the Sahel. The impediments are easy to see. The terrain of the Sahel does not lend itself to conventional warfare. There are broad expanses of sand and dunes, broken up by small villages and, occasionally, a town or city. There are no petrol stations, wells, repair shops, water stores, food stocks or fuel reserves in most of the region. Trucks and buses, as well as conventional armour, are difficult to transport in such a terrain. Air bases are usually suited only to small aircraft and lack the fuel and equipment which allow the free flow of cargo. African insurgents are bands and groups of often, irregular soldiers. On the positive side, the lack of ground cover and a tree canopy in the region enables a strategy of using the most modern weapons, the Unmanned Aerial Vehicles (UAV which can seek out, observe and destroy small and mobile enemy forces. This has meant that the logistic demands of the war in the Sahel has generated a strategy of high-tech weaponry deployed by Western forces combined with African troops on the ground as garrison forces for towns and cities.

Trend in land degradation has been the most contended issue in the Sahel. Trends documented have not been consistent across authors and science disciplines, hence little agreement has been gained on the magnitude and direction of land degradation in the Sahel. Differentiated science outputs are related to methods and data used at various scales.

Science.gov (United States)

Mbow, C.; Brandt, M.; Fensholt, R.; Ouedraogo, I.; Tagesson, T.

2015-12-01

Thematic gaps in land degradation trends in the SahelTrend in land degradation has been the most contended issue for arid and semi-arid regions. In the Sahel, depending to scale of analysis and methods and data used, the trend documented have not been consistent across authors and science disciplines. The assessment of land degradation and the quantification of its effects on land productivity have been assessed for many decades, but little agreement has been gained on the magnitude and direction in the Sahel. This lack of consistency amid science outputs can be related to many methodological underpinnings and data used for various scales of analysis. Assessing biophysical trends on the ground requires long-term ground-based data collection to evaluate and better understand the mechanisms behind land dynamics. The Sahel is seen as greening by many authors? Is that greening geographically consistent? These questions enquire the importance of scale analysis and related drivers. The questions addressed are not only factors explaining loss of tree cover but also regeneration of degraded land. The picture used is the heuristic cycle model to assess loss and damages vs gain and improvements of various land use practices. The presentation will address the following aspects - How much we know from satellite data after 40 years of remote sensing analysis over the Sahel? That section discuss agreement and divergences of evidences and differentiated interpretation of land degradation in the Sahel. - The biophysical factors that are relevant for tracking land degradation in the Sahel. Aspects such detangling human to climate factors and biophysical factors behind land dynamics will be presented - Introduce some specific cases of driver of land architecture transition under the combined influence of climate and human factor. - Based on the above we will conclude with some key recommendations on how to improve land degradation assessment in the Arid region of the Sahel.

Women's Right to Water for Agricultural Use in the Sahel (Mauritanie ...

International Development Research Centre (IDRC) Digital Library (Canada)

Women's Right to Water for Agricultural Use in the Sahel (Mauritanie, Niger, ... access of women to agricultural water resources in the three countries under study. ... long-term climate action to reduce social inequality, promote greater gender ...

The Re-Greening of the Sahel: Natural Cyclicity or Human-Induced Change?

Directory of Open Access Journals (Sweden)

Issa Ouedraogo

2014-09-01

Full Text Available The Sahel has been the focus of scientific interest in environmental-human dynamics and interactions. The objective of the present study is to contribute to the recent debate on the re-greening of Sahel. The paper examines the dynamics of barren land in the Sahel of Burkina Faso through analysis of remotely-sensed and rainfall data from 1975–2011. Discussions with farmers and land management staff have helped to understand the anthropogenic efforts toward soil restoration to enable the subsistence farming agriculture. Results showed that area of barren land has been fluctuating during the study period with approximately 10-year cyclicity. Similarly, rainfall, both at national and local levels has followed the same trends. The trends of the area of barren land and rainfall variability suggest that when rainfall increases, the area of barren land decreases and barren land increases when rainfall decreases. This implies that rainfall is one of the main factors driving the change in area of barren land. In addition, humans have contributed positively and negatively to the change by restoring barren lands for agriculture using locally known techniques and by accelerating land degradation through intensive and inappropriate land use practices.

The blurred boundaries of political violence in the Sahel-Sahara

DEFF Research Database (Denmark)

Walther, Olivier

2017-01-01

The Sahel and the Sahara are faced with exceptional political instability involving a combination of rebellions, jihadist insurgencies, coups d’état, protest movements and illegal trafficking. Analysis of the outbreaks of violence reveals that the region is not just the victim of an escalation...... of wars and conflicts that marked the 20th century. The Sahel-Sahara has also become the setting of a globalised security environment, in which boundaries between what is local and global, domestic and international, military and civilian, politics and identity are blurred....

Isotope hydrology in the Sahel zone

International Nuclear Information System (INIS)

1974-01-01

Northern Africa has recently experienced an exceptional period of severe drought. Practically no precipitation has been received during two or three years by large regions in the so-called Sahel zone, which extends over all Africa from West to East at a latitude between 10 and 20 degrees North in the following countries: Senegal, Mauritania, Mali, Upper Volta, Niger, Nigeria, Chad, Sudan and Ethiopia. Although precipitation is scarce even in normal years, important groundwater resources are present in the Sahei zone. However, groundwater is exploited mainly by dug wells, reaching only the upper part of the phreatic aquifer, which is also the one immediately affected by droughts (lowering of the water table). Deep groundwater is exploited only by a limited number of drilled wells. In recent years several hydrogeological projects have been financed by the United Nations through UNDP in the Sahel countries, with the purpose of locating and evaluating groundwater resources and of developing their exploitation. The International Atomic Energy Agency has taken or takes part in many of these projects by providing isotopic analyses of groundwater. Some of the most difficult questions to be answered in groundwater research in arid zones are: Is the recharge of a given aquifer also taking place at present? If so, from where does the major contribution to groundwater recharge come? What is the age of groundwater? Often it is not possible to answer these questions with the classical hydrogeological and geophysical methods above, but the techniques based on the so-called environmental isotopes ( 18 O and 2 H, 3 H and 14 C) may provide an answer. The information provided by isotope techniques is in many cases extremely valuable for a better understanding of groundwater resources and a better planning of their exploitation, despite the problems which always occur in actual cases. In fact, natural processes, like mixing or interaction with the aquifer material, or practical

Ponds' water balance and runoff of endorheic watersheds in the Sahel

Science.gov (United States)

Gal, Laetitia; Grippa, Manuela; Kergoat, Laurent; Hiernaux, Pierre; Mougin, Eric; Peugeot, Christophe

2015-04-01

The Sahel has been characterized by a severe rainfall deficit since the mid-twentieth century, with extreme droughts in the early seventies and again in the early eighties. These droughts have strongly impacted ecosystems, water availability, fodder resources, and populations living in these areas. However, an increase of surface runoff has been observed during the same period, such as higher "summer discharge" of Sahelian's rivers generating local floods, and a general increase in pond's surface in pastoral areas of central and northern Sahel. This behavior, less rain but more surface runoff is generally referred to as the "Sahelian paradox". Various hypotheses have been put forward to explain this paradoxical situation. The leading role of increase in cropped areas, often cited for cultivated Sahel, does not hold for pastoral areas in central and northern Sahel. Processes such as degradation of vegetation subsequent to the most severe drought events, soils erosion and runoff concentration on shallow soils, which generate most of the water ending up in ponds, seem to play an important role. This still needs to be fully understood and quantified. Our study focuses on a model-based approach to better understand the hydrological changes that affected the Agoufou watershed (Gourma, Mali), typical of the central, non-cultivated Sahel. Like most of the Sahelian basins, the Agoufou watershed is ungauged. Therefore we used indirect data to provide the information required to validate a rainfall-runoff model approach. The pond volume was calculated by combining in-situ water level measurements with pond's surface estimations derived by remote sensing. Using the pond's water balance equation, the variations of pond volume combined to estimates of open water bodies' evaporation and infiltration determined an estimation for the runoff supplying the pond. This estimation highlights a spectacular runoff increase over the last sixty years on the Agoufou watershed. The runoff

Desertification, resilience, and re-greening in the African Sahel - a matter of the observation period?

Science.gov (United States)

Kusserow, Hannelore

2017-12-01

Since the turn of the millennium various scientific publications have been discussing a re-greening of the Sahel after the 1980s drought mainly based on coarse-resolution satellite data. However, the author's own field studies suggest that the situation is far more complex and that both paradigms, the encroaching Sahara and the re-greening Sahel, need to be questioned.This paper discusses the concepts of desertification, resilience, and re-greening by addressing four main aspects: (i) the relevance of edaphic factors for a vegetation re-greening, (ii-iii) the importance of the selected observation period in the debate on Sahel greening or browning, and (iv) modifications in the vegetation pattern as possible indicators of ecosystem changes (shift from originally diffuse to contracted vegetation patterns).The data referred to in this paper cover a time period of more than 150 years and include the author's own research results from the early 1980s until today. A special emphasis, apart from fieldwork data and remote sensing data, is laid on the historical documents.The key findings summarised at the end show the following: (i) vegetation recovery predominantly depends on soil types; (ii) when discussing Sahel greening vs. Sahel browning, the majority of research papers only focus on post-drought conditions. Taking pre-drought conditions (before the 1980s) into account, however, is essential to fully understand the situation. Botanical investigations and remote-sensing-based time series clearly show a substantial decline in woody species diversity and cover density compared to pre-drought conditions; (iii) the self-organised patchiness of vegetation is considered to be an important indicator of ecosystem changes.

Desertification and a shift of forest species in the West African Sahel

Science.gov (United States)

Gonzalez, Patrick

2001-01-01

Original field data show that forest species richness and tree density in the West African Sahel declined in the last half of the 20th century. Average forest species richness of areas of 4 km2 in Northwest Senegal fell from 64 ?? 2 species ca 1945 to 43 ?? 2 species in 1993, a decrease significant at p desertification in the West African Sahel. These documented impacts of desertification foreshadow possible future effects of climate change.

Aspects of the Hematology and Serum Biochemistry of Sahel and ...

African Journals Online (AJOL)

This study was conducted to investigate effects of year, age, season and breeds on aspects of the hematology and serum biochemical indices of Sahel and Sokoto red bucks in Mubi, Adamawa state, Nigeria. Blood and serum samples were used to determine PCV, Hb, RBC and WBC, and while serum protein (BSP) and ...

Multiple outcomes of cultivation in the Sahel

DEFF Research Database (Denmark)

Rasmussen, Laura Vang; Reenberg, Anette

2015-01-01

A default assumption about the Sahel is that farmers consider food provision for the family as the sole reason for cultivation. The degree to which this ‘cultivation for food’ assumption has been embedded in the scientific literature on land use changes is signified by the fact that hardly any...

Variations in selected physical proprieties of the soils of the sahel ...

African Journals Online (AJOL)

Infiltration rate, water content and textural properties of soils in the Sahel region of Nigeria as they are affected by shelterbelts were studied. The study was conducted on three measurement positions (60, 120 and 180 m) within the shelterbelt and the control was the unsheltered area. The site was situated on the southern ...

Analyzing Sanctuary Management in the Sahel

Science.gov (United States)

2015-06-12

Afghanistan and Iraq, but they often lack the specific skills required for the multicultural , multilingual, and multinational environment of the Sahel...article/2013/11/14/us-africa-usa-military-idUSBRE9AD1AA20131114. Arieff, Alexis. 2013. Crisis in Mali. Washington, DC: U.S. Library of Congress...2011. US Special Operations Forces (SOF): Background and Issues for Congress. Washington, DC: U.S. Library of Congress, Congressional Research Service

Analysis of teleconnections between AVHRR-based sea surface temperature and vegetation productivity in the semi-arid Sahel

DEFF Research Database (Denmark)

Huber Gharib, Silvia; Fensholt, Rasmus

2011-01-01

Vegetation Index (NDVI) in the Sahel, however with different magnitudes in terms of strength for the western, central and eastern Sahel. Also the correlations based on NDVI and global SST anomalies revealed the same East–West gradient, with a stronger association for the western than the eastern Sahel......, we achieved high correlations for SSTs of oceanic basins which are geographically associated to the climate indices yet by far not always these patterns were coherent. The detected SST–NDVI patterns could provide the basis to develop new means for improved forecasts in particular of the western...

Technical Guide for conservation of wood fuel: Experiences from Sahel

International Nuclear Information System (INIS)

Jorez, J.P.

1992-03-01

The guide gives technical information in design of energy efficient cooking stoves for the wood depleted countries in sub-saharan Africa. Knowledge and experiences of the Sahel region have been used to design the stoves discussed. As an introduction, the causes and consequences of the wood fuel crises are reviewed. The main models of improved stoves that are spread in Sahel are then described, together with data on performance and design considerations. Strategies for distribution of the improved stoves are analyzed, and ways to follow-up and evaluate their use are suggested. Results of campaigns to distribute the stoves in West African countries are given and methods to improve the distribution are proposed, in particular to promote the ceramic stoves. Finally, complementary wood fuel conservation campaigns are suggested for activities other than household cooking. 22 refs, 14 figs, 5 tabs and photos

Role of Surface Wind and Vegetation Cover in Multi-decadal Variations of Dust Emission in the Sahara and Sahel

Science.gov (United States)

Kim, Dong; Chin, Mian; Remer, Lorraine A.; Diehl, Thomas L.; Bian, Huisheng; Yu, Hongbin; Brown, Molly E.; Stockwell, William R.

2016-01-01

North Africa, the world's largest dust source, is non-uniform, consisting of a permanently arid region (Sahara), a semi-arid region (Sahel), and a relatively moist vegetated region (Savanna), each with very different rainfall patterns and surface conditions. This study aims to better understand the controlling factors that determine the variation of dust emission in North Africa over a 27-year period from 1982 to 2008, using observational data and model simulations. The results show that the model-derived Saharan dust emission is only correlated with the 10-m winds (W10m) obtained from reanalysis data, but the model-derived Sahel dust emission is correlated with both W10m and the Normalized Difference Vegetation Index (NDVI) that is obtained from satellite. While the Saharan dust accounts for 82 of the continental North Africa dust emission (1340-1570 Tg year(exp -1) in the 27-year average, the Sahel accounts for 17 with a larger seasonal and inter-annual variation (230-380 Tg year(exp -1), contributing about a quarter of the transatlantic dust transported to the northern part of South America. The decreasing dust emission trend over the 27-year period is highly correlated with W10m over the Sahara (R equals 0.92). Over the Sahel, the dust emission is correlated with W10m (R 0.69) but is also anti-correlated with the trend of NDVI (R equals 0.65). W10m is decreasing over both the Sahara and the Sahel between 1982 and 2008, and the trends are correlated (R equals 0.53), suggesting that Saharan Sahelian surface winds are a coupled system, driving the inter-annual variation of dust emission.

Inventory and surveillance of natural resources as a contribution to land utilization planning in the Sahel

Energy Technology Data Exchange (ETDEWEB)

Panzer, K F

1980-09-01

The destructive land-use practices observed in large parts of the Sahel of West-Africa as a consequence of increasing population pressure must be replaced by sustained-yield management, e.g., by agro-sylvo-pastoral land-use systems. Information and planning aids required can only be obtained through the inventory and subsequent monitoring of the natural, renewable resources, i.e. water, range- and wood lands. Because of the extent and inaccessibility of the Sahel, an inventory design combining clustered fieldplots and large-scale aerial photography is being considered as most efficient in statistical and economical terms. Evidently, an inventory cannot solve the serious problems in the Sahel, but its results can contribute essentially towards defining better land-use policies and towards more effective management of the natural resource base.

Hacia un nuevo y diferente “Flanco Sur” en el Gran Magreb-Sahel

Directory of Open Access Journals (Sweden)

Raquel Barras

2015-10-01

Full Text Available La unión de espacios subgobernados, la corrupción, el crimen organizado y terrorismo es la amenaza a la que se enfrenta la UE y sus estados miembros en el Gran Magreb, el cual está recreando un nuevo y diferente Flanco Sur al que existía durante la Guerra Fría. El aumento de la actividad extremista en la región del Sahel-Sáhara a partir de 2005 ha ido en paralelo con el crecimiento de las redes de crimen organizado transnacional a través del área. Aunque hay un intenso debate sobre su relación, intensidad e impacto, es una dinámica innegable en el área. La UE no tiene realmente una política unificada Magreb-Sahel y en términos de crimen organizado y terrorismo, el Sahel no se puede separar del Magreb. Hay una comprensión limitada y parcial del problema tanto en términos de amenazas como en soluciones viables, ampliado irremediablemente por la acción de Boko Haram y desbordando la visión, proyección y estrategia de la UE. A pesar del "Sahel Regional Action Plan 2015-2020", las medidas tomadas son reducidas, muy recientes y probablemente insuficientes y tardías desde el punto de vista de la dinámica y sinergia entre terrorismo-crimen organizado en un contexto de corrupción. La UE sigue manteniendo un enfoque seguridad-desarrollo, básicamente en una concepción de seguridad humana, a pesar de que este enfoque es altamente discutible para enfrentarse a este tipo de amenazas.

Farm survey design in the Sahel : Experiences from Burkina Faso

NARCIS (Netherlands)

Graaff, de J.; Mijl, van der J.P.; Nibbering, J.W.

1999-01-01

In designing farm household surveys in the Sahel in West Africa much attention should be paid to various specific features of the farming systems. These features relate in particular to the social organisation of the farming communities. Within households, kinship relations have a strong bearing on

Extensive Admixture and Selective Pressure Across the Sahel Belt

Czech Academy of Sciences Publication Activity Database

Triska, P.; Soares, P.; Patin, E.; Fernandes, V.; Černý, Viktor; Pereira, L.

2015-01-01

Roč. 7, č. 12 (2015), s. 3484-3495 ISSN 1759-6653 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : genome-wide diversity * admixture * selection * Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 4.098, year: 2015 http://gbe.oxfordjournals.org/content/7/12/3484.full.pdf+html

Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

Science.gov (United States)

Zhang, Wenmin; Brandt, Martin; Tong, Xiaoye; Tian, Qingjiu; Fensholt, Rasmus

2018-01-01

Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy-rainfall events, longer dry spells, and a shifted timing of the wet season. Yet the aboveground net primary productivity (ANPP) in drylands is usually explained by annual-rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tested the importance of rainfall metrics in the wet season (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days, and heavy-rainfall events) for growing season ANPP. We focused on the Sahel and northern Sudanian region (100-800 mm yr-1) and applied daily satellite-based rainfall estimates (CHIRPS v2.0) and growing-season-integrated normalized difference vegetation index (NDVI; MODIS) as a proxy for ANPP over the study period: 2001-2015. Growing season ANPP in the arid zone (100-300 mm yr-1) was found to be rather insensitive to variations in the seasonal-rainfall metrics, whereas vegetation in the semi-arid zone (300-700 mm yr-1) was significantly impacted by most metrics, especially by the number of rainy days and timing (onset and cessation) of the wet season. We analysed critical breakpoints for all metrics to test if vegetation response to changes in a given rainfall metric surpasses a threshold beyond which vegetation functioning is significantly altered. It was shown that growing season ANPP was particularly negatively impacted after > 14 consecutive dry days and that a rainfall intensity of ˜ 13 mm day-1 was detected for optimum growing season ANPP. We conclude that the number of rainy days and the timing of the wet season are seasonal-rainfall metrics that are decisive for favourable vegetation growth in the semi-arid Sahel and need to be considered when modelling primary productivity from rainfall in the drylands of the Sahel and elsewhere.

Fine-scale spatial distribution of plants and resources on a sandy soil in the Sahel

NARCIS (Netherlands)

Rietkerk, M.G.; Ouedraogo, T.; Kumar, L.; Sanou, S.; Langevelde, F. van; Kiema, A.; Koppel, J. van de; Andel, J. van; Hearne, J.; Skidmore, A.K.; Ridder, N. de; Stroosnijder, L.; Prins, H.H.T.

2002-01-01

We studied fine-scale spatial plant distribution in relation to the spatial distribution of erodible soil particles, organic matter, nutrients and soil water on a sandy to sandy loam soil in the Sahel. We hypothesized that the distribution of annual plants would be highly spatially autocorrelated

Spatiotemporal variability in carbon exchange fluxes across the Sahel

DEFF Research Database (Denmark)

Tagesson, Håkan Torbern; Fensholt, Rasmus; Cappelaere, Bernard

2016-01-01

for semi-arid ecosystems. We have synthesized data on the land-atmosphere exchange of CO2 measured with the eddy covariance technique from the six existing sites across the Sahel, one of the largest semi-arid regions in the world. The overall aim of the study is to analyse and quantify the spatiotemporal...... variability in these fluxes and to analyse to which degree spatiotemporal variation can be explained by hydrological, climatic, edaphic and vegetation variables. All ecosystems were C sinks (average ± total error -162 ± 48 g C m-2 y-1), but were smaller when strongly impacted by anthropogenic influences...

Mesoscale modeling of smoke radiative feedback over the Sahel region

Science.gov (United States)

Yang, Z.; Wang, J.; Ichoku, C. M.; Ellison, L.; Zhang, F.; Yue, Y.

2013-12-01

This study employs satellite observations and a fully-coupled meteorology-chemistry-aerosol model, Weather Research and Forecasting model with Chemistry (WRF-Chem) to study the smoke radative feedback on surface energy budget, boundary layer processes, and atmospheric lapse rate in February 2008 over the Sahel region. The smoke emission inventories we use come from various sources, including but not limited to the Fire Locating and Modeling of Burning Emissions (FLAMBE) developed by NRL and the Fire Energetic and Emissions Research (FEER) developed by NASA GSFC. Model performance is evaluated using numerous satellite and ground-based datasets: MODIS true color images, ground-based Aerosol Optical Depth (AOD) measurements from AERONET, MODIS AOD retrievals, and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF-Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Statistically, 5% of the CALIPSO valid measurements of aerosols in February 2008 show aerosol layers either above the clouds or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the Sahel region. The results further show that the smoke radiative feedbacks are sensitive to assumptions of black carbon and organic carbon ratio in the particle emission inventory. Also investigated is the smoke semi-direct effect as a function of cloud fraction.

Energy needs, tasks and resources in the Sahel: Relevance to woodstoves programmes

Energy Technology Data Exchange (ETDEWEB)

Cecelski, E

1983-01-01

This article reviews the wood fuels situation in the Sahel and the findings of various needs assessment methodologies, especially as these are relevant to the numerous programmes to introduce improved cooking technologies in the region. Most people in West Africa, especially in poor and rural areas, rely primarily on wood fuels and crop wastes for energy needs, with devastating environmental consequences. Most wood is used in cooking. The quantity of fuel used depends on the type of fireplace, utensils used, how and when food is prepared, food preparation methods, types of fuels, how fuelwood is collected, and special customs surrounding the family fire - all of which are intimately associated with the economic, cultural and social fabric of Sahelian societies. Conventional fuel consumption and resource surveys have yielded useful information about quantitative energy needs in the Sahel, but increasingly sociocultural studies are being used to ensure that stove designs will meet the needs of the end-user. Economic analysis is also necessary to establish the dimensions of wood scarcity, to assess the financial attractiveness to consumers of alternative fuels and stoves, and in evaluating the costs and benefits to society of proposed national woodstoves programmes.

Impact of soil-vegetation-atmosphere interactions on the spatial rainfall distribution in the Central Sahel

Directory of Open Access Journals (Sweden)

Marcus Breil

2017-10-01

Full Text Available In a Regional Climate Model (RCM the interactions between the land surface and the atmosphere are described by a Soil-Vegetation-Atmosphere-Transfer Model (SVAT. In the presented study two SVATs of different complexity (TERRA-ML and VEG3D are coupled to the RCM COSMO-CLM (CCLM to investigate the impact of different representations of soil-vegetation-atmosphere interactions on the West African Monsoon (WAM system. In contrast to TERRA-ML, VEG3D comprises a more detailed description of the land-atmosphere coupling by including a vegetation layer in its structural design, changing the treatment of radiation and turbulent fluxes. With these two different model systems (CCLM-TERRA-ML and CCLM-VEG3D climate simulations are performed for West Africa and analyzed. The study reveals that the simulated spatial distribution of rainfall in the Sahel region is substantially affected by the chosen SVAT. Compared to CCLM-TERRA-ML, the application of CCLM-VEG3D results in higher near surface temperatures in the Sahel region during the rainy season. This implies a southward expansion of the Saharian heat-low. Consequently, the mean position of the African Easterly Jet (AEJ is also shifted to the south, leading to a southward displacement of tracks for Mesoscale Convective Systems (MCS, developing in connection with the AEJ. As a result, less precipitation is produced in the Sahel region, increasing the agreement with observations. These analyses indicate that soil-vegetation-atmosphere interactions impact the West African Monsoon system and highlight the benefit of using a more complex SVAT to simulate its dynamics.

The impacts of the dust radiative effect on vegetation growth in the Sahel

Science.gov (United States)

Evans, S. M.; Shevliakova, E.; Malyshev, S.; Ginoux, P. A.

2017-12-01

Many studies have been conducted on the effects of dust on rainfall in the Sahel, and generally show that African dust weakens the West African Monsoon, drying the region. This drying is often assumed to reduce vegetation cover for the region, providing a positive feedback with dust emission. There are, however, other competing effects of dust that are also important to plant growth, including a reduction in surface temperature, a reduction in downwelling solar radiation, and an increase in the diffuse fraction of that solar radiation. Using the NOAA/GFDL CM3 model coupled to the dynamic vegetation model LM3, we demonstrate that the combined effect of all these processes is to decrease the vegetation coverage and productivity of the Sahel and West Africa. We accomplish this by comparing experiments with radiatively active dust to experiments with radiatively invisible dust. We find that in modern conditions, the dust radiative effect reduces the net primary productivity of West Africa and the Sahel by up to 30% locally, and when summed over the region accounts for a difference of approximately 0.4 GtC per year. Experiments where the vegetation experiences preindustrial rather than modern CO2 levels show that without carbon fertilization, this loss of productivity would be approximately 10% stronger. In contrast, during preindustrial conditions the vegetation response is less than half as strong, despite the dust induced rainfall and temperature anomalies being similar. We interpret this as the vegetation being less susceptible to drought in a less evaporative climate. These changes in vegetation create the possibility of a dust-vegetation feedback loop whose strength varies with the mean state of the climate, and which may grow stronger in the future.

Household possession, use and non-use of treated or untreated mosquito nets in two ecologically diverse regions of Nigeria – Niger Delta and Sahel Savannah

Directory of Open Access Journals (Sweden)

Otsemobor Peju

2009-02-01

Full Text Available Abstract Background Current use of treated mosquito nets for the prevention of malaria falls short of what is expected in sub-Saharan Africa (SSA, though research within the continent has indicated that the use of these commodities can reduce malaria morbidity by 50% and malaria mortality by 20%. Governments in sub-Sahara Africa are investing substantially in scaling-up treated mosquito net coverage for impact. However, certain significant factors still prevent the use of the treated mosquito nets, even among those who possess them. This survey examines household ownership as well as use and non-use of treated mosquito nets in Sahel Savannah and Niger Delta regions of Nigeria. Methodology This survey employed cross-sectional survey to collect data from households on coverage and use of mosquito nets, whether treated or not. Fever episodes in previous two weeks among children under the age of five were also recorded. The study took place in August 1 – 14 2007, just five months after the March distribution of treated mosquito nets, coinciding with the second raining period of the year and a time of high malaria transmission during the wet season. EPI INFO version 2003 was used in data analysis. Results The survey covered 439 households with 2,521 persons including 739 under-fives, 585 women in reproductive age and 78 pregnant women in Niger Delta Region and Sahel Savannah Region. Of the 439 HHs, 232 had any mosquito nets. Significantly higher proportion of households in the Niger Delta Region had any treated or untreated mosquito nets than those in the Sahel Savannah Region. In the Niger Delta Region, the proportion of under-fives that had slept under treated nets the night before the survey exceeded those that slept under treated nets in the Sahel Savannah Region. Children under the age of five years in the Niger Delta Region were four times more likely to sleep under treated nets than those in the Sahel Savannah Region. Conclusion This study

Water, energy and CO2 exchange over a seasonally flooded forest in the Sahel.

Science.gov (United States)

Kergoat, L.; Le Dantec, V.; Timouk, F.; Hiernaux, P.; Mougin, E.; Manuela, G.; Diawara, M.

2014-12-01

In semi-arid areas like the Sahel, perennial water bodies and temporary-flooded lowlands are critical for a number of activities. In some cases, their existence is simply a necessary condition for human societies to establish. They also play an important role in the water and carbon cycle and have strong ecological values. As a result of the strong multi-decadal drought that impacted the Sahel in the 70' to 90', a paradoxical increase of ponds and surface runoff has been observed ("Less rain, more water in the ponds", Gardelle 2010). In spite of this, there are excessively few data documenting the consequence of such a paradox on the water and carbon cycle. Here we present 2 years of eddy covariance data collected over the Kelma flooded Acacia forest in the Sahel (15.50 °N), in the frame of the AMMA project. The flooded forest is compared to the other major component of this Sahelian landscape: a grassland and a rocky outcrop sites. All sites are involved in the ALMIP2 data/LSM model comparison. The seasonal cycle of the flooded forest strongly departs from the surroundings grassland and bare soil sites. Before the rain season, the forest displays the strongest net radiation and sensible heat flux. Air temperature within the canopy reaches extremely high values. During the flood, it turns to the lowest sensible heat flux. In fact, due to an oasis effect, this flux is negative during the late flood. Water fluxes turn from almost zero in the dry season to strong evaporation during the flood, since it uses additional energy provided by negative sensible heat flux. The eddy covariance fluxes are consistent with sap flow data, showing that the flood greatly increases the length of the growing season. CO2 fluxes over the forest were twice as large as over the grassland, and the growing season was also longer, giving a much larger annual photosynthesis. In view of these data and data over surroundings grasslands and bare soil, as well as data from a long-term ecological

Do state-of-the-art CMIP5 ESMs accurately represent observed vegetation-rainfall feedbacks? Focus on the Sahel

Science.gov (United States)

Notaro, M.; Wang, F.; Yu, Y.; Mao, J.; Shi, X.; Wei, Y.

2017-12-01

The semi-arid Sahel ecoregion is an established hotspot of land-atmosphere coupling. Ocean-land-atmosphere interactions received considerable attention by modeling studies in response to the devastating 1970s-90s Sahel drought, which models suggest was driven by sea-surface temperature (SST) anomalies and amplified by local vegetation-atmosphere feedbacks. Vegetation affects the atmosphere through biophysical feedbacks by altering the albedo, roughness, and transpiration and thereby modifying exchanges of energy, momentum, and moisture with the atmosphere. The current understanding of these potentially competing processes is primarily based on modeling studies, with biophysical feedbacks serving as a key uncertainty source in regional climate change projections among Earth System Models (ESMs). In order to reduce this uncertainty, it is critical to rigorously evaluate the representation of vegetation feedbacks in ESMs against an observational benchmark in order to diagnose systematic biases and their sources. However, it is challenging to successfully isolate vegetation's feedbacks on the atmosphere, since the atmospheric control on vegetation growth dominates the atmospheric feedback response to vegetation anomalies and the atmosphere is simultaneously influenced by oceanic and terrestrial anomalies. In response to this challenge, a model-validated multivariate statistical method, Stepwise Generalized Equilibrium Feedback Assessment (SGEFA), is developed, which extracts the forcing of a slowly-evolving environmental variable [e.g. SST or leaf area index (LAI)] on the rapidly-evolving atmosphere. By applying SGEFA to observational and remotely-sensed data, an observational benchmark is established for Sahel vegetation feedbacks. In this work, the simulated responses in key atmospheric variables, including evapotranspiration, albedo, wind speed, vertical motion, temperature, stability, and rainfall, to Sahel LAI anomalies are statistically assessed in Coupled Model

Genetic Structure of Pastoral and Farmer Populations in the African Sahel

Czech Academy of Sciences Publication Activity Database

Černý, Viktor; Pereira, L.; Musilová, E.; Kujanová, M.; Vašíková, A.; Blasi, P.; Garofalo, L.; Soares, P.; Diallo, I.; Brdička, R.; Novelletto, A.

2011-01-01

Roč. 28, č. 9 (2011), s. 2491-2500 ISSN 0737-4038 R&D Projects: GA ČR GA206/08/1587 Institutional research plan: CEZ:AV0Z80020508 Keywords : African Sahel * pastoralism * archaeogenetics Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 5.550, year: 2011 http://mbe.oxfordjournals.org/content/28/9/2491

The effect of irrigated rice cropping on the alkalinity of two alkaline rice soils in the Sahel

NARCIS (Netherlands)

Asten, van P.J.A.; Zelfde, van 't J.A.; Zee, van der S.E.A.T.M.; Hammecker, C.

2004-01-01

Irrigated rice cropping is practiced to reclaim alkaline-sodic soils in many parts of the world. This practice is in apparent contrast with earlier studies in the Sahel, which suggests that irrigated rice cropping may lead to the formation of alkaline-sodic soils. Soil column experiments were done

Political Reform, Socio-Religious Change, and Stability in the African Sahel

Science.gov (United States)

2016-12-08

research project This project proposed to analyze the socio- political factors affecting stability and instability in a set of six African countries...AFRL-AFOSR-VA-TR-2016-0360 Political Reform, Socio-Religious Change, and Stability in the African Sahel Leonard Villalon UNIVERSITY OF FLORIDA...STATEMENT DISTRIBUTION A: Distribution approved for public release. 13. SUPPLEMENTARY NOTES 14. ABSTRACT 15. SUBJECT TERMS Political stability

Remote sensing of desert dust aerosols over the Sahel : potential use for health impact studies

Science.gov (United States)

Deroubaix, A. D.; Martiny, N. M.; Chiapello, I. C.; Marticorena, B. M.

2012-04-01

Since the end of the 70's, remote sensing monitors the desert dust aerosols due to their absorption and scattering properties and allows to make long time series which are necessary for air quality or health impact studies. In the Sahel, a huge health problem is the Meningitis Meningococcal (MM) epidemics that occur during the dry season : the dust has been suspected to be crucial to understand their onsets and dynamics. The Aerosol absorption Index (AI) is a semi-quantitative index derived from TOMS and OMI observations in the UV available at a spatial resolution of 1° (1979-2005) and 0.25° (2005-today) respectively. The comparison of the OMI-AI and AERONET Aerosol Optical thickness (AOT) shows a good agreement at a daily time-step (correlation ~0.7). The comparison of the OMI-AI with the Particle Matter (PM) measurement of the Sahelian Dust Transect is lower (~0.4) at a daily time-step but it increases at a weekly time-step (~0.6). The OMI-AI reproduces the dust seasonal cycle over the Sahel and we conclude that the OMI-AI product at a 0.25° spatial resolution is suitable for health impact studies, especially at a weekly epidemiological time-step. Despite the AI is sensitive to the aerosol altitude, it provides a daily spatial information on dust. A preliminary investigation analysis of the link between weekly OMI AI and weekly WHO epidemiological data sets is presented in Mali and Niger, showing a good agreement between the AI and the onset of the MM epidemics with a constant lag (between 1 and 2 week). The next of this study is to analyse a deeper AI time series constituted by TOMS and OMI data sets. Based on the weekly ratios PM/AI at 2 stations of the Sahelian Dust Transect, a spatialized proxy for PM from the AI has been developed. The AI as a proxy for PM and other climate variables such as Temperature (T°), Relative Humidity (RH%) and the wind (intensity and direction) could then be used to analyze the link between those variables and the MM epidemics

The significance of drinking water for population migration in the Sahel zone of the Republic of Sudan.

Science.gov (United States)

Ruppert, H

1991-01-01

This study examines how the availability of water supplies affects migration in the Sahel region of Sudan. More particularly, the author shows that "through the development of watering-places and the opening-up of new water resources, the government influences considerably processes of population migration and regional concentrations of population groups." excerpt

Climatic information of Western Sahel (1535-1793 AD) in original documentary sources

Science.gov (United States)

Millán, V.; Rodrigo, F. S.

2014-09-01

The Sahel is the semi-arid transition zone between arid Sahara and humid tropical Africa, extending approximately 10-20° N from Mauritania in the West to Sudan in the East. The African continent, one of the most vulnerable regions to climate change, is subject to frequent droughts and famine. One climate challenge research is to isolate those aspects of climate variability that are natural from those that are related to human influences. Therefore, the study of climatic conditions before mid-19th century, when anthropogenic influence was of minor importance, is very interesting. In this work the frequency of extreme events, such as droughts and floods, in Western Sahel from the 16th to 18th centuries is investigated using documentary data. Original manuscripts with historical chronicles from Walata and Nema (Mauritania), Timbuktu and Arawan (Mali), and Agadez (Niger) have been analyzed. Information on droughts, intense rainfall, storms and floods, as well as socioeconomic aspects (famines, pests, scarcity, prosperity) has been codified in an ordinal scale ranging from -2 (drought and famines) to +2 (floods) to obtain a numerical index of the annual rainfall in the region. Results show wet conditions in the 17th century, as well as dry conditions in the 18th century (interrupted by a short wet period in the 1730s decade).

What Four Decades of Earth Observation Tell Us about Land Degradation in the Sahel?

Directory of Open Access Journals (Sweden)

Cheikh Mbow

2015-04-01

Full Text Available The assessment of land degradation and the quantification of its effects on land productivity have been both a scientific and political challenge. After four decades of Earth Observation (EO applications, little agreement has been gained on the magnitude and direction of land degradation in the Sahel. The large number of EO datasets and methods associated with the complex interactions among biophysical and social drivers of ecosystem changes make it difficult to apply aggregated EO indices for these non-linear processes. Hence, while many studies stress that the Sahel is greening, others indicate no trend or browning. The different generations of sensors, the granularity of studies, the study period, the applied indices and the assumptions and/or computational methods impact these trends. Consequently, many uncertainties exist in regression models between rainfall, biomass and various indices that limit the ability of EO science to adequately assess and develop a consistent message on the magnitude of land degradation. We suggest several improvements: (1 harmonize time-series data, (2 promote knowledge networks, (3 improve data-access, (4 fill data gaps, (5 agree on scales and assumptions, (6 set up a denser network of long-term field-surveys and (7 consider local perceptions and social dynamics. To allow multiple perspectives and avoid erroneous interpretations, we underline that EO results should not be interpreted without contextual knowledge.

USSOF OPERATIONS IN AFRICA: PROSPECTS FOR FUTURE ENGAGEMENTS IN THE SAHEL

Science.gov (United States)

2017-04-03

counterterrorism operations in Somalia, Yemen , Afghanistan, Pakistan, and Syria.3 Absent the operational capability of terrorists to function in these...action by USSOF comes with some challenges. A fundamental challenge to USSOF operations outside the US, as evinced in the USSOF raid in Yakla- Yemen , is...assets. 8 Additionally, poor infrastructural facilities in the Sahel exacerbate the problem of poor logistics to support USSOF operations in

Services financiers et déploiement d'innovations agricoles au Sahel ...

International Development Research Centre (IDRC) Digital Library (Canada)

Services financiers et déploiement d'innovations agricoles au Sahel. Au cours des vingt dernières années, plusieurs innovations visant à améliorer les rendements des cultures vivrières ont été développées dans les centres de recherche agronomique d'Afrique de l'Ouest et par les chercheurs de la communauté ...

The Sahel Region of West Africa: Examples of Climate Analyses Motivated By Drought Management Needs

Science.gov (United States)

Ndiaye, O.; Ward, M. N.; Siebert, A. B.

2011-12-01

failure. This can be viewed as a special case of agricultural drought. Therefore, improving climate information around the time of planting can play a key role in agricultural risk management. Rainfall onset indices have been calculated for stations across Senegal. The problem is climatically challenging because the physical processes that impact rainfall onset appear to span aspects normally studied separately: weather system character, propagating intraseasonal features, and large-scale sea-surface temperature influence. We present aspects of all these, and ideas on how to combine them into seamless information to support agriculture.

Alu insertion polymorphisms in the African Sahel and the origin of Fulani pastoralists

Czech Academy of Sciences Publication Activity Database

Čížková, M.; Hofmanová, Z.; Mokhtar, M. G.; Janoušek, V.; Diallo, I.; Munclinger, P.; Černý, Viktor

2017-01-01

Roč. 44, č. 6 (2017), s. 537-545 ISSN 0301-4460 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : Alu insertions * Fulani nomads * Western African pastoralism * African Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology OBOR OECD: Archaeology Impact factor: 1.240, year: 2016

Revisiting historical climatic signals to better explore the future: prospects of water cycle changes in Central Sahel

Science.gov (United States)

Leauthaud, C.; Demarty, J.; Cappelaere, B.; Grippa, M.; Kergoat, L.; Velluet, C.; Guichard, F.; Mougin, E.; Chelbi, S.; Sultan, B.

2015-06-01

Rainfall and climatic conditions are the main drivers of natural and cultivated vegetation productivity in the semiarid region of Central Sahel. In a context of decreasing cultivable area per capita, understanding and predicting changes in the water cycle are crucial. Yet, it remains challenging to project future climatic conditions in West Africa since there is no consensus on the sign of future precipitation changes in simulations coming from climate models. The Sahel region has experienced severe climatic changes in the past 60 years that can provide a first basis to understand the response of the water cycle to non-stationary conditions in this part of the world. The objective of this study was to better understand the response of the water cycle to highly variable climatic regimes in Central Sahel using historical climate records and the coupling of a land surface energy and water model with a vegetation model that, when combined, simulated the Sahelian water, energy and vegetation cycles. To do so, we relied on a reconstructed long-term climate series in Niamey, Republic of Niger, in which three precipitation regimes can be distinguished with a relative deficit exceeding 25% for the driest period compared to the wettest period. Two temperature scenarios (+2 and +4 °C) consistent with future warming scenarios were superimposed to this climatic signal to generate six virtual future 20-year climate time series. Simulations by the two coupled models forced by these virtual scenarios showed a strong response of the water budget and its components to temperature and precipitation changes, including decreases in transpiration, runoff and drainage for all scenarios but those with highest precipitation. Such climatic changes also strongly impacted soil temperature and moisture. This study illustrates the potential of using the strong climatic variations recorded in the past decades to better understand potential future climate variations.

Farmers´ perceptions of climate change and agricultural adaptation strategies in rural Sahel

DEFF Research Database (Denmark)

Mertz, Ole; Mbow, Cheikh; Reenberg, Anette

2009-01-01

Farmers in the Sahel have always been facing climatic variability at intra- and inter-annual and decadal time scales. While coping and adaptation strategies have traditionally included crop diversification, mobility, livelihood diversification, and migration, singling out climate as a direct driver...... of changes is not so simple. Using focus group interviews and a household survey, this study analyzes the perceptions of climate change and the strategies for coping and adaptation by sedentary farmers in the savanna zone of central Senegal. Households are aware of climate variability and identify wind...

Summary of questionnaires completed by participating countries: for the project on the management of water resources in the Sahel region, using isotopic techniques

International Nuclear Information System (INIS)

Ito, Mari

2012-07-01

This presentation was carried out as part of the project on water resources management in the Sahel region, using isotope techniques. It summarizes the two sets of questionnaires made, highlights the basins (aquifers) selected for the Sahel project which are the Lullemen Basin, Taoudeni Basin, Lake Chad Basin and Liptako Gourma. Also, as well as the number of questionnaires completed by the participating countries.

Integrated pearl millet management in the Sahel : Effects of legume rotation and fallow management on productivity and Striga hermonthica infestation

NARCIS (Netherlands)

Samaké, O.; Stomph, T.J.; Kropff, M.J.; Smaling, E.M.A.

2006-01-01

Increasing population density and food needs in the Sahel are major drivers behind the conversion of land under natural vegetation to arable land. Intensification of agriculture is a necessity for farmers to produce enough food. As manure is scarce and fertilizers expensive, this study looks into

The paradoxical evolution of runoff in the pastoral Sahel: analysis of the hydrological changes over the Agoufou watershed (Mali) using the KINEROS-2 model

Science.gov (United States)

Gal, Laetitia; Grippa, Manuela; Hiernaux, Pierre; Pons, Léa; Kergoat, Laurent

2017-09-01

In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as the Sahelian paradox, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated Sahel. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral Sahel. The kinematic runoff and erosion model (KINEROS-2) is applied to the Agoufou watershed (245 km2), in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the past case (1960-1975) preceding the Sahelian drought and the present case (2000-2015). Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1) a partial crusting of isolated dunes, (2) an increase of drainage network density, (3) a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4) important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual discharge between the

Scenarios on future land changes in the West African Sahel

DEFF Research Database (Denmark)

Lambin, Eric; D'haen, Sarah Ann Lise; Mertz, Ole

2014-01-01

by the Millennium Ecosystem Assessment: (1) ‘downward spiral’ characterized by rapid climate change, expansion of agriculture and chaotic urban growth; (2) ‘integrated economy’ with integrated land management, food production for local markets and rural–urban exchanges; (3) ‘open doors’ characterized by large......-scale out-migrations, land grabbing by foreign companies and development aid and (4) ‘climate change mitigation’ with an increase in biofuel crops, land management for carbon capture and development of off-farm activities. We conclude that the Sahel region is most likely moving away from being a highly...

A model of tree-crop competition for windbreaks systems in the Sahel : description and evaluation

NARCIS (Netherlands)

Mayus, M.; Keulen, van H.; Stroosnijder, L.

1999-01-01

A model was developed to simulate the effects of competition for soil water and radiation between windbreaks and pearl millet crops in the Sahel. These effects on millet (Pennisetum glaucum (L.) R. Br.) growth were simultaneously simulated for each millet row parallel to the windbreak with small

Local Vegetation Trends in the Sahel of Mali and Senegal Using Long Time Series FAPAR Satellite Products and Field Measurement (1982–2010

Directory of Open Access Journals (Sweden)

Martin Brandt

2014-03-01

Full Text Available Local vegetation trends in the Sahel of Mali and Senegal from Geoland Version 1 (GEOV1 (5 km and the third generation Global Inventory Modeling and Mapping Studies (GIMMS3g (8 km Fraction of Absorbed Photosynthetically Active Radiation (FAPAR time series are studied over 29 years. For validation and interpretation of observed greenness trends, two methods are applied: (1 a qualitative approach using in-depth knowledge of the study areas and (2 a quantitative approach by time series of biomass observations and rainfall data. Significant greening trends from 1982 to 2010 are consistently observed in both GEOV1 and GIMMS3g FAPAR datasets. Annual rainfall increased significantly during the observed time period, explaining large parts of FAPAR variations at a regional scale. Locally, GEOV1 data reveals a heterogeneous pattern of vegetation change, which is confirmed by long-term ground data and site visits. The spatial variability in the observed vegetation trends in the Sahel area are mainly caused by varying tree- and land-cover, which are controlled by human impact, soil and drought resilience. A large proportion of the positive trends are caused by the increment in leaf biomass of woody species that has almost doubled since the 1980s due to a tree cover regeneration after a dry-period. This confirms the re-greening of the Sahel, however, degradation is also present and sometimes obscured by greening. GEOV1 as compared to GIMMS3g made it possible to better characterize the spatial pattern of trends and identify the degraded areas in the study region.

Future supply and demand of net primary production in the Sahel

Science.gov (United States)

Sallaba, Florian; Olin, Stefan; Engström, Kerstin; Abdi, Abdulhakim M.; Boke-Olén, Niklas; Lehsten, Veiko; Ardö, Jonas; Seaquist, Jonathan W.

2017-12-01

In the 21st century, climate change in combination with increasing demand, mainly from population growth, will exert greater pressure on the ecosystems of the Sahel to supply food and feed resources. The balance between supply and demand, defined as the annual biomass required for human consumption, serves as a key metric for quantifying basic resource shortfalls over broad regions.Here we apply an exploratory modelling framework to analyse the variations in the timing and geography of different NPP (net primary production) supply-demand scenarios, with distinct assumptions determining supply and demand, for the 21st century Sahel. We achieve this by coupling a simple NPP supply model forced with projections from four representative concentration pathways with a global, reduced-complexity demand model driven by socio-economic data and assumptions derived from five shared socio-economic pathways.For the scenario that deviates least from current socio-economic and climate trends, we find that per capita NPP begins to outstrip supply in the 2040s, while by 2050 half the countries in the Sahel experience NPP shortfalls. We also find that despite variations in the timing of the onset of NPP shortfalls, demand cannot consistently be met across the majority of scenarios. Moreover, large between-country variations are shown across the scenarios, in which by the year 2050 some countries consistently experience shortage or surplus, while others shift from surplus to shortage. At the local level (i.e. grid cell), hotspots of total NPP shortfall consistently occur in the same locations across all scenarios but vary in size and magnitude. These hotspots are linked to population density and high demand. For all scenarios, total simulated NPP supply doubles by 2050 but is outpaced by increasing demand due to a combination of population growth and the adoption of diets rich in animal products. Finally, variations in the timing of the onset and end of supply shortfalls stem from

PVO / NGO initiatives. The Global Dialogues Trust -- "Scenarios from the Sahel".

Science.gov (United States)

1997-01-01

Scenarios from the Sahel is an HIV/AIDS prevention project for adolescents and young adults in Senegal, Mali, Burkina Faso, and Niger, organized by the Global Dialogues Trust and launched in January 1997. The project invites people aged 24 years and younger to engage in a competition in which they write scenarios for a 1-5 minute video on HIV/AIDS. Those 30 scenarios judged to be the most valuable to the HIV/AIDS prevention effort in the Sahel will be developed into video spots by the region's film-makers and screened at cinemas and broadcast on television stations in West Africa. The spots will also be collected upon a compilation video available for use by local nongovernmental organizations in their HIV/AIDS prevention activities in the region. The compilation video will be dubbed from French into local languages and English to facilitate its broad dissemination in the 4 participating countries and their neighbors. The video together with an education pack will also be distributed to local organizations and schools. The project, to be conducted in close partnership with local people and their organizations, will end with its evaluation in June 1998. Global Dialogues Trust is a charitable trust based in the UK dedicated to advance the education of the public throughout the world in all matters concerning the prevention of HIV/AIDS. The organization's main priority is to develop local capacity to fight HIV/AIDS through preventive education.

[Migration and urbanization in the Sahel. Consequences of the Sahelian migrations].

Science.gov (United States)

Traore, S

1997-10-01

The consequences of Sahelian migration are multiple and diverse. In rural areas there may be a loss of income in the short run and a reduced possibility of development in the long run. Apart from its implications for urban growth, Sahelian migration may have four series of consequences in the places of origin. In detaching peasants from their lands, migration may contribute to loss of appreciation and reverence for the lands. Attachment to the lands of the ancestors loses its meaning as soon as questions of survival or economic rationality are raised. Migration contributes to the restructuring of the societies of origin. Increasing monetarization of market relations and introduction of new needs create new norms that favor stronger integration into the world economy. Migration may cause a decline in production because of the loss of the most active population, and it changes the age and sex distribution of households and usually increases their dependency burden. The effects on fertility and mortality are less clear. The effects of migration on the zones of arrival in the Sahel depend on the type of area. Conflicts between natives and in-migrants are common in rural-rural migration. Degradation of land may result from the increased demands placed upon it. Migrants to cities in Africa, and especially in the Sahel, appear to conserve their cultural values and to transplant and reinterpret their village rules of solidarity.

Determination of stable and radioactive isotopes in rain water for the equatorial and Sahel zones

International Nuclear Information System (INIS)

Baudet, J.; Lesne, H.

1975-01-01

The extension of desert zones to detriment of Sahel zones lead to look for the circuit followed by water vapor between its principal source, i.e. the Guinea Gulf, and the place where it is changed in precipitation. Samples of rainwater have been collected in Abidjan, Ouagadougou, and Niamey when the Intertropical Front was beginning its moving down towards the South, i.e. at the end of the rainy season for the Sahel zone, and at the beginning of the small rainy season for the equatorial zone. The analysis of these tritium, deuterium and oxygen-18 contents show that: the rains collected in Abidjan comes mainly from Ocean; the rains collected in Ouagadougou and Niamey have followed a long journey above the continent, as shown by the tritium content. The water evaporated in the Guinea Gulf is condensed in the convergence zone above Cameroon, and mixed with re-evaporated continental water. The content of one of the Ouagadougou sample shows that the rain issued from a local cumulonimbus has drawn a part of its water from the stratosphere [fr

Hydrodynamic behaviour of crusted soils in the Sahel: a possible cause for runoff increase?

Science.gov (United States)

Malam Abdou, M.; Vandervaere, J.-P.; Bouzou Moussa, I.; Descroix, L.

2012-04-01

Crusted soils are in extension in the Sahel. As rainfall has decreased over the past decades (it is now increasing again in the central Sahel) and no significant change was observed in rainfall intensity and in its time and space distribution, it is supposed that land use management is the main cause for crusts cover increase. Fallow shortening, lack of manure, and land overexploitation (wood harvesting, overgrazing) are frequently cited as main factors of soil degradation. Based on field measurements in some small catchments of Western Niger, the hydrodynamics behaviour of the newly crusted soils of this area is described, mostly constituted by erosion crusts. A strong fall in soil saturated conductivity and in the active porosity as well as a rise in bulk density all lead to a quick onset of runoff production. Results are shown from field experiments in sedimentary and basement areas leading to similar conclusions. In both contexts, runoff plot production was measured at the rain event scale from 10-m2 parcels as well as at the catchment outlet. Soil saturated conductivity was reduced by one order of magnitude when crusting occurs, leading to a sharp runoff coefficient increase, from 4% in a weeded millet field and 10% in an old fallow to more than 60% in a erosion-crusted topsoil at the plot scale. At the experimental catchment scale, runoff coefficient has doubled in less than 20 years. In pure Sahelian basins, this resulted in endorheism breaching, and in a widespread river discharge increase. For some right bank tributaries of the Niger River, discharge is three times higher now than before the drought years, in spite of the remaining rainfall deficit. On the other hand, a general increase in flooding hazard frequency is observed in the whole Sahelian stripe. The role of surface crusts in the Sahel is discussed leading to the implementation of new experiments in the future.

Soil Management Practices to Improve Nutrient-use Efficiencies and Reduce Risk in Millet-based Cropping Systems in the Sahel

Directory of Open Access Journals (Sweden)

Koala, S.

2003-01-01

Full Text Available Low soil fertility and moisture deficit are among the main constraints to sustainable crop yields in the Sahel. A study therefore, was conducted at the ICRISAT Sahelian Center, Sadore in Niger to test the hypothesis that integrated soil husbandry practices consisting of manure, fertilizer and crop residues in rotational cropping systems use organic and mineral fertilizes efficiently, thereby resulting in higher yields and reduced risk. Results from an analysis of variance showed that choice of cropping systems explained more than 50% of overall variability in millet and cowpea grain yields. Among the cropping systems, rotation gave higher yields than sole crop and intercropping systems and increased millet yield by 46% without fertilizer. Rainfall-use efficiency and partial factor productivity of fertilizer were similarly higher in rotations than in millet monoculture system. Returns from cowpea grown in cowpea-millet rotation without fertilizer and the medium rates of fertilizers (4 kg P.ha-1 + 15 kg N.ha-1 were found to be most profitable in terms of high returns and low risk, principally because of a higher price of cowpea than millet. The study recommends crop diversification, either in the form of rotations or relay intercropping systems for the Sahel as an insurance against total crop failure.

Assessing the long-term effects of the Sahel drought on ponds and semi-arid hydrology.

Science.gov (United States)

Gal, L.; Grippa, M.; Kergoat, L.; Hiernaux, P.; Peugeot, C.; Mougin, E.

2015-12-01

The Sahel underwent a severe rainfall deficit in the late 20th century, with extreme droughts in the early 70s and early 80s. This drought is the strongest multidecadal drought of the 20th century, globally. It has strongly impacted ecosystems, water availability, and populations. However, an increase of surface water has been observed during the same period: higher discharge of Sahelian rivers, and a general increase in pond's surface. This phenomenon, "less rain but more surface runoff", is referred to as the "Sahelian paradox". The causes of this paradox are still debated. The role of the significant increase in cropped areas, often cited for cultivated Sahel, does not hold for pastoral areas in central and northern Sahel. Degradation of vegetation as a result of the drought, soils erosion, may also play an important role. Most Sahelian watersheds are still poorly gauged or ungauged, which makes it difficult to quantify surface runoff and its determinants. A method is developed to estimate runoff over ungauged ponds watersheds. It is tested for the Agoufou pond in the Gourma region in Mali, where in situ data are available for 2007-2014. A 3D model is first developed to relate water volume to height surface. This model is combined with daily evaporation and precipitation, to estimate the water supply to the pond which is a proxy for runoff over the watershed. This model highlights a spectacular increase of the runoff coefficient over the last 60 years. The method is then applied to two ungauged Sahelian watersheds in Mauritania and Niger, where pond surfaces by remote sensing are the only information. The runoff coefficients also increased in the last 60 years over these watersheds. The runoff derived for the Agoufou pond is used to evaluate simulations with the KINEROS2 model. We discuss to what extent the changes in rain intensity, soil hydrological properties and land-use land cover are able to cause the observed change in runoff over the last 60 years.

Advances in monitoring vegetation and land use dynamics in the Sahel

DEFF Research Database (Denmark)

Mbow, Cheikh; Fensholt, Rasmus; Nielsen, Thomas Theis

2014-01-01

of CO2 in the atmosphere, grazing pressure, bush fires and agricultural expansion or contraction. The use of satellite data in combination with field data played a major role in the monitoring of vegetation dynamics and land use in the Sahel, since the mega drought of the 1970s and the 1980s. This paper...... briefly reviews the advance of satellite-based monitoring of vegetation dynamics over these 40 years. We discuss the promises of current and likely future data sources and analysis tools, as well as the need to strengthen in situ data collection to support and validate satellite-based vegetation and land...

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

Directory of Open Access Journals (Sweden)

Martin Brandt

2017-01-01

Full Text Available The greening in the Senegalese Sahel has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014–2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of “greening” or “degradation”. While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in Sahel responds to its inherent climatic variability and does not follow a linear trend.

Woody vegetation die off and regeneration in response to rainfall variability in the west African Sahel

Science.gov (United States)

Brandt, Martin; Tappan, G. Gray; Aziz Diouf, Abdoul; Beye, Gora; Mbow, Cheikh; Fensholt, Rasmus

2017-01-01

The greening in the Senegalese Sahel has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall) led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014–2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of “greening” or “degradation”. While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in Sahel responds to its inherent climatic variability and does not follow a linear trend.

Rebuilding resilience in the Sahel: Regreening in the Maradi and Zinder regions of Niger

OpenAIRE

Sendzimir, J.; Reij, C.P.; Magnuszewski, P.

2011-01-01

The societies and ecosystems of the Nigerien Sahel appeared increasingly vulnerable to climatic and economic uncertainty in the late twentieth century. Severe episodes of drought and famine drove massive livestock losses and human migration and mortality. Soil erosion and tree loss reduced a woodland to a scrub steppe and fed a myth of the Sahara desert relentlessly advancing southward. Over the past two decades this myth has been shattered by the dramatic reforestation of more than 5 million...

A unifying view of climate change in the Sahel linking intra-seasonal, interannual and longer time scales

International Nuclear Information System (INIS)

Giannini, A; Salack, S; Gaye, A T; Lodoun, T; Ali, A; Ndiaye, O

2013-01-01

We propose a re-interpretation of the oceanic influence on the climate of the African Sahel that is consistent across observations, 20th century simulations and 21st century projections, and that resolves the uncertainty in projections of precipitation change in this region: continued warming of the global tropical oceans increases the threshold for convection, potentially drying tropical land, but this ‘upped ante’ can be met if sufficient moisture is supplied in monsoon flow. In this framework, the reversal to warming of the subtropical North Atlantic, which is now out-pacing warming of the global tropical oceans, provides that moisture, and explains the partial recovery in precipitation since persistent drought in the 1970s and 1980s. We find this recovery to result from increases in daily rainfall intensity, rather than in frequency, most evidently so in Senegal, the westernmost among the three Sahelian countries analyzed. Continuation of these observed trends is consistent with projections for an overall wetter Sahel, but more variable precipitation on all time scales, from intra-seasonal to multi-decadal. (letter)

The Crop Risk Zones Monitoring System for resilience to drought in the Sahel

Science.gov (United States)

Vignaroli, Patrizio; Rocchi, Leandro; De Filippis, Tiziana; Tarchiani, Vieri; Bacci, Maurizio; Toscano, Piero; Pasqui, Massimiliano; Rapisardi, Elena

2016-04-01

Food security is still one of the major concerns that Sahelian populations have to face. In the Sahel, agriculture is primarily based on rainfed crops and it is often structurally inadequate to manage the climatic variability. The predominantly rainfed cropping system of Sahel region is dependent on season quality on a year-to-year basis, and susceptible to weather extremes of droughts and extreme temperatures. Low water-storage capacity and high dependence on rainfed agriculture leave the agriculture sector even more vulnerable to climate risks. Crop yields may suffer significantly with either a late onset or early cessation of the rainy season, as well as with a high frequency of damaging dry spells. Early rains at the beginning of the season are frequently followed by dry spells which may last a week or longer. As the amount of water stored in the soil at this time of the year is negligible, early planted crops can suffer water shortage stresses during a prolonged dry spell. Therefore, the choice of the sowing date is of fundamental importance for farmers. The ability to estimate effectively the onset of the season and potentially dangerous dry spells becomes therefore vital for planning rainfed agriculture practices aiming to minimize risks and maximize yields. In this context, advices to farmers are key drivers for prevention allowing a better adaptation of traditional crop calendar to climatic variability. In the Sahel, particularly in CILSS (Permanent Interstates Committee for Drought Control in the Sahel) countries, national Early Warning System (EWS) for food security are underpinned by Multidisciplinary Working Groups (MWGs) lead by National Meteorological Services (NMS). The EWSs are mainly based on tools and models utilizing numeric forecasts and satellite data to outlook and monitor the growing season. This approach is focused on the early identification of risks and on the production of information within the prescribed time period for decision

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali

Directory of Open Access Journals (Sweden)

J. Gardelle

2010-02-01

Full Text Available Changes in the flooded area of ponds in the Gourma region from 1950 to present are studied by remote sensing, in the general context of the current multi-decennial Sahel drought. The seasonal and interannual variations of the areas covered by surface water are assessed using multi-date and multi-sensor satellite images (SPOT, FORMOSAT, LANDSAT-MSS, –TM, and -ETM, CORONA, and MODIS and aerial photographs (IGN. Water body classification is adapted to each type of spectral resolution, with or without a middle-infrared band, and each spatial resolution, using linear unmixing for mixed pixels of MODIS data. The high-frequency MODIS data document the seasonal cycle of flooded areas, with an abrupt rise early in wet season and a progressive decrease in the dry season. They also provide a base to study the inter-annual variability of the flooded areas, with sharp contrasts between dry years such as 2004 (low and early maximal area and wetter years such as 2001 and 2002 (respectively high and late maximal area.The highest flooded area reached annually greatly depends on the volume, intensity and timing of rain events. However, the overall reduction by 20% of annual rains during the last 40 years is concomitant with an apparently paradoxical large increase in the area of surface water, starting from the 1970's and accelerating in the mid 1980's. Spectacular for the two study cases of Agoufou and Ebang Mallam, for which time series covering the 1954 to present period exist, this increase is also diagnosed at the regional scale from LANDSAT data spanning 1972–2007. It reaches 108% between September 1975 and 2002 for 91 ponds identified in central Gourma. Ponds with turbid waters and no aquatic vegetation are mostly responsible for this increase, more pronounced in the centre and north of the study zone. Possible causes of the differential changes in flooded areas are discussed in relation with the specifics in topography, soil texture and vegetation

The impact of Southern Atlantic moisture source in the precipitation regime of Sahel and Brazilian Nordeste using lagrangian models

Science.gov (United States)

Drumond, A.; Nieto, R.; Gimeno, L.; Ambrizzi, T.; Trigo, R.

2009-04-01

The socio-economical problems related to the severe droughts observed over Brazilian "Nordeste" and Sahel are well known nowadays. Several studies have showed that the precipitation regimes over these regions are influenced by the Inter Tropical Convergence Zone (ITCZ) variability, which can be related with the climatic variations observed in the South and North Tropical Atlantic basins. However, a climatological detailed assessment of the annual cycle of the oceanic moisture contribution to both these regions is still needed in order to get a better understanding of their precipitation regimes and variability. To answer this question, a climatological seasonal analysis of the moisture supply from the South Atlantic to the precipitation in the "Nordeste" and Sahel was performed using a new Lagrangian method of diagnosis which identifies the humidity contributions to the moisture budget over a region. The applied methodology computes budgets of evaporation minus precipitation by calculating changes in the specific humidity along forward-trajectories for the following 10 days. In order to take into account distinct regional contributions we have divided the South Atlantic basin in several latitudinal bands (with a 5° width), and all air-masses residing over each region were tracked forward using the available 5-year dataset (2000-2004). For the Sahel, the preliminary results suggest that the oceanic band northwards 10 degrees south acts as a moisture source for the precipitation along the year and its contribution reaches the maximum during the austral winter, probably related to the ITCZ annual migration over the region. On the other hand, the precipitation over "Nordeste" can be better related to air masses emanating from the oceanic bands between 10 and 20 degrees south. However the response over the region is very heterogeneous spatially and temporally probably due to the high variability of the local climate characteristics. In order to clarify dynamically the

The Role of Meteorology and Surface Condition to Multi-Decadal Variations of Dust Emission in Sahara and Sahel

Science.gov (United States)

Kim, D.; Chin, M.; Diehl, T. L.; Bian, H.; Brown, M. E.; Remer, L. A.; Stockwell, W. R.

2014-12-01

North Africa is the world's largest dust source region influencing regional and global climate, human health, and even the local economy. However North Africa as a dust source is not uniform but it consists of the arid region (Sahara) and the semi-arid region (Sahel) with emission rates depending on meteorological and surface conditions. Several recent studies have shown that dust from North Africa seems to have a decreasing trend in the past three decades. The goal of this study is to better understand the controlling factors that determine the change of dust in North Africa using observational data and model simulations. First we analyze surface bareness conditions determined from a long-term satellite observed Normalized Difference Vegetation Index for 1980-2008. Then we examine the key meteorological variables of precipitation and surface winds. Modeling experiments were conducted using the NASA Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, which has been recently updated with a dynamic dust source function. Using the method we separate the dust originating from the Sahel from that of the Sahara desert. We find that the surface wind speed is the most dominant factor affecting Sahelian dust emission while vegetation has a modulating effect. We will show regional differences in meteorological variables, surface conditions, dust emission, and dust distribution and address the relationships among meteorology, surface conditions, and dust emission/loading in the past three decades (1980-2008).

Comparative influence of land and sea surfaces on the Sahelian drought: a numerical study

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Arona Diedhiou

Full Text Available The aim of this work is to compare the relative impact of land and sea surface anomalies on Sahel rainfall and to describe the associated anomalies in the atmospheric general circulation. This sensitivity study was done with the Météo-France climate model: ARPEGE. The sensitivity to land surface conditions consists of changes in the management of water and heat exchanges by vegetation cover and bare soil. The sensitivity to ocean surfaces consists in forcing the lower boundary of the model with worldwide composite sea surface temperature (SST anomalies obtained from the difference between 4 dry Sahel years and 4 wet Sahel years observed since 1970. For each case, the spatiotemporal variability of the simulated rainfall anomaly and changes in the modelled tropical easterly jet (TEJ and African easterly jet (AEJ are discussed. The global changes in land surface evaporation have caused a rainfall deficit over the Sahel and over the Guinea Coast. No significant changes in the simulated TEJ and an enhancement of the AEJ are found; at the surface, the energy budget and the hydrological cycle are substantially modified. On the other hand, SST anomalies induce a negative rainfall anomaly over the Sahel and a positive rainfall anomaly to the south of this area. The rainfall deficit due to those anomalies is consistent with previous diagnostic and sensitivity studies. The TEJ is weaker and the AEJ is stronger than in the reference. The composite impact of SST and land surfaces anomalies is also analyzed: the simulated rainfall anomaly is similar to the observed mean African drought patterns. This work suggests that large-scale variations of surface conditions may have a substantial influence on Sahel rainfall and shows the importance of land surface parameterization in climate change modelling. In addition, it points out the interest in accurately considering the land and sea surfaces conditions in sensitivity studies on Sahel rainfall.

Comparative influence of land and sea surfaces on the Sahelian drought: a numerical study

Directory of Open Access Journals (Sweden)

A. Diedhiou

1996-01-01

Full Text Available The aim of this work is to compare the relative impact of land and sea surface anomalies on Sahel rainfall and to describe the associated anomalies in the atmospheric general circulation. This sensitivity study was done with the Météo-France climate model: ARPEGE. The sensitivity to land surface conditions consists of changes in the management of water and heat exchanges by vegetation cover and bare soil. The sensitivity to ocean surfaces consists in forcing the lower boundary of the model with worldwide composite sea surface temperature (SST anomalies obtained from the difference between 4 dry Sahel years and 4 wet Sahel years observed since 1970. For each case, the spatiotemporal variability of the simulated rainfall anomaly and changes in the modelled tropical easterly jet (TEJ and African easterly jet (AEJ are discussed. The global changes in land surface evaporation have caused a rainfall deficit over the Sahel and over the Guinea Coast. No significant changes in the simulated TEJ and an enhancement of the AEJ are found; at the surface, the energy budget and the hydrological cycle are substantially modified. On the other hand, SST anomalies induce a negative rainfall anomaly over the Sahel and a positive rainfall anomaly to the south of this area. The rainfall deficit due to those anomalies is consistent with previous diagnostic and sensitivity studies. The TEJ is weaker and the AEJ is stronger than in the reference. The composite impact of SST and land surfaces anomalies is also analyzed: the simulated rainfall anomaly is similar to the observed mean African drought patterns. This work suggests that large-scale variations of surface conditions may have a substantial influence on Sahel rainfall and shows the importance of land surface parameterization in climate change modelling. In addition, it points out the interest in accurately considering the land and sea surfaces conditions in sensitivity studies on Sahel rainfall.

Future supply and demand of net primary production in the Sahel

Directory of Open Access Journals (Sweden)

F. Sallaba

2017-12-01

Full Text Available In the 21st century, climate change in combination with increasing demand, mainly from population growth, will exert greater pressure on the ecosystems of the Sahel to supply food and feed resources. The balance between supply and demand, defined as the annual biomass required for human consumption, serves as a key metric for quantifying basic resource shortfalls over broad regions.Here we apply an exploratory modelling framework to analyse the variations in the timing and geography of different NPP (net primary production supply–demand scenarios, with distinct assumptions determining supply and demand, for the 21st century Sahel. We achieve this by coupling a simple NPP supply model forced with projections from four representative concentration pathways with a global, reduced-complexity demand model driven by socio-economic data and assumptions derived from five shared socio-economic pathways.For the scenario that deviates least from current socio-economic and climate trends, we find that per capita NPP begins to outstrip supply in the 2040s, while by 2050 half the countries in the Sahel experience NPP shortfalls. We also find that despite variations in the timing of the onset of NPP shortfalls, demand cannot consistently be met across the majority of scenarios. Moreover, large between-country variations are shown across the scenarios, in which by the year 2050 some countries consistently experience shortage or surplus, while others shift from surplus to shortage. At the local level (i.e. grid cell, hotspots of total NPP shortfall consistently occur in the same locations across all scenarios but vary in size and magnitude. These hotspots are linked to population density and high demand. For all scenarios, total simulated NPP supply doubles by 2050 but is outpaced by increasing demand due to a combination of population growth and the adoption of diets rich in animal products. Finally, variations in the timing of the onset and end of supply

Koranic Education Centres: A viable educational alternative for the disadvantaged learner in Sahel Africa?

Science.gov (United States)

Bah-Lalya, Ibrahima

2015-08-01

Within the international momentum for achieving Education for All (EFA) and the Millennium Development Goals (MDGs), many African countries have made considerable progress during the last decade in terms of access to basic education. However, a significant number of children enrolled in the early grades of primary schools either repeat classes or drop out and never graduate. Moreover, there are currently about 30 million school-age children in sub-Saharan Africa who have never attended any form of schooling. In view of this situation, sub-Saharan African countries have been looking for alternative options to educate those who have not been accounted for in the formal school system. This note considers informal Koranic Education Centres (KECs) which are trying to fill the gap of schooling in the Sahel-Saharan strip. The author looks at the challenges this form of schooling faces and at how to meet them efficiently. He sounds out the possibility of using KECs to cater for those who have been left aside by formal schooling. Based on existing studies, data compiled by educational systems and a study conducted by the Working Group on Non-Formal Education (WGNFE) of the Association for the Development of Education in Africa (ADEA) in four West African countries (Burkina Faso, Mali, Mauritania and Senegal) in 2013, the author of this research note came to the conclusion that a holistic approach, where the two systems (the Koranic and the formal) collaborate and support one another, could effectively contribute to alleviating the dropout predicament and to reducing the number of unschooled children. It could offer a second-chance opportunity to dropout and unschooled children in the Sahel and Saharan zone. However, before this can become a viable alternative, a number of major challenges need to be addressed. Through its WGNFE, ADEA intends to further investigate the holistic approach of combining formal "modern" and informal "Koranic" schooling to come up with tangible

Building resilience to face recurring environmental crisis in African Sahel

Science.gov (United States)

Boyd, Emily; Cornforth, Rosalind J.; Lamb, Peter J.; Tarhule, Aondover; Lélé, M. Issa; Brouder, Alan

2013-07-01

The present food shortages in the Horn of Africa and the West African Sahel are affecting 31 million people. Such continuing and future crises require that people in the region adapt to an increasing and potentially irreversible global sustainability challenge. Given this situation and that short-term weather and seasonal climate forecasting have limited skill for West Africa, the Rainwatch project illustrates the value of near real-time monitoring and improved communication for the unfavourable 2011 West African monsoon, the resulting severe drought-induced humanitarian impacts continuing into 2012, and their exacerbation by flooding in 2012. Rainwatch is now coupled with a boundary organization (Africa Climate Exchange, AfClix) with the aim of integrating the expertise and actions of relevant institutions, agencies and stakeholders to broker ground-based dialogue to promote resilience in the face of recurring crisis.

Effect of pregnancy on some biochemical parameters in Sahel goats in semi-arid zones.

Science.gov (United States)

Sandabe, U K; Mustapha, A R; Sambo, E Y

2004-05-01

The effects of pregnancy on some biochemical parameters were studied using 20 sexually mature, cycling goats with weight range 20-25 kg. They were randomly separated into two groups of 10 animals each. In one group, oestrus was detected while going round with a buck in the morning and evening; a single buck on detection of oestrus mated the does and the does were tagged as pregnant after confirmation of non-return of oestrus. The other group was kept cycling and tagged as non-pregnant. The mean serum glucose concentration in pregnant does was 63.35 +/- 7.70 mg/dl, significantly lower than 71.59 +/- 1.14 mg/dl for non-pregnant does (p 0.05), as did the liver enzymes (ALT, AST). Therefore this study showed that low serum glucose and high cholesterol levels are features of mid to late pregnancy in Sahel goats.

Revisiting the coupling between NDVI trends and cropland changes in the Sahel drylands

DEFF Research Database (Denmark)

Tong, Xiaoye; Brandt, Martin Stefan; Hiernaux, Pierre

2017-01-01

The impact of human activities via land use/cover changes on NDVI trends is critical for an improved understanding of satellite-observed changes in vegetation productivity in drylands. The dominance of positive NDVI trends in the Sahel, the so-called re-greening, is sometimes interpreted...... as a combined effect of an increase in rainfall and cropland expansion or agricultural intensification. Yet, the impact of changes in land use has yet to be thoroughly tested and supported by empirical evidence. At present, no studies have considered the importance of the different seasonal NDVI signals...... of cropped and fallowed fields when interpreting NDVI trends, as both field types are commonly merged into a single ‘cropland’ class. We make use of the distinctly different phenology of cropped and fallowed fields and use seasonal NDVI curves to separate these two field types. A fuzzy classifier is applied...

Analysis for dry and wet years with the WIMISA model of tree-crop competition for wind break systems in the Sahel

NARCIS (Netherlands)

Mayus, M.; Keulen, van H.; Stroosnijder, L.

1999-01-01

A modelling approach was chosen for analyzing the effects of competition between windbreaks and crops for soil water and radiation in the Sahel. The model has a high spatial and temporal resolution to account for the heterogeneity in a windbreak-cropping system. The model was parameterised for

A simple tentative model of the losses caused by the Senegalese grasshopper, Oedaleus senegalensis (Krauss 1877) to millet in the Sahel

DEFF Research Database (Denmark)

Bal, Amadou Bocar; Ouambama, Zakaria; Dieng, Ibnou

2015-01-01

Oedaleus senegalensis is a serious pest of millet in the Sahel, but the correlation to crop loss remains largely unknown. Therefore, the correlation between densities of O. senegalensis, defoliation level and millet yields was investigated in Niger in 2008, and a simple model to foresee the yield...

The paradoxical evolution of runoff in the pastoral Sahel: analysis of the hydrological changes over the Agoufou watershed (Mali using the KINEROS-2 model

Directory of Open Access Journals (Sweden)

L. Gal

2017-09-01

Full Text Available In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as the Sahelian paradox, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated Sahel. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral Sahel. The kinematic runoff and erosion model (KINEROS-2 is applied to the Agoufou watershed (245 km2, in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the past case (1960–1975 preceding the Sahelian drought and the present case (2000–2015. Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1 a partial crusting of isolated dunes, (2 an increase of drainage network density, (3 a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4 important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual

Vegetation impoverishment despite greening: a case study from central Senegal

Science.gov (United States)

Herrmann, Stefanie M.; Tappan, G. Gray

2013-01-01

Recent remote sensing studies have documented a greening trend in the semi-arid Sahel and Sudan zones of West Africa since the early 1980s, which challenges the mainstream paradigm of irreversible land degradation in this region. What the greening trend means on the ground, however, has not yet been explored. This research focuses on a region in central Senegal to examine changes in woody vegetation abundance and composition in selected sites by means of a botanical inventory of woody vegetation species, repeat photography, and perceptions of local land users. Despite the greening, an impoverishment of the woody vegetation cover was observed in the studied sites, indicated by an overall reduction in woody species richness, a loss of large trees, an increasing dominance of shrubs, and a shift towards more arid-tolerant, Sahelian species since 1983. Thus, interpretation of the satellite-derived greening trend as an improvement or recovery is not always justified. The case of central Senegal represents only one of several possible pathways of greening throughout the region, all of which result in similar satellite-derived greening signals.

Modelling spatial and temporal dynamics of gross primary production in the Sahel from earth-observation-based photosynthetic capacity and quantum efficiency

DEFF Research Database (Denmark)

Tagesson, Håkan Torbern; Ardoe, Jonas; Cappelaere, Bernard

2017-01-01

based on earth observation (EO) (normalized difference vegetation index (NDVI), renormalized difference vegetation index (RDVI), enhanced vegetation index (EVI) and shortwave infrared water stress index (SIWSI)); and (3) to study the applicability of EO upscaled Fopt and α for GPP modelling purposes...... impacted by anthropogenic land use. Upscaled GPP for the Sahel 2001-2014 was 736 ± 39 gCm-2yr-1. This study indicates the strong applicability of EO as a tool for spatially explicit estimates of GPP, Fopt and α incorporating EO-based Fopt and α in dynamic global vegetation models could improve estimates...

Colonisation humaine et développement sur une frontière écologique. Le Despoblado, le Sahel du Piura-Pérou Septentrional

Directory of Open Access Journals (Sweden)

1991-01-01

Full Text Available Le despoblado de Piura est une formation végétale mixte arborée et herbacée, un sahel qui, malgré des précipitations très irrégulières, associe plusieurs ressources complémentaires. Elles ont été diversement utilisées au fur et à mesure de l’intervention de nouvelles techniques. - Cueillette des racines et fruits de la pampa d’interfluves. - Arboriculture sur huerta d’inférofluse à l’amont, et cultures saisonnières sur les lits intermittents et petit élevage caprin sur l’algarrobal des interfluves. - Cultures commerciales d’irrigation permanente par dérivation des eaux de la sierra et maintien d’un petit élevage de despoblado. Trois étapes de la colonisation du Piura. Mais la dernière, si elle permet de supporter une forte densité paysanne, ne peut éviter les conséquences des fortes pluies exceptionnelles. COLONIZACIÓN HUMANA Y DESARROLLO SOBRE FRONTERA ECOLÓGICA. EL DESPOBLADO, EL SAHEL DE PIURA, NORTE-PERÚ. El despoblado de Piura es una formación vegetal mixta, arboleda y savana ocasional, un sahel que, a pesar de lluvias muy irregulares, combina varios recursos complementarios. Ésos fueron aprovechados distintamente a medida de la intervención de nuevas técnicas. - Recolección de raíces y frutas en las pampas de las planicies secas - Arboricultura en las huertas de las cabezas de conos torrenciales y cultura estacional sobre los cauces inundables de las quebradas, aguas abajo, y cría de cabras y asnos en el algarrobal de las pampas - Cultivos comerciales de riego permanente por desvío de aguas de los grandes ríos de la sierra, y permanencia de la ganadería de caprinos sobre las pampas del despoblado. Son tres etapas del asentamiento humano. Pero la última, si tiene la ventaja de soportar grandes densidades campesinas, no puede arrastrar el peligro de las lluvias excepcionales. HUMAN SETTLING AND DEVELOPMENT ON AN ECOLOGIC FRONTIERS. THE DESPOBLADO, THE SAHEL OF SEPTENTRIONAL PIURA-PERU. A Piura

Bilan et perspectives des cultures vivrières dans les pays du Sahel

Directory of Open Access Journals (Sweden)

Egg Johny

2006-07-01

Full Text Available Twenty-five years after the beggining of the policies of adjustment and liberalization which is the situation of the food crops in the countries of the Sahel? The balance-sheet is approached by contrasting the cereals sub sector, facing to a very strong control by the State, and the onion whose growth is related to the increase in the demand of the great urban centers. The increase in the production of cereals was accompanied by deep changes in the structures. The market became more efficient and better integrated on a regional scale. But, the level and the instability of the prices of cereals increased, making difficult the provisioning of the poor. Clear differences in trajectories appear. Mali, which implemented a policy of reforming cereals market and successful the revival of rice sector, must manage at the same time the improvement of the competitiveness of its cereals and the access to cereals of the low incomes consumers. Niger must face the increase in the vulnerability of a great part of the rural households. The production of onion experienced a spectacular increase in Senegal after the devaluation of franc FCA in response to the urban market. That of Niger intended mainly for the close countries progressed more slowly. But in both cases, the regulation of the European onion imports constitutes a paramount stake.

Dealing with extreme environmental degradation: stress and marginalization of Sahel dwellers.

Science.gov (United States)

Van Haaften, E H; Van de Vijver, F J

1999-07-01

Psychological aspects of environmental degradation are hardly investigated. In the present study these aspects were examined among Sahel dwellers, who live in environments with different states of degradation. The degradation was assessed in terms of vegetation cover, erosion, and loss of organic matter. Subjects came from three cultural groups: Dogon (agriculturalists, n = 225), Mossi (agriculturalists, n = 914), and Fulani (pastoralists, n = 844). Questionnaires addressing marginalization, locus of control, and coping were administered. Environmental degradation was associated with higher levels of stress, marginalization, passive coping (avoidance), a more external locus of control, and lower levels of active coping (problem solving and support seeking). Compared to agriculturalists, pastoralists showed a stronger variation in all psychological variables across all regions, from the least to the most environmentally degraded. Women showed higher scores of stress, (external) locus of control, problem solving, and support seeking than men. The interaction of gender and region was significant for several variables. It was concluded that environmental degradation has various psychological correlates: people are likely to display an active approach to environmental degradation as long as the level of degradation is not beyond their control.

Rebuilding Resilience in the Sahel: Regreening in the Maradi and Zinder Regions of Niger

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Jan Sendzimir

2011-09-01

Full Text Available The societies and ecosystems of the Nigerien Sahel appeared increasingly vulnerable to climatic and economic uncertainty in the late twentieth century. Severe episodes of drought and famine drove massive livestock losses and human migration and mortality. Soil erosion and tree loss reduced a woodland to a scrub steppe and fed a myth of the Sahara desert relentlessly advancing southward. Over the past two decades this myth has been shattered by the dramatic reforestation of more than 5 million hectares in the Maradi and Zinder Regions of Niger. No single actor, policy, or practice appears behind this successful regreening of the Sahel. Multiple actors, institutions and processes operated at different levels, times, and scales to initiate and sustain this reforestation trend. We used systems analysis to examine the patterns of interaction as biophysical, livelihood, and governance indicators changed relative to one another during forest decline and rebound. It appears that forest decline was reversed when critical interventions helped to shift the direction of reinforcing feedbacks, e.g., vicious cycles changed to virtuous ones. Reversals toward de-forestation or reforestation were preceded by institutional changes in governance, then livelihoods and eventually in the biophysical environment. Biophysical change sustained change in the other two domains until interventions introduced new ideas and institutions that slowed and then reversed the pattern of feedbacks. However, while society seems better at coping with economic or climatic shock or stress, the resilience of society and nature in the Maradi/Zinder region to global sources of uncertainty remains a pressing question in a society with one of the highest population growth rates on Earth.

U.S. Army Civil Affairs Forces in the Sahel: Developing an Approach to Building Relevant Partner Capacity in Support of U.S. Africa Command

Science.gov (United States)

2015-06-12

There will likely be similar challenges within military institutions of Sahel nations. Cultural relativism posits that all religious, ethical , aesthetic...issues of cultural relativism and legality. Since independence, African nations have struggled to adopt borders and systems imposed by outsiders...

Impact of aerosols on solar energy production - Scenarios from the Sahel Zone

Science.gov (United States)

Neher, Ina; Meilinger, Stefanie; Crewell, Susanne

2017-04-01

Solar energy is one option to serve the rising global energy demand with low environmental impact. Building an energy system with a considerable share of solar power requires long-term investment and a careful investigation of potential sites. Therefore, understanding the impacts from varying regionally and locally determined meteorological conditions on solar energy production will influence energy yield projections. Aerosols reduce global solar radiation due to absorption and scattering and therewith solar energy yields. Depending on aerosol size distribution they reduce the direct component of the solar radiation and modify the direction of the diffuse component compared to standard atmospheric conditions without aerosols. The aerosol size distribution and composition in the atmosphere is highly variable due to meteorological and land surface conditions. A quantitative assessment of aerosol effects on solar power yields and its relation to land use change is of particular interest for developing countries countries when analyzing the potential of local power production. This study aims to identify the effect of atmospheric aerosols in three different land use regimes, namely desert, urban/polluted and maritime on the tilted plane of photovoltaic energy modules. Here we focus on the Sahel zone, i.e. Niamey, Niger (13.5 N;2.1 E), located at the edge of the Sahara where also detailed measurements of the atmospheric state are available over the year 2006. Guided by observations a model chain is used to determine power yields. The atmospheric aerosol composition will be defined by using the Optical Properties of Aerosols and Clouds (OPAC) library. Direct and diffuse radiation (up- and downward component) are then calculated by the radiative transfer model libRadtran which allows to calculate the diffuse component of the radiance from different azimuth and zenith angles. Then the diffuse radiance will be analytically transformed to an east, south and west facing

Applying Customized Climate Advisory Information to Translate Extreme Rainfall Events into Farming Options in the Sudan-Sahel of West Africa

Science.gov (United States)

Salack, S.; Worou, N. O.; Sanfo, S.; Nikiema, M. P.; Boubacar, I.; Paturel, J. E.; Tondoh, E. J.

2017-12-01

In West Africa, the risk of food insecurity linked to the low productivity of small holder farming increases as a result of rainfall extremes. In its recent evolution, the rainy season in the Sudan-Sahel zone presents mixed patterns of extreme climatic events. In addition to intense rain events, the distribution of events is associated with pockets of intra-seasonal long dry spells. The negative consequences of these mixed patterns are obvious on the farm: soil water logging, erosion of arable land, dwartness and dessication of crops, and loss in production. The capacity of local farming communities to respond accordingly to rainfall extreme events is often constrained by lack of access to climate information and advisory on smart crop management practices that can help translate extreme rainfall events into farming options. The objective of this work is to expose the framework and the pre-liminary results of a scheme that customizes climate-advisory information package delivery to subsistence farmers in Bakel (Senegal), Ouahigouya & Dano (Burkina Faso) and Bolgatanga (Ghana) for sustainable family agriculture. The package is based on the provision of timely climate information (48-hours, dekadal & seasonal) embedded with smart crop management practices to explore and exploite the potential advantage of intense rainfall and extreme dry spells in millet, maize, sorghum and cowpea farming communities. It is sent via mobile phones and used on selected farms (i.e agro-climatic farm schools) on which some small on-farm infrastructure were built to alleviate negative impacts of weather. Results provide prominent insight on how co-production of weather/climate information, customized access and guidiance on its use can induce fast learning (capacity building of actors), motivation for adaptation, sustainability, potential changes in cropping system, yields and family income in the face of a rainfall extremes at local scales of Sudan-Sahel of West Africa. Keywords: Climate

Investigating the Relationship between the Inter-Annual Variability of Satellite-Derived Vegetation Phenology and a Proxy of Biomass Production in the Sahel

Directory of Open Access Journals (Sweden)

Michele Meroni

2014-06-01

Full Text Available In the Sahel region, moderate to coarse spatial resolution remote sensing time series are used in early warning monitoring systems with the aim of detecting unfavorable crop and pasture conditions and informing stakeholders about impending food security risks. Despite growing evidence that vegetation productivity is directly related to phenology, most approaches to estimate such risks do not explicitly take into account the actual timing of vegetation growth and development. The date of the start of the season (SOS or of the peak canopy density can be assessed by remote sensing techniques in a timely manner during the growing season. However, there is limited knowledge about the relationship between vegetation biomass production and these variables at the regional scale. This study describes the first attempt to increase our understanding of such a relationship through the analysis of phenological variables retrieved from SPOT-VEGETATION time series of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR. Two key phenological variables (growing season length (GSL; timing of SOS and the maximum value of FAPAR attained during the growing season (Peak are analyzed as potentially related to a proxy of biomass production (CFAPAR, the cumulative value of FAPAR during the growing season. GSL, SOS and Peak all show different spatial patterns of correlation with CFAPAR. In particular, GSL shows a high and positive correlation with CFAPAR over the whole Sahel (mean r = 0.78. The negative correlation between delays in SOS and CFAPAR is stronger (mean r = −0.71 in the southern agricultural band of the Sahel, while the positive correlation between Peak FAPAR and CFAPAR is higher in the northern and more arid grassland region (mean r = 0.75. The consistency of the results and the actual link between remote sensing-derived phenological parameters and biomass production were evaluated using field measurements of aboveground herbaceous biomass

Seasonal labour migration strategies in the Sahel: coping with poverty or optimising security?

Science.gov (United States)

Hampshire, K; Randall, S

1999-01-01

This study examined the relationship between seasonal labor migration and poverty for various Fulani populations in the Sahel region of northern Burkina Faso, who represent the spectrum of production systems from pure pastoralism to agropastoralism to cultivation. There is a general trend of rising seasonal labor participation with increasing household wealth; limited financial and human resources mean that families belonging to the lower income population are excluded from this option. However, other ethnic and economic differences among the population compound this picture. Agriculturalists are more likely to migrate than pastoralists, and the Fulani subgroup Fulbe Djelgobe is unlikely to migrate at all unless desperate. The impacts of circular labor also differ. For a few agriculturalists and agropastoralists, migration to the cities is rewarding; for most the gains are small but are still essential. Pastoralists are more likely to experience negative outcomes than agriculturalists. Unless sufficient provision is made to fill in labor deficits in the migrants' absence, the cost of domestic production may seriously outweigh any benefits in the long run.

The historical spread of Arabian Pastoralists to the eastern African Sahel evidenced by the lactase persistence -13,915*G allele and mitochondrial DNA

Czech Academy of Sciences Publication Activity Database

Priehodová, E.; Austerlitz, F.; Čížková, M.; Mokhtar, M. G.; Poloni, E. S.; Černý, Viktor

2017-01-01

Roč. 29, č. 3 (2017), č. článku e22950. ISSN 1042-0533 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : lactase persistence * Arabs * pastoralism * African Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology OBOR OECD: Archaeology Impact factor: 1.780, year: 2016

A Tool for Creating Regionally Calibrated High-Resolution Land Cover Data Sets for the West African Sahel: Using Machine Learning to Scale Up Hand-Classified Maps in a Data-Sparse Environment

Science.gov (United States)

Van Gordon, M.; Van Gordon, S.; Min, A.; Sullivan, J.; Weiner, Z.; Tappan, G. G.

2017-12-01

Using support vector machine (SVM) learning and high-accuracy hand-classified maps, we have developed a publicly available land cover classification tool for the West African Sahel. Our classifier produces high-resolution and regionally calibrated land cover maps for the Sahel, representing a significant contribution to the data available for this region. Global land cover products are unreliable for the Sahel, and accurate land cover data for the region are sparse. To address this gap, the U.S. Geological Survey and the Regional Center for Agriculture, Hydrology and Meteorology (AGRHYMET) in Niger produced high-quality land cover maps for the region via hand-classification of Landsat images. This method produces highly accurate maps, but the time and labor required constrain the spatial and temporal resolution of the data products. By using these hand-classified maps alongside SVM techniques, we successfully increase the resolution of the land cover maps by 1-2 orders of magnitude, from 2km-decadal resolution to 30m-annual resolution. These high-resolution regionally calibrated land cover datasets, along with the classifier we developed to produce them, lay the foundation for major advances in studies of land surface processes in the region. These datasets will provide more accurate inputs for food security modeling, hydrologic modeling, analyses of land cover change and climate change adaptation efforts. The land cover classification tool we have developed will be publicly available for use in creating additional West Africa land cover datasets with future remote sensing data and can be adapted for use in other parts of the world.

Evaluating water controls on vegetation growth in the semi-arid sahel using field and earth observation data

DEFF Research Database (Denmark)

Abdi, Abdulhakim M.; Boke-Olen, Niklas; Tenenbaum, David E.

2017-01-01

Water loss is a crucial factor for vegetation in the semi-arid Sahel region of Africa. Global satellite-driven estimates of plant CO2 uptake (gross primary productivity, GPP) have been found to not accurately account for Sahelian conditions, particularly the impact of canopy water stress. Here, we...... identify the main biophysical limitations that induce canopy water stress in Sahelian vegetation and evaluate the relationships between field data and Earth observation-derived spectral products for up-scaling GPP. We find that plant-available water and vapor pressure deficit together control the GPP...

Climate variability and environmental stress in the Sudan-Sahel zone of West Africa

DEFF Research Database (Denmark)

Mertz, Ole; D'haen, Sarah Ann Lise; Maiga, Abdou

2012-01-01

Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic...... to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources......, vegetation, and fauna, but more so in the 500–900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region...

Rôle et place de la chèvre dans les ménages du Sahel burkinabé

OpenAIRE

Gnanda, BI.; Wereme N'Diaye, A.; O. Sanon, H.; Somda, J.; Nianogo, JA.

2016-01-01

Role and Position of the Goat in Households of the Burkinabian Sahel. A formal household survey was carried out in Burkina Faso with 150 Sahelian farms in order to appreciate the role and the position of goat breeding in the life and the functioning of these family units. The results of the investigation show that the Burkinabe Sahelian stockbreeders first start usually by raising a goat, because of its high prolificacy, but with the view to acquire more or less rapidly other species of rumin...

Sahara and Sahel vulnerability to climate changes, lessons from the past

Science.gov (United States)

Lezine, Anne-Marie; Hély, Christelle; Grenier, Christophe; Braconnot, Pascale

2010-05-01

Since the Sahelian drought in the 1970s, climate variability in north tropical Africa has been the subject of intensive research focusing on the functioning of the Atlantic monsoon system as well as on past variations in rainfall from historical and natural archives. An "abrupt" climate change has been recorded off the Mauritanian coast at the end of the African Humid Period (AHP) 5500 years ago illustrating the onset of the modern climate regime [deMenocal et al., 2000]. At lake Yoa in NE Chad, [Kroepelin et al., 2008] report a "gradual" environmental change. Was this change abrupt or gradual, and amplified or not through vegetation change and feedbacks to the atmosphere is still the subject of debate. Here, we compile paleohydrological and palynological data between 10 and 28°N in the Sahara and Sahel with the purpose of understanding the response of the hydrological system and the vegetation cover to rainfall fluctuations from the onset of the AHP. Our data set is extracted from published studies. It is composed of 1651 dated samples from about 420 localities in the present day Sahara and Sahel. The occurrence of high and intermediate lake levels, fluvial terraces and wetlands as well as of dune edification are analysed with a 1000 yr period from 16 000 yrs BP to present. Clear trends are observed in the evolution of paleohydrological indicators versus time and latitude showing the progression of the centre of the distribution of humidity from south to north during the humid period and to the south after the AHP. The humidity maximum is observed with some temporal delay as compared to the June solar radiation maximum at 30°N. The reasons are investigated along the line of pure climate based processes and/or hydrological impacts. Further, the overall coherence among these signals is examined. Using climate simulations for different key periods in the Holocene, we investigate the relative impact of the insolation forcing, of the remnant ice sheet in the early

The hydrogeological conditions in Sahel Hasheesh, Eastern Desert, Eg

Directory of Open Access Journals (Sweden)

Mohamed A. Abdalla

2016-06-01

Full Text Available The groundwater development in Egypt in the present time is of a vital importance than in past few years. A comprehensive plan for new land reclamation projects has been recently established. To achieve these plans new sources of water must be available. This has been done by conducting a number of VES’S where interpreted by a comparison with the existing drilled borehole soil samples. The optimum resistivity model is obtained by matching method using “IPI2Win” Moscow State University 2000 software computer programs for resistivity interpretation. The results of the quantitative interpretation of the resistivity curves has been represented as geoelectric sections, showing the thickness and true electric resistivity values of the different geoelectric layers. The results of quantitative interpretation of the vertical electrical soundings show subsurface five geoelectric units and the aquifer system belongs to lower Miocene and the total salinity of 2451.2 ppm. The depth to water surface is 88.05 m and the total dissolved solids are 2451.2 ppm (Mekhemer well. The salt assemblages in Sahel Hasheesh are NaCl, MgCl2, MgSO4, CaSO4, Ca(HCO32. This marine water is of brackish sodium chloride water type (NaCl.

The hydrogeological conditions in Sahel Hasheesh, Eastern Desert, Eg

Science.gov (United States)

Abdalla, Mohamed A.; Mekhemer, Hatem M.; Mabrou, Walid Abdallah

2016-06-01

The groundwater development in Egypt in the present time is of a vital importance than in past few years. A comprehensive plan for new land reclamation projects has been recently established. To achieve these plans new sources of water must be available. This has been done by conducting a number of VES'S where interpreted by a comparison with the existing drilled borehole soil samples. The optimum resistivity model is obtained by matching method using "IPI2Win" Moscow State University 2000 software computer programs for resistivity interpretation. The results of the quantitative interpretation of the resistivity curves has been represented as geoelectric sections, showing the thickness and true electric resistivity values of the different geoelectric layers. The results of quantitative interpretation of the vertical electrical soundings show subsurface five geoelectric units and the aquifer system belongs to lower Miocene and the total salinity of 2451.2 ppm. The depth to water surface is 88.05 m and the total dissolved solids are 2451.2 ppm (Mekhemer well). The salt assemblages in Sahel Hasheesh are NaCl, MgCl2, MgSO4, CaSO4, Ca(HCO3)2. This marine water is of brackish sodium chloride water type (NaCl).

Linking the sub-Saharan and West Eurasian gene pools: maternal and paternal heritage of the Tuareg nomads from the African Sahel.

Science.gov (United States)

Pereira, Luísa; Cerný, Viktor; Cerezo, María; Silva, Nuno M; Hájek, Martin; Vasíková, Alzbeta; Kujanová, Martina; Brdicka, Radim; Salas, Antonio

2010-08-01

The Tuareg presently live in the Sahara and the Sahel. Their ancestors are commonly believed to be the Garamantes of the Libyan Fezzan, ever since it was suggested by authors of antiquity. Biological evidence, based on classical genetic markers, however, indicates kinship with the Beja of Eastern Sudan. Our study of mitochondrial DNA (mtDNA) sequences and Y chromosome SNPs of three different southern Tuareg groups from Mali, Burkina Faso and the Republic of Niger reveals a West Eurasian-North African composition of their gene pool. The data show that certain genetic lineages could not have been introduced into this population earlier than approximately 9000 years ago whereas local expansions establish a minimal date at around 3000 years ago. Some of the mtDNA haplogroups observed in the Tuareg population were involved in the post-Last Glacial Maximum human expansion from Iberian refugia towards both Europe and North Africa. Interestingly, no Near Eastern mtDNA lineages connected with the Neolithic expansion have been observed in our population sample. On the other hand, the Y chromosome SNPs data show that the paternal lineages can very probably be traced to the Near Eastern Neolithic demic expansion towards North Africa, a period that is otherwise concordant with the above-mentioned mtDNA expansion. The time frame for the migration of the Tuareg towards the African Sahel belt overlaps that of early Holocene climatic changes across the Sahara (from the optimal greening approximately 10 000 YBP to the extant aridity beginning at approximately 6000 YBP) and the migrations of other African nomadic peoples in the area.

Studies of 21st-Century Precipitation Trends Over West Africa

Science.gov (United States)

Druyan, Leonard M.

2010-01-01

West Africa includes a semi-arid zone between the Sahara Desert and the humid Gulf of Guinea coast, approximately between 10 N and 20 N, which is irrigated by summer monsoon rains. This article refers to the region as the Sahel. Rain-fed agriculture is the primary sustenance for Sahel populations, and severe droughts (in the 1970s and 1980s), therefore, have devastating negative societal impacts. The future frequency of Sahel droughts and the evolution of its hydrological balance are therefore of great interest. The article reviews 10 recent research studies that attempt to discover how climate changes will affect the hydrology of the Sahel throughout the 21st century. All 10 studies rely on atmosphere ocean global climate model (AOGCM) simulations based on a range of greenhouse gas emissions scenarios. Many of the simulations are contained in the Intergovernmental Panel on Climate Change archives for Assessment Reports #3 and #4. Two of the studies use AOGCM data to drive regional climate models. Seven studies make projections for the first half of the 21st century and eight studies make projections for the second half. Some studies make projections of wetter conditions and some predict more frequent droughts, and each describes the atmospheric processes associated with its prediction. Only one study projects more frequent droughts before 2050, and that is only for continent-wide degradation in vegetation cover. The challenge to correctly simulate Sahel rainfall decadal trends is particularly daunting because multiple physical mechanisms compete to drive the trend upwards or downwards. A variety of model deficiencies, regarding the simulation of one or more of these physical processes, taints models climate change projections. Consequently, no consensus emerges regarding the impact of anticipated greenhouse gas forcing on the hydrology of the Sahel in the second half of the 21st century.

Mapping regional livelihood benefits from local ecosystem services assessments in rural Sahel.

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Malmborg, Katja; Sinare, Hanna; Enfors Kautsky, Elin; Ouedraogo, Issa; Gordon, Line J

2018-01-01

Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method) and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption) that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the Sahel.

Mapping regional livelihood benefits from local ecosystem services assessments in rural Sahel

Science.gov (United States)

Sinare, Hanna; Enfors Kautsky, Elin; Ouedraogo, Issa; Gordon, Line J.

2018-01-01

Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method) and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption) that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the Sahel. PMID:29389965

Mapping regional livelihood benefits from local ecosystem services assessments in rural Sahel.

Directory of Open Access Journals (Sweden)

Katja Malmborg

Full Text Available Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the Sahel.

The influence of land surface properties on Sahel climate. Part 1: Desertification

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Xue, Yongkang; Shukla, Jagadish

1993-01-01

This is a general circulation model sensitivity study of the physical mechanisms of the effects of desertification on the Sahel drought. The model vegetation types were changed in the prescribed desertification area, which led to changes in the surface characteristics. The model was integrated for three months (June, July, August) with climatological surface conditions (control) and desertification conditions (anomaly) to examine the summer season response to the changed surface conditions. The control and anomaly experiments consisted of five pairs of integrations with different initial conditions and/or sea surface temperature boundary conditions. In the desertification experiment, the moisture flux convergence and rainfall were reduced in the test area and increased to the immediate south of this area. The simulated anomaly dipole pattern was similar to the observed African drought patterns in which the axis of the maximum rainfall shifts to the south. The circulation changes in the desertification experiment were consistent with those observed during sub-Saharan dry years. The tropical easterly jet was weaker and the African easterly jet was stronger than normal. Further, in agreement with the observations, the easterly wave disturbances were reduced in intensity but not in number. Descending motion dominated the desertification area. The surface energy budget and hydrological cycle were also changed substantially in the anomaly experiment.

The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

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F. S. E. Vamborg

2011-02-01

Full Text Available We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: pre-industrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr⁻¹ for the pre-industrial simulation and by about 80 mm yr⁻¹ for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

Long-Term Monitoring of Water Dynamics in the Sahel Region Using the Multi-Sar

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Bertram, A.; Wendleder, A.; Schmitt, A.; Huber, M.

2016-06-01

Fresh water is a scarce resource in the West-African Sahel region, seasonally influenced by droughts and floods. Particularly in terms of climate change, the importance of wetlands increases for flora, fauna, human population, agriculture, livestock and fishery. Hence, access to open water is a key factor. Long-term monitoring of water dynamics is of great importance, especially with regard to the spatio-temporal extend of wetlands and drylands. It can predict future trends and facilitate the development of adequate management strategies. Lake Tabalak, a Ramsar wetland of international importance, is one of the most significant ponds in Niger and a refuge for waterbirds. Nevertheless, human population growth increased the pressure on this ecosystem, which is now degrading for all uses. The main objective of the study is a long-term monitoring of the Lake Tabalak's water dynamics to delineate permanent and seasonal water bodies, using weather- and daytime-independent multi-sensor and multi-temporal Synthetic Aperture Radar (SAR) data available for the study area. Data of the following sensors from 1993 until 2016 are used: Sentinel-1A, TerraSARX, ALOS PALSAR-1/2, Envisat ASAR, RADARSAT-1/2, and ERS-1/2. All SAR data are processed with the Multi-SAR-System, unifying the different characteristics of all above mentioned sensors in terms of geometric, radiometric and polarimetric resolution to a consistent format. The polarimetric representation in Kennaugh elements allows fusing single-polarized data acquired by older sensors with multi-polarized data acquired by current sensors. The TANH-normalization guarantees a consistent and therefore comparable description in a closed data range in terms of radiometry. The geometric aspect is solved by projecting all images to an earth-fixed coordinate system correcting the brightness by the help of the incidence angle. The elevation model used in the geocoding step is the novel global model produced by the TanDEM-X satellite

LONG-TERM MONITORING OF WATER DYNAMICS IN THE SAHEL REGION USING THE MULTI-SAR-SYSTEM

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A. Bertram

2016-06-01

Full Text Available Fresh water is a scarce resource in the West-African Sahel region, seasonally influenced by droughts and floods. Particularly in terms of climate change, the importance of wetlands increases for flora, fauna, human population, agriculture, livestock and fishery. Hence, access to open water is a key factor. Long-term monitoring of water dynamics is of great importance, especially with regard to the spatio-temporal extend of wetlands and drylands. It can predict future trends and facilitate the development of adequate management strategies. Lake Tabalak, a Ramsar wetland of international importance, is one of the most significant ponds in Niger and a refuge for waterbirds. Nevertheless, human population growth increased the pressure on this ecosystem, which is now degrading for all uses. The main objective of the study is a long-term monitoring of the Lake Tabalak’s water dynamics to delineate permanent and seasonal water bodies, using weather- and daytime-independent multi-sensor and multi-temporal Synthetic Aperture Radar (SAR data available for the study area. Data of the following sensors from 1993 until 2016 are used: Sentinel-1A, TerraSARX, ALOS PALSAR-1/2, Envisat ASAR, RADARSAT-1/2, and ERS-1/2. All SAR data are processed with the Multi-SAR-System, unifying the different characteristics of all above mentioned sensors in terms of geometric, radiometric and polarimetric resolution to a consistent format. The polarimetric representation in Kennaugh elements allows fusing single-polarized data acquired by older sensors with multi-polarized data acquired by current sensors. The TANH-normalization guarantees a consistent and therefore comparable description in a closed data range in terms of radiometry. The geometric aspect is solved by projecting all images to an earth-fixed coordinate system correcting the brightness by the help of the incidence angle. The elevation model used in the geocoding step is the novel global model produced by the

Management of protected areas in Sahel savannah ecoregion of Nigeria under the threat of desertification

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BOROKINI Temitope Israel

2013-12-01

Full Text Available This study was conducted to assess the challenges facing 8 selected protected areas in the Sahel Savannah ecoregion and proffer solutions to these challenges in order to ensure conservation and sustainability of Nigeria’s biodiversity. Primary data were collected from randomly-selected 120 staffs using questionnaire administration from 8 Forest Reserves within Borno and Yobe states of Nigeria. A high level of encroachment of all the studied protected areas was observed, which ranged from deforestation, overgrazing, poaching to converting protected areas into farmlands. Other notable challenges include poor staffing, inadequate equipment and funding. The respondents further reported that majority of the defaulters were farmers and local people in the area, involved in such practices for their survival in the wake of harsher climate and desert encroachment in the region. This paper calls for a revision of the Government Policy on Forestry in Nigeria to allow the people own and plant forests, implementation of community based forest resources management, provision of environment and user-friendly solar powered cooking stoves and sustainable farming systems such as crop rotation, intercropping, sustainable irrigation, organic farming and agroforestry. In addition, sources of income for the locals need to be diversified, such as honey bee production.

Diagnosis of vegetation recovery within herbaceous sub-systems in the West African Sahel Region

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Anchang, J.; Hanan, N. P.; Prihodko, L.; Sathyachandran, S. K.; Ji, W.; Ross, C. W.

2017-12-01

The West African Sahel (WAS) region is an extensive water limited environment that features a delicate balance of herbaceous and woody vegetation sub systems. These play an important role in the cycling of carbon while also supporting the dominant agro-pastoral human activities in the region. Quantifying the temporal trends in vegetation with regard to these two systems is therefore very important in assessing resource sustainability and food security. In water limited areas, rainfall is a primary driver of vegetation productivity and past watershed scale studies in the WAS region have shown that increase in the slope of the productivity-to-rainfall relationship is indicative of increasing cover and density of herbaceous plants. Given the importance of grazing resources to the region, we perform a wall-to-wall pixel based analysis of changing short-term vegetation sensitivity to changing annual rainfall (hereafter referred to as dS) to examine temporal trends in herbaceous vegetation health. Results indicate that 43% of the Sahelian region has experienced changes (P Western and Central Mali and South Western Niger. Positive dS is indicative of herbaceous vegetation recovery, in response to changing management and rainfall conditions that promote long-term herbaceous community recovery following degradation during the 1970-1980s droughts.

Selection for earlier flowering crop associated with climatic variations in the Sahel.

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Yves Vigouroux

Full Text Available Climate changes will have an impact on food production and will require costly adaptive responses. Adapting to a changing environment will be particularly challenging in sub-Saharan Africa where climate change is expected to have a major impact. However, one important phenomenon that is often overlooked and is poorly documented is the ability of agro-systems to rapidly adapt to environmental variations. Such an adaptation could proceed by the adoption of new varieties or by the adaptation of varieties to a changing environment. In this study, we analyzed these two processes in one of the driest agro-ecosystems in Africa, the Sahel. We performed a detailed study in Niger where pearl millet is the main crop and covers 65% of the cultivated area. To assess how the agro-system is responding to recent recurrent drought, we analyzed samples of pearl millet landraces collected in the same villages in 1976 and 2003 throughout the entire cultivated area of Niger. We studied phenological and morphological differences in the 1976 and 2003 collections by comparing them over three cropping seasons in a common garden experiment. We found no major changes in the main cultivated varieties or in their genetic diversity. However, we observed a significant shift in adaptive traits. Compared to the 1976 samples, samples collected in 2003 displayed a shorter lifecycle, and a reduction in plant and spike size. We also found that an early flowering allele at the PHYC locus increased in frequency between 1976 and 2003. The increase exceeded the effect of drift and sampling, suggesting a direct effect of selection for earliness on this gene. We conclude that recurrent drought can lead to selection for earlier flowering in a major Sahelian crop. Surprisingly, these results suggest that diffusion of crop varieties is not the main driver of short term adaptation to climatic variation.

Prehistoric dark soils/sediments of Central Sudan, case study from the Mesolithic landscape at the Sixth Nile Cataract

Czech Academy of Sciences Publication Activity Database

Lisá, Lenka; Bajer, A.; Pacina, J.; McCool, J-P.; Cílek, Václav; Rohovec, Jan; Matoušková, Šárka; Kallistová, Anna; Gottvald, Z.

2017-01-01

Roč. 149, č. 1 (2017), s. 273-282 ISSN 0341-8162 Institutional support: RVO:67985831 Keywords : climate change * micromorphology * sahel * saprolite * soil chemistry Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 3.191, year: 2016

Climate variability and environmental stress in the Sudan-Sahel zone of West Africa.

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Mertz, Ole; D'haen, Sarah; Maiga, Abdou; Moussa, Ibrahim Bouzou; Barbier, Bruno; Diouf, Awa; Diallo, Drissa; Da, Evariste Dapola; Dabi, Daniel

2012-06-01

Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic changes and their perceptions were compared across north-south and west-east rainfall gradients. More than 80% of all households found that rainfall had decreased, especially in the wettest areas. Increases in wind speeds and temperature were perceived by an overall 60-80% of households. Contrary to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources, vegetation, and fauna, but more so in the 500-900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region, especially in the 500-900 mm zones and the western part of SSWA.

Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 1. Modelling surface reflectance using a geometric-optical approach

International Nuclear Information System (INIS)

Franklin, J.; Duncan, J.; Huete, A.R.; Leeuwen, W.J.D. van; Li, X.; Bégué, A.

1994-01-01

To use optical remote sensing to monitor land surface-climate interactions over large areas, algorithms must be developed to relate multispectral measurements to key variables controlling the exchange of matter (water, carbon dioxide) and energy between the land surface and the atmosphere. The proportion of the ground covered by vegetation and the interception of photosynthetically active radiation (PAR) by vegetation are examples of two variables related to evapotranspiration and primary production, respectively. An areal-proportion model of the multispectral reflectance of shrub savanna, composed of scattered shrubs with a grass, forb or soil understory, predicted the reflectance of two 0.5 km 2 sites as the area-weighted average of the shrub and understory or ‘background’ reflectances. Although the shaded crown and shaded background have darker reflectances, ignoring them in the area-weighted model is not serious when shrub cover is low and solar zenith angle is small. A submodel predicted the reflectance of the shrub crown as a function of the foliage reflectance and amount of plant material within the crown, and the background reflectance scattered or transmitted through canopy gaps (referred to as a soil—plant ‘spectral interaction’ term). One may be able to combine these two models to estimate both the fraction of vegetation cover and interception of PAR by green vegetation in a shrub savanna. (author)

[Population resettlement and women's changing roles in the Sahel].

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Ouedraogo, D O

1992-01-01

For many decision makers in the Sahel, relocating populations from poor, over-populated regions to relatively fertile zones regulated by the state seemed the best approach to improving women's conditions, particularly in household affairs. In the original territories, women have their personal fields where they raise vegetables and other products which they sell to secure their own income. During the dry season, they engage in other activities for money (e.g., production and sale of millet beer and sale of pottery). Women have relative economic autonomy. Within the family household and in villages, they isolate themselves in their own spaces (e.g., kitchen and wells) and discuss their specific problems. In government-controlled zones where families resettle, the families are supposed to plant the same varieties of imposed cultivation (e.g., rice) judged to be more productive. They must sow, plow, and harvest using the same techniques. All activities are controlled. Women have no decision power and must submit to the logic of the chief of agricultural production. They no longer have time to dedicate themselves to individual economic activity (especially in irrigated zones, where there are two annual plantings), or to assure a good education for their children. They have little time to dedicate to hygiene and nutrition. These government-controlled agricultural zones have established an exploitation model that contributes to the socioeconomic destabilization of families. The retreat of women's economic power is often accompanied by degradation of family well-being. Agricultural development schemes that involve agricultural migrations have marginalized women even more than they were before resettlement in spite of improvement in family income. It is narrowly linked to short-term development. In conclusion, agricultural resettlement schemes do not improve the status of women.

Accelerating improvements in nutritional and health status of young children in the Sahel region of Sub-Saharan Africa: review of international guidelines on infant and young child feeding and nutrition.

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Wuehler, Sara E; Hess, Sonja Y; Brown, Kenneth H

2011-04-01

The United Nations Convention on the Rights of the Child holds governments responsible to ensure children's right to the highest attainable standard of health by providing breastfeeding support, and access to nutritious foods, appropriate health care, and clean drinking water. International experts have identified key child care practices and programmatic activities that are proven to be effective at reducing infant and young child undernutrition, morbidity, and mortality. Nevertheless, progress towards reducing the prevalence of undernutrition has been sporadic across countries of the Sahel sub-region of Sub-Saharan Africa. In view of this uneven progress, a working group of international agencies was convened to 'Reposition children's right to adequate nutrition in the Sahel.' The first step towards this goal was to organize a situational analysis of the legislative, research, and programmatic activities related to infant and young child nutrition (IYCN) in six countries of the sub-region: Burkina Faso, Chad, Mali, Mauritania, Niger, and Senegal. The purposes of this introductory paper are to review current information concerning the nutritional and health status of infants and young children in the Sahel and to summarize international guidelines on optimal IYCN practices. These guidelines were used in completing the above-mentioned situational analyses and encompass specific recommendations on: (i) breastfeeding (introduction within the first hour after birth, exclusivity to 6 months, continuation to at least 24 months); (ii) complementary feeding (introduction at 6 months, use of nutrient dense foods, adequate frequency and consistency, and responsive feeding); (iii) prevention and/or treatment of micronutrient deficiencies (vitamin A, zinc, iron and anaemia, and iodine); (iv) prevention and/or treatment of acute malnutrition; (v) feeding practices adapted to the maternal situation to reduce mother-to-child transmission of HIV; (vi) activities to ensure food

Sequía, inmigración y políticas locales: el Sahel en la encrucijada del desarrollo

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Sara Nso

2008-10-01

Full Text Available Este artículo trata de delimitar los principales factores socio-económicos y políticos que ponen en relación desertificación y flujos migratorios internacionales, en el área Sahel. A través del estudio -no exhaustivo para todos los países de la muestra, por ausencia de datos disponibles- de dichas realidades en Burkina Faso, Gambia, Guinea-Bissau, Guinea, Malí, Mauritania, Níger y Senegal, el análisis del elemento local será privilegiado, sin despreciar por ello el valor de las dinámicas regionales. Desde una perspectiva "transnacionalista", se aportarán así las claves para la comprensión global de la problemática saheliana, con el objetivo de sacar a esta región de la encrucijada del subdesarrollo.

Study of the climatic change impact on vector-borne diseases in West Africa: the case of tick-borne borreliosis and malaria

International Nuclear Information System (INIS)

Trape, J.F.

2005-04-01

Malaria and tick-borne borreliosis are the two first causes of morbidity due to vector-borne diseases in a large part of Sudan-sahelian West Africa. They are also the two tropical diseases which have been the most affected by climatic change in recent years. In the case of tick-borne borreliosis it has been shown in Senegal that the persistence of drought since the years 70 has been associated with a considerable extension of the geographic range of diseases and the vector tick A-sonrai, a species that was in the past limited to the Sahara and Sahel. In the case of malaria, drought has strongly reduced in these same regions of Africa the distribution, abundance and infection rate of Anopheline mosquitoes, but without any significant reduction of the burden of malaria for most populations concerned. The emergence and spread of Plasmodium falciparum resistance to antimalarial drugs only explain part of this phenomenon. (A.L.B.)

Statistical relationship between surface PM10 concentration and aerosol optical depth over the Sahel as a function of weather type, using neural network methodology

Science.gov (United States)

Yahi, H.; Marticorena, B.; Thiria, S.; Chatenet, B.; Schmechtig, C.; Rajot, J. L.; Crepon, M.

2013-12-01

work aims at assessing the capability of passive remote-sensed measurements such as aerosol optical depth (AOD) to monitor the surface dust concentration during the dry season in the Sahel region (West Africa). We processed continuous measurements of AODs and surface concentrations for the period (2006-2010) in Banizoumbou (Niger) and Cinzana (Mali). In order to account for the influence of meteorological condition on the relationship between PM10 surface concentration and AOD, we decomposed the mesoscale meteorological fields surrounding the stations into five weather types having similar 3-dimensional atmospheric characteristics. This classification was obtained by a clustering method based on nonlinear artificial neural networks, the so-called self-organizing map. The weather types were identified by processing tridimensional fields of meridional and zonal winds and air temperature obtained from European Centre for Medium-Range Weather Forecasts (ECMWF) model output centered on each measurement station. Five similar weather types have been identified at the two stations. Three of them are associated with the Harmattan flux; the other two correspond to northward inflow of the monsoon flow at the beginning or the end of the dry season. An improved relationship has been found between the surface PM10 concentrations and the AOD by using a dedicated statistical relationship for each weather type. The performances of the statistical inversion computed on the test data sets show satisfactory skills for most of the classes, much better than a linear regression. This should permit the inversion of the mineral dust concentration from AODs derived from satellite observations over the Sahel.

Sensitivity of Sahelian Precipitation to Desert Dust under ENSO variability: a regional modeling study

Science.gov (United States)

Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.

2016-12-01

Mineral dust is estimated to comprise over half the total global aerosol burden, with a majority coming from the Sahara and Sahel region. Bounded by the Sahara Desert to the north and the Sahelian Savannah to the south, the Sahel experiences high interannual rainfall variability and a short rainy season during the boreal summer months. Observation-based data for the past three decades indicates a reduced dust emission trend, together with an increase in greening and surface roughness within the Sahel. Climate models used to study regional precipitation changes due to Saharan dust yield varied results, both in sign convention and magnitude. Inconsistency of model estimates drives future climate projections for the region that are highly varied and uncertain. We use the NASA-Unified Weather Research and Forecasting (NU-WRF) model to quantify the interaction and feedback between desert dust aerosol and Sahelian precipitation. Using nested domains at fine spatial resolution we resolve changes to mesoscale atmospheric circulation patterns due to dust, for representative phases of El Niño-Southern Oscillation (ENSO). The NU-WRF regional earth system model offers both advanced land surface data and resolvable detail of the mechanisms of the impact of Saharan dust. Results are compared to our previous work assessed over the Western Sahel using the Geophysical Fluid Dynamics Laboratory (GFDL) CM2Mc global climate model, and to other previous regional climate model studies. This prompts further research to help explain the dust-precipitation relationship and recent North African dust emission trends. This presentation will offer a quantitative analysis of differences in radiation budget, energy and moisture fluxes, and atmospheric dynamics due to desert dust aerosol over the Sahel.

A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula

KAUST Repository

Masmoudi, Mohamed

2015-05-01

© 2015 Elsevier B.V. The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (<. 0.3) Ångström exponent (α) calculated between 440. nm and 870. nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii. <. 0.2. μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020. nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.

A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula

KAUST Repository

Masmoudi, Mohamed; Alfaro, Sté phane C.; El Metwally, Mossad

2015-01-01

© 2015 Elsevier B.V. The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (<. 0.3) Ångström exponent (α) calculated between 440. nm and 870. nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii. <. 0.2. μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020. nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.

The supply and demand of net primary production in the Sahel

International Nuclear Information System (INIS)

Abdi, A M; Seaquist, J; Tenenbaum, D E; Eklundh, L; Ardö, J

2014-01-01

Net primary production (NPP) is the principal source of energy for ecosystems and, by extension, human populations that depend on them. The relationship between the supply and demand of NPP is important for the assessment of socio-ecological vulnerability. We present an analysis of the supply and demand of NPP in the Sahel using NPP estimates from the MODIS sensor and agri-environmental data from FAOSTAT. This synergistic approach allows for a spatially explicit estimation of human impact on ecosystems. We estimated the annual amount of NPP required to derive food, fuel and feed between 2000 and 2010 for 22 countries in sub-Saharan Africa. When comparing annual estimates of supply and demand of NPP, we found that demand increased from 0.44 PgC to 1.13 PgC, representing 19% and 41%, respectively, of available supply due to a 31% increase in the human population between 2000 and 2010. The demand for NPP has been increasing at an annual rate of 2.2% but NPP supply was near-constant with an inter-annual variability of approximately 1.7%. Overall, there were statistically significant (p < 0.05) increases in the NPP of cropland (+6.0%), woodland (+6.1%) and grassland/savanna (+9.4%), and a decrease in the NPP of forests (−0.7%). On the demand side, the largest increase was for food (20.4%) followed by feed (16.7%) and fuel (5.5%). The supply-demand balance of NPP is a potentially important tool from the standpoint of sustainable development, and as an indicator of stresses on the environment stemming from increased consumption of biomass. (letter)

Assessing Land Degradation/Recovery in the African Sahel from Long-Term Earth Observation Based Primary Productivity and Precipitation Relationships

DEFF Research Database (Denmark)

Fensholt, Rasmus; Rasmussen, Kjeld; Kaspersen, Per Skougaard

2013-01-01

degradation. Consequently, RUE may be regarded as means of normalizing ANPP for the impact of annual precipitation, and as an indicator of non-precipitation related land degradation. Large scale and long term identification and monitoring of land degradation in drylands, such as the Sahel, can only......The ‘rain use efficiency’ (RUE) may be defined as the ratio of above-ground net primary productivity (ANPP) to annual precipitation, and it is claimed to be a conservative property of the vegetation cover in drylands, if the vegetation cover is not subject to non-precipitation related land...... useless as a means of normalizing for the impact of annual precipitation on ANPP. By replacing ΣNDVI by a ‘small NDVI integral’, covering only the rainy season and counting only the increase of NDVI relative to some reference level, this problem is solved. Using this approach, RUE is calculated...

Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel, West Africa

Science.gov (United States)

Ibrahim, Maïmouna; Favreau, Guillaume; Scanlon, Bridget R.; Seidel, Jean Luc; Le Coz, Mathieu; Demarty, Jérôme; Cappelaere, Bernard

2014-09-01

Rapid population growth in sub-Saharan West Africa and related cropland expansion were shown in some places to have increased focused recharge through ponds, raising the water table. To estimate changes in diffuse recharge, the water content and matric potential were monitored during 2009 and 2010, and modeling was performed using the Hydrus-1D code for two field sites in southwest Niger: (1) fallow land and (2) rainfed millet cropland. Monitoring results of the upper 10 m showed increased water content and matric potential to greater depth under rainfed cropland (>2.5 m) than under fallow land (≤1.0 m). Model simulations indicate that conversion from fallow land to rainfed cropland (1) increases vadose-zone water storage and (2) should increase drainage flux (˜25 mm year-1) at 10-m depth after a 30-60 year lag. Therefore, observed regional increases in groundwater storage may increasingly result from diffuse recharge, which could compensate, at least in part, groundwater withdrawal due to observed expansion in irrigated surfaces; and hence, contribute to mitigate food crises in the Sahel.

Land Cover Land Use change and soil organic carbon under climate variability in the semi-arid West African Sahel (1960-2050)

Science.gov (United States)

Dieye, Amadou M.

Land Cover Land Use (LCLU) change affects land surface processes recognized to influence climate change at local, national and global levels. Soil organic carbon is a key component for the functioning of agro-ecosystems and has a direct effect on the physical, chemical and biological characteristics of the soil. The capacity to model and project LCLU change is of considerable interest for mitigation and adaptation measures in response to climate change. A combination of remote sensing analyses, qualitative social survey techniques, and biogeochemical modeling was used to study the relationships between climate change, LCLU change and soil organic carbon in the semi-arid rural zone of Senegal between 1960 and 2050. For this purpose, four research hypotheses were addressed. This research aims to contribute to an understanding of future land cover land use change in the semi-arid West African Sahel with respect to climate variability and human activities. Its findings may provide insights to enable policy makers at local to national levels to formulate environmentally and economically adapted policy decisions. This dissertation research has to date resulted in two published and one submitted paper.

Case Study: Testing with Case Studies

Science.gov (United States)

Herreid, Clyde Freeman

2015-01-01

This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. This month's issue discusses using case studies to test for knowledge or lessons learned.

Rôle et place de la chèvre dans les ménages du Sahel burkinabé

Directory of Open Access Journals (Sweden)

Gnanda, BI.

2016-01-01

Full Text Available Role and Position of the Goat in Households of the Burkinabian Sahel. A formal household survey was carried out in Burkina Faso with 150 Sahelian farms in order to appreciate the role and the position of goat breeding in the life and the functioning of these family units. The results of the investigation show that the Burkinabe Sahelian stockbreeders first start usually by raising a goat, because of its high prolificacy, but with the view to acquire more or less rapidly other species of ruminants, in particular cattle. Although the generation of income of goat rearing remains low compared to other ruminants (bovine, ovine; their non-monetary role in poverty alleviation is highlighted. That is shown through the large proportion of the population (91% of the target-group implied in goat breeding, the first position of goats in the non-commercial (social transaction, and their position in terms of risk prevention against the climatic hazards for livestock farmers. Despite its critical role, the goat remains the least favored ruminant species in regarding health protection and food supplementation.

Analytical Tools for the Application of Operational Culture: A Case Study in the Trans-Sahel

Science.gov (United States)

2011-03-28

literatures including nursing and applied health care, management sciences, legal studies, and political science. In these fields, theory generally...Erlbaum Associates 87 Grant, J. & Davis, L. (1997). ―Selection and Use of Content Experts for Instrument Development,‖ Research in Nursing and...June 6, 2009. Due to boycotts by opposition groups, the elections were rescheduled for July 18, 2009. Following the resignation of General Aziz in

People and pixels in the Sahel: a study linking coarse-resolution remote sensing observations to land users' perceptions of their changing environment in Senegal

Directory of Open Access Journals (Sweden)

Stefanie M. Herrmann

2014-09-01

Full Text Available Mounting evidence from satellite observations of a re-greening across much of the Sahel and Sudan zones over the past three decades has raised questions about the extent and reversibility of desertification. Historical ground data that could help in interpreting the re-greening are scarce. To fill that void, we tapped into the collective memories of local land users from central and western Senegal in 39 focus groups and assessed the spatial association between their perceptions of vegetation changes over time and remote sensing-derived trends. To provide context to the vegetation changes, we also explored the land users' perspective on the evolution of other environmental and human variables that are potentially related to the greening, using participatory research methods. While increases in vegetation were confirmed by the study participants for certain areas, which spatially corresponded to satellite-observed re-greening, vegetation degradation dominated their perceptions of change. This degradation, although spatially extensive according to land users, flies under the radar of coarse-resolution remote sensing data because it is not necessarily associated with a decrease in biomass but rather with undesired changes in species composition. Few significant differences were found in the perceived trends of population pressure, environmental, and livelihood variables between communities that have greened up according to satellite data and those that have not. Our findings challenge the prevailing chain of assumptions of the satellite-observed greening trend indicating an improvement of environmental conditions in the sense of a rehabilitation of the vegetation cover after the great droughts of the 1970s and 1980s, and the improvement of environmental conditions possibly translating into more stable livelihoods and greater well-being of the populations. For monitoring desertification and rehabilitation, there is a need to develop remote sensing

Petite motorisation et exploitations maraîchères de taille limitée du Sahel tunisien Partie 2: Evaluation sur le terrain des performances et des coûts de préparation du sol

Directory of Open Access Journals (Sweden)

Chehaibi, S.

2003-01-01

Full Text Available Low Power Mechanisation and Small-scale Vegetable Production in the Tunisian Sahel Region. Part 2: On the Field Evaluation of Performances and of Soil Preparation Costs. In this study, it was investigated to what extent low power mechanisation could be introduced in vegetable production in the Tunisian Sahel region by evaluating its performance (labour input and field efficiency by means of field experiments in which different traction equipment was used for carrying out several cultivation operations. Furthermore, costs per unit area for soil preparation in both sandy clay and clayish sand were calculated for four different power classes and for small fields. The results showed that two wheel tractors had a real labour input for scuffling between plant rows ranging from 11.3 h/ha to 18.7 h/ha. These inputs ranged from 5.5 h/ha to 6.7 h/ha for tied crops. For mowing, the two wheel tractor had labour inputs of 17.3 and 14.2 h/ha for the first and the second cut, respectively, while for potato digging, the first and the second passage of secondary tillage these values were 11.5, 14.3 and 10.4 h/ha, respectively. Superficial soil preparation by means of a four wheel tractor gave rise to values between 2.7 and 3.5 h/ha. With respect to the cost estimation for soil preparation, the lowest costs were obtained by means of the low power mechanisation. Similar conclusions were drawn for the field efficiencies for the operations investigated. In general, these efficiencies were above 70%.

climatology of air mass trajectories and aerosol optical thickness ...

African Journals Online (AJOL)

George

We present in this paper a climatological study of back trajectories of air masses ... obtained by inversion of photometric measurements of AERONET network. ... the arid Sahel region adjacent in the north to the Sahara ... the city a strategic position in the study of the .... atmospheric emergencies, diagnostic case studies and.

Energy and Water Resources of Burkina Faso as Catalyst for ...

African Journals Online (AJOL)

PROF. OLIVER OSUAGWA

2014-06-01

Jun 1, 2014 ... were to study the energy situation, search for sources of water for the ... engineering and hydrological surveys on selected construction sites to ... western regions. ... assistance from France and the Development .... directly to the national network of Burkina ..... lants in the Sahel: Case study of Burkina Faso.

Seasonal contrast in the surface energy balance of the Sahel

Science.gov (United States)

Miller, R. L.; Slingo, A.; Barnard, J. C.; Kassianov, E.

2009-07-01

during a dust aerosol outbreak is balanced comparably by net surface longwave and the sensible heat flux during the dry season, with the sensible flux increasing in importance with the onset of the summer monsoon winds. Measurements of surface fluxes by the AMF indicate broader features of the West African monsoon circulation and should be used to evaluate model simulations of the Sahel climate.

Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 3. Optical dynamics and vegetation index sensitivity to biomass and plant cover

International Nuclear Information System (INIS)

Leeuwen, W.J.D. van; Huete, A.R.; Duncan, J.; Franklin, J.

1994-01-01

A shrub savannah landscape in Niger was optically characterized utilizing blue, green, red and near-infrared wavelengths. Selected vegetation indices were evaluated for their performance and sensitivity to describe the complex Sahelian soil/vegetation canopies. Bidirectional reflectance factors (BRF) of plants and soils were measured at several view angles, and used as input to various vegetation indices. Both soil and vegetation targets had strong anisotropic reflectance properties, rendering all vegetation index (VI) responses to be a direct function of sun and view geometry. Soil background influences were shown to alter the response of most vegetation indices. N-space greenness had the smallest dynamic range in VI response, but the n-space brightness index provided additional useful information. The global environmental monitoring index (GEMI) showed a large VI dynamic range for bare soils, which was undesirable for a vegetation index. The view angle response of the normalized difference vegetation index (NDVI), atmosphere resistant vegetation index (ARVI) and soil atmosphere resistant vegetation index (SARVI) were asymmetric about nadir for multiple view angles, and were, except for the SARVI, altered seriously by soil moisture and/or soil brightness effects. The soil adjusted vegetation index (SAVI) was least affected by surface soil moisture and was symmetric about nadir for grass vegetation covers. Overall the SAVI, SARVI and the n-space vegetation index performed best under all adverse conditions and were recommended to monitor vegetation growth in the sparsely vegetated Sahelian zone. (author)

The present situation of photo-electric plants in the Sahel zone: Possibilities and limits of a marketing strategy using the example of the Niger. Zur gegenwaertigen Situation photovoltaischer Anlagen in der Sahelzone: Moeglichkeiten und Grenzen einer Vermarktungsstrategie am Beispiel des Niger

Energy Technology Data Exchange (ETDEWEB)

Hempel, C. (GTZ - Sonderenergieprogramm Niger, Niamey (Niger))

1993-01-01

The report is aimed at three targets: First one deals with the meteorological data as the basis for the technical design of photo-electric plants, secondly there is a short survey of the present situation of photo-electrics in Nigeria (referring also to other Sahel countries), and thirdly, the possibilities and limits of a marketing strategy for photo-electric plants are sketched out for this region. (orig.)

Phenotypic variations in osmotic lysis of Sahel goat erythrocytes in non-ionic glucose media.

Science.gov (United States)

Igbokwe, Nanacha Afifi; Igbokwe, Ikechukwu Onyebuchi

2016-03-01

Erythrocyte osmotic lysis in deionised glucose media is regulated by glucose influx, cation efflux, and changes in cell volume after water diffusion. Transmembrane fluxes may be affected by varied expression of glucose transporter protein and susceptibility of membrane proteins to glucose-induced glycosylation and oxidation in various physiologic states. Variations in haemolysis of Sahel goat erythrocytes after incubation in hyposmotic non-ionic glucose media, associated with sex, age, late pregnancy, and lactation, were investigated. The osmotic fragility curve in glucose media was sigmoidal with erythrocytes from goats in late pregnancy (PRE) or lactation (LAC) or from kid (KGT) or middle-aged (MGT) goats. Non-sigmoidal phenotype occurred in yearlings (YGT) and old (OGT) goats. The composite fragility phenotype for males and non-pregnant dry (NPD) females was non-sigmoidal. Erythrocytes with non-sigmoidal curves were more stable than those with sigmoidal curves because of inflectional shift of the curve to the left. Erythrocytes tended to be more fragile with male than female sex, KGT and MGT than YGT and OGT, and LAC and PRE than NPD. Thus, sex, age, pregnancy, and lactation affected the haemolytic pattern of goat erythrocytes in glucose media. The physiologic state of the goat affected the in vitro interaction of glucose with erythrocytes, causing variations in osmotic stability with variants of fragility phenotype. Variations in the effect of high extracellular glucose concentrations on the functions of membrane-associated glucose transporter, aquaporins, and the cation cotransporter were presumed to be relevant in regulating the physical properties of goat erythrocytes under osmotic stress.

“El florecimiento del terrorismo islámico en el Sahel, un reto para la seguridad de Europa Occidental. Estudio de caso: Malí y España (2011- 2013)”

OpenAIRE

Rodríguez Uribe, Mónica Alejandra

2015-01-01

El objetivo central de este Estudio de Caso, consiste en investigar en qué sentido la proximidad geográfica y el hecho de que la región del Sahel constituya una zona de tránsito, influyen a que el crecimiento del terrorismo islámico en Malí comprenda una amenaza tanto para la seguridad nacional, como para la estabilidad de España. Se avanzará posteriormente con la descripción de herramientas específicas, tanto judiciales como de cooperación que el gobierno español ha buscado apoyar a nivel ...

Increasing the Effectiveness of the “Great Green Wall” as an Adaptation to the Effects of Climate Change and Desertification in the Sahel

Directory of Open Access Journals (Sweden)

David O'Connor

2014-10-01

Full Text Available The Great Green Wall (GGW has been advocated as a means of reducing desertification in the Sahel through the planting of a broad continuous band of trees from Senegal to Djibouti. Initially proposed in the 1980s, the plan has received renewed impetus in light of the potential of climate change to accelerate desertification, although the implementation has been lacking in all but two of 11 countries in the region. In this paper, we argue that the GGW needs modifying if it is to be effective, obtain the support of local communities and leverage international support. Specifically, we propose a shift from planting trees in the GGW to utilizing shrubs (e.g., Leptospermum scoparium, Boscia senegalensis, Grewia flava, Euclea undulata or Diospyros lycioides, which would have multiple benefits, including having a faster growth rate and proving the basis for silvo-pastoral livelihoods based on bee-keeping and honey production.

CASE STUDY CRITIQUE; UPPER CLINCH CASE STUDY

Science.gov (United States)

Case study critique: Upper Clinch case study (from Research on Methods for Integrating Ecological Economics and Ecological Risk Assessment: A Trade-off Weighted Index Approach to Integrating Economics and Ecological Risk Assessment). This critique answers the questions: 1) does ...

Sensitivity of MENA Tropical Rainbelt to Dust Shortwave Absorption: A High Resolution AGCM Experiment

KAUST Repository

Bangalath, Hamza Kunhu; Stenchikov, Georgiy L.

2016-01-01

Shortwave absorption is one of the most important, but the most uncertain, components of direct radiative effect by mineral dust. It has a broad range of estimates from different observational and modeling studies and there is no consensus on the strength of absorption. To elucidate the sensitivity of the Middle East and North Africa (MENA) tropical summer rainbelt to a plausible range of uncertainty in dust shortwave absorption, AMIP-style global high resolution (25 km) simulations are conducted with and without dust, using the High-Resolution Atmospheric Model (HiRAM). Simulations with dust comprise three different cases by assuming dust as a very efficient, standard and inefficient absorber. Inter-comparison of these simulations shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. The maximum response and sensitivity are predicted over the northern edge of the rainbelt, geographically over Sahel. The sensitivity of the responses over the Sahel, especially that of precipitation, is comparable to the mean state. Locally, the response in precipitation reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. Taking into account that Sahel has a very high climate variability and is extremely vulnerable to changes in precipitation, the present study suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the Sahel climate.

Sensitivity of MENA Tropical Rainbelt to Dust Shortwave Absorption: A High Resolution AGCM Experiment

KAUST Repository

Bangalath, Hamza Kunhu

2016-06-13

Shortwave absorption is one of the most important, but the most uncertain, components of direct radiative effect by mineral dust. It has a broad range of estimates from different observational and modeling studies and there is no consensus on the strength of absorption. To elucidate the sensitivity of the Middle East and North Africa (MENA) tropical summer rainbelt to a plausible range of uncertainty in dust shortwave absorption, AMIP-style global high resolution (25 km) simulations are conducted with and without dust, using the High-Resolution Atmospheric Model (HiRAM). Simulations with dust comprise three different cases by assuming dust as a very efficient, standard and inefficient absorber. Inter-comparison of these simulations shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. The maximum response and sensitivity are predicted over the northern edge of the rainbelt, geographically over Sahel. The sensitivity of the responses over the Sahel, especially that of precipitation, is comparable to the mean state. Locally, the response in precipitation reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. Taking into account that Sahel has a very high climate variability and is extremely vulnerable to changes in precipitation, the present study suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the Sahel climate.

Les unités pastorales du Sahel sénégalais, outils de gestion de l’elevage et des espaces pastoraux. projet durable ou projet de développement durable ?

Directory of Open Access Journals (Sweden)

Abdrahmane Wane

2006-12-01

Full Text Available Au Ferlo (Sahel sénégalais, la durabilité de l’élevage pastoral repose sur la diversité et la flexibilité des régimes de mobilité. Depuis les années 90, le Projet d’Appui à l’Elevage (PAPEL intervient dans la zone pour organiser la gestion des ressources naturelles à l’échelle des unités pastorales (UP, avec l’objectif affiché d’assurer le contrôle et la durabilité de cette activité. Nous avons tenté d’évaluer la pertinence de la généralisation de ce projet d’envergure à l’aune des caractéristiques propres au pastoralisme, dorénavant reconnu comme la meilleure forme de mise en valeur dans l’environnement incertain du Ferlo. Même si les unités pastorales de gestion des ressources ont prouvé leur intérêt dans plusieurs cas de la première phase du projet en zone pastorale, il semble que dans le contexte sénégalais actuel de politique sectorielle agricole, et d’accaparement privé des ressources foncières, la généralisation systématique du schéma des UP sur tout le territoire risquerait plutôt de menacer la durabilité de la mobilité pastorale.In Ferlo (Senegalese Sahel, the sustainability of the livestock farming depends on the diversity and the flexibility of the regulations of mobility. Since the 90s, the PAPEL (Senegalese Support Project for Livestock has intervened in the area in order to manage the natural resources on the scale of the pastoral units (UP with the declared objective to ensure the control and the sustainability of this activity.  We tried to estimate the relevance of the general implementation of this large-scale project by the yardstick of the characteristics peculiar to Pastoralism, henceforth known as the best valorisation form in the uncertain environment of Ferlo. Even if the pastoral units as tools of the natural resource management have demonstrated their interest in many cases of the first stage of the project in the pastoral area, it seems that, in the

GLOBAL JOURNAL OF AGRICULTURAL SCIENCES ISSN 1596-2903

African Journals Online (AJOL)

Ada Global

mean rainfall for locations in the West African Sahel will reduce yields substantially and in many cases could lead to total crop failure. The study ... roughness, and the amount of dust generation are seen as possible triggers to a .... Table 1: Coefficient of determintion (R2) for the multiple regression models. Model 1. Location.

Arthropod diversity and assemblage structure response to deforestation and desertification in the Sahel of western Senegal

Directory of Open Access Journals (Sweden)

Brandon J. Lingbeek

2017-07-01

Full Text Available Drylands are highly vulnerable to desertification and among the most endangered ecosystems. To understand how biodiversity responds to environmental degradation in these fragile ecosystems, we examined whether arthropod, beetle, spider and ant diversity and assemblage structure differed (1 between seasons, (2 among locations (3 between protected areas of tropical dry forest and adjacent communal lands suffering from desertification, as well as (4 how vegetation impacts assemblage structures. We established 12 plots spaced homogenously throughout each protected area and the adjacent communal land at three locations: Beersheba, Bandia and Ngazobil. Within each plot, we measured canopy closure, vegetation height, percent cover of bare ground, leaf litter, grasses and forbs and collected arthropods using pitfall traps during the 2014 dry (May and rainy (September seasons. We collected 123,705 arthropods representing 733 morphospecies, 10,849 beetles representing 216 morphospecies, 4969 spiders representing 91 morphospecies and 59,183 ants representing 45 morphospecies. Results showed greater arthropod and beetle diversities (P = 0.002–0.040 in the rainy season, no difference in diversity among locations for any taxonomic group and a difference (P ≤ 0.001 in diversity for all taxa between protected areas and communal lands. Assemblage structures of all taxa responded (P = 0.001 to vegetation characteristics, differed (P = 0.015–0.045 between seasons and, with a few exceptions, locations and fragments. Our results illustrate the importance of a multi-taxa approach in understanding biodiversity response to anthropogenic disturbances as well as the value of protected areas in preserving biodiversity of the Sahel.

A Review Of Preterm Admissions Into Special Care Baby Unit, In ...

African Journals Online (AJOL)

There is little or no report of preterm (babies born less than 37 completed weeks of gestation) admission from this part of Sahel Savannah of Nigeria. This study of four-year period is presented to identify areas that require improvement, such as in the Labour ward and neonatal care. The case files of the 428 preterm ...

caractérisation de la tolérance de nerica à la sécheresse de mi ...

African Journals Online (AJOL)

Administrator

1Université de Cocody, UFR des Sciences de la Terre et des Ressources Minières, laboratoire de Pédologie. Appliquée, 22 BP 582 Abidjan 22, Abidjan, ..... Caractéristiques climatiques et pédologiques du site. La Figure 1 montre les distributions ..... sandy soils of the Sahel: a case study from. Niger, West Africa. Agriculture ...

Simulation of the Impact of Climate Variability on Malaria Transmission in the Sahel

Science.gov (United States)

Bomblies, A.; Eltahir, E.; Duchemin, J.

2007-12-01

A coupled hydrology and entomology model for simulation of malaria transmission and malaria transmitting mosquito population dynamics is presented. Model development and validation is done using field data and observations collected at Banizoumbou and Zindarou, Niger spanning three wet seasons, from 2005 through 2007. The primary model objective is the accurate determination of climate variability effects on village scale malaria transmission. Malaria transmission dependence on climate variables is highly nonlinear and complex. Temperature and humidity affect mosquito longevity, temperature controls parasite development rates in the mosquito as well as subadult mosquito development rates, and precipitation determines the formation and persistence of adequate breeding pools. Moreover, unsaturated zone hydrology influences overland flow, and climate controlled evapotranspiration rates and root zone uptake therefore also influence breeding pool formation. High resolution distributed hydrologic simulation allows representation of the small-scale ephemeral pools that constitute the primary habitat of Anopheles gambiae mosquitoes, the dominant malaria vectors in the Niger Sahel. Remotely sensed soil type, vegetation type, and microtopography rasters are used to assign the distributed parameter fields for simulation of the land surface hydrologic response to precipitation and runoff generation. Predicted runoff from each cell flows overland and into topographic depressions, with explicit representation of infiltration and evapotranspiration. The model's entomology component interacts with simulated pools. Subadult (aquatic stage) mosquito breeding is simulated in the pools, and water temperature dependent stage advancement rates regulate adult mosquito emergence into the model domain. Once emerged, adult mosquitoes are tracked as independent individual agents that interact with their immediate environment. Attributes relevant to malaria transmission such as gonotrophic

Re-greening the Sahel: farmer-led innovation in Burkina Faso and Niger

Science.gov (United States)

Reij, Chris; Smale, Melinda; Tappan, G. Gray; Spielman, David J.; Pandya-Lorch, Rajul

2009-01-01

did 30 years ago. These findings suggest a human and environmental success story at a scale not seen anywhere else in Africa. The re-greening of the Sahel began when local farmers’ practices were rediscovered and enhanced in simple, low-cost ways by innovative farmers and nongovernmental organizations. An evolving coalition of local, national, and international actors then enabled large-scale diffusion and continued use of these improved practices where they benefited farmers.

Case Study Research Methodology

Directory of Open Access Journals (Sweden)

Mark Widdowson

2011-01-01

Full Text Available Commenting on the lack of case studies published in modern psychotherapy publications, the author reviews the strengths of case study methodology and responds to common criticisms, before providing a summary of types of case studies including clinical, experimental and naturalistic. Suggestions are included for developing systematic case studies and brief descriptions are given of a range of research resources relating to outcome and process measures. Examples of a pragmatic case study design and a hermeneutic single-case efficacy design are given and the paper concludes with some ethical considerations and an exhortation to the TA community to engage more widely in case study research.

Project management case studies

CERN Document Server

Kerzner, Harold R

2013-01-01

A new edition of the most popular book of project management case studies, expanded to include more than 100 cases plus a ""super case"" on the Iridium Project Case studies are an important part of project management education and training. This Fourth Edition of Harold Kerzner''s Project Management Case Studies features a number of new cases covering value measurement in project management. Also included is the well-received ""super case,"" which covers all aspects of project management and may be used as a capstone for a course. This new edition:Contains 100-plus case studies drawn from re

Tribological investigation of novel HDPE-HAp-Al2O3 hybrid biocomposites against steel under dry and simulated body fluid condition.

Science.gov (United States)

Nath, Shekhar; Bodhak, Subhadip; Basu, Bikramjit

2007-10-01

Among various biocompatible polymers, polyethylene based materials have received wider attention because of its excellent stability in body fluid, inertness, and easy formability. Attempts have been made to improve their physical properties (modulus/strength) to enable them to be used as load bearing hard tissue replacement applications. Among such attempts, high density polyethylene (HDPE)-hydroxyapatite (HAp) composite (HAPEX), has already been developed for total hip replacement (THR) acetabular cup and low load bearing bone tissue replacement. In the present work, alumina has been added as a partial replacement of HAp phase to improve the mechanical and tribological properties of the HAPEX composite. In an attempt to assess the suitability of the developed composite in THR application, the tribological properties against steel counterbody under both in air and simulated body fluid (SBF), have been investigated and efforts have been made to understand the wear mechanisms. The fretting wear study indicates the possibility of achieving extremely low COF (Coefficient of Friction approximately 0.09) as well as higher wear resistance (order of 10(-6) mm(3)/N m) with the newly developed composites in SBF. A low wear depth of approximately 4.6-5.3 microm is recorded, irrespective of fretting environment. The implication of the work is that optimal and combined addition of bioactive and bioinert ceramic filler to HDPE can provide a good opportunity to obtain hybrid biocomposites with better combination of physical properties (modulus, hardness) as well as low friction and high wear resistance.

Communications Channels in the Sahel Using Mauritania, Mali, Niger, and Chad as a Case Study

Science.gov (United States)

2007-05-01

issues, family, AIDS, etc. Malians listen to rap, but the lyrics are more positive than Western rap music. Dr. Arnoldi said the beat is similar to...Hassan, eds. The Muse of Modernity: Essays on Culture as Development in Africa. (Trenton: Africa World Press, Inc., 1996). Page 10 of 107 cultural...http://www.nollywood.net/ Essays /p2_articleid/126/p2_page/3>. Theatre for Development encourages community participation, increasing the

Evaluation of CMIP5 models in the context of food security assessments in Sahel and Eastern Africa

Science.gov (United States)

Shukla, S.; Funk, C. C.; Dettinger, M. D.; Robertson, F. R.

2012-12-01

Global climate change will adversely impact agricultural production in many African countries, mainly in the Sahel region and Eastern Africa that are already considered food insecure regions. The impacts of climate change will be particularly severe in these food insecure countries due to their high dependence on domestic agriculture production, rapid population growth, and lack of technological advances. Early planning and the targeted use of resources will therefore be critical to informing and motivating climate change adaptation actions that can save lives and mitigate economic losses. We seek to use Climate Model Intercomparison Project Phase-5 (CMIP5) global climate model projections to assess and attribute food and water security conditions in the above mentioned regions over next two decades or so. As a first order of business, however, we need to understand how the different models represent the tropical ocean response to anthropogenic warming. We pursue this question through an evaluation of the performance of eight different coupled ocean-atmosphere models under the conditions of the 'historical' experiment. The historical experiment forces the simulations with observed 1850-2005 greenhouse gas, aerosol and land cover. While all the models show substantial warming of the tropical oceans, the pattern and atmospheric response to that warming varies substantially. This analysis suggests that the Community Climate System Model (CCSM4) provides the most realistic 1850-2005 changes over the Indo-Pacific. We then present initial downscaling results, based on large scale forcing from the CCSM4, combined with statistical downscaling based on a combination of monthly simulations from Community Atmopsheric Model 4 (CAM4) and observed gridded time series of African rainfall and air temperatures.

How Does Gender Affect Sustainable Intensification of Cereal Production in the West African Sahel? Evidence from Burkina Faso.

Science.gov (United States)

Theriault, Veronique; Smale, Melinda; Haider, Hamza

2017-04-01

Better understanding of gender differences in the adoption of agricultural intensification strategies is crucial for designing effective policies to close the gender gap while sustainably enhancing farm productivity. We examine gender differences in adoption rates, likelihood and determinants of adopting strategy sets that enhance yields, protect crops, and restore soils in the West African Sahel, based on analysis of cereal production in Burkina Faso. Applying a multivariate probit model to a nationally representative household panel, we exploit the individual plot as unit of analysis and control for plot manager characteristics along with other covariates. Reflecting the socio-cultural context of farming combined with the economic attributes of inputs, we find that female managers of individual cereal fields are less likely than their male counterparts to adopt yield-enhancing and soil-restoring strategies, although no differential is apparent for yield-protecting strategies. More broadly, gender-disaggregated regressions demonstrate that adoption determinants differ by gender. Plot manager characteristics, including age, marital status, and access to credit or extension services do influence adoption decisions. Furthermore, household resources influence the probability of adopting intensification strategy sets differently by gender of the plot manager. Variables expressing the availability of household labor strongly influence the adoption of soil-restoring strategies by female plot managers. By contrast, household resources such as extent of livestock owned, value of non-farm income, and area planted to cotton affect the adoption choices of male plot managers. Rectifying the male bias in extension services along with improving access to credit, income, and equipment to female plot managers could contribute to sustainable agricultural intensification.

[Case and studies].

Science.gov (United States)

Schubert, András

2015-11-15

Case studies and case reports form an important and ever growing part of scientific and scholarly literature. The paper deals with the share and citation rate of these publication types on different fields of research. In general, evidence seems to support the opinion that an excessive number of such publications may negatively influence the impact factor of the journal. In the literature of scientometrics, case studies (at least the presence of the term "case study" in the titles of the papers) have a moderate share, but their citation rate is practically equal to that of other publication types.

Building theories from case study research: the progressive case study

NARCIS (Netherlands)

Steenhuis, H.J.; de Bruijn, E.J.

2006-01-01

Meredith (1998) argues for more case and field research studies in the field of operations management. Based on a literature review, we discuss several existing approaches to case studies and their characteristics. These approaches include; the Grounded Theory approach which proposes no prior

Specification of parameters for development of a spatial database for drought monitoring and famine early warning in the African Sahel

Science.gov (United States)

Rochon, Gilbert L.

1989-01-01

Parameters were described for spatial database to facilitate drought monitoring and famine early warning in the African Sahel. The proposed system, referred to as the African Drought and Famine Information System (ADFIS) is ultimately recommended for implementation with the NASA/FEMA Spatial Analysis and Modeling System (SAMS), a GIS/Dymanic Modeling software package, currently under development. SAMS is derived from FEMA'S Integration Emergency Management Information System (IEMIS) and the Pacific Northwest Laborotory's/Engineering Topographic Laboratory's Airland Battlefield Environment (ALBE) GIS. SAMS is primarily intended for disaster planning and resource management applications with the developing countries. Sources of data for the system would include the Developing Economics Branch of the U.S. Dept. of Agriculture, the World Bank, Tulane University School of Public Health and Tropical Medicine's Famine Early Warning Systems (FEWS) Project, the USAID's Foreign Disaster Assistance Section, the World Resources Institute, the World Meterological Institute, the USGS, the UNFAO, UNICEF, and the United Nations Disaster Relief Organization (UNDRO). Satellite imagery would include decadal AVHRR imagery and Normalized Difference Vegetation Index (NDVI) values from 1981 to the present for the African continent and selected Landsat scenes for the Sudan pilot study. The system is initially conceived for the MicroVAX 2/GPX, running VMS. To facilitate comparative analysis, a global time-series database (1950 to 1987) is included for a basic set of 125 socio-economic variables per country per year. A more detailed database for the Sahelian countries includes soil type, water resources, agricultural production, agricultural import and export, food aid, and consumption. A pilot dataset for the Sudan with over 2,500 variables from the World Bank's ANDREX system, also includes epidemiological data on incidence of kwashiorkor, marasmus, other nutritional deficiencies, and

Paraneoplastic syndromes revealing ovarian teratoma in young and ...

African Journals Online (AJOL)

Paraneoplastic syndromes revealing ovarian teratoma in young and menopausal women: report of two cases. Majdouline Boujoual, Ihsan Hakimi, Farid Kassidi, Youssef Akhoudad, Nawal Sahel, Adil Rkiouak, Mohamed Allaoui, Hafsa Chahdi, Mohamed Oukabli, Jaouad Kouach, Driss Rahali Moussaoui, Mohamed ...

West African think tank strengthens outreach and partnerships ...

International Development Research Centre (IDRC) Digital Library (Canada)

28 avr. 2016 ... Les femmes du Sahel obtiennent de meilleurs rendements de leurs cultures. Moins d'engrais et rendements plus élevés pour les agricultrices du Sahel. Voir davantageLes femmes du Sahel obtiennent de meilleurs rendements de leurs cultures ...

Bridging gender gaps with dairy goats and root crops | CRDI ...

International Development Research Centre (IDRC) Digital Library (Canada)

5 mai 2016 ... Les femmes du Sahel obtiennent de meilleurs rendements de leurs cultures. Moins d'engrais et rendements plus élevés pour les agricultrices du Sahel. Voir davantageLes femmes du Sahel obtiennent de meilleurs rendements de leurs cultures ...

Appendicitis: A Study of Negative Appendicectomies | Kpolugbo ...

African Journals Online (AJOL)

Post-operative complications were noted in 3% of the negative appendicectomy group but in the positive appendicectomy group complications were much more common particularly when the appendix was ruptured. (Key Words: Negative appendicectomy, perforated appendix and postoperative complications.) Sahel Med.

The project RUSSADE: geoethic education to face environmental problems in the Sahel

Science.gov (United States)

Ferrero, Elena; Semita, Carlo

2016-04-01

The hard environmental and climatic conditions in Sahel countries affect life choices of younger generations, whose number continues to increase especially in large Sahelian cities, with increasing levels of discomfort and lack of adequate education and governance. To improve job opportunities and consequently the quality of life at all levels of the population, it is important to guarantee a better access to basic natural resources, such as soil, water, food. At the same time it is essential to spread awareness and knowledge of the vulnerability and of the risks that threaten natural resources, both for natural processes and for the interaction with human not sustainable activities. For this purpose, a Master course has been achieved in the project RUSSADE (Réseau des Universités Sahéliennes pour la Sécurité Alimentaire et la Durabilité Environnementale - www.russade.eu), funded in the ACP-EU Cooperation Programme in higher education (EDULINK II). The Master course includes teaching modules dedicated to these issues and takes care of their integration with other modules in the technical and application fields of the rural development. For instance, the objectives of the teaching module "Land and natural resources management" provide for the transmission of skills to diagnose types of soil degradation risks, to guide options for protection, conservation and soil restoration and to identify the components of integrated soil fertility management in particular African contexts (Subunit "Land management"); to choose appropriate methods of management and exploitation of water resources (defining the limits in the use of water resources) (Subunit "Water supply"); to propose alternative solutions concerning conventional energy resources, to know and promote the various possibilities of solar and other renewable energies production (Subunit "Using solar and other renewable energies"). Some teaching modules introduce and discuss risks related to inadequate waste

Study of the climatic change impact on vector-borne diseases in West Africa: the case of tick-borne borreliosis and malaria; Etude de l'impact du changement climatique sur les maladies a transmission vectorielle en Afrique de l'Ouest: le cas de la borreliose a tiques et du paludisme

Energy Technology Data Exchange (ETDEWEB)

Trape, J.F

2005-04-15

Malaria and tick-borne borreliosis are the two first causes of morbidity due to vector-borne diseases in a large part of Sudan-sahelian West Africa. They are also the two tropical diseases which have been the most affected by climatic change in recent years. In the case of tick-borne borreliosis it has been shown in Senegal that the persistence of drought since the years 70 has been associated with a considerable extension of the geographic range of diseases and the vector tick A-sonrai, a species that was in the past limited to the Sahara and Sahel. In the case of malaria, drought has strongly reduced in these same regions of Africa the distribution, abundance and infection rate of Anopheline mosquitoes, but without any significant reduction of the burden of malaria for most populations concerned. The emergence and spread of Plasmodium falciparum resistance to antimalarial drugs only explain part of this phenomenon. (A.L.B.)

Final report on case studies

DEFF Research Database (Denmark)

Ljungberg, Daniel; McKelvey, Maureen; Lassen, Astrid Heidemann

2012-01-01

Case study as a research design means investigating a single or multiple instance(s) or setting(s) (i.e. a case) and its entire context to explain a phenomenon and its processes. This is achieved through detailed understanding, usually comprised of multiple sources of information. In this way, case...... studies attempt to provide as a complete an understanding of a (complex) phenomenon as possible. Within the AEGIS project, survey and case study research are complementary. They are complementary in the sense that the former can provide more generalizable evidence on a phenomenon in terms of cross......-sectional data, while the latter can provide more in-depth (qualitative) understanding on specific issues. In systematically examining the case studies, however, this report goes beyond a typical single case study. Here we provide a synthesis of 86 case studies. Multiple case studies, following similar focus...

Removal and Adsorption of Vanadium and Boron by Some Egyptian Clay Sediments

International Nuclear Information System (INIS)

Mahdy, R.M.

2016-01-01

Due to the increase concerns of the environmental pollution problems, to have safer environment, it seems so important to propose an effective exploration of geological barriers, which are suitable for waste materials disposal. In fact, clay sediments play an essential role as natural adsorbents to immobilize nuclear elements contaminates such as uranium, vanadium and boron. In this study, the clay sediments was collected from either clay exploitation localities or from nearby radioactive mineralization provinces in Egypt. The obtained data clarifies that the adsorption of vanadium and boron by clay sediments were increased by increasing the initial concentration of vanadium and boron The adsorption maxima (B) for vanadium in kaolin samples namely Mossaba Salama, El Teah and EL Eessala reached 71.4, 66.7 and 47.6). On the other hand, the adsorption maxima (B) in bentonite samples namely North Coast – H ( El Sahel el shamaly) (high viscosity) followed by North Coast (El Sahel el shamaly) then North Coast (El Sahel el shamaly) (low viscosity) and finally Kasr El Sagha reached 135.1, 79.4, 61.5 and 47.6 respectively.The adsorption maxima for boron in kaolinite samples namely Mossaba Salama, El Teah and EL Eessala reached 47.5, 30.6 and 27.0 while in the bentonite samples it was arranged from Kaser El Sagha (35.7), North Coast (H) El Sahel el shamaly ( H) (32.3), North Coast (L) (27.9) ( El Sahel el shamaly L) to North Coast (El Sahel el shamaly) (3.5)

[Case-non case studies: Principles, methods, bias and interpretation].

Science.gov (United States)

Faillie, Jean-Luc

2017-10-31

Case-non case studies belongs to the methods assessing drug safety by analyzing the disproportionality of notifications of adverse drug reactions in pharmacovigilance databases. Used for the first time in the 1980s, the last few decades have seen a significant increase in the use of this design. The principle of the case-non case study is to compare drug exposure in cases of a studied adverse reaction with that of cases of other reported adverse reactions and called "non cases". Results are presented in the form of a reporting odds ratio (ROR), the interpretation of which makes it possible to identify drug safety signals. This article describes the principle of the case-non case study, the method of calculating the ROR and its confidence interval, the different modalities of analysis and how to interpret its results with regard to the advantages and limitations of this design. Copyright © 2017 Société française de pharmacologie et de thérapeutique. Published by Elsevier Masson SAS. All rights reserved.

Rain-Use-Efficiency: What it Tells us about the Conflicting Sahel Greening and Sahelian Paradox

Directory of Open Access Journals (Sweden)

Cécile Dardel

2014-04-01

Full Text Available Rain Use Efficiency (RUE, defined as Aboveground Net Primary Production (ANPP divided by rainfall, is increasingly used to diagnose land degradation. Yet, the outcome of RUE monitoring has been much debated since opposite results were found about land degradation in the Sahel region. The debate is fueled by methodological issues, especially when using satellite remote sensing data to estimate ANPP, and by differences in the ecological interpretation. An alternative method which solves part of these issues relies on the residuals of ANPP regressed against rainfall (“ANPP residuals”. In this paper, we use long-term field observations of herbaceous vegetation mass collected in the Gourma region in Mali together with remote sensing data (GIMMS-3g Normalized Difference Vegetation Index to estimate ANPP, RUE, and the ANPP residuals, over the period 1984–2010. The residuals as well as RUE do not reveal any trend over time over the Gourma region, implying that vegetation is resilient over that period, when data are aggregated at the Gourma scale. We find no conflict between field-derived and satellite-derived results in terms of trends. The nature (linearity of the ANPP/rainfall relationship is investigated and is found to have no impact on the RUE and residuals interpretation. However, at odds with a stable RUE, an increased run-off coefficient has been observed in the area over the same period, pointing towards land degradation. The divergence of these two indicators of ecosystem resilience (stable RUE and land degradation (increasing run-off coefficient is referred to as the “second Sahelian paradox”. When shallow soils and deep soils are examined separately, high resilience is diagnosed on the deep soil sites. However, some of the shallow soils show signs of degradation, being characterized by decreasing vegetation cover and increasing run-off coefficient. Such results show that contrasted changes may co-exist within a region where a

Weeding method and pre-sowing tillage effects on weed growth and pearl millet yield in a sandy soil of the West African Sahelian zone.

NARCIS (Netherlands)

Klaij, M.C.; Hoogmoed, W.B.

1996-01-01

Weed control for the West African Sahel rainfed crops is done mainly manually, resulting in high labor requirements. Because of the seasonality of rainfed farming, weed control is often late and incomplete, resulting in considerable losses in crop yield. We examined the case of weed control in

Sahel Journal of Veterinary Sciences: Advanced Search

African Journals Online (AJOL)

Search tips: Search terms are case-insensitive; Common words are ignored; By default only articles containing all terms in the query are returned (i.e., AND is implied); Combine multiple words with OR to find articles containing either term; e.g., education OR research; Use parentheses to create more complex queries; e.g., ...

Case-control studies in neurosurgery.

Science.gov (United States)

Nesvick, Cody L; Thompson, Clinton J; Boop, Frederick A; Klimo, Paul

2014-08-01

Observational studies, such as cohort and case-control studies, are valuable instruments in evidence-based medicine. Case-control studies, in particular, are becoming increasingly popular in the neurosurgical literature due to their low cost and relative ease of execution; however, no one has yet systematically assessed these types of studies for quality in methodology and reporting. The authors performed a literature search using PubMed/MEDLINE to identify all studies that explicitly identified themselves as "case-control" and were published in the JNS Publishing Group journals (Journal of Neurosurgery, Journal of Neurosurgery: Pediatrics, Journal of Neurosurgery: Spine, and Neurosurgical Focus) or Neurosurgery. Each paper was evaluated for 22 descriptive variables and then categorized as having either met or missed the basic definition of a case-control study. All studies that evaluated risk factors for a well-defined outcome were considered true case-control studies. The authors sought to identify key features or phrases that were or were not predictive of a true case-control study. Those papers that satisfied the definition were further evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist. The search detected 67 papers that met the inclusion criteria, of which 32 (48%) represented true case-control studies. The frequency of true case-control studies has not changed with time. Use of odds ratios (ORs) and logistic regression (LR) analysis were strong positive predictors of true case-control studies (for odds ratios, OR 15.33 and 95% CI 4.52-51.97; for logistic regression analysis, OR 8.77 and 95% CI 2.69-28.56). Conversely, negative predictors included focus on a procedure/intervention (OR 0.35, 95% CI 0.13-0.998) and use of the word "outcome" in the Results section (OR 0.23, 95% CI 0.082-0.65). After exclusion of nested case-control studies, the negative correlation between focus on a procedure

Case Study: Mini-Case Studies: Small Infusions of Active Learning for Large-Lecture Courses

Science.gov (United States)

Carloye, Lisa

2017-01-01

In this article, the author introduces the usage of case studies to be an excellent method for engaging students through stories. The author notes she developed a series of mini-case studies that can be implemented, with a little advance preparation, within a 10- to 15-minute window during lecture. What makes them "mini" case studies?…

BioFleet case studies

International Nuclear Information System (INIS)

2007-01-01

These six case studies examined the use of different biodiesel blends as fuel supply sources for businesses in British Columbia (BC). In the first case study, 6 municipalities participated in a pilot program designed to compare the performance of biodiesel and diesel fuels. Each municipality operated 2 base vehicles running on conventional diesel along with 2 similar vehicles which used biodiesel. Real time emissions tests and analyses of the vehicles using biodiesel were also conducted by 2 of the participating municipalities. All municipalities participating in the study agreed to purchase significant volumes of biodiesel. The second case study described a pilot study conducted by the City of Vancouver's equipment services branch in 2004. As a result of the study, the city now has over 530 types of equipment that use biodiesel. The third case study described a program designed by TSI Terminals in Vancouver to assess the emission reduction impact of using biodiesel at its port facility. Six different pieces of equipment were used to confirm that biodiesel could be used throughout the terminal. Test results confirmed that biodiesel blends could be used to reduce emissions. Overall emissions were reduced by 30 per cent. The fourth case study described a waste renderer that used a fleet of 36 trucks to deliver raw products to its plants. The company made the decision to use only biodiesel for its entire fleet of trucks. Since July 2005, the company has logged over 1.7 million km using biodiesel blends. The fifth case study described a salmon hatchery that switched from diesel to biodiesel in order to reduce emissions. The biodiesel blends are used to fuel the hatchery's 2 diesel generators. The hatchery has reduced emissions of greenhouse gases (GHGs) by an estimated 1800 tonnes annually. The sixth case study described how the Township of Langley has started using biodiesel for its entire fleet of of approximately 250 pieces of equipment. The township has not

[Contribution of migrations to the process of urbanization].

Science.gov (United States)

Bocquier, P

1997-10-01

An average of 22% of the populations of the Sahel countries resided in urban areas in the mid-1970s, a lower level than in the rest of sub-Saharan Africa. The proportion urban has increased by about 5.5% annually over the past 2 decades. By 1993, four Sahel countries had over 30% of their populations in urban areas, and only Burkina Faso had less than 20% urban. The landlocked Sahel countries of Burkina Faso, Mali, Niger, and Chad have maintained rates of urbanization comparable to those of the coastal countries (Cape Verde, Gambia, Mauritania, and Senegal), which had more significant levels of urbanization in the past. The rate of growth of the urban population of all of sub-Saharan Africa was around 5.0% during the past 20 years. Only Dakar among the Sahel capitals has a population of over 1 million. Cities are small, and the urban environment is usually limited to the capital. In Guinea-Bissau, for example, the capital concentrates nearly 85% of the urban population. The increased rates of urbanization are due mainly to migration. In the landlocked countries covered by surveys of the Migration and Urbanization Networks in Western Africa (Burkina Faso, Mali, and Niger), the rural exodus was directed primarily to other countries. In Senegal and Mauritania, on the other hand, around two-thirds of migrations were internal. Women contribute more than men to urban growth in the Sahel. Returning migrants also show a strong preference for capital cities. Labor markets are international for men but national for women. Urban unemployment rates in the Sahel countries studied were lower for migrants than nonmigrants.

Why Failing Terrorist Groups Persist: The Case of Al-Qaeda in the Islamic Maghreb

Science.gov (United States)

2012-06-01

and Nigeria in the South). As an AQ franchise organization their goals now include attacking western interests within the Sahel.10 Lastly, AQIM...concerning NEA. 317 Official, interview concerning NEA. 318 Official, interview concerning NEA 76 open society and encouraged entrepreneurship as...focused on criminal entrepreneurship than the AQIM Islamist ideology.359 The Joint Staff does not see an end to AQIM without a significant change in

Describing Case Study Method and Identifying the Factors that Contribute to the Successful Conduct of Case Studies

OpenAIRE

Ahmad H. Juma'h; Mustafa Cavus

2001-01-01

This article has attempted to describe case study, the limitations and critiques on case study methodology and how the proponents have responded to these. Our special focus have been on the debate on theory building from case study research, and a framework for conducting case study research as well as the factors for a successful case study research. The overall conclusion is that the case study has been inappropriately used to generate theories.

How To Set Up Your Own Small Business. Service Company Case Study. Manufacturing Firm Case Study. Retail Store Case Study.

Science.gov (United States)

Fallek, Max

This collection of case studies is intended for use in a course in setting up a small business. The first, a case study of the process of setting up a service company, covers analyzing the pros and cons of starting one's own business, assessing the competition and local market, and selecting a site for and financing the business. The principal…

Theory Testing Using Case Studies

DEFF Research Database (Denmark)

Møller, Ann-Kristina Løkke; Dissing Sørensen, Pernille

2014-01-01

The appropriateness of case studies as a tool for theory testing is still a controversial issue, and discussions about the weaknesses of such research designs have previously taken precedence over those about its strengths. The purpose of the paper is to examine and revive the approach of theory...... testing using case studies, including the associated research goal, analysis, and generalisability. We argue that research designs for theory testing using case studies differ from theorybuilding case study research designs because different research projects serve different purposes and follow different...... research paths....

Theory testing using case studies

DEFF Research Database (Denmark)

Dissing Sørensen, Pernille; Løkke Nielsen, Ann-Kristina

2006-01-01

on the strengths of theory-testing case studies. We specify research paths associated with theory testing in case studies and present a coherent argument for the logic of theoretical development and refinement using case studies. We emphasize different uses of rival explanations and their implications for research...... design. Finally, we discuss the epistemological logic, i.e., the value to larger research programmes, of such studies and, following Lakatos, conclude that the value of theory-testing case studies lies beyond naïve falsification and in their contribution to developing research programmes in a progressive......Case studies may have different research goals. One such goal is the testing of small-scale and middle-range theories. Theory testing refers to the critical examination, observation, and evaluation of the 'why' and 'how' of a specified phenomenon in a particular setting. In this paper, we focus...

Five Misunderstandings About Case-Study Research

DEFF Research Database (Denmark)

Flyvbjerg, Bent

2006-01-01

This article examines five common misunderstandings about case-study research: (a) theoretical knowledge is more valuable than practical knowledge; (b) one cannot generalize from a single case, therefore, the single-case study cannot contribute to scientific development; (c) the case study is most...... useful for generating hypotheses, whereas other methods are more suitable for hypotheses testing and theory building; (d) the case study contains a bias toward verification; and (e) it is often difficult to summarize specific case studies. This article explains and corrects these misunderstandings one...

Fuzzy-Set Case Studies

Science.gov (United States)

Mikkelsen, Kim Sass

2017-01-01

Contemporary case studies rely on verbal arguments and set theory to build or evaluate theoretical claims. While existing procedures excel in the use of qualitative information (information about kind), they ignore quantitative information (information about degree) at central points of the analysis. Effectively, contemporary case studies rely on…

Case Study: Guidelines for Producing Videos to Accompany Flipped Cases

Science.gov (United States)

Prud'homme-Généreux, Annie; Schiller, Nancy A.; Wild, John H.; Herreid, Clyde Freeman

2017-01-01

Three years ago, the "National Center for Case Study Teaching in Science" (NCCSTS) was inspired to merge the case study and flipped classroom approaches. The resulting project aimed to create the materials required to teach a flipped course in introductory biology by assigning videos as homework and case studies in the classroom. Three…

Staying with the system

DEFF Research Database (Denmark)

Rasmussen, Laura Vang; Nielsen, Jonas Østergaard

2014-01-01

Scholars have studied the Sahel intensely since major droughts hit the region in the early 1970s. One of the most persistent of these in terms of both volume and time span is Anette Reenberg. In this paper we explore her studies of the Sahel published in peer-reviewed journals and their impact over...... the last three decades. Reenberg has had a remarkably stable theoretical agenda concerned with the importance of understanding the social and biophysical systems as one coupled human-environmental system. This agenda has influenced contemporary as well as subsequent Danish scholars publishing on the Sahel......-environmental system framework in the journal may be attributed to Reenberg’s theoretical agenda as well as a new international stream of research joining the human and environmental sciences in an interdisciplinary effort. Hence, it is also shown how Reenberg’s theoretical agenda have influenced scholars trying...

Does Jatropha curcas L. show resistance to drought in the Sahelian zone of West Africa? A case study from Burkina Faso

Science.gov (United States)

Bayen, P.; Sop, T. K.; Lykke, A. M.; Thiombiano, A.

2015-05-01

Land degradation is an environmental problem which weakens agro-sylvo-pastoral productivity in sub-Saharan Africa. The most common manifestation of land degradation is the appearance of denuded land. We carried out an experiment to test the effect of three soil and water conservation techniques on survival and growth of Jatropha curcas seedlings transplanted onto two completely denuded lands in the Sahelian and Sudanian zones of Burkina Faso. We implemented an experimental design with three replicates per restoration technique. A total of 174 seedlings were planted in each study site. The results showed that the soil water content varied according to the restoration technique used (df = 2; F = 53.21; p curcas is unsuited to denuded land in the Sahelian zone. Most of the plants died in the Sahel between April and May, which is the peak of the dry season; this may be an indication that J. curcas may not be as drought-resistant as suggested by the prolific literature which has reported on diverse claims surrounding this plant.

Five misunderstandings about case study research

DEFF Research Database (Denmark)

Flyvbjerg, Bent

2004-01-01

This article examines five common misunderstandings about case-study research: (1) Theoretical knowledge is more valuable than practical knowledge; (2) One cannot generalize from a single case, therefore the single case study cannot contribute to scientific development; (3) The case study is most...... useful for generating hypotheses, while other methods aremore suitable for hypotheses testing and theory building; (4) The case study contains a bias toward verification; and (5) It is often difficult to summarize specific case studies. The article explains and corrects these misunderstandings one by one...... and concludes with the Kuhnian insight that a scientific discipline without a large number of thoroughly executed case studies is a discipline without systematic production of exemplars, and that a discipline without exemplars is an ineffective one. Social science may be strengthened by the execution of more...

Case Study: A Picture Worth a Thousand Words? Making a Case for Video Case Studies

Science.gov (United States)

Pai, Aditi

2014-01-01

A picture, they say, is worth a thousand words. If a mere picture is worth a thousand words, how much more are "moving pictures" or videos worth? The author poses this not merely as a rhetorical question, but because she wishes to make a case for using videos in the traditional case study method. She recommends four main approaches of…

Five misunderstandings about Case-study Research

DEFF Research Database (Denmark)

Flyvbjerg, Bent

This article examines five common misunderstandings about case-study research: (1) Theoretical knowledge is more valuable than practical knowledge; (2) One cannot generalize from a single case, therefore the single case study cannot contribute to scientific development; (3) The case study is most...... useful for generating hypotheses, while other methods aremore suitable for hypotheses testing and theory building; (4) The case study contains a bias toward verification; and (5) It is often difficult to summarize specific case studies. The article explains and corrects these misunderstandings one by one...... and concludes with the Kuhnian insight that a scientific discipline without a large number of thoroughly executed case studies is a discipline without systematic production of exemplars, and that a discipline without  exemplars is an ineffective one. Social science may be strengthened by the execution of more...

Regionalizing Africa: Patterns of Precipitation Variability in Observations and Global Climate Models

Science.gov (United States)

Badr, Hamada S.; Dezfuli, Amin K.; Zaitchik, Benjamin F.; Peters-Lidard, Christa D.

2016-01-01

Many studies have documented dramatic climatic and environmental changes that have affected Africa over different time scales. These studies often raise questions regarding the spatial extent and regional connectivity of changes inferred from observations and proxies and/or derived from climate models. Objective regionalization offers a tool for addressing these questions. To demonstrate this potential, applications of hierarchical climate regionalizations of Africa using observations and GCM historical simulations and future projections are presented. First, Africa is regionalized based on interannual precipitation variability using Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data for the period 19812014. A number of data processing techniques and clustering algorithms are tested to ensure a robust definition of climate regions. These regionalization results highlight the seasonal and even month-to-month specificity of regional climate associations across the continent, emphasizing the need to consider time of year as well as research question when defining a coherent region for climate analysis. CHIRPS regions are then compared to those of five GCMs for the historic period, with a focus on boreal summer. Results show that some GCMs capture the climatic coherence of the Sahel and associated teleconnections in a manner that is similar to observations, while other models break the Sahel into uncorrelated subregions or produce a Sahel-like region of variability that is spatially displaced from observations. Finally, shifts in climate regions under projected twenty-first-century climate change for different GCMs and emissions pathways are examined. A projected change is found in the coherence of the Sahel, in which the western and eastern Sahel become distinct regions with different teleconnections. This pattern is most pronounced in high-emissions scenarios.

Theoretical pluralism in psychoanalytic case studies.

Science.gov (United States)

Willemsen, Jochem; Cornelis, Shana; Geerardyn, Filip M; Desmet, Mattias; Meganck, Reitske; Inslegers, Ruth; Cauwe, Joachim M B D

2015-01-01

The aim of this study is to provide an overview of the scientific activity of different psychoanalytic schools of thought in terms of the content and production of case studies published on ISI Web of Knowledge. Between March 2013 and November 2013, we contacted all case study authors included in the online archive of psychoanalytic and psychodynamic case studies (www.singlecasearchive.com) to inquire about their psychoanalytic orientation during their work with the patient. The response rate for this study was 45%. It appears that the two oldest psychoanalytic schools, Object-relations psychoanalysis and Ego psychology or "Classical psychoanalysis" dominate the literature of published case studies. However, most authors stated that they feel attached to two or more psychoanalytic schools of thought. This confirms that the theoretical pluralism in psychoanalysis stretches to the field of single case studies. The single case studies of each psychoanalytic school are described separately in terms of methodology, patient, therapist, or treatment features. We conclude that published case studies features are fairly similar across different psychoanalytic schools. The results of this study are not representative of all psychoanalytic schools, as some do not publish their work in ISI ranked journals.

Theoretical pluralism in psychoanalytic case studies

Science.gov (United States)

Willemsen, Jochem; Cornelis, Shana; Geerardyn, Filip M.; Desmet, Mattias; Meganck, Reitske; Inslegers, Ruth; Cauwe, Joachim M. B. D.

2015-01-01

The aim of this study is to provide an overview of the scientific activity of different psychoanalytic schools of thought in terms of the content and production of case studies published on ISI Web of Knowledge. Between March 2013 and November 2013, we contacted all case study authors included in the online archive of psychoanalytic and psychodynamic case studies (www.singlecasearchive.com) to inquire about their psychoanalytic orientation during their work with the patient. The response rate for this study was 45%. It appears that the two oldest psychoanalytic schools, Object-relations psychoanalysis and Ego psychology or “Classical psychoanalysis” dominate the literature of published case studies. However, most authors stated that they feel attached to two or more psychoanalytic schools of thought. This confirms that the theoretical pluralism in psychoanalysis stretches to the field of single case studies. The single case studies of each psychoanalytic school are described separately in terms of methodology, patient, therapist, or treatment features. We conclude that published case studies features are fairly similar across different psychoanalytic schools. The results of this study are not representative of all psychoanalytic schools, as some do not publish their work in ISI ranked journals. PMID:26483725

Browse Title Index

African Journals Online (AJOL)

Items 401 - 450 of 763 ... ... for Sahel precipitation modeling and predicting: Case of Mali, Abstract PDF ... Vol 9, No 3 (2015), Heavy metal content in fish and water from River ... Vol 7, No 9 (2013), Heavy metal levels in soil samples from highly ... Vol 10, No 12 (2016), Hydrogeochemical and isotopic characterization of the ...

Sexospécificités | Page 19 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

This collective work looks at the origins, examples, and consequences of the gender divide with regards to the access, use, and control of water in the Sahel. The book draws on the IDRC-funded research project, "Effectiveness of women's economic rights: the case of access to water for agricultural use in Mauritania, Niger, ...

Bioremediation case studies: Abstracts. Final report

International Nuclear Information System (INIS)

Devine, K.

1992-03-01

The report contains abstracts of 132 case studies of bioremediation technology applied to hazardous waste clean-up. It was prepared to compile bioremediation studies in a variety of locations and treating diverse contaminants, most of which were previously undocumented. All data are based on vendor-supplied information and there was no opportunity to independently confirm its accuracy. These 132 case studies, from 10 different biotechnology companies, provide users with reference information about on-going and/or completed field applications and studies. About two-thirds of the cases were at full-scale clean-up level with the remainder at pilot or laboratory scale. In 74 percent of the cases, soil was at least one of the media treated. Soil alone accounts for 46 percent of the cases. Petroleum-related wastes account for the largest contaminant with 82 cases. Thirty-one states are represented in the case studies

451 Case studies Cardiac

African Journals Online (AJOL)

Marinda

Case Studies. 29 ... A case of a 26-year-old ASA I physical status male undergoing septoplasty had an abrupt ... myocardial infarction, severe hypertensive crisis, cerebral .... or no formal management is required in an ASA I patient.8 One.

What we do | Page 106 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Poverty and land degradation are severe and interrelated problems in the Sahel. Burkina Faso, Niger, North Of Sahara, South Of Sahara. PROJECT ...

CASE STUDY

African Journals Online (AJOL)

2011-06-02

Jun 2, 2011 ... immunosuppression associated with HIV/AIDS puts them at a higher risk of developing oesophageal cancer. 47. CASE STUDY. A 49-year-old man was diagnosed as HIV infected, with a CD4 count of 60 cells/µl. He was started on an antiretroviral treatment regimen comprising zidovudine, lamivudine and ...

Phytochemical study of prickly pear from southern Morocco

Directory of Open Access Journals (Sweden)

Z. Bouzoubaâ

2016-06-01

Full Text Available This work concerns the phytochemical study of the prickly pear pulp’s fruits of two opuntia cultivars; Achefri and Amouslem widely present in two regions of southern Morocco; Arbaa Sahel and Asgherkis that are different in their altitude and annual rainfall. The results of the phytochemical study show that the levels of antioxidants have a non-significant difference between the fruits of the two sites (comparing Amouslem and Achefri in the same site, on the one hand, for the differences due to the variety or cultivar, on the other hand between Amouslem and Achefri from the two sites to show the site effect.

Casing study

Energy Technology Data Exchange (ETDEWEB)

Roche, P.

2000-12-01

An unorthodox method of casing drilling used by Tesco Corporation at a gas well in Wyoming to drill deeper using casings as drillpipe is discussed. The process involves either rotating the casing as drill string or using a downhole mud motor to rotate the bit. In this instance, the surface hole and the production hole were casing-drilled to a record 8,312 feet by rotating the casing. The 8 1/2-inch surface hole was drilled with 7-inch casing to 1,200 feet using a Tesco underreamer and a polycrystalline pilot bit; drilling and cementing was completed in 12 1/2 hours. The 6 1/4-inch production hole was drilled with 4 1/2-inch casing and the bottomhole assembly was retrieved after 191 hours rotating. This case was the first in which the entire well was casing-drilled from surface to TD. Penetration rate compared favorably with conventional methods: 12 1/2 hours for casing-drilling to 18.9 hours for conventional drilling, despite the fact that the casing-drilling technology is still in its infancy. It is suggested that casing-drilling has the potential to eliminate the need for the drillpipe entirely. If these expectations were to be realised, casing-drilling could be one of the most radical drilling changes in the history of the oil and gas industry. 1 photo.

MRI case studies

International Nuclear Information System (INIS)

Huggett, S.; Barber, J.

1989-01-01

Three case studies are presented to show the value of magnetic resonance imaging used in conjunction with other imaging techniques. In each case MRI proved a vital diagnostic tool and superior to CT in showing firstly the haematoma in a patient with aphasia and right-sided weakness, secondly the size of the disc herniation in a patient with severe leg and ankle pains and thirdly the existence of a metastatic lesion in a patient with a previous history of breast cancer. 11 figs

Qualitative Case Study Guidelines

Science.gov (United States)

2013-11-01

Introduction to Sociological Methods. 2nd ed. New York, McGraw-Hill 14. Denzin , N. K. and Lincoln , Y. S. (2011) The SAGE Handbook of Qualitative...The Art of Science. In: Denzin , N. K. and Lincoln , Y. S. (eds.) Handbook of Qualitative Research. Thousand Oaks, Sage 19. GAO (1990) Case Study...Rinehart & Winston 39. Stake, R. E. (1994) Case Studies. In: Denzin , N. K. and Lincoln , Y. S. (eds.) Handbook of Qualitative Research. Thousand Oaks, Sage

Calorific value of Prosopis africana and Balanites aegyptiaca wood: Relationships with tree growth, wood density and rainfall gradients in the West African Sahel

Energy Technology Data Exchange (ETDEWEB)

Montes, Carmen Sotelo; Weber, John C. [World Agroforestry Centre (ICRAF), Sahel Office, B.P. E 5118 Bamako (Mali); Silva, Dimas Agostinho da; Bolzon de Muniz, Graciela Ines [Universidade Federal do Parana (UFPR), Av. Lothario Meissner, 900, CEP.: 80270-170-Curitiba (Brazil); Garcia, Rosilei A. [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Instituto de Florestas, Departamento de Produtos Florestais, BR 465, km 07, 23890-000, Seropedica, Rio de Janeiro (Brazil)

2011-01-15

Prosopis africana and Balanites aegyptiaca are native tree species in the West African Sahel and provide wood for fuel, construction and other essential products. A provenance/progeny test of each species was established at one relatively dry site in Niger, and evaluated at 13 years. Gross calorific value of the wood was determined for a random sample of trees in each test: gross CV and CVm{sup 3} = gross calorific value in MJ kg{sup -1} and MJ m{sup -3}, respectively. The major objectives were to determine if gross CV was positively correlated with wood density and tree growth, and if gross CV and/or CVm{sup 3} varied with rainfall gradients in the sample region. Provenances were grouped into a drier and more humid zone, and correlations were computed among all trees and separately in each zone. Results indicated that gross CV was not significantly correlated with density in either species. Gross CV was positively correlated with growth of P. africana (but not B. aegyptiaca) only in the drier zone. Gross CVm{sup 3} was positively correlated with growth of both species, and the correlations were stronger in the drier zone. Multiple regressions with provenance latitude, longitude and elevation indicated that provenance means for gross CV increased, in general, from the drier to the more humid zones. Regressions with gross CVm{sup 3} were not significant. Results are compared with earlier research reports from the provenance/progeny tests and with other tropical hardwood species; and practical implications are presented for tree improvement and conservation programs in the region. (author)

Case Study: The Chemistry of Cocaine

Science.gov (United States)

Dewprashad, Brahmadeo

2011-01-01

This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. This month's case study focuses on the chemistry of cocaine to teach a number of core concepts in organic chemistry. It also requires that students read and analyze an original research paper on…

The role of radionuclide studies in emergency cases

International Nuclear Information System (INIS)

Nishimura, Tsunehiko; Hayashida, Kohei; Uehara, Toshiisa

1982-01-01

Radionuclide studies have been performed popularly because of its noninvasive and simple method recently. In this study, we applied this technique for the evaluation of emergency cases in cardiovascular diseases. There were 93 cases (1.5%) out of 6163 cases, done during 1981. The subjects were 34 cases of cardiac studies (9 cases of sup(99m)Tc-PYP myocardial imaging, 12 cases of thallium myocardial imaging, 13 cases of cardioangiography), 23 cases of peripheral diseases (12 cases of peripheral angiography, 11 cases of venography), 16 cases of pulmonary imaging, 10 cases of renal studies (6 cases of renal angiography, 9 cases of renal imaging) and 5 cases of brain angiography. These studies were proven to be useful clinically for the evaluation of emergency cases and follow-up studies. In the near future, ''emergency radionuclide studies'' would be benefit for the high-risk patients noninvasively. (author)

eCompetence Case Studies

DEFF Research Database (Denmark)

Jensen, Helle Bækkelund

2006-01-01

In this paper we present some details of the processes undertaken in the European eCompetence Initiative. We present two illustrative and representative case studies. The research aims to identify and understand patterns of individual and organisational eCompetence approaches.......In this paper we present some details of the processes undertaken in the European eCompetence Initiative. We present two illustrative and representative case studies. The research aims to identify and understand patterns of individual and organisational eCompetence approaches....

Case Study Methodology and Homelessness Research

Directory of Open Access Journals (Sweden)

Jill Pable

2013-10-01

Full Text Available This paper describes the potential suitability of case study methodology for inquiry with the homeless population. It references a research study that uses case study research method to build theory. This study's topic is the lived experience of destitute individuals who reside in homeless shelters, and explores the homeless shelter built environment's potential influence on resident satisfaction and recovery. Case study methodology may be appropriate because it explores real-life contextual issues that characterize homelessness and can also accommodate the wide range of homeless person demographics that make this group difficult to study in a generalized fashion. Further, case study method accommodates the need within research in this area to understand individualized treatments as a potential solution for homelessness.

Assembling a Case Study Tool Kit: 10 Tools for Teaching with Cases

Science.gov (United States)

Prud'homme-Généreux, Annie

2017-01-01

This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. The author shares the strategies and tools that teachers can use to manage a case study classroom effectively.

On misunderstandings in connection with case-studies

DEFF Research Database (Denmark)

Flyvbjerg, Bent

2005-01-01

This article examines five common misunderstandings about case-study research: (1) Theoretical knowledge is more valuable than practical knowledge; (2) One cannot generalize from a single case, therefore the single case study cannot contribute to scientific development; (3) The case study is most...

Qualitative Case Study Research as Empirical Inquiry

Science.gov (United States)

Ellinger, Andrea D.; McWhorter, Rochell

2016-01-01

This article introduces the concept of qualitative case study research as empirical inquiry. It defines and distinguishes what a case study is, the purposes, intentions, and types of case studies. It then describes how to determine if a qualitative case study is the preferred approach for conducting research. It overviews the essential steps in…

Methodology for the case studies

NARCIS (Netherlands)

Smits, M.J.W.; Woltjer, G.B.

2017-01-01

This document is about the methodology and selection of the case studies. It is meant as a guideline for the case studies, and together with the other reports in this work package can be a source of inform ation for policy officers, interest groups and researchers evaluating or performing impact

Performable Case Studies in Ethics Education.

Science.gov (United States)

Robeson, Richard; King, Nancy M P

2017-09-12

Bioethics education often includes the study of short stories, novels, plays, and films, because such materials present case examples that can highlight relevant issues and questions especially vividly for a wide range of students. In addition, creative writing is widely used in the education of health professional students and in continuing education settings for health professionals. There are very few academic or professional disciplines that do not use case studies, but the case study in dialogic form has not been standard practice for thousands of years. Dramatic arts casuistry-the creation and performance of short case studies designed specifically to raise bioethics issues for discussion-represents an application of literature and the medical humanities that is both unique and uniquely valuable. This essay describes the development and history of a course that has been successfully taught to medical students and graduate bioethics students, in which the class researches, writes, and performs a case study designed to elicit reflection and discussion about a topic and set of bioethics issues of current interest to both academic and general audiences. The model is also suited to the presentation and discussion of existing case studies, both live and via on-demand audio.

Emotion, Engagement, and Case Studies

Science.gov (United States)

Herreid, Clyde Freeman; Terry, David R.; Lemons, Paula; Armstrong, Norris; Brickman, Peggy; Ribbens, Eric

2014-01-01

Three college faculty taught large general biology classes using case studies and personal response systems (clickers). Each instructor taught the same eight cases in two different sections, except the questions within the cases differed. In one section the questions were lower order (LO) factual inquiries, and in the other they were largely…

Using Correspondence Analysis in Multiple Case Studies

NARCIS (Netherlands)

Kienstra, Natascha; van der Heijden, Peter G.M.

2015-01-01

In qualitative research of multiple case studies, Miles and Huberman proposed to summarize the separate cases in a so-called meta-matrix that consists of cases by variables. Yin discusses cross-case synthesis to study this matrix. We propose correspondence analysis (CA) as a useful tool to study

Using correspondence analysis in multiple case studies

NARCIS (Netherlands)

Kienstra, N.H.H.; van der Heijden, P.G.M.

2015-01-01

In qualitative research of multiple case studies, Miles and Huberman proposed to summarize the separate cases in a so-called meta-matrix that consists of cases by variables. Yin discusses cross-case synthesis to study this matrix. We propose correspondence analysis (CA) as a useful tool to study

Teaching Business French through Case Studies: Presentation of a Marketing Case.

Science.gov (United States)

Federico, Salvatore; Moore, Catherine

The use of case studies as a means for teaching business French is discussed. The approach is advocated because of the realism of case studies, which are based on actual occurrences. Characteristics of a good case are noted: it tells a story, focuses on interest-arousing issues, is set in the past 10 years, permits empathy with the main…

Case Study: Puttin' on the Ritz: How to Put Science into Cases

Science.gov (United States)

Herreid, Clyde Freeman

2017-01-01

There are multiple ways to put science into a case. This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. This month's issue discusses different ways of presenting science in case studies.

Direct Radiative Effect of Mineral Dust on the Middle East and North Africa Climate

KAUST Repository

Bangalath, Hamza Kunhu

2016-11-01

Dust-climate interaction over the Middle East and North Africa (MENA) has long been studied, as it is the "dustiest" region on earth. However, the quantitative and qualitative understanding of the role of dust direct radiative effect on MENA climate is still rudimentary. The present dissertation investigates dust direct radiative effect on MENA climate during summer with a special emphasis on the sensitivity of climate response to dust shortwave absorption, which is one of the most uncertain components of dust direct radiative effect. Simulations are conducted with and without dust radiative effect, to differentiate the effect of dust on climate. To elucidate the sensitivity of climate response to dust shortwave absorption, simulations with dust assume three different cases of dust shortwave absorption, representing dust as a very efficient, standard and inefficient shortwave absorber. The non-uniformly distributed dust perturb circulations at various scales. Therefore, the present study takes advantage of the high spatial resolution capabilities of an Atmospheric General Circulation Model (AGCM), High Resolution Atmospheric Model (HiRAM), which incorporates global and regional circulations. AMIP-style global high-resolution simulations are conducted at a spatial resolution of 25 km. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rainbelt across MENA strengthens and shifts northward. Similarly, the temperature under rainbelt cools and that over subtropical deserts warms. Inter-comparison of various dust shortwave absorption cases shows that the response of the MENA tropical rainbelt is extremely sensitive to the

Case Study Observational Research: A Framework for Conducting Case Study Research Where Observation Data Are the Focus.

Science.gov (United States)

Morgan, Sonya J; Pullon, Susan R H; Macdonald, Lindsay M; McKinlay, Eileen M; Gray, Ben V

2017-06-01

Case study research is a comprehensive method that incorporates multiple sources of data to provide detailed accounts of complex research phenomena in real-life contexts. However, current models of case study research do not particularly distinguish the unique contribution observation data can make. Observation methods have the potential to reach beyond other methods that rely largely or solely on self-report. This article describes the distinctive characteristics of case study observational research, a modified form of Yin's 2014 model of case study research the authors used in a study exploring interprofessional collaboration in primary care. In this approach, observation data are positioned as the central component of the research design. Case study observational research offers a promising approach for researchers in a wide range of health care settings seeking more complete understandings of complex topics, where contextual influences are of primary concern. Future research is needed to refine and evaluate the approach.

Beyond Clinical Case Studies in Psychoanalysis: A Review of Psychoanalytic Empirical Single Case Studies Published in ISI-Ranked Journals

Science.gov (United States)

Meganck, Reitske; Inslegers, Ruth; Krivzov, Juri; Notaerts, Liza

2017-01-01

Single case studies are at the origin of both theory development and research in the field of psychoanalysis and psychotherapy. While clinical case studies are the hallmark of psychoanalytic theory and practice, their scientific value has been strongly criticized. To address problems with the subjective bias of retrospective therapist reports and uncontrollability of clinical case studies, systematic approaches to investigate psychotherapy process and outcome at the level of the single case have been developed. Such empirical case studies are also able to bridge the famous gap between academic research and clinical practice as they provide clinically relevant insights into how psychotherapy works. This study presents a review of psychoanalytic empirical case studies published in ISI-ranked journals and maps the characteristics of the study, therapist, patient en therapies that are investigated. Empirical case studies increased in quantity and quality (amount of information and systematization) over time. While future studies could pay more attention to providing contextual information on therapist characteristics and informed consent considerations, the available literature provides a basis to conduct meta-studies of single cases and as such contribute to knowledge aggregation. PMID:29046660

HYDROGEOLOGIC CASE STUDIES

Science.gov (United States)

Hydrogeology is the foundation of subsurface site characterization for evaluations of monitored natural attenuation (MNA). Three case studies are presented. Examples of the potentially detrimental effects of drilling additives on ground-water samples from monitoring wells are d...

Objectivist case study research

DEFF Research Database (Denmark)

Ridder, Hanne Mette Ochsner; Fachner, Jörg

2016-01-01

be achieved through the use of objectivist case study research. The strength of the case study design is that it allows for uncovering or suggesting causal relationships in real-life settings through an intensive and rich collection of data. According to Hilliard (1993), the opposite applies for extensive......In order to comprehend the impact of music therapy or music therapy processes, a researcher might look for an approach where the topic under investigation can be understood within a broader context. This calls for a rich inclusion of data and consequently a limited number of participants and may...... designs, in which a small amount of data is gathered on a large number of subjects. With the richness of data, the intensive design is ―the primary pragmatic reason for engaging in single-case or small N research‖ (p. 374) and for working from an idiographic rather than a nomothetic perspective....

Methodology Series Module 2: Case-control Studies.

Science.gov (United States)

Setia, Maninder Singh

2016-01-01

Case-Control study design is a type of observational study. In this design, participants are selected for the study based on their outcome status. Thus, some participants have the outcome of interest (referred to as cases), whereas others do not have the outcome of interest (referred to as controls). The investigator then assesses the exposure in both these groups. The investigator should define the cases as specifically as possible. Sometimes, definition of a disease may be based on multiple criteria; thus, all these points should be explicitly stated in case definition. An important aspect of selecting a control is that they should be from the same 'study base' as that of the cases. We can select controls from a variety of groups. Some of them are: General population; relatives or friends; and hospital patients. Matching is often used in case-control control studies to ensure that the cases and controls are similar in certain characteristics, and it is a useful technique to increase the efficiency of the study. Case-Control studies can usually be conducted relatively faster and are inexpensive - particularly when compared with cohort studies (prospective). It is useful to study rare outcomes and outcomes with long latent periods. This design is not very useful to study rare exposures. Furthermore, they may also be prone to certain biases - selection bias and recall bias.

Catalog of NASA-Related Case Studies

Data.gov (United States)

National Aeronautics and Space Administration — The OCKO has developed over 50 case studies to enhance learning at workshops, training, retreats and conferences. Case studies make mission knowledge attractive and...

Njv Magazine 3 final

African Journals Online (AJOL)

En-Joy

Twenty-five adult Sahel does and two. Sahel bucks ... ovarian mesenterial attachment. Width was ..... TABLE II Variation in the amount of foetal fluid (ml), pH and Specific gravity with C-R length (cm) at. 28, 56 .... culture in Borno State. Nig. Vet.

All projects related to | Page 395 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

2009-03-29

Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Project. Poverty and land degradation are severe and interrelated problems in the Sahel. Start Date: March 29, 2009. End Date: December 3, 2013. Topic: Poverty, SMALLHOLDERS, DESERTIFICATION, SOIL DEGRADATION, SOIL RESOURCES, SOIL ...

Case Study: Let's Get Personal--Putting Personality into Your Cases

Science.gov (United States)

Herreid, Clyde Freeman

2017-01-01

In this case study, the subject for discussion is the need to use teaching notes in order to add personality to case studies. Personality, it is said, is more important than policy, than demographics, than finances, or amorous peccadillos. Personality is essential. It is the interaction of people that capture our interest, yet, the question is…

Case Study of 'moral injury' : Format Dutch Case Studies Project

NARCIS (Netherlands)

Korver, Sjaak; Walton, Martin N.; van Loenen, Guus

2017-01-01

The case study ‘Moral Injury’ traces care provided by a chaplain in a mental health institution to a former military marksman named Hans. Hans was in care at a specialized unit for military veterans with traumas. He sought contact with a chaplain “to set things right with God” and wanted the

Schematic representation of case study research designs.

Science.gov (United States)

Rosenberg, John P; Yates, Patsy M

2007-11-01

The paper is a report of a study to demonstrate how the use of schematics can provide procedural clarity and promote rigour in the conduct of case study research. Case study research is a methodologically flexible approach to research design that focuses on a particular case - whether an individual, a collective or a phenomenon of interest. It is known as the 'study of the particular' for its thorough investigation of particular, real-life situations and is gaining increased attention in nursing and social research. However, the methodological flexibility it offers can leave the novice researcher uncertain of suitable procedural steps required to ensure methodological rigour. This article provides a real example of a case study research design that utilizes schematic representation drawn from a doctoral study of the integration of health promotion principles and practices into a palliative care organization. The issues discussed are: (1) the definition and application of case study research design; (2) the application of schematics in research; (3) the procedural steps and their contribution to the maintenance of rigour; and (4) the benefits and risks of schematics in case study research. The inclusion of visual representations of design with accompanying explanatory text is recommended in reporting case study research methods.

Search Results | Page 2 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Poverty and land degradation are severe and interrelated problems in the Sahel. Land degradation reduces current agricultural productivity and is a form of "dissaving" natural capital that will affect future production and income. Project.

Peace Corps Water/Sanitation Case Studies and Analyses. Appropriate Technologies for Development. Case Study CS-4.

Science.gov (United States)

Talbert, Diana E., Comp.

This document provides an overview of Peace Corps water and sanitation activities, five case studies (Thailand, Yemen, Paraguay, Sierra Leone, and Togo), programming guidelines, and training information. Each case study includes: (1) background information on the country's geography, population, and economics; (2) information on the country's…

Five case studies of multifamily weatherization programs

Energy Technology Data Exchange (ETDEWEB)

Kinney, L; Wilson, T.; Lewis, G. [Synertech Systems Corp. (United States); MacDonald, M. [Oak Ridge National Lab., TN (United States)

1997-12-31

The multifamily case studies that are the subject of this report were conducted to provide a better understanding of the approach taken by program operators in weatherizing large buildings. Because of significant variations in building construction and energy systems across the country, five states were selected based on their high level of multifamily weatherization. This report summarizes findings from case studies conducted by multifamily weatherization operations in five cities. The case studies were conducted between January and November 1994. Each of the case studies involved extensive interviews with the staff of weatherization subgrantees conducting multifamily weatherization, the inspection of 4 to 12 buildings weatherized between 1991 and 1993, and the analysis of savings and costs. The case studies focused on innovative techniques which appear to work well.

Summary of case studies for cooperation mechanisms

DEFF Research Database (Denmark)

Longa, Francesco Dalla; Klinge Jacobsen, Henrik; Hansen, Lise-Lotte Pade

2012-01-01

This document is a summary report highlighting the main aspect analyzed in the RES4LESS case studies. The document starts with an introductory chapter where the background that led to the selection of the case studies is outlined. In the following three chapters the case studies are presented, hi...

Implementing Product Platforms: A Case Study

DEFF Research Database (Denmark)

Nielsen, Ole Fiil; Mortensen, Niels Henrik

2006-01-01

The paper describes a case study dealing with the process of creating and implementing a product platform. The paper espessially deals with the fact that to obtain the benefits of platforms a permanent change in behaviour in product development must be ensured. This change in behaviour requires...... acceptance and approval from the organisation in general and the commitment from management to enforce agreed-upon decisions. The case study itself was performed in the Danish company LEGO Group. The case study had two objectives: To create a technical architecture and align this architecture...

Location of existing Case Studies on Open Education

OpenAIRE

Burke, Siobhan

2014-01-01

Members of the Open Education Special Interest Group have collected a selection of short case studies on Open Education. View all of the case studies at http://repository.alt.ac.uk/view/divisions/CaseStudies/ Location of existing Case Studies on Open Education: The following lists aims to capture and amalgamate the various different case study sources which have been created and developed within the UK around experiences of Open Educational Resources.

national Case study

African Journals Online (AJOL)

This national case study reports on the development of a national network, ... system under the new policy), tends to be limited by content on problems and ... 20 credit programme; and within two Post Graduate Certificate of Education contexts, ...... descriptive with an issues focus (empirical) towards awareness production to.

Writing case studies in information systems research

NARCIS (Netherlands)

van der Blonk, H.C.

Case study research can be reported in different ways. This paper explores the various ways in which researchers may choose to write down their case studies and then introduces a subsequent typology of writing case studies. The typology is based on a 2 x 2 matrix, resulting in four forms of writing

Search Results | Page 8 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 71 - 80 of 138 ... Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). In the Sahel, agricultural production is strictly limited by drought and low soil fertility. In 2005 and 2010, these two factors led to food scarcity in Niger. Project.

All projects related to Canada | Page 10 | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

2011-03-01

Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). Project. In the Sahel, agricultural production is strictly limited by drought and low soil fertility. Start Date: March 1, 2011. End Date: September 1, 2014. Topic: FOOD CROPS, SOIL FERTILITY, FERTILIZERS, FERTILIZING, ...

Remote sensing of the biosphere; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

Science.gov (United States)

Smith, James A. (Editor)

1990-01-01

The global context and monitoring of the biological aspects relevant to the EOS program are addressed, the large-scale regional field experiments required to understand ecosystem functioning in more detail and to calibrate the application of remote-sensing techniques for extracting flux and state information are covered, and sensors of the proposed EOS platform are discussed. Attention is given to terrestrial productivity, both tropical-forest and semiarid environments, coastal environments, and global oceanic productivity. Focus is placed on the First International Field Experiment (FIFE) in Kansas, the HAPEX field experiment in France, the ABLE-2 experiment in the Amazon, and the Forest Ecosystem Study in Maine. The proposed electro-optical instruments for EOS including both MODIS-N and MODIS-T, the AIRS and MISR instruments, the ITIR, and ERBE calibration issues are considered.

The Danish National Case Study Report

DEFF Research Database (Denmark)

Brodersen, Søsser; Jørgensen, Michael Søgaard

Three case studies from Danish science shops within the environmental field are analysed with respect to societal background, interaction between the involved actors and the societal impact of the co-operation. The report is one of the seven national case study reports from the EU...

Using Case Studies in Calculus-based Physics

Science.gov (United States)

Katz, Debora M.

2006-12-01

Do your students believe that the physics only works in your classroom or laboratory? Or do they see that physics underlies their everyday experience? Case studies in physics help students connect physics principles to their everyday experience. For decades, case studies have been used to teach law, medicine and biology, but they are rarely used in physics. I am working on a calculus-based physics textbook for scientists and engineers. Case studies are woven into each chapter. Stop by and get a case study to test out in your classroom. I would love to get your feedback.

Modalities of Generalization Through Single Case Studies.

Science.gov (United States)

Zittoun, Tania

2017-06-01

The value of case studies for theory building is still doubted in psychology. The paper argues for the importance of case studies and the possibility of generalizing from these for a specific sociocultural understanding of human development. The paper first clarifies the notion of abduction within case studies, drawing on pragmatists James and Peirce and expanding it with the work of Lewin, and argues that it is the core mechanism that allows generalization from case studies. The second section presents the possibility of generalizing from individual single case studies, for which not only the subjective perspective, but also the dynamics by which the social and cultural environment guide and enable the person's development, have to be accounted for. The third section elaborates the question of institutional case studies, where the challenge is to account both for institutional dynamics, and for persons' trajectories within; this is exemplified with an ongoing study on the process of obtaining citizenship in Switzerland. The paper briefly concludes by highlighting two possible implications of the paper, one concerning the process of theoretical reasoning, the other, the fact that sociocultural psychology could itself be seen as an institution in-the-making.

Implementation of case studies in undergraduate didactic nursing courses: a qualitative study.

Science.gov (United States)

Dutra, Danette K

2013-07-04

The implementation of unfolding scenario-based case studies in the didactic classroom is associated with learner-centered education. The utilization of learner-centered pedagogies, such as case studies, removes the focus from the instructor and instead places it on the student. Learner-centered pedagogies are believed to improve students' levels of cognition. The purpose of this study was to examine how nurse educators are implementing the pedagogies of case studies in their undergraduate didactic courses. The goal was to examine, document, report, and, ultimately, implement the strategies. Purposeful sampling was utilized in this qualitative, multisite-designed study. For each of the four participants, three separate site visits were completed. Observations and post-observational interviews took place at each site visit. Transcribed data from interviews, observations, and course documents were imported into the computer program Nvivo8. Repetitive comparative analysis was utilized to complete the data coding process. The guiding research question of this study sought to investigate the implementation strategies of case studies in didactic nursing courses. The implementation of case studies by the participants reflected two primary patterns: Formal Implementation (FI) and Informal Implementation (II) of case studies. The FI of case studies was further divided into two subcategories: Formal Implementation of case studies used Inside the Classroom setting (FIIC) and Formal Implementation of cases studies used Outside of the Classroom (FIOC). Results of this investigation have led to an increased understanding of implementation strategies of unfolding scenario-based case studies in undergraduate nursing didactic courses. Data collected were rich in the description of specific methodologies for utilization of case studies and may serve as a resource for faculty in development of creative strategies to enhance the didactic classroom experience.

All projects related to | Page 290 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Region: Burkina Faso, Benin, Mali, Niger, North of Sahara, South of Sahara, Canada. Program: Agriculture and Food Security. Total Funding: CA$ 1,675,091.00. Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). Project. In the Sahel, agricultural production is strictly limited ...

Integrated Nutrient and Water Management for Sustainable Food ...

International Development Research Centre (IDRC) Digital Library (Canada)

Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). In the Sahel, agricultural production is strictly limited by drought and low soil fertility. In 2005 and 2010, these two factors led to food scarcity in Niger. However, innovative technologies such as microdose fertilization ...

CTC Sentinel. Volume 5, Issue 2, February 2012

Science.gov (United States)

2012-02-01

Los Zetas grew independent of the Gulf Cartel, the organization was at a disadvantage because it did not have contacts in Colombia or other...Terrorism in North Africa and the Sahel: Al-Qaida’s Franchise or Freelance,” Middle East Institute, August 201; “Islamist Terrorism in the Sahel

Using Case Studies to Enrich Field Experience.

Science.gov (United States)

Florio-Ruane, Susan; Clark, Christopher M.

1990-01-01

This paper discusses the use of field experience in teacher education and how it can be augmented by phenomenological case studies. It summarizes a particular case study involving three teacher education classes, noting that reflective analysis of cases can prepare students to observe in the field. (SM)

Using Case Studies to Teach About Global Issues, Bali: A Case Study

Science.gov (United States)

Oswald, James M.

1974-01-01

The South Pacific island of Bali is used as a case study of overpopulation and food shortage. A brief description of the resources, the typical lifestyle of the Balinese farmer, and possible teaching techniques are given. (DE)

Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls.

Science.gov (United States)

Verani, Jennifer R; Baqui, Abdullah H; Broome, Claire V; Cherian, Thomas; Cohen, Cheryl; Farrar, Jennifer L; Feikin, Daniel R; Groome, Michelle J; Hajjeh, Rana A; Johnson, Hope L; Madhi, Shabir A; Mulholland, Kim; O'Brien, Katherine L; Parashar, Umesh D; Patel, Manish M; Rodrigues, Laura C; Santosham, Mathuram; Scott, J Anthony; Smith, Peter G; Sommerfelt, Halvor; Tate, Jacqueline E; Victor, J Chris; Whitney, Cynthia G; Zaidi, Anita K; Zell, Elizabeth R

2017-06-05

Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide policy-relevant data on vaccine performance under 'real world' conditions, contributing to the evidence base to support and sustain introduction of new vaccines. However, case-control studies do not measure the impact of vaccine introduction on disease at a population level, and are subject to bias and confounding, which may lead to inaccurate results that can misinform policy decisions. In 2012, a group of experts met to review recent experience with case-control studies evaluating the effectiveness of several vaccines; here we summarize the recommendations of that group regarding best practices for planning, design and enrollment of cases and controls. Rigorous planning and preparation should focus on understanding the study context including healthcare-seeking and vaccination practices. Case-control vaccine effectiveness studies are best carried out soon after vaccine introduction because high coverage creates strong potential for confounding. Endpoints specific to the vaccine target are preferable to non-specific clinical syndromes since the proportion of non-specific outcomes preventable through vaccination may vary over time and place, leading to potentially confusing results. Controls should be representative of the source population from which cases arise, and are generally recruited from the community or health facilities where cases are enrolled. Matching of controls to cases for potential confounding factors is commonly used, although should be reserved for a limited number of key variables believed to be linked to both vaccination and disease. Case-control vaccine effectiveness studies can provide information useful to guide policy decisions and vaccine development, however rigorous preparation and design is essential. Published by Elsevier Ltd.

Septic Systems Case Studies

Science.gov (United States)

A collection of septic systems case studies to help community planners, elected officials, health department staff, state officials, and interested citizens explore alternatives for managing their decentralized wastewater treatment systems.

Can Old Regimes Handle New Wars?

DEFF Research Database (Denmark)

Henningsen, Troels

Research on New Wars argues that since the 1980s states and regimes have become more vulnerable to violence from non-state actors. Two developments in the Sahel region support the New Wars thesis: an increase in Islamist radicalization and new access to the global black market, both of which......, the paper finds that regimes in the Sahel region are still able to cope with the rise in non-state threats. The paper first shortly compares the longevity of the present regimes in the Sahel region to all previous ones, second examines in-depth how Chad and Mali fight the insurgents. Findings are that since...

Contextualising case studies in entrepreneurship: A tandem approach to conducting a longitudinal cross-country case study

DEFF Research Database (Denmark)

Chetty, S. K.; Partanen, J.; Rasmussen, Erik Stavnsager

2014-01-01

Using predictive and effectuation logics as a framework, this research note explains how case study research was conducted to demonstrate rigour and relevance. The study involves a longitudinal cross-country case study on small and medium-sized firm growth and networks undertaken by research teams...... in three countries (Finland, Denmark and New Zealand) involving 33 firms. This research note outlines the implications of this research and provides valuable guidance and reflections upon opportunities for future research regarding the conduct of contextual studies in entrepreneurship without compromising...

Case Study Research: Foundations and Methodological Orientations

Directory of Open Access Journals (Sweden)

Helena Harrison

2017-01-01

Full Text Available Over the last forty years, case study research has undergone substantial methodological development. This evolution has resulted in a pragmatic, flexible research approach, capable of providing comprehensive in-depth understanding of a diverse range of issues across a number of disciplines. Change and progress have stemmed from parallel influences of historical transformations in approaches to research and individual researcher's preferences, perspectives, and interpretations of this design. Researchers who have contributed to the development of case study research come from diverse disciplines with different philosophical perspectives, resulting in a variety of definitions and approaches. For the researcher new to using case study, such variety can create a confusing platform for its application. In this article, we explore the evolution of case study research, discuss methodological variations, and summarize key elements with the aim of providing guidance on the available options for researchers wanting to use case study in their work. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs1701195

Maxillofacial and mandibular phenotypes in the skulls of red Sokoto ...

African Journals Online (AJOL)

This work examined phenotypic expressions in the anatomy of the mandible and maxillofacial region of the Red Sokoto and Sahel goats in Nigeria. The infraorbital foramen was placed above premolar two (PM2) in Red Sokoto but above premolar one (PM1) in Sahel. The Red Sokoto displayed interdigital septa (ruggae) ...

Case studies on age-management in organisations: report on organisational case studies

NARCIS (Netherlands)

Punte, E.; Conen, W.S.; Schippers, J.; Henkens, C.J.I.M.

2011-01-01

The acquisition of case studies was thwarted by the economic crisis and the feeling of being ‘over-researched’ by potential organisations. Although organisations in some sectors (e.g. chemical manufacturing) reported the worst part of the economic crisis was behind, many organisations indicated

Case Study: What Makes a Good Case, Revisited: The Survey Monkey Tells All

Science.gov (United States)

Herried, Clyde Freeman; Prud'homme-Genereux, Annie; Schiller, Nancy A.; Herreid, Ky F.; Wright, Carolyn

2016-01-01

This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. In this month's issue the authors provide a more definitive answer to the "What Makes a Good Case?" question based on a just-completed Survey Monkey survey given to NCCSTS teachers.

Associative visual agnosia: a case study.

Science.gov (United States)

Charnallet, A; Carbonnel, S; David, D; Moreaud, O

2008-01-01

We report a case of massive associative visual agnosia. In the light of current theories of identification and semantic knowledge organization, a deficit involving both levels of structural description system and visual semantics must be assumed to explain the case. We suggest, in line with a previous case study, an alternative account in the framework of (non abstractive) episodic models of memory.

Case Study on Logistics Performance

Directory of Open Access Journals (Sweden)

Shahryar Sorooshian

2013-05-01

Full Text Available The paper presents research carried out at a medium‐size manufacturing organization in east Asia. The study tries to highlight the importance of supply chain management; specifically, our aim for this study is to understand logistics and performance measurement in the logistics and supply chain, and we include a theoretical discussion of online data collected and a case study of the logistic performance of a real organization. The study also examines the performance of the selected company, identifies the problems and provides recommendations for improvements. This study can be a guide for business advisers and those interested in analysing company performance, especially from a logistics viewpoint. We also suggest the methodology of this case study for those who want to have a better understanding of a business environment before starting their own business, or for benchmarking practice during strategic planning.

CASE STUDY

African Journals Online (AJOL)

HIV infection has several oral manifestations, including oral candidiasis and oral hairy leucoplakia. Occasionally unusual presentations requiring rigorous investigations are seen, and in these cases the diagnosis sometimes remains a dilemma owing to limited investigation facilities.1-3 We present the case of a patient who.

A Psychobiographical Case Study

African Journals Online (AJOL)

man, and cancer fighter. This psychobiographical case study entailed a psychosocial-historical ... does not draw more attention as a research method, as this approach has .... of the applied Levinsonian theory to the life of Jobs against the ...

Associative Visual Agnosia: A Case Study

Directory of Open Access Journals (Sweden)

A. Charnallet

2008-01-01

Full Text Available We report a case of massive associative visual agnosia. In the light of current theories of identification and semantic knowledge organization, a deficit involving both levels of structural description system and visual semantics must be assumed to explain the case. We suggest, in line with a previous case study [1], an alternative account in the framework of (non abstractive episodic models of memory [4].

Associative Visual Agnosia: A Case Study

OpenAIRE

Charnallet, A.; Carbonnel, S.; David, D.; Moreaud, O.

2008-01-01

We report a case of massive associative visual agnosia. In the light of current theories of identification and semantic knowledge organization, a deficit involving both levels of structural description system and visual semantics must be assumed to explain the case. We suggest, in line with a previous case study [1], an alternative account in the framework of (non abstractive) episodic models of memory [4].

Environmental change in the Sahel

DEFF Research Database (Denmark)

Rasmussen, Kjeld; D'haen, Sarah Ann Lise; Fensholt, Rasmus

2016-01-01

and choice of indicators, (2) biases, for example, related to selection of study sites, methodological choices, measurement accuracy, perceptions among interlocutors, and selection of temporal and spatial scales of analysis. The analysis of the root causes for different interpretations suggests...... that differences in findings could often be considered as complementary insights rather than mutually exclusive. This will have implications for the ways in which scientific results can be expected to support regional environmental policies and contribute to knowledge production....

Nanomaterial Case Studies: Nanoscale Titanium Dioxide ...

Science.gov (United States)

This draft document presents two case studies of nanoscale titanium dioxide (nano-TiO2) used (1) to remove arsenic from drinking water and (2) as an active ingredient in topical sunscreen. The draft case studies are organized around a comprehensive environmental assessment approach that combines a product life cycle framework with the risk assessment paradigm. The document does not draw conclusions about potential risks. Rather, the case studies are intended to help identify what needs to be known in order to conduct a comprehensive environmental assessment of the potential risks related to nano-TiO2. This draft document is part of a process that will inform the development of EPA’s research strategy to support nanomaterial risk assessments. The complex properties of various nanomaterials make evaluating them in the abstract or with generalizations difficult if not impossible. Thus, this document focuses on two specific uses of nano-TiO2, as a drinking water treatment and as topical sunscreen. These case studies do not represent completed or even preliminary assessments; rather, they present the structure for identifying and prioritizing research needed to support future assessments.

Case-control studies in diabetes. Do they really use a case-control design?

Science.gov (United States)

Ramos, Analía; Mendoza, Lilian Cristina; Rabasa, Fernanda; Bolíbar, Ignasi; Puig, Teresa; Corcoy, Rosa

2017-07-01

Studies defined as case-control do not always use this design. We aimed to estimate the frequency of mislabelled case-control studies in published articles in the area of diabetes and to identify the predictors of incorrect labelling. We searched Medline and Web of Science for articles with "diabetes" and "case control" in title and filtered for language (English/Romance) and period (January 2010-December 2014). Inclusion criteria were: (1) statement to use a case-control design in title, (2) to be a final full-length publication and (3) to have original data in the area of diabetes. Three independent reviewers went through titles, looked for full texts and reviewed them. Discrepancies were settled with a fourth reviewer. Expert epidemiologist advice was requested in case of doubt. case-control mislabelling; addressed predictors: publication year, journal impact factor and journal subject. proportion of mislabelled CC articles and assessment of predictors by multivariate logistic regression analysis. We retrieved 362 articles, 251 of them fulfilling inclusion criteria. The proportion of mislabelled CC studies was 43.8% (confidence interval 95% 37.7-50.0%). Most mislabelled studies had a cross-sectional design (82.7%). Predictors of mislabelling were publication year, journal impact factor and journal area. A relevant subset of studies defined as case-control in the area of diabetes correspond to mislabelled cross-sectional studies. Incorrect labelling misleads readers regarding the interpretation of results and the cause-effect hypothesis. Researchers, reviewers and editors should be aware of and commit to settle this issue.

Educational Potential of Case-Study Technology

OpenAIRE

Fedorinova, Zoya; Vorobeva, Victoria; Malyanova, Marina

2015-01-01

This article presents the results of phenomenological and typological analysis of case-study technology educational potential. The definition “educational potential of case-study technology” is given, the main characteristics of which are changed in communication and collaborative activity quality, appearance of educational initiatives, change of participants’ position in learning process, formation of “collective subject” in collaborative activity, increase of learning (subject) results. Dep...

Case Studies - Cervical Cancer

Centers for Disease Control (CDC) Podcasts

Dr. Alan Waxman, a professor of obstetrics and gynecology at the University of New Mexico and chair of the American College of Obstetricians and Gynecologists (ACOG) committee for the underserved, talks about several case studies for cervical cancer screening and management.

Nuclear forensics case studies

International Nuclear Information System (INIS)

Fedchenko, Vitaly

2016-01-01

The objective of this presentation is to share three case studies from the Institute of Transuranium Elements (ITU) which describe the application of nuclear forensics to events where nuclear and other radioactive material was found to be out of regulatory control

South of Sahara | Page 105 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

South of Sahara. Sud du Sahara. Read more about Droit des femmes à l'eau à usage agricole au Sahel (Mauritanie, Niger, Sénégal). Language French. Read more about Women's Right to Water for Agricultural Use in the Sahel (Mauritanie, Niger, Sénégal). Language English. Read more about Because Gender Matters ...

Search Results | Page 2 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 11 - 20 of 58 ... Spatial fields' dispersion as a farmer strategy to reduce agro-climatic risk at the household level in pearl millet-based systems in the Sahel : a modeling perspective. The rainfall pattern in the Sahel is very erratic with a high spatial variability.Wetested the often reported hypothesis that the dispersion of ...

South of Sahara | Page 105 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

South of Sahara. Sud du Sahara. Read more about Étude de la dynamique de la pauvreté et de la dégradation des sols au Sahel, en Afrique de l'Ouest. Language French. Read more about Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Language English. Read more about Passage à grande ...

Case study - Czechoslovakia

International Nuclear Information System (INIS)

Kovar, P.

1986-01-01

In the lecture Case Study - Czechoslovakia with the sub-title 'Unified System of Personnel Preparation for Nuclear Programme in Czechoslovakia' the actual status and the current experience of NPP personnel training and preparation in Czechoslovakia are introduced. The above mentioned training system is presented and demonstrated by the story of a proxy person who is going to become shift engineer in a nuclear power plant in Czechoslovakia. (orig./HP)

What are the prospects for intensifying soil fertility management in the Sahel? A case study from Sanmatenga, Burkina Faso

OpenAIRE

Elshout, S.; Sandwidi, B.; É. Ouédraogo; Kaboré, R.; Tapsoba, G.

2001-01-01

Metadata only record This paper discusses the results of a soil fertility management programme that was part of an integrated rural development project, and carried out as part of the pre-implementation phase of the soil fertility action plan (developed by the Burkina Faso government). It analyses the soil fertility management practices of a sample of 40 farming families that participated in project activities in 1998 and 1999.

Using Case Studies to Teach Courtesy Strategies.

Science.gov (United States)

Moore, Patrick

1990-01-01

Explains some courtesy techniques that technical professionals can use to deal with interpersonal problems that arise in writing situations. Presents three case studies with sample responses to show how case studies can teach these courtesy strategies to technical writing students. (MM)

Patterned genital injury in cases of rape - A case-control study

DEFF Research Database (Denmark)

Astrup, Birgitte Schmidt; Ravn, Pernille; Thomsen, Jørgen Lange

2013-01-01

A pattern of genital injury that separates trauma seen in sexual assault cases from trauma seen following consensual sexual intercourse has been a matter of debate. This study aimed at clarifying the question by eliminating as many confounders as possible in a prospective, case-control setup. A t...

Mathematical modelling with case studies using Maple and Matlab

CERN Document Server

Barnes, B

2014-01-01

Introduction to Mathematical ModelingMathematical models An overview of the book Some modeling approaches Modeling for decision makingCompartmental Models Introduction Exponential decay and radioactivity Case study: detecting art forgeries Case study: Pacific rats colonize New Zealand Lake pollution models Case study: Lake Burley Griffin Drug assimilation into the blood Case study: dull, dizzy, or dead? Cascades of compartments First-order linear DEs Equilibrium points and stability Case study: money, money, money makes the world go aroundModels of Single PopulationsExponential growth Density-

Making a case for case studies in psychotherapy training

DEFF Research Database (Denmark)

Mackrill, Thomas Edward; Iwakabe, Shigeru

2013-01-01

articulated explicitly or researched systematically in spite of its cardinal importance. An analysis of the role of case studies in psychotherapy training is presented. Reading, watching, or hearing about cases can offer novice psychotherapists access to a closed world; access to psychological theory...... in action; access to whole courses of therapy; access to different approaches; access to significant moments; access to the therapeutic relationship; access to a wide range of client types; access to working in different contexts; and the opportunity of identifying with therapists and clients. Writing...

Towards More Case Study Research in Entrepreneurship

Directory of Open Access Journals (Sweden)

Tom Duxbury

2012-03-01

Full Text Available Entrepreneurship as an emerging discipline has made good strides, but according to some, has fallen short of bringing its theory and literature up to the standards of others in the management sciences. Rich with the descriptive detail needed for insightful theory building in entrepreneurship, scholars have called for more case study research, particularly those incorporating non-retrospective and longitudinal observations. At the same time however, it has become rare to find such research published in A-level journals dedicated to entrepreneurship. A survey presented here of major entrepreneurship journals over the past six years revealed a publication rate of only 3% using the case study method. This presents a major impediment for developing fresh research in this field based upon the study of real cases. The author explores how the case study method has been applied to entrepreneurship research and provides recommendations for improved publication rates.

Identification of Ambiguity in the Case Study Research Typology

DEFF Research Database (Denmark)

Grünbaum, Niels Nolsøe

2015-01-01

. Relevant to varied levels and scales of case study use, the aim of this collection is to provide readers with a comprehensive overview of where we are now with case study research, so that they may better judge their own applications of the case study. From definitions to interdisciplinary methods......The purpose of this four volume collection is to provide an accessible selection of the best writing on case study in the English language internationally. Such a collection is timely and highly relevant to students, researchers and academics in higher education, especially when the case......, this set will address the practical case study by offering a structured selection of some of the best modern and classic writing on the case study in article form, together with a synoptic editorial introduction and overview of the field of research....

Present status and problems of radionuclide studies in emergency cases

International Nuclear Information System (INIS)

Ogawa, Kiyoshi

1983-01-01

Scintigraphy is just right for diagnosing emergency cases due to its noninvasive and simple method, but emergency radionuclide studies have not become practical as a result of difficulty problems. Recently, nuclear medical devices have become easier to use in operations. It is become of this, that I have submitted this report regarding the problems of radionuclide studies in emergency cases. There were 101 cases (1.4 %) out of 7,310 cases for the year period Sept. 1981 - Aug. 1982. The studies consisted of 12 brain imaging cases, 9 plumonary imaging cases, 22 cardiac study cases (cardio-angiography cases 8, 99m-Tc-PYP myocardium imaging cases 12, 201-Tl myocardium imaging cases 2), 12 renal study cases, 11 G.I. blood loss cases, 35 peripheral angiography cases. In the near future, we will have to be ready to perform emergency radionuclide studies if the need arises. (author)

SCA12 case study

Indian Academy of Sciences (India)

Home; Journals; Journal of Genetics; Volume 88; Issue 1. Utilizing linkage disequilibrium information from Indian Genome Variation Database for mapping mutations: SCA12 case study. Samira Bahl Ikhlak Ahmed The Indian Genome Variation Consortium Mitali Mukerji. Research Article Volume 88 Issue 1 April 2009 pp 55- ...

Deep Attack Weapons Mix Study (DAWMS) Case Study

National Research Council Canada - National Science Library

Bexfield, James

2001-01-01

.... This report describes the process used to conduct the Deep Attack Weapons Mix Study (DAWMS) in 1995-1997. This case study focuses on the weapons being procured by the Services and whether a joint viewpoint would result in a more effective mix...

Reverse logistics: A review of case studies

NARCIS (Netherlands)

Brito, de M.P.; Dekker, Rommert; Flapper, S.D.P.; Fleischmann, B.; Klose, A.

2004-01-01

This paper gives an overview of scientific literature that describes and discusses cases of reverse logistics activities in practice. Over sixty case studies are considered. Based on these studies we are able to indicate critical factors for the practice of reverse logistics. In addition we compare

Reverse case study: to think like a nurse.

Science.gov (United States)

Beyer, Deborah A

2011-01-01

Reverse case study is a collaborative, innovative, active learning strategy that nurse educators can use in the classroom. Groups of students develop a case study and a care plan from a list of medications and a short two- to three-sentence scenario. The students apply the nursing process to thoroughly develop a complete case study written as a concept map. The strategy builds on previous learned information and applies the information to new content, thus promoting critical thinking and problem solving. Reverse case study has been used in both associate and baccalaureate nursing degree theory courses to generate discussion and assist students in thinking like a nurse. 2011, SLACK Incorporated.

Case Study - Alpha

Directory of Open Access Journals (Sweden)

Stephen Leybourne

2016-11-01

Full Text Available This case study was developed from an actual scenario by Dr. Steve Leybourne of Boston University.  The case documents the historical evolution of an organization, and has been used successfully in courses dealing with organizational and cultural change, and the utilization of ‘soft skills’ in project-based management. This is a short case, ideal for classroom use and discussion.  The issues are easily accessible to students, and there is a single wide ranging question that allows for the inclusion of many issues surrounding strategic decision-making, and behavioural and cultural change. Alpha was one of the earlier companies in the USA to invest in large, edge-of-town superstores, with plentiful free vehicle parking, selling food and related household products. Alpha was created in the 1950s as a subsidiary of a major publicly quoted retail group.  It started business by opening a string of very large discount stores in converted industrial and warehouse premises in the south of the United States. In the early days shoppers were offered a limited range of very competitively priced products. When Alpha went public in 1981 it was the fourth largest food retailer in the US, selling an ever-widening range of food and non-food products.  Its success continued to be based on high volume, low margins and good value for money, under the slogan of ‘Alpha Price.’

The Effect of Using Case Studies in Business Statistics

Science.gov (United States)

Pariseau, Susan E.; Kezim, Boualem

2007-01-01

The authors evaluated the effect on learning of using case studies in business statistics courses. The authors divided students into 3 groups: a control group, a group that completed 1 case study, and a group that completed 3 case studies. Results evidenced that, on average, students whom the authors required to complete a case analysis received…

CAREM X INPRO case study

International Nuclear Information System (INIS)

Florido, P.C.; Brasnarof, D.; Delmastro, D.; Azpitarte, O.E.

2004-01-01

In order to assess and compare the performance of innovative nuclear energy systems INPRO has defined a set of basic principles, user requirements and criteria to be met in different areas (economics, sustainability and environment, safety, waste management and proliferation). This paper illustrates the use of INPRO methodology to a particular reactor system. Argentina is performing CAREM X Nuclear System Case Study based on CAREM nuclear reactor and Once Through Fuel Cycle, using SIGMA for enriched uranium production, and a deep geological repository for final disposal of high level waste after surface intermediate storage in horizontal natural convection silos, to verify INPRO (International Project on Innovative Nuclear Reactors and Fuel Cycles) methodology. 6 aspects have been considered: 1) enrichment based on Sigma enrichment plant (gas diffusion technology), 2) conversion to UO 2 , 3) fuel manufacturing, 4) CAREM-300 based reactor technology, 5) intermediate spent fuel storage, and 6) deep geological repository of spent fuels. Projections show that developing countries could play a crucial role in the deployment of nuclear energy, in the next fifty years. This case study will be highly useful for checking INPRO methodology for this scenario. In this paper, the preliminary findings of the Case Study are presented, including proposals to improve the INPRO methodology

A Case Study of "Empathetic Teaching Artistry"

Science.gov (United States)

Risner, Doug

2014-01-01

This case study is one of twenty cases derived from Anderson and Risner's international study of teaching artists in dance, and theatre, which investigated participants' (n=172) artistic and academic preparation in dance, and theatre, initial entry into the teaching artist field, rewards, challenges, and obstacles in participants' work, artists'…

Study on Case Teaching of Financial Management

Science.gov (United States)

Che, Zhenghong; Che, Zhengmei

2011-01-01

Case teaching is an efficient teaching method of management. It plays an important role to enhance the students' ability to practice the theory. However, case teaching of financial management has not achieved the expected results. The paper aims to study the importance, characteristics and corresponding methods of case teaching method of financial…

Case studies in atomic collision physics

CERN Document Server

McDaniel, E W

1974-01-01

Case Studies in Atomic Physics III focuses on case studies on atomic and molecular physics, including atomic collisions, transport properties of electrons, ions, molecules, and photons, interaction potentials, spectroscopy, and surface phenomena. The selection first discusses detailed balancing in the time-dependent impact parameter method, as well as time-reversal in the impact parameter method and coupled state approximation. The text also examines the mechanisms of electron production in ion. Topics include measurement of doubly differential cross sections and electron spectra, direct Coul

Music in context : Four case studies

NARCIS (Netherlands)

Randwijck, R.J.C. van

2008-01-01

In his thesis entitled “Music in Context. Four Case Studies”, R.J.C. van Randwijck investigates the context in which music has been created. It is a search in Four Case Studies, approaching four pieces of music from the context in which they were written in order to understand their meaning. The

Theory Testing Using Case Studies

DEFF Research Database (Denmark)

Sørensen, Pernille Dissing; Løkke, Ann-Kristina

2006-01-01

design. Finally, we discuss the epistemological logic, i.e., the value to larger research programmes, of such studies and, following Lakatos, conclude that the value of theory-testing case studies lies beyond naïve falsification and in their contribution to developing research programmes in a progressive...

Rigour in qualitative case-study research.

Science.gov (United States)

Houghton, Catherine; Casey, Dympna; Shaw, David; Murphy, Kathy

2013-03-01

To provide examples of a qualitative multiple case study to illustrate the specific strategies that can be used to ensure the credibility, dependability, confirmability and transferability of a study. There is increasing recognition of the valuable contribution qualitative research can make to nursing knowledge. However, it is important that the research is conducted in a rigorous manner and that this is demonstrated in the final research report. A multiple case study that explored the role of the clinical skills laboratory in preparing students for the real world of practice. Multiple sources of evidence were collected: semi-structured interviews (n=58), non-participant observations at five sites and documentary sources. Strategies to ensure the rigour of this research were prolonged engagement and persistent observation, triangulation, peer debriefing, member checking, audit trail, reflexivity, and thick descriptions. Practical examples of how these strategies can be implemented are provided to guide researchers interested in conducting rigorous case study research. While the flexible nature of qualitative research should be embraced, strategies to ensure rigour must be in place.

Variability and Predictability of West African Droughts. A Review in the Role of Sea Surface Temperature Anomalies

Science.gov (United States)

Rodriguez-Fonseca, Belen; Mohino, Elsa; Mechoso, Carlos R.; Caminade, Cyril; Biasutti, Michela; Gaetani, Marco; Garcia-Serrano, J.; Vizy, Edward K.; Cook, Kerry; Xue, Yongkang;

Guidelines for Conducting Positivist Case Study Research in Information Systems

Directory of Open Access Journals (Sweden)

Graeme Shanks

2002-11-01

Full Text Available The case study research approach is widely used in a number of different ways within the information systems community. This paper focuses on positivist, deductive case study research in information systems. It provides clear definitions of important concepts in positivist case study research and illustrates these with an example research study. A critical analysis of the conduct and outcomes of two recently published positivist case studies is reported. One is a multiple case study that validated concepts in a framework for viewpoint development in requirements definition. The other is a single case study that examined the role of social enablers in enterprise resource planning systems implementation. A number of guidelines for successfully undertaking positivist case study research are identified including developing a clear understanding of key concepts and assumptions within the positivist paradigm; providing clear and unambiguous definitions of the units and interactions when using any theory; carefully defining the boundary of the theory used in the case study; using hypotheses rather than propositions in the empirical testing of theory; using fuzzy or probabilistic propositions in recognising that reality can never be perfectly known; selecting case studies carefully, particularly single case studies; and recognising that generalisation from positivist, single case studies is inherently different from generalisation from single experiments. When properly undertaken, positivist, deductive case study research is a valuable research approach for information systems researchers, particularly when used within pluralist research programs that use a number of different research approaches from different paradigms.

Lateral extrusion of Tunisia : Contribution of Jeffara Fault (southern branch) and Petroleum Implications

Science.gov (United States)

Ghedhoui, R.; Deffontaines, B.; Rabia, M. C.

2012-04-01

Contrasting to the northward African plate motion toward Eurasia and due to its geographic position in the North African margin, since early cretaceous, Tunisia seems to be submitted to an eastward migration. The aim of this work is to study the southern branch of this inferred tectonic splay that may guide the Tunisian extrusion characterised to the east by the Mediterranean sea as a free eastern boundary. The Jeffara Fault zone (southern Tunisia), represent a case example of such deformation faced by Tunisia. Helped by the results of previous researchers (Bouaziz, 1995 ; Rabiaa, 1998 ; Touati et Rodgers, 1998 ; Sokoutis D. et al., 2000 ; Bouaziz et al., 2002 ; Jallouli et al., 2005 ; Deffontaines et al., 2008…), and new evidences developed in this study, we propose a geodynamic Tunisian east extrusion model, due to such the northern African plate migration to the Eurasian one. In this subject, structural geomorphology is undertaken herein based on both geomorphometric drainage network analysis (Deffontaines et al., 1990), the Digital Terrain Model photo-interpretation (SRTM) combined with photo-interpretation of detailed optical images (Landsat ETM+), and confirmed by field work and numerous seismic profiles at depth. All these informations were then integrated within a GIS (Geodatabase) (Deffontaines 1990 ; Deffontaines et al. 1994 ; Deffontaines, 2000 ; Slama, 2008 ; Deffontaines, 2008) and are coherent with the eastern extrusion of the Sahel block. We infer that the NW-SE Gafsa-Tozeur, which continue to the Jeffara major fault zone acting as a transtensive right lateral motion since early cretaceous is the southern branch of the Sahel block extrusion. Our structural analyses prove the presence of NW-SE right lateral en-echelon tension gashes, NW-SE aligned salt diapirs, numerous folds offsets, en-echelon folds, and so on that parallel this major NW-SE transtensive extrusion fault zone.These evidences confirm the fact that the NW-SE Jeffara faults correspond

An alternative approach for socio-hydrology: case study research

Science.gov (United States)

Mostert, Erik

2018-01-01

Currently the most popular approach in socio hydrology is to develop coupled human-water models. This article proposes an alternative approach, qualitative case study research, involving a systematic review of (1) the human activities affecting the hydrology in the case, (2) the main human actors, and (3) the main factors influencing the actors and their activities. Moreover, this article presents a case study of the Dommel Basin in Belgium and the Netherlands, and compares this with a coupled model of the Kissimmee Basin in Florida. In both basins a pendulum swing from water resources development and control to protection and restoration can be observed. The Dommel case study moreover points to the importance of institutional and financial arrangements, community values, and broader social, economic, and technical developments. These factors are missing from the Kissimmee model. Generally, case studies can result in a more complete understanding of individual cases than coupled models, and if the cases are selected carefully and compared with previous studies, it is possible to generalize on the basis of them. Case studies also offer more levers for management and facilitate interdisciplinary cooperation. Coupled models, on the other hand, can be used to generate possible explanations of past developments and quantitative scenarios for future developments. The article concludes that, given the limited attention they currently get and their potential benefits, case studies deserve more attention in socio-hydrology.

A case study of a Cuban government institution

International Nuclear Information System (INIS)

Nunez, A.L.; Vazquez, A.; Cruz Cabrera, L.

2004-01-01

The aim of this contribution is to present a case study on the partial implementation of a knowledge management system in an institution. In this case the knowledge management has been directed toward the best performance of the organization. The tool used in case study can be implemented at any institution, including institutions of nuclear or radiological profiles. (author)

The Analysis of a Murder, a Case Study

Science.gov (United States)

Dinan, Frank J.; Szczepankiewicz, Steven H.; Carnaham, Melinda; Colvin, Michael T.

2007-01-01

The analysis of a Murder case study can be used in general chemistry or nonscience major chemistry courses to teach data handling and analysis in a non-laboratory context. This case study will help students to respond more enthusiastically and with more interest to a set of material placed before them related to a real case rather than…

Using Interpretive Qualitative Case Studies for Exploratory Research in Doctoral Studies: A Case of Information Systems Research in Small and Medium Enterprises

Directory of Open Access Journals (Sweden)

Shana R. Ponelis

2015-12-01

Full Text Available The use of the case study method has gained mainstream acceptance in both entrepreneurship and information systems research to develop conceptual and theoretical models that are novel, yet grounded in the literature. In spite of many texts on the case study method and the growing acceptance and use of thereof, there are relatively few examples that discuss how to apply the case study method. The purpose of this paper is to provide such an example by drawing upon the author’s research for her doctoral dissertation in the discipline of information systems and entrepreneurship research. First, the use of qualitative case studies as research method is motivated, then the importance of the research paradigm is discussed and the interpretivist research paradigm justified followed by a detailed discussion of the research design. The paper concludes with a discussion of lessons learned and recommendations based on the author’s experience with using the case study method. The practical yet theoretically founded approach of this paper may be useful to doctoral students who are considering or using the case study method. Equally, supervisors and others involved in research training may find this paper useful as an illustrative example of the case study method for their students.

Facilitating Case Studies in Massage Therapy Clinical Education

Science.gov (United States)

Baskwill, Amanda

2013-01-01

The integration of evidence into reflective health care practice has been on the rise in recent years and is a phenomenon that has affected all health care professions, including massage therapy. Clinical case studies are a research design that follows one patient or subject, making the studies ideal for use in clinical practice. They are valuable for communicating information from clinical practice to the broader community. Case studies have face validity that may be more valuable to individual practitioners than homogeneous randomized controlled trials, as the practitioner may recognize a complex patient in the case report. At Humber College, Student Massage Therapists (SMTs) create, conduct, and communicate results of a clinical case study prior to graduation. This article describes the process and experience. PMID:23730397

Potential climate effect of mineral aerosols over West Africa: Part II—contribution of dust and land cover to future climate change

Science.gov (United States)

Ji, Zhenming; Wang, Guiling; Yu, Miao; Pal, Jeremy S.

2018-04-01

Mineral dust aerosols are an essential component of climate over West Africa, however, little work has been performed to investigate their contributions to potential climate change. A set of regional climate model experiments with and without mineral dust processes and land cover changes is performed to evaluate their climatic effects under the Representative Concentration Pathway 8.5 for two global climate models. Results suggest surface warming to be in the range of 4-8 °C by the end of the century (2081-2100) over West Africa with respect to the present day (1981-2000). The presence of mineral dusts dampens the warming by 0.1-1 °C in all seasons. Accounting for changes in land cover enhances the warming over the north of Sahel and dampens it to the south in spring and summer; however, the magnitudes are smaller than those resulting from dusts. Overall dust loadings are projected to increase, with the greatest increase occurring over the Sahara and Sahel in summer. Accounting for land cover changes tends to reduce dust loadings over the southern Sahel. Future precipitation is projected to decrease by 5-40 % in the western Sahara and Sahel and increase by 10-150 % over the eastern Sahel and Guinea Coast in JJA. A dipole pattern of future precipitation changes is attributed to dust effects, with decrease in the north by 5-20 % and increase by 5-20 % in the south. Future changes in land cover result in a noisy non-significant response with a tendency for slight wetting in MAM, JJA, and SON and drying in DJF.

A Comparative Comment on the Case Studies

DEFF Research Database (Denmark)

Kjeldsen, Christian Christrup; Ley, Thomas; Jensen, Niels Rosendal

2012-01-01

Denne konklusion sammenfatter hovedtrækkene af de gennemførte case studies i WorkAble-projektet. Vigtige pointer er, at unge på tværs af de forskellige case studies har vanskeligt ved at blive hørt og taget alvorligt. I stedet spises de af med "realistisk vejledning" eller dårlige uddannelses- og...

Logistics case study based research: Towards higher quality

DEFF Research Database (Denmark)

Pedrosa, Alex; Näslund, Dag; Jasmand, Claudia

2012-01-01

analysis of 134 case study based articles published in six leading logistics and supply chain management (SCM) journals between 1998 and 2010 is used to assess and evaluate the quality of the case study based research approach as documented in these publications. Findings – This research provides...... to address to ensure high quality of the case study based research approach in published articles. Research limitations/implications – This study is limited to the analysis of published articles in six logistics and SCM journals. Further research should investigate different journals in logistics and other...

93 une urbanisation linéaire, dynamique demographique et ...

African Journals Online (AJOL)

Mohand

d'Alger, dans l'ensemble Sahel-Mitidja sur un linéaire côtier de 2 km. Rattaché administrativement à la daira de ... connait une dynamique démographique remar- quable, dans sa périphérie orientale - composé de l'ensemble Sahel-. Mitidja ..... «Etude agro-pédologique de la plaine de la Mitidja». Florin B.; Semoud N. 2010.

Clean Cities Case Study: Barwood Cab Fleet Study Summary

International Nuclear Information System (INIS)

Whalen, P.

1999-01-01

Barwood Cab Fleet Study Summary is the second in a new series called''Alternative Fuel Information Case Studies,'' designed to present real-world experiences with alternative fuels to fleet managers and other industry stakeholders

Enhancing Systems Engineering Education Through Case Study Writing

Science.gov (United States)

Stevens, Jennifer Stenger

2016-01-01

Developing and refining methods for teaching systems engineering is part of Systems Engineering grand challenges and agenda for research in the SE research community. Retention of systems engineering knowledge is a growing concern in the United States as the baby boom generation continues to retire and the faster pace of technology development does not allow for younger generations to gain experiential knowledge through years of practice. Government agencies, including the National Aeronautics and Space Administration (NASA), develop their own curricula and SE leadership development programs to "grow their own" systems engineers. Marshall Space Flight Center (MSFC) conducts its own Center-focused Marshall Systems Engineering Leadership Development Program (MSELDP), a competitive program consisting of coursework, a guest lecture series, and a rotational assignment into an unfamiliar organization engaged in systems engineering. Independently, MSFC developed two courses to address knowledge retention and sharing concerns: Real World Marshall Mission Success course and its Case Study Writers Workshop and Writers Experience. Teaching case study writing and leading students through a hands-on experience at writing a case study on an SE topic can enhance SE training and has the potential to accelerate the transfer of experiential knowledge. This paper is an overview of the pilot experiences with teaching case study writing, its application in case study-based learning, and identifies potential areas of research and application for case study writing in systems engineering education.

Case-Control Studies - An Efficient Observational Study Design

NARCIS (Netherlands)

van Stralen, Karlijn J.; Dekker, Friedo W.; Zoccali, Carmine; Jager, Kitty J.

2010-01-01

Case-control studies are an efficient research method for investigating risk factors of a disease. The method involves the comparison of the odds of exposure in a patient group with that of the odds of exposure in a control group. As only a minority of the population is included in the study, less

Improvement of Students’ Ability to Analyzing Cases on Case Studies Through Journal and Learning Log

Directory of Open Access Journals (Sweden)

Riska Ahmad

2017-08-01

Full Text Available The purpose of this research is to improve the ability of students in guidance and counseling  to  analyzing the case through journals and learning logs This research is classroom action research consists of two cycles. The research phase consisted of planning, implementation, observation and reflection. The research subject are students in guidance and counseling while they are in sixth semester, totaling 20 people who were taking courses in Case Study. The research instrument is the observation guidelines, assessment rubrics and documentation of case studies in the form of journals and learning logs, and case study reports. The study was conducted collaboratively with student magister’s program guidance and counseling. The results showed that in cycle 1 students are able to identify cases, to develop ideas about the case, select and use instruments to analyze the cause of the problem. The results of the research cycle 2, showed 17 of the 20 students were able to analyze the cause of the problem, select the type of service and provide appropriate assistance in accordance with problem cases. Overall value obtained by the students in the subject of Case Studies also increased. In terms of the ability of explanation of the concept, the concept of truth and creativity, based on the ratings given by fellow students of average ability students were in either category, although there is less good, as are associated with the activity of the opinion and the quality of the opinions expressed.

Using Online Case Studies to Enhance Teacher Preparation

Science.gov (United States)

Richman, Laila

2015-01-01

The purpose of this study was to assess the impact interactive, online case studies have on learning for preservice teachers. More specifically, it evaluated whether the use of online case studies in instruction could enhance the level of knowledge the preservice teacher gained from the content material. This study utilized a nonequivalent group,…

Case studies in intelligent computing achievements and trends

CERN Document Server

Issac, Biju

2014-01-01

Although the field of intelligent systems has grown rapidly in recent years, there has been a need for a book that supplies a timely and accessible understanding of this important technology. Filling this need, Case Studies in Intelligent Computing: Achievements and Trends provides an up-to-date introduction to intelligent systems.This edited book captures the state of the art in intelligent computing research through case studies that examine recent developments, developmental tools, programming, and approaches related to artificial intelligence (AI). The case studies illustrate successful ma

Cases for the Net Generation: An Empirical Examination of Students' Attitude toward Multimedia Case Studies

Science.gov (United States)

Sheppard, Michael; Vibert, Conor

2016-01-01

Case studies have been an important tool in business, legal, and medical education for generations of students. Traditional text-based cases tend to be self-contained and structured in such a way as to teach a particular concept. The multimedia cases introduced in this study feature unscripted web-hosted video interviews with business owners and…

Acoustical case studies of three green buildings

Science.gov (United States)

Siebein, Gary; Lilkendey, Robert; Skorski, Stephen

2005-04-01

Case studies of 3 green buildings with LEED certifications that required extensive acoustical retrofit work to become satisfactory work environments for their intended user groups will be used to define areas where green building design concepts and acoustical design concepts require reconciliation. Case study 1 is an office and conference center for a city environmental education agency. Large open spaces intended to collect daylight through clerestory windows provided large, reverberant volumes with few acoustic finishes that rendered them unsuitable as open office space and a conference room/auditorium. Case Study 2 describes one of the first gold LEED buildings in the southeast whose primary design concepts were so narrowly focused on thermal and lighting issues that they often worked directly against basic acoustical requirements resulting in sound levels of NC 50-55 in classrooms and faculty offices, crosstalk between classrooms and poor room acoustics. Case study 3 is an environmental education and conference center with open public areas, very high ceilings, and all reflective surfaces made from wood and other environmentally friendly materials that result in excessive loudness when the building is used by the numbers of people which it was intended to serve.

Is case-chaos methodology an appropriate alternative to conventional case-control studies for investigating outbreaks?

Science.gov (United States)

Edelstein, Michael; Wallensten, Anders; Kühlmann-Berenzon, Sharon

2014-08-15

Case-chaos methodology is a proposed alternative to case-control studies that simulates controls by randomly reshuffling the exposures of cases. We evaluated the method using data on outbreaks in Sweden. We identified 5 case-control studies from foodborne illness outbreaks that occurred between 2005 and 2012. Using case-chaos methodology, we calculated odds ratios 1,000 times for each exposure. We used the median as the point estimate and the 2.5th and 97.5th percentiles as the confidence interval. We compared case-chaos matched odds ratios with their respective case-control odds ratios in terms of statistical significance. Using Spearman's correlation, we estimated the correlation between matched odds ratios and the proportion of cases exposed to each exposure and quantified the relationship between the 2 using a normal linear mixed model. Each case-control study identified an outbreak vehicle (odds ratios = 4.9-45). Case-chaos methodology identified the outbreak vehicle 3 out of 5 times. It identified significant associations in 22 of 113 exposures that were not associated with outcome and 5 of 18 exposures that were significantly associated with outcome. Log matched odds ratios correlated with their respective proportion of cases exposed (Spearman ρ = 0.91) and increased significantly with the proportion of cases exposed (b = 0.054). Case-chaos methodology missed the outbreak source 2 of 5 times and identified spurious associations between a number of exposures and outcome. Measures of association correlated with the proportion of cases exposed. We recommended against using case-chaos analysis during outbreak investigations. © The Author 2014. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

[Cerebral gliosarcoma: clinico-pathologic study of 8 cases].

Science.gov (United States)

Ayadi, Lobna; Charfi, Slim; Khabir, Abdemajid; Kalle, Rim; Sellami, Ahmed; Makni, Saloua; Boudawara, Zaher; Sellami-Boudawara, Tahya

2010-03-01

Gliosarcomas are biphasic neoplasms composed of a glioblastoma admixed to a sarcomatous component with different lines of differentiation. Histogenesis of these tumors is still discussed. Our objective is to specify clinical and pathological characteristics of this rare neoplasm and to discuss its histogenesis. Retrospective study of eight cases of gliosarcomas diagnosed between January 1998 and December 2004. Clinical, radiological, therapeutic and follow-up data were reviewed. Histological features and immunohistochemical results were also included in this review. Five patients were male, three women with a median age of 50.7 (range 31-74 years). Symptoms were dominated by intracranial hypertension and paralysis. The most common location was parietal or temporo-parietal (5 cases: 62.5%). Pathological exam including histochemical and immunohistochemical study confirmed the diagnosis of gliosarcoma in all cases. Sarcomatous component had features of fibrosarcoma in 5 cases, osteosarcoma in 2 cases and malignant fibrous histiocytoma in 1 case. All patients were treated by surgical excision (complete in five cases and partial in three cases). Adjuvant radiotherapy was received in three cases. One patient was lost on follow-up. Two patients died from postoperative. complications and the five remaining patients died with a medium follow up of 9 months (extremes: 2-24 months). Clinical, radiological and follow-up features of gliosarcomas share great similarities with glioblastomas. Histopathological, histochemical and immunohistochemical studies are helpful in accuracy diagnosis. Recent cytogenetic and molecular data support a monoclonal origin for these tumors.

Ghana Journal of Agricultural Science - Vol 20 (1987)

African Journals Online (AJOL)

A preliminary study of pre-harvest insect infestation and storability of four Ghanaian ... Seed germination and growth of Eleucine indica and Euphorbia heterophylla as ... Lambing and neonatal behaviour of Djallonke x Sahel crossbred sheep.

Qualitative case study methodology in nursing research: an integrative review.

Science.gov (United States)

Anthony, Susan; Jack, Susan

2009-06-01

This paper is a report of an integrative review conducted to critically analyse the contemporary use of qualitative case study methodology in nursing research. Increasing complexity in health care and increasing use of case study in nursing research support the need for current examination of this methodology. In 2007, a search for case study research (published 2005-2007) indexed in the CINAHL, MEDLINE, EMBASE, PsychINFO, Sociological Abstracts and SCOPUS databases was conducted. A sample of 42 case study research papers met the inclusion criteria. Whittemore and Knafl's integrative review method guided the analysis. Confusion exists about the name, nature and use of case study. This methodology, including terminology and concepts, is often invisible in qualitative study titles and abstracts. Case study is an exclusive methodology and an adjunct to exploring particular aspects of phenomena under investigation in larger or mixed-methods studies. A high quality of case study exists in nursing research. Judicious selection and diligent application of literature review methods promote the development of nursing science. Case study is becoming entrenched in the nursing research lexicon as a well-accepted methodology for studying phenomena in health and social care, and its growing use warrants continued appraisal to promote nursing knowledge development. Attention to all case study elements, process and publication is important in promoting authenticity, methodological quality and visibility.

Case Study Research in Software Engineering Guidelines and Examples

CERN Document Server

Runeson, Per; Rainer, Austen; Regnell, Bjorn

2012-01-01

Based on their own experiences of in-depth case studies of software projects in international corporations, in this book the authors present detailed practical guidelines on the preparation, conduct, design and reporting of case studies of software engineering.  This is the first software engineering specific book on the case study research method.

Industrial process heat case studies. [PROSYS/ECONMAT code

Energy Technology Data Exchange (ETDEWEB)

Hooker, D.W.; May, E.K.; West, R.E.

1980-05-01

Commercially available solar collectors have the potential to provide a large fraction of the energy consumed for industrial process heat (IPH). Detailed case studies of individual industrial plants are required in order to make an accurate assessment of the technical and economic feasibility of applications. This report documents the results of seven such case studies. The objectives of the case study program are to determine the near-term feasibility of solar IPH in selected industries, identify energy conservation measures, identify conditions of IPH systems that affect solar applications, test SERI's IPH analysis software (PROSYS/ECONOMAT), disseminate information to the industrial community, and provide inputs to the SERI research program. The detailed results from the case studies are presented. Although few near-term, economical solar applications were found, the conditions that would enhance the opportunities for solar IPH applications are identified.

Repurposing legacy data innovative case studies

CERN Document Server

Berman, Jules J

2015-01-01

Repurposing Legacy Data: Innovative Case Studies takes a look at how data scientists have re-purposed legacy data, whether their own, or legacy data that has been donated to the public domain. Most of the data stored worldwide is legacy data-data created some time in the past, for a particular purpose, and left in obsolete formats. As with keepsakes in an attic, we retain this information thinking it may have value in the future, though we have no current use for it. The case studies in this book, from such diverse fields as cosmology, quantum physics, high-energy physics, microbiology,

HYDROGEOLOGIC CASE STUDIES (DENVER PRESENTATION)

Science.gov (United States)

Hydrogeology is the foundation of subsurface site characterization for evaluations of monitored natural attenuation (MNA). Three case studies are presented. Examples of the potentially detrimental effects of drilling additives on ground-water samples from monitoring wells are d...

HYDROGEOLOGIC CASE STUDIES (CHICAGO, IL)

Science.gov (United States)

Hydrogeology is the foundation of subsurface site characterization for evaluations of monitored natural attenuation (MNA). Three case studies are presented. Examples of the potentially detrimental effects of drilling additives on ground-water samples from monitoring wells are d...

Hydrogeologic Case Studies (Seattle, WA)

Science.gov (United States)

Hydrogeology is the foundation of subsurface site characterization for evaluations of monitored natural attenuation (MNA). Three case studies are presented. Examples of the potentially detrimental effects of drilling additives on ground-water samples from monitoring wells are d...

Methodology or method? A critical review of qualitative case study reports

Directory of Open Access Journals (Sweden)

Nerida Hyett

2014-05-01

Full Text Available Despite on-going debate about credibility, and reported limitations in comparison to other approaches, case study is an increasingly popular approach among qualitative researchers. We critically analysed the methodological descriptions of published case studies. Three high-impact qualitative methods journals were searched to locate case studies published in the past 5 years; 34 were selected for analysis. Articles were categorized as health and health services (n=12, social sciences and anthropology (n=7, or methods (n=15 case studies. The articles were reviewed using an adapted version of established criteria to determine whether adequate methodological justification was present, and if study aims, methods, and reported findings were consistent with a qualitative case study approach. Findings were grouped into five themes outlining key methodological issues: case study methodology or method, case of something particular and case selection, contextually bound case study, researcher and case interactions and triangulation, and study design inconsistent with methodology reported. Improved reporting of case studies by qualitative researchers will advance the methodology for the benefit of researchers and practitioners.

Methodology or method? A critical review of qualitative case study reports

Science.gov (United States)

Hyett, Nerida; Kenny, Amanda; Dickson-Swift, Virginia

2014-01-01

Despite on-going debate about credibility, and reported limitations in comparison to other approaches, case study is an increasingly popular approach among qualitative researchers. We critically analysed the methodological descriptions of published case studies. Three high-impact qualitative methods journals were searched to locate case studies published in the past 5 years; 34 were selected for analysis. Articles were categorized as health and health services (n=12), social sciences and anthropology (n=7), or methods (n=15) case studies. The articles were reviewed using an adapted version of established criteria to determine whether adequate methodological justification was present, and if study aims, methods, and reported findings were consistent with a qualitative case study approach. Findings were grouped into five themes outlining key methodological issues: case study methodology or method, case of something particular and case selection, contextually bound case study, researcher and case interactions and triangulation, and study design inconsistent with methodology reported. Improved reporting of case studies by qualitative researchers will advance the methodology for the benefit of researchers and practitioners. PMID:24809980

Case studies of uncommon headaches.

Science.gov (United States)

Evans, Randolph W

2006-05-01

The following interesting and uncommon headache disorders are presented through case studies: exploding head syndrome, hypnic headache, neck-tongue syndrome, "Alice in Wonderland" syndrome, nummular headache, red ear syndrome, burning mouth syndrome, spontaneous intracranial hypotension syndrome, and cardiac cephalalgia.

a case study ondo state

African Journals Online (AJOL)

user

the design of a Government Cloud (G-Cloud) network for Ondo State Government which will ... network for a developing economy; a case study of ... France is one of those countries that favour .... Arequipa city. .... Where region 0 = Akure, 1 =.

Scaling Up Pulse Innovations for Food and Nutrition Security in ...

International Development Research Centre (IDRC) Digital Library (Canada)

Researchers will study the entire value chain for beans and chickpeas - from production to consumers. ... government agencies to integrate the new products into local supply chains. ... New project to improve water management in the Sahel.

Gigantic Suprapubic Lymphedema: A Case Study

Directory of Open Access Journals (Sweden)

Roozbeh Tanhaeivash

2016-08-01

Full Text Available We present the first case study of idiopathic gigantic suprapubic lymphedema and buried penis treated with puboscrotal reconstruction in a patient with initial extreme obesity after an extensive weight reduction (120 kg. Massive localized lymphedema of the suprapubic region should be differentiated from the scrotal type. Severe lymphedema could not resolve on its own and weight reduction does not seem to be helpful in such cases.

Capturing Cultural Glossaries: Case-study II

Directory of Open Access Journals (Sweden)

Matete Madiba

2011-10-01

Full Text Available

ABSTRACT: This case-study attempts to present a brief glossary of Northern Sotho medical terms. It is a follow-up of a similar case-study (Madiba, Mphahlele and Kganyago 2003, which was an attempt to capture and present Northern Sotho cooking terms. Case-study I consists of the names for utensils, ingredients and the processes involved in the preparation of cultural dishes. With both these case-studies, the intention has been to use the opportunities availing themselves for the pres-ervation and valorisation of Northern Sotho, including the extension of its corpora to support national dictionary-making processes. The case-study methodology has been very useful for the purposes of this project and the context within which it was undertaken. It aims to provide a model for the collection and presentation of authentic Northern Sotho terminology which otherwise would hardly have been accessible.

Keywords: CULTURAL GLOSSARY, INDIGENOUS KNOWLEDGE SYSTEMS, CORPUS, OUTCOMES-BASED EDUCATION, ASSESSMENT CRITERIA, TRADITIONAL MEDICAL TERMS, COMMUNICATIVE APPROACH, STRUCTURAL APPROACH, METONYMY, HANDS-ON ACTIVITIES, TASK-BASED LEARNING

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OPSOMMING: Die totstandbrenging van kulturele woordversamelings: Ge-vallestudie II. Hierdie gevallestudie probeer om 'n beperkte woordelys van Noord-Sotho- mediese terme aan te bied. Dit is 'n voortsetting van 'n soortgelyke gevallestudie (Madiba, Mpha-hlele en Kganyago 2003 wat 'n poging was om Noord-Sothokookterme te versamel en aan te bied. Gevallestudie I bestaan uit die name van gereedskap, bestanddele, en die prosesse betrokke by die voorbereiding van kulturele geregte. Met altwee hierdie gevallestudies was die bedoeling om die geleenthede te gebruik wat hulleself aanbied vir die bewaring en bestendiging van Noord-Sotho, insluitende die uitbreiding van sy korpora om die nasionale woordeboeksamestellingsprosesse te ondersteun. Die gevallestudiemetodologie was baie nuttig vir die doeleindes van

Vitiligo: A study of 120 cases

Directory of Open Access Journals (Sweden)

Kar P

2001-11-01

Full Text Available Vitiligo is a common pignientary disorder and of major social and cosmetic concern in India. Purpose of the study was to find out age at onset and sex incidence in vitiligo, role of hereditary factors and associations with other diseases. 120 self reporting vitiligo patients attending out patient department of a service hospital were selected for the study and this data was analysed. In the present series out of 120 cases 62 (51.6% were males and 58(48.35%were females. There was practically no difference in sex incidence. The lowest age of onset was two years and the oldest was 65 years. In the majority of patients,52(43.2%, disease started before twenty years of age.8 (6.6% cases gave definite family history of vitiligo. Exposed areas of the body were commonly affected in majority (66.6% of cases. The legs were commonest site of involvement in 60(50% cases. Circunicript type of vitiligo (46.6% was heading the list. Majority of patients (56.6% had multiple lesions. Diabetes mellitus was found in 2 (2.6% patients. Cause of vitiligo is still idiopathic. Hereditary factors hardly play any role in manifestation of vitiligo

Case Studies Approach in Tourism Destination Branding Research

Directory of Open Access Journals (Sweden)

Adeyinka-Ojo S.F.

2014-01-01

Full Text Available A review of literature indicates that there are different types of qualitative research methods such as action research, content analysis, ethnography, grounded theory, historical analysis, phenomenology and case study. However, which approach is to be used depends on several factors such as the nature and objectives of the research. The aim of this paper is to focus on the research methodology aspects of applying case study as a research approach and its relevance in tourism destination branding research specifically on a single case study (SCS context. There are arguments that the SCS is a weak research strategy. Some of the potentials or shortcomings highlighted in the literature include the primitive nature of SCS, flexibility of sample technique, data collection method and data analysis. Others include lack of rigour, reliability, validity, credibility of findings and generalisation. This paper has adopted content analysis of the literature on tourism destination branding. Findings indicate that the quality of SCS can be verified using specific case study tactics for four design tests such as validity (construct, internal and external; and reliability using the case study protocol. Theoretical implication suggests that SCS is an empirical enquiry use to understand complex phenomena and favoured by practitioners.

Recent variations in geopotential height associated with West African monsoon variability

Science.gov (United States)

Okoro, Ugochukwu K.; Chen, Wen; Nath, Debashis

2018-02-01

In the present study, the atmospheric circulation patterns associated with the seasonal West Africa (WA) monsoon (WAM) rainfall variability has been investigated. The observational rainfall data from the Climatic Research Unit (CRU) and atmospheric fields from the National Center for Environmental Prediction (NCEP) reanalysis 2, from 1979 to 2014, have been used. The rainfall variability extremes, classified as wet or dry years, are the outcomes of simultaneous 6-month SPI at the three rainfall zones, which shows increasing trends [Guinea Coast (GC = 0.012 year-1), Eastern Sudano Sahel (ESS = 0.045 year-1) and Western Sudano Sahel (WSS = 0.056 year-1) from Sen's slope]; however, it is significant only in the Sahel region (α = 0.05 and α = 0.001 at ESS and WSS, respectively, from Mann-Kendall test). The vertical profile of the geopotential height (GpH) during the wet and dry years reveals that the 700 hPa anomalies show remarkable pattern at about 8°N to 13°N. This shows varying correlation with the zonal averaged vertically integrated moisture flux convergence and rainfall anomalies, respectively, as well as the oceanic pulsations indexes [Ocean Nino Index (ONI) and South Atlantic Ocean dipole index (SAODI), significant from t test], identified as precursors to the Sahel and GC rainfall variability respectively. The role of GpH anomalies at 700 hPa has been identified as the facilitator to the West African Westerly Jet's input to the moisture flux transported over the WA. This is a new perspective of the circulation processes associated with WAM and serves as a basis for modeling investigations.

GLAMUR case-study report: The comparison of three Dutch pork cases (Tasks 3.5)

NARCIS (Netherlands)

Oostindië, H.A.; Horlings, L.G.; Broekhuizen, van R.E.; Hees, E.

2015-01-01

This report presents the case study results of local-global pork chain performances in The Netherlands. As part of Work Package 3, this case study was carried out in cooperation with our Italian GLAMUR partner. The Dutch pork production sector came up after World War 2 and developed into a highly

Case Study: The Mystery of the Seven Deaths--A Case Study in Cellular Respiration

Science.gov (United States)

Gazdik, Michaela

2014-01-01

Cellular respiration, the central component of cellular metabolism, can be a difficult concept for many students to fully understand. In this interrupted, problem-based case study, students explore the purpose of cellular respiration as they play the role of medical examiner, analyzing autopsy evidence to determine the mysterious cause of death…

Evaluation of indigenous tomato hybrids under plastic tunnel

International Nuclear Information System (INIS)

Farooq, M.; Ullah, H.; Nawab, N.N.; Qureshi, K.M.

2013-01-01

Evaluation of indigenous tomato hybrids under plastic tunnel Seventeen locally developed indeterminate tomato hybrids were evaluated along with 'Sahel' as check under plastic tunnel for yield and yield components at National Agricultural Research Centre, Islamabad. Maximum yield of 71.58 tha/sup -1/ was recorded in NTT-12-08 while minimum yield (34.75 tha/sup -1/) was observed in NTT-16-08. Sahel used as check bore maximum number of fruits plant/sup -1/(30.26) and followed by NTT-04-08 and NTT-03-08 bearing 28.68 and 24.16 fruits plant/sup -1/, respectively. The highest mean fruit weight of 170.63 g was recorded in NTT-05-08 while minimum fruit weight (80.90 g) was observed in Sahel (check). Maximum fruit length of 7.89 cm was recorded in Sahel which is oblong in shape while minimum (5.70 cm) in NTT-14-08. Similarly a significant difference was observed among hybrids for fruit diameter. Fruits having more diameter are round to roundish in shape. Fruit diameter ranged from 8.85 to 5.49 cm. Fruit firmness also varied significantly ranging from 3.54 to 1.67 kg m/sup -3/ in Sahel and NTT-07-08, respectively. Maximum pericarp thickness (0.90 cm) was recorded in NTT-10-08 while minimum pericarp thickness of 0.58 cm was observed in NTT-16-08. NTT-01-08 exhibits the highest number of locules (5.22). It was followed by NTT-02-08 having 4.55 locules while minimum (2.0) locules were observed in NTT-09-08. (author)

The reflexive case study method

DEFF Research Database (Denmark)

Rittenhofer, Iris

2015-01-01

This paper extends the international business research on small to medium-sized enterprises (SME) at the nexus of globalization. Based on a conceptual synthesis across disciplines and theoretical perspectives, it offers management research a reflexive method for case study research of postnational...

Persistent User Bias in Case-Crossover Studies in Pharmacoepidemiology

DEFF Research Database (Denmark)

Hallas, Jesper; Pottegård, Anton; Wang, Shirley

2016-01-01

Studying the effect of chronic medication exposure by means of a case-crossover design may result in an upward-biased odds ratio. In this study, our aim was to assess the occurrence of this bias and to evaluate whether it is remedied by including a control group (the case-time-control design...... for the retinal detachment controls were similar, leading to near-null case-time-control estimates for all 3 medication classes. For wrist fracture and stroke, the odds ratios were higher for cases than for controls, and case-time-control odds ratios were consistently above unity, thus implying significant...... residual bias. In case-crossover studies of medications, contamination by persistent users confers a moderate bias upward, which is partly remedied by using a control group. The optimal strategy for dealing with this problem is currently unknown....

[Localized scleroderma: a retrospective study about 92 cases].

Science.gov (United States)

El Fékih, Nadia; Réjaibi, Iménc; Kamoun, Hajer; Zéglaoui, Faten; Fazaa, Bécima; Kharfi, Monia; Kamoun, Mohamed Ridha

2009-09-01

Sclerodermas are rare affections which can be located or generalized. Localized form is the most frequent. The purpose of this study was to describe epidemiologic, clinics, biological, immunological, therapeutic, evolutionary characteristics of the localized scleroderma through a personal series and the data of the literature. We have performed a retrospective study on all patients followed in the department of dermatology of the Hospital Charles Nicole during 14 years period. Our study was about 92 cases of localized scleroderma (73 were females and 19 males). The mean age was 35 years (between 2 and 72 years). The majority of localised sclerodermas (66.2% of the cases) appeared before 40 years with a maximum of frequency between 10 and 30 years (41.6%). Only 11.9% of the cases were observed before 10 years. They were 51 cases (55%) of morphea, 35 cases (38%) of scleroderma in bands including 32 linear scleroderma and 3 scleroderma en coup de sabre, 5 cases (5.5%) of generalized morphea and 1 case (0.15%) of deep morphea. Average therapeutic was specified among 63 patients (87%), and the evolution could be appreciated among 45 patients. The epidemiologic data observed in our series are comparable with those reported in the literature. Therapeutic difficulties and risks of functional after-effects, particular in scleroderma in bands, remain the principal concern for all the authors.

Covert Conditioning: Case Studies in Self-Management.

Science.gov (United States)

Yager, Geoffrey G.

The self-management of thoughts and mental images was used in a series of empirical case studies to influence behavior changes. The target behaviors in the cases reported were smoking, overeating, fingernail biting, thinking self-depreciative thoughts, and responding assertively. Self-monitoring, covert positive reinforcement, covert…

A Case Study about Communication Strategies

Science.gov (United States)

Lin, Grace Hui Chin

2011-01-01

The primary purpose of this case study was to identify what were Taiwanese University English as a Foreign Language (EFL) learners' perceptions about learning communication strategies. This study collected qualitative data about students' beliefs and attitudes as they learned communication strategies. The research question guiding the study was:…

Case Studies in Modelling, Control in Food Processes.

Science.gov (United States)

Glassey, J; Barone, A; Montague, G A; Sabou, V

This chapter discusses the importance of modelling and control in increasing food process efficiency and ensuring product quality. Various approaches to both modelling and control in food processing are set in the context of the specific challenges in this industrial sector and latest developments in each area are discussed. Three industrial case studies are used to demonstrate the benefits of advanced measurement, modelling and control in food processes. The first case study illustrates the use of knowledge elicitation from expert operators in the process for the manufacture of potato chips (French fries) and the consequent improvements in process control to increase the consistency of the resulting product. The second case study highlights the economic benefits of tighter control of an important process parameter, moisture content, in potato crisp (chips) manufacture. The final case study describes the use of NIR spectroscopy in ensuring effective mixing of dry multicomponent mixtures and pastes. Practical implementation tips and infrastructure requirements are also discussed.

Robust features of future climate change impacts on sorghum yields in West Africa

International Nuclear Information System (INIS)

Sultan, B; Guan, K; Lobell, D B; Kouressy, M; Biasutti, M; Piani, C; Hammer, G L; McLean, G

2014-01-01

West Africa is highly vulnerable to climate hazards and better quantification and understanding of the impact of climate change on crop yields are urgently needed. Here we provide an assessment of near-term climate change impacts on sorghum yields in West Africa and account for uncertainties both in future climate scenarios and in crop models. Towards this goal, we use simulations of nine bias-corrected CMIP5 climate models and two crop models (SARRA-H and APSIM) to evaluate the robustness of projected crop yield impacts in this area. In broad agreement with the full CMIP5 ensemble, our subset of bias-corrected climate models projects a mean warming of +2.8 °C in the decades of 2031–2060 compared to a baseline of 1961–1990 and a robust change in rainfall in West Africa with less rain in the Western part of the Sahel (Senegal, South-West Mali) and more rain in Central Sahel (Burkina Faso, South-West Niger). Projected rainfall deficits are concentrated in early monsoon season in the Western part of the Sahel while positive rainfall changes are found in late monsoon season all over the Sahel, suggesting a shift in the seasonality of the monsoon. In response to such climate change, but without accounting for direct crop responses to CO 2 , mean crop yield decreases by about 16–20% and year-to-year variability increases in the Western part of the Sahel, while the eastern domain sees much milder impacts. Such differences in climate and impacts projections between the Western and Eastern parts of the Sahel are highly consistent across the climate and crop models used in this study. We investigate the robustness of impacts for different choices of cultivars, nutrient treatments, and crop responses to CO 2 . Adverse impacts on mean yield and yield variability are lowest for modern cultivars, as their short and nearly fixed growth cycle appears to be more resilient to the seasonality shift of the monsoon, thus suggesting shorter season varieties could be considered a

Robust features of future climate change impacts on sorghum yields in West Africa

Science.gov (United States)

Sultan, B.; Guan, K.; Kouressy, M.; Biasutti, M.; Piani, C.; Hammer, G. L.; McLean, G.; Lobell, D. B.

2014-10-01

West Africa is highly vulnerable to climate hazards and better quantification and understanding of the impact of climate change on crop yields are urgently needed. Here we provide an assessment of near-term climate change impacts on sorghum yields in West Africa and account for uncertainties both in future climate scenarios and in crop models. Towards this goal, we use simulations of nine bias-corrected CMIP5 climate models and two crop models (SARRA-H and APSIM) to evaluate the robustness of projected crop yield impacts in this area. In broad agreement with the full CMIP5 ensemble, our subset of bias-corrected climate models projects a mean warming of +2.8 °C in the decades of 2031-2060 compared to a baseline of 1961-1990 and a robust change in rainfall in West Africa with less rain in the Western part of the Sahel (Senegal, South-West Mali) and more rain in Central Sahel (Burkina Faso, South-West Niger). Projected rainfall deficits are concentrated in early monsoon season in the Western part of the Sahel while positive rainfall changes are found in late monsoon season all over the Sahel, suggesting a shift in the seasonality of the monsoon. In response to such climate change, but without accounting for direct crop responses to CO2, mean crop yield decreases by about 16-20% and year-to-year variability increases in the Western part of the Sahel, while the eastern domain sees much milder impacts. Such differences in climate and impacts projections between the Western and Eastern parts of the Sahel are highly consistent across the climate and crop models used in this study. We investigate the robustness of impacts for different choices of cultivars, nutrient treatments, and crop responses to CO2. Adverse impacts on mean yield and yield variability are lowest for modern cultivars, as their short and nearly fixed growth cycle appears to be more resilient to the seasonality shift of the monsoon, thus suggesting shorter season varieties could be considered a potential

Class 1 devices case studies in medical devices design

CERN Document Server

Ogrodnik, Peter J

2014-01-01

The Case Studies in Medical Devices Design series consists of practical, applied case studies relating to medical device design in industry. These titles complement Ogrodnik's Medical Device Design and will assist engineers with applying the theory in practice. The case studies presented directly relate to Class I, Class IIa, Class IIb and Class III medical devices. Designers and companies who wish to extend their knowledge in a specific discipline related to their respective class of operation will find any or all of these titles a great addition to their library. Class 1 Devices is a companion text to Medical Devices Design: Innovation from Concept to Market. The intention of this book, and its sister books in the series, is to support the concepts presented in Medical Devices Design through case studies. In the context of this book the case studies consider Class I (EU) and 510(k) exempt (FDA) . This book covers classifications, the conceptual and embodiment phase, plus design from idea to PDS. These title...

Role of dust direct radiative effect on the tropical rainbelt over Middle East and North Africa: A high resolution AGCM study

KAUST Repository

Bangalath, Hamza Kunhu

2015-04-25

To investigate the influence of direct radiative effect of dust on the tropical summer rainbelt across the Middle East and North Africa (MENA), the present study utilizes the high resolution capability of an Atmospheric General Circulation Model (AGCM),the High Resolution Atmospheric Model (HiRAM). Ensembles of Atmospheric Model Inter-comparison Project (AMIP)-style simulations have been conducted with and without dust radiative impacts, to differentiate the influence of dust on the tropical rainbelt. The analysis focuses on summer season. The results highlight the role of dust induced responses in global and regional scale circulations in determining the strength and the latitudinal extent of the tropical rainbelt. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet (AEJ) and West African Monsoon (WAM) circulation. Consistent with these dynamic responses at various scales, the tropical rainbelt across MENA strengthens and shifts northward. Importantly, the summer precipitation over the semi-arid strip south of Sahara, including Sahel, increases up to 20%. As this region is characterized by the “Sahel drought" , the predicted precipitation sensitivity to the dust loading over this region has a wide-range of socioeconomic implications. Overall, the study demonstrates the extreme importance of incorporating dust radiative effects and the corresponding circulation responses at various scales, in the simulations and future projections of this region\\'s climate.

Case Studies in Sports Nutrition.

Science.gov (United States)

Clark, Nancy

1988-01-01

This article presents case studies of two athletes who wanted to affect a change in their body weight in order to enhance athletic performance. Each athlete's problem and the nutrition approach used to solve it are discussed. Caloric values of fast foods are listed. (JL)

Case-Cohort Studies: Design and Applicability to Hand Surgery.

Science.gov (United States)

Vojvodic, Miliana; Shafarenko, Mark; McCabe, Steven J

2018-04-24

Observational studies are common research strategies in hand surgery. The case-cohort design offers an efficient and resource-friendly method for risk assessment and outcomes analysis. Case-cohorts remain underrepresented in upper extremity research despite several practical and economic advantages over case-control studies. This report outlines the purpose, utility, and structure of the case-cohort design and offers a sample research question to demonstrate its value to risk estimation for adverse surgical outcomes. The application of well-designed case-cohort studies is advocated in an effort to improve the quality and quantity of observational research evidence in hand and upper extremity surgery. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Television Medical Dramas as Case Studies in Biochemistry

Science.gov (United States)

Millard, Julie T.

2009-01-01

Several case studies from popular television medical dramas are described for use in an undergraduate biochemistry course. These cases, which illustrate fundamental principles of biochemistry, are used as the basis for problems that can be discussed further in small groups. Medical cases provide an interesting context for biochemistry with video…

Mining Product Data Models: A Case Study

Directory of Open Access Journals (Sweden)

Cristina-Claudia DOLEAN

2014-01-01

Full Text Available This paper presents two case studies used to prove the validity of some data-flow mining algorithms. We proposed the data-flow mining algorithms because most part of mining algorithms focuses on the control-flow perspective. First case study uses event logs generated by an ERP system (Navision after we set several trackers on the data elements needed in the process analyzed; while the second case study uses the event logs generated by YAWL system. We offered a general solution of data-flow model extraction from different data sources. In order to apply the data-flow mining algorithms the event logs must comply a certain format (using InputOutput extension. But to respect this format, a set of conversion tools is needed. We depicted the conversion tools used and how we got the data-flow models. Moreover, the data-flow model is compared to the control-flow model.

Publications | Page 230 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

Fin des deux solitudes de l'élevage et de l'agriculture au Sahel (open access). Les femmes de Toukounous, petite localité située à 20 km de Niamey, participent à un moment charnière de l''histoire agricole du Niger et du Sahel. En effet, leur région ne vit que maintenant l''intégration de l''agriculture et de l''élevage, étape ...

Case studies of non-formal music education

NARCIS (Netherlands)

Kors, Ninja

2005-01-01

Non-formal music education is the field of music education outside the regular school curriculum, and delivered by music teachers / music leaders other than the teacher in the classroom. The main body of this research consists of case studies in the Netherlands. In addition there is a number of case

Shea case study Burkina Faso

NARCIS (Netherlands)

S. Drost (Sarah); J.C.A.C. van Wijk (Jeroen); S.R. Vellema (Sietze)

2012-01-01

textabstractThis shea case study is part of a larger Partnerships Resource Centre (PrC) project elaborated in tandem with two Dutch non-governmental organisations (NGOs); ICCO and Oxfam Novib. The endeavour of this ‘action research’ project is to combine the expert knowledge of development

Couplings between the seasonal cycles of surface thermodynamics and radiative fluxes in the semi-arid Sahel

Science.gov (United States)

Guichard, F.; Kergoat, L.; Mougin, E.; Timouk, F.; Bock, O.; Hiernaux, P.

2009-04-01

A good knowledge of surface fluxes and atmospheric low levels is central to improving our understanding of the West African monsoon. This study provides a quantitative analysis of the peculiar seasonal and diurnal cycles of surface thermodynamics and radiative fluxes encountered in Central Sahel. It is based on a multi-year dataset collected in the Malian Gourma over a sandy soil at 1.5°W-15.3°N (a site referred to as Agoufou) with an automated weather station and a sunphotometer (AERONET), complemented by observations from the AMMA field campaign. The seasonal cycle of this Tropical region is characterized by a broad maximum of temperature in May, following the first minimum of the solar zenith angle by a few weeks, when Agoufou lies within the West African Heat-Low, and a late summer maximum of equivalent potential temperature within the core of the monsoon season, around the second yearly maximum of solar zenith angle, as the temperature reaches its Summer minimum. More broadly, subtle balances between surface air temperature and moisture fields are found on a range of scales. For instance, during the monsoon, apart from August, their opposite daytime fluctuations (warming, drying) lead to an almost flat diurnal cycle of the equivalent potential temperature at the surface. This feature stands out in contrast to other more humid continental regions. Here, the strong dynamics associated with the transition from a drier hot Spring to a brief cooler wet tropical Summer climate involves very large transformations of the diurnal cycles. The Summer increase of surface net radiation, Rnet, is also strong; typically 10-day mean Rnet reaches about 5 times its Winter minimum (~30 W.m-2) in August (~150 W.m-2). A major feature revealed by observations is that this increase is mostly driven by modifications of the surface upwelling fluxes shaped by rainfall events and vegetation phenology (surface cooling and darkening), while the direct impact of atmospheric changes on

Qualitative case study data analysis: an example from practice.

Science.gov (United States)

Houghton, Catherine; Murphy, Kathy; Shaw, David; Casey, Dympna

2015-05-01

To illustrate an approach to data analysis in qualitative case study methodology. There is often little detail in case study research about how data were analysed. However, it is important that comprehensive analysis procedures are used because there are often large sets of data from multiple sources of evidence. Furthermore, the ability to describe in detail how the analysis was conducted ensures rigour in reporting qualitative research. The research example used is a multiple case study that explored the role of the clinical skills laboratory in preparing students for the real world of practice. Data analysis was conducted using a framework guided by the four stages of analysis outlined by Morse ( 1994 ): comprehending, synthesising, theorising and recontextualising. The specific strategies for analysis in these stages centred on the work of Miles and Huberman ( 1994 ), which has been successfully used in case study research. The data were managed using NVivo software. Literature examining qualitative data analysis was reviewed and strategies illustrated by the case study example provided. Discussion Each stage of the analysis framework is described with illustration from the research example for the purpose of highlighting the benefits of a systematic approach to handling large data sets from multiple sources. By providing an example of how each stage of the analysis was conducted, it is hoped that researchers will be able to consider the benefits of such an approach to their own case study analysis. This paper illustrates specific strategies that can be employed when conducting data analysis in case study research and other qualitative research designs.

Case Studies - Cervical Cancer

Centers for Disease Control (CDC) Podcasts

2010-10-15

Dr. Alan Waxman, a professor of obstetrics and gynecology at the University of New Mexico and chair of the American College of Obstetricians and Gynecologists (ACOG) committee for the underserved, talks about several case studies for cervical cancer screening and management.  Created: 10/15/2010 by National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP), Division of Cancer Prevention and Control (DCPC).   Date Released: 6/9/2010.

Communicative Case Studies for EFL--Lessons for Interactivity.

Science.gov (United States)

Witte, Anne E.

1999-01-01

Discusses use of case studies and role play throughout the curriculum at the Ecole de Hautes Etudes Commerciales du Nord, a French graduate school associated with the Catholic University of Lille. Provides a case study that was developed to reconcile conflicting needs in the business English classroom at the graduate level. Students require…

Statistical and dynamical assessment of land-ocean-atmosphere interactions across North Africa

Science.gov (United States)

Yu, Yan

North Africa is highly vulnerable to hydrologic variability and extremes, including impacts of climate change. The current understanding of oceanic versus terrestrial drivers of North African droughts and pluvials is largely model-based, with vast disagreement among models in terms of the simulated oceanic impacts and vegetation feedbacks. Regarding oceanic impacts, the relative importance of the tropical Pacific, tropical Indian, and tropical Atlantic Oceans in regulating the North African rainfall variability, as well as the underlying mechanism, remains debated among different modeling studies. Classic theory of land-atmosphere interactions across the Sahel ecotone, largely based on climate modeling experiments, has promoted positive vegetation-rainfall feedbacks associated with a dominant surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback with its underlying albedo mechanism, nor its relative importance compared with oceanic drivers, has been convincingly demonstrated up to now using observational data. Here, the multivariate Generalized Equilibrium Feedback Assessment (GEFA) is applied in order to identify the observed oceanic and terrestrial drivers of North African climate and quantify their impacts. The reliability of the statistical GEFA method is first evaluated against dynamical experiments within the Community Earth System Model (CESM). In order to reduce the sampling error caused by short data records, the traditional GEFA approach is refined through stepwise GEFA, in which unimportant forcings are dropped through stepwise selection. In order to evaluate GEFA's reliability in capturing oceanic impacts, the atmospheric response to a sea-surface temperature (SST) forcing across the tropical Pacific, tropical Indian, and tropical Atlantic Ocean is estimated independently through ensembles of dynamical experiments and compared with GEFA-based assessments. Furthermore, GEFA's performance in capturing terrestrial

The Woodworker's Website: A Project Management Case Study

Science.gov (United States)

Jance, Marsha

2014-01-01

A case study that focuses on building a website for a woodworking business is discussed. Project management and linear programming techniques can be used to determine the time required to complete the website project discussed in the case. This case can be assigned to students in an undergraduate or graduate decision modeling or management science…

Case Study: A Separation of Powers Lesson.

Science.gov (United States)

Jenkins, Steve

1986-01-01

Presents a case study involving students in the issue of separation of powers as applied to the 1952 Immigration and Nationality Act. Students examine the case of Jagdish Rai Chadha, an immigrant threatened with deportation whose problems resulted in 1983 U.S. Supreme Court decision declaring legislative veto provision of Immigration and…

Epidemiological follow-up study of Japanese Thorotrast cases

International Nuclear Information System (INIS)

Mori, T.; Maruyama, T.; Kato, Y.; Takahashi, S.

1979-01-01

The authors conducted a follow-up study on 243 Thorotrast-administered war-wounded ex-servicemen in 1975, after a lapse of 30 to 38 years from Thorotrast injections, and found 18 cases of malignant hepatic tumor, 15 cases of other malignant tumors, 2 cases of blood diseases, and 9 cases of liver cirrhosis in 224 cases who had been given Thorotrast intravascularly. The incidence of hepatic and other malignant tumors, blood diseases, and liver cirrhosis was significantly higher than in the controls. The total number of deaths in the Thorotrast-administered cases was also significantly higher than in the controls. In the remaining 19 cases who had been given Thorotrast by a route other than intravascularly, no fatal case related to Thorotrast administration was discovered. In the living cases, however, one sarcoma was observed to have developed at the site of the Thorotrast injection

Shuttle Transportation System Case-Study Development

Science.gov (United States)

Ransom, Khadijah

2012-01-01

A case-study collection was developed for NASA's Space Shuttle Program. Using lessons learned and documented by NASA KSC engineers, analysts, and contractors, decades of information related to processing and launching the Space Shuttle was gathered into a single database. The goal was to provide educators with an alternative means to teach real-world engineering processes and to enhance critical thinking, decision making, and problem solving skills. Suggested formats were created to assist both external educators and internal NASA employees to develop and contribute their own case-study reports to share with other educators and students. Via group project, class discussion, or open-ended research format, students will be introduced to the unique decision making process related to Shuttle missions and development. Teaching notes, images, and related documents will be made accessible to the public for presentation of Space Shuttle reports. Lessons investigated included the engine cutoff (ECO) sensor anomaly which occurred during mission STS-114. Students will be presented with general mission infom1ation as well as an explanation of ECO sensors. The project will conclude with the design of a website that allows for distribution of information to the public as well as case-study report submissions from other educators online.

An ethical analysis of a home visit case study.

Science.gov (United States)

Pibernat, Artur Dalfó; Vidal, Jessica Rosell; Pibernat, Enric Dalfó; Rodríguez, Francisco Javier Pelegrina; Colomer, Gerard; Cid, Maria Feijoo

2017-12-01

This article will explore a clinical case study of a home visit carried out by the case manager nurse. In this case, we will discuss the dilemma of finding the balance between autonomy and beneficence from the perspective of principlist ethics, virtue ethics and the 'ethics of care'. The main conflict in this case study deals with all proposals are unsuitable and it is not necessary for a nurse to pay him a home visit, whereas for the healthcare system it is considered necessary. We could conclude that, during the home visit, the case manager aspires to achieve excellence, and throughout his clinical relationship with Francesc, searches for a series of virtues, respecting certain fundamental principles. In this way, the case managers ensure that Jaume's care is more humanised. The case has been anonymised and confidentiality maintained.

Geothermal Exploration Case Studies on OpenEI (Presentation)

Energy Technology Data Exchange (ETDEWEB)

Young, K.; Bennett, M.; Atkins, D.

2014-03-01

The U.S. Geological Survey (USGS) resource assessment (Williams et al., 2008) outlined a mean 30 GWe of undiscovered hydrothermal resource in the western United States. One goal of the U.S. Department of Energy's (DOE) Geothermal Technology Office (GTO) is to accelerate the development of this undiscovered resource. DOE has focused efforts on helping industry identify hidden geothermal resources to increase geothermal capacity in the near term. Increased exploration activity will produce more prospects, more discoveries, and more readily developable resources. Detailed exploration case studies akin to those found in oil and gas (e.g. Beaumont and Foster, 1990-1992) will give developers central location for information gives models for identifying new geothermal areas, and guide efficient exploration and development of these areas. To support this effort, the National Renewable Energy Laboratory (NREL) has been working with GTO to develop a template for geothermal case studies on the Geothermal Gateway on OpenEI. In 2012, the template was developed and tested with two case studies: Raft River Geothermal Area (http://en.openei.org/wiki/Raft_River_Geothermal_Area) and Coso Geothermal Area (http://en.openei.org/wiki/Coso_Geothermal_Area). In 2013, ten additional case studies were completed, and Semantic MediaWiki features were developed to allow for more data and the direct citations of these data. These case studies are now in the process of external peer review. In 2014, NREL is working with universities and industry partners to populate additional case studies on OpenEI. The goal is to provide a large enough data set to start conducting analyses of exploration programs to identify correlations between successful exploration plans for areas with similar geologic occurrence models.

Cryostat design case studies, principles and engineering

CERN Document Server

2016-01-01

This book enables the reader to learn the fundamental and applied aspects of practical cryostat design by examining previous design choices and resulting cryostat performance. Through a series of extended case studies the book presents an overview of existing cryostat design covering a wide range of cryostat types and applications, including the magnet cryostats that comprise the majority of the Large Hadron Collider at CERN, space-borne cryostats containing sensors operating below 1 K, and large cryogenic liquid storage vessels. It starts with an introductory section on the principles of cryostat design including practical data and equations. This section is followed by a series of case studies on existing cryostats, describing the specific requirements of the cryostat, the challenges involved and the design choices made along with the resulting performance of the cryostat. The cryostat examples used in the studies are chosen to cover a broad range of cryostat applications and the authors of each case are ...

STUDY OF 200 CASES OF PLEURAL FLUID

Directory of Open Access Journals (Sweden)

Ramakrishna R

2016-09-01

Full Text Available BACKGROUND We have studied 200 patients of pleural fluid presenting to our tertiary care centre. Presence of cases of pleural fluid is a common presentation both in pulmonary and extrapulmonary diseases. We analysed the patients having both exudates and transudates and studied the results. MATERIALS AND METHODS We selected patients above 20 years of age and classified the patients with pleural fluid as having transudates and exudates. We studied the causes of transudates and exudates. A total of 200 patients are studied in this prospective study. Diagnosis of pleural exudates is made on the basis of Light’s criteria, chest x-ray, pleural fluid analysis, CT scan in selected patients, sputum examination, bronchoscopy and bronchial washings. Moribund and non-cooperative patients and HIV positives were excluded from the study. RESULTS Among the 200 patients, 91% have exudates. 9% have transudates by Light’s criteria. Tuberculosis is the commonest cause of effusions (64.83% followed by malignancy (13.73% and sympneumonic or parapneumonic effusions (9.89%. Pleural effusions occurred predominantly in males. Prevalence of diabetes Mellitus among cases of tuberculous pleural effusions is 13.56%. Tuberculous effusions are predominantly right-sided. CONCLUSION Predominant cases of pleural fluid are exudates. Commonest cause of pleural effusion is Tuberculosis followed by malignancy both pulmonary and extrapulmonary and sym. and parapneumonic effusions. Prevalence of Diabetes among Tuberculous pleural effusion cases is more or less same as in general population. Cough, expectoration fever, chest pain and breathlessness are the common symptoms occurring in three fourths of the patients of tuberculous pleural effusion. Most of the cases of Tuberculous effusion are above 30 years of age. In the diagnosis of tuberculous pleural effusion, Pleural fluid ADA is very important. Pleural fluid cytology, pleural biopsy, bronchoscopy, bronchial washings and sputum

Hanging an Airplane: A Case Study in Static Equilibrium

Science.gov (United States)

Katz, Debora M.

2009-11-01

Our classrooms are filled with engineering majors who take a semester-long course in static equilibrium. Many students find this class too challenging and drop their engineering major. In our introductory physics class, we often breeze through static equilibrium; to physicists equilibrium is just a special case of Newton's second law. While it is difficult to find more time in the syllabus for any one topic, a hands-on case study may help students to develop their physical intuition about static equilibrium and may help them to succeed in their subsequent classes. This article describes a hands-on case study that you may wish to use in your classroom. (You may also wish to check a case study involving a boat published in this journal in the 1990s. ) The hands-on case study presented here can be easily modified to work at the high school or introductory college level. There are three major components: I) planning, II) doing, and III) calculating.

Case Studies in the Field of Marketing Education: Learner Impact, Case Performance, and Cost Efficiency

Science.gov (United States)

Spais, George S.

2005-01-01

The major objective of this study is to identify a methodology that will help educators in marketing to efficiently manage the design, impact, and cost of case studies. It is my intention is to examine the impact of case study characteristics in relation to the degree of learner involvement in the learning process. The author proposes that…

Putting Words in Their Mouth: Writing Dialogue for Case Studies

Science.gov (United States)

Herreid, Clyde Freeman

2018-01-01

This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. This issue discusses dialogue writing guidelines most relevant to case writing.

Dataset for case studies of hydropower unit commitment

Directory of Open Access Journals (Sweden)

Jinwen Wang

2018-06-01

Full Text Available This paper presents the data all needed for nine case studies of hydropower unit commitment, which determines the optimal operating zones and generating discharges of units after the quarter-hourly releases and water heads are derived by the operation of cascaded hydropower reservoirs. The power output function and feasible operating zones of units are provided, and optimization solvers are used to acquire the results in detail for the case studies, including the quarter-hourly generating discharges, power generations, as well as operating zones of individual units. Performance indices, including the spillage, energy production, and the low-efficiency generating rate, are summarized for all case studies and can be readily used for comparison between algorithms in future.

THE STATE OF THE COMMONS: CASE STUDIES 2010

Directory of Open Access Journals (Sweden)

Rachel Cobcroft

2010-01-01

Full Text Available Abstract: ‘What artists need to see before they can feel confident about the licenses are examples of other[s] taking the licenses; incorporating them into their practices.’ – OpenBusiness.cc, p. 8 The Creative Commons Case Studies initiative, established in 2008, offers the ‘free culture’community a qualitative resource to chronicle trends in open content licensing (OCL. Seeking feedback as to individual and organisational motivations towards OCL adoption, and through its provision of usage data, jurisdiction and disciplinary distribution, the CC Case Studies wiki complements current quantitative research projects such as CC Monitor. Containing over 200 entries in July 2010, the CC Case Studies wiki covers several genres such as publishing, moving images, music, visual arts, interactive resources including games, performance, education, and ‘government 2.0’ open data initiatives. Entries represent 25 contributing jurisdictions, with studies being written in several languages including English, Spanish, Portuguese, German, and Korean. By sharing stories of success and identifying areas of innovation and collaboration, the CC Case Studies wiki encourages creators to contribute to the Commons, whilst contributing to a broader understanding of the dynamics of ‘free culture.’

Collaborative Assessment: Middle School Case Study

Science.gov (United States)

Parkison, Paul T.

2014-01-01

Utilizing a participant observer research model, a case study of the efficacy of a collaborative assessment methodology within a middle school social studies class was conducted. A review of existing research revealed that students' perceptions of assessment, evaluation, and accountability influence their intrinsic motivation to learn. A…

Souvenirs: A Case Study for the 90s.

Science.gov (United States)

Shagam, Janet Yagoda; Decker, Janet; Stanley, Ethel

The case-based study, which presents students with a dilemma that encourages exploration, is becoming a popular method for teaching biology. This Web-based report offers one such case study that asks readers to solve problems and make decisions based on information gathered as they engage with characters or situations in the story. The basis for…

Employing Two Factor Authentication Mechanisms: A Case Study

Science.gov (United States)

Lawrence, Cameron; Fulton, Eric; Evans, Gerald; Firth, David

2014-01-01

This case study examines the life of a digital native who has her online accounts hacked, passwords reset, and is locked out of important online resources including her university email account and Facebook. Part one of the case study examines how the hack was perpetrated and the fallout of losing control of one's digital identity. Part two of the…

SARS: a comparative study on the chest radiography of the mortal cases and the cured cases

International Nuclear Information System (INIS)

Jiang Songfeng; Liu Jingxin; Chen Bihua; Zhang Lieguang; Yin Chibiao; Zhang Fuchun

2003-01-01

Objective: This study is mainly on the radiological findings of the mortal cases of SARS. Methods: The chest X-ray (CXR) findings of 11 mortal cases of SARS were retrospectively studied, and compared with those of the 249 cured cases. Results: The major CXR findings of the mortal cases were: patchy shadows in 10 cases out of 11 (90.90%), frosted glass like change of the lung fields in 9 (81.82%), diffuse lesions in 11 (100%), and involvement of the bilateral lung. There was a statistical difference between the mortal cases and the cured cases on the following 4 manifestations: large shadows, extensive consolidation, frosted glass like change of the lung fields, and diffuse lesions (P<0.01). Conclusion: Large shadows, extensive consolidation, frosted glass like change of the lung fields, diffuse lesions and the bilateral involvement of the lung are the main CXR findings of the mortal cases of SARS. And extensive consolidation and diffuse involvement are strongly indicative. In most of the mortal cases, the latest CXR demonstrated widespread frosted glass like appearance in the lung fields with air bronchogram

Large-scale control of the Arabian Sea monsoon inversion in August

Science.gov (United States)

Wu, Chi-Hua; Wang, S.-Y. Simon; Hsu, Huang-Hsiung

2017-12-01

The summer monsoon inversion in the Arabian Sea is characterized by a large amount of low clouds and August as the peak season. Atmospheric stratification associated with the monsoon inversion has been considered a local system influenced by the advancement of the India-Pakistan monsoon. Empirical and numerical evidence from this study suggests that the Arabian Sea monsoon inversion is linked to a broader-scale monsoon evolution across the African Sahel, South Asia, and East Asia-Western North Pacific (WNP), rather than being a mere byproduct of the India-Pakistan monsoon progression. In August, the upper-tropospheric anticyclone in South Asia extends sideways corresponding with the enhanced precipitation in the subtropical WNP, equatorial Indian Ocean, and African Sahel while the middle part of this anticyclone weakens over the Arabian Sea. The increased heating in the adjacent monsoon systems creates a suppression effect on the Arabian Sea, suggesting an apparent competition among the Africa-Asia-WNP monsoon subsystems. The peak Sahel rainfall in August, together with enhanced heating in the equatorial Indian Ocean, produces a critical effect on strengthening the Arabian Sea thermal inversion. By contrast, the WNP monsoon onset which signifies the eastward expansion of the subtropical Asian monsoon heating might play a secondary or opposite role in the Arabian Sea monsoon inversion.

Prader-Willi Disease: A Case Study.

Science.gov (United States)

Forbus, William R., III

A case study focuses on the characteristics and physical management of a 15-year-old with Prader-Willi Syndrome, a birth defect associated with hypotonia, insatiable appetite, hypogonadism, central nervous system dysfunction, and abnormal growth and development . A literature review addresses studies dealing with behavior modification of obesity…

Censored Hurdle Negative Binomial Regression (Case Study: Neonatorum Tetanus Case in Indonesia)

Science.gov (United States)

Yuli Rusdiana, Riza; Zain, Ismaini; Wulan Purnami, Santi

2017-06-01

Hurdle negative binomial model regression is a method that can be used for discreate dependent variable, excess zero and under- and overdispersion. It uses two parts approach. The first part estimates zero elements from dependent variable is zero hurdle model and the second part estimates not zero elements (non-negative integer) from dependent variable is called truncated negative binomial models. The discrete dependent variable in such cases is censored for some values. The type of censor that will be studied in this research is right censored. This study aims to obtain the parameter estimator hurdle negative binomial regression for right censored dependent variable. In the assessment of parameter estimation methods used Maximum Likelihood Estimator (MLE). Hurdle negative binomial model regression for right censored dependent variable is applied on the number of neonatorum tetanus cases in Indonesia. The type data is count data which contains zero values in some observations and other variety value. This study also aims to obtain the parameter estimator and test statistic censored hurdle negative binomial model. Based on the regression results, the factors that influence neonatorum tetanus case in Indonesia is the percentage of baby health care coverage and neonatal visits.

Synthesis across social innovation case studies

DEFF Research Database (Denmark)

Jørgensen, Michael Søgaard; Avelino, Flor; Dorland, Jens

2016-01-01

Part 1 is an overview and a comparative analysis of the findings from the 20 case study reports in TRANSIT about aspects of transformative social innovation (TSI). Each of the 20 reports, which the report is based on, includes an analysis of a transnational social innovation network and at least...... two local social innovation initiatives. Part 2 consists of extended abstracts of 8 papers which either focus on empirical phenomena surfacing in different TRANSIT cases (e.g. alternative economic arrangements), take a societal or methodological issue as starting point (e.g. inclusivity or research...... relations), address propositions from TRANSIT proto-theory (institutionalization dialectics, responses to crisis), build upon thematic clusters used for case selection (e.g. spaces for/of innovation, inclusive society, new economy, transformative science) or inductively develop specific sensitizing concepts...

The Use of Case Studies in OR Teaching

Science.gov (United States)

Penn, Marion L.; Currie, Christine S. M.; Hoad, Kathryn A.; O'Brien, Frances A.

2016-01-01

This article investigates the current use of case studies in the teaching of Operational Research (OR) in the UK: how and where they are used; how they are developed; and whether there is an interest in training this area. It is aimed at lecturers teaching OR who are using or planning to use case studies in their teaching. It may also be of…

Case Studies in Library Computer Systems.

Science.gov (United States)

Palmer, Richard Phillips

Twenty descriptive case studies of computer applications in a variety of libraries are presented in this book. Computerized circulation, serial and acquisition systems in public, high school, college, university and business libraries are included. Each of the studies discusses: 1) the environment in which the system operates, 2) the objectives of…

Guidelines for Using Case Studies in the Teaching-Learning Process

Science.gov (United States)

McFarlane, Donovan A.

2015-01-01

In this paper, the author expresses concerns regarding the extensive use of case studies in the college classroom and advises college and university faculties to be more careful in their selection and use of case studies as an effective­-based method of teaching. The author communicates the important role that case studies play in teaching and…

Homocyst(e)ine and cardiovascular disease: a systematic review of the evidence with special emphasis on case-control studies and nested case-control studies.

Science.gov (United States)

Ford, Earl S; Smith, S Jay; Stroup, Donna F; Steinberg, Karen K; Mueller, Patricia W; Thacker, Stephen B

2002-02-01

Elevated concentrations of homocyst(e)ine are thought to increase the risk of vascular diseases including coronary heart disease and cerebrovascular disease. We searched MEDLINE (1966-1999), EMBASE (1974-1999), SciSearch (1974- 1999), and Dissertation Abstracts (1999) for articles and theses about homocyst(e)ine concentration and coronary heart disease and cerebrovascular disease. We included 57 publications (3 cohort studies, 12 nested case-control studies, 42 case-control studies) that reported results on 5518 people with coronary heart disease (11,068 control subjects) and 1817 people with cerebrovascular disease (4787 control subjects) in our analysis. For coronary heart disease, the summary odds ratios (OR) for a 5-micromol/l increase in homocyst(e)ine concentration were 1.06 (95% CI : 0.99-1.13) for 2 publications of cohort studies, 1.23 (95% CI : 1.07-1.41) for 10 publications of nested case-control studies, and 1.70 (95% CI : 1.50-1.93) for 26 publications of case-control studies. For cerebrovascular disease, the summary OR for a 5-micromol/l increase in homocyst(e)ine concentration were 1.10 (95% CI : 0.94-1.28) for 2 publications of cohort studies, 1.58 (95% CI : 1.35-1.85) for 5 publications of nested case-control studies, and 2.16 (95% CI : 1.65-2.82) for 17 publications of case-control studies. Prospective studies offer weaker support than case-control studies for an association between homocyst(e)ine concentration and cardiovascular disease. Although other lines of evidence support a role for homocyst(e)ine in the pathogenesis of cardiovascular disease, more information from prospective epidemiological studies or clinical trials is needed to clarify this role.

Diagnosing GCM errors over West Africa using relaxation experiments. Part II: intraseasonal variability and African easterly waves

Science.gov (United States)

Pohl, Benjamin; Douville, Hervé

2011-10-01

A near-global grid-point nudging of the Arpege-Climat atmospheric General Circulation Model towards ECMWF reanalyses is used to diagnose the regional versus remote origin of the summer model biases and variability over West Africa. First part of this study revealed a limited impact on the monsoon climatology compared to a control experiment without nudging, but a significant improvement of interannual variability, although the amplitude of the seasonal anomalies remained underestimated. Focus is given here on intraseasonal variability of monsoon rainfall and dynamics. The reproducible part of these signals is investigated through 30-member ensemble experiments computed for the 1994 rainy season, a year abnormally wet over the Sahel but representative of the model systematic biases. In the control experiment, Arpege-Climat simulates too few rainy days that are associated with too low rainfall amounts over the central and western Sahel, in line with the seasonal dry biases. Nudging the model outside Africa tends to slightly increase the number of rainy days over the Sahel, but has little effect on associated rainfall amounts. However, results do indicate that a significant part of the monsoon intraseasonal variability simulated by Arpege-Climat is controlled by lateral boundary conditions. Parts of the wet/dry spells over the Sahel occur in phase in the 30 members of the nudging experiment, and are therefore embedded in larger-scale variability patterns. Inter-member spread is however not constant across the selected summer season. It is partly controlled by African Easterly Waves, which show dissimilar amplitude from one member to another, but a coherent phasing in all members. A lowpass filtering of the nudging fields suggests that low frequency variations in the lateral boundary conditions can lead to eastward extensions of the African Easterly Jet, creating a favorable environment for easterly waves, while high frequency perturbations seem to control their

Diagnosing GCM errors over West Africa using relaxation experiments. Part II: intraseasonal variability and African easterly waves

Energy Technology Data Exchange (ETDEWEB)

Pohl, Benjamin [CNRM-GAME, Meteo-France, CNRS, Toulouse (France); Centre de Recherches de Climatologie, CNRS, Universite de Bourgogne, Dijon (France); Douville, Herve [CNRM-GAME, Meteo-France, CNRS, Toulouse (France)

2011-10-15

A near-global grid-point nudging of the Arpege-Climat atmospheric General Circulation Model towards ECMWF reanalyses is used to diagnose the regional versus remote origin of the summer model biases and variability over West Africa. First part of this study revealed a limited impact on the monsoon climatology compared to a control experiment without nudging, but a significant improvement of interannual variability, although the amplitude of the seasonal anomalies remained underestimated. Focus is given here on intraseasonal variability of monsoon rainfall and dynamics. The reproducible part of these signals is investigated through 30-member ensemble experiments computed for the 1994 rainy season, a year abnormally wet over the Sahel but representative of the model systematic biases. In the control experiment, Arpege-Climat simulates too few rainy days that are associated with too low rainfall amounts over the central and western Sahel, in line with the seasonal dry biases. Nudging the model outside Africa tends to slightly increase the number of rainy days over the Sahel, but has little effect on associated rainfall amounts. However, results do indicate that a significant part of the monsoon intraseasonal variability simulated by Arpege-Climat is controlled by lateral boundary conditions. Parts of the wet/dry spells over the Sahel occur in phase in the 30 members of the nudging experiment, and are therefore embedded in larger-scale variability patterns. Inter-member spread is however not constant across the selected summer season. It is partly controlled by African Easterly Waves, which show dissimilar amplitude from one member to another, but a coherent phasing in all members. A lowpass filtering of the nudging fields suggests that low frequency variations in the lateral boundary conditions can lead to eastward extensions of the African Easterly Jet, creating a favorable environment for easterly waves, while high frequency perturbations seem to control their

DEVELOPMENT OF CROSS-BORDER AREAS. STUDY CASES REVIEW

Directory of Open Access Journals (Sweden)

Marcela\tȘLUSARCIUC

2015-06-01

Full Text Available The paper aims to review study cases found in the scientific literature concerning the development of cross- border areas in European Union and its neighbourhood. The introductory part of the paper is drawing few considerations about the cross-border areas. Further we identified in the specific literature relevant study cases that provide lessons learned, tools and models that can contribute to the development of the cross-border areas. The last part of the paper is focusing on an inquiry about how this lessons, learned, tools and models may be adapted in case of cross-border areas along the Romanian border with the EU Eastern Neighbourhood.

A Review of Case-Based Learning Practices in an Online MBA Program: A Program-Level Case Study

Science.gov (United States)

Lee, Seung-hee; Lee, Jieun; Liu, Xiaojing; Bonk, Curt J.; Magjuka, Richard J.

2009-01-01

This study examines how a case-based learning approach was used and facilitated in online business education. Perceptions of students and instructors regarding the practices of case-based learning in online environments are explored in terms of instructional design, facilitation, and technology support. This study finds case-based learning to be a…

The evaporative fraction as a measure of surface energy partitioning

Energy Technology Data Exchange (ETDEWEB)

Nichols, W.E. [Pacific Northwest Lab., Richland, WA (United States); Cuenca, R.H. [Oregon State Univ., Corvallis, OR (United States)

1990-12-31

The evaporative fraction is a ratio that expresses the proportion of turbulent flux energy over land surfaces devoted to evaporation and transpiration (evapotranspiration). It has been used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on mid-day remote sensing measurements. The HAPEX-MOBILHY program`s SAMER system provided surface energy balance data over a range of agricultural crops and soil types. The databases from this large-scale field experiment was analyzed for the purpose of studying the behavior and daylight stability of the evaporative fraction in both ideal and general meteorological conditions. Strong linear relations were found to exist between the mid-day evaporative fraction and the daylight mean evaporative fraction. Statistical tests however rejected the hypothesis that the two quantities were equal. The relations between the evaporative fraction and the surface soil moisture as well as soil moisture in the complete vegetation root zone were also explored.

The evaporative fraction as a measure of surface energy partitioning

Energy Technology Data Exchange (ETDEWEB)

Nichols, W.E. (Pacific Northwest Lab., Richland, WA (United States)); Cuenca, R.H. (Oregon State Univ., Corvallis, OR (United States))

1990-01-01

The evaporative fraction is a ratio that expresses the proportion of turbulent flux energy over land surfaces devoted to evaporation and transpiration (evapotranspiration). It has been used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on mid-day remote sensing measurements. The HAPEX-MOBILHY program's SAMER system provided surface energy balance data over a range of agricultural crops and soil types. The databases from this large-scale field experiment was analyzed for the purpose of studying the behavior and daylight stability of the evaporative fraction in both ideal and general meteorological conditions. Strong linear relations were found to exist between the mid-day evaporative fraction and the daylight mean evaporative fraction. Statistical tests however rejected the hypothesis that the two quantities were equal. The relations between the evaporative fraction and the surface soil moisture as well as soil moisture in the complete vegetation root zone were also explored.

Leading and leadership: Reflections on a case study.

OpenAIRE

Joyce, Pauline

2010-01-01

Aim: The aim of this case study was to explore if observing leaders in the context of their day-to-day work can provide an insight into how they lead in particular circumstances. Background: The study was carried out in small organisation which was set up five years ago. Methods: A case study methodology was used. Data was collected by field notes of non-participant and participant observations. Follow-up interviews were transcribed and analysed to contextualise the observations. A refl...

Matched case-control studies: a review of reported statistical methodology

Directory of Open Access Journals (Sweden)

Niven DJ

2012-04-01

Full Text Available Daniel J Niven1, Luc R Berthiaume2, Gordon H Fick1, Kevin B Laupland11Department of Critical Care Medicine, Peter Lougheed Centre, Calgary, 2Department of Community Health Sciences, University of Calgary, Calgary, Alberta, CanadaBackground: Case-control studies are a common and efficient means of studying rare diseases or illnesses with long latency periods. Matching of cases and controls is frequently employed to control the effects of known potential confounding variables. The analysis of matched data requires specific statistical methods.Methods: The objective of this study was to determine the proportion of published, peer reviewed matched case-control studies that used statistical methods appropriate for matched data. Using a comprehensive set of search criteria we identified 37 matched case-control studies for detailed analysis.Results: Among these 37 articles, only 16 studies were analyzed with proper statistical techniques (43%. Studies that were properly analyzed were more likely to have included case patients with cancer and cardiovascular disease compared to those that did not use proper statistics (10/16 or 63%, versus 5/21 or 24%, P = 0.02. They were also more likely to have matched multiple controls for each case (14/16 or 88%, versus 13/21 or 62%, P = 0.08. In addition, studies with properly analyzed data were more likely to have been published in a journal with an impact factor listed in the top 100 according to the Journal Citation Reports index (12/16 or 69%, versus 1/21 or 5%, P ≤ 0.0001.Conclusion: The findings of this study raise concern that the majority of matched case-control studies report results that are derived from improper statistical analyses. This may lead to errors in estimating the relationship between a disease and exposure, as well as the incorrect adaptation of emerging medical literature.Keywords: case-control, matched, dependent data, statistics

CULTURAL CHANGE IN TELECOMMUNICATIONS COMPANIES: A CASE STUDY

Directory of Open Access Journals (Sweden)

Cristiane Alves Anacleto

2014-09-01

Full Text Available This work aims to propose a model for the conduct of cultural change in the IT department of a company in the telecommunications industry. To achieve the goal proposed exploratory, technical procedures used were the case study and literature review. The techniques of data collection in the case study were: participant observation, unstructured interview and document analysis. The proposed model consists of five steps: analysis of the company's strategic planning, cultural diagnosis of the IT department, brainstorming with the staff and managers, compared to the case studies surveyed and proposed actions for the conduct of cultural change. We conclude that a receptive environment, employees not only understand why the changes are necessary, but engage with the process and faithfully executes the steps required, favoring the strategic positioning of the company.

Case studies in organic contaminant hydrogeology

International Nuclear Information System (INIS)

Baker, J.A.

1989-01-01

The effective management of domestic solid waste and hazardous, toxic, and radioactive waste is a major problem in the area of environmental geology and water sciences throughout the world. A series of case studies is presented of organic contaminants from both solid and hazardous waste disposal facilities to provide examples of these problems. The facilities were investigated to determine risks and liabilities before acquisition, to determine the site hydrogeologic conditions for design of appropriate groundwater monitoring plans, and/or to determine the potential for groundwater contamination. The case studies are of disposal facilities located in glacial tills, carbonaceous weathered clay soils, weathered shale, limestone bedrock, dolomite bedrock, and alluvial and sedimentary deposits. The results of these studies and investigations show certain relationships in the distribution of organic pollutants to the different geologic and hydrogeologic characteristics of each facility. In each of the four case studies, all 129 priority pollutants were analyzed in private wells and/or monitoring wells. The 31 volatile organic compounds (VOCs) of the priority pollutant list were the majority of organic compounds detected. When VOCs are found in groundwater impacted by disposal facilities, they are present in groups and tend to be distributed in patterns based on their relative concentrations. It is rare to find only one or two VOCs from facilities where leakage has been detected. The ethylenes and ethanes appear to be more prevalent and mobile than aromatic VOCs. The aromatics are restricted primarily to leachates and wastes and in monitoring wells located adjacent to facilities. 2 refs., 15 figs

Case Study: Student-Produced Videos for the Flipped Classroom

Science.gov (United States)

Prud'homme-Genereux, Annie

2016-01-01

This column provides original articles on innovations in case study teaching, assessment of the method, as well as case studies with teaching notes. This month's issue describes a way of building a library of student-produced videos to use in the flipped classroom.

Nanomaterial Case Studies: Nanoscale Titanium Dioxide (External Review Draft)

Science.gov (United States)

This draft document presents two case studies of nanoscale titanium dioxide (nano-TiO2) used (1) to remove arsenic from drinking water and (2) as an active ingredient in topical sunscreen. The draft case studies are organized around a comprehensive environmental asses...

A Neuroanatomy Teaching Activity Using Case Studies and Collaboration.

Science.gov (United States)

Sheldon, Jane P.

2000-01-01

Describes an activity for use in an introductory psychology course in which students collaborate and apply their neuroanatomy knowledge to three case studies. Provides a table with descriptions of and possible answers for the three case studies and discusses the students' responses. (CMK)

Pilot case-control study of paediatric falls from windows.

Science.gov (United States)

Johnston, Brian D; Quistberg, D Alexander; Shandro, Jamie R; Partridge, Rebecca L; Song, Hyun Rae; Ebel, Beth E

2011-12-01

Unintentional falls from windows are an important cause of paediatric morbidity. There have been no controlled studies to identify modifiable environmental risk factors for window falls in young children. The authors have piloted a case-control study to test procedures for case identification, subject enrolment, and environmental data collection. Case windows were identified when a child 0-9 years old presented for care after a fall from that window. Control windows were identified (1) from the child's home and (2) from the home of an age- and gender-matched child seeking care for an injury diagnosis not related to a window fall. Study staff visited enrolled homes to collect window measurements and conduct window screen performance tests. The authors enrolled and collected data on 18 case windows, 18 in-home controls, and 14 matched community controls. Six potential community controls were contacted for every one enrolled. Families who completed the home visit viewed study procedures positively. Case windows were more likely than community controls to be horizontal sliders (100% vs 50%), to have deeper sills (6.28 vs 4.31 inches), to be higher above the exterior surface (183 vs 82 inches), and to have screens that failed below a threshold derived from the static pressure of a 3-year-old leaning against the mesh (60.0% vs 16.7%). Case windows varied very little from in-home controls. Case-control methodology can be used to study risk factors for paediatric falls from windows. Recruitment of community controls is challenging but essential, because in-home controls tend to be over-matched on important variables. A home visit allows direct measurement of window type, height, sill depth, and screen performance. These variables should all be investigated in subsequent, larger studies covering major housing markets.

Transformational change in healthcare: an examination of four case studies.

Science.gov (United States)

Charlesworth, Kate; Jamieson, Maggie; Davey, Rachel; Butler, Colin D

2016-04-01

Objectives Healthcare leaders around the world are calling for radical, transformational change of our health and care systems. This will be a difficult and complex task. In this article, we examine case studies in which transformational change has been achieved, and seek to learn from these experiences. Methods We used the case study method to investigate examples of transformational change in healthcare. The case studies were identified from preliminary doctoral research into the transition towards future sustainable health and social care systems. Evidence was collected from multiple sources, key features of each case study were displayed in a matrix and thematic analysis was conducted. The results are presented in narrative form. Results Four case studies were selected: two from the US, one from Australia and one from the UK. The notable features are discussed for each case study. There were many common factors: a well communicated vision, innovative redesign, extensive consultation and engagement with staff and patients, performance management, automated information management and high-quality leadership. Conclusions Although there were some notable differences between the case studies, overall the characteristics of success were similar and collectively provide a blueprint for transformational change in healthcare. What is known about the topic? Healthcare leaders around the world are calling for radical redesign of our systems in order to meet the challenges of modern society. What does this paper add? There are some remarkable examples of transformational change in healthcare. The key factors in success are similar across the case studies. What are the implications for practitioners? Collectively, these key factors can guide future attempts at transformational change in healthcare.

Supply chain strategy: empirical case study in Europe and Asia:

OpenAIRE

Sillanpää, Ilkka; Sillanpää, Sebastian

2014-01-01

The purpose of this case study research is to present a literature review of supply chain strategy approaches, develop supply chain strategy framework and to validate a framework in empirical case study. Literature review and case study research are the research methods for this research. This study presents the supply chain strategy framework which merges together business environment, corporate strategy, supply chain demand and supply chain strategy. Research argues that all the different c...

CASE STUDY

African Journals Online (AJOL)

2010-09-01

Sep 1, 2010 ... of the two diseases surgery can be successful, recovery can be similar to that .... lymphocytes predominated in 68% of cases, and that there was an .... using ferritin is the fact that it acts as an acute-phase reactant and will be ...

EL PROGRAMA CASE STUDY HOUSE: INDUSTRIA, PROPAGANDA Y VIVIENDA / Case Study House Program: industry, propaganda and housing

Directory of Open Access Journals (Sweden)

Daniel Díez Martínez

2012-05-01

Full Text Available RESUMEN En enero de 1945, John Entenza, editor de la revista californiana Arts & Architecture, puso en marcha el programa Case Study House, un ambicioso proyecto cuyo firme objetivo era investigar las posibilidades y soluciones del problema de la vivienda al que se enfrentaba los Estados Unidos de la posguerra. Para ello, Entenza diseñó una novedosa estrategia de colaboración entre algunos de los mejores arquitectos californianos del momento y la maquinaria industrial estadounidense, abierta a un proceso de reconversión de producción bélica a objetos para la población civil que tendría lugar en un tiempo récord. Así, el artículo propone el análisis de esa relación entre empresa y domesticidad, entre viabilidad económica y calidad arquitectónica, entre procesos de prefabricación y espíritu individual. Todos ellos conceptos aparentemente opuestos pero que, de la mano del programa Case Study House, lograron un entendimiento que a día de hoy sigue resultando extraordinario. SUMMARY In January 1945, John Entenza, editor of the California Arts & Architecture magazine, launched the ‘Case Study House Program’, an ambitious project whose firm objective was to investigate the possibilities and solutions for the housing problem facing the United States after the war. To do this, Entenza designed a novel strategy for collaboration between some of the best Californian architects of the time and the U.S. industrial machine, open to a process of conversion from military production to objects for the civilian population that would take place in record time. Thus, the article proposes the analysis of the relationship between business and domesticity, between economic viability and architectural quality, between prefabrication processes and individual spirit. All of these seemingly opposing concepts reached, at the hands of the ‘Case Study House Program’, an understanding that still seems extraordinary today.

Association Between Anemia and Cerebral Venous Thrombosis: Case-Control Study

NARCIS (Netherlands)

Coutinho, Jonathan M.; Zuurbier, Susanna M.; Gaartman, Aafke E.; Dikstaal, Arienne A.; Stam, Jan; Middeldorp, Saskia; Cannegieter, Suzanne C.

2015-01-01

Anemia is often considered to be a risk factor for cerebral venous thrombosis (CVT), but this assumption is mostly based on case reports. We investigated the association between anemia and CVT in a controlled study. Unmatched case-control study: cases were adult patients with CVT included in a

Using the Case Study Method in Teaching College Physics

Science.gov (United States)

Burko, Lior M.

2016-10-01

The case study teaching method has a long history (starting at least with Socrates) and wide current use in business schools, medical schools, law schools, and a variety of other disciplines. However, relatively little use is made of it in the physical sciences, specifically in physics or astronomy. The case study method should be considered by physics faculty as part of the effort to transition the teaching of college physics from the traditional frontal-lecture format to other formats that enhance active student participation. In this paper we endeavor to interest physics instructors in the case study method, and hope that it would also serve as a call for more instructors to produce cases that they use in their own classes and that can also be adopted by other instructors.

Case study on bio-remediation. Bio remediation no case study

Energy Technology Data Exchange (ETDEWEB)

Cioffi, J; Lehmicke, L

1993-08-01

This paper introduces two cases of contamination removal using microorganisms in areas contaminated by harmful substances, carried out by ECOVA Inc. in the U.S.A. One case is a removal of soils over an area of 230,000 m[sup 3] contaminated with petroleum-based substances. The removal was intended to reduce contamination at higher than 15,000 ppm down to 1,000 ppm. Discussions on pilot soils and monitoring of activities of living organisms were carried out to determine an optimal condition. It was found that microorganisms having orange color matters have decomposing capability, produce mucopolysaccharides in long-chained hydrocarbon, and make hydrocarbon soluble. The contaminant removal in this area took 19 months. The decomposition work required consideration on temperatures, moistures, aeration frequencies, and nutrient amounts as the affecting factors. The other case is an experiment on removing perchloroethylene (PCE) and trichloroethylene (TCE) from water in the Savanna River. Microorganisms that decompose only TCE were used, with existing methane as a carbon source. An interim result has been obtained that TCE:PCE changed from 0.65:1 to 0.35:1 in twelve months. There has been neither increase nor decrease in the amount of microorganisms.

Insider Threat Case Studies at Radiological and Nuclear Facilities

Energy Technology Data Exchange (ETDEWEB)

Pope, Noah Gale [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hobbs, Christopher [Centre for Science and Security Studies, London (United Kingdom)

2015-04-13

Seven case studies are presented. The cases include thefts of various materials and sabotage. For each case there is an overview of the incident, a timeline, a profile of the perpetrator, and a discussion of the security system failures which allowed the incident to take place.

Insider Threat Case Studies at Radiological and Nuclear Facilities

International Nuclear Information System (INIS)

Pope, Noah Gale; Hobbs, Christopher

2015-01-01

Seven case studies are presented. The cases include thefts of various materials and sabotage. For each case there is an overview of the incident, a timeline, a profile of the perpetrator, and a discussion of the security system failures which allowed the incident to take place.

Clinical Study on Five Cases of Carpal tunnel syndrome

Directory of Open Access Journals (Sweden)

Kim Il Hwan

2001-12-01

Full Text Available Objections : The purpose of the study was to evaluate the effectiveness of treating the carpal tunnel syndrome by using both the Herbal Acupuncture and herbal medicine therapy on five cases. Methods : For the Herbal Acupuncture, Jungseonguhhyl No. 1 and Hwanglyunhaedoktang were used. For the herbal medicine, Dangguihwalhyul-tang was used. The patients were treated once in every two days; the result was evaluated after ten treatments. Patients' conditions were monitored through their testimony, phalen's test, nerve conduction study and electromyography. Results : In all five cases, the patients showed improvement; in four cases, the patients no longer had most of the clinical symptoms. Based on the result of the nerve conduction study, for the four cases in which the patients no longer displayed most of the clinical symptoms, their nerve conduction rate improved; for the remaining one case, the patient's nerve conduction rate deteriorated. Conclusions : The results of this study demonstrate that combining the Herbal Acupuncture and herbal medicine therapy can have noticeable effects in treating the carpal tunnel syndrome; developing more variety of the herbal acupuncture would lead to even better treatment results.

Neonatal appendicitis: a survival case study

Directory of Open Access Journals (Sweden)

Izabela Linha Secco

Full Text Available ABSTRACT Objective: To report a case of neonatal appendicitis in a children’s hospital in southern Brazil, demonstrating the impact on neonatal survival. Method: Case study with data collection from medical records, approved by the Institution and Ethics Committee for Research with Human Beings. Results: The clinical picture is initially characterized by food intolerance, evolving to hypoactivity, alteration of vital signs and septicemia due to intestinal perforation. Management is exclusively surgical, since no case described in the literature was diagnosed preoperatively and the findings usually point to acute abdomen. Conclusion: A focused clinical surveillance should be established when the infant presents peritoneal irritation. Follow-up of the evolution and the worsening of the symptoms by nurses, as part of the care team in partnership with the medical team, enables an early surgical intervention, thereby avoiding complications such as septicemia and death.

Test Automation Process Improvement A case study of BroadSoft

OpenAIRE

Gummadi, Jalendar

2016-01-01

This master thesis research is about improvement of test automation process at BroadSoft Finland as a case study. Test automation project recently started at BroadSoft but the project is not properly integrated in to existing process. Project is about converting manual test cases to automation test cases. The aim of this thesis is about studying existing BroadSoft test process and studying different test automation frameworks. In this thesis different test automation process are studied ...

Memory and Learning: A Case Study.

Science.gov (United States)

Webster, Raymond E.

1986-01-01

The usefulness of the Learning Efficency Test (LET), an approach to assessing the learning efficiency and short-term memory recall capacity in children, is described via a case study demonstrating the test's use to develop instructional strategies. (CL)

Case Study Research Methodology in Nursing Research.

Science.gov (United States)

Cope, Diane G

2015-11-01

Through data collection methods using a holistic approach that focuses on variables in a natural setting, qualitative research methods seek to understand participants' perceptions and interpretations. Common qualitative research methods include ethnography, phenomenology, grounded theory, and historic research. Another type of methodology that has a similar qualitative approach is case study research, which seeks to understand a phenomenon or case from multiple perspectives within a given real-world context.

Analysis of case studies - mining, milling and discharges

International Nuclear Information System (INIS)

McEwan, A.C.

2000-01-01

This analysis paper reviews case studies on mining and milling and on radioactive discharges. An outline is given of each of the case studies presented from the perspectives of the study background, the criteria followed in remediation, the decision making process, outcomes achieved, and an evaluation in relation to radiological criteria that are recommended internationally. Site remediation after mining and milling operations may be driven more by aesthetic and environmental concerns than radiological criteria, particularly in more populated areas. The cases illustrated that it is highly desirable that stakeholders, including the public, are involved in decision making at an early stage with agreement on remediation outcomes. In particular, the exposure pathways and dose assessment models employed should generally be agreed with or approved by the regulatory authority prior to remediation work. In the case of remediated properties at Grand Junction, Colorado, it appears the cleanup criteria employed were below or consistent with those applicable to practices, although the situation was one of intervention, and this raises a question as to the cost effectiveness of the cleanup. For some remediation projects there are long term ownership issues arising out of the need for extended public or state oversight of engineered structures or active water treatment facilities, but for these cases ownership issues did not arise for purely radiological reasons. (author)

Does EO NDVI seasonal metrics capture variations in species composition and biomass due to grazing in semi-arid grassland savannas?

DEFF Research Database (Denmark)

Olsen, J. L.; Miehe, S.; Ceccato, Pietro

2015-01-01

Most regional scale studies of vegetation in the Sahel have been based on Earth observation (EO) imagery due to the limited number of sites providing continuous and long term in situ meteorological and vegetation measurements. From a long time series of coarse resolution normalized difference...... vegetation index (NDVI) data a greening of the Sahel since the 1980s has been identified. However, it is poorly understood how commonly applied remote sensing techniques reflect the influence of extensive grazing (and changes in grazing pressure) on natural rangeland vegetation. This paper analyses the time...... exclosures as compared to grazed areas, substantially exceeding the amount of biomass expected to be ingested by livestock for this area. The seasonal integrated NDVI (NDVI small integral; capturing only the signal inherent to the growing season recurrent vegetation), derived using absolute thresholds...

Provenance Study of Archaeological Ceramics from Syria Using XRF Multivariate Statistical Analysis and Thermoluminescence Dating

OpenAIRE

Bakraji, Elias Hanna; Abboud, Rana; Issa, Haissm

2014-01-01

Thermoluminescence (TL) dating and multivariate statistical methods based on radioisotope X-ray fluorescence analysis have been utilized to date and classify Syrian archaeological ceramics fragment from Tel Jamous site. 54 samples were analyzed by radioisotope X-ray fluorescence; 51 of them come from Tel Jamous archaeological site in Sahel Akkar region, Syria, which fairly represent ceramics belonging to the Middle Bronze Age (2150 to 1600 B.C.) and the remaining three samples come from Mar-T...

Service-oriented enterprise modelling and analysis: a case study

NARCIS (Netherlands)

Iacob, Maria Eugenia; Jonkers, H.; Lankhorst, M.M.; Steen, M.W.A.

2007-01-01

In order to validate the concepts and techniques for service-oriented enterprise architecture modelling, developed in the ArchiMate project (Lankhorst, et al., 2005), we have conducted a number of case studies. This paper describes one of these case studies, conducted at the Dutch Tax and Customs

Case Study: Nutrition in the ICU and multi-organ failure ...

African Journals Online (AJOL)

The following case study was discussed at the recent SASPEN Congress held at Spier Estate, Stellenbosch, South Africa. The case study was adapted from the original and used with the kind permission of Fresenius Kabi, Germany. Herewith follows a summarised discussion of the case. It is a reflection of the general ...

Navigating political minefields: partnerships in organizational case study research.

Science.gov (United States)

Moll, Sandra

2012-01-01

The purpose of this paper is to examine key challenges associated with conducting politically sensitive research within a workplace setting, and to highlight strategic partnerships that can be developed to address these challenges. The author's research on employee mental health issues within a large healthcare facility serves as the foundation for identification and description of "political minefields" that investigators may encounter when conducting organizational case study research. Key methodological principles from the literature on qualitative case study research will frame discussion of how to understand and address political sensitivities in the research process. The benefits of conducting organizational case study research will be outlined, followed by discussion of methodological challenges that can emerge in negotiating entry, collecting data (gatekeepers, researcher reflexivity, participant authenticity and non-maleficence), and communicating research findings. Courage, collaboration and clear communication with stakeholders at all levels of the organization are critical to the success of workplace based case study research.

case study

African Journals Online (AJOL)

Elton

particularly in patients who commence ART with low CD4 counts and established opportunistic infections. IRIS results from a pathological inflammatory response to pre-existing infective, host or other antigens, alive or dead, causing clinical deterioration in HIV-infected patients after initiating ART.1 A case definition for IRIS ...

Russia Foreign Policy In Latin America - Case Study Of Nicaragua

Science.gov (United States)

2017-05-23

case study of Nicaragua deeper than the previous thesis. It relates a study to the larger, ongoing dialogue in the literature, filling in gaps and...RUSSIA FOREIGN POLICY IN LATIN AMERICA — CASE STUDY OF NICARAGUA A thesis presented to the Faculty of the U.S. Army Command and...countries, in which case further publication or sale of copyrighted images is not permissible. ii REPORT DOCUMENTATION PAGE Form Approved OMB No

Genetic history of the African Sahelian populations.

Science.gov (United States)

Černý, V; Kulichová, I; Poloni, E S; Nunes, J M; Pereira, L; Mayor, A; Sanchez-Mazas, A

2018-03-01

From a biogeographic perspective, Africa is subdivided into distinct horizontal belts. Human populations living along the Sahel/Savannah belt south of the Sahara desert have often been overshadowed by extensive studies focusing on other African populations such as hunter-gatherers or Bantu in particular. However, the Sahel together with the Savannah bordering it in the south is a challenging region where people had and still have to cope with harsh climatic conditions and show resilient behaviours. Besides exponentially growing urban populations, several local groups leading various lifestyles and speaking languages belonging to three main linguistic families still live in rural localities across that region today. Thanks to several years of consistent population sampling throughout this area, the genetic history of the African Sahelian populations has been largely reconstructed and a deeper knowledge has been acquired regarding their adaptation to peculiar environments and/or subsistence modes. Distinct exposures to pathogens-in particular, malaria-likely contributed to their genetic differentiation for HLA genes. In addition, although food-producing strategies spread within the Sahel/Savannah belt relatively recently, during the last five millennia according to recent archaeological and archaeobotanical studies, remarkable amounts of genetic differences are also observed between sedentary farmers and more mobile pastoralists at multiple neutral and selected loci, reflecting both demographic effects and genetic adaptations to distinct cultural traits, such as dietary habits. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Cultural change in telecommunications companies: a case study

OpenAIRE

Anacleto, Cristiane Alves; Irion, Crishna; Paladini, Edson Pacheco

2014-01-01

This work aims to propose a model for the conduct of cultural change in the IT department of a company in the telecommunications industry. To achieve the goal proposed exploratory, technical procedures used were the case study and literature review. The techniques of data collection in the case study were: participant observation, unstructured interview and document analysis. The proposed model consists of five steps: analysis of the company's strategic planning, cultural diagnosis of the IT ...

A Soft Systems Approach Case Study. Faustin Kamuzora Abstrac

African Journals Online (AJOL)

Kamuzora

The paper details a case study conducted in Lushoto District, Tanzania ... area's cultural and natural resources through sustainable tourism. To achieve .... As stated above, the case study used the SSM for solving the problems in ..... Constraints: time, political environment, level of education of FoUS members. ... Road sector.

A parathyroid scintigraphy case study

International Nuclear Information System (INIS)

O'Leary, Desiree

2005-01-01

Background: There has been much debate concerning the most suitable protocol for parathyroid scintigraphy; the merits of various radiopharmaceuticals versus the correct imaging protocol to visualise both ectopic and anatomically placed adenomas against the various equipment choices have been debated. Aim: To demonstrate, through the use of a case study, the necessity of changing imaging protocols for parathyroid scintigraphy where a definitive imaging diagnosis is absent in the face of strong clinical suspicion. Method: Use is made of Tc99mMIBI, full field chest scintigraphy, a clearly defined imaging protocol and SPECT imaging to locate ectopic parathyroid tissue in a female patient with significant symptoms of parathyroid hyperfunction. Results: A single hyperfunctioning adenoma is located in the pre-carinal area of the mediastinum. Using a radioguided surgical technique the hyperfunctioning tissue is excised and confirmed by histopathology. Conclusion: Whilst a dramatic reduction in patient symptoms was not seen immediately in this patient, the symptoms of the illness have been subsiding since January 2003. This case study demonstrates the necessity of changing imaging protocols for parathyroid scintigraphy where a definitive imaging diagnosis is absent in the face of strong clinical suspicion

A Case Study Application Of Time Study Model In Paint ...

African Journals Online (AJOL)

This paper presents a case study in the development and application of a time study model in a paint manufacturing company. The organization specializes in the production of different grades of paint and paint containers. The paint production activities include; weighing of raw materials, drying of raw materials, dissolving ...

Security in the Sahel

DEFF Research Database (Denmark)

Hahonou, Eric Komlavi

of volatile security. In this policy brief, Eric Hahonou argues that without complementary activities, the multiplication of border offices could even expand opportunities for corruption. Instead, security policy should focus on creating a culture of effectiveness including systematic and regular staff...

Bridging the Performance Gap with Ergonomics: A Case Study

Science.gov (United States)

Rethaber, James D.

2011-01-01

Faced with increased incidences of work-related strain and sprain injuries and OSHA-recordable injuries, the organization in this case study details how it resolved these performance-related issues. This case study also demonstrates the effectiveness of Thomas Gilbert's (1978) Behavior Engineering Model as a tool for analyzing, defining, and…

Stochastic efficiency: five case studies

International Nuclear Information System (INIS)

Proesmans, Karel; Broeck, Christian Van den

2015-01-01

Stochastic efficiency is evaluated in five case studies: driven Brownian motion, effusion with a thermo-chemical and thermo-velocity gradient, a quantum dot and a model for information to work conversion. The salient features of stochastic efficiency, including the maximum of the large deviation function at the reversible efficiency, are reproduced. The approach to and extrapolation into the asymptotic time regime are documented. (paper)

Case Studies Approach in Tourism Destination Branding Research

OpenAIRE

Adeyinka-Ojo S.F.; Nair V.; Khoo-Lattimore C.

2014-01-01

A review of literature indicates that there are different types of qualitative research methods such as action research, content analysis, ethnography, grounded theory, historical analysis, phenomenology and case study. However, which approach is to be used depends on several factors such as the nature and objectives of the research. The aim of this paper is to focus on the research methodology aspects of applying case study as a research approach and its relevance in tourism destination bran...

Regression analysis for secondary response variable in a case-cohort study.

Science.gov (United States)

Pan, Yinghao; Cai, Jianwen; Kim, Sangmi; Zhou, Haibo

2017-12-29

Case-cohort study design has been widely used for its cost-effectiveness. In any real study, there are always other important outcomes of interest beside the failure time that the original case-cohort study is based on. How to utilize the available case-cohort data to study the relationship of a secondary outcome with the primary exposure obtained through the case-cohort study is not well studied. In this article, we propose a non-parametric estimated likelihood approach for analyzing a secondary outcome in a case-cohort study. The estimation is based on maximizing a semiparametric likelihood function that is built jointly on both time-to-failure outcome and the secondary outcome. The proposed estimator is shown to be consistent, efficient, and asymptotically normal. Finite sample performance is evaluated via simulation studies. Data from the Sister Study is analyzed to illustrate our method. © 2017, The International Biometric Society.

Assessment of global phase uncertainty in case-control studies

Directory of Open Access Journals (Sweden)

van Houwelingen Hans C

2009-09-01

Full Text Available Abstract Background In haplotype-based candidate gene studies a problem is that the genotype data are unphased, which results in haplotype ambiguity. The measure 1 quantifies haplotype predictability from genotype data. It is computed for each individual haplotype, and for a measure of global relative efficiency a minimum value is suggested. Alternatively, we developed methods directly based on the information content of haplotype frequency estimates to obtain global relative efficiency measures: and based on A- and D-optimality, respectively. All three methods are designed for single populations; they can be applied in cases only, controls only or the whole data. Therefore they are not necessarily optimal for haplotype testing in case-control studies. Results A new global relative efficiency measure was derived to maximize power of a simple test statistic that compares haplotype frequencies in cases and controls. Application to real data showed that our proposed method gave a clear and summarizing measure for the case-control study conducted. Additionally this measure might be used for selection of individuals, who have the highest potential for improving power by resolving phase ambiguity. Conclusion Instead of using relative efficiency measure for cases only, controls only or their combined data, we link uncertainty measure to case-control studies directly. Hence, our global efficiency measure might be useful to assess whether data are informative or have enough power for estimation of a specific haplotype risk.

Nuclear Knowledge Management Case Studies Catalogue “NKM CSC”

International Nuclear Information System (INIS)

Atieh, T.

2016-01-01

Full text: Over the past several years, many nuclear organizations in IAEA’s Member States have accumulated considerable experiences and achievements in the development and application of nuclear knowledge management (NKM) methodology and tools to improve their organizational performance. The IAEA NKM Section has initiated a project entitled “NKM Case Studies Catalogue (NKM CSC)” to capture and document, as well as preserve NKM experience and facilitate its sharing among NKM practitioners and experts. This is done through collection and preservation of information of relevant experiential knowledge in “case study” format. The catalogue will therefore support community of practice mechanisms. An input template is currently under development and will be used to help contributors in Member States who are providing concise set of information about their respective case studies. This information will be made searchable and easily retrievable through a platform that supports collaboration among NKM practitioners and experts. It is planned to launch the Nuclear Knowledge Management Case Studies Catalogue “NKM CSC” at the occasion of the “Third International Conference on Nuclear Knowledge Management—Challenges and Approaches, 7-–11 November 2016, Vienna, Austria”, and to include the accepted case studies submitted to this Conference. (author

Clinical and laboratorial study of 19 cases of mucopolysaccharidoses

Directory of Open Access Journals (Sweden)

Albano Lilian M. J.

2000-01-01

Full Text Available The mucopolysaccharidoses (MPS are a heterogeneous group of inborn errors of lysosomal glycosaminoglycan (GAG metabolism. The importance of this group of disorders among the inborn errors of metabolism led us to report 19 cases. METHOD: We performed clinical, radiological, and biochemical evaluations of the suspected patients, which allowed us to establish a definite diagnosis in 19 cases. RESULTS: Not all patients showed increased GAG levels in urine; enzyme assays should be performed in all cases with strong clinical suspicion. The diagnosis was made on average at the age of 48 months, and the 19 MPS cases, after a full clinical, radiological, and biochemical study, were classified as follows: Hurler -- MPS I (1 case; Hunter -- MPS II (2 cases; Sanfilippo -- MPS III (2 cases; Morquio -- MPS IV (4 cases; Maroteaux-Lamy -- MPS VI (9 cases; and Sly -- MPS VII (1 case. DISCUSSION: The high relative frequency of Maroteaux-Lamy disease contrasts with most reports in the literature and could express a population variability.

Real Time Locations Systems or Outsourcing: A Case Study

Science.gov (United States)

Lawrence, Cameron; Firth, David; Khumalo, Floyd

2013-01-01

Information Technology has transformed almost all aspects of modern healthcare and is playing a vital role in the administration of hospitals around the world. This case study examines one hospital's struggle to solve crucial operational problems related to the efficient management of medical equipment inventory. This case study is the result of…

Case Study: Pancreas cancer with Whipple's operation | Blaauw ...

African Journals Online (AJOL)

The following case study was discussed at the SASPEN Workshop held during the Nutrition Congress 2014. It is a reflection of the general opinion of the audience, followed by a rationale of the latest literature on the topic. Herewith follows a summarised discussion of the case. Keywords: pancreas cancer, Whipple ...

Case Study Report about Gender Impact Assessment

DEFF Research Database (Denmark)

Faber, Stine Thidemann; Agustin, Lise Rolandsen

2013-01-01

The aim of this national case study report is to take a closer look at the use of Gender Impact Assessments in Denmark in order to describe the Danish implementation of this specific Gender Mainstreaming method. By way of analyzing two selected cases (two law proposals put forward by The Danish...... Ministry of Employment and the Danish Ministry of Transport, respectively) the aim is to assess the transformative potential of GIA as it is performed in Denmark....

Sahelian pathways : climate and society in Central and South Mali

NARCIS (Netherlands)

Bruijn, de M.E.; Kaag, A M.M.; Til, van A.; Dijk, van J.W.M.

2005-01-01

Climate change is a global problem with local consequences. However, the direction and magnitude of these consequences in extremely vulnerable regions - such as the Sahel - cannot yet be predicted with any certainty. The studies in this volume focus on people for whom climate variability, mainly

Valuation of Conditions of Mechanized Milking of Cows and of the ...

African Journals Online (AJOL)

The aim of this study is to evaluate mainly the conditions the milking and the mammary health status of cows in the central East Sousse (Tunisian Sahel). The study was conducted on a sample of 20 small and means dairy cattle herds aboveground divided into two study areas. This study examined the general conditions of ...