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Search Results: 1 - 10 of 1157 matches for " Astrid Jankielsohn "
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The Importance of Insects in Agricultural Ecosystems  [PDF]
Astrid Jankielsohn
Advances in Entomology (AE) , 2018, DOI: 10.4236/ae.2018.62006
Abstract: Sufficient food production for a growing human population has become an issue of global concern. Almost all of the world’s fertile land is currently in use and arable land areas cannot be expanded significantly. The global challenge is to secure high and quality yields and to make agricultural production environmentally compatible. Insects have been hugely successful in terms of both species richness and abundance. Insects make up the most numerous group of organisms on earth, around 66% of all animal species, and being good dispersers and exploiters of virtually all types of organic matter, can be found almost everywhere, forming an important part of every ecosystem and are vital within our food supply chains performing valuable ecosystem services. Insects have been predominantly perceived as competitors in the race for survival. Herbivorous insects damage 18% of world agricultural production. Despite this damage less than 0.5 percentage of the total number of the known insect species are considered pests. Insect pests are created through the manipulation of habitats by humans, where crops are selected for larger size, higher yields, nutritious value, and are cultivated in monocultures for maximum production. This provides a highly favourable environment for the population increase of herbivorous insects. To ensure stable crop yields we need to change the management strategies of agroecosystems. We need to manage these systems in such a way that insects performing valuable ecosystem services are also incorporated into the system. This will ensure stable, resilient and sustainable systems in a constantly changing environment and will go a long way to ensure future food security. This paper examines the important role that insects generally play in ecosystems and how the services that insects provide can improve agricultural ecosystems.
Evaluation of Dryland Wheat Cultivars on the Market in South Africa for Resistance against Four Known Russian Wheat Aphid, Diuraphis noxia, Biotypes in South Africa  [PDF]
Astrid Jankielsohn
Advances in Entomology (AE) , 2019, DOI: 10.4236/ae.2019.71001
Abstract: An increased wheat yield potential under changing environmental conditions is a challenge in agriculture. Resistant wheat lines can yield more than susceptible wheat lines in the presence of Russian wheat aphid infestation. There are currently four Russian wheat aphid (RWA) biotypes known in South Africa with different virulence against different wheat cultivars. To keep up with the ever-changing patterns it is necessary to screen the cultivars for resistance against these Russian wheat aphid (RWA) biotypes. All the dryland wheat cultivars on the market were evaluated for resistance against the four known Russian wheat aphid (RWA) biotypes in South Africa. Through this evaluation, the status of Russian wheat aphid (RWA) resistance in South African dryland wheat cultivars can be updated to adapt to environmental changes and the wheat industry can adapt to changes in virulence of Russian wheat aphid (RWA) biotypes that may cause damage to Russian wheat aphid (RWA) resistant cultivars, subsequently affecting yield. Evaluations were done in the glasshouse by screening wheat cultivars against four different South African Russian wheat aphid (RWA) biotypes, RWASA1-RWASA4, under controlled conditions. The glasshouse evaluations showed that out of the 19 dryland wheat cultivars currently on the market in South Africa 16 are resistant against RWASA1, 7 are resistant against RWASA2, 7 are resistant against RWASA3 and 5 are resistant against RWASA4. Dryland wheat cultivars were also evaluated under field conditions at four different field localities. In the field, 5 cultivars were resistant to RWASA3 at two localities, respectively, and 3 and 5 cultivars were resistant to RWASA4 at two localities, respectively. Since Russian wheat aphid (RWA) damage can influence the final yield of a wheat cultivar significantly, changing conditions can influence both resistant cultivars, and the virulence of Russian wheat aphid (RWA). It is advisable to evaluate wheat cultivars on the market under different conditions and with all known Russian wheat aphid (RWA) biotypes in an area.
Field Screening of Lesotho and South African Wheat Cultivars for Russian Wheat Aphid Resistance  [PDF]
Astrid Jankielsohn, Pitso Masupha, Lintle Mohase
Advances in Entomology (AE) , 2016, DOI: 10.4236/ae.2016.45028
Abstract:
Russian wheat aphid (Diuraphis noxia) is an international wheat pest and was first recorded in South Africa in 1978 in the Bethlehem area in the Eastern Free State. Le-sotho lies adjacent to one of the largest wheat producing areas in South Africa, the Eastern Free State, where winter wheat and facultative types are cultivated under dry land conditions. Wheat (Triticum aestivum L.) is an important crop adapted to all agro-ecological zones of Lesotho. Russian wheat aphid may have a significant impact on wheat yield. No monitoring or pest control is being done in Lesotho and at this stage there is very little information on the Russian wheat aphid resistance of wheat culti-vars cultivated in Lesotho. In view of this it is important to monitor the distribution of Russian wheat aphid biotypes in Lesotho and determine the level of Russian wheat aphid resistance in local Lesotho wheat cultivars. Two local Lesotho wheat cultivars, Bolane and Makalaote were screened together with South African cultivars Elands, Matlabas, Senqu, PAN3379, PAN3118 and SST387, in the glasshouse against all four known biotypes that occur in South Africa. All these cultivars were also planted in 5 m plots in the field at two localities Leribe and Roma in the lowlands of Lesotho. These cultivars were screened in the field for Russian wheat aphid resistance. The predomi-nant Russian wheat aphid biotypes in these areas were also determined. The Lesotho cultivar, Bolane had resistance against RWASA2 in the glasshouse, while Makalaote did not have any Russian wheat aphid resistance in either the glasshouse or field screenings. To contribute to food security an increasing wheat yield potential is a high priority. Russian wheat aphid has been included in the list of important international cereal pests. Russian wheat aphid adapts to changing environments and taking their ecology, distribution, virulence patterns, and variability into account is important in minimizing the gap between actual and attainable yields. Current management prac-tices for winter wheat in South Africa include the use of resistant cultivars, which is the most economical management strategy for Russian wheat aphid. Introducing Russian wheat aphid resistant cultivars in Lesotho will improve overall yield and as a result food security. This will also result in lower Russian wheat aphid pest pressure in the adjacent wheat production areas in the Eastern Free State, South Africa.
Contagion of Sovereign Debt in the Eurozone  [PDF]
Astrid Ayala, Szabolcs Blazsek
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.41016
Abstract:

This study reports contagion and interdependence of quarterly debt to gross domestic product (GDP) among the member states of the Eurozone over the period 2000 Q4 to 2012 Q1. We test for contagion and interdependence in two steps. First, we define an indicator variable of increasing debt to GDP for each country during the period following the United States financial crisis, by using unit root tests incorporating structural changes and breaking trend regressions. Second, the indicator variable is included in the latent-factor panel data model to separate contagion and interdependence of debt to GDP among Eurozone member states. Results show significant and country-dependent contagion and interdependence effects of debt to GDP in the Eurozone.

The Influence of Priming on Reference States
Astrid Matthey
Games , 2010, DOI: 10.3390/g1010034
Abstract: Experimental and empirical evidence shows that the utility an individual derives from a certain state depends on the reference state she compares it to. According to economic theory, the reference state is determined by past, present and future outcomes of either the individual herself or her reference group. The experiment described in this paper suggests that, in addition, reference states depend to a significant degree on environmental factors not relevant for outcomes. It indicates that reference states - and hence utility - can relatively easily be influenced without changing people’s outcomes, e.g., through priming.
A systematic review of PET and PET/CT in oncology: A way to personalize cancer treatment in a cost-effective manner?
Astrid Langer
BMC Health Services Research , 2010, DOI: 10.1186/1472-6963-10-283
Abstract: Eight electronic databases were searched from 2005 until February 2010 to identify economic evaluation studies not included in previous Health Technology Assessment (HTA) reports. Only full health economic evaluations in English, French, or German were considered for inclusion. Economic evaluations were appraised using published quality criteria for assessing the quality of decision-analytic models. Given the variety of methods used in the health economic evaluations, the economic evidence has been summarized in qualitative form.From this new search, 14 publications were identified that met the inclusion criteria. All publications were decision-analytic models and evaluated PET using Fluorodeoxyglucose F18 (FDG-PET). Eight publications were cost-effectiveness analyses; six were cost-utility analyses. The studies were from Australia, Belgium, Canada, France, Italy, Taiwan, Japan, the Netherlands, the United Kingdom, and the United States. In the base case analyses of these studies, cost-effectiveness results ranged from dominated to dominant. The methodology of the economic evaluations was of varying quality. Cost-effectiveness was primarily influenced by the cost of PET, the specificity of PET, and the risk of malignancy.Owing to improved care and less exposure to ineffective treatments, personalized medicine using PET may be cost-effective. However, the strongest evidence for the cost-effectiveness of PET is still in the staging of non-small cell lung cancer. Management decisions relating to the assessment of treatment response or radiotherapy treatment planning require further research to show the impact of PET on patient management and its cost-effectiveness. Because of the potential for increased patient throughput and the possible greater accuracy, the cost-effectiveness of PET/CT may be superior to that of PET. Only four studies of the cost-effectiveness of PET/CT were found in this review, and this is clearly an area for future research.Positron emission tomo
Intraseasonal variation in a population of Fountainea ryphea (Cramer) (Lepidoptera, Nymphalidae)
Caldas, Astrid;
Revista Brasileira de Zoologia , 1996, DOI: 10.1590/S0101-81751996000200009
Abstract: a different approach was used for the key-factor method in a population study of the tropical butterfly fountainea ryphea (cramer, [1776]) (lepidoptera, nymphalidae), marking 20 artificial cohorts to identify the mortality levels and associated instars responsible for the variation in numbers within the season of occurrence, when generations overlap broadly. highest mortality was detected during first instar in 13 cohorts; during second instar in three cohorts; third and fourth instars suffered highest mortality twice. results showed that first instar mortality due to rainfall and predation, and parasitism on fourth instar could be the main factors promoting differences in number between cohorts throughout the season, although no density-dependent processes could be identified.
Reconfiguraciones conceptuales, políticas y territoriales en las demandas de autonomía de los pueblos indígenas en Colombia
Ulloa,Astrid;
Tabula Rasa , 2010,
Abstract: in colombia, indigenous people's basic demands include: autonomy and self-determination. however, autonomic dynamics led by various peoples on territorial control, their own jurisdical practices, plans of life, environmental management and food sovereignty consolidation pose challenges and issues. indigenous peoples' autonomy is influenced and related to local and transnational contexts, y to the current state changes (dynamics of economic development, armed conflic and processes of violence being fought at indigenous territories), which give rise to new reframings and conceptual, political and territorial boundaries. therefore, indigenous autonomy needs to be reconsidered as a complex process, and analyzed as a an indigenous relational autonomy, since it articulates with specific negotiations and particular circumstances with diverse actors, in local, national and global scopes, and with partial and located processes having particular political implications. this paper is focused in the claims for autonomy by peoples kogui, arhuaco, wiwa and kankuamo from santa marta snowy mountain range -snsm-.
On HIV, Sex and Respect: Local-Global Discourse Encounters among the Datoga of Tanzania
Astrid Blystad
African Sociological Review / Revue Africaine de Sociologie , 2004,
Abstract:
Thrown Away Like Rubbish - Disposal of the Dead in Ancient Greece
Astrid Lindenlauf
Papers from the Institute of Archaeology , 2001, DOI: 10.5334/pia.161
Abstract: In this article, the literary and archaeological evidence for burial practices that can be associated with the English expression ‘to be disposed of like rubbish’ are discussed. These disposal methods (átaphon rhíptesthai) include the exposure of corpses to carrion animals, to the elements, as well as the disposal of corpses into the sea, pits or natural fissures without burial rites. They also include cases in which graves were dug up in order to throw their contents out. Here, the Greek expressions for the English phrase ‘to be thrown away like rubbish’ are explored, as well as its relation to Morris’ (1987) influential concept of the ‘non-formal burial’. The analysis of the symbolism of various disposal methods has been based on both literary and archaeological sources. Also addressed are issues such as the intersection of the exclusion from full and proper burial procedures with social status and social groups. Lastly, the dangers for the living and the dead associated with casually disposed of human remains are briefly tackled, including the transformation of the souls of the deceased into spirits and their loss of human-ness.
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