Time filter

Source Type

Yizengaw E.,Boston College | Retterer J.,Boston College | Pacheco E.E.,Boston College | Roddy P.,Air Force Research Lab | And 3 more authors.
Geophysical Research Letters | Year: 2013

While the mechanism for producing plasma irregularities in the dusk sector is believed to be fairly well understood, the cause of the formation of irregularities and bubbles during the postmidnight sector is still unknown, especially for magnetically quiet periods. This paper presents a case study of the strong postmidnight bubbles that often occur during magnetically quiet periods primarily in June solstice, along with a 4 year (2009-2012) statistical study that shows strong occurrence peak during June solstice predominantly in the African sector. We also confirm, for the first time, the presence of Rayleigh-Taylor (RT) instability during postmidnight hours by using the physics-based model for plasma densities and RT growth rates. Finally, we consider several possible sources of the eastward electric fields that permit the RT instability to develop and form bubbles in the postmidnight local time sector. Key Points Strong postmidnight bubbles occurrence during magnetically quiet periods The presence of Rayleigh-Taylor (RT) instability during postmidnight hours. Strong occurrence peak occurs during June solstice predominantly over Africa ©2013. American Geophysical Union. All Rights Reserved.

Oduor A.M.O.,University of Konstanz | Oduor A.M.O.,Technical University of Kenya | Leimu R.,University of Oxford | van Kleunen M.,University of Konstanz
Journal of Ecology | Year: 2016

Concerns over the ecological impacts of invasive alien plant species have generated great research interest in understanding the mechanisms that underlie the capacity of such plants to occupy a broad range of habitats. It has been repeatedly suggested that rapid evolution of local adaptation to novel environments may enable invasive plants to occupy a broad range of habitats. However, the classical Darwinian view on evolution by natural selection is that the process is slow and gradual, occurring over thousands of years. Invasive plants typically have a relatively short residence time in their introduced ranges (decades or just a few centuries). Besides the time constraint, founder effects (reduction in population size and genetic diversity) may also limit the capacity of invasive plants to rapidly evolve local adaption. Thus, invasive plants may be less likely than native plants to evolve local adaptation. Interestingly, however, an expanding body of literature documents the existence of local adaptation in invasive plant species within their exotic ranges. Here, we did a phylogenetically controlled meta-analysis to compare invasive and native plant species for differences in the frequency and magnitude of local adaptation. The meta-analysis was based on different experiments performed in various habitats including grasslands, steppes, deserts, forests, mountains, wetlands and dunes, and used a total of 134 plant species in 52 families. Forty seven of these species (in 24 families) are alien invaders in the region where the studies were undertaken, while the other 91 species (in 38 families) are native. On average, local plants performed better than foreign plants, and invasive plant species expressed local adaptation just as frequently, and at least as strongly as that exhibited by native plant species. An analysis performed while taking into account different plant life-history traits showed that self-incompatible invasive plants exhibited significantly higher frequencies of local adaptation than native plants characterized by the same breeding system. Synthesis. The present results support the suggestion that rapid evolution of local adaptation may enable invasive plant species to occupy a broad range of novel habitats. © 2016 The Authors. Journal of Ecology © 2016 British Ecological Society

Maringa P.M.,Workforce Development Authority | Maringa M.,Technical University of Kenya
Global Journal of Engineering Education | Year: 2013

Technical Vocational Education and Training (TVET) in Rwanda is undergoing drastic reform, moving towards becoming a well regulated, integrated TVET system. With the prevailing un-harmonised TVET and little consistent scientific data or mapping of access, it has not been possible to determine the quality of the prevailing TVET on offer. A sample of Ecole Technique Officiels (ETOs) and Agroveternaires (EAVs) were surveyed, with respondents being identified using a complex sampling approach. Well-structured, coded and graded interview schedules were used to guide enumerators. Descriptive and inferential statistical analysis was carried out to bring out the inherent patterns in the prevailing status quo. Cleary, access to TVET is unequal with respect to spatial distribution/location, age, specialisation and ownership. It is necessary for the Government of Rwanda (GoR) to adopt policies that enable improved equity of access to training opportunities. For sustainability in the future to ensue, models of TVET financing that embrace more private sector participation need to be given emphasis. © WIETE 2013.

Kwanya T.,Technical University of Kenya
Lecture Notes in Business Information Processing | Year: 2015

Indigenous knowledge plays a pivotal socioeconomic development role in indigenous communities. In Kenya, one of the economic sectors where indigenous knowledge can be applied is tourism which is among the country’s major income earners besides tea and horticulture. This study investigated the potential and the actual use of indigenous knowledge in leveraging the other efforts being made to develop and cushion tourism in Kenya. The study was designed as a survey to capture the current status of the application of indigenous knowledge in the tourism sector in Kenya. Primary data was collected through key informant interviews with tourism industry stakeholders in the country. 56 participants in the study were selected through a mix of stratified, purposive and snowballing sampling techniques. The interviews were conducted using semi-structured questionnaires administered by the researcher. Secondary data on indigenous knowledge in Kenya, indigenous tourism as well as tourism sector statistics was collected through documentary analysis. The data was analysed using content analysis. The findings of the study indicate that although indigenous tourism holds a great socioeconomic potential in Kenya, it has not been harnessed fully. Its potential is still being held back by myriad challenges such as lack of relevant business development skills; lack of adequate capital to develop and promote indigenous tourism products, services and facilities; remoteness of indigenous tourism sites; insecurity; poor infrastructure; modernisation; environmental degradation and consequences of climate change; stiff competition; and intra or inter-ethnic resource-based conflicts. The findings can be used by the Government of Kenya to mainstream indigenous knowledge into tourism by developing the requisite policies, structures and implementation frameworks. The findings may also be used by the tourism sector stakeholders in Kenya to identify, enhance, package and promote indigenous tourism products, services and facilities effectively. © Springer International Publishing Switzerland 2015.

Rashid K.,Egerton University | Rashid K.,Tea Research Foundation of Kenya | Wachira F.N.,Tea Research Foundation of Kenya | Wachira F.N.,Association for Strengthening Agricultural Research in Eastern and Central Africa | And 5 more authors.
Nutritional Neuroscience | Year: 2014

Studies on antioxidants as neuroprotective agents have been hampered by the impermeability of the blood brain barrier (BBB) to many compounds. However, previous studies have shown that a group of tea flavonoids, the catechins, are brain permeable and neuroprotective. Despite this remarkable observation, there exist no data on the bioavailability and pharmacological benefits of tea anthocyanins (ACNs) in the brain tissue. This study investigated the ability of Kenyan purple tea ACNs to cross the BBB and boost the brain antioxidant capacity. Mice were orally administered with purified and characterized Kenyan purple tea ACNs or a combination of Kenyan purple tea ACNs and coenzyme- Q10 at a dose of 200 mg/kg body weight in an experiment that lasted for 15 days. Twenty-four hours post the last dosage of antioxidants, CO2 was used to euthanize the mice after which the brain was excised and used for various biochemical analyses. Brain extracts were analysed by high-performance liquid chromatography for ACN metabolites and spectrophotometry for cellular glutathione (GSH). Kenyan purple tea ACNs significantly (P < 0.05) raised brain GSH levels implying boost in brain antioxidant capacity. However, co-administration of both antioxidants caused a reduction of these beneficial effects implying a negative interaction. Notably, ACN metabolites were detected in brain tissue of ACN-fed mice. Our results constitute the first demonstration that Kenyan purple tea ACNs can cross the BBB reinforcing the brain's antioxidant capacity. Hence, the need to study them as suitable candidates for dietary supplements that could support antioxidant capacity in the brain and have potential to provide neuroprotection in neurodegenerative conditions. © W. S. Maney & Son Ltd 2014.

Discover hidden collaborations