6 results on '"Walsh, Patrick"'
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2. English in Kenyan education.
- Author
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Campbell, David and Walsh, Patrick
- Subjects
- *
ENGLISH language education , *FOREIGN language education , *EDUCATIONAL psychology , *LANGUAGE planning , *GERMANIC languages , *PARENT-teacher relationships , *OCCUPATIONAL training , *ACTIVITY programs in education , *MULTICULTURALISM - Abstract
This paper intends not only to place English language teaching in Kenya within a specific historical context, but also to consider how it operates alongside the many other languages used in the day-to-day experiences of a secondary school community. Any consideration of the use of English in Kenya must take into account the legacy of language policies adopted by both colonial and independent administrations in the country. Use is made in this respect of the growing body of research and theory which focuses on language policy in post-colonial and neo-colonial settings. Therefore, an evaluation of the intentions and impact of these policies on attitudes towards language use is included in this paper. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
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3. Ionoregulatory strategies and the role of urea in the Magadi tilapia (Alcolapia grahami).
- Author
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Wood, Chris M., Wilson, Paul, Bergman, Harold L., Bergman, Annie N., Laurent, Pierre, Otiang'a-Owiti, George, and Walsh, Patrick J.
- Subjects
TILAPIA ,ACCLIMATIZATION ,NITROGEN excretion ,FISH habitats ,LAKES - Abstract
The unique ureotelic tilapia Alcolapia grahami lives in the highly alkaline and saline waters of Lake Magadi, Kenya. All fish succumbed upon acute transfer to one percent lake water, but tolerated acute transfer to ten percent lake water well, and gradual long-term acclimation to both ten and one percent lake water without change in plasma cortisol. Routine rates of O[sub 2] consumption and nitrogenous waste excretion are the highest ever recorded for teleost fish of comparable size, even when allowance is made for the high environmental temperature. Measurements of drinking rate were performed on three groups: freshly collected fish in 100 percent lake water (N 5), fish that had undergone long-term acclimation to 100 percent lake water (N 11), and fish that had undergone long-term acclimation to one percent lake water (N 6). There were no substantive differences in branchial morphology between control fish freshly collected from 100% lake water, control fish held long-term in 100% lake water in the laboratory, and fish that had undergone long-term acclimation to 200% lake water. There were no substantive differences in branchial morphology between control fish freshly collected from 100 percent lake water, control fish held long-term in 100 percent lake water in the laboratory, and fish that had undergone long-term acclimation to 200 percent lake water.
- Published
- 2002
- Full Text
- View/download PDF
4. Discordance between genetic structure and morphological, ecological, and physiological adaptation in Lake Magadi tilapia.
- Author
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Wilson PJ, Wood CM, Walsh PJ, Bergman AN, Bergman HL, Laurent P, and White BN
- Subjects
- Analysis of Variance, Animals, Body Weights and Measures, DNA, Mitochondrial genetics, Digestive System anatomy & histology, Fresh Water analysis, Geography, Haplotypes genetics, Hydrogen-Ion Concentration, Kenya, Models, Genetic, Osmolar Concentration, Oxygen analysis, Polymorphism, Single-Stranded Conformational, Population Density, Population Dynamics, Sequence Analysis, DNA, Temperature, Adaptation, Biological, Environment, Genetics, Population, Models, Biological, Selection, Genetic, Tilapia
- Abstract
The Magadi tilapia (Alcolapia grahami, formerly Oreochromis alcalicus grahami) is a remarkable example of teleost life in an extreme environment. Typical conditions include water pH=10, titration alkalinity>300 mM, osmolality=525 mOsm, temperatures ranging from 23 degrees to 42 degrees C, and O(2) levels fluctuating diurnally between extreme hyperoxia and anoxia. A number of relatively small tilapia populations are present in various thermal spring lagoons around the margin of the lake separated by kilometers of solid trona crust (floating Na(2)CO(3)) underlain by anoxic water. Despite the apparent isolation of different populations, annual floods may provide opportunities for exchange of fish across the surface of the trona and subsequent gene flow. To assess the question of isolation among Lake Magadi populations, we analyzed the variable control region of the mitochondrial DNA (mtDNA) from six lagoons. A total of seven mtDNA haplotypes, including three common haplotypes, were observed in all six populations. Several of the Lake Magadi populations showed haplotype frequencies indicative of differentiation, while others showed very little. However, differentiation among lagoon populations was discordant with their geographical distribution along the shoreline. All populations exhibited the unusual trait of 100% ureotelism but specialized morphological and physiological characteristics were observed among several of the lagoon systems. In addition, distinct differences were observed in the osmolality among the lagoons with levels as high as 1,400-1,700 mOsm kg(-1), with corresponding differences in the natural levels of whole-body urea. These levels of osmotic pressure proved fatal to fish from less alkaline systems but remarkably were also fatal to the fish that inhabited lagoons with this water chemistry. Upon more detailed inspection, specific adaptations to differential conditions in the lagoon habitat were identified that allowed survival of these cichlids. Additional evidence against potential for gene flow among lagoons despite the sharing of common mtDNA haplotypes was that the osmolality of floodwaters following a heavy rain showed lethal levels exceeding 1,700 mOsm kg(-1). In isolation, different mtDNA haplotypes would be predicted to go to fixation in different populations due to rapid generation times and the small effective population sizes in a number of lagoons. We propose a model of balancing selection to maintain common mtDNA sequences through a common selection pressure among lagoons that is based on microhabitats utilized by the tilapia.
- Published
- 2004
- Full Text
- View/download PDF
5. Physiological adaptations of the gut in the Lake Magadi tilapia, Alcolapia grahami, an alkaline- and saline-adapted teleost fish.
- Author
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Bergman AN, Laurent P, Otiang'a-Owiti G, Bergman HL, Walsh PJ, Wilson P, and Wood CM
- Subjects
- Animals, Biological Transport, Drinking Behavior physiology, Environment, Feeding Behavior physiology, Gastrointestinal Contents, Gastrointestinal Tract drug effects, Hydrogen-Ion Concentration, Intestines drug effects, Intestines physiology, Kenya, Muscle, Smooth drug effects, Muscle, Smooth physiology, Adaptation, Physiological drug effects, Adaptation, Physiological physiology, Fresh Water, Gastrointestinal Tract physiology, Sodium Chloride pharmacology, Tilapia physiology
- Abstract
We describe the gut physiology of the Lake Magadi tilapia (Alcolapia grahami), specifically those aspects associated with feeding and drinking while living in water of unusually high carbonate alkalinity (titratable base=245 mequiv l(-1)) and pH (9.85). Drinking of this highly alkaline lake water occurs at rates comparable to or higher than those seen in marine teleosts. Eating and drinking take place throughout the day, although drinking predominates during hours of darkness. The intestine directly intersects the esophagus at the anterior end of the stomach forming a 'T', and the pyloric sphincter, which comprises both smooth and striated muscle, is open when the stomach is empty and closed when the stomach is full. This unique configuration (a functional trifurcation) allows imbibed alkaline water to bypass the empty stomach, thereby avoiding a reactive mixing with acidic gastric fluids, and minimizes interference with a full stomach. No titratable base was present in the stomach, where the mean pH was 3.55, but the intestine was progressively more alkaline (foregut 6.96, midgut 7.74, hindgut 8.12, rectum 8.42); base levels in the intestinal fluid were comparable to those in lake water. The gut was highly efficient at absorbing water (76.6%), which accompanied the absorption of Na(+) (78.5%), titratable base (80.8%), and Cl(-) (71.8%). The majority of Na(+), base and water absorption occurred in the foregut by an apparent Na(+) plus base co-transport system. Overall, more than 70% of the intestinal flux occurred via Na(+) plus base co-transport, and less than 30% by Na(+) plus Cl(-) co-transport, a very different situation from the processes in the intestine of a typical marine teleost.
- Published
- 2003
- Full Text
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6. Obligatory urea production and the cost of living in the Magadi tilapia revealed by acclimation to reduced salinity and alkalinity.
- Author
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Wood CM, Wilson P, Bergman HL, Bergman AN, Laurent P, Otiang'a-Owiti G, and Walsh PJ
- Subjects
- Ammonia metabolism, Animals, Blood Chemical Analysis, Chlorides blood, Energy Metabolism, Fresh Water chemistry, Hydrogen-Ion Concentration, Kenya, Osmolar Concentration, Oxygen Consumption, Sodium blood, Swimming, Tilapia blood, Tilapia metabolism, Time Factors, Adaptation, Physiological, Tilapia physiology, Urea metabolism
- Abstract
Alcolapia grahami is a unique ureotelic tilapia that lives in the highly alkaline, saline Lake Magadi, Kenya (pH, approximately 10.0; alkalinity, approximately 380 mmol L(-1); Na(+), approximately 350 mmol L(-1); Cl(-), approximately 110 mmol L(-1); osmolality, approximately 580 mosm kg(-1)). The fish survived well upon gradual exposure to dilute lake water (down to 1%, essentially freshwater). Urea excretion continued, and there was no ammonia excretion despite favorable conditions, indicating that ureotelism is obligatory. Levels of most ornithine-urea cycle enzymes in the liver were unchanged relative to controls kept for the same period in 100% lake water. The fish exhibited good abilities for hypo- and hyperregulation, maintaining plasma Na(+), Cl(-), and osmolality at levels typical of marine and freshwater teleosts in 100% and 1% lake water, respectively. Plasma total CO(2) did not change with environmental dilution. Routine oxygen consumption (Mo(2)) was extremely high in 100% lake water but decreased by 40%-68% after acclimation to dilute lake water. At every fixed swimming speed, Mo(2) was significantly reduced (by 50% at high speeds), and critical swimming speed was elevated in fish in 10% lake water relative to 100% lake water. Osmotic and Cl(-) concentration gradients from water to plasma were actually increased, and osmotic and Na(+) gradients were reversed, in 10% and 1% dilutions relative to 100% lake water, whereas acid-base gradients were greatly reduced. We suggest that approximately 50% of the animal's high metabolic demand originates from the cost of acid-base regulation in the highly alkaline Lake Magadi. When this load is reduced by environmental dilution, the energy saved can be diverted to enhanced swimming performance.
- Published
- 2002
- Full Text
- View/download PDF
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