Spatial and temporal variation in community structure of phytoplankton in chebara reservoir-Kenya

River impoundments create reservoirs for many of varying, sizes which serve one or more functions, and change transform lotic aquatic systems to lentic ones, with changes in physical and chemical properties, biotic assemblage and productivity. Chebara reservoir is located at 36o E and 22o S and situated within Elgeyo-Marakwet County. The reservoir was formed as a result of damming the Moiben River to supply water to Eldoret town. A study was conducted on composition and relative abundance of phytoplankton in the reservoir from December 2007 to April 2008. Sampling was done every month at six stations distributed over the reservoir; one station at inlet of Moiben River, one station at the outlet, three at minor inlets and one within the reservoir. Phytoplankton were collected using a 28nm diameter plankton net immersed vertically below the photic depth. Photic depth was measured using 25cm diameter Secchi disk. Phytoplankton were identified and enumerated using a compound microscope. All statistical analyses were performed with STATIGRAPHIC 2.1 Plus and STATISTICA 6.0 procedures. Six phytoplankton classes were identified which included Cyanophyceae (22 genera) Bacillariophycae (25 genera), Chlorophyceae (55 genera), Euglenophyceae (3 genera), Rhodophyceae (2 genera) Pyraphyceae (6 genera) and Crysophyceae (8 genera) similar to observations made in tropical oligotrophic lakes. The order of abundance was Pyraphyceae> Cyanophyceae> Chlorophyceae> Bacillariophyceae> Crysophyceae>Euglenophyceae>Rhodophyceae. Members of the Class Chlorophyceae showed the highest species diversity and abundance. The results obtained from this study can be used track the effects of catchment land use in the drainage basin investigate the cumulative, long term effects of climate change, and river impoundment on the algal evolution. Key words: Spatial and Temporal Variation, Community Phytoplankton, Chebara Reservoi

Effects of physico-chemical parameters on abundance and biomass of phytoplankton in chebara reservoir-Kenya

River impoundment creates reservoirs of varying sizes that supply water for multiple uses including electric power generation, domestic, agriculture or industry. However, damming of rivers creates an aquatic habitat of slow moving water of varying depths and altogether changing the biotic and physico-chemical status of a waterbody. Chebara reservoir was created to supply water to Eldoret Municipality. Chebara reservoir is located at 36 05 E and 0 22 S and situated within Elgeyo-Marakwet County. A study was conducted on the physico-chemical parameters and the abundance and biomass of phytoplankton in Chebara reservoir from December 2007 to April 2008. Stratified sampling was done every month at six stations distributed over the reservoir; one station at inlet, one station at the outlet, one stationat a minor inlet draining through human settlement, one at minor inletdrainingthrough farmland and one within the reservoir. Temperature, pH and ElectricalConductivity were measured in situusing JENWAY® 3405 Electrochemical Analyser. Secchi depth visibility was measured by vertically immersing a 25cm diameter Secchi disk to disappearance. Phytoplankton were collected using a 28 m diameter plankton net immersed vertically below the photic depth. Phytoplankton was identified and enumerated usingSedgwick—Rafter cell underan invertedor microscope, or Olympus®ModelCK2, atamagnificationofX400. Primary production and biomass were determined by chemical analysis of chlorophyll-a concentration and biological oxygen demand (BOD). Nutrientconcentrations were measured spectrophotometrically, while alkalinity was measuredby acidimetric method. Phytoplankton abundance and biomass were related to the physico-chemical conditions of the reservoir. All statistical analyses were performed with STATIGRAPHIC 2.1 Plus and STATISTICA 6.0 procedures. There were no significant differences in the spatial or temporal physico-chemical parameters. The reservoir was homogenously oligotrophic and alkaline with only very slight variations. among dates and samplingstations. The productivity of Chebara reservoir was low (approximately 0.8 µgmillilitre-1) asestimated by chlorophyll a, suggesting oligotrophy. The highest abundance was observed in March and at station 3,while the lowest abundance in April and at station 5. CCA results indicated strong relationships between the various phytoplankton genera and physical and chemical conditions, except for biological oxygen demand which had a weak effect. The study also indicates that phytoplankton growth in the reservoir is more likely to be limited by availability of P than N. The results obtained from this study can be useful for tracking the effects of changing activities in the drainage basin and the tributaries that contribute water directly to the reservoir. Calcium concentrations were consistently low, but the high abundance of pyraphytes in this reservoir could suggest a need to monitor management practices in the reservoir catchment that maintain calcium concentrations and populations of pyraphytes low in order to reduce the water treatment costs. This research further recommends that a research be carried out on macro invertebrates in order to accumulate sufficient knowledge which will be useful for watershed best management practices aimed at ensuring long term protection for water supply. Keywords: Physico-chemical Parameters; Abundance and Biomass; phytoplankton; Chebara reservoi

Doping a semiconductor to create an unconventional metal

Landau Fermi liquid theory, with its pivotal assertion that electrons in metals can be simply understood as independent particles with effective masses replacing the free electron mass, has been astonishingly successful. This is true despite the Coulomb interactions an electron experiences from the host crystal lattice, its defects, and the other ~1022/cm3 electrons. An important extension to the theory accounts for the behaviour of doped semiconductors1,2. Because little in the vast literature on materials contradicts Fermi liquid theory and its extensions, exceptions have attracted great attention, and they include the high temperature superconductors3, silicon-based field effect transistors which host two-dimensional metals4, and certain rare earth compounds at the threshold of magnetism5-8. The origin of the non-Fermi liquid behaviour in all of these systems remains controversial. Here we report that an entirely different and exceedingly simple class of materials - doped small gap semiconductors near a metal-insulator transition - can also display a non-Fermi liquid state. Remarkably, a modest magnetic field functions as a switch which restores the ordinary disordered Fermi liquid. Our data suggest that we have finally found a physical realization of the only mathematically rigourous route to a non-Fermi liquid, namely the 'undercompensated Kondo effect', where there are too few mobile electrons to compensate for the spins of unpaired electrons localized on impurity atoms9-12.Comment: 17 pages 4 figures supplemental information included with 2 figure

Transport and Magnetic Measurements of Mono -Silicides.

The purpose of this dissertation is to investigate the magnetic and transport properties of the dilution series connecting the mono-silicides FeSi, CoSi, and MnSi. We have focused on these materials since they allow the exploration of carrier doping of an unusual insulator, FeSi, whose properties are dominated by strong Coulomb interactions. These monosilicides all have the same cubic B-20 crystal structure making them ideal for an exploration of Fe1--x MnxSi and Fe1--yCoySi for all x and y between 0 and 1. The carrier sip and densities, as well as the proximity to magnetic phases can be controlled by the level of chemical substitution across this series. We have investigated the transport and magnetic behavior of this system, centered on the Kondo insulator FeSi, by carrying out magnetization, Hall effect, resistivity and magnetoresistence measurements. We have discovered that MnSi and Fe1--yCo ySi, which both are itinerant helimagnetic compounds, differ in that the Co doped FeSi is nearly spin polarized and has a novel temperature and field dependent conductivity. We discovered that the MR in Fe1--y CoySi is due to quantum interference effects which are substantial in this compound up to 100 K. Fe1--yCoySi, (0 \u3c y ≤ 0.3) is a strongly scattering low charge density metal in which we have also discovered an extraordinarily large anomalous Hall effect. In contrast the hole doped insulator, Fe1--xMnxSi, remains paramagnetic up to x \u3c 0.9 with a large quasiparticle mass and a conductivity (sigma) that is dominated by electron-electron (e-e) interaction effects. At low temperatures the hole carriers are localized beyond that due to the usual square-root singularity associated with quantum interference effects. In fact, the (sigma) and susceptibility are comparable to the diluted magnetic semiconductors, such as the Mn doped II-VI compounds

Structural and magnetic properties of E-Fe_{1-x}Co_xSi thin films deposited via pulsed laser deposition

We report pulsed laser deposition synthesis and characterization of polycrystalline Fe1-xCox Si thin films on Si (111). X-ray diffraction, transmission electron, and atomic force microscopies reveal films to be dense, very smooth, and single phase with a cubic B20 crystal structure. Ferromagnetism with significant magnetic hysteresis is found for all films including nominally pure FeSi films in contrast to the very weak paramagnetism of bulk FeSi. For Fe1-xCoxSi this signifies a change from helimagnetism in bulk, to ferromagnetism in thin films. These ferromagnetic thin films are promising as a magnetic-silicide/silicon system for polarized current production, manipulation, and detection.Comment: 12 pages, 4 figures accepted in the Applied Physics Letter

Pressure-induced quantum phase transition in Fe₁−ᵪCoᵪSi (x = 0.1,0.2)

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Effect of Iron Amino Acid Chelate Supplemented Fish Feeds on Nutrients Composition of Spinach (Spinacia oleracea) in an Aquaponic System in Kenya

Aquaponics is an environmentally friendly production system involving reuse of waste and nutrients in production of fish and vegetables. Currently aquaponic system is the only solution for fish and plants production but one unique challenge is the maintaining of micro and macro-nutrient and the pH balance in the system. The study was conducted at the University of Eldoret for 119 days. A complete randomized design was used. The supplementation rates in fish diets constituted 30g, 20g, 10g and 0g Fe kg-1 respectively. Nile tilapia fry with a mean weight of 0.475 ± 0.025g and nine spinach (height 3 ± 0.131cm, 2 leaves) were stocked in 12 aquaria in an aquaponic system. 30g Fe kg-1 treatment exhibited higher minerals content than other treatments with Phosphorus 67.51 ± 2.42 mgL-1, Zinc 9.06 8± 0.45 mgL-1, Iron 5.2 ± 0.218 mgL-1, Manganese 7.655 ± 0.344 mgL-1, Total Nitrogen 11.248 ± 0.141mgL-1 and Sodium 7.218 ± 0.028 mgL-1. There was improved water quality at 30g Fe kg-1 compared to other treatments. These results revealed that 30g Fe kg-1 iron amino acid chelate supplementation had better nutritional attributes as feedstuff for spinach growth than the three other dietary treatments. The study recommends the incorporation of 30g Fe kg-1 iron amino acid chelate in on-farm formulated diets for aquaponic system where complete diets are not easily accessible for small scale farmers