86 research outputs found

    Effects of experimental Neisseria meningitis W135 infection on serotoninergic parameters in mice

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    This study investigated the effects of Neisseria menigitidis W135 infection via intraperitoneal route on plasma free tryptophan concentration, brain serotonin and 5-hydroxyindole acetic acid (5-HIAA) levels in albino mice fed normal and tryptophan-enriched diets. The kinetics of appearance of viable bacteria in the blood, brain and liver following infection were also investigated. The serotoninergic parameters were determined by colorimetric and HPLC methods while colony counts were measured by plate count technique. Compared to normal diet, the tryptophan-enriched diet resulted in significantly (

    Review of Researches on Techno-Economic Analysis and Environmental Impact of Hybrid Energy Systems

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    Hybrid energy systems, which are combinations of two or more renewable and non-renewable energy sources, have been identified as a viable mechanism to address the limitations of a single renewable energy source, utilized for electricity generation. In view of this, several research works have been carried out to determine the optimal mix of different renewable and non-renewable energy resources used for electricity generation. This paper presents a comprehensive review of the optimization approaches proposed and adopted by various authors in the literature for optimal sizing of hybrid energy systems. It is observed that the objective functions - considered by a large percentage of researchers to optimize the sizing of hybrid energy systems - are cost minimization of the generated electricity, system reliability enhancement and environmental pollution reduction. Other factors covered in the literature are equally discussed in this article. Similarly, simulation and optimization software used for the same purpose are covered in the paper. In essence, the main aim of this paper is to provide a scope into the works that have been carried out in the field of hybrid energy systems, used for electricity generation with the view to informing researchers and members of the public alike, on trends in methods applied in optimal sizing of hybrid energy systems. It is believed that the information provided in this paper is very crucial in advancing research in the field

    Geological and geophysical evaluation of the ajana area’s groundwater potential, southwestern nigeria

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    Acombined geological and geophysical evaluation was madeof the groundwater potential of the Ajana, RemoNorth area in south-western Nigeria; the geology and other structural features of the rocks there strongly influenced and correlated the aquifers' storability and transmissivity. Geological mapping revealed that the area was made up of granite, quartzite and varieties of gneiss, some of which have good secondary porosity and permeability. Ten vertical electric soundings (VES) stations were established using a Schlumberger electrode array. Five geoelectric layers consisting of topsoil, sand,clayey-sandy, fractured / weathered basement and fresh bedrock were delineated. The aquifer layers were the 38.3m thick 283 ?m resistivity sand/sandy clay and 55 - 518 ?m resistivity fractured/weathered basement. Other geoelectric parameters used in evaluating the area's hydrogeological potential included curve type, anisotropy coefficient and reflection coefficient - The QH curve type was predominant in the area. The anisotropy Coefficients suggested VES stations having high groundwater potential ranging from 1.4 - 1.56; while the reflection coefficients for the area ranged from 0.21 - 0.99. The overall results showed that VES stations 8, 9 and 10 could be possible groundwater sources having high expected yield

    Seismic Refraction and Electrical Resistivity Investigation of Building Failure: A Case Study

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    Geophysical methods involving electrical resistivity and seismic refraction were adopted to investigate the cause(s) of failure of main library complex of the Olabisi Onabanjo University, Ago-Iwoye, South-Western Nigeria. The geoelectric section generated from geosounding data revealed four geologic layers. The topsoil has resistivity values varying from 128Ωm to 220Ωm and thickness between 0.9m and 2.4m. The second layer is composed of lateritic clay with resistivity values varying from 238Ωm to 410Ωm and thickness between 2.5m and 5m. The third layer is composed of weathered basement with resistivity values ranging from 56Ω-m to 88Ω-m with thickness between 9.1m and 13.5m. The fourth layer is fresh basement with resistivity values between 1110Ωm and 1200Ωm. The depth to the rock head is between 14.1m and 18.6m. The 2-D subsurface imaging revealed that the foundation soil is composed of clayey materials with resistivity values ranging from 4.3Ωm to 80Ωm, between 0.7m to 5m which correlate well with the geoelectric section. The geovelocity layers’ characteristics substantiate the electrical resistivity imaging and vertical electrical sounding results as it revealed a 4-layer model namely: topsoil, laterite and basement bedrock as the weathered layer is blinded. The topsoil has average velocity 486m/s which is diagnostic of weak/unconsolidated materials presumably clayey materials and average thickness of 2.2m. The sub-weathering/ laterite has average velocity of 1506m/s and average thickness of 7m. The third layer is the bedrock with average velocity of 2292m/s and characterized with a displaced parallel time segment indicating fault within the bedrock. Geotechnical analysis of the subsoil sample revealed that the soils have plasticity index and strength values that are typical of clay. From the result, the building failure observed as cracks and foundation subsidence may have been caused by incompetent foundation soils. It is noteworthy that such faulted zone delineated within the bedrock is also inimical to the building foundation

    The new enclosures: critical perspectives on corporate land deals

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    The contributions to this collection use the tools of agrarian political economy to explore the rapid growth and complex dynamics of large-scale land deals in recent years, with a special focus on the implications of big land deals for property and labour regimes, labour processes and structures of accumulation. The first part of this introductory essay examines the implications of this agrarian political economy perspective. First we explore the continuities and contrasts between historical and contemporary land grabs, before examining the core underlying debate around large- versus small-scale farming futures. Next, we unpack the diverse contexts and causes of land grabbing today, highlighting six overlapping mechanisms. The following section turns to assessing the crisis narratives that frame the justifications for land deals, and the flaws in the argument around there being excess, empty or idle land available. Next the paper turns to an examination of the impacts of land deals, and the processes of inclusion and exclusion at play, before looking at patterns of resistance and constructions of alternatives. The final section introduces the papers in the collection.ESR

    The relationship between subtypes of depression and cardiovascular disease: a systematic review of biological models

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    A compelling association has been observed between cardiovascular disease (CVD) and depression, suggesting individuals with depression to be at significantly higher risk for CVD and CVD-related mortality. Systemic immune activation, hypothalamic–pituitary–adrenal (HPA) axis hyperactivity, arterial stiffness and endothelial dysfunction have been frequently implicated in this relationship. Although a differential epidemiological association between CVD and depression subtypes is evident, it has not been determined if this indicates subtype specific biological mechanisms. A comprehensive systematic literature search was conducted using PubMed and PsycINFO databases yielding 147 articles for this review. A complex pattern of systemic immune activation, endothelial dysfunction and HPA axis hyperactivity is suggestive of the biological relationship between CVD and depression subtypes. The findings of this review suggest that diagnostic subtypes rather than a unifying model of depression should be considered when investigating the bidirectional biological relationship between CVD and depression. The suggested model of a subtype-specific biological relationship between depression and CVDs has implications for future research and possibly for diagnostic and therapeutic processes

    Geological and geophysical evaluation of the Ajana area’s groundwater potential, southwestern Nigeria

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    Acombined geological and geophysical evaluation was madeof the groundwater potential of the Ajana, RemoNorth area in south-western Nigeria; the geology and other structural features of the rocks there strongly influenced and correlated the aquifers' storability and transmissivity. Geological mapping revealed that the area was made up of granite, quartzite and varieties of gneiss, some of which have good secondary porosity and permeability. Ten vertical electric soundings (VES) stations were established using a Schlumberger electrode array. Five geoelectric layers consisting of topsoil, sand,<br />clayey-sandy, fractured / weathered basement and fresh bedrock were delineated. The aquifer layers were the 38.3m thick 283 ?m resistivity sand/sandy clay and 55 - 518 ?m resistivity fractured/weathered basement. Other geoelectric parameters used in evaluating the area's hydrogeological potential included curve type, anisotropy coefficient and reflection coefficient - The QH curve type was predominant in the area. The anisotropy Coefficients suggested VES stations having high groundwater potential ranging from 1.4 - 1.56; while the reflection coefficients for the area ranged from 0.21 - 0.99. The overall results showed that VES stations 8, 9 and 10 could be possible groundwater sources having high expected yield
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