Geochemistry and mineralogy of the Campanian Sandstone of Lokoja-Basange Formation, Middle Niger Basin (Lokoja sub-basin), Nigeria: Implications for provenance, weathering, tectonic setting and paleo-redox condition

Twenty six road-cut sandstone samples from two lithological sections of Lokoja-Basange Formation in Middle Niger Basin (Lokoja sub-basin) situated by the side of Auchi-Igarra road (07º 07.201'N, 006º 13.011'E) were investigated using integrated mineralogical, geochemical and pore water chemistry studies. The medium to coarse grained sandstone bodies are poorly sorted suggestive of deposition in a low energy setting, probably in a shelf or floodplain. The observed variations in the sandstone colourations are attributed to the nature of the cementing materials. Based on the mineralogical composition, two specific geochemical intervals were established; the first interval revealed quartz and kaolinite as major crystalline minerals with traces of hematite. The second geochemical interval showed quartz and kaolinite as the major crystalline minerals with minor quantities of grossite and halloysite. The geochemical datasets obtained revealed mature, lithic arenites including sub-greywacke and protoquartzites. The inverse correlation between redox potential (Eh) and electrical conductivity (EC), total dissolved solids (TDS) and Mg (at 0.05 significant levels) suggest well oxygenated environment of deposition. The high chemical index of alteration (CIA), plagioclase index of alteration (PIA), and chemical index of weathering (CIW) indices revealed high detrital input dominated by intense chemical weathering. This process eventually led to the formation of clay minerals by hydration and leaching of all major cations, such as Ca+2, K+, and Na+, present in feldspar minerals. The average mineralogical index of alteration (MIA) values are indicative of intense to extreme weathering of mineralogical component of the detrital materials from the source areas. The studied sandstones samples are plotted in the field of the active and passive continental margin settings. The mean ratio of Ti/Zr also corroborates active and passive continental margin settings. The higher ratios of La/Y and La/Th and corresponding lower ratios of La/Co and Th/Co indicates felsic source rock. Moreover, the lower ratios of Ba/Sr, Cr/Zr, Ti/Zr and higher ratio of Zr/Y probably suggest felsic source rock. Based on the previously established thresholds, the low Cu/Zn ratios in the studied sandstone samples suggest deposition under oxidizing conditions. Keywords: Lokoja-Basange Formation, Middle Niger Basin, Mineralogy, Geochemistry, Pore water chemistry, provenance, tectonic setting, weathering, Redox proxy

Mineralogy and Geochemical Appraisal of Paleo-Redox Indicators in Maastrichtian Outcrop Shales of Mamu Formation, Anambra Basin, Nigeria

The Mamu Formation exhibits two types of shales, viz. grey and dark shales. The geochemical and mineralogical compositions of these shales were investigated using X-ray fluorescence (XRF) and Laser Ablation- Inductively Coupled Plasma Spectrometry (LA-ICPMS) and X-ray diffraction techniques. The basal part of the section is characterized by presence of quartz and kaolinite as the major crystalline minerals with minor quantity of hematite. The presence of hematite in the basal part of the shale sequence suggests oxidizing diagenetic environment of deposition. The second geochemically specific interval (upper part) is characterised by quartz and kaolinite as major crystalline minerals with traces of halloysite and grossite. The ternary plot of these major elements indicates the majority of shale samples examined are variably enriched with SiO2 relative to Al2O3 and CaO. The positive correlations of K2O, TiO2, and Na2O, with Al2O3 indicate that these elements are associated entirely with detrital phases. Some trace elements such as Cr, Ni, and V are positively correlated with Al2O3 which suggest that these elements may be bound in clay minerals and concentrated during weathering. The K2O/Al2O3 ratio is close to the lower limit of clay mineral range, which suggests that kaolinite is the dominant clay minerals. The Al2O3/TiO2 and low Cr/Ni ratios suggest that felsic components were the main components among the basement complex source rocks. The geochemical indices such as Th/Cr, Cr/Th, Th/Co and Th/Cr ratios suggest that these shales were derived from felsic source rocks. The chemical index of alteration values indicates that these shales have experienced strong chemical weathering at the source area. In addition, the depletion of Na and Ca also illustrates an intense chemical weathering of the source rocks. The mineralogical index of alteration values of the studied shale samples indicates an intense to extreme weathering of mineralogical components. The shale units exhibits different degrees of trace-element enrichment, with the approximate order of enrichment relative to an average shale being Co > Pb > Ni > Zr > Cu > Rb > V > Cr > Ba > V > Sr > U. The inverse correlation between Eh, pH, EC and TDS in outcrop Maastrichtian shale samples suggests well oxygenated environment of deposition. In addition, based on previously established thresholds, V/Cr, Ni/Co, Cu/Zn and U/Th ratios support that these shales were deposited under oxidizing diagenetic environment. Keywords: mineralogy, geochemistry, paleo-redox conditions, trace element enrichments, shales, Mamu Formation, Anambra basin, Nigeria

Perovskite solar cells: a deep analysis using current–voltage and capacitance–voltage techniques

Perovskite solar cells exhibiting~14–15% efficiency were experimentally measured using current–voltage (I–V) and capacitance–voltage (C–V) techniques in order to extract material and device properties, and understand the action of photovoltaic (PV) operation. Deep analyses were carried out on dark- and illuminated I–V curves, and dark C–V curves. Results were compared with those of graded bandgap solar cells fabricated on inorganic n-type window layers. These analyses according to a physicist’s point of view lead to understand the perovskite solar cell as a graded bandgap solar cell built on a p-type window layer. I–V and C–V results show very similar behaviour and the principle of PV action is identical. Once the stability issues with perovskites are solved, these devices have very high potential of producing next generation solar cells reaching at least mid-20% efficiency values

Mobility and Transport of Inorganic Species in Weathered Hydraulic Disposed Coal Fly Ash: An Insight from Geochemical Fractionation and Statistical Evaluation

A large volume of coal fly ash generated through combustion process has raised environmental concerns due to possible release of potentially toxic species to the surface and groundwater systems. The chemical partitioning and mobility of elements in the hydraulic disposed ash dump was investigated using modified sequential extraction scheme. The geochemical distribution of the investigated elements in 33 drilled core samples was determined by x-ray fluorescence and inductively coupled plasma mass spectrometry. The ternary plot of major elements as determined by XRF showed that hydraulic disposed ash cores are sialic, ferrosialic and ferrocalsialic in chemical composition. The relationship between SiO2 and chemical index of alteration (CIA) showed low, moderate to high degree of weathering. These chemical compositions and degree of chemical weathering depend on the ash sampling point and ash interaction chemistry. The Na+ and K+ soluble salts showed evidence of leaching and downward migration in the water soluble fraction indicating that the hydraulic disposed ash dump is not a sustainable salt sink. The geochemical partitioning reveals that mobility and transport of potentially toxic metal species are governed by the pore water pH, ash interaction chemistry and the sampling point of the ash cores.  The chemical interaction of drilled core ash with the ingress CO2 and percolating rain water led to dissolution and co-precipitation of soluble major components in fly ash. This had led to incoherent patterns of elements in carbonate fraction of the ash cores.Key words: Modified sequential extraction; Hydraulic disposed ash; Chemical index of alteration; Pore water pH; Ash interaction chemistry; Moisture content; Chemical weatherin

Mineralogy, Physicochemical Characteristics and Industrial Potential of Some Residual Clay Deposits within Ekiti State, Southwestern Nigeria

Residual clay deposits overlying Precambrian Basement Complex situated at Orin, Igbara Odo, Ikere and Ado Ekiti were investigated using several analytical techniques. Field evidence supported by mineralogical and physicochemical analyses suggests that the kaolinitic clay deposits is a product of hydrothermal and in-situ weathering of aplite, and granite. Kaolinite is the predominant clay mineral of the studied clay deposits with subordinate quartz, potassium iron oxide and aluminium phosphatic minerals. There is localised occurrence of halloysite. The absence of vanadium in the EDS data of rolled into tubes kaolinite sheets of Ado Ekiti clay match up with XRF data. This result trend combined with field observation suggests that clay bodies formed from weathering of feldspar is deficient in vanadium. The study suggests that morphology of kaolinitic minerals is influenced by the kind of parent material (i.e. feldspars or micas) and degree of chemical weathering. The pH values of pore water from clay samples range from 7.14 - 9.08. The electrical conductivities (EC) of the clay/water slurries (S/L ratio) range from 0.004mS/cm – 3.02mS/cm.  The oxidation reduction potential (ORP) values range between -62.4 and – 6.8 for the solids or slurries prepared with water. The dissolved oxygen (DO) values range from 6.73ppm – 7.26ppm for solids or slurries prepared with water. The loss on ignition ranges from 2.24-13.39. The SiO2/Al2O3 molar ratio of 1.40 and 1.50 for Orin and Ikere clay bodies indicated that a 1:1 clay mineral was the dominant component. The high chemical index of alteration (CIA = 77.97~98.64) and chemical index of weathering (CIW = 97.21~99.93) values probably indicated the complete weathering of feldspars to kaolinite. The weathering index of Parker (WIP) values grouped the analysed clay samples into moderate to intense degree of weathering. This observation is confirmed by the absence of detrital feldspar in the XRD spectra peak. Factor analysis showed enrichment and depletion of major and trace elements which could be attributed to moderate to intense leaching conditions of the presumed parent material. The data shows explicit relationship between the clayeyness value (Al2O3/SiO2 ratio), the relative base loss (RBL) and the cation exchange capacity (CEC). Cluster analysis of major and trace elements showed two groups of chemical differences amongst the elements in the clays; moderate and intense degree of weathered clays. Nevertheless, the variations in the degree of weathering or leaching process have greater contribution to clay deposits differentiation. Assessment of the industrial potential of the studied clay bodies based on their physical and chemical characteristics revealed that they are suitable for the production of refractory bricks and ceramics. Suitable processing would be compulsory if they are to meet the requirements for other industrial applications, such as rubber, paper, paint, cosmetics, and fertilizer industries. Keywords: Clay; Mineralogy; Physicochemical characteristics; Weathering indices; Pore water; Multivariable analysis; Igbara Odo Ekiti; Ikere Ekiti; Ado Ekiti

Self-medication with antibiotics for the treatment of menstrual symptoms in southwest Nigeria: a cross-sectional study

Background: Self-medication with antibiotics is an important factor contributing to the development of bacterial antibiotic resistance. The purpose of this study was to evaluate the prevalence of self-medication with antibiotics for the treatment of menstrual symptoms among university women in Southwest Nigeria. Methods: A cross-sectional survey was administered to female undergraduate and graduate students (n = 706) at four universities in Southwest Nigeria in 2008. The universities were selected by convenience and the study samples within each university were randomly selected cluster samples. The survey was self-administered and included questions pertaining to menstrual symptoms, analgesic and antibiotic use patterns, and demographics. Data were analyzed using descriptive statistics and logistic regression. Results: The response rate was 95.4%. Eighty-six percent (95% CI: 83-88%) of participants experienced menstrual symptoms, and 39% (95% CI: 36-43%) reported using analgesics to treat them. Overall, 24% (95% CI: 21-27%) of participants reported self-medicated use of antibiotics to treat the following menstrual symptoms: cramps, bloating, heavy bleeding, headaches, pimples/acne, moodiness, tender breasts, backache, joint and muscle pain. Factors associated with this usage were: lower levels of education (Odds Ratio (OR): 2.8, 95% CI: 1.1-7.1, p-value: 0.03); nonscience major (OR: 1.58, 95% CI: 1.03-2.50, p-value: 0.04); usage of analgesics (OR: 3.17, 95% CI: 2.07-4.86, p-value: <0.001); and mild to extreme heavy bleeding (OR: 1.64, 95% CI: 1.01-2.67, p-value: 0.05) and pimples/acne (OR: 1.57, 95% CI: 0.98-2.54, p-value: 0.06). Ampicillin, tetracycline, ciprofloxacin and metronidazole were used to treat the most symptoms. Doctors or nurses (6%, 95% CI: 4-7%), friends (6%, 95% CI: 4-7%) and family members (7%, 95% CI: 5-8%) were most likely to recommend the use of antibiotics for menstrual symptoms, while these drugs were most often obtained from local chemists or pharmacists (10.2%, 95% CI: 8-12%). Conclusions: This is the first formal study to report that approximately 1 out of 4 university women surveyed in Southwest Nigeria self-medicate with antibiotics to treat menstrual symptoms. This practice could provide monthly, low-dose exposures to antibiotics among users. Further studies are necessary to evaluate the impacts of selfmedication on student health

Progress in development of graded bandgap thin film solar cells with electroplated materials

Photovoltaic devices are developed mainly based on p-n or p-i-n type device structures, and these devices can utilise only a fraction of the solar spectrum. In order to further improve device parameters and move towards low-cost and high-efficiency next generation solar cells, device architectures capable of harvesting all photons available should be designed and developed. One such architecture is the fully graded bandgap device structure as proposed recently based on both n-type and p-type window layers. These designs have been experimentally tested using well researched GaAs/AlGaAs system producing impressive device parameters of open circuit voltage (Voc) ~1175 mV and fill factor (FF) ~0.85. The devices have also been experimentally tested for the evidence of impurity photovoltaic (PV) effect and impact ionisation taking place within the same device. Since these structures have been experimentally proved with a well-established semiconductor, the effort has been focussed on developing these devices using low-cost and scalable electroplated semiconductors, in order to minimise manufacturing cost. This paper reviews and summarises the work carried out during the past decade on this subject. Graded bandgap devices produced using only two or three electroplated semiconductor layers have been explored and their conversion efficiencies have gradually increased from 10.0%, through 12.8% to 15.3% for different structures. While the work is progressing along this line, the paper summarises the achievements to date

Association between Inflammation and Cardiac Geometry in Chronic Kidney Disease: Findings from the CRIC Study.

Background Left ventricular hypertrophy (LVH) and myocardial contractile dysfunction are independent predictors of mortality in patients with chronic kidney disease (CKD). The association between inflammatory biomarkers and cardiac geometry has not yet been studied in a large cohort of CKD patients with a wide range of kidney function. Methods Plasma levels of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1RA), IL-6, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, high-sensitivity C-Reactive protein (hs-CRP), fibrinogen and serum albumin were measured in 3,939 Chronic Renal Insufficiency Cohort study participants. Echocardiography was performed according to the recommendations of the American Society of Echocardiography and interpreted at a centralized core laboratory. Results LVH, systolic dysfunction and diastolic dysfunction were present in 52.3%, 11.8% and 76.3% of the study subjects, respectively. In logistic regression analysis adjusted for age, sex, race/ethnicity, diabetic status, current smoking status, systolic blood pressure, urinary albumin- creatinine ratio and estimated glomerular filtration rate, hs-CRP (OR 1.26 [95% CI 1.16, 1.37], p Conclusion In patients with CKD, elevated plasma levels of hs-CRP and IL-6 are associated with LVH and systolic dysfunction

Chronic Kidney Disease and Cognitive Function in Older Adults: Findings from the Chronic Renal Insufficiency Cohort Cognitive Study

To investigate cognitive impairment in older, ethnically diverse individuals with a broad range of kidney function, to evaluate a spectrum of cognitive domains, and to determine whether the relationship between chronic kidney disease (CKD) and cognitive function is independent of demographic and clinical factors.Cross-sectional.Chronic Renal Insufficiency Cohort Study.Eight hundred twenty-five adults aged 55 and older with CKD.Estimated glomerular filtration rate (eGFR, mL/min per 1.73 m 2 ) was estimated using the four-variable Modification of Diet in Renal Disease equation. Cognitive scores on six cognitive tests were compared across eGFR strata using linear regression; multivariable logistic regression was used to examine level of CKD and clinically significant cognitive impairment (score ≤1 standard deviations from the mean).Mean age of the participants was 64.9, 50.4% were male, and 44.5% were black. After multivariable adjustment, participants with lower eGFR had lower cognitive scores on most cognitive domains ( P <.05). In addition, participants with advanced CKD (eGFR<30) were more likely to have clinically significant cognitive impairment on global cognition (adjusted odds ratio (AOR) 2.0, 95% CI=1.1–3.9), naming (AOR=1.9, 95% CI=1.0–3.3), attention (AOR=2.4, 95% CI=1.3–4.5), executive function (AOR=2.5, 95% CI=1.9–4.4), and delayed memory (AOR=1.5, 95% CI=0.9–2.6) but not on category fluency (AOR=1.1, 95% CI=0.6–2.0) than those with mild to moderate CKD (eGFR 45–59).In older adults with CKD, lower level of kidney function was associated with lower cognitive function on most domains. These results suggest that older patients with advanced CKD should be screened for cognitive impairment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78647/1/j.1532-5415.2009.02670.x.pd