Characterization of Geotechnical Properties of Lateritic Soil-Bentonite Mixtures Relevant to Their Use as Barriar in Engineered Waste Landfills

The purpose of this study was to characterize lateritic soil bentonite mixtures intended for use as low-permeability barrier in municipal waste disposal land ll. Characterization of the soil mixtures included measurement of Atterberg limits, compaction properties, hydraulic conductivity, shear strength, and desiccation shrinkage potential. Accordingly, laboratory tests involving soil mixtures with 0, 2.5, 5, 7.5 and 10% bentonite contents, prepared at varying compaction states (2% dry of optimum, optimum and 2% wet of optimum) and compacted using West African stan- dard (WAS) compactive e ort were carried out. Results show that mixtures with bentonite are adjudged to be suitable materials for liners because they met the statutory hydraulic conductivity requirement (i.e., k ≤ 1.0 x 10-9 m/s). Acceptable volumetric shrinkage strain of ≤ 4% (a maximum allowable volumetric shrinkage found in literature and adopted by most regulatory agencies for barrier material) was maintained by most soil mixtures. Although, slight reduction in shear strength was established, uncon ned compressive strength (UCS) values for all soil mixtures met or exceeded the general speci cation i.e., UCS ≥ 200 kN/m2 required for performance in waste repositories.Keywords: barrier, bentonite, hydraulic structures, lateritic soil, waste land l

Effects of Fungal Filtrates on Seed Germination and Leaf Anatomy of Maize Seedlings (Zea mays L., Poaceae)

This study was carried out to investigate the effects of 7-day-old fungal filtrates of Aspergillus niger and Penicillium chrysogenum isolated from maize seeds on percentage germination, morphological and anatomical structures of maize seedlings. The seeds were soaked in culture filtrate of each fungus for 12hrs before planting. Blotter method was used to observe seed germination. Results showed that the percentage germination of the seeds treated with culture filtrates of A. niger and P. chrysogenum (65.33% and 79.67% respectively) was lower than the control (100%) and significantly different from each other at significant level of P ≥0.05. The leaf area showed significant difference between the experimental and control plants but there was no significant difference in the leaf number. The tetracytic stomatal complex type and wavy anticlinal walls remained constant in all the treatments and control. The stomatal index of seed treated with A. niger on abaxial leaf surface (43.61%) showed significant difference with adaxial leaf surface (31.97%). The treatments had no significant difference on stomatal density at abaxial surfaces. Reduction in stomatal size and density suggests physiological implication. © JASEMKeywords: Anatomy, fungi, fungal filtrates, seed germination and Zea may

Non-Native R1 Substitution in the S4 Domain Uniquely Alters Kv4.3 Channel Gating

The S4 transmembrane domain in Shaker (Kv1) voltage-sensitive potassium channels has four basic residues (R1–R4) that are responsible for carrying the majority of gating charge. In Kv4 channels, however, R1 is replaced by a neutral valine at position 287. Among other differences, Kv4 channels display prominent closed state inactivation, a mechanism which is minimal in Shaker. To determine if the absence of R1 is responsible for important variation in gating characteristics between the two channel types, we introduced the V287R mutant into Kv4.3 and analyzed its effects on several voltage sensitive gating transitions. We found that the mutant increased the voltage sensitivity of steady-state activation and altered the kinetics of activation and deactivation processes. Although the kinetics of macroscopic inactivation were minimally affected, the characteristics of closed-state inactivation and recovery from open and closed inactivated states were significantly altered. The absence of R1 can only partially account for differences in the effective voltage sensitivity of gating between Shaker and Kv4.3. These results suggest that the S4 domain serves an important functional role in Kv4 channel activation and deactivation processes, and also those of closed-state inactivation and recovery

A Screening Pipeline for Antiparasitic Agents Targeting Cryptosporidium Inosine Monophosphate Dehydrogenase

Persistent diarrhea is a leading cause of illness and death among impoverished children, and a growing share of this disease burden can be attributed to the parasite Cryptosporidium. There are no vaccines to prevent Cryptosporidium infection, and the treatment options are limited and unreliable. Critically, no effective treatment exists for children or adults suffering from AIDS. Cryptosporidium presents many technical obstacles for drug discovery; perhaps the most important roadblock is the difficulty of monitoring drug action. Here we have developed a set of methods to accelerate the drug discovery process for cryptosporidiosis. We exploit the opportunities for experimental manipulation in the related parasite Toxoplasma to genetically engineer a Cryptosporidium model. This new model parasite mirrors the metabolism of Cryptosporidium for a particularly promising drug target that supplies the building blocks for DNA and RNA. Drug effectiveness can be assayed through simple fluorescence measurements for many candidates. Using this assay as an initial filter, and adapting other assays to a high throughput format, we identify several novel chemical compounds that exhibit markedly improved anti-cryptosporidial activity and excellent selectivity

The EMIF-AD PreclinAD study: study design and baseline cohort overview

BACKGROUND: Amyloid pathology is the pathological hallmark in Alzheimer’s disease (AD) and can precede clinical dementia by decades. So far it remains unclear how amyloid pathology leads to cognitive impairment and dementia. To design AD prevention trials it is key to include cognitively normal subjects at high risk for amyloid pathology and to find predictors of cognitive decline in these subjects. These goals can be accomplished by targeting twins, with additional benefits to identify genetic and environmental pathways for amyloid pathology, other AD biomarkers, and cognitive decline. METHODS: From December 2014 to October 2017 we enrolled cognitively normal participants aged 60 years and older from the ongoing Manchester and Newcastle Age and Cognitive Performance Research Cohort and the Netherlands Twins Register. In Manchester we included single individuals, and in Amsterdam monozygotic twin pairs. At baseline, participants completed neuropsychological tests and questionnaires, and underwent physical examination, blood sampling, ultrasound of the carotid arteries, structural and resting state functional brain magnetic resonance imaging, and dynamic amyloid positron emission tomography (PET) scanning with [18F]flutemetamol. In addition, the twin cohort underwent lumbar puncture for cerebrospinal fluid collection, buccal cell collection, magnetoencephalography, optical coherence tomography, and retinal imaging. RESULTS: We included 285 participants, who were on average 74.8 ± 9.7 years old, 64% female. Fifty-eight participants (22%) had an abnormal amyloid PET scan. CONCLUSIONS: A rich baseline dataset of cognitively normal elderly individuals has been established to estimate risk factors and biomarkers for amyloid pathology and future cognitive declin

Forensic Investigation of Premature Failure of a Roadway Pavement in Minna, Niger state, Nigeria

Field and laboratory studies were conducted to investigate the premature failure of a township roadway pavement in Minna, Niger state, Nigeria. Tests conducted on the pavement layers of the failed road included moisture content, particle size distribution of soil samples, Atterberg limit tests, in-situ density and dynamic cone penetrometer (DCP) tests. An empirical equation from published literature was used to compute the California bearing ratio (CBR) of various pavement layers from DCP data. Data from the tests indicate that the field moisture content of the pavement layers (i.e., subgrade, sub-base and base) were high, recording values above the optimum moisture content (OMC). Some soil materials from the pavement layers at the various failed sections had fines content above specification requirements for such layers. Atterberg limits tests revealed high liquid limits as well as plasticity index values. Generally, the field density values of the subgrade layers were found to be low equivalent to 82 - 98 percent degree of compaction, while the density of the sub-base and base layers at some failed locations were equally low achieving a degree of compaction of about 85 - 99 per cent, against specification requirement of 100 per cent. CBR values were mostly lower than recommended values by local codes. Overall, high proportion of fines and plasticity index values together with inadequate compaction of pavement layers as well as low CBR were identified as key factors responsible for the failure.Keywords: California bearing ratio, degree of compaction, minna, pavement, pre-mature failur

The geotechnical properties of black cotton soil treated with crushed glass cullet

This study is an investigation into the effect of crushed glass (glass cullet), a waste material, on some of the geotechnical properties of Black Cotton Soils (BCS) of North-Eastern Nigeria. The investigation includes evaluation of properties such as consistency limits, index properties, shear strength parameters, Unconfined Compressive Strength, California Bearing Ratio, permeability and potential volume change of the soil with up to 20% glass cullet content. The results obtained showed that the liquid limit and plastic limit decreased with an increase in glass cullet content, while the plasticity index increase with an increase in glass cullet content. The specific gravity increased with an increase in glass cullet content. It was also discovered that increase in glass cullet content decreased the Optimum Moisture Content (OMC) and increased the Maximum Dry Density (MDD) in Compaction. The Optimum Moisture Content (OMC) from the Compaction test was used to prepare the samples used in Direct Shear test (Shear Strength Parameter test), Unconfined Compressive Strength (UCS) test, Permeability test, California Bearing Ratio (CBR) and Potential Volume Change tests. From these tests, cohesion was found to be decreasing with increase in glass cullet content and the angle of internal friction increases as the glass cullet content increased. The Unconfined Compressive Strength test (UCS), permeability test and California Bearing Ratio test (CBR) increases as glass cullet content increased. Also the swelling pressure reduced with increased glass cullet content. These results reveal the suitability of the material in improving the geotechnical properties of the soil and a potential solution to the environmental nuisance created by glass cullet.Keywords: Black cotton soil, Glass cullet, Geotechnical properties