Laboratory Assessment of Metakaolin Effect on the Volumetric Shrinkage of Black Cotton Soil for Flexible Pavement Construction

A dark grey Black Cotton soil treated with up to 24% Metakaolin content was compacted using British standard light (BSL),West African standard (WAS) or “intermediate”and British standard heavy (BSH) compactive efforts at moulding water contents -2,  0, 2, 4 and 6% of optimum moisture content. Specimens where extruded from compaction moulds and allowed to air dry on the table in the Laboratory in order to assess the effect of Volumetric Shrinkage on the material for use in Flexible Pavement construction. Results recorded showed that Volumetric Shrinkage strain (VSS) values were large within the first 5 days of drying; VSS values increased with higher moulding water content,water content relative to optimum. Generally, the Metakaolin improves the Shrinkage properties of the expansive soil irrespective of the compactive effort. Volumetric Shrinkage potential reduced by about 76%, 61% and 42% at 24% Metakaolin for the WAS, BSL and BSH compactive efforts respectively, as compared to the Virgin soil. It can be concluded that the Metakaolin had shown promising influence on the Shrinkage properties of expansive soil, thereby giving an advantage in improvement of problematic expansive soils. Keywords: Expansive soil, Volumetric Shrinkage Strain, Metakaolin, Compactive effort,Moulding Water content, Flexible Pavement

GIS-Based Assessment of Smallholder Farmers’ Perception of Climate Change Impacts and Their Adaptation Strategies for Maize Production in Anambra State, Nigeria

The production of Zea mays (otherwise called maize or corn), which is an important staple food crop in Nigeria, is limited by the impacts of climate change; thus, posing food insecurity in the country. The primary purpose of this study is to assess the perception of smallholders’ maize farmers on climate variability; and, their climate change adaptations practices in Anambra State, Nigeria. A multi-stage sampling technique and structure questionnaires were applied to this study. Collected data were analyzed using both descriptive/ inferential statistics, together with a simple technique of geographic information system (GIS). The results show that, approximately 57.2% of climate variability negatively impacts on maize production in the study area. Basically flooding (ׯ = 2.02 ± 1.166), erratic rainfall (ׯ = 2.02 ± 0.816), and decrease in crop yield by strange pests and diseases (ׯ = 1.59 ± 0.896) affect maize production. The well-informed farmers practice some climate change adaptations techniques such as: planting of grasses to prevent erosion, and, use of improved maize seeds to withstand environmental stress. In conclusion, the lower the standard deviation values, the more knowledgeable the farmers were about issues of climate variability and on climate change adaptations practices; and, vice-versa

Response of Oyster Shell Ash Blended Cement Concrete in Sulphuric Acid Environment

An experimental investigation was carried out to study the potentials of oyster shell ash (OSA) to be used as supplementary cementitious material (SCM) exposed to sulphuric acid environment. Experiments were carried out by supplementing 5 – 20 % of OSA by weight of cement in concrete. The mix ratio used was 1:2:4 (binder, sand and granite) with water cement ratio maintained at 0.5. A total of 320 cube specimens (150mm x 150mm x 150mm) were cast and tested for compressive strength at 7, 14, 21 and 28 days of curing in potable tap water and (5, 7.5 and 10 %) sulphuric acid solutions. It has been deduced that the compressive strength of concrete specimen progressively increased with longer curing periods and decreased with OSA content for specimen immersed in water whereas for specimen immersed in sulphuric acid solutions the compressive strength decreased with longer curing period, OSA content as well as sulphuric acid content. Generally, results of the statistical analysis showed that sulphuric acid concentrations, OSA contents and curing periods have significant effect on the compressive strength of concrete. The use of OSA as SCM did not mitigate the adverse effects of sulphuric acid on the compressive strength of cement blended with OSA. Keywords: Compressive strength, Oyster shell ash, Statistical analysis, Sulphuric acid environment, supplementary cementitious material DOI: 10.7176/CER/11-4-07 Publication date:May 31st 201

Desiccation-Induced Volumetric Shrinkage Characteristics of Highly Expansive Tropical Black Clay Treated with Groundnut Shell Ash for Barrier Consideration

Contamination of underground water as a result of excessive crack on clay liner material is a prevalent phenomenon in an engineered landfill. Volumetric shrinkage strain (VSS) is one of the veritable properties considered for selection of materials suitable for liners and cover in waste containment systems. Material devoid of excessive shrinkage and cracking during climate change could possibly make a better barrier material that will eventually limit or control infiltration of leachate in an engineered landfill. Hence, to obtain a clay liner and covers system that are safe and robust, stabilization of such soil (expansive clay soils) becomes imperative. In order to stabilize or reduce excessive cracking and shrinkage of this soil, earlier researchers have employed cement, chemicals, and fibers. However, in recent times, the ill effects of these stabilizers on the environment have been realized, and hence their replacement with sustainable materials that are mostly agro and or industry by-products is becoming necessary. Tropical dark grey clay treated with up to 8 % Groundnut shell ash (GSA), was carried out. Specimen were compacted using British standard light (BSL) and British standard heavy (BSH) compactive efforts; at water contents between 2% dry and 4% wet of optimum. The compacted specimens were extruded and subjected to drying under laboratory conditions to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment facilities. Results of this study show that changes in mass and volumetric shrinkage strain were large within the first five days of drying. Volumetric shrinkage strain increased with higher moulding water contents (MWC) and water contents relative to optimum (WRO). The effect of GSA treatment on VSS was not consistent from -2 to +2 % of optimum moisture content. For specimen prepared at +4 % of optimum moisture content, VSS decreased up to a threshold of  28% at 6 % GSA and 30% at 4% GSA for BSH and BSL compactive effort, respectively. Generally, lower compactive effort (BSL) with higher moulding water content and lower dry density produced higher VSS. A regression function was developed from the data to estimate VSS given the compaction water content relative to optimum (WRO), groundnut shell ash content (GSA), plasticity index (PI), percentage fine content (PF) and compactive effort (CE). Compaction water content relative to optimum significantly correlated with VSS, thus should be strictly regulated during field compaction to realize a durable hydraulic barrier. Keywords: Atterberg limit, compaction, desiccation, expansive soil, groundnut shell ash, statistical analysis DOI: 10.7176/CER/11-8-06 Publication date:September 30th 201

Refined saddle-point preconditioners for discretized Stokes problems

This paper is concerned with the implementation of efficient solution algorithms for elliptic problems with constraints. We establish theory which shows that including a simple scaling within well-established block diagonal preconditioners for Stokes problems can result in significantly faster convergence when applying the preconditioned MINRES method. The codes used in the numerical studies are available online

An engineered nanosugar enables rapid and sustained glucose-responsive insulin delivery in diabetic mice

Glucose-responsive insulin-delivery platforms that are sensitive to dynamic glucose concentration fluctuations and provide both rapid and prolonged insulin release have great potential to control hyperglycemia and avoid hypoglycemia diabetes. Here, biodegradable and charge-switchable phytoglycogen nanoparticles capable of glucose-stimulated insulin release are engineered. The nanoparticles are "nanosugars" bearing glucose-sensitive phenylboronic acid groups and amine moieties that allow effective complexation with insulin (approximate to 95% loading capacity) to form nanocomplexes. A single subcutaneous injection of nanocomplexes shows a rapid and efficient response to a glucose challenge in two distinct diabetic mouse models, resulting in optimal blood glucose levels (below 200 mg dL(-1)) for up to 13 h. The morphology of the nanocomplexes is found to be key to controlling rapid and extended glucose-regulated insulin delivery in vivo. These studies reveal that the injected nanocomplexes enabled efficient insulin release in the mouse, with optimal bioavailability, pharmacokinetics, and safety profiles. These results highlight a promising strategy for the development of a glucose-responsive insulin delivery system based on a natural and biodegradable nanosugar

The Gray Needle: Large Grains in the HD 15115 Debris Disk from LBT/PISCES/Ks and LBTI/LMIRcam/L' Adaptive Optics Imaging

We present diffraction-limited \ks band and \lprime adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At \ks band the disk is detected at signal-to-noise per resolution element (SNRE) \about 3-8 from \about 1-2\fasec 5 (45-113 AU) on the western side, and from \about 1.2-2\fasec 1 (63-90 AU) on the east. At \lprime the disk is detected at SNRE \about 2.5 from \about 1-1\fasec 45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 \microns . At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at \ks band, but not at \lprime . The surface brightness at \ks band declines inside 1\asec (\about 45 AU), which may be indicative of a gap in the disk near 1\asec. The \ks - \lprime disk color, after removal of the stellar color, is mostly grey for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 \microns -sized grains on the east side and 1-10 \microns dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium.Comment: Apj-accepted March 27 2012; minor correction

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO