Statistical approach to optimization of the transesterification reaction from sorrel (hibiscus sabdariffa) oil

In an effort to optimize the reaction conditions of biodiesel production from Sorrel seed oil, Response Surface Methodology (RSM) was applied and the effects of reaction temperature, catalyst amount, reaction time and methanol/oil molar ratio, and their reciprocal interactions were ascertained. A total of 30 experimental runs were designed by Central Composite Rotatable Design (CCRD) and carried out. A quadratic polynomial was obtained for predicting the Transesterification process and the ANOVA test showed the model to be significant (p<0.05). The validity of the predicted model was confirmed by carrying out three independent replicates experiments. The actual maximum biodiesel yield obtained was 99.23% (w/w) at methanol/oil molar ratio 6.21, catalyst amount 1.03 (% wt.), reaction temperature 51 oC, and reaction time 63 min. The fuel properties of Hibiscus sabdariffa methylester (HSME) produced were found to be within the ASTM D6751 and DIN EN 14214 biodiesel standards. The fatty acid profile of the HSME revealed that the dominant fatty acids were oleic (58.34%), arachidic (1.55%), palmitic (18.28%) and linoleic (21.19%). Emission assessment revealed 70% reduction of CO at B80, 80% reduction of NO concentration at B40

Modification in clay concrete properties during fluid flow permeability measurement

Abstract: In this paper, two methods consisting of triaxial water permeability and water penetration were used to evaluate changes occurring in the pores of clay concretes, during the tests. Triaxial permeability is generally used for concrete with higher permeability while concrete with very low permeability are suited for the penetration method. Clay concrete specimens of 0 to 40% clay content were used in the study. The concrete mixes had water-to-cementitious ratios (w/cc) of 0.70, 0.75, 0.80, 0.85, and the cementitious content 380 and 450 Kg/m3. Results show that concrete gains moisture during wetting at a much faster rate than it loses during subsequent drying. This could be explained by the contribution of suction pressure created upon drying. When water penetration pressure is applied, more water is driven into pore space than could be responsible for changing the network of the voids. Pore structure during drying may certainly be different in size and shape than its form during wetting, leading to a consequent effect on the permeability of the clay concretes. The modification could be one reason that the moisture gain percentage in clay concretes was higher than in normal concretes

Assessment of activity moduli and acidic resistance of slag-based geopolymer concrete incorporating pozzolan

The environmental impact of Portland cement production and utilization in the construction sector has led to the global call for the use of eco-friendly construction materials for the production of cleaner and sustainable products. Therefore, this study explored agro-industrial wastes, slag and corncob ash, for the production of geopolymer concrete (GPC). Corncob was dehydroxylated at 600 �C for 3 h and partially used as a replacement for slag at 0%, 20 %, 40 %, 60 %, 80 %, and 100 %. A 12 M, 14 M, and 16 M of both sodium silicate (SS) and sodium hydroxide (SH) were used as activators. The chemical moduli of each and mixed binder were quantified and evaluated based on the major reactive oxides, hence leading to the evaluation of reactivity indexes (RIs). Moreover, the RIs and mix design properties (MDPs) of concrete were used for the prediction of flexural strength while the chemical resistance of each concrete sample was investigated. Compared with the experimental results, the predictive flexural strengths based on the RIs and the MDPs yielded a high precision with R2 ranging from 88–92 % at 7–90 days, respectively. Moreover, the GPC, unlike Portland cement concrete (PCC), resisted the more acidic attack. Therefore, the use of GGBFS�CCA blended concrete would be more advantageous in a highly acidic environment than PCC. Ultimately, the models proposed by this study can be useful in the concrete mix design procedure for the flexural strength development of GPC incorporating agro-industrial provided the oxide compositions of each and mixed material were obtained

Radiological assessment of natural radionuclide contents in soils from Omala, Kogi State, Nigeria.

High purity germanium detector (HPGe) was employed to assess radionuclide contents of 238U, 40K and 232Th in soils obtained from Omala, Kogi State, Nigeria. The activities measured vary from 9.0 to 82.2, 12.3 to 114.86 and below detector limit (BDL) and 349.0 Bq Kg-1 in 238U, 232Th and 40K respectively. Highest activities for the three radionuclides were consistently obtained from soil samples got from Igaliwu. The measured activities were engaged to estimate the absorbed dose, annual outdoor effective dose and gamma index. It was observed from the absorbed dose, annual equivalent dose and the gamma index estimated that soils from Igaliwu, Ijeke-ogene and Bagana were found to be higher than the recommended safe limit for normal background. This suggests that those living or using the soil for construction purposes are exposed to high radiation burden from natural radionuclides

Dealing with uncertainty in GHG inventories: How to go about it?

The assessment of greenhouse gases emitted to and removed from the atmosphere is high on both political and scientific agendas. Under the United Nations Framework Convention on Climate Change, Parties to the Convention publish annual or periodic national inventories of greenhouse gas emissions and removals. Policymakers use these inventories to develop strategies and policies for emission reductions and to track the progress of these policies. However, greenhouse gas inventories (whether at the global, national, corporate, or other level) contain uncertainty for a variety of reasons, and these uncertainties have important scientific and policy implications. For scientific, political, and economic reasons it is important to deal with the uncertainty of emissions estimates proactively. Proper treatment of uncertainty affects everything from our understanding of the physical system to the economics of mitigation strategies and the politics of mitigation agreements. A comprehensive and consistent understanding of, and a framework for dealing with, the uncertainty of emissions estimates should have a large impact on the functioning and effectiveness of the Kyoto Protocol and its successor. This chapter attempts to pull together relevant fragments of knowledge, allowing us to get a better picture of how to go about dealing with the uncertainty in greenhouse gas inventories

Alternative proof for the localization of Sinai's walk

We give an alternative proof of the localization of Sinai's random walk in random environment under weaker hypothesis than the ones used by Sinai. Moreover we give estimates that are stronger than the one of Sinai on the localization neighborhood and on the probability for the random walk to stay inside this neighborhood

Continuous Percolation Phase Transitions of Two-dimensional Lattice Networks under a Generalized Achlioptas Process

The percolation phase transitions of two-dimensional lattice networks under a generalized Achlioptas process (GAP) are investigated. During the GAP, two edges are chosen randomly from the lattice and the edge with minimum product of the two connecting cluster sizes is taken as the next occupied bond with a probability $p$. At $p=0.5$, the GAP becomes the random growth model and leads to the minority product rule at $p=1$. Using the finite-size scaling analysis, we find that the percolation phase transitions of these systems with $0.5 \le p \le 1$ are always continuous and their critical exponents depend on $p$. Therefore, the universality class of the critical phenomena in two-dimensional lattice networks under the GAP is related to the probability parameter $p$ in addition.Comment: 7 pages, 14 figures, accepted for publication in Eur. Phys. J.

Statistical analysis of concrete cover in new highway bridges

Abstract: Quality control is one of the important aspects of any major construction works, that is to be undertaken to ensure work execution according to design requirements. The work presented in this paper involved measurement of cover thickness in three newly constructed highway bridges. Testing was conducted to ensure that specified requirements were attained prior to commissioning of the structures; otherwise, the quality control survey would identify problem areas for consideration of corrective measures. A total of 328 data sets were obtained during cover measurements. In this paper, the results obtained are discussed and evaluated. Data are characterised on the basis of statistical quantitie

Nonlinear equation for anomalous diffusion: unified power-law and stretched exponential exact solution

The nonlinear diffusion equation $\frac{\partial \rho}{\partial t}=D \tilde{\Delta} \rho^\nu$ is analyzed here, where $\tilde{\Delta}\equiv \frac{1}{r^{d-1}}\frac{\partial}{\partial r} r^{d-1-\theta} \frac{\partial}{\partial r}$, and $d$, $\theta$ and $\nu$ are real parameters. This equation unifies the anomalous diffusion equation on fractals ($\nu =1$) and the spherical anomalous diffusion for porous media ($\theta=0$). Exact point-source solution is obtained, enabling us to describe a large class of subdiffusion ($\theta > (1-\nu)d$), normal diffusion ($\theta= (1-\nu)d$) and superdiffusion ($\theta < (1-\nu)d$). Furthermore, a thermostatistical basis for this solution is given from the maximum entropic principle applied to the Tsallis entropy.Comment: 3 pages, 2 eps figure

Outer-Sphere Contributions to the Electronic Structure of Type Zero Copper Proteins

Bioinorganic canon states that active-site thiolate coordination promotes rapid electron transfer (ET) to and from type 1 copper proteins. In recent work, we have found that copper ET sites in proteins also can be constructed without thiolate ligation (called “type zero” sites). Here we report multifrequency electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), and nuclear magnetic resonance (NMR) spectroscopic data together with density functional theory (DFT) and spectroscopy-oriented configuration interaction (SORCI) calculations for type zero Pseudomonas aeruginosa azurin variants. Wild-type (type 1) and type zero copper centers experience virtually identical ligand fields. Moreover, O-donor covalency is enhanced in type zero centers relative that in the C112D (type 2) protein. At the same time, N-donor covalency is reduced in a similar fashion to type 1 centers. QM/MM and SORCI calculations show that the electronic structures of type zero and type 2 are intimately linked to the orientation and coordination mode of the carboxylate ligand, which in turn is influenced by outer-sphere hydrogen bonding