Polymerization of ethyl methacrylate,methyl methacrylate,and vinyl acetate using sulfonated polystyrene as the initiator

Polymerization of ethyl methacrylate (EMA) and methyl methacrylate (MMA) was achieved in glass dilatometers, at 86°C, using polystyrene sulfonate (Na⁺ and H⁺ forms) as initiators. The conversion of EMA to PEMA and MMA to PMMA increased with the time of polymerization, quantity of initiator, and size of dilatometer but decreased with volume of water. The polymer yield was higher for the Na⁺ than for the H⁺ form of the resin initiator. The average degree of polymerization increased with increase in the volume of water, but decreased with the quantity of initiator. Vinyl acetate could not be polymerized using either the Na⁺ or H⁺ forms of the polystyrene sulfonate as the initiator under the conditions of EMA or MMA polymerization.     

Failure Analysis of a Ruptured Trunkline

This article reports a detailed analysis of a failure observed in a petroleum trunkline in the Niger Delta region of southwestern Nigeria. The study was carried out using various techniques including metallurgical, chemical, and x-ray analysis. Leakage was observed along a petroleum trunkline route, and excavation of the trunkline revealed that the trunkline had actually fractured along the 6 o’clock position. The pipeline material was found to conform to the API specification for low carbon steel of X52 grade. Wormwood-like interconnecting pits typical of microbial-induced corrosion were noticed at the 6 o’clock position. Scale deposits composed of corrosion products and debris from the crude oil transported by the trunkline were also noticed. The liquid analysis result showed that the produced water was corrosive, and it has a high bacteria count. The failure of the trunkline was found to be due to the thinning of the pipeline at the 6 o’clock position by the combined effect of abrading by debris, erosion, and corrosion aided by bacteria activities, i.e., microbial-induced corrosion (MIC) and eventual rupture.     

Modelling multiphasic starch digestograms: an objective procedure for slope discontinuities†

Digestograms of 101 published in vitro starch digestion were used to investigate slope discontinuities. Polynomial equations (1 to 3 orders) adequately described the first derivative of the digestograms. The derivative(s) of the equations revealed critical point(s). The third-order equation described (P ≤ 0.05) 17% of the digestograms as triphasic, the second- and third-order equations identified (P ≤ 0.05) 32% as biphasic, while 51% exhibited (P ≤ 0.05) monophasic digestograms. Using nonlinear regression with practical constraints, a modified first-order kinetic model (D_t = D₀ + D_∞−0 {1 − exp [−K t]}) described (r² > 0.56, P ≤ 0.05) segments 1–3 of the digestograms. Rapid-slow and slow-rapid digestion rates were obtained, and maximum digestible starches, D_∞, ≤100g/100g (dry) starch for an in-depth understanding of starch digestion. This is the first comprehensive objective approach for slope discontinuities in starch digestograms for consistency in modelling digestograms that advances starch digestion studies.     

Light and Electron Microscopy Studies of the Visible Diffusion Zone of Mild Steel Pack Cyanided in Processed Cassava Leaves

This study investigates the microstructure of the processed cassava leaves. Standard parts machined from low visible diffusion zone formed in low carbon steel pack cyanided using carbon steel were pack cyanided by high temperature in-situ diffusion of nascent carbon and nitrogen into austenite. Formation of a visible diffusion zone was confirmed after observation with a Reichert-Jung Polyval optical microscope coupled with Zeiss AxioCam ICc 1 camera. High magnification Scanning Electron Microscope （SEM） imaging of the visible diffusion zone was done with a CamScan Series 2 scanning electron microscope. The zone was found variable in depth as measured from a representative position. The structure of all samples consists of ferrite and pearlite as determined by optical and SEM examination. Resulting products were thus both tough and hard suitable for service environments requiring high resistance to both wear and impact failure.     

Homogeneities in in vitro starch digestion of compositionally heterogenous white wheat breads

In vitro starch digestion of five fresh and shelved white wheat breads, compositionally heterogeneous, was investigated for heterogeneities or homogeneities in digestion patterns. The breads were significantly different (P ≤ 0.05) in some chemical and functional properties. The Rapid Visco-Analyser (RVA) revealed different pasting properties in the breads, but the breads showed monophasic starch digestograms, as there were no practical slope changes or discontinuities in the digestograms. The monophasic starch digestograms were suitably described (r² > 0.90; P ≤ 0.05) by five starch digestion kinetic models (the modified first-order kinetic, Peleg, Paolucci-Jeanjean, Logistic, and Weibull), and their parameters were mainly non-significant (P > 0.05) between the breads. The heterogeneous breads were, therefore, homogeneous in their in vitro starch digestion patterns. The study also strengthens a novel modelling approach for starch digestograms to be widely used in starch digestion research, easing inter-laboratory comparisons.     

Investigation of effects of Argenine–Glycine–Aspartate (RGD) and nano-scale titanium coatings on cell spreading and adhesion

This paper examines the effects of physical and chemical surface modifications on the biocompatibility of silicon surfaces that are relevant to implantable silicon Bio-micro-electro-mechanical systems (BioMEMS). Two types of surface modifications were explored. The first involved the deposition of nano-scale biocompatible layers of pure titanium on silicon, while the second explored the covalent attachment of the binding peptide Argenine–Glycine–Aspartic acid (RGD) for improved cell adhesion. Improvements in biocompatibility were assessed through examination of cell areas after culture, as well as the measurements of adhesion strengths, as determined by shear assay techniques. The titanium nanolayers and the RGD coating resulted in improvements in biocompatibility. Increased cell spreading areas and improved adhesion strength were obtained from short and long-term studies of Human Osteosarcoma (HOS) cells cultured on the coated surfaces. RGD functionalization resulted in the greatest improvement in cell spreading area and adhesion strength for short culture times. The effects of the titanium, while less than those of RGD for short culture times, appeared to be greater after 48 h of culture.     

Investigation of the spreading and adhesion of human osteosarcoma cells on smooth and micro-grooved polydimethylsiloxane surfaces

The paper presents recent results of the study of spreading and adhesion of human osteosarcoma cells on soft polydimethylsiloxane (PDMS) materials. Cell/surface interactions are studied on smooth and micro-grooved PDMS surfaces. The viscoelastic spreading behavior of the human osteosarcoma cells (during the spreading stages on smooth PDMS surfaces) was studied using wetting theory. The HOS cell spreading behavior was also investigated in the micro-grooved PDMS surfaces in an effort to study the contact guidance formation process. The results show that the initial stages of HOS cell spreading can be modeled as a complete wetting process. The results also show that the cell cytoplasm contributes more to the spreading process than the nucleus. In the case of cell spreading on micro-grooved surfaces, the cell tractions resulted in significant deformation of the microgrooves. The tractions were also calculated, and found to be in good agreement with the results from other studies. The results suggest that the cell spreading-induced soft substrate deformation needs to be considered in the design of implantable bioMEMS structures.