Effect of glycosylation via maillard reaction and acylation on African yam bean (Sphenostylis stenocarpa) protein functionality

The effects of glycosylation of African yam bean (AYB) protein on its nutritional and physico-functional properties were investigated and compared with those of acylated species. Both glycosylated and acylated AYB protein had reduced amino acid content, but retained their nutritional viability. The UV-visible absorption spectra of modified AYB proteins showed that glycosylation did not affect the exposure of its aromatic residue to the hydrophilic environment, but the reverse was the case with acylation. Glycosylation reduced AYB protein thermal stability compared to acylation. Glycosylation of AYB protein enhanced its solubility and emulsifying activity index significantly (p<0.05) more than acylation in various aqueous ionic media but the reverse was the case with their foaming attribute in both ionic and pH media. Both modifications maintained the good gelling attribute of AYB protein. These physico-functional attributes on acylated or glycosylated AYB protein could serve as useful guide into their plausible application in food products development.     

Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions

Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH_PZC and pH_PZNPC to be 3.4 ± 0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu²⁺ and Ni²⁺ uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu²⁺ and Ni²⁺ could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive ΔG° values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (ΔH°) for Ni²⁺ and Cu²⁺ were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of ΔS° indicate low randomness at the solid/solution interface during the uptake of both Cu²⁺ and Ni²⁺ by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.     

A Study of the Complexation Between Danazol and Hydrophilic Cyclodextrin Derivatives

Complexation between danazol, a steroid used for endometriosis, and both hydroxypropyl- β-cyclodextrin (HPCD) and sulfobutyl ether-β-cyclodextrin (SBE) was studied in solution and solid state. Complexation was evaluated in solution using solubility studies and proton magnetic resonance (¹H NMR) spectroscopy, and in the solid state using x-ray diffraction, Fourier-transform infrared spectroscopy (FTIR)), and dissolution studies. Solubility studies suggested the existence of a 1:1 complex between danazol and either HPCD or SBE. ¹H NMR showed that complexation occurs by inclusion of the isoxazole ring of danazol into the cyclodextrin cavity in both cases. Powder x-ray diffraction indicated that danazol existed in a crystalline noncomplexed form at low danazol-to-cyclodextrin ratios in the coprecipitates prepared by solvent evaporation method, while at higher ratios danazol existed in an amorphous complexed form. This ratio was 1:10 w/w for HPCD and 1:20 for SBE; the higher ratio in the case of SBE is attributed to early precipitation of danazol from the solvent used for preparation. FTIR studies showed that the complexation was accompanied by a shift of the O-H stretching of danatol hydroxyl group to a higher frequency, which is attributed to the disruption of the intermolecular hydrogen bonding. The dissolution rate of danazol from HPCD coprecipitates was higher than crystalline danazol in aqueous-isopropanolic medium, while SBE coprecipitates showed reduced dissolution rates due to the low solubility of SBE in isopropanol. However, SBE coprecipitates showed higher dissolution rates in water than in the isopropanolic medium.     

Relation between Access-Related Infection and Preinfection Serum Albumin Concentration in Patients on Chronic Hemodialysis

Background: Hemodialysis (HD) access‐related infection is a major cause of morbidity and mortality in HD patients. We tested whether hypoalbuminemia is a risk factor for HD access infection and whether mortality of HD catheter infection is affected by removal of the infected catheter. Methods: We analyzed the records of 87 patients on chronic HD who were hospitalized for HD access‐related infection. We obtained data on age, sex, preinfection serum albumin level, comorbidities, complications, infecting organism, type of infection, mode of management, and mortality. We compared preinfection serum albumin levels in 79 patients with HD access infection with the serum albumin levels of 198 control patients on chronic HD without HD access infection admitted to the hospital during the same time for other reasons. In the HD catheter infection subgroup, we compared mortalities between patients treated with catheter removal plus antibiotics as the primary mode of management and those treated initially with antibiotics alone. Results: Preadmission serum albumin level was lower in the HD access infection group (2.4 ± 0.6 g/dL) than in the control group (3.2 ± 0.6 g/dL, P < 0.0001). Logistic regression identified preadmission serum albumin level as a strong independent predictor of HD access infection. In a logistic regression model, with age, sex, HIV status, diabetes, and type of HD vascular access (excluding arterovenous fistula) as the covariates, the odds ratio of HD access infection was 9.8 (95% confidence interval [CI] 4.9–19.7) for a serum albumin level ≤ 3.0 g/dL (P < 0.0001), 10.4 (95% CI 4.97–21.6) for a serum albumin level ≤ 2.5 g/dL (P < 0.0001), and 28.0 (95% CI 5.8–135.9) for a serum albumin level ≤ 2.0 g/dL (P < 0.0001). Case mortality was 25.0% (4/16) in patients with tunneled HD catheter infection initially treated with antibiotics alone and 2.8% (2/71) in those treated with catheter removal plus antibiotics at the time of presentation (P = 0.0096). Conclusion: Hypoalbuminemia is associated with increased risk of HD access infection. Treatment of HD access infection with antibiotics alone is associated with increased risk of death.     

Distribution of clay minerals in the process streams produced by the extraction of bitumen from Athabasca oil sands

This study investigates the affinity of clay minerals in oil sands for the water‐continuous tailings and hydrocarbon‐continuous froth streams produced from the extraction of bitumen from oil sands. Clay minerals in oil sands processing impact bitumen flotation in separation vessels, emulsion formation during froth treatment, and fine tailings behaviour. X‐ray diffraction of oriented clay slides and random powder samples were used to quantify the clay minerals in the oil sands ore and process streams. Particle size distribution and clay activity balances were also conducted around the extraction process. The degree of partitioning during the conditioning and flotation stages in a batch extractor was determined by the surface properties of the clay minerals present. The water‐continuous tailings stream was further separated into fine and coarse tailings fractions through sedimentation. The bulk of the clay minerals reported to the fine tailings stream. Illite and mixed layered illite‐smectite partitioned less to the hydrocarbon‐continuous froth than kaolinite. Also, the illite‐smectite in the froth stream appeared to be different from the illite‐smectite in the water continuous streams.     

Emerging Advancements in Polypyrrole MXene Hybrid Nanoarchitectonics for Capacitive Energy Storage Applications

Journal of Inorganic and Organometallic Polymers and Materials - Recent advancement in nanotechnology has brought about the discovery of various nanomaterials such as graphene (GN),...     

Rheological characterization of acylated and dextran conjugated African yam bean (Sphenostylis stenocarpa Hochst. Ex A. Rich.) proteins

The molecular weight distribution and rheological properties of acetylated, succinylated and dextran conjugated African yam bean (Sphenostylis stenocarpa) proteins dispersion were studied. Succinylation of the protein showed the three prominent electrophoretic bands of the unmodified protein but all the bands disappeared with acetylation. Immobile band characterized dextran conjugated S. stenocarpa electrophoregram. The flow behavior indices (n) of these modified S. stenocarpa protein dispersions were in the range 0.03–0.22. This is an indication that they were pseudoplastic in nature. This pseudoplastic nature was maintained in ionic media 0.05–0.5 mol dm^?3, pH 3–8 and temperature range of 27–75 °C. The yield stresses were 0.270, 0.302 and 0.320 Pa for acetylated, succinylated and dextran conjugated protein respectively. Activation energy of acetylated and succinylated protein were in the range 6.2–8.2 and 2–5.4 J mol^?1 respectively. Thus acetylation of S. stenocarpa protein made its dispersion viscosity more susceptible to temperature change than succinylation. These results suggest that acylation and dextran conjugation of African yam bean (S. stenocarpa) protein produce protein species with different rheological properties.     

Managerial ambidexterity and the cultural toolkit in project delivery

Research has established that ambidextrous organizations can successfully outperform their non-ambidextrous counterparts through exploitative and exploratory activities. However, there remains a scarcity of research on how managers orchestrate ambidexterity at the operational level, particularly in project delivery. Drawing on 55 qualitative interviews with middle managers on two engineering projects, we examine how managerial ambidexterity is enacted at the project level. We find that middle managers enable their own exploitative, exploratory and ambidextrous behaviors by invoking a repertoire of values selected from their organization's cultural toolkit, which serve as cultural resources for action. We discuss how the cultural toolkit perspective can inform the relationship between managerial actions in day-to-day operations and organizational ambidexterity. Implications for theory and practice are presented.     

Strengthening Mechanisms and Their Relative Contributions to the Yield Strength of Microalloyed Steels

Microalloyed steels are used widely in oil and gas pipelines. They are a class of high-strength, low-carbon steels that contain small additions (in amounts less than 0.1?wt pct) of Nb,?Ti, and/or V. The steels may contain other alloying elements, such as Mo, in amounts exceeding 0.1?wt pct. Precipitation in these steels can be controlled through thermomechanical-controlled processing, leading to precipitates with sizes that range from several microns to a few nanometers. Microalloyed steels have good strength, good toughness, and excellent weldability, which are attributed in part to the presence of the nanosized carbide and carbonitride precipitates. Because of their fine sizes, wide particle size distribution, and low volume fractions, conventional microscopic methods are not satisfactory for quantifying these precipitates. Matrix dissolution is a promising alternative to extract the precipitates for quantification. Relatively large volumes of material can be analyzed so that statistically significant quantities of precipitates of different sizes are collected. In this article, the microstructure features of a series of microalloyed steels (X70, X80, and X100) as well as a Grade 100 steel are characterized using optical microscopy (OM) and scanning electron microscopy (SEM). A chemical dissolution technique is used to extract the precipitates from the steels. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) are combined to analyze the chemical composition of these precipitates. Rietveld refinement of the XRD patterns is used to quantify fully the relative amounts of these precipitates. The size distribution of the nanosized precipitates is quantified using dark-field imaging (DF) in the TEM. The effects of microalloying content, finish rolling temperature (FRT), and coiling temperature (CT)/interrupted cooling temperature (ICT) on the grain size and the amount of nanoprecipitation are discussed. Individual strengthening contributions from grain size effects, solid-solution strengthening, and precipitation strengthening are quantified to understand fully the strengthening mechanisms for these steels.     

Characterization of organic‐coated solids isolated from different oil sands

Solids isolated from weathered oil sands ores and those having low‐ and high‐fine solids content were studied. The organic matter (OM) adsorbed on the solids was found insoluble in most common solvents, contributing significantly to the change of solid surface properties. The surface properties of these solids were found to affect the entire process cycle of obtaining synthetic crude oil from surface‐mined oil sands using a water‐based extraction process, and managing the existing tailings ponds. In this study, the low‐fine solids ore possessed the lowest amount of organic‐coated solids and highest bitumen recovery. Siderite and pyrite, which tend to concentrate in the hydrocarbon phase were observed in the isolated solids from the weathered and high‐fine ores but were absent in the low‐fine ores. In all the ores studied, the solids from the bitumen froth possess less quartz, and more carbonates compared with solids from the tailings. Elemental analysis by energy dispersive X‐ray spectroscopy (EDX) and elemental analyser revealed the presence of more transition metals (iron and titanium), and carbon in the solids obtained from the bitumen froth when compared with those from the tailings. Infrared (IR) spectroscopy study substantiated the results obtained by X‐ray diffraction and elemental analysis. IR spectra showed a likely association between OM and carbonates in the organic‐coated solids isolated from bitumen froth. More organic‐coated solids were found in weathered oil sands than in other types of ores and observed to reduce bitumen recovery from oil sands.