Recent advances in shear-thinning and self-healing hydrogels for biomedical applications

Shear-thinning and self-healing hydrogels are being investigated in various biomedical applications including drug delivery, tissue engineering, and 3D bioprinting. Such hydrogels are formed through dynamic and reversible interactions between polymers or polypeptides that allow these shear-thinning and self-healing properties, including physical associations (e.g., hydrogen bonds, guest–host interactions, biorecognition motifs, hydrophobicity, electrostatics, and metal–ligand coordination) and dynamic covalent chemistry (e.g., Schiff base, oxime chemistry, disulfide bonds, and reversible Diels–Alder). Their shear-thinning properties allow for injectability, as the hydrogel exhibits viscous flow under shear, and their self-healing nature allows for stabilization when shear is removed. Hydrogels can be formulated as uniform polymer and polypeptide assemblies, as hydrogel nanocomposites, or in granular hydrogel form. This review focuses on recent advances in shear-thinning and self-healing hydrogels that are promising for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48668.     

Manufacturing cell performance improvement: a simulation study

This paper reports on the study of the “underbody front”-automated welding cell at Opel Belgium, a major automobile manufacturer of General Motors International Operations. It employs the use of simulation in an experimental design framework to identify potential improvements in average daily output through management of buffer sizes at key buffer locations within the cell. Many practical applications of animated computer simulation stop at the modeling and displaying of the process under study. Simulation as a tool for process reengineering or enhancement can only reach its full potential if incorporated in a comprehensive statistical study, so as to attain statistically significant results. The paper also reports on the reactions of, and issues raised by, management when the experimental design methodology was presented as a tool for process enhancement and productivity improvement.     

Cyclic minimizers, majorization techniques, and the expectation-maximization algorithm: a refresher

Many parameter estimation problems in signal processing can be reduced to the task of minimizing a function of the unknown parameters. This task is difficult owing to the existence of possibly local minima and the sharpness of the global minimum. In this article we review three approaches that can be used to minimize functions of the type encountered in parameter estimation problems. The first two approaches, the cyclic minimization and the majorization technique, are quite general, whereas the third one, the expectation-maximization (EM) algorithm, is tied to the use of the maximum likelihood (ML) method for parameter estimation. The article provides a quick refresher of the aforementioned approaches for a wide readership.     

Effect of pH on chlorophyll degradation and colour loss in blanched green peas

Effect of pH on the chlorophyll degradation and visual green colour loss in blanched green peas were studied at 70, 80, 90 and 100 °C in buffered solutions of pH 5.5, 6.5 and 7.5. The degradation of chlorophylls a and b followed a first-order reaction and the temperature-dependence of these reactions was modelled by the Arrhenius equation. The activation energies ranged from 4.80 ± 0.91 to 14.0 ± 0.71 kcal mol⁻¹ for chlorophyll a and from 6.84 ± 0.29 to 11.0 ± 1.06 for chlorophyll b with varying pH values. The visual green colour degradation, as represented by the change of the −a (greenness), the ratio −a/b and hue (h) values measured by tristimulus colorimeter, also followed a first-order reaction. Activation energies for −a values ranged from 8.13 ± 0.71 to 12.0 ± 1.07 kcal mol⁻¹, and for −a/b values ranged from 8.77 ± 1.34 to 12.0 ± 1.07 kcal mol⁻¹ with varying pH values at 70, 80, 90 and 100 °C.     

Monitoring the Effects of Ingredients and Baking Methods on Quality of Gluten-Free Cakes by Time-Domain (TD) NMR Relaxometry

Gluten-free products exhibit some undesirable features due to the absence of the gluten network. Effects of ingredient interactions and baking type on the food matrix have not clearly been explored. The objective of this study was to investigate the effect of ingredient and baking types on the quality characteristics of cake by using nuclear magnetic resonance (NMR) relaxometry. Carob bean flour containing gluten-free cakes formulated either with hydroxypropyl methylcellulose (HPMC) or whey protein were baked in both conventional and microwave–infrared combination ovens. Specific gravity of batters was measured and cakes were analyzed in terms of weight loss, hardness, and specific volume. Microstructure of cakes was investigated by scanning electron microscopy (SEM). NMR relaxometry was used to support the information about water retention, and water–food matrix interactions. Cakes baked in microwave–infrared (MW-IR) combination oven had some undesirable characteristics due to higher weight loss and insufficient gelatinization of starch which was supported by SEM results. Compartments of relaxation data also indicated two specific proton pools for MW-IR-baked samples, which represented gelatinized and ungelatinized parts of the cakes. Spin–spin relaxation times (T₂) were found to be good indicators for explaining the physical state and distribution of water inside the samples, having Pearson correlation of 0.96, 0.86, and ??0.98 (p?<?0.05) between monoexponential T₂ values and hardness, specific volume, and moisture, respectively.     

Some Biochemical Properties of Lipase from Bay Laurel (<Emphasis Type="Italic">Laurus nobilis</Emphasis> L.) Seeds

Lipase was isolated from bay laurel (Laurus nobilis L.) seeds, some biochemical properties were determined. The bay laurel oil was used as the substrate in all experiments. The pH optimum was found to be 8.0 in the presence of this substrate. The temperature optimum was 50 °C. The specific activity of the lipase was found to be 296 U mg protein⁻¹ in optimal conditions. The enzyme activity is quite stable in the range of pH 7.0–10. The enzyme was stable for 1 h at its optimum temperature, and retained about 68% of activity at 60 °C during this time. K _m and V _max values were determined as 0.975 g and 1.298 U mg protein⁻¹, respectively. Also, storage stability and metal effect on lipolytic activity were investigated. Enzyme activity was maintained for 9, 12, and 42 days at room temperature, 4 and −20 °C, respectively. Ca²⁺, Co²⁺, Cu²⁺, Fe²⁺, and Mg²⁺ lightly enhanced bay laurel lipase activity.     

Robust parallel hybrid artificial bee colony algorithms for the multi-dimensional numerical optimization

The Journal of Supercomputing - This study proposes a set of new robust parallel hybrid metaheuristic algorithms based on artificial bee colony (ABC) and teaching learning-based optimization (TLBO)...     

Production and characterization of pyrolytic oils by pyrolysis of waste machinery oil

The main objective of this work is to propose an alternative method for evaluation of the waste machinery oil which is an environmental problem in Turkey. For this purpose, pyrolysis of waste machinery oil was conducted in a tubular reactor. Effect of the experimental conditions (various temperatures, catalyst type) on the formation of pyrolytic oil, gas, and char was investigated. Nickel supported on silica and zeolite (HZSM-5) were used as catalysts. Properties of the pyrolytic oils were characterized by gas chromatograph equipped with a mass selective detector (GC–MS), gas chromatography with flame ionization detector (GC–FID for boiling point range distribution), nuclear magnetic resonance (¹H NMR) spectroscopy, higher heating value measurement, and elemental analysis. The behavior of the metals in the waste machinery oil and the pyrolytic oil samples was also quantitatively detected by inductively coupled plasma (ICP) analysis. As, Cd and Cr contents of the all pyrolytic oils were found as <0.05 ppm, while Cu content of the pyrolytic oils varied between 0.3 ppm and 0.61 ppm. Only Vanadium contents of the pyrolytic oils obtained at 800 °C (0.342 ppm) and in the presence of HZSM5 (0.57 ppm) increased compared to that obtained by waste machinery oil (0.1 ppm). Lower metal contents of the pyrolytic oils reveal that pyrolysis of the waste machinery oils leads to the formation of environmental friendly pyrolytic oils with higher heating values.     

Production of hydrogen over bimetallic Pt–Ni/δ-Al2O3: II. Indirect partial oxidation of LPG

Indirect partial oxidation (IPOX) of a 75:25 propane:n-butane mixture, which was used as a model for LPG, was studied over the bimetallic 0.2 wt%Pt–15 wt%Ni/δ-Al₂O₃ catalyst in 623–743 K temperature range. The effects of steam to carbon ratio (S/C), carbon to oxygen ratio(C/O₂) and residence time (W/F (g cat-h/mol LPG)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The results are compared with the results obtained in the IPOX of pure propane. An Increasing Temperature Program (ITP) was applied during all experiments and the results showed that the presence of n-butane in the feed enhances hydrogen production activity and selectivity. Considering the well established distribution network of LPG and the superior performance of the bimetallic Pt–Ni catalyst in the IPOX of LPG, Pt–Ni system seems a very promising catalyst alternative to be used in commercial fuel processors.