Determination of critical gelation conditions of κ-carrageenan by viscosimetric and FT-IR analyses

In this study, spectroscopic results, which were obtained from FT-IR at solid state, have been used for the direct determination of critical physical gelation conditions of κ-carrageenan and compared with the results obtained from viscosimetric studies. Effect of some parameters such as polymer concentration, added salt concentration and temperature on the gelation behavior of κ-carrageenan (KC) was also investigated. Influence of all these parameters on the critical gelation conditions of κ-carrageenan was followed by viscosimetric and FT-IR techniques. After a critical polymer concentration (0.7 g/dl), κ-carrageenan exhibited a complete wall-to-wall gel structure. The effect of potassium chloride (KCl) on the gelation of κ-carrageenan is discussed for non-salt and salt added systems based on the results obtained from viscosimetric measurements. It has been observed that addition of only minute amount of KCl was increased the viscosity approximately twenty fold. FT-IR results proved that critical physical gelation concentration could be determined by analyzing spectrum obtained at solid state in very short time and using only minute amount of substances.     

Antioxidant capacity and total phenolic content of selected plants from Turkey

A total of 28 different plants from different regions of Çanakkale, Turkey, were investigated for their antioxidant capacity and total phenol contents to find new potential sources of natural antioxidants. The antioxidant capacity of methanolic extracts prepared from various parts of plants was evaluated by both trolox equivalent antioxidant capacity (TEAC) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assays, while the total phenolics were determined using the Folin‐Ciocalteu method. The TEAC values of plant extracts ranged in a large scale from 1472.36 to 17.61 μmol of trolox equivalents per g dry weight (dw), and EC₅₀ values (concentration at which 50% radical scavenging occurred) varied from 0.174 to 42.475 mg dw of plant, while the total phenol content of plant extracts ranged between 117.20 and 1.27 mg of gallic acid equivalents per g dw. There was a positive linear correlation between the TEAC and total phenols of plant materials (r = 0.916). The extracts of Hypericum perforatum, Arbutus andrachne and Paliurus spina‐christii showed higher antioxidant activities (both TEAC and DPPH assays). However, there was no clear relationship between TEAC and EC₅₀ values (r = 0.477) of plant extracts.     

Investigating the in vitro bioaccessibility of polyphenols in fresh and sun‐dried figs (Ficus carica L.)

In this study, in order to evaluate the in vitro bioaccessibility of fresh and sun‐dried figs, total antioxidant capacity (TAC), total proanthocyanidin content (TPA) and the major phenolic compounds were determined at different phases of simulated gastrointestinal (GI) tract digestion for Sarilop and Bursa siyahi fig varieties. Four major phenolic compounds (chlorogenic acid, rutin, cyanidin‐3‐glucoside (C3G) and cyanidin‐3‐rutinoside (C3R)) were investigated for GI tract digestion. The results of in vitro GI tract digestion revealed that the dialysed fraction (IN) represented 9–26% and 1–22% of the initial TAC of the whole‐fresh yellow and purple figs, respectively. Moreover, in case of 2,2‐azinobis(3‐ethylbenzothiazoline)‐6‐sulphonic acid (ABTS), TPA and chlorogenic acid contents, drying caused an increase in the IN fraction of yellow figs (38, 140, 50%, respectively). The bioaccessibility of C3G and C3R were quite low for fresh figs (0–5% of the initial values), whereas for dried figs, anthocyanins were not detected at all in the IN fraction.     

Construction of quality control charts by using probability and fuzzy approaches and an application in a textile company

A method that uses statistical techniques to monitor and control product quality is called statistical process control (SPC), where control charts are test tools frequently used for monitoring the manufacturing process. In this study, statistical quality control and the fuzzy set theory are aimed to combine. As known, fuzzy sets and fuzzy logic are powerful mathematical tools for modeling uncertain systems in industry, nature and humanity; and facilitators for common-sense reasoning in decision making in the absence of complete and precise information. In this basis for a textile firm for monitoring the yarn quality, control charts proposed by Wang and Raz are constructed according to fuzzy theory by considering the quality in terms of grades of conformance as opposed to absolute conformance and nonconformance. And then with the same data for textile company, the control chart based on probability theory is constructed. The results of control charts based on two different approaches are compared. It’s seen that fuzzy theory performs better than probability theory in monitoring the product quality.     

Integral-type generalizations of operators obtained from certain multivariate polynomials

Abstract In this work, we mainly focus on the Kantorovich-type (integral-type) generalizations of the positive linear operators obtained from the Chan-Chyan-Srivastava multivariable polynomials. Using the notion of A-statistical convergence, we obtain various approximation theorems including a statistical Korovkin-type result and rates of A-statistical convergence with the help of the modulus of continuity, Lipschitz class functionals and Peetre’s K-functionals. We also introduce an sth order generalization of our approximating operators. Keywords. Chan-Chyan-Srivastava multivariable polynomials, Korovkin approximation theorem, Kantorovich-type operators, A-statistical convergence, modulus of continuity, Lipschitz class functional, Peetre’s K-functional Mathematics Subject Classification (2000): Primary: 41A25; 41A36, Secondary: 33C45     

Reconfigurable Dual Peptide Tethered Polymer System Offers a Synergistic Solution for Next Generation Dental Adhesives

Resin-based composite materials have been widely used in restorative dental materials due to their aesthetic, mechanical, and physical properties. However, they still encounter clinical shortcomings mainly due to recurrent decay that develops at the composite-tooth interface. The low-viscosity adhesive that bonds the composite to the tooth is intended to seal this interface, but the adhesive seal is inherently defective and readily damaged by acids, enzymes, and oral fluids. Bacteria infiltrate the resulting gaps at the composite-tooth interface and bacterial by-products demineralize the tooth and erode the adhesive. These activities lead to wider and deeper gaps that provide an ideal environment for bacteria to proliferate. This complex degradation process mediated by several biological and environmental factors damages the tooth, destroys the adhesive seal, and ultimately, leads to failure of the composite restoration. This paper describes a co-tethered dual peptide-polymer system to address composite-tooth interface vulnerability. The adhesive system incorporates an antimicrobial peptide to inhibit bacterial attack and a hydroxyapatite-binding peptide to promote remineralization of damaged tooth structure. A designer spacer sequence was incorporated into each peptide sequence to not only provide a conjugation site for methacrylate (MA) monomer but also to retain active peptide conformations and enhance the display of the peptides in the material. The resulting MA-antimicrobial peptides and MA-remineralization peptides were copolymerized into dental adhesives formulations. The results on the adhesive system composed of co-tethered peptides demonstrated both strong metabolic inhibition of S. mutans and localized calcium phosphate remineralization. Overall, the result offers a reconfigurable and tunable peptide-polymer hybrid system as next-generation adhesives to address composite-tooth interface vulnerability.     

Wear behaviour of organic asbestos based and bronze based powder metal brake linings

Bronze based brake linings, were produced by powder metallurgy technique and their wear behaviour was investigated and compared to that of asbestos ones. Bronze powders were compacted under 350, 500 and 600 MPa pressures and sintered at 810 °C in ammonia atmosphere for 75 min. For the same friction distance, it was determined that temperature increase in the bronze based brake linings was lower than that of asbestos based ones. However, higher wear rate was observed in the bronze based brake linings. Moreover, thermal conductivity was decreased with high porosity level with low densities. Although, friction coefficient remained the same during breaking, an increase in wear resistance was observed.     

Anthocyanin Absorption and Metabolism by Human Intestinal Caco-2 Cells—A Review

Anthocyanins from different plant sources have been shown to possess health beneficial effects against a number of chronic diseases. To obtain any influence in a specific tissue or organ, these bioactive compounds must be bioavailable, i.e., effectively absorbed from the gut into the circulation and transferred to the appropriate location within the body while still maintaining their bioactivity. One of the key factors affecting the bioavailability of anthocyanins is their transport through the gut epithelium. The Caco-2 cell line, a human intestinal epithelial cell model derived from a colon carcinoma, has been proven to be a good alternative to animal studies for predicting intestinal absorption of anthocyanins. Studies investigating anthocyanin absorption by Caco-2 cells report very low absorption of these compounds. However, the bioavailability of anthocyanins may be underestimated since the metabolites formed in the course of digestion could be responsible for the health benefits associated with anthocyanins. In this review, we critically discuss recent findings reported on the anthocyanin absorption and metabolism by human intestinal Caco-2 cells.     

The Production and Characterization of Ytterbium‐Stabilized Zirconia Films for SOFC Applications

(ZrO₂)_1–x(Yb₂O₃)_x binary systems were investigated in the doping range of 0.02 ≤ x ≤ 0.12. Ytterbium‐doped zirconia powders were synthesized using the Pechini method. X‐ray diffraction (XRD) measurements showed that fcc ZrO₂ was stabilized for 8–12 mol% Yb‐doping rate. The produced Yb‐stabilized Zr (YbSZ) films were characterized; their thickness and homogeneity properties depended on the nature of the YbSZ slurry. All coating parameters were optimized and determined with precoating treatments. The samples were characterized by differential thermal analysis/thermal gravimetry (DTA/TG), scanning electron microscopy (SEM) and ac impedance measurements.     

The solubility of apricot kernel oil in supercritical carbon dioxide

The solubility of kernel oil from apricots (Prunus armeniaca L.) in supercritical carbon dioxide at 313.15, 323.15 and 333.15 K and at 15, 30, 45, 52.5 and 60 MPa was determined. Appropriate models were fitted to the data and the crossover pressure of apricot kernel oil was found to be between 20 and 30 MPa. Crossover pressure is a pressure value at which the effect of temperature on the solubility changes. Solubility increased as the temperature increased above the crossover pressure but decreased when temperature increased below the crossover pressure. It increased with an increase in pressure over all of the temperature range. The solubility data were well represented by models based on density but the best was found to be the Adachi & Lu equation. An empirical model that did not require density data for CO₂ was proposed to relate solubility to temperature and pressure and it was found equally successful to the Adachi & Lu equation.