Showing papers by "Sylwester J. Rzoska published in 2018"

New Achievements in High-Pressure Processing to Preserve Human Milk Bioactivity.

Abstract: High-pressure processing (HPP) is a non-thermal technology that is being increasingly applied in food industries worldwide. It was proposed that this method could be used as an alternative to holder pasteurization (HoP; 62.5°C, 30 min) in milk banks but its impact on the immunologic, enzymatic and hormonal components of human milk has not yet been evaluated in detail. The aim of our study was to compare the effects of HPP in variants: (1) 600 MPa, 10 min (2) 100 MPa, 10 min, interval 10 min, 600 MPa, 10 min (3) 200 MPa, 10 min, interval 10 min, 400 MPa, 10 min (4) 200 MPa, 10 min, interval 10 min, 600 MPa, 10 min in temperature range 19-21°C and HoP on the leptin, adiponectin, insulin, hepatocyte growth factor (HGF), lactoferrin and IgG contents in human milk. HoP was done at the Regional Human Milk Bank in Warsaw at the Holy Family Hospital on S90 Eco pasteurizer (Sterifeed, Medicare Colgate Ltd). Apparatus U4000/65 (Unipress Equipment, Poland) was used for pascalization. Milk samples were obtained from women during 2-6 weeks of lactation. Post-treatment culture showed no endogenous bacterial contamination in any tested option. Concentrations of selected components were determined using ELISA tests. The level of all analyzed components were significantly decreased by HoP: leptin 77.86%, adiponectin 32.79%, insulin 32.40%, HGF 88.72%, lactoferrin 60.31@.%, IgG 49.04%. All HPP variants caused an increase in leptin concentration, respectively (1) 81.79% (2) 90.01% (3) 86.12% (4) 47.96%. Retention of insulin after HPP was (1) 88.20% (2) 81.98% (3) 94.76% (4) 90.31% HGF (1) 36.15% (2) 38.81% 97.15% (3) 97.15% (4) 43.02%, lactoferrin (1) 55.78% (2) 57.63% (3) 78.77% (4) 64.75%. Moreover, HPP variant as 200 + 400 MPa preserved IgG (82.24%) better than HoP and resulted not statistically significant change of adiponectin level (38.55%) compare to raw milk. Our results showed that HPP leads to preservation of adipokines, growth factor, and lactoferrin, IgG much better or comparable with HoP.

Structural Compromise between High Hardness and Crack Resistance in Aluminoborate Glasses.

Abstract: Alkali aluminoborate glasses have recently been shown to exhibit a high threshold for indentation cracking compared to other bulk oxide glasses. However, to enable the use of these materials in engineering applications, there is a need to improve their hardness by tuning the chemical composition. In this study, we substitute alkaline earth for alkali network-modifying species at fixed aluminoborate base glass composition and correlate it with changes in the structure, mechanical properties, and densification behavior. We find that the increase in field strength (i.e., the charge-to-size ratio) achieved by substituting alkaline earth oxide from BaO to MgO manifests itself in a monotonic increase in several properties, such as atomic packing density, glass-transition temperature, densification ability, indentation hardness, and crack resistance. Although the use of alkaline earth oxides as modifier enables higher hardness values (increasing from 2.0 GPa for Cs to 5.8 GPa for Mg), their crack resistance is g...

Combining high hardness and crack resistance in mixed network glasses through high-temperature densification

Abstract: Obtaining a combination of high toughness and strength is crucial for most structural materials, but unfortunately these tend to be mutually exclusive. The search for strong and tough damage-resistant materials has thus typically been based on achieving an acceptable compromise between hardness and crack resistance. Focusing here on brittle oxide glasses, we propose a new strategy for overcoming this conflict by identifying new structural motifs for designing hard and crack-resistant glasses. Specifically, we report that surprisingly there is no decrease in the densification contribution to deformation of a mixed network ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}\ensuremath{-}{\mathrm{B}}_{2}{\mathrm{O}}_{3}\ensuremath{-}{\mathrm{P}}_{2}{\mathrm{O}}_{5}\ensuremath{-}\mathrm{Si}{\mathrm{O}}_{2}$ bulk glass following predensification of the glass at elevated temperature. Hitherto unique to this glass composition, the treatment reduces the residual stress during subsequent sharp contact loading, which in turn leads to a simultaneous increase in hardness and crack resistance. Based on structural characterization, we show that the more densified medium-range order of the hot compressed glass results in formation of certain structural states (e.g., nonring trigonal boron), which could not be reached through any composition or thermal path. This work thus shows that accessing such ``forbidden'' structural states through the identified densification at elevated temperatures offers a way forward to overcome the conflict of strength versus toughness in structural materials.

Pressure-induced structural changes in titanophosphate glasses studied by neutron and X-ray total scattering analyses

Abstract: In this paper, the densification mechanism of two titanophosphate glasses (binary 73TiO2-27P2O5 and ternary 68TiO2-5Al2O3-27P2O5) is investigated. The glasses are densified by isostatic N2-mediated pressure treatment at elevated temperature and the pressure-induced structural changes are studied by neutron and X-ray total scattering analyses. The medium range structure change is revealed from the change in the first sharp diffraction peak (FSDP), where the density increase by pressurization is correlated with the decreased medium range repeating spacing calculated from the position of FSDP. The hot compression treatment also increases the medium range order, as shown by the increased correlation length calculated from the width of FSDP. The short range structure changes are examined by separating P O and Ti O pair distribution functions (PDF) using differential neutron and X-ray PDFs. Pressurization is also found to increase the coordination number of Ti, as previously observed for other network formers in densified glasses.

Nonlinear Dielectric Effect in Critical Liquids

Abstract: The nonlinear dielectric effect (NDE) describes changes of dielectric constant under the strong electric field, with the metric defined \( \left( {\varepsilon \left( E \right) - \varepsilon \left( {E \to 0} \right)} \right)/E^{2} \). This contribution discusses (i) miscibility, (ii) the isotropic phase of nematic liquid crystals, and (iii) the supercooled nitrobenzene. For comparison, the precritical evolution of \( \varepsilon = \varepsilon \left( {E \to 0} \right) \) is also presented. The discussion is extended for dynamic issues related to the “linear” and “nonlinear” relaxation times. Finally, basic problems of the dual-field NDE experimental technique are briefly presented.

Deformation and cracking behavior of La2O3-doped oxide glasses with high Poisson's ratio

Abstract: Oxide glasses pose high theoretical strength originating from their strong ionocovalent bonding, but they experience amplification of tensile stresses around defects under tensile loading and lack efficient stress dissipation mechanisms. Consequently, glasses exhibit low practical strength and fracture toughness, limiting the scope of their applications. Different strengthening and reinforcement approaches have thus been tested, but relatively little success has been achieved with respect to making the glasses intrinsically more ductile through composition optimization. Following earlier literature reports, a possible route to achieve this would be to prepare glasses with high Poisson's ratio above ~0.32. Yet, no oxide glasses with such high Poisson's ratio have been reported and the mechanical properties of oxide glasses with Poisson's ratio ≥ 0.30 are poorly understood. In this paper, we synthesize 25%La2O3–15%Al2O3–60%B2O3, 25%La2O3–15%Al2O3–60%SiO2, and 25%La2O3–15%Al2O3–60%GeO2 glasses (fractions in mol%), all exhibiting high Poisson's ratio values (~0.30). We evaluate the mechanical properties, including elastic moduli, Poisson's ratio, hardness, and resistance to indentation cracking of the as-prepared as well as densified glasses. In addition, the indentation deformation mechanism of the glasses along with the accompanying underlying structural changes is investigated. This study therefore presents insight into the composition-property relations of high Poisson's ratio glasses, which may be used in future design of ductile oxide glasses with potential applications in electronic devices, optical fibers, and load-bearing components of buildings or other constructions.