Modeling and Numerical Simulation of Clays Cracking During Drying

During drying or desiccation of clay-type materials, some stresses appear. Usually they are compressional inside of the material and tensional close to the surface. If the tensional stresses exceed the material strength, the clay cracks. This article is devoted to the modeling and numerical simulation of this phenomenon. The proposed model consists of two parts. The mass transfer is described by a simple diffusion equation together with convective boundary conditions. In the mechanical part it is assumed that the clay is composed of small particles linked together by cohesive forces. These forces are described with the use of mesh models. Two models are proposed: elastic (mesh consists of springs) and viscoelastic one (mesh consists of Maxwell elements). Four types of clays were tested experimentally to obtain the model parameters. The tested materials were selected with respect to different mineralogical compositions that determine the water-bonding ability. Simulations of the convective drying of bricks made of these clays were performed. It was shown that the degree of cracking depends on the quartz content of the clay. The obtained results were compared with experimental ones and good agreement between simulations and experiment was obtained. Additionally, the inner forces caused by drying are analyzed and discussed in this work.     

The influence of protein–flavonoid interactions on protein digestibility in vitro and the antioxidant quality of breads enriched with onion skin

Different types of breads enriched with onion skin were studied. The objectives were twofold: to show and examine protein–phenolic interactions and to discuss results concerning phenolic content, antioxidant activity and protein digestibility in the light of in vitro bioaccessibility. Phenolic contents and antiradical abilities were linked with the level of onion skin supplement however, the amounts determined were significantly lower than expected. Fortification influenced protein digestibility (a reduction from 78.4% for control breads to 55% for breads with a 4% supplement). Electrophoretic and chromatographic studies showed the presence of indigestible protein–flavonoid complexes – with molecular weights about 25 kDa and 14.5 kDa; however, the reduction of free amino group levels and the increase in chromatogram areas suggest that flavonoids also bind to other bread proteins. The interaction of phenolics with proteins affects antioxidant efficacy and protein digestibility; thus, they have multiple effects on food quality and pro-health properties.     

The impact of glycated pea proteins on bacterial adhesion

Adhesion is one of the bacterial strategies indispensable for colonization of the small intestine. Food components reaching the small intestine, are not only digested and absorbed there, but may also influence the microorganisms colonizing the mentioned region. In this way, nutrients, particularly the ones the enzymatic degradation of which is hindered, acquire the ability to modify the adhesive potential of the autochthonic microorganisms. The glycated food proteins are noteworthy here for they often undergo relevant structural and functional alterations. Such proteins tend to display a lowered susceptibility to enzymatic degradation and thus may act as modulators of both metabolic activity and adhesive potential of bacteria adhered to the intestinal cells. For that reason, this study aimed at establishing the impact of the glycated pea proteins on adhesion of the bacteria from the genera: Lactobacillus, Enterococcus, and Escherichia, which are typical for the human small intestine.     

Study on the new bone cement based on calcium sulfate and Mg,CO3 doped hydroxyapatite

In order to improve some features of bone substitutes the new self-setting composite-type implant material based on Mg²⁺/CO₃^2? co-substituted hydroxyapatite (Mg-CHA) and calcium sulfate hemihydrate (CSH) was developed. Synthetic hydroxyapatites doped with small amounts of additives found in natural bone (e.g. Mg²⁺ and CO₃^2?) are regarded as promising components of calcium phosphate bone cements (CPCs). The CPCs, now available on the market, due to low resorption rate are too stable to permit material degradation and are slowly replaced by the newly formed bone. To improve cement resorption we used calcium sulfate which is a well-known biodegradable and biocompatible bone defect filler. Combining properties of Mg-CHA and CSH allowed developing a new, promising, easy shapeable implant material with high potential for bone regeneration.     

New insights into the mechanism of H2 generation through NaBH4 hydrolysis on Co-based nanocatalysts studied by differential reaction calorimetry

To our knowledge, the present study is the first investigation by liquid-phase calorimetry of the mechanism of hydrogen generation by hydrolysis of sodium borohydride catalyzed by Co₂B nanoparticles generated in situ. The differential reaction calorimeter was coupled with a volumetric hydrogen measurement, allowing a simultaneous thermodynamic and kinetic study of the reaction. At the end of the reaction, the catalyst was characterized ex situ by TEM, XRD, magnetism, N₂ adsorption, TGA–DTA, and the liquid hydrolysis products were analyzed by Wet-STEM and ¹¹B-NMR. The in situ preparation method made it possible to form nanoparticles (<12 nm) of Co₂B which are the active phase for the hydrolysis reaction. In semi-batch conditions, the Co₂B catalyst formed in situ is subsequently reduced by each borohydride addition and oxidized at the end of the hydrolysis reaction by OH⁻ in the presence of metaborate. A coating of the nanoparticles has been observed by calorimetry and physico-chemical characterization, corresponding to the formation of a 2–3 nm layer of cobalt oxide or hydroxide species.     

eVEREst—SUPPORTING ESTIMATION OF REAL ESTATE VALUE

Enhanced Value Estimation of Real Estates (eVEREst) is the project carried out at the Department of Management Information Systems at the Poznań University of Economics. The paper presents the idea and the architecture of a system that supports the real estate registry with additional information that enables more precise estimation of real estate value.     

Min-max optimal instrumental variable estimation method for multivariate linear time-series systems

A min-max optimal instrumental variable (IV) estimation method for multivariate linear time-series systems is presented. A Monte Carlo study is performed to assess the merits of the min-max optimal IV method using two different parametrizations of the multivariate time series system. The analysis indicates that the proposed estimation method yields accurate estimation results at modest computational cost.     

Mid-infrared spectroscopy as a tool for rapid determination of internal quality parameters in tomato

The objective of this study was to investigate the possibility of predicting the quality parameters of tomato by mid-infrared spectroscopy. For 2 years, tomato samples, representing a large variability in the chemical composition, were scanned using the attenuated total reflectance accessory of a Fourier transform spectrometer in the wavenumber region between 4000 and 400 cm⁻¹_. Calibration models were developed using partial least squares (PLS) regression method and were tested with internal validation sample set in the first year. Different spectral preprocessing techniques were investigated and different spectral regions were selected to optimise the calibration models. In addition, the models obtained in 2007 were used to predict the soluble solids, dry matter and total acidity in tomato harvested in 2008.