Numerical analysis of the width of fracture process zone in concrete beams

There are two ways of modelling cracking in concrete structures using a finite element method (FEM). In the first concept crack is considered as densely distributed throughout the finite area of element. The alternative approach assumes an isolated sharp interelement crack. The first concept of microcracked band is often used during numerical computations of concrete structures and a crack band model can be applied in design practice where relatively simple methods of calculations are preferred. In this model the width of microcracked zone, which is called the width of fracture process zone, is the additional parameter of tensile concrete.In this paper, the influence of the fracture process zone width on numerical calculations in case of bent concrete beams is analyzed. The results of numerical simulations are presented and compared with those obtained during the experiment. The crack band model proposed by Hillerborg [Cement and Concrete Research, 6 (1976) 773–782] has been used in numerical calculations and six different widths of fracture process zone have been modelled in the analyzed specimen. When comparing the obtained FEM-results their significant differences according to the width of fracture process zone have been observed. On the basis of the performed analysis it may be concluded that the width of fracture process zone taken in numerical simulations does have an influence on FEM-results.     

Properties of pore structure of thin-layer external plasters under ageing in simulated environment

The basic and commonly used four types of thin-layer facade plasters on cement and silicate binders were subjected to 400 cycles of accelerated ageing in the simulate chamber. The main attention was focused on the character of pore structure evolution during of ageing process. To reach this objective, examinations of the microstructure by the mercury intrusion method and total porosity by the densitometry method were carried out in time per 100 cycles. During the study, the main emphasis was put on the open porosity and changes of dimensional groups of pores. On the ground of the hysteresis of the mercury pressure by mercury intrusion porosimetry testing, the presence of pores with capillary entrance was suggested. In view of this, the cylindrical and spherical model of porous structure has been defined. The contribution of capillary and spherical pores vary in time together with properties such as: average pore radius, length of cylindrical pores and their tortuosity. The changes of these values confirm that atmospherical ageing influences plasters’ binders in two zones. It appears on the one hand by the decrease of total porosity, length and diameter of capillaries but on the other hand by the increase of open porosity and the decrease of pores’ tortuosity. It indicates the tightening character of the inside pore structure of the examined plasters and at the same time it gives diverse effect in its external zone.     

Hydroprocesssing of light gas oil — rape oil mixtures

Two series of experiments of hydroprocessing of light gas oil - rape oil mixtures were carried out. The reactor feed was composed of raw material: first series — 10 wt.% rape oil and 90 wt.% of diesel oil; second series — 20 wt.% rape oil and 80 wt.% of diesel oil.     

Nutrient and polyphenolic composition of industrial strawberry press cake

The objective of the present work was to determine the nutrient and polyphenolic composition of dried strawberry press cake (SPC), as well as that of its seedless fraction, termed exhausted strawberry flesh (ESF). The study materials were obtained over three consecutive years from an industrial facility manufacturing concentrated fruit juices. On average, SPC consists of 40 % seeds, 3.5 % sand, and about 55 % ESF. In the dry matter of SPC and ESF, the mean content of fat is 9.8 and 3.5 %, protein 17.3 and 20.4 %, and total polyphenols 3,449 and 5,410 mg/100 g, respectively. Both materials are rich in total dietary fiber, whose content amounts to 60 %. The predominant polyphenols in SPC and ESF are flavanols and ellagitannins, which collectively constitute over 95 % of the determined total polyphenol content. In ESF composition, of note is the high content of the strawberry ellagitannin, agrimoniin, which is approximately 1,000 mg/100 g DW (dry weight). SPC has the disadvantage of being highly contaminated with sand (3.4 %), which accumulates in ESF (5.6 %). However, as compared to SPC, ESF contains approximately 20 % more proteins and almost three times less fat. Based on our results, it appears that SPC may be considered a potential raw material for seed recovery. Moreover, dried strawberry press cake, and especially its seedless fraction (ESF), despite substantial contamination with sand, may be used as rich and widely available raw material for the extraction of proanthocyanidins and/or ellagitannins, and especially dimeric agrimoniin.     

Changes in Molecular Characteristics of Cereal Carbohydrates after Processing and Digestion

Different extraction, purification and digestion methods were used to investigate the molecular properties of carbohydrates in arabinoxylan and β-glucan concentrates, dietary fiber (DF) rich breads and ileum content of bread fed pigs. The breads studied were: a low DF wheat bread (WF), whole meal rye bread (GR), rye bread with kernels (RK), wheat bread supplemented with wheat arabinoxylan concentrate (AX) and wheat bread supplemented with oat β-glucan concentrate (BG). The weight average molecular weight (M_w) of extractable carbohydrates in β-glucan concentrate decreased eight-fold after inclusion in the BG bread when exposed to in vitro digestion, while the M_w of purified extractable carbohydrates in AX bread was reduced two-fold, and remained almost unaffected until reaching the terminal ileum of pigs. Similarly, the M_w of purified extractable carbohydrates in GR and RK bread was not significantly changed in the ileum. The AX bread resulted in the highest concentration of dissolved arabinoxylan in the ileum among all the breads that caused a substantial increased in ileal AX viscosity. Nevertheless, for none of the breads, the M_w of extractable carbohydrates was related neither to the bread extract nor ileal viscosity.     

Influence of addition of green tea and green coffee extracts on the properties of fine yeast pastry fried products

This study investigated the influence of antioxidants of green tea aqueous extract (GTE) and green coffee aqueous extract (GCE) in concentrations of 0.25, 0.5 and 1 g·100 g^? 1 on the nutritional properties of fine yeast pastry fried products such as donuts. Yeast donuts were made according to the traditional processing technology. In fried donuts physical properties (water activity, pH, hardness and color with the use of instrumental methods) as well as sensory properties were established. Moreover, quality of fat extracted from donuts (composition of fatty acids and peroxide value), content of acrylamide, composition of polyphenols and antioxidant activity were analyzed. Obtained extracts of GTE and GCE contained 26 and 41% of polyphenols, respectively, and the degree of polyphenol degradation during production of donuts was less when the dilution in dough was greater. Both tests indicated that the highest antioxidant activity had donuts with the highest analyzed addition of extract, however depending on the applied test or GTE or GCE had better antioxidant properties. Fatty acid composition was the most beneficial when the addition of GTE and GCE was on a level of 0.25 and 0.5 g·100 g^? 1, respectively. In fried donuts relatively low amounts of acrylamide were obtained, amounting to 18–46 μg·kg^? 1. Only the lowest addition of GTE and the highest addition of GCE caused an increase of acrylamide content in donuts, while all other levels of added extracts caused a decrease in the content of formed acrylamide.     

Novel adhesive system based on 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and hyperbranched polyglycerols

Two hyperbranched polyglycerols bearing 1,1,1-tris(hydroxymethyl)propane or Bisphenol A core and terminal hydroxyl functionality were examined as components of novel wood adhesive systems. Two 1,3-dimethylol-4,5-dihydroxyethyleneurea resins (DMDHEU) were used as crosslinkers. Shear strength tests revealed that the adhesives containing up to 75 wt% of renewable glycerol-derived polyglycerols retained performance comparable to that of neat DMDHEU. The results give way to extending the area of application of hyperbranched polyglycerols in the field of wood adhesives.     

Antimicrobial Activity of a Pullulan–Caraway Essential Oil Coating on Reduction of Food Microorganisms and Quality in Fresh Baby Carrot

This research evaluated the antimicrobial efficacy of pullulan films containing caraway essential oil (CEO). The films were prepared from a 10% of pullulan, containing from 0.12% to 10.0% of CEO. The composition of the CEO was analyzed with the use of gas chromatography. The antimicrobial activity of the CEO was evaluated with the method of serial microdilutions, and the films containing CEO—with the agar diffusion method against selected Gram‐negative, Gram‐positive bacteria, and fungi. The structure of the film surface and its cross‐section were analyzed using a scanning electron microscope (SEM). Analyses were also carried out to determine the efficacy of a pullulan coating with 10% CEO on baby carrots experimentally inoculated with Salmonella enteritidis, Staphylococcus aureus, Saccharomyces cerevisiae, or Aspergillus niger and stored at a room temperature for 7 d. At a concentration of 0.12%, CEO inhibited the growth of all the tested microorganisms. Pullulan films containing 8% to 10% of CEO were active against all tested microorganisms. Populations of S. aureus on carrot samples were reduced by approximately 3 log CFU/g, while those of A. niger and S. cerevisiae by, respectively, 5 and 4 log CFU/g, after 7 d of storage. S. enteritidis was the most resistant among the tested species, since it was not significantly reduced after 7 d of storage. At the end of storage, samples treated with pullulan–caraway oil coating maintained better visual acceptability than control samples. Results of this study suggest the feasibility of applying a pullulan film with incorporated CEO to extend the microbiological stability of minimally processed foods.