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Packing density of aggregate influences greatly the properties of concrete. Maximization of packing density increases the flowing ability and segregation resistance of the fresh concrete and the compressive strength of the hardened concrete. The determination of maximum density is difficult experimentally; therefore several models have been developed for that purpose. However, these models do not take the size of the formwork into account. In this study, 20 different formwork shapes were examined with defined aggregate fractions. Results show that increasing the formwork size increases the packing density of aggregate, and the growth depends on the formwork size and compaction method.

Open access

In this article, the investigation of a press machine with 30 tons of pressing weight is presented. The beam of this machine is an I-beam, which has an open cross-section. It is known that this version of cross-section is sensitive to torsional stress. The stress from warping torsion is normal stress, so the opened cross-section is more sensitive to this type of stress. The bimoment that causes normal stress can also be very high, so dealing with this stress is very important.

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Polysaccharides from litchi (Litchi chinensis) seeds were isolated and purified using ion exchange column chromatography. Molecular weight distribution of polysaccharides and monosaccharides were detected. Preliminary structural characterisation of polysaccharides was conducted using infrared, nuclear magnetic, and other spectroscopy techniques in combination with methylation analysis. In vitro cell culture experiments were designed to detect the effects of polysaccharides on cell growth and cellular glucose consumption. We extracted and analysed three polysaccharides from litchi seed. Monosaccharide composition and infrared spectroscopy detection showed that the skeleton structure of polysaccharides consisted of glucose and mannose. Polysaccharides 1 and 2 are similar and have relatively high glucose content (around 70%); polysaccharide 3 has 39.17% glucose only but is rich in arabinose (about 21.03%). In a certain range of use (50~1000 μg ml–1), polysaccharides 1 and 2 have no significant impacts on cell growth, while polysaccharide 3 can promote proliferation to some extent. All three polysaccharides can promote in vitro cellular glucose consumption, especially polysaccharide 3, which shows the strongest promotion, a significant dose effect, and synergistic effect with insulin. The above results highlight important roles of litchi seed polysaccharides in promoting cell growth and validate litchi seed polysaccharides as potential drugs for hypoglycaemia.

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Pollack Periodica
Authors: Ivana Marko, Réka Csicsaiová, Jaroslav Hrudka, Ivona Škultétyová, Štefan Stanko, and Paula Brandeburová

The aims of the research are to focus on the analysis of qualitative parameters of surface runoff from the urbanized area (parking, roadways); subsequently, to compare the measured concentration with the recommendations of Danish and Slovak standards. Rainwater sampling carried out at several sites in Serbia and Slovakia. In the analysis were monitoring, the qualitative parameters as pH value, water conductivity, chemical oxygen demand, and heavy metals. The results show the presence of copper, zinc, lead, aluminum, cadmium, chromium and nickel. The concentration of these parameters was several times higher than the allowed limit values. Based on these results, it is necessary to design measures to ensure surface runoff before infiltration.

Open access
Acta Alimentaria
Authors: A. Dobrinčić, L. Tuđen, M. Repajić, I. Elez Garofulić, Z. Zorić, V. Dragović-Uzelac, and B. Levaj

The aim of this research was to obtain a high value powder of olive leaf extract (OLE) rich in polyphenols by spray drying. Since carrier, polyphenols/carrier ratio, and inlet temperature could have an impact on process yield and polyphenol retention, to define the most promising drying conditions for OLE experiment with gallic acid model solutions (GAS) was conducted. Influence of carrier type (maltodextrin, inulin, gum arabic, and their two-component blends), polyphenols/carrier ratio, and temperature on process yield of spray dried GAS was examined, and for each carrier the most promising temperature and ratio were selected. Optimal temperature for all GAS samples was 150 °C, and optimal gallic acid/carrier ratio for samples with inulin or gum arabic was 3:1, while for all other combinations it was 5:1. In OLE powder produced under these conditions, polyphenol content and physical properties (rehydration, bulk density) were determined. Mixture of maltodextrin and gum arabic resulted in the highest OLE product yield (54.48%) and the highest polyphenol retention (56.50%) obtaining good physical properties (bulk density=0.31 g ml–1, rehydration time=98 s), while use of inulin resulted in the lowest yield (32.71%), polyphenol retention (28.24%), bulk density (0.25 g ml–1), and the highest rehydration time (140 s).

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Acta Alimentaria
Authors: J. Krulj, N. Ćurčıć, A. Bočarov Stančıć, J. Kojıć, L. Pezo, L. Peıć Tukuljac, and M. Bodroža Solarov

During previous years, regarding the shifts in climate conditions in temperate region, such as occurrence of high temperatures and prolonged drought, increased occurrence frequencies of Aspergillus flavus and aflatoxins in cereal grains were recorded. A reliable and accurate identification of the fungi is of great importance for evaluating the microbiological risks of contamination. The essential point of the present investigation was molecular characterisation and identification of A. flavus isolates originating from common wheat and spelt grains collected after harvest during the period of three years (2015–2017) in Northern Serbia. A holistic approach that included PCR amplification of two DNA genomic regions and PCR-RFLP assay followed by fragment length analysis, provided complete and comprehensive characterisation of A. flavus isolated from wheat grains. The presented results indicate that there was no difference among the tested Aspergillus isolates on the molecular–genetic level. All 38 strains were identified as A. flavus by sequencing of combined ITS region and β-tubulin gene fragments (acc. no.: MH582473 to MH582510). PCR-RFLP method in combination with a Lab-on-a-chip (LoaC) electrophoresis can be successfully used to rapidly identify A. flavus isolates.

Open access

Recent developments of nanotechnology find its way into various fields of food production in our days. Nanotechnology could offer benefits in development of food products with enhanced functionality for health promotion, or modified texture convenient for elderly, and in quality and safety issues in the food supply chain. Nanoencapsulated bioactive components such as vitamins, antibacterial agents contribute to production of enriched food stuffs with the required appearance, flavour, taste, and texture. Nanomaterials can protect the sensitive compounds from environmental attack, release them in a programmed way, and provide favourable improvement in the bioavailability of nutraceuticals. The innovative approach in food packaging, including the detection, indication, and control of food products, serves the quality and safety improvements.

Open access
Acta Alimentaria
Authors: M. Aloudat, A. Papp, N. Magyar, L. Simon Sarkadi, and A. Lugasi

The purpose of this study was to compare the energy content and macronutrients of forty main popular traditional and modern meals in both Jordan and Hungary with the national and international recommendations. The calculation of energy content and macronutrients were done on traditional and modern recipes by two different softwares (ESHA and NutriComp). Neither Jordanian nor Hungarian foods met the recommended energy content (35% of daily energy intake, 8400 kJ for energy intake). The recipes of both nations are characterised by higher protein, fat, and salt contents than WHO recommendation, a lower fibre content, and sugar content within the recommended limits. The fat energy ratio and saturated fatty acid content of Hungarian recipes are significantly higher than WHO recommendation. In general, Jordanian meals were more likely to meet the inclusion criteria. In conclusion, neither Jordanian nor Hungarian traditional and popular meals meet the international nutritional recommendations for a healthy diet, however, the composition of the real dishes may differ significantly from the recipes depending on the available ingredients and chosen kitchen technology.

Open access

Sudan is suffering from harsh summers, but most of the modern buildings in urban areas are not compatible with the recent and future climate phenomena. Application of cooling devices is relatively expensive and therefore beyond reach. The main objective of this research is to give an overview on the overheating problem and the thermal comfort in buildings. A dynamic energy simulation has been performed for a selected case study using Design Builder Code. The results show that the share of discomfort hours for a typical modern building is 78% and 33% above 26 °C and 32 °C per year, respectively, but after using a combination of different ventilation, shading and building materials options the discomfort hours can be reduced to 77% and 26%, respectively.

Open access

The present research work is a part of a project was a semi-active structural control technique using magneto-rheological damper has to be performed. Magneto-rheological dampers are an innovative class of semi-active devices that mesh well with the demands and constraints of seismic applications; this includes having very low power requirements and adaptability. A small stroke magneto-rheological damper was mathematically simulated and experimentally tested. The damper was subjected to periodic excitations of different amplitudes and frequencies at varying voltage. The damper was mathematically modeled using parametric Modified Bouc-Wen model of magneto-rheological damper in MATLAB/SIMULINK and the parameters of the model were set as per the prototype available. The variation of mechanical properties of magneto-rheological damper like damping coefficient and damping force with a change in amplitude, frequency and voltage were experimentally verified on INSTRON 8800 testing machine. It was observed that damping force produced by the damper depended on the frequency as well, in addition to the input voltage and amplitude of the excitation. While the damping coefficient (c) is independent of the frequency of excitation it varies with the amplitude of excitation and input voltage. The variation of the damping coefficient with amplitude and input voltage is linear and quadratic respectively. More ever the mathematical model simulated in MATLAB was in agreement with the experimental results obtained.

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