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Showing 4 results for Ranjbaran
Volume 19, Issue 126 (August 2022)
Abstract
Non-ionizing ultraviolet (UV) radiation is a kind of electromagnetic radiation that has been shown to be harmful to microorganisms such as bacteria, viruses, and fungus. The goal of this study is to evaluate the effective and hazardous features of this type of radiation in three regions (UVA, UVB, and UVC), using the approach of biological properties and applications in disinfection and sterilizing. In this research study, in order to be effective on microorganisms in the ultraviolet spectrum and its surroundings near the visible area, two test samples with commercial UVC and blue-LED lamps were used. In this study, the effect of ultraviolet C radiation on pathogenic microorganisms of Staphylococcus aureus and Pseudomonas aeruginosa in liquid environment and solid surface culture, the effect of ultraviolet C radiation on the total count (total count) of microorganisms on paper and mobile surfaces, and finally to The effect of UV LED on the total number of oral microbes attached to the toothbrush after brushing was investigated. In two tests performed with radiation in the ultraviolet region and near it in the visible region, the lethal effect on bacteria and microorganisms was concluded with more than 90% effectiveness and destruction of bacteria. Which indicates the effectiveness of such radiation in disinfecting, disinfecting and sterilizing equipment. Spectroscopic investigations of UV commercial lamps, as well as their efficacy on microbes, demonstrate the use of this sort of radiation, in addition to its biological hazards, which necessitate careful consideration of how it is utilized. In comparison to alternative sterilizing methods, the use of UV radiation in business and medicine is a cool, dry, easy, effective, and economical technique that produces no ionized radiation.Volume 22, Issue 6 (11-2022)
Abstract
Concrete as the most widely used building material suffers from the inherent weakness of having high density which results in heavy structures and consequently large inertia forces during seismic excitations. A common practice to reduce the density of normal-weight concrete is to partially replace sand and gravel with natural or synthetic light-weight particles. Among them, ultra-lightweight non-absorbent closed-cell expanded polystyrene (EPS) beads can be effectively used to produce a wide range of light-weight structural and non-structural concretes with appealing physical and mechanical properties. Many empirical researches have been already conducted to reveal the key properties of this class of material such as the tensile and compressive strengths, sound and heat isolations, and durability. New findings show that, in addition to the volume content of EPS beads, the bead size can significantly alter the strengths of concrete samples. To be more precise, the bigger the size of EPS beads, the lower the strength of concrete at a constant EPS volume content. Moreover, the existing studies have shown that this size effect fades at higher EPS contents. An overview of the literature reveals that the effect of EPS bead size and volume content have not been addressed under triaxial loading conditions. Therefore, in this study, twelve different concrete mixes that differ in terms of EPS bead diameter and volume content have been prepared and tested under uniaxial compression, splitting tension, and triaxial loading conditions. Three different EPS sizes (2.25 mm, 2.75 mm, and 3.25 mm), and four EPS volume contents of 0% (witness samples), 5%, 10% and 20% are considered. The constituent materials of tested concrete samples are water, cement, river sand, superplasticizer, and EPS beads. The ratio of sand and water to cement is 2 and 0.55, respectively. The BCB23 superplasticizer is used whose weight content is 0.6% of that of the cement. Samples are all cylinders with 5 cm in diameter and 10 cm in height and are treated in water for 28 days. The results show that increasing the volume of EPS beads would reduce the compressive and tensile strengths of concrete. Moreover, the results of uniaxial compressive tests show clear dependency to the size of EPS beads which is consistent with the results reported by other researchers. Splitting tensile test results are found different as the classical splitting mode of failure has changed to crushing mode beneath the narrow linear loading region for higher EPS contents. This phenomenon cancelled the validity of splitting test for the extraction of uniaxial tensile strength as the hypotheses of the elasticity solution for the Brazilian splitting test is not valid anymore. The failure points at the compression meridian of failure surface have been measured from the triaxial tests. The results confirm that confined strength of EPS concrete is also depends on the size of EPS beads, yet this dependency fades at higher confining stresses. This observation can be interpreted by the change of failure mechanism from local discrete cracking mode to distributed crushing mode which is also the reason behind the fade of size dependency in uniaxial compressive test at higher EPS volume contents.
Volume 23, Issue 6 (11-2023)
Abstract
Nowadays, the environmental pollutions caused by the increase in population and the development of industries threaten the health of the inhabitants of the planet. The most important pollutants of water and soil resources are heavy metals that lead and zinc are the most abundant elements among them. The presence of large amounts of heavy metals in the soil causes groundwater pollution and eventually the occurrence of many dangerous diseases including cancer, digestive disorders, kidney diseases, mental retardation and blood and brain diseases. The movement of water in the surface and underground streams is one of the main causes of the release of heavy metals in the soil which causes transfer of pollutions from the contaminated soil to the surroundings and entrance of these harmful metals into the human diet. The main purpose of this study was to evaluate the selective absorption of lead and zinc by Kaolinite clay in single and binary-component systems. For this purpose, the Kaolinite clay was firstly mixed with the lead and zinc in distilled water at ratio of 1:20 to prepare model contaminated suspensions. Three specimens were prepared for each sample according to the EPA (1983) and EPA (2010) methods. The effect of different pH (i.e. 2 to 12) and pollutants concentrations (i.e. at concentration of 20 Cmol kg-1) on the adsorption capacity of Kaolinite was measured using spectrophotometer. It was found that by decreasing in pH to 2 in both single and binary component pollutant systems (at concentration of 20 Cmol kg-1), the adsorption percent decreased significantly. However, the adsorption of lead in pore fluid was higher than zinc in alkaline and acidic conditions for both binary and single-component systems. The adsorption percent of Pb2+ was not changed in both systems, however, adsorption of Zn2+ was significantly reduced in the binary system-component compared to the single system-component. In addition, the adsorption percent of Zn2+ in alkaline (pH=12) and acidic (pH=2) conditions decreased by about 50 and 20% in the binary system-component compared to the single system-component, respectively. Furthermore, the findings indicated that Langmuir isotherm had the highest consistency in the single and binary-component systems for lead and zinc contaminations at the studied concentration. The results of absorption kinetics in both systems illustrated that the lead absorption rate was decreased 0.15% in binary-component system compared to the single-component system at concentration of 20 Cmol kg-1. In contrary, the zinc absorption rate in the combination system was reduced 87.5% at this concentration. On the other hand, the adsorption kinetics of lead metal at the test concentration for kaolinite clay in both systems had the same constant as the pseudo-first and second order equations because in both systems the amount of lead adsorption did not change. Instead, the rate of adsorption on zinc had a significant change in the binary system compared to the single state. the resulting values were more consistent with the pseudo- second order equation. In general, the ion adsorption of Pb2+under all environmental conditions in the pore fluid was more than Zn2+ in both systems due to the lower value of the first hydrolysis constant (pk1) of lead compared to zinc (i.e. Pb(7.8) > Zn(9.0)). By comparing the values of k1 and k2 in the concentration of pollution in the experiment, it was found that k1 of lead and zinc metals for a concentration of 20 Cmol kg-1 was higher than k2 and this represented the higher reaction rate to the Kaolinite clay for lead compared to zinc.
Volume 27, Issue 2 (2-2025)
Abstract
There is a growing trend towards healthy meat products containing lower fat content. The use of fat replacers can solve the quality problems of low-fat products. This study aimed to produce low-fat frankfurter sausage using a new fat replacer. Thus, in the first stage, Reconstituted Agar Hydrogel (RAH) was produced by adding water to agar cryogel after homogenization. In the second stage, RAH was used as a fat substitute in frankfurter sausage at 0, 25, 50, 75, and 100%. Then, the characteristics of the resulting low-fat sausage, including chemical composition, water holding capacity, cooking loss, texture characteristics, porosity, color, percentage of fat after frying, oil absorption, pH over time, and sensory evaluation were examined. Results showed that RAH could form two kinds of gel by temperature changes: a low-set gel at 55˚C and a high-set gel at 90˚C. Substitution of oil in the sausages caused an increase in moisture content, porosity, oil absorption, and cooking loss. On the other hand, this replacement reduced fat content, cutting force, water-holding capacity, fat percentage after frying, and texture properties such as hardness, cohesiveness, springiness, gumminess, and chewiness. The results of pH measurements over time showed that sulfated antimicrobial groups in the agar structure delayed the spoilage of sausages containing RAH compared to the control sample. Sensory evaluation showed that RAH-containing sausages were not significantly different from the control sample in terms of color, juiciness, and texture. However, flavor and overall acceptance increased significantly under the influence of this substitution (P< 0.05). Therefore, the consumers selected a sample with 25% replacement as the optimal sample. As a result, RAH can be successfully used as a fat replacer in low-fat products with desirable quality characteristics.
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