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Number of results: 5
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Abstract

Stability of silver nanoparticles strongly influences the potential of their application. The literature shows wide possibilities of nanoparticles preparation, which has significantly impact on their properties. Therefore, the improvement of AgNPs preparation plays a key role in the case of their practical use. The pH values of the environment are one of the important factors, which directly influences stability of AgNPs. We present a comparing study of the silver nanoparticles prepared by „bottom-up“ methods over by chemical synthesis and biosynthesis using AgNO3 (0.29 mM) solution. For the biosynthesis of the silver nanoparticles, the green freshwater algae Parachlorella kessleri and Citrus limon extracts were used as reducing and stabilizing agents. Chemically synthesized AgNPs were performed using sodium citrate (0.5%) as a capping agent and 0.01% gelatine as a reducing agent. The formation and long term stability of those silver nanoparticles synthesized either biologically and chemically were clearly observed by solution colour changes and confirmed by UV-vis spectroscopy. The pH values of formed nanoparticle solutions were 3 and 5.8 for biosynthesized AgNPs using extract of Citrus limon and Parachlorella kessleri, respectively and 7.2 for chemically prepared AgNPs solution using citrate. The SEM as a surface imaging method was used for the characterization of nanoparticle shapes, size distribution and also for resolving different particle sizes. These micrographs confirmed the presence of dispersed and aggregated AgNPs with various shapes and sizes.
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Abstract

This paper presents initial findings from research into the possibility of using gypsum binders in quartz moulding sand that could be used in the production of casting moulds and cores. For the purposes of the research two commercial types of gypsum were used as binders: building gypsum and gypsum putty. Dry components of moulding sand i.e. medium quartz sand and gypsum were mixed in proportion of 89/11 parts by weight. In order to achieve bonding properties for the binders, 5 parts by weight of water was added to the mixture of dry components. After 24 hours of adding water and mixing all the components, the moulding sand, naturally hardened, was subjected to high temperature. The moulding sand thus produced, i.e. with cheap and environmentally-friendly gypsum binders, was eventually analysed after heating (at temperatures of 300oC, 650oC and 950oC) and cooling in order to determine changes in the following parameters: LOI – loss on ignition, chemical composition and pH. Moreover, investigated were bonding bridges, before and after the moulding sand was roasted. The research results revealed differences in the structure of bonding bridges and the occurrence of automatic adhesive destruction for both types of gypsum binders. For two types of moulding sands under the investigation of the LOI exceeded 2.59wt.% (with building gypsum) or 2.84wt.% (with putty gypsum) and pH increased to ca. 12 as a result of increasing roasting temperature from 300oC to 650oC. Next, roasting at 950oC decrease value of LOI in both types of moulding sands. Moulding sand with builoding gypsum roasted at 950oC revealed a return to the value of pH parameter measured prior to annealing.
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Abstract

Until now, dust arising from lime manufacture has been considered harmless to the environment so it has been investigated marginally from the standpoint of environmental protection, especially when it came to magnetic properties and heavy metal content. The aim of the research was filling the gap in this area. The research comprised measurements of magnetic susceptibility, the content of heavy metals, reaction (pH) and specific conductivity of lime dust and also raw material and fuel used for lime production. The samples were taken from one of the lime plants located in Opole Province. Similar investigations were also performed for dust taken from the nearby cement plant using dry method of cement production. It was proven that magnetic susceptibility, heavy metal content and conductivity of lime dust was lower in comparison to cement dust, which resulted from the fact that the lime plant used neither low raw materials nor additives. Due to the high atmosphere dust level in the vicinity of the investigated plants, extremely basic reaction of the tested dust and high content of metals, the studied dust cause alkalization of soils and contribute to the increase of heavy metal content in soils, posing a threat to the environment.
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Abstract

Casting covers major area of production all over the world. Resin bonded casting is widely used in today’s manufacturing industries. Furan No bake casting is most widely accepted in indian foundries due to its excellent surface finish and dimensional stability. It is a self-setting binder and it has a lower work and strip times. Though the casting process is also known as process of uncertainty, in the present study, an attempt has been made to investigate the effect of Grain Fineness Number, Loss of Ignition, Potential of Hydrogen, % of Resin with respect to sand, Sand Temperature and Compressive strength of the mould on Sand Inclusion defect – one of the most dominating defect in the Krislur Castomech Pvt. Ltd. Industry situated at Bhavnagar, Gujarat, India. The experiments were conducted based on response surface methodology (RSM) and sequential approach using face centered central composite design. The results show that quadratic model with removal of some insignificant term is comparatively best fits for Sand Inclusion Defect.
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Abstract

The presence of lipopolysaccharide (LPS) in blood induces an inflammatory response which leads to multiple organ dysfunction and numerous metabolic disorders. Uncontrolled, improper or late intervention may lead to tissue hypoxia, anaerobic glycolysis and a disturbance in the acid -base balance. The effects of LPS-induced toxemia on biological and immunological markers were well studied. However, parameters such as base excess, ions, and acid-base balance were not fully investigated. Therefore, the objective of this study was to examine these blood parameters collectively in LPS-induced inflammatory toxemia in rat’s model. After induction of toxemia by injecting LPS at a rate of 5 mg/kg body weight intravenously, blood was collected from the tail vein of twenty rats and immediately analyzed. After 24 hours, the animals were sacrificed and the blood was collected from the caudal vena cava. The results revealed that the levels of pH, bicarbonate, partial pressure of oxygen, oxygen saturation, Alveolar oxygen, hemoglobin, hematocrit, magnesium (Mg2+), and calcium (Ca2+) were significantly decreased. On the other side, the levels of Base excess blood, Base excess extracellular fluid, partial pressure of carbon dioxide, lactate, Ca2+/Mg2+, potassium, and chloride were significantly increased compared to those found pre toxemia induction. However, sodium level showed no significant change. In conclusion, Acute LPS-toxemia model disturbs acid-base balance, blood gases, and ions. These parameters can be used to monitor human and animal toxemic inflammatory response induced by bacterial LPS conditions to assist in the management of the diagnosed cases.
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