فهرست مطالب

  • سال دهم شماره 1 (پیاپی 37، بهار 1401)
  • تاریخ انتشار: 1401/04/18
  • تعداد عناوین: 10
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  • Raziye Namaki*, Mohammad Firoozsani, Nazanin Malkami Page 7

    In the power transmission and distribution industry, ceramic and porcelain insulators are being replaced by silicone insulators. Unlike other composite insulating materials used in the past decades, these silicone insulators are able to maintain their hydrophobicity properties even in severe pollution conditions. Because environmental pollution conditions are unpredictable during operation, the performance of the hydrophobicity dynamics of these electrical insulators is important. This dynamic performance of silicone insulators is also known as the hydrophobicity transfer mechanism. These silicone materials, in addition to transmitting hydrophobicity, also have the ability to recover hydrophobicity. The hydrophobicity transfer and recovery mechanism of silicone materials is related to the reorientation of methyl groups and the presence of low molecular weight components, which are investigated in this paper.

    Keywords: Insulator, Electrical insulation, Hydrophobicity, Hydrophobicity transfer, contact angle, Siliconematerial
  • Parastoo Erfanmanesh*, Samira Jahandari Page 15

    New technologies have increased the ability and efficiency of our methods of extracting DNA from burials. The study of ancient DNA quickly corrected our view of the origins of modern man. One of the amazing properties of DNA is its durability. Most biomolecules are rapidly destroyed after death. However, under certain conditions, DNA can remain for a long time. In order to obtain ancient DNA, there are many molecular methods that are used depending on the type and material of the samples, there are many methods for genetic testing that depending on the type and type of samples, Is used. PCR-based methods are divided into three sections based on markers based on primer detection, which are discussed in detail in this article. DNA analysis can also be used to determine gender. Genetic differences between the sexes are due to the Y chromosome in men; Therefore, by identifying a piece of DNA on the Y chromosome, it is possible to distinguish between male and female burials and determine the sex of skeletons obtained from ancient sites. Human mitochondrial DNA markers belong to the non-coding region of the human genome. A person should be the same as his mother and maternal relatives. The mtDNA trait, inherited over generations of more or less intact, and genetic recombination does not cause new diversity, is useful in tracing families and related generations. Therefore, this genetic component is very important in geoarchaeological studies.

    Keywords: ncient DNA, Y chromosome, mt-DNAmarkers, PCR methods
  • Saba Belgheisi* Page 24

    The first laboratory use of plasma in the food industry was to study the possibility of inactivating undesirable microorganisms from the surface of heat-sensitive foods such as fresh fruits and vegetables, meat, and eggs. Plasma treatment can be considered as a potential alternative to chemicals (eg chlorine treatment) or physical methods (eg high pressure, pulsed electric field, irradiation) for surface disinfection. Advantages of using plasma processes include high efficiency at low temperatures (generally <70 ° C), instantaneous production, low impact on the internal matrix of the product, no need for water or solvent and no waste left. Plasma processing can also have several benefits, such as cleaning surfaces, increasing surface energy, improving moisture, increasing printing and dyeability, and creating very thin coatings on films used in the packaging industry.

    Keywords: Plasma, food industry, processing
  • Faezeh Sayari* Page 32

    Fracture toughness is usually used as a generic term for measures if materials resistance to expansion of a crack in engineering applications such as petrochemical industries and oil and gas pipelines. The concept of fracture toughness received profound importance in engineering design and applications, after the destruction of liberty ships in the World War II. In this paper, fracture toughness test methods, evaluation and standardization of metal materials are reviewed based on linear elastic and elastic-plastic fracture mechanics. The general principles and methods of testing developed by the American Society for Testing and Materials are explained. The main parameters of fracture mechanics such as elastic energy release rate (G), stress intensity factor (K), J integral, crack tip opening displacement (CTOD) and crack tip opening angle (CTOA) are defined. Finally, the scientific and computational foundations of the two factors (K) and CTOD, as the most widely used industrial factors will be examined in detail.

    Keywords: Fracture Toughness, Fracture Mechanics, Stress Intensity Factor (K), CTOD
  • Mohamad Reza Abedi*, Hossin Batarbiat, Atena Nozari, Akram Ramezanzadeh Page 40

    Students and graduates always face difficulties in solving solution preparation problems, and textbooks usually do not provide a complete description of problem-solving methods, while problem-solving skills are essential for students. For this purpose, a book called "Different methods of solving solution preparation problems in the chemistry laboratory" has been written by the author and published in the Islamic Azad University of Quchan. One of the methods mentioned in this book, which is very simple and fast, is the crossover method. The purpose of this article is to present this method in solving solution preparation problems with the help of which solution preparation problems can be solved very quickly and easily.

    Keywords: Solution preparation, Crossover method, Chemistrylaboratory, Concentration
  • Saba Belgheisi Page 48

    For decades, supercritical fluids have been considered as an alternative to other extraction methods. The main applications of supercritical fluid are the extraction of valuable bioactive compounds as flavorings, dyes and removal of undesirable compounds such as organic contaminants, toxins and pesticides. Carbon dioxide is the main solvent used in this method, especially when the target molecule is non-polar. Equipment used for extra critical fluid extraction usually includes an extraction solvent retainer (usually carbon dioxide), a pump to apply pressure to the fluid, an oven containing the extraction vessel, and a limiter to maintain high pressure inside the system. Due to the function of the oven and the pump, carbon dioxide changes from the liquid phase to the critical condition (relatively low critical temperature 31.1 ° C and low critical pressure 7.7 MPa). Lack or limited consumption of solvent leads to the production of solvent-free extract. The decompression phase in the supercritical fluid process reduces the number of operating units because it does not require the separation and purification phase. Low temperature operation throughout the process is suitable for heat sensitive bio composites.

    Keywords: Bioactive compounds, Extraction, Supercritical fluid