مجله دانش آزمایشگاهی ایران
سال دوازدهم شماره 4 (پیاپی 48، زمستان 1403)

The installation of reinforcement in concrete using chemical adhesives is one of the most effective methods for enhancing and strengthening concrete structures, particularly in retrofitting and infrastructure reinforcement projects. This study investigates the influence of adhesive type and environmental conditions on the tensile strength of embedded reinforcement in concrete. Two types of adhesives, epoxy and epoxy-acrylate, were selected as bonding agents, and tests were conducted under various conditions, including vertical and horizontal reinforcement installations in field (in-situ) settings. The primary objective of this research is to gain a deeper understanding of how these variables affect the ultimate tensile strength of embedded reinforcement and to propose optimization strategies for improving their performance. The results indicated that epoxy adhesive, due to its higher resistance to moisture and tensile forces, demonstrated an average of 25% better performance compared to epoxy-acrylate adhesive. Epoxy adhesive exhibited superior bonding strength and stability in humid environments and under both dynamic and static loads. On the other hand, epoxy-acrylate adhesive, with its faster curing time and lower cost, proved to be a suitable option for projects requiring moderate strength and in dry environments. Additionally, the orientation of reinforcement installation significantly influenced the ultimate strength, with vertically installed reinforcement showing higher resistance compared to horizontally installed reinforcement. This study also compared the experimental results with international standards ACI 355 and ASTM E488, confirming that the findings are consistent with these standards. Overall, the results emphasize that the selection of adhesive type and adherence to appropriate environmental conditions, particularly hole cleanliness and moisture control, are critical factors in enhancing the performance of embedded reinforcement in concrete. These findings can serve as a guide for engineers and structural specialists in selecting suitable adhesives and developing optimized installation guidelines for construction and retrofitting projects.

Today, artificial intelligence and image processing are widely used for the precise analysis of radiographic images of industrial welds in non-destructive testing (NDT). These systems enhance image quality and reduce noise, enabling the automated detection and classification of welding defects. The utilization of deep learning minimizes reliance on human interpretation and limits external influencing factors. This technology empowers welding inspectors and engineers across various industries, such as oil, gas, and automotive, to analyze data swiftly and accurately, significantly improving the efficiency and safety of industrial processes.

Sample preparation for chromatography is a multi-step process that requires precision and the use of appropriate equipment. Using quality and appropriate filters for each sample and column and carefully adjusting the preparation steps can have a significant impact on the accuracy and precision of the results. Sample preparation for chromatography devices is a complex and precise process that includes various steps from sample extraction to sample injection into the device. In this article, we will discuss the importance of using a filter before sample injection into the device and before the solvent passes as the mobile phase, and their different types and applications of each separately.

Heavy metals are considered persistent pollutants, and their entry into the food chain through food products can cause serious harm to the health of consumers. One of the common methods for determining the level of heavy metals is the use of graphite furnace atomic absorption spectrometry (GFAAS), and sample preparation is an important and critical step in spectroscopic analysis to achieve reliable and accurate results. Since the digestion method in the preparation stage depends on the sample matrix, and in the codified methods for each of the matrices, a separate and special standard method has not been mentioned, the purpose of this study is to compare the two methods of acid digestion and dry ashing in the study of heavy metals in rice products using the graphite furnace atomic absorption spectrometry method. Other objectives of this article include determining the levels of lead and cadmium pollutants in rice. The results of comparing the two methods of acid digestion and dry ashing by (GFAAS) in rice samples show that the average concentration of lead and cadmium heavy metals in the acid digestion method is higher than the dry ashing method. In general, the recovery percentage of lead and cadmium determination by the acid method is 103 and 99.7%, respectively, and the recovery of the dry digestion method is 110 and 99.5%, but the results of the t-test between the two dry digestion and acid digestion methods do not show a significant difference. The analyzes performed on 45 samples of rice varieties that were randomly sampled from the market in 2022 show that the average concentration of lead and cadmium metals, respectively, in 91.1 and 97.8% of rice varieties is in the permissible range of 150 ppb and 60 ppb. Also, 8.9 and 2.2% of rice varieties, respectively, have lead and cadmium levels higher than the permissible limit mentioned in the national standard, and it is concluded that due to the nature of rice, the acid digestion method is better than the furnace method.

Since its introduction in the 1980s, the polymerase chain reaction (PCR) has revolutionized molecular biology, genetics, and medical research. However, traditional PCR faces limitations, including issues with accuracy, low sensitivity to rare mutations, and susceptibility to inhibitors. Droplet digital polymerase chain reaction (dPCR) addresses these challenges by partitioning DNA samples into thousands or millions of individual compartments, enabling precise quantification of DNA or RNA molecules without the need for calibration curves or internal controls. This paper explores the advantages of dPCR over traditional PCR, including higher accuracy in molecular quantification, increased sensitivity, reduced impact of inhibitors, and the ability to measure absolute quantities. The unique ability of dPCR to detect rare genetic mutations, analyze complex genetic variations, and perform environmental and forensic analyses makes it a valuable tool. Despite its advantages, dPCR faces challenges such as high costs, longer processing times, and the need for precise sample preparation. Overall, dPCR represents a significant advancement in molecular biology and is expected to become more widely utilized in biology and medical laboratories with technological improvements and cost reductions.

Dynamic Light Scattering (DLS) is a widely used technique for measuring particle size and distribution in the nanometer scale. The accuracy of this method depends significantly on proper sample preparation and precise instrument settings. Sample concentration plays a crucial role in measurement accuracy. High concentrations can lead to multiple scattering, resulting in an overestimation of particle size, while low concentrations reduce signal strength and increase noise. Therefore, optimizing the concentration within the ideal range (0.1 to 1 mg/mL) is essential for reliable results. Sample stability is another critical factor. Particle aggregation, sedimentation, and chemical degradation can distort measurements. To mitigate these issues, the use of chemical stabilizers, pH adjustment, and conducting tests promptly after sample preparation is recommended. Instrument parameters also require careful calibration. Scattering angle, measurement duration, and temperature control are key factors influencing results. A 173-degree angle is preferable for concentrated samples, while a 90-degree angle is more suitable for dilute samples. Additionally, selecting an appropriate measurement duration (30 to 180 seconds) and maintaining temperature control are essential to prevent unwanted variations in particle size measurements.