The development of an optical pH sensor based on immobilization of quinizarin (1,4-dihydroxyanthraquinone) on a triacetylcellulose membrane was described. The resulting membrane exhibited fast color change from yellow to violet, while changing the pH in alkaline region. The immobilized quinizarin showed a broader dynamic range from (pH 9.4-11.4) with respect to free form (pH 8.8-10.4). The sensor response was fully reversible and fast (<20 s) under the batch conditions with pH between 7 and 12.5. The sensor showed excellent long term stability (more than three months) and high reproducibility (R.S.D. less than 2%). The Ka values for free and immobilized dye were evaluated and the chemical reactivity of the quinizarin in solution and after immobilization was also described.

The protection of transmission and sub-transmission lines is conducted by overcurrent, line differential and distance protections among which the use of distance protection is very common.Mal-operation of protection equipment, including distance protection, can occur due to improper choose of the setting. This paper presents the proper method for calculation of the phase-to-phase loop resistance reach of distance protection with Quad characteristic and the impedance starter at the sub-transmission level to prevent mal-operation of the distance relay when processing its algorithm. In this work, based on the practical experiences on several industrial distance relays, it is shown that there is a possibility of improper detection of the fault loop by distance protection and then improper relay operation for out of zone faults. After review of the subject, and expressing the mathematical relations governing the problem, the appropriate phase-to-phase loop resistance reach determination method is put forward. Finally, using the information obtained from a practical incident, the efficiency of the proposed method is verified.

In this study, the effect of nitrate to ammonium ratio and pH of nutrient solution on the changes in pH and EC of rhizosphere during spinach growth period in perlite culture, under greenhouse conditions, was investigated. A split factorial experiment in a completely randomized design with four replications was conducted with three factors including nutrient solution’s pH in three levels (4.5, 6.5 and 8), nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75 and 0:100) and 10 levels of time. Three seedlings of spinach plant (Spinacia oleracea L. cv. Sirius) were cultivated per pot and nourished with 15 different nutrient solutions. During the growth period and at different times, the leachate pH and EC of cultivated and uncultivated pots were measured. The results showed that the effects of time, pH and nitrate to ammonium ratio of nutrient solution on pH and EC of rhizosphere were significant (P<0.001). By increasing the nitrate to ammonium ratio of nutrient solution, the pH of rhizosphere was increased but the EC of rhizosphere was decreased. At the end of the growth period, the pH of rhizosphere in the nitrate to ammonium ratio of 100:0 was about three units higher than the nitrate to ammonium ratio of 0:100 and two pH of 4.5 and 8. While, this difference was lower at the pH of 6.5. During the spinach plant growth period, the changes in pH and EC of rhizosphere in studied treatments were different. In the nitrate to ammonium ratio of 75:25 and pH of 6.5, the pH of rhizosphere was in the optimum range for plant growth and nutrients uptake. Except in the nitrate to ammonium ratio of 100:0 and pH of 8, in the rest of the treatments, the rhizosphere pH decreased during plant growth period. The initial pH of nutrient solution had different effects on the rhizosphere pH. The average rhizosphere pH in nutrient solutions with pH of 4.5, 6.5 and 8 was 5.94, 6.5 and 7.29, respectively. The results showed that in adaptation to adverse acidic or alkaline conditions, the spinach plant changes its rhizosphere pH actively. Also, undesirable effects of pH on the spinach growth in adverse acidic or alkaline conditions can be decreased with application of proper nitrate to ammonium ratio. The rhizosphere EC was more than the leachate EC of uncultivated pots and the initial EC of nutrient solution. By decreasing the pH of nutrient solution, the rhizosphere EC of spinach was increased.

Background and aim: Saliva plays an important role in oral and dental health by maintaining the pH balance, buffering capacity and proteins. Chemical plaque control methods, such as mouthwashes, act as supplements. Salt water alkalinizes saliva and acts as a supplement. Salt water acts as an astringent & along with baking soda are effective in reducing mouth acidity. The purpose of this study is the effect of washing with salt water or baking soda on the pH of saliva and plaque. Materials and methods: This study was conducted on 62 dental students with an average age of 25 years including 31 men & 31 women. They used mouthwash for two weeks. 2 ml of saliva and some plaque attached to the distal surface of tooth # 6 on the right side of the lower jaw were collected. The pH of saliva and plaque in each group was measured using a pH measuring device manufactured by Teb Azma company in Iran before and after washing. SPSS software and Two Way ANOVA statistical test were used for statistical analysis. Results: Both sodium chloride and sodium bicarbonate mouthwashes increase the pH of saliva and plaque. Based on the results of the 2-Way Repeated Measure ANOVA test, the increase in pH of saliva and plaque after using sodium bicarbonate mouthwash is more than the increase in pH of saliva and plaque after using sodium chloride mouthwash (p-value<0. 001) Conclusion: :   The increase in pH of saliva and plaque after using sodium bicarbonate mouthwash is more than the increase in pH of saliva and plaque after using sodium chloride mouthwash