Optical sensor for pH monitoring using a layer-by-layer deposition technique emphasizing enhanced stability and re-usability

Stable and reliable operation of an optical sensor for pH monitoring is important for many industrial applications of these types of devices. The layer-by-layer deposition technique is a simple and versatile method used to deposit a sensitive thin film on such an optical fibre-based device but creating a coating which can often be destroyed in use in highly acid or alkali solutions i.e. with very low or very high pH. It is thus important to create stable and durable sensors to meet the needs of users for operation under these extreme environments. The main aim of this study has been to prepare a number of such sensors and compare the performance of three different stabilization approaches used for the development of an effective wavelength-dependent pH-sensitive optical sensor. Techniques such as employing heat treatment, the deposition of two layers of a PAH/SiO2 thin film and the deposition of two layers of APTMS/SiO2 as topping layers have been studied to determine the optimum approach to creating a stable and reliable sensor – one yielding the same value of peak wavelength for a measurement of a known value of pH and to do so repeatibly. An improvement in performance and in shelf-life, stability and re-usability of the sensor has been achieved by the addition of two bilayers of APTMS/SiO2 (3-Aminopropyl-trimethoxy silane/Silica nanoparticle) in the work carried out and the results of the investigation undertaken are reported

Wavelength dependent pH optical sensor using the layer-by-layer technique

In this work, the design and characteristics of a wavelength-dependent pH optical sensor have been studied. To create the sensor itself, brilliant yellow (BY) as a pH indicator and poly (allylamine hydrochloride) [PAH] as a cross-linker have been deposited on the end of a bare silica core of an optical fibre by use of a ‘layer-by-layer’ technique. In the experiments carried out to characterize the sensor, it was observed that the value of pKa (the dissociation constant) of the thin film is dependent both on the outer layer and the number of bilayers. A heat treatment process was applied to the sensor to reduce the effect on the deposited layers during the testing of the probe. As a result of these series of experiments, it could be concluded that the probe design on which were deposited structured layers comprising six double layers of (PAH/BY) showed the best sensitivity for a pH range from 6.80 to 9.00 (with an accuracy of ±0.20) and showing an average wavelength shift of 4.65 nm per 0.2 pH units, while the concentration of the BY and the PAH solutions was maintained as 0.25mM and 2.5mM respectively

Modeling and predicting of the flash point of chemical compounds

Flash point is one of the most important flammability characteristics of chemical compounds. In the present study, we developed a neural network model for accurate prediction of the flash point of chemical compounds, using the number of hydrogen and carbon atoms, critical temperature, normal boiling point, acentric factor and enthalpy of formation as model inputs. Using a robust strategy to efficiently assign neural network parameters and evaluate the authentic performance of the neural networks, we could achieve an accurate model which yielded average absolute relative errors of 0. 97, 0. 96, 0.99 and 1.0% and correlation coefficients of 0.9984, 0.9985, 0.9981 and 0.9979 for the overall, training, validation and test sets, respectively. These results are among the most accurate ever reported ones, to date.in this article method for selection the best learning algorithm and transfer function are clearly presented and relative error for these parameters are represented in detail

The effect of atorvastatin treatment duration on oxidative stress markers and lipid profile in patients with coronary artery diseases: A case series study

BACKGROUND: The major aim of this study was evaluating the effect of atorvastatin treatment on thiobarbituric acid reactive substances (TBARS), ferric reducing the ability of plasma (FRAP), small dense low-density lipoprotein cholesterol (sdLDL) and lipid profile in coronary artery disease (CAD) patients.METHODS: This study was carried out on 83 patients with angiographically proven coronary artery stenosis (52 men and 31 women) at Shahid Madani Hospital, Khorramabad, Iran, in 2015. The patients were divided into the 3 groups. 27 patients were classified statins consumption less than 6 days, 28 patients for 6 to 90 days, and 28 patients for more than 90 days. The level of sdLDL, lipid profile, TBARS and FRAP were assayed.RESULTS: FRAP levels of patients that received atorvastatin for more than 90 days (832 ± 101) were significantly elevated (P = 0.01) compared to the patients received atorvastatin less than 6 days (688 ± 75), whereas the levels of TBARS diminished significantly (P = 0.04). Also, the levels of total cholesterol (TC) and LDL-C were significantly decreased after 3 months of atorvastatin receiving (158 as compared to patients that consumed atorvastatin less than 6 days), (P = 0.02 and 0.03, respectively). The level of sdLDL was slightly increased with long-time consumption of atorvastatin (37 ± 14) in patients in comparison with patients that received atorvastatin less than 6 days (32 ± 15) (P = 0.06), but was not significant.CONCLUSION: The serum level of TBARS decreased and the serum level of FRAP increased in patients with long-time receiving atorvastatin. Therefore, atorvastatin contributes to the lowering oxidative stress in these patients. </p