ABSTRACT
The formation of multiple delaminations is a frequently observed damage mechanism in composite materials, exerting a more pronounced influence on their strength properties compared to single delaminations. To tackle this issue, the incorporation of nanoparticles has been investigated as a means to enhance composite materials. This study aims to examine the effects of nano-additives, specifically carbon nanotubes and nanosilica, on the flexural behavior of glass/epoxy composites containing multiple embedded delaminations. The acoustic emission technique is employed to gain deeper insights into the damage mechanisms associated with flexural failure. Artificial delaminations of varying sizes, arranged in a triangular pattern, were introduced into four interlayers of a [(0/90)2]s oriented glass/epoxy composite. The findings reveal a notable reduction in flexural properties due to the presence of multiple delaminations. However, the addition of nanoparticles demonstrates a significant improvement in the flexural behavior of the multi-delaminated specimens. The most substantial enhancement is observed in the composite incorporating 0.3 wt% nanosilica + 0.5 wt% carbon nanotubes. Furthermore, genetic K-means and hierarchical clustering techniques are employed to classify different damage mechanisms based on the peak frequency and amplitude of the acoustic emission signals. The results indicate that the hierarchical clustering method outperforms the genetic K-means method in accurately clustering the acoustic emission signals. Moreover, the incorporation of nanoparticles' impact on the occurrence of distinct damage mechanisms is evaluated through the analysis of acoustic signals using Wavelet Packet Transform. By investigating the flexural behavior of nanomodified multi-delaminated composites and employing the acoustic emission technique, this study offers valuable insights into the role of nanoparticles in enhancing the mechanical properties and monitoring the damage mechanisms of composite materials.
ABSTRACT
PURPOSE: The aim of the present study was investigating the effects of three anti-inflammatory drugs, on Sirolimus protein biding. The binding site of Sirolimus on human serum albumin (HSA) was also determined. METHODS: Six different concentrations of Sirolimus were separately exposed to HSA at pH 7.4 and 37°C. Ultrafiltration method was used for separating free drug; then free drug concentrations were measured by HPLC. Finally, Sirolimus protein binding parameters was calculated using Scatchard plots. The same processes were conducted in the presence of NSAIDs at lower concentration of albumin and different pH conditions. To characterize the binding site of Sirolimus on albumin, the free concentration of warfarin sodium and Diazepam, site I and II specific probes, bound to albumin were measured upon the addition of increasing Sirolimus concentrations. RESULTS: Based on the obtained results presence of Diclofenac, Piroxicam and Naproxen, could significantly decrease the percentage of Sirolimus protein binding. The Binding reduction was the most in the presence of Piroxicam. Sirolimus-NSAIDs interactions were increased in higher pH values and also in lower albumin concentrations. Probe displacement study showed that Sirolimus may mainly bind to site I on albumin molecule. CONCLUSION: More considerations in co-administration of NSAIDs and Sirolimus is recommended.
ABSTRACT
STATEMENT OF THE PROBLEM: The survival of pulpless teeth restored with different post and core systems is still a controversial issue. PURPOSE: This study compared the retention of two different post and core systems and also the fracture resistance of teeth restored with these systems. MATERIAL AND METHOD: Eighty endodontically treated maxillary central incisors were sectioned perpendicular to the long axis at a point 2mm incisal to the cemento-enamel junction (CEJ) and then the root canals were obturated. The restored teeth were randomly divided into two equal groups of 40. One group was restored with Nickel-Chromium (Ni-Cr) post and core system and the other group with Non-Precious Gold alloy (NPG) system. For evaluation of fracture resistance of the restored teeth, the specimens (n=20 per each group) were mounted in acrylic resin blocks and a layer of polyvinyl siloxane was applied to cover the roots. Loads were applied at an angle of 45 degrees to the long axis of the teeth and measured with a universal testing machine. The axial retention values of the studied groups (no=20) were measured on an Instron testing machine at a crosshead speed of 0.5 mm/min. Statistical analyses were performed using SPSS version 19.00 and student's t-test (α=0.05). RESULTS: Although retention failure load for Ni-Cr system was lower than NPG system, there was no significant difference between the two systems (p= 0.7). However, fracture resistance of the teeth restored with Ni-Cr post and core system was significantly higher than NPG group (p= 0.000). CONCLUSION: There was no significant difference between the retention of the studied post and core systems. Although significantly higher fracture thresholds were recorded for Ni-Cr post and core group, the failure loads of both systems may rarely occur clinically.
ABSTRACT
PURPOSE: The aim of the present study was to develop a simple and rapid reversed-phase high performance liquid chromatographic method with UV detection for erlotinib hydrochloride quantification, which is applicable for protein binding studies. METHODS: Ultrafilteration method was used for protein binding study of erlotinib hydrochloride. For sample analysis a simple and rapid reversed-phase high performance liquid chromatographic method with UV detection at 332 nm was developed. The mobile phase was a mixture of methanol, acetonitril and potassium dihydrogen phosphate buffer (15:45:40 %v/v) set at flow rate of 1.3 ml/min. RESULTS: The run time for erlotinib hydrochloride was approximately 6 minutes. The calibration curve was linear over the range of 320-20000 ng/ml with acceptable intra- and inter-day precision and accuracy. The intra-day and inter-day precisions were less than 10% and the accuracies of intra and inter-day assays were within the range of 97.20-104.83% and 98.8-102.2% respectively. CONCLUSION: Based on the obtained results, a simple, accurate and precise reversed-phase isocratic HPLC method with UV detection has been optimized and validated for the determination of erlotinib hydrochloride in biological samples.
