ABSTRACT
Background: The dimensional accuracy of elastomeric impression materials has been evaluated by different methods but their reliability is still questionable. The aim of this study was to evaluate the dimensional accuracy of elastomeric impression material using 3D laser scanner. Method: In the present study, a metal die with its custom tray were designed. Using this die and tray, 10 impressions each were made from addition silicone (Aquasil LV; Dentsply), condensation silicone (Speedex coltene, Whaledent) and polyether (3M; ESPE). All the impressions were poured with Type IV die stone and total of 30 die replicas were obtained. These were scanned with a Picza 3D laser scanner (LPX 600, Roland,California) and the difference between the stone model was calculated by determining its volumetric changes using CAD-CAM pero version 2.0. One way analysis of variance (ANOVA) was used to compare the groups, whereas significance of mean difference between the groups was done by Tukey HSD. Results: All the three groups showed mean decrease indicating a dimensional shrinkage from the master die. Mean percentage dimensional change in condensation silicone was maximum (-319.02 ±15.50) followed by polyether (-122.59 ± 0.64) and least in addition silicone (-23.83 ± 0.43). All the results were statistically significant (p<0.001). Conclusion: Picza 3D laser scanner can precisely measure the volumetric changes in all the three elastomeric impression materials.
ABSTRACT
The present work discusses the effect of the pearlitic morphology with varying fineness on the cavitation erosion behavior of eutectoid rail steel. Cavitation erosion of three different types of the pearlitic steels (furnace-cooled, air-cooled, and forced-air-cooled) consisting of coarse, fine, and very fine microstructures were tested in 3.5% NaCl solution and compared with that of the as-received pearlitic rail steel. The variation in the mean depth of erosion (MDE) and mean depth erosion rate (MDER) with erosion time was analyzed. Furthermore, the cavitation erosion resistance of the as-received, the air-cooled, and the forced-air-cooled was found to be 1.03, 1.51, and 2.14 times better than the furnace-cooled pearlitic steel, respectively. It was concluded that the cavitation erosion resistance of the pearlitic steel increased with the increase in the fineness of the microstructure.
ABSTRACT
BACKGROUND: Ethanol-induced tumour necrosis (ETN) is a simple, readily available palliative treatment for patients with inoperable carcinoma of the oesophagus with poor performance status. In India, capital outlay needed for stenting or laser therapy is out of reach. Hence, we took up this study to calculate the effect of intratumoral injection of absolute alcohol in palliation of dysphagia due to carcinoma of the oesophagogastric junction and to monitor the improvement in quality of life (QOL). METHODS: A total of 16 patients with a mean age of 56.2 ± 7.5 years with dysphagia due to unresectable malignant oesophageal strictures involving the oesophagogastric junction were included in the study. Six to ten cubic centimetres of absolute alcohol in 1 cc aliquots was injected circumferentially into the tumour at the point of luminal obstruction using disposable sclerosing needles (23G). During each follow up dysphagia grade, QOL score and complications, if any, were noted. RESULTS: The mean alcohol injected per session was 6.9 ± 1.8 cc. The mean dysphagia grade improved from 5.5 ± 0.5 to 2.5 ± 1.1 before and after alcohol injection, respectively (p < 0.001). The time taken for recurrence of dysphagia ranged from 14 to 80 days with a median of 28 days. The mean QOL score assessed by modified EORTC questionnaire improved from a mean of 63.6 ± 6.9 to 92.6 ± 13.9 (p < 0.001). The dysphagia free survival ranged from 23 to 175 days with a mean of 71.2 days. Complications included oesophageal perforation in one patient and death in one patient. CONCLUSION: The endoscopic intratumoral injection of absolute alcohol significantly improves dysphagia and QOL. It is inexpensive and easy to perform.
ABSTRACT
We present a 'universal' phenomenon of mass accumulation and its sensing on nanostructures due to electron beam cracking of residual gas molecules during electron beam scanning. Though the extent of this phenomenon is limited to a very small increment in mass or thickness, it has significant implications for both the scientific and technological aspects of almost all processes in the nanodomain. Mass accumulation in every frame scan (or per second) is of the order of a few attograms and the thickness of deposition is of the order of picometre (fraction of a monolayer) only. Direct measurement of a mass or thickness of this order is difficult. Nanopillars having a high resonance 'Q-factor' have been successfully exploited for such high precision measurements. The mass accumulation rate has been characterized with respect to (i) electron energy and beam current, (ii) environment within the chamber (presence or absence of a precursor gas) and (iii) partial exposure of the nanopillars to the e-beam.
