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Background Endoscopic management of the nonlifting areas of a colonic polyp is a significant challenge. The traditional approach has been to use ablative techniques with mixed long-term results. Objective To evaluate the safety and efficacy of hot avulsion (HA), a modification in the use of hot biopsy forceps in the management of the nonlifting areas of a colonic polyp. Design Retrospective review of data from a prospectively maintained colonic Endoscopic Mucosal Resection database. Setting Tertiary referral hospital. Patients and Intervention Twenty patients in whom HA was used as part of the polypectomy technique. Main Outcome Measurements Location and size of polyp, reasons for nonlifting, immediate success, residual rates, and adverse events. Results In our 20 patients studied, the main reasons for nonlifting were scarring from previous EMR attempts in 55% and scarring from previous biopsy in 35%. Mean size of avulsion was 4.4 mm (range, 1-15 mm). At the index procedure, HA was successful in removing macroscopic adenomatous tissue in all patients. At follow-up examinations, 85% (17/20) had no macroscopic or microscopic neoplasia residual and 15% (3/20) had a small area of residual that was easily treated with repeat HA. There were no immediate or long-term adverse events. Limitations Nonrandomized, single-center experience. Conclusions HA appears to be a safe and effective adjunct treatment to snare polypectomy for nonlifting areas of a colonic polyp. Further randomized multicenter studies are required with direct comparison to established techniques. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Previous work has shown protection to eroded teeth offered by a resin-based adhesive lasted up to three months. The hypothesis investigated in this study was whether application of a fissure sealant would offer longer protection. Methods: Seventeen adult patients with palatal tooth wear were recruited and written consent obtained. Metal discs were cemented on the palatal surfaces of all upper anterior teeth following previously published techniques. Alternate teeth within each subject were randomly chosen and coated with a clear fissure sealant using previously published methods. The uncoated teeth were used as controls. Accurate impressions were taken in custom made trays and repeated at 3, 6, 9, 12 and 20 months and scanned using a non-contacting laser profilometer. Results: The mean (standard deviation) thickness of the fissure sealant was 290μm (500) at the start and after 3 months a mean thickness of 120μm (260) remained. At this point the control surfaces showed a mean 70μm (113) of tooth wear. At 6 and 9 months the mean wear for control teeth was higher at 120μm (114) and 110μm (114) than sealed teeth at 50μm (260) and 60μm (440), respectively. A comparison of paired sites within subjects at their final visit indicated a statistically significant difference in wear between the sealed and control teeth (p =0.016). Conclusions: The use of fissure sealant to protect palatal dentine surfaces may have a role in prevention of tooth wear for up to a period of nine months. [Copyright &y& Elsevier]

Abstract: Objectives: The role of fluoride in preventing erosion and abrasion on dentine remains unclear. The aim of this study was to investigate the effect of repeated applications of a 0.05% fluoride mouthwash and an adhesive on wear of dentine using stainless steel discs reference points and a laser profilometer. Methods: Small stainless steel discs were bonded to 60 caries free extracted molars which had previously been sectioned horizontally. The teeth were equally divided and subjected to four modalities in an erosion and abrasion laboratory model. Step heights were measured from the metal discs using a non-contacting laser profilometer at 100, 500, 1000, 2500 and 5000 cycles. Results: The results after 5000 cycles showed that dentine coated with a dentine adhesive (0.015μm, S.D. 0.090) had statistically less wear than fluoride (0.127μm, S.D. 0.150), abrasion and erosion (0.182μm, S.D. 0.150) or abrasion only (0.096μm, S.D. 0.090) (p <0.001). Conclusion: In conclusion dentine surfaces coated with a resin-based adhesive provided more protection against erosion and abrasion than a fluoride mouthrinse. There were no statistical differences between the modalities for cycles less than 5000. [Copyright &y& Elsevier]

• We develop a 1-D transient multi-phase thermal model for post-accident heat removal. • The model considers stratification of fuel and steel in the debris bed. • The model considers melting of fuel/steel particles and their re-solidification. • Influence of steel content/stratification on core catcher temperaure is studied. • Core catcher temperature is seen to be a strong function of steel content in debris. Following a core meltdown accident in a pool type sodium cooled fast breeder reactor (SFR), a debris bed is formed over the core catcher. The influence of initial material composition of the debris bed (consisting of fuel and steel) on the post accidental heat removal processes has been investigated in view of reactor safety. A one dimensional transient multiphase thermal model has been developed and employed for this purpose. The model includes sodium boiling, steel melting, fuel melting, slumping of molten particles and formation of molten pool. The overall steel fraction in the debris bed, the extent of steel stratification in the bed due to density difference between the debris particles and the overall porosity of the debris bed are considered as main parameters. It is seen that the assumption of a homogeneous initial mixture of fuel and steel in the debris bed yields a low core catcher plate (CCP) temperature compared to stratified debris beds where steel fraction increases with debris height. In a debris mixture with a low steel content (20% steel and 40% fuel), the peak temperature experienced by the CCP increases only marginally, from 872 K for homogeneous mixture to 900 K for a highly stratified mixture. But, in a debris mixture rich in steel content (30% steel and 30% fuel) the corresponding peak temperatures experienced by CCP are 886 K and 932 K respectively, suggesting that material stratification has significant effect in steel-rich debris mixture. For identical steel stratification profiles, the peak CCP temperature in a steel lean debris mixture is lower than that in a steel rich debris mixture. For 20% overall steel fraction, the peak temperature experienced by CCP is less than the creep limit of 923 K even for the worst stratification. But for 30% overall steel fraction, increasing the extent of steel stratification above a specific value results in CCP peak temperature exceeding the safe limit based on creep failure. Thus, the thermal load on the CCP increases with steel content though the thermal conductivity of steel is much higher than that of the fuel. [ABSTRACT FROM AUTHOR]

Various single tray in-vessel core catcher options to handle whole core decay heat for a 1500 MWt capacity sodium cooled Indian fast reactor (SFR) have been analyzed towards their efficiency in rendering acceptable core catcher temperatures. For this purpose, a one dimensional transient multiphase heat transfer model that considers sodium boiling, fuel particles re-melting and slumping has been adopted. The boundary conditions for the one dimensional model are obtained from computational fluid dynamics (CFD) simulations of turbulent natural convective heat transfer within the lower sodium plenum of the SFR. It is found that the top surface of the debris bed dissipates more heat than the bottom surface of the core catcher. A single plate core catcher is seen to experience melting of the core catcher plate (CCP) for a short duration in case of CCP thickness greater than 80 mm. The heat shield plate (HSP) of the double plate core catcher is observed to undergo complete melting due to vapor locking between the HSP and CCP. The phenomena of melting and slumping of debris particles is seen in double plate core catchers with a refractory lining. However, safe temperature levels of HSP and CCP were observed in the case of double plate core catchers with refractory lining. This study suggests that a double plate core catcher with a delay bed is the potential option for future sodium cooled fast reactors, which are to be designed to handle whole core meltdown scenarios. • Various types of in-vessel single tray core catcher designs to handle full core debris are analyzed. • Designs include, single plate, double plate and double plate with a delay bed. • A one dimensional thermal model that considers core debris re-melting/slumping is adopted. • By CFD simulations, natural convection heat transfer correlations for core catcher are developed. • Double plate core catcher with a delay bed restricts load bearing core catcher plate below 923 K. • This option is selected for future Indian SFR having a large core size and compact primary vessel. [ABSTRACT FROM AUTHOR]

• A single dimensional transient multi-phase thermal model has been developed. • The model is adopted for debris re-melting/re-solidification on core catcher during PAHR. • Sensitivity of multi-layer core catcher temperature on governing parameters investigated. • Referactory thickness and debris spread have been optimized for future Indian SFR. In the evolutionary design of Sodium Cooled Fast Reactors (SFR), core catcher has to handle debris generated from damage of whole core. This requirement combined with large core size demand that newer core catcher has to accommodate large volume of debris and consequently a thick debris bed having the risk of re-melting. To cater to this, a one-dimensional multi-phase heat transfer model for re-melting/re-solidification of core debris on a multi-layer core catcher is developed. Versatility of the model for various conditions is established. Then the model is applied to core catcher of future Indian SFR of 600 MWe capacity. Based on parametric studies, it is found that a 40 mm thick delay bed made of Thoria restricts the heat shield plate temperature within permissible limit. The corresponding minimum radius of debris spread is 3.25 m. This avoids core debris re-melting, provided melt-arrival time exceeds 1000 s. [ABSTRACT FROM AUTHOR]