Analysis of active cooling panels in a scramjet combustor considering the thermal cracking of hydrocarbon fuel

Sreekireddy, Pavani,Reddy, Tadisina Kishen Kumar,Selvaraj, Prabhu,Reddy, Vanteru Mahendra,Lee, Bok Jik Elsevier 2019 Applied thermal engineering Vol.147 No.-

<P><B>Abstract</B></P> <P>In this paper, a procedure is demonstrated for the numerical analysis of a cooling system using active panels for high-speed combustion chambers subjected to high thermo-mechanical loads. A promising alloy for high heat loads, namely, niobium Cb-752, is considered in this study. In addition to sensible heat transfer, endothermic heat absorption through the cracked hydrocarbon fuels is a viable option for cooling the chamber panels. The focus of the panel design is to minimize the weight with the safe thermo-mechanical characteristics of the panel. The present analysis is carried out in three steps. First, a one-dimensional (1D) analytical model is developed. The second and third steps are three-dimensional (3D) analyses without and with consideration of fuel endothermicity, respectively. The optimal channel dimensions obtained from the 1D analysis provide inputs for the 3D analysis. The channel dimensions obtained from the 1D analysis do not satisfy the targeted parameters in the 3D analysis. Thus, the channel is redesigned in 3D and tested with and without cracking. The channel dimensions are optimized for the ranges of heat fluxes (160–220 W/cm<SUP>2</SUP>) in the combustor and mass flow rates (0.011–0.015 kg/s) of the fuel in the channel. Reducing the weight of the panel is sought by considering the benefit of heat absorption through the endothermic cracking process in the fuel channel. The combination of an increased width and cracking performs better than the other non-cracking cases. The study presents the most efficient configuration suitable for applications in high-speed combustion chambers under the given heat flux conditions. By increasing the channel width and cracking (for 3D), the weight of the panel is reduced by 10.58%. The fuel exit temperature, fuel cracking behavior in the channel, structural stress distribution and weight of the panel are analyzed in terms of the operating conditions.</P>

A CAD/CAM-based strategy for concurrent endodontic and restorative treatment

Escobar, Patricia Maria,Kishen, Anil,Lopes, Fabiane Carneiro,Borges, Caroline Cristina,Kegler, Eugenio Gabriel,Sousa-Neto, Manoel Damiao The Korean Academy of Conservative Dentistry 2019 Restorative Dentistry & Endodontics Vol.44 No.3

This case report describes a technique in which endodontic treatment and permanent indirect restoration were completed in the same clinical appointment with the aid of a computer-aided design/computer-aided manufacturing (CAD/CAM) system. Two patients were diagnosed with irreversible pulpitis of the mandibular first molar. After access preparation, root canals were located, irrigation was performed until bleeding ceased, and the coronal tooth structure was prepared for indirect restoration. Then, utilizing an interim 3-mm build-up of the endodontic access cavity, a hemi-arch digital scan was performed with an intraoral scanner. Subsequent to digital scanning, restoration design was performed simultaneously with the endodontic procedure. The root canals were shaped using the Race system under irrigation with 2.5% sodium hypochlorite followed by root canal filling. The pulp chamber was subsequently filled with a 3-mm-thick composite resin restoration mimicking the interim build-up previously utilized to facilitate block milling in the CAD/CAM system. Clinical try-in of the permanent onlay restoration was followed by acid etching, application of a 5th generation adhesive, and cementation of the indirect restoration. Once the restoration was cemented, rubber dam isolation was removed, followed by occlusal adjustment and polishing. After 2 years of follow-up, the restorations were esthetically and functionally satisfactory, without complications.

A CAD/CAM-based strategy for concurrent endodontic and restorative treatment

Patricia Maria Escobar,Anil Kishen,Fabiane Carneiro Lopes,Caroline Cristina Borges,Eugenio Gabriel Kegler,Manoel Damião Sousa-Neto 대한치과보존학회 2019 Restorative Dentistry & Endodontics Vol.44 No.3

This case report describes a technique in which endodontic treatment and permanent indirect restoration were completed in the same clinical appointment with the aid of a computer-aided design/computer-aided manufacturing (CAD/CAM) system. Two patients were diagnosed with irreversible pulpitis of the mandibular first molar. After access preparation, root canals were located, irrigation was performed until bleeding ceased, and the coronal tooth structure was prepared for indirect restoration. Then, utilizing an interim 3-mm build-up of the endodontic access cavity, a hemi-arch digital scan was performed with an intraoral scanner. Subsequent to digital scanning, restoration design was performed simultaneously with the endodontic procedure. The root canals were shaped using the Race system under irrigation with 2.5% sodium hypochlorite followed by root canal filling. The pulp chamber was subsequently filled with a 3-mm-thick composite resin restoration mimicking the interim build-up previously utilized to facilitate block milling in the CAD/ CAM system. Clinical try-in of the permanent onlay restoration was followed by acid etching, application of a 5th generation adhesive, and cementation of the indirect restoration. Once the restoration was cemented, rubber dam isolation was removed, followed by occlusal adjustment and polishing. After 2 years of follow-up, the restorations were esthetically and functionally satisfactory, without complications.

Uptake pathways of anionic and cationic photosensitizers into bacteria

George, Saji,Hamblin, Michael R.,Kishen, Anil Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.6

The effect of divalent cations (calcium and magnesium) and a permeabilizing agent (EDTA) on the uptake of a cationic photosensitizer (PS), methylene blue (MB), and two anionic PSs, rose bengal (RB) and indocyanine green (ICG), by Gram-positive Enterococcus faecalis and Gram-negative Actinobacillus actinomycetemcomitans was examined. The possible roles of multidrug efflux pumps and protein transporters in photosensitizer uptake were assessed in E. faecalis cells by studies using an efflux pump inhibitor (verapamil) and trypsin treatment respectively. Divalent cations enhanced the uptake and photodynamic inactivation potential of both RB and ICG in E. faecalis and A. actinomycetemcomitans, while they decreased the uptake and bacterial killing by MB. Verapamil increased the uptake of RB (possibly due to efflux pump inhibition), whereas trypsin treatment resulted in significant decrease in RB and ICG uptake. The results suggested that the uptake of anionic PSs by bacterial cells may be mediated through a combination of electrostatic charge interaction and by protein transporters, while the uptake of cationic PSs, as previously reported, is mediated by electrostatic interactions and self promoted uptake pathways.

The effect of root canal irrigants on dentin: a focused review

Rath, Priti Pragati,Yiu, Cynthia Kar Yung,Matinlinna, Jukka Pekka,Kishen, Anil,Neelakantan, Prasanna The Korean Academy of Conservative Dentistry 2020 Restorative Dentistry & Endodontics Vol.45 No.3

Despite the vast literature on the effects of root canal irrigants on the dentin characteristics, the precise effects of clinically relevant irrigation sequences remain unclear. In this review, we systematically dissect the role of different sequential irrigation approaches that are used in clinical endodontics. Using a systematic search strategy, we attempt to answer the question: 'Which irrigating sequence has the most deleterious effects on dentin structure and properties?' The effect of irrigants on the dentin composition and mechanical properties have been reviewed. A wide variety of concentrations, duration and techniques have been employed to characterize the effects of chemicals on dentin properties, thus making it impossible to draw guidelines or recommendations of irrigant sequences to be followed clinically. It was apparent that all the studied irrigation sequences potentially result in some deleterious effects on dentin such as decrease in the flexural strength, microhardness, modulus of elasticity and inorganic content and organic-inorganic ratio of the dentin. However, the literature still lacks comprehensive investigations to compare the deleterious effect of different irrigation sequences, using a wide variety of qualitative and quantitative methods. Such investigations are essential to make clinical recommendations and strategize efforts to minimize chemically-induced damage to dentin characteristics.

Chelating and antibacterial properties of chitosan nanoparticles on dentin

Aldo del Carpio-Perochena,Clovis Monteiro Bramante,Marco Antonio Hungaro Duarte,Marcia Regina de Moura,Fauze Ahmad Aouada,Anil Kishen 대한치과보존학회 2015 Restorative Dentistry & Endodontics Vol.40 No.3

Objectives: The use of chitosan nanoparticles (CNPs) in endodontics is of interest due to their antibiofilm properties. This study was to investigate the ability of bioactive CNPs to remove the smear layer and inhibit bacterial recolonization on dentin. Materials and Methods: One hundred bovine dentin sections were divided into five groups (n = 20 per group) according to the treatment. The irrigating solutions used were 2.5% sodium hypochlorite (NaOCl) for 20 min, 17% ethylenediaminetetraacetic acid (EDTA) for 3 min and 1.29 mg/mL CNPs for 3 min. The samples were irrigated with either distilled water (control), NaOCl, NaOCl-EDTA, NaOCl-EDTA-CNPs or NaOCl-CNPs. After the treatment, half of the samples (n = 50) were used to assess the chelating effect of the solutions using portable scanning electronic microscopy, while the other half (n = 50) were infected intra-orally to examine the post-treatment bacterial biofilm forming capacity. The biovolume and cellular viability of the biofilms were analysed under confocal laser scanning microscopy. The Kappa test was performed for examiner calibration, and the non-parametric Kruskal-Wallis and Dunn tests (p < 0.05) were used for comparisons among the groups. Results: The smear layer was significantly reduced in all of the groups except the control and NaOCl groups (p < 0.05). The CNPstreated samples were able to resist biofilm formation significantly better than other treatment groups (p < 0.05). Conclusions: CNPs could be used as a final irrigant during root canal treatment with the dual benefit of removing the smear layer and inhibiting bacterial recolonization on root dentin.

Chelating and antibacterial properties of chitosan nanoparticles on dentin

del Carpio-Perochena, Aldo,Bramante, Clovis Monteiro,Duarte, Marco Antonio Hungaro,de Moura, Marcia Regina,Aouada, Fauze Ahmad,Kishen, Anil The Korean Academy of Conservative Dentistry 2015 Restorative Dentistry & Endodontics Vol.40 No.3

Objectives: The use of chitosan nanoparticles (CNPs) in endodontics is of interest due to their antibiofilm properties. This study was to investigate the ability of bioactive CNPs to remove the smear layer and inhibit bacterial recolonization on dentin. Materials and Methods: One hundred bovine dentin sections were divided into five groups (n = 20 per group) according to the treatment. The irrigating solutions used were 2.5% sodium hypochlorite (NaOCl) for 20 min, 17% ethylenediaminetetraacetic acid (EDTA) for 3 min and 1.29 mg/mL CNPs for 3 min. The samples were irrigated with either distilled water (control), NaOCl, NaOCl-EDTA, NaOCl-EDTA-CNPs or NaOCl-CNPs. After the treatment, half of the samples (n = 50) were used to assess the chelating effect of the solutions using portable scanning electronic microscopy, while the other half (n = 50) were infected intra-orally to examine the post-treatment bacterial biofilm forming capacity. The biovolume and cellular viability of the biofilms were analysed under confocal laser scanning microscopy. The Kappa test was performed for examiner calibration, and the non-parametric Kruskal-Wallis and Dunn tests (p < 0.05) were used for comparisons among the groups. Results: The smear layer was significantly reduced in all of the groups except the control and NaOCl groups (p < 0.05). The CNPs-treated samples were able to resist biofilm formation significantly better than other treatment groups (p < 0.05). Conclusions: CNPs could be used as a final irrigant during root canal treatment with the dual benefit of removing the smear layer and inhibiting bacterial recolonization on root dentin.