Evaluation of the effects of oral rinses on the retention and surface topography of the ball attachment complex for implant overdentures

Dhanapriya Gopalakrishnan(Dhanapriya Gopalakrishnan ),Azhagarasan Nagarasampatti Sivaprakasam(Azhagarasan Nagarasampatti Sivaprakasam ),Vidhya Jeyapalan(Vidhya Jeyapalan ),Jayakrishnakumar Sampathkuma 대한치과이식임플란트학회 2023 The Korean Academy of Implant Dentistry Vol.42 No.1

Purpose: To evaluate the effect of two different oral rinses on the retention and surface topography of ball attachments for implant overdentures. Materials and Methods: Thirty metal housing and the nylon cap inserts (Adin, Israel) were placed on the master block and the attachment assemblies were transferred to prosthetic blocks using the direct pickup technique. Group I had ten test samples immersed in water, Group II had ten test samples immersed in Listerine® Cool Mint®(J&J, India), Group III had ten test samples immersed in Colgate Vedshakthi oil-based herbal oral rinse (Colgate-Palmolive, India). The retention force was tested at baseline and after immersion in the respective oral rinses at 360 cycles (simulating 3 months) and 720 cycles (simulating 6 months) of clinical use, using a universal testing machine (Shimadzu, AG-X plus 50KN, Europe, GmBH) at a crosshead speed of 50 mm/min. The data was analyzed using the repeated measures ANOVA test, one-way ANOVA test, and post hoc analysis (SPSS23, Munich, Germany). The surface topography was assessed initially and subsequently after immersion in the oral rinses after 360 and 720 insertion-removal cycles using a stereomicroscope (Leica M205C, Germany). Results: At 360 cycles, the mean retention force (MRF) exhibited by Group I was higher than that of Group III and this difference was significant. The MRF of Group II was also significantly higher than Group III. At 720 cycles, the MRF exhibited by Group I was higher than that of Group II and the difference was significant. Also, the MRF of Group I was significantly higher than that of Group III, and the MRF of Group II was significantly higher than that of the Group III test samples. In Group I, the percentage loss in the MRF at the end of 360 and 720 cycles was 4.96% and 6.37%, respectively. In Group II, it was 6.82% and 9.41%, respectively, and in Group III it was 14.75% and. 16.60%, respectively. Conclusions: Colgate Vedshakti caused the highest surface topographic changes. This corroborates with the lower retention obtained, followed by Listerine® Cool Mint®, and the least changes were observed for samples immersed in water, which corroborates with the greater retention obtained in the study.

Modified Chilled Coil Model Development and Application to Turbine Inlet Air Cooling

Gopalakrishnan Anand,Ellen Makar 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.1

A Turbine Inlet Air Conditioning (TIAC) system can chill the inlet air of the turbine to maintain maximum turbine performance at all ambient temperatures. However, turbine characteristics, performance guarantees and bell-mouth icing considerations require accurate prediction of the chilling coil performance over a wide range of operating conditions. A modified wet-surface model (MWSM) is developed to more accurately predict the chilling coil performance. The higher accuracy of the model is demonstrated by applying the model to simulate performance data of two different coils. The data covered a wide range of operating conditions with ambient temperature vary from 43.3∘C to 9.7 ∘ C dry bulb and 27.2 ∘C to 6.1 ∘C wet bulb. The turbine flow rate varies from 100% to 43% with chilled air temperature in the range of 3.3–14 ∘ C and chilling load variation of 100% to 5%. The chilled water flow rate varies from 100% to 32% with supply glycol-water temperature in the range of −2.2–6.1 ∘ C. The MWSM uses 11 empirical parameters evaluated from the coil performance data and is able to correlate the data with an adjusted coefficient of determination (R 2 adjRadj2) of over 99%. The higher accuracy of the modified model enables the development of a more robust controls strategy required to maintain the inlet air temperature at the set point with varying ambient temperatures and chilling load conditions. The model can also be applied to other chilling and dehumidification applications especially those experiencing wide variations in operating conditions and load or those requiring close control of the chilling and dehumidification process.

5,7-Diaryl-4,4-dimethyl-4,5,6,7-tetrahydropyridino [3,4-d]-1,2,3-selenadiazoles의 손쉬운 One-pot 합성

Gopalakrishnan, M.,Thanusu, J.,Kanagarajan, V. 대한화학회 2008 대한화학회지 Vol.52 No.1

조사 아래 불균일촉매 NaHSO4.SiO2의 존재하에서 5,7-diaryl-4,4-dimethyl-4,5,6,7-tetrahydropyridino [3,4-d]-1,2,3-selenadiazoles의 one-pot. A simple synthetic strategy is described for one-pot synthesis of 5,7-diaryl-4,4-dimethyl-4,5,6,7-tetrahydropyridino[3,4-d]-1,2,3-selenadiazoles (11-15) in the presence of NaHSO4.SiO2 as a heterogeneous catalyst in dry media under microwave irradiation.Key words: One-pot synthesis, 3,3-Dimethyl-2,6-diarylpiperidin-4-one; 1,2,3-Selenadiazoles; Selenium dioxide; NaHSO4.SiO2 Heterogeneous catalyst.

Anaerobic Digestion of Food Waste: Meshophilic vs Thermophilic Regime

( Gopalakrishnan Kumar ),( Hyun Jun Ju ),( Sang-hyuon Kim ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 심포지움 Vol.2014 No.1

Food waste generation around the globe is a serious issue that needs to be concerned. Developing suitable treatment methods along with the generation of energy (methane) is a common practice to make the world sustainable. In this study, methane generation of food waste has been reported in mesophilic and thermophilic regimes at various hydraulic retention times (HRT) and organic loading rates (OLR). Different reactor configurations were used for mesophilic and thermophilic operations. The influent concentrations were ranged from 30 to 110 g COD/L corresponding to the OLR of 1.0 to 5.5 Kg COD/m³*d, respectively. Three different HRTs evaluated were 30, 24 and 20 days in both regimes. The production performances showed that an increase in biogas and methane production while increasing the substrate concentration in both temperatures. However, better results were obtained from thermophilic temperature due to the hydrolysis of the complex polymers at higher temperatures. Peak methane productivities attained at mesophilic and thermophilic regimes were 1.30 and 0.95 m³/m³*d, respectively. However, the maximal yield achieved were at 50 g CODL and at HRT of 24 d in both the cases and the values were 264 and 221 m3/ton COD, respectively. The COD removal rate was ranged from 54-86% in case of thermophilic and 61-87% in case of mesophilic, respectively. The results of this study could aid in the development of sustainable methane production technologies using food waste as carbon source.

Isolation, Purification, and Characterization of Haloalkaline Xylanase from a Marine Bacillus pumilus Strain, GESF-1

Gopalakrishnan Menon,Kalpana Mody,Jitendra Keshri 한국생물공학회 2010 Biotechnology and Bioprocess Engineering Vol.15 No.6

A haloalkalitolerant xylanase-producing Bacillus pumilus strain, GESF1 was isolated from an experimental salt farm of CSMCRI. Birch wood xylan and xylose induced maximum xylanase production with considerable activity seen in wheat straw and no activity at all with caboxymethyl cellulose (CMC). A three step purification yielded 21.21-fold purification with a specific activity of 112.42 U/mg protein (unit expressed as μmole of xylose released per min). Xylanase produced showed an optimum activity at pH 8.0, with approximately 50 and 30% relative activity at a pH 6.0 and 10.0, respectively. The temperature optimum was 40°C and kinetic properties such as Km and Vmax were 5.3 mg/mL and 0.42 μmol/min/mL (6593.4μmol/min/mg protein). Xylanase activity (160 ~ 120%)was considerably enhanced in 2.5 to 7.5% NaCl with 87and 73% retention of activity in 10 and 15% of NaCl. Enzyme activity was enhanced by Ca2+, Mn2+, Mg2+, and Na+ but strongly inhibited by heavy metals such as Hg2+,Fe3+, Cu2+, Cd2+, and Zn2+. Organic reagents such as β-Mercaptoethanol enhanced xylanase activity whereas EDTA strongly inhibited its activity. Xylanase, purified from the Bacillus pumilus strain, GESF1 could have potential biotechnological applications.

Effect of Marsilea quadrifolia (L.) on carbohydrate metabolic enzymes in alloxan induced diabetic rats

Gopalakrishnan Karikalan,Udayakumar Rajangam 한국약제학회 2018 Journal of Pharmaceutical Investigation Vol.48 No.4

Marsilea quadrifolia is an indigenous medicinal plant and it has a folk reputation in central and southern India as hypoglycemic agent. The present study was aimed to evaluate the effect of methanolic leaf and stem extracts of Marsilea quadrifolia on carbohydrate metabolic enzymes in alloxan induced diabetic rats. In this study, the blood glucose level was increased in alloxan induced diabetic rats when compared to normal control rats. The decreased level of blood glucose was observed in diabetic rats treated with leaf and stem of M. quadrifolia. The activities of hexokinase, pyruvate kinase, lactate dehydrogenase, glucose-6-phosphatase, fructose 1,6-bisphosphatase and glucose-6-phosphate dehydrogenase in liver and kidney and glycogen content, glycogen synthase and glycogen phosphorylase in liver were analysed. Glibenclamide was used as a reference drug in the present investigation. The activities of hexokinase, pyruvate kinase and glucose- 6-phosphate dehydrogenase were significantly decreased and the activities of lactate dehydrogenase, glucose-6-phosphatase and fructose 1,6-bisphosphatase were significantly increased in liver and kidney of alloxan induced diabetic rats when compared to normal control rats. Oral administration of methanolic leaf and stem extracts of M. quadrifolia (300 mg/kg bw) to diabetic rats for 45 days showed significantly reverted levels of above mentioned enzymes. The levels of glycogen and glycogen synthase in liver were significantly decreased and the glycogen phosphorylase activity was significantly increased in diabetic rats when compared to normal control rats. The diabetic rats treated with leaf and stem extracts of M. quadrifolia reverted the levels of glycogen, glycogen synthase and glycogen phosphorylase to near normal. The present study clearly indicates that the methanolic leaf and stem extracts of M. quadrifolia possesses potent antidiabetic activity.

A Convenient One-Pot Biginelli Reaction Catalyzed by Y(OAc)3: An Improved Protocol for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and Their Sulfur Analogues

Gopalakrishnan Aridoss,Yeon Tae Jeong 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.4

Yttrium(III) acetate hydrate-catalyzed novel synthesis of 3,4-dihydropyrimidin-2(1H)-(thio)one derivatives was achieved through one-pot three-component condensation of diversified aldehydes, β-ketoesters and urea or N-methylurea or thiourea with a molar ratio of 1:1:1.4. In comparison to the classical Biginelli approach, this catalytic method has the advantages of short reaction time and improved product yield.

Characterization of Ammonia-Water Absorption Chiller and Application

Gopalakrishnan Anand,Donald C Erickson,Ellen Makar 대한설비공학회 2018 International Journal Of Air-Conditioning and Refr Vol.26 No.4

Ammonia-absorption refrigeration units (AARUS) can supply subfreezing refrigeration for many industrial applications. Such units are usually driven by waste heat or renewable energy at relatively low temperatures. The performance of the chiller is highly dependent on the temperatures of the driving heat, the chilling load, and the cooling water. In this paper, the performance of an advanced industrial-scale ammonia-absorption unit is modeled over a representative operating range. The performance is then characterized by a set of simple equations incorporating the three external temperatures. This simple model helps to evaluate potential applications, predict performance, and perform initial optimization. Case studies are presented highlighting the application of the model.

Chilled Coil Control and Field Performance for Turbine Inlet Air Chilling

Gopalakrishnan Anand,Ellen Makar 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.2

Ambient conditions greatly affect the combustion turbine performance. The Absorption Refrigeration Cycle Turbine Inlet Chilling (ARCTIC) system can chill the inlet air of the turbine to maintain optimum performance at all ambient temperatures. However, turbine characteristics, bell-mouth icing concerns, economics and performance guarantees require maintaining the inlet air temperature within a narrow range throughout the year. These considerations require strict control of the Turbine Inlet Air Chilling (TIAC) coil performance over a wide range of operating conditions. This paper describes the field performance and control of the chilling coil for a Mars 100 turbine. The controls logic had been developed from previously published empirical model of the chilling coil and model of the chilling loop performance at the various ambient conditions. Since commissioning at the end of summer 2020, the ARCTIC has provided inlet air chilling over a range of ambient conditions. Typically, the inlet air is maintained at 7.2∘C (45∘F) by controlling the TIAC chilled water flow rate and temperature. On cooler days, if the inlet air temperature drops to 5.6∘C (42∘F) the chilled water pump turns OFF automatically to prevent bell-mouth icing. Thus, the chiller accommodates chilling load variations down to zero load. On colder days, the ARCTIC continues operating till the ambient temperature drops below 1.7∘C (35∘F) and then turns OFF. The chiller turns back ON when the 8 h average inlet air temperature exceeds 10∘C (50∘F). These parameters can be adjusted remotely by the operator and help maintain performance guarantees while minimizing chiller cycling. Quasi-steady state data were analyzed to quantify the chilling load and coil performance over a range of operating conditions.

Chilled Coil Performance Control and Application to Turbine Inlet Air Cooling

Gopalakrishnan Anand,Ellen Makar 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.2

The Absorption Refrigeration Cycle Turbine Inlet Conditioning (ARCTIC) system can chill the inlet air of the turbine to maintain optimum turbine performance at all ambient temperatures. However, turbine characteristics and bell-mouth icing concerns impose a minimum temperature limitation on the chilled air. Performance guarantees may also require maintaining the inlet air temperature within a narrow range throughout the year. These considerations require accurate prediction of the chilling coil performance over a wide range of operating conditions and the development of a robust controls strategy. A modified wet-surface model is used to model the chilling coil performance. The application of the model to a 2110kW (600 RT) ARCTIC providing inlet air chilling for a MARS 100 turbine is considered. A control strategy is developed to maintain the inlet air temperature at the desired set point with varying ambient temperatures and chilling loads. The TIAC controls help maintain the inlet air temperature at 7.22∘C to maximize turbine capacity and efficiency during most of the hot/warm days and accommodates 100% turndown. Additional safety measures are incorporated to prevent bell-mouth icing.