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RISS 인기검색어
- 검색키워드
- 저자 : Roshan George (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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A biopolymer mediated efficient synthesis of cyclic carbonates from epoxides and carbon dioxide
Roshan, Kuruppathparambil Roshith,Mathai, George,Kim, Juntae,Tharun, Jose,Park, Gyung-Ah,Park, Dae-Won The Royal Society of Chemistry 2012 Green chemistry Vol.14 No.10
<P>A promising application of carboxymethyl cellulose (CMC), which is a congener of the cellulose family, as a supporting material for a variety of imidazolium based ionic liquid catalysts in the chemical fixation of CO<SUB>2</SUB> has been studied here. The ionic liquids immobilized on the carboxymethyl cellulose (CMIL) showed high catalytic activity and selectivity in the cycloaddition of carbon dioxide with propylene oxide (PO) resulting in propylene carbonate (PC) under mild and solvent free conditions. A new pathway was proposed based on the density functional theory (DFT) calculations performed at the B3LYP/6-31G (d,p) level, where the carboxyl and hydroxyl moieties on the CMC were found to act synergistically with the halide ions to eventuate in the cycloaddition reaction. The carboxyl group entities on the carboxymethyl cellulose support supposedly stabilize the product complex <I>via</I> strong hydrogen bonds, thereby promoting the reaction. The catalyst system also displayed good reusability.</P> <P>Graphic Abstract</P><P>A DFT assisted study on the co-operative role of carboxyl groups on carboxymethyl cellulose in cycloaddition of CO<SUB>2</SUB> with epoxides. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2gc35942a'> </P>
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Varghese George,Thomas Roshan Marie 대한비과학회 2022 Journal of rhinology Vol.29 No.1
The transseptal approach to the maxillary sinus has been described for resection of extensive tumours of the nose and paranasal sinuses. We describe a modification of this method in a patient diagnosed with inverted papilloma for which he had undergone two previous operations. This method provides complete access to the maxillary sinus, particularly the anterior wall, to provide adequate reach and ensure complete removal of tumours. We describe a technique modifying the existing transseptal approach used as an adjunct to prelacrimal recess approach, wherein a hemitransfixation incision placed in the contralateral nasal cavity along the septum provides access to the maxillary sinus with angled instruments. This modified transseptal approach provided better reach and access to the maxillary sinus. Postoperatively, there was no evidence of septal scarring or perforation and no evidence of lesion recurrence. Our technique is an easy modification to the transseptal approach that is a useful tool to access hidden areas of the maxillary sinus without associated morbidity. The transseptal approach to the maxillary sinus has been described for resection of extensive tumours of the nose and paranasal sinuses. We describe a modification of this method in a patient diagnosed with inverted papilloma for which he had undergone two previous operations. This method provides complete access to the maxillary sinus, particularly the anterior wall, to provide adequate reach and ensure complete removal of tumours. We describe a technique modifying the existing transseptal approach used as an adjunct to prelacrimal recess approach, wherein a hemitransfixation incision placed in the contralateral nasal cavity along the septum provides access to the maxillary sinus with angled instruments. This modified transseptal approach provided better reach and access to the maxillary sinus. Postoperatively, there was no evidence of septal scarring or perforation and no evidence of lesion recurrence. Our technique is an easy modification to the transseptal approach that is a useful tool to access hidden areas of the maxillary sinus without associated morbidity.
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Simple and efficient synthesis of cyclic carbonates using quaternized glycine as a green catalyst
Tharun, Jose,Mathai, George,Roshan, Roshith,Kathalikkattil, Amal Cherian,Bomi, Kim,Park, Dae-Won The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.23
<P>Microwave-assisted quaternization of glycine (GLY) resulted in the synthesis of an efficient catalyst, quaternized glycine (QGLY), for the solventless synthesis of cyclic carbonates from epoxides and CO<SUB>2</SUB> under mild reaction conditions. Density functional theory was used to simulate the synergistic influence of the COOH group and the halide ion of QGLY in enhancing the catalytic activity.</P> <P>Graphic Abstract</P><P>Microwave-assisted synthesis of quaternized amino acid QGLY, an efficient catalyst for the solventless conversion of CO<SUB>2</SUB> to cyclic carbonates. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp51158h'> </P>
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Microwave-assisted synthesis of cyclic carbonates by a formic acid/KI catalytic system
Tharun, Jose,Mathai, George,Kathalikkattil, Amal Cherian,Roshan, Roshith,Kwak, Joo-Young,Park, Dae-Won The Royal Society of Chemistry 2013 Green chemistry Vol.15 No.6
<P>An environment-friendly synthesis of cyclic carbonates from CO<SUB>2</SUB> and epoxides with a HCOOH/KI catalytic system was performed in a microwave reactor. Various epoxide substrates were subjected to microwave irradiated cycloaddition using a HCOOH/KI catalyst. The effects of reaction parameters like catalyst composition, microwave power, CO<SUB>2</SUB> pressure, and reaction time have been investigated. The synergistic influence of the COOH/KI catalyst in the reaction has been compared with that of an OH/KI system and was theoretically simulated using density functional theory.</P> <P>Graphic Abstract</P><P>An environment-friendly synthesis of cyclic carbonates from CO<SUB>2</SUB> and epoxides with a HCOOH/KI catalytic system was performed in a microwave reactor. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3gc40729b'> </P>
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COVID-19 Rapid Antigen Test: Role in Screening Prior to Gastrointestinal Endoscopy
Ashok Dalal,Ujjwal Sonika,Manish Kumar,Roshan George,Ajay Kumar,Siddharth Srivastava,Sanjeev Sachdeva,Barjesh Chander Sharma 대한소화기내시경학회 2021 Clinical Endoscopy Vol.54 No.4
Background/Aims: The severe acute respiratory syndrome coronavirus 2 pandemic has affected the gastrointestinal (GI) endoscopyunits globally owing to the risk of transmission. We present our data on the use of rapid antigen test (RAT) as a screening tool priorto endoscopy to prevent the transmission of coronavirus disease (COVID-19). Methods: This study was a retrospective analysis of patients who underwent any GI endoscopic procedure from July 2020 to October2020 at a tertiary referral center in New Delhi, India. All patients underwent screening for COVID-19 using RAT, and endoscopywas performed only when the RAT was negative. The data are presented as numbers and percentages. Results: A total of 3,002 endoscopic procedures were performed during the study period. Only one endoscopic procedure wasperformed in a COVID-19 positive patient. A total of 53 healthcare workers were involved in conducting these procedures. Only2 healthcare workers (3.8%) were diagnosed COVID-19 positive, presumably due to community-acquired infection, during thisperiod. Conclusions: The COVID-19 RAT is easily usable as a simple screening tool prior to GI endoscopy during the COVID-19 pandemic.
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