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( Remi A. Kessler ),( Tomas Garzon-muvdi ),( Eileen Kim ),( Murugappan Ramanathan Jr ),( Michael Lim ) 대한뇌종양학회 대한신경종양학회 2019 Brain Tumor Research and Treatment Vol.7 No.1
Background One of the most frequent complications after endoscopic endonasal approach (EEA) for resection of pituitary tumors is cerebrospinal fluid (CSF) leaks. With the introduction of the pedicled nasoseptal flap, the reconstruction of the skull base has improved significantly resulting in a decrease in the occurrence of persistent CSF leaks. We present our experience utilizing the pedicled nasoseptal flap technique after EEA for reconstruction of the skull base in cases where CSF leak was detected. Methods Data for patients undergoing EEA for pituitary tumors was retrospectively reviewed. These included demographic, clinical, operative, radiographic, and pathological information. Incidence of post-operative complications and CSF leaks were recorded. Descriptive statistical analysis was performed. Results Between 2008 and 2015, 67 patients and 69 hospital admissions with pituitary tumors underwent a nasoseptal flap to reconstruct a skull base defect at Johns Hopkins Hospital. The mean age at surgery was 54.5±14.2 years. Fifty-two percent of patients were male. Forty-six percent of patients were white, 33% African-American, and 12% belonged to other racial groups. There was an intraoperative CSF leak in 39% of patients. Seventy percent of patients with an intraoperative CSF leak had a nasoseptal flap reconstruction of the skull base. There were zero postoperative CSF leaks. Conclusion With the introduction of the pedicled nasoseptal flap for reconstruction of the skull base after EEA for resection of pituitary adenomas, the incidence of postoperative CSF leaks has decreased significantly. In this retrospective analysis, we demonstrate the effectiveness of the use of nasoseptal flap in repairing CSF leak after EEA.
탄소나노튜브 보강 바이오러버의 기계적 및 열분석 특성 평가
김찬규,윤성호,Michael Kessler 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11
본 연구에서는 콩기름을 이용한 바이오러버 제작방법을 소개하고 탄소나노튜브가 보강된 경우의 기계적 및 열분석 특성을 평가하였다. 바이오러버는 양이온 중합법을 통해 제작되며 탄소나노튜브는 Bath형 초음파 분산기를 사용하여 분산시켰다. 인장시험을 통해 바이오러버의 인장강성, 인장강도, 파단변형률 등의 기계적 특성을 평가하였으며 DMA를 통해 저장탄성계수, 유리전이온도 등의 열분석 특성을 평가하였다. 바이오러버에 함유된 탄소나노튜브의 분산정도는 FE-SEM를 적용하여 관찰하였다. 연구결과에 따르면 탄소나노튜브의 함유량이 많을수록 바이오러버의 기계적 특성은 향상되며 유리전이온도와 가교 밀도는 높아지며 초음파 분산기를 통해 탄소나노튜브를 균일하게 분산시킬 수 있음을 알 수 있었다. In this research, manufacturing process of bio-rubber using soybean oil is introduced and the mechanical and thermal analysis characteristics of its CNT embedded bio-rubber are evaluated. The bio-rubber is produced through cationic copolymerization, and the Bath-type ultrasonic sonicator is used to disperse CNT in the bio-rubber. Tensile tests are conducted to evaluate the mechanical properties such as tensile strength, tensile modulus and failure strain. The thermal analysis properties such as storage modulus and glass transition temperature are evaluated using the DMA. CNT dispersion within the bio-rubber is examined using the FE-SEM. According to the results, enhancement of mechanical properties, increase in glass transition temperature and crosslinking density are present with the increase in CNT amount. The ultrasonic sonicator is also able to evenly disperse CNT within the bio-rubber.
Xing Liu,이종근,Michael R. Kessler 한국고분자학회 2011 Macromolecular Research Vol.19 No.10
Norbornene-based healing agent candidates, 5-ethylidene-2-norbornene (ENB) and ENB with a custom crosslinker, were prepared into uniform microspheres using a Shirasu porous glass (SPG) emulsification technique,and microencapsulated by in situ polymerization of melamine-urea-formaldehyde (MUF). The resulting microcapsules were observed by optical and scanning electron microscopy for their morphology, outer and inner surface and shell thickness. Particle size analysis revealed a more uniform size distribution with a mean diameter of 40 μm than a conventional method using a mechanical impeller. The thermal and mechanical properties of the microcapsules were also examined by considering fabrication of self-healing composites.
Burschka, Julian,Dualeh, Amalie,Kessler, Florian,Baranoff, Etienne,Cevey-Ha, Ngoc-Lê,Yi, Chenyi,Nazeeruddin, Mohammad K.,Grä,tzel, Michael American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.45
<P>Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm<SUP>–2</SUP>). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-45/ja207367t/production/images/medium/ja-2011-07367t_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207367t'>ACS Electronic Supporting Info</A></P>
A new generation of platinum and iodine free efficient dye-sensitized solar cells
Ahmad, Shahzada,Bessho, Takeru,Kessler, Florian,Baranoff, Etienne,Frey, Julien,Yi, Chenyi,Grä,tzel, Michael,Nazeeruddin, Mohammad K. The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.30
<P>We report a series of cobalt complexes with various polypyridyl ligands, where the oxidation potential is tuned from 0.17 to 0.34 V <I>vs.</I> ferrocene. The highest occupied molecular orbitals (HOMO) of the cobalt complexes were stabilized by adding electron acceptor groups on pyridyl or replacing pyridyl by pyrazole. These complexes are then used as one-electron redox mediators in dye sensitized solar cells (DSSCs) together with polymer based cathode resulting in an excellent performance. The performance of DSSCs using the molecularly engineered cobalt redox shuttle and poly(3,4-alkylthiophenes) based cathode is better than the triiodide/iodide redox shuttle with platinized cathode. The use of high surface area poly(3,4-propylenedioxythiophene) based nanoporous layers allows higher catalytic activity thus minimizing the electrode–electrolyte interface issues.</P> <P>Graphic Abstract</P><P>Molecularly engineered cobalt redox shuttles with tunable oxidation potential, when employed with polymer cathode are new work horse for DSSCs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp41611e'> </P>