5,553 research outputs found
Development of Novel Fluorine-18 Labeled PET Radioligands for Monoamine Oxidase B (MAO-B)
No full textMonoamine oxidases (MAO-A and MAO-B) are important enzymes regulating the levels of monoaminergic neurotransmitters. Selective and irreversible MAO-B inhibitors such as L-deprenyl and rasagiline are clinically used for the treatment of psychiatric and neurological disorders. Positron emission tomography (PET) is a noninvasive imaging technique which has been utilized to visualize the localization of MAO-B in monkey and human brain and thereby has potential for studying neurodegenerative diseases and epilepsy. This thesis deals with the synthesis and evaluation of novel fluorine-18 labeled PET radioligands for detection of MAO-B activity.
The present thesis demonstrates that nine fluorinated propargyl amines were synthesized and tested for inhibition of MAO-B. In order to label those compounds with fluorine-18 seven chloro-precursors and two sulphamidate-precursors were also synthesized by multi step organic synthesis. Radiolabeling of six chloro-precursors with fluorine-18 was accomplished by a one-step nucleophilic substitution reaction. Radiolabeling of two sulphamidate-precursors with fluorine-18 was performed in two steps, compromising a nucleophilic substitution followed by the removal of the protecting group. The incorporation yield of the fluorination reactions varied from 40- 70%. The radiochemical purity was >99% and the specific radioactivities were in a range of 190-240 GBq/μmol at the time of administration.
In vitro MAO inhibition and/or autoradiography (ARG) experiments demonstrated a high selectivity for MAO-B over MAO-A for five of the compounds namely [18F]fluorodeprenyl, [18F]fluororasagiline, [18F]fluoro-N,4-dimethyl-N-(prop-2-ynyl) pentan-2-amine, [18F]fluorodeprenyl-D2 and [18F]fluororasagiline-D2. All five compounds were examined by PET and showed a high initial brain uptake in known MAO-B rich regions in cynomolgus monkey. [18F]Fluorodeprenyl showed a kinetic behavior similar to [11C]deprenyl where its fast irreversible binding to the enzyme renders the distribution of this radioligand in tissue limited by blood flow rather than the MAO-B enzyme concentration. [18F]Fluororasagiline and [18F]fluoro-N,4-dimethyl-N-(prop-2-ynyl)pentan-2-amine showed continuous increase of the radioactivity throughout the PET measurement that might be an indication of a blood-brain barrier penetrating radiometabolite which might in turn complicate a reliable quantification. Only [18F]fluorodeprenyl-D2 and [18F]fluororasagiline-D2 showed fast wash-out from the brain and less accumulation in cortical and sub-cortical regions. Radiometabolite studies demonstrated that both deuterated analogues were more stable measured in monkey plasma when compared to the non-deuterated analogues.
These results together suggest that both [18F]fluorodeprenyl-D2 and [18F]fluororasagiline-D2 may be improved PET radioligands and potential molecular imaging biomarker candidates for PET studies in neuroinflammation and neurodegeneration, accompanied with astrocyte activation
Preparation and microstructure of MAO/CS composite coatings on Mg alloy
No full textMicro-arc oxidation (MAO)/chitosan (CS) composite coatings were fabricated via MAO processing and subsequent sealing with CS solution at different dipping times. The effect of dipping times on the surface morphologies, chemical compositions and corrosion resistance of the coatings was investigated in this study. The results indicated that the MAO coating was efficiently sealed by the CS film. The potentiodynamic polarization tests show that the MAO/CS coatings enhanced the corrosion resistance of the MAO coating. The corrosion resistance of MAO coating dipping in chitosan solution for three times was improved significantly compared to other composite coatings due to its fewer microcracks and greater thickness.</p
Bioactive MAO/CS composite coatings on Mg-Zn-Ca alloy for orthopedic applications
No full textMAO/CS composite coatings were generated on Mg-1.75Zn-0.56Ca alloy surface for protection and improving biocompatibility of Mg-Zn-Ca alloy in the physiological environment. The microstructure, surface analysis and corrosion resistance of samples were evaluated by scanning electronic microcopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in SBF solution. In addition, in vitro cell cytotoxicity test was performed by MTT tests. The findings of this work indicated that MAO/CS composite coatings were smooth and defect-free. The MAO/CS coatings retained a low degradation rate and the solution pH value at a moderate level (≤7.5) during immersion test. The corrosion resistance and cell proliferation were greatly enhanced by the composite coating. Furthermore, the different cell cytotoxicity on Mg alloy, MAO and MAO/CS coating was discussed.</p
PiLa-CS Professional Learning Community - Workshop 2 Resources
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from Workshop 2 of the PLC.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Translanguaging Pedagogy in CS Ed
No full textEpisode 3: Translanguaging pedagogy in CS Education
This video looks at how multilingual students already use translanguaging in their computer science classes and discusses how CS educators can further support them with translanguaging pedagogy, a framework that prompts teachers to consider their stance, design, and shifts.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgEpisode 3: Translanguaging pedagogy in CS Education
This video looks at how multilingual students already use translanguaging in their computer science classes and discusses how CS educators can further support them with translanguaging pedagogy, a framework that prompts teachers to consider their stance, design, and shifts.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgSponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Ethylene-bridged pseudo-C-s symmetric ansa-zirconocene complexes: synthesis, structures and propylene polymerization behavior
No full textThe ethylene-bridged pseudo-C-s symmetric ansa-zirconocene complexes, (1-fluorenyl-2-cyclopentadienylethane)zirconium dichloride (5b), were synthesized and their molecular structures have been determined by single crystal X-ray diffraction studies. The complex 5a is very active toward propylene polymerization in the presence of methylaluminoxane (MAO), affording polypropylene with good syndiotacticity. In comparison with the known syndiotactic polypropylene catalytic system iPr(fluorenyl)(cyclopentadienyl)ZrCl2/MAO 5a/MAO system is better in thermal stability, higher in activity and lower in syndiotacticity under the identical polymerization conditions. On the other hand, 5b/MAO system shows low activity and produces nearly atactic polypropylene with low molecular weight, which could be attributed to the increased electron density and steric bulkiness around the metal center. (C) 1998 Elsevier Science S.A. All rights reserved.Korea Science and Engineering Foundation
and the Korea Advanced Industrial Technolog
PiLa-CS Professional Learning Community - Design Journal Template
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from from the PLC for a Design Journal to act as a planing template for teachers.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
The optical properties of Cs(4)/PbBr(6)-CsPbBr(3) perovskite composites
No full textAlthough the optoelectronic applications of metal halide perovskites have been intensively investigated in recent years, the fundamental carrier dynamics of zero-dimensional (0D) Cs₄PbBr₆ perovskites has been relatively underexplored; in particular, the nature of the green fluorescence is highly debated. Nevertheless, the unique photophysical properties are of immense interest for a variety of potential applications. In this work, the green emission of the CsPbBr₃-Cs₄PbBr₆ perovskite composites is studied using temperature dependent photoluminescence (PL). The PL spectra at different temperatures simultaneously contain two sub-peaks (520 nm and 550 nm), which are ascribed to the emissions of the band-edge and the defect trapped exciton of CsPbBr₃. This finding will help to understand the controversial photoluminescence currently observed in different 0D Cs₄PbBr₆ perovskites.Zhixing Gan, Fei Zheng, Wenxin Mao, Chunhua Zhou, Weijian Chen, Udo Bach, Patrick Tapping, Tak W. Kee, Jeffrey A. Davis, Baohua Jia and Xiaoming We
Arizona Then and Now: Exploring Arizona's Five Cs Through Photography
No full textabstract: Arizona Then and Now: Exploring Arizona's Five Cs Through Photography is a photographic exploration of the evolution of Arizona's five Cs: cotton, copper, citrus, cattle, and climate. This project first looks to the past to see how these five elements shaped the state of Arizona. Photographs were taken across the valley of these elements, or lack thereof, discovering what Arizona has transformed into in the process. Each chapter of the book begins with a brief history of the element focused on in that chapter, followed by an analytical thought about the photographs taken and how the element has evolved. Each chapter shows two historical photographs followed by a series of photographs taken during the project that the author thought depicted what is seen today. The book ends on a final positive note about how the five Cs are not dead, but soon could be completely taken over. This project was a way for a non-art major to explore the state that she grew up while also challenging herself by more than just taking pictures. The photographs displayed in the book depict a sampling of what the author saw that is left of the five Cs
p53 overexpression and mutation in metaplastic carcinoma of the breast: genetic evidence for a monoclonal origin of both the carcinomatous and the heterogeneous sarcomatous components
No full text- …
