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- 저자 : P. Meredith (검색결과 4 건)
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Formation of mesostructured titania thin films using isopropoxide precursors
G.Q.M. Lu,I. Kartini,P. Meredith,Diniz da Costa,J. D. Riches 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
Mesostructured titania thin lms were prepared by an evaporation-induced self-assembly process. The highly acidic sol pre-cursors contained titanium(IV) tetraisopropoxide (TTIP) as a titanium source, a tri-block copolymer Pluronic P123 as a template,and acetylacetonate and HCl as hydrolysis inhibitors. Characteristics of the resultant titania thin lms were studied using X-raydiraction (XRD) analysis, N2-adsorption/desorption analysis, and transmission electron microscopy (TEM). XRD and TEMinvestigations on the as-synthesised lms revealed the appearance of cubic-like, pseudohexagonal, and lamellar mesophases;depending on the amount of water in the sols of lm precursors. Template removal by a calcination process yields high surface area(320360 m2/g) mesoporous materials with crystalline anatase frameworks. Water content also inuences the degree of anatasecrystallinity of the calcined lms. Higher water content resulted in improved anatase crystallinity. These nanostructured materialsare of interest for photocatalysts, photoelectrochemical solar cells and other photonic devices.
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STRINGENT LIMITS ON THE POLARIZED SUBMILLIMETER EMISSION FROM PROTOPLANETARY DISKS
Hughes, A. Meredith,Wilner, David J.,Cho, Jungyeon,Marrone, Daniel P.,Lazarian, Alexandre,Andrews, Sean M.,Rao, Ramprasad IOP Publishing 2009 The Astrophysical journal Vol.704 No.2
<P>We present arcsecond-resolution Submillimeter Array (SMA) polarimetric observations of the 880 mu m continuum emission from the protoplanetary disks around two nearby stars, HD 163296 and TW Hydrae. Although previous observations and theoretical work have suggested that a 2%-3% polarization fraction should be common for the millimeter continuum emission from such disks, we detect no polarized continuum emission above a 3 sigma upper limit of 7 mJy in each arcsecond-scale beam, or <1% in integrated continuum emission. We compare the SMA upper limits with the predictions from the exploratory Cho & Lazarian model of polarized emission from T Tauri disks threaded by toroidal magnetic fields, and rule out their fiducial model at the similar to 10 sigma level. We explore some potential causes for this discrepancy, focusing on model parameters that describe the shape, magnetic field alignment, and size distribution of grains in the disk. We also investigate related effects like the magnetic field strength and geometry, scattering off of large grains, and the efficiency of grain alignment, including recent advances in grain alignment theory, which are not considered in the fiducial model. We discuss the impact each parameter would have on the data and determine that the suppression of polarized emission plausibly arises from rounding of large grains, reduced efficiency of grain alignment with the magnetic field, and/or some degree of magnetic field tangling ( perhaps due to turbulence). A poloidal magnetic field geometry could also reduce the polarization signal, particularly for a face-on viewing geometry like the TW Hya disk. The data provided here offer the most stringent limits to-date on the polarized millimeter-wavelength emission from disks around young stars.</P>
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Lucie F Calderon,Meredith Kline,Marc Hersh,Kevin P Shah,Suprateek Kundu,Andrew Tkaczuk,Nancy McColloch,Anand S Jain 대한소화기 기능성질환·운동학회 2022 Journal of Neurogastroenterology and Motility (JNM Vol.28 No.3
Background/AimsThe mechanism via which supra-esophageal symptoms are generated is unclear. We assessed upper esophageal sphincter (UES) function in novel fashion using functional lumen imaging probe (FLIP) topography. We hypothesize that symptoms related to aspiration of esophageal contents may be associated with a more distensible UES. MethodsFLIP and reflux symptom index score data from patients undergoing diagnostic evaluation for an esophageal complaint over a 10-month period were analyzed retrospectively. UES distensibility on FLIP was studied at 40-70 mL volumes with in-depth analysis at 50 and 60 mL. Symptoms were compared between patients with low, middle, and high UES-distensibility index (UES-DI). Receiver-operating characteristic analysis was performed to determine associations between the UES-DI and individual reflux symptom index symptom item scores. ResultsOne hundred and eleven subjects were included. Overall, the associations between UES-DI and symptoms that could be related to supra-esophageal aspiration were strongest at the 50 mL FLIP volume. Choking item score was highest in the high UES-DI group (2.8) vs 1.4 (P < 0.001) in the middle UES-DI and 1.1 (P = 0.004) in the low UES-DI groups. Similarly, the cough item score was highest in the high UES-DI group (2.7) vs 1.5 (P = 0.009) and 0.9 (P = 0.002) groups. ConclusionA higher UES-DI measures defective barrier function which could may be the main pathophysiology that generates supra-esophageal symptoms.
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A PbS quantum-cube: conducting polymer composite for photovoltaic applications
A. A. R. Watt,P. Meredith,J. D. Riches,S. Atkinson,H. Rubinsztein-Dunlop 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
We have developed a new non-polar synthesis for lead sulde (PbS) ‘‘quantum-cubes’’ in the conjugated polymer poly-2-methoxy,5-(2-ethyl-hexyloxy-p-phenylenevinylene) MEH-PPV. The conducting polymer acts to template and control the quantum-cube growth. Transmission electron microscopy of the composites has shown a bimodal distribution of cube sizes between 5 and 15nm is produced with broad optical absorption from 300 to 650 nm. Photoluminescence suggests electronic coupling between thecubes and the conducting polymer matrix. The synthesis and initial characterization are presented in this paper.
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