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Urbas AM, Thomas EL, Kriegs H, Fytas G, Penciu RS, Economou LN. Acoustic excitations in a self-assembled block copolymer photonic crystal. PHYSICAL REVIEW LETTERS 2003; 90:108302. [PMID: 12689040 DOI: 10.1103/physrevlett.90.108302] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2002] [Indexed: 05/24/2023]
Abstract
High resolution Brillouin light scattering can sensitively detect acoustic phonons in concentrated solutions of a high molecular weight poly(styrene-b-isoprene) symmetric copolymer in toluene. This block copolymer lamellar forming system also possesses a photonic stop band in the visible spectrum. Based on the low but finite contrast in mechanical properties between the styrene and isoprene components and taking into account the geometrical characteristics of the layered microstructure, we calculate the acoustic band structure and represent the observed acousticlike and opticlike phonons.
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Thomas EL, Bell JD. Influence of undersampling on magnetic resonance imaging measurements of intra-abdominal adipose tissue. Int J Obes (Lond) 2003; 27:211-8. [PMID: 12587001 DOI: 10.1038/sj.ijo.802229] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Single-slice magnetic resonance imaging (MRI) and computed tomography (CT) are finding increasing use as methods to estimate visceral fat content in human studies. To assess the validity of this approach, we have compared single- and multi-slice MRI methods for the measurement of intra-abdominal adipose tissue content. MEASUREMENTS Multi-slice whole-body MR images and single-slices at the level of L2-L3 and L4-L5 were obtained from 59 healthy female volunteers chosen to cover a wide range of body size, and from 17 healthy female volunteers before and after a 6-month exercise intervention. RESULTS Taking the group as a whole, significant correlation between multi-slice and single-slices was observed (L2-L3: r=0.56; P<0.01; L4-L5: r=0.76; P<0.01). However, the ranking of subjects according to their intra-abdominal fat content was significantly altered by the choice of MRI strategy, especially using L2-L3 methodology. Whole-body (-23.8+/-20.0%; P<0.01) and single-slice (L2-L3: -31.03+/-35.0%; P<0.01; L4-L5: -22.1+/-37.24%; p<0.05) MRI methods also detected a significant decrease in intra-abdominal fat following the exercise protocol, although the latter techniques gave rise to increased spreading of the data from the mean. These results suggest that the use of single-slice imaging techniques can lead to inconsistencies in the estimation of intra-abdominal fat content, which in turn can have significant effects on data interpretation. CONCLUSION Single-slice MRI appears to be suitable for assessing changes in intra-abdominal fat content in interventional studies, especially in large cohort of subjects, where each subject can serve as its own control. However, for accurate determination of an individual's intra-abdominal fat content, and intersubject comparison, only multi-slice imaging will give precise results.
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Fasolka MJ, Goldner LS, Hwang J, Urbas AM, DeRege P, Swager T, Thomas EL. Measuring local optical properties: near-field polarimetry of photonic block copolymer morphology. PHYSICAL REVIEW LETTERS 2003; 90:016107. [PMID: 12570633 DOI: 10.1103/physrevlett.90.016107] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2002] [Indexed: 05/24/2023]
Abstract
Ultrahigh molecular weight polystyrene-b-polyisoprene block copolymers (BCs), noted for their photonic behavior, were imaged using transmission near-field scanning optical microscopy (NSOM) and NSOM polarimetry. Our improved scheme for polarization modulation (PM) polarimetry, which accounts for optical anisotropies of the NSOM aperture probe, enables mapping of the local diattenuation and birefringence (with separately aligned diattenuating and fast axes) in these specimens with subdiffraction limited resolution. PM-NSOM micrographs illuminate the mesoscopic optical nature of these BC specimens by resolving individual microphase domains and defect structures.
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Savage DB, Agostini M, Barroso I, Gurnell M, Luan J, Meirhaeghe A, Harding AH, Ihrke G, Rajanayagam O, Soos MA, George S, Berger D, Thomas EL, Bell JD, Meeran K, Ross RJ, Vidal-Puig A, Wareham NJ, O'Rahilly S, Chatterjee VKK, Schafer AJ. Erratum: Digenic inheritance of severe insulin resistance in a human pedigree. Nat Genet 2002. [DOI: 10.1038/ng0902-211] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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181
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Bender JL, Corbin PS, Fraser CL, Metcalf DH, Richardson FS, Thomas EL, Urbas AM. Site-isolated luminescent europium complexes with polyester macroligands: metal-centered heteroarm stars and nanoscale assemblies with labile block junctions. J Am Chem Soc 2002; 124:8526-7. [PMID: 12121083 DOI: 10.1021/ja0261269] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis of a series of polymeric Eu(III) complexes with polyester ligands, along with supporting emission spectra, luminescence lifetimes, and, for a Eu block copolymer film, atomic force microscopy (AFM) data, is presented. Dibenzoylmethane was derivatized with a hydroxyl initiator site (dbmOH, 1) for tin octoate catalyzed ring opening polymerization of dl-lactide. The resulting poly(lactic acid) macroligand, dbmPLA (2), was combined with EuCl3 to generate Eu(dbmPLA)3 (3). Chelation of both dbmPLA and a polycaprolactone-functionalized bipyridine ligand (bpyPCL2) led to the Eu(III)-centered heteroarm star Eu(dbmPLA)3(bpyPCL2) (4). Unpolarized emission spectra and luminescence lifetimes were recorded for the Eu polymers in CH2Cl2 and for Eu(dbmPLA)3, as a film. Solution data for Eu(dbm)3 and Eu(dbm)3(bpy) were collected for comparison. For Eu tris(dbm) complexes, data were fit to a double exponential decay, indicating the presence of multiple species. Relative amounts of the longer lifetime component increase in the series Eu(dbm)3 solutions to Eu(dbmPLA)3 solutions to Eu(dbmPLA)3 films, perhaps suggesting benefits of the "polymer shell effect" and the diminishment of aquo adducts known to shorten lifetimes. As with the nonpolymeric analogue, data for Eu(dbmPLA)3(bpyPCL2) fit to a single-exponential decay. The sharpness of the feature at 579.7 nm, attributable to the 5D0 --> 7F0 transition in the emission spectrum of 4, lends further support for a homogeneous sample. AFM studies of "as cast" thin films of 4 reveal a lamellar structure with a 17.5 nm repeat. These microstructures, inferred to contain Eu luminophores at the glassy PLA-crystalline PCL domain interfaces, are modified by thermal treatment.
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Thomas EL, Alward DB, Kinning DJ, Martin DC, Handlin DL, Fetters LJ. Ordered bicontinuous double-diamond structure of star block copolymers: a new equilibrium microdomain morphology. Macromolecules 2002. [DOI: 10.1021/ma00162a016] [Citation(s) in RCA: 305] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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183
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Gido SP, Schwark DW, Thomas EL, do Carmo Goncalves M. Observation of a non-constant mean curvature interface in an ABC triblock copolymer. Macromolecules 2002. [DOI: 10.1021/ma00062a040] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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184
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Gido SP, Thomas EL. Lamellar diblock copolymer grain boundary morphology. 2. Scherk twist boundary energy calculations. Macromolecules 2002. [DOI: 10.1021/ma00081a034] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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185
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Ding DK, Thomas EL. Influence of elastic anisotropy on the structure of Neel inversion walls in liquid crystal polymers. Macromolecules 2002. [DOI: 10.1021/ma00076a034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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186
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Cohen Y, Thomas EL. Microfibrillar network of a rigid rod polymer. 1. Visualization by electron microscopy. Macromolecules 2002. [DOI: 10.1021/ma00180a025] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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187
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Winey KI, Thomas EL, Fetters LJ. The ordered bicontinuous double-diamond morphology in diblock copolymer/homopolymer blends. Macromolecules 2002. [DOI: 10.1021/ma00027a065] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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188
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Kinning DJ, Thomas EL, Alward DB, Fetters LJ, Handlin DL. Sharpness of the functionality-induced structural transition in poly(styrene-isoprene) star block copolymers. Macromolecules 2002. [DOI: 10.1021/ma00158a067] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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189
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Hajduk DA, Gruner SM, Rangarajan P, Register RA, Fetters LJ, Honeker C, Albalak RJ, Thomas EL. Observation of a reversible thermotropic order-order transition in a diblock copolymer. Macromolecules 2002. [DOI: 10.1021/ma00080a024] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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190
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Gido SP, Gunther J, Thomas EL, Hoffman D. Lamellar diblock copolymer grain boundary morphology. 1. Twist boundary characterization. Macromolecules 2002. [DOI: 10.1021/ma00069a016] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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191
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Herman DS, Kinning DJ, Thomas EL, Fetters LJ. A compositional study of the morphology of 18-armed poly(styrene-isoprene) star block copolymers. Macromolecules 2002. [DOI: 10.1021/ma00177a050] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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192
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193
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Hajduk DA, Harper PE, Gruner SM, Honeker CC, Kim G, Thomas EL, Fetters LJ. The Gyroid: A New Equilibrium Morphology in Weakly Segregated Diblock Copolymers. Macromolecules 2002. [DOI: 10.1021/ma00093a006] [Citation(s) in RCA: 594] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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194
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Winey KI, Thomas EL, Fetters LJ. Isothermal morphology diagrams for binary blends of diblock copolymer and homopolymer. Macromolecules 2002. [DOI: 10.1021/ma00036a014] [Citation(s) in RCA: 180] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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195
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Handlin DL, Thomas EL. Phase contrast imaging of styrene-isoprene and styrene-butadiene block copolymers. Macromolecules 2002. [DOI: 10.1021/ma00243a019] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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196
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Hajduk DA, Harper PE, Gruner SM, Honeker CC, Thomas EL, Fetters LJ. A Reevaluation of Bicontinuous Cubic Phases in Starblock Copolymers. Macromolecules 2002. [DOI: 10.1021/ma00111a061] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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197
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Anderson DM, Thomas EL. Microdomain morphology of star copolymers in the strong-segregation limit. Macromolecules 2002. [DOI: 10.1021/ma00189a016] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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198
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Handlin DL, MacKnight WJ, Thomas EL. Critical evaluation of electron microscopy of ionomers. Macromolecules 2002. [DOI: 10.1021/ma50004a063] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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199
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Cohen Y, Saruyama Y, Thomas EL. Crystal solvates in the poly[p-phenylene(benzo[1,2-d:4,5-d']bisthiazole-2,6-diyl)]/poly(phosphoric acid)/water system. Macromolecules 2002. [DOI: 10.1021/ma00005a029] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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200
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Hudson SD, Fleming JW, Gholz E, Thomas EL. Disclination core structure in rigid and semiflexible main-chain polymer nematic liquid crystals. Macromolecules 2002. [DOI: 10.1021/ma00058a012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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