Investigation of the grain boundary layer characteristics of donor doped barium titanate ceramics.

SIGLEAvailable from British Library Document Supply Centre- DSC:D79515 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Zr-containing 4,4\u27-ODA/PMDA polyimide composites parts I and II

The objective of this research is to improve the atomic oxygen resistance of KaptonTM, a polyimide (PI) made from pyromellitic acid dianhydride (PMDA) and 4,4\u27-oxydianiline (ODA), while retaining or enhancing the desirable properties of the pure polymer. Toward this end, zirconium-containing complexes and polymers were used to make composites and blends. Tetra(acetylacetonato)zirconium(IV), Zr(acac)4, which is commercially available, was identified as the best zirconium-containing complex for enhancing the atomic oxygen resistance of polyimide composites of the 10 complexes screened. Films prepared from the commercially-available polyamic acid (PAA) of PMDA-ODA (DuPont) have good uniformity, flexibility, and tensile strength. A 24-layer 10% (mol) Zr(acac)4/PI composite film showed significant improvement (ca. 20 fold) of atomic oxygen resistance over the pure polyimide. However, 10% (mol) Zr(acac)4 represents an upper concentration limit, above which films undergo cracking upon thermal imidization. In order to increase the Zr complex concentration in PMDA-ODA PI films, while retaining good film properties, [Zr(adsp)2-PMDA]n coordination polymer [bis(4-amino-N,N\u27-disalicylidene-1,2-phenylenediamino)zirconium(IV)-pyromellitic dianhydride] and [Zr(adsp)2-PMDA-ODA-PMDA]n terpolymer were synthesized and blended with commercial PAA, respectively. Several techniques were used to characterize the films made from the polymer containing Zr(acac)4. Plasma studies of films having 2% (mol) incremental concentrations of Zr in the Kapton up to 10% (mol) show that the overall rate of erosion is reduced about 75 percent

The Yellow Book Volume 10

1 of 13 volumes : illustrations. Curated title for Fleet Library Special Collections book cover exhibition Bound to Please, fall 2022. An Illustrated Quarterly Imprint varies. Oct. 1896-Apr. 1897: London ; New York : J. Lane. Co-founded and illustrated by Aubrey Beardsley. Nelson, J.G. Checklist of early Bodley Head books, ǂc 1894.11 Binding design for Vols. I-V probably by Aubrey Beardsley, binding design for Vol. VII by J.D. Mackenzie, binding design for Vol. VIII by D.Y. Cameron, binding design for Vol. IX by Mrs. Percy (Mabel) Dearmer, binding design for Vol. X by J. Illingsworth Kay, binding design for Vol. XI by Nellie Syrett, binding design for Vol. XII by Ethel Reed, binding for Vol. XIII by Mabel Syrett. Chrome yellow enameled flat-weave cloth; front cover with black-stamped ruled borders, stylized vignette panel, and titling. Library accession nos.: 5717-5729. Gift of Mrs. William C. Baker.https://digitalcommons.risd.edu/specialcollections_periodicals_theyellowbook/1009/thumbnail.jp

Synthesis, structure, and reactivity of bis(N,N′-bis(2-hydroxybenzylidene)-2-hydroxyphenylmethanediaminato)zirconium(IV), a Schiff base complex with 6,4,6-membered chelate rings

The title complex Zr(dshpm)2 has been successfully prepared by heating a 1:2 mole ratio of Zr(OBun)4 and the free ligand in absolute ethanol. It is mononuclear and eight-coordinate in the solid state with a dodecahedral coordination sphere. The two O,N,N,O donor atom quadridentate Schiff base ligands each form 6,4,6-membered chelate rings. As expected, the change in a chelate ring sizes from 6,5,6- to 6,4,6- resulted in significantly more labile complex, as indicated by TLC and NMR of heated solutions and its subsequent chemical reactions. The 0.010 Å shorter average ZrN bond distance was not anticipated, and appears to result from the zirconium atom\u27s preference that the oxygen atoms occupy certain locations. Preparations of two heteroleptic complexes from the title complex were undertaken to evaluate potential of the title compound as a synthon. A new fluorine-substituted homoleptic Schiff base Zr complex was also prepared, for comparison purposes. Despite the reasonable stability of Zr(dshpm)2 in air, the decomposition of labilized Hdshpm(2-) ligand on silica gel and in heated solution interfered with the purifications of the desired heteroleptic products

Zr-Containing 4,4'-ODA/PMDA Polyimide Composites

The objective of this research is to improve the atomic oxygen resistance of Kapton(TM), a polyimide (PI) made from pyromellitic acid dianhydride (PMDA) and 4,4'-oxydianiline (ODA), while retaining or enhancing the desirable properties of the pure polymer. Toward this end, zirconium-containing complexes and polymers were used to make composites and blends. Tetra(acetylacetonato)zirconium(IV), Zr(acac)4, which is commercially available, was identified as the best zirconium-containing complex for enhancing the atomic oxygen resistance of polyimide composites of the 10 complexes screened. Films prepared from the commercially available polyamic acid (PAA) of PMDA-ODA (DuPont) have good uniformity, flexibility, and tensile strength. A 24-layer 10% (mol) Zr(acac)4/PI composite film showed significant improvement (ca. 20 fold) of atomic oxygen resistance over the pure polyimide. However, 10% (mol) Zr(acac)4 represents an upper concentration limit, above which films undergo cracking upon thermal imidization. In order to increase the Zr complex concentration in PMDA-ODA PI films, while retaining good film properties, [Zr(adsp)2-PMDA]n coordination polymer [bis(4-amino-N,N'-disalicylidene- 1,2-phenylenediamino)zirconium(IV)-pyromellitic dianhydride] and [Zr(adsp)2-PMDA-ODA-PMDA]n terpolymer were synthesized and blended with commercial PAA, respectively. Several techniques were used to characterize the films made from the polymer containing Zr(acac)4. Plasma studies of films having 2% (mol) incremental concentrations of Zr in the Kapton up to 10% (mol) show that the overall rate of erosion is reduced about 75 percent

Visual function in infants with West Syndrome: Correlation with EEG patterns

Purpose: Several studies have reported behavioral and electrophysiological evidence of visual impairment during the active stage of West syndrome. The underlying mechanisms are, however, poorly understood, and little has been reported about the correlation between visual impairment, EEG patterns, and brain lesions. The aim of the study was to assess visual function at the onset of spasm and 2 months thereafter and relate visual findings to brain lesions and EEG features. Methods: Twenty-five infants with West syndrome were enrolled and studied with (a) a full clinical assessment including a battery of tests specifically designed to assess visual function, (b) a video-polygraphic study, and (c) brain magnetic resonance imaging (MRI). Besides brain neuroimaging and EEG comparison with visual function, an intra-EEG analysis was performed to investigate the possible relation of EEG patterns to fluctuating visual behavior (fixation and following). Results: Twenty-two children had at least one abnormal result on one or more of the tests assessing visual function at To. Visual impairment at the spasm onset was related to the sleep disorganization rather than to the hypsarrhythmic pattern in awake EEG. After 2 months, both EEG features become significantly linked to visual function. Visual function improved in several cases after 2 months, in parallel with the seizure regression. No relation was found between EEG patterns and fluctuating visual behavior. Conclusions: The study supplies new evidence of the involvement of visual function in West syndrome. The presence of abnormal visual findings in infants without lesions on brain MRI suggests that visual abnormalities are due not only to brain injury but also to epileptic disorder per se. New insight is also provided into the possible mechanisms underlying clinical and EEG abnormalities