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X-Ray Absorption Spectroscopy and Computer Modelling Study of Nanocrystalline Binary Alkaline Earth Fluorides. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/1757-899x/80/1/012005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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A (27)Al MAS NMR study of a sol-gel produced alumina: Identification of the NMR parameters of the theta-Al(2)O(3) transition alumina phase. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2007; 31:169-73. [PMID: 17560090 DOI: 10.1016/j.ssnmr.2007.05.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Revised: 04/06/2007] [Accepted: 05/03/2007] [Indexed: 05/15/2023]
Abstract
(27)Al MAS NMR has been used to study a sol-gel prepared alumina annealed at various temperatures. Two-field simulation of the sample heated to 1200 degrees C confirmed the presence of corundum, as suggested by XRD, and also the presence of nanocrystalline theta-Al(2)O(3). (27)Al MAS NMR chemical shifts, quadrupolar coupling constants and asymmetry parameters are reported for the tetrahedral and octahedral aluminium sites within theta-Al(2)O(3).
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Studies of the location of precious metals in nanocrystalline titanium dioxide using XRD and XANES. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/pssc.200673843] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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A27Al,29Si,25Mg and17O NMR investigation of alumina and silica Zener pinned, sol-gel prepared nanocrystalline ZrO2and MgO. Faraday Discuss 2007; 134:83-102; discussion 103-18, 415-9. [PMID: 17326564 DOI: 10.1039/b601928e] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alumina and silica Zener pinning particles in sol-gel prepared nanocrystalline ZrO2 and MgO have been characterised using 27Al and 29Si MAS NMR after annealing at various temperatures up to 1200 degrees C. The structures of the pinning phases were found to differ not just between the two metal oxide systems but also depending on the exact method of manufacture. Three distinct transitional alumina phases have been observed in different alumina-pinned samples annealed at 1200 degrees C, one in particular identified by a peak at a shift of 95 ppm in the 27Al NMR spectrum. Both the alumina and silica pinning phases reacted with the MgO nanocrystals, forming spinel in the case of alumina, and enstatite and forsterite in the case of silica. Despite reacting readily with the MgO, the silica pinning particles were effective at restricting grain growth, with 11 nm MgO nanocrystals remaining after annealing at 1000 degrees C.
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Abstract
Tin-doped anatase TiO(2) nanopowders and nanoceramics with particle sizes between 12 and 30 nm are investigated by X-ray absorption fine-structure (EXAFS) and Mössbauer spectroscopies. Furthermore, ab initio calculations based on the density functional theory are performed to analyze changes in the electronic structure due to Sn doping. The three approaches consistently show that Sn is dissolved on substitutional bulk sites with a slight increase of the bond lengths of the inner coordination shells. The Debye-Waller factors show that the nanocrystallites are highly ordered. There is no indication of defect states or bandgap changes with Sn doping.
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The effect of carbon monoxide and methane on the electrical conductivity of TiO2single crystals. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/01418619108204873] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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NMR relaxation, ionic conductivity and the self-diffusion process in barium fluoride. ACTA ACUST UNITED AC 2001. [DOI: 10.1088/0022-3719/11/1/017] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Computer Modelling and Exafs Study of the Disorder In Cd1−xPbxF2Mixed Systems. MOLECULAR SIMULATION 1999. [DOI: 10.1080/08927029908022082] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
The pattern of water uptake into a polyacid-modified composite resin (compomer), Dyract (D), was assessed using gravimetric analysis and tritiated water absorption. The results were compared with a resin composite, Herculite (H), a resin-modified glass-ionomer, Fuji II LC (FL), and a conventional glass-ionomer, Fuji II (F). Samples were stored in tritiated water for periods varying between 6 h and 6 months. The resulting change in gravimetric weight and dimensions was recorded. The tritiated water content was then assessed using liquid scintillation counting and this was compared to the gravimetric changes. The inherent water content of each material was also established. D and H showed a slow steady net uptake to 3% and 1.3% weight by volume (WV) respectively at 6 months. FL showed a rapid uptake reaching 8.9% WV at 7 days and 9.3% WV at 6 months. F showed a steady, less dramatic water uptake reaching 5.3% WV by 6 months. For the glass-ionomer materials, values for gravimetric water uptake and tritium release differed due to the ongoing acid base reaction and an increase in firmly bound water. This phenomenon was noted in D suggesting evidence of a similar reaction in this material.
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Examination of the mixed-alkali effect in (Li,Na) disilicate glasses by nuclear magnetic resonance and conductivity measurements. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1995; 5:133-143. [PMID: 8748651 DOI: 10.1016/0926-2040(95)00033-m] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Results from 29Si, 23Na and 7Li magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy, 7Li NMR relaxation and electrical conductivity in a series of [Li(1-x).Nax]2O.2SiO2 (disilicate) glasses are used to investigate the mixed-alkali effect. From the 29Si NMR spectra there is relatively little change of the network with alkali composition. 23Na and 7Li NMR linewidths and shifts change continuously as a function of composition, indicating that the alkali ions are intimately and uniformly mixed rather than separated into lithium and sodium-rich domains. The activation energy from electrical conductivity shows a distinct maximum at the central composition (x = 0.5), whereas the local activation energy for lithium motion determined from NMR shows only a smaller but monotonic increase as the lithium-content decreases.
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Thermoelectric power studies of bismuth oxide and mixed oxides based on bismuth oxide. ACTA ACUST UNITED AC 1993. [DOI: 10.1080/01418619308213997] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Structure determination of materials using non-crystallographic techniques. Acta Crystallogr A 1993. [DOI: 10.1107/s0108767378088765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Defect structure of doped CaF2 at high temperatures. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 39:1897-1907. [PMID: 9948408 DOI: 10.1103/physrevb.39.1897] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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A New Oxygen Sensor Based on the Thermoelectric Power of Solid Solutions of Nb2O5 and Bi2O3. ACTA ACUST UNITED AC 1989. [DOI: 10.1002/anie.198900751] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Die Thermokraft fester Lösungen von Nb2O5 in Bi2O3 als Grundlage für einen neuen Sauerstoffsensor. Angew Chem Int Ed Engl 1989. [DOI: 10.1002/ange.19891010117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Nuclear magnetic resonance techniques for the study of mechanisms of diffusion in solids. INT REV PHYS CHEM 1988. [DOI: 10.1080/01442358809353214] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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The structure of LaF3 – a single-crystal neutron diffraction study at room temperature. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 1983. [DOI: 10.1107/s0108768183003249] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ethylene Effects in Pea Stem Tissue : EVIDENCE OF MICROTUBULE MEDIATION. PLANT PHYSIOLOGY 1981; 67:460-6. [PMID: 16661694 PMCID: PMC425705 DOI: 10.1104/pp.67.3.460] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The marked effects of ethylene on pea stem growth have been investigated. Low temperature and colchicine, both known microtubule depolymerization agents, reverse the effects of ethylene in straight growth tests. Low temperature (6 C) also profoundly reduces the effects of gas in terms of swelling, hook curvature, and horizontal nutation. Deuterium oxide, an agent capable of rigidifying microtubular structure, mimics the effects of ethylene. Electron microscopy shows that microtubule orientation is strikingly altered by ethylene. These findings indicate that some of the ethylene responses may be due to a stabilizing effect on microtubules in plant cells.
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Molecular reorientation and self-diffusion in the plastic solid hexamethyldisilane studied using nuclear magnetic resonance and radiotracer techniques. ACTA ACUST UNITED AC 1975. [DOI: 10.1039/f19757101610] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Effects of Cycloheximide on Indoleacetic Acid-induced Ethylene Production in Pea Root Tips. PLANT PHYSIOLOGY 1973; 52:171-3. [PMID: 16658521 PMCID: PMC366462 DOI: 10.1104/pp.52.2.171] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Cycloheximide inhibited ethylene production in excised pea root tips treated with high levels of indoleacetic acid (100 mum and 10 mum). In contrast, cycloheximide did not inhibit ethylene production induced by a lower concentration (1 mum) of indoleacetic acid unless it was added 2 hours before the indoleacetic acid treatment. These observations suggest that indoleacetic acid has two effects on the enzyme system involved in ethylene synthesis. At low concentrations (1 mum) indoleacetic acid increases ethylene production without protein synthesis, whereas at the higher concentrations, the synthesis of new protein is associated with increased ethylene production.
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Lattice defects in plastic organic crystals. Part 7.—Isotope mass effects in self-diffusion in cyclohexane. ACTA ACUST UNITED AC 1972. [DOI: 10.1039/f19726800047] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
A 1-hour application of indole-3-acetic acid to bean (Phaseolus vulgaris L. cv. Red Kidney) explants inhibited abscission for an 8-hour aging period. Use of indole-3-acetic acid-(14)C showed that the applied indole-3-acetic acid was conjugated within explant tissue and that this conjugation mechanism accounts for loss of effectiveness of indole-3-acetic acid in inhibiting abscission after 8 hours. Reapplication of indole-3-acetic acid to an explant at a later time, before the induced aging requirement was completed reinhibited abscission. 2,4-Dichlorophenoxyacetic acid, which is not destroyed or conjugated by this system, did not lose its ability to inhibit abscission. It was concluded that indole-3-acetic acid destruction is one of the processes involved in the aging stage of abscission in explants.
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Abstract
A large portion of indoleacetic acid (IAA)-induced inhibition of excised root tips and virtually all such inhibition of intact roots are the result of IAA-dependent ethylene production. Under certain conditions an additional effect of IAA accounts for a small portion of the inhibition of excised root tips. Ethylene production in response to applied IAA is governed by the level of applied auxin found inside the root. Evidence is presented to confirm the participation of ethylene in the geotropic response of roots.
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An explanation of the inhibition of root growth caused by indole-3-acetic Acid. PLANT PHYSIOLOGY 1967; 42:415-20. [PMID: 16656519 PMCID: PMC1086550 DOI: 10.1104/pp.42.3.415] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Low concentrations of indole-3-acetic acid inhibit the growth of pea root sections by inducing the formation of the growth regulator, ethylene gas. Ethylene is produced within 15 to 30 minutes after indole-3-acetic acid is applied and roots begin to swell immediately after they are exposed to the gas. Carbon dioxide competitively inhibits ethylene action in roots, impedes their geotropic response, and partially reinstates auxin inhibited growth. It is concluded that ethylene participates in the geotropic response of roots, but not that of stems.
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