| 1. |
- Khartsev, Sergiy, et al.
(författare)
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Comparative characteristics of Na0.5K0.5NbO 3 films on Pt by pulsed laser deposition and magnetron sputtering
- 2003
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 55, s. 769-779
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Tidskriftsartikel (refereegranskat)abstract
- Ferroelectric Na0.5K0.5NbO3 (NKN) thin films were grown on the Pt80Ir20 polycrystalline substrates by pulsed laser deposition (PLD) and radio frequency-magnetron sputtering (RF) technique using the same stoichiometric Na0.5K 0.5NbO3 ceramic target. X-ray diffraction proved both PLD- and RF-made Na0.5K0.5NbOj/Pt80Ir20 films are single phase and have preferential c-axis orientation. Temperature dependence of dielectric permittivity reveals the presence of two phase transitions around 210 and 410°C. Capacitance vs. applied voltage C-V @ 100 kHz, I-V, and P-E hysteresis characteristics recorded for the vertical capacitive structures yielded loss tan δ = 0.026 and 0.016, tunability about 44.5 and 30% @ 100 kV/cm, Ohmic resistivity 6.7 × 1012 Ω·cm and 0.2 × 1012 Ω·cm, remnant polarization 11.7 and 9.7 μC/cm2, coercive field 28.0 and 94.6 kV/cm for PLD- and RF-films, respectively. Piezoelectric test carried out in hydrostatic conditions showed piezoelectric coefficient dH = 21 for PLD-NKN and 15 pC/N for RF-NKN film.
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| 2. |
- Koh, J. H., et al.
(författare)
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Dielectric relaxation behavior of Ag(Ta,Nb)O-3 interdigital capacitors on oxide substrates
- 2004
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Ingår i: Japanese Journal of Applied Physics. - : IOP Publishing. - 0021-4922 .- 1347-4065. ; 43:4A, s. 1434-1437
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Tidskriftsartikel (refereegranskat)abstract
- The time-dependent dielectric relaxation behavior of Ag(Ta,Nb)O-3 interdigital capacitors was investigated for tunable device applications. Ag(Ta,Nb)03 thin films, which have high k-factor (tunability/ loss tangent), were deposited on the oxide substrates by pulsed laser deposition technique. Ag(Ta,Nb)03 thin film on the LaAlO3 substrate has an epitaxial relationship with the substrate. The observed tunabilities and K-factors of Ag(Ta,Nb)O-3/LaAlO3 and Ag(Ta,Nb)O-3/AI(2)O(3) interdigital capacitors were 5.9% and 17.8 and 3.8% and 9.9, respectively, at 40 V (maximum electric field of 100 kV/cm), 300 K, and 1 MHz. Capacitance relaxation follows the power law C(t) = C-infinity + C-0(t/ls)-(beta) with a very small exponent negligibly fitted in the time domain. Due to this small exponent, the capacitance was changed by less than 0.05% in 2V in 71 s. Time-dependent leakage current was measured by employing the Ag(Ta,Nb)O-3(0.4mum)/Al2O3 interdigital capacitor. The time-dependent relaxation current follows the power law j(t) = j(leak) +j(0)(t/ls)-(alpha) with an exponent alpha = 0-98, j(leak) = 1.14 x 10(-14), and j(0) = 11.42s.
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| 3. |
- Song, X M, et al.
(författare)
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5-Aminoimidazole-4-carboxamide ribonucleoside treatment improves glucose homeostasis in insulin-resistant diabetic (ob/ob) mice.
- 2002
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Ingår i: Diabetologia. - 0012-186X .- 1432-0428. ; 45:1, s. 56-65
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: The 5'AMP-activated protein kinase is an important mediator of muscle contraction-induced glucose transport and a target for pharmacological treatment of Type II (non-insulin-dependent) diabetes mellitus. The 5'AMP-activated protein kinase can be activated by 5-aminoimidazole-4-carboxamide ribonucleoside. We hypothesised that 5-aminoimidazole-4-carboxamide ribonucleoside treatment could restore glucose homeostasis in ob/ob mice.METHODS: Lean and ob/ob mice were given 5-aminoimidazole-4-carboxamide ribonucleoside (1 mg.g body wt(-1).day(-1) s.c) or 0.9 % NaCl (vehicle) for 1-7 days.RESULTS: Short-term 5-aminoimidazole-4-carboxamide ribonucleoside treatment normalised glucose concentrations in ob/ob mice within 1 h, with effects persisting over 4 h. After 1 week of daily injections, 5-aminoimidazole-4-carboxamide ribonucleoside treatment corrected hyperglycaemia, improved glucose tolerance, and increased GLUT4 and hexokinase II protein expression in skeletal muscle, but had deleterious effects on plasma non-esterified fatty acids and triglycerides. Treatment with 5-aminoimidazole-4-carboxamide ribonucleoside increased liver glycogen in fasted and fed ob/ob mice and muscle glycogen in fasted, but not fed ob/ob and lean mice. Defects in insulin-stimulated phosphatidylinositol 3-kinase and glucose transport in skeletal muscle from ob/ob mice were not corrected by 5-aminoimidazole-4-carboxamide ribonucleoside treatment. While ex vivo insulin-stimulated glucose transport was reduced in isolated muscle from ob/ob mice, the 5-aminoimidazole-4-carboxamide ribonucleoside stimulated response was normal.CONCLUSION/INTERPRETATION: The 5-aminoimidazole-4-carboxamide ribonucleoside mediated improvements in glucose homeostasis in ob/ob mice can be explained by effects in skeletal muscle and liver. Due to the apparently deleterious effects of 5-aminoimidazole-4-carboxamide ribonucleoside on the blood lipid profile, strategies to develop tissue-specific and pathway-specific activators of 5'AMP-activated protein kinase should be considered in order to improve glucose homeostasis.
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| 4. |
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| 5. |
- Guo, X. W., et al.
(författare)
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Effects of SiO2/Al2O3, MgO modification and hydrothermal treatment on the catalytic activity of HZSM-5 zeolites in the methylation of 4-methylbiphenyl with methanol
- 2004
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Ingår i: Applied Catalysis A. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 261:2, s. 183-189
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work is to study the effects Of SiO2/Al2O3 of HZSM-5, MgO modification and hydrothermal treatment on methylation of 4-methylbiphenyl (4-MBP) with methanol under fixed-bed down-flow conditions. The results show that, with an increase in the SiO2/Al2O3 of HZSM-5 (from 50 to 150, molar ratio), the selectivity to 4,4'-dimethylbiphenyl (4,4'-DMBP) increases from 25 to 79%. MgO modification also increases the selectivity to 4,4'-DMBP, but leads as well to low catalyst activity and rapid deactivation. Hydrothermal treatment not only increases the selectivity, but also improves the stability. When CBV1502 (SiO2/Al2O3 = 150) catalyst was hydrothermally treated at 500degreesC, the selectivity to 4,4'-DMBP increased to 85%. The selectivity to 4,4'-DMBP was further improved to about 90% by the increasing in the amount of mesitylene in the feed as solvent.
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| 6. |
- Guo, X. W., et al.
(författare)
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Methylation of 4-methylbiphenyl with methanol over metal oxide-modified HZSM-5 zeolite catalysts
- 2003
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Ingår i: Cuihuà xuébào. - 0253-9837 .- 1872-2067. ; 24:5, s. 333-337
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Tidskriftsartikel (refereegranskat)abstract
- A series of HZSM-5 zeolite catalysts modifed with metal oxides (MgO, CaO, SrO, BaO, ZnO, La2O3 and CeO2) were prepared by impregnation method and characterized by XRD, TPD and N-2-adsorption. Methylation of 4-methylbiphenyl (4-MBP) with methanol to 4,4'-dimethylbiphenyl (4,4'-DMBP) was carried out over the prepared catalysts under fixed-bed down-flow conditions. The results showed that the MgO-modified HZSM-5 can significantly improve the selectivity for target product 4,4'-DMBP (up to 80 % vs only 13 % over the parent HZSM-5). The effects of metal oxides on 4,4'-DMBP selectivity are arranged in the following order: MgO>SrOapproximate toZnOapproximate toCaOapproximate toLa(2)O(3)>BaO>CeO2. The effects of MgO contents, precursor-salt types, and loading methods were further investigated, and the results revealed that during 4-MBP conversion, proper MgO loading (5.6 %) can be more effective, and the ion-exchange methed is much better than the impregnation method. However, it is difficult to get higher metal oxide loading by using the ion-exchange method. The high selectivity over HZSM-5 modified with MgO largely results from the depression of 4,4-DMBP second reactions such as isomerization, dealkylation and alkylation, as demonstrated by the reaction of 4,4'-DMBP as reactant over MgO/ZSM-5 catalyst and HZSM-5 zeolite.
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| 7. |
- Guo, X. W., et al.
(författare)
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Shape-selective methylation of 4-methylbiphenyl to 4,4 '-dimethylbiphenyl over zeolite HZSM-5 modified with metal oxides of MgO, CaO, SrO, BaO, and ZnO
- 2003
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Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 87:02-jan, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- A series of ZSM-5 samples modified with metal oxides MO(M = Mg, Ca, Sr, Ba and Zn) were employed for the alkylation of 4-methylbiphenyl (4-MBP) with methanol to 4,4'-dimethylbiphenyl (4,4'-DMBP) under fixed-bed down-flow conditions. The methylation results showed that the use of basic metal oxides can effectively enhance the selectivity to the target product 4,4'-DMBP. MgO is the most effective modifier among the metal oxides used and it can improve selectivity to 4,4'-DMBP up to 80% as compared to only 13% over the parent zeolite HZSM-5. The modi. cation effectiveness of metal oxides on 4,4'-DMBP selectivity can be arranged in the order MgO> SrO similar to ZnO similar to CaO> BaO. The optimization of MgO modi. cation through the content, salt types and loading methods revealed that proper MgO loading (5.6 wt%) can be more effective, and the impregnation method is much better than ion exchange. The correlation of physicochemical properties (TPD, TGA, chemical analysis and chemical adsorption, etc.) of the modified HZSM-5 with the catalytic data showed that the high selectivity over ZSM-5 modified with MgO largely results from the effective suppression of 4,4'-DMBP secondary reactions such as isomerization, dealkylation and alkylation.
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| 8. |
- Kaminski, Clemens, et al.
(författare)
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Flame growth and wrinkling in a turbulent flow
- 2000
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 71:5, s. 711-716
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Tidskriftsartikel (refereegranskat)abstract
- High-speed planar laser-induced fluorescence (PLIF) and 3-D large eddy simulations (LES) are used to study turbulent flame kernel growth, wrinkling and the formation of separated flame pockets in methane/air mixtures. Turbulence was effected by a set of rotary fans situated in a cylindrical enclosure. Flame wrinkling was followed on sequential 2-D OH images captured at kHz repetition rates. Under stoichiometric conditions and low turbulence levels the flame kernel remains singly connected and close to spherical in shape. By increasing turbulence or reducing the stoichiometry of the mixture the formation of separated pockets could be observed and studied. The mechanisms behind these phenomena are investigated qualitatively by LES of a level-set G-equation describing the flame surface propagation in turbulent flows.
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| 9. |
- Kim, Jang-Yong, et al.
(författare)
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Magnetically and electrically tunable devices using ferromagnetic/ferroelectric ceramics
- 2004
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 241:7, s. 1714-1717
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Tidskriftsartikel (refereegranskat)abstract
- There has been a growing interest in tunable devices applications such as filters, phase shifters, and resonators. Both of ferromagnetic and ferroelectric materials have strong advantages in the high tunability and stability. Therefore many reports have been published by employing ferrite or dielectric materials for high frequency devices applications. Both of controllable dielectric permittivity and magnetic permeability were considered one of the solutions for impedance matching in tunable devices. In this experiment ferromagnetic/ferroelectric composite ceramics were successfully fabricated without any cracking or shrinkage. Fabricated ferromagnetic/ferroelectric composite ceramic showed ferroelectric properties of P-E hysteresis and magnetic properties of B-H hysteresis loops.
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| 10. |
- Liang, L, et al.
(författare)
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Dynamic readjustment of parental methylation patterns of the 5'-flank ofthe mouse H19 gene during in vitro organogenesis
- 2000
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Ingår i: International Journal of Developmental Biology. - 0214-6282 .- 1696-3547. ; 44, s. 785-790
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Tidskriftsartikel (refereegranskat)abstract
- Gametic marks are stably propagated in order to manifest parent of origin-specific expression patterns of imprinted genes in the developing conceptus. Although the character of the imprint has not yet been fully elucidated, there is compelling evidence that it involves a methylation mark. This is exemplified by a region upstream of the H19 gene, which is not only methylated in a parent of origin-specific manner, but also regulates the silencing of the maternal Igf2 and paternal H19 alleles, respectively. We show here that the parental-specific methylation patterns within the differentially methylated domain (DMD) are perturbed in the soma during in vitro organogenesis. Under these conditions, the paternal DMD allele becomes partially demethylated, whereas the maternal DMD allele gains methylation. Despite these effects, there were no changes in allelic Igf2 or H19 expression patterns in the embryo. Finally, we show that although TSA derepresses the paternal H19 allele in ectoplacental cone when in vitro developed, there is no discernible effect on the methylation status of the paternally inherited 5'-flank in comparison to control samples. Collectively, this data demonstrates that the parental mark is sensitive to a subset of environmental cues and that a certain degree of plasticity of the gametic mark is tolerated without affecting the manifestation of the imprinted state.
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