| 21. |
- Chen, K., et al.
(författare)
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Ti deficiency effect on the dielectric response of CaCu3Ti4O12 ceramics
- 2007
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Ingår i: Solid State Communications. - : Elsevier. - 0038-1098 .- 1879-2766. ; 141:8, s. 440-444
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Tidskriftsartikel (refereegranskat)abstract
- Single phase ceramics CaCu3Ti4.0O12 and CaCu3Ti3.9O12 have been prepared using the traditional solid-state reaction method. Compared with the stoichiometric ceramics CaCu3Ti4.0O12, Ti-deficient ceramics CaCu3Ti3.9O12 have the larger lattice parameter, the higher force constant, and smaller dielectric constant and the lower dissipation factor, although their fundamental characters of dielectric response are similar. Their characteristic relaxation frequencies are not well fitted with the Arrhenius Law but a tentatively supposed relation. With the Cole-Cole Law, the fitted broadened factors of dissipation peaks are 0.5433 and 0.8651 for CaCu3Ti3.9O12 and CaCu3Ti4.0O12, respectively. All facts mentioned above imply that mutually correlated motion of Ti ions or defects may be expected to be responsible for the giant dielectric constant and high dissipation factor of CaCu3T4.0O12. (c) 2006 Elsevier Ltd. All rights reserved.
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| 22. |
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| 23. |
- Chen, S., et al.
(författare)
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Coffin-Mansson equation of Sn-4.0Ag-0.5Cu solder joint
- 2009
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Ingår i: Soldering and Surface Mount Technology. - : Emerald. - 1758-6836 .- 0954-0911. ; 21:2, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this paper is to fit Coffin-Manson equation of Sn-4.0Ag-0.5Cu lead free solder joint by using results of solders joint reliability test and finite element analysis. Also to present a novel device for solder joint reliability test. Design/methodology/approach: Two-points bending test of Sn-4.0Ag-0.5Cu lead free solder joint was carried out at three deflection levels by using a special bending tester that can control displacement exactly by a cam system. The failure criterion was defined as resistance of solder joint getting 10 percent increase. The X-section was done for all failure samples to observe crack initiation and propagation in solder joint. Finite element analysis was presented with ANSYS for obtaining shear strain range, analyzing distribution of stress and strain and supporting experimental results. Findings: The experimental results indicate that the fatigue life decreased obviously with the displacement increased. By using optical microscope and SEM photographs, two kinds of failure mode were found in solder joint. The majority failure mode took place at the bottom corner of solder joint under the termination of resistor initially, and propagated into the solder matrix. Another failure mode was delamination. It appeared at the interface between the termination of resistor and its ceramic body. The distribution status of stress and strain in solder joint and the calculation results of shear strain range at different deflection levels were obtained from simulation result. The Coffin-Manson equation of Sn-4.0Ag-0.5Cu lead free solder joint was fitted by combining experimental data with result of finite element analysis. Originality/value: This paper presents Coffin-Manson equation of Sn-4.0Ag-0.5Cu solder joint with two-points bending test. An effective and economical device was designed and applied.
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| 24. |
- Chen, W. Z., et al.
(författare)
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Spectral and structural characterization of amidate-bridged platinum-thallium complexes with strong metal-metal bonds
- 2006
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 45:11, s. 4526-4536
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Tidskriftsartikel (refereegranskat)abstract
- The reactions of [Pt(NH3)(2)((NHCOBu)-Bu-t)(2)] and TlX3 (X = NO3-, Cl-, CF3CO2-) yielded dinuclear [{Pt(ONO2)(NH3)(2-)((NHCOBu)-Bu-t)}Tl(ONO2)(2)(MeOH)] (2) and trinuclear complexes [{PtX(RNH2)(2)((NHCOBu)-Bu-t)(2)}(2)Tl](+) [X = NO3- (3), Cl- (5), CF3CO2- (6)], which were spectroscopically and structurally characterized. Strong Pt-Tl interaction in the complexes in solutions was indicated by both Pt-195 and Tl-205 NMR spectra, which exhibit very large one-bond spin-spin coupling constants between the heteronuclei ((1)J(PtTl)), 146.8 and 88.84 kHz for 2 and 3, respectively. Both the X-ray photoelectron spectra and the Pt-195 chemical shifts reveal that the complexes have Pt centers whose oxidation states are close to that of Pt-III. Characterization of these complexes by X-ray diffraction analysis confirms that the Pt and Tl atoms are held together by very short Pt-Tl bonds and are supported by the bridging amidate ligands. The Pt-Tl bonds are shorter than 2.6 angstrom, indicating a strong metal-metal attraction between these two metals. Compound 2 was found to activate the C-H bond of acetone to yield a platinum(IV) acetonate complex. This reactivity corresponds to the property of Pt-III complexes. Density functional theory calculations were able to reproduce the large magnitude of the metal-metal spin-spin coupling constants. The couplings are sensitive to the computational model because of a delicate balance of metal 6s contributions in the frontier orbitals. The computational analysis reveals the role of the axial ligands in the magnitude of the coupling constants.
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| 25. |
- Chen, Y. C., et al.
(författare)
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Fluorescence anisotropy studies of molecularly imprinted polymers
- 2006
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Ingår i: Luminescence (Chichester, England Print). - : Wiley. - 1522-7235 .- 1522-7243. ; 21:1, s. 7-14
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Tidskriftsartikel (refereegranskat)abstract
- A molecularly imprinted polymer (MIP) is a biomimetic material that can be used as a biochemical sensing element. We studied the steady-state and time-resolved fluorescence and fluorescence anisotropy of anthracene-imprinted polyurethane. We compared MIPs with imprinted analytes present, MIPs with the imprinted analytes extracted, MIPs with rebound analytes, non-imprinted control polymers (non-MIPs) and non-MIPs bound with analytes to understand MIP’s binding behaviour. MIPs and non-MIPs had similar steady-state fluorescence anisotropy in the range 0.11-0.24. Anthracene rebound in MIPs and non-MIPs had a fluorescence lifetime of tau = 0.64 ns and a rotational correlation time of 0, = 1.2-1.5 ns, both of which were shorter than that of MIPs with imprinted analytes present (tau = 2.03 ns and phi(F) = 2.7 ns). The steady-state anisotropy of polymer solutions increased exponentially with polymerization time and might be used to characterize the polymerization extent in situ.
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Cheng, Q, et al.
(författare)
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Clinical features of patients with multiple sclerosis from a survey in Shanghai, China
- 2008
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Ingår i: Multiple sclerosis (Houndmills, Basingstoke, England). - : SAGE Publications. - 1352-4585 .- 1477-0970. ; 14:5, s. 671-678
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Tidskriftsartikel (refereegranskat)abstract
- Objective To describe clinical features of patients with multiple sclerosis (MS) in Shanghai, China. Methods Prevalent patients with MS were identified and investigated by a network of physicians in 11 districts of Shanghai during the period from 1 September 2004 to 31 August 2005. Admission registries of each hospital in the study area were checked systematically for patients with a diagnosis of MS, neuromyelitis optica or other demyelinating disorders. All patients with collected information were evaluated by four senior neurologists according to the McDonald criteria. Results There were 249 (146 female and 103 male) patients with a confirmed MS diagnosis, at a female-to-male ratio of 1.4. The mean age at onset of MS was 37.4 years for the 249 patients with MS and, on the prevalence day, 42.7 years. The most frequent location of clinical MS lesions in the central nervous system was the spinal cord (61%), followed by the cerebrum (55%) and optic nerves (41%). Nearly all (96%) of the patients with MS had been examined by magnetic resonance imaging, and 226 (94%) patients of those examined were suggestive of MS. No family history of MS was found in any of the patients. Most (86%) of the patients had no or mild disability on the prevalence day (31 December 2004). Almost all (96%) patients with MS had been treated with corticosteroids. Conclusion Clinical features of patients with MS are described based on the information from the largest case series reported among Chinese. Comparisons and discussions are made with findings from the other populations.
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| 30. |
- Evans, J D, et al.
(författare)
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Immune pathways and defence mechanisms in honey bees Apis mellifera.
- 2006
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Ingår i: Insect Mol Biol. - 0962-1075. ; 15:5, s. 645-56
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Tidskriftsartikel (refereegranskat)abstract
- Social insects are able to mount both group-level and individual defences against pathogens. Here we focus on individual defences, by presenting a genome-wide analysis of immunity in a social insect, the honey bee Apis mellifera. We present honey bee models for each of four signalling pathways associated with immunity, identifying plausible orthologues for nearly all predicted pathway members. When compared to the sequenced Drosophila and Anopheles genomes, honey bees possess roughly one-third as many genes in 17 gene families implicated in insect immunity. We suggest that an implied reduction in immune flexibility in bees reflects either the strength of social barriers to disease, or a tendency for bees to be attacked by a limited set of highly coevolved pathogens.
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