Nb-doped SrBi4Ti4O15 (SBT) was produced by conventional method. Structural and ferroelectric properties of SBT were examined as a function of
niobium composition. Analyzing the structure futures of SBT by XRD, XPS and Raman spectrum, Nb5+ substituted Ti4+ to form NbO6 octahedron and did not change the structure of SBT. The XRD patterns indicated the formation of the single phase of SBT for
x = 0.01and 0.03 and secondary phase of Sr3Ti2O7 appeared when x > 0.1. To compare the effect of Nb doping, the ferroelectric properties (hysteresis loop, piezoelectric coefficient) of Nb-doped
SBT were measured. The SBT doped with x = 0.15 was found to exhibit higher remanent polarization with d33 = 17 pC/N. 相似文献
Objective To develop a continuous arterial spin labeling (CASL) perfusion imaging method for cerebral blood flow (CBF) measurement in
rats with reduced spin-labeling length and optimized signal-to-noise ratio (SNRf ) per unit time.
Materials and methods In the proposed method, the longitudinal magnetization of brain tissue water in the imaging slice is prepared into a proper
state before spin-labeling, and a post-tagging delay is employed after spin-labeling. The method was implemented on a 4.7 T
small animal scanner. Numerical simulations and in vivo experiments were used to evaluate the performance of the method proposed.
Results With the proposed method, absolute CBF could be measured accurately from normal rat with a spin-labeling pulse as short as
400 ms, and yet employing the same formula as that used in the conventional CASL perfusion imaging method for calculation.
The method also showed improved SNRf per unit time over the conventional CASL perfusion imaging method and the pulsed arterial spin labeling perfusion imaging
method FAIR.
Conclusion Compared to the conventional CASL perfusion imaging method, the proposed method would be advantageous for CBF measurement
in small animals having short vascular transit time in terms of SNRf per unit time and other benefits brought by shortened spin-labeling pulse. 相似文献
The easy loss of crosslinking ions in alginate can result in a structural collapse of the physiological environment, thereby losing its characteristics as a bone scaffold. Meanwhile, alginate lacks osteoconductive properties, which are necessary for ideal bone scaffolds. In this study, strontium (Sr) in combination with calcium (Ca) at different ratios were used as a crosslinking agent for the alginate to investigate the effect of Ca–Sr ratio on the physicochemical properties and biological preformation of alginate hydrogel. Here, Ca and Sr in different weight ratios (4:0, 3:1, 2:2, 1:3, and 0:4) were employed as crosslinking agents. The physicochemical properties of hydrogels, including pore size, elastic modulus, degradation rate and swelling ratio, could be effectively tuned by controlling the amount of Sr. The ion release experiment revealed a burst release of Sr2+ in the first day after crosslinking. However, after 3 days, the amount of Sr2+ release had significantly declined and was proportional to the total strontium initially introduced into the alginate. Meanwhile, the live/dead results exhibited higher cell viability for alginate with 2:2 Ca–Sr weight ratio. The alginate with 2:2 Ca–Sr ratio not only improved osteoblastic attachment, but also up-regulated the alkaline phosphatase activity, the expression of osteogenic marker genes, and relative growth factors. These findings indicate that alginate with 2:2 Ca–Sr ratio might be a promising scaffold for bone tissue engineering.
采用两步固相法,在交替气氛煅烧(空气预烧,氮气煅烧)下合成了尖晶石钛酸锂粉末,并且研究了煅烧气氛(空气和氮气)对不同合成阶段(预烧和煅烧)的影响。电化学测试结果表明,经空气预烧,氮气煅烧得到的样品在5 C的电流密度下,首次充电比容量高达128 m Ah/g,100次循环后容量保持率达94.5%,其电化学性能明显优于单一气氛煅烧下所得样品。分析其原因为碳酸锂的分解反应在空气气氛下较氮气气氛下更容易进行,且氮气气氛下合成LTO有氧空位的存在。 相似文献