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101.
L-精氨酸磷酸盐(L-Arginine Phosphate Monohydrate, LAP)晶体,是一种有应用潜力的无机-有机杂化NLO晶体材料[1, 2]。Eimerl等人认为LAP晶体二阶NLO响应主要源于L-精氨酸分子(Arg ),磷酸根(H2PO4-)对LAP晶体宏观NLO响应没有重要贡献[2];而许东等人认为,LAP晶体的NLO响应是由L-精氨酸分子和磷酸根共同贡献的结果[1]。本通讯通过第一原理从头算计算,揭示了LAP晶体二阶NLO响应的电子起源。 表1. 激发态性质 Table 1. The Excited States at CIS/STO-3G Level (Dmge in Debyes; l in nm; (rx)ge in au) States… 相似文献
102.
The symmetric coupling of mixed finite element and boundaryelement methods is analysed for a model interface problem withthe Laplacian. The coupling involves a further continuous ansatzfunction on the interface to link the discontinuous displacementfield to the necessarily continuous boundary ansatz function.Quasi-optimal a priori error estimates and sharp a posteriorierror estimates are established which justify adaptive mesh-refiningalgorithms. Numerical experiments prove the adaptive couplingas an efficient tool for the numerical treatment of transmissionproblems. 相似文献
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摘要:用化学酶法合成聚己内酯(PCL)和聚N,N-二甲氨基甲基丙烯酸乙酯(PDMAEMA)双亲嵌段聚合物(PCL-b-PDMAEMA)。通过核磁共振(1H NMR),红外光谱仪(FTIR-IR),凝胶渗透色谱(GPC) 对其结构以及分子量与其分子量分布情况进行了表征。对聚合物的溶液性质进行了研究,结果表明:临界胶束浓度(CMC)嵌段聚合物中疏水链段增多有利于形成胶束,表现为CMC降低,并具有较高的热力学稳定性。PDMAEMA是PH和温度敏感材料,研究发现,在不同的温度和pH值条件下表现不同的聚集状态, 当聚合物的pH值降低时平均流体力学直径增加,温度升高平均流体力学直径降低。 相似文献
107.
Acoustic characterization in whole blood and plasma of site-targeted nanoparticle ultrasound contrast agent for molecular imaging 总被引:5,自引:0,他引:5
Hughes MS Marsh JN Hall CS Fuhrhop RW Lacy EK Lanza GM Wickline SA 《The Journal of the Acoustical Society of America》2005,117(2):964-972
The ability to enhance specific molecular markers of pathology with ultrasound has been previously demonstrated by our group employing a nanoparticle contrast agent [Lanza et al., Invest. Radiol. 35, 227-234 (2000); Ultrasound Med. Biol. 23, 863-870 (1997)]. One of the advantages of this agent is very low echogenicity in the blood pool that allows increased contrast between the blood pool and the bound, site-targeted agent. We measured acoustic backscatter and attenuation coefficient as a function of the contrast agent concentration, ambient pressure, peak acoustic pressure, and as an effect of duty cycle and wave form shape. Measurements were performed while the nanoparticles were suspended in either whole porcine blood or plasma. The nanoparticles were only detectable when insonified within plasma devoid of red blood cells and were shown to exhibit backscatter levels more than 30 dB below the backscatter from whole blood. Attenuation of nanoparticles in whole porcine blood was not measurably different from that of whole blood alone over a range of concentrations up to eight times the maximum in vivo dose. The resulting data provide upper bounds on blood pool attenuation coefficient and backscatter and will be needed to more precisely define levels of molecular contrast enhancement that may be obtained in vivo. 相似文献
108.
Hall CS Marsh JN Scott MJ Gaffney PJ Wickline SA Lanza GM 《The Journal of the Acoustical Society of America》2000,108(6):3049-3057
Complex molecular signaling heralds the early stages of pathologies such as angiogenesis, inflammation, unstable atherosclerotic plaques, and areas of remote thrombi. In previous studies, acoustic enhancement of blood clot morphology was demonstrated with the use of a nongaseous, fibrin-targeted acoustic nanoparticle emulsion delivered to areas of thrombosis both in vitro and in vivo. In this study, a system was designed and constructed that allows visualization of the evolution of acoustic contrast enhancement. To evaluate the system, two targets were examined: avidin-complexed nitrocellulose membrane and human plasma clots. The time evolution of enhancement was visualized in 10-min increments for 1 h. A monotonic increase was observed in ultrasonic reflection enhancement from specially treated nitrocellulose membranes for targeted emulsions containing perfluorooctylbromide (1.30+/-0.3 dB) and for perfluorooctane (2.64+/-0.5 dB) within the first 60 min of imaging. In comparison, the inherently nonechogenic plasma clots showed a substantial increase of 12.0+/-0.9 dB when targeted with a perfluoro-octane emulsion. This study demonstrates the concept of molecular imaging and provides the first quantifiable time-evolution report of the binding of a site-targeted ultrasonic contrast agent. Moreover, with the incorporation of specific drug treatments into the nanoparticulate contrast agent, ultrasonic molecular imaging may yield reliable detection and quantification of nascent pathologies and facilitate targeted drug therapy. 相似文献