双负超颖材料中的声学界面波

声学超颖材料中可以观察到声学界面波的存在。超胞方法被用来研究这种存在于非完全禁带中的界面波的色散关系和本征场分布。进一步,等效介质理论被用来证明这种界面波模式是由声学超颖材料的双负响应引起的。通过利用这种界面波模式,可以获得用于超声成像的声学超透镜。

桩基础支撑的周期性高架桥结构的缺陷态研究

基于传递矩阵方法,对桩基础支撑的周期性高架桥结构在面外振动下的缺陷态进行研究。为考虑高架桥上部结构与桩基础的耦合,首先建立分析桩-土相互作用的边界元模型。利用上述边界元模型,梁和墩的传递矩阵,梁-梁-墩接头处的联结条件及传递矩阵方法,推导了高架桥单跨的传递矩阵。缺陷周期性高架桥结构的缺陷态可通过标准跨和缺陷跨的传递矩阵及超原胞方法求解得到。超原胞的能带显示,缺陷高架桥存在缺陷态;当频率为缺陷态频率时,超原胞的缺陷波模态表明波动会局域在高架桥的缺陷跨处。

Current role of ultrasound for the management of hepatocellular carcinoma

Hepatocellular carcinoma （HCC） has a decisive influence on the prognosis of cirrhotic patients. Although α-fetoprotein （AFP） is a known and specific tumor maker for HCC, it is not suitable for the screening and surveillance of HCC because of its poor predictive value and low sensitivity. The use of imaging modalities is essential for the screening, diagnosis and treatment of HCC. Ultrasound （US） plays a major role among them, because it provides real-time and non-invasive observation by a simple and easy technique. In addition, US-guided needle puncture methods are frequently required for the diagnosis and/or treatment process of HCC. The development of digital technology has led to the detection of blood flow by color Doppler US, and the sensitivity for detecting tumor vascularity has shown remarkable improvement with the introduction of microbubble contrast agents. Moreover, near realtime 3-dimensional US images are now available. As for the treatment of HCC, high intensity focused ultrasound （HIFU） was developed as a novel technology that provides transcutaneous ablation effect without needle puncture. These advancements in the US field have led to rapid progress in HCC management, and continuing advances are expected. This article reviews the current application of US for HCC in clinical practice.

Overexpression of Slug is associated with malignant progression of esophageal adenocarcinoma

AIM: To characterise expression of known E-cadherin repressors; Snail, Slug and Twist in the development of esophageal adenocarcinoma. METHODS: E-cadherin, Slug, Snail and Twist mRNA expression in Barrett's metaplasia and esophageal adenocarcinoma specimens was examined by real-time reverse transcription-polymerase chain reaction (RT-PCR). Semi-quantitative immunohistochemistry was used to examine cellular localisation and protein levels. The effect of Slug on epithelial mesenchymal transition (EMT) markers was examined by transfection of Slug into an adenocarcinoma line OE33.RESULTS: Cellular localisation of Slug in Barrett's metaplasia was largely cytoplasmic whilst in adenocarcinoma it was nuclear. Semi-quantitative analysis indicated that Slug was more abundant in adenocarcinoma compared to matched Barrett's metaplastic specimens. Snail and Twist were expressed in adenocarcinoma but were cytoplasmic in location and not induced compared to Barrett's mucosa. These observations were supported by mRNA studies where only Slug mRNA was shown to be over-expressed in adenocarcinoma and inversely correlated to E-cadherin expression. Overexpression of Slug in OE33 mediated E-cadherin repression and induced the mesenchymal markers vimentin and fibronectin.CONCLUSION: Progression to adenocarcinoma is associated with increased Slug expression and this may represent a mechanism of E-cadherin silencing.

Comparative study of helical CT with contrast-enhanced ultrasound of renal carcinoma

Objective: To investigate the efficiency of helical CT comparing with contrast-enhanced ultrasound, and to im- prove the diagnosis efficiency of renal cell carcinoma (RCC). Methods: Thirty RCCs confirmed pathologically were studied retrospectively. The un-enhanced CT scan and the triphasic enhanced helical CT scan were performed in all cases, the gray-scale US and angiosonography with SonoVue were performed in all cases meantime. Results: 22 cases (73.3%) were diagnosed correctly by helical CT alone before operation. 7 cases (23.3%) were suspected as RCC with helical CT. One case (3.3%) was misdiagnosed with helical CT. 25 cases (83.3%) were diagnosed correctly with contrast-enhanced ultrasound alone pre-operation. One case (3.3%) was suspected as RCC with angiosonography. Four cases (13.3%) were misdiagnosed with angiosonography alone. 29 cases (96.7%) were diagnosed correctly by helical CT combining with angiosonography before operation, one case (3.3%) was diagnosed as renal mass with both helical CT and angiosonography. Conclusion: Contrast-enhanced ultrasound is sensitive in detecting blood flow, it can detect the enhancement of the tumor which cannot be detected by helical CT. CT and angiosonography have strong complement each other in the diagnosis of RCC.

Intravenously Injected Mesenchymal Stem Cells Home to Infarcted Myocardium Without Altering Cardiac Function

Background:Systemic delivery of mesenchymal stem cells (MSCs) to the infarcted myocardium is an attractive noninvasive strategy, but therapeutic effect of this strategy remain highly controversial. Methods: Myocardial infarction was induced in female Sprague-Dawley rats by transient ligation of the left anterior descending coronary artery for 60 min. Either 2.5×106 DiI-labeled MSCs or equivalent saline was injected into the tail vein at 24 h after infarction.Results: Three days later, MSCs localized predominantly in the infarct region of heart rather than in the remote region. MSCs were also observed in spleen, lung and liver. At 4 weeks after infarction, echocardiographic parameters, including ejection fraction, fractional shortening, left ventricular end-diastolic and end-systolic diameters, were not significantly different between MSCs and saline groups. Hemodynamic examination showed that ±dp/dtmax were similar between MSCs and saline-treated animals. Histological evaluation revealed that infarct size and vessel density were not significantly changed by MSCs infusion.Conclusion: Intravenously injected MSCs can home to infarcted myocardium, but plays a limited role in cardiac repair following myocardial infarction.