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BACKGROUND: Inhibitory coating can prevent nanoparticle oxidation, grain growth, corrosion and agglomeration, and endow nanoparticle with special properties. ABJECTIVE: To prepare SiO2/Ni core-shell type nanoparticles and assess their magnetic properties. DESIGN, TIME AND SETTING: The observation experiment was performed between November 2005 and March 2006 at Nanometer Compound Material Research Laboratory of Dalian University of Technology, Dalian, Liaoning Province, China. MATERIALS: Nanometer nickel powder prepared by DC arc plasma jet method, Na2SiO3 produced by Bazhou Chemical Industry Branch Factory of Tianjin Quartz Clock Factory (China).METHODS: SiO2/Ni core-shell type nanoparticles were synthesized by coating a layer of SiO2 on the surface of manometer nickel powder via liquid deposition method using Na2SiO3 as the main source material. MAIN OUTCOME MEASURES: Their microstructures and material properties were investigated by X-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscopy, thermo-gravimetric analysis, differential scanning calorimetry and vibrating sample magnetometer. RESULTS: The experimental results showed that SiO2 shell was in an amorphous state around Ni cores and it avoided agglomeration of the Ni nanoparticles. The oxidation temperature of nanometer nickel powder coated by SiO2 elevated from 287 ℃ to 385 ℃. The analysis result of magnetic properties indicated that the hysteresis loop of Ni had an excursion for the existence of anti-ferromagnetic NiO, the silica coating reduced the saturation magnetization and improved the coercivity. CONCLUSION: Preparation of SiO2/Ni core-shell type nanopartieles was successful; silica coating improved the oxidation resistance of nanometer nickel powder, endowed nanometer nickel powder better ferromagnetism and improved the coercivity.

8.Value of endoscopic ultrasound in distinguishing ectopic pancrease and stromal tumor in stomach

Xuan SONG ; Zhiping CUI ; Hongsheng HAO ; Wenjie LI ; Xuefeng LU ; Yanqing LI ; Lijuan SUN ; Xiaoheng LU

Chinese Journal of Ultrasonography 2012;21(9):775-778

Objective To explore the value of endoscopic ultrasound (EUS) in differential diagnosis of ectopic pancreas and stromal tumor in stomach.Methods The clinical data and endoscopic ultrasound findings of 40 patients with ectopic pancrea and 141 patients with stromal tumor were retrospectively analyzed,including the location,size,growth pattern,layer of origin,internal echo pattern and so on.All patients were diagnosed pathologically.Results Ectopic pancreas were predominantly located in the antrum (92.5％) and stromal tumor were mainly located in the gastric body (45.4％),the antrum (23.4％) and the fundus (22.0％),there was a significant difference in lesion' s location between two diseases (P ＜0.001).There was no statistical difference in the ratio of longest/shortest diameter of the lesion size(P =0.057).But there was statistical difference in lesion size between ectopic pancrease and stromal tumor [(19.98 ± 12.80)mm vs (11.25 ± 3.61)mm].Mural growth pattern was most common in ectopic pancrease (82.5％) and mural growth pattern (37.6％),extraluminal growth pattern (24.8％) and intraluminal growth pattern (22.7％) in stromal tumor (P ＜0.001).The third layer (75.0％) was predominant in ectopic pancrease while the fourth (54.6％) and the second layers (34.0％) in stromal tumor (P ＜0.001).With regard to internal echo pattern,hypoechoic (32.5％),intermediate (27.5％) and heterogeneous (27.5％) was predominant in ectopic pancrease and homogeneous hypoechoic lesion (72.3％) in the stromal tumor (P ＜ 0.001).Conclusions There were statistical differences between ectopic pancrease and stromal tumor in the location,size,layer of origin,growth pattern and internal echo pattern under EUS.EUS plays an important role in identification of ectopic pancrease and stromal tumor.