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This study aimed to compare the porcelain-fused-to-metal (PFM) crown artifact in the magnetic resonance imaging (MRI) of the two magnetic resonance deartifact techniques in studying the application value of the propeller-fast spin-echo T2-weighted sequence (FSE T2WI) in troubleshooting PFM crown artifacts.A total of 48 patients with right mandible first molar crown who underwent MRI head examination were chosen as subjects in the study. According to different metal substrates, PFM crowns were divided to three types, namely, nickel-chromium alloy crown, cobalt-chromium alloy crown and titanium crown. The patients received two MRI scan sequences, that is, FSE T2WI and propeller-FSE T2WI sequences. The MRI artifacts areas in two sequences were measured.The difference between FSE T2WI and propeller-FSE T2WI sequences in three kinds of PFM crown was significant (P0.05).Propeller-FSE T2WI sequence technique can effectively reduce the metal artifacts of various PFM crowns.目的 通过比较金属烤瓷冠在2种磁共振去伪影技术MRI成像中的伪影大小，探讨螺旋桨成像（propeller）-快速自旋回波T2加权（FSE T2WI）序列技术在降低金属伪影中的应用价值。方法 收集存在右下颌第一磨牙金属烤瓷冠且行MRI头颅检查的患者48例，根据金属基底的不同将金属烤瓷冠分为镍铬合金烤瓷冠、钴铬合金烤瓷冠、纯钛烤瓷冠。48例患者均采用MRI扫描仪进行FSE T2WI序列扫描和propeller-FSE T2WI序列扫描，比例2种序列下金属烤瓷冠的MRI伪影面积大小。结果 propeller-FSE T2WI序列下各金属烤瓷冠形成的伪影面积均小于FSE T2WI序列，差异具有统计学意义（P0.05）。结论 Propeller-FSE T2WI技术能有效降低金属烤瓷冠的金属伪影。.

The preparation of vertically or horizontally aligned self-assemblies of CoP nanowires is demonstrated for the first time by aging them in the reaction solution for a sufficient time at 20 or 0 °C. This strategy opens up a way for exploring the controlled self-assembly of various highly anisotropic nanostructures into long-range ordered structures with collective properties.

We present evidence of topological surface states in β-Ag2Te through first-principles calculations, periodic quantum interference effect and ambipolar electric field effect in single crystalline nanoribbon. Our first-principles calculations show that β-Ag2Te is a topological insulator with a gapless Dirac cone with strong anisotropy. To experimentally probe the topological surface state, we synthesized high quality β-Ag2Te nanoribbons and performed electron transport measurements. The coexistence of pronounced Aharonov-Bohm oscillations and weak Altshuler-Aronov-Spivak oscillations clearly demonstrates coherent electron transport around the perimeter of β-Ag2Te nanoribbon and therefore the existence of topological surface states, which is further supported by the ambipolar electric field effect for devices fabricated by β-Ag2Te nanoribbons. The experimental evidences of topological surface states and the theoretically predicted anisotropic Dirac cone of β-Ag2Te suggest that the material may be a promising candidate of topological insulator for fundamental study and future spintronic devices. Published version

In the field of nanoscience, the ability to prepare high-quality nanocrystals is crucial for fundamental research and technology development. Herein, we review a general route for the colloidal preparation of monodisperse nanocrystals, which is divided into five different stages, namely (i) nucleation, (ii) growth, (iii) Ostwald ripening, (iv) surfactant capping and (v) precipitation. Each of the five stages is discussed in detail to provide a comprehensive understanding of the mechanism behind nanocrystal formation and the subsequent processing steps. We put emphasis on the classical theories and experimental techniques that are most frequently practiced. These are useful for the successful design and fabrication of nanocrystals with properties that are beneficial for use in a plethora of technological applications.