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| 1 | Optimization of core-shell structure distribution in sintered Nd-Fe-B magnets by titanium addition显示文摘In view of the uneven distribution of the core-shell structure of sintered Nd-Fe-B magnets after grain boundary diffusion,this study proposes to use high-melting-point and reactive element titanium(Ti)as an additive to increase the diffusion channels and to enhance the diffusion of heavy rare earth elements along the grain boundary phase.By adding Ti element,the diffusion depth and hence the intrinsic coercivity of magnets are increased significantly.The addition of Ti increases the coercivity at two stages:initially from 16.07 to 16.29 kOe by addition effect,and then from 16.29 to 25.16 kOe by facilitating the diffusion of Tb element.The formation of TiB_(2) phase improves the periodic arrangement of the crystal structure in the surroundings of the grain boundary phase and enhances its activity.The improved grain boundary diffusion and better core-shell structure distribution provide a theoretical guidance fo r solving the problem of diffusion depth in bulk magnets. | Shuwei Zhong Munan Yang Sajjad Ur Rehman Sangen Luo Longgui Li Chao Li Jiajie Li Shuhua Xiong Ihor Bulyk Bin Yang | 2023 | Journal of Rare Earths2023，41，7： | 1 |
| 2 | Temperature dependence of photoluminescence from self-organized Ge quantum dots with large size and low density显示文摘Photoluminescence(PL) from self-organized Ge quantum dots(QDs) with large size and low density has been investigated over a temperature range from 10 to 300 K using continuous-wave(CW) optical excitation.The integrated PL intensity of QDs observed is negligible at about 10 K and rapidly increases with raising temperature up to 100 K.Through analyzing the PL experimental data of the QDs and wetting layer(WL),we provide direct evidence that there exists a potential barrier,arising from the greater compressive strain surrounding large QDs,which could trap carriers in WL at low temperatures and could be overcome via increasing temperature. | LI Hui HE Tao DAI LongGui WANG XiaoLi WANG WenXin CHEN Hong | 2011 | Science China(Physics,Mechanics & Astronomy)2011，54，2： | 1 |
| 3 | Role of Conformational Entropy in Complex Macromolecular Systems显示文摘Conformation is the key to revealing the physical characteristics of macromolecular systems and receives tremendous interest from the fields of polymer physics and biological materials.The conformational entropy,related to the number of conformations of the macromolecule,plays a predominant role in the structural formation,transition,and dynamics of macromolecular systems.In this review,we present a comprehensive overview of the research,development and applications of the conformational entropy in complex macromolecular systems.We begin by discussing the physical origin of the conformational entropy based on statistical mechanics of macromolecules in classical polymer physics,and then introduce the recent progress on the predictive modeling of the conformational entropy,associated with a variety of typical macromolecular systems.Furthermore,we also highlight several principles and rules,which have been harnessed to manipulate the structural organization of complex macromolecular systems through the conformational entropy.We anticipate that this review will further promote fundamental research in polymer physics,and offer intriguing prospects for applications in complex macromolecular systems including biomacromolecules,grafted nanoparticles,and polymer nanocomposites. | DAI Xiaobin WAN Hai-Xiao ZHANG Xuanyu WEI Wenjie CHEN Wenlong ZHANG Longgui LI Juan YAN Li-Tang | 2023 | Chemical Research in Chinese Universities2023，39，5： | 0 |
| 4 | Molecular mechanism of carvedilol on attenuating the reversion back towards fetal energy metabolism during the development of cardiac hypertrophy显示文摘Objective to explore the molecular mechanism of carvedilol effect on fetal energy metabolism during the development of cardiac hypertrophy. Methods Male Wistar rats were divided into the coarctation of abdominal aorta group (CAA), sham operation group (SH), and carvedilol intervention group (CAR+CAA, carvedilol 30mg·kg -1 ·day -1 orally) and carvedilol control group (CAR+SH). Hemodynamics, ventricular remodeling parameters, free fatty acid in blood serum and cardiac myocyte, RT PCR analysis of the expressions of Muscle Carnitine Palmitoyltransferase I (M CPT I) and Medium Chain Acyl CoA Dehydrogenase (MCAD) mRNA were measured in all rats at 16 week after operation. Results Left ventricular hypertrophy occurrd after operation 16 weeks in group of CAA, accompanying with plasma free fatty acids accumulation, and both the levels of M CPT I and MCADmRNA were decreased significantly ( P <0.05). Carvedilol can reduce the left ventricular hypertrophy induced by pressure overload. The gene expressions of rate limiting enzyme(M CPT I) and key enzyme of fatty acid (MCAD) were upregulated in the CAR+CAA group, comparing with CAA group ( P <0.05). There was no statistically significant difference between SH group and CAR + SH group. Pressure overload in CAA rats downregulates the gene expression of rate limiting enzyme and key enzyme of fatty acid oxidation. Conclusions The intervention with carvedilol may attenuates the reversion of the metabolic gene expression back towards fetal type through up regulating the expression of M CPT I and MCADmRNA. Thus, carvedilol may confer cardioprotective effects in heart failure partly by preserving of the normal metabolic gene regulation. | HU Qin 1, LI Longgui 2, WU Lirong 1, GENG Zhaohua 2 1Department of Cardiololgy, Affiliatted Hospital of Guiyang Medical College, Guiyang 550001, China. 2Cardiology center of PLA, Department of Cardiololgy, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China | 2003 | 介入放射学杂志2003，12，S1： | 0 |
| 5 | The influence of pressure on the growth of a-plane GaN on r-plane sapphire substrates by MOCVD显示文摘Nonpolar a-plane (110) GaN films have been grown on r-plane (102) sapphire by metal-organic chemical vapor deposition (MOCVD) under different growth pressures. The as-grown films are investigated by optical microscopy, high-resolution X-ray diffraction (HRXRD) and Raman scattering. As growth pressure rises from 100 mbar to 400 mbar, the surface gets rougher, and the in-plane XRD full width at half maximum (FWHM) along the c-axis [0001] increases while that along the m-axis [100] decreases. Meanwhile, residential stresses are reduced along both the c-axis and the m-axis. The structural anisotropy feature under 400 mbar is inverted with respect to 100 mbar, and the weakened anisotropy is achieved under a moderate pressure of 200 mbar, probably due to the suppressed Ga atomic migration along the c-axis under a larger pressure. We propose that pressure can affect a-plane growth through the V/III ratio. | HE Tao LI Hui DAI LongGui WANG XiaoLi CHEN Yao MA ZiGuang XU PeiQiang JIANG Yang WANG Lu JIA HaiQiang WANG WenXin CHEN Hong | 2011 | Science China(Physics,Mechanics & Astronomy)2011，54，3： | 0 |
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