High-temperature oxidation resistance and magnetic properties of Si-doped Sm2Co17-type magnets at 500 °C

The high-temperature oxidation resistance and magnetic properties of Si-doped Sm₂Co₁₇-type magnets at 500 °C were systematically investigated. The Sm(Co_0.76, Fe_0.1, Cu_0.1, Zr_0.04)₇Si_x (x=0–0.6) magnets were prepared by the conventional powder metallurgical technique. It is found that the addition of silicon in the Sm₂Co₁₇-type magnet can remarkably improve its oxidation resistance. Moreover, a small amount of silicon addition can also increase its high-temperature intrinsic coercivity. A maximum intrinsic coercivity of 6.7 kOe at 500 °C was obtained for the Sm₂Co₁₇-type magnet with Si content x=0.4, whose high-temperature maximum energy product loss was about 2.5 times smaller than pure Sm₂Co₁₇-type magnet after oxidation at 500 °C for 100 h, indicating the enhanced oxidation resistance. Its corresponding Curie temperature and saturation magnetization are about 723.9 °C and 7.4 kG, respectively.     

Design and construction progress of BRIF

A new RIB project, the Beijing Radioactive Ion-beam Facility （BRIF）, has been running at CIAE since 2004. In this project, a 100 MeV H-cyclotron, CYCIAE-100, is selected as the driving accelerator providing a 75-100 MeV, 200-500 μA proton beam. An ISOL system employs two stage separators to reach the mass resolution of 20000. Its RIB beam will be injected into the existing Tandem and a superconducting booster installed down stream of the Tandem will increase the energy by 2 MeV/q. The progress of BRIF, giving special emphasis to CYCIAE-100, will be introduced in this paper.     

FAIR�ռ���������������������ߵĸ������

阐述了FAIR收集环二极超导磁体电流引线的基本原理,给出了电流引线的主要参数及初步设计方案,提出了使用复合材料和通过结构优化以减小电流引线的漏热,并根据电流引线的传热特性进行了漏热的分析和计算,实验结果验证了概念设计的可行性。     

Absence of magnetic ordering in low dimensional mixed magnetic Mn1−xNixCl2·H2O

A new mixed magnet, Mn_1−xNi_xCl₂·H₂O, is examined by dc magnetization and susceptibility measurements across the entire composition range. The pure components are quasi-one-dimensional Heisenberg antiferromagnets ordering at 2.17 K (Mn) and 5.6₅ K (Ni) due to weaker interchain exchange supplementing the dominant exchange along MCl₂MCl₂M… chemical and structural chains. High temperature magnetic susceptibilities yield Curie and Weiss constants in χ_M=C/(T−θ). C(x) is linear but θ(x) displays curvature, which is analyzed to show that unlike-ion exchange is ferromagnetic and similar in size to like-ion. Most notable is the absence of antiferromagnetic susceptibility maxima down to 1.6 K from x=0.10 to 0.95. For x=0.05 a susceptibility maximum appears, with T_max almost 20% lower than in the pure Mn component but T_c reduced by 2%. The size of the susceptibility is enhanced by admixture, the effect of disrupted antiferromagnetic tendencies. Magnetization isotherms evolve with composition. Larger values of magnetization, under the same measuring conditions, occur for mixtures than for pure components, consistent with frustration, which weakens antiferromagnetic alignment tendencies. The competing ferromagnetic (Ni) and antiferromagnetic (Mn) intrachain interactions, along with disorder and low dimensional characteristics, presumably lead to the absence of magnetic order over a remarkably broad composition range.     

Effect of post-sintering annealing on microstructure and coercivity of Al85Cu15-added Nd-Fe-B sintered magnets

Effects of post-sintering annealing on the microstructure and coercivity have been investigated for the Al₈₅Cu₁₅-added (Pr, Nd)_14.8Fe_78.7B_6.5 sintered magnets. It is found that the optimum annealing temperature at which the coercivity _iH_c reaches a maximum decreases from 550 °C for the magnets added with 0.3% and 0.6% Al₈₅Cu₁₅ to 480 °C for the magnets added with 0.9% and 1.2% Al₈₅Cu₁₅. The decrease in optimum annealing temperature is related to the precipitation of Al-Cu or (Pr, Nd)−Cu liquid phase among (Pr, Nd)-rich phases during annealing. Existence of Al-Cu or (Pr, Nd)−Cu liquid phase is beneficial to dissolve the irregularities of (Pr, Nd)₂Fe₁₄B grain interface and increase the quantities of (Pr, Nd)-rich phases at the grain boundary, thus optimizing the grain boundary microstructure. The modifications of the microstructure are helpful to decouple the exchange interaction between (Pr, Nd)₂Fe₁₄B hard magnetic grains, thereby increasing the coercivity.     

In vivo imaging of the human brain at 1.5 T with 0.6-mm isotropic resolution

We present high-resolution in vivo anatomical scans with 3D whole-brain coverage and an isotropic resolution of 0.6 mm, obtained at a clinical field of 1.5 T. The data are acquired in 10 independent scans over two sessions using a 3D magnetization-prepared, gradient echo sequence, modified to output phase images in addition to magnitude images. The independent scans are coregistered to correct for head motion, prior to performing complex averaging. The resolution of the final, averaged image, is found to be equal to the nominal one.     

Simulating the effects of time-varying magnetic fields with a realistic simulated scanner

Transient magnetic fields induce changes in magnetic resonance (MR) images ranging from small, visually undetectable effects (caused, for instance, by neuronal currents) to more significant ones, such as those created by the gradient fields and eddy currents. Accurately simulating these effects may assist in correcting or optimising MR imaging for many applications (e.g., diffusion imaging, current density imaging, use of magnetic contrast agents, neuronal current imaging, etc.). Here we have extended an existing MR simulator (POSSUM) with a model for changing magnetic fields at a very high-resolution time-scale. This simulator captures a realistic range of scanner and physiological artifacts by modeling the scanner environment, pulse sequence details and subject properties (e.g., brain geometry and air-tissue boundaries).     

Guided e-MRI prostate biopsy can solve the discordance between Gleason score biopsy and radical prostatectomy pathology

Introduction

The aim of this study is to examine if guided prostate biopsies based on abnormalities detected by conventional and functional endorectal magnetic resonance imaging (MRI) yield a more reliable representation of the radical prostatectomy pathology and to identify probable preoperative clinical variables that stratified patients likely to harbor significant upgrading.

Patients and Methods

From April 2004 to April 2009, a review of N=70 patients records diagnosed with prostate cancer by a 3-6 core guided transrectal ultrasound (TRUS) prostate biopsy based on abnormalities detected by conventional and functional endorectal MRI and who subsequently underwent radical prostatectomy and exhibited a significant upgrading was conducted. Additionally, a multivariate analysis with a significant upgrading as the outcome was performed including the following parameters: prostate specific antigen (PSA) level, clinical stage, prostate size and duration from biopsy to radical prostatectomy.

Results

A significant upgrading was noted in only 8.5% of patients, with 1.4% exhibiting a significant downgrading and the rest 90.1% exhibiting an exact Gleason score match. No preoperative clinical variables that stratified patients likely to harbour significant upgrading were identified.

Conclusions

This type of biopsy method seems to solve the discordance between the biopsy Gleason score and radical prostatectomy pathology regardless of known preoperative clinical variables that can affect it.     

Identification of efferent flow in the superior vena cava and azygos vein confluence using cine phase-contrast MRI: speculation of the role of the azygos arch valves

Purpose

We aimed to evaluate flow patterns in the superior vena cava (SVC) and azygos vein confluence with cine phase-contrast magnetic resonance imaging with consideration for the role played by the azygos arch valves.

Materials and Methods

Two-dimensional cine phase-contrast magnetic resonance images of the SVC and azygos vein confluence were prospectively acquired in 10 healthy volunteers. Flow directions during the cardiac cycle were evaluated quantitatively using sequential flow profile graphs obtained from each orthogonal image and affirmed visually by two radiologists from the oblique sagittal cine images.

Results

Although the blood in the SVC and azygos vein confluence had an afferent flow during the systolic phase, a slight temporal efferent flow during the diastolic phase was quantitatively observed in all cases. Flow in the SVC can also be confirmed visually. The average velocity, average maximum afferent velocity during the systolic phase and average maximum efferent velocity during the diastolic phase of the SVC were 8.7±2.4, 19.9±3.7 and −1.0±3.2 cm/s, respectively; for the azygos vein confluence, these values were 2.2±1.5, 7.1±2.6 and −1.5±1.1 cm/s, respectively.

Conclusion

We verified that a slight temporal efferent flow exists in the SVC and azygos vein confluence during the diastolic phase, which suggests that the usual role of the azygos arch valves is to prevent this physiological retrograde flow.