Optimal region-of-interest MRI R2* measurements for the assessment of hepatic iron content in thalassaemia major

Objectives

To evaluate the performance of region-of-interest (ROI)-based MRI R2* measurements by using the first-moment noise-corrected model (M¹NCM) to correct the non-central Chi noise in magnitude images from phased arrays for hepatic iron content (HIC) assessment.

Methods

R2* values were quantified using the M¹NCM model. Three approaches were employed to determine the representative R2*: fitting of the ROI-averaged signal (average-then-fit, ATF); outputting the median and mean of R2*s from the pixel-wise fitting of decay signals within the ROI (denoted as PWFmed and PWFmea, respectively). The accuracy and precision of the three approaches were evaluated on synthesized data. The agreement among these approaches and their intra- and inter-observer reproducibility were assessed on 105 thalassaemia major patients.

Results

Simulations showed that ATF consistently yielded the highest accuracy and precision at varying noise levels. By contrast, PWFmed and PWFmea slightly and significantly overestimated high R2* at poor signal-to-noise ratios, respectively. Patient study showed that ATF agreed well with PWFmed, whereas PWFmea produced high R2* measurements for patients with severe HIC. No significant difference was observed in the reproducibility of the three approaches.

Conclusions

PWFmea tends to overestimate high R2*, whereas ATF and PWFmed can produce more accurate R2* measurements for HIC assessment.     

有源干扰条件下机载MIMO雷达降维STAP方法

针对机载多输入多输出雷达杂波与干扰的同时抑制问题,提出一种降维空时自适应处理方法.首先,利用系统参数离线简便构造出杂波子空间,然后,根据杂波基向量与干扰基向量的关系,对杂波加干扰协方差矩阵的秩进行分析.当存在有源干扰时,系统的杂波与干扰自由度进一步提高.最后利用干扰加噪声协方差矩阵的块对角结构,结合离线构造的杂波子空间,通过迫零方法进行空时自适应权矢量求解.该方法能够有效降低运算复杂度,具有接近全维最优处理的杂波与干扰抑制性能.     

Quantitative and qualitative assessment of articular cartilage in the goat knee with magnetization transfer imaging

We investigated the role of collagen in the magnetization transfer (MT) effect in contrast to other macromolecules. By means of phantoms made of collagen, chondroitin sulfate (CS) and albumin, MR parameters have been optimized in order to reduce the acquisition time and improve the sensitivity, as well as to minimize the contributions from CS and albumin to the MT induced signal attenuation. The same method was used to study cartilage ex vivo (bovine articular and nasal cartilage plugs) and in vivo (goat knee femoral chondyle). In phantom samples, the MT signal attenuation depended on the collagen concentration while contributions from the other macromolecules were found to be minimal. In average, analysis of MT images revealed a 25%, 35% and 30% signal attenuation in 10% w/v type I collagen gels, cartilage plugs, and cartilage from the weight-bearing areas of the goat knee, respectively. Biochemical data revealed that treatment of cartilage plugs with bacterial collagenase led to collagen depletion and correspondingly to a decrease of the MT response. In contrast, trypsin-induced proteoglycan loss in cartilage plugs did not alter the MT effect. A significant correlation was observed between the collagen content in these plugs and their respective MT ratios and the rate constant k for the exchange process bound versus free water. Finally, data obtained from in vivo MT measurement of the goat knee demonstrated that intra-articular injection of papain might not only cause degradation of proteoglycans but also a change in collagen integrity in a dose-dependent manner. We conclude that in vivo measurement of MT ratios gives quantitative and qualitative information on the collagen status and may be applied for the routine evaluation of normal and abnormal articular cartilage.     

低介电常数含氟氧化硅薄膜的红外光谱分析

用等离子体化学气相淀积 (PECVD)制备了含氟氧化硅薄膜 (Si OF薄膜 )。通过傅里叶变换红外光谱 (FTIR)分析 ,研究了氟掺入后薄膜结构的变化 ,并进一步讨论了氟对薄膜介电常数及吸水性的影响。研究表明氟掺入后改变了 Si- O键上的电荷分布 ,降低了薄膜中 Si- O键的极性 ,导致 Si- O键伸缩振动吸收峰发生蓝移。同时氟的掺入抑制了强极性 Si- OH键的形成。这些变化有利于薄膜中离子极化和偶极子转向极化的降低 ,因而使薄膜介电常数减小。对 Si- F吸收峰的高斯拟合表明 ,在氟含量较高时 ,薄膜中掺入的氟一部分会以 Si F2 结构存在。由于 Si F2 结构稳定性较差 ,易与水汽发生作用 ,因而高氟掺杂的 Si OF薄膜易吸水 ,并使薄膜性能变差     

全业务网APON光纤接入传输系统

介绍在国家八六三计划资助下研制成功的全业务网接入传输系统 ,首先简述了系统构成、用户业务接口和传输帧结构 ,接着对 HFC双向光纤传输系统进行了简介 ,最后介绍了 ATM- PON系统和HFC系统的性能指标     

Exponential Attractors in Banach Spaces

In this paper we extend the theory of exponential attractors from the Hilbert space setting in [4] to the Banach space setting. No squeezing conditions are needed; the only requirements are for the semiflow to be C ¹ in some absorbing ball, and for the linearized semiflow at every point inside the absorbing ball to split into the sum of a compact operator plus a contraction.     

Weakly Binding Molecules-Based Fast Charging Li-Ion Batteries

Fast charging of Li-ion batteries (LIBs) beyond standard 0.3 C (charged in 3.3 h) are desperately pursued but hindered by sluggish desolvation kinetics of ethylene carbonate-based traditional electrolyte, and Li-plating and dendrites growth at graphite anode and fire hazard. Herein, a new class of weakly binding all linear molecules-based nonflammable electrolyte (WNLE) is reported, comprising 1 m LiPF₆ in ethyl methyl carbonate and 2,2,2-trifluoroethyl acetate with additives for 10–20 times faster charging LIBs than traditional ones. The critical benefits of WNLE are 44% lower viscosity, 62% higher Li⁺ diffusion coefficient, 20% higher Li⁺ transference number, and 17% lower desolvation energy, which promotes diffusion kinetics and desolvation kinetics of Li⁺ in the vicinity of graphite anode enabling dendrites-free LIB, along with nonflammability. Under 3 C (charged in 20 min), WNLE-based industrial 800 mAh graphite//LiNi_0.8Mn_0.1Co_0.1O₂ (high active mass 13 mg cm⁻²) Li-ion pouch battery achieves outstanding 700 cycles, delivering 82% capacity retention and high Coulombic efficiencies ≈100%. Robust solid electrolyte interphase layers formed at the anode and cathode mitigate interfacial failures, making fast charge to 7 C and longer cycle-life. This new class of electrolyte formulation is a promising solution and a new opportunity to realize safe and long operation of fast-charging LIBs for practical applications.     

一场科学的辩论赛——谣言有罪盐无罪

Amid five tastes, only salt is indispensable. As a kind of essential nutrition, salt plays a vital role in our daily life. Although the salt is in small particle size, yet it received a lot of rumors. In recent years, rumors on salt have sprung like mushrooms including sea salt, iodized salt, low sodium salt, additive in salt and so on. To stop the rumors from spreading and to clarify that the salt is innocent, a debate competition was applied to tell the truth:rumors are guilty rather than salt!     

Improvements on the stability of Euler—Lagrange type cubic maps in quasi-Banach spaces

Analysis Mathematica - In this paper, we prove some improvements in results of Jun and Kim on stability of Euler—Lagrange type cubic functional equations in quasi-Banach spaces. The results...     

Quinolone and isoquinolone alkaloids: the structural-electronic effects and the antioxidant mechanisms

Structural Chemistry - Quinolone and isoquinolone alkaloids, which were found in the plant kingdom, are now potential antioxidants. In this case study, a quantum calculated procedure utilizing the...