Study of brain anatomy with high-field MRI: recent progress

Recent developments in high-field magnetic resonance imaging technology have led to improved contrast and resolution and are opening up new possibilities for the study of human brain anatomy. In particular, techniques sensitized to magnetic susceptibility contrast provide particular advantages at high field that have allowed visualization of brain structures that have been difficult to detect with conventional technology. In this review, some of these developments and techniques will be discussed, and an attempt will be made to interpret magnetic susceptibility contrast based on recent studies.     

Quantification of microporosity in fruit by MRI at various magnetic fields: comparison with X-ray microtomography

Microstructure determines the mechanical and transport properties of fruit tissues. One important characteristic of the microstructure is the relative volume fraction of gas-filled intercellular spaces, i.e., the tissue microporosity. Quantification of this microporosity is fundamental for investigating the relationship between gas transfer and various disorders in fruit.     

An Investigation of the Effect of Semi-Acetal Formation on the Properties of Dialdehyde Starch and its Thermoplastic Blend with Glycerol

Dialdehyde sweet potato starch (DASS) with various aldehyde contents was prepared and the properties analyzed in terms of solubility, intrinsic viscosity, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results demonstrated that when the aldehyede content of DASS was increased from 20% to 95%, the solubility, molecular weight, crystallizability, and thermal stability decreased. Thermoplastic DASS (TPDASS) was prepared by adding glycerol as a plasticizer; the thermal, rheological, hydrophobic, and tensile properties of TPDASS were investigated. The results indicated that, for the same glycerol content, with the increase of aldehyde content, the moisture adsorption decreased, while the shear viscosity, glass transition temperature, and tensile properties of TPDASS increased significantly. The effects were attributed to the introduction of aldehyde groups reducing the hydrogen bonds and decreasing the hydrophility of the starch. Moreover, the aldehyde and hydroxyl groups of DASS favored a semi-acetal formation with higher aldehyde content and cross-linking of DASS occurred with the increase of aldehyde content. In summary, compared to starch, the thermoplastic properties and hydrophobicity of DASS was improved. In the presence of water (10 wt%), the tensile strength of TPDASS with 95% aldehyde content (TPDASS95) moderately decreased, from 16.7 MPa to 14.0 MPa, when the glycerol content increased from 10% to 30%. The TPDASS with improved properties will find their applications in preparing biodegradable plastics.     

基于2-苯基-4-喹啉酸及双咪唑类配体的钴(Ⅱ)配合物的合成、表征、磁性和电化学性质

利用2-苯基-4-喹啉酸、苯-1,4-双(咪唑基-1-甲基)和乙酸钴在二甲基甲酰胺和水的混合溶剂中反应,得到配合物[Co(pqba)2(biyb)](1)(Hpqba=2-苯基-4-喹啉酸,biyb=苯-1,4-双(咪唑基-1-甲基))。采用元素分析、红外光谱、X单晶衍射结构分析、热重分析等方法对配合物进行了表征和结构测定。配合物1属单斜晶系,C2/c空间群。配合物1中的biyb配体采用双齿桥链模式连接金属钴离子首先形成一维"之"字链,通过π…π堆积作用,进一步拓展为二维超分子结构。循环伏安法测试结果说明配合物1的电解过程为准可逆过程。磁化率测量表明,配合物1具有反铁磁性质。     

FeIII in a high-spin state in bis(5-bromosalicylaldehyde 4-ethylthiosemicarbazonato-κ3O,N1,S)ferrate(III) nitrate monohydrate,the first example of such a cationic FeIII complex unit

The synthesis and crystal structure (100 K) of the title compound, [Fe(C₁₀H₁₁BrN₃OS)₂]NO₃·H₂O, is reported. The asymmetric unit consists of an octahedral [Fe^III(HL)₂]⁺ cation, where HL^? is H-5-Br-thsa-Et or 5-bromosalicylaldehyde 4-ethylthiosemicarbazonate(1?) {systematic name: 4-bromo-2-[(4-ethylthiosemicarbazidoidene)methyl]phenolate}, a nitrate anion and a noncoordinated water molecule. Each HL^? ligand binds via the thione S, the imine N and the phenolate O atom, resulting in an Fe^IIIS₂N₂O₂ chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. This [Fe(HL)₂](anion)·H₂O compound contains the first known cationic Fe^III entity containing two salicylaldehyde thiosemicarbazone derivatives. The Fe^III ion is in the high-spin state at 100 K. In addition, a comparative IR spectroscopic study of the free ligand and the ferric complex is presented, demonstrating that such an analysis provides a quick identification of the degree of deprotonation and the coordination mode of the ligand in this class of metal compounds. The variable-temperature magnetic susceptibility measurements (5–320 K) are consistent with the presence of a high-spin Fe^III ion with a zero-field splitting D = 0.439 (1) cm^?1.     

Successive approximation-like 4-bit full-optical analog-to-digital converter based on Kerr-like nonlinear photonic crystal ring resonators

Implementing of photonic sampling and quantizing analog-to-digital converters (ADCs) enable us to extract a single binary word from optical signals without need for extra electronic assisting parts. This would enormously increase the sampling and quantizing time as well as decreasing the consumed power. To this end, based on the concept of successive approximation method, a 4-bit full-optical ADC that operates using the intensity-dependent Kerr-like nonlinearity in a two dimensional photonic crystal (2DPhC) platform is proposed. The Silicon (Si) nanocrystal is chosen because of the suitable nonlinear material characteristic. An optical limiter is used for the clamping and quantization of each successive levels that represent the ADC bits. In the proposal, an energy efficient optical ADC circuit is implemented by controlling the system parameters such as ring-to-waveguide coupling coefficients, the ring’s nonlinear refractive index, and the ring’s length. The performance of the ADC structure is verified by the simulation using finite difference time domain (FDTD) method.     

GaAs pyramidal quantum dot coupled to wetting layer in an AlGaAs matrix: A strain-free system

In this contribution, the electronic and linear and nonlinear optical properties of pyramid-shaped GaAs quantum dots (QDs) coupled to wetting layer (WL) in an Al_0.3Ga_0.7As matrix have been investigated. This nanostructure is relaxed from strain effects due to very small lattice-mismatching. Three transitions of P-to-S, WL-to-P, and WL-to-S were considered and the corresponding transition dipole moments, oscillator strengths, and linear and nonlinear optical properties regarding to these transitions were investigated as a function of the QD height. The results showed that for P-to-S transition, which is a purely in-plane-polarized transition, the dependence of electronic and optical properties on the size is moderate and can be neglected. But for WL-to-P and WL-to-S transitions, which are in-plane- and z-polarized transitions, respectively, the electronic as well as optical properties are strongly size-dependent. Furthermore, a competition between WL-to-S and WL-to-P transitions was observed when the QD size changed.     

Ferrimagnetic behaviors in a double-wall cubic metal nanotube

A double-wall cubic metal nanotube consists of the ferromagnetic spin-1 inner shell and spin-3/2 surface shell. It is of the ferrimagnetic exchange coupling between two shells. Considering the single-ion anisotropy and transverse field exist together, the magnetization, the initial susceptibility, the internal energy and the specific heat have been investigated by using the effective-field theory with correlations. Some interesting phenomena have been found in the thermal variations of the system. Magnetization appears two or three compensation points in certain parameters. It is an unconventional ferrimagnetic behavior in the nanotube. The shapes of total magnetization and the initial susceptibility are great influenced by the surface exchange coupling, surface single-ion anisotropy and surface transverse field. Some results of nanotube may have potential applications in different research fields, such as electronics, optics, mechanics, and even biomedicine and molecular devices.     

近红外光谱法在红曲菌固态发酵过程参数检测中的应用

研究了近红外光谱技术快速检测红曲菌固态发酵过程参数水分含量和pH值的可行性。针对传统基于间隔策略波长选择方法忽略非线性因素的缺点,采用一种基于最小二乘支持向量机(Least squares support vector machines,LS-SVM)非线性模型的波长筛选算法：联合区间最小二乘支持向量机(Synergy interval least squares support vector machines,siLS-SVM),并将新算法与相关系数法、iPLS算法、siPLS算法对比。实验结果显示,联合siLS-SVM算法和LS-SVM模型取得了最好的预测效果,水分含量、pH值的预测集相关系数(Rp)分别为0.962 1、0.976 1,预测均方根误差(RMSEP)分别为0.012 9、0.145 2,表明模型具有较好的拟合度和预测性能。应用近红外光谱法进行红曲菌固态发酵过程的水分含量和pH值的快速检测可行,该方法为进一步实现其过程参数的在线检测及发酵条件优化提供了技术基础。