An improved 1H magnetic resonance spectroscopic imaging technique for the human breast: preliminary results

The high sensitivity but poor specificity of magnetic resonance imaging for detecting breast cancer has stimulated interest in magnetic resonance spectroscopic imaging (MRSI) as a tool to improve specificity and reduce the number of benign biopsies. The challenge of applying 1H MRSI to the diagnosis of cancer in the human breast is the need for robust lipid suppression and a clinically acceptable acquisition time. We present an improved 1H MRSI technique that uses an independently optimized chemical-shift-selective for lipid suppression and weighted elliptical k-space sampling combined with a Hamming filter for improved sampling efficiency.     

无模板合成微米管状Co3O4基复合材料高效催化电解水析氧反应

电解水制氢因具有清洁高效的优点而被认为是大规模生产氢能最有希望的技术之一.然而,电解水半反应之一的析氧反应(OER)需经历复杂且动力学缓慢的4电子转移过程.加之热力学上的阻碍,OER实际需要的电位远大于1.23 V的理论值,导致其能耗高,限制了电解水的效率和商业化应用.因此,亟待开发高效的OER电催化剂.管状结构具有较高的比表面积、充分暴露的活性位点和丰富的短路径扩散通道,是一种理想的电催化结构.同时,Co3O4基材料因其制备容易、成本低和OER电催化学活性较高等特点,成为近年来电催化材料的研究热点.此外,非金属元素P的掺杂条件温和,并且可以有效改变过渡金属电子结构.因此,本文通过合理设计管状的Co3O4基电催化剂并进行P掺杂,尝试将形貌调控和元素改性的优势发挥到最大.为了解析影响生成管状结构的因素,本文通过控制变量法系统地研究了管状Ni/Co3O4的制备条件,包括阳离子种类和含量、添加剂种类和含量、阴离子种类等对催化剂形貌和性能的影响.表征结果表明,初始的乙酸钴镍氢氧化物棱柱对反应环境较为敏感,从而成为直接影响最终微米管状结构的关键因素.此外,对Ni/Co3O4微米管进行适量的P掺杂,能提高材料的电子传输性能和优化材料的电子结构;而且P的掺杂直接提高了样品中的M3+/M2+比例(M代表Co和Ni),而M3+是M基电催化材料的活性位点,这进一步增加了OER的活性位点进而提高其催化活性.总之,通过结构和成分的优化,得到了OER催化性能显著提高的微米管状P-Ni/Co3O4,其性能甚至超过了商业化RuO2电催化剂.     

Low-Temperature Synthesis of Solution Processable Carbon Nitride Polymers

Carbon nitride materials require high temperatures (>500 °C) for their preparation, which entails substantial energy consumption. Furthermore, the high reaction temperature limits the materials’ processability and the control over their elemental composition. Therefore, alternative synthetic pathways that operate under milder conditions are still very much sought after. In this work, we prepared semiconductive carbon nitride (CN) polymers at low temperatures (300 °C) by carrying out the thermal condensation of triaminopyrimidine and acetoguanamine under a N₂ atmosphere. These molecules are isomers: they display the same chemical formula but a different spatial distribution of their elements. X-ray photoelectron spectroscopy (XPS) experiments and electrochemical and photophysical characterization confirm that the initial spatial organization strongly determines the chemical composition and electronic structure of the materials, which, thanks to the preservation of functional groups in their surface, display excellent processability in liquid media.     

Heterogeneous Photocatalytic Recycling of FeX2/FeX3 for Efficient Halogenation of C−H Bonds Using NaX

Environmental-friendly halogenation of C−H bonds using abundant, non-toxic halogen salts is in high demand in various chemical industries, yet the efficiency and selectivity of laboratory available protocols are far behind the conventional photolytic halogenation process which uses hazardous halogen sources. Here we report an FeX₂ (X=Br, Cl) coupled semiconductor system for efficient, selective, and continuous photocatalytic halogenation using NaX as halogen source under mild conditions. Herein, FeX₂ catalyzes the reduction of molecular oxygen and the consumption of generated oxygen radicals, thus boosting the generation of halogen radicals and elemental halogen for direct halogenation and indirect halogenation via the formation of FeX₃. Recycling of FeX₂ and FeX₃ during the photocatalytic process enables the halogenation of a wide range of hydrocarbons in a continuous flow, rendering it a promising method for applications.     

A Modular Tubular Flow System with Replaceable Photocatalyst Membranes for Scalable Coupling and Hydrogenation

Heterogeneous photocatalysis is effective for the selective synthesis of value-added chemicals at lab-scale, yet falls short of requirements for mass production (low cost and user friendliness). Here we report the design and fabrication of a modular tubular flow system embedded with replaceable photocatalyst membranes for scalable photocatalytic C−C, C−N homocoupling and hydrogenation reactions, which can be operated in either circular and continuous flow mode with high performance. The photocatalyst membranes almost fully occupy the volume of the reactor, thus enabling optimal absorption of the incident light. Additionally, the porous structured photocatalyst membranes facilitate the mass transfer of the reactants to efficiently use the active sites, resulting in 0^th-order reaction kinetics and a high space-time yield compared to the batch reaction system at practical application levels and prolonged reaction times.     

A high spatial resolution 1H magnetic resonance spectroscopic imaging technique for breast cancer with a short echo time

The high sensitivity but low specificity of breast MRI has prompted exploration of breast (1)H MRS for breast cancer detection. However, several obstacles still prevent the routine application of in vivo breast (1)H MRS, including poor spatial resolution, long acquisition time associated with conventional multi-voxel MRS imaging (MRSI) techniques, and the difficulty of "extra" lipid suppression in a magnetic field with relatively poor achievable homogeneity compared to the brain. Using a combination of a recently developed echo-filter (EF) suppression technique and an elliptical sampling scheme, we demonstrate the feasibility of overcoming these difficulties. It is robust (the suppression technique is insensitive to magnetic field inhomogeneity), fast (acquisition time of about 12 min) and offers high spatial resolution (up to 0.6 cm(3) per voxel at 1.5 T with a TE of only 60 ms). This approach should be even better at 3 T with higher resolution and/or shorter TE.     

新型脂肪族酯和磷酸酯共聚物的合成与表征

为了优化脂肪族聚酯和聚磷酸酯在药物控释及基因治疗领域的性能, 以己二酰氯、二氯磷酸乙酯和二缩三乙二醇为原料, 用共缩聚的方法合成了一类新型脂肪族酯和磷酸酯的共聚物. 运用1H NMR, IR对共聚物的结构进行了表征; 利用MALDI-TOF MS测定了共聚物的分子量; 研究了反应时间、投料顺序、溶剂、反应温度和缚酸剂对聚合反应的影响; 通过动态接触角的测定, 探讨了此类聚合物的亲疏水性能; 以中性红为模型药物, 研究了该类聚合物的药物缓释性能.     

以硅藻土为硅源合成NaA分子筛及其质子传导性能研究

以硅藻土为硅源,在Na₂O-Al₂O₃-SiO₂(硅藻土)-H₂O体系中,采用水浴加热搅拌的方法在较低温度下快速合成了LTA型硅铝分子筛NaA.通过调节温度和反应物的活性,优化了NaA分子筛的合成过程,实现了其在较短时间、较低温度下的快速合成.所合成的NaA分子筛展现出良好的质子传导性能,在室温和100%相对湿度条件下,其质子传导率为1. 72×10^-3S/cm,且随着温度的升高其质子传导率逐渐增大,在80℃和100%相对湿度条件下,质子传导率可以达到5. 96×10^-3S/cm.     

Characterization of the chemical constituents and in vivo metabolic profile of Scutellaria barbata D. Don by ultra high performance liquid chromatography with high-resolution mass spectrometry

Scutellaria barbata D. Don (S. barbata) is one of the most frequently used anticancer herb medicine in China. Mechanistic understanding of the biological activities of S. barbata is hindered by limited knowledge regarding its components and metabolic profile. In this study, ultra-high-performance liquid chromatography coupled with high resolution mass spectrometry (quadrupole time-of-flight mass spectrometry) was used to identify the chemical constituents in S. barbata and their metabolic profiles in rats. By applying cleavage rules and comparison with reference substances, 89 components were identified in S. barbata, which included 45 flavonoids, 28 diterpenoids, 10 phenolics, and 6 others. A total of 110 compounds, including 32 prototype compounds and 78 metabolites, were identified or tentatively characterized in vivo. Methylation, sulfonation, and glucuronidation were the main metabolic pathways, which could be attributed to the fact that several of the compounds in S. barbata have phenolic hydroxyl groups. This is the first systematic study on the chemical constituents and in vivo metabolic profile of S. barbata. The analytical method features a quick and comprehensive dissection of the chemical composition and metabolic profile of S. barbata and provides a basis for exploring its various biological activities.     

A Silylene–Germylene Molecule Containing a SiI−GeI Single Bond

The first isolable silylene–germylene complex 5 was assembled by a salt metathesis reaction between the germylene anion 3 and the N-heterocyclic chlorosilylene 4 , and structurally characterized. The central structure of 5 demonstrates a remarkable gauche-bent geometry with the silylene and germylene units, which are interconnected by a Si−Ge bond with a length of 2.4498(9) Å. This value is not only perceptibly longer than the distances known in doubly bonded germasilenes, and also slightly longer than those in germylsilanes. The DFT calculations on 5 confirmed a nearly nonpolar Si^I−Ge^I single-bond nature and its bonding orbital, as well as the aromaticity of the C₃NGe-rings in 3 and 5 . The latter increases the molecular stability of 3 and 5 , and makes the preparation of silylene–germylene complex 5 a reality.