Kinetics and isothermal adsorption of U(VI) in aqueous solution by nano-Ni0

Journal of Radioanalytical and Nuclear Chemistry - The nanoscale zero-valent nickel (nano-Ni0) was prepared by liquid-phase reduction method and characterized by BET, XPS, FT-IR and XRD and be used...     

Reconstruction of physics objects at the Circular Electron Positron Collider with Arbor

After the Higgs discovery, precise measurements of the Higgs properties and the electroweak observables become vital for the experimental particle physics. A powerful Higgs/Z factory, the Circular Electron Positron Collider (CEPC) is proposed. The Particle Flow oriented detector design is proposed to the CEPC and a Particle Flow algorithm, Arbor is optimized accordingly. We summarize the physics object reconstruction performance of the Particle Flow oriented detector design with Arbor algorithm and conclude that this combination fulfills the physics requirement of CEPC.     

A Single Molecular Diels–Alder Crosslinker for Achieving Recyclable Cross‐Linked Polymers

A triol‐functional crosslinker combining the thermoreversible properties of Diels–Alder (DA) adducts in one molecule is designed, synthesized, and used as an ideal substitute of a traditional crosslinker to prepare thermal recyclable cross‐linked polyurethanes with excellent mechanical properties and recyclability in a very simple and efficient way. The recycle property of these materials achieved by the DA/retro‐DA reaction at a suitable temperature is verified by differential scanning calorimetry and in situ variable temperature solid‐state NMR experiments during the cyclic heating and cooling processes. The thermal recyclability and remending ability of the bulk polyurethanes is demonstrated by three polymer processing methods, including hot‐press molding, injection molding, and solution casting. It is notable that all the recycled cross‐linked polymers display nearly invariable elongation/stress at break compared to the as‐synthesized samples. Further end‐group functionalization of this single molecular DA crosslinker provides the potential in preparing a wide range of recyclable cross‐linked polymers.

     

唾液酸糖苷化反应研究新进展

唾液酸是一类重要的具有多种生物学功能的糖酸化合物. 唾液酸糖苷化反应条件较一般糖苷化反应苛刻, 立体选择性通常较差, 端基碳的立体构型较难控制. 在唾液酸糖苷化反应中能否高效地得到α糖苷键是评价该反应优劣的重要标志之一. 唾液酸苷化方法的研究一般涉及以下几个方面: C-2上的离去基团的运用, C-1, C-3上辅助基团的参与作用, C-5上氨基保护基团的修饰, 以及一些新的糖苷化反应催化剂的发展. 近些年来, 这些研究领域, 尤其是C-5上氨基保护基团的研究, 取得了重要进展. 将着重对唾液酸糖苷化方法的新进展做一总结和评述.     

Droplet-based microfluidics for dose–response assay of enzyme inhibitors by electrochemical method

A simple but robust droplet-based microfluidic system was developed for dose–response enzyme inhibition assay by combining concentration gradient generation method with electrochemical detection method. A slotted-vials array and a tapered tip capillary were used for reagents introduction and concentration gradient generation, and a polydimethylsiloxane (PDMS) microfluidic chip integrated with microelectrodes was used for droplet generation and electrochemical detection. Effects of oil flow rate and surfactant on electrochemical sensing were investigated. This system was validated by measuring dose–response curves of three types of acetylcholinesterase (AChE) inhibitors, including carbamate pesticide, organophosphorus pesticide, and therapeutic drugs regulating Alzheimer's disease. Carbaryl, chlorpyrifos, and tacrine were used as model analytes, respectively, and their IC₅₀ (half maximal inhibitory concentration) values were determined. A whole enzyme inhibition assay was completed in 6 min, and the total consumption of reagents was less than 5 μL. This microfluidic system is applicable to many biochemical reactions, such as drug screening and kinetic studies, as long as one of the reactants or products is electrochemically active.     

Determining coastal mixing rates of western Taiwan Strait using 224Ra

²²⁴Ra concentrations in the coastal sea water of western Taiwan Strait in winter were measured using Mn-fiber adsorption—successive emanation scintillation method. ²²⁴Ra activities in the seawater of the western Taiwan Strait varied from 0.90 to 16.25 Bq/m³ with an average of 4.60 Bq/m³. The horizontal and vertical distributions of ²²⁴Ra were studied. The distributions of ²²⁴Ra in the surface water decreased gradually with increasing distance offshore. The apparent horizontal and vertical eddy diffusion coefficients estimated from the one dimensional steady state model of ²²⁴Ra were (5.0–55.4) × 10⁶cm²/s and (4.0–51.7) cm²/s, respectively.     

利用电光强度调制器频移特性实现可调延迟

针对光纤通信系统中数据同步处理时对脉冲可调延迟的要求,提出了一种可调延迟器的结构设计方案。对电光强度调制器(EOIM)的光频移特性进行了研究,基于EOIM对各级边带和强度的调制作用,利用EOIM对受激布里渊散射慢光装置中的泵浦光进行强度调节,从而实现延迟量可调。建立了可调延迟的数学模型,通过实验研究分别得出了在一定微波调制功率下EOIM调制深度和直流偏置电压随脉冲延迟量的变化关系。从实验结果中可以看出:在引起失真的主要因素为零的情况下,当直流偏置电压为半波电压的1/2时,脉冲相对群延迟随调制深度的增大逐渐减小;当调制深度为1.39时,脉冲相对群延迟随直流偏置电压的增大逐渐增大,延迟量最大可达到未调制情况下的1.106倍,实现了较大范围的延迟量调节。     

Synthesis and characterization of diiron dithiolate complexes containing a quinoxaline bridge

A potential model complex for the hydrogenase active site, [Fe(2){(μ-CH(2)S)(2)R}(CO)(6)] (1) (R = quinoxaline), was synthesized by condensation of [(μ-LiS)(2)Fe(2)(CO)(6)] with 2,3-bis(bromomethyl)quinoxaline. Reactions of 1 with bis(diphenylphosphino)methane (dppm) under a range of conditions yielded substituted complexes [Fe(2){(μ-CH(2)S)(2)R}(CO)(5)(dppm)] (2), [Fe(2){(μ-CH(2)S)(2)R}(CO)(4)(k(2)-dppm)] (3) and [Fe(2){(μ-CH(2)S)(2)R}(CO)(4)(μ-dppm)] (4). X-ray crystallography confirms that in 2, the dppm is terminally bonded to an iron atom via one phosphorus atom, whereas in 3, it acts as a chelating ligand to coordinate to an iron center in a dibasal-substituted manner. In 4, the dppm bridges the two iron atoms in a cis basal/basal fashion with one phosphorus bonded to each iron atom. Treatment of 1 with various tertiary phosphines at room temperature in acetonitrile (MeCN) generates a range of mono-substituted products [Fe(2){(μ-CH(2)S)(2)R}(CO)(5)L] (5, L = PEt(3); 6, PMe(3); 7, PPh(3); 8, Me(2)PPh). With Bu(t)NC, mono- and di-substituted [Fe(2){(μ-CH(2)S)(2)R}(CO)(5)(Bu(t)NC)] (9) and [Fe(2){(μ-CH(2)S)(2)R}(CO)(4)(Bu(t)NC)(2)] (10) complexes are generated. All the complexes were characterized by elemental analysis, IR, MS and NMR spectroscopy. IR and NMR spectroscopic studies suggest that addition of excess HBF(4)·OEt(2) acid to 1-4 led to the protonation of quinoxaline nitrogen atoms. In contrast, 5-10 were not stable in acidic media. Electrochemistry of 1-4 was investigated in the acetonitrile medium (0.1 M Bu(4)NPF(6)). The electrochemical instability of the reduced ligand, quinoxaline, and the reduced forms of these complexes revealed from the electrochemical studies suggests that they do not provide ideal models of the hydrogenase active site.     

Racemic synthesis of an intermediate for the formal synthesis of madindoline A and B

On the basis of the application of the Darzens/ring-expansion process of cyclobutenedione developed previously by our group, a new strategy for the multisubstituted cyclopentene units of madindoline A and madindoline B has been reported in this paper. In light of the strategy, the synthesis of racemic Omura’s intermediate was finished in four steps and 34% overall yield, which furnished a new formal synthetic route to madindolines A and B.     

Evaporative Preconcentration of Fluorescent Protein Samples in Capillary Based Microplates

The preconcentration of analytes is important in biochemical analysis as it offers the ability to detect for trace species, and increase signal-to-noise ratios when using optical sensing on fluorophores. A strong advantage of the evaporation technique lies in its ability to operate without the need of any energy source; albeit major challenges exist on how to increase the surface area exposure to air for heightened evaporation, ensure no further increases once specified analyte concentrations have been achieved, and not needing any intervening membranes. We demonstrate here that the droplet creation and retraction approach in capillary based microplates offers such abilities whilst at the same time facilitating mixing.