Electrochemical studies of the effect of lanthanide ions on the activity of glutamate dehydrogenase

Using the electrochemical method based on the "diffusion" layer concept of the convective system, the effect of lanthanide ions La3+ and Eu3+ on the activity of glutamate dehydrogenase (GLDH) has been determined. In suitable concentrations, the lanthanide ions La3+ and Eu3+ can activate the GLDH in the reductive amination of alpha-Ketoglutarate (alpha-KG). The activation mechanism would be that the lanthanide ions could interrupt the binding of NAD+ to GLDH by combining preferentially to NAD+. This mechanism was proposed by the voltammetric studies.     

Influence of boron on the giant magnetocaloric effect of La(Fe0.9Si0.1)13

The influences of boron addition on the phase formation, Curie temperature and magnetic entropy change of the NaZn₁₃-type La(Fe_0.9Si_0.1)₁₃ compound have been investigated. Eight boron containing La(Fe_0.9Si_0.1)₁₃B_x samples were prepared with x=0, 0.03, 0.06, 0.1, 0.2, 0.3, 0.5 and 0.6, respectively. Experimental results show that a small amount of B addition in La(Fe_0.9Si_0.1)₁₃ forms the solid solution NaZn₁₃-type structure phase by substituting B for Si or doping B into interstitial position of the lattice, preserves its giant magnetocaloric effects due to their first-order structural/magnetic transition, as well as increase its Curie temperature T_c slightly. The maximum magnetic entropy changes in the magnetic field change of 0–1.6 T are around 20 J kg^–1 K^–1 for the samples with Boron addition less than 0.3, while improving the Curie temperatures by 2 K.     

A high-throughput search for direct methanol fuel cell anode electrocatalysts of type PtxBiyPbz

We used a high-throughput method to screen for direct methanol fuel cell anode electrocatalysts in the Pt-Bi-Pb system. Previous studies showed that PtBi and PtPb (both NiAs structure type) were active electrocatalysts for the oxidation of formic acid, but only PtPb was active in oxidizing methanol. We synthesized thin films with continuous composition spreads of the three elements by magnetron sputtering at deposition temperatures from ambient to 510 °C. A fluorescence method was then used to identify compositions that were active toward methanol oxidation. Only films deposited between temperatures of 160 and 400 °C showed electrocatalytic activity. The areas that were active for methanol oxidation showed predominantly the NiAs structure type according to XRD, with optimal activity for compositions near PtBi_0.01Pb_0.53.     

MOSFET辐照诱生界面陷阱形成过程的1/f噪声研究

基于界面陷阱形成的氢离子运动两步模型和反应过程的热力学平衡假设,推导了金属-氧化物-半导体-场效应晶体管(MOSFET)经历电离辐照后氧化层空穴俘获与界面陷阱形成间关系的表达式.利用初始1/f噪声功率谱幅值与氧化层空穴俘获之间的联系,建立了辐照前的1/f噪声幅值与辐照诱生界面陷阱数量之间的半经验公式,并通过实验予以验证.研究结果表明,由于辐照诱生的氧化层内陷阱通过与分子氢作用而直接参与到界面陷阱的建立过程中,从而使界面陷阱生成数量正比于这种陷阱增加的数量,因此辐照前的1/f噪声功率谱幅值正比于辐照诱生的界面陷阱数量.研究结果为1/f噪声用作MOSFET辐照损伤机理研究的新工具,对其抗辐照性能进行无损评估提供了理论依据与数学模型.     

Cocaine reward and locomotion stimulation in mice with reduced dopamine transporter expression

Background  

The dopamine transporter (DAT) plays a critical role in regulating dopamine neurotransmission. Variations in DAT or changes in basal dopaminergic tone have been shown to alter behavior and drug responses. DAT is one of the three known high affinity targets for cocaine, a powerful psychostimulant that produces reward and stimulates locomotor activity in humans and animals. We have shown that cocaine no longer produces reward in knock-in mice with a cocaine insensitive mutant DAT (DAT-CI), suggesting that cocaine inhibition of DAT is critical for its rewarding effect. However, in DAT-CI mice, the mutant DAT has significantly reduced uptake activity resulting in elevated basal dopaminergic tone, which might cause adaptive changes that alter responses to cocaine. Therefore, the objective of this study is to determine how elevated dopaminergic tone affects how mice respond to cocaine.     

Poly(ascorbyl acrylate)s: Synthesis and evaluation of their redox polymerization ability in the presence of hydrogen peroxide

In this work, a strategy for chemical synthesis of ascorbic acid functionalized polyacrylates (PAAA) was accomplished in a two‐step process, first a reversible addition fragmentation chain‐transfer (RAFT) polymerization on a benzyl‐protected ascorbyl acrylate monomer, followed by a deprotection (debenzylation) reaction. The polymers were characterized by ¹H NMR, ¹³C NMR and gel permeation chromatograph. The polymerization ability of redox pair including PAAA and H₂O₂ were conducted through the measurement of 2‐hydroxyethyl acrylate (HEA) conversion against time via real‐time FT‐NIR. It was found that PAAA in the presence of H₂O₂, independent on itself chain length, exhibited much faster polymerization than small molecule ascorbic acid (smAA) as reductant at identical condition. Interestingly, when the concentration of ascorbate repeating unit was over some critical value, the polymerization kinetics of HEA could be tunable by simply adjusting the initial molar ratio of reductant to oxidant and environmental pH. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A new titanium (IV) complex bearing phenoxyimine‐fluorene ligand and its use as catalyst for ethylene homo‐ and copolymerization

A new titanium (IV) complex bearing phenoxyimine‐fluorene ligand was prepared and its behaviors in ethylene homo‐ and copolymerization with 1‐hexene, 1‐octene, and norbornene in the presence of modified methylaluminoxane (MMAO) were studied respectively. The effects of various polymerization conditions including polymerization temperature, ethylene pressure and the concentration of comonomer on the catalytic activities and properties of the resultant polymer were investigated. The broad molecular weight distribution of resulting polymer indicated that the multiple active species were formed during polymerization. Such complex showed good catalytic activities in ethylene homo‐ and copolymerizations and good capabilities of incorporating various comonomers into polyethylene backbone. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1617–1621, 2010     

Substrate cross-conduction effect on the performance of serially connected microbial fuel cell stack

This study presented a new design of scalable, air-cathode microbial fuel cell (MFC) stack that shared a common fuel feed passage. As two individual cells were electrically connected in series by metal wires and hydraulically joined by conductive substrate flow, the performance degradation phenomenon was observed. The open circuit voltage (OCV) and low current behavior of stacked MFC were lower than should be expected. This energy loss was proposed to be a consequence of parasitic current flow due to the substrate cross-conduction effect and can be likely minimized through controlling the distance between the anode electrodes or/and the cross-sectional area of substrate flow. The unique and simple water distribution system of the tubular MFC stack would contribute to the further scale-up and implementation of MFC technologies, especially for wastewater treatment.     

Thermodynamics of complexes between nucleobase-modified β-cyclodextrins and bile salts

The binding of three nucleobase-modified β-CDs, (i.e., mono(6-ade-6-deoxy)-β-CD 2, mono(6-thy-6-deoxy)-β-CD 3, and mono(6-ura-6-deoxy)-β-CD 4) with four bile salts (deoxycholate, DCA; cholate, CA; glycocholate, GCA; and taurocholate, TCA) were investigated by means of circular dichroism, 2D NMR spectroscopy and calorimetric titration. The results show the binding of host 2 with bile salts is weaker and different from hosts 3 and 4. Enthalpy changes between hosts 2–4 and bile salts are much more favorable than those of native β-CD 1, whereas the entropy changes are unfavorable.