关于具有与某集合有关的正则Gδ对角线的空间的注记

本文研究了空间X中具有一定性质的子集可度量化的问题.利用一般拓扑学证明一个空间可度量的方法,得到如下结论:若正则空间具有与其有界子集有关的正则Gδ对角线,那么该子集的闭包是可度量化的;若正则空间具有与其有界强零集A有关的Gδ对角线,那么该子集A是X的紧可度量的子空间,推广了文献[1,2]的结果.     

Thermodynamic Approach to Electrochemical Lithium Intercalation into Li1-δMn2O4 Electrode Prepared by Sol-Gel Method

Abstract

Electrochemical lithium intercalation into Li_1-δMn₂O₄ electrode prepared by sol-gel method was investigated from the thermodynamic view point by using galvanostatic intermittent titration technique (GITT) combined with EMF-temperature measurement. The electrode potential vs. lithium content curve was theoretically calculated with the aid of the lattice gas model based upon the Bragg-Williams approximation for the cubic spinel composed of two sub-lattices. Considering the considerable difference between both lithium contents in two sub-lattices due to the ordering of the intercalated lithium ions, the theoretical partial molar enthalpy and entropy were calculated at various lithium contents by a numerical method. From the comparison between the theoretical partial molar quantities and experimental results, the electrochemical lithium intercalation into the Li_1-δMn₂O₄ electrode was discussed in terms of the ordering of the intercalated lithium ions.     

Acid dissociation constants of uridine-5′-diphosphate compounds determined by phosphorus nuclear magnetic resonance spectroscopy and internal pH referencing

The acid dissociation constant (pK_a) of small, biological molecules is an important physical property used for investigating enzyme mechanisms and inhibitor design. For phosphorus-containing molecules, the ³¹P nuclear magnetic resonance (NMR) chemical shift is sensitive to the local chemical environment, particularly to changes in the electronic state of the molecule. Taking advantage of this property, we present a ³¹P NMR approach that uses inorganic phosphate buffer as an internal pH reference to determine the pK_a values of the imide and second diphosphate of uridine-5′-diphosphate compounds, including the first reported values for UDP-GlcNAc and UDP-S-GlcNAc. New methods for using inorganic phosphate buffer as an internal pH reference, involving mathematical correction factors and careful control of the chemical shift reference sample, are illustrated. A comparison of the newly determined imide and diphosphate pK_a values of UDP, UDP-GlcNAc, and UDP-S-GlcNAc with other nucleotide phosphate and thio-analogs reveals the significance of the monosaccharide and sulfur position on the pK_a values.     

Fabrication of High-performance Sm-Fe-N isotropic bulk magnets by a combination of High-pressure compaction and current sintering

TbCu₇-type Sm-Fe-N coarse powders in the flake form were consolidated without a bonding medium using a low-thermal-load process of current sintering combined with high-pressure compression. When compacted at 1.2 GPa, the relative density of the powder was increased by 80% with close stacking of the flake particles. Although the subsequent current heating was only briefly performed at a low temperature of 400 °C to avoid decomposition, the compact was consolidated into a rigid bulk in which the particles were bonded at the atomic level. Finally, by using cyclic compaction, this process produced bulk magnets with a density of 92% that exhibited the highest maximum energy product (BH)max of 16.2 MGOe, which surpasses that of conventional isotropic Sm-Fe-N bond magnets.     

A novel cathode material BaCe0.4Sm0.2Co0.4O3−δ for proton conducting solid oxide fuel cell

A novel cathode material BaCe_0.4Sm_0.2Co_0.4O_3−δ composed of two phases BaCe_1−x(Sm/Co)_xO_3−δ and BaCo_1-x(Sm/Ce)_xO_3−δ was prepared in situ via the citric–nitrate route and its performance as cathode material for proton conducting solid oxide fuel cell (SOFC-H) was characterized. BaCe_0.4Sm_0.2Co_0.4O_3−δ exhibited simultaneous protonic, electronic, and oxygen ionic conduction in air, leading to a good electrode performance. The polarization resistance of the novel cathode material in symmetrical cell was 0.36 Ω cm² with Pt as the current collector at 700 °C in wet air. The electrode performance can be further improved through microstructure optimization. It also showed good thermal expansion compatibility with BaCe_0.8Sm_0.2O_3−δ electrolyte over a 100 h duration test. BaCe_0.4Sm_0.2Co_0.4O_3−δ is a promising cathode material for SOFC-H.     

Heavy Plants and Light Plants: Hubert Ziegler's Contribution to Modern Physiological Plant Ecology Through Natural Abundance Stable Isotope Analysis

Abstract

The contributions of Hubert Ziegler to our understanding of physiological plant ecology through natural abundance studies of the stable isotopes of carbon, hydrogen and nitrogen are reviewed. These have served to expand our knowledge of plant distributions and physiological functions, especially the processes linking pathways of photosynthetic carbon metabolism and transpiration. They have also served to indicate food chain relationships and organism to organism interactions. His leadership has placed stable isotope techniques firmly on centre-stage, as indicators and integrators of plant biospheric processes in the environmental context.     

δ-Hom-Jordan Lie superalgebras

This paper is primarily concerned with δ-Hom-Jordan Lie superalgebras. We discuss the concepts of α^k-derivations, representations and T*-extensions of δ-Hom-Jordan Lie superalgebras in detail, and some cohomological characterizations are established.     

Electrical Properties of Fe-doped Perovskite-like BaNb0.75-xFexNa0.25O3-δ (0.05 < x < 0.5)

In this paper, we report the electrical properties of Fe-doped perovskite-like compounds with a nominal chemical formula of BaNb_0.75-xNa_0.25Fe_xO_3-δ (0.05 < x < 0.5) (BNF). Various solid-state structural and electrical characterization techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), alternating current (AC) impedance spectroscopy and direct current (DC) methods were used for characterization. PXRD patterns for BNF members show the formation of perovskite-like structure. The total electrical conductivity values were determined under ambient air and wet air in the temperature up to 700 °C. The Fe concentration was strongly correlated to the conductivity response, with the x = 0.5 member exhibiting the highest conductivity in air. A relationship between the humidity content and conductivity in air was also observed in low Fe concentration BNF members (x = 0.5, 0.15), suggesting the presence of potential proton conduction; while the conductivity of high Fe content samples (x ≥ 0.3) showed little dependence on the humidity. The chemical stability of BNF samples was investigated in boiling H₂O and in flowing 100% CO₂ at elevated temperatures and the results demonstrated that all members were structurally stable under both conditions, except the x = 0.5 member which decomposed into BaCO₃ in the presence of CO₂ at 800 °C.     

Efficient access to novel hexahydro-chromene and tetrahydro-pyrano[2,3-d]pyrimidine-annulated benzo-δ-sultones via a domino Knöevenagel-hetero-Diels-Alder reaction in water

An efficient catalyst-free, diastereosective synthesis of novel hexahydro-chromene and tetrahydro-pyrano[2,3-d]pyrimidine-annulated benzo-δ-sultones is described. A number of 2-formyl-4-phenyl (E)-2-phenylethenesulfonates were synthesized and underwent a one-pot domino Knöevenagel-hetero-Diels-Alder reaction, respectively, with dimedone and N,N-dimethylbarbituric acid in water, affording the desired products in moderate to excellent yields.     

Fabrication and characterization of a α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine/silica nanocomposite thin-layer membrane for detection of ppb-level heavy metal ions

A new detection membrane for filtration enrichment combined with colorimetric determination of Cd(II), Zn(II), Pb(II) and Cu(II) ions is presented. We have demonstrated the use of a dye nanoparticle coated test strip (DNTS) structured with a reagent layer for on-site analysis of trace metal ions. In this study, a [TMPyP/SA] DNTS coated with a nanocomposite layer (average thickness: 5.39 μm) of α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) and silica-SA on the top surface of a cellulose ester membrane filter was fabricated by a simple filtration of an aqueous TMPyP/silica-SA nanocomposite dispersion through a membrane filter. The nanocomposite formation of cationic TMPyP and negatively charged colloidal SA (9–80 nm) was based on electrostatic interaction and was confirmed in the 120–800 nm diameter range by a dynamic light scattering photometer (DLS). To optimize the DNTS nanocomposite layer, surface uniformity, mechanical strength, the percent retention of TMPyP, and sensitivity to Cd(II) detection for six DNTSs with five different types of silica were examined. A half[TMPyP/SA] DNTS with an average layer thickness of 2.60 μm, which was prepared by controlling the amount of TMPyP and SA, demonstrated the highest sensitivity to Cd(II) ion because it had the lowest background absorbance. In addition, factors that affected the percent retention of TMPyP, such as pH and TMPyP/SA ratio, were determined. More than 99% of the TMPyP was retained on a membrane filter at pH 7.8 with a TMPyP and SA concentration of 2 × 10⁻⁵ M and 4 × 10⁻⁵ wt%, respectively. Filtration enrichment of 100 mL of an aqueous solution containing Cd(II), Zn(II), and Pb(II) at ppb levels was achieved by concentrating the metal ions in a nanocomposite layer (the effective TMPyP area was 1.77 cm², pH 10.2). The signaling surface changed from a brown color to green when the ions were captured. The percent extraction for metal ions on a half[TMPyP/SA] DNTS were estimated by TLC scanning and ICP-MS. It was observed that, when using the half[TMPyP/SA] DNTS, Cd(II) concentrations as low as 1 ppb were detectable at a filtration rate of 4.0–5.0 mL min⁻¹.