Gowers norms and pseudorandom measures of subsets

Let $A \subset {{\Bbb Z}_N}$, and ${f_A}(s) = \left\{ {\begin{array}{*{20}{l}}{1 - \frac{{|A|}}{N},}&{{\rm{for}}\;s \in A,}\\{ - \frac{{|A|}}{N},}&{{\rm{for}}\;s \notin A.}\end{array}} \right.$ We define the pseudorandom measure of order k of the subset A as follows, P_k(A, N) = $\begin{array}{*{20}{c}}{\max }\\D\end{array}$|$\mathop \Sigma \limits_{n \in {\mathbb{Z}_N}}$f_A(n + c₁)f_A(n + c₂) … f_A(n + c_k)|, where the maximum is taken over all D = (c₁, c₂, . . . , c_k) ∈ ${\mathbb{Z}^k}$ with 0 ≤ c₁ < c₂ < … < c_k ≤ N - 1. The subset A ⊂ ${{\mathbb{Z}_N}}$ is considered as a pseudorandom subset of degree k if P_k(A, N) is “small” in terms of N. We establish a link between the Gowers norm and our pseudorandom measure, and show that “good” pseudorandom subsets must have “small” Gowers norm. We give an example to suggest that subsets with “small” Gowers norm may have large pseudorandom measure. Finally, we prove that the pseudorandom subset of degree L(k) contains an arithmetic progression of length k, where L(k) = 2·lcm(2, 4, . . . , 2|$\frac{k}{2}$|), for k ≥ 4, and lcm(a₁, a₂, . . . , a_l) denotes the least common multiple of a₁, a₂, . . . , a_l.     

Directional synthesis of furfural compounds from holocellulose catalyzed by sulfamic acid

Cellulose - The coproduction of 5-hydroxymethylfurfural (5-HMF) and furfural (FUR) via the direct hydrolysis of holocellulose analogue composed of cellulose and hemicellulose was investigated. The...     

The effect of Co ion implantation on Ge1−xMnx films

Ge_1−xMn_x (x = 0, 0.013, 0.0226, 0.0339, 0.0565, 0.0678, 0.0904, 0.113) films prepared by magnetron sputtering at 773 K had a Ge cubic structure except for x = 0.1130. Co ion implantation into these films can effectively prevent the formation of a second phase. Both single-doped and co-doped samples were ferromagnetic at room temperature. The d-d exchange interaction between the interstitial Mn (MnT) and the substituted Mn (Mn_Ge) resulted in ferromagnetism in the sputtered films. Since Co ion implantation destroyed the Mn_T-Mn_Ge-Mn_T complex, the saturated magnetization decreased. Hall measurements revealed that the Co ion implanted films were n-type semiconductors, and the anomalous Hall Effect (AHE) suggested the ferromagnetism was carrier-mediated in the implanted films.     

New Cytochalasins from the Marine‐Derived Fungus Xylaria sp. SCSIO 156

Two new cytochalasins, 18‐deoxycytochalasin Q ( 1 ) and 21‐O‐deacetylcytochalasin Q ( 2 ), together with four known analogues, cytochalasin Q ( 3 ), 19,20‐epoxycytochalasin Q ( 4 ), 21‐O‐deacetyl‐19,20‐epoxycytochalasin Q ( 5 ), and cytochalasin D ( 6 ), were isolated from the fungus Xylaria sp. SCSIO156 originated from the South China Sea marine sediment. The structures of 1 and 2 were elucidated by MS and 1D‐ and 2D‐NMR data analyses, and comparison with known compounds. The known compounds 3 – 6 were identified by comparison of their MS and NMR data with those reported in the literature. In the in vitro antitumor assay, compounds 2 – 6 showed mild cytotoxicity against three tumor cell lines (MCF‐7, SF‐268, and NCI‐H460).     

Novel templates directed synthesis of YVO4: Eu3+ (red) and Y2O3–SiO2: Tb3+(green) phosphors

Red/green emissive phosphors YVO₄: Eu³⁺ and Y₂O₃–SiO₂: Tb³⁺ have been synthesized via novel templates direction methods. Photoluminescence studies exhibit the emission intensities as significantly enhanced through pre-encapsulation treatments of designed pyridine amide compounds (YVO₄: Eu³⁺) and 3,4,5-tris(tetradecoxy) benzoic acid (Y₂O₃–SiO₂: Tb³⁺). The as-prepared vanadate particles turn out to be much less agglomerated based on the dispersion by the organic templates. The obtained composite materials, which demonstrate extraordinary fluorescence properties, could be promising candidates for future optoelectronic devices.     

Effect of Surface Decoration of CNTs on the Interfacial Interaction and Microstructure of Epoxy/MWNT Nanocomposites

Epoxy resin nanocomposites with different contents of multiwalled carbon nanotubes (MWNTs) are prepared. The interaction between MWNTs and the epoxy resin matrix and the microstructure and mechanical properties of the composites are systematically investigated by Fourier‐transform infrared (FTIR) spectroscopy, transmission electron microscopy, scanning electron microscopy, and positron annihilation technology. FTIR spectra reveal that two kinds of hydrogen bonds exist at the interface for the nanocomposites modified by amine, one between the epoxy group on the side chain and the NH group, and the other between the epoxy group on the alicycle and the NH group. Compared to unmodified MWNT composites, the modified MWNT composites possess better mechanical properties, which are attributed to stronger interfacial interaction resulting from an efficient load transfer from matrix to MWNTs. Positron annihilation lifetime spectroscopy is used to characterize the microstructure of the epoxy/MWNT composites. The subtransition and glass transition temperatures are determined by finite‐term positron lifetime analysis and the variation of the free‐volume size as a function of temperature. Shifts of structure transition temperatures of the composites are observed with increasing MWNT weight content. Interestingly, the continuous lifetime analysis reveals the existence of two long‐lived lifetime components above the glass transition temperature, which may be attributed to the formation of local ordered regions related to the packing density of chains.     

Copper Nanoflowers on Carbon Cloth as a Flexible Electrode Toward Both Enzymeless Electrocatalytic Glucose and H2O2

Herein, a novel electrochemical sensor for glucose and hydrogen peroxide (H₂O₂) detection was successfully developed through the use of Cu nanoflowers (CuNFs) combined with flexible carbon cloth (CC) substrate. The 3D flower-like CuNFs in size uniformly and firmly grow on CC substrate by a facile, scalable, one-step hydrothermal strategy. Morphology, size and surface property of the prepared CuNFs/CC were examined by SEM, EDS and TEM, respectively. The electrochemical mechanism of CuNFs/CC for glucose and H₂O₂ detection was investigated by cyclic voltammetry. High electrochemical performances were displayed with amperometric i-t curves including a wide linear range from 1.0 nM to 6.0 mM for glucose and from 1.0 μM to 36.66 mM for H₂O₂, respectively. Good sensitivity, repeatability, and stability, as well as anti-interference ability, the carbon cloth-supported CuNFs will be the promising materials for fabricating practical non-enzymatic glucose and H₂O₂ sensors.     

基于顶发射有机发光二极管的二阶微腔长度性能研究

在玻璃衬底生长金属铝作为不透明阳极,制备了结构为Al(100 nm)/TAPC(x nm)/TCTA(10 nm)/TCTA:Ir(ppy)3(10%,25 nm)/TPBi(30 nm)/LiF(2 nm)/Al(1 nm)/Ag(20 nm)/Alq3(y nm)作为顶发射的有机发光器件,其中x为30、130、160、170和180,y为20、40、60和80,研究了器件的二阶腔长及出光耦合性能。实验表明,通过改变空穴传输层的厚度,使器件微腔长度处于第二阶微腔效应增强区,可以提高器件的光电性能。同时当光输出耦合层厚度发生改变时,半透明阴极的光线穿透率与反射率发生改变,从而有效改善器件的光电性能。当微腔长度为230 nm、光输出耦合厚度为80 nm时,器件具有最佳的光电性能,并且光谱的角度稳定性强。器件最大亮度、电流效率和功率效率分别达到25 960 cd/m2、19.1 cd/A和16.01 lm/W。     

卟啉及其衍生物对生物分子的识别研究进展

卟啉及其衍生物作为主体分子对生物分子的识别具有独特的优点：分子结构多样、形状选择、稳定性好和敏感性高等。 本文着重介绍了国内外关于卟啉对DNA、氨基酸、醌和胺等的分子识别研究进展。     

Reusable voltammetric immunosensor for sCD40L,a biomarker for the acute coronary syndrome,using a glassy carbon electrode modified with a nanocomposite consisting of gold nanoparticles,branched polyethylenimine and carboxylated multiwalled carbon nanotubes

Microchimica Acta - The authors describe a nanocomposite prepared from gold nanoparticles, branched polyethylenimine and carboxylated multiwalled carbon nanotubes (AuNP/b-PEI/c-MWCNTs), and its...