Differential pulse anodic stripping voltammetric determination of traces of copper with a tobramycin-Nafion modified electrode.

A Nafion-modified glassy carbon electrode incorporated with tobramycin for the voltammetric stripping determination of Cu2+ has been explored. The electrode was fabricated by tobramycin containing Nafion on the glassy carbon electrode surface. The modified electrode exhibited a significantly increased sensitivity and selectivity for Cu2+ compared with a bare glassy carbon electrode and the Nafion modified electrode. Cu2+ was accumulated in HAc-NaAc buffer (pH 4.6) at a potential of -0.6 V (vs. SCE) for 300 s and then determined by differential pulse anodic stripping voltammetry. The effects of various parameters, such as the mass of Nafion, the concentration of tobramycin, the pH of the medium, the accumulation potential, the accumulation time and the scan rate, were investigated. Under the optimum conditions, a linear calibration graph was obtained in the concentration range of 1.0 x 10(-9) to 5.0 x 10(-7) mol l(-1) with a correlation coefficient of 0.9971. The relative standard deviations for eight successive determinations were 4.3 and 2.9% for 1.0 x 10(-8) and 2.0 x 10(-7) mol l(-1) Cu2+, respectively. The detection limit (three times signal to noise) was 5.0 x 10(-10) mol l(-1). A study of interfering substances was also performed, and the method was applied to the direct determination of copper in water samples, and also in analytical reagent-grade salts with satisfactory results.     

STUDY ON THE DUCTILE DEFORMATION DOMAIN OF THE SIMPLE SHEAR IN ROCKS——TAKING BRITTLE FAULTS OF THE COVERING STRATA IN THE SOUTHERN JIANGSU AREA AS AN EXAMPLE

A study on the ductile deformation domain of the brittle fault in the shallow level ofthe crust is a new probe field for the modern structural geology. Taking the southern Jiang-su Province area as an example the orientation measurement of quartz crystals, the com-positional texture observation of three pressure sensitive minerals and the rheological param-eter determination of dislocation densities, etc. have been demonstrated and analysed basedon typical samples in the present paper. In addition, their generation mechanisms arealso discussed from the cataclastic rheology, the dynamic differentiation and the simpleshearing, specially, from the Ode strength theory. Finally, a generative relationship betweenthe ductile deformation domain of the brittle fault system, in the regional layer--slip andthe formation of the stratabound ore deposit is shown as well.     

AN INVESTIGATION ON THE ab initio CALCULATION OF INTERMOLECULAR INTERACTION——NON-BONDED INTERACTION IN THE HYDROGEN BOND COMPLEX (HF)_2

An ab initio calculation of the hydrogen bond complex (HF)_2 is given with the 6-311 G~(**) basis set, according to which the potential surface around the balance point of the distancès and the orientations between two HF molecules is obtained. The atomic charges in the system are calculated with the PD/LSF method (potential-derived/least-square-fitting method) and then an analysis of the hydrogen bond interaction between two HF molecules is given with the (exp-6-1) potential function, by means of which it is shown that the main interaction between them is not an electro-static but a charge transfer one. The potential curve between two HF molecules is like a Morse function.     

Syntheses,Structures and Photocatalytic Degradation Properties of Two Copper(Ⅱ)Coordination Polymers with Flexible Bis(imidazole)Ligand

Two copper(Ⅱ)coordination polymers{[Cu(bib)(nip)]·1.5H2O}n(1)and[Cu2(bib)(glu)2]n(2)(bib= 1,4-bis(2-methyl-imidazol-1-yl)butane,H2nip = 5-nitroisophthalic acid,...     

Growth regulation of luminescent gold nanoparticles directed from amphiphilic block copolymers:highly-controlled nanoassemblies toward tailored in-vivo transport

The understanding of amphiphilic block copolymers(ABC)in encapsulation and transport of inorganic nanomedicines is highly desired.Still,it remains limited due to the challenges in the fabrication of nanoassemblies(NAs)with highly-controlled shape and loading of nanoparticles.Herein,through growth regulation of luminescent gold nanoparticles(Au NPs)by different reductants with ABC pluronic F127 as a template,a straightforward strategy is reported for in-situ fabrication of three wellcontrolled gold NAs(Au NAs)that display tunable shapes from spherical to elongated nanostructures and controllable surface chemistry and loading of Au NPs with distinct emissions but identical individual Au NP size.The three Au NAs exhibit tailored invivo transport behaviours:those with spherical shape and more hydrophilic surface show longer blood retention with higher tumor-targeting efficiency(~25.3%injection dose/g)and excellent long-term near-infrared tumor imaging even after 96 h postinjection.These findings provide a useful guidance in designing specific nanostructures for future nanomedicine transport.     

Giant magnetoresistance:history,development and beyond

With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.     

两维局域互联神经网络的关联存储

本文将局域互联神经网络的新概念推广到两维情形,并对两维局域互联关联存储进行了理论分析和大量的计算机模拟.结果表明,两维局域互联神经网络的优点是,在满足存储容量限制的前提下,它与全局互联神经网络具有相同的关联存储能力,而其互联权重矩阵要比全局互联网络小得多.因而,有利于使用现有的空间光调制器实现两维大规模的人工神经网络.     

α—萘酚胁迫对普通小球藻生长及抗氧化酶活性的影响

研究了α－萘酚对普通小球藻的生长、光合色素的MDA含量及抗氧化酶9SOD、CAT、POD）活性的影响,结果表明,随着α－萘酚浓度的升高,藻的生长速率、叶绿素a与类胡萝卡素的含量,SOD、CAT、POD活性均先升高后下降,除POD活性在5．00mg.L^－1时达到最大值外,其余均在2．00mg.L^-1达到最大,而在α－萘酚浓度低于2．00mg.L^-1时,MDA含量变化不大,只有当3种抗氧化酶活性呈不同的下降后,MDA含量才急剧上升,膜脂过氧化加剧,说明α－萘酚导致普通小球藻膜脂过氧化是其致毒机制之一,而抗氧化酶在一定污染物浓度范围内具有防御保护作用。