Determination of Copper at a Glassy Carbon Electrode Modified with Langmuir–Blodgett Film of p‐tert‐Butylthiacalix[4]arene

A new type of voltammetric sensor, Langmuir–Blodgett film of p‐tert‐butylthiacalix[4]arene modified glassy carbon electrode, was advanced and used for determining copper at trace levels by differential pulse stripping voltammetry. Calibration plot was found to be linear in the range of 2×10^?8 M to 5×10^?6 M; the detection limit was 2×10^?9 M. Possible recognition mechanism was also discussed. From determination of Copper in real samples (river, lake and tap water) it can be concluded that the method is rapid, sensitive in determining of copper and can be used in the analysis of natural water samples.     

On the Permanental Polynomials of Some Graphs

Let G be a simple graph with adjacency matrix A(G) and (G,x) the permanental polynomial of G. Let G × H denotes the Cartesian product of graphs G and H. Inspired by Kleins idea to compute the permanent of some matrices (Mol. Phy. 31 (3) (1976) 811–823), in this paper in terms of some orientation of graphs we study the permanental polynomial of a type of graphs. Here are some of our main results.1.If G is a bipartite graph containing no subgraph which is an even subdivision of K _2,3, then G has an orientation G ^e such that (G,x) = det (xI-A(G ^e )), where A(G ^e ) denotes the skew adjacency matrix of G ^e.2.Let G be a 2-connected outerplanar bipartite graph with n vertices. Then there exists a 2-connected outerplanar bipartite graph with 2n+2 vertices such that (G,x) is a factor of .3.Let T be an arbitrary tree with n vertices. Then , where ₁ , ₂ , ..., _n are the eigenvalues of T.     

Variable Mott-Schottky plots acquisition by potentiodynamic electrochemical impedance spectroscopy

Potentiodynamic electrochemical impedance spectroscopy provides extraction of potential-dependent space charge layer capacitance from potentiodynamic impedance spectra of non-stationary semiconductor–electrolyte interface. The new technique has been applied for acquisition of Mott-Schottky plots of cathodically treated TiO₂ anodic films. Cathodic treatment in 1 M H₂SO₄ increases donor density and flat band potential of TiO₂. Freshly doped films show hysteresis in the space charge layer capacitance in cyclic potential scans. The subsequent cycling eliminates the hysteresis but preserves the greater part of the doping effect. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16 March 2005     

Monte‐Carlo simulation of spatial distribution of characteristic x‐rays in multi‐film targets: source size of Al Kα x‐rays in W/Al film targets

A Monte‐Carlo simulation approach has been applied to describe the spatial distribution of characteristic x‐rays in W/Al film targets of different combinations of film thicknesses for the optimal design of a small‐sized x‐ray source having a high x‐ray intensity. The result has led to optimal combinations of W and Al film targets for 100 kV electrons, e.g. W(1 µm)/Al(20 µm), W(3 µm)/Al(15 µm) and W(5 µm)/Al(8 µm). These Al/W targets could be used as x‐ray sources for a medical instrument currently under development. Copyright © 2004 John Wiley & Sons, Ltd.     

A novel nomenclature of polycyclic aromatic hydrocarbons without using graph centre

In this paper, we develop a novel adjacency matrix, He-matrix, corresponding to the dualist graph. Without using the graph center concept, we advance a novel nomenclature of polycyclic aromatic hydrocarbons. Further, we derive some distinguishing theorems about PAH molecules and present some results of our automatic derivatization and automatic classification counting of fused PAH molecules.     

Effects of Lead on Temporal Response Properties of Retinal Ganglion Cells in Developing Rats

Neonatal rats have taken in lead, during the period from their parturition to their weaning, from the milk of dams fed with water containing 0.2% lead acetate solutions. The alterations in the temporal response properties of retinal ganglion cells in adult rats (90 days) following the lead exposure at their developing stage have been studied. The results of this investigation demonstrate that the lead exposure in neonatal rats causes decreases in the optimal temporal frequency, bandwidth at half amplitude, temporal resolution and response phase of the retinal ganglion cells in adult rats. Compared with the sustained cells, the transient cells have a much greater alteration in temporal response properties.     

脱铝丝光沸石的制备和结构特征

用高温水蒸气结合酸洗的方法制备了SiO_2/Al_2O_3为16～186的脱铝丝光沸石。用X光衍射和红外光谱法研究了它们的结构持征。随丝光沸石脱铝,晶格参数呈非线性和各向不同步收缩。由于α方向发生明显收缩,使椭园形主孔道的长轴方向缩小。其骨架振动频率自600～1300cm~(-1)随着脱铝明显向高频方向漂移。当Al/u.c.自4脱至3时,丝光沸石的结构特征发生了明显的变化,可能与骨架上2位铝的脱除有关。当Al/u.c.≤3时,有新的Si—O—Si骨架生成,同时晶体重排为均匀有序的结构。     

Microporous, fast response cellulose ether hydrogel prepared by freeze-drying

A simple and effective method of preparing fast-response gels is developed. The freeze-drying and subsequent rehydration of thermosensitive gels alters the microstructural properties of the gels in a way that leads to rapid shrinking rates. Microporous hydroxypropyl cellulose (HPC) gels were created by this method to investigate the influence of the process on the swelling and shrinking kinetics of the gels in response to temperature changes. Micropores of different size ranges were produced by freezing gels with different amounts of water at −20 °C. Water content was the key factor to control the microporosity and the shrinking rates of gels. After the freezing treatment, an effective diffusion coefficient for shrinking could be determined by fitting Fick's law to the data (5.2 × 10⁻⁴ cm²/s). This was an increase of two orders of magnitude over that of the untreated, non-porous gel (6.0 × 10⁻⁶ cm²/s). The magnitude of the shrinking coefficient indicates that the shrinking rate of the microporous gel is probably limited by the convective flow, as unsteady flow through porous media follows the same differential equation as Fick's law, but with much greater transport coefficients, as observed here. Physically, the shrinking rate may be determined by the level of interconnected-cells in a microporous structure present at the beginning of shrinking process because the convection through the interconnected-cells is estimated to be much slower than the polymer network diffusion rate of the struts of micropores (0.1–3.0 μm) as well as heat transfer.     

Photocurrent generation in multilayer self-assembly films fabricated from water-soluble poly(phenylene vinylene)

A novel, water-soluble, cationic PPV derivative poly[(2,5-bis(3-bromotrimethylammoniopropoxy)-phenylene-1,4-divinylene)-alt-1,4-(2,5-bis(2-(2-hydroxyethoxy)ethoxy))phenylene vinylene] (BH-PPV) has been synthesized by a Heck coupling reaction. Multilayered assemblies of the BH-PPV and the sodium salt of hexa(sulfobutyl)fullerenes (C(60)-HS) were fabricated successfully by an alternate deposition technique. The multilayer structures were studied by UV/Vis spectroscopy, small angle X-ray diffraction, and atomic force microscopy. The photoinduced charge transfer property of the self-assembled multilayer film was also measured by a three-electrode cell technique. A steady and rapid cathodic 5.5 microA cm(-2) photocurrent response was measured as the irradiation of the multilayer film was switched on and off. Importantly, the response of on/off cycling is prompt and reproducible. A possible mechanism for the electron-transfer process is proposed.     

Features and origin of the dynamic and the nonlinear piezoelectricity in poly(vinylidene fluoride)

Some of the piezoelectric coefficients of poly(vinylidene fluoride) are distinctly stress dependent. We report on their dependence on the frequency of an oscillatory stress excitation, on the amount of the remanent polarization in the sample materials, and on the magnitude of an offset stress. In order to explain the observed dynamic and nonlinear piezoelectric properties, a model is developed that attributes them to changes in the local polarization in an interphase between the crystalline and amorphous phases in this semicrystalline polymer.