Surface-sensitive method to determine calcium carbonate filler contents in cellulose matrices

This paper describes a method using attenuated total reflectance infra-red spectroscopy to determine the surface concentration of calcium carbonate in paper samples, by applying the linear relationship between the relative infra-red absorption integrals and the concentration. The method was able to detect micro-variations in the surface concentration and could also distinguish between different sheets as well as between the top and bottom side of one sheet. The samples were also split and the calcium carbonate concentration was determined within and compared to bulk calcium carbonate concentration determined from ash testing. The surface results were also compared with analysed scanning electron microscopy images generated from back-scattering electrons. The comparison shows that both sets of results are in excellent agreement. Depending on the sample, large errors (95% confidence) were observed. These, however, are caused by micro-variations of the surface concentration, rather than by inaccuracies of the technique, which is estimated to be less than 1%. Furthermore, measurements of various sample orientations suggest that anisotropic polarisation effects can be neglected. The method can be applied to paper and cellulose matrices having calcium carbonate filler contents of less than 50%. Due to spectral overlaps it is not suitable to determine kaolin filler contents.     

A paramagnetic Cu(I)/Cu(II)/Zn(II) coordination polymer with multiple CN-binding modes and its solid-state NMR characterization

A Cu(I)/Cu(II)/Zn(II) mixed-valent [Cu(en)2][Zn(NC)4(CuCN)2] polymer, which has a 2-D layer structure with six structurally inequivalent cyanides in four distinct bonding modes, has been prepared; structurally informative 13C and 15N MAS NMR spectra of this paramagnetic system are readily observable.     

Failure detection in pressured plastics pipes and vessels by electronic means

A laboratory device for detecting leaks in plastics pipes and vessels subjected to static and fluctuating internal pressures is described,. The high electrical resistivity of plastics materials is utilised in a system which identifies failures by the passage of a small signal current, following a break in the test specimen wall, by means of an electrically conductive liquid. A brief outline of experience gained with the instrument is given together with suggestions for possible alternative applications.     

稀释悬浮体中小粒子的碰并率

本文研究了稀释悬浮体中刚性粒子对的形成率。体系中布朗运动效应小于粒子的强迫运动。后者或是重力相对运动,或是轴对称纯变形运动。本文提出了一个新方法,即求解对分布边界层方程法(在边界层中,van der Waals引力与强迫运动可以相比),从而第一次得到了粒子碰并率的严格的渐近解。文中还计算了两类强迫运动中的捕获系数。对于轴对称压缩性纯变形运动的均匀粒子,结果与Zeichner和Schowalter用轨迹计算法得到的,伸展性纯变形运动的捕获系数一致。     

Amperometric assay for the ketone body 3-hydroxybutyrate

A stable dry-strip electrochemical sensor for the direct measurement of 3-hydroxybutyrate in blood is described. The sensor utilizes the electrocatalytic oxidation of enzymically generated NADH by the redox mediator 4-methyl-o-quinone. The enzyme 3-hydroxybutyrate dehydrogenase, cofactor NAD⁺ and 4-methyl-o-quinone were incorporated into single-use disposable strip electrodes.     

Logarithmic corrections to finite-size scaling in the four-state Potts model

The leading corrections to finite-size scaling predictions for eigenvalues of the quantum Hamiltonian limit of the critical four-state Potts model are calculated analytically from the Bethe ansatz equations for equivalent eigenstates of a modifiedXXZ chain. Scaled gaps are found to behave for large chain lengthL asx+dL+0[(lnL)^–1], wherex is the anomalous dimension of the associated primary scaling operator. For the gaps associated with the energy and magnetic operators, the values of the amplitudesd are in agreement with predictions of conformai invariance. The implications of these analytical results for the extrapolation of finite lattice data are discussed. Accurate estimates of x andd are found to be extremely difficult even with data available from large lattices,L500.     

Row transfer matrix spectra of cyclic solid-on-solid lattice models

The eigenvalue spectra of cyclic solid-on-solid (CSOS) row transfer matrices are studied. An equivalence is established between the inversion identity and the Bethe ansatz functional equations and these equations are solved in the thermodynamic limit by a Wiener-Hopf perturbation technique for the bands of leading excitations. TheL-state CSOS model, with crossing parameter=s/L, possesses a 2(L – s)-fold degenerate largest eigenvalue corresponding to the 2(L – s) coexisting phases. The expressions for the largest eigenvalue and free energy coincide with those of the eight-vertex model. The string excitations for 2s < L and 2s > L admit different classifications and are treated separately. The correlation length is calculated in both regimes, yielding the critical exponentv=L/2s, in agreement with the scaling relations.     

Ultra‐small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity

Carbon nanotubes decorated with ultra‐small metal nanoparticles are of great value in catalysis. We report that individual multiwalled carbon nanotubes decorated with ultra‐small palladium nanoparticles can be detected by using the nano‐impacts method. The high conductivity and reactivity of each decorated carbon nanotube is directly evidenced; this is achieved through studying the proton‐reduction reaction for the underpotential deposition of hydrogen onto the nanoparticles decorated on the carbon nanotube walls. The reductive spikes from current amplification are analyzed to estimate the approximate length of the decorated carbon nanotubes, revealing that the decorated carbon nanotubes are electroactive along its entire length of several micrometers.     

Voltammetric Study of the Influence of Various Phosphate Anions on Silver Nanoparticle Oxidation

The antibacterial properties of silver are strongly controlled by the redox couple of silver/silver(I). This work reports the influence of phosphate anions on silver nanoparticle oxidation, which is important given the abundance of phosphate species in biological systems. The three different species of anions were found to have a varying degree of influence on silver oxidation with the order PO₄³⁻>HPO₄²⁻>H₂PO₄⁻. It was found that in the presence of phosphate anions, the silver oxidation potential shifts to a less positive value, which indicated the increasing ease of the oxidation reaction of silver. Given that the interplay between silver and its cation is crucial to its antibacterial properties and significant concentrations of the HPO₄²⁻ anion are present at biological pH (near neutral), it is essential that the influence of the dibasic anion (HPO₄²⁻) on silver oxidation dynamics be considered for biological systems.