The application of dielectric analysis to drying latex films

Measurements of real and imaginary capacitance (C andC) have been made during the drying of a film-forming latex. In one experiment dielectric measurements at frequencies between 1 Hz and 100 kHz were made simultaneously with gravimetric measurements on a microbalance. It was found that both the rate of water evaporation and the a.c. conductance decrease sharply at high polymer volume fraction. These results are discussed qualitatively in terms of a model for the film-forming process. In another experimentC andC were recorded at 10 Hz along with automatic measurements of the build-up of the scratch resistance of the film. It was found that the mechanical response to film-formation appears significantly earlier than the dielectric response. This is also discussed qualitatively in terms of the model.The authors would like to thank Dr. I. Abrahams, Dr. S. Bell, and Dr. M. Reading for useful discussions regarding this work and M. Bahra for his help with the TFA measurements.     

Phenomenology of nonlocal cellular automata

Dynamical systems with nonlocal connections have potential applications to economic and biological systems. This paper studies the dynamics of nonlocal cellular automata. In particular, all two-state, three-input nonlocal cellular automata are classified according to the dynamical behavior starting from random initial configurations and random wirings, although it is observed that sometimes a rule can have different dynamical behaviors with different wirings. The nonlocal cellular automata rule space is studied using a mean-field parametrization which is ideal for the situation of random wiring. Nonlocal cellular automata can be considered as computers carrying out computation at the level of each component. Their computational abilities are studied from the point of view of whether they contain many basic logical gates. In particular, I ask the question of whether a three-input cellular automaton rule contains the three fundamental logical gates: two-input rules AND and OR, and one-input rule NOT. A particularly interesting edge-of-chaos nonlocal cellular automaton, the rule 184, is studied in detail. It is a system of coupled selectors or multiplexers. It is also part of the Fredkin's gate—a proposed fundamental gate for conservative computations. This rule exhibits irregular fluctuations of density, large coherent structures, and long transient times.     

Hydration and dielectric properties of aqueous solutions of protonated diallylmethylammonium polymer: transition from monomer to polymer

Abstract

The high-frequency dielectric relaxation of aqueous solutions of protonated diallylammonium polyelectrolyte, namely poly(diallylmethylammonium trifluoroacetate) has been studied at the maximum water dispersion frequencies, 7.5–25?GHz, and temperatures of 288, 298, and 308?K. Dielectric relaxation parameters have been calculated and compared with similar characteristics of aqueous solutions of monomer, diallylmethylammonium trifluoroacetate, and pyrrolidinium trifluoroacetate salt simulated structure of pyrrolidinium polymer link. It has been concluded that although the monomer features hydrophobic hydration, its polymer exhibits hydrophilic hydration properties. This change is related to conformation of hydrophilic-hydrophobic polycations in aqueous solutions and the change in the structure of polymer links.     

X射线荧光光谱铝环-双层压片法测定土壤中常量和微量元素

本文提出用铝环-双层压片法制片,经验系数法校正吸收-增强效应,对少量土壤样品中的常量和微量元素进行了定量测定。取样量为500 mg,制样与测量精确度好于5%,用本法对标样的分析表明,分析值与推荐值基本一致,本法具有简单、快速、成本低的特点,适用于少量样品的分析。     

A dual-electrode approach for highly selective detection of glucose based on diffusion layer theory: experiments and simulation

A dual-electrode configuration for the highly selective detection of glucose in the diffusion layer of the substrate electrode is presented. In this approach, a glassy carbon electrode (GCE, substrate) modified with a conductive layer of glucose oxidase/Nafion/graphite (GNG) was used to create an interference-free region in its diffusion layer by electrochemical depletion of interfering electroactive species. A Pt microelectrode (tip, 5 microm in radius) was located in the diffusion layer of the GNG-modified GCE (GNG-G) with the help of scanning electrochemical microscopy. Consequently, the tip of the electrode could sense glucose selectively by detecting the amount of hydrogen peroxide (H2O2) formed from the oxidization of glucose on the glucose oxidase layer. The influences of parameters, including tip-substrate distance, substrate potential, and electrolyzing time, on the interference-removing efficiency of this dual-electrode approach have been investigated systematically. When the electrolyzing time was 30 s, the tip-substrate distance was 1.8 a (9.0 microm) (where a is the radius of the tip electrode), the potentials of the tip and substrate electrodes were 0.7 V and 0.4 V, respectively, and a mixture of ascorbic acid (0.3 mM), uric acid (0.3 mM), and 4-acetaminophen (0.3 mM) had no influence on the glucose detection. In addition, the current-time responses of the tip electrode at different tip-substrate distances in a solution containing interfering species were numerically simulated. The results from the simulation are in good agreement with the experimental data. This research provides a concept of detection in the diffusion layer of a substrate electrode, as an interference-free region, for developing novel microelectrochemical devices.     

Development of B‐doped Si multiple delta‐layer reference materials for SIMS profiling

B‐doped Si multiple delta‐layers (MDL) were developed as certified reference materials (CRM) for secondary ion mass spectrometry (SIMS) depth profiling analysis. Two CRMs with different delta‐layer spacing were grown by ion beam sputter deposition (IBSD). The nominal spacing of the MDL for shallow junction analysis is 10 nm and that for high energy SIMS is 50 nm. The total thickness of the film was certified by high resolution transmission electron microscopy (HR‐TEM). The B‐doped Si MDLs can be used to evaluate SIMS depth resolution and to calibrate the depth scale. A consistency check of the calibration of stylus profilometers for measurement of sputter depth is another possible application. The crater depths measured by a stylus profilometer showed a good linear relationship with the thickness measured from SIMS profiling using the calibrated film thickness for depth scale calibration. The sputtering rate of the amorphous Si thin film grown by sputter deposition was found to be the same as that of the crystalline Si substrate, which means that the sputtering rate measured with these CRMs can be applied to a real analysis of crystalline Si. Copyright © 2005 John Wiley & Sons, Ltd.     

An effective cross-linking of polymer layer on monodisperse, poly(maleic anhydride-styrene)-modified colloidal silica particles and properties of the composite

Summary  The cross-linkings of the surface polymer layer on mono disperse, poly(maleic anhydride-styrene)-modified silica particles by the reaction with diisocyanate were studied. The extent of cross-linking was estimated by the weight decrease by immersing the particles in the buffer solution of pH 2.0, 4.0 and 9.0 at a room temperature for 24 h. The reaction of the polymer-modified silica with 1,6-diisocyanatohexane afforded relatively stable composite particles which lost less than 5 wt% of the polymer in aqueous solution in the pH range 2.0–9.0. The diisocyanate was a preferable cross-linker to 2,4-diisocyanatotoluene in terms of stability in acidic or basic aqueous solution. The flexibility of the cross-linker molecule possibly plays an important role in the cross-linking reaction. The carboxyl and amino groups were formed by treating the cross-linked composite particles with diluted HCl solution; 5–6 and 0.5–1.1 μmol g^-1, respectively. The cross-linked composite particles exhibited the characteristic property of ζ-potential, −44 to −47 mV and −102 to −107 mV in a neutral aqueous solution and ethanol, respectively. Received: 26 May 1997 Accepted: 4 August 1997     

Novel anti-inflammatory and wound healing controlled released LDH-Curcumin nanocomposite via intramuscular implantation,in-vivo study

One of the most common problems in wounds is delayed healing and complications such as infection. Therefore, the need for novel materials accelerates the healing of wounds especially abdominal wounds after surgery besides high efficiency and safety is mandatory. The rate of wound healing, anti-inflammatory and biocompatibility of Zn-Al LDH (Zn-Al layer double hydroxide) alone and loaded with Curcumin (Zn-Al LDH/Curcumin) was screened via in-vivo assays through intramuscular implantation in rat abdominal wall with intact peritoneum cavity. The implanted drugs were formed through Curcumin loaded into LDH of Zn-Al with drug release of 56.78 ± 1.51% within 24 h. The synthesized nanocomposite was characterized by (TGA/DTA) thermal analysis, (XRD) X-ray diffraction, (FESEM) Field emission scanning electron microscopy, (HRTEM) high resolution transmission electron microscope, energy dispersive X-ray (EDX) and low-temperature N₂ adsorption, pore volume and average pore size distribution. The integrity of blood circulation, inflammatory signs, wound healing rate, capacity of tissue integration, antigenicity and composite biocompatibility, auto fluorescence ability of collagen bundles and the tensile strength of the muscle were assessed histopathologically after 7 and 30 days’ post-implantation. Excellent wound healing ability was achieved with shortest length between the wound gap edges and higher tensile strength of the muscle. Besides emit florescence very well followed by good healing and tensile muscles strength in Curcumin while very low strength with scar formation in Zn-Al LDH/Curcumin in both acute and chronic wound. No signs of inflammation in Curcumin & Zn-Al LDH. No vessels obstruction or bleeding observed in both Zn-Al LDH and Curcumin more than Zn-Al LDH/Curcumin and control which examined through candling. Good healing & infiltrated immune cells in same groups through histopathological examination. This work supports the anti-inflammatory, wound healing and biocompatibility of both LDH and Curcumin with living matter, increasing their biomedical applications in this era with safety and increasing efficacy with prolonged drug release.     

Impregnated silica-based layers in thin layer chromatography

Abstract

Impregnated thin-layer chromatography (TLC) layers based on silica gel are presented. Impregnating agents such as metal cations, inorganic ions, chelating agents, chiral selectors, surfactants, ion-pairing reagents, and ionic liquids are discussed. The role of impregnated TLC layers in medicinal chemistry is highlighted. The historical overview of TLC separations on physically coated layers is given and some future prospects ahead of this technique are discussed.     

Comparative study on the inclusion behaviour of cyclodextrin derivatives with venoruton and rutin by thin layer chromatography

The interaction of rutin and venoruton (troxerutin), with alpha-, beta- and gamma-cyclodextrin (CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and methyl-beta-cyclodextrin (M-beta-CD) was investigated by reversed-phase thin layer chromatography on polyamide plates. A mobile phase consisted of NH(4)OH; NH(4)Cl buffer solution containing various CD concentrations (pH = 9.7, 20 degrees C) was used as mobile phase. The equilibrium constants (K(f)) and the retention factor (R(f)) were determined and used to study the inclusion process. The in fluence of CDs on the solubility of rutin and venoruton was characterized by R(M) values and the increasing hydrophilicity of drugs. The results show that the inclusion capacity of cyclodextrins follows the order HP-beta-CD > M-beta-CD > beta-CD > gamma-CD, and rutin is more easily included by the studied cyclodextrins than venoruton. In addition, the thermodynamic parameters (Delta H, Delta S) for the formation of complexes were obtained from the van't Hoff equation, displaying the enthalpy-entropy compensation effect.