Image Intensification in Silver Halide Photographic Materials for Detection of High-Energy Radiation by Reprecipitation of Elemental Silver

A process for the intensification of silver images on AgHal photographic materials designed for detection of high-energy (X- and γ-ray) radiation was proposed, which is based on the “reprecipitation” of elemental silver and a decrease in its dispersion and comprises the treatment of silver with an aqueous solution containing potassium hexacyanoferrate(III) and potassium chloride or bromide at the first step and with a solution containing tin(II) chloride, potassium thiocyanate, sodium N,N′-ethylenediamine tetraacetate, and potassium hydroxide at the second step. By this process, the optical densities of image over a wide (0.5–2.0) range was increased by a factor of 3–5; as a result, the photographic sensitivity S _0.85 and S _2.00 was enhanced by almost an order of magnitude with the retained or slightly increased gradient g, fog density D ₀, and resolving power of the material.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 5, 2005, pp. 373–378.Original Russian Text Copyright © 2005 by Mikhailov, Kondakov, Krikunenko.     

Enhancement of the Surface Activity for Some Monomeric and Polymeric Thiol Surfactants Using Silver Nanoparticles

In the present work, the self-assembling of some synthesized thiol surfactants namely (6-(3-amino phenoxy) hexane-1-thiol, 8-(3-amino phenoxy) octane-1-thiol, 10-(3-amino phenoxy) decane-1-thiol, 12-(3-amino phenoxy) dodecane-1-thiol, and their polymers on silver nanoparticles was investigated. The self-assembling of these surfactants on silver nanoparticles was characterized using different techniques such as ultraviolet (UV) spectroscopy, powder x-ray diffraction (XRD), electrone diffraction (ED), and transmission electron microscopy (TEM). The effect of the self-assembling of these surfactants on the stabilization of the silver nanoparticles (AgNPs) was studied using TEM images. The growth of the silver nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The effect of silver nanoparticles on the surface, interfacial tension, and the emulsion stability of these surfactants with paraffin oil was studied. The results show that the silver nanoparticles have the ability to effect on the behavior of these surfactants in solution and improve their surface activity.     

Extended Possibilities of Analysis for Supported Metal Catalysts and Nanocomposites by Dynamic Light Scattering

Kinetics and Catalysis - This study is a continuation of the work on the use of dynamic light scattering (DLS) for the analysis of active component particle sizes in supported catalysts. It was...     

设计非线性光学材料的新思路:质子转移增强光学非线性

从酸的电子给体HO-C₆H₄-CHCH-C₆H₄-NO₂(OSN)可以向碱的电子受体Me₂N-C₆H₄-CHCH-C₅H₄N(DAMS)发生质子转移,质子转移后形成的相应离子与其中性分子相比,光学非线性增强.采用ZINDO-SOS,FF/PM₃及CPHF/PM₃三种方法对其进行了系统的理论研究.三种方法研究结果均表明,质子转移后所产生的离子和相应的中性分子相比,其第一超极化率β和第二超极化率γ-都显著增强.     

Light Absorption by the Clusters of Colloidal Gold and Silver Particles Formed During Slow and Fast Aggregation

Spectra of absorption (400–800 nm) by the aggregates of colloidal gold (5, 15, and 30 nm in diameter) and silver (20 nm in diameter) particles were studied experimentally and theoretically. It was revealed that, during fast aggregation corresponding to the diffusion-limited cluster aggregation (DLCA), the pattern of spectra is dependent on the size of primary particles. Spectra with the additional absorption maximum in the red region are observed for 15 and 30 nm gold and 20 nm silver particles, while the absorption spectrum for 5 nm particles is characterized by only one maximum shifted to the red region. The slow aggregation resulted in a decrease in plasmon absorption peak with no marked shift to the red region and to the broadening of long-wave absorption wing. From data on electron microscopy, typical branched DLCA-clusters were formed during fast aggregation, whereas small compact aggregates and a noticeable number of single particles were observed in a system during slow aggregation. The computer model of the diffusion-limited cluster-cluster aggregation was used to explain these results. Optical properties of aggregates were calculated using coupled dipole method (CDM or DDA) and the exact method of a multipole expansion. Corrections for the size effect were introduced into the bulk optical constants of metals for nanosized particles. It was shown that a modified version of DDA (Markel et al.,Phys. Rev. B, 1996, vol. 53, no. 5, p. 2425) allows us to explain the pattern of experimental spectra of DLCA-aggregates and their dependence on a monomer size. The exact method was applied to calculate the extinction cross sections of metallic aggregates demonstrating strong electrodynamic interaction between particles. The number of higher multipoles that are required to adequately describe this interaction is much larger than the number of terms of an ordinary Mie series and is the main obstacle to the exact calculation of the spectra of metallic aggregates with a large number of particles.     

原子吸收光谱法测定金银样品前处理的讨论

讨论了在岩石、矿物及化学探矿样品中金、银的原子吸收光谱分析时,样品前处理应关注的一些问题实践经验表明要注意样品的加工过程和金银的赋存状态,以保证样品有足够的代表性;针对不同矿种类型,选择合适的样品前处理方法,尽量避免样品在处理过程中的挥发损失、包夹、共沉淀吸附等情况的发生;对单矿物金、银的连续测定,建议采用多次湿法酸处理来保证样品的分解,并根据其含量进行必要的分离富集或稀释,以满足测定的要求．     

Sensitivity enhancement by on-line preconcentration and in-capillary derivatization for the electrophoretic determination of amino acids

This study describes an application of on-line preconcentration by large-volume stacking in combination with in-capillary derivatization for enhancing spectrophotometric detection sensitivity in capillary electrophoresis. The method is illustrated by an example dealing with the determination of amino acids with 1,2-naphthoquinone-4-sulfonate as a labelling agent. Samples are dissolved in water in order to create a stacking process based on differences in the conductivity between this medium and a concentrated running buffer. The in-capillary derivatization is accomplished following a sandwich procedure in which the sample is inserted between two segments of reagent. Amino acid derivatives are obtained and separated in a fused-silica capillary with a sodium borate electrolyte buffer using 2-propanol as an organic modifier. The method is applied to the analysis of amino acids in pharmaceutical and feed samples. A good concordance between the predicted values and those obtained with the standard method is observed, with overall quantification error below 5%. The proposed procedure allows the detection limits sensitivity to be enhanced in 1000-fold with respect to conventional precapillary derivatization.     

Possibilities for controlling the oxygen balance and composition of fire-extinguishing aerosol generated by epoxy polymer solid fuel elements in means for firefighting

The oxygen balance of oligomer homologs of epoxy-4,4′-isopropylidenediphenol oligomers and of polymeric materials based on them was calculated. The use of oligomeric fire retardants in epoxy solid fuel elements of aerosol-generating means for firefighting was substantiated. Heat-curable oligoether phosphates were suggested for fabricating solid fuel elements with increased content of the dispersed phase in the fire-extinguishing aerosol.     

Kinetic Screening for the Acid‐Catalyzed Hydrolysis of Some Hydrophobic Fe(II) Schiff Base Amino Acid Chelates and Reactivity Trends in the Presence of Alkali Halide and Surfactant

Kinetics of acid‐catalyzed hydrolysis of some high‐spin Fe(II) Schiff base amino acid complexes were followed spectrophotometrically at 298 K under pseudo–first‐order conditions. The studied ligands were derived from the condensation of 5‐bromosalicylaldehyde with different four amino acids (phenylalanine, aspartic acid, histidine, and arginine). The acid hydrolysis reaction was studied in aqueous media and in the presence of different concentrations of the alkali halide (KBr) and cationic surfactant (cetyl‐trimethyl ammonium bromide, CTAB). The general rate equation was suggested to be rate = k_obs[complex], where k_obs = k₂[H⁺]. The increase in [KBr] enhances the reactivity of the reaction, and the addition of CTAB to the reaction mixture accelerates the reaction reactivity. The obtained kinetic data were used to determine the values of δ_mΔG^# (the change in the activation barrier) for the studied complexes when transferred from “water to water containing different [KBr]” and from “water to water containing altered [CTAB].”     

铜,硫掺杂对铁氮碳氧还原催化剂性能的提升作用

采用FeCl₃·6H₂O,Cu(NO₃)₂·3H₂O,KSCN,氧化BP-2000和三聚氰胺分别作为铁源、铜源、硫源、碳源和氮源,制备了一系列非贵金属氧还原电催化剂.通过透射电子显微镜、X射线粉末衍射、X射线光电子能谱和电感耦合等离子体原子发射光谱等表征了催化剂的形貌和结构,并通过旋转圆盘和旋转环盘测试研究了催化剂的性能,分析了铜,硫掺杂对于催化剂性能的提升作用.结果表明,与铜掺杂相比,硫掺杂能更大幅度地提高催化剂的周转率(TOF),并有效降低过氧化氢产率;同时铜,硫双掺杂的催化剂具有更高的TOF和更低的过氧化氢产率.     

Sensitivity enhancement of CE and CE-MS for the analysis of peptides by a dynamic pH junction

An analytical method of CE-MS and CE with an online preconcentration technique induced by a dynamic pH junction, addition of organic solvent and large volume injection was developed for sensitive determination of peptides in biological samples. Leucine enkephalin, methionine enkephalin, dynorphin A, β-endorphin and angiotensin II were used as model peptides. The optimal online preconcentration conditions were obtained at a sample matrix consisting of 100?mM borate buffer (pH 10.0) with 50% v/v acetonitrile and a BGE containing 1?M formic acid at pH 2.0, along with a 25-cm injection length. Under the optimized conditions, a 4.0×10(3)-1.1×10(4)-fold increase in peak intensity was achieved without degrading the peak shape. This online preconcentration method was applied to analyze the intracellular angiotensin II within the peptides extracted from HL1 cells and approximately increase of 1×10(4)-fold sensitivity was achieved compared to normal condition. Thus, the developed method could be applied to the analysis of various peptides for peptidomics study in biological samples.     

巴比妥酸衍生物荧光增强法快速测定牛奶中的三聚氰胺

建立了一种简单快速测定三聚氰胺的方法. 在pH=7.0的磷酸盐缓冲溶液中, 三聚氰胺与巴比妥酸衍生物(DBA)形成稳定的氢键, 使三聚氰胺的荧光强度显著增强, 由此建立了巴比妥酸衍生物荧光增强测定牛奶中三聚氰胺的新方法. 在优化的条件下, 该方法的线性范围为12.5~1250 μg/L, 检出限为7.5 μg/L, 相对标准偏差为2.06%, 样品平均加标回收率为96.62%. 本方法简便、快速、准确, 可用于大量牛奶样品中三聚氰胺的快速检测.     

纤维钛酸铅/纳米钛酸铅晶体复合陶瓷材料性能研究

钛酸铅（PbTiO3）在常温下属于典型的钙钛矿结构,其居里温度高达490℃,介电常数小,压电性能高,压电各向异性大,是一种优良的高温高频的压电材料,但因其轴向比c/a=1.063和矫顽场大,难于极化,在冷却过程四方至立方的相变中易出现微细裂纹,有时甚至破碎,所以制备纯相致密的PbTiO3陶瓷存在烧结上的困难,且因陶瓷本身固有的脆性,使其优良的电性能很难得到充分的开发和利用。PbTiO3的应用通常是通过掺杂改性而获得的。而掺杂改性会对其电性能产生不良的影响。如能寻找一种有效的方法,即改善其烧结特性,又不影响其电性能,而且能制得致密的PbTiO3陶瓷,则对PbTiO3的研究与应用具有重要的意义。     

Performance Evaluation of Charged Aerosol and Evaporative Light Scattering Detection for the Determination of Ginsenosides by LC

A sensitive LC-CAD method was developed for simultaneous determination of seven major triterpenoid saponins, namely ginsenosides Rg₁, Re, Rb₁, Rc, Rb₂, Rb₃ and Rd in Panax ginseng C. A. Meyer, a commonly used traditional Chinese medicine. This CAD method was evaluated in sensitivity, linearity and reproducibility compared to ELSD and UV. It was found the developed method has improved sensitivity, linearity and reproducibility compared to ELSD. This method was successfully applied to analyze the ginsenosides in ten samples of Panax ginseng. The validation results indicated that the improved method can be utilized as another approach for quality control of P. ginseng.     

Sols of Silver Nanoparticles as Analytical Reagents for the Determination of Active Chlorine in Water Samples by Spectrophotometry and Photometric Titration

Sols of silver nanoparticles surface-stabilized by cetyltrimethylammonium bromide or polyvinylpyrrolidone can be used for the determination of active chlorine in water samples. As analytes modeling active chlorine in water, we used freshly prepared sodium hypochlorite solutions. Because of the high values of standard electrode potentials of reduction half-reactions, active forms of chlorine can oxidize silver nanoparticles, exhibiting the effect of surface plazmon resonance with an absorption maximum near 400 nm. The absorption intensity of silver nanoparticles correlates with the concentration of sodium hypochlorite. This effect was used for the qualitative and quantitative determination of active chlorine in water samples. The quantitative characteristics of the described method were obtained for two versions of analysis, spectrophotometry and photometric titration. The calibration graphs for both versions were similar and linear in the range of sodium hypochlorite concentrations 0.1–2.5 mM.     

Enhancement of the detection sensitivity for volatile organic compounds by using an annular type photoionization detector and a pre-concentration system

Photoionization detector (PID) was developed for a sensitive on-site detection of trace amounts of volatile organic compounds (VOCs) based on an annular type ion collection electrode assembly. An ion collector with an annular geometry could detect more stable ion signals in the PID system when compared to the other types of ion collectors when an UV lamp of 10.6 eV was used as an ionization source. In order to enhance the detection sensitivity, a pre-concentration system, which was developed by adopting a ceramic heater packed with rod shaped molecular sieves, was adopted for a detection of VOCs. The adopted ceramic heaters had a resistance of 10-20 Ohm, and the temperature of the heater was optimized by controlling the heating time of the resistor. The enhancement of the detection sensitivity was found to be 8-10 times with the PID system when compared to the signals measured without a pre-concentrator. The overall detection sensitivity of the developed PID system was estimated as 10 ppb or better.     

Enhancement of the emission intensity of fluorophore-labeled avidin by biotin and biotin derivatives. Evaluation of different fluorophores for improved sensitivity

Fluorescein, Texas Red, Cascade Blue, 7-amino-methylcoumarin-3-acetic acid, and Lucifer Yellow were evaluated as fluorescent labels for homogeneous fluorophore-linked binding assays. Conjugates of avidin with these fluorophores exhibited an enhancement in fluorescence emission in the presence of biotin or biotin derivatives. This property was used in the development of assays for biotin. The biotin-induced fluorescence enhancement of each labeled avidin were compared. Fluorescein led to the most sensitive calibration (dose-response) curve for biotin with a detection limit of 8 x 10(-10)M.     

Uncertainty Quantification and Sensitivity Analysis for the Electrical Impedance Spectroscopy of Changes to Intercellular Junctions Induced by Cold Atmospheric Plasma

The influence of pertinent parameters of a Cole-Cole model in the impedimetric assessment of cell-monolayers was investigated with respect to the significance of their individual contribution. The analysis enables conclusions on characteristics, such as intercellular junctions. Especially cold atmospheric plasma (CAP) has been proven to influence intercellular junctions which may become a key factor in CAP-related biological effects. Therefore, the response of rat liver epithelial cells (WB-F344) and their malignant counterpart (WB-ras) was studied by electrical impedance spectroscopy (EIS). Cell monolayers before and after CAP treatment were analyzed. An uncertainty quantification (UQ) of Cole parameters revealed the frequency cut-off point between low and high frequency resistances. A sensitivity analysis (SA) showed that the Cole parameters, R₀ and α were the most sensitive, while R_inf and τ were the least sensitive. The temporal development of major Cole parameters indicates that CAP induced reversible changes in intercellular junctions, but not significant changes in membrane permeability. Sustained changes of τ suggested that long-lived ROS, such as H₂O₂, might play an important role. The proposed analysis confirms that an inherent advantage of EIS is the real time observation for CAP-induced changes on intercellular junctions, with a label-free and in situ method manner.