Comparison of the Precision and Accuracy of Digital Versus Analogue Gamma-Ray Spectrometric Systems Used in INAA for Evaluation of Homogeneity and Certification of Reference Materials of the IAEA

Performance of three commercial gamma-ray spectrometric systems was evaluated for precision and accuracy prior to use in characterization of reference materials. Two of the systems were based on fast processing of the analogue signal from the amplifier (EGG Ortec model 672) using a loss free counting module (Canberra model LFC 599) interfaced to one of two analog-to-digital converters (Canberra models 8713 or 8715). The third system was based on a digital signal processor (Canberra model DSP 9660). Performance of the systems was tested over a range of count rates up to a maximum of 70,000 counts per second (dead time up to 90%) using ⁶⁰Co and ¹³⁷Cs sources. Best resolution was achieved with an analogue system with ADC 8713. The analytical results obtained with the digital system show the lowest and well-quantified uncertainty.     

Determination of the rates of formation and hydrolysis of the Schiff bases formed by pyridoxal 5′-phosphate and hydrazinic compounds

The macroscopic rate constants of formation (k₁) and hydrolysis (k₂) for the reactions of pyridoxal 5′-phosphate (PLP) with hydrazine (PLP-HY system), carbidopa (-hydrazino--methyl-β-(3,4-dihydroxyphenyl)propionic acid, PLP-CD system), hydralazine (1-hydrazinophthalazine, PLP-HL system) and isoniazid (4-pyridinecarboxylic acid hydrazide, PLP-ISO system) were fitted to a kinetic scheme that considers the different ionic species present in the medium, their protonation constants, and their individual rates of formation (k₁ⁱ) and hydrolysis (k₂ⁱ). The results obtained for the molecules bearing the hydrazine group are compared with those for the reactions of PLP with n-hexylamine (PLP-NHA system) and poly- -lysine (PLP-LYS system). Some structural effects on the individual rate constants are also examined.     

Study of the Activity Enhancement Caused by the Addition of Hydrogen in Olefin Polymerization

Propene and 1-butene polymerizations were performed using the catalyst system of MgCl₂ · TiCl₄ · diethylphtharate (DEP)/AIEt₃/ phenyltriethoxysilane (PES). In both polymerizations, the activities were enhanced more than three times hv the hydrogen addition, while in the catalyst system not containing DEP and/or PES, the degree of the activity enhancement was decreased to about one-third of that in the above catalyst system. The results of a kinetic study on l-butene short-term polymerization suggest that the said enhancement is not due to the increase of the number of active sites.     

A spectrophotometric study of the formation of the peroxotitanium(IV) complex and its application to the determination of beryllium

The formation of peroxotitanium(IV) complexes has been studied spectrophotometrically in (a)Ti(IV)-H₂O₂,(b)Ti(IV)-H₂O₂-HF and (c)Ti(IV)-H₂O₂-HF-Be(II) systems containing 2M hydrochloric acid. In system (a),only a 1:1 peroxotitanium(IV) complex is evident. In system (b), the competitive formation of the peroxotitanium(IV) complex and fluorotitanium(IV) complexes is discussed. In system (c), the formation of fluoroberyllium(II) complexes causes an increase in concentration of the peroxotitanium(IV) complex which is proportional to the concentration of added beryllium(II). The determination of beryllium in a Cu-Be alloy was successful with a Ti(IV)-H₂O₂-HF reagent.     

Investigation of the CuBr–LiBr phase diagram

Phase diagram for the system CuBr–LiBr was determined by differential scanning calorimetry and X-ray powder diffraction. The system exhibits a significant solid solubility of the components, especially LiBr in the respective polymorphic modifications of CuBr. Another feature of the system CuBr–LiBr is the occurrence of five invariant three-phase equilibria, which have been assigned to one eutectic (684 K), one peritectoid (668 K), and three eutectoids (679, 645, and 521 K). From the experimental results, formation of a compound LiCuBr₂, at 521 K is discerned.     

Development of a long-life capillary enzyme bioreactor for the determination of blood glucose

A long-life capillary enzyme bioreactor was developed that determines glucose concentrations with high sensitivity and better stability than previous systems. The bioreactor was constructed by immobilizing glucose oxidase (GOx) onto the inner surface of a 0.53 mm i.d. fused-silica capillary that was part of a continuous-flow system. In the presence of oxygen, GOx converts glucose to gluconic acid and hydrogen peroxide (H₂O₂). Hydrogen peroxide detection was accomplished using an amperometric electrochemical detector. The integration of this capillary reactor into a flow-injection (FIA) system offered a larger surface-to-volume ratio, reduced band-broadening effects, and reduced reagent consumption compared to packed column in FIA or other settings. To obtain operational (at ambient temp) and storage (at 4 °C) stability for 20 weeks, the glucose biosensing system was prepared using an optimal GOx concentration (200 mg/mL). This exhibited an FIA peak response of 7 min and a detection limit of 10 μM (S/N = 3) with excellent reproducibility (coefficient of variation, CV < 0.75%). It also had a linear working range from 10¹ to 10⁴ μM. The enzyme activity in this proposed capillary enzyme reactor was well maintained for 20 weeks. Furthermore, 20 serum samples were analyzed using this system, and these correlated favorably (correlation coefficient, r² = 0.935) with results for the same samples obtained using a routine clinical method. The resulting biosensing system exhibited characteristics that make it suitable for in vivo application.     

Total Synthesis of the Marine Sesquiterpene Quinones Hyatellaquinone and Spongiaquinone

The synthesis of the marine sesquiterpene quinone (+)‐hyatellaquinone ( 1 ) was achieved starting from the sesquiterpene aldehyde (+)‐albicanal ((+)‐ 3 ) (Schemes 3 and 4). Coupling of (+)‐albicanal with 2,3,5,6‐tetramethoxyphenyllithium led to the aryl‐sesquiterpene system, which was modified to the target molecule. Furthermore, the first total synthesis of the marine compound spongiaquinone ( 2 ) was carried out starting from ((?)‐albicanal (?)‐ 3 ) in a reaction sequence encompassing a stereoselective C?C bond hydrogenation and a one‐pot AcOH elimination/demethylation reaction (Schemes 7 and 10). The occurrence of 1,2‐ and 1,4‐benzoquinone forms of 1 and 2 depends on the pH of the solvent system.     

Effect of Polydispersity on the Phase Behavior of Polymer Blends

Summary: The effect of polydispersity on polymer blend phase behavior is studied by in situ small‐angle X‐ray scattering. In a polydisperse polyethylene (PE)/isotactic poly(propylene) (iPP) blend, the enthalpic portion of the interaction parameter is greater than that of a corresponding blend with lower polydispersity. This is attributed to the presence of long chains, which provide a higher interaction energy and packing constraint, reducing the system miscibility. As expected, the radius of gyration is higher in the system with higher polydispersity.

Comparison of phase diagrams of the iPP/PE system used in this study (thin lines) with that obtained from the literature (thick lines). The solid lines represent binodals and the dashed lines are spinodals.     

Tracer experiments on the behavior of radioiodine in the soil-plant-atmosphere system

In order to obtain information on the behavior of long-lived¹²⁹I in the soil-plant-atmosphere system, two different experiments, transfer factors and volatilization of iodine, have been conducted by radiotracer techniques using¹²⁵I. Soil-to-plant transfer factors varied very widely. Low values were found in tomato (0.0003) and rice (0.0019). The highest value for an edible part was seen in komatsuna,Brassica rapa L. (0.016), which is comparable to the IAEA recommended value of iodine for common crops (0.02). There was a tendency for older leaves to show higher concentrations than younger ones. The values for fruit, grain and beans were significantly lower than those for their leaves. Thus translocation of iodine with photosynthate from leaves into these plant organs was very small. Iodine in soil was found to be volatilized from the soil-rice plant system into the atmosphere as an organic iodine. Volatilization markedly decreased in the late cultivation period of rice plants.     

Rate equation of the carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate

The kinetics of the carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate has been studied by a thermogravimetric analyzer (TGA). An empirical rate expression of zinc yield has been determined from the experimental data obtained. The dependencies of the rate of zinc yield on the operating variables was found to be less pronounced for the Li₂CO₃ catalyzed system than those for uncatalyzed system.     

The technological and economic management of the environmental variable in the pharmaceutical–chemical industry

Industrial risks increate with technological progress. The study of potential risks is routine in the pharmaceutical–chemical industry. Here, like in other industrial activities, a risk coefficient is introduced that varies within space time limits.A control system of environmental safety and health monitoring processes should be based on the data obtained from Hazard and Operability Studies (HAZOP).The space variable influences the chemical risk coefficient that applies to the whole the production cycle (including waste recycling). For the sake of prevention, many enterprises have adopted the integrated management system, which is now moving to an additional required feature: environment and health protection and safety assurance inside and outside the industrial area (in compliance with UNI, ISO 14000 and OHSAS 18001standards).Our goal is to examine the technological–scientific–environmental changes in the pharmaceutical–chemical sector in order to asses the new extent of chemical regarding management systems.This will entail a cultural change that will call for the necessary economic strategies for industries to implement the appropriate environmental–technological programs.     

Comparing the salting-out effects of alkali-metal nitrates on the water-isopropanol system

The salting-out effects of sodium, potassium, and cesium nitrates on the water-isopropanol system, which is homogeneous throughout its liquid-state temperature range, are compared at different temperatures. The alkali-metal nitrates, which undergo homoselective solvation in aqueous-organic solvents, exert a salting-out effect on aqueous isopropanol. As the crystallographic radius of the cation decreases in the order CsNO₃-KNO₃-NaNO₃, the monotectic critical tie line temperature for the salt-water-isopropanol system decreases (79.0, 47.2, and 6.1°C, respectively). In each ternary system, the salting-out effect on isopropanol strengthens with an increasing temperature, particularly in the system containing sodium nitrate. Among the salts examined, the strongest salting-out effect between 6.1 and 90.0°C is produced by sodium nitrate.     

Regularities governing the two-stage synthesis of cast Cr2O3/Al2O3 under conditions of the autowave synthesis

The study of the chemical, roentgen phase and structural properties of the products of combustion of system Cr₂O₃-Al-Fe₂O₃ was carried out. The analysis of the results shows the presence in the system of a set of solid solutions. The results of the study make it possible to establish the optimum regime of the heat treatment of the studied system for creating the new refractory material according to self-propagating high-temperature synthesis (SHS).     

Ring-closing olefin metathesis in the aqueous phase of amphiphilic conetworks consisting of fluorophilic and hydrophilic compartments

A Grubbs-Hoveyda-Type metathesis catalyst bearing a tris(perfluoroalkyl)silyl tag was immobilized in the fluorophilic phase of amphiphilic conetworks (APCNs). This catalytic system was applied to ring-closing metathesis (RCM) reactions in aqueous media. Different substrates were evaluated and with 10 mol% of catalyst at 60 °C good conversions were observed. Reuse of the catalytic system was possible, but resulted generally in lower conversions.     

Comprehensive two-dimensional liquid chromatography in the analysis of antioxidant phenolic compounds in wines and juices

A novel comprehensive two-dimensional liquid chromatographic (LC×LC) system was developed for the quantification of antioxidant phenolic compounds in wine and juice. The system allows parts of the sample that are well separated in the first column to pass directly to the detector after the first column, while the rest of the sample proceeds to the second column. The optimised LC×LC system employed a combination of two C18 columns, the latter column with an ion-pair reagent (tetrapentylammonium bromide). The relative standard deviations (RSD) for the retention times were better than 0.01% in the first dimension and on average 6.3% in the second. The RSD values of the peak volumes varied from 3% (protocatechuic acid) to 13% (caffeic acid, n = 3, 10 μg/ml).     

酶聚合体电流信号放大多通道电化学免疫传感体系及蛋白肿瘤标志物检测

本文构建了一种基于酶聚合体信号放大的多通道电化学免疫传感体系,并用于肝癌肿瘤标记物甲胎蛋白（AFP）的定量检测. 该传感体系由固定了抗AFP鼠单克隆抗体的多通道丝网印刷电极组成,可捕获肿瘤标记物抗原AFP,进而与抗AFP兔多抗特异性结合形成夹心免疫复合物,然后利用辣根过氧化物酶聚合体偶联的羊抗兔二抗（IgG-polyHRP）与三明治夹心免疫复合物结合,实现电流信号放大. 该体系结合多通道丝网印刷电极及自主研发的多通道电化学检测仪,可同时满足多通道电流信号的检测. 在最优化条件下,该传感体系检测AFP浓度的动态范围为64 pg·mL^-1 ~ 250 ng·mL^-1,最低检测下限为56 pg·mL^-1,具有检测灵敏度高、特异性强、操作简便以及仪器便携等优点.     

Effect of a Gas Discharge on the Ignition in the Hydrogen-Oxygen System

A kinetic model is constructed for ignition initiated by nonequilibrium gas-discharge plasma in the hydrogen-oxygen system. The model takes into account the effect of the electric field on the dissociation of molecules and on the buildup of active radicals, excited species, and charged species (electrons and positively and negatively charged ions). It is demonstrated by mathematical modeling that the induction period depends strongly on the reduced strength of the electric field (electron temperature). Four reduced kinetic networks are considered, and various components and reactions are shown to exert an effect on the nonthermal initiation of ignition in the H₂-O₂ system by low-temperature plasma.     

Implications of on-line FTIR detection in the separation of coal-derived products via HPLC with polar modifiers

Summary Fourier-transform infrared spectrometry (FTIR) was utilized as a detection system for high-performance liquid chromatography of polar compounds on a normal bonded-phase system. In addition to FTIR, UV (254 nm) and refractive index detection were employed in the separation of model compounds containing oxygen and nitrogen atoms in their molecules (phenols, alcohols, neutral and weakly basic nitrogen compounds). A polar amino-cyano (PAC) bonded-phase column was employed with a binary mobile phase (98:2 CDCl₃:CH₃CN). The separations and the information gained from each detector is discussed, including interactions between sample material and mobile phase. A polar fraction of a coal-derived product is also chromatographed under identical conditions. The results based on FTIR detection and chromatographic retention behavior suggest the exclusive presence of hindered and unhindered phenols.     

The viscosity of the methanol-<Emphasis Type="Italic">n</Emphasis>-decane system in the region of low <Emphasis Type="Italic">n</Emphasis>-decane concentrations

The kinematic viscosity and density of the methanol-n-decane system were measured at various temperatures at low n-decane concentrations (over the miscibility range). The theory of free volume with taking into account molecular association was used to calculate the dynamic viscosity of this system at 298.15 K. The results substantiated the presence of an anomaly in this system (positive Δlnη values).