流动注射-催化光度法测定不稳定反应中钼

基于pH2．9的乙酸介质中，碘化钾和邻菲口罗啉溶液存在下，钼（Ⅵ）对过氧化氢和4，4’-四甲基二氨基二苯甲烷之间的氧化还原反应有显著的催化作用，生成的蓝色不稳定产物在603nm波长处有最大吸收，利用流动注射分析技术能精确地控制反应时间的特点，建立了流动注射-催化光度法测定不稳定反应中痕量钼（Ⅵ）的方法。在36次／h的分析速度下检出限为9．6×10μg·L^-1，线性范围在0．5mg·L^-1内。应用该方法测定了废水样中钼（Ⅵ），加标回收率在95．6％～103.2％之间.

基于不稳定反应的流动注射催化光度法测定铁

Trace amounts of iron were determined by flow injection catalytic kinetic spectrophotometry,based on the catalytic effects of iron on the redox reaction between potassium bromate and 4,4′-tetramethyldiaminodiphenylmethane in the presence of potassium iodide in HAc-NaAc buffer solution.The measurements were conducted at 602nm of an unstable blue product of the reaction.Flow injection technique was utilized to precisely control the timing of merging and reaction of the reagents and samples.A stopped-flow approach was used to improve the sensitivity of the system.A detection limit of 2.6×10-9g/mL was achieved at a sampling frequency of 45/h.Calibration graphs were linear for ranges of 0～0.4mg/L for Fe(III).The proposed method was validated by the analysis of a national reference material and applied to the analyses of several water samples,with recoveries of 95.9%to 97.3%.

Effect of substrate concentration on stability of anammox biofilm reactors

Ammonium and nitrite are two substrates of anammox bacteria, but they are also inhibitors under high concentrations. The performance of two anaerobic ammonium-oxidizing (anammox) upflow biofilm (UBF) reactors was investigated. The results show that anammox UBFs become unstable under nitrogen loading rate (NLR) applied higher than 1.0 g/(L·d). The consumptions of acidity in the anammox reaction lead to the increase of pH, which is as high as 8.70-9.05. Free nitrous acid concentration is accompanied to be lower than the affinity constant of anammox bacteria, and then starvation effect appears. Moreover, free ammonia concentration increases to 57-178 mg/L, resulting in inhibitory effect on the anammox bacteria. Both negative effects contribute to the instability of the anammox bioreactors.

Modeling and optimization of the cyclic steady state operation of adsorptive reactors

Adsorptive reactors(AR),in which an adsorptive functionality is incorporated into the catalytic reactors,offer enhanced performance over their conventional counterparts due to the effective manipulation of concentration and temperature profiles.The operation of these attractive reactors is,however,inherently unsteady state,complicating the design and operation of such sorption-enhanced processes.In order to capture,comprehend and capitalize upon the rich dynamic texture of adsorptive reactors,it is necessary to employ cyclic steady state algorithms describing the entire reaction-adsorption/desorption cycle.The stability of this cyclic steady state is of great importance for the design and operation of adsorptive reactors.In this paper,the cyclic steady state of previously proposed novel adsorptive reactor designs has been calculated and then optimized to give maximum space–time yields.The results obtained revealed unambiguously that an improvement potential of up to multifold level could be attained under the optimized cyclic steady state conditions.This additional improvement resulted from the reduction of the regeneration time well below the reaction-adsorption time,which means,in turn,more space–time yield.

Different Carbon Fractions in Soils and Their Relationship with Trace Elements Content

Luvisols, Stagnogleys and Cambisols, although less fertile, are used intensively for mixed farming, grazing and as forestland. Therefore we aimed our study at determination of total organic carbon （TOC） content, humic substances （HS） content, humic acids （HA） content, fulvic acids （FA）, hot water extractable carbon （Chw） content and content total and labile trace elements content. Humic substances quality was assessed by HA/FA ratio and by coloured indexes measured in ultraviolet and visible UV-VIS spectral range. The total and labile contents of Zn, Cd, Cu, Co, Pb, Mo and Se were determined by flame or electro-thermal atomic absorption spectrometry after extraction of the soil samples in the aqua regia （total content） and in the solution of 0.01 M CaCI2. Total and labile trace elements content was correlated with determined carbon fractions and soil reaction. Results showed that studied soils content low amount of TOC and had low quality of humic substances. HA/FA ratio was less than 1 and colour indexes were higher than 4. All determined carbon fractions correlated with labile form of Zn and Cd. Correlation between soil reaction and total zinc content was found. Significant effect of humic substances content on to water-soluble forms of heavy metals was detected.

Effect of Microwave Radiation on Dielectric Behavior of Two Vegetable Oils

The effect of microwave （MW） heating on the dielectric properties and oxidation processes of virgin olive oil and refined sunflower oil were determined by dielectric and UV- spectroscopy. Samples were heated in the microwave oven （850 W, 2.450 MHz） for 0 to 14 minutes. The results show degradation of dielectric characteristics, conductivity and oxidative stability of investigated oils, increasing with the exposure time. UV spectrum shows only one defined peak at 206 nm for olive oil confirming the dominant presence of monounsaturated fats and four peaks for sunflower oil （203 nm, 230 nm, 269 nm and 278 nm） dependent on polyunsaturated acid fats contents. Increasing of absorbance at all peak wave lengths indicates production of lipid oxidation, due to formation of conjugated monoenes and dienes and in small amounts due to trienes and secondary products like ketoaldehydes. Dielectric constant for olive oil is stable and almost unchangeable with MW radiation while sunflower oil＇s c＇ oscillates around the origin value in greater rate. Dielectric loss e＂ decreases with increasing time of MW radiation and its maximum shifts towards higher frequencies for sunflower oil indicating shortening of the relaxation times, while for olive oil it is unchanged. Cole-Cole analysis show the presence of only one relaxation process in the oils. Conductivity of oils is increasing in similar way with increasing frequency following the Jonscher＇s power law and is not changed with MW exposure time. Olive oil has conductivity higher for four orders of magnitude than sunflower oil, which is connected to the high content of monounsaturated fats. The differences between sunflower and olive oil characteristics are discussed.

Alternaria toxin-induced resistance against rose aphids and olfactory response of aphids to toxin-induced volatiles of rose plants

The search for active toxins for managing weeds or plant diseases is believed to be a promising avenue of investigation. However, the effects of Alternaria toxins on insects have just begun to be investigated. Bioactivities of toxins from four strains of Altemaria alternata on Rosa chinensis and rose aphid Macrosiphum rosivorum were tested in the present study. At a concentration of 50.0 pg/ml, the crude extract （toxin） of strain 7484 was found not to be harmful to rose plants with excised leaf-puncture method （P≥0.079）, and rose plants showed enhanced resistance to rose aphids when this Altemaria toxin was sprayed on the plants （P≤0.001）. However, this toxin caused no detrimental effects on aphids in insecticidal bioassay at a concentration of 10.0 to 160.0 μg/ml （P≥0.096）. Therefore, the Alternaria toxin had significantly induced the resistance of rose plants against rose aphids, demonstrating that the resistance mechanism triggered by the Altemaria toxin in the rose plant may also be used by the plant to defend itself against insects. Further bioassays aimed to discover the olfactory responses of aphids to the toxin-induced volatiles of host plants. The aphids were significantly more attracted to both volatiles emitted and collected from control rose plants than to both volatiles emitted and collected from the toxin-treated rose plants （P≤0.014）. This result showed that the toxin-induced resistance related to the volatile changes of host plants.

Turing instability in a diffusive SIS epidemiological model

Modeling and simulation of infectious diseases help to predict the likely outcome of an epidemic. In this paper, a spatial susceptible-infective-susceptible （SIS） type of epidemiological disease model with self- and cross-diffusion are investigated. We study the effect of diffusion on the stability of the endemic equilibrium with disease-induced mortality and nonlinear incidence rate, In the absence of diffusion the stationary solution stays stable but becomes unstable with respect to diffusion and that Turing instability takes place. We show that a standard （self-diffusion） system may be either stable or unstable, cross-diffusion response can stabilize an unstable standard system or decrease a ＂ihlring space （the space which the emergence of spatial patterns is holding） compared to the ~lhlring space with self-diffusion, i.e. the cross-diffusion response is an important factor that should not be ignored when pattern emerges. Numerical simulations are provided to illustrate and extend the theoretical results.

Dynamics and pattern formation in a modified Leslie-Gower model with Allee effect and Bazykin functional response

In this paper, we study the dynamics of a diffusive modified Leslie-Cower model with the multiplicative Allee effect and Ba^zykin functional response. We give detailed study on the stability of equilibria. Non-existence of non-constant positive steady state solutions are shown to identify the rage of parameters of spatial pattern formation. We also give the conditions of Turing instability and perform a series of numerical simulations and find that the model exhibits complex patterns.