Thermal and X-ray analysis studies of UO3 gel microspheres

The thermal decomposition behaviour of UO₃ gel microspheres has been studied. Thermal analysis involved DTA, TG, DTG and X-ray examination. The effects of washing the UO₃ gel microspheres with hot water and with ammonia solution were investigated, as were the effects of soaking the microspheres in ammonia solution before or after washing on the crystallite size. The results indicate that the thermal decomposition of UO₃ gel microspheres includes five steps: the first two for dehydration, the third for ammonia removal, the fourth for ammonia oxidation and the last step for UO₃ recrystallization.

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Zusammenfassung Die thermische Zersetzung von UO₃-Gelmikrokugeln wurde mittels DTA, TG, DTG und Röntgendiffraktometrie untersucht. Die Auswirkungen des Waschens der UO₃-Gelmikrokugeln mit heißem Wasser und mit Ammoniaklösungen sowie der Einfluß des Wässerns der Mikrokugeln vor und nach dem Waschen mit Ammoniaklösungen auf die Kristallitgröße wurden untersucht. Die thermische Zersetzung der UO₃-Gelmikrokugeln verläuft in 5 Schritten: in den ersten beiden erfolgt die Dehydratisierung, im dritten die Abgabe und im vierten die Oxydation von Ammoniak und schließlich im letzten Schritt die Rekristallisation von UO₃.

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Effect of solvent on absorption and fluorescence spectra of a typical fluorinated azo dye for its acidic and basic structures

The effect of 15 polar solvents on absorption and fluorescence energies of a typical fluorinated azo dye, 4-(2,3,5,6-tetrafluoro-pyridin-4-yl azo)-phenol, was reported for its acidic, MH, and basic, M, structures.For MH, the absorption energy is described on the basis of multi-linear equation with Taft's π* (solvent polarity) and β (hydrogen bond acceptor) parameters while the fluorescence energy varies rectilinearly with free energy of transferring the proton to the surrounding solvent, ΔG_t°.For M, the hydrogen bonding donor ability of protic solvent, α, is a predominant factor which affects the absorption energy while in aprotic solvents, the absorption energy correlates linearly with Kirkwood function. As the ability of the solvent for hydrogen bonding increases, the absorption band width will increase in parallel with the transition energy.     

REBUILDING THE EASTERN BALTIC COD STOCK UNDER ENVIRONMENTAL CHANGE (PART II): TAKING INTO ACCOUNT THE COSTS OF A MARINE PROTECTED AREA

Abstract This study adds a cost analysis of the Eastern Baltic cod fishery to the existing model presented in Röckmann et al. [2007a] . As cost data on this international fishery do not exist, data from Denmark are extrapolated to the whole international fishery. Additionally, unit and total variable costs are simulated, and the sensitivity to a set of different cost–stock and cost–output elasticities is tested. The study supports preliminary conclusions that a temporary marine reserve policy, which focuses on protecting the Eastern Baltic cod spawning stock in the International Council for the Exploration of the Sea (ICES) subdivision 25, is a valuable fisheries management tool to (i) rebuild the overexploited Eastern Baltic cod stock and (ii) increase operating profits. The negative effects of climate change can be postponed for at least 20 years—depending on the assumed rate of future climate change. Including costs in the economic analysis does not change the ranking of management policies as proposed in the previous study where costs were neglected.     

Steady-state fluorescence and photo-isomerization study of 1-methyl-4′-(p-N,N dimethyl-amino styryl) pyridinium iodide

Photochemical and thermal trans/cis isomerization reactions are reported for 1-methyl-4′-(p-N,N dimethyl-amino styryl) pyridinium iodide, Cy, which is synthesized in the trans configuration. In a basic solution the trans form, Cy_tr, cannot isomerise directly to the cis form. Its protonated form, Cy_trH⁺, is active and reacts photochemically from trans to cis isomer, Cy_cH⁺. The quantum yields Φ_tc and Φ_ct are determined in water. Deprotonation process of Cy_cH⁺ yields the cis isomer, Cy_c, which can thermally revert to the stable trans form. The rate constant and the activated parameters of the thermal reaction are also determined. Due to irreversibility of the thermal reaction , a complete molecular reaction cycle is performed in one direction. To get more information on the spectral properties of protonated form, its absorption and fluorescence spectra were investigated in sixteen neat polar protic and aprotic solvents. Absorption energy correlates linearly with hydrogen bond acceptor ability of the solvent. Another linear correlation was found between fluorescence energy of CyH⁺ and free energy for transferring the proton to the surrounding solvent, ΔG_t^o.     

Electrochemical immunoassay for the prostate specific antigen using ceria mesoporous nanospheres

We report on a sensitive electrochemical immunoassay for the prostate specific antigen (PSA). An immunoelectrode was fabricated by coating a glassy carbon electrode with multiwalled carbon nanotubes, poly(dimethyldiallylammonium chloride), CeO₂ and PSA antibody (in this order) using the layer-by-layer method. The immunosensor is then placed in a sample solution containing PSA and o-phenylenediamine (OPD). It is found that the CeO₂ nanoparticles facilitate the electrochemical oxidation of OPD, and this produces a signal for electrochemical detection of PSA that depends on the concentration of PSA. There is a linear relationship between the decrease in current and the concentration of PSA in the 0.01 to 1,000 pg mL^?1 concentration range, and the detection limit is 4 fg mL^?1. The assay was successfully applied to the detection of PSA in serum samples. This new differential pulse voltammetric immunoassay is sensitive and acceptably precise, and the fabrication of the electrode is well reproducible. Figure

A novel electrochemical immunoassay for prostate specific antigen (PSA) was developed. Ceria (CeO₂) mesoporous nanospheres facilitated the electrochemical oxidation of o-phenylenediamine (OPD). The developed immunoassay has high sensitivity and can be successfully applied for the detection of PSA in serum samples     

REBUILDING THE EASTERN BALTIC COD STOCK UNDER ENVIRONMENTAL CHANGE–A PRELIMINARY APPROACH USING STOCK,ENVIRONMENTAL, AND MANAGEMENT CONSTRAINTS

ABSTRACT. . The population dynamics of the Eastern Baltic cod (Gadus morhua callarias L.), unlike many other stocks, shows a strong dependency on environmental conditions. To test the implications of different management policies on the stock and the fishery in a system of global environmental change, we apply a spatially disaggregated, discrete time, age‐structured model of the Eastern Baltic cod stock in 50 year simulation analyses. The simulation provides an analysis of stock, yield, and revenue development under various management policies and environmental scenarios. The policy analysis, focusing on different regulations of fishing mortality, is embedded into three environmental scenarios, assuming low, medium, or high climate and environmental change. The environmental assumptions are based on simulation results from a coupled atmosphere‐ocean regional climate model, which project salinity in the Baltic Sea to decrease by 7–47% in the period 2071–2100 relative to the reference period 1961 1990. Our simulation results show that a significant reduction in fishing mortality is necessary for achieving high long‐term economic yields. Moreover, under the environmental scenarios presented, a stock collapse cannot be prevented. It can, however, be postponed by the establishment of a marine reserve in ICES subdivision 25.     

Some topological dynamics properties of discrete-time control systems

This paper is concerned with the study of certain stabilityproperties of discrete-time systems by means of topologicalmethods. It turns out that suitably defined sets guarantee thestability of the reachable sets in the vicinity of compact sets.Furthermore, special properties about affine control systemsare given.