Spectroscopic and computational investigation of the ground and low excited states of some symmetrical heterocyclic disulfides

The electronic absorption and emission spectra of some symmetrical heterocyclic disulfides are investigated. The reversible disulfide — thione transformation in water is discussed in view of the complex equilibrium processes present. UV irradiation and pH influence on the above transformation is also studied. The emission properties at room and low temperature are related to the computed molecular geometries of the ground and low excited states of the compounds.     

A multicriteria facility location model for municipal solid waste management in North Greece

Up to 2002, Hellenic Solid Waste Management (SWM) policy specified that each of the country’s 54 prefectural governments plan its own SWM system. After 2002, this authority was shifted to the country’s 13 regions entirely. In this paper, we compare and contrast regional and prefectural SWM planning in Central Macedonia. To design the prefectural plan, we assume that each prefecture must be self-sufficient, and we locate waste facilities in each prefecture. In contrast, in the regional plan, we assume cooperation between prefectures and locate waste facilities to serve the entire region. We present a new multicriteria mixed-integer linear programming model to solve the location–allocation problem for municipal SWM at the regional level. We apply the lexicographic minimax approach to obtain a “fair” nondominated solution, a solution with all normalized objectives as equal to one another as possible. A solution to the model consists of locations and technologies for transfer stations, material recovery facilities, incinerators and sanitary landfills, as well as the waste flow between these locations.     

Secure Polar Coding for the Primitive Relay Wiretap Channel

With the emergence of wireless networks, cooperation for secrecy is recognized as an attractive way to establish secure communications. Departing from cryptographic techniques, secrecy can be provided by exploiting the wireless channel characteristics; that is, some error-correcting codes besides reliability have been shown to achieve information-theoretic security. In this paper, we propose a polar-coding-based technique for the primitive relay wiretap channel and show that this technique is suitable to provide information-theoretic security. Specifically, we integrate at the relay an additional functionality, which allows it to smartly decide whether it will cooperate or not based on the decoding detector result. In the case of cooperation, the relay operates in a decode-and-forward mode and assists the communication by transmitting a complementary message to the destination in order to correctly decode the initial source’s message. Otherwise, the communication is completed with direct transmission from source to the destination. Finally, we first prove that the proposed encoding scheme achieves weak secrecy, then, in order to overcome the obstacle of misaligned bits, we implement a double-chaining construction, which achieves strong secrecy.     

Thione-disulfide interchange of some heterocyclic tautomeric thiones and their symmetrical disulfides

Summary The UV/Vis spectroscopic properties of some symmetrical disulfides derived from potentially tautomeric thiones are investigated. Reversed thione-disulfide transformation is observed, and the influence of several factors including the nature of solvent, concentration, and UV irradiation, is studied. Possible implication of the tautomeric thiol form and the importance of this thione-disulfide redox system in biological aspects is suggested. A general scheme including monomer-dimer equilibrium, thione-thiol tautomeric equilibrium, and reversible thiol-disulfide redox behaviour is proposed in order to explain the factors affecting the overall thione-disulfide transformation.

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Thion-Disulfid-Umwandlung einiger heterocyclischer tautomerer Thione und ihrer symmetrischen Disulfide

Zusammenfassung Die UV/Vis-spektroskopischen Eigenschaften einiger symmetrischer Disulfide, die als Derivate von potentiell tautomeren Thionen auftreten, wurden untersucht. Es wurde eine reversible Thion-Disulfid-Transformation beobachtet. Der Einfluß einiger Faktoren wie Natur des Lösungsmittels, Konzentration und UV-Bestrahlung wurden erforscht. Die Bedeutung des untersuchten Redoxsystems in biologischer Hinsicht wird diskutiert. Um die Auswirkung der einzelnen Faktoren auf die Umsetzung zu erklären, wird ein allgemeines Schema vorgeschlagen (Monomer-Dimer-Gleichgewicht, Thion-Thiol-Gleichgewicht, reversibles Thiol-Disulfid-Redoxsystem).

     

Formal translation monoid and algebra congruences in a monoidal category

In a monoidal category we characterize algebra congruences using the free approximation of their translation monoid. We then construct explicitely the congruence generated by a relation and cogenerated by an equivalence.     

Synthesis and comparative study of biodegradable poly(alkylene sebacate)s

Novel biodegradable polyesters, such as poly(ethylene sebacate) (PESeb), poly(propylene sebacate) (PPSeb), and poly(butylene sebacate) (PBSeb), were synthesized and studied with respect to melting behavior, crystallization kinetics, and enzymatic hydrolysis. PESeb and PPSeb showed multiple melting behavior. Wide angle X‐ray diffractometry measurements at various temperatures, standard, step‐scan, and high‐rate differential scanning calorimetry methods were applied to elucidate the appearance of multiple endotherms in heating scans, which was interpreted in the context of partial melting‐recrystallization and final melting. PBSeb did not show any multiple melting behavior but only a weak tendency for recrystallization on heating. The melting temperatures of PESeb, PPSeb, and PBSeb were measured equal to 78, 57, and 71 °C, respectively. The equilibrium melting points were estimated to be T_m° = 90.2, 69.9, and 77.4 °C for PESeb, PPSeb, and PBSeb, while the corresponding enthalpy of fusion values were found to be ΔH_f = 170 ± 10, 140 ± 10, and 155 ± 10 J/g, respectively. The polyesters showed fast crystallization rates under both isothermal and nonisothermal conditions. Crystallization kinetics was thoroughly investigated using macrokinetic models and isoconversional analysis. Enzymatic hydrolysis rate in the presence of lipases Rhizopus delemar and Pseudomonas cepacia was found to be fast for PPSeb, whereas PESeb and PBSeb showed slow rates and comparable with those of PCL. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 672–686, 2010