Photochromic properties of polyimide and polysiloxane azopolymers

BACKROUND: One of the most important properties of the azobenzene chromophores is the photochemical trans–cis isomerization induced by UV or visible light. In azopolymers, the photoisomerization induces conformational changes in the polymer chains, which in turn lead to macroscopic variations in the chemical and physical properties of the surroundings and media. RESULTS: This work reports the photochromic behaviour and surface structuring capacity of azopolymers having rigid polyimide and flexible polysiloxane structures, respectively. These polymers have good thermostabilities, with the degradation process starting above 315 °C. The glass transition temperature of the azopolyimide is 228 °C, while that of the azopolysiloxane modified with thymine is 34 °C. CONCLUSION: The experiments show that the azobenzene groups can isomerize even in the case of the rigid polyimide, but the maximum degree of conversion to the cis isomer is less than in the case of the flexible polysiloxane. This behaviour is reversed in solution, probably due to both the thymine and azo group interactions and for conformational reasons. The azopolymers show a good surface structuring capacity. The polysiloxane is more sensitive in the case of low irradiation energy and irradiation time. By increasing the irradiation time for both polymers, the modulation depth increases and has comparable values. Copyright © 2008 Society of Chemical Industry     

Physico-chemical and bioactive properties of different floral origin honeys from Romania

In this study, we investigated and compared the physico-chemical properties (moisture, colour, ash, and sugars content) as well as total phenols, total flavonoids and antioxidant activity of several honey samples (24) collected from different regions of Romania. The physico-chemical values were in the range of approved limits (conforming to EU legislation); excepting the monosaccharide values for one sample (T2). For this sample, the other values were within legislation limits. The results obtained showed that the most valuable honey is the honeydew one. Correlation between RSA and total phenols and total flavonoids, respectively, was determined, and a positive correlation was found. This study demonstrates remarkable variation in antioxidant properties and content of total phenols in honey, depending on its botanic or geographic source.     

A Decentralized Grid Market Infrastructure for Service Oriented Grids

Service Oriented Computing has a deep impact on how IT infrastructures are conceived both in academia (e-science) and in industry (Service Oriented Architecture and commercial Web Services). Increasingly, economic models are being considered as suitable coordination mechanism for the management of service allocations to clients. However, few complete infrastructures have demonstrated the enabling of economics-based Service Oriented Grids (SOGs). The authors propose a complete infrastructure for economics-based SOGs and demonstrate its application in a prototype. They conduct experiments showing that practical agent-based automatic and fair trading of services at stable prices can be achieved using the proposed infrastructure.     

Efficient address space generation for an OPC UA server

The new OPC Unified Architecture has been introduced as a replacement for the existing COM‐based specifications. The article describes a generalized algorithm for the automatic generation of the address space structure for an UA server. First, we present the general startup procedure of an OPC UA server, focusing on the address space generation step. Afterwards we introduce specialized algorithms for the generation of the type nodes, of object, variable, method and view nodes. Finally the additional references are added to the fully meshed address space. The basic ideas of the algorithms are: the splitting of the nodes into groups and the sequential addition of the groups to the address space, and the naming of a main reference for every target node. The algorithms have been applied for an aggregating UA server which models the devices of an assembly line. The main advantages are: shorter development time, easier maintenance and the possibility to add nodes to the address space in both online and offline mode. Copyright © 2011 John Wiley & Sons, Ltd.     

Base oils of high aromatic,long branched aliphatic pyromellitic esters

The present paper deals with the synthesis of some tetraesters with a mixed structure of pyromellitic dianhydride, and with their characterisation as potential base oils. These esters are made on the basis of a long branched aliphatic alcohol, such as isotridecanol, and an alcohol with aromatic content, such as 2‐phenoxy‐ethanol. The variation of the principal properties as a function of both the length of the aliphatic chain introduced by the aliphatic alcohol, and the aromatic content introduced by the aryl‐alkyl alcohol has been assessed and the potential for viable products with a wide range of viscosity values has been examined. The enhanced aryl content is shown to induce superior thermal behaviour. These products present good test results and, thereby, demonstrate their versatility.     

Synthesis of libraries of 16beta-aminopropyl estradiol derivatives for targeting two key steroidogenic enzymes

Two libraries, each consisting of 48 16beta-aminopropyl estradiol derivatives, phenols and sulfamates, respectively, were synthesized by solid-phase parallel chemistry through a seven-step reaction sequence. Following the attachment of a C18-steroid sulfamate precursor on a trityl chloride resin, diversity elements were first introduced on the 16beta-aminopropyl chain of the steroid by acylation reactions with eight Fmoc-amino acids. After deprotection, the free amine function of the resulting compounds was reacted with six carboxylic acids for the introduction of a second diversity level. The two variants employed for the cleavage of compounds from the solid support, acidic and nucleophilic, allowed the corresponding libraries of sulfamate and phenol derivatives in yields of 8-50 % and 13-58 % to be obtained with an average HPLC purity of 94 % and 91 %, respectively. Potent steroid sulfatase inhibitors and interesting SAR results were generated from the screening of the sulfamate library. Furthermore, moderate inhibitors of type 1 17beta-HSD resulted from the partial screening of phenol library. Thus, these two categories of compounds were synthesized to rapidly identify potential inhibitors of steroid biosynthesis for the hormonal therapy of estrogen-dependent diseases, and also to demonstrate the versatility and efficiency of the recently developed sulfamate linker.     

Aromatic diazenes containing azulen-1-yl moieties Part 2: The synthesis,characterization, electronic spectra and basicity of novel,bis aromatic diazenes containing two azulen-1-yl moieties

Bis aromatic diazenes which possess either two identical or two different azulene-1-yl groups substituted at either 1,3 or 1,4-positions in the bridging phenylene moiety were synthesized in good yield via diazotization of the 3- or 4-azulen-1-ylazo-phenylamines followed by coupling with azulene in a buffered medium. The electronic spectra of the synthesized compounds were analyzed by comparison with those of previously published compounds. The isosbestic points obtained by protonation of the compounds enabled their pK_a values to be determined.     

Micro-structured nuclear fuel and novel nuclear reactor concepts for advanced power production

Many applications (e.g. terrestrial and space electric power production, naval, underwater and railroad propulsion and auxiliary power for isolated regions) require a compact-high-power electricity source. The development of such a reactor structure necessitates a deeper understanding of fission energy transport and materials behavior in radiation dominated structures. One solution to reduce the greenhouse-gas emissions and delay the catastrophic events' occurrences may be the development of massive nuclear power. The actual basic conceptions in nuclear reactors are at the base of the bottleneck in enhancements. The current nuclear reactors look like high security prisons applied to fission products. The micro-bead heterogeneous fuel mesh gives the fission products the possibility to acquire stable conditions outside the hot zones without spilling, in exchange for advantages – possibility of enhancing the nuclear technology for power production. There is a possibility to accommodate the materials and structures with the phenomenon of interest, the high temperature fission products free fuel with near perfect burning. This feature is important to the future of nuclear power development in order to avoid the nuclear fuel peak, and high price increase due to the immobilization of the fuel in the waste fuel nuclear reactor pools.