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Planar or nonplanar: What is the structure of urea in aqueous solution?

A combined quantum chemical statistical mechanical method has been used to study the solvation of urea in water, with emphasis on the structure of urea. The model system consists of three parts: a Hartree-Fock quantum chemical core, 99 water molecules described with a polarizable force-field, and a dielectric continuum. A free-energy profile along the transition of urea from planar to a nonplanar

The effect of UV-B and UV-C radiation on hibiscus leaves determined by ultraweak luminescence and fluorecence induction

The effects of UV-C (254 nm) and UV-B (280-320 nm) on chlorophyll fluorescence induction and ultraweak luminescence (UL) in detached leaves of Hibiscus rosa-sinensis L. were investigated. UL from leaves exposed to UV-B and UV-C radiation reached a maximum 72 h after irradiation. In both cases most of the light was of a wavelength over 600 nm. An increase in the percentage of long wavelength light

Ion-exchange chromatographic purification and quantitative analysis of Trichoderma reesei cellulases cellobiohydrolase I, II and endoglucanase II by fast protein liquid chromatography

Trichoderma cellulases appear in several isoforms which makes their purification and analysis difficult. We used fast protein liquid chromatography (FPLC) to purify three major cellulases and to quantitate these enzymes in reconstituted mixtures during cellulose hydrolysis studies (in lack of specific substrates and because of the synergism between the enzymes such analysis is very difficult, if a

Purification and characterisation of a water-soluble ferrochelatase from Bacillus subtilis

Bacillus subtilis ferrochelatase is encoded by the hemH gene of the hemEHY gene cluster and catalyses the incorporation of Fe2+ into protoporphyrin IX. B. subtilis ferrochelatase produced in Escherichia coli was purified. It was found to be a monomeric, water-soluble enzyme of molecular mass 35 kDa which in addition to Fe2+ can incorporate Zn2+ and Cu2+ into protoporphyrin IX. Chemical modificatio

Canavanine content of sword beans (Canavalia gladiata) – analysis and effect of processing

The amino acid canavanine is a potentially toxic constituent of leguminous seeds. The aim of the present study was to determine the ability of different processing methods to reduce canavanine in sword beans (Canavalia gladiata). For this purpose a method for the detection and quantification of canavanine was developed using reversed-phase high-performance liquid chromatography of the dabsylated d

Quantum mechanical wavepacket transport in quantum cascade laser structures

We present a viewpoint of the transport process in quantum cascade laser structures in which spatial transport of charge through the structure is a property of coherent quantum mechanical wave functions. In contrast, scattering processes redistribute particles in energy and momentum but do not directly cause spatial motion of charge.

Influence of urban geometry on outdoor thermal comfort in a hot dry climate: A study in Fez, Morocco

There are few studies on the microclimate and human comfort of urban areas in hot dry climates. This study investigates the influence of urban geometry on outdoor thermal comfort by comparing an extremely deep and a shallow street canyon in Fez, Morocco. Continuous measurements during the hot summer and cool winter seasons show that, by day, the deep canyon was considerably cooler than the shallow