Novel chain structures in group VI elements

Recent developments in high-pressure methods and advances in X-ray crystallography have led to a new level of understanding of phase diagrams and structures of materials under pressure. Recently discovered phenomena such as complex phases of alkali metals, incommensurate host-guest structures, and incommensurately modulated structures have rendered obsolete our conventional wisdom about the range of structures possible in the elements. Using new in situ diffraction techniques, we have resolved the long-standing problem of the phase-transition sequence of sulphur in its non-metallic state. We demonstrate that it is very different from that previously proposed, with only two phases stable between 1.5 GPa and 83 GPa (the pressure of metallization), and temperatures from 300 K to 1,100 K. The phases have a triangular chain and a squared chain structure. The same squared chain structure is found in the heavier group VI element selenium.     

Ribbons

Point clouds are usually represented either globally, as surfaces, or locally, as sets of points with small neighbourhoods. We propose an intermediate representation, called ribbons, which is obtained by partitioning a point cloud into one-dimensional strips. This representation is well suited to the placement of strokes in non-photorealistic rendering, and can be visualized efficiently using quad strips. Methods for performing hatching, cross-hatching, and silhouette renderings are presented. Ribbons also allow for the application of curve-based operations to the point cloud.     

Reassembled biosynthetic pathway for large-scale carbohydrate synthesis: alpha-Gal epitope producing "superbug"

A metabolic pathway engineered Escherichia coli strain (superbug) containing one plasmid harboring an artificial gene cluster encoding all the five enzymes in the biosynthetic pathway of Galalpha l,3Lac through galactose metabolism has been developed. The plasmid contains a lambda promoter, a c1857 repressor gene, an ampicillin resistance gene, and a T7 terminator. Each gene was preceded by a Shine - Dalgarno sequence for ribosome binding. In a reaction catalyzed by the recombinant E. coli strain, Galalpha 1,3Lac trisaccharide accumulated at concentrations of 14.2 mM (7.2 gL(-1)) in a reaction mixture containing galactose, glucose, lactose, and a catalytic amount of uridine 5'-diphosphoglucose. This work demonstrates that large-scale synthesis of complex oligosaccharides can be achieved economically and efficiently through a single, biosynthetic pathway engineered microorganism.     

Design and Implementation of the L+C Modeling Language

L-systems are parallel grammars that provide a theoretical foundation for a class of programs used in the simulation of plant development and procedural image synthesis. In particular, the formalism of L-systems guides the construction of declarative languages for specifying input to these programs. We outline key factors that have motivated the development of L-system-based languages in the past, and introduce a new language, L+C, that addresses the shortcomings of its predecessors. We also describe a simulation program, lpfg, which makes it possible to execute models specified in L+C. To this end, L+C programs are translated into C++, compiled into a DLL, and linked with lpfg at runtime. The use of this strategy simplifies the implementation of the modeling system.     

Properties of ultrafine-grained Mg-based composites modified by addition of silver and hydroxyapatite

In this study, hydroxyapatite and silver were added to Mg–1Zn–1Mn–0.3Zr alloy to fabricate ultrafine-grained metal matrix composites. Grain sizes of approximately 85?nm were recorded by atomic force microscopy for the Mg–1Zn–1Mn–0.3Zr–5 wt-% HA–1 wt-% Ag composite. The contact angles in water and simulated body fluid on the ultrafine-grained Mg–1Zn–1Mn–0.3Zr-based composites were determined. Following a hydrofluoric acid treatment, the surface wettability changed from hydrophilicity to hydrophobicity. The electrochemical test showed that the corrosion resistance of the fluoride-treated specimens was higher, when compared with the untreated samples. The Mg–1Zn–1Mn–0.3Zr–5 wt-% HA and Mg–1Zn–1Mn–0.3Zr–5?wt-% of HA–1 wt-% Ag composites modified with MgF₂ have a higher degree of biocompatibility, which makes them potential candidates for medical applications     

Sensitivity analysis of frame structures (virtual distortion method approach)

A novel approach to sensitivity analysis of frame structures based on the virtual distortion method (VDM) has been presented. The sensitivity analysis has been performed for elasto‐plastic material behaviour with respect to selected structural parameters e.g. cross‐sectional area, hardening/softening coefficient and yield stress. Advantages of applying the virtual distortion method to sensitivity analysis have been emphasised i.e. making use of the so‐called influence matrix, constant for the whole analysis and solving only local sets of equations corresponding to plastic locations. Theoretical background as well as the whole variety of examples has been presented. Copyright © 2001 John Wiley & Sons, Ltd.     

Steroid-Functionalized Imidazolium Salts with an Extended Spectrum of Antifungal and Antibacterial Activity

It is established that high rates of morbidity and mortality caused by fungal infections are related to the current limited number of antifungal drugs and the toxicity of these agents. Imidazolium salts as azole derivatives can be successfully used in the treatment of fungal infections in humans. Steroid-functionalized imidazolium salts were synthesized using a new, more efficient method. As a result, 20 salts were obtained with high yields, 12 of which were synthesized and characterized for the first time. They were derivatives of lithocholic acid and 3-oxo-23,24-dinorchol-4-ene-22-al and were fully characterized by ¹H and ¹³C nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and high resolution mass spectrometry (HRMS). Due to the excellent activity against bacteria and Candida albicans, new research was extended to include tests on five species of pathogenic fungi and molds: Aspergillus niger ATCC 16888, Aspergillus fumigatus ATCC 204305, Trichophyton mentagrophytes ATCC 9533, Cryptococcus neoformans ATCC 14116, and Microsporum canis ATCC 11621. The results showed that the new salts are almost universal antifungal agents and have a broad spectrum of activity against other human pathogens. To initially assess the safety of the synthesized salts, hemocompatibility with host cells and cytotoxicity were also examined. No toxicity was observed at the concentration at which the compounds were active against pathogens.     

UV stability of polymeric binder films used in waterborne facade paints

The UV-stability study of four polymeric binders for water-borne paints, based on acrylic, styrene-acrylic, vinyl acetate and vinyl acetate-butyl acrylate (co)polymers is described. To the best of our knowledge the UV stability of this set of binders relevant to decorative industry is systematically compared for the first time. Thin films obtained from the respective latexes were irradiated with UV light (λ ≥ 275 nm) and analysed using electrokinetic potential (ζ-potential), FTIR ATR spectroscopy, SEM microscopy and differential scanning calorimetry (DSC). The films obtained from different latexes displayed distinct changes in their surface composition and response to UV-irradiation. Among the studied compositions, the vinyl acetate-based ones seem to be the least prone to UV-degradation in the absence of other components typically present in paint formulations. The analytical techniques employed in this study are shown to be complementary and provide information on different regions of the surface layer, depending on their effective probing depth. Especially, a combination of FTIR and ζ-potential measurements is shown useful to clarify the nature of the carbonyl groups formed during photodegradation.