Untersuchungen über die Reduktion der Eisenoxide mit Kohlenstoff und nichtkonvertiertem Methan

Reduktion von Eisenoxiden mit Methan und Ruß. Verfahren im Methan-Gegenstrom mit Rückführung der Reduktionsgase, Verfahren im Gleichstrom von Methan und rückgeführten Reduktionsgasen und Verfahren mit verzweigten Gasströmen. Behandlung in Spalt-Ammoniak. Versuchsanlagen und technische Anlagen.     

The Stackelberg Minimum Spanning Tree Game

We consider a one-round two-player network pricing game, the Stackelberg Minimum Spanning Tree game or StackMST. The game is played on a graph (representing a network), whose edges are colored either red or blue, and where the red edges have a given fixed cost (representing the competitor??s prices). The first player chooses an assignment of prices to the blue edges, and the second player then buys the cheapest possible minimum spanning tree, using any combination of red and blue edges. The goal of the first player is to maximize the total price of purchased blue edges. This game is the minimum spanning tree analog of the well-studied Stackelberg shortest-path game. We analyze the complexity and approximability of the first player??s best strategy in StackMST. In particular, we prove that the problem is APX-hard even if there are only two different red costs, and give an approximation algorithm whose approximation ratio is at most min?{k,1+ln?b,1+ln?W}, where k is the number of distinct red costs, b is the number of blue edges, and W is the maximum ratio between red costs. We also give a natural integer linear programming formulation of the problem, and show that the integrality gap of the fractional relaxation asymptotically matches the approximation guarantee of our algorithm.     

Evaluation of the allergenicity of spore and mycelia extracts of Pisolithus tinctorius

The antigenic and allergenic chemical analysis of spore and mycelia extracts of Pisolithus tinctorius was carried out. The spores were collected from basidiocarps in plantations of Eucalyptus spp and the mycelia from culture in MNM medium. With basis on the fungus growth curve, the mycelia masses were obtained after 10, 20, 30, and 40 days of incubation, which correspond, respectively, to the beginning, middle and end of the log phase, and beginning of the decline phase. The mycelia masses, together with the spores, were submitted to the action of three extractors (Coca, Tris-HCl, and ammonium bicarbonate). The contents of carbohydrates and proteins were determined. The SDS-PAGE electrophoretical analysis revealed separate fractions in these extracts, besides common fractions, in function of cultivation time and extraction methods. The selected extracts for the allergic tests were the ones with the highest number of fractions. The prick-tests were conducted in 374 patients--rural workers, eucalyptus plantation workers, and college students. The positivity to the "prick test" with the antigenic extract of P. tinctorius was, respectively, 3.78%, 28.20% and 6.40%. Most prick-test positive patients (82.75%) also presented symptoms of respiratory allergy (asthma and rhinitis). There was no reactivity difference when the spore and mycelia extracts were employed. The analysis of the positive patients' sera revealed the presence of IgE specific to the P. tinctorius antigens. Since Pisolithus tinctorius is found as mycorrhiza of Eucalyptus spp, and this plant is used in reforestation in most countries, the importance of that fungus should be regarded as a possible cause of respiratory allergies, especially in occupationally exposed workers.     

New catalysts for poly(ethylene terephthalate)-bisphenol a polycarbonate reactive blending

The effects of various catalysts on the reactive blending of poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) was investigated. The various catalysts employed for PET syntheses, Ti(OBu)4, SmL₃, EuL₃, Ca + Sb, CeAc₃, Er(NO₃)₃·B₁₂C₄ and Tb (acac)₃·diPy (where L is o-formylphenolate; B₁₂C₄ is a crown ether, benzo-12-crown-4; acac is acetylacetonate; and diPy is 2,2′-dipyridyl) have shown a different catalytic activity toward exchange reactions. Solubility tests, in solvents able to separate unreacted PET and PC, and selective degradation of the PC segments, combined with ¹H NMR spectroscopy and size exclusion chromatography, made it possible to order the catalysts according to their catalytic activity: Ti(OBu)4 ? SmL₃ > EuL₃ > Ca + Sb > CeAc₃～Er(NO₃)·B₁₂C₄ > Tb (Acac)₃·diPy ≈ 0. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(ethylene isophthalate‐co‐ethylene terephthalate) copolyesters

Poly(ethylene isophthalate‐co‐ethylene terephthalate) (PEIPET) copolymers of various compositions and molecular weights were synthesized by melt polycondensation and characterized in terms of chemical structure and thermal and rheological properties. At room temperature, all copolymers were amorphous and thermally stable up to about 400°C. The main effect of copolymerization was a monotonic increase of glass transition temperature (T_g) as the content of ethylene terephthalate units increased. The Fox equation accurately describes the T_g–composition data. The presence of ethylene terephthalate units was found to influence rheological behavior in the melt, with the Newtonian viscosity increasing as the content of ethylene terephthalate units increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 186–193, 2004     

High Z bolometers for analysis of internal β and α activities

CdWO₄ bolometers were realized with the final purpose to study Double Beta Decay of¹¹⁶Cd. The test device we developed performs as a very efficient detector, with a preliminary resolution of aboout 5 keV FWHM. The detector background spectra are dominated at low energies by decay of¹¹³Cd: the calorimetric measurement of this process allows to detrmine the end point (318.8±1.4±5 keV) and with unprecedented precision the life time ((9,3±0.5±1)×10¹⁵ y). Following the same approach, we have analysed the internal contamination in²¹⁰Pb of three different types of lead used for shielding in low background experiments. Various lead bolometers were developed and operated, using common modern lead, special low activity modern lead and 2000 years old Roman lead. The presence of²¹⁰Pb was clearly observed through the decay of its daughter²¹⁰Po in the modern samples, while only a limit was set for the much purer Roman lead. The purifying effect of crystallization was clearly demontrated.as far as the part about CdWO₄ is concerned     

A valveless capillary mixing system using a novel approach for passive flow control

Using capillary-driven forces as a means to pump and actuate fluids is attractive for many applications including portable, lab-on-a-chip diagnostic systems. However, the lack of reliable and easy-to-integrate means of flow control remains a major challenge for implementing more complex bioassays using capillary microfluidics. This paper presents an easy-to-fabricate, valveless capillary system allowing for high-reliability flow control without using traditional capillary stop or trigger valves. Analytical calculations were used to deduce a design criterion for flow control in the valveless system. Furthermore, electrical analogy modeling was used to analyze and optimize the flow characteristics in the valveless system. Silicon-based test structures and capillary mixing systems were fabricated to check the design criterion and benchmark the electrical analogy model, respectively. Experimental results were in good agreement for the analytically derived flow control criterion. Experimental measurements of the liquid–vapor interface position with respect to time agreed well with the electrical analogy modeling results. The flow control scheme developed in the work provides designers with another means to realize complex fluid processing requirements without the need for traditional valve structures.     

Effects of different crosslinking conditions on the chemical–physical properties of a novel bio-inspired composite scaffold stabilised with 1,4-butanediol diglycidyl ether (BDDGE)

Serious cartilage lesions (Outerbridge III, IV) may be successfully treated with a three-layered gradient scaffold made by magnesium-doped hydroxyapatite and type I collagen, manufactured through a bio-inspired process and stabilised by a reactive bis-epoxy (1,4-butanediol diglycidyl ether, BDDGE). Each layer was analysed to elucidate the effects of crosslinking variables (concentration, temperature and pH). The chemical stabilisation led to an homogeneous and aligned collagenous matrix: the fibrous structures switched to a laminar foils-based arrangement and organic phases acquired an highly coordinated 3D-organization. These morphological features were strongly evident when crosslinking occurred in alkaline solution, with BDDGE concentration of at least 1 wt%. The optimised crosslinking conditions did not affect the apatite nano-crystals nucleated into self-assembling collagen fibres. The present work allowed to demonstrate that acting on BDDGE reaction parameters might be an useful tool to control the chemical–physical properties of bio-inspired scaffold suitable to heal wide osteochondral defects, even through arthroscopic procedure.     

Poly(1,4‐cyclohexylenedimethylene‐1, 4‐cyclohexanedicarboxylate): analysis of parameters affecting polymerization and cis–trans isomerization

Weatherable semicrystalline polyesters based on 1,4‐cyclohexanedimethanol, 1,4‐cyclohexanedicarboxylic acid (CHDA) or dimethyl 1,4‐cyclohexane dicarboxylate (DMCD) can be prepared under normal melt‐phase conditions, using titanium tetrabutoxide as catalyst. The effect of monomer ratio, reaction temperature and catalyst loading on the final polymer properties was studied. Under the proper polymerization conditions, poly(1,4‐cyclohexylenedimethylene‐1,4‐cyclohexanedicarboxylate) polymers with high molecular weight can be obtained. During polymerization, isomerization can occur towards the thermodynamically stable cis‐trans ratio of 34–66 mol%. Carboxylic acid end groups can catalyze the isomerization and therefore the polymerization is more critical starting from CHDA rather than DMCD. Moreover, temperature control becomes a key factor to avoid or to limit isomerization. The study of the isomerization of the different monomers permitted a better understanding of the isomerization and therefore of the polymerization process. Copyright © 2011 Society of Chemical Industry