Optimizing the DMFC operating conditions using a response surface method

The power density of a Direct Methanol Fuel Cell (DMFC) as a function of temperature, methanol concentration, air flow rate, methanol flow rate and air relative humidity was studied using a Response Surface Methodology (RSM). For a DMFC equipped with a membrane of Nafion 112, it was observed that only the temperature, methanol concentration and air flow rate were relevant factors or operating variables. A new design of experiments was done for a narrower range of these variables and the operating values that optimise the power density were obtained using the software JMP 7.0 (SAS). The predicted power density values were in agreement with the experimental results obtained for the optimized operating conditions. Then, the RSM was applied to membranes with different thicknesses, Nafion 112, Nafion 1135 and Nafion 117, and as a function of the temperature and methanol concentration. The DMFC was characterized for the open circuit voltage (OCV), methanol crossover at the OC, power density and global efficiency. The membrane showing the best compromise between power density and efficiency was Nafion 117.     

On the Existence of the Trimer of Gallium Trichloride in the Gaseous Phase

The dependence of the gallium trichloride saturated and unsaturated vapor pressures on temperature was studied by the static method using a quartz membrane zero‐manometer and taking into account the volume of its working chamber and substance mass. Conclusions about the presence of a distinguishable amount of trimeric molecules along with dimeric and momomeric molecules in the vapor were drawn on the basis of the obtained data. The following rough thermodynamic characteristics of a gaseous trimer of gallium trichloride were calculated: Δ_fH° (Ga₃Cl₉, gas, 298 K) = –1466 kJ · mol^–1. S°(Ga₃Cl₉, gas, 298 K) = 654 J · mol^–1 · K^–1. These data were used to elucidate the composition of the gaseous phase at a total pressure of 1 atm in the temperature range of 400–750 K. The suggested existence of trimeric molecules was not contradicted by vibrational spectroscopic analysis of gallium trichloride saturated vapor.     

New method of synthesizing pyridyl- and quinolylcarbonylarenecarboxylic acids

An original method has been developed for the synthesis of a number of pyridyl- and quinolylcarbonylarenecarboxylic acids by condensing anhydrides of aromatic dicarboxylic acids with picolinic and quinaldic acids. The characteristics of the IR spectra of the compounds synthesized are given, and their ring-chain equilibrium transformations are discussed. It has been shown that the protonation of the nitrogen atom of the heterocycle stabilizes the cyclic form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1231–1234, September, 1984.     

Breaking and disappearance of tori

A mechanism is illustrated which can cause a torus to disappear in dissipative differential equations. Three different examples give evidence that a collision with a neighbouring unstable periodic orbit, possibly preceded by a transition into a weakly chaotic attractor, causes the sudden destruction of a torus.     

Ring-chain isomerism of 3-hydroxy-3-(2-imidazolyl)isoindolinones

It was established by IR, UV, and PMR spectroscopy that N-unsubstituted and N-(n-alkyl, sec-alkyl, or aryl)-2-(2-imidazolylcarbonyl)benzamides obtained from imidazo[1,2-b]isoquinoline-5,10-dione and ammonia or amines have the 3-hydroxy-3-(2-imidazolyl)isoindolinone chain structure in the crystalline state and in solutions in dimethyl sulfoxide. The N-(tert-alkyl)amides exist in the open form under these conditions. Protonation of the imidazole nitrogen atom in the N-(tert-butyl)amide molecule leads to its cyclization to 3-hydroxyisoindolinone. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 335–339, March, 1980.     

Classification of Nebbiolo-based wines from Piedmont (Italy) by means of solid-phase microextraction-gas chromatography-mass spectrometry of volatile compounds

Sixty-eight samples of wines from Piedmont (Italy) were analysed to determine their content of volatile compounds, using the solid-phase microextraction (SPME) technique coupled with gas chromatography-mass spectrometry (GC-MS). Samples were from five groups of wines: Barolo, Barbaresco, Nebbiolo d'Alba, Roero and Langhe Nebbiolo, all produced from the Nebbiolo grape in the Langhe and Roero areas (province of Cuneo, Piedmont) but differing in vintage (respectively, 3 years, 2 years, 1 year, 8 months and few months) and production zone. Thirty-five analytes were identified; peak area data, corrected for internal standard, were used for pattern recognition treatments. Principal components analysis, hierarchical cluster analysis, Kohonen self organising map, stepwise linear discriminant analysis and soft independent modelling of class analogy were applied to the data, revealing a good separation between the five groups. A main factor, strictly connected to wine vintage, was identified and found to be related to some analytes.     

Determination of nineteen 4-alkylphenol endocrine disrupters in Geneva municipal sewage wastewater

A preconcentration technique, which involves liquid-liquid-liquid microextraction, was developed to determine phenoxy herbicides in bovine milk. A layer of organic phase was impregnated into the pores of a 3.5 cm long porous hollow fiber, while the internal volume of the fiber was filled with NaOH solution (the acceptor solution) that was connected directly to the needle of a microsyringe. The fiber was then immersed into 8 ml of acidified milk sample. When the sample solution was stirred, acidic analytes were extracted into the organic phase and back extracted simultaneously into the alkaline acceptor medium as the analytes were protonated at low pH and deprotonated at high pH. After extracting for a prescribed time, 5 microl acceptor solution was taken back into the syringe and injected directly into a HPLC system for quantification. The analytes were extracted quantitatively from the sample solution into the acceptor solution with a large enrichment factor of 900. Due to its low cost, the hollow-fiber extraction device was disposed of after a single extraction that eliminated the possibility of carry over effects. In addition, because a small volume of organic solvent was required and little waste is generated, the procedure is environmentally friendly, and is compatible with the "green chemistry" concept.     

Effect of the catalyst MCM-41 on the kinetic of the thermal decomposition of poly(ethylene terephthalate)

The aim of this work is to determine the activation energy for the thermal decomposition of poly(ethylene terephthalate)—PET, in the presence of a MCM-41 mesoporous catalyst. This material was synthesized by the hydrothermal method, using cetyltrimethylammonium as template. The PET sample has been submitted to thermal degradation alone and in presence of MCM-41 catalyst at a concentration of 25% in mass (MCM-41/PET). The degradation process was evaluated by thermogravimetry, at temperature range from 350 to 500 °C, under nitrogen atmosphere, with heating rates of 5, 10 and 25 °C min^?1. From TG, the activation energy, determined using the Flynn–Wall kinetic method, decreased from 231 kJ mol^?1, for the pure polymer (PET), to 195 kJ mol^?1, in the presence of the material (MCM-41/PET), showing the catalyst efficiency for the polymer decomposition process.     

Topological Features of Massive Bosons on Two-Dimensional Einstein Space–Time

In this paper, we tackle the problem of constructing explicit examples of topological cocycles of Roberts’ net cohomology, as defined abstractly by Brunetti and Ruzzi. We consider the simple case of massive bosonic quantum field theory on the two-dimensional Einstein cylinder. After deriving some crucial results of the algebraic framework of quantization, we address the problem of the construction of the topological cocycles. All constructed cocycles lead to unitarily equivalent representations of the fundamental group of the circle (seen as a diffeomorphic image of all possible Cauchy surfaces). The construction is carried out using only Cauchy data and related net of local algebras on the circle.