Two-dimensional thermofield bosonization II: Massive fermions

We consider the perturbative computation of the N-point function of chiral densities of massive free fermions at finite temperature within the thermofield dynamics approach. The infinite series in the mass parameter for the N-point functions are computed in the fermionic formulation and compared with the corresponding perturbative series in the interaction parameter in the bosonized thermofield formulation. Thereby we establish in thermofield dynamics the formal equivalence of the massive free fermion theory with the sine-Gordon thermofield model for a particular value of the sine-Gordon parameter. We extend the thermofield bosonization to include the massive Thirring model.     

Colloidal semiconductor quantum dots: Potential tools for new diagnostic methods

We present and discuss the application of colloidal semiconductor quantum dots for diagnostic purposes, with special emphasis for cancer. We prepared and applied core-shell cadmium sulfide-cadmium hydroxide (CdS/Cd(OH)₂) semiconductor quantum dots in aqueous medium. Tissue and cells labeling was evaluated by laser scanning confocal microscopy as well as by conventional fluorescence microscopy. The procedure presented in this work, shown to be a promising tool for fast, low-cost and precise cancer diagnostic protocols.     

Oxidation in Acidic Medium of Lignins from Agricultural Residues

Agricultural residues as sugarcane straw and bagasse are burned in boilers for generation of energy in sugar and alcohol industries. However, excess of those by-products could be used to obtain products with higher value. Pulping process generates cellulosic pulps and lignin. The lignin could be oxidized and applied in effluent treatments for heavy metal removal. Oxidized lignin presents very strong chelating properties. Lignins from sugarcane straw and bagasse were obtained by ethanol–water pulping. Oxidation of lignins was carried out using acetic acid and Co/Mn/Br catalytical system at 50, 80, and 115 °C for 5 h. Kinetics of the reaction was accomplished by measuring the UV-visible region. Activation energy was calculated for lignins from sugarcane straw and bagasse (34.2 and 23.4 kJ mol⁻¹, respectively). The first value indicates higher cross-linked formation. Fourier-transformed infrared spectroscopy data of samples collected during oxidation are very similar. Principal component analysis applied to spectra shows only slight structure modifications in lignins after oxidation reaction.     

Solubilizing mutations used to crystallize one CFTR domain attenuate the trafficking and channel defects caused by the major cystic fibrosis mutation

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) Cl(-) channel. F508del, the most frequent CF-causing mutation, disrupts both the processing and function of CFTR. Recently, the crystal structure of the first nucleotide-binding domain of CFTR bearing F508del (F508del-NBD1) was elucidated. Although F508del-NBD1 shows only minor conformational changes relative to that of wild-type NBD1, additional mutations (F494N/Q637R or F429S/F494N/Q637R) were required for domain solubility and crystallization. Here we show that these solubilizing mutations in cis with F508del partially rescue the trafficking defect of full-length F508del-CFTR and attenuate its gating defect. We interpret these data to suggest that the solubilizing mutations utilized to facilitate F508del-NBD1 production also assist folding of full-length F508del-CFTR protein. Thus, the available crystal structure of F508del-NBD1 might correspond to a partially corrected conformation of this domain.     

Comparative computational and experimental study on the thermochemistry of the chloropyrimidines

The standard (p0 = 0.1 MPa) molar enthalpies of formation, Delta fH(0)(M), for liquid 2,4,6-trichloropyrimidine and for crystalline 2-chloropyrimidine, 2,4- and 4,6-dichloropyrimidine, and 2,4,5,6-tetrachloropyrimidine compounds were determined at T = 298.15 K by rotating-bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation, Delta (g)(cr,l) H(0)(M), of these compounds at T = 298.15 K were determined by Calvet microcalorimetry. The experimental standard molar enthalpies of formation of those compounds, in the gaseous state, at T = 298.15 K, were thus obtained by combining these two sets of results. The latter values have been employed in the calibration of the computational procedure, which has been used to estimate the gas-phase enthalpies of formation for the other chloropyrimidines that were not possible to obtain in a pure form for the experimental study. It is found that the exchange-correlation functional based on the local spin density approximation (LSDA) seems to be a cheap choice for the estimation of enthalpies of formation for heterocycles containing nitrogen atoms; the well-known B3LYP hybrid method yields larger differences, with respect to the experimental values, for 2,4,6-tri- and 2,4,5,6-tetrachloropyrimidines.     

Novel Industrial Application of Miniemulsion Polymerization – Use of Alkali Soluble Resin as Surfactant in Miniemulsion Polymerization

Nowadays, the great versatility of the miniemulsion polymerization technique to synthesize novel and high value added materials attracts great interest from both the academic and the industrial community. Recently, a novel process based on the use of alkali soluble resin (ASR) as sole surfactant in miniemulsion polymerization for high solids content latexes has been disclosed. This new technology opens a vast field for the production of high performance latexes for industrial applications, as well as an interesting topic for future academic research. This work presents the key factors influencing the use of ASR in aqueous polymer dispersions, highlighting the differences in terms of types and concentrations of ASR used in conventional and miniemulsion polymerization. The effects of type of initiator, ASR concentration and type, as well as solids content on the miniemulsion polymerization of styrene and acrylic monomers are presented.     

Synthesis of High Solid‐Content Latex using Alkali‐Soluble Resin as Sole Surfactant

Summary: A novel polymerization procedure to synthesize latex stabilized by alkali‐soluble resin (ASR) is detailed. According to this process, latexes with a high solid content and low viscosity are obtained using a substantially lower amount of ASR when compared with existing techniques. Similar rewet properties were found for the latexes obtained by a standard process and for the one obtained by the process described in this work.

Comparison of the particle size distributions obtained by conventional emulsion polymerization (○) and by miniemulsion polymerization (□).     

A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.