The centimeter spectra of Wolf-Rayet (WR) binaries often show a contribution from a wind-wind collision region (WCR) between the stars. In short period systems (≲ 1 yr), such a component is expected to be absorbed by the unshocked winds, losing any effect from its binarity. Recent studies suggest that the WCR in these systems may also contribute to the emission at both centimeter and millimeter wavelengths. We analyzed and compared centimeter and millimeter observations of a total sample of 17 WR stars (including nine confirmed short-period systems) to detect any possible WCR contribution. More detailed observations are required in order to distinguish between different scenarios. We highlight the importance of analyzing the spectrum from quasi-simultaneous observations in a wide range of frequencies in order to properly characterize and distinguish any possible extra contribution.

El espectro centimétrico de binarias Wolf-Rayet (WR) muestra a menudo la contribución de una región de colisión de vientos (WCR). En sistemas de periodo corto (≲1 año), se espera que este componente sea absorbido por los vientos no chocados, perdiendo el efecto de su condición binaria. Estudios teóricos y observacionales sugieren que en estos sistemas, la WCR puede contribuir a la emisión tanto en la región centimétrica como milimétrica. Analizamos observaciones centimétricas y milimétricas de 17 estrellas WR (incluyendo nueve binarias de periodo corto). Encontramos que para distinguir entre los posibles escenarios son necesarias más observaciones. Enfatizamos la importancia de analizar el espectro utilizando observaciones cuasi-simultáneas en un amplio intervalo de frecuencias para así poder caracterizar y distinguir cualquier posible contribución extra a la emisión.

In this work, we report the synthesis and morphological characterization of ZnO nanowires grown on PET using a two-step process: (a) preparation of the seed layer, and (b) growth of the nanostructures. First step: solutions of zinc acetate dehydrate and 1-propanol of 10 mM concentration were spin coated on PET at 2000 rpm for 54 s using a syringe pump. Three of such cycles were carried out, between each cycle the layer was heating at 100°C in a furnace for 60 s. A seed layer was obtained after three layers of spin coating. Second step: vertical ZnO nanowires were grown by dipping the substrate in a 25 mM equimolar solution of zinc nitrate hexahydrate and hexamethylenetetramine. Afterwards, films were thermally treated with a commercial microwave oven at different power settings (350 and 700 W) for 5, 20 and 35 min. The ZnO nanowires obtained were characterized structural, optical and morphologically. Scanning electron microscopy analysis showed that the size of ZnO nanowires decreased in diameter when the heating time increased. XRD patterns show the presence of Zn(OH)2 overlapped with the ZnO phase. The ZnO nanowires bandgap energy was obtained from optical transmission spectra.

Chitosan microspheres with a mean size of 140 ± 119 µm were produced by the spray and coagulation methods. The microspheres were chemically modified using the following routes: a) crosslinking with glutaraldehyde b) crosslinking with epychlorohydrin and c) acetylation. For investigation of their ability as adsorbents, the following standard proteins were chosen as adsorbates: bovine serum albumin - BSA (pI = 4.8 and MW = 66 kDa) and lysozyme (pI = 11 and MW = 14 kDa). The adsorption experiments were performed using a static method. The adsorption media and equilibrium concentration of adsorbates were varied in the ranges of pH 4-11 and 0.07-0.70 mg.ml-1, respectively. The maximum adsorption capacities (q m) and the constant of the Langmuir model (Ks) were shown to be dependent on charge interactions and on the kind of treatment performed on chitosan microspheres. The satisfactory fit of a kinetic model to the experimental data shows that the step that controls the adsorption kinetics is probably the initial adsorbate transport.