Optical and structural properties of ZnO + Zn<Subscript>2</Subscript>TiO<Subscript>4</Subscript> thin films prepared by the sol–gel method

ZnO + Zn₂TiO₄ thin films were obtained by the sol–gel method using precursor solutions with different Ti/Zn ratios in the 0.18–2.13 range. The films were deposited on glass substrates and annealed in an open atmosphere at 550 °C. The oxide was characterized by X-ray diffraction and photoacoustic (PA) spectroscopy. The films were constituted of polycrystalline ZnO for the lowest Ti/Zn ratio (0.18), polycrystalline Zn₂TiO₄ for the 0.70 and 1.0 ratios, and mixes of both oxides for the intermediate ratios (0.32 and 0.50). For the highest ratios studied (1.44 and 2.13), the films were amorphous. The energy band gap (E_g) values were determined from optical absorption spectra, measured by means of the PA technique spectra. E_g varied in the 3.15 eV (ZnO) to 3.70 eV (Zn₂TiO₄) range.     

Provision of distance learning services over Interactive Digital TV with MHP

E-learning technologies have developed greatly in recent years, with considerable success. However, there is increasing evidence that web-based learning is not reaching the social sectors which are more reluctant to contact with the new technologies, thus leading to inequalities in the access to education and knowledge in the Information Society. By hiding the intricacies of computers behind the familiarity of household equipment, Interactive Digital TV (IDTV) is considered to play a key role in addressing this problem, and the term t-learning has been recently coined to mean TV-based interactive learning.     

Spectral study and classification of worldwide locations considering several multijunction solar cell technologies

Multi‐junction solar cells are widely used in high‐concentration photovoltaic systems (HCPV) attaining the highest efficiencies in photovoltaic energy generation. This technology is more dependent on the spectral variations of the impinging Direct Normal Irradiance (DNI) than conventional photovoltaics based on silicon solar cells and consequently demands a deeper knowledge of the solar resource characteristics. This article explores the capabilities of spectral indexes, namely, spectral matching ratios (SMR), to spectrally characterize the annual irradiation reaching a particular location on the Earth and to provide the necessary information for the spectral optimization of a MJ solar cell in that location as a starting point for CPV module spectral tuning. Additionally, the relationship between such indexes and the atmosphere parameters, such as the aerosol optical depth (AOD), precipitable water (PW), and air mass (AM), is discussed using radiative transfer models such as SMARTS to generate the spectrally resolved DNI. The network of ground‐based sun and sky‐scanning radiometers AErosol RObotic NETwork (AERONET) is exploited to obtain the atmosphere parameters for a selected bunch of 34 sites worldwide. Finally, the SMR indexes are obtained for every location, and a comparative analysis is carried out for four architectures of triple junction solar cells, covering both lattice match and metamorphic technologies. The differences found among cell technologies are much less significant than among locations. Copyright © 2016 John Wiley & Sons, Ltd.     

Seed oils of ten traditional Portuguese grape varieties with interesting chemical and antioxidant properties

To increase the potential and better exploring of grape seeds that are an important wine-industrial waste, oils of ten traditional Portuguese grape varieties were evaluated in relation to their vitamin E content (tocopherols and tocotrienols), fatty acid profile, as well as, antioxidant properties. Our results showed that the grape-seed oils were a good source of γ-tocotrienol (499–1575 mg/kg), α-tocopherol (85.5–244 mg/kg) and α-tocotrienol (69–319 mg/kg). Concerning fatty acid profile, linoleic (C18:2cc), oleic (C18:1), palmitic (C16:0) and stearic (C18:0) acids were the predominant. Grape-seed oils demonstrated to be a good source of polyunsaturated fatty acids (PUFAs) (63.64–73.53%), whereas monounsaturated fatty acid (MUFA) and saturated fatty acid (SFA) ranged between 14.19–21.29% and 11.64–14.94%, respectively. Interesting values of DPPH and ABTS radical scavenging activities were also obtained. This study demonstrated that these seeds may be reused and their oils incorporated in other food products, taking into account the compounds with positive effects on human health that are present in their composition.     

Social and attitudinal determinants of viral marketing dynamics

At this time of uncertainty, viral marketing is emerging as one of the most intriguing communication strategies, due to low cost and the results it obtains. However, the success of this kind of practice depends on a range of factors including what we explore and refer to in the present research as the individual’s “viral dynamics”. We thus propose a causal model in which viral dynamics is determined by the individual’s social capital and prior attitudes. Based on a survey of young adults, the authors test the effects of structural and relational capital as well as attitudes on viral dynamics. The results evidence that the individual’s connectedness in the email network does not impact viral dynamics, whereas the individual’s integration and relationship with the network and the attitudes towards viral messages prove critical to the individual involved in the receiving-forwarding process.     

Viscoelastic properties of poly(vinyl alcohol) hydrogels and ferrogels obtained through freezing-thawing cycles

We report the preparation of poly(vinyl alcohol) (PVA) hydrogels obtained through freezing-thawing cycles. The viscoelastic properties of these gels using parallel-plate shear mode were evaluated as a function of temperature, time, degree of swelling, concentration and the number of freezing-thawing cycles. The storage modulus was analyzed on the basis of a theoretical model based on the scaling approach. These results provide additional evidence for a non-crystalline nature of the structure of PVA cryogels.Furthermore, PVA ferrogels have been prepared from PVA aqueous solutions and a ferrofluid through freezing-thawing cycles. The viscoelastic properties of these materials have been evaluated. It is shown that the variation of the storage modulus with ferrofluid concentration cannot be fitted using classical theories what has been attributed to the small dimensions of the particles in the ferrogels and to the magnetic interactions between particles.     

Effects of vinyltrimethoxy silane on mechanical properties and morphology of polypropylene‐woodflour composites

The effects of composition and interface modification on the tensile properties and the impact resistance of different woodflour/polypropylene composites (WPC) were studied. The woodflour was treated with vinyltrimethoxy silane as a coupling agent, and its effect on the WPC properties was examined. In addition, the tensile data were fitted with several semiempirical models to clarify the mechanical behavior of the composites. The Pukánszky parameters obtained from the fit of the tensile strength data revealed that the distribution of the filler was more homogeneous in the composites containing silane and that interaction between components was improved. The impact strength was maximal for the composites containing 30% of silane‐treated woodflour. Morphological analysis by SEM revealed that the woodflour tended to form agglomerates when present in relatively high amounts in the formulations. For the silane‐treated composites, the dispersion of the filler into the polypropylene (PP) matrix improved, although surface treatment blocked the inclusion of PP into the wood cells. This probably decreased the elastic moduli, even when the filler‐matrix interaction was improved. The beneficial effects of the coupling agent on the WPC properties were greater in the materials containing a relatively low amount of filler (up to 30%); the effectiveness of 0.5% and 1% organosilane were very similar, demonstrating the effectiveness of the coupling agent. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Mortality due to lung, laryngeal and bladder cancer in towns lying in the vicinity of combustion installations

Background

Installations that burn fossil fuels to generate power may represent a health problem due to the toxic substances which they release into the environment.

Objectives

To investigate whether there might be excess mortality due to tumors of lung, larynx and bladder in the population residing near Spanish combustion installations included in the European Pollutant Emission Register.

Methods

Ecologic study designed to model sex-specific standardized mortality ratios for the above three tumors in Spanish towns, over the period 1994-2003. Population exposure to pollution was estimated on the basis of distance from town of residence to pollution source. Using mixed Poisson regression models, we analyzed: risk of dying from cancer in a 5-kilometer zone around installations that commenced operations before 1990; effect of type of fuel used; and risk gradient within a 50-kilometer radius of such installations.

Results

Excess mortality (relative risk, 95% confidence interval) was detected in the vicinity of pre-1990 installations for lung cancer (1.066, 1.041-1.091 in the overall population; 1.084, 1.057-1.111 in men), and laryngeal cancer among men (1.067, 0.992-1.148). Lung cancer displayed excess mortality for all types of fuel used, whereas in laryngeal and bladder cancer, the excess was associated with coal-fired industries. There was a risk gradient effect in the proximity of a number of installations.

Conclusions

Our results could support the hypothesis of an association between risk of lung, laryngeal and bladder cancer mortality and proximity to Spanish combustion installations.