Characterization of magnetic materials using a scanning microwave microprobe

We investigated the electromagnetic properties of metals of iron, nickel, cobalt, aluminum, gold, copper, silver, and permalloy thin films on SiO(2) substrates using a near-field microwave microprobe. The electromagnetic properties of metal sheets were estimated by measuring the microwave reflection coefficient S(11) and compared with the theoretical values. We observed the hysteresis behavior of permalloy thin films on SiO(2) substrates using a near-field scanning microwave microprobes (NSMM) system. Experimental results are in good agreement with the theoretical model of transmission theory. In order to better characterize the electromagnetic properties of metals and magnetic metals instead of the usual method, we take advantage of the noncontact microprobing evaluation capabilities using a near-field microwave.     

Conformal representations of the general scalar-tensor theory and cosmological models

The article is a review of cosmological models describing the accelerated expansion of the Universe built by using various conformal representations of the modified Jordan-Brans-Dicke (JBD) theory.     

The income return to entrepreneurship: theoretical model and outcomes for Swedish regions

This paper investigates the income return to entrepreneurship and wage employment by means of Lazear’s model of occupational choice. The paper has two major aims. The first is to develop a new theoretical framework for analyzing the income return to entrepreneurship by combining the Lazear model with the assumption that the skill profiles in a population are Fréchet-distributed. The second is to demonstrate that the resulting theoretical derivations can be used for a new type of regional analysis of the income return to entrepreneurship and wage employment. The empirical analysis is based on data for individuals with a Master of Science degree in Electrical Engineering. We compute their income return to self-employment and wage employment in three parts of Sweden: the Stockholm region, the combined Gothenburg and Malmö region, and the Rest of Sweden. The results show that the average return to self-employment is less than 5% in all regions and smaller in the Gothenburg and Malmö region than in the other two regions. The regional differences are explained by the differential supply curves and market values of entrepreneurial talent. The theoretical derivation of the income return to entrepreneurship is the main contribution of the paper. Another contribution is the derivation of regional supply curves for entrepreneurs.     

Aluminum drinking water treatment residuals (Al-WTRs) as sorbent for mercury: Implications for soil remediation

The potential of readily available and non-hazardous waste material, aluminum drinking water treatment residuals (Al-WTRs), to efficiently sorb and immobilize mercury (Hg) from aqueous solutions was evaluated. Al-WTR samples with average specific surface area of 48m(2)/g and internal micropore surface area of 120m(2)/g were used in a series of batch sorption experiments. Obtained sorption isotherms indicated a strong affinity of Hg for Al-WTRs. Using the Langmuir adsorption model, a relatively high maximum sorption capacity of 79mg Hg/g Al-WTRs was determined. Sorption kinetic data was best fit to a pseudo-first-order model, while the use of the Weber-Morris and Bangham models suggested that the intraparticle diffusion could be the rate-limiting step. Also, Al-WTRs effectively immoblized Hg in the pH range of 3-8. The results from these short-term experiments demonstrate that Al-WTRs can be effectively used to remove Hg from aqueous solutions. This ability points to the potential of Al-WTRs as a sorbent in soil remediation techniques based on Hg-immobilization.     

Effects of engineered nanomaterials on microbial catalyzed biogeochemical processes in sediments

Engineered nanomaterials (ENMs) are anticipated to find use in many human activities and commercial products. Concerns are therefore being raised regarding their environmental fate and toxicological implications, which remain largely unknown. In this study, we investigate the effects of C(60), nano-Ag and CdSe quantum dots (QD) on microbial-catalyzed oxidation of organic matter in freshwater sediments. Sediment slurries spiked with sodium acetate at a final concentration of 150 mg/L were separately treated with pre-identified toxic levels of the tested ENMs. The study focused primarily on acetate oxidation by nitrate reducing bacteria. Sediment slurries were incubated under anaerobic conditions in parallel with control samples, and changes in concentrations of acetate, nitrate and nitrite tracked over time. The results showed that tested C(60) concentration completely inhibited the microbial oxidation of acetate, whereas the addition of nano-Ag and CdSe QD to sediment slurries negatively affected the rates of acetate oxidation. Under conditions with nitrate as prevalent electron acceptor, reaction rates of acetate degradation decreased from 0.44 day(-1) in control slurries to 0.24 day(-1) and 0.20 day(-1) in slurries treated with nano-Ag and CdSe QD, respectively. These preliminary results call for further investigations on potential long-term effects of ENMs on microbial driven basic ecosystem services.     

Investigation of CdS thin films by a near-field microwave microprobe

Cadmium sulphide (CdS) thin films with different microstructures and morphologies were measured by using a near-field microwave microprobe (NFMM). The NFMM system was coupled to a dielectric resonator with a distance regulation system at an operating frequency f=4.1GHz. The changes in dielectric permittivity of CdS thin films due to different annealing temperatures were investigated by measuring the reflection coefficient S(11). CdS thin films with different microstructures and morphology were characterized by X-ray diffraction, atomic force microscopy and NFMM.     

Creation of Periodical Antiparallel Domain Structure in Lithium Niobate Crystals During Growth Process

The advantages of producing a periodically poled lithium niobate (PPLN) structure during crystal growth process are the possibility of obtaining thicker and wider structures that leads to greater useful surfaces in addition to the elimination of the subsequent poling process. We report in this paper a new technology of creating bulk periodically poled LiNbO 3 single crystals with antiparallel ferroelectric domains, by direct electric field poling during growth processes. Growth system configuration, crystal composition and geometry selection are explored to allow successful control of the direction of spontaneous polarization using external electric field. PPLN crystal samples with periodicity 20-100μm were grown using this electric field modulated growth technique.