Dielectric Relaxation in Thin Layers of the Ge<Subscript>28.5</Subscript>Pb<Subscript>15</Subscript>S<Subscript>56.5</Subscript> Glassy System

The results of studying dielectric relaxation processes in the Ge_28.5Pb₁₅S_56.5 glassy system are presented. The existence of the non-Debye relaxation process caused by the distribution of relaxors over the relaxation time according to the Cole–Cole model is revealed. The energy and structural parameters are calculated: the activation energy E_p = 0.40 eV and the molecular dipole moment μ = 1.08 D. The detected features are explained within the model according to which the chalcogenide-glass structure is a set of dipoles formed by charged defects such as D⁺ and D^–.     

An analysis of the numerical model influence on the ground temperature profile determination

The estimation of the ground temperature profile with respect to the depth and time is the key issue in many engineering applications which use the ground as a source of thermal energy. In the present work, the influence of the model components on the calculated ground temperature distribution has been analysed in order to develop an accurate and robust model for the prediction of the ground temperature profile. The presented mathematical model takes into account all the key phenomena occurring in the soil and on its top surface. The impact of individual model elements on the temperature of the soil has been analysed. It has been found that the simplest models and the most complex model result in a similar temperature variation over the simulation period, but only at a low depth. A detailed analysis shows that a larger depth requires more complex models and the calculation with the use of simple models results in an incorrect temperature and a theoretical COP estimation.     

Nitric acid leaching of polymetallic middlings of concentration

Investigations into the nitric acid leaching of polymetallic middlings with the purpose of the maximal recovery of copper and zinc into the solution are performed. Using methods of mathematical planning of the experiment, the optimal process parameters are determined: ratio L : S = 5, the consumption of nitric acid is 80 cm³ per 20 g of the charge, and the process duration is 120 min.     

Study of the structure of a-As2Se3〈Bi〉 x amorphous layers by dielectric spectroscopy

Dielectric polarization in amorphous arsenic triselenide layers with various bismuth impurity contents in ac electric fields is studied. The experimental results obtained are interpreted within the model according to which Bi atoms at low concentrations are incorporated into the initial matrix network of the amorphous structure as charged centers; a further increase in the dopant content is accompanied by the appearance of ordered Bi₂Se₃ inclusions (clusters) in the compositions under study.     

Promoting occupational health in secondary schools through virtual patients

Adolescents with asthma or allergies do not consider their disease when making their career choice. Therefore the aim of this project was to sensitize secondary school students for occupational diseases before they start working.     

Bulk tank raw milk microbiota differs within and between farms: A moving goalpost challenging quality control

Microbial contamination of bovine raw milk often occurs at the farm. To acquire a deeper knowledge of the microbiota of farm tank milk, we studied milk from 45 farms situated in 2 geographical areas in Norway. Each farm was visited on 3 different occasions, with at least 2 wk between visits. We combined both bacterial cell counts and a sequence variant inference method of amplicon-based high-throughput sequencing to achieve a high-resolution overview of the microbiota in each sample. Compositional variation of the farm milk microbiota was shown in relation to the 2 areas, between the farms and between the sampling times. Despite the near constant level of bacteria enumerated in milk from each individual farm, the dominant microbiota differed significantly between the samplings. The predominant microbiota was dominated by spoilage genera, such as Pseudomonas and Bacillus, as well as the dairy fermentation genus Lactococcus and mastitis-causing organisms (Streptococcus). Analysis of the identified sequence variants within these genera showed that the populations of Pseudomonas and Lactococcus in milk had similar composition between the farms, but that Bacillus and, in particular, Streptococcus populations changed between collection days from the same farm and between farms and geographical areas. Furthermore, the levels and composition of Bacillus and Paenibacillus were different between the 2 geographical areas. The results presented here provide new insight into the farm milk microbiota and show that this microbiota is a dynamic community highly subject to variation.     

Two-electron tin centers with a negative correlation energy in lead sulfide

The valence and coordination states of the impurity tin centers in the lead sulfide crystal lattice were determined by emission Mössbauer spectroscopy. Tin atoms that replace lead atoms are two-electron donors with negative correlation energy. The correlation energy U = ?0.072 ± 0.004 eV, as well as the positions of the first (E _V + E ₁ = 0.079 ± 0.002 eV) and second (E _V + E ₂ = 0.151 ± 0.004 eV) ionization energies, were determined (E _V is the energy of the top of valence band).     

Organically grown tomato (Lycopersicon esculentum Mill.): bioactive compounds in the fruit and infection with Phytophthora infestans

BACKGROUND: Tomato fruits are characterized by a good nutritional profile, including different bioactive compounds such as carotenoids, phenolic compounds and ascorbic acid. The objective of this study was to analyze the content of bioactive compounds in the fruit and the infection by Phytophthora infestans of 28 tomato genotypes from organic outdoor production. The relationship between bioactive compounds in the fruit and infection with P. infestans was estimated. Field experiments were carried out in 2004 and 2005 at two locations in central Germany. RESULTS: Significant variation among genotypes, locations and years was observed for the content of lycopene, ascorbic acid, total phenolic compounds, antioxidant capacity and the infection level of P. infestans. Antioxidant capacity seemed to be influenced mainly by the phenolics and was highest in small fruits, which were less infected with P. infestans. CONCLUSION: The large genetic variation among tomato genotypes for the content of bioactive compounds in their fruit allows for selection gains. None of the investigated bioactive compounds can be recommended for the indirect selection for increased field resistance against P. infestans. Copyright © 2011 Society of Chemical Industry