Optical spectra, crystal-field parameters, and magnetic susceptibility of the new multiferroic NdFe3(BO3)4

We report high-resolution optical absorption spectra for NdFe3(BO3)4 trigonal single crystal which is known to exhibit a giant magnetoelectric effect below the temperature of magnetic ordering TN = 33 K. The analysis of the temperature-dependent polarized spectra reveals the energies and, in some cases, symmetries and exchange splittings of Nd3+ 84 Kramers doublets. We perform crystal-field calculations starting from the exchange-charge model, obtain a set of six real crystal-field parameters, and calculate wave functions and magnetic g-factors. In particular, the values g(perpendicular) = 2.385, g(parallel) = 1.376 were found for the Nd3+ ground-state doublet. We obtain Bloc=7.88 T and |JFN|= 0.48 K for the values of the local effective magnetic field at liquid helium temperatures at the Nd3+ site and the Nd - Fe exchange integral, respectively, using the experimentally measured Nd3+ ground-state splitting of 8.8 cm-1. To check reliability of our set of crystal field parameters we model the magnetic susceptibility data from literature. A dimer containing two nearest-neighbor iron ions in the spiral chain is considered to partly account for quasi-one-dimensional properties of iron borates, and then the mean-field approximation is used. The results of calculations with the exchange parameters for Fe3+ ions Jnn = -6.25 K (intra-chain interactions) and Jnnn = -1.92 K (inter-chain interactions) obtained from fitting agree well with the experimental data.Comment: 13 pages, 8 figures, 2 table

The application of micro-wave treatment to reduce barley contamination

ArticleThe goal of this work is to study the applicability of ultra high frequency electromagnetic field treatment for decontaminating barley grain used in brewing while preserving its technological properties. The germination rates and/or yield of the treated sample seed were compared with those of the untreated seed germinated under normal conditions. To determine optimal treatment conditions, a two-factor analysis was carried out, taking the mycological state of the grain into account. The heating rate and the duration of electromagnetic exposure were chosen as variables; these values varied from 0.4 to 0.8 °C s-1 and from 30 to 90 s, respectively. It was found that germination of the treated barley seed was increased about 10.1–15.7% compared with that of the untreated seed. The microbial load decreased up to 80%. A heating rate of 0.4 °C s-1 and treatment exposure time of 30 s showed the strongest effect of decontamination while preserving the viability of the barley grain

Public Health Training Needs Assessment in Bulgaria: A Necessary and Continuous Process

The development of public health education has its solid grounds both in the modern trends of the European health policy and in the national context. It is acknowledged that public health training should adequately meet the demand for professionals to involve in practice and research. The content of the training programmes should correspond to the needs for specific public health knowledge, skills and competencies. This study is aimed at assessing the need for public health professionals in Bulgaria and exploring the specific training needs in terms of necessary knowledge and skills. The methods involved refer to opinion assessment of three target groups: experts, employers, and students at the Master of Public Health programme of Varna University of Medicine by personal (face-to-face) interviews orpostar questionnaires. The results show that the need for public health education is widely recognized and it meets the stakeholders' interest in possibilities for public health workforce training and qualification