Surface and bulk components of electrical conductivity in the (presumably special topological) Kondo insulator SmB6 at lowest temperatures

Samarium hexaboride (SmB6) has recently been considered to be a topological Kondo insulator (TKI), the first strongly correlated electron system to exhibit topological surface conduction states. In this contribution, results of electrical resistivity measurements between 80 K and 0.08 K of various SmB6 single crystalline samples are presented, analyzed and discussed. The received results imply that the residual conductivity of SmB6 below about 4 K is of non-activated (metallic-like) nature. It is shown that this metallic-like behavior can be attributed both to surface (2D) conduction states, as may be expected in case of a topological insulator, as well as to the highly correlated many-body (3D) bulk ground state which is formed within the gap of this compound. From this it follows that in SmB6, where surface conductivity states are clearly present, there is in parallel also a bulk contribution to residual electrical conductivity originating from the strongly correlated electron system with valence fluctuations. This raises the question whether SmB6 does not form a new / special type of topological insulator in which in the energy gap besides the surface conduction states, there is also a conducting narrow in-gap band originating from the bulk strongly correlated electron system.Comment: 9 pages, 5 figure

Paramagnetic Meissner effect in ZrB12 single crystal with non-monotonic vortex-vortex interactions

The magnetic response related to paramagnetic Meissner effect (PME) is studied in a high quality single crystal ZrB12 with non-monotonic vortex-vortex interactions. We observe the expulsion and penetration of magnetic flux in the form of vortex clusters with increasing temperature. A vortex phase diagram is constructed which shows that the PME can be explained by considering the interplay among the flux compression, the different temperature dependencies of the vortex-vortex and the vortex-pin interactions, and thermal fluctuations. Such a scenario is in good agreement with the results of the magnetic relaxation measurements.Comment: accepted by New Journal of Physic

Short-term oral atrazine exposure alters the plasma metabolome of male C57BL/6 mice and disrupts α -linolenate, tryptophan, tyrosine and other major metabolic pathways

Overexposure to the commonly used herbicide atrazine (ATR) affects several organ systems, including the brain. Previously, we demonstrated that short-term oral ATR exposure causes behavioral deficits and dopaminergic and serotonergic dysfunction in the brains of mice. Using adult male C57BL/6 mice, the present study aimed to investigate effects of a 10-day oral ATR exposure (0, 5, 25, 125, or 250 mg/kg) on the mouse plasma metabolome and to determine metabolic pathways affected by ATR that may be reflective of ATR’s effects on the brain and useful to identify peripheral biomarkers of neurotoxicity. Four h after the last dosing on day 10, plasma was collected and analyzed with high-performance, dual chromatography-Fourier-transform mass spectrometry that was followed by biostatistical and bioinformatic analyses. ATR exposure (≥5 mg/kg) significantly altered plasma metabolite profile and resulted in a dose-dependent increase in the number of metabolites with ion intensities significantly different from the control group. Pathway analyses revealed that ATR exposure strongly correlated with and disrupted multiple metabolic pathways. Tyrosine, tryptophan, linoleic acid and α-linolenic acid metabolic pathways were among the affected pathways, with α-linolenic acid metabolism being affected to the greatest extent. Observed effects of ATR on plasma tyrosine and tryptophan metabolism may be reflective of the previously reported perturbations of brain dopamine and serotonin homeostasis, respectively. ATR-caused alterations in the plasma profile of α-linolenic acid metabolism are a potential novel and sensitive plasma biomarker of ATR effect and plasma metabolomics could be used to better assess the risks, including to the brain, associated with ATR overexposure

Superconducting phase diagrams of LuB12_{12} and Lu1−x_{1-x}Zrx_xB12_{12} (x≤0.45x \le 0.45) down to 50 mK

Lutetium dodecaboride LuB12 is a simple weak-coupling BCS superconductor with critical temperature Tc = 0.42 K, whilst ZrB12 is a strong-coupling BCS superconductor with the highest critical temperature Tc = 6.0 K among this group of materials. In case of lutetium substitution by zirconium ions in LuB12 the crossover from weak- to strong-coupling superconductor can be studied. We have investigated the evolution of critical temperature Tc and critical field Hc in high-quality single crystalline superconducting samples of Lu(1-x)Zr(x)B12 (0 =< x =< 0.45) by measuring magnetic ac susceptibility between 1 K and 50 mK. To obtain this kind of experimental data, a new susceptometer was designed, constructed and tested, which can work in a wide temperature range of 0.05 K - 3 K in 3He-4He dilution refrigerator. The measurements with this new susceptometer revealed how Tc(x) and Hc(x) increases with increasing concentration of zirconium in Lu(1-x)Zr(x)B12 solid solutions as well as how their superconducting phase diagram develops.Comment: 6 pages, 4 figures, CSMAG conference contributio

Perinatal Docosahexaenoic Acid Supplementation Improves Cognition and Alters Brain Functional Organization in Piglets.

Epidemiologic studies associate maternal docosahexaenoic acid (DHA)/DHA-containing seafood intake with enhanced cognitive development; although, it should be noted that interventional trials show inconsistent findings. We examined perinatal DHA supplementation on cognitive performance, brain anatomical and functional organization, and the brain monoamine neurotransmitter status of offspring using a piglet model. Sows were fed a control (CON) or a diet containing DHA (DHA) from late gestation throughout lactation. Piglets underwent an open field test (OFT), an object recognition test (ORT), and magnetic resonance imaging (MRI) to acquire anatomical, diffusion tensor imaging (DTI), and resting-state functional MRI (rs-fMRI) at weaning. Piglets from DHA-fed sows spent 95% more time sniffing the walls than CON in OFT and exhibited an elevated interest in the novel object in ORT, while CON piglets demonstrated no preference. Maternal DHA supplementation increased fiber length and tended to increase fractional anisotropy in the hippocampus of offspring than CON. DHA piglets exhibited increased functional connectivity in the cerebellar, visual, and default mode network and decreased activity in executive control and sensorimotor network compared to CON. The brain monoamine neurotransmitter levels did not differ in healthy offspring. Perinatal DHA supplementation may increase exploratory behaviors, improve recognition memory, enhance fiber tract integrity, and alter brain functional organization in offspring at weaning

Contemporary Sport Policy in Bulgaria – Priorities, Problems and Future Prospects for Tackling Inactivity : focus on sport participation

Participation in sport and physical activity is considered as an important part of a healthy life and different countries have utilized it with varying success not just to achieve sport-specific objectives but also to improve public health. A key factor for having a physically active nation is the sport policies that a country has developed. In Europe, the differences in sport participation vary immensely with southern- and south-eastern European countries appearing as least active. This study has analysed contemporary sport policy in Bulgaria, which has gone through numerous socioeconomic transformations which have had their impact on the low participation levels and the subsequent public health problems. Sport development strategies, legislation and public announcements have been reviewed to determine the orientation of national sport policy. The primary research adopted a qualitative approach using a multiple case study design. Six semi-structured interviews have been conducted in order to get up-to-date information on current developments, challenges and future prospects in sport policy. Interviewees consisted of three municipality representatives, one central government official, and two non-government sport-for-all organisations (NGOs) officers. The concept of Bourdieu’s Habitus and the Multiple Streams framework have been utilized as theoretical frameworks to analyse sport participation and sport policy, respectively, with the focus being on the latter. The key priority in Bulgarian sport policy appeared to be youth competitive sport. A variety of issues were pointed out by municipalities but a common feature was the limited resources. Some gave a critical self-reflection on the need to give more attention to certain age groups such as the elderly. All three municipalities had their own policy activities implemented which signalled for good level of autonomy. A commonality was the provision of heavily discounted or free municipal sports facilities to clubs and citizens. Differences included emphasis on promoting elite sport within one municipality and enhancing sport for all in another. Cooperation with the ministry was described as good although, surprisingly, this was not the case in Sofia, where the ministry is based. Two municipalities appeared heavily involved in cooperating with NGOs and other institutions such as schools. To optimise sport policy in Bulgaria, cross-sectoral work should be enhanced, communication between the national and local authorities and between the ministry and the third sector should be improved. Stronger voice should be given to NGOs in the policy-making process as they have close contact with citizens and fresh ideas. The country’s limited resources need to be taken into account and a more strategic and realistic goals need to be put in place in the context of hugely expensive elite sport globally and high rates of non-communicable diseases nationally, which can be reduced through higher sport participation rates