Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi2Te3 heterostructure studied by high resolution Brillouin spectroscopy

The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm−1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm−1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models

Tuning of a hypersonic surface phononic band gap using a nanoscale two-dimensional lattice of pillars

We present experimental and theoretical evidence of a phononic band gap in a hypersonic range for thermally activated surface acoustic waves in two-dimensional (2D) phononic crystals. Surface Brillouin light scattering experiments were performed on the (001) surface of silicon, loaded with a 2D square lattice of 100- or 150-nm-high aluminum pillars with a spacing of 500nm. The surface Brillouin light scattering spectra revealed a different type of surface mode, related to the modulation of the lattice structure and the mechanical eigenmodes of the pillars. The experimental data were in excellent agreement with theoretical calculations performed using the finite-element method.Peer reviewe

Analysis of the impact of sex and age on the variation in the prevalence of antinuclear autoantibodies in Polish population: a nationwide observational, cross-sectional study

The detection of antinuclear autoantibody (ANA) is dependent on many factors and varies between the populations. The aim of the study was first to assess the prevalence of ANA in the Polish adult population depending on age, sex and the cutoff threshold used for the results obtained. Second, we estimated the occurrence of individual types of ANA-staining patterns. We tested 1731 patient samples using commercially available IIFA using two cutoff thresholds of 1:100 and 1:160. We found ANA in 260 participants (15.0%), but the percentage of positive results strongly depended on the cutoff level. For a cutoff threshold 1:100, the positive population was 19.5% and for the 1:160 cutoff threshold, it was 11.7%. The most prevalent ANA-staining pattern was AC-2 Dense Fine speckled (50%), followed by AC-21 Reticular/AMA (14.38%) ANA more common in women (72%); 64% of ANA-positive patients were over 50 years of age. ANA prevalence in the Polish population is at a level observed in other highly developed countries and is more prevalent in women and elderly individuals. To reduce the number of positive results released, we suggest that Polish laboratories should set 1:160 as the cutoff threshold

Sensory quality and viability of potentially probiotic strains of Lactobacillus in fermented honey beverage

Celem pracy było określenie możliwości zastosowania bakterii potencjalnie probiotycznych Lactobacillus johnsonii K4 lub Lactobacillus casei O12 do produkcji napoju miodowego akceptowanego sensorycznie i zawierającego żywe mikroorganizmy. Materiałem do badań były napoje miodowe przygotowane z miodu wielokwiatowego i wody wodociągowej (12,05 g/100 ml). Napoje poddano 2-, 3-, 4- i 5-dniowej fermentacji monokulturą bakterii (po inokulacji ok. 7 log jtk/cm³) w temp. 30 i 37 ºC. Średnia liczb bakterii po fermentacji zawierała się w przedziale 6,75 ÷ 8,14 log jtk/cm³. Wzrost bakterii był zależny od szczepu, czasu i temperatury fermentacji (p < 0,05). Te same czynniki istotnie wpłynęły na średnie wartości pH we wszystkich próbach w kolejnych dniach fermentacji i mieściły się w granicach 4,6 ÷ 4.8 (p < 0,05). Czas fermentacji był czynnikiem statystycznie istotnie wpływającym na ocenę sensoryczną (p < 0,05). Najwyższe noty w ocenie sensorycznej przyznano próbkom fermentowanym szczepem Lb. casei O12 przez 2 dni w temp. 37 ºC. Wybrane bakterie z rodzaju Lactobacillus można zastosować do wytwarzania innowacyjnego napoju o pożądanych cechach sensorycznych. Na tym etapie badań produkt nie może być nazwany probiotycznym, jednak jakość sensoryczna i zakres przeżywalności szczepów predysponuje do dalszej oceny ich właściwości probiotycznych.The objective of the research study was to determine the possibility of using potentially probiotic strains of Lactobacillus johnsonii K4 and Lactobacillus casei O12 to manufacture a honey beverage having a appropriate sensory quality and containing viable microorganisms. The research material consisted of honey beverages made of multifloral honey and tap water (12.05 g/100 ml). The beverages were fermented for 2, 3, 4 and 5 days with a bacterial monoculture (after inoculation of approx. 7 log cfu/ml) at a temperature of 30 and 37 ºC. The average count of bacteria ranged from 6.75 to 8.14 log cfu/ml. The growth of bacteria depended on the strain, the time and the temperature of fermentation (p < 0.05). The same factors significantly impacted the mean pH values of all the samples on the subsequent days of fermentation; those pH values ranged between 4.6 and 4.8 (p < 0.05). The fermentation time was a factor to statistically significantly impact the sensory evaluation (p < 0.05). The samples fermented with a Lb. casei O12 strain for 2 days at 37 ºC were given the highest scores in the sensory evaluation. The selected bacteria of the Lactobacillus species can be used to manufacture an innovative beverage having desirable sensory qualities. At this stage of the research, the product cannot be called probiotic; however, the sensory quality and the range of viability of the strains predispose them to continue evaluation of their probiotic properties

Generation of a mode in phononic crystal based on 1D/2D structures

The modification of phononic crystals by surface structuring allows obtaining a new parameter describing the dynamics of the structure produced in this way. We have investigated the dispersion relation of surface acoustic waves propagating in a phononic material which is based on nanometer-scale surface modulation using interconnected one-dimensional array of stripes and a two-dimensional array of pillars. The influence of these two array components on the dispersion relation has been determined experimentally (Brillouin light scattering) and theoretically (Finite Element Method). The interaction of these two nanostructures supports a new mode which is not observed in independent structures of pillars and stripes. The influence of the relative position of these two nanostructures on the frequency of the new mode has been determined.Peer reviewe