Reversible graphitization of SiC : a route towards high-quality graphene on a minimally step bunched substrate

We show that the thermal decomposition of SiC (0001) surface is reversible, if carried out in near-equilibrium conditions, with an external Si atomic beam applied to the substrate. Taking advantage of this observation we design a novel process, allowing for the growth of uniform, few-layers, ABC-stacked graphene. This process is composed of two phases; the first is a graphene film growth and the second is its reduction to the desired thickness. We find that, when using this scheme instead of the conventional ones the heavy step bunching on the substrate is avoided, and the step heights remain below 2.75 nm. Since the step bunching is one of the most important factors prohibiting the use of epitaxial graphene on SiC in certain application areas, such as analog electronics or sensing, our method has the potential to be applied in future wafer-scale graphene technologies and processes. Moreover, the results obtained in this work exemplify general near-equilibrium phenomena and therefore they may be also relevant for growth methods of other 2D materials

Dwuwymiarowy model TYPUZIP-CP w łącznej analizie zmiennych licznikowych

In the paper a generalization of the Berkhout and Plug (2004) bivariate Poisson regression model is proposed; in the Berkhout and Plug model one of the variables has the marginal Poisson distribution, while the other follows the conditional Poisson distribution. In the new model the marginal distribution is of the ZIP type and has the same parameterization as the hurdle model. Bayesian estimation of the model and the formal Bayesian comparison of its two alternative specifications are presented. The empirical example concerns joint modelling of the number of cash payments and bank card payments in Poland as well as inference on their correlation.W pracy zaproponowano uogólnienie modelu dwuwymiarowej regresji poissonowskiej, który wprowadzili Berkhout i Plug (2004), przyjmujący brzegowy rozkład Poissona dla jednej zmiennej i warunkowy rozkład Poissona dla drugiej. W nowym modelu rozkład brzegowy jest typu ZIP i ma taką parametryzację jak w modelu płotkowym. Przedstawiono bayesowską estymację tego modelu i formalne bayesowskie porównanie dwóch alternatywnych jego specyfikacji. Przykład empiryczny dotyczy łącznego modelowania i wnioskowania o korelacji między liczbą płatności kartą i gotówką w Polsce

Thermal degradation of biological DNA studied by dielectric spectroscopy

Dielectric spectroscopy was tested as an alternative tool to study degradation of deoxyribonucleic acid (DNA) in its solid form. The specimens, prepared from biological DNA, were periodically heated and cooled according to a programmed scheme. Simultaneously, their dielectric parameters (permittivity and dielectric loss) were monitored as function of frequency and temperature. The analysis of Bode plots allowed to determine the upper limit of thermal stability of solid DNA at 120 °C, because heating at higher temperatures resulted in irreversible changes. These changes were identified as denaturation by gel electrophoresis and UV–vis absorption methods

Solid Oxide Fuel Cells-Materials and Prospects

本文依据固体氧化物燃料电池(SOFC)于运作条件下的基本性能,诸如化学稳定性、电迁移、催化和热机械性能等评述SOFC组成部分(电极材料和电解质)的基本性质.示明由氧偏离化学计量比引起的电极材料结构缺陷与其电子性质及催化活性之间的相互关系,提出单室燃料电池概念.The paper summarizes and discusses the basic properties of solid oxide fuel cell(SOFC) components(electrode materials and electrolyte) from the point of view of their essential functional parameters suck as chemicalstability,transport,catalytic and thermomechanical properties under operational conditions in a SOFC.An interrela-tion between the defect structure of these materials related to oxygen nonstoichiometry and their electronic propertiesand catalytic activity was shown.Single-chamber fuel cell concept was also presented.作者联系地址：AGH科技大学 材料科学与陶瓷学院al.Mickiewicza 30,30-059 Krakow,波兰,AGH科技大学,材料科学与陶瓷学院al.Mickiewicza 30,30-059 Krakow,波兰,Author's Address: Faculty of Materials Science and Ceramics,AGHUniversity of Science and Technologyal.Mickiewicza 30,30-059 Krakow,Polan

Response of endolithic chroococcidiopsis strains from the polyextreme Atacama desert to light radiation

Cyanobacteria exposed to high solar radiation make use of a series of defense mechanisms, including avoidance, antioxidant systems, and the production of photoprotective compounds such as scytonemin. Two cyanobacterial strains of the genus Chroococcidiopsis from the Atacama Desert – which has one of the highest solar radiation levels on Earth- were examined to determine their capacity to protect themselves from direct photosynthetically active (PAR) and ultraviolet radiation (UVR): the UAM813 strain, originally isolated from a cryptoendolithic microhabitat within halite (NaCl), and UAM816 strain originally isolated from a chasmoendolithic microhabitat within calcite (CaCO3). The oxidative stress induced by exposure to PAR or UVR C PAR was determined to observe their short-term response, as were the long-term scytonemin production, changes in metabolic activity and ultrastructural damage induced. Both strains showed oxidative stress to both types of light radiation. The UAM813 strain showed a lower acclimation capacity than the UAM816 strain, showing an ever-increasing accumulation of reactive oxygen species (ROS) and a smaller accumulation of scytonemin. This would appear to reflect differences in the adaptation strategies followed to meet the demands of their different microhabitats.This study was supported by grant PGC2018-094076-B-I00 from MCIU/AEI (Spain) and FEDER (UE). MC was supported by grant BES 2014-069106 from the Spanish Ministry of Science and Innovation (MCINN).Peer reviewe

The own method and program of isotope quantitatively assessment of perfusion in muscles of upper limbs (initial report)

BACKGROUND: The issue of blood flow in muscles has been dealt with for many years. However, most often it was assessed qualitatively with standard vascular examinations. The quantitatively perfusion assessment is indispensable in the normal and pathological conditions. Some diseases impair the perfusion mainly in the area of upper limbs. It can be observed in Raynaud’s disease, vascular occlusive diseases, neurological disturbances, and thermal injuries. Hyperhidrosis of upper limbs after sympathectomy of thoracic part of sympathetic trunk may bring closer the diagnosis statement. Nuclear medicine has the markers and methods that allow for the assessment of the volume of perfusion in muscles. The aim for creating this method and program was the development of radioisotope method allowing for quantitative assessment of perfusion in muscles of upper limbs. This should lead to calculating the perfusion index and its range of normal values in a greater group of patients and to using this method both in the healthy and pathological conditions. MATERIAL AND METHODS: 20 patients, age 30.4 ± 7.1 years, who underwent following examinations: qualification to the group, medical history, subject examinations, USG of upper limb vessels, anthropometric examinations, biochemical and hormonal blood tests, the assessment of upper limbs with USG Doppler and FMD (flow mediated dilatation), radioisotope examinations with gamma camera BrightView XCT by own program RAPUL (Radioisotope Assessment Perfusion of Upper Limb). Acquisitions were started five minutes after intravenous injection of 99mTc-MIBI (metoxyisobutylnitrite). The whole body scintigram and scintigrams of arm and forearm muscles in A-P projections were taken. RESULTS: In the examined patients, the results of anthropometric, biochemical and hormonal test were within the range of normal values. In radioisotope quantitative assessment of perfusion, perfusion indexes of left arm were 20 < PI_left < 11.90 and of the right arm 7.00 < PI_right <12.30. The dependency correlation PI_left vs. PI_right was strong r = 0.92036. The values of perfusion symmetry index (IPS) had a normal distribution and were within the following range: 0.9231 < IPS < 1.1019. CONCLUSIONS: The RAPUL method and program allow for quantitative assessment of perfusion in muscles of upper limbs. Developed program has a high repeatability of results. The results in the bigger group will allow for defining the range of normal values of perfusion index in muscles of upper limbs at rest. These will be diagnostically used both in healthy (sports medicine, military services) and pathological conditions.BACKGROUND: The issue of blood flow in muscles has been dealt with for many years. However, most often it was assessedqualitatively with standard vascular examinations. The quantitatively perfusion assessment is indispensable in the normal andpathological conditions. Some diseases impair the perfusion mainly in the area of upper limbs. It can be observed in Raynaud’sdisease, vascular occlusive diseases, neurological disturbances, and thermal injuries. Hyperhidrosis of upper limbs after sympathectomyof thoracic part of sympathetic trunk may bring closer the diagnosis statement. Nuclear medicine has the markersand methods that allow for the assessment of the volume of perfusion in muscles. The aim for creating this method andprogram was the development of radioisotope method allowing for quantitative assessment of perfusion in muscles of upperlimbs. This should lead to calculating the perfusion index and its range of normal values in a greater group of patients and tousing this method both in the healthy and pathological conditions.MATERIAL AND METHODS: 20 patients, age 30.4 ± 7.1 years, who underwent following examinations: qualification to thegroup, medical history, subject examinations, USG of upper limb vessels, anthropometric examinations, biochemical andhormonal blood tests, the assessment of upper limbs with USG Doppler and FMD (flow mediated dilatation), radioisotopeexaminations with gamma camera BrightView XCT by own program RAPUL (Radioisotope Assessment Perfusion of UpperLimb). Acquisitions were started five minutes after intravenous injection of 99mTc-MIBI (metoxyisobutylnitrite). The whole bodyscintigram and scintigrams of arm and forearm muscles in A-P projections were taken.RESULTS: In the examined patients, the results of anthropometric, biochemical and hormonal test were within the range ofnormal values. In radioisotope quantitative assessment of perfusion, perfusion indexes of left arm were 20 < PI_left < 11.90 andof the right arm 7.00 < PI_right <12.30. The dependency correlation PI_left vs. PI_right was strong r = 0.92036.The values of perfusion symmetry index (IPS) had a normal distribution and were within the following range: 0.9231 < IPS <1.1019.CONCLUSIONS: The RAPUL method and program allow for quantitative assessment of perfusion in muscles of upper limbs.Developed program has a high repeatability of results. The results in the bigger group will allow for defining the range of normalvalues of perfusion index in muscles of upper limbs at rest. These will be diagnostically used both in healthy (sports medicine,military services) and pathological conditions

Crisis response strategies and themes during the COVID-19 pandemic in EU aviation, airlines’ executives communication with shareholders : a content analysis

PURPOSE: The aim of the article is to analyse European Union airlines top-level executives COVID-19 aviation crisis communication with their shareholders in terms of both crisis response strategies used and the themes addressed.DESIGN/METHODOLOGY/APPROACH: Context analysis method was used to examine the top-level executives of five major European Union airlines (Lufthansa, Ryanair, SAS, Wizz Air and KLM) COVID-19 aviation crisis communication with their shareholders. Analyzed data consisted of C-level executives’ letters to shareholders, collected from the available annual reports covering the period of COVID-19 aviation crisis. Data analysis of the available body of text was conducted in the dual procedure – to identify SCCT crisis response strategies.FINDINGS: Research shows that EU airlines mostly rely on diminish (mostly through justification – minimizing the perceived damage caused by the crisis) and bolstering (mostly through reminding the stakeholders about the past good works of the organization) crisis response strategies in their COVID-19 aviation crisis communication with shareholders. There is a difference in the themes present in the crisis communication between traditional and low-cost airlines, as low-cost airlines include themes of new and adjusted services and future of aviation more often than legacy airlines in their COVID-19 aviation crisis communication with shareholders.PRACTICAL IMPLICATIONS: Research results enable managers to better understand airlines crisis response strategies, and by providing examples of messages used it may help crisis response managers prepare their message. The study can be useful in future decision-making in the area of crisis communication.ORIGINALITY/VALUE: The originality of the research results primarily from the focus on crisis communication conducted by airlines top-level executives targeted towards shareholders understood as key stakeholders.peer-reviewe

Properties of DNA-CTMA monolayers obtained by Langmuir-Blodgett technique

The complex consisting of DNA and cetyltrimethylammonium chloride (DNA-CTMA) is extensively exploited in organic electronics in form of thin films with submicron or nanometer thickness. In this work, using the Langmuir-Blodgett technique, the surface films were prepared from complexes based on different types of chromosomal and plasmid DNA. The research focused on changes in their continuity after they were transferred onto a solid substrate. It was found that only the monolayer of plasmid DNA-CTMA complex remained continuous after being transferred. The other complexes underwent a spontaneous self-assembling and created elongated linear patterns. AFM images of these patterns were analysed quantitatively with Fast Fourier Transform. It was confirmed that self-assembling occurred along one privileged direction