Al 27 NMR local study of the Al0.5TiZrPdCuNi alloy in high-entropy alloy and metallic glass forms

We report a Al27 nuclear magnetic resonance (NMR) local spectroscopic study of the NMR lineshape and Knight shift of a six-component Al0.5TiZrPdCuNi metallic alloy that can be prepared either as a crystalline high-entropy alloy (HEA) or as an amorphous metallic glass (MG) at the same chemical composition. For both structural modifications of the material (HEA and MG), we have determined the distribution of electric-field-gradient (EFG) tensors and the local electronic density of states (DOS) g(ϵF) at the Fermi level at the position of Al27 nuclei. A theoretical I=52 quadrupole-perturbed NMR spectrum, pertinent to both cubic HEAs and amorphous MGs, has been derived using the Gaussian isotropic model of the EFG tensor distribution, and excellent fits of the experimental spectra were obtained. The EFG distribution function of the MG state is about twice broader than that of the HEA state, reflecting the existence of a (distorted) crystal lattice in the latter and its absence in the former. The T2 dependence of the Knight shift indicates that the DOS is changing rapidly with energy within the Fermi level region for both structural modifications. The local DOS at the Al27 sites of the HEA sample is ∼10% larger than that of the MG state, indicating comparable degrees of disorder

Stress and Anxiety Levels in Pregnant and Post-Partum Women during the COVID-19 Pandemic

The aim of this study was to analyze stress and anxiety levels experienced by pregnant and post-partum women during the COVID-19 pandemic, as well as to indicate the social and medical factors that could contribute to stress and anxiety. A total of 210 patients were enrolled in the study. Two well-established test-tools were applied: State-Trait Anxiety Inventory (STAI) and Perceived Stress Scale (PSS-10). The study revealed that the levels of stress and anxiety experienced by the surveyed patients were moderate to high. We demonstrated that women with mental treatment history, those in the first trimester of pregnancy and the ones that are single or in an informal relationship tend to experience higher levels of psychological distress and anxiety. Such factors as age, education, parity, eventful obstetric history, comorbidities, and the number of hospital stays proved to be statistically insignificant in the analysis. Our findings could be used to identify patients at greater risk of experiencing adverse mental effects and to provide them with adequate psychological support. Further multi-center studies are warranted in order to draw final conclusions

Synthesis and Magnetic Properties of Hematite Particles in a ‘‘Nanomedusa’’ Morphology

We present the synthesis, characterization, and magnetic properties of hematite particles in a peculiar “nanomedusa” morphology. The particles were prepared from an iron-silica complex by a hydrothermal process in a solution consisting of ethyl acetate and ethanol. The particles’ morphology, structure, and chemical composition were investigated by transmission electron microscopy, powder X-ray diffraction, and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. The “hairy” particles consist of a spherical-like core of about 100 nm diameter and fibrous exterior composed of thin “legs” of 5 nm diameter grown along one preferential direction. The particles’ cores are crystalline and undergo a magnetic phase transition to a weakly ferromagnetic state at a temperature of 930K thatmatches reasonably the N´eel temperature of bulk hematite. However, unlike bulk hematite that undergoesMorin transition to an antiferromagnetic state around room temperature and small hematite nanoparticles that are superparamagnetic, the “nanomedusa” particles remain weakly ferromagnetic down to the lowest investigated temperature of 2K. Each particle thus represents a nanodimensional “hairy” ferromagnet in a very broad temperature interval, extending much above the room temperature. Such high-temperature ferromagnetic nanoparticles are not frequently found among the nanomaterials

Transparenz und Evaluierbarkeit des erziehungswissenschaftlichen Publikationsaufkommens. Eine anwendungsorientierte Studie

Der Beitrag stellt Ziele und erste Ergebnisse des DFG-Projekts "Innovative bibliometrische Verfahren zur kontinuierlichen Beobachtung der sozialwissenschaftlichen Forschungsproduktion" vor. Eine Analyse des Publikationsverhaltens von Erziehungswissenschaftlern zeigt die große Bedeutung des Publikationstyps Sammelwerksbeitrag und der Publikationssprache Deutsch, aber auch eine ausgeprägte Heterogenität in der Publikationspraxis von erziehungswissenschaftlichen Institutionen. Skizziert wird schließlich der Vorschlag für einen neuen, dieser Publikationspraxis angemessenen, bibliometrischen Indikator. (DIPF/Autor

Electronic transport properties of the Al0.5TiZrPdCuNi alloy in the high-entropy alloy and metallic glass forms

High-entropy alloys (HEAs) are characterized by a simultaneous presence of a crystal lattice and an amorphous-type chemical (substitutional) disorder. In order to unravel the effect of crystal-glass duality on the electronic transport properties of HEAs, we performed a comparative study of the electronic transport coefficients of a 6-component alloy Al0.5TiZrPdCuNi that can be prepared either as a HEA or as a metallic glass (MG) at the same chemical composition. The HEA and the MG states of the Al0.5TiZrPdCuNi alloy both show large, negative-temperature-coefficient resistivity, positive thermopower, positive Hall coefficient and small thermal conductivity. The transport coefficients were reproduced analytically by the spectral conductivity model, using the Kubo-Greenwood formalism. For both modifications of the material (HEA and MG), contribution of phonons to the transport coefficients was found small, so that their temperature dependence originates predominantly from the temperature dependence of the Fermi-Dirac function and the variation of the spectral conductivity and the related electronic density of states with energy within the Fermi-level region. The very similar electronic transport coefficients of the HEA and the MG states point towards essential role of the immense chemical disorder

Nadciśnienie tętnicze u kobiet w ciąży — związek z wykonywaną pracą zawodową

Background Hypertension during pregnancy is associated with an increased risk of complications in the mother, fetus and newborn. The aim of this study was to assess the prevalence of hypertension in a selected population of pregnant women of Lower Silesia in relation to the type of occupational work performed by women. Material and methods We analyzed 6343 medical history of pregnant women who gave birth in the Clinic of Gynecology and Obstetrics, Wroclaw Medical University in 2004–2009. We analyzed also the relationship between the profession performed by mother and state of newborn health. Results The percentage of pregnant women diagnosed with hypertension was 7% of the studied population. The largest professional group of pregnant women with hypertension were the saleswomen or cashiers (13.2%), economists (10.1%) and clerks (10.1%). Two reasons may affect the incidence of hypertension in pregnancy: a coexistence a various psycho-physical factors (stress) in the workplace, and work with display screen. A statistically significant effect of the use of hypotensive pharmacotherapy or the mother’s occupational category on the birth weight infants was demonstrated. Conclusions Hypertension in pregnancy appears more frequently among women in certain professions. Greater protection should be extended to pregnant women employed in positions such as clerk or cashier. Also fetal hypotrophia may be related to the profession performed by a pregnant woman. Working using a display screen may be a factor associated with low birth weight newborn. An effect of occupational factors on the health of pregnant women and their newborns needs further investigation. Arterial Hypertension 2011, vol. 15, no 5, pages 290–298Wstęp Nadciśnienie tętnicze w okresie ciąży jest związane ze zwiększonym ryzykiem wystąpienia powikłań u matki, płodu i noworodka. Celem pracy była ocena częstości występowania nadciśnienia tętniczego w wybranej populacji kobiet w ciąży Dolnego Śląska i określenie związku między występowaniem tej patologii i rodzajem wykonywanej pracy zawodowej. Materiał i metody Analizie poddano 6343 historie chorób kobiet w ciąży, które urodziły dzieci w I Klinice Ginekologii i Położnictwa Akademii Medycznej we Wrocławiu w latach 2004–2009. Oszacowano częstość występowania nadciśnienia tętniczego w ciąży i zastosowania terapii hipotensyjnej. Dokonano oceny związku między występowaniem nadciśnienia w ciąży i zawodem matki, a także analizowano związek między zawodem wykonywanym przez matkę i stanem zdrowia noworodka. Wyniki Odsetek kobiet z nadciśnieniem w ciąży wynosił 7% badanej populacji. Najliczniejsze grupy zawodowe kobiet w ciąży z nadciśnieniem stanowiły ekspedientki lub kasjerki (13,2%), ekonomistki (10,1%) i urzędniczki (10,1%). Wyniki analizy wskazują na dwie przyczyny, które mogą mieć wpływ na występowanie nadciśnienia w ciąży: zespół czynników psychofizycznych (stres) na stanowisku pracy oraz praca przy monitorze ekranowym. Wykazano statystycznie istotny wpływ stosowania hipotensyjnej farmakoterapii oraz kategorii zawodowej matki na urodzeniową masę ciała noworodków. Wnioski Nadciśnienie tętnicze w czasie ciąży występuje częściej w grupie kobiet wykonujących określone zawody. Większą ochroną należy objąć kobiety zatrudnione na stanowiskach takich jak ekspedientka czy kasjerka. Także hipotrofia płodu może mieć związek z zawodem wykonywanym przez kobietę w ciąży. Praca przy monitorze ekranowym może być czynnikiem związanym z niską urodzeniową masą ciała noworodka. Określenie wpływu czynników zawodowych na stan zdrowia kobiet w ciąży wymaga dalszych badań. Nadciśnienie Tętnicze 2011, tom 15, nr 5, strony 290–29

Structure and superconductivity of tin-containing hftizrsnm (M = cu, fe, nb, ni) medium-entropy and high-entropy alloys

In an attempt to incorporate tin (Sn) into high-entropy alloys composed of refractory metals Hf, Nb, Ti and Zr with the addition of 3d transition metals Cu, Fe, and Ni, we synthesized a series of alloys in the system HfTiZrSnM (M = Cu, Fe, Nb, Ni). The alloys were characterized crystallographically, microstructurally, and compositionally, and their physical properties were determined, with the emphasis on superconductivity. All Sn-containing alloys are multi-phase mixtures of intermetallic compounds (in most cases four). A common feature of the alloys is a microstructure of large crystalline grains of a hexagonal (Hf, Ti, Zr)5Sn3 partially ordered phase embedded in a matrix that also contains many small inclusions. In the HfTiZrSnCu alloy, some Cu is also incorporated into the grains. Based on the electrical resistivity, specific heat, and magnetization measurements, a superconducting (SC) state was observed in the HfTiZr, HfTiZrSn, HfTiZrSnNi, and HfTiZrSnNb alloys. The HfTiZrSnFe alloy shows a partial SC transition, whereas the HfTiZrSnCu alloy is non-superconducting. All SC alloys are type II superconductors and belong to the Anderson class of “dirty” superconductors

The effect of surface oxidation on the catalytic properties of Ga3Ni2 intermetallic compound for carbon dioxide reduction

Background: In a routine handling of a catalyst material, exposure to air can usually not be avoided. For noble metal catalysts that are resistant to oxidation, this is not an issue, but becomes important for intermetallic catalysts composed of two or more non-noble chemical elements that possess much different standard enthalpies of the oxide formation. The element with higher affinity to oxygen concentrates on the surface in the oxide form, whereas the element with lower affinity sinks into the subsurface region. This changes the number of active sites and the catalytic performance of the catalyst. We have investigated the instability of the surface composition to oxidation of the Ga3Ni2 noble metal-free intermetallic compound, a new catalyst for the CO2 reduction to CO, CH4 and methanol. Methods: The instability of the oxidized Ga3Ni2 surface composition to different heating-annealing conditions was studied by X-ray photoelectron spectroscopy (XPS), used to determine the elemental composition and the chemical bonding in the near-surface region. The dispersion of active sites available for the chemisorption of H-2 and CO on the Ga3Ni2 catalyst surface was determined by H-2 and CO temperature-programmed desorption. CO2 conversion experiments were performed by using the catalyst material reduced in hydrogen at temperatures of 300 and 600 degrees C. Results: XPS study of the Ga3Ni2 surface subjected to different heating-annealing conditions has revealed that the concentration of Ga at the oxidized surface is strongly enhanced and the concentration of Ni is strongly depleted with respect to the values in the bulk. By annealing the surface at 600 degrees C in ultra-high vacuum, the oxides have evaporated and thermal diffusion of atoms near the surface has partially reconstructed the surface composition towards the energetically more favorable bulk value, whereas annealing at a lower temperature of 300 degrees C was ineffective to change the surface composition. Catalytic tests were in agreement with the XPS results, where an increased CO2 conversion for the catalyst reduced with hydrogen at a higher temperature followed an increased Ni/Ga surface concentration ratio. Conclusions: The instability of the active surface chemical composition to oxidation in air must be taken into account when considering noble metal-free intermetallic catalysts as alternatives to the conventional catalysts based on noble metals. Ga3Ni2 and other Ga-Ni intermetallic compounds are good examples of binary intermetallic catalysts, whose catalytic performance is strongly affected by exposure to the air