0.7-anomaly and magnetotransport of disordered quantum wires

The unexpected "0.7" plateau of conductance quantisation is usually observed for ballistic one-dimensional devices. In this work we study a quasi-ballistic quantum wire, for which the disorder induced backscattering reduces the conductance quantisation steps. We find that the transmission probability resonances coexist with the anomalous plateau. The studies of these resonances as a function of the in-plane magnetic field and electron density point to the presence of spin polarisation at low carrier concentrations and constitute a method for the determination of the effective g-factor suitable for disordered quantum wires.Comment: 4 pages, 6 figure

The SARS-CoV-2 Spike protein has a broad tropism for mammalian ACE2 proteins.

SARS Coronavirus 2 (SARS-CoV-2) emerged in late 2019, leading to the Coronavirus Disease 2019 (COVID-19) pandemic that continues to cause significant global mortality in human populations. Given its sequence similarity to SARS-CoV, as well as related coronaviruses circulating in bats, SARS-CoV-2 is thought to have originated in Chiroptera species in China. However, whether the virus spread directly to humans or through an intermediate host is currently unclear, as is the potential for this virus to infect companion animals, livestock, and wildlife that could act as viral reservoirs. Using a combination of surrogate entry assays and live virus, we demonstrate that, in addition to human angiotensin-converting enzyme 2 (ACE2), the Spike glycoprotein of SARS-CoV-2 has a broad host tropism for mammalian ACE2 receptors, despite divergence in the amino acids at the Spike receptor binding site on these proteins. Of the 22 different hosts we investigated, ACE2 proteins from dog, cat, and cattle were the most permissive to SARS-CoV-2, while bat and bird ACE2 proteins were the least efficiently used receptors. The absence of a significant tropism for any of the 3 genetically distinct bat ACE2 proteins we examined indicates that SARS-CoV-2 receptor usage likely shifted during zoonotic transmission from bats into people, possibly in an intermediate reservoir. Comparison of SARS-CoV-2 receptor usage to the related coronaviruses SARS-CoV and RaTG13 identified distinct tropisms, with the 2 human viruses being more closely aligned. Finally, using bioinformatics, structural data, and targeted mutagenesis, we identified amino acid residues within the Spike-ACE2 interface, which may have played a pivotal role in the emergence of SARS-CoV-2 in humans. The apparently broad tropism of SARS-CoV-2 at the point of viral entry confirms the potential risk of infection to a wide range of companion animals, livestock, and wildlife

Model przebudowy kości uwzględniający zmiany struktury i kształtu spowodowane trzema różnymi mechanizmami przebudowy. Przypadek kręgosłupa lędźwiowego

The paper presents a method of analysis of bone remodelling in the vicinity of implants. The authors aimed at building a model and numerical procedures which may be used as a tool in the prosthesis design process. The model proposed by the authors is based on the theory of adaptive elasticity and the lazy zone concept. It takes into consideration not only changes of the internal structure of the tissue (described by apparent density) but also surface remodelling and changes caused by the effects revealing some features of “creep”. Finite element analysis of a lumbar spinal segment with an artificial intervertebral disc was performed by means of the Ansys system with custom APDL code. The algorithms were in two variants: the so-called site-independent and site-specific. Resultant density distribution and modified shape of the vertebra are compared for both of them. It is shown that this two approaches predict the bone remodelling in different ways. A comparison with available clinical outcomes is also presented and similarities to the numerical results are pointed out.Artykuł prezentuje metodę analizy przebudowy kości w otoczeniu implantów. Celem pracy było opracowanie modelu i procedur numerycznych mogących służyć jako narzędzie wspomagające projektowanie protez. Zaproponowany przez autorów model opiera się na teorii adaptacyjnej sprężystości i koncepcji strefy martwej. Uwzględnia on nie tylko zmiany struktury wewnętrznej tkanki (opisanej przez gęstość pozorną), ale także przebudowę powierzchniową i zmiany związane z efektami wykazującymi pewne cechy “pełzania”. Przeprowadzona została analiza metodą elementów skończonych segmentu ruchowego kręgosłupa ze sztucznym krążkiem międzykręgowym z wykorzystaniem systemu Ansys i własnego kodu APDL. Algorytmy zbudowano w dwóch wariantach: tzw. niezależnym i zależnym od miejsca. Porównano uzyskane rozkłady gęstości i zmiany kształtu pokazując, że obydwa warianty przebudowę kości przewidują w różny sposób. Zaprezentowano również porównanie wyników numerycznych z badaniami klinicznymi wskazując na ich podobieństwa

Differences in Lumbar Spine Load Due to Posture and Upper Limb External Load

As the lumbar region of the spine is particularly predisposed to musculoskeletal disorders, the aim of this article was to assess lumbar spine load on the basis of an accurate model of this part of the body. The model was developed with the finite element method and the energy criterion for optimising muscle work. Computer calculations confirmed that stresses and compression forces in intervertebral discs increased with an increase in the load force and that they were significantly larger in the bent forwards posture than in the erect posture. This result clearly shows that lifting light objects and the erect posture are important elements in minimising spine load

Dynamic analysis of the chamber for testing mining devices in the explosion conditions

W artykule przedstawiono przebieg i wyniki analizy obciążeń działających na płaszcz komory ciśnieniowej przeznaczonej do badania urządzeń górniczych w atmosferach gazów palnych w warunkach wybuchu. Przeprowadzono analizę zależności maksymalnego ciśnienia wywołanego wybuchem od rodzaju mieszanin gazowych i charakteru ich spalania. Określono maksymalne naprężenia występujące w płaszczu komory podczas wybuchu i wymagania wytrzymałościowe materiału konstrukcyjnego przeznaczonego do jego budowy.The article presents the course and results of the analysis of loads influencing the shell of the pressure chamber meant for testing mining devices in the combustible gas atmospheres in the explosion conditions. The analysis of the dependence of maximum pressure caused by the explosion on the type of gaseous mixtures and the character of their combustion was carried out. The maximum stresses occurring in the chamber's shell during the explosion and resistance requirements of the engineering material meant for building the shell were determined

Design and verification of a non-self-supported cryostat for the DEMO tokamak

The paper presents a conceptual design and its structural verification of the cryostat for the DEMOnstration Fusion Reactor (DEMO). The cryostat is a large pressure vessel providing the vacuum required to operate the superconducting coils at cryogenic temperatures. Cryostats of existing machines typically are cylindrical and self-support the external pressure. In a nuclear machine, like DEMO, a massive bioshield will enclose the reactor providing radiological protection to maintenance areas in the primary building. The proposed design makes use of the bioshield to support the cryostat which allows substantially reducing the amount of steel needed for its construction. The cryostat is a conventional pressure vessel and designed according to ASME VIII, Div. 2. Linear and nonlinear structural and thermal-structural FEM assessments show that the proposed conceptual cryostat design provides both, the required membrane strength to withstand the external pressure as well as the required flexibility to allow the thermal contraction in case of a loss of vacuum event causing the cryostat to cool down. However, the relatively thin shell is not capable of bearing any significant internal overpressure. Therefore, a rupture disk in the cryostat to release Helium into the building in case of large internal leaks of liquid Helium is required

Komputerowo wspomagane projektowanie nowego typu protezy krążka międzykręgowego

The replacement of a damaged lumbar disc by an artificial organ is still not satisfactorily solved problem of surgery. In the study, the finite element method together with CAD programs and experimental validation was used in investigations of a new type of artificial disc for lumbar spine. The present 3D parametrical FE models take into account nonhomogenous properties of tissues, contact with friction between the parts of the analysed systems, large strains and large displacements. The stress analyses were performed for the prostheses being in clinical use and for some new designs. The conclusions concern most important determinants of the mechanical quality of the intervertebral disc prosthesis.Zastąpienie lędźwiowego krążka miedzykręgowego przez protezę jest wciąż nie w pełni rozwiązanym problemem chirurgii. W pracy zastosowano metodę elementów skończonych, techniki CAD oraz metody weryfikacji eksperymentalnej do poszukiwania konstrukcji nowego typu sztucznego krążka dla odcinka lędźwiowego kręgosłupa. Prezentowane modele metody elementów skończonych uwzględniają niejednorodne właściwości tkanek, występowanie dużych deformacji oraz oddziaływania między poszczególnymi częściami analizowanej struktury. Analizy przeprowadzono dla protez stosowanych obecnie w praktyce klinicznej oraz dla kilku nowych propozycji konstrukcji. Wnioski dotyczą najważniejszych czynników o charakterze mechanicznym, które wpływają na jakość sztucznych krążków międzykręgowych

Limit analysis of W7-X critical magnet system components with consideration of material serration effect

The paper reports on finite element (FE) method analyses aiming at the determination of the static load bearing capacity of critical components in the support structure of superconducting coils of Wendelstein 7-X (W7-X). These components are made of austenitic stainless steel that at 4 K is known to exhibit instable plastic flow – the so-called serration effect, i.e. a scattering of the stress under increasing strain. This material behavior may significantly reduce the load bearing capacity of the components. The developed modeling approach uses a special procedure to simulate the serration effect in a conservative way. The expected reduction of the material properties due to the welding process is also taken into account. It is demonstrated that the models are capable to determine the limit loads for the critical components in a flexible and efficient way