Induced Anisotropies in NiCo Obliquely Deposited Films and Their effect on Magnetic Domains

English Article: Oblique and in-plane anisotropies in obliquely evaporated NiCo thin films were investigated in order to understand their origin. All the compositions studied clearly show the effect of columnar grain morphology coupled with some intrinsic factors such as magnetostriction and crystallinity. Energy calculations are undertaken to explain the effect of

Initial growth of Ba on Ge(001): An STM and DFT study

An ordered alkaline-earth submonolayer on a clean Si(001) surface provides a template for growth of the atomically sharp, crystalline Si-oxide interface that is ubiquitous in the semiconductor device industry. It has been suggested that submonolayers of Sr or Ba on Ge(001) could play a similar role as on structurally identical Si(001), overcoming known limitations of the Ge(001) substrate such as amorphization of its oxidation layers. In this paper the initial stage of the Ba oxidation process, i.e., adsorption and organization of Ba atoms on the Ge(001) surface as a function of temperature (270−770 K) for coverage 1.0 monolayer (ML) and 0.15−0.4 ML, is studied using scanning tunneling microscopy (STM) and density functional theory (DFT). Three types of features have been identified on the Ba-covered Ge(001) surface. They originate from isolated Ba adatoms, isolated Ba ad-dimers, and the Ba ad-dimers assembled into short-range, randomly distributed chains that run across the Ge dimer rows. We find from both STM measurements and DFT calculations that the latter is the dominant structure on Ge(001) with increasing coverage

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Higher order reconstructions of the Ge(001) surface induced by a Ba layer

Structural properties of Ba-induced reconstructions on a Ge(001) surface, based on atomic-resolution ultra high-vacuum scanning tunneling microscopy measurements, are discussed. It is shown that while the Ba - Ge layer, which fully covers the surface, is dominated by a phase with an internal 2 × 3 periodicity, it also includes portions of higher order 2 × 6 and 4 × 3 surface reconstructions, always accompanied by 1D protrusions embedded into the dominating phase. Modelling the observed higher order structures, using the elementary cell of the 2 × 3 phase calculated within the density functional theory, is shown to reproduce the experimental data very well. As such the higher order reconstructions can be treated as local defects of the dominating 2 × 3 phase

STM and DFT study on formation and characterization of Ba-incorporated phases on a Ge(001) surface

We characterize the incorporation of Ba adatoms into the Ge(001) surface, resulting in the formation of one-dimensional structures with an internal 2×3 periodicity, after the deposition of Ba atoms at 970 K or at room temperature followed by a 770 K anneal. Scanning tunneling microscopy (STM) data were compared with theoretically simulated STM images generated by density functional theory electronic structure calculations. Excellent agreement between experiment and simulation was found when using an adopted structural model that assumes partial removal of the surface Ge dimers in the [1–10] surface direction and subsequent addition of a single Ba atom to the substrate second layer. Structural assignments for a number of defects observed within regions of the 2×3 reconstruction were also obtained

Measurements of natural radioactivity in the salt cavern of the Polkowice-Sieroszowice copper mine

Due to their low radioactivity background, underground physics laboratories offer a unique possibility for investigating extremely rare phenomena like proton decay, dark matter signals or neutrino physics/astrophysics related issues. The knowledge of the natural radioactivity background is essential for the success of an underground physics experiment. The following measurements of the natural radioactivity background, in the foreseen location of an underground physics laboratory in the salt layer, in the Polkowice–Sieroszowice copper mine are presented: concentration of natural radio-isotopes from in situ obtained gamma-ray spectra and from alpha spectroscopy of rock samples, radon concentration in the air and the dose determination

On the measurement uncertainty of microdosimetric quantities using diamond and silicon microdosimeters in carbon-ion beams

Purpose: The purpose of this paper is to compare the response of two different types of solid-state microdosimeters, that is, silicon and diamond, and their uncertainties. A study of the conversion of silicon microdosimetric spectra to the diamond equivalent for microdosimeters with different geometry of the sensitive volumes is performed, including the use of different stopping power databases. Method: Diamond and silicon microdosimeters were irradiated under the same conditions, aligned at the same depth in a carbon-ion beam at the MedAustron ion therapy center. In order to estimate the microdosimetric quantities, the readout electronic linearity was investigated with three different methods, that is, the first being a single linear regression, the second consisting of a double linear regression with a channel transition and last a multiple linear regression by splitting the data into odd and even groups. The uncertainty related to each of these methods was estimated as well. The edge calibration was performed using the intercept with the horizontal axis of the tangent through the inflection point of the Fermi function approximation multi-channel analyzer spectrum. It was assumed that this point corresponds to the maximum energy difference of particle traversing the sensitive volume (SV) for which the residual range difference in the continuous slowing down approximation is equal to the thickness of the SV of the microdosimeter. Four material conversion methods were explored, the edge method, the density method, the maximum-deposition energy method and the bin-by-bin transformation method. The uncertainties of the microdosimetric quantities resulting from the linearization, the edge calibration and the detectors thickness were also estimated. Results: It was found that the double linear regression had the lowest uncertainty for both microdosimeters. The propagated standard (k = 1) uncertainties on the frequency-mean lineal energy y¯F${\bar{y}}_{\rm{F}}$ and the dose-mean lineal energy y¯D${\bar{y}}_{\rm{D}}$ values from the marker point, in the spectra, in the plateau were 0.1% and 0.2%, respectively, for the diamond microdosimeter, whilst for the silicon microdosimeter data converted to diamond, the uncertainty was estimated to be 0.1%. In the range corresponding to the 90% of the amplitude of the Bragg Peak at the distal part of the Bragg curve (R90 ) the uncertainty was found to be 0.1%. The uncertainty propagation from the stopping power tables was estimated to be between 5% and 7% depending on the method. The uncertainty on the y¯F${\bar{y}}_{\rm{F}}$ and y¯D${\bar{y}}_{\rm{D}}$ coming from the thickness of the detectors varied between 0.3% and 0.5%. Conclusion: This article demonstrate that the linearity of the readout electronics affects the microdosimetric spectra with a difference in y¯F${\bar{y}}_{\rm{F}}$ values between the different linearization methods of up to 17.5%. The combined uncertainty was dominated by the uncertainty of stopping power on the edge

Hepatic ketogenic insufficiency reprograms hepatic glycogen metabolism and the lipidome

While several molecular targets are under consideration, mechanistic underpinnings of the transition from uncomplicated nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH) remain unresolved. Here we apply multiscale chemical profiling technologies to mouse models of deranged hepatic ketogenesis to uncover potential NAFLD driver signatures. Use of stable-isotope tracers, quantitatively tracked by nuclear magnetic resonance (NMR) spectroscopy, supported previous observations that livers of wild-type mice maintained long term on a high-fat diet (HFD) exhibit a marked increase in hepatic energy charge. Fed-state ketogenesis rates increased nearly 3-fold in livers of HFD-fed mice, a greater proportionate increase than that observed for tricarboxylic acid (TCA) cycle flux, but both of these contributors to overall hepatic energy homeostasis fueled markedly increased hepatic glucose production (HGP). Thus, to selectively determine the role of the ketogenic conduit on HGP and oxidative hepatic fluxes, we studied a ketogenesis-insufficient mouse model generated by knockdown of the mitochondrial isoform of 3-hydroxymethylglutaryl-CoA synthase (HMGCS2). In response to ketogenic insufficiency, TCA cycle flux in the fed state doubled and HGP increased more than 60%, sourced by a 3-fold increase in glycogenolysis. Finally, high-resolution untargeted metabolomics and shotgun lipidomics performed using ketogenesis-insufficient livers in the fed state revealed accumulation of bis(monoacylglycero)phosphates, which also accumulated in livers of other models commonly used to study NAFLD. In summary, natural and interventional variations in ketogenesis in the fed state strongly influence hepatic energy homeostasis, glucose metabolism, and the lipidome. Importantly, HGP remains tightly linked to overall hepatic energy charge, which includes both terminal fat oxidation through the TCA cycle and partial oxidation via ketogenesis