Today, it is proven that the contaminated urban soils are hazardous for the human health. Soil substrates of playgrounds call for special research as they are places where children are directly ...exposed to soil contaminants. Therefore, the objective of this work was to measure the pseudo-total contents and bioaccessibility of several metals and metalloids (As, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, V, Zn) in two grain sizes (< 150 μm and < 50 μm) of playground soils in Bratislava city (the capital of Slovakia). The content of metal(loid)s in the soils was controlled by a number of factors, with their increased contents (above 75% percentile or higher) at sites influenced by point sources of pollution (industry and agriculture) or at old sites located in the city centre. Cobalt, Cr, Fe, Mn, Ni and V had relatively uniform contents in soils compared to the other elements. As regression modelling with a categorical variable confirmed, the age of urban areas influenced the accumulation of As, Bi, Cd, Cu, Hg, Pb, Sb and Sn in playground soils. Exploratory statistical techniques with compositionally transformed data (principal component analysis, cluster analysis and construction of symmetric coordinates for correlation analysis) divided trace elements into the two main groupings, Co, Cr, Fe, Mn, Ni, V and Bi, Cd, Cu, Hg, Pb, Sb, Sn, Zn. Median concentrations of the elements in smaller soil grains (< 50 μm) were significantly higher than in coarser grains (< 150 μm). Cobalt, Cu, Mn, Pb, Sn and Zn had significantly higher bioaccessible proportions (% of the pseudo-total content) in < 50 μm soil size than in < 150 μm; however, the same order of bioaccessibility was achieved in both grain sizes. The highest bioaccessibility had Cd, Cu, Pb and Zn (~ 40% and more), followed by Co, As, Mn, Sb (18–27%), Hg, Ni, Sn (10–12%) and finally Cr, Fe and V (less than 4%). The hazard index and carcinogenic risk values were higher in < 50 μm than in < 150 μm and significantly decreased in the two soil sizes when the bioaccessibility results were included in the health hazard calculation.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Topological photonics, featured by stable topological edge states resistant to perturbations, has been utilized to design robust integrated devices. Here, we present a study exploring the intriguing ...topological rotated Weyl physics in a 3D parameter space based on quaternary waveguide arrays on lithium niobate-on-insulator (LNOI) chips. Unlike previous works that focus on the Fermi arc surface states of a single Weyl structure, we can experimentally construct arbitrary interfaces between two Weyl structures whose orientations can be freely rotated in the synthetic parameter space. This intriguing system was difficult to realize in usual 3D Weyl semimetals due to lattice mismatch. We found whether the interface can host gapless topological interface states or not is determined by the relative rotational directions of the two Weyl structures. In the experiment, we have probed the local characteristics of the TISs through linear optical transmission and nonlinear second harmonic generation. Our study introduces a novel path to explore topological photonics on LNOI chips and various applications in integrated nonlinear and quantum optics.
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Topological Dirac and Weyl semimetals have an energy spectrum that hosts Weyl nodes appearing in pairs of opposite chirality. Topological stability is ensured when the nodes are separated in momentum ...space and unique spectral and transport properties follow. In this work, we study the effect of a space-dependent Weyl node separation, which we interpret as an emergent background axial-vector potential, on the electromagnetic response and the energy spectrum of Weyl and Dirac semimetals. This situation can arise in the solid state either from inhomogeneous strain or nonuniform magnetization and can also be engineered in cold atomic systems. Using a semiclassical approach, we show that the resulting axial magnetic field B5 is observable through an enhancement of the conductivity as σ∼B52 due to an underlying chiral pseudomagnetic effect. We then use two lattice models to analyze the effect of B5 on the spectral properties of topological semimetals. We describe the emergent pseudo-Landau-level structure for different spatial profiles of B5 , revealing that (i) the celebrated surface states of Weyl semimetals, the Fermi arcs, can be reinterpreted as n=0 pseudo-Landau levels resulting from a B5 confined to the surface, (ii) as a consequence of position-momentum locking, a bulk B5 creates pseudo-Landau levels interpolating in real space between Fermi arcs at opposite surfaces, and (iii) there are equilibrium bound currents proportional to B5 that average to zero over the sample, which are the analogs of bound currents in magnetic materials. We conclude by discussing how our findings can be probed experimentally.
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Recent discoveries of topological phases realized in electronic states in solids have revealed an important role of topology, which ubiquitously appears in various materials in nature. Many ...well-known materials have turned out to be topological materials, and this new viewpoint of topology has opened a new horizon in material science. In this paper, we find that electrides are suitable for achieving various topological phases, including topological insulating and topological semimetal phases. In the electrides, in which electrons serve as anions, the bands occupied by the anionic electrons lie near the Fermi level, because the anionic electrons are weakly bound by the lattice. This property of the electrides is favorable for achieving band inversions needed for topological phases, and, thus, the electrides are prone to topological phases. From such a point of view, we find many topological electrides,Y2Cnodal-line semimetal (NLS),Sc2C(insulator with aπZak phase),Sr2Bi(NLS), HfBr (quantum spin Hall system), and LaBr (quantum anomalous Hall insulator), by using ab initio calculation. The close relationship between the electrides and the topological materials is useful in material science in both fields.
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We study the effect of long-ranged interactions on Weyl semimetals. Such interactions can give rise to unpaired Weyl nodes, which we demonstrate by explicitly constructing a system with just a single ...node-a situation that is fundamentally forbidden by fermion doubling in noninteracting band structures. Adding a magnetic field, we investigate the fate of the chiral anomaly. Remarkably, as long as a system exhibits a single Weyl node in the absence of magnetic fields, arbitrarily weak fields qualitatively restore the lowest Landau level structure of a noninteracting Weyl semimetal. This underlines the universality of the chiral anomaly in the context of Weyl semimetals. We furthermore demonstrate how the topologically protected Fermi-arc surface states are modified by long-ranged interactions.
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Using the Kubo formalism we have calculated the local dynamic conductivity of a bulk, i.e., three-dimensional (3D), Dirac semimetal (BDS). We obtain that at frequencies lower than Fermi energy the ...metallic response in a BDS film manifests in the existence of surface-plasmon polaritons, but at higher frequencies the dielectric response is dominated and it occurs that a BDS film behaves as a dielectric waveguide. At this dielectric regime we predict the existence inside a BDS film of novel electromagnetic modes, a 3D analog of the transverse electric waves in graphene. We also find that the dielectric response manifests as the wide-angle passband in the mid-infrared (IR) transmission spectrum of light incident on a BDS film, which can be used for the interferenceless omnidirectional mid-IR filtering. The tuning of the Fermi level of the system allows us to switch between the metallic and the dielectric regimes and to change the frequency range of the predicted modes. This makes BDSs promising materials for photonics and plasmonics.
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Understanding the metal and metalloid contamination and microbiota composition of pig feces is an important step required to support the design and implementation of effective pollution control and ...prevention strategies. A survey was implemented in 12 locations across China to investigate the content of metals and metalloids, and the main composition of the microbial communities of commercially reared pigs during two growth periods, defined as the early (Q group) and the later fattening growth phases (H group). These data showed widespread Al, Mn, Cu, Zn, and Fe pollution in pig feces. The concentration of Zn in the Q group feces was nearly two times higher than the levels measured in the H group. The microbial composition of the Q group exhibited greater richness of operational taxonomic units (OTUs) and fewer bacteria associated with zoonotic diseases compared with the microbial composition of the H group. Spearman rank correlation analysis showed that Cu and northern latitudes had a significant positive effect on the richness of bacterial communities in pig feces. Zn and Cd exhibited the biggest impact on microbial community composition based on canonical correspondence analysis. Functional metagenomic prediction indicated that about 0.8% genes present in the pig feces bacteria community are related to human diseases, and significantly more predicted pathogenic genes were detected in the H group than in the Q group. These results support the need to monitor heavy metal contamination and to control for zoonotic pathogens disseminated from pig feces in Chinese pig farms.
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•50% of global pig production is in China.•Waste is often used for fertilizer.•Al, Mn, Cu, Zn, and Fe pollution were frequently detected in pig feces.•Feces from pigs in the fattening stage contained more bacteria and disease genes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We identify an unusual mechanism for quantum oscillations in nodal semimetals, driven by a single pair of Landau levels periodically closing their gap at the Fermi energy as a magnetic field is ...varied. These "zero Landau level" quantum oscillations (ZQOs) appear in the nodal limit where the zero-field Fermi volume vanishes and have distinctive periodicity and temperature dependence. We link the Landau spectrum of a two-dimensional (2D) nodal semimetal to the Rabi model, and show by exact solution that, across the entire Landau fan, pairs of opposite-parity Landau levels are intertwined in a "serpentine" manner. We propose 2D surfaces of topological crystalline insulators as natural settings for ZQOs. In certain 3D nodal semimetals, ZQOs lead to oscillations of anomaly physics. We propose a transport measurement capable of observing such oscillations, which we demonstrate numerically.
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We study Josephson junctions based on inversion-asymmetric but time-reversal symmetric Weyl semimetals under the influence of Zeeman fields. We find that, due to distinct spin textures, the Weyl ...nodes of opposite chirality respond differently to an external magnetic field. Remarkably, a Zeeman field perpendicular to the junction direction results in a phase shift of opposite sign in the current-phase relations of opposite chirality. This leads to a finite chirality Josephson current (CJC) even in the absence of a phase difference across the junction. This feature could allow for applications in chiralitytronics. In the long junction and zero temperature limit, the CJC embodies a novel quantum anomaly of Goldstone bosons at π phase difference which is associated with a Z_{2} symmetry at low energies. It can be detected experimentally via an anomalous Fraunhofer pattern.
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The As
binding of two NTA-based tripodal pseudopeptides, possessing three cysteine (ligand
) or d-penicillamine residues (ligand
) as potential coordinating groups for soft semimetals or metal ions, ...was studied by experimental (UV, CD, NMR, and ESI-MS) and theoretical (DFT) methods. All of the experimental data, obtained with the variation of the As
:ligand concentration ratios or pH values in some instances, evidence the exclusive formation of species with an AsS
-type coordination mode. The UV-monitored titration of the ligands with arsenous acid at pH = 7.0 provided an absorbance data set that allowed for the determination of apparent stability constants of the forming species. The obtained stabilities (log
' = 5.26 (As
) and log
' = 3.04 (As
)) reflect high affinities, especially for the sterically less restricted cysteine derivative. DFT calculated structures correlate well with the spectroscopic results and, in line with the
H NMR data, indicate a preference for the all-
conformers resembling the As
environment at the semimetal binding sites in various metalloproteins.
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