An Artificial Lithium Protective Layer that Enables the Use of Acetonitrile‐Based Electrolytes in Lithium Metal Batteries

The resurgence of the lithium metal battery requires innovations in technology, including the use of non‐conventional liquid electrolytes. The inherent electrochemical potential of lithium metal (?3.04 V vs. SHE) inevitably limits its use in many solvents, such as acetonitrile, which could provide electrolytes with increased conductivity. The aim of this work is to produce an artificial passivation layer at the lithium metal/electrolyte interface that is electrochemically stable in acetonitrile‐based electrolytes. To produce such a stable interface, the lithium metal was immersed in fluoroethylene carbonate (FEC) to generate a passivation layer via the spontaneous decomposition of the solvent. With this passivation layer, the chemical stability of lithium metal is shown for the first time in 1 m LiPF₆ in acetonitrile.     

Hexagonal boron nitride nanosheets as adsorbents for solid-phase extraction of polychlorinated biphenyls from water samples

The adsorptive potential of hexagonal boron nitride nanosheets (h-BNNSs) for solid-phase extraction (SPE) of pollutants was investigated for the first time. Seven indicators of polychlorinated biphenyls (PCBs) were selected as target analytes. The adsorption of PCBs on the surface of the h-BNNSs in water was simulated by the density functional theory and molecular dynamics. The simulation results indicated that the PCBs are adsorbed on the surface by π–π, hydrophobic, and electrostatic interactions. The PCBs were extracted with an h-BNNS-packed SPE cartridge, and eluted by dichloromethane. Gas chromatography–tandem mass spectrometry working in the multiple reaction monitor mode was used for the sample quantification. The effect of extraction parameters, including the flow rate, pH value, breakthrough volume, and the ionic strength, were investigated. Under the optimal working conditions, the developed method showed low limits of detection (0.24–0.50 ng L⁻¹; signal-to-noise ratio = 3:1), low limits of quantification (0.79–1.56 ng L⁻¹; signal-to-noise ratio = 10:1), satisfactory linearity (r > 0.99) within the concentration range of 2–1000 ng L⁻¹, and good precision (relative standard deviation < 12%). The PCBs concentration in environmental water samples was determined by the developed method. This results demonstrate that h-BNNSs have high analytical potential in the enrichment of pollutants.     

Asymptotic rank of spaces with bicombings

The question, under what geometric assumptions on a space X an n-quasiflat in X implies the existence of an n-flat therein, has been investigated for a long time. It was settled in the affirmative for Busemann spaces by Kleiner, and for manifolds of non-positive curvature it dates back to Anderson and Schroeder. We generalize the theorem of Kleiner to spaces with bicombings. This structure is a weak notion of non-positive curvature, not requiring the space to be uniquely geodesic. Beside a metric differentiation argument, we employ an elegant barycenter construction due to Es-Sahib and Heinich by means of which we define a Riemannian integral serving us in a sort of convolution operation.     

Surface-based molecular self-assembly: Langmuir-Blodgett films of amphiphilic Ln(III) complexes

The unique photophysical properties of the Ln(III) series has led to significant research efforts being directed towards their application in sensors. However, for “real-life” applications, these sensors should ideally be immobilised onto surfaces without loss of function. The Langmuir-Blodgett (LB) technique offers a promising method in which to achieve such immobilisation. This mini-review focuses on synthetic strategies for film formation, the effect that film formation has on the physical properties of the Ln(III) amphiphile, and concludes with examples of Ln(III) LB films being used as sensors.     

Spectral line selection for time-resolved investigations of laser-induced plasmas by an iterative Boltzmann plot method

The aim of this work is to provide a procedure to determine time-resolved electron temperatures with minimized relative errors by the Boltzmann plot method. The applied procedure consists of two parts, a systematic theoretical spectral line selection and an iterative Boltzmann plot algorithm. After a pre-selection of an appropriate non-disturbed or overlapped set of spectral lines of a particular atomic or ionic species Boltzmann plots are generated using experimentally recorded data for every time window and laser pulse energy of interest. Spectral lines with the highest average deviations from the regression function are assumed as being not representative for the considered ensemble of spectral lines and are therefore discarded gradually until a threshold value for the coefficient of determination is exceeded. Laser-induced breakdown spectroscopy (LIBS) is applied for time-resolved and spatially integrated investigations of plasmas on 1.1750 C75 steel alloy samples with laser pulse energies ranging between 200 µJ and 2 mJ. For the specific chemical composition of these samples a selection of atomic and ionic Fe spectral lines has been carried out. In spite of the fact that only laser pulse energies in the low millijoule regime are applied the final sets of spectral lines comprise in total 61 Fe I and 12 Fe II emission lines. By applying this method electron temperatures can be determined with averaged relative errors of down to 1.8% for Fe I and 4.4% for Fe II emission lines.     

Configurations in abelian categories. III. Stability conditions and identities

This is the third in a series on configurations in an abelian category A. Given a finite poset (I,?), an (I,?)-configuration(σ,ι,π) is a finite collection of objects σ(J) and morphisms ι(J,K) or in A satisfying some axioms, where J,K are subsets of I. Configurations describe how an object X in A decomposes into subobjects.The first paper defined configurations and studied moduli spaces of configurations in A, using the theory of Artin stacks. It showed well-behaved moduli stacks ObjA,MA(I,?) of objects and configurations in A exist when A is the abelian category coh(P) of coherent sheaves on a projective scheme P, or mod-KQ of representations of a quiver Q. The second studied algebras of constructible functions and stack functions on ObjA.This paper introduces (weak) stability conditions(τ,T,?) on A. We show the moduli spaces , , of τ-semistable, indecomposable τ-semistable and τ-stable objects in class α are constructible sets in ObjA, and some associated configuration moduli spaces constructible in MA(I,?), so their characteristic functions and are constructible.We prove many identities relating these constructible functions, and their stack function analogues, under pushforwards. We introduce interesting algebras of constructible and stack functions, and study their structure. In the fourth paper we show are independent of (τ,T,?), and construct invariants of A,(τ,T,?).     

Electronic excitations and spectra in single-stranded DNA

Using density functional theory and molecular dynamics simulations, we show that delocalized states extending over three bases can be directly excited in single-stranded poly(A) DNA. The results are in semiquantitative agreement with recent experimental results for the delocalization length of these states in single- and double-stranded DNA. The structures used in these molecular dynamics calculations are validated by comparing calculated circular dichroic spectra for d(A)2 and d(A)4 with experiment. These spectra, which arise from highly stacked structures, are in good agreement with experiment, suggesting that the short delocalization in ssDNA arises in spite of strong stacking.     

Microscopic localisation of protoporphyrin IX in normal mouse skin after topical application of 5-aminolevulinic acid or methyl 5-aminolevulinate

Light fractionation does not enhance the response to photodynamic therapy (PDT) after topical methyl-aminolevulinate (MAL) application, whereas it is after topical 5-aminolevulinic acid (ALA). The differences in biophysical and biochemical characteristics between MAL and ALA may result in differences in localisation that cause the differences in response to PDT. We therefore investigated the spatial distribution of protoporphyrin IX (PpIX) fluorescence in normal mouse skin using fluorescence microscopy and correlated that with the PDT response histologically observed at 2.5, 24 and 48h after PDT. As expected high fluorescence intensities were observed in the epidermis and pilosebaceous units and no fluorescence in the cutaneous musculature after both MAL and ALA application. The dermis showed localised fluorescence that corresponds to the cytoplasma of dermal cells like fibroblast and mast cells. Spectral analysis showed a typical PpIX fluorescence spectrum confirming that it is PpIX fluorescence. There was no clear difference in the depth and spatial distribution of PpIX fluorescence between the two precursors in these normal mouse skin samples. This result combined with the conclusion of Moan et al. that ALA but not MAL is systemically distributed after topical application on mouse skin [Moan et al., Pharmacology of protoporphyrin IX in nude mice after application of ALA and ALA esters, Int. J. Cancer 103 (2003) 132-135] suggests that endothelial cells are involved in increased response of tissues to ALA-PDT using light fractionation. Histological analysis 2.5h after PDT showed more edema formation after ALA-PDT compared to MAL-PDT that was not accompanied by a difference in the inflammatory response. This suggests that endothelial cells respond differently to ALA and MAL-PDT. Further investigation is needed to determine the role of endothelial cells in ALA-PDT and the underlying mechanism behind the increased effectiveness of light fractionation using a dark interval of 2h found after ALA but not after MAL-PDT.