Experimental and Theoretical Analysis of Products and Reaction Intermediates of Lithium–Sulfur Batteries

We investigated the reduction process of sulfur during cycling in a lithium–sulfur battery, correlating the output of ultraviolet–visible (UV–vis) spectroscopy and further characterization techniques with a theoretical model. The experimental setup allows carrying out UV–vis absorption measurements under argon atmosphere. The characteristic absorption bands (λ_max) of sulfur and dilithium sulfide dissolved in tetra-ethylene glycol dimethyl ether (TEGDME) are determined to be at 265 and 255 nm, respectively. Reference solutions of polysulfides diminish the λ_max in the UV region with decrease of polysulfide order. The same tendency is observed in the range between 25–75% depth of discharge (DOD), caused by a progressive reduction of polysulfides in the electrolyte. At 425 and 615 nm, absorption bands are identified in the reference polysulfide solutions and also in the electrolyte at different DOD. These bands are interpreted as the characteristic bands of S₄^2– and S₃^•–, and concentration changes of these species are determined semiquantitatively. The highest concentration of polysulfides is found at around 37% DOD (450 Ah·kg_S^–1). This was confirmed by the results of electrochemical impedance spectroscopy and computer simulations

Discovery of γ‑MnP₄ and the Polymorphism of Manganese Tetraphosphide

A new polymorph of MnP₄ was prepared by reaction of the elements via chemical vapor transport with iodine as transporting agent. The crystal structure was refined using single-crystal diffraction data (space group <i>Cc</i>, no. 9, <i>a</i> = 5.1049(8) Å, <i>b</i> = 10.540(2) Å, <i>c</i> = 10.875(2) Å, β = 93.80(2)°). The phase is called γ-MnP₄ as it is isostructural with γ-FeP₄. It is the fourth reported binary polymorph in the MnP₄ system, all of which are stacking variants of nets built with manganese and phosphorus atoms. In γ-MnP₄, there are two Mn–Mn distances (2.93 and 3.72 Å) arising from a Peierls-like distortion effectively forming Mn₂ dumbbells in the structure. Magnetic and electrical conductivity measurements show diamagnetism and a small anisotropic band gap (100–200 meV) with significantly enhanced conductivity along the crystallographic <i>a</i> axis. Calculations of the electronic and vibrational (phonon) structures show the P–P and Mn–P bonds within the nets are mainly responsible for the stability of the phase. The similar bonding motifs of the polymorphs give rise to the existence of numerous dynamically stable variants. The calculated Helmholtz energy shows the polymorph formation to be closely tied to temperature with the 6-MnP₄ structure favorable at low temperatures, the 2-MnP₄ favorable between approximately 800 and 2000 K, and 8-MnP₄ preferred at high temperatures

Possible Superhardness of CrB₄

Chromium tetraboride [orthorhombic, space group <i>Pnnm</i> (No. 58), <i>a</i> = 474.65(9) pm, <i>b</i> = 548.0(1) pm, <i>c</i> = 286.81(5) pm, and <i>R</i> value (all data) = 0.041], formerly described in space group <i>Immm</i>, was found not to be superhard, despite several theory-based prognoses. CrB₄ shows an almost temperature-independent paramagnetism, consistent with low-spin Cr^I in a metallic compound. Conductivity measurements confirm the metallic character

data_sheet_1_Nrf2 Is a Central Regulator of Metabolic Reprogramming of Myeloid-Derived Suppressor Cells in Steady State and Sepsis.PDF

<p>Arising in inflammatory conditions, myeloid-derived suppressor cells (MDSCs) are constantly confronted with intracellular and extracellular reactive oxygen species molecules and oxidative stress. Generating mice with a constitutive activation of Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) we show a pivotal role of the antioxidant stress defense for development of these immune-modulatory cells. These mice are characterized by a massive increase of splenic CD11b⁺Gr-1⁺ cells, which exhibit typical suppressive characteristics of MDSCs. Whole transcriptome analysis revealed Nrf2-dependent activation of cell cycle and metabolic pathways, which resemble pathways in CD11b⁺Gr-1⁺ MDSCs expanded by in vivo LPS exposure. Constitutive Nrf2 activation thereby regulates activation and balance between glycolysis and mitochondrial metabolism and hence expansion of highly suppressive MDSCs, which mediate protection in LPS-induced sepsis. Our study establishes Nrf2 as key regulator of MDSCs and acquired tolerance against LPS-induced sepsis.</p