Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides Li1–x_{1–x}Fex_x(OH)Fe1–y_{1–y}Se

Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li$_{1–x}$Fex(OH)Fe$_{1–y}$Se (x$\sim$0.2; 0.02 < $y$ < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low ($y$ < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li$_{1–x}$Fe$_x$(OH) reservoir layer to fill vacancies in the selenide layer

Overexpression of hepatoma-derived growth factor in melanocytes does not lead to oncogenic transformation

<p>Abstract</p> <p>Background</p> <p>HDGF is a growth factor which is overexpressed in a wide range of tumors. Importantly, expression levels were identified as a prognostic marker in some types of cancer such as melanoma.</p> <p>Methods</p> <p>To investigate the presumed oncogenic/transforming capacity of HDGF, we generated transgenic mice overexpressing HDGF in melanocytes. These mice were bred with mice heterozygous for a defective copy of the Ink4a tumor suppressor gene and were exposed to UV light to increase the risk for tumor development both genetically and physiochemically. Mice were analyzed by immunohistochemistry and Western blotting. Furthermore, primary melanocytes were isolated from different strains created.</p> <p>Results</p> <p>Transgenic animals overexpressed HDGF in hair follicle melanocytes. Interestingly, primary melanocytes isolated from transgenic animals were not able to differentiate <it>in vitro </it>whereas cells isolated from wild type and HDGF-deficient animals were. Although, HDGF^-/-/Ink4a^+/-mice displayed an increased number of epidermoid cysts after exposure to UV light, no melanomas or premelanocytic alterations could be detected in this mouse model.</p> <p>Conclusions</p> <p>The results therefore provide no evidence that HDGF has a transforming capacity in tumor development. Our results in combination with previous findings point to a possible role in cell differentiation and suggest that HDGF promotes tumor progression after secondary upregulation and may represent another protein fitting into the concept of non-oncogene addiction of tumor tissue.</p

Diffusion mechanism in the superionic conductor Li 4 PS 4 I studied by first-principles calculations

Li_4PS_4I was recently discovered as a novel crystalline lithium ion conductor by applying a soft chemistry approach. It adopts a tetragonal structure type suggesting a three-dimensional migration pathway favorable for a high conductivity [S.J. Sedlmaier, Chem. Mater. 29 (2017) 1830]. Especially in view of the highly connected pathways for Li motion within a simple anion sublattice formed by PS_[4]^[3-] and iodine anions, the conductivity measured from both impedance spectroscopy and NMR data appears to be rather small, and a negative influence of impurities and of grain boundaries effects was assumed. In order to shed light on the full potential of this material, we performed a theoretical study of Li_4PS_4I in the framework of density functional theory. After creating a structural model that accurately accounts for the partial occupancies determined by diffraction experiments, we performed molecular dynamics simulations, unraveled the diffusion mechanisms and calculated diffusion coefficients and the activation barrier for diffusion. The results of the theoretical study on both a crystalline and a glassy supercell imply that Li_4PS_4I is in fact a superionic conductor with a much higher conductivity than reported so far