Intercalation effect on hyperfine parameters of Fe in FeSe superconductor with Tc = 42 K

57Fe-Mossbauer spectra of superconducting beta-FeSe, the Li/NH3 intercalate product and a subsequent sample of this intercalate treated with moist He gas have been measured in temperature range 4.7 - 290 K. A correlation is established between hyperfine parameters and critical temperature Tc in these phases. A strong increase of isomer shift upon intercalation is explained by a charge transfer from the Li/NH3 intercalate to the FeSe layers resulting in an increase of Tc up to 42 K. A significant decrease of the quadrupole splitting above 240 K has been attributed to diffusive motion of Li+ ions within the interlamellar space.Comment: 6 pages, 5 figures, 1 tabl

Editors\u27 Choice—Understanding Chemical Stability Issues between Different Solid Electrolytes in All-Solid-State Batteries

Sulfide-based solid electrolytes (SE) are quite attractive for application in all-solid-state batteries (ASSB) due to their high ionic conductivities and low grain boundary resistance. However, limited chemical and electrochemical stability demands for protection on both cathode and anode side. One promising concept to prevent unwanted reactions and simultaneously improve interfacial contacting at the anode side consists in applying a thin polymer film as interlayer between Li metal and the SE. In the present study, we investigated the combination of polyethylene oxide (PEO) based polymer films with the sulfide-based SE Li10SnP2S12 (LSPS). We analyzed their compatibility using both electrochemical and chemical techniques. A steady increase in the cell resistance during calendar aging indicated decomposition reactions at the interfaces. By means of X-ray photoelectron spectroscopy and further analytical methods, the formation of polysulfides, P–[S]n–P like bridged PS43− units and sulfite, SO32−, was demonstrated. We critically discuss potential reasons and propose a plausible mechanism for the degradation of LSPS with PEO. The main objective of this paper is to highlight the importance of understanding interfaces in ASSBs not only from an electrochemical perspective, but also from a chemical point of view

Slurry-Based Processing of Solid Electrolytes: A Comparative Binder Study

Limited energy density of today\u27s Li-ion battery technologies demands for novel cell technologies, such as the all-solid-state battery (ASSB). In order to achieve high energy densities and enable large-scale processing, thin and flexible solid electrolyte (SE) layers have to be implemented. This study focuses on slurry-based processing of the sulfidic solid electrolyte Li$_{10}$SnP$_{2}$S$_{12}$ (LSPS). Various polymers were investigated concerning their suitability as binders for thin and freestanding SE sheets. We conducted a parameter study in order to optimize e.g. LSPS-to-binder ratio, solids content and porosity. Significant differences were found with regard to the minimum amount of binder required for mechanically stable sheets as well as the homogeneity, density and flexibility of the resulting SE layers. The impacts of binder type and weight fraction on ionic conductivity were examined through lithium diffusion measurements. Impedance analysis was conducted in comparison, proving sufficiently high ionic conductivity for potential application of the SE sheets in ASSB. This work highlights the important role of the polymeric binder in slurry-based processing of SEs and gives an impression how important a well-considered selection of parameters is to achieve good processing properties as well as desirable features for the final SE sheet

Prototyping of automotive components with variable width and depth

Roll forming enables the manufacturing of longitudinal components from materials that combine high strength with limited formability and is increasingly used in the automotive industry for the manufacture of structural and crash components. An extension of conventional roll forming is the Flexible Roll Forming (FRF) process where the rolls are no longer fixed in space but are free to move which enables the forming of components with variable cross section over the length of the part. Even though FRF components have high weight saving potential the technology has found only limited application in the automotive industry. A new flexible forming facility has recently been developed that enables proof of concept studies and the production of FRF prototypes before a full FRF line is built; this may lead to a wider uptake of the FRF technology in the automotive industry. In this process, the pre-cut blank is placed between two clamps and the whole set up moves back and forth; a forming roll that is mounted on a servo-controlled platform with six degrees of freedom forms the pre-cut blank to the desired shape. In this study an initial forming concept for the flexible roll forming of an automotive component with variable height is developed using COPRA® FEA RF. This is followed by performing experimental prototyping studies on the new concept forming facility. Using the optical strain measurement system Autogrid Compact, material deformation, part shape and wrinkling severity are analysed for some forming passes and compared with the numerical results. The results show that the numerical model gives a good representation of material behaviour and that with increasing forming severity wrinkling issues need to be overcome in the process

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

Bamberger Federführer. Die besten Texte aus drei Jahren Literaturwettbewerb an der Universität Bamberg (2009-2011)

Im Kreise des Redaktions-Teams der studentischen Hochschulgruppe Feki.de entstand im November 2008 die Idee, einen Literaturwettbewerb an der Universität Bamberg zu etablieren. Das Projekt sollte es Studierenden aller Fachrichtungen ermöglichen, literarisch tätig zu werden und sich mit ihren Texten dem Urteil einer Jury bzw. der Leser zu stellen. Insgesamt drei Mal wurde der Wettbewerb durchgeführt: 2009 wurde die beste Kurzgeschichte zum Thema „Um 20 Uhr am Gabelmoo“ gesucht, im Jahr darauf lautete das Thema schlicht „fertig. Der letzte Wettbewerb stand schließlich unter dem Motto „Heimat“. Die Auswahl der Siegertexte übernahm eine Jury, bestehend aus Vertretern verschiedener Hochschulgruppen – Feki.de, Rezensöhnchen und Ottfried –, Prof. Dr. Andrea Bartl, Inhaberin der Professur für Neuere deutsche Literaturwissenschaft, dem Autor und Kritiker Rolf Bernhard Essig sowie wechselnd den Autoren Nora Gomringer, Kurt Kreiler und Nefvel Cumart. Daneben konnten die Feki.de-Leser über den jeweiligen Publikumspreisträger abstimmen. Neben den Studierenden der Universität Bamberg waren ab dem zweiten Jahr auch Teilnehmer der Schreibwerkstatt der JVA Ebrach eingeladen, ihre Texte einzu­senden. Im Vergleich mit den studentischen Texten boten die Beiträge der Gefangenen einen interessanten Perspektivwechsel für alle Teil­nehmer und Leser. Insgesamt 24 Kurzgeschichten aus den Jahren 2009 bis 2011 haben wir in diesem Band zusammengestellt. Neben den jeweiligen Siegertexten finden sich in der Anthologie auch die Beiträge der JVA-Bewohner zum Thema „fertig“, sowie ausgewählte Texte Studierender, die die Podestplätze nur knapp verfehlten