Microstructural characterization and multiscale ionic conductivity in lithium and sodium-based solid state electrolytes

In order to meet the increasing need for energy storage systems in consumer devices, electric vehicles and stationary energy storage devices, the existing battery technologies are constantly being further developed. An important criterion for the performance of the battery is its energy density. Even if the cathode accounts mostly for the weight of a lithium ion battery cell, there is a promising possibility of weight saving on the anode side by replacing graphite with pure lithium metal. To this end, an electrolyte needs to be developed that is stable against the potential of the pure metal. Liquid electrolytes cannot meet this requirement and also involve safety risks as ammability. Solid-state electrolytes are supposed to enable the use of a lithium-metal electrode. Additionally, due to the scarcity of resources for lithium, sodium-based technologies are being developed for use as stationary energy storage devices. Thiophosphates feature the highest ionic conductivities among all solid electrolytes. In many cases, amorphous thiophosphates offer even higher conductivities than their crystalline analogues and their structure can differ, too. A structural investigation of amorphous compounds may not be possible with a standard X-ray analysis. However their local structure has to be enlightened so that a reproducible synthesis can take place. The solid electrolyte Na2P2S6 was synthesized via ball milling in an amorphous state with subsequent crystallization. The structure of the crystalline phase differs markedly compared to the corresponding amorphous phase. A combination of XRD-PDF analysis and 23Na/31P MAS NMR spectroscopy measurements indicate that single PS30-4 tetrahedra and corner-sharing tetrahedra are transformed to edge-sharing-tetrahedra during crystallization of amorphous Na2P2S6 to crystalline Na2P2S6. Impedance spectroscopy shows that amorphous Na2P2S6 has a conductivity of 5.710-8 S cm-1 which is three orders of magnitude higher than crystalline Na2P2S6 (2.6 10-11 S cm-1). The higher conductivity can also be recovered by ball milling crystalline Na2P2S6, inducing a reamorphization. Lithium Lanthanum Zirconium oxide (LLZO) exhibits a high ionic conductivity and stability against lithium metal and is therefore a promising candidate as solid state electrolyte. Yet, specifcations on its conductivity are often not reliable and spread widely. Attempts are made to attribute the differences in reported conductivities to the different substituents, sintering times or surface passivations. A microstructural comparison of four differently substituted samples is performed to elucidate the reasons for the different conductivities. X-ray diffraction revealed that commercial LLZO samples crystallize in the hydrogarnet structure (space group No. 220), which is described for the first time with a substituent on Zr and La sites. Ball milling of Al3+, Nb5+, Ta5+ and W6+ substituted LLZO results in a phase transformation from the garnet structure into the hydrogarnet structure with a lower symmetry. The distribution of lithium ions in the hydrogarnet structure differs from that in the garnet structure which was investigated with 6Li MAS NMR and neutron diffraction. A targeted conversion of the hydrogarnet structure into the garnet structure is proved by calcining the material at 1100 °C for 10 h. With high-temperature X-ray diffraction, an low thermal expansion of the hydrogarnet unit cell is observed in comparison to the greater expansion of the garnet unit cell. The ionic mobility of Li ions in the hydrogarnet structure is examined by means of NMR, in particular line shape analysis, relaxometry and pulsed-field gradient NMR. This combination of techniques shows that the mobility of lithium is significantly reduced on small length scales. In combination with the structural analysis, this can be traced back to the high occupancy of the Li3 position in the hydogarnet structure, blocking long-range lithium diffusion. However, it was not possible to access the long-range mobility of Li in the hydrogarnet structure (at 25 °C). Therefore, the contribution of the ceramic component to the total ionic conductivity of polymer composite electrolytes is evaluated. The question whether the long-range lithium mobility in the hydrogarnet structure is lower compared to the garnet structure is assessed without the necessity for sintering the LLZO to pellets. Impedance spectroscopy shows a conductivity of 1.2 10-6 S cm-1 for a composite electrolyte with a hydrogarnet structure and 3.4 10-6 S cm-1 for a composite electrolyte with a garnet structure. The higher Li mobility of the garnet-based composite electrolyte compared to the hydrogarnet-based electrolyte is verified with PFG-NMR measurements of the diffusion coeffcient: 6.1 10-14 m2 s-1 (garnet), resp. 1.1 10-14 m2 s-1 (hydrogarnet). The measured activation energy of dffusion is also higher in the hydrogarnet composite. The conductivity results measured with impedance spectroscopy are compared with commercial composite electrolytes; a SiO2-ceramic-polymer and a purely polymer-based electrolyte. The next step from optimizing a solid state electrolyte in terms of ionic conductivity is to look at its compatibility with the electrodes, here the cathode. It is tested whether ball milling of LLZO with the established cathode material Lithium Nickel Cobalt Manganese oxide (NCM) results in a good contact of the two materials and consequently a low Li ion diffusion barrier. The interface between LLZO and NCM is investigated by X-ray diffraction, 6Li MAS NMR and transmission electron microscopy. A model system consisting of LLZO and NCM is characterized with impedance spectroscopy for a lithium diffusion barrier sandwiched between an auxiliary electrolyte in order to separate the ionic conductivity from the electrical. An evaluation of only the ionic conductivity apart from the electrical conductivity is not possible due to the high electrical conductivity of the auxiliary electrolyte. The electrolyte Lithium Aluminum Titanium Phosphate (LATP) is examined crystallographically against the background of upscaling of the synthesis. If the process is upscaled, local inhomogeneities of the educts can be expected in a way that varying educt contents have an effect on the product. This applies especially to phosphoric acid, the concentration of which cannot be specified precisely due to its hygroscopy. A Rietveld refinement analysis against X-ray diffraction data of LATP with varying phosphoric acid content during synthesis is performed. An excess of phosphoric acid leads to the formation of AlPO4, which impedes the ionic conductivity. Insufficient phosphoric acid causes the formation LiTiOPO4. TiO2 is formed in this material after a second sintering step. The findings in this work contribute the understanding of structural changes in solid electrolytes during processing and thus contribute to the improvement of future solidstate batteries

Charakterisierung von Apoptoseprozessen während der Differenzierung von humanen neuralen VM197-Progenitorzellen in vitro

Die humane neurale VM197-Progenitorzelllinie wurde bezüglich der Interkonnektivität von Wnt-gesteuerter neuraler Zelldeterminierung und Apoptose untersucht. Die Zelldifferenzierung ging mit der Aktivierung von pro- und anti-apoptotischen Proteinen und der Zunahme apoptotischen Zellverlustes einher. Differenzierte Zellen wiesen eine geringere Apoptosesuszeptibilität gegenüber proliferierenden Zellen auf. Beta-Catenin-Spaltung und eine geringere Apoptoserate nach GSK-3ß-Inhibierung in differenzierenden Zellen deuten auf eine Interkonnektivität von kanonischem Wnt-Signalweg und Apoptose hin.The human neural VM197 progenitor cell line was studied to elucidate the interconnectivity of Wnt-driven cell determination and apoptosis. The cell differentiation was accompanied by an activation of pro- and anti-apoptotic proteins and an increase of apoptotic cell loss. Differentiated cells showed a diminished apoptosis susceptibility compared to proliferating cells. Beta-catenin cleavage and a significantly decreased apoptosis rate after the inhibition of GSK-3ß in differentiated cells indicate an interconnectivity of the canonical Wnt-signaling pathway and apoptosis

Portland Daily Press: September 28, 1876

https://digitalmaine.com/pdp_1876/1275/thumbnail.jp

Jää-rakenne-vuorovaikutuksen numeerinen mallinnus matalassa vedessä

Moving sea ice causes high loads on Arctic offshore structures when it breaks against them. Many of these structures are built in relatively shallow water, which affects the loading process. The ice breaking process in shallow water involves complex interactions between the intact ice sheet, the ice blocks formed in the process, the structure and the seabed. In this thesis, ice-structure interaction on a wide sloping structure in shallow water is studied using a 2D combined finite-discrete element method (FEM-DEM). The intact ice is modelled as a nonlinear Timoshenko beam and its fracture into smaller pieces is modelled using the cohesive crack model. The discrete element method is used for contact force calculation between the ice blocks, the structure and the seabed. In the work reported here, the inclination angle of the structure, the ice thickness and the water depth are varied to study how these parameters affect the ice rubble grounding and the ice loading process. The simulation results suggest that grounded rubble leads to higher loads on the structure than non-grounded rubble. The loads on the structure increase with thicker ice and decreasing water depth. In addition, a larger inclination angle induces higher loads on the structure throughout the simulation. The load events on the structure are related to simultaneous ride-up events of the rubble and the loads are transmitted to the structure along so-called force chains. Furthermore, the probability of overtopping increases in shallow water. The load increase and the increased probability of overtopping in shallow water are caused by the supporting effect of the seabed. Sudden load drops on the structure are related to buckling of the force chains. When the rubble is grounded, the force chains are supported from below by the seabed and form above by the rubble above. Thus they sustain more loads than force chains in non-grounded rubble.Liikkuva jää aiheuttaa suuria kuormia arktisille merirakenteille jään murtuessa rakennetta vasten. Monet näistä rakenteista ovat rakennettu matalaan veteen, mikä vaikuttaa kuormitusprosessiin. Murtumisprosessi matalassa vedessä sisältää monimutkaisia vuorovaikutuksia jäälautan, prosessissa syntyneiden jäälohkareiden, rakenteen sekä merenpohjan välillä. Tässä työssä tutkitaan jää-rakenne-vuorovaikutusta leveää kaltevaseinäistä matalan veden rakennetta vasten käyttäen kaksiulotteista yhdistettyä diskreetti- ja elementtimenetelmää (FEM-DEM). Menetelmässä ehjä jäälautta mallinnetaan epälineaarisena Timoshenko-palkkina ja sen murtuminen pienempiin osiin mallinnetaan koheesiomurtumamallia käyttäen. Kontaktivoimat jäälohkareiden, rakenteen ja merenpohjan välillä lasketaan diskreettielementtimenetelmällä. Tämän työn simulaatioissa varioidaan rakenteen kallistuskulmaa, jään paksuutta ja veden syvyyttä, jotta niiden vaikutusta jäävallin pohjautumiseen ja jään kuormitusprosessiin voitaisiin tutkia. Simulaatioiden tulokset osoittavat, että jäävallin pohjautuminen aiheuttaa suurempia kuormia rakenteella kuin kelluva jäävalli. Kuorma rakenteella kasvaa jään paksutessa ja veden syvyyden kasvaessa. Sen lisäksi suurempi rakenteen kallistuskulma johtaa suurempiin kuormiin rakenteella koko simulaation ajan. Kuormi- tustapahtumat rakenteella liittyvät jään ylösajotilanteisiin ja voima rakenteelle välittyy niin sanottua voimaketjua pitkin. Myös jään ajautuminen rakenteen päälle on todennäköisempää matalassa vedessä. Kuormien sekä jää yliajautumisen todennäköisyyden kasvaminen matalassa vedessä johtuu merenpohjan tuesta. Äkilliset kuormanpudotukset rakenteella johtuvat voimaketjun nurjahtamisesta. Kun jäävalli on pohjautunut, merenpohja tukee voimaketjua alapuolelta ja jäävalli voimaketjun päällä tukee sitä yläpuolelta

The Conformational Universe of Proteins and Peptides: Tales of Order and Disorder

Proteins represent one of the most abundant classes of biological macromolecules and play crucial roles in a vast array of physiological and pathological processes. The knowledge of the 3D structure of a protein, as well as the possible conformational transitions occurring upon interaction with diverse ligands, are essential to fully comprehend its biological function.In addition to globular, well-folded proteins, over the past few years, intrinsically disordered proteins (IDPs) have received a lot of attention. IDPs are usually aggregation-prone and may form toxic amyloid fibers and oligomers associated with several human pathologies. Peptides are smaller in size than proteins but similarly represent key elements of cells. A few peptides are able to work as tumor markers and find applications in the diagnostic and therapeutic fields. The conformational analysis of bioactive peptides is important to design novel potential drugs acting as selective modulators of specific receptors or enzymes. Nevertheless, synthetic peptides reproducing different protein fragments have frequently been implemented as model systems in folding studies relying on structural investigations in water and/or other environments.This book contains contributions (seven original research articles and five reviews published in the journal Molecules) on the above-described topics and, in detail, it includes structural studies on globular folded proteins, IDPs and bioactive peptides. These works were conducted usingdifferent experimental methods

Spatial multilevel modelling of cancer mortality in Europe

Abstract available: p. i-ii

Die Rückgewinnung von Feuchtgebieten als eine Lösung für aktuelle Umweltprobleme : Hemmnisse und Möglichkeiten

Feuchtgebiete sind Ökosysteme, die durch die Anwesenheit von Wasser, spezielle Bodenverhältnisse und eine besondere Vegetationszusammensetzung geprägt sind. Sie zählen zu den am stärksten bedrohten Ökosystemen der Erde. Im Verlauf des 20. Jahrhunderts nahm weltweit sowohl ihre Fläche als auch ihre Qualität (bezüglich Artenvielfalt etc.) stark ab. Viele von Wasser beeinflusste Flächen, v.a. in Flussauen, wurden gezielt entwässert, um sie für Siedlungen, Industrie oder wegen der fruchtbaren Böden für intensive Landwirtschaft nutzbar zu machen. Im natürlichen Zustand stellen Flächen mit Feuchtgebieten allerdings ebenfalls wertvolle ökonomische Ressourcen dar (u.a. dienen sie dem Hochwasserschutz, der Nährstoffspeicherung, Erholung und Naturschutz), so dass eine Umwandlung bzw. Degradation dieses Naturkapitals oft nicht zu einer wirklichen Steigerung der gesellschaftlichen Wohlfahrt führt. Im Rahmen der Betrachtung der Problematik der Erhaltung und der Rückgewinnung von Überschwemmungsflächen, welche im Fokus dieser Arbeit stehen, werden Flächennutzungskonflikte in Flussgebieten in Verbindung mit den Schwierigkeiten des institutionellen Rahmens deutscher Bodenmärkte untersucht. Zur Schärfung der Argumentation wird ein extremes Beispiel für die Rückgewinnung von Feuchtgebieten - der Abbruch einer Siedlung im potenziellen Überschwemmungsbereich eines Flusses - herausgegriffen. Eine abstrakte Einheitssiedlung sowie tatsächliche Umsiedlungen dienen der Ermittlung der volkswirtschaftlichen Kosten eines solchen Vorhabens, welche dann den in anderen Studien erfassten Nutzen von Feuchtgebieten gegenübergestellt werden können. Die Berechnungen zeigen, dass es schon allein unter Berücksichtigung der zum Schutz der Siedlung notwendigen Erhaltungs- und Erneuerungskosten eines Hochwasserschutzdeiches ab einem bestimmten Zeitpunkt empfehlenswert sein kann, diese Siedlung nicht weiter aufrecht zu erhalten. Der Nutzen des zu erstellenden Feuchtgebietes muss hier gar nicht bekannt sein, um eine Entscheidung zugunsten einer Absiedlung zu treffen (allerdings: starke Sensitivität gegenüber den verwendeten Diskontsätzen). Daneben kann gezeigt werden, dass ein optimaler Zeitpunkt für Abbruch bzw. Umsiedlung ermittelt werden kann, bei welchem die Differenz zwischen Nutzen und Kosten des Vorhabens maximal ist

In-medium effects in the holographic quark-gluon plasma

In this dissertation we use the gauge/gravity duality to investigate various properties of strongly coupled gauge theories, which we interpret as models for the quark-gluon plasma (QGP). In particular, we use variants of the D3/D7 setup as an implementation of the top-down approach of connecting string theory with phenomenologically relevant gauge theories. We focus on the effects of finite temperature and finite density on fundamental matter in the holographic quark-gluon plasma, which we model as the N=2 hypermultiplet in addition to the N=4 gauge multiplet of supersymmetric Yang-Mills theory. As a key ingredient we develop a setup in which we can describe vector meson spectra in the holographic plasma at finite temperature and either baryon or isospin density. The resulting spectral functions are valid for all values of quark mass and temperature. They show the expected features of meson melting at high temperatures and are in agreement with the previously derived spectra for the zero temperature and zero density limit. Moreover, we are able to give a description of in-medium effects of finite particle density which are in qualitative agreement with phenomenological models and experimental observations. The description of vector meson excitations furthermore allows for a demonstration of the splitting of their spectrum at finite isospin chemical potential. In the effort to better understand transport processes in the QGP, we then study various diffusion coefficients in the quark-gluon plasma, including their dependence on temperature and particle density. In particular, we perform a simple calculation to obtain the diffusion coefficient of baryon charge and we derive expressions to obtain the isospin diffusion coefficient. Furthermore, we make use of an effective model to study the diffusion behavior of mesons in the plasma by setting up a kinetic model. The setup we chose allows to carry out computations at weak and strong coupling which we compare in order to estimate the effects of the coupling strength on mesonic diffusion and therewith equilibration processes in the QGP. Finally, we observe the implications of finite temperature and finite baryon or isospin density on the phase structure of fundamental matter in the holographic plasma. As one consequence we find a phase transition in the baryon diffusion coefficient which vanishes at a critical value of the particle density. The critical density we quantify matches the values of the according critical densities previously found in the phase transitions of other quantities. More important, we observe a new phase transition occurring when the isospin chemical potential excesses a critical bound, which depends on the temperature of the medium. Beyond this point we observe an instability of the system under consideration. In this way we trace out the border of a new phase in the phase diagram of fundamental matter in the holographic plasma