Nanostrukturierte Kohlenstoff-Komposite und Ammoniumvanadate als Elektrodenmaterialien für Lithium-Ionen-Batterien

In der vorliegenden Arbeit werden physikalische und elektrochemische Eigenschaften von potentiellen Elektrodenmaterialien für Lithium-Ionen-Batterien untersucht. Die elektrochemischen Untersuchungen wurden mittels zyklischer Voltammetrie und galvanostatischer Zyklierung durchgeführt. Zur physikalischen Charakterisierung der Ausgangsmaterialien und elektrochemisch zyklierter Proben kamen Röntgendiffraktometrie, Elektronenmikroskopie und Magnetisierungsmessungen zum Einsatz. Zur Untersuchung der magnetischen Eigenschaften einzelner mikro- bis nanoskaliger Partikel wurde ein Mikro-Hall-Magnetometer aufgebaut und getestet. Die dargestellten Ergebnisse zeigen insgesamt, dass die elektrochemischen Eigenschaften von Anodenmaterialien durch Nanoskalierung in Kompositen mit Kohlenstoffmodifikationen signifikant verbessert werden können. In diesem Kontext wurden sowohl die oxidischen Konversionsverbindungen Mn3O4, MnO2, Fe2O3, CoFe2O4, ZnO und SnO2, die mit Lithium legierungsbildenden Elemente Ge und Sn als auch das Interkalationsmaterial TiO2 untersucht. Im Fall von gefüllten mehrwandigen Kohlenstoffnanoröhren (CNTs) können die reversiblen theoretischen Kapazitäten der Füllmaterialien erreicht und über mindestens 50 Zyklen erhalten werden. Die Ergebnisse von erstmalig untersuchten manganoxidisch gefüllten CNTs (Mn3O4@CNT) bestätigen insbesondere den Konversionsmechanismus im Inneren der CNTs. Auch hierarchisch strukturierte Kompositmaterialien von Kohlenstoffhohlkugeln mit MnO2- beziehungsweise SnO2-Nanopartikeln weisen durch die Beiträge der oxidischen Aktivmaterialien erhöhte spezifische Kapazitäten mit guter Zyklenstabilität auf. Untersuchungen am Kathodenmaterial NH4V3O8 zeigen, dass die reversible Ein- und Auslagerung von über zwei Li+-Ionen pro Formeleinheit über einen mehrstufigen diffusionskontrollierten Interkalationsmechanismus abläuft

Cidadania mediada : processos de democratização da política municipal no Brasil

This article discusses the notion that the persistence of &ldquo;traditional&rdquo; political practices weakens Brazil&rsquo;s democracy.Drawing on the cases of three Brazilian municipalities administered by the Workers&rsquo; Party (PT), the author examines the space between &ldquo;traditional&rdquo; and &ldquo;modern&rdquo; and argues that successful democratization does not eradicate practices such as clientelism and patronage, but it tends to incorporate and build on these traditional political elements. Moreover, the article maintains that the democratization of municipal politics is inextricably bound up with the eradication of poverty and the construction of a responsive, state-based social safety net.<br /

Filled Carbon Nanotubes as Anode Materials for Lithium-Ion Batteries

Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical conductivity and integrity of bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT) encapsulating high-capacity (here: conversion and alloying) electrode materials have a high potential for use in anode materials for lithium-ion batteries (LIB). There are two essential characteristics of filled CNT relevant for application in electrochemical energy storage: (1) rigid hollow cavities of the CNT provide upper limits for nanoparticles in their inner cavities which are both separated from the fillings of other CNT and protected against degradation. In particular, the CNT shells resist strong volume changes of encapsulates in response to electrochemical cycling, which in conventional conversion and alloying materials hinders application in energy storage devices. (2) Carbon mantles ensure electrical contact to the active material as they are unaffected by potential cracks of the encapsulate and form a stable conductive network in the electrode compound. Our studies confirm that encapsulates are electrochemically active and can achieve full theoretical reversible capacity. The results imply that encapsulating nanostructures inside CNT can provide a route to new high-performance nanocomposite anode materials for LIB.Comment: Invite

TEAD-YAP Interaction Inhibitors and MDM2 Binders from DNA-Encoded Indole-Focused Ugi Peptidomimetics

DNA-encoded combinatorial synthesis provides efficient and dense coverage of chemical space around privileged molecular structures. The indole side chain of tryptophan plays a prominent role in key, or “hot spot”, regions of protein–protein interactions. A DNA-encoded combinatorial peptoid library was designed based on the Ugi four-component reaction by employing tryptophan-mimetic indole side chains to probe the surface of target proteins. Several peptoids were synthesized on a chemically stable hexathymidine adapter oligonucleotide “hexT”, encoded by DNA sequences, and substituted by azide-alkyne cycloaddition to yield a library of 8112 molecules. Selection experiments for the tumor-relevant proteins MDM2 and TEAD4 yielded MDM2 binders and a novel class of TEAD-YAP interaction inhibitors that perturbed the expression of a gene under the control of these Hippo pathway effectors

A Multi-Wavelength Perspective of Flares on HR 1099: Four Years of Coordinated Campaigns

We report on four years of multiple wavelength observations of the RS CVn system V711 Tau (HR 1099) from 1993, 1994, 1996, and 1998. This combination of radio, ultraviolet, extreme ultraviolet, and X-ray observations allows us to view, in the most comprehensive manner currently possible, the coronal and upper atmospheric variability of this active binary system. We report on the changing activity state of the system as recorded in the EUV and radio across the four years of the observations, and study the high energy variability using an assemblage of X-ray telescopes. (Longer abstract in paper).Comment: manuscript is 110 pages in length; 36 figures tota

Structural Elucidation and Functional Characterization of the Hyaloperonospora arabidopsidis Effector Protein ATR13

The oomycete Hyaloperonospora arabidopsidis (Hpa) is the causal agent of downy mildew on the model plant Arabidopsis thaliana and has been adapted as a model system to investigate pathogen virulence strategies and plant disease resistance mechanisms. Recognition of Hpa infection occurs when plant resistance proteins (R-genes) detect the presence or activity of pathogen-derived protein effectors delivered to the plant host. This study examines the Hpa effector ATR13 Emco5 and its recognition by RPP13-Nd, the cognate R-gene that triggers programmed cell death (HR) in the presence of recognized ATR13 variants. Herein, we use NMR to solve the backbone structure of ATR13 Emco5, revealing both a helical domain and a disordered internal loop. Additionally, we use site-directed and random mutagenesis to identify several amino acid residues involved in the recognition response conferred by RPP13-Nd. Using our structure as a scaffold, we map these residues to one of two surface-exposed patches of residues under diversifying selection. Exploring possible roles of the disordered region within the ATR13 structure, we perform domain swapping experiments and identify a peptide sequence involved in nucleolar localization. We conclude that ATR13 is a highly dynamic protein with no clear structural homologues that contains two surface-exposed patches of polymorphism, only one of which is involved in RPP13-Nd recognition specificity

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder