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Coherent x ray magnetic imaging with 5 nm resolution
Get PDFSoft x ray microscopy plays an important role in modern spintronics. However, the achievable resolution of most x ray magnetic imaging experiments limits access to fundamental and technologically relevant length scales in the sub 10 amp; x00A0;nm regime. Here, we demonstrate x ray magnetic microscopy with 5 amp; x00A0;nm resolution by combining holography assisted coherent diffractive imaging with heterodyne amplification of the weak magnetic signal. The gain in resolution and contrast makes magnetic pinning sites visible and allows to measure the local width of domain walls. The ability to detect and map such properties with photons opens new horizons for element specific, time resolved, and operando research on magnetic materials and beyon
Structural and biochemical characterization of USP28 inhibition by small molecule inhibitors
No full textUbiquitination is an important post translational modification that maintains cellular homeostasis by regulating various biological processes. Deubiquitinases DUBs are enzymes that reverse the ubiquitination process by catalyzing the removal of ubiquitin from a substrate. Abnormal expression or function of DUBs is often associated with the onset and progression of various diseases, including cancer. Ubiquitin specific proteases USPs , which constitute the largest family of DUBs in humans, have become the center of interest as potential targets in cancer therapy as many of them display increased activity or are overexpressed in a range of malignant tumors or the tumor microenvironment. Two related members of the USP family, USP28 and USP25, share high sequence identities but play diverse biological roles. USP28 regulates cell proliferation, oncogenesis, DNA damage repair and apoptosis, whereas USP25 is involved in the anti viral response, innate immunity and ER associated degradation in addition to carcinogenesis. USP28 and USP25 also exhibit different oligomeric states while USP28 is a constitutively active dimer, USP25 assumes an auto inhibited tetrameric structure. The catalytic domains of both USP28 and USP25 comprise the canonical, globular USP domain but contain an additional, extended insertion site called USP25 28 catalytic domain inserted domain UCID that mediates oligomerization of the proteins. Disruption of the USP25 tetramer leads to the formation of an activated dimeric protein. However, it is still not clear what triggers its activation. Due to their role in maintaining and stabilizing numerous oncoproteins, USP28 and USP25 have emerged as interesting candidates for anti cancer therapy. Recent advances in small molecular inhibitor development have led to the discovery of relatively potent inhibitors of USP28 and USP25. This thesis focuses on the structural elucidation of USP28 and the biochemical characterization of USP28 USP25, both in complex with representatives of three out of the eight compound classes reported as USP28 USP25 specific inhibitors. The crystal structures of USP28 in complex with the AZ compounds, Vismodegib and FT206 reveal that all three inhibitor classes bind into the same allosteric pocket distant from the catalytic center, located between the palm and the thumb subdomains the S1 site . Intriguingly, this binding pocket is identical to the UCID tip binding interface in the USP25 tetramer, rendering the protein in a locked, inactive conformation. Formation of the binding pocket in USP28 requires a shift in the helix amp; 945;5, which induces conformational changes and local distortion of the binding channel that typically accommodates the C terminal tail of Ubiquitin, thus preventing catalysis and abrogating USP28 activity. The key residues of the USP28 inhibitor binding pocket are highly conserved in USP25. Mutagenesis studies of these residues accompanied by biochemical and biophysical assays confirm the proposed mechanism of inhibition and similar binding to USP25. This work provides valuable insights into the inhibition mechanism of the small molecule compounds specifically for the DUBs USP28 and USP25. The USP28 inhibitor complex structures offer a framework to develop more specific and potent inhibitor
The Trials and Triumphs of Modelling X ray Spectroscopy of Strongly Correlated Transition Metal Complexes
No full textThis dissertation delves into the challenges and successes encountered while modeling spin and oxidation states of strongly correlated first row transition metal complexes using various single and multireference quantum chemical methods with a focus on X ray spectroscopy. It thoroughly examines the strengths and limitations of theoretical approaches, addressing electron correlation, multiplet effects, active space size and nature, dynamic electron correlation corrections, truncated configuration interaction CI techniques, and Density Functional Theory DFT . Furthermore, the study explores pivotal physical and chemical factors such as covalency, stability, ligand field effects, magnetic exchange interactions, and the determination of spin and oxidation states within molecular system
Anyon Condensation and the Color Code
Get PDFThe manipulation of topologically ordered phases of matter to encode and process quantum information forms the cornerstone of many approaches to fault tolerant quantum computing. Here we demonstrate that fault tolerant logical operations in these approaches can be interpreted as instances of anyon condensation. We present a constructive theory for anyon condensation and, in tandem, illustrate our theory explicitly using the color code model. We show that different condensation processes are associated with a general class of domain walls, which can exist in both spacelike and timelike directions. This class includes semitransparent domain walls that condense certain subsets of anyons. We use our theory to classify topological objects and design novel fault tolerant logic gates for the color code. As a final example, we also argue that dynamical Floquet codes can be viewed as a series of condensation operations. We propose a general construction for realizing planar dynamically driven codes based on condensation operations on the color code. We use our construction to introduce a new Calderbank Shor Steane type Floquet code that we call the Floquet color cod
Deciphering the Role of Nickel in Electrochemical Organic Oxidation Reactions
Get PDFOrganic oxidation reactions OORs powered by renewable energy sources are gaining importance as a favorable alternative to oxygen evolution reaction, with the promise of reducing the cell potential and enhancing the overall viability of the water electrolysis. This comprehensive review delves into the electrochemical oxidation of diverse organic compounds, including alcohols, aldehydes, amines, and urea, as well as biomass derived renewable feedstocks such as hydroxymethylfurfural and glycerol. The key focus centers on the role of nickel Ni based catalysts for these OORs. The unique redox activity and chemical nature of Ni have been proven instrumental for the sustainable and cost effective oxidation of various organic molecules more efficiently and selectively. This review article discusses how strategic choices, such as the selection of foreign metals, intercalating species, vacancies, defects, and a secondary element e.g. chalcogens and non metals , contribute to tuning the electrochemical performances of a Ni based pre catalyst for OORs. Moreover, this review provides insights into the active species in various reaction environments and further explores reaction mechanisms, to apparent phase changes of the catalyst with the most relevant examples. Finally, the review not only elucidates the limitations of the current approaches but also outlines potential avenues for future advancements in OO
Impact of the valence band energy alignment at the hole collecting interface on the photostability of wide band gap perovskite solar cells
No full textHalide segregation in wide band gap halide perovskites is an important bottleneck toward long operational lifetimes of perovskite based multijunction solar cells. To minimize this phenomenon, aside from other well known strategies such as perovskite defect passivation, enhancing the charge carrier collection needs to be effectively addressed. Here, we report a universal method to improve the hole collection in p i n perovskite solar cells PSCs by engineering the energetic alignment between the perovskite and the hole selective contact through blended SAMs, MeO 2PACz with Br 2PACz. With the presented correlation between carrier collection and halide segregation analysis in this study, we show that it is possible to predict which interface is less prone to promote halide segregation, and thus it can be used to accelerate the development of PSCs with increased photostability. By studying different perovskite compositions, we highlight the universality of our metho
Domain Wall Color Code
No full textWe introduce the domain wall color code, a new variant of the quantum error correcting color code that exhibits exceptionally high code capacity error thresholds for qubits subject to biased noise. In the infinite bias regime, a two dimensional color code decouples into a series of repetition codes, resulting in an error correcting threshold of 50 . Interestingly, at finite bias, our color code demonstrates thresholds identical to those of the noise tailored XZZX surface code for all single qubit Pauli noise channels. The design principle of the code is that it introduces domain walls which permute the code s excitations upon domain crossing. For practical implementation, we supplement the domain wall code with a scalable restriction decoder based on a matching algorithm. The proposed code is identified as a comparably resource efficient quantum error correcting code highly suitable for realistic nois
In situ evolution of bulk active gamma CoOOH with immobilized Gd dopants enabling efficient oxygen evolution electrocatalysis
Get PDFPromoting the in situ reconstruction of transition metal TM based precatalysts into low crystalline and well modified TM oxy hydroxides TMOxHy during the alkaline oxygen evolution reaction OER is crucial for enhancing their catalytic performances. In this study, we incorporated gadolinium Gd into a cobalt hydroxide precatalyst, achieving a deep reconstruction into cobalt oxyhydroxide amp; 947; CoOOH while retaining the incorporated Gd during the activation process of the alkaline OER. The unconventional non leaching Gd dopants endow amp; 947; CoOOH with reduced crystallinity, increasing the exposure of electrolyte accessible Co atoms and enhancing its bulk activity. Furthermore, the modulation of the electronic structure of amp; 947; CoOOH substantially boosts the intrinsic activity of the active Co sites. As a result, when supported on nickel foam, the catalyst exhibits remarkable alkaline OER performance, achieving a current density of 100 mA cm amp; 8722;2 at a low overpotential of approximately 327 mV. Notably, an ultrahigh current density of 1000 mA cm amp; 8722;2 is robustly maintained for 5 days, highlighting its immense potential for practical applications in large scale hydrogen productio
Colossal negative thermal expansion over a wide temperature span in dynamically self assembled MnCo Ge,Si epoxy composites
Get PDFThe achievement of significant negative thermal expansion NTE over a wide temperature range amp; 916;TNTE has posed a formidable challenge for NTE materials. In the present study, textured MnCo Ge,Si epoxy composites were prepared by magnetic field assisted dynamic self assembly of multi component Mn0.945Co1.055Ge1 xSix particles. The utilization of multi component particles with tunable transition temperatures significantly amplifies the temperature range over which the NTE occurs, surpassing the limitations of conventional single component composites. The textured microstructure enables the extension of lattice level NTE to reach the macroscopic level, which is manifested by a remarkably large NTE coefficient of amp; 8722;328.7 amp; 8201; amp; 8201;10 amp; 8722;6 K between 288.2 and 431.1 amp; 8201;