Resonant Photoelectron Diffraction with circularly polarized light

Resonant angle scanned x-ray photoelectron diffraction (RXPD) allows the determination of the atomic and magnetic structure of surfaces and interfaces. For the case of magnetized nickel the resonant L2 excitation with circularly polarized light yields electrons with a dichroic signature from which the dipolar part may be retrieved. The corresponding L2MM and L3MM Auger electrons carry different angular momenta since their source waves rotate the dichroic dipole in the electron emission patterns by distinct angles

Finite Element Modeling of Thermal Cycling Induced Microcracking in Carbon/Epoxy Triaxial Braided Composites

The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composit

Corrugated single layer templates for molecules: From h -BN nanomesh to graphene based quantum dot arrays

Functional nano-templates enable self-assembly of otherwise impossible arrangements of molecules. A particular class of such templates is that of sp 2 hybridized single layers of hexagonal boron nitride or carbon (graphene) on metal supports. If the substrate and the single layer have a lattice mismatch, superstructures are formed. On substrates like rhodium or ruthenium these superstructures have unit cells with ∼3-nm lattice constant. They are corrugated and contain sub-units, which behave like traps for molecules or quantum dots, which are small enough to become operational at room temperature. For graphene on Rh(111) we emphasize a new structural element of small extra hills within the corrugation landscape. For the case of molecules like water it is shown that new phases assemble on such templates, and that they can be used as "nano-laboratories” where many individual processes are studied in parallel. Furthermore, it is shown that the h-BN/Rh(111) nanomesh displays a strong scanning tunneling microscopy-induced luminescence contrast within the 3 nm unit cell which is a way to address trapped molecules and/or quantum dot

Integrated multi-omics reveals anaplerotic rewiring in methylmalonyl-CoA mutase deficiency

Multi-layered omics approaches can help define relationships between genetic factors, biochemical processes and phenotypes thus extending research of inherited diseases beyond identifying their monogenic cause 1. We implemented a multi-layered omics approach for the inherited metabolic disorder methylmalonic aciduria (MMA). We performed whole genome sequencing, transcriptomic sequencing, and mass spectrometry-based proteotyping from matched primary fibroblast samples of 230 individuals (210 affected, 20 controls) and related the molecular data to 105 phenotypic features. Integrative analysis identified a molecular diagnosis for 84% (177/210) of affected individuals, the majority (148) of whom had pathogenic variants in methylmalonyl-CoA mutase (MMUT). Untargeted analysis of all three omics layers revealed dysregulation of the TCA cycle and surrounding metabolic pathways, a finding that was further corroborated by multi-organ metabolomics of a hemizygous Mmut mouse model. Integration of phenotypic disease severity indicated downregulation of oxoglutarate dehydrogenase and upregulation of glutamate dehydrogenase, two proteins involved in glutamine anaplerosis of the TCA cycle. The relevance of disturbances in this pathway was supported by metabolomics and isotope tracing studies which showed decreased glutamine-derived anaplerosis in MMA. We further identified MMUT to physically interact with both, oxoglutarate dehydrogenase complex components and glutamate dehydrogenase providing evidence for a multi-protein metabolon that orchestrates TCA cycle anaplerosis. This study emphasizes the utility of a multi-modal omics approach to investigate metabolic diseases and highlights glutamine anaplerosis as a potential therapeutic intervention point in MMA. Take home message Combination of integrative multi-omics technologies with clinical and biochemical features leads to an increased diagnostic rate compared to genome sequencing alone and identifies anaplerotic rewiring as a targetable feature of the rare inborn error of metabolism methylmalonic aciduria

A detached stellar-mass black hole candidate in the globular cluster NGC 3201

Large scale structure and cosmolog

Tools for Investigating Molecular Magnetism: A New Mott Detector and Resonant Photoelectron Diffraction with Circular Dichroism

This thesis deals with topics that are related to the theme of molecular magnetism. The setup of a new electron spin detector, resonant x-ray photoelectron diffraction with structural and magnetic contrast, and endohedral fullerenes on surfaces are presented. In the first part, we describe the design and construction of a Mott detector for spin resolved photoelectron spectroscopy. As the detector is going to be installed in an existing electron spectrometer, it has to fulfill certain requirements concerning size, stability and availability. Therefore, a scintillation scheme is used for the detection of electrons, which allows to move all electronics to outside of the vacuum chamber, close to ground potential. Additionally, the detector design was optimized for high count rates (≈107 counts/s per channel). First proof of principle asymmetry data have been measured. The endohedral fullerene Dy 3 N @C80 has been studied with x-ray magnetic circular dichroism and resonant photoemission. We studied the coupling between the Dy 3 N cluster and a ferromagnetic surface. Additionally, two non-magnetic endofullerenes, H2 @C60 and Ar@C60 , have been examined with standard photoemission to better understand the guest-cage interaction and its consequence for the electronic structure of both the guest and the C60 molecule. For Ar@C60 , we find a large hybridization between the Ar 3p level and a C60 orbital with the same symmetry and a similar binding energy. Additionally, from the spectra the photoemission cross section of the Ar 3p level can be determined, which allows comparison to theoretical predictions where a giant enhancement compared to free Ar is proposed. However, this cannot be confirmed by our data. When studying the coupling of molecules to magnetic substrates, it is crucial to first understand the substrate itself. Therefore, we developed a new method to determine the magnetization direction relative to the crystal structure, i.e. magnetic and structural properties are accessible within the same measurement. The method relies on resonant x-ray photoelectron diffraction with magnetic circular dichroism. It was demonstrated for a Ni(111) yoke crystal. The results confirm data with spin resolved photoemission of the same crystal. Diese Arbeit beschäftigt sich mit dem Gebiet des molekularen Magnetismus. Im ersten Teil wird die Konzeption und Realisierung eines neuen Mott-Detektors für spinaufgelöste Photoemission beschrieben. Da der Detektor in ein bestehendes Photoelektronenspektrometer eingebaut wird, sind verschiedene Anforderungen bezüglich Abmessungen und Stabilität zu erfüllen. Aus diesem Grund wurde für den Detektor ein neues Konzept zur Nachweisung der Elektronen benutzt, das auf Szintillatoren beruht. Das darin erzeugte Licht wird über Lichtleiter über Durchführungen nach ausserhalb der Vakuum-Kammer geführt, wo es mit Photodetektoren nachgewiesen wird. Die notwendige Elektronik kann erdnah betrieben werden. Zusätzlich wurde der Detektor für hohe Zählraten optimiert (≈ 10 MHz pro Kanal). Ein weiteres Thema der Doktorarbeit sind endohedrale Fullerene. Dy 3 N @C80 wurde mit Röntgen-Zirkulardichroismus und resonanter Photoemission analysiert, wobei die magnetische Kopplung zwischen dem Dy 3 N -Cluster und einer ferromagnetischen Ni(111)-Oberfläche untersucht wurde. Weiters wurde die Wechselwirkung zwischen Käfig und Gastatom bzw. -Molekül in Ar@C60 und H2 @C60 mit Photoemission untersucht. Im Fall von Ar@C60 hybridisieren das Ar 3p Niveau und ein C60 -Orbital mit derselben Symmetrie. Die Aufspaltung zwischen dem resultierenden bindenden bzw. antibindenden Orbital kann über Photoemission bestimmt werden. Zusätzlich kann der Wirkungsquerschnitt aus den Daten bestimmt werden und mit theoretischen Vorhersagen verglichen werden, wo eine starke Überhöhung im Vergleich zu freiem Argon berechnet wird. Ein drittes Thema dieser Arbeit befasst sich mit einer neuen Methode zur Bestimmung der Magnetisierungsrichtung einer Probe relativ zur Kristallstruktur, dh. magnetische und geometrische Eigenschaften werden in einer einzigen Messung simultan zugänglich. Das Funktionsprinzip wurde an einem Ni(111)-Kristall demonstriert. Die Resultate bestätigen Messungen mit spinaufgelöster Photoemission am selben Kristall

Experimental and FEM Study of Thermal Cycling Induced Microcracking in Carbon/Epoxy Triaxial Braided Composites

The microcrack distribution and mass change in T700s/PR520 and T700s/3502 carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between −55 °C and 120 °C. Transverse microcrack morphology was investigated using X-ray computed tomography. The differing performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. By accounting for the obtained reduction of mechanical properties, a macro-mechanical finite element model was utilized to investigate the influence of microcracking on the high-speed impact behavior

Corrugated single layer templates for molecules: From h-BN nanomesh to graphene based quantum dot arrays

Functional nano-templates enable self-assembly of otherwise impossible arrangements of molecules. A particular class of such templates is that of sp2 hybridized single layers of hexagonal boron nitride or carbon (graphene) on metal supports. If the substrate and the single layer have a lattice mismatch, superstructures are formed. On substrates like rhodium or ruthenium these superstructures have unit cells with ∼3-nm lattice constant. They are corrugated and contain sub-units, which behave like traps for molecules or quantum dots, which are small enough to become operational at room temperature. For graphene on Rh(111) we emphasize a new structural element of small extra hills within the corrugation landscape. For the case of molecules like water it is shown that new phases assemble on such templates, and that they can be used as “nano-laboratories” where many individual processes are studied in parallel. Furthermore, it is shown that the h-BN/Rh(111) nanomesh displays a strong scanning tunneling microscopy-induced luminescence contrast within the 3 nm unit cell which is a way to address trapped molecules and/or quantum dots

3-methylcrotonyl-CoA carboxylase deficiency: clinical, biochemical, enzymatic and molecular studies in 88 individuals

BACKGROUND: Isolated 3-methylcrotonyl-CoA carboxylase (MCC) deficiency is an autosomal recessive disorder of leucine metabolism caused by mutations in MCCC1 or MCCC2 encoding the α and β subunit of MCC, respectively. The phenotype is highly variable ranging from acute neonatal onset with fatal outcome to asymptomatic adults. METHODS: We report clinical, biochemical, enzymatic and mutation data of 88 MCC deficient individuals, 53 identified by newborn screening, 26 diagnosed due to clinical symptoms or positive family history and 9 mothers, identified following the positive newborn screening result of their baby. RESULTS: Fifty-seven percent of patients were asymptomatic while 43% showed clinical symptoms, many of which were probably not related to MCC deficiency but due to ascertainment bias. However, 12 patients (5 of 53 identified by newborn screening) presented with acute metabolic decompensations. We identified 15 novel MCCC1 and 16 novel MCCC2 mutant alleles. Additionally, we report expression studies on 3 MCCC1 and 8 MCCC2 mutations and show an overview of all 132 MCCC1 and MCCC2 variants known to date. CONCLUSIONS: Our data confirm that MCC deficiency, despite low penetrance, may lead to a severe clinical phenotype resembling classical organic acidurias. However, neither the genotype nor the biochemical phenotype is helpful in predicting the clinical course