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

A cross-sectional MR study of body fat volumes and distribution in chronic schizophrenia

People with schizophrenia show higher risk for abdominal obesity than the general population, which could contribute to excess mortality. However, it is unclear whether this is driven by alterations in abdominal fat partitioning. Here, we test the hypothesis that individuals with schizophrenia show a higher proportion of visceral to total body fat measured using magnetic resonance imaging (MRI). We recruited 38 participants with schizophrenia and 38 healthy controls matched on age, sex, ethnicity and body mass index. We found no significant differences in body fat distribution between groups, suggesting that increased abdominal obesity in schizophrenia is not associated with altered fat distribution

Graphene and hexagonal boron nitride on transition metals and their application

The experimental possibility to manufacture stable single layers of graphite called graphene recently opened a new field of physics: The conduction electrons in graphene were found to behave like particles that obey the two-dimensional Dirac equation for massless fermions. For hexagonal boron nitride the fabrication of single layers and their investigation by transmission electron microscopy has been achieved a few months ago. Hexagonal boron nitride is isoelectric to graphene but unlike graphene it is an insulator. If these two sp2 -hybridized compounds are grown on transition metal substrates superstructures with nanometer periodicity may be found. Depending on the lattice mismatch between the sp2 layer and the substrate top layer the bond strength of the carbon (boron and nitrogen) atoms to the metal substrate atoms varies on a length scale of several nanometers. This variation can lead to a corrugation of the sp2 layer forming a highly regular surface texture. It is found that the electrostatic potential above the sp2 layer is inextricably linked to this surface texture leading to in-plane dipoles above the graphene (hexagonal boron nitride) layer. These dipoles introduce a new functionality: The corrugated sp2 layers evolve to nano-templates which can act as an array of traps for polarizable adsorbates like for example molecules. This array of traps has the same periodicity as the surface texture. For the corrugated dielectric hexagonal boron nitride layer a different polarization in the loosely bound and in the tightly bound regions of the superstructure unit cell leads to a peculiar electronic structure. It is also shown that the surface texture of hexagonal boron nitride on rhodium is removable through the intercalation of atomic hydrogen. In the flat state the effect of the corrugation on the electronic structure of the hexagonal boron nitride layer vanishes. The process is reversible as hydrogen may be expelled by mild annealing. This mechanism is proposed to be similarly efficient for hexagonal boron nitride on ruthenium and may also work in the case of the metallic graphene based systems. Thus a route to reversible switching of dielectric and metallic sp2-hybridized nano-templates is presented. Experiments on 150 nm thick silicon supported cobalt films show that similar to the nickel case the solid–vacuum interface may be passivated with a commensurate 1× 1 overlayer of hexagonal boron nitride. After formation of the hexagonal boron nitride layer the surface electronic structure is governed by sp2 -derived bands for which a large band gap is observed. In addition the solid–vacuum transmission probability for electrons which originate from the metal substrate is strongly reduced. The protection layer is proposed to make the metal film inert and stable against contaminations. Finally the template functionality of hexagonal boron nitride on rhodium is demonstrated using the example of metal cluster growth. Utilizing a cobalt carbonyl precursor well separated metal clusters are found to nucleate in arrays that have the nanometer periodicity of the template. With this the first step towards a new method for the growth of regular magnetic metal cluster arrays is demonstrated. Vor wenigen Jahren wurde die experimentelle Herstellung einzelner stabiler Graphit Lagen, genannt Graphene realisiert. Dies eröffnete ein neues Forschungsgebiet in der Physik: Es konnte gezeigt werden, dass sich die Leitungselektronen in Graphene wie Teilchen verhalten, die der zweidimensionalen Dirac Gleichung für masselose Fermionen gehorchen. Im Fall von hexagonalem Bornitrid wurde die Herstellung einzelner Lagen und deren Untersuchung mittels Transmissionselektronenmikroskopie erst vor wenigen Monaten erreicht. Hexagonales Bornitrid und Graphene sind isoelektrisch, jedoch ist hexagonales Bornitrid im Gegensatz zu Graphene ein Isolator. Werden diese beiden sp2 -hybridisierten Verbindungen auf der Oberfläche von Übergangsmetallen gewachsen, so entstehen Überstrukturen mit einer Periodizität im Nanometerbereich. Die Bindungsstärke zwischen den Kohlenstoff- (Bor- und Stickstoff-) atomen und den Metallatomen des Substrates variiert aufgrund der Fehlanpassung der Gitterkonstanten für die sp2 -Lagen und die oberste Substratlage auf einer Längenskala von einigen Nanometern. Diese Variation kann zu einer Wölbung der sp2 -Lage und somit zur Ausbildung einer sehr regelmässigen Oberflächenstrukturierung führen. Es wird gezeigt, dass das elektrostatische Potential über der sp2 -Lage untrennbar mit dieser Oberflächenstrukturierung verbunden ist, was zur Bildung von planaren Dipolen über dem Graphen (hexagonalen Bornitrid) führt. Diese Dipole erzeugen eine neue Funktionalität: Die korrugierten sp2 -Lagen entwickeln sich zu einer Art Nanovorlagen, welche mit einer regelmässigen Anordnung von Stellen erhöhter Bindunsgenergie für polarisierbare Adsorbate, wie zum Beispiel Moleküle, solche gezielt einfangen können. Die Periodizität innerhalb dieser Nanovorlage ist dieselbe wie in der regelmässigen Oberflächenstrukturierung. Im Falle des gewölbten, dielektrischen hexagonalen Bornitrids führt eine unterschiedliche Polarisation für die stark und die schwach gebunden Regionen zu einer eigenartigen elektronischen Struktur. Es stellt sich heraus, dass die Oberflächenstrukturierung von hexagonalem Bornitrid auf Rhodium durch die Einlagerung von atomarem Wasserstoff entfernt werden kann. In diesem flachen Zustand verschwindet auch die eigenartige elektronische Struktur der Bornitridschicht, welche durch die Wölbung hervorgerufen worden war. Der Prozess kann durch mildes Heizen der Probe umgekehrt werden. Dabei wird der eingelagerte Wasserstoff aus der Zwischenschicht ausgetrieben. Dieser Mechanismus sollte ähnlich effizient auch für hexagonales Bornitrid auf Ruthenium funktionieren. Für die metallischen, auf Graphene basierenden Systeme wird ein ähnlicher Effekt erwartet. Hiermit wird also ein Weg zum reversiblen Schalten von sp2 -hybridisierten Nanovorlagen präsentiert. Experimente mit hexagonalem Bornitrid auf einem 150 nm dicken Kobaltfilm, welcher auf einer Silizium Unterlage aufgebracht war, zeigen, dass dort eine Situation ähnlich zur Verwendung von Nickel als Metallsubstrat intritt. Die Grenzfläche zwischen Festkörper und Vakuum wird mit einer kommensurablen 1 × 1 Schicht aus hexagonalem Bornitrid passiviert. Die elektronische Struktur der Oberfläche wird nach dem Wachstum der hexagonalen Bornitrid Schicht von Bändern dominiert, die von der sp2 -Schicht herrühren. Zusätzlich wird die Übergangswahrscheinlichkeit für die Elektronen aus dem Metallsubstrat vom Festkörper ins Vakuum stark abgeschwächt. Die Schutzschicht macht die Metalloberfläche inert und unempfindlicher gegenüber Verschmutzungen. Schliesslich wird die Möglichkeit des hexagonalen Bornitrids auf Rhodium zum Einfangen von Adsorbaten noch am Beispiel von kleinen Metallhaufen demonstriert. Unter Verwendung eines Kobalt Karbonyls als Ausgangsstoff wird gezeigt, dass auf dem Bornitrid kleine, räumlich eindeutig getrennte Metallhäufchen mit der Regelmässigkeit der Nanovorlage gebildet werden. Damit wird der erste Schritt für eine neue Methode zum Wachstum regelmässig angeordneter, magnetischer Metallhäufchen aufgezeigt

Anthropogenic Litter Abundance and Composition in Urban Streams: Influence of Site and Habitat

Anthropogenic litter (AL; trash including plastic and other materials) is a global ecological concern. Rivers move AL from land to oceans, but the distribution of AL within rivers is less often studied. We examined the abundance and composition of AL in different habitats at multiple sites in an urban river. We expect sorting of AL based on density, and that sites with greater urban land use will have the most AL. These data will be helpful to improve AL mitigation and removal strategies

Applying the energy efficiency first principle based on a decision-tree framework

Energy Efficiency First (EEF) is an established principle for European Union (EU) energy policy design. It highlights the exploitation of demand-side resources and prioritizes cost-effective options from the demand-side over other options from a societal cost-benefit perspective. However, the involvement of multiple decision-makers makes it difficult to implement. Therefore, we propose a flexible decision-tree framework for applying the EEF principle based on a review of relevant areas and examples. In summary, this paper contributes to applying the EEF principle by defining and distinguishing different types of cases - (1) policy-making, and (2) system planning and investment - identifying the most common elements, and proposing a decision-tree framework that can be flexibly constructed based on the elements for different cases. Finally, we exemplify the application of this framework with two example cases: (1) planning for demand-response in the power sector, and (2) planning for a district heating system

A cross-sectional MR study of body fat volumes and distribution in chronic schizophrenia

People with schizophrenia show higher risk for abdominal obesity than the general population, which could contribute to excess mortality. However, it is unclear whether this is driven by alterations in abdominal fat partitioning. Here, we test the hypothesis that individuals with schizophrenia show a higher proportion of visceral to total body fat measured using magnetic resonance imaging (MRI). We recruited 38 participants with schizophrenia and 38 healthy controls matched on age, sex, ethnicity and body mass index. We found no significant differences in body fat distribution between groups, suggesting that increased abdominal obesity in schizophrenia is not associated with altered fat distribution

Disentangling input and output-related components of spatial neglect

Spatial neglect is a heterogeneous disorder with a multitude of manifestations and subtypes. Common clinical paper and pencil neglect tests fail to differentiate between these subtypes. For example, neglect patients typically bisect lines to the right. This bias can be caused by an underestimation of the left half of the line (input-related deficit), by the failure to direct actions toward the left side of space (output-related deficit), or by a mixture of these impairments. To disentangle these impairments, we used a test consisting of a line bisection task on a touch screen monitor (manual motor task) and the subsequent judgment of one's own bisection performance (visual perceptual task). It was hypothesized that patients with mainly output-related neglect should be better able to recognize their misbisected lines than patients with purely input-related neglect. In a group of 16 patients suffering from spatial neglect after right brain damage, we found that patients were three times more likely to suffer from a predominantly input-related than from an output-related subtype. The results thus suggest that neglect is typically an input-related impairment. Additional analysis of the line bisection task revealed that temporal (slowness in initiation and execution of contralateral movements) and spatial (insufficient movement amplitude toward the contralesional side) aspects of output-related neglect were mutually unrelated. This independence raises the possibility that a fine-grained differentiation of output-related neglect is required. That is, impairments in lateralized temporal and spatial aspects of movements may underlie different neglect subtypes

Drop-on-Demand Inkjet Printing of Functional Composites

Drop-on-Demand Inkjet printing can be used as an effective technique to deposit the sensing layer in chemical sensors. However, formulation of inks containing functional materials remains challenging due to rheological constraints imposed by the inkjet printer. Here, we show a systematic process to formulate and print functional inks containing polymer and carbon black (CB) particles. The functional ink is used for sensing different analytes considering the polarity of the polymer1,2. We formulated inks containing polyvinylpyrrolidone (PVP) with the molecular weight of 40 kDa and 360 kDa. We used high-structured carbon black as the conductive filler. Printing parameters were optimized and the polymer composite was printed on the sensor platform with screen printed interdigitated electrode (IDE). The ink showed good stability over time and no sedimentation was observed even weeks after the formulation. In the next step we characterize the sensing behavior of the printed campsites

DOD Inkjet printing of functional polymers

Inkjet printing techniques have gained a lot of attention for the micro-structuring of functional materials. This is due to their low cost, low material consumption and relatively easy fabrication process. In this project, Drop-on-Demand (DOD) inkjet printing is used as a means of depositing gas-sensitive polymer nanocomposites on interdigitated electrodes. Different shapes and patterns (e.g. lines and films) can be printed by controlling the coalescence of the neighboring droplets. The final topography of the printed structure depends strongly on parameters such as ink formulation, surface properties of the substrate as well as printing parameters

Inkjet Printing of Functional Polymer Composites for Chemiresistive Gas Sensors

Drop-on-Demand Inkjet printing can be used as an effective technique to deposit the sensing layer in chemiresistive gas sensors. In this type of gas sensors, a composite containing an insulating polymer mixed with a conductive filler is used for sensing analytes. However, formulation of inks containing functional materials remains challenging due to rheological constraints imposed by the inkjet printer. Here, we show the process of ink formulation for functional inks containing polyvinylpyrrolidone (PVP), a polar polymer, and carbon black (CB). We formulated composite inks containing PVP with different molecular weights (40 and 360 kDa) and studied their inkjet-abilities based on their shear viscosity and particle size distribution. Composite inks were successfully printed onto the sensor platforms and their electrical properties were characterized