83 research outputs found
Investigation of the Electric Field and Charge Density Distribution of pristine and defective 2D WSe by Differential Phase Contrast Imaging
Most properties of solid materials are defined by their internal electric
field and charge density distributions which so far have been difficult to
measure with sufficient spatial resolution. For 2D materials, the electric
field at the atomic level in particular influences the optoelectronic
properties. In this study, the atomic-scale electric field and charge density
distribution of 2D WSe are revealed by using an emerging microscopy
technique, differential phase contrast (DPC) imaging in the scanning
transmission electron microscope (STEM). Combined with high-angle annular
dark-field imaging the charge density distribution of bi- and trilayers of
WSe is mapped. A measured higher positive charge density located at the
selenium atomic columns compared to the tungsten atomic columns is reported,
and possible reasons are discussed. Furthermore, the change in the electric
field distribution of a selenium point defect in a trilayer is investigated
exhibiting a characteristic electric field distribution in the vicinity of the
defect: there are characteristic regions with locally enhanced and with locally
reduced electric field magnitudes compared to the pristine lattice.Comment: 20 pages including the supplementary information, 3 figures in the
main part and additional 2 figures in the supplementary informatio
Electro-elastic tuning of single particles in individual self-assembled quantum dots
We investigate the effect of uniaxial stress on InGaAs quantum dots in a
charge tunable device. Using Coulomb blockade and photoluminescence, we observe
that significant tuning of single particle energies (~ -0.5 meV/MPa) leads to
variable tuning of exciton energies (+18 to -0.9 micro-eV/MPa) under tensile
stress. Modest tuning of the permanent dipole, Coulomb interaction and
fine-structure splitting energies is also measured. We exploit the variable
exciton response to tune multiple quantum dots on the same chip into resonance.Comment: 16 pages, 4 figures, 1 table. Final versio
Mobilities of Knowledge: An Introduction
Mobilities of Knowledge examines how geographical mobility of people and (im)material things has impacted epistemic systems of knowledge in different historical and geographical contexts. In this chapter, the authors introduce concepts and debates in interdisciplinary research on spatial mobility and the production, dissemination, and transfer of knowledge. They suggest extending Urryâs (2007) typology of interdependent mobilities that constitute the space of flows and the space of places (Castells, 1996) from five to six dimensions through the consideration of mobile knowledges, concepts, and practices. Finally, they outline how the chapters of this volume help to identify generic as well as context-specific practices and processes of knowledge production, dissemination, and transfer and call for more empirical case studies to further the collective development of flexible conceptual understandings
HIF-1α determines the metastatic potential of gastric cancer cells
Gastric adenocarcinoma is characterised by rapid emergence of systemic metastases, resulting in poor prognosis due to vanished curative treatment options. Better understanding of the molecular basis of gastric cancer spread is needed to design innovative treatments. The transcription factor HIF-1α (hypoxia-inducible factor 1α) is frequently overexpressed in human gastric cancer, and inhibition of HIF-1α has proven antitumour efficacy in rodent models, whereas the relevance of HIF-1α for the metastatic phenotype of gastric adenocarcinoma remains elusive. Therefore, we have conducted a comprehensive analysis of the role of HIF-1α for pivotal metastasis-associated processes of human gastric cancer. Immunhistochemistry for HIF-1α showed specific staining at the invading tumour edge in 90% of human gastric cancer samples, whereas normal gastric tissue was negative and only a minority of early gastric cancers (T1 tumours) showed specific staining. Hypoxia-inducible factor 1α-deficient cells showed a significant reduction of migratory, invasive and adhesive properties in vitro. Furthermore, the HIF-1α-inhibitor 2-methoxy-estradiol significantly reduced metastatic properties of gastric cancer cells. The accentuated expression at the invading edge together with the in vitro requirement of HIF-1α for migration, invasion and adherence argues for a pivotal role of HIF-1α in local invasion and, ultimately, systemic tumour spread. These results warrant the exploration of HIF-1α-inhibiting substances in clinical treatment studies of advanced gastric cancer
Waveguide Coupled Resonance Fluorescence from On-Chip Quantum Emitter
Resonantly driven quantum emitters offer a very promising route to obtain highly coherent sources of single photons required for applications in quantum information processing (QIP). Realizing this for on-chip scalable devices would be important for scientific advances and practical applications in the field of integrated quantum optics. Here we report on-chip quantum dot (QD) resonance fluorescence (RF) efficiently coupled into a single-mode waveguide, a key component of a photonic integrated circuit, with a negligible resonant laser background and show that the QD coherence is enhanced by more than a factor of 4 compared to off-resonant excitation. Single-photon behavior is confirmed under resonant excitation, and fast fluctuating charge dynamics are revealed in autocorrelation g(2) measurements. The potential for triggered operation is verified in pulsed RF. These results pave the way to a novel class of integrated quantum-optical devices for on-chip quantum information processing with embedded resonantly driven quantum emitters
Foreign Banks are Branching out: Changing Geographies of Hungarian Banking, 1987â1999
Walking through the streets of Budapest in spring 1999 could have given you the following impression: the supermarkets (Spar), the milk products sold there (Danone, MĂŒller), and the property markets (OBI) come from different Western European countries such as the Netherlands, France and Germany. Almost all fast food restaurants (McDonalds, Pizza Hut, KFC) and many hotels (Hilton, Mariott) have their origins in the US; shoes and clothes offered in downtown are designed in Italy or France (Benetton, Marco Polo); medicine is predominantly produced in Switzerland (Novartis, Roche) and the banks as well as the car dealerships have their roots everywhere in the so-called Western world - usually including Japan and other Asian countries with major (car) companies - but not in Hungary itself...
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