Theory of STM junctions for \pi-conjugated molecules on thin insulating films

A microscopic theory of the transport in a scanning tunnelling microscope (STM) set-up is introduced for \pi-conjugated molecules on insulating films, based on the density matrix formalism. A key role is played in the theory by the energy dependent tunnelling rates which account for the coupling of the molecule to the tip and to the substrate. In particular, we analyze how the geometrical differences between the localized tip and extended substrate are encoded in the tunnelling rate and influence the transport characteristics. Finally, using benzene as an example of a planar, rotationally symmetric molecule, we calculate the STM current voltage characteristics and current maps and analyze them in terms of few relevant angular momentum channels.Comment: 19 pages, 12 figures, minor changes to conform to published versio

Topographical fingerprints of many-body interference blocking in STM junctions on thin insulating films

Negative differential conductance (NDC) is a non-linear transport phenomenon ubiquitous in molecular nanojunctions. Its physical origin can be the most diverse. In rotationally symmetric molecules with orbitally degenerate many-body states, it can be ascribed to interference effects. We establish in this paper a criterion to identify the interference blocking scenario by correlating the spectral and the topographical information achievable in an STM single molecule measurement. Simulations of current voltage characteristics and current maps for a Cu-Phthalocyanine (CuPc) on a thin insulating film are presented as experimentally relevant examples.Comment: 8 pages, 6 figure

Directional emission of white light via selective amplification of photon recycling and Bayesian optimization of multi-layer thin films

Over the last decades, light-emitting diodes (LED) have replaced common light bulbs in almost every application, from flashlights in smartphones to automotive headlights. Illuminating nightly streets requires LEDs to emit a light spectrum that is perceived as pure white by the human eye. The power associated with such a white light spectrum is not only distributed over the contributing wavelengths but also over the angles of vision. For many applications, the usable light rays are required to exit the LED in forward direction, namely under small angles to the perpendicular. In this work, we demonstrate that a specifically designed multi-layer thin film on top of a white LED increases the power of pure white light emitted in forward direction. Therefore, the deduced multi-objective optimization problem is reformulated via a real-valued physics-guided objective function that represents the hierarchical structure of our engineering problem. Variants of Bayesian optimization are employed to maximize this non-deterministic objective function based on ray tracing simulations. Eventually, the investigation of optical properties of suitable multi-layer thin films allowed to identify the mechanism behind the increased directionality of white light: angle and wavelength selective filtering causes the multi-layer thin film to play ping pong with rays of light

On relativity of boundaries between words and image: a study of the frontier between literature and visual art, based on

Celem mojej pracy jest wyjaśnienie pojęcia liberatury oraz zaprezentowanie literackich tekstów, w szczególności zaś utworu „Oka-leczenie” Zenona Fajfera i Katarzyny Bazarnik.W pierwszej części przedstawiłam opis liberatury, jako dzieła intermedialnego, intertekstualnego, sieciowego i wielogłosowego. Dzieła , które jest w ruchu, gdzie rola autora i czytelnika jest przemienna. Drugą część poświęciłam dziełu "Oka-leczenie" Zenona Fajfera i Katarzyny Bazarnik, które było analizowane pod kątem znaczeniowym metodą 'close reading'.Aim of this study is to clarify the concept of liberature and texts present, in particular the text of Zenon Fajfer and Katarzyna Bazarnik “Oka-leczenie”.The first part is a description of liberature as intermedia text, intertextual and multi-voices. A work which is in motion, where the role of the author and the reader is convertible.The second part described the work “Oka-leczenie” by Zenon Fajfer and Katarzyna Bazarnik, which has been analyzed in context of semantic by 'close reading' methodology

Sparse Graphical Modelling via the Sorted L1_1-Norm

Sparse graphical modelling has attained widespread attention across various academic fields. We propose two new graphical model approaches, Gslope and Tslope, which provide sparse estimates of the precision matrix by penalizing its sorted L1-norm, and relying on Gaussian and T-student data, respectively. We provide the selections of the tuning parameters which provably control the probability of including false edges between the disjoint graph components and empirically control the False Discovery Rate for the block diagonal covariance matrices. In extensive simulation and real world analysis, the new methods are compared to other state-of-the-art sparse graphical modelling approaches. The results establish Gslope and Tslope as two new effective tools for sparse network estimation, when dealing with both Gaussian, t-student and mixture data

Impaired dynamic cerebrovascular response to hypercapnia predicts development of white matter hyperintensities

Purpose: To evaluate the relationship between both dynamic and steady-state measures of cerebrovascular reactivity (CVR) and the progression of age-related white matter disease. Methods: Blood oxygen level-dependent (BOLD) MRI CVR scans were acquired from forty-five subjects (age range: 50–90 years, 25 males) with moderate to severe white matter disease, at baseline and one-year follow-up. To calculate the dynamic (τ) and steady-state (ssCVR) components of the BOLD signal response, the PETCO2 signal waveform was convolved with an exponential decay function. The τ corresponding to the best fit between the convolved PETCO2 and BOLD signal defined the speed of response, and the slope of the regression between the convolved PETCO2 and BOLD signal defined ssCVR. ssCVR and τ were compared between normal-appearing white matter (NAWM) that remains stable over time and NAWM that progresses to white matter hyperintensities (WMHs). Results: In comparison to contralateral NAWM, NAWM that progressed to WMH had significantly lower ssCVR values by mean (SD) 46.5 (7.6)%, and higher τ values by 31.9 (9.6)% (both P < 0.01). Conclusions: Vascular impairment in regions of NAWM that progresses to WMH consists not only of decreased magnitude of ssCVR, but also a pathological decrease in the speed of vascular response. These findings support the association between cerebrovascular dysregulation and the development of WMH

Regional Brain Water Content and Distribution During Diabetic Ketoacidosis

OBJECTIVE: To characterize regional differences in brain water distribution and content during diabetic ketoacidosis (DKA) in children and determine whether these differences correlate with regional vascular supply STUDY DESIGN: We compared changes in brain water distribution and water content in different brain regions during DKA by analyzing magnetic resonance diffusion weighted imaging data collected during DKA and after recovery in 45 children (<18 years). We measured the apparent diffusion coefficient of water (ADC) in the frontal and occipital cortex, basal ganglia, thalamus, hippocampus and medulla. Brain water content was also measured in a subset of patients. RESULTS: ADC values were elevated (suggesting vasogenic cerebral edema) in the frontal cortex, basal ganglia, thalamus and hippocampus during DKA. In contrast, ADC values in the medulla and the occipital cortex were not increased during DKA, and ADC changes in the medulla tended to be negatively correlated with other regions. Regions supplied by the anterior / middle cerebral artery circulation had greater elevations in both ADC and brain water content during DKA compared with regions supplied by the posterior cerebral artery circulation. CONCLUSIONS: ADC changes during DKA in the brainstem contrast with those of other brain regions, and changes in both ADC and brain water content during DKA vary according to regional vascular supply. These data suggest that brainstem blood flow might possibly be reduced during DKA concurrent with hyperemia in other brain regions