Multiband effective bond-orbital model for nitride semiconductors with wurtzite structure

A multiband empirical tight-binding model for group-III-nitride semiconductors with a wurtzite structure has been developed and applied to both bulk systems and embedded quantum dots. As a minimal basis set we assume one s-orbital and three p-orbitals, localized in the unit cell of the hexagonal Bravais lattice, from which one conduction band and three valence bands are formed. Non-vanishing matrix elements up to second nearest neighbors are taken into account. These matrix elements are determined so that the resulting tight-binding band structure reproduces the known Gamma-point parameters, which are also used in recent kp-treatments. Furthermore, the tight-binding band structure can also be fitted to the band energies at other special symmetry points of the Brillouin zone boundary, known from experiment or from first-principle calculations. In this paper, we describe details of the parametrization and present the resulting tight-binding band structures of bulk GaN, AlN, and InN with a wurtzite structure. As a first application to nanostructures, we present results for the single-particle electronic properties of lens-shaped InN quantum dots embedded in a GaN matrix.Comment: 10 pages, 5 figures, two supplementary file

Interpersonal emotion regulation: a review of social and developmental components

A staple theme in clinical psychology, emotion regulation, or the ability to manage one's emotions, is directly linked with personal wellbeing and the ability to effectively navigate the social world. Until recently, this concept has been limited to a focus on intrapersonal processes, such as suppression. Less emphasis has been placed on developmental, social, and cultural aspects of emotion regulation. We argue here that as social beings, our engagement in emotion regulation may often occur interpersonally, with trusted others helping us to regulate our emotions. This review will highlight recent research on interpersonal emotion regulation processes.Dr Hofmann receives financial support from the Alexander von Humboldt Foundation (as part of the Humboldt Prize), NIH/NCCIH (R01AT007257), NIH/NIMH (R01MH099021, U01MH108168), and the James S. McDonnell Foundation 21st Century Science Initiative in Understanding Human Cognition - Special Initiative. He receives compensation for his work as an advisor from the Palo Alto Health Sciences and for his work as a Subject Matter Expert from John Wiley & Sons, Inc. and SilverCloud Health, Inc. He also receives royalties and payments for his editorial work from various publishers. (Alexander von Humboldt Foundation; R01AT007257 - NIH/NCCIH; R01MH099021 - NIH/NIMH; U01MH108168 - NIH/NIMH; James S. McDonnell Foundation 21st Century Science Initiative in Understanding Human Cognition - Special Initiative)Accepted manuscrip

Do new sea spray aerosol source functions improve the results of a regional aerosol model?

Sea spray aerosol particle is a dominating part of the global aerosol mass load of natural origin. Thus, it strongly influences the atmospheric radiation balance and cloud properties especially over the oceans. Uncertainties of the estimated climate impacts by this aerosol type are partly caused by the uncertainties in the particle size dependent emission fluxes of sea spray aerosol particle. We present simulations with a regional aerosol transport model system in two domains, for three months and compared the model results to measurements at four stations using various sea spray aerosol particle source source functions. Despite these limitations we found the results using different source functions are within the range of most model uncertainties. Especially the model's ability to produce realistic wind speeds is crucial. Furthermore, the model results are more affected by a function correcting the emission flux for the effect of the sea surface temperature than by the use of different source functions. © 2018 The Author

Tight-Binding-Theorie für optische und magnetische Eigenschaften von Halbleitern

The subject of the first part of this thesis is the investigation of electronic and optical properties of polar and nonpolar InN/GaN quantum-dots, which was done in the framework of a cooperation with O. Marquardt and K. Schuh. The electronic properties were calculated by means of an effective-bond-orbital model (EBOM) by including the elastic properties of the nanostructure, which were provided and calculated in second-order continuum-elasticity theory by O. Marquardt. In order to solve the interacting many-body problem, K. Schuh applied a full configuration-interaction calculation and used the single-particle basis obtained by the EBOM to construct the interacting configurations. The purpose of this investigation was to study the interplay between attractive electron-hole interaction and the strong persistent intrinsic fields with piezo- and pyroelectric contributions in these nitride-heterostructures for one exciton. As a main result, the intrinsic fields were compensated by the Coulomb-interaction in the nonpolar quantum dot, thus enhancing the many-body oscillator-strength of the ground-state transition. This effect is a possible explanation for experimental findings of fast recombination rates in nonpolar nitride quantum-dots. In the second part of this thesis electronic and magnetic properties of the dilute magnetic semiconductors (DMS) Ga$_{1-x}$Mn$_{x}$As and Ga$_{1-x}$Mn$_{x}$N were studied with the goal to improve existing theoretical models describing magnetic impurities in these systems. By treating disorder effects exactly in combination with a realistic bandstructure described within the EBOM, it was shown that nonmagnetic impurity scattering terms are important to stabilize ferromagnetic order, as the effective exchange interactions are mainly ferromagnetic and agree with first-principles. The magnetic properties were examined by means of an equilibrium Green's-function theory for the disorderd Heisenberg model in Tyablikow approximation after a mapping of the exchange constants calculated earlier was done. The results for the concentration dependance of the critical temperature $T_{C}$ of Ga$_{1-x}$Mn$_{x}$As were in qualitative and quantitative agreement with existing experimental and theoretical data. Similiar studies were performed for Ga$_{1-x}$Mn$_{x}$N, but the electronic model was constructed to reproduce experimental findings of the optical conductivity, which was calculated theoretically as well. As a main result, ferromagnetic order with a low $T_{C}$ correlates with a nonvanishing AC-conductivity in the infrared spectral-region and a Fermi-level lying in the impurity-band

Social Sustainability and Alexander's Living Structure Through a New Kind of City Science

The disputed endorsement of inherited visceral and universal aesthetic preferences justifies the scientific validity of Alexander's living structure. Apart from implying a resource-efficient way to promote well-being through urban design, the premise favors a collective approach to human self-perception and social justice. To better understand the contributions of Alexander, this article explores current knowledge about visceral and universal aesthetic preferences for living structure and if and how the new kind of city science, a mathematical model describing living structure, can be used for further testing. It also elaborates on the social impact of living structure, including its premise, and the potential of the new kind of city science to support social sustainability. A literature synthesis on living structure, the new kind of city science, and the premise showed a positive link between well-being and exposure to living structure. Limitations in research design nevertheless precluded conclusions about the associated visceral and universal aesthetic preferences. The new kind of city science was found appropriate for further research by holistically representing living structure. Moreover, like the hypothesized biological origin, social learning and sociocultural transmission were found to theoretically support the premise of universality and a collective approach to human identity and social justice, with further societal implications. For the concept of living structure to support social sustainability, it must be coupled with the promotion of empowerment and community mobilization. Hence, the operationalization of the new kind of city science should align with Alexander's call for bottom-up approaches

Dissociating memory networks in early Alzheimer's disease and frontotemporal lobar degeneration - a combined study of hypometabolism and atrophy

Introduction: We aimed at dissociating the neural correlates of memory disorders in Alzheimer’s disease (AD) and frontotemporal lobar degeneration (FTLD). Methods: We included patients with AD (n = 19, 11 female, mean age 61 years) and FTLD (n = 11, 5 female, mean age 61 years) in early stages of their diseases. Memory performance was assessed by means of verbal and visual memory subtests from the Wechsler Memory Scale (WMS-R), including forgetting rates. Brain glucose utilization was measured by [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) and brain atrophy by voxel-based morphometry (VBM) of T1-weighted magnetic resonance imaging (MRI) scans. Using a whole brain approach, correlations between test performance and imaging data were computed separately in each dementia group, including a group of control subjects (n = 13, 6 female, mean age 54 years) in both analyses. The three groups did not differ with respect to education and gender. Results: Patients in both dementia groups generally performed worse than controls, but AD and FTLD patients did not differ from each other in any of the test parameters. However, memory performance was associated with different brain regions in the patient groups, with respect to both hypometabolism and atrophy: Whereas in AD patients test performance was mainly correlated with changes in the parieto-mesial cortex, performance in FTLD patients was correlated with changes in frontal cortical as well as subcortical regions. There were practically no overlapping regions associated with memory disorders in AD and FTLD as revealed by a conjunction analysis. Conclusion: Memory test performance may not distinguish between both dementia syndromes. In clinical practice, this may lead to misdiagnosis of FTLD patients with poor memory performance. Nevertheless, memory problems are associated with almost completely different neural correlates in both dementia syndromes. Obviously, memory functions are carried out by distributed networks which break down in brain degeneration

Praktische Empfehlungen zum Screening und Management von Funktionsstörungen der Nebennierenrinde bei einer akuten SARS-CoV-2-Infektion

Erkrankungen der Nebennierenrinde erfordern im Rahmen der Severe-acute-respiratory-syndrome-coronavirus-2(SARS-CoV-2)-Pandemie eine besondere Aufmerksamkeit. Zum einen können SARS-CoV-2-Infektionen sich auch extrapulmonal manifestieren und endokrine Störungen – insbesondere im Bereich der Nebennierenrinde – verursachen. Zum anderen sind Patienten mit einer vorbestehenden Nebennierenrindeninsuffizienz oder einem Hyperkortisolismus durch eine schwerwiegende Infektion wie etwa mit SARS-CoV‑2 besonders gefährdet, zusätzliche Komplikationen oder einen schwerwiegenderen Verlauf einer akuten SARS-CoV-2-Infektion mit erhöhter Mortalität zu erleiden. Insbesondere bei hämodynamisch instabilen Patienten mit SARS-CoV-2-Infektion müssen deshalb auch Erkrankungen der Nebennieren differenzialdiagnostisch erwogen und gegebenenfalls abgeklärt werden, falls diese nicht bereits anamnestisch bekannt sind. Weiterhin kann auch die Therapie einer SARS-CoV-2-Infektion mit hohen Glukokortikoiddosen über einen längeren Zeitraum eine sekundäre Nebennierenrindeninsuffizienz verursachen. Wir stellen hier deshalb eine Praxisempfehlung zur Erkennung und Therapie von Nebennierenfunktionsstörungen bei Patient*innen mit SARS-CoV-2-Infektion vor. = Diseases of the adrenal cortex require particular attention during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Firstly, SARS-CoV‑2 infections can give rise to extrapulmonary manifestations and cause endocrine disorders, particularly in the adrenal cortex. Furthermore, patients with pre-existing insufficiency of the adrenal cortex or hypercortisonism are particularly at risk from a severe infection such as SARS-CoV‑2, to suffer from additional complications or a more severe course of a SARS-CoV‑2 infection with a higher mortality. Especially in hemodynamically unstable patients with a SARS-CoV‑2 infection, diseases of the adrenal glands should also be considered in the differential diagnostics and if necessary clarified, if this is not already known. Prolonged treatment of patients with a SARS-CoV‑2 infection with regimens containing high doses of glucocorticoids can also result in a secondary adrenal insufficiency. In order to address these special aspects, some practical recommendations for the diagnostic and therapeutic management of functional disorders of the adrenal glands in patients with a SARS-CoV‑2 infection are therefore presented

The influence of environmental drivers on the enrichment of organic carbon in the sea surface microlayer and in submicron aerosol particles – measurements from the Atlantic Ocean

The export of organic matter from ocean to atmosphere represents a substantial carbon flux in the Earth system, yet the impact of environmental drivers on this transfer is not fully understood. This work presents dissolved and particulate organic carbon (DOC, POC) concentrations, their enrichment factors in the sea surface microlayer (SML), and equivalent measurements in marine aerosol particles across the Atlantic Ocean. DOC concentrations averaged 161 ± 139 μmol L–1 (n = 78) in bulk seawater and 225 ± 175 μmol L–1 (n = 79) in the SML; POC concentrations averaged 13 ± 11 μmol L–1 (n = 80) and 17 ± 10 μmol L–1 (n = 80), respectively. High DOC and POC enrichment factors were observed when samples had low concentrations, and lower enrichments when concentrations were high. The impacts of wind speed and chlorophyll-a levels on concentrations and enrichment of DOC and POC in seawater were insignificant. In ambient submicron marine aerosol particles the concentration of water-soluble organic carbon was approximately 0.2 μg m–3. Water-insoluble organic carbon concentrations varied between 0.01 and 0.9 μg m–3, with highest concentrations observed when chlorophyll-a concentrations were high. Concerted measurements of bulk seawater, the SML and aerosol particles enabled calculation of enrichment factors of organic carbon in submicron marine ambient aerosols, which ranged from 103 to 104 during periods of low chlorophyll-a concentrations and up to 105 when chlorophyll-a levels were high. The results suggest that elevated local biological activity enhances the enrichment of marine-sourced organic carbon on aerosol particles. However, implementation of the results in source functions based on wind speed and chlorophyll-a concentrations underestimated the organic fraction at low biological activity by about 30%. There may be additional atmospheric and oceanic parameters to consider for accurately predicting organic fractions on aerosol particles