A wave function based ab initio non-equilibrium Green's function approach to charge transport

We present a novel ab initio non-equilibrium approach to calculate the current across a molecular junction. The method rests on a wave function based description of the central region of the junction combined with a tight binding approximation for the electrodes in the frame of the Keldysh Green's function formalism. In addition we present an extension so as to include effects of the two-particle propagator. Our procedure is demonstrated for a dithiolbenzene molecule between silver electrodes. The full current-voltage characteristic is calculated. Specific conclusions for the contribution of correlation and two-particle effects are derived. The latter are found to contribute about 5% to the current. The order of magnitude of the current coincides with experiments.Comment: 21 pages, 3 figure

Aligning Crowdworker Perspectives and Feedback Outcomes in Crowd-Feedback System Design

Leveraging crowdsourcing in software development has received growing attention in research and practice. Crowd feedback offers a scalable and flexible way to evaluate software design solutions and the potential of crowd-feedback systems has been demonstrated in different contexts by existing research studies. However, previous research lacks a deep understanding of the effects of individual design features of crowd-feedback systems on feedback quality and quantity. Additionally, existing studies primarily focused on understanding the requirements of feedback requesters but have not fully explored the qualitative perspectives of crowd-based feedback providers. In this paper, we address these research gaps with two research studies. In study 1, we conducted a feature analysis (N=10) and concluded that from a user perspective, a crowd-feedback system should have five core features (scenario, speech-to-text, markers, categories, and star rating). In the second study, we analyzed the effects of the design features on crowdworkers’ perceptions and feedback outcomes (N=210). We learned that offering feedback providers scenarios as the context of use is perceived as most important. Regarding the resulting feedback quality, we discovered that more features are not always better as overwhelming feedback providers might decrease feedback quality. Offering feedback providers categories as inspiration can increase the feedback quantity. With our work, we contribute to research on crowd-feedback systems by aligning crowdworker perspectives and feedback outcomes and thereby making the software evaluation not only more scalable but also more human-centered

Wertigkeit der hochauflösenden craniellen Computertomographie in der Diagnose von Frakturen der Schädelbasis

Frakturen im Bereich der Schädelbasis sind mitunter (z.B. durch Aufhärtungsartefakte) schwer zu diagnostizieren. Da diese Frakturen unentdeckt und unbehandelt schwerwiegende Konsequenzen nach sich ziehen können und auch hohe Kosten verursachen, ist ihre exakte Diagnose und Darstellung von eminenter Wichtigkeit. Ziel dieser Arbeit war zu untersuchen, ob die hrCCT der bisherigen, „normalen“ CCT (nCCT) in der Detektion von Frakturen insbesondere der Schädelbasis überlegen ist. Hierbei wurden Aufnahmen in einem geräteseitig voreingestellten hochauflösenden Rekonstruktionskernel mit Kantenbetonung aus dem primären Datensatz rekonstruiert. Die Aufnahmen wurden jeweils im Knochenfenster (center 300 HU, width 2000 HU) beurteilt. Die Schichtdicke betrug 4 mm in der nCCT und 2 mm in der hrCCT. Zwei erfahrene Radiologen befundeten die CCTs im Konsensusverfahren. Es wurden insgesamt 98 Patienten mit Frakturen im Bereich des Schädels, der Schädelbasis oder der Gesichtsknochen untersucht. Insgesamt fanden sich bei 93/98 Patienten 255 Frakturen, am häufigsten lokalisiert in der Schädelbasis (70), dem Mittelgesicht (63) und der Orbita (53). In der nCCT wurden bei 64/98 Patienten insgesamt 144 Frakturen diagnostiziert. In der hrCCT wurden bei 29/98 Patienten insgesamt 77% mehr Frakturen erkannt als in der nCCT. Die hrCCT war der nCCT somit signifikant (p<0,05) überlegen. Im Bereich der Schädelbasis diagnostizierte die hrCCT bei 25 Patienten zusätzlich insgesamt 267% mehr Frakturen als die nCCT (p<0,001). Die hrCCT war der nCCT in allen untersuchten Regionen außer Frakturen der posterioren Schädelgrube und der Kalotte signifikant überlegen. Auch der Anteil der als fraglich klassifizierten Frakturen war in der hrCCT signifikant geringer als in der nCCT (p<0,05). Zusammenfassend stellt die hrCCT somit eine bedeutende Verbesserung in der Diagnostik von Frakturen insbesondere der Schädelbasis dar. Daher sollte die hrCCT routinemäßig in die CCT-Diagnostik von Patienten nach SHT implementiert werden, insbesondere da die hrCCT-Aufnahmen aus dem primären Datensatz rekonstruiert werden können und die Untersuchung somit nicht mit einer erhöhten Strahlenbelastung für die Patienten einhergeht

Analysing digital multilocality between urban centres and rural peripheries: Combining and integrating digital and analogue research methods.

The application of mixed methods in researching digitalisation and rural development has numerous benefits in terms of the integration of various data sources. In this paper, we present a novel, mixed methods approach that combines digital and analogue methods. We investigatemultilocal work arrangements of knowledge workers in Switzerland who mainly work in a central urban area but occasionally withdraw to peripheral mountain regions in order to conduct their work in a concentrated and undisturbed environment. To analyse such multilocal work arrangements, we use a mixed methods approach that incorporates six integratedmethods: geotracking, laptop and smartphone tracking, self-administered digital diaries, ethnographic walk-along observations and qualitative semi-structured interviews. Our study illustrates that mixed methods in digitalisation research provide in-depth insights, but that they also have limitations. Furthermore, we show how ethical standards can and should be used to create a basis of trust with the study participants and how this affects the recruitment of the sample

CrowdSurfer: Seamlessly Integrating Crowd-Feedback Tasks nto Everyday Internet Surfing

Crowd feedback overcomes scalability issues of feedback collection on interactive website designs. However, collecting feedback on crowdsourcing platforms decouples the feedback provider from the context of use. This creates more effort for crowdworkers to immerse into such context in crowdsourcing tasks. In this paper, we present CrowdSurfer, a browser extension that seamlessly integrates design feedback collection in crowdworkers’ everyday internet surfing. This enables the scalable collection of in situ feedback and, in parallel, allows crowdworkers to flexibly integrate their work into their daily activities. In a field study, we compare the CrowdSurfer against traditional feedback collection. Our qualitative and quantitative results reveal that, while in situ feedback with the CrowdSurfer is not necessarily better, crowdworkers appreciate the effortless, enjoyable, and innovative method to conduct feedback tasks. We contribute with our findings on in situ feedback collection and provide recommendations for the integration of crowdworking tasks in everyday internet surfing

Far away and yet so close: urban-rural linkages in the context of multilocal work arrangements

Digital technologies allow knowledge workers to work from multiple locations in both urban and rural areas, creating urban–rural linkages. Information and communication technologies (ICTs) play a critical role. We used a novel mixed-methods approach to combine quantitative data from laptop and smartphone tracking with qualitative data from ethnographic walk-along observations and semistructured interviews to analyse the creation of urban–rural linkages and temporary proximity in multilocal work arrangements. The results show that multilocal knowledge workers create urban–rural linkages on demand, thereby generating temporary proximity between the urban and the rural. Yet, the economic embedding of these workers in the rural is limited

Scalable Design Evaluation for Everyone! Designing Configuration Systems for Crowd-Feedback Request Generation

Design evaluation is an important step during software development to ensure users’ requirements are met. Crowd feedback represents an effective approach to tackling scalability issues of traditional design evaluation methods. Crowd-feedback systems are usually developed for a fixed use case and designers lack knowledge on how to build individual crowd-feedback systems by themselves. Consequently, they are rarely applied in practice. To address this challenge, we propose the design of a configuration system to support designers in creating individual crowd-feedback requests. By conducting expert interviews (N=14) and an exploratory literature review, we derive four design rationales for such configuration systems and propose a prototypical configuration system instantiation. We evaluate this instantiation in exploratory focus groups (N=10). The results show that feedback requesters appreciate guidance. However, there seems to be a trade-off between complexity and flexibility. With our research, we contribute with a generalizable concept to support feedback requesters to create individualized crowd-feedback requests to support scalable design evaluation for everyone

Microstructural changes in CoCrFeMnNi under mild tribological load

The lack of a principle element in high-entropy alloys (HEA) leads to unique and unexpected material properties. Tribological loading of metallic materials often results in deformed subsurface layers. As the microstructure feedbacks with friction forces, the microstructural evolution is highly dynamic and complex. The concept of HEAs promises high solid solution strengthening, which might decrease these microstructural changes. Here, we experimentally investigated the deformation behavior of CoCrFeMnNi in a dry, reciprocating tribological contact under a mild normal load. After only a single stroke, a surprisingly thick subsurface deformation layer was observed. This layer is characterized by nanocrystalline grains, twins and bands of localized dislocation motion. Twinning was found to be decisive for the overall thickness of this layer, and twin formation within the stress field of the moving sphere is analyzed. The localization of dislocation activity, caused by planar slip, results in a grain rotation. Fragmentation of twins and dislocation rearrangement lead to a nanocrystalline layer underneath the worn surface. In addition, oxide-rich layers were found after several sliding cycles. These oxides intermix with the nanocrystalline layer due to material transfer to the counter body and re-deposition to the wear track. Having revealed these fundamental mechanisms, the evolution of such deformation layers in CoCrFeMnNi under a tribological load might lead to other HEAs with compositions and properties specifically tailored to tribological applications in the future

Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: the role of multipole effects

We investigate theoretically the effects of interaction between an optical dipole (semiconductor quantum dot or molecule) and metal nanoparticles. The calculated absorption spectra of hybrid structures demonstrate strong effects of interference coming from the exciton-plasmon coupling. In particular, the absorption spectra acquire characteristic asymmetric lineshapes and strong anti-resonances. We present here an exact solution of the problem beyond the dipole approximation and find that the multipole treatment of the interaction is crucial for the understanding of strongly-interacting exciton-plasmon nano-systems. Interestingly, the visibility of the exciton resonance becomes greatly enhanced for small inter-particle distances due to the interference phenomenon, multipole effects, and electromagnetic enhancement. We find that the destructive interference is particularly strong. Using our exact theory, we show that the interference effects can be observed experimentally even in the exciting systems at room temperature.Comment: 9 page

Exchange interaction in chirally coupled quantum dots

We present transport measurements on a system of two lateral quantum dots in a perpendicular magnetic field. Due to edge channel formation in an open conducting region, the quantum dots are chirally coupled. When both quantum dots are tuned into the Kondo regime simultaneously, we observe a change in the temperature dependence of the differential conductance. This is explained by the RKKY exchange interaction between the two dots. As a function of bias the differential conductance shows a splitting of the Kondo resonance which changes in the presence of RKKY interaction.DFG/EXC/QUESTNTH School for Contacts in Nanosystem