Nanoskalige Spinstrukturen an Oberflächen aufgrund von Austauschfrustration und Wechselwirkungstermen höherer Ordnung

In this thesis, density functional theory (DFT) calculations using the full potential linearized augmented planewave and the projector augmented wave method in combination with an atomistic spin model are employed to explore the effect of higher-order exchange interactions on the magnetic ground state of ultrathin transition metal (TM) films on surfaces. First, a systematic study of higher-order interactions (HOI) beyond the pairwise Heisenberg exchange in magnetic trilayers comprising a single hexagonal Fe or Co layer sandwiched between 4d and 5d TM layers is presented. While for Fe based trilayers HOI terms can range on the same order of magnitude as the Heisenberg exchange interaction, they turn out relatively small for Co based systems. The trends obtained for freestanding trilayers serve as a basis to understand HOI in ultrathin films on surfaces that are amenable to experiments. Further DFT calculations show that HOI can induce spontaneous nanoscale two-dimensional multi-Q states with collinear spin structure in hexagonal Fe/Rh films with different stacking sequence and thickness on the Ir(111) surface studied by experimental collaborators via spin-polarized scanning tunneling microscopy (SP-STM). DFT combined with an atomistic spin model elucidates a competition of frustrated Heisenberg exchange and HOI as the driving mechanism for the formation of the observed complex spin structures while the DMI is weak. The same approach further demonstrates that the interplay of pairwise Heisenberg exchange, HOI and the DMI is responsible for the symmetry and collinearity of spin lattices in Fe monolayers in direct contact with Ir(111): while for fcc-Fe the well-known square nanoskyrmion lattice is obtained as the magnetic ground state, a hexagonal multi-Q state with nearly collinear magnetic moments occurs in hcp-Fe similar to the above-mentioned hexagonal spin structures in Fe/Rh bilayers

Group Conditions for Entrepreneurial Visions: Role Confidence, Hierarchical Congruences, and the Imagining of Future in Entrepreneurial Groups

An essential part of entrepreneurial activity is the drafting and narrating of an entrepreneurial vision. This study is premised on the observation that entrepreneurial groups form an interaction arena for the practice of imagining the future and asks how the content of entrepreneurial visions is shaped by the conditions of the group. Taking an entrepreneurship-as-practice lens, which we enrich with sociological theory on the future (Beckert) and small groups (Fine), we engage in an in-depth case study of 12 entrepreneurial groups. We show how the content of entrepreneurial visions is configured by four elements (i.e., fictional expectation for the business or the group; future orientation that is continuing or divergent) and name two group conditions (i.e., role confidence and hierarchical congruence) that direct their configuration. We propose that lacking role confidence can impede thinking about the future of a business and that narrative hierarchies that challenge structural hierarchies can open a window for divergent future orientation. This study contributes to a novel theoretical understanding of where entrepreneurial visions come from by emphasizing politics of expectations within groups and calling to consider group conditions as a relevant context for entrepreneurial visions

Entgeltflexibilisierung aus juristischer Sicht : juristische Beiträge des interdisziplinären Symposiums "Flexibilisierung des Arbeitsentgelts aus ökonomischer und juristischer Sicht" am 25. und 26. Januar 2001 in Mannheim

Juristische Beiträge des interdisziplinären Symposiums "Flexibilisierung des Arbeitsentgelts aus ökonomischer und juristischer Sicht" am 25. und 26.Januar 2001 in Mannheim

Giving and Following Recommendations on Video-on-Demand Services

This is an empirical paper about giving, receiving and following recommendations on Video-on-Demand (VoD) services, including results on gender-specific differences. Based upon a model for infor-mation behavior on VoD services, we applied an online survey and generated 1,258 valid question-naires from active VoD users. Participants receive recommendations from the systems once a week on average, but they follow them only occasionally. They give actively recommendations to other people sever-al times a month. Users do not receive recommenda-tions from other users as often as from the services (only several times a month); however, they follow those personal recommendations more often. The most important source for receiving personal rec-ommendations is face-to-face communication. Obvi-ously, VoD users follow personal recommendations from other people more than suggestions from algo-rithmically generated recommender systems. Besides, self-determined content selection following intrinsic motivation is important. The findings are of interest for research on digital and social media and for VoD services

Two Cases of Cerebral Sinus Venous Thrombosis Following Chemotherapy for Non-Seminomatous Germ Cell Tumor

We report on two patients with cerebral sinus venous thrombosis following chemotherapy with cisplatin, bleomycin and etoposide for non-seminomatous germ cell tumor. Headache and neurological deficits were the leading symptoms. Cancer and cisplatin chemotherapy are well-known risk factors for thromboembolic events. The therapeutic strategy is an anticoagulant therapy. Symptoms are usually reversible within weeks under this therapy. Therefore, in patients with testicular cancer and chemotherapy who present with neurological symptoms, cerebral sinus venous thrombosis should be considered in the differential diagnosis