Paraneoplastic cerebellar degeneration associated with lymphoepithelial carcinoma of the tonsil

Background: Paraneoplastic cerebellar degeneration (PCD) is a classical tumor-associated, immune-mediated disease typically associated with gynecological malignancies, small-cell lung-cancer or lymphoma. Case presentation: Here we present the case of a 38-year old male with an over 12 months rapidly progressive cerebellar syndrome. Extensive diagnostic workup revealed selective hypermetabolism of the right tonsil in whole-body PET. Histological examination after tonsillectomy demonstrated a lymphoepithelial carcinoma of the tonsil and the tongue base strongly suggesting a paraneoplastic cause of the cerebellar syndrome. To the best of our knowledge this is the first case of an association of a lymphoepithelial carcinoma, a rare pharyngeal tumor, with PCD. Conclusions: In cases of classical paraneoplastic syndromes an extensive search for neoplasms should be performed including whole-body PET to detect tumors early in the course of the disease

Coherent control of a nanomechanical two-level system

The Bloch sphere is a generic picture describing a coupled two-level system and the coherent dynamics of its superposition states under control of electromagnetic fields. It is commonly employed to visualise a broad variety of phenomena ranging from spin ensembles and atoms to quantum dots and superconducting circuits. The underlying Bloch equations describe the state evolution of the two-level system and allow characterising both energy and phase relaxation processes in a simple yet powerful manner. Here we demonstrate the realisation of a nanomechanical two-level system which is driven by radio frequency signals. It allows to extend the above Bloch sphere formalism to nanoelectromechanical systems. Our realisation is based on the two orthogonal fundamental flexural modes of a high quality factor nanostring resonator which are strongly coupled by a dielectric gradient field. Full Bloch sphere control is demonstrated via Rabi, Ramsey and Hahn echo experiments. This allows manipulating the classical superposition state of the coupled modes in amplitude and phase and enables deep insight into the decoherence mechanisms of nanomechanical systems. We have determined the energy relaxation time T1 and phase relaxation times T2 and T2*, and find them all to be equal. This not only indicates that energy relaxation is the dominating source of decoherence, but also demonstrates that reversible dephasing processes are negligible in such collective mechanical modes. We thus conclude that not only T1 but also T2 can be increased by engineering larger mechanical quality factors. After a series of ground-breaking experiments on ground state cooling and non-classical signatures of nanomechanical resonators in recent years, this is of particular interest in the context of quantum information processing

Signatures of two-level defects in the temperature-dependent damping of nanomechanical silicon nitride resonators

The damping rates of high quality factor nanomechanical resonators are well beyond intrinsic limits. Here, we explore the underlying microscopic loss mechanisms by investigating the temperature-dependent damping of the fundamental and third harmonic transverse flexural mode of a doubly clamped silicon nitride string. It exhibits characteristic maxima reminiscent of two-level defects typical for amorphous materials. Coupling to those defects relaxes the momentum selection rules, allowing energy transfer from discrete long wavelength resonator modes to the high frequency phonon environment

AFM manipulation of damping in nanomechanical resonators

Ein bedeutender Teilbereich der Nanomechanik beschäftigt sich mit der Erforschung kleiner, schwingender Systeme, welche aufgrund ihrer geringen Massen auf minimale Umgebungseinflüsse reagieren. Dies macht derartige nanoskalige Resonatoren zu äußerst empfindlichen Sensoren. Die fortschreitende Miniaturisierung nanomechanischer Systeme erfordert nun einerseits die Weiterentwicklung von Antriebs- und Detektionsmechanismen, andererseits spielt die Verbesserung der mechanischen Güte eine zentrale Rolle für die Erhöhung der Empfindlichkeit möglicher sensorischer Anwendungen. Hierfür ist die Untersuchung der Mechanismen, welche die mechanische Dämpfung der Resonatoren verursachen, erforderlich. Um das Dämpfungsverhalten eines beidseitig eingespannten nanomechanischen Siliziumnitridresonators zu untersuchen und zu kontrollieren wird in dieser Arbeit ein Rasterkraftmikroskop (AFM) eingesetzt. Dessen Spitze wird mit dem Resonator in Kontakt gebracht und beeinflusst als lokale Störung kontrolliert das nanomechanische System. Das AFM bildet hierbei einen mechanischen Punktkontakt mit der Aufhängung des Resonators aus, wodurch Schwingungsenergie vom Resonator in die AFM-Spitze abgeleitet wird. Aufgrund der hervorragenden räumlichen Auflösung des Rasterkraftmikroskops ist es somit möglich den ortsaufgelösten Energiefluss zwischen den beiden Systemen zu untersuchen. Hierfür wird die mechanische Resonanz der Siliziumnitridsaite im Radiofrequenzbereich mittels eines heterodynen Überlagerungsverfahrens elektrisch ausgelesen. Die Bewegung des zwischen zwei Goldelektroden platzierten Resonators ruft eine Kapazitätsänderung des durch die Elektroden gebildeten Kondensators hervor. Durch Kopplung an einen Mikrowellenschwingkreis kann diese Kapazitätsänderung ausgelesen werden. Zudem können Gleich- und Wechselspannungen an die Elektroden angelegt werden, wodurch einerseits die Resonanzfrequenz des Resonators verstimmt und andererseits die mechanische Bewegung angetrieben werden kann. Das derart angetriebene nanomechanische System kann nun unter Einfluss der lokalen Störung durch das AFM in positions- und kraftabhängigen Messungen untersucht werden. Es zeigt sich, dass der Energietransfer durch den mechanischen Punktkontakt einen äußerst starken Einfluss auf die mechanische Güte des Siliziumnitridbalkens hat, seine Resonanzfrequenz jedoch nur geringfügig beeinflusst wird. Dies kann durch eine Änderung der mechanischen Impedanzanpassung des Resonators an seine Umgebung erklärt werden. Die Impedanzänderung durch den mechanischen Punktkontakt ermöglicht den Übergang eines stark fehlangepassten nanomechanischen Systems hoher Güte zu einem angepassten System niedriger Güte auf einem einzigen Resonator. Hierbei bleibt die intrinsische Dämpfung des Resonators unverändert und die zusätzlich induzierte Dämpfung kann der Abstrahlung von Vibrationsenergie in die Umgebung zugeschrieben werden. Resonatoren hoher Güte ergeben sich somit als Systeme mit möglichst großer Fehlanpassung der mechanischen Impedanz. Desweiteren kann mit dieser Methode das in den Aufhängepunkt des Resonators hineinreichende Verzerrungsfeld abgebildet werden. Dies ermöglicht die Untersuchung gekoppelter Moden des Resonators sowie deren Modenform

Love at First Sight? A User Experience Study of Self-Sovereign Identity Wallets

Today’s systems for digital identity management exhibit critical security, efficiency, and privacy issues. A new paradigm, called Self-Sovereign Identity (SSI), addresses these shortcomings by equipping users with mobile wallets and empowering them to manage their digital identities. Various companies and governments back this paradigm and promote its development and diffusion. User experience often plays a subordinate role in these efforts, even though it is crucial for user satisfaction and adoption. We thus conduct a comprehensive user experience study of four prominent SSI wallets using a mixed-method approach that involves moderated and remote interviews and the User Experience Questionnaire (UEQ). We find that the examined wallets already provide a decent level of user experience, yet further improvements need to be done. In particular, the examined wallets do not make their novelty and benefits sufficiently apparent to users. Our analysis contributes to user experience research and offers guidance for SSI practitioners

Patient Specific Instruments and Patient Individual Implants-A Narrative Review.

Joint arthroplasties are one of the most frequently performed standard operations worldwide. Patient individual instruments and patient individual implants represent an innovation that must prove its usefulness in further studies. However, promising results are emerging. Those implants seem to be a benefit especially in revision situations. Most experience is available in the field of knee and hip arthroplasty. Patient-specific instruments for the shoulder and upper ankle are much less common. Patient individual implants combine individual cutting blocks and implants, while patient individual instruments solely use individual cutting blocks in combination with off-the-shelf implants. This review summarizes the current data regarding the implantation of individual implants and the use of individual instruments

Non-adiabatic dynamics of two strongly coupled nanomechanical resonator modes

The Landau-Zener transition is a fundamental concept for dynamical quantum systems and has been studied in numerous fields of physics. Here we present a classical mechanical model system exhibiting analogous behaviour using two inversely tuneable, strongly coupled modes of the same nanomechanical beam resonator. In the adiabatic limit, the anticrossing between the two modes is observed and the coupling strength extracted. Sweeping an initialized mode across the coupling region allows mapping of the progression from diabatic to adiabatic transitions as a function of the sweep rate

With or Without Blockchain? Towards a Decentralized, SSI-based eRoaming Architecture

Fragmentation and limited accessibility of charging infrastructure impede the adoption of electric vehicles. To improve the availability of charging infrastructure independent of providers, eRoaming offers a promising solution. Yet, current eRoaming systems are typically centralized, which raises concerns of market power concentration. While the use of blockchain technology can obviate such concerns, it comes with significant privacy challenges. To address these challenges, we explore a combination of blockchain with self-sovereign identity. Specifically, we apply a design science research approach, which helps us to identify requirements, derive a conceptual architecture, and deduce design principles for decentralized eRoaming and beyond. We find that blockchain may best leverage its benefits when it takes a backseat as a public registry for legal entities. Moreover, we find that the use of self-sovereign identities could improve compliance with privacy regulations, but they should not be overused

The Competition Effect of Decentralized Platforms: An Analytical Model

Envelopment angst and concerns about the exploitative appropriation of data network effects can lead to fragmented platform markets. In this paper, we investigate if this fragmentation can be mended with decentralized platform architectures. Abstracting from an exemplary case in the mobility-as-a-service sector, we model a competitive two-platform market with a centralized platform and decentralized alternative. We find that in markets with high envelopment costs, the co-existence of these platforms leads to market segmentation: Complementors with low market power join the centralized platform, while complementors with high market power join the decentralized platform. Furthermore, the existence of a decentralized alternative can increase welfare. Lastly, by considering data control aspects, we demonstrate the effect of favorable platform design on complementor decision-making

Video Games as Time Machines: Video Game Nostalgia and the Success of Retro Gaming

This article conceptually integrates research on the experience of nostalgia—defined as a predominantly positive, social, and past-oriented emotion—into the fold of video game research. We emphasize the role of nostalgia as an explanation for contemporary retro gaming trends, and suggest that nostalgia towards gaming events is a necessary area of research. To those ends, we broadly review existing literature on nostalgia before specifically focusing on media-induced nostalgia, and demonstrate how theoretical and empirical observations from this work can be applied to understand video game nostalgia. In particular, we argue that engaging in older gaming experiences indirectly (via memories) and even directly (via replaying or recreating experiences) elicits nostalgia, which in turn contributes to players’ self-optimization and enhanced well-being. Moreover, as gamers and the medium mature together, nostalgic experiences with the medium are likely to become increasingly prevalent. The broad aim of this article is to offer future directions for research on video game nostalgia and provide a research agenda for research in this area