Collusion-resistant cost-sharing mechanisms : design techniques, analyses, trade-offs

Florian SchoppmannPaderborn, Univ., Diss., 200

Production and Properties of the Liquid Scintillators used in the Stereo Reactor Neutrino Experiment

The electron antineutrino spectrum in the Stereo reactor experiment (ILL Grenoble) is measured via the inverse beta decay signals in an organic liquid scintillator. The six target cells of the Stereo detector are filled with about 1800 litres of Gd-loaded liquid scintillator optimised for the requirements of the experiment. These target cells are surrounded by similar cells containing liquid scintillator without the Gd-loading. The development and characteristics of these scintillators are reported. In particular, the transparency, light production and pulse shape discrimination capabilities of the organic liquids are discussed.Comment: 10 pages, 4 figure

MK2 and ETV1 Are Prognostic Factors in Esophageal Adenocarcinomas

Background. Esophageal cancer is ranked in the top ten of diagnosed tumors worldwide. Even though improvements in survival could be noticed over the last years, prognosis remains poor. ETS translocation variant 1 (ETV1) is a member of a family of transcription factors and is phosphorylated by mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2). Aim of this study was to evaluate the prognostic role of MK2 and ETV1 in esophageal cancer. Methods. Consecutive patients that underwent surgical resection at the department of surgery at the Medical University of Vienna between 1991 and 2012 were included into this study. After microscopic analysis, tissue micro arrays (TMAs) were created and immunohistochemistry was performed with antibodies against MK2 and ETV1. Results. 323 patients were included in this study. Clinical data was achieved from a prospective patient data base. Nuclear overexpression of MK2 was observed in 143 (44.3%) cases for nuclear staining and in 142 (44.0%) cases a cytoplasmic overexpression of MK2 was observed. Nuclear and cytoplasmic ETV1 overexpression was detected in 20 cases (6.2%) and 30 cases (9.3%), respectively. In univariate survival analysis, cMK2 and nETV1 were found to be significantly associated with patients' overall survival. Whereas overexpression of cMK2 was associated with shorter, nETV1 was associated with longer overall survival. In multivariate survival analysis, both cMK2 and nETV1 were found to be independent prognostic factors for the subgroup of EAC as well. Discussion. Expression of MK2 and ETV1 are prognostic factors in patients, with esophageal adenocarcinoma

Secure Computation Protocols for Privacy-Preserving Machine Learning

Machine Learning (ML) profitiert erheblich von der Verfügbarkeit großer Mengen an Trainingsdaten, sowohl im Bezug auf die Anzahl an Datenpunkten, als auch auf die Anzahl an Features pro Datenpunkt. Es ist allerdings oft weder möglich, noch gewollt, mehr Daten unter zentraler Kontrolle zu aggregieren. Multi-Party-Computation (MPC)-Protokolle stellen eine Lösung dieses Dilemmas in Aussicht, indem sie es mehreren Parteien erlauben, ML-Modelle auf der Gesamtheit ihrer Daten zu trainieren, ohne die Eingabedaten preiszugeben. Generische MPC-Ansätze bringen allerdings erheblichen Mehraufwand in der Kommunikations- und Laufzeitkomplexität mit sich, wodurch sie sich nur beschränkt für den Einsatz in der Praxis eignen. Das Ziel dieser Arbeit ist es, Privatsphäreerhaltendes Machine Learning mittels MPC praxistauglich zu machen. Zuerst fokussieren wir uns auf zwei Anwendungen, lineare Regression und Klassifikation von Dokumenten. Hier zeigen wir, dass sich der Kommunikations- und Rechenaufwand erheblich reduzieren lässt, indem die aufwändigsten Teile der Berechnung durch Sub-Protokolle ersetzt werden, welche auf die Zusammensetzung der Parteien, die Verteilung der Daten, und die Zahlendarstellung zugeschnitten sind. Insbesondere das Ausnutzen dünnbesetzter Datenrepräsentationen kann die Effizienz der Protokolle deutlich verbessern. Diese Beobachtung verallgemeinern wir anschließend durch die Entwicklung einer Datenstruktur für solch dünnbesetzte Daten, sowie dazugehöriger Zugriffsprotokolle. Aufbauend auf dieser Datenstruktur implementieren wir verschiedene Operationen der Linearen Algebra, welche in einer Vielzahl von Anwendungen genutzt werden. Insgesamt zeigt die vorliegende Arbeit, dass MPC ein vielversprechendes Werkzeug auf dem Weg zu Privatsphäre-erhaltendem Machine Learning ist, und die von uns entwickelten Protokolle stellen einen wesentlichen Schritt in diese Richtung dar.Machine learning (ML) greatly benefits from the availability of large amounts of training data, both in terms of the number of samples, and the number of features per sample. However, aggregating more data under centralized control is not always possible, nor desirable, due to security and privacy concerns, regulation, or competition. Secure multi-party computation (MPC) protocols promise a solution to this dilemma, allowing multiple parties to train ML models on their joint datasets while provably preserving the confidentiality of the inputs. However, generic approaches to MPC result in large computation and communication overheads, which limits the applicability in practice. The goal of this thesis is to make privacy-preserving machine learning with secure computation practical. First, we focus on two high-level applications, linear regression and document classification. We show that communication and computation overhead can be greatly reduced by identifying the costliest parts of the computation, and replacing them with sub-protocols that are tailored to the number and arrangement of parties, the data distribution, and the number representation used. One of our main findings is that exploiting sparsity in the data representation enables considerable efficiency improvements. We go on to generalize this observation, and implement a low-level data structure for sparse data, with corresponding secure access protocols. On top of this data structure, we develop several linear algebra algorithms that can be used in a wide range of applications. Finally, we turn to improving a cryptographic primitive named vector-OLE, for which we propose a novel protocol that helps speed up a wide range of secure computation tasks, within private machine learning and beyond. Overall, our work shows that MPC indeed offers a promising avenue towards practical privacy-preserving machine learning, and the protocols we developed constitute a substantial step in that direction

Search for eV Sterile Neutrinos -- The STEREO Experiment [TAUP 2017]

In the recent years, major milestones in neutrino physics were accomplished at nuclear reactors: the smallest neutrino mixing angle $\theta_{13}$ was determined with high precision and the emitted antineutrino spectrum was measured at unprecedented resolution. However, two anomalies, the first one related to the absolute flux and the second one to the spectral shape, have yet to be solved. The flux anomaly is known as the Reactor Antineutrino Anomaly and could be caused by the existence of a light sterile neutrino eigenstate participating in the neutrino oscillation phenomenon. Introducing a sterile state implies the presence of a fourth mass eigenstate, while global fits favour oscillation parameters around $\sin^{2}(2\theta)=0.09$ and $\Delta m^{2}=1.8\textrm{eV}^{2}$. The STEREO experiment was built to finally solve this puzzle. It is one of the first running experiments built to search for eV sterile neutrinos and takes data since end of 2016 at ILL Grenoble, France. At a short baseline of 10 metres, it measures the antineutrino flux and spectrum emitted by a compact research reactor. The segmentation of the detector in six target cells allows for independent measurements of the neutrino spectrum at multiple baselines. An active-sterile flavour oscillation could be unambiguously detected, as it distorts the spectral shape of each cell's measurement differently. This contribution gives an overview on the STEREO experiment, along with details on the detector design, detection principle and the current status of data analysis.Comment: 5 pages, 4 figures, contribution to the proceedings of the TAUP 2017 conferenc

Endoscopic anterior fundoplication with the Medigus Ultrasonic Surgical Endostapler (MUSE™) for gastroesophageal reflux disease: 6-month results from a multi-center prospective trial

BACKGROUND: Both long-term proton pump inhibitor (PPI) use and surgical fundoplication have potential drawbacks as treatments for chronic gastroesophageal reflux disease (GERD). This multi-center, prospective study evaluated the clinical experiences of 69 patients who received an alternative treatment: endoscopic anterior fundoplication with a video- and ultrasound-guided transoral surgical stapler. METHODS: Patients with well-categorized GERD were enrolled at six international sites. Efficacy data was compared at baseline and at 6 months post-procedure. The primary endpoint was a ≥ 50 % improvement in GERD health-related quality of life (HRQL) score. Secondary endpoints were elimination or ≥ 50 % reduction in dose of PPI medication and reduction of total acid exposure on esophageal pH probe monitoring. A safety evaluation was performed at time 0 and weeks 1, 4, 12, and 6 months. RESULTS: 66 patients completed follow-up. Six months after the procedure, the GERD-HRQL score improved by >50 % off PPI in 73 % (48/66) of patients (95 % CI 60-83 %). Forty-two patients (64.6 %) were no longer using daily PPI medication. Of the 23 patients who continued to take PPI following the procedure, 13 (56.5 %) reported a ≥ 50 % reduction in dose. The mean percent of total time with esophageal pH <4.0 decreased from baseline to 6 months (P < 0.001). Common adverse events were peri-operative chest discomfort and sore throat. Two severe adverse events requiring intervention occurred in the first 24 subjects, no further esophageal injury or leaks were reported in the remaining 48 enrolled subjects. CONCLUSIONS: The initial 6-month data reported in this study demonstrate safety and efficacy of this endoscopic plication device. Early experience with the device necessitated procedure and device changes to improve safety, with improved results in the later portion of the study. Continued assessment of durability and safety are ongoing in a three-year follow-up study of this patient group

The operation of eVTOLs in the urban air mobility sector : use case & operator assessment

Electric vertical takeoff and landing (eVTOL) technology enables a sustainable form of aviation for currently unserved connections. eVTOLs can reduce the carbon emissions of the aviation industry by replacing conventional helicopters and smaller aircrafts. In addition, traffic congestion in large cities can be decreased and travel times shortened. This thesis examines which use case is offered to the passengers. In addition, the prospective urban air mobility (UAM) market player that is expected to become a potential operator in the short term is summarized, alongside the value proposition (VP), key resources (KR), key activities (KA), and key partnerships (KP) of an eVTOL operator. The findings have been obtained through a qualitative research approach questioning 16 UAM experts, commercial as well as private aviation companies. The results reveal that eVTOL manufacturers are going to be the first market players to operate eVTOLs in the short to medium term. Commercial airlines are expected to step into the market in the long term. Interviews have additionally shown that airport shuttles will be the first served use case. The primary value proposition is saving time for the passengers. The primary key resource is human staff. The primary key activity is eVTOL maintenance. The primary key partnership is with the infrastructure provider and/or operator. Furthermore, this research adds value to the existing UAM literature on eVTOL operators, first commercially offered use cases as well as elements of an operator’s business model.A tecnologia de decolagem e aterrissagem vertical elétrica (eVTOL) permite uma forma sustentável de aviação para conexões atualmente não atendidas. Os eVTOLs podem reduzir as emissões de carbono da indústria da aviação substituindo helicópteros convencionais e aeronaves menores. Além disso, o congestionamento do tráfego nas grandes cidades pode ser reduzido e os tempos de viagem reduzidos. Esta tese examina qual caso de uso é oferecido aos passageiros. Além disso, o potencial participante do mercado de mobilidade aérea urbana (UAM) que deve se tornar um operador potencial no curto prazo é resumido, juntamente com a proposta de valor (VP), recursos-chave (KR), atividades-chave (KA) e parcerias (KP) de um operador eVTOL. Os resultados foram obtidos por meio de uma abordagem de pesquisa qualitativa questionando 16 especialistas, empresas de aviação comercial e privada. Os resultados revelam que os fabricantes de eVTOL serão os primeiros players do mercado a operar eVTOLs no curto e médio prazo. Espera-se que as companhias aéreas comerciais entrem no mercado a longo prazo. As entrevistas também mostraram que os ônibus do aeroporto serão o primeiro caso de uso servido. A principal proposta de valor é economizar tempo para os passageiros. O recurso-chave primário é a equipe humana. A atividade de chave primária é a manutenção do eVTOL. A parceria de chave primária é com o provedor e/ou operador de infraestrutura. Além disso, esta pesquisa agrega valor à literatura UAM existente sobre operadoras eVTOL, primeiros casos de uso oferecidos comercialmente, bem como elementos do modelo de negócios de uma operadora

The road to electrification: strategic analysis of enigma motors´ transition to electric vehicles

This thesis explores the strategic transformation of Enigma Motors, a simulated automotive company, during its transition from combustion to electric vehicles. The first part provides a firm analysis, examining the company's strategic, operational and marketing decisions in response to market demands, competition dynamics, and operational processes. The second part offers a personal reflection on the leadership dynamics and interpersonal challenges encountered during this transformative process. The study illuminates the complexities of handling a major industry shift and the importance of adaptability and learning in strategic decision-making

Polynomial-time computability of the edge-reliability of graphs using Gilbert's formula

Reliability is an important consideration in analyzing computer and other communication networks, but current techniques are extremely limited in the classes of graphs which can be analyzed efficiently. While Gilbert's formula establishes a theoretically elegant recursive relationship between the edge reliability of a graph and the reliability of its subgraphs, naive evaluation requires consideration of all sequences of deletions of individual vertices, and for many graphs has time complexity essentially Θ (N!). We discuss a general approach which significantly reduces complexity, encoding subgraph isomorphism in a finer partition by invariants, and recursing through the set of invariants