Near-Field Microwave Microscopy on nanometer length scales

The Near-Field Microwave Microscope (NSMM) can be used to measure ohmic losses of metallic thin films. We report on the presence of a new length scale in the probe-to- sample interaction for the NSMM. We observe that this length scale plays an important role when the tip to sample separation is less than about 10nm. Its origin can be modeled as a tiny protrusion at the end of the tip. The protrusion causes deviation from a logarithmic increase of capacitance versus decreasing height of the probe above the sample. We model this protrusion as a cone at the end of a sphere above an infinite plane. By fitting the frequency shift of the resonator versus height data (which is directly related to capacitance versus height) for our experimental setup, we find the protrusion size to be 3nm to 5nm. For one particular tip, the frequency shift of the NSMM relative to 2 micrometers away saturates at a value of about -1150 kHz at a height of 1nm above the sample, where the nominal range of sheet resistance values of the sample are 15 ohms to 150 ohms. Without the protrusion, the frequency shift would have followed the logarithmic dependence and reached a value of about -1500 kHz.Comment: 6 pages, 7 figures (included in 6 pages

Molecular analysis of human memory B-cell populations

In der vorliegenden Dissertationsschrift konnten neue Erkenntnisse über B-Lymphozyten in gesunden Menschen gewonnen werden. Der erste Teil behandelt eine sehr seltene und einzigartige B-Zell-Population, die IgD-only B-Zellen. Diese Lymphozyten zeichnet ein ungewöhnlicher Klassenwechsel zu IgD, eine überdurchschnittlich hohe Frequenz an somatischen V-Gen-Mutationen und eine präferentielle Nutzung von V-Leichtketten aus. In der vorliegenden Arbeit konnte gezeigt werden, daß IgD-only B-Zellen aus wenigen, überaus stark expandierten Klonen zusammengesetzt sind und sehr häufig das VH3-30-Gensegment nutzen. Diese neuen Erkenntnisse konnten entscheidend dazu beitragen, eine Theorie zur Superantigen-getriebenen Entstehung dieser einzigartigen B-Zell-Population in gesunden Menschen zu formulieren die im Einklang mit ihren ungewöhnlichen Eigenschaften steht. Das zweite Thema dieser Arbeit ist auf die seit langem kontrovers diskutierte Entstehung von IgM+ B-Zellen mit somatisch mutierten V-Genen fokussiert. Der Nachweis von expandierten post-GC-B-Zell-Klonen mit IgM+ und IgG+ Mitgliedern zeigte, daß IgM+ Gedächtnis-B-Zellen in TD-Immunantworten entstehen können. Weiterhin trugen zwei unabhängige Analysen molekularer Spuren von GC-Reaktionen dazu bei, eine GC-Abstammung auf den Großteil der mutierten IgM* B-Zell-Population zu extrapolieren. Damit konnte die bislang umstrittene Herkunft dieser Zellen, die bis zu 25% der PB B-Zellen in erwachsenen Menschen ausmachen, weitgehend geklärt werden. Daraus resultiert ein besseres Verständnis von verschiedenen Infektionserkrankungen, Autoimmunerkrankungen, Immundefizienzen und B-Zell-Neoplasien, die IgM+ B-Lymphozyten mit mutierten V-Genen einschließen. Darüber hinaus erlaubte die genealogische Analyse der Klone wertvolle Erkenntnisse über die Dynamik und Diversität der Entwicklung von Gedächtnis-B-Zellen in einer GC-Reaktion. Der dritte Abschnitt dieser Arbeit behandelt die Erstellung und Auswertung von Genexpressionsprofilen humaner B-Zell-Populationen. Mit diesen Analysen konnte eine generelle Ähnlichkeit von mutierten IgM+ zu klassengewechselten B-Zellen und auch Gemeinsamkeiten in Gedächtnis-B-Zell-spezifischen Eigenschaften bestätigen, daß diese beiden Populationen näher miteinander verwandt sind als mit naiven B-Zellen. Darüber hinaus konnten spezifische Eigenschaften von IgM+IgD+CD27+ B-Lymphozyten identifiziert werden, die die duale Funktion dieser Zellen in angeborener und adaptiver Immunität erklären

Quantitative Comparison of Abundance Structures of Generalized Communities: From B-Cell Receptor Repertoires to Microbiomes

The \emph{community}, the assemblage of organisms co-existing in a given space and time, has the potential to become one of the unifying concepts of biology, especially with the advent of high-throughput sequencing experiments that reveal genetic diversity exhaustively. In this spirit we show that a tool from community ecology, the Rank Abundance Distribution (RAD), can be turned by the new MaxRank normalization method into a generic, expressive descriptor for quantitative comparison of communities in many areas of biology. To illustrate the versatility of the method, we analyze RADs from various \emph{generalized communities}, i.e.\ assemblages of genetically diverse cells or organisms, including human B cells, gut microbiomes under antibiotic treatment and of different ages and countries of origin, and other human and environmental microbial communities. We show that normalized RADs enable novel quantitative approaches that help to understand structures and dynamics of complex generalize communities

Bi-Phasic Vesicles: instability induced by adsorption of proteins

The recent discovery of a lateral organization in cell membranes due to small structures called 'rafts' has motivated a lot of biological and physico-chemical studies. A new experiment on a model system has shown a spectacular budding process with the expulsion of one or two rafts when one introduces proteins on the membrane. In this paper, we give a physical interpretation of the budding of the raft phase. An approach based on the energy of the system including the presence of proteins is used to derive a shape equation and to study possible instabilities. This model shows two different situations which are strongly dependent on the nature of the proteins: a regime of easy budding when the proteins are strongly coupled to the membrane and a regime of difficult budding.Comment: 19 avr. 200

DOES THE AUGMENTATION OF SERVICE LEVEL AGREEMENTS AFFECT USER DECISIONS IN CLOUD ADOPTION SCENARIOS? – AN EXPERIMENTAL APPROACH

Despite the benefits of cloud computing, customers are reluctant to use cloud services as they have concerns about data security and privacy. Many of these concerns arise due to the lack of transparen-cy. Consequently, bridging the existing information asymmetry and, thus, fostering trust in the cloud provider is of high relevance. As service level agreements are an important trust building factor and due to their technical and complex nature, the augmentation of these is promising. Therefore, we in-vestigate the effects of augmenting service level agreements (by means of augmented browsing) on the ease of the information gathering process and simultaneously on perceived information overload, comprehension and transparency in a web-based experiment. The results of our online experiment do not confirm our assumed positive effects of augmentation. Nonetheless, we show that the ease of gath-ering information about a cloud service positively influences the perceived trustworthiness. Further-more, we demonstrate that the perceived trustworthiness of a cloud computing provider largely deter-mines the intention to use its services. Thus, besides improving security, cloud providers not only have to communicate trust-critical information but also have to identify suitable measures of information provisioning that considerably improve transparency while lowering information overload

MEASURING REGRET: EMOTIONAL ASPECTS OF AUCTION DESIGN

Recent research strengthens the conjecture that human decision-making stems from a complex interaction of rational judgment and emotional processes. A prominent example of the impact of emotions in economic decision-making is the effect of regret-related information feedback on bidding behaviour in first-price sealed-bid auctions. Revealing the information “missed opportunity to win” upon losing an auction, results in higher bids. Revealing the information “money left on the table” upon winning an auction, results in lower bids. The common explanation for this pattern is winner and loser regret. However, this explanation is still hypothetical and little is known about the actual emotional processes that underlie this phenomenon. This paper investigates actual emotional processes in auctions with varying feedback information. Thereby, we provide an approach that combines an auction experiment with psychophysiological measures which indicate emotional involvement. Our economic results are in line with those of previous studies. Moreover, we can show that loser regret results in a stronger emotional response than winner regret. Remarkably, loser regret is strong for high values of “missed opportunity.” However, the pattern for different amounts of “money left on the table” is diametric to what winner regret theory suggests

High-resolution neutron depolarization microscopy of the ferromagnetic transitions in Ni3_3Al and HgCr2_2Se4_4 under pressure

We performed neutron imaging of ferromagnetic transitions in Ni$_3$Al and HgCr$_2$Se$_4$ crystals. These neutron depolarization measurements revealed bulk magnetic inhomogeneities in the ferromagnetic transition temperature with spatial resolution of about 100~$\mu$m. To obtain such spatial resolution, we employed a novel neutron microscope equipped with Wolter mirrors as a neutron image-forming lens and a focusing neutron guide as a neutron condenser lens. The images of Ni$_3$Al show that the sample does not homogeneously go through the ferromagnetic transition; the improved resolution allowed us to identify a distribution of small grains with slightly off-stoichiometric composition. Additionally, neutron depolarization imaging experiments on the chrome spinel, HgCr$_2$Se$_4$, under pressures up to 15~kbar highlight the advantages of the new technique especially for small samples or sample environments with restricted sample space. The improved spatial resolution enables one to observe domain formation in the sample while decreasing the acquisition time despite having a bulky pressure cell in the beam

An open-source GIS-enabled lookup service for Nagoya Protocol party information

Abstract The Nagoya Protocol on Access and Benefit Sharing is a transparent legal framework, which governs the access to genetic resources and the fair and equitable sharing of benefits arising from their utilization. Complying with the Nagoya regulations ensures legal use and re-use of data from genetic resources. Providing detailed provenance information and clear re-usage conditions plays a key role in ensuring the re-usability of research data according to the FAIR (findable, accessible, interoperable and re-usable) Guiding Principles for scientific data management and stewardship. Even with the framework provided by the ABS (access and benefit sharing) Clearing House and the support of the National Focal Points, establishing a direct link between the research data from genetic resources and the relevant Nagoya information remains a challenge. This is particularly true for re-using publicly available data. The Nagoya Lookup Service was developed for stakeholders in biological sciences with the aim at facilitating the legal and FAIR data management, specifically for data publication and re-use. The service provides up-to-date information on the Nagoya party status for a geolocation provided by GPS coordinates, directing the user to the relevant local authorities for further information. It integrates open data from the ABS Clearing House, Marine Regions, GeoNames and Wikidata. The service is accessible through a REST API and a user-friendly web form. Stakeholders include data librarians, data brokers, scientists and data archivists who may use this service before, during and after data acquisition or publication to check whether legal documents need to be prepared, considered or verified. The service allows researchers to estimate whether genetic data they plan to produce or re-use might fall under Nagoya regulations or not, within the limits of the technology and without constituting legal advice. It is implemented using portable Docker containers and can easily be deployed locally or on a cloud infrastructure. The source code for building the service is available under an open-source license on GitHub, with a functional image on Docker Hub and can be used by anyone free of charge.</jats:p

Rebound Effects in Cloud Computing: Towards a Conceptual Framework

Rebound effects have been discussed in various disciplines. In the information and communication technology sector, this topic is still insufficiently studied. Basically, a rebound effect is a feedback mechanism, as a result of which savings from efficiency improvements are not or only partially realized. Due to the potential of cloud computing for efficiency improvements, not only in terms of energy efficiency, but also in terms of organizational resources in general, we describe rebound effects in this context by means of a systematic literature review and a case study. Our results provide a framework to categorize and identify potential rebound effects in cloud computing. The understanding of rebound effects and their influence on the various organizational resources (e.g., server hardware, human resources or IT know-how), is important for managers to sustainably decide for or against the adoption, integration and roll out of cloud computing services

Interplay of itinerant magnetism and reentrant spin-glass behavior in Fex_{x}Cr1−x_{1-x}

When suppressing the itinerant antiferromagnetism in chromium by doping with the isostructual itinerant ferromagnet iron, a dome of spin-glass behavior emerges around a putative quantum critical point at an iron concentration $x \approx 0.15$. Here, we report a comprehensive investigation of polycrystalline samples of Fe$_{x}$Cr$_{1-x}$ in the range $0.05 \leq x \leq 0.30$ using x-ray powder diffraction, magnetization, ac susceptibility, and neutron depolarization measurements, complemented by specific heat and electrical resistivity data for $x = 0.15$. Besides antiferromagnetic ($x < 0.15$) and ferromagnetic regimes ($0.15 \leq x$), we identify a dome of reentrant spin-glass behavior at low temperatures for $0.10 \leq x \leq 0.25$ that is preceded by a precursor phenomenon. Neutron depolarization indicates an increase of the size of ferromagnetic clusters with increasing $x$ and the Mydosh parameter $\phi$, inferred from the ac susceptibility, implies a crossover from cluster-glass to superparamagnetic behavior. Taken together, these findings consistently identify Fe$_{x}$Cr$_{1-x}$ as an itinerant-electron system that permits to study the evolution of spin-glass behavior of gradually varying character in unchanged crystalline environment