Interacting six-dimensional topological field theories

We study the gauge-fixing and symmetries (BRST-invariance and vector supersymmetry) of various six-dimensional topological models involving Abelian or non-Abelian 2-form potentials.Comment: 11 page

The Role of the Surgeon and Transurethral Resection in the Treatment of Superficial Bladder Cancer

Non-muscle invasive bladder cancers are a heterogeneous group of cancers whose spectrum includes low grade Ta lesions and high-grade T1 lesions. Accurate staging and grading during initial evaluation and TUR ensures appropriate treatment and prevents the risk of understaging. TUR should be ideally performed under spinal anesthesia, with a continuous flow video resectoscope to maintain a stable bladder capacity, and a video monitor. The entire bladder must be visualized, with both 30- and 70-degree lenses, and all abnormal areas must be resected, with separate biopsies from each tumor's base. Repeat TUR is recommended for all high grade tumors and T1 tumors, especially if muscle was not present in the initial specimen. Immediate instillation of single dose chemotherapy agents following TUR is highly recommended to reduce the risk of tumor recurrences

Dynamics of Schmallenberg virus infection within a cattle herd in Germany, 2011

In late 2011, the insect-transmitted Schmallenberg virus (SBV) emerged in Europe. In this study, a cattle farm located in the core region of the epidemic was closely monitored between May 2011 and January 2012. Up to the end of September every tested serum sample was negative by an SBV-specific antibody ELISA, suggesting the absence of an infection before autumn 2011. Around the end of September/beginning of October SBV genome was detected in blood samples of some animals, and a few cows exhibited fever during that period. Starting at the end of September the first cows seroconverted; the within-herd prevalence reached 100% within barely 1 month. Consequently, SBV spread rapidly in the tested herd during the vector season of 2011

Subitizing with Variational Autoencoders

Numerosity, the number of objects in a set, is a basic property of a given visual scene. Many animals develop the perceptual ability to subitize: the near-instantaneous identification of the numerosity in small sets of visual items. In computer vision, it has been shown that numerosity emerges as a statistical property in neural networks during unsupervised learning from simple synthetic images. In this work, we focus on more complex natural images using unsupervised hierarchical neural networks. Specifically, we show that variational autoencoders are able to spontaneously perform subitizing after training without supervision on a large amount images from the Salient Object Subitizing dataset. While our method is unable to outperform supervised convolutional networks for subitizing, we observe that the networks learn to encode numerosity as basic visual property. Moreover, we find that the learned representations are likely invariant to object area; an observation in alignment with studies on biological neural networks in cognitive neuroscience

Neuropsychological constraints to human data production on a global scale

Which are the factors underlying human information production on a global level? In order to gain an insight into this question we study a corpus of 252-633 Million publicly available data files on the Internet corresponding to an overall storage volume of 284-675 Terabytes. Analyzing the file size distribution for several distinct data types we find indications that the neuropsychological capacity of the human brain to process and record information may constitute the dominant limiting factor for the overall growth of globally stored information, with real-world economic constraints having only a negligible influence. This supposition draws support from the observation that the files size distributions follow a power law for data without a time component, like images, and a log-normal distribution for multimedia files, for which time is a defining qualia.Comment: to be published in: European Physical Journal

Topological field theories and their symmetries within the Batalin-Vilkovisky framework

We discuss the algebraic construction of topological models (of both Schwarz- and Witten-type) within the Batalin-Vilkovisky formalism and we elaborate on a simple description of vector supersymmetry within this framework

Branes with fluxes wrapped on spheres

Following an eight-dimensional gauged supergravity approach we construct the most general solution describing D6-branes wrapped on a Kahler four-cycle taken to be the product of two spheres of different radii. Our solution interpolates between a Calabi-Yau four-fold and the spaces S^2xS^2xS^2xR^2 or S^2xS^2xR^4, depending on generic choices for the parameters. Then we turn on a background four-form field strength, corresponding to D2-branes, and show explicitly how our solution is deformed. For a particular choice of parameters it represents a flow from a Calabi-Yau four-fold times the three-dimensional Minkowski space-time in the ultraviolet, to the space-time AdS_4xQ^{1,1,1} in the infrared. In general, the solution in the infrared has a singularity which within type-IIA supergravity corresponds to the near horizon geometry of the solution for the D2-D6 system. Finally, we uncover the relation with work done in the eighties on Freund-Rubin type compactifications.Comment: 15 pages, Late

Ammonia volatilization from irrigated and non-irrigated winter wheat plots in the North China Plain - Quantification and modeling

China’s growing population led to a drastic intensification of agriculture and livestock production in the last 50 years. Excessive mineral nitrogen (N) fertilizer application and intensive livestock production cause high N losses to the environment. Pathways of N losses may include gaseous N emissions via nitrification/denitrification (N2O, N2), ammonia (NH3) volatilization, nitrate leaching and surface run-off from soils. Ammonia emissions are one of the most important N loss pathways in the North China Plain (NCP) contributing to soil acidification, eutrophication of ecosystems and causing human health problems through combining with particles in the atmosphere which also impair visibility. For developing mitigation measures in a winter wheat cropping system, systematic measurements of NH3 volatilization were conducted in the NCP in Zhengding, 260 km southwest of Beijing. Ammonia emissions were measured with the calibrated Dräger-Tube method during the main crop growing season of winter wheat from April to June 2016. The treatments included urea and urea followed by immediate irrigation. Additionally, soil samples were taken from three depth increments (0-30, 30-60 and 60-90 cm) before and after fertilization and the NH3 volatilization was simulated with the HERMES model. The soils showed highest mineral nitrogen (Nmin) contents of up to 340 kg ha-1 (0-90 cm) after fertilization. A decrease in the calcium carbonate content and soil pH in topsoils (0-20 cm) (pH: 6.7) compared to subsoil horizons (pH: 7.7) was attributed to the long-term application of ammonium-based fertilizers as well as to high atmospheric deposition rates of ammonium and sulfuric compounds. Urea applied to winter wheat showed an NH3 loss equal to 22% the of applied N. Application of urea to winter wheat followed by irrigation yielded a reduction of the NH3 volatilization to 0.1% of the applied N. An improved N management based on the soil Nmin content is recommended to improve nitrogen use efficiency and to reduce N losses to the environment. Irrigation after fertilization can be recommended for reduction of NH3 volatilization, provided that other N loss pathways are of minor importance. The NH3 volatilization sub-module of the HERMES model enabled to simulate ammonia volatilization in the NCP satisfactorily. It is suggested to validate the model with further data sets from the NCP or from regions with comparable conditions

Ice dynamics and mass balance in the grounding zone of outlet glaciers in the Transantarctic Mountains

The Antarctic grounding zone has a disproportionately large effect on glacier dynamics and ice sheet stability relative to its size but remains poorly characterised across much of the continent. Accurate ice velocity and thickness information is needed in the grounding zone to determine glacier outflow and establish to what extent changing ocean and atmospheric conditions are affecting the mass balance of individual glacier catchments. This thesis describes new satellite remote sensing techniques for measuring ice velocity and ice thickness, validated using ground measurements collected on the Beardmore, Skelton and Darwin Glaciers and applied to other Transantarctic Mountain outlet glaciers to determine ice discharge. Outlet glaciers in the Transantarctic Mountains provide an important link between the East and West Antarctic Ice Sheets but remain inadequately studied. While long-term velocities in this region are shown here to be stable, instantaneous velocities are sensitive to stresses induced by ocean tides, with fluctuations of up to 50% of the mean observed in GPS measurements. The potential error induced in averaged satellite velocity measurements due to these effects is shown to be resolvable above background noise in the grounding zone but to decrease rapidly upstream. Using a new inverse finite-element modelling approach based on regularization of the elastic-plate bending equations, tidal flexure information from differential InSAR is used to calculate ice stiffness and infer thickness in the grounding zone. This technique is shown to be successful at reproducing the thickness distribution for the Beardmore Glacier, eliminating current issues in the calculation of thickness from freeboard close to the grounding line where ice is not in hydrostatic equilibrium. Modelled thickness agrees to within 10% of ground penetrating radar measurements. Calibrated freeboard measurements and tide-free velocities in the grounding zones of glaciers in the western Ross Sea are used to calculate grounding zone basal melt rates, with values between 1.4 and 11.8 m/a⁻¹ in this region. While strongly dependent on grounding line ice thickness and velocity, melt rates show no latitudinal trend between glaciers, although detailed error analysis highlights the need for much improved estimates of firn density distribution in regions of variable accumulation such as the Transantarctic Mountains