Resolving user queries using contextual information

When responding to a request from another person, human beings take into account non-verbal cues and relevant implicit contextual information to determine an appropriate response. In contrast, digital assistants do not currently take such contextual information into account. Thus, a digital assistant may provide a sub-optimal or contextually inappropriate response to the user’s request, or require the user to modify the original request iteratively until the user’s full intent is communicated. If the user permits, the techniques described in this disclosure enable a digital assistant to infer the user’s intent by using device and environmental sensors to extract available contextual information, e.g., noise level, the user’s tone of voice, the number of people in a room, objects in the room, temperature, time, location, weather, traffic, etc. The information is used, as permitted by the user, to determine an appropriate response to the user’s request

Self-consistent-field ensembles of disordered Hamiltonians: Efficient solver and application to superconducting films

The general topic of this thesis is the study of interaction effects in disordered metals. A major focus was placed on phase transitions that these systems undergo. Methodologically we employ a mean-field framework. Within such an approach self-consistent-field(scf) ensembles of random Hamiltonians naturally arise. These ensembles may exhibit novel, as of yet unstudied critical behavior and their study can thus lead to a more complete understanding of universality classes in disordered systems. The investigation of scf-ensembles is a very challenging endeavor. The difficulty is that each disorder configuration requires to find its own self-consistent fields. The solution of the scf-cycle is very difficult to do with analytical techniques. But also numerically it is demanding already at moderate systemsizes of a few thousand sites. Presumably, this is the main reason why numerical studies of scf-ensembles have been performed infrequently in the past, despite of their obvious fundamental relevance. Thus motivated, we have developed a state-of-the-art implementation of the scf-problem following a Kernel-Polynomial-Method(KPM) approach. With it the system sizes that we can address at an affordable numerical cost exceed the ones of prior studies by two orders of magnitude. The interplay of disorder induced quantum-interference and mean-field interactions can be studied on length scales that exceed the lattice constant by two orders of magnitude. Throughout this thesis we apply our code to disordered superconductors with screened Coulomb interaction. We investigate the Bogoliubov-deGennes(BdG) theory of inhomogeneous superconductors focussing on s-wave pairing in thin films. To understand how superconductors are affected by disorder it is instructive to first study the effect of a single impurity. Furthermore we are motivated by a collaboration with the experimental group of Wulf Wulfhekel at the Karlsruhe Institute of Technology to study such a system. In this group scanning tunneling microscopy(STM) measurements of superconducting bulk Al(111) around a Fe impurity have been conducted. The self-consistency requirement complicates the description of the response to an impurity at the surface of a bulk superconductor. An analytical formalism remains unknown. With our numerical simulations we find an excellent agreement of the response to the impurity with the experimental findings. The main part of the thesis focusses on homogeneously disordered s-wave superconductors with screened Coulomb interaction. These systems may exhibit a direct Superconductor-Insulator-Transition (SIT). Despite considerable effort in the study of these systems, the current situation is not fully satisfying: On the one hand, computational mean-field studies of the Hubbard model have been limited to system sizes L that do not allow to study the most interesting regime of length scales where the coherence length strongly exceeds the lattice spacing. While analytical approaches, on the other hand, operate in this regime, they rely on partial self-consistency in order to become tractable. Our computational machinery allows us to cover the full parameter space from the extreme regimes, which have been addressed computationally before, to the analytically tractable weak coupling limit. Our software package allows us to study disordered superconductors numerically for the first time on mesoscopic scales considerably exceeding the lattice constant. For example (i)we observe a non-monotonic behavior with disorder strength of the superconducting correlation length already at intermediate interaction strengths; (ii)we for the first time investigate the fluctuations of the LDoS in regimes from weak to strong disorder, where the fluctuations are particularily pronounced. Furthermore in a collaboration with Igor Burmistrov of the Landau institute, we determine a low disorder regime, in which a quantitative agreement with an analytical description of the LDoS fluctuations is found; (iii) we for the first time identify a regime, where the gap is strongly enhanced (up to ∼ 20%) by disorder. We also pay a special attention to the sensitivity of the behavior of observables to approximations made in the self-consistency procedure. For instance we find that island formation when observed in moderate parameter regions is a characteristic hallmark of full self-consistency. It escapes partial (“energy-only”) self-consistent schemes

Struktur und Eigenschaften von nanoskopischen Metall(hydroxid)fluorid-Aluminiumoxid-Kompositen

Durch die Verwendung der fluorolytischen Sol-Gel Synthese ist es möglich, röntgenamorphe bzw. partiell nanokristalline Metallhydroxidfluoride und Metallfluoride zu erhalten. Diese Verbindungen unterscheiden sich in ihren Eigenschaften stark von „klassisch“ hergestellten, kristallinen Metall(hydroxid)fluoriden. In der vorliegenden Promotionsarbeit wurden deshalb in vier aufeinander folgenden Kapiteln sowohl die Synthese und Charakterisierung von Aluminium– und Magnesium(hydroxid)fluoriden beschrieben als auch die Auswirkung dieser Verbindungen auf das Phasentransformationsverhalten von böhmitischen Xerogelen zu Korund sowie ihre Wirksamkeit als Sinterhilfsmittel bei der Korundkeramikherstellung untersucht.The application of the fluorolytic sol-gel method with aqueous hydrofluoric acid enables the synthesis of X-ray amorphous or rather partially nanocrystalline metal hydroxide fluorides and metal fluorides. These compounds strongly differ in their characteristics from “classically” manufactured, crystalline metal hydroxide fluorides. In the present dissertation both, the synthesis and characterisation of aluminium and magnesium hydroxide fluorides were described and the effect of these compounds on the phase transformation behaviour from pseudoboehmites to corundum was examined as well as their effectiveness as sintering aid during the corundum ceramics production

Model of nursing care for patients with Brugada syndrome according to the international ICNP®

Introduction Brugada syndrome is a rare disease involving genetic disorders of heart rhythm. The disease was discovered in 1992 by the Brugada brothers, Spanish cardiologists. This syndrome occurs with sporadic frequency in families with 5-66/10,000 affected worldwide, and 12/10,000 affected in Asia. Usually, the disease affects people between the age of 30 and 50 years of age. Brugada syndrome is responsible for 4-12% of all sudden cardiac arrests, and 20% of sudden cardiac arrest patients who have never had organic cardiovascular disease. The pathomechanism of this syndrome is not fully understood, but three types of factors can be distinguished: genetic, hormonal and environmental. The most common mutation causing Brugada Syndrome is the mutation of SCN5A gene. Brugada syndrome is characterized by the occurrence of syncope episodes and pre-osmotic states along with sudden cardiac arrest, which is a result of ventricular arrhythmias. The basis for the diagnosis of Brugada syndrome is the use of a 12-lead ECG and in some cases, pharmacological diagnosis, consisting of simultaneous monitoring of ECG and administration of a class I antiarrhythmic drug according to Vaughan-Williams classification. Treatment of Brugada syndrome consists of implantation of a cardioverted-defibrillator (ICD) in accordance with criteria (I, IIa and IIb), based, inter alia, on the patient’s state of health and course of cardiovascular arrest. Prognosis in asymptomatic patients is largely positive. Aim The aim of the study was to use the international ICNP® classification when presenting the problems in nursing care in patients with Brugada syndrome. Materials and Methods The nursing care model based on the international ICNP® classification was used. The diagnoses were based on symptoms and problems of patients with Brugada syndrome. Summary Although the Brugada syndrome is a rare disease entity, it should be taken into account when differentiating other factors which may lead to sudden cardiac arrest. Due to prodromal nonspecific symptoms, care should be taken into accurately diagnosing with 12-lead ECGs. The most common problems in patients with Brugada syndrome are palpitations (frequently occurring at night), fainting, and at the same time risk of falling and chest pain. Healthcare professionals caring for patients with Brugada syndrome should observe the patient for the first signs of fainting, prioritizing safety. Conclusions Brugada syndrome is a rare disease with nonspecific symptoms, which is why accurate diagnostic methods, including primarily tech 12-lead ECG are of great importance. Diagnostics, along with appropriate education of the patient and their families, allow effective care and prevention against the occurrence of negative effects of this disease

Friedel Oscillations and superconducting-gap enhancement by impurity scattering

Experiments observe an enhanced superconducting gap over impurities as compared to the clean-bulk value. In order to shed more light on this phenomenon, we perform simulations within the framework of Bogoliubov-deGennes theory applied to the attractive Hubbard model. The simulations qualitatively reproduce the experimentally observed enhancement effect; it can be traced back to an increased particle density in the metal close to the impurity site. In addition, the simulations display significant differences between a thin (2D) and a very thick (3D) film. In 2D pronounced Friedel oscillations can be observed, which decay much faster in (3D) and therefore are more difficult to resolve. Also this feature is in qualitative agreement with the experiment

Local density of state fluctuations in 2D superconductor as a probe of quantum diffusion

The interplay of superconductivity and disorder generates a wealth of complex phenomena. In particular, the peculiar structure of diffusive electronic wavefunctions is predicted to increase the superconducting critical temperature in some range of disorder. In this work, we use an epitaxial monolayer of lead showing a simple band structure and homogenous structural disorder as a model system of a 2D superconductor in the weak-antilocalization regime. Then, we perform an extensive study of the emergent fluctuations of local density of states (LDOS) and spectral energy gap in this material and compare them with both analytical results and numerical solution of the attractive Hubbard model. We show that mesoscopic LDOS fluctuations allow to probe locally both the elastic and inelastic scattering rates which are notoriously difficult to measure in transport measurements.Comment: Accepted for publication in PRB - 13 pages, 6 figure

Self-consistent-field ensembles of disordered Hamiltonians: Efficient solver and application to superconducting films

Our general interest is in self-consistent-field (scf) theories of disordered fermions. They generate physically relevant subensembles (“scf ensembles”) within a given Altland-Zirnbauer class. We are motivated to investigate such ensembles (i) by the possibility to discover new fixed points due to (long-range) interactions; (ii) by analytical scf theories that rely on partial self-consistency approximations awaiting a numerical validation; and (iii) by the overall importance of scf theories for the understanding of complex interaction-mediated phenomena in terms of effective single-particle pictures. In this paper we present an efficient, parallelized implementation solving scf problems with spatially local fields by applying a kernel-polynomial approach. Our first application is the Boguliubov-deGennes theory of the attractive-U Hubbard model in the presence of on-site disorder; the sc fields are the particle density n(r) and the gap function Δ(r). For this case, we reach system sizes unprecedented in earlier work. They allow us to study phenomena emerging at scales substantially larger than the lattice constant, such as the interplay of multifractality and interactions or the formation of superconducting islands. For example, we observe that the coherence length exhibits a nonmonotonic behavior with increasing disorder strength already at moderate U. With respect to methodology our results are important because we establish that partial self-consistency (“energy-only”) schemes as typically employed in analytical approaches tend to miss qualitative physics such as island formation

Multifractal correlations of the local density of states in dirty superconducting films

Mesoscopic fluctuations of the local density of states encode multifractal correlations in disorderedelectron systems. We study fluctuations of the local density of states in a superconducting state of weakly disordered films. We perform numerical computations in the framework of the disordered attractive Hubbard model on two-dimensional square lattices. Our numerical results are explained by an analytical theory. The numerical data and the theory together form a coherent picture of multifractal correlations of local density of states in weakly disordered superconducting films

Applications of Information Theory to Analysis of Neural Data

Information theory is a practical and theoretical framework developed for the study of communication over noisy channels. Its probabilistic basis and capacity to relate statistical structure to function make it ideally suited for studying information flow in the nervous system. It has a number of useful properties: it is a general measure sensitive to any relationship, not only linear effects; it has meaningful units which in many cases allow direct comparison between different experiments; and it can be used to study how much information can be gained by observing neural responses in single trials, rather than in averages over multiple trials. A variety of information theoretic quantities are commonly used in neuroscience - (see entry "Definitions of Information-Theoretic Quantities"). In this entry we review some applications of information theory in neuroscience to study encoding of information in both single neurons and neuronal populations.Comment: 8 pages, 2 figure