Finite Open-World Query Answering with Number Restrictions (Extended Version)

Open-world query answering is the problem of deciding, given a set of facts, conjunction of constraints, and query, whether the facts and constraints imply the query. This amounts to reasoning over all instances that include the facts and satisfy the constraints. We study finite open-world query answering (FQA), which assumes that the underlying world is finite and thus only considers the finite completions of the instance. The major known decidable cases of FQA derive from the following: the guarded fragment of first-order logic, which can express referential constraints (data in one place points to data in another) but cannot express number restrictions such as functional dependencies; and the guarded fragment with number restrictions but on a signature of arity only two. In this paper, we give the first decidability results for FQA that combine both referential constraints and number restrictions for arbitrary signatures: we show that, for unary inclusion dependencies and functional dependencies, the finiteness assumption of FQA can be lifted up to taking the finite implication closure of the dependencies. Our result relies on new techniques to construct finite universal models of such constraints, for any bound on the maximal query size.Comment: 59 pages. To appear in LICS 2015. Extended version including proof

When Can We Answer Queries Using Result-Bounded Data Interfaces?

We consider answering queries on data available through access methods, that provide lookup access to the tuples matching a given binding. Such interfaces are common on the Web; further, they often have bounds on how many results they can return, e.g., because of pagination or rate limits. We thus study result-bounded methods, which may return only a limited number of tuples. We study how to decide if a query is answerable using result-bounded methods, i.e., how to compute a plan that returns all answers to the query using the methods, assuming that the underlying data satisfies some integrity constraints. We first show how to reduce answerability to a query containment problem with constraints. Second, we show "schema simplification" theorems describing when and how result bounded services can be used. Finally, we use these theorems to give decidability and complexity results about answerability for common constraint classes.Comment: 65 pages; journal version of the PODS'18 paper arXiv:1706.0793

Detecting Changes in Pressure Using a Graphene Field Effect Transistor

Graphene is a single, atomic layer, hexagonal lattice with useful electrical properties. Discovered as a stable isolated sheet in the early 2000s, graphene field effect transistors (GFET) are an effective way to detect small changes in electrical activity. When an electrolytic fluid is placed on a GFET, a double layer capacitor can develop at the interface between the fluid and graphene. Surprisingly, this interface is sensitive to barometric pressure, making GFETs a viable device for measuring pressure changes. In this work we built a pressure vessel and placed GFETs inside to test the performance limits of graphene based on its environment

Interaural time difference processing in the mammalian medial superior olive

The dominant cue for localization of low-frequency sounds are microsecond differences in the time-of-arrival of sounds at the two ears [interaural time difference (ITD)]. In mammals, ITD sensitivity is established in the medial superior olive (MSO) by coincidence detection of excitatory inputs from both ears. Hence the relative delay of the binaural inputs is crucial for adjusting ITD sensitivity in MSO cells. How these delays are constructed is, however, still unknown. Specifically, the question of whether inhibitory inputs are involved in timing the net excitation in MSO cells, and if so how, is controversial. These inhibitory inputs derive from the nuclei of the trapezoid body, which have physiological and structural specializations for high-fidelity temporal transmission, raising the possibility that well timed inhibition is involved in tuning ITD sensitivity. Here, we present physiological and pharmacological data from in vivo extracellular MSO recordings in anesthetized gerbils. Reversible blockade of synaptic inhibition by iontophoretic application of the glycine antagonist strychnine increased firing rates and significantly shifted ITD sensitivity of MSO neurons. This indicates that glycinergic inhibition plays a major role in tuning the delays of binaural excitation. We also tonically applied glycine, which lowered firing rates but also shifted ITD sensitivity in a way analogous to strychnine. Hence tonic glycine application experimentally decoupled the effect of inhibition from the timing of its inputs. We conclude that, for proper ITD processing, not only is inhibition necessary, but it must also be precisely timed

The new neutron grating interferometer at the ANTARES beamline - Design, Principle, and Applications -

Neutron grating interferometry is an advanced method in neutron imaging that allows the simultaneous recording of the transmission, the differential phase and the dark-field image. Especially the latter has recently received high interest because of its unique contrast mechanism which marks ultra-small-angle neutron scattering within the sample. Hence, in neutron grating interferometry, an imaging contrast is generated by scattering of neutrons off micrometer-sized inhomogeneities. Although the scatterer cannot be resolved it leads to a measurable local decoherence of the beam. Here, a report is given on the design considerations, principles and applications of a new neutron grating interferometer which has recently been implemented at the ANTARES beamline at the Heinz Maier-Leibnitz Zentrum. Its highly flexible design allows to perform experiments such as directional and quantitative dark-field imaging which provide spatially resolved information on the anisotropy and shape of the microstructure of the sample. A comprehensive overview of the nGI principle is given, followed by theoretical considerations to optimize the setup performance for different applications. Furthermore, an extensive characterization of the setup is presented and its abilities are demonstrated on selected case studies: (i) dark-field imaging for material differentiation, (ii) directional dark-field imaging to mark and quantify micrometer anisotropies within the sample and (iii) quantitative dark-field imaging, providing additional size information on the sample's microstructure by probing its autocorrelation function.Comment: Submitted to the Journal of Applied Crystallograph