The combined approach to ontology-based data access

The use of ontologies for accessing data is one of the most exciting new applications of description logics in databases and other information systems. A realistic way of realising sufficiently scalable ontology- based data access in practice is by reduction to querying relational databases. In this paper, we describe the combined approach, which incorporates the information given by the ontology into the data and employs query rewriting to eliminate spurious answers. We illustrate this approach for ontologies given in the DL-Lite family of description logics and briefly discuss the results obtained for the EL family

Combined FO rewritability for conjunctive query answering in DL-Lite

Standard description logic (DL) reasoning services such as satisfiability and subsumption mainly aim to support TBox design. When the design stage is over and the TBox is used in an actual application, it is usually combined with instance data stored in an ABox, and therefore query answering becomes the most importan

Structural stability of Fe5Si3 and Ni2Si studied by high-pressure x-ray diffraction and ab initio total-energy calculations

We performed high-pressure angle dispersive x-ray diffraction measurements on Fe5Si3 and Ni2Si up to 75 GPa. Both materials were synthesized in bulk quantities via a solid-state reaction. In the pressure range covered by the experiments, no evidence of the occurrence of phase transitions was observed. On top of that, Fe5Si3 was found to compress isotropically, whereas an anisotropic compression was observed in Ni2Si. The linear incompressibility of Ni2Si along the c-axis is similar in magnitude to the linear incompressibility of diamond. This fact is related to the higher valence-electron charge density of Ni2Si along the c-axis. The observed anisotropic compression of Ni2Si is also related to the layered structure of Ni2Si where hexagonal layers of Ni2+ cations alternate with graphite-like layers formed by (NiSi)2- entities. The experimental results are supported by ab initio total-energy calculations carried out using density functional theory and the pseudopotential method. For Fe5Si3, the calculations also predicted a phase transition at 283 GPa from the hexagonal P63/mcm phase to the cubic structure adopted by Fe and Si in the garnet Fe5Si3O12. The room-temperature equations of state for Fe5Si3 and Ni2Si are also reported and a possible correlation between the bulk modulus of iron silicides and the coordination number of their minority element is discussed. Finally, we report novel descriptions of these structures, in particular of the predicted high-pressure phase of Fe5Si3 (the cation subarray in the garnet Fe5Si3O12), which can be derived from spinel Fe2SiO4 (Fe6Si3O12).Comment: 44 pages, 13 figures, 3 Table

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance

Gravitational Waves from Gravitational Collapse

Gravitational wave emission from the gravitational collapse of massive stars has been studied for more than three decades. Current state of the art numerical investigations of collapse include those that use progenitors with realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non--axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with advanced ground--based and future space--based interferometric observatories.Comment: 68 pages including 13 figures; revised version accepted for publication in Living Reviews in Relativity (http://www.livingreviews.org

Technological Change in Economic Models of Environmental Policy: A Survey

This paper provides an overview of the treatment of technological change in economic models of environmental policy. Numerous economic modeling studies have confirmed the sensitivity of mid- and long-run climate change mitigation cost and benefit projections to assumptions about technology costs. In general, technical progress is considered to be a noneconomic, exogenous variable in global climate change modeling. However, there is overwhelming evidence that technological change is not an exogenous variable but to an important degree endogenous, induced by needs and pressures. Hence, some environmenteconomy models treat technological change as endogenous, responding to socio-economic variables. Three main elements in models of technological innovation are: (i) corporate investment in research and development, (ii) spillovers from R&D, and (iii) technology learning, especially learning-by-doing. The incorporation of induced technological change in different types of environmental-economic models tends to reduce the costs of environmental policy, accelerates abatement and may lead to positive spillover and negative leakage

Evaluation of bleach-sedimentation for sterilising and concentrating Mycobacterium tuberculosis in sputum specimens

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background Bleach-sedimentation may improve microscopy for diagnosing tuberculosis by sterilising sputum and concentrating Mycobacterium tuberculosis. We studied gravity bleach-sedimentation effects on safety, sensitivity, speed and reliability of smear-microscopy. Methods This blinded, controlled study used sputum specimens (n = 72) from tuberculosis patients. Bleach concentrations and exposure times required to sterilise sputum (n = 31) were determined. In the light of these results, the performance of 5 gravity bleach-sedimentation techniques that sterilise sputum specimens (n = 16) were compared. The best-performing of these bleach-sedimentation techniques involved adding 1 volume of 5% bleach to 1 volume of sputum, shaking for 10-minutes, diluting in 8 volumes distilled water and sedimenting overnight before microscopy. This technique was further evaluated by comparing numbers of visible acid-fast bacilli, slide-reading speed and reliability for triplicate smears before versus after bleach-sedimentation of sputum specimens (n = 25). Triplicate smears were made to increase precision and were stained using the Ziehl-Neelsen method. Results M. tuberculosis in sputum was successfully sterilised by adding equal volumes of 15% bleach for 1-minute, 6% for 5-minutes or 3% for 20-minutes. Bleach-sedimentation significantly decreased the number of acid-fast bacilli visualised compared with conventional smears (geometric mean of acid-fast bacilli per 100 microscopy fields 166, 95%CI 68-406, versus 346, 95%CI 139-862, respectively; p = 0.02). Bleach-sedimentation diluted paucibacillary specimens less than specimens with higher concentrations of visible acid-fast bacilli (p = 0.02). Smears made from bleach-sedimented sputum were read more rapidly than conventional smears (9.6 versus 11.2 minutes, respectively, p = 0.03). Counting conventional acid-fast bacilli had high reliability (inter-observer agreement, r = 0.991) that was significantly reduced (p = 0.03) by bleach-sedimentation (to r = 0.707) because occasional strongly positive bleach-sedimented smears were misread as negative. Conclusions Gravity bleach-sedimentation improved laboratory safety by sterilising sputum but decreased the concentration of acid-fast bacilli visible on microscopy, especially for sputum specimens containing high concentrations of M. tuberculosis. Bleach-sedimentation allowed examination of more of each specimen in the time available but decreased the inter-observer reliability with which slides were read. Thus bleach-sedimentation effects vary depending upon specimen characteristics and whether microscopy was done for a specified time, or until a specified number of microscopy fields had been read. These findings provide an explanation for the contradictory results of previous studies.Peer Reviewe

Improved Biomass Cookstove Use in the Longer Run: results from a field experiment in rural Ethiopia

This study examines longer-run usage frequency of Mirt improved biomass cookstoves (ICS), one of the most important ICS promoted in Ethiopia. Mirt has been shown to improve childhood health, and reduce fuelwood consumption and greenhouse gas emissions, but to generate those benefits, households must regularly use it over extended periods. Thus, this paper focuses on longer-run use using stove surface temperature data over five time intervals. We find that, close to its estimated lifespan, 63 per cent of households had their stoves in place after more than 3.5 years. Of those who abandoned their stoves, over 80 per cent did so due to breakage, indicating little abandonment of functional stoves. Among those who retained their stoves, despite the relatively long time frame, we observe no decline in regular usage, suggesting the ICS deliver long-term benefits. We find no correlation of dis-adoption with three randomly assigned monetary treatments and no effect of treatments on long-run usage frequency

On the gas-phase graphene nanosheet synthesis in atmospheric microwave plasma torch: Upscaling potential and graphene nanosheet‑copper nanocomposite oxidation resistance

Efficient gas-phase synthesis of few-layer graphene nanosheets (GNS) is based on the controlled formation of the high-temperature environment and the reaction pathway of gas-phase species formed by the decomposition of organic precursors. Such a process results in the formation of high-quality carbon nanomaterial and hydrogen while the concentration of other gaseous by-products is minimized. In this work, the main factors affecting the efficiency of such processes in the TIAGO microwave plasma torch were investigated using detailed material analysis and mass spectrometry of the gas-phase products during the synthesis process. The results showed a limiting effect of increasing the microwave power (MW) on both the product yield as well as material quality, as shown by Raman and x-Ray photoelectron spectroscopy. The change in the reaction pathway increased the formation of C2H4, resulting in the upper limit of the achievable nanopowder yield. The prepared material showed a decrease in its high oxidation resistance, with increasing the delivered MW power as determined by thermogravimetry analysis. This behavior was related to the formation of GNS-Cu nanoparticles composite due to the presence of copper nanoparticles originating from erosion of the electrode of the TIAGO torch during the synthesis process at high MW powers

Evidence-based Languages for Conceptual Data Modelling Profiles

To improve database system quality as well as runtime use of conceptual models, many logic-based reconstructions of conceptual data modelling languages have been proposed in a myriad of logics. They each cover their features to a greater or lesser extent and are typically motivated from a logic viewpoint. This raises questions such as what would be an evidence-based common core and what is the optimal language profile for a conceptual modelling language family. Based on a common metamodel of UML Class Diagrams (v2.4.1), ER/EER, and ORM/2's static elements, a set of 101 conceptual models, and availing of computational complexity insights from Description Logics, we specify these profiles. There is no known DL language that matches exactly the features of those profiles and the common core is small (in the tractable $\mathcal{ALNI}$). Although hardly any inconsistencies can be derived with the profiles, it is promising for scalable runtime use of conceptual data models