Characteristic invariants in Hennessy-Milner logic

In this paper, we prove that Hennessy–Milner Logic (HML), despite its structural limitations, is sufficiently expressive to specify an initial property φ0 and a characteristic invariant χI for an arbitrary finite-state process P such that φ0∧AG(χI) is a characteristic formula for P. This means that a process Q, even if infinite state, is bisimulation equivalent to P iff Q⊨φ0∧AG(χI). It follows, in particular, that it is sufficient to check an HML formula for each state of a finite-state process to verify that it is bisimulation equivalent to P. In addition, more complex systems such as context-free processes can be checked for bisimulation equivalence with P using corresponding model checking algorithms. Our characteristic invariant is based on so called class-distinguishing formulas that identify bisimulation equivalence classes in P and which are expressed in HML. We extend Kanellakis and Smolka’s partition refinement algorithm for bisimulation checking in order to generate concise class-distinguishing formulas for finite-state processes

Einflussfaktoren von Arbeitszufriedenheit im Kontext der digitalen Transformation

Seit Jahren setzen sich wissenschaftliche Diskurse mit der Frage auseinander, welche Chancen und Risiken die zunehmende Digitalisierung der Arbeitswelt auf Beschäftigte hat. Neue Möglichkeiten der Autonomie und Flexibilität stehen dabei potenziell zunehmenden Arbeitsbelastungen durch Verdichtung von Arbeit oder stärkerer technischer Kontrolle gegenüber. Bislang ist jedoch nur unzureichend geklärt, ob solche mit der Digitalisierung einher gehenden Veränderungen die Beschäftigten zufriedener oder unzufriedener machen. Die vorliegende Arbeit greift diese Forschungslücke auf: Auf Basis arbeitspsychologischer sowie arbeits- und sozialwissenschaftlicher Forschung wird ein Modell entwickelt, welches den Digitalisierungsgrad sowie dessen Auswirkungen auf Arbeitsgestaltung und Arbeitszufriedenheit erhebt. Zentrale Annahme ist dabei, dass bestimmte Faktoren der Arbeitsgestaltung (z.B. Work-Life-Balance, Autonomie und Beziehungsqualität zu Kollegen) die Wirkungsbeziehung zwischen Digitalisierung und Arbeitszufriedenheit vermitteln. Das Forschungsmodell wird mit einer repräsentativen Befragung von 1056 Beschäftigten in drei unterschiedlich stark digitalisierten Branchen (Gesundheitswesen, Logistik, IT) überprüft. Die Datenauswertung erfolgt mittels statistischer Regressionsanalysen sowie einem Strukturgleichungsmodell. Die Analysen zeigen, dass der Zusammenhang zwischen Digitalisierung und Arbeitszufriedenheit ausschließlich über Faktoren der Arbeitsgestaltung vermittelt wird. Je niedriger der Digitalisierungsgrad, desto stärker berichten Beschäftigte von subjektiven Belastungen wie hohem Technikstress und Arbeitstempo infolge zunehmender Digitalisierung. Dies wirkt sich negativ auf die Arbeitszufriedenheit aus. Je höher der Digitalisierungsgrad, desto geringer werden diese negativen Effekte. Im Gegenzug wirken sich mehr Faktoren positiv auf die Arbeitszufriedenheit aus, so beispielsweise steigende Autonomie und Flexibilität durch zunehmende Digitalisierung. Als wichtigste positive Einflussfaktoren der Arbeitszufriedenheit werden soziale Aspekte wie die Beziehungsqualität zu Kollegen und Vorgesetzten berichtet. Die Ergebnisse plädieren somit dafür, Digitalisierungsmaßnahmen stark branchenspezifisch zu gestalten. So ist den aufgedeckten Vorbehalten der Digitalisierung im Gesundheitswesen sensibel zu begegnen, beispielsweise durch Aufklärungsarbeit und Weiterbildungen sowie durch Technologien, die unterstützend und nicht kontrollierend wahrgenommen werden. In stärker digitalisierten Branchen wie der IT können punktuelle Maßnahmen die positive Einstellung gegenüber zunehmender Digitalisierung weiter verbessern. Dazu zählen Technologien, die den Austausch sozialer Beziehungen insbesondere bei orts- und zeitflexiblem Arbeiten fördern, und Rahmenbedingungen, mittels derer Beschäftigte ihre Work-Life-Balance selbstbestimmt an ihren Lebensphasen orientieren können

Brief communication: Unravelling the composition and microstructure of a permafrost core using X-ray computed tomography

The microstructure of permafrost ground contains clues to its formation and hence its preconditioning to future change. We applied X-ray computed microtomography (CT) to obtain high-resolution data (Δx=50 µm) of the composition of a 164 cm long permafrost core drilled in a Yedoma upland in north-eastern Siberia. The CT analysis allowed the microstructures to be directly mapped and volumetric contents of excess ice, gas inclusions, and two distinct sediment types to be quantified. Using laboratory measurements of coarsely resolved core samples, we statistically estimated the composition of the sediment types and used it to indirectly quantify volumetric contents of pore ice, organic matter, and mineral material along the core. We conclude that CT is a promising method for obtaining physical properties of permafrost cores which opens novel research potentials

Image processing of multiphase images obtained via X-ray microtomography: A review

Easier access to X-ray microtomography (lCT) facilities has provided much new insight from high-resolution imaging for various problems in porous media research. Pore space analysis with respect to functional properties usually requires segmentation of the intensity data into different classes. Image segmentation is a nontrivial problem that may have a profound impact on all subsequent image analyses. This review deals with two issues that are neglected in most of the recent studies on image segmentation: (i) focus on multiclass segmentation and (ii) detailed descriptions as to why a specific method may fail together with strategies for preventing the failure by applying suitable image enhancement prior to segmentation. In this way, the presented algorithms become very robust and are less prone to operator bias. Three different test images are examined: a synthetic image with ground-truth information, a synchrotron image of precision beads with three different fluids residing in the pore space, and a lCT image of a soil sample containing macropores, rocks, organic matter, and the soil matrix. Image blur is identified as the major cause for poor segmentation results. Other impairments of the raw data like noise, ring artifacts, and intensity variation can be removed with current image enhancement methods. Bayesian Markov random field segmentation, watershed segmentation, and converging active contours are well suited for multiclass segmentation, yet with different success to correct for partial volume effects and conserve small image features simultaneously.Keywords: X-ray tomography, Soil structure, Multiphase flow, Segmentation, structure analysis, Image processin

Quantification of capillary trapping of gas clusters using X-ray microtomography

A major difficulty in modeling multiphase flow in porous media is the emergence of trapped phases. Our experiments demonstrate that gas can be trapped in either single-pores, multipores, or in large connected networks. These large connected clusters can comprise up to eight grain volumes and can contain up to 50% of the whole trapped gas volume. About 85% of the gas volume is trapped by multipore gas clusters. This variety of possible trapped gas clusters of different shape and volume will lead to a better process understanding of bubble-mediated mass transfer. Since multipore gas bubbles are in contact with the solid surface through ultrathin adsorbed water films the interfacial area between trapped gas clusters and intergranular capillary water is only about 80% of the total gas surface. We could derive a significant (R²=0.98) linear relationship between the gas-water-interface and gas saturation. We found no systematic dependency of the front velocity of the invading water phase in the velocity range from 0.1 to 0.6 cm/min corresponding to capillary numbers from 2 x 10⁻⁷ to 10⁻⁶. Our experimental results indicate that the capillary trapping mechanism is controlled by the local pore structure and local connectivity and not by thermodynamics, i.e., by the minimum of the Free Energy, at least in the considered velocity range. Consistent with this physical picture is our finding that the trapping frequency (= bubble-size distribution) reflects the pore size distribution for the whole range of pore radii, i.e., the capillary trapping process is determined by statistics and not by thermodynamics.Keywords: gas clusters, interfacial area, capillary trappin

Effects of cold atmospheric pressure plasma and disinfecting agents on Candida albicans in root canals of extracted human teeth

Reinfection in endodontically treated teeth is linked to the complexity of the root canal system, which is problematic to reach with conventional disinfection methods. As plasma is expected to have the ability to sanitize narrow areas, the aim of this study was to analyze the effect of cold atmospheric pressure plasma (CAP) on Candida albicans in root canals of extracted human teeth. CAP was applied as mono treatment and in combination with standard endodontic disinfectants (sodium hypochlorite, chlorhexidine and octenidine). Disinfection efficiency was evaluated as reduction of the logarithm of colony forming units per milliliter (log10 CFU/mL) supported by scanning electron microscopy as imaging technique. Plasma alone showed the highest reduction of log10 CFU, suggesting the best disinfection properties of all tested agents. © 2020 The Authors. Journal of Biophotonics published by Wiley-VCH GmbH

Emergent properties of microbial activity in heterogeneous soil microenvironments:Different research approaches are slowly converging, yet major challenges remain

Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the usual bulk, macroscopic parameters used to characterize soils (e.g., granulometry, pH, soil organic matter and biomass contents) provide insufficient information to describe quantitatively the activity of soil microorganisms and some of its outcomes, like the emission of greenhouse gases. Clearly, new, more appropriate macroscopic parameters are needed, which reflect better the spatial heterogeneity of soils at the microscale (i.e., the pore scale). For a long time, spectroscopic and microscopic tools were lacking to quantify processes at that scale, but major technological advances over the last 15 years have made suitable equipment available to researchers. In this context, the objective of the present article is to review progress achieved to date in the significant research program that has ensued. This program can be rationalized as a sequence of steps, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, the integration of these different perspectives into a unified theory, its upscaling to the macroscopic scale, and, eventually, the development of new approaches to measure macroscopic soil characteristics. At this stage, significant progress has been achieved on the physical front, and to a lesser extent on the (bio)chemical one as well, both in terms of experiments and modeling. In terms of microbial aspects, whereas a lot of work has been devoted to the modeling of bacterial and fungal activity in soils at the pore scale, the appropriateness of model assumptions cannot be readily assessed because relevant experimental data are extremely scarce. For the overall research to move forward, it will be crucial to make sure that research on the microbial components of soil systems does not keep lagging behind the work on the physical and (bio)chemical characteristics. Concerning the subsequent steps in the program, very little integration of the various disciplinary perspectives has occurred so far, and, as a result, researchers have not yet been able to tackle the scaling up to the macroscopic level. Many challenges, some of them daunting, remain on the path ahead

Rethinking irrigation modernisation: Realising multiple objectives through the integration of fisheries

Irrigation has been, and will remain, instrumental in addressing water security (Sustainable Development Goal (SDG) 6), food insecurity (SDG 2) and poverty (SDG 1) goals. However, the global context in which irrigation takes place is changing rapidly. A call for healthier and more sustainable food systems is placing new demands on how irrigation is developed and managed. Growing pressures from competing water uses in the domestic and industrial sectors, as well increasing environmental awareness, mean irrigation is increasingly called on to perform better, delivering acceptable returns on investment and simultaneously improving food security, rural livelihoods and nutrition, as well as supporting environmental conservation. Better integration of fisheries (including aquaculture) in irrigation planning, investment and management can contribute to the modernisation of irrigation and the achievement of the multiple objectives that it is called on to deliver. A framework illustrating how fisheries can be better integrated with irrigation, and how the two can complement each other across a range of scales, from scheme to catchment and, ultimately, national level, is presented