Boolean Dependence Logic and Partially-Ordered Connectives

We introduce a new variant of dependence logic called Boolean dependence logic. In Boolean dependence logic dependence atoms are of the type =(x_1,...,x_n,\alpha), where \alpha is a Boolean variable. Intuitively, with Boolean dependence atoms one can express quantification of relations, while standard dependence atoms express quantification over functions. We compare the expressive power of Boolean dependence logic to dependence logic and first-order logic enriched by partially-ordered connectives. We show that the expressive power of Boolean dependence logic and dependence logic coincide. We define natural syntactic fragments of Boolean dependence logic and show that they coincide with the corresponding fragments of first-order logic enriched by partially-ordered connectives with respect to expressive power. We then show that the fragments form a strict hierarchy.Comment: 41 page

Computational Aspects of Dependence Logic

In this thesis (modal) dependence logic is investigated. It was introduced in 2007 by Jouko V\"a\"aan\"anen as an extension of first-order (resp. modal) logic by the dependence operator =(). For first-order (resp. propositional) variables x_1,...,x_n, =(x_1,...,x_n) intuitively states that the value of x_n is determined by those of x_1,...,x_n-1. We consider fragments of modal dependence logic obtained by restricting the set of allowed modal and propositional connectives. We classify these fragments with respect to the complexity of their satisfiability and model-checking problems. For satisfiability we obtain complexity degrees from P over NP, Sigma_P^2 and PSPACE up to NEXP, while for model-checking we only classify the fragments with respect to their tractability, i.e. we either show NP-completeness or containment in P. We then study the extension of modal dependence logic by intuitionistic implication. For this extension we again classify the complexity of the model-checking problem for its fragments. Here we obtain complexity degrees from P over NP and coNP up to PSPACE. Finally, we analyze first-order dependence logic, independence-friendly logic and their two-variable fragments. We prove that satisfiability for two-variable dependence logic is NEXP-complete, whereas for two-variable independence-friendly logic it is undecidable; and use this to prove that the latter is also more expressive than the former.Comment: PhD thesis; 138 pages (110 main matter

Combined impact of shifts in Southern Ocean westerlies and Antarctic sea ice during LGM on atmospheric CO2

A significant influence of changes in the westerly winds over the Southern Ocean was proposed as a mechanism to explain a large portion of the glacial atmospheric pCO2 drawdown (Toggweiler et al., 2006). However, additional modelling studies with Earth System Models of Intermediate Complexity do not confirm the size and sometimes even the sign of the impact of southern hemispheric winds on the glacial pCO2 as suggested by Toggweiler (Men- viel et al., 2008; Tschumi et al., 2008, d’Orgeville et al., 2010). We here add to this discussion and explore the potential contribution of changes in the latitudinal position of the winds on Southern Ocean physics and the carbon cycle by using a state-of-the-art ocean general circulation model (MITgcm) in a spatial resolution increasing in the Southern Ocean (2◦ longitude; northern hemisphere: 2◦ latitude; southern hemisphere: 2◦cos(α)). We discuss how the change in carbon cycling is related to the upwelling strength and pattern in the Southern Ocean and how they depend on the changing wind fields and/or the sea ice coverage. While the previous studies explored the impact of the westlies starting from present day or pre-industrial back- ground conditions, we here perform simulations from LGM background climate. Ocean surface conditions are for reasons of consistency taken from output of the COSMOS Earth System model for a pre-industrial control and two LGM runs (Zhang et al., in preparation). Additionally, a northwards shift (by 10◦) of the westerly wind belt as proposed by Toggweiler is investigated

Random and externally controlled occurrences of Dansgaard-Oeschger events

Dansgaard–Oeschger (DO) events constitute the most pronounced mode of centennial to millennial climate variability of the last glacial period. Since their discovery, many decades of research have been devoted to understand the origin and nature of these rapid climate shifts. In recent years, a number of studies have appeared that report emergence of DO-type variability in fully coupled general circulation models via different mechanisms. These mechanisms result in the occurrence of DO events at varying degrees of regularity, ranging from periodic to random. When examining the full sequence of DO events as captured in the North Greenland Ice Core Project (NGRIP) ice core record, one can observe high irregularity in the timing of individual events at any stage within the last glacial period. In addition to the prevailing irregularity, certain properties of the DO event sequence, such as the average event frequency or the relative distribution of cold versus warm periods, appear to be changing throughout the glacial. By using statistical hypothesis tests on simple event models, we investigate whether the observed event sequence may have been generated by stationary random processes or rather was strongly modulated by external factors. We find that the sequence of DO warming events is consistent with a stationary random process, whereas dividing the event sequence into warming and cooling events leads to inconsistency with two independent event processes. As we include external forcing, we find a particularly good fit to the observed DO sequence in a model where the average residence time in warm periods are controlled by global ice volume and cold periods by boreal summer insolation

THE INFLUENCE OF THE PERCEPTION OF FAIRNESS ON INNOVATION IDEA VALUE AND KNOWLEDGE SHARING BEHAVIOR IN INNOVATION IDEA NETWORKS

This article explores the relationships between innovation idea valu, innovators´ perceptions of fairness, and their participation behavior and knowledge sharing behavior in the intrafirm social network. The study uses survey data and a database from a large company that is one of Europe´s top performers in idea management. In addition to the idea database, this study surveys participating employees about their perceptions of fairness and their participation behavior and knowledge sharing behavior. The results show that there is a clear relationship between innovation idea valu, employees´ perceptions of fairness, and employees´ participation behavior and knowledge sharing behavior. Furthermore, there is clear evidence that tenure increases the valu of innovation ideas. The findings suggest a number of implications for ideation management and for the design of social networks for innovation ideas. To increase the valu of innovation ideas, social networks for innovation ideas can be used if the allocation of rewards for idea providers is positively associated with the fairness perceptions of network members

The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons, without explicitly modelling dust emission and deposition processes. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated dust sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (<i>T</i>≲−40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "warm ice clouds" (<i>T</i>≳−40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "warm ice clouds" and the general influence of dust in the mixed-phase cloud region are highly uncertain due to both a considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work, and due to uncertainties in sub-grid scale vertical transport processes unresolved by the present trajectory analysis. For "classical" cirrus-forming temperatures (<i>T</i>≲−40 °C), our results show that only mineral dust ice nuclei that underwent mixed-phase cloud-processing, most likely acquiring coatings of organic or inorganic material, are likely to be relevant. While the potential paucity of deposition ice nuclei shown in this work dimishes the possibility of deposition nucleation, the absence of liquid water droplets at <i>T</i>≲−40 °C makes the less explored contact freezing mechanism (involving droplet collisions with bare ice nuclei) highly inefficient. These factors together indicate the necessity of further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings

Behavioral Constraints for Services

Recently, we introduced the concept of an operating guideline of a service as a structure that characterizes all its properly interacting partner services. The hitherto considered correctness criterion is deadlock freedom of the composition of both services. In practice, there are intended and unintended deadlock-freely interacting partners of a service. In this paper, we provide a formal approach to express intended and unintended behavior as behavioral constraints. With such a constraint, unintended partners can be “filtered" yielding a customized operating guideline. Customized operating guidelines can be applied to validate a service and for service discovery

Evaluating performance-based financing in low-income and middle-income countries: the need to look beyond average effect.

Over the last decade, performance-based financing (PBF) has gained momentum as a health financing innovation, which combines linking healthcare payments to performance with increased provider autonomy and supervision. 1 2 The combination of these elements is expected to boost supply-side efforts towards increasing quantity and quality of service provision, triggering a demand-side response towards improved service utilisation.1 3 4 A recent paper by Paul et al has critically questioned the widespread introduction of PBF in light of the limited available evidence on its effectiveness.5 The response to this paper has been varied, with authors advancing arguments for and against PBF. Some African PBF implementers have claimed that PBF is an evolving strategy with potential benefits on health systems despite its existing challenges. 6 Others have drawn attention to the unintended consequences of PBF7 or to the need to assess the economic value of such an approach.8 Beyond their diverse arguments, however, most authors have concurred with Paul et al5 on the limited scope of currently available evidence and have postulated the need to better assess how PBF works under different contextual constraints within and across settings.9 10 Our commentary positions itself against this background, acknowledges the limited scope of current evidence on PBF, and explicitly argues in favour of devoting more effort to unravel heterogeneity across and within settings. Our argument is based on the recognition that by virtue of how impact evaluations are designed, the focus has been on the average effect, which masks important heterogeneity across settings, providers and users.11-13 To date, only a handful of studies have assessed heterogeneity of PBF effects across population subgroups4 14 15 or across health providers.16-18 Similarly, little attention has been devoted to understanding which factors can explain heterogeneity in the response to PBF or why PBF stimulates changes in some instances, but not in others.3 4 10 In light of the above, we call for more systematic analyses of heterogeneity, defined in relation to both the need to report differential effects and the need to understand what drives or explains such differential effects within and across settings. We first define and outline potential sources of heterogeneity and then offer initial guidance on how to measure and understand heterogeneity