The evolution of the stellar populations in low surface brightness galaxies

We investigate the star formation history and chemical evolution of low surface brightness (LSB) disk galaxies by modelling their observed spectro-photometric and chemical properties using a galactic chemical and photometric evolution model incorporating a detailed metallicity depen dent set of stellar input data. For a large fraction of the LSB galaxies in our sample, observed properties are best explained by models incorporating an exponentially decreasing global star formation rate (SFR) ending at a present-day gas fraction (M_{gas}/(M_{gas}+M_{stars}) = 0.5 for a galaxy age of 14 Gyr. For some galaxies small amplitude star formation bursts are required to explain the contribution of the young (5-50 Myr old) stellar population to the galaxy integrated luminosity. This suggests that star formation has proceeded in a stochastic manner. The presence of an old stellar population in many late-type LSB galaxies suggests that LSB galaxies roughly follow the same evolutionary history as HSB galaxies, except at a much lower rate. In particular, our results imply that LSB galaxies do not form late, nor have a delayed onset of star formation, but simply evolve slowly.Comment: To be published in A&

Simple Axioms for Local Properties

Correspondence theory allows us to create sound and complete axiomatizations for modal logic on frames with certain properties. For example, if we restrict ourselves to transitive frames we should add the axiom $\square \phi \rightarrow \square\square\phi$ which, among other things, can be interpreted as positive introspection. One limitation of this technique is that the frame property and the axiom are assumed to hold globally, i.e., the relation is transitive throughout the frame, and the agent's knowledge satisfies positive introspection in every world. In a modal logic with local properties, we can reason about properties that are not global. So, for example, transitivity might hold only in certain parts of the model and, as a result, the agent's knowledge might satisfy positive introspection in some worlds but not in others. Van Ditmarsch et al. (2012) introduced sound and complete axiomatizations for modal logics with certain local properties. Unfortunately, those axiomatizations are rather complex. Here, we introduce far simpler axiomatizations for a wide range of local properties.Comment: In Proceedings TARK 2023, arXiv:2307.0400

The CLEANED Approach for Flagging and Addressing Environmental Issues

While livestock presents an important livelihood strategy for many smallholders, it is also held responsible for important environmental impacts. In this paper, we used an online survey to identify the perceptions of global livestock experts on environmental impacts of livestock and how these might be tackled. We then explored how the CLEANED environmental ex-ante assessment tool (Comprehensive Livestock Environmental Assessment for improved Nutrition, a secured Environment and sustainable Development = CLEANED) responds to this and how it can be used to influence decision making towards more environmentally-friendly livestock production. According to the survey, there was general agreement between researchers, development practitioners and policy makers alike that livestock production systems are at risk of global environmental change while at the same time contributing to it. The major risks are perceived to be climate-related. The major impacts associated with livestock production, on the other hand, are considered to be land-related (degradation and competition for land), closely followed by pressure on water and GHG emissions. More sustainable livestock production practices are cited as most promising to reducing livestock’s environmental impact. The preferred technologies include managed grazing, improved pastures, silvo-pastoral systems and planted forages. A lack of rapidly available, site- and system-specific knowledge about such solutions and their potential environmental impacts are considered an important barrier to their successful implementation. The CLEANED environmental ex-ante assessment model aims to fill part of this gap. It can compare the relevant environmental impact indicators of the different solutions brought forward. The model has also been designed to be flexible when applied to a wide variety of contexts and provide systems-specific results. The expert survey further revealed that researchers, development practitioners and policy makers all based decisions on information, obtained from a variety of sources such as journal papers, internet searches and professional networks. The importance of journal papers, however, decreases as an information source from researchers over policy makers to development practitioners, while the use of professional networks and internet searches increases for these groups. This finding points to the importance of the participatory approach taken by the CLEANED team and the need to present results in appropriate multi-stakeholder forums and targeted internet posts. Further recommendations are made for increasing the use of the tool, i.e. making the outputs from the tool easier to interpret and training a variety of stakeholders in its use

Playing cards with Hintikka An introduction to dynamic epistemic logic

This contribution is a gentle introduction to so-called dynamic epistemic logics, that can describe how agents change their knowledge and beliefs. We start with a concise introduction to epistemic logic, through the example of one, two and finally three players holding cards; and, mainly for the purpose of motivating the dynamics, we also very summarily introduce the concepts of general and common knowledge. We then pay ample attention to the logic of public announcements, wherein agents change their knowledge as the result of public announcements. One crucial topic in that setting is that of unsuccessful updates: formulas that become false when announced. The Moore-sentences that were already extensively discussed at the conception of epistemic logic in Hintikka’s ‘Knowledge and Belief ’ (1962) give rise to such unsuccessful updates. After that, we present a few examples of more complex epistemic updates

Alternate wet/dry irrigation in rice cultivation: a practical way to save water and control malaria and Japanese encephalitis?

Water management / Water scarcity / Water use efficiency / Water conservation / Irrigated farming / Waterborne diseases / Rice / Malaria / Disease vectors / Productivity / Flood irrigation / Environmental control / Climate / China / East Africa / India / Indonesia / Japan / Philippines / Portugal / USA

Dimensions of fluvial-tidal meanders: Are they disproportionally large?

This is the final version. Available from Geological Society of America via the DOI in this record.GSA Data Repository item 2018343, supplementary figures, tables, and a .kml file with the recorded polygons of fluvial-tidal meanders, is available online at http://www.geosociety.org/datarepository/2018/ or on request from [email protected] of the world’s major river systems seemingly have one or a few disproportionally large meanders, with tight bends, in the fluvial-tidal transition (e.g., the Thames in the UK, and the Salmon River in Canada). However, quantitative studies on meanders have so far primarily focused on rivers without tidal influence or on small tidal meanders without river inflow, providing relations between channel geometry and meander characteristics (length, amplitude, and sinuosity). Physics-based predictions of meander size and shape for the fluvial-tidal transition zone remain untested for a lack of data. Therefore, it remains unclear whether the dimensions of meanders in the fluvial-tidal transition zone are indeed disproportionally large, and whether meander characteristics can be used as an indicator for tidal influence. Here, data from 823 meanders in 68 fluvial-tidal transition zones worldwide are presented that reveal broad-brush relations between channel geometry and meander dimensions. Our results show that fluvial-tidal meanders indeed become larger in the seaward direction, but the dimensions are proportional to local channel width, as in rivers. Sinuosity maxima are an exception, rather than the rule, in the fluvial-tidal transition zone. Surprisingly, the width of the upstream river correlates with estuarine channel width and tidal meander size even though river discharge constitutes only a fraction of the tidal prism. The new scaling relations can be used to constrain dimensions of rivers and estuaries and their meanders.Dutch Technology Foundation Toegepaste en Technische Wetenschappe