The paradox of the clumps mathematically explained

The lumpy distribution of species along a continuous one-dimensional niche axis recently found by Scheffer and van Nes (Scheffer and van Ness 2006) is explained mathematically. We show that it emerges simply from the eigenvalue and eigenvectors of the community matrix. Both the transient patterns—lumps and gaps between them—as well as the asymptotic equilibrium are explained. If the species are evenly distributed along the niche axis, the emergence of these patterns can be demonstrated analytically. The more general case, of randomly distributed species, shows only slight deviations and is illustrated by numerical simulation. This is a robust result whenever the finiteness of the niche is taken into account: it can be extended to different analytic dependence of the interaction coefficients with the distance on the niche axis (i.e., different kernel interactions), different boundary conditions, etc. We also found that there is a critical value both for the width of the species distribution s and the number of species n below which the clusterization disappear

Use of open-top chambers to study the effect of climate change in aquatic ecosystems

The aim of this research was to explore the possibility to use inexpensive open-top chambers (OTCs) as passive artificial warming devices in experimental aquatic studies. Our results show that OTCs give a significant temperature increase compared with the control. The measured increase (up to an average of 2.3°C) corresponds with predicted climatic warming. Due to their open top, the light quantity and quality is only minimally reduced. We found that OTCs are especially suited for studying the effect of climate change in small waters as the vertical temperature gradients remain unchanged. They can also easily be transported to remote environments. We discuss other advantages and disadvantages of these devices for aquatic studies and compare them with other warming devices

Health and the democratic dividend in Sub-Saharan Africa: are democracies better at managing the HIV/AIDS epidemic?

The democratic dividend theory states that democraciesshould provide socio-economic benefits to their citizens.Scholars suggest that the legitimacy of African democraciesis partly dependent on this dividend. Following this theory,democracies should handle the HIV/AIDS epidemic betterthan non-democracies because of their higher level ofaccountability. A cross-national analysis is conducted toinvestigate how a country’s level of democracy is associatedwith respondents’ knowledge of HIV/AIDS and the provisionof HIV-testing places. The relationships between bothdemocracy and HIV-knowledge, and the provision of HIVtestingplaces are non-significant. This can have implicationsfor how citizens view their regimes’ legitimacy

The Impact of Alternative Access Modes on Urban Public Transport Network Design

Public transport network design determines the quality for travellers as well as operational costs. Network design is therefore crucial for the cost effectiveness of urban public transport. In urban public transport network design it is commonly assumed that all travellers walk to the stops. This might be true for short access distances, but if stop and line spacing increase other modes such as bicycles might become interesting as an alternative access mode. An analytical model is presented that determines optimal network characteristics, i.e. stop spacing, line spacing, and frequency, and that explicitly accounts for alternative access modes. The objective used is maximising social welfare. Results show that, if cycling is considered as an alternative access mode, all three network characteristics mentioned above should be increased, offering benefits for the traveller, the operator as well as the society. However, if there is a large sub-population of travellers who are not able to use the alternative mode, or if there are barriers for using an alternative mode to access the urban public transport system, it is better to assume that walking is the only access mode available. In the case of cycling as an access mode there are possibilities for positive benefits, at least in countries such as Denmark or the Netherlands. It is expected that for other access modes, such as peoplemovers and demand responsive public transport systems, the barriers are too high to have an impact on urban public transport network design

Bildschirm am Arbeitsplatz : Kurt Nagel (Ed.), DV Aktuell 1981, Oldenbourg, München, 1981

Boekbespreking

Spaces Defined by Objects

This is an exploratory written peace that attempts to define spaces, and how objects as well as people define them. The peace takes the viewer through various images, all captured by William Van Nes throughout the United States, and tries to explain meaning, and how we prescribe our own meaning to spaces. This peace will specifically address and explore the concept of defining a space, and what it actually means to define spaces.https://digitalcommons.csumb.edu/hcom434_spring2023/1022/thumbnail.jp

Plastic Pollution in the Pacific Ocean

Keywords: Preserve/Preservation, Great Pacific Garbage Patch, The 5 R’s