OH-selected AGB and post-AGB stellar objects II.Blue versus red evolution off the AGB

Using objects found in a systematic survey of the galactic Plane in the 1612-MHz OH line, we discuss in detail two ``sequences'' of post-AGB evolution, a red and a blue. We argue that the red and the blue groups separate by initial mass at 4Msun, based on evolutionary-sequence turn-off colours, spectral energy distributions, outflow velocities and scaleheight. The higher-mass (blue) objects may have earlier AGB termination. The lower-mass (red) objects undergo very sudden reddening for IRAS colour R21\sim1.2; these sources must all undergo a very similar process at AGB termination. The transition colour corresponds to average initial masses of 1.7Msun. A combined IRAS-MSX colour proves a very sensitive tool to distinguish lower-mass, early post-AGB objects from sources still on the AGB and also to distinguish more evolved post-AGB objects from star-forming regions. The high-mass blue objects are the likely precursors of bipolar planetary nebulae, whereas the low-mass red objects will evolve into elliptical planetary nebulae.Comment: 12 pages, LaTex, 7 figures (1 colour), AJ (accepted

The role of social interaction in farmers' climate adaptation choice

Adaptation to climate change might not always occur, with potentially\ud catastrophic results. Success depends on coordinated actions at both\ud governmental and individual levels (public and private adaptation). Even for a “wet” country like the Netherlands, climate change projections show that the frequency and severity of droughts are likely to increase. Freshwater is an important factor for agricultural production. A deficit causes damage to crop production and consequently to a loss of income. Adaptation is the key to decrease farmers’ vulnerability at the micro level and the sector’s vulnerability at the macro level. Individual adaptation decision-making is determined by the behavior of economic agents and social interaction among them. This can be best studied with agentbased modelling. Given the uncertainty about future weather conditions and the costs and effectiveness of adaptation strategies, a farmer in the model uses a cognitive process (or heuristic) to make adaptation decisions. In this process, he can rely on his experiences and on information from interactions within his social network. Interaction leads to the spread of information and knowledge that causes learning. Learning changes the conditions for individual adaptation decisionmaking. All these interactions cause emergent phenomena: the diffusion of adaptation strategies and a change of drought vulnerability of the agricultural sector. In this paper, we present a conceptual model and the first implementation of an agent-based model. The aim is to study the role of interaction in a farmer’s social network on adaptation decisions and on the diffusion of adaptation strategies\ud and vulnerability of the agricultural sector. Micro-level survey data will be used to parameterize agents’ behavioral and interaction rules at a later stage. This knowledge is necessary for the successful design of public adaptation strategies, since governmental adaptation actions need to be fine-tuned to private adaptation behavior

Valuation of functions of the Wadden Area

The rationale of this position paper is to explore ways to employ valuation methods to assess the impacts of alternative policy decisions on the functions of the Wadden Area. Based on this rationale, this paper aims to bring an ecological-economic perspective on the benefits of the Wadden Area. It highlights key issues involved in the notion and application of monetary valuation methods for valuing the (ecological) functions of the area. It also pays attention to the development of policy handles on the basis of the outcome of the valuation of ecological functions. Particularly, the paper discuss Payment for Environmental Services (PES), which aims at preservation and protection by purchasing conservation. The use of a valuation instrument within a Payment for Environmental Services Scheme is new. Valuation is of course an established technique within a Cost-Benefit framework. However, Payment for Environmental Services is an innovative way of designing policy instruments in the collaboration between ecologists and economist

Fifty Years of Public (Dis)Satisfaction with European Governance: Preferences, Europeanization and Support for the EU

Since its beginnings in the 1950s, the policymaking scope and authority of the European Union have dramatically expanded across a wide range of issue areas. Yet much remains unknown about the interaction between public preferences for EU-level governance, changes in such governance and overall support for European integration. This article analyses surveys ranging from 1962 to 2010 to show that while support for integration in different policy areas has fluctuated over time, it has been surprisingly stable overall; moreover, the relative preference ordering across issue areas has been even more consistent. In addition, this consistency is not affected by changes in Europeanization, nor do such changes appear to be driven by the relative strength of preferences. Finally, issue-specific support for EU-level governance has an impact on overall EU support that becomes stronger as Europeanization in that issue area increases, an effect that increases further with greater political knowledge. These findings call into question understandings of rising Euroscepticism as a reaction to Europeanization taking place primarily in areas where publics oppose it. In addition, they indicate that public awareness of European integration is far greater than political knowledge tests appear to indicate

Using agent-based modeling to depict basin closure in the Naivasha basin, Kenya: a framework of analysis

A spatially-explicit agent-based modeling (ABM) approach is applied for depicting the processes leading to basin closure in the Naivasha basin by representing interdependencies between water availability and water use. Modeling the dynamics of water use and water availability yields patterns of their distribution over space and time. The approach allows for exploring the potential effectiveness of governance alternatives such as payment for environmental services (PES) schemes. This study shows that ABM is a promising approach for supporting water governance and can assist in increasing the understanding of the occurrence of basin closure

OH-selected AGB and post-AGB objects I.Infrared and maser properties

Using 766 compact objects from a survey of the galactic Plane in the 1612-MHz OH line, new light is cast on the infrared properties of evolved stars on the TP-AGB and beyond. The usual mid-infrared selection criteria, based on IRAS colours, largely fail to distinguish early post-AGB stages. A two-colour diagram from narrower-band MSX flux densities, with bimodal distributions, provides a better tool to do the latter. Four mutually consistent selection criteria for OH-masing red PPNe are given, as well as two for early post-AGB masers and one for all post--AGB masers, including the earliest ones. All these criteria miss a group of blue, high-outflow post-AGB sources with 60-mum excess; these will be discussed in detail in Paper II. The majority of post-AGB sources show regular double-peaked spectra in the OH 1612-MHz line, with fairly low outflow velocities, although the fractions of single peaks and irregular spectra may vary with age and mass. The OH flux density shows a fairly regular relation with the stellar flux and the envelope optical depth, with the maser efficiency increasing with IRAS colour R21. The OH flux density is linearly correlated with the 60-mum flux density.Comment: 16 pages, LaTex, 22 figures, AJ (accepted

Assessing the evidence of climate variability in the northern part of Ethiopia

In semi-arid highlands of northern Ethiopia, episodes of droughts of varying severity and duration occur. The occurrence of these droughts is associated mainly with the seasonal rainfall variability. This study attempts to investigate the temporal and spatial variability of climate parameters, particularly rainfall and temperature for the period 1954-2008. Standardized rainfall anomaly was used to examine the temporal characteristics of climate variability and determine the prevalence of droughts. Analysis of variance was also employed to establish significant differences in rainfall characteristics amongst different in-situ stations. The baseline climate data from each station was also spatially interpolated using ordinary kriging technique. The temporal analysis indicated an overall slight decrease in rainfall and an overall increase in the mean annual minimum and maximum temperatures over the study period. The analysis further revealed that the average annual minimum temperature over the region has been increasing by about 0.72ºC every ten years while average annual maximum temperature has been increasing by about 0.36ºC per decade. This shows that the northern part of Ethiopia is warming faster than the national average of 0.25ºC per decade. It is also observed that the average annual minimum temperature is increasing faster than average annual maximum temperature, which is an indication of warming nights over the years

Bubble drag reduction requires large bubbles

In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.Comment: 4 pages, 2 figure