Power, competition, and the nature of history

AbstractHistorians have debated whether pathways and events from the past to the present are influenced largely by contingency, the dependence of outcomes on particular prior conditions, or whether there is long-term emergent directional change. Previous arguments for predictability in evolutionary history relied on the high frequency of convergence, but the repeated evolution of widely favored adaptations need not imply long-term directionality. Using evidence from the fossil record and arguments concerning the metabolic evolution of organisms, I show here that power (total energy taken up and expended per unit time) has increased stepwise over time at ecosystem-level and global scales thanks to the ratchet-like, cumulative effects of competition and cooperation and to the disproportionate influence of powerful top competitors and opportunistic species on emergent ecosystem properties and processes. The history of life therefore exhibits emergent directionality at large ecosystem-wide scales toward greater power

Effect of slatted and solid floors and permeability of floors in pig houses on environment, animal welfare and health and food safety: a review of literature

An integrated approach can improve understanding of floor performance. Not only gap width or percentage of slatted floor is important, but a minimum percentage of permeability of the total floor area appears to be decisiv

Effects of residential mobility on the educational opportunity of children in a society with a centralised educational system.

Research in the United States indicates that moving adversely affects children’s school performance No studies have been conducted on this subject in continental Europe yet. Unlike in the United States, most continental European societies have a national school system, which should diminish the educational consequences of moving. The question of this article is therefor “Does changing schools adversely affect the subsequent performance of good students in the Netherlands?” Our data are from the VOCL ’89 cohort, a nationally representative longitudinal cohort of high school students. The results indicate that students in VWO (pre-university) programs are more likely to repeat the year than their counterparts who do not change schools. The discrepancy is greater still in the MAVO (lower general secondary education) programs. MAVO students are more likely to transfer to less competitive programs than their counterparts who do not change schools. They also repeat the year more often. Thus, we found for a continental European society also that changing schools for non-academic reasons adversely affects subsequent school performance.euducational performance; geographic monility; moving of households

Demonstrating the potential of Accurate Absolute Cross-grain Stress and Orientation correlation using Electron Backscatter Diffraction

We report a first exploration of High-angular-Resolution Electron Backscatter Diffraction, without using simulated Electron Backscatter Diffraction patterns as a reference, for absolute stress and orientation measurements in polycrystalline materials. By co-correlating the pattern center and fully exploiting crystal symmetry and plane-stress, simultaneous correlation of all overlapping regions of interest in multiple direct-electron-detector, energy-filtered Electron Backscatter Diffraction patterns is achieved. The potential for highly accurate measurement of absolute stress, crystal orientation and pattern center is demonstrated on a virtual polycrystalline case-study, showing errors respectively below 20 MPa (or 1e-4 in strain), 7e-5 rad and 0.06 pixels.Comment: Manuscript as accepted for publication in Scripta Materiali

Energiegebruik en kosten van centrale afzuiging en afzuiging per afdeling in varkensstallen

Centrale afzuiging wordt in de praktijk bij nieuwbouw vaak toegepast. Een belangrijk voordeel van centrale afzuiging is de energiebesparing die ermee te realiseren is

Reef fishes of Saba Bank, Netherlands Antilles : Assemblage structure across a gradient of habitat types

Saba Bank is a 2,200 km2 submerged carbonate platform in the northeastern Caribbean Sea off Saba Island, Netherlands Antilles. The presence of reef-like geomorphic features and significant shelf edge coral development on Saba Bank have led to the conclusion that it is an actively growing, though wholly submerged, coral reef atoll. However, little information exists on the composition of benthic communities or associated reef fish assemblages of Saba Bank. We selected a 40 km2 area of the bank for an exploratory study. Habitat and reef fish assemblages were investigated in five shallow-water benthic habitat types that form a gradient from Saba Bank shelf edge to lagoon. Significant coral cover was restricted to fore reef habitat (average cover 11.5%) and outer reef flat habitat (2.4%) and declined to near zero in habitats of the central lagoon zone. Macroalgae dominated benthic cover in all habitats (average cover: 32.5 – 48.1%) but dominant algal genera differed among habitats. A total of 97 fish species were recorded. The composition of Saba Bank fish assemblages differed among habitat types. Highest fish density and diversity occurred in the outer reef flat, fore reef and inner reef flat habitats. Biomass estimates for commercially valued species in the reef zone (fore reef and reef flat habitats) ranged between 52 and 83 g/m2. The composition of Saba Bank fish assemblages reflects the absence of important nursery habitats, as well as the effects of past fishing. The relatively high abundance of large predatory fish (i.e. groupers and sharks), which is generally considered an indicator of good ecosystem health for tropical reef systems, shows that an intact trophic network is still present on Saba Bank

Kostprijs biologische eieren weer omlaag

In het 2e kwartaal van 2009 is de kostprijs van biologische eieren opnieuw vastgesteld. Op basis van 22 koppels, waarvan de productiegegevens in 2007 en 2008 zijn vastgelegd door Albatross, zijn nieuwe kengetallen tot stand gekomen. In combinatie met lagere voerprijzen is de kostprijs met 1 cent per ei gedaald ten opzichte van het 3e kwartaal 200

Preliminary overview of exotic and invasive marine species in the Dutch Caribbean

The marine exotic species of the Dutch Caribbean are less well-known than its terrestrial exotics. So far, only 27 known or suspected marine exotic species, some of which are also invasive are documented for one or more islands of the Dutch Caribbean. Four of these were documented only once or were only present for a certain period of time and are no longer present. Six of the species are marine epidemic diseases. As very little is known about these diseases, they might actually be native, but based on the literature and their ecological signature we regard them as special cases of invasive species. In addition to these documented species, 76 other exotic species that have already been observed elsewhere in the Caribbean may already be present or can be expected to arrive in the Dutch Caribbean in the near future. The marine communities of the Dutch Caribbean have suffered major changes based on a handful of marine exotic and/or invasive species, particularly in the special case of (opportunistic) pathogens. In certain cases experience shows that after decades, the affected systems/species may show slow signs of recovery from initial impacts (e.g. the green turtle fibropapillomas), while in other cases the impact may be long-lasting and recovery doubtful (e.g. sea fan mortality). Compared to terrestrial exotic species, eradication and control have been proven difficult or impossible for marine exotics. Therefore, management practices aimed at controlling unwanted species introductions should focus on preventing the arrival of such species by ships-- that transport exotics in their ballast water or as fouling communities on their hulls-- and (accidental) introductions from aquaculture or the aquarium trade. Busy harbors can be expected to be the areas where most marine exotics likely establish first. Because of dispersal of marine exotics is facilitated by ocean currents, local approaches to prevent their arrival or reduce their numbers will be less effective compared to similar efforts for terrestrial species. In the case of marine exotics and invasives, it is paramount that prevention, control and management efforts should be regionally integrated. We conclude this report by listing a number recommendations on how to develop effective management approaches with which to address the impacts and risks associated with marine exotic species. This research is part of the Wageningen University BO research program (BO-11-011.05-004) and has been financed by the Ministry of Economic Affairs, Agriculture and Innovation (EL&I) under project number 4308202004

Hoge kostprijs bio-ei

In 2008 is de kostprijs van biologische eieren (volièresysteem) gestegen tot een recordhoogte van 14,5 cent per eerste soort ei. De piek lag in de zomer toen de voerprijs het hoogst was en het aandeel van de voerkosten 54 procent bedroeg. Inmiddels is de kostprijs bijna 1 cent gedaald door de dalende voerprijze