Spinning bodies in curved space-time

We study the motion of neutral and charged spinning bodies in curved space-time in the test-particle limit. We construct equations of motion using a closed covariant Poisson-Dirac bracket formulation which allows for different choices of the hamiltonian. We derive conditions for the existence of constants of motion and apply the formalism to the case of spherically symmetric space-times. We show that the periastron of a spinning body in a stable orbit in a Schwarzschild or Reissner-Nordstr{\o}m background not only precesses, but also varies radially. By analysing the stability conditions for circular motion we find the innermost stable circular orbit (ISCO) as a function of spin. It turns out that there is an absolute lower limit on the ISCOs for increasing prograde spin. Finally we establish that the equations of motion can also be derived from the Einstein equations using an appropriate energy-momentum tensor for spinning particles.Comment: 26 pages, 5 figures; v2: version accepted for publication; small changes in text and references adde

Differential responses of Nile tilapia (Oreochromis niloticus) to fin clip wounding and related stress: perspectives

The debate around fish welfare is intensifying in The Netherlands. As a result, more research is carried out to enhance knowledge on fish welfare in aquaculture. Detailed information is lacking on how production procedures causing discomfort to the fish may affect welfare. That fish must perceive adversive stimuli follows from the fact that nociceptive mechanisms similar to those in mammals are present in fish. However, whether and how nociceptive stimuli are perceived or interpreted by a fish is a far more difficult question that requires significantly more effort from fundamental research, both neurophysiological and behavioural studies, than now available. The study presented in this report aimed to define selected readout for the acute response to a supposedly painful stimulus: a standardised tailfin clip to a common carp. In conclusion, we succeeded to demonstrate differential, stronger responses to a presumed painful stimulus than to the handling stress per se associated with the administration of the pain stimulus. These parameters will be the focus of future research within this welfare project

Ondernemend Waarderen : Waarderend Ondernemen. De subjectiviteit van het begrip economische waarde

The concept of economic value is widely used, but poorly understood. This study takes the proper explanation of the concept of value, as derived from the economists belonging to the Austrian School of Economics, as a starting point. During the last decades a mainstream approach to business valuation developed. This study treats the question whether this mainstream approach is based on the ideas about value which developed in the Austrian School of Economics. If so, how? If not, is it possible to derive insights from the Austrian School in order to improve the way we value in daily life?Businesses are capital goods and these are pivotal in creating wealth. Based on the Austrian perspective only real savings can lead to the existence of capital goods. The real world is not like most textbook models featuring a circular flow. Man is able to create value and obtain a higher level of wealth. As an important sidestep a flow model, based on a so-called Petrinet, was constructed to show the growth creating character of capital goods. In order to investigate the way mainstream economists and practioners determine economic value a framework was developed to structure both the theoretical approach and everyday practice. Two illustrative examples demonstrate how to calculate economic value based on Austrian principles. Furthermore the mainstream approach of valuation and three real life cases are presented and commented upon.LEI Universiteit LeidenCoherent privaatrech

Balancing the ventricular outputs of pulsatile total artificial hearts

Background: Maintaining balanced left and right cardiac outputs in a total artificial heart (TAH) is challenging due to the need for continuous adaptation to changing hemodynamic conditions. Proper balance in ventricular outputs of the left and right ventricles requires a preload-sensitive response and mechanisms to address the higher volumetric efficiency of the right ventricle. Methods: This review provides a comprehensive overview of various methods used to balance left and right ventricular outputs in pulsatile total artificial hearts, categorized based on their actuation mechanism. Results:Reported strategies include incorporating compliant materials and/or air cushions inside the ventricles, employing active control mechanisms to regulate ventricular filling state, and utilizing various shunts (such as hydraulic or intra-atrial shunts). Furthermore, reducing right ventricular stroke volume compared to the left often serves to balance the ventricular outputs. Individually controlled actuation of both ventricles in a pulsatile TAH seems to be the simplest and most effective way to achieve proper preload sensitivity and left–right output balance. Pneumatically actuated TAHs have the advantage to respond passively to preload changes. Conclusion: Therefore, a pneumatic TAH that comprises two individually actuated ventricles appears to be a more desirable option—both in terms of simplicity and efficacy—to respond to changing hemodynamic conditions.</p

A concise taxonomy for describing data as an art material.

How can we describe data when used as an art material? As the number of artists using data in their work increases, so too must our ability to describe the material in a way that is understood by both specialist and general audiences alike. In this paper we review existing vocabularies, glossaries, and taxonomies of data, and propose our own concise taxonomy. We present a number of examples of how existing data art works are described, and demonstrate our taxonomy by applying it to these works. To conclude we propose the adoption of this concise taxonomy by artists, critics, and curators, and suggest that on-going refinement of the taxonomy takes place through crowd-sourced knowledge sharing on the web

The Benefish consortium reports on the influence of system water refreshment rates on realized feed load, weight development, fish physiology and behaviour in turbot

Farmers with recirculation aquaculture systems (RAS) have a greater necessity and capacity to control the culture conditions of their farms than farmers with other aquaculture systems. Water quality is one of the factors that is closely monitored and managed in order to maintain the optimal levels of oxygen, ammonia, temperature, pH, and CO2. Effects of these parameters on growth and health are well studied and almost immediately noticeable. In RAS it often occurs that, although water quality conditions seem to be optimal, the feed intake of the fish might suddenly diminishes, thus reflecting a situation of sub optimal welfare of the animals. This phenomenon is particular relevant in marine RAS where these situations of reduced feed intake occur even though the normally monitored water quality parameters and husbandry conditions appear to be optimal. Similar phenomena also occur in other aquaculture culture systems, such as flow through systems, where feed intake fluctuates whilst the reasons are not always known, although there is typically less control and monitoring compared with RAS. It is therefore necessary to actively monitor deviation of expected feed intake, in combination with the monitoring of culture conditions and farm management on pilot-scale level. Only through this intermediate level experimental work and farm observations for the assumed relationship between deviation of expected feed intake and fish welfare can be validated. It is furthermore necessary to provide refinements to causative relationships expected to be found on commercial farms, where it is often claimed that e.g. lower system water refreshment rates or more closed RAS are leading to growth retardation and lower feed intake in fish and thus lower production. The present study is, therefore, intending to prove the hypothesis that changes in feed intake can be associated with changed fish welfare status, using turbot as model species. It is furthermore hypothesized that this changed fish welfare status is caused by different system water refreshment rates and fish and system management. As a final result, feed intake should relate by same efficiency to lower fish growth in closed RAS compared to flow through systems. The objectives are therefore to validate the relationships between deviation from expected feed intake and fish welfare, and their causative factors on the commercial farms interpreting data on feed intake, behavior, endocrinology and immune patterns as welfare indicators

Enhanced Practical Photosynthetic CO₂ Mitigation

This process is unique in photosynthetic carbon sequestration. An on-site biological sequestration system directly decreases the concentration of carbon-containing compounds in the emissions of fossil generation units. In this process, photosynthetic microbes are attached to a growth surface arranged in a containment chamber that is lit by solar photons. A harvesting system ensures maximum organism growth and rate of CO2 uptake. Soluble carbon and nitrogen concentrations delivered to the cyanobacteria are enhanced, further increasing growth rate and carbon utilization

Flow-Controlling Header

An apparatus and method for holding a membrane, screen or other flexible planar body in tension, while providing a conduit for water or other liquid to flow to the membrane being held. The membrane extends from inside a manifold body that carries the liquid, and the manifold body supports the membrane at one edge while the membrane is pulled in tension. Liquid pressure builds up inside the manifold body, preferably by entering a pressure chamber at the top of the manifold body. At a feeding pressure in the pressure chamber the liquid is distributed to the membrane for microbe growth. The liquid can be elevated to a higher, microbe-harvesting pressure by increasing the pressure in the pressure chamber, thereby deflecting a shim separating the pressure chamber from the membrane. The change in pressure is carried out by manually or automatically opening and closing a conventional water valve