1,542 research outputs found
A Lower Estimate for the Modified Steiner Functional
We prove inequality (1) for the modified Steiner functional A(M), which
extends the notion of the integral of mean curvature for convex surfaces.We
also establish an exression for A(M) in terms of an integral over all
hyperplanes intersecting the polyhedralral surface M.Comment: 6 pages, Late
Comparing feed intake, utilization of protein and energy for growth and body composition in S. solea fed natural and commercial diets
The present work was carried out to study the effect of polychaete Nereis virens on feed intake, utilization of protein and energy for growth and body composition in sole (S. solea). It is hypothesized that intake, efficiencies of protein utilization and growth rates obtained for sole fed ragworm are comparable to those previously reported for S. solea. The mussel M. edulis was used as a reference diet to allow comparisons of present results with those obtained previously, which until today serve as reference for optimum growth in sole. Intake, efficiencies of utilization for protein and energy for growth and growth rates obtained for sole fed ragworm are expected to be higher compared to commercial feed. A commercial feed, commonly used for turbot but also in sole culture served as a second reference diet to discuss differences between natural and commercial feeds
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
Modelling and dynamic simulation of struvite precipitation from source-separated urine
A model of a mixed-mode nutrient recovery reactor is developed for a urine feed, incorporating complex solution thermodynamics, dynamic conservation relations and a power-law kinetic expression for crystal growth from seed crystals. Simulations at nominal operating conditions predict phosphorus recoveries greater than 99%, based on existing process kinetic parameters and operating conditions employed in previously published studies. The overall rate of nutrient recovery depends on the saturation index of the precipitating solid, the available surface area for mass transfer and the feed rate of the limiting constituent ion. Under the conditions considered, the nutrient feed rate appears to be the limiting factor for precipitation. Simulations demonstrate that diurnal feed flow variations of ±50% have a small effect on the rate of nutrient recovery. Overall, the study shows that valuable insights are gained in relation to process performance predictions, which should lead to more confident process design, operation and control
Oral medicine case book 61: Oral malignant melanoma
A 45-year old male patient presented at the Oral and Maxillofacial
Clinic, Tygerberg, with a pathological fracture of the left
mandible following an extraction. The medical records of the
patient revealed a history of multiple myeloma that was treated
with Aredia (pamidronate disodium, an intravenous form of bisphosphonate),
cyclophosphamide (an alkylating agent) and
dexamethaxone (an anti-inflammatory and immunosuppressant
drug). An orthopantomograph revealed osteonecrosis
and pathological fracture of the left mandible, thought to be
due to the earlier biphosphonate administration. The patient
received conservative management for the osteonecrosis
and was stable at the time of the publication, (19 months after
the initial presentation with the pathological fracture).DHE
Eindrapport LNV bestek Duurzame viskweek
In Nederland wordt vis vooral in recirculatiesystemen (RAS) gekweekt , hetgeen als Ă©Ă©n van de meest duurzame manieren van viskweek wordt beschouwd. Of deze systemen echter optimaal zijn voor het welzijn en de gezondheid van de vis is nog de vraag. Een verminderde groei in recirculatiesystemen ten opzichte van doorstroomsystemen wordt gemeld voor zeebaars in de literatuur en voor een aantal andere soorten vanuit de praktijk. Dit geeft aan dat de kweekomstandigheden in RAS niet altijd optimaal zijn. Het belangrijkste verschil tussen recirculatiesystemen en doorstroomsystemen is de mate waarin het kweekwater wordt vervangen door vers water. Als gevolg van hergebruik van kweekwater treedt accumulatie op van opgeloste en gesuspendeerde stoffen die in het kweeksysteem geĂŻntroduceerd zijn of geproduceerd worden. De mate waarin accumulatie optreedt wordt bepaald door de mate van verversing van het kweekwater. De onderzoeksvragen waren daarom: wat is het effect van de mate van recirculatie van kweekwater op (1) het gedrag van vis, (2) de fysiologie van vis en (3) de groei van vis; (4) is groeiremming in RAS soortspecifiek en welk inzicht in groeiremming levert dit op en (5) wat is het effect van sorteren van vissen op niet gesorteerde vissen binnen hetzelfde RAS
Identifying Potential "Breakthrough" Publications Using Refined Citation Analyses: Three Related Explorative Approaches
Merit, Expertise and Measuremen
Selectivity and functional diversity in arbuscular mycorrhizas of co-occurring fungi and plants from a temperate deciduous woodland
1 The arbuscular mycorrhizal (AM) fungi colonizing plants at a woodland site in North Yorkshire (UK) have been characterized from the roots of five plant species (Rubus fruticosus agg. L., Epilobium angustifolium L., Acer pseudoplatanus L., Ajuga reptans L. and Glechoma hederacea L.), and identified using small-subunit rRNA (SSUrRNA) gene amplification and sequencing. 2 Interactions between five plant species from the site and four co-occurring glomalean fungi were investigated in artificial one-to-one AM symbioses. Three of the fungi were isolated from the site; the fourth was a culture genetically similar to a taxon found at the site. Phosphorus uptake and growth responses were compared with non-mycorrhizal controls. 3 Individual fungi colonized each plant with different spatial distribution and intensity. Some did not colonize at all, indicating incompatibility under the conditions used in the experiments. 4 Glomus hoi consistently occupied a large proportion of root systems and outperformed the other fungi, improving P uptake and enhancing the growth of four out of the five plant species. Only G. hoi colonized and increased P uptake in Acer pseudoplatanus, the host plant with which it associates almost exclusively under field conditions. Colonization of all plant species by Scutellospora dipurpurescens was sparse, and beneficial to only one of the host plants (Teucrium scorodonia). Archaeospora trappei and Glomus sp. UY1225 had variable effects on the host plants, conferring a range of P uptake and growth benefits on Lysimachia nummularia and T. scorodonia, increasing P uptake whilst not affecting biomass in Ajuga reptans and Glechoma hederacea, and failing to form mycorrhizas with A. pseudoplatanus. 5 These experimental mycorrhizas show that root colonization, symbiont compatibility and plant performance vary with each fungus-plant combination, even when the plants and fungi naturally co-exist. 6 We provide evidence of physical and functional selectivity in AM. The small number of described AM fungal species (154) has been ascribed to their supposed lack of host specificity, but if the selectivity we have observed is the general rule, then we may predict that many more, probably hard-to-culture glomalean species await discovery, or that members of species as currently perceived may be physiologically or functionally distinct
Algebraic approach to time-delay data analysis for LISA
Cancellation of laser frequency noise in interferometers is crucial for
attaining the requisite sensitivity of the triangular 3-spacecraft LISA
configuration. Raw laser noise is several orders of magnitude above the other
noises and thus it is essential to bring it down to the level of other noises
such as shot, acceleration, etc. Since it is impossible to maintain equal
distances between spacecrafts, laser noise cancellation must be achieved by
appropriately combining the six beams with appropriate time-delays. It has been
shown in several recent papers that such combinations are possible. In this
paper, we present a rigorous and systematic formalism based on algebraic
geometrical methods involving computational commutative algebra, which
generates in principle {\it all} the data combinations cancelling the laser
frequency noise. The relevant data combinations form the first module of
syzygies, as it is called in the literature of algebraic geometry. The module
is over a polynomial ring in three variables, the three variables corresponding
to the three time-delays around the LISA triangle. Specifically, we list
several sets of generators for the module whose linear combinations with
polynomial coefficients generate the entire module. We find that this formalism
can also be extended in a straight forward way to cancel Doppler shifts due to
optical bench motions. The two modules are infact isomorphic.
We use our formalism to obtain the transfer functions for the six beams and
for the generators. We specifically investigate monochromatic gravitational
wave sources in the LISA band and carry out the maximisiation over linear
combinations of the generators of the signal-to-noise ratios with the frequency
and source direction angles as parameters.Comment: 27 Pages, 6 figure
A variational approach to the macroscopic electrodynamics of anisotropic hard superconductors
We consider the Bean's critical state model for anisotropic superconductors.
A variational problem solved by the quasi--static evolution of the internal
magnetic field is obtained as the -limit of functionals arising from
the Maxwell's equations combined with a power law for the dissipation.
Moreover, the quasi--static approximation of the internal electric field is
recovered, using a first order necessary condition. If the sample is a long
cylinder subjected to an axial uniform external field, the macroscopic
electrodynamics is explicitly determined.Comment: 24 pages, 15 figure
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