Boundary slopes of 2-bridge links determine the crossing number

A diagonal surface in a link exterior M is a properly embedded, incompressible, boundary incompressible surface which furthermore has the same number of boundary components and same slope on each component of the boundary of M. We derive a formula for the boundary slope of a diagonal surface in the exterior of a 2-bridge link which is analogous to the formula for the boundary slope of a 2-bridge knot found by Hatcher and Thurston. Using this formula we show that the diameter of a 2-bridge link, that is, the difference between the smallest and largest finite slopes of diagonal surfaces, is equal to the crossing number.Comment: 16 pages, 6 figure

Effect of bioactive compounds from Sainfoin (Onobrychis viciifolia Scop.) on the in vitro larval migration of Haemonchus contortus: role of tannins and flavonol glycosides

Anthelmintic bioactivity against gastrointestinal nematodes has been associated with leguminous forages supporting the hypothesis of a role of condensed tannins. However, the possibility that other compounds might also been involved has received less consideration. Using bio-guided fractionation, the current study aimed at characterising the biochemical nature of the active compounds present in sainfoin (Onobrychis viciifolia), previously identified as an anthelmintic leguminous forage. The effects of sainfoin extracts were evaluated on 3rd stage larvae (L3) of Haemonchus contortus by using a larval migration inhibition (LMI) assay. Comparison of extracts obtained with several solvent systems showed that the bioactivity was associated with the 70:30 acetone/water extract. Further fractionation of the later allowed the separation of phenolic compounds. By use of a dialysis method, compounds were separated with a molecular weight cut-off of 2000 Da. The in vitro anthelmintic effects of the fraction with condensed tannins was confirmed. In the fraction containing molecules of MW < 2000 Da, 3 flavonol glycosides were identified as rutin, nicotiflorin and narcissin. At 1200 μg/ml, each inhibited significantly migration of larvae. Addition of polyvinyl pyrrolidone (PVPP) to both fractions before incubation restore larval migration. These results confirmed the role of both tannins and flavonol glycosides in the anthelmintic properties of sainfoin

The impact of primary production in the water column on benthic copepods

A phytoplankton bloom was followed from 9 March till 12 July 1999 at a subtidal station in the Southern Bight of the North Sea. Chla (in surface-, bottom- and interstitial water) and nutrient concentrations (interstitial water) as well as diatom biomass were measured in order to detect any deposition of organic material originating from the bloom on the bottom. The response of the benthic copepods to the sedimentation of the spring phytoplankton bloom was described in terms of changes in density, diversity and community structure. In March the bottom was already organically enriched, probably due to lateral transport. May and June were characterised by organic enrichment derived from the diatom and Phaeocystis spring bloom. In April and July no organic enrichment was observed. The changes in copepod density, diversity and community structure have been attributed to organic enrichment. Over the whole time series copepods were most abundant in the upper two centimetres of the sediment. Nevertheless, a migration of the copepods to the surface was observed during the organic enrichment. Individual species reacted differently to the spring bloom. Some species disappeared, others took advantage of the situation for reproduction. Most pronounced was the reaction of Apodopsyllus n. sp. 1 which was defined as an opportunistic species. The species composition along the sediment depth profile was very diverse in the months devoid of organic enrichment, in contrast with the months with organic enrichment, the community structure over the depth layers then being homogeneous

Interactions between nutrition and gastrointestinal infections with parasitic nematodes in goats

Parasitic nematodes of the digestive tract remain one of the main constraints to goat production both in temperate and tropical countries. The usual mode of control of these gastrointestinal nematodes (GIN) based on the repeated use of anthelmintics is now strongly questioned because of the increasing development of resistance to these molecules. Among the alternative methods to anthelmintics currently available, the manipulation of host nutrition in order to improve the host resistance and/or resilience to parasitic infections seems to represent one of the most promising options to reduce the dependence on conventional chemotherapy and to favour the sustainable control of gastro intestinal nematode infections. This paper will review the available information on the interactions between nutrition and nematode parasitism in dairy or meat goats both in temperate and tropical conditions. It will refer to quantitative aspects of the diet (influence of the protein and/or energy parts) as well as to qualitative components (effects of plant secondary metabolites on worm biology) and will discuss the specificities of goats in regard of theses interactions

Trypanotolerant livestock in West and Central Africa. Volume 3. A decade's results

This volume presents major results obtained since the publication of volume 1 and 2 and updates national data on trypanotolerant cattle. The first part analyses populations and their trends between the two surveys and reviews research activities and development activities. It also gives recent information available on the potential and utilisation of trypanotolerant livestock. Part two presents recent data for the 18 study countries, as well as for Equatorial Guinea which was not covered in volume 2. This information should be studied in conjuction with volume 2 for an overall and updated view of trypanotolerant livestock production in each country. Countries are discussed in the same order in both volumes. An additional section on major developments occuring during the study period has been included at the end of each country study

Theoretical and experimental study of AC loss in HTS single pancake coils

The electromagnetic properties of a pancake coil in AC regime as a function of the number of turns is studied theoretically and experimentally. Specifically, the AC loss, the coil critical current and the voltage signal are discussed. The coils are made of Bi2Sr2Ca2Cu3O10/Ag (BiSCCO) tape, although the main qualitative results are also applicable to other kinds of superconducting tapes, such as coated conductors. The AC loss and the voltage signal are electrically measured using different pick up coils with the help of a transformer. One of them avoids dealing with the huge coil inductance. Besides, the critical current of the coils is experimentally determined by conventional DC measurements. Furthermore, the critical current, the AC loss and the voltage signal are simulated, showing a good agreement with the experiments. For all simulations, the field dependent critical current density inferred from DC measurements on a short tape sample is taken into account.Comment: 22 pages, 15 figures; contents extended (sections 3.2 and 4); one new figure (figure 5) and two figures replaced (figures 3 and 8); typos corrected; title change

Haalbaarheid mobiel slachthuis en uitsnijderij = Feasibility of mobile slaughter and cutting carcasses

To develop selling of local products and biologic meat a mobile unit for slaughter farm animals with a permanent cutting and selling room at the farm can be useful