The "neutral" community structure of planktonic herbivores, tintinnid ciliates of the microzooplankton, across the SE Tropical Pacific Ocean

International audienceAcross a species-rich area, the SE Pacific Ocean, the community characteristics of a group of planktonic herbivores was assessed. A series of 22 stations between the Marquise Islands (7° S 142° W) and the coast of Chile (35° S 73° W) was sampled during the BIOSOPE cruise in 2004. The relationships between taxonomic diversity, morphological diversity, patterns of tintinnid species assemblage, and phytoplankton abundance were examined. Tintinnid community characteristics were estimated from large volume (20–60 l) discrete depth sampling and phytoplankton were characterized based on HPLC pigment signatures. Across the transect, average water column concentrations of tintinnids ranged from 2–40 cells l-1or 8–40 ng C l-1, and were positively related to chlorophyll a concentrations which varied between 0.07–2 µg l-1. Large numbers of tintinnid taxa were found, 18–41 species per station, yielding a total of 149 species. Among stations, morphological and taxonomic diversity metrics co-varied but were not significantly related to phytoplankton diversity estimated using a pigment-based size-diversity metric. Taxonomic diversity of tintinnids, as H' or Fishers' alpha, was inversely related to chlorophyll concentration and positively to the depth of the chlorophyll maximum layer. For each station, species abundance distributions were compared to geometric, log-series and log-normal distributions. For most stations, the observed distribution most closely matched log-series, coherent with the neutral theory of random colonization from a large species pool. Occurrence rates of species were correlated with average abundance rather than specific characteristics of biomass or lorica oral diameter (mouth) size. Among stations, species richness was correlated with both the variety of mouth sizes (lorica oral diameters) as well as numbers of species per mouth size, also consistent with random colonization

Magnetic nanocomposites at microwave frequencies

Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

Protei"enbronne in die rantsoene van groeiende varke 1. 'n vergelyking tussen vismeel en verhitte volvet sojaboonmeel

Summary: protein sources in the diets of growing pigs.1. A comparison between fish meal and heated full-fat soyabean mealTwo trials, one with porkers and one with baconers were conducted to determine the influence of heated full-fat soyabean meal as protein source on their growth, feed utilization, carcass development and fat refraction-index values. The results indicated that it is possible to substitute fish meal as protein source, on a biological base, with soyabean meal in diets with equivalent protein and energy levels.Twee proewe, een met vleis- en een met spekvarke, is uitgevoer om die invloed van verhitte volvet sojaboonmeel as proteienbron op hul groei, voeromset, karkasontwikkeling en refraksie-indekswaardes van karkasvet te bestudeer. Die resultate in die studie verkry dui daarop dat verhitte volvet sojaboonmeel wel vismeel suksesvol as proteienbron op 'n biologiese basis, in rantsoene met ekwivalente proteien- en energiepeile kan vervang

An Analysis of the Ability of the Second Year Students of Sman 2 Pangkalan Kerinci in Comprehending Procedure Texts

The aim of this study is to find out the reading ability of the second year students of SMAN 2 Pangkalan Kerinci in comprehending procedure texts. The population of this research were all of the second year students which consisted of 253 students. There were 25 students who participated in this study. The instrument was a test adapted from authentic material. The frame of the test covers 8 components such as: finding main idea, finding factual information, finding meaning of difficult word, finding references, finding inferences, finding social function, finding generic structure, and finding language features. Each component consist of 4 question and for finding generic structure and language features consist of 3 question because the generic structure question and the language features is too difficult for the students. The test containing 30 items was used to collect the data. Before the test was administered, the test was tried out to find out the difficulty level and the reliability of the test. To analyze the data, the raw scores of the students were calculated and the level of ability was identified by using the classification of ability level by Harris (1974). The result showed that the ability of the second year students of SMAN 2 Pangkalan Kerinci in comprehending procedure texts was at Average to Good level with mean score 67. Therefore, it can be concluded that most of the students were able to comprehend procedure texts. However, the students are suggested to do more practice in reading procedure texts in order to comprehend procedure texts to improve the ability in reading due to the poorness of their reading ability