New insights on river water chemistry by using non-centred simplicial principal component analysis: a case study

The use of perturbation and power transformation operations permits the investigation of linear processes in the simplex as in a vectorial space. When the investigated geochemical processes can be constrained by the use of well-known starting point, the eigenvectors of the covariance matrix of a non-centred principalcomponent analysis allow to model compositional changes compared with a reference point.The results obtained for the chemistry of water collected in River Arno (central-northern Italy) have open new perspectives for considering relative changes of the analysed variables and to hypothesise the relative effect of different acting physical-chemical processes, thus posing the basis for a quantitative modelling

Admission Control for TCP Flows Using Packet Classes and Edge-to-edge Measurements of Aggregates

TCP flows from applications such as the web or ftp are well supported by a Guaranteed Minimum Throughput Service (GMTS), which provides a minimum network throughput to the flow and, if possible, an extra throughput. We propose a scheme for a GMTS using Admission Control (AC) that is able to provide different minimum throughput to different users and that is suitable for "standard" TCP flows. Moreover, we consider a multidomain scenario where the scheme is used in one of the domains, and we propose some mechanisms for the interconnection with neighbor domains. The whole scheme uses a small set of packet classes in a core-stateless network where each class has a different discarding priority in queues assigned to it. The AC method involves only edge nodes and uses a special probing packet flow (marked as the highest discarding priority class) that is sent continuously from ingress to egress through a path. The available throughput in the path is obtained at the egress using measurements of flow aggregates, and then it is sent back to the ingress. At the ingress each flow is detected using an implicit way and then it is admission controlled. If it is accepted, it receives the GMTS and its packets are marked as the lowest discarding priority classes; otherwise, it receives a best-effort service. The scheme is evaluated through simulation in a simple "bottleneck" topology using different traffic loads consisting of "standard" TCP flows that carry files of varying sizes

A Factor analysis of hidrochemical composition of Llobregat river basin

Hydrogeological research usually includes some statistical studies devised to elucidate mean background state, characterise relationships among different hydrochemical parameters, and show the influence of human activities. These goals are achieved either by means of a statistical approach or by mixing modelsbetween end-members. Compositional data analysis has proved to be effective with the first approach, but there is no commonly accepted solution to the end-member problem in a compositional framework.We present here a possible solution based on factor analysis of compositions illustrated with a case study.We find two factors on the compositional bi-plot fitting two non-centered orthogonal axes to the most representative variables. Each one of these axes defines a subcomposition, grouping those variables thatlay nearest to it. With each subcomposition a log-contrast is computed and rewritten as an equilibrium equation. These two factors can be interpreted as the isometric log-ratio coordinates (ilr) of three hiddencomponents, that can be plotted in a ternary diagram. These hidden components might be interpreted as end-members.We have analysed 14 molarities in 31 sampling stations all along the Llobregat River and its tributaries, with a monthly measure during two years. We have obtained a bi-plot with a 57% of explained totalvariance, from which we have extracted two factors: factor G, reflecting geological background enhanced by potash mining; and factor A, essentially controlled by urban and/or farming wastewater. Graphicalrepresentation of these two factors allows us to identify three extreme samples, corresponding to pristine waters, potash mining influence and urban sewage influence. To confirm this, we have available analysisof diffused and widespread point sources identified in the area: springs, potash mining lixiviates, sewage, and fertilisers. Each one of these sources shows a clear link with one of the extreme samples, exceptfertilisers due to the heterogeneity of their composition.This approach is a useful tool to distinguish end-members, and characterise them, an issue generally difficult to solve. It is worth note that the end-member composition cannot be fully estimated but only characterised through log-ratio relationships among components. Moreover, the influence of each endmember in a given sample must be evaluated in relative terms of the other samples. These limitations areintrinsic to the relative nature of compositional data

Edge detection by selection of pieces of level lines

We propose an edge detector based on the selection of wellcontrasted pieces of level lines, following the proposal ofDesolneux-Moisan-Morel (DMM) [1]. The DMM edge detectorhas the problem of over-representation, that is, everyedge is detected several times in slightly different positions.In this paper we propose two modifications of the originalDMM edge detector in order to solve this problem. The firstmodification is a post-processing of the output using a generalmethod to select the best representative of a bundle of curves.The second modification is the use of Canny’s edge detectorinstead of the norm of the gradient to build the statistics. Thetwo modifications are independent and can be applied separately.Elementary reasoning and some experiments showthat the best results are obtained when both modifications areapplied together.

Comparative study of algal communities in acid and alkaline waters from Tinto, Odiel and Piedras river basins (SW Spain)

The distribution patterns of benthic algal assemblages in the Tinto, Odiel and Piedras rivers were analyzed during the winter of 2005 in 18 sampling stations. The main objective was to assess and compare the algal communities and parameters affecting them both in the zones affected by acid mine drainage (AMD) and in naturally alkaline waters. A total of 108 benthic diatom taxa and 31 non-diatom taxa were identi ed. Results showed large differences between algal communities in the two environments: Pinnularia acoricola, P. subcapitata and Eunotia exigua were the most frequent diatom taxa in regions affected by acid mine drainage, along with algae like Klebsormidium and Euglena mutabilis were the most relevant non-diatom taxa. In alkaline waters the dominant diatom taxa were Planothidium frequentissimum, Gomphonema angustum, Fragilaria capucina, and some species of Navicula (N. viridula, N. veneta or N. radiosa), accompanied by Oscillatoria and Anabaena as well as by streptophytes of the group of zygnemataceae and desmidiaceae

On the spread of the European catfish (Silurus glanis) in the Iberian Peninsula: first record in the Llobregat river basin

The first record of the European catfish (Silurus glanis L. 1758) introduced to the Llobregat river basin (NE Spain) is reported. We captured one individual of this silurid fish species (of a total of 541 fish) in La Baells reservoir on 30 August 2006. Given the low catchability of this fish species, the popularity among some anglers, and old rumours on this introduction, we hypothesize that this species has been present in the reservoir since a few years ago, despite we did not capture it in two previous surveys. The illegal introduction of this and other exotic species to other Iberian river basins should be prevented by the Spanish administration

Structure and far-infrared edge modes of quantum antidots at zero magnetic field

We have investigated edge modes of different multipolarity sustained by quantum antidots at zero magnetic field. The ground state of the antidot is described within a local-density-functional formalism. Two sum rules, which are exact within this formalism, have been derived and used to evaluate the energy of edge collective modes as a function of the surface density and the size of the antidot.

Edge excitations and topological order in rotating Bose gas

The edge excitations and related topological orders of correlated states of a fast rotating Bose gas are studied. Using exact diagonalization of small systems, we compute the energies and number of edge excitations, as well as the boson occupancy near the edge for various states. The chiral Luttinger-liquid theory of Wen is found to be a good description of the edges of the bosonic Laughlin and other states identified as members of the principal Jain sequence for bosons. However, we find that in a harmonic trap the edge of the state identified as the Moore-Read (Pfaffian) state shows a number of anomalies. An experimental way of detecting these correlated states is also discussed.

Bound states of 3He at the edge of a 4He drop on a cesium surface

We show that small amounts of 3He atoms, added to a 4He drop deposited on a flat cesium surface at zero temperature, populate bound states localized at the contact line. These edge states show up for drops large enough to develop well defined surface and bulk regions together with a contact line, and they are structurally different from the well-known Andreev states that appear at the free surface and at the liquid-solid interface of films. We illustrate the one-body density of 3He in a drop with 1000 4He atoms, and show that for a sufficiently large number of impurities the density profiles spread beyond the edge, coating both the curved drop surface and its flat base and eventually isolating it from the substrate.

Sedimen-water nutrient fluxes: Preliminary results of in situ measurements in Alfaques Bay, Ebro River Delta.

Sediment-water exchanges of oxygen, ammonium, nitrate, total dissolved nitrogen, phosphate and total dissolved phosphorus were measured by means of an in situ incubator of 7 1 volume and 700 cm2 base area. The incubations lasted for three hours and were done over a whole season on different kinds of sediments in Alfaques Bay. We present some preliminary results on: i) methodological aspects, ii) spatial and temporal variability of fluxes, and iii) estimates of contribution of benthic nutrient regeneration relative to total nutrient loading of the Bay. Oxygen uptake averaged 1700 mmo1 m-2 h-1 (range 200-3500); no differences were found between sandy and muddy sediments. The release of ammonia from the sediment averaged 70 mmo1 m-2 h-1 and was higher in muddy sediments than in sandy ones. Very low to null nitrate and nitrite fluxes and only small fluxes of organic nitrogen were detected. We conclude that ammonium release from sediment is the major path of nitrogen regeneration. Some sediments removed dissolved reactive phosphorus (DRP) from the water and released dissolved organic phosphorus (DOP). Additional manipulative experiments revealed DRP release under particular conditions (turbulence, anoxia). From these data, we estimate that at least 50% of the nitrogen requirements of phytoplankton in the area may be supplied by benthic remineralization.

Trichoptera (INSECTA) collected in Mediterranean river basins in the Iberian Peninsula: taxonomic remarks and notes on ecology

As a result of the GUADALMED project, undertaken in Iberian Mediterranean basins, to which were added samples taken by the junior author in the area, we collected numerous caddisfly larvae, pupae and adults. Some larvae were also reared in the lab to obtain adults and allow proper identification. A total of 90 species were identified, which accounts for more than a fourth of the species known in the Iberian Peninsula and Balearic Islands. Here we confirm the presence of doubtful species in the Iberian Peninsula (Glyphotaelius pellucidus) and we expand the distribution range of others (Lype reducta, Micrasema minimum, Limnephilus guadarramicus, Sericostoma pyrenaicum). Moreover, because of the unconformity of morphological larval characteristics with present taxonomical keys (Mesophylax aspersus) or lack of larvae descriptions (Allogamus mortoni, Stenophylax espanioli), here we include some relevant taxonomical aspects that are useful to identify larvae. A brief description of the larva of a possible new species of Hydropsyche (from now on H. gr. instabilis) is also given. Los tricópteros (Insecta) recolectados en las cuencas mediterráneas de la Península Ibérica: notas taxonómicas y requerimientos ecológicos Como resultado de los estudios realizados en el proyecto GUADALMED en las cuencas de los ríos mediterráneos peninsulares y otros muestreos realizados por la primera autora del trabajo se han recolectado numerosas larvas, pupas y adultos de tricópteros. Algunas larvas fueron criadas en el laboratorio para la obtención de adultos y con ello asegurar su identificación. Se han identificado un total de 90 especies que suponen más de una cuarta parte de las especies actualmente conocidas en la Península Ibérica y Baleares. En este trabajo se confirma la presencia, hasta ahora dudosa en la Península Ibérica, de algunas especies (Glyphotaelius pellucidus) y se amplia el área de distribución de otras (Lype reducta, Micrasema minimum, Limnephilus guadarramicus, Sericostoma pyrenaicum). Además, se incluyen algunos aspectos taxonómicos relevantes para la identificación de algunas larvas en futuros estudios, debido a que las claves ya existentes no describen correctamente la larva (Mesophylax aspersus) o porque se trata de larvas sin describir (Allogamus mortoni, Stenophylax espanioli). Se añade también una somera descripción de la larva de una posible nueva especie de Hydropsyche (citada aquí como H. gr. instabilis) y que requiere un estudio más detallado.

People on the Edge See More. A conversation with the cuban-american writer Cristina García

L'entrevista amb l'escriptora cubano-americana Cristina García explora el tema de la identitat cubanoamericana i desvetlla la riquesa literària que sorgeix de la fusió de dues cultures, la cubana i la nord-americana, i com aquesta fusió innova la literatura nord-americana tradicional. En la seva novel·la, Dreaming in Cuban (1992), l'escriptora explora els efectes de la Revolució castrista des de la perspectiva de les dones cubanes que van quedar-se a l'illa, així com de les dones que emigraren als Estats Units. The conversation with Cuban-American writer Cristina García explores what it means to be Cuban-American, and reveals how to grow bicultural enriches mainstream American literature. In her novel Dreaming in Cuban (1992), the writer explores the effects of the Castro Revolution from the perspective of Cuban women who remained in Cuba, as well as from the experience of women who emigrated to the United States.

People on the Edge See More. A conversation with the cuban-american writer Cristina García

L'entrevista amb l'escriptora cubano-americana Cristina García explora el tema de la identitat cubanoamericana i desvetlla la riquesa literària que sorgeix de la fusió de dues cultures, la cubana i la nord-americana, i com aquesta fusió innova la literatura nord-americana tradicional. En la seva novel·la, Dreaming in Cuban (1992), l'escriptora explora els efectes de la Revolució castrista des de la perspectiva de les dones cubanes que van quedar-se a l'illa, així com de les dones que emigraren als Estats Units. The conversation with Cuban-American writer Cristina García explores what it means to be Cuban-American, and reveals how to grow bicultural enriches mainstream American literature. In her novel Dreaming in Cuban (1992), the writer explores the effects of the Castro Revolution from the perspective of Cuban women who remained in Cuba, as well as from the experience of women who emigrated to the United States.