Les peuplements d'éphémèroptères de plécoptères et de trichoptères des ruisseaux acides et non acides du massif vosgien : première approche

Les peuplements d'Ephémèroptères, de Plécoptères et de Trichoptères de quatorze cours d'eau du massif vosgien granitique, ont été échantillonnés de mars 1988 à mars 1990. Les stations, au nombre de seize, ont été choisies en amont de toute agglomération et en dehors de zones d'activité agricole.Les mesures de pH, conductivité et aluminium total, ont établi que sept ruisseaux sont acides (pH moyens : 4,67-5,62), très faiblement minéralisés (conductivités moyennes : 17-21,5 µS/cm) et présentent des concentrations moyennes en aluminium total, comprises entre 221 et 387 µg/l.Les sept autres cours d'eau sont faiblement acides à neutres (pH moyens : 6,80-6,98), peu minéralisés (conductivité moyenne : 36-90 µS/cm) et montrent des concentrations moyennes eut aluminium variant de 41 à 78 µg/l.Seules 29 espèces ont été récoltées dans les ruisseaux acides alors que 93 l'ont été dans les cours d'eau non acides.Les Ephémèroptères se révèlent les plus sensibles aux conditions acides et disparaissent totalement. Parmi les Trichoptères, seuls les Polycentropodidae, les Rhyacophilidae et les Limnephilidae sont encore présents dans les ruisseaux acides. Alors que les Plécoptères Filipalpes sont bien représentés, certaines espèces étant même très abondantes, les Plécoptères Sétipalpes ne sont plus récoltés dans les cours d'eau acidifiés, à l'exception de Siphonoperla torrentium.Acidification of freshwaters has become a serious problem in certain parts of the Vosges Mountains (Northeastern France). Aquatic organisms at all major levels are affected by decreased pH. As the Ephemeroptera, Plecoptera and Trichoplera are a significant par of the macrobenthos in mountain streams, the objective of this preliminary study was to determine how the physico-chemical environment in acidified running waters affects the qualitative composition of mayflies, stoneflies and caddis-flies communities compared with non acidified streams and to evaluate the reliability and possible use of the taxonomic groups as indicators of the extent of acidification.A biological survey of fourteen streams was conducted in the Vosges mountains from March 1988 to March 1990. The areas investigated lie on granitic bed-rock and soils in the process of podzolisation. The sampling sites (sixteen), at altitudes of 600 to 1020 meters a.s.l. were located above built-in and agricultural areas thus avoiding organic pollution. The streams drain forested catchments regarded as sensitive to acid inputs and affected by forest decline. Silver fir (Abies alba), Norway spruce (Pecea abies) and European beech (Fagus sylvatica) are dominant.Larvae and pupae of Ephemeroptera, Plecoptera and Trichoptera were collected by band picking and Surber sampler (mesh aperture 350 µm). Adults were collected with an insert net by beating bushes and trees or sweeping low herbage near streams. A long-handled net was required for high-flying Ephemeroptera and Trichoptera. Organisms were preserved in 5 % formalin or 70 % ethanol.The pH was measured in the field using a specific glass electrode for low ionic solutions, compensated for temperature. Water samples were acidified for total aluminium analysis. Determination of aluminium was performed using an atomic absorption spectrophotometer equipped with a graphite furnace. Conductivity was measured in the laboratory al 20 °C.Determination of pH revealed that acidification occurred et seven sites (sampling sites n° 8 to 16). Six were strongly acidic (mean pH : 4.7-5.2) and one moderately acidic (mean pH : 5,6). In such streams mean total aluminium ranged from 221 µg/1 to 387 µg/1 and mean conductivity from 17,0 µS/cm to 21.5 µS/cm. Minimum pH and maximum aluminium values were recorded during snowmelt or rein event. In all these streams the fish population (Salmo trutta fario) has completely disappeared.Others streams (sampling sites n° 1 to 7) went from slightly acidic to neutral with a range pH between 6.8-7.0 and were characterized by average total aluminium varying from 41 µg/1 to 78 µg/l and average conductivity from 36 µS/cm to 90 µS/cm. These streams have been considered as reference for non acidified running waters.The number of species occurring in acidified streams contrasted markedly with those of the non acidified streams. Specific richness of Ephemeroptera, Plecoptera and Trichoptera are reduced in acidic waters. Only twenty-nine species were found in acidic streams, whereas a total of ninety-three species were collected in non acidic streams.EphemeropteraIn the reference streams, the Ephemeroptera fauna was rich and diverse with twenty taxa. Some species, for example Epeorus sylvicola, Baetis alpinus and B. rhodani were very common and widespread. In contrast, in acidic water only one species, Baetis vernus, was actually present (3 larvae).TrichopteraThirty-eight species of caddis flies were found in non acidic streams. Hydropsychidae (hydropsyche sp) Philopotamidae (Philopotamus ludificatus, P. montanus, Wormaldia sp) and Glossosomatidae (Glossosoma conformis, Agapetus sp) were the organisms most commonly present.In acidic streams, eleven species were food. Rhyacopyhilidae (Rhyacophlla obliterata, R. potamoides, R. praemorsa), Polycentropodidae (Plectrocnemia sp, P. conspersa) and Limnephilidae (Drusus annulatus, D. discolor, Caetopterygopsis maclachlani, Chaelopteryx villosa, Anitella sp) were among the most abundant taxa.PlecopteraIn acidic streams, taxonomic richness (17 species) was about 50% lower than those obtained in the non acidic streams. The common species Perla marginata, Perlodes microcephala and Isoperla oxylepis were not listed when pH was below 5.6. At the opposit, some species were dominant and very abundant. For example, Brachyptera seticornis, was dominant in April, Leuctra nigra in May, Siphonoperla torrentium in June and Leuctra cingulala in July.The sensitivity of organisms towards to acidification appeared to be different among these groupe of aquatic insects. Three types of responses can be distinguished in relation with pH and/or associated factors :- High sensitivity of Ephemeroptera, which have completely disappeared- High sensitivity of most Trichoptera families except the following : Polycentropodidae, Rhyacophilidae and Limnephilidae.- Tolerance of Plecoptera filipalpia which were sometimes very abundant, but disappearance of Plecoptera Setipalpia except for Siphonoperla torrentium.This analysis showed that many species of mayflies, stoneflies and caddis flies do not tolerate low pH (and/or) associated with low conductivity and elevated aluminium concentrations. Because the biological response is the result of present and post environmental situations, we suggest the use of these taxa as indicators of acidification in running waters, particularly when a restricted number of physico-chemical measurements is insufficient to appreciate the acidification level, as during low flow periods or during periodes of no acid stress.Nevertheless, to be considered as a useful indicator of pollution in general and acidification in particular, a taxa (species, genera or family) should be widespread, relatively abundant, present all the year round, very sensitive to the studied factor and easy or relatively easy to identity.For example, in unpolluted streams in the Vosges Mountains, Epeorus sylvicola, Perlodes microcephala, Hydropsyche sp, Philopotamus sp seem to fit these criteria.However, in evaluating aquatic organisms as indicators of pollutional conditions, great caution is necessary because knowledge of the ecological requirements of the species is essential, several ecologic conditions other than the presence of a pollutant may limit the distribution of certain species. For this reason, the benthic macrofauna of a more significant number of sites of different chemical and physical characteristics should be collected

Ullemar's formula for the Jacobian of the complex moment mapping

The complex moment sequence m(P) is assigned to a univalent polynomial P by the Cauchy transform of the P(D), where D is the unit disk. We establish the representation of the Jacobian det dm(P) in terms of roots of the derivative P'. Combining this result with the special decomposition for the Hurwitz determinants, we prove a formula for the Jacobian which was previously conjectured by C. Ullemar. As a consequence, we show that the boundary of the class of all locally univalent polynomials in $U$ is contained in the union of three irreducible algebraic surfaces.Comment: 14 pages, submitted for "Complex Variables. Theory and Application

Molecular and Electronic Structure of Electroactive Self-Assembled Monolayers

Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAM-induced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30 degrees tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. On the other hand, contrary with previous observations, we found that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at -1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.Fil: Méndez de Leo, Lucila Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: de la Llave, Ezequiel Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Scherlis Perel, Damian Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Williams, Federico Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Benign familial infantile convulsions: A clinical study of seven Dutch families

Benign familial infantile convulsions (BFIC) is a recently identified partial epilepsy syndrome with onset between 3 and 12 months of age. We describe the clinical characteristics and outcome of 43 patients with BFIC from six Dutch families and one Dutch-Canadian family and the encountered difficulties in classifying the syndrome. Four families had a pure BFIC phenotype; in two families BFIC was accompanied by paroxysmal kinesigenic dyskinesias; in one family BFIC was associated with later onset focal epilepsy in older generations. Onset of seizures was between 6 weeks and 10 months, and seizures remitted before the age of 3 years in all patients with BFIC. In all, 29 (67%) of the 43 patients had been treated with anti-epileptic drugs for a certain period of time. BFIC is often not recognized as (hereditary) epilepsy by the treating physician. Seizures often remit shortly after the start of anti-epileptic drugs but, because of the benign course of the syndrome and the spontaneous remission of seizures, patients with low seizure fr

Gravitating discs around black holes

Fluid discs and tori around black holes are discussed within different approaches and with the emphasis on the role of disc gravity. First reviewed are the prospects of investigating the gravitational field of a black hole--disc system by analytical solutions of stationary, axially symmetric Einstein's equations. Then, more detailed considerations are focused to middle and outer parts of extended disc-like configurations where relativistic effects are small and the Newtonian description is adequate. Within general relativity, only a static case has been analysed in detail. Results are often very inspiring, however, simplifying assumptions must be imposed: ad hoc profiles of the disc density are commonly assumed and the effects of frame-dragging and completely lacking. Astrophysical discs (e.g. accretion discs in active galactic nuclei) typically extend far beyond the relativistic domain and are fairly diluted. However, self-gravity is still essential for their structure and evolution, as well as for their radiation emission and the impact on the environment around. For example, a nuclear star cluster in a galactic centre may bear various imprints of mutual star--disc interactions, which can be recognised in observational properties, such as the relation between the central mass and stellar velocity dispersion.Comment: Accepted for publication in CQG; high-resolution figures will be available from http://www.iop.org/EJ/journal/CQ

Supersymmetric QCD corrections to e+e−→tbˉH−e^+e^-\to t\bar{b}H^- and the Bernstein-Tkachov method of loop integration

The discovery of charged Higgs bosons is of particular importance, since their existence is predicted by supersymmetry and they are absent in the Standard Model (SM). If the charged Higgs bosons are too heavy to be produced in pairs at future linear colliders, single production associated with a top and a bottom quark is enhanced in parts of the parameter space. We present the next-to-leading-order calculation in supersymmetric QCD within the minimal supersymmetric SM (MSSM), completing a previous calculation of the SM-QCD corrections. In addition to the usual approach to perform the loop integration analytically, we apply a numerical approach based on the Bernstein-Tkachov theorem. In this framework, we avoid some of the generic problems connected with the analytical method.Comment: 14 pages, 6 figures, accepted for publication in Phys. Rev.

Quantum field theory and Hopf algebra cohomology

We exhibit a Hopf superalgebra structure of the algebra of field operators of quantum field theory (QFT) with the normal product. Based on this we construct the operator product and the time-ordered product as a twist deformation in the sense of Drinfeld. Our approach yields formulas for (perturbative) products and expectation values that allow for a significant enhancement in computational efficiency as compared to traditional methods. Employing Hopf algebra cohomology sheds new light on the structure of QFT and allows the extension to interacting (not necessarily perturbative) QFT. We give a reconstruction theorem for time-ordered products in the spirit of Streater and Wightman and recover the distinction between free and interacting theory from a property of the underlying cocycle. We also demonstrate how non-trivial vacua are described in our approach solving a problem in quantum chemistry.Comment: 39 pages, no figures, LaTeX + AMS macros; title changed, minor corrections, references update

Branch Retinal Vein Occlusion: Pathogenesis, Visual Prognosis, and Treatment Modalities

In branch retinal vein occlusion (BRVO), abnormal arteriovenous crossing with vein compression, degenerative changes of the vessel wall and abnormal hematological factors constitute the primary mechanism of vessel occlusion. In general, BRVO has a good prognosis: 50–60% of eyes are reported to have a final visual acuity (VA) of 20/40 or better even without treatment. One important prognostic factor for final VA appears to be the initial VA. Grid laser photocoagulation is an established treatment for macular edema in a particular group of patients with BRVO, while promising results for this condition are shown by intravitreal application of steroids or new vascular endothelial growth factor inhibitors. Vitrectomy with or without arteriovenous sheathotomy combined with removal of the internal limiting membrane may improve vision in eyes with macular edema which are unresponsive to or ineligible for laser treatment

Fluids and barriers of the CNS: a historical viewpoint

Tracing the exact origins of modern science can be a difficult but rewarding pursuit. It is possible for the astute reader to follow the background of any subject through the many important surviving texts from the classical and ancient world. While empirical investigations have been described by many since the time of Aristotle and scientific methods have been employed since the Middle Ages, the beginnings of modern science are generally accepted to have originated during the 'scientific revolution' of the 16th and 17th centuries in Europe. The scientific method is so fundamental to modern science that some philosophers consider earlier investigations as 'pre-science'. Notwithstanding this, the insight that can be gained from the study of the beginnings of a subject can prove important in the understanding of work more recently completed. As this journal undergoes an expansion in focus and nomenclature from cerebrospinal fluid (CSF) into all barriers of the central nervous system (CNS), this review traces the history of both the blood-CSF and blood-brain barriers from as early as it was possible to find references, to the time when modern concepts were established at the beginning of the 20th century