Shocks and dust survival in nearby active galaxies: implications for the alignment effect

One of the most popular explanations for the so-called alignment effect in high redshift (z>0.7) radio galaxies is the scattering by dust of the hidden quasar light. As shown by De Young (1998) a problem with the dust scattering model is that the short destruction time-scale for dust grains means that they will not survive the passage of the radio jet. We investigate the survival of dust in the extended ionised gas of nearby active galaxies with jet/gas interactions. We discuss the implications on the alignment effect of high redshift (>0.7) radio galaxies. We conclude that although shocks are likely to destroy dust grains in regions of interaction, dust might survive in enough quantities to scatter light from the active nucleus and produce alignment between scattered light and the radio structures. We propose an observational test to investigate the existence of dust in shocked regions based on the sensitivity of calcium to depletion onto dust grains.Comment: 8 pages, 1 Figure, 3 tables, accepted for publication in MNRA

Suction-controlled experiments on Boom clay

The understanding of the thermo-hydro-mechanical behaviour of a clay barrier is needed for the prediction of its final in situ properties after the hydration and thermal transient in a radioactive waste repository. As part of the CEC 1990-1994 R&D programme on radioactive waste management and storage, the CEA (Fr), CIEMAT (Sp). ENRESA (Sp). SCK CEN (B). UPC (Sp) and UWCC (UK) have carried out a joint project on unsaturated clay behaviour (Volckaert et al.. 1996). The aim of the study is to analyse and model the behaviour of a clay-based engineered barrier during its hydration phase under real repository conditions. The hydro-mechanical and thermo-hydraulic models developed in this project have been coupled to describe stress/strain behaviour, moisture migration and heat transfer. A thermo-hydraulic model has also been coupled to a geochemical code to describe the migration and formation of chemical species. In this project. suction-controlled experiments have been performed on Boom clay (B), FoCa clay (Fr) and Almeria bentonite (Sp). The aim of these experiments is to test the validity of the interpretive model developed by Alonso and Gens (Alonso et al., 1990). and to build a database of unsaturated clay thermo-hydro-mechanical parameters. Such a database can then be used for validation exercises in which in situ experiments are simulated. The Boom clay is a moderately swelling clay of Rupellian age. It is studied at the SCK. CEN in Belgium as a potential host rock for a radioactive waste repository. In this paper, suction-controlled experiments carried out on Boom clay by SCK CEN are described. SCK CEN has performed experiments to measure the relation between suction, water content and temperature and the relation between suction, stress and deformation. The applied suctioncontrol techniques and experimental setups are detailed. The results of these experiments are discussed in the perspective of the model of Alonso and Gens. The influence of temperature on water uptake was rather small. The measured swelling-collapse behaviour can be explained by the Alonso and Gens model.Peer Reviewe

Interpreting the kinematics of the extended gas in distant radiogalaxies from 8-10m telescope spectra

The nature of the extreme kinematics in the extended gas of distant radio galaxies (z>0.7) is still an open question. With the advent of the 8-10 m telescope generation and the development of NIR arrays we are in the position for the first time to develop a more detailed study by using lines other than Lya and [OII]3727 depending on redshift. In this paper we review the main sources of uncertainty in the interpretation of the emission line kinematics: the presence of several kinematic components, Lya absorption by neutral gas/dust and the contribution of scattered light to some of the lines. As an example, several kinematic components can produce apparent, false rotation curves. We propose methods to solve these uncertainties. We propose to extend the methods applied to low redshift radio galaxies to investigate the nature of the kinematics in distant radio galaxies: by means of the spectral decomposition of the strong optical emission lines (redshifted into the NIR) we can isolate the different kinematic components and study the emission line ratios for the individual components. If shocks are responsible for the extreme kinematics, we should be able to isolate a kinematic component (the shocked gas) with large FWHM (>900 km/s), low ionization level [OIII]5007/Hb~2-4 and weak HeII4686/Hb<0.07, together with a narrow component (~few hundred km/s) with higher ionization level and strong HeII emission (HeII/Hb~0.5)Comment: 11 pages, 6 Figures, to be published in A&A Supplement Serie

Mechanical behaviour of heavily compacted bentonite under high suction changes

The paper reports the results of an experimental study carried out on a bentonite compacted to a dry density of up to 1&middot;7 Mg=m3, a high value for this type of soil. The soil fabric has been studied using a variety of techniques, revealing a clear bimodal pore distribution that corresponds to two distinct structural levels: a microstructural one and a macrostructural one. The main testing programme has been performed using oedometers especially designed to apply a very large range of suctions. By applying the axis-translation technique (using nitrogen as the gas fluid), it has been possible to reach suctions up to 15 MPa. The higher suction range has been achieved by applying a controlled atmosphere where the relative humidity has been fixed by a solution of sulphuric acid or salts. In this way suctions up to 550 MPa could be reached. The maximum vertical stress that could be applied in the apparatus was 10 MPa. Two types of test have been carried out: (a) tests in which a combination of loading paths at constant suction and drying/wetting paths at constant load were applied; (b) swelling tests under constant-volume conditions in order to determine the swelling pressure and the stress path followed during wetting. The results of the experimental programme are examined, taking into account the role of the soil fabric in controlling observed mechanical behaviour. In addition, the results of the laboratory tests are reproduced and interpreted using a generalised plasticity model that considers explicitly the interaction between macrostructure and microstructure. In this way, it is possible to achieve a more complete understanding of the mechanisms that underlie observed behaviour, and in particular the interplay between the two structural level

Nomenclatural Type Identification of Names in North African Tamarix (Tamaricaceae)

Tamarix is native to Eurasia plus the northern and southern territories of Africa, with some species being introduced into America and Oceania. They are usually found in arid, desertic, or subdesertic areas, often on saline or subsaline soils, in Mediterranean, temperate, or subtropical climates. The genus is renowned for its complex taxonomy, which is usually based on rather variable or unstable characters, which leads to contrasting taxonomic treatments. As part of the taxonomic revision of Tamarix undertaken by the authors, ten names (i.e., T. africana, T. bounopoea, T. brachystylis var. fluminensis, T. malenconiana, T. muluyana, T. tenuifolia, T. tingitana, T. trabutii, T. valdesquamigera, and T. weyleri) published from material collected in the southwestern parts of the Mediterranean basin are taxonomically and nomenclaturally discussed after analysing their original material. Eight intended holotypes are corrected here to lectotypes; one epitype is designated for T. africana to warrant current use of the name; and one isotype, 30 isolectotypes, and 11 syntypes are also identified for the studied names. Further, the taxonomic identity of all names and their eventual synonymic placement are accordingly discussed.This work was partly supported by the European Commission through the H2020 Research and Innovation Staff Exchange Programme, project 645636: ‘Insect-plant relationships: insights into biodiversity and new applications’ (FlyHigh); and by the grants UAUSTI19−08, UAUSTI21−04, UAUSTI22−05, UADIF21−29, UADIF22−28, VIGROB21−166, VIGROB22−166, ACIE18−03, ACIE21−01, and ACIE22−01, from diverse programmes of Universidad de Alicante

Arsenic distribution in a pasture area impacted by past mining activities

[EN]Former mine exploitations entail a serious threat to surrounding ecosystems as after closure of mining activities their unmanaged wastes can be a continuous source of toxic trace elements. Quite often these mine sites are found within agricultural farming areas, involving serious hazards as regards product (feed/food) quality. In this work a grazing land impacted by the abandoned mine exploitation of an arsenical deposit was studied so as to evaluate the fate of arsenic (As) and other trace elements and the potential risks involved. With this aim, profile soil samples (0–50 cm) and pasture plant species (Agrostis truncatula, Holcus annus and Leontodon longirostris) were collected at different distances (0–100 m) from the mine waste dump and analyzed for their trace element content and distribution. Likewise, plant trace element accumulation from impacted grazing soils and plant trace element translocation were assessed. The exposure of livestock grazing animals to As was also evaluated, establishing its acceptability regarding food safety and animal health. International soil guideline values for As in grazing land soils (50 mg kg−1) resulted greatly exceeded (up to about 20-fold) in the studied mining-affected soils. Moreover, As showed a high mobilization potential under circumstances such as phosphate application or establishment of reducing conditions. Arsenic exhibited relatively high translocation factor (TF) values (up to 0.32–0.89) in pasture plant species, reaching unsafe concentrations in their above-ground tissues (up to 32.9, 16.9 and 9.0 mg kg−1 in Agrostis truncatula, Leontodon longirostris and Holcus annus, respectively). Such concentrations represent an elevated risk of As transfer to the high trophic-chain levels as established by international legislation. The limited fraction of arsenite found in plant roots should play an important role in the relatively high As root-to-shoot translocation shown by these plant species. Both soil ingestion and pasture intake resulted important entrance pathways of As into livestock animals, showing quite close contribution levels. The cow acceptable daily intake (ADI) of As regarding food safety was surpassed in some locations of the study area when the species Agrostis truncatula was considered as the only pasture feed. Restrictions in the grazing use of lands with considerable As contents where this plant was the predominant pasture species should be established in order to preserve food quality. Therefore, the exposure of livestock animals to As via both soil ingestion and pasture consumption should be taken into account to establish the suitability of mining-impacted areas for gazing

Long-term dynamics of shrub facilitation shape the mixing of evergreen and deciduous oaks in Mediterranean abandoned fields

Recovery of Mediterranean forests after field abandonment is a slow process, even without propagule limitations. This is mainly due to stressful conditions for seedling establishment. In this context, shrubs play a critical role in facilitating tree recruitment, but how this process unfolds after field abandonment is not entirely known. We evaluated the long-term dynamics of facilitation by the nurse shrub Retama sphaerocarpa in the recruitment of two ecologically contrasting oaks, the evergreen Quercus ilex and the deciduous Quercus faginea. Thirty years after field abandonment, we dated shrubs and oak established in an old field to estimate the annual recruitment rates and investigate temporal recruitment patterns. For oaks, we differentiated recruitment at each microsite (i.e., open or under shrub). To assess how nurse shrubs modulated environmental stressors, we modelled oak recruitment as a function of climatic variables. For the evergreen oak, we assessed these effects within each microsite. Finally, we estimated the annual interaction index between shrubs and oak juveniles as a function of climatic conditions

The genus Tamarix (Tamaricaceae) in Crete (Greece)

A report on the genus Tamarix (Tamaricaceae) in Crete is provided. The previously recorded taxa are compared with new collections made on the island and with vouchers found at different herbaria. Three species were fully confirmed: T. nilotica and T. parviflora, collected in the field, and T. smyrnensis, found only in herbarium vouchers. The other previously reported taxa, T. dalmatica, T. hampeana, T. pallasii and T. tetrandra were not found; T. dalmatica was erroneously reported, the record of T. hampeana represents a fourth species but its identity requires further study, records of T. pallasii are probably misidentifications of T. nilotica and/or T. smyrnensis, and the record of T. tetrandra probably refers to T. parviflora. The presence of T. nilotica is documented, confirming that it has been historically overlooked and mistaken for T. smyrnensis. A morphological comparison between T. nilotica and T. smyrnensis is provided in order to avoid further confusion and misidentifications. A dichotomous key for the Tamarix species reported in Crete is provided.The FPU programme (Mº de Educación, Spain), the I+D+I project CGL2008-05056 (Mº de Educación y Ciencia, Spanish Government) and complementary supporting funds ACIE10-01, ACIE11-05 and ACIE13-08 (University of Alicante, Spain) made this research possible

From graphene oxide to pristine graphene: revealing the inner workings of the full structural restoration

Producción CientíficaHigh temperature annealing is the only method known to date that allows the complete repair of a defective lattice of graphenes derived from graphite oxide, but most of the relevant aspects of such restoration processes are poorly understood. Here, we investigate both experimentally (scanning probe microscopy) and theoretically (molecular dynamics simulations) the thermal evolution of individual graphene oxide sheets, which is rationalized on the basis of the generation and the dynamics of atomic vacancies in the carbon lattice. For unreduced and mildly reduced graphene oxide sheets, the amount of generated vacancies was so large that they disintegrated at 1773–2073 K. By contrast, highly reduced sheets survived annealing and their structure could be completely restored at 2073 K. For the latter, a minor atomic-sized defect with six-fold symmetry was observed and ascribed to a stable cluster of nitrogen dopants. The thermal behavior of the sheets was significantly altered when they were supported on a vacancy-decorated graphite substrate, as well as for the overlapped/stacked sheets. In these cases, a net transfer of carbon atoms between neighboring sheets via atomic vacancies takes place, affording an additional healing process. Direct evidence of sheet coalescence with the step edge of the graphite substrate was also gathered from experiments and theory.Ministerio de Economía, Industria y Competitividad (Project AT2011-26399 and MAT2011-22781)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA158A11-2

What Is Wrong with Frankenia nodiflora Lam. (Frankeniaceae)? New Insights into the South African Sea-Heaths

The taxonomic identity and phylogenetic relationships of several southern African perennial taxa related to Frankenia repens are discussed. In particular, F. nodiflora Lam., a misunderstood species described from the Cape region and synonymised to F. pulverulenta, is restored for plants endemic to salt-pans and riverbeds in the coastal lowlands across the Cape Flats (Western Cape province, South Africa). Further, a revision of morphologically close plants, usually identified as F. pulverulenta or F. repens, also occurring in similar saline ecosystems of the inland western South Africa revealed the existence of two distinct new entities not matching any described taxa of the genus. Molecular analyses of nuclear ribosomal (ITS1-5.8S-ITS2 region) DNA sequence data together with morphological divergence allow recognition of those taxa at species rank, within an independent lineage close to F. repens. In consequence, two new sea-heath species are described in the so-called “F. repens group”: F. nummularia from the Nama-Karoo Biome (Western Cape and Northern Cape provinces), and F. anneliseae from the Succulent Karoo Biome (Northern Cape province). Full morphological description and type designation are reported for each accepted species as well as data on ecology, habitat, distribution, and taxonomic relationships to other close relatives are given. Further, an identification key is presented to facilitate recognition of the southern African taxa of Frankenia.This work was partly supported by H2020 Research and Innovation Staff Exchange Programme of the European Commission, project 645636: ‘Insect-plant relationships: insights into biodiversity and new applications’ (FlyHigh) and by the grants UAUSTI19-08, UAUSTI21-04, UAUSTI22-05, UADIF21-29, UADIF22-28, VIGROB21-166, VIGROB22-166, ACIE17-01, ACIE18-03, ACIE21-01 and ACIE22-01, from diverse programmes of Universidad de Alicante. L.M. acknowledges logistic support of the Iluka Chair in Vegetation Science and Biogeography at Murdoch University, Perth, Australia