Influence of the hyporheic zone on the phosphorus dynamics of a large gravel-bed river, Garonne River, France

Phosphorus (P) concentrations in sediments and in surface and interstitial water from three gravel bars in a large river (Garonne River, southern France) were measured daily, downstream of a wastewater treatment plant for a city of 740 000 inhabitants (Toulouse). Measurements were made of vertical hydraulic gradient (VHG), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) and total phosphorus (TP) in water and of three extractable forms of phosphorus (water extractable, NaOH extractable and H2SO4 extractable) in hyporheic sediments from the gravel bars. Dissolved phosphorus was the major contributor to TP (74–79%) in both interstitial and surface waters on all sampling dates, and in most cases surface water P concentrations were significantly higher than interstitial concentrations. Hyporheic sediment TP concentrations ranged between 269 and 465 μg g -1 and were highest in fine sediment fractions. Acid-extractable P, a non-bioavailable form, represented at least 95% of sediment TP. A positive relationship was observed between VHG and TP in two of the gravel bars, with wells that were strongly downwelling having lower TP concentrations. These results suggest that in downwelling zones, hyporheic sediments can trap surface-derived dissolved P, and that much of this P becomes stored in refractory particulate forms. Bioavailable P is mainly present in dissolved form and only occupies a small fraction of total P, with particulate P comprising the majority of total P

Anomalous luminescence of subglacial sediment at Haut glacier d'Arolla, Switzerland - a consequence of resetting at the glacier bed?

<p>Luminescence has the potential to elucidate glacial geomorphic processes because primary glacial sediment sources and transport pathways are associated with contrasting degrees of exposure to light. Most notably, sediment entrained from extraglacial sources should be at least partially reset, whereas sediment produced by glacial erosion of subglacial bedrock should retain substantial luminescence commensurate with a geological irradiation history.</p> <p>We set out to test the validity of this assumption at Haut Glacier d’Arolla, Switzerland using sediment sampled extraglacially and from the glacier bed. Contrary to our expectations, the subglacial samples exhibited natural signals that were substantially lower than those of other sample groups, and further (albeit limited) analyses have indicated no obvious differences in sample group luminescence characteristics or behaviour that could account for this observation. For glaciological reasons, we can eliminate both the possibility that the subglacial sediment has been extraglacially-reset or exposed in situ to heat or light. We therefore advocate investigation of possible resetting processes related to subglacial crushing and grinding, and speculate that such processes, if more generally present, may enable the dating of subglacially-deposited tills using luminescence-based techniques.</p&gt

Late Devensian deglaciation of south‐west Wales from luminescence and cosmogenic isotope dating

The Welsh Ice Cap was a dynamic component of the last British–Irish Ice Sheet at the Last Glacial Maximum, but there are few chronological constraints on the pace and timing of deglaciation. This paper presents new geomorphological and geochronological evidence that constrains the timing of the separation of the Welsh Ice Cap from the Irish Sea Ice Stream and the subsequent deglaciation of south-west Wales; and allow these to be assessed in the context of late Pleistocene climatic events. Luminescence ages from glacial outwash sediments south of Cardigan demonstrate that the Irish Sea Ice Stream was receding by ∼26.7 ka. The subsequent recession of the Welsh Ice Cap is documented by cosmogenic ages from landforms and sediments in the Aeron and Teifi valleys and upland areas. Deglaciation of the Cambrian Mountains was underway by ∼19.6 ka. Cross-valley moraines and associated deglaciation deposits show that minor re-advances interrupted the recession of the Aeron Glacier twice, and the Teifi Glacier on at least 12 occasions. By ∼14.9 ka, the Aeron valley was probably ice-free, but the northwards withdrawal of the Teifi glacier had halted in the Tregaron area. The final rapid recession of this glacier into the uplands of central Wales was completed during the Windermere Interstadial (13.5 cal ka BP) when, in common with much of the UK, the whole of Wales is believed to have become ice-free. There is no evidence that the Cambrian Mountains contained ice-free enclaves at the Last Glacial Maximum, as has been previously suggested. The new ages presented here support suggestions that there was rapid change in the configuration of the Welsh Ice Cap between 20 and 17 ka as upland areas became exposed and there was increasing topographic control on patterns of ice discharge

Absence of the TAP2 Human Recombination Hotspot in Chimpanzees

Recent experiments using sperm typing have demonstrated that, in several regions of the human genome, recombination does not occur uniformly but instead is concentrated in “hotspots” of 1–2 kb. Moreover, the crossover asymmetry observed in a subset of these has led to the suggestion that hotspots may be short-lived on an evolutionary time scale. To test this possibility, we focused on a region known to contain a recombination hotspot in humans, TAP2, and asked whether chimpanzees, the closest living evolutionary relatives of humans, harbor a hotspot in a similar location. Specifically, we used a new statistical approach to estimate recombination rate variation from patterns of linkage disequilibrium in a sample of 24 western chimpanzees (Pan troglodytes verus). This method has been shown to produce reliable results on simulated data and on human data from the TAP2 region. Strikingly, however, it finds very little support for recombination rate variation at TAP2 in the western chimpanzee data. Moreover, simulations suggest that there should be stronger support if there were a hotspot similar to the one characterized in humans. Thus, it appears that the human TAP2 recombination hotspot is not shared by western chimpanzees. These findings demonstrate that fine-scale recombination rates can change between very closely related species and raise the possibility that rates differ among human populations, with important implications for linkage-disequilibrium based association studies

Beyond aggression: Androgen-receptor blockade modulates social interaction in wild meerkats

In male vertebrates, androgens are inextricably linked to reproduction, social dominance, and aggression, often at the cost of paternal investment or prosociality. Testosterone is invoked to explain rank-related reproductive differences, but its role within a status class, particularly among subordinates, is underappreciated. Recent evidence, especially for monogamous and cooperatively breeding species, suggests broader androgenic mediation of adult social interaction. We explored the actions of androgens in subordinate, male members of a cooperatively breeding species, the meerkat (Suricata suricatta). Although male meerkats show no rank-related testosterone differences, subordinate helpers rarely reproduce. We blocked androgen receptors, in the field, by treating subordinate males with the antiandrogen, flutamide. We monitored androgen concentrations (via baseline serum and time-sequential fecal sampling) and recorded behavior within their groups (via focal observation). Relative to controls, flutamide-treated animals initiated less and received more high-intensity aggression (biting, threatening, feeding competition), engaged in more prosocial behavior (social sniffing, grooming, huddling), and less frequently initiated play or assumed a ‘dominant’ role during play, revealing significant androgenic effects across a broad range of social behavior. By contrast, guarding or vigilance and measures of olfactory and vocal communication in subordinate males appeared unaffected by flutamide treatment. Thus, androgens in male meerkat helpers are aligned with the traditional trade-off between promoting reproductive and aggressive behavior at a cost to affiliation. Our findings, based on rare endocrine manipulation in wild mammals, show a more pervasive role for androgens in adult social behavior than is often recognized, with possible relevance for understanding tradeoffs in cooperative systems

Mucin Secretion Induced by Titanium Dioxide Nanoparticles

Nanoparticle (NP) exposure has been closely associated with the exacerbation and pathophysiology of many respiratory diseases such as Chronic Obstructive Pulmonary Disease (COPD) and asthma. Mucus hypersecretion and accumulation in the airway are major clinical manifestations commonly found in these diseases. Among a broad spectrum of NPs, titanium dioxide (TiO2), one of the PM10 components, is widely utilized in the nanoindustry for manufacturing and processing of various commercial products. Although TiO2 NPs have been shown to induce cellular nanotoxicity and emphysema-like symptoms, whether TiO2 NPs can directly induce mucus secretion from airway cells is currently unknown. Herein, we showed that TiO2 NPs (<75 nm) can directly stimulate mucin secretion from human bronchial ChaGo-K1 epithelial cells via a Ca2+ signaling mediated pathway. The amount of mucin secreted was quantified with enzyme-linked lectin assay (ELLA). The corresponding changes in cytosolic Ca2+ concentration were monitored with Rhod-2, a fluorescent Ca2+ dye. We found that TiO2 NP-evoked mucin secretion was a function of increasing intracellular Ca2+ concentration resulting from an extracellular Ca2+ influx via membrane Ca2+ channels and cytosolic ER Ca2+ release. The calcium-induced calcium release (CICR) mechanism played a major role in further amplifying the intracellular Ca2+ signal and in sustaining a cytosolic Ca2+ increase. This study provides a potential mechanistic link between airborne NPs and the pathoetiology of pulmonary diseases involving mucus hypersecretion

Developmentally regulated MAPK pathways modulate heterochromatin in Saccharomyces cerevisiae

Variegated expression of genes contributes to phenotypic variation within populations of genetically identical cells. Such variation plays a role in development and host pathogen interaction and can be important in adaptation to harsh environments. The expression state of genes placed near telomeres shows a variegated pattern of inheritance due to heterochromatin formation, a phenomenon that is called telomere position effect (TPE). We show that in budding yeast, TPE is controlled by the a1/α2 developmental repressor, which dictates developmental decisions in response to environmental changes. Two a1/α2 repressed genes, STE5, a MAPK scaffold and HOG1, a stress-activated MAPK, are the targets of this heterochromatin regulation pathway. We provide new evidence that link MAPK signaling and heterochromatin formation in yeast. Our results show that the same components that regulate gene expression states in euchromatic regions regulate heterochromatic expression states and that stress can play a part in turning on or off genes placed in heterochromatic regions

The southern Laurentide Ice Sheet

ver was a milestone that summarized our knowledge of the Quaternary of the U.S. in a single volume. Glacial geology was a major component of the volume, and it contained 125 pages on the Laurentide Ice Sheet (LIS) in the U.S. In the present volume, almost 40 years later, many fewer pages are devoted to the same topic, indicating the vast increase in other aspects of Quaternary studies. In the U.S., glacial geology has expanded greatly in knowledge and interest, and now glacial geologists have a much richer field and variety of techniques with which to study Quaternary history. The other chapters in this book are a clear indication of the diversity of fields that now make up what traditionally was classified as glacial geology or did not exist before 1965. Radiocarbon dating remains the most important tool for determining the chronology of the last glaciation. Accelerato

Technology Acceptance Model y mayores: ¿la educación y la actividad laboral desarrollada son variables moderadoras?

ResumenEl objetivo de este trabajo es analizar la influencia, como variables moderadoras, del nivel educativo y la actividad laboral desarrollada por los mayores de 50 años en su proceso de aceptación de Internet, dentro del marco del modelo TAM (Technology Acceptance Model). Proponemos un modelo basado en TAM, testado mediante PLS y multi-grupo para comprobar el cumplimiento de las hipótesis de moderación propuestas. Los resultados apoyan la idoneidad del modelo aunque el poder moderador de la actividad laboral no es significativo mientras que el nivel educativo tiene mayor capacidad explicativa en el caso de los mayores sin estudios universitarios. A su vez el TAM se muestra como una herramienta apropiada para explicar la heterogeneidad de los mayores con respecto a Internet.AbstractOur aim in this work is to analyze the impact, as moderator variables, of the level of education and the profession on the Internet acceptance level in people older than 50 years old. We propose a model based on a Technology Acceptance Model (TAM). We contrast the moderator hypotheses proposed using Partial Least Squares (PLS) and multi-group analysis. The results support the suitability of the model showing a non-significant moderator effect of the profession, whereas the education level presents a higher explanatory power for older adults with no university degree. In addition, TAM appears to be an appropriatetool to explain the heterogeneity of this segment as regards the Internet

Motion dazzle and camouflage as distinct anti-predator defenses.

BACKGROUND: Camouflage patterns that hinder detection and/or recognition by antagonists are widely studied in both human and animal contexts. Patterns of contrasting stripes that purportedly degrade an observer's ability to judge the speed and direction of moving prey ('motion dazzle') are, however, rarely investigated. This is despite motion dazzle having been fundamental to the appearance of warships in both world wars and often postulated as the selective agent leading to repeated patterns on many animals (such as zebra and many fish, snake, and invertebrate species). Such patterns often appear conspicuous, suggesting that protection while moving by motion dazzle might impair camouflage when stationary. However, the relationship between motion dazzle and camouflage is unclear because disruptive camouflage relies on high-contrast markings. In this study, we used a computer game with human subjects detecting and capturing either moving or stationary targets with different patterns, in order to provide the first empirical exploration of the interaction of these two protective coloration mechanisms. RESULTS: Moving targets with stripes were caught significantly less often and missed more often than targets with camouflage patterns. However, when stationary, targets with camouflage markings were captured less often and caused more false detections than those with striped patterns, which were readily detected. CONCLUSIONS: Our study provides the clearest evidence to date that some patterns inhibit the capture of moving targets, but that camouflage and motion dazzle are not complementary strategies. Therefore, the specific coloration that evolves in animals will depend on how the life history and ontogeny of each species influence the trade-off between the costs and benefits of motion dazzle and camouflage.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are