538 research outputs found
Los yacimientos del cuarzo-apatito (fosforita) en el Macizo Hespérico español: el caso de Aldea Moret-Zarza la Mayor (Cáceres)
[Resumen] Los filones de Q-Ap se hallan en zona orgánica intracontinental de reactivación de zócalos antiguos. Corresponden a yacimientos plutonogénicos relacionados con granitoides peralumínicos. Poseen estructuras y texturas de relleno, siendo su morfologia filoniana según se deduce de los planos de la mina. El tipo espectral (o tipoquímico) del apatito es característico de yacimientos hidroternales (caracter hipotermal) y su composición es la de fluorapatito. No existe un fondo geoquímico elevado en P, sino que es la presencia de mineralizadores como el F que concentra el P en un modelo halogénico.[Abstract] Since 1961, date of establishment of the firm, the investigations made gave as a result 35,000,000 Tm of reserves, being exploited 120,000 tpa. In this paper a description of benefitiation process and fina1 products is made, appearing that they are mainly for exporte In addition, considerations concerning the significance of magnesium in animal nutrition and its app1ication for it are made. Finally, difficulties and proposed solutions are quote
Bilan du carbone dans le lagunage anaérobie appliqué sous climat méditerranéen
Ce travail a porté sur l'application du lagunage anaérobie pour le traitement primaire des eaux résiduaires urbaines sous climat méditerranéen. Il a été réalisé sur les lagunes anaérobies de l' Ecosite de Mèze (Hérault, France). Les lagunes anaérobies constituent un traitement primaire satisfaisant avec des rendements moyens de 55% pour les MES et 30% pour la DBO5, pour une faible emprise au sol. Le taux d'accumulation des boues est de seulement 0,017 m3 /EH.an, notamment du fait de l'efficacité de la dégradation anaérobie. L'équilibre du métabolisme anaérobie des boues est atteint après un an de fonctionnement. L'accumulation des boues se fait alors de façon saisonnière avec une forte accumulation en hiver et une digestion du stock en été. Cette évolution est liée à l'influence de la température sur la méthanogénèse. La production de biogaz (83% CH4) a pu être mesurée par des collecteurs à gaz mis au point pour cette étude et dépend également fortement de la température. Le bilan du carbone montre que 74% du carbone organique épuré est converti en CH4, 13% en carbone inorganique dissous et seulement 15% est stocké dans les boues. Toutefois, les lagunes anaérobies présentent un risque de créer des nuisances olfactives dues à l'émission de H2 S.This project examined the application of anaerobic ponds for the primary treatment of urban wastewater under a Mediterranean climate. The objectives of the study were to determine removal performances and to study sludge accumulation and the production of biogas. Together, these results allowed us to calculate the carbon mass balance in the anaerobic ponds.This work was carried out in the two large primary anaerobic ponds of the waste stabilization pond system at the Ecosite of Mèze (Hérault, France), treating domestic wastewater for 13,800 person-equivalents (PE). Anaerobic ponds were 5,000 m3 in volume, 3.1 m in depth and presented a retention time of 4.6 d with a mean volumetric organic loading of 83 g BOD5 /m3 ×d× The characteristics of the influent and effluent (including: suspended solids (SS); chemical oxygen demand (COD); biological oxygen demand (BOD5); bicarbonate (HCO3 -); total organic carbon (TOC); and volatile fatty acids (VFA)) were determined twice-monthly. The volume of sludge and its characteristics (including: SS; volatile solids (VS); TOC; and VFA) were measured monthly. The production of biogas and its composition (CH4, CO2, H2 S) were measured with gas collectors specially developed for this study.Results showed that the anaerobic ponds constituted a good primary treatment with mean removal rates of 55% for SS, 30% for BOD and 22% for COD. Removal performances were relatively constant over the year. Indeed, removal rates were essentially due to the removal of particulate organic matter by sedimentation. Anaerobic degradation occurred essentially in the sludge layer and the removal of soluble COD was low.The study of sludge characteristics showed that anaerobic digestion equilibrium was reached after one year of operation. The beginning of methanogenesis could be observed by the decrease in the concentration of volatile fatty acids. The accumulation of sludge showed seasonal variation with an important accumulation in winter and the digestion of the accumulated stock in summer. This evolution could be related to the influence of temperature on methanogenesis. The mean rate of sludge accumulation was only 3.8 g SS/P-E×d or 0.017 m3/P-E×yr. This rate was significantly lower than for the primary settling tank (50-60 g SS/P-E×d) and for the facultative ponds (0.085 m3 /P-E×yr) due to the intensive anaerobic degradation.The production of biogas was measured by gas collectors specially developed for this study. The biogas contained essentially CH4 (83%); CO2 was less than 4% because it dissolved in the water column and was converted into bicarbonate alkalinity. The concentration of H2 S was less than 1% (between 75 and 4770 ppm) but was the cause of unpleasant odours. The biogas production rate was strongly dependent on temperature. A non-linear relationship was obtained (Ebiogas=4.8451 × e0.1203T, r2=0.92, n=16). The mean annual biogas production rate was calculated to be 49 L/m2 ×d. Seasonal variation in the biogas production rate could be related to seasonal variations in sludge accumulation.The carbon mass balance showed that 74% of the removed organic carbon was converted into CH4, 13% into dissolved inorganic carbon (bicarbonates) and only 15% was stored in sludge. The mass balance was well equilibrated and did not show the entry of atmospheric CO2, which occurs in aerobic ponds where CO2 is used by algae to produce their cell biomass. In an anaerobic pond, the low production of sludge was due to the efficiency of the anaerobic degradation but also to the low internal biomass production.To conclude, the use of a primary anaerobic pond was advantageous and permitted a reduction in the required surface area for a waste stabilization pond system. This process produced effluent for secondary treatment in a facultative pond with essentially the removal of the particulate organic matter. However, However, anaerobic ponds may cause odor problems linked to the emission of H2 S
Challenges and Solutions for the QB50 Telecommunication Network
QB50 space mission will provide the biggest CubeSat network in orbit. A constellation of 50 CubeSats in
a ‘string-of-pearls’ configuration will be launched together in January 2016 by a single rocket, into a
circular orbit at 380 km altitude. Due to the atmospheric drag the orbit will decay and progressively
lower layers of the atmosphere will be explored. Main goals are exploration of the lower thermosphere
with multi-point measurements, re-entry research and in-orbit science and technology demonstration.
In this analysis of communication functions the ground segment is analyzed, with a global overview of
different architectures, the main elements of a ground station, mission and control centres, and the link
between them
Effect of Land Management on Grassland Carbon Dioxide Fluxes
Grassland soils can act as both a source and sink for atmospheric carbon dioxide (CO2). Implementing grassland management practices that increase the rates of soil CO2 sequestration are urgently sought to offset Ireland’s agricultural greenhouse gas emissions. However, land management of Irish grasslands is not yet accounted for in the national inventories simultaneously posing a limitation and opportunity for refining modelled estimates of carbon sequestration. In this study, eddy covariance flux towers were established to monitor net ecosystem CO2 exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (Re) in three grassland types (intensive dairy grazing, drystock grazing and zero- grazing) in geographically distinct agricultural catchments in Ireland. The initial results show larger magnitude of NEE, GPP and Re in intensively grazed and zero-grazed grasslands that are subject to frequent grazing/defoliation followed by recovery of photosynthetic potential. The continuously grazed drystock grassland exhibited lower NEE and GPP rates but smaller seasonal fluctuations in daily fluxes which may reflect the reduction in nutrient availability to support higher GPP. However, the drystock grazed grassland had significantly higher soil water content which may stimulate higher soil CO2 respiration resulting in lower NEE over time. Management practices involving defoliation and nutrient supply influenced affected season CO2 exchange but longer-term flux monitoring is required to assess the net ecosystem carbon budgets of each grassland system
Glyphosate and AMPA in human urine of HBM4EU-aligned studies: part B adults
Within HBM4EU, human biomonitoring (HBM) studies measuring glyphosate (Gly) and aminomethylphosphonic acid (AMPA) in urine samples from the general adult population were aligned and quality-controlled/assured. Data from four studies (ESB Germany (2015-2020); Swiss HBM4EU study (2020); DIET-HBM Iceland (2019-2020); ESTEBAN France (2014-2016)) were included representing Northern and Western Europe. Overall, median values were below the reported quantification limits (LOQs) (0.05-0.1 microg/L). The 95th percentiles (P95) ranged between 0.24 and 0.37 microg/L urine for Gly and between 0.21 and 0.38 microg/L for AMPA. Lower values were observed in adults compared to children. Indications exist for autonomous sources of AMPA in the environment. As for children, reversed dosimetry calculations based on HBM data in adults did not lead to exceedances of the ADI (proposed acceptable daily intake of EFSA for Gly 0.1 mg/kg bw/day based on histopathological findings in the salivary gland of rats) indicating no human health risks in the studied populations at the moment. However, the controversy on carcinogenicity, potential endocrine effects and the absence of a group ADI for Gly and AMPA induce uncertainty to the risk assessment. Exposure determinant analysis showed few significant associations. More data on specific subgroups, such as those occupationally exposed or living close to agricultural fields or with certain consumption patterns (vegetarian, vegan, organic food, high cereal consumer), are needed to evaluate major exposure sources
Nitrous oxide emission factors from an intensively grazed temperate grassland: a comparison of cumulative emissions determined by eddy covariance and static chamber methods
Quantifying nitrous oxide (N2O) emissions from grazed pastures can be problematic due to the presence of hotspots and hot moments of N2O from animal excreta and synthetic fertilisers. In this study, we quantified field scale N2O emissions from a temperate grassland under a rotational grazing management using eddy covariance (EC) and static chamber techniques. Measurements of N2O by static chambers were made for four out of nine grazing events for a control, calcium ammonium nitrate (CAN), synthetic urine (SU) + CAN and dung + CAN treatments. Static chamber N2O flux measurements were upscaled to the field scale (FCH FIELD) using site specific emission factors (EF) for CAN, SU+CAN and dung + CAN. Mean N2O EFs were greatest from the CAN treatment while dung + CAN and SU + CAN emitted similar N2O-N emissions. Cumulative N2O-N emissions over the study period measured by FCH FIELD measurements were lower than gap-filled EC measurements. Emission factors of N2O from grazing calculated by FCH FIELD and gap-filled were 0.72% and 0.96%, respectively. N2O-N emissions were derived mainly from animal excreta (dung and urine) contributing 50% while N2O-N losses from CAN and background accounted for 36% and 14%, respectively. The study highlights the advantage of using both the EC and static chamber techniques in tandem to better quantify both total N2O-N losses from grazed pastures while also constraining the contribution of individual N sources. The EC technique was most accurate in quantifying N2O emissions, showing a range of uncertainty that was seven times lower relative to that attributed to static chamber measurements, due to the small chamber sample size per treatment and highly variable N2O flux measurements over space and time
Unexpected Novel Relational Links Uncovered by Extensive Developmental Profiling of Nuclear Receptor Expression
Nuclear receptors (NRs) are transcription factors that are implicated in several biological processes such as embryonic development, homeostasis, and metabolic diseases. To study the role of NRs in development, it is critically important to know when and where individual genes are expressed. Although systematic expression studies using reverse transcriptase PCR and/or DNA microarrays have been performed in classical model systems such as Drosophila and mouse, no systematic atlas describing NR involvement during embryonic development on a global scale has been assembled. Adopting a systems biology approach, we conducted a systematic analysis of the dynamic spatiotemporal expression of all NR genes as well as their main transcriptional coregulators during zebrafish development (101 genes) using whole-mount in situ hybridization. This extensive dataset establishes overlapping expression patterns among NRs and coregulators, indicating hierarchical transcriptional networks. This complete developmental profiling provides an unprecedented examination of expression of NRs during embryogenesis, uncovering their potential function during central nervous system and retina formation. Moreover, our study reveals that tissue specificity of hormone action is conferred more by the receptors than by their coregulators. Finally, further evolutionary analyses of this global resource led us to propose that neofunctionalization of duplicated genes occurs at the levels of both protein sequence and RNA expression patterns. Altogether, this expression database of NRs provides novel routes for leading investigation into the biological function of each individual NR as well as for the study of their combinatorial regulatory circuitry within the superfamily
Detectability of testosterone esters and estradiol benzoate in bovine hair and plasma following pour-on treatment
The abuse of synthetic esters of natural steroids such as testosterone and estradiol in cattle fattening and sports is hard to detect via routine urine testing. The esters are rapidly hydrolysed in vivo into substances which are also endogenously present in urine. An interesting alternative can be provided by the analysis of the administered synthetic steroids themselves, i.e., the analysis of intact steroid esters in hair by liquid chromatography tandem mass spectrometry (LC/MS/MS). However, retrospective estimation of the application date following a non-compliant finding is hindered by the complexity of the kinetics of the incorporation of steroid esters in hair. In this study, the incorporation of intact steroid esters in hair following pour-on treatment has been studied and critically compared with results from intramuscular treatment. To this end animals were pour-on treated with a hormone cocktail containing testosterone cypionate, testosterone decanoate and estradiol benzoate in different carriers. The animals were either treated using injection and pour-on application once or three times having 1 week between treatments using injection and pour-on application. Animals were slaughtered from 10–12 weeks after the last treatment. Both hair and blood plasma samples were collected and analysed by LC/MS/MS. From the results, it is concluded that after single treatment the levels of steroid esters in hair drop to CCβ levels (5–20 µg/kg) after 5–7 weeks. When treatment is repeated two times, the CCβ levels are reached after 9–11 weeks. Furthermore, in plasma, no steroid esters were detected; not even at the low microgramme per litre level but—in contrast with the pour-on application—after i.m. injection, significant increase of 17β-testosterone and 17β-estradiol were observed. These observations suggest that transport of steroid esters after pour-on application is not only performed by blood but also by alternative fluids in the animal so probably the steroid esters are already hydrolysed and epimerized before entering the blood
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