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Assuming heterotrophic denitrification as the dominant microbial process, Richards (1965) formulated a stoichiometry governing nitrogen loss in open-ocean oxygen deficient zones (ODZs). It prescribes the quantitative coupling between the oxidation of organic matter by NO–3
in the absence of O2 and the corresponding production of CO2, N2, and PO–34. Applied globally, this relationship defines key linkages between the C, N, and P cycles. However, the validity of Richards's stoichiometry is challenged
by recognition of complex microbial N processing in ODZs including anammox as an important pathway and nitrite reoxidation. Whereas Richards's stoichiometry would result in N2-N production to NO–3 removal rates of 1.17, dominance by anammox with respect
to biogenic N2 production could in theory result in a ratio as high as 2. Ratios with PO–34 production provide an additional constraint on the quantity and composition of respired organic matter. Here we use a mesoscale eddy with extreme N-loss in the
Peru ODZ as a "natural laboratory" to examine N-loss stoichiometry. Its intense biogeochemical signatures, relatively well-defined timescales, and simplified hydrography allowed for the development of strong co-occurring gradients in NO–3, NO–2,
biogenic N2, and PO–34. The production of biogenic N2 as compared with the removal of NO–3 (analyzed either directly or as N deficits) was slightly less than predicted by Richards's stoichiometry and did not at all
support any "excess" biogenic N2. PO–34 production, however, was twice the expectation from Richards's stoichiometry suggesting that respired organic matter was P-rich as compared with C:N:P Redfield composition. These results suggest major gaps remain
between current understanding of microbial N pathways in ODZs and their net biogeochemical output.

Water resources crisis can lead to a new concept of wastewater treatment. Wastewater cannot be considered waste but can be a renewable or non-renewable energy source. Nutrients from wastewater could be recycled and not disposed of. A circular economy can be created that can be based on the ability of algae to absorb and store nutrients: carbon (C), nitrogen (N) and phosphorus (P). This study investigates the stoichiometry between carbon, nitrogen and phosphorus in wastewater from three geographical regions of Romania. The concentrations of inorganic nitrogen, total nitrogen, total phosphorus, and total organic carbon were compared and evaluated. Three wastewater sampling points located in different areas were monitored, in the period 2013-2017 for the sampling point located in the central-northern part of the Romanian Plain and in the period 2015-2017 for the other two studied areas. The obtained results showed very high values of total nitrogen concentrations with values between 28.2 mg/L and 107.2 mg/L for the southeastern part of Romania. The values of the stoichiometric ratio's C/N, C/P, N/P have varied over time with maximums in the autumn and winter seasons which indicates the existence of significant contamination of wastewater. It may be possible in the future to improve the performance of wastewater treatment by adjusting C, N, and P parameters.

We are grateful to Drs E. Vasil'chenko and A. Maaroos for the help with experiments and useful discussions. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. In addition, the research leading to these results has received funding from the Estonian Research Council  Institutional Research Funding IUT02-26. ; Magnesium aluminate spinel single crystals with different stoichiometry, MgAl2O4 (1:1 spinel) and MgO 2.5Al2O3 (1:2.5) were investigated using different optical methods (cathode-, photo- and thermally stimulated luminescence (TSL), optical absorption, "creation spectra" of TSL peaks and phosphorescence by VUV radiation). Low-temperature charge carrier traps and the position of intrinsic UV emission bands depend on the degree of stoichiometry. Antisite defects (ADs), Mg2+ or Al3+ located in a "wrong" cation site (Mg|A1 or Al|Mg) are the main as-grown structural defects, which serve also as efficient traps for electrons and holes as well as seeds for bound excitons. AD concentration is especially high in 1:2.5 spinel. There are several manifestations of ADs (electronic excitations near ADs) in the spectral region of 7-7.5 eV, slightly below the energy gap. ; Eesti Teadusagentuur IUT02-26; H2020 Euratom 633053; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

11 páginas,4 tablas, 9 figuras, 1 apéndice (http://dx.doi.org/10.1016/j.foreco.2011.08.019) ; Although some studies have observed significant correlations between latitude and climate gradients and tree leaf nutrientconcentration and stoichiometry, others have not. This study examined the nutrientconcentrations of tree leaves in 3530 plots of the Catalonian Forest Inventory. Catalonia is a Mediterranean region located in NE Iberian Peninsula. It has a long land-use history and includes the large industrial-urban area of Barcelona but still contains a large forest area (42%). In the forests of Catalonia, leaf nutrientconcentration increased and leaf C:nutrient ratios decreased from south to north, which paralleled the increase in MAP (mean annual precipitation) and the decrease in MAT (mean annual temperature), which was expected in a Mediterranean climate where the availability of water is the most limiting factor for plant nutrient uptake. In addition, the availability of water, which influences productivity, was associated with low leaf N:P content ratios, which is consistent with the Growth Rate Hypothesis. At a regional scale, the results support the Soil-Age Hypothesis because the youngest soils in the Pyrenees had the lowest leaf N:P ratios. Furthermore, the type of forest (evergreen, deciduous, or coniferous) explained some of the variation in leaf nutrientconcentrations and stoichiometry. Nutrientconcentrations were highest in deciduous trees and lowest in coniferous trees. Leaf nutrientconcentrations and stoichiometry were mainly correlated with climate, but other factors such as the chemical properties of soil and rock, phylogenetics, and different ecological histories and anthropogenic factors such as pollution, had an effect. ; This research was supported by the European Project NEU NITROEUROPE (GOCE017841), by Spanish Government Projects CGL2006-04025/BOS, CGL2010-17172/BOS and Consolider-Ingenio Montes CSD2008-00040, and by Catalan Government Project SGR 2009-458. ; Peer reviewed

Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. Finally, we would like to thank Biol. Kaspars Tars from Latvian Biomedical research and study center for giving us the opportunity to participate in this consortium and contribute to Latvian scientists' effort in response to the COVID-19 pandemic. ; Current in vitro models have significant limitations for new respiratory disease research and rapid drug repurposing. Lung on a chip (LOAC) technology offers a potential solution to these problems. However, these devices typically are fabricated from polydimethylsiloxane (PDMS), which has small hydrophobic molecule absorption, which hinders the application of this technology in drug repurposing for respiratory diseases. Off-stoichiometry thiol–ene (OSTE) is a promising alternative material class to PDMS. Therefore, this study aimed to test OSTE as an alternative material for LOAC prototype development and compare it to PDMS. We tested OSTE material for light transmission, small molecule absorption, inhibition of enzymatic reactions, membrane particle, and fluorescent dye absorption. Next, we microfabricated LOAC devices from PDMS and OSTE, functionalized with human umbilical vein endothelial cell (HUVEC) and A549 cell lines, and analyzed them with immunofluorescence. We demonstrated that compared to PDMS, OSTE has similar absorption of membrane particles and effect on enzymatic reactions, significantly lower small molecule absorption, and lower light transmission. Consequently, the immunofluorescence of OSTE LOAC was significantly impaired by OSTE optical properties. In conclusion, OSTE is a promising material for LOAC, but optical issues should be addressed in future LOAC prototypes to benefit from the material properties.--//--This work is licensed under a CC BY 4.0 license. ; This research was funded by project Nr. VPP-COVID-2020/1-0014 awarded by Latvian Council of Science

Este artículo contiene 18 páginas, 9 figuras. ; Planktonic communities are naturally subjected to episodic nutrient enrichments that may stress or redress the imbalances in limiting nutrients. Human-enhanced atmospheric nitrogen deposition has caused profound N:P imbalance in many remote oligotrophic lakes in which phosphorus has largely become limiting. These lakes offer an opportunity to investigate the relationship between the changes in plankton stoichiometry, productivity, and community structure occurring during nutrient fluctuations in P-limited conditions. We performed P (PO3 4 ) and N (NHþ 4 or NO 3 ) pulse additions to the summer epilimnetic community of an ultraoligotrophic lake using self-filling ~100-L enclosures and analyzed the response to varying P availability, N:P imbalance, and N source. Seston C:N:P proportions remained fairly unchanged to P additions that were within the range of values seasonally found in the lake. However, the seston N:P ratio abruptly shifted and approached Redfield's proportions at P additions typical of mesotrophic conditions that provided non-limiting conditions. N surplus did not affect seston C:N:P proportions. The patterns of seston N:P stability and shift were similar for both N sources. In contrast, productivity was highly sensitive to low and medium P additions and decelerated at high P additions. Phytoplankton biomass dominated particulate organic matter. The autotrophic community differentiated almost linearly across the P gradient. Chrysophytes' dominance decreased, and diatoms and cryptophytes relative abundance increased. Nonetheless, the stoichiometry stability and non-linear shift involved large biomass proportions of the same species, which indicates that the bulk stoichiometry was related to similar physiological behavior of phylogenetically diverse organisms according to the biogeochemical context. The C:N:P seston stability in P-limited conditions—with loose coupling with productivity, nutrient supply ratios, and species dominance—and the sudden shift to Redfield proportions in P-repleted conditions suggest a complex regulation of P scarcity in planktonic communities that goes beyond immediate acclimation growth responses and might include alternative physiological and biogeochemical states. ; The research was funded by research grants of the Spanish Government NitroPir (CGL2010–19737) and Transfer (CGL2016–80124-C2-1-P) and the Catalan Government GECA (2017 SGR 910). P.G-G (FPU AP2010-3596) and A.Z. (FPI BES-2014-070196) acknowledge their respective predoctoral scholarships ; Peer reviewed

Carbon, nitrogen, and phosphorus—nutrient and restrictive elements for plant growth and important components of the plant body—are mainly transferred and exchanged between plants and the soil environment. Changes in the carbon, nitrogen, and phosphorus eco-stoichiometry greatly impact the growth and expansion of Spartina alterniflora, and understanding these changes can reveal the nutrient coordination mechanism among ecosystem components. To explore the relationship between leaf and soil eco-stoichiometry and determine the key soil factors that affect leaf eco-stoichiometry, we collected leaf and soil samples of S. alterniflora at different tidal levels (i.e., 1, 3, and 5 km away from the coastline) in a coastal wetland in the Yancheng Elk Nature Reserve, Jiangsu province. We measured the leaf and soil carbon, nitrogen, and phosphorus contents and ratios, as well as the soil salinity and soil organic carbon. The results revealed the following. (1) The leaf stoichiometric characteristics and soil properties of S. alterniflora differed significantly between tidal levels; for example, total carbon, nitrogen, soil organic carbon were detected at their highest levels at 3 km and lowest levels at 5 km. (2) Significant correlations were detected between the leaf stoichiometric characteristics and soil characteristics. Additionally, nitrogen limitation was evident in the study area, as indicated by the nitrogen–phosphorus ratio being less than 14 and the soil nitrogen–phosphorus ratio being less than 1. (3) Soil salinity and the soil carbon–nitrogen ratio were shown to be the key factors that affect the eco-stoichiometric characteristics of S. alterniflora. These findings furthered our understanding of the nutrient distribution mechanisms and invasion strategy of S. alterniflora and can thus be used to guide S. alterniflora control policies formulated by government management departments in China.

This work has been financially supported by the Spanish Ministerio de Ciencia e Innovación through grant RTI2018-096498-B-I00 (MCIU/AEI/FEDER, UE). Support by the EC's Horizon 2020 Research and Innovation Programme (grant 645776), by the Austrian Science Fund (FWF) (P24471 and P26830), and by the NATO Science for Peace Programme (grant 984735) is acknowledged. A.M-J. acknowledges the financial support through BES-2013-062593. J.M-S acknowledges financial support through the Ramón y Cajal Program from the Government of Spain and FSE (RYC2018-026196-I). We acknowledge support of the publication fee by the Austrian Science Fund (FWF) Der Wissenschaftsfonds Open Access Publication Support Initiative.

The final publication is available at Elsevier via http://doi.org/10.1016/j.bbamem.2012.02.019 © 2012. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ ; Daptomycin is a lipopeptide antibiotic that kills Gram-positive bacteria by depolarizing their cell membranes. This antibacterial action of daptomycin is correlated with the formation of membrane-associated oligomers. We here examine the number of subunits contained in one oligomer using fluorescence resonance energy transfer (FRET). The results suggest that the oligomer contains approximately 6 to 7 subunits, or possibly twice this number if it spans both membrane monolayers. ; This work was supported by an NSERC operating grant to M. Palmer. J. Muraih was supported by a scholarship from the government of Iraq.