Nitrate leaching is the process whereby the nitrate (NO3−) anion moves downwards in the soil profile with soil water. Nitrate leaching is commonly associated with chemical nitrogen (N) fertilizers ...used in agriculture. Nitrate leaching from different sources and contamination of surface and groundwater is a global phenomenon that has prompted social and political pressure to reduce nitrate leaching and contamination of water bodies. This bibliometric study analyzed global trends in nitrate leaching research. The results showed a rising interest in the last decades in this topic; given the growth tendency over the last years, it was envisaged that the importance on nitrate leaching research will continue increasing in the future. Knowledge on nitrate leaching was mostly disseminated through scientific publications (90% of total documents recovered), both as journal articles and reviews, classified in the Scopus database in the Agricultural, Biological and Environmental Sciences areas. Most publications dealt with soil nitrogen losses from agroecosystems and farmlands and the associated impact on the environment; they were published in journals with a focus on the influence of anthropogenic and soil-crop-animal systems in the environment, and on how such changes in the environment impact agroecosystems. Most documents published on nitrate leaching were indisputably from the United States, followed by China, the United Kingdom and Germany. An analysis of the main keywords showed an overall dominance of the soil nitrogen cycle, fertilizer use in agriculture and water quality aspects. The evolution of main crop species involved in nitrate leaching research showed a rising relevance of research conducted with maize, wheat and grasses from 1990 onwards. The most productive institutions in terms of number of documents dealing with nitrate leaching research, h-index and total citations, were located in the United States, China and the Netherlands. The United States Department of Agriculture stood out, followed by the Chinese Academy of Sciences and Wageningen University and Research. There were clusters of institutions with intercontinental interaction, on nitrate leaching research, between institutions from Europe, Asia and South and North America. Overall, this study has highlighted, from a bibliometric perspective, the rising concern on nitrate leaching. Progress in this field has been made particularly on the impact of the soil-plant-animal system on the environment and agroecosystems, and on fundamental and applied aspects of plant-soil interactions with an emphasis in cropping systems.
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•A rising interest in last decades in nitrate leaching research worldwide•Most research dealt with nitrate leaching from agroecosystems and farmlands•Dominance of soil nitrogen cycle, fertilizer use and water quality research topics•Most research on nitrate leaching conducted in the United States and China•Increasing relevance of research with maize, wheat and grasses from 1990
Accretion of matter onto black holes is universally associated with strong radiative feedback and powerful outflows. In particular, black-hole transients have outflows whose properties are strongly ...coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disk encircling the black hole, and collimated radio jets. Very recently, a distinct optical variability pattern has been reported in the transient stellar-mass black hole V404 Cygni, and interpreted as disrupted mass flow into the inner regions of its large accretion disk. Here we report observations of a sustained outer accretion disk wind in V404 Cyg, which is unlike any seen hitherto. We find that the outflowing wind is neutral, has a large covering factor, expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin. The large expelled mass (>10(-8) solar masses) indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk. The luminous, but brief, accretion phases shown by transients with large accretion disks imply that this outflow is probably a fundamental ingredient in regulating mass accretion onto black holes.
The present contribution offers an overview of a new area of research in the field of foreign language acquisition, which was triggered by the introduction of Positive Psychology (PP) (
MacIntyre and ...Gregersen, 2012
). For many years, a cognitive perspective had dominated research in applied linguistics. Around the turn of the millennium researchers became increasingly interested in the role of emotions in foreign language learning and teaching, beyond established concepts like foreign language anxiety and constructs like motivation and attitudes toward the foreign language. As a result, a more nuanced understanding of the role of positive and negative learner and teacher emotions emerged, underpinned by solid empirical research using a wide range of epistemological and methodological approaches. PP interventions have been carried out in schools and universities to strengthen learners and teachers’ experiences of flow, hope, courage, well-being, optimism, creativity, happiness, grit, resilience, strengths, and laughter with the aim of enhancing learners’ linguistic progress. This paper distinguishes the early period in the field that started with
MacIntyre and Gregersen (2012)
, like a snowdrop after winter, and that was followed by a number of early studies in relatively peripheral journals. We argue that 2016 is the starting point of the current period, characterized by gradual recognition in applied linguistics, growing popularity of PP, and an exponential increase in publications in more mainstream journals. This second period could be compared to a luxuriant English garden in full bloom.
There is increasing scientific and clinical interest in elucidating the biology of type I Interferons, which began approximately 60years ago with the concept of “viral interference”, a property that ...reduces the ability of a virus to infect cells. Although our understanding of the multiple cellular and molecular functions of interferons has advanced significantly, much remains to be learned and type I Interferons remain an active and fascinating area of inquiry. In this review, we cover some general aspects of type I interferon genes, with emphasis on interferon-alpha, and various aspects of molecular mechanisms triggered by type I interferons and toll-like receptor signaling by the Janus activated kinase/signal transducer activation of transcription (JAK–STAT) pathway and interferon regulatory factor pathway. We will also describe the role of type I interferons in autoimmune and inflammatory diseases, and its potential use as therapeutic agent.
•The interferon-alpha (IFNA) gene cluster consists of at 13 IFNA homologous genes.•The type I IFN genes exhibit diverse biological functions in cellular immunity.•IFN-α plays a role in several autoimmune diseases, including lupus and myositis.•Clinical trials with anti-IFN-α antibodies are underway in autoimmune disease.•In contrast, IFN-β is an effective treatment for multiple sclerosis.
A locally-adapted multitemporal two-phase burned area (BA) algorithm has been developed using as inputs Sentinel-2 MSI reflectance measurements in the short and near infrared wavebands plus the ...active fires detected by Terra and Aqua MODIS sensors. An initial burned area map is created in the first step, from which tile dependent statistics are extracted for the second step. The whole Sub-Saharan Africa (around 25 M km2) was processed with this algorithm at a spatial resolution of 20 m, from January to December 2016. This period covers two half fire seasons on the Northern Hemisphere and an entire fire season in the South. The area was selected as existing BA products account it to include around 70% of global BA. Validation of this product was based on a two-stage stratified random sampling of Landsat multitemporal images. Higher accuracy values than existing global BA products were observed, with Dice coefficient of 77% and omission and commission errors of 26.5% and 19.3% respectively. The standard NASA BA product (MCD64A1 c6) showed a similar commission error (20.4%), but much higher omission errors (59.6%), with a lower Dice coefficient (53.6%). The BA algorithm was processed over >11,000 Sentinel-2 images to create a database that would also include small fires (<100 ha). This is the first time a continental BA product is generated from medium resolution sensors (spatial resolution = 20 m), showing their operational potential for improving our current understanding of global fire impacts. Total BA estimated from our product was 4.9 M km2, around 80% larger area than what the NASA BA product (MCD64A1 c6) detected in the same period (2.7 M km2). The main differences between the two products were found in regions where small fires (<100 ha) account for a significant proportion of total BA, as global products based on coarse pixel sizes (500 m for MCD64A1) unlikely detect them. On the negative side, Sentinel-2 based products have lower temporal resolution and consequently are more affected by cloud/cloud shadows and have less temporal reporting accuracy than global BA products. The product derived from S2 imagery would greatly contribute to better understanding the impacts of small fires in global fire regimes, particularly in tropical regions, where such fires are frequent. This product is named FireCCISFD11 and it is publicly available at: https://www.esa-fire-cci.org/node/262, last accessed on November 2018.
•A Sentinel-2 MSI multitemporal two-phase burned area algorithm is presented.•A medium resolution burned area product was generated in Sub-Saharan Africa.•26.5% and 19.3% of omission and commission errors were obtained for the product.•Comparisons with a low resolution product prove previous underestimations of BA.
We present time-resolved 10.4 m Gran Telescopio Canarias and 4.2 m William Herschel Telescope intermediate resolution spectroscopy of the X-ray transient MAXI J1820+070 (=ASASSN-18ey) obtained during ...its decline to the quiescent state. Cross-correlation of the 21 individual spectra against late-type templates reveals a sinusoidal velocity modulation with a period of 0.68549 0.00001 day and semi-amplitude of 417.7 3.9 km s−1. We derive a mass function f(M) = 5.18 0.15 M , dynamically confirming the black hole (BH) nature of the compact object. Our analysis of the stellar absorption features supports a K3-5 spectral classification for the donor star, which contributes 20% of the total flux at 5200-6800 . The photometric 0.703 0.003 day periodicity observed during outburst is 2.6% longer than the orbital period supporting the presence of a superhump modulation in the outburst light curves. In line with this interpretation, we constrain the binary mass ratio to be q 0.12. In addition, we observe a sharp increase in the H emission line equivalent width during inferior conjunction of the donor star that we interpret as a grazing eclipse of the accretion disk and allows us to constrain the binary inclination to i 69°. On the other hand, the absence of X-ray eclipses during outburst imply i 77°. These inclination limits, together with our dynamical solution, lead to a BH mass in the range 7-8 M . We also measure a systemic velocity γ = −21.6 2.3 km s−1, which, combined with the Gaia second data release proper motion and parallax, implies a large peculiar velocity ∼100 km s−1.
We report our multiwavelength study of the 2011 outburst evolution of the newly discovered black hole candidate X-ray binary Swift J1357.2−0933. We analysed the Swift X-ray Telescope and ...Ultraviolet/Optical Telescope (UVOT) data taken during the ∼7 months duration of the outburst. It displayed a 2-10 keV X-ray peak luminosity of ∼1035(D/1.5 kpc)2 erg s−1, which classifies the source as a very faint X-ray transient. We found that the X-ray spectrum at the peak was consistent with the source being in the hard state, but it softened with decreasing luminosity, a common behaviour of black holes returning to quiescence from the hard state. The correlations between the simultaneous X-ray and ultraviolet/optical data suggest a system with a black hole accreting from a viscous disc, and we do not detect X-ray reprocessing on the disc surface. The UVOT filters provide the opportunity to study these correlations up to ultraviolet wavelengths, a regime so far unexplored. If the black hole nature is confirmed, Swift J1357.2−0933 would be one of the very few established black hole very-faint X-ray transients.
AX J1754.2−2754, 1RXS J171824.2−402934 and 1RXH J173523.7−354013 are three persistent neutron star low-mass X-ray binaries that display a 2-10 keV accretion luminosity L
X of only (1-10) × 1034 erg ...s−1 (i.e. only 0.005-0.05 per cent of the Eddington limit). The phenomenology of accreting neutron stars which accrete at such low accretion rates is not yet well known and the reason why they have such low accretion rates is also not clear. Therefore, we have obtained XMM-Newton data of these three sources and here we report our analysis of the high-quality X-ray spectra we have obtained for them. We find that AX J1754.2−2754 has L
X ∼ 1035 erg s−1, while the other two have X-ray luminosities about an order of magnitude lower. However, all sources have a similar, relatively soft, spectrum with a photon index of 2.3-2.5, when the spectrum is fitted with an absorbed power-law model. This model fits the data of AX J1754.2−2754 adequately, but it cannot fit the data obtained for 1RXS J171824.2−402934 and 1RXH J173523.7−354013. For those sources, a clear soft thermal component is needed to fit their spectra. This soft component contributes 40-50 per cent to the 0.5-10 keV flux of the sources. The presence of this soft component might be the reason why the spectra of these two sources are soft. When including this additional spectral component, the power-law photon indices are significantly lower. It can be excluded that a similar component with similar contributions to the 2-10 keV X-ray flux is present for AX J1754.2−2754, indicating that the soft spectrum of this source is mostly due to the fact that the power-law component itself is not hard. We note that we cannot exclude that a weaker soft component is present in the spectrum of this source which only contributes up to ∼25 per cent to the 0.5-10 keV X-ray flux. We discuss our results in the context of what is known of accreting neutron stars at very low accretion rate.
The experience of Central Americans in the United States is
marked by a vicious contradiction. In entertainment and information
media, Salvadorans, Guatemalans, Nicaraguans, and Hondurans are
...hypervisible as threatening guerrillas, MS-13 gangsters, maids, and
"forever illegals." Central Americans are unseen within the broader
conception of Latinx community, foreclosing avenues to
recognition.
Yajaira M. Padilla explores how this regime of visibility and
invisibility emerged over the past forty years-bookended by the
right-wing presidencies of Ronald Reagan and Donald Trump-and how
Central American immigrants and subsequent generations have
contested their rhetorical disfiguration. Drawing from popular
films and TV, news reporting, and social media, Padilla shows how
Central Americans in the United States have been constituted as
belonging nowhere, imagined as permanent refugees outside the
boundaries of even minority representation. Yet in documentaries
about cross-border transit through Mexico, street murals, and other
media, US Central Americans have counteracted their exclusion in
ways that defy dominant paradigms of citizenship and
integration.
All disc-accreting astrophysical objects produce powerful disc winds. In compact binaries containing neutron stars or black holes, accretion often takes place during violent outbursts. The main disc ...wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated 'soft states'
. By contrast, optical wind-formed lines have recently been detected in 'hard states', when a hot corona dominates the luminosity
. The relationship between these signatures is unknown, and no erupting system has as yet revealed wind-formed lines between the X-ray and optical bands, despite the many strong resonance transitions in this ultraviolet (UV) region
. Here we report that the transient neutron star binary Swift J1858.6-0814 exhibits wind-formed, blue-shifted absorption lines associated with C IV, N V and He II in time-resolved UV spectroscopy during a luminous hard state, which we interpret as a warm, moderately ionized outflow component in this state. Simultaneously observed optical lines also display transient blue-shifted absorption. Decomposing the UV data into constant and variable components, the blue-shifted absorption is associated with the former. This implies that the outflow is not associated with the luminous flares in the data. The joint presence of UV and optical wind features reveals a multi-phase and/or spatially stratified evaporative outflow from the outer disc
. This type of persistent mass loss across all accretion states has been predicted by radiation-hydrodynamic simulations
and helps to explain the shorter-than-expected duration of outbursts
.
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