1,035 research outputs found
Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment
Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrological connectivity, which can inhibit or facilitate DOC mobilization. To test this hypothesis, we studied the mechanisms controlling DOC mobilization and export in the GroĂe Ohe catchment, a forested headwater in a mid-elevation mountainous region in southeastern Germany. Discharge and stream DOC concentrations were measured at an interval of 15âmin using in situ UV-Vis (ultravioletâvisible) spectrometry from June 2018 until October 2020 at two topographically contrasting subcatchments of the same stream. At the upper location (888âm above sea level, a.s.l.), the stream drains steep hillslopes, whereas, at the lower location (771âmâa.s.l.), it drains a larger area, including a flat and wide riparian zone. We focus on four events with contrasting antecedent wetness conditions and event size. During the events, in-stream DOC concentrations increased up to 19âmgâLâ1 in comparison to 2â3âmgâLâ1 during baseflow. The concentrationâdischarge relationships exhibited pronounced but almost exclusively counterclockwise hysteresis loops which were generally wider in the lower catchment than in the upper catchment due to a delayed DOC mobilization in the flat riparian zone. The riparian zone released considerable amounts of DOC, which led to a DOC load up to 7.4âkgâhâ1. The DOC load increased with the total catchment
wetness. We found a disproportionally high contribution to the total DOC
export of the upper catchment during events following a long dry period. We
attribute this to the low hydrological connectivity in the lower catchment
during drought, which inhibited DOC mobilization, especially at the
beginning of the events. Our data show that not only event size but also
antecedent wetness conditions strongly influence the hydrological
connectivity during events, leading to a varying contribution to DOC export
of subcatchments, depending on topography. As the frequency of prolonged
drought periods is predicted to increase, the relative contribution of
different subcatchments to DOC export may change in the future when
hydrological connectivity will be reduced more often.</p
Conservation and global distribution of non-canonical antigens in enterotoxigenic Escherichia coli
BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) cause significant diarrheal morbidity and mortality in children of resource-limited regions, warranting development of effective vaccine strategies. Genetic diversity of the ETEC pathovar has impeded development of broadly protective vaccines centered on the classical canonical antigens, the colonization factors and heat-labile toxin. Two non-canonical ETEC antigens, the EtpA adhesin, and the EatA mucinase are immunogenic in humans and protective in animal models. To foster rational vaccine design that complements existing strategies, we examined the distribution and molecular conservation of these antigens in a diverse population of ETEC isolates.
METHODS: Geographically diverse ETEC isolates (n = 1159) were interrogated by PCR, immunoblotting, and/or whole genome sequencing (n = 46) to examine antigen conservation. The most divergent proteins were purified and their core functions assessed in vitro.
RESULTS: EatA and EtpA or their coding sequences were present in 57.0% and 51.5% of the ETEC isolates overall, respectively; and were globally dispersed without significant regional differences in antigen distribution. These antigens also exhibited \u3e93% amino acid sequence identity with even the most divergent proteins retaining the core adhesin and mucinase activity assigned to the prototype molecules.
CONCLUSIONS: EtpA and EatA are well-conserved molecules in the ETEC pathovar, suggesting that they serve important roles in virulence and that they could be exploited for rational vaccine design
Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis
The masses of ten proton-rich nuclides, including the N=Z+1 nuclides 85-Mo
and 87-Tc, were measured with the Penning trap mass spectrometer SHIPTRAP.
Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass
surface by up to 1.6 MeV is observed causing significant abundance changes of
the ashes of astrophysical X-ray bursts. Surprisingly low alpha-separation
energies for neutron-deficient Mo and Tc are found, making the formation of a
ZrNb cycle in the rp process possible. Such a cycle would impose an upper
temperature limit for the synthesis of elements beyond Nb in the rp process.Comment: Link to online abstract:
http://link.aps.org/doi/10.1103/PhysRevLett.106.12250
South Korea's automotive labour regime, Hyundai Motorsâ global production network and tradeâbased integration with the European Union
This article explores the interrelationship between global production networks(GPNs) and free trade agreements (FTAs) in the South Korean auto industry and its employment relations. It focuses on the production network of the Hyundai Motor Group (HMG) â the third biggest automobile manufacturer in the world â and the FTA between the EU and South Korea. This was the first of the EUâs ânew generationâ FTAs, which among other things contained provisions designed to protect and promote labour standards. The articleâs argument is twofold. First, that HMGâs production network and Koreaâs political economy (of which HMG is a crucial part) limited the possibilities for the FTAâs labour provisions to take effect. Second, that the commercial provisions in this same FTA simultaneously eroded HMGâs domestic market and corporate profitability, leading to adverse consequences for auto workers in the more
insecure and low-paid jobs. In making this argument, the article advances a multiscalar conceptualization of the labour regime as an analytical intermediary between GPNs and FTAs. It also provides one of the first empirical studies of the EUâSouth Korea FTA in terms of employment relations, drawing on 105 interviews with trade unions, employer associations, automobile companies and state officials across both parties
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Overview of the results of the organics PET Study of the cometary samples returned from comet Wild 2 by the Stardust mission
This presenation will provide an overview of the efforts and results produced by the Organics Preliminary Examination Team during their studies of the samples returned from comet Wild 2 by the Stardust spacecraft
New aerodynamic lens injector for single particle diffractive imaging
An aerodynamic lens injector was developed specifically for the needs of single-particle diffractive imaging experiments at free-electron lasers. Its design allows for quick changes of injector geometries and focusing properties in order to optimize injection for specific individual samples. Here, we present results of its first use at the FLASH free-electron-laser facility. Recorded diffraction patterns of polystyrene spheres are modeled using Mie scattering, which allowed for the characterization of the particle beam under diffractive-imaging conditions and yield good agreement with particle-trajectory simulations
Time-resolved XUV Opacity Measurements of Warm-Dense Aluminium
The free-free opacity in plasmas is fundamental to our understanding of
energy transport in stellar interiors and for inertial confinement fusion
research. However, theoretical predictions in the challenging dense plasma
regime are conflicting and there is a dearth of accurate experimental data to
allow for direct model validation. Here we present time-resolved transmission
measurements in solid-density Al heated by an XUV free-electron laser. We use a
novel functional optimization approach to extract the temperature-dependent
absorption coefficient directly from an oversampled pool of single-shot
measurements, and find a pronounced enhancement of the opacity as the plasma is
heated to temperatures of order the Fermi energy. Plasma heating and
opacity-enhancement is observed on ultrafast time scales, within the duration
of the femtosecond XUV pulse. We attribute further rises in the opacity on ps
timescales to melt and the formation of warm-dense matter
Every child mattered in England: but what matters to children?
âEvery Child Mattersâ under New Labour provided a framework for services for young childrenâs care and education. It was pushed aside by the Conservative led coalition and replaced by âMore Great Childcareâ. The UK as a signatory to the United Nations Convention on the Rights of the Child, and therefore has obligations for legislation, policy and curriculum, specifically with regard to childrenâs rights and participation. On the 25th anniversary of the UNCRC, in practice there may be different levels of participation employed to engage childrenâs views in the development of policy about them. This project set out to ask children about what âmattersâ to them. Ninety finalist Early Childhood Studies students worked as co-researchers in this project. Five themes are discussed highlighting the powerful thoughts and ideas of children. A range of âchild-friendlyâ methods were used to collect data from children including role-play, interviews, drawings and artefacts, and story-telling
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