Muon neutrino disappearance probability as a function of neutrino flight length L over neutrino energy E was studied. A dip in the L/E distribution was observed in the data, as predicted from the ...sinusoidal flavor transition probability of neutrino oscillation. The observed L/E distribution constrained nu(micro)<-->nu(tau) neutrino oscillation parameters; 1.9x10(-3)<Deltam(2)<3.0x10(-3) eV(2) and sin((2)2theta>0.90 at 90% confidence level.
A search for a nonzero neutrino magnetic moment has been conducted using 1496 live days of solar neutrino data from Super-Kamiokande-I. Specifically, we searched for distortions to the energy ...spectrum of recoil electrons arising from magnetic scattering due to a nonzero neutrino magnetic moment. In the absence of a clear signal, we found micro(nu)</=(3.6x10(-10))micro(B) at 90% C.L. by fitting to the Super-Kamiokande day-night spectra. The fitting took into account the effect of neutrino oscillation on the shapes of energy spectra. With additional information from other solar neutrino and KamLAND experiments constraining the oscillation region, a limit of micro(nu)</=(1.1x10(-10))micro(B) at 90% C.L. was obtained.
Human Influences on Nitrogen Removal in Lakes Finlay, Jacques C.; Small, Gaston E.; Sterner, Robert W.
Science (American Association for the Advancement of Science),
10/2013, Letnik:
342, Številka:
6155
Journal Article
Recenzirano
Human activities have increased the availability of reactive nitrogen in many ecosystems, leading to negative impacts on human health, biodiversity, and water quality. Freshwater ecosystems, ...including lakes, streams, and wetlands, are a large global sink for reactive nitrogen, but factors that determine the efficacy of freshwater nitrogen removal rates are poorly known. Using a global lake data set, we show that the availability of phosphorus, a limiting nutrient, affects both annual nitrogen removal rate and efficiency. This result indicates that increased phosphorus inputs from human activities have stimulated nitrogen removal processes in many lakes. Recent management-driven reductions in phosphorus availability promote water column accumulation and export of nitrogen from large lakes, an unintended consequence of single-element management that argues for greater control of nitrogen as well as phosphorus sources.
The United States and others should consider adopting a different approach to estimating costs and benefits in light of uncertainty.
In economic project analysis, the rate at which future benefits ...and costs are discounted relative to current values often determines whether a project passes the benefit-cost test. This is especially true of projects with long time horizons, such as those to reduce greenhouse gas (GHG) emissions. Whether the benefits of climate policies, which can last for centuries, outweigh the costs, many of which are borne today, is especially sensitive to the rate at which future benefits are discounted. This is also true of other policies, e.g., affecting nuclear waste disposal or the construction of long-lived infrastructure.
A century-long increase in nitrate (NO₃⁻) in the water column of Lake Superior is a classic example of recent nitrogen accumulation in ecosystems, but its cause and relationship to historical NO₃⁻ ...deposition is unknown. We used stable isotope ratios of oxygen and nitrogen in nitrate (δ¹⁸O-NO₃ and δ¹⁵N-NO₃) to examine its sources in this large lake, which represents 10% of the world's surficial liquid freshwater. The most parsimonious hypothesis to explain the rise NO₃⁻ in is that the lake is accruing NO₃⁻ deposited directly on the lake surface because it is too unproductive to completely assimilate all of it. Data for δ¹⁸O-NO₃ in external sources and the water column, however, are inconsistent with this hypothesis. Instead, the isotopic evidence indicates strongly that the accumulating NO₃⁻ is almost entirely derived from nitrification occurring within the lake. While increases in atmospheric deposition of NO₃⁻ may have played a role in its buildup in the lake, other factors such as increases in NHʄ⁺ and dissolved organic nitrogen inputs from precipitation or rivers, increases in nitrogen fluxes from the sediments, and decreases in burial rates must also be considered as potential drivers of rising NO₃⁻. The sustained accumulation of nitrogen in Lake Superior is thus more complex and incompletely understood than previously assumed.
Eutrophication of urban surface waters from excess nitrogen (N) and phosphorus (P) inputs remains a major issue in water quality management. Although much research has focused on understanding ...loading of nutrients from storm events, there has been little research to understand the contribution of baseflow, the water moving through storm drains between rainfall events. We investigated the relative contributions of baseflow versus stormflow for loading of water and nutrients (various forms of N and P) by the storm drain network in six urban sub-watersheds in St. Paul, MN, USA. Across sites, baseflow made substantial contributions to warm season (May–October) water yields (27–66 % across sites), total N yields (31–68 %), and total P yields (7–32 %). These results show that while P was predominantly delivered by stormflow, N loading was similar between baseflow and stormflow. We found that baseflow was dominated by groundwater inputs, likely caused by interception of shallow groundwater by storm drains, but also that variability in N and P among sites was related in part to the connectivity of the storm drains to upstream lakes and wetlands in some watersheds. The substantial loading by groundwater-dominated baseflow, especially for N, implies that N management may require a broader focus on N source reduction, perhaps through improved land management, in order to prevent contamination of shallow groundwater via infiltration.
Direct-acting antivirals are needed to combat coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). The papain-like protease (PLpro) ...domain of Nsp3 from SARS-CoV-2 is essential for viral replication. In addition, PLpro dysregulates the host immune response by cleaving ubiquitin and interferon-stimulated gene 15 protein from host proteins. As a result, PLpro is a promising target for inhibition by small-molecule therapeutics. Here we design a series of covalent inhibitors by introducing a peptidomimetic linker and reactive electrophile onto analogs of the noncovalent PLpro inhibitor GRL0617. The most potent compound inhibits PLpro with k
/K
= 9,600 M
s
, achieves sub-μM EC
values against three SARS-CoV-2 variants in mammalian cell lines, and does not inhibit a panel of human deubiquitinases (DUBs) at >30 μM concentrations of inhibitor. An X-ray co-crystal structure of the compound bound to PLpro validates our design strategy and establishes the molecular basis for covalent inhibition and selectivity against structurally similar human DUBs. These findings present an opportunity for further development of covalent PLpro inhibitors.
Ocean acidification will likely result in a drop of 0.3–0.4 pH units in the surface ocean by 2100, assuming anthropogenic CO₂ emissions continue at the current rate. Impacts of increasing ...atmosphericpCO₂ on pH in freshwater systems have scarcely been addressed. In this study, the Laurentian Great Lakes are used as a case study for the potential for CO₂-induced acidification in freshwater systems as well as for assessment of the ability of current water quality monitoring to detect pH trends. If increasing atmosphericpCO₂ is the only forcing, pH will decline in the Laurentian Great Lakes at the same rate and magnitude as the surface ocean through 2100. High-resolution numerical models and one high-resolution time series of data illustrate that the pH of the Great Lakes has significant spatio-temporal variability. Because of this variability, data from existing monitoring systems are insufficient to accurately resolve annual mean trends. Significant measurement uncertainty also impedes the ability to assess trends. To elucidate the effects of increasing atmospheric CO₂ in the Great Lakes requires pH monitoring by collecting more accurate measurements with greater spatial and temporal coverage.
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