Tungsten-182 heterogeneity in modern ocean island basalts Mundl, Andrea; Touboul, Mathieu; Jackson, Matthew G. ...
Science (American Association for the Advancement of Science),
04/2017, Letnik:
356, Številka:
6333
Journal Article
Recenzirano
Odprti dostop
New tungsten isotope data for modern ocean island basalts (OIB) from Hawaii, Samoa, and Iceland reveal variable 182W/184W, ranging from that of the ambient upper mantle to ratios as much as 18 parts ...per million lower. The tungsten isotopic data negatively correlate with ³He/⁴He. These data indicate that each OIB system accesses domains within Earth that formed within the first 60 million years of solar system history. Combined isotopic and chemical characteristics projected for these ancient domains indicate that they contain metal and are repositories of noble gases. We suggest that the most likely source candidates are mega–ultralow-velocity zones, which lie beneath Hawaii, Samoa, and Iceland but not beneath hot spots whose OIB yield normal 182W and homogeneously low ³He/⁴He.
Volatile elements have a fundamental role in the evolution of planets. But how budgets of volatiles were set in planets, and the nature and extent of volatile-depletion of planetary bodies during the ...earliest stages of Solar System formation remain poorly understood. The Moon is considered to be volatile-depleted and so it has been predicted that volatile loss should have fractionated stable isotopes of moderately volatile elements. One such element, zinc, exhibits strong isotopic fractionation during volatilization in planetary rocks, but is hardly fractionated during terrestrial igneous processes, making it a powerful tracer of the volatile histories of planets. Here we present high-precision zinc isotopic and abundance data which show that lunar magmatic rocks are enriched in the heavy isotopes of zinc and have lower zinc concentrations than terrestrial or Martian igneous rocks. Conversely, Earth and Mars have broadly chondritic zinc isotopic compositions. We show that these variations represent large-scale evaporation of zinc, most probably in the aftermath of the Moon-forming event, rather than small-scale evaporation processes during volcanism. Our results therefore represent evidence for volatile depletion of the Moon through evaporation, and are consistent with a giant impact origin for the Earth and Moon.
Evidence for NOx Control over Nighttime SOA Formation ROLLINS, A. W; BROWNE, E. C; COHEN, R. C ...
Science (American Association for the Advancement of Science),
09/2012, Letnik:
337, Številka:
6099
Journal Article
Recenzirano
Organic aerosols account for about half of the total mass of small (submicrometer) particles in the troposphere, and most of them are believed to form through the oxidation of volatile molecules, ...rather than being emitted directly from specific sources. These particles have important roles in many atmospheric processes, and therefore a better understanding of their complex composition and chemistry is desirable. Rollins et al. (p. 1210) report on measurements of particulate organic nitrates, an important class of organic aerosols that form at night. However, they also found that high concentrations of organic molecules can suppress the growth of organic nitrate particles. These observations should help improve efforts to reduce organic aerosol pollution. PUBLICATION ABSTRACT Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NOx) affect atmospheric organic aerosol (OA) production. However, these effects have not been directly observed in ambient OA. We report measurements of particulate organic nitrates in Bakersfield, California, the nighttime formation of which increases with NOx and is suppressed by high concentrations of organic molecules that rapidly react with nitrate radical (NO3)--evidence that multigenerational chemistry is responsible for organic nitrate aerosol production. This class of molecules represents about a third of the nighttime increase in OA, suggesting that most nighttime secondary OA is due to the NO3 product of anthropogenic NOx emissions. Consequently, reductions in NOx emissions should reduce the concentration of organic aerosol in Bakersfield and the surrounding region. PUBLICATION ABSTRACT
In the atmosphere nighttime removal of volatile organic compounds is initiated to a large extent by reaction with the nitrate radical (NO3) forming organic nitrates which partition between gas and ...particulate phase. Here we show based on particle phase measurements performed at a suburban site in the Netherlands that organic nitrates contribute substantially to particulate nitrate and organic mass. Comparisons with a chemistry transport model indicate that most of the measured particulate organic nitrates are formed by NO3 oxidation. Using aerosol composition data from three intensive observation periods at numerous measurement sites across Europe, we conclude that organic nitrates are a considerable fraction of fine particulate matter (PM1) at the continental scale. Organic nitrates represent 34% to 44% of measured submicron aerosol nitrate and are found at all urban and rural sites, implying a substantial potential of PM reduction by NOx emission control.
Key Points
Particulate organic nitrate is ubiquitous in Europe
The 34 to 44 percent of fine particulate nitrate is organic
Nighttime chemistry is a dominant source of particulate organic nitrates
Dual‐porosity models are often used to describe solute transport in heterogeneous media, but the parameters within these models (e.g., immobile porosity and mobile/immobile exchange rate ...coefficients) are difficult to identify experimentally or relate to measurable quantities. Here, we performed synthetic, pore‐scale millifluidics simulations that coupled fluid flow, solute transport, and electrical resistivity (ER). A conductive‐tracer test and the associated geoelectrical signatures were simulated for four flow rates in two distinct pore‐scale model scenarios: one with intergranular porosity, and a second with an intragranular porosity also defined. With these models, we explore how the effective characteristic‐length scale estimated from a best‐fit dual‐domain mass transfer (DDMT) model compares to geometric aspects of the flow field. In both model scenarios we find that: (1) mobile domains and immobile domains develop even in a system that is explicitly defined with one domain; (2) the ratio of immobile to mobile porosity is larger at faster flow rates as is the mass‐transfer rate; and (3) a comparison of length scales associated with the mass‐transfer rate (Lα) and those associated with calculation of the Peclet number (LPe) show LPe is commonly larger than Lα. These results suggest that estimated immobile porosities from a DDMT model are not only a function of physically mobile or immobile pore space, but also are a function of the average linear pore‐water velocity and physical obstructions to flow, which can drive the development of immobile porosity even in single‐porosity domains.
Immune checkpoint inhibitor (ICI) monoclonal antibodies (mAbs) targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death protein 1 (PD-1) or its ligand (PD-L1) produce unique ...toxicity profiles. The objective of this review was to identify patterns and incidence of immune-related adverse events (irAE) based on tumour type and ICI class.
Medline, EMBASE and COCHRANE databases were searched to identify prospective monotherapy trials of ICIs from 2003 to November 2015. Paired reviewers selected studies for inclusion and extracted data. Odds ratio (OR),χ2 tests and multivariable regression models were used to analyse for effect size and associations.
We identified 48 trials (6938 patients), including 26 CTLA-4, 17 PD-1, 2 PD-L1 trials, and 3 studies tested both CTLA-4 and PD-1. Grade 3/4 irAE were more common with CTLA-4 mAbs compared with PD-1 (31% versus 10%). All grades colitis (OR 8.7, 95% CI 5.8–12.9), hypophysitis (OR 6.5, 95% CI 3.0–14.3) and rash (OR 2.0, 95% CI 1.8–2.3) were more frequent with CTLA-4 mAbs; whereas pneumonitis (OR 6.4, 95% CI 3.2–12.7), hypothyroidism (OR 4.3, 95% CI 2.9–6.3), arthralgia (OR 3.5, 95% CI 2.6–4.8) and vitiligo (OR 3.5, 95% CI 2.3–5.3) were more common with PD-1 mAbs. Comparison of irAE from the three most studied tumour types in PD-1 mAbs trials melanoma (n = 2048), non-small-cell lung cancer (n = 1030) and renal cell carcinoma (n = 573) showed melanoma patients had a higher frequency of gastrointestinal and skin irAE and lower frequency of pneumonitis.
CTLA-4 and PD-1 mAbs have distinct irAE profiles. Different immune microenvironments may drive histology-specific irAE patterns. Other tumour-dependent irAE profiles may be identified as data emerge from ICI trials.
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