A global network of optical atomic clocks will enable unprecedented measurement precision in fields including tests of fundamental physics, dark matter searches, geodesy, and navigation. Free-space ...laser links through the turbulent atmosphere are needed to fully exploit this global network, by enabling comparisons to airborne and spaceborne clocks. We demonstrate frequency transfer over a 2.4 km atmospheric link with turbulence comparable to that of a ground-to-space link, achieving a fractional frequency stability of 6.1×10^{-21} in 300 s of integration time. We also show that clock comparison between ground and low Earth orbit will be limited by the stability of the clocks themselves after only a few seconds of integration. This significantly advances the technologies needed to realize a global timescale network of optical atomic clocks.
We present a global simulation of tropospheric iodine chemistry within the GEOS-Chem chemical transport model. This includes organic and inorganic iodine sources, standard gas-phase iodine chemistry, ...and simplified higher iodine oxide (I2OX, X = 2, 3, 4) chemistry, photolysis, deposition, and parametrized heterogeneous reactions. In comparisons with recent iodine oxide (IO) observations, the simulation shows an average bias of ∼ +90 % with available surface observations in the marine boundary layer (outside of polar regions), and of ∼ +73 % within the free troposphere (350 hPa < p < 900 hPa) over the eastern Pacific. Iodine emissions (3.8 Tg yr−1) are overwhelmingly dominated by the inorganic ocean source, with 76 % of this emission from hypoiodous acid (HOI). HOI is also found to be the dominant iodine species in terms of global tropospheric IY burden (contributing up to 70 %). The iodine chemistry leads to a significant global tropospheric O3 burden decrease (9.0 %) compared to standard GEOS-Chem (v9-2). The iodine-driven OX loss rate1 (748 Tg OX yr−1) is due to photolysis of HOI (78 %), photolysis of OIO (21 %), and reaction between IO and BrO (1 %). Increases in global mean OH concentrations (1.8 %) by increased conversion of hydroperoxy radicals exceeds the decrease in OH primary production from the reduced O3 concentration. We perform sensitivity studies on a range of parameters and conclude that the simulation is sensitive to choices in parametrization of heterogeneous uptake, ocean surface iodide, and I2OX (X = 2, 3, 4) photolysis. The new iodine chemistry combines with previously implemented bromine chemistry to yield a total bromine- and iodine-driven tropospheric O3 burden decrease of 14.4 % compared to a simulation without iodine and bromine chemistry in the model, and a small increase in OH (1.8 %). This is a significant impact and so halogen chemistry needs to be considered in both climate and air quality models. 1 Here OX is defined as O3 + NO2 + 2NO3 + PAN + PMN+PPN + HNO4 + 3N2O5 + HNO3 + BrO + HOBr + BrNO2+2BrNO3 + MPN + IO + HOI + INO2 + 2INO3 + 2OIO+2I2O2 + 3I2O3 + 4I2O4, where PAN = peroxyacetyl nitrate, PPN = peroxypropionyl nitrate, MPN = methyl peroxy nitrate, and MPN = peroxymethacryloyl nitrate.
We present the first detection of glyoxal (CHOCHO) over the remote tropical Pacific Ocean in the Marine Boundary Layer (MBL). The measurements were conducted by means of the University of Colorado ...Ship Multi-Axis Differential Optical Absorption Spectroscopy (CU SMAX-DOAS) instrument aboard the research vessel Ronald H. Brown. The research vessel was on a cruise in the framework of the VAMOS Ocean-Cloud-Atmosphere-Land Study – Regional Experiment (VOCALS-REx) and the Tropical Atmosphere Ocean (TAO) projects lasting from October 2008 through January 2009 (74 days at sea). The CU SMAX-DOAS instrument features a motion compensation system to characterize the pitch and roll of the ship and to compensate for ship movements in real time. We found elevated mixing ratios of up to 140 ppt CHOCHO located inside the MBL up to 3000 km from the continental coast over biologically active upwelling regions of the tropical Eastern Pacific Ocean. This is surprising since CHOCHO is very short lived (atmospheric life time ~2 h) and highly water soluble (Henry's Law constant H = 4.2 × 105 M/atm). This CHOCHO cannot be explained by transport of it or its precursors from continental sources. Rather, the open ocean must be a source for CHOCHO to the atmosphere. Dissolved Organic Matter (DOM) photochemistry in surface waters is a source for Volatile Organic Compounds (VOCs) to the atmosphere, e.g. acetaldehyde. The extension of this mechanism to very soluble gases, like CHOCHO, is not straightforward since the air-sea flux is directed from the atmosphere into the ocean. For CHOCHO, the dissolved concentrations would need to be extremely high in order to explain our gas-phase observations by this mechanism (40–70 μM CHOCHO, compared to ~0.01 μM acetaldehyde and 60–70 μM DOM). Further, while there is as yet no direct measurement of VOCs in our study area, measurements of the CHOCHO precursors isoprene, and/or acetylene over phytoplankton bloom areas in other parts of the oceans are too low (by a factor of 10–100) to explain the observed CHOCHO amounts. We conclude that our CHOCHO data cannot be explained by currently understood processes. Yet, it supports first global source estimates of 20 Tg/year CHOCHO from the oceans, which likely is a significant source of secondary organic aerosol (SOA). This chemistry is currently not considered by atmospheric models.
We have analyzed Sentinel‐5 Precursor TROPOspheric Monitoring Instrument (TROPOMI) data over the Copperbelt mining region (Democratic Republic of Congo and Zambia). Despite high background values, ...annual 2019–2022 means of TROPOMI NO2 (nitrogen dioxide) show local enhancements consistent with six point sources (four copper/cobalt mines, two cities) where high‐emission industrial activities take place. We have quantified annual NOx (nitrogen oxides) emissions from these point sources, identified temporal trends in emissions, and found strong correlations with production data from colocated mines and one oil refinery. The Copernicus Atmosphere Monitoring Service Global Anthropogenic (CAMS‐GLOB‐ANT) version 5 inventory underpredicts TROPOMI‐derived emissions and lacks the temporal trends observed in TROPOMI and mine/refinery production. These results demonstrate the potential for satellite monitoring of mining and other industrial activities, often unreported or underestimated, which impact the air quality of local communities. This is particularly important for Africa, where mining is increasing aggressively.
Plain Language Summary
We show for the first time that annual NOx gas pollution emitted by individual copper/cobalt mines can be measured with TROPOMI satellite data, even in the presence of high background pollution from biomass burning and other sources. This is important for monitoring the air quality of local communities, particularly when these industrial activities proliferate in close proximity to population centers (as is the case in the Copperbelt mining region and in other African regions) and without sufficient ground measurements of air pollution levels. Additionally, we show for the first time that the annual amount of NOx pollution emitted by these single point sources is strongly correlated with annual production from individual, colocated copper/cobalt mines and one oil refinery. Studies like this can be used to estimate mine/oil refinery production before companies release their annual reports or (for non‐publicly traded companies) in the absence of such reports. Insufficient emissions from mines claiming high production could indicate production from a different source. Joint analysis of satellite‐derived emissions and mine production reports could be useful in improving the traceability of minerals extracted in conflict areas.
Key Points
We quantified annual TROPOspheric Monitoring Instrument (TROPOMI)‐derived NOx emissions from point sources corresponding to copper/cobalt mines, despite high background values
Annual emissions from individual point sources are strongly correlated with annual production from colocated single mines, one oil refinery
TROPOMI is relevant to monitoring air quality and mining/industrial production in remote regions where these activities are growing rapidly
In National Wilms Tumor Study 5 (NWTS-5), tumor-specific combined loss of heterozygosity of chromosomes 1p and 16q (LOH1p/16q) was associated with adverse outcomes in patients with favorable ...histology Wilms tumor. The AREN0533/AREN0532 studies assessed whether augmenting therapy improved event-free survival (EFS) for these patients. Patients with stage I/II disease received regimen DD4A (vincristine, dactinomycin and doxorubicin) but no radiation therapy. Patients with stage III/IV disease received regimen M (vincristine, dactinomycin, and doxorubicin alternating with cyclophosphamide and etoposide) and radiation therapy.
Patients were enrolled through the AREN03B2 Biology study between October 2006 and October 2013; all underwent central review of pathology, surgical reports, and imaging. Tumors were evaluated for LOH1p/16q by microsatellite testing. EFS and overall survival were compared using the log-rank test between NWTS-5 and current studies.
LOH1p/16q was detected in 49 of 1,147 evaluable patients with stage I/II disease (4.27%) enrolled in AREN03B2; 32 enrolled in AREN0532. LOH1p/16q was detected in 82 of 1,364 evaluable patients with stage III/IV disease (6.01%) in AREN03B2; 51 enrolled in AREN0533. Median follow-up for 83 eligible patients enrolled in AREN0532/0533 was 5.73 years (range, 2.84 to 9.63 years). The 4-year EFS for patients with stage I/II and stage III/IV disease with LOH1p/16 was 87.3% (95% CI, 75.1% to 99.5%) and 90.2% (95% CI, 81.8% to 98.6%), respectively. These results are improved compared with the NWTS-5 updated 4-year EFS of 68.8% for patients with stage I/II disease (
= .042), and 61.3% for patients with stage III/IV disease (
= .001), with trends toward improved 4-year overall survival. The most common grade 3 or higher nonhematologic toxicities with regimen M were febrile neutropenia (39.2%) and infections (21.6%).
Augmentation of therapy improved EFS for patients with favorable histology Wilms tumor and LOH1p/16q compared with the historical NWTS-5 comparison group, with an expected toxicity profile.
Injection of iodine to the stratosphere Saiz-Lopez, A.; Baidar, S.; Cuevas, C. A. ...
Geophysical research letters,
28 August 2015, Letnik:
42, Številka:
16
Journal Article
Recenzirano
Odprti dostop
We report a new estimation of the injection of iodine into the stratosphere based on novel daytime (solar zenith angle < 45°) aircraft observations in the tropical tropopause layer and a global ...atmospheric model with the most recent knowledge about iodine photochemistry. The results indicate that significant levels of total reactive iodine (0.25–0.7 parts per trillion by volume), between 2 and 5 times larger than the accepted upper limits, can be injected into the stratosphere via tropical convective outflow. At these iodine levels, modeled iodine catalytic cycles account for up to 30% of the contemporary ozone loss in the tropical lower stratosphere and can exert a stratospheric ozone depletion potential equivalent to, or even larger than, that of very short‐lived bromocarbons. Therefore, we suggest that iodine sources and chemistry need to be considered in assessments of the historical and future evolution of the stratospheric ozone layer.
Key Points
Injection of iodine to the stratosphere can be 2 to 5 times larger than accepted upper limits
Iodine catalytic cycles could account for up to 30% of ozone loss in the tropical lower stratosphere
Iodine‐mediated depletion of stratospheric ozone can be comparable to that of VSL bromocarbons
Researchers worldwide with information about the Kirsten ras (Ki-ras) tumour genotype and outcome of patients with colorectal cancer were invited to provide that data in a schematized format for ...inclusion in a collaborative database called RASCAL (The Kirsten ras in-colorectal-cancer collaborative group). Our results from 2721 such patients have been presented previously and for the first time in any common cancer, showed conclusively that different gene mutations have different impacts on outcome, even when the mutations occur at the same site on the genome. To explore the effect of Ki-ras mutations at different stages of colorectal cancer, more patients were recruited to the database, which was reanalysed when information on 4268 patients from 42 centres in 21 countries had been entered. After predetermined exclusion criteria were applied, data on 3439 patients were entered into a multivariate analysis. This found that of the 12 possible mutations on codons 12 and 13 of Kirsten ras, only one mutation on codon 12, glycine to valine, found in 8.6% of all patients, had a statistically significant impact on failure-free survival (P = 0.004, HR 1.3) and overall survival (P = 0.008, HR 1.29). This mutation appeared to have a greater impact on outcome in Dukes' C cancers (failure-free survival, P = 0.008, HR 1.5; overall survival P = 0.02, HR 1.45) than in Dukes' B tumours (failure-free survival, P = 0.46, HR 1.12; overall survival P = 0.36, HR 1.15). Ki-ras mutations may occur early in the development of pre-cancerous adenomas in the colon and rectum. However, this collaborative study suggests that not only is the presence of a codon 12 glycine to valine mutation important for cancer progression but also that it may predispose to more aggressive biological behaviour in patients with advanced colorectal cancer.
Multi AXis Differential Optical Absorption Spectroscopy (MAX‐DOAS) observations of the oxygen dimer O4 which can serve as a new method for the determination of atmospheric aerosol properties are ...presented. Like established methods, e.g., Sun radiometer and LIDAR measurements, MAX‐DOAS O4 observations determine optical properties of aerosol under atmospheric conditions (not dried). However, the novel technique has two major advantages: It utilizes differential O4 absorption structures and thus does not require absolute radiometric calibration. In addition, O4 observations using this method provide a new kind of information: since the atmospheric O4 profile depends strongly on altitude, they can yield information on the atmospheric light path distribution and in particular on the atmospheric aerosol profile. From O4 observations during clear days and from atmospheric radiative transfer modeling, we conclude that our new method is especially sensitive to the aerosol extinction close to the ground. In addition, O4 observations using this method yield information on the penetration depth of the incident direct solar radiation. O4 observations at different azimuth angles can also provide information on the aerosol scattering phase function. We found that MAX‐DOAS O4 observations are a very sensitive method: even aerosol extinction below 0.001 could be detected. In addition to the O4 absorptions we also investigated the magnitude of the Ring effect and the (relative) intensity. Both quantities yield valuable further information on atmospheric aerosols. From the simultaneous analysis of the observed O4 absorption and the measured intensity, in particular, information on the absorbing properties of the aerosols might be derived. The aerosol information derived from MAX‐DOAS observations can be used for the quantitative analysis of various trace gases also analyzed from the measured spectra.
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