455 research outputs found
Assessing the impact of COVID-19 on liver cancer management (CERO-19)
Background & Aims: The coronavirus disease 2019 (COVID-19) pandemic has posed unprecedented challenges to healthcare
systems and it may have heavily impacted patients with liver cancer (LC). Herein, we evaluated whether the schedule of LC
screening or procedures has been interrupted or delayed because of the COVID-19 pandemic.
Methods: An international survey evaluated the impact of the COVID-19 pandemic on clinical practice and clinical trials from
March 2020 to June 2020, as the first phase of a multicentre, international, and observational project. The focus was on
patients with hepatocellular carcinoma or intrahepatic cholangiocarcinoma, cared for around the world during the first
COVID-19 pandemic wave.
Results: Ninety-one centres expressed interest to participate and 76 were included in the analysis, from Europe, South America,
North America, Asia, and Africa (73.7%,17.1%, 5.3%, 2.6%, and 1.3% per continent, respectively). Eighty-seven percent of the centres
modified their clinical practice: 40.8% the diagnostic procedures, 80.9% the screening programme, 50% cancelled curative and/or
palliative treatments for LC, and 41.7% modified the liver transplantation programme. Forty-five out of 69 (65.2%) centres in
which clinical trials were running modified their treatments in that setting, but 58.1% were able to recruit new patients. The
phone call service was modified in 51.4% of centres which had this service before the COVID-19 pandemic (n = 19/37).
Conclusions: The first wave of the COVID-19 pandemic had a tremendous impact on the routine care of patients with liver
cancer. Modifications in screening, diagnostic, and treatment algorithms may have significantly impaired the outcome of
patients. Ongoing data collection and future analyses will report the benefits and disadvantages of the strategies imple mented, aiding future decision-making
The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings
Atmospheric
marine aerosol particles impact Earth's albedo and climate. These particles
can be primary or secondary and come from a variety of sources, including sea
salt, dissolved organic matter, volatile organic compounds, and
sulfur-containing compounds. Dimethylsulfide (DMS) marine emissions
contribute greatly to the global biogenic sulfur budget, and its oxidation
products can contribute to aerosol mass, specifically as sulfuric acid and
methanesulfonic acid (MSA). Further, sulfuric acid is a known nucleating
compound, and MSA may be able to participate in nucleation when bases are
available. As DMS emissions, and thus MSA and sulfuric acid from DMS
oxidation, may have changed since pre-industrial times and may change in a
warming climate, it is important to characterize and constrain the climate
impacts of both species. Currently, global models that simulate aerosol size
distributions include contributions of sulfate and sulfuric acid from DMS
oxidation, but to our knowledge, global models typically neglect the impact
of MSA on size distributions.
In this study, we use the GEOS-Chem-TOMAS (GC-TOMAS) global aerosol
microphysics model to determine the impact on aerosol size distributions and
subsequent aerosol radiative effects from including MSA in the size-resolved
portion of the model. The effective equilibrium vapor pressure of MSA is
currently uncertain, and we use the Extended Aerosol Inorganics Model (E-AIM)
to build a parameterization for GC-TOMAS of MSA's effective volatility as a
function of temperature, relative humidity, and available gas-phase bases,
allowing MSA to condense as an ideally nonvolatile or semivolatile species or
too volatile to condense. We also present two limiting cases for MSA's
volatility, assuming that MSA is always ideally nonvolatile (irreversible
condensation) or that MSA is always ideally semivolatile (quasi-equilibrium
condensation but still irreversible condensation). We further present
simulations in which MSA participates in binary and ternary nucleation with
the same efficacy as sulfuric acid whenever MSA is treated as ideally
nonvolatile. When using the volatility parameterization described above (both
with and without nucleation), including MSA in the model changes the global
annual averages at 900 hPa of submicron aerosol mass by 1.2 %, N3
(number concentration of particles greater than 3 nm in diameter) by
â3.9 % (non-nucleating) or 112.5 % (nucleating), N80 by 0.8 %
(non-nucleating) or 2.1 % (nucleating), the cloud-albedo aerosol indirect
effect (AIE) by â8.6 mW mâ2 (non-nucleating) or â26 mW mâ2
(nucleating), and the direct radiative effect (DRE) by â15 mW mâ2
(non-nucleating) or â14 mW mâ2 (nucleating). The sulfate and
sulfuric acid from DMS oxidation produces 4â6 times more submicron mass than
MSA does, leading to an âŒ10 times stronger cooling effect in the DRE.
But the changes in N80 are comparable between the contributions from MSA and
from DMS-derived sulfate/sulfuric acid, leading to comparable changes in the
cloud-albedo AIE.
Modelâmeasurement comparisons with the Heintzenberg et al. (2000) dataset
over the Southern Ocean indicate that the default model has a missing source
or sources of ultrafine particles: the cases in which MSA participates in
nucleation (thus increasing ultrafine number) most closely match the
Heintzenberg distributions, but we cannot conclude nucleation from MSA is the
correct reason for improvement. Modelâmeasurement comparisons with
particle-phase MSA observed with a customized Aerodyne high-resolution
time-of-flight aerosol mass spectrometer (AMS) from the ATom campaign show
that cases with the MSA volatility parameterizations (both with and without
nucleation) tend to fit the measurements the best (as this is the first use
of MSA measurements from ATom, we provide a detailed description of these
measurements and their calibration). However, no one model sensitivity case
shows the best modelâmeasurement agreement for both Heintzenberg and the
ATom campaigns. As there are uncertainties in both MSA's behavior (nucleation
and condensation) and the DMS emissions inventory, further studies on both
fronts are needed to better constrain MSA's past, current, and future impacts
upon the global aerosol size distribution and radiative forcing.</p
Modeling Temporal Trends in Aphid Vector Dispersal and Cucumber Mosaic Virus Epidemics in Snap Bean
Cucumber mosaic virus (CMV) has become a major limiting factor in snap bean production in the Great Lakes region of North America, and epidemics have occurred more frequently since the soybean aphid, Aphis glycines Matsumura, was introduced. Major aphid vectors of CMV epidemics were identified by statistically relating their temporal dispersal trends to the incidence of CMV. Alates were monitored weekly using water pan traps in 74 snap bean fields in New York and Pennsylvania from 2002 to 2006. Plants were tested for CMV by ELISA one time during late bloom in 2002 and 2003 and weekly over the season from 2004 to 2006. Principal vectors of CMV included Acyrthosiphon pisum (Harris), A. glycines, Aphis gossypii Glover, and Therioaphis trifolii (Monell). Among these, A. glycines and T. trifolii were likely responsible for severe CMV epidemics because they were among the most abundant species captured, they efficiently transmit CMV, and their dispersal activity was positively correlated with periods when CMV incidence was highest. Moreover, because high numbers of A. glycines and T. trifolii disperse during July and August, snap bean fields planted beyond late June are at risk for infection during early vegetative stages and are subsequently more at risk for yield loss. In contrast, plantings up to late June are less likely to become infected during early developmental stages and should escape yield loss because major vectors are dispersing infrequently. CMV-resistant or tolerant snap bean varieties should be planted after late June to reduce the risk of yield los
Relating geostationary satellite measurements of aerosol optical depth (AOD) over East Asia to fine particulate matter (PM2.5): Insights from the KORUS-AQ aircraft campaign and GEOS-Chem model simulations
Geostationary satellite measurements of aerosol optical depth (AOD) over East Asia from the Geostationary Ocean Color Imager (GOCI) and Advanced Himawari Imager (AHI) instruments can augment surface monitoring of fine particulate matter (PM2.5) air quality, but this requires better understanding of the AODâPM2.5 relationship. Here we use the GEOS-Chem chemical transport model to analyze the critical variables determining the AODâPM2.5 relationship over East Asia by simulation of observations from satellite, aircraft, and ground-based datasets. This includes the detailed vertical aerosol profiling over South Korea from the KORUS-AQ aircraft campaign (MayâJune 2016) with concurrent ground-based PM2.5 composition, PM10, and AERONET AOD measurements. The KORUS-AQ data show that 550ânm AOD is mainly contributed by sulfateânitrateâammonium (SNA) and organic aerosols in the planetary boundary layer (PBL), despite large dust concentrations in the free troposphere, reflecting the optically effective size and high hygroscopicity of the PBL aerosols. We updated SNA and organic aerosol size distributions in GEOS-Chem to represent aerosol optical properties over East Asia by using in situ measurements of particle size distributions from KORUS-AQ. We find that SNA and organic aerosols over East Asia have larger size (number median radius of 0.11â”m with geometric standard deviation of 1.4) and 20â% larger mass extinction efficiency as compared to aerosols over North America (default setting in GEOS-Chem). Although GEOS-Chem is successful in reproducing the KORUS-AQ vertical profiles of aerosol mass, its ability to link AOD to PM2.5 is limited by under-accounting of coarse PM and by a large overestimate of nighttime PM2.5 nitrate. The GOCIâAHI AOD data over East Asia in different seasons show agreement with AERONET AODs and a spatial distribution consistent with surface PM2.5 network data. The AOD observations over North China show a summer maximum and winter minimum, opposite in phase to surface PM2.5. This is due to low PBL depths compounded by high residential coal emissions in winter and high relative humidity (RH) in summer. Seasonality of AOD and PM2.5 over South Korea is much weaker, reflecting weaker variation in PBL depth and lack of residential coal emissions
Convective transport and scavenging of peroxides by thunderstorms observed over the central U.S. during DC3
One of the objectives of the Deep Convective Clouds and Chemistry (DC3) field experiment was to determine the scavenging of soluble trace gases by thunderstorms. We present an analysis of scavenging of hydrogen peroxide (H_2O_2) and methyl hydrogen peroxide (CH_3OOH) from six DC3 cases that occurred in Oklahoma and northeast Colorado. Estimates of H_2O_2 scavenging efficiencies are comparable to previous studies ranging from 79 to 97% with relative uncertainties of 5â25%. CH_3OOH scavenging efficiencies ranged from 12 to 84% with relative uncertainties of 18â558%. The wide range of CH_3OOH scavenging efficiencies is surprising, as previous studies suggested that CH_3OOH scavenging efficiencies would be <10%. Cloud chemistry model simulations of one DC3 storm produced CH_3OOH scavenging efficiencies of 26â61% depending on the ice retention factor of CH_3OOH during cloud drop freezing, suggesting ice physics impacts CH_3OOH scavenging. The highest CH_3OOH scavenging efficiencies occurred in two severe thunderstorms, but there is no obvious correlation between the CH_3OOH scavenging efficiency and the storm thermodynamic environment. We found a moderate correlation between the estimated entrainment rates and CH_3OOH scavenging efficiencies. Changes in gas-phase chemistry due to lightning production of nitric oxide and aqueous-phase chemistry have little effect on CH_3OOH scavenging efficiencies. To determine why CH_3OOH can be substantially removed from storms, future studies should examine effects of entrainment rate, retention of CH_3OOH in frozen cloud particles during drop freezing, and lightning-NO_x production
Atmospheric Acetaldehyde: Importance of Air-Sea Exchange and a Missing Source in the Remote Troposphere.
We report airborne measurements of acetaldehyde (CH3CHO) during the first and second deployments of the National Aeronautics and Space Administration (NASA) Atmospheric Tomography Mission (ATom). The budget of CH3CHO is examined using the Community Atmospheric Model with chemistry (CAM-chem), with a newly-developed online air-sea exchange module. The upper limit of the global ocean net emission of CH3CHO is estimated to be 34 Tg a-1 (42 Tg a-1 if considering bubble-mediated transfer), and the ocean impacts on tropospheric CH3CHO are mostly confined to the marine boundary layer. Our analysis suggests that there is an unaccounted CH3CHO source in the remote troposphere and that organic aerosols can only provide a fraction of this missing source. We propose that peroxyacetic acid (PAA) is an ideal indicator of the rapid CH3CHO production in the remote troposphere. The higher-than-expected CH3CHO measurements represent a missing sink of hydroxyl radicals (and halogen radical) in current chemistry-climate models
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Interferences on aerosol acidity quantification due to gas-phase ammonia uptake onto acidic sulfate filter samples
Measurements of the mass concentration and chemical speciation of aerosols are important to investigate their chemical and physical processing from near emission sources to the most remote regions of the atmosphere. A common method to analyze aerosols is to collect them onto filters and analyze the filters offline; however, biases in some chemical components are possible due to changes in the accumulated particles during the handling of the samples. Any biases would impact the measured chemical composition, which in turn affects our understanding of numerous physicochemical processes and aerosol radiative properties. We show, using filters collected onboard the NASA DC-8 and NSF C-130 during six different aircraft campaigns, a consistent, substantial difference in ammonium mass concentration and ammonium-to-anion ratios when comparing the aerosols collected on filters versus an Aerodyne aerosol mass spectrometer (AMS). Another online measurement is consistent with the AMS in showing that the aerosol has lower ammonium-to-anion ratios than obtained by the filters. Using a gas uptake model with literature values for accommodation coefficients, we show that for ambient ammonia mixing ratios greater than 10âppbv, the timescale for ammonia reacting with acidic aerosol on filter substrates is less than 30âs (typical filter handling time in the aircraft) for typical aerosol volume distributions. Measurements of gas-phase ammonia inside the cabin of the DC-8 show ammonia mixing ratios of 45±20âppbv, consistent with mixing ratios observed in other indoor environments. This analysis enables guidelines for filter handling to reduce ammonia uptake. Finally, a more meaningful limit of detection for University of New Hampshire Soluble Acidic Gases and Aerosol (SAGA) filters collected during airborne campaigns is âŒ0.2â”gâsmâ3 of ammonium, which is substantially higher than the limit of detection of ion chromatography. A similar analysis should be conducted for filters that collect inorganic aerosol and do not have ammonia scrubbers and/or are handled in the presence of human ammonia emissions
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