In a changing climate, potential stratospheric circulation changes require long-term monitoring. Stratospheric trace gas measurements are often used as a proxy for stratospheric circulation changes ...via the “mean age of air” values derived from them. In this study, we investigated five potential age of air tracers – the perfluorocarbons CF4, C2F6 and C3F8 and the hydrofluorocarbons CHF3 (HFC-23) and HFC-125 – and compare them to the traditional tracer SF6 and a (relatively) shorter-lived species, HFC-227ea. A detailed uncertainty analysis was performed on mean ages derived from these “new” tracers to allow us to confidently compare their efficacy as age tracers to the existing tracer, SF6. Our results showed that uncertainties associated with the mean age derived from these new age tracers are similar to those derived from SF6, suggesting that these alternative compounds are suitable in this respect for use as age tracers. Independent verification of the suitability of these age tracers is provided by a comparison between samples analysed at the University of East Anglia and the Scripps Institution of Oceanography. All five tracers give younger mean ages than SF6, a discrepancy that increases with increasing mean age. Our findings qualitatively support recent work that suggests that the stratospheric lifetime of SF6 is significantly less than the previous estimate of 3200 years. The impact of these younger mean ages on three policy-relevant parameters – stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials – is investigated in combination with a recently improved methodology to calculate FRFs. Updates to previous estimations for these parameters are provided.
Methanol is the second‐most abundant organic gas in the remote atmosphere after methane, but its sources are poorly understood. Here, we report a global budget of methanol constrained by observations ...from the ATom aircraft campaign as implemented in the GEOS‐Chem global atmospheric chemistry model. ATom observations under background marine conditions can be fit in the model with a surface ocean methanol concentration of 61 nM and a methanol yield of 13% from the newly implemented CH3O2 + OH reaction. While terrestrial biogenic emissions dominate the global atmospheric methanol budget, secondary production from CH3O2 + OH and CH3O2 + CH3O2 accounts for 29% of the total methanol source, and makes up the majority of methanol in the background marine atmosphere sampled by ATom. Net emission from the ocean is comparatively minor, particularly because of rapid deposition from the marine boundary layer. Aged anthropogenic and pyrogenic plumes sampled in ATom featured large methanol enhancements to constrain the corresponding sources. Methanol enhancements in pyrogenic plumes did not decay with age, implying in‐plume secondary production. The atmospheric lifetime of methanol is only 5.3 days, reflecting losses of comparable magnitude from photooxidation and deposition. GEOS‐Chem model results indicate that methanol photochemistry contributes 5%, 4%, and 1.5% of the tropospheric burdens of formaldehyde, CO, and ozone, respectively, with particularly pronounced effects in the tropical upper troposphere. The CH3O2 + OH reaction has substantial impacts on radical budgets throughout the troposphere and should be included in global atmospheric chemistry models.
Plain Language Summary
Methanol is the most abundant nonmethane organic gas in the lower atmosphere, but the magnitudes of its sources and sinks remain uncertain. Here, we evaluate a global atmospheric chemistry model against recent observations of methanol in the remote atmosphere to better constrain the methanol budget. We show that, relative to past studies, the new data suggest a smaller atmospheric methanol source from the ocean and a larger source from gas‐phase chemistry. Methanol emitted from the oceans plays a particularly small role in the atmosphere because it is quickly deposited back to the ocean surface. We incorporate these updates into the global model and evaluate their importance for atmospheric chemistry more broadly, showing that methanol directly and indirectly influences the abundances of many other tropospheric trace gases.
Key Points
Chemical production is the dominant source of background methanol in the remote troposphere
The ocean is a net sink of atmospheric methanol and provides only a minor methanol source to the marine boundary layer
The CH3O2 + OH reaction plays a key role in the atmospheric budgets not only of methanol but of many tropospheric radical species
Transporters of the Nramp (Natural resistance-associated macrophage protein) family import divalent transition metal ions into cells of most organisms. By supporting metal homeostasis, Nramps prevent ...diseases and disorders related to metal insufficiency or overload. Previous studies revealed that Nramps take on a LeuT fold and identified the metal-binding site. We present high-resolution structures of
Deinococcus radiodurans
(Dra)Nramp in three stable conformations of the transport cycle revealing that global conformational changes are supported by distinct coordination geometries of its physiological substrate, Mn
2+
, across conformations, and by conserved networks of polar residues lining the inner and outer gates. In addition, a high-resolution Cd
2+
-bound structure highlights differences in how Cd
2+
and Mn
2+
are coordinated by DraNramp. Complementary metal binding studies using isothermal titration calorimetry with a series of mutated DraNramp proteins indicate that the thermodynamic landscape for binding and transporting physiological metals like Mn
2+
is different and more robust to perturbation than for transporting the toxic Cd
2+
metal. Overall, the affinity measurements and high-resolution structural information on metal substrate binding provide a foundation for understanding the substrate selectivity of essential metal ion transporters like Nramps.
We use a modified version of the tropical leaky pipe (TLP) model of the stratosphere to explore how well an idealized model can (1) reproduce global chemistry‐climate model (CCM) output and (2) ...constrain transport characteristics necessary to replicate measurements of long‐lived trace gases. The version of the TLP model we use includes the simulation of long‐lived trace gases, such as SF6 and CO2, as well as photochemically active trace gases such as CFC‐11, CFC‐12, and N2O. The TLP model was found to accurately replicate trace gas output from the Canadian Middle Atmosphere Model (CMAM) for time‐averaged profiles in the tropics and each extratropical region. Given confidence that the TLP model represents the basic transport features in CMAM we then used the TLP model to interpret differences between CMAM output and measurements from the Atmospheric Chemistry Experiment and balloons. The TLP model is shown to uniquely determine residual mean circulation and recirculation (mixing between the extratropics and tropics) changes necessary for CMAM to more accurately simulate the measurements. Such guidance on these transport parameters is novel due to the relatively high precision and the simultaneous derivation of important parameters, as compared to previous studies. The TLP model can ideally be used as a bridge between measurements and CCMs to potentially allow more targeted modification of the CCMs than would otherwise be possible.
Key Points
Idealized stratospheric model accurately simulates CMAM trace gas and mean age profiles
Idealized model provides quantitative transport guidance for CCM to better simulate observations
Specific suite of trace gas measurements provides unique transport information to validate CCMs
The details of aerosol processes and size distributions
in the stratosphere are important for both heterogeneous chemistry and
aerosol–radiation interactions. Using in situ, global-scale measurements ...of
the size distribution of particles with diameters > 3 nm from the
NASA Atmospheric Tomography Mission (ATom), we identify a mode of aerosol
smaller than 12 nm in the lowermost stratosphere (LMS) at mid- and high
latitudes. This mode is substantial only in the Northern Hemisphere (NH)
and was observed in all four seasons. We also observe elevated SO2, an
important precursor for new particle formation (NPF) and growth, in the NH
LMS. We use box modelling and thermodynamic calculations to show that NPF
can occur in the LMS conditions observed on ATom. Aircraft emissions are
shown as likely sources of this SO2, as well as a potential source of
nucleation mode particles directly emitted by or formed in the plume of the
engines. These nucleation mode particles have the potential to grow to
larger sizes and to coagulate with larger aerosol, affecting heterogeneous
chemistry and aerosol–radiation interactions. Understanding all sources and
characteristics of stratospheric aerosols is important in the context of
anthropogenic climate change as well as proposals for climate intervention
via stratospheric sulfur injection. This analysis not only adds to the,
currently sparse, observations of the global impact of aviation, but also
introduces another aspect of climate influence, namely a size distribution
shift of the background aerosol distribution in the LMS.
The NASA ER-2 aircraft sampled the lower stratosphere over North America during the field mission for the NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by ...Regional Surveys (SEAC4RS). This study reports observations of convectively influenced air parcels with enhanced water vapor in the overworld stratosphere over the summertime continental United States and investigates three case studies in detail. Water vapor mixing ratios greater than 10 ppmv, which is much higher than the background 4 to 6 ppmv of the overworld stratosphere, were measured by the JPL Laser Hygrometer (JLH Mark2) at altitudes between 16.0 and 17.5 km (potential temperatures of approximately 380 to 410 K). Overshooting cloud tops (OTs) are identified from a SEAC4RS OT detection product based on satellite infrared window channel brightness temperature gradients. Through trajectory analysis, we make the connection between these in situ water measurements and OT. Back trajectory analysis ties enhanced water to OT 1 to 7 days prior to the intercept by the aircraft. The trajectory paths are dominated by the North American monsoon (NAM) anticyclonic circulation. This connection suggests that ice is convectively transported to the overworld stratosphere in OT events and subsequently sublimated; such events may irreversibly enhance stratospheric water vapor in the summer over Mexico and the United States. A regional context is provided by water observations from the Aura Microwave Limb Sounder (MLS).
Variability in the strength of the stratospheric Lagrangian mean meridional or Brewer‐Dobson circulation and horizontal mixing into the tropics over the past three decades are examined using ...observations of stratospheric mean age of air and ozone. We use a simple representation of the stratosphere, the tropical leaky pipe (TLP) model, guided by mean meridional circulation and horizontal mixing changes in several reanalyses data sets and chemistry climate model (CCM) simulations, to help elucidate reasons for the observed changes in stratospheric mean age and ozone. We find that the TLP model is able to accurately simulate multiyear variability in ozone following recent major volcanic eruptions and the early 2000s sea surface temperature changes, as well as the lasting impact on mean age of relatively short‐term circulation perturbations. We also find that the best quantitative agreement with the observed mean age and ozone trends over the past three decades is found assuming a small strengthening of the mean circulation in the lower stratosphere, a moderate weakening of the mean circulation in the middle and upper stratosphere, and a moderate increase in the horizontal mixing into the tropics. The mean age trends are strongly sensitive to trends in the horizontal mixing into the tropics, and the uncertainty in the mixing trends causes uncertainty in the mean circulation trends. Comparisons of the mean circulation and mixing changes suggested by the measurements with those from a recent suite of CCM runs reveal significant differences that may have important implications on the accurate simulation of future stratospheric climate.
ONC201 was initially identified as an inducer of cell death through the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathway. The compound is currently being tested in patients ...with hematological malignancies and solid tumors, including those of the breast. We investigated strategies to convert the response of breast cancers to ONC201 from anti-proliferative to apoptotic. ONC201 treatment upregulates TRAIL and primes TRAIL-resistant non-triple negative breast cancer (TNBC) cells to undergo cell death through the extrinsic pathway. Remarkably, the addition of exogenous recombinant human TRAIL (rhTRAIL) converts the response of TRAIL-resistant non-TNBC cells to ONC201 from anti-proliferative to apoptotic in a death receptor 5 (DR5)-dependent manner
in vitro
. Importantly, normal fibroblasts do not undergo apoptosis following rhTRAIL plus ONC201.
In vivo
, MDA-MB-361 tumor growth rate is significantly reduced following treatment with a combination of ONC201 and rhTRAIL as compared to control tumors. Natural killer (NK) cells which use TRAIL to kill DR5-expressing cancer cells, exhibit greater cytotoxicity against ONC201-treated breast cancer cells compared to controls. rhTRAIL also converts the response of cells from other tumor types to ONC201 from anti-proliferative to apoptotic. A monoclonal DR5-agonistic antibody converts the response of non-TNBC cells to ONC201 from anti-proliferative to apoptotic. Our findings describe a novel therapeutic strategy that potently converts the response of a cancer cell to ONC201 from anti-proliferative to apoptotic. This approach may be clinically relevant and has potential to induce tumor regression of patient tumors with relative resistance to ONC201 monotherapy.
Coccidiosis is an intestinal disease caused by protozoal parasites of the genus Eimeria. Despite the advent of anti-coccidial drugs and vaccines, the disease continues to result in substantial annual ...economic losses to the poultry industry. There is still much unknown about the host response to infection and to date there are no reports of protein profiles in the blood of Eimeria-infected animals. The objective of this study was to evaluate the serum proteome of two genetic lines of broiler chickens after infection with one of three species of Eimeria.
Birds from lines A and B were either not infected or inoculated with sporulated oocysts from one of the three Eimeria strains at 15 d post-hatch. At 21 d (6 d post-infection), whole blood was collected and lesion scoring was performed. Serum was harvested and used for 2-dimensional gel electrophoresis. A total of 1,266 spots were quantitatively assessed by densitometry. Protein spots showing a significant effect of coccidia strain and/or broiler genetic line on density at P<0.05-0.01 (250 spots), P<0.01-0.001 (248 spots), and P<0.001 (314 spots) were excised and analyzed by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry. Proteins were identified in 172 spots. A total of 46 different proteins were identified. Of the spots with a corresponding protein identification, 57 showed a main effect of coccidia infection and/or 2-way interaction of coccidia infection×broiler genetic line at P<0.001.
Several of the metabolic enzymes identified in this study are potential candidates for early diagnostic markers of E. acervulina infection including malate dehydrogenase 2, NADH dehydrogenase 1 alpha subcomplex 9, and an ATP synthase. These proteins were detected only in Line A birds that were inoculated with E. acervulina. Results from this study provide a basic framework for future research aimed at uncovering the complex biochemical mechanisms involved in host response to Eimeria infection and in identifying molecular targets for diagnostic screening and development of alternative preventative and therapeutic methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Research on environmental governance in China has shown that centre–local relations often influence the implementation and efficacy of environmental regulations. By examining changes in resource ...allocation and rural development between 1982 and 2005 in the region worst affected by desertification in China—the Minqin oasis in Gansu—we argue that changes in macro‐level fiscal and commodity grain policies contributed to severe regional disparity and a reduction in local state capacity in hinterland China. Intergovernmental competition over fiscal revenue encouraged cash cropping and land reclamation, and the continuous decline of the oasis ecology further reduced legitimacy in rural governance. These institutional and ecological constraints shaped the behaviour of grassroots cadres and formed the conflicting interests of the state in resource distribution and environmental conservation that continued to exist until the implementation of a centralized conservation program in 2006. The data came from 157 interviews and 628 policy documents from local archives in Gansu.
PDF
