Although numerous epidemiological studies have shown that inorganic arsenicals cause skin cancers and hyperkeratoses in humans, there are currently no established mechanisms for their action or ...animal models. Previous studies in our laboratory using primary human keratinocyte cultures demonstrated that micromolar concentrations of inorganic arsenite increased cell proliferation via the production of keratinocyte-derived growth factors. As recent reports demonstrate that overexpression of keratinocyte-derived growth factors, such as transforming growth factor (TGF)-α, promote the formation of skin tumors, we hypothesized that similar events may be responsible for those associated with arsenic skin diseases. Thus, the influence of arsenic in humans with arsenic skin disease and on mouse skin tumor development in transgenic mice was studied. After low-dose application of tetradecanoyl phorbol acetate (TPA), a marked increase in the number of skin papillomas occurred in Tg.AC mice, which carry the v-Ha-
rasoncogene, that received arsenic in the drinking water as compared with control drinking water, whereas no papillomas developed in arsenic-treated transgenic mice that did not receive TPA or arsenic/TPA-treated wild-type FVB/N mice. Consistent with earlier
in vitro findings, increases in granulocyte/macrophage colony-stimulating factor (GM-CSF) and TGF-α mRNA transcripts were found in the epidermis at clinically normal sites within 10 weeks after arsenic treatment. Immunohistochemical staining localized TGF-α overexpression to the hair follicles. Injection of neutralizing antibodies to GM-CSF after TPA application reduced the number of papillomas in Tg.AC mice. Analysis of gene expression in samples of skin lesions obtained from humans chronically exposed to arsenic via their drinking water also showed similar alterations in growth factor expression. Although confirmation will be required in nontransgenic mice, these results suggest that arsenic enhances development of skin neoplasias via the chronic stimulation of keratinocyte-derived growth factors and may be a rare example of a chemical carcinogen that acts as a co-promoter.
Solar-aided upgrade of the energy content of fossil fuels, such as natural gas, can provide a near-term transition path towards a future solar-fuel economy and reduce carbon dioxide emission from ...fossil fuel consumption. Both steam and dry reforming a methane-containing fuel stream have been studied with concentrated solar power as the energy input to drive the highly endothermic reactions but the concept has not been demonstrated at a commercial scale. Under a current project with the U.S. Department of Energy, PNNL is developing an integrated solar thermochemical reaction system that combines solar concentrators with micro- and meso-channel reactors and heat exchangers to accomplish more than 20% solar augment of methane higher heating value. The objective of our three-year project is to develop and prepare for commercialization such solar reforming system with a high enough efficiency to serve as the frontend of a conventional natural gas (or biogas) combined cycle power plant, producing power with a levelized cost of electricity less than 6¢/kWh, without subsidies, by the year 2020. In this paper, we present results from the first year of our project that demonstrated a solar-to-chemical energy conversion efficiency as high as 69% with a prototype reaction system.
We analyze the precursor of a Forbush decrease (FD) observed with the Global Muon Detector Network on 2006 December 14. An intense geomagnetic storm is also recorded during this FD with the peak Kp ...index of 8+. By using the 'two-dimensional map' of the cosmic ray intensity produced after removing the contribution from the diurnal anisotropy, we succeed in extracting clear signatures of the precursor. A striking feature of this event is that a weak loss-cone (LC) signature is first recorded more than a day prior to the storm sudden commencement (SSC) onset. This suggests that the LC precursor appeared only 7 hr after the coronal mass ejection eruption from the Sun, when the interplanetary (IP) shock driven by the interplanetary coronal mass ejection was located at 0.4 AU from the Sun. We find the precursor being successively observed with multiple detectors in the network according to the Earth's spin and confirmed that the precursor continuously exists in space. The long lead time (15.6 hr) of this precursor which is almost twice the typical value indicates that the interplanetary magnetic field (IMF) was more quiet in this event than a typical power spectrum assumed for the IMF turbulence. The amplitude (-6.45%) of the LC anisotropy at the SSC onset is more than twice the FD size, indicating that the maximum intensity depression behind the IP shock is much larger than the FD size recorded at the Earth in this event. We also find the excess intensity from the sunward IMF direction clearly observed during {approx}10 hr preceding the SSC onset. It is shown that this excess intensity is consistent with the measurement of the particles accelerated by the head-on collisions with the approaching shock. This is the first detailed observation of the precursor due to the shock reflected particles with muon detectors.
Pacific Northwest National Laboratory reports on the detection of 39Ar at the location of an underground nuclear explosion on the Nevada Nuclear Security Site. The presence of 39Ar was not ...anticipated at the outset of the experimental campaign but results from this work demonstrated that it is present, along with 37Ar and 85Kr in the subsurface at the site of an underground nuclear explosion. Our analysis showed that by using state-of-the-art technology optimized for radioargon measurements, it was difficult to distinguish 39Ar from the fission product 85Kr. Proportional counters are currently used for high-sensitivity measurement of 37Ar and 39Ar. Physical and chemical separation processes are used to separate argon from air or soil gas, yielding pure argon with contaminant gases reduced to the parts-per-million level or below. However, even with purification at these levels, the beta decay signature of 85Kr can be mistaken for that of 39Ar, and the presence of either isotope increases the measurement background level for the measurement of 37Ar. Measured values for the 39Ar measured at the site ranged from 36,000 milli- Becquerel/standard-cubic-meter-of-air (mBq/SCM) for shallow bore holes to 997,000 mBq/SCM from the rubble chimney from the underground nuclear explosion.
•We report on the detection of 39Ar at the location of an underground nuclear explosion on the Nevada Nuclear Security Site.•Argon-39 was detected, along with 37Ar and 85Kr in the subsurface at the Barnwell underground nuclear explosion.•These isotopes are produced through fission (85Kr) through the 40Ca(n, alpha) 37Ar reaction or 39K(n, p) 39Ar reaction.•Measured values for the 39Ar ranged from 36,000 (mBq/SCM) for shallow bore holes to 997,000 mBq/SCM from the rubble chimney.•Argon-39 and 85Kr, could interfere with gas sampling and detection equipment used in an on-site inspection.
We demonstrate that global observations of high‐energy cosmic rays contribute to understanding unique characteristics of a large‐scale magnetic flux rope causing a magnetic storm in August 2018. ...Following a weak interplanetary shock on August 25, 2018, a magnetic flux rope caused an unexpectedly large geomagnetic storm. It is likely that this event became geoeffective because the flux rope was accompanied by a corotating interaction region and compressed by high‐speed solar wind following the flux rope. In fact, a Forbush decrease was observed in cosmic‐ray data inside the flux rope as expected, and a significant cosmic‐ray density increase exceeding the unmodulated level before the shock was also observed near the trailing edge of the flux rope. The cosmic‐ray density increase can be interpreted in terms of the adiabatic heating of cosmic rays near the trailing edge of the flux rope, as the corotating interaction region prevents free expansion of the flux rope and results in the compression near the trailing edge. A northeast‐directed spatial gradient in the cosmic‐ray density was also derived during the cosmic‐ray density increase, suggesting that the center of the heating near the trailing edge is located northeast of Earth. This is one of the best examples demonstrating that the observation of high‐energy cosmic rays provides us with information that can only be derived from the cosmic ray measurements to observationally constrain the three‐dimensional macroscopic picture of the interaction between coronal mass ejections and the ambient solar wind, which is essential for prediction of large magnetic storms.
Key Points
We derived the spatial distribution of cosmic rays associated with a peculiar interplanetary counterpart of a coronal mass ejection event that caused a large magnetic storm in August 2018
We found a cosmic‐ray density increase possibly resulting from the magnetic flux rope compression by the following faster solar wind
The Global Muon Detector Network observed this density increase as a macroscopic modification of this geoeffective flux rope
ABSTRACT We analyze the galactic cosmic ray (GCR) density and its spatial gradient in Forbush Decreases (FDs) observed with the Global Muon Detector Network (GMDN) and neutron monitors (NMs). By ...superposing the GCR density and density gradient observed in FDs following 45 interplanetary shocks (IP-shocks), each associated with an identified eruption on the Sun, we infer the average spatial distribution of GCRs behind IP-shocks. We find two distinct modulations of GCR density in FDs, one in the magnetic sheath and the other in the coronal mass ejection (CME) behind the sheath. The density modulation in the sheath is dominant in the western flank of the shock, while the modulation in the CME ejecta stands out in the eastern flank. This east-west asymmetry is more prominent in GMDN data responding to ∼60 GV GCRs than in NM data responding to ∼10 GV GCRs, because of the softer rigidity spectrum of the modulation in the CME ejecta than in the sheath. The geocentric solar ecliptic-y component of the density gradient, Gy, shows a negative (positive) enhancement in FDs caused by the eastern (western) eruptions, while Gz shows a negative (positive) enhancement in FDs caused by the northern (southern) eruptions. This implies that the GCR density minimum is located behind the central flank of IP-shocks and propagating radially outward from the location of the solar eruption. We also confirmed that the average Gz changes its sign above and below the heliospheric current sheet, in accord with the prediction of the drift model for the large-scale GCR transport in the heliosphere.
Recent threats to groundwater quality in the UK (arising from leaking sewers and burial pits used during the recent Foot and Mouth Disease epidemic) have highlighted the need to understand the fate ...and transport of pathogenic viruses in the subsurface so that a robust assessment of their potential threat to environmental and public health can be made. Non-hazardous microbial tracers (phage) that mimic the movement of pathogenic microorganisms through groundwater systems are being used. Bacteriophage have good potential as surrogates to help us better understand the fate and transport of viral pathogens and are discussed here in the light of their injection as tracers into UK aquifers. Specific bacteriophages (MS2, PRD1 and ϕX174) that exhibit good potential as tracers and have properties similar to pathogenic viruses of interest are discussed.
High Throughput Argon-37 Field System Hayes, James C.; Aalseth, Craig E.; Alexander, Thomas R. ...
Pure and applied geophysics,
10/2020, Letnik:
178
Journal Article
Recenzirano
Odprti dostop
We report Pacific Northwest National Laboratory (PNNL) has developed a unique fieldable 37Ar measurement system designed to measure 37Ar activity concentrations from soil gas samples to detect above ...ground and underground nuclear explosions. The Argon-37 Field System is modular in design to accommodate both chemical processing and nuclear detection. The system can be packed into shipping crates and shipped to a location near where the sampling is taking place. The system can process six 2-m3 whole-air samples in 24 hours and can measure the 37Ar activity in each of the samples using six proportional counters. The proportional counters, designed and built at PNNL, are surrounded with both active and passive shielding to reduce background and can achieve a minimum detection concentration of 10 mBq/m3 of 37Ar in whole-air equivalent. The Argon-37 Field System has undergone extensive testing against rigorous requirements to assure the system meets the needs of the noble gas nuclear explosion monitoring community.
As part of an underground gas migration study, two radioactive noble gases (37Ar and 127Xe) and two stable tracer gases (SF6 and PFDMCH) were injected into a historic nuclear explosion test chimney ...and allowed to migrate naturally. The purpose of this experiment was to provide a bounding case (natural transport) for the flow of radioactive noble gases following an underground nuclear explosion. To accomplish this, soil gas samples were collected from a series of boreholes and a range of depths from the shallow subsurface (3 m) to deeper levels (~160 m) over a period of eleven months. These samples have provided insights into the development and evolution of the subsurface plume and constrained the relative migration rates of the radioactive and stable gas species in the case when the driving pressure from the cavity is low. Analysis of the samples concluded that the stable tracer SF6 was consistently enriched in the subsurface samples relative to the radiotracer 127Xe, but the ratios of SF6 and 37Ar remained similar throughout the samples.
•Stable and radioactive tracer gases were injected into a historic nuclear test chimney.•Tracer sampling conducted for 11 months at multiple locations around site.•Dilutions of 37Ar and SF6 were similar while 127Xe was more dilute.•SF6 was found to be a more accurate surrogate tracer than PFDMCH (C8F16).
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