Cervical tracheogenic air cyst. Apropos of 2 cases

The authors report 2 cases of gas-containing cervical cysts. Surgical excision by cervicotomy showed that both of these well-defined cysts were attached to the right border of the cervical trachea by a blind "pseudo-pedicle" and were lined with respiratory-type epithelium. These were 2 tracheogenic cysts, analogous to bronchogenic cysts theoretically linked to an abnormality in the development of the bronchial buds during embryogenesis. These two cases were exceptional not only by virtue of their cervical site, but also the fact that they contained air and occurred in already old women.     

Foxa2 is required for transition to air breathing at birth

Toward the end of gestation in mammals, the fetal lung undergoes a process of differentiation that is required for transition to air breathing at birth. Respiratory epithelial cells synthesize the surfactant proteins and lipids that together form the pulmonary surfactant complex necessary for lung function. Failure of this process causes respiratory distress syndrome, a leading cause of perinatal death and morbidity in newborn infants. Here we demonstrate that expression of the forkhead gene Foxa2 in respiratory epithelial cells of the peripheral lung controls pulmonary maturation at birth. Newborn mice lacking Foxa2 expression in the lung develop severe pulmonary disease on the first day of life, with all of the morphological, molecular, and biochemical features of respiratory distress syndrome in preterm infants, including atelectasis, hyaline membranes, and the lack of pulmonary surfactant lipids and proteins. RNA microarray analysis at embryonic day 18.5 demonstrated that Foxa2-regulated expression of a group of genes mediating surfactant protein and lipid synthesis, host defense, and antioxidant production. Foxa2 regulates a complex pulmonary program of epithelial cell maturation required for transition to air breathing at birth.     

Economic and energetic analysis of capturing CO2 from ambient air

Capturing carbon dioxide from the atmosphere (“air capture”) in an industrial process has been proposed as an option for stabilizing global CO₂ concentrations. Published analyses suggest these air capture systems may cost a few hundred dollars per tonne of CO₂, making it cost competitive with mainstream CO₂ mitigation options like renewable energy, nuclear power, and carbon dioxide capture and storage from large CO₂ emitting point sources. We investigate the thermodynamic efficiencies of commercial separation systems as well as trace gas removal systems to better understand and constrain the energy requirements and costs of these air capture systems. Our empirical analyses of operating commercial processes suggest that the energetic and financial costs of capturing CO₂ from the air are likely to have been underestimated. Specifically, our analysis of existing gas separation systems suggests that, unless air capture significantly outperforms these systems, it is likely to require more than 400 kJ of work per mole of CO₂, requiring it to be powered by CO₂-neutral power sources in order to be CO₂ negative. We estimate that total system costs of an air capture system will be on the order of $1,000 per tonne of CO₂, based on experience with as-built large-scale trace gas removal systems.     

Direct electrolytic dissolution of silicate minerals for air CO2 mitigation and carbon-negative H2 production

We experimentally demonstrate the direct coupling of silicate mineral dissolution with saline water electrolysis and H₂ production to effect significant air CO₂ absorption, chemical conversion, and storage in solution. In particular, we observed as much as a 10⁵-fold increase in OH⁻ concentration (pH increase of up to 5.3 units) relative to experimental controls following the electrolysis of 0.25 M Na₂SO₄ solutions when the anode was encased in powdered silicate mineral, either wollastonite or an ultramafic mineral. After electrolysis, full equilibration of the alkalized solution with air led to a significant pH reduction and as much as a 45-fold increase in dissolved inorganic carbon concentration. This demonstrated significant spontaneous air CO₂ capture, chemical conversion, and storage as a bicarbonate, predominantly as NaHCO₃. The excess OH⁻ initially formed in these experiments apparently resulted via neutralization of the anolyte acid, H₂SO₄, by reaction with the base mineral silicate at the anode, producing mineral sulfate and silica. This allowed the NaOH, normally generated at the cathode, to go unneutralized and to accumulate in the bulk electrolyte, ultimately reacting with atmospheric CO₂ to form dissolved bicarbonate. Using nongrid or nonpeak renewable electricity, optimized systems at large scale might allow relatively high-capacity, energy-efficient (<300 kJ/mol of CO₂ captured), and inexpensive (<$100 per tonne of CO₂ mitigated) removal of excess air CO₂ with production of carbon-negative H₂. Furthermore, when added to the ocean, the produced hydroxide and/or (bi)carbonate could be useful in reducing sea-to-air CO₂ emissions and in neutralizing or offsetting the effects of ongoing ocean acidification.     

The urgency of the development of CO2 capture from ambient air

CO(2) capture and storage (CCS) has the potential to develop into an important tool to address climate change. Given society's present reliance on fossil fuels, widespread adoption of CCS appears indispensable for meeting stringent climate targets. We argue that for conventional CCS to become a successful climate mitigation technology-which by necessity has to operate on a large scale-it may need to be complemented with air capture, removing CO(2) directly from the atmosphere. Air capture of CO(2) could act as insurance against CO(2) leaking from storage and furthermore may provide an option for dealing with emissions from mobile dispersed sources such as automobiles and airplanes.     

Detection of SARS-CoV-2 in exhaled air using non-invasive embedded strips in masks

BackgroundSARS-CoV-2 emerged in 2019 and resulted in a pandemic causing millions of infections worldwide. Gold-standard for SARS-CoV-2 detection uses quantitative RT-qPCR on respiratory secretions to detect viral RNA (vRNA). Acquiring these samples is invasive, can be painful for those with xerostomia and other health conditions, and sample quality can vary greatly. Frequently only symptomatic individuals are tested even though asymptomatic individuals can have comparable viral loads and efficiently transmit virus.MethodsWe utilized a non-invasive approach to detect SARS-CoV-2 in individuals, using polyvinyl alcohol (PVA) strips embedded in KN95 masks. PVA strips were tested for SARS-CoV-2 vRNA via qRT-PCR and infectious virus.ResultsWe show efficient recovery of vRNA and infectious virus from virus-spiked PVA with detection limits comparable to nasal swab samples. In infected individuals, we detect both human and SARS-CoV-2 RNA on PVA strips, however, these levels are not correlated with length of time mask was worn, number of times coughed or sneezed, or level of virus in nasal swab samples. We successfully cultured and deep-sequenced PVA-associated virus.ConclusionsThese results demonstrate the feasibility of using PVA-embedded masks as a non-invasive platform for detecting SARS-CoV-2 in exhaled air in COVID-positive individuals regardless of symptom status.     

SARS-CoV-2 Detection in air samples from inside heating,ventilation, and air conditioning (HVAC) systems- COVID surveillance in student dorms

BackgroundThe COVID-19 pandemic affected universities and institutions and caused campus shutdowns with a transition to online teaching models. To detect infections that might spread on campus, we pursued research towards detecting SARS-CoV-2 in air samples inside student dorms.MethodsWe sampled air in 2 large dormitories for 3.5 months and a separate isolation suite containing a student who had tested positive for COVID-19. We developed novel techniques employing 4 methods to collect air samples: Filter Cassettes, Button Sampler, BioSampler, and AerosolSense sampler combined with direct qRT-PCR SARS-CoV-2 analysis.ResultsFor the 2 large dorms with the normal student population, we detected SARS-CoV-2 in 11 samples. When compared with student nasal swab qRT-PCR testing, we detected SARS-CoV-2 in air samples when a PCR positive COVID-19 student was living on the same floor of the sampling location with a detection rate of 75%. For the isolation dorm, we had a 100% SARS-CoV-2 detection rate with AerosolSense sampler.ConclusionsOur data suggest air sampling may be an important SARS-CoV-2 surveillance technique, especially for buildings with congregant living settings (dorms, correctional facilities, barracks). Future building designs and public health policies should consider implementation of Heating, Ventilation, and Air Conditioning surveillance.     

Traffic-related air pollution and respiratory health during the first 2 yrs of life.

As part of an international collaborative study on the impact of Traffic-Related Air Pollution on Childhood Asthma (TRAPCA), the health effects associated with long-term exposure to particles with a 50% cut-off aerodynamic diameter of 2.5 microm (PM2.5), PM2.5 absorbance, and nitrogen dioxide (NO2) were analysed. The German part of the TRAPCA study used data from subpopulations of two ongoing birth cohort studies (German Infant Nutrition Intervention Programme (GINI) and Influences of Lifestyle Related Factors on the Human Immune System and Development of Allergies in Children (LISA)) based in the city of Munich. Geographic information systems (GIS)-based exposure modelling was used to estimate traffic-related air pollutants at the birth addresses of 1,756 infants. Logistic regression was used to analyse possible health effects and potential confounding factors were adjusted for. The ranges in estimated exposures to PM2.5, PM2.5 absorbance, and NO2 were 11.9-21.9 microg m(-3), 1.38-4.39 x 10(-5) m(-1), and 19.5-66.9 microg x m3, respectively. Significant associations between these pollutants and cough without infection (odds ratio (OR) (95% confidence interval (CI)): 1.34 (1.11-1.61), 1.32 (1.10-1.59), and 1.40 (1.12-1.75), respectively) and dry cough at night (OR (95% CI): 1.31 (1.07-1.60), 1.27 (1.04-1.55), and 1.36 (1.07-1.74), respectively) in the first year of life were found. In the second year of life, these effects were attenuated. There was some indication of an association between traffic-related air pollution and symptoms of cough. Due to the very young age of the infants, it was too early to draw definitive conclusions from this for the development of asthma.     

H2 in Antarctic firn air: Atmospheric reconstructions and implications for anthropogenic emissions

The atmospheric history of molecular hydrogen (H₂) from 1852 to 2003 was reconstructed from measurements of firn air collected at Megadunes, Antarctica. The reconstruction shows that H₂ levels in the southern hemisphere were roughly constant near 330 parts per billion (ppb; nmol H₂ mol⁻¹ air) during the mid to late 1800s. Over the twentieth century, H₂ levels rose by about 70% to 550 ppb. The reconstruction shows good agreement with the H₂ atmospheric history based on firn air measurements from the South Pole. The broad trends in atmospheric H₂ over the twentieth century can be explained by increased methane oxidation and anthropogenic emissions. The H₂ rise shows no evidence of deceleration during the last quarter of the twentieth century despite an expected reduction in automotive emissions following more stringent regulations. During the late twentieth century, atmospheric CO levels decreased due to a reduction in automotive emissions. It is surprising that atmospheric H₂ did not respond similarly as automotive exhaust is thought to be the dominant source of anthropogenic H_2. The monotonic late twentieth century rise in H₂ levels is consistent with late twentieth-century flask air measurements from high southern latitudes. An additional unknown source of H₂ is needed to explain twentieth-century trends in atmospheric H₂ and to resolve the discrepancy between bottom-up and top-down estimates of the anthropogenic source term. The firn air–based atmospheric history of H₂ provides a baseline from which to assess human impact on the H₂ cycle over the last 150 y and validate models that will be used to project future trends in atmospheric composition as H₂ becomes a more common energy source.

Molecular hydrogen (H₂) is an abundant and reactive constituent of Earth’s atmosphere. The utilization of H₂ as an energy source emits no carbon to the atmosphere if produced from water using renewables, and increasing adoption of H₂ as a substitute for fossil fuels is likely (1). As the H₂ energy sector expands, anthropogenic emissions are expected to increase due to leakage. Projecting the effects of increasing anthropogenic emissions requires a comprehensive understanding of the biogeochemical cycle of H₂. Reconstructing the paleoatmospheric levels of H₂ contributes to that understanding by establishing the baseline for quantifying anthropogenic emissions since the industrial revolution.Presently, the average atmospheric abundance of H₂ is 530 parts per billion (ppb; nmol H₂ mol⁻¹ air), and the atmospheric lifetime is about 2 y (2). The budget of H₂ is complex, including both natural and anthropogenic terms. Globally, the largest source of H₂ is the photolysis of formaldehyde, formed by the atmospheric oxidation of methane and nonmethane hydrocarbons (NMHCs). Other major sources include direct emissions from fossil fuel combustion and biomass burning. N₂ fixation both on land and in the ocean is a small additional source. The major sink for atmospheric H₂ is uptake by soil microbes, with oxidation by OH accounting for the remaining losses. H₂ levels are higher by about 3% in the southern hemisphere than in the northern hemisphere due to the hemispheric asymmetry of the soil sink (2–5).Atmospheric H₂ levels impact Earth’s radiative budget and air quality. H₂ serves as a sink for the OH radical, increasing the atmospheric lifetime of radiatively important trace gases like methane. Additionally, the reaction of H₂ with OH results in the catalytic production of O₃ in the troposphere (2, 6–8). Oxidation of H₂ by OH in the stratosphere leads to increased concentrations of HO₂ and water vapor. The increase in these species will have indirect radiative effects due to losses of ozone and alterations to the distribution of polar stratospheric clouds. Increased stratospheric concentrations of water vapor will also have direct radiative effects via increased infrared absorption (7, 9–12).The modern instrumental record of tropospheric H₂ abundance began in the late 1980s (2, 13). Mid-twentieth century studies reported a wide range (400 to 2,000 ppb), which likely reflects analytical issues and/or influence from urban pollutants (14–16). The surface flask air measurements of Khalil and Rasmussen (13), the National Oceanic and Atmospheric Administration Global Monitoring Laboratory (NOAA/GML; refs. 2, 17), and the Commonwealth Scientific and Industrial Research Organisation (CSIRO; ref. 18) show atmospheric levels of H₂ of 510 to 550 ppb during the late 20th and early 21st centuries at background sites around the world. In situ measurements from Cape Grim, Tasmania, and Mace Head, Ireland, made by the Advanced Global Atmospheric Gases Experiment (AGAGE) show similar levels of atmospheric H₂ during the same time period (19). To date, there have been two published firn air studies of the historical trends of atmospheric H₂. Petrenko et al. (20) reconstructed northern hemisphere H₂ from Greenland firn air measurements. Their results show an increase in atmospheric H₂ levels from 450 to 520 ppb during the 1960s to a peak near 550 ppb during the late 1980s or early 1990s, then a recent decline to about 515 ppb in 2010. The peak and recent decline are inconsistent with modern flask measurements that show roughly constant H₂ levels during the 1990s (2, 17, 19). The authors note that the firn air model used for the reconstruction does not include pore close-off fractionation of H₂, and it is possible that the inferred peak is a modeling artifact (20, 21). Firn air measurements of H₂ from the South Pole showed that atmospheric H₂ increased from 350 ppb to 550 ppb over the twentieth century in the high southern latitudes (22). This reconstruction does not include a late twentieth century peak or decline, and the reconstructed levels of H₂ are consistent with available modern flask measurements beginning in the late 1980s. The increase in atmospheric H₂ is primarily attributed to increasing anthropogenic emissions and increasing atmospheric concentrations of methane over the twentieth century.Here we report H₂ measurements in firn air samples collected from the Megadunes site (80.78 °S, 124.49 °E, Alt: 2,283 m) in central Antarctica during January of 2004 and analyzed at NOAA/GML in April 2004 (23, 24). Megadunes is a complex site, with very low annual accumulation rates and an unusually large amplitude of surface topography. The oldest firn air ever recovered, with a mean CO₂ age of 140 y, was sampled during this campaign (23). A firn air model is used to reconstruct southern-hemisphere atmospheric H₂ levels since the 1850s. The reconstruction is compared to the existing South Pole firn air reconstruction (22), and implications of the reconstructed atmospheric history for the global budget of H₂ are discussed.     

气道组胺H2受体与支气管哮喘发病机理关系的临床研究

应用组胺Ｈ２受体（Ｈ２Ｒ）激动剂甲双咪胍治疗缓解期哮喘患者１９例，观察其对气道高反应性（ＢＨＲ）的作用，以进一步探讨Ｈ２Ｒ与哮喘发病机理的关系。研究提示Ｈ２Ｒ激动剂可主要作为抗气道炎症用药，也可作为平喘药的辅助用药，说明Ｈ２Ｒ在哮喘气道炎症反应中具有保护作用。