Apollo experience report guidance and control systems: Lunar module abort guidance system

The history of a unique development program that produced an operational fixed guidance system of inertial quality is presented. Each phase of development, beginning with requirement definition and concluding with qualification and testing, is addressed, and developmental problems are emphasized. Software generation and mission operations are described, and specifications for the inertial reference unit are included, as are flight performance results. Significant program observations are noted

Nitrogen oxides and PAN in plumes from boreal fires during ARCTAS-B and their impact on ozone: an integrated analysis of aircraft and satellite observations

We determine enhancement ratios for NO_x, PAN, and other NO_y species from boreal biomass burning using aircraft data obtained during the ARCTAS-B campaign and examine the impact of these emissions on tropospheric ozone in the Arctic. We find an initial emission factor for NO_x of 1.06 g NO per kg dry matter (DM) burned, much lower than previous observations of boreal plumes, and also one third the value recommended for extratropical fires. Our analysis provides the first observational confirmation of rapid PAN formation in a boreal smoke plume, with 40% of the initial NO_x emissions being converted to PAN in the first few hours after emission. We find little clear evidence for ozone formation in the boreal smoke plumes during ARCTAS-B in either aircraft or satellite observations, or in model simulations. Only a third of the smoke plumes observed by the NASA DC8 showed a correlation between ozone and CO, and ozone was depleted in the plumes as often as it was enhanced. Special observations from the Tropospheric Emission Spectrometer (TES) also show little evidence for enhanced ozone in boreal smoke plumes between 15 June and 15 July 2008. Of the 22 plumes observed by TES, only 4 showed ozone increasing within the smoke plumes, and even in those cases it was unclear that the increase was caused by fire emissions. Using the GEOS-Chem atmospheric chemistry model, we show that boreal fires during ARCTAS-B had little impact on the median ozone profile measured over Canada, and had little impact on ozone within the smoke plumes observed by TES

ORMDL3 expression in ASM regulates hypertrophy, hyperplasia via TPM1 and TPM4, and contractility

ORM1-like 3 (ORMDL3) has strong genetic linkage to childhood onset asthma. To determine whether ORMDL3 selective expression in airway smooth muscle (ASM) influences ASM function, we used Cre-loxP techniques to generate transgenic mice (hORMDL3Myh11eGFP-cre), which express human ORMDL3 selectively in smooth muscle cells. In vitro studies of ASM cells isolated from the bronchi of hORMDL3Myh11eGFP-cre mice demonstrated that they developed hypertrophy (quantitated by FACS and image analysis), developed hyperplasia (assessed by BrdU incorporation), and expressed increased levels of tropomysin proteins TPM1 and TPM4. siRNA knockdown of TPM1 or TPM4 demonstrated their importance to ORMDL3-mediated ASM proliferation but not hypertrophy. In addition, ASM derived from hORMDL3Myh11eGFP-cre mice had increased contractility to histamine in vitro, which was associated with increased levels of intracellular Ca2+; increased cell surface membrane Orai1 Ca2+ channels, which mediate influx of Ca2+ into the cytoplasm; and increased expression of ASM contractile genes sarco/endoplasmic reticulum Ca2+ ATPase 2b and smooth muscle 22. In vivo studies of hORMDL3Myh11eGFP-cre mice demonstrated that they had a spontaneous increase in ASM and airway hyperreactivity (AHR). ORMDL3 expression in ASM thus induces changes in ASM (hypertrophy, hyperplasia, increased contractility), which may explain the contribution of ORMDL3 to the development of AHR in childhood onset asthma, which is highly linked to ORMDL3 on chromosome 17q12-21

Large methane releases lead to strong aerosol forcing and reduced cloudiness

The release of vast quantities of methane into the atmosphere as a result of clathrate destabilization is a potential mechanism for rapid amplification of global warming. Previous studies have calculated the enhanced warming based mainly on the radiative effect of the methane itself, with smaller contributions from the associated carbon dioxide or ozone increases. Here, we study the effect of strongly elevated methane (CH4) levels on oxidant and aerosol particle concentrations using a combination of chemistry-transport and general circulation models. A 10-fold increase in methane concentrations is predicted to significantly decrease hydroxyl radical (OH) concentrations, while moderately increasing ozone (O3). These changes lead to a 70 % increase in the atmospheric lifetime of methane, and an 18 % decrease in global mean cloud droplet number concentrations (CDNC). The CDNC change causes a radiative forcing that is comparable in magnitude to the longwave radiative forcing ("enhanced greenhouse effect") of the added methane. Together, the indirect CH4-O3 and CH4-OH-aerosol forcings could more than double the warming effect of large methane increases. Our findings may help explain the anomalously large temperature changes associated with historic methane releases

The charging of neutral dimethylamine and dimethylamine-sulfuric acid clusters using protonated acetone

Sulfuric acid is generally considered one of the most important substances taking part in atmospheric particle formation. However, in typical atmospheric conditions in the lower troposphere, sulfuric acid and water alone are unable to form particles. It has been suggested that strong bases may stabilize sulfuric acid clusters so that particle formation may occur. More to the point, amines - strong organic bases - have become the subject of interest as possible cause for such stabilization. To probe whether amines play a role in atmospheric nucleation, we need to be able to measure accurately the gas-phase amine vapour concentration. Such measurements often include charging the neutral molecules and molecular clusters in the sample. Since amines are bases, the charging process should introduce a positive charge. This can be achieved by, for example, using chemical ionization with a positively charged reagent with a suitable proton affinity. In our study, we have used quantum chemical methods combined with a cluster dynamics code to study the use of acetone as a reagent ion in chemical ionization and compared the results with measurements performed with a chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF). The computational results indicate that protonated acetone is an effective reagent in chemical ionization. However, in the experiments the reagent ions were not depleted at the predicted dimethylamine concentrations, indicating that either the modelling scheme or the experimental results - or both - contain unidentified sources of error.Peer reviewe

Atmospheric nucleation: highlights of the EUCAARI project and future directions

Within the project EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions), atmospheric nucleation was studied by (i) developing and testing new air ion and cluster spectrometers, (ii) conducting homogeneous nucleation experiments for sulphate and organic systems in the laboratory, (iii) investigating atmospheric nucleation mechanism under field conditions, and (iv) applying new theoretical and modelling tools for data interpretation and development of parameterisations. The current paper provides a synthesis of the obtained results and identifies the remaining major knowledge gaps related to atmospheric nucleation. The most important technical achievement of the project was the development of new instruments for measuring sub-3 nm particle populations, along with the extensive application of these instruments in both the laboratory and the field. All the results obtained during EUCAARI indicate that sulphuric acid plays a central role in atmospheric nucleation. However, also vapours other than sulphuric acid are needed to explain the nucleation and the subsequent growth processes, at least in continental boundary layers. Candidate vapours in this respect are some organic compounds, ammonia, and especially amines. Both our field and laboratory data demonstrate that the nucleation rate scales to the first or second power of the nucleating vapour concentration(s). This agrees with the few earlier field observations, but is in stark contrast with classical thermodynamic nucleation theories. The average formation rates of 2-nm particles were found to vary by almost two orders of magnitude between the different EUCAARI sites, whereas the formation rates of charged 2-nm particles varied very little between the sites. Overall, our observations are indicative of frequent, yet moderate, ion-induced nucleation usually outweighed by much stronger neutral nucleation events in the continental lower troposphere. The most concrete outcome of the EUCAARI nucleation studies are the new semi-empirical nucleation rate parameterizations based on field observations, along with updated aerosol formation parameterizations

Nitrogen oxides and PAN in plumes from boreal fires during ARCTAS-B and their impact on ozone: an integrated analysis of aircraft and satellite observations

We determine enhancement ratios for NO<sub>x</sub>, PAN, and other NO<sub>y</sub> species from boreal biomass burning using aircraft data obtained during the ARCTAS-B campaign and examine the impact of these emissions on tropospheric ozone in the Arctic. We find an initial emission factor for NO<sub>x</sub> of 1.06 g NO per kg dry matter (DM) burned, much lower than previous observations of boreal plumes, and also one third the value recommended for extratropical fires. Our analysis provides the first observational confirmation of rapid PAN formation in a boreal smoke plume, with 40% of the initial NO<sub>x</sub> emissions being converted to PAN in the first few hours after emission. We find little clear evidence for ozone formation in the boreal smoke plumes during ARCTAS-B in either aircraft or satellite observations, or in model simulations. Only a third of the smoke plumes observed by the NASA DC8 showed a correlation between ozone and CO, and ozone was depleted in the plumes as often as it was enhanced. Special observations from the Tropospheric Emission Spectrometer (TES) also show little evidence for enhanced ozone in boreal smoke plumes between 15 June and 15 July 2008. Of the 22 plumes observed by TES, only 4 showed ozone increasing within the smoke plumes, and even in those cases it was unclear that the increase was caused by fire emissions. Using the GEOS-Chem atmospheric chemistry model, we show that boreal fires during ARCTAS-B had little impact on the median ozone profile measured over Canada, and had little impact on ozone within the smoke plumes observed by TES

Causes and importance of new particle formation in the present-day and preindustrial atmospheres

New particle formation has been estimated to produce around half of cloud-forming particles in the present-day atmosphere, via gas-to-particle conversion. Here we assess the importance of new particle formation (NPF) for both the present-day and the preindustrial atmospheres. We use a global aerosol model with parametrizations of NPF from previously published CLOUD chamber experiments involving sulfuric acid, ammonia, organic molecules, and ions. We find that NPF produces around 67% of cloud condensation nuclei at 0.2% supersaturation (CCN0.2%) at the level of low clouds in the preindustrial atmosphere (estimated uncertainty range 45-84%) and 54% in the present day (estimated uncertainty range 38-66%). Concerning causes, we find that the importance of biogenic volatile organic compounds (BVOCs) in NPF and CCN formation is greater than previously thought. Removing BVOCs and hence all secondary organic aerosol from our model reduces low-cloud-level CCN concentrations at 0.2% supersaturation by 26% in the present-day atmosphere and 41% in the preindustrial. Around three quarters of this reduction is due to the tiny fraction of the oxidation products of BVOCs that have sufficiently low volatility to be involved in NPF and early growth. Furthermore, we estimate that 40% of preindustrial CCN0.2% are formed via ion-induced NPF, compared with 27% in the present day, although we caution that the ion-induced fraction of NPF involving BVOCs is poorly measured at present. Our model suggests that the effect of changes in cosmic ray intensity on CCN is small and unlikely to be comparable to the effect of large variations in natural primary aerosol emissions. Plain Language Summary New particle formation in the atmosphere is the process by which gas molecules collide and stick together to form atmospheric aerosol particles. Aerosols act as seeds for cloud droplets, so the concentration of aerosols in the atmosphere affects the properties of clouds. It is important to understand how aerosols affect clouds because they reflect a lot of incoming solar radiation away from Earth's surface, so changes in cloud properties can affect the climate. Before the Industrial Revolution, aerosol concentrations were significantly lower than they are today. In this article, we show using global model simulations that new particle formation was a more important mechanism for aerosol production than it is now. We also study the importance of gases emitted by vegetation, and of atmospheric ions made by radon gas or cosmic rays, in preindustrial aerosol formation. We find that the contribution of ions and vegetation to new particle formation was also greater in the preindustrial period than it is today. However, the effect on particle formation of variations in ion concentration due to changes in the intensity of cosmic rays reaching Earth was small.Peer reviewe

Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles

Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations

A Crucial Role of Activin A-Mediated Growth Hormone Suppression in Mouse and Human Heart Failure

Infusion of bone marrow-derived mononuclear cells (BMMNC) has been reported to ameliorate cardiac dysfunction after acute myocardial infarction. In this study, we investigated whether infusion of BMMNC is also effective for non-ischemic heart failure model mice and the underlying mechanisms. Intravenous infusion of BMMNC showed transient cardioprotective effects on animal models with dilated cardiomyopathy (DCM) without their engraftment in heart, suggesting that BMMNC infusion improves cardiac function via humoral factors rather than their differentiation into cardiomyocytes. Using conditioned media from sorted BMMNC, we found that the cardioprotective effects were mediated by growth hormone (GH) secreted from myeloid (Gr-1(+)) cells and the effects was partially mediated by signal transducer and activator of transcription 3 in cardiomyocytes. On the other hand, the GH expression in Gr-1(+) cells was significantly downregulated in DCM mice compared with that in healthy control, suggesting that the environmental cue in heart failure might suppress the Gr-1(+) cells function. Activin A was upregulated in the serum of DCM models and induced downregulation of GH levels in Gr-1(+) cells and serum. Furthermore, humoral factors upregulated in heart failure including angiotensin II upregulated activin A in peripheral blood mononuclear cells (PBMNC) via activation of NFκB. Similarly, serum activin A levels were also significantly higher in DCM patients with heart failure than in healthy subjects and the GH levels in conditioned medium from PBMNC of DCM patients were lower than that in healthy subjects. Inhibition of activin A increased serum GH levels and improved cardiac function of DCM model mice. These results suggest that activin A causes heart failure by suppressing GH activity and that inhibition of activin A might become a novel strategy for the treatment of heart failure