Comparison of wind tunnel test results at free stream Mach 0.7 with results from the Boeing TEA-230 subsonic flow method

The use of the Boeing TEA-230 Subsonic Flow Analysis method as a primary design tool in the development of cruise overwing nacelle configurations is presented. Surface pressure characteristics at 0.7 Mach number were determined by the TEA-230 method for a selected overwing flow-through nacelle configuration. Results of this analysis show excellent overall agreement with corresponding wind tunnel data. Effects of the presence of the nacelle on the wing pressure field were predicted accurately by the theoretical method. Evidence is provided that differences between theoretical and experimental pressure distributions in the present study would not result in significant discrepancies in the nacelle lines or nacelle drag estimates

Upper-surface blowing nacelle design study for a swept wing airplane at cruise conditions

A study was made to design two types of overwing nacelles for an existing wing-body at a design condition of Mach = 0.8 and C sub L = 0.2. Internal and external surface contours were developed for nacelles having either a D-shaped nozzle or a high-aspect-ratio nozzle for upper-surface blowing in the powered-lift mode of operation. The goal of the design was the development of external nacelle lines that would minimize high-speed aerodynamic interference effects. Each nacelle type was designed for both two- and four-engine airplanes using an iterative process of aerodynamic potential flow analysis. Incremental nacelle drag estimates were made for flow-through wind tunnel models of each configuration

Long-term warming alters the composition of Arctic soil microbial communities

Despite the importance of Arctic soils in the global carbon cycle, we know very little of the impacts of warming on the soil microbial communities that drive carbon and nutrient cycling in these ecosystems. Over a 2-year period, we monitored the structure of soil fungal and bacterial communities in organic and mineral soil horizons in plots warmed by greenhouses for 18 years and in control plots. We found that microbial communities were stable over time but strongly structured by warming. Warming led to significant reductions in the evenness of bacterial communities, while the evenness of fungal communities increased significantly. These patterns were strongest in the organic horizon, where temperature change was greatest and were associated with a significant increase in the dominance of the Actinobacteria and significant reductions in the Gemmatimonadaceae and the Proteobacteria. Greater evenness of the fungal community with warming was associated with significant increases in the ectomycorrhizal fungi, Russula spp., Cortinarius spp., and members of the Helotiales suggesting that increased growth of the shrub Betula nana was an important mechanism driving this change. The shifts in soil microbial community structure appear sufficient to account for warming-induced changes in nutrient cycling in Arctic tundra as climate warm

Transfer of 13C between paired Douglas-fir seedlings reveals plant kinship effects and uptake of exudates by ectomycorrhizas

• Processes governing the fixation, partitioning, and mineralization of carbon in soils are under increasing scrutiny as we develop a more comprehensive understanding of global carbon cycling. Here we examined fixation by Douglas-fir seedlings and transfer to associated ectomycorrhizal fungi, soil microbes, and full-sibling or non-sibling neighbouring seedlings. • Stable isotope probing with 99% 13C-CO2 was applied to trace 13C-labelled photosynthate throughout plants, fungi, and soil microbes in an experiment designed to assess the effect of relatedness on 13C-transfer between plant pairs. The fixation and transfer of 13C-label to plant, fungal, and soil microbial tissue was examined in biomass and PLFAs. • After a 6-day chase period, approximately 26.8% of the 13C remaining in the system was translocated belowground. Enrichment was proportionally greatest in ectomycorrhizal biomass. The presence of mesh barriers (0.5 or 35 µm) between seedlings did not restrict 13C-transfer. • Fungi were the primary recipients of 13C-labelled photosynthate throughout the system, representing 60–70% of total 13C-enriched phospholipids. Full-sibling pairs exhibited significantly greater 13C-transfer to recipient roots in two of four Douglas-fir families, representing 3- and 4-fold increases (+ approx. 4 µg excess 13C) compared to non-sibling pairs. The existence of a root/mycorrhizal exudation – hyphal uptake pathway was supported

Spontaneous separation of two-component Fermi gases in a double-well trap

The two-component Fermi gas in a double-well trap is studied using the density functional theory and the density profile of each component is calculated within the Thomas-Fermi approximation. We show that the two components are spatially separate in the two wells once the repulsive interaction exceeds the Stoner point, signaling the occurrence of the ferromagnetic transition. Therefore, the double-well trap helps to explore itinerant ferromagnetism in atomic Fermi gases, since the spontaneous separation can be examined by measuring component populations in one well.Comment: 6 pages, 6 figures, to appear in ep

Finite-temperature magnetism of Fex_xPd1−x_{1-x} and Cox_xPt1−x_{1-x} alloys

The finite-temperature magnetic properties of Fe$_x$Pd$_{1-x}$ and Co$_x$Pt$_{1-x}$ alloys have been investigated. It is shown that the temperature-dependent magnetic behaviour of alloys, composed of originally magnetic and non-magnetic elements, cannot be described properly unless the coupling between magnetic moments at magnetic atoms (Fe,Co) mediated through the interactions with induced magnetic moments of non-magnetic atoms (Pd,Pt) is included. A scheme for the calculation of the Curie temperature ($T_C$) for this type of systems is presented which is based on the extended Heisenberg Hamiltonian with the appropriate exchange parameters $J_{ij}$ obtained from {\em ab-initio} electronic structure calculations. Within the present study the KKR Green's function method has been used to calculate the $J_{ij}$ parameters. A comparison of the obtained Curie temperatures for Fe$_x$Pd$_{1-x}$ and Co$_x$Pt$_{1-x}$ alloys with experimental data shows rather good agreement.Comment: 10 pages, 12 figure

High precision and continuous field measurements of δ 13C and δ 18O in carbon dioxide with a cryogen-free QCLAS

The present paper describes a compact and cryogen-free, quantum cascade laser based absorption spectrometer (QCLAS) designed for in situ, continuous and high precision isotope ratio measurements of atmospheric CO2. The mobile instrument incorporates several new features including a novel astigmatic multi-pass cell assembly, a quasi-room temperature quantum cascade laser, thermoelectrically cooled detectors as well as a new retrieval approach. The combination of these features now makes it possible to measure isotope ratios of ambient CO2 with a precision of 0.03 and 0.05‰ for δ13C and δ18O, respectively, using a 100s integration time. A robust and optimized calibration procedure was developed to bring the retrieved isotope ratios on an absolute scale. This assures an accuracy better than 0.1‰ under laboratory conditions. The instrument performance was also assessed in a field campaign in which the spectrometer operated autonomously and provided mixing ratio values for the main three CO2 isotopologues at one second time resolution. An accuracy of 0.2‰ was routinely obtained for both isotope ratios during the entire period. The results were in excellent agreement with the standard laboratory-based isotope ratio mass spectrometer measurements made on field-collected flask samples. A few illustrative examples are used to depict the potential of this optical method in atmosphere-biosphere researc

In-depth analysis of N2O fluxes in tropical forest soils of the Congo Basin combining isotope and functional gene analysis

Primary tropical forests generally exhibit large gaseous nitrogen (N) losses, occurring as nitric oxide (NO), nitrous oxide (N2O) or elemental nitrogen (N2). The release of N2O is of particular concern due to its high global warming potential and destruction of stratospheric ozone. Tropical forest soils are predicted to be among the largest natural sources of N2O; however, despite being the world’s second-largest rainforest, measurements of gaseous N-losses from forest soils of the Congo Basin are scarce. In addition, long-term studies investigating N2O fluxes from different forest ecosystem types (lowland and montane forests) are scarce. In this study we show that fluxes measured in the Congo Basin were lower than fluxes measured in the Neotropics, and in the tropical forests of Australia and South East Asia. In addition, we show that despite different climatic conditions, average annual N2O fluxes in the Congo Basin’s lowland forests (0.97 ± 0.53 kg N ha−1 year−1) were comparable to those in its montane forest (0.88 ± 0.97 kg N ha−1 year−1). Measurements of soil pore air N2O isotope data at multiple depths suggests that a microbial reduction of N2O to N2 within the soil may account for the observed low surface N2O fluxes and low soil pore N2O concentrations. The potential for microbial reduction is corroborated by a significant abundance and expression of the gene nosZ in soil samples from both study sites. Although isotopic and functional gene analyses indicate an enzymatic potential for complete denitrification, combined gaseous N-losses (N2O, N2) are unlikely to account for the missing N-sink in these forests. Other N-losses such as NO, N2 via Feammox or hydrological particulate organic nitrogen export could play an important role in soils of the Congo Basin and should be the focus of future research

Emergence of magnetism in graphene materials and nanostructures

Magnetic materials and nanostructures based on carbon offer unique opportunities for future technological applications such as spintronics. This article reviews graphene-derived systems in which magnetic correlations emerge as a result of reduced dimensions, disorder and other possible scenarios. In particular, zero-dimensional graphene nanofragments, one-dimensional graphene nanoribbons, and defect-induced magnetism in graphene and graphite are covered. Possible physical mechanisms of the emergence of magnetism in these systems are illustrated with the help of computational examples based on simple model Hamiltonians. In addition, this review covers spin transport properties, proposed designs of graphene-based spintronic devices, magnetic ordering at finite temperatures as well as the most recent experimental achievements.Comment: tutorial-style review article -- 18 pages, 19 figure