Light aircraft sound transmission study

The plausibility of using the two microphone sound intensity technique to study noise transmission into light aircraft was investigated. In addition, a simple model to predict the interior sound pressure level of the cabin was constructed

The Relevance of Maize Pollen for Assessing the Extent of Maize Production in Chaco Canyon

Opinion is hardly unanimous, but many authors endorse the idea that Chaco Canyon is and was a marginal place for growing corn (Zea mays), a chief source of food energy for Puebloan groups in the Southwest. Poor soils with “toxic” levels of salts, inadequate and unpredictable precipitation, and a short growing season have all been identified as contributing to the agricultural marginality of the place (Benson 2011a; Bryan 1954; Force et al. 2002; Judd 1954:59–61). Benson has been the most vocal proponent of this view of late, and his research has culminated in the conclusion that “the San Juan Basin, including Chaco Canyon, appears to be the least promising area for dryland farming; that is, it is too dry and its soils are Npoor, saline and too basic (high pH values) for the production of maize” (Benson 2011a:49–50; Benson 2011b). The Chaco Project’s experimental maize fields in the late 1970s seem to bear out this statement: “Chaco, under modern conditions, is indeed marginal as a corn growing environment” (Toll et al. 1985:124). If Chaco Canyon is as marginal for farming as many claim, then the cultural achievements of the Puebloans that lived there are all the more remarkable, and this marginality has figured prominently in many interpretations about how and why Chaco Canyon developed as it did (Judge 1979, 1989; Schelberg 1981, 1982; Sebastian 1983, 1991, 1992; Vivian 1984, 1990). Chacoans had to import not only beams for building, pottery for cooking and storage, and stone for flaked tools but also even the staff of life—corn. And when you add in such exotics as turquoise, parrots, copper bells, and cacao, the potential “trade” deficit looms large. If Chaco Canyon did not provide even enough food for basic sustenance, what was it that made the place so special in the first place? More importantly, what literally fueled the obvious cultural fluorescence of Chaco Canyon and ts massive labor-intensive construction projects? Wills and Dorshow (2012:138) observe that “the popular perspective that Chaco was mysterious or enigmatic is largely a response to this view of the canyon as agriculturally marginal.” Yet, how do we know what the agricultural potential of the canyon was during the Bonito phase (ca. A.D. 850–1140) or that Chacoans could not provide for themselves? Perhaps the pendulum has swung too far toward a pessimistic assessment of the maize farming in and around the canyon. Certainly, Navajo farmers with considerable traditional knowledge and a real stake in the outcome successfully grew corn within Chaco Canyon (Judd 1954:52–59), and in 1898, George Pepper photographed Navajo fields on the floodplain of Chaco Canyon proper that produced a bountiful corn harvest ( Figure 1a). Since photo documentation is not anecdotal, it seems a sufficient counter to assertions that farming of the Chaco floodplain was impossible because of high salinity. Judd’s records of Navajo maize harvests evidently come from a time of more favorable precipitation and growingseason length, but this, too, could have characterized much of the Bonito phase. Figure 1b shows another Navajo field on the main floodplain at harvest time. Navajo farmers clearly experienced agricultural risk (Huntington 1914:81), but evidently the canyon proved a sufficient attraction to entice early settlement by them (Brugge 1986), perhaps precisely because of its productive potential. Farming potential was likely the prime motivation for initial Basketmaker settlement, a time when supplemental extra-local sources of maize were improbable. Since everything is relative, Chaco Canyon may have seemed like a small Eden in the context of the vast “dreary wastes” (Huntington 1914:81) of the San Juan Basin at large

Sexual reproduction of human fungal pathogens

We review here recent advances in our understanding of sexual reproduction in fungal pathogens that commonly infect humans, including Candida albicans, Cryptococcus neoformans/gattii, and Aspergillus fumigatus. Where appropriate or relevant, we introduce findings on other species associated with human infections. In particular, we focus on rapid advances involving genetic, genomic, and population genetic approaches that have reshaped our view of how fungal pathogens evolve. Rather than being asexual, mitotic, and largely clonal, as was thought to be prevalent as recently as a decade ago, we now appreciate that the vast majority of pathogenic fungi have retained extant sexual, or parasexual, cycles. In some examples, sexual and parasexual unions of pathogenic fungi involve closely related individuals, generating diversity in the population but with more restricted recombination than expected from fertile, sexual, outcrossing and recombining populations. In other cases, species and isolates participate in global outcrossing populations with the capacity for considerable levels of gene flow. These findings illustrate general principles of eukaryotic pathogen emergence with relevance for other fungi, parasitic eukaryotic pathogens, and both unicellular and multicellular eukaryotic organisms

Sensible heat measurements indicating depth and magnitude of subsurface soil water evaporation

Most measurement approaches for determining evaporation assume that the latent heat flux originates from the soil surface. Here, a new method is described for determining in situ soil water evaporation dynamics from fine-scale measurements of soil temperature and thermal properties with heat pulse sensors. A sensible heat balance is computed using soil heat flux density at two depths and change in sensible heat storage in between; the sensible heat balance residual is attributed to latent heat from evaporation of soil water. Comparisons between near-surface soil heat flux density and Bowen ratio energy balance measurements suggest that evaporation originates below the soil surface several days after rainfall. The sensible heat balance accounts for this evaporation dynamic in millimeter-scale depth increments within the soil. Comparisons of sensible heat balance daily evaporation estimates to Bowen ratio and mass balance estimates indicate strong agreement (r2 = 0.96, root-mean-square error = 0.20 mm). Potential applications of this technique include location of the depth and magnitude of subsurface evaporation fluxes and estimation of stage 2–3 daily evaporation without requirements for large fetch. These applications represent new contributions to vadose zone hydrology

A Multiple Classifier System Identifies Novel Cannabinoid CB2 Receptor Ligands

open access articleDrugs have become an essential part of our lives due to their ability to improve people’s health and quality of life. However, for many diseases, approved drugs are not yet available or existing drugs have undesirable side effects, making the pharmaceutical industry strive to discover new drugs and active compounds. The development of drugs is an expensive process, which typically starts with the detection of candidate molecules (screening) for an identified protein target. To this end, the use of high-performance screening techniques has become a critical issue in order to palliate the high costs. Therefore, the popularity of computer-based screening (often called virtual screening or in-silico screening) has rapidly increased during the last decade. A wide variety of Machine Learning (ML) techniques has been used in conjunction with chemical structure and physicochemical properties for screening purposes including (i) simple classifiers, (ii) ensemble methods, and more recently (iii) Multiple Classifier Systems (MCS). In this work, we apply an MCS for virtual screening (D2-MCS) using circular fingerprints. We applied our technique to a dataset of cannabinoid CB2 ligands obtained from the ChEMBL database. The HTS collection of Enamine (1.834.362 compounds), was virtually screened to identify 48.432 potential active molecules using D2-MCS. This list was subsequently clustered based on circular fingerprints and from each cluster, the most active compound was maintained. From these, the top 60 were kept, and 21 novel compounds were purchased. Experimental validation confirmed six highly active hits (>50% displacement at 10 μM and subsequent Ki determination) and an additional five medium active hits (>25% displacement at 10 μM). D2-MCS hence provided a hit rate of 29% for highly active compounds and an overall hit rate of 52%

An Improved Approach for Measurement of Coupled Heat and Water Transfer in Soil Cells

Laboratory experiments on coupled heat and water transfer in soil have been limited in their measurement approaches. Inadequate temperature control creates undesired two-dimensional distributions of both temperature and moisture. Destructive sampling to determine soil volumetric water content (θ) prevents measurement of transient θ distributions and provides no direct information on soil thermal properties. The objectives of this work were to: (i) develop an instrumented closed soil cell that provides one-dimensional conditions and permits in situ measurement of temperature, θ, and thermal conductivity (λ) under transient boundary conditions, and (ii) test this cell in a series of experiments using four soil type–initial θ combinations and 10 transient boundary conditions. Experiments were conducted using soil-insulated cells instrumented with thermo-time domain reflectometry (T-TDR) sensors. Temperature distributions measured in the experiments show nonlinearity, which is consistent with nonuniform thermal properties provided by thermal moisture distribution but differs from previous studies lacking one-dimensional temperature control. The T-TDR measurements of θ based on dielectric permittivity, volumetric heat capacity, and change in volumetric heat capacity agreed well with post-experiment sampling, providing r 2 values of 0.87, 0.93, and 0.95, respectively. Measurements of θ and λ were also consistent with the shapes of the observed temperature distributions. Techniques implemented in these experiments allowed observation of transient temperature, θ, and λ distributions on the same soil sample for 10 sequentially imposed boundary conditions, including periods of rapid redistribution. This work demonstrates that, through improved measurement techniques, the study of heat and water transfer processes can be expanded in ways previously unavailable

Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics

Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patterns. Immediately after rainfall, evaporation occurred near the soil surface. Within 6 days after rainfall, the evaporation zone proceeded \u3e 13 mm into the soil profile. Evaporation rates at the 3-mm depth reached peak values \u3e 0.25 mm h−1. Evaporation occurred simultaneously at multiple measured depth increments, but with time lag between peak evaporation rates for depths deeper below the soil surface. Implementation of finescale measurement techniques for the soil sensible heat balance provides a new opportunity to improve understanding of soil-water evaporation

Bare Soil Carbon Dioxide Fluxes with Time and Depth Determined by High-Resolution Gradient-Based Measurements and Surface Chambers

Soil CO2 production rates and fluxes vary with time and depth. The shallow near-surface soil layer is important for myriad soil processes, yet knowledge of dynamic CO2 concentrations and fluxes in this complex zone is limited. We used a concentration gradient method (CGM) to determine CO2 production and effluxes with depth in shallow layers of a bare soil. The CO2concentration was continuously measured at 13 depths in the 0- to 200-mm soil layer. For an 11-d period, 2% of the soil CO2 was produced below a depth of 175 mm, 8% was produced in the 50- to 175-mm soil layer, and 90% was produced in the 0- to 50-mm soil layer. Soil CO2concentration showed similar diurnal patterns with temperature in deeper soil layers and out-of-phase diurnal patterns in surface soil layers. Soil CO2 flux from most of the soil layers can be described by an exponential function of soil temperature, with temperature sensitivity (Q10) ranging from 1.40 to 2.00 (1.62 ± 0.17). The temperature-normalized CO2 fluxes are related to soil water content with a positive linear relationship in surface soil layers and a negative relationship in deep soil layers. The CO2 fluxes from CGM and chamber methods had good agreement at multiple time scales, which showed that the CGM method was able to estimate near-surface soil CO2 fluxes and production. The contrasting patterns between surface and deep layers of soil CO2 concentration and fluxes suggest the necessity of intensive CO2concentration measurements in the surface soil layer for accurate determination of soil-atmosphere CO2 flux when using the CGM

Cumulative Soil Water Evaporation as a Function of Depth and Time

Soil water evaporation is an important component of the surface water balance and the surface energy balance. Accurate and dynamic measurements of soil water evaporation enhance the understanding of water and energy partitioning at the land–atmosphere interface. The objective of this study was to measure the cumulative soil water evaporation with time and depth in a bare field. Cumulative water evaporation at the soil surface was measured by the Bowen ratio method. Subsurface cumulative soil water evaporation was determined with the heat pulse method at fine-scale depth increments. Following rainfall, the subsurface cumulative evaporation curves followed a pattern similar to the surface cumulative evaporation curve, with approximately a 2-d lag before evaporation was indicated at the 3- and 9-mm soil depths, and several more days\u27 delay in deeper soil layers. For a 21-d period in 2007, the cumulative evaporation totals at soil depths of 0, 3, 9, 15, and 21 mm were 60, 44, 29, 13, and 8 mm, respectively. For a 16-d period in 2008, the cumulative evaporation totals at soil depths of 0, 3, 9, 15, and 21 mm were 32, 25, 16, 10, and 5 mm, respectively. Cumulative evaporation results from the Bowen ratio and heat pulse methods indicated a consistent dynamic pattern for surface and subsurface water evaporation with both time and depth. These findings suggest that heat pulse sensors can accurately measure subsurface soil water evaporation during several wetting–drying cycles