Genetic Variation in the Common Reed, <Emphasis Type="Italic">Phragmites australis</Emphasis>, in the Mississippi River Delta Marshes: Evidence for Multiple Introductions

Multiple introductions are believed to play an important role in increasing genetic diversity and adaptability of invasive species, but there are few well-documented examples. The common reed, Phragmites australis, has dramatically increased in tidal wetlands throughout the USA in the past century due primarily to the introduction of a Eurasian lineage. In the Mississippi River “Balize” delta, P. australis is the dominant vegetation where monotypic stands of an introduced form blanket the outer marshes. The delta’s interior marshes, on the other hand, are more vegetatively diverse, serving as important waterfowl foraging habitat. Recent encroachment by various phenotypic forms of P. australis into the interior marshes led to this study examining genetic variation in these stands. Our results revealed four chloroplast DNA haplotypes that also segregate based on microsatellite variation. Three of these are closely related and introduced, but differ relative to time and likely mode of introduction. The “Delta” type (haplotype M1), which is unique to the region and the most common lineage, displays considerable microsatellite diversity. The Eurasian introduced lineage of P. australis (haplotype M), which is invasive elsewhere in North America, is increasing its distribution in the delta. A novel haplotype, AD, was also identified which is phenotypically and genetically similar to haplotype M. Despite the close relatedness, we found no evidence for inter-haplotype gene exchange at the nuclear level, suggesting that intraspecific hybridization is not a contributing factor to these invasions. The site provides a unique opportunity for researchers to understand the dynamics of multiple P. australis invasions.     

Big Data from the Ground Up: Mobile Maps and Geographic Knowledge

Consumer users of maps on mobile devices are producing noteworthy geographic knowledges in the contexts of their own lives that are distinct from those of professional data scientists. By leveraging the streaming nature of big data in mobile maps and zooming multiscalar views, consumer users' mobile map practices produce a popular, multiscalar form of visual geographic knowledge that is both enabled and limited by its big data assemblage and associated technologies. The first half of this article outlines the role of consumer user practices amidst spatial big data assemblages, not for volunteered geographic information or aggregate analysis but for contextual, everyday use. Consumer users and their knowledges are coconstituted through mobile map viewing and as materially limited technological practices. This article focuses specifically on the consumer users' concept of scale in this context, for Web-based maps' multiscalar views differentiate them from older maps. The second half analyzes mobile map consumer users' concepts of scale in a series of focus groups that involved both questions and observing participants' actions with maps on their own phones. Instead of passively accepting maps at predetermined optimized scales from the map application, consumer users actively viewed the map across scales while searching but not while navigating.     

Infrared polarimetry of the southern massive star-forming region G333.6−0.2

We present     spectropolarimetry, and 12- and 2-μm imaging polarimetry of the southern massive star-forming region G333.6−0.2. Spectro-polarimetry measurements show that the polarization observed towards the nebula contains a mixture of both absorptive and emissive polarizations. Model fitting to the spectra indicates that the temperature of the mid-infrared emitting dust grains is generally ∼200 K and the optical depth of the absorbing dust at 9.7 μm is ∼1.5. Fits are also made to the polarimetry spectra, which show a reasonably constant peak absorptive polarization (∼3.4 per cent at 43°) across the face of the H  ii region. This absorptive polarization position angle is consistent with that found by the 2-μm imaging polarimetry     and is most likely due to the Galactic magnetic field local to G333.6−0.2. When the absorptive polarization is subtracted from the 12-μm polarization image, the emissive polarization pattern that is intrinsic to the star-forming region is revealed. A probable magnetic field configuration implied by the intrinsic polarization suggests star formation initially influenced by the Galactic magnetic field which is eventually perturbed by the star formation process.     

Visco–Resistive Dissipation in Transient Reconnection Driven by the Orszag–Tang Vortex

Viscous effects are expected to significantly contribute to reconnective energy release mechanisms in solar flares. While simple scaling arguments based on head-on reconnection suggest that viscous dissipation may dominate resistive dissipation, it is not clear whether these findings can be applied in more general merging situations. Here we perform side-by-side planar reconnection simulations driven by the Orszag–Tang vortex, for both classical and Braginskii forms of the viscosity. This formulation has the advantage of providing an autonomous MHD system that develops strong current layers, sustained by large-scale vortical shearing flows. The dissipation rates are shown to follow analytically based scaling laws, which suggest that viscous losses generated from large-scale non-uniform velocity fields are likely to dominate resistive losses in current-sheet reconnection solutions.     

Near-infrared imaging observations of the southern massive star-forming region G333.6−0.2

We present near-infrared broad-band JHK ' images of the southern massive star-forming region G333.6−0.2. The slope of the K -luminosity function towards the region  (0.24 ± 0.01)  is considered to be equivalent to that expected for main-sequence stars in the solar neighbourhood. Point sources with their ( H − K ) colour greater than 1 are more likely to be located in extended emission and it is suggested that these objects are physically associated with the H  ii region.     

The Effect of Porous Medium Storage on Unstable Density‐Driven Solute Transport

Unstable density‐driven groundwater flow and solute transport (i.e., free convection) leads to spatiotemporal variations in pressure. Specific storage (S_o) indicates the capability of a confined aquifer to release or store groundwater associated with a pressure change. Although S_o is known to dampen pressure propagation, S_o has been implicitly assumed to have a negligible impact on the unstable free convective process in prior studies. This work explores the effect of S_o on both the classic onset criterion and the fingering process using numerical models. Results show that the classic onset criterion is applicable when S_o is smaller than 10^–1 m^–1. Results also demonstrate that S_o does not play a significant role in the free convective fingering process unless it is greater than 10^–3 m^–1. For most practical purposes in hydrogeology (large Rayleigh number and small S_o), the implicit assumption of small or zero S_o is appropriate.     

Cladding influence on dynamics response of tall buildings

Precast concrete panels form attractive facades for steel frame buildings and are generally regarded as non-structural by structural engineers. However, panels have been found to add lateral stiffness until their capacity or that of their connections is exceeded. Consequently, the computed dynamic response based on a model of the structural framing alone may be quite different from that experienced by the actual structure. As a case study, the influence of precast concrete panels on lateral and torsional stiffness of a 25-storey building was investigated. The effect of cladding on dynamic properties and linear seismic response was explored by varying panel stiffness. Cladding stiffness was added to the bare frame model until analytical frequency values matched vibration test results. Then, using the cladding stiffness values obtained, an accidental eccentricity between centres of mass and rigidity at each floor level was imposed and linear seismic response computed. Torsional response effects were increased substantially. Finally, a modified cladding panel connection was developed based on previously-reported studies for panelized construction. The influence of the proposed connection on overall structural response was determined for different ground motion inputs.     

Geochemical, mineralogical and isotopic signatures of the Semikan, West Kasrık “Turkish” phosphorites from the Derik–Mazıdağı–Mardin area, SE Anatolia

The geochemistry and mineralogy of a condensed section, ~6 m thick of the West Kasrik member (Coniacian–Santonian) near the uplifted northern flank of the Mardin–Derik anticline (south-eastern Turkey) was studied. The only deposit exploited in Turkey is found in this area. The sediment textures as well as the mineralogical and the geochemical results collectively suggest that these recycled phosphorites accumulated in areas of intensive very early diagenesis of the sediments in highly oxic bottom waters, and almost no detrital apport. The total concentration of redox-sensitive trace metals is very low (<600 μg/g); in addition the structural CO₂ and F/P₂O₅ are unusually high (~5 wt % and 0.14, respectively). REE distribution shows a clear “seawater” pattern with a strongly negative Ce-anomaly (0.20 ± 0.02) and heavy REE enrichment (Lu_N/La_N = 1.50 ± 0.12), however their total concentration is very low. The low REE contents, quite unexpected in recycled phosphorites, are explained by the scarcity of terrigenous components which leads to minimal incorporation of REEs from detrital clastic phases in the CFA fraction. Weathering previously suggested as responsible for the high P enrichment of the Mazidagi phosphorites is rather improbable in the samples we studied, in view of their high structural CO₂, high F/P₂O₅, high (La/Nd)_N and (La/Sm)_N ratios, and high Sr/P and Ca/P of separated CFA fractions that all negate post-depositional weathering. More likely, the high P enrichment of some rocks (P₂O₅ content reaches 34%) was produced by sedimentary and early diagenetic processes acting in oxygenated areas of starved sedimentation on and around tectonic highs.     

Carbon and nitrogen stable isotope ratios in surface sediments from lakes of western Ireland: implications for inferring past lake productivity and nitrogen loading

We used statistical analyses to determine which subset of 36 environmental variables best explained variations in surface sediment δ¹³C and δ¹⁵N from 50 lakes in western Ireland that span a human-impact gradient. The factors controlling lake sediment δ¹³C and δ¹⁵N depended on whether organics in the lake sediment were mostly derived from the lake catchment (allochthonous) or from productivity within the lake (autochthonous). Lake sediments with a dominantly allochthonous organic source (high C:N ratio sediments) produced δ¹³C and δ¹⁵N measurements similar to values from catchment vegetation. δ¹³C and δ¹⁵N measurements from lake sediments with a dominantly autochthonous organic source (low C:N ratio sediments) were influenced by fractionation in the lake and catchment leading up to assimilation of carbon and nitrogen by lacustrine biota. δ¹³C values from lake sediment samples in agricultural catchments were more negative than δ¹³C values from lake sediment samples in non-impacted, bogland catchments. Hypolimnetic oxygen concentrations and methane production had a greater influence on δ¹³C values than fractionation due to algal productivity. δ¹⁵N from lake sediment samples in agricultural catchments were more positive than δ¹⁵N in non-impacted bogland catchments. Lower δ¹⁵N values from non-impacted lake catchments reflected δ¹⁵N values of catchment vegetation, while higher δ¹⁵N values in agricultural catchments reflected the high δ¹⁵N values of cattle manure and inorganic fertilisers. The influence of changing nitrogen sources and lake/catchment fractionation processes were more important than early diagenesis for lake sediment δ¹⁵N values in this dataset. The results from this study suggest a possible influence of bound inorganic nitrogen on the bulk sediment δ¹⁵N values. We recommend using a suitable method to control for bound inorganic nitrogen in lake sediments, especially when working with clay-rich sediments. This study confirms the usefulness of δ¹³C and δ¹⁵N from bulk lake sediments, as long as we are mindful of the multiple factors that can influence these values. This study also highlights how stable isotope datasets from lake surface sediments can complement site-specific isotope source/process studies and help identify key processes controlling lake sediment δ¹³C and δ¹⁵N in a study area.