Impact of redox and transport processes in a riparian wetland on stream water quality in the Fichtelgebirge region,southern Germany

Biologically mediated redox processes in the riparian zone, like denitrification, can have substantially beneficial impacts on stream water quality. The extent of these effects, however, depends greatly on the hydrological boundary conditions. The impact of hydrological processes on a wetland's nitrogen sink capacity was investigated in a forested riparian fen which is drained by a first‐order perennial stream. Here, we analysed the frequency distributions and time‐series of pH and nitrogen, silica, organic carbon and oxygen concentrations in throughfall, soil solution, groundwater and stream water, and the groundwater levels and stream discharges from a 3‐year period. During baseflow conditions, the stream was fed by discharging shallow, anoxic groundwater and by deep, oxic groundwater. Whereas the latter delivered considerable amounts of nitrogen (～0·37 mg l^?1) to the stream, the former was almost entirely depleted of nitrogen. During stormflow, near‐surface runoff in the upper 30 cm soil layer bypassed the denitrifying zone and added significant amounts to the nitrogen load of the stream. Nitrate‐nitrogen was close to 100% of deep groundwater and stream‐water nitrogen concentration. Stream‐water baseflow concentrations of nitrate, dissolved carbon and silica were about 1·6 mg l^?1, 4 mg l^?1 and 7·5 mg l^?1 respectively, and >3 mg l^?1, >10 mg l^?1 and <4 mg l^?1 respectively during discharge peaks. In addition to that macroscale bypassing effect, there was evidence for a corresponding microscale effect: Shallow groundwater sampled by soil suction cups indicated complete denitrification and lacked any seasonal signal of solute concentration, which was in contrast to piezometer samples from the same depth. Moreover, mean solute concentration in the piezometer samples resembled more that of suction‐cup samples from shallower depth than that of the same depth. We conclude that the soil solution cups sampled to a large extent the immobile soil‐water fraction. In contrast, the mobile fraction that was sampled by the piezometers exhibited substantially shorter residence time, thus being less exposed to denitrification, but predominating discharge of that layer to the stream. Consequently, assessing the nitrogen budget based on suction‐cup data tended to overestimate the nitrogen consumption in the riparian wetland. These effects are likely to become more important with the increased frequency and intensity of rainstorms that are expected due to climate change. Copyright © 2006 John Wiley & Sons, Ltd.     

Approximate coseismic displacements and near-field fling pulse from the Mw 6.5 30 October 2016 Central Italy earthquake

A study of the coseismic displacement and fling pulse recorded during the Mw 6.5 30 October 2016 Central Italy earthquake is presented. The near-field has been well documented, owing to the deployment of additional strong-motion stations following the earlier events of the 2016 Central Italy seismic sequence. As a result, there are numerous stations with evidence of coseismic displacement and fling pulse. In this study, 25 records with strike distance of less than 25 km and rupture distance under 28 km are considered. Approximate coseismic displacements have been recovered by a bilinear model to remove the low frequency noise in the records. The bilinear noise model uses two linear regression segments on the velocity trace to remove baseline offsets. After obtaining the coseismic displacement time series, the fling pulse period is examined. Existing methods of obtaining the fling pulse period are reviewed and a proposed algorithm is considered for automatic fling pulse detection. Both horizontal and vertical fling periods are obtained, unlike many studies which neglect the vertical fling. It is shown that the fling pulse period is highly variable (~?2–16 s) in the near-field region but exhibits some trends with various site-to-source distances.     

Singled Out: Scaling Violence and Social Groups as Legal Borderwork in U.S. Asylum Law

Through legal interpretation of immigration categories, such as the refugee definition, signatories to the UN Refugee Convention restrict access to political asylum. This paper examines how scalar logics are used in legal interpretation to filter out particular people from national space and control the number legally entitled to enter and remain in the U.S. Scalar logics shape access by requiring asylum seekers to prove they have been ‘singled out’ for persecution and by steering the meaning of the ‘particular social group’ provision of the refugee definition. The restrictive effects of these scalar logics are analyzed in relation to case law involving Central American asylum seekers fleeing gang‐related violence. These cases are often rejected on the basis that the asylum seekers possess identities and experiences exceeding the limited protection offered by asylum. Through analysis of these scalar logics, the paper highlights how interpretations of the refugee definition are an ongoing site of struggle over the scope of asylum protection.     

Qualitative Methods for Research on Mapmaking and Map Use

Contemporary cartographic research on mapmaking and map use has a broad mandate and, as a consequence, researchers need a broad suite of methods. Consistent with research developments in other geographic subdisciplines, cartographic researchers now use qualitative methods. They offer the advantage of bringing research closer to the problem‐solving realms of mapmakers and map users. Our purpose here is to discuss an array of qualitative methods for mapmaking and map use. Questionnaires, interviews, and protocol methods are used to gather verbal data about mapmaking and map use. Ethnographies produce data from direct observation of mapmakers and users. Maps also are sources for document analysis. We use examples of published cartographic research to elaborate on each of these methods.     

A mystery solved: the mass ratio of the dwarf nova EM Cygni

We have discovered that the spectrum of the well-known dwarf nova EM Cyg is contaminated by light from a K25V star (in addition to the K-type mass donor star). The K25V star contributes approximately 16 per cent of the light from the system and if not taken into account has a considerable effect upon radial velocity measurements of the mass donor star. We obtain a new radial velocity amplitude for the mass donor star of K ₂=202±3 km s¹, compared with the value of K ₂=135±3 km s¹ obtained in Stover, Robinson & Nather's classic study of EM Cyg. The revised value of the amplitude, combined with a measurement of rotational broadening of the mass donor, v  sin  i =140±6 km s¹, leads to a new mass ratio of q M ₂ M ₁=0.88±0.05. This solves a long-standing problem with EM Cyg, because Stover et al.'s measurements indicated a mass ratio q >1, a value that should have led to dynamically unstable mass transfer for the secondary mass deduced by Stover et al. The revised value of the mass ratio, combined with the orbital inclination i =67±2°, leads to masses of 0.99±0.12 M and 1.12±0.08 M for the mass donor and white dwarf respectively. The mass donor is evolved, because it has a later spectral type (K3) than its mass would imply.
We discuss whether the K star could be physically associated with EM Cyg or not, and present the results of the spectroscopic study.     

On the late spectral types of cataclysmic variable secondaries

We investigate why the spectral type of most cataclysmic variable (CV) secondaries is significantly later than that of a zero-age main-sequence (ZAMS) star with the same mean density. Using improved stellar input physics, tested against observations of low-mass stars at the bottom of the main sequence, we calculate the secular evolution of CVs with low-mass donors. We consider sequences with different mass transfer rates and with a different degree of nuclear evolution of the donor prior to mass transfer.
Systems near the upper edge of the gap ( P ∼3–6 h) can be reproduced by models with a wide range of mass transfer rates from 1.5×10⁻⁹ M_⊙ yr⁻¹ to 10⁻⁸ M_⊙ yr⁻¹. Evolutionary sequences with a small transfer rate and donors that are substantially evolved off the ZAMS (central hydrogen content 0.05–0.5) reproduce CVs with late spectral types above P ≳6 h. Systems with the most discrepant (late) spectral type should have the smallest donor mass at any given P .
Consistency with the period gap suggests that the mass transfer rate increases with decreasing donor mass for evolved sequences above the period gap. In this case, a single-parameter family of sequences with varying X _c and increasing mass transfer rate reproduces the full range of observed spectral types. This would imply that CVs with such evolved secondaries dominate the CV population.     

The Morpheus ultramodular autonomous underwater vehicle

The Advanced Marine Systems Lab at Florida Atlantic University has developed a new ultramodular plastic mini autonomous underwater vehicle (AUV), called the Morpheus, for littoral military and coastal oceanographic sampling, survey, and mapping. The name Morpheus was chosen because the Greek god Morpheus could change shape or "morph." The higher degree of modularity of the Morpheus AUV allows it to "morph" or change its size and components for different applications. This vehicle is composed of modular injection-molded plastic pressure vessels and a cabling system that allow the modules to be rearranged without rewiring bulkheads. The plastic pressure vessels are inexpensive, inherently mass-producible, extremely corrosion-resistant, and have low magnetic signatures. The pressure vessels are small but are sized to fit most standard electronic board standards. The mini AUV can be anywhere from 4 to 10 ft in length, depending on its mission. The vehicle architecture is an adaptation of the Ocean Explorer AUV system and uses an ANSI 709.1 (LonTalk) distributed control network for connecting all sensors and actuator subsystems as smart nodes. The modularity in containers, control, and power makes this vehicle rapidly reconfigurable and easy to repair or upgrade. This paper will present details of the motivation, design, and construction of the new mini AUV. The Morpheus was deployed during the summer of 2000 in field exercises for very shallow and shallow water mine counter measures. Some results from these tests will be presented     

How can spirals persist?

The image of a spiral galaxy is one of the most tantalizing images in nature. It demands that we ask: why do so many galaxies present this morphology? We currently have two main schools of thought concerning galaxy morphology, one based on gravitational effects and the other based on electromagnetic effects. The older gravitational models can explain how spirals might form, but they also predict that the spirals would quickly disintegrate. And the observed pervasiveness of spirals seems to imply not only their formation, but also their persistence over time. The newer plasma cosmology model is an improvement in that it explains how spirals might form and persist so long as plasma persists. But the formation of charge-neutral stars seems to return the scenario to the gravitational domain, and to subsequent dissolution. Clearly we need an additional idea to account for pervasive and persistent spiral galaxy structure. The present paper attempts to uncover a previously unrecognized gravitational mechanism that can serve as a viable candidate for sustaining persistent spiral galaxy structure.     

Chemical evidence for advection of hydrothermal solutions in the sediments of the Galapagos Mounds Hydrothermal Field

Pore water profiles of Ca, Mg, F, PO₄^?3 and Mn in the Galapagos Mounds Hydrothermal Field are believed to reflect, in part, upwelling of hydrothermal solutions through the sediments. Concentration-depth profiles in a low heat flow area just north of the Mounds Field display diagenetic changes typical of those found in pore waters underlying highly productive surface waters, consistent with the inference of no water flow or very slow downwelling ($\text{w < 5}\text{cm/yr}$) of bottom water through these sediments. Rates of upward advection calculated from Mounds Field pore water profiles of Ca, Mg, and F profiles agree well with each other, averaging about 1 cm/yr in the pelagic sediments near the mounds and 15–30 cm/yr within the hydrothermal mounds themselves. The upward advection also modifies the shape of PO₄^?3 and Mn profiles.Advection rates inferred from the pore water data are generally in reasonable agreement with those made from heat flow data.The higher Ca and lower Mg, F, PO₄^?3 and Mn concentrations in Mounds Field pore waters (compared with those of the low heat flow area) suggest chemical exchange between the solution and basalt prior to upwelling. Li⁺, K⁺, Rb⁺, Sr⁺⁺ and SO₄^? concentrations are indistinguishable from bottom water. This suggests very high effective water/rock ratios during the reactions which produced the upwelling solutions, perhaps due to extensive prior alteration of basalt adjacent to the flow path of water through the crust Inferred reaction temperatures are between 70–150°C.