FPGA based Soft-core SIMD Processing: A MIMO-OFDM Fixed-Complexity Sphere Decoder Case Study

To enable reliable data transfer in next generation Multiple-Input Multiple-Output (MIMO) communication systems, terminals must be able to react to fluctuating channel conditions by having flexible modulation schemes and antenna configurations. This creates a challenging real-time implementation problem: to provide the high performance required of cutting edge MIMO standards, such as 802.11n, with the flexibility for this behavioural variability. FPGA softcore processors offer a solution to this problem, and in this paper we show how heterogeneous SISD/SIMD/MIMD architectures can enable programmable multicore architectures on FPGA with similar performance and cost as traditional dedicated circuit-based architectures. When applied to a 4×4 16-QAM Fixed-Complexity Sphere Decoder (FSD) detector we present the first soft-processor based solution for real-time 802.11n MIMO.

A Kernel Interleaved Scheduling Method for Streaming Applications on Soft-core Vector Processors

Massively parallel networks of highly efficient, high performance Single Instruction Multiple Data (SIMD) processors have been shown to enable FPGA-based implementation of real-time signal processing applications with performance and
cost comparable to dedicated hardware architectures. This is achieved by exploiting simple datapath units with deep processing pipelines. However, these architectures are highly susceptible to pipeline bubbles resulting from data and control hazards; the only way to mitigate against these is manual interleaving of
application tasks on each datapath, since no suitable automated interleaving approach exists. In this paper we describe a new automated integrated mapping/scheduling approach to map algorithm tasks to processors and a new low-complexity list scheduling technique to generate the interleaved schedules. When applied to a spatial Fixed-Complexity Sphere Decoding (FSD) detector
for next-generation Multiple-Input Multiple-Output (MIMO) systems, the resulting schedules achieve real-time performance for IEEE 802.11n systems on a network of 16-way SIMD processors on FPGA, enable better performance/complexity balance than current approaches and produce results comparable to handcrafted implementations.

Spatial Heterogeneity and Kinetic Regulation of Arsenic Dynamics in Mangrove Sediments: The Sundarbans, Bangladesh

The biogeochemistry of arsenic (As) in sediments is regulated by multiple factors such as particle size, dissolved organic matter (DOM), iron mobilization, and sediment binding characteristics, among others. Understanding the heterogeneity of factors affecting As deposition and the kinetics of mobilization, both horizontally and vertically, across sediment depositional environments was investigated in Sundarban mangrove ecosystems, Bengal Delta, Bangladesh. Sediment cores were collected from 3 different Sundarbans locations and As concentration down the profiles were found to be more associated with elevated Fe and Mn than with organic matter (OM). At one site chosen for field monitoring, sediment cores, pore and surface water, and in situ diffusive gradients in thin films (DGT) measurements (which were used to model As sediment pore-water concentrations and resupply from the solid phase) were sampled from four different subhabitats. Coarse-textured riverbank sediment porewaters were high in As, but with a limited resupply of As from the solid phase compared to fine-textured and high organic matter content forest floor sediments, where porewater As was low, but with much higher As resupply. Depositional environment (overbank verses forest floor) and biological activity (input of OM from forest biomass) considerably affected As dynamics over very short spatial distances in the mosaic of microhabitats that constitute a mangrove ecosystem.

Assessment of bioavailable arsenic and copper in soils and sediments from the Antofagasta region of northern Chile

Copper levels of nearly 500 mg l(-1) were measured in aqueous extracts of soil and sediment samples from the lowlands of Antofagasta. Arsenic levels of up to 183 mg l(-1) were found in river sediments, and 27.5 mg l(-1) arsenic was found at the location of a dam where potable water is extracted. This indicates that the arsenic contamination of water supplies reported recently for the pre-Andes may be a widespread problem throughout the region. Copper contamination from smelting activities also provides cause for concern as elevated levels were found in aqueous extracts of soil up to 20 km away from a smelter. This study went beyond traditional chemical analysis by assessing the potential benefits of using microbial biosensors as an alternative to determination of chemical speciation, to provide an environmentally relevant interpretation of soil/sediment residue levels. This approach is simple to use and enables a rapid, low cost assessment of pollutant bioavailability. It may, therefore, be of use for further investigations in the region and beyond.

Optimisation of time/temperature treatment, for heat treated soft wheat flour

Chlorination of wheat flour in the EU countries has been replaced in recent years, to some extent, by heat treated flour which is used to produce high ratio cakes. Heat treated flour allows high ratio recipes to be developed which generate products with longer shelf life, finer texture, moist crumb and sweeter taste. The mechanism by which heat treatment improves the flour is not fully understood, but it is known that during the heat treatment process, protein denaturation and partial gelatinisation of the starch granules occurs, as well as an increase in batter viscosity. Therefore, it is important to optimize the flour heat treatment process, in order to enhance baking quality. Laboratory preparation of heat treated base wheat flour (culinary, soft, low protein) was carried out in a fluidised bed drier using a range of temperatures and times. The gluten was extracted from the final product and its quality was tested, to obtain objective and comparative information on the extent of protein denaturation. The results indicated that heat treatment of flour decreases gluten extensibility and partial gelatinisation of the starch granules occurred. After heat treatment the gluten appeared to retain moisture. The optimum time/temperature for the heat treatment of base flour was 120-130°C for 30 min with moisture content of ˜12.5%.© 2012 Elsevier Ltd. All rights reserved.

The (Soft) Power of Commitment:The EU and Conflict Resolution in Northern Ireland

This paper examines the potential of international actors to contribute to conflict resolution by analysing the evolving role of the European Union (EU) in embedding Northern Ireland's peace process. Scrutiny of the EU's approach to conflict resolution in Northern Ireland offers useful insights into the scope and potential of soft power for facilitating behavioural change from governmental to grass-roots levels. This paper traces the development of the EU's approach to conflict resolution in Northern Ireland from one concentrated on encouraging state-level agreement, to nurturing peace through multilevel funding, through now to consolidating the peace by facilitating regional-level empowerment. The core argument is that, in sum, the most critical element of the EU's contribution to peace in Northern Ireland has been, quite simply, that of enduring commitment.

On the relativistic iron line and soft excess in the Seyfert 1 galaxy Markarian 335

We report a 133-ks XMM-Newton observation of the Seyfert 1 galaxy Markarian 335. The 0.4-12 keV spectrum contains an underlying power-law continuum, a soft excess below 2 keV, and a double-peaked iron emission feature in the 6-7 keV range. We investigate the possibility that the double-peaked emission might represent the characteristic signature of the accretion disc. Detailed investigations show that a moderately broad accretion disc line is most likely present, but that the peaks may be due to narrower components from more distant material. The peaks at 6.4 and 7 keV can be identified, respectively, with the molecular torus in active galactic nucleus unification schemes, and very highly ionized, optically thin gas filling the torus. The X-ray variability spectra on both long (~100 ks) and short (~1 ks) time-scales do not support the recent suggestion that the soft excess is an artefact of variable, moderately ionized absorption. © 2007 The Authors. Journal compilation © 2007 RAS.

Field observation of sequestration of uranium in iron-rich sediments under sequential reduction-oxidation conditions at the DOE Oak Ridge IFRC

At the U.S. DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) site, the iron content of shallow subsurface materials (i.e. weathered saprolite) is relatively high (up to 5-6% as w/w), and therefore, the forms of the iron species present plays a critical role in the long-term sequestration of uranium. A long term pilot-scale study of the bioreduction and reoxidation of uranium conducted at the ORIFRC area 3 site, adjacent to the former S-3 disposal ponds (source zone), has provided us with the opportunity to study the impact of iron species on the sequestration of U(VI). The aqueous U(VI) concentrations at the site were decreased to below the EPA MCL through the intermittent injection of ethanol as the electron donor. Previous field tests indicated that both oxygen and nitrate could oxidize the bioreduced U(IV) and cause a short-term rebound of aqueous phase uranium concentration after the oxidative agents were delivered directly to the bioreduced zone.

A field test has been conducted to examine the long-term effect of exposure of bioreduced sediments to nitrate in contaminated groundwater for more than 1,380 days at the Area 3 site. Contaminated groundwater was allowed to invade the previously bioreduced zone via the natural groundwater gradient after an extended period in which reducing conditions were maintained and the bioreduced zone was protected from the influx of upgradient contaminated groundwater. The geochemical response to the invasion of contaminated groundwater was dependent on whether the monitoring location is in the middle or the fringe of the previously bioreduced zone. In general, the nitrate concentrations in the previously bioreduced area, increased gradually from near zero to ~50-300 mM within 200 days and then stabilized. The pH declined from bioreduced levels of 6.2-6.7 to below 5.0. Uranium concentrations rebounded in all monitoring wells but at different rates. At most locations U concentrations rebounded, declined and then rebounded again. Methane gas disappeared while a significant level (20,000 to 44,000 ppmv) N2O was found in the groundwater of monitoring wells after three years of reoxidization.

The U(IV) in sediments was mainly reoxidized to U(VI) species. Based on XANES analysis, the predominate uranium in all samples after re-oxidation was similar to a uranyl nitrate form. But the U content in the sediment remained as high as that determined after bioreduction activates were completed, indicating that much of the U is still sequestrated in situ. SEM observations of surged fine sediments revealed that clusters of colloidal-sized (200-500nm) U-containing precipitates appeared to have formed in situ, regardless from sample of FW106 in non-bioactivity control area or of pre-bioreduced FW101-2 and FW102-3. Additionally, SEM-EDS and microprobe analysis, showed that the U-containing precipitates (~1% U) in FW106 are notably higher in Fe, compared to the precipitates (~1-2.5% U) from FW101-2 and FW102-3. However, XRF analysis indicated that the U content was remained as high as 2180 and 1810 mg/kg with U/Fe ratio at 0.077 and 0.055 vs 0.037 g/g, respectively in pre-bioreduced FW101-2 and FW102-3, suggesting more U sequestrated by Fe in pre-bioreduced sediments.

Vegetation changes and human settlement of Easter Island during the last millennia: a multiproxy study of the Lake Raraku sediments

Earlier palynological studies of lake sediments from Easter Island suggest that the island underwent a recent and abrupt replacement of palm-dominated forests by grasslands, interpreted as a deforestation by indigenous people. However, the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied. This has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown. Our multiproxy study of a core recovered from Lake Raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late Holocene. The sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes. The results show a long, gradual and stepped landscape shift from palm-dominated forests to grasslands. This change started c. 450 BC and lasted about two thousand years. The presence of Verbena litoralis, a common weed, which is associated with human activities in the pollen record, the significant correlation between shifts in charcoal influx, and the dominant pollen types suggest human disturbance of the vegetation. Therefore, human settlement on the island occurred c. 450 BC, some 1500 years earlier than is assumed. Climate variability also exerted a major influence on environmental changes. Two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the Medieval Climate Anomaly and the Little Ice Age, respectively. At c. AD 1200, the water table rose and the former Raraku mire turned into a shallow lake, suggesting higher precipitation/evaporation rates coeval with a cooler and wetter Pan-Pacific AD 1300 event. Pollen and diatom records show large vegetation changes due to human activities c. AD 1200. Other recent vegetation changes also due to human activities entail the introduction of taxa (e.g. Psidium guajava, Eucalyptus sp.) and the disappearance of indigenous plants such as Sophora toromiro during the two last centuries. Although the evidence is not conclusive, the American origin of V. litoralis re-opens the debate about the possible role of Amerindians in the human colonisation of Easter Island.

Molecular- and pollen-based vegetation analysis in lake sediments from central Scandinavia

Plant and animal biodiversity can be studied by obtaining DNA directly from the environment. This new approach in combination with the use of generic barcoding primers (metabarcoding) has been suggested as complementary or alternative to traditional biodiversity monitoring in ancient soil sediments. However, the extent to which metabarcoding truly reflects plant composition remains unclear, as does its power to identify species with no pollen or macrofossil evidence. Here, we compared pollen-based and metabarcoding approaches to explore the Holocene plant composition around two lakes in central Scandinavia. At one site, we also compared barcoding results with those obtained in earlier studies with species-specific primers. The pollen analyses revealed a larger number of taxa (46), of which the majority (78%) was not identified by metabarcoding. The metabarcoding identified 14 taxa (MTUs), but allowed identification to a lower taxonomical level. The combined analyses identified 52 taxa. The barcoding primers may favour amplification of certain taxa, as they did not detect taxa previously identified with species-specific primers. Taphonomy and selectiveness of the primers are likely the major factors influencing these results. We conclude that metabarcoding from lake sediments provides a complementary, but not an alternative, tool to pollen analysis for investigating past flora. In the absence of other fossil evidence, metabarcoding gives a local and important signal from the vegetation, but the resulting assemblages show limited capacity to detect all taxa, regardless of their abundance around the lake. We suggest that metabarcoding is followed by pollen analysis and the use of species-specific primers to provide the most comprehensive signal from the environment. © 2013 Blackwell Publishing Ltd.

Spatial autocorrelation in the response of soft-bottom marine benthos to gas extraction activities: The case of amphipods in the Ionian Sea

The spatial distributions of marine fauna and of pollution are both highly structured, and thus the resulting high levels of autocorrelation may invalidate conclusions based on classical statistical approaches. Here we analyse the close correlation observed between proxies for the disturbance associated with gas extraction activities and amphipod distribution patterns around four hydrocarbon platforms. We quantified the amount of variation independently accounted for by natural environmental variables, proxies for the disturbance caused by platforms, and spatial autocorrelation. This allowed us to demonstrate how each of these three factors significantly affects the community structure of amphipods. Sophisticated statistical techniques are required when taking into account spatial autocorrelation: nevertheless our data demonstrate that this approach not only enables the formulation of robust statistical inferences but also provides a much deeper understanding of the subtle interactions between human disturbance and natural factors affecting the structure of marine invertebrates communities. (C) 2012 Elsevier Ltd. All rights reserved.