Coronagraphic observations of an enhanced coronal region

Ratios of emission line intensities are used to calculate the variation of temperature and the variation of electron density as a function of ion class for differing paths through a coronal enhancement. The data indicate (a) a peak mean electron density of 2.3 × 10⁹ cm^–3, (b) a temperature maximum greater than 2.3 × 10⁶ K, and (c) the non-coincidence of the peak temperature and peak mean electron density. The latter demonstrates the invalidity of the assumption of symmetric models for coronal enhancements.The abundance of Ni was found to be equal to 0.045 that of Fe from the line ratio I( 6702)/ /I( 7059) and a density model based on the variation of the ratio I( 8024)/I( 6702).     

Detection of Extended Thermal Infrared Emission around the Vega-like Source HD 141569

We report the detection of extended IR emission at 10.8 and 18.2 μm around the Vega-like source HD 141569. Mid-IR imaging with OSCIR on Keck II shows emission from dust extending out to 100 AU from the B9.5 Ve star. Our modeling of the dust places an upper limit of approximately 2 μm on the diameter of the mid-IR-emitting particles if they are Mie spheres of astronomical silicates. Comparison of our mid-IR images to the near-IR (1.1 μm) NICMOS images of HD 141569 (Weinberger et al. 1999) shows that the mid-IR emission originates at smaller distances from the star than the scattered near-IR light, as also previously observed for the archetype Vega-like source beta Pictoris.     

The state and future of Mars polar science and exploration.

As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of approximately 10(6) km2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young--preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past approximately 10(5)-10(8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet--documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason--providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.     

Quaternary interaction of cryospheric and oceanographic processes along the central‐east Greenland margin

The east Greenland margin has been influenced by oceanographic and cryospheric processes since the late Miocene, when the southwards flow of the East Greenland Current (EGC) initiated and ice sheets first advanced across the margin. However, the relative importance of these processes, and their influence on the sedimentation of the margin through time remains poorly understood. High‐resolution single‐channel seismic, chirp sub‐bottom profiles and swath bathymetry data were acquired along the middle/lower slope and proximal basinal area off Liverpool Land, central‐east Greenland margin. In this study, seismic‐stratigraphical and morphological analyses allowed us to distinguish between the major sedimentary processes that influenced this margin during the Quaternary. The stratigraphical architecture reveals mass transport deposits (MTDs) related to glacially influenced down‐slope sedimentation. These are intercalated with buried contourite systems associated with bottom‐current controlled along‐slope sedimentation. The distribution of the MTDs suggests the influence of two distinct ice‐stream systems. Initial phases of down‐slope deposition during the early‐middle Quaternary appears to be related to distal deposition fed by an ice stream from the Scoresby Sund area in the south. Shallow sedimentary processes, together with morphological analysis of the sea floor, show that the most recent activity of down‐slope processes during the latest Quaternary has occurred in the north, linked to an ice stream from the Kong Oscar Fjord area. These observations document a temporal shift in the relative dominance of the Scoresby Sund and Kong Oscar Fjord ice‐stream systems. The glacial influence on the margin has been interrupted by periods of stronger activity of along‐slope bottom‐current flow, demonstrating that the EGC periodically controlled sedimentation on the continental margin.     

Mainstreaming local perceptions of hurricane risk into policymaking: A case study of community GIS in Mexico

This article suggests a framework for incorporating and communicating local perceptions of hurricane risk into policymaking through a case study conducted at El Zapotito commune in the State of Veracruz, Mexico. The authors constructed a geographical information system (GIS)-based model to quantify and spatially assess specific household-level vulnerabilities from information generated through interviews. This research developed a household vulnerability index applied to a participatory GIS to map vulnerability to hurricane hazard. The results indicate that infrastructural weaknesses are the most important factor contributing to vulnerability, explaining on their own 72.2% of the variation in the vulnerability patterns. These findings are corroborated by a vulnerability and capacity assessment (VCA), which shows that the community lacks strategies to cope with unsafe housing. It is suggested that linking community participation with modern techniques to analyse risk can empower communities and mobilise their capacities to address very specific vulnerabilities.     

Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes

This study combined water- and sediment flux measurements with mass balances of dissolved gas and inorganic matter to determine the importance of pelagic and benthic processes for whole-system metabolism in a eutrophic fluvial lake. Mass balances of dissolved O₂, inorganic carbon (DIC), nitrogen (DIN), phosphorous (SRP), particulate N (PN) and P (PP) and Chl a were calculated at a nearly monthly frequency by means of repeated sampling at the lake inlet and outlet. Simultaneously, benthic fluxes of gas and nutrients, including denitrification rates, and the biomass of the dominant pleustophyte (Trapa natans) were measured, and fluxes of O₂ and CO₂ across the water–atmosphere interface were estimated from diel changes in outlet concentrations. On an annual scale, Middle Lake exhibited CO₂ supersaturation, averaging 313% (range 86–562%), but was autotrophic with a net O₂ production (6.35 ± 2.05 mol m⁻² y⁻¹), DIC consumption (−31.18 ± 18.77 mol m⁻² y⁻¹) and net export of Chl a downstream (8.38 ± 0.95 mol C m⁻² y⁻¹). Phytoplankton was the main driver of Middle Lake metabolism, with a net primary production estimated at 33.24 mol O₂ m⁻² y⁻¹, corresponding to a sequestration of 4.18 and 0.26 mol m⁻² y⁻¹ of N and P, respectively. At peak biomass, T. natans covered about 18% of Middle Lake’s surface and fixed 2.46, 0.17 and 0.02 mol m⁻² of C, N and P, respectively. Surficial sediments were a sink for O₂ (−14.47 ± 0.65 mol O₂ m⁻² y⁻¹) and a source of DIC and NH₄ ⁺ (18.84 ± 2.80 mol DIC m⁻² y⁻¹ and 0.83 ± 0.16 mol NH₄ ⁺ m⁻² y⁻¹), and dissipated nitrate via denitrification (1.44 ± 0.11 mol NO₃ ⁻ m⁻² y⁻¹). Overall, nutrient uptake by primary producers and regeneration from sediments were a minor fraction of external loads. This work suggests that the creation of fluvial lakes can produce net autotrophic systems, with elevated rates of phytoplanktonic primary production, largely sustained by allochtonous nutrient inputs. These hypereutrophic aquatic bodies are net C sinks, although they simultaneously release CO₂ to the atmosphere.     

High-temperature vesuvianite: crystal chemistry and surface considerations

A multi-methodical approach has been applied for characterizing the bulk and surface crystal chemical features of a high-temperature vesuvianite crystal from skarns of Mount Somma-Vesuvius Volcano (Naples, Italy). Vesuvianite belongs to the space group P4/nnc with unit cell parameters a = 15.633(1) Å, c = 11.834(1) Å and chemical formula (Ca_18.858 Na_0.028 Ba_0.004 K_0.006 Sr_0.005 □_0.098)_19.000 (Al_8.813 Ti_0.037 Mg_2.954 Mn_0.008 Fe_0.114²⁺ Fe_1.375³⁺ Cr_0.008 B_0.202)_13.511 Si_18.000(O_0.261 F_0.940 OH_7.799)_9.000. Structure refinement, which converges at R = 0.0328, demonstrates a strong positional disorder down the fourfold axes, indicating that the Y1 site is split into two positions (Y1A and Y1B) alternatively occupied. However, because of X4 proximity to Y1B and Y1A, X4 cannot be occupied if Y1B or Y1A are. Overall Y1 occupancy (Y1A + Y1B) reaches approximately 0.5, as common in vesuvianite and occupancy of Y1B site is extremely limited. Moreover, T1 position, limitedly occupied, accommodates the excess of cations generally related to Y position. A small quantity (0.202 apfu) of boron is sited at the T2 site that, like T1, is poorly occupied. The determination of the amount of each element on the (100) vesuvianite surface, obtained through X-ray photoelectron spectroscopy high-resolution spectra in the region of the Si_2p, Al_2p, Mg_1s, and Ca_2p core levels, evidences that a greater amount of aluminum and a smaller amount of calcium characterize the surface with respect to the bulk. Although both of these features require further investigation, we may consider the Al increase can be related to preferential orientation of Al-rich sites on the (100) plane. Furthermore, the surface structure of vesuvianite suggests that Al, Ca, and Mg cations maintain coordination features at the surface similar to the bulk. Silica, however, while presenting fourfold coordination, shows also a [1]-fold small coordinated component at binding energy 99.85 eV, due to broken Si–O bonds at the surface. The presence of eight- and nine-coordinated Ca cations is suggested by a large XPS feature resulting from the merging of Ca_2p3/2 and Ca_2p1/2 peaks at 348.45 and 352.05 eV, respectively.     

Going West: Nutrient Limitation of Primary Production in the Northern Gulf of Mexico and the Importance of the Atchafalaya River

To investigate controls on phytoplankton production along the Louisiana coastal shelf, we mapped salinity, nutrient concentrations (dissolved inorganic nitrogen (DIN) and phosphorus (P_i), silicate (Si)), nutrient ratios (DIN/P_i), alkaline phosphatase activity, chlorophyll and ¹⁴C primary productivity on fine spatial scales during cruises in March, May, and July 2004. Additionally, resource limitation assays were undertaken in a range of salinity and nutrient regimes reflecting gradients typical of this region. Of these, seven showed P_i limitation, five revealed nitrogen (N) limitation, three exhibited light (L) limitation, and one bioassay had no growth. We found the phytoplankton community to shift from being predominately N limited in the early spring (March) to P limited in late spring and summer (May and July). Light limitation of phytoplankton production was recorded in several bioassays in July in water samples collected after peak annual flows from both the Mississippi and Atchafalaya Rivers. We also found that organic phosphorus, as glucose-6-phosphate, alleviated P limitation while phosphono-acetic acid had no effect. Whereas DIN/P_i and DIN/Si ratios in the initial water samples were good predictors of the outcome of phytoplankton production in response to inorganic nutrients, alkaline phosphatase activity was the best predictor when examining organic forms of phosphorus. We measured the rates of integrated primary production (0.33?C7.01 g C m^?2 d^?1), finding the highest rates within the Mississippi River delta and across Atchafalaya Bay at intermediate salinities. The lowest rates were measured along the outer shelf at the highest salinities and lowest nutrient concentrations (<0.1 ??M DIN and Pi). The results of this study indicate that P_i limitation of phytoplankton delays the assimilation of riverine DIN in the summer as the plume spreads across the shelf, pushing primary production over a larger region. Findings from water samples, taken adjacent the Atchafalaya River discharge, highlighted the importance of this riverine system to the overall production along the Louisiana coast.     

Strengthening conceptual foundations: Analysing frameworks for ecosystem services and poverty alleviation research

A research agenda is currently developing around the linkages between ecosystem services and poverty alleviation. It is therefore timely to consider which conceptual frameworks can best support research at this nexus. Our review of frameworks synthesises existing research on poverty/environment linkages that should not be overlooked with the adoption of the topical language of ecosystem services. A total of nine conceptual frameworks were selected on the basis of relevance. These were reviewed and compared to assess their ability to illuminate the provision of ecosystem services, the condition, determinants and dynamics of poverty, and political economy factors that mediate the relationship between poverty and ecosystem services. The paper synthesises the key contributions of each of these frameworks, and the gaps they expose in one another, drawing out lessons that can inform emerging research. Research on poverty alleviation must recognize social differentiation, and be able to distinguish between constraints of access and constraints of aggregate availability of ecosystem services. Different frameworks also highlight important differences between categories of services, their pathways of production, and their contribution to poverty alleviation. Furthermore, we highlight that it is important to acknowledge the limits of ecosystem services for poverty alleviation, given evidence that ecosystem services tend to be more associated with poverty prevention than reduction. We conclude by reflecting on the relative merits of dynamic Social–Ecological Systems frameworks versus more static checklists, and suggest that research on ecosystem services and poverty alleviation would be well served by a new framework distilling insights from the frameworks we review.