Supernova remnants, planetary nebulae and the distance to NGC 4214

We present narrow band, continuum subtracted Hα, [S ii], Hβ, [O iii] and [O ii] data taken with the Wide Field Camera 3 on the Hubble Space Telescope in the nearby dwarf starburst galaxy NGC 4214. From these images, we identify seventeen new planetary nebula candidates, and seven supernova remnant candidates. We use the observed emission line luminosity function of the planetary nebulae to establish a new velocity-independent distance to NGC 4214. We conclude that the PNLF technique gives a reddening independent distance to NGC 4214 of 3.19±0.36 Mpc, and that our current best-estimate of the distance to this galaxy ids 2.98±0.13 Mpc.     

Comparative Analysis of Stability—Genetic Diversity in Seagrass (<Emphasis Type="Italic">Posidonia oceanica</Emphasis>) Meadows Yields Unexpected Results

The diversity–stability relationship is the subject of a long-standing debate in ecology, but the genetic component of diversity has seldom been explored. In this study, we analyzed the interplay between genetic diversity and demographic responses to environmental pressures. This analysis included 30 meadows formed by the Mediterranean endemic seagrass, Posidonia oceanica, showing a wide range of population dynamics ranging from a near equilibrium state to steep decline due to strong environmental pressures close to aquaculture installations. Our results show that sedimentation rates are much better predictors of mortality than clonal or genetic components. An unexpected positive trend was observed between genotypic diversity and mortality, along with a negative relationship between allelic richness and net population growth. Yet such trends disappeared when excluding the most extreme cases of disturbance and mortality, suggesting the occurrence of a threshold below which no relationship exists. These results contrast with the positive relationship between genotypic diversity and resistance or resilience observed in previous manipulative experiments on seagrass. We discuss the reasons for this discrepancy, including the difficulties in designing experiments reflecting the complexity of natural meadows.     

Symplectite formation during decompression induced garnet breakdown in lower crustal mafic granulite xenoliths: mechanisms and rates

The complex microstructure of kelyphitic rims around garnet in lower crustal garnet granulite xenoliths from the Bakony–Balaton Highland Volcanic Field, Central Pannonian Basin has been studied in order to identify controls on garnet breakdown. Symplectites comprised of a vermicular intergrowth of submicron sized anorthite, orthopyroxene and spinel replace garnet at a sharp reaction front. Based on element distribution maps the transformation of garnet to symplectite is isochemical. Phase diagram calculations indicate that this reaction was induced by a pressure decrease and/or a temperature increase. In site-specific TEM foils prepared by focused ion beam technique and oriented parallel and perpendicular to the reaction front 200 nm wide rods of anorthite and 20 nm wide rods of spinel are identified. The rods are oriented approximately perpendicular to the replacement front and are embedded in an orthopyroxene matrix. The regular spacing of the symplectite phases along the reaction front suggests that their growth is controlled by diffusion. The kinetics of symplectite formation has been modelled based on irreversible thermodynamics. During interaction of the xenolith with the host basalt the microstructure and chemistry of the An–Opx–Spl symplectite was significantly modified and it was partially replaced by an olivine bearing symplectite. In contrast to primary symplectite formation, these processes were metasomatic in nature including addition of sodium, titanium and some trace elements from the basaltic melt and can clearly be discerned from the garnet breakdown. Based on these observations it is inferred that symplectite formation took place within the deep crust during the extension of the Pannonian Basin between 15 and 30 km depth at high temperature (850–1,050°C) prior to the volcanic transport to the surface.     

The Weierbach experimental catchment in Luxembourg: A decade of critical zone monitoring in a temperate forest - from hydrological investigations to ecohydrological perspectives

The Weierbach experimental catchment (0.45 km²) is the most instrumented and studied sub-catchment in the Alzette River basin in Luxembourg. Within the last decade, it has matured towards an interdisciplinary critical zone observatory focusing on a better understanding of hydrological and hydro-geochemical processes. The Weierbach catchment is embedded in an elevated sub-horizontal plateau, characterized by slate bedrock and representative of the Ardennes Massif. Its climate is semi-marine, with precipitation being rather evenly distributed throughout the year. Base flow is lowest from July to September, essentially due to higher losses through evapotranspiration in summer. The regolith is composed of Devonian slates, overlaid by Pleistocene slope deposits and entirely covered by forest with 70% deciduous and 30% coniferous trees. Since 2009, the Weierbach has been extensively equipped for continuously monitoring water fluxes and physico-chemical parameters within different compartments of the critical zone. Additionally, these compartments are sampled fortnightly at several locations to analyze δ¹⁸O and δ²H isotopic composition of water including rainfall, throughfall, soil water, groundwater and streamwater. This ongoing monitoring and sampling programme is used for answering pressing questions related to fundamental catchment functions of water infiltration, storage, mixing and release in forest ecosystems. A recently started research line aims at investigating interactions between forest eco-hydrosystems with the atmosphere and understanding how catchments will respond to a non-stationary climate.     

Reproductive traits of Euterpina acutifrons in a coastal area of Southeastern Brazil

We investigated the reproductive biology of the planktonic harpacticoid copepod Euterpina acutifrons, including morphometric data, egg production rates (EPR) and viability, and weight‐specific egg production. Experiments were carried out during 1 year in an inner‐shelf area off Ubatuba (SE Brazil), a site seasonally influenced by bottom intrusions of the relatively cold and nutrient‐rich South Atlantic Central Water (SACW). We hypothesized that E. acutifrons attain higher reproductive rates when SACW penetrates in this region. Live females were incubated individually in cell culture plates during two periods of 24 h each, under controlled temperature and light conditions. Euterpina acutifrons carried on average 16.9 ± 6.9 eggs·sac^?1, ranging between 10.8 ± 5.7 and 30.8 ± 7.4 eggs·sac^?1. Estimated EPRs ranged from 6.3 ± 3.4 to 13.6 ± 4.2 eggs·female^?1·day^?1, with mean weight‐specific egg production rates of 0.06 ± 0.04 and 0.17 ± 0.08 per day. Euterpina acutifrons was not directly influenced by SACW intrusions, but body length and clutch size were positively related to temperature and chlorophyll content. Egg hatching time was clearly dependent on water temperature, as a 2 °C increase resulted in a decrease of 15 h in egg hatching time. This shows that even a small variation in temperature may considerably affect E. acutifrons population dynamics. Reproductive traits of this pelagic harpacticoid seem, therefore, to be controlled by the trade‐offs between increased food supply and the metabolic demands at low temperatures associated with SACW bottom intrusions toward this coastal area.     

The importance of the vertical accuracy of digital elevation models in gauging inundation by sea level rise along the Valdelagrana beach and marshes (Bay of Cádiz, SW Spain)

The identification of potential coastal inundation caused by future sea level rise requires not only time series records from tide gauges, but also high-quality digital elevation models (DEMs). This study assesses the importance of DEM vertical accuracy in predicting inundation by sea level rise along the Valdelagrana beach and marshes of the Bay of Cádiz (SW Spain). A present-day (2000) and a projected (2100) high tide have been spatialized over a traditional (aerial photogrammetry) regional DEM of Andalusia with a horizontal spatial resolution of 10 m and a vertical accuracy of 0.68 m RMSE (root mean square error), and a LIDAR-derived DEM of the Valdelagrana study site with the same spatial resolution but a vertical accuracy of 0.205 m RMSE. The simulations are based on a bathtub model, which accounts for the effect of vertical barriers. The results reveal that the presence of infrastructures such as roads and salterns is the key to delimit the extent of water penetration during high tides in an otherwise homogeneously flat area comprising the beach and marshes of Valdelagrana. Moreover, in comparison with the highly accurate LIDAR DEM, the inundation areas derived from the lower-resolution DEM are overestimated by 72 % and 26 % for the present-day and future scenarios respectively. These findings demonstrate that DEM vertical accuracy is a critical variable in meaningfully gauging the impacts of sea level rise.     

Large-scale atmospheric conditions associated with heavy rainfall episodes in Southeast Brazil

Heavy rainfall events in austral summer are responsible for almost all the natural disasters in Southeast Brazil. They are mostly associated with two types of atmospheric perturbations: Cold Front (53%) and the South Atlantic Convergence Zone (47%). The important question of what synoptic characteristics distinguish a heavy rainfall event (HRE) from a normal rainfall event (NRE) is addressed in this study. Here, the evolutions of such characteristics are identified through the anomalies with respect to climatology of the composite fields of atmospheric variables. The anomalies associated with HRE are significantly more intense than those associated with NRE in all fundamental atmospheric variables such as outgoing long-wave radiation, sea-level pressure, 500-hPa geopotential, lower and upper tropospheric winds. The moisture flux convergence over Southeast Brazil in the HRE composites is 60% larger than in the NRE composites. The energetics calculations for the HRE that occurred in the beginning of February 1988 strongly suggest that the barotropic instability played an important role in the intensification of the perturbation. These results, especially the intensities of the wind, pressure anomalies, and the moisture convergence are useful for the meteorologists of the Southeast Brazil for forecasting heavy precipitation.     

Analyzing the genesis, intensity, and tracks of western Mediterranean cyclones

Midlatitude cyclones are analyzed on a selected region covering most of southern Europe and the western part of the Mediterranean Sea (35–50°N, 10°W–25°E). On the basis of mean sea level pressure fields of the ECMWF (European Centre for Medium-range Weather Forecast) Reanalysis Dataset (ERA-40), detailed evaluation of Mediterranean cyclones is accomplished for the period between 1957 and 2002 on a 1° horizontal resolution grid. Cyclone centers are identified and their paths are tracked with a 6-h time step (using 00 UTC, 06 UTC, 12 UTC, and 18 UTC). Decadal, annual, and seasonal statistical analysis of cyclone tracks includes the study of the genesis, frequency, and activity of the Mediterranean cyclones as well as the variability of cyclone tracks. The results suggest that the cyclone frequency in the western Mediterranean region increased in summer and autumn, and decreased in winter and spring. A special belt-shaped area is identified, which plays a special role in cyclogenesis, and also, the cyclone tracks often remain within this belt. An overall decreasing trend is detected in winter and spring in the entire Mediterranean belt, while cyclone frequency increased in autumn. The largest positive and negative trend coefficients are identified in summer.     

Multi-spacecraft Observations of CIR-Associated Ion Increases During the Ulysses 2007 Ecliptic Crossing

The period between 21 June and 8 October, 2007 (Carrington rotations 2058 to 2061), comprising the Ulysses ecliptic plane crossing, was characterized by low solar activity. Excluding the small solar energetic particle events observed during July, the ion increases observed in the inner heliosphere between 100?keV/n and 10?MeV/n were associated with Corotating Interaction Regions (CIRs). In this work, we investigate CIR-related ion increases using multipoint observations from Ulysses, ACE, and the twin STEREO spacecraft. The ballistic backmapping technique has been used to correlate in situ observations of these spacecraft and remote-sensing observations of coronal holes. Although the radial, longitudinal and latitudinal separation of the spacecraft (except Ulysses) are relatively small, we find discrepancies when a detailed comparison of narrow structures like stream interfaces and CIR-associated shocks is performed. Therefore we concentrate on the two CIR events from day 5 to day 10 of August 2007 and from day 25 to day 31 of August 2007, which lend themselves to a more undisturbed comparison. Using the multi-spacecraft measurements we could determine a radial gradient of 230±30% AU^?1, which is consistent with previous results by van Hollebeke et al. (J. Geophys. Res. 83, 4723, 1978) of ～?350% AU^?1 using Helios and Pioneer data.

     

Decomposition of functions for elliptic orbits

In the algebraA of functions periodic in the mean anomaly we relate the problem of integrating over the mean anomaly with that of decomposing an element ofA as the direct sum of two functions, one in the kernel of the Lie derivative in the Keplerian flow and one in the image of this Lie derivative. We propose recursive rules amenable to general purpose symbolic processors for accomplishing such decomposition in a wide subclass ofA. We introduce the dilogarithmic function to express in exact terms quadratures involving the equation of the center.