A possible theoretical explanation of metallicity gradients in elliptical galaxies

Models of chemical evolution of elliptical galaxies taking into account different escape velocities at different galactocentric radii are presented. As a consequence of this, the chemical evolution develops differently in different galactic regions; in particular, we find that the galactic wind, powered by supernovae (of Type II and I) starts, under suitable conditions, in the outer regions and successively develops in the central ones. The star formation is assumed to stop after the onset of the galactic wind in each region. The main result found in the present work is that this mechanism is able to reproduce metallicity gradients, namely the gradients in the Mg₂ index, in good agreement with observational data. We also find that in order to honour the constant [〈Mg/Fe〉] ratio with galactocentric distance, as inferred from metallicity indices, a variable initial mass function as a function of galactocentric distance is required. This is only a suggestion, as trends on abundances inferred purely from metallicity indices are still uncertain.     

Seagrass meadows at the extreme of environmental tolerance: the case of Posidonia oceanica in a semi-enclosed coastal lagoon

Atoll‐like structures of the endemic Mediterranean seagrass Posidonia oceanica were encountered in the innermost area of the Stagnone di Marsala, a semi‐enclosed coastal lagoon along the western coasts of Sicily. The area is characterized by limited water exchange with the open sea and by a marked seasonal variation of water salinity and temperature, reaching beyond the theoretical tolerance limits of the species. In the present study we determined the genetic composition of the atoll‐like structures, as well as the growth performance and flowering rate of these stands. We also assessed whether and to what extent the atoll‐like structures are genetically isolated from plants growing in meadows outside the lagoon. For this purpose we utilized 13 microsatellite markers to genotype single shoots sampled inside and outside the lagoon. Lepidochronological analyses were performed on the same shoots to determine the annual rhizome growth rate, the number of leaves and the inflorescences formed as an estimate of growth‐ and reproductive performance over the years. The innermost area of the lagoon showed a lower number of alleles, a lower percentage of polymorphic loci, a lower clonal diversity, but higher heterozygosis excess with respect to the other areas analysed. Spatial autocorrelation was here significant, up to slightly below 300 m. Shoots collected in the atolls exhibited a 25% lower vertical growth rate and 16% lower leaf formation in comparison to those in open‐sea meadows. No flowering events were recorded during 24 years of investigation, whereas inflorescences were observed frequently in meadows outside the lagoon. Results from F_st and factorial correspondence analysis confirmed the expected genetic isolation of the confined atolls with respect to the meadows outside the lagoon and revealed limited gene flow within the lagoon itself. Apparently, the enclosed system of the Stagnone lagoon is genetically isolated, with a possible selection of genotypes adapted to persistent stressful conditions, consistent with reduced growth and lack of flowering events.     

Sounding-derived indices for neural network based short-term thunderstorm and rainfall forecasts

A neural network-based scheme to do a multivariate analysis for forecasting the occurrence and intensity of a meteo event is presented. Many sounding-derived indices are combined together to build a short-term forecast of thunderstorm and rainfall events, in the plain of the Friuli Venezia Giulia region (hereafter FVG, NE Italy).For thunderstorm forecasting, sounding, lightning strikes and mesonet station data (rain and wind) from April to November of the years 1995–2002 have been used to train and validate the artificial neural network (hereafter ANN), while the 2003 and 2004 data have been used as an independent test sample. Two kind of ANNs have been developed: the first is a “classification model” ANN and is built for forecasting the thunderstorm occurrence. If this first ANN predicts convective activity, then a second ANN, built as a “regression model”, is used for forecasting the thunderstorm intensity, as defined in a previous article.The classification performances are evaluated with the ROC diagram and some indices derived from the Table of Contingency (like KSS, FAR, Odds Ratio). The regression performances are evaluated using the Mean Square Error and the linear cross correlation coefficient R.A similar approach is applied to the problem of 6 h rainfall forecast in the Friuli Venezia Giulia plain, but in this second case the data cover the period from 1992 to 2004. Also the forecasts of binary events (defined as the occurrence of 5, 20 or 40 mm of maximum rain), made by classification and regression ANN, were compared. Particular emphasis is given to the sounding-derived indices which are chosen in the first places by the predictor forward selection algorithm.     

基于GIS技术的三维可视化数字校园建设研究——以贵州大学为例

“数字化校园”通过对校区内地物地貌进行数字化建模,形成可视的校园基础地理信息模型,具有覆盖面积小、资料容易获取、实地踏勘方便等优势,对于现代化校园建设管理具有积极意义。通过高清卫星影像图与实地调查相结合的方法,进行了ArcGIS区域矢量化、三维建模以及编写HTML网页的工作,实现了三维可视化校园成果在ArcScene平台和网页平台的展示。结果表明,利用SketchUp建模并通过网页浏览的效果较好,普适性更强,更易被大众所接受,拓宽了三维可视化成果的受众范围。     

An investigation about natural radioactivity,hydrochemistry, and metal pollution in groundwater from Calabrian selected areas,southern Italy

The increasing interest in radioactivity has brought about the need for an assessment of human exposure to radiation. It is, therefore, necessary to examine naturally occurring radioactivity in the environment, especially its occurrence in groundwater. The aim of this work was then to study the levels and behavior of the most significant natural radionuclides, also in order to improve the knowledge of the hydrochemical processes involved in the selected groundwater systems. Natural radioactivity in fifteen Calabrian groundwaters for human use was investigated through high-resolution gamma spectrometry (with a negative-biased Ortec HPGe detector) and liquid scintillation measurements. Particular attention was given on those radionuclides (³H, ²³⁸U, ²²⁶Ra, and ²²⁸Ra), which contribute in a significant way to the overall effective dose received by members of the public due to the intake of drinking water originating from groundwater systems. The activity concentration of ²³⁸U varied from 1 to 51 mBq/L, as a result of the geology of the investigated area and of the oxidizing conditions that favored U dissolution. ²²⁶Ra presented a broad range of activity concentrations (0.011–0.14 mBq/L), lower than uranium ones because radium occurs in groundwater under reducing conditions. Some heavy metals (Cd, Pb, Be, Hg, Ag, As, Tl, Sb, Se, and Ni) were also investigated through ICP-MS measurements and compared with the limits set by the Italian Legislation. Metals are released into the environment by both natural and anthropogenic sources; they leach into underground waters, moving along water pathways and eventually depositing in the aquifer.     

A statistical analysis of climate variability and ecosystem response in the German Bight

We compiled homogeneous long-term time series comprising 39 variables representing the German Bight and for the period 1975–2004. A diverse set of variables was selected to cover multiple trophic levels and different environmental forcing thus to examine long-term changes in this coastal region. Previous studies have hypothesised the presence of regime shifts in observations extending over the entire North Sea. Focusing on a smaller spatial scale, and closer to the coast, we investigated the major modes of variability in the compiled time series using principal component analysis. The results obtained confirm a previously identified regime shift in the North Sea in 1987/1988 and suggest that the German Bight is dominantly characterised by long-term modes of variability. In the German Bight, the shift of 1987/1988 is driven primarily by temperature, Gulf Stream index, frost days and Secchi depth. Changes in some of the ecosystem variables (plankton and fish) appear to be related to changes in these driving variables. In particular, we documented strong positive correlations between the long-term trend showed by the first principal component and herring, Noctiluca scintillans, and, to a lesser extent, Pleurobrachia pileus. Two gadoids, namely cod and saithe, showed negative correlations with the observed long-term mode of variability. Changes in the sum of five small calanoid copepods were, however, less marked. Phosphate and ammonium exhibited a decreasing trend over the last 30 years. Diatoms and Calanus helgolandicus did not show evidence of changes in concert to this trend. Specific analyses of the data divided into three different subsets (biological, climatic and chemical) characterise the climate of the German Bight as highly dynamic also on short timescales (a few years) as compared to much smoother biological and chemical components. The dynamic regime of the German Bight taken together with a low correlation between the major mode of variability and phytoplankton and zooplankton data suggests that the lower trophic levels of this ecosystem are remarkably resilient.     

Structural setting of the Southern Apennine fold-and-thrust belt (Italy) at hypocentral depth: The Calore Valley case history

The reconstruction of the main structural features of the Southern Apennines (Italy), in correspondence with the focal volume of some strong earthquakes that have affected this chain, can be attempted by analysing reflection seismic lines and deep well logs in comparison with surface geology.For instance, the Calore Valley and its surroundings have been the object of intense hydrocarbon exploration, and a wealth of subsurface data is available. Moreover, this area was affected by the 1688 Sannio earthquake (macroseismic magnitude 7.1), and a new location has recently been proposed for the related causative fault system. The present work defines the structural setting of the Southern Apennine chain in correspondence with this new location, and compares it with similar cases along the Italian peninsula.The analysis was focussed on the reconstruction of deep tectonic units (formed by the buried Apulia carbonate platform succession), which generally correspond to the hypocentral depths of strong earthquakes along the axis of the Southern Apennines. The results show that the Apulia platform succession is affected by three main thrusts, locally accompanied by backthrusts. The top of this succession is relatively shallow: the maximum depth does not exceed 1.8 s TWT (i.e. about 3500 m b.s.l.), while minimum depths occur in correspondence with the ramp anticlines culminations, at 0.5 s TWT (i.e. at about 500 m b.s.l.). Moreover, data suggest that the underlying Paleozoic basement is possibly involved in thrusting.In a regional perspective, extensional seismogenic structures along the axis of the Southern Apennines seem to share some common characteristics. Indeed, they develop (i) in correspondence with an uplifted Paleozoic basement; (ii) at the rear of a set of thrusts that account for the shallow Apulia units; (iii) at the surface, in proximity to the leading edge of a surficial tectonic unit formed by the Apennine carbonate platform succession. The 1688 seismogenic fault system fits in with these common traits. In the light of this, we finally speculate that these common characteristics in the architecture of the chain could provide a key to the location of the major seismicity along the axis of the Southern Apennines and an interpretative model for the identification of possible areas of seismic gap in this part of the Italian peninsula.     

The effects of post-orogenic extension on different scales: an example from the Apennine–Maghrebide fold-and-thrust belt, SW Sicily

ABSTRACT Many structures produced under one single deformation regime, namely extensional, contractional or strike-slip, exhibit remarkable geometrical analogies when analysed at different scales. By contrast, field examples that illustrate the scale effects on structures resulting from superimposed deformations, which were produced under different tectonic regimes, are rare. Yet the change from contraction to extension is known to occur often in the most thickened portions of the continental crust. The Apennine–Maghrebide fold-and-thrust belt of Sicily shows many examples of post-orogenic extensional deformations. Composite structures, resulting from late normal faults that offset folds and thrusts, are observed at four different scales, from regional to mesoscopic, in the south-western portion of Sicily and in the adjacent Isle of Favignana. The recognized analogies in the geometry of these composite structures may provide a key for the interpretation of the features of regional structures, whose deep geometry is often poorly constrained. Moreover, comparison of normalized displacements accommodated by contractional and extensional faults of different scales indicates that self-similarity is not unique to structures produced under single tectonic regimes.     

Combining relative and absolute gravity measurements to enhance volcano monitoring

To achieve a balance between uncertainty and efficiency in gravity measurements, we have investigated the applicability of combined measurements of absolute and relative gravity as a hybrid method for volcano monitoring. Between 2007 and 2009, three hybrid gravity surveys were conducted at Mt Etna volcano, in June 2007, July 2008, and July 2009. Absolute gravity data were collected with two absolute gravimeters, which represent the state of the art in recent advances in ballistic gravimeter technology: (1) the commercial instrument FG5#238 and (2) the prototype instrument IMGC-02. We carried out several field surveys and confirmed that both the absolute gravimeters can still achieve a 10 μGal or better uncertainty even when they are operated in severe environmental conditions. The use of absolute gravimeters in a field survey of the summit area of Mt Etna is unprecedented. The annual changes of the gravity measured over 2007–2008 and 2008–2009 provide unequivocal evidence that during the 2007–2009 period, two main phenomena of subsurface mass redistribution occurred in distinct sectors of the volcano, accompanying different eruptive episodes. From 2007 to 2008, a gravity change of ?60?μGal was concentrated around the North-East Rift. This coincided with a zone affected by strong extensional tectonics, and hence might have been related to the opening of new voids. Between 2008 and 2009, a North-South elongate feature with a maximum gravity change of +80?μGal was identified in the summit craters area. This is interpreted to indicate recharge of a deep-intermediate magma storage zone, which could have occurred when the 2008–2009 eruption was still ongoing.     

地物光谱的颜色分析技术及其在颜色装饰生产中的开发应用

讲述了遥感地物光错研究中地物光语的颜色分析技术的原理和光谱的测量设备及解译方法，并且列举了光讲与颜色分析技米在颜色装饰工业生产中的开发应用实例。