The composition and conservation of Romania's plant cover     

E. Cristina Muica  Ana Popova-Cucu 《GeoJournal》1993,29(1):9-18

Romania is characterised by great floristic diversity and there are many distinctive aspects to the distribution of vegetation units. However, even the sparsely-populated mountainous country has been affected by anthropic activity, increasing in intensity through the expansion of agriculture during the nineteenth century and the recent emphasis on industrial development. It is therefore essential that the diverse plant cover should be given the protection of national park or nature reserve status. The present designations are substantial, though not yet adequate, and careful monitoring is needed to establish the extent or further provision.  相似文献   

Total oxyradical scavenging capacity responses in Mytilus galloprovincialis transplanted into the Venice lagoon (Italy) to measure the biological impact of anthropogenic activities     

Camus L  Pampanin DM  Volpato E  Delaney E  Sanni S  Nasci C 《Marine pollution bulletin》2004,49(9-10):801-808

Oxidative stress related investigations to monitor the impact of the pollutant discharges into the Venice lagoon (Italy) originating from anthropogenic activities (raw sewage water, agricultural and industrial effluents, oil tanker traffic), on marine organisms have classically been carried out by analyzing specific, single antioxidants (i.e. catalase, superoxide dismutase). In this paper, two studies are reported where the total oxyradical scavenging capacity assay (TOSC) was selected and measured toward peroxyl, and hydroxyl free radicals, and peroxynitrite in mussels (Mytilus galloprovincialis) transplanted into the Venice city and throughout the lagoon to measure the biological effects of anthropogenic activities. In the first experiment, mussels from a clean site (farm) were transplanted to the urban area of Venice for 0, 1, 2 and 4 weeks; cytosolic TOSC toward peroxyl and hydroxyl free radicals, and peroxynitrite revealed that the transplantation process caused a stress (handling stress, anoxia, oxidative burst) resulting in a reduction of TOSC in both control and urban sites, therefore, preventing clear interpretation of the data after one week. At week 2, a significant TOSC reduction (P < 0.05) toward peroxyl and hydroxyl radicals in the urban site revealed that mussels experienced oxidative pressure exerted by pollutants. Most TOSC values returned to initial levels at week 4; however, TOSC induction was noticed in the control group toward peroxyl and hydroxyl radicals while in the exposed group it was not indicating an inhibition of the oxidative metabolism. In the second experiment, mussels were deployed at seven different sites throughout the lagoon. After five weeks of exposure, significant TOSC reduction was measured (P < 0.05) toward peroxyl for Palude della Rosa, Chioggia and Valle Millecampi, toward hydroxyl radicals for Valle Millecampi and Campalto and toward peroxynitrite for Valle Millecampi. Although these data indicate a depletion of the low molecular weight scavengers, additional biomarkers are needed to draw a conclusion on the health of the mussels. TOSC was proved to be an interesting health index parameter to measure pollution impact in a transplantation study provided that the mussels are exposed for two weeks and a control is run in parallel.  相似文献   

Principal Component Analysis of the Solar Magnetic Field I: The Axisymmetric Field at the Photosphere     

John?K.?LawrenceEmail author  Ana?Cristina?Cadavid  Alexander?Ruzmaikin 《Solar physics》2004,225(1):1-19

A principal component analysis, or proper orthogonal decomposition, of the axisymmetric magnetic field at the photosphere is carried out to find an optimal representation of the observed solar cycle. The 22-year periodic field requires just two modes. NSO Kitt Peak synoptic maps for Carrington rotations 1664–2007 were reduced by taking both the mean and the median field over longitude to produce two sequences of functions of sine latitude spanning 25.7 years. The lowest modes of each are determined by the polar fields. The mean field is most efficient at representing the periodic field, but the median field is more efficient at representing the evolution of the diffuse field patterns.  相似文献   

The use of a non-lethal tool for evaluating toxicological hazard of organochlorine contaminants in Mediterranean cetaceans: new data 10 years after the first paper published in MPB     

Fossi MC  Marsili L  Neri G  Natoli A  Politi E  Panigada S 《Marine pollution bulletin》2003,46(8):972-982

In the Mediterranean Sea, top predators, and particularly cetacean odontocetes, accumulate high concentrations of organochlorine contaminants and toxic metals, incurring high toxicological risk. In this paper we investigate the use of the skin biopsies as a non-lethal tool for evaluating toxicological hazard of organochlorines in Mediterranean cetaceans, presenting new data 10 years after the paper published by Fossi and co-workers [Mar. Poll. Bull. 24 (9) (1992) 459] in which this new methodology was first presented. Some organochlorine compounds, now with worldwide distribution, are known as endocrine disrupting chemicals (EDCs). Here the unexplored hypothesis that Mediterranean cetaceans are potentially at risk due to organochlorines with endocrine disrupting capacity is investigated. High concentrations of DDT metabolites and PCB congeners (known as EDCs) were found in the different Mediterranean species (Stenella coeruleoalba, Delphinus delphis, Tursiops truncatus and Balaenoptera physalus). In this paper we also propose benzo(a)pyrene monooxygenase (BPMO) activity in marine mammal skin biopsies (non-lethal biomarker) as a potential indicator of exposure to organochlorines, with special reference to the compounds with endocrine disrupting capacity. A statistically significant correlation was found between BPMO activity and organochlorine levels (DDTs, pp(')DDT, op(')DDT, PCBs and PCB99) in skin biopsies of males of B. physalus. Moreover a statistical correlation was also found between BPMO activity and DDT levels in skin biopsies of the endangered Mediterranean population of D. delphis. These results suggest that BPMO induction may be an early sign of exposure to organochlorine EDCs and can be used for periodic monitoring of Mediterranean marine mammal toxicological status.  相似文献   

7th Latin-American Conference on Space Geophysics, Atibaia, SP, Brazil, March 29–April 2, 2004     

Barclay Clemesha  Chairman&#x;Colage Editorial Committee  Cristina Mandrini  Paulo Batista  Inez Batista  Abraham Chian  Co-editors 《Journal of Atmospheric and Solar》2005,67(17-18)

  相似文献   

New data (U–Pb, K–Ar) on the geochronology of the alkaline-carbonatitic association of Fuerteventura, Canary Islands, Spain     

Mercedes Muoz  Juana Sagredo  Cristina de Ignacio  Javier Fernndez-Surez  Teresa E. Jeffries 《Lithos》2005,85(1-4):140-153

Zircons from a nepheline-syenite of the Fuerteventura Basal Complex were dated by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The age obtained from a total of 21 U–Th–Pb analyses is 25.4 ± 0.3 Ma (2σ) indicating a late Oligocene–early Miocene crystallization. This age is consistent with new K–Ar ages on nepheline-syenites and pyroxenites, and contradicts previously published ³⁹Ar–⁴⁰Ar (feldspar) ages that were interpreted to represent a late Cretaceous–early Paleocene, pyroxenitic–syenitic magmatic episode. These new geochronological data are consistent with both field observations and most of the previously published ages on alkaline silicate rocks and associated carbonatites of Fuerteventura. Therefore, they strongly support the existence of a single, late Oligocene–early Miocene event of alkaline–carbonatitic magmatism in the Basal Complex of Fuerteventura, taking place at approximately 25 Ma and comprising: alkaline-pyroxenites, melteigites-ijolites, nepheline-syenites and carbonatites, as well as their volcanic equivalents and associated dykes.

These new data provide an estimate for the length of time that it took the island to grow, thus eliminating one of the major problems in explaining its development by a hot-spot model.  相似文献   

Kamafugitic diatremes: facies characterisation and genesis—examples from the Goiás Alkaline Province, Brazil     

Tereza Cristina Junqueira-Brod  Jos Affonso Brod  Jos Carlos Gaspar  Hardy Jost 《Lithos》2004,76(1-4):261-282

This paper describes the internal organisation of two diatremes (Águas Emendadas and Neuzinha) and one small breccia-filled conduit (Tigre) in the central portion of the Late Cretaceous Goiás Alkaline Province (GAP), central Brazil, and explores the criteria for facies recognition. The GAP kamafugitic diatremes are emplaced into Carboniferous sandstones of the Aquidauana Formation, at the northern margin of the Paraná Basin. They are usually elliptical structures, not longer than 900 m, filled with breccia and partially covered by thin kamafugitic to basanitic lava flows. The breccias are dominated by juvenile pyroclasts, with subordinate amounts of cognate fragments and xenoliths. In addition to variations in ash and lapilli proportions, juvenile fragment types may be used to discriminate genetic processes and the corresponding pyroclastic deposits.

An extensive field, textural and compositional dataset was analysed by multivariate statistical techniques. Combined with field observations, this allowed us to define a set of facies for kamafugitic diatremes, and, more importantly, to understand the internal structure of the studied bodies and to cross-correlate them. Seven distinct facies were recognised. The Fluidised Conduit Facies (FCF) represents high-energy, strongly fluidised but only moderately fragmented systems. It occurs in a confined environment, and is typical of deeper parts of the conduit, before the actual diatreme level is reached by the ascending fluidised magma. Large amounts of spinning droplets are formed within this region. The Fluidised Conduit–Diatreme Facies (FCDF) is characteristic of intermediate depths in the conduit, where highly fluidised and highly fragmented systems produce large amounts of ash. Spinning droplets decrease in abundance, ordinary juvenile fragments become very common, and xenoliths from the country rock in the immediate vicinity of the diatreme are present. The Fluidised Fragmented Facies (FFF) and the Magmatic Fluidised Facies (MFF) produce very heterogeneous deposits that dominate the shallower part of the system, making up most of the diatreme-filling materials. The Fluidised Fragmented Facies can be distinguished by much higher degrees of fluidisation, fragmentation and system energy. It occupies the internal part of the diatreme and is characterised by the common presence of tuff pockets, tuff fragments, and accretionary and armoured lapilli. The Magmatic Fluidised Facies typically occupies the outer portion of the diatreme and can be distinguished from the Fluidised Fragmented Facies by the dominance of lapilli over ash and by the presence of abundant wrapped fragments. The Magmatic Facies (MF) and the Coherent Magmatic Facies (CMF) are volumetrically subordinate and represent late stages, when less fluidised and less fragmented material, or even coherent magma erupts relatively passively, in the aftermath of the main explosive stage that generated the diatreme. The Border Facies is defined by the increased abundance of material from the immediate country rock. At Águas Emendadas and Neuzinha this facies is marked by the presence of fragments of peperite-like rock, formed by the interaction of the fluidised magma with friable sandstone.  相似文献   

A 16,000 C yr B.P. packrat midden series from the USA–Mexico Borderlands     

Camille A. Holmgren  M. Cristina Pealba  Kate Aasen Rylander  Julio L. Betancourt 《Quaternary Research》2003,60(3):319-329

A new packrat midden chronology from Playas Valley, southwestern New Mexico, is the first installment of an ongoing effort to reconstruct paleovegetation and paleoclimate in the U.S.A.–Mexico Borderlands. Playas Valley and neighboring basins supported pluvial lakes during full and/or late glacial times. Plant macrofossil and pollen assemblages from nine middens in the Playas Valley allow comparisons of two time intervals: 16,000–10,000 and 4000–0 ¹⁴C yr B.P. Vegetation along pluvial lake margins consisted of open pinyon–juniper communities dominated by Pinus edulis, Juniperus scopulorum, Juniperus cf. coahuilensis, and a rich understory of C₄ annuals and grasses. This summer-flowering understory is also characteristic of modern desert grassland in the Borderlands and indicates at least moderate summer precipitation. P. edulis and J. scopulorum disappeared or were rare in the midden record by 10,670 ¹⁴C yr B.P. The late Holocene is marked by the arrival of Chihuahuan desert scrub elements and few departures as the vegetation gradually became modern in character. Larrea tridentata appears as late as 2190 ¹⁴C yr B.P. based on macrofossils, but may have been present as early as 4095 ¹⁴C yr B.P. based on pollen. Fouquieria splendens, one of the dominant desert species present at the site today, makes its first appearance only in the last millennium. The midden pollen assemblages are difficult to interpret; they lack modern analogs in surface pollen assemblages from stock tanks at different elevations in the Borderlands.  相似文献   

The use of GPR for characterizing underground weathered profiles in the sub-humid tropics     

Paulo Roberto Antunes Aranha  Cristina Helena Ribeiro Rocha Augustin  Frederico Garcia Sobreira   《Journal of Applied Geophysics》2002,49(4)

Ground penetrating radar (GPR) has been used as a tool to access information about ground subsurface features. Such information is very important for different types of studies, varying from those related to archeological research to those studying geological elements of bedrock. More recently, however, GPR has been increasingly applied to environmental studies, especially for soil research. This paper presents the results of an application of GPR for the study of weathered profiles. GPR was used to discover the degree of trustworthiness of the information on the ground subsurface through the interpretation of the results of the radar sections as well as the data collected from boreholes, which reached until 21 m. The results show a relatively high degree of details obtained by GPR, indicating the possibility of speeding up ground subsurface surveys related to geomorphological, geological, and pedological studies.  相似文献   

Variations in the dynamic response of structures founded on piles induced by obliquely incident SV waves     

Cristina Medina  Guillermo M. Álamo  Juan J. Aznárez  Luis A. Padrón  Orlando Maeso 《地震工程与结构动力学》2019,48(7):772-791

Although the seismic actions generally consist of a combination of waves, which propagates with an angle of incidence not necessarily vertical, the common practice when analyzing the dynamic behavior of pile groups is based on the assumption of vertically incident wave fields. The aim of this paper is to analyze how the angle of incidence of SV waves affects the dynamic response of pile foundations and piled structures. A three-dimensional boundary element-finite element coupling formulation is used to compute impedances and kinematic interaction factors corresponding to several configurations of vertical pile groups embedded in an isotropic homogeneous linear viscoelastic half-space. These results, which are provided in ready-to-use dimensionless graphs, are used to determine the effective dynamic properties of an equivalent single-degree-of-freedom oscillator that reproduces, within the range where the peak response occurs, the response of slender and nonslender superstructures through a procedure based on a substructuring model. Results are expressed in terms of effective flexible-base period and damping as well as maximum shear force at the base of the structure. The relevance and main trends observed in the influence of the wavefront angle of incidence on the dynamic behavior of the superstructure are inferred from the presented results. It is found that effective damping is significantly affected by the variations of the wave angle of incidence. Furthermore, it comes out that the vertical incidence is not always the worst-case scenario.  相似文献