Cosmic-ray exposure ages of four acapulcoites and two differentiated achondrites and evidence for a two-layer structure of the acapulcoite/lodranite parent asteroid   总被引：1，自引：0，他引：1  

Otto Eugster  Silvio Lorenzetti 《Geochimica et cosmochimica acta》2005,69(10):2675-2685

We determined the He, Ne, and Ar isotopic abundances in the four acapulcoites Dhofar (DHO) 125, DHO 290, DHO 312, and Graves Nunataks 98028, the metal-rich diogenite Northwest Africa (NWA) 1982, and a unique achondrite, NWA 1058, that resembles the acapulcoites in its chemical composition. The noble gases in these meteorites consist of three components: trapped gases, cosmic-ray produced nuclides, and nuclides produced by K, Th, and U decay. The four acapulcoites yield cosmic-ray exposure (CRE) ages in the range of 5.0-5.7 Ma and confirm earlier conclusions concerning break-up of all acapulcoites from a common S-type parent asteroid, possibly in three events 4.9, 5.9, and 14.8 Ma ago. We also discuss the other characteristics (mineralogy, chemistry, formation ages, and oxygen and trapped noble gas isotopes) of all other acapulcoites and their relatives, the lodranites. We propose that the acapulcoite/lodranite parent asteroid had a shell structure similar to that of the H chondrites: The less metamorphosed acapulcoites correspond to the H3 and H4 chondrites and originate from the exterior layers, whereas the more severely metamorphosed lodranites, similar to the H5 and H6 chondrites, represent the inner regions of their parent body. Ungrouped achondrite NWA 1982, probably a diogenite, shows a CRE age of 18.9 ± 2.0 Ma that falls on the major exposure age cluster of the diogenites. The unique achondrite NWA 1058 differs in cosmic-ray exposure age (38.9 ± 4.0 Ma) and in oxygen-isotopic composition from the acapulcoites and lodranites and is probably a winonaite.  相似文献   

Tabelle per il calcolo delle derivate seconde del potenziale relativo a settori di anelli cilindrici omogenei     

Prof. Dr. Silvio Ballarin 《Pure and Applied Geophysics》1943,5(1-2):1-10

Riassunto Le tabelle numeriche contenute in questa Nota, costruite per facilitare il calcolo delle derivate seconde del potenziale generato da masse che si possono scomporre in settori di anelli cilindrici omogenei coassiali con la verticale del punto di stazione, sono precedute da brevi cenni sul loro impiego e sulle formole assunte a fondamento di esse.

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Zusammenfassung Zur Berechnung der zweiten partiellen Ableitungen des Schwerepotentials von Massen welche sich in gleichartige zylindrische Ringsektoren, konzentrisch mit der Vertikallinie der Station (Nullpunkt), zerlegen lassen, gibt der Verf. zwei numerische Tafeln, die diese Rechnungen erleichtern. Erläuterungen betreffs der Formeln die zu Grunde gelegt wurden und die betreffenden Anwendungsmöglichkeiten der angegebenen numerischen Wertestehen den Tafeln voran.

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The Gulf of California: Review of ecosystem status and sustainability challenges     

Salvador E. Lluch-Cota  Eugenio A. Aragón-Noriega  David Aurioles-Gamboa  Richard C. Brusca  Roberto Cortés-Altamirano  Alfonso Esquivel-Herrera  Michel E. Hendrickx  Hugo Herrera-Cervantes  Miguel Lavín  Daniel B. Lluch-Cota  Silvio G. Marinone  Sofia Ortega-García  Alejandro Parés-Sierra  Mauricio Ramírez-Rodríguez  Richard A. Schwartzlose  Arturo P. Sierra-Beltrán 《Progress in Oceanography》2007,73(1):1-26

The Gulf of California is unique because of its geographical location and conformation. It hosts diverse ecosystems and important fisheries that support industry and provide livelihood to coastal settlements. It is also the site of interests and problems, and an intense interaction among managers, producers, and conservationists. In this report, we scrutinize the abiotic (hydrography, climate, ocean circulation, and chemistry) and biotic (phyto- and zooplankton, fish, invertebrates, marine mammals, birds, and turtles) components of the marine ecosystem, and some particular aspects of climate variability, endemisms, harmful algal blooms, oxygen minimum layer, and pollution. We also review the current conditions and conflicts around the main fisheries (shrimp, small and large pelagic fishes, squid, artisanal and sportfishing), the most important human activity in the Gulf of California. We cover some aspects of management and conservation of fisheries, especially the claimed overexploitation of fish resources and the ecosystems, and review proposals for creating networks of marine protected areas. We conclude by identifying main needs for information and research, particularly the integration of data bases, the implementation of models and paleoreconstructions, establishment of monitoring programs, and the evaluation of fishing impacts and management actions.  相似文献   

Biogeochemistry of surface sediments off Concepción (∼36°S), Chile: El Niño vs. non-El Niño conditions     

Sergio Contreras  Silvio Pantoja  Carina B. Lange 《Progress in Oceanography》2007,75(3):576-585

We compared the signals of several water column properties (upwelling intensity, sea level anomaly, temperature, nutrients, dissolved oxygen, chlorophyll-a, and surface sediments) of the continental shelf off Concepción (36°S) during the 1997-1998 El Niño with those of a normal year (2002-2003). We found that the primary hydrographic effect of El Niño 1997-1998 was a reduction in the input of nutrient-rich, oxygen-poor Equatorial Subsurface Water over the shelf. This affected the biology of the water column, as evidenced by the reduced phytoplankton biomass. Surface sediment properties (biogenic opal, organic carbon, bulk δ¹⁵N) observed during El Niño 1997-1998 reflected a reduced export production and the sediments failed to show the water column seasonality that occurs under normal conditions. In addition, weakened denitrification and/or upper water column fertilization could be inferred from the sedimentary δ¹⁵N. Although diminished, export production was preserved in the surface sediments, revealing less degraded organic matter in the upwelling period of the El Niño year than in the normal year. We suggest that the fresher organic material on the seafloor was probably associated with a severe reduction in the polychaete Parapronospio pinnata, which is considered to be the most important metazoan remineralizer of organic carbon at the sediment-water interface in the study area.  相似文献   

Stato attuale del ghiacciaio del Mandrone (Adamello) e fattori climatici     

Prof. Dr. Silvio Polli 《Pure and Applied Geophysics》1950,17(3-4):224-229

Riassunto Premesse alcune considerazioni generali si descrivono alcuni particolari fenomeni osservati al ghiacciaio del Mandrone e dovuti al rapido arretramento della fronte e assottigliamento del ghiaccio come: strozzatura della lingua ghiacciaio di rimpasto, ghiacciaio morto, lago alla bocca, crepacci circolari, valle ad U. Si fanno alcune considerazioni sul futuro andamento climatico alpino.

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Summary After some general considerations, there are described some particular phenomena noticed about the glacier of Mandrone (Adamello). They are due to the swift retirement of the front and to the diminution of the thickness of the glacier as following: the strangling of the icetongue, glacier rigenerated, glacier dead, lake at the glacier-mouth, round ice-crevices, valley like U. They are done some suppositions on the future alpine-climatical proceeding.

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La realta' fisica del ciclo climatico di 5,6 anni     

Dott. Silvio Polli 《Pure and Applied Geophysics》1946,8(1-2):94-103

Riassunto Date le condizioni perchè un ciclo climatico possa considerarsi una realtà fisica ed esaminate le analisi periodali di lunghe serie di elementi climatici si mette in evidenza l'esistenza, la notevole ampiezza e la realtà fisica del ciclo di 5,6 anni. Esso si presenta sempre, in tutti i fattori geofisici e in tutte le regioni della terra. E' molto ampio, spesso più di ogni altro. Mantiene costante il periodo; la fase varia con la regione. Presenta particolari smorzamenti di carattere universale.

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Summary The conditions are given to a climatic cycle in order to have a physically reality. To 30 long series of annual values of climatic elements has been applied the periodal analysis after the method of Vercelli. In all the cases results with strong evidence a remarkable oscillation of 5,6 years. Attention is drawn to the physically reality of that cycle. It has an amplitude often greater that all other component-waves; the period remains almost constant, the phase change from region to region.

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Zusammenfassung Es werden die Bedingungen, damit ein klimatischer Cyklus als eine physische Realität betrachtet werden kann, angegeben. Man untersucht die periodalen Analysen von längeren Reihen klimatischer Elemente und es wird die Existenz, die bemerkenswerte Amplitude und die physische Realität des 5,6 jährigen Cyklus angedeutet. Derselbe ist immer vorhanden, in allen geophysischen Faktoren und in allen Erdteilen. Der Cycklus hat eine grosse Amplitude, ofter mehr als jeder andere. Behält constant seine Periode. Die Phase wechselt je nach der Zone. Er stellt im allgemeinen eigenartige Dämpfungen vor.

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Analisi periodale della successione dei numeri relativi delle macchie solari     

Dott. Silvio Polli 《Pure and Applied Geophysics》1946,9(1-2):95-105

Riassunto Alla successione dei numeri relativi delle macchie solari (numeri di Wolf) si applica il procedimento dell'analisi periodale delVercelli e si eseguisce la scomposizione completa del diagramma. Si ottengono onde componenti di anni 16,0-11,15-8,32-5,68-4,05-2,9-2,0 e altre di periodi più lunghi ma meno precisi. Esse hanno caratteri di quasi-periodicità e di quasipersistenza. Si determinano le loro ampiezze e si confrontano con quelle corrispondenti dei cicli climatici terrestri.

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Summary To the series of the sun-spot relative-numbers (Wolf-numbers) has been applied the periodal analysis after the method ofVercelli. From this are derived component waves of 16,0-11,15-8,32-5,68-4,05-2,9-2,0 years and others with periods longer but less precise. They have almost-periodical and almost-persistent characters. Theirs amplitudes are determinated in Wolf's units. The waves found by these means are compared with the corresponding waves of the climatical cycles.

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Zusammenfassung An der Reihe der Relativzahlen der Sonnenflecke (Wolfer-Relativzahlen) wird dieVercelli Periodalanalyse angewendet. Es folgt die ganze Zerlegung. Man erhält Komponentwellen, die Perioden von 16,0-11,15-8,32-5,68-4,05-2,9-2,0 Jahren und andere mit längeren, aber umbestimmten Perioden, haben. Sie haben fast-periodische und fast-bestehende Kennzeichen. Es wird ihre Amplitude bestimmt. Dieselben Komponenten werden mit den entsprechenden Wellen der klimatischen Zyklen verglichen.

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Lavoro eseguito con il contributo del Consiglio Nazionale delle Ricerche.  相似文献   

Kumdykolite,kokchetavite, and cristobalite crystallized in nanogranites from felsic granulites,Orlica-Snieznik Dome (Bohemian Massif): not an evidence for ultrahigh-pressure conditions     

Silvio Ferrero  Martin A. Ziemann  Ross J. Angel  Patrick J. O’Brien  Bernd Wunder 《Contributions to Mineralogy and Petrology》2016,171(1):1-23

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Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments     

Lorena Rebolledo  Julio Sepúlveda  Carina B. Lange  Silvio Pantoja  Sébastien Bertrand  Konrad Hughen  Dante Figueroa 《Estuarine, Coastal and Shelf Science》2008

A multi-proxy approach based on organic (organic carbon, alkenones, and C/N) and inorganic geochemical proxies (biogenic opal, inorganic carbon, Fe, Ti, and Ca) preserved in the sediments of the Jacaf channel (CF7-PC33; 44°21′S, 72°58′W, 510 m water depth), Chilean fjords, yields evidence of major past productivity fluctuations in accordance with climatic changes over the last ∼1800 years. The downcore record clearly shows two productivity/climate modes. The first period, prior to 900 cal yr BP, is characterized by decreased marine productivity and a reduced continental signal, pointing to diminished precipitation and runoff. In contrast, the second period between ∼750 cal yr BP and the late 1800s (top of core) is illustrated by elevated productivity and an increased continental signal, suggesting higher precipitation and runoff. Both time intervals are separated by a relatively abrupt transition of ∼150 years which roughly coincides with the beginning of the Little Ice Age. The increased content of freshwater diatoms and Chrysophyte cysts that characterize the last 200 years of the latter mode coincides with a significant decrease in the carbonate content of the sediment; together they further indicate increased terrigenous contributions and decreased marine carbonate productivity at the end of the Little Ice Age. The correspondence between our record and other paleoclimate studies carried out in South America and Antarctica demonstrates that the Chilean fjord area of Northern Patagonia is not just sensitive to local climatic variability but also to regional and possibly global variability.  相似文献   

Genetic diversity in old populations of sessile oak from Calabria assessed by nuclear and chloroplast SSR     

Antonio LUPINI  Meriem Miyassa ACI  Antonio MAUCERI  Giuseppe LUZZI  Silvio BAGNATO  Giuliano MENGUZZATO  Francesco MERCATI  Francesco SUNSERI 《山地科学学报》2019,(5)

In the framework of forest resources conservation, this study aims to understand the dynamic and the genetic structure of sessile oak forests in Calabria, Italy. Two old populations of sessile oak(Quercus petraea(Mattuschka) Liebl.) from two areas of Sila and Aspromonte massifs in Calabria were analyzed for genetic diversity and population structure based on 6 nuclear simple sequence repeat(nSSR) and 4 chloroplastic SSR(cpSSR) loci. The populations displayed high amount of genetic diversity, which was toughly structured according to their geographical origins. Number of alleles at SSR loci ranged from 11 to 20 with an average of 13.5 per locus. Gene diversity(expected heterozygosity, He) estimates ranged from 0.575 to 0.834 with a mean of 0.749. The observed heterozygosity(Ho) was on average 0.458 ranging from 0.150 to 0.682. Polymorphism information content(PIC) values ranged from 0.625 to 0.865 with an average of 0.787. The analysis of molecular variance(AMOVA) highlighted a significant higher estimated variance within populations compared to among populations. Finally, the analysis of haplotypes by using cpSSR suggested a higher diversification in the population from Sila. Hierarchical clustering analysis grouped the genotypes into two major clusters, which agreed with the geographic origin of populations, and was confirmed by the Discriminant Analysis of Principal Components(DAPC). The first cluster included plants/population from Sila massif, while the second encompassed mostly plants/population sampled in Aspromonte massif. Finally, model-based clustering by STRUCTURE analysis also supported the presence of clear genetic structuring in the collection with two major populations(K=2) supported to PCoA analysis as well. Finally, our data indicated the Aspromonte population as a marginal forest with fragmented distribution suggesting different strategies of preservation than in Sila massif.  相似文献