Growth and Production of the Ark Shell Scapharca inaequlvalvis (BRUGUIÈRE) in a Lagoon of the Po River Delta     

Michele  Mistri  Remigio  Rossi Victor Ugo  Ceccherelli 《Marine Ecology》1988,9(1):35-49

Abstract. Scapharcu inuequivalvis is an Indopacific bivalve which has recently immigrated to the Adriatic Sea and has progressively replaced dominant species within some infauna communities. Density, growth, and secondary production of this Arcidae were investigated between 1984 and 1985 in a bed located in a brackish environment of the Northern Adriatic coast.  相似文献   

Comparison of the fish assemblages associated with Posidonia oceanica after the partial loss and consequent fragmentation of the meadow     

Toms Vega Fernndez  Marco Milazzo  Fabio Badalamenti  Giovanni D'Anna 《Estuarine, Coastal and Shelf Science》2005,65(4):645-653

An extensive Posidonia oceanica meadow was partially destroyed by excavation, resulting in areas of seagrass habitat of equal complexity (shoot density) but different heterogeneity (degree of fragmentation). The fish assemblages associated with differently fragmented beds were compared from a landscape perspective. Differences in the fish assemblages were detected, with several species showing different patterns: (1) species that increased their abundance along with the degree of bed fragmentation, (2) species that were more abundant in fragmented beds, but did not show differences between more or less fragmented beds, and (3) species that were mostly abundant in large seagrass patches or in the continuous meadow. The fish assemblages were also affected by depth, but further research is needed to determine properly this effect. Some ecological mechanisms are suggested to operate in the interaction between P. oceanica and the held fish assemblage.  相似文献   

Tethya (Porifera,Demosponglae) Species Coexisting in a Maldivian Coral Reef Lagoon: Taxonomical,Genetic and Ecological Data     

Michele Sar  Giuseppe Corriero  Giorgio Bavestrello 《Marine Ecology》1993,14(4):341-355

Abstract. Tethya microstella, T. orphei, T. robusta, and T. seychellensis live in sympatry in a Maldivian coral reef lagoon (Gangehi Island, Ari Atoll). A morphological, morphometric, and electrophoretical study of these species show that their Maldivian populations are well separated morphologically and genetically. The genetic distances and the other data are more consistent with an immigration than with a local speciation hypothesis. Their coexistence may be explained by a differentiation in ecological requirements. The four species inhabit the shallow water biotope of the lagoon among the rubble of dead corals. Our data show that T. orphei and T. seychellensis occupy the upper rubble layer, T. microstella and T. robusta the lower one. This distinction agrees with the different morpho-functional features of the two pairs of species.  相似文献   

Il terremoto delle Prealpi carniche dell'8 giugno 1934 e sua profondita' ipocentrale     

Prof. Dott. Giovanni Agamennone 《Pure and Applied Geophysics》1946,8(1-2):43-72

Riassunto Nel riesaminare i risultati cui sono pervenuti altri studiosi nella determinazione della profondità alla quale furono originati alcuni terremoti, l'A. ha dovuto riconoscere che le conclusioni dei loro calcoli non sono attendibili. Lo stesso è avvenuto recentemente per il terremoto veneto dell'8-6-1934, pel quale il prof. P. Caloi aveva trovato 37 km, basati su dati sismografici. Adoperando invece il metodo della decrescenza dell'intensità con la distanza, l'A. ha ottenuto ca. 10 km. Tale grave disaccordo lo ha indotto a riesaminare i vari metodi adottati dal Caloi — specie quello dell'angolo di emergenza delle onde sismiche — ed è giunto alla conclusione che la profondità di 37 km, in apparenza assai lusinghiera tanto da presentare un errore medio di soli 0,4 km, è ben lontana da raggiungere tanta esattezza.

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Summary The methods for estimate the depth of a earthquake are examined again by the Author, who come to the conclusion that some results of calculation are unreliable. This is explain for the earthquake of 8th June 1934 (Veneto), already examined by P. Caloi, who found a depth of 37 km, by means of elements deduced from seismological diagrams only. Instead, the A., using the method grounded on the decreasing of the intensity with the distance, has obtained 10 km. The analysis of this great discrepance show that some methods, as that of the angle of emergency, should be applied with prudence and limitation to assure reliable results.

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Zusammenfassung Der Verf. überprüft die Ergebnisse erhalten in der Tiefe-Bestimmung eines Bebens und zeigt wie einige Schlussfolgerungen unzulässig sind. Das wird ausführlich für das Erdbeben vom 8. Juni 1934 (Venetien) gezeigt, welches P. Caloi schon untersucht hat, erhaltend eine Tiefe von 37 km und zwar allein auf Grund von mikroseismischen Elementen. Dagegen, mit Anwendung des Verfahrens der Intensität-Abnahme mit dem Abstand, hat der Verf. eine Tiefe von nur 10 km erhalten. Diese grosse Verschiedenheit wird da me stesso studiato (1): di Costantinopoli del 1894 dal franceseLacoine (4) e (5); dei Colli Laziali del 1911, 1927 e 1928 dall'Oddone (2) e (34); dell'Istria del 29-VIII-1931, del Friuli del 25-XII-1931, di Belluno del 27-XII-1933, tutti studiati dalCaloi (14), (21), (23); quello Calabro-Siculo del 1938 dal rumenoDemetrescu (6) e (7).

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Sulla costituzione interna terrestre     

Prof. Giovanni Boaga 《Pure and Applied Geophysics》1940,2(1):185-199

Riassunto L'A., ricordata la classica equazione di Clairaut sulla costituzione interna terrestre ed accennate le varie ipotesi sulla variazione continua della densità escogitate per integrare l'equazione di Clairaut, riporta i dati numerici ottenuti da Bullen per una distribuzione discontinua di densità. Determina in base ai dati di Bullen i coefficienti di quattro funzioni atte a fornire la densità a qualsiasi profondità e istituisce notevoli confronti fra le ipotesi di Roche, Helmert, Legendre, De Chaurand, Helmert generalizzata e Bullen. — Da ultimo studia il problema della variazione della gravità nell'interno della terra prendendo a base dei calcoli la ipotesi sulla variazione discontinua della densità di Bullen e qualla sulla variazione continua dovuta all'A. e da lui denominata ipotesi di Helmert generalizzata.

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Summary The Author, having summarized the classical equation of Clairaut on the internal structure of the earth and having touched upon the sundry hypotheses on the continual variation of density devised for the integration of Clairaut's equation, reports the numerical data obtained by Bullen for a discontinual distribution of density. The Author determines, after bullen's data, the coefficients of four functions apt to furnish the density at any dept whatever and makes some remarkable comparisons among the hypotheses of Roche, Helmert, Legendre, De Chaurand, Helmert generalized and Bullen. Lastly the Author studies the problem of the variation of gravity in the interior of the errth taking as a foundation of his calculations the hypothesis on the discontinual variation by Bullen and his own hypothesis on the continual variation that he calls Helmert's generalized hypothesis.

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Zusammenfassung Der Verf. erinnert zuerst die Gleichung von Clairaut betreffs der innere Beschaffenheit der Erde, sowie die verschiedenen Annahmen über die Veränderungen seiner Dichte. Auf Grund der Verteilung von Bullen bestimmt er die Koeffizienten von vier Funktionen durch welche möglich ist die Dichte in von Roche, Helmert, Legender, De Chaurand, Helmert verallgem. und Bellen. Ausserdem untersucht er das Problem der Schwere-Verteilung im Innern der Erde für die Annahme von Bullen sowie für die stetige Verteilung nach einer Formel des Verf. welche eine Verallgemeineung der Helmertschen Formel darstellt.

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Su un programma di ricerche geofisiche in Toscana per l'individuazione di giacimenti metalliferi     

Giovanni Boaga 《Pure and Applied Geophysics》1940,2(1):153-158

Riassunto L'A., premessi brevi cenni sulle caratteristiche fisiche di alcuni minerali metallici (di piombo, zinco ed antimonio) e richiamate le condizioni geo-minerarie della Toscana, segnala l'opportunità di misure gravimetriche specialmente nella zona del Bottino allo scopo di individuare giaciture, spessori e pendenze di nuovi filoni e dove possono essere applicati i procedimenti di Jung sui rilievi eötvössiani relativi a figure bidimensionali.

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Summary The Author, after some hints on the physical characters of sundry metallic minerals (such of lead, zinc and antimony) and having summarized the geominerary conditions of Tuscany, points out the necessity of gravimetrical measurements particularly in the zone of Bottino in order to find out the layers, the thickness and inclination of new veins and the place where the methods of Jung on the eötvössian reliefs cancerning bidimensional figures may be applied.

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Zusammenfassung Bezugsnehmend auf die physik. Eigenschaften einiger Erzen (besonders von Blei, Zink und Antimon) und auf die geologischen Verhältnisse von Toskana, hebt der Verf. die Zweckmässigkeit gravimetrischer Messungen hervor und vor allem in der Zone des Bottino um die Erzmassen in der betreffenden Lage zu bestimmen.

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Pisa, 14 aprile 1940-XVIII  相似文献   

Magnetostratigraphic dating of an intensification of glacial activity in the southern Italian Alps during Marine Isotope Stage 22     

Giovanni Muttoni  Cesare Ravazzi  Marzia Breda  Carlo Laj  Alain Mazaud 《Quaternary Research》2007,67(1):161-173

We applied magnetostratigraphy and mammal biostratigraphy to date climate-sensitive pollen cycles and lithostratigraphic units of the Pliocene-Pleistocene Leffe sedimentary succession from the Southern Alps, Italy. The Leffe section was correlated to additional sections (Casnigo, Fornaci di Ranica, and Pianengo) to construct a stratigraphic network along a common fluviatile system (the Serio River) sourced in the Southern Alps and flowing southward into the Po River Basin. We obtained a coherent scenario of climate variability for the last ∼ 2 Myr. At Leffe, lacustrine deposition commenced during the Olduvai Normal Subchron (1.94-1.78 Ma) and lasted up to a chronologic level compatible with Marine Isotope Stage (MIS) 22 (0.87 Ma). Pollen analysis revealed that climate varied cyclically from warm-temperate to cool during this time interval, but never as cold as during glacial intervals. At around MIS 22, climate cooled globally. Gravels, attributed to high-energy braided river systems fed locally by alluvial fans, prograded from the Serio River catchment area over the Leffe Basin and toward the Po Plain in response to a generalized event of vegetation withdrawal and enhanced physical erosion. At this time, Alpine valley glaciers reached their first maximum southward expansion with glacier fronts located at only ∼ 5 km upstream from Leffe.  相似文献   

An Overview of the Small BAseline Subset Algorithm: a DInSAR Technique for Surface Deformation Analysis   总被引：1，自引：0，他引：1  

Riccardo Lanari  Francesco Casu  Mariarosaria Manzo  Giovanni Zeni  Paolo Berardino  Michele Manunta  Antonio Pepe 《Pure and Applied Geophysics》2007,164(4):637-661

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Decorrugation and removal of directional trends of magnetic fields by the wavelet transform: application to archaeological areas   总被引：1，自引：0，他引：1  

Maurizio Fedi  Giovanni Florio 《Geophysical Prospecting》2003,51(4):261-272

The problem of removing directional trends frequently occurs in the processing of magnetic data and also in the subsequent steps of data interpretation. The so-called corrugations are typical directional trends occurring in levelled data, which may be removed in several ways. Classical techniques are based on high-pass filtering of the data and successively filtering these transformed data with directional cosine filters. Other linear features are due to real sources, such as pipelines in shallow surveys or dike swarms in regional surveys. They should, nevertheless, be considered as noise, due to the fact that their effect is strong and tends to hide the field features related to structures of more interest. We deal with both kinds of problem, presenting the results of a study in an archaeological area of southern Italy. Decorrugation of magnetic field anomalies is performed using a method based on the excellent space–frequency localization properties of wavelet bases, allowing a very sharp filtering of the field along a selected direction. We compare this technique with the classical one in a synthetic case and find that the wavelet decorrugation is simpler and produces low distortion maps. Besides the field decorrugation, the wavelet approach was also shown to be useful in the subsequent enhancement of the measured field. In fact, we show that the wavelet analysis offers a unique framework where various filtering problems (directional, isotropic, global or local as well) may be easily solved. As regards the archaeological case, strong noisy effects from elongated sources (pipelines) were successfully removed in a sharp and local way.  相似文献   

Seismic response of multi‐supported structures by proper orthogonal decomposition     

Federica Tubino  Luigi Carassale  Giovanni Solari 《地震工程与结构动力学》2003,32(11):1639-1654

The seismic analysis of structures is usually carried out considering the ground motion as fully‐correlated in space and determining the structural response by pseudo‐deterministic methods such as the response spectrum technique. Actually, the partial correlation of the seismic acceleration may influence heavily the behaviour of spatially extended structures, such as bridges, viaducts or pipelines. In order to take its partial correlation into account, the seismic ground motion is schematized as a stochastic process dependent on time and on space; the hypotheses of stationarity and homogeneity are used to obtain simple and general results. The influence of the partial correlation of the seismic ground motion on the structural response is investigated by introducing suitable Equivalent Spectra. The acceleration of the support‐points of the structure is represented by the Proper Orthogonal Decomposition (POD), defining the modes of the earthquake. The method is formulated for any kind of multi‐degree‐of‐freedom system and is applied, as a case study, to an ideal single‐storey multi‐supported frame with an axially rigid beam. In the case of two supports, the POD decouples the pseudo‐static and the dynamic contributions to the structural response. This property is preserved for structural systems with many supports, where only the lower modes of the earthquake, usually the first two POD modes, are responsible for the structural response. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献