Polymorphism of As4S3 (tris-(μ2-sulfido)-tetra-arsenic): accurate structure refinement on natural α- and β-dimorphites and inferred room temperature thermodynamic properties     

Angelo Gavezzotti  Francesco Demartin  Carlo Castellano  Italo Campostrini 《Physics and Chemistry of Minerals》2013,40(2):175-182

An accurate structure refinement, using single-crystal X-ray diffraction data, on natural α- and β-dimorphites collected at Solfatara di Pozzuoli, in the Phlegraean Fields, near Naples and at Vesuvius (Italy) is reported. Theoretical calculations at various levels of sophistication have been used to calculate molecular vibrational frequencies and gas-phase specific heats, to analyze the crystal packing, and to estimate lattice energies of both phases. All computational methods contribute to demonstrate that the β-phase is the thermodynamically stable one at room temperature.  相似文献   

Contrasting regional discharge evolutions in the Amazon basin (1974–2004)   总被引：1，自引：0，他引：1  

Jhan Carlo Espinoza Villar  Jean Loup Guyot  Josyane Ronchail  Grard Cochonneau  Naziano Filizola  Pascal Fraizy  David Labat  Eurides de Oliveira  Juan Julio Ordoez  Philippe Vauchel 《Journal of Hydrology》2009,375(3-4):297-311

Former hydrological studies in the Amazon Basin generally describe annual discharge variability on the main stem. However, the downstream Amazon River only represents the mean state of the Amazonian hydrological system. This study therefore uses a new data set including daily discharge in 18 sub-basins to analyze the variability of regional extremes in the Amazon basin, after recalling the diversity of the hydrological annual cycles within the Amazon basin. Several statistical tests are applied in order to detect trends and breaks in the time series. We show that during the 1974–2004 period, the stability of the mean discharge on the main stem in Óbidos is explained by opposite regional features that principally involve Andean rivers: a decrease in the low stage runoff, particularly important in the southern regions, and an increase in the high stage runoff in the northwestern region. Both features are observed from the beginning of the nineties. These features are also observed in smaller meridian sub-basins in Peru and Bolivia. Moreover we show that the changes in discharge extremes are related to the regional pluriannual rainfall variability and the associated atmospheric circulation as well as to tropical large-scale climatic indicators.  相似文献   

Main differences between thrust belts     

Carlo Doglioni 《地学学报》1992,4(2):152-164

It is useful to differentiate between thrust belts that are related to east(E)-dipping or west(W)-dipping subduction. More precisely, these either follow or resist the overall ‘eastward’ mantle flow detected by the hot-spot reference frame. Because of the overall ‘westward’ drift of the lithosphere we find in E-dipping subduction that the basal decollement underlying the eastern plate reaches the surface and involves deep crustal rocks. With W-dipping subduction, however, we find that the basal decollement of the eastern plate is warped as well as subducted. Consequently thrust belts related to E- (or NE-) dipping subduction show conspicuous structural and morphologic relief, involve deep crustal rocks, and are associated with shallow foredeeps. On the other hand, thrust belts related to W- (or SW-) dipping subduction show relatively low structural and morphological relief, involve only shallow upper crustal rocks and are associated with deep foredeeps as well as back-arc extension. The accretionary wedge-foredeep-back-arc basin association is visualized as an overall eastward propagating tectonic wave. The accretionary wedge forms in the frontal parts and generally below sea-level. This is followed by forward migrating extension that cuts the earlier accretionary wedge. Typically such a system occurs in the context of overall W-dipping subduction and is characterized by an arcuate shape (e.g. Carpathians, Apennines, Barbados, etc.). Along the branches of the arc external transpression and internal transtension co-exist but with different sense (i.e. sinistral transpression contrasting with dextral transtension). We also observe that with W-dipping subduction the tangent to a pre- deformation marker is descending into the foredeep at an angle in the range of 1–10° while with E-(or NE-)dipping subduction the same marker would rise towards the hinterland with typical angles of about 5–10°. Foredeep subsidence is mainly controlled by the load of the thrust sheets in thrust belts due to E-(or NE-)dipping subduction and by the roll-back of the subduction hinge in accretionary wedges due to W-dipping subduction. Subsidence or uplift rates in the foredeeps and accretionary wedges related to the two different types of subduction are very different, providing different P-T-t paths in the two geodynamic realms. The present shape and structure of the thrust belts belonging to one of these two general types may help us in reconstructing the location of thinned lithosphere and basin evolution in the past.  相似文献   

High-resolution infrared spectra of NGC 6342 and 6528: two moderately reddened bulge globular clusters     

L. Origlia  E. Valenti  R. M. Rich 《Monthly notices of the Royal Astronomical Society》2005,356(4):1276-1282

Using the Near Infrared Spectrometer (NIRSPEC) spectrograph at Keck II, we have obtained infrared (IR) echelle spectra covering the range  1.5 –1.8 μm  for the moderately reddened bulge globular clusters NGC 6342 and 6528, finding  [Fe/H]=−0.60  and −0.17 dex, respectively. We measure an average α-enhancement of ≈+0.33 dex in both clusters, consistent with previous measurements on other metal-rich bulge clusters, and favouring the scenario of a rapid bulge formation and chemical enrichment. We also measure very low ¹²C/¹³C isotopic ratios (≈5 in NGC 6342 and ≈8 in NGC 6528), suggesting that extra-mixing mechanisms resulting from cool bottom processing are at work during evolution along the red giant branch (RGB).  相似文献   

Paleomagnetic evidence for a diachronic clockwise rotation of the Coastal Range, eastern Taiwan     

Teh-Quei Lee  Catherine Kissel  Eric Barrier  Carlo Laj  Wen-Rong Chi 《Earth and Planetary Science Letters》1991,104(2-4)

Paleomagnetic results obtained from over 2100 cores sampled at 132 early Pliocene to late Pleistocene sites in the Coastal Range of eastern Taiwan indicate that, since the late Pliocene, the margin of the Philippine Sea plate has undergone a clockwise rotation of about 30° as a direct consequence of the Plio-Pleistocene collision of this plate with the Chinese Continental plate. The rotation is diachronic and started between 3 and 4 Ma ago in the northern Coastal Range then propagated southward at an average speed of the order of 70 ± 10 km/Ma. This value is in very good agreement with estimates of the southward propagation of the collision between the Philippine Sea plate and the Eurasian margin in Taiwan. It is suggested that the rotation reflects the deformation of the Philippine Sea plate at depth and does not results from the shallow deformations involved in the building of the Coastal Range orogen.  相似文献   

Very hot,very shallow hydrothermal dolomitization: An example from the Maritime Alps (north‐west Italy–south‐east France)          下载免费PDF全文

Luca Barale  Carlo Bertok  Namam Salih Talabani  Anna d'Atri  Luca Martire  Fabrizio Piana  Alain Préat 《Sedimentology》2016,63(7):2037-2065

In the Maritime Alps (north‐west Italy – south‐east France), the Middle Triassic–lowermost Cretaceous platform carbonates of the Provençal Domain locally show an intense dolomitization. Dolomitized bodies, irregularly shaped and variable in size from some metres to hundreds of metres, are associated with tabular bodies of dolomite‐cemented breccias, cutting the bedding at a high angle, and networks of dolomite veins. Field and petrographic observations indicate that dolomitization was a polyphase process, in which episodes of hydrofracturing and host‐rock dissolution, related to episodic expulsion of overpressured fluids through faults and fracture systems, were associated with phases of host‐rock dolomitization and void cementation. Fluid inclusion analysis indicates that dolomitizing fluids were relatively hot (170 to 260°C). The case study represents an outstanding example of a fossil hydrothermal system, which significantly contributes to the knowledge of such dolomitization systems in continental margin settings. The unusually favourable stratigraphic framework allows precise constraint of the timing of dolomitization (earliest Cretaceous) and, consequently, direct evaluation of the burial setting of dolomitization which, for the upper part of the dolomitized succession, was very shallow or even close to the surface. The described large‐scale hydrothermal system was probably related to deep‐rooted faults, and provides indirect evidence of a significant earliest Cretaceous fault activity in this part of the Alpine Tethys European palaeomargin.  相似文献   

Sull'analisi periodale dei diagrammi     

Dr. Carlo Bernasconi 《Pure and Applied Geophysics》1950,16(3-4):181-187

Riassunto Dopo aver indicato un nuovo artificio per rendere più rapida la formazione di combinazioni selettive nella analisi periodale, si illustra un modello di analizzatore armonico che traduce con mezzi fotoelettrici gli schemi diLabrouste e diVercelli. Infine, si propone una variante costruttiva dell'analizzatore elettrico progettato dalLovera.

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Summary After having showed a new way by which the process for making the selective combinations used for periodical analysis is hastened, an harmonic analysing device which traducts with photoelectric means the schemes ofLabrouste andVercelli is illustrated. Further, a change in the construction ofLovera's electric analyser is proposed.

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Proiezioni cartografiche di carattere speciale     

Dr. Carlo Bernasconi 《Pure and Applied Geophysics》1953,24(1):5-10

Riassunto Si espone, attraverso la risoluzione di due problemi, un procedimento di carattere generale per la determinazione di proiezioni cartografiche della sfera, secondo il principio che a determinate linee sulla sfera corrispondano linee di prefissata equazione sulla carta. I problemi trattati sono i seguenti: 1) Determinare l'equazione di una carta a meridiani rettilinei e convergenti in cui le lossodromie siano rappresentate con linee rette. 2) Ricercare se esistono altre proiezioni, oltre la centrografica prospettica, che trasformano i cerchi massimi in rette.

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Summary Here is explained, through the solution of two problems, a procedure for the determination of the cartographic projections of the sphere, according to the principle that lines of a forfixed equation on paper correspond to determined lines on the sphere. Here are the problems in question: 1) To determine the equation of a rectilineal and convergent meridian lined paper in which the loxodromies are represented by straight lines. 2) To point out if there are other projections, besides the perspective centrographic one, turning maximum circles into straight lines.

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Monitoring meiobenthos using cm-, m- and km-scales in the Southern Bight of the North Sea     

Jian Li  Magda Vincx  Peter M.J. Herman  Carlo Heip 《Marine environmental research》1997,43(4):265-278

Meiobenthos at the mouth of the Grevelingen and Oosterschelde Estuaries in the Southern Bight of the North Sea was monitored using meiobenthic abundance and nematode community structure. Hierarchical sampling included 54 subsamples nested within 18 cores within six stations within two transects. The spatial patterns of the meiofaunal populations and communities are presented in cm-scale (among subsamples), m-scale (among cores), km-scale (among stations) and 10 km-scale (between transects). The variance components analysis of meiofaunal abundances showed that km-scale and 10 km-scale represented 63–90% of total variance while m-scale and cm-scale provided only 10–37%. Different communities were found among stations rather than among cores or subsamples by detrended correspondence analysis ordination and clustering analysis. The main assemblage of meiofauna occurred at the km-scale. Nematode diversity was more powerful than meiofaunal abundance in detecting spatial variation at all scales. However, at least two replicates are required for monitoring when sampling using a 10 cm² subsampling core.  相似文献   

The Meiobenthos Along a Mediterranean Deep-Sea Transect off Calvi (Corsica) and in an Adjacent Canyon     

Karline  Soetaert  Carlo  Heip Magda  Vincx 《Marine Ecology》1991,12(3):227-242

Abstract. Meiobenthos densities (excluding hard-shcllcd foraminifcrans) were compared along a Mediterranean deep-sea transect off Calvi (Corsica) and in an adjacent canyon. Chloroplastic Pigment Equivalent values (CPE) provided an estimate of the amount of primary production reaching the bottom.
The stations along the transect were characterized by a low CPE content of the sediment, decreasing with increasing station depth. CPE values in the canyon were much higher, which probably resulted from import of material from the adjacent bay of Calvi. Similarly, meiobenthos densities along the transect were much lower than at comparable depths along the canyon.
Meiobenthos density was significantly and positively correlated with CPE values.
Nematodes were the most abundant taxon at all stations, followed by copepods + nauplii and the soft-shelled foraminiferans. The meiobenthos was most abundant in the upper half centimeter. Nematode and foraminiferan densities tended to decline less rapidly with increasing depth into the sediment. Specimens belonging to the recently described phylum Loricifera, larvae of the parasitic crustacean class Tantulocarida, and fragments of an infaunal Xenophyophoria (large protozoans) are reported for the first time from the Mediterranean.  相似文献