A maximal background spectrum of gravitational radiation     

Leonard A. Rosi  Robert L. Zimmerman 《Astrophysics and Space Science》1976,45(2):447-466

A maximal spectrum of gravitational radiation from sources outside our galaxy is calculated. The sources are galaxies, quasars and events that occur in the early history of the universe. The major contribution is from galaxies whose effect extends over the frequency region 10^–810⁺⁴Hz, peaking at 10^–110 Hz, with a spectral flux of 10 erg cm^–2, s^–1. The main processes of gravitational radiation in the galaxies are stellar collapse into a black hole and dying binary systems. In the region 10^–410⁴ Hz the background spectrum is well above the detection levels of currently proposed detectors. FromMinimal considerations of this spectrum it is determined that the density of gravitational radiation is 10^–39g cm^–3. This background spectrum is sensitive to galactic evolution and especially sensitive to the upper mass limits and mass distribution of stars in galactic models. Therefore, the spectrum could provide information about galactic evolution complementary to that obtained by electromagnetic investigations.  相似文献   

Fall vs flow activity during the 1991 climactic eruption of Pinatubo Volcano (Philippines)     

M. Rosi  M. Paladio-Melosantos  A. Di Muro  R. Leoni  T. Bacolcol 《Bulletin of Volcanology》2001,62(8):549-566

Six years after the 1991 Mt. Pinatubo eruption, deep erosion incisions into the pyroclastic deposits accumulated around the volcano enabled us to investigate the stratigraphy of the climactic deposits both in valley bottoms and on contiguous ridges. Stratigraphic relationships between fall, flow, and surge deposits in the Marella drainage system indicate that during the climactic eruption a progressive shift occurred from an early convective regime, to a transitional regime feeding both the plinian convective column and mostly dilute density currents, to a fully collapsing regime producing mostly dense pyroclastic flows. Syn-plinian dilute density currents (surges) propagated up to ~10 km from the crater, both along valley bottoms and on contiguous ridges of the Marella Valley, whereas post-plinian pyroclastic flows had greater runout (~13 km), were confined to valleys and were not associated with significant surges. Stratigraphic study and grain-size analyses allow the identification of three types of intra-plinian deposits: (a) lower and often coarse-grained surge deposits, emplaced during the accumulation of the coarsest portion of the fallout bed at time intervals of ~16-24 min; (b) upper fine-grained surge deposits, interstratified with the fine-grained portion of the fall bed and emplaced at shorter time intervals of ~3-13 min; and (c) small-volume, channel-confined, massive pumiceous flow deposits interbedded with the upper surges in the upper fine-grained fall bed. Maximum clast size isopleths of 1.6 and 0.8 cm for lithics (ML) and 2.0 and 4.0 cm for pumices (MP) show almost symmetrical distribution around the vent, indicating that the passing of the typhoon Yunya during the climactic eruption had little effect on trajectories of high-Reynold-number clasts. Significant distortion was, however, observed for the 3.2-cm ML and 6.0-cm MP proximal isopleths, whose patterns were probably influenced by the interaction of the clasts falling from column margins with the uprising co-ignimbrite ash plumes. Application of the Carey and Sparks (1986) model to the undisturbed isopleths generated by the umbrella cloud yields a maximum column height of ~42 km, in good agreement with satellite measurements. Systematic stratigraphic and vertical grain-size studies of the plinian fall deposit in the Marella Valley, combined with satellite data and eyewitness accounts, reveal that the carrying capacity of the convective column and related fallout activity peaked in the early phase of the eruption, beginning slightly before 13:41 and gradually declined until its cessation 3 h later. Most of the pumiceous pyroclastic flow deposits were emplaced after the end of the fallout activity at ~16:30 but before the summit caldera collapse at approximately 19:11. Only a small volume of pumiceous flow deposits accumulated after the final caldera collapse. In contrast to the previous reconstruction of Holasek et al. (1996), which interpreted the progressive lowering of the column, documented by satellite data, as due to a decreasing mass eruption rate, we suggest that a progressive shift from a plinian column to a large co-ignimbrite column could also account for such a variation.  相似文献   

A case of no-wind plinian fallout at Pululagua caldera (Ecuador): implications for models of clast dispersal     

Paolo Papale  Mauro Rosi 《Bulletin of Volcanology》1993,55(7):523-535

The caldera of Pululagua is an eruptive centre of the Northern Volcanic Zone of the South American volcanic arc, located about 15 km north of Quito, Ecuador. Activity leading to formation of the caldera occurred about 2450 b.p. as a series of volcanic episodes during which an estimated 5–6 km³ (DRE) of hornblende-bearing dacitic magma was erupted. A basal pumice-fall deposit covers more than 2.2x10⁴ km² with a volume of about 1.1 km³ and represents the principal and best-preserved plinian layer. Circular patterns of isopachs and pumice, lithic and Md isopleths of the Basal Fallout (BF) around the caldera indicate emplacement in wind-free conditions. Absence of wind is confirmed by an ubiquitous, normally graded, thin ash bed at the top of the lapilli layer which originated from slow settling of fines after cessation of the plinian column (co-plinian ash). The unusual atmospheric conditions during deposition make the BF deposit particularly suitable for the application and evaluation of pyroclast dispersal models. Application of the Carey and Sparks' (1986) model shows that whereas the 3.2-, 1.6-, and 0.8-cm lithic isopleths predict a model column height of about 36 km, the 6.4-cm isopleth yields and estimate of only 21 km. The 4.9- and 6.4-cm isopleths yield a column height of 28 km using the model of Wilson and Walker (1987). The two models give the same mass discharge rate of 2x10⁸ kg s^-1. A simple exponential decrease of thickness with distance, as proposed by Pyle (1989) for plinian falls, fits well with the BF. Exponential decrease of size with distance is followed by clasts less than about 3 cm, suggesting, in agreement with Wilson and Walker (1987), that only a small proportion of large clasts reach the top of the column. Variations with distance in clast distribution patterns imply that, in order to obtain column heights by clast dispersal models, the distribution should be known from both proximal and distal zones. Knowledge of only a few isopleths, irrespective of their distance from the vent, is not sufficient as seemed justified by the method of Pyle (1989).  相似文献   

The 1631 Vesuvius eruption. A reconstruction based on historical and stratigraphical data   总被引：1，自引：0，他引：1  

Mauro Rosi  Claudia Principe  Raffaella Vecci 《Journal of Volcanology and Geothermal Research》1993,58(1-4)

The eruption of 1631 A.D. was the most violent and destructive event in the recent history of Vesuvius. More than fifty primary documents, written in either Italian or Latin, were critically examined, with preference given to the authors who eyewitnessed volcanic phenomena. The eruption started at 7 a.m. on December 16 with the formation of an eruptive column and was followed by block and lapilli fallout east and northeast of the volcano until 6 p.m. of the same day. At 10 a.m. on December 17, several nuées ardentes were observed to issue from the central crater, rapidly descending the flanks of the cone and devastating the villages at the foot of Vesuvius. In the night between the 16th and 17th and on the afternoon of the 17th, extensive lahars and floods, resulting from rainstorms, struck the radial valleys of the volcano as well as the plain north and northeast.Deposits of the eruption were identified in about 70 localities on top of an ubiquitous paleosol formed during a long preeruptive volcanic quiescence. The main tephra unit consists of a plinian fallout composed of moderately vesicular dark green lapilli, crystals and lithics. Isopachs of the fallout are elongated eastwards and permit a conservative volume calculation of 0.07 km³. The peak mass flux deduced from clast dispersal models is estimated in the range 3–6 × 10⁷ kg/s, corresponding to a column height of 17–21 km. East of the volcano the plinian fallout is overlain by ash-rich low-grade ignimbrite, surges, phreatomagmatic ashes and mud flows. Ash flows occur in paleovalleys around the cone of Vesuvius but are lacking on the Somma side, suggesting that pyroclastic flows had not enough energy to overpass the caldera wall of Mt. Somma. Deposits are generally unconsolidated, massive with virtually no ground layer and occasionally bearing sparse rests of charred vegetation. Past interpretations of the products emitted on the morning of December 17 as lava flows are inconsistent with both field observations and historical data. Features of the final phreatomagmatic ashes are suggestive of alternating episodes of wet ash fallout and rainfalls. Lahars interfingered with primary ash fallout confirm episodes of massive remobilization of loose tephra by heavy rainfalls during the final stage of the eruption.Chemical analyses of scoria clasts suggest tapping of magma from a compositionally zoned reservoir. Leucite-bearing, tephritic-phonolite (SiO₂ 51.17%) erupted in the early plinian phase was in fact followed by darker and slightly more mafic magma richer in crystals (SiO₂ 49.36%). During the nuées ardentes phase the composition returned to that of the early phase of the eruption.The reconstruction of the 1631 eruptive scenario supplies new perspectives on the hazards related to plinian eruptions of Vesuvius.  相似文献   

Dynamics of magma mixing and degassing recorded in plagioclase at Stromboli (Aeolian Archipelago,Italy)   总被引：12，自引：0，他引：12  

Patrizia?LandiEmail author  Nicole?Métrich  Antonella?Bertagnini  Mauro?Rosi 《Contributions to Mineralogy and Petrology》2004,147(2):213-227

Crystal-rich materials (scoriae and lava flows) emitted during the 1985–2000 activity of Stromboli were taken into consideration for systematic study of bulk rock/matrix glass chemistry and in particular for the study of chemical and textural zoning of plagioclase, the most abundant mineral phase. Over the considered time period, bulk rock composition remained fairly constant in both major (SiO₂ 49.2–50.9 wt% and K₂O 1.96–2.18 wt%) and trace elements. The quite constant chemistry of matrix glasses also indicates that the degree of crystallization of magma was maintained at around 50 vol%. Plagioclase ranges in composition between An₆₂ and An₈₈ and is characterized by alternating, <10–100 m thick, bytownitic and labradoritic concentric layers, although the dominant and representative plagioclase of scoriae is An_68. The labradoritic layers (An_62–70) show small-scale (1–5 µm), oscillatory zoning, are free of inclusions, and appear to record episodes of slow crystal growth in equilibrium with a degassed liquid having the composition of the matrix glass. In contrast the bytownitic layers (An₇₀-An₈₈) are patchy zoned, show sieve structure with abundant micrometric glass inclusions and voids, and are attributed to rapid crystal growth.A key to understanding the origin of bytownitic layers can be retrieved from the texture and composition of the coronas of plagioclase xenocrysts, inherited from crystal-rich magma, in nearly aphyric pumice which are erupted during more energetic events and represent a deep, volatile-rich, HK-basaltic magma. They show a continuum from fine-sieve to evident skeletal texture from the inner to the outer part of the corona associated with normal compositional zoning from An₉₀ to An₇₅. In the light of these observations, we propose that input of H₂O-rich melt blobs, and their mixing with the residing magma, causes partial dissolution of the labradoritic layers followed by the growth of bytownitic composition whose sieve texture attests of rapid crystallization occurring under undercooling conditions mainly induced by degassing. As a whole, the zoning of plagioclase in the scoriae records successive and discrete intrusions of volatile-rich magma blobs, its degassing and mixing with the resident degassed magma at shallow level.Editorial responsibility: T.L. GroveAn erratum to this article can be found at  相似文献   

Taphonomic analysis of small mammal bone remains preyed upon by wildcats (Carnivora: Felidae) from the central Monte Desert (Mendoza,Argentina)          下载免费PDF全文

José Manuel López  María I. Rosi  Solana Tabeni  Benjamín Bender  Horacio Chiavazza 《Boreas: An International Journal of Quaternary Research》2017,46(2):282-293

The present study analysed the taphonomic characteristics of small mammal bone accumulations produced by small felids in an area from the central Monte Desert (Mendoza, Argentina). In order to provide criteria to identify the role that these predators had in the formation of zooarchaeological assemblages, the anatomical representation, bone breakage patterns and degrees of digestive corrosion were evaluated. The main taphonomic results are: low average values for the relative abundance of skeletal elements; greater representation of mandibles, maxillae, isolated incisors, humeri and femora than the remaining elements; preponderance of cranial elements with high proportion of isolated teeth; elevated frequencies of proximal limb bones compared with distal parts; high degree of breakage in all skeletal elements and digestive corrosion on almost all diagnostic bones (mainly moderate and heavy). The values of the studied taphonomic variables indicate that small felids in this area made severe alterations to the bones of their prey (mainly rodents), attributable to the category of extreme modifier, while preserving enough skeletal elements to allow their taphonomic characterization. Tooth marks or grooves on bone surfaces produced by scratching and chewing were not detected. The low relative abundance of skeletal elements, the high degree of breakage and the elevated frequency of elements with digestion traces represent general taphonomic patterns that fall within those reported for other South American small carnivores.  相似文献   

Diet of a fossorial rodent (Octodontidae), above-ground food availability,and changes related to cattle grazing in the Central Monte (Argentina)     

M.I. Rosi  S. Puig  M.I. Cona  F. Videla  E. Méndez  V.G. Roig 《Journal of Arid Environments》2009,73(3):273-279

Overgrazing by livestock has caused desertification in the Monte, where ctenomyids and livestock share grasses as main food items. The diet of Ctenomys eremophilus, above-ground food availability and changes related to cattle grazing are analyzed in the arid plain of Mendoza, Argentina. The most available categories were grasses, followed by low shrubs and tall shrubs. Tuco-tucos showed dietary generalism, ate mainly above-ground plant parts, preferred grasses and avoided shrubs at both grazed and ungrazed sites. Plant cover, grass diversity and availability decreased under livestock grazing, which was reflected in the diet by a lower percentage of grasses, a shift toward low shrubs and higher number of frequently used resources. Tuco-tucos in the grazed paddock compensated for lower consumption of vegetative plant parts by increasing the use of Prosopis flexuosa pods stored inside burrows. Moreover, greater dietary variation among individuals suggests foraging restricted to the items closest to burrow holes. These feeding tactics would allow them to reduce above-ground foraging as a response to high raptor predation risk due to increased bare soil. The plant recovery detected during the rest period, favoured by moderate stocking rate and rotational grazing system, would allow coexistence of tuco-tucos and cattle.  相似文献   

INVESTIGATIONS ON EROSIONAL PROCESSES OF COHESIVE SEDIMENT USING AN IN-SITU MEASURING DEVICE     

Rosi LIEM Research Engineers  Institute of Hydraulic Engineering  Water Resources Management  Aachen Univer-s of Technology  Germany Volker SPORK Research Engineers  Institute of Hydraulic Engineering  Water Resources Management  Aachen Univer- 《国际泥沙研究》1997,(3)

I.INTRODUCTIONToconstructanidealmeasuringdeviceforin-situstUdiesincomparisontolaboratorydeVicesastrongeremphasishastobesetonthehandlingoftheSystemandtheresistanceunderwater,whichaughtbethereasonwhynotmanyapproachesonrealin-situinvestigationwerecaaccedoutlately.Sincetheedupandtheconstructionseemtodemandahigheramountofcostsandeffort,quasiin-siamstudieswerecAnedoutrefetringtoanundisturbedsedimentsampledrawnfromthesedimentbedoutofthewaterintothesamplingchamberofameasuringdevice.Evenifthisisa…  相似文献   

Exploring a landslide inventory created by automated web data mining: the case of Italy     

Franceschini  Rachele  Rosi  Ascanio  Catani  Filippo  Casagli  Nicola 《Landslides》2022,19(4):841-853

Landslides - Nowadays, several systems to set up landslide inventories exist although they rarely rely on automated or real-time updates. Mass media can provide reliable info about natural hazard...  相似文献   

Chronology and dispersal characteristics of recently (last 5000 years) erupted tephra of Cotopaxi (Ecuador): implications for long-term eruptive forecasting     

F. Barberi  M. Coltelli  A. Frullani  M. Rosi  E. Almeida 《Journal of Volcanology and Geothermal Research》1995,69(3-4)

Cotopaxi, the highest active volcano on earth and one of the most dangerous of Ecuador is constituted by a composite cone made up of lava and tephra erupted from the summit crater. The activity of the present volcano begun with large-volume plinian eruptions followed by a succession of small-volume lava emissions and pyroclastic episodes which led to the edification of a symmetrical cone. The growth of the cone was broken by an episode of slope failure, the scar of which is now obliterated by recent and historical products. Volcanic history, eruptive frequency and characteristics of the activity were investigated by studying the stratigraphy of tephra and carrying out fifteen new ¹⁴C dating on paleosols and charcoals. The investigated period is comprised between the slope failure and the present. The deposit of the volcanic landside (dry debris avalanche of Rio Pita), previously believed to be between 13,000 and 25,000 yr B.P., is now considered to have an age slightly older than 5000 yr B.P. The stratigraphy of tephra of the last 2000 years reveals the existence of 22 fallout layers. Seven of them were dated with ¹⁴C whereas three were ascribed to the eruptions of 1534, 1768 and 1877 on the basis of comparison with historical information.Maximum clast size distribution (isopleths) of 9 tephra layers points out that the sustained explosive eruptions of Cotopaxi during the last 2000 years are characterized by very high dispersive power (plinian plumes with column heights between 28 and 39 km) and high intensity (peak mass discharges from 1.1 to 4.1 × 10⁸kg/s). The magnitude (mass) of tephra fallout deposits calculated from distribution of thickness (isopaches) are, however, moderate (from 0.8 to 7.2 × 10¹¹ kg). The limited volume of magma erupted during each explosive episode is consistent with the lack of caldera collapses. Small-volume pyroclastic flows and surges virtually accompanied all identified tephra fallouts. During such an activity large scale snow/ice melting of the summit glacier produced devastating mudflows comparable in scale to those of 1877 eruption. By assuming a 1:1 correspondence between fallout episodes and generation of large-scale lahar, we have estimated an average recurrence of one explosive, lahartriggering event every 117 years over the last two millennia. This value compares well with that calculated by considering the period since Spanish Conquest. The probability of having an eruption like this in 100 or 200 years is respectively of 0.57 and 0.82. Such an high probability underscores the need for quick actions aimed at the mitigation of Cotopaxi lahar hazard along all the main valleys which originate from the volcano.  相似文献