The Swift gamma-ray burst GRB 050422     

A. P. Beardmore  K. L. Page  P. T. O'Brien  J. P. Osborne  S. Kobayashi  B. Zhang  D. N. Burrows  M. Capalbi  M. R. Goad  O. Godet  J. E. Hill  V. La Parola  F. Marshall  A. A. Wells 《Monthly notices of the Royal Astronomical Society》2007,374(4):1473-1478

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Holocene vegetation and fire dynamics in the supra‐mediterranean belt of the Nebrodi Mountains (Sicily,Italy)     

Martina Bisculm  Daniele Colombaroli  Elisa Vescovi  Jacqueline F. N. van Leeuwen  Paul D. Henne  Julian Rothen  Giovanni Procacci  Salvatore Pasta  Tommaso La Mantia  Willy Tinner 《第四纪科学杂志》2012,27(7):687-698

High‐resolution pollen, macrofossil and charcoal data, combined with accelerator mass spectrometry ¹⁴C dating and multivariate analysis, were used to reconstruct Holocene vegetation and fire dynamics at Urio Quattrocchi, a small lake in the supra‐mediterranean belt in the Nebrodi Mountains of Sicily (Italy). The data suggest that after 10 000 cal a BP increasing moisture availability supported closed forests with deciduous (Quercus cerris, Fagus sylvatica and Fraxinus spp.) and evergreen (Quercus ilex) species. Species‐rich closed forest persisted until 6850 cal a BP, when Neolithic activities caused a forest decline and affected plant diversity. Secondary forest with abundant Ilex aquifolium recovered between 6650 and 6000 cal a BP, indicating moist conditions. From 5000 cal a BP, agriculture and pastoralism led to the currently fragmented landscape with sparse deciduous forests (Quercus cerris). The study suggests that evergreen broadleaved species were more important at elevations above 1000 m a.s.l. before ca. 5000 cal a BP than subsequently, which might reflect less human impact or warmer‐than‐today climatic conditions between 10 000 and 5000 cal a BP. Despite land use since Neolithic times, deciduous supra‐mediterranean forests were never completely displaced from the Nebrodi Mountains, because of favourable moist conditions that persisted throughout the Holocene. Reconstructed vegetation dynamics document the absence of any pronounced mid‐ or late‐Holocene ‘aridification’ trend at the site, an issue which is controversially debated in Italy and the Mediterranean region. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Practical versus absolute salinity measurements: New advances in high performance seawater salinity sensors     

Philippe Grosso  Marc Le Menn  Jean-Louis De Bougrenet De La Tocnaye  Zong Yan Wu  Damien Malardé 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):151-156

Optical salinity sensors described here measure directly the seawater refractive index and thus enable a measurement of the seawater density and composition variation. We detail the measurement dependence to environmental parameters (in particular temperature and pressure) compared to conductivity sensors, and demonstrate that it may be advantageous to directly measure refractive index rather than electrical conductivity and so obtain a more direct route to density and absolute salinity.  相似文献   

Reproductive resilience of ice‐dependent Antarctic silverfish in a rapidly changing system along the Western Antarctic Peninsula          下载免费PDF全文

Mario La Mesa  Emilio Riginella  Carlotta Mazzoldi  Julian Ashford 《Marine Ecology》2015,36(2):235-245

The Western Antarctic Peninsula (wAP) is globally one of the systems most heavily impacted by climate change, notably steep declines in sea ice extent. In forage species, reproductive resilience to change is particularly important because population fluctuations are rapidly communicated through the system via trophic interactions. The reproductive traits of the ice‐dependent forage species Antarctic silverfish (Pleuragramma antarctica) from different areas along the wAP and at the tip of the Antarctic Peninsula were investigated through macroscopic and histological analyses of gonads, with the aim to assess its reproductive potential and to test for spatial differences in fecundity and spawning season. Fish samples were collected in late summer off Charcot Island, in Marguerite Bay and off Joinville Island; no fish were caught in the central wAP. Samples from Charcot Island and Marguerite Bay consisted of adults in developing gonad stage, whereas those from Joinville consisted almost exclusively of juveniles. Mean GSI was relatively low (2–3%) and similar in both sexes, as specimens were still far from being actively reproducing. Developing females exhibited two discrete, though partially overlapping modes of oocytes of different size, with vitellogenic oocytes measuring 0.5–1.0 mm. Absolute and relative fecundity ranged between 3000 and 12,000 eggs per female and between 80 and 190 eggs·g^?1, with a strong relationship between absolute fecundity and body size. These results were consistent with a single population at Charcot Island and Marguerite Bay and indicated substantial reproductive potential, which may mitigate population isolation and reductions in habitat availability but cannot ultimately offset catastrophic loss of spawning habitat linked to sea‐ice retreat.  相似文献   

The HELLAS2XMM survey – XII. The infrared/submillimetre view of an X-ray selected type 2 quasar at z≈ 2     

C. Vignali  F. Pozzi  J. Fritz  A. Comastri  C. Gruppioni  E. Bellocchi  F. Fiore  M. Brusa  R. Maiolino  M. Mignoli  F. La Franca  L. Pozzetti  G. Zamorani  A. Merloni 《Monthly notices of the Royal Astronomical Society》2009,395(4):2189-2195

We present multiwavelength observations (from optical to submillimetre, including Spitzer and Submillimetre Common-User Bolometer Array) of H2XMMJ 003357.2−120038 (also GD 158_19), an X-ray selected, luminous narrow-line (type 2) quasar at   z = 1.957  selected from the HELLAS2XMM survey. Its broad-band properties can be reasonably well modelled assuming three components: a stellar component to account for the optical and near-infrared (IR) emission; an active galactic nucleus (AGN) component (i.e. dust heated by an accreting active nucleus), dominant in the mid-IR, with an optical depth at 9.7      along the line of sight (close to the equatorial plane of the obscuring matter) of  τ(9.7) = 1  and a full covering angle of the reprocessing matter (torus) of 140° and a far-IR starburst component (i.e. dust heated by star formation) to reproduce the wide bump observed longward of 70      .
The derived star formation rate is  ≈1500 M_⊙ yr⁻¹  . The overall modelling indicates that GD 158_19 is a high-redshift X-ray luminous, obscured quasar with coeval powerful AGN activity and intense star formation. It is probably caught before the process of expelling the obscuring gas has started, thus quenching the star formation.  相似文献   

2005年南京市PM_(10)浓度时间序列分析   总被引：6，自引：2，他引：4  

任永建  周锁铨  石顺吉  拉巴 《气象科学》2009,29(3)

根据南京市2005年的PM10日均浓度和气象观测资料,利用Maflab小波分析工具,对PM10浓度的年时间序列进行分析,得出了该地区PM10日均浓度的变化规律：2—5月较大,6-9月较小,10—12月较大;并且全年共有5个突变点。结合HYSPLIT4污染扩散模式,对污染源进行追踪,结果表明：造成南京市大气污染主要有局地污染物的排放和外来污染物的输送两种类型;在垂直方向上,污染物的长距离输送一直稳定在低层。  相似文献   

Coupling between cold dark matter and dark energy from neutrino mass experiments     

J.R. Kristiansen  G. La Vacca  L.P.L. Colombo  R. Mainini  S.A. Bonometto 《New Astronomy》2010,15(7):609-613

We consider cosmological models with dynamical dark energy (dDE) coupled to cold dark matter (CDM), while simultaneously allowing neutrinos to be massive. Using a MCMC approach, we compare these models with a wide range of cosmological data sets. We find a strong correlation between this coupling strength and the neutrino mass. This correlation persists when BAO data are included in the analysis. We add then priors on $\nu$ mass from particle experiments. The claimed detection of $\nu$ mass from the Heidelberg–Moscow neutrinoless double-$\beta$ decay experiment would imply a 7–$8\sigma$ detection of CDM–DE coupling. Similarly, the detection of $\nu$ mass from coming KATRIN tritium $\beta$ decay experiment will imply a safe detection of a coupling in the dark sector. Previous attempts to accommodate cosmic phenomenology with such possible $\nu$ mass data made recourse to a $w<-1$ eoS. We compare such an option with the coupling option and find that the latter allows a drastic improvement.  相似文献   

Technological study of “ghiara” mortars from the historical city centre of Catania (Eastern Sicily, Italy) and petro-chemical characterisation of raw materials     

Cristina M. Belfiore  Mauro F. La Russa  Paolo Mazzoleni  Antonino Pezzino  Marco Viccaro 《Environmental Earth Sciences》2010,61(5):995-1003

This paper presents new petro-chemical data on some typical mortars found in many buildings in the historic city centre of Catania (Eastern Sicily). Extensively used in the architecture of the city from the second half of the nineteenth century until the mid-twentieth century, these mortars are characterised by a particular aggregate locally known as “agghiara” or “ghiara”. This is the product of thermal transformation induced by the heating undergone by palaeo-soils, originally rich in organic matter, covered by lava flows, which change their colour to reddish nuances. The volcanic origin of ghiara is a peculiar feature of the Etnean area. Mixed with lime, it gives to mortars an intense reddish colour, as well as hydraulic properties, which are comparable with those of the historically used pozzolana. This work aimed at complete characterisation of these ghiara mortars, for providing information on several important technological aspects. In order to get information on used raw materials, sampling of some ancient underground quarries, located both in the historic city centre and at the periphery, was also performed. Results led to the complete characterisation of the selected ghiara mortars and yielded information on some technological features and the composition of both newly formed and secondary phases, these latter due to alteration processes. The hydraulic properties of mortars have been related to the occurrence of amorphous phases within the ghiara aggregate, which were identified by means of SEM morphological observations. These phases, formed during the “firing” process of palaeo-soils, react with lime producing hydraulic compounds (C–S–H and C–A–H), which are responsible for the mortars durability.  相似文献   

Holocene environmental and climatic changes at Gorgo Basso,a coastal lake in southern Sicily,Italy     

Willy Tinner  Jacqueline F.N. van Leeuwen  Daniele Colombaroli  Elisa Vescovi  W.O. van der Knaap  Paul D. Henne  Salvatore Pasta  Stefania D'Angelo  Tommaso La Mantia 《Quaternary Science Reviews》2009,28(15-16):1498-1510

We used a new sedimentary record to reconstruct the Holocene vegetation and fire history of Gorgo Basso, a coastal lake in south-western Sicily (Italy). Pollen and charcoal data suggest a fire-prone open grassland near the site until ca 10,000 cal yr BP (8050 cal BC), when Pistacia shrubland expanded and fire activity declined, probably in response to increased moisture availability. Evergreen Olea europaea woods expanded ca 8400 to decline abruptly at 8200 cal yr BP, when climatic conditions became drier at other sites in the Mediterranean region. Around 7000 cal yr BP evergreen broadleaved forests (Quercus ilex, Quercus suber and O. europaea) expanded at the cost of open communities. The expansion of evergreen broadleaved forests was associated with a decline of fire and of local Neolithic (Ficus carica–Cerealia based) agriculture that had initiated ca 500 years earlier. Vegetational, fire and land-use changes ca 7000 cal yr BP were probably caused by increased precipitation that resulted from (insolation-forced) weakening of the monsoon and Hadley circulation ca 8000–6000 cal yr BP. Low fire activity and dense coastal evergreen forests persisted until renewed human activity (probably Greek, respectively Roman colonists) disrupted the forest ca 2700 cal yr BP (750 BC) and 2100 cal yr BP (150 BC) to gain open land for agriculture. The intense use of fire for this purpose induced the expansion of open maquis, garrigue, and grassland-prairie environments (with an increasing abundance of the native palm Chamaerops humilis). Prehistoric land-use phases after the Bronze Age seem synchronous with those at other sites in southern and central Europe, possibly as a result of climatic forcing. Considering the response of vegetation to Holocene climatic variability as well as human impact we conclude that under (semi-)natural conditions evergreen broadleaved Q. ilex–O. europaea (s.l.) forests would still dominate near Gorgo Basso. However, forecasted climate change and aridification may lead to a situation similar to that before 7000 cal yr BP and thus trigger a rapid collapse of the few relict evergreen broadleaved woodlands in coastal Sicily and elsewhere in the southern Mediterranean region.  相似文献   

Fire and drought as drivers of early Holocene tree line changes in the Peruvian Andes     

Dunia H. Urrego  Brittany A. Niccum  Christopher F. La Drew  Miles R. Silman  Mark B. Bush 《第四纪科学杂志》2011,26(1):28-36

Three pollen and charcoal records from three lakes lying at 3400 m elevation in southern Peru provided a record of landscape change spanning the last ca.18 000 cal. a BP. The tree line lay close to the site between ca. 16 000 and 12 000 cal. a BP, with Polylepis woodlands growing near the lakes. Progressively drying conditions led to increased fire after 12 000 cal. a BP, coinciding with a decline in Polylepis cover and Andean forest relicts as puna grasslands expanded. A strong decrease in the rate of sediment deposition between ca. 12 000 and ca. 4400 cal. a BP was interpreted to indicate the presence of sedimentary hiatuses. With the return of wet conditions after 4400 cal. a BP, forests did not reassemble around the lakes. Instead, fire‐maintained grasslands dominated the landscape. Humans probably induced the intensified fire activity during the late Holocene and thereby deflected local successions. The modern fragmented landscape, with Polylepsis woodlands existing in fire‐resistant pockets above the general limit of the Andean tree line, resulted from the intensification of human land use practices during the last 4400 cal. a BP. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献