Dynamical evolution of an unstable gravastar with zero mass

Using the conventional gravastar model, that is, an object constituted by two components where one of them is a massive infinitely thin shell and the other one is a de Sitter interior spacetime, we physically interpret a solution characterized by a zero Schwarzschild mass. No stable gravastar is formed and it collapses without forming an event horizon, originating what we call a massive non-gravitational object. The most surprise here is that the collapse occurs with an exterior de Sitter vacuum spacetime. This creates an object which does not interact gravitationally with an outside test particle and it may evolve to a point-like topological defect.     

Sedimentologic and palynologic records of the last deglaciation and Holocene from Ballston Lake, New York

Continuous pollen and sediment records from two ∼8.5-m-long cores document late Pleistocene and Holocene sedimentation and vegetation change in the Ballston Lake basin, eastern New York State. Pebbles at the base of both cores and the geomorphology of the watershed reflect the presence of the Mohawk River in the basin prior to ∼12,900 ± 70 cal yr B.P. Ballston Lake formed at the onset of the Younger Dryas (YD) by an avulsion of the Mohawk River. The transition from clay to gyttja with low magnetic susceptibility (MS), low bulk density, and high organic carbon indicates rapid warming and increased lake productivity beginning 11,020 cal yr B.P. MS measurements reveal that the influx of magnetic particles, associated with pre-Holocene clastic sedimentation, ceased after ∼10,780 cal yr B.P. The pollen record is subdivided into six zones: BL1 (12,920 to 11,020 cal yr B.P.) is dominated by boreal forest pollen; BL2 (11,020 to 10,780 cal yr B.P.) by pine (Pinus) forest pollen; BL3 (10,780 to 5290 cal yr B.P.) by hemlock (Tsuga) and mixed hardwood pollen; BL4 (5290 to 2680 cal yr B.P.) by mixed hardwood pollen; BL5a (2680 cal yr B.P. to 1030 cal yr B.P.) by conifer and mixed hardwood pollen; and BL5b (1030 cal B.P. to present) by increasing ragweed (Ambrosia) pollen. A 62% decrease in spruce (Picea) pollen in <320 cal years during BL1 reflects rapid warming at the end of the YD. Holocene pollen zones record more subtle climatic shifts than occurred at the end of the YD. One of the largest changes in the Holocene pollen spectra began ∼5300 cal yr B.P., and is characterized by a marked decline in hemlock pollen. This has been noted in other pollen records from the region and may record preferential selection of hemlock by a pathogen or parasites.     

Laboratory tests of steel simple torsionally unbalanced models

The objective of this work is to obtain estimations of the amplification factors α and δ used for torsion design of buildings, from experiments. For this study, simple one‐storey torsionally unbalanced (TU) steel models were considered. Models consisted of a deck supported on four columns with a selected arrangement of hinges at column ends. Two theoretical structural eccentricities (e = 0.05 and 0.15) were considered. Models were excited with a simple long‐period pendulum consisting of a hanging platform with a forced‐vibration generator on it. Eight models were tested at several excitation levels (frequencies and force magnitudes) in both ranges of behaviour: elastic and inelastic. Experiments were conducted at three frequency ratios of excitation. Registered accelerations of the pendulum platform indicate that the experimental set‐up leads to excitations that resemble narrow‐band seismic ground motions. Frame shear force estimations, based on accelerations recorded at both deck sides, indicate that torsion design factors (α and δ) depend on eccentricity. Estimations of frame shears based on measurements indicate that for normalized eccentricities e ? 0.025, the amplification α can be between 2 and 3; while δ factor resulted between 0.0 and 1.6. Copyright © 2006 John Wiley & Sons, Ltd.     

Characterization of distal turbidites in marine sedimentary sequences using magnetic mineral data and factor analysis of microfossils assemblages

Results of a study of turbiditic deposits in a sequence of middle to late Holocene marine sediments from Alfonso Basin in the southern Gulf of California are presented. Turbidites are identified from analyses of core sections, X-ray images, texture and granulometry. Characterization of distal turbidites could be difficult, particularly for thin fine-grained deposits with little contrast in grain size, mineralogy and texture. We have here included analyses of microfossil and magnetic mineral data. Turbiditic currents transport material from various depths in the continental slope into the basin and it can be expected that turbiditic deposits are characterized by re-worked material, lack of microfossils or mixed assemblages with no content of paleoceanographic and paleoclimatic record. This may show in lack of internal coherence as quantified by factor analysis of microfossil assemblages. Turbidites in some cases may also show distinct magnetic properties as compared with those in the sediment sequence. In Alfonso Basin, turbidites show increased contents of detrital magnetic minerals volcanic-derived and transported from the basin slope. We identify twelve turbiditic layers through the sequence that present high magnetic susceptibility and low communalities from factor model to the microfossils data providing characterization of the turbidites.     

Validation of precipitation events in a regional climate model simulation using methods from complex systems theory

Summary We show that daily precipitation is characterized by a behaviour regulated by power laws. Both for the frequency distribution of both event intensity and drought duration. In this respect, precipitation appears to follow self-organized criticality laws, much as other geophysical phenomena such as avalanches and earthquakes. We use this feature to validate the simulation of daily precipitation events in a multi-decadal regional climate model experiment for the European region. Our focus is on the Italian peninsula and we show that both the model results and the station observations for daily precipitation intensity and drought length follow power laws with comparable values of the relevant parameters. We suggest that complex systems theory can provide useful tools for the validation of precipitation statistics in climate models.     

Insights from experimental economics on local cooperation in a small-scale fishery management system

Cooperation is central to collective management of small-scale fisheries management, including marine protected areas. Thus an understanding of the factors influencing stakeholders’ propensity to cooperate to achieve shared benefits is essential to accomplishing successful collective fisheries management. In this paper we study stakeholders’ cooperative behavioral disposition and elucidate the role of various socio-economic factors in influencing it in the Roviana Lagoon, Western Solomon Islands. We employed a Public Goods Game from experimental economics tailored to mimic the problem of common pool fisheries management to elucidate peoples’ cooperative behavior. Using Ostrom's framework for analyzing social-ecological systems to guide our analysis, we examined how individual-scale variables (e.g., age, education, family size, ethnicity, occupational status, personal norms), in the context of village-scale variables (e.g., village, governance institutions, group coercive action), influence cooperative behavior, as indexed by game contribution. Ostrom's framework provides an effective window for conceptually peeling back the various socio-economic and governance layers which influence cooperation within these communities. The results of our research show that the most important resource user characteristics influencing cooperative behavior were age, occupation and beliefs about giving access to others to fish for commercial gain. Through elucidating the factors affecting stakeholders’ propensity to cooperate to achieve shared benefits, our analysis provides guidance in understanding cooperation in relation to collective management of marine resources.     

Peering inside the peak ring of the Chicxulub Impact Crater—its nature and formation mechanism

The IODP‐ICDP Expedition 364 drilled into the Chicxulub crater, peering inside its well‐preserved peak ring. The borehole penetrated a sequence of post‐impact carbonates and a unit of suevites and clast‐poor impact melt rock at the top of the peak ring. Beneath this sequence, basement rocks cut by pre‐impact and impact dykes, with breccias and melt, were encountered at shallow depths. The basement rocks are fractured, shocked and uplifted, consistent with dynamic collapse, uplift and long‐distance transport of weakened material during collapse of the transient cavity and final crater formation.     

Reconstruction of a complex late Quaternary glacial landscape in the Cordillera de Cochabamba (Bolivia) based on a morphostratigraphic and multiple dating approach

Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating (¹⁴C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regarding the latter, a first advance dated to ~ 29-25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20-18 ka. The local last glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~ 17-16 ka, followed by several smaller readvances until ~ 10-11 ka, and complete deglaciation at the end of the Early Holocene.     

Further constraints for Permo-Carboniferous magnetostratigraphy: case study of the sedimentary sequence from San Salvador–Patlanoaya (Mexico)De nouvelles contraintes pour la magnétostratigraphie du Permo-Carbonifères : cas d'étude de la séquence sédimentaire de San Salvador–Patlanoaya (Mexique)

We report rock-magnetic and magnetostratigraphic results from one of the best exposed Permo-Carboniferous outcrops in Mexico, in order to determine some decisive magnetostratigraphy constraints. Some spinels, most probably titanomagnetites, seem to be responsible for aimantation, although greigite may also exist judging from thermal desaimantation of isothermal remanence. Remanence analyses indicate that only one remanent component could be recognized with minor secondary overprint, which were easily removed applying 100–180 °C. Six normal and four reverse magnetozones were recognized from bottom to top in Patlanoya section between 340 and 280 Myr. Both normal and reverse polarity rocks were found in Carboniferous time around 340 Myr, in agreement with previous paleomagnetic works. Our record revealed two normal subchrons within PCRS (Kiaman), the dominantly reverse superchron, at 305 and 280 Myr, respectively. These, which may be speculatively correlated to normal aimantation, occasionally occurred during PCRS interval. More detailed studies are needed in order to establish a more precise magnetostratigraphy for Permo-Carboniferous time. To cite this article: L.M. Alva-Valdivia et al., C. R. Geoscience 334 (2002) 811–817.     

Diverse stigmaphronid wasps in Early Cretaceous amber from Spain (Hymenoptera: Ceraphronoidea: Stigmaphronidae)

A diverse fauna of wasps of the extinct parasitoid family Stigmaphronidae (Ceraphronoidea) are recorded in Early Cretaceous (Lower Albian) amber from Spain. Seven new species in five genera are described and figured based on 51 specimens, representing more material than in all the world’s other amber deposits combined. New species include: Elasmophron mari sp. nov., Libanophron sugaar sp. nov., Hippocoon basajauni sp. nov., Burmaphron jentilak sp. nov., B. sorginak sp. nov., B. iratxoak sp. nov., and Tagsmiphron olentzero sp. nov. The significance of the fauna is discussed and compared with that of other Cretaceous amber deposits, in particular the tremendous richness of the Spanish fauna is contrasted with the complete absence of stigmaphronids in the slightly younger and nearby French amber. Whether this stark difference represents particularly favorable conditions for these parasitoids, or their hosts, in the Cretaceous Spanish archipelago, or whether it is owing to taphonomic factors is discussed.