Search results for "Rarefaction"
showing 10 items of 12 documents
Blast waves from violent explosive activity at Yasur Volcano, Vanuatu
2013
[1] Infrasonic and seismic waveforms were collected during violent strombolian activity at Yasur Volcano (Vanuatu). Averaging ~3000 seismic events showed stable waveforms, evidencing a low-frequency (0.1–0.3 Hz) signal preceding ~5–6 s the explosion. Infrasonic waveforms were mostly asymmetric with a sharp compressive (5–106 Pa) onset, followed by a small long-lasting rarefaction phase. Regardless of the pressure amplitude, the ratio between the positive and negative phases was constant. These waveform characteristics closely resembled blast waves. Infrared imagery showed an apparent cold spherical front ~20 m thick, which moved between 342 and 405 m/s before the explosive hot gas/fragments…
Spreading introgression in the wake of a moving contact zone
2006
An increasing number of studies describe moving hybrid zones. This raises the issue of their actual frequency and emphasizes the need for methods that enable the detection of zone movements without historical records. Asymmetric introgression, usually considered as a signature of geographical shift, might be misleading when applied to mitochondrial or potentially non-neutral markers. We investigated mitochondrial and genomic introgression, using 30 AFLP derived markers, in a well-documented moving avian contact zone between two warblers. We found no instances of cross-species transmission of mitochondrial DNA but we detected nuclear introgression. Introgression levels were higher in the exp…
Analysis of spatial patterns informs community assembly and sampling requirements for Collembola in forest soils
2018
Abstract The relative importance of niche separation, non-equilibrial and neutral models of community assembly has been a theme in community ecology for many decades with none appearing to be applicable under all circumstances. In this study, Collembola species abundances were recorded over eleven consecutive years in a spatially explicit grid and used to examine (i) whether observed beta diversity differed from that expected under conditions of neutrality, (ii) whether sampling points differed in their relative contributions to overall beta diversity, and (iii) the number of samples required to provide comparable estimates of species richness across three forest sites. Neutrality could not…
Global patterns and drivers of alpine plant species richness
2021
B.J.-A. was funded by the Marie Curie Clarín-COFUND program of the Principality of Asturias-EU (ACB17-26) and the Spanish Research Agency (AEI/10.13039/501100011033).
Small Mammals in Forests of Romania: Habitat Type Use and Additive Diversity Partitioning
2021
Small mammals are key components of forest ecosystems, playing vital roles for numerous groups of forest organisms: they exert bottom-up and top-down regulatory effects on vertebrate and invertebrate populations, respectively
Dynamical efficiency of collisionless magnetized shocks in relativistic jets
2010
The so-called internal shock model aims to explain the light-curves and spectra produced by non-thermal processes originated in the flow of blazars and gamma-ray bursts. A long standing question is whether the tenuous collisionless shocks, driven inside a relativistic flow, are efficient enough to explain the amount of energy observed as compared with the expected kinetic power of the outflow. In this work we study the dynamic efficiency of conversion of kinetic-to- thermal/magnetic energy of internal shocks in relativistic magnetized outflows. We find that the collision between shells with a non-zero relative velocity can yield either two oppositely moving shocks (in the frame where the co…
Ammonite diversity and its palaeobiogeographical structure during the early Pliensbachian (Jurassic) in the western Tethys and adjacent areas.
2009
14 pages; International audience; The early Pliensbachian (Early Jurassic) is known as a time of marked provincialism in the marine realm, notably between the Mediterranean Tethys and North–West Europe. In order to test this observation quantitatively, we compiled 104 locality-level species lists from those areas based on a comprehensive revision of early Pliensbachian ammonites. With this dataset, we also explore the relationship between ammonite richness and biogeography at the scale of the sub-chronozone during the early Pliensbachian. Using various multivariate statistics and rarefaction techniques, we show that: (i) there is a sharp contrast between the NW European (NWE) and the Medite…
Percorsi architettonici. Un caso di studio alla Cala di Palermo
2022
Il caso di studio è stato presentato nel 2019 alla Biennale di Pisa. Si tratta di una ricerca progettuale che sovrappone lo stato fisico del fare architettura verso ‘territori’ mediati da luce/ombra, interno/esterno e viceversa. Il progetto è un fatto complesso che va affrontato in modo semplice per un tempo che cambia abitudini e stili di vita. Deve saper ascoltare le condizioni fisiche e ambientali di un luogo e interrogarsi costantemente per stabilire un dialogo necessario e ricomprendere la connessione che lega realtà e mimesis. Ed è proprio all’interno di questa sequenza che individuiamo, nel sistema complesso di segni, il nuovo. Questi sono identificabili come ‘limiti’ o ‘risorse’ ent…
On the dynamic efficiency of internal shocks in magnetized relativistic outflows
2009
We study the dynamic efficiency of conversion of kinetic-to-thermal/magnetic energy of internal shocks in relativistic magnetized outflows. We model internal shocks as being caused by collisions of shells of plasma with the same energy flux and a non-zero relative velocity. The contact surface, where the interaction between the shells takes place, can break up either into two oppositely moving shocks (in the frame where the contact surface is at rest), or into a reverse shock and a forward rarefaction. We find that for moderately magnetized shocks (magnetization $\sigma\simeq 0.1$), the dynamic efficiency in a single two-shell interaction can be as large as 40%. Thus, the dynamic efficiency…
Marine caves of the Southern Tyrrhenian Sea: a First Census of Benthic Biodiversity
2017
This is the first paper documenting research on a selection of marine caves located along the coast of Capo Milazzo in the southern Tyrrhenian Sea. Three submarine and one semi-submerged caves were surveyed and sampled using underwater photo sampling. Surveys have only taken into account the sessile species belonging to the main taxa: Porifera, Anthozoa, Bryozoa and Polychaeta. Diversity indices and abundances were calculated for three sections within each explored cave: the Entrance Zone, Intermediate Zone and Bottom Zone. The richest group was Porifera with 21 taxa, followed by cnidarians, (Anthozoa), with 8 taxa, Polychaeta (5 taxa), and Bryozoa (5 taxa). Among Porifera, the presence of …