Features of spin-charge separation in the equilibrium conductance through finite rings

We calculate the conductance through rings with few sites $L$ described by the $t-J$ model, threaded by a magnetic flux $\Phi$ and weakly coupled to conducting leads at two arbitrary sites. The model can describe a circular array of quantum dots with large charging energy $U$ in comparison with the nearest-neighbor hopping $t$. We determine analytically the particular values of $\Phi$ for which a depression of the transmittance is expected as a consequence of spin-charge separation. We show numerically that the equilibrium conductance at zero temperature is depressed at those particular values of $\Phi$ for most systems, in particular at half filling, which might be easier to realize experimentally.Comment: 8 pages, 7 figure

Are Historical Biogeographical Events Able to Promote Biological Diversification?

One of the goals of evolutionary biology is understanding how biological diversification change across spatial and temporal scales. Theoretically, it has been established that external (i.e., dispersals) and internal (i.e., origin of a key innovations) factors can modulate shifts in rates of species diversification. However, the role of historical events as trigger of species diversification rates have not been well understood in empirical studies. I reviewed the literature linking historical biogeographic events and species diversification in many groups. Many of studies conclude that dispersals can be associated with exceptional changes in species diversification rates in insular and mainland areas. I discuss the limitations of some approaches used to discover the link between historical biogeography and macroevolution. I propose some predictions under biogeographic scenarios to gain understanding in how historical events promote biological diversification. I suggest that future studies linking biogeography and macroevolution should incorporate ecologically-relevant traits to discern the mechanisms underlying these historical associations. Although new developments in phylogenetic comparative methods have been done, still is necessary more traditional field-based ecological and evolutionary research. The link between biogeography and diversification still remains narrative and a comprehensive approach is necessary to establish how diversification was triggered by historical events

Spin-charge separation in strongly interacting finite ladder rings

We study the conductance through Aharonov-Bohm finite ladder rings with strongly interacting electrons, modelled by the prototypical t-J model. For a wide range of parameters we observe characteristic dips in the conductance as a function of magnetic flux, predicted so far only in chains which are a signature of spin and charge separation. These results open the possibility of observing this peculiar many-body phenomenon in anisotropic ladder systems and in real nanoscopic devices.Comment: 4 pages, 6 figure

Centrolene savagei

Number of Pages: 11Geological SciencesIntegrative Biolog

First fossil record of Discocephalinae (Insecta, Pentatomidae): a new genus from the middle Eocene of Río Pichileufú, Patagonia, Argentina

A new genus and species of Discocephalini, Acanthocephalonotum martinsnetoi gen. n. et sp. n. is described from Río Pichileufú, middle Eocene of Patagonia, Argentina at palaeolatitude ~ 46°S. The new species is the first fossil representative of the Discocephalinae. This taxon is extant in equatorial to subtropical America, and some species reach warm temperate latitudes (Buenos Aires province). The new genus is distinguished from the other genera of Discocephalini by the combination of these characters: interocular width greater than head length; head massive and quadrangular with the anterior margin almost straight; juga touching each other; labrum thick and curved; triangular ante-ocular process extending beyond the eye; broad spine-like antero-lateral process of the pronotum; pronotum explanate and bean shaped; scutellum triangular with a circular tongue reaching the anterior side of abdominal segment 7; and wings well developed with membrane just surpassing end of abdomen.Facultad de Ciencias Naturales y Muse

Rediscovery of the poorly known lichen-mantis Pogonogaster tristani Rehn, 1918 (MANTODEA: THESPIDAE, OLIGONICINAE) in Costa Rica and ecological notes

En el presente trabajo se divulga el redescubrimiento de la poco conocida mantisliquen Pogonogaster tristani Rehn, 1918 para una nueva localidad en Costa Rica, después de 96 años en ser descrita. Se incluyen notas relativas a la diagnosis de la especie, el conocimiento del macho, el hábitat natural y comportamiento.In this paper the rediscovery of the little known Lichen-Mantis Pogonogaster tristani Rehn, 1918 from a new location in Costa Rica, 96 years of being described, is published. Notes concerning the diagnosis of the species, knowledge of the male, the natural habitat and behavior are included

AC-DCFS: a toolchain implementation to Automatically Compute Coulomb Failure Stress changes after relevant earthquakes

We present an automated free software-based toolchain to obtain Coulomb Failure Stress change maps on fault planes of interest following the occurrence of a relevant earthquake. The system uses as input the focal mechanism data of the event occurred and an active fault database for the region. From the focal mechanism the orientations of the possible rupture planes, the location of the event and the size of the earthquake are obtained. From the size of the earthquake, the dimensions of the rupture plane are obtained by means of an algorithm based on empirical relations. Using the active fault database in the area, the stress-receiving planes are obtained and a verisimilitude index is assigned to the source plane from the two nodal planes of the focal mechanism. The obtained product is a series of layers in a format compatible with any type of GIS (or map completely edited in PDF format) showing the possible stress change maps on the different families of fault planes present in the epicentral zone. These type of products are presented generally in technical reports developed in the weeks following the occurrence of the event, or in scientific publications; however they have been proven useful for emergency management in the hours and days after a major event being these stress changes responsible of aftershocks, in addition to the mid-term earthquake forecasting. The automation of the calculation allows its incorporation within the products generated by the alert and surveillance agencies shortly after the earthquake occurred. It is now being implemented in the Spanish Geological Survey as one of the products that this agency would provides after the occurrence of relevant seismic series in Spain