Enhanced thermionic-dominated photoresponse in graphene Schottky junctions

Vertical heterostructures of van der Waals materials enable new pathways to tune charge and energy transport characteristics in nanoscale systems. We propose that graphene Schottky junctions can host a special kind of photoresponse which is characterized by strongly coupled heat and charge flows that run vertically out of the graphene plane. This regime can be accessed when vertical energy transport mediated by thermionic emission of hot carriers overwhelms electron-lattice cooling as well as lateral diffusive energy transport. As such, the power pumped into the system is efficiently extracted across the entire graphene active area via thermionic emission of hot carriers into a semiconductor material. Experimental signatures of this regime include a large and tunable internal responsivity ${\cal R}$ with a non-monotonic temperature dependence. In particular, ${\cal R}$ peaks at electronic temperatures on the order of the Schottky potential $\phi$ and has a large upper limit ${\cal R} \le e/\phi$ ($e/\phi=10\,{\rm A/W}$ when $\phi = 100\,{\rm meV}$). Our proposal opens up new approaches for engineering the photoresponse in optically-active graphene heterostructures.Comment: 6 pages, 2 figure

HCAD, closing the gap between breakpoints and genes

Recurrent chromosome aberrations are an important resource when associating human pathologies to specific genes. However, for technical reasons a large number of chromosome breakpoints are defined only at the level of cytobands and many of the genes involved remain unidentified. We developed a web-based information system that mines the scientific literature and generates textual and comprehensive information on all human breakpoints. We show that the statistical analysis of this textual information and its combination with genomic data can identify genes directly involved in DNA rearrangements. The Human Chromosome Aberration Database (HCAD) is publicly accessible at http://www.pdg.cnb.uam.es/UniPub/HCAD/

Cuantificación de la contribución de las fuentes de liquidez en el Sistema de Pagos de Alto Valor en Colombia: una aproximación preliminar

En el presente trabajo se realiza un análisis de estática comparativa relacionado con la cuantificación de la contribución de las distintas fuentes de liquidez que utilizan las entidades financieras en Colombia para cumplir (liquidar) sus obligaciones en el sistema de pagos de alto valor operado por el Banco de la República, al que se denomina sistema CUD. Con base en ello se evalúa también la incidencia de diversas políticas adoptadas por el banco central para propender por la liquidación más temprana de las operaciones y mitigar riesgos de liquidez en el sistema de pagos de alto valor. Para tales efectos, se consideró el comportamiento transaccional y de liquidez intradía de los participantes en el CUD correspondiente a dos periodos de marcadas diferencias tanto en la funcionalidad del sistema como en el entorno económico (mayo de 2002 y mayo de 2010), agregando la información por grupos de agentes más activos como son los bancos, comisionistas de bolsa y sociedades fiduciarias. En la metodología propuesta se asume que los participantes utilizan como fuente primaria su saldo en cuentas de depósito en el banco central (encaje) con el cual inician un día de operaciones, luego se calcula el valor efectivo de la liquidez provista por el Banco de la República u obtenida en el mercado monetario y se toma como residuo la dinámica de los pagos entre los agentes (liquidez de los pagos entrantes). Este análisis permite hacer una aproximación preliminar a la identificación de las estrategias utilizadas por las entidades financieras respecto al uso de cada una de las fuentes alternativas de liquidez en el sistema de pagos y a identificar riesgos potenciales que se derivan de las mismas para cada tipo de participantes y sobre el sistema en su conjunto. También provee elementos de juicio a las autoridades financieras para el diseño de políticas macroprudenciales que mitiguen el riesgo de liquidez y el riesgo sistémico.Sistema de pagos de alto valor, sistemas de liquidación bruta en tiempo real, fuentes de liquidez, encaje, provisión de liquidez del banco central, dinámica de pagos interbancarios. Classification JEL: E42, E41, E51, C70.

The warm interstellar medium around the Cygnus Loop

Observations of the oxygen lines [OII]3729 and [OIII]5007 in the medium immediately beyond the Cygnus Loop supernova remnant were carried out with the scanning Fabry-P\'erot spectrophotometer ESOP. Both lines were detected in three different directions - east, northeast and southwest - and up to a distance of 15 pc from the shock front. The ionized medium is in the immediate vicinity of the remnant, as evinced by the smooth brightening of both lines as the adiabatic shock transition (defined by the X-ray perimeter) is crossed. These lines are usually brighter around the Cygnus Loop than in the general background in directions where the galactic latitude is above 5 degrees. There is also marginal (but significant) evidence that the degree of ionization is somewhat larger around the Cygnus Loop. We conclude that the energy necessary to ionize this large bubble of gas could have been supplied by an O8 or O9 type progenitor or the particles heated by the expanding shock front. The second possibility, though highly atractive, would have to be assessed by extensive modelling.Comment: 18 pages, 8 figures, ApJ 512 in pres

Quantum effective actions from nonperturbative worldline dynamics

We demonstrate the feasibility of a nonperturbative analysis of quantum field theory in the worldline formalism with the help of an efficient numerical algorithm. In particular, we compute the effective action for a super-renormalizable field theory with cubic scalar interaction in four dimensions in quenched approximation (small-$N_f$ expansion) to all orders in the coupling. We observe that nonperturbative effects exert a strong influence on the infrared behavior, rendering the massless limit well defined in contrast to the perturbative expectation. Our numerical method is based on a direct use of probability distributions for worldline ensembles, preserves all Euclidean spacetime symmetries, and thus represents a new nonperturbative tool for an investigation of continuum quantum field theory.Comment: 33 pages, 10 figure

Muknalia is a Collared Peccary (Pecari Tajacu): A Reply to Stinnesbeck et al.

Several years ago, a new genus and species of peccary, “Muknalia minima”, was described from the Pleistocene of Mexico. We previously examined that specimen and concluded that it was synonymous with the extant collared peccary, Pecari tajacu, but that taxonomic revision is rejected by the authors of the original study (this volume). Here, we provide further analysis of “Muknalia” and expand on previous evidence from both morphology and taphonomy that support synonymy with P. tajacu. We argue that morphological features, both in terms of size and shape, that were used to diagnose “Muknalia” all fall within the range of variation of the extant P. tajacu, or are a consequence of taphonomic modification, including human handling