2,279 research outputs found
Regional trends and controlling factors of fatal landslides in Latin America and the Caribbean
A new data set of landslides that caused loss of life in Latin America and the
Caribbean in the 10-year period from 2004 and 2013 inclusive has been
compiled, providing new insight into the impact of landslides in this key
part of the world. This data set indicates that in the 10-year period a total
of 11 631 people lost their lives across the region in 611 landslides. The
geographical distribution of the landslides is highly heterogeneous, with
areas of high incidence in parts of the Caribbean (most notably Haiti),
Central America, Colombia, and southeast Brazil. There is significant interannual
variation in the number of landslides, with the El Niño/La Niña cycle
emerging as a key control. Our analysis suggests that on a continental scale
the mapped factors that best explain the observed distribution are
topography, annual precipitation and population density. On a national basis
we have compared the occurrence of fatality-inducing landslide occurrence
with the production of locally authored research articles, demonstrating that
there is a landslide research deficit in Latin America and the Caribbean.
Understanding better the mechanisms, distribution causes and triggers of
landslides in Latin America and the Caribbean must be an essential first step
towards managing the hazard
Family Ownership and Firm Performance: A Closer Look at the Evidence from Public Companies in Chile
We revisit the evidence presented in Martinez et al. (2007) using new data and estimation techniques that take into account unobserved firm heterogeneity. The results of the earlier study are found to be robust to the new procedures since performance of family firms continues to be superior to non-family firms. We then add the risk dimension to the earlier analysis using a risk-adjusted ROA variable, and family firms again performed better. A test of the standard deviations of ROA for both firm categories revealed that family firms not only perform better but also show less volatility in their returns.Family firms, performance.
Ensambles de arqueas y bacterias en la Zona de MĂnimo OxĂgeno del ecosistema de surgencia de Chile central determinados mediante biomarcadores orgĂĄnicos
IndexaciĂłn: Web of Science; Scielo.Organic biomarkers were used to investigate the influence of seasonal changes in oxygenation and water chemistry on the distribution of archaea and bacteria in the water column and surface sediments of the continental shelf off central Chile (ca. 36°S), an area influenced by seasonal upwelling and the development of an oxygen minimum zone. We were interested in establishing if occurrence of archaea and bacteria responds to oxygenation and water chemistry for which we analyzed archaeal isoprenoid (i) and bacterial branched (br) glycerol dialkyl glycerol tetraethers (GDGTs). Our results combined with molecular data from a year round observational program at the same sampling site and depths indicatives the occurrence and dominance of the marine pelagic group Thaumarchaeota. Changes in the distribution of iGDGTs might be explained by (i) the presence of archaeal populations in sub-oxic waters, phylogenetically different from those in surface water, (ii) changes in the relative contribution of Euryarchaeota with depth, and (iii) a relationship between Thaumarchaeota and environmental factors other than temperature. Branched GDGTs were more abundant in the upper, oxic layer during the non-upwelling season, may be a result of higher river runoff, whereas their diversity was higher within sub-oxic waters. Our results indicate a vertical segregation of iGDGTs and brGDGTs, with predominance of archaeal biomarkers during the low productivity season.Se utilizaron biomarcadores orgĂĄnicos en para investigar la influencia de cambios estacionales en los niveles de oxigenaciĂłn y la quĂmica del agua sobre la distribuciĂłn de arqueas y bacterias en la columna de agua y los sedimentos superficiales de la plataforma continental frente a Chile central, un ĂĄrea influenciada por surgencia estacional asociada al desarrollo de una zona de mĂnimo oxĂgeno. Nuestro interĂ©s es establecer si la ocurrencia de arquea y bacteria responde a la oxigenaciĂłn y quĂmica del agua para lo cual analizamos gliceroles dialquil gliceroles tetra-Ă©teres (GDGTs) isoprenoides arqueanos (i) y ramificados bacterianos (r). Nuestros resultados, combinados con datos moleculares de observaciones durante un año en el mismo lugar y profundidades del sitio de estudio indican la presencia y dominancia del grupo arqueano marino- pelĂĄgico Thaumarchaeota. Los cambios observados en la distribuciĂłn de iGDGTs podrĂan explicarse por (i) la presencia de poblaciones de arqueas marinas en la capa de agua sub-Ăłxica, filogenĂ©ticamente diferentes a las de aguas superficiales, (ii) cambio en la contribuciĂłn relativa de Euryarchaeota con profundidad, y (iii) una relaciĂłn entre Thaumarchaeota y factores ambientales distintos a la temperatura. Los GDGTs ramificados fueron mĂĄs abundantes en la capa Ăłxica superior durante el periodo de no-surgencia, tal vez influenciado por la alta descarga de rĂos, mientras que su diversidad fue mĂĄs alta en el agua sub-Ăłxica. Nuestros resultados indican una segregaciĂłn vertical de los GDGTs isoprenoides y ramificados, con el predominio de biomarcadores arqueanos durante el periodo de baja productividad.http://ref.scielo.org/vq5y7
Semiclassical propagator of the Wigner function
Propagation of the Wigner function is studied on two levels of semiclassical
propagation, one based on the van-Vleck propagator, the other on phase-space
path integration. Leading quantum corrections to the classical Liouville
propagator take the form of a time-dependent quantum spot. Its oscillatory
structure depends on whether the underlying classical flow is elliptic or
hyperbolic. It can be interpreted as the result of interference of a
\emph{pair} of classical trajectories, indicating how quantum coherences are to
be propagated semiclassically in phase space. The phase-space path-integral
approach allows for a finer resolution of the quantum spot in terms of Airy
functions.Comment: 4 pages, 3 figure
Transparent conducting oxides for active hybrid metamaterial devices
We present here a study of the combined nonlinear response of plasmonic antennaâtransparent conducting oxide hybrids for activation of metamaterial devices. Nanoantenna layers consisting of randomly positioned gold nanodisk dimers are fabricated using hole-mask lithography. The nanoantenna layers are covered with a 20 nm thin layer of transparent conducting oxide (TCO). We investigate the response of atomic layer deposited aluminum-doped zinc oxide (AZO) next to indiumâtin oxide (ITO) produced using sputter coating. We show that our results are in agreement with the hypothesis of fast electron-mediated cooling, facilitated by the Ohmic interface between the gold nanodisks and the TCO substrate, which appears a universal mechanism for providing a new hybrid functionality to active metamaterial device
- âŠ