6,975 research outputs found
Platelet Collapse Model of Pulsar Glitches
A platelet collapse model of starquakes is introduced. It displays
self-organized criticality with a robust power-law behavior. The simulations
indicate a near-constant exponent, whenever scaling is present.Comment: Figures available by sending request to Ivan Schmidt:
[email protected]
Arquitectura, oportunismo y la planificación del rostro de un imperio
La carrera de Sir Aston Webb (1849-1930) es posiblemente una de las más impresionantes de todos los arquitectos tardovictorianos y de la época eduardiana. En una importante época de la sociedad, la política y la historia británicas, la carrera de Webb y su salto a la fama anduvieron paralelos a uno de los períodos más excitantes en la historia de la arquitectura británica, alcanzando su pico de protagonismo cuando le concedieron el rango de Presidente del Royal Institute of British Architects (RIBA), el de Presidente de la Royal Academy (RA) y el de Presidente de Town Planning de la RIBA. El célebre historiador de arquitectura Alastair Service, por ejemplo, apuntó que, a pesar de los ideales arquitectónicos del período, el mayor arquitecto en términos de volumen total de trabajo o de dinero ganado fue Webb, aunque la historia haya ignorado casi absolutamente su importancia, debido en parte a que sus proyectos carecían de la creatividad estilística que poseían muchos de sus coetáneos. Es por ello que en este artículo se intenta rectificar esta situación, subrayando la importancia del trabajo más grande de Webb, el proyecto del Queen Victoria Memorial (1901-1912) –una empresa monumental a la misma altura que los proyectos American City Beautiful, que junto al plan London County Council’s Kingsway-Aldwych “haussmanizaron” la metrópolis. De este modo, este trabajo también demostrará que Webb no era simplemente un arquitecto de incomparables aptitudes, sino que posiblemente fue el diseñador que más ayudó en este período a definir el diseño cívico y la planificación urbana británicas de un modo práctico, antes del comienzo de la Primera Guerra Mundial en 1914
Photolytic Hazes in the Atmosphere of 51 Eri b
We use a 1D model to address photochemistry and possible haze formation in
the irradiated warm Jupiter, 51 Eridani b. The intended focus was to be carbon,
but sulfur photochemistry turns out to be important. The case for organic
photochemical hazes is intriguing but falls short of being compelling. If
organic hazes form, they are likeliest to do so if vertical mixing in 51 Eri b
is weaker than in Jupiter, and they would be found below the altitudes where
methane and water are photolyzed. The more novel result is that photochemistry
turns HS into elemental sulfur, here treated as S. In the cooler
models, S is predicted to condense in optically thick clouds of solid
sulfur particles, whilst in the warmer models S remains a vapor along with
several other sulfur allotropes that are both visually striking and potentially
observable. For 51 Eri b, the division between models with and without
condensed sulfur is at an effective temperature of 700 K, which is within error
its actual effective temperature; the local temperature where sulfur condenses
is between 280 and 320 K. The sulfur photochemistry we have discussed is quite
general and ought to be found in a wide variety of worlds over a broad
temperature range, both colder and hotter than the 650-750 K range studied
here, and we show that products of sulfur photochemistry will be nearly as
abundant on planets where the UV irradiation is orders of magnitude weaker than
it is on 51 Eri b.Comment: 24 pages including 11 figures and a tabl
Ammonia oxidation is not required for growth of Group 1.1c soil Thaumarchaeota
© FEMS 2015. FUNDING EBW is funded by Centre for Genome Enabled Biology and Medicine, University of Aberdeen.Peer reviewedPublisher PD
On the rationality of the moduli space of L\"uroth quartics
We prove that the moduli space M_L of L"uroth quartics in P^2, i.e. the space
of quartics which can be circumscribed around a complete pentagon of lines
modulo the action of PGL_3(CC) is rational, as is the related moduli space of
Bateman seven-tuples of points in P^2.Comment: 7 page
A Graph-based Approach for Higher Order Gis Topological Analysis
Retrieving structured information from an initial random collection of objects may be carried out by understanding the spatial
arrangement between them, assuming no prior knowledge about those objects. As far as topology is concerned, contemporary
desktop GIS packages do not generally support further analysis beyond adjacency. Thus, one of the original motivations of this work
was to develop new ideas for scene analysis by building up a graph-based technique for better interpretation and understanding of
spatial relationships between GIS vector-based objects beyond its first level of adjacency; the final aim is the performance of some
kind of local feature organization into a more meaningful global scene by using graph theory. As the example scenario, a LiDAR
data set is being used to test the technique that we plan to develop and implement. After the generation of the respective TIN, two
different binary classifications were applied to the TIN facets (based on two different slope thresholds) and TIN facets have been
aggregated into homogeneous polygons according to their slope characteristics. A graph-based clustering procedure inside these
polygonal regions, by establishing a neighbourhood graph, followed by the delineation of cluster shapes and the derivation of cluster
characteristics in order to obtain higher level geographic entities information (regarding sets of buildings, vegetation areas, and say,
land-use parcels) is object of further work. The results we are expecting to obtain might be useful to support land-use mapping,
image understanding or, generally speaking, to support clustering analysis and generalization processes
A containment-first search algorithm for higher-order analysis of urban topology
Research has revealed the importance of the concepts from the mathematical areas of both topology and graph theory for interpreting the spatial arrangement of spatial entities. Graph theory in particular has been used in different applications of a wide range of fields for that purpose, however not many graph-theoretic approaches to analyse entities within the urban environment are available in the literature. Some examples should be mentioned though such as, Bafna (2003), Barr and Barnsley (2004), Bunn et al. (2000), Krüger (1999), Nardinochi et al. (2003), and Steel et al. (2003).
Very little work has been devoted in particular to the interpretation of initially unstructured geospatial datasets. In most of the applications developed up-to-date for the interpretation and analysis of spatial phenomena within the urban context, the starting point is to some extent a meaningful dataset in terms of the urban scene. Starting at a level further back, before meaningful data are obtained, the interpretation and analysis of spatial phenomena are more challenging tasks and require further investigation.
The aim of retrieving structured information from initial unstructured spatial data, translated into more meaningful homogeneous regions, can be achieved by identifying meaningful structures within the initial random collection of objects and by understanding their spatial arrangement (Anders et al., 1999). It is believed that the task of understanding topological relationships between objects can be accomplished by both applying graph theory and carrying out graph analysis (de Almeida et al., 2007)
Near-Infrared Spectroscopy of the Y0 WISEP J173835.52+273258.9 and the Y1 WISE J035000.32-565830.2: the Importance of Non-Equilibrium Chemistry
We present new near-infrared spectra, obtained at Gemini Observatory, for two
Y dwarfs: WISE J035000.32-565830.2 (W0350) and WISEP J173835.52+273258.9
(W1738). A FLAMINGOS-2 R=540 spectrum was obtained for W0350, covering 1.0 <
lambda um < 1.7, and a cross-dispersed GNIRS R=2800 spectrum was obtained for
W1738, covering 0.993-1.087 um, 1.191-1.305 um, 1.589-1.631 um, and 1.985-2.175
um, in four orders. We also present revised YJH photometry for W1738, using new
NIRI Y and J imaging, and a re-analysis of the previously published NIRI H band
images. We compare these data, together with previously published data for
late-T and Y dwarfs, to cloud-free models of solar metallicity, calculated both
in chemical equilibrium and with disequilibrium driven by vertical transport.
We find that for the Y dwarfs the non-equilibrium models reproduce the
near-infrared data better than the equilibrium models. The remaining
discrepancies suggest that fine-tuning the CH_4/CO and NH_3/N_2 balance is
needed. Improved trigonometric parallaxes would improve the analysis. Despite
the uncertainties and discrepancies, the models reproduce the observed
near-infrared spectra well. We find that for the Y0, W1738, T_eff = 425 +/- 25
K and log g = 4.0 +/- 0.25, and for the Y1, W0350, T_eff = 350 +/- 25 K and log
g = 4.0 +/- 0.25. W1738 may be metal-rich. Based on evolutionary models, these
temperatures and gravities correspond to a mass range for both Y dwarfs of 3-9
Jupiter masses, with W0350 being a cooler, slightly older, version of W1738;
the age of W0350 is 0.3-3 Gyr, and the age of W1738 is 0.15-1 Gyr.Comment: Accepted on March 30 2016 for publication in Ap
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