3,054 research outputs found
Quantum diffusion on a cyclic one dimensional lattice
The quantum diffusion of a particle in an initially localized state on a
cyclic lattice with N sites is studied. Diffusion and reconstruction time are
calculated. Strong differences are found for even or odd number of sites and
the limit N->infinit is studied. The predictions of the model could be tested
with micro - and nanotechnology devices.Comment: 17 pages, 5 figure
Participatory Militias: An Analysis of an Armed Movement's Online Audience
Armed groups of civilians known as "self-defense forces" have ousted the
powerful Knights Templar drug cartel from several towns in Michoacan. This
militia uprising has unfolded on social media, particularly in the "VXM"
("Valor por Michoacan," Spanish for "Courage for Michoacan") Facebook page,
gathering more than 170,000 fans. Previous work on the Drug War has documented
the use of social media for real-time reports of violent clashes. However, VXM
goes one step further by taking on a pro-militia propagandist role, engaging in
two-way communication with its audience. This paper presents a descriptive
analysis of VXM and its audience. We examined nine months of posts, from VXM's
inception until May 2014, totaling 6,000 posts by VXM administrators and more
than 108,000 comments from its audience. We describe the main conversation
themes, post frequency and relationships with offline events and public
figures. We also characterize the behavior of VXM's most active audience
members. Our work illustrates VXM's online mobilization strategies, and how its
audience takes part in defining the narrative of this armed conflict. We
conclude by discussing possible applications of our findings for the design of
future communication technologies.Comment: Participatory Militias: An Analysis of an Armed Movement's Online
Audience. Saiph Savage, Andres Monroy-Hernandez. CSCW: ACM Conference on
Computer-Supported Cooperative Work 201
Central Structural Parameters of Early-Type Galaxies as Viewed with HST/NICMOS
We present surface photometry for the central regions of a sample of 33
early-type (E, S0, and S0/a) galaxies observed at 1.6 microns (H band) using
the Hubble Space Telescope (HST). We employ a new technique of two-dimensional
fitting to extract quantitative parameters for the bulge light distribution and
nuclear point sources, taking into consideration the effects of the
point-spread function. Parameterizing the bulge profile with a ``Nuker'' law,
we confirm that the central surface-brightness distributions largely fall into
two categories, each of which correlates with the global properties of the
galaxies. ``Core'' galaxies tend to be luminous ellipticals with boxy or pure
elliptical isophotes, whereas ``power-law'' galaxies are preferentially lower
luminosity systems with disky isophotes. Unlike most previous studies, however,
we do not find a clear gap in the distribution of inner cusp slopes; several
objects have inner cusp slopes (0.3 < gamma < 0.5) which straddle the regimes
conventionally defined for core and power-law type galaxies. The nature of
these intermediate objects is unclear. We draw attention to two objects in the
sample which appear to be promising cases of galaxies with isothermal cores
that are not the brightest members of a cluster. Unresolved nuclear point
sources are found in about 50% of the sample galaxies, roughly independent of
profile type, with magnitudes in the range m^{nuc}_H = 12.8 to 17.4 mag, which
correspond to M_H^{nuc} = -12.8 to -18.4 mag. (Abridged)Comment: To appear in The Astronomical Journal. Latex, 24 pages and 17 JPEG
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Factors influencing organic carbon recycling and burial in Skagerrak sediments
Different factors influencing recycling and burial rates of organic carbon (OC) were investigated in the continental margin sediments of the Skagerrak (NE North Sea). Two different areas, one in the southern and one in the northeastern part of the Skagerrak were visited shortly after a spring bloom (March 1999) and in late summer (August 2000). Results suggested that: (1) Organic carbon oxidation rates (Cox) (2.2–18 mmol C m-2d-11) were generally larger than the O2 uptake rates (1.9 –25 mmol m-2d-1). Both rates were measured in situ using a benthic lander. A mean apparent respiration ratio (Cox:O2corr) of 1.3±0.5 was found, indicating some long-term burial of reduced inorganic substances in these sediments. Measured O2 fluxes increased linearly with increasing Cox rates during the late summer cruise but not on the early spring cruise, indicating a temporal uncoupling of anaerobic mineralization and reoxidation of reduced substances. (2) Dissolved organic carbon (DOC) fluxes (0.2–1.0 mmol C m-2d-1) constituted 3–10% of the Cox rates and were positively correlated with the latter, implying that net DOC production rates were proportional to the overall sediment OC remineralization rates. (3) Chlorophyll a (Chl-a) concentrations in the sediment were significantly higher in early spring compared to late summer. The measured Cox rates, but not O2 fluxes, showed a strong positive correlation with the Chl-a inventories in the top 3 cm of the sediment. (4) Although no relationship was found between the benthic fluxes and the macrofaunal biomass in the chambers, total in situ measured dissolved inorganic carbon (CT) fluxes were 1–5.4 times higher than diffusive mediated CT fluxes, indicating that macrofauna have a significant impact on benthic exchange rates of OC remineralization products in Skagerrak sediments. (5) OC burial fluxes were generally higher in northeastern Skagerrak than in the southern part. The same pattern was observed for burial efficiencies, with annual means of ~62% and ~43% for the two areas respectively. (6) On a basin-wide scale, there was a significant positive linear correlation between the burial efficiencies and sediment accumulation rates. (7) The calculated particulate organic carbon (POC) deposition, from benthic flux and burial measurements, was only 24 –78% of the sediment trap measured POC deposition, indicating a strong near-bottom lateral transport and resuspension of POC. (8) A larger fraction of the laterally advected material of lower quality seemed to settle in the northeastern Skagerrak rather than in the southern Skagerrak. (9) Skagerrak sediments, especially in the northeastern part, act as an efficient net sink for organic carbon, even in a global continental margin context
Female sex is associated with comparable 5-year outcomes after contemporary endovascular aneurysm repair despite more challenging anatomy
Cancer symptom awareness and barriers to symptomatic presentation in England – Are we clear on cancer?
Background: Low cancer awareness may contribute to delayed diagnosis and poor cancer survival. We aimed to quantify socio-demographic differences in cancer symptom awareness and barriers to symptomatic presentation in the English population.
Methods: Using a uniquely large data set (n=49?270), we examined the association of cancer symptom awareness and barriers to presentation with age, gender, marital status and socio-economic position (SEP), using logistic regression models to control for confounders.
Results: The youngest and oldest, the single and participants with the lowest SEP recognised the fewest cancer symptoms, and reported most barriers to presentation. Recognition of nine common cancer symptoms was significantly lower, and embarrassment, fear and difficulties in arranging transport to the doctor’s surgery were significantly more common in participants living in the most deprived areas than in the most affluent areas. Women were significantly more likely than men to both recognise common cancer symptoms and to report barriers. Women were much more likely compared with men to report that fear would put them off from going to the doctor.
Conclusions: Large and robust socio-demographic differences in recognition of some cancer symptoms, and perception of some barriers to presentation, highlight the need for targeted campaigns to encourage early presentation and improve cancer outcomes
CCD photometric search for peculiar stars in open clusters. V. NGC 2099, NGC 3114, NGC 6204, NGC 6705 and NGC 6756
We have investigated 1008 objects in the area of five intermediate age open
clusters (NGC 2099, NGC 3114, NGC 6204, NGC 6705 and NGC 6756) via the narrow
band Delta a-system. The detection limit for photometric peculiarity is very
low (always less than 0.009mag) due to the high number of individual frames
used (193 in total). We have detected six peculiar objects in NGC 6705 and NGC
6756 from which one in the latter is almost certainly an unreddened late type
foreground star. The remaining five stars are probably cluster members and bona
fide chemically peculiar objects (two are lambda Bootis type candidates).
Furthermore, we have investigated NGC 3114, a cluster for which already
photoelectric Delta a-measurements exist. A comparison of the CCD and
photoelectric values shows very good agreement. Again, the high capability of
our CCD Delta a-photometric system to sort out true peculiar objects together
with additional measurements from broad or intermediate band photometry is
demonstrated.Comment: 6 pages, 2 figures, accepted by A&
4pi Models of CMEs and ICMEs
Coronal mass ejections (CMEs), which dynamically connect the solar surface to
the far reaches of interplanetary space, represent a major anifestation of
solar activity. They are not only of principal interest but also play a pivotal
role in the context of space weather predictions. The steady improvement of
both numerical methods and computational resources during recent years has
allowed for the creation of increasingly realistic models of interplanetary
CMEs (ICMEs), which can now be compared to high-quality observational data from
various space-bound missions. This review discusses existing models of CMEs,
characterizing them by scientific aim and scope, CME initiation method, and
physical effects included, thereby stressing the importance of fully 3-D
('4pi') spatial coverage.Comment: 14 pages plus references. Comments welcome. Accepted for publication
in Solar Physics (SUN-360 topical issue
Complex circular subsidence structures in tephra deposited on large blocks of ice: Varða tuff cone, Öræfajökull, Iceland
Several broadly circular structures up to 16 m in diameter, into which higher strata have sagged and locally collapsed, are present in a tephra outcrop on southwest Öræfajökull, southern Iceland. The tephra was sourced in a nearby basaltic tuff cone at Varða. The structures have not previously been described in tuff cones, and they probably formed by the melting out of large buried blocks of ice emplaced during a preceding jökulhlaup that may have been triggered by a subglacial eruption within the Öræfajökull ice cap. They are named ice-melt subsidence structures, and they are analogous to kettle holes that are commonly found in proglacial sandurs and some lahars sourced in ice-clad volcanoes. The internal structure is better exposed in the Varða examples because of an absence of fluvial infilling and reworking, and erosion of the outcrop to reveal the deeper geometry. The ice-melt subsidence structures at Varða are a proxy for buried ice. They are the only known evidence for a subglacial eruption and associated jökulhlaup that created the ice blocks. The recognition of such structures elsewhere will be useful in reconstructing more complete regional volcanic histories as well as for identifying ice-proximal settings during palaeoenvironmental investigations
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