1,922 research outputs found
Weak lensing evidence for a filament between A222/A223
We present a weak lensing analysis and comparison to optical and X-ray maps
of the close pair of massive clusters A222/223. Indications for a filamentary
connection between the clusters are found and discussed.Comment: 6 pages, 1 figure. To appear in Proc. IAU Colloquium 195: Outskirts
of Galaxy Clusters - Intense Life in the Suburbs. Version with higher
resolution available at
http://www.astro.uni-bonn.de/~dietrich/torino_proc.ps.g
Beyond reality - extending a presentation trainer with an immersive VR module
The development of multimodal sensor-based applications designed to support learners with the improvement of their skills is expensive since most of these applications are tailor-made and built from scratch. In this paper, we show how the Presentation Trainer (PT), a multimodal sensor-based application designed to support the development of public speaking skills, can be modularly extended with a Virtual Reality real-time feedback module (VR module), which makes usage of the PT more immersive and comprehensive. The described study consists of a formative evaluation and has two main objectives. Firstly, a technical objective is concerned with the feasibility of extending the PT with an immersive VR Module. Secondly, a user experience objective focuses on the level of satisfaction of interacting with the VR extended PT. To study these objectives, we conducted user tests with 20 participants. Results from our test show the feasibility of modularly extending existing multimodal sensor-based applications, and in terms of learning and user experience, results indicate a positive attitude of the participants towards using the application (PT+VR module). (DIPF/Orig.
Dancing salsa with machines - filling the gap of dancing learning solutions
Dancing is an activity that positively enhances the mood of people that consists of feeling the music and expressing it in rhythmic movements with the body. Learning how to dance can be challenging because it requires proper coordination and understanding of rhythm and beat. In this paper, we present the first implementation of the Dancing Coach (DC), a generic system designed to support the practice of dancing steps, which in its current state supports the practice of basic salsa dancing steps. However, the DC has been designed to allow the addition of more dance styles. We also present the first user evaluation of the DC, which consists of user tests with 25 participants. Results from the user test show that participants stated they had learned the basic salsa dancing steps, to move to the beat and body coordination in a fun way. Results also point out some direction on how to improve the future versions of the DC. (DIPF/Orig.
Weak lensing peak count as a probe of f(R) theories
Weak gravitational lensing by galaxy clusters on faint higher redshift
galaxies has been traditionally used to study the cluster mass distribution and
as a tool to identify clusters as peaks in the shear maps. However, it becomes
soon clear that peaks statistics can also be used as a way to constrain the
underlying cosmological model due to its dependence on both the cosmic
expansion rate and the growth rate of structures. This feature makes peak
statistics particularly interesting from the point of view of discriminating
between General Relativity and modified gravity. Here we consider a general
class of theories and compute the observable mass function based on the
aperture mass statistics. We complement our theoretical analysis with a Fisher
matrix forecast of the constraints that an Euclid\,-\,like survey can impose on
the model parameters. We show that peak statistics alone can in
principle discriminate between General Relativity and models and
strongly constrain the parameters that are sensitive to the non-linear
growth of structure. However, further analysis is needed in order to include
possible selection function in the peaks redshift determination.Comment: 17 pages, 9 figures, 1 table, accepted for publication on MNRAS on
Jan 14, 2013; updated to match the published versio
Potential of attraction of people of municipalities in the region of the Parana Second Plateau.
Displacements of passengers intercity bus transportation in a region represents a flow pattern or interaction between municipalities, and these relationships provide a regional dynamic. In the study specifically observed the municipalities of Telemaco Borba, Ortigueira, Sapopema, Curiuva, Figueira, São Jeronimo da Serra, Imbau, Reserva, Tibagi and Ventania. For the application of modeling proposed by Isard (1975), we used the distances between the cities under study, their respective populations and passenger flows observed, which occurred in 2010, the intercity public transportation. The Observed Flows (Iij) in intercity public transportation are directly proportional to the size of the masses (Pi) and inversely proportional to the distance that separates them, and can be expressed by an attractive central force, hierarchically organized by the size of the populations and distances separates them. The municipality that presented the greatest potential attraction (Vi) was people Telemaco Borba, followed by Reserva, Ortigueira, Tibagi, Curiuva.Os deslocamentos de passageiros no transporte coletivo intermunicipal de uma determinada região representam um padrão de fluxo ou de interação entre os municípios, sendo que essas relações proporcionam uma dinâmica regional. No estudo observaram-se especificamente os municípios de Telêmaco Borba, Ortigueira, Sapopema, Curiúva, Figueira, São Jerônimo da Serra, Imbaú, Reserva, Tibagi e Ventania. Para a aplicação da modelagem proposta por Isard (1975), se utilizou das distâncias entre os municípios em estudo, suas respectivas populações e os fluxos de passageiros observados, que ocorreram no ano de 2010, no transporte coletivo intermunicipal. Os Fluxos Observados (Iij) no transporte coletivo intermunicipal são diretamente proporcionais ao tamanho das massas (Pi) e inversamente proporcionais a distância que as separa, e pode ser expressa por uma força central, atrativa, hierarquicamente organizada pelo tamanho das populações e as distâncias que as separa. O município que apresentou maior Potencial de Atração (Vi) de pessoas foi Telêmaco Borba, seguido de Reserva, Ortigueira, Tibagi, Curiúva
Balanced hydroxyethylstarch (HES 130/0.4) impairs kidney function in-vivo without inflammation
Volume therapy is a standard procedure in daily perioperative care, and there is an ongoing discussion about the benefits of colloid resuscitation with hydroxyethylstarch (HES). In sepsis HES should be avoided due to a higher risk for acute kidney injury (AKI). Results of the usage of HES in patients without sepsis are controversial. Therefore we conducted an animal study to evaluate the impact of 6% HES 130/0.4 on kidney integrity with sepsis or under healthy conditions Sepsis was induced by standardized Colon Ascendens Stent Peritonitis (sCASP). sCASP-group as well as control group (C) remained untreated for 24 h. After 18 h sCASP+HES group (sCASP+VOL) and control+HES (C+VOL) received 50 ml/KG balanced 6% HES (VOL) 130/0.4 over 6h. After 24h kidney function was measured via Inulin- and PAH-Clearance in re-anesthetized rats, and serum urea, creatinine (crea), cystatin C and Neutrophil gelatinase-associated lipocalin (NGAL) as well as histopathology were analysed. In vitro human proximal tubule cells (PTC) were cultured +/- lipopolysaccharid (LPS) and with 0.1–4.0% VOL. Cell viability was measured with XTT-, cell toxicity with LDH-test. sCASP induced severe septic AKI demonstrated divergent results regarding renal function by clearance or creatinine measure focusing on VOL. Soleley HES (C+VOL) deteriorated renal function without sCASP. Histopathology revealed significantly derangements in all HES groups compared to control. In vitro LPS did not worsen the HES induced reduction of cell viability in PTC cells. For the first time, we demonstrated, that application of 50 ml/KG 6% HES 130/0.4 over 6 hours induced AKI without inflammation in vivo. Severity of sCASP induced septic AKI might be no longer susceptible to the way of volume expansio
Scaling relations of metallicity, stellar mass, and star formation rate in metal-poor starbursts: II. Theoretical models
Scaling relations of metallicity (O/H), star formation rate (SFR), and
stellar mass give important insight on galaxy evolution. They are obeyed by
most galaxies in the Local Universe and also at high redshift. In a companion
paper, we compiled a sample of ~1100 galaxies from redshift 0 to ~3, spanning
almost two orders of magnitude in metal abundance, a factor of in
SFR, and of ~10^5 in stellar mass. We have characterized empirically the
star-formation "main sequence" (SFMS) and the mass-metallicity relation (MZR)
for this sample, and also identified a class of low-metallicity starbursts,
rare locally but more common in the distant universe. These galaxies deviate
significantly from the main scaling relations, with high SFR and low metal
content for a given M*. In this paper, we model the scaling relations and
explain these deviations from them with a set of multi-phase chemical evolution
models based on the idea that, independently of redshift, initial physical
conditions in a galaxy's evolutionary history can dictate its location in the
scaling relations. Our models are able to successfully reproduce the O/H, M*,
and SFR scaling relations up to z~3, and also successfully predict the
molecular cloud fraction as a function of stellar mass. These results suggest
that the scaling relations are defined by different modes of star formation: an
"active" starburst mode, more common at high redshift, and a quiescent
"passive" mode that is predominant locally and governs the main trends.Comment: 17 pages, 7 figures, accepted for publication by MNRA
Cusp-core problem and strong gravitational lensing
Cosmological numerical simulations of galaxy formation have led to the cuspy
density profile of a pure cold dark matter halo toward the center, which is in
sharp contradiction with the observations of the rotation curves of cold dark
matter-dominated dwarf and low surface brightness disk galaxies, with the
latter tending to favor mass profiles with a flat central core. Many efforts
have been devoted to resolve this cusp-core problem in recent years, among
them, baryon-cold dark matter interactions are considered to be the main
physical mechanisms erasing the cold dark matter (CDM) cusp into a flat core in
the centers of all CDM halos. Clearly, baryon-cold dark matter interactions are
not customized only for CDM-dominated disk galaxies, but for all types,
including giant ellipticals. We first fit the most recent high resolution
observations of rotation curves with the Burkert profile, then use the
constrained core size-halo mass relation to calculate the lensing frequency,
and compare the predicted results with strong lensing observations.
Unfortunately, it turns out that the core size constrained from rotation curves
of disk galaxies cannot be extrapolated to giant ellipticals. We conclude that,
in the standard cosmological paradigm, baryon-cold dark matter interactions are
not universal mechanisms for galaxy formation, and therefore, they cannot be
true solutions to the cusp-core problem.Comment: 11 pages, 3 figures, references updated, typos correcte
Short Gamma Ray Bursts: a bimodal origin?
Short-hard Gamma Ray Bursts (SGRBs) are currently thought to arise from
gravitational wave driven coalescences of double neutron star systems forming
either in the field or dynamically in globular clusters. For both channels we
fit the peak flux distribution of BATSE SGRBs to derive the local burst
formation rate and luminosity function. We then compare the resulting redshift
distribution with Swift 2-year data, showing that both formation channels are
needed in order to reproduce the observations. Double neutron stars forming in
globular clusters are found to dominate the distribution at z<0.3, whereas the
field population from primordial binaries can account for the high-z SGRBs.
This result is not in contradiction with the observed host galaxy type of
SGRBs.Comment: 5 pages, 2 figures, accepted for publication in MNRA
The effects of Population III stars and variable IMF on the chemical evolution of the Galaxy
We studied the effects of a hypothetical initial stellar generation (PopIII)
of only massive and very massive stars (VMS) on the chemical evolution of the
Galaxy. We adopted the two-infall chemical evolution model of Chiappini et al.
and tested several sets of yields for primordial VMS (Pair-Creation SNe), which
produce different amounts of heavy elements than lower mass stars. We focused
on the evolution of alpha-elements, C, N, Fe. The effects of PopIII stars on
the Galactic evolution of these elements is negligible if a few generations of
such stars occurred, whereas they produce different results from the standard
models if they formed for a longer period. Also the effects of a more strongly
variable IMF were discussed, making use of suggestions appeared in the
literature to explain the lack of metal-poor stars in the Galactic halo with
respect to model predictions. The predicted variations in abundances, SN rates,
G-dwarf [Fe/H] distribution are here more dramatic and in contrast with
observations; we concluded that a constant or slightly varying IMF is the best
solution. Our main conclusion is that if VMS existed they must have formed only
for a very short period of time (until the halo gas reached the threshold
metallicity for the formation of very massive objects); in this case, their
effects on the evolution of the studied elements was negligible also in the
earliest phases. We thus cannot prove or disprove the existence of such stars
on the basis of the available data. Due to their large metal production and
short lives, primordial VMS should have enriched the halo gas beyond the
metallicity of the most metal poor stars known in a few Myrs. This constrains
the number of Pair-Creation SNe: we find that a number of 2-20 of such SNe
occurred in our Galaxy depending on the stellar yields.Comment: 30 pages, 10 figures, accepted for publication in New Astronom
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