1,959 research outputs found
Globular Cluster Scale Sizes in Giant Galaxies: Orbital Anisotropy and Tidally Under-filling Clusters in M87, NGC 1399, and NGC 5128
We investigate the shallow increase in globular cluster half-light radii with
projected galactocentric distance observed in the giant galaxies M87,
NGC 1399, and NGC 5128. To model the trend in each galaxy, we explore the
effects of orbital anisotropy and tidally under-filling clusters. While a
strong degeneracy exists between the two parameters, we use kinematic studies
to help constrain the distance beyond which cluster orbits become
anisotropic, as well as the distance beyond which clusters are
tidally under-filling. For M87 we find kpc and kpc and kpc.
The connection of with each galaxy's mass profile indicates the
relationship between size and may be imposed at formation, with only
inner clusters being tidally affected. The best fitted models suggest the
dynamical histories of brightest cluster galaxies yield similar present-day
distributions of cluster properties. For NGC 5128, the central giant in a small
galaxy group, we find kpc and kpc. While we
cannot rule out a dependence on , NGC 5128 is well fitted by a tidally
filling cluster population with an isotropic distribution of orbits, suggesting
it may have formed via an initial fast accretion phase. Perturbations from the
surrounding environment may also affect a galaxy's orbital anisotropy profile,
as outer clusters in M87 and NGC 1399 have primarily radial orbits while outer
NGC 5128 clusters remain isotropic.Comment: 16 pages, 7 figures, 4 tables, Accepted for publication in MNRA
A Green's function approach to Topological Insulator junctions with magnetic and superconducting regions
This work presents a Green's function approach, originally implemented in
graphene with well-defined edges, to the surface of a strong 3D Topological
Insulator (TI) with a sequence of proximitized superconducting (S) and
ferromagnetic (F) surfaces. This consists of the derivation of the Green's
functions for each region by the asymptotic solutions method, and their
coupling by a tight-binding Hamiltonian with the Dyson equation to obtain the
full Green's functions of the system. These functions allow the direct
calculation of the momentum-resolved spectral density of states, the
identification of subgap interface states, and the derivation of the
differential conductance for a wide variety of configurations of the junctions.
We illustrate the application of this method for some simple systems with two
and three regions, finding the characteristic chiral state of the Quantum
Anomalous Hall Effect (QAHE) at the NF interfaces, and chiral Majorana modes at
the NS interfaces. Finally, we discuss some geometrical effects present in
three-region junctions such as weak Fabry-P\'erot resonances and Andreev bound
states.Comment: 14 pages, 6 figure
Effects of oil palm and human presence on activity patterns of terrestrial mammals in the Colombian Llanos
The ability of animals to adjust their behaviour can influence how they respond to environmental changes and human presence. We quantified activity patterns of terrestrial mammals in oil palm plantations and native riparian forest in Colombia to determine if species exhibited behavioural changes depending on the type of habitat and the presence of humans. Despite the large sampling effort (12,403 camera-days), we were only able to examine the activity patterns of ten species in riparian forests and seven species in oil palm plantations, with four species (capybara, giant anteater, lesser anteater and common opossum) being represented by enough records (i.e. n > 20) in both oil palm and forest to allow robust comparisons. Only capybaras showed an apparent change in activity patterns between oil palm plantations and riparian forests, shifting from being crepuscular in forest to predominantly nocturnal inside oil palm plantations. Further, capybaras, giant anteaters and white-tailed deer appeared to modify their activities to avoid human presence inside oil palm plantations by increasing nocturnality (temporal overlap Δ ^ ranged from 0.13 to 0.36), whereas jaguarundi had high overlap with human activities [Δ ^ =0.85 (0.61–0.90)]. Species pair-wise analysis within oil palm revealed evidence for temporal segregation between species occupying the same trophic position (e.g. foxes and jaguarundi), whereas some predators and their prey (e.g. ocelots and armadillos) had high overlaps in temporal activity patterns as might be expected. Our findings shed light on the potential behavioural adaptation of mammals to anthropogenic landscapes, a feature not captured in traditional studies that focus on measures such as species richness or abundance
Structural Parameters of the M87 Globular Clusters
We derive structural parameters for ~2000 globular clusters in the giant
Virgo elliptical M87 using extremely deep Hubble Space Telescope images in
F606W (V) and F814W (I) taken with the ACS/WFC. The cluster scale sizes
(half-light radii r_h) and ellipticities are determined from PSF-convolved
King-model profile fitting. We find that the r_h distribution closely resembles
the inner Milky Way clusters, peaking at r_h~2.5 pc and with virtually no
clusters more compact than r_h ~ 1 pc. The metal-poor clusters have on average
an r_h 24% larger than the metal-rich ones. The cluster scale size shows a
gradual and noticeable increase with galactocentric distance. Clusters are very
slightly larger in the bluer waveband V a possible hint that we may be
beginning to see the effects of mass segregation within the clusters. We also
derived a color magnitude diagram for the M87 globular cluster system which
show a striking bimodal distribution.Comment: ApJ accepte
Recovery and management of actual acid sulphate soils in boyacá (colombia)
Acid sulphate soils (ASS), having very resÂtricted use due to their extreme acidity, have been idenÂtified within the upper Chicamocha river basin, Boyacá (Colombia). This situation has led to increasing degraÂdation of the land, rendering around 3,000 ha of land unproductive. Production alternatives are thus being sought for recovering these flat upland areas, currently suffering from ASS, as they do have agricultural potenÂtial. Soils were initially characterised and identified in a problem area so that possible management of such ASS could then be inferred from the initial study. Increasing doses of calcium hydroxide (Ca(OH)2) (5 to 100 t· ha-1) were then evaluated and determined for neutralising extreme acid conditions in laboratory incubation assays (5-100 t· ha-1). Greenhouse and field tests (random block experimental design with 10 treatments and 4 repeats) were used for observing the response of Avena sativa as an indicator plant; just hen-dung (5-10 t· ha-1) and hen-dung mixed with lime (dry and wet matter) were also evaluated as amendment material. The experiments reÂvealed the soils’ chemical changes and reactions following these treatments: pH, Al, ECEC, % AL, % Ca, total S, Mn, Fe and P (i.e. after statistical correlations had been made). These studies led to the soils being recognised as non-coast actual ASS and classifying them as Typic Sulfaquept. The findings indicated that Ca(OH)2 12.5 t· ha-1 mixed with 10 t· ha-1 organic matter (hen-dung) represented the best treatment for obtaining the best A. sativa performance in terms of dry matter production, reflected in positive ASS chemical changes
The close limit from a null point of view: the advanced solution
We present a characteristic algorithm for computing the perturbation of a
Schwarzschild spacetime by means of solving the Teukolsky equation. We
implement the algorithm as a characteristic evolution code and apply it to
compute the advanced solution to a black hole collision in the close
approximation. The code successfully tracks the initial burst and quasinormal
decay of a black hole perturbation through 10 orders of magnitude and tracks
the final power law decay through an additional 6 orders of magnitude.
Determination of the advanced solution, in which ingoing radiation is absorbed
by the black hole but no outgoing radiation is emitted, is the first stage of a
two stage approach to determining the retarded solution, which provides the
close approximation waveform with the physically appropriate boundary condition
of no ingoing radiation.Comment: Revised version, published in Phys. Rev. D, 34 pages, 13 figures,
RevTe
Globular Cluster Systems in Giant Ellipticals: the Mass/Metallicity Relation
Hubble Space Telescope ACS/WFC data in (B,I) are used to investigate the
globular cluster populations around 6 gE galaxies ~40 Mpc distant. The total
comprises a sample of ~8000 high-probability globular clusters. PSF-convolved
King-model profiles are used to measure their individual total magnitudes,
colors, and effective radii. The classic bimodal form of the GC color-magnitude
distribution shows up unambiguously in all the galaxies, allowing an accurate
definition of the mean colors along each of the two sequences as a function of
magnitude (the mass/metallicity relation or MMR). The blue, metal-poor cluster
sequence shows a clearly defined but nonlinear MMR, changing smoothly from a
near-vertical sequence at low luminosity to an increasingly redward slope at
higher luminosity, while the red, metal-rich sequence is nearly vertical at all
luminosities. All the observed features of the present data agree with the
interpretation that the MMR is created primarily by GC self-enrichment, along
the lines of the quantitative model of Bailin and Harris (2009): The
"threshold" mass at which this effect should become noticeable is near 1
million Solar masses, which is closely consistent with the transition region
that is seen in the data. Correlation of the median half-light radii of the GCs
with other parameters shows that the metal-poor clusters are consistently 17%
larger than those of the metal-rich clusters, at all galactocentric distances
and luminosities. At the same time, cluster size scales with halo location as
r_h ~ R_gc^0.11, indicating that both metallicity and the external tidal
environment play roles in determining the scale size of a given cluster.
Lastly, both the red and blue GC components show metallicity gradients with
galactocentric distance, following Z ~ R_gc^-0.1.Comment: In press for Astrophysical Journal. Complete preprint with higher
quality figures is available at
http://physwww.mcmaster.ca/%7Eharris/Publications.htm
Comparación de los perfiles farmacodinámicos de tres moléculas de remifentanilo en cuanto a su respuesta hemodinámica a las maniobras de laringoscopia e intubación traqueal
ResumenIntroducciĂłnEn Colombia se comercializan diferentes molĂ©culas de remifentanilo que nunca han sido comparadas en un entorno clĂnico.ObjetivoEl objetivo de este estudio fue investigar el perfil farmacodinámico de la molĂ©cula innovadora de remifentanilo (grupo O: Glaxo SmithKline Manufacturing S.P.A.) y 2 molĂ©culas genĂ©ricas (grupo A: Laboratorios Chalver de Colombia S.A. y grupo B: Instituto BiolĂłgico Contemporáneo, Argentina) registradas en Colombia.MĂ©todosSe llevĂł a cabo un experimento clĂnico doble ciego, aleatorizado, controlado. Se comparĂł la molĂ©cula original de remifentanilo (grupo O, n=29) frente a las 2 molĂ©culas genĂ©ricas (grupo A, n=29; grupo B, n=32) durante la inducciĂłn anestĂ©sica e intubaciĂłn orotraqueal de pacientes adultos ASAI sin predictores de vĂa aĂ©rea difĂcil. Se evaluaron las dosis 6, 8 y 10ng/ml (TCI, Target Controlled Infusion) con el modelo de Minto. La inducciĂłn se complementĂł con propofol 5ÎĽg/ml (TCI) con modelo de Schneider y rocuronio 0,6mg/kg. El desenlace primario se evaluĂł como las diferencias en la presiĂłn arterial media y en la frecuencia cardiaca preintubaciĂłn (momento en que se alcanza la concentraciĂłn objetivo en sitio efecto) y postintubaciĂłn (máximo valor alcanzado en 5min).ResultadosSe observĂł similitud en el perfil farmacodinámico de las molĂ©culas de remifentanilo estudiadas. Las diferencias en el cambio de frecuencia cardiaca fue de 1,27 (IC95%: –3,11;5,67) con la molĂ©cula A y 1,40 (IC95%: –2,65;5,46) con la molĂ©cula B frente a la molĂ©cula O (latidos/min). Las diferencias en el cambio de presiĂłn arterial media fueron de 1 (IC95%: –4,81;6,81) para la molĂ©cula A y de 1,82 (IC95%: –4,08;7,74) para la molĂ©cula B frente a la molĂ©cula O (mmHg). Hubo un caso de hipotensiĂłn arterial en cada grupo.ConclusiĂłnLos resultados sugieren que desde un punto de vista farmacodinámico las molĂ©culas innovadora y genĂ©ricas de remifentanilo son similares para la laringoscopia/intubaciĂłn con dosis TCI de 6, 8 y 10ng/ml.AbstractIntroductionSeveral remifentanil products are commercialized in Colombia while these have never been compared in a clinical setting.ObjectiveThe aim of this study was to investigate the pharmacodynamic profile of the branded molecule of remifentanil (group O: Glaxo SmithKline Manufacturing S.P.A.) and two unbranded molecules (group A: Laboratorios Chalver de Colombia S.A. and group B: Instituto BiolĂłgico Contemporaneo, Argentina) registered in Colombia.MethodsWe carried out a double-blind, randomized, controlled trial. The branded molecule of remifentanil (group O, n=29) was compared with the two unbranded molecules (group A, n=29; group B, n=32) during anesthetic induction and tracheal intubation in adult patients ASAI without predictors for difficult airway. The target controlled infusion (TCI) doses evaluated were 6, 8 and 10ng/ml with the Minto model. Induction was complemented with propofol 5mcg/ml (TCI) with the Schneider model and rocuronium 0.6mg/kg. The primary outcome was defined as the difference in mean arterial pressure and heart rate pre-intubation (TCI equilibrium) and post-intubation (maximum measurement within 5minutes).ResultsA similar pharmacodinamic profile was observed between the studied remifentanil molecules. The differences in the change in heart rate were 1.27 (95% CI: –3.11;5.67) with molecule A and 1.40 (95%CI: –2.65;5.46) with molecule B against molecule O (beats/minute). The differences in the change in mean arterial pressure were 1 (95%CI: –4.81;6.81) for molecule A and 1.82 (95%CI: –4.08;7.74) for molecule B against molecule O (mmHg). There was a case of arterial hypotension in each group.ConclusionThe results suggest that from a pharmacodynamic point of view branded and unbranded remifentanil molecules are similar for laryngoscopy/intubation with TCI doses 6, 8 and 10ng/ml
The Ages, Metallicities and Alpha Element Enhancements of Globular Clusters in the Elliptical NGC 5128: A Homogeneous Spectroscopic Study with Gemini/GMOS
We present new integrated light spectroscopy of globular clusters (GCs) in
NGC 5128 in order to measure radial velocities and derive ages, metallicities,
and alpha-element abundance ratios. Using Gemini-S 8-m/GMOS, we obtained
spectroscopy in the range of ~3400-5700 AA for 72 GCs with S/N > 30 /AA and we
have also discovered 35 new GCs within NGC 5128 from our radial velocity
measurements. We measured and compared the Lick indices from HdeltaA through
Fe5406 with the single stellar population (SSP) models of Thomas et
al.(2003,2004). We also measure Lick indices for 41 Milky Way GCs from Puzia et
al. (2002) and Schiavon et al. (2005) with the same methodology for direct
comparison. Our results show that 68% of the NGC 5128 GCs have old ages (> 8
Gyr), 14% have intermediate ages (5-8 Gyr), and 18% have young ages (< 5 Gyr).
However, when we look at the metallicity of the GCs as a function of age, we
find 92% of metal-poor GCs and 56% of metal-rich GCs in NGC 5128 have ages > 8
Gyr, indicating that the majority of both metallicity subpopulations of GCs
formed early, with a significant population of young and metal-rich GCs forming
later. Our metallicity distribution function generated directly from
spectroscopic Lick indices is clearly bimodal, as is the color distribution of
the same set of GCs. Thus the metallicity bimodality is real and not an
artifact of the color to metallicity conversion. The [alpha/Fe] values are
supersolar with a mean value of 0.14pm0.04, indicating a fast formation
timescale. However, the GCs in NGC 5128 are not as [alpha/Fe] enhanced as the
Milky Way GCs also examined in this study. Our results support a rapid, early
formation of the GC system in NGC 5128, with subsequent major accretion and/or
GC and star forming events in more recent times (abridged).Comment: Accepted to The Astrophysical Journal, 36 pages, 14 figures, 7 table
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