Spiral structure of the Third Galactic Quadrant and the solution to the Canis Major debate

With the discovery of the Sagittarius dwarf spheroidal (Ibata et al. 1994), a galaxy caught in the process of merging with the Milky Way, the hunt for other such accretion events has become a very active field of astrophysical research. The identification of a stellar ring-like structure in Monoceros, spanning more than 100 degrees (Newberg et al. 2002), and the detection of an overdensity of stars in the direction of the constellation of Canis Major (CMa, Martin et al. 2004), apparently associated to the ring, has led to the widespread belief that a second galaxy being cannibalised by the Milky Way had been found. In this scenario, the overdensity would be the remaining core of the disrupted galaxy and the ring would be the tidal debris left behind. However, unlike the Sagittarius dwarf, which is well below the Galactic plane and whose orbit, and thus tidal tail, is nearly perpendicular to the plane of the Milky Way, the putative CMa galaxy and ring are nearly co-planar with the Galactic disk. This severely complicates the interpretation of observations. In this letter, we show that our new description of the Milky Way leads to a completely different picture. We argue that the Norma-Cygnus spiral arm defines a distant stellar ring crossing Monoceros and the overdensity is simply a projection effect of looking along the nearby local arm. Our perspective sheds new light on a very poorly known region, the third Galactic quadrant (3GQ), where CMa is located.Comment: 5 pages, 2 figures. Quality of Fig 1 has been degraded to make it smaller. Original fig. available on request. accepted for publication in MNRAS letter

The graphene sheet versus the 2DEG: a relativistic Fano spin-filter via STM and AFM tips

We explore theoretically the density of states (LDOS) probed by an STM tip of 2D systems hosting an adatom and a subsurface impurity,both capacitively coupled to AFM tips and traversed by antiparallel magnetic fields. Two kinds of setups are analyzed, a monolayer of graphene and a two-dimensional electron gas (2DEG). The AFM tips set the impurity levels at the Fermi energy, where two contrasting behaviors emerge: the Fano factor for the graphene diverges, while in the 2DEG it approaches zero. As result, the spin-degeneracy of the LDOS is lifted exclusively in the graphene system, in particular for the asymmetric regime of Fano interference. The aftermath of this limit is a counterintuitive phenomenon, which consists of a dominant Fano factor due to the subsurface impurity even with a stronger STM-adatom coupling. Thus we find a full polarized conductance, achievable just by displacing vertically the position of the STM tip. To the best knowledge, our work is the first to propose the Fano effect as the mechanism to filter spins in graphene. This feature arises from the massless Dirac electrons within the band structure and allows us to employ the graphene host as a relativistic Fano spin-filter

Modelo de hargreaves-samani ajustado as condições climáticas do estado do Rio de Janeiro para estimativa da evapotranspiração de referência.

Utilizando-se como padrão para determinação da evapotranspiração de referência (ETo) o modelo de Penman-Monteith parametrizado no boletim Nº 56 de irrigação e drenagem da FAO (PM-FAO56) ajustou-se o modelo de Hargreaves-Samani (HS) para as condições climáticas do Estado do Rio de Janeiro. Nas estimativas da ETo foram utilizadas séries climáticas de 10 estações meteorológicas convencionais pertencentes ao Instituto Nacional de Meteorologia. Os valores dos coeficientes do modelo de HS ajustados para o Estado do Rio de Janeiro não variaram significativamente (cv 3,4%), sendo indicado a utilização de um valor médio (0,0116 ± 0,0004) para todo o Estado. O modelo de Hargreaves-Samani ajustado e o original apresentaram elevada precisão (r2 = 0,94) das estimativas de ETo. Contudo, a acurácia das estimativas de ETo foram superiores com o modelo HS ajustado (d = 0,99 e EPE = 0,25 mm d-1) em relação ao original (d = 0,93 e EPE = 0,65 mm d-1)

Compactness in the Thermal Evolution of Twin Stars

In this work, we study for the first time the thermal evolution of twin star pairs, i.e., stars that present the same mass but different radius and compactness. We collect available equations of state that give origin to a second branch of stable compact stars with quarks in their core. For each equation of state, we investigate the particle composition inside stars and how differently each twin evolves over time, which depends on the central density/pressure and consequent crossing of the threshold for the Urca cooling process. We find that, although the general stellar thermal evolution depends on mass and particle composition, withing one equation of state, only twin pairs that differ considerably on compactness can be clearly distinguished by how they cool down

Metallic-insulator phase transitions in the extended Harper model

In this work we investigate the transport properties of non-relativistic quantum particles on incommensurate multilayered structures with the thicknesses $w_n$ of the layers following an extended Harper model given by $w_n = w_0 |\cos(\pi a n^{\nu})|$. For the normal incidence case, which means an one-dimensional system, we obtained that for a specific range of energy, it is possible to see a metallic-insulator transition with the exponent $\nu$. A metallic phase is supported for $\nu<1$. We also obtained that for the specific value $\nu=1$ there is an alternation between metallic and insulator phases as we change the disorder strength $w_0$. When we integrate out all incidence angles, which means a two-dimensional system, the metallic-insulator transition can be seen for much larger range of energy compared to the normal incidence case

Critical wave-packet dynamics in the power-law bond disordered Anderson Model

We investigate the wave-packet dynamics of the power-law bond disordered one-dimensional Anderson model with hopping amplitudes decreasing as $H_{nm}\propto |n-m|^{-\alpha}$. We consider the critical case ($\alpha=1$). Using an exact diagonalization scheme on finite chains, we compute the participation moments of all stationary energy eigenstates as well as the spreading of an initially localized wave-packet. The eigenstates multifractality is characterized by the set of fractal dimensions of the participation moments. The wave-packet shows a diffusive-like spread developing a power-law tail and achieves a stationary non-uniform profile after reflecting at the chain boundaries. As a consequence, the time-dependent participation moments exhibit two distinct scaling regimes. We formulate a finite-size scaling hypothesis for the participation moments relating their scaling exponents to the ones governing the return probability and wave-function power-law decays

On wave interference in planet migration: dead zone torques modified by active zone forcing

We investigate planetary migration in the dead zone of a protoplanetary disk where there are a set of spiral waves propagating inward due to the turbulence in the active zone and the Rossby wave instability (RWI), which occurs at the transition between the dead and active zones. We perform global 3D unstratified magnetohydrodynamical (MHD) simulations of a gaseous disk with the FARGO3D code, using weak gradients in the static resistivity profiles that trigger the formation of a vortex at the outer edge of the dead zone. We find that once the Rossby vortex develops, spiral waves in the dead zone emerge and interact with embedded migrating planets by wave interference, which notably changes their migration. The inward migration becomes faster depending on the mass of the planet, due mostly to the constructive (destructive) interference between the outer (inner) spiral arm of the planet and, the destruction of the dynamics of the horseshoe region by means of the set of background spiral waves propagating inward. The constructive wave interference produces a more negative Lindblad differential torque which inevitably leads to an inward migration. Lastly, for massive planets embedded in the dead zone, we find that the spiral waves can create an asymmetric wider and depeer gap than in the case of $\alpha$-disks, and can prevent the formation of vortices at the outer edge of the gap. The latter could generate a faster or slower migration compared to the standard type-II migration.Comment: 18 pages, 14 figures, accepted for publication in Ap

Abstract 482: Differences in Ground Reaction Forces and Chest Compression Release Velocity in Professional and Lay Rescuers With and Without the Use of Real-Time CPR Feedback

Purpose: Chest compression release velocity (CCRV) has been associated with survival and favorable neurological outcome after cardiac resuscitation. Both complete chest release and high CCRV contribute to improved venous return during CPR. Differences in compression forces delivered by professional and lay rescuers are reported, which may contribute to differences in CCRV. The aim of this pilot study was to investigate differences in ground reaction force (GRF) and CCRV between professional and lay rescuers during CPR performed on a manikin with and without real-time feedback. Methods: Professional (n = 5) and lay rescuers (n = 11) performed two minutes of continuous compressions on a manikin positioned over a force plate for two trials. CPR feedback provided by a defibrillator was disabled in the first trial and enabled in the second. CPR pads containing an accelerometer were used to calculate individual compression characteristics. Relative maximum and minimum GRFs were calculated for each compression cycle and averaged over each trial. Paired and independent sample t tests and Pearson correlations were conducted in STATA 15.1. Results: CCRV was higher in professionals vs. lay rescuers with feedback disabled and enabled (p\u3c0.05). Professionals had greater maximal and lower minimum forces than lay rescuers without feedback (p\u3c0.05), though there were no differences between groups with feedback enabled (Table 1). CCRV was associated with minimum force (r = -0.63, p\u3c0.01) and force range (r = 0.78, p\u3c0.01) in all rescuers. Analysis of GRFs by CCRV for all rescuers indicated lower force minimum (9.71 + 3.16 N, p\u3c0.05) with CCRV \u3e400 mm/s in comparison to CCRV 300-400 mm/s (39.73 + 8.91 N) and CCRV 200-300 mm/s (63.82 + 16.98 N). Conclusions: CPR feedback attenuated differences in GRF between professional and lay rescuers. CCRV was greater in professionals and was associated with measures of GRF, and thus may serve as an indicator of both velocity and amount of chest release

Animal pointing: changing trends and findings from 30 years of research

The past 30 years have witnessed a continued and growing interest in the production and comprehension of manual pointing gestures in nonhuman animals. Captive primates with diverse rearing histories have shown evidence of both pointing production and comprehension, though there certainly are individual and species differences, as well as substantive critiques of how to interpret pointing or “pointing-like” gestures in animals. Early literature primarily addressed basic questions about whether captive apes point, understand pointing, and use the gesture in a way that communicates intent (declarative) rather than motivational states (imperative). Interest in these questions continues, but more recently there has been a dramatic increase in the number of papers examining pointing in a diverse array of species, with an especially large literature on canids. This proliferation of research on pointing and the diversification of species studied has brought new and exciting questions about the evolution of social cognition, and the effects of rearing history and domestication on pointing production and, more prolifically, comprehension. A review of this work is in order. In this paper we examine trends in the literature on pointing in nonhumans. Specifically, we examine publication frequencies of different study species from 1987 to 2016. We also review data on the form and function of pointing, and evidence either supporting or refuting the conclusion that various nonhuman species comprehend the meaning of pointing gestures