Anthropogenic Disturbance in Nocturnal Primates & Conservation Perception in Zaraninge Forest, Tanzania

Galagos are an understudied family of primates which inhabit much of Sub-Saharan Africa, some of which are potentially at risk. The coastal forests of East Africa are home to many galagos, however this habitat is under threat from an increasing human population seeking timber, charcoal and land for agriculture, amongst other pressures. This study used repeated transect methods when estimating the density of both the Zanzibar galago (Galagoides zanzibaricus) and Garnett’s galago (Otolemur garnetti) in a human influenced forest and a relatively undisturbed forest which were otherwise similar. Densities of Zanzibar galagos were not significantly influenced by human activities. Garnett’s galago numbers showed a statistically significant though slight increase when their environment displayed signs of modification by human activities. Results also indicate that the future use of territory mapping style methods may give reliable estimates of species that have been difficult to monitor in the past, as well as providing a more comprehensive view of social structure in surveyed populations. A survey of 60 households in close proximity to these forests found that 56.7% of household heads thought that conservation of the forests and their resources were worth conserving. It also identified that problems need to be addressed in the management of the park to prevent loss of crops for farmers and that many of them resent stringent restrictions they must abide by when living in proximity to this protected forest. This study shows that proposed agroecosytems to be used to help the conservation of primates will only aid certain species and that further study is necessary of the Galago family to determine how they will fare in rapidly changing coastal forest environments.Galagos are a family of primates which inhabit much of Sub-Saharan Africa, some of which are potentially at risk. Many species are not very well studied and so as a result there is little known about them. Some species of galago often co-exist in the same habitats as they exploit different resources of the environments. Many species inhabit the coastal forests of East Africa, including some potentially threatened species. The coastal forests of East Africa are home to many species of galagos, however this habitat is under threat from an increasing human population seeking timber, charcoal and land for agriculture. For these reasons it was thought necessary to measure population changes in some species when their habitat has been modified in some way by human activity, which has been suggested as a useful tool in the conservation of some primate species. This study estimated the density of both the Zanzibar galago (Galagoides zanzibaricus) and Garnett’s galago (Otolemur garnetti) in a human influenced forest and a relatively undisturbed forest, which were similar in other aspects. Densities of Zanzibar galagos were not significantly influenced by human activities. Garnett’s galago numbers showed a statistically significant, though slight increase, when their environment had been changed in some way by humans. Results also indicate that the future use of territory mapping style methods may give reliable estimates of galago species which have been difficult to monitor in the past, as well as providing a more comprehensive view of social structure in surveyed populations. A survey of households in close proximity to these forests found that 56.7% of household heads thought that conservation of the forests and their resources were worth conserving. It also identified that problems need to be addressed in the management of the park to prevent loss of crops for farmers and that many of them resent stringent restrictions they must abide by when living in proximity to this protected forest. This study shows that proposed agroecosytems to be used in the conservation of primates will only aid certain species and that further study is necessary of the Galago family to determine how they will fare in rapidly changing coastal forest environments. Further study is needed into these animals in order to better understand them and how they will respond to human induced changes to these environments

Dimensional Dependence of the Hydrodynamics of Core-Collapse Supernovae

The multidimensional character of the hydrodynamics in core-collapse supernova (CCSN) cores is a key facilitator of explosions. Unfortunately, much of this work has necessarily been performed assuming axisymmetry and it remains unclear whether or not this compromises those results. In this work, we present analyses of simplified two- and three-dimensional CCSN models with the goal of comparing the multidimensional hydrodynamics in setups that differ only in dimension. Not surprisingly, we find many differences between 2D and 3D models. While some differences are subtle and perhaps not crucial to understanding the explosion mechanism, others are quite dramatic and make interpreting 2D CCSN models problematic. In particular, we find that imposing axisymmetry artificially produces excess power at the largest spatial scales, power that has been deemed critical in the success of previous explosion models and has been attributed solely to the standing accretion shock instability. Nevertheless, our 3D models, which have an order of magnitude less power on large scales compared to 2D models, explode earlier. Since we see explosions earlier in 3D than in 2D, the vigorous sloshing associated with the large scale power in 2D models is either not critical in any dimension or the explosion mechanism operates differently in 2D and 3D. Possibly related to the earlier explosions in 3D, we find that about 25% of the accreted material spends more time in the gain region in 3D than in 2D, being exposed to more integrated heating and reaching higher peak entropies, an effect we associate with the differing characters of turbulence in 2D and 3D. Finally, we discuss a simple model for the runaway growth of buoyant bubbles that is able to quantitatively account for the growth of the shock radius and predicts a critical luminosity relation.Comment: Submitted to the Astrophysical Journa

Training Big Random Forests with Little Resources

Without access to large compute clusters, building random forests on large datasets is still a challenging problem. This is, in particular, the case if fully-grown trees are desired. We propose a simple yet effective framework that allows to efficiently construct ensembles of huge trees for hundreds of millions or even billions of training instances using a cheap desktop computer with commodity hardware. The basic idea is to consider a multi-level construction scheme, which builds top trees for small random subsets of the available data and which subsequently distributes all training instances to the top trees' leaves for further processing. While being conceptually simple, the overall efficiency crucially depends on the particular implementation of the different phases. The practical merits of our approach are demonstrated using dense datasets with hundreds of millions of training instances.Comment: 9 pages, 9 Figure

Criteria for Core-Collapse Supernova Explosions by the Neutrino Mechanism

We investigate the criteria for successful core-collapse supernova explosions by the neutrino mechanism. We find that a critical-luminosity/mass-accretion-rate condition distinguishes non-exploding from exploding models in hydrodynamic one-dimensional (1D) and two-dimensional (2D) simulations. We present 95 such simulations that parametrically explore the dependence on neutrino luminosity, mass accretion rate, resolution, and dimensionality. While radial oscillations mediate the transition between 1D accretion (non-exploding) and exploding simulations, the non-radial standing accretion shock instability characterizes 2D simulations. We find that it is useful to compare the average dwell time of matter in the gain region with the corresponding heating timescale, but that tracking the residence time distribution function of tracer particles better describes the complex flows in multi-dimensional simulations. Integral quantities such as the net heating rate, heating efficiency, and mass in the gain region decrease with time in non-exploding models, but for 2D exploding models, increase before, during, and after explosion. At the onset of explosion in 2D, the heating efficiency is $\sim$2% to $\sim$5% and the mass in the gain region is $\sim$0.005 M_{\sun} to $\sim$0.01 M_{\sun}. Importantly, we find that the critical luminosity for explosions in 2D is $\sim$70% of the critical luminosity required in 1D. This result is not sensitive to resolution or whether the 2D computational domain is a quadrant or the full 180$^{\circ}$. We suggest that the relaxation of the explosion condition in going from 1D to 2D (and to, perhaps, 3D) is of a general character and is not limited by the parametric nature of this study.Comment: 32 pages in emulateapj, including 17 figures, accepted for publication in ApJ, included changes suggested by the refere

Perspectives on Allyship in Academia

Allyship in academia is critical for creating inclusive communities that are welcoming to all students, but the perception of its benefits and challenges can vary depending on a number of factors. This session will explore perspectives of allyship in academia by bringing together a diverse group of faculty and students who can share a wide range of experiences and insights, and aims to facilitate a discussion among all attendees that leads to an exchange of ideas, the strengthening of our community, and progress toward our common goal of inclusion in computing

BETHE-Hydro: An Arbitrary Lagrangian-Eulerian Multi-dimensional Hydrodynamics Code for Astrophysical Simulations

In this paper, we describe a new hydrodynamics code for 1D and 2D astrophysical simulations, BETHE-hydro, that uses time-dependent, arbitrary, unstructured grids. The core of the hydrodynamics algorithm is an arbitrary Lagrangian-Eulerian (ALE) approach, in which the gradient and divergence operators are made compatible using the support-operator method. We present 1D and 2D gravity solvers that are finite differenced using the support-operator technique, and the resulting system of linear equations are solved using the tridiagonal method for 1D simulations and an iterative multigrid-preconditioned conjugate-gradient method for 2D simulations. Rotational terms are included for 2D calculations using cylindrical coordinates. We document an incompatibility between a subcell pressure algorithm to suppress hourglass motions and the subcell remapping algorithm and present a modified subcell pressure scheme that avoids this problem. Strengths of this code include a straightforward structure, enabling simple inclusion of additional physics packages, the ability to use a general equation of state, and most importantly, the ability to solve self-gravitating hydrodynamic flows on time-dependent, arbitrary grids. In what follows, we describe in detail the numerical techniques employed and, with a large suite of tests, demonstrate that BETHE-hydro finds accurate solutions with 2$^{nd}$-order convergence.Comment: 51 pages in emulateapj, including 25 figures, replace with version accepted to ApJS, corrected typos and included minor referee's comment

Completing RHINO

The right-handed (RH) Higgs-induced neutrino mixing (RHINO) model explains neutrino masses and origin of matter in the universe within a unified picture. The mixing, effectively described by a dimension five operator, is responsible both for the production of dark neutrinos, converting a small fraction of seesaw neutrinos acting as source, and for their decays. We show that including the production of source neutrinos from Higgs portal interactions, their abundance can thermalise prior to the onset of source-dark neutrino oscillations, resulting into an enhanced production of dark neutrinos that thus can play the role of decaying dark matter (DM) for a much higher seesaw scale. This can be above the sphaleron freeze-out temperature and as high as $\sim 100\,{\rm TeV}$, so that strong thermal resonant leptogenesis for the generation of the matter-antimatter asymmetry is viable. We obtain a $\sim 1\,{\rm TeV}$--$1\,{\rm PeV}$ allowed dark neutrino mass range. Intriguingly, their decays can also explain a neutrino flux excess at ${\cal O}(100\,{\rm TeV})$ energies recently confirmed by the IceCube collaboration analysing 7.5yr HESE data. Our results also point to an effective scale for Higgs portal interactions nicely identifiable with the grandunified scale and many orders of magnitude below the effective scale for the mixing. We explain this hierarchy in a UV-complete model with a very heavy fermion as mediator: the first scale corresponds to the fundamental scale of new physics, while the second is much higher because of a very small coupling identifiable with a symmetry breaking parameter. Therefore, RHINO realises a simple unified model of neutrino masses and origin of matter in the universe currently under scrutiny at neutrino telescopes and potentially embeddable within a grandunified model.Comment: 29 pages, 10 figures; v2 matching version to appear in JHE

Induced Rotation in 3D Simulations of Core Collapse Supernovae: Implications for Pulsar Spins

It has been suggested that the observed rotation periods of radio pulsars might be induced by a non-axisymmetric spiral-mode instability in the turbulent region behind the stalled supernova bounce shock, even if the progenitor core was not initially rotating. In this paper, using the three-dimensional AMR code CASTRO with a realistic progenitor and equation of state and a simple neutrino heating and cooling scheme, we present a numerical study of the evolution in 3D of the rotational profile of a supernova core from collapse, through bounce and shock stagnation, to delayed explosion. By the end of our simulation ($\sim$420 ms after core bounce), we do not witness significant spin up of the proto-neutron star core left behind. However, we do see the development before explosion of strong differential rotation in the turbulent gain region between the core and stalled shock. Shells in this region acquire high spin rates that reach $\sim$$150\,$ Hz, but this region contains too little mass and angular momentum to translate, even if left behind, into rapid rotation for the full neutron star. We find also that much of the induced angular momentum is likely to be ejected in the explosion, and moreover that even if the optimal amount of induced angular momentum is retained in the core, the resulting spin period is likely to be quite modest. Nevertheless, induced periods of seconds are possible.Comment: Accepted to the Astrophysical Journa

Examination of tourists’ willingness to pay under different conservation scenarios; Evidence from reef manta ray snorkeling in Fiji

Wildlife-focused tourism is often considered as having the potential to play an integral part of threatened species conservation efforts, particularly through financial support. We focused on the direct financing of conservation by investigating tourists’ willingness to pay to snorkel with reef manta rays (Mobula alfredi) at Barefoot Manta, an ecotourism resort in the Yasawa group of islands in Fiji. Our results indicate that 82.4% of people surveyed would be willing to pay a mean value of ~ USD $9.2 (SE 0.9) more than the current cost, a 28$10.2 (SE 0.9) more for a hypothetical scenario where they would snorkel with 50% fewer people, a 31% increase. We also investigated tourists’ willingness to make voluntary donations to the local community above an existing payment of ~ USD $10 that is built into the current snorkel payment of ~ USD$32.5. On average, 91.3% of the tourists interviewed were willing to donate additional funds with an average additional donation of ~ USD $8.6 (SE 0.5) to the community to pay for educational and environmental support, an 86% increase. There were few significant relationships between willingness to pay and demographic factors (including age, income, nationality, education, and others), suggesting that willingness to pay was widely held by the tourist population staying at Barefoot Manta Resort. Together, these results indicate that wildlife-based nature tourism could represent a potential, but not unlimited, income source to fund conservation in the Yasawa group, Fiji islands, and that conservation can arise from partnerships between local communities and the tourism sector