The Orion Fingers: Near-IR Adaptive Optics Imaging of an Explosive Protostellar Outflow

Aims. Adaptive optics images are used to test the hypothesis that the explosive BN/KL outflow from the Orion OMC1 cloud core was powered by the dynamical decay of a non-hierarchical system of massive stars. Methods. Narrow-band H2, [Fe II], and broad-band Ks obtained with the Gemini South multi-conjugate adaptive optics (AO) system GeMS and near-infrared imager GSAOI are presented. The images reach resolutions of 0.08 to 0.10", close to the 0.07" diffraction limit of the 8-meter telescope at 2.12 microns. Comparison with previous AO-assisted observations of sub-fields and other ground-based observations enable measurements of proper motions and the investigation of morphological changes in H2 and [Fe II] features with unprecedented precision. The images are compared with numerical simulations of compact, high-density clumps moving ~1000 times their own diameter through a lower density medium at Mach 1000. Results. Several sub-arcsecond H2 features and many [Fe II] 'fingertips' on the projected outskirts of the flow show proper motions of ~300 km/s. High-velocity, sub-arcsecond H2 knots ('bullets') are seen as far as 140" from their suspected ejection site. If these knots propagated through the dense Orion A cloud, their survival sets a lower bound on their densities of order 10^7 cm^-3, consistent with an origin within a few au of a massive star and accelerated by a final multi-body dynamic encounter that ejected the BN object and radio source I from OMC1 about 500 years ago. Conclusions. Over 120 high-velocity bow-shocks propagating in nearly all directions from the OMC1 cloud core provide evidence for an explosive origin for the BN/KL outflow triggered by the dynamic decay of a non-hierarchical system of massive stars. Such events may be linked to the origin of runaway, massive stars.Comment: Accepted to A&A. 25 pages, 18 figures. Figure 1 (http://goo.gl/whAz3m) is particularly colorful. The FITS images will be made available from CDS. Resubmission fixed broken bibliograph

A Theory of Aesthetic Justice

Theories of distributive justice give us the appropriate determination of who ought to have what, where ?who? are the members of society and ?what? are social goods and burdens. Traditionally, social goods have taken the form of rights and privileges, as well as more tangible economic goods. However, it is not clear that these are the only kinds of social goods relevant to justice. There is a substantial body of literature showing that environmental benefits and burdens can and should be thought of as social goods. In this paper, I will argue that we ought to make a comparable extension for aesthetic benefits and burdens. Specifically, I will show that aesthetic goods are objects of significant public interest, and therefore must be subject to our principles of justice. I begin by explaining and evaluating a theory of aesthetic justice offered by Monroe Beardsley. I will expand this theory by showing its broad applicability to myriad examples, especially to aesthetic objects in nature. Then I will show that this theory is compatible with two leading conceptions of justice: John Rawls?s liberal conception and Michael Walzer?s communitarian conception. In doing so, I will show that the theory of aesthetic justice must be taken seriously by those who have these philosophical commitments

Validating Semi-Analytic Models of High-Redshift Galaxy Formation using Radiation Hydrodynamical Simulations

We use a cosmological hydrodynamic simulation calculated with Enzo and the semi-analytic galaxy formation model (SAM) GAMMA to address the chemical evolution of dwarf galaxies in the early universe. The long-term goal of the project is to better understand the origin of metal-poor stars and the formation of dwarf galaxies and the Milky Way halo by cross-validating these theoretical approaches. We combine GAMMA with the merger tree of the most massive galaxy found in the hydrodynamic simulation and compare the star formation rate, the metallicity distribution function (MDF), and the age-metallicity relationship predicted by the two approaches. We found that the SAM can reproduce the global trends of the hydrodynamic simulation. However, there are degeneracies between the model parameters and more constraints (e.g., star formation efficiency, gas flows) need to be extracted from the simulation to isolate the correct semi-analytic solution. Stochastic processes such as bursty star formation histories and star formation triggered by supernova explosions cannot be reproduced by the current version of GAMMA. Non-uniform mixing in the galaxy's interstellar medium, coming primarily from self-enrichment by local supernovae, causes a broadening in the MDF that can be emulated in the SAM by convolving its predicted MDF with a Gaussian function having a standard deviation of ~0.2 dex. We found that the most massive galaxy in the simulation retains nearby 100% of its baryonic mass within its virial radius, which is in agreement with what is needed in GAMMA to reproduce the global trends of the simulation.Comment: 26 pages, 13 figures, 2 tables, submitted to ApJ (version 2

Comparison of Family 9 Cellulases from Mesophilic and Thermophilic Bacteria

Cellulases containing a family 9 catalytic domain and a family 3c cellulose binding module (CBM3c) are important components of bacterial cellulolytic systems. We measured the temperature dependence of the activities of three homologs: Clostridium cellulolyticum Cel9G, Thermobifida fusca Cel9A, and C. thermocellum Cel9I. To directly compare their catalytic activities, we constructed six new versions of the enzymes in which the three GH9-CBM3c domains were fused to a dockerin both with and without a T. fusca fibronectin type 3 homology module (Fn3). We studied the activities of these enzymes on crystalline cellulose alone and in complex with a miniscaffoldin containing a cohesin and a CBM3a. The presence of Fn3 had no measurable effect on thermostability or cellulase activity. The GH9-CBM3c domains of Cel9A and Cel9I, however, were more active than the wild type when fused to a dockerin complexed to scaffoldin. The three cellulases in complex have similar activities on crystalline cellulose up to 60°C, but C. thermocellum Cel9I, the most thermostable of the three, remains highly active up to 80°C, where its activity is 1.9 times higher than at 60°C. We also compared the temperature-dependent activities of different versions of Cel9I (wild type or in complex with a miniscaffoldin) and found that the thermostable CBM is necessary for activity on crystalline cellulose at high temperatures. These results illustrate the significant benefits of working with thermostable enzymes at high temperatures, as well as the importance of retaining the stability of all modules involved in cellulose degradation

Absence of an embryonic stem cell DNA methylation signature in human cancer.

BackgroundDifferentiated cells that arise from stem cells in early development contain DNA methylation features that provide a memory trace of their fetal cell origin (FCO). The FCO signature was developed to estimate the proportion of cells in a mixture of cell types that are of fetal origin and are reminiscent of embryonic stem cell lineage. Here we implemented the FCO signature estimation method to compare the fraction of cells with the FCO signature in tumor tissues and their corresponding nontumor normal tissues.MethodsWe applied our FCO algorithm to discovery data sets obtained from The Cancer Genome Atlas (TCGA) and replication data sets obtained from the Gene Expression Omnibus (GEO) data repository. Wilcoxon rank sum tests, linear regression models with adjustments for potential confounders and non-parametric randomization-based tests were used to test the association of FCO proportion between tumor tissues and nontumor normal tissues. P-values of < 0.05 were considered statistically significant.ResultsAcross 20 different tumor types we observed a consistently lower FCO signature in tumor tissues compared with nontumor normal tissues, with 18 observed to have significantly lower FCO fractions in tumor tissue (total n = 6,795 tumor, n = 922 nontumor, P < 0.05). We replicated our findings in 15 tumor types using data from independent subjects in 15 publicly available data sets (total n = 740 tumor, n = 424 nontumor, P < 0.05).ConclusionsThe results suggest that cancer development itself is substantially devoid of recapitulation of normal embryologic processes. Our results emphasize the distinction between DNA methylation in normal tightly regulated stem cell driven differentiation and cancer stem cell reprogramming that involves altered methylation in the service of great cell heterogeneity and plasticity

Heat, Charge and Spin Transport of Thin Film Nanostructures

Understanding of fundamental physics of transport properties in thin film nanostructures is crucial for application in spintronic, spin caloritronics and thermoelectric applications. Much of the difficulty in the understanding stems from the measurement itself. In this dissertation I present our thermal isolation platform that is primarily used for detection of thermally induced effects in a wide variety of materials. We can accurately and precisely produce in-plane thermal gradients in these membranes, allowing for thin film measurements on 2-D structures. First, we look at thermoelectric enhancements of doped semiconducting single-walled carbon nanotube thin films. We use the Wiedemann-Franz law to calculate contributions to thermal conductivity and find interesting underlying physics as we dope the films, thus changing the Fermi level. Adapting the tube diameter leads to structural differences, which greatly affects both phonon and electron contributions to thermal conductivity. These unique films can be designed as thermoelectric materials that are easy to manufacture and can be utilized in a variety of situations. Second, we look at work measuring enhanced contributions to thermopower and thermal conductivity of unique ferromagnetic metals. We observe improved thermopower due to the ultra-low damping of the magnon system. For spintronic and spin caloritronic applications, having a low damping is important for device engineering and allows for long spin lifetimes. Third, we present on spin transport through disordered magnetic insulators. We observe spin Hall effect driven magnon transport through materials with no long-range order but with local antiferromagnetic exchange interactions. We are the first to observe this type of transport, which may lead spintronic investigations in a new and profound direction. Finally, we look at transverse effects in a thin ferromagnetic metal. Our observation of the planer Nernst effect and planar Hall effect across long length scales shows that effects in this range are dominated by traditional magneto-thermoelectric effects without any evidence of spin transport. A careful understanding of thermal and electric gradients is needed to aid in understanding of transport properties of thin films

A diverse diapsid tooth assemblage from the Early Triassic (Driefontein locality, South Africa) records the recovery of diapsids following the end-Permian mass extinction

Mass extinctions change the trajectory of evolution and restructure ecosystems. The largest mass extinction, the end-Permian, is a particularly interesting case due to the hypothesized delay in the recovery of global ecosystems, where total trophic level recovery is not thought to have occurred until 5–9 million years after the extinction event. Diapsids, especially archosauromorphs, play an important role in this recovery, filling niches left vacant by therapsids and anapsids. However, the nature of lineage and ecological diversification of diapsids is obscured by the limited number of continuous, well-dated stratigraphic sections at the Permian-Triassic boundary and continuing through the first half of the Triassic. The Karoo Basin of South Africa is one such record, and particularly the late Early Triassic (Olenekian) Driefontein locality fills this gap in the diapsid fossil record. We collected a total of 102 teeth of which 81 are identified as diapsids and the remaining 21 as identified as temnospondyls. From the sample, seven distinct tooth morphotypes of diapsids are recognized, six of which are new to the locality. We used a combination of linear measurements, 3D geomorphometrics, and nMDS ordination to compare these morphotypes and made inferences about their possible diets. Although the morphotypes are readily differentiated in nMDS, the overall morphological disparity is low, and we infer five morphotypes are faunivorous with the other two potentially omnivorous or piscivorous based on their morphological similarities with dentitions from extant diapsids, demonstrating an unsampled taxonomic and ecological diversity of diapsids in the Early Triassic based on teeth. Although ecological specialization at Driefontein may be low, it records a diversity of diapsid taxa, specifically of archosauromorph lineages

Muscle Oxygen Demands of the Vastus Lateralis in Back and Front Squats

International Journal of Exercise Science 13(6): 734-743, 2020. In resistance training squats are often used to strengthen the muscles of the lower extremities and core muscles. There are two common forms of squats that use a barbell for loading, the back squat and the front squat. The technique and loading of each squat differ markedly. However, the energetic demands on the muscle between the two forms are not well understood. The purpose of this study was to investigate the difference in energy demands between front and back squats by measuring the change in skeletal muscle oxygen saturation (SmO2) through the use of near infrared spectroscopy (NIRS). Methods: Eleven resistance trained individuals, (5 female, 6 male) with an average age of 23.7 ± 1.4, completed 3 sets of 15 repetitions at 70% of their 1-RM weight for both back and front squats. Skeletal muscle oxygen saturation (SmO2) of the vastus lateralis was measured using a wireless NIRS device. Results: The ΔSmO2 was not significantly different between back and front squats but was different between sets 1-3 (44.76 ± 3.24% vs. 55.19 ± 2.75% vs. 56.30 ± 2.63%), main effect p ≤ 0.0001 . The recovery of SmO2 was significantly different between back (42.5 ± 3.4 sec) and front squats (30.9 ± 2.8 sec), main effect p ≤ 0.05. Conclusions: The findings of this study suggest that the energetic demands placed on the vastus lateralis during both front and back squats are similar with a slower recovery of energetics in the back squat