Geometric Morphometrics of Gary Dart Points from the Davy Crockett National Forest

Three-dimensional scans of Gary dart points recovered from the Davy Crockett National Forest are employed in tests of basal morphology by site, size (allometry), and asymmetry. Variability in basal morphology for Gary points from sites on the Davy Crockett National Forest is presented and compared to specimens from the published type books. The hypothesis that Gary basal morphology differs between sites containing Woodland-era sand temped ceramics and those where no sand tempered ceramics were recovered is then tested and the results discussed

Identification of red supergiants in nearby galaxies with mid-IR photometry

The role of episodic mass loss in massive star evolution is one of the most important open questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the mid-infrared and dim at optical wavelengths. We aim to increase the number of investigated luminous mid-IR sources to shed light on the late stages of these objects. To achieve this we employed mid-IR selection criteria to identity dusty evolved massive stars in two nearby galaxies. The method is based on mid-IR colors, using 3.6 {\mu}m and 4.5 {\mu}m photometry from archival Spitzer Space Telescope images of nearby galaxies and J-band photometry from 2MASS. We applied our criteria to two nearby star-forming dwarf irregular galaxies, Sextans A and IC 1613, selecting eight targets, which we followed up with spectroscopy. Our spectral classification and analysis yielded the discovery of two M-type supergiants in IC 1613, three K-type supergiants and one candidate F-type giant in Sextans A, and two foreground M giants. We show that the proposed criteria provide an independent way for identifying dusty evolved massive stars, that can be extended to all nearby galaxies with available Spitzer/IRAC images at 3.6 {\mu}m and 4.5 {\mu}m.Comment: 8 pages, 4 figures, A&A in pres

Monitoring luminous yellow massive stars in M33: new yellow hypergiant candidates

The evolution of massive stars surviving the red supergiant (RSG) stage remains unexplored due to the rarity of such objects. The yellow hypergiants (YHGs) appear to be the warm counterparts of post-RSG classes located near the Humphreys-Davidson upper luminosity limit, which are characterized by atmospheric instability and high mass-loss rates. We aim to increase the number of YHGs in M33 and thus to contribute to a better understanding of the pre-supernova evolution of massive stars. Optical spectroscopy of five dust-enshrouded YSGs selected from mid-IR criteria was obtained with the goal of detecting evidence of extensive atmospheres. We also analyzed BVI photometry for 21 of the most luminous YSGs in M33 to identify changes in the spectral type. To explore the properties of circumstellar dust, we performed SED-fitting of multi-band photometry of the 21 YSGs. We find three luminous YSGs in our sample to be YHG candidates, as they are surrounded by hot dust and are enshrouded within extended, cold dusty envelopes. Our spectroscopy of star 2 shows emission of more than one H$\alpha$ component, as well as emission of CaII, implying an extended atmospheric structure. In addition, the long-term monitoring of the star reveals a dimming in the visual light curve of amplitude larger than 0.5 mag that caused an apparent drop in the temperature that exceeded 500 K. We suggest the observed variability to be analogous to that of the Galactic YHG $\rho$ Cas. Five less luminous YSGs are suggested as post-RSG candidates showing evidence of hot or/and cool dust emission. We demonstrate that mid-IR photometry, combined with optical spectroscopy and time-series photometry, provide a robust method for identifying candidate YHGs. Future discovery of YHGs in Local Group galaxies is critical for the study of the late evolution of intermediate-mass massive stars.Comment: 24 pages, 12 figures, 7 Tables. A&A in pres

Echo Emission From Dust Scattering and X-Ray Afterglows of Gamma-Ray Bursts

We investigate the effect of X-ray echo emission in gamma-ray bursts (GRBs). We find that the echo emission can provide an alternative way of understanding X-ray shallow decays and jet breaks. In particular, a shallow decay followed by a "normal" decay and a further rapid decay of X-ray afterglows can be together explained as being due to the echo from prompt X-ray emission scattered by dust grains in a massive wind bubble around a GRB progenitor. We also introduce an extra temporal break in the X-ray echo emission. By fitting the afterglow light curves, we can measure the locations of the massive wind bubbles, which will bring us closer to finding the mass loss rate, wind velocity, and the age of the progenitors prior to the GRB explosions.Comment: 25 pages, 3 figures, 2 tables. Accepted for publication in Ap

Addressing Survey Bias: Maxent Models and Public Archaeology at the Davy Crockett National Forest

Over the past 30+ years, compliance-based archaeological projects conducted on the Davy Crockett National Forest have yielded an impressive contribution to the archaeological record. However, those efforts were limited to specific survey areas based upon specific needs. To begin to address survey bias and the impact that it can have on site probability models, a stratified random sample of 50 locations was generated for the forest. In early 2018, a public archaeology (Passport-in-Time) project was used to engage interested volunteers who assisted in testing these sample locations. These results, as well as other new data, were added to the maxent site probability model in advance of running a second iteration. A second call for volunteers in early 2019 will aid with site relocation and delineation of known resources, as well as an additional test using a new stratified random sample

First Test of Habitat Suitability Models for the Davy Crockett National Forest

The test for this suite of models was conducted as a double-blind survey since neither the United States Forest Service personnel (excepting Garcia) nor the participants were provided with any information regarding the model in advance of testing. Input from the model was shared with the crew the day after each location was tested. Enlistment of the double-blind survey method aids in reducing survey bias. Collection of data for this project begins with the stratified random sample. The sample consists of random locations throughout compartments of the Davy Crockett National Forest. Those locations not visited in the first test of the model will be surveyed following the Passport-in-Time project. To test the stratified random sample, a three-by-three grid of nine shovel tests were excavated at each location. Those resources discovered during the survey were assigned a forest-specific number, were documented, and the collections were subsequently transferred to the Center for Regional Heritage Research at Stephen F. Austin State University for analysis and processing

ParaMT: a Paraphraser for Machine Translation

In this paper we present ParaMT, a bilingual/multilingual paraphraser to be applied in machine translation. We select paraphrases of support verb constructions and use the NooJ linguistic environment to formalize and generate translation equivalences through the use of dictionary and local grammars with syntactic and semantic content. Our research shows that linguistic paraphrasal knowledge constitutes a key element in conversion of source language into controlled language text that presents more successful translation result

Recent Technological Developments on LGAD and iLGAD Detectors for Tracking and Timing Applications

This paper reports the last technological development on the Low Gain Avalanche Detector (LGAD) and introduces a new architecture of these detectors called inverse-LGAD (iLGAD). Both approaches are based on the standard Avalanche Photo Diodes (APD) concept, commonly used in optical and X-ray detection applications, including an internal multiplication of the charge generated by radiation. The multiplication is inherent to the basic n++-p+-p structure, where the doping profile of the p+ layer is optimized to achieve high field and high impact ionization at the junction. The LGAD structures are optimized for applications such as tracking or timing detectors for high energy physics experiments or medical applications where time resolution lower than 30 ps is required. Detailed TCAD device simulations together with the electrical and charge collection measurements are presented through this work.Comment: Keywords: silicon detectors, avalanche multiplication, timing detectors, tracking detectors. 8 pages. 8 Figure

Magnetic properties, anisotropy, and microstructure of sputtered rare-earth iron multilayers

A study of compositionally modulated magnetic films of the form Fe/RE, particularly for RE=Nd and Dy, has been performed by vibrating sample magnetometry, ac susceptibility and x-ray diffraction. The relationship between the magnetic properties and the layer thickness was studied systematically for X-Å Fe/Y-Å Dy, as the layer thicknesses X and Y were varied from 1.8 to 20 Å. The ranges of layer thicknesses required for perpendicular anisotropy were determined. The interface and volume anisotropy energies were estimated for X-Å Fe/Y-Å Nd and the differences in the magnetic properties between X-Å Fe/7-Å Dy and X-Å Fe/7-Å Nd are discussed. Journal of Applied Physics is copyrighted by The American Institute of Physics