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Teotihuacan's Tlajinga district is a cluster of neighborhoods on the southern periphery of the city best known for earlier investigations at Compound 33:S3W1. New research includes excavations at two other apartment compounds and along the southern extension of the Street of the Dead. Excavation contexts, major finds, chronology, and preliminary interpretations are the subject of this article. We highlight evidence attesting to a major obsidian-blade workshop at Compound 17:S3E1, offerings, and other features at that compound and Compound 18:S3E1, and the tempo and processes of urbanization viewed through well-recorded stratigraphic sequences of the compounds and the Street of the Dead. We conclude that significant occupation began in the Miccaotli phase, but it was not until some point in the Early Tlamimilolpa phase that the dominant housing type became apartment compounds; the continuation of the axis of Street of the Dead in the district was accomplished by excavating in the volcanic tuft substrate (tepetate) and could have been undertaken by the inhabitants of the district themselves; and the presence of items such as a sculpted stone face, marine shell, and polychrome pottery demonstrates that commoners at Teotihuacan enjoyed some access to finer items within the interregional economy.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
The Dark Energy Survey is undertaking an observational programme imaging 1/4 of the southern hemisphere sky with unprecedented photometric accuracy. In the process of observing millions of faint stars and galaxies to constrain the parameters of the dark energy equation of state, the Dark Energy Survey will obtain pre-discovery images of the regions surrounding an estimated 100 gamma-ray bursts over 5 yr. Once gamma-ray bursts are detected by, e.g., the Swift satellite, the DES data will be extremely useful for follow-up observations by the transient astronomy community. We describe a recently-commissioned suite of software that listens continuously for automated notices of gamma-ray burst activity, collates information from archival DES data, and disseminates relevant data products back to the community in near-real-time. Of particular importance are the opportunities that non-public DES data provide for relative photometry of the optical counterparts of gamma-ray bursts, as well as for identifying key characteristics (e.g., photometric redshifts) of potential gamma-ray burst host galaxies. We provide the functional details of the DESAlert software, and its data products, and we show sample results from the application of DESAlert to numerous previously detected gamma-ray bursts, including the possible identification of several heretofore unknown gamma-ray burst hosts.
We report on the identifications of 15 new X-ray selected Active Galactic Nuclei (AGN). The AGN have been discovered during an ongoing program to identify and study the optical counterparts of X-ray sources detected by the HEAO-1 satellite. The new AGN add to our existing data base of 26 making a sample of 41 objects which are the subject of a multiwavelength study including radio, infrared, optical, UV and X-ray observations. As part of this study 8.4 GHz flux measurements have been made at Parkes. Radio-optical-X-ray continuum spectral index comparisons are presented.
We report the analysis of 154 hours of nearly continuous high-speed photometric data on the pulsating DB white dwarf (DBV) GD 358 obtained during the Whole Earth Telescope (WET) run of May 1990. The Fourier transform (FT) of the light curve is dominated by power in the range from 1200 – 1700μHz with more than 180 significant peaks in the total transform. We also see significant power at the sums and differences of the dominant frequencies, indicating the importance of nonlinear behavior. We can use this data to obtain an accurate total stellar mass, and surface He layer mass. The implied surface He layer mass, if correct, provides a significant and surprising challenge to stellar evolution theory, as well as the theory of chemical mixing.
The variability of CD-24 7599 (V=11.48 mag) was discovered by JCC during observing run XCOV7 of the Whole Earth Telescope (WET, Nather et al. 1990) network in February, 1992. The star was observed as an additional target and 117 hours of high-quality temporal spectroscopic observations were obtained.
Our analysis of these data revealed the presence of 7 independent pulsation modes between 27.0 and 38.1 cycles per day (313 – 441 μHz) with semiamplitudes of 2.1 – 10.2 milli-modulation amplitudes (mma). We showed that peaks at linear combination frequencies detected in the power spectra were not due to eigenmodes excited to visible amplitude by resonant mode coupling.
Two new integral field units (IFUs) were installed recently on the WIYN Observatory's 3.5-meter telescope at Kitt Peak. These unique IFUs contain fibers of different sizes in the same head. This design allows smaller fibers to sample regions of higher surface brightness, providing higher spatial resolution while maintaining adequate signal-to-noise (S/N). Conversely, larger fibers maintain S/N at the expense of spatial resolution in the lower surface brightness regions of galaxies. The new IFUs were built with funds from NSF award ATI-0804576.
A long cropmark enclosure at Springfield, Essex, interpreted as a Neolithic cursus, was investigated betwee 1979–85 to confirm its date and establish a site sequence. The enclosure was c. 690 m long and 37–49 m wide the ditch being uninterrupted in all areas examined, features within the interior at the eastern end included a incomplete ring of substantial post-pits which it is suggested originally formed a complete circle. Peterborou pottery, predominately Mortlake style, Grooved Ware, a small amount of Beaker pottery, earlier Bronze Age urn sherds, and flint artefacts of the late 3rd-early 2nd millennium were recovered from the cursus ditch an other features. Collectively the evidence indicates a prolonged period of use. The results of the excavations a described, the site is discussed in its local and regional context and the implications of the excavation for our understanding of cursus monuments are considered.
In this paper we demonstrate the usefulness of a nearest neighbor force model for studying the structural dependence of the lattice dynamics of zeolites. Interpreting Raman scattering in the context of this model confirms earlier empirical vibrational assignments in zeolites and underlines the importance of short range forces in determining the frequencies of certain zeolite vibrational modes. The model describes fully the low frequency bond bending mode of A1 symmetry, although long range forces are shown to be required to model complete zeolite vibrational spectra.
It is important to understand the diffusion sun light in sea ice as this interaction exerts a strong influence over the weather in polar regions and over the growth of microbial communities in the sub-ice water column. Sea ice is a granular composite of ice, brine, air and at low temperatures precipitated salts, in which the proportion and disposition of these components vary with depth, with temperature and thermal history. It is demonstrated that by using a simple in situ technique, supported by Monto Carlo simulations, the diffusive transport of light through a weakly absorbing composite such as sea ice can be characterised. The radiation field both within and emergent from the ice is found to reflect the anisotropic structure of the ice, in particular, the scattering is found to be highly anisotropic so that the light is channelled predominantly vertically. The technique will be illustrated with experimental results collected in McMurdo Sound, Antarctica.
The irreversibility lines, Hirr(T), for the series of superconducting compoundsTlmA2CunO2+m+2n, where A is Ba or Sr, are measured between 0 and 1 tesla for m = 1,2 and n = 1,2,3 and 4 and show a marked steepening with decreasing anisotropy i.e. as m is lowered from 2 to 1. In addition, for m=2 material Hlrr(T) is observed to steepen with decreasing number of CuO2 layers. The hole dependence of the irreversibility line is also investigated in TI2Ba2CuO6+6 by changing the oxygen stoichiometry, 6. Hirr(T) progressively steepens with increasing hole concentration on the overdoped sida of Tc(max). These results are consistent with a model of flux motion arising from a crossover from 3-D vortex lines to 2-D pancake vortices which are decoupled in the c-direction, and provide guidance for materials selection and optimum doping.
Carboxyl functional poly(arylene ether) oligomers of controlled number average molecular weight were synthesized via nucleophilic aromatic substitution step polymerization using p-hydroxy benzoic acid as the molecular weight and end group controlling reagents. The subsequent functionalized polyarylene ethers were copolymerized with acetoxy benzoic acid or acetoxyphenoxy benzoic acid via melt acidolysis procedures. Successful copolymers were generated using chlorobenzene as a solvent for the first s age of the reaction followed by melt reaction at temperatures as high as 325°C. Resulting copolymer composition and segment size were investigated. It was possible to prepare improved solvent resistant copolymers through incorporation of the liquid crystal polyester (LCP) segment. Extraction tests using boiling chloroform showed that a high percentage of segmented copolymer were generated. Swelling characteristics were also noted and were observed to decrease as a function of the LCP concentration utilized. Multiple transitions were observed in differential scanning calorimetry consistent with Tg's, Tm's and possibly with liquid crystal transitions. Optical microscopy showed an ordered microstructure developed which is consistent with the presence of liquid crystalline phases. The materials were successfully compression molded to afford tough coherent films at all compositions, implying the likelihood of improved compressive strength relative to the LCP homo- or copolyesters.
Protective coatings for both titanium-aluminum (Ti-Al) alloys and for carbon-carbon (C-C) composites have been synthesized and characterized for high temperature, light weight, structural applications. Coatings of choice must show protection against oxygen and hydrogen in severe environments. Aluminum-silicate glass ceramics were chosen as coating candidates because they are stable to temperatures of 1500°C, are nonreactive to oxygen, and have minimal reactivity with respect to hot hydrogen.
Physical properties intrinsic to linear inorganic polymer systems can be modified through replacement of chemical groups external to the chain backbone. This substitution also perturbs chemical bonding along the chain which can further influence polymer properties. Several phosphazene polymers deposited as thin dielectric films exhibit extended ultraviolet transmission. Second harmonic generation (SHG) has been observed in these polymers as well as in cyclic polymer precursors. The relative magnitude of SHG is found to correlate both with the nature of the substitutional group and molecular conformation. Influence of these parameters on substrate-film adhesion and measured optical properties is discussed in terms of substitutional group electronegativity, and electronic charge localization in the polymer chain which is probed using molecular spectroscopic techniques.
Electrically conducting composite polypyrrole/poly(p-phenyleneterephthalamide) (PPTA or KEVLAR) fibers have been prepared by chemical polymerization of pyrrole within the interstices of the hydrogen-bonded gel structure of never-dried PPTA fibers. The resultant fibers contain a uniform dispersion of polypyrrole, as evidenced by scanning electron microscopy. The temperature dependence of the electrical conductivity of these hybrid fibers is presented. The conductivity is well described by the fluctuation-induced charge transport model over the entire temperature range of interest. However, the low temperature electrical conductivity also exhibits a hoppinglike temperature dependence, and an Arrhenius-like temperature dependence is observed in the high temperature limit. Measurements of the temperaturedependent tbermopower are indicative of a p-type carrier.
New approaches to both second-order and third-order nonlinear optical materials are presented. A series of organometallic and organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared and the SHG efficiencies were measured. Partially substituted derivatives of polyacetylene are synthesized via the ring-opening metathesis polymerization (ROMP) of cyclooctatetraene (COT) and its derivatives. Certain poly-COT derivatives afford soluble, highly conjugated polyacetylenes. These materials exhibit large third-order optical nonlinearities and low scattering losses.
New organic/inorganic hybrid materials were prepared by hydrolysis and co-condensation of tetramethylorthosilicate (TMOS) with trimethoxysilane functionalized polyimide oligomers via sol-gel ultrastructure processing. In the first reaction step, amine terminated, fully imidized, soluble, high Tg polyimides were prepared from appropriate diamines and dianhydrides by solution imidization techniques. The amine end-groups were then quantitativell derivatized to nadimide structures through reaction with cis-norbornene 2,3 dicarboxylic anhydride. Subsequently, the nadimides were quantitatively derivatized to trimethoxysilane functionalities via hydrosilylation reactions in the presence of chloroplatinic acid catalyst. The resulting hexamethoxy functionalized polyimide oligomers were hydrolyzed and co-condensed at elevated temperatures under mild pressure with TMOS via sol-gel processing to generate thermally stable polyimidesilicate hybrids. The synthesis and characterization of these materials is discussed.