Bridging prehistory and history in the archaeology of cities

Archaeology is ideally suited for examining the deep roots of urbanism, its materialization and physicality, and the commonalities and variability in urban experiences cross-culturally and temporally. We propose that the significant advances archaeologists have made in situating the discipline within broader urban studies could be furthered through increased dialog between scholars working on urbanism during prehistoric and historical periods, as a means of bridging concerns in the study of the past and present. We review some major themes in urban studies by presenting archaeological cases from two areas of the Americas: central Mexico and Atlantic North America. Our cases span premodern and early modern periods, and three of the four covered in greatest depth live on as cities of today. Comparison of the cases highlights the complementarity of their primary datasets: the long developmental trajectories and relatively intact urban plans offered by many prehistoric cities, and the rich documentary sources offered by historic cities

Framing the Lowcountry: The Evolution of the Region’s Vernacular Tradition

Timber-framing systems are the foundation of Early Modern vernacular architecture traditions. The fabrication, construction, and finish details of such assemblies are indexes of the character-defining features of building practices and the wider socio-cultural context. The Lowcountry of South Carolina is no exception. From the late seventeenth-century onwards builders from Old World traditions came together to erect unrivalled British edifices in the colonial and Early Republic periods. While other scholars have closely scrutinized and interpreted the framing traditions of the Chesapeake and New England, there has yet to be a consideration of the nature and evolution of the Lowcountry’s framing. Bringing together architectural evidence from fifteen sites in the region, this study explores the emergence and evolution of the Lowcountry frame, ultimately positioning the region’s vernacular landscape within the context of the British Atlantic world

Framing God’s House: The timber-framing practices of the Carolina Lowcountry’s Anglican Parish Churches and Chapels of Ease

Houses of worship formed the backbone of colonial society in the New World. They functioned both as sites of religious devotion as well as spaces of social interactions–merging the sacred and secular. The Lowcountry of South Carolina and Georgia retains one of the best assemblages of colonial Anglican architecture from the 18th and 19th centuries. While these structures are monuments to Anglican (and later Episcopal) religiosity they also articulate the broader rhythms of the Lowcountry’s vernacular timber-framing tradition. This paper brings together framing data from ten Anglican Parish Churches, and Chapels of Ease from both Charleston’s urban context and the parishes of the Lowcounty recorded using both traditional hand measurements as well as 3D point cloud data. In doing so, it interprets the framing solutions that Lowcountry builders devised on how to best enclose their colonial sacred spaces in both city and country and how those choices changed over time. More broadly this work further explores the emergence of the region’s vernacular traditions within the context of Early Modern English Atlantic building practices as it relates to the period’s notions of Anglican practices and beliefs

Anharmonic Vibrational Frequencies and Spectroscopic Constants for the Detection of Ethynol in Space

The ethynol (HCCOH) molecule has recently been shown to be present in simulated astrochemical ices possibly linking it to molecular building blocks for interstellar complex organic molecules like amino acids. The proposed reaction mechanism suggests the simultaneous formation of both ketene and ethynol from mixed carbon monoxide/water ice in simulated interstellar conditions. Rigorous anharmonic spectral data within both the IR and microwave regions are needed for possible detection of ethynol in the interstellar medium. This study provides the first such data for this molecule from high-level quantum chemical computations where experiment is currently lacking. Ethynol has a (Formula presented.) comparable to, but distinct from acetonitrile at 9,652.1 MHz and three notable infrared features with two in the hydride stretching-regions and the C–C stretch at 2,212.8 cm−1. The ketene isomer has already been detected in the interstellar medium, and the possible detection of ethynol made possible by this work may lead to a deeper understanding of the proposed ice formation mechanism involving both species and how this relates to the molecular origins of life

Theoretical spectra and energetics for c-C3HC2H, l-C5H2, and bipyramidal D3h C5H2

The recent astronomical detection of c-C3HC2H and l-C5H2 has led to increased interest in C5H2 isomers and their relative stability. The present work provides the first complete list of anharmonic vibrational spectral data with infrared intensities for three such isomers as well as including the first set of rotational data for the bipyramidal C5H2 isomer allowing for these molecules to serve as potential tracers of interstellar carbon. All three isomers have fundamental vibrational frequencies with at least one notably intense fundamental frequency. The l-C5H2 isomer has, by far, the highest intensities out of the three isomers at 2076.3 cm−1 (738 km mol−1) and 1887.5 cm−1 (182 km mol −1). The c-C3HC2H isomer has one intense peak at 3460.6 cm−1 (84 km mol−1), and the bipyramidal C5H2 isomer has one intense peak at 489.3 cm−1 (78 km mol−1). The relative intensities highlight that while l-C5H2 is not the lowest energy isomer, its notable intensities should make it more detectable in the infrared than the lower energy c-C3HC2H form. The bipyramidal isomer is firmly established here to lie 44.98 kcal mol−1 above the cyclic form. The explicitly correlated coupled cluster rovibrational spectral data presented herein should assist with future laboratory studies of these C5H2 isomers and aid in detection in astronomical environments especially through the newly operational James Webb Space Telescope

The spectral features and detectability of small, cyclic silicon carbide clusters

Rovibrational spectral data for several tetra-atomic silicon carbide clusters (TASCCs) are computed in this work using a CCSD(T)-F12b/cc-pCVTZ-F12 quartic force field. Accurate theoretical spectroscopic data may facilitate the observation of TASCCs in the interstellar medium which may lead to a more complete understanding of how the smallest silicon carbide (SiC) solids are formed. Such processes are essential for understanding SiC dust grain formation. Due to SiC dust prevalence in the interstellar medium, this may also shed light on subsequent planetary formation. Rhomboidal Si2C2 is shown here to have a notably intense (247 km mol−1) anharmonic vibrational frequency at 988.1 cm−1 (10.1 μm) for ν2, falling into one of the spectral emission features typically associated with unknown infrared bands of various astronomical regions. Notable intensities are also present for several of the computed anharmonic vibrational frequencies including the cyclic forms of C4, SiC3, Si3C, and Si4. These features in the 6–10 μm range are natural targets for infrared observation with the James Webb Space Telescope (JWST)’s MIRI instrument. Additionally, t-Si2C2, d-Si3C, and r-SiC3 each possess dipole moments of greater than 2.0 D making them interesting targets for radioastronomical searches especially since d-SiC3 is already known in astrophysical media

Gas-phase formation and spectroscopic characterization of the disubstituted cyclopropenylidenes c-C3(C2H)2, c-C3(CN)2, and c-C3(C2H)(CN)

Aims. The detection of c-C3HC2H and possible future detection of c-C3HCN provide new molecules for reaction chemistry in the dense ISM where R-C2 and R-CN species are prevalent. Determination of chemically viable c-C3HC2H and c-C3HCN derivatives and their prominent spectral features can accelerate potential astrophysical detection for this chemical family. This work will characterize three such derivatives: c-C3(C2H)2, c-C3(CN)2, and c-C3(C2H)(CN). Methods. Interstellar reaction pathways of small carbonaceous species are well-replicated through quantum chemical means. Highly-accurate cc-pVX Z-F12/CCSD(T)-F12 (X =D,T) calculations generate the energetics of chemical formation pathways as well as the basis for quartic force field and second-order vibrational perturbation theory rovibrational analysis of the vibrational frequencies and rotational constants of the molecules under study. Results. The formation of c-C3(C2H)2 is as thermodynamically and, likely, stepwise favorable as the formation of c-C3HC2H, rendering its detectability to be mostly dependent on the concentrations of the reactants. c-C3(C2H)2 and c-C3(C2H)(CN) will be detectable through radioastronomical observation with large dipole moments of 2.84 D and 4.26 D, respectively, while c-C3(CN)2 has an exceedingly small and likely unobservable dipole moment of 0.08 D. The most intense frequency for c-C3(C2H)2 is ν2 at 3316.9 cm−1 (3.01 µm) with an intensity of 140 km mol−1. c-C3(C2H)(CN) has one frequency with a large intensity, ν1, at 3321.0 cm−1 (3.01 µm) with an intensity of 82 km mol−1. c-C3(CN)2 lacks intense vibrational frequencies within the range that current instrumentation can readily observe. Conclusions. c-C3(C2H)2 and c-C3(C2H)(CN) are viable candidates for astrophysical observation with favorable reaction profiles and spectral data produced herein, but c-C3(CN)2 will not be directly observable through any currently-available remote sensing means even if it forms in large abundances

Molecular oxygen generation from the reaction of water cations with oxygen atoms

© 2019 Author(s). The oxywater cation (H2OO+), previously shown to form barrierlessly in the gas phase from water cations and atomic oxygen, is proposed here potentially to possess a 2A″ ← 4A″ excitation leading to the H2⋯O2+ complex. This complex could then easily decompose into molecular hydrogen and the molecular oxygen cation. The present quantum chemical study shows that the necessary electronic transition takes place in the range of 1.92 eV (645 nm), in the orange-red range of the visible and solar spectrum, and dissociation of the complex only requires 5.8 kcal/mol (0.25 eV). Such a process for the abiotic, gas phase formation of O2 would only need to be photocatalyzed by visible wavelength photons. Hence, such a process could produce O2 at the mesosphere/stratosphere boundary as climate change is driving more water into the upper atmosphere, in the comet 67P/Churyumov-Gerasimenko where surprisingly high levels of O2 have been observed, or at gas-surface (ice) interfaces

Continuous Measurement of Reactive Oxygen Species Inside and Outside of a Residential House during Summer

Reactive oxygen species (ROS) are an important contributor to adverse health effects associated with ambient air pollution. Despite infiltration of ROS from outdoors, and possible indoor sources (eg, combustion), there are limited data available on indoor ROS. In this study, part of the second phase of Air Composition and Reactivity from Outdoor aNd Indoor Mixing campaign (ACRONIM-2), we constructed and deployed an online, continuous, system to measure extracellular gas- and particle-phase ROS during summer in an unoccupied residence in St. Louis, MO, USA. Over a period of one week, we observed that the non-denuded outdoor ROS (representing particle-phase ROS and some gas-phase ROS) concentration ranged from 1 to 4 nmol/m3 (as H2O2). Outdoor concentrations were highest in the afternoon, coincident with peak photochemistry periods. The indoor concentrations of particle-phase ROS were nearly equal to outdoor concentrations, regardless of window-opening status or air exchange rates. The indoor/outdoor ratio of non-denuded ROS (I/OROS) was significantly less than 1 with windows open and even lower with windows closed. Combined, these observations suggest that gas-phase ROS are efficiently removed by interior building surfaces and that there may be an indoor source of particle-phase ROS