Cenotes as Conceptual Boundary Markers at the Ancient Maya Site of T’isil, Quintana Roo, México

Ancient Maya communities, from small village sites to urban centers, have long posed problems to archaeologists in attempting to define the boundaries or limits of settlement. These ancient communities tend to be relatively dispersed, with settlement densities dropping toward the periphery, but lacking any clear boundary. At a limited number of sites, the Maya constructed walled enclosures or earthworks, which scholars have generally interpreted as defensive projects, often hastily built to protect the central districts of larger administrative centers during times of warfare (e.g., Demarest et al. 1997; Inomata 1997; Kurjack and Andrews 1976; Puleston and Callender 1967; Webster 2000; Webster et al. 2007). As another response to conflict in the southern lowlands, small villages or hamlets are reported to have been established on defensive hilltop locations and surrounded by palisades (Demarest et al. 1997; O\u27Mansky and Dunning 2004). At some walled sites, walls may have served more to define gated communities in the modern sense of the phrase; a boundary that separates an elite community from the more common folk living just outside of the walls

Preliminary Evidence for the Existence of a Regional Sacbe Across the Northern Maya Lowlands

Ancient road systems have often been used by archaeologists to reconstruct interaction and political ties among prehistoric settlements. Roads built by the ancient Maya offer many insights into the political geography of the area, particularly in the northern lowlands where hieroglyphic texts are rare. This study examines ethnohistoric, historic, and archaeological data that suggest that a regional road, some 300 km in length, once spanned the northern lowlands from the modern location of Mérida to the east coast facing the island of Cozumel. The political implications of such a road, if it once existed, are discussed

Wetland Manipulation in the Yalahau Region of the Northern Maya Lowlands

Manipulation of wetlands for agricultural purposes by the ancient Maya of southern Mexico and Central America has been a subject of much research and debate since the 1970s. Evidence for wetland cultivation systems, in the form of drained or channelized fields, and raised planting platforms, has been restricted primarily to the southern Maya Lowlands. New research in the Yalahau region of Quintana Roo, Mexico, has recorded evidence for wetland manipulation in the far northern lowlands, in the form of rock alignments that apparently functioned to control water movement and soil accumulation in seasonally inundated areas. Nearby ancient settlements date primarily to the Late Preclassic period (ca. 100 B.C. to A.C. 350), and this age is tentatively attributed to wetland management in the area

Landuse and soil degradation in the southern Maya lowlands, from Pre-Classic to Post-Classic times : The case of La Joyanca (Petén, Guatemala)

International audienceThis work focuses on the impact of Maya agriculture on soil degradation. In site and out site studies in the area of the city of La Joyanca (NW Petén) show that "Maya clays" do not constitute a homogeneous unit, but represent a complex sedimentary record. A high resolution analysis leads us to document changes in rates and practices evolving in time in relation with major socio-political and economic changes. It is possible to highlight extensive agricultural practices between Early Pre-classical to Late Pre-classical times. Intensification occurs in relation with reduction of the fallow duration during Pre-classic to Classic periods. The consequences of these changes on soil erosion are discussed. However, it does not seem that the agronomic potential of the soils was significantly degraded before the end of the Classic period

The Yalahau Regional Human Ecology Project: An Introduction and Summary of Recent Research

This chapter will introduce the Yalahau region and summarize research activities and findings from 1998 through 2001, with some observations based on our 2002-2003 investigations, which are still under analysis (Fedick 2004; Mathews 2003a)

Molecular Characterization of the Thermal Degradation of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foams via Temperature-Programmed Thermal Desorption–Pyrolysis–Direct Analysis in Real Time–Mass Spectrometry

The release of aqueous film-forming foam (AFFF), containing per- and polyfluoroalkyl substances (PFAS), from Department of Defense activities has received attention over the years due to the environmental persistence and bioaccumulation of PFAS. As a result, the National Defense Act established that the removal of PFAS-containing waste is critical. Thermal destruction methods are commonly used techniques, yet the fate of degraded PFAS remains poorly understood. In this study, we employ thermal desorption–pyrolysis–direct analysis in real time–mass spectrometry (TD-pyro-DART-MS) to characterize products of pyrolysis and determine the extent of degradation from 25 to 600 °C. PFAS ranging from 4–14 carbon atoms were monitored in situ, followed by legacy AFFF. Headgroup scission was observed, followed by carbon–carbon bond cleavages in the structures resulting in [CxFy]− fragments differing by -CF2 (50 Da) and -C2F4 (100 Da). High-molecular weight PFAS resulted in more detectable pyrolytic fragments than low-molecular weight counterparts. AFFF concentrate thermal degradation analysis was more complex and was determined to require higher-resolution mass spectrometers for molecular assignment. This study demonstrates the development of a robust analytical methodology for in situ characterization of the products of thermal degradation of PFAS related to thermal remediation or when PFAS are used to extinguish fuel fires

Mass Spectrometric Detection of Nanoparticle Host-Guest Interactions in Cells

Synthetic host–guest chemistry is a versatile tool for biomedical applications. Characterization and detection of host–guest complexes in biological systems, however, is challenging due to the complexity of the biological milieu. Here, we describe and apply a mass spectrometric method to monitor the association and dissociation of nanoparticle (NP)-based host–guest interactions that integrates NP-assisted laser desorption/ionization (LDI) and matrix assisted laser desoption/ionization (MALDI) mass spectrometry. This LDI/MALDI approach reveals how NP surface functionality affects host–guest interactions in cells, information difficult to achieve using other techniques