Objectives/Goals: Transgender women who have sex with men (TGWSM) have higher HIV risk. The rectal mucosal (RM) immune environment of TGWSM who choose feminizing hormone therapy (FHT) has been shown to be distinct from the RM of cisgender men who have sex with men (MSM). We studied the impact of FHT on the adaptive immune cellular composition of the RM. Methods/Study Population: We sampled cross-sectional and longitudinal cohorts of TGWSM and cisgender MSM from The Silom Clinic in Bangkok, Thailand from December 2020 to December 2023. We included participants aged >18 years, all cisgender MSM and TGWSM with FHT levels in the therapeutic range for cisgender women. We performed RM biopsies and analyzed the adaptive immune cell characteristics via flow cytometry. We will perform binary linear regression to assess the association between systemic FHT levels and the percentage of CD4+ T cells expressing key biomarkers. Primary outcomes include the percentage of CD4+ T cells that express CCR5, with a secondary outcome of the percentage of CD4+ T cells that express Ki67. Results/Anticipated Results: The cross-sectional cohort included 100 TGWSM on FHT and 50 cisgender MSM. The longitudinal cohort included 25 TGWSM who were initiating FHT. Similar primary and secondary outcomes are to be elucidated in both cohorts. We anticipate the RM environment of TGWSM using FHT in both cohorts compared to the RM environment of cisgender MSM in the cross-sectional cohort will be associated with greater percentages of activation/co-receptor expression of CD4+ T cells that express biomarkers of interest. In the longitudinal cohort, we similarly anticipate increased percentages and activation/co-receptor expression of CD4+ T cells expressing biomarkers of interest in TGWSM after in comparison to before initiating FHT. Discussion/Significance of Impact: This is the largest study of its kind to compare HIV target cells in RM of TGSWM, which challenges prevailing perspectives suggesting to group cisgender MSM with TGWSM. Anticipated results will inform HIV prevention strategies and future vaccine studies in this high-risk population.

The appearance of a statistical paper in a symposium honoring the founding of psychophysies was surely to have been expected. These two disciplines had their modern beginnings in about the same period of time and the well-known founders of each made at least some contributions in the other. Karl Pearson’s research on the personal equation is still a good example of painstaking psychophysical experimentation. Indeed much of his statistical reputation rests on techniques he developed to analyze this data. Fifty years ago Urban published, in a psychological journal, the final form of the Müller-Urban weights. Twenty years later biologists rediscovered Urban’s weights and now use them routinely. Spearman, too, contributed to both fields.

A statistical model for verbal learning is presented and tested against experimental data. The model describes a Markov process with a realizable absorbing state, allowing complete learning on some finite trial as well as imperfect retention prior to this trial.

Rift propagation, rather than basal melt, drives the destabilization and disintegration of the Thwaites Eastern Ice Shelf. Since 2016, rifts have episodically advanced throughout the central ice-shelf area, with rapid propagation events occurring during austral spring. The ice shelf's speed has increased by ~70% during this period, transitioning from a rate of 1.65 m d−1 in 2019 to 2.85 m d−1 by early 2023 in the central area. The increase in longitudinal strain rates near the grounding zone has led to full-thickness rifts and melange-filled gaps since 2020. A recent sea-ice break out has accelerated retreat at the western calving front, effectively separating the ice shelf from what remained of its northwestern pinning point. Meanwhile, a distributed set of phase-sensitive radar measurements indicates that the basal melting rate is generally small, likely due to a widespread robust ocean stratification beneath the ice–ocean interface that suppresses basal melt despite the presence of substantial oceanic heat at depth. These observations in combination with damage modeling show that, while ocean forcing is responsible for triggering the current West Antarctic ice retreat, the Thwaites Eastern Ice Shelf is experiencing dynamic feedbacks over decadal timescales that are driving ice-shelf disintegration, now independent of basal melt.

Recent drilling successes on Rutford Ice Stream in West Antarctica demonstrate the viability of hot water drilling subglacial access holes to depths >2000 m. Having techniques to access deep subglacial environments reliably paves the way for subglacial lake exploration beneath the thick central West Antarctic Ice Sheet. An ideal candidate lake, overlain by ~2650 m of ice, identified by Centro de Estudios Científicos (CECs), Chile, has led to collaboration with British Antarctic Survey to access Subglacial Lake CECs (SLCECs). To conform with the Scientific Committee on Antarctic Research code of conduct, which provides a guide to responsible scientific exploration and stewardship of these pristine systems, any access drilling must minimise all aspects of contamination and disturbance of the subglacial environment. To meet these challenges, along with thicker ice and 2000 m elevation, pumping and water treatment systems developed for the Subglacial Lake Ellsworth project, together with new diesel generators, additional water heating and longer drill hose, are currently being integrated with the BEAMISH hot water drill. A dedicated test season near SLCECs will commission the new clean hot water drill, with testing and validation of all clean operating procedures. A subsequent season will then access SLCECs cleanly.

During the 2018/19 Antarctic field season, the British Antarctic Survey (BAS) Basal conditions on Rutford Ice Stream: BEd Access, Monitoring and Ice Sheet History’ (BEAMISH) project drilled three holes through the Rutford Ice Stream, West Antarctica. At up to 2154 m, these are the deepest hot water drilled subglacial access holes yet created, enabling the recovery of sediment from the subglacial environment, and instrumenting the ice stream and its bed. The BEAMISH hot-water drill system was built on extensive experience with the BAS ice shelf hot-water drill and utilises many identical components. With up to 1 MW of heating power available, the hot water drill produces 140 L min−1 of water at 85°C to create a 300 mm diameter access hole to the base of the ice stream. New systems and processes were developed for BEAMISH to aid critical aspects of deep access drilling, most notably the creation of cavities interlinking boreholes at 230 m below the surface and enabling water recirculation throughout the deep drilling operations. The modular design of the BEAMISH drill offers many benefits in its adaptability, redundancy, and minimal logistical footprint. These design features can easily accommodate the modifications needed for future deep, clean access hole creation in the exploration of subglacial environments.

Subglacial sediments have the potential to reveal information about the controls on glacier flow, changes in ice-sheet history and characterise life in those environments. Retrieving sediments from beneath the ice, through hot water drilled access holes at remote field locations, present many challenges. Motivated by the need to minimise weight, corer diameter and simplify assembly and operation, British Antarctic Survey, in collaboration with UWITEC, developed a simple mechanical percussion corer. At depths over 1000 m however, manual operation of the percussion hammer is compromised by the lack of clear operator feedback at the surface. To address this, we present a new auto-release-recovery percussion hammer mechanism that makes coring operations depth independent and improves hammer efficiency. Using a single rope tether for both the corer and hammer operation, this modified percussion corer is relatively simple to operate, easy to maintain, and has successfully operated at a depth of >2130 m.

The peoples of southern Mesoamerica, including the Classic period Maya, are often claimed to exhibit a distinct type of spatial organization relative to contemporary urban systems. Here, we use the settlement scaling framework and properties of settlements recorded in systematic, full-coverage surveys to examine ways in which southern Mesoamerican settlement systems were both similar to and different from contemporary systems. We find that the population-area relationship in these settlements differs greatly from that reported for other agrarian settlement systems, but that more typical patterns emerge when one considers a site epicenter as the relevant social interaction area, and the population administered from a given center as the relevant interacting population. Our results imply that southern Mesoamerican populations mixed socially at a slower temporal rhythm than is typical of contemporary systems. Residential locations reflected the need to balance energetic and transport costs of farming with lower-frequency costs of commuting to central places. Nevertheless, increasing returns in activities such as civic construction were still realized through lower-frequency social mixing. These findings suggest that the primary difference between low-density urbanism and contemporary urban systems lies in the spatial and temporal rhythms of social mixing.

George L. Cowgill had a major influence on the study of the ancient city of Teotihuacan and the development and promotion of quantitative methods in archaeology. His wit, teaching, and research influenced many in the profession. We draw on two published autobiographical works (Cowgill 2008a, 2013a), some unpublished autobiographical notes (Cowgill 1983), his many publications, and our own associations with George.

The scarcity of Romano-British human remains from north-west England has hindered understanding of burial practice in this region. Here, we report on the excavation of human and non-human animal remains1 and material culture from Dog Hole Cave, Haverbrack. Foetal and neonatal infants had been interred alongside a horse burial and puppies, lambs, calves and piglets in the very latest Iron Age to early Romano-British period, while the mid- to late Roman period is characterised by burials of older individuals with copper-alloy jewellery and beads. This material culture is more characteristic of urban sites, while isotope analysis indicates that the later individuals were largely from the local area. We discuss these results in terms of burial ritual in Cumbria and rural acculturation. Supplementary material is available online (https://doi.org/10.1017/S0068113X20000136), and contains further information about the site and excavations, small finds, zooarchaeology, human osteology, site taphonomy, the palaeoenvironment, isotope methods and analysis, and finds listed in Benson and Bland 1963.