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Background: For locally advanced rectal cancer, neoadjuvant therapy (NT) is an established element of therapy. Endoscopic vacuum therapy (EVT) has been a relevant treatment option for anastomotic leakage after rectal resection since 2008. The aim was to evaluate the influence of NT on the duration and success of EVT in anastomotic leakage after rectal resection for rectal cancer. Methods: This was a monocentric, retrospective cohort study including patients who underwent rectal resection with primary anastomosis because of histologically proven carcinoma of the rectum in the Department for General and Visceral Surgery of Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin over a period of ten years (2012 to 2022). Results: Overall, 243 patients were included, of which 47 patients (19.3%) suffered from anastomotic leakage grade B with consecutive EVT. A total of 29 (61.7%) patients received NT and 18 patients (38.3%) did not. The median duration of EVT until the removal of the sponge did not differ between patients with and without NT: 24.0 days (95% CI 6.44–41.56) versus 20.0 days (95% CI 17.03–22.97); p = 0.273. The median duration from insertion of EVT until complete healing was 74.0 days with NT (95% CI 10.07–137.93) versus 62.0 days without NT (95% CI 45.99–78.01); p = 0.490. Treatment failure—including early persistence and late onset of recurrent anastomotic leakage—was evident in 27.6% of patients with NT versus 27.8% without NT; p = 0.989. Ostomy was reversed in 19 patients (79.2%) with NT compared to 11 patients (68.8%) without NT; p = 0.456. Overall, continuity was restored in 75% of patients in the long term after EVT. Conclusion: This trial comprised—to our knowledge—the largest study cohort to analyze the outcome of EVT in anastomotic leakage after rectal resection for rectal cancer. We conclude that neoadjuvant therapy neither prolongs EVT nor the time to healing from anastomotic leakage. The rates of treatment failure of EVT and permanent ostomy were not higher when neoadjuvant therapy was used.

Glendonites are pseudomorphs of the mineral ikaite (CaCO3·6H2O) after loss of hydration water and occur in distinctive euhedral crystalline forms, sometimes clustered as rosettes of up to tens of centimeters in diameter. While it is generally accepted that organic-rich environments, methane seeps, and high phosphate levels are important for ikaite formation, glendonite occurrences in ancient sedimentary sequences are widely considered to reflect near-freezing temperatures, even at high latitudes during periods of greenhouse climates. To fully understand the paleoenvironmental significance of glendonites, a comprehensive examination of the modern ikaite setting is necessary. Temperature is the most important parameter that has been quantitatively constrained for the presence of ikaite. Low bottom-water temperature, while a required condition for formation of the mineral, is not adequate for its growth; other controls are necessary to explain the absence of ikaite in many cold environments. In this study, we discuss the control of carbonate chemistry on ikaite formation. Our compilation of geochemical data from sediment cores with well-preserved ikaite provide further evidence for the importance of phosphate. A phosphate concentration above ∼400 μM in shallow and cold porewater may be the requisite parameter for extensive ikaite precipitation. Thus, abundant glendonites in ancient successions mark past periods and regions of elevated porewater phosphorus concentrations, which may also be related to high surface productivity and/or iron fertilization.

The Antarctic Peninsula is considered to be the last region of Antarctica to have been fully glaciated as a result of Cenozoic climatic cooling. As such, it was likely the last refugium for plants and animals that had inhabited the continent since it separated from the Gondwana supercontinent. Drill cores and seismic data acquired during two cruises (SHALDRIL I and II) in the northernmost Peninsula region yield a record that, when combined with existing data, indicates progressive cooling and associated changes in terrestrial vegetation over the course of the past 37 million years. Mountain glaciation began in the latest Eocene (approximately 37-34 Ma), contemporaneous with glaciation elsewhere on the continent and a reduction in atmospheric CO₂ concentrations. This climate cooling was accompanied by a decrease in diversity of the angiosperm-dominated vegetation that inhabited the northern peninsula during the Eocene. A mosaic of southern beech and conifer-dominated woodlands and tundra continued to occupy the region during the Oligocene (approximately 34-23 Ma). By the middle Miocene (approximately 16-11.6 Ma), localized pockets of limited tundra still existed at least until 12.8 Ma. The transition from temperate, alpine glaciation to a dynamic, polythermal ice sheet took place during the middle Miocene. The northernmost Peninsula was overridden by an ice sheet in the early Pliocene (approximately 5.3-3.6 Ma). The long cooling history of the peninsula is consistent with the extended timescales of tectonic evolution of the Antarctic margin, involving the opening of ocean passageways and associated establishment of circumpolar circulation.

Silt-rich meltwater plume deposits (MPDs) analyzed from marine sediment cores have elucidated relationships that are clearly connected, yet difficult to constrain, between subglacial hydrology, ice-marginal landforms, and grounding-zone retreat patterns for several glacial catchments. Few attempts have been made to infer details of subglacial hydrology, such as flow regime, geometry of drainage pathways, and mode(s) of sediment transport through time, from grain-scale characteristics of MPDs. Using sediment samples from MPD, till, and grounding-zone proximal diamicton collected offshore of six modern and relict glacial catchments in both hemispheres, we examine grain shape distributions and microtextures (collectively, grain micromorphology) of the silt fraction to explore whether grains are measurably altered from their subglacial sources via meltwater action. We find that 75 % of all imaged grains (n = 9400) can be described by 25 % of the full range of measured shape morphometrics, indicating grain shape homogenization through widespread and efficient abrasive processes in subglacial environments. Although silt grains from MPDs exhibit edge rounding more often than silt grains from tills, grain surface textures indicative of fluvial transport (e.g., v-shaped percussions) occur in only a modest number of grains. Furthermore, MPD grain surfaces retain several textures consistent with transport beneath glacial ice (e.g., straight or arcuate steps, (sub)linear fractures) in comparable abundances to till grains. Significant grain shape alteration in MPDs compared to their till sources is observed in sediments from glacial regions where (1) high-magnitude, potentially catastrophic meltwater drainage events are inferred from marine sediment records and (2) submarine landforms suggest supraglacial melt contributed to the subglacial hydrological budget. This implies that quantifiable grain shape alteration in MPDs could reflect a combination of high-energy flow of subglacial meltwater, persistent sediment entrainment, and/or long sediment transport distances through subglacial drainage pathways. Integrating grain micromorphology into analysis of MPDs in site-specific studies could therefore aid in distinguishing periods of persistent, well-connected subglacial discharge from periods of sluggish or disorganized drainage. In the wider context of deglacial marine sedimentary and bathymetric records, a grain micromorphological approach may bolster our ability to characterize ice response to subglacial meltwater transmission through time. This work additionally demonstrates that glacial and fluvial surface textures are retained on silt-sized quartz grains in adequate amounts for microtexture analysis, which has heretofore been conducted exclusively on the sand fraction. Therefore, grain microtextures can be examined on silt-rich glaciogenic deposits that contain little to no sand as a means to evaluate sediment transport processes.

The geometry of the sea floor immediately beyond Antarctica's marine-terminating glaciers is a fundamental control on warm-water routing, but it also describes former topographic pinning points that have been important for ice-shelf buttressing. Unfortunately, this information is often lacking due to the inaccessibility of these areas for survey, leading to modelled or interpolated bathymetries being used as boundary conditions in numerical modelling simulations. At Thwaites Glacier (TG) this critical data gap was addressed in 2019 during the first cruise of the International Thwaites Glacier Collaboration (ITGC) project. We present more than 2000 km2 of new multibeam echo-sounder (MBES) data acquired in exceptional sea-ice conditions immediately offshore TG, and we update existing bathymetric compilations. The cross-sectional areas of sea-floor troughs are under-predicted by up to 40 % or are not resolved at all where MBES data are missing, suggesting that calculations of trough capacity, and thus oceanic heat flux, may be significantly underestimated. Spatial variations in the morphology of topographic highs, known to be former pinning points for the floating ice shelf of TG, indicate differences in bed composition that are supported by landform evidence. We discuss links to ice dynamics for an overriding ice mass including a potential positive feedback mechanism where erosion of soft erodible highs may lead to ice-shelf ungrounding even with little or no ice thinning. Analyses of bed roughnesses and basal drag contributions show that the sea-floor bathymetry in front of TG is an analogue for extant bed areas. Ice flow over the sea-floor troughs and ridges would have been affected by similarly high basal drag to that acting at the grounding zone today. We conclude that more can certainly be gleaned from these 3D bathymetric datasets regarding the likely spatial variability of bed roughness and bed composition types underneath TG. This work also addresses the requirements of recent numerical ice-sheet and ocean modelling studies that have recognised the need for accurate and high-resolution bathymetry to determine warm-water routing to the grounding zone and, ultimately, for predicting glacier retreat behaviour.

Benthic foraminiferal assemblages are useful tools for paleoenvironmental studies but rely on the calibration of live populations to modern environmental conditions to allow interpretation of this proxy downcore. In regions such as the region offshore of Thwaites Glacier, where relatively warm Circumpolar Deep Water is driving melt at the glacier margin, it is especially important to have calibrated tracers of different environmental settings. However, Thwaites Glacier is difficult to access, and therefore there is a paucity of data on foraminiferal populations. In sediment samples with in situ bottom-water data collected during the austral summer of 2019, we find two live foraminiferal populations, which we refer to as the Epistominella cf. exigua population and the Miliammina arenacea population, which appear to be controlled by oceanographic and sea ice conditions. Furthermore, we examined the total foraminiferal assemblage (i.e., living plus dead) and found that the presence of Circumpolar Deep Water apparently influences the calcite compensation depth. We also find signals of retreat of the Thwaites Glacier Tongue from the low proportion of live foraminifera in the total assemblages closest to the ice margin. The combined live and dead foraminiferal assemblages, along with their environmental conditions and calcite preservation potential, provide a critical tool for reconstructing paleoenvironmental changes in ice-proximal settings.

The sensitivity of sea level to melting from polar ice sheets and glaciers during recent natural and anthropogenic climate fluctuations is poorly constrained beyond the period of direct observation by satellite. We have investigated glacial meltwater events during the Anthropocene by adapting the pioneering approach of modeling trends in δ18O in the pore waters of deep‐sea cores, previously used to constrain the size of ice sheets during the Last Glacial Maximum. We show that during recent warm periods, meltwater from glacier retreat drains into the coastal fjords, leaving a signature of depleted δ18O values and low Cl concentrations in the pore water profiles of rapidly accumulating sediments. Here we model such pore water profiles in a piston core to constrain the timing and magnitude of an ice sheet retreat event at Caley Glacier on the west Antarctic Peninsula, and the result is compared with local ice front movement. This approach of pore water modeling was then applied in another kasten core and tested by a series of sensitivity analyses. The results suggest that our approach may be applied in fjords of different sedimentary settings to reconstruct the glacier history and allow insight into the sensitivity of polar glaciers to abrupt warming events.