A lower-than-expected saltation threshold at Martian pressure and below.

Aeolian sediment transport is observed to occur on Mars as well as other extraterrestrial environments, generating ripples and dunes as on Earth. The search for terrestrial analogs of planetary bedforms, as well as environmental simulation experiments able to reproduce their formation in planetary conditions, are powerful ways to question our understanding of geomorphological processes toward unusual environmental conditions. Here, we perform sediment transport laboratory experiments in a closed-circuit wind tunnel placed in a vacuum chamber and operated at extremely low pressures to show that Martian conditions belong to a previously unexplored saltation regime. The threshold wind speed required to initiate saltation is only quantitatively predicted by state-of-the art models up to a density ratio between grain and air of [Formula: see text] but unexpectedly falls to much lower values for higher density ratios. In contrast, impact ripples, whose emergence is continuously observed on the granular bed over the whole pressure range investigated, display a characteristic wavelength and propagation velocity essentially independent of pressure. A comparison of these findings with existing models suggests that sediment transport at low Reynolds number but high grain-to-fluid density ratio may be dominated by collective effects associated with grain inertia in the granular collisional layer.

Lipid-based paleoecological and biogeochemical reconstruction of Store Saltsø, an extreme lacustrine system in SW Greenland.

Polar lakes harbour a unique biogeochemistry that reflects the implications of climatic fluctuations against a susceptible yet extreme environment. In addition to polar, Store Saltsø (Kangerlussuaq, southwestern Greenland) is an endorheic lake with alkaline and oligotrophic waters that host a distinctive ecology adapted to live in such particular physico-chemical and environmental conditions. By exploring the sedimentary record of Store Saltsø at a molecular and compound-specific isotopic level, we were able to understand its ecology and biogeochemical evolution upon climate change. We employed lipid biomarkers to identify biological sources and metabolic traits in different environmental samples (shore terrace, sediment core, and white precipitates at the shore), and their succession over time to reconstruct the lake paleobiology. Different molecular ratios and geochemical proxies provided further insights toward the evolution of environmental conditions in the frame of the deglaciation history of Kangerlussuaq. The relative abundance of terrestrial (i.e., plant derived) biomarkers (odd long-chain n-alkanes, even long-chain n-alkanols, and phytosterols) in the upper half of the shore terrace versus the relatively more present aquatic biomarkers (botryococcenes and long-chain alkenones) in its lower half revealed higher lake water levels in the past. Moreover, the virtual absence of organics in the deepest section of the sediment core (32-29 cm depth) suggested that the lake did not yet exist at the northwestern shore of Store Saltsø ∼5100 years ago. According to the relative abundance of lipid biomarkers detected in the adjacent section above (29-25 cm depth), we hypothesize that the northwestern shore of Store Saltsø formed ∼4900 years ago. By combining the molecular and compound-specific isotopic analysis of lipids in a ∼360 cm sedimentary sequence, we recreated the paleobiology and evolution of an extreme lacustrine environment suitable for the study of the limits of life and the effects of climate warming.

PEA3/ETV4-related transcription factors coupled with active ERK signalling are associated with poor prognosis in gastric adenocarcinoma.

BACKGROUND: Transcription factors often play important roles in tumourigenesis. Members of the PEA3 subfamily of ETS-domain transcription factors fulfil such a role and have been associated with tumour metastasis in several different cancers. Moreover, the activity of the PEA3 subfamily transcription factors is potentiated by Ras-ERK pathway signalling, which is itself often deregulated in tumour cells. METHODS: Immunohistochemical patterns of PEA3 expression and active ERK signalling were analysed and mRNA expression levels of PEA3, ER81, MMP-1 and MMP-7 were determined in gastric adenocarcinoma samples. RESULTS: Here, we have studied the expression of the PEA3 subfamily members PEA3/ETV4 and ER81/ETV1 in gastric adenocarcinomas. PEA3 is upregulated at the protein level in gastric adenocarcinomas and both PEA3/ETV4 and ER81/ETV1 are upregulated at the mRNA level in gastric adenocarcinoma tissues. This increased expression correlates with the expression of a target gene associated with metastasis, MMP-1. Enhanced ERK signalling is also more prevalent in late-stage gastric adenocarcinomas, and the co-association of ERK signalling and PEA3 expression also occurs in late-stage gastric adenocarcinomas. Furthermore, the co-association of ERK signalling and PEA3 expression correlates with decreased survival rates. CONCLUSIONS: This study shows that members of the PEA3 subfamily of transcription factors are upregulated in gastric adenocarcinomas and that the simultaneous upregulation of PEA3 expression and ERK pathway signalling is indicative of late-stage disease and a poor survival prognosis.

Pathogenesis, investigation and dietary and medical management of gastroparesis.

Delayed gastric emptying (gastroparesis) is associated with significant morbidity and, occasionally, mortality; clinicians therefore need a high index of suspicion to avoid missing the diagnosis. This review discusses the aetiology, diagnostic criteria and investigations pertinent to gastroparesis, and also critically reviews the evidence for nutritional and medical management strategies. Dietary manipulation plays a key role in management, and simple adjustment to meal routines and diets can lead to an improvement in symptoms, whereas alternative feeding routes play an important role in more severe cases. The role of pharmaceutical intervention is less clear; prokinetics and antiemetics are often prescribed; however, evidence for their efficacy is lacking, whereas gastric electric stimulation has an evolving role in the management of patients with symptoms refractory to medical therapies. The optimal treatment of gastroparesis would be to resolve symptoms and normalise gastric emptying times, and this may be achieved with future treatments that target the underlying pathology. For most patients with mild to moderate disease, dietary intervention plays a central role in the management of gastroparesis.

Flow depletion in a small stream caused by ground water abstraction from wells.

The interaction between a gaining stream and a water-table aquifer is studied at an outwash plain. The aquifer is hydraulically well connected to the stream. Pumping tests were carried out in 1997 and 1998 in two wells 60 m from the stream, screening different depths of the aquifer. Drawdown was measured on both sides of the stream. Hydraulic head, drawdown, and stream depletion data were analyzed using numerical flow models. Similar models were fitted to each of two different data sets: Model A was fitted to steady-state hydraulic head and streamflow gain data not influenced by pumping; and model B was fitted to drawdown data measured during the 1998 pumping test. Each calibrated model closely fits its calibration data; however, predictions were biased if model A was used to predict the calibration data of model B, and vice versa. To further test the models, they were used to predict streamflow depletion during the two pumping tests as well as the drawdown during the 1997 test. Neither of these data were used for calibration. Model A predicted the measured depletions fairly accurately during both tests, whereas the predicted drawdowns in 1997 were significantly larger than actually measured. Contrary to this, the 1997 drawdowns predicted by model B were nearly unbiased; the predicted depletions deviate significantly from the measured depletions in 1997, but they compare well with the observations in 1998. Thus, although field work and analyses were extensive and done carefully to develop a ground water flow model that could predict both drawdown and streamflow depletion, the model predictions are biased. Analyses indicate that the deviations between model and data may be because of error in the models' representations of either the release of water from storage or of the hydrology in the riparian zone.