FGF Signaling Regulates the Number of Posterior Taste Papillae by Controlling Progenitor Field Size

The sense of taste is fundamental to our ability to ingest nutritious substances and to detect and avoid potentially toxic ones. Sensory taste buds are housed in papillae that develop from epithelial placodes. Three distinct types of gustatory papillae reside on the rodent tongue: small fungiform papillae are found in the anterior tongue, whereas the posterior tongue contains the larger foliate papillae and a single midline circumvallate papilla (CVP). Despite the great variation in the number of CVPs in mammals, its importance in taste function, and its status as the largest of the taste papillae, very little is known about the development of this structure. Here, we report that a balance between Sprouty (Spry) genes and Fgf10, which respectively antagonize and activate receptor tyrosine kinase (RTK) signaling, regulates the number of CVPs. Deletion of Spry2 alone resulted in duplication of the CVP as a result of an increase in the size of the placode progenitor field, and Spry1−/−;Spry2−/− embryos had multiple CVPs, demonstrating the redundancy of Sprouty genes in regulating the progenitor field size. By contrast, deletion of Fgf10 led to absence of the CVP, identifying FGF10 as the first inductive, mesenchyme-derived factor for taste papillae. Our results provide the first demonstration of the role of epithelial-mesenchymal FGF signaling in taste papilla development, indicate that regulation of the progenitor field size by FGF signaling is a critical determinant of papilla number, and suggest that the great variation in CVP number among mammalian species may be linked to levels of signaling by the FGF pathway

An early Little Ice Age brackish water invasion along the south coast of the Caspian Sea (sediment of Langarud wetland) and its wider impacts on environment and people

Caspian Sea level has undergone significant changes through time with major impacts not only on the surrounding coasts, but also offshore. This study reports a brackish water invasion on the southern coast of the Caspian Sea constructed from a multi-proxy analysis of sediment retrieved from the Langarud wetland. The ground surface level of wetland is >6 m higher than the current Caspian Sea level (at -27.41 m in 2014) and located >11 km far from the coast. A sequence covering the last millennium was dated by three radiocarbon dates. The results from this new study suggest that Caspian Sea level rose up to at least -21.44 m (i.e. >6 m above the present water level) during the early Little Ice Age. Although previous studies in the southern coast of the Caspian Sea have detected a high-stand during the Little Ice Age period, this study presents the first evidence that this high-stand reached so far inland and at such a high altitude. Moreover, it confirms one of the very few earlier estimates of a high-stand at -21 m for the second half of the 14th century. The effects of this large-scale brackish water invasion on soil properties would have caused severe disruption to regional agriculture, thereby destabilizing local dynasties and facilitating a rapid Turko-Mongol expansion of Tamerlane’s armies from the east.N Ghasemi (INIOAS), V Jahani (Gilan Province Cultural Heritage and Tourism Organisation) and A Naqinezhad (University of Mazandaran), INQUA QuickLakeH project (no. 1227) and to the European project Marie Curie, CLIMSEAS-PIRSES-GA-2009-24751

Droplets Formation and Merging in Two-Phase Flow Microfluidics

Two-phase flow microfluidics is emerging as a popular technology for a wide range of applications involving high throughput such as encapsulation, chemical synthesis and biochemical assays. Within this platform, the formation and merging of droplets inside an immiscible carrier fluid are two key procedures: (i) the emulsification step should lead to a very well controlled drop size (distribution); and (ii) the use of droplet as micro-reactors requires a reliable merging. A novel trend within this field is the use of additional active means of control besides the commonly used hydrodynamic manipulation. Electric fields are especially suitable for this, due to quantitative control over the amplitude and time dependence of the signals, and the flexibility in designing micro-electrode geometries. With this, the formation and merging of droplets can be achieved on-demand and with high precision. In this review on two-phase flow microfluidics, particular emphasis is given on these aspects. Also recent innovations in microfabrication technologies used for this purpose will be discussed

Direct Visualization of Evaporation in a Two-Dimensional Nanoporous Model for Unconventional Natural Gas

Evaporation at the nanoscale is critical to many natural and synthetic systems including rapidly emerging unconventional oil and gas production from nanoporous shale reservoirs. During extraction processes, hydrocarbons confined to nanoscopic pores (ranging from one to a few hundred nanometers in size) can undergo phase change as pressure is reduced. Here, we directly observe evaporation in two-dimensional (2D) nanoporous media at the sub-10 nm scale. Using an experimental procedure that mimics pressure drawdown during shale oil/gas production, our results show that evaporation takes place at pressures significantly lower than predictions from the Kelvin equation (maximum deviation of 11%). We probe evaporation dynamics as a function of superheat and find that vapor transport resistance dominates evaporation rate. The transport resistance is made up of both Knudsen and viscous flow effects, with the magnitude of the Knudsen effect being approximately twice that of the viscous effects here. We also observe a phenomenon in sub-10 nm confinement wherein lower initial liquid saturation pressures trigger discontinuous evaporation, resulting in faster evaporation rates

Direct Visualization of Evaporation in a Two-Dimensional Nanoporous Model for Unconventional Natural Gas

Evaporation at the nanoscale is critical to many natural and synthetic systems including rapidly emerging unconventional oil and gas production from nanoporous shale reservoirs. During extraction processes, hydrocarbons confined to nanoscopic pores (ranging from one to a few hundred nanometers in size) can undergo phase change as pressure is reduced. Here, we directly observe evaporation in two-dimensional (2D) nanoporous media at the sub-10 nm scale. Using an experimental procedure that mimics pressure drawdown during shale oil/gas production, our results show that evaporation takes place at pressures significantly lower than predictions from the Kelvin equation (maximum deviation of 11%). We probe evaporation dynamics as a function of superheat and find that vapor transport resistance dominates evaporation rate. The transport resistance is made up of both Knudsen and viscous flow effects, with the magnitude of the Knudsen effect being approximately twice that of the viscous effects here. We also observe a phenomenon in sub-10 nm confinement wherein lower initial liquid saturation pressures trigger discontinuous evaporation, resulting in faster evaporation rates

Direct Visualization of Evaporation in a Two-Dimensional Nanoporous Model for Unconventional Natural Gas

Evaporation at the nanoscale is critical to many natural and synthetic systems including rapidly emerging unconventional oil and gas production from nanoporous shale reservoirs. During extraction processes, hydrocarbons confined to nanoscopic pores (ranging from one to a few hundred nanometers in size) can undergo phase change as pressure is reduced. Here, we directly observe evaporation in two-dimensional (2D) nanoporous media at the sub-10 nm scale. Using an experimental procedure that mimics pressure drawdown during shale oil/gas production, our results show that evaporation takes place at pressures significantly lower than predictions from the Kelvin equation (maximum deviation of 11%). We probe evaporation dynamics as a function of superheat and find that vapor transport resistance dominates evaporation rate. The transport resistance is made up of both Knudsen and viscous flow effects, with the magnitude of the Knudsen effect being approximately twice that of the viscous effects here. We also observe a phenomenon in sub-10 nm confinement wherein lower initial liquid saturation pressures trigger discontinuous evaporation, resulting in faster evaporation rates

Capillary Condensation in 8 nm Deep Channels

Condensation on the nanoscale is essential to understand many natural and synthetic systems relevant to water, air, and energy. Despite its importance, the underlying physics of condensation initiation and propagation remain largely unknown at sub-10 nm, mainly due to the challenges of controlling and probing such small systems. Here we study the condensation of <i>n</i>-propane down to 8 nm confinement in a nanofluidic system, distinct from previous studies at ∼100 nm. The condensation initiates significantly earlier in the 8 nm channels, and it initiates from the entrance, in contrast to channels just 10 times larger. The condensate propagation is observed to be governed by two liquid–vapor interfaces with an interplay between film and bridging effects. We model the experimental results using classical theories and find good agreement, demonstrating that this 8 nm nonpolar fluid system can be treated as a continuum from a thermodynamic perspective, despite having only 10–20 molecular layers