Convection in a mushy-layer along a heated wall

Motivated by the mushy zones of sea ice, volcanoes, and icy moons of the outer solar system, we perform a theoretical and numerical study of boundary-layer convection along a vertical heated wall in a bounded ideal mushy region. The mush is comprised of a porous and reactive binary alloy with a mixture of saline liquid in a solid matrix, and is studied in the near-eutectic approximation. Here we demonstrate the existence of four regions and study their behavior asymptotically. Starting from the bottom of the wall, the four regions are (i) an isotropic corner region; (ii) a buoyancy dominated vertical boundary layer; (iii) an isotropic connection region; and (iv) a horizontal boundary layer at the top boundary with strong gradients of pressure and buoyancy. Scalings from numerical simulations are consistent with the theoretical predictions. Close to the heated wall, the convection in the mushy layer is similar to a rising buoyant plume abruptly stopped at the top, leading to increased pressure and temperature in the upper region, whose impact is discussed as an efficient melting mechanism

Expression and function of aquaporins in human skin: Is aquaporin-3 just a glycerol transporter?

AbstractThe aquaporins (AQPs) are a family of transmembrane proteins forming water channels. In mammals, water transport through AQPs is important in kidney and other tissues involved in water transport. Some AQPs (aquaglyceroporins) also exhibit glycerol and urea permeability. Skin is the limiting tissue of the body and within skin, the stratum corneum (SC) of the epidermis is the limiting barrier to water loss by evaporation. The aquaglyceroporin AQP3 is abundantly expressed in keratinocytes of mammalian skin epidermis. Mice lacking AQP3 have dry skin and reduced SC hydration. Interestingly, however, results suggested that impaired glycerol, rather than water transport was responsible for this phenotype. In the present work, we examined the overall expression of AQPs in cells from human skin and we reviewed data on the functional role of AQPs in skin, particularly in the epidermis. By RT-PCR on primary cell cultures, we found that up to 6 different AQPs (AQP1, 3, 5, 7, 9 and 10) may be selectively expressed in various cells from human skin. AQP1, 5 are strictly water channels. But in keratinocytes, the major cell type of the epidermis, only the aquaglyceroporins AQP3, 10 were found. To understand the role of aquaglyceroporins in skin, we examined the relevance to human skin of the conclusion, from studies on mice, that skin AQP3 is only important for glycerol transport. In particular, we find a correlation between the absence of AQP3 and intercellular edema in the epidermis in two different experimental models: eczema and hyperplastic epidermis. In conclusion, we suggest that in addition to glycerol, AQP3 may be important for water transport and hydration in human skin epidermis

PLA scaffolds production from Thermally Induced Phase Separation: effect of process parameters and development of an environmentally improved route assisted by supercritical carbon dioxide

In this work, a relatively large scale of PLA scaffolds was produced using thermally induced phase separation (TIPS) combined with a supercritical carbon dioxide (SC-CO2) drying step as a green alternative. For the TIPS step, the phase separation of PLA and 1,4-dioxane solvent was controlled by adjusting the process conditions such as the polymer concentration and molecular weight, the 1,4-dioxane solvent power and the cooling conditions. The scaffolds morphology was analyzed by scanning electron microscopy. Their structural and mechanical properties were correlated together with the possibility to tune them by controlling the process conditions. An environmental analysis using the Life Cycle Assessment (LCA) methodology confirmed a reduction of at least 50% of the environmental impact of the whole process using the SC-CO2 drying compared to the traditional freeze-drying technology. This work is the first known attempt to conduct the LCA methodology on TIPS process for the PLA scaffolds production

Self-assembled monolayers of bisphosphonates: Influence of side chain steric hindrance

Bisphosphonates form self-assembled monolayers (SAMs) spontaneously on stainless steel, silicon, and titanium oxidized surfaces. We used contact angle measurements, atomic force microscopy, and X-ray reflectivity analysis to study the formation of SAMs on a model surface of ultraflat titanium (rms=0.2 nm). The results were extended to standard materials (mechanically polished titanium, stainless steel, and silicon) and showed that water-soluble bisphosphonic perfluoropolyether can easily form SAMs, with 100% surface coverage and a layer thickness of less than 3 nm. Hydrophobic (water contact angle >110° on stainless steel or titanium) and lipophobic (methylene iodide contact angle >105° on titanium) properties are discussed in terms of industrial applications

ClbP is a prototype of a peptidase subgroup involved in biosynthesis of nonribosomal peptides

The pks genomic island of Escherichia coli encodes polyketide (PK) and nonribosomal peptide (NRP) synthases that allow assembly of a putative hybrid PK-NRP compound named colibactin that induces DNA double-strand breaks in eukaryotic cells. The pks-encoded machinery harbors an atypical essential protein, ClbP. ClbP crystal structure and mutagenesis experiments revealed a serine-active site and original structural features compatible with peptidase activity, which was detected by biochemical assays. Ten ClbP homologs were identified in silico in NRP genomic islands of closely and distantly related bacterial species. All tested ClbP homologs were able to complement a clbP-deficient E. coli mutant. ClbP is therefore a prototype of a new subfamily of extracytoplasmic peptidases probably involved in the maturation of NRP compounds. Such peptidases will be powerful tools for the manipulation of NRP biosynthetic pathways

Optimization of an Injectable Hydrogel Depot System for the Controlled Release of Retinal-Targeted Hybrid Nanoparticles

A drawback in the development of treatments that can reach the retina is the presence of barriers in the eye that restrain compounds from reaching the target. Intravitreal injections hold promise for retinal delivery, but the natural defenses in the vitreous can rapidly degrade or eliminate therapeutic molecules. Injectable hydrogel implants, which act as a reservoir, can allow for long-term drug delivery with a single injection into the eye, but still suffer due to the fast clearance of the released drugs when traversing the vitreous and random diffusion that leads to lower pharmaceutic efficacy. A combination with HA-covered nanoparticles, which can be released from the gel and more readily pass through the vitreous to increase the delivery of therapeutic agents to the retina, represents an advanced and elegant way to overcome some of the limitations in eye drug delivery. In this article, we developed hybrid PLGA-Dotap NPs that, due to their hyaluronic acid coating, can improve in vivo distribution throughout the vitreous and delivery to retinal cells. Moreover, a hydrogel implant was developed to act as a depot for the hybrid NPs to better control and slow their release. These results are a first step to improve the treatment of retinal diseases by protecting and transporting the therapeutic treatment across the vitreous and to improve treatment options by creating a depot system for long-term treatments

Development of an eco-friendly Thermal Induced Phase Separation (TIPS) process assisted by supercritical CO2 for the production of PLA scaffolds with tunable structural and mechanical properties

Many routes are nowadays utilized for the production of PLA scaffolds. In this study, a relative large scale of scaffolds was produced combining thermal induced phase separation and supercritical CO2 as a green alternative drying. The phase separation between polylactic acid and 1,4-dioxane was monitored by adjusting the process parameters such as the polymer concentration, the molecular weight, the solvent power and the cooling conditions. The morphologic changes occurring during the phase separation were analyzed by scanning electron microscopy. Structural and mechanical properties of scaffolds were correlated and it was possible to tune them depending on the process parameters. Moreover, an environmental analysis of the thermal induced phase separation (TIPS) process and the comparison between supercritical CO2 and the traditional freeze drying technologies were investigated. This work is the first known attempt to conduct the life cycle assessment (LCA) methodology on TIPS process and the polylactic acid scaffolds production. The results of the LCA have demonstrated that using supercritical-CO2 drying technology allows to reduce by at least 50 % the environmental impact of the whole process and to drastically diminish the production time