Earth-like sand fluxes on Mars

Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving—implying large sand fluxes—or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar

Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux

Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1–100 km scale) of T_s=0.01±0.0015 N m^(−2)

Structures of the Ets Protein DNA-binding Domains of Transcription Factors Etv1, Etv4, Etv5, and Fev: Determinants of DNA Binding and Redox Regulation by Disulfide Bond Formation.

Ets transcription factors, which share the conserved Ets DNA-binding domain, number nearly 30 members in humans and are particularly involved in developmental processes. Their deregulation following changes in expression, transcriptional activity, or by chromosomal translocation plays a critical role in carcinogenesis. Ets DNA binding, selectivity, and regulation have been extensively studied; however, questions still arise regarding binding specificity outside the core GGA recognition sequence and the mode of action of Ets post-translational modifications. Here, we report the crystal structures of Etv1, Etv4, Etv5, and Fev, alone and in complex with DNA. We identify previously unrecognized features of the protein-DNA interface. Interactions with the DNA backbone account for most of the binding affinity. We describe a highly coordinated network of water molecules acting in base selection upstream of the GGAA core and the structural features that may account for discrimination against methylated cytidine residues. Unexpectedly, all proteins crystallized as disulfide-linked dimers, exhibiting a novel interface (distant to the DNA recognition helix). Homodimers of Etv1, Etv4, and Etv5 could be reduced to monomers, leading to a 40-200-fold increase in DNA binding affinity. Hence, we present the first indication of a redox-dependent regulatory mechanism that may control the activity of this subset of oncogenic Ets transcription factors

ECMO for COVID-19 patients in Europe and Israel

Since March 15th, 2020, 177 centres from Europe and Israel have joined the study, routinely reporting on the ECMO support they provide to COVID-19 patients. The mean annual number of cases treated with ECMO in the participating centres before the pandemic (2019) was 55. The number of COVID-19 patients has increased rapidly each week reaching 1531 treated patients as of September 14th. The greatest number of cases has been reported from France (n = 385), UK (n = 193), Germany (n = 176), Spain (n = 166), and Italy (n = 136) .The mean age of treated patients was 52.6 years (range 16–80), 79% were male. The ECMO configuration used was VV in 91% of cases, VA in 5% and other in 4%. The mean PaO2 before ECMO implantation was 65 mmHg. The mean duration of ECMO support thus far has been 18 days and the mean ICU length of stay of these patients was 33 days. As of the 14th September, overall 841 patients have been weaned from ECMO support, 601 died during ECMO support, 71 died after withdrawal of ECMO, 79 are still receiving ECMO support and for 10 patients status n.a. . Our preliminary data suggest that patients placed on ECMO with severe refractory respiratory or cardiac failure secondary to COVID-19 have a reasonable (55%) chance of survival. Further extensive data analysis is expected to provide invaluable information on the demographics, severity of illness, indications and different ECMO management strategies in these patients

Surface modifications of metallic electrodes for the reduction of inflammatory response after implantation

Nerve implanted prostheses are of great interest for the recovery of damaged neurological functions by the electrical stimulation of the peripheral or central nervous system. The small size of the stimulation electrodes requires optimized electrical properties for sufficient recording/stimulating ability. This involves a close and long-lasting contact between the stimulation electrode and the biological tissues, weakened by the inflammatory reaction occuring after implantation. Improving this contact is one of the main challenges that must be faced in the development of long-term active implantable stimulators. Surface modifications of the materials intended for implantation are one of the keys evoked to control and improve the occurrence of the reactions to implantation, and reconcile both sides of the nerve/electrode interface. In this thesis, we explore three types of surface modifications to address interfacial issues of stimulation electrodes. First, the physical (or structural) modification of the stimulation surface itself is performed through the creation of a model nano-structuration on the metallic surface, by a brush of self-standing metallic pillars of nanometric dimensions. The structures are observed and characterized, and the electrical properties of nano-featured electrodes are shown to be improved. Moreover, this model nanotopography is shown to have peculiar effects on cells adhesion, morphology and growth. In the second chapter, we present the development of a method allowing the easy and reproducible fabrication of switchable conducting polymer-coated electrodes (polypyrrole) for the local and electrically-controlled delivery of anti-inflammatory dexamethasone molecules. Two techniques are investigated for the liberation of molecules and optimized for the control on the quantity liberated and the properties of the films, cyclic voltammetry and biphasic pulse potential pulses stimulation. Moreover, the development of a new device for the in-vivo stimulation of polypyrrole-coated metallic electrodes by biphasic potential pulses with determined parameters is evoked, and the first in-vivo experiments carried out. Finally, we present a fabrication process of polypyrrole copolymeric films with specific chemical groups allowing further modifications. We demonstrate that the composition of the copolymer films based on modified pyrrole units can be tailored by playing on different independent electrosynthesis parameters. We also prove the possibility to synthesize multilayer polypyrrole structures for the simultaneous controlled delivery of molecules and grafting of biologically active groups at the surface of the outer layer.(FSA 3) -- UCL, 201

Nanostructured electrodes covered with polypyrrole to improve impedance and controlled local anti-inflammatory drug delivery.

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Dexamethasone electrically controlled release from polypyrrole-coated nanostructured electrodes.

One of the key challenges to engineering neural interfaces is to reduce their immune response toward implanted electrodes. One potential approach to minimize or eliminate this undesired early inflammatory tissue reaction and to maintain signal transmission quality over time is the delivery of anti-inflammatory biomolecules in the vicinity of the implant. Here, we report on a facile and reproducible method for the fabrication of high surface area nanostructured electrodes coated with an electroactive polymer, polypyrrole (PPy) that can be used to precisely release drug by applying an electrical stimuli. The method consists of the electropolymerization of PPy incorporated with drug, dexamethasone (DEX), onto a brush of metallic nanopillars, obtained by electrodeposition of the metal within the nanopores of gold-coated polycarbonate template. The study of the release of DEX triggered by electrochemical stimuli indicates that the system is a true electrically controlled release system. Moreover, it appears that the presence of metallic nanowires onto the electrode surface improves the adherence between the polymer and the electrode and increases the electroactivity of the PPy coating

Device and method for electrochemically releasing a composition in a controlled manner

According to a first aspect, the invention relates to a device (10) for electrochemically releasing a composition and comprising: one working electrode (30) comprising an electroactive conjugated polymer (40) containing or doped with said composition, a counter electrode (50), and a reference electrode (60). The device (10) is characterized in that it comprises electrical means (95, 100; 320; 165, 180) connected to the working electrode (30) and to the counter electrode (50) for obtaining at said working electrode (30) at least one composition releasing sequence (65) with respect to said reference electrode (60), each composition releasing sequence (65) comprising: a first voltametric pulse (70), followed by a rest period (80) during which no current is able to flow through said working electrode (30), followed by a second voltametric pulse (90), followed by an intermediate period (160) during which no current is able to flow through said working electrode (30)

Multifunctional nanostructures for controlled and targeted drug delivery

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Electrosynthesis of pyrrole 3-carboxylic acid copolymer films and nanotubes with tunable degree of functionalization for biomedical applications

Tailoring polypyrrole (PPy), an electroactive polymer, with functional groups to which a variety of bioactive molecules can be tethered is highly attractive for building biological structures on conducting surfaces for a range of biomedical applications. In this respect, we investigate the effects of three independent electrosynthesis parameters, namely the applied potential, the composition of the comonomer solution and the film thickness on the incorporation of carboxylic acid-functionalized pyrrole units (Py-COOH) into polypyrrole/Py-COOH copolymer films. FT-IR, XPS and fluorescence microscopy results show that a larger Py-COOH content is inserted in films electrosynthesized at low potential, that the surface functionality of the copolymer films increases with the molar percentage of Py-COOH in the comonomer solution, and that Py-COOH units are preferentially incorporated in the earlier stage of the electrosynthesis process. The method is further adapted for preparing functionalized PPy copolymer nanotubes with potential application in drug delivery. Specifically, functionalized copolymer nanotubes are electrosynthesized through the template method in polycarbonate membrane. Carboxylic acid groups available at the outer surface of these nanostructures are then derivatized to covalently immobilize poly(ethylene glycol) chains, a protein-repellent polymer, so as to enhance the antifouling properties of these promising delivery vehicles