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Abstract--Understanding how endangered species use nursery habitats is vital for recovery planning. Research on the smalltooth sawfish (Pristis pectinata) has shown that areas of estuarine nurseries, called hotspots, are used [...]

Background: The cadherin‐associated protein p120 catenin regulates convergent extension through interactions with cadherin proteins, Cdc42, and Rac1, as we previously showed in zebrafish (Danio rerio). Phosphorylation of p120 catenin changes the nature of its activity in vitro but is virtually unexplored in embryos. We used our previously developed antisense RNA splice‐site morpholino targeted to endogenous p120 catenin‐δ1 to cause defects in axis elongation probing the functions of three p120 catenin tyrosine‐phosphorylation sites in gastrulating zebrafish embryos. Results: The morpholino‐induced defects were rescued by co‐injections with mouse p120 catenin‐δ1‐3A mRNAs mutated at residues Y228 and Y217 to a non‐phosphorylatable phenylalanine (F) or mutated at residue Y335 to a phosphomimetic glutamic acid (E). Co‐injection of the complementary mutations Y228E, Y217E, or Y335F mRNAs partially rescued embryos whereas dual mutation to Y228E‐Y217E blocked rescue. Immunopurification showed Y228F mutant proteins preferentially interacted with Rac1, potentially promoting cell migration. In contrast, the phosphomimetic Y228E preferentially interacted with E‐cadherin increasing adhesion. Both Y228F and Y335F strongly bind VAV2. Conclusions: p120 catenin serves dual roles during gastrulation of zebrafish. Phosphorylation and dephosphorylation of tyrosine residues Y217, Y228, and Y335 precisely balance cell adhesion and cell migration to facilitate somite compaction and axis elongation. Key Findings: Knockdown of zebrafish p120 catenin‐δ1 with a morpholino blocks migration of presomitic mesoderm and extension of the dorsal axis.We compared rescue of morphology by injecting mouse p120 catenin‐δ1‐3A (CTNND1‐3A) mRNAs mutated to phosphomimetic (E) and nonphosphorylatable (F) versions of tyrosine residues.Mutations to Y228F, Y228E, Y217F, or Y335E rescued morphology; mutation to Y217E, or Y335F mRNAs only partially rescued; and dual mutation to Y228E‐Y217E blocked rescue.Immunopurification showed Y228F mutant proteins preferentially binding to Rac1, potentially promoting cell migration, and the Y228E protein preferentially binding with E‐cadherin increasing adhesion. Both Y228F and Y335F bound strongly to VAV2.We show the importance of phosphorylation state for regulating adhesion and mesodermal cell migration in early vertebrate morphogenesis. [ABSTRACT FROM AUTHOR]

Thin films bonded to compliant substrates often develop wrinkles when subjected to an applied or inherent compressive stress. This paper presents a bilayer model to account for surface effects on the wrinkling of ultrathin solid films. Assuming a surface layer of finite thickness, effects of surface properties on the critical strain, the equilibrium wavelength, and the wrinkle amplitude are discussed in comparison with conventional analysis. We apply this model to explain experimental observations of wrinkling in thin polymer films. The measured wrinkle wavelengths and amplitudes deviate from conventional analysis for ultrathin films with thickness less than 30 nm. The bilayer model provides a consistent understanding of the observed deviations, based on which a set of material properties for the surface and the bulk of the polymer films are deduced from the experimental data. DOI: 10.1061/(ASCE)0893-1321(2007)20:1(38) CE Database subject headings: Models; Aerospace engineering; Compressive strength; Polymers; Material properties.

We investigate the relaxation dynamics of thin polymer films at temperatures below the bulk glass transition Tg by first compressing polystyrene films supported on a polydimethylsiloxane substrate to create wrinkling patterns and then observing the slow relaxation of the wrinkled films back to their final equilibrium flat state by small angle light scattering. As with recent relaxation measurements on thin glassy films reported by Fakhraai and co-workers, we find the relaxation time of our wrinkled films to be strongly dependent on film thickness below an onset thickness on the order of 100 nm. By varying the temperature between room temperature and Tg (*100 °C), we find that the relaxation time follows an Arrhenius-type temperature dependence to a good approximation at all film thicknesses investigated, where both the activation energy and the relaxation time pre-factor depend appreciably on film thickness. The wrinkling relaxation curves tend to cross at a common temperature somewhat below Tg, indicating an entropy-enthalpy compensation relation between the activation free energy parameters. This compensation effect has also been observed recently in simulated supported polymer films in the high temperature Arrhenius relaxation regime rather than the glassy state. In addition, we find that the film stress relaxation function, as well as the height of the wrinkle ridges, follows a stretched exponential time dependence and the short-time effectiveYoung's modulus derived from our modeling decreases sigmoidally with increasing temperature--both characteristic features of glassy materials. The relatively facile nature of the wrinkling-based measurements in comparison to other film relaxation measurements makes our method attractive for practical materials development, as well as fundamental studies of glass formation. [ABSTRACT FROM AUTHOR]

Scalable, solution‐deposited metal oxide (MO) thin films could enable low‐cost, flexible, large‐area electronics; however, the poor morphology of the typically polycrystalline films limits performance. It is demonstrated that optimized coating thickness leads to high‐quality crystalline films in blade‐coated indium oxide (In2O3) ultra‐thin‐film (8 nm) transistors (TFTs). TFTs are fabricated with total channel thickness ranging from 2 to 16 nm via varied multistep processes. Transport in channels fabricated from sequential, thin (≤4 nm) coatings significantly exceeds that from thicker coatings. A marked change is found in the In2O3 crystal texture with coating thickness. Single, thin coatings ≤4 nm produce smooth films with strong (111) texture while thicker coatings are rougher and exhibit little texture. Sequential thin coatings exhibit homoepitaxy. In addition to the improved transport due to the smooth, aligned films, it is found that deposition of sequential thin layers leads to the highest mobility, with either In2O3 or ZnO as the overcoat. This suggests defects at the air interface of the initial thin films limit performance. Optimizing coating thickness and sequence, it is demonstrated 8 nm thick channel In2O3 TFTs exhibiting percolation conduction with an impressive average saturation electron mobility (μsat) of (36.1 ± 0.9) cm2 V−1 s−1 (best‐performing device of 58.0 cm2 V−1 s−1). [ABSTRACT FROM AUTHOR]

Reverse osmosis using aromatic polyamide membranes is currently the most important technology for seawater desalination. The performance of reverse osmosis membranes is highly dependent on the interplay of their surface chemical groups with water and water contaminants. In order to better understand the underlying mechanisms of these membranes, we study ultrathin polyamide films that chemically resemble reverse osmosis membranes, using ambient pressure X-ray photoelectron spectroscopy. This technique can identify the functional groups at the membrane–water interface and allows monitoring of small shifts in the electron binding energy that indicate interaction with water. We observe deprotonation of free acid groups and formation of a 'water complex' with nitrogen groups in the polymer upon exposure of the membrane to water vapour. The chemical changes are reversed when water is removed from the membrane. While the correlation between functional groups and water uptake is an established one, this experiment serves to understand the nature of their chemical interaction, and opens up possibilities for tailoring future materials to specific requirements. [ABSTRACT FROM AUTHOR]

Oxidation of the Ag nanoparticle surface is shown to have an impact on the adsorption, orientation, and SERS detection limit of nitroaromatic molecules in aqueous solution. Ultrasensitive SERS detection of p-nitrophenol is achieved when oxidation of surface-immobilized Ag nanoparticles is inhibited by replacing the oxygen dissolved in water with argon gas.

The properties of thin supported polymer films can be dramatically impacted by the substrate upon which it resides. A simple way to alter the properties of the substrate (chemistry, rigidity, dynamics) is by coating it with an immiscible polymer. Here, we describe how ultrathin (ca. 2 nm) hydrophilic polymer layers of poly(acrylic acid) and poly(styrene sulfonate) (PSS) impact the aging behavior and the residual stress in thin films of poly(butylnorbornene‐ran‐hydroxyhexafluoroisopropyl norbornene) (BuNB‐r‐HFANB). The aging rate decreases as the film thickness (h) is decreased, but the extent of this change depends on the adjacent layer. Even for the thickest films (h > 500 nm), there is a decrease in the aging rate at 100 °C when BuNB‐r‐HFANB is in contact with PSS. In an effort to understand the origins of these differences in the aging behavior, the elastic modulus and residual stress (σR) in the films were determined by wrinkling as a function of aging time. The change in the elastic modulus during aging does not appear to be directly correlated with the densification or expansion of the films, but the aging rates appear to roughly scale as hσR1/3. These results illustrate that the physical aging of thin polymer films can be altered by adjacent polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 992–1000 [ABSTRACT FROM AUTHOR]

Abstract Polymers with a strong size-sieving ability and superior H 2 /CO 2 selectivity at 100 °C or above are of great interests for pre-combustion CO 2 capture. Polyimides (such as Matrimid and 6FDA-durene) have been cross-linked using diamines and show superior H 2 /CO 2 selectivity. However, these cross-linked polymers cannot be used for the pre-combustion CO 2 capture because of the lack of thermal stability at 100 °C. Herein we demonstrate that commercial P84™ can be chemically cross-linked using 1,4-butanediamine (BuDA) to achieve robust H 2 /CO 2 separation properties at 100–150 °C. The cross-linked P84 were thoroughly evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The effects of the cross-linking time on the physical properties and H 2 /CO 2 separation properties at various temperatures were determined and interpreted using a free volume model. An exemplary sample based on P84 cross-linked by BuDA for 6 h exhibits a H 2 permeability of 47 Barrers (1 Barrer = 3.35 × 10–16 mol m/m2 s Pa) and H 2 /CO 2 selectivity of 14 at 100 °C, which is on the Robeson's upper bound, indicating their potential for practical applications. Graphic abstract fx1 Highlights • Cross-linking P84™ using 1,4-butanediamine improves H 2 /CO 2 selectivity at 150 °C. • Cross-linked P84 is stable at temperatures up to 400 °C. • Cross-linking decreases the polymer free volume and increases size-sieving ability. [ABSTRACT FROM AUTHOR]