Corrosion Protection by Trivalent Chromium Process (TCP) Coatings on Aluminum Alloys during Atmospheric Testing

Abstract Chromate conversion coatings (CCCs) provide effective localized corrosion protection to high strength aluminum alloys. As such, they have been widely employed in the aerospace industry. 1 However, the Cr(VI) they contain is a hazardous environmental pollutant. Therefore, significant effort has been focused on development of non-chrome alternatives that provide corrosion protection equivalent to CCCs. The Trivalent Chrome Process (TCP) coating is one of the leading replacements for CCCs. 2 Our previous study has revealed that the TCP coating has a biphasic structure with a hydrated ZrO 2 ·2H 2 O overlayer and an aluminofluoride interfacial layer on the three aluminum alloys (AA2024, 6061 and 7075). 3,4 The coating exhibited good stability during full immersion testing in air-saturated 0.5 M Na 2 SO 4 or NaCl. The good structural and chemical stability of the TCP coating on three alloys (AA2024, 6061 and 7075) was evidenced by an unchanging pit density on the TCPcoated samples during a 14-day exposure to humid air at both room temperature and 55 °C. Several electrochemical properties also reflect the stability of the TCP coating. For example, the polarization resistance (R p ) of the TCP-coated samples increased during a 14-day humidified air exposure at room temperature. This may be due to the formation of an aluminum oxide layer in the defects and imperfections of the coating. The R p values increased to a greater extent after a 14-day exposure at 55 °

Topography induced stiffness alteration of stem cells influences osteogenic differentiation

Topography-driven alterations in cell morphology tremendously influence cell biological processes, particularly stem cell differentiation. Aligned topography is known to alter the cell shape, which we anticipated to also induce altered physical properties of the cell. Here, we show that topography has a significant influence on single cell stiffness of human bone marrow derived-Mesenchymal Stem Cells (hBM-MSCs) and the osteogenic differentiation of these. Aligned topographies were used to control the cell elongation, depicted as the cell aspect ratio (C-AR). Intriguingly, an equal C-AR elicited from different topographies, resulted in highly altered differentiation behavior and the underlying single cell mechanics was found to be critical. The cell behavior was found to be focal adhesion-mediated and induced stiffness alterations rather than just influencing the cell elongation. The effect was further corroborated by investigations of the transcriptional regulators YAP. Our study provides insight into how mechanical properties of the cell, which are stimulated by topography, modulate the osteogenesis of hBM-MSCs, which is beneficial for improving the understanding of interactions between stem cells and topography for developing applications of tissue engineering and regenerative medicine

The BAF and PRC2 Complex Subunits Dpf2 and Eed Antagonistically Converge on Tbx3 to Control ESC Differentiation.

BAF complexes are composed of different subunits with varying functional and developmental roles, although many subunits have not been examined in depth. Here we show that the Baf45 subunit Dpf2 maintains pluripotency and ESC differentiation potential. Dpf2 co-occupies enhancers with Oct4, Sox2, p300, and the BAF subunit Brg1, and deleting Dpf2 perturbs ESC self-renewal, induces repression of Tbx3, and impairs mesendodermal differentiation without dramatically altering Brg1 localization. Mesendodermal differentiation can be rescued by restoring Tbx3 expression, whose distal enhancer is positively regulated by Dpf2-dependent H3K27ac maintenance and recruitment of pluripotency TFs and Brg1. In contrast, the PRC2 subunit Eed binds an intragenic Tbx3 enhancer to oppose Dpf2-dependent Tbx3 expression and mesendodermal differentiation. The PRC2 subunit Ezh2 likewise opposes Dpf2-dependent differentiation through a distinct mechanism involving Nanog repression. Together, these findings delineate distinct mechanistic roles for specific BAF and PRC2 subunits during ESC differentiation

Identification and Quantification of Proteoforms by Mass Spectrometry

A proteoform is a defined form of a protein derived from a given gene with a specific amino acid sequence and localized post-translational modifications. In top-down proteomic analyses, proteoforms are identified and quantified through mass spectrometric analysis of intact proteins. Recent technological developments have enabled comprehensive proteoform analyses in complex samples, and an increasing number of laboratories are adopting top-down proteomic workflows. In this review, we outline some recent advances and discuss current challenges and future directions for the field

Tumor Microbiome Diversity and Composition Influence Pancreatic Cancer Outcomes

Most patients diagnosed with resected pancreatic adenocarcinoma (PDAC) survive less than 5 years, but a minor subset survives longer. Here, we dissect the role of the tumor microbiota and the immune system in influencing long-term survival. Using 16S rRNA gene sequencing, we analyzed the tumor microbiome composition in PDAC patients with short-term survival (STS) and long-term survival (LTS). We found higher alpha-diversity in the tumor microbiome of LTS patients and identified an intra-tumoral microbiome signature (Pseudoxanthomonas-Streptomyces-Saccharopolyspora-Bacillus clausii) highly predictive of long-term survivorship in both discovery and validation cohorts. Through human-into-mice fecal microbiota transplantation (FMT) experiments from STS, LTS, or control donors, we were able to differentially modulate the tumor microbiome and affect tumor growth as well as tumor immune infiltration. Our study demonstrates that PDAC microbiome composition, which cross-talks to the gut microbiome, influences the host immune response and natural history of the disease. The distinct tumor microbiome from pancreatic cancer long-term survivors can be used to predict PDAC survival in humans, and transfer of long-term survivor gut microbiomes can alter the tumor microbiome and tumor growth in mouse models

Low Contact Barrier in 2H/1T' MoTe2 In-Plane Heterostructure Synthesized by Chemical Vapor Deposition.

Metal-semiconductor contact has been a critical topic in the semiconductor industry because it influences device performance remarkably. Conventional metals have served as the major contact material in electronic and optoelectronic devices, but such a selection becomes increasingly inadequate for emerging novel materials such as two-dimensional (2D) materials. Deposited metals on semiconducting 2D channels usually form large resistance contacts due to the high Schottky barrier. A few approaches have been reported to reduce the contact resistance but they are not suitable for large-scale application or they cannot create a clean and sharp interface. In this study, a chemical vapor deposition (CVD) technique is introduced to produce large-area semiconducting 2D material (2H MoTe2) planarly contacted by its metallic phase (1T' MoTe2). We demonstrate the phase-controllable synthesis and systematic characterization of large-area MoTe2 films, including pure 2H phase or 1T' phase, and 2H/1T' in-plane heterostructure. Theoretical simulation shows a lower Schottky barrier in 2H/1T' junction than in Ti/2H contact, which is confirmed by electrical measurement. This one-step CVD method to synthesize large-area, seamless-bonding 2D lateral metal-semiconductor junction can improve the performance of 2D electronic and optoelectronic devices, paving the way for large-scale 2D integrated circuits

Low Contact Barrier in 2H/1T′ MoTe2 In-Plane Heterostructure Synthesized by Chemical Vapor Deposition

Metal–semiconductor contact has been a critical topic in the semiconductor industry because it influences device performance remarkably. Conventional metals have served as the major contact material in electronic and optoelectronic devices, but such a selection becomes increasingly inadequate for emerging novel materials such as two-dimensional (2D) materials. Deposited metals on semiconducting 2D channels usually form large resistance contacts due to the high Schottky barrier. A few approaches have been reported to reduce the contact resistance but they are not suitable for large-scale application or they cannot create a clean and sharp interface. In this study, a chemical vapor deposition (CVD) technique is introduced to produce large-area semiconducting 2D material (2H MoTe2) planarly contacted by its metallic phase (1T′ MoTe2). We demonstrate the phase-controllable synthesis and systematic characterization of large-area MoTe2 films, including pure 2H phase or 1T′ phase, and 2H/1T′ in-plane heterostructure. Theoretical simulation shows a lower Schottky barrier in 2H/1T′ junction than in Ti/2H contact, which is confirmed by electrical measurement. This one-step CVD method to synthesize large-area, seamless-bonding 2D lateral metal–semiconductor junction can improve the performance of 2D electronic and optoelectronic devices, paving the way for large-scale 2D integrated circuits

A reversible single-molecule switch based on activated antiaromaticity

Single-molecule electronic devices provide researchers with an unprecedented ability to relate novel physical phenomena to molecular chemical structures. Typically, conjugated aromatic molecular backbones are relied upon to create electronic devices, where the aromaticity of the building blocks is used to enhance conductivity. We capitalize on the classical physical organic chemistry concept of Hückel antiaromaticity by demonstrating a single-molecule switch that exhibits low conductance in the neutral state and, upon electrochemical oxidation, reversibly switches to an antiaromatic high-conducting structure. We form single-molecule devices using the scanning tunneling microscope–based break-junction technique and observe an on/off ratio of ~70 for a thiophenylidene derivative that switches to an antiaromatic state with 6-4-6-π electrons. Through supporting nuclear magnetic resonance measurements, we show that the doubly oxidized core has antiaromatic character and we use density functional theory calculations to rationalize the origin of the high-conductance state for the oxidized single-molecule junction. Together, our work demonstrates how the concept of antiaromaticity can be exploited to create single-molecule devices that are highly conducting