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  1. The patterning of silicon and silicon oxide nanocones onto the surfaces of devices introduces interesting phenomena such as anti-reflection and super-transmissivity. While silicon nanocone formation is well-documented, current techniques to fabricate silicon oxide nanocones either involve complex fabrication procedures, non-deterministic placement, or poor uniformity. Here, we introduce a single-mask dry etching procedure for the fabrication of sharp silicon oxide nanocones with smooth sidewalls and deterministic distribution using electron beam lithography. Silicon oxide films deposited using plasma-enhanced chemical vapor deposition are etched using a thin alumina hard mask of selectivity > 88, enabling high aspect ratio nanocones with smooth sidewalls and arbitrary distribution across the target substrate. We further introduce a novel multi-step dry etching technique to achieve ultra-sharp amorphous silicon oxide nanocones with tip diameters of ~10 nm. The processes presented in this work may have applications in the fabrication of amorphous nanocone arrays onto arbitrary substrates or as nanoscale probes. 
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    Free, publicly-accessible full text available November 28, 2024
  2. Free, publicly-accessible full text available November 1, 2024
  3. Abstract

    In eukaryotes, many DNA/RNA-binding proteins possess intrinsically disordered regions (IDRs) with large negative charge, some of which involve a consecutive sequence of aspartate (D) or glutamate (E) residues. We refer to them as D/E repeats. The functional role of D/E repeats is not well understood, though some of them are known to cause autoinhibition through intramolecular electrostatic interaction with functional domains. In this work, we investigated the impacts of D/E repeats on the target DNA search kinetics for the high-mobility group box 1 (HMGB1) protein and the artificial protein constructs of the Antp homeodomain fused with D/E repeats of varied lengths. Our experimental data showed that D/E repeats of particular lengths can accelerate the target association in the overwhelming presence of non-functional high-affinity ligands (‘decoys’). Our coarse-grained molecular dynamics (CGMD) simulations showed that the autoinhibited proteins can bind to DNA and transition into the uninhibited complex with DNA through an electrostatically driven induced-fit process. In conjunction with the CGMD simulations, our kinetic model can explain how D/E repeats can accelerate the target association process in the presence of decoys. This study illuminates an unprecedented role of the negatively charged IDRs in the target search process.

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  4. High-precision potassium (K) isotope measurements in marine carbonates allow using this novel geochemical proxy to constrain seawater chemistry through geologic time. However, these measurements are still scarce due to the challenges of low-K contents in carbonates during K ion chromatography, such as insufficient sample purification, non-quantitative yield, and high accumulative blank. Here we optimize a dual-column K purification method that addresses these challenges, achieving a satisfactory K separation using 100–150 mg carbonates for routine high-precision K isotope analysis on the Sapphire™ MC-ICP-MS. We then report K isotope compositions in multiple certified reference materials, including limestone, dolostone, coral, and basalt for future inter-laboratory comparisons. The optimized K purification method provides great potential for future K isotope studies of marine carbonates. 
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    Multi-band photometric observations of 11 totally eclipsing contact binaries were carried out. Applying the Wilson–Devinney program, photometric solutions were obtained. There are two W-subtype systems, which are CRTS J133031.1+161202 and CRTS J154254.0+324652, and the rest of the systems are A-subtype systems. CRTS J154254.0 + 324652 has the highest fill-out factor with 94.3 per cent, and the lowest object is CRTS J155009.2 + 493639 with only 18.9 per cent. The mass ratios of the 11 systems are all less than 0.1, which means that they are extremely low-mass ratio binary systems. We performed period variation investigation and found that the orbital periods of three systems decrease slowly, which may be caused by the materials may transfer from the primary component to the secondary component, and those of six systems increase slowly, which indicates that the materials may transfer from the secondary component to the primary component. LAMOST low-resolution spectra of four objects were analysed, and using the spectral subtraction technique, Hα emission line was detected, which means that the four objects exhibit chromospheric activity. In order to understand their evolutionary status, the mass–luminosity and mass–radius diagrams were plotted. The two diagrams indicate that the primary component is in the main sequence evolution stage, and the secondary component is above TAMS, indicating that they are over-luminous. To determine whether the 11 systems are in a stable state, the ratio of spin angular momentum to orbital angular momentum (Js/Jo) and the instability parameters were calculated, and we argued that CRTS J234634.7 + 222824 is on the verge of a merger.

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