Cellulose can be dissolved in precooled (-12 °C) 7 wt % NaOH-12 wt % urea aqueous solution within 2 min. This interesting process, to our knowledge, represents the most rapid dissolution of native cellulose. The results from 13 C NMR, 15 N NMR, 1 H NMR, FT-IR, small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and wide-angle X-ray diffraction (WAXD) suggested that NaOH "hydrates" could be more easily attracted to cellulose chains through the formation of new hydrogen-bonded networks at low temperatures, while the urea hydrates could not be associated directly with cellulose. However, the urea hydrates could possibly be self-assembled at the surface of the NaOH hydrogen-bonded cellulose to form an inclusion complex (IC), leading to the dissolution of cellulose. Scattering experiments, including dynamic and static light scattering, indicated that most cellulose molecules, with limited amounts of aggregation, could exist as extended rigid chains in dilute solution. Further, the cellulose solution was relatively unstable and could be very sensitive to temperature, polymer concentration, and storage time, leading to additional aggregations. TEM images and WAXD provided experimental evidence on the formation of a wormlike cellulose IC being surrounded with urea. Therefore, we propose that the cellulose dissolution at -12 °C could arise as a result of a fast dynamic self-assembly process among solvent small molecules (NaOH, urea, and water) and the cellulose macromolecules.

We combine two amazing abilities found in nature: the superhydrophobic property of lotus leaf and the adhesive ability of mussel adhesive protein. The molecular structure mimic of the single units of adhesive proteins, dopamine, was polymerized in an alkaline aqueous solution to encapsulate microparticles. The as-formed thin polydopamine walls worked as reactive templates to generate silver nanoparticles on the capsuled particles. As a result, core/shell/satellite composite particles were generated with a hierarchical structure similar to the micromorphology of lotus leaf. The composite particles exhibited extremely water repellence after fluorination. Because dopamine can deposit and adhere to all kinds of materials, this method can be applied to diverse microparticles, from organic to inorganic. In addition, particles of different sizes and matters can be modified to superhydrophobic particles in one pot. Magnetic particles have also been prepared which could be used as oil-absorbent and magnetic controlled carriers. "Oil marbles" formed underwater were achieved for the first time.

In nature, there are vast singular structures or morphologies on biological surfaces that exhibit super-water-repellent properties. [1,2] The two-length-scaled hierarchical structure of the surface of the sacred lotus leaf is a good example. [3] In the meantime, the wetting ability of liquids on solid surfaces has become very important in daily life as well as in many industrial processes. Super-hydrophobic surfaces and super-amphiphobic surfacesÐi.e., surfaces that exhibit both water-repellent and oil-repellent propertiesÐhave attracted much interest because of potential practical applications.[4] Previous works on obtaining super-hydrophobic or super-amphiphobic surfaces have often used a combination of depressed surface energy and enhanced surface roughness.[4±16] However, the strict preparation conditions, multi-step processes, limited applicability, and high cost of the previous methods made forming large-area super-hydrophobic surfaces in ambient atmosphere for applications very difficult. Hence real applications of such super-hydrophobic or super-amphiphobic surfaces have been very limited. We describe in this communication a simple one-step casting process for creating a super-amphiphobic polymeric coating from two easily synthesized or commonly available polymer materialsÐpoly(methyl methacrylate) (PMMA) and fluorine-end-capped polyurethane (FPU)Ðin air without further modification. It is very exciting that such a polymer coating exhibits super-hydrophobic and lypophobic properties. The study also shows that the polymer surface possesses natural lotus-like micro-and nano-hierarchical structure. Our method reveals the possibility of one-step preparation of a super-hydrophobic polymer surface utilizing the difference in solubility of two common polymers in a solvent. We believe that this is the first report of creating a super-hydrophobic surface with such a simple casting process under ambient atmosphere.The scanning electron microscopy (SEM) images of the synthesized polymer surfaces are shown in Figure 1. No obvious structures were observed by SEM for the pure FPUcoated surface (Fig. 1a). The contact angle (CA) on the surface is about 95 (Fig. 2a), which indicates that FPU film has better hydrophobicity than pure polyurethane without the fluorine group, whose CA is about 65. The pure PMMA surface (Figs. 1b,c) is rough and the water CA on it is relatively high (145, Fig. 2b). However, the water drop is pinned on the PMMA surface. It is interesting that the hydrophobicity of the polymer surface changes dramatically if the film is directly prepared by a one-step coating of a FPU/PMMA mixture solution between 10 and 40 C. The CA increases to 166 (Fig. 2c).We also use sliding angle (SA) as a criterion for the evaluation of hydrophobicity of a solid surface. SA is a measure of the sliding properties of water droplets on the surface and is also considered an important property in deciding the superhydrophobicity. [17,18] Figure 3a shows that SA can be dramatically decreased with a small amount of FPU, reaching...

Hafnium oxide based ferroelectric thin films have shown potential as a promising alternative material for non-volatile memory applications. This work reports the switching stability of a Si-doped HfO2 film under bipolar pulsed-field operation. High field cycling causes a "wake-up" in virgin "pinched" polarization hysteresis loops, demonstrated by an enhancement in remanent polarization and a shift of negative coercive voltage. The rate of wake-up is accelerated by either reducing the frequency or increasing the amplitude of the cycling field. We suggest de-pinning of domains due to reduction of the defect concentration at bottom electrode interface as origin of the wake-up

With the development of microelectronic technology, the demand of insulating electronic encapsulation materials with high thermal conductivity is ever growing and much attractive. Surface modification of chemical inert h-BN is yet a distressing issue which hinders its applications in thermal conductive composites. Here, dopamine chemistry has been used to achieve the facile surface modification of h-BN microplatelets by forming a polydopamine (PDA) shell on its surface. The successful and effective preparation of h-BN@PDA microplatelets has been confirmed by SEM, EDS, TEM, Raman spectroscopy, and TGA investigations. The PDA coating increases the dispersibility of the filler and enhances its interaction with PVA matrix as well. Based on the combination of surface modification and doctor blading, composite films with aligned h-BN@PDA are fabricated. The oriented fillers result in much higher in-plane thermal conductivities than the films with disordered structures produced by casting or using the pristine h-BN. The thermal conductivity is as high as 5.4 W m(-1) K(-1) at 10 vol % h-BN@PDA loading. The procedure is eco-friendly, easy handling, and suitable for the practical application in large scale.

It was recently brought to our attention that our paper was missing information regarding when the patient chest computed tomography (CT) scans were obtained and that there were some discrepancies in the clinical metadata, associated with the very large image dataset, that we made publicly available through the China National Center for Bioinformation (http://ncov-ai.big.ac.cn/ download?lang=en). All of the chest CT and clinical metadata used in our prognostic analysis were collected from patients at the time of hospital admission, and we have now added this statement to the STAR Methods section of our paper. We believe that the errors in the clinical metadata were introduced when the chest CT images, clinical metadata, and codes were transferred to the web server, and we have now corrected the errors manually. Although these corrections do not alter any of the conclusions made in the paper, we do apologize for these errors and any confusion that they may have caused.

No abstract

In this article, we report a bioinspired approach to preparing stable, functional multilayer films by the integration of mussel-inspired catechol oxidative chemistry into a layer-by-layer (LbL) assembly. A polyanion of poly(acrylic acid-g-dopamine) (PAA-dopamine) bearing catechol groups, a mussel adhesive protein-mimetic polymer, was synthesized as the building block for LbL assembly with poly(allylamine hydrochloride) (PAH). The oxidization of the incorporated catechol group under mild oxidative condition yields o-quinone, which exhibits high reactivity with amine and catechol, thus endowing the chemical covalence and retaining the assembled morphology of multilayer films. The cross-linked films showed excellent stability even in extremely acidic, basic, and highly concentrated aqueous salt solutions. The efficient chemical cross-linking allows for the production of intact free-standing films without using a sacrificial layer. Moreover, thiol-modified multilayer films with good stability were exploited by a combination of thiols-catechol addition and then oxidative cross-linking. The outstanding stability under harsh conditions and the facile functionalization of the PAA-dopamine/PAH multilayer films make them attractive for barriers, separation, and biomedical devices.