A three-dimensional covalent organic framework (COF-505) constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)-bisphenanthroline tetrafluoroborate, Cu(PDB)2(BF4), and benzidine (BZ). The copper centers are topologically independent of the weaving within the COF structure and serve as templates for bringing the threads into a woven pattern rather than the more commonly observed parallel arrangement. The copper(I) ions can be reversibly removed and added without loss of the COF structure, for which a tenfold increase in elasticity accompanies its demetalation. The threads in COF-505 have many degrees of freedom for enormous deviations to take place between them, throughout the material, without undoing the weaving of the overall structure.

Lignin as a polymer of monomeric aromatic compounds retains great potential to be a source for liquid fuels and valuable chemicals. However, lignin from biomass has been traditionally treated as a waste byproduct and in most applications burned for its heat value. In this work, we report the catalytic conversion of lignin in Miscanthus into aromatic products by using earth-abundant Ni catalyst supported on activated carbon, under relatively mild conditions. The special ferulate linkage in grasses gives methyl ferulate ester and its derivatives, which were not observed for wood biomass substrates. By modification of the reaction conditions, saturated or unsaturated branched products can be obtained selectively. Optimal conditions give over 68% yield of select aromatic products from lignin. Furthermore, after lignin depolymerization and upgrading, the carbohydrates of miscanthus were recovered as a solid residue, which upon treatment with iron chloride produced useful platform chemicals (furfurals and levulinic acid). On the basis of our study, all three major components of biomass (lignin, cellulose and hemicellulose) are effectively utilized, with an overall 55% conversion of total accessible biomass into high value chemicals with 98% mass balance.

We report a simple and continuous spinning method that combines twisting and shrinking processes to produce carbon nanotube yarns. In this method, a yarn freshly spun from a super-aligned carbon nanotube array is first twisted and then passes through a volatile solvent for shrinking. The as-produced yarn consists of densely packed carbon nanotubes, and thus has a tensile strength up to about 1 GPa. The tensile strength depends on the diameter and the twisting angle of the yarn. Different kinds of solvents, such as water, ethanol, and acetone, are used to shrink the twisted yarns, and acetone shows the best shrinking effect. The origin of the solvent shrinking effect is investigated. Our method is favorable for continuous mass production of high strength carbon nanotube yarns with a wide range of diameters, especially ultra-thin yarns.

Despite the tremendous advances that have been made in the last decade on developing useful machine-learning applications, their wider adoption has been hindered by the lack of strong assurance guarantees that can be made about their behavior. In this paper, we consider how formal verification techniques developed for traditional software systems can be repurposed for verification of reinforcement learningenabled ones, a particularly important class of machine learning systems. Rather than enforcing safety by examining and altering the structure of a complex neural network implementation, our technique uses blackbox methods to synthesizes deterministic programs, simpler, more interpretable, approximations of the network that can nonetheless guarantee desired safety properties are preserved, even when the network is deployed in unanticipated or previously unobserved environments. Our methodology frames the problem of neural network verification in terms of a counterexample and syntax-guided inductive synthesis procedure over these programs. The synthesis procedure searches for both a deterministic program and an inductive invariant over an infinite state transition system that represents a specification of an application's control logic. Additional specifications defining environment-based constraints can also be provided to further refine the search space. Synthesized programs deployed in conjunction with a neural network implementation dynamically enforce safety conditions by monitoring and preventing potentially unsafe actions proposed by neural policies. Experimental results over a wide range of cyberphysical applications demonstrate that software-inspired formal verification techniques can be used to realize trustworthy reinforcement learning systems with low overhead.

With limited current biomass utilization as a renewable resource, it is important to develop a method to convert biomass into materials to replace fossil fuel products.

ABSTRACT:The article presents an investigation into the use of plasticizers for reducing the degree of association existing within lignin molecules, in order to overcome adverse effects on the mechanical properties of its blends with a vinyl chloride-vinyl acetate (VC-VAc) copolymer. Infrared spectroscopy and differential scanning calorimetry were performed to examine the effect of the plasticizer type and concentration in plasticizing Alcell, an organosolv lignin. The results show that the compatibility and efficiency of a plasticizer are strongly influenced by the solubility parameter, which should be close to that of the lignin. Polyblends prepared with several plasticizers, Alcell lignin, and the VC-VAc copolymer were also investigated by thermal analysis and mechanical testing. Variations in the mechanical properties of these blends were found to correlate with the lignin dispersion quality and with the plasticizer efficiency in Alcell lignin.

Summary Mimivirus was initially identified as a bacterium because its dense, 125nm-long fibers stained Gram-positive. These fibers probably play a role during the infection of some host cells. The normal hosts of Mimivirus are unknown, but in the laboratory Mimivirus is usually propagated in amoeba. The structure of R135, a major component of the fibrous outer layer of Mimivirus, has been determined to 2Å resolution. The protein's structure is similar to members of the glucose-methanol-cholin oxidoreductase family, which have an N-terminal FAD binding domain and a C-terminal substrate recognition domain. The closest homologue to R135 is an aryl alcohol oxidase that participates in lignin biodegradation of plant cell walls. Thus R135 might participate in the degradation of their normal hosts, including some lignin-containing algae.

A commercial fast pyrolysis probe coupled with a high-resolution tandem mass spectrometer was employed to identify the initial reactions and products of fast pyrolysis of xylobiose and xylotriose, model compounds of xylans. Fragmentation of the reducing end by loss of an ethenediol molecule via ring-opening and retro-aldol condensation was found to be the dominant pyrolysis pathway for xylobiose, and the structure of the productβ-d-xylopyranosylglyceraldehydewas identified by comparing collision-activated dissociation of the ionized product and an ionized authentic compound. This intermediate can undergo further decomposition via the loss of formaldehyde to form β-d-xylopyranosylglycolaldehyde. In addition, the mechanisms of reactions leading to the loss of a water molecule or dissociation of the glycosidic linkages were explored computationally. These reactions are proposed to occur via pinacol ring contraction and/or Maccoll elimination mechanisms.