Multiscale structural design of columns made of regular octet-truss lattice material

This paper focuses on the structural design of the microscopic architecture of a lattice material with regular octet-truss cell topology and on the multiscale design of an axially loaded member manufactured of this type of cellular solid. The rationale followed here hinges on the coincidence of the failure modes of a stretching dominated lattice material, which experiences two types of microscopic failure modes, namely, elastic buckling and plastic yielding. A lattice material that fails by the elastic buckling of its cell elements without reaching the plastic yielding is far from optimum. To avoid this event and improve the material strength, we first start to tailor the structural efficiencies of the cell elements. We show that by shaping the cell element cross-sections, the lattice material buckling resistance can increase until it equals the cell element yield strength, thereby exploiting fully the lattice material strength. The coincidence of these two failure modes is the structural criterion used to develop selection charts for the micro-structural design of the octet-truss lattice material. In the second part of the paper, we examine the design of a structural column manufactured by regular octet-truss lattice material. We show that to maximize the structural failure resistance at both the structural and the material levels, the global buckling and the yielding failure of the column must occur simultaneously with the microscopic failure modes of the lattice material, namely the local buckling and the yielding of its microscopic cell elements. The paper concludes by illustrating how the micro-truss geometry and the column cross-section can be simultaneously designed to fully exploit the strength of the material and the overall macrostructure.     

Aggregation and fractal formation of Au and TiO<Subscript>2</Subscript> nanostructures obtained by fs-pulsed laser deposition: experiment and simulation

In the synthesis of nanostructures by pulsed laser deposition (PLD), a crucial role is played by the environmental deposition pressure and the substrate temperature. Due to the high temperature of nanoparticles (NPs) at landing, other factors may determine the structure of the resulting aggregates. Here, Au and TiO₂ nanostructures are obtained by non-thermal fs-PLD in ambient conditions. On Si(100), only TiO₂ NPs form fractals with areas up to ~ 1 × 10⁶ nm², while on quartz Au NPs also form fractals with areas up to ~ 5 × 10³ nm², a much smaller size with respect to the TiO₂ case. The aggregation is described by a simple diffusive model, taking into account isotropic diffusion of the NPs, allowing quantitative simulations of the NPs and fractal area. The results highlight the key role of substrate thermal conductivity in determining the formation of fractals.

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Functionality‐Independent DNA Encoding of Complex Natural Products

DNA encoded chemical libraries (DELs) link the powers of genetics and chemical synthesis via combinatorial optimization. Through combinatorial chemistry, DELs can grow to the unprecedented size of billions to trillions. To take full advantage of the DEL approach, linking the power of genetics directly to chemical structures would offer even greater diversity in a finite chemical world. Natural products have evolved an incredible structural diversity along with their biological evolution. Herein, we used traditional Chinese medicines (TCMs) as examples in a late‐stage modification toolbox approach to annotate these complex organic compounds with amplifiable DNA barcodes, which could be easily incorporated into a DEL. The method of end‐products labeling also generates a cluster of isomers with a single DNA tag at different sites. These isomers provide an additional spatial diversity for multiple accessible pockets of targeted proteins. Notably, a novel PARP1 inhibitor from TCM has been identified from the natural products enriched DEL (nDEL).     

Isothermal and non-isothermal water transport in porous membranes. I. The power balance

A quantitative study of water transport through porous, unselective membranes of various types is presented. Effects produced by hydraulic pressure are compared with those due to a transmembrane temperature gradient. p]The quantities directly determined for five types of porous partitions of different structure are: hydraulic permeability, thermoosmotic permeability, activation energies of both these transport processes and thermal pressure. Experiments have been systematically conducted at temperatures from +20°C to +60°C. From the experimental data, thermohydraulic conductivity, thermal conductivity, heat of transport, ratio of conductive to convective heat fluxes and thermodynamic efficiency of the transport process have been calculated. Each of these quantities is expressed in terms of specific physical properties of system's components. p]These findings provide deeper insight in the fundamental physico-chemical aspects of thermodialysis, and open at the same time promising perspectives of practical applications for this process of direct transformation of thermal into mechanical (and electrochemical) energy.     

Indoles from Alkynes and Aryl Azides: Scope and Theoretical Assessment of Ruthenium Porphyrin-Catalyzed Reactions

A symbiotic experimental/computational study analyzed the Ru(TPP)(NAr)₂-catalyzed one-pot formation of indoles from alkynes and aryl azides. Thirty different C₃-substituted indoles were synthesized and the best performance, in term of yields and regioselectivities, was observed when reacting ArC≡CH alkynes with 3,5-(EWG)₂C₆H₃N₃ azides, whereas the reaction was less efficient when using electron-rich aryl azides. A DFT analysis describes the reaction mechanism in terms of the energy costs and orbital/electronic evolutions; the limited reactivity of electron-rich azides was also justified. In summary, PhC≡CH alkyne interacts with one NAr imido ligand of Ru(TPP)(NAr)₂ to give a residually dangling C(Ph) group, which, by coupling with a C(H) unit of the N-aryl substituent, forms a 5+6 bicyclic molecule. In the process, two subsequent spin changes allow inverting the conformation of the sp² C(Ph) atom and its consequent electrophilic-like attack to the aromatic ring. The bicycle isomerizes to indole via a two-step outer sphere H-migration. Eventually, a ′Ru(TPP)(NAr)′ mono-imido active catalyst is reformed after each azide/alkyne reaction.     

Identification of Broad-Spectrum MMP Inhibitors by Virtual Screening

Matrix metalloproteinases (MMPs) are the family of proteases that are mainly responsible for degrading extracellular matrix (ECM) components. In the skin, the overexpression of MMPs as a result of ultraviolet radiation triggers an imbalance in the ECM turnover in a process called photoaging, which ultimately results in skin wrinkling and premature skin ageing. Therefore, the inhibition of different enzymes of the MMP family at a topical level could have positive implications for photoaging. Considering that the MMP catalytic region is mostly conserved across different enzymes of the MMP family, in this study we aimed to design a virtual screening (VS) workflow to identify broad-spectrum MMP inhibitors that can be used to delay the development of photoaging. Our in silico approach was validated in vitro with 20 VS hits from the Specs library that were not only structurally different from one another but also from known MMP inhibitors. In this bioactivity assay, 18 of the 20 compounds inhibit at least one of the assayed MMPs at 100 μM (with 5 of them showing around 50% inhibition in all the tested MMPs at this concentration). Finally, this VS was used to identify natural products that have the potential to act as broad-spectrum MMP inhibitors and be used as a treatment for photoaging.