Total Syntheses of (±)-Rhodonoids C, D, E, F, and G and Ranhuadujuanine B

Here we describe the divergent, biosynthetically inspired syntheses of (±)-rhodonoids C–G and (±)-ranhuadujuanine B. The key steps of the syntheses include the construction of the chromene unit through a formal oxa-[3 + 3] annulation and a biomimetic acid-catalyzed ring cyclization. Cationic [2 + 2] cycloaddition is accomplished to form the cyclobutane core of (±)-rhodonoids E and F

MADM-based smart parking guidance algorithm

<div><p>In smart parking environments, how to choose suitable parking facilities with various attributes to satisfy certain criteria is an important decision issue. Based on the multiple attributes decision making (MADM) theory, this study proposed a smart parking guidance algorithm by considering three representative decision factors (i.e., walk duration, parking fee, and the number of vacant parking spaces) and various preferences of drivers. In this paper, the expected number of vacant parking spaces is regarded as an important attribute to reflect the difficulty degree of finding available parking spaces, and a queueing theory-based theoretical method was proposed to estimate this expected number for candidate parking facilities with different capacities, arrival rates, and service rates. The effectiveness of the MADM-based parking guidance algorithm was investigated and compared with a blind search-based approach in comprehensive scenarios with various distributions of parking facilities, traffic intensities, and user preferences. Experimental results show that the proposed MADM-based algorithm is effective to choose suitable parking resources to satisfy users’ preferences. Furthermore, it has also been observed that this newly proposed Markov Chain-based availability attribute is more effective to represent the availability of parking spaces than the arrival rate-based availability attribute proposed in existing research.</p></div

An Efficient, Practical, and Enantioselective Method for Synthesis of Homoallenylamides Catalyzed by an Aminoalcohol-Derived, Boron-Based Catalyst

A practical catalytic method for enantio­selective addition of an allene unit to aldimines is disclosed. Transformations are promoted by an in-situ-generated B-based catalyst that is derived from a simple, robust, and readily accessible (in multigram quantities) chiral aminoalcohol. A range of aryl-, heteroaryl-, and alkyl-substituted homoallenylamides can be obtained in 66–91% yield and 84:16 to >99:1 enantiomeric ratio through reactions performed at ambient temperature and in the presence of 0.1–3.0 mol% of the chiral catalyst and a commercially available allenylboron reagent. The catalytic protocol does not require strict anhydrous conditions, can be performed on gram scale, and promotes highly selective addition of an allenyl unit (vs a propargyl group). The utility of the approach is demonstrated through development of succinct approaches to syntheses of anisomycin and <i>epi</i>-cytoxazone

Total Syntheses of (±)-Rhodonoids A and B and C12-<i>epi</i>-Rhodonoid B

Total syntheses of (±)-rhodonoids A and B and C12-<i>epi</i>-rhodonoid B are described here. A unified strategy employed in these syntheses is an intramolecular <i>oxa</i>-[3 + 3] annulation for accessing the chromene unit. A Fe­(OTf)₃-promoted diastereoselective cationic [2 + 2] cycloaddition and a photochemical [2 + 2] cycloaddition were featured to construct the cyclobutane core of (±)-rhodonoids A and B and C12-<i>epi</i>-rhodonoid B, respectively. Fe­(OTf)₃ also leads to an interesting bridged tetracycle, which was unambiguously confirmed by single crystal X-ray analysis

Control parameters for generating parking facilities and vehicles.

<p>Control parameters for generating parking facilities and vehicles.</p

Strain Concentration at the Boundaries in 5‑Fold Twins of Diamond and Silicon

Widely found in metals, semiconductors, oxides, and even organic materials, multiple twinning has important implications in engineering applications of materials. In this work, the intrinsic strain in 5-fold twins of diamond and silicon has been studied combining aberration-corrected electron microscopy and first-principles calculations. In contrast to metallic 5-fold twins, where the strain distribution is relatively smooth, the semiconductor systems show significant strain concentration at the twin boundaries, which is shear modulus dependent. In silicon with moderate strain concentration, the electronic frontier orbitals are located at the center of the 5-fold twins. Accompanying the increased strain concentration in diamond, however, the frontier orbitals are pushed to the surface. The modification of strain state and surface electronic structure by materials elasticity suggest possible routes to tune catalytic, electronic, and mechanical properties of materials

Framework of the online realtime smart parking guidance system.

<p>Framework of the online realtime smart parking guidance system.</p

Representative preferences of the MADM-based parking guidance algorithm.

<p>Representative preferences of the MADM-based parking guidance algorithm.</p

Example transition probabilities and the availability of vacant parking spaces of two parking facilities <i>P</i>₁ and <i>P</i>₂ with capacity 5.

<p>Example transition probabilities and the availability of vacant parking spaces of two parking facilities <i>P</i>₁ and <i>P</i>₂ with capacity 5.</p

Quadruple-Stimuli-Sensitive Polymeric Nanocarriers for Controlled Release under Combined Stimulation

Here we report a novel quadruple-stimuli-responsive block copolymer nanocarrier sensitive to pH, temperature, light, and reducing agent. The well-defined amphiphilic diblock copolymer poly­(2-nitrobenzyl methacrylate)-SS-poly­(dimethylaminoethyl methacrylate) (PNBM-SS-PDMAEMA) was synthesized via two steps of atom transfer radical polymerization (ATRP). In aqueous solution, the diblock copolymer self-assembled into nanoparticles consisting of a light-responsive hydrophobic PNBM core, a pH- and temperature-responsive hydrophilic PDMAEMA corona, and a redox-sensitive disulfide linker. The multi-stimuli-responsive behaviors of the block copolymer assemblies were revealed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The release of encapsulated molecules from the polymeric nanocarriers could be enhanced under combined stimulation. The prepared multi-stimuli-responsive nanocarriers may offer significant opportunities in diverse applications in the fields of nanotechnology and biotechnology for controlled release