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The stereoselective preparation of a novel 4′-spirocyclopropyl nucleoside analogue has been developed by using a semibenzilic Favorskii rearrangement of a 4′-(2-chloro-3-oxocyclobutyl)spirofuranose as a key step. These chiral spirocyclic intermediates, readily obtained on a multigram scale from chiral-pool starting materials, were shown to be highly suitable precursors for achieving full stereoselectivity in the reduction–ring contraction sequence. The downstream introduction of a nucleobase through Vorbrüggen glycosylation successfully resulted in the formation of the corresponding novel 4′-spirocyclic nucleoside analogue in a stereospecific manner.

This article reports a classroom-based study of the effects of two types of corrective feedback (CF) on the acquisition of 3rd person -s. One hundred and nine Chinese university students completed three communicative tasks: One group received implicit CF consisting of a single corrective move (implicit recasts), a second group received explicit CF consisting of a dual corrective move (a prompt followed by a more explicit recast), a third group performed the tasks without feedback, and a control group just completed two tests. The groups completed two pre-tests, immediate post-tests and delayed post-tests. Gains in accuracy in a test of procedural knowledge (an elicited imitation test) and in a test of declarative knowledge (an untimed grammaticality judgement test) were evident in the first three groups but with few differences among the test scores of these groups. No gains occurred in the test control group. Explicit feedback involving a dual feedback move elicited more uptake-with-repair but this was unrelated to gains in accuracy and overall the implicit CF involving a single feedback move was as effective as the explicit. This finding, which was unexpected, may reflect the Chinese learners’ general orientation to form in this particular classroom context.

Cyclopropane fusion of the only rotatable carbon-carbon bond in furanosyl nucleosides (i.e., exocyclic 4'-5') is a powerful design strategy to arrive at conformationally constrained analogues. Herein, we report a direct stereodivergent route toward the synthesis of the four possible configurations of 4-spirocyclopropane furanoses, which have been transformed into the corresponding 4'-spirocyclic adenosine analogues. The latter showed differential inhibition of the protein methyltransferase PRMT5-MEP50 complex, with one analogue inhibiting more effectively than adenosine itself, demonstrating the utility of rationally probing 4'-5' side chain orientations.

Novel C-4′,C-5′ cyclobutane-fused spirocyclic ribonucleoside analogues were prepared. Thermal [2 + 2] cycloaddition between dichloroketene and readily derived 4′-exo-methylene furanoses afforded a first entry to the required constrained ribofuranoses, relying on a carbonyl transposition sequence. Alternatively, an unusual stereoselective ionic [2 + 2] cycloaddition using methyl propiolate promoted by methylaluminoxane gave a complementary, more direct approach to such ribofuranoses. Further conversion to the constrained adenosine analogues revealed promising structure-dependent inhibition of the protein methyltransferase PRMT5:MEP50 complex in the (sub)micromolar range.

Functional particles self-assembled from polymer single chain nanoparticles have potential applications in various fields, but functionality incorporation is difficult due to their ultrasmall sizes...

Photoresponsive wormlike block copolymer nanoparticles (NPs) have potential applications in versatile fields, but their preparation suffers from narrow worm phase region and tedious approaches. In this work, azobenzene-containing wormlike NPs based on poly(methylacrylic acid)-b-poly(4-((4-butylphenyl)diazenyl)phenyl methacrylate) are prepared via polymerization-induced self-assembly at high solids concentration in ethanol. The pure wormlike NPs occupy a remarkably broad region in the morphological phase diagram because of the rigid nature of the core-forming block. These wormlike NPs expand resulting from trans–cis transformation upon UV irradiation, and slim near to the original state via visible light irradiation. The diameter and its variation amplitude of worms increase with the chain length of core-forming block. Moreover, a nanofiltration switch for rhodamine B is assembled to illustrate one of its potential applications by remote trigger using light.

Supplemental material, LTR903343_Supplemental_Material_CLN_ed for The relative effects of implicit and explicit corrective feedback on the acquisition of 3rd person -s by Chinese university students: A classroom-based study by Yongbin Zhao and Rod Ellis in Language Teaching Research

It is of great importance to extend the UV response of anatase TiO2 into the visible light range for the practical applications. Here, a facile rout to carbon and nitrogen co-doped, Au loaded bowl-like TiO2 nanostructures with tunable size are proposed by using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) spherical micelles as templates. Amphiphilic PS-b-P4VP self-assembles to form PS@P4VP core–shell spherical micelles with P4VP as the out layer in an evaporable mixed solvents of ethanol/tetrahydrofuran (THF). The size of uniform PS@P4VP spherical micelles can be precisely tuned in the range of a few nm to several hundred nm by controlling the molecular composition of the BCPs. Bowl-like TiO2 nanostructures with a replicate size loaded with highly dispersed Au nanoparticles (NPs) of ∼5 nm in diameter are fabricated from these spherical micelles because of strong complex ability of pyridine groups. PS-b-P4VP provides carbon and nitrogen sources to dope the resulting samples simultaneously. The special carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures exhibit much higher photocatalytic activity in the photodegradation of rhodamine B (RhB) compared to Au/P25 under visible light irradiation. Furthermore, the photocatalytic activity is significantly influenced by the BCP molecular composition due to different surface area and loading capacity of the resulting samples. This study provides a facile way to synthesize multi-element doped hollow or bowl-like nanoparticles with tunable size in the nanometer range which have potential application at photocatalysis, oxygen reduction reaction, etc.

Block copolymer (BCP) lithography, as one of the most promising techniques for the next-generation integrated circuits, has been extensively investigated in recent years. Among the diverse types of BCPs, liquid-crystalline BCPs (LC-BCPs) formed by incorporating LC moieties into the BCPs have become increasingly attractive because of the tunable alignment of the LC chains. This review highlights the control of the microdomain orientation of PEO-b-PMA(Az) thin films via novel and convenient processing methods, including micropore extrusion and the introduction of polydimethylsiloxane (PDMS). Meanwhile, the mechanisms of the microdomain alignment transition are clarified and are closely related to the soft shearing field and the change in the block surface energy. Furthermore, some new perspectives for future research on the self-assembly of LC-BCP thin films are outlined from the point of view of material design, orientation control, and technological innovation. The facile control of the microdomain orientation in the liquid-crystalline block copolymer (LC-BCP) thin films has been realized by means of micropore extrusion and introducing polydimethylsiloxane (PDMS), instead of complicated processes or costly apparatus. In extrusion process, the alignment can be recovered via ultrasonicating the extruded BCP solution or as-placing upon long-time thermal annealing.

Objectives Following the Xiongnu and Xianbei, the Rouran Khaganate (Rouran) was the third great nomadic tribe on the Mongolian Steppe. However, few human remains from this tribe are available for archaeologists and geneticists to study, as traces of the tombs of these nomadic people have rarely been found. In 2014, the IA-M1 remains (TL1) at the Khermen Tal site from the Rouran period were found by a Sino-Mongolian joint archaeological team in Mongolia, providing precious material for research into the genetic imprint of the Rouran. Materials and methods The mtDNA hypervariable sequence I (HVS-I) and Y-chromosome SNPs were analyzed, and capture of the paternal non-recombining region of the Y chromosome (NRY) and whole-genome shotgun sequencing of TL1 were performed. The materials from three sites representing the three ancient nationalities (Donghu, Xianbei, and Shiwei) were selected for comparison with the TL1 individual. Results The mitochondrial haplotype of the TL1 individual was D4b1a2a1. The Y-chromosome haplotype was C2b1a1b/F3830 (ISOGG 2015), which was the same as that of the other two ancient male nomadic samples (ZHS5 and GG3) related to the Xianbei and Shiwei, which were also detected as F3889; this haplotype was reported to be downstream of F3830 by Wei et al. (). Discussion We conclude that F3889 downstream of F3830 is an important paternal lineage of the ancient Donghu nomads. The Donghu-Xianbei branch is expected to have made an important paternal genetic contribution to Rouran. This component of gene flow ultimately entered the gene pool of modern Mongolic- and Manchu-speaking populations.

Polymeric nanoparticles (NPs) containing liquid crystalline (LC) mesogens with tunable anisotropic morphologies have applications in various fields, but their preparation typically suffers from tedious and low-throughput approaches. Here we present an efficient route to the preparation of anisotropic morphologies of azobenzene-containing block copolymers (BCPs) at high solids content via a polymerization-induced hierarchical self-assembly in ethanol. Various anisotropic NPs, including cuboids, short belts, lamellae, and ellipsoidal vesicles, have been obtained in a remarkably broad range of BCP compositions. The NPs exhibit a smectic phase with ordered stripes when observed under TEM. This internal LC ordering plays a significant role on the formation of these intriguing anisotropic morphologies. Morphological transitions from anisotropic to isotropic spheres can be obtained upon UV illumination due to the photoresponsive properties of the azobenzene mesogens. This work significantly expands the scope of accessible morphologies in PISA and suggests that the under explored LC BCPs may have an impactful role in the PISA field.

The i.i.d assumption is the corner stone of most conventional machine learning algorithms. However, reducing the bias and variance of the learning model on the i.i.d dataset may not help the model to prevent from their failure on the adversarial samples, which are intentionally generated by either the malicious users or its rival programs. This paper gives a brief introduction of machine learning and adversarial learning, discussing the research frontier of the adversarial issues noticed by both the machine learning and network security field. We argue that one key reason of the adversarial issue is that the learning algorithms may not exploit the input feature set enough, so that the attackers can focus on a small set of features to trick the model. To address this issue, we consider two important classes of classifiers. For random forest, we propose a type of random forest called Weighted Random Forest (WRF) to encourage the model to give even credits to the input features. This approach can be further improved by careful selection of a subset of trees based on the clustering analysis during the run time. For neural networks, we propose to introduce extra soft constraints based on the weight variance to the objective function, such that the model would base the classification decision on more evenly distributed feature impact. Empirical experiments show that these approaches can effectively improve the robustness of the learnt model against their baseline systems.

A hierarchical porous structure is significant for carbon materials to achieve excellent performance in catalysis, separation, and energy applications due to its advantageous mass transport and high specific surface area properties. Herein, hierarchical porous particle-based nitrogen-doped carbon spheres (PNCSs) are prepared via carbonization of hydrothermal melamine-formaldehyde (MF) spheres in the presence of F127. F127 facilitates the nucleation of MF forming primary particles and stabilizes the primary particles. Later on in the process, the primary polymerized nanoparticles assemble into a micrometer-sized spherical structure. Thus, the textural features of MF/F127 composite microspheres are tuned by simply adjusting the amount of F127. After carbonization of the as-prepared MF/F127 microspheres, hierarchical porous microspheres composed of interconnected nitrogen-doped carbon nanoparticles with high specific surface area (1270 m2 g−1) are obtained. Owing to their unique structural feature and nitrogen-doping, PNCSs as electrode materials for supercapacitors exhibit enhanced electrochemical properties with remarkable specific capacitance (204.1 F g−1 at 1 A g−1, two-electrode system), high energy/power density and long cycling stability.

Block copolymer (BCP) films with perpendicularly aligned cylindrical domains of high aspect ratio have important applications in diverse fields. However, an aspect ratio of the cylinders as high as 200 has rarely been reported so far. Here we demonstrate an efficient route to the formation of normally aligned P4VP cylinders with high aspect ratio surrounded by a matrix of azobenzene-containing block (PMA(Az)) via hierarchical self-assembly. A crisscross structure, consisting of parallelly aligned liquid crystalline (LC) layers and normally aligned self-assembly domains, is expected to assist the formation of well-defined nanostructures. The LC layers in the cylindrical films self-assemble to form smectic phase after solvent annealing, as confirmed by WAXD and UV-vis spectra. We found that the aspect ratio of the vertical P4VP cylinders is up to 200 and the film thickness reaches 6 μm. P4VP is a functional polymer, making this P4VP-b-PMA(Az) film more suitable for advanced filters, multi-nanochannels, nanolithography, and high-density storage media, etc.

In this paper, we first provide some properties of truth tables of bent functions. Furthermore, a upper bound of truth table’s runs length of a bent function is presented. Based on these results, we propose a new algorithm for enumerating bent functions. At last, we find that our algorithm requires lower storage complexity and is easier to implement with parallel/distributed computing infrastructures by comparing with some known searching algorithms.

Crosslinked liquid crystalline polymers (CLCPs) have garnered extensive attention in recent years for their significant values in the design of light-driven soft actuators. However, poor processabilities due to the insoluble and infusible crosslinked networks prevent their practical applications severely. In this study, a weldable azobenzene-containing CLCP is designed with photo- and humidity-responsive actuations, which enables a cut-and-weld process to 3D CLCP architectures. The tensile properties and stability are almost unchanged after welding, much better than those of the films pasted by common adhesive tapes. Meanwhile, the mechanisms of the welding process are clarified on the base of surface hydrogen bonding and further crosslinking. By taking advantage of the cut-and-weld process, a 3D "claw" integrated into a robotic arm is realized for grabbing millimeter-scale objects by remote control. This work enhances significantly not only the processability of CLCP films but also the utilization of leftover pieces, which provides an efficient approach to create functional 3D structures from film precursors for the potential application in the smart materials.

As an extension of support vector machine in ordinal regression problem, support vector ordinal regression (SVOR) finds ( r − 1 ) parallel hyperplanes by solving a quadratic programming which has n ( r − 1 ) constraints. Here, n and r represent the number of training sample and ranks, respectively. Therefore, it would costs much more time to train SVOR than SVC or SVR. Fortunately, the solution of SVOR is only decided by minor constraints which are associated with non-zero Lagrange multipliers. Other constraints with zero Lagrange multipliers have no influence on the solution. Because a training sample is associated with ( r − 1 ) constraints, retaining potential support vector may still induce that many redundant constraints are reserved. In this paper, we try to remove these potential redundant constraints for SVOR learning. For the j th parallel hyperplane, the potential constraints with non-zero Lagrange multipliers are associated with the samples near the j th parallel hyperplane. These samples can be identified by a chain near the j th parallel hyperplane. Then, other constraints for the j th parallel hyperplane can be discarded before learning. The number of the constraints can be reduced to less than 17 percent of the original in our experiments. Additionally, it only executes once to find potential critical constraints. Obviously, it is easy to tune parameters after removing potential redundant constraints. The experimental results on several datasets demonstrate that SVOR becomes much faster after removing potential redundant constraints and the performance does not degrade seriously.

The orientation transition from perpendicular to parallel alignment of PEO cylindrical microdomains within PEO-b-PMA(Az) films has been demonstrated via introducing a small amount of polydimethylsiloxane (PDMS) into block copolymers (BCPs). The introduced PDMS can change the surface energy difference of the two blocks and induce a soft shearing force during the annealing process, which affects the alignment of PEO cylindrical domains synergically. With this understanding, the PDMS-assisted method can possibly be generalized to align a wide variety of other BCPs. The BCP films with controllable alignment can be used as lithographic nanotemplates to prepare nanowire arrays, which have enormous potential application in the field of integrated circuits.

Ordered mesoporous crystalline titania with high thermal stability is directly synthesized in a simple one-pot procedure via an integrated approach of a solvent evaporation-induced self-assembly (EISA) technique and template-carbonization strategy by using a comb-like amphiphilic liquid crystal (LC) block copolymer (BCP) PEO-b-PMA(Az) with abundant sp2-carbons as a structure-directing agent. These BCP containing LC rigid segments with distinct hydrophilic/hydrophobic contrast can form robust micelles and co-assemble with titania sol into ordered mesostructures which are stable during the whole EISA process. Template carbonization in nitrogen after ageing is the key step to obtain the ordered crystalline mesostructures. The synthesized titania materials have a large pore size (∼4.87 nm) and pore volume (∼0.37 cm3 g−1) and high surface area (∼239 m2 g−1), as well as high thermal stability (>700 °C). Additionally, mesoporous titania shows good photocatalytic activity for the degradation of rhodamine B in an aqueous suspension due to its highly crystalline framework and large surface area. This simple, yet facile method can therefore be expanded to other ordered crystalline mesoporous materials through high-temperature heat treatments.

A fully rollable nanocomposite-based nanogenerator (NCG) is developed by integrating a lead-free piezoelectric hybrid layer with a type of nanofiber-supported silver nanowire (AgNW) network as electrodes. The thin-film nanocomposite is composed of electroactive polyvinylidene fluoride (PVDF) polymer matrix and compositionally modified potassium sodium niobate-based nanoparticles (NPs) with a high piezoelectric coefficient (d33) of 53 pm/V, which is revealed by the piezoresponse force microscopy measurements. Under periodical agitation at a compressive force of 50 N and 1 Hz, the NCG can steadily render high electric output up to an open-circuit voltage of 18 V and a short-circuit current of 2.6 μA. Of particular importance is the decent rollability of the NCG, as indicated by the negligible decay in the electric output after it being repeatedly rolled around a gel pen for 200 cycles. Besides, the biocompatible NCG can potentially be used to scavenge biomechanical energy from low-frequency human motions, a...