The neural origin for asymmetric coding of surface color in the primate visual cortex.

The coding privilege of end-spectral hues (red and blue) in the early visual cortex has been reported in primates. However, the origin of such bias remains unclear. Here, we provide a complete picture of the end-spectral bias in visual system by measuring fMRI signals and spiking activities in macaques. The correlated end-spectral biases between the LGN and V1 suggest a subcortical source for asymmetric coding. Along the ventral pathway from V1 to V4, red bias against green peaked in V1 and then declined, whereas blue bias against yellow showed an increasing trend. The feedforward and recurrent modifications of end-spectral bias were further revealed by dynamic causal modeling analysis. Moreover, we found that the strongest end-spectral bias in V1 was in layer 4C[Formula: see text]. Our results suggest that end-spectral bias already exists in the LGN and is transmitted to V1 mainly through the parvocellular pathway, then embellished by cortical processing.

Total Synthesis of Metaphanine and Oxoepistephamiersine.

Herein, we report a concise and divergent synthesis of the complex hasubanan alkaloids metaphanine and oxoepistephamiersine from commercially available and inexpensive cyclohexanedione monoethylene acetal. Our synthesis features a palladium-catalyzed cascade cyclization reaction to set the tricyclic carbon framework of the desired molecules, a regioselective Baeyer-Villiger oxidation followed by a MeNH2 triggered skeletal reorganization cascade to construct the benzannulated aza[4.4.3]propellane, and a strategically late-stage regio-/diastereoselective oxidative annulation of sp3 C-H bond to form the challenging THF ring system and hemiketal moiety in a single step. In addition, a highly enantioselective alkylation of cyclohexanedione monoethylene acetal paved the way for the asymmetric synthesis of target molecular.

Synergistic Effect and Electrical Properties of Microporous Liquid Metal/Carbon Nanotube Polymer Sponge.

Sensing sponge materials with light weight, high elasticity, and electrical sensing properties are in enormous demand in electronic fields, but there is an imminent need to develop a scalable and facile method for the manufacture of the sensing material. Herein, an efficient in situ polymerization and convenient preparation process is reported to manufacture the microporous liquid metal/carbon nanotube-polysulfide rubber (LM/CNT-PSR) sponges with excellent mechanical and electrical properties, based on fluidic LMs and rigid CNTs with unique synergistic effect for sponge composites. Excellent mechanical properties of LM/CNT-PSR sponges, such as low density, excellent elasticity, remarkable mechanical recoverability, and self-healing property, are endowed by the interconnected microporous structure of sponge and flexible polysulfide rubber matrix with disulfide bonds. In addition, the synergistic effect of LMs and CNTs leads to excellent conductivity and unique electrical sensing property under mechanical pressure. Microporous LM/CNT-PSR sponges with high performance and simple fabrication process are promising sensing materials for various electronic devices, such as human motion monitoring, and weighing sensing.

Self-Healable, Malleable, Ecofriendly Recyclable and Robust Polyimine Thermosets Derived from Trifluoromethyl Diphenoxybenzene Backbones.

Dynamic covalent chemistry opens up great opportunities for a sustainable society by producing reprocessable networks of polymers and even thermosets. However, achieving the closed-loop recycling of polymers with high performance remains a grand challenge. The introduction of aromatic monomers and fluorine into covalent adaptable networks is an attractive method to tackle this challenge. Therefore, we present a facile and universal strategy to focus on the design and applications of polyimine vitrimers containing trifluoromethyl diphenoxybenzene backbones in applications of dynamic covalent polymers. In this study, fluorine-containing polyimine vitrimer networks (FPIVs) were fabricated, and the results revealed that the FPIVs not only exhibited good self-healability, malleability and processability without the aid of any catalyst, but also possessed decent mechanical strength, superior toughness and thermal stability. We hope that this work could provide a novel pathway for the design of high-performance polyimine vitrimers by recycling of plastic wastes.

Electroconvulsive therapy modulates critical brain dynamics in major depressive disorder patients.

BACKGROUND: Electroconvulsive therapy (ECT) is widely considered as an effective and fast-acting option for treating patients with major depressive disorder (MDD). However, the neural basis underlying this powerful therapy remains uncertain. Recent studies have suggested that the healthy brain may operate near a critical state, which may reflect a balance between neuronal excitation and inhibition. OBJECTIVE: In the present study, we investigated whether there are any changes regarding criticality in MDD and, if so, whether ECT can reverse them. Critical dynamics analyses were performed on resting-state functional magnetic resonance imaging (rs-fMRI) data collected from 39 MDD patients and 38 healthy controls (HCs). RESULTS: We found that compared with HCs, MDD patients, especially those who responded positively to ECT, tended to have smaller average avalanch sizes and lower branching ratios, suggesting a sub-critical state, at both the whole-brain and functional network levels. Importantly, ECT effectively corrected such anomalies, accompanied by enhanced degree centrality and functional connectivity of high-degree nodes located in the networks including the default-mode and the frontoparietal networks. CONCLUSION: These results indicate that ECT can modulate large-scale brain dynamics of MDD patients to be closer to criticality. Our study sheds new light on the pathology of MDD and the network mechanism by which ECT influences treatment.

Transient Electrically Driven Stiffness-Changing Materials from Liquid Metal Polymer Composites.

Stiffness-changing materials (SCMs) have received lots of interests due to their reversible transition between their soft and rigid states for modern applications. However, the irreversible stiffness transition, slow response, and sustained external stimuli strictly hinder the broad utilizations of SCMs. Here, this work reports electrically driven SCMs based on supercooled liquid metals (LMs). A small voltage (5 V) can successfully initiate the stable and reversible stiffness change of the SCMs in electrolyte solution. Surprisingly, the LM-based SCMs (LM-SCMs) exhibited a significant change in 1000 times difference of moduli (65 kPa versus 79 MPa). Moreover, such a stiffness transition of the LM-SCM was ultrarapidly completed in a few seconds (<30 s). Importantly, after transient stimulation of LM nucleation, the rigidity of the LM-SCM could be maintained when the external stimulus (voltage) was removed, highly different from previously reported SCMs that require sustained energy to maintain their mechanical states. Based on the unique features of LM-SCMs, advanced robotics like smart valves and mechanical paws in seawater were successfully fabricated.

Stimuli-Driven Insulator-Conductor Transition in a Flexible Polymer Composite Enabled by Biphasic Liquid Metal.

Metal-polymer composites (MPCs) with combined properties of metals and polymers have achieved much industrial success. However, metals in MPCs are thought to be ordinary and invariable electrically conductive fillers in supportive polymers to show limited use in modern technologies. This work that is disclosed here, for the first time, introduces stimuli-driven transition from biphasic to monophasic state of liquid metal into polymer science to form dynamic soft conductors from the binary metal-polymer composites. The binary metal that exhibits temperature-driven reversible transition between solid and liquid states via a biphasic state is fabricated. A conducting stretchable polymer composite is developed using the judiciously chosen biphasic binary metal that undergoes conductor to insulator transition upon stretching. Insulating stretched films become conducting upon heating. A "tube" model elegantly describes such distinctive deformation/temperature-dependent behaviors. Moreover, the conducting polymer composite shows decrease in its resistance upon increasing the sample temperature. The resistance can be tuned from 1 to 108  Ω depending on the state of binary metal in the phase diagram. This work would build the intimate and interesting connection between metal phases and polymer science toward next-generation soft conductors and beyond.

Vapor-Mediated Stretchable and Reversible Conductors from Microporous Liquid Metal Polymers.

Flexible electronic devices have penetrated into a variety of industry sectors (i.e., consumer electronics, automotive, and medical) in human life, and this calls for better properties of stretchable conductive composites as the crucial elements. Traditionally, conductive inorganic fillers are incorporated in flexible polymers to prepare conductive composites, which falls short of the required properties in more demanding devices nowadays due to limited deformation, low conductivity, and poor processability. Herein, liquid metals were successfully incorporated in microporous polymer matrixes using a simple codissolving and film casting/solvent evaporation approach. The microporous liquid metal-embedded polymer (LMEP) was insulative as fabricated due to discontinuous liquid metals (LMs), while it became conductive upon stretching. Interestingly, the LMEP films showed a reversible insulator-conductor transition due to the regenerated pores in polymer matrix under organic vapor. Negligible changes in the resistance value were seen even after 50 solvent exposure-tensile strain cycles, demonstrating the excellent stability of the electrical properties of these films. Furthermore, most of the commercially available soluble polymers including rigid plastics and soft elastomers are suitable for the fabrication of LMEP. With the ideal characteristics, they have been successfully exploited in model alarm systems to prevent temperature overloads and solvent leakage, showcasing the great potential in next generation sensors used in industry settings.

Substituent changes in the salen ligands of CuIINaI-complexes to induce various structures and catalytic activities towards 2-imidazolines from nitriles and 1,2-diaminopropane.

Based on various comparable salen ligands, three synthesized CuIINaI-complexes present efficient catalytic activities for the coupling and cyclization reaction of 1,2-diaminopropane with nitriles towards 2-imidazolines. The catalytic results show that salen ligands with an electron-donating substituent and small steric hindrance improve the catalytic activity.

Highly Emissive and Color-Tunable Perovskite Cross-linkers for Luminescent Polymer Networks.

Emissive cross-linkers are of special interest for polymer science because of their ability to endow polymer networks with luminescent properties. Methylammonium lead halide perovskite nanoparticles (MAPbCl xBr3- x NPs) are extensively explored for optical and optoelectronic applications. In this work, MAPbCl xBr3- x NPs with cross-linkable and polymerizable ligands are successfully prepared as new emissive cross-linkers for polymer networks. Commercially available reagent 2-aminoethyl methacrylate hydrochloride (AMHCl) can act as a ligand to stabilize MAPbBr3 NPs in solution. Compared with traditional ligands (oleic acid and oleylamine), AMHCl retains the architecture of perovskite effectively and affords polymerizable groups (vinyl) on the surface of perovskites. The as-prepared MAPbCl xBr3- x NPs can serve as cross-linkers in the radical polymerization of (meth)acrylates by UV-light to form polymer networks. Meanwhile, such cross-linkable emitters exhibit bright luminescence and color-tunability at room temperature, attributed by a unique halide exchange of perovskites between CH3NH3Br and AMHCl, which provides the polymer networks with varied emissive bands. These perovskite-crosslinked networks showed high air stability, water stability, and prominent photoluminescence quantum yields. On the basis of these excellent properties, white-light-emitting diodes were successfully fabricated from these perovskite-crosslinked composites with color-coordinate values at (0.316, 0.315), very close to the standard coordinates of white light. This work elucidates a new and convenient technique to convert nanocrystals into luminescent cross-linkers to build functional polymeric networks for technological applications.

Robust and Reversible Vapoluminescent Organometallic Copper Polymers.

Emissive organometallic polymers are an important class of functional materials characterized by the combined photoluminescent features of organometallic molecules and the properties of traditional polymers. In this work, the emissive organometallic complex, [CuBr(PPh3 )2 (4-methylpyridine)], is successfully, mechanically ground into a random copolymer built on 4-(diphenylphosphino)styrene (DPVP) and n-butyl acrylate (BA) monomers. The resultant hybrid materials successfully inherit the emissive centers, and are significantly reinforced by the copper complexes as chemical crosslinkers in the polymeric continuum. These organometallic polymers are also proved to have excellent vapoluminescent properties, exhibiting unique responses to many organic solvent vapors, reflecting their rapid loss and recovery of photoluminescence. Mechanically robust and flexible films prepared with these organometallic Cu(I)-polymers are tested as recoverable sensors for hazardous volatile chemical compounds (VOCs) such as toluene, acetone, chloroform, and dichloromethane, and the low limits of detection (LOD) can reach as low as 1 × 10-3 -8 × 10-3 mg L-1 (0.2-3.3 ppmV, parts per million-volume) for various VOCs. This work sheds lights on the design and fabrication of organometallic polymers for advanced applications.

Highly Stable and Luminescent Perovskite-Polymer Composites from a Convenient and Universal Strategy.

Extensive attention has been received in recent years for perovskite-polymer composites because of their combination of properties from polymers and perovskites. In this work, a convenient and universal strategy is reported to prepare cesium lead bromide or organolead halide methylammonium bromide polymer composites. This technique integrates the formation of perovskite crystals and the polymer matrix in a one-pot reaction, avoiding the tedious separation and preparation of perovskites. The method is universal for most of the commercially available monomers and polymers, which has been verified in this report using poly(methyl methacrylate), poly(butyl methacrylate), and polystyrene. The physical properties of the varied polymers lead to different luminescent properties and stabilities of the composites. No organic solvent is required during the preparation, indicating a green technique for the composites. Additionally, the resulted perovskite-polymer composites are extraordinarily stable, maintaining their quantum yield for more than 1 month in air. On the basis of the above properties, a prototype of white light-emitting diodes was successfully constructed with feasible color characters and narrow bandwidths. Furthermore, large-area (dimension: 10 × 7 × 0.15 cm) perovskite-polymer plates are easily prepared via the one-pot strategy, showing that the technique is ready for possible large-area optical devices. This work provides an efficient technique toward various kinds of perovskite-polymer composites for both scientific research studies and future applications.