The innovation contest is well organized to provide solutions or ideas for companies. In the existing innovation contest literature, several articles assume that the contestants are risk neutral and ...show that a single‐winner award scheme is optimal. In this article, we assume that the contestants are risk averse and show that the risk aversion of contestants can explain the popularity of the multiple‐winner, convex (unequal) allocation scheme, which generalizes the findings of a prior study and coincides with practical observations. This result also possesses a certain robustness in several cases.
Regulating the fluorescent properties of organic small molecules in a controlled and dynamic manner has been a fundamental research goal. Although several strategies have been exploited, realizing ...multi-color molecular emission from a single fluorophore remains challenging. Herein, we demonstrate an emissive system by combining pyrene fluorophore and acylhydrazone units, which can generate multi-color switchable fluorescent emissions at different assembled states. Two kinds of supramolecular tools, amphiphilic self-assembly and γ-cyclodextrin mediated host-guest recognition, are used to manipulate the intermolecular aromatic stacking distances, resulting in the tunable fluorescent emission ranging from blue to yellow, including a pure white-light emission. Moreover, an external chemical signal, amylase, is introduced to control the assembly states of the system on a time scale, generating a distinct dynamic emission system. The dynamic properties of this multi-color fluorescent system can be also enabled in a hydrogel network, exhibiting a promising potential for intelligent fluorescent materials.
Fear behavior is under tight control of the prefrontal cortex, but the underlying microcircuit mechanism remains elusive. In particular, it is unclear how distinct subtypes of inhibitory interneurons ...(INs) within prefrontal cortex interact and contribute to fear expression. We employed a social fear conditioning paradigm and induced robust social fear in mice. We found that social fear is characterized by activation of dorsal medial prefrontal cortex (dmPFC) and is largely diminished by dmPFC inactivation. With a combination of in vivo electrophysiological recordings and fiber photometry together with cell-type-specific pharmacogenetics, we further demonstrated that somatostatin (SST) INs suppressed parvalbumin (PV) INs and disinhibited pyramidal cells and consequently enhanced dmPFC output to mediate social fear responses. These results reveal a previously unknown disinhibitory microcircuit in prefrontal cortex through interactions between IN subtypes and suggest that SST INs-mediated disinhibition represents an important circuit mechanism in gating social fear behavior.
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•Social fear conditioning induces robust and specific social fear in mice•The dmPFC participates in social fear expression•SST INs disinhibit principal neurons via their inhibition of FS-PV INs•The disinhibitory microcircuitry is crucial for social fear expression
Prefrontal cortex plays an essential role in fear expression. Xu et al. reveal a disinhibitory microcircuit in prefrontal cortex through interactions between interneuron subtypes and suggest that SST INs-mediated disinhibition represents an important circuit mechanism in gating social fear behavior.
A high efficiency piezoelectric footwear energy harvester is designed, optimized, modeled and tested for energy scavenging from human walking.
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•A piezoelectric footwear harvester is ...designed, modeled and tested.•A force amplification frame is designed and optimized.•The dynamic force at a heel is measured at different walking speeds.•A SDOF model is developed for the proposed footwear harvester.•Simulations show that an average power output of 20 mW is obtained.
A footwear harvester needs to fulfill both technical and practical functionalities, including but not limited to energy extracting and storage, easy implantation and durability. The very limited space in a shoe is the key challenge to the design of a footwear harvester. This paper presents the design, optimization, modeling and testing of an embedded piezoelectric footwear harvester for energy scavenging from human walking. A force amplification frame is designed and optimized to transmit and amplify the vertical heel-strike force to the inner piezoelectric stack deployed in the horizontal direction. Two heel-shaped aluminum plates are employed to gather and transfer the dynamic force over the heel to the sandwiched force amplification frames. The dynamic force at the heel is measured to design, optimize and simulate the piezoelectric footwear harvester. A numerical model is developed and validated to be capable of precisely predicting the electrical outputs of the harvester. Two prototypes, respectively including eight and six stacks, are fabricated and tested on a treadmill at different walking speeds and external resistances. The numerical simulations agree well with experiments. The harvester with fewer piezoelectric stacks could produce more power at the same walking speed and matched resistance. Experimental results manifest that the footwear harvesters with eight and six stacks, respectively, have 7 mW/shoe and 9 mW/shoe average power outputs at the walking speeds of 3.0 mph (4.8 km/h). Simulation results from the validated numerical model show that the harvester with four piezoelectric stacks could harvest 14 mW/shoe and 20 mW/shoe average power at 3.0 mph (4.8 km/h) and 3.5 mph (5.6 km/h), respectively.
Cold atoms with laser-induced spin-orbit (SO) interactions provide a platform to explore quantum physics beyond natural conditions of solids. Here we propose and experimentally realize ...two-dimensional (2D) SO coupling and topological bands for a rubidium-87 degenerate gas through an optical Raman lattice, without phase-locking or fine-tuning of optical potentials. A controllable crossover between 2D and 1D SO couplings is studied, and the SO effects and nontrivial band topology are observed by measuring the atomic cloud distribution and spin texture in momentum space. Our realization of 2D SO coupling with advantages of small heating and topological stability opens a broad avenue in cold atoms to study exotic quantum phases, including topological superfluids.
This paper presents the design, modeling and experimental tests of a novel piezoelectric energy harvester with a two-stage force-amplification compliant mechanism for scavenging energy from human ...walking. The harvester consists of four units of two-stage force amplification piezoelectric transducers sandwiched between two heel-shaped plates. The dynamic reaction force at a heel is amplified twice by the two-stage force amplification frames before applied to the 33-mode piezoelectric stacks and therefore a large power output is achieved. Experiments were performed on the prototype of the two-stage piezoelectric energy harvester over different load levels and frequencies. Numerical simulation results based on a simplified single degree-of-freedom model agreed well with the experiment results. An average power of 34.3 mW and a peak power of 110.2 mW were obtained from the simulation under the dynamic force with the amplitude of 500 N and frequency of 3 Hz. At 2 Hz and 1.0 Hz, the average power outputs of 23.9 mW and 11.0 mW, peak power outputs of 65.8 mW and 31.7 mW were experimentally achieved. Numerical simulations show that the average power output of 12.8 mW and peak power output of 204.7 mW could be obtained at the walking speed of 3.5 mph (5.6 km/h) from a male subject with the body weight of 84 kg and height of 172 cm. Comparison study demonstrated that the proposed two-stage piezoelectric harvester has a larger power output than the reported results in literature.
•A heel-shaped energy harvester is designed, fabricated, tested and modeled.•The input force of the harvester is amplified twice by the two-stage force amplification mechanism.•The proposed two-stage piezoelectric harvester has a larger power output than the reported results in literature.•An average power of 24 mW and a peak power of 66 mW were experimentally achieved.
Humans can naturally and effectively find salient regions in complex scenes. Motivated by this observation, attention mechanisms were introduced into computer vision with the aim of imitating this ...aspect of the human visual system. Such an attention mechanism can be regarded as a dynamic weight adjustment process based on features of the input image. Attention mechanisms have achieved great success in many visual tasks, including image classification, object detection, semantic segmentation, video understanding, image generation, 3D vision, multimodal tasks, and self-supervised learning. In this survey, we provide a comprehensive review of various attention mechanisms in computer vision and categorize them according to approach, such as channel attention, spatial attention, temporal attention, and branch attention; a related repository
https://github.com/MenghaoGuo/Awesome-Vision-Attentions
is dedicated to collecting related work. We also suggest future directions for attention mechanism research.
International trade, through global supply chains, is central to global sustainable production and consumption. Redistribution of environmental resources impacts through international trade has ...become apparent in ecological research - and may have long-term design and planning implications for production and supply chain management. However, current trade and production accounting methods are still incapable of providing accurate and reliable results for policymakers and organisational decision makers to manage global and supply chain trade issues. In this study, a blockchain-based conceptual framework for embodied environmental resources accounting in trade is proposed to address global supply chain and trade issues. Framework design, benefits, and challenges are also discussed. Future research and linkage to theory are also provided. This study provides a strong systemic foundation for managing environmental resources at the nexus of international trade, sustainable production, and global supply chains.
The inherent heterogeneity of individual cells in cell populations plays significant roles in disease development and progression, which is critical for disease diagnosis and treatment. Substantial ...evidences show that the majority of traditional gene profiling methods mask the difference of individual cells. Single cell sequencing can provide data to characterize the inherent heterogeneity of individual cells, and reveal complex and rare cell populations. Different microfluidic technologies have emerged for single cell researches and become the frontiers and hot topics over the past decade. In this review article, we introduce the processes of single cell sequencing, and review the principles of microfluidics for single cell analysis. Also, we discuss the common high-throughput single cell sequencing technologies along with their advantages and disadvantages. Lastly, microfluidics applications in single cell sequencing technology for the diagnosis of cancers and immune system diseases are briefly illustrated.
Two-dimensional nanomaterials have exhibited considerable potential for gas sensing applications in recent years owing to their unique physical and chemical properties such as a large ...surface-to-volume ratio, abundant edge sites, versatile surface chemistry, etc. Herein, we demonstrate a two-dimensional Ti3C2TX MXene@TiO2/MoS2 nanocomposite gas sensor for ammonia detection at room temperature. MoS2 nanosheets are grown on an etched Ti3C2TX MXene surface by a hydrothermal method, and rectangular TiO2 particles are derived from Ti3C2TX MXene in the hydrothermal process. Meanwhile, nanocomposites with different Ti3C2TX MXene additions are also designed for gas sensing performance comparison. Such a novel hierarchical structure based gas sensor (MTM-0.2 sensor) exhibits fast response/recovery time and excellent long-term stability to ammonia. Meanwhile, outstanding selectivity to ammonia against triethylamine, trimethylamine, n-butanol, acetone, formaldehyde, and nitrogen dioxide at room temperature is also shown. The sensor shows 1.79-fold and 2.75-fold enhancement in the gas sensing response toward 100 ppm ammonia compared with the pristine Ti3C2TX MXene and MoS2 gas sensors, respectively. And its detection limit for ammonia is 500 ppb. The sensing mechanisms of the Ti3C2TX MXene@TiO2/MoS2 nanocomposites toward ammonia are attributed to the layered nanostructure, p–n heterojunction created at the interface of p-type Ti3C2TX MXene and n-type MoS2. Finally, density-functional theory (DFT) is performed to investigate the adsorption behavior and charge transfer of ammonia molecules on the surface of the nanocomposite. The synthesized Ti3C2TX MXene@TiO2/MoS2 nanocomposite can be regarded as a promising candidate for high-performance ammonia detection at room temperature.
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