Pooling plays an important role in generating a discriminative video representation. In this paper, we propose a new semantic pooling approach for challenging event analysis tasks (e.g., event ...detection, recognition, and recounting) in long untrimmed Internet videos, especially when only a few shots/segments are relevant to the event of interest while many other shots are irrelevant or even misleading. The commonly adopted pooling strategies aggregate the shots indifferently in one way or another, resulting in a great loss of information. Instead, in this work we first define a novel notion of semantic saliency that assesses the relevance of each shot with the event of interest. We then prioritize the shots according to their saliency scores since shots that are semantically more salient are expected to contribute more to the final event analysis. Next, we propose a new isotonic regularizer that is able to exploit the constructed semantic ordering information. The resulting nearly-isotonic support vector machine classifier exhibits higher discriminative power in event analysis tasks. Computationally, we develop an efficient implementation using the proximal gradient algorithm, and we prove new and closed-form proximal steps. We conduct extensive experiments on three real-world video datasets and achieve promising improvements.
Manganese photocatalysts enabled versatile room‐temperature C−H arylation reactions by means of continuous visible‐light photoflow, thus allowing for efficient C−H arylations in 30 minutes with ample ...scope. The robustness of the manganese‐catalyzed photoflow strategy was shown by visible light‐induced gram‐scale synthesis, clearly outperforming the batch performance.
Photochemistry in the flow: Earth‐abundant manganese catalysts enabled visible‐light‐induced C−H arylations at room temperature in a continuous photoflow manifold.
This paper aims to improve the full speed sensorless drive for permanent-magnet (PM) synchronous machines on the region of initial zero speed and the region of medium speed. At zero and low speed, ...the saliency-based drive using the square-wave voltage injection has demonstrated the comparable performance to the sensor-based drive using the encoder with hundreds of pulses per revolution. For PM machines at initial state, the magnet polarity is typically identified based on the injection of voltage pulses before the saliency-based drive. Instead of pulses injection, this paper directly adds the polarity detection capability in the saliency-based drive by superimposing the same square-wave voltage. A fast detection period and negligible current spikes are benefits for the drive using the same square-wave injection voltage for both the polarity detection and position estimation. At medium speed, electromotive force voltage can be estimated to replace the saliency for the sensorless drive. To achieve a smooth operation between two estimation methods, a transition algorithm is also proposed based on a single-phase-lock loop by blending two feedback position signals. According to the experimental evaluation, the reduced power consumption as well as the smooth switch between two different drives is achieved. All the sensorless methods are verified by an interior PM machine with a saliency ratio of 1.37 (L q /L d = 1.37).
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•Corrosion behavior of laser powder bed fusion produced Ti–6Al–4V samples was investigated.•Static and dynamic Hank’s solutions were selected as the corrosion environments.•Flow ...solution degrades passive film of sample and thereby the corrosion resistance.•Flow solution promotes the deposition of calcium phosphate and hydroxyapatite.
The corrosion behavior of laser powder bed fusion produced (L-PBF-produced) titanium alloys involving flowing body fluid is still unclear. Therefore, this work investigates in vitro corrosion behavior and the characteristics of passive films formed on L-PBF-produced Ti–6Al–4V in both static and dynamic Hank’s solutions. Electrochemical measurements, immersion tests, X-ray photoelectron spectroscopy and scanning electron microscopy were conducted. In comparison to the L-PBF-produced Ti–6Al–4V in static Hank’s solution, the samples showed lower charge transfer resistance and higher passivation current density (anodic current density as well) in dynamic Hank’s solution. Meanwhile, a more apparent deposition of apatite and hydroxyapatite is found on the L-PBF-produced Ti–6Al–4V in dynamic Hank’s solution. Such outcomes mainly result from the enhancement of film/solution interfacial transportation in dynamic Hank’s solution. The dynamic Hank’s solution provides more calcium and phosphate ions to the surface of the passive film and also takes away the dissolved metal ions. Therefore, more salt deposition and a lower-quality passive film are found.
Ruthenium(IV) complexes were identified as key intermediates of C−H/O−H activations by weak O‐coordination. Thus, the annulations of sulfoxonium ylides by benzoic acids provided expedient access to ...diversely‐decorated isocoumarins with ample scope. Detailed experimental and computational studies provided strong support for a facile BIES‐C−H activation, along with cyclometalated ruthenium(IV) intermediates within a versatile ruthenium(II/IV) catalysis regime (BIES=base‐assisted internal electrophilic substitution).
RuIV for O: Versatile C−H/O−H functionalizations by weak O‐coordination were accomplished with sulfoxonium ylides through a ruthenium(II/IV) manifold.
The discovery of modern medicine relies on the sustainable development of synthetic methodologies to meet the needs associated with drug molecular design. Heterocycles containing difluoromethyl ...groups are an emerging but scarcely investigated class of organofluoro molecules with potential applications in pharmaceutical, agricultural and material science. Herein, we developed an organophotocatalytic direct difluoromethylation of heterocycles using O
as a green oxidant. The C-H oxidative difluoromethylation obviates the need for pre-functionalization of the substrates, metals and additives. The operationally straightforward method enriches the efficient synthesis of many difluoromethylated heterocycles in moderate to excellent yields. The direct difluoromethylation of pharmaceutical moleculars demonstrates the practicability of this methodology to late-stage drug development. Moreover, 2'-deoxy-5-difluoromethyluridine (F
TDR) exhibits promising activity against some cancer cell lines, indicating that the difluoromethylation methodology might provide assistance for drug discovery.
For most metal-containing CO
reduction reaction (CO
RR) electrocatalysts, the unavoidable self-reduction to zero-valence metal will promote hydrogen evolution, hence lowering the CO
RR selectivity. ...Thus it is challenging to design a stable phase with resistance to electrochemical self-reduction as well as high CO
RR activity. Herein, we report a scenario to develop hydrocerussite as a stable and active electrocatalyst via in situ conversion of a complex precursor, tannin-lead(II) (TA-Pb) complex. A comprehensive characterization reveals the in situ transformation of TA-Pb to cerussite (PbCO
), and sequentially to hydrocerussite (Pb
(CO
)
(OH)
), which finally serves as a stable and active phase under CO
RR condition. Both experiments and theoretical calculations confirm the high activity and selectivity over hydrocerussite. This work not only offers a new approach of enhancing the selectivity in CO
RR by suppressing the self-reduction of electrode materials, but also provides a strategy for studying the reaction mechanism and active phases of electrocatalysts.
Artificial synapses can boost neuromorphic computing to overcome the inherent limitations of von Neumann architecture. As a promising memristor candidate, ferroelectric tunnel junctions (FTJ) enable ...the authors to successfully emulate spike‐timing‐dependent synapses. However, the nonlinear and asymmetric synaptic weight update under repeated presynaptic stimulation hampers neuromorphic computing by favoring the runaway of synaptic weights during learning. Here, the authors demonstrate an FTJ whose conductivity varies linearly and symmetrically by judiciously combining ferroelectric domain switching and oxygen vacancy migration. The artificial neural network based on this FTJ‐synapse achieves classification accuracy of 96.7% during supervised learning, which is the closest to the maximum theoretical value of 98% achieved to date. This artificial synapse also demonstrates stable unsupervised learning in a noisy environment for its well‐balanced spike‐timing‐dependent plasticity response. The novel concept of controlling ionic migration in ferroelectric materials paves the way toward highly reliable and reproducible supervised and unsupervised learning strategies.
By combining ferroelectric domain switching and oxygen vacancy migration, a ferroelectric tunnel junction artificial synapse with intrinsic nonlinearity as low as 0.13–0.17 and symmetric weight updating is developed, which greatly improved the classification accuracy of neural network hardware in supervised learning to 96.7% and enhanced robustness to noise during unsupervised learning.
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•Microplastics (MPs) released more Cr in the in-vitro digestive model than in fresh water.•Gastric phase aroused the most bioaccessible Cr(VI) and Cr(III).•Cr on degradable MP was ...more bioaccessible than Cr on nondegradable MPs.•The Cr exposure via MP consumption was estimated for different human groups.•Cr on degradable MP may pose higher noncarcinogenic risks to human.
Microplastics (MPs), polymer particles capable of adsorbing heavy metals from ambient environment, have been found in diverse human food resources. Through the consumption of MPs, heavy metals adsorbed on MPs might be transported into human body. This study aims to explore the behavior of heavy metal-contaminated MPs in human digestive system which is not previously researched. Firstly, a chromium (Cr) adsorption/desorption study was conducted with four commonly used nondegradable MPs polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS) as well as one degradable MP (polylactic, PLA). Then, the whole digestive system in-vitro method (WDSM), a systematic model including mouth, gastric, small intestine, and large intestine digestive phases, was conducted on the Cr-loaded MPs. Additionally, the bioaccessibilities and hazard quotients (HQs) of Cr(VI) and Cr(III) were evaluated. Among five MPs, although PLA showed the weakest adsorption capacity for Cr, the Cr(VI) bioaccessibilities for PLA reached the highest values of 19.9%, 15.6% and 3.9% in gastric, small intestinal and large intestinal phases, respectively. The bioaccessibilities of Cr(VI) in gastric phase were significantly higher than those in other phases, while no Cr release from MPs was detected in the mouth phase. In gastric phase, the bioaccessibilities of Cr(VI) were significantly higher than those of Cr(III) in the gastric phase, and both of them approached to a similar level in intestinal phases. In the WDSM, the HQs of Cr(VI) and Cr(III) on MPs were lower than the critical level for both adults and children. Based on the measured bioaccessibilities, the maximum daily total Cr intake for different human groups (female children, male children, female adults and male adults) through MP consumption was estimated from 0.50 to 1.18 μg/day. In general, the five tested MPs were potential to serve as Cr vectors in the WDSM.
Biodiversity experiments have shown that species loss reduces ecosystem functioning in grassland. To test whether this result can be extrapolated to forests, the main contributors to terrestrial ...primary productivity, requires large-scale experiments. We manipulated tree species richness by planting more than 150,000 trees in plots with 1 to 16 species. Simulating multiple extinction scenarios, we found that richness strongly increased stand-level productivity. After 8 years, 16-species mixtures had accumulated over twice the amount of carbon found in average monocultures and similar amounts as those of two commercial monocultures. Species richness effects were strongly associated with functional and phylogenetic diversity. A shrub addition treatment reduced tree productivity, but this reduction was smaller at high shrub species richness. Our results encourage multispecies afforestation strategies to restore biodiversity and mitigate climate change.
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