The present work identifies two types of La Niña based on the spatial distribution of sea surface temperature (SST) anomaly. In contrast to the eastern Pacific (EP) La Niña event, a new type of La ...Niña (central Pacific, or CP La Niña) is featured by the SST cooling center over the CP. These two types of La Niña exhibit a fundamental difference in SST anomaly evolution: the EP La Niña shows a westward propagation feature while the CP La Niña exhibits a standing feature over the CP. The two types of La Niña can give rise to a significantly different teleconnection around the globe. As a response to the EP La Niña, the North Atlantic (NA)–Western European (WE) region experiences the atmospheric anomaly resembling a negative North Atlantic Oscillation (NAO) pattern accompanied by a weakening Atlantic jet. It leads to a cooler and drier than normal winter over Western Europe. However, the CP La Niña has a roughly opposing impact on the NA–WE climate. A positive NAO-like climate anomaly is observed with a strengthening Atlantic jet, and there appears a warmer and wetter than normal winter over Western Europe. Modeling experiments indicate that the above contrasting atmospheric anomalies are mainly attributed to the different SST cooling patterns for the two types of La Niña. Mixing up their signals would lead to difficulty in seasonal prediction of regional climate. Since the La Niña-related SST anomaly is clearly observed during the developing autumn, the associated winter climate anomalies over Western Europe could be predicted a season in advance.
C dots (CDs) have shown great potential in bioimaging and phototherapy. However, it is challenging to manipulate their fluorescent properties and therapeutic efficacy to satisfy the requirements for ...clinic applications. In this study, we prepared S, Se-codoped CDs via a hydrothermal method and demonstrated that the doping resulted in excitation wavelength-independent near-infrared (NIR) emissions of the CDs, with peaks at 731 and 820 nm. Significantly, the CDs exhibited a photothermal conversion efficiency of ~58.2%, which is the highest reported value for C nanostructures and is comparable to that of Au nanostructures. Moreover, the CDs had a large two-photon absorption cross section (~30,045 GM), which allowed NIR emissions and the photothermal conversion of the CDs through the two-photon excitation (TPE) mechanism.
In vitro
and
in vivo
tests suggested that CDs can function as new multifunctional phototheranostic agents for the TPE fluorescence imaging and photothermal therapy of cancer cells.
Exploring of new catalyst activation principle holds a key to unlock catalytic powers of cheap and earth‐abundant materials for large‐scale applications. In this regard, the vacancy defects have been ...proven to be effective to initiate catalytic active sites and endow high electrocatalytic activities. However, such electrocatalytically active defects reported to date have been mostly formed by anion vacancies. Herein, it is demonstrated for the first time that iron cation vacancies induce superb water splitting bifunctionality in alkaline media. A simple wet‐chemistry method is developed to grow ultrathin feroxyhyte (δ‐FeOOH) nanosheets with rich Fe vacancies on Ni foam substrate. The theoretical and experimental results confirm that, in contrast to anion vacancies, the formation of rich second neighboring Fe to Fe vacancies in δ‐FeOOH nanosheets can create catalytic active centers for both hydrogen and oxygen evolution reactions. The atomic level insight into the new catalyst activation principle based on metal vacancies is adaptable for developing other transition metal electrocatalysts, including Fe‐based ones.
Ultrathin feroxyhyte (δ‐FeOOH) nanosheets with rich Fe‐vacancies on Ni foam are synthesized, based on which an iron‐vacancy‐based catalyst activation principle to induce water‐splitting bifunctionality is proposed. Theoretical studies confirm that the formation of the second neighboring Fe to Fe vacancies in δ‐FeOOH nanosheets can create active centers for both hydrogen and oxygen evolution reactions.
A Psychovisual Quality Metric in Free-Energy Principle Zhai, Guangtao; Wu, Xiaolin; Yang, Xiaokang ...
IEEE transactions on image processing,
2012-Jan., 2012, 2012-Jan, 2012-01-00, 20120101, Letnik:
21, Številka:
1
Journal Article
Recenzirano
In this paper, we propose a new psychovisual quality metric of images based on recent developments in brain theory and neuroscience, particularly the free-energy principle. The perception and ...understanding of an image is modeled as an active inference process, in which the brain tries to explain the scene using an internal generative model. The psychovisual quality is thus closely related to how accurately visual sensory data can be explained by the generative model, and the upper bound of the discrepancy between the image signal and its best internal description is given by the free energy of the cognition process. Therefore, the perceptual quality of an image can be quantified using the free energy. Constructively, we develop a reduced-reference free-energy-based distortion metric (FEDM) and a no-reference free-energy-based quality metric (NFEQM). The FEDM and the NFEQM are nearly invariant to many global systematic deviations in geometry and illumination that hardly affect visual quality, for which existing image quality metrics wrongly predict severe quality degradation. Although with very limited or even without information on the reference image, the FEDM and the NFEQM are highly competitive compared with the full-reference SSIM image quality metric on images in the popular LIVE database. Moreover, FEDM and NFEQM can measure correctly the visual quality of some model-based image processing algorithms, for which the competing metrics often contradict with viewers' opinions.
The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes. Although nitrogen is abundant in the atmosphere and the ammonia ...synthesis reaction is exothermic on the thermodynamics, the conversion of N
2
to ammonia is actually hard to proceed owing to the chemical inertness and stability of N
2
molecules. In industry, ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300–500 °C, 20–30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g., CO
2
). Recently, a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention, which holds great promise for nitrogen fixation under room temperature and atmospheric pressure. However, the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems. Here we provide an overview of the latest progresses, remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation. Moreover, this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results. We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.
To enhance the visibility and usability of images captured in hazy conditions, many image dehazing algorithms (DHAs) have been proposed. With so many image DHAs, there is a need to evaluate and ...compare these DHAs. Due to the lack of the reference haze-free images, DHAs are generally evaluated qualitatively using real hazy images. But it is possible to perform quantitative evaluation using synthetic hazy images since the reference haze-free images are available and full-reference (FR) image quality assessment (IQA) measures can be utilized. In this paper, we follow this strategy and study DHA evaluation using synthetic hazy images systematically. We first build a synthetic haze removing quality (SHRQ) database. It consists of two subsets: regular and aerial image subsets, which include 360 and 240 dehazed images created from 45 and 30 synthetic hazy images using 8 DHAs, respectively. Since aerial imaging is an important application area of dehazing, we create an aerial image subset specifically. We then carry out subjective quality evaluation study on these two subsets. We observe that taking DHA evaluation as an exact FR IQA process is questionable, and the state-of-the-art FR IQA measures are not effective for DHA evaluation. Thus, we propose a DHA quality evaluation method by integrating some dehazing-relevant features, including image structure recovering, color rendition, and over-enhancement of low-contrast areas. The proposed method works for both types of images, but we further improve it for aerial images by incorporating its specific characteristics. Experimental results on two subsets of the SHRQ database validate the effectiveness of the proposed measures.
Nanoscale surface‐engineering plays an important role in improving the performance of battery electrodes. Nb2O5 is one typical model anode material with promising high‐rate lithium storage. However, ...its modest reaction kinetics and low electrical conductivity obstruct the efficient storage of larger ions of sodium or potassium. In this work, partially surface‐amorphized and defect‐rich black niobium oxide@graphene (black Nb2O5−x@rGO) nanosheets are designed to overcome the above Na/K storage problems. The black Nb2O5−x@rGO nanosheets electrodes deliver a high‐rate Na and K storage capacity (123 and 73 mAh g−1, respectively at 3 A g−1) with long‐term cycling stability. Besides, both Na‐ion and K‐ion full batteries based on black Nb2O5−x@rGO nanosheets anodes and vanadate‐based cathodes (Na0.33V2O5 and K0.5V2O5 for Na‐ion and K‐ion full batteries, respectively) demonstrate promising rate and cycling performance. Notably, the K‐ion full battery delivers higher energy and power densities (172 Wh Kg−1 and 430 W Kg−1), comparable to those reported in state‐of‐the‐art K‐ion full batteries, accompanying with a capacity retention of ≈81.3% over 270 cycles. This result on Na‐/K‐ion batteries may pave the way to next‐generation post‐lithium batteries.
Surface‐amorphized and defect‐rich black niobium oxide@graphene nanosheets are constructed as anode materials for sodium and potassium storage, delivering a high‐rate Na/K storage capacity (123 and 73 mAh g−1, respectively at 3 A g−1) and long‐term cycling stability. Na/K full batteries based on the prepared anodes also demonstrate high energy and power densities.
NiO nanoflakes are created with a simple hydrothermal method on 3D (three‐dimensional) graphene scaffolds grown on Ni foams by microwave plasma enhanced chemical vapor deposition (MPCVD). Such ...as‐grown NiO‐3D graphene hierarchical composites are then applied as monolithic electrodes for a pseudo‐supercapacitor application without needing binders or metal‐based current collectors. Electrochemical measurements impart that the hierarchical NiO‐3D graphene composite delivers a high specific capacitance of ≈1829 F g−1 at a current density of 3 A g−1 (the theoretical capacitance of NiO is 2584 F g−1). Furthermore, a full‐cell is realized with an energy density of 138 Wh kg−1 at a power density of 5.25 kW kg−1, which is much superior to commercial ones as well as reported devices in asymmetric capacitors of NiO. More attractively, this asymmetric supercapacitor exhibits capacitance retention of 85% after 5000 cycles relative to the initial value of the 1st cycle.
Hierarchical nickel oxide nanoflake 3D graphene electrodes are developed by growing NiO nanoflakes atop 3D architecture of graphene on Ni foam. The optimum structure enables the 3‐electrode pseudocapacitors and 2‐electrode full cells to deliver outstanding electrochemical performance. In a full cell configuration, the achieved power density is much higher than that of commercially available asymmetric capacitors.
The treatment of cancers is a significant challenge in the healthcare context today. Spreading circulating tumor cells (CTCs) throughout the body will eventually lead to cancer metastasis and produce ...new tumors near the healthy tissues. Therefore, separating these invading cells and extracting cues from them is extremely important for determining the rate of cancer progression inside the body and for the development of individualized treatments, especially at the beginning of the metastasis process. The continuous and fast separation of CTCs has recently been achieved using numerous separation techniques, some of which involve multiple high-level operational protocols. Although a simple blood test can detect the presence of CTCs in the blood circulation system, the detection is still restricted due to the scarcity and heterogeneity of CTCs. The development of more reliable and effective techniques is thus highly desired. The technology of microfluidic devices is promising among many other bio-chemical and bio-physical technologies. This paper reviews recent developments in the two types of microfluidic devices, which are based on the size and/or density of cells, for separating cancer cells. The goal of this review is to identify knowledge or technology gaps and to suggest future works.
The ampacity of photoelectric composite cables largely depends on the temperature of their conductors, which in turn is related to other internal and external factors of the cable. Due to the thermal ...degradation associated with these factors, the cable can be damaged, regardless of its quality. To avoid this damage, an iterative parameter correction method (IPCM) is proposed and developed to correct the parameters of the cable before determining its ampacity based on the fitting function. Different optical fiber temperatures of the cable are collected using Brillouin optical time-domain analysis (BOTDA); together with the material parameters of the cable, they are modeled in ANSYS, which is a finite element modeling engineering software. Then, the IPCM is performed before determining the corrected ampacity. After conducting experiments on multiple groups of data, the results show that the calculation error is within the engineering error range. The mean error obtained with the proposed method is less than that obtained by the finite element method (FEM); it shows that the engineering adaptability improved by about 0.41%.
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