Practical application of aqueous Zn‐ion batteries (AZIBs) is significantly limited by poor reversibility of the Zn anode. This is because of 1) dendrite growth, and 2) water‐induced parasitic ...reactions including hydrogen evolution, during cycling. Here for the first time an elegantly simple method is reported that introduces ethylene diamine tetraacetic acid tetrasodium salt (Na4EDTA) to a ZnSO4 electrolyte. This is shown to concomitantly suppress dendritic Zn deposition and H2 evolution. Findings confirm that EDTA anions are adsorbed on the Zn surface and dominate active sites for H2 generation and inhibit water electrolysis. Additionally, adsorbed EDTA promotes desolvation of Zn(H2O)62+ by removing H2O molecules from the solvation sheath of Zn2+. Side reactions and dendrite growth are therefore suppressed by using the additive. A high Zn reversibility with Coulombic efficiency (CE) of 99.5% and long lifespan of 2500 cycles at 5 mAh cm−2, 2 mAh cm−2 is demonstrated. Additionally, the highly reversible Zn electrode significantly boosts overall performance of VO2//Zn full‐cells. These findings are expected to be of immediate benefit to a range of researchers in using dual‐function additives to suppress Zn dendrite and parasitic reactions for electrochemistry and energy storage applications.
A dual‐function additive, ethylene diamine tetraacetic acid tetrasodium salt (Na4EDTA), is applied in a ZnSO4 electrolyte to boost the reversibility of Zn anodes via electrolysis inhibition and desolvation promotion. These characteristics originate from the high adsorption ability of EDTA on the Zn surface, and strong interaction with Zn2+ hydrated ions. The EDTA‐containing electrolyte endows high Coulombic efficiency, stable voltage profiles and stable cycling performance to VO2//Zn cells.
Defects have been found to enhance the electrocatalytic performance of NiFe‐LDH for oxygen evolution reaction (OER). Nevertheless, their specific configuration and the role played in regulating the ...surface reconstruction of electrocatalysts remain ambiguous. Herein, cationic vacancy defects are generated via aprotic‐solvent‐solvation‐induced leaking of metal cations from NiFe‐LDH nanosheets. DFT calculation and in situ Raman spectroscopic observation both reveal that the as‐generated cationic vacancy defects tend to exist as VM (M=Ni/Fe); under increasing applied voltage, they tend to assume the configuration VMOH, and eventually transform into VMOH‐H which is the most active yet most difficult to form thermodynamically. Meanwhile, with increasing voltage the surface crystalline Ni(OH)x in the NiFe‐LDH is gradually converted into disordered status; under sufficiently high voltage when oxygen bubbles start to evolve, local NiOOH species become appearing, which is the residual product from the formation of vacancy VMOH‐H. Thus, we demonstrate that the cationic defects evolve along with increasing applied voltage (VM → VMOH → VMOH‐H), and reveal the essential motif for the surface restructuration process of NiFe‐LDH (crystalline Ni(OH)x → disordered Ni(OH)x → NiOOH). Our work provides insight into defect‐induced surface restructuration behaviors of NiFe‐LDH as a typical precatalyst for efficient OER electrocatalysis.
Along with increasing voltage during the OER process, the structural evolution of cationic defects within NiFe‐LDH, where the simple vacancy VM changes to VMOH and then to the most reactive VMOH‐H, and the surface restructuration, where surface crystalline Ni(OH)x is converted to disordered Ni(OH)x and then to the surface local NiOOH species, are voltage‐regulated concurrent events defining the eventual catalytic performance of the precatalyst.
Aqueous Zn–iodine (Zn–I2) batteries have been regarded as a promising energy‐storage system owing to their high energy/power density, safety, and cost‐effectiveness. However, the polyiodide shuttling ...results in serious active mass loss and Zn corrosion, which limits the cycling life of Zn–I2 batteries. Inspired by the chromogenic reaction between starch and iodine, a structure confinement strategy is proposed to suppress polyiodide shuttling in Zn–I2 batteries by hiring starch, due to its unique double‐helix structure. In situ Raman spectroscopy demonstrates an I5−‐dominated I−/I2 conversion mechanism when using starch. The I5− presents a much stronger bonding with starch than I3−, inhibiting the polyiodide shuttling in Zn–I2 batteries, which is confirmed by in situ ultraviolet–visible spectra. Consequently, a highly reversible Zn–I2 battery with high Coulombic efficiency (≈100% at 0.2 A g−1) and ultralong cycling stability (>50 000 cycles) is realized. Simultaneously, the Zn corrosion triggered by polyiodide is effectively inhibited owing to the desirable shuttling‐suppression by the starch, as evidenced by X‐ray photoelectron spectroscopy analysis. This work provides a new understanding of the failure mechanism of Zn–I2 batteries and proposes a cheap but effective strategy to realize high‐cyclability Zn–I2 batteries.
Inspired by the significant chromogenic reaction between starch and iodine, the shuttle effect of Zn–I2 batteries is effectively addressed by using starch, which strongly anchors polyiodide anions due to its unique double‐helix structure. Benefiting from this structure confinement, a Coulombic efficiency of almost 100% and an ultralong life of 50 000 cycles are realized in Zn–I2 batteries.
The Z-source inverter, utilizing a unique LC network and previously forbidden shoot-through states, provides unique features, such as the ability to buck and boost voltage with a simple single-stage ...structure. The analysis and control methods provided in the literature are based on an assumption that the inductor current is relatively large, continuous, and has small ripple. This assumption becomes invalid when the load power factor is low or the inductance is small in order to minimize the inductor's size and weight for some applications where volume and weight are crucial. Under these conditions, the inductor current has high ripple or even becomes discontinuous. As a result, the Z-source inverter exhibits new operation modes that have not been discussed before. This paper analyzes these new operation modes and the associated circuit characteristics.
Transmission and distribution (T&D) networks are a critical part of the power grid. As moving towards a smart-grid, it is essential to modernize the T&D networks and make it "Smart-grid ready". The ...concept of flexible ac transmission systems (FACTS) has been well-known for three decades. Rapid advancements in power electronics technology in the past decades have led to a new generation of FACTS devices. The Modern FACTS technology helps the transition of transmission networks to "smart". With increasing penetration of distributed generation, the distribution network is seeing unprecedented variation in terms of its fundamental operation and control, from renewable energy integration to microgrid, from active control of power quality, volt/var and frequency to self-healing and islanding operation. As a key part of smart-grid at the distribution level, we summarize the current efforts as a concept of resilient ac distribution systems (RACDS). The concepts of both FACTS and RACDS for a smart grid are introduced in this paper. Different configurations, key benefits, operating principles and world-wide installations of FACTS and RACDS devices are presented in detail. The ongoing and future direction of R&D leading to newer generations of FACTS and RACDS are also discussed.
Objective
The purpose of this article was to perform a systematic review and meta-analysis regarding the diagnostic test accuracy of chest CT for detecting coronavirus disease 2019 (COVID-19).
...Methods
PubMed, Embase, Web of Science, and CNKI were searched up to March 12, 2020. We included studies providing information regarding diagnostic test accuracy of chest CT for COVID-19 detection. The methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Sensitivity and specificity were pooled.
Results
Sixteen studies (
n
= 3186 patients) were included. The risks of bias in all studies were moderate in general. Pooled sensitivity was 92% (95% CI = 86–96%), and two studies reported specificity (25% 95% CI = 22–30% and 33% 95% CI = 23–44%, respectively). There was substantial heterogeneity according to Cochran’s
Q
test (
p
< 0.01) and Higgins
I
2
heterogeneity index (96% for sensitivity). After dividing the studies into two groups based on the study site, we found that the sensitivity of chest CT was great in Wuhan (the most affected city by the epidemic) and the sensitivity values were very close to each other (97%, 96%, and 99%, respectively). In the regions other than Wuhan, the sensitivity varied from 61 to 98%.
Conclusion
Chest CT offers the great sensitivity for detecting COVID-19, especially in a region with severe epidemic situation. However, the specificity is low. In the context of emergency disease control, chest CT provides a fast, convenient, and effective method to early recognize suspicious cases and might contribute to confine epidemic.
Key Points
•
Chest CT has a high sensitivity for detecting COVID-19, especially in a region with severe epidemic, which is helpful to early recognize suspicious cases and might contribute to confine epidemic.
An epidemic of Coronavirus Disease 2019 (COVID-19) began in December 2019 and triggered a Public Health Emergency of International Concern (PHEIC). We aimed to find risk factors for the progression ...of COVID-19 to help reducing the risk of critical illness and death for clinical help.
The data of COVID-19 patients until March 20, 2020 were retrieved from four databases. We statistically analyzed the risk factors of critical/mortal and non-critical COVID-19 patients with meta-analysis.
Thirteen studies were included in Meta-analysis, including a total number of 3027 patients with SARS-CoV-2 infection. Male, older than 65, and smoking were risk factors for disease progression in patients with COVID-19 (male: OR = 1.76, 95% CI (1.41, 2.18), P < 0.00001; age over 65 years old: OR =6.06, 95% CI(3.98, 9.22), P < 0.00001; current smoking: OR =2.51, 95% CI(1.39, 3.32), P = 0.0006). The proportion of underlying diseases such as hypertension, diabetes, cardiovascular disease, and respiratory disease were statistically significant higher in critical/mortal patients compared to the non-critical patients (diabetes: OR=3.68, 95% CI (2.68, 5.03), P < 0.00001; hypertension: OR = 2.72, 95% CI (1.60,4.64), P = 0.0002; cardiovascular disease: OR = 5.19, 95% CI(3.25, 8.29), P < 0.00001; respiratory disease: OR = 5.15, 95% CI(2.51, 10.57), P < 0.00001). Clinical manifestations such as fever, shortness of breath or dyspnea were associated with the progression of disease fever: 0R = 0.56, 95% CI (0.38, 0.82), P = 0.003;shortness of breath or dyspnea: 0R=4.16, 95% CI (3.13, 5.53), P < 0.00001. Laboratory examination such as aspartate amino transferase(AST) > 40U/L, creatinine(Cr) ≥ 133mol/L, hypersensitive cardiac troponin I(hs-cTnI) > 28pg/mL, procalcitonin(PCT) > 0.5ng/mL, lactatede hydrogenase(LDH) > 245U/L, and D-dimer > 0.5mg/L predicted the deterioration of disease while white blood cells(WBC)<4 × 109/L meant a better clinical statusAST > 40U/L:OR=4.00, 95% CI (2.46, 6.52), P < 0.00001; Cr ≥ 133μmol/L: OR = 5.30, 95% CI (2.19, 12.83), P = 0.0002; hs-cTnI > 28 pg/mL: OR = 43.24, 95% CI (9.92, 188.49), P < 0.00001; PCT > 0.5 ng/mL: OR = 43.24, 95% CI (9.92, 188.49), P < 0.00001;LDH > 245U/L: OR = 43.24, 95% CI (9.92, 188.49), P < 0.00001; D-dimer > 0.5mg/L: OR = 43.24, 95% CI (9.92, 188.49), P < 0.00001; WBC < 4 × 109/L: OR = 0.30, 95% CI (0.17, 0.51), P < 0.00001.
Male, aged over 65, smoking patients might face a greater risk of developing into the critical or mortal condition and the comorbidities such as hypertension, diabetes, cardiovascular disease, and respiratory diseases could also greatly affect the prognosis of the COVID-19. Clinical manifestation such as fever, shortness of breath or dyspnea and laboratory examination such as WBC, AST, Cr, PCT, LDH, hs-cTnI and D-dimer could imply the progression of COVID-19.
Organometallic halide perovskite films with good surface morphology and large grain size are desirable for obtaining high‐performance photovoltaic devices. However, defects and related trap sites are ...generated inevitably at grain boundaries and on surfaces of solution‐processed polycrystalline perovskite films. Seeking facial and efficient methods to passivate the perovskite film for minimizing defect density is necessary for further improving the photovoltaic performance. Here, a convenient strategy is developed to improve perovskite crystallization by incorporating a 2D polymeric material of graphitic carbon nitride (g‐C3N4) into the perovskite layer. The addition of g‐C3N4 results in improved crystalline quality of perovskite film with large grain size by retarding the crystallization rate, and reduced intrinsic defect density by passivating charge recombination centers around the grain boundaries. In addition, g‐C3N4 doping increases the film conductivity of perovskite layer, which is beneficial for charge transport in perovskite light‐absorption layer. Consequently, a champion device with a maximum power conversion efficiency of 19.49% is approached owing to a remarkable improvement in fill factor from 0.65 to 0.74. This finding demonstrates a simple method to passivate the perovskite film by controlling the crystallization and reducing the defect density.
Graphitic carbon nitride (g‐C3N4) is incorporated into the perovskite precursor solution to modify the perovskite film by controlling the perovskite crystallization, reducing the intrinsic defect density, and improving the film conductivity. As a result, a champion device with a maximum power conversion efficiency of 19.49% is approached.
A recent analysis by the LHCb Collaboration suggests the existence of three narrow pentaquarklike states-the P_{c}(4312), P_{c}(4440), and P_{c}(4457)-instead of just one in the previous analysis the ...P_{c}(4450). The closeness of the P_{c}(4312) to the Dover ¯Σ_{c} threshold and the P_{c}(4440) and P_{c}(4457) to the Dover ¯^{*}Σ_{c} threshold suggests a molecular interpretation of these resonances. We show that these three pentaquarklike resonances can be naturally accommodated in a contact-range effective field theory description that incorporates heavy-quark spin symmetry. This description leads to the prediction of all the seven possible S-wave heavy antimeson-baryon molecules that is, there should be four additional molecular pentaquarks in addition to the P_{c}(4312), P_{c}(4440), and P_{c}(4457), providing the first example of a heavy-quark spin symmetry molecular multiplet that is complete. If this is confirmed, it will not only give us an impressive example of the application of heavy-quark symmetries and effective field theories in hadron physics, it will also uncover a clear and powerful ordering principle for the molecular spectrum, reminiscent of the SU(3)-flavor multiplets to which the light hadron spectrum conforms.
This study aims to discuss the fundamentals of music copywriting in music education and identify pathways for integrating musical compositions into the learning process without infringing copyright ...and prohibiting the use of specific music pieces. To achieve this goal, the authors used methods of analysis to identify the available resources in the field of music copywriting and education. The study reports that 35% of students give their preference to classical music, 32% want to use traditional Chinese music, and only 22% consider it possible to play modern melodies. To avoid copyright infringement in the presentation of theory that is available on the Internet, authors should document their original approach to learning and publish the data in books and monographs. The authors found that the use of classical music in the classroom was not an infringement of copyright because the statute of limitations had expired. The findings suggested that the students whose similarity scores ranged from 0 to 24% in the music compositions got better knowledge, with the coefficient of effectiveness of 2.5.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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