In this paper, we propose and demonstrate a gas pressure fiber probe with high sensitivity magnified by Vernier effect. The probe is composed of two cascaded Fabry-Perot interferometers based on a ...SMF-SOHST-OFC structure (SMF: single-mode fiber; SOHST: side-opened hollow silica tube; OFC: optical fiber column). The high-frequency CO 2 laser drilling method for hollow silica tube can effectively maintain the transient balance of the air pressure inside and outside the cavity without destroying the reflective ends of the optical fibers. Experimental results show that the prepared fiber probe with the SOHST length of 375.2 μm and column length of 247.3 μm has high gas pressure sensitivity of 80.3 pm/kPa by demodulating Vernier envelope, and it has relatively low temperature cross-sensitivity of -1.33 kPa/°C. This sensor is highly sensitive and of compact size, which not only can be applied in gas pressure sensing but also has the potential for application in microfluidic detection.
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•Inducing surface oxygen vacancy defects on 2D/2D coupled Bi2WO6/BiOI nanosheets.•Oxygen vacancies as surface active sites and extend photo-absorption to NIR region.•p-n ...heterojunctions across 2D/2D motif allow directional migration of charge flow.•Electrons trapped at oxygen vacancies endow spatial separation of charge carriers.•Exhibits highest CH4 yield among all existing 2D BiOI and Bi2WO6-based composites.
Semiconductor-based photocatalytic CO2 conversion is a promising and sustainable avenue in response to the anthropogenic climate change and imminent energy crisis, which however is unavoidably impeded by the limited photo-absorption, undesirable recombination of photogenerated charge carriers and insufficient surface active sites on semiconductors. In this study, all these challenges were overcome by selectively and chemically assembly of oxygen-deficient Bi2WO6 nanosheets onto BiOI nanosheets, forming a novel surface defect-engineered 2D/2D motif with built-in nanoscale p-n heterojunctions. This rational cascade configuration with internal electric field renders ultrafast directional migration and spatial separation of photogenerated charge carriers. Meanwhile, the oxygen vacant sites with abundant trapped electrons serve as the active sites for CO2 reduction and extend the light absorption of the photocatalytic system to NIR region. Combining these propitious properties, our delineated nanoscale p-n heterojunction on the basis of 2D/2D assembly of surface defect-engineered nanosheets presents a new and unprecedented concept for effective generation of charge carriers, directional steering of charge flow and manipulation of surface active sites, which cooperatively lead to superior photocatalytic performance. Notably, our developed oxygen-deficient Bi2WO6/BiOI binanosheets exhibit a remarkably high production yield of CH4, which represents the state-of-the-art visible light-driven CH4 production activity among all the existing 2D BiOI-based and Bi2WO6-based composites.
An interleaved current-fed full bridge (ICFFB) dc-dc converter is proposed in this paper that has low input current ripple to meet the fuel cell demands. By interleaving two isolated CFFB converters ...with parallel input and series output connection, both input current ripple and output voltage ripple can be reduced. In addition, the size of the magnetic components and current stress of the semiconductor devices on the input side are also reduced. Similarly, smaller voltage rating components can be used on the output side. Only one digital signal processor microcontroller is used to generate phase-shifted gate signals and to implement a cascaded digital control system. The main features of the proposed converter are high efficiency, small passive component size, and small input current ripple. Experimental results for a 1.2-kW interleaved CFFB converter are provided in the paper
In this paper, we separate the integrated (spot) volatility of an individual Itô process into integrated (spot) systematic and idiosyncratic volatilities, and estimate them by aggregation of local ...factor analysis (localization) with large-dimensional high-frequency data. We show that, when both the sampling frequency n and the dimensionality p go to infinity and p ≥ C √n for some constant C, our estimators of High dimensional Itô process; common driving process; specific driving process, integrated High dimensional Itô process, common driving process, specific driving process, systematic and idiosyncratic volatilities are √n (n
1/4 for spot estimates) consistent, the best rate achieved in estimating the integrated (spot) volatility which is readily identified even with univariate high-frequency data. However, when Cn
1/4 ≤ p < C √n, aggregation of n
1/4-consistent local estimates of systematic and idiosyncratic volatilities results in p-consistent (not √n-consistent) estimates of integrated systematic and idiosyncratic volatilities. Even more interesting, when p < Cn
1/4, the integrated estimate has the same convergence rate as the spot estimate, both being p-consistent. This reveals a distinctive feature from aggregating local estimates in the low-dimensional high-frequency data setting. We also present estimators of the integrated (spot) idiosyncratic volatility matrices as well as their inverse matrices under some sparsity assumption. We finally present a factor-based estimator of the inverse of the spot volatility matrix. Numerical studies including theMonte Carlo experiments and real data analysis justify the performance of our estimators.
In this paper, we introduce a local principal component analysis approach to determining the number of common factors of a continuous-time factor model with time-varying factor loadings using ...high-frequency data. The model is approximated locally on shrinking blocks using discrete-time factor models. The number of common factors is estimated by minimizing the penalized aggregated mean squared residual error over all shrinking blocks. While the local mean squared residual error on each block converges at rate min(n1/4,p), where n is the sample size and p is the dimension, the aggregated mean squared residual error converges at rate min(n1/2,p); this achieves the convergence rate of the penalized criterion function of the global principal component analysis method, assuming restrictive constant factor loading. An estimator of the number of factors based on the local principal component analysis is consistent. Simulation results justify the performance of our estimator. A real financial dataset is analysed.
Improving the stability of cuprous oxide (Cu2O) is imperative to its practical applications in artificial photosynthesis. In this work, Cu2O nanowires are encapsulated by metal–organic frameworks ...(MOFs) of Cu3(BTC)2 (BTC=1,3,5‐benzene tricarboxylate) using a surfactant‐free method. Such MOFs not only suppress the water vapor‐induced corrosion of Cu2O but also facilitate charge separation and CO2 uptake, thus resulting in a nanocomposite representing 1.9 times improved activity and stability for selective photocatalytic CO2 reduction into CH4 under mild reaction conditions. Furthermore, direct transfer of photogenerated electrons from the conduction band of Cu2O to the LUMO level of non‐excited Cu3(BTC)2 has been evidenced by time‐resolved photoluminescence. This work proposes an effective strategy for CO2 conversion by a synergy of charge separation and CO2 adsorption, leading to the enhanced photocatalytic reaction when MOFs are integrated with metal oxide photocatalyst.
Cu2O nanowires are decorated with Cu3(BTC)2 by a surfactant‐free method. The Cu2O@Cu3(BTC)2 core–shell structure offers enlarged active surfaces and prolonged lifetime of separated electrons for CO2 reduction into CH4, exhibiting enhanced photocatalytic activity and stability compared to the bare Cu2O.
Multi-drug resistance (MDR) and hypervirulence (hv) were exhibited by different well-separated
lineages in the past, but their convergence clones-MDR-hypervirulent
(HvKPs)-both highly pathogenic and ...resistant to most available antibiotics, have increasingly been reported. In light of the clonal lineages and molecular characteristics of the studied MDR-HvKP strains found in the literature since 2014, this review discusses the epidemiology of MDR-HvKPs, in particular summarizing the three general aspects of plasmids-associated mechanisms underlying the formation of MDR-HvKPs clones: MDR-classic
(cKPs) acquiring hv plasmids, hvKPs obtaining MDR plasmids, and the acquisition of hybrid plasmids harboring virulence and resistance determinants. A deeper understanding of epidemiological characteristics and possible formation mechanisms of MDR-HvKPs is greatly needed for the proper surveillance and management of this potential threat.
In order to study the degradation of polycyclic aromatic hydrocarbons (PAHs) in an aged and highly contaminated soil, four bioremediation strategies (indigenous microorganisms, microbial ...bioaugmentation with a PAH-degrading and bioemulsifier-producing strain, Rhodococcus ruber Em1, plant bioaugmentation with Orychophragmus violaceus and their combination) were compared and the enhanced degradation mechanism was investigated in soil mesocosms. Degradation rates over a period of 175 days showed that Em1 combined with Orychophragmus violaceus promoted a significant enhancement of PAHs degradation. In inoculated microcosms with Rhodococcus ruberEm1, mineralization reached a lower level in the absence than in the presence of plants. Elimination of PAHs was significantly enhanced (increased by 54.45%) in the bioaugmented mesocosms. Quantitative PCR indicated that copy numbers of linA and RHD-like gene (encoding PAH-ring hydroxylating dioxygenase) in the mesocosm with plant were three and five times higher than those in the mesocosm without plant, respectively. Transcript copy numbers of RHD-like gene and 16S rRNA gene of strain Em1 in mesocosm with plant were two and four times higher than those in the mesocosm without plant, respectively. Taken together, the results of this study show that plants or Rhodococcus ruber Em1 enhance total PAHs removal, moreover their effects are necessarily cumulative by combined strains and plants.
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•Four bioremediation strategies were employed and the degradation of PAHs was examined in soil mesocosms.•The elimination of PAHs was greatly enhanced by strain Em1 combined with O. violaceus.•Quantitative PCR indicated that copy numbers of linA and RHD-like gene in the mesocosm with plant were higher.•Transcript copy numbers of RHD-like gene and 16S rRNA gene of strain Em1 in mesocosm with plant were higher.
Herein, we describe an unprecedented cascade reaction to β‐stereogenic γ‐lactams involving Pd(II)‐catalyzed enantioselective aliphatic methylene C(sp3)−H alkenylation–aza‐Wacker cyclization through ...syn‐aminopalladation. Readily available 3,3′‐substituted BINOLs are used as chiral ligands, providing the corresponding γ‐lactams with broad scope and high enantioselectivities (up to 98 % ee).
An unprecedented cascade reaction to β‐stereogenic γ‐lactams involving Pd(II)‐catalyzed enantioselective aliphatic methylene C(sp3)−H alkenylation–aza‐Wacker cyclization through syn‐aminopalladation is reported. Readily available 3,3′‐substituted BINOLs are used as chiral ligands, providing the corresponding γ‐lactams with broad scope and high enantioselectivities (up to 98 % ee).
In this article, we demonstrate a "Fabry-Perot + Michelson" hybrid interferometer based on a polymer micro-cap located on asymmetric 2-core fiber (2CF) facet. Because the polymer micro-cap comprises ...a flat reflector and a concave reflector, the light propagating in the centric core will be reflected twice forming Fabry-Perot interference. Due to the bias angle between the eccentric core and the concave reflector, the light in the eccentric core reflects only once on the flat reflector and would interfere with the other reflected light in the 2CF. The experimental results show that Fabry-Perot and Michelson interference occur and are superimposed on the directly detected spectrum. Independent interferometric spectrums can be separated by Discrete Fourier Transform to achieve humidity-temperature simultaneous measurement based on coefficient matrix demodulation. Moreover, this new optical fiber sensing platform is all-solid, high-integration, and flexible, so it has potential in lab-on-fiber applications.
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