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The concept of endoscopic ultrasound (EUS) has been introduced to non-destructive testing for the internal inspection of tubular structure. It is a typical inspection application on layered media with a non-planar interface. Existing research in this area is hindered by two significant limitations: i) the absence of an EUS acoustic field model that is adaptable to the layered medium with non-planar interfaces; ii) the lack of a generalizable analysis and regularity of the EUS acoustic field distribution. This paper derives a refraction model for the tube interface and delay law. By combining these with the angular spectrum model, an analytical acoustic field model for EUS in tubular structure is developed, providing the theoretical framework for acoustic field analysis and interpretation. Subsequently, the geometric and acoustic parameters of the transducer and the tubular object are non-dimensionalized to normalize diverse EUS inspection scenarios. A parametric analysis is then conducted to identify and comprehend the regularity of the EUS acoustic field distribution, which is the main object of this study. The derived EUS acoustic field regularity is validated through an EUS inspection experiment of a tube using control variate method. The quantitative analysis result of the EUS imaging aligns with the expectations from beam analysis. The proposed analytical model is applicable to any scenarios with multi-layered media and with arbitrary interfaces. Its primary strength lies in its intuitive ability to demonstrate the impact of various parameters on the acoustic field distribution. The methodology of non-dimensionalization provides a paradigm for deriving generalizable regularities in the field of ultrasonic testing and imaging. • The established analytical model aids in comprehending the acoustic field distribution in the layered medium. • The non-dimensionalization normalizes diverse inspection scenarios, facilitating the identification of acoustic patterns. • Experimental imaging performance consistently align with the regularities derived from beam analysis. • The methodology offers a paradigm for extracting generalizable regularities in ultrasonics testing. [ABSTRACT FROM AUTHOR]

• By utilizing Green's formula, the earth potential under multi-train operating conditions is calculated. • Two stray current intrusion paths from the substation grid and armored cable are considered. • The main intrusion path of stray current is the metal protection layer of the armored cable. • Change the grounding strategy of the metal protection layer and use BCD to control DCBMC. The DC magnetic bias phenomenon in transformers can result in increased noise and harmonic components. This study focuses on the DC magnetic bias generated by stray currents in the DC traction power supply system of neutral grounding transformers under multiple train operation conditions. A two-layer soil model is utilized to calculate geodetic potential, with rail potentials from both mainline and depot serving as sources for stray current within the model. Two paths of stray current intrusion into the transformer via the grounding network and cable armor layer from the Main substation have been modeled and analyzed. A simulation test has been designed to verify that the maximum error between experimental data and model calculation data is 8.87%. The implementation of a blocking connection device between the depot and mainline, as well as a change in grounding strategy for the metal protective layer, can effectively reduce DC bias magnetic current in the substation. [ABSTRACT FROM AUTHOR]

Inorganic lead halide perovskites have attracted wide attention in photovoltaic and photocatalytic applications due to their high photoelectric conversion efficiency. However, improving the stability and charge transfer efficiency of perovskites remains a significant challenge, especially in polarity solvent-based photocatalytic applications. Here, we successfully grew CsPb 2 Br 5 particles on g-C 3 N 4 to construct p-n heterojunctions in an aqueous solution. The prepared CsPb 2 Br 5 /g-C 3 N 4 p-n heterojunctions exhibited enhanced photoelectrochemical and photocatalytic performance, as well as better environmental stability in polar solvents (such as water). This enhancement is considered that p-n heterojunctions can effectively promote the separation and transfer of photogenerated carriers and no ligands that hinder the charge transfer are used. The successful synthesis of ligand-free CsPb 2 Br 5 /g-C 3 N 4 p-n heterojunction extends the application of perovskite materials in the fields of photoelectrochemistry and photocatalysis. [Display omitted] • Ligand-free CsPb 2 Br 5 /g-C 3 N 4 p-n heterojunction was synthesized in aqueous solution. • The CsPb 2 Br 5 /g-C 3 N 4 exhibits superior photocatalytic activity and enhanced photoelectrochemical performance. • The p-n heterojunctions exhibited better environmental stability in polar solvents (such as water). [ABSTRACT FROM AUTHOR]

Microbial cell factories have been engineered to produce a variety of biochemicals, ranging from biofuels, food addtives to pharmaceuticals. However, for most compounds, the production yield is far from reaching economical targets. Accumulation of excess biomass contributes to decreasing production yields, and a method for limiting biomass formation while allowing for continued production of biochemicals is therefore desirable. In this study, we investigated eight different culturing setups aiming at inhibiting biomass formation of Escherichia coli , based on nutrient limitations or the addition of growth inhibitors. The ability to control cell growth and the production of biochemicals, exemplified by mevalonate and tyrosine, was characterized. An increased mass yield of both mevalonate and tyrosine was achieved by limiting phosphate, sulfate or magnesium in the media. Sulfate limitation, in particular, resulted in an increase in mass yield of mevalonate and tyrosine by 80% and 50%, respectively. By tracking production and biomass concentrations, it was observed that the production was maintained for more than 10 h after inhibition of cell growth, despite cell maintenance requirements. The outlined method serves as promising approach for increasing production yield of a range of different biochemicals. [ABSTRACT FROM AUTHOR]

It has been found in this study that the combination of ZIF-8 and g-C 3 N 4 turns the photo-inactive ZIF-8 into "active" and significantly enhances the photocatalytic performance for H 2 production. The experimental results such as contact potential difference (CPD) and photodeposition analysis suggest that a built-in electric field exists at the interface of g-C 3 N 4 and ZIF-8, and the direction is from ZIF-8 to g-C 3 N 4. Furthermore, the theoretical calculation of charge density difference and work functions uncover the potential forming mechanism of the built-in electric field. The mechanism analysis exhibits that the built-in electric field is conducive to promote the directional transfer of photo-induced electrons from g-C 3 N 4 to ZIF-8, which significantly boosts the catalytic ability. Hence, the construction of a built-in electric field is considered to be an effective strategy to synthesize robust photocatalysts, and the strategy can be extended to prepare a range of advanced catalysts needing directional charge transfer. [Display omitted] • Photo-inactive ZIF-8 is turned into "active" by built-in electric field. • Photo-inactive ZIF-8 become "active" and acts as the photo-reduction site. • The incorporation of ZIF-8 and g-C 3 N 4 improve the photocatalytic ability for 10 times. • The mechanism was detailly uncovered by the consistent experiments and calculations. [ABSTRACT FROM AUTHOR]

We define a three-dimensional quantum theory of gravity as the holographic dual of the Liouville conformal field theory. The theory is consistent and unitary by definition. The corresponding theory of gravity with negative cosmological constant has peculiar properties. The quantum theory has no normalizable A d S 3 vacuum. The model contains primary black holes with zero spin. All states can be interpreted as BTZ geometries dressed with boundary gravitons. There is a unique universal interaction between these states consistent with unitarity and the conformal symmetry of the model. This theory of gravity, though conceptually isolated from other models of quantum gravity, is worth scrutinizing. [ABSTRACT FROM AUTHOR]