Terminal Structure Research Articles

NusG-dependent RNA polymerase pausing is a common feature of riboswitch regulatory mechanisms.

Transcription by RNA polymerase is punctuated by transient pausing events. Pausing provides time for RNA folding and binding of regulatory factors to the paused elongation complex. We previously identified 1600 NusG-dependent pauses throughout the Bacillus subtilis genome, with ∼20% localized to 5' leader regions, suggesting a regulatory role for these pauses. We examined pauses associated with known riboswitches to determine whether pausing is a common feature of these mechanisms. NusG-dependent pauses in the fmnP, tenA, mgtE, lysP and mtnK riboswitches were in strategic positions preceding the critical decision between the formation of alternative antiterminator or terminator structures, which is a critical feature of transcription attenuation mechanisms. In vitro transcription assays demonstrated that pausing increased the frequency of termination in the presence of the cognate ligand. NusG-dependent pausing also reduced the ligand concentration required for efficient termination. In vivo expression studies with transcriptional fusions confirmed that NusG-dependent pausing is a critical component of each riboswitch mechanism. Our results indicate that pausing enables cells to sense a broader range of ligand concentrations for fine-tuning riboswitch attenuation mechanisms.

Force analysis and improvement of main transformer bushing terminal structure

Abstract After investigation, it was found that due to natural environmental conditions such as rain and snow temperature, equipment such as down conductor above the terminals, and natural swings of wires, the terminal blocks of the down conductor bushing on the high voltage side of the main transformer of a 500kV substation will deteriorate and deform. Following the force analysis and experiment on the down conductor bushing terminal block on the high voltage side of the main transformer, it is found that the weak structure of the bushing terminal block lies in the vertical orientation of the terminal and the connection point of the transverse structure, and its horizontal external force limit value is 1.91KN. In this paper, it was finally decided to improve the terminal structure by erecting diagonal supports between the vertical and transverse structures of the terminals. The improved terminal block can be subjected to an external force of 5KN horizontally, and the terminal shape is within the safe range. It can ensure the safety and stability of the main transformer bushing terminal block.

Distinct interactions with pentaalanine tuned by terminal structures of polyisoprene that determine their mechanical properties

The terminal aggregates of natural rubber exhibit multi-scale reinforcing effects, but the synthetic counterpart still lacks of readily available terminal functionalized polymers, and the corresponding terminal structure-function correlation remains obscure. In this work, by utilizing commercial raw materials, four kinds of polyisoprene (PIP) derivatives with different terminal structures (PEO, ene-PEO, COOH, H) were prepared and blended with pentaalanine to investigated the change of terminal structures and impact on rubber performance. It is revealed that the tight hydrogen-bonded β-sheet in the terminal nanoconfinements is correlated to the overall performance of the elastomers. As the polarity of the terminal group of the main chain increases, the content of the β-sheet formed with 5A also increases, and the corresponding properties such as tensile strength, dimensional stability, strain recovery, apparent activation energy and cross-linking density are all enhanced. Among them, two elastomers (PIP-PEO, PIP-ene-PEO) have high tensile strength and great dimensional stability, which are comparable to Malaysian natural rubber. These results present the multi-scale reinforcement process of terminal H-bonding aggregates due to the synergistic changes and stable co-assembly of polar main chains and peptide, giving an inspiration for the development of large-scale, high strength and creep resistant synthetic elastomers.

Pan-Genome-Wide Investigation and Co-Expression Network Analysis of HSP20 Gene Family in Maize.

Heat shock protein 20 (HSP20) is a diverse and functionally important protein family that plays a crucial role in plants' tolerance to various abiotic stresses. In this study, we systematically analyzed the structural and functional characteristics of the HSP20 gene family within the Zea pan-genome. By identifying 56 HSP20 pan-genes, we revealed the variation in the number of these genes across different maize inbreds or relatives. Among those 56 genes, only 31 are present in more than 52 inbreds or relatives. Further phylogenetic analysis classified these genes into four major groups (Class A, B, C, D) and explored their diversity in subcellular localization, physicochemical properties, and the terminal structures of those HSP20s. Through collinearity analysis and Ka/Ks ratio calculations, we found that most HSP20 genes underwent purifying selection during maize domestication, although a few genes showed signs of positive selection pressure. Additionally, expression analysis showed that several HSP20 genes were significantly upregulated under high temperatures, particularly in tassels and leaves. Co-expression network analysis revealed that HSP20 genes were significantly enriched in GO terms related to environmental stress responses, suggesting that HSP20 genes not only play key roles in heat stress but may also be involved in regulating various other biological processes, such as secondary metabolism and developmental processes. These findings expand our understanding of the functions of the maize HSP20 family and provide new insights for further research into maize's response mechanisms to environmental stresses.

Design and Optimization of High Performance Multi-Step Separated Trench 4H-SiC JBS Diode

In this paper, a novel 3300 V/40 A 4H-SiC junction barrier Schottky diode (JBS) with a multi-step separated trench (MST) structure is proposed and thoroughly investigated using TCAD simulations. The results show that the introduction of MST expands the Schottky contact area, resulting in a decrease in the forward voltage drop. Furthermore, the combination of the deep P+ shielded region and the central P+ region effectively reduces the leakage current, leading to a 43.7% increase in the blocking voltage compared to conventional 4H-SiC JBS. The effects of the step depth (ds) and the width of the central P+ region (wm) on the device performance are analyzed in depth. In addition, a multi-step trenched linearly graded field-limiting rings (MTLG-FLR) termination ensures a more uniform electric field distribution, and the terminal protection efficiency reaches up to 90%, which further enhances the reliability of the terminal structure.

Scheduling optimization of continuous climb and descent operations in busy terminal airspace

Based on the current terminal airspace structure, a method for scheduling aircraft arrival and departure that integrates trajectory optimization, conflict detection and multi-objective optimization is proposed to help implement continuous climb and descent operations in busy terminal airspace. First, based on the multi-stage optimal control theory, the Gaussian pseudo-spectral method is used to propose a vertical profile optimization method for continuous climb and descent operations, and the trajectory optimization of continuous climb and descent operations based on the cost index is realized. Secondly, according to the wake turbulence interval and release interval used by the runway, and the horizontal and vertical intervals of air operations, the Mahalanobis distance is used to establish an aircraft conflict detection model. Then, considering the demands of air traffic control, airlines, airports and other operating units, a multi-objective scheduling model and method for aircraft arrival and departure that can achieve the optimization results are proposed. Finally, two sets of arrival and departure data at Guangzhou Baiyun Airport during busy periods are selected, multiple interval parameters are set, alternative paths are introduced, and case analysis and comparative studies are carried out. The results show that during the busy period dominated by departures, the terminal airspace of Guangzhou Baiyun Airport can achieve continuous climb and descent operations during busy periods; during the busy period dominated by arrivals, two aircraft could not be dispatched. The introduction of alternative paths can reduce the number of aircraft that cannot be dispatched.

At the border of peri-Gondwana and Baltica – the structure of the eastern termination of the Variscan belt

The termination of the eastern Variscan belt has been a matter of long-standing debates since it is deeply concealed beneath younger sediments. Its geometry has been addressed by two competing hypotheses of the Variscan orocline and right-lateral strike-slip tectonics. Therefore, a set of new gravity and magnetic maps was compiled for Czechia, Poland and eastern Germany to track Variscan structures in the subsurface. These maps clearly show that the Rheno-Hercynian Suture turns almost 90° east the of the Harz Mts. and continues into Poland toward the ESE. Therefore, our study favours a concept of semi-orocline that terminates in the east against the Brunovistulian Block. The pattern of magnetic and gravity anomalies combined with geological evidence indicates two stages of accretion superimposed in the eastern Variscan belt. The initial W-E convergence led to the formation of NNE-SSW-trending structures that dominate the southern Bohemian Massif. These structures were overprinted by an important N-S shortening event that shaped WNW-ESE oriented features. The latter run parallel to the Baltica margin and dominate the area NE of the Elbe Fault. This is consistent with seismic data showing large-scale underthrusting of the Baltica crust beneath the Variscan belt at a distance of at least 100 km.

Non-damaged preparation and energy band structure modulation of silicon-based nitrogen-terminated diamond films

The surface terminal structure of diamond film determines its surface physical properties. In this paper, the surface of silicon-based polycrystalline diamond film was nitrided by radio frequency (RF) plasma, and the evolution of the diamond surface termination structure under different nitridation temperatures and times was investigated. In-situ X-ray photoelectron spectroscopy (XPS) analysis showed that nitridation at 600 °C is beneficial for the more effective formation of nitrogen terminal diamond (N-diamond) structure dominated by CN bonds on the diamond surface. In-situ ultraviolet photoelectron spectroscopy (UPS) indicated that the electron affinity of diamond surface can gradually change from negative to positive with prolonged nitridation time. The increased positive electron affinity (PEA) of surface terminations made it more difficult for electrons to escape from the diamond surface, resulting in a significant decrease in the intensity of the secondary electron peak. Furthermore, AFM and Raman measurements indicated that nitridation treatment does not significantly improve the surface roughness of diamond or form graphite phase, which realized the preparation of non-damaged N-diamond.

Vertical GaN Schottky barrier diodes with ohmic contact on N-polar by the atomic layer deposition of aluminum oxide interfacial layer

In this paper, high-performance vertical GaN on GaN Schottky Barrier Diodes (SBDs) on 2-inch free-standing (FS)-GaN is presented with the specific on-state resistance (Ron) of 1.34 mΩ·cm2, breakdown voltage (Vbr) of 1150 V and figure of merit (FOM) of 0.98 GW/cm2. He-implanted edge termination (ET) structure is introduced to alleviate the peak electric field concentration effect at the anode edge of GaN SBDs. Furthermore, A new ohmic contact structure is explored by atomic layer deposition (ALD)-grown AlOx interfacial layer. Based on the self-cleaning effect of ALD and Ultra-thin AlOx interfacial layer, the Fermi-level Pinning (FLP) effect is alleviated effectively, the specific contact resistivity (ρc) on N-polar GaN was reduced from 1.63 × 10−3 to 7.14 × 10−5 Ω·cm2.The temperature variation test demonstrate the devices has potential of temperature sensors under high voltage and high temperature.

Expanding the Plant Virome: Umbra-Like Viruses Use Host Proteins for Movement.

Before the very recent discovery of umbra-like viruses (ULVs), the signature defining feature of all plant RNA viruses was the encoding of specialized RNA-binding movement proteins (MPs) for transiting their RNA genomes through gated plasmodesmata to establish systemic infections. The vast majority of ULVs share umbravirus-like RNA-dependent RNA polymerases and 3'-terminal structures, but they differ by not encoding cell-to-cell and long-distance MPs and by not relying on a helper virus for trans-encapsidation and plant-to-plant transmission. The recent finding that two groups of ULVs do not necessarily encode MPs is expanding our understanding of the minimum requirements for modern plant RNA viruses. ULV CY1 from citrus uses host protein PHLOEM PROTEIN 2 (PP2) for systemic movement, and related ULVs encode a capsid protein, thereby providing an explanation for the lack of helper viruses present in many ULV-infected plants. ULVs thus resemble the first viruses that infected plants, which were likely deposited from feeding organisms and would have similarly required the use of host proteins such as PP2 to exit initially infected cells.

Gate mesa terminal with drain-field-plated β-Ga2O3 MOSFET with ultra-high power figure of merit

In this article, a novel gate mesa terminal (GMT) device structure incorporating a drain field plate is proposed. This design features mesa terminals with varying bevel angles positioned atop the gate. The objective is to enhance the breakdown voltage (Vbr) and reduce the on-resistance (Ron) of the lateral β-Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET). Through the implementation of the GMT structure, the peak electric field within the β-Ga2O3 MOSFET is redirected towards the passivation layer. This effectively mitigates the electric field in the epitaxial layer, thereby increasing Vbr. The optimal values for Vbr, specific on-resistance (Ron,sp) and maximum transconductance (gm) across various GMT structures are 4827 V, 9.9 mΩ·cm2 and 15.32 mS/mm, respectively. These metrics represent a 2.63-fold, 0.88-fold, and 1.25-fold improvement compared to the non-GMT structure. Additionally, when the doping concentration of epitaxial layer is 1 × 1016 cm−3, the GMT achieves an enhanced threshold voltage of +0.26 V. By simulating different bevel angles, field plate parameters, epitaxial layer doping concentrations, and mesa thicknesses, an optimal power figure of merit (PFOM) of 1.914 GW cm−2 is attained. This innovative design introduces a fresh concept for the development of the next generation of high voltage and high-power devices rated above 4 KV.

A Unique Failure Mode of SiC MOSFETs under Accelerated HTRB

Device lifetime under reverse bias conditions is an important reliability concern for SiC devices. Provided that the termination structure is well designed, device failure in the active cell is driven by gate oxide breakdown due to the high field in the semiconductor and gate dielectric. For planar MOSFETs, the largest field occurs in the JFET region [1,2]. Standard HTRB testing is insufficient to estimate failure rates under operating conditions and hence testing under accelerated off-state conditions (ALT-HTRB) is required. This paper provides data, statistical analysis, failure analysis and finally a Weibull statistics-based temperature, Vd and stress time dependent model.

Optimal design of pseudo-vertical Schottky diode with n-type junction terminal extension structure

In the study, a pseudo-vertical Schottky barrier diode (pVSBD) with n-type junction terminal extension (JTE) is proposed. The impacts of key parameters, including cover distance, junction depth, and stretch distance, are evaluated on the electrical characteristics of the designed pVSBD. In the designed device, the homoepitaxial pn-junction constructed with n-type JTE and p- drift layer can reshape the electric field and alleviate the electric field crowding around the corner of Schottky contact, which enables the p- drift layer withstand the higher reverse bias voltage. Thus, the blocking capacity of the pVSBD device is improved, and the maximum breakdown voltage of 2885 V can be obtained. Meanwhile, it is also shown that the doping concentration of n-type diamond termination can influence the electrical characteristics obviously. The trade-off between the breakdown voltage and the specific ON-state resistance is considered in the paper. The pVSBD device with high blocking voltage can be realized based on the proposed pVSBD structure.

Augmented contour scoring snake for instance segmentation of placental separable villi

Segmenting terminal villous structures as separable instances is a prerequisite task for quantitative and explainable analysis of placental histopathology. Inspired by the fact that villous structure is typically surrounded by syncytiotrophoblast cells which yield critical hints for segmentation, we focus on designing a contour-based instance segmentation method. Previous contour-based methods usually utilize the confidence of object localization (or classification) as the instance score, without contour scores which explicitly measure the contour refinement quality (i.e., the distance discrepancy between the predicted contour and its ground truth). In this paper, we propose an augmented contour Scoring Snake framework, termed as SSnake, which learns both contour deformation and refinement quality estimation. To form contour quality measurement, we devise an axis-aware size-adaptive smooth function mapping from predicted contours to normalized scores in point resolution. Besides, to estimate scores of long-distance cases and strengthen the score learning process, a contour-augmented training scheme is designed for initial box contours. Our method recalibrates instance scores using contour quality by prioritizing instances with finer contours. Experimental results on the in-house separable villi segmentation dataset and a public cell nucleus segmentation dataset demonstrate that our proposed method significantly outperforms all competitors including state-of-the-art approaches. In villi segmentation dataset, our proposed SSnake achieves 3.7% improvements in COCO APm over the baseline DeepSnake. The source code is available at https://github.com/Psilym/SSnake.

Regulating the active hydroxyl group of starch: Revealing the evolution of hard carbon structure and sodium storage behavior

The active hydroxyl group of starch has a crucial effect in regulating the microstructure of hard carbon anodes for sodium-ion batteries. By optimizing the chemical structure of starch and controlling the pyrolysis process, high-performance hard carbon materials can be obtained. These active hydroxyl groups are primarily located on the terminal and ring structures of glucose units, exerting significant influence on the formation and performance of hard carbon. Our results demonstrate that low-temperature oxidation treatment effectively modifies the terminal hydroxyl groups in precursor materials, facilitating chain cross-linking and leading to a more robust hard carbon structure. This cross-linking effect helps suppress excessive foaming during pyrolysis, thereby enhancing the stability of the hard carbon structure. Furthermore, by modifying the hydroxyl group on the ring structure of precursors, we can control the pyrolysis process, promote pore closure, and further improve the low plateau capacity of hard carbon anode materials from 153.95 to 219.58 mAh g −1. This study offers novel insights into harnessing and understanding starch's active hydroxyl groups in preparing hard carbon materials—a significant contribution towards optimizing their performance as anode materials.

Visual localization and quantitative detection method for thermal defects in cable terminals of high-speed trains based on a temperature derivative

Abstract Cable terminal defect detection plays an important role in ensuring the safe and stable operation of high-speed trains (HST). In this paper, a numerical model of the electromagnetic thermal field of overheating defects of cable terminal shielding grids and a method of detecting internal defects of cable terminals - even-order temperature derivative (EOTD) is proposed for quantitative detection of internal defective structures of vehicle-mounted cable terminals. Firstly, a numerical model of the electromagnetic thermal field of cable terminals under the condition of leakage current is constructed, through which the temperature field distribution characteristics of different defective structures are analyzed. Then, the intuitive location of the defective region is obtained by investigating the derivative characteristics of the temperature image, and the depth and intensity of the defects are quantitatively assessed by using the main side peak (MSP) distances and the MSP values extracted from the derivative curves. Finally, the simulation and experimental results achieve the identification of defect structures and the quantitative detection of defect depth and intensity, proving the effectiveness and accuracy of the proposed method.

Demonstration of a lateral p-NiO/n-GaN JFET fabricated by selective-area regrowth

In this paper, we demonstrated experimentally a lateral GaN-based junction field effect transistor (JFET). A selective area regrowth of p-NiO on the as-grown n-GaN channel layer was developed by magnetron sputtering at room temperature to form the p–n junction. A self-aligned gate process and a post metal annealing process were employed to improve the device performances. The measured results show that the annealed JFET exhibits an ON/OFF ratio exceeding 106 and a higher breakdown voltage up to 814 V without any terminal structure. The breakdown voltage is determined by the reverse breakdown of parasitic PN junction between gate and drain. Further, the threshold voltage of the p-NiO/n-GaN JFET exhibits excellent temperature stability in the range of 300–500 K.

Tailoring Highly Branched Poly(β-amino ester)s for Efficient and Organ-Selective mRNA Delivery.

Development of mRNA therapeutics necessitates targeted delivery technology, while the clinically advanced lipid nanoparticles face difficulty for extrahepatic delivery. Herein, we design highly branched poly(β-amino ester)s (HPAEs) for efficacious organ-selective mRNA delivery through tailoring their chemical compositions and topological structures. Using an "A2+B3+C2" Michael addition platform, a combinatorial library of 219 HPAEs with varied backbone structures, terminal groups, and branching degrees are synthesized. The branched topological structures of HPAEs provide enhanced serum resistance and significantly higher mRNA expression in vivo. The terminal amine structures of HPAEs determine the organ-selectivity of mRNA delivery following systemic administration: morpholine facilitates liver targeting, ethylenediamine favors spleen delivery, while methylpentane enables mRNA delivery to the liver, spleen, and lungs simultaneously. This study represents a comprehensive exploration of the structure-activity relationship governing both the efficiency and organ-selectivity of mRNA delivery by HPAEs, suggesting promising candidates for treating various organ-related diseases.

Integrated Information for Pathogenicity and Treatment of Spiroplasma.

Spiroplasma, belonging to the class Mollicutes, is a small, helical, motile bacterium lacking a cell wall. Its host range includes insects, plants, and aquatic crustaceans. Recently, a few human cases of Spiroplasma infection have been reported. The diseases caused by Spiroplasma have brought about serious economic losses and hindered the healthy development of agriculture. The pathogenesis of Spiroplasma involves the ability to adhere, such as through the terminal structure of Spiroplasma, colonization, and invasive enzymes. However, the exact pathogenic mechanism of Spiroplasma remains a mystery. Therefore, we systematically summarize all the information about Spiroplasma in this review article. This provides a reference for future studies on virulence factors and treatment strategies of Spiroplasma.

Spliceosomal snRNAs, the Essential Players in pre-mRNA Processing in Eukaryotic Nucleus: From Biogenesis to Functions and Spatiotemporal Characteristics.

Spliceosomal small nuclear RNAs (snRNAs) are a fundamental class of non-coding small RNAs abundant in the nucleoplasm of eukaryotic cells, playing a crucial role in splicing precursor messenger RNAs (pre-mRNAs). They are transcribed by DNA-dependent RNA polymerase II (Pol II) or III (Pol III), and undergo subsequent processing and 3' end cleavage to become mature snRNAs. Numerous protein factors are involved in the transcription initiation, elongation, termination, splicing, cellular localization, and terminal modification processes of snRNAs. The transcription and processing of snRNAs are regulated spatiotemporally by various mechanisms, and the homeostatic balance of snRNAs within cells is of great significance for the growth and development of organisms. snRNAs assemble with specific accessory proteins to form small nuclear ribonucleoprotein particles (snRNPs) that are the basal components of spliceosomes responsible for pre-mRNA maturation. This article provides an overview of the biological functions, biosynthesis, terminal structure, and tissue-specific regulation of snRNAs.