Junction Barrier Research Articles

Regulatory Effects of Ishige okamurae extract and Diphlorethohydroxycarmalol on Skin Barrier Function

Ethnopharmacological relevanceThe pharmacological potential of marine organisms remains largely unexplored. Ishige Okamurae, commonly known as Pae, is extensively distributed over Asia. Its antioxidant, antibacterial, antiobesity, and anti-inflammatory properties are also being investigated. Aim of the studyIn most cases of atopic dermatitis, the stratum corneum, the outermost layer of the epidermis, is damaged, causing symptoms such as dryness and hyperproliferation of the epidermis. In particular, the disruption of cell junctions leads to damage of the skin barrier, exacerbating the disease and becoming a target for therapeutic development. Our study aims to investigate of Ishige okamurae extract (IOE) and a major compound derived from it, called Diphlorethohydroxycarmalol (DPHC), can help strengthen the skin barrier in animals with atopic dermatitis induced by 2,4-dinitrochlorobenzene (DNCB). Materials and methodsIn keratinocyte cell lines, HaCaT cells, the cytotoxicity of IOE and DPHC was assessed by MTT analysis. The gene expression of skin barrier factors and tight junctions were determined by real-time PCR in tumor necrosis factor-α/interferon-γ-stimulated HaCaT cells. In addition, JAK/STAT signaling pathway was performed to evaluating the mechanism of drugs by Western blot. Next, we studied the effects of IOE and DPHC on the skin of animals with DNCB-induced atopic dermatitis. We measured the expression of genes related of the skin barrier and tight junctions in their ear tissue. ResultsAs a result, IOE and DPHC confirmed that the expression of skin barrier proteins (thymic stromal lymphopoietin, filaggrin, loricrin, and involucrin) was improved in the DNCB-induced atopic dermatitis model and HaCaT cells. In addition, the expression of tight junction-related proteins (claudin, occludin, and tight junction protein-1) were improved. ConclusionIOE and DPHC ameliorated the atopic dermatitis lesions through alleviating the pro-inflammatory responses and tight junction protein destruction. Our results suggest that IOE and DPHC could be promising candidates for enhancing skin barrier function.

Black Rice Extract Reduces Body Weight, Waist Circumference, Body Mass Index and Lipopolysaccharide in Obese Subjects: A Preliminary Study

BACKGROUND: The prevalence of obesity, or an excessive fat accumulation, is keep increasing. In obesity, inflammation can be induced by leaky gut due to the intestinal tight junction barrier dysfunction. Zonula occludens-1 (ZO-1) plays a role in developing intestinal tight junction barrier dysfunction and gut microbiota imbalance, thus promote the translocation of bacterial endotoxin characterized by lipopolysaccharide (LPS) into circulation. Black rice extract (BRE) has been known to have anti-inflammatory property. This study was conducted to investigate the effect of BRE on body weight (BW), waist circumference (WC), body mass index (BMI), ZO-1 and LPS of obese patients.METHODS: Twenty-three male subjects were divided into non-obese group (NOG), obese group (COG) and BRE-obese group (BOG). Subjects in BOG received a daily dose of 5.6 g/day BRE for 4 weeks. BW, WC and BMI, serum ZO-1 and LPS were measured before and after treatment.RESULTS: BRE was prepared successfully and free from microbial contamination. Treatment of BRE for 4 weeks reduce BW (95.40±5.78 vs. 94.59±6.00 kg, p=0.043), WC (109.25±3.55 vs. 107.50±3.46 cm, p=0.000) BMI (32.65±1.86 vs. 32.18±1.80, p=0.000) and LPS (222.27±38.63 vs. 131.63±9.70 ng/mL, p=0.020) of obese subjects. The pre-post ZO-1 levels in all groups were not significantly different (p>0.05).CONCLUSION: Treatment of 5.6 gr BRE daily for four weeks can reduce BW, WC, BMI and serum LPS, but not serum ZO-1 in obese patients. Therefore, BRE may reduce inflammation in obesity.KEYWORDS: black rice, obesity, BW, WC, BMI, LPS, ZO-1

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.

Rift Valley fever virus is able to cross the human blood-brain barrier in vitro by direct infection with no deleterious effects.

Rift Valley fever (RVF) is a zoonotic arboviral disease that causes recurrent epidemics in Africa that may trigger fatal neurological disorders. However, the mechanisms of neuroinvasion by which the RVF virus (RVFV) reaches the human central nervous system (CNS) remain poorly characterized. In particular, it is not clear how RVFV is able to cross the human blood-brain barrier (hBBB), which is a neurovascular endothelium that protects the brain by regulating brain and blood exchanges. To explore these mechanisms, we used an in vitro hBBB model to mimic in vivo hBBB selectiveness and apicobasal polarity. Our results highlight the ability of RVFV to cross the hBBB by direct infection in a non-structural protein S (NSs)-independent but strain-dependent manner, leading to astrocyte and pericyte infections. Interestingly, RVFV infection did not induce hBBB disruption and was associated with progressive elimination of infected cells with no impairment of the tight junction protein scaffold and barrier function. Our work also shows that NSs, a well described RVFV virulence factor, limited the establishment of the hBBB-induced innate immune response and subsequent lymphocyte recruitment. These results provide in vitro confirmation of the ability of RVFV to reach human CNS by direct infection of the hBBB without altering its barrier function, and provide new directions to explore human RVFV neurovirulence and neuroinvasion mechanisms.IMPORTANCEThe RVF virus (RVFV) is capable of infecting humans and inducing severe and fatal neurological disorders. Neuropathogenesis and human central nervous system (CNS) invasion mechanisms of RVFV are still unknown, with only historical studies of autopsy data from fatal human cases in the 1980s and exploration studies in rodent models. One of the gaps in understanding RVFV human pathogenesis is how RVFV is able to cross the blood-brain barrier (BBB) in order to reach the human CNS. For the first time, we show that RVFV is able to directly infect cells of the human BBB in vitro to release viral particles into the human CNS, a well-characterized neuroinvasion mechanism of pathogens. Furthermore, we demonstrate strain-dependent variability of this neuroinvasion mechanism, identifying possible viral properties that could be explored to prevent neurological disorders during RVFV outbreaks.

Swiprosin-1 participates in the berberine-regulated AMPK/MLCK pathway to attenuate colitis-induced tight junction damage

Background and purposeActivation of AMP-activated protein kinase (AMPK) is essential in maintaining the epithelial tight junction (TJ) barrier. Berberine, a phytochemical AMPK agonist, has been widely reported to ameliorate colitis. Berberine or AMPK activation inhibits cytoskeletal contraction induced by myosin light chain kinase (MLCK), thereby ameliorating TJ barrier defects. We previously found that swiprosin-1, an actin-binding protein, affects MLCK expression. Here, we aimed to reveal the role of swiprosin-1 in the regulation of AMPK/MLCK by berberine. MethodsCaco-2 monolayer transfected with AMPKα1 (or swiprosin-1) siRNA was treated with berberine after being stimulated with TNFα/IFNγ to assess the effect on the TJ barrier. Intestinal epithelial conditional knockout mice for AMPKα1 (or swiprosin-1) were treated with berberine after experimental colitis to evaluate the effect on the TJ barrier. TJ integrity was evaluated by immunoblotting and immunofluorescence for ZO-1 and Occludin. ResultsThe protection of berberine against TJ barrier damage was blocked by AMPK inhibitor or knockout of AMPKα1 in epithelial cells. Swiprosin-1 was distributed in colonic epithelial cells and upregulated in colitis. Knockout of swiprosin-1 in intestinal epithelial cells ameliorated TJ barrier damage and abolished the protective effect of berberine. Impaired assembly of TJ caused by overexpression of swiprosin-1 was alleviated by MLCK inhibitor, and inhibition of the MLCK pathway by berberine also required the presence of swiprosin-1. In addition, berberine downregulated swiprosin-1 expression in an AMPK-dependent manner. ConclusionSwiprosin-1 may be a key intermediate molecule in the regulation of the AMPK/MLCK pathway by berberine to attenuate colitis-induced TJ barrier damage.

Mechanosensitive recruitment of Vinculin maintains junction integrity and barrier function at epithelial tricellular junctions

Apical cell-cell junctions, including adherens junctions and tight junctions, adhere epithelial cells to one another and regulate selective permeability at both bicellular junctions and tricellular junctions (TCJs). Although several specialized proteins are known to localize at TCJs, it remains unclear how actomyosin-mediated tension transmission at TCJs contributes to the maintenance of junction integrity and barrier function at these sites. Here, utilizing the embryonic epithelium of gastrula-stage Xenopus laevis embryos, we define a mechanism by which the mechanosensitive protein Vinculin helps anchor the actomyosin network at TCJs, thus maintaining TCJ integrity and barrier function. Using an optogenetic approach to acutely increase junctional tension, we find that Vinculin is mechanosensitively recruited to apical junctions immediately surrounding TCJs. In Vinculin knockdown (KD) embryos, junctional actomyosin intensity is decreased and becomes disorganized at TCJs. Using fluorescence recovery after photobleaching (FRAP), we show that Vinculin KD reduces actin stability at TCJs and destabilizes Angulin-1, a key tricellular tight junction protein involved in regulating barrier function at TCJs. When Vinculin KD embryos are subjected to increased tension, TCJ integrity is not maintained, filamentous actin (F-actin) morphology at TCJs is disrupted, and breaks in the signal of the tight junction protein ZO-1 signal are detected. Finally, using a live imaging barrier assay, we detect increased barrier leaks at TCJs in Vinculin KD embryos. Together, our findings show that Vinculin-mediated actomyosin organization is required to maintain junction integrity and barrier function at TCJs and reveal new information about the interplay between adhesion and barrier function at TCJs.

Deltamethrin increased susceptibility to Aeromonas hydrophila in crucian carp through compromising gill barrier

Pyrethroids serve as a significant method for managing and preventing parasitic diseases in fish. Among these, deltamethrin (DEL) is used extensively in aquatic environments. Our previous work has been confirmed that DEL exposure can induce oxidative stress and immunosuppression on the gill mucosal barrier of crucian carp (Carassius auratus). However, it is not clear whether DEL affects the susceptibility of farmed fish to bacterial infection. In this study, fish was pre-exposed to different DEL concentration (0, 0.3 and 0.6 μg L−1) and then challenged by immersion with Aeromonas hydrophila (1.0 × 10^8 CFU mL−1). After immersion challenge, fish pre-exposed to DEL developed prominent lipopolysaccharides level in gill and serum and had a significantly lower survival rate compared to the control group. In DEL pre-exposure fish after immersion, the gill apoptosis levels were significantly higher and disrupted the tight junction barrier by downregulating the zo1 and claudin12. Furthermore, fish pre-exposed to DEL exhibited increased activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malonaldehyde (MDA) levels in the early stage after immersion but experiencing decreased activities of glutathione peroxidase (GPx) and lysozyme (LZM) in the later stage after immersion. And this process was regulated by the NRF2 pathway. Additionally, fish pre-exposed to DEL after immersion had significantly lower mRNA levels of immune-related genes tlr4, myd88, tnfα, and il-1β. Overall, these findings indicate that DEL damaged the gill barrier, weakened the immune response, raised LPS levels, and heightened vulnerability to A. hydrophila infection in crucian carp, resulting in mortality. Thus, this work will help social groups and aquaculture workers to understand the potential risk of DEL exposure for bacterial secondary infection in cultured fish.

Study of leakage current degradation based on stacking faults expansion in irradiated SiC junction barrier Schottky diodes

Abstract A comprehensive investigation was conducted to explore the degradation mechanism of leakage current in SiC junction barrier Schottky (JBS) diodes under heavy ion irradiation. We propose and verify that the generation of stacking faults (SFs) induced by the recombination of massive electron--hole pairs during irradiation is the cause of reverse leakage current degradation based on experiments results. The irradiation experiment was carried out based on Ta ions with high linear energy transfer (LET) of 90.5 MeV/(mg/cm2). It is observed that the leakage current of the diode undergoes the permanent increase during irradiation when biased at 20% of the rated reverse voltage. Micro-PL spectroscopy and PL micro-imaging were utilized to detect the presence of SFs in the irradiated SiC JBS diodes. We combined the degraded performance of irradiated samples with SFs introduced by heavy ion irradiation. Finally, three-dimensional (3D) TCAD simulation was employed to evaluate the excessive electron–hole pairs (EHPs) concentration excited by heavy ion irradiation. It was observed that the excessive hole concentration under irradiation exceeded significantly the threshold hole concentration necessary for the expansion of SFs in the substrate. The proposed mechanism suggests that the process and material characteristics of the silicon carbide should be considered in order to reinforcing against the single event effect of SiC power devices.

Ultrahigh-performance heterojunction bipolar phototransistor enabled by bilateral piezoelectric charge modulation effect

Heterojunction photodiodes based on p-n junction with enhanced piezo-phototronic effect have been extensively studied. However, the photoresponsivity of conventional photodiodes is small due to the natural zero current gain. Heterojunction phototransistor usually has greater photoresponsivity due to the non-zero current gain. More importantly, heterojunction phototransistor owns two interfaces, offering the opportunity to introduce the bilateral piezoelectric charge modulation effect for further performance enhancement compared to the conventional single-interface piezo-phototronic effect in photodiode. In this work, a base-floating heterojunction bipolar phototransistor (FHPT) based on n-ZnO/p-Si/n-ZnO structure with a spectral detection range from ultraviolet (UV)–visible is demonstrated. The positive piezoelectric charge generated at the two interfaces of the collector junction and the emitter junction, combined with the optimal base width and low resistance base doping concentration of the FHPT, leads to an excellent photoresponsivity (18046 A/W, 365 nm), high detectivity (5.7×1012 Jones), and a wider modulation (7120 %). The physical mechanism leading to the ultrahigh performance is attributed to the cooperative positive piezoelectric charge at the two interfaces, simultaneously reducing the effective base width and lowering the emitter junction barrier. This work illustrates the regulation of heterojunction phototransistor performance by the bilateral piezoelectric charge modulation effect, providing insightful guidance to high-performance phototransistor design.

Design and evaluation of β-Ga2O3 junction barrier schottky diode with p-GaN heterojunction

A novel design for a junction barrier Schottky (JBS) diode based on a p-GaN/n-Ga2O3 heterojunction is proposed, exhibiting superior static characteristics and a higher breakdown capability compared to the traditional Ga2O3 Schottky barrier diode (SBD). By utilizing wide-bandgap p-type GaN, the β-Ga2O3 JBS diodes demonstrate a turn-on voltage (V on ) of approximately 0.8 V. Moreover, a breakdown voltage (V br ) of 880 V and a specific on-resistance (R on,sp ) of 3.96 mΩ·cm2 are achieved, resulting in a Baliga’s figure of merit (BFOM) of approximately 0.2 GW /cm 2. A forward current density of 465 A cm−2 at a forward voltage of 3 V is attained. The simulated reverse leakage current density remains low at 9.0 mA cm−2 at 800 V. Floating field rings, in conjunction with junction termination extension (JTE), were utilized as edge termination methods to attain a high breakdown voltage. The impact of β-Ga2O3 periodic fin width fluctuations on the electrical characteristics of JBS was investigated. Due to the enhanced sidewall depletion effect caused by p-type GaN, the forward current (I F ) and reverse current (I R ) decrease when the β-Ga2O3 periodic fin width decreases. The findings of this study indicate the remarkable promise of p-GaN/n-Ga2O3 JBS diodes for power device applications.

Field management in NiO x /β-Ga2O3 merged-PIN Schottky diodes: simulation studies and experimental validation

In recent years, p-type NiO x has emerged as a promising alternative to realize kilovolt-class β-Ga2O3-based PN junction diodes. However, only a handful of studies could realize β–Ga2O3-based unipolar diodes using NiO x as a guard ring or floating rings. In this work, we investigate the device design of NiO x /β-Ga2O3 unipolar diodes using the technology computer aided design simulations and experimental validations. We show that a systematic electric field management approach can potentially lead to NiO x /β-Ga2O3 heterojunction unipolar diode and offer enhanced breakdown characteristics without a severe compromise in the ON-state resistance. Accordingly, the NiO x /β-Ga2O3 heterojunction diode in the merged-PIN Schottky configuration is shown to outperform the regular Schottky diode or junction barrier Schottky diode counterpart. The analysis performed in this work is believed to be valuable in the device design of β-Ga2O3-based unipolar diodes that use a different p-type semiconductor candidate as guard rings and floating rings.

(Invited) Breakdown Improvement of Mg-Diffused Current Blocking Layer in Ga2O3

The path towards an all-planar highly efficient vertical Ga2O3 transistor requires the construction of a buried gate barrier junction to circumvent the pre-mature breakdown near the gate often seen in lateral structures. An effective selective doping technique is necessary to achieve this. By taking advantage of the high diffusivity of dopants and defects in Ga2O3, we propose the use of diffusion doping as a rapid and non-invasive technique to explore the possibility of an effective current blocking layer (CBL) in vertical Ga2O3 transistors. Unlike ion implantation, diffusion doping does not require an 1100°C annealing for the repair of crystal damage. Thus, the desired Mg doping profile can be maintained by the end of device fabrication, which is the key to achieving a high blocking voltage with Mg-doped CBL. In addition, diffusion doping can easily form a much deeper dope junction and be very useful for high-voltage and super-junction devices.Recently, we have demonstrated the first Ga2O3 vertical-diffused-barrier field-effect transistor (or VDBFET) utilizing a Mg-diffusion doped CBL with a spin-on-glass source. The transistor exhibited excellent FET behavior with decent saturation, enhancement-mode operation, and an on/off ratio of more than 109. However, the breakdown voltage is measured to be only 72V most likely due to the punch-through of the Mg-diffused CBL. This is likely caused by a lower-than-expected Mg doping rendering an inefficient electron blocking. In addition, SIMS analysis indicated the existence of Mg-H complex that deactivated the Mg. Thus, the effective Mg doping is even lower than its chemical concentration. Here we will discuss a new strategy to resolve this problem and showcase the characteristics of the improved CBL with a higher breakdown. This development paves the way for the development of high-voltage Ga2O3 VDBFETs.

4-methylimidazole exposure impairs sperm mobility by reducing the expression of blood-testis barrier junction protein in mouse testes

4-methylimidazole (4-MI), a derivative of imidazole, is a widely used component in caramel-colored food products such as soy sauce, beer and other soft drinks. The present study is aimed to investigate the effects of 4-MI on the male reproduction. The results revealed that 8 weeks of 4-MI exposure did not significantly alter the body weight and testicular weight of male mice. However, testicular morphology and computer-assisted sperm analysis showed that exposed to 4-MI caused irregular arrangement of spermatogenic cells in the testes and weakened sperm motility. Consistently, we observed the decreased fertilization ability in vivo of 4-MI-treated male mice. We further demonstrated that 4-MI disrupted the blood-testis barrier (BTB) integrity by decreasing the protein expression of BTB-related junction with permeability assay and western blot. In addition, the apoptosis of Sertoli cells (TM4) occurred in 4-MI treated mice, which might be caused by the generation of oxidative stress. Collectively, our findings document that 4-MI exposure damages the sperm mobility via disruption of BTB integrity.

Design optimization of wide-gate swing E-mode GaN HEMTs with junction barrier Schottky gate

To increase the gate swing, a GaN-based high-electron-mobility transistor with a junction barrier Schottky gate (JBS-HEMT) was proposed. Compared to conventional p-GaN Schottky gate HEMTs (Conv-HEMT), the high electric field at the surface is transferred to the pn junction inside the body, and the extended depletion region of the pn junction shields the surface Schottky contact interface for the JBS-HEMT. After fitting the model to the reported device, the proposed JBS-HEMT was simulated and optimized using the Sentaurus TCAD tool. The simulation results of the optimized JBS-HEMT demonstrate a high gate breakdown voltage (17.6 V), which is 158.5% higher than the gate breakdown voltage of the Conv-HEMT (11.1 V) and a lower gate leakage current of six orders of magnitude than the Conv-HEMT at the gate-to-source voltage of 10 V. The proposed JBS-HEMT exhibits a positive threshold voltage (1.68 V) and excellent threshold voltage stability, and the maximum threshold voltage drift of the JBS-HEMT (+0.237 V) is smaller than that of the Conv-HEMT (−0.714 V) under gate stress conditions. The peak transconductance of the JBS-HEMT (186 mS mm−1) at athe drain-to-source voltage of 10 V showed almost no reduction compared to the Conv-HEMT (189 mS mm−1), which solves the problem of decreased transconductance capability of the reported GaN HEMT with a p-n junction gate (PNJ-HEMT). It was confirmed that the JBS-HEMT has excellent gate stability and potential for power electronics applications.

Unveiling microstructural damage for leakage current degradation in SiC Schottky diode after heavy ions irradiation under 200 V

Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes.

Active reallocation of photogenerated carriers by triboelectric electro-field for improving nonuniformly illuminated photovoltaic module

Different from standard indoor testing for photovoltaic (PV) cells, the outdoor working of large PV modules suffers an inevitable issue of nonuniform illumination. Even a 10 % partial area shading results in an 80 % power attenuation. This can be attributed to the endogenous lateral transfer of photogenerated carriers between differently illuminated zones. Herein, we presented an active reallocation strategy for rationalizing lateral carrier transfer inside PV modules, which utilizes triboelectric electro-field to dynamically balance the p-n junction barrier height at interfaces of different illumination states. As demonstrated by a flexible hybrid energy harvester combining triboelectric nanogenerators (TENGs) and solar cells, by managing with rectifier-free circuits or even small chips, a small power sacrifice of TENGs exchanges for remarkable performance improvement of PV modules, leading to a power output gain of up to 87.7 % for half-shaded PV modules of different material and structural configurations. Besides, the reallocation electric field adapts well to a wide range of voltage or even pulsed triboelectric voltage, providing a mutually beneficial energy management technology for multi-source energy harvesting. This strategy of active reallocation by triboelectric effect provides an endogenous PV module promotion approach with prominent structural adaptability for distributed or even portable on-body power generation.

In vitro model to evaluate effect of acidic pepsin on vocal fold barrier function

The pathophysiology of laryngopharyngeal reflux (LPR) and its impact on the vocal fold is not well understood, but may involve acid damage to vocal fold barrier functions. Two different components encompass vocal fold barrier function: the mucus barrier and tight junctions. Mucus retained on epithelial microprojections protects the inside of the vocal fold by neutralizing acidic damage. Tight junctions control permeability between cells.Here we developed an in vitro experimental system to evaluate acidic injury and repair of vocal fold barrier functions. We first established an in vitro model of rat vocal fold epithelium that could survive at least one week after barrier function maturation. The model enabled repeated evaluation of the course of vocal fold repair processes. Then, an injury experiment was conducted in which vocal fold cells were exposed to a 5-min treatment with acidic pepsin that injured tight junctions and cell surface microprojections.Both of them healed within one day of injury. Comparing vocal fold cells treated with acid alone with cells treated with acidic pepsin showed that acidic pepsin had a stronger effect on intercellular permeability than acid alone, whereas pepsin had little effect on microprojections.This result suggests that the proteolytic action of pepsin has a larger effect on protein-based tight junctions than on phospholipids in microprojections. This experimental system could contribute to a better understanding of vocal fold repair processes after chemical or physical injuries, as well as voice problems due to LPR pathogenesis.

Novel design and modelling of SiC junction barrier Schottky diode with improved Baliga FOM under high-temperature applications

A novel 650 V/50 A 4H–SiC junction barrier Schottky diode (JBSD) featuring a stripe-square composite cell design (SSC-JBSD) is proposed in this paper to improve the high-temperature performance. A model of the resistance of the JBS (RJBS) is established to explain the mechanism. The particular cell design of the SSC-JBSD forms a circular current distribution, which can improve the forward current and suppress the degeneration of RJBS caused by the lower electron mobility at high temperatures. The combination of the stripe and square P+ regions achieves a high current and a lower power loss under high temperature while maintaining a high breakdown voltage. Specifically, the power loss of the SSC-JBSD with a forward current of 50 A only increases by 6.9 % under 450 K compared to that under 300 K, while that of the conventional JBS diode (Conv-JBSD) increases by 14.1 %. And the Baliga figure of merit (FOM) of the SSC-JBSD is 15.6 % higher than that of the Conv-JBSD under a temperature of 450 K. The on-state self-heating measurement shows that the temperature of the SSC-JBSD is approximately 30 K lower than that of the Conv-JBSD after 5 s of constant on-state operation with a forward current of 50 A. The proposed SSC-JBSD demonstrates superior performance at high temperatures, making it an available replacement for Conv-JBSD in harsh environments characterized by high temperatures and large currents.

The C-terminal proline-rich repeats of Enteropathogenic E. coli effector EspF are sufficient for the depletion of tight junction membrane proteins and interactions with early and recycling endosomes

BackgroundEnteropathogenic E. coli (EPEC) causes acute infantile diarrhea accounting for significant morbidity and mortality in developing countries. EPEC uses a type three secretion system to translocate more than twenty effectors into the host intestinal cells. At least four of these effectors, namely EspF, Map, EspG1/G2 and NleA, are reported to disrupt the intestinal tight junction barrier. We have reported earlier that the expression of EspF and Map in MDCK cells causes the depletion of the TJ membrane proteins and compromises the integrity of the intestinal barrier. In the present study, we have examined the role of the proline-rich repeats (PRRs) within the C-terminus of EspF in the depletion of the tight junction membrane proteins and identified key endocytosis markers that interact with EspF via these repeats.ResultsWe generated mutant EspF proteins which lacked one or more proline-rich repeats (PRRs) from the N-terminus of EspF and examined the effect of their expression on the cellular localization of tight junction membrane proteins. In lysates derived from cells expressing the mutant EspF proteins, we found that the C-terminal PRRs of EspF are sufficient to cause the depletion of TJ membrane proteins. Pull-down assays revealed that the PRRs mediate interactions with the TJ adaptor proteins ZO-1 and ZO-2 as well as with the proteins involved in endocytosis such as caveolin-1, Rab5A and Rab11.ConclusionsOur study demonstrates the direct role of the proline-rich repeats of EspF in the depletion of the TJ membrane proteins and a possible involvement of the PRRs in the endocytosis of host proteins. New therapeutic strategies can target these PRR domains to prevent intestinal barrier dysfunction in EPEC infections.

Defects evolution in n-type 4H-SiC induced by electron irradiation and annealing

Radiation damage produced in 4H-SiC by electrons of different doses is presented by using multiple characterization techniques. Raman spectra results indicate that SiC crystal structures are essentially impervious to 10 MeV electron irradiation with doses up to 3000 kGy. However, irradiation indeed leads to the generation of various defects, which are evaluated through photoluminescence (PL) and deep level transient spectroscopy (DLTS). The PL spectra feature a prominent broad band centered at 500 nm, accompanied by several smaller peaks ranging from 660 to 808 nm. The intensity of each PL peak demonstrates a linear correlation with the irradiation dose, indicating a proportional increase in defect concentration during irradiation. The DLTS spectra reveal several thermally unstable and stable defects that exhibit similarities at low irradiation doses. Notably, after irradiating at the higher dose of 1000 kGy, a new stable defect labeled as R 2 (Ec − 0.51 eV) appeared after annealing at 800 K. Furthermore, the impact of irradiation-induced defects on SiC junction barrier Schottky diodes is discussed. It is observed that high-dose electron irradiation converts SiC n-epilayers to semi-insulating layers. However, subjecting the samples to a temperature of only 800 K results in a significant reduction in resistance due to the annealing out of unstable defects.