Plasma-discharge-integrated slot structure for microwave power limiter.

A slot structure was combined with a discharge electrode to limit incident high-power microwaves via the integration of plasma discharge. At the target resonating frequency of 9.45 GHz, the surface current was concentrated at an electrode, and the electric field was enhanced by the proposed design to lower the response power level of the incident signal. When a low-power signal is injected, plasma is not generated, and the incident wave travels without insertion loss. Double-stage slot structures were utilized to broaden the band-pass characteristics in the frequency domain, and the demonstrated plasma limiter exhibited an insertion loss of 1.01 dB at 9.45 GHz. The xenon gas pressure was optimized with the shortest distance of 100 µm between the upper and lower electrodes to reduce the discharge power of the plasma. In the case of a high-power signal input, as xenon-gas breakdown occurred, the transmitted signal was close to zero, and most of the high-power signal was reflected with a blocking efficiency of 40.55 dB. The demonstrated result will be useful to protect the receiver of a radio detection and ranging system from the high power microwave.

Transparent and Flexible Graphene Pressure Sensor with Self-Assembled Topological Crystalline Ionic Gel.

This study demonstrates transparent and flexible capacitive pressure sensors using a high-k ionic gel composed of an insulating polymer (poly(vinylidene fluoride-co-trifluoroethylene-co-chlorofluoroethylene), P(VDF-TrFE-CFE)) blended with an ionic liquid (IL; 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, [EMI][TFSA]). The thermal melt recrystallization of the P(VDF-TrFE-CFE):[EMI][TFSA] blend films develops the characteristic topological semicrystalline surface of the films, making them highly sensitive to pressure. Using optically transparent and mechanically flexible graphene electrodes, a novel pressure sensor is realized with the topological ionic gel. The sensor exhibits a sufficiently large air dielectric gap between graphene and the topological ionic gel, resulting in a large variation in capacitance before and after the application of various pressures owing to the pressure-sensitive reduction of the air gap. The developed graphene pressure sensor exhibits a high sensitivity of 10.14 kPa-1 at 20 kPa, rapid response times of <30 ms, and durable device operation with 4000 repeated ON/OFF cycles. Furthermore, broad-range detections from lightweight objects to human motion are successfully achieved, demonstrating that the developed pressure sensor with a self-assembled crystalline topology is potentially suitable for a variety of cost-effective wearable applications.

6-Bromo-2-naphthol from Silene armeria extract sensitizes Acinetobacter baumannii strains to polymyxin.

The overuse of antibiotics has led to the emergence of multidrug-resistant bacteria, which are resistant to various antibiotics. Combination therapies using natural compounds with antibiotics have been found to have synergistic effects against several pathogens. Synergistic natural compounds can potentiate the effects of polymyxins for the treatment of Acinetobacter baumannii infection. Out of 120 types of plant extracts, only Silene armeria extract (SAE) showed a synergistic effect with polymyxin B (PMB) in our fractional inhibitory concentration and time-kill analyses. The survival rate of G. mellonella infected with A. baumannii ATCC 17978 increased following the synergistic treatment. Interestingly, the addition of osmolytes, such as trehalose, canceled the synergistic effect of SAE with PMB; however, the underlying mechanism remains unclear. Quadrupole time-of-flight liquid chromatography-mass spectrometry revealed 6-bromo-2-naphthol (6B2N) to be a major active compound that exhibited synergistic effects with PMB. Pretreatment with 6B2N made A. baumannii cells more susceptible to PMB exposure in a time- and concentration-dependent manner, indicating that 6B2N exhibits consequential synergistic action with PMB. Moreover, the exposure of 6B2N-treated cells to PMB led to higher membrane leakage and permeability. The present findings provide a promising approach for utilizing plant extracts as adjuvants to reduce the toxicity of PMB in A. baumannii infection.

Seasonal dynamics of the bacterial communities associated with cyanobacterial blooms in the Han River.

DNA-based analyses of bacterial communities were performed to identify the bacteria co-occurring with cyanobacterial blooms in samples collected at a single site over 2 years. Microcystis aeruginosa was the most predominant species (81% in 2018, and 94% in 2019) within the phylum Cyanobacteria, and microcystins were detected during all cyanobacterial blooms. The stereo microscope and scanning electron microscope observations showed bacterial associations on and around the aggregated M. aeruginosa cells. Culture-independent analyses of filtered bacterial communities showed that the Flavobacterium species in phylum Bacteroidetes (19%) was dominant in the cyanobacterial phycosphere, followed by the Limnohabitans species in Betaproteobacteria (11%). Using principal component analysis, major bacterial genus, including Microcystis and Flavobacterium species, were clustered during cyanobacterial blooms in both years. To identify key bacterial species that develop long-term symbiosis with M. aeruginosa, another culture-independent analysis was performed after the environmental sample had been serially subcultured for 1 year. Interestingly, Brevundimonas (14%) was the most dominant species, followed by Porphyrobacter (7%) and Rhodobacter (3.5%) within the Alphaproteobacteria. Screening of 100 colonies from cyanobacterial bloom samples revealed that the majority of culturable bacteria belonged to Gammaproteobacteria (28%) and Betaproteobacteria (57%), including Pseudomonas, Curvibacter, and Paucibacter species. Several isolates of Brevundimonas, Curvibacter, and Pseudomonas species could promote the growth of axenic M. aeruginosa PCC7806. The sensitivity of M. aeruginosa PCC7806 cells to different environmental conditions was monitored in bacteria-free pristine freshwater, indicating that nitrogen addition promotes the growth of M. aeruginosa.

Slippery and Wear-Resistant Surfaces Enabled by Interface Engineered Graphene.

Friction and wear remain the primary cause of mechanical energy dissipation and system failure. Recent studies reveal graphene as a powerful solid lubricant to combat friction and wear. Most of these studies have focused on nanoscale tribology and have been limited to a few specific surfaces. Here, we uncover many unknown aspects of graphene's contact-sliding at micro- and macroscopic tribo-scales over a broader range of surfaces. We discover that graphene's performance reduces for surfaces with increasing roughness. To overcome this, we introduce a new type of graphene/silicon nitride (SiNx, 3 nm) bilayer overcoats that exhibit superior performance compared to native graphene sheets (mono and bilayer), that is, display the lowest microscale friction and wear on a range of tribologically poor flat surfaces. More importantly, two-layer graphene/SiNx bilayer lubricant (<4 nm in total thickness) shows the highest macroscale wear durability on tape-head (topologically variant surface) that exceeds most previous thicker (∼7-100 nm) overcoats. Detailed nanoscale characterization and atomistic simulations explain the origin of the reduced friction and wear arising from these nanoscale coatings. Overall, this study demonstrates that engineered graphene-based coatings can outperform conventional coatings in a number of technologies.

Amentoflavone, a novel cyanobacterial killing agent from Selaginella tamariscina.

Harmful cyanobacterial bloom (HCB) by Microcystis aeruginosa is increasingly becoming a serious concern to the environment and human health alike. Currently, many physical, chemical, and biological controls are underway to eliminate HCB, but natural chemicals are rarely used. To find a control agent with low environmental toxicity and high potential for practical use, 60 plant extracts were screened. Only Selaginella tamariscina extract killed all four Microcystis aeruginosa strains, but not the other tested bacteria. Chloroform fraction of S. tamariscina extract (CSE) showed the highest killing activity. The effects of CSE on M. aeruginosa were monitored using differential interference contrast microscopy and flow-cytometry analysis, scanning electron microscopy, and transmission electron microscopy. The images showed that CSE-treated cells were abnormally altered, with damaged cell membranes, peptidoglycan layers, and cytoplasm. Quadrupole time-of-flight liquid chromatography-mass spectrometry was used to identify amentoflavone as a major active compound. Pure amentoflavone, even at low concentrations showed a powerful killing effect on M. aeruginosa, but not on other non-cyanobacteria. Overall, in this study, we have highlighted the potentials of S. tamariscina extracts and amentoflavone as selective HCB control agents.

Direct Synthesis of a Self-Assembled WSe2 /MoS2 Heterostructure Array and its Optoelectrical Properties.

Functional van der Waals heterojunctions of transition metal dichalcogenides are emerging as a potential candidate for the basis of next-generation logic devices and optoelectronics. However, the complexity of synthesis processes so far has delayed the successful integration of the heterostructure device array within a large scale, which is necessary for practical applications. Here, a direct synthesis method is introduced to fabricate an array of self-assembled WSe2 /MoS2 heterostructures through facile solution-based directional precipitation. By manipulating the internal convection flow (i.e., Marangoni flow) of the solution, the WSe2 wires are selectively stacked over the MoS2 wires at a specific angle, which enables the formation of parallel- and cross-aligned heterostructures. The realized WSe2 /MoS2 -based p-n heterojunction shows not only high rectification (ideality factor: 1.18) but also promising optoelectrical properties with a high responsivity of 5.39 A W-1 and response speed of 16 µs. As a feasible application, a WSe2 /MoS2 -based photodiode array (10 × 10) is demonstrated, which proves that the photosensing system can detect the position and intensity of an external light source. The solution-based growth of hierarchical structures with various alignments could offer a method for the further development of large-area electronic and optoelectronic applications.

Atomic-Level Customization of 4 in. Transition Metal Dichalcogenide Multilayer Alloys for Industrial Applications.

Despite many encouraging properties of transition metal dichalcogenides (TMDs), a central challenge in the realm of industrial applications based on TMD materials is to connect the large-scale synthesis and reproducible production of highly crystalline TMD materials. Here, the primary aim is to resolve simultaneously the two inversely related issues through the synthesis of MoS2(1- x ) Se2 x ternary alloys with customizable bichalcogen atomic (S and Se) ratio via atomic-level substitution combined with a solution-based large-area compatible approach. The relative concentration of bichalcogen atoms in the 2D alloy can be effectively modulated by altering the selenization temperature, resulting in 4 in. scale production of MoS1.62 Se0.38 , MoS1.37 Se0.63 , MoS1.15 Se0.85 , and MoS0.46 Se1.54 alloys, as well as MoS2 and MoSe2 . Comprehensive spectroscopic evaluations for vertical and lateral homogeneity in terms of heteroatom distribution in the large-scale 2D TMD alloys are implemented. Se-stimulated strain effects and a detailed mechanism for the Se substitution in the MoS2 crystal are further explored. Finally, the capability of the 2D alloy for industrial application in nanophotonic devices and hydrogen evolution reaction (HER) catalysts is validated. Substantial enhancements in the optoelectronic and HER performances of the 2D ternary alloy compared with those of its binary counterparts, including pure-phase MoS2 and MoSe2 , are unambiguously achieved.

Electronic Structure of Nonionic Surfactant-Modified PEDOT:PSS and Its Application in Perovskite Solar Cells with Reduced Interface Recombination.

The interfacial properties of organolead halide perovskite solar cells (PSCs) affect the exciton and charge-transport dynamics significantly. Thus, proper modification of the interfaces between perovskite and charge-transport layers is an efficient method to increase the power conversion efficiency (PCE) of PSCs. In this work, we explore the effect of a nonionic surfactant, that is, Triton X-100 (TX) additive, in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole-transport layer. The electronic structure of TX-modified PEDOT:PSS is investigated with ultraviolet/X-ray photoelectron spectroscopy and X-ray absorption spectroscopy with various TX concentrations. The surface of the TX-modified PEDOT:PSS layer showed high TX content, and thus the semimetallic properties of PEDOT:PSS were suppressed conspicuously by its insulating nature. With the TX-modified PEDOT:PSS, the PCE of methylammonium lead iodide (MAPbI3) PSCs increased significantly. To elucidate the origin of the improved device performance, the electrical properties and photoluminescence were investigated comprehensively. Consequently, it was found that the TX additive inhibits interface recombination between PEDOT:PSS and MAPbI3, which is caused by the suppression of semimetallic properties of the PEDOT:PSS surface. Hence, we fabricated flexible PSCs successfully using a graphene electrode and TX-modified PEDOT:PSS.

Stretchable Electroluminescent Display Enabled by Graphene-Based Hybrid Electrode.

Stretchable alternating-current electroluminescent (ACEL) devices are required due to their potential in wearable, biomedical, e-skin, robotic, lighting, and display applications; however, one of the main hurdles is to achieve uniform electroluminescence with an optimal combination of transparency, conductivity, and stretchability in electrodes. We therefore propose a fabrication scheme involving strategically combining two-dimensional graphene layers with a silver nanowire (Ag NW)-embedded PEDOT:PSS film. The developed hybrid electrode overcomes the limitations of commonly known metallic NWs and ionic conductor-based electrodes for ACEL applications. Furthermore, the potential of the hybrid electrode is realized in demonstrating large-area stretchable ACEL devices composed of an 8 × 8 passive array. The prototype ACEL passive array demonstrates efficient and uniform electroluminescence under high levels of mechanical deformation such as bending, rolling, twisting, and stretching.

Culture-independent and culture-dependent analyses of the bacterial community in the phycosphere of cyanobloom-forming Microcystis aeruginosa.

Confocal and scanning electron microscopic observations have previously shown the strong bacterial association of Microcystis aeruginosa cells on their surfaces. DNA-based analyses of the associated bacterial communities were carried out using two M. aeruginosa strains grown in the laboratory and eight newly collected cyanobacterial bloom samples. M. aeruginosa was the most predominant species (66-100%) within the phylum Cyanobacteria. Rhizobium, Hydrogenophaga and Brevundimonas species were commonly found, and Flavobacterium species were present in all the cyanobacterial bloom samples. In total, 396 colonies from various samples were screened, revealing that most culturable bacteria belonged to the class Alphaproteobacteria (19%) including Rhizobium, Brevundimonas, and Porphyrobacter species. The genetic variation among the M. aeruginosa strains and different habitat conditions may have led to the presence of distinct bacterial populations among the tested samples. Among all the tested seven culturable isolates, Rhizobium sp. MK23 showed the best growth-promotion effect on the axenic M. aeruginosa strains. H2O2 was observed to be produced during the growth of M. aeruginosa PCC7806 under light conditions, this strain was more resistant to H2O2 when associated with Rhizobium sp. MK23. Our data suggested that Rhizobium species along with other associated bacteria might help the growth of M. aeruginosa by decomposing H2O2 under the aerobic growing conditions.

Lithography-free plasma-induced patterned growth of MoS2 and its heterojunction with graphene.

Application-oriented patterned growth of transition metal dichalcogenides (TMDCs) and their heterojunctions is of critical importance for sophisticated, customized two-dimensional (2D) electronic and optoelectronic devices; however, it is still difficult to fabricate these patterns in a simple, clean, and high controllability manner without using optical lithography. Here, we report the direct synthesis of patterned MoS2 and graphene-MoS2 heterojunctions via selective plasma treatment of a SiO2/Si substrate and chemical vapor deposition of MoS2. This method has multiple merits, such as simple steps, a short operating time, easily isolated MoS2 layers with clean surfaces and controllable locations, shapes, sizes and thicknesses, which enable their integration into the device structure without using a photoresist. In addition, we demonstrate the direct growth of patterned graphene-MoS2 heterojunctions for the fabrication of transistor. This study reveals a novel method to fabricate and use patterned MoS2 and graphene-MoS2 heterojunctions, which could be generalized to the rational design of other 2D materials, heterojunctions and devices in the future.

Detection of graphene domains and defects using liquid crystals.

The direct observation of the domain size and defect distribution in a graphene film is important for the development of electronic applications involving graphene. Here we report a promising method for observing graphene domains grown by chemical vapour deposition. The unavoidable development of crack or pinhole defects during the growth and transfer processes is visualized using a liquid crystal layer. Liquid crystal molecules align anisotropically with respect to the graphene domains and exhibit distinct birefringence properties that can be used to image the graphene domains. This approach is useful for visualizing the crack distributions and their generation process in graphene films under external strain. This type of simple observation method provides an effective route to evaluating the quality and reliability of graphene sheets for use in various electronic devices.

YKL-40 expression could be a poor prognostic marker in the breast cancer tissue.

YKL-40 is a glycoprotein involved in cellular growth, migration, and the inflammatory process. Elevation in serum levels of YKL-40 has been associated with worse prognosis in various cancers, including breast cancer. Given that the clinical significance of YKL-40 expression in breast cancer tissue is unclear, we aimed to determine the prognostic value of YKL-40 expression in breast cancer tissue using immunohistochemistry. We performed tissue microarray (TMA) analysis of 425 breast cancer tissues collected during operation. Immunohistochemical staining was performed to measure expression of YKL-40 and several breast cancer biomarkers, such as aldehyde dehyadrogenase1, TGF-beta, and Gli-1 as well as hormonal receptor and Her-2/neu status. Statistical analysis of the relationship of YKL-40 expression with clinicopathological characteristics was performed for 390 TMA samples. YKL-40 was expressed to varying degrees in 84.9% of breast cancer tissues. YKL-40 expression was correlated with estrogen receptor and progesterone receptor negativity and was positively correlated with TGF-beta and Gli-1 expression. Strong YKL-40 expression was associated with a larger proportion of Her-2/neu-enriched and basal-like tumors. The results of this study demonstrate that YKL-40 expression in breast cancer tissues is associated with hormone receptor negativity and Her-2/neu-enriched molecular subtypes of breast cancer, and therefore could be considered a poor prognostic predictor.

Calcium-sensing receptor and apoptosis in parathyroid hyperplasia of patients with secondary hyperparathyroidism.

OBJECTIVE: This retrospective study investigated the characteristics of secondary hyperparathyroidism (SHPT) by examining the presence of the calcium-sensing receptor (CaSR) and the rate of cell proliferation and apoptosis in parathyroid glands. METHODS: Eighteen diffuse and 57 nodular hyperplastic parathyroid glands from 24 patients with SHPT were compared with 14 primary adenomas and 33 normal parathyroid glands using immunohistochemical staining of CaSR and a marker of proliferative activity (Ki67 antigen). Apoptosis was measured using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling assay. RESULTS: The mean ± SE labelling index (LI) of CaSR (12.8% ± 1.5%) in nodular hyperplasia was significantly lower than that in normal parathyroid glands (26.8% ± 0.8%), whereas the mean ± SE LI of CaSR in diffuse hyperplasia was similar to that in normal parathyroid glands (23.3% ± 1.8%). The mean ± SE LI of Ki67 antigen was significantly higher in primary adenoma and nodular hyperplasia than in normal parathyroid glands. CONCLUSION: These results indicate that downregulation of CaSR, and a higher rate of proliferation over apoptosis, could contribute to the pathological progression of SHPT.

The anatomy of the external branch of the superior laryngeal nerve in Koreans.

BACKGROUND: Preservation of the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy is important because its injury may lead to frequent occurrence of vocal fatigue and the inability to perform superenergetic phonation. Most studies on the anatomy of EBSLN have been performed in Western countries and, thus, have some limitations in their application to Koreans. We explored the anatomy of EBSLNs using intraoperative neuromonitoring (IONM) in Korean adults. METHODS: Between August 2011 and December 2011, 50 patients underwent thyroidectomy at Korea University, Anam Hospital in Seoul, Korea. IONM was performed with the NIM response 3.0 system. RESULTS: Forty-two total thyroidectomies and eight lobectomies were performed with IONM and 92 EBSLNs were evaluated. Type I EBSLN was observed in 15 of the 92 nerves (16.3%), type IIa EBSLN was noted in 52 (56.5%) and type IIb EBSLN was noted in 25 (27.2%). Patients with types IIa and IIb were at higher risk of injuries and these types were more frequently observed (83.7%) compared with previous Western studies. We found that 35.9% of distal insertion sites of EBSLNs were located within 1cm of the center of the cricoid cartilage. CONCLUSION: Surgeons should pay close attention to preserving the EBSLN during thyroidectomy in Korean patients because their EBSLNs are more frequently located beneath the superior thyroid vessels.

The relationship between preeclampsia, pregnancy-induced hypertension and maternal risk of breast cancer: a meta-analysis.

BACKGROUND: It has long been recognized that some human breast cancers are hormone dependent. Preeclampsia is a syndrome of pregnancy defined by the onset of hypertension and proteinuria and characterized by dysfunction of the maternal endothelium. Many hormonal changes occur with preeclampsia, and we hypothesize that these changes may influence the risk of maternal breast cancer. We also analyzed the relation between pregnancy-induced hypertension (PIH) and maternal risk of breast cancer. METHODS: Among 13 relevant publications about preeclampsia and six relevant publications about PIH, some studies find preeclampsia associated with a lower risk of breast cancer, but others did not. Therefore, these results are inconclusive. We conducted meta-analysis to evaluate more precisely the relationship between preeclampsia, PIH and maternal risk of breast cancer. RESULTS: The pooled estimate of the hazard ratio (HR) associated with preeclampsia was 0.86 (95% CI 0.73-1.01), and that associated with PIH was 0.83 (0.66-1.06), both based on the random effects model. CONCLUSION: Some suggestive but not entirely consistent nor conclusive evidence was found on the association between the history of preeclampsia or PIH with the subsequent risk of breast cancer.

The relationship between twin births and maternal risk of breast cancer: a meta-analysis.

Women who undergo a greater number of menstrual cycles may be at increased risk of breast cancer, possibly due to cumulative exposure to ovarian hormones. Pregnancy reduces the lifetime number of menstrual cycles and also influences the levels of ovarian hormones. Twin pregnancies differ from singleton pregnancies in both hormone levels and perinatal changes. To date, a meta-analysis on the effects of twin birth on the risk of maternal breast cancer has not been conducted. Among 17 relevant publications identified in a systematic search, some suggest that twin births may be associated with lower breast cancer risk but others do not; therefore, the results are inconclusive. Although our pooled results of all 17 published studies did not show a reduced maternal risk of breast cancer for twin births (HR 0.94; 95% CI = 0.87-1.02; P = 0.127), a trend toward reduced maternal risk of breast cancer was identified in a subgroup analysis of cohort studies (HR 0.91; 95% CI = 0.83-1.01; P = 0.068). The results of this meta-analysis suggest that twin pregnancy does not significantly decrease the maternal risk of breast cancer.

A wideband spiral antenna for ingestible capsule endoscope systems: experimental results in a human phantom and a pig.

This paper presents the design of a wideband spiral antenna for ingestible capsule endoscope systems and a comparison between the experimental results in a human phantom and a pig under general anesthesia. As wireless capsule endoscope systems transmit real-time internal biological image data at a high resolution to external receivers and because they operate in the human body, a small wideband antenna is required. To incorporate these properties, a thick-arm spiral structure is applied to the designed antenna. To make practical and efficient use of antennas inside the human body, which is composed of a high dielectric and lossy material, the resonance characteristics and radiation patterns were evaluated through a measurement setup using a liquid human phantom. The total height of the designed antenna is 5 mm and the diameter is 10 mm. The fractional bandwidth of the fabricated antenna is about 21% with a voltage standing-wave ratio of less than 2, and it has an isotropic radiation pattern. These characteristics are suitable for wideband capsule endoscope systems. Moreover, the received power level was measured using the proposed antenna, a circular polarized receiver antenna, and a pig under general anesthesia. Finally, endoscopic capsule images in the stomach and large intestine were captured using an on-off keying transceiver system.