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Background/Aims: This study aimed to review the indications, methods, cooperation, complications, and outcomes of percutaneous endoscopic gastrostomy (PEG). Methods: Questionnaires were sent to 200 hospitals, of which 62 returned their questionnaires, with a response rate of approximately 30%. Descriptive statistics were calculated to analyze the responses to the questionnaires. Results: In 2019, a total of 1,052 PEGs were performed in 1,017 patients at 62 hospitals. The main group who underwent PEG was older adult patients with brain disease, particularly stroke. Nutritional supply was an important purpose of the PEG procedure. “The pull method” was the most commonly used for initial PEG insertion. The complications related to PEG were mostly mild, with leakage being the most common. Patients who underwent PEG procedures were primarily educated regarding the post-procedure management and complications related to PEG. Preoperative meetings were skipped at >50% of the institutions. Regarding the cooperation between the nutrition support team (NST) and the physician performing PEG, few endoscopists answered that they cooperated with NST before and after PEG. Moreover, the rate of NST certification obtained by physicians performing PEG and the frequency of attendance at NST-related conferences were relatively low. Conclusions: This study shows a similar trend to that found in the previous PEG guidelines. However, it covers new aspects, including team-based work for PEG procedure, nutrition support, and education for patients and guardians. Therefore, each medical institution needs to select an appropriate method considering the medical environment and doctor’s abilities. [ABSTRACT FROM AUTHOR]

Background/Aims: This study aimed to evaluate the characteristics of endoscopic retrograde cholangiopancreatography (ERCP) or endoscopic ultrasonography (EUS)-related adverse events (AEs) that eventually lead to medical disputes or claims on medical professional liability. Methods: Medical disputes for ERCP/EUS-related AEs filed in the Korea Medical Dispute Mediation and Arbitration Agency between April 2012 and August 2020 were evaluated using corresponding medical records. AEs were categorized into three sections: procedure-related, sedation-related, and safety-related AEs. Results: Among a total of 34 cases, procedure-related AEs were 26 (76.5%; 12 duodenal perforations, 7 post-ERCP pancreatitis, 5 bleedings, 2 perforations combined with post-ERCP pancreatitis); sedation-related AEs were 5 (14.7%; 4 cardiac arrests, 1 desaturation), and safety-related AEs were 3 (8.8%; 1 follow-up loss for stent removal, 1 asphyxia, 1 fall). Regarding clinical outcomes, 20 (58.8%) were fatal and eventually succumbed to AEs. For the types of medical institutions, 21 cases (61.8%) occurred at tertiary or academic hospitals, and 13 (38.2%) occurred at community hospitals. Conclusions: The ERCP/EUS-related AEs filed in Korea Medical Dispute Mediation and Arbitration Agency showed distinct features: duodenal perforation was the most frequent AE, and clinical outcomes were fatal, resulting in at least more than permanent physical impairment. [ABSTRACT FROM AUTHOR]

Background/Aims: Endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) is integral to the diagnosis of gastrointestinal (GI) subepithelial tumors (SETs). The impact of different EUS-FNB tissue sampling techniques on specimen adequacy and diagnostic accuracy in SETs has not been fully evaluated. This study aimed to compare the diagnostic outcomes of slow-pull (SP) and standard suction (SS) in patients with GI SETs. Methods: In this retrospective comparative study, 54 patients were enrolled. Medical records were reviewed for location and size of the target lesion, FNB needle type/size, technical order, specimen adequacy, diagnostic yield, and adverse events. The acquisition rate of adequate specimens and diagnostic accuracy were compared according to EUS-FNB techniques. Results: The mean lesion size was 42.6±36.4 mm, and most patients were diagnosed with GI stromal tumor (75.9%). The overall diagnostic accuracies of the SP and SS techniques were 83.3% and 81.5%, respectively (p=0.800). The rates of obtaining adequate core tissue were 79.6% and 75.9%, respectively (p=0.799). No significant clinical factors affected the rate of obtaining adequate core tissue, including lesion location and size, FNB needle size, and final diagnosis. Conclusions: SP and SS had comparable diagnostic accuracies and adequate core tissue acquisition for GI SETs via EUS-FNB. [ABSTRACT FROM AUTHOR]

Background/Aims Non-celiac gluten sensitivity is characterized by intestinal and extra intestinal symptoms associated with the consumption of glutencontaining food. Since biomarkers for non-celiac gluten sensitivity are lacking, its prevalence is estimated based on self-reported symptoms. However, no data exist on self-reported non-celiac gluten sensitivity in the Korean population. Thus, we aim to investigate the prevalence of self-reported non-celiac gluten sensitivity in the Korean population and to determine its demographic and clinical characteristics. Methods This study surveyed Korean participants aged 18-80 years who visited gastroenterology outpatient clinics at 9 tertiary hospitals in South Korea from January 2016 to February 2017. They were questioned regarding symptoms related to gluten ingestion: degree of discomfort (visual analog scale score), frequency, time of symptom onset, and duration. Abdominal discomfort caused by 11 different kinds of gluten-containing Korean food items was investigated. Results More non-celiac gluten sensitivity self-reporters were identified among those with irritable bowel syndrome (33.6%) than among controls (5.8%). Major gastrointestinal symptoms included bloating (75.0%), abdominal discomfort (71.3%), and belching (45.0%). Common extra-intestinal symptoms included fatigue (20.0%) and headache (13.7%). More than half of those who self-reported nonceliac gluten sensitivity (66.3%) developed symptoms within 1 hour of food ingestion, and symptoms were localized in the upper abdomen (37.5%) and entire abdomen (30.0%). Conclusion Our findings suggest that if there are gluten-related symptoms in irritable bowel syndrome, the possibility of accompanying non-celiac gluten sensitivity should be considered. [ABSTRACT FROM AUTHOR]

Background/Aims: After esophagogastroduodenoscopy (EGD) with biopsy, some patients experience gastrointestinal symptoms. This study investigated the effect of sodium alginate on biopsy-related gastrointestinal symptoms. Methods: In this open-label, randomized, controlled trial, patients undergoing EGD with biopsy were randomly assigned to a treatment or control group. In the treatment group, sodium alginate was orally administered for 3 days after EGD. Patients completed questionnaires about their gastrointestinal symptoms at baseline (past week), the day after returning home, and after another 3 days. Gastrointestinal symptoms, including abdominal pain, epigastric pain/soreness, heartburn, acid reflux, nausea/vomiting, borborygmus, abdominal distension, and belching, were rated using an upper gastrointestinal symptom rating scale (GSRS). Results: A total of 210 persons (138 men) who underwent EGD with biopsy were enrolled and allocated to the treatment (n=104) or control (n=106) group. At baseline, the demographic factors and GSRS scores were not different between the control and treatment groups. The epigastric pain/soreness score increased in the control group after endoscopic biopsy (+0.056), whereas the score was decreased in the treatment group (–0.067) (p=0.042). In the treatment group, the scores for acid regurgitation and epigastric soreness decreased during follow-up from those at baseline (p<0.05), whereas there were no significant reductions in the control group. The scores for belching and borborygmus decreased during follow-up only in the treatment group. Abdominal bloating decreased in both the control and treatment groups. Conclusions: Sodium alginate reduced epigastric pain/soreness after EGD with biopsy. Therefore, the prescription of sodium alginate should be considered after endoscopic biopsy. [ABSTRACT FROM AUTHOR]

Background/Aims: To date, no reports have compared the diagnostic efficacy of narrow-band imaging (NBI) and i-scan for the histologic prediction of intermediate-to-large colorectal polyps. We aimed to compare the diagnostic accuracy of NBI and i-scan in predicting histology, and their inter-/intra-observer agreement. Methods: We performed a prospective, randomized study that included 66 patients (NBI, n=33 vs. i-scan, n=33) with colorectal polyps (size >10 mm but <50 mm) who underwent colonoscopic resection. During the procedure, three endoscopists documented their prediction using the Japan NBI Expert Team (JNET) classification. Two months after study completion, the endoscopists reviewed still images and video clips for analysis. Results: The overall diagnostic accuracies in the NBI and i-scan groups were 73.7% (73/99) and 75.8% (75/99), respectively, and there was no statistical significance between the two groups (p=0.744). The JNET classification as applied to NBI and i-scan showed substantial inter-observer agreement (NBI κ-value 0.612, p=0.001 vs. i-scan κ-value 0.662, p=0.002). Additionally, the κ-values of intra-observer agreement were in the range of 0.385-0.660 with NBI and 0.364-0.741 with i-scan. Conclusions: NBI and i-scan have similar diagnostic accuracies for the histologic prediction of intermediate-to-large colorectal polyps. Furthermore, the inter-/intra-observer agreement was acceptable for both modalities when the JNET classification was applied. [ABSTRACT FROM AUTHOR]

Background/Aims: Several clinical factors have been used to predict the response for concurrent chemoradiotherapy (CCRT); however, these factors are insufficient for prognostic predictions. We investigated clinical factors to assess whether they could be used to predict the response to CCRT and the survival of patients with esophageal cancer. Methods: Patients with esophageal cancer underwent CCRT from January 2005 to December 2015. Response to CCRT was classified as progressive disease (PD), stationary disease (SD), partial remission (PR), or complete remission (CR). Factors to predict the response to CCRT and patient survival were subsequently investigated. Results: A total of 535 esophageal cancer patients underwent CCRT. Four hundred ninety-three patients were followed up, and patient outcomes were investigated. In the adjusted analysis, patients with advanced stage disease (relative risk [RR], 0.28 in stage III and 0.12 in stage IV compared to stage I), poor performance status, circumferential involvement (RR, 0.61), and male sex (RR, 0.31) were less likely to achieve CR. Advanced stage disease (hazard ratio [HR], 1.71 in stage III/IV), poor CCRT response (HR, 2.82 in PR, 4.47 in SD, 4.77 in PD compared to CR), and poor performance status (HR, 1.38 in ECOG 2–4) were found to increase mortality. Conclusions: Advanced stage disease, poor performance status, male sex, and circumferential involvement were independent predictive factors for a poor response to CCRT. Advanced stage, poor performance status, and poor CCRT response were independent factors for decreased survival. (Gut Liver 2020;14:450-458) [ABSTRACT FROM AUTHOR]

Endoscopic submucosal dissection (ESD) is widely used for the treatment of colorectal neoplasia in patients who are candidates for endoscopic resection. In particular, pyogenic liver abscess (PLA), although rare, can occur. To our knowledge, there are no reports of PLA cases after ESD. Therefore, we report a rare case of PLA caused by ESD. A 76-year-old man was referred from a local clinic and admitted to our hospital for colonic ESD for a large polypoid mass. During colonoscopy, a 5-cm mass was seen in the cecum. ESD was performed. Four days after the procedure, he complained of myalgia and abdominal discomfort. Computed tomography revealed a 5.4- cm PLA in the medial segments of the liver. He was treated with antibiotics, and a percutaneous drainage catheter was inserted. Here, we report a very rare complication (PLA) after ESD. In conclusion, comprehensive awareness of the development of PLA is needed in ESD cases. [ABSTRACT FROM AUTHOR]

Background/Aims: The validity of 13C-urea breath test (13C-UBT) for Helicobacter pylori detection is influenced by atrophic gastritis. The aim of this study was to evaluate the effect of citric acid on the accuracy of 13C-Urea breath test after H. pylori eradication therapy in a region where atrophic gastritis is common. Methods: In this prospective study, H. pylori-positive patients received 13C-UBT after H. pylori eradication regimen. They were classified into citric acid group and control group. To determine diagnostic accuracy of 13CUBT, patients were offered invasive methods. Results: A total of 1,207 who successfully took H. pylori -eradication regimen received UBT. They were assigned into the citric acid group (n=562) and the control group (n=645). The mean 13CUBT value of the citric acid group was 10.3±26.4%, which was significantly (p<0.001) higher than that of that control group (5.1%±12.6%). Of these patients 122 patients were evaluated by endoscopic biopsy methods. Based on invasive tests, the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 13C-UBT for the citric acid group were 83.3%, 91.7%, 81.3%, 55.0%, and 97.5%, respectively. Those of the control group were 87.7%, 90.9%, 88.2%, 62.5%, and 97.8%, respectively. They were not significantly different between the two groups. Although the presence of gastric atrophy and intestinal metaplasia (IM) decreased the accuracy, the decrease was not significant. Conclusions: In a country with high prevalence of atrophic gastritis or IM, false positivity remained common despite the use of citric acid in 13C-UBT. [ABSTRACT FROM AUTHOR]

Background/Aims: Contrast-enhanced harmonic endoscopic ultrasonography (CEH-EUS) is a promising imaging modality that can differentiate subepithelial tumors (SETs) by detecting the degree of enhancement. However, whether CEHEUS alone can predict the malignancy risk of gastrointestinal stromal tumors (GISTs) remains unclear. This study aimed to evaluate the feasibility of CEH-EUS by using perfusion analysis software for distinguishing among SETs and predicting the malignancy risk of GISTs. Methods: We retrospectively included patients with SETs who underwent preoperative CEH-EUS. In this study, 44 patients with histologically proven GISTs and benign SETs were enrolled. Perfusion analysis was performed using perfusion quantification software. Peak enhancement (PE), wash-in rate (WiR), wash-in perfusion index (WiPI), and wash-in and wash-out areas under the time-intensity curve (WiWoAUC) were calculated and compared between the GISTs and benign SETs. Results: When we allocated the enrolled patients into the leiomyoma group and low- and high-grade malignancy GIST groups, significant statistical differences in PE (p<0.001), WiR (p=0.009), WiPI (p<0.001), and WiWoAUC (p<0.001) were identified in the high-grade malignancy group compared with the leiomyoma group. Conclusions: CEH-EUS with perfusion analysis using perfusion analysis software could be a quantitative and independent method for predicting malignancy risk in gastrointestinal SETs. [ABSTRACT FROM AUTHOR]

In 2011, the Korean Society of Neurogastroenterology and Motility (KSNM) published clinical practice guidelines on the management of irritable bowel syndrome (IBS) based on a systematic review of the literature. The KSNM planned to update the clinical practice guidelines to support primary physicians, reduce the socioeconomic burden of IBS, and reflect advances in the pathophysiology and management of IBS. The present revised version of the guidelines is in continuity with the previous version and targets adults diagnosed with, or suspected to have, IBS. A librarian created a literature search query, and a systematic review was conducted to identify candidate guidelines. Feasible documents were verified based on predetermined inclusion and exclusion criteria. The candidate seed guidelines were fully evaluated by the Guidelines Development Committee using the Appraisal of Guidelines for Research and Evaluation II quality assessment tool. After selecting 7 seed guidelines, the committee prepared evidence summaries to generate data exaction tables. These summaries comprised the 4 main themes of this version of the guidelines: colonoscopy; a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols; probiotics; and rifaximin. To adopt the core recommendations of the guidelines, the Delphi technique (ie, a panel of experts on IBS) was used. To enhance dissemination of the clinical practice guidelines, a Korean version will be made available, and a food calendar for patients with IBS is produced. [ABSTRACT FROM AUTHOR]

We present a cost-effective dual polarization quadrature phase-shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two 90° optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of 2%-Δ. Two four-channel spot-size converter integrated waveguide-photodetector (PD) arrays are bonded on PD carriers for transverse-electric/ transverse-magnetic polarization, and butt-coupled to a polished facet of the PLC using a simple chip-to-chip bonding method. Instead of a ceramic sub-mount, a lowcost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans-impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3-dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of 8.3 × 10-11 is achieved at a 112-Gbps back-to-back transmission with off-line digital signal processing. [ABSTRACT FROM AUTHOR]

This paper demonstrates the effect of fluoride-based plasma treatment on the performance of Al2O3/AlGaN/ GaN metal-insulator-semiconductor heterostructure field effect transistors (MISHFETs) with a T-shaped gate length of 0.20 μm. For the fabrication of the MISHFET, an Al2O3 layer as a gate dielectric was deposited using atomic layer deposition, which greatly decreases the gate leakage current, followed by the deposition of the silicon nitride layer. The silicon nitride layer on the gate foot region was then selectively removed through a reactive ion etching technique using CF4 plasma. The etching process was continued for a longer period of time even after the complete removal of the silicon nitride layer to expose the Al2O3 gate dielectric layer to the plasma environment. The thickness of the Al2O3 gate dielectric layer was slowly reduced during the plasma exposure. Through this plasma treatment, the device exhibited a threshold voltage shift of 3.1 V in the positive direction, an increase of 50 mS/mm in trans conductance, a degraded off-state performance and a larger gate leakage current compared with that of the reference device without a plasma treatment. [ABSTRACT FROM AUTHOR]

Background/Aims: Controversy exists regarding the characteristics of Helicobacter pylori infection-negative gastric cancer (HPIN-GC). The aim of this study was to evaluate clinicopathologic features of HPIN-GC compared to H. pylori infection-positive gastric cancer (HPIP-GC) using a comprehensive analysis that included genetic and environmental factors. Methods: H. pylori infection status of 705 resectable gastric cancer patients was determined by the rapid urease test, testing for anti-H. pylori antibodies, histologic analysis and culture of gastric cancer tissue samples, and history of H. pylori eradication. HPIN-GC was defined as gastric cancer that was negative for H. pylori infection based on all five methods and that had no evidence of atrophy in histology or serology. Results: The prevalence of HPIN-GC was 4% (28/705). No significant differences with respect to age, sex, smoking, drinking, family history of gastric cancer or obesity were observed between the two groups. HPIN-GC tumors were marginally more likely to involve the cardia (14.3% for HPIN-GC vs 5.3% for HPIP-GC, p=0.068). The Lauren classification, histology, and TNM stage did not differ according to H. pylori infection status. Microsatellite instability was not different between the two groups, but p53 overexpression in HPIN-GC was marginally higher than in HPIP-GC (56.0% for HPIN-GC vs 37.0% for HPIP-GC, p=0.055). Conclusions: The prevalence of HPIN-GC was extremely low, and its clinicopathologic characteristics were similar to HPIP-GC. [ABSTRACT FROM AUTHOR]

Candida is a rare cause of infectious arthritis, and it can be found in infants and immunocompromised patients. Patients with maintenance hemodialysis are prone to opportunistic infections because of altered immunity, and frequent exposures to health-care associated infections. Herein, we report a case of candida arthritis of right shoulder with preceding fungemia in patients with maintenance hemodialysis. The diagnosis is based on the isolation of Candida Tropicalis from blood and synovial fluids of the shoulder joint. The patient has received intravenous fluconazole and arthroscopic surgical debridement. We then changed the fluconazole into amphotericin B due to the abnormal signs in the liver function tests, although the fluconazole successfully controlled fungemia and arthritis. To the best of our knowledge, this is the first case of candida arthritis in patients with maintenance hemodialysis in South Korea. [ABSTRACT FROM AUTHOR]

We present the optimization of a birefringence-enhanced-waveguide (BWG)-based polarization beam splitter (PBS) in a Mach-Zehnder interferometer (MZI) configuration and analyze the structure-dependent or polarization-dependent phase difference, using a delay-line MZI (DL-MZI). We fabricate the DL-MZI using silica-based planar lightwave circuit technology and, using the DL-MZI, demonstrate the ability to optimize a PBS by measuring the birefringence of the BWG and structure-dependent phase offset. [ABSTRACT FROM AUTHOR]

Flow aggregation is a scalable method to provide quality of service guarantees to a large number of flows economically. A round-robin scheduler is an efficient scheduling algorithm. We investigate flow aggregation using a round-robin scheduler and propose the use of periodic timer interrupts for rate control of the round-robin scheduler. The proposed flow aggregator is a single-stage scheduler compared to Cobb's two-stage flow aggregator consisting of an aggregator and non-aggregating scheduler. It is possible to implement flow aggregation in the existing routers with only a software upgrade. We also present a simulation study showing the delay behaviors of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In this paper, we present the fabrication of 40 Gb/s traveling-wave electroabsorption modulator-integrated laser (TW-EML) modules. A selective area growth method is first employed in 40 Gb/s EML fabrication to simultaneously provide active layers for lasers and modulators. The 3 dB bandwidth of a TW-EML module is measured to be 34 GHz, which is wider than that of a lumped EML module. The 40 Gb/s non-return-to-zero eye diagram shows clear openings with an average output power of +0.5 dBm. [ABSTRACT FROM AUTHOR]

We have developed 40-Gb/s traveling-wave electroabsorption-modulator-integrated distributed feedback laser (TW-EML) modules using several advanced technologies. First, we have adopted a selective area growth (SAG) method in the fabrication of the 40-Gb/s EML device to provide active layers for the laser and the electroabsorption modulators (EAMs) simultaneously. The fabricated device shows that the measured 3-dB bandwidth of electrical-to-optical (E/O) response reaches about 45 GHz and the return loss (S11) is kept below -10 dB up to 50GHz. For the module design of the device, we mainly considered electrical and optical factors. The measured S11 of the fabricated 40 Gb/s TW-EML module is below -10 dB up to about 30 GHz and the 3-dB bandwidth of the E/O response reaches over 35 GHz. We also have developed two types of coplanar waveguide (CPW) for the application of the driver amplifier integrated 40 Gb/s TW-EML module, which is a system-on-package (SoP) composed of an EML device and a driver amplifier device in a module. The measured S11 of the two-step-bent CPW is below -10 dB up to 35 GHz and the measured S11 of the parallel type CPW is below -10 dB up to 39 GHz. [ABSTRACT FROM AUTHOR]

We propose crossed stripe-electrode patterns for a vertically-aligned liquid crystal (LC) cell. The proposed electrode structure forms the radial LC distribution with the point singularity S = + 1 in the presence of the applied electric field, resulting in the wide viewing angle characteristics as well as the reduced color-shift compared to the conventional patterned vertical alignment (PVA) cell. Moreover, the radial LC distribution with the point singularity results in an increased transmittance compared to the conventional PVA cell, because the region with zero transmittance only occurs at the singular point. [ABSTRACT FROM AUTHOR]

We developed high-speed optoelectronics packaging technologies for a waveguide photodiode and a traveling wave electro-absorption modulator device for 40-Gb/s digital communication systems. The effects of the device and the packaging designs on the broadband performance were investigated to optimize broadband characteristics. For the receiver, inductive peaking was used for bandwidth control and an internal bias tee was implemented; in addition, two types of preamplifier devices were used to develop high-gain receiver and wide-bandwidth receiver. In the optical-to-electrical response, a 3-dB bandwidth of the high-gain module was about 32 GHz as compared to 42 GHz for the wide-bandwidth module. The clear 40-Gb/s nonreturn-to-zero (NRZ) eye diagrams showed a good system applicability of these modules. In addition, an optimized modulator module showed a 3-dB bandwidth of 38 GHz in the electrical-to-optical response, an electrical return loss of less than 10 dB at up to 26 GHz, an rms jitter of 1.832 ps, and an extinction ratio of 5.38 dB in a 40-Gb/s NRZ eye diagram [ABSTRACT FROM PUBLISHER]

In this paper, the circuit models of a waveguide photodiode (WGPD) and its submodule were investigated, and the O/E characteristics of a WGPD submodule are examined. Test structures of the WGPD and WGPD submodule were fabricated and microwave return loss (S11) was measured and compared with simulated data to validate the circuit models. With the established submodule model, optical to electrical (O/E) characteristics were measured and compared with the modeled data to analyze the effects of model parameters on the submodule performance. Based on the results, it can be concluded that the suggested submodule model can explain the characteristics of the submodule performance. In addition, parasitic components that originated from the ribbon bonding block can crucially impact on the performance of WGPD submodule. [ABSTRACT FROM AUTHOR]

The reliability of 1.55-μm wavelength InGaAs waveguide photodiodes (WGPDs) fabricated by metal-organic chemical vapor deposition is investigated for 40-Gb/s optical receiver applications. Reliability for both high-temperature storage and accelerated life tests obtained by monitoring both the dark current and the breakdown voltage is examined. The median device lifetime and the activation energy of the degradation mechanism are extracted for WGPD test structures. The device lifetimes are examined via statistical analysis which is highly reliable in predicting the device lifetime under practical conditions. The degradation mechanism for the WGPD test structures can be explained by the formation of leakage current path by ionic impurities in the passivation layer on the exposed p-n junction. Nevertheless, it can be concluded that the WGPD test structures exhibit sufficient reliability for practical 40-Gb/s optical receiver applications. [ABSTRACT FROM PUBLISHER]

We propose a new type of the traveling-wave photodetector (TWPD) that has an asymmetric intrinsic layer cross section to enhance bandwidth. In this paper, analysis and design of TWPDs are presented using the finite-difference time-domain method. A full-wave analysis is performed by a numerical technique and impulse responses are obtained in a linear regime. The simulation and experiment results show that 3-dB bandwidth is increased by the difference between electron and hole saturation velocities. [ABSTRACT FROM PUBLISHER]

Background/Aims The depth of tumor invasion is an important factor in the management of T1 colorectal cancer (CRC). To date, many reports have been suggested about endoscopic features predicting deep submucosa invasion (SMI). However, most of them were restricted to non-pedunculated CRC. Pedunculated polyps are considered difficult to evaluate invasion depth due to its polypoid morphologic trait. Therefore, this study aimed to determine the endoscopic predictors of deep SMI in pedunculated T1 CRC. Methods We performed a retrospective study from January 2012 through June 2019 in a tertiary referral center. A total of 149 pedunculated T1 CRCs treated by endoscopic resection or surgery were eligible. We divided them into a superficial SMI group (n=121) and a deep SMI group (n=28) according to the depth of SMI (less or more than 3000 μm, respectively) We included endoscopic size, mucosal depression, chicken-skin mucosa (CSM) and a large nodule (≥10 mm) as the features of predicting deep SMI. Results Endoscopic size was statistically different between the superficial SMI group and deep SMI group (16.40±4.42 mm vs 18.63±4.52 mm, p=0.018). In addition, CSM (40% vs 64.3%, p=0.020) and a large nodule (1.7% vs 10.7%, p=0.016) were both statistically significant predictors for deep SMI. Multivariate analysis determined that the only risk factor for deep SMI was CSM (OR, 3.25; 95% CI, 1.29-8.13; p=0.012) (Table 1). Conclusions The presence of CSM was associated with an increased risk of deep SMI. Other features such as endoscopic size and a large nodule of polyps could also help to predict the deep SMI and identify candidates for endoscopic resection or surgery. [ABSTRACT FROM AUTHOR]

Background/Aims There is still controversy over the optimal endoscopic interval for gastric cancer screening. In the previous study, we confirmed that there was no significant difference between 2- and 3-year interval, but the number of samples was small. Thus, we analyzed further through prospectively maintained database to define appropriate endoscopic interval and characteristics of missed cancer. Methods We analyzed the questionnaire including interval between penultimate endoscopy and diagnosis of gastric cancer, the endoscopic findings, stage and treatment at the time of diagnosis. The patients were divided into two groups according to cancer type (early gastric cancer [EGC] vs advanced gastric cancer [AGC]) and endoscopic examinations (2 and 3 years). Results From February 2014 to July 2018, 1,987 patients with gastric cancer were enrolled prospectively and, 176 (8.9%) patients with endoscopic interval less than 1 year were classified as missed gastric cancer group. There were significant differences in endoscopic interval (p<0.001), age (p=0.046), family history of gastric cancer (p=0.046), tumor location (p<0.001), histology (p<0.001), stage (p<0.001) and treatment modality (p<0.001) between EGC and AGC group. Endoscopic intervals of less than 2 or 3 years were associated with higher proportions of EGC (adjusted odd ratio [OR], 4.243; 95% confidence interval [CI], 3.384 to 5.321; adjusted OR, 4.277; 95% CI, 3.385 to 5.403; respectively, p<0.001). The incidence of missed gastric cancer was tend to be higher in men than women (p=0.034) and in young than old age (p=0.038 among age groups <40, 40 to 74, ≥75). Conclusions Endoscopic gastric cancer screening at 2- and 3-year intervals did not differ in terms of increasing the detection rate of EGC and enabling endoscopic resection. It is necessary to establish optimal endoscopic interval through large-scale randomized controlled trials. [ABSTRACT FROM AUTHOR]

Background/Aims As the prevalence of antibiotic resistance is increasing, the effectiveness of traditional Helicobacter pylori therapies is gradually declining. In particular, the effectiveness of the triple regimen containing clarithromycin (CLA) or metronidazole (MET), proton pump inhibitor, and amoxicillin (AMX) has decreased with a corresponding increase in CLA or MET resistance. In this study, we evaluated the current status of antibiotic resistance of H. pylori in Daegu and Kyungpook province. Methods Patients who revealed H. pylori infection were prospectively enrolled from June 2016 to April 2019 in Daegu and Kyungpook province. The patients' clinical data and H. pylori culture and antibiotic susceptibility tests were evaluated. For antibiotic susceptibility of H. pylori, minimum inhibitory concentrations (MICs) of AMX, CLA, MET, tetracycline (TC), and levofloxacin (LEV) were determined according to the agar dilution method. Results Of 101 consecutive patients, the H. pylori strains of 82 patients (81.2%) were successfully cultured. Total antibiotic resistance to AMX, CLA, MET, TC, and LEV was 7.3%, 36.6%, 35.4%, 3.9% and 32.9%. The prevalence of antibiotic resistance based on previous eradication showed in Fig. 1. In these patients, 27 patients' H. pylori strains (32.9%) showed two or more antibiotic resistance. The dual and multi drug resistance of these patients based on previous eradication history showed in Tables 1 and 2. The prevalence of antibiotic resistance was significant different between primary resistance and failure of 1st or more eradication group (p<0.001). Conclusions Primary antibiotic resistance in Daegu and Kyungpook province was lower compared to other area in Korea, especially Seoul and Gyeonggi province. However, the multi drug resistance was the main cause of in failure of H. pylori eradication. [ABSTRACT FROM AUTHOR]

High-power characteristics of waveguide photodetectors (PDs) with various absorbing layer thicknesses were analyzed. When large photocurrent was generated by high-power optical input, the saturation of radio frequency response was closely related with the optical absorption efficiency. The device with a single quantum well absorbing layer showed no saturation behavior until the device failure, while PDs with a thicker absorbing layer were saturated at photocurrent of a few milliamperes. It was also found that as optical confinement decreases, the maximum photocurrent the device can endure increases by more than three times. [ABSTRACT FROM PUBLISHER]

We propose a deep floating guard ring (DFGR) structure which effectively prevents the curvature breakdown of a central junction in a planar InGaAs/InP avalanche photodiode (APD). In order to investigate the DFGR APD performance, the dark current, photocurrent, and radial dependence of gain were measured and analyzed. In addition, the relation between breakdown voltage and multiplication layer thickness was calculated using a nonlocal history-dependent model. Reliable operation in the device center region was examined by measuring the radial gain. As a result, it has been confirmed that the DFGR is very useful for an APD with a very thin multiplication layer. [ABSTRACT FROM AUTHOR]

This letter presents the reliability of planar InP-InGaAs avalanche photodiodes (APDs) with recess etching, which is very crucial for the commercial 10-Gb/s optical receiver application. The reliability is examined by accelerated life tests by monitoring dark current and breakdown voltage. The activation energy of the degradation mechanism and device median lifetime were estimated. Based on the test results, it is concluded that the planar InP-InGaAs APDs with recess etching shows the sufficient reliability for practical 10-Gb/s optical receivers. [ABSTRACT FROM PUBLISHER]

Studies the structural and optical properties of In[sub x]Ga[sub 1-x]N/GaN multiple quantum wells with different In compositions. High-resolution x-ray diffraction; Photoluminescence (PL); PL excitation; Stimulated emission.