High energy density in artificial heterostructures through relaxation time modulation.

Electrostatic capacitors are foundational components of advanced electronics and high-power electrical systems owing to their ultrafast charging-discharging capability. Ferroelectric materials offer high maximum polarization, but high remnant polarization has hindered their effective deployment in energy storage applications. Previous methodologies have encountered problems because of the deteriorated crystallinity of the ferroelectric materials. We introduce an approach to control the relaxation time using two-dimensional (2D) materials while minimizing energy loss by using 2D/3D/2D heterostructures and preserving the crystallinity of ferroelectric 3D materials. Using this approach, we were able to achieve an energy density of 191.7 joules per cubic centimeter with an efficiency greater than 90%. This precise control over relaxation time holds promise for a wide array of applications and has the potential to accelerate the development of highly efficient energy storage systems.

Monolithic 3D integration of 2D materials-based electronics towards ultimate edge computing solutions.

Three-dimensional (3D) hetero-integration technology is poised to revolutionize the field of electronics by stacking functional layers vertically, thereby creating novel 3D circuity architectures with high integration density and unparalleled multifunctionality. However, the conventional 3D integration technique involves complex wafer processing and intricate interlayer wiring. Here we demonstrate monolithic 3D integration of two-dimensional, material-based artificial intelligence (AI)-processing hardware with ultimate integrability and multifunctionality. A total of six layers of transistor and memristor arrays were vertically integrated into a 3D nanosystem to perform AI tasks, by peeling and stacking of AI processing layers made from bottom-up synthesized two-dimensional materials. This fully monolithic-3D-integrated AI system substantially reduces processing time, voltage drops, latency and footprint due to its densely packed AI processing layers with dense interlayer connectivity. The successful demonstration of this monolithic-3D-integrated AI system will not only provide a material-level solution for hetero-integration of electronics, but also pave the way for unprecedented multifunctional computing hardware with ultimate parallelism.

Functionalizing nanophotonic structures with 2D van der Waals materials.

The integration of two-dimensional (2D) van der Waals materials with nanostructures has triggered a wide spectrum of optical and optoelectronic applications. Photonic structures of conventional materials typically lack efficient reconfigurability or multifunctionality. Atomically thin 2D materials can thus generate new functionality and reconfigurability for a well-established library of photonic structures such as integrated waveguides, optical fibers, photonic crystals, and metasurfaces, to name a few. Meanwhile, the interaction between light and van der Waals materials can be drastically enhanced as well by leveraging micro-cavities or resonators with high optical confinement. The unique van der Waals surfaces of the 2D materials enable handiness in transfer and mixing with various prefabricated photonic templates with high degrees of freedom, functionalizing as the optical gain, modulation, sensing, or plasmonic media for diverse applications. Here, we review recent advances in synergizing 2D materials to nanophotonic structures for prototyping novel functionality or performance enhancements. Challenges in scalable 2D materials preparations and transfer, as well as emerging opportunities in integrating van der Waals building blocks beyond 2D materials are also discussed.

Applications of remote epitaxy and van der Waals epitaxy.

Epitaxy technology produces high-quality material building blocks that underpin various fields of applications. However, fundamental limitations exist for conventional epitaxy, such as the lattice matching constraints that have greatly narrowed down the choices of available epitaxial material combinations. Recent emerging epitaxy techniques such as remote and van der Waals epitaxy have shown exciting perspectives to overcome these limitations and provide freestanding nanomembranes for massive novel applications. Here, we review the mechanism and fundamentals for van der Waals and remote epitaxy to produce freestanding nanomembranes. Key benefits that are exclusive to these two growth strategies are comprehensively summarized. A number of original applications have also been discussed, highlighting the advantages of these freestanding films-based designs. Finally, we discuss the current limitations with possible solutions and potential future directions towards nanomembranes-based advanced heterogeneous integration.

Impacts of sleeve gastrectomy on gastroesophageal reflux disease in severely obese Korean patients.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) has established popularity as a bariatric and metabolic surgery. However, the incidence of gastroesophageal reflux disease (GERD) following LSG is controversial. This study aims to describe the prevalence of de novo GERD after LSG. METHODS: A retrospective chart review was performed for 130 patients who underwent a routine endoscopic surveillance before and after LSG between January 2013 and October 2018. The diagnosis of GERD was determined by presence of symptoms, history of PPI treatment, and endoscopic findings. The esophagogastroduodenoscopy (EGD) was performed annually after LSG and/or when the patients complained of severe reflux symptoms. RESULTS: The prevalence of GERD before surgery was 18.5%. At 1 year after LSG, GERD was present in 70 (53.8%) of the 130 patients. GERD consisted of 55 patients with newly developed GERD, and 15 with preexisting GERD. 9 (37.5%) out of pre-existing GERD patients were free of symptoms and abnormal finding at EGD following LSG. During the LSG, 66 (50.8%) patients with hiatal hernia underwent re-approximation of the diaphragmatic crura. There was no significant relationship between hiatal hernia repair and postoperative GERD (p = 0.39). Number of patients taking PPI medication before and after LSG were 34 (26.2%) and 49 (37.7%). Out of 56 (43.1%) patients with endoscopic lesions, LA grade A was 31 (23.9%), B = 15 (11.5%), C = 4 (3.1%), and D = 6 (4.6%). CONCLUSION: In this study, 42.3% (n = 55) of total patients developed newly developed GERD, and 7.7% (n = 10) had LA grade C or D esophagitis.

Self-powered image array composed of touch-free sensors fabricated with semiconductor nanowires.

We successfully develop a self-powered image array (IA) composed of 16 touch-free sensors (TFSs) fabricated with semiconductor InN nanowires (NWs) as a response medium. Without using a power supply, the InN-NW TFS can detect the position of a human hand 30 cm away from the device surface. It also distinguishes different materials such as polyimide, Al foil, printing paper, latex, and polyvinyl chloride in non-contact mode at a distance of 1 cm. The self-powered TFS-IA clearly distinguishes square-shaped transparent polydimethylsiloxane film attached to the back of a human hand positioned 5 cm from the device, indicating the possibility for detecting changes in the surface texture of human skin, such as skin burns or skin cancer. The performance of the self-powered TFS and TFS-IA is attributed to high electrostatic induction of InN NWs by external triboelectricity resulting from the simple movement of the target object, which differs markedly from conventional sensors designed to detect variations in the temperature or light essentially using a power supply.

Flexible 1.3 µm photodetector fabricated with InN nanowires and graphene on overhead projector transparency sheet.

We report the first demonstration of flexible photodetectors, operating at the wavelength window of 1.3 µm, fabricated with InN nanowires (NWs) and graphene on an overhead projector transparency (OHP) sheet. The InN NWs, used as an absorption medium for the device, were formed on a Si substrate and exhibited strong emission with a peak wavelength of 1.3 µm at room temperature. They were randomly and horizontally embedded in the graphene sandwich structure functioned as a carrier channel. The photocurrent and photoresponsivity of the flexible photodetector were found to be 1.17 mA and 0.48 A W-1, respectively, at a voltage of 1 V and a light intensity of 60 mW cm-2 of a xenon lamp. The photocurrent measured when the photodetector was bent under a strain of 3% was 1.15 mA, which corresponds to 98.3% compared to that before bending. Moreover, the photocurrent and photoresponsivity of the flexible photodetector measured after the 200 cyclic-bending tests are comparable to those measured before bending.

Bariatric surgery versus medical therapy in Korean obese patients: prospective multicenter nonrandomized controlled trial (KOBESS trial).

PURPOSE: The aim of this study was to show that bariatric surgery (BS) is more effective than medical therapy (MT) in Asian obese patients. METHODS: In this prospective, multicenter, nonrandomized, controlled trial, obese patients with body mass index of ≥35 kg/m2 or 30.0-34.9 kg/m2 with obesity-related comorbidities were assigned to undergo BS, such as laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass, or MT. Patients who underwent BS were evaluated 4, 12, 24, and 48 weeks after surgery, whereas patients who received MT were monitored at a hospital every 6 weeks for 1 year. At each visit, weight, waist and hip circumference, and blood pressure were measured, and patients underwent physical examination and laboratory testing. Health-related quality of life (HQOL) was investigated using Euro QOL-5 Dimension, Impact of Weight on Quality of Life questionnaire-Lite and Obesity-related Problems scale. RESULTS: The study included 264 patients from 13 institutions; of these, 64 underwent BS and 200 received MT. Of the patients who underwent BS, 6.3% experienced early complications. Relative weight changes from baseline to 48 weeks were significantly greater in the BS than in the MT group (26.9% vs. 2.1%, P < 0.001), as were the rates of remission of diabetes (47.8% vs. 16.7%, P = 0.014), hypertension (60.0% vs. 26.1%, P < 0.001), and dyslipidemia (63.2% vs. 22.0%, P < 0.001). HQOL was better in the BS than in the MT group at 48 weeks. CONCLUSION: BS was safe and effective in Korean obese patients, with greater weight reduction, remission of comorbidities, and quality of life improvement than MT.

Room-temperature operation of light-assisted NO2gas sensor based on GaN nanowires and graphene.

We report the successful demonstration of a light-assisted NO2gas sensor that operates at room temperature with high response. The gas sensor was fabricated with high-crystalline undoped-GaN nanowires (NWs) and graphene functioning as the light-absorbing medium and carrier channel, respectively. Exposure of the gas sensor to the NO2concentration of 100 ppm at a light intensity of 1 mW cm-2of a xenon lamp delivered a response of 16% at room temperature, which increased to 23% when the light intensity increased to 100 mW cm-2. This value is higher than those previously reported for GaN-based NO2gas sensors operating at room temperature. The room-temperature response of the gas sensor measured after six months was calculated to be 21.9%, which corresponds to 95% compared to the value obtained immediately after fabricating the devices. The response of the gas sensor after independently injecting NO2, H2S, H2, CO, and CH3CHO gases were measured to be 23, 5, 2.6, 2.2, and 1.7%, respectively. These results indicate that the gas sensor using GaN NWs and graphene provides high response, long-term stability, and good selectivity to NO2gas at room temperature. In addition, the use of undoped-GaN NWs without using additional catalysts makes it possible to fabricate gas sensors that operate at room temperature simpler and better than conventional technologies.

Short-term changes in the serum metabolome after laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass.

INTRODUCTION: Bariatric surgery is known to be the most effective treatment for weight loss in obese patients and for the rapid remission of obesity-related comorbidities. These short-term improvements result from not only limited digestion or absorption but also dynamic changes in metabolism throughout the whole body. However, short-term metabolism studies associated with bariatric surgery in Asian individuals have not been reported. OBJECTIVES: The aim of this study was to investigate the short-term metabolome changes in the serum promoted by laparoscopic sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) and to determine the underlying mechanisms that affect obesity-related comorbidities. METHODS: Serum samples were collected from Korean patients who underwent RYGB or SG before and 4 weeks after the surgery. Metabolomic and lipidomic profiling was performed using UPLC-Orbitrap-MS, and data were analyzed using statistical analysis. RESULTS: Metabolites mainly related to amino acids, lipids (fatty acids, glycerophospholipids, sphingolipids, glycerolipids) and bile acids changed after surgery, and these changes were associated with the lowering of risk factors for obesity-related diseases such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D) and atherosclerosis. Interestingly, the number of significantly altered metabolites related to the lipid metabolism were greater in SG than in RYGB. Furthermore, the metabolites related to amino acid metabolism were significantly changed only after SG, whereas bile acid changed significantly only following RYGB. CONCLUSION: These differences could result from anatomical differences between the two surgeries and could be related to the gut microbiota. This study provides crucial information to expand the knowledge of the common but different molecular mechanisms involved in obesity and obesity-related comorbidities affected by each bariatric procedure.

Stretchable Inorganic GaN-Nanowire Photosensor with High Photocurrent and Photoresponsivity.

To effectively implement wearable systems, their constituent components should be made stretchable. We successfully fabricated highly efficient stretchable photosensors made of inorganic GaN nanowires (NWs) as light-absorbing media and graphene as a carrier channel on polyurethane substrates using the pre-strain method. When a GaN-NW photosensor was stretched at a strain level of 50%, the photocurrent was measured to be 0.91 mA, corresponding to 87.5% of that (1.04 mA) obtained in the released state, and the photoresponsivity was calculated to be 11.38 A/W. These photosensors showed photocurrent and photoresponsivity levels much higher than those previously reported for any stretchable semiconductor-containing photosensor. To explain the superior performances of the stretchable GaN-NW photosensor, it was approximated as an equivalent circuit with resistances and capacitances, and in this way, we analyzed the behavior of the photogenerated carriers, particularly at the NW-graphene interface. In addition, the buckling phenomenon typically observed in organic-based stretchable devices fabricated using the pre-strain method was not observed in our photosensors. After a 1000-cycle stretching test with a strain level of 50%, the photocurrent and photoresponsivity of the GaN-NW photosensor were measured to be 0.96 mA and 11.96 A/W, respectively, comparable to those measured before the stretching test. To evaluate the potential of our stretchable devices in practical applications, the GaN-NW photosensors were attached to the proximal interphalangeal joint of the index finger and to the back of the wrist. Photocurrents of these photosensors were monitored during movements made about these joints.

Highly Efficient Photoelectrochemical Water Splitting Using GaN-Nanowire Photoanode with Tungsten Sulfides.

In the present study, we have achieved high-performance photoelectrochemical water splitting (PEC-WS) using GaN nanowires (NWs) coated with tungsten sulfide (WxS1-x) (GaN-NW-WxS1-x) as a photoanode. The measured current density and applied-bias photon-to-current efficiency were 20.38 mA/cm2 and 13.76%, respectively. These values were much higher than those reported previously for photoanodes with any kind of III-nitride nanostructure. The amount of hydrogen gas formed was 1.01 mmol/cm2 from 7 h PEC-WS, which was also much higher than the previously reported values. The drastic improvement in the PEC-WS performance using the GaN-NW-WxS1-x photoanode was attributed to an increase in the number of photogenerated carriers due to the highly crystalline GaN NWs, and acceleration of separation of photogenerated carriers and consequent suppression of charge recombination because of nitrogen-terminated surfaces of NWs, sulfur vacancies in WxS1-x, and type-II band alignment between NW and WxS1-x. The degree of impedance matching, evaluated from Nyquist plots, was considered to analyze charge transfer characteristics at the interface between the GaN-NW-WxS1-x photoanode and 0.5-M H2SO4 electrolyte. Considering the material system and scheme for the PEC-WS, our approach provides an efficient way to improve hydrogen evolution reaction.

Metabolomic Profiles Predict Diabetes Remission after Bariatric Surgery.

BACKGROUND: Amino acid metabolites (AAMs) have been linked to glucose homeostasis and type 2 diabetes (T2D). We investigated whether (1) baseline AAMs predict T2D remission 12 months after bariatric surgery and (2) whether AAMs are superior for predicting T2D remission postoperatively compared with existing prediction models. METHODS: Among 24 participants undergoing bariatric surgery, 16 diabetes-related AAMs were quantified at baseline and postoperative 3 and 12 months. Existing prediction models included the ABCD, DiaRem, and IMS models. RESULTS: Baseline L-dihydroxyphenylalanine (L-DOPA) (areas under receiver operating characteristic curves (AUROC), 0.92; 95% confidence interval (CI), 0.75 to 1.00) and 3-hydroxyanthranilic acid (3-HAA) (AUROC, 0.85; 95% CI, 0.67 to 1.00) better predicted T2D remission 12 months postoperatively than the ABCD model (AUROC, 0.81; 95% CI, 0.54 to 1.00), which presented the highest AUROC value among the three models. The superior prognostic performance of L-DOPA (AUROC at 3 months, 0.97; 95% CI, 0.91 to 1.00) and 3-HAA (AUROC at 3 months, 0.86; 95% CI, 0.63 to 1.00) continued until 3 months postoperatively. CONCLUSIONS: The AAM profile predicts T2D remission after bariatric surgery more effectively than the existing prediction models.

Fast Response Characteristics of Flexible Ultraviolet Photosensors with GaN Nanowires and Graphene.

We report the fast response characteristics of flexible ultraviolet photosensors with GaN nanowires (NWs) and a graphene channel. The GaN NWs used as light-absorbing media are horizontally and randomly embedded in a graphene sandwich structure in which the number of bottom graphene layers is varied from zero to three and the top is a fixed single layer of graphene. In the response curve of the photosensor with a double-layer bottom graphene, as obtained under pulsed illumination with a pulse width of 50 ms and a duty cycle of 50%, the rise and decay times were measured as 24.1 ± 0.1 and 28.2 ± 0.1 ms, respectively. The eye-crossing percentage was evaluated as 52.1%, indicating no substantial distortion of the duty cycle and no pulse symmetry problem. The rise and decay times estimated from an equivalent circuit analysis represented by resistances and capacitances agree well with the measured values. When the device was under the bending condition, the rise and decay times of the photosensor were comparable to those in the unbent state.

Long-term effect of bariatric surgery versus conventional therapy in obese Korean patients: a multicenter retrospective cohort study.

PURPOSE: Long-term results following bariatric surgery compared to conventional treatments has never been reported in morbidly obese Korean patients. This study aimed to evaluate the long-term efficacy of bariatric surgery in morbidly obese Korean patients compared to conventional medical treatments. METHODS: In this multicenter retrospective cohort study, we reviewed 137 obese subjects between January 2008 and February 2011 with a body mass index (BMI) > 30 kg/m2 who had more than 5 years of follow-up clinical data after bariatric surgery (surgery group, n = 49) or conventional treatment (conventional treatment group, n = 88). Anthropometric data and the status of comorbidities were compared between the 2 groups. RESULTS: The median follow-up period was 72.1 months (range 19.3-109.7 months). At the last follow-up, the surgery group showed a greater amount of total weight loss than the conventional treatment group (24.9% vs. 2.8%, P < 0.001). The prevalence of diabetes and hypertension significantly decreased in the surgery group, while the conventional treatment group showed a marked increase in these comorbidities. In the surgery group, Roux-en-Y gastric bypass and sleeve gastrectomy achieved comparable long-term weight loss (26.5% vs. 22.4%, respectively; P = 0.087). CONCLUSION: In the long-term, bariatric surgery achieved and maintained significantly greater weight reduction, as well as a decrease in obesity-related comorbidities, than did conventional medical therapy in morbidly obese Korean patients.

Outcomes of primary sleeve gastrectomy versus conversion sleeve gastrectomy in morbidly obese patients.

PURPOSE: Our aim for this study was to evaluate early and late complications and outcomes of primary sleeve gastrectomy (PSG) versus conversion sleeve gastrectomy (CSG). METHODS: From February 2013 to December 2016, a total of 180 patients underwent sleeve gastrectomy (150 PSG and 30 CSG). All patients received a metal clipping at the end of the stapling line and a continuous seromuscular suture at the resection margin, for reinforcement. RESULTS: There were no differences in the percentages among males and females or age between the 2 groups, but the body mass index (BMI) of the PSG group was higher at 36.8 ± 4.7 than that of the CSG group (32.4 ± 5.7, P < 0.001). Three early postoperative complications were noted in the PSG group; 1 patient underwent repeat laparoscopic exploration due to pancreatic injury, and 2 other patients developed pulmonary atelectasis. On the contrary, 2 early minor complications were noted in the CSG group. Thirty-eight patients (25.3%) in the PSG group developed 43 late, minor complications, while 9 patients (30.0%) developed 11 late minor and 1 major complication in the CSG group. However, there was no difference in complication rate between PSG and CSG. Percentage excess BMI loss at 3, 6, and 12 months after surgery was comparable between the groups. CONCLUSION: PSG and CSG were comparable in terms of postoperative complications and loss of weight. Therefore, CSG could be used for failed primary restrictive bariatric surgery. However, the durability of these outcomes remains unknown.

Influence of Asian Ethnicities on Short- and Mid-term Outcomes Following Laparoscopic Sleeve Gastrectomy.

PURPOSE: Prevalence of obesity in Asia has been on the increasing trend, with corresponding increase in utilisation of bariatric surgery. The objective of this study was to examine differences in weight loss outcomes following bariatric surgery between Asian ethnicities. MATERIALS AND METHODS: A retrospective database review was conducted of patients undergoing primary laparoscopic sleeve gastrectomy between 2009 and 2013 in 14 centres from Singapore, Malaysia, Taiwan, Hong Kong, Japan, Korea, India, Australia, Switzerland, and the USA. All patients with available follow-up data at 12 months and 36 months post-surgery were included in this study. Outcome measures used were percentage excess weight loss (%EWL) and percentage total weight loss (%TWL). Differences in outcomes between ethnicities were analysed after adjusting for age, gender, baseline body mass index (BMI), and presence of diabetes. RESULTS: The study population (n = 2150) consisted of 1122 Chinese, 187 Malays, 309 Indians, 67 Japanese, 259 Koreans, and 206 Caucasians. 67.1% were female and 32.9% were male. Mean age was 37.1 ± 11.2 years. Mean pre-operative BMI was 40.7 ± 8.1 kg/m2. With the Caucasian population as reference, Japanese had the best %TWL (3.90, 95% CI 1.16-6.63, p < 0.05) and %EWL (18.55, 95% CI 10.33-26.77, p < 0.05) while the Malays had the worst outcomes. Both Chinese and Koreans had better %EWL but worse %TWL as compared to Caucasians and there were no significant differences with the Indian study group. CONCLUSION: There are differences in weight loss outcomes following bariatric surgery between Asian ethnicities.

Highly Efficient and Flexible Photosensors with GaN Nanowires Horizontally Embedded in a Graphene Sandwich Channel.

In this study, we report highly efficient and flexible photosensors with GaN nanowires (NWs) horizontally embedded in a graphene sandwich structure fabricated on polyethylene terephthalate. GaN NWs and the graphene sandwich structure are used as light-absorbing media and the channel for carrier movement, respectively. To form uniform high-quality crystalline GaN NWs on Si(111) substrates, the initial nucleation behavior of the NWs was manipulated by applying the new growth technique of Ga predeposition. High-resolution transmission electron microscopic images obtained along the vertical direction of GaN NWs showed that stacking faults, typically observed in Si-based (In,Ga)As NWs, were rare. Consequently, narrow and strong optical emission was observed from the GaN NWs at wavelengths of 365.12 nm at 300 K. The photocurrent and photoresponsivity of the flexible photosensor with 802 nm long GaN NWs horizontally embedded in the graphene sandwich channel were measured as 9.17 mA and 91.70 A/W, respectively, at the light intensity of 100 mW/cm2, which are much higher than those previously reported. The high optical-to-electrical conversion characteristics of our flexible photosensors are attributed to the increase in the effective interface between the light-absorbing media and the carrier channel by the horizontal distribution of the GaN NWs within the graphene sandwich structure. After 200 cyclic-bending test of the GaN NW photosensor at the strain of 3%, the photoresponsivity under strain was measured as 89.04 A/W at 100 mW/cm2, corresponding to 97.1% of the photoresponsivity obtained before bending. The photosensor proposed in this study is relatively simple in device design and fabrication, and it requires no sophisticated nanostructural design to minimize the resistance to metal contacts.

Korean OBEsity Surgical Treatment Study (KOBESS): protocol of a prospective multicentre cohort study on obese patients undergoing laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass.

INTRODUCTION: Bariatric surgery effectively induces long-term weight loss in Western populations. However, its effectiveness in Asians remains to be confirmed objectively. The Korean Society for Metabolic and Bariatric Surgery proposes the first prospective cohort study on Koreans undergoing bariatric surgery. METHODS AND ANALYSIS: The Korean OBEsity Surgical treatment Study (KOBESS) is a prospective, multicentre, single-arm, observational, cohort study on morbidly obese patients who undergo primary sleeve gastrectomy or Roux-en-Y gastric bypass in Korea. In total, 100 consecutive obese Asian patients who will undergo bariatric surgery will be recruited in 2016-2017; follow-up will be for 1 year. Primary outcomes are change in body weight and waist circumference at 1 year. All patients will undergo anthropometry, laboratory tests, bioelectrical impedance analysis, gastrofibroscopy, polysomnography and fat-measuring CT before and after surgery. Patients with diabetes will also undergo perioperative oral glucose tolerance and endocrinological hormone tests. Hypertensive patients will also undergo perioperative echocardiography and carotid Doppler ultrasonography. Female patients suspected of having polycystic ovarian syndrome will also undergo perioperative hormone tests and abdominal ultrasonography. Visceral and subcutaneous fat will be harvested during surgery. Blood, stool and urine samples will be taken at various perioperative time points. Although the cohort is small and the follow-up duration is relatively short, this study will determine whether bariatric surgery induces satisfactory weight loss in obese Koreans. Significantly, the tissue samples will also facilitate many studies examining the effects of bariatric surgery and their mechanisms. ETHICS AND DISSEMINATION: Ethics approval was obtained from the institutional review board of each participating hospital. All findings arising from this cohort study will be published in open-access peer-reviewed journals and will be presented at national and international meetings. All KOBESS investigators will be able to propose research studies and potential publications based on KOBESS data and tissue samples. TRIAL REGISTRATION NUMBER: NCT03100292; Pre-results.