Highly Sensitive and Reusable Membraneless Field-Effect Transistor (FET)-Type Tungsten Diselenide (WSe2) Biosensors.

In recent years when the demand for high-performance biosensors has been aroused, a field-effect transistor (FET)-type biosensor (BioFET) has attracted great interest because of its high sensitivity, label-free detection, fast detection speed, and miniaturization. However, the insulating membrane in the conventional BioFET, which is essential in preventing the surface dangling bonds of typical semiconductors from nonspecific bindings, has limited the sensitivity of biosensors. Here, we present a highly sensitive and reusable membraneless BioFET based on a defect-free van der Waals material, tungsten diselenide (WSe2). We intentionally generated a few surface defects that serve as extra binding sites for the bioreceptor immobilization through weak oxygen plasma treatment, consequently magnifying the sensitivity values to 2.87 × 105 A/A for 10 mM glucose. The WSe2 BioFET also maintained its high sensitivity even after several cycles of rinsing and glucose application were repeated.

The Fatty Liver Index: A Simple and Accurate Predictor of Colorectal Adenoma in an Average-Risk Population.

BACKGROUND: Nonalcoholic fatty liver disease, the hepatic manifestation of metabolic syndrome, is associated with increased risk of colorectal adenoma, a precursor of colorectal cancer. Because nonalcoholic fatty liver disease and colorectal adenoma share many common risk factors of metabolic syndrome, the association between these 2 pathological findings has been investigated in multiple studies, but the results have been conflicting. OBJECTIVE: The present study aimed to assess the relationship between the fatty liver index, a predictor of nonalcoholic fatty liver disease, and the prevalence of colorectal adenomas. DESIGN: This is a retrospective observational study. SETTINGS: This study was conducted at a single expert center. PATIENTS: A total of 2976 consecutive subjects over 40 years of age undergoing routine checkups including abdominal ultrasonography and colonoscopy at Chung-Ang University Hospital Health Care Center were included. MAIN OUTCOME MEASURES: The primary outcome measured was the prevalence of colorectal adenomas according to fatty liver index. RESULTS: Among these subjects, 932 (31.3%) had colorectal adenoma, 691 (23.2%) had metabolic syndrome, and 1512 (50.8%) had fatty liver on ultrasonography. In multivariate analysis, fatty liver index ≥30 was associated with an increased risk of colorectal adenoma (OR, 1.269; 95% CI, 1.06-1.49; p = 0.008). The fatty liver index-high group (fatty liver index ≥30) had more colorectal adenomas and more advanced colorectal adenomas than the fatty liver index-low group (fatty liver index <30) (p < 0.001 and p = 0.042). The prevalence of colorectal adenomas increased with increasing quartile of fatty liver index (p < 0.05). LIMITATIONS: The study was limited by a relatively healthy Asian population. CONCLUSION: The high fatty liver index may be a useful predictor of colorectal adenoma. See Video Abstract at http://links.lww.com/DCR/A478.

Nanostructured GaAs solar cells via metal-assisted chemical etching of emitter layers.

GaAs solar cells with nanostructured emitter layers were fabricated via metal-assisted chemical etching. Au nanoparticles produced via thermal treatment of Au thin films were used as etch catalysts to texture an emitter surface with nanohole structures. Epi-wafers with emitter layers 0.5, 1.0, and 1.5 um in thickness were directly textured and a window layer removal process was performed before metal catalyst deposition. A nanohole-textured emitter layer provides effective light trapping capabilities, reducing the surface reflection of a textured solar cell by 11.0%. However, because the nanostructures have high surface area to volume ratios and large numbers of defects, various photovoltaic properties were diminished by high recombination losses. Thus, we have studied the application of nanohole structures to GaAs emitter solar cells and investigated the cells' antireflection and photovoltaic properties as a function of the nanohole structure and emitter thickness. Due to decreased surface reflection and improved shunt resistance, the solar cell efficiency increased from 4.25% for non-textured solar cells to 7.15% for solar cells textured for 5 min.

Influence of Growth Temperature on the Characteristics of Single-Junction p­i­n InGaP Solar Cells.

Single-junction p­i­n InGaP solar cells are grown at various temperatures from 620 to 700 °C by low pressure metalorganic chemical vapor deposition on GaAs (001) substrates. The short circuit current density of the p­i­n InGaP solar cells increases by up to 38.8% when the growth temperature is reduced from 700 to 620 °C, while the open circuit voltage and fill factor show relatively small changes. The external quantum efficiency, especially, in the wavelength regime below 500 nm, is improved for the p­i­n InGaP solar cells grown at lower temperatures. The improvement might be attributed to the reduced absorption loss of the photons in the n-InGaP emitter region. The highest conversion efficiency of 11.01% is attributed from the p­i­n InGaP solar cell grown at 640 °C. Electron mobility and concentration of undoped InGaP layers are investigated as a function of the growth temperature and correlated with the p­i­n InGaP solar cell performance.

Preoperative Body Mass Index May Determine the Prognosis of Advanced Gastric Cancer.

Radical gastrectomy followed by adjuvant chemotherapy for advanced gastric cancer causes serious nutritional impairment. Our study evaluated the clinical impact of body mass index (BMI) on the long-term outcomes of advanced gastric cancer (stage II and III). We analyzed 211 cases of stage II and III gastric cancer between January 2005 and December 2010 at Chung-Ang University Hospital, Seoul, Korea. Patients were divided into four groups according to BMI: underweight, normal, overweight, and obese. In addition, we divided patients into two groups: BMI-High (BMI ≥ 23 kg/m2) vs. BMI-Low (BMI < 23 kg/m2). We assessed age, sex, tumor location, lymph node (LN) involvement, operation method, initial cancer stage, recurrence, and survival between the two groups. There was significant difference in overall survival (OS) between the underweight group and the other groups (P = 0.005). The survival of the BMI-High group was better than that of the BMI-Low group. The rate of cancer-related death in the BMI-High group was significantly lower than that in the BMI-Low group (cancer-related death: BMI-Low 27% vs. BMI-High 12.6%, P = 0.022). Our findings suggest that preoperative BMI may have an influence on the long-term outcomes of advanced gastric cancer after radical surgery and chemotherapy.

InGaAs/InP Avalanche Photodiode for Single Photon Detection with Zinc Diffusion Process Using Metal Organic Chemical Vapor Deposition.

In this paper, we describe a design, simulation, and fabrication of an InGaAs/InP single photon avalanche photodiode (SPAD), which requires a much higher gain, compared to APD's for conventional optical communications. To achieve a higher gain, an efficient multiplication width control is essential because it significantly affects the overall performance including not only gain but also noise characteristics. Normally, the multiplication layer width is controlled by the Zinc diffusion process. For the reliable and controllable diffusion process, we used metal organic chemical vapor deposition (MOCVD). The controllability of the proposed diffusion process is proved by the diffusion depth measurement of the fabricated devices which show the proportional dependence on the square root of the diffusion time. As a result, we successfully implemented the SPAD that exhibits a high gain enough to detect single photons and a very low dark current level of about 0.1 nA with 0.95 breakdown voltage. The single photon detection efficiency of 15% was measured at the 100 kHz gate pulse rate and the temperature of 230 K.

Two-Step Growth of Epitaxial InP Layers by Metal Organic Chemical Vapor Deposition.

In this study, we report experimental results on the epitaxial growth of InP layer on GaAs (001) substrate by using MOCVD. We have systematically controlled nucleation steps in order to obtain InP epitaxial layers with high crystallinity quality. The controlling parameters were flow ratio of V/IIIsources and thicknesses of nucleation layer for nucleation steps. We successfully improved the surface roughness and crystallinity of IIP epitaxial layers on GaAs substrates.

Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.

We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (η) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., η~13%).

Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.

We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (η) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., η~13%).

Single-material zinc sulfide bi-layer antireflection coatings for GaAs solar cells.

We demonstrated the efficiency improvement of GaAs single-junction (SJ) solar cells with the single-material zinc sulfide (ZnS) bi-layer based on the porous/dense film structure, which was fabricated by the glancing angle deposition (GLAD) method, as an antireflection (AR) coating layer. The porous ZnS film with a low refractive index was formed at a high incident vapor flux angle of 80° in the GLAD. Each optimum thickness of ZnS bi-layer was determined by achieving the lowest solar weighted reflectance (SWR) using a rigorous coupled-wave analysis method in the wavelength region of 350-900 nm, extracting the thicknesses of 20 and 50 nm for dense and porous films, respectively. The ZnS bi-layer with a low SWR of ~5.8% considerably increased the short circuit current density (J(sc)) of the GaAs SJ solar cell to 25.57 mA/cm(2), which leads to a larger conversion efficiency (η) of 20.61% compared to the conventional one without AR layer (i.e., SWR~31%, J(sc) = 18.81 mA/cm(2), and η = 14.82%). Furthermore, after the encapsulation, its J(sc) and η values were slightly increased to 25.67 mA/cm(2) and 20.71%, respectively. For the fabricated solar cells, angle-dependent reflectance properties and external quantum efficiency were also studied.

Incidence and predictors of silent embolic cerebral infarction following diagnostic coronary angiography.

BACKGROUND: Coronary angiography (CAG) is an invasive diagnostic procedure, which could lead to procedure related complications. One of the well known post-procedural complications is cerebral embolic infarction with or without symptoms. Silent embolic cerebral infarction (SECI) has clinical significance because it can progress to a decline in cognitive function and increase the risk of dementia in the long term. The aim of this study was to detect the incidence and predictors of SECI after diagnostic CAG using diffusion-weighted magnetic resonance imaging (DW-MRI). METHODS: A total of 197 patients with coronary artery disease who underwent DW-MRI for evaluation of intracranial vasculopathy before coronary artery bypass graft surgery were retrospectively enrolled in the present study. DW-MRI was performed within 48 h after diagnostic CAG. SECI was diagnosed as presence of focal bright high signal intensity in DW-MRI. Patients were divided into groups according to presence/absence of SECI (+ SECI vs. - SECI, respectively). The clinical and angiographic characteristics were analyzed and independent predictors were evaluated. RESULTS: Of the 197 patients, SECI occurred in 20 patients (10.2%) after diagnostic CAG. Age, female gender, frequency of underlying atrial fibrillation, extent of coronary disease, and fluoroscopic time during diagnostic CAG were not different between the + SECI and - SECI groups. Left ventricular ejection fraction was significantly lower in the + SECI group than in the - SECI group (45.9 ± 8.5% vs. 51.4 ± 13.1%, p=0.014) and performance rate of internal mammary artery (IMA) angiography was significantly higher in the + SECI group compared with the - SECI group (85% vs. 37.2%, p<0.001). By multivariate analysis, performing IMA angiography was the only predictor of SECI (OR=14.642; 95% CI=3.201 to 66.980, p=0.001). CONCLUSIONS: The incidence of SECI after diagnostic CAG was not infrequent. Diagnostic CAG with IMA angiography may increase the risk of SECI.

Pulmonary emboli originating from infective endocarditis of the mitral valve migrating through an atrial septal defect.

We report a case of infective endocarditis of the mitral valve, which was accompanied by pulmonary emboli traveling through an atrial septal defect. An 18-year-old male was admitted to our hospital due to a fever, polyarthritis and subcutaneous hemorrhage. Transthoracic echocardiography revealed a mobile mass and possible vegetation lodged in the mitral valve and a secundum-type atrial septal defect. Computed tomography revealed a hepatic, splenic and renal embolic infarction. During antibiotic therapy, he felt a sudden right flank pain. Follow-up computed tomography revealed a pulmonary embolic infarction that drifted through an atrial septal defect. This association is the first report, of pulmonary emboli which migrated through an atrial septal defect from the mitral valve.

Prognostic implications of the NT-ProBNP level and left atrial size in non-ischemic dilated cardiomyopathy.

BACKGROUND: The ratio of peak early diastolic mitral inflow to annular velocity (E/E') and left atrial size could provide prognosis on congestive heart failure (CHF). N-terminal Pro B-type natriuretic peptide (NT-ProBNP) has also been useful for predicting adverse cardiac events. However, it is not clear how these parameters compare with conventional risk factors. Thus, we investigated whether E/E', left atrial dimension index (LADI) and NT-ProBNP would predict adverse events and add incremental value to conventional risk factors, even in non-ischemic advanced dilated cardiomyopathy (DCM). METHODS AND RESULTS: Both NT-ProBNP and echocardiography were evaluated in 105 patients. The cardiac events were defined as the composite of cardiac death and re-admission for CHF. At follow up, cardiac events occurred in 24 patients who had high NT-ProBNP and showed higher LADI and E/E'. In multivariate analysis, both NT-ProBNP and LADI, but not E/E', remained as independent predictors; patients with both increased LADI and NT-ProBNP had a 27-fold higher risk of cardiac events than those without any risk factors (p = 0.003). Moreover, LADI and NT-ProBNP showed a better incremental prognostic value over conventional risk factors (global chi-square increase from 7 to 17 to 49, p = 0.003, p < 0.001, respectively). CONCLUSIONS: Both NT-ProBNP and LADI might have the most predictable power, particularly in non-ischemic advanced DCM.

Spontaneous closure of ventricular septal defect complicated with acute myocardial infarction.

A 79-year-old man was followed in our hospital for 4 years following primary percutaneous coronary intervention at another hospital to deploy two stents at the left anterior descending coronary artery for acute myocardial infarction (AMI). At the first visit in our hospital, echocardiography revealed a small ventricular septal defect (VSD, 0.8 to 1.0 cm) in the apicoseptal wall with an aneurysm that was probably the result of the AMI. There was no hemodynamic decompensation, and because the patient refused surgical correction we instead placed him under close follow-up observation in the outpatient clinic. A second follow-up echocardiography 6 months later still revealed a VSD. However, after 3 years the VSD murmur was no longer audible and follow-up echocardiography showed the defect to be nearly closed.

Drug-eluting stent thrombosis during perioperative period.

Recently, the number of patients in whom a drug-eluting stent (DES) has recently been implanted and who need to undergo surgery or the most invasive procedure is increasing. However, there are limited data about the risk of perioperative thrombosis of DES. We evaluated the incidence and the risk factors of DES thrombosis during the perioperative period. Between January 2002 and December 2006, 141 patients who underwent surgery requiring discontinuation of a dual antiplatelet agent within 12 months of DES implantation were enrolled in one of the 3 study hospitals. We reviewed the clinical and procedural characteristics of the patients who developed stent thrombosis during the perioperative period. Stent thrombosis occurred in 7 cases (5.0%). The clinical outcomes of the patients with stent thrombosis were death in 5 cases and nonfatal MI in 2 cases. The patients with stent thrombosis were found to be older (64.2 +/- 9.7 versus 71.7 +/- 6.0 years, P = 0.045), to use a Taxus stent more frequently (36.6 versus 85.7%, P = 0.014), and to have a more prolonged period of discontinuation of clopidogrel (12.7 +/- 10.0 versus 51.3 +/- 33.2 days, P = 0.022) than the patients without stent thrombosis. Multivariate analysis revealed that 7 days or longer discontinuation of clopidogrel (OR 12.8, 95% CI 1.3-121.6, P = 0.021) and the use of a Taxus stent (OR 10.2, 95% CI 1.1-95.7, P = 0.043) were significant independent predictors of stent thrombosis during the perioperative period. A prolonged period of discontinuation of clopidogrel was associated with higher risk of stent thrombosis during the perioperative period. An earnest effort to continue antiplatelet therapy throughout the perioperative period can minimize the risk of stent thrombosis.