Sul Lee

Organic-inorganic hybrid dielectrics with low leakage current for organic thin-film transistors

Using a thermally cross-linkable organosiloxane-based organic-inorganic hybrid material, a solution-processable gate dielectric layer for organic thin-film transistors has been fabricated. The hybrid dielectric was synthesized by a sol-gel process, followed by heat treatment at below 190°C. Dielectric strength of 1.4–1.65MV∕cm was measured and it was confirmed that the leakage current is governed by the Poole-Frenkel emission mechanism in which the silanol groups act as trap sites. An organic thin-film transistor utilizing the hybrid dielectric shows similar electrical performance to a transistor fabricated using surface-modified thermally grown SiO2.

Irisin, a novel myokine is an independent predictor for sarcopenia and carotid atherosclerosis in dialysis patients

OBJECTIVE In end-stage renal disease, deleterious effect of sarcopenia on cardiovascular disease has been explained mainly by chronic inflammation. However, evidence emerged that skeletal muscles mediate their protective effect against sarcopenia by secreting myokines. Therefore, we sought to investigate the effect of irisin, a recently introduced myokine, on the association between sarcopenia and cardiovascular disease in peritoneal dialysis (PD) patients. METHODS Serum irisin concentrations were assessed by enzyme-linked immunosorbent assay in 102 prevalent PD patients and 35 age- and sex-matched controls. To determine sarcopenia and cardiovascular disease, anthropometric indices including mid-arm muscle circumference (MAMC) and carotid intima-media thickness (cIMT) were measured. RESULTS Serum irisin concentrations were significantly lower in PD patients than in controls (184.2 ± 88.0 vs. 457.2 ± 105.5 ng/mL, P < 0.001). In PD patients, univariate linear regression analysis showed that serum irisin was positively correlated with MAMC and thigh circumference, but negatively correlated with residual renal function and cIMT. Multivariate analysis revealed that MAMC (per 1 cm increase, B = 8.78, 95% confidence interval [CI] = 0.77-16.79, P = 0.03) had an independent association with serum irisin. In addition, serum irisin was a significant independent predictor for carotid atherosclerosis even after adjustment for high-sensitivity C-reactive protein in PD patients (per 1 g/mL increase, odds ratio = 0.990, 95% CI = 0.982-0.997, P = 0.007). CONCLUSION This study demonstrated that serum irisin was significantly associated with sarcopenia and carotid atherosclerosis in PD patients. Additional studies to provide a confirmation and examine possible mechanisms are warranted.

Influence of silanol groups on the electrical performance of organic thin-film transistors utilizing organosiloxane-based organic–inorganic hybrid dielectrics

A solution-processable organosiloxane-based organic–inorganic hybrid gate dielectric layer for application in organic thin-film transistors has been synthesized by a sol–gel process. In the sol–gel derived hybrid film, owing to an incomplete condensation reaction, silanol groups serve as functional groups of the inorganic siloxane backbone. In order to investigate the influence of the silanol groups on the electrical performance of transistors with organosiloxane-based dielectrics, transistors employing hybrid dielectrics with different amounts of the silanol group were prepared and electrical performance parameters such as off-current, threshold voltage, field-effect mobility, and hysteresis were analysed.

Serum Ferritin Predicts Mortality Regardless of Inflammatory and Nutritional Status in Patients Starting Dialysis: A Prospective Cohort Study

Background: The impact of serum ferritin on prognosis in patients starting hemodialysis (HD) is not fully elucidated. Methods: A prospective cohort of 946 incident HD patients from 26 dialysis centers in Korea was selected for this study. Patients were divided into tertiles according to natural logarithm (Ln) ferritin concentrations. Results: During a median follow-up of 39 months, 88 (9.3%) patients died. Multivariate Cox proportional hazard analysis demonstrated that Ln ferritin was independently associated with an increase in cardiovascular mortality risk (hazard ratio (HR) 1.604, 95% CI 1.040-2.474, p = 0.033), infection-related mortality risk (HR 1.916, 95% CI 1.056-3.476, p = 0.032), and all-cause mortality risk (HR 1.547, 95% CI 1.156-2.069, p = 0.003). Conclusion: Serum ferritin levels at the time of HD commencement were a significant independent risk factor for mortality regardless of systemic inflammation and nutritional status. Therefore, elevated serum ferritin levels could be an effective indicator for prognosis.

Role of Immune Cells in Acute Kidney Injury and Repair

Acute kidney injury (AKI) is a significant problem in both native and transplant kidneys. There have been significant advances in understanding the role of immune cells in the early injury and repair from AKI. In this brief review, we aim to update information on the pathophysiologic impact of various immune cells in AKI, with special emphasis on repair. An improved understanding of the AKI immunopathology will lead to new therapies that prevent AKI, accelerate repair, and prevent the progression of AKI to chronic kidney disease.

Rifampicin-Induced Minimal Change Disease Is Improved after Cessation of Rifampicin without Steroid Therapy

There are several reports to demonstrate that rifampicin, a major anti-tuberculosis agent, is associated with some adverse renal effects, with a few cases of rifampicin-induced minimal change disease (MCD). In the present case, a 68-year-old female presented with nausea, vomiting, foamy urine, general weakness and edema. She had been taking rifampicin for 4 weeks due to pleural tuberculosis. The patient had no proteinuria before the anti-tuberculosis agents were started, but urine tests upon admission showed heavy proteinuria with a 24-h urinary protein of 9.2 g/day, and serum creatinine, albumin, and total cholesterol levels were 1.36 mg/dL, 2.40 g/dL, and 283 mg/dL, respectively. MCD was diagnosed, and the patient achieved complete remission after cessation of rifampicin without undergoing steroid therapy.

Fabrication of the Organic Thin-Film Transistors Based on Ink-Jet Printed Silver Electrodes

We present the organic thin-film transistors (OTFTs) based on the ink-jet printed silver electrodes as the source and drain electrodes. To fabricate the conductive silver electrodes by the low-temperature heat-treatment below 200°C, the inks containing silver nano-particles with the size of about 20 nm were printed on the silicon substrate with a 300 nm-thick SiO2. It was observed that the conductivity of the ink-jet printed lines after heat-treatment at 200°C was similar to that of a bulk silver material. Poly(3,3″-dialkylquarterthiophene) (PQT-12) was deposited over the printed silver electrodes to fabricate the organic transistor. I–V character was measured to investigate an electrical performance of the fabricated transistor.

Preoperative Low Serum Bicarbonate Levels Predict Acute Kidney Injury After Cardiac Surgery.

AbstractAcute kidney injury (AKI) after cardiac surgery is a common and serious complication. Although lower than normal serum bicarbonate levels are known to be associated with consecutive renal function deterioration in patients with chronic kidney injury, it is not well-known whether preoperative low serum bicarbonate levels are associated with the development of AKI in patients who undergo cardiac surgery. Therefore, the clinical implication of preoperative serum bicarbonate levels on AKI occurrence after cardiac surgery was investigated. Patients who underwent coronary artery bypass or valve surgery at Yonsei University Health System from January 2013 to December 2014 were enrolled. The patients were divided into 3 groups based on preoperative serum bicarbonate levels, which represented group 1 (below normal levels) <23 mEq/L; group 2 (normal levels) 23 to 24 mEq/L; and group 3 (elevated levels) >24 mEq/L. The primary outcome was the predicated incidence of AKI 48 hours after cardiac surgery. AKI was defined according to Acute Kidney Injury Network criteria. Among 875 patients, 228 (26.1%) developed AKI within 48 hours after cardiac surgery. The incidence of AKI was higher in group 1 (40.9%) than in group 2 (26.5%) and group 3 (19.5%) (P < 0.001). In addition, the duration of postoperative stay in a hospital intensive care unit (ICU) was longer for AKI patients and for those in the low-preoperative-serum-bicarbonate-level groups. A multivariate logistic regression analysis showed that low preoperative serum bicarbonate levels were significantly associated with AKI even after adjustment for age, sex, hypertension, diabetes mellitus, operation type, preoperative hemoglobin, and estimated glomerular filtration rate. In conclusion, low serum bicarbonate levels were associated with higher incidence of AKI and prolonged ICU stay. Further studies are needed to clarify whether strict correction of bicarbonate levels close to normal limits may have a protective role in preventing further AKI development.

Surface Modification of Novel Organic-Inorganic Hybrid Dielectrics Using Self-Assembled Monolayers

Using a thermally-crosslinkable organosiloxane-based organic-inorganic hybrid material, solution-processable gate dielectric layer for organic thin-film transistors (OTFTs) have been fabricated. The hybrid dielectric was synthesized by the sol-gel process. The surface of the prepared dielectric was modified by self-assembled monolayers (SAMs) treatment using wet chemical method. Prior to surface modification, the chemical inertness of prepared dielectric was investigated by immersing into various solvents such as toluene, acetone, isopropyl alcohol, and DI-water. The existence of SAMs on the surface of dielectric was confirmed by measuring current density-electric field characteristics and it was observed that surface morphology of SAMs-treated hybrid dielectric was very smooth.