Minkyung Lee

Ultrasensitive Room-Temperature Operable Gas Sensors Using p-Type Na:ZnO Nanoflowers for Diabetes Detection

Ultrasensitive room-temperature operable gas sensors utilizing the photocatalytic activity of Na-doped p-type ZnO (Na:ZnO) nanoflowers (NFs) are demonstrated as a promising candidate for diabetes detection. The flowerlike Na:ZnO nanoparticles possessing ultrathin hierarchical nanosheets were synthesized by a facile solution route at a low processing temperature of 40 °C. It was found that the Na element acting as a p-type dopant was successfully incorporated in the ZnO lattice. On the basis of the synthesized p-type Na:ZnO NFs, room-temperature operable chemiresistive-type gas sensors were realized, activated by ultraviolet (UV) illumination. The Na:ZnO NF gas sensors exhibited high gas response (S of 3.35) and fast response time (∼18 s) and recovery time (∼63 s) to acetone gas (100 ppm, UV intensity of 5 mW cm-2), and furthermore, subppm level (0.2 ppm) detection was achieved at room temperature, which enables the diagnosis of various diseases including diabetes from exhaled breath.

Brain-Inspired Photonic Neuromorphic Devices using Photodynamic Amorphous Oxide Semiconductors and their Persistent Photoconductivity

The combination of a neuromorphic architecture and photonic computing may open up a new era for computational systems owing to the possibility of attaining high bandwidths and the low-computation-power requirements. Here, the demonstration of photonic neuromorphic devices based on amorphous oxide semiconductors (AOSs) that mimic major synaptic functions, such as short-term memory/long-term memory, spike-timing-dependent plasticity, and neural facilitation, is reported. The synaptic functions are successfully emulated using the inherent persistent photoconductivity (PPC) characteristic of AOSs. Systematic analysis of the dynamics of photogenerated carriers for various AOSs is carried out to understand the fundamental mechanisms underlying the photoinduced carrier-generation and relaxation behaviors, and to search for a proper channel material for photonic neuromorphic devices. It is found that the activation energy for the neutralization of ionized oxygen vacancies has a significant influence on the photocarrier-generation and time-variant recovery behaviors of AOSs, affecting the PPC behavior.

Metabolic Health Is More Important than Obesity in the Development of Nonalcoholic Fatty Liver Disease: A 4-Year Retrospective Study

Background The aim of this study is to compare the risk for future development of nonalcoholic fatty liver disease (NAFLD) according to different status of metabolic health and obesity. Methods A total of 3,045 subjects without NAFLD and diabetes at baseline were followed for 4 years. Subjects were categorized into four groups according to the following baseline metabolic health and obesity statuses: metabolically healthy, non-obese (MHNO); metabolically healthy, obese (MHO); metabolically unhealthy, non-obese (MUHNO); and metabolically unhealthy, obese (MUHO). Being metabolically healthy was defined as having fewer than two of the following five components: high blood pressure, high fasting blood glucose, high triglyceride, low high density lipoprotein cholesterol, and being in the highest decile of the homeostasis model assessment-insulin resistance index. Obesity was defined as a body mass index >25 kg/m2. The presence of NAFLD was assessed by ultrasonography. Results The proportions of subjects included in the MHNO, MHO, MUHNO, and MUHO groups were 71.4%, 9.8%, 13.0%, and 5.8%, respectively. The proportions of subjects who developed NAFLD were 10.5%, 31.4%, 23.2%, and 42% in the MHNO, MHO, MUHNO, and MUHO groups, respectively. The risk for developing NAFLD was highest in subjects who were metabolically unhealthy both at baseline and after 4 years compared with subjects who were consistently metabolically healthy during the follow-up period (odds ratio, 2.862). Using the MHNO group as reference, the odds ratios for the MHO, MUHNO, and MUHO groups were 1.731, 1.877, and 2.501, respectively. Conclusion The risk for NAFLD was lower in MHO subjects than in MUNO subjects.

Increased association of coronary artery calcification in apparently healthy Korean adults with hypertriglyceridemic waist phenotype: The Kangbuk Samsung Health Study

BACKGROUND Hypertriglyceridemic waist phenotype is a simple screening parameter to identify people at increased risk for cardiovascular disease. We evaluated whether hypertriglyceridemic waist (HTGW) phenotype increases the risk for coronary artery calcification (CAC) in apparently healthy Korean adults. METHODS A total of 32,186 participants (mean age 41.3, 80.2% men) in a health screening program, in whom the coronary artery calcium score (CACS) was measured, were analyzed. Subjects were divided into four groups: 1) normal waist circumference (WC)-normal triglyceride (TG) (NWNT), 2) normal WC-high TG (NWHT), 3) enlarged WC-normal TG (EWNT), and 4) enlarged WC-high TG (EWHT). Enlarged WC was defined as WC ≥ 90 cm for men and ≥ 85 cm for women; high serum TG was defined as TG ≥ 150 mg/dL. The presence of CAC was defined by CACS >0, and CACS was analyzed in a logarithmized form of CACS plus 1 {ln(CACS+1)}. RESULTS A total of 14.9% of the participants had CAC. The EWHT group showed the highest mean value for ln(CACS+1) among the four groups. The EWHT group showed the highest odds ratio for CAC, with NWHT group the second, and with EWNT group the third compared with the NWNT group after adjusting for confounding variables (1.579, 1.302, and 1.266 vs. NWNT). CONCLUSIONS The EWHT group showed the highest association for CAC, suggesting this HTGW phenotype as a useful marker for the detection of subjects with high cardiometabolic risk in healthy Korean adults.

Unique Crystallization of Fullerenes: Fullerene Flowers.

Solution-phase crystallization of fullerene molecules strongly depends on the types of solvent and their ratios because solvent molecules are easily included in the crystal lattice and distort its structure. The C70 (solute)–mesitylene (solvent) system yields crystals with various morphologies and structures, such as cubes, tubes, and imperfect rods. Herein, using C60 and C70 dissolved in mesitylene, we present a novel way to grow unique flower-shaped crystals with six symmetric petals. The different solubility of C60 and C70 in mesitylene promotes nucleation of C70 with sixfold symmetry in the early stage, which is followed by co-crystallization of both C60 and C70 molecules, leading to lateral petal growth. Based on the growth mechanism, we obtained more complex fullerene crystals, such as multi-deck flowers and tube-flower complexes, by changing the sequence and parameters of crystallization.

Suppression of persistent photo-conductance in solution-processed amorphous oxide thin-film transistors

This study offers a combinatorial approach for suppressing the persistent photo-conductance (PPC) characteristic in solution-processed amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) in order to achieve rapid photo-recovery. Various analyses were used to examine the photo-instability of indium-gallium-zinc-oxide (IGZO) TFTs including negative-bias-illumination-stress (NBIS) and transient photo-response behaviors. It was found that the indium ratio in metallic components had a significant impact on their PPC and photo-recovery characteristics. In particular, when the indium ratio was low (51.5%), the PPC characteristic was significantly suppressed and achieving rapid photo-recovery was possible without significantly affecting the electrical performance of AOSs. These results imply that the optimization of the indium composition ratio may allow achieving highly photo-stable and near PPC-free characteristics while maintaining high electrical performance of AOSs. It is considered that the neg...

Impact of initial active engagement in self-monitoring with a telemonitoring device on glycemic control among patients with type 2 diabetes

This study aimed to investigate the effect of patient engagement in self-monitoring with a telemonitoring device on glycemic control among patients with type 2 diabetes. We conducted a subanalysis of the telemonitoring device study in Kaiser Permanente Northern California members. We divided the telemonitoring group into 53 frequent and 54 infrequent users based on self-monitoring of blood glucose (SMBG) frequency of the first 6 weeks. The frequency of SMBG transmitted from the telemonitoring device was examined over 24 weeks. Clinic and laboratory tests were collected at baseline, 6 weeks and 6 months. There was no significant difference in baseline HbA1c level between the two groups. After 6 months, change in HbA1c was −2.4 ± 1.6% among frequent users and −1.5 ± 1.5% among infrequent users (p = 0.003). The proportion of patients achieving target HbA1C level at 6 months was significantly higher among frequent users than among infrequent users. An increased frequency of SMBG was significantly correlated with a reduction in HbA1c at 6 months. In conclusion, initial active engagement in self-monitoring with a telemonitoring device could provide incremental improvement of glycemic control over 6 months.

Normal-to-mildly increased albuminuria predicts the risk for diabetic retinopathy in patients with type 2 diabetes

Albuminuria is closely associated with diabetic retinopathy (DR), but the precise role of the albumin-to-creatinine ratio (ACR) in screening for DR remains to be determined. This study aimed to investigate an ACR threshold for predicting DR in patients with type 2 diabetes. A cross-sectional study was conducted on 1,102 type 2 diabetes patients, aged ≥30 years and recruited from the Korea National Health and Nutrition Examination Survey, 2010–2011. Participants were grouped by stage of DR: mild-to-moderate nonproliferative DR (NPDR), severe NPDR, and proliferative diabetic retinopathy (PDR). An early morning spot urine sample was obtained for ACR measurement. ROC curve analysis revealed that the optimal cut-off value of ACR for predicting DR was 2.26 mg/mmol (20 μg/mg). The prevalence of ACR ≥ 2.26 mg/mmol tended to increase with severity of DR. The risk for DR in patients with ACR ≥ 2.26 mg/mmol was higher than in those with ACR < 2.26 mg/mmol. The risk for severe NPDR and PDR also increased at ACR ≥ 2.26 mg/mmol. Normal-to-mildly increased albuminuria (an ACR of 2.26 mg/mmol) may predict the risk for DR development and progression in patients with type 2 diabetes.

High hemoglobin levels are associated with decreased risk of diabetic retinopathy in Korean type 2 diabetes

Anemia is an independent risk factor for the development of diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (DM). Hemoglobin levels may also be associated with DR. We investigated the association between hemoglobin levels and DR risk. This cross-sectional, population-based study utilized data from 2,123 type 2 DM patients aged ≥30 years who participated in the Korea National Health and Nutrition Examination Survey from 2008 to 2012. Participants underwent an ophthalmic examination, including fundus photographs. A multiple logistic regression analysis was performed to evaluate the relationship between hemoglobin levels and DR risk. The mean hemoglobin levels in patients with and without DR were 13.76 ± 0.12 and 14.33 ± 0.05 g/dL, respectively, with anemia observed in 16.2 (2.4)% and 7.8 (0.8)%, respectively. A 19% decrease in DR risk was found with a 1.0-g/dL increase in hemoglobin level. DR risk exhibited a decreasing trend with increasing hemoglobin levels (P for trend <0.0001). The adjusted odds ratio of DR was significantly lower in the highest hemoglobin quartile. Our findings indicate that high hemoglobin levels are significantly related to a decreased DR risk in Korean type 2 diabetes.

Publisher Correction: Normal-to-mildly increased albuminuria predicts the risk for diabetic retinopathy in patients with type 2 diabetes

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