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Chisnell R, Helton JS, Freedman DE, Singh DK, Bewley RI, Nocera DG, Lee YS. Topological Magnon Bands in a Kagome Lattice Ferromagnet. PHYSICAL REVIEW LETTERS 2015; 115:147201. [PMID: 26551820 DOI: 10.1103/physrevlett.115.147201] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Indexed: 06/05/2023]
Abstract
There is great interest in finding materials possessing quasiparticles with topological properties. Such materials may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence that magnons in an insulating kagome ferromagnet can have a topological band structure. Our neutron scattering measurements further reveal that one of the bands is flat due to the unique geometry of the kagome lattice. Spin wave calculations show that the measured band structure follows from a simple Heisenberg Hamiltonian with a Dzyaloshinkii-Moriya interaction. This serves as the first realization of an effectively two-dimensional topological magnon insulator--a new class of magnetic material that should display both a magnon Hall effect and protected chiral edge modes.
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Noh M, Lee YS. Optical Characterization on Perovskite Zirconate Nanocrystals. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2015; 15:8267-8270. [PMID: 26726500 DOI: 10.1166/jnn.2015.11283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We performed an optical study on the electronic properties of perovskite zirconate AZrO3 (A = Ca and Ba) nanocrystals (NCs), which depend strongly on the size of A ion as well as the post-annealing process. The zirconate NCs were synthesized in the combustion method, which was found to be quite effective for synthesizing highly orthorhombic CaZrO3 NCs in the sense that their grain sizes are relatively larger and as-synthesized NCs do not include any raw material phase in the XRD pattern, compared with the cubic BaZrO3 NCs. The room-temperature visible emission is commonly quite strong in both NCs. Interestingly, the dominance of the green-yellow emission over the violet-blue emission with increasing the post-annealing temperature (Tanneal) appears to be in agreement with the formation of the mid-gap state identified in the absorption spectra. While the optical bandgaps of NCs increased with increasing Tanneal, a systematic trend that the optical bandgap in the AZrO3 NCs decreased with the increasingly larger size of the A ion occurred. We discuss our findings in relation to the oxygen vacancy formation, lattice distortion, and size effect.
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Kim T, Jung J, Kim SM, Seo DW, Lee YS, Kim WY, Lim KS, Sung H, Kim MN, Chong YP, Lee SO, Choi SH, Kim YS, Woo JH, Kim SH. Transmission among healthcare worker contacts with a Middle East respiratory syndrome patient in a single Korean centre. Clin Microbiol Infect 2015; 22:e11-e13. [PMID: 26384679 PMCID: PMC7128147 DOI: 10.1016/j.cmi.2015.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 09/07/2015] [Indexed: 11/12/2022]
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Tan VMH, Lee YS, Venkataraman K, Khoo EYH, Tai ES, Chong YS, Gluckman P, Leow MKS, Khoo CM. Ethnic differences in insulin sensitivity and beta-cell function among Asian men. Nutr Diabetes 2015; 5:e173. [PMID: 26192451 PMCID: PMC4521178 DOI: 10.1038/nutd.2015.24] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 06/17/2015] [Accepted: 06/21/2015] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND AND OBJECTIVES Lean Asian Indians are less insulin sensitive compared with Chinese and Malays, but the pancreatic beta-cell function among these ethnic groups has yet to be studied in depth. We aimed to study beta-cell function in relation to insulin sensitivity among individuals of Chinese, Malay and Asian-Indian ethnicity living in Singapore. SUBJECTS AND METHODS This is a sub-group analysis of 59 normoglycemic lean (body mass index (BMI) <23 kg m(-)(2)) adult males (14 Chinese, 21 Malays and 24 Asian Indians) from the Singapore Adults Metabolism Study. Insulin sensitivity was determined using fasting state indices (homeostatic model assessment-insulin resistance), the euglycemic-hyperinsulinemic clamp (ISI-clamp) and a liquid mixed-meal tolerance test (LMMTT) (Matsuda insulin sensitivity index (ISI-Mat)). Beta-cell function was assessed using fasting state indices (homeostatic model assessment-beta-cell function) and from the LMMTT (insulinogenic index and insulin secretion index). The oral disposition index (DI), a measure of beta-cell function relative to insulin sensitivity during the LMMTT, was calculated as a product of ISI-Mat and insulin secretion index. RESULTS Asian Indians had higher waist circumference and percent body fat than Chinese and Malays despite similar BMI. Overall, Asian Indians were the least insulin sensitive whereas the Chinese were most insulin sensitive. Asian Indians had higher beta-cell function compared with Chinese or Malays but these were not statistically different. Malays had the highest incremental area under the curve for glucose during LMMTT compared with Asian Indians and Chinese. However, there were no significant ethnic differences in the incremental insulin area under the curve. The oral DI was the lowest in Malays, followed by Asian Indians and Chinese. CONCLUSION Among lean Asians, Chinese are the most insulin sensitive whereas Asian Indians are the least insulin sensitive. However, Malays demonstrate higher postprandial glucose excursion with lower beta-cell response compare with Chinese or Asian Indians. The paths leading to type 2 diabetes mellitus might differ between these Asian ethnic groups.
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Iyer MR, Cinar R, Liu J, Godlewski G, Szanda G, Puhl H, Ikeda SR, Deschamps J, Lee YS, Steinbach PJ, Kunos G. Structural Basis of Species-Dependent Differential Affinity of 6-Alkoxy-5-Aryl-3-Pyridinecarboxamide Cannabinoid-1 Receptor Antagonists. Mol Pharmacol 2015; 88:238-44. [PMID: 26013543 DOI: 10.1124/mol.115.098541] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 05/26/2015] [Indexed: 12/15/2022] Open
Abstract
6-Alkoxy-5-aryl-3-pyridincarboxamides, including the brain-penetrant compound 14G: [5-(4-chlorophenyl)-6-(cyclopropylmethoxy)-N-[(1R,2R)-2-hydroxy-cyclohexyl]-3-pyridinecarboxamide] and its peripherally restricted analog 14H: [5-(4-chlorophenyl)-N-[(1R,2R)-2-hydroxycyclohexyl]-6-(2-methoxyethoxy)-3-pyridinecarboxamide], have been recently introduced as selective, high-affinity antagonists of the human cannabinoid-1 receptor (hCB1R). Binding analyses revealed two orders of magnitude lower affinity of these compounds for mouse and rat versus human CB1R, whereas the affinity of rimonabant is comparable for all three CB1Rs. Modeling of ligand binding to CB1R and binding assays with native and mutant (Ile105Met) hCB1Rs indicate that the Ile105 to Met mutation in rodent CB1Rs accounts for the species-dependent affinity of 14G: and 14H: . Our work identifies Ile105 as a new pharmacophore component for developing better hCB1R antagonists and invalidates rodent models for assessing the antiobesity efficacy of 14G: and 14H: .
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Halder D, Mandal C, Lee BH, Lee JS, Choi MR, Chai JC, Lee YS, Jung KH, Chai YG. PCDHB14- and GABRB1-like nervous system developmental genes are altered during early neuronal differentiation of NCCIT cells treated with ethanol. Hum Exp Toxicol 2015; 34:1017-27. [PMID: 25566775 DOI: 10.1177/0960327114566827] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Ethanol (EtOH) exposure during embryonic development causes dysfunction of the central nervous system (CNS). Here, we examined the effects of chronic EtOH on gene expression during early stages of neuronal differentiation. Human embryonic carcinoma (NCCIT) cells were differentiated into neuronal precursors/lineages in the presence or absence of EtOH and folic acid. Gene expression profiling and pathway analysis demonstrated that EtOH deregulates many genes and pathways that are involved in early brain development. EtOH exposure downregulated several important genes, such as PCDHB14, GABRB1, CTNND2, NAV3, RALDH1, and OPN5, which are involved in CNS development, synapse assembly, synaptic transmission, and neurotransmitter receptor activity. GeneGo pathway analysis revealed that the deregulated genes mapped to disease pathways that were relevant to fetal alcohol spectrum disorders (FASD, such as neurotic disorders, epilepsy, and alcohol-related disorders). In conclusion, these findings suggest that the impairment of the neurological system or suboptimal synapse formation resulting from EtOH exposure could underlie the neurodevelopmental disorders in individuals with FASD.
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Ravi SP, Praveen P, Sreelakshmi KV, Balakrishnan A, Subramanian KRV, Shantikumar V, Lee YS, Sivakumar N. Electrochemical Performance of Electrophoretically Deposited Nanostructured LiMnPO4-Sucrose Derived Carbon Composite Electrodes for Lithium Ion Batteries. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2015; 15:747-751. [PMID: 26328437 DOI: 10.1166/jnn.2015.9174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The present study reports an approach by which thin films of sucrose added olivine type LiMnPO4-Ccomposite and pristine LiMnPO4 is made by a technique of electrophoretic co-deposition in which pristine and composite samples were synthesized by a sol-gel route. These thin films with enhanced surface area is used to fabricate cathodes for rechargeable Li ion batteries. XRD confirms phase pure single crystalline orthorhombic structure. Transmission Electron Microscopy (TEM) images shows the carbon coating over LiMnPO4 and the particle size restricted in the nano regime. The presence of sp2 hybridized carbon on LiMnPO4 particles is confirmed by X-ray Photon spectroscopy (XPS). To explore the electrochemical behavior, cyclic voltammetry (CV) and cycling studies were performed. The specific capacity for LiMnPO4-C is found to be increased by 43% in comparison to the pristine LiMnPO4. It also exhibited 86% retention in capacity compared to the pristine LiMnPO4 (52%). The result indicates that a proper carbon coating can significantly improve the electronic conductivity and hence the specific capacity.
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Soumya MS, Binitha G, Praveen P, Subramanian KRV, Lee YS, Nair VS, Sivakumar N. Electrochemical Performance of PbO2 and PbO2-CNT Composite Electrodes for Energy Storage Devices. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2015; 15:703-708. [PMID: 26328430 DOI: 10.1166/jnn.2015.9172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this work we report the electrochemical performance comparison of two new hybrid supercapacitors one based on graphene as negative electrode and lead dioxide thin film as positive electrode and the other with graphene as negative electrode and lead dioxide-carbon nanotube composite as positive electrode in 0.1 M KOH electrolyte. In the present work, PbO2 was synthesized using sol-gel method which is one of the promising materials for hybrid supercapacitors. The XRD confirmed the single phase of the PbO2 and the grain size is 39 nm which has been determined using Scherrer's formula. Thin films of PbO2, PbO2-CNT composite and graphene were coated on the titanium substrate by electrophoretic deposition. Further material characterisation has been carried out using SEM, TEM, XPS and electrochemical characterisation using CV, charge/discharge and electrochemical impedance spectroscopy (EIS) for obtaining energy density and power density, cyclic stability and internal resistance respectively. The present results revealed that PbO2-CNT composite/graphene asymmetric hybrid supercapacitor exhibits large specific capacitance and energy density over PbO2/graphene based system. The PbO2-CNT composite/graphene asymmetric hybrid supercapacitor exhibited maximum power density and energy density of 1200 W/Kg and 65 Wh/Kg respectively at a current density of 2 A/g. The PbO2-CNT composite/graphene asymmetric hybrid system exhibited excellent cycling stability with the capacitance retained 85% of its maximum value up to 3000 cycles.
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Kim JM, Lim KS, Hong JS, Kang JH, Lee YS, Hong KC. A polymorphism in the porcine miR-208b is associated with microRNA biogenesis and expressions of SOX-6 and MYH7 with effects on muscle fibre characteristics and meat quality. Anim Genet 2014; 46:73-7. [PMID: 25530254 DOI: 10.1111/age.12255] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2014] [Indexed: 11/29/2022]
Abstract
MicroRNAs (miRNAs) encoded by the myosin heavy chain (MHC) genes are muscle-specific miRNAs (myomiRs) and regulate the expression of MHC isoforms in skeletal muscle. These miRNAs have been implicated in muscle fibre types and their characteristics by affecting the heterogeneity of myosin. In pigs, miR-208b and miR-499 are embedded in introns of MYH7 and MYH7b respectively. Here, we identified a novel single nucleotide polymorphism (SNP) in intron 30 of MYH7 by which porcine miR-208b is encoded. Based on the association study using a total of 487 pigs including Berkshire (n = 164), Landrace (n = 121) and Yorkshire (n = 202), the miR-208b SNP (g.17104G>A) had significant effects on the proportions of types I and IIb fibre numbers (P < 0.010) among muscle fibre characteristics and on drip loss (P = 0.012) in meat quality traits. Moreover, the SNP affected the processing of primary miR-208b into precursor miR-208b with a marginal trend towards significance (P = 0.053), thereby leading to significant changes in the levels of mature miR-208b (P = 0.009). These SNP-dependent changes in mature miR-208b levels were negatively correlated with the expression levels of its target gene, SOX-6 (P = 0.038), and positively associated with the expression levels of its host gene, MYH7 (P = 0.046). Taken together, our data suggest that the porcine miR-208b SNP differentially represses the expression of SOX-6 by regulating miRNA biogenesis, thereby affecting the expression of MYH7 and the traits of muscle fibre characteristics and meat quality.
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Yang SW, Lee YS, Chang LC, Hsieh TY, Chen TA. Outcome of excision of oral erythroplakia. Br J Oral Maxillofac Surg 2014; 53:142-7. [PMID: 25467247 DOI: 10.1016/j.bjoms.2014.10.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 10/27/2014] [Indexed: 11/19/2022]
Abstract
Oral erythroplakia is a precancerous lesion with high malignant potential, and resection is the recommended treatment. We designed a retrospective study to analyse the outcome of treatment in patients who had operations for oral erythroplakia. A total of 84 patients (74 men and 10 women, mean (SD) age 54 (12) years, range 29-83) were enrolled. Histopathologically the diagnoses were invasive carcinoma (n=3), dysplasia/carcinoma in situ (n=61), and squamous hyperplasia (n=20), and all patients were treated by carbon dioxide laser excision. There was no postoperative malignant transformation, but invasive carcinoma found after initial excision (n=3) was treated by further radical excision. The mean (SD) follow-up period was 46 (29) months (range 1-124), The postoperative recurrent rate was 14/84 (16.7%). The area of oral erythroplakia was the only factor associated with postoperative recurrence on univariate analysis, and was also the only independent factor that predicted postoperative recurrence in multivariate logistic regression analysis. An area exceeding 80 mm2 had the best predictive value (sensitivity=0.71, specificity=0.67) with a 5.1 times increased risk (odds ratio=5.1, CI 95% 1.45 to 18.05, p=0.01) of recurrence. Laser excision is effective for oral erythroplakia that is still confined to dysplasia of any degree, with low morbidity. The area of oral erythroplakia is a predictive factor for postoperative recurrence.
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Park HD, Lee YS, Lee EK. Effectiveness of Cardiac Resynchronization Therapy in Patients with Mild-Moderate Heart Failure: A Systematic Review and Bayesian Approach Network Meta-Analysis. VALUE IN HEALTH : THE JOURNAL OF THE INTERNATIONAL SOCIETY FOR PHARMACOECONOMICS AND OUTCOMES RESEARCH 2014; 17:A757. [PMID: 27202759 DOI: 10.1016/j.jval.2014.08.234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
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Amaresh S, Karthikeyan K, Kim KJ, An JY, Cho SJ, Chung KY, Cho BW, Nam KW, Lee YS. Metal oxide coated lithium cobalt fluorophosphate cathode materials for lithium secondary batteries--effect of aging and temperature. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2014; 14:7545-7552. [PMID: 25942823 DOI: 10.1166/jnn.2014.9561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Lithium cobalt fluorophosphate (Li2CoPO4F) is a promising 5 V class cathode material for lithium secondary batteries. In this study, surface coating with ZrO2 improved the electrochemical activity of Li2CoPO4F with a maximum discharge capacity of 144 mA h g(-1). The effectiveness of ZrO2 coating was evaluated using aging analysis with a commercial electrolyte, i.e., 1 M LiPF6 in EC:DMC (1:1, v/v). The metal ion dissolution was reduced to 1/8th of that observed in the non-coated Li2CoPO4F. It was found that the thin coating layer had less or no contribution to the additional resistance for the cell, both at an open circuit potential and at a fully charged state; hence, the capacity of the cell was retained over cycling. Elevated temperature aging did not affect the intrinsic property of the coated Li2CoPO4F, as observed from the complete anodic and cathodic peaks from cyclic voltammetry studies after 30 days of storage at 50 degrees C. An increase in impedance was observed for aged cells, which could be due to the thick SEI layer formed during storage. The ZrO2 coating over Li2CoPO4F was crucial for the improved performance of electrode active material at higher operating potentials of up to 5.2 V.
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Lee SN, Kim HS, An JY, Amaresh S, Lee YG, Nam KW, Lee YS. Preparation and characterization of chlorine doped Li3V2(PO4)3 as high rate cathode active material for lithium secondary batteries. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2014; 14:7516-7520. [PMID: 25942818 DOI: 10.1166/jnn.2014.9560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Monoclinic Li3V2(PO4)2.99Cl0.01 was synthesized using the conventional solid state method and the X-ray diffraction pattern was indexed based on P2(1)/n space group. The sharp cyclic voltammetric curves clearly revealed three lithium extraction/insertion processes at approximately 3.64, 3.72, 4.13, and 4.58 V during the anodic scan and 3.96, 3.58, and 3.48 V during the cathodic scan. Charge/discharge studies showed reduced electrolyte decomposition contribution in the case of the chlorine doped Li3V2(PO4)2.99Cl0.01 sample with an initial capacity of 176 mA h g(-1) at a 0.1 C current rate. The chlorine doped Li3V2(PO4)3 sample showed an increased capacity retention with an increase in current rate, even at a very high C-rate (20 C), than the pristine and carbon coated samples. The pristine and carbon coated Li3V2(PO4)3 samples showed a lower capacity retention of 71% and 84%, respectively, at a current rate of 0.1 C. In contrast, the chlorine doped Li3V,(PO4)3 sample retained 87% of the initial capacity (176 mA h g(-1)) at the same current rate but with a higher coulombic efficiency of 91%. The enhanced capacity retention for the chlorine doped Li3V2(PO4)3 was attributed to the reduction in polarization and decreased charge transfer resistance of the electrode.
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Sun CH, Lew T, Tan D, Hoi SY, Khandan R, Poi CH, Surender R, Tay S, Wan G, Lee YS, Lim LL, Solikin H, Yeak S. Paperless reporting and electronically verifying clinical investigations. Int J Health Care Qual Assur 2014; 27:382-90. [PMID: 25087336 DOI: 10.1108/ijhcqa-12-2012-0124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE The purpose of this paper is to outline considerations and steps taken to introduce electronic reporting and verification from systems design and multidisciplinary collaborations to gap analysis and devising solutions. It also evaluates carefully placed forcing functions' impact on verification rates. DESIGN/METHODOLOGY/APPROACH A multidisciplinary workgroup was formed to stop print and establish electronic reporting. The electronic verification's success was assessed by weekly activity analysis. FINDINGS Introducing a verification forcing function markedly improved verification activity. Thereafter, non-verified results stabilized at 7 percent up to 75 weeks post-implementation. PRACTICAL IMPLICATIONS This paper illustrates how results reporting and verification could be implemented in a tertiary hospital using a mixed electronic and paper record. Factors that were critical to success include stakeholder engagement and applying systems design that focussed on patient safety as a key priority. The electronic reporting system was augmented by strategically inserted forcing functions, clear clinical-responsibility lines and ancillary alert systems. ORIGINALITY/VALUE The systems design method's value in managing non-critical but abnormal results appears to have been under-appreciated. This paper describes how systems design could be used to improve health information delivery and management.
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Amaresh S, Karthikeyan K, Kim KJ, Lee YG, Lee YS. Aluminum based sulfide solid lithium ionic conductors for all solid state batteries. NANOSCALE 2014; 6:6661-6667. [PMID: 24816684 DOI: 10.1039/c4nr00804a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The present work focuses on the synthesis of lithium ionic conductors based on a Li2S-Al2S3-GeS-P2S5 system due to the high ionic conductivity exhibited by the constituents of this system. Mechanical milling for a short duration and a single step heat treatment at a moderate temperature of 550 °C resulted in crystalline powders with high lithium ionic conductivity at room temperature that are comparable to the organic liquid electrolytes. The effect of various aluminum to germanium ratios was studied. Among the samples containing Al : Ge, the ratio of 30 : 70 was found to show high ionic conductivities of 1.7 × 10(-3) S cm(-1) at 25 °C and ∼ 6 × 10(-3) S cm(-1) at 100 °C equivalent. The activation energy of this material was significantly less (Ea = 17 kJ mol(-1)), which can be considered to be the best value among solid electrolytes. The electrochemical stability was analyzed using cyclic voltammetry between -0.3 and 5.0 V and it was found that the voltammetric profile was smooth without any additional current response, due to electrolyte decomposition, or any other side reaction, except a pair of lithium deposition and stripping peaks.
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Guérard F, Lee YS, Brechbiel MW. Rational design, synthesis, and evaluation of tetrahydroxamic acid chelators for stable complexation of zirconium(IV). Chemistry 2014; 20:5584-91. [PMID: 24740517 DOI: 10.1002/chem.201304115] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 02/20/2014] [Indexed: 11/06/2022]
Abstract
Metals of interest for biomedical applications often need to be complexed and associated in a stable manner with a targeting agent before use. Whereas the fundamentals of most transition-metal complexation processes have been thoroughly studied, the complexation of Zr(IV) has been somewhat neglected. This metal has received growing attention in recent years, especially in nuclear medicine, with the use of (89) Zr, which a β(+) -emitter with near ideal characteristics for cancer imaging. However, the best chelating agent known for this radionuclide is the trishydroxamate desferrioxamine B (DFB), the Zr(IV) complex of which exhibits suboptimal stability, resulting in the progressive release of (89) Zr in vivo. Based on a recent report demonstrating the higher thermodynamic stability of the tetrahydroxamate complexes of Zr(IV) compared with the trishydroxamate complexes analogues to DFB, we designed a series of tetrahydroxamic acids of varying geometries for improved complexation of this metal. Three macrocycles differing in their cavity size (28 to 36-membered rings) were synthesized by using a ring-closing metathesis strategy, as well as their acyclic analogues. A solution study with (89) Zr showed the complexation to be more effective with increasing cavity size. Evaluation of the kinetic inertness of these new complexes in ethylenediaminetetraacetic acid (EDTA) solution showed significantly improved stabilities of the larger chelates compared with (89) Zr-DFB, whereas the smaller complexes suffered from insufficient stabilities. These results were rationalized by a quantum chemical study. The lower stability of the smaller chelates was attributed to ring strain, whereas the better stability of the larger cyclic complexes was explained by the macrocyclic effect and by the structural rigidity. Overall, these new chelating agents open new perspectives for the safe and efficient use of (89) Zr in nuclear imaging, with the best chelators providing dramatically improved stabilities compared with the reference DFB.
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Ooi SQ, Chan RME, Poh LKS, Loke KY, Heng CK, Chan YH, Gan SU, Lee KO, Lee YS. Visfatin and its genetic variants are associated with obesity-related morbidities and cardiometabolic risk in severely obese children. Pediatr Obes 2014; 9:81-91. [PMID: 23447513 DOI: 10.1111/j.2047-6310.2013.00149.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Revised: 12/28/2012] [Accepted: 01/10/2013] [Indexed: 12/12/2022]
Abstract
BACKGROUND Visfatin is an adipokine, associated with obesity and possibly glucose regulation. OBJECTIVE The aim of this study was to examine the association of visfatin and its genetic variants with adiposity, cardiometabolic risk factors and obesity-related morbidities in obese children. METHODS Anthropometric measurements, dual energy X-ray absorptiometry scan, fasting blood samples and oral glucose tolerance tests were performed for 243 obese children. We screened the visfatin gene of 24 obese subjects and then performed genotyping of identified genetic variants in other 219 obese children through direct DNA sequencing. RESULTS Fasting serum visfatin correlated with measures of obesity and liver enzymes and was elevated in obese children with abnormal glucose tolerance and non-alcoholic fatty liver disease. The two upstream single nucleotide polymorphisms, -3187G>A (rs11977021) and -1537C>T (rs61330082), were at complete linkage disequilibrium. The AA genotype of -3187G>A was associated with higher serum visfatin (6.17 ± 0.76 ng mL(-1) vs. 3.92 ± 0.44 ng mL(-1)) and higher triglyceride (1.39 ± 0.08 mmol L(-1) vs. 1.19 ± 0.07 mmol L(-1)) as compared with the GG genotype. There was also a significant linear increase in serum visfatin across GG to GA to AA genotype of -3187G>A, indicating possible additive effect of A allele. The dominant GA + AA genotype model of +21426G>A (rs2302559) was associated with lower serum visfatin (3.83 ± 0.56 ng mL(-1) vs. 5.13 ± 0.34 ng mL(-1)) and lower plasma glucose (4.37 ± 0.08 mmol L(-1) vs. 4.77 ± 0.12 mmol L(-1)) as compared with the GG genotype. CONCLUSION Visfatin and its genetic variants were associated with adiposity, obesity-related morbidities and adverse cardiometabolic parameters. This supported our hypothesis that visfatin plays a significant role in the development of obesity-related morbidities and cardiometabolic risk.
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Kim D, Kim JH, Lee M, Lee YS, Kang S. Experimental investigation into effect of annealing treatment on springback of magnesium alloy sheets. ACTA ACUST UNITED AC 2013. [DOI: 10.1179/143307511x12858956848191] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Yang PLS, Lu Y, Khoo CM, Leow MKS, Khoo EYH, Teo A, Lee YS, Das De S, Chong YS, Gluckman PD, Tai ES, Venkataraman K, Ng CMA. Associations between ethnicity, body composition, and bone mineral density in a Southeast Asian population. J Clin Endocrinol Metab 2013; 98:4516-23. [PMID: 24037892 DOI: 10.1210/jc.2013-2454] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT AND OBJECTIVE Chinese men in Singapore have a higher incidence of hip fractures than Malay and Indian men. We investigated whether there were corresponding ethnic differences in peak bone mineral density (BMD) in young men and whether differences in body composition influenced peak BMD. DESIGN AND SETTING This was a cross-sectional study of healthy volunteers in a tertiary medical center. PARTICIPANTS A total of 100 Chinese, 82 Malay, and 80 Indian men aged 21 to 40 years, with body mass index between 18 and 30 kg/m(2) underwent dual-energy x-ray absorptiometry to assess BMD, lean mass (LM) and fat mass (FM), and magnetic resonance imaging to quantify abdominal subcutaneous and visceral adipose tissue. Multiple linear regression models, with adjustment for age and height (as a proxy for skeletal size), were used. RESULTS Malay and Indian men had significantly higher BMD than Chinese men at the lumbar spine (Malay: B, 0.06 ± 0.02, P = .001; Indian: B, 0.03 ± 0.02, P = .049), femoral neck (Malay: B 0.04 ± 0.02, P = .034; Indian: B, 0.04 ± 0.02, P = .041), hip (Malay: B, 0.05 ± 0.02, P = .016; Indian: B, 0.06 ± 0.02, P = .001), and ultradistal radius (Malay: B, 0.03 ± 0.01, P < .001; Indian: B, 0.02 ± 0.01, P = .029), and this difference was retained after adjustment for LM and FM, except in Malay men at the femoral neck and in Indian men at the ultradistal radius. LM was an important independent determinant of BMD at all sites, whereas FM, subcutaneous adipose tissue, and visceral adipose tissue were not significantly associated with BMD at any site. CONCLUSIONS Lower peak BMD in Chinese men may partly explain the higher fracture incidence in this ethnic group. Further studies are needed to elucidate the reasons for these ethnic differences in bone accumulation.
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Kim BJ, Lee YS, Lee SY, Park SY, Dieplinger H, Yea K, Lee SH, Koh JM, Kim GS. Afamin stimulates osteoclastogenesis and bone resorption via Gi-coupled receptor and Ca2+/calmodulin-dependent protein kinase (CaMK) pathways. J Endocrinol Invest 2013; 36:876-82. [PMID: 23698732 DOI: 10.3275/8975] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Afamin was recently identified as a novel osteoclast-derived coupling factor that can stimulate the in vitro and in vivo migration of preosteoblasts. AIM In order to understand in more detail the biological roles of afamin in bone metabolism, we investigated its effects on osteoclastic differentiation and bone resorption. METHODS Osteoclasts were differentiated from mouse bone marrow cells. Tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells were considered as osteoclasts, and the resorption area was determined by incubating the cells on dentine discs. The intracellular cAMP level was determined using a direct enzyme immunoassay. Signaling pathways were investigated using western blot and RT-PCR. Recombinant afamin was administered exogenously to bone cell cultures. RESULTS Afamin stimulated both osteoclastogenesis and in vitro bone resorption. Consistently, the expressions of osteoclast differentiation markers were significantly increased by afamin. Although afamin mainly affected the late-differentiation stages of osteoclastogenesis, the expression levels of receptor activator of nuclear factor-κB ligand (RANKL)-dependent signals were not changed. Afamin markedly decreased the levels of intracellular cAMP with reversal by pretreatment with pertussis toxin (PTX), a specific inhibitor of Gi-coupled receptor signaling. In addition, PTX almost completely blocked afamin-stimulated osteoclastogenesis. Furthermore, pretreatment with KN93 and STO609 - Ca2+/cal - mo dulin-dependent protein kinase (CaMK) and CaMK kinase inhibitors, respectively - significantly prevented decreases in the intracellular cAMP level by afamin while attenuating afamin-stimulated osteoclastogenesis. CONCLUSION Afamin enhances osteoclastogenesis by decreasing intracellular cAMP levels via Gi-coupled receptor and CaMK pathways.
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Kang JH, Kim YK, Park JY, Noh ES, Jeong JE, Lee YS, Choi TJ. Development of microsatellite markers for a hard-shelled mussel, Mytilus coruscus, and cross-species transfer. GENETICS AND MOLECULAR RESEARCH 2013; 12:4009-17. [PMID: 24089090 DOI: 10.4238/2013.september.27.2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The Korean mussel Mytilus coruscus, an endemic marine bivalve mollusk, is economically important. Its population is currently decreasing due to overexploitation and invasion of a more competitive species, Mytilus galloprovincialis. In this study, microsatellite markers for M. coruscus were developed using a cost-effective pyrosequencing technique. Among the 33,859 dinucleotide microsatellite sequences identified, 176 loci that contained more than 8 CA, CT, or AT repeats were selected for primer synthesis. Sixty-four (36.4%) primer sets were produced from the 100- to 200-bp polymerase chain reaction products obtained from 2 M. coruscus individuals. Twenty of these were chosen to amplify DNA from 82 M. coruscus individuals, and 18 polymorphic loci and 2 monomorphic loci were selected as microsatellite markers. The number of alleles and the allele richness of the polymorphic loci ranged from 2 to 22 and from 2.0 to 19.7 with means of 10.8 and 10.1, respectively. Null alleles were detected for all but three loci, which resulted in an observed heterozygosity lower than the expected heterozygosity and therefore an excess of homozygotes. In a cross-species transfer analysis of these markers using 7 Mytilidae species, the locus Mc65 was amplified from all species tested and was found to be polymorphic in all of them. Among the species, M. galloprovincialis, Lithophaga curta, and Hormomya mutabilis showed the same transferability of 25%, but the five amplified loci were polymorphic only in M. galloprovincialis and H. mutabilis. These microsatellite markers may be useful for future resource management and artificial production of juveniles for aquaculture.
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98
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Pilon DV, Lui CH, Han TH, Shrekenhamer D, Frenzel AJ, Padilla WJ, Lee YS, Gedik N. Spin-induced optical conductivity in the spin-liquid candidate herbertsmithite. PHYSICAL REVIEW LETTERS 2013; 111:127401. [PMID: 24093299 DOI: 10.1103/physrevlett.111.127401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Indexed: 06/02/2023]
Abstract
We report a direct measurement of the low-frequency optical conductivity of large-area single-crystal herbertsmithite, a promising spin-liquid candidate material, by means of terahertz time-domain spectroscopy. In the spectral range below 1.4 THz, we observe a contribution to the real part of the in-plane conductivity σ(ab)(ω) from the spin degree of freedom. This spin-induced conductivity exhibits a power-law dependence on frequency σ(ab)(ω) ~ ω(β) with β ≈ 1.4. Our observation is consistent with the theoretically predicted low-frequency conductivity arising from an emergent gauge field of a gapless U(1) Dirac spin liquid.
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99
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Karthikeyan K, Amaresh S, Kim KJ, Kim SH, Chung KY, Cho BW, Lee YS. A high performance hybrid capacitor with Li2CoPO4F cathode and activated carbon anode. NANOSCALE 2013; 5:5958-5964. [PMID: 23708774 DOI: 10.1039/c3nr00760j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
For the first time, we report the possibility of utilizing Li2CoPO4F as a novel cathode material for hybrid capacitor applications. Li2CoPO4F powders were prepared by a conventional two-step solid state method. A hybrid cell was fabricated using Li2CoPO4F as the cathode along with activated carbon (AC) as the anode in 1 M LiPF6 dissolved in 1 : 1 EC/DMC electrolyte and its electrochemical properties were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge-discharge (C-D) techniques. The Li2CoPO4F/AC cell is capable of delivering a discharge capacitance of 42 F g(-1) at 150 mA g(-1) current density within 0-3 V region having excellent coulombic efficiency of over 99% even after 1000 cycles. Furthermore, the Li2CoPO4F/AC cell exhibited excellent rate performance with an energy density of ~24 W h kg(-1) at 1100 mA g(-1) current and maintained about 92% of its initial value even after 30,000 C-D cycles. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.
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100
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Kim H, Lee SK, Hong MW, Park SR, Lee YS, Kim JW, Lee HK, Jeong DK, Song YH, Lee SJ. Association of a single nucleotide polymorphism in the akirin 2 gene with economically important traits in Korean native cattle. Anim Genet 2013; 44:750-3. [PMID: 23718263 DOI: 10.1111/age.12055] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2013] [Indexed: 11/29/2022]
Abstract
The akirin 2 gene, located on chromosome 9 in cattle, was previously reported to be associated with nuclear factor-kappa B (NF-κB), involved in immune reactions and marbling of meat. To determine whether a single nucleotide polymorphism (SNP) in akirin 2 is associated with economically important traits of Korean native cattle, the c.*188G>A SNP DNA marker in the 3'-UTR region of akirin 2 was analyzed for its association with carcass weight, longissimus muscle area and marbling. The c.*188G>A SNP was genotyped by polymerase chain reaction restriction fragment length polymorphism, and the frequency of the AA, AG, and GG genotypes were 6.82%, 71.29% and 21.88% respectively. This SNP was significantly associated with longissimus muscle area (Bonferroni corrected P < 0.05), and marbling score (Bonferroni corrected P < 0.01). These results suggest that the c.*188G>A SNP of akirin 2 might be useful as a DNA marker for longissimus muscle area and marbling scores in Korean native cattle.
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