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Longitudinal Changes in Resting-State Brain Activity in a Capsular Infarct Model
Kim, Donghyeon,Kim, Ra Gyung,Kim, Hyung-Sun,Kim, Jin-Myung,Jun, Sung Chan,Lee, Boreom,Jo, Hang Joon,Neto, Pedro R,Lee, Min-Cheol,Kim, Hyoung-Ihl SAGE Publications 2015 Journal of cerebral blood flow and metabolism Vol.35 No.1
<P> Strokes attributable to subcortical infarcts have been increasing recently in elderly patients. To gain insight how this lesion influences the motor outcome and responds to rehabilitative training, we used circumscribed photothrombotic capsular infarct models on 36 Sprague-Dawley rats (24 experimental and 12 sham-operated). We used 2-deoxy-2-[<SUP>18</SUP>F]-fluoro-D-glucose-micro positron emission tomography (FDG-microPET) to assess longitudinal changes in resting-state brain activity (rs-BA) and daily single-pellet reaching task (SPRT) trainings to evaluate motor recovery. Longitudinal FDG-microPET results showed that capsular infarct resulted in a persistent decrease in rs-BA in bilateral sensory and auditory cortices, and ipsilesional motor cortex, thalamus, and inferior colliculus ( P<0.0025, false discovery rate (FDR) q<0.05). The decreased rs-BA is compatible with diaschisis and contributes to manifest the malfunctions of lesion-specific functional connectivity. In contrast, capsular infarct resulted in increase of rs-BA in the ipsilesional internal capsule, and contralesional red nucleus and ventral hippocampus in recovery group ( P<0.0025, FDR q<0.05), implying that remaining subcortical structures have an important role in conducting the recovery process in capsular infarct. The SPRT training facilitated motor recovery only in rats with an incomplete destruction of the posterior limb of the internal capsule (PLIC) (Pearson's correlation, P<0.05). Alternative therapeutic interventions are required to enhance the potential for recovery in capsular infarct with complete destruction of PLIC. </P>
Longitudinal Changes in Resting-State Brain Activity in a Capsular Infarct Model
Kim, Donghyeon,Kim, Ra Gyung,Kim, Hyung-Sun,Kim, Jin-Myung,Jun, Sung Chan,Lee, Boreom,Jo, Hang Joon,Neto, Pedro R,Lee, Min-Cheol,Kim, Hyoung-Ihl SAGE Publications 2015 Journal of cerebral blood flow and metabolism Vol.35 No.5
Detection of Differentially Expressed Gene Sets in a Partially Paired Microarray Data Set
Lim, Johan,Kim, Jayoun,Kim, Sang-cheol,Yu, Donghyeon,Kim, Kyunga,Kim, Byung Soo Walter de Gruyter GmbH 2012 Statistical applications in genetics and molecular Vol.11 No.3
<P>Partially paired data sets often occur in microarray experiments (Kim et al., 2005; Liu, Liang and Jang, 2006). Discussions of testing with partially paired data are found in the literature (Lin and Stivers 1974; Ekbohm, 1976; Bhoj, 1978). Bhoj (1978) initially proposed a test statistic that uses a convex combination of paired and unpaired t statistics. Kim et al. (2005) later proposed the t3 statistic, which is a linear combination of paired and unpaired t statistics, and then used it to detect differentially expressed (DE) genes in colorectal cancer (CRC) cDNA microarray data. In this paper, we extend Kim et al.'s t3 statistic to the Hotelling's T2 type statistic Tp for detecting DE gene sets of size p. We employ Efron's empirical null principle to incorporate inter-gene correlation in the estimation of the false discovery rate. Then, the proposed Tp statistic is applied to Kim et al's CRC data to detect the DE gene sets of sizes p=2 and p=3. Our results show that for small p, particularly for p=2 and marginally for p=3, the proposed Tp statistic compliments the univariate procedure by detecting additional DE genes that were undetected in the univariate test procedure. We also conduct a simulation study to demonstrate that Efron's empirical null principle is robust to the departure from the normal assumption.</P>
Hye Weon Kim(Hye Weon Kim),ZunHyan Rieu(ZunHyan Rieu),Donghyeon Kim(Donghyeon Kim),Hyun Kook Lim(Hyun Kook Lim) 대한신경정신의학회 2023 신경정신의학 Vol.62 No.2
Brain magnetic resonance imaging (MRI) is a key tool for diagnosing neurodegenerative diseases such as Alzheimer’s disease (AD). However, MRI analysis by visual interpretation and reading can be time-consuming and requires specialized expertise. Brain MRI-based artificial intelligence (AI) software has been developed to aid clinicians in diagnosing and managing neurodegenerative disorders, including AD. This study demonstrates the clinical application of the AI software for volumetric analysis of brain MRI scans in patients within the AD spectrum. In the current case series, four patients with memory impairment visited the memory clinic of Yeouido St. Mary’s Hospital. They underwent a series of assessments, including automated analysis of AI-based software for brain MRI volumetric measurements. The information provided by the software was highly accurate, consistent, and was especially valuable for the early diagnosis and monitoring of disease progression. The results imply that this technology potentially aids in the early detection and management of AD, making it a valuable tool for clinicians in the diagnosis of neurodegenerative diseases.
Kim, Donghyeon,Park, Doyoung,Oh, Namgyeong,Kim, Jaegyeom,Jeong, Euh Duck,Kim, Seung-Joo,Kim, Sungyun,Park, Jung-Chul American Chemical Society 2015 Inorganic Chemistry Vol.54 No.4
<P>Novel LiCe9(SiO4)(6)O-2 and LiTb9(SiO4)(6)O-2 compounds have been successfully synthesized, and the site selectivity and occupancy of activator ions have been estimated including LiEu9(SiO4)(6)O-2 compound. The rare earth (RE) fully occupied compounds, as well as the RE partially occupied congeners are required for the assessment of site selectivity of RE (activator) ions in apatite-type compounds. The splitting energies of the 6H and 4F Wycoff positions of LiRE9(SiO4)(6)O-2 (RE = Ce, Eu, and Tb) compounds are calculated based on crystal field theory: Delta E-Ce(6H) = 3849.3 cm(-1), Delta E-Ce(4F) = 4228.1 cm(-1), Delta E-Eu(6H) = 3870.0 cm(-1), Delta E-Eu(4F) = 4092.8 cm(-1), Delta E-Tb(6H) = 3637.6 cm(-1), Delta E-Tb(4F) = 4396.1 cm(-1), indicating that the splitting energy for the 4F site is larger than that for the 6H site in all compounds; thus the absorption energy is higher for the 6H site. In apatite-type LiRE9(SiO4)(6)O-2 (RE = Ce, Eu, and Tb) compounds, the Ce3+ ions predominantly occupy the 4F site associated with the absorption band around 300 nm at lower Ce3+ concentration, and then enter the 6H site associated the absorption band around 245 nm. For the Eu3+-doped compounds, the 4F site and 6H site are mixed within the charge transfer band (CTB) between 220 and 350 nm. Eu3+ ions initially preferentially occupy the 6H site (around 290 nm) at lower Eu3+ concentration and subsequently enter the 4F site (around 320 nm) with increasing Eu3+ concentration. For the Tb3+-doped compounds, the absorption due to the two different sites is mixed within f-d absorption band between 200 and 300 nm. At lower Tb3+ concentration, the Tb3+ ions enter favorably 6H site around 240 nm and then enter 4F site around 270 nm. These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field.</P>
Kim, Donghyeon,Lim, Daeseong,Ryu, Hyeonjeong,Lee, Jungjun,Ahn, Sung Il,Son, Bong Soo,Kim, Seung-Joo,Kim, Chang Hae,Park, Jung-Chul ACS AMERICAN CHEMICAL SOCIETY 2017 Inorganic Chemistry Vol. No.
<P>Blue-emitting Ca2-xMgxSiO4:Ce (0.0 <= x <= 1.0) phosphors were successfully synthesized and characterized. Rietveld refinement revealed that four main phases exist within the solid-solution range of CaO-MgO-SiO2, namely, beta-Ca2SiO4 (Mg (x) = 0.0), Ca14Mg2(SiO4)(8) (Mg (x) = 0.25), Ca3Mg(SiO4)(2) (Mg (x) = 0.5), and CaMgSiO4 (Mg (x) = 1.0). The variation of the IR modes was more prominent with increasing Mg2+ content in the Ca2-xMgxSiO4 materials. The sharing of O atoms of the SiO4- tetrahedra by the MgO6-octahedra induced weakening of the Si O bonds, which resulted in the red shift of the [SiO4] internal modes and appearance of a Mg-O stretching vibration at similar to 418 cm(-1). Raman measurement revealed that the change of the Ca-O bond lengths because of the Mg2+-substitution directly reflected the frequency shift of the Si-O stretching-Raman modes. Notably, the thermal stability of Ca2-xMgxSiO4:Ce (Mg (x) > 0.0) phosphors was superior to that of beta-Ca2SiO4:Ce (Mg (x) = 0.0) as confirmed by temperature-dependent photoluminescence (PL) measurements. This indicated that Mg2+ ions play an important role in enhancement of the thermal stability. In combination with the results from PL and electroluminescence (EL), it was elucidated that the luminous efficiency of Ca2-xMgxSiO4:Ce (Mg (x) = 0.1) was approximately twice as much as beta-Ca2SiO4:Ce (Mg (x) = 0.00), directly indicating a 'Mg2+-substitution effect'. The large enhancements of PL, EL, and thermal stability because of Mg2+-substitution may provide a platform in the discovery of more efficient phosphors for NUV-LEDs.</P>
Kim, Donghyeon,Bae, Jong-Seong,Hong, Tae Eun,Hui, Kwun Nam,Kim, Sungyun,Kim, Chang Hae,Park, Jung-Chul American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.27
<P>In the search for well-defined phosphor materials for white NUV-LEDs, the highly enhanced luminous efficacy by N-3(-) doping as well as color tunability via Ca substitution has been successfully obtained in Ba(2-x)Ca(3)SiO(4-delta)6N(2/3 delta):Eu2+ (x = 0.0, 0.5, 0.8, 1.0) phosphors. With increasing Ca -substitution rate, the crystal structures of the phosphor materials are changed from the primitive orthorhombic structure to the hexagonal one, so that the CIE coordinates move from bluish-green (at Ca = 0.0), to blue (at Ca = 0.5), and finally to near white region (at Ca = 0.8 and 1.0) in these materials. In combination with the results from X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy, the elemental distribution of the phosphor materials found from secondary-ion mass spectrometry (SIMS) directly indicates that the N3- ions are partially substituted for 02- ions into the crystal lattice of alkaline-earth orthosilicates and thus critically improves the color-tunable photoluminescence (PL) and electroluminescence (EL) efficiency of the phosphor materials for white NUV-LEDs. The newly found 'the N-3(-) doping and color-tunable effect' on large PL and EL enhancement may provide a platform in the discovery of new efficient phosphors for solid state lighting.</P>
Kim, Donghyeon,Kim, Sung-Chul,Bae, Jong-Seong,Kim, Sungyun,Kim, Seung-Joo,Park, Jung-Chul American Chemical Society 2016 Inorganic Chemistry Vol.55 No.17
<P>Eu2+-activated M-5(PO4)(3)X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M-5(PO4)(3)Cl:Eu2+ (M = Ca, Sr, Ba) compounds were blue shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr-5(PO4)(3)X:Eu2+ (X = F, Cl, Br) compounds were red-shifted along the series of halides, F -> Cl -> Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu2+) in the M-5(PO4)(3)X:Eu2+ (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d -> 4f transition energies of Eu2+ using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu2+ ions preferably enter the fully oxygen-coordinated sites, in the M-5(PO4)(3)X:Eu2+ (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by 'Pauling's rules'. These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field.</P>