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Characterization of Transparent Fluorapatite Ceramics Fabricated by Spark Plasma Sintering. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8157. [PMID: 36431642 PMCID: PMC9698385 DOI: 10.3390/ma15228157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 10/28/2022] [Accepted: 11/11/2022] [Indexed: 06/16/2023]
Abstract
Highly optically transparent polycrystalline fluorapatite ceramics with hexagonal crystal structures were fabricated via a liquid-phase synthesis of fluorapatite powder, followed by spark plasma sintering (SPS). The effect of sintering temperature, as observed using a thermopile, on the optical transmittance and microstructure of the ceramics was investigated in order to determine suitable sintering conditions. As a result, high optical transmittance was obtained in the SPS temperature range of 950-1100 °C. The highest optical transmittance was obtained for the ceramic sample sintered at 1000 °C, and its average grain size was evaluated at only 134 nm. The grain size dramatically increased with temperature, and the ceramics became translucent at SPS temperatures above 1200 °C. The mechanical and thermal properties of the ceramics were measured to evaluate the thermal shock parameter, which was found to be comparable to or slightly smaller than that of single-crystal fluorapatite. This transparent polycrystalline fluorapatite ceramic material should prove useful in a wide range of applications, for example as a biomaterial or optical/laser material, in the future. Furthermore, the knowledge obtained in this study should help to promote the application of this ceramic material.
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Effect of volume ratio on optical and mechanical properties of Y2O3-MgO composites fabricated by spark-plasma-sintering process. Ann Ital Chir 2021. [DOI: 10.1016/j.jeurceramsoc.2020.10.074] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Malate-aided selective crystallization and luminescence comparison of tetragonal and monoclinic LaVO 4:Eu nanocrystals. Dalton Trans 2021; 50:10147-10158. [PMID: 34231601 DOI: 10.1039/d1dt01644j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
With malate (Mal2-) as a new type of chelate, tetragonal (t-) and monoclinic (m-) structured LaVO4:Eu crystals (∼10-60 nm) were selectively crystallized as nanosquares and nanorods via a hydrothermal reaction at 200 °C for 24 h. The effects of the Mal2-:(La,Eu)3+ molar ratio, solution pH and Eu3+ content on the phase structure and crystal morphology were systematically investigated and elucidated. The competition between OH- and Mal2- toward rare earth ions was discussed to play a critical role in phase selection, and the t-phase can only be fabricated at pH ∼ 6-8 with the assistance of Mal2-. The optimal Eu3+ content for luminescence was determined to be ∼5 at% under the VO43- → Eu3+ energy transfer mechanism. Experimental comparison showed that t-(La0.95Eu0.05)VO4 (λex = 275 nm, λem = 620 nm) emits ∼5.3 times as strong as m-(La0.95Eu0.05)VO4 does (λex = 313 nm, λem = 616 nm), while theoretical analysis revealed that the 5D0 level of Eu3+ has a quantum efficiency of ∼80% for the former and ∼70% for the latter. Besides, the t- and m-(La0.95Eu0.05)VO4 nanocrystal phosphors were analyzed to have fluorescence lifetimes of ∼1.53 ± 0.01 and 2.28 ± 0.01 ms for their 620 and 616 nm red emissions, respectively.
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Abstract
Crystal engineering of ZnWO4 was achieved with oxalic acid and (NH4)2SO4 as modifiers upon hydrothermal reaction, which produced nanorods, microplates and well-organized architectures that clearly show morphology-dependent photoluminescence.
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Post-annealing effect on transparent Mg-Zn aluminate solid solutions fabricated by spark plasma sintering. Ann Ital Chir 2019. [DOI: 10.1016/j.jeurceramsoc.2019.08.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Transparent non-cubic laser ceramics with fine microstructure. Sci Rep 2019; 9:10300. [PMID: 31311952 PMCID: PMC6635367 DOI: 10.1038/s41598-019-46616-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/02/2019] [Indexed: 11/17/2022] Open
Abstract
Transparent polycrystalline ceramics with cubic crystal structure have played important roles in a wide variety of solid-state laser applications, whereas for non-cubic structures, single crystal only has been used. For further progress in optical technologies, effective materials beyond the current limitations are necessary. Here we report a new type of non-cubic ceramic laser material that overturns conventional common sense. It is hexagonal Nd-doped fluorapatite (Nd:FAP) ceramics with an optical quality comparable to single crystal while having random crystal orientation. It is composed of ultrafine grains with a loss coefficient of 0.18 cm−1 at a lasing wavelength of 1063 nm, and its laser oscillation was demonstrated. This is the first verification of lasing in randomly oriented non-cubic ceramics. Laser oscillation in the non-cubic ceramics was realized through both advanced liquid-phase nano-powder synthesis technology and highly controlled pulsed-current sintering techniques. Our findings should open new avenues for future solid-state laser and optical applications.
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Morphology Tailoring of ZnWO4 Crystallites/Architectures and Photoluminescence of the Doped RE3+ Ions (RE = Sm, Eu, Tb, and Dy). Inorg Chem 2019; 58:9432-9442. [PMID: 31241327 DOI: 10.1021/acs.inorgchem.9b01271] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Transparent tetragonal-cubic zirconia composite ceramics densified by spark plasma sintering and hot isostatic pressing. Ann Ital Chir 2019. [DOI: 10.1016/j.jeurceramsoc.2018.12.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Multi-Color Luminescent m-LaPO 4:Ce/Tb Monospheres of High Efficiency via Topotactic Phase Transition and Elucidation of Energy Interaction. Inorg Chem 2019; 58:890-899. [PMID: 30570255 DOI: 10.1021/acs.inorgchem.8b03029] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Monoclinic (m-) structured (La0.96- xCe0.04Tb x)PO4 phosphor monospheres ( x = 0-0.12) of excellent dispersion and morphology uniformity were calcined (≥600 °C) from their precipitated precursor spheres (∼2.0 μm) of a hexagonal (h-) structure for efficient and multicolor luminescence. The h → m phase transition, driven by dehydration, was originally proposed to proceed in a topotactic manner, which involves displacement of the RE-O polyhedra (RE: rare-earth) along the a/ b axis and slight expansion of the {010} and {100} interplanar spacings of the hydrated h-phase to form the {120} and {100} planes of the anhydrous m-phase, respectively. Analysis of the energy process involving the optically active Ce3+ and Tb3+ ions found efficient Ce3+ → Tb3+ energy transfer occurring via electric dipole-quadrupole interaction, whose efficiency reached the highest value of ∼44.48% at x = 0.10. The Tb3+ codoped phosphors simultaneously displayed the characteristic emissions of Ce3+ (∼313 nm) and Tb3+ (∼545 nm) upon exciting the Ce3+ ions with 275 nm UV light, with which the emission color was finely tuned from dark blue to green by increasing the Tb3+ content. Fluorescence decay analysis found decreasing and almost constant lifetime values for the Ce3+ and Tb3+ emissions at a higher Tb3+ content, respectively, and the phosphor presented the highest external quantum efficiency of ∼84.67% at x = 0.10. The excellent luminescent performance and morphology uniformity may allow the monospheres to find application in lighting and display technologies.
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Selective Crystallization of Four Tungstates (La 2W 3O 12, La 2W 2O 9, La 14W 8O 45, and La 6W 2O 15) via Hydrothermal Reaction and Comparative Study of Eu 3+ Luminescence. Inorg Chem 2018; 57:6632-6640. [PMID: 29775048 DOI: 10.1021/acs.inorgchem.8b00807] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hydrothermal reaction at 200 °C was systematically undertaken in wide ranges of solution pH (4-13) and W/La molar ratio ( R = 0.5-2), without using any organic additive, to investigate the effect of hydrothermal parameter on product property and the underlying mechanism. Combined analysis by X-ray diffraction (XRD), inductively coupled plasma (ICP) spectroscopy, elemental mapping, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that either a decreasing pH or increasing R value yielded a product richer in W and, conversely, richer in La. The results were interpreted from the solution chemistry of La3+ and tungstate ions. As an outcome of our 40 well-designed experiments, four La tungstates-La2W3O12, La2W2O9, La14W8O45, and La6W2O15-were successfully obtained in a phase-pure form by calcining their hydrothermal precursors. Phase and morphology evolution, structure features, and properties of Eu3+ emission were, for the first time, comparatively investigated for the four compounds. Spectral analysis found that the 5 at. % Eu3+-doped La2W3O12 phosphor exhibits the highest quantum efficiency (∼47%), more red component, and the shortest fluorescence lifetime of luminescence (∼0.72 ms).
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Distribution of carbon contamination in MgAl 2 O 4 spinel occurring during spark-plasma-sintering (SPS) processing: I – Effect of heating rate and post-annealing. Ann Ital Chir 2018. [DOI: 10.1016/j.jeurceramsoc.2017.09.038] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Enhanced hydrothermal crystallization and color tailorable photoluminescence of hexagonal structured YPO4:Sm/Tb nanorods. CrystEngComm 2018. [DOI: 10.1039/c8ce00183a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mal2− and superfluous PO43− jointly ensured the hydrothermal crystallization of hexagonal structured YPO4:Tb/Sm nanorods with color-tailorable photoluminescence and large aspect ratios of up to ∼32.
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Breaking the strong 1D growth habit to yield quasi-equiaxed REPO4 nanocrystals (RE = La–Dy) via solvothermal reaction and investigation of photoluminescence. CrystEngComm 2018. [DOI: 10.1039/c7ce01880k] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Quasi-equiaxed REPO4 (RE = La–Dy) nanocrystals have been solvothermally synthesized and white-light emission has been achieved with h-(Gd0.95Dy0.05)PO4 nanocrystals.
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Combining complexing agent and solvothermal reaction for the morphology controlled synthesis of (Y,Eu)PO4crystals with size-dependent photoluminescence. CrystEngComm 2018. [DOI: 10.1039/c8ce00956b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An organic additive assisted solvothermal reaction has led to the phase/morphology controlled synthesis of YPO4crystals, whose size-dependent luminescence was also investigated.
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Interacting layered hydroxide nanosheets with KF leading to Y/Eu hydroxyfluoride, oxyfluoride, and complex fluoride nanocrystals and investigation of photoluminescence. RSC Adv 2017. [DOI: 10.1039/c7ra10508h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Reacting nanosheets (∼4 nm thick) of RE2(OH)5NO3·nH2O layered hydroxyl nitrate with KF has led to various types of fluorides for photoluminescence.
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Hydrothermal crystallization of a Ln2(OH)4SO4·nH2O layered compound for a wide range of Ln (Ln = La–Dy), thermolysis, and facile transformation into oxysulfate and oxysulfide phosphors. RSC Adv 2017. [DOI: 10.1039/c7ra00645d] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ln-Dependent crystallization, structure, and thermolysis were systematically studied for layered Ln2(OH)4SO4·nH2O compounds, and their transformation into oxysulfate and oxysulfide phosphors was demonstrated.
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Two-step crystallization of a phase-pure Ln2(OH)5NO3·nH2O layered compound for the smallest Ln ions of Tm, Yb and Lu, anion exchange, and exfoliation. Dalton Trans 2017; 46:12683-12691. [DOI: 10.1039/c7dt02891a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
TEM morphology of ∼1.7 nm thick nanosheets exfoliated from DS− exchanged LLnH in formamide.
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Dicarboxylate mediated efficient morphology/phase tailoring of YPO4:Ln3+ crystals and investigation of down-/up-conversion luminescence. CrystEngComm 2017. [DOI: 10.1039/c7ce01248a] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Both hexagonal (h-) and tetragonal (t-) structured YPO4 crystals with multiform morphologies of high uniformity were selectively synthesized by using dicarboxylates as morphology/structure modifiers.
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EDTA-assisted phase conversion synthesis of (Gd 0.95RE 0.05)PO 4 nanowires (RE = Eu, Tb) and investigation of photoluminescence. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2017; 18:447-457. [PMID: 28740561 PMCID: PMC5507148 DOI: 10.1080/14686996.2017.1338495] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Revised: 05/31/2017] [Accepted: 05/31/2017] [Indexed: 05/22/2023]
Abstract
Hexagonal (Gd0.95RE0.05)PO4·nH2O nanowires ~300 nm in length and ~10 nm in diameter have been converted from (Gd0.95RE0.05)2(OH)5NO3·nH2O nanosheets (RE = Eu, Tb) in the presence of monoammonium phosphate (NH4H2PO4) and ethylene diamine tetraacetic acid (EDTA). They were characterized by X-ray diffraction, thermogravimetry, electron microscopy, and Fourier transform infrared and photoluminescence spectroscopies. It is shown that EDTA played an essential role in the morphology development of the nanowires. The hydrothermal products obtained up to 180 °C are of a pure hexagonal phase, while monoclinic phosphate evolved as an impurity at 200 °C. The nanowires undergo hexagonal→monoclinic phase transformation upon calcination at ≥600 °C to yield a pure monoclinic phase at ~900 °C. The effects of calcination on morphology, excitation/emission, and fluorescence decay kinetics were investigated in detail with (Gd0.95Eu0.05)PO4 as example. The abnormally strong 5D0→7F4 electric dipole Eu3+ emission in the hexagonal phosphates was ascribed to site distortion. The process of energy migration was also discussed for the optically active Gd3+ and Eu3+/Tb3+ ions.
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Qualitative Analysis of Patents Concerning Cathode Active Materials for Lithium-Ion Secondary Batteries Based on Layer Structure. APPLIED CHEMISTRY FOR ENGINEERING 2015. [DOI: 10.14478/ace.2015.1025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Quantitative Analysis of Patents Concerning Cathode Active Materials for Lithium-Ion Secondary Batteries Based on Layer Structure. APPLIED CHEMISTRY FOR ENGINEERING 2015. [DOI: 10.14478/ace.2015.1026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
Based on the work of both Eysenck and Nideffer, we hypothesized that higher ranking players (HRP) would have lower competitive anxiety and more flexible attention-shifting, compared to lower ranking players (LRP). In addition, different patterns of attention (low anxiety and flexible attention) would be represented by a different pattern of brain activity within the temporal lobe and dorsolateral prefrontal cortex. In accordance with the rookie draft ranking, the players were classified into 2 groups: HRP (top 30% of those selected in the draft) vs. LRP (bottom 30% of those selected in the draft). For assessment of executive function, a computerized version of the Wisconsin Card-sorting Test (WCST) was used. Brain activity was assessed using 1.5-Tesla functional magnetic resonance imaging. In response to scenes depicting baseball errors, HRP showed increased activation in the left cingulate cortex and decreased activation in right middle temporal gyrus, compared to LRP. In response to the simplified WCST in the scanner, HRP showed increased activation in left superior frontal cortex (DLPFC), compared to LRP. The present results suggest that HRP may demonstrate elevated cingulate activation and lower temporal cortex activation in response to scenes depicting baseball errors.
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Association between urine cotinine levels, continuous performance test variables, and attention deficit hyperactivity disorder and learning disability symptoms in school-aged children. Psychol Med 2013; 43:209-219. [PMID: 22608159 DOI: 10.1017/s0033291712001109] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND We examined the cross-sectional relationship between environmental tobacco smoke exposure, continuous performance test (CPT) measures, and attention deficit hyperactivity disorder (ADHD) or learning disability symptoms in school-aged children. METHOD In total, 989 children (526 boys, mean age 9.1 ± 0.7 years), recruited from five South Korean cities participated in this study. We used urine cotinine as a biomarker for environmental tobacco smoke exposure, and obtained the children's scores on a CPT. Parents completed the Korean versions of the ADHD rating scale-IV (ADHD-RS) and learning disability evaluation scale (LDES). Using generalized linear mixed model (GLMM), we assessed the associations between urine cotinine concentrations, neuropsychological variables, and symptoms of ADHD and learning disabilities. Additionally, we conducted structural equation models to explore the effects' pathways. RESULTS After adjusting for a range of relevant covariates, GLMM showed urinary cotinine levels were significantly and positively associated with CPT scores on omission errors, commission errors, response time, and response time variability, and with parent- and teacher-rated ADHD-RS scores. In addition, urine cotinine levels were negatively associated with LDES scores on spelling and mathematical calculations. The structural equation model revealed that CPT variables mediated the association between urine cotinine levels and parental reports of symptoms of ADHD and learning disabilities. CONCLUSIONS Our data indicate that environmental exposure to tobacco smoke is associated with ADHD and learning disabilities in children, and that impairments in attention and inhibitory control probably mediate the effect.
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A study on knowledge and attitude toward brain death and organ retrieval among health care professionals in Korea. Transplant Proc 2012; 44:859-61. [PMID: 22564567 DOI: 10.1016/j.transproceed.2012.02.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
PURPOSE The practice of retrieving vital organs from brain-dead donors is legally and medically accepted in Korea, but health care professionals' beliefs and opinions regarding these matters have not been sufficiently explored. The purpose of this study was to evaluate the knowledge and attitudes of health care professionals to the concepts of brain death and organ retrieval. METHODS Data were collected using a 41-item questionnaire during a week in June 2011. Sixty-one doctors and 109 nurses from five hospitals with more than 2000 beds in Seoul, Korea, participated in the survey. The data was analyzed using SPSS version 17.0 (SPSS Inc. Chicago, Illinois, USA). RESULTS There were statistically significant differences in the scores on knowledge according to marital status (P = .001) education level (P = .019), whether the participants were informed about organ donation from a brain-dead donor (P = .002), and the participant's experience managing potential brain-dead patients (P = .037). There were statistically significant differences in the scores on the attitude according to gender (P < .001), age (P < .001), marital status (P < .001), education level (P = .003), job position (P < .001), and the participant's experience referring brain-dead patients to the hospital-based organ procurement organization (P = .001). Significantly, attitude's positively correlated with knowledge about brain-dead organ donation (P < .001). CONCLUSION Compared with previous studies, the knowledge and attitudes of health care professionals' regarding brain death and organ retrieval were not improved. There are passive attitudes to brain death and organ retrieval. More research must be performed to promote knowledge and understanding toward brain death and organ retrieval among health care professionals.
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Abstract
Organ donation after cardiac death (DCD) has been suggested due to the shortage of allografts in Korea. We investigated the outcomes of 446 deceased donor kidney transplant recipients in our center between September 1, 1995, and December 31, 2009. Twenty-four (5.4%) of those patients received DCD kidney grafts. The DCD group had a long intensive care unit stay, frequent inotropics use (such as norepinephrine and dopamine), low mean blood pressure and estimated glomerular filtration rate, and high serum creatinine and deceased donor scores compared to the standard criteria donor (SCD) group and the expanded criteria donor (ECD) group. Mean true warm ischemic time of the DCD group was 59.7 minutes based on asystole time. The DCD group had a long hospital stay after transplantation, but there was no statistically significant difference in delayed graft function and primary nonfunction. Serum creatinine levels at 3 months after transplantation in the ECD and DCD group were significantly higher than the SCD group (P < .001) but lower in the DCD group than in the ECD group at 6 months and 9 months (P < .001 and P = .004) posttransplantation. There were no statistically significant differences in serum creatinine levels or in the graft survival rates between groups at 12 months (P = .160 and P = .737). The use of DCD attracted Korean surgeons because DCD allografts are equivalent to a heart-beating donor. Donors who die during the evaluation of brain death should not be abandoned for procurement, and we need to try to harvest allografts after cardiac death (type 4 DCD) to expand donor pools.
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Effect of sintering temperature on optical properties and microstructure of translucent zirconia prepared by high-pressure spark plasma sintering. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2011; 12:055003. [PMID: 27877441 PMCID: PMC5074435 DOI: 10.1088/1468-6996/12/5/055003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 09/07/2011] [Accepted: 07/19/2011] [Indexed: 06/04/2023]
Abstract
Aiming to characterize the effect of sintering temperature on transparency of zirconia, we have evaluated the optical properties and microstructure of translucent cubic zirconia prepared by high-pressure spark plasma sintering (SPS) at 1000-1200 ○C. Color centers (oxygen vacancies with trapped electrons) and residual pores were primary defects in the samples. In SPS samples, the total forward transmittance and in-line transmittance are mainly affected by color centers with a limited contribution from residual pores; in contrast, the changes in reflectance are only related to the porosity. The amounts of color centers and residual pores increase with sintering temperature that reduces the total forward and in-line transmittance of the as-sintered zirconia. Annealing in oxidizing atmosphere improves the total forward and in-line transmittance. During the annealing, the concentration of color centers decreases but the porosity increases.
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Improvement of polymer electrolyte membrane by radiation-induced grafting of styrene onto FEP film with subsequent sulfonation. KOREAN J CHEM ENG 2009. [DOI: 10.1007/s11814-008-0201-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Thermal, mechanical and electrical properties on the styrene-grafted and subsequently sulfonated FEP film induced by electron beam. Polym Degrad Stab 2008. [DOI: 10.1016/j.polymdegradstab.2008.01.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
This study was undertaken to identify psychiatric morbidity among Korean second and third elementary school children using an objective diagnostic interview tool. Data from 5,118 (2,723 boys, 2,395 girls; mean age = 8.41 years (SD = 0.66)) second and third grade schoolchildren were drawn from 28 elementary schools. After initial screening assessments using the 28-item Child Problem-Behavior Screening Test for parents, 672 primary caregivers were subjected to secondary screening using the Korean version of the CBCL. Two hundred and seventy-one high-risk children selected according to the K-CBCL results, 138 (50.9%) children and their primary caregivers were interviewed using the Korean version of K-SADS-PL for objective DSM-IV psychiatric diagnoses. Sixty-four (46.4%) of the hundred and thirty eight children were determined to have at least one psychiatric disorder. More boys were diagnosed as psychiatric patients than girls (46 males, 18 females; OR = 2.21). The most frequently diagnosed disorder was ADHD (46/64; 71.9%), followed by tic disorder, anxiety disorders, mental retardation, oppositional defiant disorder, and separation anxiety disorder. Two or more comorbid psychiatric disorders were found in 22 (34.4%) of the 64 patients. The computed crude percentage of psychiatric patients in this study was 4.12%, which is similar to previously published data.
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Melt complex viscosity and molecular weights for homo-polypropylene modified by grafting bifunctional monomers under electron beam irradiation. POLYMER 2006. [DOI: 10.1016/j.polymer.2006.07.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Manufacturing and foaming of high melt viscosity of polypropylene by using electron beam radiation technology. POLYM ENG SCI 2006. [DOI: 10.1002/pen.20470] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Resistance to extended-spectrum cephalosporins and mortality in patients with Citrobacter freundii bacteremia. Infection 2003; 31:202-7. [PMID: 14562942 DOI: 10.1007/s15010-003-2176-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND This study was performed to characterize the clinical features and to identify the risk factors for resistance to extended-spectrum cephalosporins (ESCs) and for mortality in patients with Citrobacter freundii bacteremia. PATIENTS AND METHODS 105 patients (aged > or = 15 years) with C. freundii bacteremia in 1991-2000 were retrospectively analyzed. RESULTS Nosocomial acquisition was identified in 78.1% of the patients. Hepatic, biliary and pancreatic disease was the most common underlying disease (65.7%) and the biliary tract was the most common site of infection (50.5%). The overall resistance rate to ESCs was 59.0% and was significantly associated with hepatic, biliary and pancreatic disease, recent surgery and procedure, biliary drainage catheter and previous antibiotic therapy in univariate analysis. However, only previous antibiotic therapy with ESCs (OR = 5.0, 95% CI 1.6-15.7, p = 0.006) and recent surgery or procedure (OR = 3.1, 95% CI 1.1-8.4, p = 0.03) were strong, independent risk factors in multivariate analysis. Mortality directly related to C. freundii bacteremia was 21.9% and there was no difference between cases with resistance and susceptibility to ESCs (19.4% vs 25.6%; p = 0.45). Mortality was significantly associated with rapidly fatal or ultimately fatal underlying disease, a solid tumor, septic shock and polymicrobial bacteremia in univariate analysis. Among patients who had therapeutic surgical procedures, mortality was lower (4.5%, p = 0.04). Multivariate analysis revealed rapidly or ultimately fatal disease, septic shock and polymicrobial bacteremia as independent prognostic factors. CONCLUSION Biliary infection was the leading cause of C. freundii bacteremia. Previous antibiotic therapy, especially with ESCs, frequently predisposed for resistance to these antibiotics. However, resistance to ESCs was not associated with increased mortality.
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Impact of previous use of antibiotics on development of resistance to extended-spectrum cephalosporins in patients with enterobacter bacteremia. Eur J Clin Microbiol Infect Dis 2002; 21:577-81. [PMID: 12226687 DOI: 10.1007/s10096-002-0772-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This retrospective study was conducted to determine the risk factors for resistance to extended-spectrum cephalosporins (ESCs) and to examine the influence of previous use of an aminoglycoside with an ESC on resistance to ESCs in patients with Enterobacter bacteremia from January 1991 through December 2000. A total of 423 episodes of Enterobacter bacteremia among 414 patients were documented during the 10-year study period. Three hundred thirty-two (78%) isolates were Enterobacter cloacae, 72 (17%) Enterobacter aerogenes, and 19 (4%) other Enterobacter species. Causative isolates exhibited resistance to ESCs in 225 episodes and susceptibility in 198 episodes. Nosocomial acquisition was an independent risk factor for resistance to ESCs (odds ratio [OR], 3.4; 95% confidence interval [95%CI], 1.7-6.8). The median number of antibiotics used was significantly greater in cases caused by resistant isolates than in cases caused by susceptible isolates (OR, 1.8; 95%CI, 1.2-2.6). Resistance to ESCs was associated with previous use of any ESC (OR, 5.0; 95%CI, 2.5-10.2). The proportion of resistant episodes in patients treated previously with an aminoglycoside plus an ESC was not different from that in patients treated with an ESC alone. In conclusion, previous use of ESCs was associated with resistance to ESCs in patients with Enterobacter bacteremia; moreover, previous use of an aminoglycoside with an ESC did not significantly decrease the risk of resistance to ESCs.
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Retrospective analysis of clinical and microbiological aspects of Klebsiella oxytoca bacteremia over a 10-year period. Eur J Clin Microbiol Infect Dis 2002; 21:419-26. [PMID: 12111596 DOI: 10.1007/s10096-002-0738-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
From 1991 to 2000, 125 sporadic cases of Klebsiella oxytoca bacteremia were analyzed retrospectively to review clinical features and to identify the risk factors associated with resistance to extended-spectrum cephalosporins and fatal outcome. Bacteremia was acquired nosocomially in 52% of the patients. Almost all patients (97%) had an underlying disease, with biliary and pancreatic disease occurring most frequently (55%). The biliary tract was the most common site of infection (44%). Resistance to extended-spectrum cephalosporins was identified in 22 of the 125 (18%) Klebsiella oxytoca blood isolates and resistance to ciprofloxacin in 9 (7%). Only previous antibiotic therapy was strongly associated with resistance to extended-spectrum cephalosporins in patients with Klebsiella oxytoca bacteremia ( P=0.009). The mortality rate was 24% and was higher in patients infected with isolates resistant to extended-spectrum cephalosporins (41% vs. 20%; P=0.04). In multivariate analysis, fatal outcome was independently associated with septic shock, deteriorated mental status, polymicrobial bacteremia, and solid tumor. Surgical therapy had a protective effect (OR, 0.06; 95% CI, 0.005-0.7; P=0.03). In conclusion, Klebsiella oxytoca bacteremia was most commonly associated with biliary tract infection. Previous antibiotic therapy was strongly associated with resistance to extended-spectrum cephalosporins in patients with Klebsiella oxytoca bacteremia.
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Risk factors for penicillin resistance and mortality in Korean adults with Streptococcus pneumoniae bacteremia. Eur J Clin Microbiol Infect Dis 2002; 21:35-42. [PMID: 11913499 DOI: 10.1007/s10096-001-0650-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A retrospective analysis was performed to measure the incidence of pneumococcal bacteremia and to identify risk factors for penicillin resistance and prognostic factors for outcome in adults. A total of 151 cases of pneumococcal bacteremia were identified from 149 adults during the period 1996-2000. The overall rate of penicillin resistance was 49%, ranging from 54.2% in 1996 to 48.5% in 2000 (P=0.93). Rates of resistance to ceftriaxone, clindamycin, erythromycin, and trimethoprim-sulfamethoxazole were 21.6%, 51%, 62%, and 44.7%, respectively. Multidrug resistance was documented in 47.7% of the cases. Penicillin resistance was significantly associated with solid tumor, biliary drainage catheter, and previous beta-lactam therapy in the univariate analysis. However, the associations were not as significant as independent risk factors in the multivariate analysis. Mortality was 23.8% and did not change significantly during the study period (P=0.06). Mortality rates in cases caused by penicillin-susceptible Streptococcus pneumoniae and penicillin-resistant Streptococcus pneumoniae were 23% and 24.7%, respectively (P=0.81). Mortality was not significantly influenced by penicillin resistance, even high-level resistance (24.4% vs. 20%; P=0.64). Multivariate analysis revealed that antineoplastic chemotherapy, respiratory failure, and acute renal failure were independent prognostic factors for mortality. In conclusion, the rate of penicillin resistance among pneumococcal blood isolates was high in the late 1990s, but penicillin resistance, and even high-level penicillin resistance, was not significantly associated with increased mortality in adults with pneumococcal bacteremia.
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A case of spontaneous bacterial empyema and bacteremia caused by Aeromonas hydrophila. Eur J Clin Microbiol Infect Dis 2001; 20:214-5. [PMID: 11347676 DOI: 10.1007/pl00011255] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Abstract
High-strain-rate superplasticity describes the ability of a material to sustain large plastic deformation in tension at high strain rates of the order of 10-2 to 10-1 s-1 and is of great technological interest for the shape-forming of engineering materials. High-strain-rate superplasticity has been observed in aluminium-based and magnesium-based alloys. But for ceramic materials, superplastic deformation has been restricted to low strain rates of the order of 10-5 to 10-4 s-1 for most oxides and nitrides with the presence of intergranular cavities leading to premature failure. Here we show that a composite ceramic material consisting of tetragonal zirconium oxide, magnesium aluminate spinel and alpha-alumina phases exhibits superplasticity at strain rates up to 1 s-1. The composite also exhibits a large tensile elongation, exceeding 1,050 per cent for a strain rate of 0.4 s-1. The tensile flow behaviour and deformed microstructure of the material indicate that superplasticity is due to a combination of limited grain growth in the constitutive phases and the intervention of dislocation-induced plasticity in the zirconium oxide phase. We suggest that the present results hold promise for the application of shape-forming technologies to ceramic materials.
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Group B streptococcal bacteremia in nonpregnant adults with hepatic disease in Korea. Eur J Clin Microbiol Infect Dis 2001; 20:639-42. [PMID: 11714045 DOI: 10.1007/s100960100586] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Sixty-seven cases of group B streptococcal bacteremia in adults were retrospectively reviewed during the period 1991-2000. Not one case occurred in pregnant women. The mean age of the patients was 57 years, and 67.2% were men. Of the 67 cases of illness, 25.4% were hospital acquired and 11.9% were polymicrobial. Common predisposing diseases included hepatic disease (55.2%), diabetes mellitus (28.4%), malignancy (20.9%), and cardiovascular diseases (17.9%). Primary bacteremia, peritonitis, bone and joint infections, and skin and soft tissue infections accounted for most presentations. Peritonitis was a more common presentation in patients with hepatic disease (P<0.001), whereas skin and soft tissue infection was more common in patients with non-hepatic disease (P=0.008). More patients with hepatic disease had polymicrobial bacteremia than did patients with nonhepatic disease (P=0.018). Death occurred in 9.8% of cases, and mortality did not differ between patients with hepatic disease and those with nonhepatic disease. Hepatic disease was found to be an important predisposing condition in adults with group B streptococcal bacteremia. However, mortality for patients with hepatic disease was similar to that for patients with nonhepatic disease.
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A case of disseminated Trichosporon beigelii infection in a patient with myelodysplastic syndrome after chemotherapy. J Korean Med Sci 2001; 16:505-8. [PMID: 11511798 PMCID: PMC3054774 DOI: 10.3346/jkms.2001.16.4.505] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Trichosporonosis is a potentially life-threatening infection with Trichosporon beigelii, the causative agent of white piedra. The systemic infection by this fungus has been most frequently described in immunocompromised hosts with neutropenia. Here, we report the first patient with disseminated infection by T. beigelii in Korea, acquired during a period of severe neutropenia after chemo-therapy for myelodysplastic syndrome. The patient recovered from the infection after an early-intensified treatment with amphotericin B and a rapid neutrophil recovery. The disseminated infection by T. beigelii is still rare, however, is an emerging fatal mycosis in immunocompromised patients with severe neutropenia.
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Methylphenidate increased regional cerebral blood flow in subjects with attention deficit/hyperactivity disorder. Yonsei Med J 2001; 42:19-29. [PMID: 11293498 DOI: 10.3349/ymj.2001.42.1.19] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The regional cerebral blood flow (rCBF) responses to methylphenidate (MPH) treatment were examined in children with attention deficit/hyperactivity disorder (ADHD). Thirty-two male children, diagnosed with ADHD by the DSM-IV diagnostic criteria, other behavioral assessment scales and neuropsychological battery, were studied using 99mTc-HMPAO-single photon emission computed tomography (SPECT). Subjects were studied before and after MPH treatment. First, using an image subtraction method, we obtained a NDR parametric image of each patient and found increased cerebral blood flow in the frontal lobes, caudate nuclei and thalamic areas after treatment. When the changes in SPECT and clinical response were compared, the matching rate, sensitivity and specificity between them were found to be 77.1, 80.0 and 79.2%, respectively. Second, three transaxial brain slices delineating anatomically defined regions of interest (ROI) at 20, 40, and 60mm above the orbitomeatal line (OML) were used, with the average number of counts for each region of interest normalized to the area of the cerebellar maximal uptake. The left and right prefrontal areas, and caudate and thalamic areas showed significant increases in rCBF after MPH treatment. These findings suggested MPH could affect the function of the fronto-striato-thalamic circuit, which is known as the pathophysiologic site of ADHD and could be used to correct the underlying brain dysfunction of ADHD.
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Time-kill studies of antimicrobial combinations including cefotaxime, ceftriaxone, vancomycin and meropenem against cephalosporin-resistant Streptococcus pneumoniae. Chemotherapy 2000; 46:303-8. [PMID: 10965094 DOI: 10.1159/000007302] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Resistance of Streptococcus pneumoniae to penicillin is now widespread and rapidly increasing all over the world. This has led to the critical need for alternative antimicrobial therapy. METHODS To assess the activities of antimicrobial combinations, including cefotaxime, ceftriaxone, vancomycin and meropenem, time-kill studies were conducted against five strains of penicillin- and cephalosporin-resistant S. pneumoniae at clinically achievable antimicrobial concentrations in cerebrospinal fluid. RESULTS Combinations of an extended-spectrum cephalosporin with vancomycin were not synergistic. Meropenem had a comparable bactericidal activity to those combinations, and its killing activity was not affected by the addition of cefotaxime, ceftriaxone or vancomycin. CONCLUSIONS It is suggested that meropenem could be an effective alternative for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. However, more clinical data are required before it can be recommended as an effective antimicrobial agent for such cases.
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Compressive Strength and Failure Mechanisms of Laminated C/C Composites by using Acoustic Emission Method. ACTA ACUST UNITED AC 1996. [DOI: 10.2320/matertrans1989.37.1156] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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