Publications by authors named "Hyeok Chan Kwon"

23 Publications

  • Page 1 of 1

Increased prevalence rate of metabolic syndrome is an independent predictor of cardiovascular disease in patients with antineutrophil cytoplasmic antibody-associated vasculitis.

Rheumatol Int 2021 Jun 4. Epub 2021 Jun 4.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea.

Objective: We investigated the prevalence of metabolic syndrome (MetS) in all or nonobese patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and compared it with age- and gender-matched controls. Also, we assessed the effect of variables at diagnosis on the risk of cardiovascular disease (CVD) in all or nonobese AAV patients.

Methods: In this study, 173 AAV patients and 344 controls were included and MetS was defined by the National Cholesterol Education Program Adults Treatment Panel III criteria. The obesity based on body mass index (BMI) was defined as BMI ≥ 25 kg/m. The follow-up duration was defined as the period from diagnosis to the last visit or to each poor outcome occurrence.

Results: The median age of AAV patients was 58.7 years and 57 patients were men. The prevalence of MetS was 50.9% in all AAV patients and 46.5% in nonobese AAV patients, which were significantly higher than 37.8% in all controls and 28.2% in nonobese controls. In Kaplan-Meier survival analysis, Mets at diagnosis significantly reduced the cumulative CVD-free survival rate in both all and nonobese AAV patients. In the multivariable Cox hazards model analysis, CVD during follow-up was significantly associated with both Birmingham vasculitis activity score (BVAS) (HR 1.159) and MetS at diagnosis (HR 9.036) in nonobese AAV patients.

Conclusions: The prevalence of MetS at diagnosis in all or nonobese AAV patients was significantly higher than those in all or nonobese controls. Furthermore, both BVAS and MetS at diagnosis increased the risk of CVD in nonobese AAV patients.
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http://dx.doi.org/10.1007/s00296-021-04908-1DOI Listing
June 2021

Male Sex Is a Significant Predictor of All-cause Mortality in Patients with Antineutrophil Cytoplasmic Antibody-associated Vasculitis.

J Korean Med Sci 2021 May 10;36(18):e120. Epub 2021 May 10.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.

Background: We investigated and compared the initial clinical features at diagnosis and the poor outcomes during follow-up in Korean patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) based on sex.

Methods: The medical records of 223 immunosuppressive drug-naïve patients with AAV were reviewed. Age, body mass index (BMI), smoking history, AAV subtypes, ANCA positivity, clinical manifestations, Birmingham vasculitis activity score (BVAS), five-factor score (FFS), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) at diagnosis were collected. All-cause mortality, end-stage renal disease (ESRD), cerebrovascular accident (CVA) and cardiovascular disease (CVD) were assessed as the poor outcomes of AAV during follow-up.

Results: The median age was 59.0 years and 74 of 223 AAV patients (33.2%) were men. Among variables at diagnosis, male patients exhibited higher BMI than female. However, there were no differences in other demographic data, AAV subtypes, ANCA positivity, BVAS, FFS, ESR and CRP between the two groups. Male patients received cyclophosphamide more frequently, but there were no significant differences in the frequencies of the poor outcomes of AAV between the two groups. Male patients exhibited a significantly lower cumulative patients' survival rate than female patients during the follow-up period based on all-cause mortality ( = 0.037). In the multivariable analysis, both male sex (hazard ratio [HR], 2.378) and FFS (HR, 1.693) at diagnosis were significantly and independently associated with all-cause mortality during follow-up.

Conclusion: Male sex is a significant and independent predictor of all-cause mortality in AAV patients.
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http://dx.doi.org/10.3346/jkms.2021.36.e120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8111045PMC
May 2021

Fibrosis-5 predicts end-stage renal disease in patients with microscopic polyangiitis and granulomatosis with polyangiitis without substantial liver diseases.

Clin Exp Med 2021 Feb 20. Epub 2021 Feb 20.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, Republic of Korea.

We previously reported that fibrosis-4 (FIB-4) was associated with poor outcomes of microscopic polyangiitis (MPA) and granuloma with polyangiitis (GPA). We also investigated the potential of FIB-5, a novel index, in predicting all-cause mortality and end-stage renal disease (ESRD) during follow-up in patients with MPA and GPA without substantial liver diseases. Clinical and laboratory data at diagnosis were collected by reviewing the medical records of 180 patients with MPA and GPA. FIB-5 was obtained by a following equation: FIB-5 = (serum albumin (g/L) × 0.3 + platelet count (10/L) × 0.05) - (alkaline phosphatase (IU/L) × 0.014 + aspartate aminotransferase/alanine aminotransferase ratio × 6 + 14). The median age of the patients at diagnosis was 61.0 years. FIB-5 at diagnosis could not reflect the cross-sectional vasculitis activity. The cutoffs of FIB-5 for poor outcomes was set as 0.82 (the lowest tertile) and -0.42 (the lowest quartile) at diagnosis. In Kaplan-Meier survival analysis, patients with FIB-5 < 0.82 and those with FIB-5 < -0.42 exhibited lower ESRD-free survival rates than those without. However, it could not predict all-cause mortality. In multivariable Cox hazards analysis, both FFS (Hazard ratio (HR) 1.554) and FIB-5 < 0.82 (HR 2.096) as well as both FFS (HR 1.534) and FIB-5 < -0.42 (HR 2.073) at diagnosis independently predicted ESRD during follow-up. In conclusion, FIB-5 < 0.82 and FIB-5 < -0.42 at diagnosis could predict the occurrence of ESRD, but not all-cause mortality, during follow-up in patients with MPA and GPA without substantial liver diseases.
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http://dx.doi.org/10.1007/s10238-021-00691-2DOI Listing
February 2021

Antineutrophil Cytoplasmic Antibody Positivity Is Associated with Vascular Involvement in Behçet's Disease.

Yonsei Med J 2021 Feb;62(2):149-158

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.

Purpose: We investigated whether antineutrophil cytoplasmic antibody (ANCA) positivity is associated with vascular manifestations at diagnosis of Behçet's disease (BD) and poor outcomes during follow-up.

Materials And Methods: We retrospectively reviewed the medical records of 1060 patients with BD. Among them, 808 patients could be diagnosed with BD based on the revised version of the International Criteria for Behçet's Disease (ICBD) in 2014 (2014 ICBD criteria) and 588 patients could be diagnosed with BD based on the International Study Group (ISG) criteria proposed in 1990 (1990 ISG criteria). We examined the sites and patterns of vascular involvement in the BD patients at diagnosis and evaluated adverse outcomes during follow up, such as all-cause mortality, acute coronary syndrome, and deep vein thrombosis.

Results: Among the 808 patients with BD based on the 2014 ICBD criteria, the rate of ANCA positivity at diagnosis was 2.2%. ANCA-positive BD patients exhibited a higher frequency of overall vascular manifestations (22.2% vs. 6.1%) and higher frequencies of vascular involvement in the upper extremities and visceral arteries than ANCA-negative BD patients (5.6% vs. 0.1% and 5.6% vs. 0.1%). Among the 588 BD patients based on the 1990 ISG criteria, similarly, ANCA-positive BD patients exhibited a higher frequency of vascular manifestations than ANCA-negative BD patients. ANCA positivity, however, did not seem to be associated with poor outcomes in BD patients during follow up.

Conclusion: ANCA positivity in BD patients was found to be associated with cross-sectional vascular involvement in the upper extremities and visceral arteries at diagnosis but was not predictive of poor outcomes during follow-up.
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http://dx.doi.org/10.3349/ymj.2021.62.2.149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7859684PMC
February 2021

Evaluation of body composition using computed tomography in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis.

Korean J Intern Med 2020 Aug 18. Epub 2020 Aug 18.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.

Background/aims: Measures of body composition, including visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and skeletal muscle area (SMA), are considered important prognostic factors in chronic diseases. The association of these measures with auto-inflammatory disorders, such as anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV), remains unclear. We investigated the clinical significance of VAT, SAT, and SMA in patients with AAV.

Methods: Patients with AAV subjected to chest computed tomography (CT), abdominal CT, or positron emission tomography-CT on diagnosis of AAV were evaluated. Quantitative assessment of VAT, SAT, and SMA was performed at the third lumbar vertebral level and computed by summing the pixel attenuation for tissue-specific Hounsfield units in the corresponding region. Associations of VAT, SAT, and SMA with clinical and laboratory data and clinical outcome measures were evaluated.

Results: Of the 117 patients, 61 (52.1%) were classified as having microscopic polyangiitis, 28 (23.9%) as granulomatosis with polyangiitis, and 28 (23.9%) as eosinophilic granulomatosis with polyangiitis. VAT significantly correlated with age, weight, body mass index (BMI), and Birmingham Vasculitis Activity Score, whereas SAT correlated with weight, BMI, and creatinine levels. A significant association was found between SMA and age, height, weight, BMI, and the Five-Factor Score. Cox proportional hazards analysis showed that creatinine levels (odds ratio [OR], 1.346; 95% confidence interval [CI], 1.034 to 1.753; p = 0.027) and high VAT (OR, 7.137; 95% CI, 1.343-37.946; p = 0.021) were independently associated with all-cause mortality during follow-up.

Conclusions: Evaluation of VAT using CT is useful for estimating disease activity and all-cause mortality in patients with AAV.
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http://dx.doi.org/10.3904/kjim.2020.064DOI Listing
August 2020

Multifunctional Self-Combustion Additives Strategy to Fabricate Highly Responsive Hybrid Perovskite Photodetectors.

ACS Appl Mater Interfaces 2020 Sep 1;12(37):41674-41686. Epub 2020 Sep 1.

Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.

To resolve the inherent trade-off issue between responsivity and detectivity in FACsPbI perovskite photodetectors, this paper proposes a novel strategy using multifunctional self-combustion additives (urea and ammonium nitrate). During the early stages of crystallization, urea allows for the formation of a strong Lewis complex-derived low-dimensional intermediate phase; this suppresses the formation of perovskite nuclei, while ammonium ions assist the preferred grain growth along the [110] direction. During the high-temperature annealing steps, a self-combusting exothermic reaction occurs between urea as a fuel and NHNO as an oxidizer, through which a locally supplied heat facilitates the removal of residual urea and byproducts. These multifunctional roles of self-combustible additives facilitate the production of high-quality, enlarged grain-structured perovskite films with improved optoelectronic properties, as confirmed by various analyses, including impedance spectroscopy and intensity-modulated photocurrent spectroscopy. The resulting FACsPbI-based photodiode-type photodetectors exhibit outstanding performance, such as a high responsivity (0.762 A W) and specific detectivity (over 5.08 × 10 Jones) at a very low external reverse bias (-0.5 V). Our findings clearly suggest that the multifunctional self-combustion additives strategy could help realize the full potential of FACsPbI as a photodiode-type photodetector.
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http://dx.doi.org/10.1021/acsami.0c08485DOI Listing
September 2020

Rituximab Biosimilar Prevents Poor Outcomes of Microscopic Polyangiitis and Granulomatosis with Polyangiitis as Effectively as Rituximab Originator.

Yonsei Med J 2020 Aug;61(8):712-719

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.

Purpose: There has been no extensive study to compare the efficacy between rituximab originator (Mabthera®) and its biosimilar (Truxima®) for microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA). Here, we investigated the clinical effects of rituximab on poor outcomes of MPA and GPA in Korean patients, and compared those between Mabthera® and Truxima®.

Materials And Methods: We retrospectively reviewed the medical records of a total of 139 patients, including 97 MPA patients and 42 GPA patients. At diagnosis, antineutrophil cytoplasmic antibody positivity and comorbidities were assessed. During follow-up, all-cause mortality, relapse, end-stage renal disease, cerebrovascular accident and acute coronary syndrome were evaluated as poor outcomes. In this study, rituximab was used as either Mabthera® or Truxima®.

Results: The median age at diagnosis was 60.1 years and 46 patients were men (97 MPA and 42 GPA patients). Among poor outcomes, patients receiving rituximab exhibited a significantly lower cumulative relapse-free survival rate compared to those not receiving rituximab (=0.002). Nevertheless, rituximab use did not make any difference in other poor outcomes of MPA and GPA except for relapse, which might be a rebuttal to the fact that rituximab use after relapse eventually led to better prognosis. There were no significant differences in variables at diagnosis and during follow-up between patients receiving Mabthera® and those receiving Truxima®. Patients receiving Truxima® exhibited a similar pattern of the cumulative survival rates of each poor outcome to those receiving Mabthera®.

Conclusion: Truxima® prevents poor outcomes of MPA and GPA as effectively as does Mabthera®.
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http://dx.doi.org/10.3349/ymj.2020.61.8.712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393299PMC
August 2020

Serum Mannose-Binding Lectin Levels Are Correlated with the Disease Activity of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Single-Center Study.

Tohoku J Exp Med 2020 06;251(2):117-123

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine.

Mannose-binding lectin (MBL) is a soluble pattern-recognition molecule, which plays a crucial role in the innate immune system and the activation of lectin complement pathway. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune disease affecting the small vasculatures and is characterized by the alteration of innate and adaptive immunity and complement activation. In this study, we investigated whether serum MBL is associated with disease activity of AAV, which was measured by ELISA. Associations between serum MBL and AAV-specific indices, as well as clinical and laboratory data were assessed using Kendall's tau. Among the 80 patients, 42 (52.5%), 21 (26.3), and 17 (21.3%) patients were classified as microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA), respectively. The median values of erythrocyte sedimentation rate, C-reactive protein, and serum MBL were 36.5 (normal range < 20) mm/h, 2.4 (normal range < 8) mg/dL, and 8.6 ng/mL, respectively. The median serum levels of MBL in MPA, GPA, and EGPA patients were 8.4, 9.3, and 8.2 ng/mL. Correlation analysis showed that serum MBL was associated with Birmingham Vasculitis Activity Score (BVAS) (R = 0.169, p = 0.027), but not with other AAV-specific indices and clinical and laboratory data. In addition, serum MBL was significantly associated with the pulmonary manifestation score based on BVAS (R = 0.247, p = 0.001). In summary, among the AAV-specific indices and clinical and laboratory variables analyzed, serum MBL is correlated with BVAS and pulmonary manifestation score based on the BVAS.
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http://dx.doi.org/10.1620/tjem.251.117DOI Listing
June 2020

Association between the antineutrophil cytoplasmic antibody and late coronary arterial occlusive disease in patients with Takayasu arteritis.

J Cardiol 2020 10 30;76(4):407-412. Epub 2020 May 30.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea; Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, Republic of Korea. Electronic address:

Background: No study has provided evidence of the clinical significance of the antineutrophil cytoplasmic antibody (ANCA) in patients with Takayasu arteritis (TAK). Therefore, we investigated the frequency of ANCA positivity and its clinical implications in patients with TAK.

Methods: We retrospectively reviewed the medical records of 121 patients with established TAK, who had results for ANCA status at diagnosis. We collected demographic and clinical data and the ANCA results at diagnosis. Additionally, we obtained information on patients' medications and complications during follow-up. Early coronary arterial occlusive disease (CAOD) and late CAOD were defined based on a 30-day interval after TAK classification. The chi-square test, Fisher's exact test, Mann-Whitney test, and Kaplan-Meier survival analysis were used to analyze the data.

Results: The patients' mean age was 44.6 years, and 21 patients were men (17.4%). ANCA was detected in 8 patients (6.6%), of which 2 had both the myeloperoxidase ANCA (or perinuclear ANCA) and proteinase 3 ANCA (or cytoplasmic ANCA). Early CAOD was observed in 10 patients (8.3%), and late CAOD was found in 9 patients (7.4%). In the comparative analysis, the proportion of late CAOD exhibited a tendency to increase in the ANCA-positive group compared to that in the ANCA-negative group. Kaplan-Meier analysis showed that patients with ANCA exhibited a lower cumulative late CAOD-free survival rate than those without ANCA (p=0.012). When the algorithm for the classification of ANCA-associated vasculitis (AAV) proposed by the European Medicine Agency in 2007 was applied to 8 patients with ANCA, all were not reclassified as having AAV.

Conclusions: ANCA can be detected in a minority of patients with established TAK, and it may not contribute to the reclassification of AAV. Furthermore, ANCA positivity may be associated with late CAOD in patients with TAK.
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http://dx.doi.org/10.1016/j.jjcc.2020.04.010DOI Listing
October 2020

Hyperuricemia is associated with decreased renal function and occurrence of end-stage renal disease in patients with microscopic polyangiitis and granulomatosis with polyangiitis: a retrospective study.

Rheumatol Int 2020 Jul 20;40(7):1089-1099. Epub 2020 Apr 20.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea.

Current evidence suggests that high uric acid levels are associated with accelerated renal damage. However, the clinical impact of serum uric acid level on patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) is unknown. We aimed to evaluate the impact of hyperuricemia on such patients. A retrospective study was performed to obtain patients' demographic, clinical, and laboratory data from when they were diagnosed with MPA and GPA. Multivariable logistic regression and Cox hazard model analyses were performed to evaluate factors associated with hyperuricemia at diagnosis and predictive factors of end-stage renal disease (ESRD) development. Among 156 patients, 35 (22.4%) had hyperuricemia at baseline. Hyperuricemic patients had renal manifestation and impaired renal function more frequently than non-hyperuricemic patients. Logistic regression analysis revealed that serum creatinine was significantly associated with hyperuricemia at diagnosis [odds ratio 1.995; 95% confidence interval (CI), 1.503-2.648; P < 0.001]. Cox hazard model analysis revealed that body mass index and serum creatinine were significantly associated with ESRD when all variables were included, but hyperuricemia was independently associated with ESRD [hazard ratio (HR), 3.799; 95% CI 1.719-8.222; P < 0.001) when serum creatinine was excluded. Additionally, in a subgroup analysis of patients with decreased glomerular filtration rates (GFRs), serum uric acid was the sole predictor of ESRD (HR, 1.243; 95% CI 1.048-1.475; P = 0.013). Hyperuricemia is associated with renal damage and ESRD occurrence in MPA and GPA patients. Serum uric acid level is associated with ESRD occurrence in patients with decreased GFRs.
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http://dx.doi.org/10.1007/s00296-020-04579-4DOI Listing
July 2020

Application of the 2019 classification criteria for systemic lupus erythematosus to patients with established ANCA-associated vasculitis.

Clin Exp Rheumatol 2020 Mar-Apr;38 Suppl 124(2):243-244. Epub 2020 Mar 13.

Division of Rheumatology, Department of Internal Medicine and Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, Republic of Korea.

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September 2020

Energy Level-Graded Al-Doped ZnO Protection Layers for Copper Nanowire-Based Window Electrodes for Efficient Flexible Perovskite Solar Cells.

ACS Appl Mater Interfaces 2020 Mar 16;12(12):13824-13835. Epub 2020 Mar 16.

Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.

Flexible perovskite solar cells (PSCs) have attracted significant interest as promising candidates for portable and wearable devices. Copper nanowires (CuNWs) are promising candidates for transparent conductive electrodes for flexible PSCs because of their excellent conductivity, flexibility, and cost-effectiveness. However, because of the thermal/chemical instability of CuNWs, they require a protective layer for application in PSCs. Previous PSCs with CuNW-based electrodes generally exhibited poor performances compared with their indium tin oxide-based counterparts because of the neglect of the interfacial energetics between the electron transport layer (ETL) and CuNWs. Herein, an Al-doped ZnO (AZO) protective layer fabricated using atomic layer deposition is introduced. The AZO/CuNW-based composite electrode exhibits improved thermal/chemical stability and favorable band alignment between the ETL and CuNWs, based on the Al dopant concentration tuning. As a result, the Al content gradient AZO (g-AZO), composed of three successively deposited AZO layers, leads to highly efficient flexible PSCs with a power conversion efficiency (PCE) of 14.18%, whereas the PCE of PSCs with a non-g-AZO layer is 12.34%. This improvement can be attributed to the efficient electron extraction and reduced charge recombination. Furthermore, flexible PSCs based on g-AZO-based composite electrodes retain their initial PCE, even after 600 bending cycles, demonstrating excellent mechanical stability.
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http://dx.doi.org/10.1021/acsami.9b21290DOI Listing
March 2020

Clinical implication of chronic paranasal sinusitis for the classification of microscopic polyangiitis.

Int J Clin Pract 2020 Jan 14;74(1):e13431. Epub 2019 Oct 14.

Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.

Background: Chronic paranasal sinusitis (CPS) has been known as a surrogate marker for granulomatosis with polyangiitis (GPA). We investigated whether CPS at diagnosis may have an influence on the classification and outcomes of microscopic polyangiitis (MPA).

Methods: We retrospectively reviewed the medical records of 106 immunosuppressive drug-naïve patients with MPA. We compared variables at diagnosis of MPA patients with CPS with either MPA patients without CPS or 29 GPA patients with CPS. We applied the algorithm for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) proposed by the European Medicine Agency to 22 MPA patients with CPS and reclassify them. Death, relapse and end-stage renal disease were assessed as the poor outcomes.

Results: Except for ENT manifestations, only pulmonary manifestation was more frequently observed in MPA patients with CPS than those without (77.3% vs 47.6%). No proteinase 3-ANCA was detected in all MPA patients with CPS. Meanwhile, general (63.6% vs 27.6%) and renal manifestations (81.8% vs 44.8%) more often developed in MPA patients with CPS than GPA patients with CPS. Of 22 MPA patients with CPS, 21 patients underwent biopsies. When CPS was not considered as a surrogate marker for GPA, all patients with CPS were reclassified as MPA. Ground glass opacity and reticulation on high-resolution computed tomography and renal vasculitis were helpful clues supporting the classification of MPA in patients with CPS. CPS at diagnosis was not associated with the outcomes of MPA.

Conclusion: CPS might not be a sufficient surrogate marker for GPA in the classification of AAV.
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http://dx.doi.org/10.1111/ijcp.13431DOI Listing
January 2020

Strain-Mediated Phase Stabilization: A New Strategy for Ultrastable α-CsPbI Perovskite by Nanoconfined Growth.

Small 2019 May 4;15(21):e1900219. Epub 2019 Apr 4.

Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Republic of Korea.

All-inorganic cesium lead triiodide (CsPbI ) perovskite is considered a promising solution-processable semiconductor for highly stable optoelectronic and photovoltaic applications. However, despite its excellent optoelectronic properties, the phase instability of CsPbI poses a critical hurdle for practical application. In this study, a novel stain-mediated phase stabilization strategy is demonstrated to significantly enhance the phase stability of cubic α-phase CsPbI . Careful control of the degree of spatial confinement induced by anodized aluminum oxide (AAO) templates with varying pore sizes leads to effective manipulation of the phase stability of α-CsPbI . The Williamson-Hall method in conjunction with density functional theory calculations clearly confirms that the strain imposed on the perovskite lattice when confined in vertically aligned nanopores can alter the formation energy of the system, stabilizing α-CsPbI at room temperature. Finally, the CsPbI grown inside nanoporous AAO templates exhibits exceptional phase stability over three months under ambient conditions, in which the resulting light-emitting diode reveals a natural red color emission with very narrow bandwidth (full width at half maximum of 33 nm) at 702 nm. The universally applicable template-based stabilization strategy can give in-depth insights on the strain-mediated phase transition mechanism in all-inorganic perovskites.
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http://dx.doi.org/10.1002/smll.201900219DOI Listing
May 2019

Time-Resolved Observations of Photo-Generated Charge-Carrier Dynamics in SbSe Photocathodes for Photoelectrochemical Water Splitting.

ACS Nano 2018 Nov 29;12(11):11088-11097. Epub 2018 Oct 29.

Solar-energy conversion by photoelectrochemical (PEC) devices is driven by the separation and transfer of photogenerated charge carriers. Thus, understanding carrier dynamics in a PEC device is essential to realizing efficient solar-energy conversion. Here, we investigate time-resolved carrier dynamics in emerging low-cost SbSe nanostructure photocathodes for PEC water splitting. Using terahertz spectroscopy, we observed an initial mobility loss within tens of picoseconds due to carrier localization and attributed the origin of carrier localization to the rich surface of SbSe nanostructures. In addition, a possible recombination at the interface between SbSe and the back contact is elucidated by time-resolved photoluminescence analysis. We also demonstrated the dual role of the RuO co-catalyst in reducing surface recombination and enhancing charge transfer in full devices using intensity-modulated spectroscopy. The relatively low onset potential of the SbSe photocathode is attributed to the sluggish charge transfer at a low applied bias rather than to fast surface recombination. We believe that our insights on carrier dynamics would be an important step toward achieving highly efficient SbSe photocathodes.
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http://dx.doi.org/10.1021/acsnano.8b05446DOI Listing
November 2018

All-Solution-Processed Thermally and Chemically Stable Copper-Nickel Core-Shell Nanowire-Based Composite Window Electrodes for Perovskite Solar Cells.

ACS Appl Mater Interfaces 2018 Sep 30;10(36):30337-30347. Epub 2018 Aug 30.

Department of Materials Science and Engineering , Yonsei University , 50 Yonsei-ro , Seodaemun-gu, Seoul 03722 , Republic of Korea.

Organic-inorganic hybrid perovskite solar cells (PSCs) have recently attracted tremendous attention because of their excellent efficiency and the advantage of a low-cost fabrication process. As a transparent electrode for PSCs, the application of copper nanowire (CuNW)-network was limited because of its thermal/chemical instability, despite its advantages in terms of high optical/electrical properties and low-cost production. Here, the copper-nickel core-shell nanowire ([email protected] NW)-based composite electrode is proposed as a bottom window electrode for PSCs, without the involvement of a high-cost precious metal and vacuum process. The dense and uniform Ni protective shell for CuNWs is attainable by simple electroless plating, and the resulting [email protected] NWs exhibit outstanding chemical stability as well as thermal stability compared with bare CuNWs. When the Ni layer with the optimal thickness is introduced, the [email protected] NW electrode shows a high transmittance of 80.5% AVT at 400-800 nm, and a sheet resistance of 49.3 ± 5 Ω sq. Using the highly stable [email protected] NWs, the composite electrode structure is fabricated with sol-gel-derived Al-doped zinc oxide (AZO) over-layer for better charge collection and additional protection against iodine ions from the perovskite. The PSCs fabricated with AZO/[email protected] NW-based composite electrode demonstrate a power conversion efficiency (PCE) of 12.2% and excellent long-term stability maintaining 91% of initial PCE after being stored for 500 h at room temperature. Experimental results demonstrate the potential of highly stable [email protected] NW-based electrodes as the cost-effective alternative transparent electrode, which can facilitate the commercialization of PSCs.
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http://dx.doi.org/10.1021/acsami.8b09266DOI Listing
September 2018

Investigating Recombination and Charge Carrier Dynamics in a One-Dimensional Nanopillared Perovskite Absorber.

ACS Nano 2018 05 24;12(5):4233-4245. Epub 2018 Apr 24.

Department of Materials Science and Engineering , Yonsei University 50 Yonsei-ro , Seodaemun-gu, Seoul 120-749 , Republic of Korea.

Organometal halide perovskite materials have become an exciting research topic as manifested by intense development of thin film solar cells. Although high-performance solar-cell-based planar and mesoscopic configurations have been reported, one-dimensional (1-D) nanostructured perovskite solar cells are rarely investigated despite their expected promising optoelectrical properties, such as enhanced charge transport/extraction. Herein, we have analyzed the 1-D nanostructure effects of organometal halide perovskite (CHNHPbICl ) on recombination and charge carrier dynamics by utilizing a nanoporous anodized alumina oxide scaffold to fabricate a vertically aligned 1-D nanopillared array with controllable diameters. It was observed that the 1-D perovskite exhibits faster charge transport/extraction characteristics, lower defect density, and lower bulk resistance than the planar counterpart. As the aspect ratio increases in the 1-D structures, in addition, the charge transport/extraction rate is enhanced and the resistance further decreases. However, when the aspect ratio reaches 6.67 (diameter ∼30 nm), the recombination rate is aggravated due to high interface-to-volume ratio-induced defect generation. To obtain the full benefits of 1-D perovskite nanostructuring, our study provides a design rule to choose the appropriate aspect ratio of 1-D perovskite structures for improved photovoltaic and other optoelectrical applications.
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http://dx.doi.org/10.1021/acsnano.7b07559DOI Listing
May 2018

Facile Sol-Gel-Derived Craterlike Dual-Functioning TiO Electron Transport Layer for High-Efficiency Perovskite Solar Cells.

ACS Appl Mater Interfaces 2018 May 17;10(17):14649-14658. Epub 2018 Apr 17.

Department of Materials Science and Engineering , Yonsei University , 50 Yonsei-ro Seodaemun-gu , Seoul 03722 , Republic of Korea.

Organic-inorganic hybrid perovskite solar cells (PSCs) are considered promising materials for low-cost solar energy harvesting technology. An electron transport layer (ETL), which facilitates the extraction of photogenerated electrons and their transport to the electrodes, is a key component in planar PSCs. In this study, a new strategy to concurrently manipulate the electrical and optical properties of ETLs to improve the performance of PSCs is demonstrated. A careful control over the Ti alkoxide-based sol-gel chemistry leads to a craterlike porous/blocking bilayer TiO ETL with relatively uniform surface pores of 220 nm diameter. Additionally, the phase separation promoter added to the precursor solution enables nitrogen doping in the TiO lattice, thus generating oxygen vacancies. The craterlike surface morphology allows for better light transmission because of reduced reflection, and the electrically conductive craterlike bilayer ETL enhances charge extraction and transport. Through these synergetic improvements in both optical and electrical properties, the power conversion efficiency of craterlike bilayer TiO ETL-based PSCs could be increased from 13.7 to 16.0% as compared to conventional dense TiO-based PSCs.
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http://dx.doi.org/10.1021/acsami.8b00549DOI Listing
May 2018

Enhanced compatibility between a copper nanowire-based transparent electrode and a hybrid perovskite absorber by poly(ethylenimine).

Nanoscale 2017 Nov;9(44):17207-17211

Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.

Copper nanowires (CuNWs) have been applied to hybrid perovskite solar cells (PSCs) as a window electrode. By sandwiching the CuNW network between aluminum-doped zinc oxide and adopting a poly(ethylenimine) buffer layer, the compatibility between the CuNWs and the perovskite layer could be dramatically improved. PSCs containing the CuNW-based composite electrode exhibited an average power conversion efficiency of 8.65%.
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http://dx.doi.org/10.1039/c7nr04739hDOI Listing
November 2017

Retarding Crystallization during Facile Single Coating of NaCl-Incorporated Precursor Solution for Efficient Large-Area Uniform Perovskite Solar Cells.

ACS Appl Mater Interfaces 2016 Nov 21;8(43):29419-29426. Epub 2016 Oct 21.

Department of Materials Science and Engineering, Yonsei University , Seoul 120-749, Republic of Korea.

We demonstrated crystallization retardation of CHNHPbI thin film during single coating of precursor solution by simple addition of NaCl. NaCl was codissolved into a precursor mixture solution containing PbI and methylammonium iodide (MAI). Dissolved NaCl interacted with the PbI in solution and produced a stable intermediate phase, which was converted to a full-coverage uniform perovskite absorber layer via reaction with MAI during a single spin-coating. The resulting planar-structure perovskite solar cell made from NaCl-supplemented precursor solution showed a 48% improvement in power conversion efficiency (PCE) (maximum value 15.16%) over the device fabricated without the additive. Our NaCl-supplemented single coating represents an easy approach to effectively obtain highly reproducible uniform performance at an overall position in 5 cm × 5 cm sized cells (divided into 20 subcells with an active area of 0.06 cm) with average PCEs of 12.00 ± 0.48%.
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http://dx.doi.org/10.1021/acsami.6b08783DOI Listing
November 2016

Enhancing the developmental competence of the early embryo using secretory leukocyte peptidase inhibitor.

Differentiation 2016 Jul-Aug;92(1-2):24-34. Epub 2016 Feb 28.

Department of Biosciences, Institute of Basic Sciences, College of Natural Sciences, Sungshin Women's University, Seoul 136-742, Republic of Korea. Electronic address:

Secretory leukocyte peptidase inhibitor (SLPI) plays a role in proliferation and differentiation via the autocrine and paracrine systems. SLPI's expression is well-documented in the reproductive tract, but it remains unclear whether it is active during early embryonic development. In this study, the expression and role of Slpi in the early embryo were evaluated. In vitro embryo cultures in chemically defined simple medium resulted in a reduction in developmental speed from the 8-cell stage, as well as implantation rate compared with in vivo embryos. SLPI protein was localized to the membrane or submembrane cytoplasm in an embryonic stage-dependent manner. In vitro cultured embryos exhibited lower levels of Slpi mRNA expression than in vivo embryos. Slpi knockdown by antisense oligonucleotides attenuated the developmental speed and implantation rate compared with Slpi sense oligonucleotide-transfected embryos and in vitro controls. The critical period for the attenuation of developmental speed occurred after the 8-cell stage. SLPI treatment accelerated development, increased implantation rate, and ameliorated the suppressive effects of Slpi knockdown. Slpi knockdown did not induce changes in the total cell number or inner cell number in blastocysts. Meanwhile, SLPI upregulated the expression of the developmental factors matrix metalloproteinase-14, neutrophil elastase, and tissue inhibitor of metalloproteinase-1. Together, these results suggest that SLPI is an effective regulator of developmental speed and implantation competence in an autocrine and paracrine manner, respectively, and plays a role in controlling the expression of embryonic development factors, such as MMP family members.
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http://dx.doi.org/10.1016/j.diff.2016.02.004DOI Listing
September 2017

Fully solution-processed transparent electrodes based on silver nanowire composites for perovskite solar cells.

Nanoscale 2016 Mar;8(12):6308-16

Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, Republic of Korea.

We report all-solution-processed transparent conductive electrodes based on Ag nanowire (AgNW)-embedded metal oxide composite films for application in organometal halide perovskite solar cells. To address the thermal instability of Ag nanowires, we used combustive sol-gel derived thin films to construct ZnO/ITO/AgNW/ITO composite structures. The resulting composite configuration effectively prevented the AgNWs from undergoing undesirable side-reactions with halogen ions present in the perovskite precursor solutions that significantly deteriorate the optoelectrical properties of Ag nanowires in transparent conductive films. AgNW-based composite electrodes had a transmittance of ∼80% at 550 nm and sheet resistance of 18 Ω sq(-1). Perovskite solar cells fabricated using a fully solution-processed transparent conductive electrode, Au/spiro-OMeTAD/CH3NH3PbI3 + m-Al2O3/ZnO/ITO/AgNW/ITO, exhibited a power conversion efficiency of 8.44% (comparable to that of the FTO/glass-based counterpart at 10.81%) and were stable for 30 days in ambient air. Our results demonstrate the feasibility of using AgNWs as a transparent bottom electrode in perovskite solar cells produced by a fully printable process.
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http://dx.doi.org/10.1039/c5nr04585aDOI Listing
March 2016

Clinical utility of chimerism status assessed by lineage-specific short tandem repeat analysis: experience from four cases of allogeneic stem cell transplantation.

Korean J Lab Med 2009 Aug;29(4):277-81

Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.

Chimerism testing permits early prediction and documentation of successful engraftment, and also facilitates detection of impending graft rejection. In this study, we serially monitored chimerism status by short tandem repeat-based PCR in nucleated cells (NC), T cells and natural killer (NK) cells after myeloablative allogeneic stem cell transplantation (SCT). Four patients with myeloid malignancies showed discrepant chimerism results among those three fractions. Three patients had mixed chimerism (MC) of donor/host T cells at a time point around the onset of chronic graft-versus-host disease (GVHD). In two patients with disease relapse, MC of NK cells preceded a morphological relapse or NK cells showed a higher percentage of patient cells compared to NC. Therefore, our study shows that chimerism analysis in lineage-specific cells might be useful in predicting clinical outcome after allogeneic SCT in certain patients.
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http://dx.doi.org/10.3343/kjlm.2009.29.4.277DOI Listing
August 2009