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Structural and magnetic properties of tetragonal Mn1.19Fe0.81As thin film grown on Si(001)
황영훈,조성래,최정용,이민규,한석희,Sungyoul Choi,김용함 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.-
We have successfully grown MnxFe2-xAs (x = 1.19) thin film on Si(001) substrate by molecular beam epitaxy. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) studies indicate the rough film surface and c-axis orientation in a tetragonal crystal structure. Mn1.19Fe0.81As film exhibited ferrimagnetic ordering at room temperature, which is supported by magnetization, magnetoresistance and anomalous-Hall-effect measurements.
황영훈,Youngho Um,Hyekyeong Kim,Sunglae Cho,Sungyeol Choi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.4
We have investigated the Mn composition x and the temperature (12 K T 300 K) dependences of the energy gap of Zn1−xMnxSiAs2 crystals. Single crystals were grown by using the vertical Bridgman method for a series of Mn compositions x. The variation of the enery gap, Eg, with temperature follows the Varshni’s relation for all compositions. The energy gap decreased up to x 0.04. Thereafter, it increased with x. The energy gap bowing effect is related to the sp-d exchange interaction between the 3d electrons of magnetic Mn ions and the band electrons and to magnetic and chemical disorder.
황영훈,김동환,강창경,최평균,박완범,김남중,오명돈 대한의진균학회 2022 대한의진균학회지 Vol.27 No.4
Background: Coronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) is a life-threatening invasive fungal infection in critically ill patients with COVID-19. However, only a few studies have reported CAPA in the Republic of Korea. Objective: To describe clinical characteristics of CAPA in patients at a tertiary care hospital in the Republic of Korea. Methods: This retrospective, observational consecutive case series study was conducted by reviewing the electronic medical records of patients who developed CAPA at Seoul National University Hospital from January 1, 2020, to August 31, 2021. CAPA was defined by European Confederation of Medical Mycology/International Society for Human and Animal Mycology (ECMM/ISHAM) consensus criteria. Patient demographics, comorbidities, corticosteroid use, clinical presentation, treatment, and outcomes were investigated. Results: Eleven patients were diagnosed with probable CAPA according to the ECMM/ISHAM criteria. One patient had classical host factor for invasive pulmonary aspergillosis before admission. All patients received corticosteroid therapy before CAPA diagnosis. The mean total corticosteroid administered before CAPA diagnosis was 220 mg of dexamethasone equivalent dose (range, 80~572 mg), and the mean duration of steroid therapy was 15 days (range, 4~34 days). The median time from intensive care unit admission to CAPA diagnosis was 12 days (range, 5~36 days). All individuals showed aggravation on chest X-rays. Ten patients were diagnosed with positive serum galactomannan (GM), and one was diagnosed with positive GM in a bronchoalveolar lavage specimen. Of the 11 patients, 8 received voriconazole-based antifungal therapy for a median of 30.5 days. Only two patients survived after antifungal treatment. Conclusion: These cases illustrate CAPA complicated in critically ill COVID-19 patients. The challenges in diagnosis and poor outcomes of CAPA emphasize the clinical suspicion and needs for further investigation.
Coronavirus Disease 2019-Associated Pulmonary Aspergillosis
황영훈,박완범 대한의진균학회 2022 대한의진균학회지 Vol.27 No.1
As the coronavirus disease 2019 (COVID-19) pandemic continues, a new disease, COVID-19-associated pulmonary aspergillosis (CAPA), is on the rise. CAPA is a secondary fungal infection in patients with critical COVID-19 receiving mechanical ventilation in intensive care units (ICUs). Although the incidence rate of CAPA is estimated to be 10.2% in ICU patients, CAPA appears to be associated with an increase in overall mortality. CAPA is like classical invasive pulmonary aspergillosis (IPA) but has an ambiguous clinical manifestation and occurs without typical host factors. It is also like influenza-associated pulmonary aspergillosis but differs in clinical characteristics. For research and clinical practice, the European Confederation for Medical Mycology and the International Society for Human and Animal Mycology proposed novel case definition criteria for CAPA. Although CAPA management is not much different from typical IPA, areas of uncertainty remain that require further investigation.
황영훈,Youngho Um,Hyekyeong Kim,Hyoyeol Park,Sunglae Cho 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
We investigated the magneto-optical properties of diluted magnetic semiconductor Cd$_{0.63-y}$ Mn$_{0.37}$Co$_{y}$Te single crystals grown using a vertical Bridgman method. From the temperature dependence of the band-gap energy, the Varshni temperature parameter $\alpha$ was found to increase linearly with increasing Co concentration $y$ while $\beta$ decreased with $y$. The Faraday rotation as a function of photon energy with various Co compositions for CdMnCoTe in the temperature range of 10 to 300 K was measured. The Verdet dispersion curves were enhanced near the fundamental band gap energy. The Verdet constant becomes larger since because the effect of the $sp$-$d$ exchange interaction is enhanced as the temperature is lowered. At 10 K, the Verdet constants of the Faraday rotation for the samples with $y$ = 0, 0.01, 0.02, and 0.04 were observed to be --0.94, --1.41, --1.69, and --2.11 deg/G cm at 610 nm, respectively. The Verdet constant showed a maximum for the sample with $y$ = 0.04, and the value was approximately 2.3 times larger than that of the Cd$_{0.63}$Mn$_{0.37}$Te crystal. The Faraday rotation increased as Co content was increased, and the origin of the enhancement of the Faraday rotation in CdMnCoTe crystals could be explained in terms of the magnetization.
황영훈,이상목,강명승,임경오 연세대학교의과대학 2012 Yonsei medical journal Vol.53 No.1
We report a case of toxic epidermal necrolysis with ocular involvement following vaccination for hemorrhagic fever with renal syndrome. A healthy 20-year-old male soldier presented with confluent purpuric and erythematous dusky red macules evolving to flaccid blister and epidermal detachment on the whole body with conjunctival injection. The patient had no antecedent medical or surgical conditions except for two doses of hemorrhagic fever with renal syndrome vaccination. With supportive care, skin lesions were improved. Ophthalmic examinations revealed conjunctival injection with epithelial defects in both eyes. Ocular complications were resolved after amniotic membrane transplantation. Toxic epidermal necrolysis may be considered as a possible complication of hemorrhagic fever with renal syndrome vaccination.