[Show abstract][Hide abstract] ABSTRACT: Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.
[Show abstract][Hide abstract] ABSTRACT: We numerically and experimentally demonstrated a metamaterial perfect absorber (MPA) in MHz region based on a planar sandwiched metal-dielectric-metal structure. First, the single-peak perfect absorption was obtained at 400 MHz. The ratios of the periodicity of unit cells and the thickness to the absorption wavelength are 1/12 and 1/94, respectively. The advantage of structural design and the mechanism for the low-frequency MPA are described in detail by the comparison between calculation, simulation, and experiment. Influence of the incident angle of electromagnetic (EM) wave for both transverse-electric (TE) and transverse-magnetic (TM) polarization on absorption was also investigated, and the absorption was maintained to be above 95% at incident angles up to
. Finally, we propose a self-asymmetric structure, which induces the dual-band perfect absorption in the same range of frequency. The EM behavior of the excitation modes and the mechanism of the dual-band MPA are clearly explained. Especially, when two resonance modes are finely controlled to be close enough, the bandwidth (full width at half maximum) of MPA is enhanced to be nearly wider twice than that in case of single-peak perfect absorption. The enhanced bandwidth is still well preserved by varying the incident angle up to
for both TE and TM polarization. The results were also confirmed by both simulation and experiment. Our work is promising for potential practical applications in the radio range, such as radio-frequency shielding devices, single/dual-frequency filters, and switching devices.
[Show abstract][Hide abstract] ABSTRACT: We propose polarization-independent and dual-broadband metamaterial absorbers at microwave frequencies. This is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones. We demonstrate not only one broadband absorption from the fundamental magnetic resonances but additional broadband absorption in high-frequency range using the third-harmonic resonance, by both simulation and experiment. In simulation, the absorption was over 90% in 3.93–6.05 GHz, and 11.64–14.55 GHz. The corresponding experimental absorption bands over 90% were 3.88–6.08 GHz, 9.95–10.46 GHz and 11.86–13.84 GHz, respectively. The origin of absorption bands was elucidated. Furthermore, it is independent of polarization angle owing to the multilayered circular structures. The design is scalable to smaller size for the infrared and the visible ranges.
[Show abstract][Hide abstract] ABSTRACT: A small-size metamaterial perfect absorber operating at low frequency is proposed. Due to the special design, the unit-cell dimension with respect to wavelength is very small, a/λ ~ 1/17, at the absorption frequency of 377 MHz. The absorption frequency is strongly dependent on the length of zigzag wire. In addition, the absorption is more than 94% in a wide range of incident angle of electromagnetic wave up to 50°. The results show that the proposed absorber is promising to be applied into devices in radio region.
Advances in Natural Sciences: Nanoscience and Nanotechnology 11/2014; 5(4):045008. DOI:10.1088/2043-6262/5/4/045008
[Show abstract][Hide abstract] ABSTRACT: Objective
We aimed to investigate the prevalence and psychosocial and neurophysiological correlates of depression in a large county-based cohort of Korean adults.
We recruited 2355 adults from a rural county-based health promotion program. The following psychometric scales were used: the Center for Epidemiologic Studies Depression scale (CES-D) was used to assess depression, the General Health Questionnaire (GHQ) was used to evaluate stress, and the Medical Outcome Study Social Support Survey (MOS-SSS) was used to determine perceived social support. Heart rate variability (HRV) was used to assess neurophysiological properties. The psychosocial and neurophysiological variables of adults with depression (CES-D score ≥25) and without depression (CES-D score <25) were statistically compared. A logistic regression model was constructed to identify factors independently associated with depression.
We estimated that 17.7% of the subjects had depression, which was associated with old age, being female, being single, less religious affiliation, high education, low body mass index (BMI), low levels of aerobic exercise, low social support, and a low HRV triangular index. The explanatory factors of depression included high education, less religious affiliation, low levels of current aerobic exercise, low BMI, and low social support.
Given the relatively high prevalence of overall depression, subsyndromal depression should also be regarded as an important issue in screening. The independent factors associated with depression suggest that practical psychosocial intervention, including brief psychotherapy, aerobic exercise, and other self-help methods should be considered. In addition, the HRV results suggest that further depression screening accompanied by neurophysiological features would require fine methodological modifications with proactive efforts to prevent depressive symptoms.
[Show abstract][Hide abstract] ABSTRACT: The effects of the electron mobilities and energy levels of different electron transport layer (ETL) materials on the performances were systemically investigated in blue phosphorescent organic light-emitting diodes. The spatial control of recombination zone (RZ) which was accompanied with triplet exciton quenching affected the balance between holes and electrons in the emission layer, resulting in the variations of the device performances. An optical micro-cavity effect in the electroluminescence (EL) spectrum around 500 nm was noticed by employing tris(8-hydroxyquinolinolato)aluminum (Alq(3)) ETL. This was attributed to the broadening of the emission zone through the emission layer over the ETL, exhibiting the greenish color coordinates. The current efficiency of the device with 3-phenyl-4(10-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) ETL was much higher than that of the same structured device with any other ETL due to better charge balance as Well as the suppression of triplet exciton quenching by the narrow RZ with low electron mobility and proper band alignment.
[Show abstract][Hide abstract] ABSTRACT: We propose a dual-band metamaterial perfect absorber at microwave frequencies. Using a planar metamaterial, which consists of periodic metallic donut-shape meta-atoms at the front separated from the metallic plane at the back by a dielectric layer, we demonstrate the multi-plasmonic high-frequency perfect absorptions induced by the third-harmonic as well as the fundamental magnetic resonances. The origin of the induced multi-plasmonic perfect absorption was elucidated. It was also found that the perfect absorptions at dual peaks are persistent with varying polarization.
[Show abstract][Hide abstract] ABSTRACT: The classical electromagnetically-induced transparency (EIT)-like switching in metamaterials was experimentally demonstrated in the microwave-frequency region. The metameterial unit cell consists of two identical split-ring resonators, which are arranged on both sides of a dielectric substrate with 90°-rotation asymmetry. In our scheme, the classical EIT-like switching can be achieved by changing the polarization of the incident electromagnetic wave.
[Show abstract][Hide abstract] ABSTRACT: We propose multi-band metamaterial absorbers at microwave frequencies. The design, the analysis, the fabrication, and the measurement of the absorbers working in multiple bands are presented. The numerical simulations and the experiments in the microwave anechoic chamber were performed. The metamaterial absorbers consist of an delicate arrangement of donut-shape resonators with different sizes and a metallic background plane, separated by a dielectric. The near-perfect absorptions of dual, triple and quad peaks are persistent with polarization independence, and the effect of angle of incidence for both TE and TM modes was also elucidated. It was also found that the multiple-reflection theory was not suitable for explaining the absorption mechanism of our investigated structures. The results of this study are promising for the practical applications.
[Show abstract][Hide abstract] ABSTRACT: Q fever is a zoonosis caused by a Coxiella burnetii. Q fever is clinically variable, presenting as asymptomatic infection, pneumonia, hepatitis and endocarditis. Treatment of acute Q fever with doxycycline is usually successful. Autoantibodies, such as anti-mitochondrial antibodies, smooth muscle antibodies (SMA), anti-cardiolipin and lupus anticoagulant, often rise in acute Q fever infection. Some cases may occasionally meet the criteria for autoimmune disease like systemic lupus erythematosus. We report a first case of Q fever that may mimic systemic lupus erythematosus in Korea.
[Show abstract][Hide abstract] ABSTRACT: LiCoO2 thin films were fabricated by direct current magnetron sputtering method on STS304 and Ti substrates. The effects of substrate and annealing on their structural and electrochemical properties of LiCoO2 thin film cathode were studied. Crystal structures and surface morphologies of the deposited films were investigated by X-ray diffraction and field emission scanning electron microscopy. The as-deposited films on both substrates have amorphous structure. The (104) oriented perfect crystallization was obtained by annealing over 600 degrees C in STS304 substrate. The LiCoO2 thin film deposited on Ti substrate shows the (003) texture after annealing at 700 degrees C. The electrochemical properties were investigated by the cyclic voltammetry and charge-discharge measurement. The 600 degrees C-annealed LiCoO2 film deposited on STS304 substrate exhibits the inithial discharge capacity of 22 uAh/cm2 and the 96% capacity retention rate at 50th cycles. The electrochemical measurement on annealed films over 600 degrees C was impossible due to the formed TiO2 insulator layer using Ti substrate. As a result, it was found that the STS304 substrate seems to be more suitable material than the Ti substrate in fabricating LiCoO2 thin film cathode.
Journal of Nanoscience and Nanotechnology 07/2012; 12(7):5937-41. DOI:10.1166/jnn.2012.6399 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We experimentally demonstrated a controllable electromagnetically induced transparency (EIT)-like spectral response at microwave frequencies in a planar metamaterial consisting of two identical split-ring resonators (SRRs) with side-by-side symmetry. In our scheme, phase coupling between the two SRRs (serving as the bright mode), which were excited strongly by the incident wave, was employed, and it was found that the EIT-like spectral response could be controlled by simply adjusting the incident angle. Thus, our scheme may be used for electromagnetic-wave switching. A high group index for slow-light application and a high quality factor could be obtained by simply controlling the incident angle.
[Show abstract][Hide abstract] ABSTRACT: A 30-year-old man was admitted to our hospital because of fatigue, palpitation and severe weakness of both legs. The admission laboratory findings revealed thyrotoxicosis, and 131I thyroid scintigraphic imaging revealed a low radioactive iodine uptake. He was treated for painless thyroiditis for about 4 months. However, thyrotoxic state had continued and radioactive iodine uptake was markedly increased in the follow up scan. Painless thyroiditis often relapses, but rarely develops into Graves' disease. This is a rare case in which painless thyroiditis was followed by Graves' disease.
[Show abstract][Hide abstract] ABSTRACT: Insulin autoimmune syndrome is characterized by spontaneous hypoglycemia, elevated insulin level and a high level of insulin autoantibodies without previous insulin exposure. Among the clinical manifestations of insulin autoimmune syndrome, diabetic ketoacidosis is extremely rare. A 72-year-old diabetic woman was hospitalized with diabetic ketoacidosis. She suffered repeated fasting hypoglycemia after treatment of the diabetic ketoacidosis. Here we describe this case of insulin autoimmune syndrome manifested as diabetic ketoacidosis followed by recurrent hypoglycemia with a review of the relevant literature.
[Show abstract][Hide abstract] ABSTRACT: Hyperfunctioning thyroid carcinoma is very rare. Hence, radionuclide imaging of thyroid hot nodules usually suggests a benign tumor, and less than 4% of cases have been reported as malignant. We would like to present a case of a hyperfunctioning papillary thyroid carcinoma that was initially treated with radioactive iodine. A 58-year-old woman was referred to our hospital for palpable thyroid nodule and a 5-kg weight loss within 6 months. Thyroid function test revealed thyrotoxicosis, and thyroid autoantibodies were absent. 99mTc thyroid scintigraphy showed a 2 × 2 cm-sized hyperactive hot nodule at the left lobe. Despite radioactive iodine treatment with a dose of 10 mCi 131I, thyroid function did not improve. Fine needle aspiration revealed papillary thyroid cancer. The patient underwent total thyroidectomy. Although clinical features and thyroid scans suggest a benign nodule, the possibility of malignancy should not be ruled out. Malignant thyroid hot nodules are rare; however, its possibility should be taken into account. Therefore, we suggest that ruling out malignancy by existing diagnostic guidelines can misdiagnose even a typical case with benign features. As thyroid nodule detection is getting sensitive and accurate, we present this case to discuss whether additional diagnostic approaches would be necessary for thyroid nodules.
[Show abstract][Hide abstract] ABSTRACT: Using a planar metamaterial, which consists of two silver strips, we theoretically demonstrate the plasmonic electromagnetically-induced transparency (EIT)-like spectral response at optical frequencies. The two silver strips serve as the bright modes, and are excited strongly by the incident wave. Based on the weak hybridization between the two bright modes, a highly-dispersive plasmonic EIT-like spectral response appears in our scheme. Moreover, the group index is higher than that of another scheme which utilizes the strong coupling between the bright and dark modes.
[Show abstract][Hide abstract] ABSTRACT: We propose that the plasmonic electromagnetically-induced transparency (EIT) is accessible based on the second-order magnetic plasmon resonance (MPR) in the stacked optical metamaterial with a symmetric structure. In order to clarify the role of high-order MPR, we systematically analyze the propagation and the distribution of electromagnetic waves of the plasmonic EIT in both the symmetric and the asymmetric structures. This not only sharpens our understanding of the existing concept, but also provides a profound insight into the plasmonic coherent interference in the near-field zone.
[Show abstract][Hide abstract] ABSTRACT: Small bowel metastasis of pleomorphic carcinoma of the lung is very rare. A 58-year-old man was admitted to our hospital with abdominal palpable mass in the right upper quadrant area. He underwent right middle and lower lobectomy for early stage pleomorphic carcinoma of the lung approximately 3 months ago. USG-guided biopsy was performed for abdominal mass. Pathologic examination revealed a metastatic pleomorphic carcinoma from the lung. He received chemotherapy followed by radiation therapy but died due to septic shock caused by intestinal stenosis and adhesion. We report the first case of small bowel metastasis by pleomorphic carcinoma of the lung after curative surgery.
Tuberculosis and Respiratory Diseases 08/2011; 71(2):139. DOI:10.4046/trd.2011.71.2.139
[Show abstract][Hide abstract] ABSTRACT: Carbon nanotubes (CNTs) were purified using acid solution, and CNT-sulfur composite powder was prepared via precipitation, using the purified CNTs. In addition, the effect of the purified CNTs (PUCNTs) on the electrochemical performance of the Li/S cell was investigated. After the purification, almost all the impurities in the as-synthesized CNTs (ASCNTs) were removed, and the dispersibility of the CNTs was improved. On the other hand, the concentration of the structural defects and of the disordered structures in the PUCNTs was increased due to the surface oxidation of the tubes during acid treatment. In the case of the PUCNT-S composite powder, the outer wall of the tubes was well covered with sulfur, as opposed to the tubes in the ASCNT-S composite powder. The Li/S cell containing ASCNT-S composite cathode showed a large voltage decrease and a 680 mAh/g capacity during the first discharge process. The Li/S cell with PUCNT-S composite cathode, however, showed a higher discharge capacity and better cycle performance than the cell with ASCNT-S composite cathode. The electrochemical performance of the Li/S cell was improved for the PUCNT-S composite cathode using the CNTs purified by acid treatment.
Journal of Nanoscience and Nanotechnology 07/2011; 11(7):5800-5. DOI:10.1166/jnn.2011.4331 · 1.56 Impact Factor