D H Lee

Korea Centers for Disease Control and Prevention, Daiden, Daejeon, South Korea

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Publications (368)816.38 Total impact

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    ABSTRACT: We have examined relativistic electron flux losses at geosynchronous orbit under quiet geomagnetic conditions. One 3-day period, from 11 to 13 October 2007, was chosen for analysis because geomagnetic conditions were very quiet (3-day average of Kp <1), and significant losses of geosynchronous relativistic electrons were observed. During this interval, there was no geomagnetic storm activity. Thus, the loss processes associated with geomagnetic field modulations caused by ring current buildup can be excluded. The >2 MeV electron flux at geosynchronous orbit shows typical diurnal variations with a maximum near noon and a minimum near midnight for each day. The flux level of the daily variation significantly decreased from first day to thirdday for the 3-day period by a factor of >10. The total magnetic field strength (BT) of the daily variation on the third day, however, is comparable to that on the first day. Unlike electron flux decreases, the flux of protons with energies between 0.8 and 4 MeV adiabatically responses to the daily variation of BT. That is, there is no significant decrease of the proton flux when the electron flux decreases. During the interval of quiet geomagnetic conditions, well-defined electromagnetic ion cyclotron (EMIC) waves were detected at geosynchronous spacecraft. Low-altitude polar orbiting spacecraft observed the precipitation of energetic protons and relativistic electrons in the interval of EMIC waves enhancement. From these observations, we suggest that the EMIC waves at geosynchronous orbit cause pitch-angle scattering and relativistic electron losses to the atmosphere under quiet geomagnetic conditions.
    Journal of Geophysical Research: Space Physics 10/2014; · 3.44 Impact Factor
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    ABSTRACT: For 2-d X-ray imaging, such as mammography and non-destructive test, a sensor should have a large-area because the sensor for typical X-ray beams cannot use optical lens system. To make a large-area 2-d X-ray image sensor using crystal Si, a technique of tiling unit CMOS image sensors into 2 × 2 or 2 × 3 array can be used. In a unit CMOS image sensor made of most common 8-inch Si wafers, the signal line can be up to ~ 180 mm long. Then its parasitic capacitance is up to ~ 25 pF and its resistance is up to ~ 51 kΩ (0.18 μm, 1P3M process). This long signal line may enlarge the row time up to ~ 50 μsec in case of the signal from the top row pixels to the readout amplifiers located at the bottom of the sensor chip. The output signal pulse is typically characterized by three components in sequence; a charging time (a rising part), a reading time and a discharging time (a falling part). Among these, the discharging time is the longest, and it limits the speed or the frame rate of the X-ray imager. We proposed a forced discharging method which uses a bypass transistor in parallel with the current source of the column signal line. A chip for testing the idea was fabricated by a 0.18 μm process. A active pixel sensor with three transistors and a 3-π RC model of the long line were simulated together. The test results showed that the turning on-and-off of the proposed bypass transistor only during the discharging time could dramatically reduce the discharging time from ~ 50 μsec to ~ 2 μsec, which is the physically minimum time determined by the long metal line capacitance.
    Journal of Instrumentation 08/2014; 9(08):P08011. · 1.66 Impact Factor
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    ABSTRACT: When an interplanetary (IP) shock passes over the Earth's magnetosphere, the geosynchronous magnetic field strength near noon is always enhanced except for the magnetopause crossing events. Near midnight, however, it increases or decreases. This indicates that the nightside magnetosphere is not always compressed by a sudden increase in the solar wind dynamic pressure. To understand midnight geosynchronous magnetic field responses to IP shocks, we statistically examined geosynchronous magnetic field perturbations, corresponding to 120 sudden commencements (SCs), observed when geosynchronous spacecraft were near midnight between 2200 and 0200 magnetic local times. Out of the 120 SCs, 107 SCs were identified by one geosynchronous spacecraft, and 13 SCs were identified by two geosynchronous spacecraft. Thus, 133 events were used in our statistical study. We observed 23 events in spring, 40 events in summer, 32 events in fall, and 38 events in winter, respectively. A statistical study of the midnight geosynchronous SC perturbations reveals the following characteristics. (1) In summer, all events show a positive enhancement (+ΔBT) in the magnetic field strength. (2) In winter, however, ΔBT exhibits a positive (+ΔBT) or negative (−ΔBT) enhancement. (3) In summer, the midnight geosynchronous SC perturbations in the BH component (positive northward) in VDH coordinates are mostly (~88%, 35 out of 40 events) positive (+ΔBH), while the occurrence rate of the positive perturbation (~43%) in the Bz component (positive northward) in GSM coordinates is lower than that of the negative perturbation (~57%). (4) In winter, the negative perturbations in ΔBH (~61%) and ΔBz (~74%) are dominant. (5) Both the north-south components (BH and Bz) in spring and fall are scattered around zero. To explain the observations we suggest that SC-associated cross-tail current (JSC) has a peak intensity around geosynchronous orbit thus is a main controlling factor of midnight geosynchronous magnetic field perturbations during SCs. Specifically, we suggest that the seasonal variation of the sign of ΔBH, ΔBz, and ΔBT is due to the seasonal variation of the spacecraft position relative to JSC.
    Journal of Geophysical Research: Space Physics 06/2014; · 3.44 Impact Factor
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    ABSTRACT: Purpose A national organ transplant registry is an indispensable organizational requirement for patient care, research, and planning. Even though the Korean Network for Organ Sharing (KONOS) has established a database for a waiting list, organ allocation, and incidence of organ transplantation since 2000, an integrated registry including post-transplantation data is needed for better understanding of organ transplantation. Recently, the Korean Society for Transplantation (KST) and the Korean Center for Disease Control (KCDC) designed a web-based organ transplant registry, named the Korean Organ Transplant Registry (KOTRY). As an initial project of KOTRY, we retrospectively analyzed kidney transplantations (KTs) performed in 2009 and 2010. Methods A total of 2292 KTs (91.9%) from 46 hospitals (80.7%) were collected and analyzed. Ninety-five elements related to KT were selected and analyzed. Results Proportions of male recipients and retransplantations were 58.4% and 7.1%, respectively. Even though glomerulonephritis was the most common cause of end-stage renal disease (ESRD) (28.4%), the number of diabetic nephropathy cases was increasing. The living donor (LD) to deceased donor (DD) ratio was 1.69:1. Because of a serious organ shortage in Korea, DD kidneys with a low initial estimated glomerular filtration rate (eGFR) of <45 mL/min/1.73 m2 (21.2%) and expanded criteria donors (ECDs; 18.3%) are frequently used. Other noticeable findings are the increasing number of wife donors and ABO-incompatible (ABOi) transplants for O+ recipients. Conclusions The epidemiological profile of transplantation is different from country to country. The number of organ transplantations in East Asian countries is rapidly growing, however, there are few epidemiological data about this region in the literature. With the establishment of KOTRY, it was possible to present the first nationwide epidemiological data of Korean KTs.
    Transplantation Proceedings 01/2014; 46(2):425–430. · 0.95 Impact Factor
  • S H Park, S Jeong, D H Lee
    Endoscopy 01/2014; 46 Suppl 1:E240-1. · 5.74 Impact Factor
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    ABSTRACT: Field line resonances, which represent shear Alfven standing modes of magnetohydrodynamic (MHD) waves are studied in space for the case in which magnetosphere is being perturbed in time by solarwind variations. A linearizedMHD wave model has been developed with time-varying Alfven speeds. When the magnetosphere becomes quiet, field line resonances consistently occur over many harmonics. A time-varying Alfven speed is found to cause a significant broadening of each spectral peak, which strongly depends on the frequency. While fundamental mode or lower harmonics become relatively stable with less broadening, higher harmonics appear with strong dispersion. Our results are consistent with the observed feature that fundamental or lower harmonic modes are dominant and higher harmonics are less frequently excited in space where the system is often perturbed in time.
    12/2013; 64(2).
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    ABSTRACT: BACKGROUND AND PURPOSE:Life-threatening bleeding in the head and neck requires urgent management. This study evaluated the angiographic findings related to head and neck bleeding and presents endovascular management techniques.MATERIAL AND METHODS:Sixty-one consecutive patients who presented with acute bleeding in the head and neck areas and subsequently underwent endovascular therapy between January 2002 and October 2012 were included in our study. We evaluated the angiographic findings, techniques, and results of endovascular management.RESULTS:Contrast leakage (n = 10), pseudoaneurysm (n = 20), or both (n = 10) were the most common life-threatening angiographic findings (66%) and were the foci of immediate embolization or endoluminal vessel reconstruction. Seventeen patients (28%) had hypervascular staining of the tumor or mucosa, and 4 patients (6%) did not have any abnormal findings. The acute bleeding was successfully controlled by endovascular management according to the bleeding foci. Carotid arterial lesions, so-called "carotid blowout," required reconstructive or deconstructive therapy. Bleeding of the external carotid artery required specific branch embolization by a combination of various embolic materials. No procedure-related complications occurred except in 1 patient who experienced acute infarction caused by thromboemboli from the covered stent. Seventeen patients (28%) were retreated due to rebleeding after the mean 20-month follow-up.CONCLUSIONS:Contrast leakage or a pseudoaneurysm or both seen on angiography are active bleeding foci and targets for therapy in patients with acute bleeding in the head and neck area. Despite different bleeding-control strategies according to vessel involvement, endovascular treatment is safe and effective for controlling hemorrhage.
    American Journal of Neuroradiology 10/2013; · 3.17 Impact Factor
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    ABSTRACT: BACKGROUND AND PURPOSE:Acute occlusion of the ICA is often associated with poor outcomes and severe neurologic deficits. This study was conducted to evaluate outcome of the occluded ICA and efficacy of recanalization under protective flow arrest.MATERIALS AND METHODS:Fifty consecutive patients who underwent endovascular treatment for acute ICA occlusion were identified from the prospectively collected data base. We assessed NIHSSo, occlusion type (cardioembolism vs atherosclerosis), occlusion level (supraclinoid-terminal, petrocavernous, or bulb-cervical), recanalization degree (TICI), and efficacy of recanalization (protective flow arrest vs nonprotection) leading to better outcome.RESULTS:Successful recanalization (TICI ≥ 2) was obtained in 90% of patients and good recovery (mRS ≤ 2) in 60% of patients. Good outcome was related to National Institutes of Health Stroke Scale score on admission (P < .001), TICI (P < .007), occlusion type (P = .022), and occlusion level (P = .038). Poor initial patient status, less recanalization, cardioembolism, and supraclinoid-terminal occlusion were associated with poor prognosis. Application of protective flow arrest led to better outcome in the distal ICA segment than in the bulb-cervical segment.CONCLUSIONS:In addition to the initial patient status and successful recanalization, the occlusion level or type of the occluded ICA could affect clinical outcome. In this study, treatment benefits of protective flow arrest were accentuated in patients with ICA occlusion above the bulb-cervical segment.
    American Journal of Neuroradiology 10/2013; · 3.17 Impact Factor
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    ABSTRACT: [1] It has been reported that Pi2 pulsations can be excited under extremely quiet geomagnetic conditions (Kp=0). However, there have been few comprehensive reports of Pi2 pulsations in such a near ground state magnetosphere. To understand the characteristics of quiet-time Pi2 pulsations, we statistically examined Pi2 events observed on the nightside between 1800 and 0600 local time at the low-latitude Bohyun (BOH, L = 1.35) station in South Korea. We chose year 2008 for analysis because geomagnetic activity was unusually low in that year. A total of 982 Pi2 events were identified when Kp≤1. About 80% of the Pi2 pulsations had a period between 110 and 300 s, which significantly differs from the conventional Pi2 period from 40 to 150 s. Comparing Pi2 periods and solar wind conditions, we found that Pi2 periods decrease with increasing solar wind speed, consistent with the result of Troitskaya (1967). The observed wave properties are discussed in terms of plasmaspheric resonance, which has been proposed for Pi2 pulsations in the inner magnetosphere. We also found that Pi2 pulsations occur quasi-periodically with a repetition period of ∼23–38 min. We will discuss what determines such a recurrence time of Pi2 pulsations under quiet geomagnetic conditions.
    Journal of Geophysical Research: Space Physics 10/2013; 118(10). · 3.44 Impact Factor
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    ABSTRACT: Vertebral artery recanalization in symptomatic stenosis/occlusion remains controversial, as no definite evidence exists regarding this topic. There are only a few reports regarding the feasibility and safety of recanalization in the first segment of the vertebral artery with atherosclerotic vertebral ostial occlusion. We report our experience treating first segment occlusion in 8 patients and present a balloon protection technique used to reduce the thromboembolic burden during the stent placement procedure. The outcome at 3 months showed an mRS ≤2 except for a patient with a poor initial status with basilar artery occlusion. Revascularization of a rather long first segment occlusion is technically feasible and can be safely performed by use of embolic protection methods.
    American Journal of Neuroradiology 08/2013; · 3.17 Impact Factor
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    ABSTRACT: We have made a comparison of near-real time Kp forecast models based on neural network (NN) and support vector machine (SVM) algorithms. For this, we consider four models as follows: (1) a NN model using solar wind data, (2) a SVM model using solar wind data, (3) a NN model using solar wind data and preliminary Kp values from ground-based magnetometers, and (4) a SVM model using the same input data used in model 3. For the comparison, we estimate the correlation coefficients and the RMS errors, and the mean absolute errors between the observed Kp and the predicted one. As a result, we find that model 3 shows the best performance. The correlation coefficients, the RMS error, and the mean absolute error of model 3 are 0.93, 0.48, and 0.61, respectively. For the forecast evaluation of high magnetic activity occurrence for the four models, we present contingency tables and their statistical parameters such as probability of detection yes, false alarm ratio, bias, critical success index, and true skill statistic. From a comparison of these statistical parameters, we find that model 3 is superior to the other models for the forecasting of high magnetic activities (Kp ≥ 6).
    Journal of Geophysical Research 08/2013; 118(8):5109-5117. · 3.17 Impact Factor
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    ABSTRACT: We have developed a near-infrared spectrometer designed to measure the absolute intensity of the Solar 854.2 nm CaII Fraunhofer line, scattered by interplanetary dust, in the Zodiacal light spectrum. Based on the known equivalent line width in the Solar spectrum, this measurement can derive the Zodiacal brightness, testing models of the Zodiacal light based on morphology that are used to determine the extragalactic background light in absolute photometry measurements. The spectrometer is based on a simple high-resolution tipped filter placed in front of a compact camera with wide-field refractive optics to provide the large optical throughput and high sensitivity required for rocket-borne observations. We discuss the instrument requirements for an accurate measurement of the absolute Zodiacal light brightness, the measured laboratory characterization, and the instrument performance in flight.
    The Astrophysical Journal Supplement Series 06/2013; 207(2). · 16.24 Impact Factor
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    ABSTRACT: Along with intracranial atherosclerotic disease (ICAD), moyamoya disease (MMD) is the most common cause of middle cerebral artery (MCA) occlusion in Asians. Although they have differing vascular wall pathologies, conventional angiographic evaluation methods cannot easily differentiate MMD from ICAD in certain situations, such as in young patients with atherosclerotic risk factors. High resolution magnetic resonance imaging (HR-MRI) findings for the diseased segments of MCAs in MMD and symptomatic ICAD were compared to further elucidate differences in arterial wall changes. Angiographically confirmed patients, 12 MMD and 20 ICAD, who suffered a stroke due to MCA occlusion were recruited and underwent HR-MRI. The size of the outer diameter and other stenotic vessel wall characteristics revealed by HR-MRI, including enhancement, eccentricity and other lesion patterns, were analyzed by two independent reviewers in a blind fashion. MMD patients were younger than ICAD patients (32.92 ± 11.08 years vs. 51.85 ± 11.97 years; mean ± SD) and displayed a smaller outer diameter in the stenotic portion (1.61 ± 0.43 mm for MMD vs. 3.03 ± 0.53 mm for ICAD, P < 0.0001). Eccentric lesions (three of 12 in MMD vs. 19 of 20 in ICAD, P < 0.0001) and focal enhancements in diseased areas (two of seven in MMD vs. 13 of 17 in ICAD, P = 0.061) were less common in MMD cases. Our HR-MRI findings show that MMD is associated with smaller, concentric occlusive lesions which are rarely enhanced compared with symptomatic ICAD, consistent with the results of previous pathological reports. HR-MRI may therefore have utility in differentiating MMD from ICAD.
    European Journal of Neurology 06/2013; · 4.16 Impact Factor
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    ABSTRACT: BACKGROUND AND PURPOSE: The association between past stroke subtypes and recurrent stroke subtypes in non-cardiogenic stroke remains unknown. METHODS: Patients with ischaemic stroke who had a past history of large-artery disease (LAD) or small-artery disease (SAD) subtypes were assessed. LAD was subdivided into intracranial atherosclerosis (ICAS) and extracranial atherosclerosis (ECAS). LAD stroke mechanisms were categorized as artery-to-artery embolism, in situ thrombotic occlusion and local branch occlusion, while SAD was subdivided into lacunar infarction (LI) and branch atheromatous disease (BAD) on the basis of magnetic resonance imaging findings. The relationship between past and current strokes was analyzed. RESULTS: Among the 202 patients enrolled, the LAD group (n = 111) had 64 and 47 patients with ICAS and ECAS, and the SAD group (n = 91) had 63 and 28 patients with LI and BAD, respectively, at the time of past stroke. Patients with LAD developed LAD-associated strokes most often (n = 99, 89.2%), and patients with SAD developed SAD most often (n = 69, 75.8%; P < 0.001). Patients with ICAS were more likely to develop ICAS later (n = 46, 79.3%), whereas those with ECAS developed ECAS more often (n = 31, 75.6%; P < 0.001). Patients with ICAS presenting with artery-to-artery embolism more often developed artery-to-artery embolism later (n = 26, 72.2%), whereas those with local branch occlusion developed recurrent local branch occlusion most often (n = 10, 66.7%, P = 0.005). In the SAD group, patients with BAD developed LAD more frequently than the LI group (n = 11, 39.3% vs. n = 9, 14.3%, P = 0.022). CONCLUSIONS: The subtypes and mechanisms of recurrent stroke are significantly influenced by those of the past stroke.
    European Journal of Neurology 02/2013; · 4.16 Impact Factor
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    ABSTRACT: We evaluated the clinical efficacy and safety of the coadministration of a PDE5 inhibitor and an α-adrenergic blocker in patients with both benign prostatic hyperplasia/lower urinary tract symptoms (BPH-LUTS) and ED using mirodenafil 50 mg (Mvixx) once daily (OD) in patients already receiving stable α-blocker therapy. This study was a prospective, multicenter, open-label trial. We selected 147 patients undergoing stable (longer than 4 weeks) α-blocker therapy for BPH-LUTS as recipients of the additive mirodenafil 50 mg OD for 8 weeks. The coprimary measures were the International Prostate Symptom Score (IPSS) and the International Index of Erectile Function (IIEF-5). The key secondary measures were peak flow rate (Q(max)) and postvoiding residual (PVR) volume. Safety was assessed by evaluating cardiovascular parameters and the participant-reported treatment-emergent adverse events (TEAEs). The additional administration of mirodenafil 50 mg OD significantly improved IPSS results (18.70-14.30 at 4 weeks and 18.70-13.72 at 8 weeks; P<0.001). The IIEF-5 score was improved at 8 weeks (10.94-16.16; P<0.001). There was no significant change in systolic blood pressure/diastolic blood pressure (124.8 mm Hg/78.6 mm Hg-122.0 mm Hg/79.6 mm Hg; P=0.638) and heart rates (78.8 per min to 80.2 per min; P=0.452). The most common TEAEs were hot flashes (10.9%) and headache (8.1%). The combination of mirodenafil with an α-blocker did not significantly improve PVR; however, Q(max) was improved at 8 weeks (14.51-16.80 ml s(-1); P=0.026). Mirodenafil 50 mg OD in combination with an α-blocker appeared to have few adverse effects, to improve BPH-LUTS and restore sexual function.International Journal of Impotence Research advance online publication, 10 January 2013; doi:10.1038/ijir.2012.44.
    International journal of impotence research 01/2013; · 2.73 Impact Factor
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    ABSTRACT: Cytokine and activation of lymphocytes are critical for tumor growth. We investigated whether interleukin (IL)-32β overexpression changes other cytokine levels and activates cytotoxic lymphocyte, and thus modify tumor growth. Herein, IL-32β inhibited B16 melanoma growth in IL-32β-overexpressing transgenic mice (IL-32β mice), and downregulated the expressions of anti-apoptotic proteins (bcl-2, IAP, and XIAP) and cell growth regulatory proteins (Ki-67 antigen (Ki-67) and proliferating cell nuclear antigen (PCNA)), but upregulated the expressions of pro-apoptotic proteins (bax, cleaved caspase-3, and cleaved caspase-9). IL-32β also inhibited colon and prostate tumor growth in athymic nude mice inoculated with IL-32β-transfected SW620 colon or PC3 prostate cancer cells. The forced expression of IL-32β also inhibited cell growth in cultured colon and prostate cancer cells, and these inhibitory effects were abolished by IL-32 small interfering RNA (siRNA). IL-10 levels were elevated, but IL-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) levels were reduced in the tumor tissues and spleens of IL-32β mice, and athymic nude mice. The number of cytotoxic T (CD8(+)) and natural killer (NK) cells in tumor tissues, spleen, and blood was significantly elevated in IL-32β mice and athymic nude mice inoculated with IL-32β-transfected cancer cells. Constituted activated NF-κB and STAT3 levels were reduced in the tumor tissues of IL-32β mice and athymic nude mice, as well as in IL-32β-transfected cultured cancer cells. These findings suggest that IL-32β inhibits tumor growth by increasing cytotoxic lymphocyte numbers, and by inactivating the NF-κB and STAT3 pathways through changing of cytokine levels in tumor tissues.
    Cell Death & Disease 01/2013; 4:e640. · 6.04 Impact Factor
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    ABSTRACT: The clinical course and outcome of isolated anastomotic leaks (IALs) after esophagectomy are significantly different from those of necrotic leaks. The purpose of this study was to investigate the clinical features, diagnosis, treatment, and long-term outcome in patients with IALs after esophagectomy with reconstruction for esophageal cancer. A total of 663 patients underwent esophagectomy with esophageal reconstruction because of esophageal cancer between 2000 and 2010 at the Seoul Asan Medical Center. IALs occurred in 23 patients (3.5%). All patients with IAL were male, with a median age of 61 years. Patients with IAL were divided into three groups based on their clinical course. group A comprised patients who had definite clinical symptoms and/or signs indicating mediastinal contamination or leak before routine contrast esophagography was performed. Groups B and C comprised patients who had no definite clinical symptoms and/or signs of leaks before the routine contrast examination. Furthermore, group B contained those patients who resumed oral intake because no leak was found in the routine contrast examination and was diagnosed some days after resuming oral intake. Group C contained those patients who kept fasting because the leak was found in the routine contrast examination. The median follow-up period was 30 months. The mean time to closure of the IAL was 70.1 ± 96.0 days (range 4-364). There was a 72.7% overall closure rate within 60 days. By univariate analysis, the mean time to closure of the IAL was found to be significantly longer for group A patients or in cases where the patients had an uncontained leak, leukocytosis, or empyema. However, there was no statistically significant differences in age, neoadjuvant treatment, site of anastomosis (cervical vs. thoracic), fever, or treatment of the leak. By multivariate analysis, group A was found to be an independent predictive factor for the time to closure of the IAL. Repeat contrast studies revealed no anastomotic leaks in 18 patients and the formation of contained fistula in four cases (excluding one patient who died in hospital). The four patients with a contained fistula showed no clinical symptoms or signs, and tolerated resumed oral intake. IALs were resolved in most cases with low leak-related mortality, and resolution of the leaks occurred within 2 months in the majority of patients.
    Diseases of the Esophagus 12/2012; · 1.64 Impact Factor
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    ABSTRACT: The passage of an interplanetary (IP) shock was detected by Wind, ACE, Geotail, and THEMIS-B in the solar wind on 24 November 2008. From the propagation time of the IP shock at the spacecraft, it is expected that the IP shock front is aligned with the Parker spiral and strikes the postnoon dayside magnetopause first. Using multipoint observations of the sudden commencement (SC) at THEMIS probes, GOES 11, and ETS in the dayside magnetosphere, we confirmed that the magnetospheric response to the IP shock starts earlier in the postnoon sector than in the prenoon sector. We found that the estimated normal direction of the SC front is nearly aligned with the estimated IP shock normal. We also found that the SC front normal speed is much slower than the fast mode speed and is about 22-56% of the IP shock speed traveling in the solar wind. Thus, we suggest that the major field changes of the SC in the dayside magnetosphere are not due to the magnetic flux carried by hydromagnetic waves but to the increased solar wind dynamic pressure behind the shock front sweeping the magnetopause. The SC event appears as a step-like increase in the H component at the low-latitude Bohyun station and a negative-then-positive variation in the H component at the high-latitude Chokurdakh (CHD) station in the morning sector. During the negative perturbation at CHD, the SuperDARN Hokkaido radar detected a downward motion in the ionosphere, implying westward electric field enhancement. Using the THEMIS electric field data, it is confirmed that the westward electric field corresponds to the inward plasma motion in the dayside magnetosphere due to the magnetospheric compression.
    Journal of Geophysical Research 10/2012; 117(A10):10209-. · 3.17 Impact Factor
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    ABSTRACT: Here we compare the traditional analog measure of geomagnetic activity, Ak, with the more recent digital indices of IHV and Ah based on hourly mean data, and their derivatives at the auroral station Sodankylä. By this selection of indices we study the effects of (i) analog vs. digital technique, and (ii) full local-time vs. local night-time coverage on quantifying local geomagnetic activity. We find that all other indices are stronger than Ak during the low-activity cycles 15–16 suggesting an excess of very low scalings in Ak at this time. The full-day indices consistently depict stronger correlation with the interplanetary magnetic field strength, while the night-time indices have higher correlation with solar wind speed. The Ak index correlates better with the digital indices of full-day coverage than with any night-time index. However, Ak depicts somewhat higher activity levels than the digital full-day indices in the declining phase of the solar cycle, indicating that, due to their different sampling rates, the latter indices are less sensitive to high-frequency variations driven by the Alfvén waves in high-speed streams. On the other hand, the night-time indices have an even stronger response to solar wind speed than Ak. The results strongly indicate that at auroral latitudes, geomagnetic indices with different local time coverage reflect different current systems, which, by an appropriate choice of indices, allows studying the century-scale dynamics of these currents separately.
    Advances in Space Research 09/2012; 50(6):690–699. · 1.18 Impact Factor

Publication Stats

2k Citations
816.38 Total Impact Points


  • 2014
    • Korea Centers for Disease Control and Prevention
      Daiden, Daejeon, South Korea
  • 2002–2014
    • Korea Advanced Institute of Science and Technology
      • • Department of Nuclear and Quantum Engineering
      • • Department of Physics
      Sŏul, Seoul, South Korea
  • 1999–2014
    • Inha University Hospital
      Sinhyeon, South Gyeongsang, South Korea
  • 2013
    • Yonsei University
      • Department of Urology
      Sŏul, Seoul, South Korea
  • 2011–2013
    • University of California, San Diego
      • Department of Physics
      San Diego, California, United States
    • Korea Atomic Energy Research Institute (KAERI)
      Daiden, Daejeon, South Korea
    • Korea Electrotechnology Research Institute-KERI
      Tsau-liang-hai, Busan, South Korea
    • California Institute of Technology
      • Division of Physics, Mathematics, and Astronomy
      Pasadena, California, United States
    • Yeungnam University
      • Division of Internal Medicine
      Onyang, South Chungcheong, South Korea
  • 2005–2013
    • University of Ulsan
      • • College of Medicine
      • • Department of Radiology
      Urusan, Ulsan, South Korea
    • Gangneung Asan Hospital
      Sŏul, Seoul, South Korea
  • 1998–2013
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 1992–2013
    • Kyung Hee University
      • • School of Space Research
      • • Department of Astronomy and Space Science
      • • Graduate School of East-West Medical Science
      Sŏul, Seoul, South Korea
    • Soonchunhyang University
      • College of Medicine
      Asan, South Chungcheong, South Korea
    • Hanyang University Medical Center
      Sŏul, Seoul, South Korea
  • 2012
    • Konkuk University Medical Center
      Changnyeong, South Gyeongsang, South Korea
  • 2008–2012
    • Seoul National University
      • • Department of Physics and Astronomy
      • • Department of Dermatology
      Sŏul, Seoul, South Korea
  • 2005–2012
    • Ulsan University Hospital
      Urusan, Ulsan, South Korea
  • 2006–2011
    • Seoul National University Hospital
      • Department of Dermatology
      Seoul, Seoul, South Korea
  • 2010
    • Seoul Medical Center
      Sŏul, Seoul, South Korea
    • Chonbuk National University
      Tsiuentcheou, North Jeolla, South Korea
  • 2007–2010
    • Seoul National University Bundang Hospital
      Sŏul, Seoul, South Korea
    • Korea Institute of Radiological & Medical Sciences
      Sŏul, Seoul, South Korea
    • National Cancer Center Korea
      Kōyō, Gyeonggi Province, South Korea
  • 2006–2010
    • Korea Astronomy and Space Science Institute
      • Division of Space Science
      Daiden, Daejeon, South Korea
  • 2003–2010
    • Pohang University of Science and Technology
      • • Department of Chemistry
      • • Department of Electronic and Electrical Engineering
      Geijitsu, North Gyeongsang, South Korea
  • 2009
    • Hannam University
      • Department of Biological Sciences
      Daiden, Daejeon, South Korea
    • Chonnam National University
      Gwangju, Gwangju, South Korea
  • 2007–2009
    • Asan Medical Center
      • Department of Neurology
      Sŏul, Seoul, South Korea
  • 2001–2007
    • Sungkyunkwan University
      • • Samsung Medical Center
      • • School of Advanced Materials Science and Engineering (AMSE)
      Seoul, Seoul, South Korea
    • Korea University
      • Department of Neurology
      Seoul, Seoul, South Korea
    • Chung-Ang University Hospital
      Sŏul, Seoul, South Korea
  • 2004
    • Dartmouth College
      • Department of Physics & Astronomy
      Hanover, NH, United States
  • 1990–2001
    • Kyung Hee University Medical Center
      • Department of Diagnotic Radiology
      Seoul, Seoul, South Korea
  • 1988–1995
    • Hanyang University
      • Department of Medicine
      Ansan, Gyeonggi, South Korea
  • 1989
    • Los Alamos National Laboratory
      Los Alamos, California, United States
  • 1985–1989
    • University of Florida
      • Department of Electrical and Computer Engineering
      Gainesville, FL, United States