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Search Results: 1 - 10 of 15328 matches for " Do Hyun Ryu "
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Patterned thin metal film for the lateral resolution measurement of photoacoustic tomography
Do-Hyun Kim, Dong Ho Shin, Sang-Hun Ryu, Chul-Gyu Song
BioMedical Engineering OnLine , 2012, DOI: 10.1186/1475-925x-11-37
Abstract: A patterned thin metal film deposited on silica glass provides high contrast in optical imaging due to high reflectivity from the metal film and high transmission from the glass. It provides high contrast when it is used for photoacoustic tomography because thin metal film can absorb pulsed laser energy. An US Air Force 1951 resolution target was used to generate patterned photoacoustic signal to measure the lateral resolution. Transducer with 2.25?MHz bandwidth and a sample submerged in water and gelatinous block were tested for lateral resolution measurement.Photoacoustic signal generated from a thin metal film deposited on a glass can propagate along the surface or through the surrounding medium. First, a series of experiments with tilted sample confirmed that the measured photoacoustic signal is what is propagating through the medium. Lateral resolution of the photoacoustic tomography system was successfully measured for water and gelatinous block as media: 0.33?mm and 0.35?mm in water and gelatinous material, respectively, when 2.25?MHz transducer was used. Chicken embryo was tested for biomedical applications.A patterned thin metal film sample was tested for its feasibility of measuring lateral resolution of a photoacoustic tomography system. Lateral resolutions in water and gelatinous material were successfully measured using the proposed method. Measured resolutions agreed well with theoretical values.
Acetic acid-indigo carmine chromoendoscopy for delineating early gastric cancers: its usefulness according to histological type
Bong Lee, Gwang Kim, Do Park, Dae Kim, Tae Jeon, Su Park, Hyun You, Dong Ryu, Dong Kim, Geun Song
BMC Gastroenterology , 2010, DOI: 10.1186/1471-230x-10-97
Abstract: We prospectively included 151 lesions of 141 patients that had an endoscopic diagnosis of EGC. All the lesions were examined by conventional endoscopy and AI chromoendoscopy before ESD or laparoscopic gastrectomy. The border clarification between the lesion and the normal mucosa was classified as distinct or indistinct before and after AI chromoendoscopy.The borders of the lesions were distinct in 66.9% (101/151) with conventional endoscopy and in 84.1% (127/151) with AI chromoendoscopy (P < 0.001). Compared with conventional endoscopy, AI chromoendoscopy clarified the border in a significantly higher percentage of differentiated adenocarcinomas (74/108 [68.5%] vs 97/108 [89.8%], respectively, P < 0.001). However, the border clarification rate for undifferentiated adenocarcinomas did not differ between conventional endoscopy and AI chromoendoscopy (27/43 [62.8%] vs 30/43 [70.0%], respectively, P = 0.494).AI chromoendoscopy is useful in determining the lateral extent of EGCs. However, its usefulness is reduced in undifferentiated adenocarcinomas.There has been a reduced incidence of gastric cancer in western countries over the past few decades. However, gastric cancer is still the second leading cause of cancer deaths in the world, and it is the most prevalent malignancy in Korea [1,2]. Early gastric cancer (EGC) is defined as a gastric cancer that is confined to the mucosa or submucosa, regardless of the presence or absence of lymph node metastasis [3]. The proportion of EGC cases is increasing in Korea because endoscopic screening for gastric cancer has been adopted [4]. As a result, endoscopic treatments such as endoscopic submucosal dissection (ESD) and laparoscopic gastrectomy are increasingly used to treat a subset of patients with EGC in both Korea and Japan [5-8].To achieve a successful outcome, it is very important to accurately determine the lateral extent of the tumor. This has traditionally been done with conventional endoscopy and chromoendoscopy using i
Endoscopic removal of gastric ectopic pancreas: An initial experience with endoscopic submucosal dissection
Dong Yup Ryu, Gwang Ha Kim, Do Youn Park, Bong Eun Lee, Jae Hoon Cheong, Dong Uk Kim, Hyun Young Woo, Jeong Heo, Geun Am Song
World Journal of Gastroenterology , 2010,
Abstract: AIM: To evaluate the therapeutic usefulness and safety of endoscopic resection in patients with gastric ectopic pancreas.METHODS: A total of eight patients with ectopic pancreas were included. All of them underwent endoscopic ultrasonography before endoscopic resection. Endoscopic resection was performed by two methods: endoscopic mucosal resection (EMR) by the injection-and-cut technique or endoscopic mucosal dissection (ESD).RESULTS: We planned to perform EMR in all eight cases but EMR was successful in only four cases. In the other four cases, saline spread into surrounding normal tissues and the lesions became flattened, which made it impossible to remove them by EMR. In those four cases, we performed ESD and removed the lesions without any complications.CONCLUSION: If conventional EMR is difficult to remove gastric ectopic pancreas, ESD is a feasible alternative method for successful removal.
1H NMR-Based Metabolite Profiling of Plasma in a Rat Model of Chronic Kidney Disease
Ju-Ae Kim, Hyo-Jung Choi, Yong-Kook Kwon, Do Hyun Ryu, Tae-Hwan Kwon, Geum-Sook Hwang
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085445
Abstract: Chronic kidney disease (CKD) is characterized by the gradual loss of the kidney function to excrete wastes and fluids from the blood. 1H NMR-based metabolomics was exploited to investigate the altered metabolic pattern in rats with CKD induced by surgical reduction of the renal mass (i.e., 5/6 nephrectomy (5/6 Nx)), particularly for identifying specific metabolic biomarkers associated with early of CKD. Plasma metabolite profiling was performed in CKD rats (at 4- or 8-weeks after 5/6 Nx) compared to sham-operated rats. Principle components analysis (PCA), partial least squares-discriminant analysis (PLS-DA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) score plots showed a significant separation between the groups. The resulting metabolic profiles demonstrated significantly increased plasma levels of organic anions, including citrate, β-hydroxybutyrate, lactate, acetate, acetoacetate, and formate in CKD. Moreover, levels of alanine, glutamine, and glutamate were significantly higher. These changes were likely to be associated with complicated metabolic acidosis in CKD for counteracting systemic metabolic acidosis or increased protein catabolism from muscle. In contrast, levels of VLDL/LDL (CH2)n and N-acetylglycoproteins were decreased. Taken together, the observed changes of plasma metabolite profiles in CKD rats provide insights into the disturbed metabolism in early phase of CKD, in particular for the altered metabolism of acid-base and/or amino acids.
Two-Dimensional Axisymmetric Collapse of Thermally Unstable Primordial Clouds
Chang Hyun Baek,Hyesung Kang,Dongsu Ryu
Physics , 2002, DOI: 10.1086/345814
Abstract: We have performed two-dimensional hydrodynamic simulations of the collapse of isolated axisymmetric clouds condensing via radiative cooling in a primordial background gas. In order to study the development of the so-called ``shape-instability'', we have considered two types of axisymmetric clouds, oblate and prolate clouds of various sizes and with axial ratios of $0.5 \leq {R_{\rm c,R}} /{R_{\rm c,z}} \leq 2$. We find that the degree of oblateness or prolateness is enhanced during the initial cooling phase. But it can be reversed later, if the initial contrast in cooling times between the cloud gas and the background gas is much greater than one. In such cases an oblate cloud collapses to a structure composed of an outer thin disk and a central prolate component. A prolate cloud, on the other hand, becomes a thin cigar-shape structure with a central dense oblate component. The reversal of shape in the central part of the cooled clouds is due to supersonic motions either along the disk plane in the case of oblate clouds or along the symmetry axis in the case of prolate clouds. For a background gas of $T_h=1.7\times 10^6$K and $n_h=0.1 \cm3$ in a protogalactic halo environment, the mean density of the cloud gas that has cooled to $10^4$K increases to $100 n_h$ or so, in our simulations where nonequilibrium cooling is adopted and the background gas cools too. The spherical Jeans mass of such gas is estimated to be about $M_J \sim 5\times10^{7}\Msun$. In order for cloud mass to exceed the Jeans mass and at the same time in order for the thermal instability to operate, the initial cloud size should be around $1 - 1.5 l_{\rm cool}$ where $l_{\rm cool}$ is the cooling length.
Wireless Power Transfer for High-precision Position Detection of Railroad Vehicles
Hyun-Gyu Ryu,Dongsoo Har
Physics , 2015,
Abstract: Detection of vehicle position is critical for successful operation of intelligent transportation system. In case of railroad transportation systems, position information of railroad vehicles can be detected by GPS, track circuits, and so on. In this paper, position detection based on tags onto sleepers of the track is investigated. Position information stored in the tags is read by a reader placed at the bottom of running railroad vehicle. Due to limited capacity of battery or its alternative in the tags, power required for transmission of position information to the reader is harvested by the tags from the power wirelessly transferred from the reader. Basic mechanism in wireless power transfer is magnetic induction and power transfer efficiency according to the relative location of the reader to a tag is discussed with simulation results. Since power transfer efficiency is significantly affected by the ferromagnetic material (steel) at the bottom of the railroad vehicle and the track, magnetic beam shaping by ferrite material is carried out. With the ferrite material for magnetic beam shaping, degradation of power transfer efficiency due to the steel is substantially reduced. Based on the experimental results, successful wireless power transfer to the tag coil is possible when transmitted power from the reader coil is close to a few watts.
Inverse transitions in a spin-glass model on a scale-free network
Do-Hyun Kim
Physics , 2014, DOI: 10.1103/PhysRevE.89.022803
Abstract: In this paper, we will investigate critical phenomena by considering a model spin-glass on scale-free networks. For this purpose, we consider the Ghatak-Sherrington (GS) model, a spin-1 spin-glass model with a crystal field, instead of the usual Ising-type model. Scale-free networks on which the GS model is placed are constructed from the static model, in which the number of vertices is fixed from the beginning. On the basis of the replica-symmetric solution, we obtain the analytical solutions, i.e., free energy and order parameters, and we derive the various phase diagrams consisting of the paramagnetic, ferromagnetic, and spin glass phases as functions of temperature $T$, the degree exponent $\lambda$, the mean degree $K$, and the fraction of the ferromagnetic interactions $\rho$. Since the present model is based on the GS model, which considers the three states ($S=0, \pm 1$), the $S=0$ state plays a crucial role in the $\lambda$-dependent critical behavior: glass transition temperature $T_{g}$ has a finite value, even when $2 < \lambda < 3$. In addition, when the crystal field becomes nonzero, the present model clearly exhibits three types of inverse transitions, which occur when an ordered phase is more entropic than a disordered one.
Spin-glass splitting in the quantum Ghatak-Sherrington model
Do-Hyun Kim
Physics , 2014, DOI: 10.1103/PhysRevE.87.042127
Abstract: We propose an expanded spin-glass model, called the quantum Ghatak-Sherrington model, which considers spin-1 quantum spin operators in a crystal field and in a transverse field. The analytic solutions and phase diagrams of this model are obtained by using the one-step replica symmetry-breaking ansatz under the static approximation. Our results represent the splitting within one spin-glass (SG) phase depending on the values of crystal and transverse fields. The two separated SG phases, characterized by a density of filled states, show certain differences in their shapes and phase boundaries. Such SG splitting becomes more distinctive when the degeneracy of the empty states of spins is larger than one of their filled states.
Nardostachys jatamansi extract protects against cytokine-induced β-cell damage and streptozotocin-induced diabetes
Mi-Young Song, Ui-Jin Bae, Bong-Hee Lee, Kang-Beom Kwon, Eun-A Seo, Sung-Joo Park, Min-Sun Kim, Ho-Joon Song, Keun-Sang Kwon, Jin-Woo Park, Do-Gon Ryu, Byung-Hyun Park
World Journal of Gastroenterology , 2010,
Abstract: AIM: To investigate the anti-diabetogenic mechanism of Nardostachys jatamansi extract (NJE).METHODS: Mice were injected with streptozotocin via a tail vein to induce diabetes. Rat insulinoma RINm5F cells and isolated rat islets were treated with interleukin-1β and interferon-γ to induce cytotoxicity.RESULTS: Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was confirmed by immunohistochemical staining of the islets. The diabetogenic effects of streptozotocin were completely abolished when mice were pretreated with NJE. Inhibition of streptozotocin-induced hyperglycemia by NJE was mediated by suppression of nuclear factor (NF)-κB activation. In addition, NJE protected against cytokine-mediated cytotoxicity. Incubation of RINm5F cells and islets with NJE resulted in a significant reduction in cytokine-induced NF-κB activation and downstream events, inducible nitric oxide synthase expression and nitric oxide production. The protective effect of NJE was further demonstrated by the normal insulin secretion of cytokine-treated islets in response to glucose.CONCLUSION: NJE provided resistance to pancreatic β-cell damage from cytokine or streptozotocin treatment. The β-cell protective effect of NJE is mediated by suppressing NF-κB activation.
Localization between Curved Shell Plate and Its Unfolded Shape in Different Coordinate Systems for Ship-Hull Plate Forming
Se Yun Hwang,Cheol Ho Ryu,Jang Hyun Lee
Mathematical Problems in Engineering , 2011, DOI: 10.1155/2011/257804
Abstract: This paper describes a mathematical formulation for the efficient localization of 3D surfaces including free-form surfaces and flat surfaces. An important application of this paper is to register flat surface calculated from unfolding process with a curved surface extracted from ship CAD prior to the multipoint press forming works. The mathematical formulation handles the registration and comparison of two free surfaces represented by sparse points based on the iterative closest point (ICP) algorithm and localization that can be applicable to ship-hull plate forming. The ICP algorithm gives an adequate set of initial translation and rotation for surface objects with little correspondence through the minimization of mean square distance metric. Comparison of surfaces is explained in order to determine a corresponding set which gives the optimized press stroke between unfold surface and referential object surface. It thereby allows the optimized press works in ship-hull forming. The combination of registration and comparison is applied to decide the shape equivalence of correspondent surfaces as well as to estimate the transform matrix between point sets where similarity is low. Experimental results show the capabilities of the registration on unfolding surface and curved surface.
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