Biomedical subjects

Y Jeong

Publications and source records attributed to Y Jeong.

At least 19 recordsLinked to original sources

PubMed2006

High-power continuous-wave cladding-pumped Raman fiber laser.

We demonstrate a high-power single-mode cladding-pumped Raman fiber laser. The Raman fiber laser consists of a 1.2 km long germanium-doped double-clad fiber in a linear cavity, which is spliced to a single-mode fiber. The laser is end pumped by a multimode erbium-ytterbium-doped fiber, which is coupled to the inner cladding of the Raman fiber. The embedded core was designed to be single mode at the Raman Stokes wavelength, and up to 10 W of power was obtained at 1660 nm from the single-mode fiber end. The laser has a slope efficiency of 67% and a threshold of 6.5 W.

Journal Article↗

PubMed2006

Fiber-optic color synthesizer.

Full-color synthesis was achieved, for what we believe is the first time, utilizing a novel 3x1 hard polymer-clad fiber coupler along with red, green, and blue (RGB) LED primaries. By using RGB LEDs that are coupled to three input ports, the device rendered full color from the output port with a circular emitting pixel of 135 microm in diameter with an extended color gamut. The proposed fiber-optic color synthesizer can provide a compact waveguide solution for the beam scanning display and the tunable pure white source for LED backlighting.

Journal Article↗

PubMed2006

Incremental limb hypometria.

To find out if patients with right hemisphere strokes (RHD) demonstrate a form of progressive or incremental limb hypometria (ILH), 11 RHD patients and eight matched controls were tested by having them draw a series of horizontal lines while blindfolded. Unlike controls, six RHD patients displayed an incremental decrease in the length of lines they drew, a sign of ILH. ILH might be a common source of disability and hinder rehabilitation efforts.

Aged↗

PubMed2005

High-power tunable single-frequency single-mode erbium:ytterbium codoped large-core fiber master-oscillator power amplifier source.

We present a cladding-pumped single-frequency, single-mode erbium:ytterbium codoped fiber master-oscillator power amplifier source generating up to 151 W of continuous-wave output power at 1563 nm with 33% slope efficiency and 20 dB gain. This source was also tunable and had a stable operation range of 1546 to 1566 nm at an output power level in excess of 125 W. The doped fiber exploited a large-core design for improved power handling and mitigation of stimulated Brillouin scattering. There was no sign of having stimulated Brillouin scattering even at the highest power. Despite a large core (V = 12), the output beam was nearly diffraction limited (M2 = 1.1). The source showed slight rollover at over 100 W of output power because of the onset of emission from ytterbium, centered at 1060 nm.

Journal Article↗

PubMed2005

Multiport N x N multimode air-clad holey fiber coupler for high-power combiner and splitter.

We report 2 x 2 and 4 x 4 multimode air-clad holey fiber couplers fabricated by a novel fusion and tapering technique. The devices showed excellent port-to-port coupling uniformity over a wide spectral range of 800-1650 nm. The 4 x 4 coupler showed a low insertion loss of 9.9 dB and excess loss of 3.9 dB at 1310 nm. Because of its unique air cladding and the high numerical aperture of the holey fiber structure, the device showed strong potential in high-power applications.

Journal Article↗

PubMed2005

Stimulation of the lateral hypothalamus produces antinociception mediated by 5-HT1A, 5-HT1B and 5-HT3 receptors in the rat spinal cord dorsal horn.

The lateral hypothalamus is part of an efferent system that modifies pain at the spinal cord dorsal horn, but the mechanisms by which lateral hypothalamus-induced antinociception occur are not fully understood. Previous work has shown that antinociception produced from electrical stimulation of the lateral hypothalamus is mediated in part by spinally projecting 5-hydroxytryptamine (5-HT) neurons in the ventromedial medulla. To further examine the role of the lateral hypothalamus in antinociception, the cholinergic agonist carbamylcholine chloride (125 nmol) was microinjected into the lateral hypothalamus of female Sprague-Dawley rats and nociceptive responses measured on the tail-flick and foot-withdrawal tests. Intrathecal injections of the selective 5-HT1A, 5-HT1B, 5-HT3 receptor antagonists, WAY 100135, SB-224289, and tropisetron, respectively, and the non-specific antagonist methysergide, were given. Lateral hypothalamus stimulation with carbamylcholine chloride produced significant antinociception that was blocked by WAY 100135, tropisetron, and SB-224289 on both the tail-flick and foot-withdrawal tests. Methysergide was not different from controls on the tail flick test, but increased foot-withdrawal latencies compared with controls. These results suggest that the lateral hypothalamus modifies nociception in part by activating spinally projecting serotonin neurons that act at 5-HT1A, 5-HT1B, and 5-HT3 receptors in the dorsal horn.

Animals↗

PubMed2005

Glucose metabolism in early onset versus late onset Alzheimer's disease: an SPM analysis of 120 patients.

The aims of this cross-sectional study were (i) to compare the overall glucose metabolism between early onset and late onset Alzheimer's disease in a large sample of patients; and (ii) to investigate the pattern of glucose metabolism as a function of dementia severity in early onset versus late onset Alzheimer's disease, using a statistical parametric mapping (SPM) analysis. Subjects consisted of four groups: 74 patients with early onset Alzheimer's disease, 46 patients with late onset of the disease, and two control groups age matched to each patient group. All the subjects underwent 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG)-PET under the same scanning conditions. Severity of dementia was rated with the Clincial Dementia Rating (CDR). Voxel-based SPM99 was used for statistical analyses. Overall glucose hypometabolism of early onset Alzheimer's disease patients was much greater in magnitude and extent than that of late onset patients, though both groups were similar in dementia severity: the early onset group showed more severe hypometabolism in parietal, frontal and subcortical (basal ganglia and thalamus) areas. When the decline of glucose metabolism was compared as a function of CDR stage, the slope was steeper in early onset than in late onset Alzheimer's disease. The rapid decline occurred at CDR 0.5-1 in the early onset group, whereas similar changes occurred at CDR 2-3 in the late onset group. The greater hypometabolism in early onset than in late onset patients is required to reach the same severity of dementia, probably reflecting greater functional reserve in younger than in older subjects. Alternatively, the metabolic decline curve suggests that the early onset patients may take a more rapid course in the reduction of glucose metabolism than the late onset patients.

Age of Onset↗

PubMed2005

Single-mode plane-polarized ytterbium-doped large-core fiber laser with 633-W continuous-wave output power.

We demonstrate a cladding-pumped single-mode plane-polarized ytterbium-doped fiber laser generating 633 W of continuous-wave output power at 1.1 microm with 67% slope efficiency and a polarization extinction ratio better than 16 dB. The laser is end pumped through both fiber ends and shows no evidence of roll-over, even at the highest output power, which is limited only by the available pump power.

Journal Article↗

PubMed2005

Single-frequency, single-mode, plane-polarized ytterbium-doped fiber master oscillator power amplifier source with 264 W of output power.

We present a single-frequency, single-mode, plane-polarized ytterbium-doped all-fiber master oscillator power amplifier source at 1060 nm generating 264 W of continuous-wave output power. The final-stage amplifier operated with a high gain of 19 dB and a high conversion efficiency of 68%. There was no evidence of rollover from stimulated Brillouin scattering even at the highest output power, and the maximum output was limited only by the available pump power.

Journal Article↗

PubMed2005

Pattern of glucose hypometabolism in frontotemporal dementia with motor neuron disease.

Frontotemporal dementia (FTD) often coexists with motor neuron disease (MND). To characterize glucose hypometabolism in patients with FTD with MND (FTD/MND), the authors compared the glucose metabolism of 8 patients with FTD/MND with that of 29 patients with FTD. All of the patients with FTD/MND showed glucose hypometabolism only in the frontal area, whereas most patients with FTD had hypometabolism in the frontal and temporal areas. FTD/MND also showed a more symmetric pattern of glucose hypometabolism than FTD.

Aged↗

PubMed2005

Correlation of ventricular asymmetry with metabolic asymmetry in frontotemporal dementia.

BACKGROUND AND PURPOSE: The clinical presentation of frontotemporal dementia (FTD) is often asymmetrical in terms of both its clinical features and atrophy on MRI. Asymmetry in the lateral ventricle size on structural neuroimaging in FTD patients may have clinical significance. However, this has not been systematically investigated yet. This study compares the ventricular asymmetry seen on MRI with that of the asymmetric glucose metabolism using FDG-PET in patients with FTD. METHODS: Nineteen FTD patients who underwent both brain MRI and FDG-PET were retrospectively selected. As control groups, 23 and 11 age and sex-matched healthy normal subjects underwent either brain MRI or FDG-PET, respectively. The ventricular asymmetry index (VAI) was obtained in two ways: by visual rating (VAI-V) and by measuring the lateral ventricular volumes (VAI-ROI). The hemispheric asymmetry of the glucose metabolism on FDG-PET (MAI) was assessed in three ways: 1) by visual rating (MAI-V), 2) by counting the FDG activity of each hemisphere on normalized and smoothed PET images (MAI-ROI) and 3) by counting the number of voxels with significant hypometabolism based on statistical parametric mapping results (MAI-SPM). RESULTS: The VAIs on MRI (VAI-V and VAI-ROI) were highly correlated, as were the MAIs (MAI-V, MAI-ROI, and MAI-SPM) on FDG-PET. More importantly, the VAIs on MRI and the MAIs on FDG-PET showed high correlation. CONCLUSIONS: Ventricular asymmetry in FTD patients was common (78.9%) and there was a high correlation between the ventricular structural asymmetry and the hemispheric metabolic asymmetry. Therefore, it would be reasonable to interpret that the hemisphere with larger ventricle on MRI in FTD patients is undergoing a more active degenerative process.

Adult↗

PubMed2005

High performance biofilm process for treating wastewater discharged from coal refining plants containing nitrogen, cyanide and thiocyanate.

Wastewater discharge from coal refining plants contains a number of biologically toxic compounds; 2000-2500 mg/l of COD of which 40% is composed of phenol, 100-400 mg/l of thiocyanate, 10-40 mg/l of cyanide, 100-250 mg/l of NH4+-N and 150-300 mg/l of total nitrogen. In order to treat this kind of high strength wastewater, we have developed a high performance biofilm process using fluidizing bio-carriers of the tube chip type. The fluidizing biofilm carriers are made of a composite of polyethylene and several inorganic materials, whose density is controlled at 0.97-0.98 g/ml. The fluidizing biofilm carriers show sound fluidization characteristics inside bioreactors. The wastewater is treated using three consecutive series reactors in oxic-anoxic-oxic arrangement. Each reactor is charged with the fluidizing biofilm carriers of 50 vol%. Furthermore, newly cultured active microorganisms for the thiocyanate biodegradation are added in the biofilm process. At total hydraulic retention time of 2.2 days, this process can achieve steady state removal efficiencies: COD, 99%; thiocyanate, 99%; NH4+-N, 99% and total nitrogen, 90%.

Aerobiosis↗

PubMed2004

Attentional bias induced by viewing actual or illusory movements.

OBJECTIVE: To learn to which portions of a line normal subjects would attend when watching this line actually moving or when perceiving movement even in the absence of actual movement, an illusory movement. METHODS: Twenty normal subjects watched a computer monitor on which either lines or dots moved to the right or left. They also watched stationary lines, which appeared to be moving to the left or right because the background was moving in the opposite direction. While watching these lines or dots, their eye movements were monitored to determine the position of fixation. RESULTS: Overall, subjects fixated on the side of the line that was in the direction of real or illusory movement. In the actual movement condition, leftward motion induced more of an attentional bias than rightward motion. In the illusory movement condition, however, rightward illusory movement condition induced more of an attentional bias than leftward movement. CONCLUSIONS: Objects moving leftward or rightward primarily activate the contralateral hemisphere. This hemispheric activation may induce a contralateral overt orienting response that is reflected by eccentric eye fixation. Treatments of neglect, such as caloric vestibular stimulation, may alter an attentional bias by inducing the illusion of movement.

Adult↗

PubMed2003

Dietary taurine intake and serum taurine levels of women on Jeju Island.

The purpose of this study was to investigate the dietary taurine intake and serum taurine levels of women on Jeju Island in Korea. Sixty six married women aged 43.5 +/- 7.1 volunteered for this study: 34 from the city area and 32 from two fishing-farming areas. Diet samples were collected from the participants; the samples included three meals (breakfast, lunch and supper), including snacks, drinks and whatever else the participants had eaten for 24 hours. Taurine levels in the diet and serum were determined as the dabsyl derivative by HPLC with a Rf-detector. The intake of taurine ranged from 8.4 to 767.6 mg/day and its mean value was 163.9 +/- 150.2 mg/day (mean +/- SD). There was a significant difference between the two groups: 114.9 +/- 78.7 for the women from the city area and 215.9 +/- 187.9 mg/day for the women from the fishing-farming areas (p<0.001). The taurine intake of the total diet, including all snacks and drinks, was 2300 +/- 584 g/day for the city area and 2342 +/- 528 g/day for the fishing-farming areas. The daily protein intake was 58.8 +/- 16.4 g for the women of the city area and 65.5 +/- 17.1 g for the women of the fishing-farming areas. There was a significant correlation between the intake of fish/shellfish and taurine (p=0.001) while there was no correlation between the intake of protein and taurine (p=0.057). The taurine levels in serum ranged from 68.6 to 261.6 micromol/L and the mean value was 169.7 +/- 41.5 micromol/L. There was no significant difference between the women from the city area and the women from the fishing-farming areas in serum taurine levels. The correlations of serum taurine levels with serum retinol levels (p=0.016) and alpha-tocopherol (p=0.014) levels were significant. These results suggest that taurine intake is dependent on the fish/shellfish intake and that taurine may play an important role in the retention of antioxidative nutrients.

Adult↗

PubMed2001

Methodology for miniaturized CE and insulation on a silicon substrate.

We have developed a synchronously switched cyclic capillary electrophoresis (CE) separator that is fabricated on a silicon substrate and glass. Au electrodes were also integrated on the chip that could be wire bonded to the printed circuit board (PCB). The advantage of using a cyclic separator is that it has the high resolution and the ability to separate each sample to the designated reservoir from mixed samples. This approach makes it possible to reduce the supplied voltage and the total chip size. Another goal of this work was to introduce the methodology of electroosmotic flow (EOF) on the silicon substrate and to separate DNA samples using a modified double-T injector.

Journal Article↗

PubMed2001

Anodic oxide films containing Ca and P of titanium biomaterial.

Anodic oxidation and oxide films of titanium in the new electrolyte of calcium glycerophosphate (Ca-GP) and calcium acetate (CA) were investigated by galvanostatic mode, SEM, XRD and EPMA. The anodic oxide film displayed porosity, intermediate roughness, and high crystallinity. Also, the oxide film is enriched with Ca and P and high in thickness without microcracks. According to the surface properties of the oxide film, the optimum condition was that the concentration of the electrolyte was 0.02 M Ca-GP and 0.15 M CA, and current density and final voltage were 70 A/m2 and ca. 350 V. The oxide film formed in the condition is 0.98 microm (Ra) rough, 5-7 microm thick, adhesive to the underlying substrate, and near 1.67 Ca/P ratio in the oxide film.

Biocompatible Materials↗

PubMed2001

The electrochemical oxide growth behaviour on titanium in acid and alkaline electrolytes.

Titanium implants have a thin oxide surface layer. The properties of this oxide layer may explain the good biocompatibility of titanium implants. Anodic oxidation results in a thickening of the oxide film, with possible improved biocompatability of anodized implants. The aim of the present study was twofold: (1) firstly, to characterize the growth behaviour of galvanostatically prepared anodic oxide films on commercially pure (c.p.) titanium and (2) secondly, to establish a better understanding of the electroche0mical growth behaviour of anodic oxide on commercially pure titanium (ASTM grade 1) after changes of the electrochemical parameters in acetic acid, phosphoric acid, calcium hydroxide, and sodium hydroxide under galvanostatic anodizing mode. The oxide thickness was measured by Ar sputter etching in Auger Electron spectroscopy (AES) and the colours were estimated by an L*a*b* system (lightness, hue and saturation) using a spectrophotometer. In the first part of our study, it was demonstrated that the interference colours were useful to identify the thickness of titanium oxide. It was also found that the anodic forming voltages with slope (dV/dt) in acid electrolytes were higher than in alkaline electrolytes. Each of the used electrolytes demonstrates an intrinsically specific growth constant (nm/V) in the range of 1.4--2.78 nm/V. In the second part of our study we found, as a general trend, that an increase of electrolyte concentration and electrolyte temperature respectively decreases the anodic forming voltage, the anodic forming rate (nm/s) and the current efficiency (nm.cm(2)/C), while an increase of the current density and the surface area ratio of the anode to cathode increase the anodic forming voltage, the anodic forming rate and the current efficiency. The effects of electrolyte concentration, electrolyte temperature, and agitation speed were explained on the basis of the model of the electrical double layer.

Acetic Acid↗

PubMed2001

Early Vlambda diversification in sheep.

This study examined a number of tissues during early gestation in foetal sheep to determine the earliest site of Vlambda expression and time of generation of the Vlambda repertoire. Tissues, including spleen, liver, gut, blood and bone marrow, were obtained from 48, 55, 60 and 63 gestational day (g.d.) ovine foetuses and cDNA libraries were prepared from them by reverse transcription-polymerase chain reaction. Clones were randomly selected from cDNA libraries and subjected to sequencing. Analysis of these sequences and comparison with a pool of germline genes led to the following conclusions. The expression of Vlambda occurs earlier in spleen (48 g.d.) than in all of the other tissues examined. Also, diversity is seen earlier and at higher levels in early foetal spleen than in all of the other tissues examined. In this regard, it is notable that splenic Vlambda expression is readily apparent even before such gut-associated lymphoid tissue as the ileal Peyer's patch (IPP) has developed. Two germline Vlambda genes, 5.1 and 5.3 predominate in early immunoglobulin lambda light-chain gene rearrangement. Examination of Jlambda usage revealed the existence of a new Jlambda gene and its utilization during the early phases of the development of the ovine antibody repertoire. This study indicates that sites other than the IPP contribute to the diversification of the Vlambda repertoire in sheep. We suggest that it is likely that foetal spleen may provide a partially diversified B-cell repertoire before the IPP becomes active as a major site for massive clonal expansion and extensive diversification of B cells.

Animals↗