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Biomedical subjects

C H Yoon

Publications and source records attributed to C H Yoon.

At least 19 recordsLinked to original sources
PubMed2006

Effects of addition sequence and rapid mixing conditions on use of dual coagulants.

The performance of dual coagulants in clay suspension was investigated in this study using aluminium chloride and the cationic polymer as coagulants. According to the study results, the performance of dual coagulants was affected by dosage of aluminium chloride. Beneficial effect by use of dual coagulants were only noted when aluminium chloride was underdosed. The addition sequence of coagulants was important for the performance of dual coagulants. Simultaneous addition resulted in the best performance, while addition of the polymer first resulted in the worst performance. Addition of aluminium chloride first resulted in the similar performance as single use of aluminium chloride. Although sulphate ion improved the floc characteristics, similar results were obtained. The effectiveness of rapid mixing depended on dosage of aluminium chloride. Extending rapid mixing (6 min) was beneficial when aluminium chloride was underdosed so that coagulation occurred at the combination region. However, such benefit was not observed at the optimum condition, which belonged to the sweep coagulation region. Different floc formation caused the difference. Extended rapid mixing would be beneficial when collision between clay particles and Al(III) was necessary. However, such benefit would disappear at the optimum condition because rapid mixing could break up the floc already formed.

Aluminum Chloride↗
PubMed2005

The fouling characterization and control in the high concentration PAC membrane bioreactor HCPAC-MBR.

This study focuses on the experimental investigation to identify the effect of PAC at high concentrations on the fouling of membranes. A pilot-scale experimental apparatus was installed at a water treatment plant located downstream of Nakdong river basin, Korea. Effluent of rapid sand filter was used as influent of the system, which consists of PAC bio-reactor, submerged membrane module (hollow fiber with pore size 0.1 m) and air supply facility. PAC was dosed at 40 g/L initially and it was not replaced during the operation period. Suction type filtration was carried out at intervals of 12 min. suction and 3 min. idling. At the initial flux 0.36 m/d, the system could be operated stably for around 90 days at target trans-membrane pressure (TMP) of 40 kPa. Among total resistance of membrane filtration, cake and gel layer resistance, Rc+Rg, was the dominant fraction (more than 90% of the total) to increase the filtration pressure, which means that the filtration resistance could be controlled by the PAC cake layer and then irreversible membrane fouling could be prevented. Three minutes air backwashing every 3 days could extend the operation period to 127 days. Organics were analyzed in terms of molecular weight structure. The influent of the system consists of 15.0% and 74.4% of hydrophobic and hydrophilic natural organic matter (NOM), respectively. Hydrophobic and hydrophilic (electrostatic) interaction was the main factor on fouling of the membrane in the reactor. Hydrophobic fraction decreased slightly in the effluent, which means hydrophobic NOM removal in the reactor by adsorption. Organics accumulated in the membrane were extracted for analysis after a certain period of operation. The fraction of hydrophobic and hydrophilic organics was 41.4% and 38.9%, respectively. On the basis of the experimental results, the hydrophobic organics were the major materials causing the fouling of the membrane, which should be changed to other types of material.

Bioreactors↗
PubMed2004

Organic and detergent degradation in combined O3/UF for domestic laundry wastewater reclamation.

This paper focuses on the evaluation of organic and detergent degradation in a combined Ozone/UF system for domestic laundry wastewater reclamation. Formation of by-product was investigated by GC/MS for the reclaimed water. Ozone was injected into the raw wastewater in a 10 L contact tank and the wastewater was circulated through the membrane module for inner pressurized cross-flow filtration. The concentrate was returned back to the contact tank. The membrane used in this experiment was hollow fiber polysulfone UF membrane with MWCO 10,000. It has an effective filtration area of 0.06 m2. The experiment was carried out with intermittent ozone injection, 5 min injection and 10 min idling. Ozone was dosed at the concentration of 1.5 mg/L. The flux of the UF could be maintained at 0.24 m/d under filtration pressure 40-45 kPa and water temperature, 20-22 degrees C. The organic removal efficiency by the system was 90% in terms of COD. Ozone was considerably effective to degrade organics in the wastewater. Molecular weight of organics in the raw waste was mostly greater than 10,000 (72% of 950 mgCOD/L). However 86% of effluent COD (94-100 mg/L) was composed of organics smaller than MWCO 500 by ozone injection. No harmful by-products by ozone contact were detected from the analysis of treated water using GC/MS. It was identified that residual organics in the treated water were 1,1'-Oxybisbenzene, Octadecanoic acid, Squalene and Benzenmethanol, etc., which were additives contained originally in the detergent. Consequently the reclaimed water quality could be estimated safe enough to recycle for the rinsing cycle in a washing machine.

Biodegradation, Environmental↗
PubMed2003

Effects of salt concentration on floc characteristics and pollutants removal efficiencies in treatment of seafood wastewater by SBR.

Most seafood wastewater has been treated by the activated sludge process. Due to changes in salt concentration, pollutant loadings and raw materials, the process is not operated satisfactorily to meet effluent regulation. Most problems faced at present are solid liquid separation. In this study, effects of salt concentration on floc characteristics and pollutants removal efficiencies were investigated in treatment of seafood wastewater by SBR. For analyzing fractal dimension of flocs, the small angle laser light scattering (SALLS) method was applied using a Diffraction Particle Sizer (Malvern Instruments). Organic removal efficiencies (in terms of COD(Mn)) decreased with increasing salt concentration, but eventually reached a steady state. Fractal dimension and floc size also showed similar trends with changing salt concentration. The main reasons to reduced pollutant removal efficiencies were deteriorated biological activity and settling properties. The biological activity was affected faster than the floc characteristics by increasing salt concentration. The deteriorated settling properties were explained by decreased size and fractal dimension of floc due to increasing salt concentration. The settling properties of floc such as sludge volume index (SVI) and zone settling velocity (ZSV) were related to size and fractal dimension of floc. The fractal dimension of floc was better related to the settling properties than the size of floc.

Bioreactors↗
PubMed2001

Changes in voltage-gated calcium channel alpha(1) gene expression in rat dorsal root ganglia following peripheral nerve injury.

Although an increase in the excitability and ectopic spontaneous discharge (ESD) of primary sensory neurons can lead to abnormal burst activity, which is associated with neuropathic pain, the underlying molecular mechanisms are not fully understood. To investigate the relationship between these electrical abnormalities in injured neurons and voltage-gated calcium channel (VGCC) gene expression, reverse transcription-polymerase chain reaction (RT-PCR) was used to monitor the expression of the VGCC alpha(1) gene in the dorsal root ganglion (DRG) following chronic constriction injury (CCI) and axotomy of the rat sciatic nerve. Electrophoresis of the RT-PCR products showed the presence of multiple types of VGCC alpha(1) transcripts with various levels of basal expression in lumbar 4, 5, and 6 DRGs. CCI decreased alpha(1C), alpha(1D), alpha(1H), and alpha(1I) mRNA expression at 7 days in the ipsilateral DRG, to approximately 34-50% of the contralateral side. The same transcripts were repressed 7 days after sciatic axotomy and their reduction levels proved similar to those of CCI. Considering that changes of the intracellular calcium concentration modify the maintenance of ESD in injured DRG, these results suggest that the downregulation of alpha(1C), alpha(1D), alpha(1H) and alpha(1I) subunit gene expression in the rat DRG following peripheral nerve injury may contribute to the production of ESD associated with damaged nerves.

Animals↗
PubMed2001

Regio- and stereocontrol elements in Rh(II)-catalyzed intramolecular C-H insertion of alpha-diazo-alpha-(phenylsulfonyl)acetamides.

[reaction: see text]. Intramolecular C-H insertion reaction of alpha-diazo-alpha-(phenylsulfonyl)acetamides proceeded with high regio- and stereoselectivities to afford highly functionalized gamma-lactams predominantly or exclusively. The high regioselectivity was attributed to the use of the phenylsulfonyl moiety, which altered electron density at the carbenoid center and exerted a steric effect during the insertion reaction. Also described herein are three control elements to determine regioselectivity, which are amide conformational, stereoelectronic, and substituent effects.

Acetamides↗
PubMed2001

Bombycis corpus extract prevents amyloid-beta-induced cytotoxicity and protects superoxide dismutase activity in cultured rat astrocytes.

Bombycis corpus(BC) or Bombyx Batryticatus, a batryticated silkworm and white-stiff silkworm, is a drug consisting of the dried larva of silkworm, Mobyz mori L., dead and stiffened due to the infection of Beauveria (Bals.) Vuill. In the present study, we have examined the protective effect of the water extracts against Amyloid- beta(A beta) 25-35 peptide-induced cytotoxicity by microscopic observation and LDH assay, and its action on antioxidative enzymes using cultured astrocyte cells. A beta 25-35-induced cell death was protected by the application of water extract of BC in a dose-dependent manner, and concentrations of 10(-6)to 10(-7)g ml(-1)showed a significant effect compared to exposure of A beta 25-35 alone. When antioxidative enzyme activities such as catalase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione-S transferase (GST) were assayed after A beta 25-35 treatment, most enzyme activities were decreased in a similar fashion. BC treatment of A beta 25-35-treated astrocytes did not affect the enzyme activities of catalase, GSH-Px and GST. However, only SOD activity was enhanced by BC treatment and this may result from the potentiation of the antioxidative ability of BC. The protective effect of BC against cytotoxicity induced by Abeta 25-35 strongly indicates that BC could be a protective agent for free radical generating compounds, and that Abeta 25-35 is not only a potent lipid peroxide inducer, but can also cause changes in antioxidative enzymes. From the results, it was concluded that BC has a protective effect against Abeta -induced cytotoxicity in cultured astrocyte cells through the inhibition of lipid peroxidation and protection of antioxidative enzymes.

Amyloid beta-Peptides↗
PubMed2001

Sonographic windsock sign of a duodenal web.

We report a neonate with a duodenal web demonstrating the windsock appearance on US. In neonates, duodenal web is rare and its windsock appearance is also rarely seen. The windsock sign of duodenal web has been a well-known finding on upper gastrointestinal series. The corresponding windsock appearance may be demonstrated on US. Duodenal web can, therefore, be accurately diagnosed by identifying the sonographic windsock sign even in neonates.

Ampulla of Vater↗
PubMed2001

Various applications of titanium mesh screen implant to orbital wall fractures.

As the number of high velocity injuries increases, orbital wall fractures that involve other facial bone fractures, especially those showing multiple crushed fractures have become increasingly common. However, owing to its complex anatomic structure, our inability to visualize details and relatively thin orbital wall, corrective restorations and fixations are very difficult. Recently several reports have claimed good results using titanium implants to repair orbital fracture. Over a period of 36 months, Titanium mesh screen 1.0 (SYNTHES) were applied to the repair of orbital fracture in various ways, taking 39 examples of orbital wall fracture patients requiring operating treatment. A titanium mesh screen 1.0 was used either as an onlay implant after it was shaped to fit the anatomical shape of the fracture portion, or as cover implant to fix bony pieces after repairing a severely crushed fracture on the orbital rim or maxillary wall segments. 1.3-mm micro-screws were used to fix the titanium mesh screen when needed. The titanium mesh screen 1.0 was rigid, yet malleable enough to get the desired shape. It could be folded and screwed easily, and was also easy for follow-up with fewer artifacts on the CT findings. Therefore, we could restore and fix much easier and faster even crushed tiny bony pieces without loss and achieve more accurate three-dimensional anatomical reconstruction of orbital wall fracture.

Adolescent↗
PubMed2001

Intussusception in children: US-guided pneumatic reduction--initial experience.

PURPOSE: To assess the feasibility and effectiveness of ultrasonography (US)-guided pneumatic reduction of intussusception in children. MATERIALS AND METHODS: The study group consisted of 49 consecutive patients (aged 2 months to 7 years; 36 boys, 13 girls) who underwent 52 reductions of intussusception during 9 months. Intussusception was diagnosed in all patients with the known US criteria, and all patients underwent a US-guided pneumatic reduction attempt wholly within the US examination room. A pressure of 60 mm Hg was maintained for 30 seconds, with US guidance. The procedure was considered to be successful when US showed the disappearance of the intussusceptum and the edematous terminal ileum with an abrupt transition into the normal proximal ileum. When the intussusception was not reduced, the procedure was repeated, with pressure increased to 120 mm Hg. RESULTS: The overall success rate of US-guided pneumatic reduction was 92% (48 of 52 reductions), with no immediate recurrence. Of the two patients who had intussusceptions that were irreducible, one had residual ileoileal intussusception at surgery, and the other had an ileal polyp as a lead point. Perforation occurred in two (4%) of 52 cases; one patient underwent right hemicolectomy due to bowel necrosis and had a pinpoint perforation in the normal proximal transverse colon, and the other underwent manual reduction of ileoileocolic intussusception, with microperforation in the proximal transverse colon. CONCLUSION: US-guided pneumatic reduction seems to be a feasible and effective method for the treatment of intussusception in children because of its radiation-sparing effect and high success rate.

Child↗
PubMed2001

Salviae radix extract prevents cisplatin-induced acute renal failure in rabbits.

The present study was carried out to determine if salviae radix extract (SRE) exerts a beneficial effect against cisplatin-induced renal failure in rabbits. Rabbits were pretreated with SRE orally for 7 days, followed by cisplatin injection (5 mg/kg i.p.). Cisplatin injection caused a reduction in GFR, which was accompanied by an increase in serum creatinine levels. The fractional Na+ excretion was increased by cisplatin injection. PAH uptake by renal cortical slices was inhibited by the administration of cisplatin. Such changes were prevented by SRE pretreatment. Cisplatin injection increased lipid peroxidation, which was prevented by SRE pretreatment. The protective effect of SRE was supported by morphological studies. Cisplatin injection reduced renal blood flow that was not affected by SRE pretreatment. Cisplatin treatment in vitro in renal cortical slices increased LDH release and lipid peroxidation, which were prevented by 0.05% SRE. These results indicate that lipid peroxidation plays a critical role in cisplatin-induced acute renal failure. SRE exerts a protective effect against renal cell injury induced by cisplatin, and its effect may be attributed to its antioxidant action. However, the underlying mechanism by which SRE has antioxidant action remains to be defined.

Acute Kidney Injury↗
PubMed2001

Using edge enhancement to identify subtle findings on soft-copy neonatal chest radiographs.

OBJECTIVE: The purpose of this study was to evaluate whether edge enhancement could improve the visibility of subtle findings on soft copies of neonatal chest radiographs. MATERIALS AND METHODS: Two radiologists reviewed 82 soft-copy neonatal chest radiographs before and after the application of edge enhancement on our picture archiving and communication system (PACS). The visibility of a pneumothorax (n = 22), central venous catheter (n = 32), umbilical arterial catheter (n = 36), endotracheal tube (n = 40), and normal anatomic structures (the minor fissure, anterior segmental bronchus of the right upper lobe, and aortic arch, n = 57) was evaluated. Six of 22 soft-copy images depicting a pneumothorax were excluded from the evaluation of image quality either because of the large size of the pneumothorax itself (n = 7) or because of the lack of confirmatory evidence that would have been provided by an additional lateral decubitus (n = 6) or cross-table lateral radiograph (n = 3). Image quality was evaluated by visual grading analysis. RESULTS: The visibility of a pneumothorax (p < 0.01), vascular catheters (p < 0.001), the minor fissure (p < 0.001), and the anterior segmental bronchus of the right upper lobe (p < 0.001) improved significantly after applying edge enhancement to soft copies of neonatal chest radiographs, whereas the visibility of the aortic arch did not improve. Evaluations of the improvements in the visibility of the endotracheal tube were inconsistent. CONCLUSION: Application of edge enhancement to soft copies of neonatal chest radiographs helps radiologists to identify small pneumothoraces, vascular catheters, and delicate normal structures, thereby improving the detection of subtle chest findings in the neonatal intensive care unit.

Catheterization, Central Venous↗
PubMed2001

Catalytic wet air oxidation of p-nitrophenol (PNP) aqueous solution using multi-component heterogeneous catalysts.

This study investigated the decomposition of high strength p-nitrophenol (PNP) of 2,000 mg/l (3,400 mg of COD/1,250 mg of TOC) by catalytic wet air oxidation. Multi-component heterogeneous catalysts were used as catalysts for this purpose. The study results using a batch reactor showed that catalyst "D" (Mn-Ce-Zr 22.4 g plus CuSO4 1.0 g; Mn-Ce-Zr-Cu [CuSO4]) was more effective (56-74%) than catalyst "A" (Mn-Ce-Zr 22.4 g) under the given conditions (O2 partial pressure of 1.0 MPa; temperature of 170-190 degrees C; 30 min of reaction time). The best result was obtained when 2 g of Mn-Ce-Zr-Cu [CuSO4] was used per 1L of PNP aqueous solution. COD and TOC removal efficiencies were 18% and 23% without catalysts during 20 min of reaction at 190 degrees C. They were improved to 79% and 71% with 2 g/L of Mn-Ce-Zr-Cu [CuSO4] under the same conditions. The ratio of BOD5/COD was measured to evaluate biodegradability. It was 0.05 without catalyst and increased to 0.33 with 2 g/L of Mn-Ce-Zr-Cu [CuSO4] for 20 min of reaction.

Catalysis↗
PubMed2000

Requirements of multiple domains of SLI-1, a Caenorhabditis elegans homologue of c-Cbl, and an inhibitory tyrosine in LET-23 in regulating vulval differentiation.

SLI-1, a Caenorhabditis elegans homologue of the proto-oncogene product c-Cbl, is a negative regulator of LET-23-mediated vulval differentiation. Lack of SLI-1 activity can compensate for decreased function of the LET-23 epidermal growth factor receptor, the SEM-5 adaptor, but not the LET-60 RAS, suggesting that SLI-1 acts before RAS activation. SLI-1 and c-Cbl comprise an N-terminal region (termed SLI-1:N/Cbl-N, containing a four-helix bundle, an EF hand calcium-binding domain, and a divergent SH2 domain) followed by a RING finger domain and a proline-rich C-terminus. In a transgenic functional assay, the proline-rich C-terminal domain is not essential for sli-1(+) function. A protein lacking the SH2 and RING finger domains has no activity, but a chimeric protein with the SH2 and RING finger domains of SLI-1 replaced by the equivalent domains of c-Cbl has activity. The RING finger domain of c-Cbl has been shown recently to enhance ubiquitination of active RTKs by acting as an E3 ubiquitin-protein ligase. We find that the RING finger domain of SLI-1 is partially dispensable. Further, we identify an inhibitory tyrosine of LET-23 requiring sli-1(+) for its effects: removal of this tyrosine closely mimics the loss of sli-1 but not of another negative regulator, ark-1. Thus, we suggest that this inhibitory tyrosine mediates its effects through SLI-1, which in turn inhibits signaling upstream of LET-60 RAS in a manner not wholly dependent on the ubiquitin-ligase domain.

Amino Acid Motifs↗
PubMed1997

Gastrointestinal involvement in Henoch-Schönlein syndrome: CT findings.

OBJECTIVE: The purpose of this study was to describe the CT features of gastrointestinal involvement in seven patients with Henoch-Schönlein syndrome. CONCLUSION: Although the incidence of Henoch-Schönlein syndrome is low, it should be considered when CT scans show multifocal areas of bowel-wall thickening, mesenteric edema, vascular engorgement, and nonspecific lymphadenopathy. It should be considered especially in young patients with acute gastrointestinal symptoms.

Adolescent↗