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Jeong-Ho Park

Publications and source records attributed to Jeong-Ho Park.

6 recordsLinked to original sources
PubMed2006

Doped colloidal photonic crystal structure with refractive index chirping to the [111] crystallographic axis.

A three-dimensionally ordered array of close-packed colloidal spheres, a photonic crystal structure in which the refractive index of the medium interstitial lattice in a colloidal crystal spatially changes in the [111] crystallographic axis, is demonstrated. The colloidal photonic crystal structure with refractive index chirping was produced by infiltration of a monomer and organic dopants with a high refractive index into a silica opal, followed by interfacial gel polymerization. The resulting photonic crystal structure has a gradually varying stop band at each different (111) plane in the face-centered cubic (fcc) crystal structure at a normal incidence. This novel structure exhibited optical characteristics that have band-gap broadening by the superposition of stop bands at each plane of the crystal with different dielectric functions. Moreover, the refractive index perturbation in the [111] fcc opal also showed a defect state within a pseudo-photonic band gap. This new type of photonic crystal structure should be useful for the band-gap engineering of photonic-band-gap materials.

Journal Article↗
PubMed2005

Synthesis of two types of nanoparticles in polyelectrolyte capsule nanoreactors and their dual functionality.

Polyelectrolyte multilayer capsule reactors (PEMCRs) for the synthesis of two types of nanoparticles were prepared. The tunable PEMCRs containing two different functional groups that can be used to synthesize two types of nanoparticles simultaneously and to control the composition of two types of nanoparticles within the shell of PEMCs. These PEMCRs enabled the composition as well as the amount of the loaded two types of nanoparticles within the shell of PEMCs to be controlled by the copolymer ratio and the number of reaction cycles. Another interesting finding is that, as a result of the synthesis of two types of nanoparticles, these specially designed PEMCs containing both silver and goethite nanocrystals can be used as antimicrobial capsules, which can move by an external magnetic field. Such a technology has the potential for use in sterilization at the desirable sites.

Journal Article↗
PubMed2004

PCR amplification of DNA containing non-standard base pairs by variants of reverse transcriptase from Human Immunodeficiency Virus-1.

As the next step towards generating a synthetic biology from artificial genetic information systems, we have examined variants of HIV reverse transcriptase (RT) for their ability to synthesize duplex DNA incorporating the non-standard base pair between 2,4-diaminopyrimidine (pyDAD), a pyrimidine presenting a hydrogen bond 'donor-acceptor-donor' pattern to the complementary base, and xanthine (puADA), a purine presenting a hydrogen bond 'acceptor-donor-acceptor' pattern. This base pair fits the Watson-Crick geometry, but is joined by a pattern of hydrogen bond donor and acceptor groups different from those joining the GC and AT pairs. A variant of HIV-RT where Tyr 188 is replaced by Leu, has emerged from experiments where HIV was challenged to grow in the presence of drugs targeted against the RT, such as L-697639, TIBO and nevirapine. These drugs bind at a site near, but not in, the active site. This variant accepts the pyDAD-puADA base pair significantly better than wild type HIV-RT, and we used this as a starting point. A second mutation, E478Q, was introduced into the Y188L variant, in the event that the residual nuclease activity observed is due to the RT, and not a contaminant. The doubly mutated RT incorporated the non-standard pair with sufficient fidelity that the variant could be used to amplify oligonucleotides containing pyDAD and puADA through several rounds of a polymerase chain reaction (PCR) without losing the non-standard base pair. This is the first time where DNA containing non-standard base pairs with alternative hydrogen bonding patterns has been amplified by a full PCR. This work also illustrates a research strategy that combines in clinico pre-evolution of proteins followed by rational design to obtain an enzyme that meets a particular technological specification.

Amino Acid Substitution↗
PubMed2004

Optimal injection volume of epinephrine for endoscopic prevention of recurrent peptic ulcer bleeding.

BACKGROUND: Although the initial rate of hemostasis achieved by endoscopic epinephrine injection for peptic ulcer bleeding is high, bleeding recurs in 14.6% to 35.5% of patients. The aim of this study was to compare rates of recurrent bleeding after endoscopic injection of two different volumes of epinephrine in patients with peptic ulcer bleeding. METHODS: A total of 72 patients with peptic ulcer with active bleeding or a non-bleeding visible vessel were randomly assigned to 15 to 25 mL or 35 to 45 mL injections of a 1:10,000 solution of epinephrine. RESULTS: The two groups were similar with respect to all background variables. The mean volume of epinephrine injected was 19.4 mL: 95% CI [18.7, 20.1] in the 15 to 25 mL group and 41.1 mL: 95% CI [40.0, 42.2] in the 35 to 45 mL group. Initial hemostasis was achieved in 35 of 36 patients (97.2%) in the 15 to 25 mL group and in all 36 patients in the 35 to 45 mL group. The 35 to 45 mL volume was significantly more effective in preventing recurrent bleeding than the 15 to 25 mL volume (0% vs. 17.1%; p < 0.05). For ulcers in the gastric body, the 35 to 45 mL volume was significantly more effective in preventing recurrent bleeding than the 15 to 25 mL volume (0% vs. 31.6%; p = 0.003). For ulcers in other locations, including the gastric antrum and the duodenum, there were no significant differences in the rate of recurrent bleeding between the two groups. CONCLUSIONS: Injection of 35 to 45 mL of a 1:10,000 solution of epinephrine is more effective than injection of 15 to 25 mL of the same solution for prevention of recurrent bleeding from ulcers in the body of the stomach.

Dose-Response Relationship, Drug↗
PubMed2002

Neuro-Behçet's disease mimicking a cerebral tumor: a case report.

We report a rare case of neuro-Behcet's disease (NBD) presenting as an inflammatory pseudotumor in the brain. A 52-year-old woman was evaluated for subacute dizziness and headache. Brain magnetic resonance (MR) imaging showed a right cerebellar mass, which disappeared 2 weeks later. After a year, recurrent mucocutaneous manifestations of Beh et's disease were observed. Immunosuppressant and steroid maintenance treatment were started. She experienced two more neurologic attacks and brain MR imaging revealed an enhancing mass in the right temporal lobe. The second attack showed a good response to steroid pulse therapy, but the third attack did not respond to steroid and her neurologic signs suggested an impending transtentorial hernia. The right temporal lobectomy was performed for the purpose of life-saving. The pathologic finding of the mass was a chronic inflammatory vasculitis, compatible with NBD.

Behcet Syndrome↗