Search PubMed⌕ Search

Biomedical subjects

J H Jung

Publications and source records attributed to J H Jung.

At least 19 recordsLinked to original sources
PubMed2006

Effect of orbital rotation and mixing on the optical properties of orthorhombic RMnO3 (R=La, Pr, Nd, Gd, and Tb).

We investigated the ab-plane absorption spectra of RMnO3 (R=La, Pr, Nd, Gd, and Tb) thin films. As the ionic radius of the R ion decreases, we observed a drastic suppression of the 2 eV peak, i.e., the intersite optical transition between spin- and orbital-aligned states across the Mott gap. We found that, in addition to orbital rotation, orbital mixing in the orbital-ordered state should play an important role in the suppression of 2 eV peak. We also found that the spectral weight of 2 eV peak is proportional to the A-type antiferromagnetic ordering temperature, which suggests that the magnetic interaction should be sensitively coupled to the orbital degree of freedom.

Journal Article↗
PubMed2004

Optical magnetoelectric effect in the polar GaFeO3 ferrimagnet.

The optical magnetoelectric (ME) effect, i.e., the change of optical absorption upon the reversal of the light propagation direction, has been investigated for a polar ferrimagnet GaFeO3. For dipole- and spin-forbidden d-d transition bands located at 1.2-2.3 eV, a clear signal of the optical ME effect (Deltaalphat approximately 3x10(-3)) is observed with an applied magnetic field as low as 500 Oe and a sample thickness (t) of 50 microm. The observation of a large ME effect in the present compound suggests a possible route to magnification of this novel phenomenon for application.

Journal Article↗
PubMed2004

Colonoscopic manifestations of typhoid fever with lower gastrointestinal bleeding.

BACKGROUND: Intestinal bleeding in patients with typhoid fever usually occurs in the ileum. However, endoscopic findings in such patients are not well established. We examined the colonoscopic manifestations of intestinal lesions with bleeding in patients with typhoid fever. PATIENTS AND METHODS: The colonoscopic findings of seven patients who presented with haematochezia due to typhoid fever were reviewed retrospectively. Typhoid fever was diagnosed when the Salmonella typhi was isolated or when the Widal test showed strongly positive reactions. RESULTS: Clinical data and colonoscopic findings were reviewed in seven patients (four men and three women with an average age of 42 years). The most commonly involved area was the terminal ileum (100%), followed by the ileocecal valve (57%), the ascending colon (43%), and the transverse colon (29%). Left colon was intact in all cases. The most common colonoscopic finding was multiple variable-sized punched-out ulcers with slightly elevated margin, as found in five patients. In two patients, only several oedematous hyperaemic mucosal patches with haemorrhagic spots or shallow erosions were seen. Active bleeding was noticed only in one patient, who received endoscopic haemostasis twice. The remaining six patients were treated by conservative treatment including antibiotic therapy. There was no complication during or after the colonoscopic examination. CONCLUSIONS: Intestinal bleeding in typhoid fever usually occurs from the ulcers in the ileum or proximal colon, and the most common colonoscopic manifestations are multiple variable-sized punched-out ulcerations.

Adult↗
PubMed2003

Change of electronic structure in Ca2RuO4 induced by orbital ordering.

Optical conductivity spectra sigma(omega) were used to investigate the effect of orbital ordering on the electronic structure of Ca2RuO4. Our LDA+U calculation predicts Ru 4d(xy) ferro-orbital ordering at the ground state, and well explains the present sigma(omega) as well as the reported O 1s x-ray absorption spectra. Variation of temperature (T) causes a large change of spectral weight over several eV as well as collapse of a charge gap accompanied by elongation of the c-axis Ru-O bond length. These results clearly indicate that the d(xy) orbital ordering plays a crucial role in the metal-insulator transition and the T-dependent electronic structure on a large energy scale.

Journal Article↗
PubMed2002

Spin-orbital pattern dependent polaron absorption in manganites.

We systematically investigated optical properties of Nd1-xSrxMnO3 single crystals ( x = 0.40, 0.50, 0.55, and 0.65). They are similar in their spin-orbital (SO) disordered states at room temperature. At low temperature, the crystals enter into various SO ordered states, i.e., F-, CE-, A-, and C-type orderings, and their mid-infrared absorptions become quite different. The remarkable variation can be explained by polaron dynamics which depend on the ordering patterns. This SO pattern dependent polaron model can also explain the pseudo CE-type ordering case, demonstrating that this scheme can explain the carrier dynamics in complex SO configurations.

Journal Article↗
PubMed2001

Direct duplication of 8p21.3-->p23.1: a cytogenetic anomaly associated with developmental delay without consistent clinical features.

We report six cases in two families and a sporadic case with a direct duplication of region 8p21.3-->23.1. In one family, the duplication started in the mother and was transmitted to one son and one daughter. In the second family, the father was mosaic for the anomaly that was transmitted to his two daughters. The cytogenetic anomaly was initially described as an 8p+ with banding analysis and then delineated with fluorescence in situ hybridization (FISH) using whole-chromosome 8 painting, 8p specific painting, and 8p or 8p/8q subtelomeric probes. Deletion was not detected in the subtelomeric region of the abnormal chromosome 8 examined in one family and in the sporadic case. The phenotypic picture varies from normal to moderate mental retardation in the affected individuals. No consistent minor anomalies or congenital defects were observed among these cases. After comparing the chromosome region involved in our cases with those in others having direct or inverted duplications of 8p, it is thought that the segment 8p21.1-->21.3 might be the critical region for an 8p duplication syndrome. The parental origin of the duplication does not seem to impact its clinical significance.

Chromosome Aberrations↗
PubMed2001

Helical ribbon aggregate composed of a crown-appended cholesterol derivative which acts as an amphiphilic gelator of organic solvents and as a template for chiral silica transcription.

New crown-appended cholesterol-based organogelator 1, which has two cholesterol skeletons as a chiral aggregate-forming site, two amino groups as an acidic proton-binding site, and one crown moiety as a cation-binding site, was synthesized, and the gelation ability was evaluated in organic solvents. It can gelate acetic acid, acetonitrile, acetone, ethanol, 1-butanol, 1-hexanol, DMSO, and DMF under 1.0 wt %, indicating that 1 acts as a versatile gelator of various organic solvents. To characterize the aggregation mode in the organogel system, we observed a CD spectrum of the acetic acid gel 1. In the CD spectrum, the lambda(theta)=0 value appears at 353 nm, which is the same as the absorption maximum lambda(max) = 353 nm. The positive sign for the first Cotton effect indicates that the dipole moments of azobenzene chromophores tend to orient in a clockwise direction. Very surprisingly, the TEM images of the 1 + acetic acid gel resulted in the helical ribbon and the tubular structures. Sol-gel polymerization of tetraethoxysilane was carried out using 1 in the gel phase. The silica obtained from the 1 + acetic acid gel showed the helical ribbon with 1700-1800-nm pitches and the tubular structure of the silica with approximately 560-nm outer diameter. As far as can be recognized, all the helicity possesses a right-handed helical motif. Since the exciton-coupling band of the organogel also shows R (right-handed) helicity, we consider that a microscopic helicity is reflected by a macroscopic helicity.

Journal Article↗
PubMed2001

Structural determination of lysophosphatidylcholines extracted from marine sponges by fast atom bombardment tandem mass spectrometry.

A series of lysophosphatidylcholines were isolated from the marine sponge Spirastrella abata by reversed-phase high performance liquid chromatography (HPLC) and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their structural elucidation was carried out with fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The collision-induced dissociation (CID) of protonated and sodiated molecular ions produced diverse product ions via a series of dissociative processes. Because of the positive charge of the amine group at the end of the molecules, charge-remote fragmentation patterns of specific ions, [M + H](+) or [M + Na](+), were very helpful for the identification of product ions which are characteristic for choline and long hydrocarbon chains substituted at the glycerol back bone. Moreover, the CID-MS/MS spectra of sodium adducted molecular ions for lysophosphatidylcholines yielded common characteristic fragment ions for the choline moiety and characteristic ions [M + Na-103](+), [M + Na-85](+) and [M + Na-59](+) in the higher mass region.

Animals↗
PubMed2001

A triterpene glucosyl ester from the roots of Rubus crataegifolius.

Along with five known triterpene glycosides, a new triterpene glucosyl ester, named crataegioside, was isolated from the roots of Rubus crataegifolius Bunge. The structure was established as ilexosapogenin A 28-O-beta-D-glucopyranosyl ester by chemical and spectroscopic methods.

Dealkylation↗
PubMed2001

A new cyclic phenyllactamide from Salvia miltiorrhiza.

From the rhizome of Salvia miltiorrhiza, a new cyclic phenyllactamide was isolated and characterized as 2,10,11-trihydroxy-8-methoxy-1,6,7,8-tetrahydro-2H-benzo[e]azecine-3,5-dione (1) from spectroscopic evidence. The new compound was found to be a scavenger of 1,1-diphenyl-2-picrylhydrazyl radical.

Acetamides↗
PubMed2001

Additional cytotoxic polyacetylenes from the marine sponge Petrosia species.

Ten new polyacetylenic alcohols (1-6, 8-11), along with a known compound, petrocortyne C (7), were isolated from the marine sponge Petrosia sp. The gross structures were established based on NMR and MS data, and the absolute configuration was determined by the modified Mosher's method. These compounds displayed considerable cytotoxicity against a small panel of human solid tumor cell lines. Compounds 1-11 were further evaluated for in vitro inhibitory activity on DNA replication.

Animals↗
PubMed2001

Additional bioactive Lyso-PAF congeners from the sponge Spirastrella abata.

A known (1) and four new (2--5) lyso-PAF (platelet activating factor) derivatives were isolated from the sponge Spirastrella abata. Two of them are unprecedented in having a methoxy group at C-2'. The structures have been determined by combined spectroscopic methods. Their inhibitory effect on the biosynthesis of cholesterol and cytotoxicity against human solid tumor cell lines are reported.

Animals↗
PubMed2001

Cytotoxic diacetylenes from the stony coral Montipora species.

Ten new (1, 4-6, 9-14) and four known (2, 3, 7, 8) diacetylenes have been isolated from a brine shrimp active fraction of the methanolic extract of the stony coral Montipora sp. The structures were determined by combined spectroscopic methods. The compounds exhibited significant cytotoxicity against a small panel of human solid tumor cell lines. Montiporyne A (15), a previously reported congener, was also found to induce apoptosis in human colon tumor cell.

Acetylene↗
PubMed2001

New cytotoxic sesterterpenes from the sponge Sarcotragus species.

Five new (1-3, 5, and 7) and two known (4, 6) furanosesterterpene tetronic acids were isolated from the marine sponge Sarcotragus sp. by bioactivity-guided fractionation. These compounds showed cytotoxicity against a panel of five human tumor cell lines. The gross structures were established on the basis of NMR and MS analyses. The compounds showed interesting variations of geometry and absolute configuration.

Animals↗
PubMed2001

Cytotoxic polyacetylenic alcohols from the marine sponge Petrosia species.

New polyacetylenic alcohols (1-5) have been isolated as cytotoxic principles from the marine sponge Petrosia sp. The compounds were particularly cytotoxic against a human melanoma cell line (SK-MEL-2). The gross structures were established on the basis of NMR and MS data, and the absolute configuration was determined by the modified Mosher's method.

Acetylene↗
PubMed2001

New galactolipids from the marine bacillariophycean microalga Nitzschia sp.

Two new galactopyranosyldiacylglycerols have been isolated from the marine bacillariophycean microalga Nitzschia sp. and their structures were determined as (2S)-3-O-beta-D-galactopyranosyl-1,2-di-O-(9Z-hexadecenoyl)glycerol (1) and (2S)-3-O-beta-D-galactopyranosyl-1-O-(5Z,8Z,11Z,14Z,17Z-eicosapentaenoyl)-2-O-(9Z-hexadecenoyl)glycerol (2) by physicochemical evidence.

Chromatography, High Pressure Liquid↗