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Biomedical subjects

K H Kim

Publications and source records attributed to K H Kim.

At least 55 records · Page 3Linked to original sources

Orbital ordering in LaMnO3 investigated by resonance Raman spectroscopy.

Orbital ordering leads to an unconventional excitation spectrum that we investigate by resonance Raman scattering using incident photon energies between 1.7 and 5.0 eV. We use spectral ellipsometry to determine the corresponding dielectric function. Our results show resonant behavior of the phonon Raman cross section when the laser frequency is close to the orbiton-excitation energy of 2 eV in LaMnO3. We show an excellent agreement between theoretical calculations based on the Franck-Condon mechanism activating multiphonon Raman scattering in first order of the electron-phonon coupling and the experimental data of phonons with different symmetries.

Journal Article↗

Anisotropies of the lower and upper critical fields in MgB2 single crystals.

The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

Journal Article↗

Emotion recognition system using short-term monitoring of physiological signals.

A physiological signal-based emotion recognition system is reported. The system was developed to operate as a user-independent system, based on physiological signal databases obtained from multiple subjects. The input signals were electrocardiogram, skin temperature variation and electrodermal activity, all of which were acquired without much discomfort from the body surface, and can reflect the influence of emotion on the autonomic nervous system. The system consisted of preprocessing, feature extraction and pattern classification stages. Preprocessing and feature extraction methods were devised so that emotion-specific characteristics could be extracted from short-segment signals. Although the features were carefully extracted, their distribution formed a classification problem, with large overlap among clusters and large variance within clusters. A support vector machine was adopted as a pattern classifier to resolve this difficulty. Correct-classification ratios for 50 subjects were 78.4% and 61.8%, for the recognition of three and four categories, respectively.

Autonomic Nervous System↗

Intraoperative assessment of hepatic venous congestion with direct clamping of the hepatic vein trunk for living donor liver transplantation.

We devised a hepatic vein clamping method to assess the amount of hepatic venous congestion (HVC) before liver transection. From February 2003 to May 2003, this method was applied to 5 of 58 living donor livers especially to assess donor safety. The left portal vein and proper hepatic artery as well as the middle hepatic vein (MHV)-left hepatic vein (LHV) trunk were clamped simultaneously to assess the HVC in the remnant right lobe before performing extended left lobectomy. As three donors demonstrated the extent of the HVC equivalent to about 40% of the right lobe volume (RLV), their operations proceeded according to the preoperative plan. The territory of HVC after liver transection was the same as that observed with direct clamping of the hepatic vein. However, one donor showed massive HVC more than 50% of RLV and the operative plan was adjusted to harvest only the left lobe without the MHV trunk for donor safety. To assess the HVC in the remnant left lobe, the isolated LHV trunk was occluded after clamping the donor's proper hepatic artery. The whole left lobe except for a small area at the anterior portion of the medial segment became discolored on LHV clamping: the opposite demarcation appeared on MHV clamping. The amount of HVC was so small that we harvested the right lobe with the MHV trunk. All donors and recipients recovered uneventfully. We believe that this direct clamping method makes the assessment of HVC feasible before parenchymal transection of a donor liver.

Adult↗

A case report of split liver transplantation for two adult recipients in Korea.

We report a case of split liver transplantation (SLT) for two adult recipients, which was the first successful case in Korea. The brain-dead donor was a 22-year-old man weighing 65 kg, but his liver volume was estimated as 2120 mL on computed tomographic volumetry. As it seemed to be too large for a 60-kg recipient candidate, SLT was planned after assessment of lobar liver volume and middle hepatic vein anatomy. The right lobe was mobilized first and the liver parenchyma transected along the right border of the middle hepatic vein. The 1240-g right lobe (segments 5 to 8) graft was implanted into a 57-year-old male patient with acute-on-chronic liver failure in the same manner as a living-donor graft. After that, routine procedures of cadaveric multiorgan procurement were performed. The 670-g left lobe (segments 1 to 4) with a retrohepatic vena cava, common bile duct, and aortic patch was implanted into another 37-year-old male recipient. These two recipients recovered uneventfully surviving 12 months to date. We integrated the surgical techniques learned from hundreds of adult-to-adult living donor liver transplants into this first trial of two adult SLT.

Adult↗

A multicenter trial of the efficacy and safety of 0.03% tacrolimus ointment for atopic dermatitis in Korea.

BACKGROUND: Atopic dermatitis is a chronically relapsing, common inflammatory skin disease, which significantly affects quality of life negatively in many respects. Topical steroids are the mainstay of atopic dermatitis treatment but they carry the risk of local side effects. A topical formulation of tacrolimus, a macrolide calcineurin inhibitor, has recently been developed. OBJECTIVE: To evaluate the efficacy and safety of 0.03% tacrolimus ointment for the treatment of moderate to severe atopic dermatitis in Korea. METHODS: An open, non-comparative, multi-center study with 4 weeks' follow-up was performed. A total of 180 patients (aged 2-57 years old) were enrolled. Tacrolimus ointment (0.03%) was applied to all involved areas twice daily. Efficacy was evaluated by an investigator's global assessment, the eczema area and severity index score, and by the patient's assessment of pruritus and clinical response at baseline, and after weeks 1, 2 and 4. Dermatology life quality index (DLQI), children's DLQI (CDLQI) and toddler's DLQI were assessed at baseline and at week 4. The safety assessment included monitoring all adverse events and clinical laboratory values. RESULTS: All efficacy parameters were improved. The mean EASI (eczema area and severity index) score was 19.7 at baseline and reduced to 8.0 at the end of the study. Moderate improvement was observed by the investigator's global assessment after 4 weeks' treatment. A marked decrease of pruritus was observed, and mild or moderate improvement was observed by patients' global assessments after the treatment period. Significant benefits in terms of quality of life in adults and children with atopic dermatitis were obtained. The most common adverse events associated with tacrolimus treatment were transient skin burning sensation (45.3%) and pruritus (41.6%) at the site of application. CONCLUSION: 0.03% tacrolimus ointment should be considered effective and safe in both Korean children and adults with moderate to severe atopic dermatitis.

Administration, Cutaneous↗

Magnetic-field-induced quantum critical point and competing order parameters in URu2Si2.

A comprehensive transport study, as a function of temperature and continuous magnetic fields of up to 45 T, reveals that URu2Si2 possesses all the essential hallmarks of quantum criticality at fields around 37+/-1 T. The formation of multiple phases at low temperatures at and around the quantum critical point suggests the existence of competing order parameters.

Journal Article↗

The effect of 30% hydrogen peroxide on the color of compomers.

The interaction between bleaching agents and recently introduced compomers has several issues that need to be explored, including morphology and mechanical properties. To investigate the effect of 30% hydrogen peroxide, a bleaching agent, on the color of compomers, three compomers (Compoglass F, Elan, and F2000) were polymerized, bleached up to 120 h, and then measured to determine the reflectance of the specimen during the bleaching process. Color differences were evaluated from the reflectance and color values that were represented by CIE L*a*b* values. Compomers stored in distilled water were used as a source of reference. Teeth were also used for comparison. Color differences for both the tested teeth and compomers and different periods of bleaching and soaking in distilled water showed statistically significant difference (p < 0.0001). Among the tested compomers, Compoglass F demonstrated the highest color difference. In addition, the color differences were maximal during the first 24 h. After 24 h, the color difference increased nearly linearly. Compomers stored in both a bleaching agent and distilled water did not exhibit much color difference between them. However, the color difference between teeth and compomers was considerable.

Animals↗

Procedure-related haemorrhage in embolisation of intracranial aneurysms with Guglielmi detachable coils.

We reviewed the haemorrhagic complications of the endovascular treatment of intracranial aneurysms, in terms of frequency, pre-embolisation clinical status, clinical and radiological manifestations, management and prognosis. In 275 patients treated for 303 aneurysms over 7 years we had seven (one man and six women--2.3%) with haemorrhage during or immediately after endovascular treatment. All procedures were performed with a standardised protocol of heparinisation and anaesthesia. Four had ruptured aneurysms, two at the tip of the basilar artery, and one ach on the internal carotid and posterior cerebral artery, treated after 12, 5, 14, and 2 days, respectively, three were in Hunt and Hess grade 2 and one in grade 1. Bleeding occurred during coiling in three, after placement of at least four coils, and during manipulation of the guidewire to enter the aneurysm in the fourth. Haemorrhage was manifest as extravasation of contrast medium, with a sudden rise in systolic blood pressure in three patients. The other three patients had unruptured aneurysms; they had stable blood pressure and angiographic findings during the procedure, but one, under sedation, had seizures immediately after insertion of four coils, and the other two had seizures, headache and vomiting on the day following the procedure. Heparin reversal with protamine sulphate was started promptly started when bleeding was detected in four patients, and the embolisation was completed with additional coils in three. Emergency ventricular drainage was performed in the two patients with ruptured aneurysm and one with an unruptured aneurysm who had abnormal neurological responses or hydrocephalus. The bleeding caused a third nerve palsy in one patient, which might have been due to ischaemia and progressively improved.

Adult↗

Dynamic and quantitative evaluation of eyelid motion using image analysis.

Evaluation of facial movement, especially eyelid movement, has depended on the subjective judgment of trained clinicians. Recently, a few objective methods have been reported, but they required uncomfortable markers to be attached to the eyelids and a special-purpose, high-speed video camera. This study had two aims: one was to develop a new device for measuring eyelid motion dynamically and quantitatively, without eyelid markers or a high-speed camera; the other was to devise feasible parameters for eyelid motion. The system consisted of a personal computer with a general-purpose multimedia board and a software program that the authors named blepharokymography. A sequence of blinking eyes was recorded with a video camera. After the capturing process of the video, kymograms were produced from the movie file. Kymograms were converted to binary images by threshold filtering. The lower margin of the upper eyelid was traced, and displacement and velocity curves were obtained. Some parameters were devised and verified in preliminary clinical data. The analysis revealed that the displacement (8 mm in normal compared with 5.2 mm in paralysis), average closing velocity (74 mm s(-1) in normal compared with 30.6 mm s(-1) in paralysis) and peak closing velocity (154 mm s(-1) in normal against 63.4 mm s(-1) in paralysis) were useful parameters for differentiating the normal and facial-paralysis states.

Adolescent↗

Religion and body weight.

OBJECTIVES: Relationships between religion and body weight were examined in a US national sample. METHODS: Data from the National Survey of Midlife Development in the United States (MIDUS), collected through telephone and postal questionnaires, were analyzed for 3032 adults aged 25-74. RESULTS: Religious denomination was significantly related to higher body weight in men after accounting for sociodemographic controls. Conservative Protestant men had a 1.1 +/- 0.45 higher body mass index (BMI) than those reporting no religious affiliation. Other religion variables that initially had significant relationships with greater body weight before adjusting for control variables became nonsignificant after smoking was controlled. No significant relationships between religion and body weight were present in women. CONCLUSIONS: Religious denomination was related to body weight in men. Other dimensions of religiosity showing a relationship with higher BMI appeared to be because of the lower rates of smoking among more religious individuals.

Adult↗

MR findings of desmoplastic cerebral astrocytoma of infancy.

Desmoplastic cerebral astrocytoma of infancy (DCAI) presents as a large supratentorial mass consisting of a central cystic component and an enhancing solid component associated with peripheral dural attachment. We report the unusual MR findings of a DCAI that differed from previously reported cases in terms of the presence of calcification, which is not considered a feature of this tumor, and the absence of an enhancing peripheral dural component.

Astrocytoma↗

Characterization and dissolution behavior of sputtered calcium phosphate coatings after different postdeposition heat treatment temperatures.

There is a lack of correlation between specific properties of hydroxyapatite coating surfaces, osseointegration processes, and implant success. The aim of this study was to evaluate the relationship between well-characterized structural and chemical properties of radio-frequency sputtered calcium phosphate (CaP) coatings and their dissolution behavior. Sputtered CaP coatings were evaluated as-sputtered (non-heat treated) or after 1 hour of postsputter heat treatments at 400 degrees C or 600 degrees C. All coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and contact angle measurement. The dissolution behavior of CaP coatings in the presence and absence of proteins was also investigated. It was observed from this study that as-sputtered CaP coatings were amorphous. The 400 degrees C heat-treated CaP coatings exhibited low crystallinity (1.9% +/- 0.4%), whereas the 600 degrees C heat-treated CaP coatings were highly crystalline (67.0% +/- 2.4%). The increase of Ca/P ratio, PO4/HPO4 ratio, and the number of PO4 peaks were observed to be consistent with the increase in heating temperature and the degrees of coating crystallinity. Phosphorus ions released from CaP coatings decreased with the increase of crystallinity of CaP coatings. In addition, immersion of CaP coatings in media containing proteins resulted in an increase in P ions released as compared with coatings immersed in media without proteins. It was concluded that the degree of CaP coating crystallinity can be controlled by varying the postdeposition heat-treatment temperature. It was also concluded that, aside from coating crystallinity, dissolution and reprecipitation of the coatings can be controlled by knowing the presence of proteins in the media and PO4/HPO4 ratio within the coatings.

Calcium Phosphates↗

No association of the TGF-beta1 gene polymorphisms with the renal progression in autosomal dominant polycystic kidney disease (ADPKD) patients.

BACKGROUND: Two genetic loci, PKD I and PKD2, have been identified as being responsible for ADPKD, and PKD1 is known to be associated with a poor prognosis. However, the presence of an intrafamilial study clinical diversity suggests that there are disease-modifying loci. Because the mechanism ofthe renal failure in ADPKD includes a cystic growth and tubulointerstitial atrophy and fibrosis, we studied the associations between 2 polymorphisms in the TGF-beta1 gene, which are known to be associated with chronic tubulointerstitial inflammation, and ADPKD progression in Korean patients. PATIENTS AND METHODS: One hundred and twenty-five individuals who had ADPKD and 47 normal control subjects were genotyped by PCR-RFLP, the T869C (Leu10Pro) variant of TGF-beta gene leader sequence was discriminated with MspA1I and the G915C (Arg25Pro) variants with Bg1I. Statistical significances were determined using the Chi-square test. RESULTS: The distribution of the alleles for the TGF beta1 Leu10Pro polymorphism in ADPKD was: T 54%, C 46%, which was similar to the Korean (56: 44, p = 0.887) and Western controls (65: 35). In addition, no differences were found between the ESRD and the non-ESRD groups (p = 0.888) or the early hypertension and the normotension groups (p = 0.249). The distribution of alleles for the TGF beta1 Arg25Pro polymorphism showed only the GG type which was different from the Western population controls (G:C = 90:10, p = 0.000). CONCLUSIONS: Our results suggest that the polymorphism at Arg25Pro of TGF-beta1 in the Korean population has an allele distribution different from that ofthe Western population and that the polymorphism at Leu10Pro of TGF-beta1 has no association with the renal progression in Korean ADPKD patients.

Adult↗

High magnetic field studies of the hidden order transition in URu2Si2.

We studied in detail the low temperature/high magnetic field phases of URu2Si2 single crystals with specific heat, magnetocaloric effect, and magnetoresistance in magnetic fields up to 45 T. Data obtained down to 0.5 K, and extrapolated to T=0, show a suppression of the hidden-order phase at H0(0)=35.9+/-0.35 T and the appearance of a new phase for magnetic fields in excess of H1(0)=36.1+/-0.35 T observed only at temperatures lower than 6 K. In turn, complete suppression of this high field state is attained at a critical magnetic field H2(0)=39.7+/-0.35 T. No phase transitions are observed above 40 T. We discuss our results in the context of itinerant versus localized f electrons.

Journal Article↗

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↗

Charge ordering fluctuation and optical pseudogap in La(1-x)Ca(x)MnO(3).

Optical spectroscopy was used to investigate the optical gap ( 2 Delta) due to charge ordering (CO) and related pseudogap developments with x and temperature ( T) in La(1-x)Ca(x)MnO(3) ( 0.48< or =x< or =0.67). Surprisingly, we found 2 Delta/k(B)T(CO) is as large as 30 for x approximately 0.5, and decreases rapidly with increasing x. Simultaneously, the optical pseudogap, possibly starting from T* far above T(CO) becomes drastically enhanced near x = 0.5, producing non-BCS T-dependence of 2 Delta with the large magnitude far above T(CO), and systematic increase of T* for x approximately 0.5. These results unequivocally indicate systematically enhanced CO correlation when x approaches 0.5 even though T(CO) decreases.

Journal Article↗