Biomedical subjects

Sunghyun Kim

Publications and source records attributed to Sunghyun Kim.

4 recordsLinked to original sources

PubMed2003

In situ Fe K-edge X-ray absorption fine structure of a nitrosyl adduct of iron phthalocyanine irreversibly adsorbed on a high area carbon electrode in an acidic electrolyte.

Key aspects of the microenvironment surrounding the Fe center in the nitrosyl adduct of iron phthalocyanine, [Fe(Pc)(NO)], have been elucidated from the analysis of the Fe K-edge extended X-ray absorption fine structure (EXAFS) of the material adsorbed on the surface of a high area carbon electrode recorded in situ, in 0.5 M H(2)SO(4). Statistical best fits to the EXAFS data place the Fe center in a five-coordinated square pyramidal configuration shifted away from the Pc plane toward the axially bound NO bent at an angle of ca. 40 degrees with respect to the normal to the Pc plane. This environment is analogous to that of Fe in the nitrosyl adduct of crystalline [Fe(TPP)], where TPP = meso-tetraphenylporphyrinato(2-), determined from X-ray diffraction.

Journal Article↗

PubMed2003

Membrane fluidity sensoring microbial fuel cell.

A study has been performed to examine the effect of temperature and ethanolic stresses on the coulombic efficiency of a microbial fuel cell. The conventional-type fuel cell containing Gram-negative bacteria, Proteus vulgaris, was investigated as a model system. From current output measurements, it was found that the coulombic yields were altered by environmental stresses such as temperature shock or ethanol treatment to the bacteria. While high-temperature or ethanolic shock led to a remarkable decrement in coulombic output, the low-temperature shock induced a slight increase in microbial fuel cell efficiency. These results indicate that the membrane fluidity is affected considerably by environmental stress, which in turn affects the electron transfer process through the bacterial cell membrane to and from the electrode. This interpretation was confirmed by the cyclic voltammetric study of a mediator on an electrode surface modified with the lipids extracted from the membrane of P. vulgaris under the given stress. Markedly different electrochemical behaviors were observed depending on the environmental stress. A reciprocal relationship between coulomb output and the ratio of saturation/unsaturation of fatty acids has been observed. This is the first report, to our knowledge, that the structural adaptation of membrane fatty acids in response to the environmental shock can regulate the coulombic efficiency of a microbial fuel cell.

Bioelectric Energy Sources↗

PubMed2002

Effect of initial carbon sources on the electrochemical detection of glucose by Gluconobacter oxydans.

An electrochemical system consisted of Gluconobacter oxydans as a microorganism and 2-hydroxy-1,4-naphthoquinone (HNQ) as a mediator has been setup to examine the effect of initial carbon sources on the detection of glucose. Catalytic current due to the oxidation of glucose was observed only when both G. oxydans and HNQ were present. From amperometric measurements, it was found that the sensitivity strongly depended on the initial carbon sources. The sensitivity was highest for the cells cultured in a fructose-containing medium and decreased in the order, mannitol > sucrose > glucose > galactose > glycerol. The difference in sensitivity was explained by considering the current rising pattern at an initial stage of a microbial fuel cell constructed with the same components. The rising time, not the fuel cell efficiency, could directly be related to the sensitivity order. A sensor where G. oxydans was confined at the vicinity of the electrode by the semipermeable membrane was constructed. A linear response over a millimolar range of glucose concentration was observed with a cell grown in galactose-containing medium. This work demonstrates that the initial carbon source play an important role on glucose sensoring and should be considered in a real application.

Bioelectric Energy Sources↗

PubMedDate not supplied

Evaluation of a behavioral assessment tool for the individual unable to self-report pain.

Assessment of pain intensity using a standard self-reported pain score is standard practice in most institutions. These instruments require the cognitive ability to process the pain intensity into a numeric or descriptive value. Many institutions are considering adopting an assessment tool for cognitive impairment. The purpose of this study is to evaluate a clinician-administered assessment tool, PAINAD, in patients with cognitive impairment. Opioid consumption and frequency of documented unknown pain were collected in 2 cognitive impaired groups. In the control group, a self-reporting pain intensity tool was used, and in a second group, the PAINAD was used. Opioid use was significantly higher (P = .003) and the rates of reported unknown pain were significantly lower (P < .01) in the group using the PAINAD instrument compared to the control group of patients with cognitive impairment. There were no noted differences in opioid-induced adverse reactions in either group.

Aged↗