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Biomedical subjects

Hyun K Kim

Publications and source records attributed to Hyun K Kim.

7 recordsLinked to original sources
PubMed2006

Continuous shared control for stabilizing reaching and grasping with brain-machine interfaces.

Research on brain-machine interfaces (BMI's) is directed toward enabling paralyzed individuals to manipulate their environment through slave robots. Even for able-bodied individuals, using a robot to reach and grasp objects in unstructured environments can be a difficult telemanipulation task. Controlling the slave directly with neural signals instead of a hand-master adds further challenges, such as uncertainty about the intended trajectory coupled with a low update rate for the command signal. To address these challenges, a continuous shared control (CSC) paradigm is introduced for BMI where robot sensors produce reflex-like reactions to augment brain-controlled trajectories. To test the merits of this approach, CSC was implemented on a 3-degree-of-freedom robot with a gripper bearing three co-located range sensors. The robot was commanded to follow eighty-three reach-and-grasp trajectories estimated previously from the outputs of a population of neurons recorded from the brain of a monkey. Five different levels of sensor-based reflexes were tested. Weighting brain commands 70% and sensor commands 30% produced the best task performance, better than brain signals alone by more than seven-fold. Such a marked performance improvement in this test case suggests that some level of machine autonomy will be an important component of successful BMI systems in general.

Arm↗
PubMed2006

Race disparities in childhood asthma: does where you live matter?

OBJECTIVE: This study investigates whether racial/ethnic disparities in childhood asthma prevalence can be explained by differences in family and neighborhood socioeconomic position (SEP). METHODS: Data were from the 2001 Rhode Island Health Interview Survey (RI HIS), a statewide representative sample of 2,600 Rhode Island households, and the 2000 U.S. Census. A series of weighted multivariate models were fitted using generalized estimating equations (GEE) for the logistic case to analyze the independent and joint effects of race/ethnicity and SEP on doctor-diagnosed asthma among 1,769 white, black and Hispanic children <18 years old. RESULTS: Compared with white children, black children were at increased odds for asthma and this effect persisted when measures of family and neighborhood SEP were included in multivariate models (AOR: 2.49; 95% Cl: 1.30-4.77). Black children living in poverty neighborhoods had substantially higher odds of asthma than Hispanic and white children in poverty areas and children in moderate- and high-income neighborhoods (AOR: 3.20: 95% Cl: 1.62-6.29). CONCLUSION: The high prevalence of asthma among black children in poor neighborhoods is consistent with previous research on higher-than-average prevalence of childhood asthma in poor urban minority communities. Changing neighborhood social structures that contribute to racial disparities in asthma prevalence remains a challenge.

Adolescent↗
PubMed2005

Impact of caring for children with special health care needs on the family: Rhode Island's experience.

OBJECTIVES: The impact of caring for children with special health care needs (CSHCN) on their families' finances and employment was studied. METHODS: Data from the 2001 National Survey of Children with Special Health Care Needs were used to measure financial and employment problems. The level of impact was examined by child's age, gender, ethnicity, race, mother's education, poverty status, and severity of the child's condition. The association between core outcome measures and the level of family impact was determined after adjusting for potential confounding factors. RESULTS: Financial or employment problems were more likely to occur among families with young children, with incomes below 200% poverty and with children whose condition usually/always affected their activities. Compared to families without these problems, impacted families were less likely to partner in decision making, be satisfied with services, receive comprehensive care in a medical home, have adequate health insurance, and feel service systems are organized for easy use. CONCLUSIONS: Many families of CSHCN face financial and employment problems and are less likely to have a medical home, adequate insurance, and access to health care services.

Adolescent↗
PubMed2005

Upregulation of LPS-induced chemokine KC expression by 15-deoxy-delta12,14-prostaglandin J2 in mouse peritoneal macrophages.

15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) was initially identified as a high affinity natural ligand for the peroxisome proliferator-activated receptor (PPAR)-gamma. Recent studies have shown that it has a potent anti-inflammatory effect by attenuating the expression of proinflammatory mediators in activated macrophages, mainly through the inhibition of nuclear factor (NF)-kappaB-dependent transcription of inflammatory genes. In this study, we investigated the synergistic effect of 15d-PGJ(2) on the expression of LPS-induced chemokine KC mRNA in mouse peritoneal macrophages. The time course of KC mRNA expression in cells stimulated with 15d-PGJ(2) plus LPS simultaneously (15d-PGJ(2)/LPS) showed similar patterns to the cells treated with LPS alone, and 15d-PGJ(2) had no effect on the stability of LPS-induced KC mRNA expression. Although NF-kappaB activity in cells treated with LPS was augmented by 15d-PGJ(2), pyrrolidone dithiocarbamate (PDTC) did not block the synergistic effect of 15d-PGJ(2) on LPS-induced KC mRNA expression. However, the synergistic effect of 15d-PGJ(2) was markedly inhibited when the macrophages were treated with a inhibitor of the mitogen-activated protein kinase (MAPK) signalling pathway, 2'-amino-3'-methoxyflavine (PD98059). Therefore, the mechanism of synergistic action of 15d-PGJ(2) on the expression of LPS-induced KC mRNA in mouse peritoneal macrophages is possibly related to the MAPK signalling pathway, not to NF-kappaB activation. These data may contribute to unravelling some of the different mechanisms contrary to the anti-inflammatory effect of 15d-PGJ(2).

Animals↗
PubMed2004

Virtual-reality-based laparoscopic surgical training: the role of simulation fidelity in haptic feedback.

Although there have been significant advances in the development of virtual-reality-based surgical simulations, there remain fundamental questions concerning the fidelity required for effective surgical training. A dual-station experimental platform was built for the purpose of investigating these fidelity requirements. Analogous laparoscopic surgical tasks were implemented on a virtual station and a real station, with the virtual station modeling the real environment with various degrees of fidelity. After measuring the subjects' initial performance on the real station, different groups of subjects were trained on the virtual station under a variety of conditions and finally tested on the real station. Experiments involved bimanual pushing and cutting tasks on a nonlinear elastic object. The results showed that force feedback results in significantly improved training transfer as compared to training without force feedback. The training effectiveness of a linear approximation model was approximately the same as that of a more accurate nonlinear model.

Analysis of Variance↗
PubMedDate not supplied

Interaction of protonated anticancer thiazines with water-insoluble phospholipids and antineoplastic agents.

A series of neuroleptic protonated phenothiazine derivatives (promethazine, promazine, triflupromazine, methotrimeprazine, propiomazine, trifluoperazine and fluphenazine), some with known anticancer properties, were complexed with water-insoluble antineoplastice agents such as 5-fluorouracil (5FU), methotrexate (MTX) and sulindac, as well as with components of biomembrane and synthetic phospholipids as possible models of cancer and microbial cells. In all cases water-soluble micellar inclusion adducts were formed exhibiting electron charge transfer complex behaviour, with the appearance of thazine free radicals. The thiazines sequestered the drugs and phospholipids in well-defined molar ratios (MR) parabolically-dependent on the dipole moments (mu) of the protonated phenothiazine derivatives. pH comparisons showed that the inclusion adducts followed a model in which the compounds were enveloped in the lipophilic interior of the thiazine aggregates, while the side-chains of the latter faced the aqueous environment. In the model experiment, interaction of the thiazines and the 5FU adducts with E. coli F' lac was additive to marginally synergistic, confirmed by the checkerboard technique. The parabolic dependence of the molar minimum inhibitory concentration of the thiazines and thiazine/5FU adducts on the thiazine dipole moments suggests that their primary loci of interaction are the cell wall or membrane phospholipid components. Thiazines, especially those with dipole moments centered on about 6 D, near which the lowest MR occurs, can act as effective carriers for insoluble or sparsely soluble drugs. Any new thiazine drug for use alone or as a carrier in anticancer therapy should be designed with this criterion in mind.

Antineoplastic Agents↗