Publications by authors named "Ji Hyun Kwak"
The quantitative label-free detection of neurotransmitters provides critical clues in understanding neurological functions or disorders. However, the identification of neurotransmitters remains challenging for surface-enhanced Raman spectroscopy (SERS) due to the presence of noise. Here, we report spread spectrum SERS (ss-SERS) detection for the rapid quantification of neurotransmitters at the attomolar level by encoding excited light and decoding SERS signals with peak autocorrelation and near-zero cross-correlation.
View Article and Find Full Text PDFWe investigated the physical and chemical properties of non-exhaust coarse and fine particles generated by on-road driving and in a laboratory setting using a mobile sampling system. The on-road driving and laboratory measurements performed under constant speed driving revealed that particles produced by tire wear had a size distribution in the range of 2-3 μm, while roadway particles (RWPs) measured behind the front tire during on-road driving largely comprised crustal materials such as road surface wear particles and road dust as well as tire wear particles (TWPs). The mode diameters of particles obtained from on-road driving under cornering conditions were similar to those obtained under constant speed conditions, but with higher concentrations of crustal elements.
View Article and Find Full Text PDFObjective: We evaluated the diagnostic validity of the 9-item depression module of the Patient Health Questionnaire-9 (PHQ-9) in elderly Korean patients and suggest an optimal cutoff score to screen for major depressive disorders.
Method: The PHQ-9 and an elderly health questionnaire were administered to 1060 subjects older than 60 years, chosen using a stratified random sample of the community. The PHQ-9 was measured and compared with the Geriatric Depression Scale, Center for Epidemiological Studies Depression Scale, and Beck Depression Inventory scores.