Spread spectrum SERS allows label-free detection of attomolar neurotransmitters.

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. Compared to conventional SERS measurements, the experimental result of ss-SERS shows an exceptional improvement in the signal-to-noise ratio of more than three orders of magnitude, thus achieving a high temporal resolution of over one hundred times. The ss-SERS measurement further allows the attomolar SERS detection of dopamine, serotonin, acetylcholine, γ-aminobutyric acid, and glutamate without Raman reporters. This approach opens up opportunities not only for investigating the early diagnostics of neurological disorders or highly sensitive biomedical SERS applications but also for developing low-cost spectroscopic biosensing applications.

Characterization of non-exhaust coarse and fine particles from on-road driving and laboratory measurements.

We 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. Under braking conditions, the particulate matter (PM) concentrations of brake wear particles (BWPs) sampled near the brake pad increased significantly and were much higher than the concentration of RWPs during deceleration, indicating that BWPs are one of the main sources of non-exhaust emissions. In addition, BWPs observed from on-road and laboratory measurements had a broader PM size range (1-10 µm) than RWPs. Size-segregated chemical analysis of PM samples indicated that the concentrations of Fe and Ca were highest in the coarse fraction emitted under constant speed and cornering conditions, while Fe, Ba, and Ti were most abundant in the fine fraction emitted during braking events.

Validation of the Patient Health Questionnaire-9 Korean version in the elderly population: the Ansan Geriatric study.

OBJECTIVE: 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. Reliability and validity tests, factor analysis, and receiver operating characteristic curve analysis were performed. RESULTS: The PHQ-9 indicated that 175 subjects had depressive disorders, and 885 subjects were rated as healthy. The PHQ-9 showed significant positive internal consistency (r = 0.88) and test-retest reliability (r = 0.60). The convergent validity with Geriatric Depression Scale and Center for Epidemiological Studies Depression Scale was significantly positive (r = 0.74 and 0.66, respectively). We suggest a score of 5 as the optimal cutoff point when screening for depressive disorders using the PHQ-9. CONCLUSIONS: The Korean version of the PHQ-9 is an appropriate diagnostic tool for depression, and a score of 5 is the optimal cutoff for Korean elderly subjects. Screening for depression in the elderly population using the PHQ-9 would be valuable when medically ill patients show depressive symptoms in a primary health care setting.