Fully reconfigurable MEMS-based second-order coupled-resonator optical waveguide (CROW) with ultra-low tuning energy.

Integrated microring resonators are well suited for wavelength-filtering applications in optical signal processing, and cascaded microring resonators allow flexible filter design in coupled-resonator optical waveguide (CROW) configurations. However, the implementation of high-order cascaded microring resonators with high extinction ratios (ERs) remains challenging owing to stringent fabrication requirements and the need for precise resonator tunability. We present a fully integrated on-chip second-order CROW filter using silicon photonic microelectromechanical systems (MEMS) to adjust tunable directional couplers and a phase shifter using nanoscale mechanical out-of-plane waveguide displacement. The filter can be fully reconfigured with regard to both the ER and center wavelength. We experimentally demonstrated an ER exceeding 25 dB and continuous wavelength tuning across the full free spectral range of 0.123 nm for single microring resonator, and showed reconfigurability in second-order CROW by tuning the ER and resonant wavelength. The tuning energy for an individual silicon photonic MEMS phase shifter or tunable coupler is less than 22 pJ with sub-microwatt static power consumption, which is far better than conventional integrated phase shifters based on other physical modulation mechanisms.

Programmable MZI based on a silicon photonic MEMS-tunable delay line.

We report on a scalable and programmable integrated Mach-Zehnder interferometer (MZI) with a tunable free spectral range (FSR) and extinction ratio (ER). For the tunable path of the MZI, we designed and utilized a tunable delay line having high flexibility based on silicon photonic microelectromechanical systems (MEMS). By utilizing MEMS, the length of the delay line can be geometrically modified. In this way, there is no optical loss penalty other than the waveguide propagation loss as the number of tunable steps increases. Therefore, our device is more scalable in terms of optical loss than the previous approaches based on cascaded MZIs. In addition, the tuning energy required to reconfigure the length is only 8.46 pJ.

Immortalized gingival fibroblasts as a cytotoxicity test model for dental materials.

In vitro cytotoxicity test is an initial step to identify the harmful effects of new dental materials. Aim of this study was to develop a stable human cell line derived from normal gingival fibroblasts (hNOF) and to assess its feasibility in in vitro cytotoxicity testing. Immortalized human gingival fibroblasts (hTERT-hNOF) were successfully established with human telomerase reverse transcriptase gene transfection, preserving its phenotypical characteristics, replicative potential and biological properties. Utilizing standard cytotoxicity test modeling and dental materials, hTERT-hNOF were evaluated for their feasibility in cytotoxicity testing, compared with hNOF and L929 cells. Similar pattern of cytotoxic response was observed among hNOF, hTERT-hNOF and L929 cells. Cytotoxicity response of hTERT-hNOF was significantly similar to hNOF, moreover hTERT-hNOF and hNOF were found to be more sensitive towards the tested dental materials compared to L929 cells. This study suggested that hTERT-hNOF is an effective cytotoxic test model for dental materials.

Determination of etomidate and etomidate acid in hair using liquid chromatography-tandem mass spectrometry.

Etomidate, with efficacy similar to that of propofol, has been used as a propofol substitute because propofol is a designated narcotic drug, and an increase in the frequency of illegal distribution and misuse has been reported in Korea. Previous analytical studies on etomidate used blood and urine. For long-term use and timing estimation, a method for etomidate analysis using hair should be developed. Therefore, in this study, an analytical method using LC-MS/MS was developed to determine etomidate and its major metabolite in hair. Human hair samples were segmented after washing to eliminate possible contaminants on the hair and stirred with methanol. The LC-MS/MS conditions were optimized, and the chromatographic separation time was 10 min. Selectivity, linearity, limit of detection, limit of quantification, precision, accuracy, recovery, process efficiency, matrix effect, and stability were evaluated to validate the analytical method. The calibration curves ranged from 0.25 to 50 pg/mg for etomidate and 2-250 pg/mg for etomidate acid; the coefficients of determination were higher than 0.997. The intra- and inter-assay precision results for all the compounds were <15% and satisfied at recovery, process efficiency, matrix effect, and stability. In addition, this method was applied to the hair of 4 rats which are administered with etomidate to evaluate. The etomidate concentrations in the rat hair ranged from 2.60 to 8.50 pg/mg, and the etomidate acid concentrations were 2.06-7.13 pg/mg. Thus, this method can be used as basic data for monitoring etomidate in hair.

Vascular and baroreceptor abnormalities in young males with a family history of hypertension.

Vascular and baroreceptor abnormalities in 44 young males, mean age 21 years, comprising of offspring with (FH(+); n = 22) and without (FH(-); n = 22) hypertensive parents, were investigated. Peak forearm blood flow (FBF), which was defined as the highest blood flow obtained following reactive hyperaemia, was assessed using strain gauge plethysmography following 5 min of ischemia. Cardiopulmonary baroreceptor sensitivity was assessed using lower body negative pressure for 5 min at -20 mmHg and was determined by calculating change of stroke volume and forearm vascular resistance (FVR) to lower body negative pressure. Carotid baroreceptor sensitivity was assessed using neck suction at -20, -40, -60, and -80 mmHg and was calculated by dividing RR interval by systolic blood pressure. Augmentation index, a measure of wave reflection, was assessed using applanation tonometry and was calculated as the ratio of augmented pressure and pulse pressure. Peak FBF of FH(+) was 19% lower than the FH(-) (p = 0.02). Also FH(+) had 17% higher peak FVR compared to FH(-) (p = 0.04). However, there were no significant differences between groups for cardiopulmonary, carotid baroreceptor sensitivity, and augmentation index. These results suggest that peripheral vascular dysfunction appears earlier than abnormal baroreceptor sensitivity in young males with a family history of hypertension.

Combined impact of adiponectin and retinol-binding protein 4 on metabolic syndrome in elderly people: the Korean Longitudinal Study on Health and Aging.

The prevalence of metabolic syndrome (MS) increases with progressing and is potentially associated with changes in adipose-derived cytokines, including adiponectin and retinol-binding protein 4 (RBP4). We aimed to determine the prevalence of MS, and the relationships between these factors and MS in elderly people. A population-based cohort study, the Korean Longitudinal Study on Health and Aging (KLoSHA), was performed on subjects aged > or =65 years by random stratified sampling in 2005-2006 (439 men and 561 women). Anthropometrics, biochemical factors including adiponectin and RBP4 levels, body composition, and abdominal fat by computed tomography (CT) were measured. The prevalence of MS was 61.0% in women and 39.9% in men. After adjustment for age, gender, smoking, alcohol, and exercise status and muscle mass, participants with the lowest quartile of adiponectin had a higher risk for having MS than those with the highest quartile (odds ratio (OR) = 4.12, P < 0.01). Similarly, subjects with the highest quartile of RBP4 showed an increased risk for having MS (OR = 1.73, P < 0.01). When both the lowest adiponectin and the highest RBP4 quartiles were combined, the OR increased to 6.22 compared with the opposite quartiles (i.e., highest adiponectin and lowest RBP4 concentrations). Furthermore, circulating levels of adiponectin and RBP4 were significantly correlated with visceral fat and insulin resistance index. In this study, the increased prevalence of MS in elderly but relatively lean population was associated with low adiponectin and high RBP4 levels. The combination of these factors might predict older subjects at high risk for having MS.