Gas-phase fragmentation of deprotonated p-hydroxyphenacyl derivatives.

Electrospray ionization of methanolic solutions of p-hydroxyphenacyl derivatives HO-C(6)H(4)-C(O)-CH(2)-X (X = leaving group) provides abundant signals for the deprotonated species which are assigned to the corresponding phenolate anions (-)O-C(6)H(4)-C(O)-CH(2)-X. Upon collisional activation in the gas phase, these anions inter alia undergo loss of a neutral "C(8)H(6)O(2)" species concomitant with formation of the corresponding anions X(-). The energies required for the loss of the neutral roughly correlate with the gas phase acidities of the conjugate acids (HX). Extensive theoretical studies performed for X = CF(3)COO in order to reveal the energetically most favorable pathway for the formation of neutral "C(8)H(6)O(2)" suggest three different routes of similar energy demands, involving a spirocyclopropanone, epoxide formation, and a diradical, respectively.

Serum lycopene levels in patients with diabetic retinopathy.

PURPOSE: Accumulating evidence indicates that oxidative stress may play an important role in the pathogenesis of type 2 diabetes and its complications. Lycopene, a very potent antioxidant of carotenoids, has received considerable scientific interest in recent years for its potential role in the prevention of oxidative stress-related chronic diseases. This study was undertaken to investigate whether the serum levels of lycopene are altered between type 2 diabetic patients with and without diabetic retinopathy. METHODS: A total of 71 patients with type 2 diabetes were analyzed and compared with 23 nondiabetic healthy controls. Serum lycopene concentrations were assayed using high-performance liquid chromatography. RESULTS: Lycopene level was found to be significantly lower in diabetic patients than in controls (p = 0.021). In the diabetic group, subjects with proliferative diabetic retinopathy had significantly lower lycopene levels than subjects without diabetic retinopathy or with nonproliferative diabetic retinopathy. In the analysis of correlations, hemoglobin A1c were negatively correlated with lycopene (r = -0.345, p = 0.007) after multivariate adjustment. A stepwise linear multiple regression model revealed that age and hemoglobin A1c were significant determinants of lycopene. CONCLUSIONS: Our findings show that measuring serum lycopene is a novel convenient method for evaluating oxidative damage. Diabetic patients, especially those with advanced diabetic retinopathy, had significantly lower serum lycopene levels; this suggests that lycopene may be helpful for the diagnosis, severity, and therapeutic evaluation of diabetic retinopathy.

Anti-Symmetric Mode Vibration of Electrostatically Actuated Clamped-Clamped Microbeams for Mass Sensing.

This paper details study of the anti-symmetric response to the symmetrical electrostatic excitation of a Micro-electro-mechanical-systems (MEMS) resonant mass sensor. Under higher order mode excitation, two nonlinear coupled flexural modes to describe MEMS mass sensors are obtained by using Hamilton's principle and Galerkin method. Static analysis is introduced to investigate the effect of added mass on the natural frequency of the resonant sensor. Then, the perturbation method is applied to determine the response and stability of the system for small amplitude vibration. Through bifurcation analysis, the physical conditions of the anti-symmetric mode vibration are obtained. The corresponding stability analysis is carried out. Results show that the added mass can change the bifurcation behaviors of the anti-symmetric mode and affect the voltage and frequency of the bifurcation jump point. Typically, we propose a mass parameter identification method based on the dynamic jump motion of the anti-symmetric mode. Numerical studies are introduced to verify the validity of mass detection method. Finally, the influence of physical parameters on the sensitivity of mass sensor is analyzed. It is found that the DC voltage and mass adsorption position are critical to the sensitivity of the sensor. The results of this paper can be potentially useful in nonlinear mass sensors.

Electroencephalogram global field synchronization analysis: a new method for assessing the progress of cognitive decline in Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of dementia. Global field synchronization (GFS) can measure functional synchronization in frequency-domain electroencephalogram (EEG) data. The aim of this study is to explore GFS values and its clinical significance for severity of cognitive decline in AD. EEGs were recorded from 37 AD patients and 37 age-matched healthy individuals. GFS values were calculated in delta, theta, alpha, beta 1, beta 2, beta 3, gamma, and full frequency bands. The Montreal Cognitive Assessment (MoCA) and Clinical Dementia Rating scale (CDR) were employed to assess symptom severity in AD patients. Correlation analysis, clustering analysis, and concordance analysis were performed to analyze the relationship between GFS values and MoCA scores in AD patients. GFS values of the beta 1, beta 2, beta 3, and full bands were lower in AD patients than in healthy individuals, and positively correlated with MoCA and CDR scores in the combined group (AD patients and healthy individuals). GFS values were positively correlated with MoCA socres in 3 beta bands and full bands, and with CDR scores in the delta band. There was a good concordance between K-means clustering algorithm calculating of GFS values and MoCA scoring (κ = .913, P < .001). In conclusion, the present results indicated that GFS can serve as an indicator of cognitive decline or impairment in AD patients. Furthermore, the GFS method of EEG holds considerable promise to distinguish mild cognitive impairment from serious cognitive impairment in patients with AD.