Comparison of frequency difference reconstruction algorithms for the detection of acute stroke using EIT in a realistic head-shaped tank.

Imaging of acute stroke might be possible using multi-frequency electrical impedance tomography (MFEIT) but requires absolute or frequency difference imaging. Simple linear frequency difference reconstruction has been shown to be ineffective in imaging with a frequency-dependant background conductivity; this has been overcome with a weighted frequency difference approach with correction for the background but this has only been validated for a cylindrical and hemispherical tank. The feasibility of MFEIT for imaging of acute stroke in a realistic head geometry was examined by imaging a potato perturbation against a saline background and a carrot-saline frequency-dependant background conductivity, in a head-shaped tank with the UCLH Mk2.5 MFEIT system. Reconstruction was performed with time difference (TD), frequency difference (FD), FD adjacent (FDA), weighted FD (WFD) and weighted FDA (WFDA) linear algorithms. The perturbation in reconstructed images corresponded to the true position to <9.5% of image diameter with an image SNR of >5.4 for all algorithms in saline but only for TD, WFDA and WFD in the carrot-saline background. No reliable imaging was possible with FD and FDA. This indicates that the WFD approach is also effective for a realistic head geometry and supports its use for human imaging in the future.

Vitamin C increases the fecal fat excretion by chitosan in guinea-pigs, thereby reducing body weight gain.

The aims of this study were to investigate the antiobesity properties of chitosan on its own, as well as in the presence of vitamin C, in vivo. Hartley guinea-pigs were divided into Control (normal diet), F-control (high fat diet), Chitosan (high fat diet with 5.0% chitosan) and Chito-vit C (high fat diet with 5.0% chitosan containing 0.5% vitamin C) groups, respectively. The effects of chitosan, both alone and in the presence of vitamin C, on body weight, total fecal weight, fecal composition and plasma lipid level were studied for 5 weeks. The results of this study indicated that the fat-binding and water-holding capacity of chitosan might decrease body weight by reducing the absorption of cholesterol and fat, subsequently increasing total fecal weight, fecal fat excretion and fecal water excretion. Vitamin C increased the fecal fat excretion by chitosan in guinea-pigs, thereby reducing body weight gain.

Modeling spatiotemporal covariance for magnetoencephalography or electroencephalography source analysis.

We propose a new model to approximate spatiotemporal noise covariance for use in neural electromagnetic source analysis, which better captures temporal variability in background activity. As with other existing formalisms, our model employs a Kronecker product of matrices representing temporal and spatial covariance. In our model, spatial components are allowed to have differing temporal covariances. Variability is represented as a series of Kronecker products of spatial component covariances and corresponding temporal covariances. Unlike previous attempts to model covariance through a sum of Kronecker products, our model is designed to have a computationally manageable inverse. Despite increased descriptive power, inversion of the model is fast, making it useful in source analysis. We have explored two versions of the model. One is estimated based on the assumption that spatial components of background noise have uncorrelated time courses. Another version, which gives closer approximation, is based on the assumption that time courses are statistically independent. The accuracy of the structural approximation is compared to an existing model, based on a single Kronecker product, using both Frobenius norm of the difference between spatiotemporal sample covariance and a model, and scatter plots. Performance of ours and previous models is compared in source analysis of a large number of single dipole problems with simulated time courses and with background from authentic magnetoencephalography data.

A generalized spatiotemporal covariance model for stationary background in analysis of MEG data.

Using a noise covariance model based on a single Kronecker product of spatial and temporal covariance in the spatiotemporal analysis of MEG data was demonstrated to provide improvement in the results over that of the commonly used diagonal noise covariance model. In this paper we present a model that is a generalization of all of the above models. It describes models based on a single Kronecker product of spatial and temporal covariance as well as more complicated multi-pair models together with any intermediate form expressed as a sum of Kronecker products of spatial component matrices of reduced rank and their corresponding temporal covariance matrices. The model provides a framework for controlling the tradeoff between the described complexity of the background and computational demand for the analysis using this model. Ways to estimate the value of the parameter controlling this tradeoff are also discussed.

Effect of serum type and concentration on the expression ofß-galactosidase in recombinant vaccinia virus infected HeLa S3 cells.

The effect of serum type and concentration on recombinant protein expression in vaccinia virus infected HeLa S3 cells was studied in both static and suspension culture. A model heterologous protein,ß-galactosidase (ß-gal), was used. Calf and horse sera in the range of 0.5-10%(v/v) were investigated. In static culture, the calf serum concentration did not show any significant influence on the ß-gal production which was almost completed within 24h postinfection (pi). Higher horse serum concentration, on the other hand, resulted in higher ß-gal concentration which continued to increase until 48 h pi. Total ß-gal concentrations in 0.5% calf serum at 24 h pi and 10% horse serum at 48 h pi were 2.2±0.7 and 2.2±0.1 IU/ml, respectively. In suspension culture, both sera showed their respective effects on the ß-gal production similar to those observed in static culture, indicating that the cultivation method had little influence on ß-gal production. Accordingly, the use of 0.5% calf serum after virus infection in recommended for economical ß-gal production.