We have constructed a chitosan nonwoven nanofiber mesh tube consisting of oriented fibers by the electrospinning method. The efficacy of oriented nanofibers on Schwann cell alignment and positive effect of this tube on peripheral nerve regeneration were confirmed. The physical properties of the chitosan nanofiber mesh sheets prepared by electrospinning with or without fiber orientation were characterized. Then, immortalized Schwann cells were cultured on these sheets. Furthermore, the chitosan nanofiber mesh tubes with or without orientation, and bilayered chitosan mesh tube with an inner layer of oriented nanofibers and an outer layer of randomized nanofibers were bridgegrafted into rat sciatic nerve defect. As a result of fiber orientation, the tensile strength along the axis of the sheet increased. Because Schwann cells aligned along the nanofibers, oriented fibrous sheets could exhibit a Schwann cell column. Functional recovery and electrophysiological recovery occurred in time in the oriented group as well as in the bilayered group, and approximately matched those in the isograft. Furthermore, histological analysis revealed that the sprouting of myelinated axons occurred vigorously followed by axonal maturation in the isograft, oriented, and bilayered group in the order. The oriented chitosan nanofiber mesh tube may be a promising substitute for autogenous nerve graft.

Background Previous studies have reported that the signal attenuation of diffusion-weighted magnetic resonance imaging (DWI) for normal breast tissue and tumor were well fitted by a monoexponential and a biexponential function, respectively. The aim of this study was to investigate the optimal b-value to detect breast tumors from DWI signal attenuations. Methods Sixty-four subjects with breast cancer underwent DWI using six b-values up to 3500 s/mm 2 . The signal attenuations of normal breast and tumor were fitted by mono- and biexponential functions, respectively. The maximum contrast b-values were estimated and compared in terms of frequency. Results In almost all cases, the contrast increased with a b-value from 0 to approximately 1500 s/mm 2 . For b > 1500 s/mm 2 , the contrast decreased. The highest contrast b-value in the range of 0 to 2500 s/mm 2 most frequently was b = 1500 and the next most frequent was 1400 s/mm 2 . Comparing sensitivity and specificity between b = 700 and b = 1400 s/mm 2 , b =1400 s/mm 2 was slightly superior. Conclusion Based on these results, DWI with a b-value of approximately 1400-1500 s/mm 2 is recommended for optimizing breast tumor detectability.

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We are developing a simple variable-structure-type 4-wheeled robot that maneuvers over steps, having enabled it to step dynamically over steps of known height and of unknown height within a known small range. We consider cdntrol enabling it to negotiate steps whose height and position are unknown by detecting step position and height using a laser range sensor. We propose in-process planning of a dynamic trajectory during an experiment, enabling the robot to quickly negotiate steps whose position and height are both unknown.