Refractive index tomography of turbid media by bifocal optical coherence refractometry

We demonstrate tomographic imaging of the refractive index of turbid media using bifocal optical coherence refractometry (BOCR). The technique, which is a variant of optical coherence tomography, is based on the measurement of the optical pathlength difference between two foci simultaneously present in a medium of interest. We describe a new method to axially shift the bifocal optical pathlength that avoids the need to physically relocate the objective lens or the sample during an axial scan, and present an experimental realization based on an adaptive liquid-crystal lens. We present experimental results, including video clips, which demonstrate refractive index tomography of a range of turbid liquid phantoms, as well as of human skin in vivo.<br /

Hedgehog Spikes Pancreas Regeneration

5 páginas, 1 figura.The report by Fendrich et al provides provocative data linking the Hh signaling pathway to pancreas acinar regeneration. Future studies need to address whether the positive effect of the pathway during normal regeneration can be high jacked in diseased pancreas marked by the expression of k-Ras mutation that sensitize toward pancreatic adenocarcinoma. Under these conditions, inhibition, rather than stimulation of Hh signaling, could prevent unwanted proliferative responses resulting in pancreatic cancer.Supported by the "Ramón y Cajal" program from the Spanich Ministry of Science and Education (D.C.) and grants from the NIH (DK60533, CA112537 to M.H.)Peer reviewe

The role of spatial context in shaping adolescents’ peer relationships

This article explores the role of neighbourhoods as a spatial context for peer relationships among adolescents. We examine the correlations between neighbourhood composition and places suitable for young people for friendship intimacy and peer belonging. We hypothesise that favourable demographic and social neighbourhood compositions, knowledge, and use of places suitable for young people, as well as the spatial appropriation of such places, promote peer relationships. The present study carries out empirical testing of the spatial hypotheses with survey data from adolescents (N = 3225) in two German cities with 30 neighbourhoods. Our results show that neighbourhood composition is not related to peer relationships. Nevertheless, knowledge of safe places suitable for adolescents, as well as the appropriation of unsupervised (hang out) places, correlate with peer relationships. Interestingly, there are divergent results for 7th and 9th graders that can be explained by the developmental stages of the adolescents