The interatomic structure of water at supercritical temperatures

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Infrared polarimetry of the nucleus of Centaurus A - The nearest blazar?

Original article can be found at: http://www.nature.com/nature/ Copyright Nature Publishing Group. DOI: 10.1038/322150a0 [Full text of this article is not available in the UHRA]As one of the nearest examples of an active galaxy, NGC5128 (Centaurus A) has been studied in detail over a wide range of wavelengths. The nucleus of the galaxy is seen clearly in the X-ray, radio and infrared, but is obscured in the optical by the prominent warped dust lane. We have made polarization observations of the infrared nucleus at wavelengths from 1.2 to 3.8 µm. We find that after correction for the polarization caused by the dust lane, and for dilution by starlight, the nucleus has a large intrinsic polarization of 9% at position angle 147°. This position angle is perpendicular to the direction of the X-ray and radio jet. We interpret the polarized emission from the nucleus as synchrotron radiation from a region whose magnetic field is parallel to the jet direction. The properties of the Cen A nucleus are essentially identical to those of the much more luminous blazars. This suggest that blazar-type activity extends over a very wide range in luminosity, and low-luminosity blazars may be common in elliptical galaxies.Peer reviewe

miRNA-132: a dynamic regulator of cognitive capacity

Within the central nervous system, microRNAs have emerged as important effectors of an array of developmental, physiological, and cognitive processes. Along these lines, the CREB-regulated microRNA miR-132 has been shown to influence neuronal maturation via its effects on dendritic arborization and spinogenesis. In the mature nervous system, dysregulation of miR-132 has been suggested to play a role in a number of neurocognitive disorders characterized by aberrant synaptogenesis. However, little is known about the inducible expression and function of miR-132 under normal physiological conditions in vivo. Here, we begin to explore this question within the context of learning and memory. Using in situ hybridization, we show that the presentation of a spatial memory task induced a significant ~1.5-fold increase in miR-132 expression within the CA1, CA3, and GCL excitatory cell layers of the hippocampus. To examine the role of miR-132 in hippocampal-dependent learning and memory, we employ a doxycycline-regulated miR-132 transgenic mouse strain to drive varying levels of transgenic miR-132 expression. These studies revealed that relatively low levels of transgenic miR-132 expression, paralleling the level of expression in the hippocampus following a spatial memory task, significantly enhanced cognitive capacity. In contrast, higher (supra-physiological) levels of miR-132 (>3-fold) inhibited learning. Interestingly, both the impaired cognition and elevated levels of dendritic spines resulting from supra-physiological levels of transgenic miR-132 were reversed by doxycycline suppression of transgene expression. Together, these data indicate that miR-132 functions as a key activity-dependent regulator of cognition, and that miR-132 expression must be maintained within a limited range to ensure normal learning and memory formation