Toward Large-Area Sub-Arcsecond X-Ray Telescopes II

In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (approx. = 3 sq m) and fine angular resolution (approx. = 1"). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 sq m) of lightweight (approx. = 2 kg/sq m areal density) high-quality mirrors, at an acceptable cost (approx. = 1 M$/sq m of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates

ACVIM consensus statement: Guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats

An update to the 2007 American College of Veterinary Internal Medicine (ACVIM) consensus statement on the identification, evaluation, and management of systemic hypertension in dogs and cats was presented at the 2017 ACVIM Forum in National Harbor, MD. The updated consensus statement is presented here. The consensus statement aims to provide guidance on appropriate diagnosis and treatment of hypertension in dogs and cats

Toward Large-Area Sub-Arcsecond X-Ray Telescopes

The future of x-ray astronomy depends upon development of x-ray telescopes with larger aperture areas (>1 sq m) and finer angular resolution(100 sq m) of lightweight (1 kg/sq m areal density) high quality mirrors-possibly entailing active (in-space adjustable) alignment and figure correction. This paper discusses relevant programmatic and technological issues and summarizes progress toward large area sub-arcsecond x-ray telescopes. Key words: X-ray telescopes, x-ray optics, active optics, electroactive devices, silicon mirrors, differential deposition, ion implantation

Sustained Glutamate Receptor Activation Down-regulates GABAB Receptors by Shifting the Balance from Recycling to Lysosomal Degradation*

Metabotropic GABAB receptors are abundantly expressed at glutamatergic synapses where they control excitability of the synapse. Here, we tested the hypothesis that glutamatergic neurotransmission may regulate GABAB receptors. We found that application of glutamate to cultured cortical neurons led to rapid down-regulation of GABAB receptors via lysosomal degradation. This effect was mimicked by selective activation of AMPA receptors and further accelerated by coactivation of group I metabotropic glutamate receptors. Inhibition of NMDA receptors, blockade of L-type Ca2+ channels, and removal of extracellular Ca2+ prevented glutamate-induced down-regulation of GABAB receptors, indicating that Ca2+ influx plays a critical role. We further established that glutamate-induced down-regulation depends on the internalization of GABAB receptors. Glutamate did not affect the rate of GABAB receptor endocytosis but led to reduced recycling of the receptors back to the plasma membrane. Blockade of lysosomal activity rescued receptor recycling, indicating that glutamate redirects GABAB receptors from the recycling to the degradation pathway. In conclusion, the data indicate that sustained activation of AMPA receptors down-regulates GABAB receptors by sorting endocytosed GABAB receptors preferentially to lysosomes for degradation on the expense of recycling. This mechanism may relieve glutamatergic synapses from GABAB receptor-mediated inhibition resulting in increased synaptic excitability