Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space-and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2-to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Chimeric cGMP phosphodiesterases (PDEs) have been constructed using components of the cGMP-binding PDE (PDE5) and cone photoreceptor phosphodiesterase (PDE6␣) in order to study structure and function of the photoreceptor enzyme. A fully functional chimeric PDE6␣/PDE5 enzyme containing the PDE6␣ noncatalytic cGMP-binding sites, and the PDE5 catalytic domain has been efficiently expressed in the baculovirus/ High Five cell system. The catalytic properties of this chimera were practically indistinguishable from those of PDE5, whereas the noncatalytic cGMP binding was similar to that of native purified PDE6␣. The inhibitory Photoreceptor phosphodiesterases (PDEs) 1 serve as effector enzymes in the G protein-mediated visual transduction cascade (1-3). During transduction of the visual signal in vertebrate photoreceptor rod and cone cells, the activated G protein (transducin) ␣ subunit stimulates PDE catalytic activity by relieving the inhibitory constraint imposed by two identical inhibitory P␥ subunits. A recently adopted classification of cyclic nucleotide PDEs recognizes seven different families based on primary sequence and regulation (4). PDEs within each of the families have 60% or more homology while similarities between different families are 40% or less. According to this nomenclature, photoreceptor rod and cone PDEs comprise the PDE6 family (4). Rod photoreceptor PDE is composed of two large homologous catalytic ␣ and ␤ subunits of nearly identical size (molecular masses of 99.2 and 98.3 kDa) and two copies of an inhibitory ␥ subunit (molecular mass 9.7 kDa) (5-8). Cone PDE is composed of two identical ␣Ј subunits (molecular masses of 98.7 kDa) (9, 10), which share Ͼ60% homology with PDE6␣ and PDE6␤ (11). An inhibitory cone P␥ subunit that is highly homologous to rod P␥ and specific for a subset of cone photoreceptors has been identified (12). Recently, a rod-specific

We present a study of the plerionic supernova remnant 0540 − 69.3 in the LMC in X-ray, radio, optical, and infrared. We find that the shell of 0540 − 69.3 is characterized in the X-ray by thermal nonequilibrium plasma with depleted Mg and Si abundances and a temperature of kT ∼ 0.7 keV. This thermal emission is superimposed with synchrotron emission in several regions. Based on X-ray spectra and on morphological considerations in all surveyed wavebands, we conclude that the shell is expanding into a clumpy and highly inhomogeneous medium. In one region of the shell we find an overabundance of Ne, suggesting the presence of ejecta near the edge of the remnant. We also see evidence for reheating of material via a reverse shock originating from the interaction of the supernova blast wave with a particularly dense cloud in the surrounding medium. Finally, we perform the first detailed study of the "halo" region extending 1.2 − 2.2 pc from the central pulsar. We detect the presence of thermal and nonthermal spectral components but do not find evidence for mixing or ejecta. We conclude that the thermal component is not a counterpart to similar optical and infrared halos and that it is most likely due to the projection of shell material along the line of sight.

We present the methodology used to fabricate an X-ray reflection grating and describe a technique for grating replication. Further, we present the experimental procedure and results of a study to measure the diffraction efficiency of a replicated X-ray reflection grating in an extreme off-plane geometry. The blazed grating demonstrates a total diffraction efficiency of ∼60% from 0.34 to 1.2 keV at a grazing angle of ∼1.°5, with single-order efficiency ranging from ∼35% to 65% for energies within the blaze envelope. The diffraction efficiency of the grating measured relative to the reflectivity of the metal coating averages ∼90% above 0.34 keV. Data collected as a function of beam position on the grating indicate a relative variation in total efficiency of <1% rms across the grating surface.

Members of the RGS family serve as