Rapid carrier phase acquisition for large QAM signal constellations

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: p. 94-95.Issued also on microfiche from Lange Micrographics.This work addresses the problem of rapid carrier-phase acquisition for QAM constellations, and specifically for the 32-QAM, 64-QAM, 128-QAM, and 256-QAM constellations, operating over an AWGN channel. It is assumed that there is no frequency or symbol timing error. Seven algorithms in all are derived and tested. The first is the maximum-likelihood (ML) estimator, which is found to be accurate but impractical to implement. A suboptimal ML type estimator is derived from the ML algorithm and is found to be simpler but still impractical. The power-law (PL) estimator is derived as the low SNR limit of the ML estimator, and is found to be very simple, but having poor error performance. A threshold is added to the PL algorithm and the performance is improved, but not enough for rapid phase acquisition for most cases. An algorithm is derived specifically for use on the cross constellations which further improves performance, but this algorithm is superseded by an estimator based on a trellis structure and the Viterbi Algorithm which is developed. Finally a suboptimal version of the trellis algorithm is developed which reduces the complexity of the trellis algorithm by two-thirds. Both the trellis and the suboptimal trellis algorithm perform well enough for phase acquisition and are simple and practical to implement

Scintillation detectors constructed with an optimized 2x2 silicon photomultiplier array

Silicon photomultipliers (SiPMs) are a good alternative to photomultiplier tubes (PMTs) because their gain and quantum efficiency are comparable to PMTs. However, the largest single-chip SiPM is still less than 1~cm$^2$. In order to use SiPMs with scintillators that have reasonable sensitivity, it is necessary to use multiple SiPMs. In this work, scintillation detectors are constructed and tested with a custom 2x2 SiPM array. The layout of the SiPMs and the geometry of the scintillator were determined by performing Geant4 simulations. Cubic NaI, CsI, and CLYC with 18~mm sides have been tested. The output of the scintillation detectors are stabilized over the temperature range between --20 and 50~$^{\circ}$C by matching the gain of the SiPMs in the array. The energy resolution for these detectors has been measured as a function of temperature. Furthermore, neutron detection for the CLYC detector was studied in the same temperature range. Using pulse-shape discrimination, neutrons can be cleanly identified without contribution from $\gamma$-photons. As a result, these detectors are suitable for deploying in spectroscopic personal radiation detectors (SPRD).Comment: IEEE Nuclear Science Symposium Conference Record (2016

RASCAL: DARPA’s Solution to Responsive, Affordable, Micro-Satellite Space Access

RASCAL is a revolutionaryspace access program initiated by the Defense Advanced Research Projects Agency (DARPA). RASCAL will demonstrate the capability to launch microsatellites into low earth orbit routinelyand onshort notice using an air-launch systemarchitecture. A propulsion enhancement – Mass Injection Pre-Compressor Cooling (MIPCC) - allows the air vehicle toobtain high-energyflight conditions and provides the capability for exo-atmospheric staging ofan expendable rocket with satellite payload attached. This architecture effectively reduces recurring launch costs, which are targetedto be $750,000 per launch

Short-Term Calorie Restriction in Male Mice Feminizes Gene Expression and Alters Key Regulators of Conserved Aging Regulatory Pathways

Background: Calorie restriction (CR) is the only intervention known to extend lifespan in a wide range of organisms, including mammals. However, the mechanisms by which it regulates mammalian aging remain largely unknown, and the involvement of the TOR and sirtuin pathways (which regulate aging in simpler organisms) remain controversial. Additionally, females of most mammals appear to live longer than males within species; and, although it remains unclear whether this holds true for mice, the relationship between sex-biased and CR-induced gene expression remains largely unexplored. Methodology/Principal Findings: We generated microarray gene expression data from livers of male mice fed high calorie or CR diets, and we find that CR significantly changes the expression of over 3,000 genes, many between 10- and 50-fold. We compare our data to the GenAge database of known aging-related genes and to prior microarray expression data of genes expressed differently between male and female mice. CR generally feminizes gene expression and many of the most significantly changed individual genes are involved in aging, hormone signaling, and p53-associated regulation of the cell cycle and apoptosis. Among the genes showing the largest and most statistically significant CR-induced expression differences are Ddit4, a key regulator of the TOR pathway, and Nnmt, a regulator of lifespan linked to the sirtuin pathway. Using western analysis we confirmed post-translational inhibition of the TOR pathway. Conclusions: Our data show that CR induces widespread gene expression changes and acts through highly evolutionarily conserved pathways, from microorganisms to mammals, and that its life-extension effects might arise partly from a shift toward a gene expression profile more typical of females

Ferrets exclusively synthesize Neu5Ac and express naturally humanized influenza A virus receptors

Mammals express the sialic acids ​N-acetylneuraminic acid (​Neu5Ac) and ​N-glycolylneuraminic acid (​Neu5Gc) on cell surfaces, where they act as receptors for pathogens, including influenza A virus (IAV). ​Neu5Gc is synthesized from ​Neu5Ac by the enzyme cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH). In humans, this enzyme is inactive and only ​Neu5Ac is produced. Ferrets are susceptible to human-adapted IAV strains and have been the dominant animal model for IAV studies. Here we show that ferrets, like humans, do not synthesize ​Neu5Gc. Genomic analysis reveals an ancient, nine-exon deletion in the ferret CMAH gene that is shared by the Pinnipedia and Musteloidia members of the Carnivora. Interactions between two human strains of IAV with the sialyllactose receptor (sialic acid—α2,6Gal) confirm that the type of terminal sialic acid contributes significantly to IAV receptor specificity. Our results indicate that exclusive expression of ​Neu5Ac contributes to the susceptibility of ferrets to human-adapted IAV strains