Antenna beam-shaping apparatus Patent

Device for improving efficiency of parabolic horn antenna system for linearly polarized signal

Parabolic reflector horn feed with spillover correction Patent

Device for improving efficiency of parabolic reflector horn for linearly or circularly polarized wave

Searching for Light Dark Matter with the SLAC Millicharge Experiment

New sub-GeV gauge forces ("dark photons") that kinetically mix with the photon provide a promising scenario for MeV-GeV dark matter, and are the subject of a program of searches at fixed-target and collider facilities around the world. In such models, dark photons produced in collisions may decay invisibly into dark matter states, thereby evading current searches. We re-examine results of the SLAC mQ electron beam dump experiment designed to search for millicharged particles, and find that it was strongly sensitive to any secondary beam of dark matter produced by electron-nucleus collisions in the target. The constraints are competitive for dark photon masses in the ~1-30 MeV range, covering part of the parameter space that can reconcile the apparent (g-2)_{\mu} anomaly. Simple adjustments to the original SLAC search for millicharges may extend sensitivity to cover a sizable portion of the remaining (g-2)_{\mu} anomaly-motivated region. The mQ sensitivity is therefore complementary to on-going searches for visible decays of dark photons. Compared to existing direct detection searches, mQ sensitivity to electron-dark matter scattering cross sections is more than an order of magnitude better for a significant range of masses and couplings in simple models.Comment: 4 pages, 5 figures, 1 tabl

Insertion loss measuring apparatus having transformer means connected across a pair of bolometers Patent

High impedance alternating current sensing transformer device between two bolometers for measuring insertion loss of test componen

Improved insertion-loss tester

An improved test method accurately measures the insertion loss of RF components while avoiding amplifier drift. Currents are balanced across a bridge transformer with shorted probes and then with each component to be tested. Differences in adjustments indicate the loss

Investigation of ground effects on large and small scale models of a three fan V/STOL aircraft configuration

Induced lift of a subsonic, three fan, lift/cruise, V/STOL aircraft configuration was investigated using scale modes of a multimission aircraft whose design incorporates a nose mounted lift fan and two lift/cruise units located over the wing. Configuration effects were assessed for lift improvement devices, lift/cruise nozzle rails, nozzle perimeter plates, and alternate nose fan exit hubs. Tests were conducted at four model heights (H/D = 0.95, 1.53, 3.06 and 6.45, where D is the average nozzle exit diameter equal to 0.997 m.) Results are presented and discussed

A Selective Advantage for Conservative Viruses

In this letter we study the full semi-conservative treatment of a model for the co-evolution of a virus and an adaptive immune system. Regions of viability are calculated for both conservatively and semi-conservatively replicating viruses interacting with a realistic semi-conservatively replicating immune system. The conservative virus is found to have a selective advantage in the form of an ability to survive in regions with a wider range of mutation rates than its semi-conservative counterpart. This may help explain the existence of a rich range of viruses with conservatively replicating genomes, a trait which is found nowhere else in nature.Comment: 4 pages, 2 figure

Host-Parasite Co-evolution and Optimal Mutation Rates for Semi-conservative Quasispecies

In this paper, we extend a model of host-parasite co-evolution to incorporate the semi-conservative nature of DNA replication for both the host and the parasite. We find that the optimal mutation rate for the semi-conservative and conservative hosts converge for realistic genome lengths, thus maintaining the admirable agreement between theory and experiment found previously for the conservative model and justifying the conservative approximation in some cases. We demonstrate that, while the optimal mutation rate for a conservative and semi-conservative parasite interacting with a given immune system is similar to that of a conservative parasite, the properties away from this optimum differ significantly. We suspect that this difference, coupled with the requirement that a parasite optimize survival in a range of viable hosts, may help explain why semi-conservative viruses are known to have significantly lower mutation rates than their conservative counterparts