Hardware simulation of Ku-band spacecraft receiver and bit synchronizer, volume 1

A hardware simulation which emulates an automatically acquiring transmit receive spread spectrum communication and tracking system and developed for use in future NASA programs involving digital communications is considered. The system architecture and tradeoff analysis that led to the selection of the system to be simulated is presented

Hardware simulation of KU-band spacecraft receiver and bit synchronizer, phase 2, volume 1

The acquisition behavior of the PN subsystem of an automatically acquiring spacecraft receiver was studied. A symbol synchronizer subsystem was constructed and integrated into the composite simulation of the receiver. The overall performance of the receiver when subjected to anomalies such as signal fades was evaluated. Potential problems associated with PN/carrier sweep interactions were investigated

A finite-temperature liquid-quasicrystal transition in a lattice model

We consider a tiling model of the two-dimensional square-lattice, where each site is tiled with one of the sixteen Wang tiles. The ground states of this model are all quasi-periodic. The systems undergoes a disorder to quasi-periodicity phase transition at finite temperature. Introducing a proper order-parameter, we study the system at criticality, and extract the critical exponents characterizing the transition. The exponents obtained are consistent with hyper-scaling

Androgen Receptor and Vasopressin Receptor (AVPR1a) Genetic Polymorphisms are not associated with Marital Status or Fertility among Ariaal Men of Northern Kenya

A growing body of scholarship implicates testosterone and vasopressin in male reproductive behavior, including in humans. Since hormones exert their effects through their respective receptors, an open question has been whether genetic polymorphisms in the androgen receptor and vasopressin 1a receptor (AVPR1a) impact human male social behavior. Here, we sought to test for associations between polymorphisms in the coding region of the androgen receptor and promoter region of AVPR1a in relation to marital status and fertility among pastoralist Ariaal men of northern Kenya. None of the three polymorphisms were related to marital status (single, monogamously married, polygynously married) or fertility (number of current living children). We discuss these null findings in light of existing data

Preferential attachment in the protein network evolution

The Saccharomyces cerevisiae protein-protein interaction map, as well as many natural and man-made networks, shares the scale-free topology. The preferential attachment model was suggested as a generic network evolution model that yields this universal topology. However, it is not clear that the model assumptions hold for the protein interaction network. Using a cross genome comparison we show that (a) the older a protein, the better connected it is, and (b) The number of interactions a protein gains during its evolution is proportional to its connectivity. Therefore, preferential attachment governs the protein network evolution. The evolutionary mechanism leading to such preference and some implications are discussed.Comment: Minor changes per referees requests; to appear in PR

A Conserved Vector Current test using low energy beta-beams

We discuss the possibility of testing the weak currents and, in particular, the weak magnetism term through the measurement of the electron anti-neutrinos capture by protons at a low energy beta-beam facility. We analyze the sensitivity using both the total number of events and the angular distribution of the positrons emitted in a water Cerenkov detector. We show that the weak magnetism form factor might be determined with better than several percent accuracy using the angular distribution. This offers a new way of testing the Conserved Vector Current hypothesis.Comment: 8 pages, 5 figure

Relativistic Multiple Scattering Theory and the Relativistic Impulse Approximation

It is shown that a relativistic multiple scattering theory for hadron-nucleus scattering can be consistently formulated in four-dimensions in the context of meson exchange. We give a multiple scattering series for the optical potential and discuss the differences between the relativistic and non-relativistic versions. We develop the relativistic multiple scattering series by separating out the one boson exchange term from the rest of the Feynman series. However this particular separation is not absolutely necessary and we discuss how to include other terms. We then show how to make a three-dimensional reduction for hadron-nucleus scattering calculations and we find that the relative energy prescription used in the elastic scattering equation should be consistent with the one used in the free two-body t-matrix involved in the optical potential. We also discuss what assumptions are involved in making a Dirac Relativistic Impulse Approximation (RIA).Comment: 20 pages, 9 figures, Accepted for publication in Journal of Physics

Phenomenological local potentials for \pi^- + ^{12}C scattering from 120 to 766 MeV

Pion-nucleus scattering cross sections are calculated by solving a Schr\"{o}dinger equation reduced from the Klein-Gordon equation. Local potentials are assumed, and phenomenological potential parameters are searched energy-dependently for $\pi^{-} + ^{12}$C system so as to reproduce not only elastic differential cross sections but also total elastic, reaction and total cross sections at 13 pion incident energies from 120 to 766 MeV. The real and imaginary parts of the local potentials thus obtained are shown to satisfy the dispersion relation. The imaginary part of the potentials as a function of the pion energy is found to peak near the $\Delta$(1232)-resonance energy. The strong absorption radius of the pion projectile with incident energies near the $\Delta$-resonance region is found to be about $1.6 A^{1/3}$ fm, which is consistent with previous studies of the region where the decay of the $\Delta$'s takes place in nuclei. The phenomenological local potentials are then compared with the local potentials exactly phase-shift equivalent to Kisslinger potentials for pion energies near the $\Delta$-resonance