Enhancing efficiency of single, large-aperture antennas

Numerical analysis method provides means of describing energy distribution in focal plane of parabolic surface in terms of phase and wavelength. Two approaches for enhancing antenna efficiency include single, large reflector focused to feeding element, and array of smaller apertures whose individual outputs are summed

Hydrogen solubility in zirconium intermetallic second phase particles

The enthalpies of solution of H in Zr binary intermetallic compounds formed with Cu, Cr, Fe, Mo, Ni, Nb, Sn and V were calculated by means of density functional theory simulations and compared to that of H in {\alpha}-Zr. It is predicted that all Zr-rich phases (formed with Cu, Fe, Ni and Sn), and those phases formed with Nb and V, offer lower energy, more stable sites for H than {\alpha}-Zr. Conversely, Mo and Cr containing phases do not provide preferential solution sites for H. In all cases the most stable site for H are those that offer the highest coordination fraction of Zr atoms. Often these are four Zr tetrahedra but not always. Implications with respect to H-trapping properties of commonly observed ternary phases such as Zr(Cr,Fe)2, Zr2(Fe,Ni) and Zr(Nb,Fe)2 are also discussed.Comment: manuscript accepted for publication in Journal of Nuclear Materials (2013

Test of nuclear level density inputs for Hauser-Feshbach model calculations

The energy spectra of neutrons, protons, and alpha-particles have been measured from the d+59Co and 3He+58Fe reactions leading to the same compound nucleus, 61$Ni. The experimental cross sections have been compared to Hauser-Feshbach model calculations using different input level density models. None of them have been found to agree with experiment. It manifests the serious problem with available level density parameterizations especially those based on neutron resonance spacings and density of discrete levels. New level densities and corresponding Fermi-gas parameters have been obtained for reaction product nuclei such as 60Ni,60Co, and 57Fe

Coupled phonon-ripplon modes in a single wire of electrons on the liquid-helium surface

The coupled phonon-ripplon modes of the quasi-one-dimensional electron chain on the liquid helium sutface are studied. It is shown that the electron-ripplon coupling leads to the splitting of the collective modes of the wire with the appearance of low-frequency modes and high-frequency optical modes starting from threshold frequencies. The effective masses of an electron plus the associated dimple for low frequency modes are estimated and the values of the threshold frequencies are calculated. The results obtained can be used in experimental attempts to observe the phase transition of the electron wire into a quasi-ordered phase.Comment: 5 pages, 1 figure, Physical Review (in press

Crew Motion and the Dynamic Environment of Spaceborne Experiments

Analytical study of crew motion on dynamic environment of orbiting laboratorie

Interplanetary communications study Final report

Mathematical expression for phase and amplitude distribution in focal plane of apertur

Extending HIV Prevention: People Living With HIV/AIDS (PLWHA) Strategize to Reduce Stigma and Promote HIV Testing

Strategies to reduce acquired immunodeficiency syndrome (AIDS)‐related stigma are paramount to promoting effective HIV prevention. As in the case of HIV antibody testing, despite the benefits of early detection, links to care, and risk behavior modification, nearly 250,000 people are unaware of their HIV status. AIDS‐related stigma has impeded such efforts due to discrimination, ignorance and other forms of stigma. These issues related to stigma and HIV testing are magnified when placed in the context of the rural Deep South region of the United States, where the incidence of HIV/AIDS are growing at alarming rates. The purpose of this paper was to examine strategies to reduce AIDS‐related stigma that in turn promotes HIV testing as proposed by people living with HIV/AIDS (PLWHA) who reside in the Deep South. An exploratory descriptive qualitative research design was utilized. The sample consisted of 18 PLWHA. Data was collected using a focus group and individual, semi‐structured interviews. The analysis revealed the importance of ongoing education as a mediator between reducing stigma and promoting HIV testing. Other salient findings were related to reframing HIV/AIDS‐related health messages to reflect a sense of empowerment; the need to normalize testing; the use of less stigmatizing testing sites; and the continuance of anonymous HIV testing. This article is significant because it illuminates the challenges of HIV prevention in the Deep South, while also generating culturally‐sensitive strategies to counter these barriers

Level density of 56^{56}Fe and low-energy enhancement of γ\gamma-strength function

The $^{55}$Mn$(d,n)^{56}$Fe differential cross section is measured at $E_d=7$ MeV\@. The $^{56}$Fe level density obtained from neutron evaporation spectra is compared to the level density extracted from the $^{57}$Fe$(^3$He,$\alpha\gamma)^{56}$Fe reaction by the Oslo-type technique. Good agreement is found between the level densities determined by the two methods. With the level density function obtained from the neutron evaporation spectra, the $^{56}$Fe $\gamma$-strength function is also determined from the first-generation $\gamma$ matrix of the Oslo experiment. The good agreement between the past and present results for the $\gamma$-strength function supports the validity of both methods and is consistent with the low-energy enhancement of the $\gamma$ strength below $\sim 4$ MeV first discovered by the Oslo method in iron and molybdenum isotopes.Comment: 7 pages, 5 figure