Supersymmetric U(1) Gauge Realization of the Dark Scalar Doublet Model of Radiative Neutrino Mass

Adding a second scalar doublet (eta^+,eta^0) and three neutral singlet fermions N_{1,2,3} to the Standard Model of particle interactions with a new Z_2 symmetry, it has been shown that Re(eta^0) or Im(eta^0) is a good dark-matter candidate and seesaw neutrino masses are generated radiatively. A supersymmetric U(1) gauge extension of this new idea is proposed, which enforces the usual R parity of the Minimal Supersymmetric Standard Model, and allows this new Z_2 symmetry to emerge as a discrete remnant.Comment: 8 pages, 3 figure

NASA propagation information center

The NASA Propagation Information Center became formally operational in July 1988. It is located in the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. The center is several things: a communications medium for the propagation with the outside world, a mechanism for internal communication within the program, and an aid to management

NASA Propagation Information Center

The NASA Propagation Information Center became formally operational in July 1988. It is located in the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. The Center is several things: a communications medium for the propagation with the outside world, a mechanism for internal communication within the program, and an aid to management

Phase diagram of spin-11 chains with Dzyaloshinskii-Moriya interaction

We investigate an antiferromagnetic spin-$1$ Heisenberg chain in the presence of Dyzaloshinskii-Moriya interactions (DMI) and an external magnetic field. We study the resulting spin chain using a combination of numerical and analytical techniques. Using DMRG simulations to determine the spectral gap and the entanglement spectrum, we map out the phase diagram as a function of magnetic field strength and DMI strength. We provide a qualitative interpretation for these numerical findings by mapping the spin-$1$ chain on a spin-$1/2$ ladder and using a bosonization approach.Comment: 7 pages, 5 figure

Utility of a Special Second Scalar Doublet

This Brief Review deals with the recent resurgence of interest in adding a second scalar doublet (eta^+,eta^0) to the Standard Model of particle interactions. In most studies, it is taken for granted that eta^0 should have a nonzero vacuum expectation value, even if it may be very small. What if there is an exactly conserved symmetry which ensures =0? The phenomenological ramifications of this idea include dark matter, radiative neutrino mass, leptogenesis, and grand unification.Comment: 9 pages, 1 figur

Propagation effects on spread-spectrum mobile satellite systems

In contrast to the situation at L-band, wide bandwidths of 500 MHz or more have been allocated for mobile satellite service at frequencies between 20 and 50 GHz. These broad bandwidths are well suited for the use of spread-spectrum. Certain system considerations about the use of such high frequencies for mobile satellite service are mentioned first, and attention is then given to propagation effects on high-frequency broad-band systems. Attenuation due to rain is a constant at 20 to 50 MHz, but would not be a serious problem if outages occurring for one to three percent of the time, depending on location, are considered to be acceptable. Clear air absorption becomes a significant factor above 40 GHz, but should not exceed 2 dB at a 10 degree elevation angle and frequencies below 40 GHz. Spread-spectrum provides a form of frequency diversity that helps to minimize the effects of multipath

European Springtails Orchesella cincta (L.) and O. villosa (L.) (Collembola: Entomobryidae): Vagabond Species of the Nearctic Region

North American specimens of the European invasive springtail Orchesella cincta (L.) were compared to several published European haplotypes in a phylogenetic framework using likelihood methods based on a portion of cytochrome oxidase II (cox2). Our analyses provide direct evidence of at least two distinct introductions of this invasive to North America from different regions of Europe. Additional introduction events cannot be ruled out because detection is limited by extremely low sequence divergence among populations inhabiting different regions of the continent. Orchesella villosa (L.), another invasive from Europe, is another candidate for multiple introductions. Herein we include the cox2 sequence from single specimens of O. villosa from Maine and Oregon. Although these two specimens are identical in sequence, they differ from a published sequence from a European specimen by 15%, indicating significant undocumented genetic variation in the natal range of O. villosa. Additional sampling of Nearctic populations of O. villosa might reveal the same situation reported herein for O. cincta

WARC 92 and some thoughts as to its impact on the NASA propagation program

The World Administrative Radio Conference of 1992 (WARC 92) was held in Torremolinos, Spain, 3 Feb. - 3 Mar. 1992. Major topics considered included shortwave broadcasting, mobile and mobile-satellite service, broadcasting satellite service (sound and HDTV), space services above 20 GHz, and space research. Considerable attention was given to the congested 1-3 GHz band in general and to Low Earth Orbit (LEO) Mobile-Satellite Service, including 'little' LEO's operating below 1 GHz and to 'big' LEO's operating above 1 GHz. Significant new allocations were made for generic Mobile-Satellite Services (MSS). Proposals for allocations for uplink power control beacons and for space research received favorable treatment

The NTD-CTD intersubunit interface plays a critical role in assembly and stabilization of the HIV-1 capsid

BACKGROUND: Lentiviruses exhibit a cone-shaped capsid composed of subunits of the viral CA protein. The intrinsic stability of the capsid is critical for HIV-1 infection, since both stabilizing and destabilizing mutations compromise viral infectivity. Structural studies have identified three intersubunit interfaces in the HIV-1 capsid, two of which have been previously studied by mutational analysis. In this present study we analyzed the role of a third interface, that which is formed between the amino terminal domain (NTD) and carboxyl terminal domain (CTD) of adjacent subunits. RESULTS: We provided evidence for the presence of the NTD-CTD interface in HIV-1 particles by engineering intersubunit NTD-CTD disulfide crosslinks, resulting in accumulation of disulfide-linked oligomers up to hexamers. We also generated and characterized a panel of HIV-1 mutants containing substitutions at this interface. Some mutants showed processing defects and altered morphology from that of wild type, indicating that the interface is important for capsid assembly. Analysis of these mutants by transmission electron microscopy corroborated the importance of this interface in assembly. Other mutants exhibited quantitative changes in capsid stability, many with unstable capsids, and one mutant with a hyperstable capsid. Analysis of the mutants for their capacity to saturate TRIMCyp-mediated restriction in trans confirmed that the unstable mutants undergo premature uncoating in target cells. All but one of the mutants were markedly attenuated in replication owing to impaired reverse transcription in target cells. CONCLUSIONS: Our results demonstrate that the NTD-CTD intersubunit interface is present in the mature HIV-1 capsid and is critical for proper capsid assembly and stability