9,077 research outputs found
Study of guidance techniques for aerial application of agricultural compounds
Candidate systems were identified for evaluation of suitability in meeting specified accuracy requirements for a swath guidance system in an agriculture aircraft. Further examination reduced the list of potential candidates to a single category, i.e., transponder type systems, for detailed evaluation. Within this category three systems were found which met the basic accuracy requirements of the work statement. The Flying Flagman, the Electronic Flagging and the Raydist Director System. In addition to evaluating the systems against the specified requirements, each system was compared with the other two systems on a relative basis. The conclusions supported by the analyses show the Flying Flagman system to be the most suitable system currently available to meet the requirements
Neutrinos and Nucleosynthesis in Supernova
The type II supernova is considered as a candidate site for the production of
heavy elements. The nucleosynthesis occurs in an intense neutrino flux, we
calculate the electron fraction in this environment.Comment: RevTex4 style, 3 pages including 1 figure. Presented at Mexican
School of Astrophysics 2002, Guanajuato, Mexico, 31 Jul - 7 Aug 2002. Final
version to appear in the Proceedings of IX Mexican Workshop on Particles and
Fields Physics Beyond the Standard Model, Colima Col. Mexico, November 17-22,
200
A recombinant Chlamydia trachomatis major outer membrane protein binds to heparan sulfate receptors on epithelial cells.
Perfect interferenceless absorption at infrared frequencies by a van der Waals crystal
Citation: Baranov, D. G., Edgar, J. H., Hoffman, T., Bassim, N., & Caldwell, J. D. (2015). Perfect interferenceless absorption at infrared frequencies by a van der Waals crystal. Physical Review B, 92(20), 6. doi:10.1103/PhysRevB.92.201405Traditionally, efforts to achieve perfect absorption have required the use of complicated metamaterial-based structures as well as relying on destructive interference to eliminate back reflections. Here, we have demonstrated both theoretically and experimentally that such perfect absorption can be achieved using a naturally occurring material, hexagonal boron nitride (hBN) due to its high optical anisotropy without the requirement of interference effects to absorb the incident field. This effect was observed for p-polarized light within the mid-infrared spectral range, and we provide the full theory describing the origin of the perfect absorption as well as the methodology for achieving this effect with other materials. Furthermore, while this is reported for the uniaxial crystal hBN, this is equally applicable to biaxial crystals and more complicated crystal structures. Interferenceless absorption is of fundamental interest to the field of optics; moreover, such materials may provide additional layers of flexibility in the design of frequency selective surfaces, absorbing coatings, and sensing devices operating in the infrared
Models for Little Rip Dark Energy
We examine in more detail specific models which yield a little rip cosmology,
i.e., a universe in which the dark energy density increases without bound but
the universe never reaches a finite-time singularity. We derive the conditions
for the little rip in terms of the inertial force in the expanding universe and
present two representative models to illustrate in more detail the difference
between little rip models and those which are asymptotically de Sitter. We
derive conditions on the equation of state parameter of the dark energy to
distinguish between the two types of models. We show that coupling between dark
matter and dark energy with a little rip equation of state can alter the
evolution, changing the little rip into an asymptotic de Sitter expansion. We
give conditions on minimally-coupled phantom scalar field models and on
scalar-tensor models that indicate whether or not they correspond to a little
rip expansion. We show that, counterintuitively, despite local instability, a
little-rip cosmology has an infinite lifetime.Comment: LaTeX, 10 pages, no figure, version to appear in Phys.Lett
Neutrino Mass Texture with Large Mixing
We propose a simple texture for the right-handed Majorana mass matrix to give
a large mixing angle and hierarchical left-handed neutrino
mass pattern. Consistently with the Dirac mass texture of the quark sector
realizing the CKM mixing, this naturally explains the recent experimental
results on both the atmospheric neutrino anomaly observed by the
Superkamiokande collaboration and the solar neutrino problem. In this texture
the right-handed Majorana mass of the third generation is of the order of GUT
scale, which is favorable for reproducing the observed bottom-tau mass ratio.Comment: 10 pages, LaTeX, comments and references adde
Polarization forces in water deduced from single molecule data
Intermolecular polarization interactions in water are determined using a
minimal atomic multipole model constructed with distributed polarizabilities.
Hydrogen bonding and other properties of water-water interactions are
reproduced to fine detail by only three multipoles , , and
and two polarizabilities and , which
characterize a single water molecule and are deduced from single molecule data.Comment: 4 revtex pages, 3 embedded color PS figure
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