2-aminophenols containing electron-withdrawing groups from N-aryl hydroxylamines

Reaction of substituted N-aryl hydroxylamines with methanesulfonyl chloride, p-toluenesulfonyl chloride, or trifluoromethanesulfonic anhydride under basic conditions leads to the rearranged 2-aminophenols (45-94%). The overall reaction sequence can be performed using polymer-supported sulfonyl chloride resin allowing for the effective conversion of N-aryl hydroxylamines to the 2-aminophenols without the need for chromatography

LunaNet: a Flexible and Extensible Lunar Exploration Communications and Navigation Infrastructure

NASA has set the ambitious goal of establishing a sustainable human presence on the Moon. Diverse commercial and international partners are engaged in this effort to catalyze scientific discovery, lunar resource utilization and economic development on both the Earth and at the Moon. Lunar development will serve as a critical proving ground for deeper exploration into the solar system. Space communications and navigation infrastructure will play an integral part in realizing this goal. This paper provides a high-level description of an extensible and scalable lunar communications and navigation architecture, known as LunaNet. LunaNet is a services network to enable lunar operations. Three LunaNet service types are defined: networking services, position, navigation and timing services, and science utilization services. The LunaNet architecture encompasses a wide variety of topology implementations, including surface and orbiting provider nodes. In this paper several systems engineering considerations within the service architecture are highlighted. Additionally, several alternative LunaNet instantiations are presented. Extensibility of the LunaNet architecture to the solar system internet is discussed

A BPS Interpretation of Shape Invariance

We show that shape invariance appears when a quantum mechanical model is invariant under a centrally extended superalgebra endowed with an additional symmetry generator, which we dub the shift operator. The familiar mathematical and physical results of shape invariance then arise from the BPS structure associated with this shift operator. The shift operator also ensures that there is a one-to-one correspondence between the energy levels of such a model and the energies of the BPS-saturating states. These findings thus provide a more comprehensive algebraic setting for understanding shape invariance.Comment: 15 pages, 2 figures, LaTe

The determination of the structure of Saturn's F ring by nearby moonlets

International audienceSaturn's narrow F ring exhibits several unusual features that vary on timescales of hours to years. These include transient clumps, a central core surrounded by a multistranded structure and a regular series of longitudinal channels associated with Prometheus, one of the ring's two 'shepherding' satellites. Several smaller moonlets and clumps have been detected in the ring's immediate vicinity, and a population of embedded objects has been inferred. Here we report direct evidence of moonlets embedded in the ring's bright core, and show that most of the F ring's morphology results from the continual gravitational and collisional effects of small satellites, often combined with the perturbing effect of Prometheus. The F-ring region is perhaps the only location in the Solar System where large-scale collisional processes are occurring on an almost daily basis

Thermodynamic calculations of oxygen self-diffusion in mixed-oxide nuclear fuels

Molecular dynamics calculations are used to provide a self-consistent prediction of the elastic, thermal expansion and oxygen self-diffusion properties of mixed oxide nuclear fuels at arbitrary compositions.</p

Image of the Energy Gap Anisotropy in the Vibrational Spectum of a High Temperature Superconductor

We present a new method of determining the anisotropy of the gap function in layered high-Tc superconductors. Careful inelastic neutron scattering measurements at low temperature of the phonon dispersion curves in the (100) direction in La_(1.85)Sr_(.15)CuO_4 would determine whether the gap is predominately s-wave or d-wave. We also propose an experiment to determine the gap at each point on a quasi-two-dimensional Fermi surface.Comment: 12 pages + 2 figures (included