A Palladium-Catalyzed Vinylcyclopropane (3 + 2) Cycloaddition Approach to the Melodinus Alkaloids

A palladium-catalyzed (3 + 2) cycloaddition of a vinylcyclopropane and a β-nitrostyrene is employed to rapidly assemble the cyclopentane core of the Melodinus alkaloids. The ABCD ring system of the natural product family is prepared in six steps from commercially available materials

The Icarus Student Satellite - A Fully Autonomous Student Built Small Satellite for NASA

University of Michigan students, with the mentoring support of engineers from NASA, Michigan, and elsewhere, have developed a small endmass satellite—dubbed Icarus—for NASA’s ProSEDS (Propulsive Small Expendable Deployer System) electrodynamic-tether propulsion mission. The ProSEDS experiment will be launched in late 2002 as a secondary payload attached to the second stage of a Delta–II launch vehicle. Following the completion of the Delta–II primary mission, the second stage will initiate a series of burns to place ProSEDS into a 360-km, near-circular orbit at an inclination of 35°. The Icarus endmass satellite will be cast off from the Delta–II second stage and be deployed in the zenith direction. The endmass will remain connected to the Delta–II via a combination space tether consisting of 5-km aluminum conducting tether nearest the Delta–II attached to 10-km nonconducting Spectra fiber, connected to the endmass. Throughout tether deployment, and for the duration of the ProSEDS mission, Icarus will collect and transmit data on tether deployment and dynamics. The endmass is responsible for providing tetherendbody location information (using a GPS receiver) and endbody attitude dynamics (using an aspect magnetometer). The data from these instruments will be stored and transmitted to ground telemetry stations. Power to the endmass will be provided by rechargable batteries and solar cells; an onboard command and data handling system will provide control functions. The endmass will continue to record and transmit data as ProSEDS lowers its altitude. Icarus also serves as a backup for mission location information to the main ProSEDS GPS receiver located on the Delta-II second stage

Vacuum Stability of Standard Model^{++}

The latest results of the ATLAS and CMS experiments point to a preferred narrow Higgs mass range (m_h \simeq 124 - 126 GeV) in which the effective potential of the Standard Model (SM) develops a vacuum instability at a scale 10^{9} -10^{11} GeV, with the precise scale depending on the precise value of the top quark mass and the strong coupling constant. Motivated by this experimental situation, we present here a detailed investigation about the stability of the SM^{++} vacuum, which is characterized by a simple extension of the SM obtained by adding to the scalar sector a complex SU(2) singlet that has the quantum numbers of the right-handed neutrino, H", and to the gauge sector an U(1) that is broken by the vacuum expectation value of H". We derive the complete set of renormalization group equations at one loop. We then pursue a numerical study of the system to determine the triviality and vacuum stability bounds, using a scan of 10^4 random set of points to fix the initial conditions. We show that, if there is no mixing in the scalar sector, the top Yukawa coupling drives the quartic Higgs coupling to negative values in the ultraviolet and, as for the SM, the effective potential develops an instability below the Planck scale. However, for a mixing angle -0.35 \alt \alpha \alt -0.02 or 0.01 \alt \alpha \alt 0.35, with the new scalar mass in the range 500 GeV \alt m_{h"} \alt 8 TeV, the SM^{++} ground state can be absolutely stable up to the Planck scale. These results are largely independent of TeV-scale free parameters in the model: the mass of the non-anomalous U(1) gauge boson and its branching fractions.Comment: 17 revtex pages, 8 figures; to be published in JHE

Large Scale Anisotropy of Cosmic Rays and Directional Neutrino Signals from Galactic Sources

We investigate the neutrino - cosmic ray connection for sources in the Galaxy in terms of two observables: the shape of the energy spectrum and the distribution of arrival directions. We also study the associated gamma ray emission from these sources.Comment: Proceedings of the 2nd Cosmic Ray Anisotropy Workshop, 26-28 September 2013, Madison, Wisconsin. To appear in IOP Conference Serie

Label-free detection of single nanoparticles and biological molecules using microtoroid optical resonators

Single-molecule detection is one of the fundamental challenges of modern biology. Such experiments often use labels that can be expensive, difficult to produce, and for small analytes, might perturb the molecular events being studied. Analyte size plays an important role in determining detectability. Here we use laser-frequency locking in the context of sensing to improve the signal-to-noise ratio of microtoroid optical resonators to the extent that single nanoparticles 2.5 nm in radius, and 15.5 kDa molecules are detected in aqueous solution, thereby bringing these detectors to the size limits needed for detecting the key macromolecules of the cell. Our results, covering several orders of magnitude of particle radius (100 nm to 2 nm), agree with the ‘reactive’ model prediction for the frequency shift of the resonator upon particle binding. This confirms that the main contribution of the frequency shift for the resonator upon particle binding is an increase in the effective path length due to part of the evanescent field coupling into the adsorbed particle. We anticipate that our results will enable many applications, including more sensitive medical diagnostics and fundamental studies of single receptor–ligand and protein–protein interactions in real time