118214092
Addressing LISA Science Analysis Challenges
The principal goal of the \emph{LISA Science Analysis Workshop} is to encourage the development and maturation of science analysis technology in preparation for LISA science operations. Exactly because LISA is a pathfinder for a new scientific discipline -- gravitational wave astronomy -- LISA data processing and science analysis methodologies are in their infancy and require considerable maturation if they are to be ready to take advantage of LISA data. Here we offer some thoughts, in anticipation of the LISA Science Analysis Workshop, on analysis research problems that demonstrate the capabilities of different proposed analysis methodologies and, simultaneously, help to push those techniques toward greater maturity. Particular emphasis is placed on formulating questions that can be turned into well-posed problems involving tests run on specific data sets, which can be shared among different groups to enable the comparison of techniques on a well-defined platform.
31236089
Baryon-antibaryon annihilation in the Skyrme model.
The dynamics of Skyrmion-anti-Skyrmion annihilations in 3+1 dimensions is examined by the numerical integration of the classical Hamilton equations of motion. The baryon number is found to disappear extremely rapidly, close to the causal limit, while the energy distribution still remains concentrated in the annihilation region. The emission of pion waves emitted by the annihilation process is investigated.
17000862
Space Missions to Detect the Cosmic Gravitational-Wave Background
It is thought that a stochastic background of gravitational waves was produced during the formation of the universe. A great deal could be learned by measuring this cosmic gravitational-wave background (CGB), but detecting the CGB presents a significant technological challenge. The signal strength is expected to be extremely weak, and there will be competition from unresolved astrophysical foregrounds such as white dwarf binaries. Our goal is to identify the most promising approach to detecting the CGB. We study the sensitivities that can be reached using both individual, and cross-correlated pairs of space-based interferometers. Our main result is a general, coordinate-free formalism for calculating the detector response that applies to arbitrary detector configurations. We use this general formalism to identify some promising designs for a gravitational background interferometer mission. Our conclusion is that detecting the CGB may not be out of reach.
98032634
Progress in the Development of an Alternative Approach to Macromolecular Crystallization
We are developing an alternate strategy for the crystallization of macromolecules that does not, like current methods, depend on the optimization of traditional variables such as pH and precipitant concentration, but is based on the hypothesis that many conventional small molecules might establish stabilizing, intermolecular, noncovalent cross-links in crystals, and thereby promote lattice formation. Earlier experiments provided encouraging results that suggested further research was warranted (Larson, S. B.; Day, J. S.; Cudney, R.; McPherson, A. A novel strategy for the crystallization of proteins: X-ray diffraction validation. Acta Crystallogr., D: Biol. Crystallogr. 2007, 63, 310−318. McPherson, A.; Cudney, B. Searching for silver bullets: an alternative strategy for crystallizing macromolecules. J. Struct. Biol. 2006, 156, 387−406). Here we report additional, large-scale crystallization screening experiments that lend further support, though they suggest that additional mechanisms may play a positive ...
38714824
The structure of tomato aspermy virus by X-ray crystallography.
The three-dimensional structure of tomato aspermy virus (TAV) has been solved by X-ray crystallography and refined to an R factor of 0.218 for 3.4-40 A data (effective resolution of 4A). Molecular replacement, using cucumber mosaic virus (Smith et al., 2000), provided phases for the initial maps used for model building. The coat protein of the 280 A diameter virion has the canonical "Swiss roll" beta-barrel topology with a distinctive amino-terminal alpha-helix directed into the interior of the virus where it interacts with encapsidated RNA. The N-terminal helices are joined to the beta-barrels of protein subunits by extended polypeptides of six amino acids, which serve as flexible hinges allowing movement of the helices in response to local RNA distribution. Segments of three nucleotides of partially disordered RNA interact with the capsid, primarily through arginine residues, at interfaces between A and B subunits. Side chains of cys64 and cys106 form the first disulfide observed in a cucumovirus, including a unique cysteine, 106, in a region otherwise conserved. A positive ion, putatively modeled as a Mg(+)ion, lies on the quasi-threefold axis surrounded by three quasi-symmetric glutamate 175 side chains.