Biomedical subjects

V Elser

Publications and source records attributed to V Elser.

At least 19 recordsLinked to original sources

PubMed2007

Searching with iterated maps.

In many problems that require extensive searching, the solution can be described as satisfying two competing constraints, where satisfying each independently does not pose a challenge. As an alternative to tree-based and stochastic searching, for these problems we propose using an iterated map built from the projections to the two constraint sets. Algorithms of this kind have been the method of choice in a large variety of signal-processing applications; we show here that the scope of these algorithms is surprisingly broad, with applications as diverse as protein folding and Sudoku.

Algorithms↗

PubMed2000

Solving the crystallographic phase problem in i(AlPdMn).

We apply a new technique for ab initio phase determination [Acta Crystallogr. Sect. A 55, 48 (1999)] to solve for the average structure of the icosahedral ( i) phase of AlPdMn. After an introduction to the crystallographic phase problem and a description of the method, we present a brief report of our findings for the structure of i(AlPdMn). Despite the use of data from extremely high quality samples, we find strong evidence of disorder in the structure, lending support to the random tiling model of quasicrystal stabilization.

Journal Article↗

PubMed1999

X-ray phase determination by the principle of minimum charge.

When the electron density in a crystal or a quasicrystal is reconstructed from its Fourier modes, the global minimum value of the density is sensitively dependent on the relative phases of the modes. The set of phases that maximizes the value of the global minimum corresponds, by positivity of the density, to the density having the minimum total charge that is consistent with the measured Fourier amplitudes. Phases that minimize the total electronic charge (i.e. the average electron density) have the additional property that the lowest minima of the electron density become exactly degenerate and proliferate within the unit cell. The large number of degenerate minima have the effect that density maxima are forced to occupy ever smaller regions of the unit cell. Thus, by minimization of the electronic charge, the atomicity of the electron density is enhanced as well. Charge minimization applied to simulated crystalline and quasicrystalline diffraction data successfully reproduces the correct phases starting from random initial phases.

Journal Article↗

PubMed1995