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in creator/contributor: "Shapiro, D"

open access

Polarized light scattering as a probe for changes in chromosome structure

Measurements and calculations of polarized light scattering are applied to chromosomes. Calculations of the Mueller matrix, which completely describes how the polarization state of light is altered upon scattering, are developed for helical structures related to that of chromosomes. Measurements of the Mueller matrix are presented for octopus sperm heads, and dinoflagellates. Comparisons of theory and experiment are made. A working theory of polarized light scattering from helices is developed.… more

Date: October 1, 1993

Creator: Shapiro, D. B.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

High-resolution ab initio Three-dimensional X-ray Diffraction Microscopy

Coherent X-ray diffraction microscopy is a method of imaging non-periodic isolated objects at resolutions only limited, in principle, by the largest scattering angles recorded. We demonstrate X-ray diffraction imaging with high resolution in all three dimensions, as determined by a quantitative analysis of the reconstructed volume images. These images are retrieved from the 3D diffraction data using no a priori knowledge about the shape or composition of the object, which has never before been … more

Date: August 19, 2005

Creator: Chapman, H. N.; Barty, A.; Marchesini, S.; Noy, A.; Cui, C.; Howells, M. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Damped and Thermal Motion of Large, Laser-Aligned Molecules in Droplet Beams

We consider a monodispersed Rayleigh droplet beam of water droplets doped with proteins. An intense infrared laser is used to align these droplets. The arrangement has been proposed for electron and X-ray diffraction studies of proteins which are difficult to crystallize. This paper considers the effect of thermal fluctuations on the angular spread of alignment in thermal equilibrium, and relaxation phenomena, particularly the damping of oscillations excited as the molecules enter the field. Th… more

Date: September 29, 2005

Creator: Starodub, D.; Doak, B.; Schmidt, K.; Weierstall, U.; Wu, J.; Spence, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Progress in Three-Dimensional Coherent X-Ray Diffraction Imaging

The Fourier inversion of phased coherent diffraction patterns offers images without the resolution and depth-of-focus limitations of lens-based tomographic systems. We report on our recent experimental images inverted using recent developments in phase retrieval algorithms, and summarize efforts that led to these accomplishments. These include ab-initio reconstruction of a two-dimensional test pattern, infinite depth of focus image of a thick object, and its high-resolution ({approx}10 nm resol… more

Date: September 30, 2005

Creator: Marchesini, S.; Chapman, H. N.; Barty, A.; Howells, M. R.; Cui, C.; Spence, J. H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Femtosecond Diffractive Imaging with a Soft-X-ray Free-Electron Laser

Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 x 10{sup 13} W/cm{sup 2} pulse, containing 10{sup 12} photons at 32 nm wavelength, produced a coherent diffraction pattern from a nano… more

Date: March 13, 2006

Creator: Chapman, H. N.; Barty, A.; Bogan, M.; Boutet, S.; Frank, M.; Hau-Riege, S. P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Dose, exposure time, and resolution in Serial X-ray Crystallography

Using detailed simulation and analytical models, the exposure time is estimated for serial crystallography, where hydrated laser-aligned proteins are sprayed across a continuous synchrotron beam. The resolution of X-ray diffraction microscopy is limited by the maximum dose that can be delivered prior to sample damage. In the proposed Serial Crystallography method, the damage problem is addressed by distributing the total dose over many identical hydrated macromolecules running continuously in a… more

Date: March 22, 2007

Creator: Starodub, D.; Rez, P.; Hembree, G.; Howells, M.; Shapiro, D.; Chapman, H. N. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Camera for Coherent Diffractive Imaging and Holography With a Soft-X-Ray Free Electron Laser

We describe a camera to record coherent scattering patterns with a soft-X-ray free-electron laser. The camera consists of a laterally-graded multilayer mirror which reflects the diffraction pattern onto a CCD detector. The mirror acts as a bandpass filter both for wavelength and angle, which isolates the desired scattering pattern from non-sample scattering or incoherent emission from the sample. The mirror also solves the particular problem of the extreme intensity of the FEL pulses, which are… more

Date: September 24, 2007

Creator: Bajt, S.; Chapman, H. N.; Spiller, E.; Alameda, J.; Woods, B.; Frank, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department