skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Shape transform phasing of edgy nanocrystals
Diffraction patterns from small protein crystals illuminated by highly coherent X-rays often contain measurable interference signals between Bragg peaks. This coherent `shape transform' signal introduces enough additional information to allow the molecular densities to be determined from the diffracted intensities directly, without prior information or resolution restrictions. However, the various correlations amongst molecular occupancies/vacancies at the crystal surface result in a subtle yet critical problem in shape transform phasing whereby the sublattices of symmetry-related molecules exhibit a form of partial coherence amongst lattice sites when an average is taken over many crystal patterns. Here an iterative phase retrieval algorithm is developed which is capable of treating this problem; it is demonstrated on simulated data.  more » « less
Award ID(s):
1231306
PAR ID:
10588798
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Acta Crystallographica Section A Foundations and Advances
Date Published:
Journal Name:
Acta Crystallographica Section A Foundations and Advances
Volume:
75
Issue:
2
ISSN:
2053-2733
Page Range / eLocation ID:
239 to 259
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; (, Science Advances)
    Morphogenesis of living systems involves topological shape transformations which are highly unusual in the inanimate world. Here, we demonstrate that a droplet of a nematic liquid crystal changes its equilibrium shape from a simply connected tactoid, which is topologically equivalent to a sphere, to a torus, which is not simply connected. The topological shape transformation is caused by the interplay of nematic elastic constants, which facilitates splay and bend of molecular orientations in tactoids but hinders splay in the toroids. The elastic anisotropy mechanism might be helpful in understanding topology transformations in morphogenesis and paves the way to control and transform shapes of droplets of liquid crystals and related soft materials. 
    more » « less
  2. ; ; ; ; ; ; ; (, Advanced Optical Materials)
    Abstract Shaping the intensity profile of a laser beam is desired by various industrial applications. In this paper, a new approach is presented to design and fabricate liquid crystal (LC) micro‐optical elements (MOEs) with engineered Pancharatnam–Berry (PB) phases for beam shaping. By generalizing the Snell's law for spatially variant PB phases, molecular orientation patterns are designed for the liquid crystal MOEs to shape a Gaussian laser beam into flattop intensity profiles with circular and square cross‐sections, with the β parameter varied from 4 to 42. It is demonstrated that such liquid crystal beam shaping MOEs can be fabricated with high throughput and high resolution by using a photopatterning technique based on plasmonic metamasks and that they produce excellent beam quality, no zero‐order light leakage with a beam size from 10 to 600 µm. As the plasmonic metamasks allow for encoding arbitrary molecular orientations, i.e., arbitrary geometric phase profiles, the approaches presented here are widely applicable to large‐scale manufacturing of liquid crystal MOEs for any beam shapes. 
    more » « less
  3. ; ; (, Advanced Materials)
    Abstract During morphogenesis, cells collectively execute directional forces that drive the programmed folding and growth of the layers, forming tissues and organs. The ability to recapitulate aspects of these processes in  vitro will constitute a significant leap forward in the field of tissue engineering. Free‐standing, self‐organizing, cell‐laden matrices are fabricated using a sequential deposition approach that uses liquid crystal‐templated hydrogel fibers to direct cell arrangements. The orientation of hydrogel fibers is controlled using flow or boundary cues, while their microstructures are controlled by depletion interaction and probed by scattering and microscopy. These fibers effectively direct cells embedded in a collagen matrix, creating multilayer structures through contact guidance and by leveraging steric interactions amongst the cells. In uniformly aligned cell matrices, oriented cells exert traction forces that can induce preferential contraction of the matrix. Simultaneously, the matrix densifies and develops anisotropy through cell remodeling. Such an approach can be extended to create cell arrangements with arbitrary in‐plane patterns, allowing for coordinated cell forces and pre‐programmed, macroscopic shape changes. This work reveals a fundamentally new path for controlled force generation, emphasizing the role of a carefully designed initial orientational field for manipulating shape transformations of reconstituted matrices. 
    more » « less
  4. ; ; ; ; ; (, Ecology Letters)
    ABSTRACT Wind is the primary dispersal mechanism of most fungal spores but is rarely considered in studies of fungal communities, limiting inference of assembly mechanisms and forecasting responses to climate change. We compiled wind‐connectivity models—‘windscapes’—to model potential dispersal of fungal spores at the continental scale and linked them with a molecular dataset of North American soil fungi. Our analyses demonstrate that prevailing windflow patterns exhibit a significantly stronger signal on fungal community structure than do geographic distances amongst sites. Notably, the signature of wind was detectable for mushrooms and fungi producing primarily wind‐dispersed spores. Contrastingly, fungi primarily reliant on animal dispersal exhibited a strong signature of geographic distance but not wind‐connectivity. Additionally, we show that directionally ‘downwind’ sites are more diverse than comparatively ‘upwind’ sites. Altogether, our findings suggest that future wind patterns will shape the adaptation potential of fungal communities dispersing into suitable climatic niches. 
    more » « less
  5. (, CG Week Young Researcher's Forum)
    The weighted Euler curve transform (WECT) was recently introduced as a tool to extract meaningful information from shape data, when the shape is equipped with a weight function. In this extended abstract, we provide an experimental investigation on using the WECT for image classification. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email