X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is being practiced at several third-generation synchrotron-radiation x-ray facilities. Nine years have elapsed since the technique was first introduced and it has made rapid progress in demonstrating high-resolution threedimensional imaging and promises few-nm resolution with much larger samples than can be imaged in the transmission electron microscope. Both life-and materials-science applications of XDM are intended, and it is expected that the principal limitation to resolution will be radiation damage for life science and the coherent power of available x-ray sources for material science. In this paper we address the question of the role of radiation damage. We use a statistical analysis based on the socalled "dose fractionation theorem" of Hegerl and Hoppe to calculate the dose needed to make an image of a single life-science sample by XDM with a given resolution. We find that for simplyshaped objects the needed dose scales with the inverse fourth power of the resolution and present experimental evidence to support this finding. To determine the maximum tolerable dose we have assembled a number of data taken from the literature plus some measurements of our own which cover ranges of resolution that are not well covered otherwise. The conclusion of this study is that, based on the natural contrast between protein and water and "Rose-criterion" image quality, one should be able to image a frozen-hydrated biological sample using XDM at a resolution of about 10 nm.6Corresponding author: mrhowells@lbl.gov, phone 510 486 4949, fax 510 486 7696.

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 demonstrated on a non-periodic object. We also construct 2D images of thick objects with infinite depth of focus (without loss of transverse spatial resolution). These methods can be used to image biological and materials science samples at high resolution using X-ray undulator radiation, and establishes the techniques to be used in atomic-resolution ultrafast imaging at X-ray free-electron laser sources.

We have used the method of x-ray diffraction microscopy to image the complex-valued exit wave of an intact and unstained yeast cell. The images of the freeze-dried cell, obtained by using 750-eV x-rays from different angular orientations, portray several of the cell's major internal components to 30-nm resolution. The good agreement among the independently recovered structures demonstrates the accuracy of the imaging technique. To obtain the best possible reconstructions, we have implemented procedures for handling noisy and incomplete diffraction data, and we propose a method for determining the reconstructed resolution. This work represents a previously uncharacterized application of x-ray diffraction microscopy to a specimen of this complexity and provides confidence in the feasibility of the ultimate goal of imaging biological specimens at 10-nm resolution in three dimensions. coherent x-ray diffraction imaging ͉ x-ray microscopy X -ray diffraction microscopy is a recently developed method in which only the coherent diffraction pattern of the sample is measured. It provides a path to high resolution without the limitations imposed by an x-ray optical system. The idea to image a noncrystalline object by phasing and inverting its diffraction pattern goes back to a suggestion by Sayre (1, 2) and was first demonstrated with x-rays by Miao et al. (3). In this article, we report the imaging of the complex-valued exit wavefront (both phase and magnitude) of a whole freeze-dried and unstained yeast cell. The images, at 30-nm resolution from multiple angular orientations of the cell, required an exposure of approximately one minute each using 750-eV x-rays (1 eV ϭ 1.602 ϫ 10 Ϫ19 J). This demonstration paves the way for the application of 3D x-ray diffraction microscopy (XDM) (4, 5) to frozen-hydrated samples in the future.High-resolution 3D images of biological samples are currently made by at least three methods: zone-plate x-ray microscopy (6-9), transmission electron microscopy (10, 11), and x-ray crystallography. All three have particular strengths and limitations. Both water-window (7-9) and multi-keV (12) zone-plate microscopes are currently limited to Ϸ60-nm 3D resolution by details of zone-plate resolution, depth of field, and operation. On the other hand, high-resolution transmission electron microscopes, although capable of extraordinary resolution, are limited by multiple electron scattering to specimens thinner than 0.5-1 m (10, 13). The third method, x-ray crystallography, traditionally yields the highest resolution structures and is the structural technique of choice, but it is limited to specimens that can be crystallized. In summary, the traditional structural techniques do not provide a capability for 3D imaging of an intact eukaryotic cell with resolution around 10 nm, and it is toward this end that our present efforts are directed.Since its introduction, XDM has been demonstrated with metal test objects in two dimensions (3, 14) and three dimensions (4) and with stained biological specimens (15) an...

We simultaneously determined the physical structure and optical transition energies of individual single-walled carbon nanotubes by combining electron diffraction with Rayleigh scattering spectroscopy. These results test fundamental features of the excited electronic states of carbon nanotubes. We directly verified the systematic changes in transition energies of semiconducting nanotubes as a function of their chirality and observed predicted energy splittings of optical transitions in metallic nanotubes.

This study details a new derivative of the contorted HBCs that self-organizes into one-dimensional, single-crystalline fibers. X-ray diffraction, transmission electron microscopy, and electron diffraction studies show that they have an orthorhombic unit cell with dimensions of 5.8 nm x 4.5 nm x 0.45 nm. Each fiber is composed of a few thousands columns. A method is put forth that utilizes elastomer stamps to manipulate and position isolated fibers in organic field effect transistors.

Radiation damage sets a fundamental limit for studies with ionizing radiation; cryo-methods are known to ease these limits. Here, measurements on mass loss and the decrease in the C=O bond density as measured by oxygen-edge XANES (NEXAFS) spectroscopy in thin films of poly(methylmethacrylate) (PMMA), studied in a vacuum, are reported. While cryo-methods allow more than 95% of the mass to remain at doses up to 10(7) Gy, there is little difference in C=O bond density versus dose between 298 K and 113 K sample temperatures. At both temperatures the critical dose for bond breaking is approximately 15 x 10(6) Gy.

We report the growth of ultralong (>10 cm) multi-walled and single-walled carbon nanotubes such that the length is limited by the size of the furnace rather than by the termination of growth. The disturbance of microscale laminar flows results in disordered or shorter growth of carbon nanotubes. By downsizing reaction pipes, reaction gas flows are stabilized with low Reynolds numbers. In this way, the catalyst nanoparticles at the end of growing carbon nanotubes can travel a longer distance to grow ultralong nanotubes.

Polarons, the combined motion of electrons in a cloth of their lattice distortions, are a key transport feature in doped manganites. To develop a profound understanding of the colossal resistance effects induced by external fields, the study of polaron correlations and the resulting collective polaron behavior, i.e., polaron ordering and transition from polaronic transport to metallic transport is essential. We show that static long-range ordering of Jahn-Teller polarons forms a polaron solid which represents a new type of charge and orbital ordered state. The related noncentrosymmetric lattice distortions establish a connection between colossal resistance effects and multiferroic properties, i.e., the coexistence of ferroelectric and antiferromagnetic ordering. Colossal resistance effects due to an electrically induced polaron solid-liquid transition are directly observed in a transmission electron microscope with local electric stimulus applied in situ using a piezo-controlled tip. Our results shed light onto the colossal resistance effects in magnetic field and have a strong impact on the development of correlated electron-device applications such as resistive random access memory (RRAM).correlated electrons ͉ magnetism ͉ oxide M aterials with a coexistence of a variety of electronic and lattice interactions of similar strength are able to create fundamentally differing electronic ground states (1). In doped manganites (Re 1Ϫx A x MnO 3 ; Re and A are rare-and alkaline-earth cations), this includes ferromagnetic metallic, paramagnetic insulating and antiferromagnetic charge and orbital ordered states, representing different collective behavior of the microscopic lattice, charge, orbital, and spin degrees of freedom (2). External fields influence the subtle balance of the interactions and the induced phase transitions between different ground states are related to colossal resistance effects in magnetic (3, 4), electric (5), photon (6), and strain fields (7). They offer great opportunities for new correlated electron devices (8), e.g., in magnetoelectronics and nonvolatile electronic data storage.Among various interactions, two different basic types of electron-lattice coupling (9) play a distinct role in manganites: One is the effect of the static crystal structure on electron transport and bonding. Different ion radii of the involved Re and A cations generate different internal stress on the MnOOOMn bonds. The different resulting types of lattice distortions involve transitions from the ideal cubic to hexagonal, rhombohedral, and orthorhombic structures (10, 11), which may induce polar distortions or even multiferroic ordering, i.e., the presence of electric and magnetic order of electrons in a single phase (12). In doped systems, the decrease of the MnOOOMn bonding angle below 180°due to rigid rotations of the MnO 6 octahedra (for example, see Fig. 2a) results in a strong reduction of the bandwidth of the e g conduction electrons, the conductivity, and the related ferromagnetic double exchange (13).In addit...