Demonstration of a novel focusing small-angle neutron scattering instrument equipped with axisymmetric mirrors.

Small-angle neutron scattering (SANS) is the most significant neutron technique in terms of impact on science and engineering. However, the basic design of SANS facilities has not changed since the technique's inception about 40 years ago, as all SANS instruments, save a few, are still designed as pinhole cameras. Here we demonstrate a novel concept for a SANS instrument based on axisymmetric focusing mirrors.

Intense superradiant x rays from a compact source using a nanocathode array and emittance exchange.

A novel method of producing intense short wavelength radiation from relativistic electrons is described. The electrons are periodically bunched at the wavelength of interest enabling in-phase superradiant emission that is far more intense than from unbunched electrons. The periodic bunching is achieved in steps beginning with an array of beamlets emitted from a nanoengineered field emission array.

Structure of cholesterol helical ribbons and self-assembling biological springs.

We report the results of x-ray-scattering studies of individual helical ribbons formed in multicomponent solutions of cholesterol solubilized by various surfactants. The solutions were chemically defined lipid concentrate (CDLC) and model bile. In these and many analogous multicomponent surfactant-cholesterol solutions, helical ribbons of two well defined pitch angles, namely 11 degrees and 54 degrees, are formed.

The advanced photon source: performance and results from early operation.

The Advanced Photon Source at Argonne National Laboratory is now providing researchers with high-brilliance undulator radiation from below 1 keV to beyond 100 keV. All technical facilities and components are operational and have met design specifications. Fourteen research teams, with responsibility for 40 beamlines on the APS experiment hall floor, are currently installing beamline instrumentation or actively taking data.

Melting of two-dimensional solids.

Recent theoretical predictions indicate that melting of a two-dimensional solid may be caused by spontaneous creation of dislocations. The theory predicts that melting occurs by a two-step process involving an intermediate phase, called the hexatic phase, in which there is order in the local crystalline axes but not in the positions of atoms. These ideas are being tested by numerical simulations and by experiments on electrons on liquid helium, liquid crystal films, and rare gas layers adsorbed on graphite.

Direct observation of the hydrocarbon chain tilt angle in phospholipid bilayers.

By means of X-ray diffraction we have observed the tilting of hydrocarbon chains within a dipalmitoyl phosphatidylcholine multilayer. The tilting produces a distribution of intensity in the (4.2 A)-1 region that provides a quantitative measure of the angle of tilt.