Further progress in the development of the remarkable electrochemical, electron field emission, hightemperature diode, and optical properties of n-type ultrananocrystalline diamond films requires a better understanding of electron transport in this material. Of particular interest is the origin of the transition to the metallic regime observed when about 10% by volume of nitrogen has been added to the synthesis gas. Here, we present data showing that the transition to the metallic state is due to the formation of partially oriented diamond nanowires surrounded by an sp 2-bonded carbon sheath. These have been characterized by scanning electron microscopy, transmission electron microscopy techniques ͑high-resolution mode, selected area electron diffraction, and electron-energy-loss spectroscopy͒, Raman spectroscopy, and small-angle neutron scattering. The nanowires are 80-100 nm in length and consist of ϳ5 nm wide and 6-10 nm long segments of diamond crystallites exhibiting atomically sharp interfaces. Each nanowire is enveloped in a sheath of sp 2-bonded carbon that provides the conductive path for electrons. Raman spectroscopy on the films coupled with a consideration of plasma chemical and physical processes reveals that the sheath is likely composed of a nanocarbon material resembling in some respects a polymer-like mixture of polyacetylene and polynitrile. The complex interactions governing the simultaneous growth of the diamond core and the sp 2 sheath responsible for electrical conductivity are discussed as are attempts at a better theoretical understanding of the transport mechanism.

Boehmite (γ-AlOOH) and gibbsite (α-Al(OH) 3 ) are important archetype (oxy)hydroxides of aluminum in nature that also play diverse roles across a plethora of industrial applications. Developing the ability to understand and predict the properties and characteristics of these materials, on the basis of their natural growth or synthesis pathways, is an important 1 fundamental science enterprise with wide ranging impacts. The present study describes bulk and surface characteristics of these novel materials in comprehensive detail, using a collectively-sophisticated set of experimental capabilities, including a range of conventional laboratory solids analyses and national user facility analyses such as synchrotron X-ray absorption and scattering spectroscopies, as well as small angle neutron scattering. Their thermal stability is investigated using in situ temperature-dependent Raman spectroscopy. These pure and effectively defect-free materials are ideal for synthesis of advanced alumina products.

We investigated the molecular dynamics of unilamellar liposomes by neutron spin echo spectroscopy. We report the first experimental evidence of a short-range motion at the length scale of the size of the headgroup of a lipid. The associated mean squared displacement shows a t dependence in the pico- to nanosecond region that indicates another process beyond the predictions of the Zilman-Granek (ZG) model ( t) and translational diffusion ( t). A comparison with theory shows that the observed low exponent is associated with a non-Gaussian transient trapping of lipid molecules in a local area and supports the continuous time random walk model. The analysis of the mean squared displacement leads to the important conclusion that the friction at the interface between water and liposomes plays a minor role. Center of mass diffusion of liposomes and transient trapping of lipids define the range in which the ZG model can be applied to analyze membrane fluctuations.

Identification, understanding, and manipulation of novel magnetic textures are essential for the discovery of new quantum materials for future spin-based electronic devices. In particular, materials that manifest a large response to external stimuli such as a magnetic field are subject to intense investigation. Here, we study the kagome-net magnet YMn6Sn6 by magnetometry, transport, and neutron diffraction measurements combined with first-principles calculations. We identify a number of nontrivial magnetic phases, explain their microscopic nature, and demonstrate that one of them hosts a large topological Hall effect (THE). We propose a previously unidentified fluctuation-driven mechanism, which leads to the THE at elevated temperatures. This interesting physics comes from parametrically frustrated interplanar exchange interactions that trigger strong magnetic fluctuations. Our results pave a path to chiral spin textures, promising for novel spintronics.