Observation of quantum Hall "valley Skyrmions"

We report measurements of the interaction-induced quantum Hall effect in a spin-polarized AlAs two-dimensional electron system where the electrons occupy two in-plane conduction band valleys. Via the application of in-plane strain, we tune the energies of these valleys and measure the energy gap of the quantum Hall state at filling factor nu = 1. The gap has a finite value even at zero strain and, with strain, rises much faster than expected from a single-particle picture, suggesting that the lowest energy charged excitations at nu = 1 are "valley Skyrmions."     

Optical microrheology using rotating laser-trapped particles

We demonstrate an optical system that can apply and accurately measure the torque exerted by the trapping beam on a rotating birefringent probe particle. This allows the viscosity and surface effects within liquid media to be measured quantitatively on a micron-size scale using a trapped rotating spherical probe particle. We use the system to measure the viscosity inside a prototype cellular structure.     

High temperature synthesis of a noncentrosymmetric site-ordered cobalt aluminophosphate related to the pollucite structure

A straightforward synthesis of a transition metal-loaded derivative of the pollucite structure is presented, with non-centric cation ordering over the tetrahedral sites.     

High-throughput manual parallel synthesis using SynPhase crowns and lanterns

The high-throughput manual solid-phase parallel synthesis of libraries comprising thousands of discrete samples using pellicular supports (i.e. SynPhase crowns and lanterns) and a suite of novel tools and techniques is described. Key aspects of this approach include the combination of a split-split-split synthesis strategy with spatial encoding to differentiate thousands of crowns, the rapid washing and filtration of up to 48 reaction vessels in parallel, the application of an inexpensive and environmentally friendly technique to remove trifluoroacetic acid from sixteen 96-well plates in parallel, and a high-throughput method for removing cleaved crowns from reusable pin racks. Tens of thousands of discrete samples have been produced in-house using this conceptually and operationally straightforward strategy.     

Localized structures in nonlinear lattices with diffusive coupling and external driving

We study the stabilization of localized structures by discreteness in one-dimensional lattices of diffusively coupled nonlinear sites. We find that in an external driving field these structures may lose their stability by either relaxing to a homogeneous state or nucleating a pair of oppositely moving fronts. The corresponding bifurcation diagram demonstrates a cusp singularity. The obtained analytic results are in good quantitative agreement with numerical simulations.     

Nanoscale Science and Technology at Los Alamos National Laboratory

Research in the emerging field of nanoscale science and technology has grown steadily at Los Alamos National Laboratory since 1990. This article summarizes some of this work, examining research highlights within the seven key categories of nanoscience in which Los Alamos has ongoing projects, capabilities, and facilities: (1) Materials and chemistry, (2) Theory and modeling, (3) Bioscience, (4) Investigative tools and facilities, (5) Sensors and devices, (6) Synthesis and fabrication, and (7) Education and outreach. Future research horizons are indicated throughout while institutional strategies for advancing nanoscale science are summarized at the end.     

Die Wasserstoffentwicklung beim Arsennachweis im Marsh'schen Apparat

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