Micromagnetic Domain Structures in Cylindrical Nickel Dots

The magnetic domain structures of cylindrical nickel dots (diameters from 40 nm to 1700 nm) with anisotropy parallel to the cylinder axis is predicted by the ratio of the dot diameter to the stripe period of unpatterned films with the same perpendicular anisotropy. The dominant domain structure for a given ratio increases in complexity as the ratio increases. We present evidence for the full micromagnetic domain structure for the simplest cases

Magnetic Response Versus Lift Height of Thin Ferromagnetic Films

The interaction between a magnetic force microscope (MFM) tip and ferromagnetic films of Ni, Co90Fe10 and Py with in-plane magnetization has been investigated. The measured interaction, due to the magnetizing of the films by the MFM tip field, was determined by the phase shift of the cantilever response. The tip-film separation or lift height dependent phase shift was found to be independent of the saturation magnetization of the ferromagnetic film. The result is identical for all three films and micromagnetic simulations give similar results. The reason is at a given tip-sample separation the tip induced magnetization of the film creates a demagnetization field which is equal in magnitude to the tip field at that separation

Interferometric scattering enables fluorescence-free electrokinetic trapping of single nanoparticles in free solution

Anti-Brownian traps confine single particles in free solution by closed-loop feedback forces that directly counteract Brownian motion. The extended-duration measurement of trapped objects allows detailed characterization of photophysical and transport properties, as well as observation of infrequent or rare dynamics. However, this approach has been generally limited to particles that can be tracked by fluorescent emission. Here we present the Interferometric Scattering Anti-Brownian ELectrokinetic trap (ISABEL trap), which uses interferometric scattering rather than fluorescence to monitor particle position. By decoupling the ability to track (and therefore trap) a particle from collection of its spectroscopic data, the ISABEL trap enables confinement and extended study of single particles that do not fluoresce, that only weakly fluoresce, or which exhibit intermittent fluorescence or photobleaching. This new technique significantly expands the range of nanoscale objects that may be investigated at the single-particle level in free solution.Comment: Manuscript and SI; videos available upon reques

Hazmat Storage Near NYC Waterways Endangers Communities

New York City has 520 miles of shoreline--that’s more than Miami and Los Angeles combined. These waterfronts are home to some of the city’s most polluted sites because major part of it is zoned for industrial use. Dozens of industrial plants in this area store toxic chemicals in flood zones: substances that are hazardous to our health, like Benzene, which is used in rocket fuel, toluene, a paint thinner, and lead a neurotoxin. In a flood, these chemicals can easily get caught up in moving waters and pollute entire neighborhoods. That’s exactly what happened when Hurricane Sandy hit in 2012. In an attempt to avoid these types of incidents, Congress passed a law called the Emergency Planning and Community Right to Know Act back in the 1980s. Its authors designed the law to help businesses keep their toxic substances tightly sealed and protected from rising waters, with the help of civilian oversight. The New York City News Service’s Brett Dahlberg and Nicole Acevedo found the city has a funny definition of “right to know” and has been falling short of the promises it made after Sandy to secure those chemicals and minimize industrial pollution near waterways. The link to the project: https://medium.com/@nicole.acevedo/five-years-after-sandy-hazmat-storage-near-nyc-waterways-endangers-communities-dfab72df7ad