Near-field coupling of gold plasmonic antennas for sub-100 nm magneto-thermal microscopy

The development of spintronic technology with increasingly dense, high-speed, and complex devices will be accelerated by accessible microscopy techniques capable of probing magnetic phenomena on picosecond time scales and at deeply sub-micron length scales. A recently developed time-resolved magneto-thermal microscope provides a path towards this goal if it is augmented with a picosecond, nanoscale heat source. We theoretically study adiabatic nanofocusing and near-field heat induction using conical gold plasmonic antennas to generate sub-100 nm thermal gradients for time-resolved magneto-thermal imaging. Finite element calculations of antenna-sample interactions reveal focused electromagnetic loss profiles that are either peaked directly under the antenna or are annular, depending on the sample's conductivity, the antenna's apex radius, and the tip-sample separation. We find that the thermal gradient is confined to 40 nm to 60 nm full width at half maximum for realistic ranges of sample conductivity and apex radius. To mitigate this variation, which is undesirable for microscopy, we investigate the use of a platinum capping layer on top of the sample as a thermal transduction layer to produce heat uniformly across different sample materials. After determining the optimal capping layer thickness, we simulate the evolution of the thermal gradient in the underlying sample layer, and find that the temporal width is below 10 ps. These results lay a theoretical foundation for nanoscale, time-resolved magneto-thermal imaging.Comment: 24 pages including Supporting Information, 6 figures in the main text, 4 supporting figure

Evaluation of Two Systems Used to Extract Alfalfa Weevil Larvae (Coleoptera: Curculionidae) from Alfalfa Samples

A modified Berlese funnel system was developed to extract alfalfa weevil larvae (Hypera postica) from quadrats 30.5 cm on a side. Data from this system were comp.wed with simultaneous data from a hand sorting extraction system. In most instances, the modified Berlese system was as efficient as the hand sorting method and the number of man hours required to process samples by hand was far greater than that required by the Berlese system

Disease as a Larval Mortality Factor in Alfalfa Weevil, \u3ci\u3eHypera Postica\u3c/i\u3e (Coleoptera: Curculionidae) Populations in Illinois

During the 1974 growing season, larvae of the alfalfa weevil, Hypera postica (Gyllenhal), were examined for pathogens. Three larvae out of 715 examined were infected with a microsporidium. This infection was present in both Washington and Mason counties in Illinois

Low Velocity Granular Drag in Reduced Gravity

We probe the dependence of the low velocity drag force in granular materials on the effective gravitational acceleration (geff) through studies of spherical granular materials saturated within fluids of varying density. We vary geff by a factor of 20, and we find that the granular drag is proportional to geff, i.e., that the granular drag follows the expected relation Fprobe = {\eta} {\rho}grain geff dprobe hprobe^2 for the drag force, Fprobe on a vertical cylinder with depth of insertion, hprobe, diameter dprobe, moving through grains of density {\rho}grain, and where {\eta} is a dimensionless constant. This dimensionless constant shows no systematic variation over four orders of magnitude in effective grain weight, demonstrating that the relation holds over that entire range to within the precision of our data

Electron Densities from Gas‐Phase Electron Diffraction Intensities. II. Molecular Hartree–Fock Cross Sections

Differential cross sections for electron scattering based on molecular Hartree–Fock electron densities are compared with cross sections based on the independent‐atom approximation for the molecules C2, N2, O2, F2, and CO. The results show that bonding effects on the electron density manifest themselves to the extent of several percent in the scattered intensity at small scattering angles. Furthermore, molecule‐to‐molecule variations in the shifts of electron density are clearly reflected in variations in the functional form of the scattered intensity. A comparison of the calculated intensities for N2 and O2 with preliminary experimental intensities suggests that electron scattering techniques now in development should be able to provide information about bonding and electron correlation effects competitive in accuracy with that of current quantum‐mechanical calculations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70136/2/JCPSA6-51-7-2896-1.pd

Electron Densities from Gas‐Phase Electron Diffraction Intensities. I. Preliminary Considerations

The intensity of electrons and x rays scattered by a freely rotating molecule is determined, in the kinematic approximation, solely by the nuclear–nuclear, electron–nuclear, and electron–electron radial distribution functions of the molecule. Although these functions are one‐dimensional, the latter two contain some information about the three‐dimensional distribution of electrons in the molecule because the electrons are distributed relative to several nuclear reference positions and the spatial distribution of the nuclei is known. The purpose of this series of papers is to investigate the extent to which this information can be deciphered. Although published accounts have purported to show that the electron density ρ(r)ρ(r) can be determined uniquely from the scattered intensity, we demonstrate that, in fact, the transfomation is not unique. Nevertheless, if certain, not unreasonable, restrictions are imposed upon the form of ρ(r)ρ(r), it becomes possible to make fairly detailed inferences about the three‐dimensional character of the density. We propose a procedure which, although not guaranteeing a unique transformation, provides a means for deriving chemically significant knowledge about the molecular electron density from experimental gas‐phase intensities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69800/2/JCPSA6-51-7-2891-1.pd

Does blending an RGP lens move or remove plastic?

Blending of RGP lenses is widely used to Increase patient comfort while wearing the lenses. The blending process smooths the peripheral curves of the lens, but it has not been determined if this process moved or actually removed the lens material. Twenty fluoroperm 30 bicurve, unfinished lenses were weighed on a Sartorius analytical balance to the ten-thousandth of a gram. The lenses were then modified with a tool that would simulate the blending process and reweighed. The data was then compared using a paired one-tailed t-Test and the results were shown to have a statistically significant lower lens weight. Thus, we determined that blending actually removes the lens material