We have investigated a second-order phase transition of the vortex lattice in thin-film Nd₁.₈₅Ce₀.₁₅CuO[subscript 4-y] from 1 mT to 1 T applied magnetic fields. The dc resistivity-current density data for each field exhibit critical scaling consistent with a second-order vortex-liquid to vortex-solid phase transition. The high-field data support the vortex-glass...
We have measured voltage-current characteristics for YBa₂Cu₃O₇ thin films in magnetic fields from 5
T to ambient, including some in the millitesla range. In all cases, the resistivity —current density isotherms
can be separated into two classes: those which exhibit upward curvature, and have constant
resistivity at low currents, and...
We have measured sweep-rate-dependent magnetization hysteresis curves of thin-film Bi₂Sr₂CaCu₂O[subscript 8+δ] using a Hall probe magnetometer in an unconventional geometry. We find a structure in the response well below the three-dimensional to two-dimensional crossover field. The observed strong enhancement of the perpendicular field component’s creep rate in the presence of...
We present a decade-long (1981–1990) high-resolution (subseasonal) record of Pb and Cd concentrations and Pb isotopic composition in a series of 119 snow samples from a 6-m snow pit at Summit, Greenland. Both metals show order of magnitude seasonal variability, with maxima in spring of every year, coinciding with sulfate...
This paper highlights the influence of contact line (pinning) forces on the mobility of dry bubbles in microchannels. Bubbles moving at velocities less than the dewetting velocity of liquid on the surface are essentially dry, meaning that there is no thin liquid film around the bubbles. For these “dry” bubbles,...
Low-temperature combustion (LTC) engine concepts such as homogeneous charge compression ignition (HCCI) offer the potential of improved efficiency and reduced emissions of NOₓ and particulates. However, engines can only successfully operate in HCCI mode for limited operating ranges that vary depending on the fuel composition. Unfortunately, traditional ratings such as...
Because of their unique physiology, lichen communities are highly sensitive to climatic conditions, making them ideal bioindicators for climate change. Southeast and south-central Alaska host diverse and abundant lichen communities and are faced with a more rapidly changing climate than many more southerly latitudes. We develop sensitive lichen-based indicators for...
Rinodina pallidescens is described as a new species, endemic to southern Alaska. Rinodina buckii and R. oregana are discussed in terms of their range extensions and possible phytogeographic histories.
We describe Umbilicaria nodulospora, a distinctive new species occurring on steep rock faces on old lava flows in California and Oregon. The species is unusual among lichenized ascomycetes in consistently having one or two shallowly bulging knobs at one end of each ascospore, suggesting a T, Y, or L shape;...
We investigated habitat attributes related to the occupancy of the globally rare and endangered
epiphytic lichen, Erioderma pedicellatum, in a newly discovered (2009) population center in Denali National
Park and Preserve (DNPP), Alaska. We measured forest, tree and epiphytic lichen community
characteristics on eighty-five systematically selected plots in four study...