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 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 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...
Measurements of the U₃₇ K’ index and the absolute abundance of alkenones in marine sediments are increasingly used in paleoceanographic research as proxies of past sea surface
temperature and haptophyte (mainly coccolith-bearing species) primary productivity, respectively. An
important aspect of these studies is to be able to compare reliably data...
We determined the spatial pattern of dwarf mistletoe (Arceuthobium
spp.) associated with two different conifer hosts, white fir (Abies
concolor) and Jeffrey pine (Pinus jeffreyi), in forests around the Lake
Tahoe Basin and at the Teakettle Experimental Forest, both located in the
Sierra Nevada. We also examined a number of...
Isolation, detection with diagnostic polymerase chain reaction (PCR), and microscopy demonstrated the presence of Phytophthora ramorum in the sapwood of mature, naturally infected tanoak (Lithocarpus densiflorus) trees. The pathogen was strongly associated with discolored sapwood (P < 0.001), and was recovered or detected from 83% of discolored sapwood tissue samples....
We report measurements of the structural, optical, transport, and magnetic properties of single crystals of the
anisotropic p-type transparent semiconductor CuAlO₂. The indirect and direct band gaps are 2.97 and 3.47 eV,
respectively. Temperature-dependent Hall measurements yield a positive Hall coefficient in the measured range
and an activated carrier temperature...
Double excitonic absorption peaks are observed in textured BaCuSF and BaCuSeF thin films. The excitonic doublet separation increases with increasing fraction of heavy chalcogen in the thin-film solid solutions, in good agreement with the spin-orbit splitting of the valence bands calculated by density-functional theory. In BaCuSF and BaCuSeF, the excitons...