1,201 research outputs found
Probing the Sensitivity of Electron Wave Interference to Disorder-Induced Scattering in Solid-State Devices
The study of electron motion in semiconductor billiards has elucidated our
understanding of quantum interference and quantum chaos. The central assumption
is that ionized donors generate only minor perturbations to the electron
trajectories, which are determined by scattering from billiard walls. We use
magnetoconductance fluctuations as a probe of the quantum interference and show
that these fluctuations change radically when the scattering landscape is
modified by thermally-induced charge displacement between donor sites. Our
results challenge the accepted understanding of quantum interference effects in
nanostructures.Comment: 8 pages, 5 figures, Submitted to Physical Review
Bostonia: The Boston University Alumni Magazine. Volume 9
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
Communications Biophysics
Contains reports on six research projects.National Institutes of Health (Grant 2 P01 GM-14940-01)Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E)National Aeronautics and Space Administration (Grant NsG-496)National Institutes of Health (Grant 2 ROl NB-05462-03
Late Holocene variability in Florida Current surface density : patterns and possible causes
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA4001, doi:10.1029/2004PA001008.Planktonic foraminiferal δ18O time series from three well-dated, high sedimentation rate cores near the Florida Keys (24.4°N, 83.3°W) exhibit repeated centennial to millennial-scale oscillations during the late Holocene. Isotopic shifts of 0.2–0.3‰ over the past 5200 years represent changes in sea-surface temperature (SST) of 1.0–1.5°C or salinity variability of 1–2 psu. The largest significant isotopic events are centered at approximately 200, 2000, 3200, and prior to 4000 calendar years BP. High Florida Current δ18O during the Little Ice Age (LIA) correlates with published records of high δ18O in the Sargasso Sea and low SST off the coast of west Africa. An interval of generally low δ18O in the Florida Straits from 1800 to 500 years BP is synchronous with the Medieval Warm Period off west Africa but leads low δ18O in the Sargasso Sea by several hundred years. Synchronous cooling across the subtropical gyre during the LIA is difficult to explain using interannual North Atlantic Oscillation patterns but may be consistent with the simulated effects of reduced solar irradiance. At frequencies between 1/1000 and 1/300 years during the Late Holocene, Florida Current δ18O is coherent with a published estimate of 14C production rate. Radiocarbon production seems to lead δ18O at these frequencies, but uncertainty in the phase calculation precludes a clear lead-lag relationship. At frequencies lower than 1/300 years, Florida Current δ18O is coherent and in phase with atmospheric Δ14C. The coherence of Δ14C and δ18O at periods >1000 years implies oceanic circulation may play a role in modulating atmospheric radiocarbon on millennial timescales.This work was supported by NSF grants
OCE-9905605 and OCE-0096469
IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP
Author Posting. © Arizona Board of Regents on behalf of the University of Arizona, 2004. This article is posted here by permission of Dept. of Geosciences, University of Arizona for personal use, not for redistribution. The definitive version was published in Radiocarbon 46 (2004): 1029-1058.A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed
and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950).
The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond
11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0–12.4 cal kyr BP.
Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric
equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4–26.0 cal kyr BP. A
substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk
model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration
curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here.
The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief,
but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr
BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue)
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