1,548 research outputs found
A⁴⁰/K⁴⁰ Ages of Micas and Feldspars from the Glenarm Series near Baltimore, Maryland
The inner zone of the central Appalachian Mountains is a belt of metamorphic and plutonic rocks which crop out in the Blue Ridge province and underlie most of the Piedmont province. In southeastern Pennsylvania and adjacent parts of Maryland, the oldest rock is the Baltimore gneiss, which forms domical uplifts surrounded and overlain by the Glenarm series. This series consists of a basal quartzite (Setters) overlain by a marble (Cockeysville) and a thick series of mica schists (Wissahickon and Peters Creek) of sedimentary origin but including in some places altered volcanics (1). The Glenarm group is locally cut by pegmatite, granite, and other plutonic rocks
Observation of Macroscopic Structural Fluctuations in bcc Solid 4He
We report neutron diffraction studies of low density bcc and hcp solid 4He.
In the bcc phase, we observed a continuous dynamical behaviour involving
macroscopic structural changes of the solid. The dynamical behaviour takes
place in a cell full of solid, and therefore represents a solidsolid
transformation. The structural changes are consistent with a gradual rotation
of macroscopic grains separated by low angle grain boundaries. We suggest that
these changes are triggered by random momentary vibrations of the experimental
system. An analysis of Laue diffraction patterns indicates that in some cases
these structural changes, once initiated by a momentary impulse, seem to
proceed at a constant rate over times approaching an hour. The energy
associated with these macroscopic changes appears to be on the order of kT.
Under similar conditions (temperature and pressure), these effects were absent
in the hcp phase.Comment: 14 pages, 6 figure, accepted for PR
Self-Doping of Gold Chains on Silicon: A New Structural Model for Si(111)5x2-Au
A new structural model for the Si(111)5x2-Au reconstruction is proposed and
analyzed using first-principles calculations. The basic model consists of a
"double honeycomb chain" decorated by Si adatoms. The 5x1 periodicity of the
honeycomb chains is doubled by the presence of a half-occupied row of Si atoms
that partially rebonds the chains. Additional adatoms supply electrons that
dope the parent band structure and stabilize the period doubling; the optimal
doping corresponds to one adatom per four 5x2 cells, in agreement with
experiment. All the main features observed in scanning tunneling microscopy and
photoemission are well reproduced.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Lett. (preprint with high
quality figures available at
http://cst-www.nrl.navy.mil/~erwin/papers/ausi111
Colonic ulcerations may predict steroid-refractory course in patients with ipilimumab-mediated enterocolitis
To investigate management of patients who develop ipilimumab-mediated enterocolitis, including association of endoscopic findings with steroid-refractory symptoms and utility of infliximab as second-line therapy
Connective Tissue Growth Factor Promotes Fibrosis Downstream of TGFΒ and IL-6 in Chronic Cardiac Allograft Rejection
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72574/1/j.1600-6143.2009.02826.x.pd
Perfect imaging: they don't do it with mirrors
Imaging with a spherical mirror in empty space is compared with the case when
the mirror is filled with the medium of Maxwell's fish eye. Exact
time-dependent solutions of Maxwell's equations show that perfect imaging is
not achievable with an electrical ideal mirror on its own, but with Maxwell's
fish eye in the regime when it implements a curved geometry for full
electromagnetic waves
Effective Soft-Core Potentials and Mesoscopic Simulations of Binary Polymer Mixtures
Mesoscopic molecular dynamics simulations are used to determine the large
scale structure of several binary polymer mixtures of various chemical
architecture, concentration, and thermodynamic conditions. By implementing an
analytical formalism, which is based on the solution to the Ornstein-Zernike
equation, each polymer chain is mapped onto the level of a single soft colloid.
From the appropriate closure relation, the effective, soft-core potential
between coarse-grained units is obtained and used as input to our mesoscale
simulations. The potential derived in this manner is analytical and explicitly
parameter dependent, making it general and transferable to numerous systems of
interest. From computer simulations performed under various thermodynamic
conditions the structure of the polymer mixture, through pair correlation
functions, is determined over the entire miscible region of the phase diagram.
In the athermal regime mesoscale simulations exhibit quantitative agreement
with united atom simulations. Furthermore, they also provide information at
larger scales than can be attained by united atom simulations and in the
thermal regime approaching the phase transition.Comment: 19 pages, 11 figures, 3 table
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