7,105 research outputs found
Elasticity, Shape Fluctuations and Phase Transitions in the New Tubule Phase of Anisotropic Tethered Membranes
We study the shape, elasticity and fluctuations of the recently predicted
(cond-mat/9510172) and subsequently observed (in numerical simulations)
(cond-mat/9705059) tubule phase of anisotropic membranes, as well as the phase
transitions into and out of it. This novel phase lies between the previously
predicted flat and crumpled phases, both in temperature and in its physical
properties: it is crumpled in one direction, and extended in the other. Its
shape and elastic properties are characterized by a radius of gyration exponent
and an anisotropy exponent . We derive scaling laws for the radius of
gyration (i.e. the average thickness) of the tubule about a
spontaneously selected straight axis and for the tubule undulations
transverse to its average extension. For phantom (i.e.
non-self-avoiding) membranes, we predict , and
, exactly, in excellent agreement with simulations. For
membranes embedded in the space of dimension , self-avoidance greatly
swells the tubule and suppresses its wild transverse undulations, changing its
shape exponents and . We give detailed scaling results for the shape
of the tubule of an arbitrary aspect ratio and compute a variety of correlation
functions, as well as the anomalous elasticity of the tubules. Finally we
present a scaling theory for the shape of the membrane and its specific heat
near the continuous transitions into and out of the tubule phase and perform
detailed renormalization group calculations for the crumpled-to-tubule
transition for phantom membranes.Comment: 34 PRE pages, RevTex and 11 postscript figures, also available at
http://lulu.colorado.edu/~radzihov/ version to appear in Phys. Rev. E, 57, 1
(1998); minor change
Rotorcraft technology at Boeing Vertol: Recent advances
An overview is presented of key accomplishments in the rotorcraft development at Boeing Vertol. Projects of particular significance: high speed rotor development and the Model 360 Advanced Technology Helicopter. Areas addressed in the overview are: advanced rotors with reduced noise and vibration, 3-D aerodynamic modeling, flight control and avionics, active control, automated diagnostics and prognostics, composite structures, and drive systems
REGIONAL GAINS AND LOSSES FOR CONSUMERS AND PRODUCERS FROM CHANGES IN FLUID MILK PRICES
Agribusiness,
A collection of edge-based elements
Edge-based elements have proved useful in solving electromagnetic problems since they are nondivergent. Previous authors have presented several two and three dimensional elements. Herein, we present four types of elements which are suitable for modeling several types of three dimensional geometries. Distorted brick and triangular prism elements are given in cartesian coordinates as well as the specialized cylindrical shell and pie-shaped prism elements which are suitable for problems best described in polar cylindrical coordinates
"Soft" Anharmonic Vortex Glass in Ferromagnetic Superconductors
Ferromagnetic order in superconductors can induce a {\em spontaneous} vortex
(SV) state. For external field , rotational symmetry guarantees a
vanishing tilt modulus of the SV solid, leading to drastically different
behavior than that of a conventional, external-field-induced vortex solid. We
show that quenched disorder and anharmonic effects lead to elastic moduli that
are wavevector-dependent out to arbitrarily long length scales, and non-Hookean
elasticity. The latter implies that for weak external fields , the magnetic
induction scales {\em universally} like , with
. For weak disorder, we predict the SV solid is a
topologically ordered vortex glass, in the ``columnar elastic glass''
universality class.Comment: minor corrections; version published in PR
On the Complexity of the Single Individual SNP Haplotyping Problem
We present several new results pertaining to haplotyping. These results
concern the combinatorial problem of reconstructing haplotypes from incomplete
and/or imperfectly sequenced haplotype fragments. We consider the complexity of
the problems Minimum Error Correction (MEC) and Longest Haplotype
Reconstruction (LHR) for different restrictions on the input data.
Specifically, we look at the gapless case, where every row of the input
corresponds to a gapless haplotype-fragment, and the 1-gap case, where at most
one gap per fragment is allowed. We prove that MEC is APX-hard in the 1-gap
case and still NP-hard in the gapless case. In addition, we question earlier
claims that MEC is NP-hard even when the input matrix is restricted to being
completely binary. Concerning LHR, we show that this problem is NP-hard and
APX-hard in the 1-gap case (and thus also in the general case), but is
polynomial time solvable in the gapless case.Comment: 26 pages. Related to the WABI2005 paper, "On the Complexity of
Several Haplotyping Problems", but with more/different results. This papers
has just been submitted to the IEEE/ACM Transactions on Computational Biology
and Bioinformatics and we are awaiting a decision on acceptance. It differs
from the mid-August version of this paper because here we prove that 1-gap
LHR is APX-hard. (In the earlier version of the paper we could prove only
that it was NP-hard.
A Paleomagnetic Age Investigation of Pre-Salmon Springs Drift Pleistocene Deposits in the Southern Puget Lowland, Washington
The Pleistocene history of the southern Puget Lowland is marked by repeated invasions by the Puget Lobe of the Cordilleran ice sheet. The present stratigraphic sequence is represented by four glaciations (Orting, Stuck, Salmon Springs, and Fraser) of northern provenance, separated by unconformities and two nonglacial formations (Alderton and Puyallup) of central Cascade and Mount Rainier provenances. Paleomagnetic work conducted on pre-Salmon Springs sediments at their type localities and correlative exposures in the Puyallup Valley provide evidence for the ages of the Orting Drift, Alderton Formation, Stuck Drift, and Puyallup Formation.
The silts sampled demonstrate an array of soft (unconsolidated) sediment magnetic behavior. Overprinting is common and is largely attributed to VRM or CRM, yet the sediments do preserve remanent components identified as DRM or PDRM. These primary components are the result of grain alignment during a period of reversed polarity. The successful isolation of reversed remanent directions in the pre-Salmon Springs units leads to a magnetostratigraphic interpretation which restricts the deposition of these sediments to the Matuyama Reverse Epoch
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