14,384 research outputs found
Bending rigidity of stiff polyelectrolyte chains: Single chain and a bundle of multichains
We study the bending rigidity of highly charged stiff polyelectrolytes, for
both a single chain and many chains forming a bundle. A theory is developed to
account for the interplay between competitive binding of counterions and charge
correlations in softening the polyelectrolyte (PE) chains. The presence of even
a small concentration of multivalent counterions leads to a dramatic reduction
in the bending rigidity of the chains that are nominally stiffened by the
repulsion between their backbone charges. The variation of the bending rigidity
as a function of , the fraction of charged monomers on the chain, does
not exhibits simple scaling behavior; it grows with increasing below a
critical value of . Beyond the critical value, however, the chain
becomes softer as increases. The bending rigidity also exhibits
intriguing dependence on the concentration of multivalent counterion ;
for highly charged PEs, the bending rigidity decreases as increases from
zero, while it increases with increasing beyond a certain value of
. When polyelectrolyte chains form a -loop condensate (e.g., a
toroidal bundle formed by turns (winds) of the chain), the inter-loop
coupling further softens the condensate, resulting in the bending free energy
of the condensate that scales as for large .Comment: 11 pages, 2 figure
Applicability valuation for evaluation of surface deflection in automotive outer panels
Upon unloading in a forming process there is elastic recovery, which is the release of the elastic strains and the redistribution of the residual stresses through the thickness direction, thus producing surface deflection. It causes changes in shape and dimensions that can create major problem in the external appearance of outer panels. Thus surface deflection prediction is an important issue in sheet metal forming industry. Many factors could affect surface deflection in the process, such as material variations in mechanical properties, sheet thickness, tool geometry, processing parameters and lubricant condition. The shape and dimension problem in press forming is defined as a trouble mainly caused by the elastic recovery of materials during the forming. The use of high strength steel sheets in the manufacturing of automobile outer panels has increased in the automotive industry over the years because of its lightweight and fuel-efficient improvement. But one of the major concerns of stamping is surface deflection in the formed outer panels. Hence, to be cost effective, accurate prediction must be made of its formability. The automotive industry places rigi
Stretching Homopolymers
Force induced stretching of polymers is important in a variety of contexts.
We have used theory and simulations to describe the response of homopolymers,
with monomers, to force () in good and poor solvents. In good solvents
and for {{sufficiently large}} we show, in accord with scaling predictions,
that the mean extension along the axis for small , and
(the Pincus regime) for intermediate values of . The
theoretical predictions for \la Z\ra as a function of are in excellent
agreement with simulations for N=100 and 1600. However, even with N=1600, the
expected Pincus regime is not observed due to the the breakdown of the
assumptions in the blob picture for finite . {{We predict the Pincus scaling
in a good solvent will be observed for }}. The force-dependent
structure factors for a polymer in a poor solvent show that there are a
hierarchy of structures, depending on the nature of the solvent. For a weakly
hydrophobic polymer, various structures (ideal conformations, self-avoiding
chains, globules, and rods) emerge on distinct length scales as is varied.
A strongly hydrophobic polymer remains globular as long as is less than a
critical value . Above , an abrupt first order transition to a
rod-like structure occurs. Our predictions can be tested using single molecule
experiments.Comment: 24 pages, 7 figure
Neutron and muon-induced background studies for the AMoRE double-beta decay experiment
AMoRE (Advanced Mo-based Rare process Experiment) is an experiment to search
a neutrinoless double-beta decay of Mo in molybdate crystals. The
neutron and muon-induced backgrounds are crucial to obtain the zero-background
level (< counts/(keVkgyr)) for the AMoRE-II experiment,
which is the second phase of the AMoRE project, planned to run at YEMI
underground laboratory. To evaluate the effects of neutron and muon-induced
backgrounds, we performed Geant4 Monte Carlo simulations and studied a
shielding strategy for the AMORE-II experiment. Neutron-induced backgrounds
were also included in the study. In this paper, we estimated the background
level in the presence of possible shielding structures, which meet the
background requirement for the AMoRE-II experiment
Effects of adsorbed phase on diffusion of subcritical hydrocarbons in activated carbon at low pressures
Diffusions of free and adsorbed molecules of subcritical hydrocarbons in activated carbon were investigated to study the influence of adsorbed molecules on both diffusion processes at low pressures. A collision reflection factor, defined as the fraction of molecules undergoing collision to the solid surface over reflection from the surface, is incorporated into Knudsen diffusivity and surface diffusivity in meso/macropores. Since the porous structure of activated carbon is bimodal in nature, the diffusion of adsorbed molecules is contributed by that of weakly adsorbed molecules on the meso/macropore surfaces and that of strongly adsorbed molecules in the small confinement of micropores. The mobility of adsorbed molecules on the meso/macropore surface is characterized by the surface diffusivity D-mu 2, while that in the micropore is characterized by D-mu 1. In our study with subcritical hydrocarbons, we have found that the former increases almost linearly with pressure, while the latter exhibits a sharp increase at a very low-pressure region and then decreases beyond a critical pressure. This critical pressure is identified as a pressure at which the micropores are saturated
Measurement and models accounting for cell death capture hidden variation in compound response.
Cancer cell sensitivity or resistance is almost universally quantified through a direct or surrogate measure of cell number. However, compound responses can occur through many distinct phenotypic outcomes, including changes in cell growth, apoptosis, and non-apoptotic cell death. These outcomes have divergent effects on the tumor microenvironment, immune response, and resistance mechanisms. Here, we show that quantifying cell viability alone is insufficient to distinguish between these compound responses. Using an alternative assay and drug-response analysis amenable to high-throughput measurement, we find that compounds with identical viability outcomes can have very different effects on cell growth and death. Moreover, additive compound pairs with distinct growth/death effects can appear synergistic when only assessed by viability. Overall, these results demonstrate an approach to incorporating measurements of cell death when characterizing a pharmacologic response
Recommended from our members
Atomic and nano-scale characterization of a 50-year-old hydrated C3S paste
This paper investigates the atomic and nano-scale structures of a 50-year-old hydrated alite paste. Imaged by TEM, the outer product C-S-H fibers are composed of particles that are 1.5-2 nm thick and several tens of nanometers long. 29Si NMR shows 47.9% Q1 and 52.1% Q2, with a mean SiO4 tetrahedron chain length (MCL) of 4.18, indicating a limited degree of polymerization after 50 years' hydration. A Scanning Transmission X-ray Microscopy (STXM) study was conducted on this late-age paste and a 1.5 year old hydrated C3S solution. Near Edge X-ray Absorption Fine Structure (NEXAFS) at Ca L3,2-edge indicates that Ca2 + in C-S-H is in an irregular symmetric coordination, which agrees more with the atomic structure of tobermorite than that of jennite. At Si K-edge, multi-scattering phenomenon is sensitive to the degree of polymerization, which has the potential to unveil the structure of the SiO44 - tetrahedron chain
On magnetic leaf-wise intersections
In this article we introduce the notion of a magnetic leaf-wise intersection
point which is a generalization of the leaf-wise intersection point with
magnetic effects. We also prove the existence of magnetic leaf-wise
intersection points under certain topological assumptions.Comment: 43 page
- …