531 research outputs found
Molecular modeling of intermolecular and intramolecular excluded volume interactions for polymers at interfaces
A hybrid modeling approach is proposed for inhomogeneous polymer solutions. The method is illustrated for the depletion problem with polymer chains up to N=103 segments in semidilute solutions and good solvent conditions. In a three-dimensional volume, a set of freely jointed chains is considered for which the translational degrees of freedom are sampled using a coarse grained Monte Carlo simulation and the conformational degrees of freedom of the chains are computed using a modified self-consistent field theory. As a result, both intramolecular and intermolecular excluded volume effects are accounted for, not only for chains near the surface, but in the bulk as well. Results are consistent with computer simulations and scaling considerations. More specifically, the depletion thickness, which is a measure for the bulk correlation length, scales as d~J-0.75 and converges to the mean field result in the concentrated regim
Sign switch of Gaussian bending modulus for microemulsions; a self-consistent field analysis exploring scale invariant curvature energies
Bending rigidities of tensionless balanced liquid-liquid interfaces as
occurring in microemulsions are predicted using self-consistent field theory
for molecularly inhomogeneous systems. Considering geometries with scale
invariant curvature energies gives unambiguous bending rigidities for systems
with fixed chemical potentials: The minimal surface Im3m cubic phase is used to
find the Gaussian bending rigidity, , and a torus with Willmore
energy allows for direct evaluation of the mean bending modulus,
. Consistent with this, the spherical droplet gives access to . We observe that tends to be negative for strong
segregation and positive for weak segregation; a finding which is instrumental
for understanding phase transitions from a lamellar to a sponge-like
microemulsion. Invariably, remains positive and increases with
increasing strength of segregation.Comment: 7 pages, 5 figure
Influence of trace metal and organic pollution on the community structure of intertidal gastropods at the coast of Cameroon
Influence of trace metals pollution on the community structure of soft bottom macrofauna in intertidal areas of the Dar es Salaam coast, Tanzania
Band inversion driven by electronic correlations at the (111) LaAlO/SrTiO interface
Quantum confinement at complex oxide interfaces establishes an intricate
hierarchy of the strongly correlated -orbitals which is widely recognized as
a source of emergent physics. The most prominent example is the (001)
LaAlO/SrTiO(LAO/STO) interface, which features a dome-shaped phase
diagram of superconducting critical temperature and spin-orbit coupling (SOC)
as a function of electrostatic doping, arising from a selective occupancy of
orbitals of different character. Here we study (111)-oriented LAO/STO
interfaces - where the three orbitals contribute equally to the
sub-band states caused by confinement - and investigate the impact of this
unique feature on electronic transport. We show that transport occurs through
two sets of electron-like sub-bands, and the carrier density of one of the sets
shows a non-monotonic dependence on the sample conductance. Using tight-binding
modeling, we demonstrate that this behavior stems from a band inversion driven
by on-site Coulomb interactions. The balanced contribution of all
orbitals to electronic transport is shown to result in strong SOC with reduced
electrostatic modulation.Comment: 5 pages, 4 figures, (+ supplemental material
Self-consistent field predictions for quenched spherical biocompatible triblock copolymer micelles
We have used the Scheutjens-Fleer self-consistent field (SF-SCF) method to
predict the self-assembly of triblock copolymers with a solvophilic middle
block and sufficiently long solvophobic outer blocks. We model copolymers
consisting of polyethylene oxide (PEO) as solvophilic block and
poly(lactic-co-glycolic) acid (PLGA) or poly({\ko}-caprolactone) (PCL) as
solvophobic block. These copolymers form structurally quenched spherical
micelles provided the solvophilic block is long enough. Predictions are
calibrated on experimental data for micelles composed of PCL-PEO-PCL and
PLGA-PEO-PLGA triblock copolymers prepared via the nanoprecipitation method. We
establish effective interaction parameters that enable us to predict various
micelle properties such as the hydrodynamic size, the aggregation number and
the loading capacity of the micelles for hydrophobic species that are
consistent with experimental finding.Comment: accepted for publication in Soft Matte
Two Dimensional Ising Superconductivity in Gated MoS
The Zeeman effect, which is usually considered to be detrimental to
superconductivity, can surprisingly protect the superconducting states created
by gating a layered transition metal dichalcogenide. This effective Zeeman
field, which is originated from intrinsic spin orbit coupling induced by
breaking in-plane inversion symmetry, can reach nearly a hundred Tesla in
magnitude. It strongly pins the spin orientation of the electrons to the
out-of-plane directions and protects the superconductivity from being destroyed
by an in-plane external magnetic field. In magnetotransport experiments of
ionic-gate MoS transistors, where gating prepares individual
superconducting state with different carrier doping, we indeed observe a spin-
protected superconductivity by measuring an in-plane critical field
far beyond the Pauli paramagnetic limit. The
gating-enhanced is more than an order of magnitude larger
compared to the bulk superconducting phases where the effective Zeeman field is
weakened by interlayer coupling. Our study gives the first experimental
evidence of an Ising superconductor, in which spins of the pairing electrons
are strongly pinned by an effective Zeeman field
Determination of atmospheric mercury during the North Sea experiment
Total gaseous mercury (TGM) and rainwater were collected on board of two research vessels (F. S. ALKOR and R.V. BELGICA) positioned 200 km apart in the center of the North Sea during the North Sea Experiment, September 1991. On the F. S. ALKOR (up-wind ship) TGM concentrations ranged from 0.7 to 2.6 ng.m(-3) with an average of 1.5 ng.m(-3) and on the R. V. BELGICA (down-wind ship) TGM ranged from 0.7 to 1.9 ng.m(-3) with an average of 1.2 ng.m(-3). An average 20% decrease is observed from the up-wind to the downwind ship. which may largely be affected by entrainment into the free troposphere. An overall removal (entrainment) velocity of 0.95 cm.s(-1) was calculated for the whole experiment. The average removal velocity was 0.5 cm.s(-1) for dry periods and varied between 1 to 5 cm.s(-1) during rain events. Rainwater concentrations varied between 5 and 25 ng.l(-1). Based on these data an annual wet deposition flux of 1.08 ng Hg cm(-2) yr(1-) was estimated for the North Sea
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