220 research outputs found
Lattice Boltzmann simulations of segregating binary fluid mixtures in shear flow
We apply lattice Boltzmann method to study the phase separation of a
two-dimensional binary fluid mixture in shear flow. The algorithm can simulate
systems described by the Navier-Stokes and convection-diffusion equations. We
propose a new scheme for imposing the shear flow which has the advantage of
preserving mass and momentum conservation on the boundary walls without
introducing slip velocities. Our main results concern the presence of two
typical lenght scales in the phase separation process, corresponding to domains
with two different thicknesses. Our simulations at low viscosity confirm
previous results only valid in the limit of infinite viscosity.Comment: 32 pages, 7 figure
Three-dimensional lattice-Boltzmann simulations of critical spinodal decomposition in binary immiscible fluids
We use a modified Shan-Chen, noiseless lattice-BGK model for binary
immiscible, incompressible, athermal fluids in three dimensions to simulate the
coarsening of domains following a deep quench below the spinodal point from a
symmetric and homogeneous mixture into a two-phase configuration. We find the
average domain size growing with time as , where increases
in the range , consistent with a crossover between
diffusive and hydrodynamic viscous, , behaviour. We find
good collapse onto a single scaling function, yet the domain growth exponents
differ from others' works' for similar values of the unique characteristic
length and time that can be constructed out of the fluid's parameters. This
rebuts claims of universality for the dynamical scaling hypothesis. At early
times, we also find a crossover from to in the scaled structure
function, which disappears when the dynamical scaling reasonably improves at
later times. This excludes noise as the cause for a behaviour, as
proposed by others. We also observe exponential temporal growth of the
structure function during the initial stages of the dynamics and for
wavenumbers less than a threshold value.Comment: 45 pages, 18 figures. Accepted for publication in Physical Review
Microbial ligand costimulation drives neutrophilic steroid-refractory asthma
Funding: The authors thank the Wellcome Trust (102705) and the Universities of Aberdeen and Cape Town for funding. This research was also supported, in part, by National Institutes of Health GM53522 and GM083016 to DLW. KF and BNL are funded by the Fonds Wetenschappelijk Onderzoek, BNL is the recipient of an European Research Commission consolidator grant and participates in the European Union FP7 programs EUBIOPRED and MedALL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
Locus-specific epigenetic remodeling controls addiction- and depression-related behaviors
Chronic exposure to drugs of abuse or stress regulates transcription factors, chromatin-modifying enzymes and histone post-translational modifications in discrete brain regions. Given the promiscuity of the enzymes involved, it has not yet been possible to obtain direct causal evidence to implicate the regulation of transcription and consequent behavioral plasticity by chromatin remodeling that occurs at a single gene. We investigated the mechanism linking chromatin dynamics to neurobiological phenomena by applying engineered transcription factors to selectively modify chromatin at a specific mouse gene in vivo. We found that histone methylation or acetylation at the Fosb locus in nucleus accumbens, a brain reward region, was sufficient to control drug- and stress-evoked transcriptional and behavioral responses via interactions with the endogenous transcriptional machinery. This approach allowed us to relate the epigenetic landscape at a given gene directly to regulation of its expression and to its subsequent effects on reward behavior
Morphology Development in Amorphous Polymer: Fullerene Photovoltaic Blend Films During Solution Casting
The evolution of film structure is reported during solution casting of PCDTBT:PCBM 1:4 wt%, a polymer:fullerene blend system that finds application in an organic photovoltaic device. Using the complimentary techniques of grazing-incidence wide-angle X-ray scattering and spectroscopic ellipsometry, a number of distinct processes that occur during film formation are identified. This includes the growth of fullerene molecules into nanoscale aggregates, the onset of which coincides with the solubility limit of the material in the casting solvent being reached. An apparent delay in Bragg scatter from the PCDTBT-rich phase of the film suggests that, for the film composition studied here, the aggregation of PCBM precedes weak self-organisation of the conjugated polymer. This behaviour is compared with the drying dynamics of a number of different polymer:fullerene blends that each contain a high weight fraction of fullerene molecules, and a range of comparable solid concentrations are identified beyond which the precipitation of fullerene aggregates from solution occurs. These observations provide an insight into the development of structure in relatively amorphous polymer:fullerene blends for organic photovoltaic applications and potentially assists the future optimisation of this category of materials. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Recommended from our members
Mother-infant interactions and regional brain volumes in infancy: an MRI study
Background: It is generally agreed that the human brain is responsive to environmental influences, and that the male brain may be particularly sensitive to early adversity. However, this is largely based on retrospective studies of older children and adolescents exposed to extreme environments in childhood. Less is understood about how normative variations in parent-child interactions are associated with the development of the infant brain in typical settings.
Method: To address this, we used magnetic resonance imaging to investigate the relationship between observational measures of mother-infant interactions and regional brain volumes in a community sample of 3-6 month old infants (N=39). In addition, we examined whether this relationship differed in male and female infants.
Results: We found that lower maternal sensitivity was correlated with smaller subcortical grey matter volumes in the whole sample, and that this was similar in both sexes. However, male infants who showed greater levels of positive communication and engagement during early interactions had smaller cerebellar volumes.
Conclusion These preliminary findings suggest that variations in mother-infant interaction dimensions are associated with differences in infant brain development. Although the study is cross-sectional and causation cannot be inferred, the findings reveal a dynamic interaction between brain and environment that may be important when considering interventions to optimize infant outcomes
Correlating molecular morphology with optoelectronic function in solar cells based on low band-gap copolymer:fullerene blends
We review recent progress in the development of organic bulk heterojunction (BHJ) solar cells employing
donor–acceptor copolymers as the electron-donor and fullerene derivatives as the electron-acceptor. We
discuss the role of the donor and acceptor moieties, side-chains, bridging units and atomic substitutions
of the copolymers on their optoelectronic functionality. The physical properties, e.g. molecular
conformation, miscibility, phase-separated lateral and vertical morphology, of various photovoltaic
blends prepared via solution casting and post-treatments are reviewed and correlated with photovoltaic
device performance. Factors influencing the morphological stability of polymer:fullerene BHJ thin-films
are briefly discussed. Finally, we address the use of thin organic interlayers to increase the efficiency of
BHJ solar cells
- …