The Effect of Solutes on the Temperature of Miscibility Transitions in Multi-component Membranes

We address questions posed by experiments which show that most small-chain alcohols reduce the miscibility transition temperature when added to giant plasma membrane vesicles, but increase that temperature when added to giant unilamellar vesicles. In both systems the change in temperature depends non-monotonically on the length of the alcohol chain. To emphasize the roles played by the internal entropies of the components, we model them as linear polymers. We show that, within Flory-Huggins theory, the addition of alcohol causes an increase or decrease of the transition temperature depending upon the competition of two effects. One is the dilution of the solvent interactions caused by the introduction of solute, which tends to lower the temperature. The other is the preference of the solute for one phase or the other, which tends to raise the temperature. The magnitude of this term depends on the entropies of all components. Lastly we provide a reasonable explanation for the behavior of the transition temperature with alcohol chain length observed in experiment

Positive and negative feedback by AGN jets in high-redshift galaxies

Simulations of feedback by jets from active galactic nuclei (AGN) in the past mostly focused on the interaction at large scales as the circumgalactic medium or intra-cluster medium for clusters of galaxies. Only in recent years, simulations have included the interaction of jets with a highly inhomogeneous medium as required by a multi-phase interstellar medium (ISM). At the same time, feedback by AGN has become a common component for cosmological simulations of galaxy evolution to form massive galaxies compatible with observations. I will present some of our recent results and will put them into further context of other feedback simulations and how the opposing effects of positive and negative feedback by jets might be understood in terms of different properties of the ISM.Comment: 6 pages, 1 figure, published in final form in Reviews in Modern Astronomy, Vol. 26, AN 335, 531. Based on invited talk at annual meeting 2013 of the Astronomische Gesellschaf

Coarse topology, enlargeability, and essentialness

Using methods from coarse topology we show that fundamental classes of closed enlargeable manifolds map non-trivially both to the rational homology of their fundamental groups and to the K-theory of the corresponding reduced C*-algebras. Our proofs do not depend on the Baum--Connes conjecture and provide independent confirmation for specific predictions derived from this conjecture.Comment: 21 pages, 2 figures. Revised version. To appear in Ann. Sci. Ecole Norm. Su

Thermoelastic study of nanolayered structures using time-resolved x-ray diffraction at high repetition rate

We investigate the thermoelastic response of a nanolayered sample composed of a metallic SrRuO3 (SRO) electrode sandwiched between a ferroelectric Pb(Zr0.2Ti0.8)O3 (PZT) film with negative thermal expansion and a SrTiO3 substrate. SRO is rapidly heated by fs-laser pulses with 208 kHz repetition rate. Diffraction of x-ray pulses derived from a synchrotron measures the transient out-of-plane lattice constant c of all three materials simultaneously from 120 ps to 5 mus with a relative accuracy up to Delta c/c = 10^-6. The in-plane propagation of sound is essential for understanding the delayed out of plane expansion.Comment: 5 pages, 3 figure

Wetting on a spherical wall: influence of liquid-gas interfacial properties

We study the equilibrium of a liquid film on an attractive spherical substrate for an intermolecular interaction model exhibiting both fluid-fluid and fluid-wall long-range forces. We first reexamine the wetting properties of the model in the zero-curvature limit, i.e., for a planar wall, using an effective interfacial Hamiltonian approach in the framework of the well known sharp-kink approximation (SKA). We obtain very good agreement with a mean-field density functional theory (DFT), fully justifying the use of SKA in this limit. We then turn our attention to substrates of finite curvature and appropriately modify the so-called soft-interface approximation (SIA) originally formulated by Napi\'orkowski and Dietrich [Phys. Rev. B 34, 6469 (1986)] for critical wetting on a planar wall. A detailed asymptotic analysis of SIA confirms the SKA functional form for the film growth. However, it turns out that the agreement between SKA and our DFT is only qualitative. We then show that the quantitative discrepancy between the two is due to the overestimation of the liquid-gas surface tension within SKA. On the other hand, by relaxing the assumption of a sharp interface, with, e.g., a simple smoothing of the density profile there, markedly improves the predictive capability of the theory, making it quantitative and showing that the liquid-gas surface tension plays a crucial role when describing wetting on a curved substrate. In addition, we show that in contrast to SKA, SIA predicts the expected mean-field critical exponent of the liquid-gas surface tension

Language and Reading Progress of Young Deaf and Hard-of-Hearing Children.

We examined the language and reading progress of 336 young DHH children in kindergarten, first and second grades. Trained assessors tested children's language, reading, and spoken and fingerspelled phonological awareness in the fall and spring of the school year. Children were divided into groups based on their auditory access and classroom communication: a spoken-only group (n = 101), a sign-only group (n = 131), and a bimodal group (n = 104). Overall, children showed delays in language and reading compared to norms established for hearing children. For language, vocabulary standard scores were higher than for English syntax. Although delayed in language, children made expected gains based on hearing norms from kindergarten to second grade. Reading scores declined from kindergarten to second grade. Spoken-only and bimodal children had similar word reading and reading comprehension abilities and higher scores than sign-only children. Spoken-only children had better spoken phonological awareness and nonword reading skills than the other two groups. The sign-only and bimodal groups made similar and significant gains in ASL syntax and fingerspelling phonological awareness

Quantum interface unbinding transitions

We consider interfacial phenomena accompanying bulk quantum phase transitions in presence of surface fields. On general grounds we argue that the surface contribution to the system free energy involves a line of singularities characteristic of an interfacial phase transition, occurring below the bulk transition temperature T_c down to T=0. This implies the occurrence of an interfacial quantum critical regime extending into finite temperatures and located within the portion of the phase diagram where the bulk is ordered. Even in situations, where the bulk order sets in discontinuously at T=0, the system's behavior at the boundary may be controlled by a divergent length scale if the tricritical temperature is sufficiently low. Relying on an effective interfacial model we compute the surface phase diagram in bulk spatial dimensionality $d\geq 2$ and extract the values of the exponents describing the interfacial singularities in $d\geq 3$

Heterogeneous nucleation near a metastable vapour-liquid transition: the effect of wetting transitions

Phase transformations such as freezing typically start with heterogeneous nucleation. Heterogeneous nucleation near a wetting transition, of a crystalline phase is studied. The wetting transition occurs at or near a vapour-liquid transition which occurs in a metastable fluid. The fluid is metastable with respect to crystallisation, and it is the crystallisation of this fluid phase that we are interested in. At a wetting transition a thick layer of a liquid phase forms at a surface in contact with the vapour phase. The crystalline nucleus is then immersed in this liquid layer, which reduces the free energy barrier to nucleation and so dramatically increases the nucleation rate. The variation in the rate of heterogeneous nucleation close to wetting transitions is calculated for systems in which the longest-range forces are dispersion forces.Comment: 11 pages including 3 figure

An experiment of the impact of a neonicotinoid pesticide on honeybees : the value of a formal analysis of the data

This work received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (Grant reference HR09011) and contributing institutions.Background: We assess the analysis of the data resulting from a field experiment conducted by Pilling et al. (2013) on the potential effects of thiamethoxam on honey bees. The experiment had low levels of replication, so Pilling et al. concluded that formal statistical analysis would be misleading. This would be true if such an analysis merely comprised tests of statistical significance and if the investigators concluded that lack of significance meant little or no effect. However, an analysis that includes estimation of the size of any effects—with confidence limits—allows one to reach conclusions that are not misleading and that produce useful insights. Main Body: For the data of Pilling et al. we use straightforward statistical analysis to show that the confidence limits are generally so wide that any effects of thiamethoxam could have been large without being statistically significant. Instead of formal analysis, Pilling et al. simply inspected the data and concluded that they provided no evidence of detrimental effects and from this that thiamethoxam poses a “low risk” to bees. Conclusions: Conclusions derived from inspection of the data were not just misleading in this case but are unacceptable in principle, for if data are inadequate for a formal analysis (or only good enough to provide estimates with wide confidence intervals) then they are bound to be inadequate as a basis for reaching any sound conclusions. Given that the data in this case are largely uninformative with respect to the treatment effect, any conclusions reached from such informal approaches can do little more than reflect the prior beliefs of those involved.Publisher PDFPeer reviewe