28,400 research outputs found

    Glassy correlations and microstructures in randomly crosslinked homopolymer blends

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    We consider a microscopic model of a polymer blend that is prone to phase separation. Permanent crosslinks are introduced between randomly chosen pairs of monomers, drawn from the Deam-Edwards distribution. Thereby, not only density but also concentration fluctuations of the melt are quenched-in in the gel state, which emerges upon sufficient crosslinking. We derive a Landau expansion in terms of the order parameters for gelation and phase separation, and analyze it on the mean-field level, including Gaussian fluctuations. The mixed gel is characterized by thermal as well as time-persistent (glassy) concentration fluctuations. Whereas the former are independent of the preparation state, the latter reflect the concentration fluctuations at the instant of crosslinking, provided the mesh size is smaller than the correlation length of phase separation. The mixed gel becomes unstable to microphase separation upon lowering the temperature in the gel phase. Whereas the length scale of microphase separation is given by the mesh size, at least close to the transition, the emergent microstructure depends on the composition and compressibility of the melt. Hexagonal structures, as well as lamellae or random structures with a unique wavelength, can be energetically favorable.Comment: 19 pages, 10 figures. Submitted to the Journal of Chemical Physics (http://jcp.aip.org

    Cosmological Implications of a Non-Separable 5D Solution of the Vacuum Einstein Field Equations

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    An exact class of solutions of the 5D vacuum Einstein field equations (EFEs) is obtained. The metric coefficients are found to be non-separable functions of time and the extra coordinate ll and the induced metric on ll = constant hypersurfaces has the form of a Friedmann-Robertson-Walker cosmology. The 5D manifold and 3D and 4D submanifolds are in general curved, which distinguishes this solution from previous ones in the literature. The singularity structure of the manifold is explored: some models in the class do not exhibit a big bang, while other exhibit a big bang and a big crunch. For the models with an initial singularity, the equation of state of the induced matter evolves from radiation like at early epochs to Milne-like at late times and the big bang manifests itself as a singular hypersurface in 5D. The projection of comoving 5D null geodesics onto the 4D submanifold is shown to be compatible with standard 4D comoving trajectories, while the expansion of 5D null congruences is shown to be in line with conventional notions of the Hubble expansion.Comment: 8 pages, in press in J. Math. Phy

    Draft genome sequence of Pseudomonas moraviensis R28-S

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    We report the draft genome sequence of Pseudomonas moraviensis R28-S, isolated from the municipal wastewater treatment plant of Moscow, ID. The strain carries a native mercury resistance plasmid, poorly maintains introduced IncP-1 antibiotic resistance plasmids, and has been useful for studying the evolution of plasmid host range and stability

    Adiabatic-Nonadiabatic Transition in the Diffusive Hamiltonian Dynamics of a Classical Holstein Polaron

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    We study the Hamiltonian dynamics of a free particle injected onto a chain containing a periodic array of harmonic oscillators in thermal equilibrium. The particle interacts locally with each oscillator, with an interaction that is linear in the oscillator coordinate and independent of the particle's position when it is within a finite interaction range. At long times the particle exhibits diffusive motion, with an ensemble averaged mean-squared displacement that is linear in time. The diffusion constant at high temperatures follows a power law D ~ T^{5/2} for all parameter values studied. At low temperatures particle motion changes to a hopping process in which the particle is bound for considerable periods of time to a single oscillator before it is able to escape and explore the rest of the chain. A different power law, D ~ T^{3/4}, emerges in this limit. A thermal distribution of particles exhibits thermally activated diffusion at low temperatures as a result of classically self-trapped polaronic states.Comment: 15 pages, 4 figures Submitted to Physical Review

    On the ordeal of quinolone preparation via cyclisation of aryl-enamines; synthesis and structure of ethyl 6-methyl-7-iodo-4-(3-iodo-4-methylphenoxy)-quinoline-3-carboxylate

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    Recent studies directed to the design of compounds targeting the bc(1) protein complex of Plasmodium falciparum, the parasite responsible for most lethal cases of malaria, identified quinolones (4-oxo-quinolines) with low nanomolar inhibitory activity against both the enzyme and infected erythrocytes. The 4-oxo-quinoline 3-ester chemotype emerged as a possible source of potent bc(1) inhibitors, prompting us to expand the library of available analogs for SAR studies and subsequent lead optimization. We now report the synthesis and structural characterization of unexpected ethyl 6-methyl-7-iodo-4-(3-iodo-4-methylphenoxy)quinoline-3-carboxylate, a 4-aryloxy-quinoline 3-ester formed during attempted preparation of 6-methyl-7-iodo-4-oxo-quinoline-3-carboxylate (4-oxo-quinoline 3-ester). We propose that the 4-aryloxy-quinoline 3-ester derives from 6-methyl-7-iodo-4-hydroxy-quinoline-3-carboxylate (4-hydroxy-quinoline 3-ester), the enol form of 6-methyl-7-iodo-4-oxo-quinoline-3-carboxylate. Formation of the 4-aryloxy-quinoline 3-ester confirms the impact of quinolone/hydroxyquinoline tautomerism, both on the efficiency of synthetic routes to quinolones and on pharmacologic profiles. Tautomers exhibit different cLogP values and interact differently with the enzyme active site. A structural investigation of 6-methyl-7-iodo-4-oxo-quinoline-3-carboxylate and 6-methyl-7-iodo-4-hydroxy-quinoline-3-carboxylate, using matrix isolation coupled to FTIR spectroscopy and theoretical calculations, revealed that the lowest energy conformers of 6-methyl-7-iodo-4-hydroxy-quinoline-3-carboxylate, lower in energy than their most stable 4-oxo-quinoline tautomer by about 27 kJ mol(-1), are solely present in the matrix, while the most stable 4-oxo-quinoline tautomer is solely present in the crystalline phase.Fundacao para a Ciencia e Tecnologia (FCT - Portugal) [UID/Multi/04326/2013]; QREN-COMPETE-UE; CCMAR; FCT [SFRH/BD/81821/2011, RECI/BBB-BQB/0230/2012, UI0313/QUI/2013, UID/FIS/04564/2016]; FEDER/COMPETE-UE; [PTDC/QEQ-QFI/3284/2014 - POCI-01-0145-FEDER-016617]info:eu-repo/semantics/publishedVersio

    Four-dimensional topological Einstein-Maxwell gravity

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    The complete on-shell action of topological Einstein-Maxwell gravity in four-dimensions is presented. It is shown explicitly how this theory for SU(2) holonomy manifolds arises from four-dimensional Euclidean N=2 supergravity. The twisted local BRST symmetries and twisted local Lorentz symmetries are given and the action and stress tensor are shown to be BRST-exact. A set of BRST-invariant topological operators is given. The vector and antisymmetric tensor twisted supersymmetries and their algebra are also found.Comment: Published version. Expanded discussion of new results in the introduction and some clarifying remarks added in later sections. 22 pages, uses phyzz

    Cluster Ellipticities as a Cosmological Probe

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    We investigate the dependence of ellipticities of clusters of galaxies on cosmological parameters using large-scale cosmological simulations. We determine cluster ellipticities out to redshift unity for LCDM models with different mean densities Ωm\Omega_m and amplitudes of mass fluctuation σ8,0\sigma_{8,0}. The mean ellipticity increases monotonically with redshift for all models. Larger values of σ8,0\sigma_{8,0}, i.e., earlier cluster formation time, produce lower ellipticities. The dependence of ellipticity on Ωm\Omega_m is relatively weak in the range 0.2Ωm0.50.2 \leq \Omega_m \leq 0.5 for high mass clusters. The mean ellipticity eˉ(z)\bar{e}(z) decreases linearly with the amplitude of fluctuations at the cluster redshift zz, nearly independent of Ωm\Omega_m; on average, older clusters are more relaxed and are thus less elliptical. The distribution of ellipticities about the mean is approximated by a Gaussian, allowing a simple characterization of the evolution of ellipticity with redshift as a function of cosmological parameters. At z=0z=0, the mean ellipticity of high mass clusters is approximated by eˉ(z=0)=0.2480.069σ8,0+0.013Ωm,0\bar{e}(z=0) = 0.248-0.069 \sigma_{8,0} + 0.013 \Omega_{m,0}. This relation opens up the possibility that, when compared with future observations of large cluster samples, the mean cluster ellipticity and its evolution could be used as a new, independent tool to constrain cosmological parameters, especially the amplitude of mass fluctuations, σ8,0\sigma_{8,0}.Comment: 16 pages, 4 figure

    Legendrian Distributions with Applications to Poincar\'e Series

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    Let XX be a compact Kahler manifold and LXL\to X a quantizing holomorphic Hermitian line bundle. To immersed Lagrangian submanifolds Λ\Lambda of XX satisfying a Bohr-Sommerfeld condition we associate sequences {Λ,k}k=1\{ |\Lambda, k\rangle \}_{k=1}^\infty, where k\forall k Λ,k|\Lambda, k\rangle is a holomorphic section of LkL^{\otimes k}. The terms in each sequence concentrate on Λ\Lambda, and a sequence itself has a symbol which is a half-form, σ\sigma, on Λ\Lambda. We prove estimates, as kk\to\infty, of the norm squares Λ,kΛ,k\langle \Lambda, k|\Lambda, k\rangle in terms of Λσσ\int_\Lambda \sigma\overline{\sigma}. More generally, we show that if Λ1\Lambda_1 and Λ2\Lambda_2 are two Bohr-Sommerfeld Lagrangian submanifolds intersecting cleanly, the inner products Λ1,kΛ2,k\langle\Lambda_1, k|\Lambda_2, k\rangle have an asymptotic expansion as kk\to\infty, the leading coefficient being an integral over the intersection Λ1Λ2\Lambda_1\cap\Lambda_2. Our construction is a quantization scheme of Bohr-Sommerfeld Lagrangian submanifolds of XX. We prove that the Poincar\'e series on hyperbolic surfaces are a particular case, and therefore obtain estimates of their norms and inner products.Comment: 41 pages, LaTe
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