Chemically and physically crosslinked porous gels

Chemically crosslinked gels made by polymerization and copolymerization of trimethylolpropane trimethacrylate have been characterized. Bimodal pore size distributions were obtained. The radii of the large pores (100 Å to 1 μm) varied with concentration while the small ones (20 to 30 Å) were largely independent of the concentration of TRIM. A mechanism of formation of the pores is outlined. Physically crosslinked gels of polyacrylonitrile with highly porous structures were made by cooling polymer solutions in DMF containing varying amounts of water. By controlling the thermal treatment the pore sizes could be varied from 0.1 to 1 μm. Finally the surface modification of cellulose fibers with derivatives of dichlorotriazine is described. It is shown that derivatives containing double bonds in the side chain can form covalent bonds across the interface between cellulose and an unsaturated polyester.     

LLT polynomials,chromatic quasisymmetric functions and graphs with cycles

We use a Dyck path model for unit-interval graphs to study the chromatic quasisymmetric functions introduced by Shareshian and Wachs, as well as unicellular LLT polynomials, revealing some parallel structure and phenomena regarding their $\mathrm{e}$-positivity.The Dyck path model is also extended to circular arc digraphs to obtain larger families of polynomials, giving a new extension of LLT polynomials. Carrying over a lot of the non-circular combinatorics, we prove several statements regarding the $\mathrm{e}$-coefficients of chromatic quasisymmetric functions and LLT polynomials, including a natural combinatorial interpretation for the $\mathrm{e}$-coefficients for the line graph and the cycle graph for both families. We believe that certain $\mathrm{e}$-positivity conjectures hold in all these families above.Furthermore, beyond the chromatic analogy, we study vertical-strip LLT polynomials, which are modified Hall–Littlewood polynomials.     

Efficient computation of the Gauss-Newton direction when fitting NURBS using ODR

We consider a subproblem in parameter estimation using the Gauss-Newton algorithm with regularization for NURBS curve fitting. The NURBS curve is fitted to a set of data points in least-squares sense, where the sum of squared orthogonal distances is minimized. Control-points and weights are estimated. The knot-vector and the degree of the NURBS curve are kept constant. In the Gauss-Newton algorithm, a search direction is obtained from a linear overdetermined system with a Jacobian and a residual vector. Because of the properties of our problem, the Jacobian has a particular sparse structure which is suitable for performing a splitting of variables. We are handling the computational problems and report the obtained accuracy using different methods, and the elapsed real computational time. The splitting of variables is a two times faster method than using plain normal equations.     

Decay of the neutron-rich isotope 113Ru to 113Rh

The decay of neutron-rich isotope ¹¹³Ru obtained as on-line mass separated product of proton-induced fission has been investigated by γγ coincidence and spectrum multiscaling measurements. Decay schemes for both low- and high-spin isomers of ¹¹³Ru have been constructed. The level scheme of ¹¹³Rh is considerably extended. Systematics of the lowest-lying rhodium levels is smooth. The picture of shape coexistence established for neutron-rich Rh isotopes near-neutron midshell is confirmed with the observation of a K = 1/2 deformed band, with its 3/2⁺ state at 600 keV being the lowest-lying level and of probable 7/2⁺ and 5/2⁺ band members. A large fraction of β feeding is found to populate high-lying levels in ¹¹³Rh. The GT strength in ¹¹³Ru^m decay is significantly larger than for the decay of ¹¹³Ru_g and of lighter rhodium isotopes. Received: 18 January 2001 / Accepted: 14 January 2002     

Convergence of generalized conjugate partial Fourier integrals

Generalized conjugate partial Fourier integrals are used to find jumps of functions. The rate of convergence is studied and sharp results are obtained.     

Rotational CARS N2 thermometry: validation experiments for the influence of nitrogen spectral line broadening by hydrogen

Rotational coherent anti‐Stokes Raman spectroscopy (CARS) in fuel‐rich hydrocarbon flames, with a large content of hydrogen in the product gases (∼20%), has in previous work shown that evaluated temperatures are raised several tens of Kelvin by taking newly derived N₂ H₂ Raman line widths into account. To validate these results, in this work calibrated temperature measurements at around 300, 500 and 700 K were performed in a cell with binary gas mixtures of nitrogen and hydrogen. The temperature evaluation was made with respect to Raman line widths either from self‐broadened nitrogen only, N₂ N₂ [energy‐corrected‐sudden (ECS)], or by also taking nitrogen broadened by hydrogen, N₂ H₂ [Robert–Bonamy (RB)], Raman line widths into account. With increased amount of hydrogen in the cell at constant temperature, the evaluated CARS temperatures were clearly lowered with the use of Raman line widths from self‐broadened nitrogen only, and the case with inclusion of N₂ H₂ Raman line widths was more successful. The difference in evaluated temperatures between the two different sets increases approximately linearly, reaching 20 K (at T ∼ 300 K), 43 K (at T = 500 K) and 61 K (at T = 700 K) at the highest hydrogen concentration (90%). The results from this work further emphasize the importance of using adequate Raman line widths for accurate rotational CARS thermometry. Copyright © 2010 John Wiley & Sons, Ltd.     

Reversible addition–fragmentation chain transfer polymerization of alkyl‐2‐cyanoacrylates: An assessment of livingness

Alkyl 2‐cyanoacrylates (CAs) are primarily used as instant adhesives, including those sold under the Loctite brand. The adhesive action can be inhibited with acid stabilizers allowing radical polymerization to be employed. The following article details the first attempted controlled/living radical polymerization of alkyl CAs: Reversible addition fragmentation chain transfer (RAFT) polymerization mediated by a poly(methyl methacrylate) dithiobenzoate macroRAFT agent for three different CA monomers (ethyl 2‐cyanoacrylate, n‐butyl 2‐cyanoacrylate, and 2‐phenylethyl cyanoacrylate) allowed the preparation of the first block copolymers of this challenging but commercially important monomer class. Nevertheless, GPC with UV detection indicated significant loss of the RAFT end‐group for all three CAs limiting control/living character. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1397–1408     

Formation of homogeneous nanocomposite films at ambient temperature via miniemulsion polymerization using graphene oxide as surfactant

A convenient and industrially scalable method for synthesis of homogeneous nanocomposite films comprising poly(styrene‐stat‐butyl acrylate) and nanodimensional graphene oxide (GO) or reduced GO (rGO) is presented. Importantly, the nanocomposite latex undergoes film formation at ambient temperature, thus alleviating any need for high temperature or high pressure methods such as compression molding. The method entails synthesis of an aqueous nanocomposite latex via miniemulsion copolymerization relying on nanodimensional GO sheets as sole surfactant, followed by ambient temperature film formation resulting in homogeneous film. For comparison, a similar latex obtained by physical mixing of a polymer latex with an aqueous GO dispersion results in severe phase separation, illustrating that the miniemulsion approach using GO as surfactant is key to obtaining homogeneous nanocomposite films. Finally, it is demonstrated that the GO sheets can be readily reduced to rGO in situ by heat treatment of the film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2289–2297     

A new σ‐transform based Fourier‐Legendre‐Galerkin model for nonlinear water waves

This paper presents a new spectral model for solving the fully nonlinear potential flow problem for water waves in a single horizontal dimension. At the heart of the numerical method is the solution to the Laplace equation which is solved using a variant of the $\sigma$‐transform. The method discretizes the spatial part of the governing equations using the Galerkin method and the temporal part using the classical fourth‐order Runge‐Kutta method. A careful investigation of the numerical method's stability properties is carried out, and it is shown that the method is stable up to a certain threshold steepness when applied to nonlinear monochromatic waves in deep water. Above this threshold artificial damping may be employed to obtain stable solutions. The accuracy of the model is tested for: (i) highly nonlinear progressive wave trains, (ii) solitary wave reflection, and (iii) deep water wave focusing events. In all cases it is demonstrated that the model is capable of obtaining excellent results, essentially up to very near breaking.