Diepoxide treatment of softwood kraft pulp: influence on absorption properties of fibre networks

Many different approaches to the introduction of intra-fibre cross-links in fibres for use in absorption products are described in the patent literature, but relatively little has been done in terms of academic research. In this study, the long fibre fraction of a Scandinavian softwood kraft pulp has been cross-linked with the diepoxide 1,4-butanediol diglycidyl ether (BDDE). The fibre properties and the performance of the pulp in low density fibre networks were analyzed. In experiments, the cross-linking agent (BDDE) was dissolved in acetone and then mixed with the pulp. It was shown that a prior wash with NaOH (0.1 M) activates the polysaccharides and increases the extent of cross-linking, detected as a decrease in the water retention value. Chemical analysis of modified fibres also gave a clear indication of that cross-linking reactions actually occurred. The pulp properties could furthermore be influenced by varying time, temperature and the amount of BDDE in the reaction. It was also shown that it is possible to use water as a solvent for the cross-linking agent, even though the reactivity of water towards diepoxide must be considered to be high. The cross-linked pulps showed wet bulk under load comparable to that of the mechanical pulps and enhanced properties than unmodified Scandinavian softwood kraft pulp. It was also observed that fibre network test pads of the cross-linked pulp fibres, after being tested in the wet state, regained a substantially large part of their low-density structure when air-dried.     

Assessing market uncertainty by means of a time-varying intermittency parameter for asset price fluctuations

Maximum likelihood estimation techniques for multifractal processes are applied to high-frequency data in order to quantify intermittency in the fluctuations of asset prices. From time records as short as one month these methods permit extraction of a meaningful intermittency parameter λ$\lambda$ characterising the degree of volatility clustering. We can therefore study the time evolution of volatility clustering and test the statistical significance of this variability. By analysing data from the Oslo Stock Exchange, and comparing the results with the investment grade spread, we find that the estimates of λ$\lambda$ are lower at times of high market uncertainty.     

Surface modification and oxidation kinetics of hot-pressed AlN–SiC–MoSi2 electroconductive ceramic composite

The effects of oxidation on the microstructural modification and on the electrical resistivity and mechanical strength of a hot-pressed AlN–SiC–MoSi₂ electroconductive ceramic composite were studied. The kinetic of the oxidation was also evaluated. After the oxidation at temperatures below 1000 °C samples do not gain weight, due to simultaneous formation of SiO₂ and evaporation of MoO₃ formed by the oxidation of MoSi₂. However, the AlN/SiC matrix disables the “pesting” phenomena and strength degradation, despite the fact that at these temperatures MoSi₂ oxidizes rapidly. At temperatures above 1000 °C, the composite gains weight due to protective mullite layer formation on the surface, that provides a good oxidation resistance for use at higher temperatures. The kinetics of the oxidation follows the parabolic law. The possible rate-controlling mechanism is the diffusion of oxygen through the mullite-rich surface oxide scale.     

A Thermally Populated,Perpendicularly Twisted Alkene Triplet Diradical

Variable‐temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) 1 possesses a singlet ground state, 1 (S₀), while the 90° twisted triplet 1 (T₁) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic 1 (T₁) at temperatures between 300 and 500 K yields the exchange interaction J_ex/h c=3351 cm⁻¹ and a singlet–triplet energy splitting of 9.6 kcal mol⁻¹, which is in excellent agreement with calculations (9.3 kcal mol⁻¹ at the UKS BP86/B3LYP/revPBE level of theory). In contrast, the zero‐field splitting parameter D is very small (calculated value −0.018 cm⁻¹) and unmeasurable.     

Multimaterial hydrogel with widely tunable elasticity by selective photopolymerization of PEG diacrylate and epoxy monomers

We present a method to make continuous multi‐material structures from a monomer solution that becomes a soft hydrogel when exposed to blue light and a hard solid when exposed to UV light. We show that the material can be varied between a hard epoxy material to a several hundred times softer poly(ethylene glycol)‐diacrylate material. Moreover, the elastic properties of the material depend on both the wavelength of and exposure time of the light, which is used to produce a material with an elasticity gradient. We expect our material to find use in a range of fields, with immediate applications as 2D sheets with tunable mechanical properties for cell durotaxis studies, and 3D stereolithographically printed tissue mimicks, for example, for disease models and tissue engineering. Spatially resolved photo‐polymerization of a mixture of epoxy and acrylate monomers can be used to make multi‐material structure, with unique freedom to polymerize each monomer individually. The elastic compressive properties of the material are shown to be fully tunable from <100 kPa to >20 MPa depending on the light exposure time. This is used to make a functionally graded continuous material with a large variation in elastic properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1195–1201     

Modulation of the ligand-field anisotropy in a series of ferric low-spin cytochrome c mutants derived from Pseudomonas aeruginosa cytochrome c-551 and Nitrosomonas europaea cytochrome c-552: a nuclear magnetic resonance and electron paramagnetic resonance study

Cytochromes of the c type with histidine-methionine (His-Met) heme axial ligation play important roles in electron-transfer reactions and in enzymes. In this work, two series of cytochrome c mutants derived from Pseudomonas aeruginosa (Pa c-551) and from the ammonia-oxidizing bacterium Nitrosomonas europaea (Ne c-552) were engineered and overexpressed. In these proteins, point mutations were induced in a key residue (Asn64) near the Met axial ligand; these mutations have a considerable impact both on heme ligand-field strength and on the Met orientation and dynamics (fluxionality), as judged by low-temperature electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectra. Ne c-552 has a ferric low-spin (S = 1/2) EPR signal characterized by large g anisotropy with g(max) resonance at 3.34; a similar large g(max) value EPR signal is found in the mitochondrial complex III cytochrome c1. In Ne c-552, deletion of Asn64 (NeN64Delta) changes the heme ligand field from more axial to rhombic (small g anisotropy and g(max) at 3.13) and furthermore hinders the Met fluxionality present in the wild-type protein. In Pa c-551 (g(max) at 3.20), replacement of Asn64 with valine (PaN64V) induces a decrease in the axial strain (g(max) at 3.05) and changes the Met configuration. Another set of mutants prepared by insertion (ins) and/or deletion (Delta) of a valine residue adjacent to Asn64, resulting in modifications in the length of the axial Met-donating loop (NeV65Delta, NeG50N/V65Delta, PaN50G/V65ins), did not result in appreciable alterations of the originally weak (Ne c-552) or very weak (Pa c-551) axial field but had an impact on Met orientation, fluxionality, and relaxation dynamics. Comparison of the electronic fingerprints in the overexpressed proteins and their mutants reveals a linear relationship between axial strain and average paramagnetic heme methyl shifts, irrespective of Met orientation or dynamics. Thus, for these His-Met axially coordinated Fe(III), the large g(max) value EPR signal does not represent a special case as is observed for bis-His axially coordinated Fe(III) with the two His planes perpendicular to each other.     

Goal‐oriented error estimation for Cahn–Hilliard models of binary phase transition

A posteriori estimates of errors in quantities of interest are developed for the nonlinear system of evolution equations embodied in the Cahn–Hilliard model of binary phase transition. These involve the analysis of wellposedness of dual backward‐in‐time problems and the calculation of residuals. Mixed finite element approximations are developed and used to deliver numerical solutions of representative problems in one‐ and two‐dimensional domains. Estimated errors are shown to be quite accurate in these numerical examples. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010     

What’s so Good about a Wise and Knowledgeable Public?

Philosophers have been concerned for some time with the epistemic caliber of the general public, qua the body that is, ultimately, tasked with political decision-making in democratic societies. Unfortunately, the empirical data paint a pretty dismal picture here, indicating that the public tends to be largely ignorant on the issues relevant to governance. To make matters worse, empirical research on how ignorance tends to breed overconfidence suggests that the public will not only lack knowledge on the relevant issues, but also wisdom, in the Socratic sense of an awareness of your ignorance. While increasing the knowledge and wisdom of the public might be thought an obvious remedy, there is, as far as sound political decision-making and action are concerned, nothing particularly valuable about knowledge or wisdom per se. In fact, it might just be that what the public needs is nothing but the most basic epistemic good: true belief.     

Erratum: Fluorescent gel particles in the nanometer range for detection of metabolites in living cells

In the article above published in Volume 17 of Polymers for Advanced Technologies, pages 790–793 (2006) and online in Wiley InterScience , ( www.wileyinterscience.wiley.com ) DOI 10.1002/pat.786 the following changes should be recognised: On the second page of the paper, page 791, the sentence above figure 2 should have read ‘Since the headgroup areas of surfactants are a weak function of the condition under which they are used the function …’     

Combining aryltriazenes and electrogenerated acids to create well-defined aryl-tethered films and patterns on surfaces

Immobilization of submonolayers to 4-5 multilayers of organic molecules on carbon surfaces can be performed by in situ generation of aryl radicals from aryltriazenes. The central idea consists of oxidatively forming an electrogenerated acid of N,N'-diphenylhydrazine to convert the aryltriazene to the corresponding diazonium salt in the diffusion layer of the electrode. In a second step, the diazonium salt is reduced at the same electrode to give a surface of covalently attached aryl groups. In this manner, various moieties tethered to the aryl groups can be immobilized on the surface. Here a ferrocenyl group was introduced as redox marker, the electrochemical signal of which is extraordinarily well-defined. This behavior is independent of film thickness, the latter being easily controlled by the number of repetitive cycles performed. It is also demonstrated that the new approach is suitable for patterning of surfaces using scanning electrochemical microscopy.