Photo-attaching functional polymers to cellulose fibers for the design of chemically modified paper

We introduce a novel approach for preparing polymer-modified and chemically microstructured paper substrates by a photo-chemical attachment of functional polymers to cellulose microfibers inside model filter papers. Poly(methyl methacrylate), PMMA copolymers, which carry a defined amount of photo-reactive benzophenone functional groups, are adsorbed to paper substrates from solution by a simple dip coating process, followed by covalent attachment of the physisorbed polymers through UV-light irradiation. Non-bound macromolecules can be removed from paper sheets by simple solvent extraction, and the resulting polymer-modified substrates were analysed with respect to chemical identity, attached polymer mass, and homogeneity of the polymer attachment. The amount of paper-attached polymers can be conveniently controlled in a wide range from a few mg/g cellulose fiber up to several tenth of mg/g cellulose fiber, by adjusting the polymer concentration in the coating solution. Polymers are being attached by photo-chemical means, and chemical micro patterns on paper can be designed by lithographical means. In first proof-of-concept studies, millimeter-scale channels were prepared that can be used to control fluid penetration by capillary actions. Because of the modularity in the design of photo-reactive polymers, a number of different chemically microstructured papers can be envisioned which may become potentially interesting in lab-on-paper devices.     

Recent Advances in Cross-Linking

Abstract

The topics of cross-linking methods and network polymers encompass an enormous literature covering many facets of polymer science. This review selects several areas from the broad field of cross-linking which represent more recent technology, particularly that not covered in earlier reviews [1].     

Polymers for the Cell‐Specific Immobilisation of Megakaryocytic Cell Lines

Primary human megakaryocytes, the precursor cells of platelets, are difficult to collect and cultivate. Polymers that enrich these cells without affecting their regulation or function are of interest for basic research as well as for cord blood transplantation purposes since co‐transplantation of enriched megakaryocyte concentrates increase the success of stem cell therapy. Herein, polymer microarrays were used for the discovery of substrates for MEG‐01 cells, with five polymers identified which selectively bound cells of the megakaryocytic lineage. Flow cytometry and miRNA profiling revealed that immobilisation had only a minor effect on the cellular maturation status, making the identified substrates potential candidates for concentrating megakaryocytes from patients prior to transplantation.

     

An unprecedented gedunin rearrangement reaction converts a methyl group into the methylene group of a cyclopropyl ring

Herein we describe an unprecedented formation of a cyclopropane ring through the conversion of a methyl group that was not functionalized for the purpose. In a one-step reaction, 7-deacetoxy-7α-hydroxygedunin (4) afforded two new gedunin derivatives, namely 7-deacetoxy-13,14,18-cyclopropyl-7α,15β, 17ξ-trihydroxy-gedu-16-oic acid (7) and 7-deacetoxy-9,11-en-7α,15β-dihydroxygedunin (8) along with the known 7-deacetoxy-7,9-diene-15β-hydroxygedunin (5).     

VT-NMR and cytotoxic evaluation of some new ortho-(alkylchalcogen)acetanilides

Several novel atropisomeric N-alkyl-N-[(2-alkylchalcogen)phenyl)]acetamides have been synthesized and fully characterized by ¹H and ¹³C NMR, FTIR, and HRMS (FAB). The barriers of the restricted rotation about the N-aryl bond between the two atropisomeric forms were measured by accurate lineshape simulation of variable temperature NMR (VT-NMR) spectra obtained in DMSO-d₆ solution and ranged from 17.0 to 20.5 kcal/mol. The relationship between the structure of the different acetanilide moieties and both coalescence temperature and energy of rotation are herein discussed. Taking in mind the acetamide structural resemblances with nimesulide related compounds known by their anticancer activity, the in vitro cytotoxicity of 20 representative acetanilides, against human breast (MCF-7) and prostate (LNCaP) cancer cell lines as well as normal human dermal fibroblasts (NHDF) was also preliminary evaluated. Interestingly a selective antiproliferative activity was observed for cancerous cells with prominence to LNCaP within the most potent O- and/or N-benzylic and -hexyl acetanilides.     

Synthesis of 2,6-diaryl-1,2-dihydropyridines through a 6π-electrocyclization of N-sulfonylazatrienes

The development of an efficient synthetic method toward substituted 1,2-dihydropyridines from cinnamylideneacetophenones is reported. The key intermediates N-sulfonylazatrienes were synthesized through a TiCl₄-mediated direct condensation of primary sulfonamides with the substituted (E,E)-cinnamylideneacetophenones. The 6π-electrocyclization of these intermediates, catalyzed by a Lewis acid, selectively afforded the desired products in good yields.     

Interocular induction of illusory size perception

Background  

The perceived size of objects not only depends on their physical size but also on the surroundings in which they appear. For example, an object surrounded by small items looks larger than a physically identical object surrounded by big items (Ebbinghaus illusion), and a physically identical but distant object looks larger than an object that appears closer in space (Ponzo illusion). Activity in human primary visual cortex (V1) reflects the perceived rather than the physical size of objects, indicating an involvement of V1 in illusory size perception. Here we investigate the role of eye-specific signals in two common size illusions in order to provide further information about the mechanisms underlying illusory size perception.     

Identification of the nitrate contamination sources of the Brusselian sands groundwater body (Belgium) using a dual-isotope approach

Isotopic fingerprinting is an advanced technique allowing the classification of the nitrate source pollution of groundwater, but needs further development and validation. In this study, we performed measurements of natural stable isotopic composition of nitrate ((15)N and (18)O) in the groundwater body of the Brussels sands (Belgium) and studied the spatial and temporal dynamics of the isotope signature of this aquifer. Potential nitrogen sources sampled in the region had isotopic signatures that fell within the corresponding typical ranges found in the literature. For a few monitoring stations, the isotopic data strongly suggest that the sources of nitrate are from mineral fertiliser origin, as used in agriculture and golf courses. Other stations suggest that manure leaching from unprotected stockpiles in farms, domestic gardening practices, septic tanks and probably cemeteries contribute to the nitrate pollution of this groundwater body. For most monitoring stations, nitrate originates from a mixing of several nitrogen sources. The isotopic signature of the groundwater body was poorly structured in space, but exhibited a clear temporal structure. This temporal structure could be explained by groundwater recharge dynamics and cycling process of nitrogen in the soil-nitrogen pool.     

Augmented Lagrangian for cone constrained topology optimization

Algorithmic aspects for the solution of topological shape optimization problems subject to a cone constraint are addressed in this paper. In this framework, an augmented Lagrangian method based on the concept of topological derivative is proposed. It is illustrated by some numerical experiments in structural optimization with compliance and eigenfrequency constraints and multiple loads.     

The conjugacy problem for the automorphism group of the random graph

We prove that the conjugacy problem for the automorphism group of the random graph is Borel complete, and discuss the analogous problem for some other countably categorical structures.