6-dimensional manifolds with effective T4-actions

Suppose the four dimensional torus T⁴ acts effectively on a 6-manifold M so that the orbit space M¹ is a closed 2-disk, and there exist no exceptional orbits, and the isotropy groups span T⁴. Then the fundamental group of M is a finite abelian group with at most two generators. In this paper, we obtain a homology classification of manifolds of this type under an additional hypothesis that one of the two generators is trivial. We then use this result to obtain a complete classification of simply connected 6-manifolds supporting effective T⁴-actions.     

Influence of Material Properties on the Damage-Reporting and Self-Healing Performance of a Mechanically Active Dynamic Network Polymer in Coating Applications

We conducted a detailed investigation of the influence of the material properties of dynamic polymer network coatings on their self-healing and damage-reporting performance. A series of reversible polyacrylate urethane networks containing the damage-reporting diarylbibenzofuranone unit were synthesized, and their material properties (e.g., indentation modulus, hardness modulus, and glass-transition temperature) were measured conducting nanoindentation and differential scanning calorimetry experiments. The damage-reporting and self-healing performances of the dynamic polymer network coatings exhibited opposite tendencies with respect to the material properties of the polymer network coatings. Soft polymer network coatings with low glass-transition temperature (~10 °C) and indentation hardness (20 MPa) exhibited better self-healing performance (almost 100%) but two times worse damage-reporting properties than hard polymer network coatings with high glass-transition temperature (35~50 °C) and indentation hardness (150~200 MPa). These features of the dynamic polymer network coatings are unique; they are not observed in elastomers, films, and hydrogels, whereby the polymer networks are bound to the substrate surface. Evidence indicates that controlling the polymer’s physical properties is a key factor in designing high-performance self-healing and damage-reporting polymer coatings based on mechanophores.     

Amphiphilic Nanoparticles Control the Growth and Stability of Lipid Bilayers with Open Edges

Molecular amphiphiles self‐assemble in polar media to form ordered structures such as micelles and vesicles essential to a broad range of industrial and biological processes. Some of these architectures such as bilayer sheets, helical ribbons, and hollow tubules are potentially useful but inherently unstable owing to the presence of open edges that expose the hydrophobic bilayer core. Here, we describe a strategy to stabilize open bilayer structures using amphiphilic nanoparticle surfactants that present mixtures of hydrophilic and hydrophobic ligands on their surface. We observe that these particles bind selectively to the open edge of bilayer membranes to stabilize otherwise transient amphiphile assemblies. We show how such particles can precisely control the size of lipid tubules, how they can inhibit the formation of undesirable assemblies such as gallstone precursors, and how they can stabilize free‐floating lipid microdiscs.     

Montmorillonite‐based nanocomposites of polybenzoxazole: Synthesis and characterization (I)

Poly(amic acid) was synthesized by means of low‐temperature‐solution polymerization of 3,3′‐dihydroxybenzidine and pyromellitic dianhydride in N,N‐dimethylacetamide. The precursor polymer was heat‐treated at different temperatures to create a polybenzoxazole (PBO) through a polyimide (PI). PI containing the hydroxyl group was rearranged by decarboxylation with heat treatment, resulting in a fully aromatic PBO. Hexadecylamine was used as an organophilic alkylamine in organo‐clay. We have tried to clarify the intercalation of heterocyclic polymer chains to hexadecylamine–montmorillonite (C₁₆‐MMT) and improve tensile properties. It was found that the addition of only a small amount of organo‐clay was enough to improve the mechanical properties of PBO. Maximum enhancement in the ultimate tensile strength for PBO hybrids was observed for the blends containing 4% C₁₆‐MMT. The initial modulus monotonically increased with further increases in the C₁₆‐MMT content. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 471–476, 2001     

Two‐step thermal conversion from poly(amic acid) to polybenzoxazole via polyimide: Their thermal and mechanical properties

Poly(amic acid) was synthesized with a low‐temperature solution polymerization of 3,3′‐dihydroxybenzidine and pyromellitic dianhydride in N,N‐dimethylacetamide. The cast films were thermally treated at various temperatures. The polyimide containing the hydroxyl group was rearranged by decarboxylation, resulting in a fully aromatic polybenzoxazole at temperatures higher than 430 °C. These stepwise cyclizations were monitored with elemental analysis, Fourier transform infrared, and nuclear magnetic resonance. Microanalysis results confirmed the chemical compositions of poly(amic acid), polyimide, and polybenzoxazole, respectively. A cyclodehydration from poly(amic acid) to polyimide occurred between 150 and 250 °C in differential scanning calorimetry, and a cyclodecarboxylation to polybenzoxazole appeared at 400–500 °C. All the samples were stable up to 625 °C in nitrogen and displayed excellent thermal stability. Polybenzoxazole showed better thermal stability than polyimide, but polyimide exhibited better mechanical properties than polybenzoxazole. However, polyimide showed a crystalline pattern under a wide‐angle X‐ray, whereas polybenzoxazole was amorphous. The precursor poly(amic acid) was readily soluble in a variety of solvents, whereas the polyimide and polybenzoxazole were not soluble at all. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2537–2545, 2000     

Facile selective detritylation of 5′-primary alcohols of pyrimidine nucleosides using tetra-n-butylammonium peroxydisulfate

Tetra-n-butylammonium peroxydisulfate has been found to be a good deprotecting reagent for removal of the trityl group: Treatment of 5′-O-dimethoxytrityl uridine or thymidine with tetra-n-butylammonium peroxydisulfate gave the corresponding dedimethoxytritylated nucleosides in excellent yields under neutral and mild conditions and without causing any side reactions such as cleavage of the glycosidic bond. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 435–438, 1997     

Synthesis of Poly(2,5‐benzimidazole) for Use as a Fuel‐Cell Membrane

Summary: Poly(2,5‐benzimidazole) (ABPBI) was synthesized in a novel polymerization medium containing CH₃SO₃H and P₂O₅. 3,4‐Diaminobenzoic acid, a monomer for ABPBI, is soluble in the medium and the polymerization was therefore performed in a homogeneous state. It produced polymer fibers, thus simplifying the work‐up process. The membrane was cast directly from the polymerization mixture. Proton conductivities of the ABPBI membranes ranged from 0.02 to 0.06 S · cm⁻¹ above 100 °C, without humidification, and the tensile strength of the membrane was approximately 100 MPa.

Synthesis of ABPBI in a medium containing methanesulfonic acid and P₂O₅.     

Multimodal evaluation of an interphotoreceptor retinoid-binding protein-induced mouse model of experimental autoimmune uveitis

We aimed to characterize the vascular phenotypes of an experimental autoimmune retinal uveitis (EAU) model induced by interphotoreceptor retinoid-binding protein (IRBP) using multimodal imaging techniques. We systemically administered IRBP or vehicle to adult C57BL/6 mice. Fundus photography, optical coherence tomography (OCT), in vivo live confocal imaging using different tracers, OCT angiography (OCTA), and electroretinography (ERG) were performed after IRBP immunization. Hematoxylin and eosin and immunofluorescence staining were performed to characterize the immune response and vascular permeability. Mice with EAU exhibited perivascular inflammation, vitritis, and superficial retinal inflammation on fundus photography and OCT. H&E revealed immune cell infiltration in the perivascular area of the retina and choroid accompanied by a significant degree of perivasculitis that subsequently damaged photoreceptors 3 weeks postimmunization. Immunofluorescence staining showed subsequent transcytosis induction after local microglial activation followed by neutrophil recruitment in the perivascular area. Transcytosis in the superficial and deep vascular areas was improved by immune cell suppression. Intravital in vivo confocal imaging showed signs of neutrophil infiltration and obstructive vasculitis with perivascular leakage 3 weeks postimmunization. OCTA revealed a significant decrease in vascular flow in the deep capillary layer of the retina. Functional analysis showed that scotopic responses were intact at 2 weeks; however, normal photopic and scotopic responses were hardly detected in mice with EAU mice at 3 weeks postimmunization. Our data suggest that inflammatory cell activation and subsequent transcytosis induction in endothelial cells might be a major pathogenic factor for vascular leakage in uveitis, providing new insights into the pathophysiology of retinal vasculitis in noninfectious uveitis.Subject terms: Vasculitis, Imaging, Retina, Retina