Biobased Photopolymer Resin for 3D Printing Containing Dynamic Imine Bonds for Fast Reprocessability.

Acrylic photopolymer resins are widely used in stereolithographic 3D printing. However, the growing demand for such thermosetting resins is weighing on global issues such as waste management and fossil fuel consumption. Therefore, there is an increasing demand for reactive components that are biobased and enable recyclability of the resulting thermoset products. In this work, the synthesis of a photo-cross-linkable molecule containing dynamic imine bonds based on biobased vanillin and dimer fatty diamine is described. Using the biobased building blocks, formulations containing reactive diluent and a photoinitiator were prepared. The mixtures could be rapidly cross-linked under UV light, yielding vitrimers. Using digital light processing, 3D-printed parts were prepared, which were rigid, thermally stable, and reprocessed within 5 min at elevated temperature and pressure. The addition of a building block containing a higher concentration of imine bonds accelerated the stress relaxation and improved the mechanical rigidity of the vitrimers. This work will contribute to the development of biobased and recyclable 3D-printed resins to facilitate the transition to a circular economy.

Biobased 2,5-Bis(hydroxymethyl)furan as a Versatile Building Block for Sustainable Polymeric Materials.

Furanic polymers, currently mainly represented by polyethylene 2,5-furandicarboxylate (PEF), also known as polyethylene furanoate, have a fantastic potential to replace fossil-based polymers: for example, polyethylene terephthalate (PET). While 2,5-furandicarboxylic acid (FDCA), a precursor of PEF, and its derived polymers have been studied extensively, 2,5-bis(hydroxymethyl)furan (BHMF) has received relatively little attention so far. Similarly to FDCA, BHMF is a biobased platform chemical derived from renewable sources such as sugars. This review highlights different polymerization techniques for BHMF-based polyesters and addresses BHMF's relative instability during the synthesis of BHMF-derived polymers, including polycarbonates and polyurethanes. Furthermore, the degradability of furanic polyesters is discussed and BHMF's toxicity is briefly elaborated.

Robust Superamphiphilic Membrane with a Closed-Loop Life Cycle.

Oil-spill remediation is an international environmental challenge, and superamphiphilic membranes, as a promising solution, have recently drawn lots of attention. However, the robustness of the conventional membrane design is less satisfying under severe conditions during practical applications. Additionally, it is unavoidable for the membranes to face a series of foulants in their practical working environment, for example, algae and sand. These foulants will block the membrane, which leads to a new economic and environmental problem in terms of waste management at the end of their life. To address the aforementioned challenges, a new generation of superamphiphilic vitrimer epoxy resin membranes (SAVER) to separate oil and water efficiently is reported. Similar to classical epoxy resins, SAVER shows strong mechanical robustness and sustains exposure to aqua regia and sodium hydroxide solutions. Furthermore, the blocked membrane can be easily recovered when contaminated with mixed foulants by using dynamic transesterification reactions in the polymer network. The ease with which biobased SAVER can be manufactured, used, recycled, and re-used without losing value points to new directions in designing a closed-loop superamphiphilic membrane life cycle.

Sustainable Photopolymers in 3D Printing: A Review on Biobased, Biodegradable, and Recyclable Alternatives.

The global market for 3D printing materials has grown exponentially in the last decade. Today, photopolymers claim almost half of the material sales worldwide. The lack of sustainable resins, applicable in vat photopolymerization that can compete with commercial materials, however, limits the widespread adoption of this technology. The development of "green" alternatives is of great importance in order to reduce the environmental impact of additive manufacturing. This paper reviews the recent evolutions in the field of sustainable photopolymers for 3D printing. It highlights the synthesis and application of biobased resin components, such as photocurable monomers and oligomers, as well as reinforcing agents derived from natural resources. In addition, the design of biologically degradable and recyclable thermoset products in vat photopolymerization is discussed. Together, those strategies will promote the accurate and waste-free production of a new generation of 3D materials for a sustainable plastics economy in the near future.

Stereolithographic 3D Printing with Renewable Acrylates.

The accessibility of cost-competitive renewable materials and their application in additive manufacturing is essential for an efficient biobased economy. We demonstrate the rapid prototyping of sustainable resins using a stereolithographic 3D printer. Resin formulation takes place by straightforward mixing of biobased acrylate monomers and oligomers with a photoinitiatior and optical absorber. Resin viscosity is controlled by the monomer to oligomer ratio and is determined as a function of shear rate by a rheometer with parallel plate geometry. A stereolithographic apparatus charged with the biobased resins is employed to produce complex shaped prototypes with high accuracy. The products require a post-treatment, including alcohol rinsing and UV irradiation, to ensure complete curing. The high feature resolution and excellent surface finishing of the prototypes is revealed by scanning electron microscopy.

Biobased Acrylate Photocurable Resin Formulation for Stereolithography 3D Printing.

To facilitate the ongoing transition toward a circular economy, the availability of renewable materials for additive manufacturing becomes increasingly important. Here, we report the successful fabrication of complex shaped prototypes from biobased acrylate photopolymer resins, employing a commercial stereolithography apparatus (SLA) 3D printer. Four distinct resins with a biobased content ranging from 34 to 67% have been developed. All formulations demonstrated adequate viscosity and were readily polymerizable by the UV-laser-based SLA process. Increasing the double-bond concentration within the resin results in stiff and thermally resilient 3D printed products. High-viscosity resins lead to high-resolution prototypes with a complex microarchitecture and excellent surface finishing, comparable to commercial nonrenewable resins. These advances can facilitate the wide application of biobased resins for construction of new sustainable products via stereolithographic 3D printing methods.

Bioinspired Synthesis of Well-Ordered Layered Organic-Inorganic Nanohybrids: Mimicking the Natural Processing of Nacre by Mineralization of Block Copolymer Templates.

The unique mechanical performance of nacre, the pearly internal layer of shells, is highly dependent on its complex morphology. Inspired by the structure of nacre, the fabrication of well-ordered layered inorganic-organic nanohybrids is presented herein. This biomimetic approach includes the use of a block copolymer template, consisting of hydrophobic poly(vinylidene fluoride) (PVDF) lamellae covered with hydrophilic poly(methacrylic acid) (PMAA), to direct silica (SiO2 ) mineralization. The resulting PVDF/PMAA/SiO2 nanohybrid material resembles biogenic nacre with respect to its well-ordered and layered nanostructure, alternating organic-inorganic phases, macromolecular template, and mild processing conditions.

Gyroid nickel nanostructures from diblock copolymer supramolecules.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

Poly(vinylidene fluoride)/nickel nanocomposites from semicrystalline block copolymer precursors.

The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric ß-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the ß-crystalline phase are conserved during the etching procedure and electroless nickel deposition.

SU-E-J-85: Anthropomorphic Development for Intermodality Deformation Algorithms Validation.

PURPOSE: Radiation therapy is often based on a single treatment plan calculated on patient's anatomy at the time of the simulation scan. Deformation algorithms offer the possibility to register initial treatment plan on a daily CBCT. This way, the planning can be adapted to the evolution of patient anatomy. Validation of deformable image registration algorithms (DRA) ideally requires the use of phantoms offering some deformation possibilitiesMethods: An anthropomorphic, pelvic phantom was built to test volume variation (bladder), deformation of contours (prostate) and translation (all organs). Algorithms must be able to perform intermodality registration. Therefore, images were acquired for both CT and CBCT. The phantom has been created in a way to allow total control of the deformation amplitude. Each of the three types of deformations studied were realized independently and scanned in a manner to have the same initial and deformed images set for each modality. RESULTS: Two algorithm systems were use to compare their efficiency; an open-source software, a toolbox for registration that offers parameter adjustment and a commercial system with limited control for user. The phantom provides us usable images for DRA validation. For a 2 cm mass center organ translation, the first one reduced 98% of the distance while the other only performed 60%. For a 100 ml volume variation, we get 88% and 62%. CONCLUSIONS: Comparison of each intermodal deformation registration performed by the two algorithm systems show how control on parameters improves registration quality. DRA allow the initial planning adaptation on different deformations which occur in human body.

Interface segregating fluoralkyl-modified polymers for high-fidelity block copolymer nanoimprint lithography.

Block copolymer (BCP) lithography is a powerful technique to write periodic arrays of nanoscale features into substrates at exceptionally high densities. In order to place these features at will on substrates, nanoimprint offers a deceptively clear path toward high throughput production: nanoimprint molds are reusable, promote graphoepitaxial alignment of BCP microdomains within their topography, and are efficiently aligned with respect to the substrate using interferometry. Unfortunately, when thin films of BCPs are subjected to thermal nanoimprint, there is an overwhelming degree of adhesion at the mold-polymer interface, which compromises the entire process. Here we report the synthesis of additives to mitigate adhesion based on either PS or PDMS with short, interface-active fluoroalkyl chains. When blended with PS-b-PDMS BCPs and subjected to a thermal nanoimprint, fluoroalkyl-modified PS in particular is observed to substantially reduce film adhesion to the mold, resulting in a nearly defect-free nanoimprint. Subsequent lithographic procedures revealed excellent graphoepitaxial alignment of sub-10 nm BCP microdomains, a critical step toward lower-cost, high-throughput nanofabrication.

The need for standardisation of peak flow charts.

Peak expiratory flow (PEF) monitoring is recommended in asthma guidelines as a tool for assessing severity, monitoring response to treatment, detecting exacerbations, identifying triggers, and providing objective justification for treatment to the patient, but some clinicians have expressed concerns about its relevance in the management of asthma. We have identified a sevenfold variation in the scale of existing PEF charts, with resulting wide variation in the appearance of the same PEF date on different charts. There is an obvious need for standardisation of PEF charts to avoid confusion for patients and to allow development of pattern recognition skills by clinicians. Evidence is provided from visual perception studies to suggest that preference should be given to a horizontally compressed PEF chart to facilitate identification of exacerbations and of overall trends, but this needs to be formally evaluated by retrospective and prospective studies. It is hoped that clinical expertise in PEF pattern recognition can eventually be incorporated into electronic decision making algorithms, as has occurred in occupational asthma, but, in the meantime, the ideal PEF chart for asthma management will represent a compromise between ease of manual data entry and ease of interpretation.

Acquired tufted angioma: a unique vascular lesion not previously reported in the oral mucosa.

We describe two patients with acquired tufted angioma, a unique vascular lesion not previously reported in the oral mucosa. In one patient, the lesion manifested as a purple-red papule and, in the other, as a blue submucosal swelling. Both lesions were non-painful and neither was associated with a history of trauma. The histopathological features consisted of scattered, irregularly shaped tufts, primarily composed of poorly formed capillary spaces and slit-like vascular channels. Capillary spaces were often closely packed, producing solid areas which stained for smooth muscle actin. Staining for factor VIII-related antigen was positive only within endothelial cells lining well-formed vascular channels. Both lesions were treated by excision; short-term follow-up of one patient revealed no evidence of recurrence. Similarities between this and other vascular processes may have resulted in misdiagnosis of this lesion in the past. The clinical significance of acquired tufted angioma in the oral mucosa is not known.

Sequence-specificity of Holliday junction resolution: identification of RuvC mutants defective in metal binding and target site recognition.

The RuvC protein of Escherichia coli resolves Holliday intermediates in recombination and DNA repair by a dual strand incision mechanism targeted to specific DNA sequences located symmetrically at the crossover. Two classes of amino acid substitutions are described that provide new insights into the sequence-specificity of the resolution reaction. The first includes D7N and G14S, which modify or eliminate metal binding and prevent catalysis. The second, defined by G114D, G114N, and A116T, interfere with the ability of RuvC to cleave at preferred sequences, but allow resolution at non-consensus target sites. All five mutant proteins bind junction DNA and impose an open conformation. D7N and G14S fail to induce hypersensitivity to hydroxyl radicals, a property of RuvC previously thought to reflect junction opening. A different mechanism is proposed whereby ferrous ions are co-ordinated in the complex to induce a high local concentration of radicals. The open structure imposed by wild-type RuvC in Mg2+ is similar to that observed previously using a junction with a different stacking preference. G114D and A116T impose slightly altered structures. This subtle change may be sufficient to explain the failure of these proteins to cleave the sequences normally preferred. Gly114 and Ala116 residues link two alpha-helices lining the wall of the catalytic cleft in each subunit of RuvC. We suggest that substitutions at these positions realign these helices and interfere with the ability to establish base-specific contacts at resolution hotspots.

Recognition and manipulation of branched DNA by the RusA Holliday junction resolvase of Escherichia coli.

Homologous recombination is a fundamental cellular process that shapes and reshapes the genomes of all organisms and promotes repair of damaged DNA. A key step in this process is the resolution of Holliday junctions formed by homologous DNA pairing and strand exchange. In Escherichia coli , a Holliday junction is processed into recombinant products by the concerted activities of the RuvA and RuvB proteins, which together drive branch migration, and RuvC endonuclease, which resolves the structure. In the absence of RuvABC, recombination can be promoted by increasing the expression of the RusA endonuclease, a Holliday junction resolvase encoded by a cryptic prophage gene. Here, we describe the DNA binding properties of RusA. We found that RusA was highly selective for branched molecules and formed complexes with these structures even in the presence of a large excess of linear duplex DNA. However, it does bind weakly to linear duplex DNA. Under conditions where there was no detectable binding to duplex DNA, RusA formed a highly structured complex with a synthetic Holliday junction that was remarkably stable and insensitive to divalent metal ions. The duplex arms were found to adopt a specific alignment within this complex that approximated to a tetrahedral conformation of the junction.

The RecG branch migration protein of Escherichia coli dissociates R-loops.

The RuvAB and RecG proteins of Escherichia coli promote branch migration of Holliday junction intermediates in genetic recombination. Both are structure-specific helicases that unwind and rewind DNA at the junction point. The helicase activities of these proteins were investigated using RNA:DNA hybrid molecules. RuvAB catalyses the unwinding of RNA:DNA partial duplexes of at least 218 bp in a reaction that requires both RuvA and RuvB, ATP and Mg2+. RecG failed to unwind these substrates even when the duplex region was reduced to 35 bp. In contrast, RecG rapidly removes a 218 nt RNA from an R-loop substrate, whereas RuvAB does not. RecG's ability to dissociate R-loops is correlated with an ability to reduce the copy number of pUC plasmids and other constructs based on the ColE1 replicon. Copy number is reduced severely when the plasmid carries recG+. RecG is assumed to reduce copy number by interfering with RNA II's ability to form an R-loop at the plasmid origin of replication and prime DNA synthesis. The dissociation of R-loops by RecG is discussed in terms of the functions needed to promote recombination and to prime DNA replication at D-loops formed during the early stages of RecA-mediated recombination.

Magnetic resonance imaging used to assess patients with trigeminal neuralgia.

To assess the value of magnetic resonance imaging in the evaluation of trigeminal neuralgia, 51 patients were studied by magnetic resonance imaging after a trigeminal protocol. Clinical and magnetic resonance imaging results were correlated. Seventeen (33%) nonvascular abnormalities and 27 (53%) vascular contacts or compressions of the trigeminal nerve were demonstrated. Of the patients younger than of 29 and 39 years of age, 100% and 45%, respectively, had a tumor or multiple sclerosis compared with 20% and 18% of those older than 40 and 60 years of age, respectively. One third of the patients with pain in more than one branch of the trigeminal nerve had tumors. On the basis of this study, magnetic resonance imaging may be useful in discovering underlying pathoses associated with trigeminal neuralgia if patients have failed to respond to an initial conservative treatment. The patients most likely to exhibit significant magnetic imaging resonance findings are young and with pain in more than one trigeminal branch.