Multicenter experience of upper extremity access in complex endovascular aortic aneurysm repair

Purpose: Upper extremity access (UEA) for antegrade cannulation of aortic side branches is a relevant part of endovascular treatment of complex aortic aneurysms and can be achieved using several techniques, sites, and sides. The purpose of this study was to evaluate different UEA strategies in a multicenter registry of complex endovascular aortic aneurysm repair (EVAR). Methods: In six aortic centers in the Netherlands, all endovascular aortic procedures from 2006 to 2019 were retrospectively reviewed. Patients who received UEA during complex EVAR were included. The primary outcome was a composite end point of any access complication, excluding minor hematomas. Secondary outcomes were access characteristics, access complications considered individually, access reinterventions, and incidence of ischemic cerebrovascular events. Results: A total of 417 patients underwent 437 UEA for 303 fenestrated/branched EVARs and 114 chimney EVARs. Twenty patients had bilateral, 295 left-sided, and 102 right-sided UEA. A total of 413 approaches were performed surgically and 24 percutaneously. Distal brachial access (DBA) was used in 89 cases, medial brachial access (MBA) in 149, proximal brachial access (PBA) in 140, and axillary access (AA) in 59 cases. No significant differences regarding the composite end point of access complications were seen (DBA: 11.3% vs MBA: 6.7% vs PBA: 13.6% vs AA: 10.2%; P =.29). Postoperative neuropathy occurred most after PBA (DBA: 1.1% vs MBA: 1.3% vs PBA: 9.3% vs AA: 5.1%; P =.003). There were no differences in cerebrovascular complications between access sides (right: 5.9% vs left: 4.1% vs bilateral: 5%; P =.75). Significantly more overall access complications were seen after a percutaneous approach (29.2% vs 6.8%; P =.002). In multivariate analysis, the risk for access complications after an open approach was decreased by male sex (odds ratio [OR]: 0.27; 95% confidence interval [CI]: 0.10-0.72; P =.009), whereas an increase in age per year (OR: 1.08; 95% CI: 1.004-1.179; P =.039) and diabetes mellitus type 2 (OR: 3.70; 95% CI: 1.20-11.41; P =.023) increased the risk. Conclusions: Between the four access localizations, there were no differences in overall access complications. Female sex, diabetes mellitus type 2, and aging increased the risk for access complications after a surgical approach. Furthermore, a percutaneous UEA resulted in higher complication rates than a surgical approach

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Organocatalyzed ring opening polymerization of lactide from the surface of cellulose nanofibrils

The surface initiated ring opening polymerization (SI-ROP) of cellulose nanofibers (CNF) with rac-Lactide under mild conditions using N,N-dimethyl aminopyridine (DMAP) was investigated. The influence of catalyst amount, monomer-to-initiator (cellulose surface -OH groups) ratio, temperature, and cellulose preconditioning (lyophilization vs solvent exchange) were studied to determine the best SI-ROP conditions, and to understand the effect of the parameters on grafting efficiency. The fibers modified after lyophilization had a PLA content comparable to those obtained with traditional metal catalysts (e.g. tin-(II)ethylhexanoate). Starting from a stable dispersion of CNF in dichloromethane obtained through solvent-exchange showed better results at low catalyst amounts. Furthermore, DMAP was readily removed from the products whereas metal catalysts can be hard to remove from the final material, potentially shortening the material lifespan and making it unfit for some applications. Therefore, the use of an easily removable and more efficient organocatalyst can be considered a good alternative to metal catalysts.status: publishe

Organocatalyzed ring opening polymerization of lactide from the surface of cellulose nanofibrils

International audienceThe surface initiated ring opening polymerization (SI-ROP) of cellulose nanofibers (CNF) with rac-Lactide under mild conditions using N,N-dimethyl aminopyridine (DMAP) was investigated. The influence of catalyst amount, monomer-to-initiator (cellulose surface –OH groups) ratio, temperature, and cellulose preconditioning (lyophilization vs solvent exchange) were studied to determine the best SI-ROP conditions, and to understand the effect of the parameters on grafting efficiency. The fibers modified after lyophilization had a PLA content comparable to those obtained with traditional metal catalysts (e.g. tin-(II)ethylhexanoate). Starting from a stable dispersion of CNF in dichloromethane obtained through solvent-exchange showed better results at low catalyst amounts. Furthermore, DMAP was readily removed from the products whereas metal catalysts can be hard to remove from the final material, potentially shortening the material lifespan and making it unfit for some applications. Therefore, the use of an easily removable and more efficient organocatalyst can be considered a good alternative to metal catalysts

Amidation of methyl ester side chain bearing poly(2-oxazoline)s with tyramine: a quest for a selective and quantitative approach

© 2019 The Royal Society of Chemistry. Poly(2-alkyl/aryl-2-oxazoline)s (PAOx) are a class of cytocompatible polymers that have received growing interest over the past decade. This growing interest can mainly be attributed to their greater chemical versatility compared to other cytocompatible polymers, such as poly(ethylene glycol) (PEG), that originate from the diverse set of monomers compatible with the cationic ring-opening polymerization. Within this contribution we focus on the modification of methyl ester functional PAOx, on which we recently reported the quantitative conversion of methyl ester side chain bearing PAOx via direct amidation for a number of amines. While this approach is robust, it can be challenging to introduce certain amines, due to their high cost, poor solubility or additional functionalities. Here we evaluated three alternative amidation approaches of methyl ester side chain bearing PAOx with tyramine in terms of selectivity and quantitative conversion to the respective secondary amides. The amidation proceeded successfully via DMTMM coupling, PFP-activation and TBD catalysis, although only the latter 2 methods selectively yielded the desired product. In summary, we present valuable alternatives to our earlier reported method, contributing further to the biomedical application potential of PAOx.status: publishe

Modification of Linear Polyethylenimine with Supercritical CO2: From Fluorescent Materials to Covalent Cross-Links

Along with their DNA binding ability, the secondary amines in linear polyethylenimine (L-PEI) units can also act as a reaction platform to introduce new functionalities. This renders the possibility to make a plethora of copolymers without the burden of new monomer synthesis. In this work the modification of the secondary amines of L-PEI, in either a pure L-PEI polymer or in a PEtOx-PEI copolymer, with supercritical CO2 is reported. This reaction between a secondary amine and CO2 results in formation of a carbamate, a fluorescent zwitterionic group. This gives a facile route to fluorescent carbamate-functionalzied L-PEI and PEtOx, thereby expanding the chemical toolbox of both polymers. In depth analysis of the obtained polymers by 2D nuclear magnetic resonance spectroscopy revealed that, besides the expected carbamate groups, there were also some side reactions leading to the irreversible introduction of (cyclic) urea groups and partial cross-linking of the L-PEI. Altogether, this work introduces a new simple tool for the preparation of fluorescent L-PEI and PEtOx, while also shedding light on the occurrence of side reactions in PEI-based materials for CO2 sorption

Unprecendeted fluoroalkene-based copolymers through cobalt-mediated radical polymerization

The precision design of fluorinated copolymers is challenging but also attractive for future developments in a wide range of applications involving fluoropolymers, such as advanced coatings or purification membranes. In particular, controlling the radical polymerization of fluoroalkenes remains extremely difficult because of the high reactivity of these monomers due to the lack of resonance stabilizing group on their double bond. Herein, Cobalt-Mediated Radical Polymerization (CMRP) was used to efficiently control the bulk copolymerization of perfluorohexylethylene (PFHE) and vinyl acetate (VAc). Well-defined statistical poly(PFHE-stat-VAc) copolymers with different compositions (0 < FPFHE < 0.5) were obtained accordingly. In some cases, fluorinated monomer content as high as 80 % by weight were achieved. Reactivity ratios were determined (rVAc = 0.18 and rPFHE = 0) and emphasized a clear tendency for alternation. Single step approach and sequential polymerization were assessed for the synthesis of novel PFHE/VAc block copolymers. Finally, the acidic hydrolysis of the pendant ester groups of these block copolymers led to the formation of novel highly amphiphilic macromolecules bearing a PVOH hydrophilic segment and a hydrophobic PFHE-based block

Controlled synthesis of fluorinated copolymers via cobalt-mediated radical copolymerization of perfluorohexylethylene and vinyl acetate

Designing novel polyfluoropolymer architectures is attractive for the development of new applications, such as advanced coatings, purification membranes, or materials for energy. Nevertheless, controlling the radical polymerization of fluoroalkenes is very challenging due to the high reactivity of the propagating fluorinated macroradicals. This study aims at exploring the controlled copolymerization of perfluoro- hexylethylene (PFHE) and vinyl acetate (VAc) in order to prepare a range of well-defined statistical poly(PFHE-stat-VAc) copolymers with different compositions. Cobalt-mediated radical polymerization demonstrated to be active at 40 °C starting from an alkylcobalt(III) initiator, and copolymers with a fluorinated monomer content as high as ca. 80 wt % were successfully prepared. Reactivity ratios were determined to be rVAc = 0.18 and rPFHE = 0 at 40 °C and emphasized a clear tendency for alternation. Unprecedented PFHE/VAc containing block copolymers were also prepared via a single-step approach or through sequential copolymerizations. Finally, hydrolysis of the pendant ester groups of these copolymers led to the corresponding fluorinated copolymers bearing vinyl alcohol (VOH). A preliminary solution behavior study, carried out by dynamic light scattering and transmission electron microscopy on block copolymers composed of PFHE and VAc or VOH units, evidenced a marked amphiphilicity of the copolymer composed of an extremely hydrophobic PFHE block associated with a highly hydrophilic PVOH segment