Search

A detailed mechnaistic study into the copolymerization of CO2 and cyclohexene oxide utilizing Cr(super III) x complexes and N-methylimidazoile is conducted. By studying salen ligands with various groups on the diimine backbone, it is observed that bulky groups oriented perpendicular to the salen plane reduce the activity of the catalyst significantly, it is further stated that while such groups oriented parallel to the salen plane do not retard copolymer formation.

Quantitative studies on the influences of the nature of nucleophile, cocatalyst, and ligand on the activity of (salen)Cr(super III)(Nu) catalysts for the copolymerization of epoxides and carbon dioxide are examined. The copolymers are produced with >95% carbonate linkages with TOFs in the presence of phosphine cocatalysts, no cyclic carbonate was produced as a byproduct.

Research has been conducted on [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane and carbon dioxide. The authors report that copolymerization of these compounds, catalyzed by (salen)CrCl, with N-Melm as cocatalyst produces a polycarbonate devoid of polyether linkages.

Research has been conducted on zinc halides. The authors describe the reactions of these compounds with 2,6-di-methoxypyridine of 3-trifluoromethylpyridine in dichloromethane.

Background: There is great debate about the costs and benefits of technology-driven medical interventions such as instrumented lumbar fusion. With most analyses using charge data, the actual costs incurred by medical institutions performing these procedures are not well understood. The object of the current study was to examine the differences in hospital operating costs between open and minimally invasive spine surgery (MIS) during the perioperative period. Methods: Data were collected in the form of a prospective registry from a community hospital after specific Institutional Review Board approval was obtained. The analysis included consecutive adult patients being surgically treated for degenerative conditions of the lumbar spine, with either an MIS or open approach for two-level instrumented lumbar fusion. Patient outcomes and costs were collected for the perioperative period. Hospital operating costs were grouped by hospitalization/operative procedure, transfusions, reoperations, and residual events (health care interactions). Results: One hundred and one open posterior lumbar interbody fusion (Open group) and 109 MIS patients were treated primarily for stenosis coupled with instability (39.6% and 59.6%, respectively). Mean total hospital costs were $27,055.53 for the Open group and $24,320.16 for the MIS group. This represents a statistically significant cost savings of $2,825.37 (10.4% [95% confidence interval: $522.51-$5,128.23]) when utilizing MIS over traditional Open techniques. Additionally, residual events, complications, and blood transfusions were significantly more frequent in the Open group, compared to the MIS group. Conclusions/level of evidence: Utilizing minimally invasive techniques for instrumented spinal fusion results in decreased hospital operating costs compared to similar open procedures in the early perioperative period. Additionally, patient benefits of minimally invasive techniques include significantly less blood loss, shorter hospital stays, lower complication rate, and a lower number of residual events. Long-term outcome comparisons are needed to evaluate the efficacy of the two treatments. Level of evidence: III Clinical relevance: This work represents a true cost-of-operating comparison between open and MIS approaches for lumbar spine fusion, which has relevance to surgeons, hospitals and payers in medical decision-making. [ABSTRACT FROM AUTHOR]

The copolymerization of 2-(3,4-epoxycydohexyl)ethyl-trimethoxysilane and carbon dioxide catalyzed by (salen)Cr[sup III]Cl (H[sub 2]salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine) with 2.5 equiv of N-Melm as cocatalyst affords a polycarbonate devoid of polyether linkages, along with only a trace quantity of cyclic carbonate. The presence of the trimethoxysilane functionality in the epoxide not only provided the reactant monomer and product copolymer high solubility in liquid carbon dioxide but also provided the ability to cross-link the copolymer and thereby greatly alter the physical properties of the thus formed polycarbonate. In addition, the enhanced solubility of the copolymer in liquid CO[sub 2] furnishes a ready means of removing the highly colored metal catalyst from the polycarbonate product. [ABSTRACT FROM AUTHOR]

Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination-driven self-assembly of tris(meta-pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand-template approach, in which the ligand acts as a template for cage formation. Previously, first-generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported. Binding studies demonstrate that the association constant for the formation of second-generation cage L2 is nearly an order of magnitude higher than that of L1. This strengthened binding allows cage L2 to remain intact in polar and industrially relevant solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be maintained in polar and coordinating solvents by using the second-generation assembly., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Unlabelled: Spondylolisthesis is one of the most common indications for spinal surgery. However, no one approach has been proven to be more effective in treating spondylolisthesis. Recent advances in minimally invasive spine technology have allowed for different approaches to be applied to this indication, notably extreme lateral interbody fusion (XLIF). The risk, however, of using XLIF in treating grade II spondylolisthesis is the ventral position of the lumbar plexus, particularly at L4-5., Objective: This study reports the safety and midterm clinical and radiographic outcomes of patients with grade II lumbar spondylolisthesis treated with XLIF., Methods: 63 patients with grade II spondylolisthesis and spinal stenosis were treated with XLIF and were available for 12-month followup. Of those, 61 (97%) were treated at L4-5. Clinical (VAS, complications, and reoperation rate) and radiographic (anterolisthesis, disk height, and fusion) parameters were assessed., Study Design: Data were collected via a prospective registry and analyzed retrospectively., Results: Sixty-three patients were available for evaluations at least one year postoperatively. Average pain (visual analog scale) decreased from a score of 8.7 at baseline to 2.2 at 12 months postoperatively. Average anterior slippage was reduced by 73% and was well maintained. Average disk height (4.6 mm pre-op and 9.0 mm post-op) nearly doubled after surgery. Slight settling (average 1.3 mm) occurred over the twelve-month follow-up period. There were no neural injuries and no nonunions noted., Conclusions: XLIF is a safe and effective minimally invasive treatment alternative for grade II spondylolisthesis. Real-time neurological monitoring and attention to technique are mandatory.

The mechanism of the copolymerization of cyclohexene oxide and carbon dioxide to afford poly(cyclohexylene)carbonate catalyzed by (salen)CrN3 (H2salen = N,N,'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylene-diimine) in the presence of a broad range of cocatalysts has been studied. We have previously established the rate of copolymer formation to be very sensitive to both the electron-donating ability of the salen ligand and the [cocatalyst], where N-heterocyclic amines, phosphines, and ionic salts were effective cocatalysts. Significant increases in the rate of copolymerization have been achieved with turnover frequencies of approximately 1200 h(-1), thereby making these catalyst systems some of the most active and robust thus far uncovered. Herein we offer a detailed explanation of the role of the cocatalyst in the copolymerization of CO2 and cyclohexene oxide catalyzed by chromium salen derivatives. A salient feature of the N-heterocyclic amine- or phosphine-cocatalyzed processes is the presence of an initiation period prior to reaching the maximum rate of copolymerization. Importantly, this is not observed for comparable processes involving ionic salts as cocatalysts, e.g., PPN+ X-. In these latter cases the copolymerization reaction exhibits ideal kinetic behavior and is proposed to proceed via a reaction pathway involving anionic six-coordinate (salen)Cr(N3)X- derivatives. By way of infrared and 31P NMR spectroscopic studies, coupled with in situ kinetic monitoring of the reactions, a mechanism of copolymerization is proposed where the neutral cocatalysts react with CO2 and/or epoxide to produce inner salts or zwitterions which behave in a manner similar to that of ionic salts.