Publications by authors named "David Powers"

 To summarize patient characteristics and outcomes for the historical and current methods of long-segment tracheal replacement in humans.  A single reviewer screened the abstracts and full texts using Covidence for file management. Studies published in English that reported human subjects with circumferential or near-circumferential (>270 degrees) cervical tracheal replacements were included.

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Nitrenes (R-N) have been subject to a large body of experimental and theoretical studies. The fundamental reactivity of this important class of transient intermediates has been attributed to their electronic structures, particularly the accessibility of triplet vs singlet states. In contrast, electronic structure trends along the heavier pnictinidene analogues (R-Pn; Pn = P-Bi) are much less systematically explored.

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Terminal metal-phosphorus (M-P) complexes are of significant contemporary interest as potential platforms for P-atom transfer (PAT) chemistry. Decarbonylation of metal-phosphaethynolate (M-PCO) complexes has emerged as a general synthetic approach to terminal M-P complexes. M-P complexes that are stabilized by strong M-P multiple bonds are kinetically persistent and isolable.

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We describe a metal-free aziridination of unactivated olefins to generate pyridinium aziridines. Subsequent cross-coupling affords -aryl aziridines, and reductive depyridylation affords N-H aziridines. Kinetics experiments, based on a variable time normalization analysis (VTNA), indicate that aziridination proceeds via a highly electrophilic -pyridinium iminoiodinane intermediate.

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Study Design: Single-institution retrospective financial analysis.

Objective: Trauma care is consistently linked to inadequate reimbursement, posing a significant financial burden for large trauma centers. Data show that declining Medicare reimbursement rates have indirectly led to declining payment for all procedures covered by insurance.

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Aziridines are the smallest nitrogen-containing heterocycles. Strain-enhanced electrophilicity renders aziridines useful synthetic intermediates and gives rise to biological activity. Classical aziridine syntheses─based on either [2 + 1] cycloadditions or intramolecular substitution chemistry─assemble aziridines from acyclic precursors.

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Cellular metabolism plays a role in the observed variability of a drug substance's Critical Quality Attributes (CQAs) made by biomanufacturing processes. Therefore, here we describe a new approach for monitoring biomanufacturing processes that measures a set of metabolic reaction rates (named Critical Metabolic Parameters (CMP) in addition to the macroscopic process conditions currently being used as Critical Process Parameters (CPP) for biomanufacturing. Constraint-based systems biology models like Flux Balance Analysis (FBA) are used to estimate metabolic reaction rates, and metabolic rates are used as inputs for multivariate Batch Evolution Models (BEM).

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Iminoiodinanes comprise a class of hypervalent iodine reagents that is often encountered in nitrogen-group transfer (NGT) catalysis. In general, transition metal catalysts are required to effect efficient NGT to unactivated olefins because iminoiodinanes are insufficiently electrophilic to engage in direct aziridination chemistry. Here, we demonstrate that 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) activates -arylsulfonamide-derived iminoiodinanes for the metal-free aziridination of unactivated olefins.

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Arylamines are common structural motifs in pharmaceuticals, natural products, and materials precursors. While olefin aminofunctionalization chemistry can provide entry to arylamines, classical polar reactions typically afford Markovnikov products. Nitrogen-centered radical intermediates provide the opportunity to access anti-Markovnikov selectivity; however, anti-Markovnikov arylamination is unknown in large part due to the lack of arylamine radical precursors.

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The objective of this study was to examine the association between portal use and end-of-life (EOL) outcomes in the last year of life. A retrospective cohort ( = 6,517) study at Kaiser Permanente Colorado among adults with serious illness deceased between January 1, 2016, and June 30, 2019. Portal use was categorized into engagement types: no use, nonactive, active without a provider, and active with a provider.

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-centered nucleophilicity increases upon alkylation, and thus selective partial alkylation of ammonia and primary amines can be challenging: Poor selectivity and overalkylation are often observed. Here we introduce -aminopyridinium salts as ammonia surrogates for the synthesis of secondary amines via self-limiting alkylation chemistry. Readily available -aryl--aminopyridinium salts engage in -alkylation and depyridylation to afford secondary aryl-alkyl amines without any overalkylation products.

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The association between current use of oral contraceptives (OCs) among women younger than 50 years (n = 306 541), and hormone therapy (HT) among women aged 50 years or older (n = 323 203), and coronavirus 2019 (COVID-19) infection and hospitalization was evaluated in this population-based cohort. Current OC/HT use was recorded monthly using prescription dispensing data. COVID-19 infections were identified from March 2020 through February 2021.

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β-Phenethylamines are widely represented in biologically and pharmacologically active organic small molecules. Here, we introduce N-pyridinium aziridines as latent dual electrophiles for the synthesis of β-phenethylamines. Bromide-promoted ring opening generates β-halopyridinium amines.

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Objective: Rehabilitation for adults with traumatic brain injury (TBI) incorporates client-centred goal-setting and motivational support to achieve goals. However, face-to-face rehabilitation is time-limited. New therapy approaches which leverage care are warranted.

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Synthetic porous materials continue to garner attention as platforms for solid-state chemistry and as designer heterogeneous catalysts. Applications in photochemistry and photocatalysis, however, are plagued by poor light harvesting efficiency due to light scattering resulting from sample microcrystallinity and poor optical penetration that arises from inner filter effects. Here we demonstrate the layer-by-layer growth of optically transparent, photochemically active thin films of porous salts.

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Purpose: Lung cancer screening (LCS) guidelines in the United States recommend LCS for those age 50-80 years with at least 20 pack-years smoking history who currently smoke or quit within the last 15 years. We tested the performance of simple smoking-related criteria derived from electronic health record (EHR) data and developed and tested the performance of a multivariable model in predicting LCS eligibility.

Methods: Analyses were completed within the Population-based Research to Optimize the Screening Process Lung Consortium (PROSPR-Lung).

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C-N bond forming reactions hold immense significance to synthetic organic chemistry. In pursuit of efficient methods for the introduction of nitrogen in organic small molecules, myriad synthetic methods have been developed, and methods based on both nucleophilic and electrophilic aminating reagents have received sustained research effort. In response to continued challenges - the need for substrate prefunctionalization, the requirement for vestigial -activating groups, and the need to incorporate nitrogen in ever more complex molecular settings - the development of novel aminating reagents remains a central challenge in method development.

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Characterization of reactive intermediates in C-H functionalization is challenging due to the fleeting lifetimes of these species. Synthetic photochemistry provides a strategy to generate post-turnover-limiting-step intermediates in catalysis under cryogenic conditions that enable characterization. We have a long-standing interest in the structure and reactivity of Rh nitrene intermediates, which are implicated as transient intermediates in Rh-catalyzed C-H amination.

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ConspectusHypervalent iodine reagents find application as selective chemical oxidants in a diverse array of oxidative transformations. The utility of these reagents is often ascribed to (1) the proclivity to engage being selective two-electron redox transformations; (2) facile ligand exchange at the three-centered, four-electron (3c-4e) hypervalent iodine-ligand (I-X) bonds; and (3) the hypernucleofugacity of aryl iodides. One-electron redox and iodine radical chemistry is well-precedented in the context of inorganic hypervalent iodine chemistry─for example, in the iodide-triiodide couple that drives dye-sensitized solar cells.

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The facial trauma surgeon will see a variety of facial injuries. Recognition of emergency cases and proper intervention is and this article aims to highlight those cases and the respective proper interventions.

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This case series reviews 2 patients worked up and treated for unilateral synovial chondromatosis of the temporomandibular joint (TMJ). The first was a 58-year-old female evaluated and treated for synovial chondromatosis of the left TMJ using an arthrotomy of the joint to remove the cartilaginous and osteocartilaginous nodules. The second is a 63-year-old male who was evaluated and treated for synovial chondromatosis of the right TMJ with the removal of extracapsular masses and an arthrotomy with intra-joint removal of nodules.

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