Publications by authors named "A John Barrett"

2,181 Publications

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Hydrogen/Halogen Exchange of Phosphines for the Rapid Formation of Cyclopolyphosphines.

Inorg Chem 2021 Oct 14. Epub 2021 Oct 14.

Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.

The hydrogen/halogen exchange of phosphines has been exploited to establish a truly useable substrate scope and straightforward methodology for the formation of cyclopolyphosphines. Starting from a single dichlorophosphine, a sacrificial proton "donor phosphine" makes the rapid, mild synthesis of cyclopolyphosphines possible: reactions are complete within 10 min at room temperature. Novel (aryl)cyclopentaphosphines (ArP) have been formed in good conversion, with the crystal structures presented. The use of catalytic quantities of iron(III) acetylacetonate provides significant improvements in conversion in the context of diphosphine (ArP) and alkyl-substituted cyclotetra- or cyclopentaphosphine ((AlkylP), where = 4 or 5) formation. Both iron-free and iron-mediated reactions show high levels of selectivity for one specific ring size. Finally, investigations into the reactivity of Fe(acac) suggest that the iron species is acting as a sink for the hydrochloric acid byproduct of the reaction.
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http://dx.doi.org/10.1021/acs.inorgchem.1c02734DOI Listing
October 2021

Brain Network Dysfunction in Poststroke Delirium and Spatial Neglect: An fMRI Study.

Stroke 2021 Oct 8:STROKEAHA121035733. Epub 2021 Oct 8.

Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Medical Center, Decatur, GA (A.M.B.).

Background And Purpose: Delirium, an acute reduction in cognitive functioning, hinders stroke recovery and contributes to cognitive decline. Right-hemisphere stroke is linked with higher delirium incidence, likely, due to the prevalence of spatial neglect (SN), a right-brain disorder of spatial processing. This study tested if symptoms of delirium and SN after right-hemisphere stroke are associated with abnormal function of the right-dominant neural networks specialized for maintaining attention, orientation, and arousal.

Methods: Twenty-nine participants with right-hemisphere ischemic stroke undergoing acute rehabilitation completed delirium and SN assessments and functional neuroimaging scans. Whole-brain functional connectivity of 4 right-hemisphere seed regions in the cortical-subcortical arousal and attention networks was assessed for its relationship to validated SN and delirium severity measures.

Results: Of 29 patients, 6 (21%) met the diagnostic criteria for delirium and 16 (55%) for SN. Decreased connectivity of the right basal forebrain to brain stem and basal ganglia predicted more severe SN. Increased connectivity of the arousal and attention network regions with the parietal, frontal, and temporal structures in the unaffected hemisphere was also found in more severe delirium and SN.

Conclusions: Delirium and SN are associated with decreased arousal network activity and an imbalance of cortico-subcortical hemispheric connectivity. Better understanding of neural correlates of poststroke delirium and SN will lead to improved neuroscience-based treatment development for these disorders.
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http://dx.doi.org/10.1161/STROKEAHA.121.035733DOI Listing
October 2021

Impact of Delirium on Outcomes After Intracerebral Hemorrhage.

Stroke 2021 Oct 5:STROKEAHA120034023. Epub 2021 Oct 5.

Department of Neurology, Brown University, Alpert Medical School, Providence, RI. (M.E.R., A.M., L.C.W., B.B.T., C.S., L.A.D., R.N.J., K.L.F.).

Background And Purpose: Delirium portends worse outcomes after intracerebral hemorrhage (ICH), but it is unclear if symptom resolution or postacute care intensity may mitigate its impact. We aimed to explore differences in outcome associated with delirium resolution before hospital discharge, as well as the potential mediating role of postacute discharge site.

Methods: We performed a single-center cohort study on consecutive ICH patients over 2 years. Delirium was diagnosed according to DSM-5 criteria and further classified as persistent or resolved based on delirium status at hospital discharge. We determined the impact of delirium on unfavorable 3-month outcome (modified Rankin Scale score, 4-6) using logistic regression models adjusted for established ICH predictors, then used mediation analysis to examine the indirect effect of delirium via postacute discharge site.

Results: Of 590 patients (mean age 70.5±15.5 years, 52% male, 83% White), 59% (n=348) developed delirium during hospitalization. Older age and higher ICH severity were delirium risk factors, but only younger age predicted delirium resolution, which occurred in 75% (161/215) of ICH survivors who had delirium. Delirium was strongly associated with unfavorable outcome, but patients with persistent delirium fared worse (adjusted odds ratio [OR], 7.3 [95% CI, 3.3-16.3]) than those whose delirium resolved (adjusted OR, 3.1 [95% CI, 1.8-5.5]). Patients with delirium were less likely to be discharged to inpatient rehabilitation than skilled nursing facilities (adjusted OR, 0.31 [95% CI, 0.17-0.59]), and postacute care site partially mediated the relationship between delirium and functional outcome in ICH survivors, leading to a 25% reduction in the effect of delirium (without mediator: adjusted OR, 3.0 [95% CI, 1.7-5.6]; with mediator: adjusted OR, 2.3 [95% CI, 1.2-4.3]).

Conclusions: Acute delirium resolves in most patients with ICH by hospital discharge, which was associated with better outcomes than in patients with persistent delirium. The impact of delirium on outcomes may be further mitigated by postacute rehabilitation.
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http://dx.doi.org/10.1161/STROKEAHA.120.034023DOI Listing
October 2021

Decomposing Spectral and Phasic Differences in Nonlinear Features between Datasets.

Phys Rev Lett 2021 Sep;127(12):124101

Department of Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom.

When employing nonlinear methods to characterize complex systems, it is important to determine to what extent they are capturing genuine nonlinear phenomena that could not be assessed by simpler spectral methods. Specifically, we are concerned with the problem of quantifying spectral and phasic effects on an observed difference in a nonlinear feature between two systems (or two states of the same system). Here we derive, from a sequence of null models, a decomposition of the difference in an observable into spectral, phasic, and spectrum-phase interaction components. Our approach makes no assumptions about the structure of the data and adds nuance to a wide range of time series analyses.
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http://dx.doi.org/10.1103/PhysRevLett.127.124101DOI Listing
September 2021

Prism Adaptation Treatment Improves Inpatient Rehabilitation Outcome in Individuals With Spatial Neglect: A Retrospective Matched Control Study.

Arch Rehabil Res Clin Transl 2021 Sep 19;3(3):100130. Epub 2021 May 19.

Department of Neurology, Emory University School of Medicine, Atlanta, GA.

Objective: To determine whether prism adaptation treatment (PAT) integrated into the standard of care improves rehabilitation outcome in patients with spatial neglect (SN).

Design: Retrospective matched control study based on information extracted from June 2017-September 2019.

Setting: Inpatient rehabilitation.

Participants: Patients from 14 rehabilitation hospitals scoring >0 on the Catherine Bergego Scale (N=312). The median age was 69.5 years, including 152 (49%) female patients and 275 (88%) patients with stroke.

Interventions: Patients were matched 1:1 by age (±5 years), FIM score at admission (±2 points), and SN severity using the Catherine Bergego Scale (±2 points) and classified into 2 groups: treated (8-12 daily sessions of PAT) vs untreated (no PAT).

Main Outcome Measures: FIM and its minimal clinically important difference (MCID) were the primary outcome variables. Secondary outcome was home discharge.

Results: Analysis included the 312 matched patients (156 per group). FIM scores at discharge were analyzed using repeated-measures analyses of variance. The treated group showed reliably higher scores than the untreated group in Total FIM, =5.57, =.020, partial η=0.035, and Cognitive FIM, =19.20, <.001, partial η=0.110, but not Motor FIM, =0.35, =.553, partial η 0.002. We used conditional logistic regression to examine the odds ratio of reaching MCID in each FIM score and of returning home after discharge. No reliable difference was found between groups in reaching MCID or home discharge.

Conclusions: Patients with SN receiving PAT had better functional and cognitive outcomes, suggesting that integrating PAT into the standard of care is beneficial. However, receiving PAT may not determine home discharge.
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http://dx.doi.org/10.1016/j.arrct.2021.100130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8463461PMC
September 2021
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