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Evolutionary Map of the Universe (EMU): Observations of Filamentary Structures in the Abell S1136 Galaxy Cluster
- Peter. J. Macgregor, Ray P. Norris, Andrew O’Brien, Mohammad Akhlaghi, Craig Anderson, Jordan D. Collier, Evan J. Crawford, Stefan W. Duchesne, Miroslav D. Filipović, Bärbel S. Koribalski, Florian Pacaud, Thomas H. Reiprich, Christopher J. Riseley, Lawrence Rudnick, Tessa Vernstrom, Andrew. M. Hopkins, Melanie Johnston-Hollitt, Josh Marvil, Matthew Whiting, Steven Tingay
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- Journal:
- Publications of the Astronomical Society of Australia / Accepted manuscript
- Published online by Cambridge University Press:
- 23 May 2024, pp. 1-18
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We present radio observations of the galaxy cluster Abell S1136 at 888 MHz, using the Australian Square Kilometre Array Pathfinder radio telescope, as part of the Evolutionary Map of the Universe Early Science program. We compare these findings with data from the Murchison Widefield Array, XMM-Newton, theWide-field Infrared Survey Explorer, the Digitised Sky Survey, and the Australia Telescope Compact Array. Our analysis shows the X-ray and radio emission in Abell S1136 are closely aligned and centered on the BCG, while the X-ray temperature profile shows a relaxed cluster with no evidence of a cool core. We find that the diffuse radio emission in the centre of the cluster shows more structure than seen in previous low-resolution observations of this source, which appeared formerly as an amorphous radio blob, similar in appearance to a radio halo; our observations show the diffuse emission in the Abell S1136 galaxy cluster contains three narrow filamentary structures visible at 888 MHz, between ∼80 and 140 kpc in length; however the properties of the diffuse emission do not fully match that of a radio (mini-)halo or (fossil) tailed radio source.
Head and Neck Cancer: United Kingdom National Multidisciplinary Guidelines, Sixth Edition
- Jarrod J Homer, Stuart C Winter, Elizabeth C Abbey, Hiba Aga, Reshma Agrawal, Derfel ap Dafydd, Takhar Arunjit, Patrick Axon, Eleanor Aynsley, Izhar N Bagwan, Arun Batra, Donna Begg, Jonathan M Bernstein, Guy Betts, Colin Bicknell, Brian Bisase, Grainne C Brady, Peter Brennan, Aina Brunet, Val Bryant, Linda Cantwell, Ashish Chandra, Preetha Chengot, Melvin L K Chua, Peter Clarke, Gemma Clunie, Margaret Coffey, Clare Conlon, David I Conway, Florence Cook, Matthew R Cooper, Declan Costello, Ben Cosway, Neil J A Cozens, Grant Creaney, Daljit K Gahir, Stephen Damato, Joe Davies, Katharine S Davies, Alina D Dragan, Yong Du, Mark R D Edmond, Stefano Fedele, Harriet Finze, Jason C Fleming, Bernadette H Foran, Beth Fordham, Mohammed M A S Foridi, Lesley Freeman, Katherine E Frew, Pallavi Gaitonde, Victoria Gallyer, Fraser W Gibb, Sinclair M Gore, Mark Gormley, Roganie Govender, J Greedy, Teresa Guerrero Urbano, Dorothy Gujral, David W Hamilton, John C Hardman, Kevin Harrington, Samantha Holmes, Jarrod J Homer, Deborah Howland, Gerald Humphris, Keith D Hunter, Kate Ingarfield, Richard Irving, Kristina Isand, Yatin Jain, Sachin Jauhar, Sarra Jawad, Glyndwr W Jenkins, Anastasios Kanatas, Stephen Keohane, Cyrus J Kerawala, William Keys, Emma V King, Anthony Kong, Fiona Lalloo, Kirsten Laws, Samuel C Leong, Shane Lester, Miles Levy, Ken Lingley, Gitta Madani, Navin Mani, Paolo L Matteucci, Catriona R Mayland, James McCaul, Lorna K McCaul, Pádraig McDonnell, Andrew McPartlin, Valeria Mercadante, Zoe Merchant, Radu Mihai, Mufaddal T Moonim, John Moore, Paul Nankivell, Sonali Natu, A Nelson, Pablo Nenclares, Kate Newbold, Carrie Newland, Ailsa J Nicol, Iain J Nixon, Rupert Obholzer, James T O'Hara, S Orr, Vinidh Paleri, James Palmer, Rachel S Parry, Claire Paterson, Gillian Patterson, Joanne M Patterson, Miranda Payne, L Pearson, David N Poller, Jonathan Pollock, Stephen Ross Porter, Matthew Potter, Robin J D Prestwich, Ruth Price, Mani Ragbir, Meena S Ranka, Max Robinson, Justin W G Roe, Tom Roques, Aleix Rovira, Sajid Sainuddin, I J Salmon, Ann Sandison, Andy Scarsbrook, Andrew G Schache, A Scott, Diane Sellstrom, Cherith J Semple, Jagrit Shah, Praveen Sharma, Richard J Shaw, Somiah Siddiq, Priyamal Silva, Ricard Simo, Rabin P Singh, Maria Smith, Rebekah Smith, Toby Oliver Smith, Sanjai Sood, Francis W Stafford, Neil Steven, Kay Stewart, Lisa Stoner, Steve Sweeney, Andrew Sykes, Carly L Taylor, Selvam Thavaraj, David J Thomson, Jane Thornton, Neil S Tolley, Nancy Turnbull, Sriram Vaidyanathan, Leandros Vassiliou, John Waas, Kelly Wade-McBane, Donna Wakefield, Amy Ward, Laura Warner, Laura-Jayne Watson, H Watts, Christina Wilson, Stuart C Winter, Winson Wong, Chui-Yan Yip, Kent Yip
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- Journal:
- The Journal of Laryngology & Otology / Volume 138 / Issue S1 / April 2024
- Published online by Cambridge University Press:
- 14 March 2024, pp. S1-S224
- Print publication:
- April 2024
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53 2-Back Performance Does Not Differ Between Cognitive Training Groups in Older Adults Without Dementia
- Nicole D Evangelista, Jessica N Kraft, Hanna K Hausman, Andrew O’Shea, Alejandro Albizu, Emanuel M Boutzoukas, Cheshire Hardcastle, Emily J Van Etten, Pradyumna K Bharadwaj, Hyun Song, Samantha G Smith, Steven DeKosky, Georg A Hishaw, Samuel Wu, Michael Marsiske, Ronald Cohen, Gene E Alexander, Eric Porges, Adam J Woods
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 360-361
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Objective:
Cognitive training is a non-pharmacological intervention aimed at improving cognitive function across a single or multiple domains. Although the underlying mechanisms of cognitive training and transfer effects are not well-characterized, cognitive training has been thought to facilitate neural plasticity to enhance cognitive performance. Indeed, the Scaffolding Theory of Aging and Cognition (STAC) proposes that cognitive training may enhance the ability to engage in compensatory scaffolding to meet task demands and maintain cognitive performance. We therefore evaluated the effects of cognitive training on working memory performance in older adults without dementia. This study will help begin to elucidate non-pharmacological intervention effects on compensatory scaffolding in older adults.
Participants and Methods:48 participants were recruited for a Phase III randomized clinical trial (Augmenting Cognitive Training in Older Adults [ACT]; NIH R01AG054077) conducted at the University of Florida and University of Arizona. Participants across sites were randomly assigned to complete cognitive training (n=25) or an education training control condition (n=23). Cognitive training and the education training control condition were each completed during 60 sessions over 12 weeks for 40 hours total. The education training control condition involved viewing educational videos produced by the National Geographic Channel. Cognitive training was completed using the Posit Science Brain HQ training program, which included 8 cognitive training paradigms targeting attention/processing speed and working memory. All participants also completed demographic questionnaires, cognitive testing, and an fMRI 2-back task at baseline and at 12-weeks following cognitive training.
Results:Repeated measures analysis of covariance (ANCOVA), adjusted for training adherence, transcranial direct current stimulation (tDCS) condition, age, sex, years of education, and Wechsler Test of Adult Reading (WTAR) raw score, revealed a significant 2-back by training group interaction (F[1,40]=6.201, p=.017, η2=.134). Examination of simple main effects revealed baseline differences in 2-back performance (F[1,40]=.568, p=.455, η2=.014). After controlling for baseline performance, training group differences in 2-back performance was no longer statistically significant (F[1,40]=1.382, p=.247, η2=.034).
Conclusions:After adjusting for baseline performance differences, there were no significant training group differences in 2-back performance, suggesting that the randomization was not sufficient to ensure adequate distribution of participants across groups. Results may indicate that cognitive training alone is not sufficient for significant improvement in working memory performance on a near transfer task. Additional improvement may occur with the next phase of this clinical trial, such that tDCS augments the effects of cognitive training and results in enhanced compensatory scaffolding even within this high performing cohort. Limitations of the study include a highly educated sample with higher literacy levels and the small sample size was not powered for transfer effects analysis. Future analyses will include evaluation of the combined intervention effects of a cognitive training and tDCS on nback performance in a larger sample of older adults without dementia.
2 Higher White Matter Hyperintensity Load Adversely Affects Pre-Post Proximal Cognitive Training Performance in Healthy Older Adults
- Emanuel M Boutzoukas, Andrew O’Shea, Jessica N Kraft, Cheshire Hardcastle, Nicole D Evangelista, Hanna K Hausman, Alejandro Albizu, Emily J Van Etten, Pradyumna K Bharadwaj, Samantha G Smith, Hyun Song, Eric C Porges, Alex Hishaw, Steven T DeKosky, Samuel S Wu, Michael Marsiske, Gene E Alexander, Ronald Cohen, Adam J Woods
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 671-672
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Objective:
Cognitive training has shown promise for improving cognition in older adults. Aging involves a variety of neuroanatomical changes that may affect response to cognitive training. White matter hyperintensities (WMH) are one common age-related brain change, as evidenced by T2-weighted and Fluid Attenuated Inversion Recovery (FLAIR) MRI. WMH are associated with older age, suggestive of cerebral small vessel disease, and reflect decreased white matter integrity. Higher WMH load associates with reduced threshold for clinical expression of cognitive impairment and dementia. The effects of WMH on response to cognitive training interventions are relatively unknown. The current study assessed (a) proximal cognitive training performance following a 3-month randomized control trial and (b) the contribution of baseline whole-brain WMH load, defined as total lesion volume (TLV), on pre-post proximal training change.
Participants and Methods:Sixty-two healthy older adults ages 65-84 completed either adaptive cognitive training (CT; n=31) or educational training control (ET; n=31) interventions. Participants assigned to CT completed 20 hours of attention/processing speed training and 20 hours of working memory training delivered through commercially-available Posit Science BrainHQ. ET participants completed 40 hours of educational videos. All participants also underwent sham or active transcranial direct current stimulation (tDCS) as an adjunctive intervention, although not a variable of interest in the current study. Multimodal MRI scans were acquired during the baseline visit. T1- and T2-weighted FLAIR images were processed using the Lesion Segmentation Tool (LST) for SPM12. The Lesion Prediction Algorithm of LST automatically segmented brain tissue and calculated lesion maps. A lesion threshold of 0.30 was applied to calculate TLV. A log transformation was applied to TLV to normalize the distribution of WMH. Repeated-measures analysis of covariance (RM-ANCOVA) assessed pre/post change in proximal composite (Total Training Composite) and sub-composite (Processing Speed Training Composite, Working Memory Training Composite) measures in the CT group compared to their ET counterparts, controlling for age, sex, years of education and tDCS group. Linear regression assessed the effect of TLV on post-intervention proximal composite and sub-composite, controlling for baseline performance, intervention assignment, age, sex, years of education, multisite scanner differences, estimated total intracranial volume, and binarized cardiovascular disease risk.
Results:RM-ANCOVA revealed two-way group*time interactions such that those assigned cognitive training demonstrated greater improvement on proximal composite (Total Training Composite) and sub-composite (Processing Speed Training Composite, Working Memory Training Composite) measures compared to their ET counterparts. Multiple linear regression showed higher baseline TLV associated with lower pre-post change on Processing Speed Training sub-composite (ß = -0.19, p = 0.04) but not other composite measures.
Conclusions:These findings demonstrate the utility of cognitive training for improving postintervention proximal performance in older adults. Additionally, pre-post proximal processing speed training change appear to be particularly sensitive to white matter hyperintensity load versus working memory training change. These data suggest that TLV may serve as an important factor for consideration when planning processing speed-based cognitive training interventions for remediation of cognitive decline in older adults.
1 Task-Based Functional Connectivity and Network Segregation of the Useful Field of View (UFOV) fMRI task
- Jessica N Kraft, Hanna K Hausman, Cheshire Hardcastle, Alejandro Albizu, Andrew O’Shea, Nicole D Evangelista, Emanuel M Boutzoukas, Emily J Van Etten, Pradyumna K Bharadwaj, Hyun Song, Samantha G Smith, Steven T DeKosky, Georg A Hishaw, Samuel Wu, Michael Marsiske, Ronald Cohen, Eric Porges, Adam J Woods
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 606-607
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Objective:
Interventions using a cognitive training paradigm called the Useful Field of View (UFOV) task have shown to be efficacious in slowing cognitive decline. However, no studies have looked at the engagement of functional networks during UFOV task completion. The current study aimed to (a) assess if regions activated during the UFOV fMRI task were functionally connected and related to task performance (henceforth called the UFOV network), (b) compare connectivity of the UFOV network to 7 resting-state functional connectivity networks in predicting proximal (UFOV) and near-transfer (Double Decision) performance, and (c) explore the impact of network segregation between higher-order networks and UFOV performance.
Participants and Methods:336 healthy older adults (mean age=71.6) completed the UFOV fMRI task in a Siemens 3T scanner. UFOV fMRI accuracy was calculated as the number of correct responses divided by 56 total trials. Double Decision performance was calculated as the average presentation time of correct responses in log ms, with lower scores equating to better processing speed. Structural and functional MRI images were processed using the default pre-processing pipeline within the CONN toolbox. The Artifact Rejection Toolbox was set at a motion threshold of 0.9mm and participants were excluded if more than 50% of volumes were flagged as outliers. To assess connectivity of regions associated with the UFOV task, we created 10 spherical regions of interest (ROIs) a priori using the WFU PickAtlas in SPM12. These include the bilateral pars triangularis, supplementary motor area, and inferior temporal gyri, as well as the left pars opercularis, left middle occipital gyrus, right precentral gyrus and right superior parietal lobule. We used a weighted ROI-to-ROI connectivity analysis to model task-based within-network functional connectivity of the UFOV network, and its relationship to UFOV accuracy. We then used weighted ROI-to-ROI connectivity analysis to compare the efficacy of the UFOV network versus 7 resting-state networks in predicting UFOV fMRI task performance and Double Decision performance. Finally, we calculated network segregation among higher order resting state networks to assess its relationship with UFOV accuracy. All functional connectivity analyses were corrected at a false discovery threshold (FDR) at p<0.05.
Results:ROI-to-ROI analysis showed significant within-network functional connectivity among the 10 a priori ROIs (UFOV network) during task completion (all pFDR<.05). After controlling for covariates, greater within-network connectivity of the UFOV network associated with better UFOV fMRI performance (pFDR=.008). Regarding the 7 resting-state networks, greater within-network connectivity of the CON (pFDR<.001) and FPCN (pFDR=. 014) were associated with higher accuracy on the UFOV fMRI task. Furthermore, greater within-network connectivity of only the UFOV network associated with performance on the Double Decision task (pFDR=.034). Finally, we assessed the relationship between higher-order network segregation and UFOV accuracy. After controlling for covariates, no significant relationships between network segregation and UFOV performance remained (all p-uncorrected>0.05).
Conclusions:To date, this is the first study to assess task-based functional connectivity during completion of the UFOV task. We observed that coherence within 10 a priori ROIs significantly predicted UFOV performance. Additionally, enhanced within-network connectivity of the UFOV network predicted better performance on the Double Decision task, while conventional resting-state networks did not. These findings provide potential targets to optimize efficacy of UFOV interventions.
78 BVMT-R Learning Ratio Moderates Cognitive Training Gains in Useful Field of View Task in Healthy Older Adults
- Cheshire Hardcastle, Jessica N. Kraft, Hanna K. Hausman, Andrew O’Shea, Alejandro Albizu, Nicole D. Evangelista, Emanuel Boutzoukas, Emily J. Van Etten, Pradyumna K. Bharadwaj, Hyun Song, Samantha G. Smith, Eric Porges, Steven DeKosky, Georg A. Hishaw, Samuel Wu, Michael Marsiske, Ronald Cohen, Gene E. Alexander, Adam J. Woods
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 180-181
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Objective:
Cognitive training using a visual speed-of-processing task, called the Useful Field of View (UFOV) task, reduced dementia risk and reduced decline in activities of daily living at a 10-year follow-up in older adults. However, there is variability in the level of cognitive gains after cognitive training across studies. One potential explanation for this variability could be moderating factors. Prior studies suggest variables moderating cognitive training gains share features of the training task. Learning trials of the Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R) recruit similar cognitive abilities and have overlapping neural correlates with the UFOV task and speed-ofprocessing/working memory tasks and therefore could serve as potential moderators. Exploring moderating factors of cognitive training gains may boost the efficacy of interventions, improve rigor in the cognitive training literature, and eventually help provide tailored treatment recommendations. This study explored the association between the HVLT-R and BVMT-R learning and the UFOV task, and assessed the moderation of HVLT-R and BVMT-R learning on UFOV improvement after a 3-month speed-ofprocessing/attention and working memory cognitive training intervention in cognitively healthy older adults.
Participants and Methods:75 healthy older adults (M age = 71.11, SD = 4.61) were recruited as part of a larger clinical trial through the Universities of Florida and Arizona. Participants were randomized into a cognitive training (n=36) or education control (n=39) group and underwent a 40-hour, 12-week intervention. Cognitive training intervention consisted of practicing 4 attention/speed-of-processing (including the UFOV task) and 4 working memory tasks. Education control intervention consisted of watching 40-minute educational videos. The HVLT-R and BVMT-R were administered at the pre-intervention timepoint as part of a larger neurocognitive battery. The learning ratio was calculated as: trial 3 total - trial 1 total/12 - trial 1 total. UFOV performance was measured at pre- and post-intervention time points via the POSIT Brain HQ Double Decision Assessment. Multiple linear regressions predicted baseline Double Decision performance from HVLT-R and BVMT-R learning ratios controlling for study site, age, sex, and education. A repeated measures moderation analysis assessed the moderation of HVLT-R and BVMT-R learning ratio on Double Decision change from pre- to post-intervention for cognitive training and education control groups.
Results:Baseline Double Decision performance significantly associated with BVMT-R learning ratio (β=-.303, p=.008), but not HVLT-R learning ratio (β=-.142, p=.238). BVMT-R learning ratio moderated gains in Double Decision performance (p<.01); for each unit increase in BVMT-R learning ratio, there was a .6173 unit decrease in training gains. The HVLT-R learning ratio did not moderate gains in Double Decision performance (p>.05). There were no significant moderations in the education control group.
Conclusions:Better visuospatial learning was associated with faster Double Decision performance at baseline. Those with poorer visuospatial learning improved most on the Double Decision task after training, suggesting that healthy older adults who perform below expectations may show the greatest training gains. Future cognitive training research studying visual speed-of-processing interventions should account for differing levels of visuospatial learning at baseline, as this could impact the magnitude of training outcomes.
6 Adjunctive Transcranial Direct Current Stimulation and Cognitive Training Alters Default Mode and Frontoparietal Control Network Connectivity in Older Adults
- Hanna K Hausman, Jessica N Kraft, Cheshire Hardcastle, Nicole D Evangelista, Emanuel M Boutzoukas, Andrew O’Shea, Alejandro Albizu, Emily J Van Etten, Pradyumna K Bharadwaj, Hyun Song, Samantha G Smith, Eric S Porges, Georg A Hishaw, Samuel Wu, Steven DeKosky, Gene E Alexander, Michael Marsiske, Ronald A Cohen, Adam J Woods
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 675-676
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Aging is associated with disruptions in functional connectivity within the default mode (DMN), frontoparietal control (FPCN), and cingulo-opercular (CON) resting-state networks. Greater within-network connectivity predicts better cognitive performance in older adults. Therefore, strengthening network connectivity, through targeted intervention strategies, may help prevent age-related cognitive decline or progression to dementia. Small studies have demonstrated synergistic effects of combining transcranial direct current stimulation (tDCS) and cognitive training (CT) on strengthening network connectivity; however, this association has yet to be rigorously tested on a large scale. The current study leverages longitudinal data from the first-ever Phase III clinical trial for tDCS to examine the efficacy of an adjunctive tDCS and CT intervention on modulating network connectivity in older adults.
Participants and Methods:This sample included 209 older adults (mean age = 71.6) from the Augmenting Cognitive Training in Older Adults multisite trial. Participants completed 40 hours of CT over 12 weeks, which included 8 attention, processing speed, and working memory tasks. Participants were randomized into active or sham stimulation groups, and tDCS was administered during CT daily for two weeks then weekly for 10 weeks. For both stimulation groups, two electrodes in saline-soaked 5x7 cm2 sponges were placed at F3 (cathode) and F4 (anode) using the 10-20 measurement system. The active group received 2mA of current for 20 minutes. The sham group received 2mA for 30 seconds, then no current for the remaining 20 minutes.
Participants underwent resting-state fMRI at baseline and post-intervention. CONN toolbox was used to preprocess imaging data and conduct region of interest (ROI-ROI) connectivity analyses. The Artifact Detection Toolbox, using intermediate settings, identified outlier volumes. Two participants were excluded for having greater than 50% of volumes flagged as outliers. ROI-ROI analyses modeled the interaction between tDCS group (active versus sham) and occasion (baseline connectivity versus postintervention connectivity) for the DMN, FPCN, and CON controlling for age, sex, education, site, and adherence.
Results:Compared to sham, the active group demonstrated ROI-ROI increases in functional connectivity within the DMN following intervention (left temporal to right temporal [T(202) = 2.78, pFDR < 0.05] and left temporal to right dorsal medial prefrontal cortex [T(202) = 2.74, pFDR < 0.05]. In contrast, compared to sham, the active group demonstrated ROI-ROI decreases in functional connectivity within the FPCN following intervention (left dorsal prefrontal cortex to left temporal [T(202) = -2.96, pFDR < 0.05] and left dorsal prefrontal cortex to left lateral prefrontal cortex [T(202) = -2.77, pFDR < 0.05]). There were no significant interactions detected for CON regions.
Conclusions:These findings (a) demonstrate the feasibility of modulating network connectivity using tDCS and CT and (b) provide important information regarding the pattern of connectivity changes occurring at these intervention parameters in older adults. Importantly, the active stimulation group showed increases in connectivity within the DMN (a network particularly vulnerable to aging and implicated in Alzheimer’s disease) but decreases in connectivity between left frontal and temporal FPCN regions. Future analyses from this trial will evaluate the association between these changes in connectivity and cognitive performance post-intervention and at a one-year timepoint.
9 Connecting memory and functional brain networks in older adults: a resting state fMRI study
- Jori L Waner, Hanna K Hausman, Jessica N Kraft, Cheshire Hardcastle, Nicole D Evangelista, Andrew O’Shea, Alejandro Albizu, Emanuel M Boutzoukas, Emily J Van Etten, Pradyumna K Bharadwaj, Hyun Song, Samantha G Smith, Steven T DeKosky, Georg A Hishaw, Samuel S Wu, Michael Marsiske, Ronald Cohen, Gene E Alexander, Eric C Porges, Adam J Woods
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- Journal:
- Journal of the International Neuropsychological Society / Volume 29 / Issue s1 / November 2023
- Published online by Cambridge University Press:
- 21 December 2023, pp. 527-528
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Objective:
Nonpathological aging has been linked to decline in both verbal and visuospatial memory abilities in older adults. Disruptions in resting-state functional connectivity within well-characterized, higherorder cognitive brain networks have also been coupled with poorer memory functioning in healthy older adults and in older adults with dementia. However, there is a paucity of research on the association between higherorder functional connectivity and verbal and visuospatial memory performance in the older adult population. The current study examines the association between resting-state functional connectivity within the cingulo-opercular network (CON), frontoparietal control network (FPCN), and default mode network (DMN) and verbal and visuospatial learning and memory in a large sample of healthy older adults. We hypothesized that greater within-network CON and FPCN functional connectivity would be associated with better immediate verbal and visuospatial memory recall. Additionally, we predicted that within-network DMN functional connectivity would be associated with improvements in delayed verbal and visuospatial memory recall. This study helps to glean insight into whether within-network CON, FPCN, or DMN functional connectivity is associated with verbal and visuospatial memory abilities in later life.
Participants and Methods:330 healthy older adults between 65 and 89 years old (mean age = 71.6 ± 5.2) were recruited at the University of Florida (n = 222) and the University of Arizona (n = 108). Participants underwent resting-state fMRI and completed verbal memory (Hopkins Verbal Learning Test - Revised [HVLT-R]) and visuospatial memory (Brief Visuospatial Memory Test - Revised [BVMT-R]) measures. Immediate (total) and delayed recall scores on the HVLT-R and BVMT-R were calculated using each test manual’s scoring criteria. Learning ratios on the HVLT-R and BVMT-R were quantified by dividing the number of stimuli (verbal or visuospatial) learned between the first and third trials by the number of stimuli not recalled after the first learning trial. CONN Toolbox was used to extract average within-network connectivity values for CON, FPCN, and DMN. Hierarchical regressions were conducted, controlling for sex, race, ethnicity, years of education, number of invalid scans, and scanner site.
Results:Greater CON connectivity was significantly associated with better HVLT-R immediate (total) recall (ß = 0.16, p = 0.01), HVLT-R learning ratio (ß = 0.16, p = 0.01), BVMT-R immediate (total) recall (ß = 0.14, p = 0.02), and BVMT-R delayed recall performance (ß = 0.15, p = 0.01). Greater FPCN connectivity was associated with better BVMT-R learning ratio (ß = 0.13, p = 0.04). HVLT-R delayed recall performance was not associated with connectivity in any network, and DMN connectivity was not significantly related to any measure.
Conclusions:Connectivity within CON demonstrated a robust relationship with different components of memory function as well across verbal and visuospatial domains. In contrast, FPCN only evidenced a relationship with visuospatial learning, and DMN was not significantly associated with memory measures. These data suggest that CON may be a valuable target in longitudinal studies of age-related memory changes, but also a possible target in future non-invasive interventions to attenuate memory decline in older adults.
Agricultural Research Service Weed Science Research: Past, Present, and Future
- Stephen L. Young, James V. Anderson, Scott R. Baerson, Joanna Bajsa-Hirschel, Dana M. Blumenthal, Chad S. Boyd, Clyde D. Boyette, Eric B. Brennan, Charles L. Cantrell, Wun S. Chao, Joanne C. Chee-Sanford, Charlie D. Clements, F. Allen Dray, Stephen O. Duke, Kayla M. Eason, Reginald S. Fletcher, Michael R. Fulcher, John F. Gaskin, Brenda J. Grewell, Erik P. Hamerlynck, Robert E. Hoagland, David P. Horvath, Eugene P. Law, John D. Madsen, Daniel E. Martin, Clint Mattox, Steven B. Mirsky, William T. Molin, Patrick J. Moran, Rebecca C. Mueller, Vijay K. Nandula, Beth A. Newingham, Zhiqiang Pan, Lauren M. Porensky, Paul D. Pratt, Andrew J. Price, Brian G. Rector, Krishna N. Reddy, Roger L. Sheley, Lincoln Smith, Melissa C. Smith, Keirith A. Snyder, Matthew A. Tancos, Natalie M. West, Gregory S. Wheeler, Martin M. Williams, Julie Wolf, Carissa L. Wonkka, Alice A. Wright, Jing Xi, Lew H. Ziska
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- Journal:
- Weed Science / Volume 71 / Issue 4 / July 2023
- Published online by Cambridge University Press:
- 16 August 2023, pp. 312-327
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The U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) has been a leader in weed science research covering topics ranging from the development and use of integrated weed management (IWM) tactics to basic mechanistic studies, including biotic resistance of desirable plant communities and herbicide resistance. ARS weed scientists have worked in agricultural and natural ecosystems, including agronomic and horticultural crops, pastures, forests, wild lands, aquatic habitats, wetlands, and riparian areas. Through strong partnerships with academia, state agencies, private industry, and numerous federal programs, ARS weed scientists have made contributions to discoveries in the newest fields of robotics and genetics, as well as the traditional and fundamental subjects of weed–crop competition and physiology and integration of weed control tactics and practices. Weed science at ARS is often overshadowed by other research topics; thus, few are aware of the long history of ARS weed science and its important contributions. This review is the result of a symposium held at the Weed Science Society of America’s 62nd Annual Meeting in 2022 that included 10 separate presentations in a virtual Weed Science Webinar Series. The overarching themes of management tactics (IWM, biological control, and automation), basic mechanisms (competition, invasive plant genetics, and herbicide resistance), and ecosystem impacts (invasive plant spread, climate change, conservation, and restoration) represent core ARS weed science research that is dynamic and efficacious and has been a significant component of the agency’s national and international efforts. This review highlights current studies and future directions that exemplify the science and collaborative relationships both within and outside ARS. Given the constraints of weeds and invasive plants on all aspects of food, feed, and fiber systems, there is an acknowledged need to face new challenges, including agriculture and natural resources sustainability, economic resilience and reliability, and societal health and well-being.
Cerebrospinal fluid neurofilament light predicts longitudinal diagnostic change in patients with psychiatric and neurodegenerative disorders
- Matthew J. Y. Kang, Dhamidhu Eratne, Hannah Dobson, Charles B. Malpas, Michael Keem, Courtney Lewis, Jasleen Grewal, Vivian Tsoukra, Christa Dang, Ramon Mocellin, Tomas Kalincik, Alexander F. Santillo, Henrik Zetterberg, Kaj Blennow, Christiane Stehmann, Shiji Varghese, Qiao-Xin Li, Colin L. Masters, Steven Collins, Samuel F. Berkovic, Andrew Evans, Wendy Kelso, Sarah Farrand, Samantha M. Loi, Mark Walterfang, Dennis Velakoulis
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- Journal:
- Acta Neuropsychiatrica / Volume 36 / Issue 1 / February 2024
- Published online by Cambridge University Press:
- 28 April 2023, pp. 17-28
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Objective:
People with neuropsychiatric symptoms often experience delay in accurate diagnosis. Although cerebrospinal fluid neurofilament light (CSF NfL) shows promise in distinguishing neurodegenerative disorders (ND) from psychiatric disorders (PSY), its accuracy in a diagnostically challenging cohort longitudinally is unknown.
Methods:We collected longitudinal diagnostic information (mean = 36 months) from patients assessed at a neuropsychiatry service, categorising diagnoses as ND/mild cognitive impairment/other neurological disorders (ND/MCI/other) and PSY. We pre-specified NfL > 582 pg/mL as indicative of ND/MCI/other.
Results:Diagnostic category changed from initial to final diagnosis for 23% (49/212) of patients. NfL predicted the final diagnostic category for 92% (22/24) of these and predicted final diagnostic category overall (ND/MCI/other vs. PSY) in 88% (187/212), compared to 77% (163/212) with clinical assessment alone.
Conclusions:CSF NfL improved diagnostic accuracy, with potential to have led to earlier, accurate diagnosis in a real-world setting using a pre-specified cut-off, adding weight to translation of NfL into clinical practice.
Development of the Residual Lesion Score for congenital heart surgery: the RAND Delphi methodology
- Meena Nathan, Jane W. Newburger, Margaret Bell, Alexander Tang, Russell Gongwer, Carolyn Dunbar-Masterson, Andrew M. Atz, Emile Bacha, Steven Colan, J. William Gaynor, Kirk Kanter, Jami C. Levine, Richard Ohye, Christian Pizarro, Steven Schwartz, Girish Shirali, Lloyd Tani, James Tweddell, Michelle Gurvitz, for the Pediatric Heart Network Investigators
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- Journal:
- Cardiology in the Young / Volume 33 / Issue 6 / June 2023
- Published online by Cambridge University Press:
- 23 December 2022, pp. 977-990
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Background and Objective:
The Residual Lesion Score is a novel tool for assessing the achievement of surgical objectives in congenital heart surgery based on widely available clinical and echocardiographic characteristics. This article describes the methodology used to develop the Residual Lesion Score from the previously developed Technical Performance Score for five common congenital cardiac procedures using the RAND Delphi methodology.
Methods:A panel of 11 experts from the field of paediatric and congenital cardiology and cardiac surgery, 2 co-chairs, and a consultant were assembled to review and comment on validity and feasibility of measuring the sub-components of intraoperative and discharge Residual Lesion Score for five congenital cardiac procedures. In the first email round, the panel reviewed and commented on the Residual Lesion Score and provided validity and feasibility scores for sub-components of each of the five procedures. In the second in-person round, email comments and scores were reviewed and the Residual Lesion Score revised. The modified Residual Lesion Score was scored independently by each panellist for validity and feasibility and used to develop the “final” Residual Lesion Score.
Results:The Residual Lesion Score sub-components with a median validity score of ≥7 and median feasibility score of ≥4 that were scored without disagreement and with low absolute deviation from the median were included in the “final” Residual Lesion Score.
Conclusion:Using the RAND Delphi methodology, we were able to develop Residual Lesion Score modules for five important congenital cardiac procedures for the Pediatric Heart Network’s Residual Lesion Score study.
Texture and strain analysis of tungsten films via Tilt-A-Whirl methodology
- Mark A. Rodriguez, Jamin Pillars, Nichole R. Valdez, James J. M. Griego, Matthew V. Gallegos, John A. Krukar, Andrew Polonsky, Steven L. Wolfley
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- Journal:
- Powder Diffraction / Volume 37 / Issue 2 / June 2022
- Published online by Cambridge University Press:
- 01 August 2022, pp. 52-61
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Tungsten (W) films have many applications in the semiconducting industry for sensor technology. Deposition conditions can significantly impact the resulting W films in terms of the phases present (α-BCC or β-A12), microstructural grain orientation (texture), and residual strain. Tilt-A-Whirl methodology has been employed for the evaluation of a W film showing both texture and residual strain. Sin2(ψ) analysis of the film was performed to quantify the strongly tensile in-plane strain (+0.476%) with an estimated in-plane tensile stress of ~1.9 GPa. The 3D dataset was also evaluated qualitatively via 3D visualization. Visualization of 3D texture/strain data poses challenges due to peak broadening resulting from defocusing of the beam at high ψ tilt angles. To address this issue, principal component analysis (PCA) was employed to diagnose, model, and remove the broadening component from the diffraction data. Evaluation of the raw data and subsequent corrected data (after removal of defocusing effects) has been performed through projection of the data into a virtual 3D environment (via CAD2VR software) to qualitatively detect the impact of residual strain on the observed pole figure.
Microstructural Study of Organic Mixed Ionic-Electronic Conductor Thin Films Using 4D-STEM and HRTEM
- Yael Tsarfati, Karen C. Bustillo, Luke Balhorn, Tyler J. Quill, Jennifer Donohue, Steven E. Zeltmann, Benjamin Savitzky, Colin Ophus, Christopher J. Takacs, Iain McCulloch, Andrew M. Minor, Alberto Salleo
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- Journal:
- Microscopy and Microanalysis / Volume 28 / Issue S1 / August 2022
- Published online by Cambridge University Press:
- 22 July 2022, pp. 350-351
- Print publication:
- August 2022
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12 - Reform of the Scottish Floating Charge
- Edited by Jonathan Hardman, University of Glasgow, Alisdair MacPherson
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- Floating Charges in Scotland
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- Edinburgh University Press
- Published online:
- 18 November 2022
- Print publication:
- 30 June 2022, pp 473-509
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Summary
A. INTRODUCTION
B. PREVIOUS REFORM ATTEMPTS
(1) General
(2) Failed expansionism: the Murray Report
(3) Failed revisionism: the Bankruptcy and Diligence etc. (Scotland) Act 2007 Part 2
C. THE SLC MOVEABLE TRANSACTIONS PROJECT
(1) Beginnings
(2) Discussion paper
(3) Consultation
(4) Report
D. REFORM OF ENGLISH LAW
(1) Impetuses
(2) City of London Law Society
(3) Secured Transactions Law Reform Project
E. FUTURE REFORM IN SCOTLAND
(1) Introduction
(2) UK PPSA
(3) UK Secured Transactions Code
(4) Insolvency law (plus?) reform
(5) Reform leading to single security rights in England and Scotland
F. CONCLUSION
A. INTRODUCTION
In MacMillan v T Leith Developments Ltd (in receivership and liquidation), towards the end of his judgment, Lord Drummond Young states:
‘The introduction of the floating charge into Scots law, and subsequently the concept of receivership, have created significant practical problems. A large part of the difficulty has, I think, been an attempt to reproduce concepts of English equity in a legal system that has no similar institution … It is difficult to translate the institutions of English equity into another legal system, especially one based on the more rigorous conceptual structure of Roman law, as is the case with Scots law and most other European legal systems other than English law.’
He goes on to say that the solution to the difficulty is reform, citing in particular the Scottish Law Commission's work on moveable transactions. I declare an interest here as the lead commissioner responsible for the report on that subject, which was published in 2017. That role reinforced to me the persistent difficulties of achieving reform in this area and in the law of security over moveable property more generally. As shall be seen, a similar pattern has been observable south of the Scottish border. To a certain extent this is unsurprising given the commonality of the law in relation to floating charges, their source, of course, being English law.
This chapter focuses with some tentativeness on future prospects. It begins by trying to learn lessons from the past. Part B looks relatively briefly at previous attempts to reform floating charge law in Scotland that proved unsuccessful. There is particular emphasis on the Murray Report and Part 2 of the Bankruptcy and Diligence etc. (Scotland) Act 2007 (the 2007 Act). Part C then considers the moveable transactions project. At the time of writing there is reasonable confidence that its recommendations will lead to legislation, although progress has been hindered by the COVID-19 pandemic. Part D examines the reform debate in England and Wales. A significant aspect of that is the move by other common law legal systems to a functional approach to security rights over moveable property as exemplified by art. 9 of the Uniform Commercial Code (UCC) of the USA and ‘The introduction of the floating charge into Scots law, and subsequently the concept of receivership, have created significant practical problems.
The Hierarchical Taxonomy of Psychopathology (HiTOP) in psychiatric practice and research
- Roman Kotov, David C. Cicero, Christopher C. Conway, Colin G. DeYoung, Alexandre Dombrovski, Nicholas R. Eaton, Michael B. First, Miriam K. Forbes, Steven E. Hyman, Katherine G. Jonas, Robert F. Krueger, Robert D. Latzman, James J. Li, Brady D. Nelson, Darrel A. Regier, Craig Rodriguez-Seijas, Camilo J. Ruggero, Leonard J. Simms, Andrew E. Skodol, Irwin D. Waldman, Monika A. Waszczuk, David Watson, Thomas A. Widiger, Sylia Wilson, Aidan G. C. Wright
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- Journal:
- Psychological Medicine / Volume 52 / Issue 9 / July 2022
- Published online by Cambridge University Press:
- 02 June 2022, pp. 1666-1678
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The Hierarchical Taxonomy of Psychopathology (HiTOP) has emerged out of the quantitative approach to psychiatric nosology. This approach identifies psychopathology constructs based on patterns of co-variation among signs and symptoms. The initial HiTOP model, which was published in 2017, is based on a large literature that spans decades of research. HiTOP is a living model that undergoes revision as new data become available. Here we discuss advantages and practical considerations of using this system in psychiatric practice and research. We especially highlight limitations of HiTOP and ongoing efforts to address them. We describe differences and similarities between HiTOP and existing diagnostic systems. Next, we review the types of evidence that informed development of HiTOP, including populations in which it has been studied and data on its validity. The paper also describes how HiTOP can facilitate research on genetic and environmental causes of psychopathology as well as the search for neurobiologic mechanisms and novel treatments. Furthermore, we consider implications for public health programs and prevention of mental disorders. We also review data on clinical utility and illustrate clinical application of HiTOP. Importantly, the model is based on measures and practices that are already used widely in clinical settings. HiTOP offers a way to organize and formalize these techniques. This model already can contribute to progress in psychiatry and complement traditional nosologies. Moreover, HiTOP seeks to facilitate research on linkages between phenotypes and biological processes, which may enable construction of a system that encompasses both biomarkers and precise clinical description.
Respiratory viral infections are prevalent but uncomplicated in single ventricle CHD
- Brandon J. Calley, Liyun Zhang, Amy Y. Pan, Salil Ginde, Steven J. Kindel, Andrew D. Spearman
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- Journal:
- Cardiology in the Young / Volume 33 / Issue 4 / April 2023
- Published online by Cambridge University Press:
- 19 April 2022, pp. 557-563
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Background:
Patients with single ventricle CHD have significant morbidity and healthcare utilisation throughout their lifetime, including non-cardiac hospital admissions. Respiratory viral infections are the main cause of hospitalisation in children, but few data exist for single ventricle patients. We sought to identify how respiratory viral infections impact patients with single ventricle CHD and potential differences between Glenn and Fontan circulation.
Methods:We conducted a retrospective study of patients seen from 01/01/2011–12/31/2020. We identified patients with a history of single ventricle CHD and Glenn palliation, and a normoxic control group with isolated atrial septal defect requiring surgical closure. We compared viral-related clinical presentations, admissions, and admission characteristics.
Results:A total of 312 patients were included (182 single ventricle, 130 atrial septal defect). Single ventricle patients were more likely than children with isolated atrial septal defect to be admitted with a respiratory virus (odds ratio 4.15 [2.30–7.46]), but there was no difference in mechanical ventilation or hospital length of stay (p = 0.4709). Single ventricle patients with Glenn circulation were more likely than those with Fontan circulation to present and be admitted (odds ratio 3.25 [1.62–6.52]), but there was no difference in ICU admission, mechanical ventilation, or hospital length of stay (p = 0.1516).
Conclusions:Respiratory viral infections are prevalent but uncomplicated in patients with single ventricle CHD. Viral-related presentations and admissions are more prevalent during the period of Glenn circulation compared to Fontan circulation; however, rate of mechanical ventilation and hospital length of stay are similar.
Nomenclature for Pediatric and Congenital Cardiac Care: Unification of Clinical and Administrative Nomenclature – The 2021 International Paediatric and Congenital Cardiac Code (IPCCC) and the Eleventh Revision of the International Classification of Diseases (ICD-11)
- Part of
- Jeffrey P. Jacobs, Rodney C. G. Franklin, Marie J. Béland, Diane E. Spicer, Steven D. Colan, Henry L. Walters III, Frédérique Bailliard, Lucile Houyel, James D. St. Louis, Leo Lopez, Vera D. Aiello, J. William Gaynor, Otto N. Krogmann, Hiromi Kurosawa, Bohdan J. Maruszewski, Giovanni Stellin, Paul Morris Weinberg, Marshall Lewis Jacobs, Jeffrey R. Boris, Meryl S. Cohen, Allen D. Everett, Jorge M. Giroud, Kristine J. Guleserian, Marina L. Hughes, Amy L. Juraszek, Stephen P. Seslar, Charles W. Shepard, Shubhika Srivastava, Andrew C. Cook, Adrian Crucean, Lazaro E. Hernandez, Rohit S. Loomba, Lindsay S. Rogers, Stephen P. Sanders, Jill J. Savla, Elif Seda Selamet Tierney, Justin T. Tretter, Lianyi Wang, Martin J. Elliott, Constantine Mavroudis, Christo I. Tchervenkov
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- Journal:
- Cardiology in the Young / Volume 31 / Issue 7 / July 2021
- Published online by Cambridge University Press:
- 29 July 2021, pp. 1057-1188
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Substantial progress has been made in the standardization of nomenclature for paediatric and congenital cardiac care. In 1936, Maude Abbott published her Atlas of Congenital Cardiac Disease, which was the first formal attempt to classify congenital heart disease. The International Paediatric and Congenital Cardiac Code (IPCCC) is now utilized worldwide and has most recently become the paediatric and congenital cardiac component of the Eleventh Revision of the International Classification of Diseases (ICD-11). The most recent publication of the IPCCC was in 2017. This manuscript provides an updated 2021 version of the IPCCC.
The International Society for Nomenclature of Paediatric and Congenital Heart Disease (ISNPCHD), in collaboration with the World Health Organization (WHO), developed the paediatric and congenital cardiac nomenclature that is now within the eleventh version of the International Classification of Diseases (ICD-11). This unification of IPCCC and ICD-11 is the IPCCC ICD-11 Nomenclature and is the first time that the clinical nomenclature for paediatric and congenital cardiac care and the administrative nomenclature for paediatric and congenital cardiac care are harmonized. The resultant congenital cardiac component of ICD-11 was increased from 29 congenital cardiac codes in ICD-9 and 73 congenital cardiac codes in ICD-10 to 318 codes submitted by ISNPCHD through 2018 for incorporation into ICD-11. After these 318 terms were incorporated into ICD-11 in 2018, the WHO ICD-11 team added an additional 49 terms, some of which are acceptable legacy terms from ICD-10, while others provide greater granularity than the ISNPCHD thought was originally acceptable. Thus, the total number of paediatric and congenital cardiac terms in ICD-11 is 367. In this manuscript, we describe and review the terminology, hierarchy, and definitions of the IPCCC ICD-11 Nomenclature. This article, therefore, presents a global system of nomenclature for paediatric and congenital cardiac care that unifies clinical and administrative nomenclature.
The members of ISNPCHD realize that the nomenclature published in this manuscript will continue to evolve. The version of the IPCCC that was published in 2017 has evolved and changed, and it is now replaced by this 2021 version. In the future, ISNPCHD will again publish updated versions of IPCCC, as IPCCC continues to evolve.
Is the Anthropause a useful symbol and metaphor for raising environmental awareness and promoting reform?
- Nathan Young, Andrew N Kadykalo, Christine Beaudoin, Diana M Hackenburg, Steven J Cooke
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- Journal:
- Environmental Conservation / Volume 48 / Issue 4 / December 2021
- Published online by Cambridge University Press:
- 28 July 2021, pp. 274-277
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Lockdowns associated with the COVID-19 pandemic temporarily restricted human activity and removed people from many places of work and recreation. The resulting ‘Anthropause’ generated much media and research interest and has become an important storyline in the public history of the pandemic. As an ecological event, the Anthropause is fleeting and unlikely to alter the long-term human impact on the planet. But the Anthropause is also a cultural symbol whose effects may be more enduring. Will the Anthropause inspire people and governments to mobilize for meaningful reform, or does it present a misleading and too-comforting portrayal of resilient nature and wildlife that could ultimately discourage action? While it is too early to gauge the impact of the Anthropause on human behaviour and politics, we use existing research on environmental symbols and metaphors to identify factors that may influence long-term behavioural and political responses to this globally significant period of time.
Fast Grain Mapping with Sub-Nanometer Resolution Using 4D-STEM with Grain Classification by Principal Component Analysis and Non-Negative Matrix Factorization
- Frances I. Allen, Thomas C. Pekin, Arun Persaud, Steven J. Rozeveld, Gregory F. Meyers, Jim Ciston, Colin Ophus, Andrew M. Minor
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- Journal:
- Microscopy and Microanalysis / Volume 27 / Issue 4 / August 2021
- Published online by Cambridge University Press:
- 25 June 2021, pp. 794-803
- Print publication:
- August 2021
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High-throughput grain mapping with sub-nanometer spatial resolution is demonstrated using scanning nanobeam electron diffraction (also known as 4D scanning transmission electron microscopy, or 4D-STEM) combined with high-speed direct-electron detection. An electron probe size down to 0.5 nm in diameter is used and the sample investigated is a gold–palladium nanoparticle catalyst. Computational analysis of the 4D-STEM data sets is performed using a disk registration algorithm to identify the diffraction peaks followed by feature learning to map the individual grains. Two unsupervised feature learning techniques are compared: principal component analysis (PCA) and non-negative matrix factorization (NNMF). The characteristics of the PCA versus NNMF output are compared and the potential of the 4D-STEM approach for statistical analysis of grain orientations at high spatial resolution is discussed.
Remnant radio galaxies discovered in a multi-frequency survey
- Part of
- Benjamin Quici, Natasha Hurley-Walker, Nicholas Seymour, Ross J. Turner, Stanislav S. Shabala, Minh Huynh, H. Andernach, Anna D. Kapińska, Jordan D. Collier, Melanie Johnston-Hollitt, Sarah V. White, Isabella Prandoni, Timothy J. Galvin, Thomas Franzen, C. H. Ishwara-Chandra, Sabine Bellstedt, Steven J. Tingay, Bryan M. Gaensler, Andrew O’Brien, Johnathan Rogers, Kate Chow, Simon Driver, Aaron Robotham
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- Journal:
- Publications of the Astronomical Society of Australia / Volume 38 / 2021
- Published online by Cambridge University Press:
- 09 February 2021, e008
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The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a $8.31$ deg$^2$ subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1–9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an ‘absent radio core’ criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum ($\alpha<-1.2$) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to $4\%\lesssim f_{\mathrm{rem}} \lesssim 10\%$; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5–10 Myr at 5.5 GHz after the jets switch of—radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants.