Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of ...nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors, which covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with the Boolean digital data, unconventional approaches, such as neuromorphic computing, and the progress toward magnon-based quantum computing. This article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.
We modeled, both analytically and numerically, the magnitude and phase of spin waves propagating in thin magnetic films and scattered from mesoscale chiral magnonic resonators. Our calculations ...reveal a remarkably strong chiral scattering of propagating spin waves from magnon dark modes hosted by the resonator, exceeding in strength the scattering from its quasiuniform mode. We formulate conditions for the waveguide-resonator system to be used as an efficient spin-wave diode and as a phase shifter. Both these applications are found to be feasible when using the available ferromagnetic materials for the resonators.
We have used micromagnetic simulations to model backward-volume dipole-exchange spin waves in graded profiles of the bias magnetic field. We demonstrate spin-wave wavelength conversion upon the ...wave's reflection from turning points due to the two characteristic minima (" U points") occurring in their dispersion at finite (nonzero) wave vectors. As a result, backward-volume dipole-exchange spin waves confined in "spin-wave wells" either form Möbius modes, making multiple real-space turns for each reciprocal-space round trip, or split into pairs of degenerate modes in the valleys near the two U points. The latter modes may therefore be assigned a pseudospin. We show that the pseudospin can be switched by scattering the spin wave from decreases of the bias magnetic field, while it is immune to scattering from field increases. Pseudospin creation and read-out can be accomplished using chiral spin-wave transducers, as described in Au et al. Appl. Phys. Lett. 100, 182404 (2012) and Au et al. Appl. Phys. Lett. 100, 172408 (2012), respectively. Taken together, the possibility of pseudospin creation, manipulation, and read-out suggests a path to development of a spin-wave version of valleytronics ("magnon valleytronics"), in which the pseudospin (rather than amplitude or phase) of spin waves would be used to encode data. Our results are not limited to graded bias magnetic field but can be generalized to other magnonic media with spatially varying characteristics, produced using the toolbox of graded index magnonics.
Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of ...nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.
To investigate whether global and regional beta-amyloid (Abeta) burden as measured with 11C Pittsburgh compound B (PIB) PET is associated with hippocampal atrophy characterized using MRI in healthy ...controls and patients with amnestic mild cognitive impairment (aMCI) or Alzheimer disease (AD).
Ninety-two elderly healthy controls, 32 subjects with aMCI, and 35 patients with AD were imaged using 11C-PIB PET and MRI. Hippocampal volume was measured and PIB standardized uptake value ratio was extracted after partial volume correction within 41 regions of interest. Global, regional, and voxel-based correlations between PIB and hippocampal volume were computed for each group.
In healthy control participants with elevated neocortex PIB retention, significant correlation was found between PIB retention in the inferior temporal region and hippocampal volume using both region-based and voxel-based approaches. No correlation was found in any other group.
The strong correlation between hippocampal atrophy and beta-amyloid (Abeta) burden in the Pittsburgh compound B-positive healthy control group suggests that Abeta deposition in the inferior temporal neocortex is related to hippocampal synaptic and neuronal degeneration.
Abstract
Background
Studies into cognitive changes typically employ detailed in person cognitive testing, which is not always feasible. Therefore, we compared the relationship between brain ...morphology (sulcal width) and cognitive functioning, using an online and an in‐person modality and disentangled the influence of age, sex, β‐Amyloid (Aβ) and APOE‐status.
Method
141 healthy participants (mean age 60, range 46‐71 years, 75% female) assessed with structural MRI; cognitive batteries both, face‐to‐face and online (Cambridge Brain Systems), Aβ status (Fluorine‐18 florbetaben‐PET scan) and APOE genotype (Lupton et al., 2021); Canonical Partial Least Square method to compare cognitive modalities and Sulcal width (SW; Morphologist pipeline‐BrainVISA toolbox; Borne et al., 2020). Age effects tested with two‐sided Wald Test. Analysis of covariance to test age and sex‐interactions, amyloid and APOE status, sex‐effects (controlling for age), Aβ, and APOE (controlling for age and sex).
Result
The single robust mode for brain (SW) ‐ behaviour (cognition) covariation loaded most strongly onto memory and executive functions for both the onsite (1st mode, p = 0.013, cov = 3.55, z‐cov = 2.93, R
2
= 0.18, z‐R
2
= 0.95; 2nd mode, p>0.99), and the online battery (1st mode, p<0.001, cov = 2.76, z‐cov = 4.71, R
2
= 0.14, z‐R
2
= 1.15; 2nd mode, p = 0.99) (Fig. 1).
Cognition‐related SW showed a regional pattern similar for online and in person cognitive appraisal. Significant effect of sex on SW projections in both the online and onsite conditions with larger sulcal width for men (p<0.001) and a similar effect on onsite cognitive projections with lower performance for men (p<0.001) (Fig. 2a). Cognitive performance ‐ both online (p = 0.03) and in‐person (p<0.01) – showed a significantly steeper decline with age for Aβ‐positive participants (Fig. 2b). Variance explained for the online cognitive assay (R
2
= 0.15) was only slightly less than for the in‐person testing (R
2
= 0.18). Brain‐behaviour z‐transformed covariance was likewise comparable across modalities.
Conclusion
Similar sulcal width brain projections for both cognitive modalities, with memory and executive domains showing the strongest loadings. Aβ‐aggregation associated with a steeper cognitive projection slope for both batteries, suggesting that in our preclinical sample the early stages of Aβ accumulation accelerate cognitive ageing potentially before translation into structural brain changes. Adequate sensitivity of online cognitive tests for studying age‐related neurobiology of cognition is suggested.
Background
Recent research demonstrates a bidirectional relationship between sleep and Alzheimer’s Disease (AD) pathology, with supporting evidence that changes in sleep pattern occurs from the ...preclinical stage of AD. The cooccurrence of sleep disturbances and amyloid‐beta (Aβ) accumulation suggests the importance of monitoring sleep patterns in adults that are at high‐risk of developing AD later in life. We first investigated whether resting heart rate (RHR) and nocturnal sleep restlessness (NSR) are different in cognitively impaired (CI) and cognitively unimpaired (CU) mid‐life to older adults. We also examined any association of these sleep characteristics with hippocampus volume (HV) and Aβ, as neuroimaging biomarkers of AD, regardless of the cognitive status.
Method
107 middle to old age (46‐75 years old) adults (age 61.5±6.5, 74 Females, 64 APOE ε4 carriers, and 88 CU) underwent 3T MRI and PET scans as part of the Prospective Imaging Study of Ageing (PISA) study. A ballistocardiograph sleep monitoring device was used to track their RHR and NSR for approximately 5 months after their PET scan. NSR was quantified by total time in bed, total duration and number of bed‐exits, and multi‐episodic sleep. HV was normalised using total intracranial volume, and Aβ load was calculated in Centiloid scale (CL) with Aβ positivity defined as CL>20. Generalised Linear Models were used to examine the relationship between sleep and imaging biomarkers. Age, gender, BMI, APOE, and years of education were used as independent covariates.
Result
CIs spent more time in bed (p = 0.002) and had more bed‐exits (p = 0.009) than CUs. However, no significant difference was found on RHR and multi‐episodic sleep between CUs and CIs. Individuals with higher Aβ load, regardless of their cognitive status, had lower RHR (p = 0.04) and more bed‐exits (p = 0.04), and spent more time in bed (p = 0.01). Also, individuals with smaller HV frequently exited the bed during the night (p = 0.03) and spent more time in bed (p = 0.003).
Conclusion
Individuals with cognitive impairment experienced higher levels of NSR with frequent bed‐exits and more time in bed. Also, these sleep characteristics were significantly associated with the Centiloid value, Aβ status, and HV, regardless of the cognitive status.
•Detailed protocol of the Prospective Imaging Study of Ageing (PISA) Study.•Genetic risk prediction to identify those at differing risk of Alzheimer’s disease.•Longitudinal cohort for the study of ...precursors and lifestyle risk factors.•Use of online surveys and cognitive testing for large scale phenotyping.•Functional, structural and molecular neuroimaging with neurocognitive testing.
This prospective cohort study, “Prospective Imaging Study of Ageing: Genes, Brain and Behaviour” (PISA) seeks to characterise the phenotype and natural history of healthy adult Australians at high future risk of Alzheimer’s disease (AD). In particular, we are recruiting midlife and older Australians with high and low genetic risk of dementia to discover biological markers of early neuropathology, identify modifiable risk factors, and establish the very earliest phenotypic and neuronal signs of disease onset. PISA utilises genetic prediction to recruit and enrich a prospective cohort and follow them longitudinally. Online surveys and cognitive testing are used to characterise an Australia-wide sample currently totalling over 3800 participants. Participants from a defined at-risk cohort and positive controls (clinical cohort of patients with mild cognitive impairment or early AD) are invited for onsite visits for detailed functional, structural and molecular neuroimaging, lifestyle monitoring, detailed neurocognitive testing, plus blood sample donation. This paper describes recruitment of the PISA cohort, study methodology and baseline demographics.
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