71 research outputs found
Graph-Based Permutation Patterns for the Analysis of Task-Related fMRI Signals on DTI Networks in Mild Cognitive Impairment
Permutation Entropy () is a powerful nonlinear analysis technique for
univariate time series. Very recently, Permutation Entropy for Graph signals
() has been proposed to extend to data residing on irregular
domains. However, is limited as it provides a single value to
characterise a whole graph signal. Here, we introduce a novel approach to
evaluate graph signals at the vertex level: graph-based permutation patterns.
Synthetic datasets show the efficacy of our method. We reveal that dynamics in
graph signals, undetectable with , can be discerned using our graph-based
permutation patterns. These are then validated in the analysis of DTI and fMRI
data acquired during a working memory task in mild cognitive impairment, where
we explore functional brain signals on structural white matter networks. Our
findings suggest that graph-based permutation patterns change in individual
brain regions as the disease progresses. Thus, graph-based permutation patterns
offer promise by enabling the granular scale analysis of graph signals.Comment: 5 pages, 5 figures, 1 tabl
Electrical and thermal generation of spin currents by magnetic bilayer graphene
Ultracompact spintronic devices greatly benefit from the implementation of two-dimensional materials that provide large spin polarization of charge current together with long-distance transfer of spin information. Here spin-transport measurements in bilayer graphene evidence a strong spinâcharge coupling due to a large induced exchange interaction by the proximity of an interlayer antiferromagnet (CrSBr). This results in the direct detection of the spin polarization of conductivity (up to 14%) and a spin-dependent Seebeck effect in the magnetic graphene. The efficient electrical and thermal spinâcurrent generation is the most technologically relevant aspect of magnetism in graphene, controlled here by the antiferromagnetic dynamics of CrSBr. The high sensitivity of spin transport in graphene to the magnetization of the outermost layer of the adjacent antiferromagnet, furthermore, enables the read-out of a single magnetic sublattice. The combination of gate-tunable spin-dependent conductivity and Seebeck coefficient with long-distance spin transport in a single two-dimensional material promises ultrathin magnetic memory and sensory devices based on magnetic graphene
Graph-based permutation patterns for the analysis of task-related fMRI signals on DTI networks in mild cognitive impairment
Permutation Entropy (PE) is a powerful nonlinear analysis technique for univariate time series. Very recently, Permutation Entropy for Graph signals (PEG) has been proposed to extend PE to data residing on irregular domains. However, PEG is limited as it provides a single value to characterise a whole graph signal. Here, we introduce a novel approach to evaluate graph signals at the vertex level: graph-based permutation patterns. Synthetic datasets show the efficacy of our method. We reveal that dynamics in graph signals, undetectable with PEG, can be discerned using our graph-based permutation patterns. These are then validated in the analysis of DTI and fMRI data acquired during a working memory task in mild cognitive impairment, where we explore functional brain signals on structural white matter networks. Our findings suggest that graph-based permutation patterns change in individual brain regions as the disease progresses. Thus, graph-based permutation patterns offer promise by enabling the granular scale analysis of graph signals
Exchange bias between van der Waals materials: tilted magnetic states and field-free spin-orbit-torque switching
Magnetic van der Waals heterostructures provide a unique platform to study
magnetism and spintronics device concepts in the two-dimensional limit. Here,
we report studies of exchange bias from the van der Waals antiferromagnet CrSBr
acting on the van der Waals ferromagnet Fe3GeTe2 (FGT). The orientation of the
exchange bias is along the in-plane easy axis of CrSBr, perpendicular to the
out-of-plane anisotropy of the FGT, inducing a strongly tilted magnetic
configuration in the FGT. Furthermore, the in-plane exchange bias provides
sufficient symmetry breaking to allow deterministic spin-orbit torque switching
of the FGT in CrSBr/FGT/Pt samples at zero applied magnetic field. A minimum
thickness of the CrSBr greater than 10 nm is needed to provide a non-zero
exchange bias at 30 K
Hidden low-temperature magnetic order revealed through magnetotransport in monolayer CrSBr
Magnetic semiconductors are a powerful platform for understanding, utilizing
and tuning the interplay between magnetic order and electronic transport.
Compared to bulk crystals, two-dimensional magnetic semiconductors have greater
tunability, as illustrated by the gate modulation of magnetism in exfoliated
CrI and CrGeTe, but their electrically insulating properties
limit their utility in devices. Here we report the simultaneous electrostatic
and magnetic control of electronic transport in atomically-thin CrSBr, an
A-type antiferromagnetic semiconductor. Through magnetotransport measurements,
we find that spin-flip scattering from the interlayer antiferromagnetic
configuration of multilayer flakes results in giant negative magnetoresistance.
Conversely, magnetoresistance of the ferromagnetic monolayer CrSBr vanishes
below the Curie temperature. A second transition ascribed to the ferromagnetic
ordering of magnetic defects manifests in a large positive magnetoresistance in
the monolayer and a sudden increase of the bulk magnetic susceptibility. We
demonstrate this magnetoresistance is tunable with an electrostatic gate,
revealing that the ferromagnetic coupling of defects is carrier mediated
HIP 67506 C: MagAO-X Confirmation of a New Low-Mass Stellar Companion to HIP 67506 A
We report the confirmation of HIP 67506 C, a new stellar companion to HIP
67506 A. We previously reported a candidate signal at 2/D (240~mas) in
L in MagAO/Clio imaging using the binary differential imaging
technique. Several additional indirect signals showed that the candidate signal
merited follow-up: significant astrometric acceleration in Gaia DR3,
Hipparcos-Gaia proper motion anomaly, and overluminosity compared to single
main sequence stars. We confirmed the companion, HIP 67506 C, at 0.1" with
MagAO-X in April, 2022. We characterized HIP 67506 C MagAO-X photometry and
astrometry, and estimated spectral type K7-M2; we also re-evaluated HIP 67506 A
in light of the close companion. Additionally we show that a previously
identified 9" companion, HIP 67506 B, is a much further distant unassociated
background star. We also discuss the utility of indirect signposts in
identifying small inner working angle candidate companions.Comment: 10 pages, 9 figures, 4 tables, accepted to MNRA
Gene editing improves endoplasmic reticulum-mitochondrial contacts and unfolded protein response in Friedreichâs ataxia iPSC-derived neurons
Friedreich ataxia (FRDA) is a multisystemic, autosomal recessive disorder caused by homozygous GAA expansion mutation in the first intron of frataxin (FXN) gene. FXN is a mitochondrial protein critical for iron-sulfur cluster biosynthesis and deficiency impairs mitochondrial electron transport chain functions and iron homeostasis within the organelle. Currently, there is no effective treatment for FRDA. We have previously demonstrated that single infusion of wild-type hematopoietic stem and progenitor cells (HSPCs) resulted in prevention of neurologic and cardiac complications of FRDA in YG8R mice, and rescue was mediated by FXN transfer from tissue engrafted, HSPC-derived microglia/macrophages to diseased neurons/myocytes. For a future clinical translation, we developed an autologous stem cell transplantation approach using CRISPR/Cas9 for the excision of the GAA repeats in FRDA patientsâ CD34+ HSPCs; this strategy leading to increased FXN expression and improved mitochondrial functions. The aim of the current study is to validate the efficiency and safety of our gene editing approach in a disease-relevant model. We generated a cohort of FRDA patient-derived iPSCs and isogenic lines that were gene edited with our CRISPR/Cas9 approach. iPSC derived FRDA neurons displayed characteristic apoptotic and mitochondrial phenotype of the disease, such as non-homogenous microtubule staining in neurites, increased caspase-3 expression, mitochondrial superoxide levels, mitochondrial fragmentation, and partial degradation of the cristae compared to healthy controls. These defects were fully prevented in the gene edited neurons. RNASeq analysis of FRDA and gene edited neurons demonstrated striking improvement in gene clusters associated with endoplasmic reticulum (ER) stress in the isogenic lines. Gene edited neurons demonstrated improved ER-calcium release, normalization of ER stress response gene, XBP-1, and significantly increased ER-mitochondrial contacts that are critical for functional homeostasis of both organelles, as compared to FRDA neurons. Ultrastructural analysis for these contact sites displayed severe ER structural damage in FRDA neurons, that was undetected in gene edited neurons. Taken together, these results represent a novel finding for disease pathogenesis showing dramatic ER structural damage in FRDA, validate the efficacy profile of our FXN gene editing approach in a disease relevant model, and support our approach as an effective strategy for therapeutic intervention for Friedreichâs ataxia
The state of the Martian climate
60°N was +2.0°C, relative to the 1981â2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
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