Demonstration of non-Abelian frame charge flow in photonic crystals

In PT symmetric systems, the notion of non-Abelian frame charges enables multiband topological characterization of the degeneracy nodes through examining the eigenvector frame rotations. Interestingly, some features of these frame charges can be viewed as an analogue of electric charges confined in conducting wires, only that they flow in momentum space along nodal lines. However, these frame charges are not integers, and non-Abelian signatures emerge when braiding between adjacent band nodal lines occurs, which flips the direction of the flow. In photonic systems, we discover that the photonic {\Gamma} point serves as the source or sink of such frame charge flow due to a hidden braiding induced by the often-ignored electrostatic mode at zero-frequency. We use biaxial photonic crystals as examples and show how complex nodal line configurations can be explained as the topological consequences of the frame charge flow from the {\Gamma} point to the Brillouin zone boundaries. We further designed and fabricated meta-crystals to experimentally observe these line nodes as manifestation of the non-Abelian frame charge flow

Loss of intranetwork and internetwork resting state functional connections with Alzheimer\u27s disease progression

Alzheimer\u27s disease (AD) is the most common cause of dementia. Much is known concerning AD pathophysiology but our understanding of the disease at the systems level remains incomplete. Previous AD research has used resting-state functional connectivity magnetic resonance imaging (rs-fcMRI) to assess the integrity of functional networks within the brain. Most studies have focused on the default-mode network (DMN), a primary locus of AD pathology. However, other brain regions are inevitably affected with disease progression. We studied rs-fcMRI in five functionally defined brain networks within a large cohort of human participants of either gender (n = 510) that ranged in AD severity from unaffected [clinical dementia rating (CDR) 0] to very mild (CDR 0.5) to mild (CDR 1). We observed loss of correlations within not only the DMN but other networks at CDR 0.5. Within the salience network (SAL), increases were seen between CDR 0 and CDR 0.5. However, at CDR 1, all networks, including SAL, exhibited reduced correlations. Specific networks were preferentially affected at certain CDR stages. In addition, cross-network relations were consistently lost with increasing AD severity. Our results demonstrate that AD is associated with widespread loss of both intranetwork and internetwork correlations. These results provide insight into AD pathophysiology and reinforce an integrative view of the brain\u27s functional organization

Intrinsic triple degeneracy point bounded by nodal surfaces in chiral photonic crystal

In periodic systems, band degeneracies are usually protected and classified by spatial symmetries. However, the Gamma point at zero-frequency of a photonic system is an intrinsic degeneracy due to the polarization degree of freedom of electromagnetic waves. We show here that in chiral photonic crystals, such an intrinsic degeneracy node carries +(-)2 chiral topological charge and the topological characters is the same as a spin-1 Weyl point manifested as a triple degeneracy of two linear propagating bands intersecting a flat band representing the electrostatic solution. Such an intrinsic triple degeneracy point (TDP) at Gamma is usually buried in bulk band projections and the topological charge at photonic zero-frequency has never been observed. Here, by imposing space-group screw symmetry to the chiral photonic crystal, the Brillouin zone boundary is transformed into an oppositely charged nodal surface enclosing the Gamma point. The emergent Fermi-arcs on sample surface are then forced to connect the bulk band projections of these topological singularities, revealing the embedded non-trivial topology

Photonic nodal lines with quadrupole Berry curvature distribution

In periodic systems, nodal lines are loops in the three-dimensional momentum space where two bands are degenerate with each other. Nodal lines exhibit rich topological features as they can take various configurations such as rings, links, chains and knots. These line nodes are usually protected by mirror or PT symmetry. Here we propose and demonstrate a novel type of photonic straight nodal lines in a D2d meta-crystal which are protected by roto-inversion time (roto-PT) symmetry. The nodal lines are located at the central axis and hinges of the Brillouin zone. They appear as quadrupole sources of Berry curvature flux and allow for the precise control of the quadrupole strength. Interestingly, there exist topological surface states at all three cutting surfaces, as guaranteed by the pi-quantized Zak phases along all three directions. As frequency changes, the surface state equi-frequency contours evolve from closed to open contours, and become straight lines at a critical transition frequency, at which diffraction-less surface wave propagation are demonstrated, paving way towards development of super-imaging photonic devices

Clustering of resting state networks

BACKGROUND: The goal of the study was to demonstrate a hierarchical structure of resting state activity in the healthy brain using a data-driven clustering algorithm. METHODOLOGY/PRINCIPAL FINDINGS: The fuzzy-c-means clustering algorithm was applied to resting state fMRI data in cortical and subcortical gray matter from two groups acquired separately, one of 17 healthy individuals and the second of 21 healthy individuals. Different numbers of clusters and different starting conditions were used. A cluster dispersion measure determined the optimal numbers of clusters. An inner product metric provided a measure of similarity between different clusters. The two cluster result found the task-negative and task-positive systems. The cluster dispersion measure was minimized with seven and eleven clusters. Each of the clusters in the seven and eleven cluster result was associated with either the task-negative or task-positive system. Applying the algorithm to find seven clusters recovered previously described resting state networks, including the default mode network, frontoparietal control network, ventral and dorsal attention networks, somatomotor, visual, and language networks. The language and ventral attention networks had significant subcortical involvement. This parcellation was consistently found in a large majority of algorithm runs under different conditions and was robust to different methods of initialization. CONCLUSIONS/SIGNIFICANCE: The clustering of resting state activity using different optimal numbers of clusters identified resting state networks comparable to previously obtained results. This work reinforces the observation that resting state networks are hierarchically organized

Experimental demonstration of non-adjacent band topology connecting multiple nodal links

Nodal links are special configurations of band degeneracies in the momentum space, where nodal line branches encircle each other. In PT symmetric systems, nodal lines can be topologically characterized using the eigenvector frame rotations along an encircling loop and the linking structure can be described with non-Abelian frame charges interacting among adjacent bands. In this paper, we present a photonic multiple nodal links system, where non-adjacent band topology is proposed to characterize the hidden relation between nodal lines from non-adjacent band pairs. Through an orthogonal nodal chain, the nodal line from the lower two bands predicts the existence of nodal lines formed between the higher bands. We designed and fabricated a metamaterial, with which the multiple nodal links and non-adjacent band topology are experimentally demonstrated

The Origin of Separable States and Separability Criteria from Entanglement-breaking Channels

In this paper, we show that an arbitrary separable state can be the output of a certain entanglement-breaking channel corresponding exactly to the input of a maximally entangled state. A necessary and sufficient separability criterion and some sufficient separability criteria from entanglement-breaking channels are given.Comment: EBCs with trace-preserving and EBCs without trace-preserving are separately discusse

RP-HPLC-DAD metoda za određivanje olmesartan medoksomila kao čiste supstancije i u tabletama izloženih razgradnji

A simple, sensitive and precise RP-HPLC-DAD method was developed and validated for the determination of olmesartan medoxomil (AT-II receptor blocker) in the presence of its degradation products. Olmesartan medoxomil and all the degradation products were resolved on a C18 column with the mobile phase composed of methanol, acetonitrile and water (60:15:25, V/V/V, pH 3.5 by orthophosphoric acid) at 260 nm using a photodiode array detector. The method was linear over the concentration range of 1–18 µg mL 1 and precise with RSD 2.0 for each peak and sensitive with LOD 0.03 µg mL−1 and LOQ 0.1 µg mL−1. The method was used to study the drug degradation behavior under forced conditions. Four degradation products (DP-I, II, III, IV) were formed during the degradation study in 0.1 mol L−1 HCl whereas only DP-I, II and III were formed in water, 0.01 mol L−1 NaOH and 3 % H2O2. No significant thermal or photolytic degradation was observed in solid drug. The method was applied successfully for the assay of olmesartan medoxomil in the tablet dosage form.U ovom radu razvijena je i validirana jednostavna, osjetljiva i precizna RP-HPLC-DAD metoda za određivanje olmesartan medoksomila (inhibitor AT-II receptora) u prisutnosti njegovih razgradnih produkata. Olmesartan medoksomil i razgradni produkti kromatografirani su na C18 koloni uz mobilnu fazu metanol/ acetonitril/vo da (60:15:25 V/V/V; pH 3,5 podešen ortofosfornom kiselinom) pri 260 nm uz detektor s fotodiodnim nizom. Metoda je linearna u koncentracijskom rasponu 1–18 µg mL 1 i precizna s RSD < 1 % tijekom ispitivanja repetabilnosti i intermedijarne ponovljivosti. Povrat od 99,3 ± 0,9 do 100,8 ± 1,2 % dokazuje točnost metode. Razvijena metoda je specifična na što ukazuje kromatografsku rezoluciju veću od 2,0 i osjetljiva (LOD = 0,03 µg mL−1 i LOQ = 0,1 µg mL−1). Metoda je upotrebljena za praćenje razgradnje olmesartan medoksomila u uvjetima potencirane razgradnje. U 0,1 mol L−1 HCl detektirana su četiri razgradna produkta (DP-I, II, III, IV), a u vodi, 0,01 mol L−1 NaOH i 3 % H2O2 samo DP-I, II i III. U čvrstom agregatnom stanju nije primjećena značajna termička ni fotolitička razgradnja ljekovite tvari. Metoda je uspješno primijenjena za određivanje olmesartan medoksomila u tabletama

Photoluminescence and electrochemiluminescence of thermally activated delayed fluorescence (TADF) emitters containing diphenylphosphine chalcogenide-substituted carbazole donors

SK acknowledges the financial support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska Curie Individual Fellowship (MCIF; Agreement No. 748430-THF-OLED). P. R acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (No. 749557). The work has been supported in Mons by European Union through the Interreg V initiative France-Wallonie-Vlaanderen project LUMINOPTEX and the Belgian National Fund for Scientific Research (FRS-FNRS). Computational resources were provided by the Consortium des Équipements de Calcul Intensif (CÉCI) funded by F. R. S.-FNRS under Grant 2.5020.11. J. C. is an FNRS research director. Y. O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant no F.4534.21 (MIS-IMAGINE). We acknowledge the research support from Natural Sciences and Engineering Research Council Canada (NSERC, DG RGPIN-2013-201697, DG RGPIN-2018-06556, and SPG STPGP-2016-493924), Canada Foundation of Innovation, Ontario Innovation Trust (CFI/OIT, 9040) and Western University. J. R. A. appreciates the Ontario graduate scholarships (2018–2022). EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089).Aiming to develop efficient blue-emitting thermally activated delayed fluorescence (TADF) compounds, we have designed and synthesized derivatives of the well-known sky-blue emitter 2CzPN that contain electron-accepting phosphine chalcogenide groups to stabilize the HOMO level relative to the pristine compound, thus increasing the HOMO–LUMO gap and blue-shifting the emission wavelength. By cyclic voltammetry, photophysical data and quantum-chemical calculations, it was found that polar solvents and matrices validated the proposed concept, but these trends were not recovered in non-polar media. The suitability of these 2CzPN derivatives in polar matrices for optoelectronic applications was explored with electrochemiluminescence (ECL) by measuring emission delays, radical stability, emission stabilities, emission efficiencies and emission spectra. Some of the 2CzPN derivatives showed an unprecedented delayed onset of the ECL, and delayed rising time to the ECL maximum, as well as long ECL emission decay. All of these mentioned delay times suggest that these luminophores primarily emit via organic long-persistent electrochemiluminescence (OLECL) mechanisms. The derivatization of the donor groups of the emitters affected both the radical stability and the predominant emission mechanism, providing important insight into their potential as emitters in solid-state electroluminescent devices.Publisher PDFPeer reviewe

Maturing Thalamocortical Functional Connectivity Across Development

Recent years have witnessed a surge of investigations examining functional brain organization using resting-state functional connectivity MRI (rs-fcMRI). To date, this method has been used to examine systems organization in typical and atypical developing populations. While the majority of these investigations have focused on cortical–cortical interactions, cortical–subcortical interactions also mature into adulthood. Innovative work by Zhang et al. (2008) in adults have identified methods that utilize rs-fcMRI and known thalamo-cortical topographic segregation to identify functional boundaries in the thalamus that are remarkably similar to known thalamic nuclear grouping. However, despite thalamic nuclei being well formed early in development, the developmental trajectory of functional thalamo-cortical relations remains unexplored. Thalamic maps generated by rs-fcMRI are based on functional relationships, and should modify with the dynamic thalamo-cortical changes that occur throughout maturation. To examine this possibility, we employed a strategy as previously described by Zhang et al. to a sample of healthy children, adolescents, and adults. We found strengthening functional connectivity of the cortex with dorsal/anterior subdivisions of the thalamus, with greater connectivity observed in adults versus children. Temporal lobe connectivity with ventral/midline/posterior subdivisions of the thalamus weakened with age. Changes in sensory and motor thalamo-cortical interactions were also identified but were limited. These findings are consistent with known anatomical and physiological cortical–subcortical changes over development. The methods and developmental context provided here will be important for understanding how cortical–subcortical interactions relate to models of typically developing behavior and developmental neuropsychiatric disorders