Nanotwin governed toughening mechanism in hierarchically structured materials

As an important class of natural biocomposite materials, mollusk shells possess remarkable mechanical strength and toughness as a consequence of their hierarchical structuring of soft organic and hard mineral constituents through biomineralization. Strombus gigas, one of the toughest mollusk shell (99 wt% CaCO3, 1 wt% organic), contains high density of nanoscale {110} growth twins in its third order lamellae, the basic building block of the material [1]. Although the existence of these nanotwins has been known for decades their roles and functions in mechanical behaviors and properties of biological materials are still unrevealed because numerous studies in recent years aimed to investigate the relationship between mechanical properties and the elegant nano- and hierarchical structures[1-2]. To evaluate the actual role of these nanotwins, we performed in situ TEM deformation experiment, large scale atomistic simulations and finite element modeling. With these analytic tools, we revealed nano scale twins in conch shell provide a basis of the several orders higher toughness comparing to twin free aragonite. In terms of qualitative experiment, we observed nanotwins can hinder crack propagation effectively comparing to twin free single crystal aragonite and leaving phase transformed area near crack tip (Fig 1 a-c) by in situ TEM deformation experiment. Through large scale MD simulation, we confirmed this phase transformation as a hitherto unknown toughening mechanism governed by nanoscale twins. For the quantitative comparison in terms of toughness, we performed specially designed in situ TEM experiments additionally for conch shell and aragonite single crystal so as to assess the contributions of these nanoscale twins on toughness of conch shell (Fig 1.d). By combining in situ TEM nanoscale mechanical test and FEM simulation, we found that nanotwins in 3rd order lamellar can increase fracture energy an order magnitude higher than twin free aragonite and this effect become amplified via structural hierarchy. The unique properties and structural features of nanotwinned aragonitic conch shell are expected to provide a guide to designing and fabricating hierarchically structured biomimetic materials with high toughness and high modulus

Large-scale filamentary structures around the Virgo cluster revisited

We revisit the filamentary structures of galaxies around the Virgo cluster, exploiting a larger dataset based on the HyperLeda database than previous studies. In particular, this includes a large number of low-luminosity galaxies, resulting in better sampled individual structures. We confirm seven known structures in the distance range 4~$h^{-1}$~Mpc~$<$ SGY~$<$ 16~$h^{-1}$ Mpc, now identified as filaments, where SGY is the axis of the supergalactic coordinate system roughly along the line of sight. The Hubble diagram of the filament galaxies suggests they are infalling toward the main-body of the Virgo cluster. We propose that the collinear distribution of giant elliptical galaxies along the fundamental axis of the Virgo cluster is smoothly connected to two of these filaments (Leo~II~A and B). Behind the Virgo cluster (16~$h^{-1}$~Mpc~$<$ SGY~$<$ 27~$h^{-1}$~Mpc), we also identify a new filament elongated toward the NGC 5353/4 group ("NGC 5353/4 filament") and confirm a sheet that includes galaxies from the W and M clouds of the Virgo cluster ("W-M sheet"). In the Hubble diagram, the NGC 5353/4 filament galaxies show infall toward the NGC 5353/4 group, whereas the W-M sheet galaxies do not show hints of gravitational influence from the Virgo cluster. The filamentary structures identified can now be used to better understand the generic role of filaments in the build-up of galaxy clusters at z~$\approx$~0.Comment: 8 pages, 4 figures, accepted for publication in Ap

Metabolic flux from the Krebs cycle to glutamate transmission tunes a neural brake on seizure onset

Kohlschutter-Tonz syndrome (KTS) manifests as neurological dysfunctions, including early-onset seizures. Mutations in the citrate transporter SLC13A5 are associated with KTS, yet their underlying mechanisms remain elusive. Here, we report that a Drosophila SLC13A5 homolog, I&apos;m not dead yet (Indy), constitutes a neurometabolic pathway that suppresses seizure. Loss of Indy function in glutamatergic neurons caused &quot;bang-induced&quot; seizure-like behaviors. In fact, glutamate biosynthesis from the citric acid cycle was limiting in Indy mutants for seizure-suppressing glutamate transmission. Oral administration of the rate-limiting alpha-ketoglutarate in the metabolic pathway rescued low glutamate levels in Indy mutants and ameliorated their seizure-like behaviors. This metabolic control of the seizure susceptibility was mapped to a pair of glutamatergic neurons, reversible by optogenetic controls of their activity, and further relayed onto fan-shaped body neurons via the ionotropic glutamate receptors. Accordingly, our findings reveal a micro-circuit that links neural metabolism to seizure, providing important clues to KTS-associated neurodevelopmental deficits. Author summary Kohlschutter-Tonz syndrome (KTS) is a neurodevelopmental disorder linked to two distinct genomic loci encoding the citrate transporter SLC13A5 and synaptic protein ROGDI, respectively. An early-onset seizure is the most prominent neurological symptom in KTS patients, yet how these genes contribute to the control of seizure susceptibility remains poorly understood. Our study establishes behavioral models of seizure in Drosophila mutants of KTS-associated genes and demonstrates a genetic, metabolic, and neural pathway of seizure suppression. We discover that the metabolic flux of the Krebs cycle to glutamate biosynthesis plays a critical role in scaling seizure-relevant glutamate transmission. We further map this seizure-suppressing pathway to a surprisingly small number of glutamatergic neurons and their ionotropic glutamate transmission onto a key sleep-promoting locus in the adult fly brain. Given that the excitatory amino acid glutamate is considered a general seizure-promoting neurotransmitter, our findings illustrate how glutamatergic transmission can have opposing effects on seizure susceptibility in the context of a micro-neural circuit, possibly explaining drug-resistant epilepsy. This seizure-suppressing locus in the Drosophila brain is also implicated in metabolism, circadian rhythms, and sleep, revealing the conserved neural principles of their intimate interaction with epilepsy across species

A Wideband Doherty Combiner with Phase Variation Compensation Using LTCC Applicable for High Power Transmission

In this paper, we propose a small-sized Doherty combiner with phase variation compensation using low temperature co-fired ceramic (LTCC) substrate. The proposed design theory for the Doherty combiner is derived using the phase calculation of the S-parameter based on the relation between the input and output ports. The proposed circuit is designed after determining the band edge frequency and the targeted degree of the phase balance. The proposed circuit is verified using the microstrip line and the LTCC substrate. The implemented structure, using LTCC as the substrate, is operated under a high-power test of continuous wave 50 W, the results of which also show that the amplitude and phase balance have variations within 0.2 dB and ±1°, respectively. The high-power test shows that the implemented structure is applicable for high power Doherty amplifiers or combiners