Region Filament Research Articles

Effects of Ambient Sensing on SiOx-Based Resistive Switching and Resilience Modulation by Stacking Engineering

The SiOx-based resistive random access memory (RRAM) is reported as the gas sensor with the spontaneous response i.e. memory window closure as air-vacuum switches, meanwhile enlarged the switching voltages in the vacuum. The HfOx/SiOx stacked structure is proposed with a superior resilience with response to ambient changes through inserting an interface structure, which attributed to the gain of the source of high defect density and Hf-encapsulation of the filamentary region as compared to single layer SiOx structures. Besides, the intrinsic nonlinear behavior is demonstrated by integrating a low dielectric layer, which suppresses the sneak path issues for large-scale SiOx-based RRAM crossbar array implementation in near future.

Global Self-Focusing and Features of Multiple Filamentation of Radiation of a Subterawatt Ti:Sapphire Laser with a Centimeter Output Aperture Along a 150-m Path

The formation and propagation of postfilamentation channels along a controllable path 150 m long are studied experimentally for collimated beams of different diameters. During multiple filamentation, a laser beam is compressed into a global focus, after passing which its angular divergence is much greater than the divergence of postfilamentation channels generated during the filamentation. It is shown that the intensity of the postfilamentation channels is sufficient for starting multiple filamentation in optical elements at distances much longer than the filamentation region length.

Microstructural study of brass matrix internal tin multifilamentary Nb3Sn superconductors

Zn addition to the Cu matrix in internal-tin-processed Nb3Sn superconductors is attractive in terms of the growth kinetics of the Nb3Sn layers. Sn activity is enhanced in the Cu–Zn (brass) matrix, which accelerates Nb3Sn layer formation. Here, we prepared multifilamentary wires using a brass matrix with a Nb core diameter of less than 10 µm and investigated the potential for further Jc improvement through microstructural and microchemical studies. Ti was added into the Sn cores in the precursor wire. Microchemical analysis showed that Ti accumulates between subelements consisting of Nb cores, which blocks Sn diffusion through this region when the spacing between the subelements in the precursor wire is a few microns. The average grain size was found to be about 230 nm through image analysis. To date, matrix Jc values of 1470 and 640 A/mm−2 have been obtained at 12 and 16 T, respectively. The area fraction of Nb cores in the filamentary region of the precursor wire was about 36.3%. There was still some unreacted Nb core area after heat treatment. Insufficient Ti diffusion into the Nb3Sn layers was identified in the outer subelements. These findings suggest that there is still room for improvement in Jc.

Suzaku observations of the outskirts of the galaxy cluster Abell 3395, including a filament toward Abell 3391

Abstract The results of Suzaku observations of the outskirts of Abell 3395, including a large-scale structure filament toward Abell 3391, are presented. We measured temperature and abundance distributions from the southern outskirt of A 3395 to the north at the virial radius, where a filament structure has been found in the former X-ray and Sunyaev–Zel’dovich (SZ) effect observations between A 3391 and A 3395. The overall temperature structure is consistent with the universal profile proposed by Okabe, N., et al. 2014, PASJ, 66, 99 for relaxed clusters, except for the filament region. A hint of intracluster medium heating is found between the two clusters, which might be due to their interaction in the early phase of a cluster merger. Although we obtained a relatively low metal abundance of $Z=0.169^{+0.164+0.009+0.018 }_{-0.150-0.004-0.015 }$ solar, where the first, second, and third errors are statistical, cosmic X-ray background systematic, and non-X-ray background systematic, respectively, at the virial radius in the filament, our results are still consistent with previous results for other clusters (Z ∼ 0.3 solar) within errors. Therefore, our results are also consistent with the early enrichment scenario. We estimated Compton y parameters only from X-ray results in the region between A 3391 and A 3395 assuming a simple geometry. They are smaller than the previous SZ results with the Planck satellite. The difference could be attributed to a more elaborate geometry such as a filament inclined to the line-of-sight direction, or underestimation of the X-ray temperature because of the unresolved multi-temperature structures or undetected hot X-ray emission of the shock-heated gas.

Probing the Critical Region of Conductive Filament in Nanoscale HfO2 Resistive-Switching Device by Random Telegraph Signals

Resistive-switching random access memory (RRAM) is widely considered as a disruptive technology. Despite tremendous efforts in theoretical modeling and physical analysis, details of how the conductive filament (CF) in metal-oxide-based filamentary RRAM devices is modified during normal device operations remain speculative, because direct experimental evidence at defect level has been missing. In this paper, a random-telegraph-signal-based defect-tracking technique (RDT) is developed for probing the location and movements of individual defects and their statistical spatial and energy characteristics in the CF of state-of-the-art hafnium-oxide RRAM devices. For the first time, the critical filament region of the CF is experimentally identified, which is located near, but not at, the bottom electrode with a length of nanometer scale. We demonstrate with the RDT technique that the modification of this key constriction region by defect movements can be observed and correlated with switching operation conditions, providing insight into the resistive switching mechanism.

In Operando Characterization of Pt-TaOx-Ta Bipolar Vacancy Change Memories

Clear and unambiguous experimental observation of the physical processes leading to resistance change during formation and switching of bipolar valence change memories (VCM) remains one of the main remaining challenges in the characterization and understanding of resistive memory devices[1]. Presented here is a Scanning Transmission Electron Microscopy (STEM) Electron Energy Loss Spectroscopy (EELS) study which reveals a valence change filamentary switching mechanism during low-current bipolar resistive switching operation in Pt-TaOx-Ta resistive memory devices. No change in the film stack is observed in High Angle Annular Dark Field (HAADF) STEM during SET or RESET operation, which is consistent with expectations for a low-current operation VCM. A ~50 nm wide filamentary region is observed in EELS maps analyzed with multivariate statistical analysis disappearing on RESET operation and reappearing during SET operation. In this filamentary region, the Ta O2,3 edge is consistent with oxidized Ta but there is a sharp metallic plasmon feature which is blue shifted in accordance with our previous ab initiopredictions for metallic oxides. [1] Yang Y and Lu W D 2016 Progress in the Characterizations and Understanding of Conducting Filaments in Resistive Switching Devices IEEE Transactions on Nanotechnology 15 465-72

Post-filamentation light channels in air

The results are presented of the experimental study of spatial characteristics of postfilamentation light channels in air formed by femtosecond pulses of a Ti:Sapphire laser with different energy for focused and collimated beams. It is found that the angular divergence of channels is dozens of times lower than the angular divergence of a beam as a whole for focused beams in the far zone from the filamentation region. The angular divergence of the channels first significantly decreases with an increase in the pulse energy and then saturates. For collimated beams, at a fixed distance from the source, an increase in the pulse energy also leads to stabilization of the channel cross section.

A hot X-ray filament associated with A3017 galaxy cluster

Recent simulations and observations have shown large scale filaments in the cosmic web connecting nodes, with accreting materials (baryonic and dark matter) flowing through them. Current high sensitivity observations also show that the propagation of shocks through filaments can heat them up, and make filaments visible between two or more galaxy clusters or around massive clusters, based on optical and/or X-ray observations. We are reporting here the special case of the cluster A3017 associated with a hot filament. The temperature of the filament is 3.4$^{-0.77}_{+1.30}$ ~keV and its length is $\sim$ 1 Mpc. We have analysed its archival {\it Chandra} data and report various properties. We also analysed GMRT 235/610 MHz radio data. Radio observations have revealed symmetric two-sided lobes which fill cavities in the A3017 cluster core region, associated with central AGN. In the radio map, we also noticed a peculiar linear vertical radio structure in the X-ray filament region which might be associated with a cosmic filament shock. This radio structure could be a radio phoenix or old plasma where an old relativistic population is re-accelerated by shock propagation. Finally we put an upper limit on the radio luminosity of the filament region.

First Results from BISTRO: A SCUBA-2 Polarimeter Survey of the Gould Belt

Abstract We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array 2 camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope in Hawaii. We discuss the survey’s aims and objectives. We describe the rationale behind the survey, and the questions that the survey will aim to answer. The most important of these is the role of magnetic fields in the star formation process on the scale of individual filaments and cores in dense regions. We describe the data acquisition and reduction processes for POL-2, demonstrating both repeatability and consistency with previous data. We present a first-look analysis of the first results from the BISTRO survey in the OMC 1 region. We see that the magnetic field lies approximately perpendicular to the famous “integral filament” in the densest regions of that filament. Furthermore, we see an “hourglass” magnetic field morphology extending beyond the densest region of the integral filament into the less-dense surrounding material, and discuss possible causes for this. We also discuss the more complex morphology seen along the Orion Bar region. We examine the morphology of the field along the lower-density northeastern filament. We find consistency with previous theoretical models that predict magnetic fields lying parallel to low-density, non-self-gravitating filaments, and perpendicular to higher-density, self-gravitating filaments.

Wetting and dewetting processes in the axial retraction of liquid filaments.

We study the hydrodynamic mechanisms involved in the motion of the contact line formed at the end region of a liquid filament laying on a planar and horizontal substrate. Since the flow develops under partially wetting conditions, the tip of the filament recedes and forms a bulged region (head) that subsequently develops a neck region behind it. Later the neck breaks up leading to a separated drop, while the rest of the filament restarts the sequence. One main feature of this flow is that the whole dynamics and final drop shapes are strongly influenced by the hysteresis of the contact angle typical in most of the liquid-substrate systems. The time evolution till breakup is studied experimentally and pictured in terms of a hybrid wettability theory which involves the Cox-Voinov hydrodynamic approach combined with the molecular kinetic theory developed by Blake. The parameters of this theory are determined for our liquid-substrate system (silicone oil-coated glass). The experimental results of the retracting filament are described in terms of a simple heuristic model and compared with numerical simulations of the full Navier-Stokes equations. This study is of special interest in the context of pulsed laser-induced dewetting.

Mitochondria-rich cells changes induced by nitrite exposure in tambaqui (Colossoma macropomum Cuvier, 1818).

The gill mitochondria-rich cells of the juvenile Amazonian fish Colossoma macropomum were analyzed using light and scanning and transmission electron microscopy after 96 h exposure to 0.04 and 0.2 mM nitrite. Although the number of mitochondria-rich cells decreased significantly in the lamellar epithelium, no decrease was found in the interlamellar region of the gill filament. Nitrite exposure caused significant reduction on the apical surface area of individual mitochondria-rich cells (p < 0.05), with a resulting reduction of the fractional area of these cells in both the lamellar and filament epithelium. Swelling of endoplasmic reticulum cisternae, nuclear envelope and mitochondria were the main changes found in the mitochondria-rich cells. Cristae lysis and matrix vacuolization characterized the mitochondrial changes. The overall ultrastructural changes indicated cellular functional disruption caused by exposure to nitrite. The changes observed in the gill indicate that the cellular structures involved in the process of energy production become severely damaged by exposure to nitrite indicating irreversible damage conducting to cell death.

Control of Morphology in Polymer Blends through Light Self-Trapping: An in Situ Study of Structure Evolution, Reaction Kinetics, and Phase Separation

We report on how polymer morphology is controlled through the self-trapping of transmitted optical beams in photoreactive polymer blends. Self-trapped optical beams, characterized by divergence-free propagation, drives the growth of a congruent arrangement of polymer filaments in the blends. With suitable component weight fractions and exposure intensity, binary phase morphologies form in precisely the same pattern as the beams’ arrangement, thereby producing 2D structures in polymer blend volumes of large depth and area. Morphology evolution and the formation processes were observed by in situ microscopy. In situ confocal Raman measurements of polymer conversion and molecular weight increase along the filament regions reveal that polymerization undergoes autoacceleration, followed by the onset of mixing instability which leads to phase separation. These phenomena begin at the front end of the filament and propagate along its length over the depth of the blend. Control over morphology is discussed with respect to the competitive processes of phase separation and photo-cross-linking.

3D simulation of AC loss in a twisted multi-filamentary superconducting wire

In the AC loss simulation, it is a huge challenge to model the twisted wire at the filament level, due to the complex structure as well as long-time computation consumption. In this paper, we use 3D finite-element method based on H-formulation to study the AC loss in a twisted superconducting wire. The wire is treated as a homogenous material with the anisotropic conductivity in the filament region. We quantitatively simulate the AC loss induced by the AC transport current and magnetic field profile, and the effect of the twist pitch on the AC loss. In the case of AC transport current, larger pitch length leads to higher loss, and the pitch length effect is contrary to the case of applied magnetic field. The influences of the magnetic field direction and non-uniform current distribution subjected to the strand bending are also investigated. It is observed that, the transverse magnetic field has a more significant influence on the AC loss than the longitudinal magnetic field. The non-uniform current distribution can result in a higher AC loss, compared to a corresponding uniform current distribution.

The weak-lensing masses of filaments between luminous red galaxies

In the standard model of non-linear structure formation, a cosmic web of dark-matter dominated filaments connects dark matter halos. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies. Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between SDSS-III/BOSS luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the $5\sigma$ level, finding a mass of $(1.6 \pm 0.3) \times 10^{13} M_{\odot}$ for a stacked filament region 7.1 $h^{-1}$ Mpc long and 2.5 $h^{-1}$ Mpc wide. This filament signal is compared with a model based on the three-point galaxy-galaxy-convergence correlation function, as developed in Clampitt, Jain & Takada (2014), yielding reasonable agreement.

Near- and mid-IR ultrashort laser pulse filamentation in a molecular atmosphere: a comparative analysis

Self-focusing and filamentation of high-power pulsed laser radiation along a spectrally selective absorbing air path are numerically simulated in three spectral ranges centered at 0.8, 3.9, and 10.6 μm. A detailed comparative analysis of the main pulse parameters in the filamentation area is performed to examine the potential of various laser sources for atmospheric optics. We found that the radiation of mid-IR lasers (3.9 and 10.6 μm) forms the longest filamentation region and the widest supercontinual spectrum in comparison with near-IR radiation. Filamentation of the 3.9 μm laser pulse results in the best spatially continued plasma channel, while the 10.6 μm pulse retains the widest spectral composition under the conditions of strong molecular absorption in the atmosphere.

Electron Microscopy of the Complex Formed by Heavy Meromyosin and C-Protein

Most studies of regulation of vertebrate striated muscle contraction have focussed on activation of the thin filament via calcium binding to the troponin-tropomyosin complex. There is accumulating evidence, however, that thick filament activation is an additional regulatory mechanism. Under relaxing conditions, the two heads of a myosin can interact to form an inactive asymmetric off-state, called the interacting-heads motif (IHM). The off-state inhibits cross-bridge formation and cycling by blocking actin binding in one head and ATPase activity in the other. Docking of the IHM onto the thick filament backbone results in the super-relaxed state (SRX) observed in muscle fibres, where the myosin ATPase is strongly inhibited. What regulates formation and disruption of the IHM is largely uncharacterised. Myosin binding protein C, also known as C-protein, is a key sarcomere component, bound at sites spaced by 43 nm in the cross-bridge regions of thick filaments. The arrangement, mode of action, and interactions of C-protein with myosin are poorly understood. In the heart, phosphorylation of C-protein increases the rate of contraction and its ablation disrupts the SRX. To investigate the interaction of human cardiac C-protein with β-cardiac heavy meromyosin (HMM), we have imaged the complex by electron microscopy and single particle averaging. Cardiac HMM in the IHM motif has the characteristic blocked and inhibited head conformations. The fraction of HMM in the IHM motif is increased when dephosphorylated C-protein is bound, suggesting it stabilises the IHM. Characterization of the complex should provide insight into the regulatory and structural roles of the cardiac C-protein/myosin interaction in heart.

Skeletal Myosin-Binding Protein C Modulates Actomyosin Contractility in an Isoform-Dependent Manner

Myosin-binding protein C (MyBP-C) is a sarcomeric protein localized to discrete regions (C-zones) of myosin thick filaments in all striated muscles. Unlike cardiac muscle with its specific MyBP-C isoform, mass spectrometry shows that rat slow-twitch soleus (SOL) muscle expresses two different slow MyBP-C isoforms (sMyBP-C), having one (sMyBP-C1) or two N-terminal inserts (sMyBP-C2), while fast-twitch extensor digitorum longus (EDL) expresses these same sMyBP-C isoforms and a fast MyBP-C isoform (fMyBP-C). Do these MyBP-C isoforms differentially regulate skeletal actomyosin contractility in a muscle-specific manner? To address this, we characterized Ca2+-regulated motion of SOL and EDL native actin-thin filaments (NTFs) over their corresponding native myosin-thick filaments, having the physiological complement of MyBP-C in the C-zone. At low calcium (pCa7.5) where NTFs should be inhibited, motion occurred within the C-zone of both SOL and EDL native thick filaments. Whereas, at high Ca2+ (pCa5), SOL and EDL NTFs had initial fast velocities followed by ∼30% slower velocities within the C-zone. These data suggest that one or more of these MyBP-C can sensitize NTFs to Ca2+ and modulate contractility at high Ca2+. To determine how each isoform contributes to these modulatory capacities, we bacterially-expressed N-terminal fragments (sMyBP-C1, sMyBP-C2, fMyBP-C) and assessed their individual impact on SOL or EDL NTF motility over their respective monomeric myosins. For the EDL where all three MyBP-Cs are expressed, at pCa7.5 sMyBP-C1 was most effective at activating NTFs, while at pCa5 all three reduced velocity by ∼50%. For SOL, where only sMyBP-C isoforms are expressed, at pCa7.5 sMyBP-C1 activated NTFs while at pCa5 sMyBP-C2 reduced velocity ∼40%. Our data suggest that the distinctive mixture of MyBP-C isoforms expressed in the SOL and EDL is matched to the muscle's physiological demands. Each MyBP-C isoform possesses specific modulatory capacities that may be called upon under different contractile states. Specifically, to fine-tune actomyosin contractility within the C-zone by Ca2+-sensitizing the thin filament and/or modulating velocity at maximal activation.

Nuclear and structural dynamics during the establishment of a specialized effector-secreting cell by Magnaporthe oryzae in living rice cells

BackgroundTo cause an economically important blast disease on rice, the filamentous fungus Magnaporthe oryzae forms a specialized infection structure, called an appressorium, to penetrate host cells. Once inside host cells, the fungus produces a filamentous primary hypha that differentiates into multicellular bulbous invasive hyphae (IH), which are surrounded by a host-derived membrane. These hyphae secrete cytoplasmic effectors that enter host cells presumably via the biotrophic interfacial complex (BIC). The first IH cell, also known as the side BIC-associated cell, is a specialized effector-secreting cell essential for a successful infection. This study aims to determine cellular processes that lead to the development of this effector-secreting first IH cell inside susceptible rice cells.ResultsUsing live-cell confocal imaging, we determined a series of cellular events by which the appressorium gives rise to the first IH cell in live rice cells. The filamentous primary hypha extended from the appressorium and underwent asymmetric swelling at its apex. The single nucleus in the appressorium divided, and then one nucleus migrated into the swollen apex. Septation occurred in the filamentous region of the primary hypha, establishing the first IH cell. The tip BIC that was initially associated with the primary hypha became the side BIC on the swollen apex prior to nuclear division in the appressorium. The average distance between the early side BIC and the nearest nucleus in the appressorium was estimated to be more than 32 μm. These results suggest an unknown mechanism by which effectors that are expressed in the appressorium are transported through the primary hypha for their secretion into the distantly located BIC. When M. oryzae was inoculated on heat-killed rice cells, penetration proceeded as normal, but there was no differentiation of a bulbous IH cell, suggesting its specialization for establishment of biotrophic infection.ConclusionsOur studies reveal cellular dynamics associated with the development of the effector-secreting first IH cell. Our data raise new mechanistic questions concerning hyphal differentiation in response to host environmental cues and effector trafficking from the appressorium to the BIC.

Roles of conducting filament and non-filament regions in the Ta2O5 and HfO2 resistive switching memory for switching reliability.

The endurance of switching cycles, which is a critical measure of device reliability, in an ultra-thin (1.5 nm) Ta2O5 and HfO2 resistive random access (ReRAM) memory cell with a 28 nm lateral dimension was studied using current-voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. The two devices showed the typical oxygen-deficient conducting-filament (CF)-mediated bipolar resistance switching behaviour, which was induced by the asymmetric electrode configuration: Ta as the oxygen vacancy (VO) source/reservoir and TiN as the inert electrode. In these device geometries, the CF is supposed to initiate at the oxide/TiN interface and to grow towards the Ta electrode during the switch-on process, while the switch-off process was induced by the contraction of the CF from the Ta/oxide interface. Both devices, however, showed inversion (anomalous SET; switching from the off- to on-state) behaviour in the RESET (switching from the on- to off-state) process, which can be explained by the authors' previous model of the hourglass-shaped CF. In this model, once the CF is ruptured, the RESET polarity bias makes the lower portion of the CF regrow to slightly reconnect such a CF through the accelerated migration of VO from the upper-portion CF to the lower-portion CF, which induces switching performance degradation. In the I-V sweeps, the on- and off-states of the devices showed an overall conductance difference approximately corresponding to the integer multiple values of quantum point contact (G0), but there were arbitrary 0.25 and 0.125G0 differences in the conductance values of the on-state for the Ta2O5 and HfO2 devices, respectively. This suggests that these are the minimal units of conductance variation even for a given CF with a standard G0. Although the precise reason for the emergence of such an abnormal conductance unit is not yet understood, its implication for the reliability is critical. Reliable resistive switching was achieved only for the cases where the minimum point conductance was retained even in the off-state; in the other cases, over-SET and over-RESET were induced, which eventually degraded the device reliability. The detailed quantitative analysis of the device failure revealed that the increasing concentration of VO within the non-CF region in the cell decreased the resistance values of that region, which eventually resulted in the over-SET and over-RESET behaviours during the CLPS tests.

Hyperactivity in 103P/Hartley 2: Chunks from the sub-surface in Type IIa jet regions

We analyze the observed radial distribution of column densities of water-ice particulates embedded in the primary jet region (J1) of 103P's inner coma at altitudes between 439 and 1967m (Protopapa et al., 2014, Icarus 238, 191–204) and determine the speed and acceleration of particles and their mass-flow within the filaments of the jet. This is done by applying a CO2 driven (Type IIa) jet model proposed by Belton (2010, Icarus 210, 881–897). The model utilizes water-ice particles dislodged in the source regions of the jet filaments and accelerated by CO2 to explain the radial distribution of water-ice particulates. We provide an explanation for the remarkably different radial distribution of refractory dust particles by hypothesizing that the majority of the dust originates directly from the nucleus surface in inter-filament regions of the jet complex and is accelerated by H2O. Our model provides a mass-flow of water from the J1 jet complex that is ∼40 times greater than the constant speed sublimation model discussed by Protopapa et al. but is still too small to explain the hyperactivity of the comet. Speeds in the flow are increased by a factor up to ∼20 over those found by Protopapa et al.To account for the hyperactivity, most of the mass dislodged in the filament source regions must be in weakly accelerated large chunks that achieve only low speeds en route to the region of observation. These chunks soon leave the filamentary jet structure due to the rotation of the nucleus and do not contribute to the column densities observed at higher altitudes in the jet filaments. Employing the results of Kelley et al. (2015. Icarus 262, 187–189)) on total cross-section and mass-flow in the coma we find that large chunks with the same bulk properties as the nucleus can increase the active fraction of the comet by two or three times. With the exception that the chunks do not need to be “nearly pure water ice”, these results support the hypothesis that hyperactivity in comet 103P/Hartley 2 is the result of super-volatiles that “… drag out chunks of nearly pure water ice that then sublime to provide a large fraction of the total H2O gaseous output of the comet (A'Hearn et al., 2011. Science 332, 1396–1400). We find that the largest chunks (effective radius ∼4m) are probably dislodged at an average rate less than 1 chunk/filament/1–3 rotation periods near perihelion and we estimate that the filamentary source regions, if 50–100m in diameter, could be excavated to a depth of 44–171m in a single perihelion passage. We note similarities with groups of active pits discovered on 67P (Vincent et al., 2015. Nature 523, 63–66) and suggest that these features may have, in the past, supported Type IIa super-volatile jet outflows that are now essentially exhausted.