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https://www.readbyqxmd.com/read/29347384/bifurcation-analysis-and-phase-diagram-of-a-spin-string-model-with-buckled-states
#1
M Ruiz-Garcia, L L Bonilla, A Prados
We analyze a one-dimensional spin-string model, in which string oscillators are linearly coupled to their two nearest neighbors and to Ising spins representing internal degrees of freedom. String-spin coupling induces a long-range ferromagnetic interaction among spins that competes with a spin-spin antiferromagnetic coupling. As a consequence, the complex phase diagram of the system exhibits different flat rippled and buckled states, with first or second order transition lines between states. This complexity translates to the two-dimensional version of the model, whose numerical solution has been recently used to explain qualitatively the rippled to buckled transition observed in scanning tunneling microscopy experiments with suspended graphene sheets...
December 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347243/analytical-scalings-of-the-linear-richtmyer-meshkov-instability-when-a-rarefaction-is-reflected
#2
F Cobos-Campos, J G Wouchuk
The Richtmyer-Meshkov instability for the case of a reflected rarefaction is studied in detail following the growth of the contact surface in the linear regime and providing explicit analytical expressions for the asymptotic velocities in different physical limits. This work is a continuation of the similar problem when a shock is reflected [Phys. Rev. E 93, 053111 (2016)1539-375510.1103/PhysRevE.93.053111]. Explicit analytical expressions for the asymptotic normal velocity of the rippled surface (δv_{i}^{∞}) are shown...
July 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347053/radiation-pressure-driven-ion-weibel-instability-and-collisionless-shocks
#3
A Grassi, M Grech, F Amiranoff, A Macchi, C Riconda
The Weibel instability from counterstreaming plasma flows is a basic process highly relevant for collisionless shock formation in astrophysics. In this paper we investigate, via two- and three-dimensional simulations, suitable configurations for laboratory investigations of the ion Weibel instability (IWI) driven by a fast quasineutral plasma flow launched into the target via the radiation pressure of an ultra-high-intensity laser pulse ("hole-boring" process). The use of S-polarized light at oblique incidence is found to be an optimal configuration for driving IWI, as it prevents the development of surface rippling observed at normal incidence that would lead to strong electron heating and would favor competing instabilities...
September 2017: Physical Review. E
https://www.readbyqxmd.com/read/29346880/emergence-and-detailed-structure-of-terraced-surfaces-produced-by-oblique-incidence-ion-sputtering
#4
Matt P Harrison, Daniel A Pearson, R Mark Bradley
We study the nanoscale terraced topographies that arise when a solid surface is bombarded with a broad ion beam that has a relatively high angle of incidence θ. We find that the surface is not completely flat between the regions in which the surface slope changes rapidly with position: Instead, small-amplitude ripples propagate along the surface. Our analytical work on these ripples yields their propagation velocity as well as the scaling behavior of their amplitude. Our simulations establish that the surfaces exhibit interrupted coarsening, i...
September 2017: Physical Review. E
https://www.readbyqxmd.com/read/29341322/isthmus-sites-identified-by-ripple-mapping-are-usually-anatomically-stable-a-novel-method-to-guide-atrial-substrate-ablation
#5
Vishal Luther, Norman Qureshi, Phang Boon Lim, Michael Koa-Wing, Shahnaz Jamil-Copley, Fu Siong Ng, Zachary Whinnett, D Wyn Davies, Nicholas S Peters, Prapa Kanagaratnam, Nick Linton
BACKGROUND: Post ablation reentrant ATs depend upon conducting isthmuses bordered by scar. Bipolar voltage maps highlight scar as sites of low voltage, but the voltage amplitude of an electrogram depends upon the myocardial activation sequence. Furthermore, a voltage threshold that defines atrial scar is unknown. We used Ripple Mapping (RM) to test whether these isthmuses were anatomically fixed between different activation vectors and atrial rates. METHODS: We studied post-AF ablation ATs where > 1 rhythm was mapped...
January 17, 2018: Journal of Cardiovascular Electrophysiology
https://www.readbyqxmd.com/read/29336788/grey-wolf-based-control-for-speed-ripple-reduction-at-low-speed-operation-of-pmsm-drives
#6
Ali Djerioui, Azeddine Houari, Mourad Ait-Ahmed, Mohamed-Fouad Benkhoris, Aissa Chouder, Mohamed Machmoum
Speed ripple at low speed-high torque operation of Permanent Magnet Synchronous Machine (PMSM) drives is considered as one of the major issues to be treated. The presented work proposes an efficient PMSM speed controller based on Grey Wolf (GW) algorithm to ensure a high-performance control for speed ripple reduction at low speed operation. The main idea of the proposed control algorithm is to propose a specific objective function in order to incorporate the advantage of fast optimization process of the GW optimizer...
January 11, 2018: ISA Transactions
https://www.readbyqxmd.com/read/29335778/hippocampal-area-ca2-properties-and-contribution-to-hippocampal-function
#7
REVIEW
Vincent Robert, Sadiyah Cassim, Vivien Chevaleyre, Rebecca A Piskorowski
This review focuses on area CA2 of the hippocampus, as recent results have revealed the unique properties and surprising role of this region in encoding social, temporal and contextual aspects of memory. Originally identified and described by Lorente de No, in 1934, this region of the hippocampus has unique intra-and extra-hippocampal connectivity, sending and receiving input to septal and hypothalamic regions. Recent in vivo studies have indicated that CA2 pyramidal neurons encode spatial information during immobility and play an important role in the generation of sharp-wave ripples...
January 15, 2018: Cell and Tissue Research
https://www.readbyqxmd.com/read/29335604/dentate-network-activity-is-necessary-for-spatial-working-memory-by-supporting-ca3-sharp-wave-ripple-generation-and-prospective-firing-of-ca3-neurons
#8
Takuya Sasaki, Verónica C Piatti, Ernie Hwaun, Siavash Ahmadi, John E Lisman, Stefan Leutgeb, Jill K Leutgeb
Complex spatial working memory tasks have been shown to require both hippocampal sharp-wave ripple (SWR) activity and dentate gyrus (DG) neuronal activity. We therefore asked whether DG inputs to CA3 contribute to spatial working memory by promoting SWR generation. Recordings from DG and CA3 while rats performed a dentate-dependent working memory task on an eight-arm radial maze revealed that the activity of dentate neurons and the incidence rate of SWRs both increased during reward consumption. We then found reduced reward-related CA3 SWR generation without direct input from dentate granule neurons...
January 15, 2018: Nature Neuroscience
https://www.readbyqxmd.com/read/29331447/sharp-wave-ripples-as-a-signature-of-hippocampal-prefrontal-reactivation-for-memory-during-sleep-and-waking-states
#9
Wenbo Tang, Shantanu P Jadhav
It is widely believed that memories that are encoded and retrieved during waking behavior are consolidated during sleep. Recent studies on the interactions between the hippocampus and the prefrontal cortex have greatly advanced our understanding of the physiological bases of these memory processes. Although hippocampal-prefrontal network activity differs in many aspects during waking and sleep states, here we review evidence that hippocampal sharp-wave ripples (SWRs) emerge as a common neurophysiological pattern in both states, facilitating communication between these two regions via coordinated reactivation of stored memory information...
January 10, 2018: Neurobiology of Learning and Memory
https://www.readbyqxmd.com/read/29315516/strong-coupling-between-slow-oscillations-and-wide-fast-ripples-in-children-with-epileptic-spasms-investigation-of-modulation-index-and-occurrence-rate
#10
Yasushi Iimura, Kevin Jones, Lynne Takada, Itsuki Shimizu, Misaki Koyama, Kyoko Hattori, Yushi Okazawa, Yutaka Nonoda, Eishi Asano, Tomoyuki Akiyama, Cristina Go, Ayako Ochi, O Carter Snead, Elizabeth J Donner, James T Rutka, James M Drake, Hiroshi Otsubo
OBJECTIVE: Epileptic spasms (ES) often become drug-resistant. To reveal the electrophysiological difference between children with ES (ES+) and without ES (ES-), we compared the occurrence rate (OR) of high-frequency oscillations (HFOs) and the modulation index (MI) of coupling between slow and fast oscillations. In ES+, we hypothesized that (1) pathological HFOs are more widely distributed and (2) slow oscillations show stronger coupling with pathological HFOs than in ES-. METHODS: We retrospectively reviewed 24 children with drug-resistant multilobar onset epilepsy, who underwent intracranial video electroencephalography prior to multilobar resections...
January 6, 2018: Epilepsia
https://www.readbyqxmd.com/read/29303186/geometric-and-electronic-structure-of-multilayered-graphene-synergy-of-the-nondirective-ripples-and-the-number-of-layers
#11
Ting Ting Cui, Jian Chen Li, Wang Gao, Qing Jiang
According to the Mermin-Wagner theorem, ripple deformation is ubiquitous in a two-dimensional (2D) free-standing sheet, influencing the electronic properties. However, the synergistic effects of the unrestricted ripples and the number of layers have still been a topic of extensive debate. To address this issue, we employed density functional theory including many-body van der Waals (vdW) correction to investigate the effects of the nondirective ripples on the geometric and electronic structures of multilayered graphene...
January 5, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29302486/early-multicentre-experience-of-pre-pectoral-implant-based-immediate-breast-reconstruction-using-braxon%C3%A2
#12
Sadaf Jafferbhoy, Mihir Chandarana, Maria Houlihan, Rishikesh Parmeshwar, Sankaran Narayanan, Soni Soumian, Simon Harries, Lucie Jones, Dayalan Clarke
Background: The last two decades have seen significant changes in surgical management of breast cancer. The offer of immediate breast reconstruction (IBR) following mastectomy is currently standard practice. Skin sparing and nipple sparing mastectomy with implant-based IBR have emerged as oncologically safe treatment options. Prepectoral implant placement and complete coverage of implant with acellular dermal matrix (ADM) eliminates the need to detach the muscle from underlying chest wall in contrast to the subpectoral technique...
December 2017: Gland Surgery
https://www.readbyqxmd.com/read/29294811/playing-by-the-rules-agency-policy-and-procedure-in-service-experience-of-ipv-survivors
#13
Leila Wood, Laurie Cook Heffron, Molly Voyles, Shanti Kulkarni
More than 1,800 programs exist in the United States, providing not only shelter but also transitional housing, advocacy and support, transportation, legal aid, and group and individual counseling for women who have experienced intimate partner violence (IPV). Shelter and transitional housing provide critical support for survivors, but have also been critiqued for having too many restrictive rules and code of conduct. More information is needed about the impact of rules and agency policy on women seeking services in IPV residential settings...
June 1, 2017: Journal of Interpersonal Violence
https://www.readbyqxmd.com/read/29289338/full-order-observer-for-direct-torque-control-of-induction-motor-based-on-constant-v-f-control-technique
#14
Narongrit Pimkumwong, Ming-Shyan Wang
This paper presents another control method for the three-phase induction motor that is direct torque control based on constant voltage per frequency control technique. This method uses the magnitude of stator flux and torque errors to generate the stator voltage and phase angle references for controlling the induction motor by using constant voltage per frequency control method. Instead of hysteresis comparators and optimum switching table, the PI controllers and space vector modulation technique are used to reduce torque and stator-flux ripples and achieve constant switching frequency...
December 27, 2017: ISA Transactions
https://www.readbyqxmd.com/read/29282211/late-ca2-sparks-and-ripples-during-the-systolic-ca2-transient-in-heart-muscle-cells
#15
Ewan D Fowler, Cherrie H Kong, Jules Hancox, Mark B Cannell
Rationale: The development of a refractory period for Ca2+ spark initiation after Ca2+ release in cardiac myocytes, should inhibit further Ca2+ release during the action potential (AP) plateau. However, Ca2+ release sites that did not initially activate, or which have prematurely recovered from refractoriness might release Ca2+ later during the AP and alter the cell-wide Ca2+ transient. Objective: To investigate the possibility of late Ca2+ spark (LCS) activity in intact isolated cardiac myocytes using fast confocal line scanning with improved confocality and signal to noise...
December 27, 2017: Circulation Research
https://www.readbyqxmd.com/read/29279309/evidence-for-long-timescale-patterns-of-synaptic-inputs-in-ca1-of-awake-behaving-mice
#16
Ilya Kolb, Giovanni Talei Franzesi, Michael Wang, Suhasa B Kodandaramaiah, Craig R Forest, Edward S Boyden, Annabelle C Singer
Repeated sequences of neural activity are a pervasive feature of neural networks in vivo and in vitro. In the hippocampus, sequential firing of many neurons over 100-300 ms periods re-occurs during behavior and during periods of quiescence. However, it is not known whether the hippocampus produces longer sequences of activity or whether such sequences are restricted to specific network states. Furthermore, whether long repeated patterns of activity are transmitted to single cells downstream is unclear. To answer these questions, we recorded intracellularly from hippocampal CA1 of awake, behaving male mice, to examine both subthreshold activity and spiking output in single neurons...
December 26, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/29277640/using-image-attributes-to-assure-accurate-particle-size-and-count-using-nanoparticle-tracking-analysis
#17
Adrian P Defante, Wyatt N Vreeland, Kurt D Benkstein, Dean C Ripple
Nanoparticle tracking analysis (NTA) obtains particle size by analysis of particle diffusion through a time series of micrographs and particle count by a count of imaged particles. The number of observed particles imaged is controlled by the scattering cross-section of the particles and by camera settings such as sensitivity and shutter speed. Appropriate camera settings are defined as those that image, track, and analyze a sufficient number of particles for statistical repeatability. Here, we test if image attributes, features captured within the image itself, can provide measurable guidelines to assess the accuracy for particle size and count measurements using NTA...
December 22, 2017: Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/29251801/the-role-of-replay-and-theta-sequences-in-mediating-hippocampal-prefrontal-interactions-for-memory-and-cognition
#18
Mark C Zielinski, Wenbo Tang, Shantanu P Jadhav
Sequential activity is seen in the hippocampus during multiple network patterns, prominently as replay activity during both awake and sleep sharp-wave ripples (SWRs), and as theta sequences during active exploration. Although various mnemonic and cognitive functions have been ascribed to these hippocampal sequences, evidence for these proposed functions remains primarily phenomenological. Here, we briefly review current knowledge about replay events and theta sequences in spatial memory tasks. We reason that in order to gain a mechanistic and causal understanding of how these patterns influence memory and cognitive processing, it is important to consider how these sequences influence activity in other regions, and in particular, the prefrontal cortex, which is crucial for memory-guided behavior...
December 18, 2017: Hippocampus
https://www.readbyqxmd.com/read/29244226/high-frequency-oscillations-are-not-better-biomarkers-of-epileptogenic-tissues-than-spikes
#19
Nicolas Roehri, Francesca Pizzo, Stanislas Lagarde, Isabelle Lambert, Anca Nica, Aileen McGonigal, Bernard Giusiano, Fabrice Bartolomei, Christian-George Bénar
OBJECTIVE: High-frequency oscillations (HFOs) in intracerebral EEG (stereoelectroencephalography, SEEG) are considered as better biomarkers of epileptogenic tissues than spikes. How this can be applied at the patient level remains poorly understood. We investigated how well the HFOs and the spikes can predict epileptogenic regions with a large spatial sampling at the patient level. METHODS: We analyzed non-REM sleep SEEG recordings sampled at 2,048Hz of thirty patients...
December 15, 2017: Annals of Neurology
https://www.readbyqxmd.com/read/29234075/replay-of-large-scale-spatio-temporal-patterns-from-waking-during-subsequent-nrem-sleep-in-human-cortex
#20
Xi Jiang, Isaac Shamie, Werner K Doyle, Daniel Friedman, Patricia Dugan, Orrin Devinsky, Emad Eskandar, Sydney S Cash, Thomas Thesen, Eric Halgren
Animal studies support the hypothesis that in slow-wave sleep, replay of waking neocortical activity under hippocampal guidance leads to memory consolidation. However, no intracranial electrophysiological evidence for replay exists in humans. We identified consistent sequences of population firing peaks across widespread cortical regions during complete waking periods. The occurrence of these "Motifs" were compared between sleeps preceding the waking period ("Sleep-Pre") when the Motifs were identified, and those following ("Sleep-Post")...
December 12, 2017: Scientific Reports
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