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Electric current spread

Monique A M de Jong, Jeroen J Briaire, Johan H M Frijns
OBJECTIVES: In an attempt to improve spectral resolution and speech intelligibility, several current focusing methods have been proposed to increase spatial selectivity by decreasing intracochlear current spread. For example, tripolar stimulation administers current to a central electrode and uses the two flanking electrodes as the return pathway, creating a narrower intracochlear electrical field and hence increases spectral resolution when compared with monopolar (MP) stimulation. However, more current is required, and in some patients, specifically the ones with high electrode impedances, full loudness growth cannot be supported because of compliance limits...
May 8, 2018: Ear and Hearing
Ning Zhou, Matthew Cadmus, Lixue Dong, Juliana Mathews
Prior research has shown that in electrical hearing, cochlear implant (CI) users' speech recognition performance is related in part to their ability to detect temporal modulation (i.e., modulation sensitivity). Previous studies have also shown better speech recognition when selectively stimulating sites with good modulation sensitivity rather than all stimulation sites. Site selection based on channel interaction measures, such as those using imaging or psychophysical estimates of spread of neural excitation, has also been shown to improve speech recognition...
April 25, 2018: Journal of the Association for Research in Otolaryngology: JARO
Jack M Craig, Vanessa Correa-roldÁn, HernÁn Ortega, William G R Crampton, James S Albert
Banded Knifefishes (Gymnotus, Gymnotidae) comprise the most species-rich genus of Neotropical electric fishes, with 41 species currently described from throughout the humid Neotropics, from Mexico to Argentina. Despite substantial alpha-taxonomic work in recent years, the diversity of Gymnotus in some regions remains poorly understood. Here we describe the Gymnotus fauna of the Upper Madeira basin of Bolivia and Peru from examination of more than 240 adult specimens. Species are delimited and described using body proportions (traditional morphometrics), fin-ray, squamation and laterosensory-pore counts (meristics), quantitative shape differences (geometric morphometrics), osteological traits, and color patterns...
April 20, 2018: Zootaxa
Tae Kyoung Kim, Yeo Jin Yoon, Seung Kyu Oh, Yu-Jung Cha, In Yeol Hong, Moon Uk Cho, Chan-Hwa Hong, Hong Kyw Choi, Joon Seop Kwak
In order to improve EQE, we have investigated on the role of multilayer graphene (MLG) on the electrical and optical properties of GaN based light-emitting diodes (LEDs) with ultrathin ITO (5 nm or 10 nm)/p-GaN contacts. The MLG was transferred on the ITO/p-GaN to decrease sheet resistance of thin ITO p-electrode and improve the current spreading of LEDs. The LEDs with the ITO 5 nm and MLG/ITO 5 nm structures showed 3.25 and 3.06 V at 20 mA, and 11.69 and 13.02 mW/sr at 400 mA, respectively. After forming MLG on ITO 5 nm, the electro-optical properties were enhanced...
September 1, 2018: Journal of Nanoscience and Nanotechnology
G Ten Haaf, S H W Wouters, D F J Nijhof, P H A Mutsaers, E J D Vredenbregt
The energy distribution of a high brightness rubidium ion beam, which is intended to be used as the source for a focused ion beam instrument, is measured with a retarding field analyzer. The ions are created from a laser-cooled and compressed atomic beam by two-step photoionization in which the ionization laser power is enhanced in a build-up cavity. Particle tracing simulations are performed to ensure the analyzer is able to resolve the distribution. The lowest achieved full width 50% energy spread is (0.205 ± 0...
April 5, 2018: Ultramicroscopy
Tim Jürgens, Volker Hohmann, Andreas Büchner, Waldo Nogueira
The relation of the individual speech-in-noise performance differences in cochlear implant (CI) users to underlying physiological factors is currently poorly understood. This study approached this research question by a step-wise individualization of a computer model of speech intelligibility mimicking the details of CI signal processing and some details of the physiology present in CI users. Two factors, the electrical field spatial spread and internal noise (as a coarse model of the individual cognitive performance) were incorporated...
2018: PloS One
Sanja Brolih, Scott K Parks, Valérie Vial, Jérôme Durivault, Livio Mostosi, Jacques Pouysségur, Gilles Pagès, Vincent Picco
BACKGROUND: In mammals, the AKT/PKB protein kinase family comprises three members (AKT1-3). PI3-Kinase (PI3K), a key oncogene involved in a wide variety of cancers, drives AKT activity. Constitutive activation of the PI3K/AKT pathway has been associated with tumorigenic properties including uncontrolled cell proliferation and survival, angiogenesis, promotion of cellular motility, invasiveness and metastasis. However, AKT1 activity has also been recently shown to repress the invasive properties of breast cancer cells in specific contexts...
March 5, 2018: BMC Cancer
Timothy B Esler, Robert R Kerr, Bahman Tahayori, David B Grayden, Hamish Meffin, Anthony N Burkitt
Currently, a challenge in electrical stimulation of the retina with a visual prosthesis (bionic eye) is to excite only the cells lying directly under the electrode in the ganglion cell layer, while avoiding excitation of axon bundles that pass over the surface of the retina in the nerve fiber layer. Stimulation of overlying axons results in irregular visual percepts, limiting perceptual efficacy. This research explores how differences in fiber orientation between the nerve fiber layer and ganglion cell layer leads to differences in the electrical activation of the axon initial segment and axons of passage...
2018: PloS One
Olga Cozzolino, Maria Marchese, Francesco Trovato, Enrico Pracucci, Gian Michele Ratto, Maria Gabriella Buzzi, Federico Sicca, Filippo M Santorelli
Spreading depression (SD) is a neurophysiological phenomenon characterized by abrupt changes in intracellular ion gradients and sustained depolarization of neurons. It leads to loss of electrical activity, changes in the synaptic architecture, and an altered vascular response. Although SD is often described as a unique phenomenon with homogeneous characteristics, it may be strongly affected by the particular triggering event and by genetic background. Furthermore, SD may contribute differently to the pathogenesis of widely heterogeneous clinical conditions...
2018: Frontiers in Neurology
E B Montufar, M Casas-Luna, M Horynová, S Tkachenko, Z Fohlerová, S Diaz-de-la-Torre, K Dvořák, L Čelko, J Kaiser
In this work alpha tricalcium phosphate (α-TCP)/iron (Fe) composites were developed as a new family of biodegradable, load-bearing and cytocompatible materials. The composites with composition from pure ceramic to pure metallic samples were consolidated by pulsed electric current assisted sintering to minimise processing time and temperature while improving their mechanical performance. The mechanical strength of the composites was increased and controlled with the Fe content, passing from brittle to ductile failure...
April 1, 2018: Acta Biomaterialia
Ilias Pagkalos, Michelle L Rogers, Martyn G Boutelle, Emmanuel M Drakakis
This paper presents the first application specific integrated chip (ASIC) for the monitoring of patients who have suffered a Traumatic Brain Injury (TBI). By monitoring the neurophysiological (ECoG) and neurochemical (glucose, lactate and potassium) signals of the injured human brain tissue, it is possible to detect spreading depolarisations, which have been shown to be associated with poor TBI patient outcome. This paper describes the testing of a new 7.5 mm2 ASIC fabricated in the commercially available AMS 0...
January 31, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Petro M Lytvyn, Andrian V Kuchuk, Yuriy I Mazur, Chen Li, Morgan E Ware, Zhiming M Wang, Vasyl P Kladko, Alexander E Belyaev, Gregory J Salamo
We experimentally demonstrate that the conductivity of graded Alx Ga1-x N increases as a function of the magnitude of the Al concentration gradient (%Al/nm) due to polarization doping effects, without the use of impurity dopants. Using three up/down-graded Alx Ga1-x N nanolayers with Al gradients ranging from ∼0.16 to ∼0.28%Al/nm combined in one structure, the effects of polarization engineering for localized electric fields and current transport were investigated. Cross-sectional Kelvin probe force microscopy and conductive atomic force microscopy were used to directly probe the electrical properties of the films with spatial resolution along the thickness of the growth...
February 21, 2018: ACS Applied Materials & Interfaces
Quoc Vo, Haibin Su, Tuan Tran
Droplet spreading on substrates by electrowetting exhibits either of the two transient behaviours: one characterised by contact line oscillation, and the other one by slow spreading dynamics. The transition between these behaviours remains elusive due to the current limited understanding of the spreading dynamics on the hydrodynamical and electrical properties of electrowetting systems. To understand this transition we propose a model capturing the transition's occurrence based on both the hydrodynamical and electrical parameters...
January 16, 2018: Scientific Reports
Qian-Jie Fu, John J Galvin, Xiaosong Wang
Differences in current spread and/or spread of excitation may differently affect integration of acoustic and electric hearing within (electric-acoustic stimulation, or EAS) or across ears (bimodal). In this study, vowel recognition was measured in normal-hearing subjects listening to simulations of cochlear implant (CI), EAS, and bimodal listening. Residual acoustic hearing was limited between 0.1 and 0.6 kHz. The carrier bandwidth in the CI simulations was varied across carriers: broad-band noise, narrow-band noise, and sine waves...
December 2017: Journal of the Acoustical Society of America
Ewan D Fowler, Cherrie H T Kong, Jules C 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 plateau. However, Ca2+ release sites that did not initially activate or which have prematurely recovered from refractoriness might release Ca2+ later during the action potential 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...
February 2, 2018: Circulation Research
Jean Isnard, Delphine Taussig, Fabrice Bartolomei, Pierre Bourdillon, Hélène Catenoix, Francine Chassoux, Mathilde Chipaux, Stéphane Clémenceau, Sophie Colnat-Coulbois, Marie Denuelle, Stéphane Derrey, Bertrand Devaux, Georg Dorfmüller, Vianney Gilard, Marc Guenot, Anne-Sophie Job-Chapron, Elisabeth Landré, Axel Lebas, Louis Maillard, Aileen McGonigal, Lorella Minotti, Alexandra Montavont, Vincent Navarro, Anca Nica, Nicolas Reyns, Julia Scholly, Jean-Christophe Sol, William Szurhaj, Agnès Trebuchon, Louise Tyvaert, Maria Paola Valenti-Hirsch, Luc Valton, Jean-Pierre Vignal, Paul Sauleau
Stereoelectroencephalography (SEEG) was designed and developed in the 1960s in France by J. Talairach and J. Bancaud. It is an invasive method of exploration for drug-resistant focal epilepsies, offering the advantage of a tridimensional and temporally precise study of the epileptic discharge. It allows anatomo-electrical correlations and tailored surgeries. Whereas this method has been used for decades by experts in a limited number of European centers, the last ten years have seen increasing worldwide spread of its use...
February 2018: Neurophysiologie Clinique, Clinical Neurophysiology
Linjing Xu, Alison E Seline, Braden Leigh, Mark Ramirez, C Allan Guymon, Marlan R Hansen
HYPOTHESIS: Microtopographical patterns generated by photopolymerization of methacrylate polymer systems will direct growth of neurites from adult neurons, including spiral ganglion neurons (SGNs). BACKGROUND: Cochlear implants (CIs) provide hearing perception to patients with severe to profound hearing loss. However, their ability to encode complex auditory stimuli is limited due, in part, to poor spatial resolution caused by spread of the electrical currents in the inner ear...
January 2018: Otology & Neurotology
Francesca Eroli, Inge C M Loonen, Arn M J M van den Maagdenberg, Else A Tolner, Andrea Nistri
Endocannabinoids are suggested to control pain, even though their clinical use is not fully validated and the underlying mechanisms are incompletely understood. To clarify the targets of endocannabinoid actions, we studied how activation of the endocannabinoid CB1 receptor (CB1R) affects neuronal responses in two in vitro preparations of rodents, namely the trigeminal sensory ganglion (TG) in culture and a coronal slice of the cerebral cortex. On TG small-medium size neurons, we tested whether submicromolar concentrations of the endogenous CB1R agonist anandamide (AEA) modulated inhibitory GABAA receptors and excitatory ATP-gated P2X3 receptors...
March 15, 2018: Neuropharmacology
T A K Nguyen, Samuel Cavuscens, Maurizio Ranieri, Konrad Schwarz, Nils Guinand, Raymond van de Berg, Thomas van den Boogert, Floor Lucieer, Marc van Hoof, Jean-Philippe Guyot, Herman Kingma, Silvestro Micera, Angelica Perez Fornos
The peripheral vestibular system is critical for the execution of activities of daily life as it provides movement and orientation information to motor and sensory systems. Patients with bilateral vestibular hypofunction experience a significant decrease in quality of life and have currently no viable treatment option. Vestibular implants could eventually restore vestibular function. Most vestibular implant prototypes to date are modified cochlear implants to fast-track development. These use various objective measurements, such as the electrically evoked compound action potential (eCAP), to supplement behavioral information...
2017: Frontiers in Neuroscience
Adam Kapela, Erik J Behringer, Steven S Segal, Nikolaos M Tsoukias
OBJECTIVE: Electrical signaling along the endothelium underlies spreading vasodilation and blood flow control. We use mathematical modeling to determine the electrical properties of the endothelium and gain insight into the biophysical determinants of electrical conduction. METHODS: Electrical conduction data along endothelial tubes (40 μm wide, 2.5 mm long) isolated from mouse skeletal muscle resistance arteries were analyzed using cable equations and a multicellular computational model...
February 2018: Microcirculation: the Official Journal of the Microcirculatory Society, Inc
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