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Sample records for brain surface electric

  1. Brain surface temperature under a craniotomy.

    Science.gov (United States)

    Kalmbach, Abigail S; Waters, Jack

    2012-12-01

    Many neuroscientists access surface brain structures via a small cranial window, opened in the bone above the brain region of interest. Unfortunately this methodology has the potential to perturb the structure and function of the underlying brain tissue. One potential perturbation is heat loss from the brain surface, which may result in local dysregulation of brain temperature. Here, we demonstrate that heat loss is a significant problem in a cranial window preparation in common use for electrical recording and imaging studies in mice. In the absence of corrective measures, the exposed surface of the neocortex was at ∼28°C, ∼10°C below core body temperature, and a standing temperature gradient existed, with tissue below the core temperature even several millimeters into the brain. Cooling affected cellular and network function in neocortex and resulted principally from increased heat loss due to convection and radiation through the skull and cranial window. We demonstrate that constant perfusion of solution, warmed to 37°C, over the brain surface readily corrects the brain temperature, resulting in a stable temperature of 36-38°C at all depths. Our results indicate that temperature dysregulation may be common in cranial window preparations that are in widespread use in neuroscience, underlining the need to take measures to maintain the brain temperature in many physiology experiments.

  2. Electrically Conductive Anodized Aluminum Surfaces

    Science.gov (United States)

    Nguyen, Trung Hung

    2006-01-01

    Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In comparison with these competing finishes, the present nanocomposite finishes are expected to cost 50

  3. Electrical bioimpedance enabling prompt intervention in traumatic brain injury

    Science.gov (United States)

    Seoane, Fernando; Atefi, S. Reza

    2017-05-01

    Electrical Bioimpedance (EBI) is a well spread technology used in clinical practice across the world. Advancements in Textile material technology with conductive textile fabrics and textile-electronics integration have allowed exploring potential applications for Wearable Measurement Sensors and Systems exploiting. The sensing principle of electrical bioimpedance is based on the intrinsic passive dielectric properties of biological tissue. Using a pair of electrodes, tissue is electrically stimulated and the electrical response can be sensed with another pair of surface electrodes. EBI spectroscopy application for cerebral monitoring of neurological conditions such as stroke and perinatal asphyxia in newborns have been justified using animal studies and computational simulations. Such studies have shown proof of principle that neurological pathologies indeed modify the dielectric composition of the brain that is detectable via EBI. Similar to stroke, Traumatic Brain Injury (TBI) also affects the dielectric properties of brain tissue that can be detected via EBI measurements. Considering the portable and noninvasive characteristics of EBI it is potentially useful for prehospital triage of TBI patients where. In the battlefield blast induced Traumatic Brain Injuries are very common. Brain damage must be assessed promptly to have a chance to prevent severe damage or eventually death. The relatively low-complexity of the sensing hardware required for EBI sensing and the already proven compatibility with textile electrodes suggest the EBI technology is indeed a candidate for developing a handheld device equipped with a sensorized textile cap to produce an examination in minutes for enabling medically-guided prompt intervention.

  4. Electric Brain Stimulation No Better Than Meds for Depression: Study

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_166920.html Electric Brain Stimulation No Better Than Meds For Depression: ... can't find relief, stimulating the brain with electric impulses may help. But a new study by ...

  5. Corrosion Protection of Electrically Conductive Surfaces

    Directory of Open Access Journals (Sweden)

    Jian Song

    2012-11-01

    Full Text Available The basic function of the electrically conductive surface of electrical contacts is electrical conduction. The electrical conductivity of contact materials can be largely reduced by corrosion and in order to avoid corrosion, protective coatings must be used. Another phenomenon that leads to increasing contact resistance is fretting corrosion. Fretting corrosion is the degradation mechanism of surface material, which causes increasing contact resistance. Fretting corrosion occurs when there is a relative movement between electrical contacts with surfaces of ignoble metal. Avoiding fretting corrosion is therefore extremely challenging in electronic devices with pluggable electrical connections. Gold is one of the most commonly used noble plating materials for high performance electrical contacts because of its high corrosion resistance and its good and stable electrical behavior. The authors have investigated different ways to minimize the consumption of gold for electrical contacts and to improve the performance of gold plating. Other plating materials often used for corrosion protection of electrically conductive surfaces are tin, nickel, silver and palladium. This paper will deal with properties and new research results of different plating materials in addition to other means used for corrosion protection of electrically conductive surfaces and the testing of corrosion resistance of electrically conductive surfaces.

  6. Order/disorder in brain electrical activity

    Science.gov (United States)

    Rosso, O. A.; Figliola, Y. A.

    2004-04-01

    The processing of information by the brain is reflected in dynamical changes of the electrical activity in time, frequency, and space. Therefore, the concomitant studies require methods capable of describing the quantitative variation of the signal in both time and frequency. Here we present a quantitative EEG (qEEG) analysis, based on the Orthogonal Discrete Wavelet Transform (ODWT), of generalized epileptic tonic-clonic EEG signals. Two quantifiers: the Relative Wavelet Energy (RWE) and the Normalized Total Wavelet Entropy (NTWS) have been used. The RWE gives information about the relative energy associated with the different frequency bands present in the EEG and their corresponding degree of importance. The NTWS is a measure of the order/disorder degree in the EEG signal. These two quantifiers were computing in EEG signals as provided by scalp electrodes of epileptic patients. We showed that the epileptic recruitment rhythm observed for generalized epileptic tonic-clonic seizures is accurately described by the RWE quantifier. In addition, a significant decrease in the NTWS was observed in the recruitment epoch, indicating a more rhythmic and ordered behavior in the brain electrical activity.

  7. Noninvasive Deep Brain Stimulation via Temporally Interfering Electric Fields

    OpenAIRE

    Grossman, Nir; De Bono, David; Dedic, Nina; Kodandaramaiah, Suhasa B.; Rudenko, Andrii; Suk, Ho-Jun; Cassara, Antonio M.; Neufeld, Esra; Kuster, Niels; Tsai, Li-Huei; Pascual-Leone, Alvaro; Boyden, Edward S.

    2017-01-01

    We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) conc...

  8. Noninvasive method to assess the electrical brain activity from rats

    Directory of Open Access Journals (Sweden)

    Rosana Ferrari

    2013-10-01

    Full Text Available This research presents a noninvasive method for the acquisition of brain electrical signal in rat. Was used an electroencephalography (EEG system developed for bovine and adapted to rats. The bipolar electrode system (needle electrodes was glued on the surface of the head of the animal without surgical procedures and the other electrode was glued to the tail, as ground. The EEG activity was sampled at 120Hz for an hour. The accuracy and precision of the EEG measurement was performed using Fourier analysis and signal energy. For this, the digital signal was divided into sections successive of 3 seconds and was decomposed into four frequency bands: delta (0.3 to 4Hz, theta (4-8Hz, alpha (8-12Hz and beta (12-30Hz and energy (µV² of the series of time filtered were calculated. The method allowed the acquisition of non-invasive electrical brain signals in conscious rats and their frequency patterns were in agreement with previous studies that used surgical procedures to acquire EEG in rats. This system showed accuracy and precision and will allow further studies on behavior and to investigate the action of drugs on the central nervous system in rats without surgical procedures.

  9. Look at Epilepsy: Electrical Outbursts in the Brain

    Science.gov (United States)

    ... November 2015 Print this issue A Look at Epilepsy Electrical Outbursts in the Brain En español Send us your comments When you hear the word epilepsy, you might think of intense seizures with muscle ...

  10. Look at Epilepsy: Electrical Outbursts in the Brain

    Science.gov (United States)

    ... Print this issue Health Capsule A Look at Epilepsy Electrical Outbursts in the Brain En español Send us your comments When you hear the word epilepsy, you might think of intense seizures with muscle ...

  11. Electric Field Encephalography as a tool for functional brain research: a modeling study.

    Directory of Open Access Journals (Sweden)

    Yury Petrov

    Full Text Available We introduce the notion of Electric Field Encephalography (EFEG based on measuring electric fields of the brain and demonstrate, using computer modeling, that given the appropriate electric field sensors this technique may have significant advantages over the current EEG technique. Unlike EEG, EFEG can be used to measure brain activity in a contactless and reference-free manner at significant distances from the head surface. Principal component analysis using simulated cortical sources demonstrated that electric field sensors positioned 3 cm away from the scalp and characterized by the same signal-to-noise ratio as EEG sensors provided the same number of uncorrelated signals as scalp EEG. When positioned on the scalp, EFEG sensors provided 2-3 times more uncorrelated signals. This significant increase in the number of uncorrelated signals can be used for more accurate assessment of brain states for non-invasive brain-computer interfaces and neurofeedback applications. It also may lead to major improvements in source localization precision. Source localization simulations for the spherical and Boundary Element Method (BEM head models demonstrated that the localization errors are reduced two-fold when using electric fields instead of electric potentials. We have identified several techniques that could be adapted for the measurement of the electric field vector required for EFEG and anticipate that this study will stimulate new experimental approaches to utilize this new tool for functional brain research.

  12. Electrical Guidance of Human Stem Cells in the Rat Brain

    Directory of Open Access Journals (Sweden)

    Jun-Feng Feng

    2017-07-01

    Full Text Available Limited migration of neural stem cells in adult brain is a roadblock for the use of stem cell therapies to treat brain diseases and injuries. Here, we report a strategy that mobilizes and guides migration of stem cells in the brain in vivo. We developed a safe stimulation paradigm to deliver directional currents in the brain. Tracking cells expressing GFP demonstrated electrical mobilization and guidance of migration of human neural stem cells, even against co-existing intrinsic cues in the rostral migration stream. Transplanted cells were observed at 3 weeks and 4 months after stimulation in areas guided by the stimulation currents, and with indications of differentiation. Electrical stimulation thus may provide a potential approach to facilitate brain stem cell therapies.

  13. Brain Surface Conformal Parameterization Using Riemann Surface Structure

    Science.gov (United States)

    Wang, Yalin; Lui, Lok Ming; Gu, Xianfeng; Hayashi, Kiralee M.; Chan, Tony F.; Toga, Arthur W.; Thompson, Paul M.; Yau, Shing-Tung

    2011-01-01

    In medical imaging, parameterized 3-D surface models are useful for anatomical modeling and visualization, statistical comparisons of anatomy, and surface-based registration and signal processing. Here we introduce a parameterization method based on Riemann surface structure, which uses a special curvilinear net structure (conformal net) to partition the surface into a set of patches that can each be conformally mapped to a parallelogram. The resulting surface subdivision and the parameterizations of the components are intrinsic and stable (their solutions tend to be smooth functions and the boundary conditions of the Dirichlet problem can be enforced). Conformal parameterization also helps transform partial differential equations (PDEs) that may be defined on 3-D brain surface manifolds to modified PDEs on a two-dimensional parameter domain. Since the Jacobian matrix of a conformal parameterization is diagonal, the modified PDE on the parameter domain is readily solved. To illustrate our techniques, we computed parameterizations for several types of anatomical surfaces in 3-D magnetic resonance imaging scans of the brain, including the cerebral cortex, hippocampi, and lateral ventricles. For surfaces that are topologically homeomorphic to each other and have similar geometrical structures, we show that the parameterization results are consistent and the subdivided surfaces can be matched to each other. Finally, we present an automatic sulcal landmark location algorithm by solving PDEs on cortical surfaces. The landmark detection results are used as constraints for building conformal maps between surfaces that also match explicitly defined landmarks. PMID:17679336

  14. Noninvasive Deep Brain Stimulation via Temporally Interfering Electric Fields.

    Science.gov (United States)

    Grossman, Nir; Bono, David; Dedic, Nina; Kodandaramaiah, Suhasa B; Rudenko, Andrii; Suk, Ho-Jun; Cassara, Antonino M; Neufeld, Esra; Kuster, Niels; Tsai, Li-Huei; Pascual-Leone, Alvaro; Boyden, Edward S

    2017-06-01

    We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. BrainK for Structural Image Processing: Creating Electrical Models of the Human Head

    Directory of Open Access Journals (Sweden)

    Kai Li

    2016-01-01

    Full Text Available BrainK is a set of automated procedures for characterizing the tissues of the human head from MRI, CT, and photogrammetry images. The tissue segmentation and cortical surface extraction support the primary goal of modeling the propagation of electrical currents through head tissues with a finite difference model (FDM or finite element model (FEM created from the BrainK geometries. The electrical head model is necessary for accurate source localization of dense array electroencephalographic (dEEG measures from head surface electrodes. It is also necessary for accurate targeting of cerebral structures with transcranial current injection from those surface electrodes. BrainK must achieve five major tasks: image segmentation, registration of the MRI, CT, and sensor photogrammetry images, cortical surface reconstruction, dipole tessellation of the cortical surface, and Talairach transformation. We describe the approach to each task, and we compare the accuracies for the key tasks of tissue segmentation and cortical surface extraction in relation to existing research tools (FreeSurfer, FSL, SPM, and BrainVisa. BrainK achieves good accuracy with minimal or no user intervention, it deals well with poor quality MR images and tissue abnormalities, and it provides improved computational efficiency over existing research packages.

  16. Equilibrium drop surface profiles in electric fields

    Science.gov (United States)

    Mugele, F.; Buehrle, J.

    2007-09-01

    Electrowetting is becoming a more and more frequently used tool to manipulate liquids in various microfluidic applications. On the scale of the entire drop, the effect of electrowetting is to reduce the apparent contact angle of partially wetting conductive liquids upon application of an external voltage. Microscopically, however, strong electric fields in the vicinity of the three phase contact line give rise to local deformations of the drop surface. We determined the equilibrium surface profile using a combined numerical, analytical, and experimental approach. We find that the local contact angle in electrowetting is equal to Young's angle independent of the applied voltage. Only on the scale of the thickness of the insulator and beyond does the surface slope assume a value consistent with the voltage-dependent apparent contact angle. This behaviour is verified experimentally by determining equilibrium surface profiles for insulators of various thicknesses between 10 and 250 µm. Numerically and analytically, we find that the local surface curvature diverges algebraically upon approaching the contact line with an exponent -1<μ<0. We discuss the relevance of the local surface properties for dynamic aspects of the contact line motion.

  17. Electric field calculations in brain stimulation based on finite elements

    DEFF Research Database (Denmark)

    Windhoff, Mirko; Opitz, Alexander; Thielscher, Axel

    2013-01-01

    The need for realistic electric field calculations in human noninvasive brain stimulation is undisputed to more accurately determine the affected brain areas. However, using numerical techniques such as the finite element method (FEM) is methodologically complex, starting with the creation...... elements. The latter is crucial to guarantee the numerical robustness of the FEM calculations. The pipeline will be released as open-source, allowing for the first time to perform realistic field calculations at an acceptable methodological complexity and moderate costs....

  18. Role of electric field on surface wetting of polystyrene surface.

    Science.gov (United States)

    Bhushan, Bharat; Pan, Yunlu

    2011-08-02

    The role of surface charge in fluid flow in micro/nanofluidics systems as well as the role of electric field to create switchable hydrophobic surfaces is of interest. In this work, the contact angle (CA) and contact angle hysteresis (CAH) of a droplet of deionized (DI) water were measured with applied direct current (DC) and alternating current (AC) electric fields. The droplet was deposited on a polystyrene (PS) surface, commonly used in various nanotechnology applications, coated on a doped silicon (Si) wafer. With the DC field, CA decreased with an increase in voltage. Because of the presence of a silicon oxide layer and a space charge layer, the change of the CA was found to be lower than with a metal substrate. The CAH had no obvious change with a DC field. An AC field with a positive value was applied to the droplet to study its effect on CA and CAH. At low frequency (lower than 10 Hz), the droplet was visibly oscillating. The CA was found to increase when the frequency of the applied AC field increased from 1 Hz to 10 kHz. On the other hand, the CA decreased with an increasing peak-peak voltage at or lower than 10 kHz. The CAH in the AC field was found to be lower than in the DC field and had a similar trend to static CA with increasing frequency. A model is presented to explain the data.

  19. Syncing your brain: electric currents to enhance cognition

    NARCIS (Netherlands)

    Schutter, D.J.L.G.

    2014-01-01

    Contemporary studies in cognitive neuroscience demonstrate that cognitive performance can be enhanced by applying exogenous low-intensity electric currents to the brain. These findings have resulted in a widespread interest from both scientists and popular media, particularly, regarding the host of

  20. Ownership of an artificial limb induced by electrical brain stimulation.

    Science.gov (United States)

    Collins, Kelly L; Guterstam, Arvid; Cronin, Jeneva; Olson, Jared D; Ehrsson, H Henrik; Ojemann, Jeffrey G

    2017-01-03

    Replacing the function of a missing or paralyzed limb with a prosthetic device that acts and feels like one's own limb is a major goal in applied neuroscience. Recent studies in nonhuman primates have shown that motor control and sensory feedback can be achieved by connecting sensors in a robotic arm to electrodes implanted in the brain. However, it remains unknown whether electrical brain stimulation can be used to create a sense of ownership of an artificial limb. In this study on two human subjects, we show that ownership of an artificial hand can be induced via the electrical stimulation of the hand section of the somatosensory (SI) cortex in synchrony with touches applied to a rubber hand. Importantly, the illusion was not elicited when the electrical stimulation was delivered asynchronously or to a portion of the SI cortex representing a body part other than the hand, suggesting that multisensory integration according to basic spatial and temporal congruence rules is the underlying mechanism of the illusion. These findings show that the brain is capable of integrating "natural" visual input and direct cortical-somatosensory stimulation to create the multisensory perception that an artificial limb belongs to one's own body. Thus, they serve as a proof of concept that electrical brain stimulation can be used to "bypass" the peripheral nervous system to induce multisensory illusions and ownership of artificial body parts, which has important implications for patients who lack peripheral sensory input due to spinal cord or nerve lesions.

  1. Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation.

    Science.gov (United States)

    Huang, Yu; Liu, Anli A; Lafon, Belen; Friedman, Daniel; Dayan, Michael; Wang, Xiuyuan; Bikson, Marom; Doyle, Werner K; Devinsky, Orrin; Parra, Lucas C

    2017-02-07

    Transcranial electric stimulation aims to stimulate the brain by applying weak electrical currents at the scalp. However, the magnitude and spatial distribution of electric fields in the human brain are unknown. We measured electric potentials intracranially in ten epilepsy patients and estimated electric fields across the entire brain by leveraging calibrated current-flow models. When stimulating at 2 mA, cortical electric fields reach 0.4 V/m, the lower limit of effectiveness in animal studies. When individual whole-head anatomy is considered, the predicted electric field magnitudes correlate with the recorded values in cortical (r = 0.89) and depth (r = 0.84) electrodes. Accurate models require adjustment of tissue conductivity values reported in the literature, but accuracy is not improved when incorporating white matter anisotropy or different skull compartments. This is the first study to validate and calibrate current-flow models with in vivo intracranial recordings in humans, providing a solid foundation to target stimulation and interpret clinical trials.

  2. Functional electrical stimulation improves brain perfusion in cranial trauma patients

    Directory of Open Access Journals (Sweden)

    Bárbara Juarez Amorim

    2011-08-01

    Full Text Available OBJECTIVE: Demonstrate brain perfusion changes due to neuronal activation after functional electrical stimulation (FES. METHOD: It was studied 14 patients with hemiplegia who were submitted to a program with FES during fourteen weeks. Brain perfusion SPECT was performed before and after FES therapy. These patients were further separated into 2 groups according to the hemiplegia cause: cranial trauma and major vascular insults. All SPECT images were analyzed using SPM. RESULTS: There was a significant statistical difference between the two groups related to patient's ages and extent of hypoperfusion in the SPECT. Patients with cranial trauma had a reduction in the hypoperfused area and patients with major vascular insult had an increase in the hypoperfused area after FES therapy. CONCLUSION: FES therapy can result in brain perfusion improvement in patients with brain lesions due to cranial trauma but probably not in patients with major vascular insults with large infarct area.

  3. Evaluation method for in situ electric field in standardized human brain for different transcranial magnetic stimulation coils.

    Science.gov (United States)

    Iwahashi, Masahiro; Gomez-Tames, Jose; Laakso, Ilkka; Hirata, Akimasa

    2017-03-21

    This study proposes a method to evaluate the electric field induced in the brain by transcranial magnetic stimulation (TMS) to realize focal stimulation in the target area considering the inter-subject difference of the brain anatomy. The TMS is a non-invasive technique used for treatment/diagnosis, and it works by inducing an electric field in a specific area of the brain via a coil-induced magnetic field. Recent studies that report on the electric field distribution in the brain induced by TMS coils have been limited to simplified human brain models or a small number of detailed human brain models. Until now, no method has been developed that appropriately evaluates the coil performance for a group of subjects. In this study, we first compare the magnetic field and the magnetic vector potential distributions to determine if they can be used as predictors of the TMS focality derived from the electric field distribution. Next, the hotspots of the electric field on the brain surface of ten subjects using six coils are compared. Further, decisive physical factors affecting the focality of the induced electric field by different coils are discussed by registering the computed electric field in a standard brain space for the first time, so as to evaluate coil characteristics for a large population of subjects. The computational results suggest that the induced electric field in the target area cannot be generalized without considering the morphological variability of the human brain. Moreover, there was no remarkable difference between the various coils, although focality could be improved to a certain extent by modifying the coil design (e.g., coil radius). Finally, the focality estimated by the electric field was more correlated with the magnetic vector potential than the magnetic field in a homogeneous sphere.

  4. Evaluation method for in situ electric field in standardized human brain for different transcranial magnetic stimulation coils

    Science.gov (United States)

    Iwahashi, Masahiro; Gomez-Tames, Jose; Laakso, Ilkka; Hirata, Akimasa

    2017-03-01

    This study proposes a method to evaluate the electric field induced in the brain by transcranial magnetic stimulation (TMS) to realize focal stimulation in the target area considering the inter-subject difference of the brain anatomy. The TMS is a non-invasive technique used for treatment/diagnosis, and it works by inducing an electric field in a specific area of the brain via a coil-induced magnetic field. Recent studies that report on the electric field distribution in the brain induced by TMS coils have been limited to simplified human brain models or a small number of detailed human brain models. Until now, no method has been developed that appropriately evaluates the coil performance for a group of subjects. In this study, we first compare the magnetic field and the magnetic vector potential distributions to determine if they can be used as predictors of the TMS focality derived from the electric field distribution. Next, the hotspots of the electric field on the brain surface of ten subjects using six coils are compared. Further, decisive physical factors affecting the focality of the induced electric field by different coils are discussed by registering the computed electric field in a standard brain space for the first time, so as to evaluate coil characteristics for a large population of subjects. The computational results suggest that the induced electric field in the target area cannot be generalized without considering the morphological variability of the human brain. Moreover, there was no remarkable difference between the various coils, although focality could be improved to a certain extent by modifying the coil design (e.g., coil radius). Finally, the focality estimated by the electric field was more correlated with the magnetic vector potential than the magnetic field in a homogeneous sphere.

  5. Magnetic resonance electric property imaging of brain tissues.

    Science.gov (United States)

    Zhang, Xiaotong; Zhu, Shanan; He, Bin

    2009-01-01

    The electric properties (EPs) of brain tissues, i.e., the electric conductivity and permittivity, can provide important information for diagnosis of various brain disorders. A high-field MRI system is accompanied by significant wave propagation effects, and the radio frequency (RF) radiation is dependent on EPs of the biological tissue. Based on the measurement of the active transverse magnetic component of the applied RF field (known as B1-mapping technique), we have developed a dual-excitation algorithm, which uses two sets of measured B1 data, to noninvasively reconstruct the biological tissue's electric properties. A series of computer simulations were conducted to evaluate the feasibility and performance of the proposed method on a 3-D head model within a birdcage coil and a transverse electromagnetic coil. Compared with other B1-mapping based reconstruction algorithms, our approach provides superior performance without the need for iterative computations. The present simulation results indicate good reconstruction of electric properties of brain tissues from noninvasive MRI B1 mapping.

  6. Brain evolution triggers increased diversification of electric fishes.

    Science.gov (United States)

    Carlson, Bruce A; Hasan, Saad M; Hollmann, Michael; Miller, Derek B; Harmon, Luke J; Arnegard, Matthew E

    2011-04-29

    Communication can contribute to the evolution of biodiversity by promoting speciation and reinforcing reproductive isolation between existing species. The evolution of species-specific signals depends on the ability of individuals to detect signal variation, which in turn relies on the capability of the brain to process signal information. Here, we show that evolutionary change in a region of the brain devoted to the analysis of communication signals in mormyrid electric fishes improved detection of subtle signal variation and resulted in enhanced rates of signal evolution and species diversification. These results show that neural innovations can drive the diversification of signals and promote speciation.

  7. Lunar electric fields, surface potential and associated plasma sheaths

    Science.gov (United States)

    Freeman, J. W.; Ibrahim, M.

    1975-01-01

    A review is given of studies of the electric-field environment of the moon. Surface electric potentials are reported for the dayside and terminator regions, electron and ion densities in the plasma sheath adjacent to each surface-potential regime are evaluated, and the corresponding Debye lengths are estimated. The electric fields, which are approximated by the surface potential over the Debye length, are shown to be at least three orders of magnitude higher than the pervasive solar-wind electric field and to be confined to within a few tens of meters of the lunar surface.

  8. Variation of surface electric field during geomagnetic disturbed ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 124; Issue 8. Variation of surface electric field ... Diurnal variation of surface electric field measured at Maitri shows a similar variation with worldwide thunderstorm activity, whereas the departure of the field is observed during disturbed periods. This part of the field ...

  9. Todd, Faraday, and the electrical basis of brain activity.

    Science.gov (United States)

    Reynolds, Edward H

    2004-09-01

    Robert Bentley Todd (1809-60) was the UK's first eminent neurologist and neuroscientist. An anatomist, physiologist, and clinical scientist with an interest in the nervous system, he was the first to confirm the electrical basis of brain activity in the 1840s. He was influenced by his contemporary, Michael Faraday at the Royal Institution, and by two colleagues at King's College, John Daniell and Charles Wheatstone, who were also working at the cutting edge of electrical science. Todd conceived of nervous polarity (force) generated in nervous centres and compared this with the polar force of voltaic electricity developed in the galvanic battery. He brilliantly foresaw each nerve vesicle (cell) and its related fibres (ie, neuron) as a distinct apparatus for the development and transmission of nervous polarity. Epilepsy was the result of periodic unnatural development of nervous force leading to the "disruptive discharge" described by Faraday. Faraday, who studied animal electricity in the Gymnotus (electric eel), and Todd saw nervous polarity as a higher form of interchangeable energy.

  10. Brain surface motion imaging to predict adhesions between meningiomas and the brain surface

    Energy Technology Data Exchange (ETDEWEB)

    Taoka, Toshiaki; Yamatani, Yuya; Akashi, Toshiaki; Miyasaka, Toshiteru; Emura, Tomoko; Kichikawa, Kimihiko [Nara Medical University, Department of Radiology, Nara (Japan); Yamada, Syuichi; Nakase, Hiroyuki [Nara Medical University, Department of Neurosurgery, Nara (Japan)

    2010-11-15

    ''Brain surface motion imaging'' (BSMI) is the subtraction of pulse-gated, 3D, heavily T2-weighted image of two different phases of cerebrospinal fluid (CSF) pulsation, which enables the assessment of the dynamics of brain surface pulsatile motion. The purpose of this study was to evaluate the feasibility of this imaging method for providing presurgical information about adhesions between meningiomas and the brain surface. Eighteen cases with surgically resected meningioma in whom BSMI was presurgically obtained were studied. BSMI consisted of two sets of pulse-gated, 3D, heavily T2-weighted, fast spin echo scans. Images of the systolic phase and the diastolic phase were obtained, and subtraction was performed with 3D motion correction. We analyzed the presence of band-like texture surrounding the tumor and judged the degree of motion discrepancy as ''total,'' ''partial,'' or ''none.'' The correlation between BSMI and surgical findings was evaluated. For cases with partial adhesions, agreements in the locations of the adhesions were also evaluated. On presurgical BSMI, no motion discrepancy was seen in eight cases, partial in six cases, and total in four cases. These presurgical predictions about adhesions and surgical findings agreed in 13 cases (72.2%). The locations of adhesions agreed in five of six cases with partial adhesions. In the current study, BSMI could predict brain and meningioma adhesions correctly in 72.2% of cases, and adhesion location could also be predicted. This imaging method appears to provide presurgical information about brain/meningioma adhesions. (orig.)

  11. Lunar Surface Solar Electric Power System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a concentrated photovoltaic electric power system for lunar operations called C-Lite Lunar. The novel technology produces a near-term solar array system...

  12. Multi-Scale Computational Models for Electrical Brain Stimulation

    Science.gov (United States)

    Seo, Hyeon; Jun, Sung C.

    2017-01-01

    Electrical brain stimulation (EBS) is an appealing method to treat neurological disorders. To achieve optimal stimulation effects and a better understanding of the underlying brain mechanisms, neuroscientists have proposed computational modeling studies for a decade. Recently, multi-scale models that combine a volume conductor head model and multi-compartmental models of cortical neurons have been developed to predict stimulation effects on the macroscopic and microscopic levels more precisely. As the need for better computational models continues to increase, we overview here recent multi-scale modeling studies; we focused on approaches that coupled a simplified or high-resolution volume conductor head model and multi-compartmental models of cortical neurons, and constructed realistic fiber models using diffusion tensor imaging (DTI). Further implications for achieving better precision in estimating cellular responses are discussed. PMID:29123476

  13. Todd, Faraday and the electrical basis of brain activity.

    Science.gov (United States)

    Reynolds, Edward

    2007-10-01

    The origins of our understanding of brain electricity and electrical discharges in epilepsy can be traced to Robert Bentley Todd (1809-60). Todd was influenced by his contemporary in London, Michael Faraday (1791-1867), who in the 1830 s and 1840 s was laying the foundations of our modern understanding of electromagnetism. Todd's concept of nervous polarity, generated in nerve vesicles and transmitted in nerve fibres (neurons in later terminology), was confirmed a century later by the Nobel Prize-winning work of Hodgkin and Huxley, who demonstrated the ionic basis of neuro-transmission, involving the same ions which had had been discovered by Faraday's mentor, Sir Humphry Davy (1778-1829).

  14. Electrical stunning and exsanguination decrease the extracellular volume in the broiler brain as studied with brain impedance recordings

    NARCIS (Netherlands)

    Savenije, B; Lambooij, E; Pieterse, C; Korf, J

    Electrical stunning in the process of slaughtering poultry is used to induce unconsciousness and immobilize the animal for easier processing. Unconsciousness is a function of brain damage. Brain damage has been studied with brain impedance recordings under ischemic conditions. This experiment

  15. Surface electric fields for North America during historical geomagnetic storms

    Science.gov (United States)

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  16. Electric field distribution in a finite-volume head model of deep brain stimulation.

    Science.gov (United States)

    Grant, Peadar F; Lowery, Madeleine M

    2009-11-01

    This study presents a whole-head finite element model of deep brain stimulation to examine the effect of electrical grounding, the finite conducting volume of the head, and scalp, skull and cerebrospinal fluid layers. The impedance between the stimulating and reference electrodes in the whole-head model was found to lie within clinically reported values when the reference electrode was incorporated on a localized surface in the model. Incorporation of the finite volume of the head and inclusion of surrounding outer tissue layers reduced the magnitude of the electric field and activating function by approximately 20% in the region surrounding the electrode. Localized distortions of the electric field were also observed when the electrode was placed close to the skull. Under bipolar conditions the effect of the finite conducting volume was shown to be negligible. The results indicate that, for monopolar stimulation, incorporation of the finite volume and outer tissue layers can alter the magnitude of the electric field and activating function when the electrode is deep within the brain, and may further affect the shape if the electrode is close to the skull.

  17. Electric fields associated with transient surface currents

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1992-01-01

    The boundary condition to be fulfilled by the potential functions associated with a transient surface current is derived and expressed in terms of generalized orthogonal coordinates. From the analysis, it can be deduced that the use of the method of separation of variables is restricted to three ...

  18. Electrical Excitation of Surface Plasmon Polaritons

    NARCIS (Netherlands)

    Loon, R.V.A. van

    2009-01-01

    A surface plasmon polariton (SPP) is an electromagnetic wave propagating at the interface between a metal and a dielectric material. The two-dimensional confinement of SPPs and the tunability of their dispersion enable optical functionality that cannot be achieved with regular dielectrics. Several

  19. Quantitative Brain Electrical Activity in the Initial Screening of Mild Traumatic Brain Injuries

    Directory of Open Access Journals (Sweden)

    Robert Chabot

    2012-12-01

    Full Text Available Introduction: The incidence of emergency department (ED visits for Traumatic Brain Injury (TBIin the United States exceeds 1,000,000 cases/year with the vast majority classified as mild (mTBI.Using existing computed tomography (CT decision rules for selecting patients to be referred for CT,such as the New Orleans Criteria (NOC, approximately 70% of those scanned are found to havea negative CT. This study investigates the use of quantified brain electrical activity to assess itspossible role in the initial screening of ED mTBI patients as compared to NOC.Methods: We studied 119 patients who reported to the ED with mTBI and received a CT. Using ahand-held electroencephalogram (EEG acquisition device, we collected data from frontal leadsto determine the likelihood of a positive CT. The brain electrical activity was processed off-line togenerate an index (TBI-Index, biomarker. This index was previously derived using an independentpopulation, and the value found to be sensitive for significant brain dysfunction in TBI patients. Wecompared this performance of the TBI-Index to the NOC for accuracy in prediction of positive CTfindings.Results: Both the brain electrical activity TBI-Index and the NOC had sensitivities, at 94.7% and92.1% respectively. The specificity of the TBI-Index was more than twice that of NOC, 49.4%and 23.5% respectively. The positive predictive value, negative predictive value and the positivelikelihood ratio were better with the TBI-Index. When either the TBI-Index or the NOC are positive(combining both indices the sensitivity to detect a positive CT increases to 97%.Conclusion: The hand-held EEG device with a limited frontal montage is applicable to the EDenvironment and its performance was superior to that obtained using the New Orleans criteria.This study suggests a possible role for an index of brain function based on EEG to aid in the acuteassessment of mTBI patients.

  20. Graphene-enabled electrically switchable radar-absorbing surfaces

    Science.gov (United States)

    Balci, Osman; Polat, Emre O.; Kakenov, Nurbek; Kocabas, Coskun

    2015-03-01

    Radar-absorbing materials are used in stealth technologies for concealment of an object from radar detection. Resistive and/or magnetic composite materials are used to reduce the backscattered microwave signals. Inability to control electrical properties of these materials, however, hinders the realization of active camouflage systems. Here, using large-area graphene electrodes, we demonstrate active surfaces that enable electrical control of reflection, transmission and absorption of microwaves. Instead of tuning bulk material property, our strategy relies on electrostatic tuning of the charge density on an atomically thin electrode, which operates as a tunable metal in microwave frequencies. Notably, we report large-area adaptive radar-absorbing surfaces with tunable reflection suppression ratio up to 50 dB with operation voltages <5 V. Using the developed surfaces, we demonstrate various device architectures including pixelated and curved surfaces. Our results provide a significant step in realization of active camouflage systems in microwave frequencies.

  1. Electric field vector measurements in a surface ionization wave discharge

    Science.gov (United States)

    Goldberg, Benjamin M.; Böhm, Patrick S.; Czarnetzki, Uwe; Adamovich, Igor V.; Lempert, Walter R.

    2015-10-01

    This work presents the results of time-resolved electric field vector measurements in a short pulse duration (60 ns full width at half maximum), surface ionization wave discharge in hydrogen using a picosecond four-wave mixing technique. Electric field vector components are measured separately, using pump and Stokes beams linearly polarized in the horizontal and vertical planes, and a polarizer placed in front of the infrared detector. The time-resolved electric field vector is measured at three different locations across the discharge gap, and for three different heights above the alumina ceramic dielectric surface, ~100, 600, and 1100 μm (total of nine different locations). The results show that after breakdown, the discharge develops as an ionization wave propagating along the dielectric surface at an average speed of 1 mm ns-1. The surface ionization wave forms near the high voltage electrode, close to the dielectric surface (~100 μm). The wave front is characterized by significant overshoot of both vertical and horizontal electric field vector components. Behind the wave front, the vertical field component is rapidly reduced. As the wave propagates along the dielectric surface, it also extends further away from the dielectric surface, up to ~1 mm near the grounded electrode. The horizontal field component behind the wave front remains quite significant, to sustain the electron current toward the high voltage electrode. After the wave reaches the grounded electrode, the horizontal field component experiences a secondary rise in the quasi-dc discharge, where it sustains the current along the near-surface plasma sheet. The measurement results indicate presence of a cathode layer formed near the grounded electrode with significant cathode voltage fall, ≈3 kV, due to high current density in the discharge. The peak reduced electric field in the surface ionization wave is 85-95 Td, consistent with dc breakdown field estimated from the Paschen curve for

  2. Corona Discharge from Water Droplet on Electrically Stressed Polymer Surface

    Science.gov (United States)

    Zhu, Yong; Otsubo, Masahisa; Honda, Chikahisa; Tanaka, Shou

    2006-01-01

    This paper describes the results of experiments and simulations made to examine the corona discharges from water droplets on a polymer surface exposed to electrical stress. In this study, water droplets with different conductivities and volumes were placed on the surface of plate-shaped high temperature vulcanized silicone rubber (HTV-SR) energized with ac voltage, and the corona discharge phenomena were observed by a high-speed camera with an image intensifier. The electric-field distributions were calculated by the finite element method (FEM). It is demonstrated that the electric field is intensified at the triple junction of the water droplet, air and the insulating material due to the difference in their permittivities, which can ionize the surrounding air and trigger a corona discharge. It can also be confirmed that the contact angle, volume, conductivity and number of water droplets are shown to have a marked effect on the mode of the corona discharge development.

  3. A silicon-based electrical source for surface plasmon polaritons

    NARCIS (Netherlands)

    Walters, Robert J.; van Loon, Rob V.A.; Brunets, I.; Schmitz, Jurriaan; Polman, Albert

    2009-01-01

    This work demonstrates the fabrication of a silicon-based electrical source for surface plasmon polaritons (SPPs) at low temperatures using silicon nanocrystal doped alumina within a metal-insulator-metal (MIM) waveguide geometry. The fabrication method uses established microtechnology processes

  4. Review of Electrical and Gravity Methods of Near-Surface ...

    African Journals Online (AJOL)

    USER

    been attributed to poor pre-drill geophysical survey, data mis- interpretation due to handlers' inexperience, and poor ... Groundwater application of near surface geophysics include mapping the depth and thickness of .... applications of electrical techniques for siting wells and boreholes locations in crystalline basement ...

  5. Brain surface maps from 3-D medical images

    Science.gov (United States)

    Lu, Jiuhuai; Hansen, Eric W.; Gazzaniga, Michael S.

    1991-06-01

    The anatomic and functional localization of brain lesions for neurologic diagnosis and brain surgery is facilitated by labeling the cortical surface in 3D images. This paper presents a method which extracts cortical contours from magnetic resonance (MR) image series and then produces a planar surface map which preserves important anatomic features. The resultant map may be used for manual anatomic localization as well as for further automatic labeling. Outer contours are determined on MR cross-sectional images by following the clear boundaries between gray matter and cerebral-spinal fluid, skipping over sulci. Carrying this contour below the surface by shrinking it along its normal produces an inner contour that alternately intercepts gray matter (sulci) and white matter along its length. This procedure is applied to every section in the set, and the image (grayscale) values along the inner contours are radially projected and interpolated onto a semi-cylindrical surface with axis normal to the slices and large enough to cover the whole brain. A planar map of the cortical surface results by flattening this cylindrical surface. The projection from inner contour to cylindrical surface is unique in the sense that different points on the inner contour correspond to different points on the cylindrical surface. As the outer contours are readily obtained by automatic segmentation, cortical maps can be made directly from an MR series.

  6. Self-collimation phenomena of surface waves in structured perfect electric conductors and metal surfaces.

    Science.gov (United States)

    Oh, Sang Soon; Lee, Sun-Goo; Kim, Jae-Eun; Park, Hae Yong

    2007-02-05

    We demonstrate that surface waves in structured perfect electric conductor surfaces can be self-collimated using the finite-difference time-domain method. The self-collimation frequency is obtained from the equi-frequency contours of a perfect electric conductor patterned with an array of square holes. The field patterns of the self-collimated surface wave, obtained using the periodic boundary conditions, show that the surface waves propagate with almost no spreading. We also show that self-collimation phenomena can be observed for the hybrid surface plasmon waves in structured metal surfaces using the finite-difference time-domain method with the Drude model. It is shown that for a structured silver surface the self-collimation can be achieved at the frequencies in the infrared region.

  7. Seeing surfaces: The brain's vision of the world

    Science.gov (United States)

    Neumann, Heiko; Yazdanbakhsh, Arash; Mingolla, Ennio

    2007-09-01

    Surfaces of environmental objects are the key to understanding the visual experience of primates. Surfaces create structure in patterns of light available for sampling by visual systems, and delineate potential interactions that an animal can have with its environment, such as approaching goals, avoiding obstacles, grasping an object, or identifying members of a social group. Recent progress in modeling the perception of visual surfaces highlights the importance of feedforward and feedback connections in visual neural networks that segregate and group visual input into coherent regions related to corresponding surfaces in the visual world. Rich non-linear network dynamics in the brain underlie surface perception, including the detection, regularization, and grouping of visual boundaries between surfaces, the determination of “ownership” of a boundary by a closer surface that partially occludes a background, and the apprehension of a surface's visual quality, such as color or texture. Recent modeling efforts on these fronts are reviewed.

  8. Graphene-enabled electrically switchable radar absorbing surfaces

    Science.gov (United States)

    Balci, Osman; Polat, Emre Ozan; Kakenov, Nurbek; Kocabas, Coskun

    2015-03-01

    Radar absorbing materials are used in stealth technologies for concealment of an object from radar detection. Resistive and/or magnetic composite materials are used to reduce the backscattered microwave signals. Inability to control electrical properties of these materials however, hinders the realization of active camouflage systems which require adaptive surfaces operating in microwave frequencies. Here, using large-area graphene electrodes, we demonstrate a new class of active surfaces which enables unprecedented ability to control reflection, transmission and absorption of microwaves by electrical means. Instead of tuning bulk material property, our strategy relies on electrostatic tuning of the charge density on an atomically thin electrode which operates as a tunable metal in microwave frequencies. Notably, we fabricated large area adaptive radar absorbing surfaces with tunable reflection suppression ratio up to 50 dB with operation voltages less than 5 V. These electrically switchable radar absorbing surfaces provide a significant step in realization of active camouflage systems and adaptive cloaking in microwave frequencies, which cannot be realized by conventional materials.

  9. In vivo assessment of human brain oscillations during application of transcranial electric currents

    NARCIS (Netherlands)

    Soekadar, S.R.; Witkowski, M.; Garcia Cossio, E.; Birbaumer, N.; Robinson, S.E.; Cohen, L.G.

    2013-01-01

    Brain oscillations reflect pattern formation of cell assemblies’ activity, which is often disturbed in neurological and psychiatric diseases like depression, schizophrenia and stroke. In the neurobiological analysis and treatment of these conditions, transcranial electric currents applied to the

  10. Electric Charge Characteristics of Biofilms Formed on Various Surfaces

    Directory of Open Access Journals (Sweden)

    Andi Kurniawan

    2016-06-01

    Full Text Available Biofilm is predominant habitats of microbes in aquatic environments. Biofilm forms when microbes attach on surfaces and produce extracellular polymeric substances. Biofilm matrix has been showed to have high sorption capacity to accumulate various ions including nutrient ions. The main driving force of the accumulation of the ions is supposed to be an electrostatic interaction between the nutrient and the biofilm polymer. Hence, the understanding of electric charge properties of biofilm polymer is critically important to understand the accumulation process. The present study aimed to investigate the characteristics of electric charge properties of biofilm polymer from biofilms formed on various surfaces (stone, wood, glass bottle, teflon, rubber, and stainless steel. The electric charge properties of biofilm polymers were investigated by measuring the electrophoretic mobility of the biofilms in various pHs (range from pH 2 to pH 9 and titrated HCl and NaOH aqueous solution to the biofilm suspension. The results indicated that biofilm matrices seemed to have both negatively and positively charged sites as a result of ionization of functional groups existed in biofilm polymers. According to the results of this study, there is a universal characteristic of electric charge properties of biofilms regardless of the kind of substrate.

  11. Inhibition of brain tumor cell proliferation by alternating electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Hyesun; Oh, Seung-ick; Hong, Sunghoi, E-mail: shong21@korea.ac.kr, E-mail: radioyoon@korea.ac.kr [School of Biosystem and Biomedical Science, Korea University, Seoul 136-703 (Korea, Republic of); Sung, Jiwon; Jeong, Seonghoon; Yoon, Myonggeun, E-mail: shong21@korea.ac.kr, E-mail: radioyoon@korea.ac.kr [Department of Bio-convergence Engineering, Korea University, Seoul 136-703 (Korea, Republic of); Koh, Eui Kwan [Seoul Center, Korea Basic Science Institute, Seoul 136-713 (Korea, Republic of)

    2014-11-17

    This study was designed to investigate the mechanism by which electric fields affect cell function, and to determine the optimal conditions for electric field inhibition of cancer cell proliferation. Low-intensity (<2 V/cm) and intermediate-frequency (100–300 kHz) alternating electric fields were applied to glioblastoma cell lines. These electric fields inhibited cell proliferation by inducing cell cycle arrest and abnormal mitosis due to the malformation of microtubules. These effects were significantly dependent on the intensity and frequency of applied electric fields.

  12. Atomistic modeling of metal surfaces under electric fields: direct coupling of electric fields to a molecular dynamics algorithm

    CERN Document Server

    Djurabekova, Flyura; Pohjonen, Aarne; Nordlund, Kai

    2011-01-01

    The effect of electric fields on metal surfaces is fairly well studied, resulting in numerous analytical models developed to understand the mechanisms of ionization of surface atoms observed at very high electric fields, as well as the general behavior of a metal surface in this condition. However, the derivation of analytical models does not include explicitly the structural properties of metals, missing the link between the instantaneous effects owing to the applied field and the consequent response observed in the metal surface as a result of an extended application of an electric field. In the present work, we have developed a concurrent electrodynamic–molecular dynamic model for the dynamical simulation of an electric-field effect and subsequent modification of a metal surface in the framework of an atomistic molecular dynamics (MD) approach. The partial charge induced on the surface atoms by the electric field is assessed by applying the classical Gauss law. The electric forces acting on the partially...

  13. Optical electric-field enhancement at a metal surface arising from surface-plasmon excitation.

    Science.gov (United States)

    Weber, W H; Ford, G W

    1981-03-01

    Surface plasmons can be excited on a metal by an external plane-wave beam through the use of prism or grating couplers or by introducing roughness. This can enhance the electric field at the surface compared with that in the incident beam, and it has been suggested that this effect is an important aspect of surface-enhanced Raman scattering. A general upper limit for this field enhancement is derived on the basis of energy conservation. Numerical results are given for Ag, Au, and Cu. With a perfect coupler on a Ag surface, the maximum increase of the square of the electric field in the 2-3-eV range is congruent with300. On randomly roughened surfaces, the estimated enhancements are of the order of unity.

  14. Emerging subspecialties in neurology: deep brain stimulation and electrical neuro-network modulation.

    Science.gov (United States)

    Hassan, Anhar; Okun, Michael S

    2013-01-29

    Deep brain stimulation (DBS) is a surgical therapy that involves the delivery of an electrical current to one or more brain targets. This technology has been rapidly expanding to address movement, neuropsychiatric, and other disorders. The evolution of DBS has created a niche for neurologists, both in the operating room and in the clinic. Since DBS is not always deep, not always brain, and not always simply stimulation, a more accurate term for this field may be electrical neuro-network modulation (ENM). Fellowships will likely in future years evolve their scope to include other technologies, and other nervous system regions beyond typical DBS therapy.

  15. Effect of metallic and hyperbolic metamaterial surface on electric and magnetic dipole emission

    DEFF Research Database (Denmark)

    Ni, Xingjie; Naik, Gururaj V.; Kildishev, Alexander V.

    2010-01-01

    Spontaneous emission patterns of electric and magnetic dipoles on different material surfaces were studied numerically and experimentally. The results show the modified behavior of electric and magnetic dipoles on metallic and HMM surfaces....

  16. Laboratory Simulation of Electrical Discharge in Surface Lunar Regolith

    Science.gov (United States)

    Shusterman, M.; Izenberg, N.; Wing, B. R.; Liang, S.

    2016-12-01

    Physical, chemical, and optical characteristics of space-weathered surface materials on airless bodies are produced primarily from bombardment by solar energetic particles and micrometeoroid impacts. On bodies such as the Moon and Mercury, soils in permanently shadowed regions (PSRs) are very cold, have low electrical conductivities, and are subjected to a high flux of incoming energetic particles accelerated by solar events. Theoretical models predict that up to 25% of gardened soils in the lunar polar regions are altered by dielectric breakdown; a potentially significant weathering process that is currently unconfirmed. Although electrical properties of lunar soils have been studied in relation to flight electronics and spacecraft safety, no studies have characterized potential alterations to soils resulting from electrical discharge. To replicate the surface charge field in PSRs, lunar regolith simulant JSC-1A was placed between two parallel plane electrodes under both low and high vacuum environments, 10e-3 torr and 2.5e-6 torr, respectively. Voltage was increased until discharge occurred within the sample. Grains were analyzed using an SVC fiber-fed point spectrometer, Olympus BX51 upright metallurgical microscope, and a Hitachi TM3000 scanning electron microscope with Bruker Quantax-70 X-ray spectrometer. Discharges occurring in samples under low vacuum resulted in surficial melting, silicate vapor deposition, coalescence of metallic iron, and micro-scale changes to surface topography. Samples treated under a high vacuum environment showed similar types of effects, but fewer in number compared to low vacuum samples. The variation in alteration abundances between the two environments implies that discharges may be occurring across surface contaminants, even at high vacuum conditions, inhibiting dielectric breakdown in our laboratory simulations.

  17. Surface chemistry governs cellular tropism of nanoparticles in the brain

    Science.gov (United States)

    Song, Eric; Gaudin, Alice; King, Amanda R.; Seo, Young-Eun; Suh, Hee-Won; Deng, Yang; Cui, Jiajia; Tietjen, Gregory T.; Huttner, Anita; Saltzman, W. Mark

    2017-05-01

    Nanoparticles are of long-standing interest for the treatment of neurological diseases such as glioblastoma. Most past work focused on methods to introduce nanoparticles into the brain, suggesting that reaching the brain interstitium will be sufficient to ensure therapeutic efficacy. However, optimized nanoparticle design for drug delivery to the central nervous system is limited by our understanding of their cellular deposition in the brain. Here, we investigated the cellular fate of poly(lactic acid) nanoparticles presenting different surface chemistries, after administration by convection-enhanced delivery. We demonstrate that nanoparticles with `stealth' properties mostly avoid internalization by all cell types, but internalization can be enhanced by functionalization with bio-adhesive end-groups. We also show that association rates measured in cultured cells predict the extent of internalization of nanoparticles in cell populations. Finally, evaluating therapeutic efficacy in an orthotopic model of glioblastoma highlights the need to balance significant uptake without inducing adverse toxicity.

  18. Efficacy of brain-computer interface-driven neuromuscular electrical stimulation for chronic paresis after stroke.

    Science.gov (United States)

    Mukaino, Masahiko; Ono, Takashi; Shindo, Keiichiro; Fujiwara, Toshiyuki; Ota, Tetsuo; Kimura, Akio; Liu, Meigen; Ushiba, Junichi

    2014-04-01

    Brain computer interface technology is of great interest to researchers as a potential therapeutic measure for people with severe neurological disorders. The aim of this study was to examine the efficacy of brain computer interface, by comparing conventional neuromuscular electrical stimulation and brain computer interface-driven neuromuscular electrical stimulation, using an A-B-A-B withdrawal single-subject design. A 38-year-old male with severe hemiplegia due to a putaminal haemorrhage participated in this study. The design involved 2 epochs. In epoch A, the patient attempted to open his fingers during the application of neuromuscular electrical stimulation, irrespective of his actual brain activity. In epoch B, neuromuscular electrical stimulation was applied only when a significant motor-related cortical potential was observed in the electroencephalogram. The subject initially showed diffuse functional magnetic resonance imaging activation and small electro-encephalogram responses while attempting finger movement. Epoch A was associated with few neurological or clinical signs of improvement. Epoch B, with a brain computer interface, was associated with marked lateralization of electroencephalogram (EEG) and blood oxygenation level dependent responses. Voluntary electromyogram (EMG) activity, with significant EEG-EMG coherence, was also prompted. Clinical improvement in upper-extremity function and muscle tone was observed. These results indicate that self-directed training with a brain computer interface may induce activity- dependent cortical plasticity and promote functional recovery. This preliminary clinical investigation encourages further research using a controlled design.

  19. Electric field enhanced dropwise condensation on hydrophobic surfaces

    Science.gov (United States)

    Baratian, Davood; Hoek, Harmen; van den Ende, Dirk; Mugele, Frieder; Physics of Complex Fluids Team

    2016-11-01

    Dropwise condensation occurs when vapor condenses on a low surface energy surface, and the substrate is just partially wetted by the condensate. Dropwise condensation has attracted significant attention due to its reported superior heat transfer performance compared to filmwise condensation. Extensive research efforts are focused on how to promote, and enhance dropwise condensation by considering both physical and chemical factors. We have studied electrowetting-actuated condensation on hydrophobic surfaces, aiming for enhancement of heat transfer in dropwise condensation. The idea is to use suitably structured patterns of micro-electrodes that generate a heterogeneous electric field at the interface and thereby promote both the condensation itself and the shedding of condensed drops. Comforting the shedding of droplets on electrowetting-functionalized surfaces allows more condensing surface area for re-nucleation of small droplets, leading to higher condensation rates. Possible applications of this innovative concept include heat pipes for (micro) coolers in electronics as well as in more efficient heat exchangers. We acknowledge financial support by the Dutch Technology Foundation STW, which is part of the Netherlands Organization for Scientific Research (NWO), within the VICI program.

  20. Controlling magnetism on metal surfaces with non-magnetic means: electric fields and surface charging.

    Science.gov (United States)

    Brovko, Oleg O; Ruiz-Díaz, Pedro; Dasa, Tamene R; Stepanyuk, Valeri S

    2014-03-05

    We review the state of the art of surface magnetic property control with non-magnetic means, concentrating on metallic surfaces and techniques such as charge-doping or external electric field (EEF) application. Magneto-electric coupling via EEF-based charge manipulation is discussed as a way to tailor single adatom spins, exchange interaction between adsorbates or anisotropies of layered systems. The mechanisms of paramagnetic and spin-dependent electric field screening and the effect thereof on surface magnetism are discussed in the framework of theoretical and experimental studies. The possibility to enhance the effect of EEF by immersing the target system into an electrolyte or ionic liquid is discussed by the example of substitutional impurities and metallic alloy multilayers. A similar physics is pointed out for the case of charge traps, metallic systems decoupled from a bulk electron bath. In that case the charging provides the charge carrier density changes necessary to affect the magnetic moments and anisotropies in the system. Finally, the option of using quasi-free electrons rather than localized atomic spins for surface magnetism control is discussed with the example of Shockley-type metallic surface states confined to magnetic nanoislands.

  1. Stereotactic biopsy with electrical monitoring for deep-seated brain tumors.

    Science.gov (United States)

    Ooba, Hiroshi; Abe, Tatsuya; Momii, Yasutomo; Fujiki, Minoru

    2013-01-01

    The stereotactic biopsy is widely integrated into clinical practice as an efficient and safe procedure for histologic diagnoses. However, the surgical risk increases when the lesions are close to the eloquence of the adjacent brain. The present report describes two patients with deep-seated brain tumors who underwent a stereotactic biopsy with electrical monitoring and demonstrates the importance of this technique. The tentative target and trajectory were determined on a stereotactic map from the Schaltenbrand and Wahren atlas. A Cosman-Roberts-Wells stereotactic frame was applied to the patient. Electrical recording along a single trajectory was used to identify the circumscribed neuronal structures, and electrical simulation was administered to the target. The biopsy point was decided when no adverse events were observed with a low electric current level. A 34-year-old male patient with anaplastic astrocytoma in the putamen and thalamus and an 81-year-old female patient with malignant lymphoma in the midbrain underwent stereotactic biopsies with electrical monitoring. The biopsies were successfully performed without any resulting neurologic deficits. This report describes two patients with deep-seated brain tumors who underwent stereotactic biopsies with electrical recording and stimulation. The electrical monitoring appears to be a useful technique to complement the ordinary image-guided biopsy. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Electricity and Magnetism: Insights into the brain from multimodal imaging.

    Science.gov (United States)

    Cohen, M S

    2009-11-01

    The windows into brain function given us by the instruments of neuroimaging each are murky and their view is limited. Simultaneous collection of data from multiple modalities offers the potential to overcome the weaknesses of any tool alone. We argue that the combination of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) offers observations - and hypothesis testing - not possible using either single instrument. Because of their safety profiles and their non-invasive natures, EEG fMRI are among the best available devices for the study of human brain. These methods are complementary. EEG is fast, operating in a time domain comparable to single unit activity, but its localizing power is poor and the field of view is limited. While fMRI has the highest spatial resolution of any noninvasive imaging method and can reveal multiple centers of brain activity implicated in cognitive tasks, it is very slow compared to mental activity and is a poor choice for studying rapidly evolving processes. Here, we address theoretical models of the coupling between EEG and fMRI signals based on cellular physiology and energetics and argue that both tools observe principally synaptic activity. We discuss the technical problems of mutual interference then present several models of brain rhythms for which the joint EEG and fMRI observations provide significant evidence.

  3. Predicting the electric field distribution in the brain for the treatment of glioblastoma.

    Science.gov (United States)

    Miranda, Pedro C; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J

    2014-08-07

    The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a 'virtual lesion' in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V cm( - 1) and exceeded 1.0 V cm( - 1) in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor's necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning.

  4. Invasive and transcranial photoacoustic imaging of the vascular response to brain electrical stimulation

    Science.gov (United States)

    Tsytsarev, Vassiliy; Yao, Junjie; Hu, Song; Li, Li; Favazza, Christopher P.; Maslov, Konstantin I.; Wang, Lihong V.

    2010-02-01

    Advances in the brain functional imaging greatly facilitated the understanding of neurovascular coupling. For monitoring of the microvascular response to the brain electrical stimulation in vivo we used optical-resolution photoacoustic microscopy (OR-PAM) through the cranial openings as well as transcranially. Both types of the vascular response, vasoconstriction and vasodilatation, were clearly observed with good spatial and temporal resolution. Obtained results confirm one of the primary points of the neurovascular coupling theory that blood vessels could present vasoconstriction or vasodilatation in response to electrical stimulation, depending on the balance between inhibition and excitation of the different parts of the elements of the neurovascular coupling system.

  5. 30 CFR 57.4130 - Surface electric substations and liquid storage facilities.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Surface electric substations and liquid storage... accumulate within 25 feet of the following: (1) Electric substations. (2) Unburied, flammable or combustible... NONMETAL MINES Fire Prevention and Control Prohibitions/precautions/housekeeping § 57.4130 Surface electric...

  6. Investigation of Brain Arterial Circle Malformations Using Electrical Modelling and Simulation

    Directory of Open Access Journals (Sweden)

    Klara Capova

    2006-01-01

    Full Text Available The paper deals with the cerebral arterial system investigation by means of electrical modelling and simulations. The main attention is paid to the brain arterial circle malformations (stenoses and aneurysms and their determination and evaluation by computer-aided methods as tools of a non-invasive diagnostics. The compensation possibilities of brain arterial circle in case of presence of concrete arterial malformations are modelled and simulated. The simulation results of brain arteries blood pressures and volume flow velocities time dependences are presented and discussed under various health conditions.

  7. Surface electrical charge of bloodstream trypomastigotes of Trypanosoma cruzi strains

    Directory of Open Access Journals (Sweden)

    Maria Auxiliadora de Sousa

    1983-12-01

    Full Text Available Bloodstream trypomastigotes of some Trypanosoma cruzi strains were processed through DEAE-cellulose columns under standardized conditions. The results obtained suggest mainly that these strains present different surface charges, that there are subpopulations of bloodstream trypomastigotes as regards electrical charges and that the broad forms are less negative than the slender ones.Tripomastigotas sanguíneos de algumas cepas de Trypanosoma cruzi foram processadas em colunas de DEAE-celulose sob condições padronizadas. Os resultados obtidos sugerem principalmente que estas cepas possuem cargas superficiais diferentes, que em relação a este aspecto existem subpopulações de tripomastigotas e que as formas largas são menos negativas do que as finas.

  8. Patterns recognition of electric brain activity using artificial neural networks

    Science.gov (United States)

    Musatov, V. Yu.; Pchelintseva, S. V.; Runnova, A. E.; Hramov, A. E.

    2017-04-01

    An approach for the recognition of various cognitive processes in the brain activity in the perception of ambiguous images. On the basis of developed theoretical background and the experimental data, we propose a new classification of oscillating patterns in the human EEG by using an artificial neural network approach. After learning of the artificial neural network reliably identified cube recognition processes, for example, left-handed or right-oriented Necker cube with different intensity of their edges, construct an artificial neural network based on Perceptron architecture and demonstrate its effectiveness in the pattern recognition of the EEG in the experimental.

  9. Dynamic Variation in Pleasure in Children Predicts Nonlinear Change in Lateral Frontal Brain Electrical Activity

    Science.gov (United States)

    Light, Sharee N.; Coan, James A.; Frye, Corrina; Goldsmith, H. Hill; Davidson, Richard J.

    2009-01-01

    Individual variation in the experience and expression of pleasure may relate to differential patterns of lateral frontal activity. Brain electrical measures have been used to study the asymmetric involvement of lateral frontal cortex in positive emotion, but the excellent time resolution of these measures has not been used to capture…

  10. Patterns of Brain-Electrical Activity during Declarative Memory Performance in 10-Month-Old Infants

    Science.gov (United States)

    Morasch, Katherine C.; Bell, Martha Ann

    2009-01-01

    This study of infant declarative memory concurrently examined brain-electrical activity and deferred imitation performance in 10-month-old infants. Continuous electroencephalogram (EEG) measures were collected throughout the activity-matched baseline, encoding (modeling) and retrieval (delayed test) phases of a within-subjects deferred imitation…

  11. Electroconvulsive therapy in the presence of deep brain stimulation implants: electric field effects.

    Science.gov (United States)

    Deng, Zhi-De; Hardesty, David E; Lisanby, Sarah H; Peterchev, Angel V

    2010-01-01

    The safety of electroconvulsive therapy (ECT) in patients who have deep brain stimulation (DBS) implants represents a significant clinical issue. A major safety concern is the presence of burr holes and electrode anchoring devices in the skull, which may alter the induced electric field distribution in the brain. We simulated the electric field using finite-element method in a five-shell spherical head model. Three DBS electrode anchoring techniques were modeled, including ring/cap, microplate, and burr-hole cover. ECT was modeled with bilateral (BL), right unilateral (RUL), and bifrontal (BF) electrode placements and with clinically-used stimulus current amplitude. We compared electric field strength and focality among the DBS implantation techniques and ECT electrode configurations. The simulation results show an increase in the electric field strength in the brain due to conduction through the burr holes, especially when the burr holes are not fitted with nonconductive caps. For typical burr hole placement for subthalamic nucleus DBS, the effect on the electric field strength and focality is strongest for BF ECT, which runs contrary to the belief that more anterior ECT electrode placements are safer in patients with DBS implants.

  12. [Geomagnetic storm decreases coherence of electric oscillations of human brain while working at the computer].

    Science.gov (United States)

    Novik, O B; Smirnov, F A

    2013-01-01

    The effect of geomagnetic storms at the latitude of Moscow on the electric oscillations of the human brain cerebral cortex was studied. In course of electroencephalogram measurements it was shown that when the voluntary persons at the age of 18-23 years old were performing tasks using a computer during moderate magnetic storm or no later than 24 hrs after it, the value of the coherence function of electric oscillations of the human brain in the frontal and occipital areas in a range of 4.0-7.9 Hz (so-called the theta rhythm oscillations of the human brain) decreased by a factor of two or more, sometimes reaching zero, although arterial blood pressure, respiratory rate and the electrocardiogram registered during electroencephalogram measurements remained within the standard values.

  13. Human perception of electrical stimulation on the surface of somatosensory cortex.

    Directory of Open Access Journals (Sweden)

    Shivayogi V Hiremath

    Full Text Available Recent advancement in electrocorticography (ECoG-based brain-computer interface technology has sparked a new interest in providing somatosensory feedback using ECoG electrodes, i.e., cortical surface electrodes. We conducted a 28-day study of cortical surface stimulation in an individual with arm paralysis due to brachial plexus injury to examine the sensation produced by electrical stimulation of the somatosensory cortex. A high-density ECoG grid was implanted over the somatosensory and motor cortices. Stimulation through cortical surface electrodes over the somatosensory cortex successfully elicited arm and hand sensations in our participant with chronic paralysis. There were three key findings. First, the intensity of perceived sensation increased monotonically with both pulse amplitude and pulse frequency. Second, changing pulse width changed the type of sensation based on qualitative description provided by the human participant. Third, the participant could distinguish between stimulation applied to two neighboring cortical surface electrodes, 4.5 mm center-to-center distance, for three out of seven electrode pairs tested. Taken together, we found that it was possible to modulate sensation intensity, sensation type, and evoke sensations across a range of locations from the fingers to the upper arm using different stimulation electrodes even in an individual with chronic impairment of somatosensory function. These three features are essential to provide effective somatosensory feedback for neuroprosthetic applications.

  14. Mechanism of surface modification in the plasma surface interaction in electrical arcs

    CERN Document Server

    Timko, Helga; Djurabekova, Flyura; Nordlund, Kai; Matyash, Konstantin; Schneider, Ralf; Toerklep, Anders; Arnau-Izquierdo, Gonzalo; Descoeudres, Antoine; Calatroni, Sergio; Taborelli, Mauro; Wuensch, Walter

    2010-01-01

    Electrical sparks and arcs are plasma discharges that carry large currents and can strongly modify surfaces. This damage usually comes in the form of micrometer-sized craters and frozen-in liquid on the surface. Using a combination of experiments, plasma and atomistic simulation tools, we now show that the observed formation of deep craters and liquidlike features during sparking in vacuum is explained by the impacts of energetic ions, accelerated under the given conditions in the plasma sheath to kiloelectron volt energies, on surfaces. The flux in arcs is so high that in combination with kiloelectron volt energies it produces multiple overlapping heat spikes, which can lead to cratering even in materials such as Cu, where a single heat spike normally does not.

  15. Mechanism of surface modification in the plasma-surface interaction in electrical arcs

    CERN Document Server

    Timko, H; Nordlund, K; Costelle, L; Matyash, K; Schneider, R; Toerklep, A; Arnau-Izquierdo, G; Descoeudres, A; Calatroni, S; Taborelli, M; Wuensch, W

    2010-01-01

    Electrical sparks and arcs are plasma discharges that carry large currents and can strongly modify surfaces. This damage usually comes in the form of micrometer-sized craters and frozen-in liquid on the surface. Using a combination of experiments, plasma and atomistic simulation tools, we now show that the observed formation of deep craters and liquidlike features during sparking in vacuum is explained by the impacts of energetic ions, accelerated under the given conditions in the plasma sheath to kiloelectron volt energies, on surfaces. The flux in arcs is so high that in combination with kiloelectron volt energies it produces multiple overlapping heat spikes, which can lead to cratering even in materials such as Cu, where a single heat spike normally does not.

  16. Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility

    CERN Document Server

    Paramonov, V V

    2004-01-01

    The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.

  17. Decreased central fatigue in multiple sclerosis patients after 8 weeks of surface functional electrical stimulation

    National Research Council Canada - National Science Library

    Chang, Ya-Ju; Hsu, Miao-Ju; Chen, Shin-Man; Lin, Cheng-Hsiang; Wong, Alice M K

    2011-01-01

    .... Surface functional electrical stimulation (FES), which can challenge the peripheral neuromuscular system without overloading the central nervous system, is a relatively safe therapeutic strategy...

  18. Multi circular-cavity surface coil for magnetic resonance imaging of monkey's brain at 4 Tesla

    Science.gov (United States)

    Osorio, A. I.; Solis-Najera, S. E.; Vázquez, F.; Wang, R. L.; Tomasi, D.; Rodriguez, A. O.

    2014-11-01

    Animal models in medical research has been used to study humans diseases for several decades. The use of different imaging techniques together with different animal models offers a great advantage due to the possibility to study some human pathologies without the necessity of chirurgical intervention. The employ of magnetic resonance imaging for the acquisition of anatomical and functional images is an excellent tool because its noninvasive nature. Dedicated coils to perform magnetic resonance imaging experiments are obligatory due to the improvement on the signal-to-noise ratio and reduced specific absorption ratio. A specifically designed surface coil for magnetic resonance imaging of monkey's brain is proposed based on the multi circular-slot coil. Numerical simulations of the magnetic and electric fields were also performed using the Finite Integration Method to solve Maxwell's equations for this particular coil design and, to study the behavior of various vector magnetic field configurations and specific absorption ratio. Monkey's brain images were then acquired with a research-dedicated magnetic resonance imaging system at 4T, to evaluate the anatomical images with conventional imaging sequences. This coil showed good quality images of a monkey's brain and full compatibility with standard pulse sequences implemented in research-dedicated imager.

  19. Electrically-driven modulation of surface-grafted RGD peptides for manipulation of cell adhesion.

    Science.gov (United States)

    Lashkor, Minhaj; Rawson, Frankie J; Stephenson-Brown, Alex; Preece, Jon A; Mendes, Paula M

    2014-12-21

    Reported herein is a switchable surface that relies on electrically-induced conformational changes within surface-grafted arginine-glycine-aspartate (RGD) oligopeptides as the means of modulating cell adhesion.

  20. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    DEFF Research Database (Denmark)

    Minjoli, Sena; Saturnino, Guilherme B.; Blicher, Jakob Udby

    2017-01-01

    Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) are two types of non-invasive transcranial brain stimulation (TBS). They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large...... aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible...

  1. Improved Stability of Whole Brain Surface Parcellation with Multi-Atlas Segmentation

    OpenAIRE

    Huo, Yuankai; Bao, Shunxing; Parvathaneni, Prasanna; Landman, Bennett A.

    2017-01-01

    Whole brain segmentation and cortical surface parcellation are essential in understanding the anatomical-functional relationships of the brain. Multi-atlas segmentation has been regarded as one of the leading segmentation methods for the whole brain segmentation. In our recent work, the multi-atlas technique has been adapted to surface reconstruction using a method called Multi-atlas CRUISE (MaCRUISE). The MaCRUISE method not only performed consistent volume-surface analyses but also showed a...

  2. The influence of argon ion bombardment on the electrical and optical properties of clean silicon surfaces

    NARCIS (Netherlands)

    Martens, J.W.D.; van den Bogert, W.F.; van Silfhout, Arend

    1981-01-01

    The effect of low energy noble gas ion bombardment on the electrical and optical properties of Si(211) surfaces has been investigated by surface conductivity and field effect measurements, ellipsometry and AES. With this combination of techniques, information is obtained concerning the electrical

  3. A Closed Loop Brain-machine Interface for Epilepsy Control Using Dorsal Column Electrical Stimulation.

    Science.gov (United States)

    Pais-Vieira, Miguel; Yadav, Amol P; Moreira, Derek; Guggenmos, David; Santos, Amílcar; Lebedev, Mikhail; Nicolelis, Miguel A L

    2016-09-08

    Although electrical neurostimulation has been proposed as an alternative treatment for drug-resistant cases of epilepsy, current procedures such as deep brain stimulation, vagus, and trigeminal nerve stimulation are effective only in a fraction of the patients. Here we demonstrate a closed loop brain-machine interface that delivers electrical stimulation to the dorsal column (DCS) of the spinal cord to suppress epileptic seizures. Rats were implanted with cortical recording microelectrodes and spinal cord stimulating electrodes, and then injected with pentylenetetrazole to induce seizures. Seizures were detected in real time from cortical local field potentials, after which DCS was applied. This method decreased seizure episode frequency by 44% and seizure duration by 38%. We argue that the therapeutic effect of DCS is related to modulation of cortical theta waves, and propose that this closed-loop interface has the potential to become an effective and semi-invasive treatment for refractory epilepsy and other neurological disorders.

  4. Modifying the photodetachment near a metal surface by a weak electric field

    OpenAIRE

    Yang, B. C.; Du, M. L.

    2009-01-01

    We show the photodetachment cross sections of H near a metal surface can be modified using a weak static electric field. The modification is possible because the oscillatory part of the cross section near a metal surface is directly connected with the transit-time and the action of the detached-electron closed-orbit which can be changed systematically by varying the static electric field strength. Photodetachment cross sections for various photon energies and electric field values are calcula...

  5. Low-frequency dielectric dispersion of brain tissue due to electrically long neurites

    Science.gov (United States)

    Monai, Hiromu; Inoue, Masashi; Miyakawa, Hiroyoshi; Aonishi, Toru

    2012-12-01

    The dielectric properties of brain tissue are important for understanding how neural activity is related to local field potentials and electroencephalograms. It is known that the permittivity of brain tissue exhibits strong frequency dependence (dispersion) and that the permittivity is very large in the low-frequency region. However, little is known with regard to the cause of the large permittivity in the low-frequency region. Here, we postulate that the dielectric properties of brain tissue can be partially accounted for by assuming that neurites are of sufficient length to be “electrically long.” To test this idea, we consider a model in which a neurite is treated as a long, narrow body, and it is subjected to a stimulus created by electrodes situated in the region external to it. With regard to this electric stimulus, the neurite can be treated as a passive cable. Assuming adequate symmetry so that the tissue packed with multiple cables is equivalent to an isolated system consisting of a single cable and a surrounding extracellular resistive medium, we analytically calculate the extracellular potential of the tissue in response to such an externally created alternating-current electric field using a Green's function that we obtained previously. Our results show that brain tissue modeled by such a cable existing within a purely resistive extracellular medium exhibits a large effective permittivity in the low-frequency region. Moreover, we obtain results suggesting that an extremely large low-frequency permittivity can coexist with weak low-pass filter characteristics in brain tissue.

  6. Brain electrical activities of dancers and fast ball sports athletes are different.

    Science.gov (United States)

    Ermutlu, Numan; Yücesir, Ilker; Eskikurt, Gökçer; Temel, Tan; İşoğlu-Alkaç, Ümmühan

    2015-04-01

    Exercise training has been shown not only to influence physical fitness positively but also cognition in healthy and impaired populations. However, some particular exercise types, even though comparable based on physical efforts, have distinct cognitive and sensorimotor features. In this study, the effects of different types of exercise, such as fast ball sports and dance training, on brain electrical activity were investigated. Electroencephalography (EEG) scans were recorded in professional dancer, professional fast ball sports athlete (FBSA) and healthy control volunteer groups consisting of twelve subjects each. In FBSA, power of delta and theta frequency activities of EEG was significantly higher than those of the dancers and the controls. Conversely, dancers had significantly higher amplitudes in alpha and beta bands compared to FBSA and significantly higher amplitudes in the alpha band in comparison with controls. The results suggest that cognitive features of physical training can be reflected in resting brain electrical oscillations. The differences in resting brain electrical oscillations between the dancers and the FBSA can be the result of innate network differences determining the talents and/or plastic changes induced by physical training.

  7. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    Directory of Open Access Journals (Sweden)

    Sena Minjoli

    2017-01-01

    Full Text Available Transcranial magnetic stimulation (TMS and transcranial direct current stimulation (TDCS are two types of non-invasive transcranial brain stimulation (TBS. They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large cerebral lesions, which are commonly accompanied by a secondary enlargement of the ventricles and atrophy. These structural alterations substantially change the conductivity distribution inside the head, which may have potentially important consequences for both brain stimulation methods. We therefore aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible. Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field “hot spots” in the cortex. However, these maxima were not substantially stronger than those seen in a healthy control. The electric field pattern induced by TMS was not substantially changed by the lesions. However, the average field strength generated by TDCS was substantially decreased. This effect occurred for both head models and even when both electrodes were distant to the lesion, caused by increased current shunting through the lesion and enlarged ventricles. Judging from the similar peak field strengths compared

  8. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation.

    Science.gov (United States)

    Minjoli, Sena; Saturnino, Guilherme B; Blicher, Jakob Udby; Stagg, Charlotte J; Siebner, Hartwig R; Antunes, André; Thielscher, Axel

    2017-01-01

    Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) are two types of non-invasive transcranial brain stimulation (TBS). They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large cerebral lesions, which are commonly accompanied by a secondary enlargement of the ventricles and atrophy. These structural alterations substantially change the conductivity distribution inside the head, which may have potentially important consequences for both brain stimulation methods. We therefore aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible. Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field "hot spots" in the cortex. However, these maxima were not substantially stronger than those seen in a healthy control. The electric field pattern induced by TMS was not substantially changed by the lesions. However, the average field strength generated by TDCS was substantially decreased. This effect occurred for both head models and even when both electrodes were distant to the lesion, caused by increased current shunting through the lesion and enlarged ventricles. Judging from the similar peak field strengths compared to the healthy

  9. Timing of intervention affects brain electrical activity in children exposed to severe psychosocial neglect.

    Directory of Open Access Journals (Sweden)

    Ross E Vanderwert

    Full Text Available BACKGROUND: Early psychosocial deprivation has profound effects on brain activity in the young child. Previous reports have shown increased power in slow frequencies of the electroencephalogram (EEG, primarily in the theta band, and decreased power in higher alpha and beta band frequencies in infants and children who have experienced institutional care. METHODOLOGY/PRINCIPAL FINDINGS: We assessed the consequences of removing infants from institutions and placing them into a foster care intervention on brain electrical activity when children were 8 years of age. We found the intervention was successful for increasing high frequency EEG alpha power, with effects being most pronounced for children placed into foster care before 24 months of age. CONCLUSIONS/SIGNIFICANCE: The dependence on age of placement for the effects observed on high frequency EEG alpha power suggests a sensitive period after which brain activity in the face of severe psychosocial deprivation is less amenable to recovery.

  10. Non-invasive electrical and magnetic stimulation of the brain, spinal cord, roots and peripheral nerves

    DEFF Research Database (Denmark)

    Rossini, P M; Burke, D; Chen, R

    2015-01-01

    These guidelines provide an up-date of previous IFCN report on "Non-invasive electrical and magnetic stimulation of the brain, spinal cord and roots: basic principles and procedures for routine clinical application" (Rossini et al., 1994). A new Committee, composed of international experts, some...... theoretical, physiological and practical aspects of non-invasive stimulation of brain, spinal cord, nerve roots and peripheral nerves in the light of more updated knowledge, and include some recent extensions and developments....... of whom were in the panel of the 1994 "Report", was selected to produce a current state-of-the-art review of non-invasive stimulation both for clinical application and research in neuroscience. Since 1994, the international scientific community has seen a rapid increase in non-invasive brain stimulation...

  11. Syndrome of Electrical Status Epilepticus During Sleep: Epileptic Encephalopathy Related to Brain Development.

    Science.gov (United States)

    Chen, Xiao-Qiao; Zhang, Wei-Na; Hu, Lin-Yan; Liu, Meng-Jia; Zou, Li-Ping

    2016-03-01

    Epileptic encephalopathy with electrical status epilepticus during sleep is an age-related and self-limited disorder. The present study analyzed the etiology, demographics, and pathogenesis of patients with electrical status epilepticus during sleep to provide information on the diagnosis and therapy of this syndrome. The etiologies of epileptic encephalopathy with electrical status epilepticus during sleep in patients admitted in Chinese People's Liberation Army General Hospital from 2009 to 2014 were retrospectively analyzed. Patients were classified into the genetic, structural-metabolic, and unknown groups according to the etiology. Demographics and clinical characteristics of all the patients were then analyzed and compared among groups. The etiologies of epileptic encephalopathy with electrical status epilepticus during sleep in 75 patients mainly included benign childhood epilepsy with centrotemporal spikes, Landau-Kleffner syndrome, polymicrogyria, and migration disorders. Age at onset of epilepsy did not show a specific pattern, but age at onset of epileptic encephalopathy with electrical status epilepticus during sleep was concentrated at age 6-9 years. The mean age at onset of epilepsy in the genetic group was significantly older than that in the structural-metabolic group (P sleep did not significantly differ between the two groups. Electrical status epilepticus during sleep is an epileptic encephalopathy related to brain development and presents an age-dependent occurrence. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. The morphological and molecular changes of brain cells exposed to direct current electric field stimulation.

    Science.gov (United States)

    Pelletier, Simon J; Lagacé, Marie; St-Amour, Isabelle; Arsenault, Dany; Cisbani, Giulia; Chabrat, Audrey; Fecteau, Shirley; Lévesque, Martin; Cicchetti, Francesca

    2014-12-07

    The application of low-intensity direct current electric fields has been experimentally used in the clinic to treat a number of brain disorders, predominantly using transcranial direct current stimulation approaches. However, the cellular and molecular changes induced by such treatment remain largely unknown. Here, we tested various intensities of direct current electric fields (0, 25, 50, and 100V/m) in a well-controlled in vitro environment in order to investigate the responses of neurons, microglia, and astrocytes to this type of stimulation. This included morphological assessments of the cells, viability, as well as shape and fiber outgrowth relative to the orientation of the direct current electric field. We also undertook enzyme-linked immunosorbent assays and western immunoblotting to identify which molecular pathways were affected by direct current electric fields. In response to direct current electric field, neurons developed an elongated cell body shape with neurite outgrowth that was associated with a significant increase in growth associated protein-43. Fetal midbrain dopaminergic explants grown in a collagen gel matrix also showed a reorientation of their neurites towards the cathode. BV2 microglial cells adopted distinct morphological changes with an increase in cyclooxygenase-2 expression, but these were dependent on whether they had already been activated with lipopolysaccharide. Finally, astrocytes displayed elongated cell bodies with cellular filopodia that were oriented perpendicularly to the direct current electric field. We show that cells of the central nervous system can respond to direct current electric fields both in terms of their morphological shape and molecular expression of certain proteins, and this in turn can help us to begin understand the mechanisms underlying the clinical benefits of direct current electric field. © The Author 2015. Published by Oxford University Press on behalf of CINP.

  13. Effect of electrical vs. chemical deep brain stimulation at midbrain sites on micturition in anaesthetized rats.

    Science.gov (United States)

    Stone, E; Coote, J H; Lovick, T A

    2015-05-01

    To understand how deep brain stimulation of the midbrain influences control of the urinary bladder. In urethane-anaesthetized male rats, saline was infused continuously into the bladder to evoke cycles of filling and voiding. The effect of electrical (0.1-2.0 ms pulses, 5-180 Hz, 0.5-2.5 V) compared to chemical stimulation (microinjection of D,L-homocysteic acid, 50 nL 0.1 M solution) at the same midbrain sites was tested. Electrical stimulation of the periaqueductal grey matter and surrounding midbrain disrupted normal coordinated voiding activity in detrusor and sphincters muscles and suppressed urine output. The effect occurred within seconds was reversible and not secondary to cardiorespiratory changes. Bladder compliance remained unchanged. Chemical stimulation over the same area using microinjection of D,L-homocysteic acid (DLH) to preferentially activate somatodendritic receptors decreased the frequency of micturition but did not disrupt the coordinated pattern of voiding. In contrast, chemical stimulation within the caudal ventrolateral periaqueductal grey, in the area where critical synapses in the micturition reflex pathway are located, increased the frequency of micturition. Electrical deep brain stimulation within the midbrain can inhibit reflex micturition. We suggest that the applied stimulus entrained activity in the neural circuitry locally, thereby imposing an unphysiological pattern of activity. In a way similar to the use of electrical signals to 'jam' radio transmission, this may prevent a synchronized pattern of efferent activity being transmitted to the spinal outflows to orchestrate a coordinated voiding response. Further experiments to record neuronal firing in the midbrain during the deep brain stimulation will be necessary to test this hypothesis. © 2015 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  14. SURFACE CONDITIONING ROUGHNESS FACTOR FOR IN PROCESSING TECHNOLOGICAL ELECTRICAL EROSION

    Directory of Open Access Journals (Sweden)

    Marcel S.POPA

    2014-12-01

    Full Text Available EDM phenomenon consists in the deployment of material from the work piece and electrode electrically conductive at a distance from one another and between which there is an electric potential difference. Suppose two objects (parts initially at distance D and the electric potential difference, begin to be close to each other. Distance that will pierce the dielectric (the environment in which the two objects are - air, water, oil and will begin to show electric discharge between the two parts is called the interstitium. Following electrical arcing, a certain quantity of material dislodged from the two pieces. If there is no intervention on their arc will continue until the distance between the two parts will increase (due to displacement of material. The amount of material displaced by erosion of the electrode and the piece is asymmetric and depends heavily on certain parameters like: polarity, thermal conductivity, melting point of the material that makes up the piece and electrode characteristics and current applied between the electrode track.

  15. Quantitative conductivity and permittivity imaging of the human brain using electric properties tomography.

    Science.gov (United States)

    Voigt, Tobias; Katscher, Ulrich; Doessel, Olaf

    2011-08-01

    The electric properties of human tissue can potentially be used as an additional diagnostic parameter, e.g., in tumor diagnosis. In the framework of radiofrequency safety, the electric conductivity of tissue is needed to correctly estimate the local specific absorption rate distribution during MR measurements. In this study, a recently developed approach, called electric properties tomography (EPT) is adapted for and applied to in vivo imaging. It derives the patient's electric conductivity and permittivity from the spatial sensitivity distributions of the applied radiofrequency coils. In contrast to other methods to measure the patient's electric properties, EPT does not apply externally mounted electrodes, currents, or radiofrequency probes, which enhances the practicability of the approach. This work shows that conductivity distributions can be reconstructed from phase images and permittivity distributions can be reconstructed from magnitude images of the radiofrequency transmit field. Corresponding numerical simulations using finite-difference time-domain methods support the feasibility of this phase-based conductivity imaging and magnitude-based permittivity imaging. Using this approximation, three-dimensional in vivo conductivity and permittivity maps of the human brain are obtained in 5 and 13 min, respectively, which can be considered a step toward clinical feasibility for EPT. Copyright © 2011 Wiley-Liss, Inc.

  16. Amplification of surface plasmon polariton wave in single-walled carbon nanotube using electric current pump

    Science.gov (United States)

    Moiseev, Sergey; Dadoenkova, Yuliya; Kadochkin, Aleksey; Zolotovskii, Igor

    2017-10-01

    We propose a surface plasmon polariton amplification technique based on direct energy transfer from a dc electric current flowing in a carbon nanotube. It is shown that when the synchronization conditions are satisfied, when the surface plasmon polariton wave velocity is close to the drift velocity of the charge carriers in the nanotube, the surface wave is significantly enhanced.

  17. Surface-roughness fractality effects in electrical conductivity of single metallic and semiconducting films

    NARCIS (Netherlands)

    Palasantzas, G.; Barnaś, J.

    1997-01-01

    Surface-roughness effects in electrical conductivity of thin metallic and semiconducting films with self-affine fractal surfaces are considered in the framework of the Born approximation. The surface roughness is described by the k-correlation model, and is characterized by the roughness exponent H

  18. Amplification of surface plasmon polariton wave in single-walled carbon nanotube using electric current pump

    Directory of Open Access Journals (Sweden)

    Moiseev Sergey

    2017-01-01

    Full Text Available We propose a surface plasmon polariton amplification technique based on direct energy transfer from a dc electric current flowing in a carbon nanotube. It is shown that when the synchronization conditions are satisfied, when the surface plasmon polariton wave velocity is close to the drift velocity of the charge carriers in the nanotube, the surface wave is significantly enhanced.

  19. Magnetic fields and brain tumour risks in UK electricity supply workers.

    Science.gov (United States)

    Sorahan, T

    2014-04-01

    To investigate whether brain tumour risks are related to occupational exposure to low-frequency magnetic fields. Brain tumour risks experienced by 73 051 employees of the former Central Electricity Generating Board of England and Wales were investigated for the period 1973-2010. All employees were hired in the period 1952-82 and were employed for at least 6 months with some employment in the period 1973-82. Detailed calculations had been performed by others to enable an assessment to be made of exposures to magnetic fields. Poisson regression was used to calculate relative risks (rate ratios) of developing a brain tumour (or glioma or meningioma) for categories of lifetime, distant (lagged) and recent (lugged) exposure. Findings for glioma and for the generality of all brain tumours were unexceptional; risks were close to (or below) unity for all exposure categories and there was no suggestion of risks increasing with cumulative (or recent or distant) magnetic field exposures. There were no statistically significant dose-response effects shown for meningioma, but there was some evidence of elevated risks in the three highest exposure categories for exposures received >10 years ago. This study found no evidence to support the hypothesis that exposure to magnetic fields is a risk factor for gliomas, and the findings are consistent with the hypotheses that both distant and recent magnetic field exposures are not causally related to gliomas. The limited positive findings for meningioma may be chance findings; national comparisons argue against a causal interpretation.

  20. Investigation of surface charge density on solid-liquid interfaces by modulating the electrical double layer.

    Science.gov (United States)

    Moon, Jong Kyun; Song, Myung Won; Pak, Hyuk Kyu

    2015-05-20

    A solid surface in contact with water or aqueous solution usually carries specific electric charges. These surface charges attract counter ions from the liquid side. Since the geometry of opposite charge distribution parallel to the solid-liquid interface is similar to that of a capacitor, it is called an electrical double layer capacitor (EDLC). Therefore, there is an electrical potential difference across an EDLC in equilibrium. When a liquid bridge is formed between two conducting plates, the system behaves as two serially connected EDLCs. In this work, we propose a new method for investigating the surface charge density on solid-liquid interfaces. By mechanically modulating the electrical double layers and simultaneously applying a dc bias voltage across the plates, an ac electric current can be generated. By measuring the voltage drop across a load resistor as a function of bias voltage, we can study the surface charge density on solid-liquid interfaces. Our experimental results agree very well with the simple equivalent electrical circuit model proposed here. Furthermore, using this method, one can determine the polarity of the adsorbed state on the solid surface depending on the material used. We expect this method to aid in the study of electrical phenomena on solid-liquid interfaces.

  1. Spatio-temporal analysis of brain electrical activity in epilepsy based on cellular nonlinear networks

    Science.gov (United States)

    Gollas, Frank; Tetzlaff, Ronald

    2009-05-01

    Epilepsy is the most common chronic disorder of the nervous system. Generally, epileptic seizures appear without foregoing sign or warning. The problem of detecting a possible pre-seizure state in epilepsy from EEG signals has been addressed by many authors over the past decades. Different approaches of time series analysis of brain electrical activity already are providing valuable insights into the underlying complex dynamics. But the main goal the identification of an impending epileptic seizure with a sufficient specificity and reliability, has not been achieved up to now. An algorithm for a reliable, automated prediction of epileptic seizures would enable the realization of implantable seizure warning devices, which could provide valuable information to the patient and time/event specific drug delivery or possibly a direct electrical nerve stimulation. Cellular Nonlinear Networks (CNN) are promising candidates for future seizure warning devices. CNN are characterized by local couplings of comparatively simple dynamical systems. With this property these networks are well suited to be realized as highly parallel, analog computer chips. Today available CNN hardware realizations exhibit a processing speed in the range of TeraOps combined with low power consumption. In this contribution new algorithms based on the spatio-temporal dynamics of CNN are considered in order to analyze intracranial EEG signals and thus taking into account mutual dependencies between neighboring regions of the brain. In an identification procedure Reaction-Diffusion CNN (RD-CNN) are determined for short segments of brain electrical activity, by means of a supervised parameter optimization. RD-CNN are deduced from Reaction-Diffusion Systems, which usually are applied to investigate complex phenomena like nonlinear wave propagation or pattern formation. The Local Activity Theory provides a necessary condition for emergent behavior in RD-CNN. In comparison linear spatio

  2. Clinical usefulness of brain-computer interface-controlled functional electrical stimulation for improving brain activity in children with spastic cerebral palsy: a pilot randomized controlled trial

    OpenAIRE

    Kim, Tae-Woo; Lee, Byoung-Hee

    2016-01-01

    [Purpose] Evaluating the effect of brain-computer interface (BCI)-based functional electrical stimulation (FES) training on brain activity in children with spastic cerebral palsy (CP) was the aim of this study. [Subjects and Methods] Subjects were randomized into a BCI-FES group (n=9) and a functional electrical stimulation (FES) control group (n=9). Subjects in the BCI-FES group received wrist and hand extension training with FES for 30 minutes per day, 5 times per week for 6 weeks under the...

  3. Endogenous and exogenous electric fields as modifiers of brain activity: rational design of noninvasive brain stimulation with transcranial alternating current stimulation.

    Science.gov (United States)

    Fröhlich, Flavio

    2014-03-01

    Synchronized neuronal activity in the cortex generates weak electric fields that are routinely measured in humans and animal models by electroencephalography and local field potential recordings. Traditionally, these endogenous electric fields have been considered to be an epiphenomenon of brain activity. Recent work has demonstrated that active cortical networks are surprisingly susceptible to weak perturbations of the membrane voltage of a large number of neurons by electric fields. Simultaneously, noninvasive brain stimulation with weak, exogenous electric fields (transcranial current stimulation, TCS) has undergone a renaissance due to the broad scope of its possible applications in modulating brain activity for cognitive enhancement and treatment of brain disorders. This review aims to interface the recent developments in the study of both endogenous and exogenous electric fields, with a particular focus on rhythmic stimulation for the modulation of cortical oscillations. The main goal is to provide a starting point for the use of rational design for the development of novel mechanism-based TCS therapeutics based on transcranial alternating current stimulation, for the treatment of psychiatric illnesses.

  4. Research on electric field distribution of UHVDC transmission lines and body surface during live working

    Science.gov (United States)

    Jiang, Chilong; Zou, Dehua; Li, Jinliang; Zhang, Zhanlong; Mei, Daojun

    2017-09-01

    Electric field distortion emerges around personnel working on live Ultra High Voltage Direct Current UHVDC transmission lines, especially when they move from ground-potential to equipotential positions. Unreliable protection threatens the safety of both workers and transmission lines. The current study investigates the electric field distribution of body surface during live working under transmission lines. To provide safety advice, live working person and tower models were established. The body surface field was calculated in different positions under ±800 kV transmission lines, and the distribution of the electric field was summarized.

  5. Electrical resistance of individual defects at a topological insulator surface

    Science.gov (United States)

    Lüpke, Felix; Eschbach, Markus; Heider, Tristan; Lanius, Martin; Schüffelgen, Peter; Rosenbach, Daniel; von den Driesch, Nils; Cherepanov, Vasily; Mussler, Gregor; Plucinski, Lukasz; Grützmacher, Detlev; Schneider, Claus M.; Voigtländer, Bert

    2017-06-01

    Three-dimensional topological insulators host surface states with linear dispersion, which manifest as a Dirac cone. Nanoscale transport measurements provide direct access to the transport properties of the Dirac cone in real space and allow the detailed investigation of charge carrier scattering. Here we use scanning tunnelling potentiometry to analyse the resistance of different kinds of defects at the surface of a (Bi0.53Sb0.47)2Te3 topological insulator thin film. We find the largest localized voltage drop to be located at domain boundaries in the topological insulator film, with a resistivity about four times higher than that of a step edge. Furthermore, we resolve resistivity dipoles located around nanoscale voids in the sample surface. The influence of such defects on the resistance of the topological surface state is analysed by means of a resistor network model. The effect resulting from the voids is found to be small compared with the other defects.

  6. Effect of metallic and hyperbolic metamaterial surfaces on electric and magnetic dipole emission transitions

    DEFF Research Database (Denmark)

    Ni, X.; Naik, G. V.; Kildishev, A. V.

    2011-01-01

    Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial (HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental results obtained by measuring angular-depende......-dependent emission spectra of europium ions on top of different films. The results show the modified behavior of electric and magnetic dipoles on metallic and HMM surfaces. The results of numerical calculations agree well with experimental data.......Spontaneous emission patterns of electric and magnetic dipoles on different metallic surfaces and a hyperbolic metamaterial (HMM) surface were simulated using the dyadic Green’s function technique. The theoretical approach was verified by experimental results obtained by measuring angular...

  7. Non-Invasive Electrical Brain Stimulation Montages for Modulation of Human Motor Function.

    Science.gov (United States)

    Curado, Marco; Fritsch, Brita; Reis, Janine

    2016-02-04

    Non-invasive electrical brain stimulation (NEBS) is used to modulate brain function and behavior, both for research and clinical purposes. In particular, NEBS can be applied transcranially either as direct current stimulation (tDCS) or alternating current stimulation (tACS). These stimulation types exert time-, dose- and in the case of tDCS polarity-specific effects on motor function and skill learning in healthy subjects. Lately, tDCS has been used to augment the therapy of motor disabilities in patients with stroke or movement disorders. This article provides a step-by-step protocol for targeting the primary motor cortex with tDCS and transcranial random noise stimulation (tRNS), a specific form of tACS using an electrical current applied randomly within a pre-defined frequency range. The setup of two different stimulation montages is explained. In both montages the emitting electrode (the anode for tDCS) is placed on the primary motor cortex of interest. For unilateral motor cortex stimulation the receiving electrode is placed on the contralateral forehead while for bilateral motor cortex stimulation the receiving electrode is placed on the opposite primary motor cortex. The advantages and disadvantages of each montage for the modulation of cortical excitability and motor function including learning are discussed, as well as safety, tolerability and blinding aspects.

  8. A pioneer work on electric brain stimulation in psychotic patients. Rudolph Gottfried Arndt and his 1870s studies.

    Science.gov (United States)

    Steinberg, Holger

    2013-07-01

    Today's brain stimulation methods are commonly traced back historically to surgical brain operations. With this one-sided historical approach it is easy to overlook the fact that non-surgical electrical brain-stimulating applications preceded present-day therapies. The first study on transcranial electrical brain stimulation for the treatment of severe mental diseases in a larger group of patients was carried out in the 1870s. Between 1870 and 1878 German psychiatrist Rudolph Gottfried Arndt published the results of his studies in three reports. These are contextualized with contemporary developments of the time, focusing in particular on the (neuro-) sciences. As was common practice at the time, Arndt basically reported individual cases in which electricity was applied to treat severe psychoses with depressive symptoms or even catatonia, hypochondriac delusion and melancholia. Despite their lengthiness, there is frequently a lack of precise physical data on the application of psychological-psychopathological details. Only his 1878 report includes general rules for electrical brain stimulation. Despite their methodological shortcomings and lack of precise treatment data impeding exact understanding, Arndt's studies are pioneering works in the field of electric brain stimulation with psychoses and its positive impacts. Today's transcranial direct current stimulation, and partly vagus nerve stimulation, can be compared with Arndt's methods. Although Arndt's only tangible results were indications for the application of faradic electricity (for inactivity, stupor, weakness and manic depressions) and galvanic current (for affective disorders and psychoses), a historiography of present-day brain stimulation therapies should no longer neglect studies on electrotherapy published in German and international psychiatric and neurological journals and monographs in the 1870s and 1880s. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Integrated electrically driven surface plasmon resonance device for biosensing applications.

    Science.gov (United States)

    Jimenez, Alvaro; Lepage, Dominic; Beauvais, Jacques; Dubowski, Jan J

    2015-07-27

    Compact and portable surface plasmon resonance (SPR) biosensors of high sensitivities can be made through integration of discrete components in a single device. We report on a device comprising a vertical cavity light emitting diode (VLED) integrated with gold-based biosensing nanostructures fabricated atop its surface. Coupling of surface plasmon waves was achieved by the introduction of a spacer SiO2 layer located between the light source and the functionalized Au thin film. The SPR signal was extracted in far field with a Au-based nanograting and detected using a custom designed hyperspectral imager. We discuss the performance of a VLED-based SPR device employed for detection of different concentration saltwater solutions.

  10. Electrically driven surface plasmon light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  11. Core networks for visual-concrete and abstract thought content: a brain electric microstate analysis.

    Science.gov (United States)

    Lehmann, Dietrich; Pascual-Marqui, Roberto D; Strik, Werner K; Koenig, Thomas

    2010-01-01

    Commonality of activation of spontaneously forming and stimulus-induced mental representations is an often made but rarely tested assumption in neuroscience. In a conjunction analysis of two earlier studies, brain electric activity during visual-concrete and abstract thoughts was studied. The conditions were: in study 1, spontaneous stimulus-independent thinking (post-hoc, visual imagery or abstract thought were identified); in study 2, reading of single nouns ranking high or low on a visual imagery scale. In both studies, subjects' tasks were similar: when prompted, they had to recall the last thought (study 1) or the last word (study 2). In both studies, subjects had no instruction to classify or to visually imagine their thoughts, and accordingly were not aware of the studies' aim. Brain electric data were analyzed into functional topographic brain images (using LORETA) of the last microstate before the prompt (study 1) and of the word-type discriminating event-related microstate after word onset (study 2). Conjunction analysis across the two studies yielded commonality of activation of core networks for abstract thought content in left anterior superior regions, and for visual-concrete thought content in right temporal-posterior inferior regions. The results suggest that two different core networks are automatedly activated when abstract or visual-concrete information, respectively, enters working memory, without a subject task or instruction about the two classes of information, and regardless of internal or external origin, and of input modality. These core machineries of working memory thus are invariant to source or modality of input when treating the two types of information.

  12. Increased determinism in brain electrical activity occurs in association with multiple sclerosis.

    Science.gov (United States)

    Carrubba, Simona; Minagar, Alireza; Chesson, Andrew L; Frilot, Clifton; Marino, Andrew A

    2012-04-01

    Increased determinism (decreased complexity) of brain electrical activity has been associated with some brain diseases. Our objective was to determine whether a similar association occurred for multiple sclerosis (MS). Ten subjects with a relapsing-remitting course of MS who were in remission were studied; the controls were age- and gender-matched clinically normal subjects. Recurrence plots were calculated using representative electroencephalogram (EEG) epochs (1-7 seconds) from six derivations; the plots were quantified using the nonlinear variables percent recurrence (%R) and percent determinism (%D). The results were averaged over all derivations for each participant, and the means were compared between the groups. As a linear control procedure the groups were also compared using spectral analysis. The mean±SD of %R for the MS subjects was 6·6±1·3%, compared with 5·1±1·3% in the normal group (P = 0·017), indicating that brain activity in the subjects with MS was less complex, as hypothesized. The groups were not distinguishable using %D or spectral analysis. Taken together with our earlier report that %R could be used to discriminate between MS and normal subjects based on the ability to exhibit evoked potentials, the evidence suggests that complexity analysis of the EEG has potential for development as a diagnostic test for MS.

  13. A device for long-term perfusion, imaging, and electrical interfacing of brain tissue in vitro

    Directory of Open Access Journals (Sweden)

    Nathaniel J Killian

    2016-03-01

    Full Text Available Distributed microelectrode array (MEA recordings from consistent, viable, ≥ 500 µm thick tissue preparations over time periods from days to weeks may aid in studying a wide range of problems in neurobiology that require in vivo-like organotypic morphology. Existing tools for electrically interfacing with organotypic slices do not address necrosis that inevitably occurs within thick slices with limited diffusion of nutrients and gas, and limited removal of waste. We developed an integrated device that enables long-term maintenance of thick, functionally active, brain tissue models using interstitial perfusion and distributed recordings from thick sections of explanted tissue on a perforated multi-electrode array. This novel device allows for automated culturing, in situ imaging, and extracellular multi-electrode interfacing with brain slices, 3 D cell cultures, and potentially other tissue culture models. The device is economical, easy to assemble, and integrable with standard electrophysiology tools. We found that convective perfusion through the culture thickness provided a functional benefit to the preparations as firing rates were generally higher in perfused cultures compared to their respective unperfused controls. This work is a step towards the development of integrated tools for days-long experiments with more consistent, healthier, thicker, and functionally more active tissue cultures with built-in distributed electrophysiological recording and stimulation functionality. The results may be useful for the study of normal processes, pathological conditions, and drug screening strategies currently hindered by the limitations of acute (a few hours long brain slice preparations.

  14. Soil Moisture Monitoring using Surface Electrical Resistivity measurements

    Science.gov (United States)

    Calamita, Giuseppe; Perrone, Angela; Brocca, Luca; Straface, Salvatore

    2017-04-01

    The relevant role played by the soil moisture (SM) for global and local natural processes results in an explicit interest for its spatial and temporal estimation in the vadose zone coming from different scientific areas - i.e. eco-hydrology, hydrogeology, atmospheric research, soil and plant sciences, etc... A deeper understanding of natural processes requires the collection of data on a higher number of points at increasingly higher spatial scales in order to validate hydrological numerical simulations. In order to take the best advantage of the Electrical Resistivity (ER) data with their non-invasive and cost-effective properties, sequential Gaussian geostatistical simulations (sGs) can be applied to monitor the SM distribution into the soil by means of a few SM measurements and a densely regular ER grid of monitoring. With this aim, co-located SM measurements using mobile TDR probes (MiniTrase), and ER measurements, obtained by using a four-electrode device coupled with a geo-resistivimeter (Syscal Junior), were collected during two surveys carried out on a 200 × 60 m2 area. Two time surveys were carried out during which Data were collected at a depth of around 20 cm for more than 800 points adopting a regular grid sampling scheme with steps (5 m) varying according to logistic and soil compaction constrains. The results of this study are robust due to the high number of measurements available for either variables which strengthen the confidence in the covariance function estimated. Moreover, the findings obtained using sGs show that it is possible to estimate soil moisture variations in the pedological zone by means of time-lapse electrical resistivity and a few SM measurements.

  15. Latent synthesis of electrically conductive surface-silvered polyimide films.

    Science.gov (United States)

    Davis, Luke M; Abelt, Christopher J; Scott, Joseph L; Orlova, Evguenia; Thompson, David W

    2009-01-01

    A facile ambient temperature route to the fabrication of surface silver-metallized polyimide films is described. Silver(I) trifluoromethanesulfonate or silver(I) nitrate and a polyimide, derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and an equimolar amount of 4,4'-oxydianiline and 3,5-diaminobenzoic acid, were dissolved together in dimethylacetamide. Silver(I)-doped films were prepared at thicknesses of 25-40 microm and depleted of solvent by evaporation at ambient temperature and low humidity. The silver(I)-ion-containing films were then treated with aqueous solutions of the reducing agents hydrazine hydrate and hydroxylamine, which brought forth surface-silvered films exhibiting conductivity on the order of bulk polycrystalline silver accompanied by modest-to-high specular reflectivity.

  16. Surface thermohardening by the fast-moving electric arch

    Science.gov (United States)

    Gabdrakhmanov, Az T.; Shafigullin, L. N.; Galimov, E. R.; Ibragimov, A. R.

    2017-01-01

    This paper describes the technology of modern engineering-plasma hardening steels and prospects of its application. It gives the opportunity to manage the process without using of cooling media, vacuum, special coatings to improve the absorptive capacity of hardened surfaces; the simplicity, the low cost, the maneuverability, a small size of the process equipment; a possibility of the automation and the robotization of technological process.

  17. Long-duration transcutaneous electric acupoint stimulation alters small-world brain functional networks.

    Science.gov (United States)

    Zhang, Yue; Jiang, Yin; Glielmi, Christopher B; Li, Longchuan; Hu, Xiaoping; Wang, Xiaoying; Han, Jisheng; Zhang, Jue; Cui, Cailian; Fang, Jing

    2013-09-01

    Acupuncture, which is recognized as an alternative and complementary treatment in Western medicine, has long shown efficiencies in chronic pain relief, drug addiction treatment, stroke rehabilitation and other clinical practices. The neural mechanism underlying acupuncture, however, is still unclear. Many studies have focused on the sustained effects of acupuncture on healthy subjects, yet there are very few on the topological organization of functional networks in the whole brain in response to long-duration acupuncture (longer than 20 min). This paper presents a novel study on the effects of long-duration transcutaneous electric acupoint stimulation (TEAS) on the small-world properties of brain functional networks. Functional magnetic resonance imaging was used to construct brain functional networks of 18 healthy subjects (9 males and 9 females) during the resting state. All subjects received both TEAS and minimal TEAS (MTEAS) and were scanned before and after each stimulation. An altered functional network was found with lower local efficiency and no significant change in global efficiency for healthy subjects after TEAS, while no significant difference was observed after MTEAS. The experiments also showed that the nodal efficiencies in several paralimbic/limbic regions were altered by TEAS, and those in middle frontal gyrus and other regions by MTEAS. To remove the psychological effects and the baseline, we compared the difference between diffTEAS (difference between after and before TEAS) and diffMTEAS (difference between after and before MTEAS). The results showed that the local efficiency was decreased and that the nodal efficiencies in frontal gyrus, orbitofrontal cortex, anterior cingulate gyrus and hippocampus gyrus were changed. Based on those observations, we conclude that long-duration TEAS may modulate the short-range connections of brain functional networks and also the limbic system. Copyright © 2013 Elsevier Inc. All rights reserved.

  18. Role of Surface Electric Charge in Red Blood Cell Interactions

    Science.gov (United States)

    Jan, Kung-Ming; Chien, Shu

    1973-01-01

    The role of the surface charge of human red blood cells (RBC's) in affecting RBC aggregation by macromolecules was studied by comparing the behavior of normal RBC's with that of RBC's treated with neuraminidase, which removes the sialic acids from the cell membrane and reduces the zeta potential. RBC aggregation in dextrans with different molecular weights (Dx 20, Dx 40, and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. Dx 20 did not cause aggregation of normal RBC's, but caused considerable aggregation of neuraminidase-treated RBC's. Neuraminidase-treated RBC's also showed stronger aggregation than normal RBC's in Dx 40 and 80. Together with the electron microscopic findings that the intercellular distance in the RBC rouleaux varies with the molecular size of dextrans used, the present study indicates that the surface charge of RBC's inhibits their aggregation by dextrans and that the electrostatic repulsive force between cell surfaces may operate over a distance of 20 nm. PMID:4705641

  19. Surface plasmon resonance biomolecular recognition nanosystem: influence of the interfacial electrical potential.

    Science.gov (United States)

    Lopatynskyi, Andrii; Guiver, Michael; Chegel, Volodymyr

    2014-09-01

    It is shown that the response of a surface plasmon resonance nanosystem designed according to Kretschmann geometry on the application of an external electric potential to the gold-electrolyte interface is well described by the proposed mathematical model, which takes into account the geometric surface imperfection and dependence of optical constants of the surface layer of gold film and capacitance of the electrical double layer on applied voltage. This model allows the appropriate correction for results of electrochemical surface plasmon resonance measurements. The dependence of a value of biomolecules adsorption in a surface plasmon resonance nanosystem on applied electric potential is shown for the first time. It is found that a shift of surface plasmon resonance angular position (Δθ(SPR)) and a change of capacitance of electrical double layer on the surface of gold (ΔC(dl)) for the adsorption of proteins under applied voltage are related to the nonlinear dependence Δθ(SPR) = (a + b x ΔC(dl))(-1). This phenomenon can be exploited in biochemical analysis to monitor the interaction of biomolecules, enhance response of biosensors, block unwanted adsorption, etc.

  20. Engineering Topological Surface State of Cr-doped Bi2Se3 under external electric field

    Science.gov (United States)

    Zhang, Jian-Min; Lian, Ruqian; Yang, Yanmin; Xu, Guigui; Zhong, Kehua; Huang, Zhigao

    2017-03-01

    External electric field control of topological surface states (SSs) is significant for the next generation of condensed matter research and topological quantum devices. Here, we present a first-principles study of the SSs in the magnetic topological insulator (MTI) Cr-doped Bi2Se3 under external electric field. The charge transfer, electric potential, band structure and magnetism of the pure and Cr doped Bi2Se3 film have been investigated. It is found that the competition between charge transfer and spin-orbit coupling (SOC) will lead to an electrically tunable band gap in Bi2Se3 film under external electric field. As Cr atom doped, the charge transfer of Bi2Se3 film under external electric field obviously decreases. Remarkably, the band gap of Cr doped Bi2Se3 film can be greatly engineered by the external electric field due to its special band structure. Furthermore, magnetic coupling of Cr-doped Bi2Se3 could be even mediated via the control of electric field. It is demonstrated that external electric field plays an important role on the electronic and magnetic properties of Cr-doped Bi2Se3 film. Our results may promote the development of electronic and spintronic applications of magnetic topological insulator.

  1. Brain Surface Heating After Exposure to Ultrasound: An Analysis Using Thermography.

    Science.gov (United States)

    Schneider, Michal E; Lombardo, Paul

    2016-05-01

    Ultrasound is the imaging modality of choice to monitor brain pathologies in neonates after complicated deliveries. Animal studies have indicated that ultrasound may cause heating of brain tissues. To date, no study has explored brain surface heating by ultrasound during clinically relevant exposure. Hence, we investigated heating effects of B-mode and pulsed Doppler (PD) mode on ex vivo lamb brains using thermography. Five brains were scanned for 5 min in B-mode or for 3 min, 1 min, 30 s or 15 s in PD mode. Brain surface temperature was measured pre- and post-exposure using thermography. The highest mean temperature increase was recorded by B-mode (3.82 ± 0.43°C). All five PD exposure protocols were associated with surface temperature increases of 2.1-2.7°C. These outcomes highlight for the first time that B-mode ultrasound can contribute to brain surface heating during a routine cranial scan. Scan duration should be minimised whenever possible. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  2. Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces.

    Science.gov (United States)

    Geminiani, Alessandro; Abdel-Azim, Tamer; Ercoli, Carlo; Feng, Changyong; Meirelles, Luiz; Massironi, Domenico

    2014-07-01

    Rotary and nonrotary cutting instruments are used to produce specific characteristics on the axial and marginal surfaces of teeth being prepared for fixed restorations. Oscillating instruments have been suggested for tooth preparation, but no comparative surface roughness data are available. To compare the surface roughness of simulated tooth preparations produced by oscillating instruments versus rotary cutting instruments with turbine and electric handpieces. Different grit rotary cutting instruments were used to prepare Macor specimens (n=36) with 2 handpieces. The surface roughness obtained with rotary cutting instruments was compared with that produced by oscillating cutting instruments. The instruments used were as follows: coarse, then fine-grit rotary cutting instruments with a turbine (group CFT) or an electric handpiece (group CFE); coarse, then medium-grit rotary cutting instruments with a turbine (group CMT) or an electric handpiece (group CME); coarse-grit rotary cutting instruments with a turbine handpiece and oscillating instruments at a low-power (group CSL) or high-power setting (group CSH). A custom testing apparatus was used to test all instruments. The average roughness was measured for each specimen with a 3-dimensional optical surface profiler and compared with 1-way ANOVA and the Tukey honestly significant difference post hoc test for multiple comparisons (α=.05). Oscillating cutting instruments produced surface roughness values similar to those produced by similar grit rotary cutting instruments with a turbine handpiece. The electric handpiece produced smoother surfaces than the turbine regardless of rotary cutting instrument grit. Rotary cutting instruments with electric handpieces produced the smoothest surface, whereas the same instruments used with a turbine and oscillating instruments achieved similar surface roughness. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights

  3. Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

    Directory of Open Access Journals (Sweden)

    Saurav Z. K. Sajib

    2016-06-01

    Full Text Available Anisotropy of biological tissues is a low-frequency phenomenon that is associated with the function and structure of cell membranes. Imaging of anisotropic conductivity has potential for the analysis of interactions between electromagnetic fields and biological systems, such as the prediction of current pathways in electrical stimulation therapy. To improve application to the clinical environment, precise approaches are required to understand the exact responses inside the human body subjected to the stimulated currents. In this study, we experimentally evaluate the anisotropic conductivity tensor distribution of canine brain tissues, using a recently developed diffusion tensor-magnetic resonance electrical impedance tomography method. At low frequency, electrical conductivity of the biological tissues can be expressed as a product of the mobility and concentration of ions in the extracellular space. From diffusion tensor images of the brain, we can obtain directional information on diffusive movements of water molecules, which correspond to the mobility of ions. The position dependent scale factor, which provides information on ion concentration, was successfully calculated from the magnetic flux density, to obtain the equivalent conductivity tensor. By combining the information from both techniques, we can finally reconstruct the anisotropic conductivity tensor images of brain tissues. The reconstructed conductivity images better demonstrate the enhanced signal intensity in strongly anisotropic brain regions, compared with those resulting from previous methods using a global scale factor.

  4. Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

    Energy Technology Data Exchange (ETDEWEB)

    Sajib, Saurav Z. K.; Jeong, Woo Chul; Oh, Tong In; Kim, Hyung Joong, E-mail: bmekim@khu.ac.kr, E-mail: ejwoo@khu.ac.kr; Woo, Eung Je, E-mail: bmekim@khu.ac.kr, E-mail: ejwoo@khu.ac.kr [Department of Biomedical Engineering, Kyung Hee University, Seoul 02447 (Korea, Republic of); Kyung, Eun Jung [Department of Pharmacology, Chung-Ang University, Seoul 06974 (Korea, Republic of); Kim, Hyun Bum [Department of East-West Medical Science, Kyung Hee University, Yongin 17104 (Korea, Republic of); Kwon, Oh In [Department of Mathematics, Konkuk University, Seoul 05029 (Korea, Republic of)

    2016-06-15

    Anisotropy of biological tissues is a low-frequency phenomenon that is associated with the function and structure of cell membranes. Imaging of anisotropic conductivity has potential for the analysis of interactions between electromagnetic fields and biological systems, such as the prediction of current pathways in electrical stimulation therapy. To improve application to the clinical environment, precise approaches are required to understand the exact responses inside the human body subjected to the stimulated currents. In this study, we experimentally evaluate the anisotropic conductivity tensor distribution of canine brain tissues, using a recently developed diffusion tensor-magnetic resonance electrical impedance tomography method. At low frequency, electrical conductivity of the biological tissues can be expressed as a product of the mobility and concentration of ions in the extracellular space. From diffusion tensor images of the brain, we can obtain directional information on diffusive movements of water molecules, which correspond to the mobility of ions. The position dependent scale factor, which provides information on ion concentration, was successfully calculated from the magnetic flux density, to obtain the equivalent conductivity tensor. By combining the information from both techniques, we can finally reconstruct the anisotropic conductivity tensor images of brain tissues. The reconstructed conductivity images better demonstrate the enhanced signal intensity in strongly anisotropic brain regions, compared with those resulting from previous methods using a global scale factor.

  5. Electrical conductivity and permittivity maps of brain tissues derived from water content based on T1 -weighted acquisition.

    Science.gov (United States)

    Michel, Eric; Hernandez, Daniel; Lee, Soo Yeol

    2017-03-01

    To develop an electrical properties tomography (EPT) technique that can provide in vivo electrical conductivity and permittivity images of biological tissue without performing complex-valued radiofrequency field measurements. Electrical conductivity and permittivity images are modeled as a monotonic function of tissues' water content (W) under the principle of Maxwell's mixture theory. Water content maps are estimated from two spin-echo images having different repetition times (TRs). For the modeling functions, physically measured parameters (electrical properties, water content, and T1 ) of brain cerebrospinal fluid (CSF), gray matter, and white matter are used as landmark literature references. The formulations are validated by a developed electrolyte-protein phantom and by human brain studies at 3 Tesla (T). The electrical properties (EPs) of the phantom estimated by the proposed method match well with the values measured on the bench. The conductivity and permittivity maps from all experiments show uncompromised spatial resolution without boundary artifacts and higher contrast when compared with water content maps. Human brain and phantom EP images suggest that water content is a dominating factor in determining the electrical properties of tissues. Despite possible literature inaccuracies, the proposed method offers EP maps that can provide complementary information to current approaches, to facilitate EPT scans in clinical applications. Magn Reson Med 77:1094-1103, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  6. Laser-based surface preparation of composite laminates leads to improved electrodes for electrical measurements

    Energy Technology Data Exchange (ETDEWEB)

    Almuhammadi, Khaled; Selvakumaran, Lakshmi [King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division, COHMAS Laboratory, Thuwal 23955-6900 (Saudi Arabia); Alfano, Marco [Department of Mechanical, Energy and Management Engineering, University of Calabria, Via P. Bucci 44C, 87036 Rende, CS (Italy); Yang, Yang [King Abdullah University of Science and Technology (KAUST), Imaging and Characterization Core Laboratory, Thuwal 23955-6900 (Saudi Arabia); Bera, Tushar Kanti [King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division, COHMAS Laboratory, Thuwal 23955-6900 (Saudi Arabia); Lubineau, Gilles, E-mail: gilles.lubineau@kaust.edu.sa [King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division, COHMAS Laboratory, Thuwal 23955-6900 (Saudi Arabia)

    2015-12-30

    Highlights: • Laser ablation is used to prepare surface of laminate for electrical measurements. • Laser ablation provides better surface fiber exposure than sand polishing. • Optimal parameters for laser ablation is identified by Raman spectroscopy. • Electrodes produced on laser ablated surfaces show low and uniform contact impedance. • With laser ablation, contact impedance becomes independent of the electrode material. - Abstract: Electrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified. A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.

  7. An appraisal of the electrical resistance method for assessing root surface area

    Science.gov (United States)

    Cao, Yang; Repo, Tapani; Silvennoinen, Raimo; Lehto, Tarja; Pelkonen, Paavo

    2010-01-01

    Electrical resistances of roots and stems of hydroponically raised willows (Salix schwerinii) were studied and related to root morphology. Willow cuttings with and without roots were set in a constant electric field (effective voltage of 0.1 V, sine-AC, 128 Hz) in a hydroponic solution. The electrical resistance of different components in the measurement system was measured and analysed in relation to root surface area in contact with the cultivation solution. Axial resistivities of single root segments and of stems were measured. The results showed that the resistance decreased in relation to an increase in the contact surface area of the roots with the solution. The resistance depended strongly on the contact area of the stem with the solution, however, thus causing bias in the evaluation of root surface area. This work is a new contribution for the understanding of current pathways in the root system as exposed to an external electric field and for developing a non-destructive method to study plant roots accordingly. It may be concluded that the electrical resistance method is a useful non-destructive method to study roots and their physiological properties. Electrical analogues for roots and stem comprising resistors are discussed in relation to in situ measurements. PMID:20363862

  8. [Functional asymmetry of electric processes in the rabbit brain cortex at formation of the hunger dominant].

    Science.gov (United States)

    Rusinova, E V

    2011-01-01

    The motivational condition of hunger and formation of the hunger dominant after daily food deprivation was studied in the conditions of chronic experiments on rabbits. It was shown, that the hunger condition was accompanied by left sided interhemispher asymmetry on indicators of spectral capacity of EEG frontal and right-hand asymmetry sensorimotor areas of the cortex. A hunger dominant was accompanied by falling of spectral capacity of EEG of areas of both hemispheres. The condition of hunger and a hunger dominant were characterized by right-hand asymmetry on average level of EEG coherence of frontal and sensorimotor areas. At transition of a condition of hunger in a hunger dominant there was an average level of EEG coherence decrease in areas of the right hemisphere. Electric processes of the cortex of the brain at a motivational condition of hunger and a hunger dominant were different.

  9. Functional asymmetry between the left and right human fusiform gyrus explored through electrical brain stimulation.

    Science.gov (United States)

    Rangarajan, Vinitha; Parvizi, Josef

    2016-03-01

    The ventral temporal cortex (VTC) contains several areas with selective responses to words, numbers, faces, and objects as demonstrated by numerous human and primate imaging and electrophysiological studies. Our recent work using electrocorticography (ECoG) confirmed the presence of face-selective neuronal populations in the human fusiform gyrus (FG) in patients implanted with intracranial electrodes in either the left or right hemisphere. Electrical brain stimulation (EBS) disrupted the conscious perception of faces only when it was delivered in the right, but not left, FG. In contrast to our previous findings, here we report both negative and positive EBS effects in right and left FG, respectively. The presence of right hemisphere language dominance in the first, and strong left-handedness and poor language processing performance in the second case, provide indirect clues about the functional architecture of the human VTC in relation to hemispheric asymmetries in language processing and handedness. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Brain electric activity during the preattentive perception of speech sounds in tonal languages

    Directory of Open Access Journals (Sweden)

    Naiphinich Kotchabhakdi

    2004-05-01

    Full Text Available The present study was intended to make electrophysiological investigations into the preattentive perception of native and non-native speech sounds. We recorded the mismatch negativity, elicited by single syllable change of both native and non-native speech-sound contrasts in tonal languages. EEGs were recorded and low-resolution brain electromagnetic tomography (LORETA was utilized to explore the neural electrical activity. Our results suggested that the left hemisphere was predominant in the perception of native speech sounds, whereas the non-native speech sound was perceived predominantly by the right hemisphere, which may be explained by the specialization in processing the prosodic and emotional components of speech formed in this hemisphere.

  11. Laser-based surface preparation of composite laminates leads to improved electrodes for electrical measurements

    KAUST Repository

    Almuhammadi, Khaled

    2015-10-19

    Electrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified. A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.

  12. Nanoscale roughness and morphology affect the IsoElectric Point of titania surfaces.

    Directory of Open Access Journals (Sweden)

    Francesca Borghi

    Full Text Available We report on the systematic investigation of the role of surface nanoscale roughness and morphology on the charging behaviour of nanostructured titania (TiO2 surfaces in aqueous solutions. IsoElectric Points (IEPs of surfaces have been characterized by direct measurement of the electrostatic double layer interactions between titania surfaces and the micrometer-sized spherical silica probe of an atomic force microscope in NaCl aqueous electrolyte. The use of a colloidal probe provides well-defined interaction geometry and allows effectively probing the overall effect of nanoscale morphology. By using supersonic cluster beam deposition to fabricate nanostructured titania films, we achieved a quantitative control over the surface morphological parameters. We performed a systematical exploration of the electrical double layer properties in different interaction regimes characterized by different ratios of characteristic nanometric lengths of the system: the surface rms roughness Rq, the correlation length ξ and the Debye length λD. We observed a remarkable reduction by several pH units of IEP on rough nanostructured surfaces, with respect to flat crystalline rutile TiO2. In order to explain the observed behavior of IEP, we consider the roughness-induced self-overlap of the electrical double layers as a potential source of deviation from the trend expected for flat surfaces.

  13. Quantitative spatial analysis of the mouse brain lipidome by pressurized liquid extraction surface analysis

    DEFF Research Database (Denmark)

    Almeida, Reinaldo; Berzina, Zane; Christensen, Eva Arnspang

    2015-01-01

    Here we describe a novel surface sampling technique termed pressurized liquid extraction surface analysis (PLESA), which in combination with a dedicated high-resolution shotgun lipidomics routine enables both quantification and in-depth structural characterization of molecular lipid species extra...... distribution and molar abundance of 170 molecular lipid species across different anatomical mouse brain regions....

  14. The fractionation of spoken language understanding by measuring electrical and magnetic brain signals.

    Science.gov (United States)

    Hagoort, Peter

    2008-03-12

    This paper focuses on what electrical and magnetic recordings of human brain activity reveal about spoken language understanding. Based on the high temporal resolution of these recordings, a fine-grained temporal profile of different aspects of spoken language comprehension can be obtained. Crucial aspects of speech comprehension are lexical access, selection and semantic integration. Results show that for words spoken in context, there is no 'magic moment' when lexical selection ends and semantic integration begins. Irrespective of whether words have early or late recognition points, semantic integration processing is initiated before words can be identified on the basis of the acoustic information alone. Moreover, for one particular event-related brain potential (ERP) component (the N400), equivalent impact of sentence- and discourse-semantic contexts is observed. This indicates that in comprehension, a spoken word is immediately evaluated relative to the widest interpretive domain available. In addition, this happens very quickly. Findings are discussed that show that often an unfolding word can be mapped onto discourse-level representations well before the end of the word. Overall, the time course of the ERP effects is compatible with the view that the different information types (lexical, syntactic, phonological, pragmatic) are processed in parallel and influence the interpretation process incrementally, that is as soon as the relevant pieces of information are available. This is referred to as the immediacy principle.

  15. Language selection in bilinguals: a spatio-temporal analysis of electric brain activity.

    Science.gov (United States)

    Khateb, Asaid; Abutalebi, Jubin; Michel, Christoph M; Pegna, Alan J; Lee-Jahnke, Hannelore; Annoni, Jean-Marie

    2007-09-01

    Language selection refers to the cognitive mechanism that allows bilinguals to communicate in one language or the other and to switch between languages depending on the listener. Previous studies suggested that various brain areas might be involved in this process. However, the question remains whether language selection is achieved through a language-specific mechanism or through a general cognitive control process. To address this question, we compared event-related potentials (ERPs) induced by language selection and task selection processes during image naming. ERPs were collected from bilingual subjects while tested in two different contexts: a monolingual task selection context (TSc) where a post-stimulus cue instructed subjects either to name the image or generate a corresponding verb in their first language (L1), and a bilingual language selection context (LSc) where the cue indicated to name the image either in the first or the second language. By comparing the ERPs induced by the same L1 naming as a function of context, we assumed that if the selection processes varied across contexts, then electric brain responses should differ rapidly after the cue presentation. Our analysis indicated that the first ERP differences accounting for the diverging processes involved appeared between approximately 220 and 300 ms after the cue. The estimation by source localisation of brain regions accounting for these differences pointed to an increased activation during LSc in the left middle frontal-precentral gyri, supramarginal and angular gyri. Our results suggest that language selection is achieved through a neural network involving areas implicated in both general cognitive processes and language processing.

  16. Effects of auditory stimuli on electrical activity in the brain during cycle ergometry.

    Science.gov (United States)

    Bigliassi, Marcelo; Karageorghis, Costas I; Wright, Michael J; Orgs, Guido; Nowicky, Alexander V

    2017-08-01

    The present study sought to further understanding of the brain mechanisms that underlie the effects of music on perceptual, affective, and visceral responses during whole-body modes of exercise. Eighteen participants were administered light-to-moderate intensity bouts of cycle ergometer exercise. Each exercise bout was of 12-min duration (warm-up [3min], exercise [6min], and warm-down [3min]). Portable techniques were used to monitor the electrical activity in the brain, heart, and muscle during the administration of three conditions: music, audiobook, and control. Conditions were randomized and counterbalanced to prevent any influence of systematic order on the dependent variables. Oscillatory potentials at the Cz electrode site were used to further understanding of time-frequency changes influenced by voluntary control of movements. Spectral coherence analysis between Cz and frontal, frontal-central, central, central-parietal, and parietal electrode sites was also calculated. Perceptual and affective measures were taken at five timepoints during the exercise bout. Results indicated that music reallocated participants' attentional focus toward auditory pathways and reduced perceived exertion. The music also inhibited alpha resynchronization at the Cz electrode site and reduced the spectral coherence values at Cz-C4 and Cz-Fz. The reduced focal awareness induced by music led to a more autonomous control of cycle movements performed at light-to-moderate-intensities. Processing of interoceptive sensory cues appears to upmodulate fatigue-related sensations, increase the connectivity in the frontal and central regions of the brain, and is associated with neural resynchronization to sustain the imposed exercise intensity. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  17. Social anxiety disorder: radio electric asymmetric conveyor brain stimulation versus sertraline.

    Science.gov (United States)

    Fontani, Vania; Mannu, Piero; Castagna, Alessandro; Rinaldi, Salvatore

    2011-01-01

    Social anxiety disorder (SAD) is a disabling condition that affects almost 5% of the general population. Many types of drugs have shown their efficacy in the treatment of SAD. There are also some data regarding psychotherapies, but no data are available today about the efficacy of brain stimulation techniques. The aim of the study is to compare the efficacy of noninvasive brain stimulation neuro psycho physical optimization (NPPO) protocol performed by radio electric asymmetric conveyor (REAC) with that of sertraline in adults with SAD. Twenty SAD patients on sertraline were compared with 23 SAD patients who refused any drug treatment and who chose to be treated with NPPO-REAC brain stimulation. This was a 6-month, open-label, naturalistic study. Patients on sertraline received flexible doses, whereas NPPO-REAC patients received two 18-session cycles of treatment. Clinical Global Improvement scale items "much improved" or "very much improved" and Liebowitz Social Anxiety Scale total score variation on fear and avoidance components were used to detect the results. The statistical analysis was performed with t-test. All measures <0.05 have been considered statistically significant. Ten of 23 subjects on NPPO-REAC and six of the 20 taking sertraline were much improved or very much improved 1 month after the first NPPO-REAC cycle (t1). Sixteen of the subjects on NPPO-REAC and ten of the subjects taking sertraline were much improved or very much improved 1 month after the second NPPO-REAC cycle (t2). In respect of the Liebowitz Social Anxiety Scale, at t1 NPPO-REAC resulted in statistically more efficacy for sertraline on both fear and avoidance total scores. At t2, NPPO-REAC resulted in statistically more efficacy for sertraline on fear but not on avoidance. NPPO-REAC is an effective treatment for SAD, allowing substantial and clinically meaningful reductions in symptoms and disability in comparison with sertraline.

  18. Fabrication of Superhydrophobic Surfaces with Controllable Electrical Conductivity and Water Adhesion.

    Science.gov (United States)

    Ye, Lijun; Guan, Jipeng; Li, Zhixiang; Zhao, Jingxin; Ye, Cuicui; You, Jichun; Li, Yongjin

    2017-02-14

    A facile and versatile strategy for fabricating superhydrophobic surfaces with controllable electrical conductivity and water adhesion is reported. "Vine-on-fence"-structured and cerebral cortex-like superhydrophobic surfaces are constructed by filtering a suspension of multiwalled carbon nanotubes (MWCNTs), using polyoxymethylene nonwovens as the filter paper. The nonwovens with micro- and nanoporous two-tier structures act as the skeleton, introducing a microscale structure. The MWCNTs act as nanoscale structures, creating hierarchical surface roughness. The surface topography and the electrical conductivity of the superhydrophobic surfaces are controlled by varying the MWCNT loading. The vine-on-fence-structured surfaces exhibit "sticky" superhydrophobicity with high water adhesion. The cerebral cortex-like surfaces exhibit self-cleaning properties with low water adhesion. The as-prepared superhydrophobic surfaces are chemically resistant to acidic and alkaline environments of pH 2-12. They therefore have potential in applications such as droplet-based microreactors and thin-film microextraction. These findings aid our understanding of the role that surface topography plays in the design and fabrication of superhydrophobic surfaces with different water-adhesion properties.

  19. Amplification of surface acoustic waves by transverse electric current in piezoelectric semiconductors

    DEFF Research Database (Denmark)

    Gulyaev, Yuri V.

    1974-01-01

    It is shown that the principal characteristic feature of the surface acoustic waves in piezoelectrics—the presence of an alternating electric field transverse to the surface, which can be of the same order of magnitude as the longitudinal field—may not only give rise to the known transverse...... acoustoelectric effect but also lead to amplification of surface acoustic waves by electron drift perpendicular to the surface. For Love waves in a piezoelectric semiconductor film on a highly conducting substrate, the amplification coefficient is found and the conditions necessary for amplification...

  20. Specific features of learning with nociceptive electrical reinforcement in rats of different genetic strains: role of brain neurotransmitter systems.

    Science.gov (United States)

    Kalyuzhnyi, A L; Litvinova, S V; Shulgovskii, V V; Panchenko, L F

    2005-01-01

    The interaction between neurotransmitter systems and opioid system in rats of different strains was studied during learning and emotional stress. The interaction between noradrenergic, serotoninergic, and opioid systems in the brain is the main neurochemical mechanism underlying learning reinforced by nociceptive electrical stimulation, which determine individual differences in the rate and type of learning.

  1. Infants of Depressed and Nondepressed Mothers Exhibit Differences in Frontal Brain Electrical Activity during the Expression of Negative Emotions.

    Science.gov (United States)

    Dawson, Geraldine; And Others

    1997-01-01

    Examined electrical brain activity during negative and positive emotion expression in infants of depressed and nondepressed mothers. Found that, compared with infants of nondepressed mothers, infants of depressed mothers exhibited increased EEG activation in the frontal but not parietal region when expressing negative emotions. There were no…

  2. Radio frequency surface plasma oscillations: electrical excitation and detection by Ar/Ag(111).

    Science.gov (United States)

    Serrano, Giulia; Tebi, Stefano; Wiespointner-Baumgarthuber, Stefan; Müllegger, Stefan; Koch, Reinhold

    2017-08-29

    We electrically excite surface plasma oscillations on a Ag(111) single crystal by alternating electric charging at radio frequency. The radio frequency signal energy of 2.2 μeV, used to induce surface plasma oscillations, is about 5 to 6 orders of magnitude lower than the plasmon energies reachable by optical excitation or electron impact. The detection of the surface plasma oscillations is achieved by nano-fabricated 2D single-crystal sensor-islands of Ar atoms, which are shown by imaging with a scanning tunneling microscope to restructure in response to the radio frequency surface plasma oscillations, providing nanometer spatial resolution and a characteristic decay time of ≈150 ns.

  3. Separation of the tumor and brain surface by "water jet" in cases of meningiomas.

    Science.gov (United States)

    Toth, S; Vajda, J; Pasztor, E; Toth, Z

    1987-01-01

    In the surgery of meningiomas one of the most delicate problems is the separation of the tumor from the brain surface. The authors generally recommend microsurgery to preserve the brain surface anatomically and functionally. For this purpose we have developed a new surgical technique according to our concepts of tissue care. After excavating the tumor from inside the tumor brain surface was separated by repeated "water jets" into the tumor arachnoideal space. The "water jet" was produced by an ordinary bulb syringe. The front pressure of the jets was 300-1000 mm of water and the side pressure 100-300 mm of water. In the tumor-arachnoideal space the spreading water (phys. NaCl) separates the brain from the tumor with utmost care. We operated on 55 meningiomas of different types with the "water jet" technique. The immediate results were anatomically excellent. Intraoperative and postoperative acute and late edemas appeared only in a few cases. The functions of the nearby brain were generally preserved. The surgery was uneventful when the tumor surface was smooth and the tumor was spherical. When the tumor surface was uneven, one part of the tumor extended under the dura as a thin layer or the tumor was multilobulated with expanded vessels between the lobules, more microseparation was necessary. We compared the results of the "water jet" technique with the results of the "pre-water jet" series. The surgery with the "water jet" technique was much shorter and its results were better than those of microsurgery alone.

  4. In vivo bioimpedance measurement of healthy and ischaemic rat brain: implications for stroke imaging using electrical impedance tomography.

    Science.gov (United States)

    Dowrick, T; Blochet, C; Holder, D

    2015-06-01

    In order to facilitate the imaging of haemorrhagic and ischaemic stroke using frequency difference electrical impedance tomography (EIT), impedance measurements of normal and ischaemic brain, and clotted blood during haemorrhage, were gathered using a four-terminal technique in an in vivo animal model, a first for ischaemic measurements. Differences of 5-10% in impedance were seen between the frequency spectrums of healthy and ischaemic brain, over the frequency range 0-3 kHz, while the spectrum of blood was predominately uniform. The implications of imaging blood/ischaemia in the brain using electrical impedance tomography are discussed, supporting the notion that it will be possible to differentiate stroke from haemorrhage.

  5. On electric field magnitude on the cathode surface in the negative corona discharge

    Science.gov (United States)

    Petrov, A.; Savinov, S.; Pestovskii, N.; Korostylev, E.; Amirov, R.; Samoylov, I.; Barengolts, S.

    2013-09-01

    Negative corona discharge has been studied in air in the Trichel pulse mode in point-to-plane configuration on graphite cathodes. Electric field magnitude of the positive space charge in the active phase of a Trichel pulse has been estimated on the range of 107 V/cm. The discharge flame on the cathode surface is localized in the region with maximum electric field. The wandering of the discharge is self-organized in such way that the electric field magnitude caused by the positive space charge in the region of the discharge flame localization exceeds the field magnitude on the microasperities in some distance from this region. So the proposed estimate of electric field magnitude is based on the results of the topography analysis of the cathode surface and on the results of registration of the discharge wandering over the cathode surface. Microasperities formed due to redeposition of erosion products with field magnification coefficient 10-102 were found. Finally the occurrence of electric field with magnitude 108 V/cm argues in favor of electroexplosive mechanism of cathode erosion in the negative corona discharge. The work is made under support of RBRF grants 12-08-01223 and 12-08-33031 and under financial support of Ministry of Education and Science of Russian Federation.

  6. Decreased central fatigue in multiple sclerosis patients after 8 weeks of surface functional electrical stimulation

    OpenAIRE

    Ya-Ju Chang, PhD; Miao-Ju Hsu, PhD; Shin-Man Chen, MS; Cheng-Hsiang Lin, PhD; Alice M. K. Wong, MD

    2011-01-01

    Effective treatments for multiple sclerosis (MS)-associated central fatigue have not been established. Surface functional electrical stimulation (FES), which can challenge the peripheral neuromuscular system without overloading the central nervous system, is a relatively safe therapeutic strategy. We investigated the effect of 8 weeks of surface FES training on the levels of general, central, and peripheral fatigue in MS patients. Seven of nine individuals with MS (average age: 42.86 +/– 13.4...

  7. Electrical characterization of large surface area semi-transparent Si solar cells

    Science.gov (United States)

    Makris, Th.; Skuras, E.

    2013-12-01

    In this paper, we present an analysis of preliminary electrical data deduced from I-V characteristic curves recorded on large surface area semi-transparent Si cells fabricated using a novel experimental technique. The semi-transparency is achieved by laser cutting two-dimensional periodic patterns of ellipses through highly efficient commercially-manufactured mono-crystalline Si solar cells with a surface area of 156 × 156 mm2.

  8. Fabrication of surface micro- and nanostructures for superhydrophobic surfaces in electric and electronic applications

    Science.gov (United States)

    Xiu, Yonghao

    In our study, the superhydrophobic surface based on biomimetic lotus leave is explored to maintain the desired properties for self-cleaning. Parameters in controlling bead-up and roll-off characteristics of water droplets were investigated on different model surfaces. The governing equations were proposed. Heuristic study is performed. First, the fundamental understanding of the effect of roughness on superhydrophobicity is performed. The effect of hierarchical roughness, i.e., two scale roughness effect on roughness is investigated using systems of (1) monodisperse colloidal silica sphere (submicron) arrays and Au nanoparticle on top and (2) Si micrometer pyramids and Si nanostructures on top from KOH etching and metal assisted etching of Si. The relation between the contact area fraction and water droplet contact angles are derived based on Wenzel and Cassie-Baxter equation for the systems and the two scale effect is explained regarding the synergistic combination of two scales. Previously the microscopic three-phase-contact line is thought to be the key factor in determining contact angles and hystereses. In our study, Laplace pressure was brought up and related to the three-phase-contact line and taken as a key figure of merit in determining superhydrophobicity. In addition, we are one of the first to study the effect of tapered structures (wall inclination). Combining with a second scale roughness on the tapered structures, stable Cassie state for both water and low surface energy oil may be achieved. This is of great significance for designing both superhydrophobicity and superoleophobicity. Regarding the origin of contact angle hysteresis, study of superhydrophobicity on micrometer Si pillars was performed. The relation between the interface work of function and contact angle hysteresis was proposed and derived mathematically based on the Young-Dupre equation. The three-phase-contact line was further related to a secondary scale roughness induced. Based on

  9. Effect of diet with omega-3 in basal brain electrical activity and during status epilepticus in rats.

    Science.gov (United States)

    Pessoa, Daniella Tavares; da Silva, Eva Luana Almeida; Costa, Edbhergue Ventura Lola; Nogueira, Romildo Albuquerque

    2017-11-01

    Western diets are high in saturated fat and low in omega-3. Certain animals cannot produce omega-3 from their own lipids, making it necessary for it to be acquired from the diet. However, omega-3s are important components of the plasma membrane, and altering their proportions can promote physical and chemical alterations in the membranes, which may modify neuronal excitability. These alterations occur in healthy individuals, as well as in patients with epilepsy who are more sensitive to changes in brain electrical activity. This study evaluated the effect of a diet supplemented with omega-3 on the basal brain electrical activity both before and during status epilepticus in rats. To evaluate the brain electrical activity, we recorded electrocorticograms (ECoG) of animals both with and without omega-3 supplementation before and during status epilepticus induced by pilocarpine. Calculation of the average brain wave power by a power spectrum revealed that omega-3 supplementation reduced the average power of the delta wave by 20% and increased the average power of the beta wave by 45%. These effects were exacerbated when status epilepticus was induced in the animals supplemented with omega-3. The animals with and without omega-3 supplementation exhibited increases in basal brain electrical activities during status epilepticus. The two groups showed hyperactivity, but no significant difference between them was noted. Even though the brain activity levels observed during status epilepticus were similar between the two groups, neuron damage to the animals supplemented with omega-3 was more slight, revealing the neuroprotective effect of the omega-3. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Accuracy for predicting adhesion between meningioma and the brain by using brain surface motion imaging: comparison between single and double acquisition methods

    Energy Technology Data Exchange (ETDEWEB)

    Taoka, Toshiaki; Sakamoto, Masahiko; Akashi, Toshiaki; Miyasaka, Toshiteru; Ochi, Tomoko; Wada, Takeshi; Kichikawa, Kimihiko [Nara Medical University, Department of Radiology, Kashihara, Nara (Japan); Yamada, Syuichi; Nakase, Hiroyuki [Nara Medical University, Department of Neurosurgery, Kashihara, Nara (Japan); Uchikoshi, Masato [Siemens Japan K.K., Tokyo (Japan)

    2012-12-15

    The presence of adhesions between the brain and the meningioma is an important factor that determines the success of total surgical removal. Brain surface motion imaging enables assessment of the dynamics of brain surface motion. A subtraction image of pulse-gated heavily T2-weighted images in different phases of the cardiac cycle provides a stripe pattern on the surface of the pulsating brain. Thus, the lack of a stripe pattern on the surface of extraaxial tumor indicates the presence of tumor-brain adhesion. The purpose of the present experiment was to evaluate the accuracy of predicting tumor-brain adhesion using the original double acquisition method and the improved single acquisition method. The subjects were 67 meningioma cases patients who were surgically treated after brain surface motion imaging. Thirty-three cases were evaluated using the double acquisition method and 34 cases were evaluated with the single acquisition method. In the double acquisition method, the two sets of images are acquired as two independent scans, and in the single acquisition method, the images are acquired serially as a single scan. The findings for the double acquisition method agreed with the surgical findings in 23 cases (69.7 %), while findings from the single acquisition method agreed with the surgical findings in 26 cases (76.5 %). Pre-surgical evaluation for tumor-brain adhesion by brain surface motion imaging provides helpful information for meningioma surgery, especially when using the single acquisition method. (orig.)

  11. Nanoscale lubrication of ionic surfaces controlled via a strong electric field.

    Science.gov (United States)

    Strelcov, Evgheni; Kumar, Rajeev; Bocharova, Vera; Sumpter, Bobby G; Tselev, Alexander; Kalinin, Sergei V

    2015-01-27

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. The demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems.

  12. The application of surface electrical and shallow geothermic methods in monitoring network design.

    Science.gov (United States)

    Gilkeson, R.H.; Cartwright, K.

    1983-01-01

    There are a variety of surface geophysical methods that are routinely used in geologic investigations. The three broad applications of these methods to evaluate the impact of waste disposal on shallow groundwater flow systems are: 1) evaluation of proposed waste disposal sites; 2) monitoring of site performance; and 3) investigation of contaminant migration at existing sites. Electrical and shallow geothermic are two surface geophysical methods that have application to waste disposal investigations. Of the electrical methods, electrical resistivity has the greatest application with a variety of techniques available. The distribution of temperature in shallow geologic materials (shallow geothermics) may define characteristics of shallow groundwater flow systems including zones of recharge and discharge and lithologic variation in the shallow geologic materials.-from Authors

  13. Surface roughness and grain boundary scattering effects on the electrical conductivity of thin films

    NARCIS (Netherlands)

    Palasantzas, George

    1998-01-01

    In this work, we investigate surface/interface roughness and grain boundary scattering effects on the electrical conductivity of polycrystalline thin films in the Born approximation. We assume for simplicity a random Gaussian roughness convoluted with a domain size distribution ~e^-πr^2/ζ^2 to

  14. Investigation of transient temperature's influence on damage of high-speed sliding electrical contact rail surface

    Science.gov (United States)

    Zhang, Yuyan; Sun, Shasha; Guo, Quanli; Yang, Degong; Sun, Dongtao

    2016-11-01

    In the high speed sliding electrical contact with large current, the temperature of contact area rises quickly under the coupling action of the friction heating, the Joule heating and electric arc heating. The rising temperature seriously affects the conductivity of the components and the yield strength of materials, as well affects the contact state and lead to damage, so as to shorten the service life of the contact elements. Therefore, there is vital significance to measure the temperature accurately and investigate the temperature effect on damage of rail surface. Aiming at the problem of components damage in high speed sliding electrical contact, the transient heat effect on the contact surface was explored and its influence and regularity on the sliding components damage was obtained. A kind of real-time temperature measurement method on rail surface of high speed sliding electrical contact is proposed. Under the condition of 2.5 kA current load, based on the principle of infrared radiation non-contact temperature sensor was used to measure the rail temperature. The dynamic distribution of temperature field was obtained through the simulation analysis, further, the connection between temperature changes and the rail surface damage morphology, the damage volume was analyzed and established. Finally, the method to reduce rail damage and improve the life of components by changing the temperature field was discussed.

  15. Engineering support activities for the Apollo 17 Surface Electrical Properties Experiment.

    Science.gov (United States)

    Cubley, H. D.

    1972-01-01

    Description of the engineering support activities which were required to ensure fulfillment of objectives specified for the Apollo 17 SEP (Surface Electrical Properties) Experiment. Attention is given to procedural steps involving verification of hardware acceptability to the astronauts, computer simulation of the experiment hardware, field trials, receiver antenna pattern measurements, and the qualification test program.

  16. Control of thumb force using surface functional electrical stimulation and muscle load sharing

    NARCIS (Netherlands)

    Westerveld, A.J.; Schouten, A.C.; Veltink, P.H.; Van der Kooij, H.

    2013-01-01

    Background Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of

  17. Control of thumb force using surface functional electrical stimulation and muscle load sharing

    NARCIS (Netherlands)

    Westerveld, Ard; Westerveld, Ard J.; Schouten, Alfred Christiaan; Veltink, Petrus H.; van der Kooij, Herman

    2013-01-01

    Background: Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of

  18. Cycle-to-cycle control of swing phase of paraplegic gait induced by surface electrical stimulation

    NARCIS (Netherlands)

    Franken, H.M.; Franken, H.M.; Veltink, Petrus H.; Baardman, G.; Redmeijer, R.A.; Boom, H.B.K.

    1995-01-01

    Parameterised swing phase of gait in paraplegics was obtained using surface electrical stimulation of the hip flexors, hamstrings and quadriceps; the hip flexors were stimulated to obtain a desired hip angle range, the hamstrings to provide foot clearance in the forward swing, and the quadriceps to

  19. Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface

    Science.gov (United States)

    Homin, Taras; Korsun, Anatolii

    High electric fields and currents are occurred in the spacecrafts plasma environment by onboard electric generators. Thus the high voltage solar array (SA) of the American segment of International Space Station (ISS) generates potential 160 V. Its negative pole is shorted to the frames of all the ISS segments. There is electric current between the SA and the frame through the plasma environment, i.e. electric discharge occurs. As a result a potential drop exists between the frames of all the ISS segments and the environmental plasma [1], which is cathode drop potential varphi _{c} defined. When ISS orbiting, the φc varies greatly in the range 0-100 V. A large area of the ISS frames and SA surface is coated with a thin dielectric film. Because of cathode drop potential the frame surfaces accumulate ion charges and the SA surfaces accumulate electron charges. These surfaces become plasma capacitors, which accumulate much charge and energy. Micrometeorite impacts or buildup of potential drop in excess of breakdown threshold varphi_{b} (varphi _{c} > varphi _{b} = 60 V) may cause breakdowns of these capacitors. Following a breakdown, the charge collected at the surfaces disperses and transforms into a layer of dense plasma [2]. This plasma environment of the spacecraft produces great pulsed electric fields E at the frame surfaces as well as heavy currents between construction elements which in turn induce great magnetic fields H. Therefore the conductive frame and the environmental plasma is plasma inductors. We have calculated that the densities of these pulsing and high-frequency fields E and H generated in the plasma environment of the spacecraft may exceed values hazardous to human. Besides, these fields must induce large electromagnetic impulses in the space-suit and in the power supply and control circuits of onboard systems. During astronaut’s space-suit activity, these fields will penetrate the space-suit and the human body with possible hazardous effects

  20. Modulating protein behaviors on responsive surface by external electric fields: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yun, E-mail: xieyunxx@gdpu.edu.cn; Pan, Yufang; Zhang, Rong; Liang, Ying; Li, Zhanchao

    2015-01-30

    Graphical abstract: The adsorption of Cyt c on phosphorylcholine self-assembled monolayers (N atoms of the choline groups are colored in blue while the P atoms of the phosphate groups in orange). - Highlights: • PC-SAM could sensitively adjust its charge distribution to applied electric fields. • Adsorption of Cyt c on the PC-SAM is promoted or retarded as the charge distribution of the SAM changes. • Orientations of Cyt c on the PC-SAM are regulated by the structural changes of the SAM. • The structural changes of the SAM cause little deformation in Cyt c. - Abstract: Molecular dynamics simulations were employed to investigate the modulation of protein behaviors on the electrically responsive zwitterionic phosphorylcholine self-assembled monolayers (PC-SAMs). Results show that PC-SAMs could sensitively respond to the applied electric fields and exhibit three states with different charge distributions, namely both the negatively charged phosphate groups and the positively charged choline groups are exposed to the solution in the absence of electric fields (state 1), phosphate groups exposed in the presence of positive electric fields (state 2), and choline groups exposed in the presence of negative electric fields (state 3). Under state 1, the adsorption of Cyt c on the PC-SAM is reversible and the orientations of Cyt c are randomly distributed. Under state 2, the adsorption of Cyt c is enhanced due to the electrostatic attractions between the exposed phosphate groups and the positively charged protein; when adsorbed on the PC-SAMs, Cyt c tends to adopt the orientation with the heme plane perpendicular to the surface plane, and the percentage of this orientation increases as the field strength rises up. Under state 3, the adsorption of Cyt c is retarded because of the electrostatic repulsions between the exposed choline groups and the protein; however, if the gaps between PC chains are large enough, Cyt c could insert into the PC-SAM and access the

  1. Surface plasmon-mediated energy transfer of electrically-pumped excitons

    Energy Technology Data Exchange (ETDEWEB)

    An, Kwang Hyup; Shtein, Max; Pipe, Kevin P.

    2015-08-25

    An electrically pumped light emitting device emits a light when powered by a power source. The light emitting device includes a first electrode, a second electrode including an outer surface, and at least one active organic semiconductor disposed between the first and second electrodes. The device also includes a dye adjacent the outer surface of the second electrode such that the second electrode is disposed between the dye and the active organic semiconductor. A voltage applied by the power source across the first and second electrodes causes energy to couple from decaying dipoles into surface plasmon polariton modes, which then evanescently couple to the dye to cause the light to be emitted.

  2. Effects of brain-computer interface-based functional electrical stimulation on brain activation in stroke patients: a pilot randomized controlled trial.

    Science.gov (United States)

    Chung, EunJung; Kim, Jung-Hee; Park, Dae-Sung; Lee, Byoung-Hee

    2015-03-01

    [Purpose] This study sought to determine the effects of brain-computer interface-based functional electrical stimulation (BCI-FES) on brain activation in patients with stroke. [Subjects] The subjects were randomized to in a BCI-FES group (n=5) and a functional electrical stimulation (FES) group (n=5). [Methods] Patients in the BCI-FES group received ankle dorsiflexion training with FES for 30 minutes per day, 5 times under the brain-computer interface-based program. The FES group received ankle dorsiflexion training with FES for the same amount of time. [Results] The BCI-FES group demonstrated significant differences in the frontopolar regions 1 and 2 attention indexes, and frontopolar 1 activation index. The FES group demonstrated no significant differences. There were significant differences in the frontopolar 1 region activation index between the two groups after the interventions. [Conclusion] The results of this study suggest that BCI-FES training may be more effective in stimulating brain activation than only FES training in patients recovering from stroke.

  3. An electric field induced in the retina and brain at threshold magnetic flux density causing magnetophosphenes

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, Akimasa; Takano, Yukinori; Fujiwara, Osamu [Nagoya Institute of Technology, Department of Computer Science and Engineering (Japan); Dovan, Thanh [SP AusNet, Division of Network Strategy and Development (Australia); Kavet, Robert, E-mail: ahirata@nitech.ac.jp [Electric Power Research Institute, Palo Alto, CA (United States)

    2011-07-07

    For magnetic field exposures at extremely low frequencies, the electrostimulatory response with the lowest threshold is the magnetophosphene, a response that corresponds to an adult exposed to a 20 Hz magnetic field of nominally 8.14 mT. In the IEEE standard C95.6 (2002), the corresponding in situ field in the retinal locus of an adult-sized ellipsoidal was calculated to be 53 mV m{sup -1}. However, the associated dose in the retina and brain at a high level of resolution in anatomically correct human models is incompletely characterized. Furthermore, the dose maxima in tissue computed with voxel human models are prone to staircasing errors, particularly for the low-frequency dosimetry. In the analyses presented in this paper, analytical and quasi-static finite-difference time-domain (FDTD) solutions were first compared for a three-layer sphere exposed to a uniform 50 Hz magnetic field. Staircasing errors in the FDTD results were observed at the tissue interface, and were greatest at the skin-air boundary. The 99th percentile value was within 3% of the analytic maximum, depending on model resolution, and thus may be considered a close approximation of the analytic maximum. For the adult anatomical model, TARO, exposed to a uniform magnetic field, the differences in the 99th percentile value of in situ electric fields for 2 mm and 1 mm voxel models were at most several per cent. For various human models exposed at the magnetophosphene threshold at three orthogonal field orientations, the in situ electric field in the brain was between 10% and 70% greater than the analytical IEEE threshold of 53 mV m{sup -1}, and in the retina was lower by roughly 50% for two horizontal orientations (anterior-posterior and lateral), and greater by about 15% for a vertically oriented field. Considering a reduction factor or safety factors of several folds applied to electrostimulatory thresholds, the 99th percentile dose to a tissue calculated with voxel human models may be used as an

  4. Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Pons, Jerome; Moreau, Eric; Touchard, Gerard [LEA, University of Poitiers/CNRS/ENSMA, Bd. Curie, Teleport 2, BP 30179, 86962 Futuroscope Cedex (France)

    2005-10-07

    The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s{sup -1} at heights of 1-2 mm are reached when filamentary discharges with current peaks up to 20 mA are produced along the surface. In terms of powers, mechanical powers (output) of a few milliwatts are obtained for electrical powers (input) up to 10 W. Variation laws or behaviour with several discharge parameters (applied voltage waveform, distance between electrodes, dielectric thickness and permittivity) have been experimentally determined.

  5. Large apparent electric size of solid-state nanopores due to spatially extended surface conduction.

    Science.gov (United States)

    Lee, Choongyeop; Joly, Laurent; Siria, Alessandro; Biance, Anne-Laure; Fulcrand, Rémy; Bocquet, Lydéric

    2012-08-08

    Ion transport through nanopores drilled in thin membranes is central to numerous applications, including biosensing and ion selective membranes. This paper reports experiments, numerical calculations, and theoretical predictions demonstrating an unexpectedly large ionic conduction in solid-state nanopores, taking its origin in anomalous entrance effects. In contrast to naive expectations based on analogies with electric circuits, the surface conductance inside the nanopore is shown to perturb the three-dimensional electric current streamlines far outside the nanopore in order to meet charge conservation at the pore entrance. This unexpected contribution to the ionic conductance can be interpreted in terms of an apparent electric size of the solid-state nanopore, which is much larger than its geometric counterpart whenever the number of charges carried by the nanopore surface exceeds its bulk counterpart. This apparent electric size, which can reach hundreds of nanometers, can have a major impact on the electrical detection of translocation events through nanopores, as well as for ionic transport in biological nanopores.

  6. Electric-field Assisted Deposition of the DNA on Polymer Surface

    Science.gov (United States)

    Ryu, Junhwan; Zhu, Ke; Budassi, Julia; Sokolov, Jonathan

    2012-02-01

    Recently, the interaction of DNA with surfaces has been widely studied for its range of applications, including mapping, sequencing and analyzing DNAs. In this study, the Lambda DNA molecules were aligned in 6:50(0.1M NaOH:0.02M MES) buffer solution with different electric fields and deposited onto polymethylmetacrylate (PMMA) surfaces by dipping and retracting PMMA coated silicon wafers into the solution. Electric field was set up with platinum wire and gold plated Si wafer. The DNA strands were dyed with YoYo-1 and observed using a fluorescence microscope. The efficiency of deposition was optimized with respect to DNA concentration, DNA length and electric field. The results indicate that the density and possibly the lengths of the DNA deposited on surface can be controlled by this method. Enhancement of adsorption density of greater than twenty-fold were found using electric field strengths of 10v/cm. This study is supported by NSF-DMR-MRSEC program.

  7. Electric field effects on the dynamics of bubble detachment from an inclined surface

    Science.gov (United States)

    Di Marco, P.; Morganti, N.; Saccone, G.

    2015-11-01

    An experimental apparatus to study bubble detachment from an inclined surface under the action of electric forces is described. It consists of a container filled with FC72 at room temperature and pressure where a train of gas bubbles is injected from an orifice. An electrostatic field can be imposed around the bubble, while the cell can be tilted from 0 to 90°. It is possible to study interface growth with the aid of high-speed cinematography. Since the interface is asymmetrical, a mirror system allowed to acquire, in the same frame, two images at 90° of the bubble. Different inclinations, injection rates and voltages were tested in order to couple the effects of shear gravity and electric field. Curvature and contact angles have been derived with appropriate interpolation methods of the profile. Force balances on the bubble were checked, finding an electric force, which, at first pulls the bubbles from the orifice, then pushes it against the surface. The motion of the center of gravity confirms this behaviour. A power balance has been developed to determine the energy contributions, revealing that surface growth incorporates both the effects of inlet power and electric field.

  8. Structural and Electrical Characterization of Oxidated, Nitridated and Oxi-nitridated (100) GaAs Surfaces

    Science.gov (United States)

    Paul, Narayan Chandra; Nakamura, Kazuki; Takebe, Masahide; Takemoto, Akira; Inokuma, Takao; Iiyama, Koichi; Takamiya, Saburo; Higashimine, Koichi; Ohtsuka, Nobuo; Yonezawa, Yasuto

    2003-07-01

    Oxidation by the UV & ozone process, nitridation by the nitrogen helicon-wave-excited plasma process, and the combination of these processes are applied to (100) GaAs wafers. An atomic force microscope, X-ray photoelectron spectroscopy, a transmission electron microscope, photoluminescence and electrical characteristics (current-voltage and capacitance-voltage) were used to analyze the influences of these processes on the structure and composition of the surfaces and the interfaces. Metal-insulator-semiconductor (MIS) diodes and Schottky diodes were fabricated in order to investigate the electrical influences of these processes. The oxidation slightly disorders GaAs surfaces. Nitridation of a bare surface creates about a 2-nm-thick strongly disordered layer, which strongly deteriorates the electrical and photoluminescence characteristics. Nitridation of oxidated wafers (oxi-nitridation) forms firm amorphous GaON layers, which contain GaN, with very flat and sharp GaON/GaAs interfaces, where crystal disorder is hardly observed. It improves the current-voltage (I-V) and capacitance-voltage (C-V) characteristics and the photoluminescence intensity. Results of the structural and the electrical characterizations qualitatively coincide well with each other.

  9. Social anxiety disorder: radio electric asymmetric conveyor brain stimulation versus sertraline

    Science.gov (United States)

    Fontani, Vania; Mannu, Piero; Castagna, Alessandro; Rinaldi, Salvatore

    2011-01-01

    Purpose Social anxiety disorder (SAD) is a disabling condition that affects almost 5% of the general population. Many types of drugs have shown their efficacy in the treatment of SAD. There are also some data regarding psychotherapies, but no data are available today about the efficacy of brain stimulation techniques. The aim of the study is to compare the efficacy of noninvasive brain stimulation neuro psycho physical optimization (NPPO) protocol performed by radio electric asymmetric conveyor (REAC) with that of sertraline in adults with SAD. Patients and methods Twenty SAD patients on sertraline were compared with 23 SAD patients who refused any drug treatment and who chose to be treated with NPPO-REAC brain stimulation. This was a 6-month, open-label, naturalistic study. Patients on sertraline received flexible doses, whereas NPPO-REAC patients received two 18-session cycles of treatment. Clinical Global Improvement scale items “much improved” or “very much improved” and Liebowitz Social Anxiety Scale total score variation on fear and avoidance components were used to detect the results. The statistical analysis was performed with t-test. All measures <0.05 have been considered statistically significant. Results Ten of 23 subjects on NPPO-REAC and six of the 20 taking sertraline were much improved or very much improved 1 month after the first NPPO-REAC cycle (t1). Sixteen of the subjects on NPPO-REAC and ten of the subjects taking sertraline were much improved or very much improved 1 month after the second NPPO-REAC cycle (t2). In respect of the Liebowitz Social Anxiety Scale, at t1 NPPO-REAC resulted in statistically more efficacy for sertraline on both fear and avoidance total scores. At t2, NPPO-REAC resulted in statistically more efficacy for sertraline on fear but not on avoidance. Conclusion NPPO-REAC is an effective treatment for SAD, allowing substantial and clinically meaningful reductions in symptoms and disability in comparison with

  10. Surface charges and J H Poynting’s disquisitions on energy transfer in electrical circuits

    Science.gov (United States)

    Matar, M.; Welti, R.

    2017-11-01

    In this paper we review applications given by J H Poynting (1884) on the transfer of electromagnetic energy in DC circuits. These examples were strongly criticized by O Heaviside (1887). Heaviside stated that Poynting had a misconception about the nature of the electric field in the vicinity of a wire through which a current flows. The historical review of this conflict and its resolution based on the consideration of electrical charges on the surface of the wires can be useful for student courses on electromagnetism or circuit theory.

  11. Electric field measurements in nanosecond pulse discharges in air over liquid water surface

    Science.gov (United States)

    Simeni Simeni, Marien; Baratte, Edmond; Zhang, Cheng; Frederickson, Kraig; Adamovich, Igor V.

    2018-01-01

    Electric field in nanosecond pulse discharges in ambient air is measured by picosecond four-wave mixing, with absolute calibration by a known electrostatic field. The measurements are done in two geometries, (a) the discharge between two parallel cylinder electrodes placed inside quartz tubes, and (b) the discharge between a razor edge electrode and distilled water surface. In the first case, breakdown field exceeds DC breakdown threshold by approximately a factor of four, 140 ± 10 kV cm‑1. In the second case, electric field is measured for both positive and negative pulse polarities, with pulse durations of ∼10 ns and ∼100 ns, respectively. In the short duration, positive polarity pulse, breakdown occurs at 85 kV cm‑1, after which the electric field decreases over several ns due to charge separation in the plasma, with no field reversal detected when the applied voltage is reduced. In a long duration, negative polarity pulse, breakdown occurs at a lower electric field, 30 kV cm‑1, after which the field decays over several tens of ns and reverses direction when the applied voltage is reduced at the end of the pulse. For both pulse polarities, electric field after the pulse decays on a microsecond time scale, due to residual surface charge neutralization by transport of opposite polarity charges from the plasma. Measurements 1 mm away from the discharge center plane, ∼100 μm from the water surface, show that during the voltage rise, horizontal field component (Ex ) lags in time behind the vertical component (Ey ). After breakdown, Ey is reduced to near zero and reverses direction. Further away from the water surface (≈0.9 mm), Ex is much higher compared to Ey during the entire voltage pulse. The results provide insight into air plasma kinetics and charge transport processes near plasma-liquid interface, over a wide range of time scales.

  12. Influence of Wire Electrical Discharge Machining (WEDM) process parameters on surface roughness

    Science.gov (United States)

    Yeakub Ali, Mohammad; Banu, Asfana; Abu Bakar, Mazilah

    2018-01-01

    In obtaining the best quality of engineering components, the quality of machined parts surface plays an important role. It improves the fatigue strength, wear resistance, and corrosion of workpiece. This paper investigates the effects of wire electrical discharge machining (WEDM) process parameters on surface roughness of stainless steel using distilled water as dielectric fluid and brass wire as tool electrode. The parameters selected are voltage open, wire speed, wire tension, voltage gap, and off time. Empirical model was developed for the estimation of surface roughness. The analysis revealed that off time has a major influence on surface roughness. The optimum machining parameters for minimum surface roughness were found to be at a 10 V open voltage, 2.84 μs off time, 12 m/min wire speed, 6.3 N wire tension, and 54.91 V voltage gap.

  13. [The changes in the brain's electrical activity in children with cerebral palsy during the complex rehabilitation].

    Science.gov (United States)

    Ukhanova, T A; Gorbunov, F E; Dement'eva, E V; Volkova, E A; Novikova, E E

    2012-01-01

    One hundred and five children, aged from 3 to 7 years, with the diagnosis "spastic diplegia cerebral palsy" were treated. Patients were stratified into three groups: group I (n=36) received three courses of microcurrent therapy (MENS) in addition to standard treatment; group II (n=38) received three courses of MENS in the combination with two treatment courses with the nootropic drug cortexin; children of group III (n=31) received standard therapy using massage and gymnastics. MENS was carried out in courses, including 15 sessions each, using the apparatus "MEKS". Cortexin was introduced intramuscular in dosage 10 mg, the treatment course consisted of 10 injections. To the end of the rehabilitation program, positive changes were found: 50% patients of group I, 66% patients of group II and 16% patients of group III could perform complex instructions and acquired skills in modeling and recognition of geometric forms. Positive changes in the brain's electrical activity were found in 75% of children in group I, in 82% of children in group II and in 64% of children in group III.

  14. Memory scrutinized through electrical brain stimulation: A review of 80 years of experiential phenomena.

    Science.gov (United States)

    Curot, Jonathan; Busigny, Thomas; Valton, Luc; Denuelle, Marie; Vignal, Jean-Pierre; Maillard, Louis; Chauvel, Patrick; Pariente, Jérémie; Trebuchon, Agnès; Bartolomei, Fabrice; Barbeau, Emmanuel J

    2017-07-01

    Electrical brain stimulations (EBS) sometimes induce reminiscences, but it is largely unknown what type of memories they can trigger. We reviewed 80 years of literature on reminiscences induced by EBS and added our own database. We classified them according to modern conceptions of memory. We observed a surprisingly large variety of reminiscences covering all aspects of declarative memory. However, most were poorly detailed and only a few were episodic. This result does not support theories of a highly stable and detailed memory, as initially postulated, and still widely believed as true by the general public. Moreover, memory networks could only be activated by some of their nodes: 94.1% of EBS were temporal, although the parietal and frontal lobes, also involved in memory networks, were stimulated. The qualitative nature of memories largely depended on the site of stimulation: EBS to rhinal cortex mostly induced personal semantic reminiscences, while only hippocampal EBS induced episodic memories. This result supports the view that EBS can activate memory in predictable ways in humans. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  15. Surface-Controlled Properties of Myosin Studied by Electric Field Modulation.

    Science.gov (United States)

    van Zalinge, Harm; Ramsey, Laurence C; Aveyard, Jenny; Persson, Malin; Mansson, Alf; Nicolau, Dan V

    2015-08-04

    The efficiency of dynamic nanodevices using surface-immobilized protein molecular motors, which have been proposed for diagnostics, drug discovery, and biocomputation, critically depends on the ability to precisely control the motion of motor-propelled, individual cytoskeletal filaments transporting cargo to designated locations. The efficiency of these devices also critically depends on the proper function of the propelling motors, which is controlled by their interaction with the surfaces they are immobilized on. Here we use a microfluidic device to study how the motion of the motile elements, i.e., actin filaments propelled by heavy mero-myosin (HMM) motor fragments immobilized on various surfaces, is altered by the application of electrical loads generated by an external electric field with strengths ranging from 0 to 8 kVm(-1). Because the motility is intimately linked to the function of surface-immobilized motors, the study also showed how the adsorption properties of HMM on various surfaces, such as nitrocellulose (NC), trimethylclorosilane (TMCS), poly(methyl methacrylate) (PMMA), poly(tert-butyl methacrylate) (PtBMA), and poly(butyl methacrylate) (PBMA), can be characterized using an external field. It was found that at an electric field of 5 kVm(-1) the force exerted on the filaments is sufficient to overcome the frictionlike resistive force of the inactive motors. It was also found that the effect of assisting electric fields on the relative increase in the sliding velocity was markedly higher for the TMCS-derivatized surface than for all other polymer-based surfaces. An explanation of this behavior, based on the molecular rigidity of the TMCS-on-glass surfaces as opposed to the flexibility of the polymer-based ones, is considered. To this end, the proposed microfluidic device could be used to select appropriate surfaces for future lab-on-a-chip applications as illustrated here for the almost ideal TMCS surface. Furthermore, the proposed methodology can

  16. Electrical and Surface Properties of InAs/InSb Nanowires Cleaned by Atomic Hydrogen.

    Science.gov (United States)

    Webb, James L; Knutsson, Johan; Hjort, Martin; Gorji Ghalamestani, Sepideh; Dick, Kimberly A; Timm, Rainer; Mikkelsen, Anders

    2015-08-12

    We present a study of InAs/InSb heterostructured nanowires by X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM), and in-vacuum electrical measurements. Starting with pristine nanowires covered only by the native oxide formed through exposure to ambient air, we investigate the effect of atomic hydrogen cleaning on the surface chemistry and electrical performance. We find that clean and unreconstructed nanowire surfaces can be obtained simultaneously for both InSb and InAs by heating to 380 ± 20 °C under an H2 pressure 2 × 10(-6) mbar. Through electrical measurement of individual nanowires, we observe an increase in conductivity of 2 orders of magnitude by atomic hydrogen cleaning, which we relate through theoretical simulation to the contact-nanowire junction and nanowire surface Fermi level pinning. Our study demonstrates the significant potential of atomic hydrogen cleaning regarding device fabrication when high quality contacts or complete control of the surface structure is required. As hydrogen cleaning has recently been shown to work for many different types of III-V nanowires, our findings should be applicable far beyond the present materials system.

  17. Direct electrical control of IgG conformation and functional activity at surfaces

    Science.gov (United States)

    Ghisellini, Paola; Caiazzo, Marialuisa; Alessandrini, Andrea; Eggenhöffner, Roberto; Vassalli, Massimo; Facci, Paolo

    2016-11-01

    We have devised a supramolecular edifice involving His-tagged protein A and antibodies to yield surface immobilized, uniformly oriented, IgG-type, antibody layers with Fab fragments exposed off an electrode surface. We demonstrate here that we can affect the conformation of IgGs, likely pushing/pulling electrostatically Fab fragments towards/from the electrode surface. A potential difference between electrode and solution acts on IgGs’ charged aminoacids modulating the accessibility of the specific recognition regions of Fab fragments by antigens in solution. Consequently, antibody-antigen affinity is affected by the sign of the applied potential: a positive potential enables an effective capture of antigens; a negative one pulls the fragments towards the electrode, where steric hindrance caused by neighboring molecules largely hampers the capture of antigens. Different experimental techniques (electrochemical quartz crystal microbalance, electrochemical impedance spectroscopy, fluorescence confocal microscopy and electrochemical atomic force spectroscopy) were used to evaluate binding kinetics, surface coverage, effect of the applied electric field on IgGs, and role of charged residues on the phenomenon described. These findings expand the concept of electrical control of biological reactions and can be used to gate electrically specific recognition reactions with impact in biosensors, bioactuators, smart biodevices, nanomedicine, and fundamental studies related to chemical reaction kinetics.

  18. Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures

    Directory of Open Access Journals (Sweden)

    Luis Zamora-Peredo

    2016-01-01

    Full Text Available Photoreflectance (PR and Raman are two very useful spectroscopy techniques that usually are used to know the surface electronic states in GaAs-based semiconductor devices. However, although they are exceptional tools there are few reports where both techniques were used in these kinds of devices. In this work, the surface electronic states on AlGaAs/GaAs heterostructures were studied in order to identify the effect of factors like laser penetration depth, cap layer thickness, and surface passivation over PR and Raman spectra. PR measurements were performed alternately with two lasers (532 nm and 375 nm wavelength as the modulation sources in order to identify internal and surface features. The surface electric field calculated by PR analysis decreased whereas the GaAs cap layer thickness increased, in good agreement with a similar behavior observed in Raman measurements (IL-/ILO ratio. When the heterostructures were treated by Si-flux, these techniques showed contrary behaviors. PR analysis revealed a diminution in the surface electric field due to a passivation process whereas the IL-/ILO ratio did not present the same behavior because it was dominated by the depletion layers width (cap layer thickness and the laser penetration depth.

  19. Facile fabrication of iron-based superhydrophobic surfaces via electric corrosion without bath

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Qinghe [College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Liu, Hongtao, E-mail: liuht100@126.com [College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Chen, Tianchi [College of Mechanical & Electrical Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Wei, Yan; Wei, Zhu [College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China)

    2016-04-30

    Graphical abstract: - Highlights: • This paper investigates the fabrication techniques towards superhydrophobic surface on carbon steel substrate via electric corrosion without a bath. • It has a vital significance to the industrialization of the fabrication of superhydrophobic surface on hard metal due to the advantages such as low cost, high efficiency, can be prepared in a large area, easy to construct in the field. • The preparation approach is so facile and time-saving that it delivers an opportunity to construct a superhydrophobic surface on carbon steel substrate and provides the feasibility for industrial application of superhydrophobic surface. • The as-prepared surface has many excellent properties, like low adhesive property, anti-corrosion ability, mechanical durability and anti-icing performance. - Abstract: Superhydrophobic surface is of wide application in the field of catalysis, lubrication, waterproof, biomedical materials, etc. The superhydrophobic surface based on hard metal is worth further study due to its advantages of high strength and wear resistance. This paper investigates the fabrication techniques towards superhydrophobic surface on carbon steel substrate via electric corrosion and studies the properties of as-prepared superhydrophobic surface. The hydrophobic properties were characterized by a water sliding angle (SA) and a water contact angle (CA) measured by the Surface tension instrument. A Scanning electron microscope was used to analyze the structure of the corrosion surface. The surface compositions were characterized by an Energy Dispersive Spectrum. The Electrochemical workstation was used to measure its anti-corrosion property. The anti-icing performance was characterized by a steam-freezing test in Environmental testing chamber. The SiC sandpaper and 500 g weight were used to test the friction property. The research result shows that the superhydrophobic surface can be successfully fabricated by electrocorrosion on

  20. Machining Performance and Surface Integrity of AISI D2 Die Steel Machined Using Electrical Discharge Surface Grinding Process

    Science.gov (United States)

    Choudhary, Rajesh; Kumar, Harmesh; Singh, Shankar

    2013-12-01

    The aim of this study is to establish optimum machining conditions for EDSG of AISI D2 die steel through an experimental investigation using Taguchi Methodology. To achieve combined grinding and electrical discharge machining, metal matrix composite electrodes (Cu-SiCp) were processed through powder metallurgy route. A rotary spindle attachment was developed to perform the EDSG experimental runs on EDM machine. Relationships were developed between various input parameters such as peak current, speed, pulse-on time, pulse-off time, abrasive particle size, and abrasive particle concentration, and output characteristics such as material removal rate and surface roughness. The optimized parameters were further validated by conducting confirmation experiments.

  1. INORGANIC PLUME DELINEATION USING SURFACE HIGH RESOLUTION ELECTRICAL RESISTIVITY AT THE BC CRIBS & TRENCHES SITE HANFORD

    Energy Technology Data Exchange (ETDEWEB)

    BENECKE, M.W.

    2007-05-29

    A surface resistivity survey was conducted on the Hanford Site over a waste disposal trench that received a large volume of liquid inorganic waste. The objective of the survey was to map the extent of the plume that resulted from the disposal activities approximately 50 years earlier. The survey included six resistivity transects of at least 200m, where each transect provided two-dimensional profile information of subsurface electrical properties. The results of the survey indicated that a low resistivity plume resides at a depth of approximately 25-44 m below ground surface. The target depth was calibrated with borehole data of pore-water electrical conductivity. Due to the high correlation of the pore-water electrical conductivity to nitrate concentration and the high correlation of measured apparent resistivity to pore-water electrical conductivity, inferences were made that proposed the spatial distribution of the apparent resistivity was due to the distribution of nitrate. Therefore, apparent resistivities were related to nitrate, which was subsequently rendered in three dimensions to show that the nitrate likely did not reach the water table and the bounds of the highest concentrations are directly beneath the collection of waste sites.

  2. In vivo measurement of brain extracellular space diffusion by cortical surface photobleaching.

    Science.gov (United States)

    Binder, Devin K; Papadopoulos, Marios C; Haggie, Peter M; Verkman, A S

    2004-09-15

    Molecular diffusion in the brain extracellular space (ECS) is an important determinant of neural function. We developed a brain surface photobleaching method to measure the diffusion of fluorescently labeled macromolecules in the ECS of the cerebral cortex. The ECS in mouse brain was labeled by exposure of the intact dura to fluorescein-dextrans (M(r) 4, 70, and 500 kDa). Fluorescein-dextran diffusion, detected by fluorescence recovery after laser-induced cortical photobleaching using confocal optics, was slowed approximately threefold in the brain ECS relative to solution. Cytotoxic brain edema (produced by water intoxication) or seizure activity (produced by convulsants) slowed diffusion by >10-fold and created dead-space microdomains in which free diffusion was prevented. The hindrance to diffusion was greater for the larger fluorescein-dextrans. Interestingly, slowed ECS diffusion preceded electroencephalographic seizure activity. In contrast to the slowed diffusion produced by brain edema and seizure activity, diffusion in the ECS was faster in mice lacking aquaporin-4 (AQP4), an astroglial water channel that facilitates fluid movement between cells and the ECS. Our results establish a minimally invasive method to quantify diffusion in the brain ECS in vivo, revealing stimulus-induced changes in molecular diffusion in the ECS with unprecedented spatial and temporal resolution. The in vivo mouse data provide evidence for: (1) dead-space ECS microdomains after brain swelling; (2) slowed molecular diffusion in the ECS as an early predictor of impending seizure activity; and (3) a novel role for AQP4 as a regulator of brain ECS.

  3. ELECTRICALLY CONDUCTIVE SURFACE MODIFICATIONS OF THREE-DIMENSIONAL POLYPROPYLENE FUMARATE SCAFFOLDS

    Science.gov (United States)

    Runge, M. Brett; Dadsetan, Mahrokh; Baltrusaitis, Jonas; Yaszemski, Michael J.

    2014-01-01

    Summary Polypropylene fumarate (PPF) scaffolds fabricated by rapid prototyping technique were surface modified by solution deposition of electrically conductive polypyrrole coatings with or without hydroxyapatite. Scaffolds were electrically conductive with resistivity as low as 2Ω. Scaffold characterization by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermo gravimetric analysis shows both polypyrrole and hydroxyapatite are present. Cell viability, attachment, proliferation, and differentiation were analyzed using human fetal osteoblast cells. These studies show that surface modification using hydroxyapatite improved cell attachment and proliferation of osteoblasts onto the PPF scaffolds. Alkaline phosphatase activity as a marker for osteogenic differentiation of cell to mature osteoblasts was analyzed. Our data reveal that osteoblasts maintained their phenotype on PPF scaffolds with and without coatings. Thus, these scaffolds could be appropriate candidates for our future in vivo studies. PMID:22051167

  4. An Electric Field Volume Integral Equation Approach to Simulate Surface Plasmon Polaritons

    Directory of Open Access Journals (Sweden)

    R. Remis

    2013-02-01

    Full Text Available In this paper we present an electric field volume integral equation approach to simulate surface plasmon propagation along metal/dielectric interfaces. Metallic objects embedded in homogeneous dielectric media are considered. Starting point is a so-called weak-form of the electric field integral equation. This form is discretized on a uniform tensor-product grid resulting in a system matrix whose action on a vector can be computed via the fast Fourier transform. The GMRES iterative solver is used to solve the discretized set of equations and numerical examples, illustrating surface plasmon propagation, are presented. The convergence rate of GMRES is discussed in terms of the spectrum of the system matrix and through numerical experiments we show how the eigenvalues of the discretized volume scattering operator are related to plasmon propagation and the medium parameters of a metallic object.

  5. Clinical usefulness of brain-computer interface-controlled functional electrical stimulation for improving brain activity in children with spastic cerebral palsy: a pilot randomized controlled trial.

    Science.gov (United States)

    Kim, Tae-Woo; Lee, Byoung-Hee

    2016-09-01

    [Purpose] Evaluating the effect of brain-computer interface (BCI)-based functional electrical stimulation (FES) training on brain activity in children with spastic cerebral palsy (CP) was the aim of this study. [Subjects and Methods] Subjects were randomized into a BCI-FES group (n=9) and a functional electrical stimulation (FES) control group (n=9). Subjects in the BCI-FES group received wrist and hand extension training with FES for 30 minutes per day, 5 times per week for 6 weeks under the BCI-based program. The FES group received wrist and hand extension training with FES for the same amount of time. Sensorimotor rhythms (SMR) and middle beta waves (M-beta) were measured in frontopolar regions 1 and 2 (Fp1, Fp2) to determine the effects of BCI-FES training. [Results] Significant improvements in the SMR and M-beta of Fp1 and Fp2 were seen in the BCI-FES group. In contrast, significant improvement was only seen in the SMR and M-beta of Fp2 in the control group. [Conclusion] The results of the present study suggest that BCI-controlled FES training may be helpful in improving brain activity in patients with cerebral palsy and may be applied as effectively as traditional FES training.

  6. Clinical usefulness of brain-computer interface-controlled functional electrical stimulation for improving brain activity in children with spastic cerebral palsy: a pilot randomized controlled trial

    Science.gov (United States)

    Kim, Tae-Woo; Lee, Byoung-Hee

    2016-01-01

    [Purpose] Evaluating the effect of brain-computer interface (BCI)-based functional electrical stimulation (FES) training on brain activity in children with spastic cerebral palsy (CP) was the aim of this study. [Subjects and Methods] Subjects were randomized into a BCI-FES group (n=9) and a functional electrical stimulation (FES) control group (n=9). Subjects in the BCI-FES group received wrist and hand extension training with FES for 30 minutes per day, 5 times per week for 6 weeks under the BCI-based program. The FES group received wrist and hand extension training with FES for the same amount of time. Sensorimotor rhythms (SMR) and middle beta waves (M-beta) were measured in frontopolar regions 1 and 2 (Fp1, Fp2) to determine the effects of BCI-FES training. [Results] Significant improvements in the SMR and M-beta of Fp1 and Fp2 were seen in the BCI-FES group. In contrast, significant improvement was only seen in the SMR and M-beta of Fp2 in the control group. [Conclusion] The results of the present study suggest that BCI-controlled FES training may be helpful in improving brain activity in patients with cerebral palsy and may be applied as effectively as traditional FES training. PMID:27799677

  7. Investigation of properties of surfaces, recovered by electric-arc coatings

    Directory of Open Access Journals (Sweden)

    Микола Федорович Дмитриченко

    2016-12-01

    Full Text Available Physical and mechanical properties of the recovered surfaces of the machine parts by electric-arc coating are considered from position of influence of technological parameters of coating process. Dependences of adhesion strength, porosity and gas permeability of coatings from the technological coating modes (current voltage of arc, spraying distance, pressure of the compressed air are set as a result of the conducted experiments

  8. Research into action of surface soil moistening, drying or freezing on electrical characteristics of grounding device

    Directory of Open Access Journals (Sweden)

    I.V. Nizhevskiy

    2014-03-01

    Full Text Available The analysis made has shown expediency of modernization rather than reconstruction of earth electrodes, after inspection of long operating substations grounding grids, via building a two-level structure. It will result in both technical and economic effects. The novelty of the results consists in studying, by means of a mathematical model, electrical characteristics of a two-level earth electrode versus the depth of surface soil drying or freezing.

  9. The role of electric charge in microdroplets impacting on conducting surfaces

    Science.gov (United States)

    Deng, Weiwei; Gomez, Alessandro

    2010-05-01

    A rich phenomenology is revealed by temporally resolved image sequences of electrically charged ethanol microdroplets impacting on a conductive surface at temperatures bracketing the liquid boiling point. Notable phenomena include the flattening of the sessile droplets with reduced contact angle, increased evaporation rates for substrate temperatures below the fluid boiling point, and the hindrance of droplet rebound at the Leidenfrost temperature. Scaling considerations are presented to rationalize the observed behavior and to generalize conclusions to a broader droplet size range.

  10. Quantum-continuum calculation of the surface states and electrical response of silicon in solution

    Science.gov (United States)

    Campbell, Quinn; Dabo, Ismaila

    2017-05-01

    A wide range of electrochemical reactions of practical importance occur at the interface between a semiconductor and an electrolyte. We present an embedded density-functional theory method using the recently released self-consistent continuum solvation (SCCS) approach to study these interfaces. In this model, a quantum description of the surface is incorporated into a continuum representation of the bending of the bands within the electrode. The model is applied to understand the electrical response of silicon electrodes in solution, providing microscopic insights into the low-voltage region, where surface states determine the electrification of the semiconductor electrode.

  11. Shaping of steel mold surface of lens array by electrical discharge machining with single rod electrode.

    Science.gov (United States)

    Takino, Hideo; Hosaka, Takahiro

    2014-11-20

    We propose a method for fabricating a lens array mold by electrical discharge machining (EDM). In this method, the tips of rods are machined individually to form a specific surface, and then a number of the machined rods are arranged to construct an electrode for EDM. The repetition of the EDM process using the electrode enables a number of lens elements to be produced on the mold surface. The effectiveness of our proposed method is demonstrated by shaping a lens array mold made of stainless steel with 16 spherical elements, in which the EDM process with a single rod electrode is repeatedly conducted.

  12. Surface, electrical and mechanical modifications of PMMA after implantation with laser produced iron plasma ions

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Qazi Salman; Bashir, Shazia, E-mail: shaziabashir@gcu.edu.pk; Jalil, Sohail Abdul; Shabbir, Muhammad Kaif; Mahmood, Khaliq; Akram, Mahreen; Khalid, Ayesha; Yaseen, Nazish; Arshad, Atiqa

    2016-07-01

    Laser Produced Plasma (LPP) was employed as an ion source for the modifications in surface, electrical and mechanical properties of poly methyl (methacrylate) PMMA. For this purpose Nd:YAG laser (532 nm, 6 ns, 10 Hz) at a fluence of 12.7 J/cm{sup 2} was employed to generate Fe plasma. The fluence and energy measurements of laser produced Fe plasma ions were carried out by employing Thomson Parabola Technique in the presence of magnetic field strength of 0.5 T, using CR-39 as Solid State Nuclear Track Detector (SSNTD). It has been observed that ion fluence ejecting from ablated plasma was maximum at an angle of 5° with respect to the normal to the Fe target surface. PMMA substrates were irradiated with Fe ions of constant energy of 0.85 MeV at various ion fluences ranging from 3.8 × 10{sup 6} ions/cm{sup 2} to 1.8 × 10{sup 8} ions/cm{sup 2} controlled by varying laser pulses from 3000 to 7000. Optical microscope and Scanning Electron Microscope (SEM) were utilized for the analysis of surface features of irradiated PMMA. Results depicted the formation of chain scission, crosslinking, dendrites and star like structures. To explore the electrical behavior, four probe method was employed. The electrical conductivity of ion irradiated PMMA was increased with increasing ion fluence. The surface hardness was measured by shore D hardness tester and results showed the monotonous increment in surface hardness with increasing ion fluence. The increasing trend of surface hardness and electrical conductivity with increasing Fe ion fluence has been well correlated with the surface morphology of ion implanted PMMA. The temperature rise of PMMA surface due to Fe ion irradiation is evaluated analytically and comes out to be in the range of 1.72 × 10{sup 4} to 1.82 × 10{sup 4} K. The values of total Linear Energy Transfer (LET) or stopping power of 0.8 MeV Fe ions in PMMA is 61.8 eV/Å and their range is 1.34 μm evaluated by SRIM simulation.

  13. Exposure to static electric fields leads to changes in biogenic amine levels in the brains of Drosophila

    Science.gov (United States)

    Newland, Philip L.; Al Ghamdi, Mesfer S.; Sharkh, Suleiman; Aonuma, Hitoshi; Jackson, Christopher W.

    2015-01-01

    Natural and anthropogenic static electric fields are commonly found in the environment and can have both beneficial and harmful effects on many animals. Here, we asked how the fruitfly responds to these fields and what the consequences of exposure are on the levels of biogenic amines in the brain. When given a choice in a Y-tube bioassay Drosophila avoided electric fields, and the greater the field strength the more likely Drosophila were to avoid it. By comparing wild-type flies, flies with wings surgically removed and vestigial winged flies we found that the presence of intact wings was necessary to produce avoidance behaviour. We also show that Coulomb forces produced by electric fields physically lift excised wings, with the smaller wings of males being raised by lower field strengths than larger female wings. An analysis of neurochemical changes in the brains showed that a suite of changes in biogenic amine levels occurs following chronic exposure. Taken together we conclude that physical movements of the wings are used by Drosophila in generating avoidance behaviour and are accompanied by changes in the levels of amines in the brain, which in turn impact on behaviour. PMID:26224706

  14. Influence of surface properties on the electrical conductivity of silicon nanomembranes

    Directory of Open Access Journals (Sweden)

    Zhao Xiangfu

    2011-01-01

    Full Text Available Abstract Because of the large surface-to-volume ratio, the conductivity of semiconductor nanostructures is very sensitive to surface chemical and structural conditions. Two surface modifications, vacuum hydrogenation (VH and hydrofluoric acid (HF cleaning, of silicon nanomembranes (SiNMs that nominally have the same effect, the hydrogen termination of the surface, are compared. The sheet resistance of the SiNMs, measured by the van der Pauw method, shows that HF etching produces at least an order of magnitude larger drop in sheet resistance than that caused by VH treatment, relative to the very high sheet resistance of samples terminated with native oxide. Re-oxidation rates after these treatments also differ. X-ray photoelectron spectroscopy measurements are consistent with the electrical-conductivity results. We pinpoint the likely cause of the differences. PACS: 73.63.-b, 62.23.Kn, 73.40.Ty

  15. Experimental Investigation of Surface Layer Properties of High Thermal Conductivity Tool Steel after Electrical Discharge Machining

    Directory of Open Access Journals (Sweden)

    Rafał Świercz

    2017-12-01

    Full Text Available New materials require the use of advanced technology in manufacturing complex shape parts. One of the modern materials widely used in the tool industry for injection molds or hot stamping dies is high conductivity tool steel (HTCS 150. Due to its hardness (55 HRC and thermal conductivity at 66 W/mK, this material is difficult to machine by conventional treatment and is being increasingly manufactured by nonconventional technology such as electrical discharge machining (EDM. In the EDM process, material is removed from the workpiece by a series of electrical discharges that cause changes to the surface layers properties. The final state of the surface layer directly influences the durability of the produced elements. This paper presents the influence of EDM process parameters: discharge current Ic and the pulse time ton on surface layer properties. The experimental investigation was carried out with an experimental methodology design. Surface layers properties including roughness 3D parameters, the thickness of the white layer, heat affected zone, tempered layer and occurring micro cracks were investigated and described. The influence of the response surface methodology (RSM of discharge current Ic and the pulse time ton on the thickness of the white layer and roughness parameters Sa, Sds and Ssc were described and established.

  16. Electric field stabilization of viscous liquid layers coating the underside of a surface

    Science.gov (United States)

    Anderson, Thomas G.; Cimpeanu, Radu; Papageorgiou, Demetrios T.; Petropoulos, Peter G.

    2017-05-01

    We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a horizontal surface in the presence of an electric field applied parallel to the surface. The model includes the effect of bounding solid dielectric regions above and below the liquid-air system that are typically found in experiments. The competition between gravitational forces, surface tension, and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semispectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations using the volume-of-fluid methodology and assess the accuracy of the obtained solutions in the long-wave (thin-film) regime when varying the electric field strength from zero up to the point when complete stabilization occurs. We employ DNS to examine the limitations of the asymptotically derived behavior as the liquid layer thickness increases and find excellent agreement even beyond the regime of strict applicability of the asymptotic solution. Finally, the asymptotic and computational approaches are utilized to identify robust and efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.

  17. In doped CdO films: Electrical, optical, structural and surface properties

    Energy Technology Data Exchange (ETDEWEB)

    Kose, Salih; Atay, Ferhunde; Akyuz, Idris [Eskisehir Osmangazi University, Department of Physics, Art and Science Faculty, 26480 Eskisehir (Turkey); Bilgin, Vildan [Canakkale Onsekiz Mart University, Department of Physics, 17100 Canakkale (Turkey)

    2009-06-15

    Recently, there has been a lot of work on the production and investigation of the physical properties of Transparent Conducting Oxide (TCO) materials which have common application area in photovoltaic solar cells and some optoelectronic devices. In this work, CdO film which is a material belongs to TCO family has been produced by Ultrasonic Spray Pyrolysis technique on microscope glass substrates at the substrate temperature of 250 {+-} 5 C. Electrical, optical, structural and surface properties of undoped and In doped (at 1.3 and 5%) CdO films and the effect of In doping percentage on the physical properties of CdO films have been investigated. It has been determined that electrical conductivity of CdO film is high and this value has been decreased by In doping. After the optical investigations, it has been observed that the transmittances of the films are about 30% and decreased dramatically by In doping. XRD investigations showed that, films have polycrystalline structure and good crystallinity levels. It has been found that In element hasn't got an important effect on the morphology of the films after the examination of surface micrographs. It has been determined that Cd and O elements are present in the solid film by using EDS. After all investigations, it has been concluded that In doping has an important effect on the electrical, optical, structural and surface properties of CdO films. (author)

  18. Cell Proliferation, Migration, and Neurogenesis in the Adult Brain of the Pulse Type Weakly Electric Fish, Gymnotus omarorum

    Science.gov (United States)

    Olivera-Pasilio, Valentina; Lasserre, Moira; Castelló, María E.

    2017-01-01

    Adult neurogenesis, an essential mechanism of brain plasticity, enables brain development along postnatal life, constant addition of new neurons, neuronal turnover, and/or regeneration. It is amply distributed but negatively modulated during development and along evolution. Widespread cell proliferation, high neurogenic, and regenerative capacities are considered characteristics of teleost brains during adulthood. These anamniotes are promising models to depict factors that modulate cell proliferation, migration, and neurogenesis, and might be intervened to promote brain plasticity in mammals. Nevertheless, the migration path of derived cells to their final destination was not studied in various teleosts, including most weakly electric fish. In this group adult brain morphology is attributed to sensory specialization, involving the concerted evolution of peripheral electroreceptors and electric organs, encompassed by the evolution of neural networks involved in electrosensory information processing. In wave type gymnotids adult brain morphology is proposed to result from lifelong region specific cell proliferation and neurogenesis. Consistently, pulse type weakly electric gymnotids and mormyrids show widespread distribution of proliferation zones that persists in adulthood, but their neurogenic potential is still unknown. Here we studied the migration process and differentiation of newborn cells into the neuronal phenotype in the pulse type gymnotid Gymnotus omarorum. Pulse labeling of S-phase cells with 5-Chloro-2′-deoxyuridine thymidine followed by 1 to 180 day survivals evidenced long distance migration of newborn cells from the rostralmost telencephalic ventricle to the olfactory bulb, and between layers of all cerebellar divisions. Shorter migration appeared in the tectum opticum and torus semicircularis. In many brain regions, derived cells expressed early neuronal markers doublecortin (chase: 1–30 days) and HuC/HuD (chase: 7–180 days). Some newborn

  19. Cell Proliferation, Migration, and Neurogenesis in the Adult Brain of the Pulse Type Weakly Electric Fish, Gymnotus omarorum

    Directory of Open Access Journals (Sweden)

    Valentina Olivera-Pasilio

    2017-08-01

    Full Text Available Adult neurogenesis, an essential mechanism of brain plasticity, enables brain development along postnatal life, constant addition of new neurons, neuronal turnover, and/or regeneration. It is amply distributed but negatively modulated during development and along evolution. Widespread cell proliferation, high neurogenic, and regenerative capacities are considered characteristics of teleost brains during adulthood. These anamniotes are promising models to depict factors that modulate cell proliferation, migration, and neurogenesis, and might be intervened to promote brain plasticity in mammals. Nevertheless, the migration path of derived cells to their final destination was not studied in various teleosts, including most weakly electric fish. In this group adult brain morphology is attributed to sensory specialization, involving the concerted evolution of peripheral electroreceptors and electric organs, encompassed by the evolution of neural networks involved in electrosensory information processing. In wave type gymnotids adult brain morphology is proposed to result from lifelong region specific cell proliferation and neurogenesis. Consistently, pulse type weakly electric gymnotids and mormyrids show widespread distribution of proliferation zones that persists in adulthood, but their neurogenic potential is still unknown. Here we studied the migration process and differentiation of newborn cells into the neuronal phenotype in the pulse type gymnotid Gymnotus omarorum. Pulse labeling of S-phase cells with 5-Chloro-2′-deoxyuridine thymidine followed by 1 to 180 day survivals evidenced long distance migration of newborn cells from the rostralmost telencephalic ventricle to the olfactory bulb, and between layers of all cerebellar divisions. Shorter migration appeared in the tectum opticum and torus semicircularis. In many brain regions, derived cells expressed early neuronal markers doublecortin (chase: 1–30 days and HuC/HuD (chase: 7–180 days

  20. Enhancing performance of a motor imagery based brain-computer interface by incorporating electrical stimulation-induced SSSEP

    Science.gov (United States)

    Yi, Weibo; Qiu, Shuang; Wang, Kun; Qi, Hongzhi; Zhao, Xin; He, Feng; Zhou, Peng; Yang, Jiajia; Ming, Dong

    2017-04-01

    Objective. We proposed a novel simultaneous hybrid brain-computer interface (BCI) by incorporating electrical stimulation into a motor imagery (MI) based BCI system. The goal of this study was to enhance the overall performance of an MI-based BCI. In addition, the brain oscillatory pattern in the hybrid task was also investigated. Approach. 64-channel electroencephalographic (EEG) data were recorded during MI, selective attention (SA) and hybrid tasks in fourteen healthy subjects. In the hybrid task, subjects performed MI with electrical stimulation which was applied to bilateral median nerve on wrists simultaneously. Main results. The hybrid task clearly presented additional steady-state somatosensory evoked potential (SSSEP) induced by electrical stimulation with MI-induced event-related desynchronization (ERD). By combining ERD and SSSEP features, the performance in the hybrid task was significantly better than in both MI and SA tasks, achieving a ~14% improvement in total relative to the MI task alone and reaching ~89% in mean classification accuracy. On the contrary, there was no significant enhancement obtained in performance while separate ERD feature was utilized in the hybrid task. In terms of the hybrid task, the performance using combined feature was significantly better than using separate ERD or SSSEP feature. Significance. The results in this work validate the feasibility of our proposed approach to form a novel MI-SSSEP hybrid BCI outperforming a conventional MI-based BCI through combing MI with electrical stimulation.

  1. Surface displacement based shape analysis of central brain structures in preterm-born children

    Science.gov (United States)

    Garg, Amanmeet; Grunau, Ruth E.; Popuri, Karteek; Miller, Steven; Bjornson, Bruce; Poskitt, Kenneth J.; Beg, Mirza Faisal

    2016-03-01

    Many studies using T1 magnetic resonance imaging (MRI) data have found associations between changes in global metrics (e.g. volume) of brain structures and preterm birth. In this work, we use the surface displacement feature extracted from the deformations of the surface models of the third ventricle, fourth ventricle and brainstem to capture the variation in shape in these structures at 8 years of age that may be due to differences in the trajectory of brain development as a result of very preterm birth (24-32 weeks gestation). Understanding the spatial patterns of shape alterations in these structures in children who were born very preterm as compared to those who were born at full term may lead to better insights into mechanisms of differing brain development between these two groups. The T1 MRI data for the brain was acquired from children born full term (FT, n=14, 8 males) and preterm (PT, n=51, 22 males) at age 8-years. Accurate segmentation labels for these structures were obtained via a multi-template fusion based segmentation method. A high dimensional non-rigid registration algorithm was utilized to register the target segmentation labels to a set of segmentation labels defined on an average-template. The surface displacement data for the brainstem and the third ventricle were found to be significantly different (p MRI data and reveal shape changes that may be due to preterm birth.

  2. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    DEFF Research Database (Denmark)

    Minjoli, Sena; Saturnino, Guilherme B.; Blicher, Jakob Udby

    2017-01-01

    . Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative...... to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field " hot spots" in the cortex. However, these maxima were...... aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible...

  3. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    DEFF Research Database (Denmark)

    Minjoli, Sena; Saturnino, Guilherme B.; Blicher, Jakob Udby

    2017-01-01

    aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible....... Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative...... to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field " hot spots" in the cortex. However, these maxima were...

  4. The characterization of the antibacterial efficacy of an electrically activated silver ion-based surface system

    Science.gov (United States)

    Shirwaiker, Rohan A.

    There have been growing concerns in the global healthcare system about the eradication of pathogens in hospitals and other health-critical environments. The problem has been aggravated by the overuse of antibiotics and antimicrobial agents leading to the emergence of antibiotic-resistant superbugs such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) which are difficult to kill. Lower immunity of sick patients coupled with the escalating concurrent problem of antibiotic-resistant pathogens has resulted in increasing incidences of hospital acquired (nosocomial) infections. There is an immediate need to control the transmission of such infections, primarily in healthcare environments, by creating touch-contact and work surfaces (e.g., door knobs, push plates, countertops) that utilize alternative antibacterial materials like the heavy metal, silver. Recent research has shown that it is silver in its ionic (Ag+ ) and not elemental form that is antibacterial. Thus, silver-based antibacterial surfaces have to release silver ions directly into the pathogenic environment (generally, an aqueous media) in order to be effective. This dissertation presents the study and analysis of a new silver-based surface system that utilizes low intensity direct electric current (LIDC) for generation of silver ions to primarily inhibit indirect contact transmission of infections. The broader objective of this research is to understand the design, and characterization of the electrically activated silver ion-based antibacterial surface system. The specific objectives of this dissertation include: (1) Developing a comprehensive system design, and identifying and studying its critical design parameters and functional mechanisms. (2) Evaluating effects of the critical design parameters on the antibacterial efficacy of the proposed surface system. (3) Developing a response surface model for the surface system performance. These objectives are

  5. Electrical injection to contactless near-surface InGaN quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Riuttanen, L., E-mail: lauri.riuttanen@aalto.fi; Svensk, O.; Suihkonen, S. [Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Kivisaari, P.; Oksanen, J. [Department of Biomedical Engineering and Computational Science, Aalto University, P.O. Box 12200, FI-00076 Aalto (Finland)

    2015-08-03

    Charge injection to the prevailing and emerging light-emitting devices is almost exclusively based on the double heterojunction (DHJ) structures that have remained essentially unchanged for decades. In this letter, we report the excitation of a near surface indium gallium nitride (InGaN) quantum well (QW) by bipolar carrier diffusion from a nearby electrically excited pn-homojunction. The demonstrated near surface QW emitter is covered only by a 10 nm GaN capping leaving the light-emitting mesa perfectly free of metals, other contact, or current spreading structures. The presented proof-of-principle structure, operating approximately with a quantum efficiency of one fifth of a conventional single QW reference structure, provides conclusive evidence of the feasibility of using diffusion injection to excite near surface light-emitting structures needed, e.g., for developing light emitters or photo-voltaic devices based on nanoplasmonics or free-standing nanowires. In contrast to the existing DHJ solutions or optical pumping, our approach allows exciting nanostructures without the need of forming a DHJ, absorbing layers or even electrical contacts on the device surface.

  6. Effects of single application of a moisturizer: evaporation of emulsion water, skin surface temperature, electrical conductance, electrical capacitance, and skin surface (emulsion) lipids.

    Science.gov (United States)

    Blichmann, C W; Serup, J; Winther, A

    1989-01-01

    Effects of single application of an oil in water emulsion were studied on the forearm skin of 12 healthy volunteers. Five different non-invasive methods were used. Values were followed for 360 min after application of the emulsion, with the contralateral forearm as untreated control. The evaporation of emulsion water from the skin surface immediately rose to high values, but within 15 min returned to the original level. A parallel initial increase in conductance was observed; however, this was followed by a slightly increased level throughout the 360 min study. Electrical capacitance was also slightly increased throughout the study. Skin surface lipids, dominated by emulsion lipids, were increased, with high values for at least 120 min, followed by a gradual decline toward normal. Single application of emulsion is characterized by an initial evaporation phase, with evaporation of emulsion water, which lasts less than 15 min, followed by a lipidization phase, which lasts at least 360 min, dominated by the oil-constituent of the emulsion undergoing epidermal absorption. During the lipidization phase, epidermal hydration parameters are slightly but consistently improved.

  7. Electrocommunication signals alone are sufficient to increase neurogenesis in the brain of adult electric fish, Apteronotus leptorhynchus.

    Science.gov (United States)

    Dunlap, Kent D; McCarthy, Elizabeth A; Jashari, Denisa

    2008-10-01

    Social interaction can have profound influences on the structure of the adult brain, but little is known about the precise stimulus feature found within social interaction that induces such brain plasticity. We examined the effects of social stimuli on cell addition and radial glial fiber formation in the brains of adult electric fish. These fish communicate primarily through weak, quasi-sinusoidal electric signals. Fish were housed in isolation, paired with another fish or exposed to only the electrocommunication signals of another fish for 7 days. After 3 days of exposure to these stimulus conditions, fish were injected with bromodeoxyuridine (BrdU) to mark newborn cells. We sacrificed the fish 4 days after BrdU injection and used immunohistochemistry to measure cell addition (BrdU+), the fraction of added cells that differentiated into neurons (BrdU+/NeuroTrace+) and the density of radial glia fibers (vimentin+) in the periventricular zone of the diencephalon. Fish that were exposed only to the electrocommunication signals of another fish and no other social stimuli had equivalent levels of cell addition and radial glial fiber density to fish that were housed with full social interaction and higher levels than fish housed in isolation. About 60% of the added cells differentiated into neurons; this fraction did not differ among treatment groups. Artificial sine wave electrical stimuli that mimicked electrocommunication signals were ineffective in increasing cell addition and glia fiber formation above those found in isolated fish. Thus, stimuli through a single modality are sufficient for inducing this brain plasticity, but the waveform or dynamic features of communication signals are crucial for the effect. (c) 2008 Wiley Periodicals, Inc.

  8. Automated analysis of seizure semiology and brain electrical activity in presurgery evaluation of epilepsy: A focused survey.

    Science.gov (United States)

    Ahmedt-Aristizabal, David; Fookes, Clinton; Dionisio, Sasha; Nguyen, Kien; Cunha, João Paulo S; Sridharan, Sridha

    2017-11-01

    Epilepsy being one of the most prevalent neurological disorders, affecting approximately 50 million people worldwide, and with almost 30-40% of patients experiencing partial epilepsy being nonresponsive to medication, epilepsy surgery is widely accepted as an effective therapeutic option. Presurgical evaluation has advanced significantly using noninvasive techniques based on video monitoring, neuroimaging, and electrophysiological and neuropsychological tests; however, certain clinical settings call for invasive intracranial recordings such as stereoelectroencephalography (SEEG), aiming to accurately map the eloquent brain networks involved during a seizure. Most of the current presurgical evaluation procedures focus on semiautomatic techniques, where surgery diagnosis relies immensely on neurologists' experience and their time-consuming subjective interpretation of semiology or the manifestations of epilepsy and their correlation with the brain's electrical activity. Because surgery misdiagnosis reaches a rate of 30%, and more than one-third of all epilepsies are poorly understood, there is an evident keen interest in improving diagnostic precision using computer-based methodologies that in the past few years have shown near-human performance. Among them, deep learning has excelled in many biological and medical applications, but has advanced insufficiently in epilepsy evaluation and automated understanding of neural bases of semiology. In this paper, we systematically review the automatic applications in epilepsy for human motion analysis, brain electrical activity, and the anatomoelectroclinical correlation to attribute anatomical localization of the epileptogenic network to distinctive epilepsy patterns. Notably, recent advances in deep learning techniques will be investigated in the contexts of epilepsy to address the challenges exhibited by traditional machine learning techniques. Finally, we discuss and propose future research on epilepsy surgery assessment

  9. Effects of an electric field on the adsorption of water molecules on the Cd(0001) surface

    Science.gov (United States)

    Tu, Yu-Bing; Tao, Min-Long; Sun, Kai; Wang, Jun-Zhong

    2018-02-01

    The adsorption of water molecules on the Cd(0001) surface has been systematically investigated in the absence or presence of the electric field using first principles calculations based on density functional theory. It has been determined that the adsorption is enhanced by the electric field. From the geometries and energetics, we find that the water-cadmium interaction become stronger (weaker) under a negative (positive) field in the adsorbed monomer. Otherwise, the formation of the hydrogen bonds makes it difficult for molecules in the water clusters to response the electric field. Most importantly, the stability of the water bilayers depends on the strength of the negative electric field. Instead of the H-up bilayer, the H-down bilayer is more stable when the negative field is sufficiently strong. In this case, the dipole-field interaction is the dominant interaction in the change of stability. These results are helpful in the understanding of the fundamental processes at the water-electrode interfaces.

  10. High-Surface-Area Nitrogen-Doped Reduced Graphene Oxide for Electric Double-Layer Capacitors.

    Science.gov (United States)

    Youn, Hee-Chang; Bak, Seong-Min; Kim, Myeong-Seong; Jaye, Cherno; Fischer, Daniel A; Lee, Chang-Wook; Yang, Xiao-Qing; Roh, Kwang Chul; Kim, Kwang-Bum

    2015-06-08

    A two-step method consisting of solid-state microwave irradiation and heat treatment under NH3 gas was used to prepare nitrogen-doped reduced graphene oxide (N-RGO) with a high specific surface area (1007 m(2)  g(-1) ), high electrical conductivity (1532 S m(-1) ), and low oxygen content (1.5 wt %) for electrical double-layer capacitor applications. The specific capacitance of N-RGO was 291 F g(-1) at a current density of 1 A g(-1) , and a capacitance of 261 F g(-1) was retained at 50 A g(-1) , which indicated a very good rate capability. N-RGO also showed excellent cycling stability and preserved 96 % of the initial specific capacitance after 100 000 cycles. Near-edge X-ray absorption fine-structure spectroscopy results provided evidenced for the recovery of π conjugation in the carbon networks with the removal of oxygenated groups and revealed chemical bonding of the nitrogen atoms in N-RGO. The good electrochemical performance of N-RGO is attributed to its high surface area, high electrical conductivity, and low oxygen content. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Electrical conduction through surface superstructures measured by microscopic four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanabe, F.

    2003-01-01

    (STM) are used for measurements of four-point probe conductivity. The probe spacing can be changed from 500 nm to 1 mm. The other method involves monolithic micro-four-point probes, fabricated on silicon chips, whose probe spacing is fixed around several mum. These probes are installed in scanning......For in-situ measurements of the local electrical conductivity of well-defined crystal surfaces in ultra-high vacuum, we have developed two kinds of microscopic four-point probe methods. One involves a "four-tip STM prober," in which four independently driven tips of a scanning tunneling microscope......-electron-microscopy/electron-diffraction chambers, in which the structures of sample surfaces and probe positions are observed in situ. The probes can be positioned precisely on aimed areas on the sample with the aid of piezoactuators. By the use of these machines, the surface sensitivity in conductivity measurements has been greatly enhanced...

  12. The Drosophila surface glia transcriptome: evolutionary conserved blood-brain barrier processes.

    Directory of Open Access Journals (Sweden)

    Michael K DeSalvo

    2014-11-01

    Full Text Available AbstractCentral nervous system (CNS function is dependent on the stringent regulation of metabolites, drugs, cells, and pathogens exposed to the CNS space. Cellular blood-brain barrier (BBB structures are highly specific checkpoints governing entry and exit of all small molecules to and from the brain interstitial space, but the precise mechanisms that regulate the BBB are not well understood. In addition, the BBB has long been a challenging obstacle to the pharmacologic treatment of CNS diseases; thus model systems that can parse the functions of the BBB are highly desirable. In this study, we sought to define the transcriptome of the adult Drosophila melanogaster BBB by isolating the BBB surface glia with FACS and profiling their gene expression with microarrays. By comparing the transcriptome of these surface glia to that of all brain glia, brain neurons, and whole brains, we present a catalog of transcripts that are selectively enriched at the Drosophila BBB. We found that the fly surface glia show high expression of many ABC and SLC transporters, cell adhesion molecules, metabolic enzymes, signaling molecules, and components of xenobiotic metabolism pathways. Using gene sequence-based alignments, we compare the Drosophila and Murine BBB transcriptomes and discover many shared chemoprotective and small molecule control pathways, thus affirming the relevance of invertebrate models for studying evolutionary conserved BBB properties. The Drosophila BBB transcriptome is valuable to vertebrate and insect biologists alike as a resource for studying proteins underlying diffusion barrier development and maintenance, glial biology, and regulation of drug transport at tissue barriers.

  13. The Drosophila surface glia transcriptome: evolutionary conserved blood-brain barrier processes.

    Science.gov (United States)

    DeSalvo, Michael K; Hindle, Samantha J; Rusan, Zeid M; Orng, Souvinh; Eddison, Mark; Halliwill, Kyle; Bainton, Roland J

    2014-01-01

    Central nervous system (CNS) function is dependent on the stringent regulation of metabolites, drugs, cells, and pathogens exposed to the CNS space. Cellular blood-brain barrier (BBB) structures are highly specific checkpoints governing entry and exit of all small molecules to and from the brain interstitial space, but the precise mechanisms that regulate the BBB are not well understood. In addition, the BBB has long been a challenging obstacle to the pharmacologic treatment of CNS diseases; thus model systems that can parse the functions of the BBB are highly desirable. In this study, we sought to define the transcriptome of the adult Drosophila melanogaster BBB by isolating the BBB surface glia with fluorescence activated cell sorting (FACS) and profiling their gene expression with microarrays. By comparing the transcriptome of these surface glia to that of all brain glia, brain neurons, and whole brains, we present a catalog of transcripts that are selectively enriched at the Drosophila BBB. We found that the fly surface glia show high expression of many ATP-binding cassette (ABC) and solute carrier (SLC) transporters, cell adhesion molecules, metabolic enzymes, signaling molecules, and components of xenobiotic metabolism pathways. Using gene sequence-based alignments, we compare the Drosophila and Murine BBB transcriptomes and discover many shared chemoprotective and small molecule control pathways, thus affirming the relevance of invertebrate models for studying evolutionary conserved BBB properties. The Drosophila BBB transcriptome is valuable to vertebrate and insect biologists alike as a resource for studying proteins underlying diffusion barrier development and maintenance, glial biology, and regulation of drug transport at tissue barriers.

  14. Connectomic and surface-based morphometric correlates of acute mild traumatic brain injury

    Directory of Open Access Journals (Sweden)

    Patrizia eDall'Acqua

    2016-03-01

    Full Text Available Reduced integrity of white matter (WM pathways and subtle anomalies in gray matter (GM morphology have been hypothesized as mechanisms in mild traumatic brain injury (mTBI. However, findings on structural brain changes in early stages after mTBI are inconsistent and findings related to early symptoms severity are rare.Fifty-one patients were assessed with multimodal neuroimaging and clinical methods exclusively within 7 days following mTBI and compared to 53 controls. Whole-brain connectivity based on diffusion tensor imaging was subjected to network-based statistics, whereas cortical surface area, thickness, and volume based on T1-weighted MRI scans were investigated using surface-based morphometric analysis. Reduced connectivity strength within a subnetwork of 59 edges located predominantly in bilateral frontal lobes was significantly associated with higher levels of self-reported symptoms. In addition, cortical surface area decreases were associated with stronger complaints in five clusters located in bilateral frontal and postcentral cortices, and in the right inferior temporal region. Alterations in WM and GM were localized in similar brain regions and moderately-to-strongly related to each other. Furthermore, the reduction of cortical surface area in the frontal regions was correlated with poorer attentive-executive performance in the mTBI group. Finally, group differences were detected in both the WM and GM, especially when focusing on a subgroup of patients with greater complaints, indicating the importance of classifying mTBI patients according to severity of symptoms. This study provides evidence that mTBI affects not only the integrity of WM networks by means of axonal damage but also the morphology of the cortex during the initial post-injury period. These anomalies might be greater in the acute period than previously believed and the involvement of frontal brain regions was consistently pronounced in both findings. The dysconnected

  15. Electromagnetic Scattering of Electrically Large Ship above Sea Surface with SBR-SDFM Method

    Directory of Open Access Journals (Sweden)

    Lixin Guo

    2017-01-01

    Full Text Available Hybrid scheme combining shooting and bouncing ray with semi-deterministic facet model is proposed to analyze composite scattering from ship-ocean scene in this study. This model can deal with complex electromagnetic interaction between ship and sea surface. Thus, scattering properties of composite ship-ocean scenes with influence of various parameters (such as incident angle and wind speed can be studied and analyzed efficiently. Studying such properties is of significance for target detection and high-resolution radar imaging in sea environments. Accuracy and performance of this method are validated and evaluated by comparing with multilevel fast multipole method of FEKO for electrically small objects. All simulation results indicate that the proposed method is suitable for providing preliminary radar cross section prediction of electrically large composite model.

  16. A simple tool for estimating city-wide annual electrical energy savings from cooler surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Pomerantz, Melvin; Rosado, Pablo J.; Levinson, Ronnen

    2015-12-01

    We present a simple method to estimate the maximum possible electrical energy saving that might be achieved by increasing the albedo of surfaces in a large city. We restrict this to the “indirect effect”, the cooling of outside air that lessens the demand for air conditioning (AC). Given the power demand of the electric utilities and data about the city, we can use a single linear equation to estimate the maximum savings. For example, the result for an albedo change of 0.2 of pavements in a typical warm city in California, such as Sacramento, is that the saving is less than about 2 kWh per m2 per year. This may help decision makers choose which heat island mitigation techniques are economical from an energy-saving perspective.

  17. Prediction of material removal rate and surface roughness for wire electrical discharge machining of nickel using response surface methodology

    Directory of Open Access Journals (Sweden)

    Thangam Chinnadurai

    2016-12-01

    Full Text Available This study focuses on investigating the effects of process parameters, namely, Peak current (Ip, Pulse on time (Ton, Pulse off time (Toff, Water pressure (Wp, Wire feed rate (Wf, Wire tension (Wt, Servo voltage (Sv and Servo feed setting (Sfs, on the Material Removal Rate (MRR and Surface Roughness (SR for Wire electrical discharge machining (Wire-EDM of nickel using Taguchi method. Response Surface Methodology (RSM is adopted to evolve mathematical relationships between the wire cutting process parameters and the output variables of the weld joint to determine the welding input parameters that lead to the desired optimal wire cutting quality. Besides, using response surface plots, the interaction effects of process parameters on the responses are analyzed and discussed. The statistical software Mini-tab is used to establish the design and to obtain the regression equations. The developed mathematical models are tested by analysis-of-variance (ANOVA method to check their appropriateness and suitability. Finally, a comparison is made between measured and calculated results, which are in good agreement. This indicates that the developed models can predict the responses accurately and precisely within the limits of cutting parameter being used.

  18. All-diamond functional surface micro-electrode arrays for brain-slice neural analysis

    OpenAIRE

    Vahidpour, Farnoosh; Curley, Lowry; Biró, István; McDonald, Matthew; Croux, Dieter; POBEDINSKAS, Paulius; Haenen, Ken; Giugliano, Michele; Zivcova, Zuzana Vlckova; Kavan, Ladislav; Nesladek, Milos

    2017-01-01

    Abstract: Diamond-based microelectrode arrays were fabricated by using nanocrystalline diamond as an insulating layer and conductive boron-doped in order to used them for analysis of brain cortical slices. MEA surface is solely composed of diamond, exposed to the cells. The impedance measurements showed negligible cross-talk between neighbouring diamond microelectrodes. Local field potentials related to neural signals were then successfully recorded from pharmacologically disinhibited rat cor...

  19. Electrically controllable twisted-coiled artificial muscle actuators using surface-modified polyester fibers

    Science.gov (United States)

    Park, Jungwoo; Yoo, Ji Wang; Seo, Hee Won; Lee, Youngkwan; Suhr, Jonghwan; Moon, Hyungpil; Koo, Ja Choon; Ryeol Choi, Hyouk; Hunt, Robert; Kim, Kwang Jin; Kim, Soo Hyun; Nam, Jae-Do

    2017-03-01

    As a new class of thermally activated actuators based on polymeric fibers, we investigated polyethylene terephthalate (PET) yarns for the development of a twisted-coiled polymer fiber actuator (TCA). The PET yarn TCA exhibited the maximum linear actuation up to 8.9% by external heating at above the glass transition temperature, 160 °C-180 °C. The payload of the actuator was successfully correlated with the preload and training-load conditions by an empirical equation. Furthermore, the PET-based TCA was electrically driven by Joule heating after the PET surface was metallization with silver. For the fast and precise control of PET yarn TCA, electroless silver plating was conducted to form electrical conductive layers on the PET fiber surface. The silver plated PET-based TCA was tested by Joule heating and the tensile actuation was increased up to 12.1% (6 V) due to the enhanced surface hardness and slippage of PET fibers. Overall, silver plating of the polymeric yarn provided a fast actuation speed and enhanced actuation performance of the TCA actuator by Joule heating, providing a great potential for being used in artificial muscle for biomimetic machines including robots, industrial actuators and powered exoskeletons.

  20. Brain-controlled functional electrical stimulation therapy for gait rehabilitation after stroke: a safety study.

    Science.gov (United States)

    McCrimmon, Colin M; King, Christine E; Wang, Po T; Cramer, Steven C; Nenadic, Zoran; Do, An H

    2015-07-11

    Many stroke survivors have significant long-term gait impairment, often involving foot drop. Current physiotherapies provide limited recovery. Orthoses substitute for ankle strength, but they provide no lasting therapeutic effect. Brain-computer interface (BCI)-controlled functional electrical stimulation (FES) is a novel rehabilitative approach that may generate permanent neurological improvements. This study explores the safety and feasibility of a foot-drop-targeted BCI-FES physiotherapy in chronic stroke survivors. Subjects (n = 9) operated an electroencephalogram-based BCI-FES system for foot dorsiflexion in 12 one-hour sessions over four weeks. Gait speed, dorsiflexion active range of motion (AROM), six-minute walk distance (6MWD), and Fugl-Meyer leg motor (FM-LM) scores were assessed before, during, and after therapy. The primary safety outcome measure was the proportion of subjects that deteriorated in gait speed by ≥0.16 m/s at one week or four weeks post-therapy. The secondary outcome measures were the proportion of subjects that experienced a clinically relevant decrease in dorsiflexion AROM (≥2.5°), 6MWD (≥20 %), and FM-LM score (≥10 %) at either post-therapy assessment. No subjects (0/9) experienced a clinically significant deterioration in gait speed, dorsiflexion AROM, 6MWT distance, or FM-LM score at either post-therapy assessment. Five subjects demonstrated a detectable increase (≥0.06 m/s) in gait speed, three subjects demonstrated a detectable increase (≥2.5°) in dorsiflexion AROM, five subjects demonstrated a detectable increase (≥10 %) in 6MWD, and three subjects demonstrated a detectable increase (≥10 %) in FM-LM. Five of the six subjects that exhibited a detectable increase in either post-therapy gait speed or 6MWD also exhibited significant (p stroke gait function in future studies, it could provide a new gait rehabilitation option for severely impaired patients. Formal clinical trials are warranted.

  1. A Comprehensive Model of Electric-Field-Enhanced Jumping-Droplet Condensation on Superhydrophobic Surfaces.

    Science.gov (United States)

    Birbarah, Patrick; Li, Zhaoer; Pauls, Alexander; Miljkovic, Nenad

    2015-07-21

    Superhydrophobic micro/nanostructured surfaces for dropwise condensation have recently received significant attention due to their potential to enhance heat transfer performance by shedding positively charged water droplets via coalescence-induced droplet jumping at length scales below the capillary length and allowing the use of external electric fields to enhance droplet removal and heat transfer, in what has been termed electric-field-enhanced (EFE) jumping-droplet condensation. However, achieving optimal EFE conditions for enhanced heat transfer requires capturing the details of transport processes that is currently lacking. While a comprehensive model has been developed for condensation on micro/nanostructured surfaces, it cannot be applied for EFE condensation due to the dynamic droplet-vapor-electric field interactions. In this work, we developed a comprehensive physical model for EFE condensation on superhydrophobic surfaces by incorporating individual droplet motion, electrode geometry, jumping frequency, field strength, and condensate vapor-flow dynamics. As a first step toward our model, we simulated jumping droplet motion with no external electric field and validated our theoretical droplet trajectories to experimentally obtained trajectories, showing excellent temporal and spatial agreement. We then incorporated the external electric field into our model and considered the effects of jumping droplet size, electrode size and geometry, condensation heat flux, and droplet jumping direction. Our model suggests that smaller jumping droplet sizes and condensation heat fluxes require less work input to be removed by the external fields. Furthermore, the results suggest that EFE electrodes can be optimized such that the work input is minimized depending on the condensation heat flux. To analyze overall efficiency, we defined an incremental coefficient of performance and showed that it is very high (∼10(6)) for EFE condensation. We finally proposed mechanisms

  2. Effects of various surfactants on the dispersion stability and electrical conductivity of surface modified graphene

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, Md. Elias [WCU Program, Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Kuila, Tapas [Surface Engineering and Tribology, CSIR – Central Mechanical Engineering Research Institute, Durgapur 721 302 (India); Nayak, Ganesh Chandra [Department of Applied Chemistry, ISM Dhanbad, Dhanbad 826 004, Jharkhand (India); Kim, Nam Hoon [Department of Hydrogen and Fuel Cell Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Ku, Bon-Cheol [Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Dunsan-ri, Bongdong-eup, Wanju-gun, Jeollabuk-do 864-9 (Korea, Republic of); Lee, Joong Hee, E-mail: jhl@chonbuk.ac.kr [WCU Program, Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Department of Hydrogen and Fuel Cell Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)

    2013-06-15

    Highlights: ► Water dispersible graphene has been prepared using ionic and non-ionic surfactants. ► XPS and FTIR spectra analysis confirm surface modification and reduction of GO. ► The highest water dispersibility is observed in the graphene modified with of SDBS. ► The best properties of modified graphene is achieved with GO/surfactant ratio of two. -- Abstract: Ionic and non-ionic surfactant functionalized, water dispersible graphene were prepared to investigate the effects on the dispersion stability and electrical conductivity of graphene. In this study, sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate and 4-(1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol (Triton X-100) were used as ionic and non-ionic surfactants. The effects of surfactant concentrations on the dispersibility and electrical conductivity of the surface modified graphene were investigated. The dispersion stability of SDBS functionalized graphene (SDBS-G) was found to be best in water at 1.5 mg ml{sup −1}. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis indicate that the presence of surfactants does not prevent the reduction of graphene oxide (GO). These measurements also demonstrated that the surfactants were present on the surface of graphene, resulting in the formation of functionalized graphene. The thickness of different functionalized graphene was measured by Atomic force microscopy and varied significantly with different surfactants. The thermal properties of the functionalized graphene were also found to be dependent on the nature of the surfactants. The electrical conductivity of SDBS-G (108 S m{sup −1}) was comparatively higher than SDS and Triton X-100 functionalized graphene.

  3. Electrical resistivity imaging of the near-surface structure of the Solfatara volcano

    Science.gov (United States)

    Giulia Di Giuseppe, Maria; Troiano, Antonio; Fedele, Alessandro; Patella, Domenico; Troise, Claudia; De Natale, Giuseppe

    2014-05-01

    We describe the results from an high-resolution study of the near-surface electrical resistivity structures carried out in the Solfatara area, located in the central part of the Campi Flegrei (CF) composite caldera, west of Naples, Italy. This area represents the most active zone within the CF area. It has been the site of an intense hydrothermal activity since Greek times, and currently exhibits the most impressive degassing manifestations. A direct relationship has always been observed between the increase of hydrothermal activity and ground uplift in the caldera. For this reason, dynamic of the Solfatara zone is considered a direct indicator of the volcanism taking place in the CF caldera. Since 2005 a new gradual increase of the hydrothermal activity and ground uplift has been observed. A steep growth of these effects has been recorded from 2012, accompanied by seismic events with hypocentres mostly concentrated below the area of Pozzuoli at depths ranging between 1 and 3 km, and highest magnitude of 1.8. It is thought that a further increase of the activity might lead to more critical conditions, including the occurrence of phreatic explosions. The detailed recovery of the structure and features of the shallow aquifers, mainly in the largest fumarole areas, is a crucial step for interpreting the ground movements and to improve our capability to forecast future pre-eruptive scenarios. Electrical resistivity results particularly sensitive to the presence of aqueous fluids and partial melts. By electrical imaging the volume of subsurface fluids can be constrained and the rheology of the subsoil can be reconstructed. To this aim, we have carried out eight profiles for electrical resistivity imaging, crossing the fumaroles field, deducting an electric model of the structural setting of the hydrothermal system in the first 100 m depth. Six of the profiles were 250 m long, with an electrodic distance of 5 m. Two longer profiles, up to 750 m, characterised by an

  4. Decoherence and electric field noise analysis of nitrogen vacancy center diamonds due to the surface charge fluctuations and lattice strain

    Science.gov (United States)

    Santamore, Deborah

    2017-04-01

    We theoretically investigate the decoherence mechanisms due to the electric field noise in nitrogen vacancy (NV) center diamonds. The noise is caused by both the surface charge fluctuations and strain due to surface contaminants and bulk impurities. The system is modeled with nitrogen impurities in diamond and hydrogen surface terminations with water. We obtain the equations of motion, calculate the electric field fluctuations, and analyze noise. We find that the surface effect is greater than lattice distortion by the bulk impurity substitution. We also discuss how to minimize the noise. Finally, we examine lattice distortion and stability of NV centers under high pressure. NSF: DMR-1505641.

  5. Mapping effective connectivity in the human brain with concurrent intracranial electrical stimulation and BOLD-fMRI.

    Science.gov (United States)

    Oya, Hiroyuki; Howard, Matthew A; Magnotta, Vincent A; Kruger, Anton; Griffiths, Timothy D; Lemieux, Louis; Carmichael, David W; Petkov, Christopher I; Kawasaki, Hiroto; Kovach, Christopher K; Sutterer, Matthew J; Adolphs, Ralph

    2017-02-01

    Understanding brain function requires knowledge of how one brain region causally influences another. This information is difficult to obtain directly in the human brain, and is instead typically inferred from resting-state fMRI. Here, we demonstrate the safety and scientific promise of a novel and complementary approach: concurrent electrical stimulation and fMRI (es-fMRI) at 3T in awake neurosurgical patients with implanted depth electrodes. We document the results of safety testing, actual experimental setup, and stimulation parameters, that safely and reliably evoke activation in distal structures through stimulation of amygdala, cingulate, or prefrontal cortex. We compare connectivity inferred from the evoked patterns of activation with that estimated from standard resting-state fMRI in the same patients: while connectivity patterns obtained with each approach are correlated, each method produces unique results. Response patterns were stable over the course of 11min of es-fMRI runs. COMPARISON WITH EXISTING METHOD: es-fMRI in awake humans yields unique information about effective connectivity, complementing resting-state fMRI. Although our stimulations were below the level of inducing any apparent behavioral or perceptual effects, a next step would be to use es-fMRI to modulate task performances. This would reveal the acute network-level changes induced by the stimulation that mediate the behavioral and cognitive effects seen with brain stimulation. es-fMRI provides a novel and safe approach for mapping effective connectivity in the human brain in a clinical setting, and will inform treatments for psychiatric and neurodegenerative disorders that use deep brain stimulation. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. The Surface Layer States in Metallic Materials Subjected to Dry Sliding and Electric Current

    Science.gov (United States)

    Fadin, V. V.; Aleutdinova, M. I.; Potekaev, A. I.; Kulikova, O. A.

    2017-09-01

    The structure and properties of surface layers of metallic materials undergoing structural-phase changes as a result of their contact interactions in the form of dry sliding friction on steel in combination with exposure to electric currents are investigated. This impact results in the formation of a composite surface layer whose structural constituents are the particles of FeO oxide, FCC- and BCC-iron, and quasi-amorphous initial material. Sliding of materials at the contact current density higher than 150 A/cm2 gives rise to the formation of local, low-stability structures which, as a result of phase transformations, are observed as sectors of quasiliquid plastic flow on the sliding surface. It is shown that the average temperatures of the Cu - steel material contact do not exceed 300°C, i.e., none of the surface-layer constituents reaches its melting temperature. It is shown that quasi-liquid plastic flow favors stress relaxation and maintains the strength of the surface layer, which ensures its lower wear.

  7. Regional brain differences in cortical thickness, surface area and subcortical volume in individuals with Williams syndrome.

    Directory of Open Access Journals (Sweden)

    Shashwath A Meda

    Full Text Available Williams syndrome (WS is a rare genetic neurodevelopmental disorder characterized by increased non-social anxiety, sensitivity to sounds and hypersociability. Previous studies have reported contradictory findings with regard to regional brain variation in WS, relying on only one type of morphological measure (usually volume in each study. The present study aims to contribute to this body of literature and perhaps elucidate some of these discrepancies by examining concurrent measures of cortical thickness, surface area and subcortical volume between WS subjects and typically-developing (TD controls. High resolution MRI scans were obtained on 31 WS subjects and 50 typically developing control subjects. We derived quantitative regional estimates of cortical thickness, cortical surface area, and subcortical volume using FreeSurfer software. We evaluated between-group ROI differences while controlling for total intracranial volume. In post-hoc exploratory analyses within the WS group, we tested for correlations between regional brain variation and Beck Anxiety Inventory scores. Consistent with our hypothesis, we detected complex patterns of between-group cortical variation, which included lower surface area in combination with greater thickness in the following cortical regions: post central gyrus, cuneus, lateral orbitofrontal cortex and lingual gyrus. Additional cortical regions showed between-group differences in one (but not both morphological measures. Subcortical volume was lower in the basal ganglia and the hippocampus in WS versus TD controls. Exploratory correlations revealed that anxiety scores were negatively correlated with gray matter surface area in insula, OFC, rostral middle frontal, superior temporal and lingual gyrus. Our results were consistent with previous reports showing structural alterations in regions supporting the socio-affective and visuospatial impairments in WS. However, we also were able to effectively capture novel and

  8. In-vivo measurements of human brain tissue conductivity using focal electrical current injection through intracerebral multicontact electrodes.

    Science.gov (United States)

    Koessler, Laurent; Colnat-Coulbois, Sophie; Cecchin, Thierry; Hofmanis, Janis; Dmochowski, Jacek P; Norcia, Anthony M; Maillard, Louis G

    2017-02-01

    In-vivo measurements of human brain tissue conductivity at body temperature were conducted using focal electrical currents injected through intracerebral multicontact electrodes. A total of 1,421 measurements in 15 epileptic patients (age: 28 ± 10) using a radiofrequency generator (50 kHz current injection) were analyzed. Each contact pair was classified as being from healthy (gray matter, n = 696; white matter, n = 530) or pathological (epileptogenic zone, n = 195) tissue using neuroimaging analysis of the local tissue environment and intracerebral EEG recordings. Brain tissue conductivities were obtained using numerical simulations based on conductivity estimates that accounted for the current flow in the local brain volume around the contact pairs (a cube with a side length of 13 mm). Conductivity values were 0.26 S/m for gray matter and 0.17 S/m for white matter. Healthy gray and white matter had statistically different median impedances (P Brain Mapp 38:974-986, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  9. A Permutation Disalignment Index-Based Complex Network Approach to Evaluate Longitudinal Changes in Brain-Electrical Connectivity

    Directory of Open Access Journals (Sweden)

    Nadia Mammone

    2017-10-01

    Full Text Available In the study of neurological disorders, Electroencephalographic (EEG signal processing can provide valuable information because abnormalities in the interaction between neuron circuits may reflect on macroscopic abnormalities in the electrical potentials that can be detected on the scalp. A Mild Cognitive Impairment (MCI condition, when caused by a disorder degenerating into dementia, affects the brain connectivity. Motivated by the promising results achieved through the recently developed descriptor of coupling strength between EEG signals, the Permutation Disalignment Index (PDI, the present paper introduces a novel PDI-based complex network model to evaluate the longitudinal variations in brain-electrical connectivity. A group of 33 amnestic MCI subjects was enrolled and followed-up with over four months. The results were compared to MoCA (Montreal Cognitive Assessment tests, which scores the cognitive abilities of the patient. A significant negative correlation could be observed between MoCA variation and the characteristic path length ( λ variation ( r = - 0 . 56 , p = 0 . 0006 , whereas a significant positive correlation could be observed between MoCA variation and the variation of clustering coefficient (CC, r = 0 . 58 , p = 0 . 0004 , global efficiency (GE, r = 0 . 57 , p = 0 . 0005 and small worldness (SW, r = 0 . 57 , p = 0 . 0005 . Cognitive decline thus seems to reflect an underlying cortical “disconnection” phenomenon: worsened subjects indeed showed an increased λ and decreased CC, GE and SW. The PDI-based connectivity model, proposed in the present work, could be a novel tool for the objective quantification of longitudinal brain-electrical connectivity changes in MCI subjects.

  10. A Calderón multiplicative preconditioner for coupled surface-volume electric field integral equations

    KAUST Repository

    Bagci, Hakan

    2010-08-01

    A well-conditioned coupled set of surface (S) and volume (V) electric field integral equations (S-EFIE and V-EFIE) for analyzing wave interactions with densely discretized composite structures is presented. Whereas the V-EFIE operator is well-posed even when applied to densely discretized volumes, a classically formulated S-EFIE operator is ill-posed when applied to densely discretized surfaces. This renders the discretized coupled S-EFIE and V-EFIE system ill-conditioned, and its iterative solution inefficient or even impossible. The proposed scheme regularizes the coupled set of S-EFIE and V-EFIE using a Calderón multiplicative preconditioner (CMP)-based technique. The resulting scheme enables the efficient analysis of electromagnetic interactions with composite structures containing fine/subwavelength geometric features. Numerical examples demonstrate the efficiency of the proposed scheme. © 2006 IEEE.

  11. Electric control of magnetism in low-dimensional magnets on ferroelectric surfaces

    Directory of Open Access Journals (Sweden)

    Dorj Odkhuu

    2017-05-01

    Full Text Available Employing first-principles electronic structure calculations, we have studied the electric field controls of magnetism and magnetic anisotropy energy (MAE of the Fe adatoms on ferroelectric BaTiO3 and PbTiO3 surfaces. Remarkably, those effects exhibit dependence of the level of coverage as well as adsorption site of Fe atoms. While the magnitude of MAE is shown tunable by ferroelectric polarization in the full coverage of Fe monolayer, the direction of magnetization undergoes a transition from perpendicular to in-plane for the half or lower coverages. This magnetization reorientation is mainly ascribed to the site-dependent Fe d–O p hybridization, as a consequence of the formation of FeTiO2 layer at the surface.

  12. Modelling the Influence of Ground Surface Relief on Electric Sounding Curves Using the Integral Equations Method

    Directory of Open Access Journals (Sweden)

    Balgaisha Mukanova

    2017-01-01

    Full Text Available The problem of electrical sounding of a medium with ground surface relief is modelled using the integral equations method. This numerical method is based on the triangulation of the computational domain, which is adapted to the shape of the relief and the measuring line. The numerical algorithm is tested by comparing the results with the known solution for horizontally layered media with two layers. Calculations are also performed to verify the fulfilment of the “reciprocity principle” for the 4-electrode installations in our numerical model. Simulations are then performed for a two-layered medium with a surface relief. The quantitative influences of the relief, the resistivity ratios of the contacting media, and the depth of the second layer on the apparent resistivity curves are established.

  13. A laboratory investigation of stain removal from enamel surface: comparative efficacy of three electric toothbrushes.

    Science.gov (United States)

    Schemehorn, B R; Henry, G M

    1996-07-01

    To evaluate in a controlled laboratory investigation the efficacy of three electric toothbrushes with respect to removal of extrinsic dental stain from labial enamel surfaces of bovine permanent central incisors. Enamel specimens were treated to produce a uniformly stained pellicle film. Staining was assessed photometrically, before and after brushing 16 specimens per group for 4.5 minutes with either the Braun Oral-B Plaque Remover (D7), the Braun Oral-B Ultra Plaque Remover (D9) or a high frequency electric toothbrush. A manual brush with the ADA reference abrasive was used as a positive control, and this was compared with the three electric toothbrushes, using a dentifrice slurry prepared from Crest toothpaste. Tension on the enamel specimens was set at 150 g, except for the high frequency toothbrush which was set at the manufacturer's recommended tension of 50 g. Stain removal was expressed as a cleaning ratio (CR), where larger values represented greater removal of stained pellicle. Compared with the ADA control (CR = 100), the D9 was the most effective (CR = 98) removing significantly more stain (P toothbrush was found to be the least effective (CR = 48), removing significantly less stain than any of the other toothbrushes (P < 0.05).

  14. Assessment of Electrically Evoked Auditory Brain Stem Response of 30 Implanted Patients With Nucleus Multichannel Cochlear Implant

    Directory of Open Access Journals (Sweden)

    Dr. Soqrat Faghihzadeh

    2001-05-01

    Full Text Available Methods and Materials: Investigation of electrically evoked auditory brain stem response (EABR is a new issue, especially in implanted patients. Experiments were performed in C.I Center of Iranian Institute for Science and research expansion,1996 on 30 implanted patients with 22 spectra and MSP cochlear implant system and 30 normal subjects with the range of 3-33 years. Findings: I- EABR was obtained in the implanted patients. 2- Absolute latency of EABR waves is 1-1.5 ms shorter than ABR waves ‘P<0.05. 3-Absolute latency of wave V decreases as a function of electric stimulus magnitude (P<0.05. 4- No significant difference was observed in IPL Ill-V between ABR and EABR.

  15. Surface Electrical Potentials of Root Cell Plasma Membranes: Implications for Ion Interactions, Rhizotoxicity, and Uptake

    Directory of Open Access Journals (Sweden)

    Yi-Min Wang

    2014-12-01

    Full Text Available Many crop plants are exposed to heavy metals and other metals that may intoxicate the crop plants themselves or consumers of the plants. The rhizotoxicity of heavy metals is influenced strongly by the root cell plasma membrane (PM surface’s electrical potential (ψ0. The usually negative ψ0 is created by negatively charged constituents of the PM. Cations in the rooting medium are attracted to the PM surface and anions are repelled. Addition of ameliorating cations (e.g., Ca2+ and Mg2+ to the rooting medium reduces the effectiveness of cationic toxicants (e.g., Cu2+ and Pb2+ and increases the effectiveness of anionic toxicants (e.g., SeO42− and H2AsO4−. Root growth responses to ions are better correlated with ion activities at PM surfaces ({IZ}0 than with activities in the bulk-phase medium ({IZ}b (IZ denotes an ion with charge Z. Therefore, electrostatic effects play a role in heavy metal toxicity that may exceed the role of site-specific competition between toxicants and ameliorants. Furthermore, ψ0 controls the transport of ions across the PM by influencing both {IZ}0 and the electrical potential difference across the PM from the outer surface to the inner surface (Em,surf. Em,surf is a component of the driving force for ion fluxes across the PM and controls ion-channel voltage gating. Incorporation of {IZ}0 and Em,surf into quantitative models for root metal toxicity and uptake improves risk assessments of toxic metals in the environment. These risk assessments will improve further with future research on the application of electrostatic theory to heavy metal phytotoxicity in natural soils and aquatic environments.

  16. Near-Surface Fault Structures of the Seulimuem Segment Based on Electrical Resistivity Model

    Science.gov (United States)

    Ismail, Nazli; Yanis, Muhammad; Idris, Syafrizal; Abdullah, Faisal; Hanafiah, Bukhari

    2017-05-01

    The Great Sumatran Fault (GSF) system is arc-parallel strike-slip fault system along the volcanic front related to the oblique subduction of the oceanic Indo-Australian plate. Large earthquakes along the southern GSF since 1892 have been reported, but the Seulimuem segment at the northernmost Sumatran has not produced large earthquakes in the past 100 years. The 200-km-long segment is considered to be a seismic gap. Detailed geological study of the fault and thus its surface trace locations, late Quaternary slip rate, and rupture history are urgently needed for earthquake disaster mitigation in the future. However, finding a suitable area for paleoseismic trenching is an obstacle when the fault traces are not clearly shown on the surface. We have conducted geoelectrical measurement in Lamtamot area of Aceh Besar District in order to locate the fault line for paleoseismic excavation. Apparent resistivity data were collected along 40 m profile parallel to the planned trenching site. The 2D electrical resistivity model provided evidence of some resistivity anomalies by high lateral contrast. This anomaly almost coincides with the topographic scarp which is modified by agriculture on the surface at the northern part of Lamtamot. The steep dipping electrical contrast may correspond to a fault. However, the model does not resolve well evidences from minor faults that can be related to the presence of surface ruptures. A near fault paleoseismic investigation requires trenching across the fault in order to detect and analyze the geological record of the past large earthquakes along the Seulimuem segment.

  17. Laser surface modification of electrically conductive fabrics: Material performance improvement and design effects

    Science.gov (United States)

    Tunakova, Veronika; Hrubosova, Zuzana; Tunak, Maros; Kasparova, Marie; Mullerova, Jana

    2018-01-01

    Development of lightweight flexible materials for electromagnetic interference shielding has obtained increased attention in recent years particularly for clothing, textiles in-house use and technical applications especially in areas of aircraft, aerospace, automobiles and flexible electronics such as portable electronics and wearable devices. There are many references in the literature concerning development and investigation of electromagnetic shielding lightweight flexible materials especially textile based with different electrically conductive additives. However, only little attention is paid to designing and enhancing the properties of these special fabrics by textile finishing processes. Laser technology applied as a physical treatment method is becoming very popular and can be used in different applications to make improvement and even overcome drawbacks of some of the traditional processes. The main purpose of this study is firstly to analyze the possibilities of transferring design onto the surface of electrically conductive fabrics by laser beam and secondly to study of effect of surface modification degree on performance of conductive fabric including electromagnetic shielding ability and mechanical properties. Woven fabric made of yarns containing 10% of extremely thin stainless steel fiber was used as a conductive substrate.

  18. Measurement of the electric potential at the surface of nonuniformly charged polypropylene nonwoven media

    Science.gov (United States)

    Fatihou, Ali; Zouzou, Noureddine; Iuga, Gheorghe; Dascalescu, Lucian

    2015-10-01

    The aim of this paper is to establish the conditions in which the vibrating capacitive probe of an electrostatic voltmeter could be employed for mapping the electric potential at the surface of non-uniformly charged insulating bodies. A first set of experiments are performed on polypropylene non-woven media (thickness: 0.4 mm; fiber diameter: 20 μm) in ambient air. In a second set of experiments the non-uniformity of charge is simulated using five copper strips (width: 2 mm or 3 mm; distance between strips: 2 mm). All the strips are connected to a high-voltage supply (Vs = 1000 V). The sample carrier is attached to a computer-controlled positioning system that transfers it under the capacitive probe (TREK, model 3451) of an electrostatic voltmeter (TREK, model 1341B). The measurements are performed at various relative speeds Vb between the sample and the probe, and for various sample rates Fe. A first set of experiments point out that the electric potential displayed by the electrostatic voltmeter depends on the spacing h between the sample and the probe. The diameter D of the spot “seen” by the probe is approximately D ≈ 8h/3. From the second set of experiments performed with the test plate, it can be concluded that the surface potential can be measured with the media in motion, but the accuracy is limited by the spatial resolution defined by k = Vb/Fe.

  19. Possible Time-Dependent Effect of Ions and Hydrophilic Surfaces on the Electrical Conductivity of Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Marija Zupancic

    2012-03-01

    Full Text Available The purpose of this work was to determine the influence of mechanical and electrical treatment on the electrical conductivity of aqueous solutions. Solutions were treated mechanically by iteration of two steps: 1:100 dilution and vigorous shaking. These two processes were repeated until extremely dilute solutions were obtained. For electrical treatment the solutions were exposed to strong electrical impulses. Effects of mechanical (as well as electrical treatment could not be demonstrated using electrical conductivity measurements. However, significantly higher conductivity than those of the freshly prepared chemically analogous solutions was found in all aged solutions except for those samples stored frozen. The results surprisingly resemble a previously observed weak gel-like behavior in water stored in closed flasks. We suggest that ions and contact with hydrophilic glass surfaces could be the determinative conditions for the occurrence of this phenomenon.

  20. Possible time-dependent effect of ions and hydrophilic surfaces on the electrical conductivity of aqueous solutions.

    Science.gov (United States)

    Verdel, Nada; Jerman, Igor; Krasovec, Rok; Bukovec, Peter; Zupancic, Marija

    2012-01-01

    The purpose of this work was to determine the influence of mechanical and electrical treatment on the electrical conductivity of aqueous solutions. Solutions were treated mechanically by iteration of two steps: 1:100 dilution and vigorous shaking. These two processes were repeated until extremely dilute solutions were obtained. For electrical treatment the solutions were exposed to strong electrical impulses. Effects of mechanical (as well as electrical) treatment could not be demonstrated using electrical conductivity measurements. However, significantly higher conductivity than those of the freshly prepared chemically analogous solutions was found in all aged solutions except for those samples stored frozen. The results surprisingly resemble a previously observed weak gel-like behavior in water stored in closed flasks. We suggest that ions and contact with hydrophilic glass surfaces could be the determinative conditions for the occurrence of this phenomenon.

  1. Possible Time-Dependent Effect of Ions and Hydrophilic Surfaces on the Electrical Conductivity of Aqueous Solutions

    Science.gov (United States)

    Verdel, Nada; Jerman, Igor; Krasovec, Rok; Bukovec, Peter; Zupancic, Marija

    2012-01-01

    The purpose of this work was to determine the influence of mechanical and electrical treatment on the electrical conductivity of aqueous solutions. Solutions were treated mechanically by iteration of two steps: 1:100 dilution and vigorous shaking. These two processes were repeated until extremely dilute solutions were obtained. For electrical treatment the solutions were exposed to strong electrical impulses. Effects of mechanical (as well as electrical) treatment could not be demonstrated using electrical conductivity measurements. However, significantly higher conductivity than those of the freshly prepared chemically analogous solutions was found in all aged solutions except for those samples stored frozen. The results surprisingly resemble a previously observed weak gel-like behavior in water stored in closed flasks. We suggest that ions and contact with hydrophilic glass surfaces could be the determinative conditions for the occurrence of this phenomenon. PMID:22605965

  2. Critical surface roughness for wall bounded flow of viscous fluids in an electric submersible pump

    Science.gov (United States)

    Deshmukh, Dhairyasheel; Siddique, Md Hamid; Kenyery, Frank; Samad, Abdus

    2017-11-01

    Surface roughness plays a vital role in the performance of an electric submersible pump (ESP). A 3-D numerical analysis has been carried out to find the roughness effect on ESP. The performance of pump for steady wall bounded turbulent flows is evaluated at different roughness values and compared with smooth surface considering a non-dimensional roughness factor K. The k- ω SST turbulence model with fine mesh at near wall region captures the rough wall effects accurately. Computational results are validated with experimental results of water (1 cP), at a design speed (3000 RPM). Maximum head is observed for a hydraulically smooth surface (K=0). When roughness factor is increased, the head decreases till critical roughness factor (K=0.1) due to frictional loss. Further increase in roughness factor (K>0.1) increases the head due to near wall turbulence. The performance of ESP is analyzed for turbulent kinetic energy and eddy viscosity at different roughness values. The wall disturbance over the rough surface affects the pressure distribution and velocity field. The roughness effect is predominant for high viscosity oil (43cP) as compared to water. Moreover, the study at off-design conditions showed that Reynolds number influences the overall roughness effect.

  3. Surface element segregation and electrical conductivity of lithium layered transition-metal oxide cathode materials

    Science.gov (United States)

    Li, Guohua; Li, Qi; Li, Liping; Fan, Jianming; Ge, Qingqin; Xie, Dongjiu; Zheng, Jing; Li, Guangshe

    2018-01-01

    Surface element segregation and electric conductivity are critical in determining lithium storage ability of given cathode materials, which are poorly understood and not correlated with the structure and overall performance. Here, layered lithium transition-metal oxides, one of the state-of-the-art cathode materials for lithium ion batteries are chosen to study. A serial of LiNixCo1-2xMnxO2 samples were prepared via a solid state reaction and subsequently characterized by XRD in conjunction with structural refinement, XPS depth profiling, and AC impedance spectroscopy. Slightly different expansion rates are observed for lattice parameters (a and c/3) with varying of Ni content, which is attributed to the increase of average metal-ion radius and an increase of eg electron that enhances the columbic repulsion between transition metal and oxygen atoms. XPS depth profiling results show that surface composition is significantly deviated from bulk, in which Ni and Mn atoms tend to enrich in the surface region, while Co element is relatively deficient. Further, surface element segregation is alleviated by the increase of Ni/Mn content. Moreover, increasing the Ni/Mn content also raises the activation energy of bulk conduction.

  4. Decreased central fatigue in multiple sclerosis patients after 8 weeks of surface functional electrical stimulation.

    Science.gov (United States)

    Chang, Ya-Ju; Hsu, Miao-Ju; Chen, Shin-Man; Lin, Cheng-Hsiang; Wong, Alice M K

    2011-01-01

    Effective treatments for multiple sclerosis (MS)-associated central fatigue have not been established. Surface functional electrical stimulation (FES), which can challenge the peripheral neuromuscular system without overloading the central nervous system, is a relatively safe therapeutic strategy. We investigated the effect of 8 weeks of surface FES training on the levels of general, central, and peripheral fatigue in MS patients. Seven of nine individuals with MS (average age: 42.86 +/- 13.47 years) completed 8 weeks of quadriceps muscle surface FES training. Maximal voluntary contraction, voluntary activation level, twitch force, General Fatigue Index (FI), Central Fatigue Index (CFI), Peripheral Fatigue Index, and Modified Fatigue Impact Scale (MFIS) scores were determined before and after training. The results showed that FI (p = 0.01), CFI (p = 0.02), and MFIS (p = 0.02) scores improved significantly after training. Improvements in central fatigue contributed significantly to improvements in general fatigue (p fatigue was a primary limitation in patients with MS during voluntary exercise and that 8 weeks of surface FES training for individuals with MS led to significantly reduced fatigue, particularly central fatigue.

  5. Structural and electrical properties of an Au film system deposited on silicone oil surfaces

    CERN Document Server

    Yang Bo; Jin Jin Sheng; Ye Quan Lin; Lao Yan Feng; Jiao Zheng Kuan; Ye Gao Xiang

    2002-01-01

    An Au thin film system, deposited on silicone oil surfaces by the thermal deposition method, has been fabricated and its structure as well as electrical properties has been studied. A web-shaped characteristic surface morphology of the films is observed. The dc sheet resistance R of the metal films on the liquid surfaces is measured during and after deposition in situ by the four-probe method. The time dependence of the sheet resistance can be explained in terms of the film growth mechanism on the oil surface. The anomalous I-V characteristics of the film system can be interpreted as a competition among the local Joule heating, hopping and tunnelling effects. It is found that the dc third-harmonic coefficient B sub 0 and the zero-power resistance R sub 0 satisfy the power-law relation B sub 0 propor to R sub 0 sup 2 sup + sup w and the exponent w is close to zero. This result indicates that the hopping and tunnelling effects in the samples are much stronger than those of the other film systems. We also find I...

  6. Investigation of electrical characteristics of no-insulation coil wound with surface-processed HTS tape

    Science.gov (United States)

    Jeon, Haeryong; Lee, Woo Seung; Kim, Jinsub; Baek, Geonwoo; Jeon, Sangsu; Yoon, Yong Soo; Ko, Tae Kuk

    2017-08-01

    This paper deals with the electrical characteristics of no-insulation coil wound with surface-processed HTS tape. The bypassing current path through turn-to-turn contacts within a coil is formed in the no-insulation coil, and this bypassing current path determines two characteristics: 1) self-protection and 2) charge-discharge delay. The amplitude of bypassing current is determined by contact resistance between the turn-to-turn contacts of the no-insulation coil. The surface roughness of the HTS tape is one of the parameters to change the contact resistance. The HTS tapes were processed to roughen by bead blast and abrasive paper, and the no-insulation coil is fabricated using processed HTS tape. We have studied the charge-discharge delay and self-protecting characteristic of each no-insulation coil by 1) sudden discharge tests and 2) overcurrent tests. The FEM simulations of contact resistance of no-insulation coil were carried out. The contact surface resistance of a case processed by abrasive paper has almost three times larger than that of reference no-insulation coil, and a case processed by bead blast presents almost same contact surface resistance with reference no-insulation coil.

  7. Carboplatin loaded Surface modified PLGA nanoparticles: Optimization, characterization, and in vivo brain targeting studies.

    Science.gov (United States)

    Jose, S; Juna, B C; Cinu, T A; Jyoti, H; Aleykutty, N A

    2016-06-01

    The carboplatin (CP) loaded poly-lactide-co-glycolide (PLGA) nanoparticles (NPs) were formulated by modified solvent evaporation method. Its surface modification is done by 1% polysorbate80 (P80) to improve their entry into the brain after intraperitoneal administration (i.p) via receptor-mediated pathways. A formulation with maximum entrapment efficiency and minimal particle size was optimized by central composite design (CCD) based on mean particle size, and entrapment efficiencies as responses. The optimized formulation was characterized by mean particle size, entrapment efficiency, zeta potential, Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) analysis. The surface modified NPs were analysed for mean particle, zeta potential, FTIR, and in vitro release studies. The spherical particles with mean particle size 161.9nm, 162.4nm and zeta potential value of -26.5, -23.9 were obtained for unmodified and surface modified NPs respectively. The in vitro release experiments of the surface modified PLGA NPs exhibited sustained release for more than 48h, which was in accordance with Higuchi's equation with Fickian diffusion-based release mechanism. The in vivo bio distribution of P80 coated CP loaded PLGA NPs was compared with CP solution, and CP loaded NPs, in adult wistar rats. In the brain, compared with CP solution, both types of NPs especially NPs coated with P80 increased the concentration of carboplatin by 3.27 fold. All these results suggest that the developed formulation may improve the targeted therapy for malignant brain tumors in future. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. A NOVEL METHOD FOR ANALYZING ELECTRIC FIELD DISTRIBUTION OF ELECTRO CAPACITIVE CANCER TREATMENT (ECCT USING WIRE MESH ELECTRODES: A CASE STUDY OF BRAIN CANCER THERAPY.

    Directory of Open Access Journals (Sweden)

    Linahtadiya Andiani

    2017-12-01

    Full Text Available Electric field distribution analysis generated by ECCT in a human head model with or without brain cancer using wire mesh electrode has been conductedsuccessfully. The analysis of electric field distribution was done using simulation in a human head model with ECCT Apparel Helmet system type A which is three dimensional model. The electric field distribution was measured with and without a wire mesh electrode which was either passive or active using COMSOL Multiphysics 5.2 software and was then processed using MATLAB R2010a. The aim of the research was to assess the performance of wire mesh electrode in detecting electric field distribution. ECCT which is utilized in brain cancer therapy with input 10 V is able to produce an electric field with an average of 178.8 V/m. The input voltage influences electric field distribution whereas the signal frequency does not affect the electric field distribution. Wire mesh electrode which is either active or passive can measure the electric field distribution generated by ECCT that neither the active nor the passive wire mesh electrode changed the pattern of the electric field distribution and the change in the measured electric field value is not significant.

  9. Strongly Enhanced Electric Fields in Laser-Matter Coupling via Surface Plasmon Resonances

    Science.gov (United States)

    Kupersztych, Joseph; Monchicourt, Patrick; Raynaud, Michele

    2001-10-01

    Laser-matter coupling can be improved when collective modes, such as surface plasmons, are resonantly excited during the interaction. Recent experiments performed at Saclay demonstrate that these resonant modes are efficient for increasing laser absorption, electron emission rates and also, kinetic energies/1/. This is because the electrons located at the surface -within the skin depth- see a resonant surface plasmon field much higher than the laser field. The effect of this strongly inhomogeneous enhanced field is to accelerate electrons toward the vacuum via the ponderomotive force of the surface plasmon from high field to low field regions. If the laser pulse duration is such that electrons have enough time to fully explore the spatial extension of the surface plasmon field, then the quiver energy U_sp=e^2E^2_sp/4m ω^2 (where E_sp is the plasmon field and ω the laser frequency) is totally converted into kinetic energy. As a result, electron energy spectra exhibit important shifts and broadenings which can be used for evaluating the amplitude of the resonance. The electron spectra emitted by a periodic gold target irradiated by short laser pulses at moderate intensities ( ~ 10^9-10^10 W/cm^2) will be presented for illustrating the above effects. The energy shifts measured as a function of laser intensity and pulse duration (60 to 800 fs) are, in the presence of the resonance, of the order of several tens of eV. These values are much higher than those corresponding to the classical photoelectric effect (of the order of 1 eV). The shifts obtained in the presence of the surface plasmon resonance are those that might be expected out of resonance at laser intensities four orders of magnitude higher. In terms of field amplitude, the enhancement of the electric field due to this resonance is found to be ca. 200. Extensions of these results to higher intensities and solid-state density plasmas for producing superintense electric fields will be discussed. [1] J

  10. Nanoparticle technology for treatment of Parkinson's disease: the role of surface phenomena in reaching the brain.

    Science.gov (United States)

    Leyva-Gómez, Gerardo; Cortés, Hernán; Magaña, Jonathan J; Leyva-García, Norberto; Quintanar-Guerrero, David; Florán, Benjamín

    2015-07-01

    The absence of a definitive treatment for Parkinson's disease has driven the emerging investigation in the search for novel therapeutic alternatives. At present, the formulation of different drugs on nanoparticles has represented several advantages over conventional treatments. This type of multifunctional carrier, owing to its size and composition, has different interactions in biological systems that can lead to a decrease in ability to cross the blood-brain barrier. Therefore, this review focuses on the latest advances in obtaining nanoparticles for Parkinson's disease and provides an overview of technical aspects in the design of brain drug delivery of nanoparticles and an analysis of surface phenomena, a key aspect in the development of functional nanoparticles for Parkinson's disease. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Posterolateral surface electrical stimulation of abdominal expiratory muscles to enhance cough in spinal cord injury.

    Science.gov (United States)

    Butler, Jane E; Lim, Julianne; Gorman, Robert B; Boswell-Ruys, Claire; Saboisky, Julian P; Lee, Bonsan B; Gandevia, Simon C

    2011-02-01

    Spinal cord injury (SCI) patients have respiratory complications because of abdominal muscle weakness and paralysis, which impair the ability to cough. This study aims to enhance cough in high-level SCI subjects (n = 11, SCI at or above T6) using surface electrical stimulation of the abdominal muscles via 2 pairs of posterolaterally placed electrodes. From total lung capacity, subjects performed maximum expiratory pressure (MEP) efforts against a closed airway and voluntary cough efforts. Both efforts were performed with and without superimposed trains of electrical stimulation (50 Hz, 1 second) at a submaximal intensity set to evoke a gastric pressure (P(ga)) of 40 cm H(2)O at functional residual capacity. In the MEP effort, stimulation increased the maximal P(ga) (from 21.4 ± 7.0 to 59.0 ± 5.7 cm H(2)O) and esophageal pressure (P(es); 47.2 ± 11.7 to 65.6 ± 13.6 cm H(2)O). During the cough efforts, stimulation increased P(ga) (19.5 ± 6.0 to 57.9 ± 7.0 cm H(2)O) and P(es) (31.2 ± 8.7 to 56.6 ± 10.5 cm H(2)O). The increased expiratory pressures during cough efforts with stimulation increased peak expiratory flow (PEF, by 36% ± 5%), mean expiratory flow (by 80% ± 8%), and expired lung volume (by 41% ± 16%). In every subject, superimposed electrical stimulation improved peak expiratory flow during cough efforts (by 0.99 ± 0.12 L/s; range, 0.41-1.80 L/s). Wearing an abdominal binder did not improve stimulated cough flows or pressures. The increases in P(ga) and PEF with electrical stimulation using the novel posterolateral electrode placement are 2 to 3 times greater than improvements reported in other studies. This suggests that posterolateral electrical stimulation of abdominal muscles is a simple noninvasive way to enhance cough in individuals with SCI.

  12. Plasma-Surface Interactions in Hollow Cathode Discharges for Electric Propulsion

    Science.gov (United States)

    Capece, Angela Maria

    Electric thrusters generate high exhaust velocities and can achieve specific impulses in excess of 1000 s. The low thrust generation and high specific impulse make electric propulsion ideal for interplanetary missions, spacecraft station keeping, and orbit raising maneuvers. Consequently, these devices have been used on a variety of space missions including Deep Space 1, Dawn, and hundreds of commercial spacecraft in Earth orbit. In order to provide the required total impulses, thruster burn time can often exceed 10,000 hours, making thruster lifetime essential. One of the main life-limiting components on ion engines is the hollow cathode, which serves as the electron source for ionization of the xenon propellant gas. Reactive contaminants such as oxygen can modify the cathode surface morphology and degrade the electron emission properties. Hollow cathodes that operate with reactive impurities in the propellant will experience higher operating temperatures, which increase evaporation of the emission materials and reduce cathode life. A deeper understanding of the mechanisms initiating cathode failure will improve thruster operation, increase lifetime, and ultimately reduce cost. A significant amount of work has been done previously to understand the effects of oxygen poisoning on vacuum cathodes; however, the xenon plasma adds complexity, and its role during cathode poisoning is not completely understood. The work presented here represents the first attempt at understanding how oxygen impurities in the xenon discharge plasma alter the emitter surface and affect operation of a 4:1:1 BaO-CaO-Al2O3 hollow cathode. A combination of experimentation and modeling was used to investigate how oxygen impurities in the discharge plasma alter the emitter surface and reduce the electron emission capability. The experimental effort involved operating a 4:1:1 hollow cathode at various conditions with oxygen impurities in the xenon flow. Since direct measurements of the emitter

  13. Electric field calculations in brain stimulation based on finite elements: an optimized processing pipeline for the generation and usage of accurate individual head models.

    Science.gov (United States)

    Windhoff, Mirko; Opitz, Alexander; Thielscher, Axel

    2013-04-01

    The need for realistic electric field calculations in human noninvasive brain stimulation is undisputed to more accurately determine the affected brain areas. However, using numerical techniques such as the finite element method (FEM) is methodologically complex, starting with the creation of accurate head models to the integration of the models in the numerical calculations. These problems substantially limit a more widespread application of numerical methods in brain stimulation up to now. We introduce an optimized processing pipeline allowing for the automatic generation of individualized high-quality head models from magnetic resonance images and their usage in subsequent field calculations based on the FEM. The pipeline starts by extracting the borders between skin, skull, cerebrospinal fluid, gray and white matter. The quality of the resulting surfaces is subsequently improved, allowing for the creation of tetrahedral volume head meshes that can finally be used in the numerical calculations. The pipeline integrates and extends established (and mainly free) software for neuroimaging, computer graphics, and FEM calculations into one easy-to-use solution. We demonstrate the successful usage of the pipeline in six subjects, including field calculations for transcranial magnetic stimulation and transcranial direct current stimulation. The quality of the head volume meshes is validated both in terms of capturing the underlying anatomy and of the well-shapedness of the mesh elements. The latter is crucial to guarantee the numerical robustness of the FEM calculations. The pipeline will be released as open-source, allowing for the first time to perform realistic field calculations at an acceptable methodological complexity and moderate costs. Copyright © 2011 Wiley Periodicals, Inc.

  14. Rotational electrical impedance tomography using electrodes with limited surface coverage provides window for multimodal sensing

    Science.gov (United States)

    Lehti-Polojärvi, Mari; Koskela, Olli; Seppänen, Aku; Figueiras, Edite; Hyttinen, Jari

    2018-02-01

    Electrical impedance tomography (EIT) is an imaging method that could become a valuable tool in multimodal applications. One challenge in simultaneous multimodal imaging is that typically the EIT electrodes cover a large portion of the object surface. This paper investigates the feasibility of rotational EIT (rEIT) in applications where electrodes cover only a limited angle of the surface of the object. In the studied rEIT, the object is rotated a full 360° during a set of measurements to increase the information content of the data. We call this approach limited angle full revolution rEIT (LAFR-rEIT). We test LAFR-rEIT setups in two-dimensional geometries with computational and experimental data. We use up to 256 rotational measurement positions, which requires a new way to solve the forward and inverse problem of rEIT. For this, we provide a modification, available for EIDORS, in the supplementary material. The computational results demonstrate that LAFR-rEIT with eight electrodes produce the same image quality as conventional 16-electrode rEIT, when data from an adequate number of rotational measurement positions are used. Both computational and experimental results indicate that the novel LAFR-rEIT provides good EIT with setups with limited surface coverage and a small number of electrodes.

  15. Impacts of hematite nanoparticle exposure on biomechanical, adhesive, and surface electrical properties of Escherichia coli cells.

    Science.gov (United States)

    Zhang, Wen; Hughes, Joseph; Chen, Yongsheng

    2012-06-01

    Despite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties of Escherichia coli cells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that E. coli cells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treated E. coli cells was 120 nm, which is significantly lower (P hematite-treated E. coli cells (0.28 ± 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ± 0.01 nN/nm). The zeta potential of E. coli cells, measured by dynamic light scattering (DLS), was shown to shift from -4 ± 2 mV to -27 ± 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials.

  16. Anisotropic quantum confinement effect and electric control of surface states in Dirac semimetal nanostructures.

    Science.gov (United States)

    Xiao, Xianbo; Yang, Shengyuan A; Liu, Zhengfang; Li, Huili; Zhou, Guanghui

    2015-01-20

    The recent discovery of Dirac semimetals represents a new achievement in our fundamental understanding of topological states of matter. Due to their topological surface states, high mobility, and exotic properties associated with bulk Dirac points, these new materials have attracted significant attention and are believed to hold great promise for fabricating novel topological devices. For nanoscale device applications, effects from finite size usually play an important role. In this report, we theoretically investigate the electronic properties of Dirac semimetal nanostructures. Quantum confinement generally opens a bulk band gap at the Dirac points. We find that confinement along different directions shows strong anisotropic effects. In particular, the gap due to confinement along vertical c-axis shows a periodic modulation, which is absent for confinement along horizontal directions. We demonstrate that the topological surface states could be controlled by lateral electrostatic gating. It is possible to generate Rashba-like spin splitting for the surface states and to shift them relative to the confinement-induced bulk gap. These results will not only facilitate our fundamental understanding of Dirac semimetal nanostructures, but also provide useful guidance for designing all-electrical topological spintronics devices.

  17. Electrical Capacitance Tomography Measurement of the Migration of Ice Frontal Surface in Freezing Soil

    Directory of Open Access Journals (Sweden)

    Liu J.

    2016-12-01

    Full Text Available The tracking of the migration of ice frontal surface is crucial for the understanding of the underlying physical mechanisms in freezing soil. Owing to the distinct advantages, including non-invasive sensing, high safety, low cost and high data acquisition speed, the electrical capacitance tomography (ECT is considered to be a promising visualization measurement method. In this paper, the ECT method is used to visualize the migration of ice frontal surface in freezing soil. With the main motivation of the improvement of imaging quality, a loss function with multiple regularizers that incorporate the prior formation related to the imaging objects is proposed to cast the ECT image reconstruction task into an optimization problem. An iteration scheme that integrates the superiority of the split Bregman iteration (SBI method is developed for searching for the optimal solution of the proposed loss function. An unclosed electrodes sensor is designed for satisfying the requirements of practical measurements. An experimental system of one dimensional freezing in frozen soil is constructed, and the ice frontal surface migration in the freezing process of the wet soil sample containing five percent of moisture is measured. The visualization measurement results validate the feasibility and effectiveness of the ECT visualization method

  18. Mid-sagittal plane and mid-sagittal surface optimization in brain MRI using a local symmetry measure

    DEFF Research Database (Denmark)

    Stegmann, Mikkel Bille; Skoglund, Karl; Ryberg, Charlotte

    2005-01-01

    This paper describes methods for automatic localization of the mid-sagittal plane (MSP) and mid-sagittal surface (MSS). The data used is a subset of the Leukoaraiosis And DISability (LADIS) study consisting of three-dimensional magnetic resonance brain data from 62 elderly subjects (age 66 to 84...... years). Traditionally, the mid-sagittal plane is localized by global measures. However, this approach fails when the partitioning plane between the brain hemispheres does not coincide with the symmetry plane of the head. We instead propose to use a sparse set of profiles in the plane normal direction......, the mid-sagittal plane is not always planar, but a curved surface resulting in poor partitioning of the brain hemispheres. To account for this, this paper also investigates an optimization strategy which fits a thin-plate spline surface to the brain data using a robust least median of squares estimator...

  19. Electric controlling of surface metal-insulator transition in the doped BaTiO3 film

    Directory of Open Access Journals (Sweden)

    Wei Xun

    2017-07-01

    Full Text Available Based on first-principles calculations, the BaTiO3(BTO film with local La-doping is studied. For a selected concentration and position of doping, the surface metal-insulator transition occurs under the applied electric field, and the domain appears near the surface for both bipolar states. Furthermore, for the insulated surface state, i.e., the downward polarization state in the doped film, the gradient bandgap structure is achieved, which favors the absorption of solar energy. Our investigation can provide an alternative avenue in modification of surface property and surface screening effect in polar materials.

  20. Understanding the life cycle surface land requirements of natural gas-fired electricity

    Science.gov (United States)

    Jordaan, Sarah M.; Heath, Garvin A.; Macknick, Jordan; Bush, Brian W.; Mohammadi, Ehsan; Ben-Horin, Dan; Urrea, Victoria; Marceau, Danielle

    2017-10-01

    The surface land use of fossil fuel acquisition and utilization has not been well characterized, inhibiting consistent comparisons of different electricity generation technologies. Here we present a method for robust estimation of the life cycle land use of electricity generated from natural gas through a case study that includes inventories of infrastructure, satellite imagery and well-level production. Approximately 500 sites in the Barnett Shale of Texas were sampled across five life cycle stages (production, gathering, processing, transmission and power generation). Total land use (0.62 m2 MWh-1, 95% confidence intervals ±0.01 m2 MWh-1) was dominated by midstream infrastructure, particularly pipelines (74%). Our results were sensitive to power plant heat rate (85-190% of the base case), facility lifetime (89-169%), number of wells per site (16-100%), well lifetime (92-154%) and pipeline right of way (58-142%). When replicated for other gas-producing regions and different fuels, our approach offers a route to enable empirically grounded comparisons of the land footprint of energy choices.

  1. Augmented visual feedback counteracts the effects of surface muscular functional electrical stimulation on physiological tremor

    Science.gov (United States)

    2013-01-01

    Background Recent studies suggest that surface muscular functional electrical stimulation (FES) might suppress neurological upper limb tremor. We assessed its effects on upper limb physiological tremor, which is mainly driven by mechanical-reflex oscillations. We investigated the interaction between FES and augmented visual feedback, since (a) most daily activities are performed using visual cues, and (b) augmented visual feedback exacerbates upper limb tremor. Methods 10 healthy subjects (23.4 ± 7.7 years) performed 2 postural tasks with combinations of FES (4 sites; frequency of stimulation: 30 Hz; pulse width: 300 microsec; range of current delivered 10–34 mAmp) and augmented visual feedback. Results Spectral analysis of tremor showed a decrease of power spectral density to 62.18% (p = 0.01), of the integral in the 8-12 Hz frequency band to 57.67% (p = 0.003), and of tremor root mean square (RMS) to 57.16% (p = 0.002) during FES, without any changes in tremor frequency. Augmented visual feedback blocked the beneficial effect of FES, as confirmed by power spectral analysis (p = 0.01). We found a statistically significant interaction between augmented visual feedback and electrical stimulation (p = 0.039). Conclusions Augmented visual feedback antagonizes the effects of FES on physiological tremor. The absence of changes of peak frequency argues against an effect of FES on mechanical properties of the upper limb. PMID:24063436

  2. Understanding the life cycle surface land requirements of natural gas-fired electricity

    Energy Technology Data Exchange (ETDEWEB)

    Heath, Garvin A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Macknick, Jordan E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bush, Brian W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jordaan, Sarah [University of Calgary; Johns Hopkins University; Mohammadi, Ehsan [University of Calgary; Ben-Horin, Dan [Formerly NREL; Urrea, Victoria [Formerly NREL; Marceau, Danielle [University of Calgary

    2017-10-01

    The surface land use of fossil fuel acquisition and utilization has not been well characterized, inhibiting consistent comparisons of different electricity generation technologies. Here we present a method for robust estimation of the life cycle land use of electricity generated from natural gas through a case study that includes inventories of infrastructure, satellite imagery and well-level production. Approximately 500 sites in the Barnett Shale of Texas were sampled across five life cycle stages (production, gathering, processing, transmission and power generation). Total land use (0.62 m2 MWh-1, 95% confidence intervals +/-0.01 m2 MWh-1) was dominated by midstream infrastructure, particularly pipelines (74%). Our results were sensitive to power plant heat rate (85-190% of the base case), facility lifetime (89-169%), number of wells per site (16-100%), well lifetime (92-154%) and pipeline right of way (58-142%). When replicated for other gas-producing regions and different fuels, our approach offers a route to enable empirically grounded comparisons of the land footprint of energy choices.

  3. Numerical Studies of Friction Between Metallic Surfaces and of its Dependence on Electric Currents

    Science.gov (United States)

    Meintanis, Evangelos; Marder, Michael

    2009-03-01

    We will present molecular dynamics simulations that explore the frictional mechanisms between clean metallic surfaces. We employ the HOLA molecular dynamics code to run slider-on-block experiments. Both objects are allowed to evolve freely. We recover realistic coefficients of friction and verify the importance of cold-welding and plastic deformations in dry sliding friction. We also find that plastic deformations can significantly affect both objects, despite a difference in hardness. Metallic contacts have significant technological applications in the transmission of electric currents. To explore the effects of the latter to sliding, we had to integrate an electrodynamics solver into the molecular dynamics code. The disparate time scales involved posed a challenge, but we have developed an efficient scheme for such an integration. A limited electrodynamic solver has been implemented and we are currently exploring the effects of currents in the friction and wear of metallic contacts.

  4. Surface quality analysis of die steels in powder-mixed electrical discharge machining using titan powder in fine machining

    Directory of Open Access Journals (Sweden)

    Banh Tien Long

    2016-06-01

    Full Text Available Improving the quality of surface molds after electrical discharge machining is still being considered by many researchers. Powder-mixed dielectric in electrical discharge machining showed that it is one of the processing methods with high efficiency. This article reports on the results of surface quality of mold steels after powder-mixed electrical discharge machining using titanium powder in fine machining. The process parameters such as electrode material, workpiece material, electrode polarity, pulse on-time, pulse off-time, current, and titanium powder concentration were considered in the research. These materials are most commonly used with die-sinking electrical discharge machining in the manufacture of molds and has been selected as the subject of research: workpiece materials were SKD61, SKT4, and SKD11 mold steels, and electrode materials were copper and graphite. Taguchi’s method is used to design experiments. The influence of the parameters on surface roughness was evaluated through the average value and ratio (S/N. Results showed that the parameters such as electrical current, electrode material, pulse on-time, electrode polarity, and interaction between the electrode materials with concentration powder mostly influence surface roughness and surface roughness at optimal parameters SRopt = 1.73 ± 0.39 µm. Analysis of the surface layer after powder-mixed electrical discharge machining using titanium powder in optimal conditions has shown that the white layer with more uniform thickness and increased hardness (≈861.0 HV, and amount and size of microscopic cracks, is reduced. This significantly leads to the increase in the quality of the surface layer.

  5. Tacit Knowledge Capture and the Brain-Drain at Electrical Utilities

    Science.gov (United States)

    Perjanik, Nicholas Steven

    As a consequence of an aging workforce, electric utilities are at risk of losing their most experienced and knowledgeable electrical engineers. In this research, the problem was a lack of understanding of what electric utilities were doing to capture the tacit knowledge or know-how of these engineers. The purpose of this qualitative research study was to explore the tacit knowledge capture strategies currently used in the industry by conducting a case study of 7 U.S. electrical utilities that have demonstrated an industry commitment to improving operational standards. The research question addressed the implemented strategies to capture the tacit knowledge of retiring electrical engineers and technical personnel. The research methodology involved a qualitative embedded case study. The theories used in this study included knowledge creation theory, resource-based theory, and organizational learning theory. Data were collected through one time interviews of a senior electrical engineer or technician within each utility and a workforce planning or training professional within 2 of the 7 utilities. The analysis included the use of triangulation and content analysis strategies. Ten tacit knowledge capture strategies were identified: (a) formal and informal on-boarding mentorship and apprenticeship programs, (b) formal and informal off-boarding mentorship programs, (c) formal and informal training programs, (d) using lessons learned during training sessions, (e) communities of practice, (f) technology enabled tools, (g) storytelling, (h) exit interviews, (i) rehiring of retirees as consultants, and (j) knowledge risk assessments. This research contributes to social change by offering strategies to capture the know-how needed to ensure operational continuity in the delivery of safe, reliable, and sustainable power.

  6. Current Directions in Non-Invasive Low Intensity Electric Brain Stimulation for Depressive Disorder

    NARCIS (Netherlands)

    Schutter, D.J.L.G.; Sack, A.T.

    2014-01-01

    Non-invasive stimulation of the human brain to improve depressive symptoms is increasingly finding its way in clinical settings as a viable form of somatic treatment. Following successful modulation of neural excitability with subsequent antidepressant effects, neural polarization by administrating

  7. Electric brain responses to inappropriate harmonies during listening to expressive music

    NARCIS (Netherlands)

    Koesch, S; Mulder, J

    Objectives: Recent studies with event-related brain potentials (ERPs) investigating music processing found (early) negativities with right-hemispheric predominance as a response to inappropriate harmonies within sequences of chords. The stimuli used in those studies were fairly artificial in order

  8. Determination of fluid transmissivity and electric transverse resistance for shallow aquifers and deep reservoirs from surface and well-log electric measurements

    Directory of Open Access Journals (Sweden)

    H. S. Salem

    1999-01-01

    Full Text Available Fluid transmissivity (layer thickness times permeability and electric transverse resistance (layer thickness time resistivity are important parameter in groundwater and hydrocarbon exploration. Determination of these parameters provides a good knowledge of the potential of porous media, because they relate fluid flow to electric-current conduction, in terms of layer thickness, permeability and resistivity. In this study, both parameters were determined for shallow aquifers (Schleswig-Holstein, northern Germany and deep reservoirs (Jeanne d'Arc Basin, offshore of eastern Canada, utilizing surface and well-log electric measurements. Direct relationships between both parameters, with coefficients of correlation of 0.99 (for the aquifers and 0.94 (for the reservoirs, were obtained. The relationships suggest that an increase in both parameters indicate presence of zones of high fluid potential within the aquifers and the reservoirs.

  9. Local changes of work function near rough features on Cu surfaces operated under high external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Djurabekova, Flyura, E-mail: flyura.djurabekova@helsinki.fi; Ruzibaev, Avaz; Parviainen, Stefan [Helsinki Institute of Physics and Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 Helsinki (Finland); Holmström, Eero [Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki (Finland); Department of Earth Sciences, Faculty of Maths and Physical Sciences, UCL Earth Sciences, Gower Street, London WC1E 6BT (United Kingdom); Hakala, Mikko [Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki (Finland)

    2013-12-28

    Metal surfaces operated under high electric fields produce sparks even if they are held in ultra high vacuum. In spite of extensive research on the topic of vacuum arcs, the mystery of vacuum arc origin still remains unresolved. The indications that the sparking rates depend on the material motivate the research on surface response to extremely high external electric fields. In this work by means of density-functional theory calculations we analyze the redistribution of electron density on (100) Cu surfaces due to self-adatoms and in presence of high electric fields from −1 V/nm up to −2 V/nm (−1 to −2 GV/m, respectively). We also calculate the partial charge induced by the external field on a single adatom and a cluster of two adatoms in order to obtain reliable information on charge redistribution on surface atoms, which can serve as a benchmarking quantity for the assessment of the electric field effects on metal surfaces by means of molecular dynamics simulations. Furthermore, we investigate the modifications of work function around rough surface features, such as step edges and self-adatoms.

  10. Non-Invasive Characterization of Brain Tissue Electrical Properties with MRI

    NARCIS (Netherlands)

    Mandija, Stefano

    2017-01-01

    The study of the electrical properties (EPs) of tissues, i.e. conductivity and permittivity, is of fundamental importance to understand the biophysical interactions and the effects of electromagnetic fields on our body, such as those produced by MRI scanners or by Transcranial Magnetic Stimulators

  11. The brain-specific Beta4 subunit downregulates BK channel cell surface expression.

    Directory of Open Access Journals (Sweden)

    Sonal Shruti

    Full Text Available The large-conductance K(+ channel (BK channel can control neural excitability, and enhanced channel currents facilitate high firing rates in cortical neurons. The brain-specific auxiliary subunit β4 alters channel Ca(++- and voltage-sensitivity, and β4 knock-out animals exhibit spontaneous seizures. Here we investigate β4's effect on BK channel trafficking to the plasma membrane. Using a novel genetic tag to track the cellular location of the pore-forming BKα subunit in living cells, we find that β4 expression profoundly reduces surface localization of BK channels via a C-terminal ER retention sequence. In hippocampal CA3 neurons from C57BL/6 mice with endogenously high β4 expression, whole-cell BK channel currents display none of the characteristic properties of BKα+β4 channels observed in heterologous cells. Finally, β4 knock-out animals exhibit a 2.5-fold increase in whole-cell BK channel current, indicating that β4 also regulates current magnitude in vivo. Thus, we propose that a major function of the brain-specific β4 subunit in CA3 neurons is control of surface trafficking.

  12. Characterization of electric discharge machining, subsequent etching and shot-peening as a surface treatment for orthopedic implants

    Science.gov (United States)

    Stráský, Josef; Havlíková, Jana; Bačáková, Lucie; Harcuba, Petr; Mhaede, Mansour; Janeček, Miloš

    2013-09-01

    Presented work aims at multi-method characterization of combined surface treatment of Ti-6Al-4V alloy for biomedical use. Surface treatment consists of consequent use of electric discharge machining (EDM), acid etching and shot peening. Surface layers are analyzed employing scanning electron microscopy and energy dispersive X-ray spectroscopy. Acid etching by strong Kroll's reagent is capable of removing surface layer of transformed material created by EDM. Acid etching also creates partly nanostructured surface and significantly contributes to the enhanced proliferation of the bone cells. The cell growth could be positively affected by the superimposed bone-inspired structure of the surface with the morphological features in macro-, micro- and nano-range. Shot peening significantly improves poor fatigue performance after EDM. Final fatigue performance is comparable to benchmark electropolished material without any adverse surface effect. The proposed three-step surface treatment is a low-cost process capable of producing material that is applicable in orthopedics.

  13. Electrically tunable surface plasmon for THz emission, detection, and other applications

    Science.gov (United States)

    Khoury, Jed; Haji-Saeed, Bahareh; Buchwald, Walter; Woods, Charles

    2010-08-01

    In this paper, we present a design for a widely tunable solid-state optically and electrically pumped THz laser based on the Smith-Purcell free-electron laser. In the free-electron laser, an energetic electron beam pumps a metallic grating to generate surface plasmons. Our solid-state optically pumped design consists of a thin layer of dielectic, such as SiNx, sandwiched between a corrugated structure and a thin metal or semiconductor layer. The lower layer is for current streaming, and replaces the electron beam in the original design. The upper layer consists of one micro-grating for coupling the electromagnetic field in, another for coupling out, and a nano-grating for coupling with the current in the lower layer for electromagnetic field generation. The surface plasmon waves generated from the upper layer by an external electromagnetic field, and the lower layer by the applied current, are coupled. Emission enhancement occurs when the plasmonic waves in both layers are resonantly coupled.

  14. Radiofrequency electric field hyperthermia with gold nanostructures: role of particle shape and surface chemistry.

    Science.gov (United States)

    Amini, Seyed Mohammad; Kharrazi, Sharmin; Rezayat, Seyed Mahdi; Gilani, Kambiz

    2017-09-10

    Hyperthermia treatment of cancerous cells has been recently developed drastically with the help of nanostructures. Heating of gold nanoparticles in non-invasive radiofrequency electric field (RF-EF) is a promising and unique technique for cancer hyperthermia. However, because of differences between particles (i.e. their surface chemistry and dispersion medium) and between RF-EF sources, the research community has not reached a consensus yet. Here, we report the results of investigations on heating of gold nanoparticles and gold nanorods under RF-EF and feasibility of in-vitro cancer hyperthermia. The heating experiments were performed to investigate the role of particle shape and surface chemistry (CTAB, citrate and PEG molecules). In-vitro hyperthermia was performed on human pancreatic cancer cell (MIA Paca-2) with PEG-coated GNPs and GNRs at concentrations that were found non-toxic based on the results of cytotoxicity assay. Application of RF-EF on cells treated with PEG-GNPs and PEG-GNRs proved highly effective in killing cells.

  15. Experimental study of surface roughness in Electric Discharge Machining (EDM based on Grey Relational Analysis

    Directory of Open Access Journals (Sweden)

    Mat Deris Ashanira

    2016-01-01

    Full Text Available Electric Discharge Machining (EDM is one of the modern machining which is capable in handling hard and difficult-to-machine material. The successful of EDM basically depends on its performances such as surface roughness (Ra, material removal rate (MRR, electrode wear rate (EWR and dimensional accuracy (DA. Ra is considered as the most important performance due to it role as a technological quality measurement for a product and also a factor that significantly affects the manufacturing process. This paper presents the experimental study of surface roughness in die sinking EDM using stainless steel SS316L with copper impregnated graphite electrode. The machining experimental is conducted based on the two levels full factorial design of design of experiment (DOE with five machining parameters which are peak current, servo voltage, servo speed, pulse on time and pulse off time. The results were analyzed using grey relational analysis (GRA and it was found that pulse on time and servo voltage give the most influence to the Ra value.

  16. Electrical Characteristics of Carbon Nanotubes by Plasma and Microwave Surface Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Sangjin; Lee, Soonbo; Boo, Jinhyo [Sungkyunkwan Univ., Suwon (Korea, Republic of); Shrestha, Shankar Prasad [Tribhuvan Univ., Kathmandu (Nepal)

    2014-03-15

    The plasma and microwave surface treatments of carbon nanotubes that loaded on plastic substrates were carried out with expecting a change of carbon nanotube dispersion by increasing treatment time. The microwave treatment process was undergone by commercial microwave oven (800 W). The electrical property was measured by hall measurement and resistance was increased by increasing O{sub 2} flow rate of plasma, suggesting an improvement of carbon nanotube dispersion and a possibility of controlling the resistances of carbon nanotubes by plasma surface treatment. The resistance was increased in both polyethylene terephthalate and polyimide substrates by increasing O{sub 2} flow rate. Resistance changes only slightly with different O{sub 2} flow treatment in measure rho for all polyimide samples. Sheet resistance is lowest in polyimide substrate not due to high carbon nanotube loading but due to tendency to remain in elongated structure. O{sub 2} or N{sub 2} plasma treatments on both polyethylene terephthalate and polyimide substrates lead to increase in sheet resistance.

  17. Chemical Surface, Thermal and Electrical Characterization of Nafion Membranes Doped with IL-Cations

    Directory of Open Access Journals (Sweden)

    María del Valle Martínez de Yuso

    2014-04-01

    Full Text Available Surface and bulk changes in a Nafion membrane as a result of IL-cation doping (1-butyl-3-methylimidazolium tetrafluoroborate or BMIM+BF4 and phenyltrimethylammonium chloride or TMPA+Cl− were studied by X-ray photoelectron spectroscopy (XPS, contact angle, differential scanning calorimetry (DSC and impedance spectroscopy (IS measurements performed with dry samples after 24 h in contact with the IL-cations BMIM+ and TMPA+. IL-cations were selected due to their similar molecular weight and molar volume but different shape, which could facilitate/obstruct the cation incorporation in the Nafion membrane structure by proton/cation exchange mechanism. The surface coverage of the Nafion membrane by the IL-cations was confirmed by XPS analysis and contact angle, while the results obtained by the other two techniques (DSC and IS seem to indicate differences in thermal and electrical behaviour depending on the doping-cation, being less resistive the Nafion/BMIM+ membrane. For that reason, determination of the ion transport number was obtained for this membrane by measuring the membrane or concentration potential with the samples in contact with HCl solutions at different concentrations. The comparison of these results with those obtained for the original Nafion membrane provides information on the effect of IL-cation BMIM+ on the transport of H+ across wet Nafion/BMIM+ doped membranes.

  18. Localization of Brain Electrical Activity Sources and Hemodynamic Activity Foci during Motor Imagery

    Czech Academy of Sciences Publication Activity Database

    Frolov, A. A.; Húsek, Dušan; Mokienko, O.; Bobrov, P.; Chernikova, L.; Konovalov, R.

    2014-01-01

    Roč. 40, č. 3 (2014), s. 273-283 ISSN 0362-1197 Grant - others:GA MŠk(CZ) ED1.1.00/02.0070; GA MŠk(CZ) EE.2.3.20.0073 Program:ED Institutional support: RVO:67985807 Keywords : brain computer interface * independent component analysis * EEG pattern classification * motor imagery * inverse EEG problem Subject RIV: IN - Informatics, Computer Science

  19. Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise.

    Directory of Open Access Journals (Sweden)

    Christos I Ioannou

    Full Text Available The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB. The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians' brains are often associated with enhanced auditory processing. In this study, we analysed EEG brain responses from two groups, musicians and non-musicians, when stimulated by short presentation (1 min of binaural beats with beat frequency varying from 1 Hz to 48 Hz. We focused our analysis on alpha and gamma band EEG signals, and they were analysed in terms of spectral power, and functional connectivity as measured by two phase synchrony based measures, phase locking value and phase lag index. Finally, these measures were used to characterize the degree of centrality, segregation and integration of the functional brain network. We found that beat frequencies belonging to alpha band produced the most significant steady-state responses across groups. Further, processing of low frequency (delta, theta, alpha binaural beats had significant impact on cortical network patterns in the alpha band oscillations. Altogether these results provide a neurophysiological account of cortical responses to BB stimulation at varying frequencies, and demonstrate a modulation of cortico-cortical connectivity in musicians' brains, and further suggest a kind of neuronal entrainment of a linear and nonlinear relationship to the beating frequencies.

  20. Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise

    Science.gov (United States)

    Ioannou, Christos I.; Pereda, Ernesto; Lindsen, Job P.; Bhattacharya, Joydeep

    2015-01-01

    The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB). The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians' brains are often associated with enhanced auditory processing. In this study, we analysed EEG brain responses from two groups, musicians and non-musicians, when stimulated by short presentation (1 min) of binaural beats with beat frequency varying from 1 Hz to 48 Hz. We focused our analysis on alpha and gamma band EEG signals, and they were analysed in terms of spectral power, and functional connectivity as measured by two phase synchrony based measures, phase locking value and phase lag index. Finally, these measures were used to characterize the degree of centrality, segregation and integration of the functional brain network. We found that beat frequencies belonging to alpha band produced the most significant steady-state responses across groups. Further, processing of low frequency (delta, theta, alpha) binaural beats had significant impact on cortical network patterns in the alpha band oscillations. Altogether these results provide a neurophysiological account of cortical responses to BB stimulation at varying frequencies, and demonstrate a modulation of cortico-cortical connectivity in musicians' brains, and further suggest a kind of neuronal entrainment of a linear and nonlinear relationship to the beating frequencies. PMID:26065708

  1. Effect of metal fragments in brain on electrical monitoring: In vitro and in vivo rat studies

    Science.gov (United States)

    Ahmed, A.; Bodo, M.; Armonda, R. A.

    2010-04-01

    Preliminary results showed, measurements by rheoencephalography (REG) very promising as a practical, noninvasive continuous monitoring modality of traumatic brain/blast injuries. As the impact of metal fragments on the REG signal is unknown, we report here results of our study .The in vitro study confirmed that impedance pulse amplitude waves do not change in the presence of metal (needles) placed between electrodes. In vivo studies: rats under anesthesia (10 rats, 101 trials) were measured after implantation of EEG and REG electrodes in the brain. Metal fragments were represented by 18 g needles inserted and removed between EEG and REG electrodes. Data were stored in a PC. EEG recording typically showed amplitude decrease; REG showed transitory amplitude increase after placement of a needle into either hemisphere. Removal of needles caused a decrease in REG amplitude after a transitory increase. The change in REG amplitude statistically was non-significant. Cerebral blood flow (CBF) autoregulation(AR) persisted following placement of metal fragments in rat brain.

  2. Brain Basics

    Medline Plus

    Full Text Available ... go awry, leading to mental illnesses. Brain Basics will introduce you to some of this science, such ... released it increases the chance that the neuron will fire. This enhances the electrical flow among brain ...

  3. Brain Basics

    Medline Plus

    Full Text Available ... than ever before. Brain Imaging Using brain imaging technologies such as magnetic resonance imaging (MRI), which uses ... the body's response to stress. impulse —An electrical communication signal sent between neurons by which neurons communicate ...

  4. Brain Basics

    Medline Plus

    Full Text Available ... mainly involved in controlling movement and aiding the flow of information to the front of the brain, ... the neuron will fire. This enhances the electrical flow among brain cells required for normal function and ...

  5. Brain Basics

    Medline Plus

    Full Text Available ... control specific body functions such as sleep and speech. The brain continues maturing well into a person's ... as in areas of the brain that control movement. When electrical signals are abnormal, they can cause ...

  6. Brain Basics

    Medline Plus

    Full Text Available ... it increases the chance that the neuron will fire. This enhances the electrical flow among brain cells ... This area of the brain also helps to control the amygdala during stressful events. Some research shows ...

  7. Brain Basics

    Medline Plus

    Full Text Available ... the brain How different parts of the brain communicate and work with each other How changes in ... occur when this process does not work correctly. Communication between neurons can also be electrical, such as ...

  8. Brain-computer interface driven functional electrical stimulation system for overground walking in spinal cord injury participant.

    Science.gov (United States)

    King, Christine E; Wang, Po T; McCrimmon, Colin M; Chou, Cathy C Y; Do, An H; Nenadic, Zoran

    2014-01-01

    The current treatment for ambulation after spinal cord injury (SCI) is to substitute the lost behavior with a wheelchair; however, this can result in many co-morbidities. Thus, novel solutions for the restoration of walking, such as brain-computer interfaces (BCI) and functional electrical stimulation (FES) devices, have been sought. This study reports on the first electroencephalogram (EEG) based BCI-FES system for overground walking, and its performance assessment in an individual with paraplegia due to SCI. The results revealed that the participant was able to purposefully operate the system continuously in real time. If tested in a larger population of SCI individuals, this system may pave the way for the restoration of overground walking after SCI.

  9. Investigation of Thermostressed State of Coating Formation at Electric Contact Surfacing of “Shaft” Type Parts

    Directory of Open Access Journals (Sweden)

    Olena V. Berezshnaya

    2016-01-01

    Full Text Available The forming of coating at electric contact surfacing is considered. The mathematical model of the coating formation is developed. The method of numerical recurrent solution of the finite-difference form of static equilibrium conditions of the selected elementary volume of coating is used. This model considers distribution of thermal properties and geometric parameters along the thermal deformation zone during the process of electric contact surfacing by compact material. It is found that the change of value of speed asymmetry factor leads to increasing of the friction coefficient in zone of surfacing. This provides the forming of the coating of higher quality. The limitation of the technological capabilities of equipment for electric contact surfacing is related to the size of recoverable parts and application of high electromechanical powers. The regulation of the speed asymmetry factor allows for expanding the technological capabilities of equipment for electric contact surfacing. The nomograms for determination of the stress on the roller electrode and the finite thickness of the coating as the function of the initial thickness of the compact material and the deformation degree are shown.

  10. Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

    Science.gov (United States)

    Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

    2017-10-01

    The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

  11. Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

    Science.gov (United States)

    Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

    2017-09-01

    The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

  12. Application of Electric-Arc Pulsed Mode for Obtaining Surfacings of Fe–Mo–Cr–Ti–Ni–Cu–Al-System

    Science.gov (United States)

    Knyaz’kov, Anatoly F.; Ditenberg, Ivan A.; Gavrilin, Aleksey N.; Grinyaev, Konstantin V.; Knyaz’kov, Sergey A.; Smirnov, Ivan V.

    2017-10-01

    Method of electric-arc melting with nonconsumable electrode in a protective argon atmosphere with using a pulsed mode was used to show possibility in principle of obtaining multi-component metallic surfacing of Fe–Mo–Cr–Ti–Ni–Cu–Al system on uncooled steel substrate. Features of structure and elemental composition were studied using scanning electron microscopy methods. Component intermixing of the surfacing is observed. Surfacing microhardness is 5 times greater than that of the substrate. «Surfacing-substrate» boundary has high adhesion strength.

  13. Evaluation of the electric field in the brain during transcranial direct current stimulation: A sensitivity analysis.

    Science.gov (United States)

    Santos, Laura; Martinho, Miguel; Salvador, Ricardo; Wenger, Cornelia; Fernandes, Sofia R; Ripolles, Oscar; Ruffini, Giulio; Miranda, Pedro C

    2016-08-01

    The use of computational modeling studies accounts currently for the best approach to predict the electric field (E-field) distribution in transcranial direct current stimulation. As with any model, the values attributed to the physical properties, namely the electrical conductivity of the tissues, affect the predicted E-field distribution. A wide range of values for the conductivity of most tissues is reported in the literature. In this work, we used the finite element method to compute the E-field induced in a realistic human head model for two electrode montages targeting the left dorso-lateral prefrontal cortex (DLPFC). A systematic analysis of the effect of different isotropic conductivity profiles on the E-field distribution was performed for the standard bipolar 7×5 cm2 electrodes configuration and also for an optimized multielectrode montage. Average values of the E-field's magnitude, normal and tangential components were calculated in the target region in the left DLPFC. Results show that the field decreases with increasing scalp, cerebrospinal fluid (CSF) and grey matter (GM) conductivities, while the opposite is observed for the skull and white matter conductivities. The tissues whose conductivity most affects the E-field in the cortex are the scalp and the CSF, followed by the GM and the skull. Uncertainties in the conductivity of individual tissues may affect electric field values by up to about 80%.

  14. Brain Basics

    Medline Plus

    Full Text Available ... illnesses, such as depression, can occur when this process does not work correctly. Communication between neurons can also be electrical, such as in areas of the brain that control movement. When electrical signals are abnormal, they can ...

  15. Brain Basics

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    Full Text Available ... neuron's point of contact for receiving chemical and electrical signals called impulses from neighboring neurons. Axon which ... from one neuron to another as chemical or electrical signals. The brain begins as a small group ...

  16. Brain Basics

    Medline Plus

    Full Text Available ... Brain Neurotransmitters Everything we do relies on neurons communicating with one another. Electrical impulses and chemical signals ... depression, can occur when this process does not work correctly. Communication between neurons can also be electrical, ...

  17. Can transcranial electrical stimulation improve learning difficulties in atypical brain development? A future possibility for cognitive training.

    Science.gov (United States)

    Krause, Beatrix; Cohen Kadosh, Roi

    2013-10-01

    Learning difficulties in atypical brain development represent serious obstacles to an individual's future achievements and can have broad societal consequences. Cognitive training can improve learning impairments only to a certain degree. Recent evidence from normal and clinical adult populations suggests that transcranial electrical stimulation (TES), a portable, painless, inexpensive, and relatively safe neuroenhancement tool, applied in conjunction with cognitive training can enhance cognitive intervention outcomes. This includes, for instance, numerical processing, language skills and response inhibition deficits commonly associated with profound learning difficulties and attention-deficit hyperactivity disorder (ADHD). The current review introduces the functional principles, current applications and promising results, and potential pitfalls of TES. Unfortunately, research in child populations is limited at present. We suggest that TES has considerable promise as a tool for increasing neuroplasticity in atypically developing children and may be an effective adjunct to cognitive training in clinical settings if it proves safe. The efficacy and both short- and long-term effects of TES on the developing brain need to be critically assessed before it can be recommended for clinical settings. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. Diffusion of hydrogen interstitials in the near-surface region of Pd(111) under the influence of surface coverage and external static electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Blanco-Rey, M. [Departamento de Física de Materiales, Facultad de Químicas UPV/EHU, Apartado 1072, 20018 Donostia-San Sebastián (Spain); Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Tremblay, J. C. [Institute for Chemistry and Biochemistry, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin (Germany)

    2015-04-21

    Past scanning tunneling microscopy (STM) experiments of H manipulation on Pd(111), at low temperature, have shown that it is possible to induce diffusion of surface species as well as of those deeply buried under the surface. Several questions remain open regarding the role of subsurface site occupancies. In the present work, the interaction potential of H atoms with Pd(111) under various H coverage conditions is determined by means of density functional theory calculations in order to provide an answer to two of these questions: (i) whether subsurface sites are the final locations for the H impurities that attempt to emerge from bulk regions, and (ii) whether penetration of the surface is a competing route of on-surface diffusion during depletion of surface H on densely covered Pd(111). We find that a high H coverage has the effect of blocking resurfacing of H atoms travelling from below, which would otherwise reach the surface fcc sites, but it hardly alters deeper diffusion energy barriers. Penetration is unlikely and restricted to high occupancies of hcp hollows. In agreement with experiments, the Pd lattice expands vertically as a consequence of H atoms being blocked at subsurface sites, and surface H enhances this expansion. STM tip effects are included in the calculations self-consistently as an external static electric field. The main contribution to the induced surface electric dipoles originates from the Pd substrate polarisability. We find that the electric field has a non-negligible effect on the H-Pd potential in the vicinity of the topmost Pd atomic layer, yet typical STM intensities of 1-2 VÅ{sup −1} are insufficient to invert the stabilities of the surface and subsurface equilibrium sites.

  19. Brain surface anatomy in adults with autism: the relationship between surface area, cortical thickness, and autistic symptoms.

    Science.gov (United States)

    Ecker, Christine; Ginestet, Cedric; Feng, Yue; Johnston, Patrick; Lombardo, Michael V; Lai, Meng-Chuan; Suckling, John; Palaniyappan, Lena; Daly, Eileen; Murphy, Clodagh M; Williams, Steven C; Bullmore, Edward T; Baron-Cohen, Simon; Brammer, Michael; Murphy, Declan G M

    2013-01-01

    Neuroimaging studies of brain anatomy in autism spectrum disorder (ASD) have mostly been based on measures of cortical volume (CV). However, CV is a product of 2 distinct parameters, cortical thickness (CT) and surface area (SA), that in turn have distinct genetic and developmental origins. To investigate regional differences in CV, SA, and CT as well as their relationship in a large and well-characterized sample of men with ASD and matched controls. Multicenter case-control design using quantitative magnetic resonance imaging. Medical Research Council UK Autism Imaging Multicentre Study. A total of 168 men, 84 diagnosed as having ASD and 84 controls who did not differ significantly in mean (SD) age (26 [7] years vs 28 [6] years, respectively) or full-scale IQ (110 [14] vs 114 [12], respectively). Between-group differences in CV, SA, and CT investigated using a spatially unbiased vertex-based approach; the degree of spatial overlap between the differences in CT and SA; and their relative contribution to differences in regional CV. Individuals with ASD differed from controls in all 3 parameters. These mainly consisted of significantly increased CT within frontal lobe regions and reduced SA in the orbitofrontal cortex and posterior cingulum. These differences in CT and SA were paralleled by commensurate differences in CV. The spatially distributed patterns for CT and SA were largely nonoverlapping and shared only about 3% of all significantly different locations on the cerebral surface. Individuals with ASD have significant differences in CV, but these may be underpinned by (separable) variations in its 2 components, CT and SA. This is of importance because both measures result from distinct developmental pathways that are likely modulated by different neurobiological mechanisms. This finding may provide novel targets for future studies into the etiology of the condition and a new way to fractionate the disorder.

  20. Electrical brain responses in language-impaired children reveal grammar-specific deficits.

    Directory of Open Access Journals (Sweden)

    Elisabeth Fonteneau

    2008-03-01

    Full Text Available Scientific and public fascination with human language have included intensive scrutiny of language disorders as a new window onto the biological foundations of language and its evolutionary origins. Specific language impairment (SLI, which affects over 7% of children, is one such disorder. SLI has received robust scientific attention, in part because of its recent linkage to a specific gene and loci on chromosomes and in part because of the prevailing question regarding the scope of its language impairment: Does the disorder impact the general ability to segment and process language or a specific ability to compute grammar? Here we provide novel electrophysiological data showing a domain-specific deficit within the grammar of language that has been hitherto undetectable through behavioural data alone.We presented participants with Grammatical(G-SLI, age-matched controls, and younger child and adult controls, with questions containing syntactic violations and sentences containing semantic violations. Electrophysiological brain responses revealed a selective impairment to only neural circuitry that is specific to grammatical processing in G-SLI. Furthermore, the participants with G-SLI appeared to be partially compensating for their syntactic deficit by using neural circuitry associated with semantic processing and all non-grammar-specific and low-level auditory neural responses were normal.The findings indicate that grammatical neural circuitry underlying language is a developmentally unique system in the functional architecture of the brain, and this complex higher cognitive system can be selectively impaired. The findings advance fundamental understanding about how cognitive systems develop and all human language is represented and processed in the brain.

  1. Evaporation of water droplets on Pt-surface in presence of external electric field—A molecular dynamics study

    Science.gov (United States)

    Hens, Abhiram; Biswas, Gautam; De, Sudipta

    2015-09-01

    Evaporation of a sessile droplet on a hot solid substrate is an important problem in fluid mechanics. It is relevant to theoretical issues in heat transfer as well as several practical applications. This study investigates the spreading and evaporation of a nanoscale water droplet on a solid platinum surface. The major objective was to analyze the effect of an external electric field on these phenomena. Varying the intensity and direction of the external electric field, a series of molecular dynamics simulations were carried out to understand these phenomena at a molecular level. The results reveal that a horizontal electric field assists in droplet spreading, whereas a vertical electric field enhances the rate of evaporation for a certain range of field intensities. It also shows that the substrate temperature plays an important role in such processes. It is seen that the effect of an external electric field on droplet evaporation becomes significant at an intermediate range of surface temperatures and this effect is not clearly visible for either very high or very low range of surface temperatures.

  2. Learned EEG-based regulation of motor-related brain oscillations during application of transcranial electric currents: feasibility and limitations

    Directory of Open Access Journals (Sweden)

    Surjo R Soekadar

    2014-03-01

    Full Text Available Objective: Transcranial direct current stimulation (tDCS improves motor learning and can influence emotional processing or attention. However, it remained unclear whether learned electroencephalography (EEG-based brain-machine interface (BMI control during tDCS is feasible and how application of transcranial electric currents during BMI control would interfere with feature-extraction of physiological brain signals. Here we tested this combination and evaluated stimulation-dependent artifacts across different EEG frequencies and stability of motor imagery-based BMI control. Approach: Ten healthy volunteers were invited to two BMI-sessions, each comprising two 60-trial blocks. During the trials, modulation of mu-rhythms (8-15Hz associated with motor imagery recorded over C4 was translated into online cursor movements on a computer screen. During block 2, either sham (session A or anodal tDCS (session B was applied at 1mA with the stimulation electrode placed 1cm anterior of C4. Main results: tDCS was associated with a significant signal power increase in the lower frequencies most evident in the signal spectrum of the EEG channel closest to the stimulation electrode. Stimulation-dependent signal power increase exhibited a decay of 12dB per decade, leaving frequencies above 9Hz unaffected. Analysis of BMI control performance did not indicate a difference between blocks and tDCS conditions. Conclusion: Application of tDCS during learned EEG-based self-regulation of brain oscillations above 9Hz is feasible and safe, and might improve applicability of BMI systems in patient populations.

  3. Electrical resistivity dynamics beneath a fractured sedimentary bedrock riverbed in response to temperature and groundwater-surface water exchange

    Science.gov (United States)

    Steelman, Colby M.; Kennedy, Celia S.; Capes, Donovan C.; Parker, Beth L.

    2017-06-01

    Bedrock rivers occur where surface water flows along an exposed rock surface. Fractured sedimentary bedrock can exhibit variable groundwater residence times, anisotropic flow paths, and heterogeneity, along with diffusive exchange between fractures and rock matrix. These properties of the rock will affect thermal transients in the riverbed and groundwater-surface water exchange. In this study, surface electrical methods were used as a non-invasive technique to assess the scale and temporal variability of riverbed temperature and groundwater-surface water interaction beneath a sedimentary bedrock riverbed. Conditions were monitored at a semi-daily to semi-weekly interval over a full annual period that included a seasonal freeze-thaw cycle. Surface electromagnetic induction (EMI) and electrical resistivity tomography (ERT) methods captured conditions beneath the riverbed along a pool-riffle sequence of the Eramosa River in Canada. Geophysical datasets were accompanied by continuous measurements of aqueous specific conductance, temperature, and river stage. Time-lapse vertical temperature trolling within a lined borehole adjacent to the river revealed active groundwater flow zones along fracture networks within the upper 10 m of rock. EMI measurements collected during cooler high-flow and warmer low-flow periods identified a spatiotemporal riverbed response that was largely dependent upon riverbed morphology and seasonal groundwater temperature. Time-lapse ERT profiles across the pool and riffle sequence identified seasonal transients within the upper 2 and 3 m of rock, respectively, with spatial variations controlled by riverbed morphology (pool versus riffle) and dominant surficial rock properties (competent versus weathered rock rubble surface). While the pool and riffle both exhibited a dynamic resistivity through seasonal cooling and warming cycles, conditions beneath the pool were more variable, largely due to the formation of river ice during the winter season

  4. Surface layer structure of AISI 1020 steel at different stages of dry sliding under electric current of high density

    OpenAIRE

    Aleutdinov, K. A.; Rubtsov, Valery Evgenjevich; Fadin, V. V.; Aleutdinova, M. I.

    2016-01-01

    Wear intensity of the sliding electric contact steel 1020/steel 1045 depending on sliding time is presented at the contact current density higher than 100 A/cm{2} without lubricant. It is shown that wear intensity of 1020 steel decreases at increasing of sliding time. Wear intensity is stabilized after some sliding time. This time (burn-in time) decreases at reduction of current density. Structural changes are realized in surface layer. Signs of liquid phase are observed on sliding surface. T...

  5. Surface electrical capacitance as an index of epidermal barrier properties of composite skin substitutes and skin autografts.

    Science.gov (United States)

    Goretsky, M J; Supp, A P; Greenhalgh, D G; Warden, G D; Boyce, S T

    1995-01-01

    Restoration of the epidermal barrier is a requirement for burn wound closure. A rapid, reliable, and noninvasive measure of the rate of restoration of the epidermal barrier is not readily available. To monitor the reformation of the epidermal barrier, we measured surface electrical capacitance on cultured skin substitutes (human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates) and split-thickness skin autografts grafted to patients. Data were collected from four patients with burns and one pediatric patient with a congenital hairy nevus comprising > 60% total body surface area. Capacitance measurements were performed at days 7, 10, 12, 14, and 28 by direct contact of the capacitance probe for 10 seconds to the cultured skin substitutes or split-thickness autograft. On postoperative days 7, 10, 12, 14, 21, and 28, the surface electrical capacitance of cultured skin substitutes after 10 seconds of sampling was 2468 +/- 268, 1443 +/- 439, 129 +/- 43, 200 +/- 44, 88 +/- 20, and 74 +/- 19 picofarads (mean +/- standard error of the mean), respectively. Surface electrical capacitance for split-thickness autograft on the same days was 1699 +/- 371, 1914 +/- 433, 125 +/- 16, 175 +/- 63, 110 +/- 26, 271 +/- 77 picofarads, respectively. Surface electrical capacitance in all of the grafts decreased with time. Cultured skin substitutes had approximately the same 10-second capacitance values as split-thickness autograft during 3 weeks of healing and approached values for uninjured skin (32 +/- 5 picofarads) by 12 days. Measurement of surface electrical capacitance is a direct, inexpensive, and convenient index for noninvasive monitoring of epidermal barrier formation.

  6. Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water

    Directory of Open Access Journals (Sweden)

    Htet Htet Kyaw

    2015-10-01

    Full Text Available Surface Plasmon Resonance (SPR sensors are widely used in diverse applications. For detecting heavy metal ions in water, surface functionalization of the metal surface is typically used to adsorb target molecules, where the ionic concentration is detected via a resonance shift (resonance angle, resonance wavelength or intensity. This paper studies the potential of a possible alternative approach that could eliminate the need of using surface functionalization by the application of an external electric field in the flow channel. The exerted electrical force on the ions pushes them against the surface for enhanced adsorption; hence it is referred to as “Electric-Field assisted SPR system”. High system sensitivity is achieved by monitoring the time dynamics of the signal shift. The ion deposition dynamics are discussed using a derived theoretical model based on ion mobility in water. On the application of an appropriate force, the target ions stack onto the sensor surface depending on the ionic concentration of target solution, ion mass, and flow rate. In the experimental part, a broad detection range of target cadmium ions (Cd2+ in water from several parts per million (ppm down to a few parts per billion (ppb can be detected.

  7. Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water

    Energy Technology Data Exchange (ETDEWEB)

    Kyaw, Htet Htet [Department of Physics, College of Science, Sultan Qaboos University, P. O. Box 36, Al-Khoud 123 (Oman); Boonruang, Sakoolkan, E-mail: sakoolkan.boonruang@nectec.or.th, E-mail: waleed.m@bu.ac.th [Photonics Technology Laboratory, National Electronics and Computer Technology Center (NECTEC), 112 Thailand Science Park, PathumThani 12120 (Thailand); Mohammed, Waleed S., E-mail: sakoolkan.boonruang@nectec.or.th, E-mail: waleed.m@bu.ac.th [Center of Research in Optoelectronics, Communication and Control Systems (BUCROCCS), School of Engineering, Bangkok University, PathumThani 12120 (Thailand); Dutta, Joydeep [Functional Materials Division, School of Information and Communication Technology, KTH Royal Institute of Technology, Isafjordsgatan 22, SE-164 40 Kista, Stockholm (Sweden)

    2015-10-15

    Surface Plasmon Resonance (SPR) sensors are widely used in diverse applications. For detecting heavy metal ions in water, surface functionalization of the metal surface is typically used to adsorb target molecules, where the ionic concentration is detected via a resonance shift (resonance angle, resonance wavelength or intensity). This paper studies the potential of a possible alternative approach that could eliminate the need of using surface functionalization by the application of an external electric field in the flow channel. The exerted electrical force on the ions pushes them against the surface for enhanced adsorption; hence it is referred to as “Electric-Field assisted SPR system”. High system sensitivity is achieved by monitoring the time dynamics of the signal shift. The ion deposition dynamics are discussed using a derived theoretical model based on ion mobility in water. On the application of an appropriate force, the target ions stack onto the sensor surface depending on the ionic concentration of target solution, ion mass, and flow rate. In the experimental part, a broad detection range of target cadmium ions (Cd{sup 2+}) in water from several parts per million (ppm) down to a few parts per billion (ppb) can be detected.

  8. The advantages of the surface Laplacian in brain-computer interface research.

    Science.gov (United States)

    McFarland, Dennis J

    2015-09-01

    Brain-computer interface (BCI) systems frequently use signal processing methods, such as spatial filtering, to enhance performance. The surface Laplacian can reduce spatial noise and aid in identification of sources. In BCI research, these two functions of the surface Laplacian correspond to prediction accuracy and signal orthogonality. In the present study, an off-line analysis of data from a sensorimotor rhythm-based BCI task dissociated these functions of the surface Laplacian by comparing nearest-neighbor and next-nearest neighbor Laplacian algorithms. The nearest-neighbor Laplacian produced signals that were more orthogonal while the next-nearest Laplacian produced signals that resulted in better accuracy. Both prediction and signal identification are important for BCI research. Better prediction of user's intent produces increased speed and accuracy of communication and control. Signal identification is important for ruling out the possibility of control by artifacts. Identifying the nature of the control signal is relevant both to understanding exactly what is being studied and in terms of usability for individuals with limited motor control. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Effects of on-board storage and electrical stunning of wild cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on brain and heart activity

    NARCIS (Netherlands)

    Lambooij, E.; Digre, H.; Reimert, H.G.M.; Aursand, I.G.; Grimso, L.; Vis, van de J.W.

    2012-01-01

    Cod and haddock captured with commercial trawling gear were taken immediately after landing on deck to on-board storage in dry bins for measuring brain and heart activity, and behaviour. Other groups were first stored in holding tanks and then electrically stunned with a prototype "dry stunner". For

  10. A bioluminescence ATP assay for estimating surface hydrophobicity and membrane damage of Escherichia coli cells treated with pulsed electric fields

    Science.gov (United States)

    Pulse Electric Field (PEF) treatments, a non-thermal process have been reported to injure and inactivate bacteria in liquid foods. However, the effect of this treatment on bacterial cell surface charge and hydrophobicity has not been investigated. Apple juice (AJ, pH 3.8) purchased from a wholesale ...

  11. The role of the cell surface LRP and soluble LRP in blood-brain barrier Abeta clearance in Alzheimer's disease.

    Science.gov (United States)

    Deane, R; Sagare, A; Zlokovic, B V

    2008-01-01

    Low-density lipoprotein receptor related protein-1 (LRP) is a member of the low-density lipoprotein (LDL) receptor family which has been linked to Alzheimer's disease (AD) by biochemical and genetic evidence. Levels of neurotoxic amyloid beta-peptide (Abeta) in the brain are elevated in AD contributing to the disease process and neuropathology. Faulty Abeta clearance from the brain appears to mediate focal Abeta accumulations in AD. Central and peripheral production of Abeta from Abeta-precursor protein (APP), transport of peripheral Abeta into the brain across the blood-brain barrier (BBB) via receptor for advanced glycation end products (RAGE), enzymatic Abeta degradation, Abeta oligomerization and aggregation, neuroinflammatory changes and microglia activation, and Abeta elimination from brain across the BBB by cell surface LRP; all may control brain Abeta levels. Recently, we have shown that a soluble form of LRP (sLRP) binds 70 to 90 % of plasma Abeta, preventing its access to the brain. In AD individuals, the levels of LRP at the BBB are reduced, as are levels of Abeta binding to sLRP in plasma. This, in turn, may increase Abeta brain levels through a decreased efflux of brain Abeta at the BBB and/or reduced sequestration of plasma Abeta associated with re-entry of free Abeta into the brain via RAGE. Thus, therapies which increase LRP expression at the BBB and/or enhance the peripheral Abeta "sink" activity of sLRP, hold potential to control brain Abeta accumulations, neuroinflammation and cerebral blood flow reductions in AD.

  12. Re-Inversion of Surface Electrical Resistivity Tomography Data from the Hanford Site B-Complex

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Timothy C.; Wellman, Dawn M.

    2013-05-01

    This report documents the three-dimensional (3D) inversion results of surface electrical resistivity tomography (ERT) data collected over the Hanford Site B-Complex. The data were collected in order to image the subsurface distribution of electrically conductive vadose zone contamination resulting from both planned releases of contamination into subsurface infiltration galleries (cribs, trenches, and tile fields), as well as unplanned releases from the B, BX, and BY tank farms and/or associated facilities. Electrically conductive contaminants are those which increase the ionic strength of pore fluids compared to native conditions, which comprise most types of solutes released into the subsurface B-Complex. The ERT data were collected and originally inverted as described in detail in report RPP-34690 Rev 0., 2007, which readers should refer to for a detailed description of data collection and waste disposal history. Although the ERT imaging results presented in that report successfully delineated the footprint of vadose zone contamination in areas outside of the tank farms, imaging resolution was not optimized due to the inability of available inversion codes to optimally process the massive ERT data set collected at the site. Recognizing these limitations and the potential for enhanced ERT characterization and time-lapse imaging at contaminated sites, a joint effort was initiated in 2007 by the U.S. Department of Energy – Office of Science (DOE-SC), with later support by the Office of Environmental Management (DOE-EM), and the U.S. Department of Defense (DOD), to develop a high-performance distributed memory parallel 3D ERT inversion code capable of optimally processing large ERT data sets. The culmination of this effort was the development of E4D (Johnson et al., 2010,2012) In 2012, under the Deep Vadose Zone Applied Field Research Initiative (DVZ-AFRI), the U.S. Department of Energy – Richland Operations Office (DOE-RL) and CH2M Hill Plateau Remediation

  13. Surface-based brain morphometry and diffusion tensor imaging in schizoaffective disorder.

    Science.gov (United States)

    Landin-Romero, Ramón; Canales-Rodríguez, Erick J; Kumfor, Fiona; Moreno-Alcázar, Ana; Madre, Mercè; Maristany, Teresa; Pomarol-Clotet, Edith; Amann, Benedikt L

    2017-01-01

    The profile of grey matter abnormalities and related white-matter pathology in schizoaffective disorder has only been studied to a limited extent. The aim of this study was to identify grey- and white-matter abnormalities in patients with schizoaffective disorder using complementary structural imaging techniques. Forty-five patients meeting Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition criteria and Research Diagnostic Criteria for schizoaffective disorder and 45 matched healthy controls underwent structural-T1 and diffusion magnetic resonance imaging to enable surface-based brain morphometry and diffusion tensor imaging analyses. Analyses were conducted to determine group differences in cortical volume, cortical thickness and surface area, as well as in fractional anisotropy and mean diffusivity. At a threshold of p = 0.05 corrected, all measures revealed significant differences between patients and controls at the group level. Spatial overlap of abnormalities was observed across the various structural neuroimaging measures. In grey matter, patients with schizoaffective disorder showed abnormalities in the frontal and temporal lobes, striatum, fusiform, cuneus, precuneus, lingual and limbic regions. White-matter abnormalities were identified in tracts connecting these areas, including the corpus callosum, superior and inferior longitudinal fasciculi, anterior thalamic radiation, uncinate fasciculus and cingulum bundle. The spatial overlap of abnormalities across the different imaging techniques suggests widespread and consistent brain pathology in schizoaffective disorder. The abnormalities were mainly detected in areas that have commonly been reported to be abnormal in schizophrenia, and to some extent in bipolar disorder, which may explain the clinical and aetiological overlap in these disorders.

  14. Determination of Surface Potential and Electrical Double-Layer Structure at the Aqueous Electrolyte-Nanoparticle Interface

    Directory of Open Access Journals (Sweden)

    Matthew A. Brown

    2016-01-01

    Full Text Available The structure of the electrical double layer has been debated for well over a century, since it mediates colloidal interactions, regulates surface structure, controls reactivity, sets capacitance, and represents the central element of electrochemical supercapacitors. The surface potential of such surfaces generally exceeds the electrokinetic potential, often substantially. Traditionally, a Stern layer of nonspecifically adsorbed ions has been invoked to rationalize the difference between these two potentials; however, the inability to directly measure the surface potential of dispersed systems has rendered quantitative measurements of the Stern layer potential, and other quantities associated with the outer Helmholtz plane, impossible. Here, we use x-ray photoelectron spectroscopy from a liquid microjet to measure the absolute surface potentials of silica nanoparticles dispersed in aqueous electrolytes. We quantitatively determine the impact of specific cations (Li^{+}, Na^{+}, K^{+}, and Cs^{+} in chloride electrolytes on the surface potential, the location of the shear plane, and the capacitance of the Stern layer. We find that the magnitude of the surface potential increases linearly with the hydrated-cation radius. Interpreting our data using the simplest assumptions and most straightforward understanding of Gouy-Chapman-Stern theory reveals a Stern layer whose thickness corresponds to a single layer of water molecules hydrating the silica surface, plus the radius of the hydrated cation. These results subject electrical double-layer theories to direct and falsifiable tests to reveal a physically intuitive and quantitatively verified picture of the Stern layer that is consistent across multiple electrolytes and solution conditions.

  15. Influence of Surface Modified MWCNTs on the Mechanical, Electrical and Thermal Properties of Polyimide Nanocomposites

    Directory of Open Access Journals (Sweden)

    Singh Deepankar

    2008-01-01

    Full Text Available Abstract Polyamic acid, the precursor of polyimide, was used for the preparation of polyimide/multiwalled carbon nanotubes (MWCNTs nanocomposite films by solvent casting technique. In order to enhance the chemical compatibility between polyimide matrix and MWCNTs, the latter was surface modified by incorporating acidic and amide groups by chemical treatment with nitric acid and octadecylamine (C18H39N, respectively. While the amide-MWCNT/polyimide composite shows higher mechanical properties at low loadings (<3 wt%, the acid-MWCNT/polyimide composites perform better at higher loadings (5 wt%. The tensile strength (TS and the Young’s modulus (YM values of the acid-MWCNT/polyimide composites at 5 wt% MWCNT loadings was 151 and 3360 MPa, respectively, an improvement of 54% in TS and 35% in YM over the neat polyimide film (TS = 98 MPa; YM = 2492 MPa. These MWCNT-reinforced composites show remarkable improvement in terms of thermal stability as compared to that for pure polyimide film. The electrical conductivity of 5 wt% acid modified MWCNTs/polyimide nanocomposites improved to 0.94 S cm −1(6.67 × 10 −18 S cm−1for pure polyimide the maximum achieved so far for MWCNT-polyimide composites.

  16. Gum ghatti based novel electrically conductive biomaterials: A study of conductivity and surface morphology

    Directory of Open Access Journals (Sweden)

    S. Kalia

    2014-04-01

    Full Text Available Gum ghatti-cl-poly(acrylamide-aniline interpenetrating network (IPN was synthesized by a two-step aqueous polymerization method, in which aniline monomer was absorbed into the network of gum ghatti-cl-poly(acrylamide and followed by a polymerization reaction between aniline monomers. Initially, semi-IPN based on acrylamide and gum ghatti was prepared by free-radical copolymerization in aqueous media with optimized process parameters, using N,N'-methylenebis-acrylamide, as cross-linker and ammonium persulfate, as an initiator system. Optimum reaction conditions affording maximum percentage swelling were: solvent [mL] =12, Acrylamide (AAm [mol•L–1] = 1.971, Ammonium peroxydisulfate (APS [mol•L–1] = 0.131•10–1, N,N'-methylene-bis-acrylamide (MBA [mol•L–1] = 0.162•10–1, reaction time [min] = 210, temperature [°C] = 100 and pH = 7.0. The resulting IPN was doped with different protonic acids. The effect of the doping has been investigated on the conductivity and surface morphology of the IPN hydrogel. The maximum conductivity was observed with 1.5N HClO4 concentration. The morphological, structural and electrical properties of the candidate polymers were studied using scanning electron micrscopy (SEM, Fourier transform infrared spectroscopy FTIR and two-probe method, respectively.

  17. Optical and electrical characteristics of N2 micro-discharges produced in coplanar surface DBD geometry

    Science.gov (United States)

    Simek, Milan; Prukner, Vaclav; Schmidt, Jiri

    2008-10-01

    Basic optical and electrical characteristics of nitrogen micro-discharges generated in an AC surface DBD reactor with coplanar electrode arrangement were studied at atmospheric pressure by means of the ICCD microscopy and spectrometry complemented with the multi-channel photon-counting. Temporal evolutions of N2-2.PG (second positive), N2-HIR (Hermann infrared), NO-gamma and N2^+-1.NG (first negative) bands induced by an individual H-shaped micro-discharge generated during positive/negative AC half-cycle were acquired and analyzed. Typical emission waveforms were inspected as function of both frequency and amplitude of the modulated AC driving high-voltage, in the case of a) a single micro-discharge produced during an AC half-cycle and b) multiple, equally spaced micro-discharges produced during an AC half-cycle. Observed waveforms and obtained characteristic time constants will be discussed in the frame of electron impact excitation/ionization, N2(A)+N2(A) energy pooling and N2(A)+NO resonant energy transfer processes.

  18. Wire Electrical Discharge Machining of a Hybrid Composite: Evaluation of Kerf Width and Surface Roughness

    Directory of Open Access Journals (Sweden)

    Abdil KUŞ

    2016-06-01

    Full Text Available In this study, the machinability characteristics of Al/B4C-Gr hybrid composite were investigated using wire electrical discharge machining (WEDM. In the experiments, the machining parameters of wire speed, pulse-on time and pulse-off time were varied in order to explaiın their effects on machining performance, including the width of slit (kerf and surface roughness values (Rz and Rt. According to the Taguchi quality design concept, a L18 (21×32 orthogonal array was used to determine the S/N ratio, and analysis of variance (ANOVA and the F-test were used to indicate the significant machining parameters affecting the machining performance. From the ANOVA and F-test results, the significant factors were determined for each of the machining performance criteria of kerf, Rz and Rt. The variations of kerf, Rz and Rt with the machining parameters were statistically modeled via the regression analysis method. The optimum levels of the control factors for kerf, Rz and Rt were specified as A1B1C1, A1B1C2 and A1B1C2, respectively. The correlation coefficients of the predictive equations developed for kerf, Rz and Rt were calculated as 0.98, 0.828 and 0.855, respectively.

  19. Evidence of self-organization in brain electrical activity using wavelet-based informational tools

    Science.gov (United States)

    Rosso, O. A.; Martin, M. T.; Plastino, A.

    2005-03-01

    In the present work, we show that appropriate information-theory tools based on the wavelet transform (relative wavelet energy; normalized total wavelet entropy, H; generalized wavelet complexity, CW), when applied to tonic-clonic epileptic EEG data, provide one with valuable insights into the dynamics of neural activity. Twenty tonic-clonic secondary generalized epileptic records pertaining to eight patients have been analyzed. If the electromyographic activity is excluded the difference between the ictal and pre-ictal mean entropic values (ΔH=-) is negative in 95% of the cases (p-) is positive in 85% of the cases (p=0.0002). Thus during the seizure entropy diminishes while complexity grows. This is construed as evidence supporting the conjecture that an epileptic focus in this kind of seizures triggers a self-organized brain state characterized by both order and maximal complexity.

  20. Significance probability mapping: an aid in the topographic analysis of brain electrical activity.

    Science.gov (United States)

    Duffy, F H; Bartels, P H; Burchfiel, J L

    1981-05-01

    We illustrate the application of significance probability mapping (SPM) to the analysis of topographic maps of spectral analyzed EEG and visual evoked potential (VEP) activity from patients with brain tumors, boys with dyslexia, and control subjects. When the VEP topographic plots of tumor patients were displayed as number of standard deviations from a reference mean, more subjects were correctly identified than by inspection of the underlying raw data. When topographic plots of EEG alpha activity obtained while listening to speech or music were compared by t statistic to plots of resting alpha activity, regions of cortex presumably activated by speech or music were delineated. DIfferent regions were defined in dyslexic boys and controls. We propose that SPM will prove valuable in the regional localization of normal and abnormal functions in other clinical situations.

  1. A hybrid Taguchi-artificial neural network approach to predict surface roughness during electric discharge machining of titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sanjeev; Batish, Ajay [Thapar University, Patiala (India); Singh, Rupinder [GNDEC, Ludhiana (India); Singh, T. P. [Symbiosis Institute of Technology, Pune (India)

    2014-07-15

    In the present study, electric discharge machining process was used for machining of titanium alloys. Eight process parameters were varied during the process. Experimental results showed that current and pulse-on-time significantly affected the performance characteristics. Artificial neural network coupled with Taguchi approach was applied for optimization and prediction of surface roughness. The experimental results and the predicted results showed good agreement. SEM was used to investigate the surface integrity. Analysis for migration of different chemical elements and formation of compounds on the surface was performed using EDS and XRD pattern. The results showed that high discharge energy caused surface defects such as cracks, craters, thick recast layer, micro pores, pin holes, residual stresses and debris. Also, migration of chemical elements both from electrode and dielectric media were observed during EDS analysis. Presence of carbon was seen on the machined surface. XRD results showed formation of titanium carbide compound which precipitated on the machined surface.

  2. The feasibility of a brain-computer interface functional electrical stimulation system for the restoration of overground walking after paraplegia.

    Science.gov (United States)

    King, Christine E; Wang, Po T; McCrimmon, Colin M; Chou, Cathy C Y; Do, An H; Nenadic, Zoran

    2015-09-24

    Direct brain control of overground walking in those with paraplegia due to spinal cord injury (SCI) has not been achieved. Invasive brain-computer interfaces (BCIs) may provide a permanent solution to this problem by directly linking the brain to lower extremity prostheses. To justify the pursuit of such invasive systems, the feasibility of BCI controlled overground walking should first be established in a noninvasive manner. To accomplish this goal, we developed an electroencephalogram (EEG)-based BCI to control a functional electrical stimulation (FES) system for overground walking and assessed its performance in an individual with paraplegia due to SCI. An individual with SCI (T6 AIS B) was recruited for the study and was trained to operate an EEG-based BCI system using an attempted walking/idling control strategy. He also underwent muscle reconditioning to facilitate standing and overground walking with a commercial FES system. Subsequently, the BCI and FES systems were integrated and the participant engaged in several real-time walking tests using the BCI-FES system. This was done in both a suspended, off-the-ground condition, and an overground walking condition. BCI states, gyroscope, laser distance meter, and video recording data were used to assess the BCI performance. During the course of 19 weeks, the participant performed 30 real-time, BCI-FES controlled overground walking tests, and demonstrated the ability to purposefully operate the BCI-FES system by following verbal cues. Based on the comparison between the ground truth and decoded BCI states, he achieved information transfer rates >3 bit/s and correlations >0.9. No adverse events directly related to the study were observed. This proof-of-concept study demonstrates for the first time that restoring brain-controlled overground walking after paraplegia due to SCI is feasible. Further studies are warranted to establish the generalizability of these results in a population of individuals with paraplegia

  3. Processing and Characterization of Novel Biomimetic Nanoporous Bioceramic Surface on β-Ti Implant by Powder Mixed Electric Discharge Machining

    Science.gov (United States)

    Prakash, Chander; Kansal, H. K.; Pabla, B. S.; Puri, Sanjeev

    2015-09-01

    Herein, a β-Ti-based implant was subjected to powder mixed electric discharge machining (PMEDM) for surface modification to produce a novel biomimetic nanoporous bioceramic surface. The microstructure, surface topography, and phase composition of the non-machined and machined (PMEDMed) surfaces were investigated using field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. The microhardness of the surfaces was measured on a Vickers hardness tester. The corrosion resistance of the surfaces was evaluated via potentiodynamic polarization measurements in simulated body fluid. The application of PMEDM not only altered the surface chemistry, but also imparted the surface with a nanoporous topography or a natural bone-like surface structure. The characterization results confirmed that the alloyed layer mainly comprised bioceramic oxides and carbide phases (TiO2, Nb2O5, ZrO2, SiO2, TiC, NbC, SiC). The microhardness of PMEDMed surface was twofold higher than that of the base material (β-Ti alloy), primarily because of the formation of the hard carbide phases on the machined layer. Electrochemical analysis revealed that PMEDMed surface featured insulative and protective properties and thus displayed higher corrosion resistance ability when compared with the non-machined surface. This result was attributed to the formation of the bioceramic oxides on the machined surface. Additionally, the in vitro biocompatibility of the surfaces was evaluated using human osteoblastic cell line MG-63. PMEDMed surface with a micro-, sub-micro-, and nano-structured topography exhibited bioactivity and improved biocompatibility relative to β-Ti surface. Furthermore, PMEDMed surface enabled better adhesion and growth of MG-63 when compared with the non-machined substrate.

  4. Three-dimensional brain-surface MR images of brain anomalies in Fukuyama congenital muscular dystrophy and its differentiation from Duchenne muscular dystrophy with severe mental retardation

    Energy Technology Data Exchange (ETDEWEB)

    Toda, Tatsushi; Watanabe, Toshiaki; Shimizu, Teruo; Iwata, Makoto; Kanazawa, Ichiro (Tokyo Univ. (Japan). Faculty of Medicine); Matsumura, Kiichiro

    1993-12-01

    Fukuyama congenital muscular dystrophy (FCMD) is the second most common form of muscular dystrophy in Japan and is peculiarly associated with brain anomalies such as micropolygyria. Since these anomalies are preferentially observed on the brain surface, it is difficult to identify them by either X-ray CT or conventional MRI. In addition, FCMD has an atypical (mild) form in which the patients are capable of walking. In such cases, clinical differential diagnosis from Duchenne muscular dystrophy with severe mental retardation (DMD-MR) is not necessarily easy. We analyzed the brain-surface structures of 4 typical FCMD cases. 1 atypical FCMD case, 4 DMD-MR cases, and 1 undiagnosed case using a method of 3-dimensional (3-D) brain-surface MR imaging; we then compared the results with dystrophin immuno-stainings of the biopsied skeletal muscles. In both typical and atypical FCMD cases, micropolygyria could be clearly demonstrated, with individual variations. The 3-D images were verified by neuropathology. Of the 4 DMD-MR cases, 3 cases showed no gyral abnormality. However, in 1 DMD-MR case the diagnosis was corrected to atypical FCMD because of micropolygyria found on 3-D MRI. The one undiangosed case was diagnosed as DMD-MR on the basis of 3-D MRI. There was a good correspondence between the results of the 3-D imaging and the dystrophin test. Recently, some FCMD cases with a complete deficiency of dystrophin have been reported. Therefore, the detection of brain anomalies is important for the precise diagnosis of FCMD; the present method is considered effective for this purpose. (author).

  5. The costs of a big brain: extreme encephalization results in higher energetic demand and reduced hypoxia tolerance in weakly electric African fishes.

    Science.gov (United States)

    Sukhum, Kimberley V; Freiler, Megan K; Wang, Robert; Carlson, Bruce A

    2016-12-28

    A large brain can offer several cognitive advantages. However, brain tissue has an especially high metabolic rate. Thus, evolving an enlarged brain requires either a decrease in other energetic requirements, or an increase in overall energy consumption. Previous studies have found conflicting evidence for these hypotheses, leaving the metabolic costs and constraints in the evolution of increased encephalization unclear. Mormyrid electric fishes have extreme encephalization comparable to that of primates. Here, we show that brain size varies widely among mormyrid species, and that there is little evidence for a trade-off with organ size, but instead a correlation between brain size and resting oxygen consumption rate. Additionally, we show that increased brain size correlates with decreased hypoxia tolerance. Our data thus provide a non-mammalian example of extreme encephalization that is accommodated by an increase in overall energy consumption. Previous studies have found energetic trade-offs with variation in brain size in taxa that have not experienced extreme encephalization comparable with that of primates and mormyrids. Therefore, we suggest that energetic trade-offs can only explain the evolution of moderate increases in brain size, and that the energetic requirements of extreme encephalization may necessitate increased overall energy investment. © 2016 The Author(s).

  6. Experimental assessment of the surface temperature of copper electrodes submitted to an electric arc in air at atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Landfried, R; Leblanc, T; Andlauer, R; Teste, Ph, E-mail: teste@lgep.supelec.fr [Laboratoire de Genie Electrique de Paris : SUPELEC - CNRS - Universites Paris VI et Paris XI - Plateau de Moulon - 91192 Gif sur Yvette Cedex (France)

    2011-01-01

    This paper concerns the assessment of the surface temperature of copper electrodes submitted to an electric arc in a non stationary regime in air. An infrared camera is used to measure the decrease of the temperature surface just after a controlled and very fast arc extinction. In the first part, the experimental method is described. In the second part, results are presented for 60-70 A with an electric arc duration in the range 3-4 ms. The temperature decrease after the arc extinction allows to reach an assessment of the surface temperature just at the arc switching off. In the present experimental conditions the mean temperatures reached for copper cathodes and anodes are in the range 750-850 deg. C.

  7. The Dynamics of the Electric Field Distribution in the Surface of Insulating Film Irradiated by Air Ions

    Directory of Open Access Journals (Sweden)

    Julionas KALADE

    2016-05-01

    Full Text Available When deposited on a surface, electric charge usually accumulates near the tips of surface irregularities, from where it can be transferred to nearby objects due to ionization of ambient air. The amount of transferred charge, the rate of charge transfer, the size of the charged spot (e.g., on the surface of an insulator and its tendency to spread will depend on properties of air during electric discharge, on the magnitude of charge accumulated at the tip of an object, on possibilities for replenishing that charge, on the time spent for charge transfer from the tip onto the insulating layer, on properties of the insulating layer, etc. Those properties are discussed in this work by comparing the results of measurements and theoretical analysis.

  8. Large-scale surface dielectric barrier discharge type reactor : effect of the electric wind on the conversion effectiveness

    Energy Technology Data Exchange (ETDEWEB)

    Jolibois, J. [Univ. de Poitiers, Poitiers (France). Centre national de la recherche scientifique, Laboratoire de Catalyse en Chimie Organique; Poitiers Univ., Futuroscope Chasseneuil Cedex (France). Centre national de la recherche scientifique, Inst. Pprime; Zouzou, N.; Moreau, E. [Poitiers Univ., Futuroscope Chasseneuil Cedex (France). Centre national de la recherche scientifique, Inst. Pprime; Tatibouet, J.M. [Univ. de Poitiers, Poitiers (France). Centre national de la recherche scientifique, Laboratoire de Catalyse en Chimie Organique

    2010-07-01

    Non-thermal plasma (NTP) techniques offer an innovative approach for air pollution reduction. Most studies in NTP techniques use volumetric discharge reactors with small dimensions and low flow rates at laboratory scale. The objective of this study was to develop an air pollution control plasma reactor at industrial scale with surface discharge. Propene (C{sub 3}H{sub 6}) was oxidized at high flow rates in a large-scale plasma reactor based on surface dielectric barrier discharge (DBD). Three different configurations of surface discharges were tested with 15 ppm of C{sub 3}H{sub 6} in air at ambient temperature for a flow rate of 50 m{sup 3} per hour. The properties of these different surface discharges were analyzed using chemical measurements and 3 component particle image velocimetry (PIV) measurements. PIV measurements were used characterize the effect of the electric wind on the polluted gas airflow inside the reactor and to explain the differences of effectiveness of the three tested plasma generators. For the three plasma generators, a propene oxidation of up to 45 percent was obtained at one J per liter. The electric wind produced by the surface discharge resulted in the formation of vortices inside the plasma reactor. This electric wind can increase gas mixing inside the plasma reactor and therefore plays a key role in conversion efficiency. It was concluded that the electric wind produced by surface discharges enables the use of this type of discharge for VOC elimination at high flow rate, with the same effectiveness of volumetric discharges. 5 refs., 10 figs.

  9. Surface-enhanced IR absorption spectroscopy of the KcsA potassium channel upon application of an electric field.

    Science.gov (United States)

    Yamakata, Akira; Shimizu, Hirofumi; Oiki, Shigetoshi

    2015-09-07

    Surface-enhanced IR absorption spectroscopy (SEIRAS) is a powerful tool for studying the structure of molecules adsorbed on an electrode surface (ATR-SEIRA). Coupled with an electrochemical system, structural changes induced by changes in the electric field can be detected. All the membrane proteins are subjected to the effect of membrane electric field, but conformational changes at different membrane potentials and their functional relevance have not been studied extensively except for channel proteins. In this contribution, background information of potential-dependent functional and structural changes of a prototypical channel, the KcsA channel, is summarized, and SEIRAS applied to the KcsA channel under the application of the potential is shown. The potassium channels allow K(+) to permeate selectively through the structural part called the selectivity filter, in which dehydrated K(+) ions interact with backbone carbonyls. In the absence of K(+), the selectivity filter undergoes conformational changes to the non-conductive collapsed conformation. To apply the electric field, the KcsA channels were fixed on the gold surface in either upside or reverse orientation. The SEIRA spectrum in K(+) or Na(+) solution revealed both backbone structural changes and local changes in the OCO-carboxylate groups. Upon application of the negative electric field, the spectrum of OCO was enhanced only in the K(+) solution. These results indicate that the negative electric field accumulates local K(+) concentration, which turned the collapsed filter to the conductive conformation. ATR-SEIRA serves as an unprecedented experimental system for examining membrane proteins under an electric field.

  10. New superjuction LDMOS with surface and bulk electric field modulation by buffered step doping and multi floating buried layers

    Science.gov (United States)

    Cao, Zhen; Duan, Baoxing; Yuan, Song; Shi, Tongtong; Yang, Yintang

    2017-11-01

    A new superjunction lateral double diffused MOSFET with surface and bulk electric field modulation (SBEFM SJ-LDMOS) by applying of multiple floating buried layers and buffered step doping is proposed in this paper. The Multiple N-type floating buried layers are embedded in P-substrate, to reduce the amount of field crowding at N+/N-buffer/P-substrate junction by spreading the vertical depletion layer, which effectively improves the bulk electric field distribution in SJ-LDMOS, and the N+/N-buffer/P-substrate junction and the auxiliary MFB layers/substrate junctions jointly sustain a high vertical breakdown voltage (BV). In addition, based on the buffered step doping layer under the SJ layer, a uniform lateral electric field at the drift region surface of the device is obtained. Therefore, the bulk and surface electric field are both optimized simultaneously in SBEFM SJ-LDMOS. Simulated results show that compared with the conventional Buffered SJ-LDMOS and BSD SJ-LDMOS, the proposed SBEFM SJ-LDMOS improves BV by 131.7% and 80.4%, respectively, at the same drift region length and with low specific ON-resistance (RON,sp). SBEFM SJ-LDMOS exhibits excellent performance with the power figure-of-merit (FOM=BV2/RON,sp) of 13.07 MW/cm2.

  11. Effects of strong earthquakes in variations of electrical and meteorological parameters of the near-surface atmosphere in Kamchatka region

    Science.gov (United States)

    Smirnov, S. E.; Mikhailova, G. A.; Mikhailov, Yu. M.; Kapustina, O. V.

    2017-09-01

    The diurnal variations in electrical (quasistatic electric field and electrical conductivity) and meteorological (temperature, pressure, relative humidity of the atmosphere, and wind speed) parameters, measured simultaneously before strong earthquakes in Kamchatka region (November 15, 2006, M = 8.3; January 13, 2007, M = 8.1; January 30, 2016, M = 7.2), are studied for the first time in detail. It is found that a successively anomalous increase in temperature, despite the negative regular trend in these winter months, was observed in the period of six-seven days before the occurrences of earthquakes. An anomalous temperature increase led to the formation of "winter thunderstorm" conditions in the near-surface atmosphere of Kamchatka region, which was manifested in the appearance of an anomalous, type 2 electrical signal, the amplification of and intensive variations in electrical conductivity, heavy precipitation (snow showers), high relative humidity of air, storm winds, and pressure changes. With the weak flow of natural heat radiation in this season, the observed dynamics of electric and meteorological processes can likely be explained by the appearance of an additional heat source of seismic nature.

  12. Tuning and disrupting the brain – modulating the McGurk illusion with electrical stimulation

    Directory of Open Access Journals (Sweden)

    Lucas M Marques

    2014-08-01

    Full Text Available In the so-called McGurk illusion, when the synchronized presentation of the visual stimulus /ga/ is paired with the auditory stimulus /ba/, people in general hear it as /da/. Multisensory integration processing underlying this illusion seems to occur within the Superior Temporal Sulcus (STS. Herein, we present evidence demonstrating that bilateral cathodal transcranial direct current stimulation (tDCS of this area can decrease the McGurk illusion-type responses. Additionally, we show that the manipulation of this audio-visual integrated output occurs irrespective of the number of eye-fixations on the mouth of the speaker. Bilateral anodal tDCS of the Parietal Cortex also modulates the illusion, but in the opposite manner, inducing more illusion-type responses. This is the first demonstration of using non-invasive brain stimulation to modulate multisensory speech perception in an illusory context (i.e., both increasing and decreasing illusion-type responses to a verbal audio-visual integration task. These findings provide clear evidence that both the superior temporal and parietal areas contribute to multisensory integration processing related to speech perception. Specifically, STS seems fundamental for the temporal synchronization and integration of auditory and visual inputs. For its part, PPC may adjust the arrival of incoming audio and visual information to STS thereby enhancing their interaction in this latter area.

  13. [Synchronization and propagation of electrical potentials in neural networks of the brain cortex].

    Science.gov (United States)

    Marchenko, V G; Zaĭchenko, M I

    2014-01-01

    On the basis of the published data the scheme is proposed which explains the spread and synhronization of oscillatory activity in cortex. The main property of the neocortex is the existence of vertically oriented functional columns. Within and between the neuronal columns exist a feedforward and feedback morphological and functional connections. At the certain conditions inside the single module temporal windows are created using inhibitory process, and a synchronized activity can be generated of variable frequency (oscillations). The activity in the columns is enhanced by the synchronous involvement of great amount of neurons which is expressed in the form of local field potentials of high amplitude. Further the information about arisen in a single generator activity is transmitted through direct links to the nearby generator or to the group of such generators. In the nearby generator the activity increases and is transferred to the next generator. At the same time the signal is transmitted through feedback to the primary generator, and the activity is terminated until the next cycle will be initiated and so on along the cortex. The most important notion is that in the transfer of activity from one generator to another is involved a small number of elements. The major part of recorded oscillations of different frequency or epileptiform discharges, is not transmitted via the brain, but is generated in each module according to the characteristics transferred to it. The generation of epileptiform spikes occurs in cases when balance of inhibition determined by GABA A and GABA B receptors is disturbed.

  14. Regional brain electrical activity in posttraumatic stress disorder after motor vehicle accident.

    Science.gov (United States)

    Rabe, Sirko; Beauducel, André; Zöllner, Tanja; Maercker, Andreas; Karl, Anke

    2006-11-01

    This study examined whether patients with posttraumatic stress disorder (PTSD) related to motor vehicle accidents (MVAs) would show an abnormal pattern of electroencephalographic (EEG) alpha asymmetries, which has been proposed for particular types of anxiety. Patients with PTSD (n = 22) or subsyndromal PTSD (n = 21), traumatized controls without PTSD (non-PTSD with MVA; n = 21), and healthy controls without MVA (n = 23) underwent measurement of EEG activity during baseline and exposure to a neutral, a positive, a negative, and an accident-related picture. Differences in brain asymmetry between groups were observed only during exposure to trauma-related material. PTSD and subsyndromal PTSD patients showed a pattern of enhanced right anterior and posterior activation, whereas non-PTSD with MVA participants showed the opposite pattern. Furthermore, posterior asymmetry in nontraumatized healthy controls varied with gender, with female participants showing a pattern of higher right posterior activation. The results support the hypothesis that symptomatic MVA survivors are characterized by a pattern of right hemisphere activation that is associated with anxious arousal and symptoms of PTSD during processing of trauma-specific information. (c) 2006 APA, all rights reserved.

  15. The effect of surface electric stimulation of the gluteal muscles on the interface pressure in seated people with spinal cord injury

    NARCIS (Netherlands)

    van Londen, A.; Herwegh, M.; van der Zee, C.H.; Daffertshofer, A.; Smit, C.A.; Niezen, A.; Janssen, T.W.J.

    2008-01-01

    van Londen A, Herwegh M, van der Zee CH, Daffertshofer A, Smit CA, Niezen A, Janssen TW. The effect of surface electric stimulation of the gluteal muscles on the interface pressure in seated people with spinal cord injury. Objective: To study effects of surface electric stimulation of the gluteal

  16. Effect of fluorination on the surface electrical properties of epoxy resin insulation

    Science.gov (United States)

    Liu, Yaqiang; Li, Liqiang; Du, Xuelian

    2015-02-01

    Epoxy samples were surface fluorinated in a laboratory vessel using a F2/N2 gas mixture to suppress surface charge accumulation. Attenuated total reflection infrared analyses indicate that the fluorination led to substantial variations in chemical composition and structure of the sample surface layer. Measurement results of surface properties indicate that surface conductivity and wettability or polarity were dramatically increased by the fluorination. A very likely decrease in charge trap depth and the adsorbed water on the surface in air are responsible for the high surface conductivity. As a result, charge cannot accumulate on the fluorinated surface even at room temperature, rapidly transporting along the surface. Surface charging current measurements further show a much larger steady state current flowing along the fluorinated surface, suggesting much lower dynamic surface potential or charge density during charging, compared with those for the original surface.

  17. Restoration of Hindlimb Movements after Complete Spinal Cord Injury Using Brain-Controlled Functional Electrical Stimulation

    Directory of Open Access Journals (Sweden)

    Eric B. Knudsen

    2017-12-01

    Full Text Available Single neuron and local field potential signals recorded in the primary motor cortex have been repeatedly demonstrated as viable control signals for multi-degree-of-freedom actuators. Although the primary source of these signals has been fore/upper limb motor regions, recent evidence suggests that neural adaptation underlying neuroprosthetic control is generalizable across cortex, including hindlimb sensorimotor cortex. Here, adult rats underwent a longitudinal study that included a hindlimb pedal press task in response to cues for specific durations, followed by brain machine interface (BMI tasks in healthy rats, after rats received a complete spinal transection and after the BMI signal controls epidural stimulation (BMI-FES. Over the course of the transition from learned behavior to BMI task, fewer neurons were responsive after the cue, the proportion of neurons selective for press duration increased and these neurons carried more information. After a complete, mid-thoracic spinal lesion that completely severed both ascending and descending connections to the lower limbs, there was a reduction in task-responsive neurons followed by a reacquisition of task selectivity in recorded populations. This occurred due to a change in pattern of neuronal responses not simple changes in firing rate. Finally, during BMI-FES, additional information about the intended press duration was produced. This information was not dependent on the stimulation, which was the same for short and long duration presses during the early phase of stimulation, but instead was likely due to sensory feedback to sensorimotor cortex in response to movement along the trunk during the restored pedal press. This post-cue signal could be used as an error signal in a continuous decoder providing information about the position of the limb to optimally control a neuroprosthetic device.

  18. Geophysical investigation of tumuli by means of surface 3D Electrical Resistivity Tomography

    Science.gov (United States)

    Papadopoulos, Nikos G.; Yi, Myeong-Jong; Kim, Jung-Ho; Tsourlos, Panagiotis; Tsokas, Gregory N.

    2010-03-01

    Tumuli are artificially erected small hills that cover monumental tombs or graves. In this work, the surface three-dimensional (3D) Electrical Resistivity Tomography (ERT) method, composed of dense parallel two-dimensional (2D) tomographies, was used to investigate the properties of the tumuli filling material and to resolve buried archaeological structures inside the tumuli. The effectiveness of the method was investigated by numerical modeling and through 3D inversion of synthetic apparent resistivity data. A resistivity model that simulates the inhomogeneous tumulus material and the tombs that are buried inside the tumulus was assumed. The Dipole-Dipole (DD), Pole-Dipole (PD), Pole-Pole (PP), Gradient (GRAD), Midpoint-Potential-Referred (MPR) and Schlumberger Reciprocal (SCR) arrays, which are suitable for multichannel resistivity instruments, were tested. The tumulus topography (pyramid or capsized cup) was incorporated into the inversion procedure through a distorted finite element mesh. The inversion procedure was based on a smoothness constrained Gauss-Newton algorithm in which the Active Constraint Balancing (ACB) method was also applied in order to enhance the least-squares resolving power and stability. Synthetic modeling showed that the different tumulus layers and the horizontal contact of the artificial tumulus material with the natural background soil were reconstructed by all of the tested electrode arrays. Generally, PD and the GRAD arrays comprise the optimum choices to investigate the subsurface properties of a tumulus and locate buried tombs. The MPR model was inferior to the GRAD model, while the DD, PP and SCR models had the poorest resolution. It was also shown that the inversion models are practically independent from the survey direction and the topography shape of the tumulus. The real field data collected employing the PD array along a small tumulus from the archaeological site of Vergina in northern Greece enhanced the synthetic modeling

  19. Electrical polarization of titanium surfaces for the enhancement of osteoblast differentiation.

    Science.gov (United States)

    Gittens, Rolando A; Olivares-Navarrete, Rene; Rettew, Robert; Butera, Robert J; Alamgir, Faisal M; Boyan, Barbara D; Schwartz, Zvi

    2013-12-01

    Electrical stimulation has been used clinically to promote bone regeneration in cases of fractures with delayed union or nonunion, with several in vitro and in vivo reports suggesting its beneficial effects on bone formation. However, the use of electrical stimulation of titanium (Ti) implants to enhance osseointegration is less understood, in part because of the few in vitro models that attempt to represent the in vivo environment. In this article, the design of a new in vitro system that allows direct electrical stimulation of osteoblasts through their Ti substrates without the flow of exogenous currents through the media is presented, and the effect of applied electrical polarization on osteoblast differentiation and local factor production was evaluated. A custom-made polycarbonate tissue culture plate was designed to allow electrical connections directly underneath Ti disks placed inside the wells, which were supplied with electrical polarization ranging from 100 to 500 mV to stimulate MG63 osteoblasts. Our results show that electrical polarization applied directly through Ti substrates on which the cells are growing in the absence of applied electrical currents may increase osteoblast differentiation and local factor production in a voltage-dependent manner. © 2013 Wiley Periodicals, Inc.

  20. Sensitivity of the near-surface vertical electric field land Controlled-Source Electromagnetic monitoring

    NARCIS (Netherlands)

    Schaller, A.M.; Hunziker, J.W.; Streich, R.; Drijkoningen, G.G.

    2014-01-01

    We investigate potential benefits of measuring the vertical electric field component in addition to the routinely measured horizontal electric field components in onshore time-lapse controlled-source electromagnetics. Synthetic electromagnetic data based on a model of the Schoonebeek onshore oil

  1. Sensitivity of the near-surface vertical electric field land Controlled-Source Electromagnetic monitoring

    NARCIS (Netherlands)

    Schaller, A.M.; Hunziker, J.W.; Streich, R.; Drijkoningen, G.G.

    We investigate potential benefits of measuring the vertical electric field component in addition to the routinely measured horizontal electric field components in onshore time-lapse controlled-source electromagnetics. Synthetic electromagnetic data based on a model of the Schoonebeek onshore oil

  2. Two-dimensional electric current effects on a magnetized plasma in contact with a surface

    NARCIS (Netherlands)

    Shumack, A. E.; de Blank, H. J.; Westerhout, J.; van Rooij, G. J.

    2012-01-01

    Significant electric fields both parallel and perpendicular to a magnetic field have been observed and modeled self-consistently in an ITER divertor relevant plasma–wall experiment. Due to magnetization, electric current is found to penetrate the plasma beam outside of the cascaded arc plasma source

  3. Naval Academy: Low Grades in Electrical Engineering Courses Surface Broader Issues. Report to Congressional Requesters.

    Science.gov (United States)

    General Accounting Office, Washington, DC. National Security and International Affairs Div.

    This report discusses findings of a study of two issues during the 1989-90 academic year at the United States Naval Academy: the removal of the Chairman of the Electrical Engineering Department, and the Superintendent's decision to give a final electrical engineering examination that might have been compromised. The study reviewed the effect of…

  4. Spatio-temporal dynamics of kind versus hostile intentions in the human brain: An electrical neuroimaging study.

    Science.gov (United States)

    Wang, Yiwen; Huang, Liang; Zhang, Wei; Zhang, Zhen; Cacioppo, Stephanie

    2015-01-01

    Neuroscience research suggests that inferring neutral intentions of other people recruits a specific brain network within the inferior fronto-parietal action observation network as well as a putative social network including brain areas subserving theory of mind, such as the posterior superior temporal sulcus (pSTS), the temporo-parietal junction (TPJ), and also the anterior cingulate cortex (ACC). Recent studies on harmful intentions have refined this network by showing the specific involvement of the ACC, amygdala, and ventromedial prefrontal cortex (vmPFC) in early stages (within 200 ms) of information processing. However, the functional dynamics for kind intentions within and among these networks remains unclear. To address this question, we measured electrical brain activity from 18 healthy adult participants while they were performing an intention inference task with three different types of intentions: kind, hostile and non-interactive. Electrophysiological results revealed that kind intentions were characterized by significantly larger peak amplitudes of N2 over the frontal sites than those for hostile and non-interactive intentions. On the other hand, there were no significant differences between hostile and non-interactive intentions at N2. The source analysis suggested that the vicinity of the left cingulate gyrus contributed to the N2 effect by subtracting the kindness condition from the non-interactive condition within 250-350 ms. At a later stage (i.e., during the 270-500 ms epoch), the peak amplitude of the P3 over the parietal sites and the right hemisphere was significantly larger for hostile intentions compared to the kind and non-interactive intentions. No significant differences were observed at P3 between kind and non-interactive intentions. The source analysis showed that the vicinity of the left anterior cingulate cortex contributed to the P3 effect by subtracting the hostility condition from the non-interactive condition within 450-550 ms

  5. Language and motor function thresholds during pediatric extra-operative electrical cortical stimulation brain mapping.

    Science.gov (United States)

    Zea Vera, Alonso; Aungaroon, Gewalin; Horn, Paul S; Byars, Anna W; Greiner, Hansel M; Tenney, Jeffrey R; Arthur, Todd M; Crone, Nathan E; Holland, Katherine D; Mangano, Francesco T; Arya, Ravindra

    2017-10-01

    To examine current thresholds and their determinants for language and motor mapping with extra-operative electrical cortical stimulation (ECS). ECS electrocorticograph recordings were reviewed to determine functional thresholds. Predictors of functional thresholds were found with multivariable analyses. In 122 patients (age 11.9±5.4years), average minimum, frontal, and temporal language thresholds were 7.4 (± 3.0), 7.8 (± 3.0), and 7.4 (± 3.1) mA respectively. Average minimum, face, upper and lower extremity motor thresholds were 5.4 (± 2.8), 6.1 (± 2.8), 4.9 (± 2.3), and 5.3 (± 3.3) mA respectively. Functional and after-discharge (AD)/seizure thresholds were significantly related. Minimum, frontal, and temporal language thresholds were higher than AD thresholds at all ages. Minimum motor threshold was higher than minimum AD threshold up to 8.0years of age, face motor threshold was higher than frontal AD threshold up to 11.8years age, and lower subsequently. UE motor thresholds remained below frontal AD thresholds throughout the age range. Functional thresholds are frequently above AD thresholds in younger children. These findings raise concerns about safety and neurophysiologic validity of ECS mapping. Functional and AD/seizure thresholds relationships suggest individual differences in cortical excitability which cannot be explained by clinical variables. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

  6. Changing the optical and electrical properties of a crown dielectric surface using a 532 nm diode laser

    Science.gov (United States)

    Khairuzzaman, Md

    The optical response of a dielectric surface to a given laser radiation can be modified when this surface receives a supplemental uniform energy from an external source such as from the uniform electric field set up by a capacitor voltage. A low capacitor voltage across the dielectric can shift the wavelength of the probe laser as perceived by the dielectric surface toward smaller values. This shift is due to an increase of the vibrational frequency of the electric dipoles located on the dielectric surface. The change in the polarization properties of the dielectric surface suggests the usage of this configuration as an optoelectronic switch driven by a relatively small capacitor voltage. Another goal of this work is to observe the coupling between two lasers through a simultaneous interaction on the surface of a crown dielectric material. We analyze the destructive interference pattern between a weak probe laser and a stronger coupling laser in an electromagnetic induced transparency (EIT)-type configuration. We compare our destructive interference pattern obtained with crown glass illuminated with a diode laser of 532 nm, with previous results where a flint dielectric material was illuminated with the same radiation in similar experimental conditions.

  7. Laser micro-machinability of borosilicate glass surface-modified by electric field-assisted ion-exchange method

    Science.gov (United States)

    Matsusaka, S.; Kobayakawa, T.; Hidai, H.; Morita, N.

    2012-08-01

    In order to improve the laser micro-machinability of borosilicate glass, the glass surface was doped with metal (silver or copper) ions by an electric field-assisted ion-exchange method. Doped ions drifted and diffused into the glass substrate under a DC electric field. The concentration of metal ions within the doped area was approximately constant because the ion penetration was caused by substitution between dopant metal and inherent sodium ions. Nanosecond ultraviolet laser irradiation of metal-containing regions produced flat, smooth and defect-free holes. However, the shapes of holes were degraded when the processed hole bottoms reached ion penetration depths. A numerical analysis of ionic drift-diffusion behaviour in glass material under an electric field was also carried out. The calculated results for penetration depth and ionic flux showed good agreement with the measured values.

  8. Simulasi Rekonstruksi Citra Pada Sensor Brain ECVT (Electrical Capacitance Volume Tomography dengan Metode ILBP (Iterative Linear Back Projection

    Directory of Open Access Journals (Sweden)

    Nita Handayani

    2017-02-01

    Full Text Available The purpose of this study is to simulate the sensor 32-channel Brain ECVT image reconstruction using ILBP (Iterative Linear Back Projection methods. ECVT is a dynamic volume imaging technique that utilizes non-linear difference of electric field distribution to determine the distribution of permittivity in the sensing area. ECVT has measured the capacitance of data as a result of changes in the permittivity distribution between the electrode pairs. ECVT device consists of three main parts: helmet-shaped sensors, DAS (Data Acquisition System, PC for display and image reconstruction process. Simulation of sensor design using COMSOL Multiphysics 3.5 software, while the process of image reconstruction and analysis of the results using Matlab software 2009a. The principle of ECVT includes two stages of data collection capacitance of electrodes (forward problem and image reconstruction from the measured capacitance (inverse problem. In the study, the simulation of image reconstruction was done by varying the object position, the number of objects and charge density of the object. From the simulation results showed that the reconstructed image with ILBP method is influenced by several parameters: the object's position in the sensor,charge density value of the object, an alpha value and the number of iterations was selected.

  9. How to trust a perfect stranger: predicting initial trust behavior from resting-state brain-electrical connectivity.

    Science.gov (United States)

    Hahn, Tim; Notebaert, Karolien; Anderl, Christine; Teckentrup, Vanessa; Kaßecker, Anja; Windmann, Sabine

    2015-06-01

    Reciprocal exchanges can be understood as the updating of an initial belief about a partner. This initial level of trust is essential when it comes to establishing cooperation with an unknown partner, as cooperation cannot arise without a minimum of trust not justified by previous successful exchanges with this partner. Here we demonstrate the existence of a representation of the initial trust level before an exchange with a partner has occurred. Specifically, we can predict the Investor's initial investment--i.e. his initial level of trust toward the unknown trustee in Round 1 of a standard 10-round Trust Game-from resting-state functional connectivity data acquired several minutes before the start of the Trust Game. Resting-state functional connectivity is, however, not significantly associated with the level of trust in later rounds, potentially mirroring the updating of the initial belief about the partner. Our results shed light on how the initial level of trust is represented. In particular, we show that a person's initial level of trust is, at least in part, determined by brain electrical activity acquired well before the beginning of an exchange. © The Author (2014). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  10. Rehabilitation of hand in subacute tetraplegic patients based on brain computer interface and functional electrical stimulation: a randomised pilot study

    Science.gov (United States)

    Osuagwu, Bethel C. A.; Wallace, Leslie; Fraser, Mathew; Vuckovic, Aleksandra

    2016-12-01

    Objective. To compare neurological and functional outcomes between two groups of hospitalised patients with subacute tetraplegia. Approach. Seven patients received 20 sessions of brain computer interface (BCI) controlled functional electrical stimulation (FES) while five patients received the same number of sessions of passive FES for both hands. The neurological assessment measures were event related desynchronization (ERD) during movement attempt, Somatosensory evoked potential (SSEP) of the ulnar and median nerve; assessment of hand function involved the range of motion (ROM) of wrist and manual muscle test. Main results. Patients in both groups initially had intense ERD during movement attempt that was not restricted to the sensory-motor cortex. Following the treatment, ERD cortical activity restored towards the activity in able-bodied people in BCI-FES group only, remaining wide-spread in FES group. Likewise, SSEP returned in 3 patients in BCI-FES group, having no changes in FES group. The ROM of the wrist improved in both groups. Muscle strength significantly improved for both hands in BCI-FES group. For FES group, a significant improvement was noticed for right hand flexor muscles only. Significance. Combined BCI-FES therapy results in better neurological recovery and better improvement of muscle strength than FES alone. For spinal cord injured patients, BCI-FES should be considered as a therapeutic tool rather than solely a long-term assistive device for the restoration of a lost function.

  11. Deep brain stimulation of the pallidum internum for Gilles de la Tourette syndrome: a patient-specific model-based simulation study of the electric field.

    Science.gov (United States)

    Wårdell, Karin; Kefalopoulou, Zinovia; Diczfalusy, Elin; Andersson, Mats; Åström, Mattias; Limousin, Patricia; Zrinzo, Ludvic; Hariz, Marwan

    2015-02-01

    The aim of this study was to investigate the deep brain stimulation (DBS) electric field distribution in proton-density MRI scans visualizing the globus pallidus internus (GPi) of patients with Gilles de la Tourette syndrome (GTS), along with its relation to the anatomy. Patient-specific brain tissue models (n = 7) with bilateral DBS electrodes in the GPi were set up using the finite element method in five patients who had undergone stereotactic proton-density MRI-guided surgery and showed variable improvement with DBS. Simulations (n = 27) of the electric field were performed and the results visualized on the respective preoperative stereotactic MRI scans. The mean electric field volumes (n = 81) within the 0.1, 0.15, and 0.2 V/mm isosurfaces were calculated and compared with the anatomy. Visualization of the simulated electric field confirmed that the anteromedial limbic GPi was the main stimulated target for four of the patients and the posteromedial sensorimotor GPi for one. Larger volumes extended asymmetrically, with parts of fields stretching into the lamina between GPi and globus pallidus externus and into the internal capsule. There was a high correlation (r = 0.994, n = 54) between volumes and brain sides, but with a systematic shift toward the right side, especially for the larger volumes. Simulations with homogeneous tissue models showed no differences. Patient-specific DBS electric field simulations in the GPi as visualized on proton-density MR scans can be implemented in patients with GTS. Visualization of electric fields together with stereotactic thin-slice MRI can provide further support when predicting anatomical structures possibly influenced by DBS in this complex disorder. © 2014 International Neuromodulation Society.

  12. Identification and comparison of electrical tapes using instrumental and statistical techniques: I. Microscopic surface texture and elemental composition.

    Science.gov (United States)

    Goodpaster, John V; Sturdevant, Amanda B; Andrews, Kristen L; Brun-Conti, Leanora

    2007-05-01

    Comparisons of polyvinyl chloride electrical tape typically rely upon evaluating class characteristics such as physical dimensions, surface texture, and chemical composition. Given the various techniques that are available for this purpose, a comprehensive study has been undertaken to establish an optimal analytical scheme for electrical tape comparisons. Of equal importance is the development of a quantitative means for sample discrimination. In this study, 67 rolls of black electrical tape representing 34 different nominal brands were analyzed via scanning electron microscopy and energy dispersive spectroscopy. Differences in surface roughness, calendering marks, and filler particle size were readily apparent, including between some rolls of the same nominal brand. The relative amounts of magnesium, aluminum, silicon, sulfur, lead, chlorine, antimony, calcium, titanium, and zinc varied greatly between brands and, in some cases, could be linked to the year of manufacture. For the first time, quantitative differentiation of electrical tapes was achieved through multivariate statistical techniques, with 36 classes identified within the sample population. A single-blind study was also completed where questioned tape samples were correctly associated with known exemplars. Finally, two case studies are presented where tape recovered from an improvised explosive device is compared with tape recovered from a suspect.

  13. Surface layer structure of AISI 1020 steel at different stages of dry sliding under electric current of high density

    Science.gov (United States)

    Aleutdinov, K. A.; Rubtsov, V. Ye; Fadin, V. V.; Aleutdinova, M. I.

    2016-02-01

    Wear intensity of the sliding electric contact steel 1020/steel 1045 depending on sliding time is presented at the contact current density higher than 100 A/cm2 without lubricant. It is shown that wear intensity of 1020 steel decreases at increasing of sliding time. Wear intensity is stabilized after some sliding time. This time (burn-in time) decreases at reduction of current density. Structural changes are realized in surface layer. Signs of liquid phase are observed on sliding surface. This liquid isn't a result of melting. It is established using Auger spectrometry that the contact layer contains up to 50 at.% of oxygen.

  14. Electrical resistivity dynamics beneath a fractured sedimentary bedrock riverbed in response to temperature and groundwater–surface water exchange

    Directory of Open Access Journals (Sweden)

    C. M. Steelman

    2017-06-01

    Full Text Available Bedrock rivers occur where surface water flows along an exposed rock surface. Fractured sedimentary bedrock can exhibit variable groundwater residence times, anisotropic flow paths, and heterogeneity, along with diffusive exchange between fractures and rock matrix. These properties of the rock will affect thermal transients in the riverbed and groundwater–surface water exchange. In this study, surface electrical methods were used as a non-invasive technique to assess the scale and temporal variability of riverbed temperature and groundwater–surface water interaction beneath a sedimentary bedrock riverbed. Conditions were monitored at a semi-daily to semi-weekly interval over a full annual period that included a seasonal freeze–thaw cycle. Surface electromagnetic induction (EMI and electrical resistivity tomography (ERT methods captured conditions beneath the riverbed along a pool–riffle sequence of the Eramosa River in Canada. Geophysical datasets were accompanied by continuous measurements of aqueous specific conductance, temperature, and river stage. Time-lapse vertical temperature trolling within a lined borehole adjacent to the river revealed active groundwater flow zones along fracture networks within the upper 10 m of rock. EMI measurements collected during cooler high-flow and warmer low-flow periods identified a spatiotemporal riverbed response that was largely dependent upon riverbed morphology and seasonal groundwater temperature. Time-lapse ERT profiles across the pool and riffle sequence identified seasonal transients within the upper 2 and 3 m of rock, respectively, with spatial variations controlled by riverbed morphology (pool versus riffle and dominant surficial rock properties (competent versus weathered rock rubble surface. While the pool and riffle both exhibited a dynamic resistivity through seasonal cooling and warming cycles, conditions beneath the pool were more variable, largely due to the formation of river

  15. Effects of microwave electric fields on the translational diffusion of dipolar molecules in surface potential: A simulation study

    Science.gov (United States)

    Kapranov, Sergey V.; Kouzaev, Guennadi A.

    2018-01-01

    Variations of effective diffusion coefficient of polar molecules exposed to microwave electric fields in a surface potential are studied by solving coupled stochastic differential equations of motion with a deterministic component of the surface force. Being an essential tool for the simulation interpretation, a theoretical approach to effective diffusion in surface potential is first developed. The effective diffusion coefficient is represented as the product of the normal diffusion coefficient and potential-dependent correction function, whose temperature dependence is close to the Arrhenius form. The analytically found zero-diffusion condition defines the state of thermal equilibrium at the surface. The diffusion of a water-like dipole molecule in the potential of graphite surface is simulated in the field-free conditions and in the presence of the alternating electric fields of various magnitude intensities and frequencies. Temperature dependence of the correction function exhibits field-induced variations of the effective Lennard-Jones energy parameter. It demonstrates maximum departure from the zero-field value at certain frequencies and intensities, which is associated with variations in the rotational dynamics. A concept of the amplitude-frequency resonance put forward to interpret the simulation results is explained using a heuristic reasoning and is corroborated by semi-quantitative considerations in terms of the Dissado-Hill cluster theory of dielectric relaxation.

  16. The mechanical analysis of thermo-magneto-electric laminated composites in nanoscale with the consideration of surface and flexoelectric effects

    Science.gov (United States)

    Shi, Shuanhu; Li, Peng; Jin, Feng

    2018-01-01

    A theoretical thermo-magneto-electric (TME) bilayer model is established based on the Hamilton principle, in which both surface effect and flexoelectricity are all taken into account. The governing equations are proposed with the aid of the nonlinear constitutive relations of giant magnetostrictive materials. These equations are general, which can be applied to analyze the coupled extensional, shear and bending deformations at both macroscale and nanoscale. As a specific example, the coupled extensional and bending motion of a slender beam suffering from external magnetic field and thermal variation is investigated, in which the Miller–Shenoy coefficient, magneto-electric (ME) effect, strain gradient and displacement are discussed in detail. After the necessary verification, a critical thickness of the TME model is proposed, below which the surface effect exhibits a remarkable influence on the mechanical behaviors and can not be ignored. It is revealed that the surface effect, flexoelectric effect and temperature increment are beneficial for the enhancement of the induced electric field. This study can provide theoretical basis for the design of nanoscale laminates, especially for the performance evaluation of ME composites under complex environment.

  17. Additional enhancement of electric field in surface-enhanced Raman Scattering due to Fresnel mechanism

    National Research Council Canada - National Science Library

    Jayawardhana, Sasani; Rosa, Lorenzo; Juodkazis, Saulius; Stoddart, Paul R

    2013-01-01

    .... In this paper, finite difference time domain modeling is presented to show that the electric field intensity at the dielectric interface between metal particles is higher for "far-side" excitation than "near-side...

  18. Signal features of surface electromyography in advanced Parkinson's disease during different settings of deep brain stimulation.

    Science.gov (United States)

    Rissanen, Saara M; Ruonala, Verneri; Pekkonen, Eero; Kankaanpää, Markku; Airaksinen, Olavi; Karjalainen, Pasi A

    2015-12-01

    Electromyography (EMG) and acceleration (ACC) measurements are potential methods for quantifying efficacy of deep brain stimulation (DBS) treatment in Parkinson's disease (PD). The treatment efficacy depends on the settings of DBS parameters (pulse amplitude, frequency and width). This study quantified, if EMG and ACC signal features differ between different DBS settings and if DBS effect is unequal between different muscles. EMGs were measured from biceps brachii (BB) and tibialis anterior (TA) muscles of 13 PD patients. ACCs were measured from wrists. Measurements were performed during seven different settings of DBS and analyzed using methods based on spectral analysis, signal morphology and nonlinear dynamics. The results showed significant within-subject differences in the EMG signal kurtosis, correlation dimension, recurrence rate and EMG-ACC coherence between different DBS settings for BB but not for TA muscles. Correlations between EMG feature values and clinical rest tremor and rigidity scores were weak but significant. Surface EMG features differed between different DBS settings and DBS effect was unequal between upper and lower limb muscles. EMG changes pointed to previously defined optimal settings in most of patients, which should be quantified even more deeply in the upcoming studies. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  19. Control of thumb force using surface functional electrical stimulation and muscle load sharing

    Science.gov (United States)

    2013-01-01

    Background Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of individual muscle forces, described by a sigmoidal muscle recruitment curve and a single force direction. Methods Five able bodied subjects and five stroke subjects were strapped in a custom built setup. The forces perpendicular to the thumb in response to FES applied to three thumb muscles were measured. We evaluated the feasibility of using recruitment curve based force vector maps in predicting output forces. In addition, we developed a closed loop force controller. Load sharing between the three muscles was used to solve the redundancy problem having three actuators to control forces in two dimensions. The thumb force was controlled towards target forces of 0.5 N and 1.0 N in multiple directions within the individual’s thumb work space. Hereby, the possibilities to use these force vector maps and the load sharing approach in feed forward and feedback force control were explored. Results The force vector prediction of the obtained model had small RMS errors with respect to the actual measured force vectors (0.22±0.17 N for the healthy subjects; 0.17±0.13 N for the stroke subjects). The stroke subjects showed a limited work range due to limited force production of the individual muscles. Performance of feed forward control without feedback, was better in healthy subjects than in stroke subjects. However, when feedback control was added performances were similar between the two groups. Feedback force control lead, especially for the stroke subjects, to a reduction in stationary errors, which improved performance. Conclusions Thumb muscle responses to FES can be described by a single force direction and a sigmoidal recruitment curve. Force in desired direction can be

  20. Control of thumb force using surface functional electrical stimulation and muscle load sharing.

    Science.gov (United States)

    Westerveld, Ard J; Schouten, Alfred C; Veltink, Peter H; van der Kooij, Herman

    2013-10-09

    Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of individual muscle forces, described by a sigmoidal muscle recruitment curve and a single force direction. Five able bodied subjects and five stroke subjects were strapped in a custom built setup. The forces perpendicular to the thumb in response to FES applied to three thumb muscles were measured. We evaluated the feasibility of using recruitment curve based force vector maps in predicting output forces. In addition, we developed a closed loop force controller. Load sharing between the three muscles was used to solve the redundancy problem having three actuators to control forces in two dimensions. The thumb force was controlled towards target forces of 0.5 N and 1.0 N in multiple directions within the individual's thumb work space. Hereby, the possibilities to use these force vector maps and the load sharing approach in feed forward and feedback force control were explored. The force vector prediction of the obtained model had small RMS errors with respect to the actual measured force vectors (0.22 ± 0.17 N for the healthy subjects; 0.17 ± 0.13 N for the stroke subjects). The stroke subjects showed a limited work range due to limited force production of the individual muscles. Performance of feed forward control without feedback, was better in healthy subjects than in stroke subjects. However, when feedback control was added performances were similar between the two groups. Feedback force control lead, especially for the stroke subjects, to a reduction in stationary errors, which improved performance. Thumb muscle responses to FES can be described by a single force direction and a sigmoidal recruitment curve. Force in desired direction can be generated through load sharing among

  1. Characterization of electric discharge machining, subsequent etching and shot-peening as a surface treatment for orthopedic implants

    Energy Technology Data Exchange (ETDEWEB)

    Stráský, Josef, E-mail: josef.strasky@gmail.com [Charles University, Department of Physics of Materials (Czech Republic); Havlíková, Jana; Bačáková, Lucie [Institute of Physiology, Academy of Sciences of the Czech Republic (Czech Republic); Harcuba, Petr [Charles University, Department of Physics of Materials (Czech Republic); Mhaede, Mansour [Clausthal University of Technology, Institute of Materials Science and Engineering (Germany); Faculty of Engineering, Zagazig University (Egypt); Janeček, Miloš [Charles University, Department of Physics of Materials (Czech Republic)

    2013-09-15

    Presented work aims at multi-method characterization of combined surface treatment of Ti–6Al–4V alloy for biomedical use. Surface treatment consists of consequent use of electric discharge machining (EDM), acid etching and shot peening. Surface layers are analyzed employing scanning electron microscopy and energy dispersive X-ray spectroscopy. Acid etching by strong Kroll's reagent is capable of removing surface layer of transformed material created by EDM. Acid etching also creates partly nanostructured surface and significantly contributes to the enhanced proliferation of the bone cells. The cell growth could be positively affected by the superimposed bone-inspired structure of the surface with the morphological features in macro-, micro- and nano-range. Shot peening significantly improves poor fatigue performance after EDM. Final fatigue performance is comparable to benchmark electropolished material without any adverse surface effect. The proposed three-step surface treatment is a low-cost process capable of producing material that is applicable in orthopedics.

  2. Standing with electrical stimulation and splinting is no better than standing alone for management of ankle plantarflexion contractures in people with traumatic brain injury: a randomised trial.

    Science.gov (United States)

    Leung, Joan; Harvey, Lisa A; Moseley, Anne M; Whiteside, Bhavini; Simpson, Melissa; Stroud, Katarina

    2014-12-01

    Is a combination of standing, electrical stimulation and splinting more effective than standing alone for the management of ankle contractures after severe brain injury? A multi-centre randomised trial with concealed allocation, assessor blinding and intention-to-treat analysis. Thirty-six adults with severe traumatic brain injury and ankle plantarflexion contractures. All participants underwent a 6-week program. The experimental group received tilt table standing, electrical stimulation and ankle splinting. The control group received tilt table standing alone. The primary outcome was passive ankle dorsiflexion with a 12Nm torque. Secondary outcomes included: passive dorsiflexion with lower torques (3, 5, 7 and 9Nm); spasticity; the walking item of the Functional Independence Measure; walking speed; global perceived effect of treatment; and perceived treatment credibility. OUTCOME MEASURES were taken at baseline (Week 0), end of intervention (Week 6), and follow-up (Week 10). The mean between-group differences (95% CI) for passive ankle dorsiflexion at Week 6 and Week 10 were -3 degrees (-8 to 2) and -1 degrees (-6 to 4), respectively, in favour of the control group. There was a small mean reduction of 1 point in spasticity at Week 6 (95% CI 0.1 to 1.8) in favour of the experimental group, but this effect disappeared at Week 10. There were no differences for other secondary outcome measures except the physiotherapists' perceived treatment credibility. Tilt table standing with electrical stimulation and splinting is not better than tilt table standing alone for the management of ankle contractures after severe brain injury. ACTRN12608000637347. [Leung J, Harvey LA, Moseley AM, Whiteside B, Simpson M, Stroud K (2014) Standing with electrical stimulation and splinting is no better than standing alone for management of ankle plantarflexion contractures in people with traumatic brain injury: a randomised trial.Journal of Physiotherapy60: 201-208]. Copyright © 2014

  3. Standing with electrical stimulation and splinting is no better than standing alone for management of ankle plantarflexion contractures in people with traumatic brain injury: a randomised trial

    Directory of Open Access Journals (Sweden)

    Joan Leung

    2014-12-01

    Full Text Available Question: Is a combination of standing, electrical stimulation and splinting more effective than standing alone for the management of ankle contractures after severe brain injury? Design: A multi-centre randomised trial with concealed allocation, assessor blinding and intention-to-treat analysis. Participants: Thirty-six adults with severe traumatic brain injury and ankle plantarflexion contractures. Intervention: All participants underwent a 6-week program. The experimental group received tilt table standing, electrical stimulation and ankle splinting. The control group received tilt table standing alone. Outcome measures: The primary outcome was passive ankle dorsiflexion with a 12 Nm torque. Secondary outcomes included: passive dorsiflexion with lower torques (3, 5, 7 and 9 Nm; spasticity; the walking item of the Functional Independence Measure; walking speed; global perceived effect of treatment; and perceived treatment credibility. Outcome measures were taken at baseline (Week 0, end of intervention (Week 6, and follow-up (Week 10. Results: The mean between-group differences (95% CI for passive ankle dorsiflexion at Week 6 and Week 10 were –3 degrees (–8 to 2 and –1 degrees (–6 to 4, respectively, in favour of the control group. There was a small mean reduction of 1 point in spasticity at Week 6 (95% CI 0.1 to 1.8 in favour of the experimental group, but this effect disappeared at Week 10. There were no differences for other secondary outcome measures except the physiotherapists’ perceived treatment credibility. Conclusion: Tilt table standing with electrical stimulation and splinting is not better than tilt table standing alone for the management of ankle contractures after severe brain injury. Trial registration: ACTRN12608000637347. [Leung J, Harvey LA, Moseley AM, Whiteside B, Simpson M, Stroud K (2014 Standing with electrical stimulation and splinting is no better than standing alone for management of ankle plantarflexion

  4. Emergency Department Triage of Traumatic Head Injury Using a Brain Electrical Activity Biomarker: A Multisite Prospective Observational Validation Trial.

    Science.gov (United States)

    Hanley, Daniel; Prichep, Leslie S; Bazarian, Jeffrey; Huff, J Stephen; Naunheim, Rosanne; Garrett, John; Jones, Elizabeth B; Wright, David W; O'Neill, John; Badjatia, Neeraj; Gandhi, Dheeraj; Curley, Kenneth C; Chiacchierini, Richard; O'Neil, Brian; Hack, Dallas C

    2017-05-01

    A brain electrical activity biomarker for identifying traumatic brain injury (TBI) in emergency department (ED) patients presenting with high Glasgow Coma Scale (GCS) after sustaining a head injury has shown promise for objective, rapid triage. The main objective of this study was to prospectively evaluate the efficacy of an automated classification algorithm to determine the likelihood of being computed tomography (CT) positive, in high-functioning TBI patients in the acute state. Adult patients admitted to the ED for evaluation within 72 hours of sustaining a closed head injury with GCS 12 to 15 were candidates for study. A total of 720 patients (18-85 years) meeting inclusion/exclusion criteria were enrolled in this observational, prospective validation trial, at 11 U.S. EDs. GCS was 15 in 97%, with the first and third quartiles being 15 (interquartile range = 0) in the study population at the time of the evaluation. Standard clinical evaluations were conducted and 5 to 10 minutes of electroencephalogram (EEG) was acquired from frontal and frontal-temporal scalp locations. Using an a priori derived EEG-based classification algorithm developed on an independent population and applied to this validation population prospectively, the likelihood of each subject being CT+ was determined, and performance metrics were computed relative to adjudicated CT findings. Sensitivity of the binary classifier (likely CT+ or CT-) was 92.3% (95% confidence interval [CI] = 87.8%-95.5%) for detection of any intracranial injury visible on CT (CT+), with specificity of 51.6% (95% CI = 48.1%-55.1%) and negative predictive value (NPV) of 96.0% (95% CI = 93.2%-97.9%). Using ternary classification (likely CT+, equivocal, likely CT-) demonstrated enhanced sensitivity to traumatic hematomas (≥1 mL of blood), 98.6% (95% CI = 92.6%-100.0%), and NPV of 98.2% (95% CI = 95.5%-99.5%). Using an EEG-based biomarker high accuracy of predicting the likelihood of being CT+ was obtained, with

  5. The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study

    Science.gov (United States)

    Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J.; Miranda, Pedro C.

    2015-09-01

    Tumor treating fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1-3 V cm-1. Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V cm-1, independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields.

  6. STUDY OF STATIC ELECTRICITY CHARGE ACCUMULATION ON SURFACE OF FLUOROPOLYMER-4 PRODUCTS USING VIBRATING CAPACITOR METHOD

    Directory of Open Access Journals (Sweden)

    H. Vershina

    2012-01-01

    Full Text Available The paper presents investigations of processes pertaining to surface charge accumulation and running of fluoropolymer-4 products using vibrating capacitor method. Modification of a measurement technique allowing to register distribution of dielectric surface potential without disturbance of the surface charged state has been described in the paper. The paper contains graphics of spatial distribution of surface potential of fluoropolymer-4 products after various treatments. The paper reveals that thermal treatment (tempering reduces static characteristics of fluoropolymer-4.

  7. Effects of vacuum heat treatment on the photoelectric work function and surface morphology of multilayered silver–metal electrical contacts

    Energy Technology Data Exchange (ETDEWEB)

    Akbi, Mohamed, E-mail: akbi_mohamed@umbb.dz [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France); Department of Physics, Faculty of Sciences, University of Boumerdes (UMBB), Independence Avenue, 35000 Boumerdes (Algeria); Bouchou, Aïssa [Faculty of Physics, University of Algiers (USTHB), B.P. 32, El-Alia, Bab-Ezzouar, 16111 Algiers (Algeria); Zouache, Noureddine [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France)

    2014-06-01

    Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermodynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver–metal (Ag–Me) electrical contacts (Ag–Ni (60/40) and Ag–W (50/50)), before and after surface heat treatments at 513 K–873 K, under UHV conditions (residual gas pressure of 1.4 × 10{sup −7} mbar). The electron work function (EWF) of silver alloyed contacts was measured photoelectrically, using both Fowler's method of isothermal curves and linearized Fowler plots. An interesting fact brought to light by this investigation is that after vacuum heat treatments, the diffusion and/or evaporation phenomena, affecting the atomic composition of the alloy surface, somehow confine the EWF of the silver–nickel alloy, Φ(Ag–Ni), determined at room temperature in interval]Φ(Ag), Φ(Ni) [=] 4.26 eV, 4.51 eV[. Surface analysis of two specimens before and after heating showed a significant increase of tungsten atomic proportion on the contact surface for Ag–W contacts after VH treatments. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results.

  8. Optical and electrical study of CdZnTe surfaces passivated by KOH and NH{sub 4}F solutions

    Energy Technology Data Exchange (ETDEWEB)

    Zázvorka, J., E-mail: zazvorka.jakub@gmail.com [Institute of Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Prague (Czech Republic); Franc, J.; Statelov, M.; Pekárek, J.; Veis, M.; Moravec, P. [Institute of Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Prague (Czech Republic); Mašek, K. [Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ, 18000 Prague (Czech Republic)

    2016-12-15

    Highlights: • Surface of CdZnTe samples was passivated after chemical etching. • KOH and NH{sub 4}F solutions were used as passivation agents. • Growth of surface oxide after passivation is observed. • Surface oxide thickness was evaluated over time after chemical treatment. • Oxidation of the sample correlates with decreased leakage current. - Abstract: Performance of CdZnTe-based detectors is highly related to surface preparation. Mechanical polishing, chemical etching and passivation are routinely employed for this purpose. However, the relation between these processes and the detector performance in terms of underlying physical phenomena has not been fully explained. The dynamics and properties of CdZnTe surface oxide layers, created by passivation with KOH and NH4F/H2O2 solutions, were studied by optical ellipsometry and X-ray photoelectron spectroscopy (XPS). Thicknesses and growth rates of the surface oxide layers differed for each of the passivation methods. Leakage currents which influence the final spectral resolution of the detector were measured simultaneously with ellipsometry. Results of both optical and electrical investigation showed the same trends in the time evolution and correlated to each other. NH4F/H2O2 passivation showed to be a method which produces the most desirable properties of the surface oxide layer.

  9. Toward the Restoration of Hand Use to a Paralyzed Monkey: Brain-Controlled Functional Electrical Stimulation of Forearm Muscles

    Science.gov (United States)

    Pohlmeyer, Eric A.; Oby, Emily R.; Perreault, Eric J.; Solla, Sara A.; Kilgore, Kevin L.; Kirsch, Robert F.; Miller, Lee E.

    2009-01-01

    Loss of hand use is considered by many spinal cord injury survivors to be the most devastating consequence of their injury. Functional electrical stimulation (FES) of forearm and hand muscles has been used to provide basic, voluntary hand grasp to hundreds of human patients. Current approaches typically grade pre-programmed patterns of muscle activation using simple control signals, such as those derived from residual movement or muscle activity. However, the use of such fixed stimulation patterns limits hand function to the few tasks programmed into the controller. In contrast, we are developing a system that uses neural signals recorded from a multi-electrode array implanted in the motor cortex; this system has the potential to provide independent control of multiple muscles over a broad range of functional tasks. Two monkeys were able to use this cortically controlled FES system to control the contraction of four forearm muscles despite temporary limb paralysis. The amount of wrist force the monkeys were able to produce in a one-dimensional force tracking task was significantly increased. Furthermore, the monkeys were able to control the magnitude and time course of the force with sufficient accuracy to track visually displayed force targets at speeds reduced by only one-third to one-half of normal. Although these results were achieved by controlling only four muscles, there is no fundamental reason why the same methods could not be scaled up to control a larger number of muscles. We believe these results provide an important proof of concept that brain-controlled FES prostheses could ultimately be of great benefit to paralyzed patients with injuries in the mid-cervical spinal cord. PMID:19526055

  10. Learning-Related Brain-Electrical Activity Dynamics Associated with the Subsequent Impact of Learnt Action-Outcome Associations

    Directory of Open Access Journals (Sweden)

    Fabian Baum

    2017-05-01

    Full Text Available Goal-directed behavior relies on the integration of anticipated outcomes into action planning based on acquired knowledge about the current contingencies between behavioral responses (R and desired outcomes (O under specific stimulus conditions (S. According to ideomotor theory, bidirectional R-O associations are an integral part of this knowledge structure. Previous EEG studies have identified neural activity markers linked to the involvement of such associations, but the initial acquisition process has not yet been characterized. The present study thus examined brain-electrical activity dynamics during the rapid acquisition of novel bidirectional R-O associations during instructed S-R learning. Within a trial, we inspected response-locked and stimulus-locked activity dynamics in order to identify markers linked to the forward and backward activation of bidirectional R-O associations as they were being increasingly strengthened under forced choice conditions. We found that a post-response anterior negativity following auditory outcomes was increasingly attenuated as a function of the acquired association strength. This suggests that previously reported action-induced sensory attenuation effects under extensively trained free choice conditions can be established within few repetitions of specific R-O pairings under forced choice conditions. Furthermore, we observed the even more rapid development of a post-response but pre-outcome fronto-central positivity which was reduced for high R-O learners which might indicate the rapid deployment of preparatory attention towards predictable outcomes. Finally, we identified a learning-related stimulus-locked activity modulation within the visual P1-N1 latency range which might reflect the multi-sensory integration of the perceived antecedent visual stimulus the anticipated auditory outcome.

  11. Toward the restoration of hand use to a paralyzed monkey: brain-controlled functional electrical stimulation of forearm muscles.

    Directory of Open Access Journals (Sweden)

    Eric A Pohlmeyer

    2009-06-01

    Full Text Available Loss of hand use is considered by many spinal cord injury survivors to be the most devastating consequence of their injury. Functional electrical stimulation (FES of forearm and hand muscles has been used to provide basic, voluntary hand grasp to hundreds of human patients. Current approaches typically grade pre-programmed patterns of muscle activation using simple control signals, such as those derived from residual movement or muscle activity. However, the use of such fixed stimulation patterns limits hand function to the few tasks programmed into the controller. In contrast, we are developing a system that uses neural signals recorded from a multi-electrode array implanted in the motor cortex; this system has the potential to provide independent control of multiple muscles over a broad range of functional tasks. Two monkeys were able to use this cortically controlled FES system to control the contraction of four forearm muscles despite temporary limb paralysis. The amount of wrist force the monkeys were able to produce in a one-dimensional force tracking task was significantly increased. Furthermore, the monkeys were able to control the magnitude and time course of the force with sufficient accuracy to track visually displayed force targets at speeds reduced by only one-third to one-half of normal. Although these results were achieved by controlling only four muscles, there is no fundamental reason why the same methods could not be scaled up to control a larger number of muscles. We believe these results provide an important proof of concept that brain-controlled FES prostheses could ultimately be of great benefit to paralyzed patients with injuries in the mid-cervical spinal cord.

  12. Modification of Nafion Membranes by IL-Cation Exchange: Chemical Surface, Electrical and Interfacial Study

    Directory of Open Access Journals (Sweden)

    V. Romero

    2012-01-01

    A study of time evolution of the impedance curves measured in the system “IL aqueous solution/Nafion-112 membrane/IL aqueous solution” was also performed. This study allows us monitoring the electrical changes associated to the IL-cation incorporation in both the membrane and the membrane/IL solution interface, and it provides supplementary information on the characteristic of the Nafion/DTA+ hybrid material. Moreover, the results also show the significant effect of water on the electrical resistance of the Nafion-112/IL-cation-modified membrane.

  13. Splitting a droplet with oil encapsulation using surface acoustic wave excited by electric signal with low power

    Directory of Open Access Journals (Sweden)

    Anliang Zhang

    2013-07-01

    Full Text Available A new method for splitting a droplet with oil encapsulation is presented. An interdigital transducer and a reflector are fabricated on a 128° yx-LiNbO3 piezoelectric substrate using microelectric technology. An electric signal with the power of 12.3 dBm is applied to the interdigital transducer to generate surface acoustic wave, which is radiated into a droplet with oil encapsulation, leading to surface acoustic wave streaming force. When the electric signal is suddenly moved off, the breakup of the droplet occurs due to inertial force. Color dye solution droplets encapsulated by oil droplets are demonstrated. The effects of electric power, the volume ratio of color dye solution to oil, and the volume of mother droplet on the breakup of droplets are studied. As applications, the presented method is successfully applied to mixture operation and color development reaction of two droplets. The method provides a new sample preparation technique, which is helpful for microfluidic biochemical analysis in a piezoelectric microfluidic system.

  14. Enhancement in electrical conductivity of pastes containing submicron Ag-coated Cu filler with palmitic acid surface modification

    Science.gov (United States)

    Choi, Eun Byeol; Lee, Jong-Hyun

    2017-09-01

    The fabrication and applied use of submicron Ag-coated Cu (Cu@Ag) particles as a filler material for epoxy-based conductive pastes having the advantages of a lower material cost and antioxidation behavior were studied. Submicron Cu@Ag particles were successfully prepared and surface-modified using palmitic acid. Diffuse reflectance infrared Fourier transform spectroscopy and thermogravimetric differential scanning calorimetry results indicated the formation of an organic layer by the chemical interaction between the Cu@Ag surface and palmitic acid and the survival of the organic layer after treatment at 160 °C for 3 h in air. The printed pastes containing both commercial micron Cu@Ag flakes and the fabricated submicron Cu@Ag particles showed a greatly reduced electrical resistivity (4.68 × 10-4 Ω cm) after surface modification compared to an initial value of 1.85 × 10-3 Ω cm when cured.

  15. Electric-field noise from carbon-adatom diffusion on a Au(110) surface: First-principles calculations and experiments

    Science.gov (United States)

    Kim, E.; Safavi-Naini, A.; Hite, D. A.; McKay, K. S.; Pappas, D. P.; Weck, P. F.; Sadeghpour, H. R.

    2017-03-01

    The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from the trap-electrode surfaces. In this work, we investigate the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by density functional theory, based on detailed scanning probe microscopy, how the carbon adatom diffusion on the gold surface changes the energy landscape and how the adatom dipole moment varies with the diffusive motion. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, predicts a noise spectrum, in accordance with the measured values.

  16. Direct observations of surface water-groundwater interaction using electrical resistivity tomography

    NARCIS (Netherlands)

    Noell, Ursula; Wießner, Claudia; Ganz, Christina; Westhoff, Martijn

    2011-01-01

    Electrical resistivity tomography is a helpful tool to observe the infiltration process in and through the soil. Array 3-D measurements and 3-D inversion schemes are required for reliable interpretation of heterogeneous subsurface structures. Smoothing of the inversion can be minimized by using

  17. Beyond the Point Charge: Equipotential Surfaces and Electric Fields of Various Charge Configurations

    Science.gov (United States)

    Phillips, Jeffrey A.; Sanny, Jeff; Berube, David; Hoemke, Anatol

    2017-01-01

    A laboratory experiment often performed in an introductory electricity and magnetism course involves the mapping of equipotential lines on a conductive sheet between two objects at different potentials. In this article, we describe how we have expanded this experiment so that it can be used to illustrate the electrostatic properties of conductors.…

  18. Computer modeling and laboratory experiments of a specific borehole to surface electrical monitoring technique (BSEMT)

    NARCIS (Netherlands)

    Meekes, J.A.C.; Zhang, X.; Abdul Fattah, R.

    2011-01-01

    Geophysical monitoring of the dynamical behavior of subsurface reservoirs (oil, gas, CO2) remains an important issue in geophysical research. A new idea for reservoir monitoring based on electrical resistivity tomography was developed at TNO. The essential element of the so-called BSEMT (Borehole to

  19. Spatial and temporal monitoring of soil moisture using surface electrical resistivity tomography in Mediterranean soils

    NARCIS (Netherlands)

    Alamry, Abdulmohsen S.; van der Meijder, Mark; Noomen, Marleen; Addink, Elisabeth A.; van Benthem, Rik; de Jong, Steven M.

    2017-01-01

    ERT techniques are especially promising in (semi-arid) areas with shallow and rocky soils where other methods fail to produce soil moisture maps and to obtain soil profile information. Electrical Resistivity Tomography (ERT) was performed in the Peyne catchment in southern France at four sites

  20. Opto-electrical surface engineering of wafer based c-Si solar cells

    NARCIS (Netherlands)

    Ingenito, A.

    2016-01-01

    Climate changes due to increase of CO2 emission are becoming a serious issue for this planet. The so called climate crisis has been the main topic of the last United Nations Climate Change Conference (COP 21) . Direct conversion of sunlight into electricity is one of the most promising technology

  1. Micro- and nanostructure of a titanium surface electric-spark-doped with tantalum and modified by high-frequency currents

    Science.gov (United States)

    Fomin, A. A.; Fomina, M. A.; Koshuro, V. A.; Rodionov, I. V.; Voiko, A. V.; Zakharevich, A. M.; Aman, A.; Oseev, A.; Hirsch, S.; Majcherek, S.

    2016-09-01

    We have studied the characteristics of the porous microstructure of tantalum coatings obtained by means of electric spark spraying on the surface of commercial grade titanium. It is established that, at an electric spark current within 0.8-2.2 A, a mechanically strong tantalum coating microstructure is formed with an average protrusion size of 5.1-5.4 µm and pore sizes from 3.5 to 9.2 µm. On the nanoscale, a structurally heterogeneous state of coatings has been achieved by subsequent thermal modification at 800-830°C with the aid of high-frequency currents. A metal oxide nanostructure with grain sizes from 40 to 120 nm is formed by short-time (~30 s) thermal modification. The coating hardness reaches 9.5-10.5 GPa at an elastic modulus of 400-550 GPa.

  2. Surface and Electrical Characterization of Ag/AgCl Pseudo-Reference Electrodes Manufactured with Commercially Available PCB Technologies

    Directory of Open Access Journals (Sweden)

    Despina Moschou

    2015-07-01

    Full Text Available Lab-on-Chip is a technology that could potentially revolutionize medical Point-of-Care diagnostics. Considerable research effort is focused towards innovating production technologies that will make commercial upscaling financially viable. Printed circuit board manufacturing techniques offer several prospects in this field. Here, we present a novel approach to manufacturing Printed Circuit Board (PCB-based Ag/AgCl reference electrodes, an essential component of biosensors. Our prototypes were characterized both structurally and electrically. Scanning Electron Microscopy (SEM and X-Ray Photoelectron Spectroscopy (XPS were employed to evaluate the electrode surface characteristics. Electrical characterization was performed to determine stability and pH dependency. Finally, we demonstrate utilization along with PCB pH sensors, as a step towards a fully integrated PCB platform, comparing performance with discrete commercial reference electrodes.

  3. A Review of Additive Mixed-Electric Discharge Machining: Current Status and Future Perspectives for Surface Modification of Biomedical Implants

    Directory of Open Access Journals (Sweden)

    Abdul’Azeez Abdu Aliyu

    2017-01-01

    Full Text Available Surface treatment remained a key solution to numerous problems of synthetic hard tissues. The basic methods of implant surface modification include various physical and chemical deposition techniques. However, most of these techniques have several drawbacks such as excessive cost and surface cracks and require very high sintering temperature. Additive mixed-electric discharge machining (AM-EDM is an emerging technology which simultaneously acts as a machining and surface modification technique. Aside from the mere molds, dies, and tool fabrication, AM-EDM is materializing to finishing of automobiles and aerospace, nuclear, and biomedical components, through the concept of material migrations. The mechanism of material transfer by AM-EDM resembles electrophoretic deposition, whereby the additives in the AM-EDM dielectric fluids are melted and migrate to the machined surface, forming a mirror-like finishing characterized by extremely hard, nanostructured, and nanoporous layers. These layers promote the bone in-growth and strengthen the cell adhesion. Implant shaping and surface treatment through AM-EDM are becoming a key research focus in recent years. This paper reports and summarizes the current advancement of AM-EDM as a potential tool for orthopedic and dental implant fabrication. Towards the end of this paper, the current challenges and future research trends are highlighted.

  4. High-resolution random mesh algorithms for creating a probabilistic 3D surface atlas of the human brain.

    Science.gov (United States)

    Thompson, P M; Schwartz, C; Toga, A W

    1996-02-01

    Striking variations exist, across individuals, in the internal and external geometry of the brain. Such normal variations in the size, orientation, topology, and geometric complexity of cortical and subcortical structures have complicated the problem of quantifying deviations from normal anatomy and of developing standardized neuroanatomical atlases. This paper describes the design, implementation, and results of a technique for creating a three-dimensional (3D) probabilistic surface atlas of the human brain. We have developed, implemented, and tested a new 3D statistical method for assessing structural variations in a data-base of anatomic images. The algorithm enables the internal surface anatomy of new subjects to be analyzed at an extremely local level. The goal was to quantify subtle and distributed patterns of deviation from normal anatomy by automatically generating detailed probability maps of the anatomy of new subjects. Connected systems of parametric meshes were used to model the internal course of the following structures in both hemispheres: the parieto-occipital sulcus, the anterior and posterior rami of the calcarine sulcus, the cingulate and marginal sulci, and the supracallosal sulcus. These sulci penetrate sufficiently deeply into the brain to introduce an obvious topological decomposition of its volume architecture. A family of surface maps was constructed, encoding statistical properties of local anatomical variation within individual sulci. A probability space of random transformations, based on the theory of Gaussian random fields, was developed to reflect the observed variability in stereotaxic space of the connected system of anatomic surfaces. A complete system of probability density functions was computed, yielding confidence limits on surface variation. The ultimate goal of brain mapping is to provide a framework for integrating functional and anatomical data across many subjects and modalities. This task requires precise quantitative

  5. Near-surface processing on AlGaN/GaN heterostructures: a nanoscale electrical and structural characterization

    Directory of Open Access Journals (Sweden)

    Greco Giuseppe

    2011-01-01

    Full Text Available Abstract The effects of near-surface processing on the properties of AlGaN/GaN heterostructures were studied, combining conventional electrical characterization on high-electron mobility transistors (HEMTs, with advanced characterization techniques with nanometer scale resolution, i.e., transmission electron microscopy, atomic force microscopy (AFM and conductive atomic force microscopy (C-AFM. In particular, a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values. Two-dimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material. The results are compared with a recently introduced gate control processing: the local rapid thermal oxidation process of the AlGaN layer. By this process, a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally.

  6. Electrical And Optical Properties Of Colloidal Quantum Dots And Quantum Dot Networks: Role Of Surface States And Using Biomolecular Links In Network Assembly

    National Research Council Canada - National Science Library

    Stroscio, Michael A; Dutta, Mitra; Ramadurai, Dinakar; Shi, Peng; Li, Yang; Alexson, Dimitri; Kohanpour, Babak; Sethuraman, Akil; Saini, Vikas; Raichura, Amit; Yang, Jianyong

    2004-01-01

    .... Absorption spectra and photoluminescence (PL) spectra of colloidal cadmium sulfide (CdS) quantum dots are analyzed to investigate the role of surface states in determining the electrical and optical properties of these semiconductor quantum dots...

  7. Electrical stimulation and splinting were not clearly more effective than splinting alone for contracture management after acquired brain injury: a randomised trial.

    Science.gov (United States)

    Leung, Joan; Harvey, Lisa A; Moseley, Anne M; Tse, Charis; Bryant, Jane; Wyndham, Shirley; Barry, Siobhan

    2012-01-01

    Is electrical stimulation and splinting more effective than splinting alone for the management of wrist contracture following acquired brain injury? A multi-centre randomised trial with concealed allocation, assessor blinding, and intention-to-treat analysis. Thirty-six adults with first stroke or traumatic brain injury and mild to moderate wrist flexion contractures. The experimental group received electrical stimulation to the wrist and finger extensor muscles for 1 hour a day over 4 weeks while the control group did not. Both groups wore a splint for 12 hours a day during this 4-week period. The primary outcome was passive wrist extension measured with a 3Nm torque and with the fingers in extension. Secondary outcomes included passive wrist extension, wrist and finger extensor strength, wrist flexor spasticity, motor control of the hand, and Global Perceived Effect of Treatment, and perception of treatment credibility. Outcome measures were taken at baseline, at the end of the intervention period (4 weeks), and after a 2-week follow-up period (6 weeks). At 4 and 6 weeks, the mean between-group difference (95% CI) for passive wrist extension was 7 degrees (-2 to 15) and -3 degrees (-13 to 7), respectively. Secondary outcomes were statistically non-significant or were of borderline statistical significance. It is not clear whether electrical stimulation and splinting is more effective than splinting alone for the management of wrist contracture after acquired brain injury. Therapists' confidence in the efficacy of electrical stimulation for contracture management is not yet justified. Copyright © 2012 Australian Physiotherapy Association. Published by .. All rights reserved.

  8. Potential of electrical resistivity tomography and muon density imaging to study spatio-temporal variations in the sub-surface

    Science.gov (United States)

    Lesparre, Nolwenn; Cabrera, Justo; Courbet, Christelle

    2015-04-01

    We explore the capacity of electrical resistivity tomography and muon density imaging to detect spatio-temporal variations of the medium surrounding a regional fault crossing the underground platform of Tournemire (Aveyron, France). The studied Cernon fault is sub-vertical and intersects perpendicularly the tunnel of Tournemire and extends to surface. The fault separates clay and limestones layers of the Dogger from limestones layers of the Lias. The Cernon fault presents a thickness of a ten of meters and drives water from an aquifer circulating at the top of the Dogger clay layer to the tunnel. An experiment combining electrical resistivity imaging and muon density imaging was setup taking advantage of the tunnel presence. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault in order to acquire data in transmission across the massif to better cover the sounded medium. Electrical resistivity is particularly sensitive to water presence in the medium and thus carry information on the main water flow paths and on the pore space saturation. At the same time a muon sensor was placed in the tunnel under the fault region to detect muons coming from the sky after their crossing of the rock medium. Since the muon flux is attenuated as function of the quantity of matter crossed, muons flux measurements supply information on the medium average density along muons paths. The sensor presents 961 angles of view so measurements performed from one station allows a comparison of the muon flux temporal variations along the fault as well as in the medium surrounding the fault. As the water saturation of the porous medium fluctuates through time the medium density might indeed present sensible variations as shown by gravimetric studies. During the experiment important rainfalls occurred leading variations of the medium properties

  9. Effects of Surface Modification of MWCNT on the Mechanical and Electrical Properties of Fluoro Elastomer/MWCNT Nanocomposites

    Directory of Open Access Journals (Sweden)

    Tao Xu

    2012-01-01

    Full Text Available Surface modification is a good way to improve the surface activity and interfacial strength of multiwalled carbon nanotubes (MWCNTs when used as fillers in the polymer composites. Among the reported methods for nanotube modification, mixed acid oxidation and plasma treatment is often used by introducing polar groups to the sidewall of MWCNT successfully. The purpose of this study is to evaluate the effect of different surface modification of MWCNT on the mechanical property and electrical conductivity of Fluoro-elastomer (FE/MWCNT nanocomposites. MWCNTs were surface modified by mixed oxidation and CF4 plasma treatment and then used to reinforce the fluoro elastomer (FE, a copolymer of trifluorochloroethylene and polyvinylidene fluoride. FE/MWCNT composite films were prepared from mixture solutions of ethylacetate and butylacetate, using untreated CNTs (UCNTs, acid-modified CNTs (ACNTs, and CF4 plasma-modified CNT (FCNTs. In each case, MWCNT content was 0.01 wt%, 0.05 wt%, 0.1 wt%, and 0.2 wt% with respect to the polymer. Morphology and mechanical properties were characterized by using scanning electron microscopy (SEM, Raman spectroscopy, as well as dynamic mechanical tests. The SEM results indicated that dispersion of ACNTs and especially FCNTs in FE was better than that of UCNTs. DMA indicated mechanical properties of FCNT composites were improved over ACNT and UCNT filled FE. The resulting electrical properties of the composites ranged from dielectric behavior to bulk conductivities of 10-2 Sm-1 and were found to depend strongly on the surface modification methods of MWCNTs.

  10. Electric and magnetic surface polariton mediated near-field radiative heat transfer between metamaterials made of silicon carbide particles.

    Science.gov (United States)

    Francoeur, Mathieu; Basu, Soumyadipta; Petersen, Spencer J

    2011-09-26

    Near-field radiative heat transfer between isotropic, dielectric-based metamaterials is analyzed. A potassium bromide host medium comprised of silicon carbide (SiC) spheres with a volume filling fraction of 0.4 is considered for the metamaterial. The relative electric permittivity and relative magnetic permeability of the metamaterial are modeled via the Clausius-Mossotti relations linking the macroscopic response of the medium with the polarizabilities of the spheres. We show for the first time that electric and magnetic surface polariton (SP) mediated near-field radiative heat transfer occurs between dielectric-based structures. Magnetic SPs, existing in TE polarization, are physically due to strong magnetic dipole resonances of the spheres. We find that spherical inclusions with radii of 1 μm (or greater) are needed in order to induce SPs in TE polarization. On the other hand, electric SPs existing in TM polarization are generated by surface modes of the spheres, and are thus almost insensitive to the size of the inclusions. We estimate that the total heat flux around SP resonance for the metamaterial comprised of SiC spheres with radii of 1 μm is about 35% greater than the flux predicted between two bulks of SiC, where only surface phonon-polaritons in TM polarization are excited. The results presented in this work show that the near-field thermal spectrum can be engineered via dielectric-based metamaterials, which is crucial in many emerging technologies, such as in nanoscale-gap thermophotovoltaic power generation. © 2011 Optical Society of America

  11. Mechanical and electrical cold bonding based on metallic nanowire surface fasteners.

    Science.gov (United States)

    Ju, Yang; Amano, Masahiro; Chen, Mingji

    2012-09-14

    Mass production of surface mount devices (SMDs) relies heavily on reflow soldering and has become the cornerstone of today's electronic industry. However, the traditional reflow soldering technique is characterized by high heating temperatures, toxic solder materials and low recycling rate of SMDs. Here, we propose a new patterned structure of Au nanowire arrays named a surface fastener through which cold bonding for surface mount technology can be realized. The mechanical bonding enables normal and shear bonding strengths of more than 5 N cm(-2). Simultaneously, the parasitic resistance of a pair of surface fasteners is only approximately 2 Ω. The present technique can be performed at room temperature, thereby improving the process compatibility and reliability of SMDs. Surface fasteners based on high melting point metallic nanowires are temperature-resistant for many critical applications. In addition, bonding without solder material is positive for the recycling of rare metals in SMDs.

  12. Apparatus for sensing patterns of electrical field variations across a surface

    Energy Technology Data Exchange (ETDEWEB)

    Warren, William L. (Arlington, VA); Devine, Roderick A. B. (Paris, FR)

    2001-01-01

    An array of nonvolatile field effect transistors used to sense electric potential variations. The transistors owe their nonvolatility to the movement of protons within the oxide layer that occurs only in response to an externally applied electric potential between the gate on one side of the oxide and the source/drain on the other side. The position of the protons within the oxide layer either creates or destroys a conducting channel in the adjacent source/channel/drain layer below it, the current in the channel being measured as the state of the nonvolatile memory. The protons can also be moved by potentials created by other instrumentalities, such as charges on fingerprints or styluses above the gates, pressure on a piezoelectric layer above the gates, light shining upon a photoconductive layer above the gates. The invention allows sensing of fingerprints, handwriting, and optical images, which are converted into digitized images thereof in a nonvolatile format.

  13. Surface neuromuscular electrical stimulation for quadriceps strengthening pre and post total knee replacement.

    LENUS (Irish Health Repository)

    Monaghan, Brenda

    2010-01-01

    Total knee replacement has been demonstrated to be one of the most successful procedures in the treatment of osteoarthritis. However quadriceps weakness and reductions in function are commonly reported following surgery. Recently Neuromuscular Electrical Stimulation (NMES) has been used as an adjunct to traditional strengthening programmes. This review considers the effectiveness of NMES as a means of increasing quadriceps strength in patients before and after total knee replacement.

  14. Surface Morphology and Electrical Resistivity in Polycrystalline Au/Cu/Si(100 System

    Directory of Open Access Journals (Sweden)

    T. E. Novelo

    2017-01-01

    Full Text Available This work describes the analysis of morphology and electrical resistivity (ρ obtained in the Au/Cu/Si system. The Au/Cu bilayers were deposited by thermal evaporation technique with thicknesses from 50 to 250 nm on SiOx/Si(100 substrates. The Au : Cu concentration ratio of the samples was of 25 : 75 at%. The bilayers were annealed into a vacuum oven with argon atmosphere at 660 K for one hour. The crystalline structures of AuCu and CuSi alloys were confirmed by X-ray diffraction analysis. The scanning electron microscopy (SEM, the atomic force microscopy (AFM, and the energy dispersive spectroscopy (EDS were used to study the morphology, final thickness, and the atomic concentration of the alloys formed, respectively. The four-point probe technique was used to measure the electrical resistivity (ρ in the prepared alloys as a function of thickness. The ρ value was measured and it was numerically compared with the Fuchs–Sondheimer (FS and the Mayadas–Shatzkes (MS models of resistivity. Results show values of electrical resistivity between 0.9 and 1.9 μΩ-cm. These values are four times smaller than the values of the AuCu systems reported in literature.

  15. Method of Integral Equations for the Problem of Electrical Tomography in a Medium with Ground Surface Relief

    Directory of Open Access Journals (Sweden)

    Tolkyn Mirgalikyzy

    2015-01-01

    Full Text Available The direct task of the subsurface exploration of a homogeneous medium with surface relief by the resistivity method is analyzed. To calculate the resistivity field for such a medium, the method of integral equations was successfully applied for the first time. The corresponding integral equation for the density of secondary current sources on the surface of the medium was established. The method of computational grid construction, adapted to the characteristics of the surface relief, was developed for the numerical solution of the integral equation. This method enables the calculation of the resistivity field of a point source on a surface that is not smooth and allows for steep ledges. Numerical examples of the calculation of resistivity fields and apparent resistivity are shown. The anomalies of apparent resistivity arising from the deviation of the surface shape from a flat medium were quantitatively established as model examples. Calculations of apparent resistivity for the direct current sounding method were carried out using modifications of the electrical tomography approach.

  16. A combined solenoid-surface RF coil for high-resolution whole-brain rat imaging on a 3.0 Tesla clinical MR scanner.

    Science.gov (United States)

    Underhill, Hunter R; Yuan, Chun; Hayes, Cecil E

    2010-09-01

    Rat brain models effectively simulate a multitude of human neurological disorders. Improvements in coil design have facilitated the wider utilization of rat brain models by enabling the utilization of clinical MR scanners for image acquisition. In this study, a novel coil design, subsequently referred to as the rat brain coil, is described that exploits and combines the strengths of both solenoids and surface coils into a simple, multichannel, receive-only coil dedicated to whole-brain rat imaging on a 3.0 T clinical MR scanner. Compared with a multiturn solenoid mouse body coil, a 3-cm surface coil, a modified Helmholtz coil, and a phased-array surface coil, the rat brain coil improved signal-to-noise ratio by approximately 72, 61, 78, and 242%, respectively. Effects of the rat brain coil on amplitudes of static field and radiofrequency field uniformity were similar to each of the other coils. In vivo, whole-brain images of an adult male rat were acquired with a T(2)-weighted spin-echo sequence using an isotropic acquisition resolution of 0.25 x 0.25 x 0.25 mm(3) in 60.6 min. Multiplanar images of the in vivo rat brain with identification of anatomic structures are presented. Improvement in signal-to-noise ratio afforded by the rat brain coil may broaden experiments that utilize clinical MR scanners for in vivo image acquisition. 2010 Wiley-Liss, Inc.

  17. Electric Double Layer Composed of an Antagonistic Salt in an Aqueous Mixture: Local Charge Separation and Surface Phase Transition

    Science.gov (United States)

    Yabunaka, Shunsuke; Onuki, Akira

    2017-09-01

    We examine an electric double layer containing an antagonistic salt in an aqueous mixture, where the cations are small and hydrophilic but the anions are large and hydrophobic. In this situation, a strong coupling arises between the charge density and the solvent composition. As a result, the anions are trapped in an oil-rich adsorption layer on a hydrophobic wall. We then vary the surface charge density σ on the wall. For σ >0 the anions remain accumulated, but for σ cations are attracted to the wall with increasing |σ |. Furthermore, the electric potential drop Ψ (σ ) is nonmonotonic when the solvent interaction parameter χ (T ) exceeds a critical value χc determined by the composition and the ion density in the bulk. This leads to a first-order phase transition between two kinds of electric double layers with different σ and common Ψ . In equilibrium such two-layer regions can coexist. The steric effect due to finite ion sizes is crucial in these phenomena.

  18. Stimulation parameter optimization for functional electrical stimulation assisted gait in human spinal cord injury using response surface methodology.

    Science.gov (United States)

    Kim, Yongchul; Schmit, Brian D; Youm, Youngil

    2006-06-01

    The aims of this study were to identify the reflex moment induced by flexion withdrawal reflex and to optimize stimulation parameters for restoring swing motion with respect to initial kinematic conditions in human with spinal cord injury. The influence of hip position and passive movement in the reflex moment were tested in six subjects with chronic spinal cord injury. The two-dimensional dynamic models consisted of thigh, shank and foot segments were developed to compute the swing-phase response and the response surface method was also used to optimize stimulation parameters for restoration of gait by functional electrical stimulation. At three different hip positions, significant linear relationship was found between the reflex moment and hip angle (P spinal cord injured patients. From dynamic simulation, we concluded that optimal solutions of pulse amplitude, frequency and duration time of burst for electrical stimulation assisted gait were influenced by initial kinematic conditions at toe-off. The reflex model and the results of this study can be applied to the design and control strategies of neuroprosthetic devices using functional electrical stimulation for spinal cord injured patients.

  19. Electric field-induced metallic transition of (3,3) carbon nanotube supported on patterned hydrogen-terminated Si(001):1 Multiplication-Sign 1 surface

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Bikash C., E-mail: bikashc.gupta@visva-bharati.ac.in [Virginia Commonwealth University, Department of Physics (United States); Konar, Shyamal [Visva-Bharati, Department of Physics (India); Jena, Puru [Virginia Commonwealth University, Department of Physics (United States)

    2012-08-15

    Using density functional theory, we systematically investigate the adsorption geometries and electrical properties of (3,3) carbon nanotube (CNT) integrated on hydrogen-terminated Si(001):1 Multiplication-Sign 1 surface. Prior to adsorption of the CNT, the surface is patterned in two different ways by desorbing selective hydrogen atoms from the surface. The (3,3) CNT which is metallic in nature becomes semiconducting with a band gap around the fermi level when it is supported on patterned hydrogen-terminated Si(001):1 Multiplication-Sign 1 surface. However, the band gap is reduced when a transverse electric field is applied, allowing the (3,3) CNT on the patterned hydrogen-terminated Si(001):1 Multiplication-Sign 1 to become metallic at a critical field strength. The tuning of electrical properties of the (3,3) CNT integrated with Si surface may have potential technological applications.

  20. Scalloped electrodes for highly sensitive electrical measurements

    DEFF Research Database (Denmark)

    Vazquez Rodriguez, Patricia; Dimaki, Maria; Svendsen, Winnie Edith

    2011-01-01

    In this work we introduce a novel out-of-plane electrode with pronounced scalloped surface and high aspect ratio for electrical recordings of brain tissue in vitro, with the aim to reduce significantly the impedance of the measuring system. The profile and height of the structures is tailored by ...

  1. Brain Basics

    Medline Plus

    Full Text Available ... and certain abilities, such as a good singing voice. A gene is a segment of DNA that ... as in areas of the brain that control movement. When electrical signals are abnormal, they can cause ...

  2. Brain Basics

    Medline Plus

    Full Text Available ... another as chemical or electrical signals. The brain begins as a small group of cells in the ... how she's responding to the treatment. She also begins regular talk therapy sessions with her psychiatrist. In ...

  3. Brain Basics

    Medline Plus

    Full Text Available ... Us Home About the Director Advisory Boards and Groups Strategic Plan Offices and Divisions Budget Careers at ... electrical signals. The brain begins as a small group of cells in the outer layer of a ...

  4. Brain Basics

    Medline Plus

    Full Text Available ... and information that the cell needs for growth, metabolism, and repair. Cytoplasm is the substance that fills ... as in areas of the brain that control movement. When electrical signals are abnormal, they can cause ...

  5. Brain Basics

    Medline Plus

    Full Text Available ... as in areas of the brain that control movement. When electrical signals are abnormal, they can cause ... normal mood functioning. Dopamine —mainly involved in controlling movement and aiding the flow of information to the ...

  6. Surface Morphology and Electrical Resistivity in Polycrystalline Au/Cu/Si(100) System

    OpenAIRE

    Novelo, T. E.; Alonzo-Medina, G. M.; P. Amézaga-Madrid; Maldonado, R.D.

    2017-01-01

    This work describes the analysis of morphology and electrical resistivity (ρ) obtained in the Au/Cu/Si system. The Au/Cu bilayers were deposited by thermal evaporation technique with thicknesses from 50 to 250 nm on SiOx/Si(100) substrates. The Au : Cu concentration ratio of the samples was of 25 : 75 at%. The bilayers were annealed into a vacuum oven with argon atmosphere at 660 K for one hour. The crystalline structures of AuCu and CuSi alloys were confirmed by X-ray diffraction analysis. T...

  7. Human Missions to Mars Orbit, Phobos, and Mars Surface Using 100-kWe-Class Solar Electric Propulsion

    Science.gov (United States)

    Price, Humphrey W.; Woolley, Ryan C.; Strange, Nathan J.; Baker, John D.

    2014-01-01

    Solar electric propulsion (SEP) tugs in the 100-kWe range, may be utilized to preposition cargo in the Mars system to enable more affordable human missions to Phobos and to the surface of Mars. The SEP tug, a high heritage follow-on to the 50-kWe SEP spacecraft proposed for the Asteroid Redirect Robotic Mission (ARRM), would have the same structure, tankage, electric propulsion components, and avionics as the ARRM version, But with double the number of solar arrays, Hall thrusters, and power processor units (PPUs) and would be accommodated within the same launch envelope defined for ARRM. As a feasibility study, a 950-day human mission to Phobos using a conjunction class trajectory, such as the 2033 opportunity, was developed using two 100-kWe SEP vehicles to preposition a habitat at Phobos and propulsion stages in high Mars orbit (HMO). An architecture concept for a crewed Mars surface lander mission was also developed as a reference to build on the Phobos mission architecture, adding a lander element that could be delivered using chemical propulsion and aerocapture.

  8. P-I-N Silicon Nanowires: Raman Spectroscopy, Electrical Characterization, and TCAD Simulation of Doping and Surface States

    Science.gov (United States)

    O'Regan, Terrance; Krylyuk, Sergiy; Birdwell, A. Glen; Sharma, Deepak; Crowne, Frank; Motayed, Abhishek; Shah, Pankaj; Davydov, Albert V.

    2013-03-01

    We investigated the alternate axial doping of silicon nanowires with Raman spectroscopy, electrical characterization, and TCAD simulation. The P-I-N nanowires were grown in a hot-wall CVD reactor via the vapor-liquid-solid mechanism with gold catalyst and doped in-situ. The resulting nanowire diameters and lengths were nominally 140 nm and 10 ?m, respectively. Peak broadening as a result of the Fano effect seen in the Raman line shape was compared to the bulk Si data in the literature to estimate the doping type and concentration. Electrical characterization and TCAD simulation confirmed the Raman results and were used to estimate the doping distribution, especially at the diode junctions and nanowire surface. Although Raman spectroscopy was useful in determining type and concentration of doping along the length of the nanowires, it was unable to resolve doping concentration along the nanowire diameter or at the axial junctions due to limited spatial resolution (about 350 nm). Furthermore, the Raman results showed sensitivity to surface states at the ends of the nanowires.

  9. Influence of surface roughness on the tribo-electric process for a sliding contact between polymeric plate materials

    Science.gov (United States)

    Neagoe, M. B.; Prawatya, Y. E.; Zeghloul, T.; Dascalescu, L.

    2017-02-01

    Polymers are used in many industrial applications due to their good mechanical and thermal properties. Studies have shown that electrical insulators, such as the polymers, are generating electrostatic charge by frictional contact. This tribo-charging effect influences de sliding conditions, and the level of charge depends of several factors. The aim of this paper is to validate two paradigms: (I) the electrostatic charge increases with contact pressure; (II) the level of charge is influenced by the number of contact points on the surface. The tribocharging experiments were carried out with samples cut from two polymers: Acrylonitrile-Butadiene-Styrene, 5 mm x 15mm x100 mm, roughness: Ra = 0.4 µm and Polyvinyl Chloride, 5 mm x 50 mm x 180 mm, with various roughness values: Ra = 3-12 µm and RSm = 150-350 µm. The modification of asperity density was accompanied by changes in the electric potential measured at the surface of the PVC samples. Thus, its average value V increased from -0.33 to -0.85 kV, and its maximum value Vmax, from -1.56 to -4.83 kV.

  10. Modeling the effects of electrical and non-electrical parameters on the material removal and surface integrity in case of µEDM of a non-conductive ceramic material using a combined fuzzy-AOM approach

    DEFF Research Database (Denmark)

    Puthumana, Govindan

    2016-01-01

    Micro-EDM is a non-contact process based on the thermoelectric energy between a tool electrode and a workpiece. In μEDM process, the mechanism of material removal is melting and evaporation. The thermal energy in the discharge plasma helps remove material from the workpiece, at the same time...... and surface integrity for a non-conductive ceramic material. The fuzzy logic modeling system is employed for predicting the μEDM process responses. The trends in the material removal rate and hardness values with the chosen electrical and non-electrical parameter for the model and obtained using AOM approach...... deteriorates the quality and integrity of the workpiece surface. The material removal phenomenon in μEDM of partially conductive and non-conductive materials is very complex. This paper presents a novel approach to model the effects of electrical and non-electrical parameters on the material removal phenomenon...

  11. Surface Laplacian of scalp electrical signals and independent component analysis resolve EMG contamination of electroencephalogram.

    Science.gov (United States)

    Fitzgibbon, S P; DeLosAngeles, D; Lewis, T W; Powers, D M W; Whitham, E M; Willoughby, J O; Pope, K J

    2015-09-01

    The serious impact of electromyogram (EMG) contamination of electroencephalogram (EEG) is well recognised. The objective of this research is to demonstrate that combining independent component analysis with the surface Laplacian can eliminate EMG contamination of the EEG, and to validate that this processing does not degrade expected neurogenic signals. The method involves sequential application of ICA, using a manual procedure to identify and discard EMG components, followed by the surface Laplacian. The extent of decontamination is quantified by comparing processed EEG with EMG-free data that was recorded during pharmacologically induced neuromuscular paralysis. The combination of the ICA procedure and the surface Laplacian, with a flexible spherical spline, results in a strong suppression of EMG contamination at all scalp sites and frequencies. Furthermore, the ICA and surface Laplacian procedure does not impair the detection of well-known, cerebral responses; alpha activity with eyes-closed; ERP components (N1, P2) in response to an auditory oddball task; and steady state responses to photic and auditory stimulation. Finally, more flexible spherical splines increase the suppression of EMG by the surface Laplacian. We postulate this is due to ICA enabling the removal of local muscle sources of EMG contamination and the Laplacian transform being insensitive to distant (postural) muscle EMG contamination. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Surface roughness dependence of the electrical resistivity of W(001) layers

    Science.gov (United States)

    Zheng, P. Y.; Zhou, T.; Engler, B. J.; Chawla, J. S.; Hull, R.; Gall, D.

    2017-09-01

    The resistivity ρ of epitaxial W(001) layers grown on MgO(001) at 900 °C increases from 5.63 ± 0.05 to 27.6 ± 0.6 μΩ-cm with decreasing thickness d = 390 to 4.5 nm. This increase is due to electron-surface scattering but is less pronounced after in situ annealing at 1050 °C, leading to a 7%-13% lower ρ for d contrast, introducing an additive resistivity term ρmound which accounts for surface roughness resolves both shortcomings. The new term is due to electron reflection at surface mounds and is, therefore, proportional to the ballistic resistance times the average surface roughness slope, divided by the layer thickness. This is confirmed by a measured linear relationship between ρmound and σ/(Ld), where the root-mean-square roughness σ and the lateral correlation length L of the surfaces are directly measured using atomic force microscopy and X-ray reflectivity.

  13. Review of Electrical and Gravity Methods of Near-Surface Exploration for Groundwater

    Directory of Open Access Journals (Sweden)

    W. O. Raji

    2014-12-01

    Full Text Available The theory and practice of electrical and gravity methods of geophysics for groundwater exploration was reviewed with illustrations and data examples. With the goal of reducing cases of borehole/water-well failure attributed to the lack of the knowledge of the methods of geophysics for groundwater exploration and development, the paper reviews the basic concepts, field procedures for data acquisition, data processing, and interpretation as applied to the subject matter. Given a case study of groundwater exploration in University of Ilorin Campus, the three important techniques of electrical method of groundwater exploration are explained and illustrated using field data obtained in a previous study. Interpretation of resistivity data shows that an area measuring low resistivity (high conductivity, having thick pile of unconsolidated rock, and underlained by fracture crystalline is a ‘bright spot’ for citing borehole for groundwater abstraction in a basement complex area. Further to this, gravity method of groundwater exploration was discussed with field data from Wokbedilo community in Ethopia. Bouguer and reduced gravity anomaly results were presented as maps and contours to demonstrate how gravity data can be inverted to map groundwater aquifers and subsurface geological structures during groundwater exploration.

  14. Surface-effect enhanced magneto-electric coupling in FePt/PMN-PT multiferroic heterostructures

    Science.gov (United States)

    Yang, Y. T.; Li, J.; Peng, X. L.; Hong, B.; Wang, X. Q.; Ge, H. L.; Wang, D. H.; Du, Y. W.

    2017-05-01

    A series of FePt films with different film thickness are deposited on Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) substrates. A standard symmetric `Butterfly' shaped Δ M /M -Ed c loops is obtained in 8 nm FePt/PMN-PT heterostrucuture via strain mediated magnetoelectric coupling. For the 3 nm FePt/PMN-PT heterostructure, the loop-like in-plane magnetization (M) -E curve shares a similar shape with the electric polarization of PMN-PT as a function of electric field. The value of MS shows a dramatic change of 30.9% with Edc changing from 0 to 8 kV/cm, this giant magnetoelectric effect in 3 nm FePt/PMN-PT heterostructure results from the remnant polarization induced charge on FePt/PMN-PT interface via the screening charge effect. The enhanced magnetoelectric coupling in thin magnetic/ferroelectric heterostructures opens a promising avenue for the design of ultralow power magnetoelectric devices and information storage devices.

  15. Surface-effect enhanced magneto-electric coupling in FePt/PMN-PT multiferroic heterostructures

    Directory of Open Access Journals (Sweden)

    Y. T. Yang

    2017-05-01

    Full Text Available A series of FePt films with different film thickness are deposited on Pb(Mg1/3Nb2/3O3–PbTiO3 (PMN-PT substrates. A standard symmetric ‘Butterfly’ shaped ΔM/M-Edc loops is obtained in 8 nm FePt/PMN-PT heterostrucuture via strain mediated magnetoelectric coupling. For the 3 nm FePt/PMN-PT heterostructure, the loop-like in-plane magnetization (M -E curve shares a similar shape with the electric polarization of PMN-PT as a function of electric field. The value of MS shows a dramatic change of 30.9% with Edc changing from 0 to 8 kV/cm, this giant magnetoelectric effect in 3 nm FePt/PMN-PT heterostructure results from the remnant polarization induced charge on FePt/PMN-PT interface via the screening charge effect. The enhanced magnetoelectric coupling in thin magnetic/ferroelectric heterostructures opens a promising avenue for the design of ultralow power magnetoelectric devices and information storage devices.

  16. INVESTIGATION OF SURFACE PROPERTIES IN MANGANESE POWDER MIXED ELECTRICAL DISCHARGE MACHINING OF OHNS AND D2 DIE STEELS

    Directory of Open Access Journals (Sweden)

    S. Kumar

    2010-12-01

    Full Text Available The electrical discharge machining (EDM process is used for generating accurate internal profiles in hardened materials. An powder additive in the hydrocarbon dielectric affects the energy distribution and sparking efficiency, and consequently the surface finish and micro-hardness. In this paper the Taguchi approach has been used to optimize and compare the surface properties in manganese powder-mixed EDM of oil-hardening non-shrinkable (OHNS and high-carbon high-chromium (D2 die steels. The results of the study show an improvement of 73% and 71.6% in the micro-hardness of OHNS and D2 die steels, respectively. The machining parameters for the best value of micro-hardness are found to be the same for both work materials. A scanning electron microscopy and X-ray diffraction analysis of the machined surfaces show a transfer of manganese and carbon from the plasma channel in the form of manganese carbide. The chemical composition of the machined surface has been further checked on an optical emission spectrometer to verify and quantify the results.

  17. Electrical potential-assisted DNA hybridization. How to mitigate electrostatics for surface DNA hybridization.

    Science.gov (United States)

    Tymoczko, Jakub; Schuhmann, Wolfgang; Gebala, Magdalena

    2014-12-24

    Surface-confined DNA hybridization reactions are sensitive to the number and identity of DNA capture probes and experimental conditions such as the nature and the ionic strength of the electrolyte solution. When the surface probe density is high or the concentration of bulk ions is much lower than the concentration of ions within the DNA layer, hybridization is significantly slowed down or does not proceed at all. However, high-density DNA monolayers are attractive for designing high-sensitivity DNA sensors. Thus, circumventing sluggish DNA hybridization on such interfaces allows a high surface concentration of target DNA and improved signal/noise ratio. We present potential-assisted hybridization as a strategy in which an external voltage is applied to the ssDNA-modified interface during the hybridization process. Results show that a significant enhancement of hybridization can be achieved using this approach.

  18. Bacterial inhibiting surfaces caused by the effects of silver release and/or electrical field

    DEFF Research Database (Denmark)

    Chiang, Wen-Chi; Hilbert, Lisbeth Rischel; Schroll, Casper

    2008-01-01

    In this study, silver-palladium surfaces and silver-bearing stainless steels were designed and investigated focusing on electrochemical principles to form inhibiting effects on planktonic and/or biofilm bacteria in water systems. Silver-resistant Escherichia coli and silver-sensitive E. coli were...... silver ions release can occur from their Surfaces. For silver-bearing stainless steels, the inhibiting effect can only be explained by high local silver ions release. and can be limited or deactivated dependent on the specific environment. (c) 2008 Elsevier Ltd. All rights reserved....

  19. Learned EEG-based brain self-regulation of motor-related oscillations during application of transcranial electric brain stimulation: Feasibility and limitations

    NARCIS (Netherlands)

    Soekadar, S.R.; Witkowski, M.; Garcia Cossio, E.; Birbaumer, N.; Cohen, L.G.

    2014-01-01

    Objective: Transcranial direct current stimulation (tDCS) improves motor learning and can affect emotional processing and attention. However, it is unclear whether learned electroencephalography (EEG)-based brain-machine interface (BMI) control during tDCS is feasible, how application of

  20. A Study on the Effect of Electrical Stimulation as a User Stimuli for Motor Imagery Classification in Brain-Machine Interface.

    Science.gov (United States)

    Bhattacharyya, Saugat; Clerc, Maureen; Hayashibe, Mitsuhiro

    2016-06-13

    Functional Electrical Stimulation (FES) provides a neuroprosthetic interface to non-recovered muscle groups by stimulating the affected region of the human body. FES in combination with Brain-machine interfacing (BMI) has a wide scope in rehabilitation because this system directly links the cerebral motor intention of the users with its corresponding peripheral muscle activations. In this paper, we examine the effect of FES on the electroencephalography (EEG) during motor imagery (left- and right-hand movement) training of the users. Results suggest a significant improvement in the classification accuracy when the subject was induced with FES stimuli as compared to the standard visual one.

  1. Involvement of the middle frontal gyrus in language switching as revealed by electrical stimulation mapping and functional magnetic resonance imaging in bilingual brain tumor patients.

    Science.gov (United States)

    Sierpowska, Joanna; Fernandez-Coello, Alejandro; Gomez-Andres, Alba; Camins, Àngels; Castañer, Sara; Juncadella, Montserrat; Gabarrós, Andreu; Rodríguez-Fornells, Antoni

    2018-02-01

    Neural basis of language switching and the cognitive models of bilingualism remain controversial. We explored the functional neuroanatomy of language switching implementing a new multimodal protocol assessing neuropsychological, functional magnetic resonance and intraoperative electrical stimulation mapping results. A prospective series of 9 Spanish-Catalan bilingual candidates for awake brain surgery underwent a specific language switching paradigm implemented both before and after surgery, throughout the electrical stimulation procedure and during functional magnetic resonance both pre- and postoperatively. All patients were harboring left-hemispheric intrinsic brain lesions and were presenting functional language-related activations within the affected hemisphere. Language functional maps were reconstructed on the basis of the intraoperative electrical stimulation results and compared to the functional magnetic resonance findings. Single language-naming sites (Spanish and Catalan), as well as language switching naming sites were detected by electrical stimulation mapping in 8 patients (in one patient only Spanish related sites were detected). Single naming points outnumbered the switching points and did not overlap with each other. Within the frontal lobe, the single language naming sites were found significantly more frequently within the inferior frontal gyrus as compared to the middle frontal gyrus [X 2 (1) = 20.3, p language switching and their neuropsychological scores did not differ significantly from the pre-surgical examinations. Our results suggest a functional division of the frontal cortex between naming and language switching functions, supporting that non-language specific cognitive control prefrontal regions (middle frontal gyrus) are essential to maintain an effective communication together with the classical language-related sites (inferior frontal gyrus). Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Bipolar electrode behaviour of the aluminium surface in a lateral electric field

    NARCIS (Netherlands)

    Duval, J.F.L.; Kleijn, J.M.; Leeuwen, van H.P.

    2001-01-01

    This paper reports on the electrochemical processes at the surface of conducting materials such as aluminium in a thin-layer cell usually employed for electrokinetic measurements. The cell contains one or more planar Al wafers in contact with an electrolyte solution, which is subjected to an

  3. The electrical double layer on gold probed by electrokinetic and surface force measurements

    NARCIS (Netherlands)

    Giesbers, M.; Kleijn, J.M.; Cohen Stuart, M.A.

    2002-01-01

    Gold surfaces, obtained by vacuum deposition of 15-nm gold films on glass and silica wafers, were studied in aqueous solutions by streaming potential measurements and colloidal-probe AFM force measurements. In the force measurements both a bare and a gold-coated silica particle (6 m in diameter)

  4. Materials Handling for Electrical Modification of a Complex Target Surface: Analysis and Feasibility

    Energy Technology Data Exchange (ETDEWEB)

    Giles, D K; Law, S E; Tringe, J W

    2009-01-06

    This project effort, conducted as feasibility investigations addresses the transport and deposition of particulates using traveling field, electrohydrodynamic atomization and gas carrier methods. The method of investigation was experimental, using existing experimental and pre-commercial apparatus. All methods were found to be successful to varying degrees. Preliminary results were presented at LLNL in a project review meeting. The most promising methods for particle delivery were electrodynamic atomization/spraying and gas-carrier propulsion. Traveling field delivery is limited by scale up considerations and the requirement for transport through close tolerances. Electrodynamic atomization requires use of low electrical conductivity liquid carrier phases but is scalable by ganging multiple orifices and atomizing tips. Gas carrier delivery is attractive because no liquid carrier is needed and momentum can higher than the other traveling field or electrodynamic processes. Subsequent phases of the project will address electrodynamic and gas-carrier delivery.

  5. Electrical performance of distribution insulators with chlorella vulgaris growth on its surface

    Directory of Open Access Journals (Sweden)

    H. E. Rojas

    2015-11-01

    Full Text Available This paper presents a study about electrical performance of ceramic and polymeric insulators bio-contaminated with alga Chlorella vulgaris. The performed tests involve ANSI 55-2 and ANSI 52-1 ceramic insulators and ANSI DS-15 polymeric insulators, all of them used in distribution systems of Colombia. Biological contamination of insulators is realized using a controlled environment chamber that adjusts the temperature, humidity and light radiation. The laboratory tests include measurements of flashover voltages and leakage currents and they were performed to determine how insulators are affected by biological contamination. After a series of laboratory tests, it was concluded that the presence of Chlorella vulgaris on the contaminated ceramic insulators reduces the wet flashover voltage up to 12% and increases their leakage currents up to 80%. On the other hand, for polymeric insulators the effect of algae growth on flashover voltages was not to strong, although the leakage currents increase up to 60%.

  6. A study of electric transmission lines for use on the lunar surface

    Science.gov (United States)

    Gaustad, Krista L.; Gordon, Lloyd B.; Weber, Jennifer R.

    1994-01-01

    The sources for electrical power on a lunar base are said to include solar/chemical, nuclear (static conversion), and nuclear (dynamic conversion). The transmission of power via transmission lines is more practical than power beaming or superconducting because of its low cost and reliable, proven technology. Transmission lines must have minimum mass, maximum efficiency, and the ability to operate reliably in the lunar environment. The transmission line design includes conductor material, insulator material, conductor geometry, conductor configuration, line location, waveform, phase selection, and frequency. This presentation oulines the design. Liquid and gaseous dielectrics are undesirable for long term use in the lunar vacuum due to a high probability of loss. Thus, insulation for high voltage transmission line will most likely be solid dielectric or vacuum insulation.

  7. Brain Basics

    Medline Plus

    Full Text Available ... will fire. This enhances the electrical flow among brain cells required for normal function and plays an important ... of neurons and their interconnections. neuron —A nerve cell that is the basic, working unit of the brain and nervous system, which processes and transmits information. ...

  8. Physiologic and anatomic characterization of the brain surface glia barrier of Drosophila.

    Science.gov (United States)

    DeSalvo, Michael K; Mayer, Nasima; Mayer, Fahima; Bainton, Roland J

    2011-09-01

    Central nervous system (CNS) physiology requires special chemical, metabolic, and cellular privileges for normal function, and blood-brain barrier (BBB) structures are the anatomic and physiologic constructs that arbitrate communication between the brain and body. In the vertebrate BBB, two primary cell types create CNS exclusion biology, a polarized vascular endothelium (VE), and a tightly associated single layer of astrocytic glia (AG). Examples of direct action by the BBB in CNS disease are constantly expanding, including key pathophysiologic roles in multiple sclerosis, stroke, and cancer. In addition, its role as a pharmacologic treatment obstacle to the brain is long standing; thus, molecular model systems that can parse BBB functions and understand the complex integration of sophisticated cellular anatomy and highly polarized chemical protection physiology are desperately needed. Compound barrier structures that use two primary cell types (i.e., functional bicellularity) are common to other humoral/CNS barrier structures. For example, invertebrates use two cell layers of glia, perineurial and subperineurial, to control chemical access to the brain, and analogous glial layers, fenestrated and pseudocartridge, to maintain the blood-eye barrier. In this article, we summarize our current understanding of brain-barrier glial anatomy in Drosophila, demonstrate the power of live imaging as a screening methodology for identifying physiologic characteristics of BBB glia, and compare the physiologies of Drosophila barrier layers to the VE/AG interface of vertebrates. We conclude that many unique BBB physiologies are conserved across phyla and suggest new methods for modeling CNS physiology and disease. Copyright © 2011 Wiley-Liss, Inc.

  9. Surface structure and electrical properties of solution processed lanthanum nickelate films

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Nirav C., E-mail: usjoshi@gmail.com; Joshi, U. S., E-mail: usjoshi@gmail.com [Department of Physics, University School of Sciences, Gujarat University, Ahmedabad-380009 (India)

    2014-04-24

    Conducting oxides with perovskite crystal structure have many advantages over the simple Pt or Au, Pt based metal bottom electrodes (BE), particularly in fabrication of ferroelectric as well as resistive random access memory devices, if they possess smooth surface morphology. LaNiO{sub 3} (LNO) thin films were prepared by modified chemical solution deposition method. Precursor solutions were spin coated onto SiO{sub 2}-substrates. Deposited layers were thermally treated in a pre-heated furnace at 550 °C and oxygenated up to 800 °C. Results of AFM and FESEM showed that films are very smooth (Ra = 1.69 nm), dense, crack-free and with monodispersed nanocrystallites. Growth conditions such as spinning rate, annealing rates and temperatures etc. have been optimized for mono dispersed crystallinity with very smooth surface morphology. Sheet resistivity, carrier concentration and RMS roughness were correlated with growth temperatures.

  10. Calculation of t8/5 by response surface methodology for electric arc welding applications

    Directory of Open Access Journals (Sweden)

    Meseguer-Valdenebro José Luis

    2014-01-01

    Full Text Available One of the greatest difficulties traditionally found in stainless steel constructions has been the execution of welding parts in them. At the present time, the available technology allows us to use arc welding processes for that application without any disadvantage. Response surface methodology is used to optimise a process in which the variables that take part in it are not related to each other by a mathematical law. Therefore, an empiric model must be formulated. With this methodology the optimisation of one selected variable may be done. In this work, the cooling time that takes place from 800 to 500ºC, t8/5, after TIG welding operation, is modelled by the response surface method. The arc power, the welding velocity and the thermal efficiency factor are considered as the variables that have influence on the t8/5 value. Different cooling times,t8/5, for different combinations of values for the variables are previously determined by a numerical method. The input values for the variables have been experimentally established. The results indicate that response surface methodology may be considered as a valid technique for these purposes.

  11. The effect of electron-surface scattering and thiol adsorption on the electrical resistivity of gold ultrathin films

    Energy Technology Data Exchange (ETDEWEB)

    Henriquez, Ricardo, E-mail: ricardo.henriquez@usm.cl [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2390123 (Chile); Del Campo, Valeria; Gonzalez-Fuentes, Claudio [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2390123 (Chile); Correa-Puerta, Jonathan [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma, Valparaíso (Chile); Moraga, Luis [Universidad Central de Chile, Toesca 1783, Santiago 8370178 (Chile); Flores, Marcos [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago (Chile); Segura, Rodrigo [Instituto de Química y Bioquímica, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso (Chile); Donoso, Sebastián; Marín, Francisca; Bravo, Sergio; Häberle, Patricio [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2390123 (Chile)

    2017-06-15

    Highlights: • We prepared ultra thin films (10 nm) on mica on top of a chromium seedlayer (<1 nm). • We prepared samples with different topographies controlling the substrate temperature. • We studied the contribution of the different scattering mechanims on the resistivity. • We developed a discernment method based on thiol adsorption. - Abstract: In order to study the effect of electron-surface scattering in gold ultrathin films (∼10 nm), we have prepared a set of Au samples on mica on top of a chromium seedlayer (<1 nm). Chromium is added as a metallic surfactant which enables surpassing the electric percolation threshold for substrate temperatures above room temperature. We prepared samples with the same thickness but different topographies setting different substrate temperatures. These modifications modulate the contributions of the different electronic scattering mechanisms to the film resistivity. A second set of gold thin films deposited on mica at room temperature, with different thicknesses between 8 and 100 nm, was also prepared to compare the resisitivities of both sets through Mayadas and Shatzkes theory. We found that in samples with thicknesses below 15 nm, the electron-surface scattering is indeed the dominant mechanism influencing the film resistivity. To obtain further evidence of this prevalence, we developed a discrimination method based on thiol adsorption. The film with the highest resistivity increase is the sample in which electron-surface scattering is dominant. With this method, we observed that a large enhancement of the electron-surface scattering not only occurs in samples with large diameters grains, but also if the film has a reduced surface roughness.​.

  12. Improvement of MRR and surface roughness during electrical discharge machining (EDM) using aluminum oxide powder mixed dielectric fluid

    Science.gov (United States)

    Khan, A. A.; Mohiuddin, A. K. M.; Latif, M. A. A.

    2018-01-01

    This paper discusses the effect of aluminium oxide (Al203) addition to dielectric fluid during electrical discharge machining (EDM). Aluminium oxide was added to the dielectric used in the EDM process to improve its performance when machining the stainless steel AISI 304, while copper was used as the electrode. Effect of the concentration of Al203 (0.3 mg/L) in dielectric fluid was compared with EDM without any addition of Al203. Surface quality of stainless steel and the material removal rate were investigated. Design of the experiment (DOE) was used for the experimental plan. Statistical analysis was done using ANOVA and then appropriate model was designated. The experimental results show that with dispersing of aluminium oxide in dielectric fluid surface roughness was improved while the material removal rate (MRR) was increased to some extent. These indicate the improvement of EDM performance using aluminium oxide in dielectric fluid. It was also found that with increase in pulse on time both MRR and surface roughness increase sharply.

  13. Impact of surface electric properties of carbon-based thin films on platelets activation for nano-medical and nano-sensing applications

    Science.gov (United States)

    Karagkiozaki, Varvara; Logothetidis, Stergios; Lousinian, Sylvie; Giannoglou, George

    2008-01-01

    Electric surface properties of biomaterials, playing key role to various biointerfacial interactions, were related to hemocompatibility and biosensing phenomena. In this study, the examination of surface electric properties of amorphous hydrogenated carbon thin films (a-C:H) was carried out by means of electrostatic force microscope (EFM) and observation of differences in spatial charge distribution on the surface of the examined films during platelets adhesion was made. The thrombogenic potential of a-C:H thin films developed by magnetron sputtering with ~42% sp3 content and hydrogen partial pressure during deposition was evaluated, by in situ observation with atomic force microscope (AFM) of platelets’ activation and their subsequent adhesion. Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied. Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus. The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects. PMID:19337414

  14. Guiding Brain Tumor Resection Using Surface-Enhanced Raman Scattering Nanoparticles and a Hand-Held Raman Scanner

    Science.gov (United States)

    2015-01-01

    The current difficulty in visualizing the true extent of malignant brain tumors during surgical resection represents one of the major reasons for the poor prognosis of brain tumor patients. Here, we evaluated the ability of a hand-held Raman scanner, guided by surface-enhanced Raman scattering (SERS) nanoparticles, to identify the microscopic tumor extent in a genetically engineered RCAS/tv-a glioblastoma mouse model. In a simulated intraoperative scenario, we tested both a static Raman imaging device and a mobile, hand-held Raman scanner. We show that SERS image-guided resection is more accurate than resection using white light visualization alone. Both methods complemented each other, and correlation with histology showed that SERS nanoparticles accurately outlined the extent of the tumors. Importantly, the hand-held Raman probe not only allowed near real-time scanning, but also detected additional microscopic foci of cancer in the resection bed that were not seen on static SERS images and would otherwise have been missed. This technology has a strong potential for clinical translation because it uses inert gold–silica SERS nanoparticles and a hand-held Raman scanner that can guide brain tumor resection in the operating room. PMID:25093240

  15. The effect of current intensity during 'head-only' electrical stunning on brain function in force-fed ducks

    OpenAIRE

    Beyssen, Clotilde; Babilé, René; Fernandez, Xavier

    2004-01-01

    International audience; A preliminary study was carried out to determine the minimum current required for head-only electrical stunning of force-fed ducks. Forty-five force-fed ducks were implanted with electrocorticogram (ECoG) recording electrodes, and the changes occurring in the ECoG frequencies were quantitatively evaluated with Fast Fourier Transformations (FFT) to determine the effectiveness of a range of electrical stunning currents. A 50 Hz alternating current (AC) was used to apply ...

  16. Electrical Performance of Distribution Insulators with Chlorella vulgaris Growth on its Surface

    Directory of Open Access Journals (Sweden)

    Herbert Enrique Rojas Cubides

    2015-06-01

    Full Text Available This paper presents a study about electrical performance of ceramic and polymeric insulators bio-contaminated with alga Chlorella vulgaris. The performed tests involve ANSI 55-2 and ANSI 52-1 ceramic insulators and ANSI DS-15 polymeric insulators, all of them used in distribution systems of Colombia. Biological contamination of insulators is realized using a controlled environment chamber that adjusts the temperature, humidity and light radiation. The laboratory tests include measurements of flashover voltages and leakage currents and they were performed to determine how insulators are affected by biological contamination. After a series of laboratory tests, it was concluded that the presence of Chlorella vulgaris on the contaminated ceramic insulators reduces the wet flashover voltage up to 12% and increases their leakage currents up to 80%. On the other hand, for polymeric insulators the effect of algae growth on flashover voltages was not to strong, although the leakage currents increase up to 60%.

  17. Epoxy composites filled with high surface area-carbon fillers: Optimization of electromagnetic shielding, electrical, mechanical, and thermal properties

    Science.gov (United States)

    Kuzhir, P.; Paddubskaya, A.; Plyushch, A.; Volynets, N.; Maksimenko, S.; Macutkevic, J.; Kranauskaite, I.; Banys, J.; Ivanov, E.; Kotsilkova, R.; Celzard, A.; Fierro, V.; Zicans, J.; Ivanova, T.; Merijs Meri, R.; Bochkov, I.; Cataldo, A.; Micciulla, F.; Bellucci, S.; Lambin, Ph.

    2013-10-01

    A comprehensive analysis of electrical, electromagnetic (EM), mechanical, and thermal properties of epoxy resin composites filled with 0.25-2.0 wt. % of carbon additives characterized by high surface area, both nano-sized, like carbon nanotubes (CNTs) and carbon black (CBH), and micro-sized exfoliated graphite (EG), was performed. We found that the physical properties of both CNTs- and CBH-based epoxy resin composites increased all together with filler content and even more clearly for CBH than for CNTs. In the case of EG-based composites, good correlation between properties and filler amount was observed for concentrations below 1.5 wt. %. We conclude that CBH and, to a lower extent, EG could replace expensive CNTs for producing effective EM materials in microwave and low-frequency ranges, which are, in addition, mechanically and thermally stable.

  18. Room temperature continuous wave lasing of electrically injected GaN-based vertical cavity surface emitting lasers

    Science.gov (United States)

    Liu, Wen-Jie; Hu, Xiao-Long; Ying, Lei-Ying; Zhang, Jiang-Yong; Zhang, Bao-Ping

    2014-06-01

    Continuous wave (CW) lasing of electrically injected GaN-based vertical cavity surface emitting lasers (VCSELs) was achieved at room temperature. First, a high quality factor (Q) VCSEL-structured device with very narrow linewidth of 0.12 nm, corresponding to a Q-value of 3570 was obtained through two-step substrate transfer technique. However, poor heat dissipation ability prevented the device from lasing. Based on the high-Q resonant cavity design, we further fabricated vertical-structured VCSELs through metal bonding technique on Si substrate. CW lasing from vertical-structured VCSELs was observed with threshold current of density of 1.2 kA/cm2 and lasing linewidth of about 0.20 nm.

  19. Effects of lateral electrical surface stimulation on scoliosis in children with severe cerebral palsy: a pilot study.

    Science.gov (United States)

    Ko, Eun Jae; Sung, In Young; Yun, Gi Jeong; Kang, Jung-A; Kim, JaYoung; Kim, Go Eun

    2018-01-01

    To evaluate the effects of lateral electrical surface stimulation (LESS) on scoliosis and trunk balance in children with severe cerebral palsy (CP). Children with severe CP (GMFCS level IV or V) and stationary or progressive scoliosis were enrolled. Children were recommended of two sessions of LESS/day, 1 h/session, for 3 months at home: at 40-80 mA intensity, 200 μs pulse width, 25 Hz frequency, on for 6 s and then off for 6 s on the convex side of the trunk curve. Radiologic (Cobb's, kyphotic, and sacral angles) and functional [gross motor function measurement (GMFM)-88 sitting score, and trunk control measurement scale (TCMS)] measurements were evaluated at 4 periods: (a) 3 months before, (b) just before, (c) 1 month after, and (d) 3 months after LESS. The median Cobb's angle of 11 children (median age, 9 years) was 25°, and it showed significant improvements after both 1 and 3 months of LESS. The LESS intensity correlated with the improvement of GMFM-88 siting score. The parents or main caregivers of the children believed LESS had several positive effects without major adverse effects. LESS is effective in scoliosis in children with severe CP and it may improve trunk balance. Implications for rehabilitation Scoliosis is a very complicated problem for the children with severe CP. They do not have many options for treatments and scoliosis is usually refractory. Lateral electrical surface stimulation (LESS) is effective in scoliosis in children with severe CP and it may improve trunk balance. LESS may be another option of managing stationary or progressive scoliosis in the children with severe CP who are unable to undergo surgery.

  20. Crystal Orientation and Electrical Properties of Tin Oxide Transparent Conducting Films Deposited on Rutile Surface

    Science.gov (United States)

    Sawada, Y.; Hashimoto, Y.; Hoshi, Y.; Uchida, T.; Kobayashi, S.; Sun, L.; Yue, B.

    2017-10-01

    Thin films of tin oxide (SnO2) without doping are attractive transparent conducting film since environmentally unfavorable elements of antimony or fluorine are eliminated. Tin oxide films without doping were fabricated very cheaply on (001) and (100) planes of single crystal of rutile (TiO2) by spray chemical vapor deposition (mist CVD). The film deposited on rutile (001) surface was poorly epitaxial (double domain) but with higher mobility (24 cm2 V-1 s-1) and lower resistivity (1.6×10-3 Ω cm) than that deposited on glass substrate (16 cm2 V-1 s-1 and 2.4×10-3 Ω cm) for reference. Deposition on rutile (100) surface resulted in better epitaxial growth (single domain). The mobility (39 cm2 V-1 s-1) and the carrier electron density (2.7×1020 cm-3) were much higher. The resistivity (6.2×10-4 Ω cm) was compatible with those doped with antimony or fluorine and will be the lowest among tin oxide films without doping.

  1. Low-temperature aluminum reduction of graphene oxide, electrical properties, surface wettability, and energy storage applications.

    Science.gov (United States)

    Wan, Dongyun; Yang, Chongyin; Lin, Tianquan; Tang, Yufeng; Zhou, Mi; Zhong, Yajuan; Huang, Fuqiang; Lin, Jianhua

    2012-10-23

    Low-temperature aluminum (Al) reduction is first introduced to reduce graphene oxide (GO) at 100-200 °C in a two-zone furnace. The melted Al metal exhibits an excellent deoxygen ability to produce well-crystallized reduced graphene oxide (RGO) papers with a low O/C ratio of 0.058 (Al-RGO), compared with 0.201 in the thermally reduced one (T-RGO). The Al-RGO papers possess outstanding mechanical flexibility and extremely high electrical conductivities (sheet resistance R(s) ~ 1.75 Ω/sq), compared with 20.12 Ω/sq of T-RGO. More interestingly, very nice hydrophobic nature (90.5°) was observed, significantly superior to the reported chemically or thermally reduced papers. These enhanced properties are attributed to the low oxygen content in the RGO papers. During the aluminum reduction, highly active H atoms from H(2)O reacted with melted Al promise an efficient oxygen removal. This method was also applicable to reduce graphene oxide foams, which were used in the GO/SA (stearic acid) composite as a highly thermally conductive reservoir to hold the phase change material for thermal energy storage. The Al-reduced RGO/SnS(2) composites were further used in an anode material of lithium ion batteries possessing a higher specific capacity. Overall, low-temperature Al reduction is an effective method to prepare highly conductive RGO papers and related composites for flexible energy conversion and storage device applications.

  2. Reproducibility of brain-cognition relationships using three cortical surface-based protocols: An exhaustive analysis based on cortical thickness.

    Science.gov (United States)

    Martínez, Kenia; Madsen, Sarah K; Joshi, Anand A; Joshi, Shantanu H; Román, Francisco J; Villalon-Reina, Julio; Burgaleta, Miguel; Karama, Sherif; Janssen, Joost; Marinetto, Eugenio; Desco, Manuel; Thompson, Paul M; Colom, Roberto

    2015-08-01

    People differ in their cognitive functioning. This variability has been exhaustively examined at the behavioral, neural and genetic level to uncover the mechanisms by which some individuals are more cognitively efficient than others. Studies investigating the neural underpinnings of interindividual differences in cognition aim to establish a reliable nexus between functional/structural properties of a given brain network and higher order cognitive performance. However, these studies have produced inconsistent results, which might be partly attributed to methodological variations. In the current study, 82 healthy young participants underwent MRI scanning and completed a comprehensive cognitive battery including measurements of fluid, crystallized, and spatial intelligence, along with working memory capacity/executive updating, controlled attention, and processing speed. The cognitive scores were obtained by confirmatory factor analyses. T1 -weighted images were processed using three different surface-based morphometry (SBM) pipelines, varying in their degree of user intervention, for obtaining measures of cortical thickness (CT) across the brain surface. Distribution and variability of CT and CT-cognition relationships were systematically compared across pipelines and between two cognitively/demographically matched samples to overcome potential sources of variability affecting the reproducibility of findings. We demonstrated that estimation of CT was not consistent across methods. In addition, among SBM methods, there was considerable variation in the spatial pattern of CT-cognition relationships. Finally, within each SBM method, results did not replicate in matched subsamples. © 2015 Wiley Periodicals, Inc.

  3. Relationship Between Surface-Based Brain Morphometric Measures and Intelligence in Autism Spectrum Disorders: Influence of History of Language Delay.

    Science.gov (United States)

    Balardin, Joana Bisol; Sato, João Ricardo; Vieira, Gilson; Feng, Yeu; Daly, Eileen; Murphy, Clodagh; Murphy, Declan; Ecker, Christine

    2015-10-01

    Autism spectrum disorders (ASD) are a group of conditions that show abnormalities in the neuroanatomy of multiple brain regions. The variability in the development of intelligence and language among individuals on the autism spectrum has long been acknowledged, but it remains unknown whether these differences impact on the neuropathology of ASD. In this study, we aimed to compare associations between surface-based regional brain measures and general intelligence (IQ) scores in ASD individuals with and without a history of language delay. We included 64 ASD adults of normal intelligence (37 without a history of language delay and 27 with a history of language delay and 80 neurotypicals). Regions with a significant association between verbal and nonverbal IQ and measures of cortical thickness (CT), surface area, and cortical volume were first identified in the combined sample of individuals with ASD and controls. Thicker dorsal frontal and temporal cortices, and thinner lateral orbital frontal and parieto-occipital cortices were associated with greater and lower verbal IQ scores, respectively. Correlations between cortical volume and verbal IQ were observed in similar regions as revealed by the CT analysis. A significant difference between ASD individuals with and without a history of language delay in the association between CT and verbal IQ was evident in the parieto-occipital region. These results indicate that ASD subgroups defined on the basis of differential language trajectories in childhood can have different associations between verbal IQ and brain measures in adulthood despite achieving similar levels of cognitive performance. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

  4. The potential for brain injury on selected surfaces used by cheerleaders.

    Science.gov (United States)

    Shields, Brenda J; Smith, Gary A

    2009-01-01

    Although playground surfaces have been investigated for fall impact attenuation, the surfaces that cheerleaders use have received little attention. To determine (1) the critical height for selected surfaces used by cheerleaders at or below which a serious head impact injury from a fall is unlikely to occur, (2) the critical heights for non-impact-absorbing surfaces for comparison purposes, and (3) the effect of soil moisture and grass height on g(max) (which is defined as the multiple of g [acceleration due to gravity at the earth's surface at sea level: ie, 32.2 feet x s(-1) x s(-1)] that represents the maximum deceleration experienced during an impact) and the Head Injury Criterion (HIC) at the critical height for a dry grass surface. Observational study. A local cheerleading gym, indoor locations within the authors' institution, and various outdoor locations. g(max), HIC, and critical height. Critical heights for the surfaces tested ranged from 0.5 ft (0.15 m) for concrete and vinyl tile installed over concrete to more than 11 ft (3.35 m) for a spring floor. Increases in grass height and soil moisture resulted in an increase in the critical height for grass surfaces. Only spring floors and 4-in (0.10-m)-thick landing mats placed on traditional foam floors had critical heights greater than 10.5 ft (3.20 m), thus providing enough impact-absorbing capacity for performance of 2-level stunts. The potential for serious head impact injuries can be minimized by increasing the shock-absorbing capacity of the surface, decreasing the height from which the person falls, or both. Cheerleaders and cheerleading coaches should use the critical heights reported in this study to compare the relative impact-absorbing capacities of the various surfaces tested, with critical height as an indicator of the impact-absorption capacity of the surface. The findings of this study can be used to select the most appropriate surface for the type of maneuver to be performed, based on the

  5. Optimizing electrically pumped vertical extended cavity surface emitting semiconductor lasers (E-VECSELs)

    Science.gov (United States)

    McInerney, John G.; Mooradian, Aram

    2011-03-01

    The future evolution of photonics, for a wide spectrum of applications ranging from established optical telecommunications to emerging opportunities such as biotechnology, reprographics and projection displays, will depend on availability of compact, rugged, efficient and inexpensive lasers which deliver high power, good beam quality, excellent wavelength stability, low noise and long lifetime in the near infrared and visible regions. This combination is not readily available from either of the traditional classes of semiconductor laser, edge-emitters and vertical cavity surface emitters (VCSELs). Here we describe a novel class of laser based on geometry similar to VCSELs but controlled by an extended coupled cavity. These devices are scalable to high powers while maintaining fundamental spatial mode performance, a feature that is essential to efficient coupling into a single mode optical fibre or waveguide, or long range propagation in free space. They are also ideally suited to mode locking, gain-switching and intracavity frequency conversion, among other applications.

  6. Machining and Surface Characteristics of AISI 304L After Electric Discharge Machining for Copper and Graphite Electrodes in Different Dielectric Liquids

    Directory of Open Access Journals (Sweden)

    S. Anjum

    2017-08-01

    Full Text Available In Electric Discharge Machining (EDM, the thermal energy used for material erosion depends on the intensity of electric sparks, the thermal conductivities of electrode material and the dielectric liquid. In this paper, the effect of EDM on AISI 304L steel is studied using copper and graphite electrodes and distilled water and kerosene oil as dielectric liquids. Material Removal Rates (MRR, Tool Wear Rates (TWR and surface conditions are calculated for four different combinations with the two electrode materials and the two dielectric liquids. These investigations are carried out at different pulse currents. Machined surfaces are evaluated by morphological studies, energy dispersive spectrographs (EDS and white layer thickness using Scanning Electron Microscopy (SEM. It is found that a transfer of carbon takes place from the kerosene oil and the graphite electrodes into the machined surface which alters the metallurgical characteristics, depending on the electrical and thermal conductivities of the electrode material and the dielectric liquid.

  7. Experimental investigation on the effect of surface electric field in the growth of tungsten nano-tendril morphology due to low energy helium irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Woller, K.B., E-mail: kbwoller@mit.edu; Whyte, D.G.; Wright, G.M.; Brunner, D.

    2016-12-01

    The mechanisms responsible for and controlling the growth of tungsten nano-tendrils (or “fuzz”) under low-energy helium plasma exposure remain unclear. For the first time in nano-tendril experiments, the plasma sheath-produced electric field and the helium (He) ion energy have been decoupled, showing that the sheath electric field has little impact on nano-tendril growth, eliminating a possible cause for tendril growth. The well-established necessary growth conditions for W fuzz were maintained with He ion flux density Γ{sub He} > 10{sup 21} He m{sup −2} s{sup −1}, surface temperature T{sub s} = 1273 K, He ion energy E{sub He} = 64 eV, and He ion fluence Φ{sub He} > 10{sup 24} He m{sup −2}. A grid is situated between the tungsten sample and plasma, with the grid and sample potentials independently controlled in order to control the electric field at the surface of the sample while maintaining the same incident He ion energy to the surface. A calculation of the potential profile in the drift space between the grid and sample was used to account for space charge and calculate the electric field at the surface of the sample. Tungsten fuzz formed at all electric fields tested, even near zero electric field. Also, the depth of the resulting W fuzz layer was unaltered by the electric field when compared to the calculated depth determined from an empirical growth model. The conclusion is that the sheath electric field is not necessary to cause the changes in surface morphology. - Highlights: • Surface electric field is proposed as a possible driver of tungsten fuzz growth. • A method that decouples plasma sheath electric field and ion energy is described. • Tungsten fuzz is shown to grow even without direct exposure to plasma. • Tungsten fuzz grows to the same depth with and without the plasma sheath.

  8. 3D surface analysis of hippocampal microvasculature in the irradiated brain.

    Science.gov (United States)

    Craver, Brianna M; Acharya, Munjal M; Allen, Barrett D; Benke, Sarah N; Hultgren, Nan W; Baulch, Janet E; Limoli, Charles L

    2016-06-01

    Cranial irradiation used to control CNS malignancies can also disrupt the vasculature and impair neurotransmission and cognition. Here we describe two distinct methodologies for quantifying early and late radiation injury in CNS microvasculature. Intravascular fluorescently labeled lectin was used to visualize microvessels in the brain of the irradiated mouse 2 days post exposure and RECA-1 immunostaining was similarly used to visualize microvessels in the brain of the irradiated rat 1-month post exposure. Confocal microscopy, image deconvolution and 3-dimensional rendering methods were used to define vascular structure in a ∼4 × 10(7) μm(3) defined region of the brain. Quantitative analysis of these 3D images revealed that irradiation caused significant short- and long-term reductions in capillary density, diameter and volume. In mice, irradiation reduced mean vessel volume from 2,250 to 1,470 μm(3) and mean vessel diameter from 5.0 to 4.5 μm, resulting in significant reductions of 34% and 10%, in the hippocampus respectively. The number of vessel branch points and area was also found to also drop significantly in mice 2 days after irradiation. For rats, immunostaining revealed a significant, three-fold drop in capillary density 1 month after exposure compared to controls. Such radiation-induced disruption of the CNS microvasculature may be contributory if not causal to any number of neurocognitive side effects that manifest in cancer patients following cranial radiotherapy. This study demonstrates the utility of two distinct methodologies for quantifying these important adverse effects of radiotherapy. Environ. Mol. Mutagen. 57:341-349, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  9. Imaging of molecular surface dynamics in brain slices using single-particle tracking

    NARCIS (Netherlands)

    Biermann, N.B.; Sokoll, S.; Klueva, J.; Missler, M.; Wiegert, J.S.; Sibarita, J.B.; Heine, M.

    2014-01-01

    Organization of signalling molecules in biological membranes is crucial for cellular communication. Many receptors, ion channels and cell adhesion molecules are associated with proteins important for their trafficking, surface localization or function. These complexes are embedded in a lipid

  10. Parental Rearing Behavior Prospectively Predicts Adolescents' Risky Decision-Making and Feedback-Related Electrical Brain Activity

    Science.gov (United States)

    Euser, Anja S.; Evans, Brittany E.; Greaves-Lord, Kirstin; Huizink, Anja C.; Franken, Ingmar H. A.

    2013-01-01

    The present study examined the role of parental rearing behavior in adolescents' risky decision-making and the brain's feedback processing mechanisms. Healthy adolescent participants ("n" = 110) completed the EMBU-C, a self-report questionnaire on perceived parental rearing behaviors between 2006 and 2008 (T1). Subsequently, after an…

  11. Study of the surface heterogeneity of topographic and electric nature by atomic force microscopy by the example of triglycine sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Tolstikhina, A. L., E-mail: alla@ns.crys.ras.r; Gainutdinov, R. V.; Belugina, N. V.; Sorokina, K. L. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2013-11-15

    Triglycine sulfate crystals with an ideal (010) cleavage plane are used as model objects to reveal problems in interpreting atomic force microscopy (AFM) images of surfaces with nonuniform charge distribution. Specific microrelief features of two types are found: lenslike formations with different contrast and rounded protrusions/valleys of different size but fixed height. An analysis of their evolution with a change in temperature and under an electric field and mechanical impacts has made it possible to separate relief elements from the crystal domain structure. The interpretation proposed is confirmed by the multimode AFM data. The specific features of the images of dynamic domains and aged domains (which cannot undergo polarization reversal) are studied. The domain-wall width found in the AFM measurements depends on the technique used and the specificity of probe-surface interaction; it varies from 9 to 2000 nm. The most reliable data on the domain-wall width in triglycine sulfate crystals are provided by piezoelectric force microscopy, according to which the wall width does not exceed 30 nm.

  12. The influence of the surface conductivity on the local electric fields and the motion of charged dust grains on the Moon

    Science.gov (United States)

    Borisov, N.; Zakharov, A.

    2015-11-01

    It is investigated how finite regolith conductivity influences the magnitude of strong electric fields required for lofting dust grains above the surface. It is shown that even very weak conductivity typical for the lunar regolith restricts the maximum values of the local electric fields formed near mini-craters or mini-hills on the dark side of the Moon. As a result the lofting of dust grains from the surface of the Moon is suppressed significantly. The effect depends on the regolith conductivity, parameters of the solar wind plasma, and the steepness of the slopes of the mini-crater or mini-hill.

  13. Thermal, Electrical and Surface Hydrophobic Properties of Electrospun Polyacrylonitrile Nanofibers for Structural Health Monitoring.

    Science.gov (United States)

    Alarifi, Ibrahim M; Alharbi, Abdulaziz; Khan, Waseem S; Swindle, Andrew; Asmatulu, Ramazan

    2015-10-14

    This paper presents an idea of using carbonized electrospun Polyacrylonitrile (PAN) fibers as a sensor material in a structural health monitoring (SHM) system. The electrospun PAN fibers are lightweight, less costly and do not interfere with the functioning of infrastructure. This study deals with the fabrication of PAN-based nanofibers via electrospinning followed by stabilization and carbonization in order to remove all non-carbonaceous material and ensure pure carbon fibers as the resulting material. Electrochemical impedance spectroscopy was used to determine the ionic conductivity of PAN fibers. The X-ray diffraction study showed that the repeated peaks near 42° on the activated nanofiber film were α and β phases, respectively, with crystalline forms. Contact angle, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were also employed to examine the surface, thermal and chemical properties of the carbonized electrospun PAN fibers. The test results indicated that the carbonized PAN nanofibers have superior physical properties, which may be useful for structural health monitoring (SHM) applications in different industries.

  14. Hybrid brain-computer interface and functional electrical stimulation for sensorimotor training in participants with tetraplegia: a proof-of-concept study.

    Science.gov (United States)

    Vučković, Aleksandra; Wallace, Leslie; Allan, David B

    2015-01-01

    Impaired hand function decreases quality of life in persons with tetraplegia. We tested functional electrical stimulation (FES) controlled by a hybrid brain-computer interface (BCI) for improving hand function in participants with tetraplegia. Two participants with subacute tetraplegia (participant 1: C5 Brown-Sequard syndrome, participant 2: complete C5 lesion) took part in this proof-of-concept study. The goal was to determine whether the BCI system could drive the FES device by accurately classifying participants' intent (open or close the hand). Participants 1 and 2 received 10 sessions and 4 sessions of BCI-FES, respectively. A novel time-switch BCI strategy based on motor imagery was used to activate the FES. In one session, we tested a hybrid BCI-FES based on 2 spontaneously generated brain rhythms: a sensory-motor rhythm during motor imagery to activate a stimulator and occipital alpha rhythms to deactivate the stimulator. Participants received BCI-FES therapy 2 to 3 times a week in addition to conventional therapy. Imagery ability and muscle strength were measured before and after treatment. Visual feedback was associated with a 4-fold increase of brain response during motor imagery in both participants. For participant 1, classification accuracy (open/closed) for motor imagery-based BCI was 83.5% (left hand) and 83.8% (right hand); participant 2 had a classification accuracy of 83.8% for the right hand. Participant 1 had moderate improvement in muscle strength, while there was no change for participant 2. We demonstrated feasibility of BCI-FES, using 2 naturally generated brain rhythms. Studies on a larger number of participants are needed to separate the effects of BCI training from effects of conventional therapy.Video Abstract available. (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A84) for more insights from the authors.

  15. Effect of the 5-HT(1A) partial agonist buspirone on regional brain electrical activity in man: a functional neuroimaging study using low-resolution electromagnetic tomography (LORETA).

    Science.gov (United States)

    Anderer, P; Saletu, B; Pascual-Marqui, R D

    2000-12-04

    In a double-blind, placebo-controlled study, the effects of 20 mg buspirone - a 5-HT(1A) partial agonist - on regional electrical generators within the human brain were investigated utilizing three-dimensional EEG tomography. Nineteen-channel vigilance-controlled EEG recordings were carried out in 20 healthy subjects before and 1, 2, 4, 6 and 8 h after drug intake. Low-resolution electromagnetic tomography (LORETA; Key Institute for Brain-Mind Research, software: http://www.keyinst.unizh.ch) was computed from spectrally analyzed EEG data, and differences between drug- and placebo-induced changes were displayed as statistical parametric maps. Data were registered to the Talairach-Tournoux human brain atlas available as a digitized MRI (McConnell Brain Imaging Centre: http://www.bic.mni.mcgill.ca). At the pharmacodynamic peak (1st hour), buspirone increased theta and decreased fast alpha and beta sources. Areas of theta increase were mainly the left temporo-occipito-parietal and left prefrontal cortices, which is consistent with PET studies on buspirone-induced decreases in regional cerebral blood flow and fenfluramine-induced serotonin activation demonstrated by changes in regional cerebral glucose metabolism. In later hours (8th hour) with lower buspirone plasma levels, delta, theta, slow alpha and fast beta decreased, predominantly in the prefrontal and anterior limbic lobe. Whereas the results of the 1st hour speak for a slight CNS sedation (more in the sense of relaxation), those obtained in the 8th hour indicate activation. Thus, LORETA may provide useful and direct information on drug-induced changes in central nervous system function in man.

  16. [The utilization of brain plasticity by cochlear implants : Molecular and cellular changes due to electrical intracochlear stimulation].

    Science.gov (United States)

    Rosskothen-Kuhl, N; Illing, R-B

    2015-02-01

    During pre- and postnatal development, a high level of growth-associated protein 43 (Gap43) is expressed in the brain. This neuron-specific protein is expressed in somata, axons, and growth cones and plays a key role in neurite outgrowth and synaptogenesis. With maturation of the brain, Gap43 is down-regulated by most neurons, except in brain areas such as the hippocampal CA3 region or the binaural auditory regions lateral superior olive (LSO) and central inferior colliculus (CIC). This study investigated how changes in sensory activity levels and patterns can modulate the adult plasticity response. To study the effect of sensory activity on adult Gap43 expression, mRNA and protein levels were determined in LSO and CIC of hearing-experienced rats, unilaterally and bilaterally deafened rats, or rats unilaterally stimulated by a cochlear implant (CI). Unilateral hearing loss of an adult auditory system causes asymmetrical expression of Gap43 mRNA between ipsi- and contralateral LSOs or CICs of the brain stem. While the mRNA level rose on the contralateral side of the LSO, CIC neurons increased their gap43 transcription ipsilaterally compared to the control level (pstimulation resulted in a bilaterally symmetric but increased gap43 transcription. Our data indicate that Gap43 is not only a marker for neuronal growth and synaptogenesis, but also reflects modified patterns of synaptic activities on auditory neurons. Thus, unilateral deafness directly results in an asymmetrical adaptation of the gap43 transcription between both sides of the auditory brain stem. This can be prevented by simple-patterned stimulation of the auditory nerve via a CI.

  17. The coil orientation dependency of the electric field induced by TMS for M1 and other brain areas

    NARCIS (Netherlands)

    Janssen, A.M.; Oostendorp, T.F.; Stegeman, D.F.

    2015-01-01

    BACKGROUND: The effectiveness of transcranial magnetic stimulation (TMS) depends highly on the coil orientation relative to the subject's head. This implies that the direction of the induced electric field has a large effect on the efficiency of TMS. To improve future protocols, knowledge about the

  18. Application of stereological methods to estimate post-mortem brain surface area using 3T MRI

    DEFF Research Database (Denmark)

    Furlong, Carolyn; García-Fiñana, Marta; Puddephat, Michael

    2013-01-01

    The Cavalieri and Vertical Sections methods of design based stereology were applied in combination with 3 tesla (i.e. 3T) Magnetic Resonance Imaging (MRI) to estimate cortical and subcortical volume, area of the pial surface, area of the grey-white matter boundary, and thickness of the cerebral...... cortex. The material comprises eight human cadaveric cerebri which had been separated into sixteen cerebral hemisphere specimens prior to embedding in agar gel. The results from MRI were compared with corresponding 'gold standard' values subsequently obtained by application of the same methodology using...... physical sectioning of the specimens. 95% agreement intervals revealed poor agreement between MR imaging and physical sectioning, specially for pial surface and thickness, as well as cerebral cortex and subcortex volumes. On average, pial surface area was estimated to be almost half the extent using MRI...

  19. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Zaugg, C. A., E-mail: zauggc@phys.ethz.ch; Mangold, M.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U. [Department of Physics, Institute for Quantum Electronics, ETH Zürich, 8093 Zürich (Switzerland); Gronenborn, S.; Moench, H.; Weichmann, U. [Philips Technologie GmbH Photonics Aachen, Steinbachstrasse 15, 52074 Aachen (Germany); Miller, M. [Philips Technologie GmbH U-L-M Photonics, Lise-Meitner-Strasse 13, 89081 Ulm (Germany)

    2014-03-24

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM{sub 00} mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiN{sub x} and SiO{sub 2}) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm{sup 2} to 1.1 μJ/cm{sup 2}, respectively.

  20. Systematization, distribution and territory of the caudal cerebral artery on the brain's surface of the turkey (Meleagris gallopavo

    Directory of Open Access Journals (Sweden)

    Amarílis Díaz de Carvalho

    2014-10-01

    Full Text Available Thirty Meleagris gallopavo heads with their neck segments were used. Animals were contained and euthanized with the association of mebezonium iodide, embutramide and tetracaine hydrochloride (T 61, Intervet by intravenous injection. The arterial system was rinsed with cold saline solution (15°C, with 5000IU heparin and filled with red-colored latex. The samples were fixed in 20% formaldehyde for seven days. The brains were removed with a segment of cervical spinal cord and after, the dura-mater was removed and the arteries dissected. The cerebral carotid arteries, after the intercarotid anastomosis, were projected around the hypophysis, until they reached the tuber cinereum and divided into their terminal branches, the caudal branch and the rostral branch. The rostral branch was projected rostrolateralwards and gave off, in sequence, two collateral branches, the caudal cerebral and the middle cerebral arteries and the terminal branch was as cerebroethmoidal artery. The caudal cerebral artery of one antimere formed the interhemispheric artery, which gave off dorsal hemispheric branches to the convex surface of both antimeres. Its dorsal tectal mesencephalic branch, of only one antimere, originated the dorsal cerebellar artery. In the interior of the cerebral transverse fissure, after the origin of the dorsal tectal mesencephalic artery, the caudal cerebral artery emitted occipital hemispheric branches, pineal branches and medial hemispheric branches, on both antimeres. The caudal cerebral artery's territory comprehended the entire surface of the dorsal hemioptic lobe, the rostral surface of the cerebellum, the diencephalic structures, the caudal pole and the medial surface of the cerebral hemisphere and in the convex surface, the sagittal eminence except for its most rostral third. Due to the asymmetry found in the caudal cerebral arteries' ramifications, the models were classified into three types and their respective subtypes.

  1. Non-invasive electrical brain stimulation: from acute to late-stage treatment of central nervous system damage

    Directory of Open Access Journals (Sweden)

    Petra Henrich-Noack

    2017-01-01

    Full Text Available Non-invasive brain current stimulation (NIBS is a promising and versatile tool for inducing neuroplasticity, protection and functional rehabilitation of damaged neuronal systems. It is technically simple, requires no surgery, and has significant beneficial effects. However, there are various technical approaches for NIBS which influence neuronal networks in significantly different ways. Transcranial direct current stimulation (tDCS, alternating current stimulation (ACS and repetitive transcranial magnetic stimulation (rTMS all have been applied to modulate brain activity in animal experiments under normal and pathological conditions. Also clinical trials have shown that tDCS, rTMS and ACS induce significant behavioural effects and can – depending on the parameters chosen – enhance or decrease brain excitability and influence performance and learning as well as rehabilitation and protective mechanisms. The diverse phaenomena and partially opposing effects of NIBS are not yet fully understood and mechanisms of action need to be explored further in order to select appropriate parameters for a given task, such as current type and strength, timing, distribution of current densities and electrode position. In this review, we will discuss the various parameters which need to be considered when designing a NIBS protocol and will put them into context with the envisaged applications in experimental neurobiology and medicine such as vision restoration, motor rehabilitation and cognitive enhancement.

  2. Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface. Cooperative research

    CERN Document Server

    Yamamoto, K; Kishi, T; Kumada, H; Matsumura, A; Nose, T; Torii, Y; Uchiyama, J; Yamamoto, T

    2002-01-01

    Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient.

  3. Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface. Cooperative research

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Torii, Yoshiya; Uchiyama, Junzo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Endo, Kiyoshi; Yamamoto, Tetsuya; Matsumura, Akira; Nose, Tadao [Tsukuba Univ., Tsukuba, Ibaraki (Japan)

    2002-12-01

    Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient. (author)

  4. Brain plasticity after implanted peroneal nerve electrical stimulation to improve gait in chronic stroke patients: Two case reports.

    Science.gov (United States)

    Thibaut, Aurore; Moissenet, Florent; Di Perri, Carol; Schreiber, Céline; Remacle, Angélique; Kolanowski, Elisabeth; Chantraine, Frédéric; Bernard, Claire; Hustinx, Roland; Tshibanda, Jean-Flory; Filipetti, Paul; Laureys, Steven; Gosseries, Olivia

    2017-01-01

    Recent studies have shown that stimulation of the peroneal nerve using an implantable 4-channel peroneal nerve stimulator could improve gait in stroke patients. To assess structural cortical and regional cerebral metabolism changes associated with an implanted peroneal nerve electrical stimulator to correct foot drop related to a central nervous system lesion. Two stroke patients presenting a foot drop related to a central nervous system lesion were implanted with an implanted peroneal nerve electrical stimulator. Both patients underwent clinical evaluations before implantation and one year after the activation of the stimulator. Structural magnetic resonance imaging (MRI) and [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) were acquired before and one year after the activation of the stimulator. Foot drop was corrected for both patients after the implantation of the stimulator. After one year of treatment, patient 1 improved in three major clinical tests, while patient 2 only improved in one test. Prior to treatment, FDG-PET showed a significant hypometabolism in premotor, primary and supplementary motor areas in both patients as compared to controls, with patient 2 presenting more widespread hypometabolism. One year after the activation of the stimulator, both patients showed significantly less hypometabolism in the damaged motor cortex. No difference was observed on the structural MRI. Clinical improvement of gait under peroneal nerve electrical stimulation in chronic stroke patients presenting foot drop was paralleled to metabolic changes in the damaged motor cortex.

  5. Integration of sparse electrophysiological measurements with preoperative MRI using 3D surface estimation in deep brain stimulation surgery

    Science.gov (United States)

    Husch, Andreas; Gemmar, Peter; Thunberg, Johan; Hertel, Frank

    2017-03-01

    Intraoperative microelectrode recordings (MER) have been used for several decades to guide neurosurgeons during the implantation of Deep Brain Stimulation (DBS) electrodes, especially when targeting the subthalamic nucleus (STN) to suppress the symptoms of Parkinson's Disease. The standard approach is to use an array of up to five MER electrodes in a fixed configuration. Interpretation of the recorded signals yields a spatially very sparse set of information about the morphology of the respective brain structures in the targeted area. However, no aid is currently available for surgeons to intraoperatively integrate this information with other data available on the patient's individual morphology (e.g. MR imaging data used for surgical planning). This integration might allow surgeons to better determine the most probable position of the electrodes within the target structure during surgery. This paper suggests a method for reconstructing a surface patch from the sparse MER dataset utilizing additional a priori knowledge about the geometrical configuration of the measurement electrodes. The conventional representation of MER measurements as intervals of target region/non-target region is therefore transformed into an equivalent boundary set representation, allowing ecient point-based calculations. Subsequently, the problem is to integrate the resulting patch with a preoperative model of the target structure, which can be formulated as registration problem minimizing a distance measure between the two surfaces. When restricting this registration procedure to translations, which is reasonable given certain geometric considerations, the problem can be solved globally by employing an exhaustive search with arbitrary precision in polynomial time. The proposed method is demonstrated using bilateral STN/Substantia Nigra segmentation data from preoperative MRIs of 17 Patients with simulated MER electrode placement. When using simulated data of heavily perturbed electrodes

  6. Applying electrical resistivity tomography and biological methods to assess the surface-groundwater interaction in two Mediterranean rivers (central Spain)

    Science.gov (United States)

    Iepure, Sanda; Gómez Ortiz, David; Lillo Ramos, Javier; Rasines Ladero, Ruben; Persoiu, Aurel

    2014-05-01

    Delineation of the extent of hyporheic zone (HZ) in river ecosystems is problematic due to the scarcity of spatial information about the structure of riverbed sediments and the magnitude and extent of stream interactions with the parafluvial and riparian zones. The several existing methods vary in both quality and quantity of information and imply the use of hydrogeological and biological methods. In the last decades, various non-invasive geophysical techniques were developed to characterise the streambed architecture and also to provide detailed spatial information on its vertical and horizontal continuity. All classes of techniques have their strengths and limitations; therefore, in order to assess their potential in delineating the lateral and vertical spatial extents of alluvial sediments, we have combined the near-surface images obtained by electrical resistivity tomography (ERT) with biological assessment of invertebrates in two Mediterranean lowland rivers from central Spain. We performed in situ imaging of the thickness and continuity of alluvial sediments under the riverbed and parafluvial zone during base-flow conditions (summer 2013 and winter 2014) at two different sites with distinct lithology along the Tajuña and Henares Rivers. ERT was performed by installing the electrodes (1 m spacing) on a 47 m long transect normal to the river channel using a Wener-Schlumberger array, across both the riparian zones and the river bed. Invertebrates were collected in the streambed from a depth of 20-40 cm, using the Bou-Rouch method, and from boreholes drilled to a depth of 1.5 m in the riparian zone. The ERT images obtained at site 1 (medium and coarse sand dominated lithology) shows resistivity values ranging from ~20 to 80 ohm•m for the in-stream sediments, indicating a permeable zone up to ~ 0.5 m thick and extending laterally for ca. 5 m from the channel. These sediments contribute to active surface/hyporheic water exchanges and to low water retention in

  7. Resting and reactive frontal brain electrical activity (EEG among a non-clinical sample of socially anxious adults: Does concurrent depressive mood matter?

    Directory of Open Access Journals (Sweden)

    Elliott A Beaton

    2008-03-01

    Full Text Available Elliott A Beaton1, Louis A Schmidt2, Andrea R Ashbaugh2,5, Diane L Santesso2, Martin M Antony1,3,4, Randi E McCabe1,31Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada; 2Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, Ontario, Canada; 3Anxiety Treatment and Research Centre, St. Joseph’s Healthcare, Hamilton, Ontario, Canada; 4Department of Psychology, Ryerson University, Toronto, Ontario, Canada; 5Concordia University, Montreal, Quebec, CanadaAbstract: A number of studies have noted that the pattern of resting frontal brain electrical activity (EEG is related to individual differences in affective style in healthy infants, children, and adults and some clinical populations when symptoms are reduced or in remission. We measured self-reported trait shyness and sociability, concurrent depressive mood, and frontal brain electrical activity (EEG at rest and in anticipation of a speech task in a non-clinical sample of healthy young adults selected for high and low social anxiety. Although the patterns of resting and reactive frontal EEG asymmetry did not distinguish among individual differences in social anxiety, the pattern of resting frontal EEG asymmetry was related to trait shyness after controlling for concurrent depressive mood. Individuals who reported a higher degree of shyness were likely to exhibit greater relative right frontal EEG activity at rest. However, trait shyness was not related to frontal EEG asymmetry measured during the speech-preparation task, even after controlling for concurrent depressive mood. These findings replicate and extend prior work on resting frontal EEG asymmetry and individual differences in affective style in adults. Findings also highlight the importance of considering concurrent emotional states of participants when examining psychophysiological correlates of personality.Keywords: social anxiety, shyness, sociability

  8. Effects of the South American psychoactive beverage ayahuasca on regional brain electrical activity in humans: a functional neuroimaging study using low-resolution electromagnetic tomography.

    Science.gov (United States)

    Riba, Jordi; Anderer, Peter; Jané, Francesc; Saletu, Bernd; Barbanoj, Manel J

    2004-01-01

    Ayahuasca, a South American psychotropic plant tea obtained from Banisteriopsis caapi and Psychotria viridis, combines monoamine oxidase-inhibiting beta-carboline alkaloids with N,N-dimethyltryptamine (DMT), a psychedelic agent showing 5-HT(2A) agonist activity. In a clinical research setting, ayahuasca has demonstrated a combined stimulatory and psychedelic effect profile, as measured by subjective effect self-assessment instruments and dose-dependent changes in spontaneous brain electrical activity, which parallel the time course of subjective effects. In the present study, the spatial distribution of ayahuasca-induced changes in brain electrical activity was investigated by means of low-resolution electromagnetic tomography (LORETA). Electroencephalography recordings were obtained from 18 volunteers after the administration of a dose of encapsulated freeze-dried ayahuasca containing 0.85 mg DMT/kg body weight and placebo. The intracerebral power density distribution was computed with LORETA from spectrally analyzed data, and subjective effects were measured by means of the Hallucinogen Rating Scale (HRS). Statistically significant differences compared to placebo were observed for LORETA power 60 and 90 min after dosing, together with increases in all six scales of the HRS. Ayahuasca decreased power density in the alpha-2, delta, theta and beta-1 frequency bands. Power decreases in the delta, alpha-2 and beta-1 bands were found predominantly over the temporo-parieto-occipital junction, whereas theta power was reduced in the temporomedial cortex and in frontomedial regions. The present results suggest the involvement of unimodal and heteromodal association cortex and limbic structures in the psychological effects elicited by ayahuasca. Copyright 2004 S. Karger AG, Basel

  9. Targeted delivery of rosmarinic acid across the blood-brain barrier for neuronal rescue using polyacrylamide-chitosan-poly(lactide-co-glycolide) nanoparticles with surface cross-reacting material 197 and apolipoprotein E.

    Science.gov (United States)

    Kuo, Yung-Chih; Rajesh, Rajendiran

    2017-08-07

    Rosmarinic acid-loaded polyacrylamide-chitosan-poly(lactide-co-glycolide) nanoparticles (RA-PAAM-CH-PLGA NPs) were grafted with cross-reacting material 197 (CRM197) and apolipoprotein E (ApoE) for targeting of the blood-brain barrier (BBB) and rescuing degenerated neurons. The polymeric nanocarriers were prepared by microemulsion, solvent diffusion, grafting, and surface modification, and CRM197-ApoE-RA-PAAM-CH-PLGA NPs were used to treat human brain-microvascular endothelial cells, RWA264.7 cells, and Aβ-insulted SK-N-MC cells. Experimental results revealed that an increase in the weight percentage of PAAM decreased the particle size, zeta potential, and grafting efficiency of CRM197 and ApoE. In addition, surface DSPE-PEG(2000) could protect CRM197-ApoE-RA-PAAM-CH-PLGA NPs against uptake by RWA264.7 cells. An increase in the concentration of CRM197 and ApoE decreased the transendothelial electrical resistance and increased the ability of propidium iodide and RA to cross the BBB. The order in the viability of apoptotic SK-N-MC cells was CRM197-ApoE-RA-PAAM-CH-PLGA NPs > CRM197-RA-PAAM-CH-PLGA NPs > RA. Thus, CRM197-ApoE-RA-PAAM-CH-PLGA NPs can be a promising formulation to deliver RA to Aβ-insulted neurons in the pharmacotherapy of Alzheimer's disease. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. A randomized, controlled, double-blind pilot study of the effects of cranial electrical stimulation on activity in brain pain processing regions in individuals with fibromyalgia.

    Science.gov (United States)

    Taylor, Ann Gill; Anderson, Joel G; Riedel, Shannon L; Lewis, Janet E; Bourguignon, Cheryl

    2013-01-01

    To investigate the effects of microcurrent cranial electrical stimulation (CES) therapy on activity in pain processing brain regions. A randomized, controlled, three-group, double-blind pilot study. Persons with physician-diagnosed fibromyalgia. Active CES device, sham device, and usual care alone. Those individuals using the active device had a greater decrease in average pain (P = .023) than individuals using the sham device or receiving usual care alone over time. Preliminary analyses of the functional magnetic resonance imaging data on a subset of six participants from each of the two device groups show that individuals using an active CES device had a decrease in activation in the pain processing regions of the brain compared to those using a sham device. The observed decrease in activation in the pain processing regions may indicate a decrease in neural activity in these regions that may be related to decreased pain. This is the first randomized, controlled trial of CES in patients diagnosed with fibromyalgia to report functional magnetic resonance imaging data. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Research on Lessening of Bonding Effects Between the Metallic and Non-Metallic Surfaces Through the Graphite Films Deposited with Pulsed Electrical Discharges Process

    Science.gov (United States)

    Marin, L.; Topala, P.

    2017-06-01

    The paper presents the results of experimental research on the physics of natural graphite film formation, the establishment of chemical composition and functional properties of the graphite films, formed on metal surfaces, as a result of the action of plasma in the air environment, at a normal pressure, under the electrical discharge in impulse conditions (EDI). The researchings were performed in the frame of doctoral thesis “Research on lessening of the bonding effects between the metallic and nonmetallic surfaces through the graphite films” and aimed to identify the phenomena that occur at the interface metal/ film of graphite, and to identify also the technological applications that it may have the surface treatment for submitting the films of graphite on metallic surfaces achieved through an innovative process of electrical pulsed discharges. After the research works from the PhD theme above mentioned, a number of interesting properties of graphite pellicle have been identified ie reducing of metal surface polarity. This led to drastic decreases for the values of adhesion when bonding of metal surfaces was performed using a structural polyurethane adhesive designed by ICECHIM. Following the thermo-gravimetric analysis, performed of the graphite film obtained by process of electrical pulsed discharges, have been also discovered other interesting properties for this, ie reversible mass additions at specific values of the working temperature Chemical and scanning electron microscopy analysis have revealed that on the metallic surface subjected to electrical pulsed discharges process, outside the graphite film, it is also obtained a series of spatial formation composed of carbon atoms fullerenes type which are responsible for the phenomenon of addition of mass.

  12. OPTIMIZATION OF PATCHOULI OIL (POGOSTEMON CABLIN, BENTH WITH STEAM DISTILLATION ASSISTED BY PULSED ELECTRIC FIELD VIA RESPONSE SURFACE METHODOLOGY

    Directory of Open Access Journals (Sweden)

    SUKARDI

    2017-08-01

    Full Text Available The study was aimed to determine the role of pulsed electric field (PEF treatment before hydro-distillation of the patchouli oil. Response Surface Methodology (RSM was employed to optimize PEF treatment (voltages, frequencies and times of distillation of patchouli oil from dried patchouli crops. The experimental design and analysis the result to obtain the optimal processing parameters was a Box-Behnken Design (BBD. Three variables were examined in this study: voltages (1,000-2,000 volt; frequencies (1,000-2,000 Hz; and distillation time (4-8 hours. The results showed that the voltage greatly affects the volume of patchouli oil obtained and optimum condition of PEF was voltages of 2,000 volts, frequencies of 1,874 Hz, and 8 hours distillation. The patchouli oil obtained is 8.037 ml of 300 g of dry material (±2.7%. The verification of the model shows that 96.6% (7.76±0.15 ml can adequately for reflecting the expected optimization.

  13. Ultrastructural features of supraspinal muscles in rabbits after long-term transcutaneous lateral electrical surface stimulation (LESS

    Directory of Open Access Journals (Sweden)

    Mariusz Majewski

    2005-12-01

    Full Text Available Lateral electrical surface stimulation is one of methods used in the therapy of the progressive form of idiopathic scoliosis (IS in children and youth. However, there are data suggesting that this method may lead to serious adverse side effects, when used for a too long period of time per day. To clarify this issue, the present study was aimed at disclosing possible changes in the ultrastructural appearance of rabbit supraspinal muscles undergoing long-term stimulation (9 h per day, 3 months, an animal model successfully used to mimic the situation in humans. In comparison to the control animals, muscles of "overstimulated" rabbits exhibited clear signs of microscopical lesions, including depletion and disintegration of myofilaments, proliferation, dilatation and, sometimes, swelling of sarcoplasmic reticulum and/or mitochondria, as well as signs of destruction of the Z line. The above-mentioned abnormalities, especially the signs of degenerative processes associated with the Z line and the observed microlesions strongly suggest that the failure of the long-term LESS therapy of the IS may be attributable to these ultrastructural lesions.

  14. Characteristics of lateral electrical surface stimulation (LESS) and its effect on the degree of spinal deformity in idiopathic scoliosis

    Science.gov (United States)

    Kowalski, Ireneusz M.; Palko, Tadeusz; Pasniczek, Roman; Szarek, Jozef

    2009-01-01

    Clinical studies were carried out in the period of 2003-2006 at the Provincial Children's Rehabilitation Hospital in Ameryka near Olsztyn (Poland). The study involved a group of children and youth exhibiting spinal deformity progression in idiopathic scoliosis (IS) of more than 5° per year according to the Cobb scale. Four hundred and fifty patients between 4 and 15 years of age were divided into three groups (n = 150). Group I and group II received 2-hour and 9-hour lateral electrical surface stimulation (LESS), respectively, whereas group III (control) was treated only with corrective exercises for 30 minutes twice a day. LESS was performed with the use of a battery-operated SCOL-2 stimulator manufactured by Elmech, Warsaw, Poland. The effectiveness of this method was confirmed in the treatment of spinal IS in children and youth, especially when the initial spinal deformity did not exceed 20° according to the Cobb scale. A short-duration electrostimulation (2 hours daily) was found to produce results similar to those obtained after overnight (9 h) electrostimulation. Moreover, the analysis of the Harrington prognostic index F confirms the positive effect of LESS in both groups of patients (2 h and 9 h of LESS).

  15. Electric wind produced by a surface dielectric barrier discharge operating in air at different pressures: aeronautical control insights

    Energy Technology Data Exchange (ETDEWEB)

    Benard, N; Balcon, N; Moreau, E [Laboratoire d' Etudes Aerodynamiques (LEA), Universite de Poitiers, ENSMA, CNRS Bld Marie et Pierre Curie, Teleport 2, 86962 Futuroscope Cedex (France)

    2008-02-21

    The effects of the ambient air pressure level on the electric wind produced by a single dielectric barrier discharge (DBD) have been investigated by Pitot velocity measurements. Pressures from 1 down to 0.2 atm were tested with a 32 kV{sub p-p} 1 kHz excitation. This preliminary study confirms the effectiveness of surface DBD at low pressure. Indeed, the induced velocity is strongly dependent on the ambient air pressure level. Quite surprisingly the produced airflow presents a local maximum at 0.6 atm. The measured velocities at 1 atm and 0.2 atm are 2.5 m s{sup -1} and 3 m s{sup -1}, respectively while 3.5 m s{sup -1} is reached at 0.6 atm. The position of the maximal velocity always coincides with the plasma extension. Mass flow rate calculations indicate that the DBD is effective in real flight pressure conditions. (fast track communication)

  16. Efficacy and safety of transcutaneous electrical acupoint stimulation to treat muscle spasticity following brain injury: a double-blinded, multicenter, randomized controlled trial.

    Directory of Open Access Journals (Sweden)

    Wenli Zhao

    Full Text Available OBJECTIVE: This study was aimed at evaluating the clinical efficacy and safety of transcutaneous electrical acupoint stimulation (TEAS to treat muscle spasticity after brain injury (Chinese Clinical Trial Registry: ChiCTR-TRC-11001310. METHODS: A total of 60 patients with muscle spasticity after brain injury were randomized to the following 3 groups: 100, 2, and 0 Hz (sham TEAS. The acupoints Hegu (LI4--Yuji (LU10 and Zusanli (ST36--Chengshan (BL57 on the injured side were stimulated at 0, 2, or 100 Hz, 5 times per week for 4 weeks. The patients were followed up for 1 and 2 months after the treatments. The effects of the treatments on muscle spasticity at the wrist, thumb, the other 4 fingers, elbow, shoulder, knee, and ankle were evaluated by the Modified Ashworth Scale, and the effects on disability were assessed by the Disability Assessment Scale. The walking capability was evaluated by the Holden functional ambulation classification score. The overall performance was assessed by the Global Assessment Scale score and the improved Barthel Index. The safety of the treatments administered was also monitored. RESULTS: The wrist spasticity was significantly reduced from baseline at weeks 2, 3, and 4 of treatment and at the 1- and 2-month follow-up visits in the 100 Hz group (P < 0.01. Compared with 2 Hz or sham TEAS, 100 Hz TEAS decreased wrist spasticity at weeks 2, 3, and 4 of treatment and 1 month after treatment (P < 0.001. The other endpoints were not affected by the treatments. No treatment-emergent adverse events were reported during treatments and follow-up visits. CONCLUSIONS: TEAS appears to be a safe and effective therapy to relieve muscle spasticity after brain injury, although large-scale studies are required to further verify the findings. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR-TRC-11001310 http://www.chictr.org.

  17. Efficacy and safety of combining clozapine with electrical or magnetic brain stimulation in treatment-refractory schizophrenia.

    Science.gov (United States)

    Arumugham, Shyam Sundar; Thirthalli, Jagadisha; Andrade, Chittaranjan

    2016-09-01

    A substantial proportion (40-70%) of patients with treatment-resistant schizophrenia experience persistent symptoms despite an adequate clozapine trial. Brain stimulation techniques (BST) such as electroconvulsive therapy (ECT), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS) have shown promise in medication-refractory schizophrenia. However, their co-administration with clozapine raises some safety concerns. We conducted a systematic literature search through Pubmed and cross-references for relevant publications evaluating the safety and efficacy of combining BST with clozapine. Expert commentary: Evidence from a randomized controlled trial and open-label trials suggest that ECT is an effective intervention in clozapine-refractory schizophrenia. There is limited evidence that the combination is safe. However, until sufficient data accumulate, it would be prudent to be vigilant against adverse effects related to lowered seizure threshold, cognitive impairment, and cardiovascular events. Both high frequency rTMS over the dorsolateral prefrontal cortex and low frequency rTMS over the temporoparietal cortex have been safely administered in patients receiving clozapine. However, rTMS efficacy in clozapine-refractory patients remains uncertain. The evidence for tDCS-clozapine combination is in the form of case reports and needs to be evaluated in controlled trials. Newer methods of brain stimulation and refinement of existing BSTs hold promise for the future.

  18. The effects of typical and atypical antipsychotics on the electrical activity of the brain in a rat model

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    Oytun Erbaş

    2013-09-01

    Full Text Available Objective: Antipsychotic drugs are known to have strongeffect on the bioelectric activity in the brain. However,some studies addressing the changes on electroencephalography(EEG caused by typical and atypical antipsychoticdrugs are conflicting. We aimed to compare the effectsof typical and atypical antipsychotics on the electricalactivity in the brain via EEG recordings in a rat model.Methods: Thirty-two Sprague Dawley adult male ratswere used in the study. The rats were divided into fivegroups, randomly (n=7, for each group. The first groupwas used as control group and administered 1 ml/kg salineintraperitoneally (IP. Haloperidol (1 mg/kg (group 2,chlorpromazine (5 mg/kg (group 3, olanzapine (1 mg/kg(group 4, ziprasidone (1 mg/ kg (group 5 were injectedIP for five consecutive days. Then, EEG recordings ofeach group were taken for 30 minutes.Results: The percentages of delta and theta waves inhaloperidol, chlorpromazine, olanzapine and ziprasidonegroups were found to have a highly significant differencecompared with the saline administration group (p<0.001.The theta waves in the olanzapine and ziprasidonegroups were increased compared with haloperidol andchlorpromazine groups (p<0.05.Conclusion: The typical and atypical antipsychotic drugsmay be risk factor for EEG abnormalities. This studyshows that antipsychotic drugs should be used with caution.J Clin Exp Invest 2013; 4 (3: 279-284Key words: Haloperidol, chlorpromazine, olanzapine,ziprasidone, EEG, rat

  19. Changes in brain electrical activity after cognitive behavioral therapy for posttraumatic stress disorder in patients injured in motor vehicle accidents.

    Science.gov (United States)

    Rabe, Sirko; Zoellner, Tanja; Beauducel, Andrë; Maercker, Andreas; Karl, Anke

    2008-01-01

    To explore changes for the first time in neural processing due to effective cognitive behavioral therapy (CBT) in posttraumatic stress disorder (PTSD) after severe motor vehicle accidents. Recent studies have highlighted the role of right hemisphere activation during withdrawal-related emotions (e.g., anxiety). There has been little research on changes in brain function due to cognitive-behavioral interventions in anxiety disorders. We conducted a randomized, controlled trial comparing cognitive-behavioral therapy with an assessment-only Wait-list condition. Spontaneous electroencephalographic activity was recorded from left and right anterior and posterior regions in participants with PTSD/subsyndromal PTSD receiving CBT (n = 17) before and after a CBT program. Wait-list controls (n = 18) were investigated before and after 3 months. At the pretreatment assessment, a pattern of increased right-sided activation during exposure to a trauma-related picture (relative to a neutral picture) was observed in both CBT and Wait-list participants. At posttreatment, there was a greater reduction of right anterior activation in the CBT group as compared with Wait-list controls. Across both groups, PTSD symptom reduction was significantly positively correlated with a decrease in right anterior activation to the trauma stimulus. These findings suggest that effective CBT treatment of PTSD may be accompanied by adaptive changes in asymmetrical brain function. Future studies are needed to confirm our findings.

  20. The role of electro-osmosis in the electric-field-induced movement of charged macromolecules on the surfaces of cells

    OpenAIRE

    McLaughlin, S; Poo, M M

    1981-01-01

    The surfaces of most cells bear a net negative charge. The imposition of an electric field parallel to the surface of the cell should produce, therefore, an electro-osmotic flow of fluid towards the cathodal side of the cell. Our analysis of a simple model of the cell surface indicates that a negatively charged mobile macromolecule will be swept by this electro-osmotic flow of fluid to the cathodal side of the cell if its zeta potential, zeta 1, is less negative than the zeta potential of the...

  1. Permeability surface area product analysis in malignant brain edema prediction - A pilot study.

    Science.gov (United States)

    Volny, O; Cimflova, P; Lee, T-Y; Menon, B K; d'Esterre, C D

    2017-05-15

    Using an extended CT perfusion acquisition (150s), we sought to determine the association between perfusion parameters and malignant edema after ischemic stroke. Patients (from prospective study PROVE-IT, NCT02184936) with terminal internal carotid artery±proximal middle cerebral occlusion were involved. CTA was assessed for clot location and status of leptomeningeal collaterals. The following CTP parameters were calculated within the ischemic territory and contralaterally: permeability surface area product (PS), cerebral blood flow (CBF) and cerebral blood volume (CBV). PS was calculated using the adiabatic approximation to the Johnson and Wilson model. Outcome was evaluated by midline shift and infarction volume on follow-up imaging. Of 200 patients enrolled, 7 patients (3.5%) had midline shift≥5mm (2 excluded for poor-quality scans). Five patients with midline shift and 5 matched controls were analysed. There was no significant difference in mean PS, CBF and CBV within the ischemic territory between the two groups. A CBV threshold of 1.7ml/100g had the highest AUC=0.72, 95% CI=0.54-0.90 for early midline shift prediction, sensitivity and specificity were 0.83 and 0.67 respectively. Our preliminary results did not show significant differences in permeability surface area analysis if analysed for complete ischemic region. CBV parameter had the highest accuracy and there was a trend for the mean PS values for midline shift prediction. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Deleted in Malignant Brain Tumors 1 (DMBT1 is present in hyaline membranes and modulates surface tension of surfactant

    Directory of Open Access Journals (Sweden)

    Griese Matthias

    2007-10-01

    Full Text Available Abstract Background Deleted in Malignant Brain Tumors 1 (DMBT1 is a secreted scavenger receptor cysteine-rich protein that binds various bacteria and is thought to participate in innate pulmonary host defense. We hypothesized that pulmonary DMBT1 could contribute to respiratory distress syndrome in neonates by modulating surfactant function. Methods DMBT1 expression was studied by immunohistochemistry and mRNA in situ hybridization in post-mortem lungs of preterm and full-term neonates with pulmonary hyaline membranes. The effect of human recombinant DMBT1 on the function of bovine and porcine surfactant was measured by a capillary surfactometer. DMBT1-levels in tracheal aspirates of ventilated preterm and term infants were determined by ELISA. Results Pulmonary DMBT1 was localized in hyaline membranes during respiratory distress syndrome. In vitro addition of human recombinant DMBT1 to the surfactants increased surface tension in a dose-dependent manner. The DMBT1-mediated effect was reverted by the addition of calcium depending on the surfactant preparation. Conclusion Our data showed pulmonary DMBT1 expression in hyaline membranes during respiratory distress syndrome and demonstrated that DMBT1 increases lung surface tension in vitro. This raises the possibility that DMBT1 could antagonize surfactant supplementation in respiratory distress syndrome and could represent a candidate target molecule for therapeutic intervention in neonatal lung disease.

  3. Deleted in Malignant Brain Tumors 1 (DMBT1) is present in hyaline membranes and modulates surface tension of surfactant

    Science.gov (United States)

    Müller, Hanna; End, Caroline; Renner, Marcus; Helmke, Burkhard M; Gassler, Nikolaus; Weiss, Christel; Hartl, Dominik; Griese, Matthias; Hafner, Mathias; Poustka, Annemarie; Mollenhauer, Jan; Poeschl, Johannes

    2007-01-01

    Background Deleted in Malignant Brain Tumors 1 (DMBT1) is a secreted scavenger receptor cysteine-rich protein that binds various bacteria and is thought to participate in innate pulmonary host defense. We hypothesized that pulmonary DMBT1 could contribute to respiratory distress syndrome in neonates by modulating surfactant function. Methods DMBT1 expression was studied by immunohistochemistry and mRNA in situ hybridization in post-mortem lungs of preterm and full-term neonates with pulmonary hyaline membranes. The effect of human recombinant DMBT1 on the function of bovine and porcine surfactant was measured by a capillary surfactometer. DMBT1-levels in tracheal aspirates of ventilated preterm and term infants were determined by ELISA. Results Pulmonary DMBT1 was localized in hyaline membranes during respiratory distress syndrome. In vitro addition of human recombinant DMBT1 to the surfactants increased surface tension in a dose-dependent manner. The DMBT1-mediated effect was reverted by the addition of calcium depending on the surfactant preparation. Conclusion Our data showed pulmonary DMBT1 expression in hyaline membranes during respiratory distress syndrome and demonstrated that DMBT1 increases lung surface tension in vitro. This raises the possibility that DMBT1 could antagonize surfactant supplementation in respiratory distress syndrome and could represent a candidate target molecule for therapeutic intervention in neonatal lung disease. PMID:17908325

  4. Cortical surface-based analysis reduces bias and variance in kinetic modeling of brain PET data

    DEFF Research Database (Denmark)

    Greve, Douglas N; Svarer, Claus; Fisher, Patrick M

    2014-01-01

    -based smoothing, level of smoothing, use of voxelwise partial volume correction (PVC), and PVC masking threshold. PVC was implemented using the Muller-Gartner method with the masking out of voxels with low gray matter (GM) partial volume fraction. Dynamic PET scans of an antagonist serotonin-4 receptor...... radioligand ([(11)C]SB2307145) were collected on sixteen healthy subjects using a Siemens HRRT PET scanner. Kinetic modeling was used to compute maps of non-displaceable binding potential (BPND) after preprocessing. The results showed a complicated interaction between smoothing, PVC, and masking on BPND...... estimates. Volume-based smoothing resulted in large bias and intersubject variance because it smears signal across tissue types. In some cases, PVC with volume smoothing paradoxically caused the estimated BPND to be less than when no PVC was used at all. When applied in the absence of PVC, cortical surface...

  5. Electric field dependent structural and vibrational properties of the Si(100)-H(2 x 1) surface and its implications for STM induced hydrogen desorption

    DEFF Research Database (Denmark)

    Stokbro, Kurt

    1999-01-01

    We report a first principles study of the structure and the vibrational properties of the Si(100)-H(2 x 1) surface in an electric field. The calculated vibrational parameters are used to model the vibrational modes in the presence of the electric field corresponding to a realistic scanning...... at room temperature). We calculate the implications for current induced desorption of H using a recently developed first principles model of electron inelastic scattering. The calculations show that inelastic scattering events with energy transfer n (h) over bar omega, where n>1, play an important role...

  6. Applications of electrical resistivity imaging for characterizing groundwater-surface water interactions from local to regional scales

    Science.gov (United States)

    Cardenas, M. B.; Befus, K. M.; Zamora, P. B.; Ong, J.; Zlotnik, V. A.; Cook, P. L.; Tait, D. R.; Erler, D.; Santos, I. R.; Siringan, F. P.

    2012-12-01

    Surface water (SW) and groundwater (GW) interact across multiple spatial and temporal scales and their interaction is important for ecological and biogeochemical functions. The mixing of GW and SW has been challenging to simultaneously map with sufficient detail and coverage. Fortunately, ambient differences in salinity of waters occupying geologic formations and sediment are an ideal target for electrical resistivity imaging (ERI). We present examples of the application of ERI for mapping GW discharge and for understanding GW-SW interactions at: (1) a large regulated river, (2) neighboring lakes with differing salinity, (3) fringing coral reefs and lagoons, (4) beaches, and (5) estuaries. In all these cases, the ER tomograms were critical for improving conceptual understanding of GW-SW interactions. At the Lower Colorado River in Austin, Texas (USA), time-lapse ERI was conducted across a 12-hour dam-release cycle when the river stage varied by 0.7 m. Using temporal variability in electrical resistivity (ER) signatures, we identified a shallow well-flushed hyporheic zone, a transition zone where SW and GW mix, and a stable deep zone hosting only GW. In alkaline lakes in the Nebraska Sand Hills (Nebraska, USA), ER surveys using boat-towed cables allowed for mapping the 3D electrical structure underneath the lake. The tomograms were used to distinguish flow-through lakes, which have decreasing subsurface ER from GW inflow to outflow area, from pure GW discharge lakes, which have uniformly stratified increasing-with-depth ER profiles. Moreover, GW plumes in both discharge and recharge zones were clearly outlined underneath the lake. More than 30 km of ER profiles collected via boat-towed surveys over a fringing coral reef in the Philippines identified areas of high ER within the reef that coincide with resistive zones in the seawater. Analysis of 222Rn of bottom waters and vertical conductivity-temperature-depth measurements show the persistence of fresh GW input into

  7. Integrative assessment of kick boxers’ brain blood circulation and bio-electrical activity in conditions of correction technologies’ application

    Directory of Open Access Journals (Sweden)

    Romanov Y.N.

    2016-06-01

    Full Text Available Purpose: to scientifically substantiate the role of para-vertebral impacts on blood circulation and bio-electrical activity of kick boxers’ cortex. Material: in the research participated kick boxers (main group, n=62 and university students (control group, n=25 of 18-23 years’ age. Assessment of para-vertebral impacts with device Armos and classic massage was fulfilled with the help of the following methodic: trans-cranial dopplerography of head main arteries and cortex EEG of the tested. Results: it was found that with the help of para-vertebral impacts by device Armos linear velocity of cerebral blood flow reduces to normal limits and in- and inter-hemispheres’ interaction strength increases. Conclusions: para-vertebral impacts by device Armos activate integrative processes and inter-hemispheres’ interactions of different cortex areas of kick boxers. It can witness about better formation of functional systems, ensuring sports efficiency.

  8. Annealing effects on electrical, structural, and surface morphological properties of Ir/n-InGaN Schottky structures

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, V. Rajagopal; Padma, R.; Reddy, M.S.P. [Department of Physics, Sri Venkateswara University, Tirupati (India); Choi, C.J. [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center (SPRC), Chonbuk National University, Jeonju (Korea, Republic of)

    2012-10-15

    The effects of thermal annealing on electrical and structural characteristics of iridium (Ir) Schottky contacts to n-type InGaN have been studied using current-voltage (I-V), capacitance-voltage (C-V), secondary ion mass spectrometer (SIMS), and X-ray diffraction (XRD) measurements. Measurements showed that the Schottky barrier height (SBH) of as-deposited sample is 0.79 eV (I-V) and 1.07 eV (C-V). It is observed that the barrier height increases to 0.85 eV (I-V) and 1.21 eV (C-V) after annealing at 300 C for 1 min in N{sub 2} ambient. However, it is found that the SBH slightly decreases when the contacts are annealed at 400 and 500 C and the corresponding values are 0.84 eV (I-V), 1.17 eV (C-V) for 400 C and 0.80 eV (I-V), 1.11 eV (C-V) for 500 C, respectively. Using Cheung's functions, the barrier height ({Phi}{sub b}), ideality factor (n), and series resistance (R{sub s}) are also calculated. From the above results, it is clear that the optimum annealing temperature for Ir Schottky contact is 300 C. SIMS and XRD results shows that the formation of gallide phases at Ir/n-InGaN interfaces could be the reason for variation in the SBHs upon annealing at elevated temperatures. Atomic force microscopy (AFM) results show that the overall surface morphology of Ir Schottky contacts on n-InGaN stays reasonably smooth. These results make Ir Schottky contacts attractive for high-temperature device applications. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Mechanism of equivalent electric dipole oscillation for high-order harmonic generation from grating-structured solid-surface by femtosecond laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yang; Song, Hai-Ying; Liu, H.Y.; Liu, Shi-Bing, E-mail: sbliu@bjut.edu.cn

    2017-07-12

    Highlights: • Proposed a valid mechanism of high harmonic generation by laser grating target interaction: oscillation of equivalent electric dipole (OEED). • Found that there also exist harmonic emission at large emission angle but not just near-surface direction as the former researches had pointed out. • Show the process of the formation and motion of electron bunches at the grating-target surface irradiating with femtosecond laser pulse. - Abstract: We theoretically study high-order harmonic generation (HHG) from relativistically driven overdense plasma targets with rectangularly grating-structured surfaces by femtosecond laser pulses. Our particle-in-cell (PIC) simulations show that, under the conditions of low laser intensity and plasma density, the harmonics emit principally along small angles deviating from the target surface. Further investigation of the surface electron dynamics reveals that the electron bunches are formed by the interaction between the laser field and the target surface, giving rise to the oscillation of equivalent electric-dipole (OEED), which enhances specific harmonic orders. Our work helps understand the mechanism of harmonic emissions from grating targets and the distinction from the planar harmonic scheme.

  10. Neuronal coupling by endogenous electric fields: cable theory and applications to coincidence detector neurons in the auditory brain stem.

    Science.gov (United States)

    Goldwyn, Joshua H; Rinzel, John

    2016-04-01

    The ongoing activity of neurons generates a spatially and time-varying field of extracellular voltage (Ve). This Ve field reflects population-level neural activity, but does it modulate neural dynamics and the function of neural circuits? We provide a cable theory framework to study how a bundle of model neurons generates Ve and how this Ve feeds back and influences membrane potential (Vm). We find that these "ephaptic interactions" are small but not negligible