WorldWideScience

Sample records for optimal current direction

  1. Sensorless optimal sinusoidal brushless direct current for hard disk drives

    Science.gov (United States)

    Soh, C. S.; Bi, C.

    2009-04-01

    Initiated by the availability of digital signal processors and emergence of new applications, market demands for permanent magnet synchronous motors have been surging. As its back-emf is sinusoidal, the drive current should also be sinusoidal for reducing the torque ripple. However, in applications like hard disk drives, brushless direct current (BLDC) drive is adopted instead of sinusoidal drive for simplification. The adoption, however, comes at the expense of increased harmonics, losses, torque pulsations, and acoustics. In this paper, we propose a sensorless optimal sinusoidal BLDC drive. First and foremost, the derivation for an optimal sinusoidal drive is presented, and a power angle control scheme is proposed to achieve an optimal sinusoidal BLDC. The scheme maintains linear relationship between the motor speed and drive voltage. In an attempt to execute the sensorless drive, an innovative power angle measurement scheme is devised, which takes advantage of the freewheeling diodes and measures the power angle through the detection of diode voltage drops. The objectives as laid out will be presented and discussed in this paper, supported by derivations, simulations, and experimental results. The proposed scheme is straightforward, brings about the benefits of sensorless sinusoidal drive, negates the need for current sensors by utilizing the freewheeling diodes, and does not incur additional cost.

  2. High voltage direct current modelling in optimal power flows

    Energy Technology Data Exchange (ETDEWEB)

    Ambriz-Perez, H. [Comision Federal de Electricidad, Mexico, Unidad de Ingenieria Especializada, Rio Rodano No. 14 - Piso 10, Sala 1002, Col. Cuauhtemoc, C.P. 06598, Mexico, D.F. (Mexico); Acha, E. [Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow G128LT, Scotland (United Kingdom); Fuerte-Esquivel, C.R. [Faculty of Electrical Engineering, Universidad Michoacana de San Nicolas de Hidalgo, Morelia 58030, Michoacan (Mexico)

    2008-03-15

    Two-terminal high voltage direct current (HVDC) transmission links are in operation throughout the world. They are key elements in electrical power networks; their representation is oversimplified or ignored in most power system studies. This is particularly the case in Optima Power Flow (OPF) studies. Hence, an OPF program has been extended to incorporate HVDC links, taking due account of overlapping and power transfer control characteristics. This is a new development in Newton Optimal Power Flows, where the converter equations are included directly in the matrix W. The method is indeed a unified one since the solution vector is extended to accommodate the DC variables. The HVDC link model correctly takes into account the relevant DC limit variables. The impact of HVDC links on OPF studies is illustrated by numeric examples, which includes a 5-node system, the AEP 14-node and a 166-node system. (author)

  3. Optimization of focality and direction in dense electrode array transcranial direct current stimulation (tDCS)

    Science.gov (United States)

    Guler, Seyhmus; Dannhauer, Moritz; Erem, Burak; Macleod, Rob; Tucker, Don; Turovets, Sergei; Luu, Phan; Erdogmus, Deniz; Brooks, Dana H.

    2016-06-01

    Objective. Transcranial direct current stimulation (tDCS) aims to alter brain function non-invasively via electrodes placed on the scalp. Conventional tDCS uses two relatively large patch electrodes to deliver electrical current to the brain region of interest (ROI). Recent studies have shown that using dense arrays containing up to 512 smaller electrodes may increase the precision of targeting ROIs. However, this creates a need for methods to determine effective and safe stimulus patterns as the number of degrees of freedom is much higher with such arrays. Several approaches to this problem have appeared in the literature. In this paper, we describe a new method for calculating optimal electrode stimulus patterns for targeted and directional modulation in dense array tDCS which differs in some important aspects with methods reported to date. Approach. We optimize stimulus pattern of dense arrays with fixed electrode placement to maximize the current density in a particular direction in the ROI. We impose a flexible set of safety constraints on the current power in the brain, individual electrode currents, and total injected current, to protect subject safety. The proposed optimization problem is convex and thus efficiently solved using existing optimization software to find unique and globally optimal electrode stimulus patterns. Main results. Solutions for four anatomical ROIs based on a realistic head model are shown as exemplary results. To illustrate the differences between our approach and previously introduced methods, we compare our method with two of the other leading methods in the literature. We also report on extensive simulations that show the effect of the values chosen for each proposed safety constraint bound on the optimized stimulus patterns. Significance. The proposed optimization approach employs volume based ROIs, easily adapts to different sets of safety constraints, and takes negligible time to compute. An in-depth comparison study gives

  4. Novel methods to optimize the effects of transcranial direct current stimulation: a systematic review of transcranial direct current stimulation patents.

    Science.gov (United States)

    Malavera, Alejandra; Vasquez, Alejandra; Fregni, Felipe

    2015-01-01

    Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that has been extensively studied. While there have been initial positive results in some clinical trials, there is still variability in tDCS results. The aim of this article is to review and discuss patents assessing novel methods to optimize the use of tDCS. A systematic review was performed using Google patents database with tDCS as the main technique, with patents filling date between 2010 and 2015. Twenty-two patents met our inclusion criteria. These patents attempt to address current tDCS limitations. Only a few of them have been investigated in clinical trials (i.e., high-definition tDCS), and indeed most of them have not been tested before in human trials. Further clinical testing is required to assess which patents are more likely to optimize the effects of tDCS. We discuss the potential optimization of tDCS based on these patents and the current experience with standard tDCS.

  5. Bat algorithm optimized fuzzy PD based speed controller for brushless direct current motor

    Directory of Open Access Journals (Sweden)

    K. Premkumar

    2016-06-01

    Full Text Available In this paper, design of fuzzy proportional derivative controller and fuzzy proportional derivative integral controller for speed control of brushless direct current drive has been presented. Optimization of the above controllers design is carried out using nature inspired optimization algorithms such as particle swarm, cuckoo search, and bat algorithms. Time domain specifications such as overshoot, undershoot, settling time, recovery time, and steady state error and performance indices such as root mean squared error, integral of absolute error, integral of time multiplied absolute error and integral of squared error are measured and compared for the above controllers under different operating conditions such as varying set speed and load disturbance conditions. The precise investigation through simulation is performed using simulink toolbox. From the simulation test results, it is evident that bat optimized fuzzy proportional derivative controller has superior performance than the other controllers considered. Experimental test results have also been taken and analyzed for the optimal controller identified through simulation.

  6. Inter-individual variability in optimal current direction for transcranial magnetic stimulation of the motor cortex

    DEFF Research Database (Denmark)

    Balslev, Daniela; Braet, Wouter; McAllister, Craig

    2007-01-01

    We evaluated inter-individual variability in optimal current direction for biphasic transcranial magnetic stimulation (TMS) of the motor cortex. Motor threshold for first dorsal interosseus was detected visually at eight coil orientations in 45 degrees increments. Each participant (n=13) completed...... two experimental sessions. One participant with low test-retest correlation (Pearson's rvisual detection of motor threshold was compared to EMG detection; motor thresholds were very similar and highly correlated (0.94-0.99). Similar with previous studies...

  7. Pediatric Stroke and transcranial Direct Current Stimulation: Methods for Rational Individualized Dose Optimization

    Directory of Open Access Journals (Sweden)

    Bernadette T Gillick

    2014-09-01

    Full Text Available Background- Transcranial direct current stimulation (tDCS has been investigated mainly in adults and doses may not be appropriate in pediatric applications. In perinatal stroke where potential applications are promising, rational adaptation of dosage for children remains under investigation.Objective - Construct child-specific tDCS dosing parameters through case study within a perinatal stroke tDCS safety and feasibility trial. Methods- 10-year-old subject with a diagnosis of presumed perinatal ischemic stroke and hemiparesis was identified. T1 MRI scans used to derive computerized model for current flow and electrode positions. Workflow using modeling results and consideration of dosage in previous clinical trials was incorporated. Prior Ad hoc adult montages versus de novo optimized montages provided distinct risk benefit analysis. Approximating adult dose required consideration of changes in both peak brain current flow and distribution which further tradeoff between maximizing efficacy and adding safety factors. Electrode size, position, current intensity, compliance voltage, and duration were controlled independently in this process.Results- Brain electric fields modeled and compared to values previously predicted models. Approximating conservative brain current flow patterns and intensities used in previous adult trials for comparable indications, the optimal current intensity established was 0.7 mA for 10 minutes with a tDCS C3/C4 montage. Specifically 0.7 mA produced comparable peak brain current intensity of an average adult receiving 1.0 mA. Electrode size of 5x7 cm2 with 1.0 mA and low-voltage tDCS was employed to maximize tolerability. Safety and feasibility confirmed with subject tolerating the session well and no serious adverse events.Conclusion- Rational approaches to dose customization, with steps informed by computational modeling, may improve guidance for pediatric stroke tDCS trials.

  8. Optimal marine mammal welfare under human care: Current efforts and future directions.

    Science.gov (United States)

    Brando, Sabrina; Broom, Donald M; Acasuso-Rivero, Cristina; Clark, Fay

    2017-09-18

    Marine mammals include cetaceans, pinnipeds, sirenians, sea otters and polar bears, many of which are charismatic and popular species commonly kept under human care in zoos and aquaria. However, in comparison with their fully terrestrial counterparts their welfare has been less intensively studied, and their partial or full reliance on the aquatic environment leads to unique welfare challenges. In this paper we attempt to collate and review the research undertaken thus far on marine mammal welfare, and identify the most important gaps in knowledge. We use 'best practice case studies' to highlight examples of research promoting optimal welfare, include suggestions for future directions of research efforts, and make recommendations to strive for optimal welfare, where it is currently lacking, above and beyond minimum legislation and guidelines. Our review of the current literature shows that recently there have been positive forward strides in marine mammal welfare assessment, but fundamental research is still required to validate positive and negative indicators of welfare in marine mammals. Across all marine mammals, more research is required on the dimensions and complexity of pools and land areas necessary for optimal welfare, and the impact of staff absence for most of the 24-h day, as standard working hours are usually between 0900 and 1700. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Differentiation of motor cortical representation of hand muscles by navigated mapping of optimal TMS current directions in healthy subjects.

    Science.gov (United States)

    Bashir, Shahid; Perez, Jennifer M; Horvath, Jared C; Pascual-Leone, Alvaro

    2013-08-01

    The precision of navigated transcranial magnetic stimulation (TMS) to map the human primary motor cortex may be effected by the direction of TMS-induced current in the brain as determined by the orientation of the stimulation coil. In this study, the authors investigated the effect of current directionality on motor output mapping using navigated brain stimulation. The goal of this study was to determine the optimal coil orientation (and, thus, induced brain current) to activate hand musculature representations relative to each subject's unique neuroanatomical landmarks. The authors studied motor output maps for the first dorsal interosseous, abductor pollicis brevis, and abductor digiti minimi muscles in 10 normal volunteers. Monopolar current pulses were delivered through a figure-of-eight-shaped TMS coil, and motor evoked potentials were recorded using electromyography. At each targeted brain region, the authors systematically rotated the TMS coil to determine the direction of induced current in the brain for induction of the largest motor evoked potentials. These optimal current directions were expressed as an angle relative to each subject's central sulcus. Consistency of the optimal current direction was assessed by repeating the entire mapping procedure on two different occasions across subjects. The authors demonstrate that systematic optimization of current direction as guided by MRI-based neuronavigation improves the resolution of cortical output motor mapping with TMS.

  10. Optimization of brushless direct current motor design using an intelligent technique.

    Science.gov (United States)

    Shabanian, Alireza; Tousiwas, Armin Amini Poustchi; Pourmandi, Massoud; Khormali, Aminollah; Ataei, Abdolhay

    2015-07-01

    This paper presents a method for the optimal design of a slotless permanent magnet brushless DC (BLDC) motor with surface mounted magnets using an improved bee algorithm (IBA). The characteristics of the motor are expressed as functions of motor geometries. The objective function is a combination of losses, volume and cost to be minimized simultaneously. This method is based on the capability of swarm-based algorithms in finding the optimal solution. One sample case is used to illustrate the performance of the design approach and optimization technique. The IBA has a better performance and speed of convergence compared with bee algorithm (BA). Simulation results show that the proposed method has a very high/efficient performance.

  11. Optimal state feedback control of brushless direct-current motor drive systems based on Lyapunov stability criterion

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper develops a unified methodology for a real-time speed control of brushless direct-current motor drive systems in the presence of measurement noise and load torque disturbance. First, the mathematical model and hardware structure of system is established. Next, an optimal state feed back controller using the Kalman filter state estimation technique is derived.This is followed by an adaptive control algorithm to compensate for the effects of noise and disturbance. Those two algorithms working together can provide a very-high-speed regulation and dynamic response over a wide range of operating conditions.Simulated responses are presented to highlight the effectiveness of the proposed control strategy.

  12. Optimization of bone health in children before and after renal transplantation: current perspectives and future directions

    Directory of Open Access Journals (Sweden)

    Kristen eSgambat

    2014-02-01

    Full Text Available The accrual of healthy bone during the critical period of childhood and adolescence sets the stage for lifelong skeletal health. However, in children with chronic kidney disease (CKD, disturbances in mineral metabolism and endocrine homeostasis begin early on, leading to alterations in bone turnover, mineralization, and volume, and impairing growth. Risk factors for CKD-mineral and bone disorder (CKD-MBD include nutritional vitamin D deficiency, secondary hyperparathyroidism, increased fibroblast growth factor 23 (FGF23, altered growth hormone and insulin like growth factor-1 (GH/IGF-1 axis, delayed puberty, malnutrition, and metabolic acidosis. After kidney transplantation, nutritional vitamin D deficiency, persistent hyperparathyroidism, tertiary FGF23 excess, hypophosphatemia, hypomagnesaemia, immunosuppressive therapy, and alteration of sex hormones continue to impair bone health and growth. As function of the renal allograft declines over time, CKD-MBD associated changes are reactivated, further impairing bone health. Strategies to optimize bone health post-transplant include healthy diet, weight-bearing exercise, correction of vitamin D deficiency and acidosis, electrolyte abnormalities, steroid avoidance, and consideration of recombinant human growth hormone therapy. Other drug therapies have been used in adult transplant recipients, but there is insufficient evidence for use in the pediatric population at the present time. Future therapies to be explored include anti-FGF23 antibodies, FGF23 receptor blockers, and treatments targeting the colonic microbiota by reduction of generation of bacterial toxins and adsorption of toxic end products that affect bone mineralization.

  13. Direct current transformer

    Science.gov (United States)

    Khanna, S. M.; Urban, E. W. (Inventor)

    1979-01-01

    A direct current transformer in which the primary consists of an elongated strip of superconductive material, across the ends of which is direct current potential is described. Parallel and closely spaced to the primary is positioned a transformer secondary consisting of a thin strip of magnetoresistive material.

  14. What is the optimal anodal electrode position for inducing corticomotor excitability changes in transcranial direct current stimulation?

    Science.gov (United States)

    Lee, Minji; Kim, Yun-Hee; Im, Chang-Hwan; Kim, Jung-Hoon; Park, Chang-hyun; Chang, Won Hyuk; Lee, Ahee

    2015-01-01

    Transcranial direct current stimulation (tDCS) non-invasively modulates brain function by inducing neuronal excitability. The conventional hot spot for inducing the highest current density in the hand motor area may not be the optimal site for effective stimulation. In this study, we investigated the influence of the center position of the anodal electrode on changes in motor cortical excitability. We considered three tDCS conditions in 16 healthy subjects: (i) real stimulation with the anodal electrode located at the conventional hand motor hot spot determined by motor evoked potentials (MEPs); (ii) real stimulation with the anodal electrode located at the point with the highest current density in the hand motor area as determined by electric current simulation; and (iii) sham stimulation. Motor cortical excitability as measured by MEP amplitude increased after both real stimulation conditions, but not after sham stimulation. Stimulation using the simulation-derived anodal electrode position, which was found to be posterior to the MEP hot spot for all subjects, induced higher motor cortical excitability. Individual positioning of the anodal electrode, based on the consideration of anatomical differences between subjects, appears to be important for maximizing the effects of tDCS.

  15. Optimization in supply chain management, the current state and future directions: A systematic review and bibliometric analysis

    Directory of Open Access Journals (Sweden)

    Mahmood Movahedipour

    2016-11-01

    Full Text Available Purpose: The purpose of this paper is finding the current state of research and identifies high-potential area for future investigation in optimization in supply chain management. Design/methodology/approach: In this paper we present Bibliometric and Network analysis to examine current state research on optimization in supply chain management to identify established and emergent research field for future investigation. The systematic research review which we used in our study have not grasp or assess by other researchers on this topic. Firstly, based on our methodology Bibliometric analysis began by identifying 1610 publications raised from scientific journals, included literatures from 1994 to March of 2016. Secondly, we applied PageRank algorithm in our data for citation analysis to indicate the significance of a publication. Thirdly, the topological decision variables analysis is done based on Louvain method for network data clustering, for this proposes we used the rigorous tools. Finding: Based on our Network analysis result, the optimization in supply chain management research can be divided into four clusters /modules that introduced fundamental skill, knowledge, theory, application and method. Research limitations/implications: We presented some limitation in our research in some fields which could allow new researchers and practitioners conduct the future research to grow up in different dimensions. Practical implications: Practitioners or policy maker usually are not familiar with these type researches so this is why mush of these survey remain in theatrical and conceptual .Future investigation needs to play in practical application  domain instead stop merely in opinion.    Originality/value: Based on our research, the researchers have more attention to work in conceptual analysis due to other fields but we believe that in facility location problem there many remarkable rooms still exist for future research to development

  16. EOP Current Magnitude and Direction

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data contain shipboard current magnitudes and directions collected in the Pacific, both pelagic and near shore environments. Data is collected using an RD...

  17. A Hybrid Shuffled Frog Leaping Algorithm to Solve Optimal Directional Over Current Relay Coordination Problem for Power Delivery System with DGs

    Directory of Open Access Journals (Sweden)

    Mohammad Sadegh Payam

    2012-01-01

    Full Text Available This study presents a new approach for simultaneous coordinated tuning of over current relay for a Power Delivery System (PDS including Distribution Generations (DGs. In the proposed scheme, instead of changing in protection system structure or using new elements, solving of relay coordination problem is done with revising of relays setting in presence of DGs. For this, the relay coordination problem is formulated as the optimization problem by considering two strategies: minimizing the relays operation time and minimizing the number of changes in relays setting. Also, an efficient hybrid algorithm based on Shuffled Frog Leaping (SFL algorithm and Linear Programming (LP is introduced for solving complex and non-convex optimization problem. To investigate the ability of the proposed method, a 30-bus IEEE test system is considered. Three scenarios are examined to evaluate the effectiveness of the proposed approach to solve the directional overcurrent relay coordination problem for a PDS with DGs. Simulation result show the efficiency of proposed method.

  18. Current Direct Neutrino Mass Experiments

    Directory of Open Access Journals (Sweden)

    G. Drexlin

    2013-01-01

    Full Text Available In this contribution, we review the status and perspectives of direct neutrino mass experiments, which investigate the kinematics of β-decays of specific isotopes (3H, 187Re, 163Ho to derive model-independent information on the averaged electron (antineutrino mass. After discussing the kinematics of β-decay and the determination of the neutrino mass, we give a brief overview of past neutrino mass measurements (SN1987a-ToF studies, Mainz and Troitsk experiments for 3H, cryobolometers for 187Re. We then describe the Karlsruhe Tritium Neutrino (KATRIN experiment currently under construction at Karlsruhe Institute of Technology, which will use the MAC-E-Filter principle to push the sensitivity down to a value of 200 meV (90% C.L.. To do so, many technological challenges have to be solved related to source intensity and stability, as well as precision energy analysis and low background rate close to the kinematic endpoint of tritium β-decay at 18.6 keV. We then review new approaches such as the MARE, ECHO, and Project8 experiments, which offer the promise to perform an independent measurement of the neutrino mass in the sub-eV region. Altogether, the novel methods developed in direct neutrino mass experiments will provide vital information on the absolute mass scale of neutrinos.

  19. Current Direct Neutrino Mass Experiments

    CERN Document Server

    Drexlin, G; Mertens, S; Weinheimer, C

    2013-01-01

    In this contribution we review the status and perspectives of direct neutrino mass experiments. These experiments investigate the kinematics of $\\beta$-decays of specific isotopes ($^3$H, $^{187}$Re, $^{163}$Ho) to derive model-independent information on the averaged electron (anti-) neutrino mass, which is formed by the incoherent sum of the neutrino mass eigenstates contributing to the electron neutrino. We first review the kinematics of $\\beta$-decay and the determination of the neutrino mass, before giving a brief overview of past neutrino mass measurements (SN1987a-ToF studies, Mainz and Troitsk experiments for $^3$H, cryo-bolometers for $^{187}$Re). We then describe the Karlsruhe Tritium Neutrino (KATRIN) experiment which is currently under construction at Karlsruhe Institute of Technology. The large-scale setup will use the MAC-E-Filter principle pioneered earlier to push the sensitivity down to a value of 200 meV(90% C.L.). KATRIN faces many technological challenges that have to be resolved with regar...

  20. Transcranial Direct Current Stimulation Combined with Aerobic Exercise to Optimize Analgesic Responses in Fibromyalgia: A Randomized Placebo-Controlled Clinical Trial

    OpenAIRE

    Mendonca, Mariana E.; Simis, Marcel; Grecco, Luanda C.; Battistella, Linamara R.; Baptista, Abrahão F; Fregni, Felipe

    2016-01-01

    Fibromyalgia is a chronic pain syndrome that is associated with maladaptive plasticity in neural central circuits. One of the neural circuits that are involved in pain in fibromyalgia is the primary motor cortex. We tested a combination intervention that aimed to modulate the motor system: transcranial direct current stimulation (tDCS) of the primary motor cortex (M1) and aerobic exercise (AE). In this phase II, sham-controlled randomized clinical trial, 45 subjects were assigned to 1 of 3 gr...

  1. Optimizing Rehabilitation for Phantom Limb Pain Using Mirror Therapy and Transcranial Direct Current Stimulation: A Randomized, Double-Blind Clinical Trial Study Protocol.

    Science.gov (United States)

    Pinto, Camila Bonin; Saleh Velez, Faddi Ghassan; Bolognini, Nadia; Crandell, David; Merabet, Lotfi B; Fregni, Felipe

    2016-07-06

    Despite the multiple available pharmacological and behavioral therapies for the management of chronic phantom limb pain (PLP) in lower limb amputees, treatment for this condition is still a major challenge and the results are mixed. Given that PLP is associated with maladaptive brain plasticity, interventions that promote cortical reorganization such as non-invasive brain stimulation and behavioral methods including transcranial direct current stimulation (tDCS) and mirror therapy (MT), respectively, may prove to be beneficial to control pain in PLP. Due to its complementary effects, a combination of tDCS and MT may result in synergistic effects in PLP. The objective of this study is to evaluate the efficacy of tDCS and MT as a rehabilitative tool for the management of PLP in unilateral lower limb amputees. A prospective, randomized, placebo-controlled, double-blind, factorial, superiority clinical trial will be carried out. Participants will be eligible if they meet the following inclusion criteria: lower limb unilateral traumatic amputees that present PLP for at least 3 months after the amputated limb has completely healed. Participants (N=132) will be randomly allocated to the following groups: (1) active tDCS and active MT, (2) sham tDCS and active MT, (3) active tDCS and sham MT, and (4) sham tDCS and sham MT. tDCS will be applied with the anodal electrode placed over the primary motor cortex (M1) contralateral to the amputation side and the cathode over the contralateral supraorbital area. Stimulation will be applied at the same time of the MT protocol with the parameters 2 mA for 20 minutes. Pain outcome assessments will be performed at baseline, before and after each intervention session, at the end of MT, and in 2 follow-up visits. In order to assess cortical reorganization and correlate with clinical outcomes, participants will undergo functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) before and after the

  2. Differentiation of sensorimotor neuronal structures responsible for induction of motor evoked potentials, attenuation in detection of somatosensory stimuli, and induction of sensation of movement by mapping of optimal current directions.

    Science.gov (United States)

    Pascual-Leone, A; Cohen, L G; Brasil-Neto, J P; Valls-Solé, J; Hallett, M

    1994-06-01

    Transcranial magnetic stimulation (TMS) of the sensorimotor cortex can evoke motor evoked potentials (MEPs), attenuation in detection of somatosensory stimuli (ADSS), and sensation of movement (SOM) referred to the same body part. In this study we tried to differentiate the substrates responsible for these effects. In 6 normal volunteers, TMS was applied with a nearly monopolar Dantec stimulator and a butterfly coil. Optimal scalp location and current direction were determined for induction of MEPs in abductor pollicis brevis (APB), first dorsal interosseous (FDI), and adductor digiti minimi (ADM); SOM in digits 2 and 5 in an ischemically paralyzed hand; and ADSS applied to digits 2 and 5. All 3 muscles' MEPs and SOM and ADSS in both digits were optimally activated from a single scalp position. In all subjects, optimal current directions for MEPs pointed anteriorly; those for ADSS and SOM pointed posteriorly. Optimal current directions showed the same progression in all subjects for MEPs (ADM, FDI, and APB from antero-lateral to antero-medial), ADSS (digit 5 postero-medial, 2 postero-lateral), and SOM (digit 1 through 5 postero-lateral to postero-medial). We conclude that neuronal networks targeting corticospinal neurons responsible for MEPs are different from those leading to SOM and ADSS (which could not be differentiated).

  3. Current trends and future directions

    DEFF Research Database (Denmark)

    Harboe, Peter G.; Madsen, Sabine; Svejvig, Per

    2012-01-01

    This book is an attempt to gather current state-of-the-art research on project management from multiple universities and university colleges in Denmark. This chapter first discuss a literature review of Danish and Scandinavian research on project management thereby complementing the short review...

  4. Current trends and future directions

    DEFF Research Database (Denmark)

    Harboe, Peter G.; Madsen, Sabine; Svejvig, Per

    2012-01-01

    This book is an attempt to gather current state-of-the-art research on project management from multiple universities and university colleges in Denmark. This chapter first discuss a literature review of Danish and Scandinavian research on project management thereby complementing the short review...

  5. Optimal Current Transfer in Dendrites

    Science.gov (United States)

    Bird, Alex D.

    2016-01-01

    Integration of synaptic currents across an extensive dendritic tree is a prerequisite for computation in the brain. Dendritic tapering away from the soma has been suggested to both equalise contributions from synapses at different locations and maximise the current transfer to the soma. To find out how this is achieved precisely, an analytical solution for the current transfer in dendrites with arbitrary taper is required. We derive here an asymptotic approximation that accurately matches results from numerical simulations. From this we then determine the diameter profile that maximises the current transfer to the soma. We find a simple quadratic form that matches diameters obtained experimentally, indicating a fundamental architectural principle of the brain that links dendritic diameters to signal transmission. PMID:27145441

  6. Theology Today - Currents and Directions

    OpenAIRE

    Fergusson, David

    2011-01-01

    While more fragmented than in mid-20th century, recent trends and directions reveal some dominant approaches and particular sub-areas that have become the focus of significant attention. Although overlapping and intersecting, these are discernible both methodologically and thematically. Approaches include a commitment to cross-disciplinarity, contextuality, strategies of retrieval, articulation of confessional identity, and the re-appropriation of liberalism. Important sub-areas include the r...

  7. Optimal selection for direct mail

    NARCIS (Netherlands)

    Bult, [No Value; Wansbeek, T

    1995-01-01

    Direct marketing (mail) is a growing area of marketing practice, yet the academic journals contain very little research on this topic. The most important issue for direct marketers is how to sample targets from a population for a direct mail campaign. Although some selection methods are described in

  8. Optimal selection for direct mail

    NARCIS (Netherlands)

    Bult, [No Value; Wansbeek, T

    1995-01-01

    Direct marketing (mail) is a growing area of marketing practice, yet the academic journals contain very little research on this topic. The most important issue for direct marketers is how to sample targets from a population for a direct mail campaign. Although some selection methods are described in

  9. Transcranial direct current stimulation combined with aerobic exercise to optimize analgesic responses in fibromyalgia: A randomized placebo-controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Mariana Emerenciano Mendonça

    2016-03-01

    Full Text Available Fibromyalgia is a chronic pain syndrome that is associated with maladaptive plasticity in neural central circuits. One of the neural circuits that are involved in pain in fibromyalgia is the primary motor cortex. We tested a combination intervention that aimed to modulate the motor system: transcranial direct current stimulation (tDCS of the primary motor cortex (M1 and aerobic exercise (AE. In this phase II, sham-controlled randomized clinical trial, 45 subjects were assigned to 1 of 3 groups: tDCS + AE, AE only, and tDCS only. The following outcomes were assessed: intensity of pain, level of anxiety, quality of life, mood, pressure pain threshold, and cortical plasticity, as indexed by transcranial magnetic stimulation. There was a significant effect for the group-time interaction for intensity of pain, demonstrating that tDCS/AE was superior to AE (F(13,364=2.25, p=0.007 and tDCS (F(13.364=2.33, p=0.0056 alone. Post hoc adjusted analysis showed a difference between tDCS/AE and tDCS group after the first week of stimulation and after one month intervention period (p=0.02 and p=0.03, respectively. Further, after treatment there was a significant difference between groups in anxiety and mood levels. The combination treatment effected the greatest response. The three groups had no differences regarding responses in motor cortex plasticity, as assessed by TMS. The combination of tDCS with aerobic exercise is superior compared with each individual intervention (cohen’s d effect sizes > 0.55. The combination intervention had a significant effect on pain, anxiety and mood. Based on the similar effects on cortical plasticity outcomes, the combination intervention might have affected other neural circuits, such as those that control the affective-emotional aspects of pain.

  10. Characterizing optimism and pessimism directly though comonotonicity

    NARCIS (Netherlands)

    Wakker, P.

    1990-01-01

    Schmeidler (1982) introduced comonotonic independence to characterize nonadditivity of probabilities. This note obtains natural and very simple characterizations of convexity, concavity (and additivity) of nonadditive probabilities, by relating these directly to the pessimism and optimism inherent

  11. A three-port direct current converter

    DEFF Research Database (Denmark)

    2016-01-01

    The three-port direct current converter comprising: at least one input direct current source; at least one storage battery; a primary side circuit; a secondary side circuit; a first single magnetic component shared by the primary side circuit and the secondary side circuit, wherein the primary side...... circuit comprises a connection between the at least one input direct current source and the at least one storage battery, the primary side circuit configured for operating as a buck converter; a second magnetic component serially coupled to the first single magnetic component, wherein the first and second...... magnetic components are configured to perform a voltage step-up, wherein the secondary side circuit comprises a connection between the at least one storage battery and at least one load, the secondary side configured for operating as a tapped boost converter; wherein the three-port direct current converter...

  12. Three Magnetic Direct-Current Sensors

    Science.gov (United States)

    Sullender, Craig C.; Stagg, David A.

    1994-01-01

    Three direct-current-measuring circuits based on magnetic (transformer) coupling, with periodic reset of magnetic flux to reverse saturation. Unidirectional and bidirectional versions demonstrated. Offers greater realibility and lower power consumption.

  13. The Application of Auto-Disturbance Rejection Control Optimized by Least Squares Support Vector Machines Method and Time-Frequency Representation in Voltage Source Converter-High Voltage Direct Current System.

    Directory of Open Access Journals (Sweden)

    Ying-Pei Liu

    Full Text Available In order to improve the performance of voltage source converter-high voltage direct current (VSC-HVDC system, we propose an improved auto-disturbance rejection control (ADRC method based on least squares support vector machines (LSSVM in the rectifier side. Firstly, we deduce the high frequency transient mathematical model of VSC-HVDC system. Then we investigate the ADRC and LSSVM principles. We ignore the tracking differentiator in the ADRC controller aiming to improve the system dynamic response speed. On this basis, we derive the mathematical model of ADRC controller optimized by LSSVM for direct current voltage loop. Finally we carry out simulations to verify the feasibility and effectiveness of our proposed control method. In addition, we employ the time-frequency representation methods, i.e., Wigner-Ville distribution (WVD and adaptive optimal kernel (AOK time-frequency representation, to demonstrate our proposed method performs better than the traditional method from the perspective of energy distribution in time and frequency plane.

  14. The Application of Auto-Disturbance Rejection Control Optimized by Least Squares Support Vector Machines Method and Time-Frequency Representation in Voltage Source Converter-High Voltage Direct Current System.

    Science.gov (United States)

    Liu, Ying-Pei; Liang, Hai-Ping; Gao, Zhong-Ke

    2015-01-01

    In order to improve the performance of voltage source converter-high voltage direct current (VSC-HVDC) system, we propose an improved auto-disturbance rejection control (ADRC) method based on least squares support vector machines (LSSVM) in the rectifier side. Firstly, we deduce the high frequency transient mathematical model of VSC-HVDC system. Then we investigate the ADRC and LSSVM principles. We ignore the tracking differentiator in the ADRC controller aiming to improve the system dynamic response speed. On this basis, we derive the mathematical model of ADRC controller optimized by LSSVM for direct current voltage loop. Finally we carry out simulations to verify the feasibility and effectiveness of our proposed control method. In addition, we employ the time-frequency representation methods, i.e., Wigner-Ville distribution (WVD) and adaptive optimal kernel (AOK) time-frequency representation, to demonstrate our proposed method performs better than the traditional method from the perspective of energy distribution in time and frequency plane.

  15. Stability analysis of direct current control in current source rectifier

    DEFF Research Database (Denmark)

    Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Current source rectifier with high switching frequency has a great potential for improving the power efficiency and power density in ac-dc power conversion. This paper analyzes the stability of direct current control based on the time delay effect. Small signal model including dynamic behaviors...... of dc link is developed to identify the control plants of grid ac current control and dc current control. Analysis on the poles and zeros under dq frame is carried out. Base on this model, it turns out that the phase lag caused by the time delay can stabilized the grid ac current control while reduces...... the stable region for dc current control. Simulation and experimental results are presented to validate the theoretical analysis....

  16. Hybrid high direct current circuit interrupter

    Science.gov (United States)

    Rockot, J.H.; Mikesell, H.E.; Jha, K.N.

    1998-08-11

    A device and a method are disclosed for interrupting very high direct currents (greater than 100,000 amperes) and simultaneously blocking high voltages (greater than 600 volts). The device utilizes a mechanical switch to carry very high currents continuously with low loss and a silicon controlled rectifier (SCR) to bypass the current around the mechanical switch while its contacts are separating. A commutation circuit, connected in parallel with the SCR, turns off the SCR by utilizing a resonant circuit to divert the SCR current after the switch opens. 7 figs.

  17. Direct current power delivery system and method

    Science.gov (United States)

    Zhang, Di; Garces, Luis Jose; Dai, Jian; Lai, Rixin

    2016-09-06

    A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

  18. Directional interactions between current and prior saccades

    Directory of Open Access Journals (Sweden)

    Stephanie Anne Holland Jones

    2014-10-01

    Full Text Available One way to explore how prior sensory and motor events impact eye movements is to ask someone to look to targets located about a central point, returning gaze to the central point after each eye movement. Concerned about the contribution of this return to centre movement, Anderson et al. (2008 used a sequential saccade paradigm in which participants made a continuous series of saccades to peripheral targets that appeared to the left or right of the currently fixated location in a random sequence (the next eye movement began from the last target location. Examining the effects of previous saccades (n-x on current saccade latency (n, they found that saccadic reaction times (RT were reduced when the direction of the current saccade matched that of a preceding saccade (e.g. two left saccades, even when the two saccades in question were separated by multiple saccades in any direction. We examined if this pattern extends to conditions in which targets appear inside continuously marked locations that provide stable visual features (i.e. target ‘placeholders’ and when saccades are prompted by central arrows. Participants completed 3 conditions: peripheral targets (PT; continuous, sequential saccades to peripherally presented targets without placeholders; PT with placeholders; and centrally presented arrows (CA; left or right pointing arrows at the currently fixated location instructing participants to saccade to the left or right. We found reduced saccadic RT when the immediately preceding saccade (n-1 was in the same (vs. opposite direction in the PT without placeholders and CA conditions. This effect varied when considering the effect of the previous 2-5 (n-x saccades on current saccade latency (n. The effects of previous eye movements on current saccade latency may be determined by multiple, time-varying mechanisms related to sensory (i.e., retinotopic location, motor (i.e., saccade direction, and environmental (i.e., persistent visual objects

  19. Optimal current waveforms for brushless permanent magnet motors

    Science.gov (United States)

    Moehle, Nicholas; Boyd, Stephen

    2015-07-01

    In this paper, we give energy-optimal current waveforms for a permanent magnet synchronous motor that result in a desired average torque. Our formulation generalises previous work by including a general back-electromotive force (EMF) wave shape, voltage and current limits, an arbitrary phase winding connection, a simple eddy current loss model, and a trade-off between power loss and torque ripple. Determining the optimal current waveforms requires solving a small convex optimisation problem. We show how to use the alternating direction method of multipliers to find the optimal current in milliseconds or hundreds of microseconds, depending on the processor used, which allows the possibility of generating optimal waveforms in real time. This allows us to adapt in real time to changes in the operating requirements or in the model, such as a change in resistance with winding temperature, or even gross changes like the failure of one winding. Suboptimal waveforms are available in tens or hundreds of microseconds, allowing for quick response after abrupt changes in the desired torque. We demonstrate our approach on a simple numerical example, in which we give the optimal waveforms for a motor with a sinusoidal back-EMF, and for a motor with a more complicated, nonsinusoidal waveform, in both the constant-torque region and constant-power region.

  20. Alzheimer disease: current concepts & future directions.

    Science.gov (United States)

    Musiek, Erik S; Schindler, Suzanne E

    2013-01-01

    Alzheimer disease (AD) is the most common cause of dementia in individuals over age 65, and is expected to cause a major public health crisis as the number of older Americans rapidly expands in the next three decades. Herein, we review current strategies for diagnosis and management of AD, and discuss ongoing clinical research and future therapeutic directions in the battle against this devastating disease.

  1. Transcranial Direct Current Stimulation in Stroke Recovery

    OpenAIRE

    Schlaug, Gottfried; Renga, Vijay; Nair, Dinesh

    2008-01-01

    TDCS - Transcranial Direct Current Stimulation - is an emerging technique of non-invasive brain stimulation that has been found useful in examining cortical function in normal subjects and in facilitating treatments of various neurological disorders. A better understanding of adaptive as well as maladaptive post-stroke neuroplasticity and its modulation through non-invasive brain stimulation has opened up experimental treatment options using TDCS for patients recovering from stroke. We will r...

  2. Optimization of direct-write polarization gratings

    Science.gov (United States)

    Miskiewicz, Matthew N.; Escuti, Michael J.

    2015-02-01

    We recently reported on a mathematical formalism for analyzing the result of a direct-write scanning system applied to photoaligned liquid crystal films. We use that formalism to study the direct-write recording of polarization gratings (PGs). First, we evaluate three scan paths in simulation and experiment, describe their tradeoffs and practical constraints, and identify the most favorable. Second, we explore the parameter space of direct-write PGs in simulation, which includes four dimensions in general: grating period, line spacing, beam size, and spatially averaged fluence. Using this analysis, we predict that a certain portion of the parameter space should be optimal, leading to high diffraction efficiency and well-aligned PGs. Finally, we experimentally fabricate and characterize nine PGs with scan parameters within and around this optimal parameter space and conclude that the prediction is validated. This work is the first in-depth study of direct-write PGs; it identifies many challenges and solutions, and shows, for the first time, direct-write recorded PGs with quality equivalent to those recorded via holography. In particular, we demonstrate a PG (20 μm period) with first-order diffraction efficiency 99.5%, 0.2% haze, and polarization contrast of 2000.

  3. [Transcranial direct current stimulation for depressive disorders].

    Science.gov (United States)

    Aust, S; Palm, U; Padberg, F; Bajbouj, M

    2015-12-01

    Major depressive disorders are one of the most prevalent psychiatric disorders worldwide but approximately 20-30 % of patients do not respond to standard guideline conform treatment. Recent neuroimaging studies in depressive patients revealed altered activation patterns in prefrontal brain areas and that successful cognitive behavioral therapy and psychopharmacological interventions are associated with a reversal of these neural alterations. Therefore, a direct modulation of prefrontal brain activation by non-invasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS) seems to be a promising and innovative approach for the treatment of depressive disorders. In addition, recent neuropsychological findings indicated an augmentation of positive tDCS effects by simultaneous external activation of the stimulated brain area, for example by cognitive training tasks. Based on these findings, the possibility to augment cognitive-emotional learning processes during cognitive behavioral therapy by simultaneous tDCS to increase antidepressive therapeutic effects is discussed in this article.

  4. LANMAS core: Update and current directions

    Energy Technology Data Exchange (ETDEWEB)

    Claborn, J. [Los Alamos National Lab., NM (United States). Safeguards Systems Group; Alvarado, A. [Sandia National Labs., Albuquerque, NM (United States)

    1994-08-01

    Local Area Network Material Accountability System (LANMAS) core software will provide the framework of a material accountability system. LANMAS is a network-based nuclear material accountability system. It tracks the movement of material throughout a site and generates the required reports on material accountability. LANMAS will run in a client/server mode. The database of material type and location will reside on the server, while the user interface runs on the client. The user interface accesses the server via a network. The LANMAS core can be used as the foundation for building required Materials Control and Accountability (MC&A) functionality at any site requiring a new MC&A system. An individual site will build on the LANMAS core by supplying site-specific software. This paper will provide an update on the current LANMAS development activities and discuss the current direction of the LANMAS project.

  5. Direct Current and Pulsed Direct Current Plasma Nitriding of Ferrous Materials a Critical Review

    Directory of Open Access Journals (Sweden)

    Łępicka Magdalena

    2016-06-01

    Full Text Available Nowadays, the improvement of ferrous materials performance is a problem of high interest. One of well-known wear- and corrosion properties improving technique is plasma nitriding, in which elemental nitrogen is introduced to the surface of a metal part for subsequent diffusion into the material. As a result, a compound, “white” layer and a diffusion zone are formed at the detail’s surface. Most of the authors positively describe the effects of surface ion nitiding. On the other hand, there are also reports on adverse effects of direct current and pulsed direct current plasma nitriding on ferrous materials performance. Therefore, an attempt to provide comprehensive summary on direct current and pulsed direct current ion nitriding and its influence on ferrous materials’ mechanical and corrosion properties has been made. According to the results, some of the technique drawbacks are hard to avoid in mass production.

  6. Directed genome engineering for genome optimization.

    Science.gov (United States)

    D'Halluin, Kathleen; Ruiter, Rene

    2013-01-01

    The ability to develop nucleases with tailor-made activities for targeted DNA double-strand break induction at will at any desired position in the genome has been a major breakthrough to make targeted genome optimization feasible in plants. The development of site specific nucleases for precise genome modification has expanded the repertoire of tools for the development and optimization of traits, already including mutation breeding, molecular breeding and transgenesis.Through directed genome engineering technology, the huge amount of information provided by genomics and systems biology can now more effectively be used for the creation of plants with improved or new traits, and for the dissection of gene functions. Although still in an early phase of deployment, its utility has been demonstrated for engineering disease resistance, herbicide tolerance, altered metabolite profiles, and for molecular trait stacking to allow linked transmission of transgenes. In this article, we will briefly review the different approaches for directed genome engineering with the emphasis on double strand break (DSB)-mediated engineering to-wards genome optimization for crop improvement and towards the acceleration of functional genomics.

  7. Direct current hopping conductance along DNA chain

    Institute of Scientific and Technical Information of China (English)

    Ma Song-Shan; Xu Hui; Liu Xiao-Liang; Li Ming-Jun

    2007-01-01

    This paper proposes a model of direct current(DC) electron hopping transport in DNA,in which DNA is considered as a binary one-dimensional disordered system.To quantitatively study the DC conductivity in DNA,it numerically calculates the DC conductivity of DNA chains with difierent parameter values.The result shows that the DC conductivity of DNA chain increases with the increase of temperature.And the conductivity of DNA chain is depended on the probability P.which represents the degree of compositional disorder in a DNA sequence to some extent.For P<0.5,the conductivity of DNA chain decreases with the increase of P,while for P≥0.5,the conductivity increases with the increase of p.The DC conductivity in DNA chain also varies with the change of the electric field,it presents non-Ohm's law conductivity characteristics.

  8. Optimal management of genital herpes: current perspectives

    Directory of Open Access Journals (Sweden)

    Sauerbrei A

    2016-06-01

    Full Text Available Andreas Sauerbrei Institute of Virology and Antiviral Therapy, German Consulting Laboratory for Herpes Simplex Virus and Varicella-Zoster Virus, Jena University Hospital, Friedrich-Schiller University of Jena, Jena, Germany Abstract: As one of the most common sexually transmitted diseases, genital herpes is a global medical problem with significant physical and psychological morbidity. Genital herpes is caused by herpes simplex virus type 1 or type 2 and can manifest as primary and/or recurrent infection. This manuscript provides an overview about the fundamental knowledge on the virus, its epidemiology, and infection. Furthermore, the current possibilities of antiviral therapeutic interventions and laboratory diagnosis of genital herpes as well as the present situation and perspectives for the treatment by novel antivirals and prevention of disease by vaccination are presented. Since the medical management of patients with genital herpes simplex virus infection is often unsatisfactory, this review aims at all physicians and health professionals who are involved in the care of patients with genital herpes. The information provided would help to improve the counseling of affected patients and to optimize the diagnosis, treatment, and prevention of this particular disease. Keywords: herpes simplex virus, epidemiology, infection, antiviral therapy, laboratory diagnosis, prevention

  9. Directed Motivational Currents: Using vision to create effective motivational pathways

    Directory of Open Access Journals (Sweden)

    Christine Muir

    2013-10-01

    Full Text Available Vision, that is, the mental representation of the sensory experience of a future goal state (involving imagination and imagery, is currently at the forefront of motivational innovation, and in recent years it has been seen increasingly more often in the motivational tool kit of practicing language teachers. Theories such as Dörnyei’s L2 motivational self system have explored the power that creating effective visions can harness (see, e.g., Dörnyei & Kubanyiova, 2014 and when viewed in conjunction with other current research avenues, such as future time perspective and dynamic systems theory, vision offers exciting potential. A Directed Motivational Current is a new motivational construct that we suggest is capable of integrating many current theoretical strands with vision: It can be described as a motivational drive which energises long-term, sustained behaviour (such as language learning, and through placing vision and goals as critical central components within this construct, it offers real and practical motivational potential. In this conceptual paper, we first discuss current understandings of vision and of Directed Motivational Currents, and then analyse how they may be optimally integrated and employed to create effective motivational pathways in language learning environments.

  10. Optimal directed searches for continuous gravitational waves

    CERN Document Server

    Ming, Jing; Papa, Maria Alessandra; Aulbert, Carsten; Fehrmann, Henning

    2015-01-01

    Wide parameter space searches for long lived continuous gravitational wave signals are computationally limited. It is therefore critically important that available computational resources are used rationally. In this paper we consider directed searches, i.e. targets for which the sky position is known accurately but the frequency and spindown parameters are completely unknown. Given a list of such potential astrophysical targets, we therefore need to prioritize. On which target(s) should we spend scarce computing resources? What parameter space region in frequency and spindown should we search? Finally, what is the optimal search set-up that we should use? In this paper we present a general framework that allows to solve all three of these problems. This framework is based on maximizing the probability of making a detection subject to a constraint on the maximum available computational cost. We illustrate the method for a simplified problem.

  11. Armentum: a hybrid direct search optimization methodology

    Science.gov (United States)

    Briones, Francisco Zorrilla

    2016-07-01

    Design of experiments (DOE) offers a great deal of benefits to any manufacturing organization, such as characterization of variables and sets the path for the optimization of the levels of these variables (settings) trough the Response surface methodology, leading to process capability improvement, efficiency increase, cost reduction. Unfortunately, the use of these methodologies is very limited due to various situations. Some of these situations involve the investment on production time, materials, personnel, equipment; most of organizations are not willing to invest in these resources or are not capable because of production demands, besides the fact that they will produce non-conformant product (scrap) during the process of experimentation. Other methodologies, in the form of algorithms, may be used to optimize a process. Known as direct search methods, these algorithms search for an optimum on an unknown function, trough the search of the best combination of the levels on the variables considered in the analysis. These methods have a very different application strategy, they search on the best combination of parameters, during the normal production run, calculating the change in the input variables and evaluating the results in small steps until an optimum is reached. These algorithms are very sensible to internal noise (variation of the input variables), among other disadvantages. In this paper it is made a comparison between the classical experimental design and one of these direct search methods, developed by Nelder and Mead (1965), known as the Nelder Mead simplex (NMS), trying to overcome the disadvantages and maximize the advantages of both approaches, trough a proposed combination of the two methodologies.

  12. Targeted transcranial direct current stimulation for rehabilitation after stroke.

    Science.gov (United States)

    Dmochowski, Jacek P; Datta, Abhishek; Huang, Yu; Richardson, Jessica D; Bikson, Marom; Fridriksson, Julius; Parra, Lucas C

    2013-07-15

    Transcranial direct current stimulation (tDCS) is being investigated as an adjunctive technique to behavioral rehabilitation treatment after stroke. The conventional "dosage", consisting of a large (25 cm(2)) anode over the target with the cathode over the contralateral hemisphere, has been previously shown to yield broadly distributed electric fields whose intensities at the target region are less than maximal. Here, we report the results of a systematic targeting procedure with small "high-definition" electrodes that was used in preparation for a pilot study on 8 stroke patients with chronic aphasia. We employ functional and anatomical magnetic resonance imagery (fMRI/MRI) to define a target and optimize (with respect to the electric field magnitude at the target) the electrode configuration, respectively, and demonstrate that electric field strengths in targeted cortex can be substantially increased (63%) over the conventional approach. The optimal montage exhibits significant variation across subjects as well as when perturbing the target location within a subject. However, for each displacement of the target co-ordinates, the algorithm is able to determine a montage which delivers a consistent amount of current to that location. These results demonstrate that MRI-based models of current flow yield maximal stimulation of target structures, and as such, may aid in reliably assessing the efficacy of tDCS in neuro-rehabilitation.

  13. Adventure Therapy: Current Status and Future Directions.

    Science.gov (United States)

    Berman, Dene

    1995-01-01

    Overviews articles in this issue that focus on the current status of adventure therapy and describe efforts aimed at defining a framework for conceptualizing adventure therapy. Notes changes in the field, including introduction of state laws requiring licensure of programs, the drive for program accreditation, and growing training opportunities in…

  14. College Advising: Current Perceptions, Future Directions.

    Science.gov (United States)

    Chapman, David W.; Gill, Stephen J.

    1981-01-01

    Examines the college admissions activities that high school counselors believe are most effective in providing accurate information to students. Also examines the current role of the counselor in college advising and reports on what counselors predict will be the trends in college advising. (Author/RC)

  15. Loyalty Programmes : Current Knowledge and Research Directions

    NARCIS (Netherlands)

    Dorotic, Matilda; Bijmolt, Tammo H. A.; Verhoef, Peter C.

    2012-01-01

    Loyalty programmes (LPs) have increased in number and popularity, but their effects on customer behaviour remain equivocal, due to a lack of understanding of the drivers of LP effectiveness and insufficient generalizable conclusions across prior studies. This paper synthesizes current knowledge pert

  16. Loyalty Programmes : Current Knowledge and Research Directions

    NARCIS (Netherlands)

    Dorotic, Matilda; Bijmolt, Tammo H. A.; Verhoef, Peter C.

    Loyalty programmes (LPs) have increased in number and popularity, but their effects on customer behaviour remain equivocal, due to a lack of understanding of the drivers of LP effectiveness and insufficient generalizable conclusions across prior studies. This paper synthesizes current knowledge

  17. Loyalty Programmes : Current Knowledge and Research Directions

    NARCIS (Netherlands)

    Dorotic, Matilda; Bijmolt, Tammo H. A.; Verhoef, Peter C.

    2012-01-01

    Loyalty programmes (LPs) have increased in number and popularity, but their effects on customer behaviour remain equivocal, due to a lack of understanding of the drivers of LP effectiveness and insufficient generalizable conclusions across prior studies. This paper synthesizes current knowledge pert

  18. Directional Convexity and Finite Optimality Conditions.

    Science.gov (United States)

    1984-03-01

    system, Necessary Conditions for optimality. Work Unit Number 5 (Optimization and Large Scale Systems) *Istituto di Matematica Applicata, Universita...that R(T) is convex would then imply x(u,T) e int R(T). Cletituto di Matematica Applicata, Universita di Padova, 35100 ITALY. Sponsored by the United

  19. Cellular Mechanisms of Transcranial Direct Current Stimulation

    Science.gov (United States)

    2016-07-14

    effects of any number of cellular processes , where the endogenous state is such that it can only be modulated in one direction. Conclusions and...activated synaptic processes and provided a cellular substrate for these changes. This proposal therefore provided a detailed cellular-level...which are involved in synaptic processing , might additionally contribute to the effects of DCS (Purpura and McMurtry, 1965a, b; Bikson et al., 2004

  20. Hybrid Direct-Current Circuit Breaker

    Science.gov (United States)

    Wang, Ruxi (Inventor); Premerlani, William James (Inventor); Caiafa, Antonio (Inventor); Pan, Yan (Inventor)

    2017-01-01

    A circuit breaking system includes a first branch including at least one solid-state snubber; a second branch coupled in parallel to the first branch and including a superconductor and a cryogenic contactor coupled in series; and a controller operatively coupled to the at least one solid-state snubber and the cryogenic contactor and programmed to, when a fault occurs in the load circuit, activate the at least one solid-state snubber for migrating flow of the electrical current from the second branch to the first branch, and, when the fault is cleared in the load circuit, activate the cryogenic contactor for migrating the flow of the electrical current from the first branch to the second branch.

  1. Cellular Mechanisms of Transcranial Direct Current Stimulation

    Science.gov (United States)

    2016-07-14

    Durand DM (1999) Modulation of burst frequency, duration, and amplitude in the zero-Ca(2...polarizing current on action potential and transmitter release in crayfish motor nerve terminals. Pflugers Arch 324:227-248. Durand DM, Bikson M (2001...Markram H, Herz AV (1997) Neural codes: firing rates and beyond. Proc Natl Acad Sci U S A 94:12740-12741. Ghai RS, Bikson M, Durand DM

  2. Medical Robots: Current Systems and Research Directions

    OpenAIRE

    Beasley, Ryan A.

    2012-01-01

    First used medically in 1985, robots now make an impact in laparoscopy, neurosurgery, orthopedic surgery, emergency response, and various other medical disciplines. This paper provides a review of medical robot history and surveys the capabilities of current medical robot systems, primarily focusing on commercially available systems while covering a few prominent research projects. By examining robotic systems across time and disciplines, trends are discernible that imply future capabilities ...

  3. Optimal counter-current exchange networks

    CERN Document Server

    Farr, Robert S

    2016-01-01

    We construct a general analysis for exchange devices linking their efficiency to the (potentially fractal) geometry of the exchange surface and supply network. For certain parameter ranges, we show that the optimal exchanger consists of densely packed pipes which span a thin sheet of large area, which may be crumpled into a fractal surface and supplied with a fractal network of pipes. We present the efficiencies of such fractal exchangers, showing factor gains compared to regular exchangers, using parameters relevant for systems such as pigeon lungs and salmon gills.

  4. Optimal control novel directions and applications

    CERN Document Server

    Aronna, Maria; Kalise, Dante

    2017-01-01

    Focusing on applications to science and engineering, this book presents the results of the ITN-FP7 SADCO network’s innovative research in optimization and control in the following interconnected topics: optimality conditions in optimal control, dynamic programming approaches to optimal feedback synthesis and reachability analysis, and computational developments in model predictive control. The novelty of the book resides in the fact that it has been developed by early career researchers, providing a good balance between clarity and scientific rigor. Each chapter features an introduction addressed to PhD students and some original contributions aimed at specialist researchers. Requiring only a graduate mathematical background, the book is self-contained. It will be of particular interest to graduate and advanced undergraduate students, industrial practitioners and to senior scientists wishing to update their knowledge.

  5. Medical Robots: Current Systems and Research Directions

    Directory of Open Access Journals (Sweden)

    Ryan A. Beasley

    2012-01-01

    Full Text Available First used medically in 1985, robots now make an impact in laparoscopy, neurosurgery, orthopedic surgery, emergency response, and various other medical disciplines. This paper provides a review of medical robot history and surveys the capabilities of current medical robot systems, primarily focusing on commercially available systems while covering a few prominent research projects. By examining robotic systems across time and disciplines, trends are discernible that imply future capabilities of medical robots, for example, increased usage of intraoperative images, improved robot arm design, and haptic feedback to guide the surgeon.

  6. The Cassava Genome: Current Progress, Future Directions.

    Science.gov (United States)

    Prochnik, Simon; Marri, Pradeep Reddy; Desany, Brian; Rabinowicz, Pablo D; Kodira, Chinnappa; Mohiuddin, Mohammed; Rodriguez, Fausto; Fauquet, Claude; Tohme, Joseph; Harkins, Timothy; Rokhsar, Daniel S; Rounsley, Steve

    2012-03-01

    The starchy swollen roots of cassava provide an essential food source for nearly a billion people, as well as possibilities for bioenergy, yet improvements to nutritional content and resistance to threatening diseases are currently impeded. A 454-based whole genome shotgun sequence has been assembled, which covers 69% of the predicted genome size and 96% of protein-coding gene space, with genome finishing underway. The predicted 30,666 genes and 3,485 alternate splice forms are supported by 1.4 M expressed sequence tags (ESTs). Maps based on simple sequence repeat (SSR)-, and EST-derived single nucleotide polymorphisms (SNPs) already exist. Thanks to the genome sequence, a high-density linkage map is currently being developed from a cross between two diverse cassava cultivars: one susceptible to cassava brown streak disease; the other resistant. An efficient genotyping-by-sequencing (GBS) approach is being developed to catalog SNPs both within the mapping population and among diverse African farmer-preferred varieties of cassava. These resources will accelerate marker-assisted breeding programs, allowing improvements in disease-resistance and nutrition, and will help us understand the genetic basis for disease resistance.

  7. Bone regeneration: current concepts and future directions

    Directory of Open Access Journals (Sweden)

    McGonagle Dennis

    2011-05-01

    Full Text Available Abstract Bone regeneration is a complex, well-orchestrated physiological process of bone formation, which can be seen during normal fracture healing, and is involved in continuous remodelling throughout adult life. However, there are complex clinical conditions in which bone regeneration is required in large quantity, such as for skeletal reconstruction of large bone defects created by trauma, infection, tumour resection and skeletal abnormalities, or cases in which the regenerative process is compromised, including avascular necrosis, atrophic non-unions and osteoporosis. Currently, there is a plethora of different strategies to augment the impaired or 'insufficient' bone-regeneration process, including the 'gold standard' autologous bone graft, free fibula vascularised graft, allograft implantation, and use of growth factors, osteoconductive scaffolds, osteoprogenitor cells and distraction osteogenesis. Improved 'local' strategies in terms of tissue engineering and gene therapy, or even 'systemic' enhancement of bone repair, are under intense investigation, in an effort to overcome the limitations of the current methods, to produce bone-graft substitutes with biomechanical properties that are as identical to normal bone as possible, to accelerate the overall regeneration process, or even to address systemic conditions, such as skeletal disorders and osteoporosis.

  8. Direct current modulation of a photomixing signal

    Science.gov (United States)

    Constantin, Florin L.

    2016-04-01

    Direct modulation of the bias voltage of a LTG-GaAs photomixer is exploited to modulate the signal generated at the frequency of the optical beat between two diode lasers at 820 nm. The photomixing signal is calculated from an expansion in power series of the amplitude of the modulation voltage and displays amplitude modulation sidebands equidistantly spaced to the frequency of the optical beat by integer multiples of the modulation frequency. Modulation at harmonics of the modulation frequency is allowed by the electrical nonlinear response of the photomixer, driven at low voltage by the saturation of the electron drift velocity. Coupling of an alternative voltage to the photomixer operated at zero-bias leads to bifrequency operation. Modulation of the photomixing signal and bifrequency operation of the photomixer are observed experimentally with an optical beat in the microwave regime.

  9. Leadership: current theories, research, and future directions.

    Science.gov (United States)

    Avolio, Bruce J; Walumbwa, Fred O; Weber, Todd J

    2009-01-01

    This review examines recent theoretical and empirical developments in the leadership literature, beginning with topics that are currently receiving attention in terms of research, theory, and practice. We begin by examining authentic leadership and its development, followed by work that takes a cognitive science approach. We then examine new-genre leadership theories, complexity leadership, and leadership that is shared, collective, or distributed. We examine the role of relationships through our review of leader member exchange and the emerging work on followership. Finally, we examine work that has been done on substitutes for leadership, servant leadership, spirituality and leadership, cross-cultural leadership, and e-leadership. This structure has the benefit of creating a future focus as well as providing an interesting way to examine the development of the field. Each section ends with an identification of issues to be addressed in the future, in addition to the overall integration of the literature we provide at the end of the article.

  10. Design of Bi-Directional Hydrofoils for Tidal Current Turbines

    Science.gov (United States)

    Nedyalkov, Ivaylo; Wosnik, Martin

    2015-11-01

    Tidal Current Turbines operate in flows which reverse direction. Bi-directional hydrofoils have rotational symmetry and allow such turbines to operate without the need for pitch or yaw control, decreasing the initial and maintenance costs. A numerical test-bed was developed to automate the simulations of hydrofoils in OpenFOAM and was utilized to simulate the flow over eleven classes of hydrofoils comprising a total of 700 foil shapes at different angles of attack. For promising candidate foil shapes physical models of 75 mm chord and 150 mm span were fabricated and tested in the University of New Hampshire High-Speed Cavitation Tunnel (HiCaT). The experimental results were compared to the simulations for model validation. The numerical test-bed successfully generated simulations for a wide range of foil shapes, although, as expected, the k - ω - SST turbulence model employed here was not adequate for some of the foils and for large angles of attack at which separation occurred. An optimization algorithm is currently being coupled with the numerical test-bed and additional turbulence models will be implemented in the future.

  11. Superconducting Fault Current Limiter optimized design

    Energy Technology Data Exchange (ETDEWEB)

    Tixador, Pascal, E-mail: Pascal.Tixador@grenoble-inp.fr [Univ. Grenoble Alpes, G2Elab – Institut Néel, F-38000 Grenoble (France); CNRS, G2Elab – Institut Néel, F-38000 Grenoble (France); Badel, Arnaud [CNRS, G2Elab – Institut Néel, F-38000 Grenoble (France)

    2015-11-15

    Highlights: • A low cost design of YBCO Fault Current Limiter. • A high resistance conductor for reduced length. • An asymmetrical YBCO conductor (injection and AC losses). • A thickness suitable for non destructive hot spots. - Abstract: The SuperConducting Fault Current Limiter (SCFCL) appears as one of the most promising SC applications for the electrical grids. Despite its advantages and many successful field experiences the market of SCFCL has difficulties to take off even if the first orders for permanent operation in grids are taken. The analytical design of resistive SCFCL will be discussed with the objective to reduce the quantity of SC conductor (length and section) to be more cost-effective. For that the SC conductor must have a high resistivity in normal state. It can be achieved by using high resistivity alloy for shunt, such as Hastelloy®. One of the most severe constraint is that the SCFCL should operate safely for any faults, especially those with low prospective short-circuit currents. This constraint requires to properly design the thickness of the SC tape in order to limit the hot spot temperature. An operation at 65 K appears as very interesting since it decreases the SC cost at least by a factor 2 with a simple LN2 cryogenics. Taking into account the cost reduction in a near future, the SC conductor cost could be rather low, half a dollar per kV A.

  12. Saliva diagnostics - Current views and directions.

    Science.gov (United States)

    Kaczor-Urbanowicz, Karolina Elżbieta; Martin Carreras-Presas, Carmen; Aro, Katri; Tu, Michael; Garcia-Godoy, Franklin; Wong, David Tw

    2017-03-01

    In this review, we provide an update on the current and future applications of saliva for diagnostic purposes. There are many advantages of using saliva as a biofluid. Its collection is fast, easy, inexpensive, and non-invasive. In addition, saliva, as a "mirror of the body," can reflect the physiological and pathological state of the body. Therefore, it serves as a diagnostic and monitoring tool in many fields of science such as medicine, dentistry, and pharmacotherapy. Introduced in 2008, the term "Salivaomics" aimed to highlight the rapid development of knowledge about various "omics" constituents of saliva, including: proteome, transcriptome, micro-RNA, metabolome, and microbiome. In the last few years, researchers have developed new technologies and validated a wide range of salivary biomarkers that will soon make the use of saliva a clinical reality. However, a great need still exists for convenient and accurate point-of-care devices that can serve as a non-invasive diagnostic tool. In addition, there is an urgent need to decipher the scientific rationale and mechanisms that convey systemic diseases to saliva. Another promising technology called liquid biopsy enables detection of circulating tumor cells (CTCs) and fragments of tumor DNA in saliva, thus enabling non-invasive early detection of various cancers. The newly developed technology-electric field-induced release and measurement (EFIRM) provides near perfect detection of actionable mutations in lung cancer patients. These recent advances widened the salivary diagnostic approach from the oral cavity to the whole physiological system, and thus point towards a promising future of salivary diagnostics for personalized individual medicine applications including clinical decisions and post-treatment outcome predictions. Impact statement The purpose of this mini-review is to make an update about the present and future applications of saliva as a diagnostic biofluid in many fields of science such as dentistry

  13. Regenerative nanomedicine: current perspectives and future directions

    Directory of Open Access Journals (Sweden)

    Chaudhury K

    2014-09-01

    Full Text Available Koel Chaudhury, Vishu Kumar, Jayaprakash Kandasamy, Sourav RoyChoudhurySchool of Medical Science and Technology, Indian Institute of Technology, Kharagpur, West Bengal, IndiaAbstract: Nanotechnology has considerably accelerated the growth of regenerative medicine in recent years. Application of nanotechnology in regenerative medicine has revolutionized the designing of grafts and scaffolds which has resulted in new grafts/scaffold systems having significantly enhanced cellular and tissue regenerative properties. Since the cell–cell and cell-matrix interaction in biological systems takes place at the nanoscale level, the application of nanotechnology gives an edge in modifying the cellular function and/or matrix function in a more desired way to mimic the native tissue/organ. In this review, we focus on the nanotechnology-based recent advances and trends in regenerative medicine and discussed under individual organ systems including bone, cartilage, nerve, skin, teeth, myocardium, liver and eye. Recent studies that are related to the design of various types of nanostructured scaffolds and incorporation of nanomaterials into the matrices are reported. We have also documented reports where these materials and matrices have been compared for their better biocompatibility and efficacy in supporting the damaged tissue. In addition to the recent developments, future directions and possible challenges in translating the findings from bench to bedside are outlined.Keywords: regenerative medicine, nanomedicine, nanotechnology

  14. Pacemakers, defibrillators, and direct current cardioversion.

    Science.gov (United States)

    Sgarbossa, E B; Black, I W; Maloney, J D

    1993-01-01

    Technology for pacemakers and automatic implantable defibrillators continues to evolve. Emphasis is placed not only on preventing cardiac death, but also on improving symptoms and quality of life. The basic antibradycardia function of pacemakers is complemented by highly sophisticated rate-responsive capabilities. The search for the perfect physiologic sensor has not ended; potential limitations of the systems currently available are considered in this review. Reports on outcome with pacing in different populations are also discussed. There have been two important advances in automatic implantable defibrillators. One is the introduction of the third generation defibrillator in clinical investigation. A tiered therapy (including antitachycardia pacing, cardioversion, and defibrillation) can now be programmed in the same device, with the protection of back-up antibradycardia pacing. The other remarkable innovation is the expanding use of nonthoracotomy techniques for implantable cardioverter-defibrillator placement. This approach permits the avoidance of a subcutaneous patch electrode in some cases, the system being entirely transvenous. Finally, recent insights on external cardioversion for atrial arrhythmias are briefly reviewed.

  15. Behavioral cardiology: current advances and future directions.

    Science.gov (United States)

    Rozanski, Alan

    2014-07-08

    Growing epidemiological evidence identifies key domains relevant to behavioral cardiology, including health behaviors, emotions, mental mindsets, stress management, social connectedness, and a sense of purpose. Each of these domains exists along a continuum, ranging from positive factors that promote health, to negative factors, which are pathophysiological. To date, there has been relatively little translation of this growing knowledge base into cardiology practice. Four initiatives are proposed to meet this challenge: 1) promulgating greater awareness of the potency of psychosocial risks factors; 2) overcoming a current "artificial divide" between conventional and psychosocial risk factors; 3) developing novel cost-effective interventions using Internet and mobile health applications, group-based counseling, and development of tiered-care behavioral management; and 4) in recognition that "one size does not fit all" with respect to behavioral interventions, developing specialists who can counsel patients in multidisciplinary fashion and use evidence-based approaches for promoting patient motivation and execution of health goals. Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  16. Current research directions definition of economic security

    Directory of Open Access Journals (Sweden)

    Anna Falovych

    2013-05-01

    Full Text Available The article features the topical issue of the established level of the enterprise's economic security. The objective of this article is to research, to base and to supplement the tendency for generalization of the categorical system in order to clarify the matter meaning of the enterprise's economic security. The systematized analyses of the matter meaning of the enterprise's economic security were done by domestic and foreign scientists-economists. The results of the study were expounded and also some vital approaches to the definition of the enterprise's economic security were presented and proved particularly: strategically, resource-functional, marketable, combined, deductive, systematic and criminal.Based on the analyzed content-conceptual interpretations and detailed characteristics of each approach to the definition of this meaning, there was proposed its own meaning of the interpretation of the enterprise's economic security. A systematic approach was adopted due to the matters concerning enterprise's economic security. As in this approach the vital economic interests of thee enterprise were stipulated, also gained the topicality in the current crisis economic conditions

  17. Telehealth: current practices and future directions

    Science.gov (United States)

    David, Yadin B.

    1996-02-01

    When we review the positive impact that the integration of ostensibly independent patient-care services have on the efficient management of quality care, education, and collaborative research, it is not surprising that telehealth deployment is on the rise. The forces that drive this phenomenon include: the need to manage the entire disease episode; the desire for wider geographically-distributed quality health care; the escalation of customer expectations; globalization of healthcare and its support services; an increase in patient and provider convenience; and the acceptance of the present technological community. At the Telehealth Center at the Texas Children's Hospital, current classifications of clinical applications are listed: (1) initial urgent evaluation of patients, (2) triage decisions and pretransfer arrangements, (3) medical and surgical follow-up and medication review, (4) consultation for primary care encounters, (5) real-time subspecialty care consultation and planning, (6) management of chronic diseases and conditions, (7) extended diagnostic work-ups, (8) review of diagnostic images, and (9) preventive medicine and patient education. The delivery of such services is associated with challenges and opportunities. As we move forward from limited data processing to an integrated communication system, from centralized main frame functions to personalized and location-independent workstations, and from hospitals to clinics and homecare, an increase in the minimum features provided by the equipment and the communication systems must accompany the widening variety of clinical applications. Future expansion of telehealth systems stands to revolutionize the delivery of services to the benefits of providers' networks, our economy, and patients through integration.

  18. Superconducting Fault Current Limiter optimized design

    Science.gov (United States)

    Tixador, Pascal; Badel, Arnaud

    2015-11-01

    The SuperConducting Fault Current Limiter (SCFCL) appears as one of the most promising SC applications for the electrical grids. Despite its advantages and many successful field experiences the market of SCFCL has difficulties to take off even if the first orders for permanent operation in grids are taken. The analytical design of resistive SCFCL will be discussed with the objective to reduce the quantity of SC conductor (length and section) to be more cost-effective. For that the SC conductor must have a high resistivity in normal state. It can be achieved by using high resistivity alloy for shunt, such as Hastelloy®. One of the most severe constraint is that the SCFCL should operate safely for any faults, especially those with low prospective short-circuit currents. This constraint requires to properly design the thickness of the SC tape in order to limit the hot spot temperature. An operation at 65 K appears as very interesting since it decreases the SC cost at least by a factor 2 with a simple LN2 cryogenics. Taking into account the cost reduction in a near future, the SC conductor cost could be rather low, half a dollar per kV A.

  19. Optimization of directional elastic energy propagation

    DEFF Research Database (Denmark)

    Andreassen, Erik; Chang, Hannah R.; Ruzzene, Massimo;

    2016-01-01

    The aim of this paper is to demonstrate how topology optimization can be used to design a periodically perforated plate, in order to obtain a tailored anisotropic group velocity profile. The main method is demonstrated on both low and high frequency bending wave propagation in an aluminum plate, ...

  20. Pulsed direct and constant direct currents in the pilocarpine iontophoresis sweat chloride test.

    Science.gov (United States)

    Gomez, Carla Cristina Souza; Servidoni, Maria de Fatima; Marson, Fernando Augusto de Lima; Canavezi, Paulo Jose Coelho; Vinagre, Adriana Mendes; Costa, Eduardo Tavares; Ribeiro, Antonio Fernando; Ribeiro, Maria Angela Gonçalves de Oliveira; Toro, Adyleia Aparecida Dalbo Contrera; Pavan, Celia Regina; Rondon, Michelle Vivine Sá Dos Santos; Lorena, Sonia Leticia Silva; Vieria, Francisco Ubaldi; Ribeiro, Jose Dirceu

    2014-12-13

    The classic sweat test (CST) is the golden standard for cystic fibrosis (CF) diagnosis. Then, our aim was compare the production and volume of sweat, and side effects caused by pulsed direct current (PDC) and constant direct current (CDC). To determine the optimal stimulation time (ST) for the sweat collection. To verify the PDC as CF diagnosis option. Prospective study with cross-sectional experimental intervention. Experiment 1 (right arm): PDC and CDC. ST at 10 min and sweat collected at 30 min. Currents of 0.5; 0.75; 1.0 and 1.5 mA and frequencies of 0, 200, 1,000 and 5,000 Hz applied. Experiment 2 (left arm): current of 1.0 mA, ST at 5 and 10 min and sweat collected at 15 and 30 min with frequencies of 0; 200; 1,000 and 5,000 Hz applied Experiments 1 and 2 were performed with current density (CD) from 0.07 to 0.21 mA/cm2. Experiment 3: PDC was used in typical CF patients with two CFTR mutations screened and or with CF diagnosis by rectal biopsy and patients with atypical CF. 48 subjects (79.16% female) with average of 29.54 ± 8.87 years old were enrolled. There was no statistical difference between the interaction of frequency and current in the sweat weight (p = 0.7488). Individually, positive association was achieved between weight sweat and stimulation frequency (p = 0.0088); and current (p = 0.0025). The sweat production was higher for 10 min of stimulation (p = 0.0023). The sweat collection was better for 30 min (p = 0.0019). The skin impedance was not influenced by ST and sweat collection (p > 0.05). The current frequency was inversely associated with the skin impedance (p < 0.0001). The skin temperature measured before stimulation was higher than after (p < 0.0001). In Experiment 3 (29 subjects) the PDC showed better kappa index compared to CDC (0.9218 versus 0.5205, respectively). The performance of the CST with CDC and PDC with CD of 0.14 to 0.21 mA/cm2 showed efficacy in steps of stimulation and collection of sweat, without side effects. The optimal

  1. Neurobiological effects of transcranial direct current stimulation: a review.

    Science.gov (United States)

    Medeiros, Liciane Fernandes; de Souza, Izabel Cristina Custodio; Vidor, Liliane Pinto; de Souza, Andressa; Deitos, Alícia; Volz, Magdalena Sarah; Fregni, Felipe; Caumo, Wolnei; Torres, Iraci L S

    2012-01-01

    Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation technique that is affordable and easy to operate compared to other neuromodulation techniques. Anodal stimulation increases cortical excitability, while the cathodal stimulation decreases it. Although tDCS is a promising treatment approach for chronic pain as well as for neuropsychiatric diseases and other neurological disorders, several complex neurobiological mechanisms that are not well understood are involved in its effect. The purpose of this systematic review is to summarize the current knowledge regarding the neurobiological mechanisms involved in the effects of tDCS. The initial search resulted in 171 articles. After applying inclusion and exclusion criteria, we screened 32 full-text articles to extract findings about the neurobiology of tDCS effects including investigation of cortical excitability parameters. Overall, these findings show that tDCS involves a cascade of events at the cellular and molecular levels. Moreover, tDCS is associated with glutamatergic, GABAergic, dopaminergic, serotonergic, and cholinergic activity modulation. Though these studies provide important advancements toward the understanding of mechanisms underlying tDCS effects, further studies are needed to integrate these mechanisms as to optimize clinical development of tDCS.

  2. Mechanisms and Effects of Transcranial Direct Current Stimulation

    Science.gov (United States)

    Giordano, James; Bikson, Marom; Kappenman, Emily S.; Clark, Vincent P.; Coslett, H. Branch; Hamblin, Michael R.; Hamilton, Roy; Jankord, Ryan; Kozumbo, Walter J.; McKinley, R. Andrew; Nitsche, Michael A.; Reilly, J. Patrick; Richardson, Jessica; Wurzman, Rachel

    2017-01-01

    The US Air Force Office of Scientific Research convened a meeting of researchers in the fields of neuroscience, psychology, engineering, and medicine to discuss most pressing issues facing ongoing research in the field of transcranial direct current stimulation (tDCS) and related techniques. In this study, we present opinions prepared by participants of the meeting, focusing on the most promising areas of research, immediate and future goals for the field, and the potential for hormesis theory to inform tDCS research. Scientific, medical, and ethical considerations support the ongoing testing of tDCS in healthy and clinical populations, provided best protocols are used to maximize safety. Notwithstanding the need for ongoing research, promising applications include enhancing vigilance/attention in healthy volunteers, which can accelerate training and support learning. Commonly, tDCS is used as an adjunct to training/rehabilitation tasks with the goal of leftward shift in the learning/treatment effect curves. Although trials are encouraging, elucidating the basic mechanisms of tDCS will accelerate validation and adoption. To this end, biomarkers (eg, clinical neuroimaging and findings from animal models) can support hypotheses linking neurobiological mechanisms and behavioral effects. Dosage can be optimized using computational models of current flow and understanding dose–response. Both biomarkers and dosimetry should guide individualized interventions with the goal of reducing variability. Insights from other applied energy domains, including ionizing radiation, transcranial magnetic stimulation, and low-level laser (light) therapy, can be prudently leveraged. PMID:28210202

  3. Direct and Evolutionary Approaches for Optimal Receiver Function Inversion

    Science.gov (United States)

    Dugda, Mulugeta Tuji

    Receiver functions are time series obtained by deconvolving vertical component seismograms from radial component seismograms. Receiver functions represent the impulse response of the earth structure beneath a seismic station. Generally, receiver functions consist of a number of seismic phases related to discontinuities in the crust and upper mantle. The relative arrival times of these phases are correlated with the locations of discontinuities as well as the media of seismic wave propagation. The Moho (Mohorovicic discontinuity) is a major interface or discontinuity that separates the crust and the mantle. In this research, automatic techniques to determine the depth of the Moho from the earth's surface (the crustal thickness H) and the ratio of crustal seismic P-wave velocity (Vp) to S-wave velocity (Vs) (kappa= Vp/Vs) were developed. In this dissertation, an optimization problem of inverting receiver functions has been developed to determine crustal parameters and the three associated weights using evolutionary and direct optimization techniques. The first technique developed makes use of the evolutionary Genetic Algorithms (GA) optimization technique. The second technique developed combines the direct Generalized Pattern Search (GPS) and evolutionary Fitness Proportionate Niching (FPN) techniques by employing their strengths. In a previous study, Monte Carlo technique has been utilized for determining variable weights in the H-kappa stacking of receiver functions. Compared to that previously introduced variable weights approach, the current GA and GPS-FPN techniques have tremendous advantages of saving time and these new techniques are suitable for automatic and simultaneous determination of crustal parameters and appropriate weights. The GA implementation provides optimal or near optimal weights necessary in stacking receiver functions as well as optimal H and kappa values simultaneously. Generally, the objective function of the H-kappa stacking problem

  4. Optimization of Orchestral Layouts Based on Instrument Directivity Patterns

    Science.gov (United States)

    Stroud, Nathan Paul

    The experience of hearing an exceptional symphony orchestra perform in an excel- lent concert hall can be profound and moving, causing a level of excitement not often reached for listeners. Romantic period style orchestral music, recognized for validating the use of intense emotion for aesthetic pleasure, was the last significant development in the history of the orchestra. In an age where orchestral popularity is waning, the possibil- ity of evolving the orchestral sound in our modern era exists through the combination of our current understanding of instrument directivity patterns and their interaction with architectural acoustics. With the aid of wave field synthesis (WFS), newly proposed variations on orchestral layouts are tested virtually using a 64-channel WFS array. Each layout is objectively and subjectively compared for determination of which layout could optimize the sound of the orchestra and revitalize the excitement of the performance.

  5. Bound Alternative Direction Optimization for Image Deblurring

    Directory of Open Access Journals (Sweden)

    Xiangrong Zeng

    2014-01-01

    the ℓp regularizer by a novel majorizer and then, based on a variable splitting, to reformulate the bound unconstrained problem into a constrained one, which is then addressed via an augmented Lagrangian method. The proposed algorithm actually combines the reweighted ℓ1 minimization method and the alternating direction method of multiples (ADMM such that it succeeds in extending the application of ADMM to ℓp minimization problems. The conducted experimental studies demonstrate the superiority of the proposed algorithm for the synthesis ℓp minimization over the state-of-the-art algorithms for the synthesis ℓ1 minimization on image deblurring.

  6. The Generalized Direct Optimization Technique for Printed Reflectarrays

    DEFF Research Database (Denmark)

    Zhou, Min; Sørensen, Stig Busk; Kim, Oleksiy S.;

    2014-01-01

    A generalized direct optimization technique (GDOT) for the design of printed reflectarrays using arbitrarily shaped elements with irregular orientation and position is presented. The GDOT is based on the spectral domain method of moments (SDMoM) assuming local periodicity (LP) and a minimax optim...

  7. Transcranial direct current stimulation: electrode montage in stroke.

    Science.gov (United States)

    Mahmoudi, Hooman; Borhani Haghighi, Afshin; Petramfar, Peyman; Jahanshahi, Sepehr; Salehi, Zahra; Fregni, Felipe

    2011-01-01

    Neurophysiological and computer modelling studies have shown that electrode montage is a critical parameter to determine the neuromodulatory effects of transcranial direct current stimulation (tDCS). We tested these results clinically by systematically investigating optimal tDCS electrode montage in stroke. Ten patients received in a counterbalanced and randomised order the following conditions of stimulation (i) anodal stimulation of affected M1 (primary motor cortex) and cathodal stimulation of unaffected M1 ('bilateral tDCS'); (ii) anodal stimulation of affected M1 and cathodal stimulation of contralateral supraorbital area ('anodal tDCS'); (iii) cathodal stimulation of unaffected M1 and anodal stimulation of contralateral supraorbital area ('cathodal tDCS'); (iv) anodal stimulation of affected M1 and cathodal stimulation of contralateral deltoid muscle ('extra-cephalic tDCS') and (v) sham stimulation. We used the Jebsen-Taylor Test (JTT) as a widely accepted measure of upper limb function. Bilateral tDCS, anodal tDCS and cathodal tDCS were shown to be associated with significant improvements on the JTT. Placing the reference electrode in an extracephalic position and use of sham stimulation did not induce any significant effects. This small sham controlled cross-over clinical trial is important to provide additional data on the clinical effects of tDCS in stroke and for planning and designing future large tDCS trials in patients with stroke.

  8. Treatment of congenital pseudarthrosis of the tibia with direct current.

    Science.gov (United States)

    Lavine, L S; Lustrin, I; Shamos, M H

    1977-05-01

    Bone possesses a bioelectric property that is important in maintaining its structural and architectural integrity. In vivo experiments demonstrate that bone formation can be accelerated by the application of direct current. We hypothesize that bone formation occurs through an electrochemical rather than an electromechanical effect. Two cases of congenital pseudarthrosis of the tibia treated by direct current stimulation are presented. A bone graft may be added to enhance bony union in conjunction with direct current. The implications of this work are that there is need for further fundamental studies including ultrastructural observations.

  9. Eddy current testing probe optimization using a parallel genetic algorithm

    Directory of Open Access Journals (Sweden)

    Dolapchiev Ivaylo

    2008-01-01

    Full Text Available This paper uses the developed parallel version of Michalewicz's Genocop III Genetic Algorithm (GA searching technique to optimize the coil geometry of an eddy current non-destructive testing probe (ECTP. The electromagnetic field is computed using FEMM 2D finite element code. The aim of this optimization was to determine coil dimensions and positions that improve ECTP sensitivity to physical properties of the tested devices.

  10. Optimal control of stochastic magnetization dynamics by spin current

    Science.gov (United States)

    Wang, Yong; Zhang, Fu-Chun

    2013-05-01

    Fluctuation-induced stochastic magnetization dynamics plays an important role in spintronics devices. Here we propose that it can be optimally controlled by spin currents to minimize or maximize the Freidlin-Wentzell action functional of the system hence to increase or decrease the probability of the large fluctuations. We apply this method to study the thermally activated magnetization switching problem and to demonstrate the merits of the optimal control strategy.

  11. DPSS Laser Beam Quality Optimization Through Pump Current Tuning

    Energy Technology Data Exchange (ETDEWEB)

    Omohundro, Rob; /Newport Spectra-Physics, Santa Clara; Callen, Alice; /SLAC; Sukuta, Sydney; /San Jose City Coll.

    2012-03-30

    The goal of this study is to demonstrate how a DPSS laser beam's quality parameters can be simultaneously optimized through pump current tuning. Two DPSS lasers of the same make and model were used where the laser diode pump current was first varied to ascertain the lowest RMS noise region. The lowest noise was found to be 0.13% in this region and the best M{sup 2} value of 1.0 and highest laser output power were simultaneously attained at the same current point. The laser manufacturer reported a M{sup 2} value of 1.3 and RMS noise value of .14% for these lasers. This study therefore demonstrates that pump current tuning a DPSS laser can simultaneously optimize RMS Noise, Power and M{sup 2} values. Future studies will strive to broaden the scope of the beam quality parameters impacted by current tuning.

  12. Distributed Cooperative Optimal Control for Multiagent Systems on Directed Graphs: An Inverse Optimal Approach.

    Science.gov (United States)

    Zhang, Huaguang; Feng, Tao; Yang, Guang-Hong; Liang, Hongjing

    2015-07-01

    In this paper, the inverse optimal approach is employed to design distributed consensus protocols that guarantee consensus and global optimality with respect to some quadratic performance indexes for identical linear systems on a directed graph. The inverse optimal theory is developed by introducing the notion of partial stability. As a result, the necessary and sufficient conditions for inverse optimality are proposed. By means of the developed inverse optimal theory, the necessary and sufficient conditions are established for globally optimal cooperative control problems on directed graphs. Basic optimal cooperative design procedures are given based on asymptotic properties of the resulting optimal distributed consensus protocols, and the multiagent systems can reach desired consensus performance (convergence rate and damping rate) asymptotically. Finally, two examples are given to illustrate the effectiveness of the proposed methods.

  13. Transition for Optimal Paths in Bimodal Directed Polymers

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Hong

    2005-01-01

    @@ The problem for optimal paths in bimodal directed polymers is studied. It is shown that the distribution of the thermal average position of the endpoints of the optimal paths is discontinuous below the threshold p < pc. The origin is that there is a finite possibility that only one endpoint takes the global minimum energy for p < pc. Our results suggest that the percolation threshold for directed percolation is also the critical point of the transition for the possibility that the optimal paths converge to one endpoint.

  14. Differential modulation of corticospinal excitability by different current densities of anodal transcranial direct current stimulation.

    Directory of Open Access Journals (Sweden)

    Andisheh Bastani

    Full Text Available BACKGROUND: Novel non-invasive brain stimulation techniques such as transcranial direct current stimulation (tDCS have been developed in recent years. TDCS-induced corticospinal excitability changes depend on two important factors current intensity and stimulation duration. Despite clinical success with existing tDCS parameters, optimal protocols are still not entirely set. OBJECTIVE/HYPOTHESIS: The current study aimed to investigate the effects of four different anodal tDCS (a-tDCS current densities on corticospinal excitability. METHODS: Four current intensities of 0.3, 0.7, 1.4 and 2 mA resulting in current densities (CDs of 0.013, 0.029, 0.058 and 0.083 mA/cm(2 were applied on twelve right-handed (mean age 34.5±10.32 yrs healthy individuals in different sessions at least 48 hours apart. a-tDCS was applied continuously for 10 minute, with constant active and reference electrode sizes of 24 and 35 cm(2 respectively. The corticospinal excitability of the extensor carpi radialis muscle (ECR was measured before and immediately after the intervention and at 10, 20 and 30 minutes thereafter. RESULTS: Post hoc comparisons showed significant differences in corticospinal excitability changes for CDs of 0.013 mA/cm(2 and 0.029 mA/cm(2 (P = 0.003. There were no significant differences between excitability changes for the 0.013 mA/cm(2 and 0.058 mA/cm(2 (P = 0.080 or 0.013 mA/cm(2 and 0.083 mA/cm(2 (P = 0.484 conditions. CONCLUSION: This study found that a-tDCS with a current density of 0.013 mA/cm(2 induces significantly larger corticospinal excitability changes than CDs of 0.029 mA/cm(2. The implication is that might help to avoid applying unwanted amount of current to the cortical areas.

  15. Soft commutated direct current motor [summary of proposed paper

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, John S.

    1998-10-22

    A novel soft commutated direct current (DC) motor is introduced. The current of the commutated coil is intentionally drained before the brush disconnects the coil. This prevents the spark generation that normally occurs in conventional DC motors. A similar principle can be applied for DC generators.

  16. Experimental observation of direct current voltage-induced phase synchronization

    Indian Academy of Sciences (India)

    Haihong Li; Weiqing Liu; Qiongling Dai; Jinghua Xiao

    2006-09-01

    The dynamics of two uncoupled distinct Chua circuits driven by a common direct current voltage is explored experimentally. It was found that, with increasing current intensity, the dominant frequencies of these two Chua circuits will first vary at different speeds, approach an identical value for a certain current intensity and then separate. Techniques such as synchronization index and phase difference distribution were employed to analyze the phase coherence between these two Chua circuits.

  17. An optimal current observer for predictive current controlled buck DC-DC converters.

    Science.gov (United States)

    Min, Run; Chen, Chen; Zhang, Xiaodong; Zou, Xuecheng; Tong, Qiaoling; Zhang, Qiao

    2014-05-19

    In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed current may diverge due to the parasitic resistors and the forward conduction voltage of the diode. Moreover, the divergence of the observed current will cause steady state errors in the output voltage. In this paper, an optimal current observer is proposed. It achieves the highest observation accuracy by compensating for all the known parasitic parameters. By employing the optimal current observer-based predictive current controller, a buck converter is implemented. The converter has a convergently and accurately observed inductor current, and shows preferable transient response than the conventional voltage mode controlled converter. Besides, costs, power loss and size are minimized since the strategy requires no additional hardware for current sensing. The effectiveness of the proposed optimal current observer is demonstrated experimentally.

  18. Dynamic Optimization of Trajectory for Ramp-up Current Profile in Tokamak Plasmas

    CERN Document Server

    Ren, Zhigang; Ou, Yongsheng

    2016-01-01

    In this paper, we consider an open-loop, finite-time, optimal control problem of attaining a specific desired current profile during the ramp-up phase by finding the best open-loop actuator input trajectories. Average density, total power, and plasma current are used as control actuators to manipulate the profile shape in tokamak plasmas. Based on the control parameterization method, we propose a numerical solution procedure directly to solve the original PDE-constrained optimization problem using gradient-based optimization techniques such as sequential quadratic programming (SQP). This paper is aimed at proposing an effective framework for the solution of PDE-constrained optimization problem in tokamak plasmas. A more user-friendly and efficient graphical user interface (GUI) is designed in MATLAB and the numerical simulation results are verified to demonstrate its applicability. In addition, the proposed framework of combining existing PDE and numerical optimization solvers to solve PDE-constrained optimiz...

  19. Optimal linear array heading in a directional noise field

    OpenAIRE

    McDonnell, David C.

    1992-01-01

    Approved for public release; distribution is unlimited. This thesis discusses a procedure that optimizes the signal-to-noise ratio (SNR) detected by a linear array in a directional ambient noise field. The SNR can be optimized by minimizing the ambient noise detected by the array. For a given target location, each possible heading of the array centers the ambiguous beam of the array at a different true bearing. Therefore, each heading of the array will receive a different ambient noise lev...

  20. Direct current blowers with a microprocessor; Gelijkstroomventilatoren met een microprocessor

    Energy Technology Data Exchange (ETDEWEB)

    Deltenre, B. [Auerhaan, Lelystad (Netherlands)

    2000-11-01

    For mechanical ventilation of a building energy is required in order to transport fresh air to the rooms. In principle this energy is completely consumed by friction, for example in the air ducting, and therefore can not be recovered. Some manufacturers have been looking into high efficiency fans in order to save as much energy as possible. One solution has been found in the form of direct-current motors directly connected to the fan shaft.

  1. Ensemble Optimal Interpolation Data Assimilation of Surface Currents by Utilizing Monte Carlo Simulation

    Science.gov (United States)

    Hartnett, Michael; Ren, Lei

    2013-04-01

    This paper describes the application of Ensemble Optimal Interpolation (EnOI) with Monte Carlo (MC) simulation for surface currents forecasting. Environment Fluid Dynamics Codes (EFDC) is run for 7 days with initial conditions and boundary conditions. For the assimilation process, Direct Insertion (DI), Optimal Interpolation (OI) and Ensemble Optimal Interpolation (EnOI) approaches are applied from t=5.0d, and wind forcing is switched off during updating process. For Optimal Interpolation, background error covariance is estimated from the first run combining empirical correlation function, while for Ensemble Optimal Interpolation, background error covariance is calculated from the ensemble of first run, optimal number of ensemble is acquired by comparing different assimilation. Different strategies have been proposed to obtain the measurement error covariance, optimal measurement error covariance gives the least forecast error. Different kinds of pseudo measurements are produced from Monte Carlo simulation by adding different type of perturbations, which obey certain distribution. A series of experiments with distinct perturbations are carried out to show the improvement of simulating the stochastic process. Three types of reference points: inside of the assimilation area, outside of the assimilation area, and the boundary points are analyzed to show the improvement of the assimilation process and the influence after assimilation. This study also investigates the impacts of the updating interval for the assimilation process, the felicitous updating interval is chosen by comparison. To compare the improvement of operating Ensemble Optimal Interpolation with Direct Insertion and Optimal Interpolation, RMS error and data assimilation skill are calculated.

  2. Technology-based suicide prevention: current applications and future directions.

    Science.gov (United States)

    Luxton, David D; June, Jennifer D; Kinn, Julie T

    2011-01-01

    This review reports on current and emerging technologies for suicide prevention. Technology-based programs discussed include interactive educational and social networking Web sites, e-mail outreach, and programs that use mobile devices and texting. We describe innovative applications such as virtual worlds, gaming, and text analysis that are currently being developed and applied to suicide prevention and outreach programs. We also discuss the benefits and limitations of technology-based applications and discuss future directions for their use.

  3. Distributed Optimization of Multi Beam Directional Communication Networks

    Science.gov (United States)

    2017-06-30

    Distributed Optimization of Multi-Beam Directional Communication Networks Theodoros Tsiligkaridis MIT Lincoln Laboratory Lexington, MA 02141, USA...based routing. I. INTRODUCTION Missions where multiple communication goals are of in- terest are becoming more prevalent in military applications...Multilayer communications may occur within a coalition; for example, a team consisting of ground vehicles and an airborne set of assets may desire to

  4. Improved Four-Switch BLDCM Direct Current Control

    Directory of Open Access Journals (Sweden)

    Pan Lei

    2013-08-01

    Full Text Available The main purpose of this study is to describe a low cost four-switch brushless dc motor (BLDCM drive. An improved direct current controlled scheme is designed and implemented to produce the desired dynamic and static current and speed characteristics. Eight voltage vectors are summarized, which are selected to control BLDCM in SVPWM pattern. This method avoids the undesired current distortion which is caused by uncontrollable phase. The operational principle of the four-switch BLDC motor drive and the developed control scheme are theoretically analyzed and the performance is demonstrated by both simulation and experimental results.

  5. Direct calculation of current drive efficiency in FISIC code

    Energy Technology Data Exchange (ETDEWEB)

    Wright, J.C.; Phillips, C.K. [Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543-0451 (United States); Bonoli, P.T. [Plasma Fusion Center, MIT Cambridge, Massachusetts 02139 (United States)

    1996-02-01

    Two-dimensional RF modeling codes use a parameterization (1) of current drive efficiencies to calculate fast wave driven currents. This parameterization assumes a uniform quasi-linear diffusion coefficient and requires {ital a} {ital priori} knowledge of the wave polarizations. These difficulties may be avoided by a direct calculation of the quasilinear diffusion coefficient from the Kennel-Englemann form with the field polarizations calculated by the full wave code, FISIC (2). Current profiles are calculated using the adjoint formulation (3). Comparisons between the two formulations are presented. {copyright} {ital 1996 American Institute of Physics.}

  6. Direct calculation of current drive efficiency in FISIC code

    Science.gov (United States)

    Wright, J. C.; Phillips, C. K.; Bonoli, P. T.

    1996-02-01

    Two-dimensional RF modeling codes use a parameterization (1) of current drive efficiencies to calculate fast wave driven currents. This parameterization assumes a uniform quasi-linear diffusion coefficient and requires a priori knowledge of the wave polarizations. These difficulties may be avoided by a direct calculation of the quasilinear diffusion coefficient from the Kennel-Englemann form with the field polarizations calculated by the full wave code, FISIC (2). Current profiles are calculated using the adjoint formulation (3). Comparisons between the two formulations are presented.

  7. Image Filtering using All Neighbor Directional Weighted Pixels: Optimization using Particle Swarm Optimization

    CERN Document Server

    Mandal, J K

    2012-01-01

    In this paper a novel approach for de noising images corrupted by random valued impulses has been proposed. Noise suppression is done in two steps. The detection of noisy pixels is done using all neighbor directional weighted pixels (ANDWP) in the 5 x 5 window. The filtering scheme is based on minimum variance of the four directional pixels. In this approach, relatively recent category of stochastic global optimization technique i.e., particle swarm optimization (PSO) has also been used for searching the parameters of detection and filtering operators required for optimal performance. Results obtained shows better de noising and preservation of fine details for highly corrupted images.

  8. Optimal Selection of Floating Platform for Tidal Current Power Station

    Directory of Open Access Journals (Sweden)

    Fengmei Jing

    2013-06-01

    Full Text Available With continuous development of marine engineering, more and more new structures are used in the exploring of tidal current energy. Three are there different kinds of support structures for tidal current power station, which are sea-bed mounted/gravity based system, pile mounted system and floating moored platform. Comparison with them, the floating mooring system is suit for deep water and the application of which will be widely. In this study, catamaran and semi-submersible as floating platform of tidal current power station are studied. And they are compared with its economic, efficiency of turbine and stability of station. It is found that the catamaran is optimal choice. Based on basic ship theory and using software MOSES, the stability of Catamaran tidal current power station is also calculated. The research of this study is significant and it will be as the reference for the future study.

  9. Bi-directional evolutionary optimization for photonic band gap structures

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Fei [Centre for Innovative Structures and Materials, School of Civil, Environmental and Chemical Engineering, RMIT University, GPO Box 2476, Melbourne, VIC 3001 (Australia); School of Civil Engineering, Central South University, Changsha 410075 (China); Huang, Xiaodong, E-mail: huang.xiaodong@rmit.edu.au [Centre for Innovative Structures and Materials, School of Civil, Environmental and Chemical Engineering, RMIT University, GPO Box 2476, Melbourne, VIC 3001 (Australia); Key Laboratory of Advanced Technology for Vehicle Body Design & Manufacture, Hunan University, Changsha, 410082 (China); Jia, Baohua [Centre for Micro-Photonics, Faculty of Engineering & Industrial Science, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122 (Australia)

    2015-12-01

    Toward an efficient and easy-implement optimization for photonic band gap structures, this paper extends the bi-directional evolutionary structural optimization (BESO) method for maximizing photonic band gaps. Photonic crystals are assumed to be periodically composed of two dielectric materials with the different permittivity. Based on the finite element analysis and sensitivity analysis, BESO starts from a simple initial design without any band gap and gradually re-distributes dielectric materials within the unit cell so that the resulting photonic crystal possesses a maximum band gap between two specified adjacent bands. Numerical examples demonstrated the proposed optimization algorithm can successfully obtain the band gaps from the first to the tenth band for both transverse magnetic and electric polarizations. Some optimized photonic crystals exhibit novel patterns markedly different from traditional designs of photonic crystals.

  10. Cerebellar transcranial direct current stimulation effects on saccade adaptation

    NARCIS (Netherlands)

    E. Avila (Eric); J.N. van der Geest (Jos); S. Kengne Kamga (Sandra); M.C. Verhage (M. Claire); O. Donchin (Opher); M.A. Frens (Maarten)

    2015-01-01

    textabstractSaccade adaptation is a cerebellar-mediated type of motor learning in which the oculomotor system is exposed to repetitive errors. Different types of saccade adaptations are thought to involve distinct underlying cerebellar mechanisms. Transcranial direct current stimulation (tDCS) induc

  11. Transcranial direct current stimulation enhances propulsion during walking

    NARCIS (Netherlands)

    Asseldonk, van E.H.F.; Jensen, W.; Andersen, O.K.; Akay, M.

    2014-01-01

    Transcranial direct current stimulation (tDCS) has been shown to improve force generation and control in single leg joints in healthy subjects and stroke survivors. However, it is unknown whether these effects also result in improved force production and coordination during walking. Here we investig

  12. Optimization of two methods for the analysis of hydrogen peroxide: high performance liquid chromatography with fluorescence detection and high performance liquid chromatography with electrochemical detection in direct current mode.

    Science.gov (United States)

    Tarvin, Megan; McCord, Bruce; Mount, Kelly; Sherlach, Katy; Miller, Mark L

    2010-11-26

    Two complementary methods were optimized for the separation and detection of trace levels of hydrogen peroxide. The first method utilized reversed-phase high-performance liquid chromatography with fluorescence detection (HPLC-FD). With this approach, hydrogen peroxide was detected based upon its participation in the hemin-catalyzed oxidation of p-hydroxyphenylacetic acid to yield the fluorescent dimer. The second method utilized high performance liquid chromatography with electrochemical detection (HPLC-ED). With this approach, hydrogen peroxide was detected based upon its oxidation at a gold working electrode at an applied potential of 400 mV vs. hydrogen reference electrode (Pd/H(2)). Both methods were linear across the range of 15-300 μM, and the electrochemical method was linear across a wider range of 7.4-15,000 μM. The limit of detection for hydrogen peroxide was 6 μM by HPLC/FD, and 0.6 μM by HPLC/ED. A series of organic peroxides and inorganic ions were evaluated for their potential to interfere with the detection of hydrogen peroxide. Studies investigating the recovery of hydrogen peroxide with three different extraction protocols were also performed. Post-blast debris from the detonation of a mixture of concentrated hydrogen peroxide with nitromethane was analyzed on both systems. Hydrogen peroxide residues were successfully detected on this post-blast debris.

  13. Optimal encoding and decoding of a spin direction

    CERN Document Server

    Bagán, E; Brey, A; Muñoz-Tàpia, R; Tarrach, Rolf

    2001-01-01

    For a system of N spins 1/2 there are quantum states that can encode a direction in an intrinsic way. Information on this direction can later be decoded by means of a quantum measurement. We present here the optimal encoding and decoding procedure using the fidelity as a figure of merit. We compute the maximal fidelity and prove that it is directly related to the largest zeroes of the Legendre and Jacobi polynomials. We show that this maximal fidelity approaches unity quadratically in 1/N. We also discuss this result in terms of the dimension of the encoding Hilbert space.

  14. Transformer coupling for transmitting direct current through a barrier

    Science.gov (United States)

    Brown, Ralph L.; Guilford, Richard P.; Stichman, John H.

    1988-01-01

    The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level.

  15. Direct aperture optimization for IMRT using Monte Carlo generated beamlets.

    Science.gov (United States)

    Bergman, Alanah M; Bush, Karl; Milette, Marie-Pierre; Popescu, I Antoniu; Otto, Karl; Duzenli, Cheryl

    2006-10-01

    This work introduces an EGSnrc-based Monte Carlo (MC) beamlet does distribution matrix into a direct aperture optimization (DAO) algorithm for IMRT inverse planning. The technique is referred to as Monte Carlo-direct aperture optimization (MC-DAO). The goal is to assess if the combination of accurate Monte Carlo tissue inhomogeneity modeling and DAO inverse planning will improve the dose accuracy and treatment efficiency for treatment planning. Several authors have shown that the presence of small fields and/or inhomogeneous materials in IMRT treatment fields can cause dose calculation errors for algorithms that are unable to accurately model electronic disequilibrium. This issue may also affect the IMRT optimization process because the dose calculation algorithm may not properly model difficult geometries such as targets close to low-density regions (lung, air etc.). A clinical linear accelerator head is simulated using BEAMnrc (NRC, Canada). A novel in-house algorithm subdivides the resulting phase space into 2.5 X 5.0 mm2 beamlets. Each beamlet is projected onto a patient-specific phantom. The beamlet dose contribution to each voxel in a structure-of-interest is calculated using DOSXYZnrc. The multileaf collimator (MLC) leaf positions are linked to the location of the beamlet does distributions. The MLC shapes are optimized using direct aperture optimization (DAO). A final Monte Carlo calculation with MLC modeling is used to compute the final dose distribution. Monte Carlo simulation can generate accurate beamlet dose distributions for traditionally difficult-to-calculate geometries, particularly for small fields crossing regions of tissue inhomogeneity. The introduction of DAO results in an additional improvement by increasing the treatment delivery efficiency. For the examples presented in this paper the reduction in the total number of monitor units to deliver is approximately 33% compared to fluence-based optimization methods.

  16. Direct current hybrid breakers: A design and its realization

    Science.gov (United States)

    Atmadji, Ali Mahfudz Surya

    2000-12-01

    The use of semiconductors for electric power circuit breakers instead of conventional breakers remains a utopia when designing fault current interrupters for high power networks. The major problems concerning power semiconductor circuit breakers are the excessive heat losses and their sensitivity to transients. However, conventional breakers are capable of dealing with such matters. A combination of the two methods, or so-called `hybrid breakers', would appear to be a solution; however, hybrid breakers use separate parallel branches for conducting the main current and interrupting the short-circuit current. Such breakers are intended for protecting direct current (DC) traction systems. In this thesis hybrid switching techniques for current limitation and purely solidstate current interruption are investigated for DC breakers. This work analyzes the transient behavior of hybrid breakers and compares their operations with conventional breakers and similar solid-state devices in DC systems. Therefore a hybrid breaker was constructed and tested in a specially designed high power test circuit. A vacuum breaker was chosen as the main breaker in the main conducting path; then a commutation path was connected across the vacuum breaker where it provided current limitation and interruption. The commutation path operated only during any current interruption and the process required additional circuits. These included a certain energy storage, overvoltage suppressor and commutation switch. So that when discharging this energy, a controlled counter-current injection could be produced. That counter-current opposed the main current in the breaker by superposition in order to create a forced current-zero. One-stage and two-stage commutation circuits have been treated extensively. This study project contains both theoretical and experimental investigations. A direct current shortcircuit source was constructed capable of delivering power equivalent to a fault. It supplied a direct

  17. Transcranial direct current stimulation as a treatment for auditory hallucinations.

    Directory of Open Access Journals (Sweden)

    Sanne eKoops

    2015-03-01

    Full Text Available Auditory hallucinations (AH are a symptom of several psychiatric disorders, such as schizophrenia. In a significant minority of patients, AH are resistant to antipsychotic medication. Alternative treatment options for this medication-resistant group are scarce and most of them focus on coping with the hallucinations. Finding an alternative treatment that can diminish AH is of great importance.Transcranial direct current stimulation (tDCS is a safe and non-invasive technique that is able to directly influence cortical excitability through the application of very low electric currents. A 1-2 mA direct current is applied between two surface electrodes, one serving as the anode and the other as the cathode. Cortical excitability is increased in the vicinity of the anode and reduced near the cathode. The technique, which has only a few transient side effects and is cheap and portable, is increasingly explored as a treatment for neurological and psychiatric symptoms. It has shown efficacy on symptoms of depression, bipolar disorder, schizophrenia, Alzheimer’s disease, Parkinson’s disease, epilepsy and stroke. However, the application of tDCS as a treatment for AH is relatively new. This article provides an overview of the current knowledge in this field and provides guidelines for future research.

  18. Direct numerical simulation of double-diffusive gravity currents

    Science.gov (United States)

    Penney, Jared; Stastna, Marek

    2016-08-01

    This paper presents three-dimensional direct numerical simulations of laboratory-scale double-diffusive gravity currents. Flow is governed by the incompressible Navier-Stokes equations under the Boussinesq approximation, with salinity and temperature coupled to the equations of motion using a nonlinear approximation to the UNESCO equation of state. The effects of vertical boundary conditions and current volume are examined, with focus on flow pattern development, current propagation speed, three-dimensionalization, dissipation, and stirring and mixing. It was observed that no-slip boundaries cause the gravity current head to take the standard lobe-and-cleft shape and encourage both a greater degree and an earlier onset of three-dimensionalization when compared to what occurs in the case of a free-slip boundary. Additionally, numerical simulations with no-slip boundary conditions experience greater viscous dissipation, stirring, and mixing when compared to similar configurations using free-slip conditions.

  19. Direct current electrical stimulation chamber for treating cells in vitro.

    Science.gov (United States)

    Mobini, Sahba; Leppik, Liudmila; Barker, John H

    2016-02-01

    Electrical stimulation has been shown to promote healing and regeneration in skin, bone, muscle, and nerve tissues in clinical studies. Recently, studies applying electrical stimulation to influence cell behavior associated with proliferation, differentiation, and migration have provided a better understanding of the underlying mechanisms of electrical stimulation-based clinical treatments and improved tissue-engineered products through electro-bioreactor technologies. Here, we present a novel device for delivering direct current (DC) electrical stimulation (ES) to cultivated cells in vitro. Our simplified electro-bioreactor is customized for applying DC electrical current simultaneously in six individual tissue culture wells. The design overcomes previous experimental replicate limitations, thus reducing experimental time and cost.

  20. Direction for optimization of the training process in junior hockey

    Directory of Open Access Journals (Sweden)

    Kygaevskiy S.A.

    2014-02-01

    Full Text Available Purpose: to consider the possible directions of optimization of training activity in youth hockey and offer practical advice. Material : study analyzed data from the literature and the latest achievements in the practice of training the player’s domestic and foreign authors on training in youth sports. Results : innovative approaches are considered in the initial stages of training sports perfection, as well as various areas of optimization of the training process in the initial stages of hockey and preliminary basic training. The examples of the training process in the North American and European hockey schools. The questions concerning the construction and orientation of training process at the initial stages and pre- basic training. Conclusions : highlighted promising areas for optimization of the training process of young hockey players in the initial stages of sports perfection.

  1. Optimizing the Pulsed Current Gas Tungsten Arc Welding Parameters

    Institute of Scientific and Technical Information of China (English)

    M. Balasubramanian; V. Jayabalan; V. Balasubramanian

    2006-01-01

    The selection of process parameter in the gas tungsten arc (GTA) welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy (Ti-6Al-4V) is one of the most important non-ferrous metals which offers great potential application in aerospace, biomedical and chemical industries,because of its low density (4.5 g/cm3), excellent corrosion resistance, high strength, attractive fracture behaviour and high melting point (1678℃). The preferred welding process for titanium alloy is frequent GTA welding due to its comparatively easier applicability and better economy. In the case of single pass (GTA)welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. Many considerations come into the picture and one needs to carefully balance various pulse current parameters to reach an optimum combination. Four factors, five level, central composite, rotatable design matrix were used to optimize the required number of experimental conditions. Mathematical models were developed to predict the fusion zone grain size using analysis of variance (ANOVA) and regression analysis. The developed models were optimized using the traditional Hooke and Jeeve's algorithm. Experimental results were provided to illustrate the proposed approach.

  2. Science and cycling: current knowledge and future directions for research.

    Science.gov (United States)

    Atkinson, Greg; Davison, Richard; Jeukendrup, Asker; Passfield, Louis

    2003-09-01

    In this holistic review of cycling science, the objectives are: (1) to identify the various human and environmental factors that influence cycling power output and velocity; (2) to discuss, with the aid of a schematic model, the often complex interrelationships between these factors; and (3) to suggest future directions for research to help clarify how cycling performance can be optimized, given different race disciplines, environments and riders. Most successful cyclists, irrespective of the race discipline, have a high maximal aerobic power output measured from an incremental test, and an ability to work at relatively high power outputs for long periods. The relationship between these characteristics and inherent physiological factors such as muscle capilliarization and muscle fibre type is complicated by inter-individual differences in selecting cadence for different race conditions. More research is needed on high-class professional riders, since they probably represent the pinnacle of natural selection for, and physiological adaptation to, endurance exercise. Recent advances in mathematical modelling and bicycle-mounted strain gauges, which can measure power directly in races, are starting to help unravel the interrelationships between the various resistive forces on the bicycle (e.g. air and rolling resistance, gravity). Interventions on rider position to optimize aerodynamics should also consider the impact on power output of the rider. All-terrain bicycle (ATB) racing is a neglected discipline in terms of the characterization of power outputs in race conditions and the modelling of the effects of the different design of bicycle frame and components on the magnitude of resistive forces. A direct application of mathematical models of cycling velocity has been in identifying optimal pacing strategies for different race conditions. Such data should, nevertheless, be considered alongside physiological optimization of power output in a race. An even distribution

  3. Transcranial direct current stimulation as a treatment for auditory hallucinations

    OpenAIRE

    Sanne eKoops; Hilde evan den Brink; Sommer, Iris E C

    2015-01-01

    Auditory hallucinations (AH) are a symptom of several psychiatric disorders, such as schizophrenia. In a significant minority of patients, AH are resistant to antipsychotic medication. Alternative treatment options for this medication-resistant group are scarce and most of them focus on coping with the hallucinations. Finding an alternative treatment that can diminish AH is of great importance.Transcranial direct current stimulation (tDCS) is a safe and non-invasive technique that is able to...

  4. Cerebellar transcranial direct current stimulation in neurological disease

    OpenAIRE

    Ferrucci, Roberta; Bocci, Tommaso; Cortese, Francesca; Ruggiero, Fabiana; Priori, Alberto

    2016-01-01

    Several studies have highlighted the therapeutic potential of transcranial direct current stimulation (tDCS) in patients with neurological diseases, including dementia, epilepsy, post-stroke dysfunctions, movement disorders, and other pathological conditions. Because of this technique’s ability to modify cerebellar excitability without significant side effects, cerebellar tDCS is a new, interesting, and powerful tool to induce plastic modifications in the cerebellum. In this report, we review...

  5. Optimal design method for magnetization directions of a permanent magnet array

    Science.gov (United States)

    Choi, Jae Seok; Yoo, Jeonghoon

    2010-08-01

    In many magnetic systems, the permanent magnet (PM) pattern has a great influence on their performance. This study proposes a systematic optimization method for designing discrete magnetization directions. While previous works have been mostly dependent on researchers' intuition, the developed method is systematic and can be applied to a two-dimensional PM-type eddy current brake model. The effectiveness of the method is confirmed, where the design's aim is to maximize the braking force on a moving conductor. The sensitivity analysis is accomplished by the adjoint variable method and the sequential linear programming is used as an optimizer. Several optimization results for various conditions through the proposed design method are compared to each other and the optimal magnet configuration for an eddy current brake is suggested.

  6. Determinants of the electric field during transcranial direct current stimulation

    DEFF Research Database (Denmark)

    Opitz, Alexander; Paulus, Walter; Will, Susanne

    2015-01-01

    Transcranial direct current stimulation (tDCS) causes a complex spatial distribution of the electric current flow in the head which hampers the accurate localization of the stimulated brain areas. In this study we show how various anatomical features systematically shape the electric field...... over the motor cortex in small steps to examine the resulting changes of the electric field distribution in the underlying cortex. We examined the effect of skull thickness and composition on the passing currents showing that thinner skull regions lead to higher electric field strengths. This effect...... fluid and the skull, the gyral depth and the distance to the anode and cathode. These factors account for up to 50% of the spatial variation of the electric field strength. Further, we demonstrate that individual anatomical factors can lead to stimulation "hotspots" which are partly resistant...

  7. Optimization of high-temperature superconductor current leads

    Science.gov (United States)

    Seol, S. Y.; Hull, J. R.; Chyu, M. C.

    Methods to improve the performance of high-temperature superconducting current leads are analyzed. Designs are considered that are inherently safe from burnup, even if the lead enters the normal state. The effect of a tapered lead that takes advantage of the increase in critical current density with decreasing temperature will decrease helium boiloff by about a factor of two for an area ratio of four. A new concept, in which Ag powder is distributed in increasing concentration from the cold end to the hot end of the lead in sintered YBCO, is shown to have comparable performance to that of leads made with Ag-alloy sheaths. Performance of the best inherently safe designs is about one order of magnitude better than that of optimized nonsuperconducting leads. BSCCO leads with Ag-alloy sheaths show improved performance for Au fractions up to about 3%, after which increases in Au fraction yield negligible performance improvement.

  8. Optimal adaptation to extreme rainfalls in current and future climate

    Science.gov (United States)

    Rosbjerg, Dan

    2017-01-01

    More intense and frequent rainfalls have increased the number of urban flooding events in recent years, prompting adaptation efforts. Economic optimization is considered an efficient tool to decide on the design level for adaptation. The costs associated with a flooding to the T-year level and the annual capital and operational costs of adapting to this level are described with log-linear relations. The total flooding costs are developed as the expected annual damage of flooding above the T-year level plus the annual capital and operational costs for ensuring no flooding below the T-year level. The value of the return period T that corresponds to the minimum of the sum of these costs will then be the optimal adaptation level. The change in climate, however, is expected to continue in the next century, which calls for expansion of the above model. The change can be expressed in terms of a climate factor (the ratio between the future and the current design level) which is assumed to increase in time. This implies increasing costs of flooding in the future for many places in the world. The optimal adaptation level is found for immediate as well as for delayed adaptation. In these cases, the optimum is determined by considering the net present value of the incurred costs during a sufficiently long time-span. Immediate as well as delayed adaptation is considered.

  9. Optimal Function Computation in Directed and Undirected Graphs

    CERN Document Server

    Kowshik, Hemant

    2011-01-01

    We consider the problem of information aggregation in sensor networks, where one is interested in computing a function of the sensor measurements. We allow for block processing and study in-network function computation in directed graphs and undirected graphs. We study how the structure of the function affects the encoding strategies, and the effect of interactive information exchange. We begin by considering a directed graph G = (V, E) on the sensor nodes, where the goal is to determine the optimal encoders on each edge which achieve function computation at the collector node. Our goal is to characterize the rate region in R^{|E|}, i.e., the set of points for which there exist feasible encoders with given rates which achieve zero-error computation for asymptotically large block length. We determine the solution for directed trees, specifying the optimal encoder and decoder for each edge. For general directed acyclic graphs, we provide an outer bound on the rate region by finding the disambiguation requiremen...

  10. Transport critical current of MgB2 wires: pulsed current of varying rate compared to direct current method

    Science.gov (United States)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2011-10-01

    The measurement of transport critical current (Ic) for MgB2 wires and tapes has been investigated with two different techniques, the conventional four-probe arrangement with direct current (DC) power source, and a tailored triangle pulse at different rates of current change. The DC method has been widely used and practiced by various groups, but suffers from inevitable heating effects when high currents are used at low magnetic fields. The pulsed current method has no heating effects, but the critical current can depend on the rate of the current change (dI/dt) in the pulse. Our pulsed current measurements with varying dI/dt show that the same values of Ic are obtained as with the DC method, but without the artifacts of heating. Our method is particularly useful at low field regions which are often inaccessible by DC methods. We also performed a finite element method (FEM) analysis to obtain the time dependent heat distribution in MgB2 due to the electric potential produced at the current contacts to the superconducting sample and its gradient around the contacts. This gradient is defined as the current transfer length (CTL) of the samples and leads to Joule heating of the wire near the contacts. The FEM results provide further evidence of the limitation of the DC method in obtaining high transport critical current.

  11. Direct current stimulation : new approach to enhancing heavy oil production

    Energy Technology Data Exchange (ETDEWEB)

    Whittle, J.K. [Electro-Petroleum Inc., Wayne, PA (United States); Hill, D.G. [Southern California Univ., Los Angeles, CA (United States)

    2006-07-01

    The limited recovery of heavy crude oil can be attributed to the high viscosity of the liquids in the oil reservoirs. A viable technology has been lacking for the economic recovery of heavy oil. This paper discussed the advantages of direct current electrical stimulation or electro-enhanced oil recovery (EEOR). The paper outlined the advantages, including data produced from field demonstrations as well as the results of recent laboratory studies. The paper provided a historical and electro-chemical background of EEOR. Field operations that were discussed included electric field maps and a comparison of direct current versus alternating current electrical power. A series of EEOR field demonstrations were presented for the Santa Maria basin in California and the eastern Alberta plains. The paper also discussed produced fluid chemical changes and electro-osmosis and effective permeability. Last, the paper provided a comparison of EEOR to other existing and emerging technologies including steam flood; surfactant flood; co-solvent flood; carbon dioxide flood; and fire flood. It was concluded that the biggest EEOR limitation is its limited field application portfolio. EEOR has produced encouraging field demonstrations to date and has facilitated beneficial chemical changes in the produced fluids. 26 refs., 5 tabs., 10 figs.

  12. Fluid-dynamic design optimization of hydraulic proportional directional valves

    Science.gov (United States)

    Amirante, Riccardo; Catalano, Luciano Andrea; Poloni, Carlo; Tamburrano, Paolo

    2014-10-01

    This article proposes an effective methodology for the fluid-dynamic design optimization of the sliding spool of a hydraulic proportional directional valve: the goal is the minimization of the flow force at a prescribed flow rate, so as to reduce the required opening force while keeping the operation features unchanged. A full three-dimensional model of the flow field within the valve is employed to accurately predict the flow force acting on the spool. A theoretical analysis, based on both the axial momentum equation and flow simulations, is conducted to define the design parameters, which need to be properly selected in order to reduce the flow force without significantly affecting the flow rate. A genetic algorithm, coupled with a computational fluid dynamics flow solver, is employed to minimize the flow force acting on the valve spool at the maximum opening. A comparison with a typical single-objective optimization algorithm is performed to evaluate performance and effectiveness of the employed genetic algorithm. The optimized spool develops a maximum flow force which is smaller than that produced by the commercially available valve, mainly due to some major modifications occurring in the discharge section. Reducing the flow force and thus the electromagnetic force exerted by the solenoid actuators allows the operational range of direct (single-stage) driven valves to be enlarged.

  13. Borehole Radar Evaluation Program: Antenna designs for optimal directionality

    Science.gov (United States)

    Castle, J. G.; Morris, H. E.

    1991-05-01

    The thrust of this progress report deals with the significant advances we have made in the past few months toward optimal radiating efficiency and optimal directionality from antenna arrays that fit inside a 5.5 in.-OD tool. The reasons spawning this development effort on antennas are the many uses for underground radar systems that can be built around such high-performance antennas. Targets of interest include large man-made voids, natural voids in strata, fractures zones in hard rock, edges and internal faults in salts domes and glaciers, etc. Recent progress includes observation of the radiation patterns of several dipole arrays which we designed to fit within a 5.5-inch OD borehole tool and to radiate efficiently at wavelengths in the band from 0.4 meter to 2 meters with optimal directionality. Front-to-back ratios of 15 dB are consistently observed in the horizontal plane of these arrays. These antennas are observed to radiate with high efficiencies, less than 1 dB loss, into air at 1.3 meter wavelength.

  14. Borehole Radar Evaluation Program: Antenna designs for optimal directionality

    Energy Technology Data Exchange (ETDEWEB)

    Castle, J.G.; Morris, H.E.

    1991-05-01

    The thrust of this progress report deals with the significant advances we have made in the past few months toward optimal radiating efficiency and optimal directionality from antenna arrays that fit inside a 5.5 in.-OD tool. The reasons spawning this development effort on antennas are the many uses for underground radar systems that can be built around such high-performance antennas. Targets of interest include large man-made voids, natural voids in strata, fractures zones in hard rock, edges and internal faults in salts domes and glaciers, etc. Recent progress includes observation of the radiation patterns of several dipole arrays which we designed to fit within a 5.5-inch OD borehole tool and to radiate efficiently at wavelengths in the band from 0.4 meter to 2 meters with optimal directionality. Front-to-back ratios of 15 dB are consistently observed in the horizontal plane of these arrays. These antennas are observed to radiate with high efficiencies, less than 1 dB loss, into air at 1.3 meter wavelength. 18 figs.

  15. Transcranial direct current stimulation (tDCS) - application in neuropsychology.

    Science.gov (United States)

    Shin, Yong-Il; Foerster, Águida; Nitsche, Michael A

    2015-03-01

    Non-invasive brain stimulation is a versatile tool to modulate psychological processes via alterations of brain activity, and excitability. It is applied to explore the physiological basis of cognition and behavior, as well as to reduce clinical symptoms in neurological and psychiatric diseases. Neuromodulatory brain stimulation via transcranial direct currents (tDCS) has gained increased attention recently. In this review we will describe physiological mechanisms of action of tDCS, and summarize its application to modulate psychological processes in healthy humans and neuropsychiatric diseases. Furthermore, beyond giving an overview of the state of the art of tDCS, including limitations, we will outline future directions of research in this relatively young scientific field.

  16. Computer-Aided Design of a Direct Current Electromagnet

    Directory of Open Access Journals (Sweden)

    Iancu Tătucu

    2009-10-01

    Full Text Available The paper presents the mathematical model and the simulation of a direct current electromagnet used for the transport of the steel ingots. For the simulation of any device one must dispose of a mathematical model, able to describe as accurately as possible the phenomena that take place. As the processes occurred in the case of an electromagnet are of an electromagnetic nature, one used the model of the electromagnetic potentials, and the simulation was performed with the help of the specialised software ANSYS.

  17. CT myocardial perfusion imaging: current status and future directions.

    Science.gov (United States)

    Williams, M C; Newby, D E

    2016-08-01

    Computed tomography (CT) imaging of the heart has advanced rapidly, and it is now possible to perform a comprehensive assessment at a low radiation dose. CT myocardial perfusion imaging can provide additive information to CT coronary angiography, and is particularly useful in patients with heavily calcified coronary arteries or coronary artery stents. A number of protocols are now available for CT myocardial perfusion including static, dynamic, and dual-energy techniques. This review will discuss the current status of CT myocardial perfusion imaging, its clinical application, and future directions for this technology.

  18. Animal models of transcranial direct current stimulation: Methods and mechanisms.

    Science.gov (United States)

    Jackson, Mark P; Rahman, Asif; Lafon, Belen; Kronberg, Gregory; Ling, Doris; Parra, Lucas C; Bikson, Marom

    2016-11-01

    The objective of this review is to summarize the contribution of animal research using direct current stimulation (DCS) to our understanding of the physiological effects of transcranial direct current stimulation (tDCS). We comprehensively address experimental methodology in animal studies, broadly classified as: (1) transcranial stimulation; (2) direct cortical stimulation in vivo and (3) in vitro models. In each case advantages and disadvantages for translational research are discussed including dose translation and the overarching "quasi-uniform" assumption, which underpins translational relevance in all animal models of tDCS. Terminology such as anode, cathode, inward current, outward current, current density, electric field, and uniform are defined. Though we put key animal experiments spanning decades in perspective, our goal is not simply an exhaustive cataloging of relevant animal studies, but rather to put them in context of ongoing efforts to improve tDCS. Cellular targets, including excitatory neuronal somas, dendrites, axons, interneurons, glial cells, and endothelial cells are considered. We emphasize neurons are always depolarized and hyperpolarized such that effects of DCS on neuronal excitability can only be evaluated within subcellular regions of the neuron. Findings from animal studies on the effects of DCS on plasticity (LTP/LTD) and network oscillations are reviewed extensively. Any endogenous phenomena dependent on membrane potential changes are, in theory, susceptible to modulation by DCS. The relevance of morphological changes (galvanotropy) to tDCS is also considered, as we suggest microscopic migration of axon terminals or dendritic spines may be relevant during tDCS. A majority of clinical studies using tDCS employ a simplistic dose strategy where excitability is singularly increased or decreased under the anode and cathode, respectively. We discuss how this strategy, itself based on classic animal studies, cannot account for the

  19. STATOR FLUX OPTIMIZATION ON DIRECT TORQUE CONTROL WITH FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Fatih Korkmaz

    2012-07-01

    Full Text Available The Direct Torque Control (DTC is well known as an effective control technique for high performance drives in a wide variety of industrial applications and conventional DTC technique uses two constant reference value: torque and stator flux. In this paper, fuzzy logic based stator flux optimization technique for DTC drives that has been proposed. The proposed fuzzy logic based stator flux optimizer self-regulates the stator flux reference using induction motor load situation without need of any motor parameters. Simulation studies have been carried out with Matlab/Simulink to compare the proposed system behaviors at vary load conditions. Simulation results show that the performance of the proposed DTC technique has been improved and especially at low-load conditions torque ripple are greatly reduced with respect to the conventional DTC.

  20. Individually Directional Evolutionary Algorithm for Solving Global Optimization Problems-Comparative Study

    Directory of Open Access Journals (Sweden)

    Łukasz Kubuś

    2015-08-01

    Full Text Available Limited applicability of classical optimization methods influence the popularization of stochastic optimization techniques such as evolutionary algorithms (EAs. EAs are a class of probabilistic optimization techniques inspired by natural evolution process, witch belong to methods of Computational Intelligence (CI. EAs are based on concepts of natural selection and natural genetics. The basic principle of EA is searching optimal solution by processing population of individuals. This paper presents the results of simulation analysis of global optimization of benchmark function by Individually Directional Evolutionary Algorithm (IDEA and other EAs such as Real Coded Genetic Algorithm (RCGA, elite RCGA with the one elite individual, elite RCGA with the number of elite individuals equal to population size. IDEA is a newly developed algorithm for global optimization. Main principle of IDEA is to monitor and direct the evolution of selected individuals of population to explore promising areas in the search space. The idea of IDEA is an independent evolution of individuals in current population. This process is focused on indicating correct direction of changes in the elements of solution vector. This paper presents a flowchart, selection method and genetic operators used in IDEA. Moreover, similar mechanisms and genetic operators are also discussed.

  1. Consumer Mobile Health Apps: Current State, Barriers, and Future Directions.

    Science.gov (United States)

    Kao, Cheng-Kai; Liebovitz, David M

    2017-05-01

    This paper discusses the current state, barriers, and future directions of consumer-facing applications (apps). There are currently more than 165,000 mobile health apps publicly available in major app stores, the vast majority of which are designed for patients. The top 2 categories are wellness management and disease management apps, whereas other categories include self-diagnosis, medication reminder, and electronic patient portal apps. Apps specific to physical medicine and rehabilitation also are reviewed. These apps have the potential to provide low-cost, around-the-clock access to high-quality, evidence-based health information to end users on a global scale. However, they have not yet lived up to their potential due to multiple barriers, including lack of regulatory oversight, limited evidence-based literature, and concerns of privacy and security. The future directions may consist of improving data integration into the health care system, an interoperable app platform allowing access to electronic health record data, cloud-based personal health record across health care networks, and increasing app prescription by health care providers. For consumer mobile health apps to fully contribute value to health care delivery and chronic disease management, all stakeholders within the ecosystem must collaborate to overcome the significant barriers. Copyright © 2017 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

  2. Current Cloud Computing Review and Cost Optimization by DERSP

    Directory of Open Access Journals (Sweden)

    M. Gomathy

    2014-03-01

    Full Text Available Cloud computing promises to deliver cost saving through the “pay as you use” paradigm. The focus is on adding computing resources when needed and releasing them when the need is serviced. Since cloud computing relies on providing computing power through multiple interconnected computers, there is a paradigm shift from one large machine to a combination of multiple smaller machine instances. In this paper, we review the current cloud computing scenario and provide a set of recommendations that can be used for designing custom applications suited for cloud deployment. We also present a comparative study on the change in cost incurred while using different combinations of machine instances for running an application on cloud; and derive the case for optimal cost

  3. A conjugate gradient method with descent direction for unconstrained optimization

    Science.gov (United States)

    Yuan, Gonglin; Lu, Xiwen; Wei, Zengxin

    2009-11-01

    A modified conjugate gradient method is presented for solving unconstrained optimization problems, which possesses the following properties: (i) The sufficient descent property is satisfied without any line search; (ii) The search direction will be in a trust region automatically; (iii) The Zoutendijk condition holds for the Wolfe-Powell line search technique; (iv) This method inherits an important property of the well-known Polak-Ribière-Polyak (PRP) method: the tendency to turn towards the steepest descent direction if a small step is generated away from the solution, preventing a sequence of tiny steps from happening. The global convergence and the linearly convergent rate of the given method are established. Numerical results show that this method is interesting.

  4. Perception-based transparency optimization for direct volume rendering.

    Science.gov (United States)

    Chan, Ming-Yuen; Wu, Yingcai; Mak, Wai-Ho; Chen, Wei; Qu, Huamin

    2009-01-01

    The semi-transparent nature of direct volume rendered images is useful to depict layered structures in a volume. However, obtaining a semi-transparent result with the layers clearly revealed is difficult and may involve tedious adjustment on opacity and other rendering parameters. Furthermore, the visual quality of layers also depends on various perceptual factors. In this paper, we propose an auto-correction method for enhancing the perceived quality of the semi-transparent layers in direct volume rendered images. We introduce a suite of new measures based on psychological principles to evaluate the perceptual quality of transparent structures in the rendered images. By optimizing rendering parameters within an adaptive and intuitive user interaction process, the quality of the images is enhanced such that specific user requirements can be met. Experimental results on various datasets demonstrate the effectiveness and robustness of our method.

  5. Transcranial Direct Current Stimulation: Considerations for Research in Adolescent Depression

    Directory of Open Access Journals (Sweden)

    Jonathan C. Lee

    2017-06-01

    Full Text Available Adolescent depression is a prevalent disorder with substantial morbidity and mortality. Current treatment interventions do not target relevant pathophysiology and are frequently ineffective, thereby leading to a substantial burden for individuals, families, and society. During adolescence, the prefrontal cortex undergoes extensive structural and functional changes. Recent work suggests that frontolimbic development in depressed adolescents is delayed or aberrant. The judicious application of non-invasive brain stimulation techniques to the prefrontal cortex may present a promising opportunity for durable interventions in adolescent depression. Transcranial direct current stimulation (tDCS applies a low-intensity, continuous current that alters cortical excitability. While this modality does not elicit action potentials, it is thought to manipulate neuronal activity and neuroplasticity. Specifically, tDCS may modulate N-methyl-d-aspartate receptors and L-type voltage-gated calcium channels and effect changes through long-term potentiation or long-term depression-like mechanisms. This mini-review considers the neurobiological rationale for developing tDCS protocols in adolescent depression, reviews existing work in adult mood disorders, surveys the existing tDCS literature in adolescent populations, reviews safety studies, and discusses distinct ethical considerations in work with adolescents.

  6. Optimizing legacy molecular dynamics software with directive-based offload

    Science.gov (United States)

    Michael Brown, W.; Carrillo, Jan-Michael Y.; Gavhane, Nitin; Thakkar, Foram M.; Plimpton, Steven J.

    2015-10-01

    Directive-based programming models are one solution for exploiting many-core coprocessors to increase simulation rates in molecular dynamics. They offer the potential to reduce code complexity with offload models that can selectively target computations to run on the CPU, the coprocessor, or both. In this paper, we describe modifications to the LAMMPS molecular dynamics code to enable concurrent calculations on a CPU and coprocessor. We demonstrate that standard molecular dynamics algorithms can run efficiently on both the CPU and an x86-based coprocessor using the same subroutines. As a consequence, we demonstrate that code optimizations for the coprocessor also result in speedups on the CPU; in extreme cases up to 4.7X. We provide results for LAMMPS benchmarks and for production molecular dynamics simulations using the Stampede hybrid supercomputer with both Intel® Xeon Phi™ coprocessors and NVIDIA GPUs. The optimizations presented have increased simulation rates by over 2X for organic molecules and over 7X for liquid crystals on Stampede. The optimizations are available as part of the "Intel package" supplied with LAMMPS.

  7. Simulation studies of direct-current microdischarges for electric propulsion

    Science.gov (United States)

    Deconinck, Thomas Dominique

    The structure of direct-current microdischarges is investigated using a detailed two-dimensional multi-species continuum model. Microdischarges are direct-current discharges that operate at a relatively high pressure of about 100 Torr and geometric dimensions in the 10-100 micrometer range. Our motivation for the study of microdischarges comes from a potential application of these devices in microthrusters for small satellite propulsion. The Micro Plasma Thruster (MPT) concept consists of a direct-current microdischarge in a geometry comprising a constant area flow section followed by a diverging exit nozzle. A detailed description of the plasma dynamics inside the MPT including power deposition, ionization, coupling of the plasma phenomena with high-speed flow, and propulsion system performance is reported in this study. A two-dimensional model is developed as part of this study. The model consists of a plasma module coupled to a flow module and is solved on a hybrid unstructured mesh framework. The plasma module provides a self-consistent, multi-species, multi-temperature description of the microdischarge phenomena while the flow module provides a description of the low Reynolds number compressible flow through the system. The plasma module solves conservation equations for plasma species continuity and electron energy, and Poisson's equation for the self-consistent electric field. The flow module solves mass, bulk gas momentum and energy equations. The coupling of energy from the electrostatic field to the plasma species is modeled by the Joule heating term which appears in the electron and heavy species energy equations. Discretization of the Joule heating term on unstructured meshes requires special attention. We propose a new robust method for the numerical discretization of the Joule heating term on such meshes using a cell-centered, finite volume approach. A prototypical microhollow cathode discharge (MHCD) is studied to guide and validate the modeling

  8. Development and implementation of a rail current optimization program

    Energy Technology Data Exchange (ETDEWEB)

    King, T.L.; Dharamshi, R. [Univ. of Houston, TX (United States). Dept. of Electrical and Computer Engineering; Kim, K.; Zhang, J.; Tompkins, M.W.; Anderson, M.A.; Feng, Q. [Univ. of Illinois, Urbana, IL (United States). Dept. of Electrical and Computer Engineering

    1997-01-01

    Efforts are underway to automate the operation of a railgun hydrogen pellet injector for fusion reactor refueling. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. Consequently, the plasma armature ablates and accumulates material from the pellet and gun barrel. This increases inertial and viscous drag, lowering acceleration. A railgun model has been developed to compute the acceleration in the presence of these losses. In order to quantify these losses, the ablation coefficient, {alpha}, and drag coefficient, C{sub d}, must be determined. These coefficients are estimated based on the pellet acceleration. The sensitivity of acceleration to {alpha} and C{sub d} has been calculated using the model. Once {alpha} and C{sub d} have been determined, their values are applied to the model to compute the appropriate current pulse width. An optimization program was written in LabVIEW software to carry out this procedure. This program was then integrated into the existing code used to operate the railgun system. Preliminary results obtained after test firing the gun indicate that the program computes reasonable values for {alpha} and C{sub d} and calculates realistic pulse widths.

  9. Optimizing direct amplification of forensic commercial kits for STR determination.

    Science.gov (United States)

    Caputo, M; Bobillo, M C; Sala, A; Corach, D

    2017-04-01

    Direct DNA amplification in forensic genotyping reduces analytical time when large sample sets are being analyzed. The amplification success depends mainly upon two factors: on one hand, the PCR chemistry and, on the other, the type of solid substrate where the samples are deposited. We developed a workflow strategy aiming to optimize times and cost when starting from blood samples spotted onto diverse absorbent substrates. A set of 770 blood samples spotted onto Blood cards, Whatman(®) 3 MM paper, FTA™ Classic cards, and Whatman(®) Grade 1 was analyzed by a unified working strategy including a low-cost pre-treatment, a PCR amplification volume scale-down, and the use of the 3500 Genetic Analyzer as the analytical platform. Samples were analyzed using three different commercial multiplex STR direct amplification kits. The efficiency of the strategy was evidenced by a higher percentage of high-quality profiles obtained (over 94%), a reduced number of re-injections (average 3.2%), and a reduced amplification failure rate (lower than 5%). Average peak height ratio among different commercial kits was 0.91, and the intra-locus balance showed values ranging from 0.92 to 0.94. A comparison with previously reported results was performed demonstrating the efficiency of the proposed modifications. The protocol described herein showed high performance, producing optimal quality profiles, and being both time and cost effective. Copyright © 2017 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

  10. Improving Data Transfer Throughput with Direct Search Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Balaprakash, Prasanna; Morozov, Vitali; Kettimuthu, Rajkumar; Kumaran, Kalyan; Foster, Ian

    2016-01-01

    Improving data transfer throughput over high-speed long-distance networks has become increasingly difficult. Numerous factors such as nondeterministic congestion, dynamics of the transfer protocol, and multiuser and multitask source and destination endpoints, as well as interactions among these factors, contribute to this difficulty. A promising approach to improving throughput consists in using parallel streams at the application layer.We formulate and solve the problem of choosing the number of such streams from a mathematical optimization perspective. We propose the use of direct search methods, a class of easy-to-implement and light-weight mathematical optimization algorithms, to improve the performance of data transfers by dynamically adapting the number of parallel streams in a manner that does not require domain expertise, instrumentation, analytical models, or historic data. We apply our method to transfers performed with the GridFTP protocol, and illustrate the effectiveness of the proposed algorithm when used within Globus, a state-of-the-art data transfer tool, on productionWAN links and servers. We show that when compared to user default settings our direct search methods can achieve up to 10x performance improvement under certain conditions. We also show that our method can overcome performance degradation due to external compute and network load on source end points, a common scenario at high performance computing facilities.

  11. Optimized light-directed synthesis of aptamer microarrays.

    Science.gov (United States)

    Franssen-van Hal, Nicole L W; van der Putte, Pepijn; Hellmuth, Klaus; Matysiak, Stefan; Kretschy, Nicole; Somoza, Mark M

    2013-06-18

    Aptamer microarrays are a promising high-throughput method for ultrasensitive detection of multiple analytes, but although much is known about the optimal synthesis of oligonucleotide microarrays used in hybridization-based genomics applications, the bioaffinity interactions between aptamers and their targets is qualitatively different and requires significant changes to synthesis parameters. Focusing on streptavidin-binding DNA aptamers, we employed light-directed in situ synthesis of microarrays to analyze the effects of sequence fidelity, linker length, surface probe density, and substrate functionalization on detection sensitivity. Direct comparison with oligonucleotide hybridization experiments indicates that aptamer microarrays are significantly more sensitive to sequence fidelity and substrate functionalization and have different optimal linker length and surface probe density requirements. Whereas microarray hybridization probes generate maximum signal with multiple deletions, aptamer sequences with the same deletion rate result in a 3-fold binding signal reduction compared with the same sequences synthesized for maximized sequence fidelity. The highest hybridization signal was obtained with dT 5mer linkers, and the highest aptamer signal was obtained with dT 11mers, with shorter aptamer linkers significantly reducing the binding signal. The probe hybridization signal was found to be more sensitive to molecular crowding, whereas the aptamer probe signal does not appear to be constrained within the density of functional surface groups commonly used to synthesize microarrays.

  12. Determinants of the electric field during transcranial direct current stimulation.

    Science.gov (United States)

    Opitz, Alexander; Paulus, Walter; Will, Susanne; Antunes, Andre; Thielscher, Axel

    2015-04-01

    Transcranial direct current stimulation (tDCS) causes a complex spatial distribution of the electric current flow in the head which hampers the accurate localization of the stimulated brain areas. In this study we show how various anatomical features systematically shape the electric field distribution in the brain during tDCS. We constructed anatomically realistic finite element (FEM) models of two individual heads including conductivity anisotropy and different skull layers. We simulated a widely employed electrode montage to induce motor cortex plasticity and moved the stimulating electrode over the motor cortex in small steps to examine the resulting changes of the electric field distribution in the underlying cortex. We examined the effect of skull thickness and composition on the passing currents showing that thinner skull regions lead to higher electric field strengths. This effect is counteracted by a larger proportion of higher conducting spongy bone in thicker regions leading to a more homogenous current over the skull. Using a multiple regression model we could identify key factors that determine the field distribution to a significant extent, namely the thicknesses of the cerebrospinal fluid and the skull, the gyral depth and the distance to the anode and cathode. These factors account for up to 50% of the spatial variation of the electric field strength. Further, we demonstrate that individual anatomical factors can lead to stimulation "hotspots" which are partly resistant to electrode positioning. Our results give valuable novel insights in the biophysical foundation of tDCS and highlight the importance to account for individual anatomical factors when choosing an electrode montage. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Evaluation of microelectrode materials for direct-current electrocorticography.

    Science.gov (United States)

    Li, Chunyan; Narayan, Raj K; Wu, Pei-Ming; Rajan, Neena; Wu, Zhizhen; Mehan, Neal; Golanov, Eugene V; Ahn, Chong H; Hartings, Jed A

    2016-02-01

    Direct-current electrocorticography (DC-ECoG) allows a more complete characterization of brain states and pathologies than traditional alternating-current recordings (AC-ECoG). However, reliable recording of DC signals is challenging because of electrode polarization-induced potential drift, particularly at low frequencies and for more conducting materials. Further challenges arise as electrode size decreases, since impedance is increased and the potential drift is augmented. While microelectrodes have been investigated for AC-ECoG recordings, little work has addressed microelectrode properties for DC-signal recording. In this paper, we investigated several common microelectrode materials used in biomedical application for DC-ECoG. Five of the most common materials including gold (Au), silver/silver chloride (Ag/AgCl), platinum (Pt), Iridium oxide (IrOx), and platinum-iridium oxide (Pt/IrOx) were investigated for electrode diameters of 300 μm. The critical characteristics such as polarization impedance, AC current-induced polarization, long-term stability and low-frequency noise were studied in vitro (0.9% saline). The two most promising materials, Pt and Pt/lrOx were further investigated in vivo by recording waves of spreading depolarization, one of the most important applications for DC-ECoG in clinical and basic science research. Our experimental results indicate that IrOx-based microelectrodes, particularly with composite layers of nanostructures, are excellent in all of the common evaluation characteristics both in vitro and in vivo and are most suitable for multimodal monitoring applications. Pt electrodes suffer high current-induced polarization, but have acceptable long-term stability suitable for DC-ECoG. Major significance. The results of this study provide quantitative data on the electrical properties of microelectrodes with commonly-used materials and will be valuable for development of neural recordings inclusive of low frequencies.

  14. Evaluation of microelectrode materials for direct-current electrocorticography

    Science.gov (United States)

    Li, Chunyan; Narayan, Raj K.; Wu, Pei-Ming; Rajan, Neena; Wu, Zhizhen; Mehan, Neal; Golanov, Eugene V.; Ahn, Chong H.; Hartings, Jed A.

    2016-02-01

    Objective. Direct-current electrocorticography (DC-ECoG) allows a more complete characterization of brain states and pathologies than traditional alternating-current recordings (AC-ECoG). However, reliable recording of DC signals is challenging because of electrode polarization-induced potential drift, particularly at low frequencies and for more conducting materials. Further challenges arise as electrode size decreases, since impedance is increased and the potential drift is augmented. While microelectrodes have been investigated for AC-ECoG recordings, little work has addressed microelectrode properties for DC-signal recording. In this paper, we investigated several common microelectrode materials used in biomedical application for DC-ECoG. Approach. Five of the most common materials including gold (Au), silver/silver chloride (Ag/AgCl), platinum (Pt), Iridium oxide (IrOx), and platinum-iridium oxide (Pt/IrOx) were investigated for electrode diameters of 300 μm. The critical characteristics such as polarization impedance, AC current-induced polarization, long-term stability and low-frequency noise were studied in vitro (0.9% saline). The two most promising materials, Pt and Pt/lrOx were further investigated in vivo by recording waves of spreading depolarization, one of the most important applications for DC-ECoG in clinical and basic science research. Main results. Our experimental results indicate that IrOx-based microelectrodes, particularly with composite layers of nanostructures, are excellent in all of the common evaluation characteristics both in vitro and in vivo and are most suitable for multimodal monitoring applications. Pt electrodes suffer high current-induced polarization, but have acceptable long-term stability suitable for DC-ECoG. Major significance. The results of this study provide quantitative data on the electrical properties of microelectrodes with commonly-used materials and will be valuable for development of neural recordings inclusive of

  15. Optimizing SFR transmutation performance through direct adjoining control theory

    Science.gov (United States)

    Davis, Jeffrey C.

    2007-12-01

    We have developed the CORTANA code to optimize the transmutation performance of sodium cooled fast reactors (SFRs). We obtain the necessary conditions for optimal fuel and burnable absorber loadings using Pontryagin's maximum principle with a direct adjoining approach to explicitly account for either a flat flux or a power peaking inequality constraint providing a set of coupled system, Euler-Lagrange (E-L), and optimality equations which are iteratively solved with the method of conjugate gradients until no further improvement in the objective function is achieved. To satisfy the inequality constraints throughout the operating cycle, we have implemented a backwards diffusion theory (BDT) to establish a relationship between fuel loading and the relative assembly power distribution during the cycle and systematically eliminate the constraint violations with each conjugate gradient iteration. The CORTANA SFR optimization code uses multi-group, three-dimensional neutron diffusion theory, with a microscopic depletion scheme. We solve the system equations in a quasi-static fashion forward in time from beginning-of-cycle (BOC) to end-of-cycle (EOC), while we solve the E-L equations backwards in time from EOC to BOC, reflecting the adjoint nature of the Lagrange multipliers. A two enrichment-zone SFR problem verifies our formulation, yielding a TRU enrichment distribution nearly identical to that of the reference SFR core in the Generation IV Roadmap. Using a full heavy metal recycling mode, we coupled our optimization methodology with the REBUS-3 equilibrium cycle methodology to optimize an SFR operating as a second tier transmuter. We model the system using a three-dimensional triangular-z finite differencing scheme with full core symmetry and a time-independent 33-group microscopic cross section library. Beginning from a uniform TRU distribution, our CORTANA improves the SFR performance by reducing the maximum relative assembly power from 1.7 to 1.25, minimizes

  16. Controlled Levitation of Colloids through Direct Current Electric Fields.

    Science.gov (United States)

    Silvera Batista, Carlos A; Rezvantalab, Hossein; Larson, Ronald G; Solomon, Michael J

    2017-07-07

    We report the controlled levitation of surface-modified colloids in direct current (dc) electric fields at distances as far as 75 μm from an electrode surface. Instead of experiencing electrophoretic deposition, colloids modified through metallic deposition or the covalent bonding of poly(ethylene glycol) (PEG) undergo migration and focusing that results in levitation at these large distances. The levitation is a sensitive function of the surface chemistry and magnitude of the field, thus providing the means to achieve control over the levitation height. Experiments with particles of different surface charge show that levitation occurs only when the absolute zeta potential is below a threshold value. An electrodiffusiophoretic mechanism is proposed to explain the observed large-scale levitation.

  17. Transcranial direct current stimulation in the treatment of anorexia.

    Science.gov (United States)

    Hecht, David

    2010-06-01

    Transcranial direct current stimulation (tDCS) is a non-invasive technique for brain stimulation and it increasingly being used in the treatments of some neurological/psychiatric conditions (e.g. chronic pain, epilepsy, depression, motor rehabilitation after stroke and Parkinson's disease). With tDCS, cortical neurons excitability increases in the vicinity of the anodal electrode and suppressed near the cathodal electrode. There is evidence that anorexia is associated with hyperactivity in right-hemisphere frontal regions. tDCS, therefore has a promising potential in facilitating inter-hemispheric balance. A tDCS protocol is proposed: the anode electrode placed over the left prefrontal cortex and the cathode electrode located, either on the right homotopic region for non-SSRI-medicated anorexics, or on a non-cephalic site for SSRI-medicated anorexics. Together with nutritional supplements, psychotherapy and other treatments, tDCS have a good potential, as a complementary tool, in the treatment of anorexia.

  18. Current approaches and future directions in the treatment of leprosy

    Directory of Open Access Journals (Sweden)

    Worobec SM

    2012-08-01

    Full Text Available Sophie M WorobecDepartment of Dermatology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, USAAbstract: This review surveys current treatments and future treatment trends in leprosy from a clinical perspective. The World Health Organization provides a multidrug treatment regimen that targets the Mycobacterium leprae bacillus which causes leprosy. Several investigational drugs are available for the treatment of drug-resistant M. leprae. Future directions in leprosy treatment will focus on: the molecular signaling mechanism M. leprae uses to avoid triggering an immune response; prospective studies of the side effects experienced during multiple-drug therapy; recognition of relapse rates post-completion of designated treatments; combating multidrug resistance; vaccine development; development of new diagnostic tests; and the implications of the recent discovery of a genetically distinct leprosy-causing bacillus, Mycobacterium lepromatosis.Keywords: epidemiology, leprosy, Hansen’s disease, multidrug resistance, multidrug therapy

  19. ELECTRON TRANSPORT BEHAVIOURS IN THE NITROGEN DIRECT CURRENT GLOW DISCHARGE

    Institute of Scientific and Technical Information of China (English)

    ZHANG LIAN-ZHU; YU WEI; WANG JIU-LI; HAN LI; FU GUANG-SHENG

    2001-01-01

    A Monte Carlo simulation is presented to describe the electron transport behaviours in the nitrogen direct current glow discharge. The energy and angular distributions of the electrons at different positions of the cathode dark space are calculated; their energy and density distribution features throughout the entire discharge are discussed. The influence of molecular vibrational excitation, typical for electron-molecule collisions, has been studied and the elementary process of active species generation has been illustrated. The simulated results reveal that, in the cathode dark space, the high-energy electrons are mainly forward scattering and behave as a high-energy ‘electron beam'. The sharp increase of the number of secondary electrons plays an important role in producing active species at the interface between the cathode dark space and the negative glow region. The vibrational excitation enhances the energy loss of electrons in the negative glow region.

  20. Individualized model predicts brain current flow during transcranial direct-current stimulation treatment in responsive stroke patient.

    Science.gov (United States)

    Datta, Abhishek; Baker, Julie M; Bikson, Marom; Fridriksson, Julius

    2011-07-01

    Although numerous published reports have demonstrated the beneficial effects of transcranial direct-current stimulation (tDCS) on task performance, fundamental questions remain regarding the optimal electrode configuration on the scalp. Moreover, it is expected that lesioned brain tissue will influence current flow and should therefore be considered (and perhaps leveraged) in the design of individualized tDCS therapies for stroke. The current report demonstrates how different electrode configurations influence the flow of electrical current through brain tissue in a patient who responded positively to a tDCS treatment targeting aphasia. The patient, a 60-year-old man, sustained a left hemisphere ischemic stroke (lesion size = 87.42 mL) 64 months before his participation. In this study, we present results from the first high-resolution (1 mm(3)) model of tDCS in a brain with considerable stroke-related damage; the model was individualized for the patient who received anodal tDCS to his left frontal cortex with the reference cathode electrode placed on his right shoulder. We modeled the resulting brain current flow and also considered three additional reference electrode positions: right mastoid, right orbitofrontal cortex, and a "mirror" configuration with the anode over the undamaged right cortex. Our results demonstrate the profound effect of lesioned tissue on resulting current flow and the ability to modulate current pattern through the brain, including perilesional regions, through electrode montage design. The complexity of brain current flow modulation by detailed normal and pathologic anatomy suggest: (1) That computational models are critical for the rational interpretation and design of individualized tDCS stroke-therapy; and (2) These models must accurately reproduce head anatomy as shown here.

  1. Cytokine release assays: current practices and future directions.

    Science.gov (United States)

    Finco, D; Grimaldi, C; Fort, M; Walker, M; Kiessling, A; Wolf, B; Salcedo, T; Faggioni, R; Schneider, A; Ibraghimov, A; Scesney, S; Serna, D; Prell, R; Stebbings, R; Narayanan, P K

    2014-04-01

    As a result of the CD28 superagonist biotherapeutic monoclonal antibody (TGN 1412) "cytokine storm" incident, cytokine release assays (CRA) have become hazard identification and prospective risk assessment tools for screening novel biotherapeutics directed against targets having a potential risk for eliciting adverse pro-inflammatory clinical infusion reactions. Different laboratories may have different strategies, assay formats, and approaches to the reporting, interpretation, and use of data for either decision making or risk assessment. Additionally, many independent contract research organizations (CROs), academic and government laboratories are involved in some aspect of CRA work. As a result, while some pharmaceutical companies are providing CRA data as part of the regulatory submissions when necessary, technical and regulatory practices are still evolving to provide data predictive of cytokine release in humans and that are relevant to safety. This manuscript provides an overview of different approaches employed by the pharmaceutical industry and CROs, for the use and application of CRA based upon a survey and post survey follow up conducted by ILSI-Health and Environmental Sciences Institute (HESI) Immunotoxicology Committee CRA Working Group. Also discussed is ongoing research in the academic sector, the regulatory environment, current limitations of the assays, and future directions and recommendations for cytokine release assays.

  2. Effect-directed analysis: Current status and future challenges

    Science.gov (United States)

    Hong, Seongjin; Giesy, John P.; Lee, Jung-Suk; Lee, Jong-Hyeon; Khim, Jong Seong

    2016-09-01

    Effect-directed analysis (EDA) has become useful for identification of toxicant(s) that occur in mixtures in the environment, especially those that are causative agents of specific adverse effects. Here, we summarize and review EDA methodology including preparation of samples, biological analyses, fractionations, and instrumental analyses, highlighting key scientific advancements. A total of 63 documents since 1999 (Scopus search) including 46 research articles, 13 review papers, and 4 project descriptions, have been collected and reviewed in this study. At the early stage (1999-2010), most studies that applied EDA focused on organic extracts of freshwater and coastal contaminated sediments and wastewater. Toxic effects were often measured using cell-based bioassays ( in vitro) and the causative chemicals were identified by use of low resolution gas chromatography with mass selective detector (GCMSD). More recently (2010-present), EDA has been extended to various matrices such as biota, soil, crude oil, and suspended solids and techniques have been improved to include determination of bioavailability in vivo. In particular, methods for non-target screenings of organic chemicals in environmental samples using cutting-edge instrumentation such as time of flight-mass spectrometry (ToF-MS), Fourier transform-ion cyclotron resonance (FT-ICR), and Orbitrap mass spectrometer have been developed. This overview provides descriptions of recent improvements of EDA and suggests future research directions based on current understandings and limitations.

  3. HIV Vaccine: Recent Advances, Current Roadblocks, and Future Directions

    Directory of Open Access Journals (Sweden)

    Muni Rubens

    2015-01-01

    Full Text Available HIV/AIDS is a leading cause of mortality and morbidity worldwide. In spite of successful interventions and treatment protocols, an HIV vaccine would be the ultimate prevention and control strategy. Ever since identification of HIV/AIDS, there have been meticulous efforts for vaccine development. The specific aim of this paper is to review recent vaccine efficacy trials and associated advancements and discuss the current challenges and future directions. Recombinant DNA technologies greatly facilitated development of many viral products which were later incorporated into vectors for effective vaccines. Over the years, a number of scientific approaches have gained popularity and include the induction of neutralizing antibodies in late 1980s, induction of CD8 T cell in early 1990s, and combination approaches currently. Scientists have hypothesized that stimulation of right sequences of somatic hypermutations could induce broadly reactive neutralizing antibodies (bnAbs capable of effective neutralization and viral elimination. Studies have shown that a number of host and viral factors affect these processes. Similarly, eliciting specific CD8 T cells immune responses through DNA vaccines hold future promises. In summary, future studies should focus on the continuous fight between host immune responses and ever-evasive viral factors for effective vaccines.

  4. Investigation of in vitro bone cell adhesion and proliferation on Ti using direct current stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Bodhak, Subhadip; Bose, Susmita [W. M. Keck Biomedical Materials Research Laboratory, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920 (United States); Kinsel, William C. [Mechanical Engineering, Washington State University, Tri-Cities, WA (United States); Bandyopadhyay, Amit, E-mail: amitband@wsu.edu [W. M. Keck Biomedical Materials Research Laboratory, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920 (United States)

    2012-12-01

    Our objective was to establish an in vitro cell culture protocol to improve bone cell attachment and proliferation on Ti substrate using direct current stimulation. For this purpose, a custom made electrical stimulator was developed and a varying range of direct currents, from 5 to 25 {mu}A, was used to study the current stimulation effect on bone cells cultured on conducting Ti samples in vitro. Cell-material interaction was studied for a maximum of 5 days by culturing with human fetal osteoblast cells (hFOB). The direct current was applied in every 8 h time interval and the duration of electrical stimulation was kept constant at 15 min for all cases. In vitro results showed that direct current stimulation significantly favored bone cell attachment and proliferation in comparison to nonstimulated Ti surface. Immunochemistry and confocal microscopy results confirmed that the cell adhesion was most pronounced on 25 {mu}A direct current stimulated Ti surfaces as hFOB cells expressed higher vinculin protein with increasing amount of direct current. Furthermore, MTT assay results established that cells grew 30% higher in number under 25 {mu}A electrical stimulation as compared to nonstimulated Ti surface after 5 days of culture period. In this work we have successfully established a simple and cost effective in vitro protocol offering easy and rapid analysis of bone cell-material interaction which can be used in promotion of bone cell attachment and growth on Ti substrate using direct current electrical stimulation in an in vitro model. - Highlights: Black-Right-Pointing-Pointer D.C. stimulation was used to enhance in vitro bone cell adhesion and proliferation. Black-Right-Pointing-Pointer Cells cultured on Ti were stimulated by using a custom made electrical stimulator. Black-Right-Pointing-Pointer Optimization was performed by using a varying range of direct currents {approx} 5 to 25 {mu}A. Black-Right-Pointing-Pointer 25 {mu}A stimulation was found most beneficial

  5. The Optimal Interest Rates and the Current Interest Rate System

    Directory of Open Access Journals (Sweden)

    Ioannis N. Kallianiotis

    2014-12-01

    Full Text Available The paper discusses the current target interest rate, which is closed to zero with the new experiment of quantitative easing since 2009 and has reduced the rate of return and the income and has made the real savings rate negative. This target rate has not reduced unemployment and has not improved growth (it is not optimal, but has increased the debt of individuals and the low taxes on businesses have magnified the budget deficits and the national debt. People were borrowing the present value of their uncertain future wealth and their high debt and low income raise the risk and this high risk premium heighten the interest rate on loans, especially on credit cards. The current monetary system needs to be changed and an interest rate floor on deposits (savings and an interest rate ceiling on individuals‟ loans (borrowings is necessary to improve social welfare, fairness, and justice in our society and not to support only disintermediation (financial markets. The middle class cannot work only to pay taxes and interest on its debt (redistribution of their wealth to government and banks or worse to be in chronic unemployment. Many home owners defaulted on their loans payments and their homes are foreclosed. They will end up without property (real assets. The unconcern towards the middle class will affect negatively the entire socio-economic structure of the nation and after losing its productive power, it will start declining, as history has shown to us with so many empires that do not exist anymore. We hope the leaders (the democratic governments to improve public policies, to regulate the financial market and institutions, and to satisfy their policy ultimate objective, which is citizens‟ perfection and the nation‟s highest point of prosperity.

  6. TECHNIQUES ABOUT DIRECT OPTIMIZING CONTROL OF GREEN SAND QUALITY*

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Green sand casting is still a main method in the world at present and it is very significant to develop the technology of controlling green sand quality. A new concept, from contents test to contents control, is advanced. In order to realize the new idea, a new method to on-line test active clay and moisture of green sand - double powers energizing alternately (DPEA) method is put forwards. The principle of the new method is to energize standard sand sample with AC and DC powers and to test the electric parameters, and then, to calculate active clay and moisture of green sand by using artificial neural network (ANN). Based on this new method, a direct optimizing system for controlling green sand quality is developed. Techniques about testing and controlling methods, hardware and software are discussed.

  7. Optimizing direct intense-field laser acceleration of ions

    Energy Technology Data Exchange (ETDEWEB)

    Harman, Zoltan [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); ExtreMe Matter Institute EMMI, Planckstrasse 1, D-64291 Darmstadt (Germany); Salamin, Yousef I. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Department of Physics, American University of Sharjah, POB 26666, Sharjah (United Arab Emirates); Galow, Benjamin J.; Keitel, Christoph H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

    2011-11-15

    The dynamics of ion acceleration in tightly focused laser beams is investigated in relativistic simulations. Studies are performed to find the optimal parameters which maximize the energy gain, beam quality, and flux. The exit ionic kinetic energy and its uncertainty are improved and the number of accelerated particles is increased by orders of magnitude over our earlier results, especially when working with a longer laser wavelength. Laser beams of powers of 0.1-10 petawatts and focused to subwavelength spot radii are shown to directly accelerate protons and bare nuclei of helium, carbon, and oxygen from a few to several hundred MeV/nucleon. Variation of the volume of the initial ionic ensemble, as well as the introduction of a pulse shape on the laser fields, have been investigated and are shown to influence the exit particle kinetic energies only slightly.

  8. Direct-current-like Phase Space Manipulation Using Chirped Alternating Current Fields

    Energy Technology Data Exchange (ETDEWEB)

    P.F. Schmit and N.J. Fisch

    2010-02-01

    Waves in plasmas can accelerate particles that are resonant with the wave. A dc electric field also accelerates particles, but without a resonance discrimination, which makes the acceleration mechanism profoundly different. Whereas wave-particle acceleration mechanisms have been widely discussed in the literature, this work discusses the direct analogy between wave acceleration and dc field acceleration in a particular parameter regime explored in previous works. Apart from the academic interest of this correspondence, there may be practical advantages in using waves to mimic dc electric fields, for example, in driving plasma current with high efficiency.

  9. Direct Electrical Current Reduces Bacterial and Yeast Biofilm Formation

    Directory of Open Access Journals (Sweden)

    Maria Ruiz-Ruigomez

    2016-01-01

    Full Text Available New strategies are needed for prevention of biofilm formation. We have previously shown that 24 hr of 2,000 µA of direct current (DC reduces Staphylococcus epidermidis biofilm formation in vitro. Herein, we examined the effect of a lower amount of DC exposure on S. epidermidis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Propionibacterium acnes, and Candida albicans biofilm formation. 12 hr of 500 µA DC decreased S. epidermidis, S. aureus, E. coli, and P. aeruginosa biofilm formation on Teflon discs by 2, 1, 1, and 2 log10 cfu/cm2, respectively (p<0.05. Reductions in S. epidermidis, S. aureus, and E. coli biofilm formation were observed with as few as 12 hr of 200 µA DC (2, 2 and 0.4 log10 cfu/cm2, resp.; a 1 log10 cfu/cm2 reduction in P. aeruginosa biofilm formation was observed at 36 hr. 24 hr of 500 µA DC decreased C. albicans biofilm formation on Teflon discs by 2 log10 cfu/cm2. No reduction in P. acnes biofilm formation was observed. 1 and 2 log10 cfu/cm2 reductions in E. coli and S. epidermidis biofilm formation on titanium discs, respectively, were observed with 12 hr of exposure to 500 µA. Electrical current is a potential strategy to reduce biofilm formation on medical biomaterials.

  10. Starship Sails Propelled by Cost-Optimized Directed Energy

    Science.gov (United States)

    Benford, J.

    Microwave and laser-propelled sails are a new class of spacecraft using photon acceleration. It is the only method of interstellar flight that has no physics issues. Laboratory demonstrations of basic features of beam-driven propulsion, flight, stability (`beam-riding'), and induced spin, have been completed in the last decade, primarily in the microwave. It offers much lower cost probes after a substantial investment in the launcher. Engineering issues are being addressed by other applications: fusion (microwave, millimeter and laser sources) and astronomy (large aperture antennas). There are many candidate sail materials: carbon nanotubes and microtrusses, beryllium, graphene, etc. For acceleration of a sail, what is the cost-optimum high power system? Here the cost is used to constrain design parameters to estimate system power, aperture and elements of capital and operating cost. From general relations for cost-optimal transmitter aperture and power, system cost scales with kinetic energy and inversely with sail diameter and frequency. So optimal sails will be larger, lower in mass and driven by higher frequency beams. Estimated costs include economies of scale. We present several starship point concepts. Systems based on microwave, millimeter wave and laser technologies are of equal cost at today's costs. The frequency advantage of lasers is cancelled by the high cost of both the laser and the radiating optic. Cost of interstellar sailships is very high, driven by current costs for radiation source, antennas and especially electrical power. The high speeds necessary for fast interstellar missions make the operating cost exceed the capital cost. Such sailcraft will not be flown until the cost of electrical power in space is reduced orders of magnitude below current levels.

  11. Robust fluence map optimization via alternating direction method of multipliers with empirical parameter optimization

    Science.gov (United States)

    Gao, Hao

    2016-04-01

    For the treatment planning during intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT), beam fluence maps can be first optimized via fluence map optimization (FMO) under the given dose prescriptions and constraints to conformally deliver the radiation dose to the targets while sparing the organs-at-risk, and then segmented into deliverable MLC apertures via leaf or arc sequencing algorithms. This work is to develop an efficient algorithm for FMO based on alternating direction method of multipliers (ADMM). Here we consider FMO with the least-square cost function and non-negative fluence constraints, and its solution algorithm is based on ADMM, which is efficient and simple-to-implement. In addition, an empirical method for optimizing the ADMM parameter is developed to improve the robustness of the ADMM algorithm. The ADMM based FMO solver was benchmarked with the quadratic programming method based on the interior-point (IP) method using the CORT dataset. The comparison results suggested the ADMM solver had a similar plan quality with slightly smaller total objective function value than IP. A simple-to-implement ADMM based FMO solver with empirical parameter optimization is proposed for IMRT or VMAT.

  12. Transcranial Direct Current Stimulation in Disorders of Consciousness: A Review.

    Science.gov (United States)

    Zhang, Ye; Song, Weiqun

    2017-09-18

    It is a challenge to evaluate and treat the patients with disorders of consciousness (DOC) in the clinic. Due to the huge costs of prolonged intensive care, the management of these patients raises great financial strain on families and important ethical questions. To date, several studies have attempted to specifically detect pharmacologic or non-pharmacologic effectiveness, until now there were no evidence-based guidelines about the treatment of patients with DOC. Recently, because of ethical and procedural limitations on the use of invasive stimulation techniques, non-invasive brain stimulation, such as the transcranial direct current stimulation (tDCS), has been investigated for improving the level of consciousness in patients with DOC. This paper briefly reviewed the key clinical investigations using tDCS with the aim of better understanding the pathophysiological mechanism of DOC or improving the level of consciousness in patients with DOC. In conclusion, some beneficial results of tDCS protocols have been shown in patients with DOC, especially targeting the left dorsolateral prefrontal cortex (DLPFC) in minimally conscious state (MCS). However, these investigations must be continued in larger controlled, randomized, blinded and prospective studies in order to transpose these preliminary data to clinical effects. Furthermore, an encouraging perspective for the future is the combination of neurophysiological or functional neuroimaging techniques with non-invasive brain stimulation to evaluate neuro-modulatory effects of stimulation in patients with DOC.

  13. Molecular ultrasound imaging: current status and future directions

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, N. [Department of Radiology, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, California (United States); Needles, A. [Visualsonics, Toronto (Canada); Willmann, J.K., E-mail: willmann@stanford.ed [Department of Radiology, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, California (United States)

    2010-07-15

    Targeted contrast-enhanced ultrasound (molecular ultrasound) is an emerging imaging strategy that combines ultrasound technology with novel molecularly-targeted ultrasound contrast agents for assessing biological processes at the molecular level. Molecular ultrasound contrast agents are nano- or micro-sized particles that are targeted to specific molecular markers by adding high-affinity binding ligands onto the surface of the particles. Following intravenous administration, these targeted ultrasound contrast agents accumulate at tissue sites overexpressing specific molecular markers, thereby enhancing the ultrasound imaging signal. High spatial and temporal resolution, real-time imaging, non-invasiveness, relatively low costs, lack of ionising irradiation and wide availability of ultrasound systems are advantages compared to other molecular imaging modalities. In this article we review current concepts and future directions of molecular ultrasound imaging, including different classes of molecular ultrasound contrast agents, ongoing technical developments of pre-clinical and clinical ultrasound systems, the potential of molecular ultrasound for imaging different diseases at the molecular level, and the translation of molecular ultrasound into the clinic.

  14. Improving Myoelectric Control for Amputees through Transcranial Direct Current Stimulation.

    Science.gov (United States)

    Pan, Lizhi; Zhang, Dingguo; Sheng, Xinjun; Zhu, Xiangyang

    2015-08-01

    Most prosthetic myoelectric control studies have shown good performance for unimpaired subjects. However, performance is generally unacceptable for amputees. The primary problem is the poor quality of electromyography (EMG) signals of amputees compared with healthy individuals. To improve clinical performance of myoelectric control, this study explored transcranial direct current stimulation (tDCS) to modulate brain activity and enhance EMG quality. We tested six unilateral transradial amputees by applying active and sham anodal tDCS separately on two different days. Surface EMG signals were acquired from the affected and intact sides for 11 hand and wrist motions in the pre-tDCS and post-tDCS sessions. Autoregression coefficients and linear discriminant analysis classifiers were used to process the EMG data for pattern recognition of the 11 motions. For the affected side, active anodal tDCS significantly reduced the average classification error rate (CER) by 10.1%, while sham tDCS had no such effect. For the intact side, the average CER did not change on the day of sham tDCS but increased on the day of active tDCS. These results demonstrated that tDCS could modulate brain function and improve EMG-based classification performance for amputees. It has great potential in dramatically reducing the length of learning process of amputees for effectively using myoelectrically controlled multifunctional prostheses.

  15. Transcranial direct current stimulation during sleep improves declarative memory.

    Science.gov (United States)

    Marshall, Lisa; Mölle, Matthias; Hallschmid, Manfred; Born, Jan

    2004-11-03

    In humans, weak transcranial direct current stimulation (tDCS) modulates excitability in the motor, visual, and prefrontal cortex. Periods rich in slow-wave sleep (SWS) not only facilitate the consolidation of declarative memories, but in humans, SWS is also accompanied by a pronounced endogenous transcortical DC potential shift of negative polarity over frontocortical areas. To experimentally induce widespread extracellular negative DC potentials, we applied anodal tDCS (0.26 mA) [correction] repeatedly (over 30 min) bilaterally at frontocortical electrode sites during a retention period rich in SWS. Retention of declarative memories (word pairs) and also nondeclarative memories (mirror tracing skills) learned previously was tested after this period and compared with retention performance after placebo stimulation as well as after retention intervals of wakefulness. Compared with placebo stimulation, anodal tDCS during SWS-rich sleep distinctly increased the retention of word pairs (p affect declarative memory. Procedural memory was also not affected by tDCS. Mood was improved both after tDCS during sleep and during wake intervals. tDCS increased sleep depth toward the end of the stimulation period, whereas the average power in the faster frequency bands (,alpha, and beta) was reduced. Acutely, anodal tDCS increased slow oscillatory activity sleep-dependent consolidation of declarative memories.

  16. Current frontiers and future directions of telecoupling research

    Science.gov (United States)

    Liu, J.

    2016-12-01

    The world has been increasingly interconnected over long distances though processes such as international trade, migration, telecommunication, and disease spread. However, previous studies often focused on socioeconomic or environmental issues of distant processes. While these studies have generated useful information for individual disciplines, integrating socioeconomic and environmental information is essential for holistic understanding of complex global challenges and unbiased decision making to address the challenges. To advance integrated research, the framework of telecoupling (socioeconomic and environmental interactions over distances) has been developed to explicitly address both socioeconomic and environmental issues simultaneously. Although the framework is relatively new, it has already been applied to tackle a variety of globally important issues, such as food security, water resources, energy sustainability, land use, international trade (e.g., food, forest products, energy, wildlife, industrial products), species invasion, investment, ecosystem services, conservation, information dissemination, and tourism. These applications have identified many important research gaps (e.g. spillover systems) and hidden linkages (e.g. feedbacks) among distant areas of the world with profound implications for sustainable development, ecosystem health, and human well-being. While working with telecoupling presents more challenges than focusing only on disciplinary issues, support from funding agencies has helped accelerate research on telecoupling and more efforts are being aimed at framework quantification and operationalization. The presenter will provide an overview of the current frontiers, discuss future research directions, and highlight emerging opportunities and challenges in telecoupling research and governance.

  17. Sarcoidosis: an update on current pharmacotherapy options and future directions.

    Science.gov (United States)

    Brito-Zerón, Pilar; Pérez-Alvarez, Roberto; Pallarés, Lucio; Retamozo, Soledad; Baughman, Robert P; Ramos-Casals, Manuel

    2016-12-01

    Sarcoidosis is a systemic disease of unknown etiology characterized by the development of non-caseating epitheloid granulomas. The lungs are the most commonly involved organ (>90% of cases), followed by the lymph nodes, the skin, and the eyes. Areas covered: This review summarizes current pharmacotherapy options and future directions for the development of new therapies. Glucocorticoids are the first-line therapy for sarcoidosis. For patients with the most severe forms of sarcoidosis (who will need glucocorticoids for long periods) and for those intolerant or refractory, immunosuppressive drugs are used as sparing agents. The management of extrathoracic sarcoidosis must be tailored to the specific organ or organs involved; however, there is limited data from controlled trials to guide the treatment of these patients. The emergence of biological therapies has increased the therapeutic armamentarium available to treat sarcoidosis, with monoclonal anti-TNF agents being the most promising, but their use is still limited by a lack of licensing and costs. Expert commentary: The treatment of sarcoidosis is still not totally standardized. New effective therapies are urgently needed to enable the reduction or replacement of long-term therapy with glucocorticoids in patients with sarcoidosis.

  18. Errorless and errorful learning modulated by transcranial direct current stimulation

    Directory of Open Access Journals (Sweden)

    Schmicker Marlen

    2011-07-01

    Full Text Available Abstract Background Errorless learning is advantageous over trial and error learning (errorful learning as errors are avoided during learning resulting in increased memory performance. Errorful learning challenges the executive control system of memory processes as the erroneous items compete with the correct items during retrieval. The left dorsolateral prefrontal cortex (DLPFC is a core region involved in this executive control system. Transcranial direct current stimulation (tDCS can modify the excitability of underlying brain functioning. Results In a single blinded tDCS study one group of young healthy participants received anodal and another group cathodal tDCS of the left DLPFC each compared to sham stimulation. Participants had to learn words in an errorless and an errorful manner using a word stem completion paradigm. The results showed that errorless compared to errorful learning had a profound effect on the memory performance in terms of quality. Anodal stimulation of the left DLPFC did not modulate the memory performance following errorless or errorful learning. By contrast, cathodal stimulation hampered memory performance after errorful learning compared to sham, whereas there was no modulation after errorless learning. Conclusions Concluding, the study further supports the advantages of errorless learning over errorful learning. Moreover, cathodal stimulation of the left DLPFC hampered memory performance following the conflict-inducing errorful learning as compared to no modulation after errorless learning emphasizing the importance of the left DLPFC in executive control of memory.

  19. Enhancing the mirror illusion with transcranial direct current stimulation.

    Science.gov (United States)

    Jax, Steven A; Rosa-Leyra, Diana L; Coslett, H Branch

    2015-05-01

    Visual feedback has a strong impact on upper-extremity movement production. One compelling example of this phenomena is the mirror illusion (MI), which has been used as a treatment for post-stroke movement deficits (mirror therapy). Previous research indicates that the MI increases primary motor cortex excitability, and this change in excitability is strongly correlated with the mirror's effects on behavioral performance of neurologically-intact controls. Based on evidence that primary motor cortex excitability can also be increased using transcranial direct current stimulation (tDCS), we tested whether bilateral tDCS to the primary motor cortices (anode right-cathode left and anode left-cathode right) would modify the MI. We measured the MI using a previously-developed task in which participants make reaching movements with the unseen arm behind a mirror while viewing the reflection of the other arm. When an offset in the positions of the two limbs relative to the mirror is introduced, reaching errors of the unseen arm are biased by the reflected arm's position. We found that active tDCS in the anode right-cathode left montage increased the magnitude of the MI relative to sham tDCS and anode left-cathode right tDCS. We take these data as a promising indication that tDCS could improve the effect of mirror therapy in patients with hemiparesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Transcranial Direct Current Stimulation and behavioral models of smoking addiction

    Directory of Open Access Journals (Sweden)

    Paige eFraser

    2012-08-01

    Full Text Available While few studies have applied transcranial direct current stimulation (tDCS to smoking addiction, existing work suggests that the intervention holds promise for altering the complex system by which environmental cues interact with cravings to drive behavior. Imaging and repetitive transcranial magnetic stimulation (rTMS studies suggest that increased dorsolateral prefrontal cortex (DLPFC activation and integrity may be associated with increased resistance to smoking cues. Anodal tDCS of the DLPFC, believed to boost activation, reduces cravings in response to these cues. The finding that noninvasive stimulation modifies cue induced cravings has profound implications for understanding the processes underlying addiction and relapse. TDCS can also be applied to probe mechanisms underlying and supporting nicotine addiction, as was done in a pharmacologic study that applied nicotine, tDCS, and TMS paired associative stimulation to find that stopping nicotine after chronic use induces a reduction in plasticity, causing difficulty in breaking free from association between cues and cravings. This mini-review will place studies that apply tDCS to smokers in the context of research involving the neural substrates of nicotine addiction.

  1. United States current account deficits: a stochastic optimal control analysis

    OpenAIRE

    Stein, Jerome L.

    2006-01-01

    The "Pessimists" and the "Optimists" disagree whether the US external deficits and the associated buildup of US net foreign liabilities are problems that require urgent attention. A warning signal should be that the debt ratio deviates significantly from the optimal ratio. The optimal debt ratio or debt burden should take into account the vulnerability of consumption to shocks from the productivity of capital, the interest rate and exchange rate. The optimal debt ratio is derived from inter-t...

  2. Directed migration of human bone marrow mesenchymal stem cells in a physiological direct current electric field

    Directory of Open Access Journals (Sweden)

    Z Zhao

    2011-11-01

    Full Text Available At sites of bone fracture, naturally-occurring electric fields (EFs exist during healing and may guide cell migration. In this study, we investigated whether EFs could direct the migration of bone marrow mesenchymal stem cells (BM-MSCs, which are known to be key players in bone formation. Human BM-MSCs were cultured in direct current EFs of 10 to 600 mV/mm. Using time-lapse microscopy, we demonstrated that an EF directed migration of BM-MSCs mainly to the anode. Directional migration occurred at a low threshold and with a physiological EF of ~25 mV/mm. Increasing the EF enhanced the MSC migratory response. The migration speed peaked at 300 mV/mm, at a rate of 42 ±1 µm/h, around double the control (no EF migration rate. MSCs showed sustained response to prolonged EF application in vitro up to at least 8 h. The electrotaxis of MSCs with either early (P3-P5 or late (P7-P10 passage was also investigated. Migration was passage-dependent with higher passage number showing reduced directed migration, within the range of passages examined. An EF of 200 mV/mm for 2 h did not affect cell senescence, phenotype, or osteogenic potential of MSCs, regardless of passage number within the range tested (P3-P10. Our findings indicate that EFs are a powerful cue in directing migration of human MSCs in vitro. An applied EF may be useful to control or enhance migration of MSCs during bone healing.

  3. Direct optimization of heterogeneous systems in electrical engineering; Optimisation directe de systemes heterogenes en Genie electrique

    Energy Technology Data Exchange (ETDEWEB)

    Fefermann, Y.

    2002-12-15

    Today, a global viewpoint in the design of devices called 'system approach', is imposed by couplings between physical fields and multiple interactions between sub-systems. Indeed, concerning static and electromechanical converters, or control systems, numerous issues of design are more and more mastered when each element is separately conceived. However, as soon as designing an heterogeneous system seen as a 'complex of elements in interaction' is at stake, arises the problem of the global optimization with respect to multiple criteria which characterize the quality of its behavior. The works realized in this thesis concern the multi-criteria optimization of systems by direct methods not related to the analytical calculation of the gradient. These techniques are applied to a typical electrical vehicle. We propose for each of the sub-systems a modeling adapted to the problem. In particular, an original method based on variations by similarity was elaborated for the design procedure of the PMSM machine. The parameters (DC supply voltage, geometrical parameters,...) can be fitted to all the system levels. They optimize performance criteria: minimization of the losses, of the embedded mass,... The methods of optimization used to resolve this non-linear problem are the Nelder and Mead's Simplex and Hooke and Jeeves algorithm. The constraints of the problem are treated by penalties (exact and quadratic) and a simple heuristic is proposed allowing a constraints normalization and a better algorithm convergence. The optimization results enable to underline the couplings between the various sub-systems, a significant point of the analysis. They have also shown the interest of a global approach in the design and the study of electric systems. (author)

  4. Magnetic particle imaging: current developments and future directions

    Directory of Open Access Journals (Sweden)

    Panagiotopoulos N

    2015-04-01

    of different theories and technical approaches on the way to the actual implementation of the basic concept of MPI have been seen in the last few years. Research groups around the world are working on different scanner geometries, from closed bore systems to single-sided scanners, and use reconstruction methods that are either based on actual calibration measurements or on theoretical models. This review aims at giving an overview of current developments and future directions in MPI about a decade after its first appearance. Keywords: magnetic particle imaging, superparamagnetic iron oxide nanoparticles, magnetic particle spectrometer, peripheral nerve stimulation, cardiovascular interventions

  5. Optimization of negative ion current in a compact microwave driven upper hybrid resonance multicusp plasma source.

    Science.gov (United States)

    Sahu, D; Bhattacharjee, S; Singh, M J; Bandyopadhyay, M; Chakraborty, A

    2012-02-01

    Performance of a microwave driven upper hybrid resonance multicusp plasma source as a volume negative ion source is reported. Microwaves are directly launched into the plasma chamber predominantly in the TE(11) mode. The source is operated at different discharge conditions to obtain the optimized negative H(-) ion current which is ∼33 μA (0.26 mA∕cm(2)). Particle balance equations are solved to estimate the negative ion density, which is compared with the experimental results. Future prospects of the source are discussed.

  6. Optimization of negative ion current in a compact microwave driven upper hybrid resonance multicusp plasma sourcea)

    Science.gov (United States)

    Sahu, D.; Bhattacharjee, S.; Singh, M. J.; Bandyopadhyay, M.; Chakraborty, A.

    2012-02-01

    Performance of a microwave driven upper hybrid resonance multicusp plasma source as a volume negative ion source is reported. Microwaves are directly launched into the plasma chamber predominantly in the TE11 mode. The source is operated at different discharge conditions to obtain the optimized negative H- ion current which is ˜33 μA (0.26 mA/cm2). Particle balance equations are solved to estimate the negative ion density, which is compared with the experimental results. Future prospects of the source are discussed.

  7. Direction- and Salt-Dependent Ionic Current Signatures for DNA Sensing with Asymmetric Nanopores.

    Science.gov (United States)

    Chen, Kaikai; Bell, Nicholas A W; Kong, Jinglin; Tian, Yu; Keyser, Ulrich F

    2017-02-28

    Solid-state nanopores are promising tools for single-molecule detection of both DNA and proteins. In this study, we investigated the patterns of ionic current blockades as DNA translocates into or out of the geometric confinement of conically shaped pores across a wide range of salt conditions. We studied how the geometry of a nanopore affects the detected ionic current signal of a translocating DNA molecule over a wide range of salt concentration. The blockade level in the ionic current depends on the translocation direction at a high salt concentration, and at lower salt concentrations we find a nonintuitive ionic current decrease and increase within each single event for the DNA translocations exiting from confinement. We use a recently developed method for synthesizing DNA molecules with multiple position markers, which provides further experimental characterization by matching the position of the DNA in the pore with the observed ionic current signal. Finally, we employ finite element calculations to explain the shapes of the signals observed at all salt concentrations and show that the unexpected current decrease and increase are due to the competing effects of ion concentration polarization and geometric exclusion of ions. Our analysis shows that over a wide range of geometries, voltages, and salt concentrations, we are able to understand the ionic current signals of DNA in asymmetric nanopores, enabling signal optimization in molecular sensing applications.

  8. Physicochemical Properties of Biopolymer Hydrogels Treated by Direct Electric Current

    Directory of Open Access Journals (Sweden)

    Żaneta Król

    2016-07-01

    Full Text Available The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%, carrageenan (1.5%; 2%; 2.5% and sodium alginate (0.75%; 1%; 1.25% hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC of 400 mA for a duration of five minutes. There were three types of gels prepared for the purpose of the study: C, control; H, gels on the basis of hydrosols that were treated with DC; and G, gels treated with DC. In the course of the study, the authors carried out the following analyses: Texture Profile Analysis (TPA, Fourier Transform Infrared spectroscopy (FTIR, Scanning Electron Microscopy (SEM and Swelling Ratio (SR. Furthermore, the color and pH of hydrogels were measured. The FTIR spectra showed that the structures of gelatine, carrageenan and sodium alginate do not significantly change upon applying DC. The results of TPA, SR, color and pH measurement indicate that hydrogels’ properties are significantly dependent on the type of polymer, its concentration and the type of the gel. By changing those parameters, the characteristics of such gels can be additionally tuned, which extends their applicability, e.g., in the food industry. Moreover, the analysis revealed that SR of H gel gelatine after 72 h of storage was 1.84-times higher than SR of the control sample, which indicated that this gel may be considered as a possible component for wound dressing materials.

  9. Transcutaneous spinal direct current stimulation modulates human corticospinal system excitability.

    Science.gov (United States)

    Bocci, Tommaso; Marceglia, Sara; Vergari, Maurizio; Cognetto, Valeria; Cogiamanian, Filippo; Sartucci, Ferdinando; Priori, Alberto

    2015-07-01

    This study aimed to assess the effects of thoracic anodal and cathodal transcutaneous spinal direct current stimulation (tsDCS) on upper and lower limb corticospinal excitability. Although there have been studies assessing how thoracic tsDCS influences the spinal ascending tract and reflexes, none has assessed the effects of this technique over upper and lower limb corticomotor neuronal connections. In 14 healthy subjects we recorded motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) from abductor hallucis (AH) and hand abductor digiti minimi (ADM) muscles before (baseline) and at different time points (0 and 30 min) after anodal or cathodal tsDCS (2.5 mA, 20 min, T9-T11 level). In 8 of the 14 subjects we also tested the soleus H reflex and the F waves from AH and ADM before and after tsDCS. Both anodal and cathodal tsDCS left the upper limb MEPs and F wave unchanged. Conversely, while leaving lower limb H reflex unchanged, they oppositely affected lower limb MEPs: whereas anodal tsDCS increased resting motor threshold [(mean ± SE) 107.33 ± 3.3% increase immediately after tsDCS and 108.37 ± 3.2% increase 30 min after tsDCS compared with baseline] and had no effects on MEP area and latency, cathodal tsDCS increased MEP area (139.71 ± 12.9% increase immediately after tsDCS and 132.74 ± 22.0% increase 30 min after tsDCS compared with baseline) without affecting resting motor threshold and MEP latency. Our results show that tsDCS induces polarity-specific changes in corticospinal excitability that last for >30 min after tsDCS offset and selectively affect responses in lower limb muscles innervated by lumbar and sacral motor neurons.

  10. Cerebellar Transcranial Direct Current Stimulation (ctDCS)

    Science.gov (United States)

    Grimaldi, Giuliana; Argyropoulos, Georgios P.; Bastian, Amy; Cortes, Mar; Davis, Nicholas J.; Edwards, Dylan J.; Ferrucci, Roberta; Fregni, Felipe; Galea, Joseph M.; Hamada, Masahi; Manto, Mario; Miall, R. Chris; Morales-Quezada, Leon; Pope, Paul A.; Priori, Alberto; Rothwell, John; Tomlinson, S. Paul; Celnik, Pablo

    2016-01-01

    The cerebellum is critical for both motor and cognitive control. Dysfunction of the cerebellum is a component of multiple neurological disorders. In recent years, interventions have been developed that aim to excite or inhibit the activity and function of the human cerebellum. Transcranial direct current stimulation of the cerebellum (ctDCS) promises to be a powerful tool for the modulation of cerebellar excitability. This technique has gained popularity in recent years as it can be used to investigate human cerebellar function, is easily delivered, is well tolerated, and has not shown serious adverse effects. Importantly, the ability of ctDCS to modify behavior makes it an interesting approach with a potential therapeutic role for neurological patients. Through both electrical and non-electrical effects (vascular, metabolic) ctDCS is thought to modify the activity of the cerebellum and alter the output from cerebellar nuclei. Physiological studies have shown a polarity-specific effect on the modulation of cerebellar–motor cortex connectivity, likely via cerebellar–thalamocortical pathways. Modeling studies that have assessed commonly used electrode montages have shown that the ctDCS-generated electric field reaches the human cerebellum with little diffusion to neighboring structures. The posterior and inferior parts of the cerebellum (i.e., lobules VI-VIII) seem particularly susceptible to modulation by ctDCS. Numerous studies have shown to date that ctDCS can modulate motor learning, and affect cognitive and emotional processes. Importantly, this intervention has a good safety profile; similar to when applied over cerebral areas. Thus, investigations have begun exploring ctDCS as a viable intervention for patients with neurological conditions. PMID:25406224

  11. Current trends and future directions in flower development research.

    Science.gov (United States)

    Scutt, Charlie P; Vandenbussche, Michiel

    2014-11-01

    Flowers, the reproductive structures of the approximately 400 000 extant species of flowering plants, exist in a tremendous range of forms and sizes, mainly due to developmental differences involving the number, arrangement, size and form of the floral organs of which they consist. However, this tremendous diversity is underpinned by a surprisingly robust basic floral structure in which a central group of carpels forms on an axis of determinate growth, almost invariably surrounded by two successive zones containing stamens and perianth organs, respectively. Over the last 25 years, remarkable progress has been achieved in describing the molecular mechanisms that control almost all aspects of flower development, from the phase change that initiates flowering to the final production of fruits and seeds. However, this work has been performed almost exclusively in a small number of eudicot model species, chief among which is Arabidopsis thaliana. Studies of flower development must now be extended to a much wider phylogenetic range of flowering plants and, indeed, to their closest living relatives, the gymnosperms. Studies of further, more wide-ranging models should provide insights that, for various reasons, cannot be obtained by studying the major existing models alone. The use of further models should also help to explain how the first flowering plants evolved from an unknown, although presumably gymnosperm-like ancestor, and rapidly diversified to become the largest major plant group and to dominate the terrestrial flora. The benefits for society of a thorough understanding of flower development are self-evident, as human life depends to a large extent on flowering plants and on the fruits and seeds they produce. In this preface to the Special Issue, we introduce eleven articles on flower development, representing work in both established and further models, including gymnosperms. We also present some of our own views on current trends and future directions of the

  12. Optimization of RF power absorption by optimization techniques using the lower hybrid current drive of FTU

    Energy Technology Data Exchange (ETDEWEB)

    Centioli, C. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Iannone, F. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Mazza, G. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Panella, M. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Pangione, L. [Dipartimento di Informatica, Sistemi e Produzione, Universita di Roma, Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy)]. E-mail: pangione@frascati.enea.it; Podda, S. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Tuccillo, A. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Vitale, V. [Associazione Euratom/ENEA Sulla Fusione, Centro Ricerche Frascati, Via E. Fermi 45, CP 65, 00044 Frascati, Rome (Italy); Zaccarian, L. [Dipartimento di Informatica, Sistemi e Produzione, Universita di Roma, Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy)

    2005-11-15

    In this paper, we will report on the experimental results arising from the implementation of optimization techniques to maximize the RF power coupling versus the plasma conditions in the FTU experimental facility. These experiments are carried out by employing the open-source Linux-RTAI control system currently running on the FTU digital feedback loop. The RF power source under consideration is a lower hybrid system (LH) based on six gyrotrons with a nominal power output capability of 1.1 MW each. The optimization of the coupling level between the plasma and the emitting antenna reduces the reflected power, thus maximizing the heating effects in addition to avoiding danger to the emitter (equivalently, annoying safety shutdowns of the system). To this aim, the plasma displacement is modified by suitably adjusting the reference input to the stabilizing feedback, according to a steepest descent algorithm. It will be shown in the paper how this algorithm achieves a satisfactory level of robustness with respect to measurement errors and well performs both in simulation and in experimental tests, thus leading to an improved effectiveness of the RF heating system.

  13. Heterogeneous SIS model for directed networks and optimal immunization

    CERN Document Server

    Ottaviano, Stefania; Bonaccorsi, Stefano

    2016-01-01

    We investigate the influence of a contact network structure over the spread of epidemics in an heterogeneous population. Basically the epidemics spreads over a directed weighted graph. We describe the epidemic process as a continuous-time individual-based susceptible-infected-susceptible (SIS) model using a first-order mean-field approximation. First we consider a network without a specific topology, investigating the epidemic threshold and the stability properties of the system. Then we analyze the case of a community network, relying on the graph-theoretical notion of equitable partition, and using a lower-dimensional dynamical system in order to individuate the epidemic threshold. Moreover we prove that the positive steady-state of the original system, that appears above the threshold, can be computed by this lower-dimensional system. In the second part of the paper we treat the important issue of the infectious disease control. Taking into account the connectivity of the network, we provide a cost-optimal...

  14. Parietal transcranial direct current stimulation modulates primary motor cortex excitability.

    Science.gov (United States)

    Rivera-Urbina, Guadalupe Nathzidy; Batsikadze, Giorgi; Molero-Chamizo, Andrés; Paulus, Walter; Kuo, Min-Fang; Nitsche, Michael A

    2015-03-01

    The posterior parietal cortex is part of the cortical network involved in motor learning and is structurally and functionally connected with the primary motor cortex (M1). Neuroplastic alterations of neuronal connectivity might be an important basis for learning processes. These have however not been explored for parieto-motor connections in humans by transcranial direct current stimulation (tDCS). Exploring tDCS effects on parieto-motor cortical connectivity might be functionally relevant, because tDCS has been shown to improve motor learning. We aimed to explore plastic alterations of parieto-motor cortical connections by tDCS in healthy humans. We measured neuroplastic changes of corticospinal excitability via motor evoked potentials (MEP) elicited by single-pulse transcranial magnetic stimulation (TMS) before and after tDCS over the left posterior parietal cortex (P3), and 3 cm posterior or lateral to P3, to explore the spatial specificity of the effects. Furthermore, short-interval intracortical inhibition/intracortical facilitation (SICI/ICF) over M1, and parieto-motor cortical connectivity were obtained before and after P3 tDCS. The results show polarity-dependent M1 excitability alterations primarily after P3 tDCS. Single-pulse TMS-elicited MEPs, M1 SICI/ICF at 5 and 7 ms and 10 and 15 ms interstimulus intervals (ISIs), and parieto-motor connectivity at 10 and 15 ms ISIs were all enhanced by anodal stimulation. Single pulse-TMS-elicited MEPs, and parieto-motor connectivity at 10 and 15 ms ISIs were reduced by cathodal tDCS. The respective corticospinal excitability alterations lasted for at least 120 min after stimulation. These results show an effect of remote stimulation of parietal areas on M1 excitability. The spatial specificity of the effects and the impact on parietal cortex-motor cortex connections suggest a relevant connectivity-driven effect.

  15. Optimizing pulsed current micro plasma arc welding parameters to ...

    African Journals Online (AJOL)

    user

    Pulsed current MPAW involves cycling the welding current at selected regular frequency. ..... At high pulse, the vibration amplitude and temperature oscillation induced on .... received his Masters Degree from JNTU Hyderabad, India in 2002.

  16. Microbiological aspects of biofuel production: Current status and future directions

    Directory of Open Access Journals (Sweden)

    Mostafa S. Elshahed

    2010-04-01

    Full Text Available Biofuel research is currently an area of immense interest due to the increase in global energy demand by emerging economies and the recent increases in global oil prices. Multiple approaches are currently being researched for the use of microorganisms in the production of various biofuel (e.g. alcohols, hydrogen, biodiesel, and biogas from multiple starting materials. This review provides a brief overview on the research currently underway on laboratory and industrial scales in the area of biofuels, with specific emphasis on the economic viability of various approaches currently being utilized.

  17. Optimization of hydrofoil for tidal current turbine based on particle swarm optimization and computational fluid dynamic method

    OpenAIRE

    Zhang De-Sheng; Chen Jian; Shi Wei-Dong; Shi Lei; Geng Lin-Lin

    2016-01-01

    Both efficiency and cavitation performance of the hydrofoil are the key technologies to design the tidal current turbine. In this paper, the hydrofoil efficiency and lift coefficient were improved based on particle swarm optimization method and XFoil codes. The cavitation performance of the optimized hydrofoil was also discussed by the computational fluid dynamic. Numerical results show the efficiency of the optimized hydrofoil was improved 11% ranging from...

  18. Direct Drive Unit with Autonomous Cathode Current Regulation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An approach for maximizing Hall thruster electrical system efficiency is to power the thruster directly from a high voltage solar array by a method commonly referred...

  19. Current status and future directions of research on facial attractiveness

    National Research Council Canada - National Science Library

    Kościński, Krzysztof

    2009-01-01

    The aim of the present paper was to evaluate the current state of knowledge on the perception of facial attractiveness and to assess the opportunity for research on poorly explored issues regarding facial preferences...

  20. Optimal allocation of fault current limiters for sustaining overcurrent relays coordination in a power system with distributed generation

    Directory of Open Access Journals (Sweden)

    A. Elmitwally

    2015-12-01

    Full Text Available This paper addresses the problem of overcurrent relays (OCRs coordination in the presence of DGs. OCRs are optimally set to work in a coordinated manner to isolate faults with minimal impacts on customers. The penetration of DGs into the power system changes the fault current levels seen by the OCRs. This can deteriorate the coordinated operation of OCRs. Operation time difference between backup and main relays can be below the standard limit or even the backup OCR can incorrectly work before the main OCR. Though resetting of OCRs is tedious especially in large systems, it cannot alone restore the original coordinated operation in the presence of DGs. The paper investigates the optimal utilization of fault current limiters (FCLs to maintain the directional OCRs coordinated operation without any need to OCRs resetting irrespective of DGs status. It is required to maintain the OCRs coordination at minimum cost of prospective FCLs. Hence, the FCLs location and sizing problem is formulated as a constrained multi-objective optimization problem. Multi-objective particle swarm optimization is adopted for solving the optimization problem to determine the optimal locations and sizes of FCLs. The proposed algorithm is applied to meshed and radial power systems at different DGs arrangements using different types of FCLs. Moreover, the OCRs coordination problem is studied when the system includes both directional and non-directional OCRs. Comparative analysis of results is provided.

  1. High-speed pulse train amplification in semiconductor optical amplifiers with optimized bias current.

    Science.gov (United States)

    Xia, Mingjun; Ghafouri-Shiraz, H; Hou, Lianping; Kelly, Anthony E

    2017-02-01

    In this paper, we have experimentally investigated the optimized bias current of semiconductor optical amplifiers (SOAs) to achieve high-speed input pulse train amplification with high gain and low distortion. Variations of the amplified output pulse duration with the amplifier bias currents have been analyzed and, compared to the input pulse duration, the amplified output pulse duration is broadened. As the SOA bias current decreases from the high level (larger than the saturated bias current) to the low level, the broadened pulse duration of the amplified output pulse initially decreases slowly and then rapidly. Based on the analysis, an optimized bias current of SOA for high-speed pulse train amplification is introduced. The relation between the SOA optimized bias current and the parameters of the input pulse train (pulse duration, power, and repetition rate) are experimentally studied. It is found that the larger the input pulse duration, the lower the input pulse power or a higher repetition rate can lead to a larger SOA optimized bias current, which corresponds to a larger optimized SOA gain. The effects of assist light injection and different amplifier temperatures on the SOA optimized bias current are studied and it is found that assist light injection can effectively increase the SOA optimized bias current while SOA has a lower optimized bias current at the temperature 20°C than that at other temperatures.

  2. CONE-DIRECTED CONTINGENT DERIVATIVES AND GENERALIZED PREINVEX SET-VALUED OPTIMIZATION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    By using cone-directed contingent derivatives, the unified necessary and sufficient optimality conditions are given for weakly and strongly minimal elements respectively in generalized preinvex set-valued optimization.

  3. Measurement of sub-picoampere direct currents with uncertainties below ten attoamperes

    Science.gov (United States)

    Krause, C.; Drung, D.; Scherer, H.

    2017-02-01

    A new type of the ultrastable low-noise current amplifier (ULCA) is presented. It involves thick-film resistors to achieve a high feedback resistance of 185 GΩ at the input amplifier. An improved noise level of 0.4 fA/√{Hz} with a 1/f corner of about 30 μHz and an effective input bias current well below 100 aA are demonstrated. For small direct currents, measurement uncertainties below 10 aA are achievable even without current reversal or on/off switching. Above about 1 pA, the stability of the ULCA's resistor network limits the relative measurement uncertainty to about 10 parts per million. The new setup is used to characterize and optimize the noise in the wiring installed on a dilution refrigerator for current measurements on single-electron transport pumps. In a test configuration connected to the wiring in a pulse tube refrigerator, a total noise floor of 0.44 fA/√{Hz} was achieved including the contributions of amplifier and cryogenic wiring.

  4. Current density imaging using directly measured harmonic Bz data in MREIT.

    Science.gov (United States)

    Park, Chunjae; Kwon, Oh In

    2013-01-01

    Magnetic resonance electrical impedance tomography (MREIT) measures magnetic flux density signals through the use of a magnetic resonance imaging (MRI) in order to visualize the internal conductivity and/or current density. Understanding the reconstruction procedure for the internal current density, we directly measure the second derivative of Bz data from the measured k-space data, from which we can avoid a tedious phase unwrapping to obtain the phase signal of Bz . We determine optimal weighting factors to combine the derivatives of magnetic flux density data, [Symbol: see text](2) Bz , measured using the multi-echo train. The proposed method reconstructs the internal current density using the relationships between the induced internal current and the measured [Symbol: see text](2) Bz data. Results from a phantom experiment demonstrate that the proposed method reduces the scanning time and provides the internal current density, while suppressing the background field inhomogeneity. To implement the real experiment, we use a phantom with a saline solution including a balloon, which excludes other artifacts by any concentration gradient in the phantom.

  5. Different current intensities of anodal transcranial direct current stimulation do not differentially modulate motor cortex plasticity.

    Science.gov (United States)

    Kidgell, Dawson J; Daly, Robin M; Young, Kayleigh; Lum, Jarrod; Tooley, Gregory; Jaberzadeh, Shapour; Zoghi, Maryam; Pearce, Alan J

    2013-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive technique that modulates the excitability of neurons within the motor cortex (M1). Although the aftereffects of anodal tDCS on modulating cortical excitability have been described, there is limited data describing the outcomes of different tDCS intensities on intracortical circuits. To further elucidate the mechanisms underlying the aftereffects of M1 excitability following anodal tDCS, we used transcranial magnetic stimulation (TMS) to examine the effect of different intensities on cortical excitability and short-interval intracortical inhibition (SICI). Using a randomized, counterbalanced, crossover design, with a one-week wash-out period, 14 participants (6 females and 8 males, 22-45 years) were exposed to 10 minutes of anodal tDCS at 0.8, 1.0, and 1.2 mA. TMS was used to measure M1 excitability and SICI of the contralateral wrist extensor muscle at baseline, immediately after and 15 and 30 minutes following cessation of anodal tDCS. Cortical excitability increased, whilst SICI was reduced at all time points following anodal tDCS. Interestingly, there were no differences between the three intensities of anodal tDCS on modulating cortical excitability or SICI. These results suggest that the aftereffect of anodal tDCS on facilitating cortical excitability is due to the modulation of synaptic mechanisms associated with long-term potentiation and is not influenced by different tDCS intensities.

  6. Different Current Intensities of Anodal Transcranial Direct Current Stimulation Do Not Differentially Modulate Motor Cortex Plasticity

    Directory of Open Access Journals (Sweden)

    Dawson J. Kidgell

    2013-01-01

    Full Text Available Transcranial direct current stimulation (tDCS is a noninvasive technique that modulates the excitability of neurons within the motor cortex (M1. Although the aftereffects of anodal tDCS on modulating cortical excitability have been described, there is limited data describing the outcomes of different tDCS intensities on intracortical circuits. To further elucidate the mechanisms underlying the aftereffects of M1 excitability following anodal tDCS, we used transcranial magnetic stimulation (TMS to examine the effect of different intensities on cortical excitability and short-interval intracortical inhibition (SICI. Using a randomized, counterbalanced, crossover design, with a one-week wash-out period, 14 participants (6 females and 8 males, 22–45 years were exposed to 10 minutes of anodal tDCS at 0.8, 1.0, and 1.2 mA. TMS was used to measure M1 excitability and SICI of the contralateral wrist extensor muscle at baseline, immediately after and 15 and 30 minutes following cessation of anodal tDCS. Cortical excitability increased, whilst SICI was reduced at all time points following anodal tDCS. Interestingly, there were no differences between the three intensities of anodal tDCS on modulating cortical excitability or SICI. These results suggest that the aftereffect of anodal tDCS on facilitating cortical excitability is due to the modulation of synaptic mechanisms associated with long-term potentiation and is not influenced by different tDCS intensities.

  7. Optimization of Exactness of Direct Digital Correlation-Interferometer Direction-finder with Double Сorrelation Processing

    Directory of Open Access Journals (Sweden)

    V. V. Tsyporenko

    2016-03-01

    Full Text Available Introduction. In this paper considered unsolved part of general issue of research of direct digital methods of correlation-interferometer radio direction-finding. The purpose of the article is optimization of exactness of direct digital correlation-interferometer direction-finder with double сorrelation processing. Fundamentals of researches. As a result of the conducted researches was defined that the basic parameter of equalization of dispersion of error of estimation of direction on the source of radio radiation for the direct digital correlation-interferometric direction-finder with double correlation processing, which it is expedient to optimize, there is the size of frequency converting change. Optimization. It was conducted parametrical optimization of the explored direction-finder for the selective model of frequency change. As a result of design was obtained dependence of middle deviation of estimation of direction from the relation of signal/noise at the action of normal gaussian noise for the different possible values of circular frequency converting shift. Conclusions. Analytical calculations and results of design coincided fully, that confirmed the rightness of the conducted researches and authenticity of results of optimization.

  8. Direct Calculations of Current Drive with a Full Wave Code

    Science.gov (United States)

    Wright, John C.; Phillips, Cynthia K.

    1997-11-01

    We have developed a current drive package that evaluates the current driven by fast magnetosonic waves in arbitrary flux geometry. An expression for the quasilinear flux has been derived which accounts for coupling between modes in the spectrum of waves launched from the antenna. The field amplitudes are calculated in the full wave code, FISIC, and the current response function, \\chi, also known as the Spitzer function, is determined with Charles Karney's Fokker-Planck code, adj.f. Both codes have been modified to incorporate the same numerical equilibria. To model the effects of a trapped particle population, the bounce averaged equations for current and power are used, and the bounce averaged flux is calculated. The computer model is benchmarked against the homogenous equations for a high aspect ratio case in which the expected agreement is confirmed. Results from cases for TFTR, NSTX and CDX-U are contrasted with the predictions of the Ehst-Karney parameterization of current drive for circular equilibria. For theoretical background, please see the authors' archive of papers. (http://w3.pppl.gov/ ~jwright/Publications)

  9. Optimal adaptation to extreme rainfalls in current and future climate

    DEFF Research Database (Denmark)

    Rosbjerg, Dan

    2017-01-01

    and the annual capital and operational costs of adapting to this level are described with log-linear relations. The total flooding costs are developed as the expected annual damage of flooding above the T-year level plus the annual capital and operational costs for ensuring no flooding below the T-year level......More intense and frequent rainfalls have increased the number of urban flooding events in recent years, prompting adaptation efforts. Economic optimization is considered an efficient tool to decide on the design level for adaptation. The costs associated with a flooding to the T-year level....... The value of the return period T that corresponds to the minimum of the sum of these costs will then be the optimal adaptation level. The change in climate, however, is expected to continue in the next century, which calls for expansion of the above model. The change can be expressed in terms of a climate...

  10. Xenon excimer emission from multicapillary discharges in direct current mode

    Science.gov (United States)

    Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon; Giapis, Konstantinos P.; Iberler, Marcus; Jacoby, Joachim; Frank, Klaus

    2011-08-01

    Microdischarges in xenon have been generated in a pressure range of 400-1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, the irradiance of the VUV emission is strongly dependent on pressure as well as the discharge current.

  11. Xenon excimer emission from multicapillary discharges in direct current mode

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Giapis, Konstantinos P. [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); Iberler, Marcus; Jacoby, Joachim [Institute of Applied Physics, Goethe University, Max-von-Laue-St. 1, 60438 Frankfurt am Main (Germany); Frank, Klaus [Physics Department I, F.A., University of Erlangen-Nuremberg, D-91058 Erlangen (Germany)

    2011-08-15

    Microdischarges in xenon have been generated in a pressure range of 400-1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, the irradiance of the VUV emission is strongly dependent on pressure as well as the discharge current.

  12. Noninvasive transcranial direct current stimulation in a genetic absence model

    NARCIS (Netherlands)

    Zobeiri, M.; Luijtelaar, E.L.J.M. van

    2013-01-01

    The proposed area of onset for absence epilepsy characteristic of spontaneously occurring spike and slow-wave discharges (SWDs) in the genetic absence rat model is the subgranular layer of the somatosensory cortex. Modulation of the hyperexcitable cortical foci by bilateral transcranial direct curre

  13. Direct Optimization of Printed Reflectarrays for Contoured Beam Satellite Antenna Applications

    DEFF Research Database (Denmark)

    Zhou, Min; Sorensen, Stig B.; Kim, Oleksiy S.

    2013-01-01

    An accurate and efficient direct optimization technique for the design of contoured beam reflectarrays is presented. It is based on the spectral domain method of moments assuming local periodicity and minimax optimization. Contrary to the conventional phase-only optimization techniques, the geome......An accurate and efficient direct optimization technique for the design of contoured beam reflectarrays is presented. It is based on the spectral domain method of moments assuming local periodicity and minimax optimization. Contrary to the conventional phase-only optimization techniques...

  14. Directed Motivational Currents: Using Vision to Create Effective Motivational Pathways

    Science.gov (United States)

    Muir, Christine; Dörnyei, Zoltán

    2013-01-01

    Vision, that is, the mental representation of the sensory experience of a future goal state (involving imagination and imagery), is currently at the forefront of motivational innovation, and in recent years it has been seen increasingly more often in the motivational tool kit of practicing language teachers. Theories such as Dörnyei's L2…

  15. Sustainable practices in medicinal chemistry: current state and future directions.

    Science.gov (United States)

    Bryan, Marian C; Dillon, Barry; Hamann, Lawrence G; Hughes, Gregory J; Kopach, Michael E; Peterson, Emily A; Pourashraf, Mehrnaz; Raheem, Izzat; Richardson, Paul; Richter, Daniel; Sneddon, Helen F

    2013-08-08

    The medicinal chemistry subgroup of the American Chemical Society's Green Chemistry Institute Pharmaceutical Roundtable (ACS GCI PR) offers a perspective on the current state of environmentally sustainable practices in medicinal chemistry with the aim of sharing best practices more widely and highlighting some potential future developments.

  16. Business Education at Catholic Universities: Current Status and Future Directions

    Science.gov (United States)

    Porth, Stephen J.; McCall, John J.; DiAngelo, Joseph A.

    2009-01-01

    Is business education at Catholic colleges and universities different than business education at secular institutions? This study assesses the current state of business education at Catholic colleges and universities based on a national survey of business school deans and faculty members and an audit of business unit web sites. Results suggest…

  17. Business Education at Catholic Universities: Current Status and Future Directions

    Science.gov (United States)

    Porth, Stephen J.; McCall, John J.; DiAngelo, Joseph A.

    2009-01-01

    Is business education at Catholic colleges and universities different than business education at secular institutions? This study assesses the current state of business education at Catholic colleges and universities based on a national survey of business school deans and faculty members and an audit of business unit web sites. Results suggest…

  18. Transcranial Direct Current Stimulation in Stroke Rehabilitation: A Review of Recent Advancements

    Science.gov (United States)

    Gomez Palacio Schjetnan, Andrea; Faraji, Jamshid; Metz, Gerlinde A.; Tatsuno, Masami; Luczak, Artur

    2013-01-01

    Transcranial direct current stimulation (tDCS) is a promising technique to treat a wide range of neurological conditions including stroke. The pathological processes following stroke may provide an exemplary system to investigate how tDCS promotes neuronal plasticity and functional recovery. Changes in synaptic function after stroke, such as reduced excitability, formation of aberrant connections, and deregulated plastic modifications, have been postulated to impede recovery from stroke. However, if tDCS could counteract these negative changes by influencing the system's neurophysiology, it would contribute to the formation of functionally meaningful connections and the maintenance of existing pathways. This paper is aimed at providing a review of underlying mechanisms of tDCS and its application to stroke. In addition, to maximize the effectiveness of tDCS in stroke rehabilitation, future research needs to determine the optimal stimulation protocols and parameters. We discuss how stimulation parameters could be optimized based on electrophysiological activity. In particular, we propose that cortical synchrony may represent a biomarker of tDCS efficacy to indicate communication between affected areas. Understanding the mechanisms by which tDCS affects the neural substrate after stroke and finding ways to optimize tDCS for each patient are key to effective rehabilitation approaches. PMID:23533955

  19. Transcranial Direct Current Stimulation in Stroke Rehabilitation: A Review of Recent Advancements

    Directory of Open Access Journals (Sweden)

    Andrea Gomez Palacio Schjetnan

    2013-01-01

    Full Text Available Transcranial direct current stimulation (tDCS is a promising technique to treat a wide range of neurological conditions including stroke. The pathological processes following stroke may provide an exemplary system to investigate how tDCS promotes neuronal plasticity and functional recovery. Changes in synaptic function after stroke, such as reduced excitability, formation of aberrant connections, and deregulated plastic modifications, have been postulated to impede recovery from stroke. However, if tDCS could counteract these negative changes by influencing the system’s neurophysiology, it would contribute to the formation of functionally meaningful connections and the maintenance of existing pathways. This paper is aimed at providing a review of underlying mechanisms of tDCS and its application to stroke. In addition, to maximize the effectiveness of tDCS in stroke rehabilitation, future research needs to determine the optimal stimulation protocols and parameters. We discuss how stimulation parameters could be optimized based on electrophysiological activity. In particular, we propose that cortical synchrony may represent a biomarker of tDCS efficacy to indicate communication between affected areas. Understanding the mechanisms by which tDCS affects the neural substrate after stroke and finding ways to optimize tDCS for each patient are key to effective rehabilitation approaches.

  20. As it happens: current directions in experimental evolution.

    Science.gov (United States)

    Bataillon, Thomas; Joyce, Paul; Sniegowski, Paul

    2013-02-23

    Recent decades have seen a significant rise in studies in which evolution is observed and analysed directly-as it happens-under replicated, controlled conditions. Such 'experimental evolution' approaches offer a degree of resolution of evolutionary processes and their underlying genetics that is difficult or even impossible to achieve in more traditional comparative and retrospective analyses. In principle, experimental populations can be monitored for phenotypic and genetic changes with any desired level of replication and measurement precision, facilitating progress on fundamental and previously unresolved questions in evolutionary biology. Here, we summarize 10 invited papers in which experimental evolution is making significant progress on a variety of fundamental questions. We conclude by briefly considering future directions in this very active field of research, emphasizing the importance of quantitative tests of theories and the emerging role of genome-wide re-sequencing.

  1. HEADROOM APPROACH TO DEVICE DEVELOPMENT: CURRENT AND FUTURE DIRECTIONS

    OpenAIRE

    Girling, A; Lilford, R; Cole, A; Young, T

    2015-01-01

    OBJECTIVES: The headroom approach to medical device development relies on the estimation of a value-based price ceiling at different stages of the development cycle. Such price-ceilings delineate the commercial opportunities for new products in many healthcare systems. We apply a simple model to obtain critical business information as the product proceeds along a development pathway, and indicate some future directions for the development of the approach. METHODS: Health economic modelling in...

  2. Optimization of Transformation Coefficients Using Direct Search and Swarm Intelligence

    Directory of Open Access Journals (Sweden)

    Manusov V.Z.

    2017-04-01

    Full Text Available This research considers optimization of tap position of transformers in power systems to reduce power losses. Now, methods based on heuristic rules and fuzzy logic, or methods that optimize parts of the whole system separately, are applied to this problem. The first approach requires expert knowledge about processes in the network. The second methods are not able to consider all the interrelations of system’s parts, while changes in segment affect the entire system. Both approaches are tough to implement and require adjustment to the tasks solved. It needs to implement algorithms that can take into account complex interrelations of optimized variables and self-adapt to optimization task. It is advisable to use algorithms given complex interrelations of optimized variables and independently adapting from optimization tasks. Such algorithms include Swarm Intelligence algorithms. Their main features are self-organization, which allows them to automatically adapt to conditions of tasks, and the ability to efficiently exit from local extremes. Thus, they do not require specialized knowledge of the system, in contrast to fuzzy logic. In addition, they can efficiently find quasi-optimal solutions converging to the global optimum. This research applies Particle Swarm Optimization algorithm (PSO. The model of Tajik power system used in experiments. It was found out that PSO is much more efficient than greedy heuristics and more flexible and easier to use than fuzzy logic. PSO allows reducing active power losses from 48.01 to 45.83 MW (4.5%. With al, the effect of using greedy heuristics or fuzzy logic is two times smaller (2.3%.

  3. Excimer Emission from Direct Current Microhollow Cathode Discharges

    Science.gov (United States)

    Stark, R. H.; El-Habachi, A.; Shi, W.; Schoenbach, K. H.

    1997-10-01

    Reducing the dimensions of the cathode hole to less than 200 micrometer has allowed us to operate argon discharges in a hollow cathode discharge mode, dc, up to pressures of one atmosphere. Spectral measurements in the VUV have shown that the microdischarges are strong sources of argon excimer radiation at 128 nm. This points to a nonthermal electron energy distribution where a considerable part of the electrons have energies exceeding the ionization potential of argon. Whereas the discharges in argon were dc up to atmospheric pressure, discharges in xenon became unstable at pressures exceeding 300 Torr, and current spikes were observed. The xenon excimer emission at 172 nm, however, was found to increase, independent of the mode, dc or pulsed, when the pressure was increased to one atmosphere. The microdischarges have resistive current-voltage characteristics. This has allowed us to generate simple arrays of these discharges, with possible applications as flat panel excimer lamps.

  4. Xenon excimer emission from multicapillary discharges in direct current mode

    OpenAIRE

    Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon; Giapis, Konstantinos P.; Iberler, Marcus; Jacoby, Joachim; Frank, Klaus

    2012-01-01

    Microdischarges in xenon have been generated in a pressure range of 400–1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, t...

  5. A Novel Quantum-Behaved Bat Algorithm with Mean Best Position Directed for Numerical Optimization.

    Science.gov (United States)

    Zhu, Binglian; Zhu, Wenyong; Liu, Zijuan; Duan, Qingyan; Cao, Long

    2016-01-01

    This paper proposes a novel quantum-behaved bat algorithm with the direction of mean best position (QMBA). In QMBA, the position of each bat is mainly updated by the current optimal solution in the early stage of searching and in the late search it also depends on the mean best position which can enhance the convergence speed of the algorithm. During the process of searching, quantum behavior of bats is introduced which is beneficial to jump out of local optimal solution and make the quantum-behaved bats not easily fall into local optimal solution, and it has better ability to adapt complex environment. Meanwhile, QMBA makes good use of statistical information of best position which bats had experienced to generate better quality solutions. This approach not only inherits the characteristic of quick convergence, simplicity, and easy implementation of original bat algorithm, but also increases the diversity of population and improves the accuracy of solution. Twenty-four benchmark test functions are tested and compared with other variant bat algorithms for numerical optimization the simulation results show that this approach is simple and efficient and can achieve a more accurate solution.

  6. Current challenges and future directions in cardiac imaging.

    Science.gov (United States)

    Wann, Samuel; Tunio, Javed

    2010-07-01

    Imaging is one of the most important accomplishments of medicine during the last 1000 years. The contribution of modern imaging to progress in the delivery of health care is unquestioned. However, we need to refine our use of imaging, limiting its use to those occasions when it can contribute directly or indirectly to improving and lengthening the lives of patients. Technology prowess in imaging alone is not sufficient to deliver value to individuals or to society. Continued investment in imaging technology requires critical appraisal of its use in clinical decision making and patient outcomes.

  7. Vitamin D in pregnancy: current perspectives and future directions.

    Science.gov (United States)

    Kiely, Mairead; Hemmingway, Andrea; O'Callaghan, Karen M

    2017-06-01

    As neonatal vitamin D status is determined by circulating maternal 25-hydroxyvitamin D [25(OH)D] concentrations, prevention of maternal vitamin D deficiency during pregnancy is essential for the avoidance of neonatal deficiency. However, a high prevalence of vitamin D deficiency has been extensively reported among gravidae and neonates from ethnic minorities and white populations resident at high latitude. Currently, regulatory authorities recommend vitamin D intakes for pregnant women that are similar to non-pregnant adults of the same age, at 10-15 µg/day (400-600 IU), to meet 25(OH)D thresholds of 25-50 nmol/liter. The lack of pregnancy-specific dietary recommendations is due to inadequate data indicating whether nutritional requirements for vitamin D during pregnancy differ from the non-pregnant state. In addition, there are few dose-response studies to determine the maternal 25(OH)D response to vitamin D intake throughout pregnancy at high latitude. These data are also required to determine vitamin D requirements during pregnancy for prevention of neonatal deficiency, an outcome which is likely to require a higher maternal 25(OH)D concentration than prevention of maternal deficiency only. With regard to the impact of vitamin D on perinatal health outcomes, which could guide pregnancy-specific 25(OH)D thresholds, dietary intervention studies to date have been inconsistent and recent systematic reviews have highlighted issues of low quality and a high risk of bias as drawbacks in the trial evidence to date. Many observational studies have been hampered by a reliance on retrospective data, unclear reporting, suboptimal clinical phenotyping and incomplete subject characterization. Current investigations of vitamin D metabolism during pregnancy have potentially exciting implications for clinical research. This paper provides an update of current dietary recommendations for vitamin D in pregnant women and a synopsis of the evidence relating vitamin D status with

  8. The Vaginal Microbiome: Current Understanding and Future Directions.

    Science.gov (United States)

    Martin, David H; Marrazzo, Jeanne M

    2016-08-15

    This article summarizes the highlights of the expert technical consultation on bacterial vaginosis (BV), sponsored by the National Institute of Allergy and Infectious Disease and held in Washington, DC, on 8-9 April 2015. Many issues touched on in this article are discussed in much greater detail in the 6 preceding articles in this supplement to The Journal of Infectious Diseases There was a consensus among the meeting attendees concerning the most important research issues in the field: the pathogenesis of the syndrome, way to optimize treatment, and the relative roles of sexual transmission and endogenous infection in BV epidemiology. This article concludes with a listing of BV and genitourinary tract research priorities that were discussed and agreed on by attendees. The most important of these included better characterization of vaginal microbiome community state subtypes, application of advanced "-omic" technologies to improve understanding of BV pathogenesis, further investigation of the relationships between the male and female genitourinary tract microbiomes, and the development of new drugs for BV treatment. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

  9. Enhancing attention in neurodegenerative diseases: current therapies and future directions

    Directory of Open Access Journals (Sweden)

    Sharma Kanchan

    2016-01-01

    Full Text Available We all experience at least occasional lapses in attention but in some neurological conditions, loss of attention is pervasive and debilitating. Treating deficits in attention first requires an understanding of the neurobiology of attention, which we now understand to be a set of different cognitive processes. Cholinesterase inhibitors are already established as effective attentional enhancers used in the treatment of certain dementias. Other stimulant agents such as modafanil, amphetamine and methylphenidate have demonstrated limited success in healthy individuals where attention is already optimal and clinical trials in patients with neurological disease are sparse. Dietary and lifestyle changes are gaining increasing prominence, as are experimental treatments such as deep brain stimulation and transcranial magnetic stimulation. As the therapeutic arsenal widens, clinicians will be able to match specific treatments to selective deficits in attention, giving patients a tailored management plan. Here we review common diseases that impair attention and emphasise how an understanding of attentional processing within the brain might lead to improved therapeutic strategies.

  10. Pragma Directed Shared Memory Centric Optimizations on GPUs

    Institute of Scientific and Technical Information of China (English)

    Jing Li; Lei Liu; Yuan Wu; Xiang-Hua Liu; Yi Gao; Xiao-Bing Feng; Cheng-Yong Wu

    2016-01-01

    GPUs become a ubiquitous choice as coprocessors since they have excellent ability in concurrent processing. In GPU architecture, shared memory plays a very important role in system performance as it can largely improve bandwidth utilization and accelerate memory operations. However, even for affine GPU applications that contain regular access patterns, optimizing for shared memory is not an easy work. It often requires programmer expertise and nontrivial parameter selection. Improper shared memory usage might even underutilize GPU resource. Even using state-of-the-art high level programming models (e.g., OpenACC and OpenHMPP), it is still hard to utilize shared memory since they lack inherent support in describing shared memory optimization and selecting suitable parameters, let alone maintaining high resource utilization. Targeting higher productivity for affine applications, we propose a data centric way to shared memory optimization on GPU. We design a pragma extension on OpenACC so as to convey data management hints of programmers to compiler. Meanwhile, we devise a compiler framework to automatically select optimal parameters for shared arrays, using the polyhedral model. We further propose optimization techniques to expose higher memory and instruction level parallelism. The experimental results show that our shared memory centric approaches effectively improve the performance of five typical GPU applications across four widely used platforms by 3.7x on average, and do not burden programmers with lots of pragmas.

  11. Current and future directions of DNA in wildlife forensic science.

    Science.gov (United States)

    Johnson, Rebecca N; Wilson-Wilde, Linzi; Linacre, Adrian

    2014-05-01

    Wildlife forensic science may not have attained the profile of human identification, yet the scale of criminal activity related to wildlife is extensive by any measure. Service delivery in the arena of wildlife forensic science is often ad hoc, unco-ordinated and unregulated, yet many of those currently dedicated to wildlife conservation and the protection of endangered species are striving to ensure that the highest standards are met. The genetic markers and software used to evaluate data in wildlife forensic science are more varied than those in human forensic identification and are rarely standardised between species. The time and resources required to characterise and validate each genetic maker is considerable and in some cases prohibitive. Further, issues are regularly encountered in the construction of allelic databases and allelic ladders; essential in human identification studies, but also applicable to wildlife criminal investigations. Accreditation and certification are essential in human identification and are currently being strived for in the forensic wildlife community. Examples are provided as to how best practice can be demonstrated in all areas of wildlife crime analysis and ensure that this field of forensic science gains and maintains the respect it deserves. This review is aimed at those conducting human identification to illustrate how research concepts in wildlife forensic science can be used in the criminal justice system, as well as describing the real importance of this type of forensic analysis.

  12. CRISPR system in filamentous fungi: Current achievements and future directions.

    Science.gov (United States)

    Deng, Huaxiang; Gao, Ruijie; Liao, Xiangru; Cai, Yujie

    2017-09-05

    As eukaryotes, filamentous fungi share many features with humans, and they produce numerous active metabolites, some of which are toxic. Traditional genetic approaches are generally inefficient, but the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system that has been widely used for basic research on bacteria, mammals and plants offers a simple, fast, versatile technology for systemic research on filamentous fungi. In this review, we summarized the current knowledge on Cas9 and its variants, various selective markers used to screen positive clones, different ways used to detect off-target mutations, and different approaches used to express and transform the CRISPR complex. We also highlight several methods that improve the nuclease specificity and efficiency, and discuss current and potential applications of CRISPR/Cas9 system in filamentous fungi for pathogenesis decoding, confirmation of the gene and pathway, bioenergy process, drug discovery, and chromatin dynamics. We also describe how the synthetic gene circuit of CRISPR/Cas9 systems has been used in the response to various complex environmental signals to redirect metabolite flux and ensure continuous metabolite biosynthesis. Copyright © 2017. Published by Elsevier B.V.

  13. Direct-current proton-beam measurements at Los Alamos

    Energy Technology Data Exchange (ETDEWEB)

    Sherman, J.; Stevens, R.R.; Schneider, J.D.; Zaugg, T.

    1994-08-01

    Recently, a CW proton accelerator complex was moved from Chalk River Laboratories (CRL) to Los Alamos National Laboratory. This includes a 50-keV dc proton injector with a single-solenoid low-energy beam transport system (LEBT) and a CW 1.25-MeV, 267-MHz radiofrequency quadrupole (RFQ). The move was completed after CRL had achieved 55-mA CW operation at 1.25 MeV using 250-kW klystrode tubes to power the RFQ. These accelerator components are prototypes for the front end of a CW linac required for an accelerator-driven transmutation linac, and they provide early confirmation of some CW accelerator components. The injector (ion source and LEBT) and emittance measuring unit are installed and operational at Los Alamos. The dc microwave ion source has been operated routinely at 50-keV, 75-mA hydrogen-ion current. This ion source has demonstrated very good discharge and H{sub 2} gas efficiencies, and sufficient reliability to complete CW RFQ measurements at CRL. Proton fraction of 75% has been measured with 550-W discharge power. This high proton fraction removes the need for an analyzing magnet. Proton LEBT emittance measurements completed at Los Alamos suggest that improved transmission through the RFQ may be achieved by increasing the solenoid focusing current. Status of the final CW RFQ operation at CRL and the installation of the RFQ at Los Alamos is given.

  14. SECOND LANGUAGE VOCABULARY ASSESSMENT: CURRENT PRACTICES AND NEW DIRECTIONS

    Directory of Open Access Journals (Sweden)

    John Read

    2007-12-01

    Full Text Available This paper surveys some current developments in second language vocabulary assessment, with particular attention to the ways in which computer corpora can provide better quality information about the frequency of words and how they are used in specific contexts. The relative merits of different word lists are discussed, including the Academic Word List and frequency lists derived from the British National Corpus. Word frequency data is needed for measures of vocabulary size, such as the Yes/No format, which is being developed and used for a variety of purposes. The paper also reviews work on testing depth of knowledge of vocabulary, where rather less progress has been made, both in defining depth as a construct and in developing tests for practical use. Another important perspective is the use of vocabulary within particular contexts of use or registers, and recent corpus research is extending our understanding of the lexical features of academic registers. This provides a basis for assessing learners’ ability to deploy their vocabulary knowledge effectively for functional communication in specific academic contexts. It is concluded that, while current tests of vocabulary knowledge are valuable for certain purposes, they need to be complemented by more contextualised measures of vocabulary use.

  15. Pediatric airway management: current practices and future directions.

    Science.gov (United States)

    Sunder, Rani A; Haile, Dawit T; Farrell, Patrick T; Sharma, Anshuman

    2012-10-01

    Management of a pediatric airway can be a challenge, especially for the non-pediatric anesthesiologists. Structured algorithms for an unexpected difficult pediatric airway have been missing so far. A recent step wise algorithm, based on the Difficult Airway society (DAS) adult protocol, is a step in the right direction. There have been some exciting advances in development of pediatric extra-glottic devices for maintaining ventilation, and introduction of pediatric versions of new 'non line of sight' laryngoscopes and optical stylets. The exact role of these devices in routine and emergent situations is still evolving. Recent advances in simulation technology has become a valuable tool in imparting psychomotor and procedural skills to trainees and allied healthcare workers. Moving toward the goal of eliminating serious adverse events during the management of routine and difficult pediatric airway, authors propose that institutions develop a dedicated Difficult Airway Service comprising of a team of experts in advanced airway management. © 2012 Blackwell Publishing Ltd.

  16. Reducing hospital readmission rates: current strategies and future directions.

    Science.gov (United States)

    Kripalani, Sunil; Theobald, Cecelia N; Anctil, Beth; Vasilevskis, Eduard E

    2014-01-01

    New financial penalties for institutions with high readmission rates have intensified efforts to reduce rehospitalization. Several interventions that involve multiple components (e.g., patient needs assessment, medication reconciliation, patient education, arranging timely outpatient appointments, and providing telephone follow-up) have successfully reduced readmission rates for patients discharged to home. The effect of interventions on readmission rates is related to the number of components implemented; single-component interventions are unlikely to reduce readmissions significantly. For patients discharged to postacute care facilities, multicomponent interventions have reduced readmissions through enhanced communication, medication safety, advanced care planning, and enhanced training to manage medical conditions that commonly precipitate readmission. To help hospitals direct resources and services to patients with greater likelihood of readmission, risk-stratification methods are available. Future work should better define the roles of home-based services, information technology, mental health care, caregiver support, community partnerships, and new transitional care personnel.

  17. [Oral medicine in Israel: Current status and future directions].

    Science.gov (United States)

    Aframian, D J; Vered, M

    2016-04-01

    The oral cavity-body relationships are bi-directional: oral diseases affect the welfare and health of the individual, while diseases and conditions of organs and tissues in the human body affect oral health. The global policy of the World Health Organization is to improve oral health in the 21st century as an integral part of promoting our general health. During the recent years the knowledge of the dental profession has grown exponentially and widened its fields of interest and this has led to impressive advances at both clinical and research levels. Oral medicine, which is a recognized, licensed specialty in Israel, is a definite example that reflects this process. In the last decade residency programs in oral medicine are in the process of constant increased demand. The authors discuss this trend and comment on the need to maintain excellence in this specialty.

  18. Relationship Education Research: Current Status and Future Directions

    Science.gov (United States)

    Markman, Howard J.; Rhoades, Galena K.

    2011-01-01

    The overarching aim of this paper is to review research on relationship education programs and approaches that have been published or accepted for publication since the last review article in 2002. This paper provides a critical overview of the relationship education field and sets an agenda for research and practice for the next decade. A theme weaved throughout the paper are the ways in which relationship education is similar and different from couples therapy and we conclude that there can be a synergistic, healthy marriage between the two. We then provide recommendations for future directions for research in the relationship education field. Finally, the co-authors comment on our experiences in both the relationship education field and couples therapy field as both researchers and interventionists. PMID:22283386

  19. Direct Current Electric Arc-Electroslag Ladle Furnace

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to solve the high consumption problem of small capacity ladle furnace (LF), the operation principle and control method of the DC arc and electroslag heating ladle furnace are introduced. With only one arcing electrode, the distance between the arc and the wall of ladle is enlarged, and consequently the consumption of the ladle refractory is decreased. In the invention, a signal electrode is embedded in the refractory lining of the ladle, which contacts directly with the liquid steel and the ladle shell. Two graphite anode ends are submerged in the slag layer. The signal electrode is used as voltage reference during refining process. The electroslag voltage between anode end and liquid steel is applied to control the depth of anode end in the slag layer during the refining process with this ladle furnace.

  20. Individualized treatment with transcranial direct current stimulation in patients with chronic nonfluent aphasia due to stroke

    Directory of Open Access Journals (Sweden)

    Priyanka eShah

    2015-04-01

    Full Text Available While evidence suggests that transcranial direct current stimulation (tDCS may facilitate language recovery in chronic post-stroke aphasia, individual variability in patient response to different patterns of stimulation remains largely unexplored. We sought to characterize this variability among chronic aphasic individuals, and to explore whether repeated stimulation with an individualized optimal montage could lead to persistent reduction of aphasia severity. In a two-phase study, we first stimulated patients with 4 active montages (left hemispheric anode or cathode; right hemispheric anode or cathode and one sham montage (Phase 1. We examined changes in picture naming ability to address 1 variability in response to different montages among our patients, and 2 whether individual patients responded optimally to at least one montage. During Phase 2, subjects who responded in Phase 1 were randomized to receive either real-tDCS or to receive sham stimulation (10 days; patients who were randomized to receive sham stimulation first were then crossed over to receive real-tDCS (10 days. In both phases, 2mA tDCS was administered for 20 minutes per real-tDCS sessions and patients performed a picture naming task during stimulation. Patients’ language ability was re-tested after 2-weeks and 2-months following real and sham tDCS in Phase 2.In Phase 1, despite considerable individual variability, the greatest average improvement was observed after left-cathodal stimulation. Seven out of 12 subjects responded optimally to at least 1 montage as demonstrated by transient improvement in picture-naming. In Phase 2, aphasia severity improved at 2-weeks and 2-months following real-tDCS but not sham.Despite individual variability with respect to optimal tDCS approach, certain montages result in consistent transient improvement in persons with chronic post-stroke aphasia. This preliminary study supports the notion that individualized tDCS treatment may enhance

  1. The Optimal Taxation and the Current Tax System

    OpenAIRE

    Ioannis N. Kallianiotis

    2015-01-01

    Purpose:The paper discusses the current U.S. tax system, which reduces the disposable income and makes savings negative (dissaving or borrowing). This has increased the debt of individuals and the low taxes on businesses have magnified the budget deficits and the national debt. Methodology:People are borrowing the present value of their uncertain future wealth and their high debt and low income raise the risk and this high risk premium heighten the interest rate on loans, especially on credit...

  2. Perfectionism and eating disorders: current status and future directions.

    Science.gov (United States)

    Bardone-Cone, Anna M; Wonderlich, Stephen A; Frost, Randy O; Bulik, Cynthia M; Mitchell, James E; Uppala, Saritha; Simonich, Heather

    2007-04-01

    The literature examining the relation between perfectionism and eating disorders was reviewed and content and methodological comparisons were made with the perfectionism literature in anxiety disorders and depressive disorders. A PsychInfo search using the key words "perfectionism/perfect/perfectionistic," "anorexia," "bulimia," and "eating disorders" was performed and the generated list of papers was supplemented based on a review of reference lists in the papers. A total of 55 papers published between 1990 and 2005 were identified that assessed perfectionism among individuals with diagnosed eating disorders. The key research questions were distilled from these publications and empirical findings were summarized for each question, followed by a comparison with perfectionism papers in the anxiety and depressive disorder literatures. Also, key research design methodological parameters were identified and comparisons made across the three literatures: eating disorders, anxiety disorders, depressive disorders. The current review concludes with conceptual and methodological recommendations for researchers interested in perfectionism and eating disorders.

  3. Transformational leadership in sport: current status and future directions.

    Science.gov (United States)

    Arthur, Calum A; Bastardoz, Nicolas; Eklund, Robert

    2017-08-01

    Borrowed from organizational psychology, the concept of transformational leadership has now been applied to a sport context for a decade. Our review covers and critically discusses empirical articles published on this growing topic. However, because the majority of studies used cross-sectional designs and single-source questionnaires to tap what has been a fuzzy construct, current theoretical and methodological issues impede understanding of whether transformational leadership matters for sport outcomes. To make a difference to applied practice and policy, the transformational leadership construct requires a refined definition and stronger empirical tests allowing for robust causal inference. We highlight avenues for advancing research on transformational leadership in the sport context. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  4. Female sex trafficking: conceptual issues, current debates, and future directions.

    Science.gov (United States)

    Meshkovska, Biljana; Siegel, Melissa; Stutterheim, Sarah E; Bos, Arjan E R

    2015-01-01

    Female sex trafficking is a pressing concern. In this article, we provide a comprehensive overview of relevant issues regarding the concept of female sex trafficking and research in the field of human trafficking, drawing on a variety of disciplines, including economics, gender and sexuality studies, psychology, sociology, law, and social work. We discuss the debates surrounding the definition of human trafficking, compare and contrast it with human smuggling, and outline connections between female sex trafficking and the issue of sex work and prostitution. We further discuss the history and current estimations of female sex trafficking. We then outline the main actors in female sex trafficking, including trafficked persons, traffickers, clients, and service providers, and we overview the trafficking process from recruitment to identification, recovery, and (re)integration. Finally, we conclude with recommendations for future research that tie together the concepts of vulnerability, exploitation, and long-term recovery and (re)integration.

  5. Cyberbullying Prevention and Intervention Efforts: Current Knowledge and Future Directions.

    Science.gov (United States)

    Espelage, Dorothy L; Hong, Jun Sung

    2017-06-01

    Bullying is a serious public health concern that is associated with significant negative mental, social, and physical outcomes. Technological advances have increased adolescents' use of social media, and online communication platforms have exposed adolescents to another mode of bullying- cyberbullying. Prevention and intervention materials, from websites and tip sheets to classroom curriculum, have been developed to help youth, parents, and teachers address cyberbullying. While youth and parents are willing to disclose their experiences with bullying to their health care providers, these disclosures need to be taken seriously and handled in a caring manner. Health care providers need to include questions about bullying on intake forms to encourage these disclosures. The aim of this article is to examine the current status of cyberbullying prevention and intervention. Research support for several school-based intervention programs is summarised. Recommendations for future research are provided.

  6. Perturbation of blood flow as a mechanism of anti-tumour action of direct current electrotherapy.

    Science.gov (United States)

    Jarm, Tomaz; Cemazar, Maja; Steinberg, Fritz; Streffer, Christian; Sersa, Gregor; Miklavcic, Damijan

    2003-02-01

    Anti-tumour effects of direct current electrotherapy are attributed to different mechanisms depending on the electrode configuration and on the parameters of electric current. The effects mostly arise from the electrochemical products of electrolysis. Direct toxicity of these products to tumour tissue is, however, not a plausible explanation for the observed tumour growth retardation in the case when the electrodes are placed into healthy tissue surrounding the tumour and not into the tumour itself. The hypothesis that the anti-tumour effectiveness of electrotherapy could result from disturbed blood flow in tumours was tested by the measurement of changes in blood perfusion and oxygenation in tumours with three different methods (in vivo tissue staining with Patent Blue Violet dye, polarographic oximetry, near-infrared spectroscopy). The effects induced by electrotherapy were evaluated in two experimental tumour models: Sa-1 fibrosarcoma in A/J mice and LPB fibrosarcoma in C57B1/6 mice. We found that perfusion and oxygenation were significantly decreased after electrotherapy. Good agreement between the results of different methods was observed. The effect of electrotherapy on local perfusion of tumours is probably the prevalent mechanism of anti-tumour action for the particular type of electrotherapy used in the study. The importance of this effect should be considered for the optimization of electrotherapy protocols in experimental and clinical trials. The non-invasive technique of near-infrared spectroscopy proved to be a reliable method for detecting perfusion and oxygenation changes in small solid tumours.

  7. Computing at DESY — current setup, trends and strategic directions

    Science.gov (United States)

    Ernst, Michael

    1998-05-01

    Since the HERA experiments H1 and ZEUS started data taking in '92, the computing environment at DESY has changed dramatically. Running a mainframe centred computing for more than 20 years, DESY switched to a heterogeneous, fully distributed computing environment within only about two years in almost every corner where computing has its applications. The computing strategy was highly influenced by the needs of the user community. The collaborations are usually limited by current technology and their ever increasing demands is the driving force for central computing to always move close to the technology edge. While DESY's central computing has a multidecade experience in running Central Data Recording/Central Data Processing for HEP experiments, the most challenging task today is to provide for clear and homogeneous concepts in the desktop area. Given that lowest level commodity hardware draws more and more attention, combined with the financial constraints we are facing already today, we quickly need concepts for integrated support of a versatile device which has the potential to move into basically any computing area in HEP. Though commercial solutions, especially addressing the PC management/support issues, are expected to come to market in the next 2-3 years, we need to provide for suitable solutions now. Buying PC's at DESY currently at a rate of about 30/month will otherwise absorb any available manpower in central computing and still will leave hundreds of unhappy people alone. Though certainly not the only region, the desktop issue is one of the most important one where we need HEP-wide collaboration to a large extent, and right now. Taking into account that there is traditionally no room for R&D at DESY, collaboration, meaning sharing experience and development resources within the HEP community, is a predominant factor for us.

  8. Current issues and future directions in pyrolysis of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Preto, F. [Natural Resources Canada, Ottawa, ON (Canada). CANMET Energy Technology Centre

    2005-02-01

    Biomass is a diverse grouping of low energy content, low density and high moisture heterogenous materials. An overview of pyrolysis processes and procedures was presented with a list of potential applications for industrial processes and power generation. The chemical energy content of various fuels was presented and with the advantages of pyrolysis with reference to improved transport, handling and storage. Details of technical requirements were outlined along with some of the undesirable characteristics of biofuel including the highly corrosive nature of the fuel, pungency, high solids content, immiscibility with hydrocarbon fuels and the fact that over time, chemical composition shifts, resulting in increased viscosity and decreased volatility. Various issues concerning pyrolysis regarding current technologies, composition and standards, applications and biorefinery feedstock were summarized. A flow chart presenting the conversion of biomass to biofuel was provided. Various reactor types were also overviewed and included such as fluidized beds, transport, heated augers, vacuum pyrolysis and ablative and rotating cones. Details of pilot plants in Erie and Renfrew, Ontario were provided along with details of a plant in Alabama operating entirely on chicken litter. Various specifications for pyrolysis oils were presented. A chart of biofuel composition in mass fractions was provided, with an accompanying list of commonly quoted pyrolysis oil properties. A series of biofuel combustion tests conducted at CANMET Energy Technology Centre (CETC) in Ottawa were described. Photographs of the pre-test refractory were exhibited. Details of current research on drying kiln applications were outlined. The suitability of pyrolytic biofuel for producing microemulsion fuels was discussed. A biorefinery model was included. Challenges to biomass pyrolysis include feed preparation, scale-up issues, heat transfer to reactor rates, char separation, liquid collection, liquid quality

  9. Current and future directions for treating hepatitis B virusinfection

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    Hepatitis B virus (HBV) persistently infects approximately350 million people, and approximately 600000 liverrelateddeaths are observed per year worldwide.HBV infection is also one of the major risk factors forhepatocellular carcinoma (HCC). The persistence ofserum hepatitis B e antigen (HBeAg) and high levelof serum HBV DNA are thought to reflect a high HBVreplication status in hepatocytes, causing cirrhosis,HCC and liver-related deaths. It has been reported thatantiviral therapy, such as peginterferon and nucleos(t)ideanalogues (NUCs), could suppress liver-relateddeath by inhibiting the HBV DNA levels and inducingseroconversion from HBeAg to antibody to HBe antigen.Currently, peginterferon is widely used, but there arealso several disadvantages in the use of peginterferon,such as various adverse events, the administrationroute and duration. It is difficult to predict the effectsof treatment and interferon is contraindicated for thepatients with advanced fibrosis of the liver and cirrhosis.With respect to NUCs, entecavir and tenofovir disoproxilfumarate are current the first-choice drugs. NUCs canbe administered orally, and their anti-viral effects arestronger than that of peginterferon. However, becausecessation of NUC administration leads to high levels ofviral replication and causes severe hepatitis, they mustbe administered for a long time. On the other hand,the use of both interferon and NUCs cannot eliminatecovalently closed circular DNA of HBV. In this review, weevaluate the natural course of chronic HBV infection andthen provide an outline of these representative drugs,such as peginterferon, entecavir and tenofovir disoproxilfumarate.

  10. Capnography during cardiopulmonary resuscitation: Current evidence and future directions

    Directory of Open Access Journals (Sweden)

    Bhavani Shankar Kodali

    2014-01-01

    Full Text Available Capnography continues to be an important tool in measuring expired carbon dioxide (CO 2 . Most recent Advanced Cardiac Life Support (ACLS guidelines now recommend using capnography to ascertain the effectiveness of chest compressions and duration of cardiopulmonary resuscitation (CPR. Based on an extensive review of available published literature, we selected all available peer-reviewed research investigations and case reports. Available evidence suggests that there is significant correlation between partial pressure of end-tidal CO 2 (PETCO 2 and cardiac output that can indicate the return of spontaneous circulation (ROSC. Additional evidence favoring the use of capnography during CPR includes definitive proof of correct placement of the endotracheal tube and possible prediction of patient survival following cardiac arrest, although the latter will require further investigations. There is emerging evidence that PETCO 2 values can guide the initiation of extracorporeal life support (ECLS in refractory cardiac arrest (RCA. There is also increasing recognition of the value of capnography in intensive care settings in intubated patients. Future directions include determining the outcomes based on capnography waveforms PETCO 2 values and determining a reasonable duration of CPR. In the future, given increasing use of capnography during CPR large databases can be analyzed to predict outcomes.

  11. Direct Laser Cladding , Current Status and Future Scope of Application

    Science.gov (United States)

    Weisheit, A.; Gasser, A.; Backes, G.; Jambor, T.; Pirch, N.; Wissenbach, K.

    During the last decades Direct Laser Cladding has become an established technique in many industrial fields for applying wear and corrosion protection layers on metallic surfaces as well as for the repair of high value-added components. The most important application fields are die and tool making, turbine components for aero engines and power generation, machine components such as axes and gears, and oil drilling components. Continuous wave (CW) lasers with a power up to 18 kW are used on automated machines with three or more axes, enabling 3D cladding . The outstanding feature of DLC is the high precision which leads to a minimum heat input into the work piece and a very low distortion. Due to the high cooling rates a fine grained microstructure is achieved during solidification. A new development in laser cladding is micro cladding in a size range below 50 \\upmum especially for electronic and medical applications. Furthermore, additive manufacturing is coming again into focus as a clean and resource-efficient method to manufacture and modify functional prototypes as well as unique and small lot parts.

  12. Diabetic peripheral neuropathy: current perspective and future directions.

    Science.gov (United States)

    Singh, Randhir; Kishore, Lalit; Kaur, Navpreet

    2014-02-01

    Diabetic neuropathy is a heterogeneous group of disorders with extremely complex pathophysiology and affects both somatic and autonomic components of the nervous system. Neuropathy is the most common chronic complication of diabetes mellitus. Metabolic disruptions in the peripheral nervous system, including altered protein kinase C activity, and increased polyol pathway activity in neurons and Schwann cells resulting from hyperglycemia plays a key role in the development of diabetic neuropathy. These pathways are related to the metabolic and/or redox state of the cell and are the major source of damage. Activation of these metabolic pathways leads to oxidative stress, which is a mediator of hyperglycemia induced cell injury and a unifying theme for all mechanisms of diabetic neuropathy. The therapeutic intervention of these metabolic pathways is capable of ameliorating diabetic neuropathy but therapeutics which target one particular mechanism may have a limited success. Available therapeutic approaches are based upon the agents that modulate pathogenetic mechanisms (glycemic control) and relieve the symptoms of diabetic neuropathy. This review emphasizes the pathogenesis, presently available therapeutic approaches and future directions for the management of diabetic neuropathy.

  13. Current status and future directions of pharmacological therapy for acromegaly.

    Science.gov (United States)

    Mercado, Moisés; Espinosa, Etual; Ramírez, Claudia

    2016-09-01

    Acromegaly is a chronic systemic disorder caused in the vast majority of cases by a GH-secreting pituitary adenoma and resulting in significant morbidity and mortality if left untreated. The treatment of choice is the trans-sphenoidal resection of the adenoma, and although 80% of patients with microadenomas or confined macroadenomas achieve biochemical remission, the surgical success rate for patients harboring tumors with extrasellar extension is below 50%. Thus, a considerable proportion of patients will require some form of adjuvant treatment. Acromegaly can be approached pharmacologically by inhibiting GH secretion by the tumor (somatostatin analogues, dopamine agonists) or by antagonizing GH actions at its target tissues (GH receptor antagonists). The primary pharmacological treatment of acromegaly is increasingly gaining acceptance by both physicians and patients. The decision to use primary pharmacological treatment has to take into account the clinical characteristics of the patient (presence of comorbidities that significantly increase the surgical risk) and the biological nature of the adenoma (tumor size and location), as well as other aspects such as the availability of a pituitary surgeon and the cost of medications. This review provides a critical summary and update of the pharmacological treatment of acromegaly focusing both, on well-established agents and strategies as well as on novel compounds that are currently being developed.

  14. Precision therapy for lymphoma--current state and future directions.

    Science.gov (United States)

    Intlekofer, Andrew M; Younes, Anas

    2014-10-01

    Modern advances in genomics and cancer biology have produced an unprecedented body of knowledge regarding the molecular pathogenesis of lymphoma. The diverse histological subtypes of lymphoma are molecularly heterogeneous, and most likely arise from distinct oncogenic mechanisms. In parallel to these advances in lymphoma biology, several new classes of molecularly targeted agents have been developed with varying degrees of efficacy across the different types of lymphoma. In general, the development of new drugs for treating lymphoma has been mostly empiric, with a limited knowledge of the molecular target, its involvement in the disease, and the effect of the drug on the target. Thus, the variability observed in clinical responses likely results from underlying molecular heterogeneity. In the era of personalized medicine, the challenge for the treatment of patients with lymphoma will involve correctly matching a molecularly targeted therapy to the unique genetic and molecular composition of each individual lymphoma. In this Review, we discuss current and emerging biomarkers that can guide treatment decisions for patients with lymphoma, and explore the potential challenges and strategies for making biomarker-driven personalized medicine a reality in the cure and management of this disease.

  15. The Evolution of Process Safety: Current Status and Future Direction.

    Science.gov (United States)

    Mannan, M Sam; Reyes-Valdes, Olga; Jain, Prerna; Tamim, Nafiz; Ahammad, Monir

    2016-06-01

    The advent of the industrial revolution in the nineteenth century increased the volume and variety of manufactured goods and enriched the quality of life for society as a whole. However, industrialization was also accompanied by new manufacturing and complex processes that brought about the use of hazardous chemicals and difficult-to-control operating conditions. Moreover, human-process-equipment interaction plus on-the-job learning resulted in further undesirable outcomes and associated consequences. These problems gave rise to many catastrophic process safety incidents that resulted in thousands of fatalities and injuries, losses of property, and environmental damages. These events led eventually to the necessity for a gradual development of a new multidisciplinary field, referred to as process safety. From its inception in the early 1970s to the current state of the art, process safety has come to represent a wide array of issues, including safety culture, process safety management systems, process safety engineering, loss prevention, risk assessment, risk management, and inherently safer technology. Governments and academic/research organizations have kept pace with regulatory programs and research initiatives, respectively. Understanding how major incidents impact regulations and contribute to industrial and academic technology development provides a firm foundation to address new challenges, and to continue applying science and engineering to develop and implement programs to keep hazardous materials within containment. Here the most significant incidents in terms of their impact on regulations and the overall development of the field of process safety are described.

  16. Microorganisms in Fermented Apple Beverages: Current Knowledge and Future Directions.

    Science.gov (United States)

    Cousin, Fabien J; Le Guellec, Rozenn; Schlusselhuber, Margot; Dalmasso, Marion; Laplace, Jean-Marie; Cretenet, Marina

    2017-07-25

    Production of fermented apple beverages is spread all around the world with specificities in each country. 'French ciders' refer to fermented apple juice mainly produced in the northwest of France and often associated with short periods of consumption. Research articles on this kind of product are scarce compared to wine, especially on phenomena associated with microbial activities. The wine fermentation microbiome and its dynamics, organoleptic improvement for healthy and pleasant products and development of starters are now widely studied. Even if both beverages seem close in terms of microbiome and process (with both alcoholic and malolactic fermentations), the inherent properties of the raw materials and different production and environmental parameters make research on the specificities of apple fermentation beverages worthwhile. This review summarizes current knowledge on the cider microbial ecosystem, associated activities and the influence of process parameters. In addition, available data on cider quality and safety is reviewed. Finally, we focus on the future role of lactic acid bacteria and yeasts in the development of even better or new beverages made from apples.

  17. Phocine Distemper Virus: Current Knowledge and Future Directions

    Directory of Open Access Journals (Sweden)

    Pádraig J. Duignan

    2014-12-01

    Full Text Available Phocine distemper virus (PDV was first recognized in 1988 following a massive epidemic in harbor and grey seals in north-western Europe. Since then, the epidemiology of infection in North Atlantic and Arctic pinnipeds has been investigated. In the western North Atlantic endemic infection in harp and grey seals predates the European epidemic, with relatively small, localized mortality events occurring primarily in harbor seals. By contrast, PDV seems not to have become established in European harbor seals following the 1988 epidemic and a second event of similar magnitude and extent occurred in 2002. PDV is a distinct species within the Morbillivirus genus with minor sequence variation between outbreaks over time. There is now mounting evidence of PDV-like viruses in the North Pacific/Western Arctic with serological and molecular evidence of infection in pinnipeds and sea otters. However, despite the absence of associated mortality in the region, there is concern that the virus may infect the large Pacific harbor seal and northern elephant seal populations or the endangered Hawaiian monk seals. Here, we review the current state of knowledge on PDV with particular focus on developments in diagnostics, pathogenesis, immune response, vaccine development, phylogenetics and modeling over the past 20 years.

  18. Phocine distemper virus: current knowledge and future directions.

    Science.gov (United States)

    Duignan, Pádraig J; Van Bressem, Marie-Françoise; Baker, Jason D; Barbieri, Michelle; Colegrove, Kathleen M; De Guise, Sylvain; de Swart, Rik L; Di Guardo, Giovanni; Dobson, Andrew; Duprex, W Paul; Early, Greg; Fauquier, Deborah; Goldstein, Tracey; Goodman, Simon J; Grenfell, Bryan; Groch, Kátia R; Gulland, Frances; Hall, Ailsa; Jensen, Brenda A; Lamy, Karina; Matassa, Keith; Mazzariol, Sandro; Morris, Sinead E; Nielsen, Ole; Rotstein, David; Rowles, Teresa K; Saliki, Jeremy T; Siebert, Ursula; Waltzek, Thomas; Wellehan, James F X

    2014-12-22

    Phocine distemper virus (PDV) was first recognized in 1988 following a massive epidemic in harbor and grey seals in north-western Europe. Since then, the epidemiology of infection in North Atlantic and Arctic pinnipeds has been investigated. In the western North Atlantic endemic infection in harp and grey seals predates the European epidemic, with relatively small, localized mortality events occurring primarily in harbor seals. By contrast, PDV seems not to have become established in European harbor seals following the 1988 epidemic and a second event of similar magnitude and extent occurred in 2002. PDV is a distinct species within the Morbillivirus genus with minor sequence variation between outbreaks over time. There is now mounting evidence of PDV-like viruses in the North Pacific/Western Arctic with serological and molecular evidence of infection in pinnipeds and sea otters. However, despite the absence of associated mortality in the region, there is concern that the virus may infect the large Pacific harbor seal and northern elephant seal populations or the endangered Hawaiian monk seals. Here, we review the current state of knowledge on PDV with particular focus on developments in diagnostics, pathogenesis, immune response, vaccine development, phylogenetics and modeling over the past 20 years.

  19. Phocine Distemper Virus: Current Knowledge and Future Directions

    Science.gov (United States)

    Duignan, Pádraig J.; Van Bressem, Marie-Françoise; Baker, Jason D.; Barbieri, Michelle; Colegrove, Kathleen M.; De Guise, Sylvain; de Swart, Rik L.; Di Guardo, Giovanni; Dobson, Andrew; Duprex, W. Paul; Early, Greg; Fauquier, Deborah; Goldstein, Tracey; Goodman, Simon J.; Grenfell, Bryan; Groch, Kátia R.; Gulland, Frances; Hall, Ailsa; Jensen, Brenda A.; Lamy, Karina; Matassa, Keith; Mazzariol, Sandro; Morris, Sinead E.; Nielsen, Ole; Rotstein, David; Rowles, Teresa K.; Saliki, Jeremy T.; Siebert, Ursula; Waltzek, Thomas; Wellehan, James F.X.

    2014-01-01

    Phocine distemper virus (PDV) was first recognized in 1988 following a massive epidemic in harbor and grey seals in north-western Europe. Since then, the epidemiology of infection in North Atlantic and Arctic pinnipeds has been investigated. In the western North Atlantic endemic infection in harp and grey seals predates the European epidemic, with relatively small, localized mortality events occurring primarily in harbor seals. By contrast, PDV seems not to have become established in European harbor seals following the 1988 epidemic and a second event of similar magnitude and extent occurred in 2002. PDV is a distinct species within the Morbillivirus genus with minor sequence variation between outbreaks over time. There is now mounting evidence of PDV-like viruses in the North Pacific/Western Arctic with serological and molecular evidence of infection in pinnipeds and sea otters. However, despite the absence of associated mortality in the region, there is concern that the virus may infect the large Pacific harbor seal and northern elephant seal populations or the endangered Hawaiian monk seals. Here, we review the current state of knowledge on PDV with particular focus on developments in diagnostics, pathogenesis, immune response, vaccine development, phylogenetics and modeling over the past 20 years. PMID:25533658

  20. Current perspectives of the signaling pathways directing neural crest induction.

    Science.gov (United States)

    Stuhlmiller, Timothy J; García-Castro, Martín I

    2012-11-01

    The neural crest is a migratory population of embryonic cells with a tremendous potential to differentiate and contribute to nearly every organ system in the adult body. Over the past two decades, an incredible amount of research has given us a reasonable understanding of how these cells are generated. Neural crest induction involves the combinatorial input of multiple signaling pathways and transcription factors, and is thought to occur in two phases from gastrulation to neurulation. In the first phase, FGF and Wnt signaling induce NC progenitors at the border of the neural plate, activating the expression of members of the Msx, Pax, and Zic families, among others. In the second phase, BMP, Wnt, and Notch signaling maintain these progenitors and bring about the expression of definitive NC markers including Snail2, FoxD3, and Sox9/10. In recent years, additional signaling molecules and modulators of these pathways have been uncovered, creating an increasingly complex regulatory network. In this work, we provide a comprehensive review of the major signaling pathways that participate in neural crest induction, with a focus on recent developments and current perspectives. We provide a simplified model of early neural crest development and stress similarities and differences between four major model organisms: Xenopus, chick, zebrafish, and mouse.

  1. Alcohol and NMDA Receptor: Current research and future direction

    Directory of Open Access Journals (Sweden)

    Raman eChandrasekar

    2013-05-01

    Full Text Available The brain is one of the major targets of alcohol actions. Most of the excitatory synaptic transmission in the central nervous system is mediated by NMDA receptors. However, one of the most devastating effects of alcohol leads to brain shrinkage, loss of nerve cells at specific regions through a mechanism involving excitotoxicity, oxidative stress. Earlier studies have indicated that chronic exposure to ethanol both in vivo and in vitro, increases NR1 and NR2B gene expression and their polypeptide levels. The effect of alcohol and molecular changes on the regulatory process, which modulates NMDAR functions including factors altering transcription, translation, post-translational modifications and protein expression, as well as those influencing their interactions with different regulatory proteins (downstream effectors are incessantly increasing at the cellular level. Further, I discuss the various genetically altered mice approaches that have been used to study NMDA receptor subunits and their functional implication. In a recent countable review, epigenetic dimension (i.e., histone modification-induced chromatin remodeling and DNA methylation, in the process of alcohol related neuroadapation is one of the key molecular mechanisms in alcohol mediated NMDAR alteration. Here, I provide a recount on what has already been achieved, current trends and how the future research/studies of the NMDA receptor might lead to even greater engagement with many possible new insights into the neurobiology and treatment of alcoholism.

  2. Alcohol and NMDA receptor: current research and future direction.

    Science.gov (United States)

    Chandrasekar, Raman

    2013-01-01

    The brain is one of the major targets of alcohol actions. Most of the excitatory synaptic transmission in the central nervous system is mediated by N-methyl-D-aspartate (NMDA) receptors. However, one of the most devastating effects of alcohol leads to brain shrinkage, loss of nerve cells at specific regions through a mechanism involving excitotoxicity, oxidative stress. Earlier studies have indicated that chronic exposure to ethanol both in vivo and in vitro, increases NR1 and NR2B gene expression and their polypeptide levels. The effect of alcohol and molecular changes on the regulatory process, which modulates NMDAR functions including factors altering transcription, translation, post-translational modifications, and protein expression, as well as those influencing their interactions with different regulatory proteins (downstream effectors) are incessantly increasing at the cellular level. Further, I discuss the various genetically altered mice approaches that have been used to study NMDA receptor subunits and their functional implication. In a recent countable review, epigenetic dimension (i.e., histone modification-induced chromatin remodeling and DNA methylation, in the process of alcohol related neuroadaptation) is one of the key molecular mechanisms in alcohol mediated NMDAR alteration. Here, I provide a recount on what has already been achieved, current trends and how the future research/studies of the NMDA receptor might lead to even greater engagement with many possible new insights into the neurobiology and treatment of alcoholism.

  3. Brain tumors in children--current therapies and newer directions.

    Science.gov (United States)

    Khatua, Soumen; Sadighi, Zsila Sousan; Pearlman, Michael L; Bochare, Sunil; Vats, Tribhawan S

    2012-07-01

    Brain tumors are the second most common malignancy and the major cause of cancer related mortality in children. Though significant advances in neuroimaging, neurosurgery, radiation therapy and chemotherapy have evolved over the years, overall survival rate remains less than 75%. Malignant gliomas, high risk medulloblastoma with recurrence and infant brain tumors continue to be a major cause of therapeutic frustration. Even today diffuse pontine gliomas are universally fatal. Though tumors like low grade glioma have an overall excellent survival, recurrences and progression in eloquent areas pose therapeutic challenges. As research continues to unravel the biology including key molecules and signaling pathways responsible for the oncogenesis of different childhood brain tumors, novel targeted therapies are profiled. Identification of major targets like the Epidermal Growth factor Receptor (EGFR), Platelet Derived Growth Factor Receptor (PDGFR), Vascular Endothelial Growth factor (VEGF) and key signaling pathways like the MAPK and PI3K/Akt/mTOR has enabled us over the recent years to better understand tumor behavior and design tailored therapy. These efforts have improved overall survival of children with brain tumors. This review article discusses the current status of common brain tumors in children and the newer therapeutic approaches.

  4. Current directions in screening-level ecological risk assessments

    Energy Technology Data Exchange (ETDEWEB)

    Carlsen, T M; Efroymson, R A

    2000-12-11

    Ecological risk assessment (ERA) is a tool used by many regulatory agencies to evaluate the impact to ecological receptors from changes in environmental conditions. Widespread use of ERAs began with the United States Environmental Protection Agency's Superfund program to assess the ecological impact from hazardous chemicals released to the environment. Many state hazardous chemical regulatory agencies have adopted the use of ERAs, and several state regulatory agencies are evaluating the use of ERAs to assess ecological impacts from releases of petroleum and gas-related products. Typical ERAs are toxicologically-based, use conservative assumptions with respect to ecological receptor exposure duration and frequency, often require complex modeling of transport and exposure and are very labor intensive. In an effort to streamline the ERA process, efforts are currently underway to develop default soil screening levels, to identify ecological screening criteria for excluding sites from formal risk assessment, and to create risk-based corrective action worksheets. This should help reduce the time spent on ERAs, at least for some sites. Work is also underway to incorporate bioavailability and spatial considerations into ERAs. By evaluating the spatial nature of contaminant releases with respect to the spatial context of the ecosystem under consideration, more realistic ERAs with respect to the actual impact to ecological receptors at the population, community or ecosystem scale should be possible. In addition, by considering the spatial context, it should be possible to develop mitigation and monitoring efforts to more appropriately address such sites within the context of an ecological framework.

  5. Is transcranial direct current stimulation a potential method for improving response inhibition?

    Science.gov (United States)

    Kwon, Yong Hyun; Kwon, Jung Won

    2013-04-15

    Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments. This study used a stop-signal task to determine whether transcranial direct-current stimulation over the pre-supplementary motor area alters the reaction time in motor inhibition. Forty healthy subjects were recruited for this study and were randomly assigned to either the transcranial direct-current stimulation condition or a sham-transcranial direct-current stimulation condition. All subjects consecutively performed the stop-signal task before, during, and after the delivery of anodal transcranial direct-current stimulation over the pre-supplementary motor area (pre-transcranial direct-current stimulation phase, transcranial direct-current stimulation phase, and post-transcranial direct-current stimulation phase). Compared to the sham condition, there were significant reductions in the stop-signal processing times during and after transcranial direct-current stimulation, and change times were significantly greater in the transcranial direct-current stimulation condition. There was no significant change in go processing-times during or after transcranial direct-current stimulation in either condition. Anodal transcranial direct-current stimulation was feasibly coupled to an interactive improvement in inhibitory control. This coupling led to a decrease in the stop-signal process time required for the appropriate responses between motor execution and inhibition. However, there was no transcranial direct-current stimulation effect on the no-signal reaction time during the stop-signal task. Transcranial direct-current stimulation can adjust certain behaviors, and it could be a useful clinical intervention for patients who have difficulties with response inhibition.

  6. Is transcranial direct current stimulation a potential method for improving response inhibition?

    Institute of Scientific and Technical Information of China (English)

    Yong Hyun Kwon; Jung Won Kwon

    2013-01-01

    Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments. This study used a stop-signal task to determine whether transcranial direct-current stimulation over the pre-supplementary motor area alters the reaction time in motor inhibition. Forty healthy subjects were recruited for this study and were randomly assigned to either the transcranial direct-current stimulation condition or a sham-transcranial direct-current stimulation condition. All subjects consecutively performed the stop-signal task before, during, and after the delivery of anodal transcranial direct-current stimulation over the pre-supplementary motor area (pre-transcranial direct-current stimulation phase, transcranial direct-current stimulation phase, and post-transcranial direct-current stimulation phase). Compared to the sham condition, there were significant reductions in the stop-signal processing times during and after transcranial direct-current stimulation, and change times were significantly greater in the transcranial direct-current stimulation condition. There was no significant change in go processing-times during or after transcranial direct-current stimulation in either condition. Anodal transcranial direct-current stimulation was feasibly coupled to an interactive improvement in inhibitory control. This coupling led to a decrease in the stop-signal process time required for the appropriate responses between motor execution and inhibition. However, there was no transcranial direct-current stimulation effect on the no-signal reaction time during the stop-signal task. Transcranial direct-current stimulation can adjust certain behaviors, and it could be a useful clinical intervention for patients who have difficulties with response inhibition.

  7. Design and optimization of a flexible arrayed eddy current sensor

    Science.gov (United States)

    Sun, Zhenguo; Cai, Dong; Zou, Cheng; Zhang, Wenzeng; Chen, Qiang

    2017-04-01

    The inspection of the hollow axle inner surfaces is a key process to guarantee the safety of high-speed trains. A novel flexible arrayed eddy current sensor was developed to improve the reliability of the non-destructive testing of the hollow axle inner surfaces, whose main innovative aspect was the new design of excitation/sensing traces to achieve a differential and arrayed configuration. Only two independent excitation traces were used in the sensor to induce eddy currents, which can be detected by 16 differential sensing elements. The lift-off effects and the influence of the excitation frequency and geometrical parameters of the proposed sensor was investigated and presented in this paper. Finite element models were built to analyze the effects of each parameter on the sensor response amplitude. Experimental validations were conducted using a representative set of sensors. Results from experiments and simulations were consistent with each other, which showed that the sensor design can substantially suppress the lift-off effects and modifications of the studied parameters can substantially improve the sensor performance.

  8. Munchausen by Internet: Current Research and Future Directions

    Science.gov (United States)

    Taylor, Jacqui

    2012-01-01

    about their health in the online environment. We also suggest directions for future research. PMID:22914203

  9. Argon metastable dynamics and lifetimes in a direct current microdischarge

    Science.gov (United States)

    Stefanović, Ilija; Kuschel, Thomas; Schröter, Sandra; Böke, Marc

    2014-09-01

    In this paper we study the properties of a pulsed dc microdischarge with the continuous flow of argon. Argon metastable lifetimes are measured by tunable diode laser absorption spectroscopy (TDLAS) and are compared with calculated values which yield information about excitation and de-excitation processes. By increasing the gas flow-rate about 5 times from 10 to 50 sccm, the Arm lifetime increases from 1 to 5 μs due to the reduction of metastable quenching with gas impurities. Optical emission spectroscopy reveals nitrogen and water molecules as the main gas impurities. The estimated N2 density [N2] = 0.1% is too low to explain the measured metastable lifetimes. Water impurity was found to be the main de-excitation source of argon metastable atoms due to high quenching coefficients. The water impurity level of [H2O] = 0.15% to 1% is sufficient to bring calculated metastable lifetimes in line with experiments. The maximum value of water content in the discharge compared to the argon atoms is estimated to approximately 6%, due to the large surface to volume ratio of the microdischarge. The current pulse releases the water molecules from the electrode surface and they are either re-adsorbed in the time between 0.4 ms for [H2O] = 1% and 2.6 ms for [H2O] = 0.15% or pumped out of the discharge with the speed equal to the gas flow-rate. Depending on its partial pressure, the water impurity re-adsorption time is of the order of magnitude or less then the argon gas residence time.

  10. Argon metastable dynamics and lifetimes in a direct current microdischarge

    Energy Technology Data Exchange (ETDEWEB)

    Stefanović, Ilija [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kuschel, Thomas; Schröter, Sandra; Böke, Marc [Ruhr-Universität Bochum, Institute for Experimental Physics II, Universitätsstraße 150, 44780 Bochum (Germany)

    2014-09-21

    In this paper we study the properties of a pulsed dc microdischarge with the continuous flow of argon. Argon metastable lifetimes are measured by tunable diode laser absorption spectroscopy (TDLAS) and are compared with calculated values which yield information about excitation and de-excitation processes. By increasing the gas flow-rate about 5 times from 10 to 50 sccm, the Ar{sup m} lifetime increases from 1 to 5 μs due to the reduction of metastable quenching with gas impurities. Optical emission spectroscopy reveals nitrogen and water molecules as the main gas impurities. The estimated N₂ density [N₂]=0.1% is too low to explain the measured metastable lifetimes. Water impurity was found to be the main de-excitation source of argon metastable atoms due to high quenching coefficients. The water impurity level of [H₂O]=0.15% to 1% is sufficient to bring calculated metastable lifetimes in line with experiments. The maximum value of water content in the discharge compared to the argon atoms is estimated to approximately 6%, due to the large surface to volume ratio of the microdischarge. The current pulse releases the water molecules from the electrode surface and they are either re-adsorbed in the time between 0.4 ms for [H₂O]=1% and 2.6 ms for [H₂O]=0.15% or pumped out of the discharge with the speed equal to the gas flow-rate. Depending on its partial pressure, the water impurity re-adsorption time is of the order of magnitude or less then the argon gas residence time.

  11. Systemic Immunotherapy for Urothelial Cancer: Current Trends and Future Directions.

    Science.gov (United States)

    Gupta, Shilpa; Gill, David; Poole, Austin; Agarwal, Neeraj

    2017-01-27

    Urothelial cancer of the bladder, renal pelvis, ureter, and other urinary organs is the fifth most common cancer in the United States, and systemic platinum-based chemotherapy remains the standard of care for first-line treatment of advanced/metastatic urothelial carcinoma (UC). Until recently, there were very limited options for patients who are refractory to chemotherapy, or do not tolerate chemotherapy due to toxicities and overall outcomes have remained very poor. While the role of immunotherapy was first established in non-muscle invasive bladder cancer in the 1970s, no systemic immunotherapy was approved for advanced disease until the recent approval of a programmed death ligand-1 (PD-L1) inhibitor, atezolizumab, in patients with advanced/metastatic UC who have progressed on platinum-containing regimens. This represents a significant milestone in this disease after a void of over 30 years. In addition to atezolizumab, a variety of checkpoint inhibitors have shown a significant activity in advanced/metastatic urothelial carcinoma and are expected to gain Food and Drug Administration (FDA) approval in the near future. The introduction of novel immunotherapy agents has led to rapid changes in the field of urothelial carcinoma. Numerous checkpoint inhibitors are being tested alone or in combination in the first and subsequent-line therapies of metastatic disease, as well as neoadjuvant and adjuvant settings. They are also being studied in combination with radiation therapy and for non-muscle invasive bladder cancer refractory to BCG. Furthermore, immunotherapy is being utilized for those ineligible for firstline platinum-based chemotherapy. This review outlines the novel immunotherapy agents which have either been approved, or are currently being investigated in clinical trials in UC.

  12. Systemic Immunotherapy for Urothelial Cancer: Current Trends and Future Directions

    Directory of Open Access Journals (Sweden)

    Shilpa Gupta

    2017-01-01

    Full Text Available Urothelial cancer of the bladder, renal pelvis, ureter, and other urinary organs is the fifth most common cancer in the United States, and systemic platinum-based chemotherapy remains the standard of care for first-line treatment of advanced/metastatic urothelial carcinoma (UC. Until recently, there were very limited options for patients who are refractory to chemotherapy, or do not tolerate chemotherapy due to toxicities and overall outcomes have remained very poor. While the role of immunotherapy was first established in non-muscle invasive bladder cancer in the 1970s, no systemic immunotherapy was approved for advanced disease until the recent approval of a programmed death ligand-1 (PD-L1 inhibitor, atezolizumab, in patients with advanced/metastatic UC who have progressed on platinum-containing regimens. This represents a significant milestone in this disease after a void of over 30 years. In addition to atezolizumab, a variety of checkpoint inhibitors have shown a significant activity in advanced/metastatic urothelial carcinoma and are expected to gain Food and Drug Administration (FDA approval in the near future. The introduction of novel immunotherapy agents has led to rapid changes in the field of urothelial carcinoma. Numerous checkpoint inhibitors are being tested alone or in combination in the first and subsequent-line therapies of metastatic disease, as well as neoadjuvant and adjuvant settings. They are also being studied in combination with radiation therapy and for non-muscle invasive bladder cancer refractory to BCG. Furthermore, immunotherapy is being utilized for those ineligible for firstline platinum-based chemotherapy. This review outlines the novel immunotherapy agents which have either been approved, or are currently being investigated in clinical trials in UC.

  13. The European Drought Observatory (EDO): Current State and Future Directions

    Science.gov (United States)

    Vogt, Jürgen; Sepulcre, Guadalupe; Magni, Diego; Valentini, Luana; Singleton, Andrew; Micale, Fabio; Barbosa, Paulo

    2013-04-01

    Europe has repeatedly been affected by droughts, resulting in considerable ecological and economic damage and climate change studies indicate a trend towards increasing climate variability most likely resulting in more frequent drought occurrences also in Europe. Against this background, the European Commission's Joint Research Centre (JRC) is developing methods and tools for assessing, monitoring and forecasting droughts in Europe and develops a European Drought Observatory (EDO) to complement and integrate national activities with a European view. At the core of the European Drought Observatory (EDO) is a portal, including a map server, a metadata catalogue, a media-monitor and analysis tools. The map server presents Europe-wide up-to-date information on the occurrence and severity of droughts, which is complemented by more detailed information provided by regional, national and local observatories through OGC compliant web mapping and web coverage services. In addition, time series of historical maps as well as graphs of the temporal evolution of drought indices for individual grid cells and administrative regions in Europe can be retrieved and analysed. Current work is focusing on validating the available products, developing combined indicators, improving the functionalities, extending the linkage to additional national and regional drought information systems and testing options for medium-range probabilistic drought forecasting across Europe. Longer-term goals include the development of long-range drought forecasting products, the analysis of drought hazard and risk, the monitoring of drought impact and the integration of EDO in a global drought information system. The talk will provide an overview on the development and state of EDO, the different products, and the ways to include a wide range of stakeholders (i.e. European, national river basin, and local authorities) in the development of the system as well as an outlook on the future developments.

  14. Sequential Optimization of Paths in Directed Graphs Relative to Different Cost Functions

    KAUST Repository

    Abubeker, Jewahir Ali

    2011-05-14

    This paper is devoted to the consideration of an algorithm for sequential optimization of paths in directed graphs relative to di_erent cost functions. The considered algorithm is based on an extension of dynamic programming which allows to represent the initial set of paths and the set of optimal paths after each application of optimization procedure in the form of a directed acyclic graph.

  15. Social anxiety disorder and stuttering: current status and future directions.

    Science.gov (United States)

    Iverach, Lisa; Rapee, Ronald M

    2014-06-01

    diagnostic assessment of social anxiety disorder among people who stutter; (d) describe approaches for the assessment and treatment of social anxiety in stuttering, including the efficacy of Cognitive Behaviour Therapy; and (e) outline clinical implications and future directions associated with heightened social anxiety in stuttering. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  16. Current management of diabetes mellitus and future directions in care.

    Science.gov (United States)

    Chatterjee, Sudesna; Davies, Melanie J

    2015-11-01

    outcomes, but macrovascular outcomes and cardiovascular safety remain controversial with several glucose-lowering agents. Future directions in diabetes care include strategies such as the 'bionic pancreas', stem cell therapy and targeting the intestinal microbiome. All of these treatments are still being refined, and it may be several decades before they are clinically useful. Prevention and cure of diabetes is the Holy Grail but remain elusive due to lack of detailed understanding of the metabolic, genetic and immunological causes that underpin diabetes. Much progress has been made since the time of Prof MacLean 90 years ago, but there are still great strides to be taken before the life of the patient with diabetes improves even more significantly.

  17. The temporary and accumulated effects of transcranial direct current stimulation for the treatment of advanced Parkinson’s disease monkeys

    OpenAIRE

    Hao Li; Xiaoguang Lei; Ting Yan; Hongwei Li; Baihui Huang; Ling Li; Liqi Xu; Li Liu; Nanhui Chen; Longbao Lü; Yuanye Ma; Lin Xu; Jiali Li; Zhengbo Wang; Baorong Zhang

    2015-01-01

    Transcranial direct current stimulation (tDCS) is a useful noninvasive technique of cortical brain stimulation for the treatment of neurological disorders. Clinical research has demonstrated tDCS with anodal stimulation of primary motor cortex (M1) in Parkinson’s disease (PD) patients significantly improved their motor function. However, few studies have been focused on the optimization of parameters which contributed significantly to the treatment effects of tDCS and exploration of the under...

  18. Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection

    Directory of Open Access Journals (Sweden)

    Chaofeng Ye

    2016-09-01

    Full Text Available In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density ( B x of the orthogonal coils is not uniform over the sensor region, resulting in an output signal magnitude that depends on the relative location of the defect to the sensor array. In this paper, the rotating excitation coil is optimized to achieve a uniform B x field in the sensor array area and minimize the probe size. The current density distribution of the coil is optimized using the polynomial approximation method. A non-uniform coil design is derived from the optimized current density distribution. Simulation results, using both an optimized coil and a conventional coil, are generated using the finite element method (FEM model. The signal magnitude for an optimized coil is seen to be more robust with respect to offset of defects from the coil center. A novel multilayer coil structure, fabricated on a multi-layer printed circuit board, is used to build the optimized coil. A prototype probe with the optimized coil and 32 giant magnetoresistive (GMR sensors is built and tested on a two-layer riveted aluminum sample. Experimental results show that the optimized probe has better defect detection capability compared with a conventional non-optimized coil.

  19. Transcranial direct current stimulation in post-stroke dysphagia: a systematic review of randomized controlled trials

    Directory of Open Access Journals (Sweden)

    Kavian Ghandehari

    2016-07-01

    Full Text Available Introduction: The aim of this research was to systematically review all the randomized controlled trials that have evaluated the effect of transcranial direct current stimulation (tDCS on post-stroke dysphagia. Methods: Three electronic databases were searched for relevant articles that were uploaded from their inception to March 2015: PubMed, Cochrane Library (Cochrane Central Register of Controlled Trials, and Scopus. All data was that was related to the location of the cerebrovascular accident (CVA, the parameters of tDCS, post-stroke time to commencement of tDCS, the stimulated hemisphere, stimulation dose, any outcome measurements, and follow-up duration were extracted and assessed. Finally, a number of observations were generated through a qualitative synthesis of the extracted data.Result: Three eligible randomized controlled trials were included in the systematic review. All three trials reported that, in comparison to a placebo, tDCS had a statistically significant effect on post-stroke dysphagia.Discussion: The results of our systematic review suggest that tDCS may represent a promising novel treatment for post-stroke dysphagia. However, to date, little is known about the optimal parameters of tDCS for relieving post-stroke dysphagia. Further studies are warranted to refine this promising intervention by exploring the optimal parameters of tDCS.Conclusion: Since brainstem swallowing centers have bilateral cortical innervations, measures that enhance cortical input and sensorimotor control of brainstem swallowing may facilitate recovery from dysphagia.

  20. Optimal management of multiple sclerosis during pregnancy: current perspectives

    Directory of Open Access Journals (Sweden)

    Borisow N

    2014-08-01

    Full Text Available Nadja Borisow, Friedemann Paul, Jan DörrNeuroCure Clinical Research Center and Clinical and Experimental Research Center for Multiple Sclerosis, Charité – Universitätsmedizin Berlin, Berlin, GermanyAbstract: Multiple sclerosis (MS is a common inflammatory demyelinating disorder of the central nervous system. It frequently affects females in their reproductive phase of life. Therefore, family planning, pregnancy, and breastfeeding are important issues in the management of MS, particularly with respect to counseling and drug treatment. This paper reviews currently available data on the outcome of pregnancies in MS patients and the influence of pregnancy on the course of the disease. We give an update on the use of various disease-modifying MS drugs during pregnancy and breastfeeding. In addition to established therapies such as interferon-β, glatiramer acetate, natalizumab, and fingolimod, we also discuss the state of knowledge about new agents such as dimethyl fumarate, teriflunomide, and alemtuzumab in the context of pregnancy and breastfeeding.Keywords: multiple sclerosis, pregnancy, lactation, disease-modifying therapy

  1. Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation

    OpenAIRE

    Kwon, Yong Hyun; Jang, Sung Ho

    2012-01-01

    We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel coun...

  2. The Morphological and Molecular Changes of Brain Cells Exposed to Direct Current Electric Field Stimulation

    OpenAIRE

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

    2015-01-01

    Background: 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. Methods: 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 r...

  3. Direct trajectory optimization based on a mapped Chebyshev pseudospectral method

    Institute of Scientific and Technical Information of China (English)

    Guo Xiao; Zhu Ming

    2013-01-01

    In view of generating optimal trajectories of Bolza problems,standard Chebyshev pseudospectral (PS) method makes the points' accumulation near the extremities and rarefaction of nodes close to the center of interval,which causes an ill-condition of differentiation matrix and an oscillation of the optimal solution.For improvement upon the difficulties,a mapped Chebyshev pseudospectral method is proposed.A conformal map is applied to Chebyshev points to move the points closer to equidistant nodes.Condition number and spectral radius of differentiation matrices from both methods are presented to show the improvement.Furthermore,the modification keeps the Chebyshev pseudospectral method's advantage,the spectral convergence rate.Based on three numerical examples,a comparison of the execution time,convergence and accuracy is presented among the standard Chebyshev pseudospectral method,other collocation methods and the proposed one.In one example,the error of results from mapped Chebyshev pseudospectral method is reduced to 5% of that from standard Chebyshev pseudospectral method.

  4. Extracting DC bus current information for optimal phase correction and current ripple in sensorless brushless DC motor drive

    Institute of Scientific and Technical Information of China (English)

    Zu-sheng HO; Chii-maw UANG; Ping-chieh WANG

    2014-01-01

    Brushless DC motor (BLDCM) sensorless driving technology is becoming increasingly established. However, op-timal phase correction still relies on complex calculations or algorithms. In finding the correct commutation point, the problem of phase lag is introduced. In this paper, we extract DC bus current information for auto-calibrating the phase shift to obtain the correct commutation point and optimize the control of BLDC sensorless driving. As we capture only DC bus current information, the original shunt resistor is used in the BLDCM driver and there is no need to add further current sensor components. Software processing using only simple arithmetic operations successfully accomplishes the phase correction. Experimental results show that the proposed method can operate accurately and stably at low or high speed, with light or heavy load, and is suitable for practical applications. This approach will not increase cost but will achieve the best performance/cost ratio and meet market expectations.

  5. Directional Microphone Hearing Aids in School Environments: Working toward Optimization

    Science.gov (United States)

    Ricketts, Todd A.; Picou, Erin M.; Galster, Jason

    2017-01-01

    Purpose: The hearing aid microphone setting (omnidirectional or directional) can be selected manually or automatically. This study examined the percentage of time the microphone setting selected using each method was judged to provide the best signalto-noise ratio (SNR) for the talkers of interest in school environments. Method: A total of 26…

  6. Directional Microphone Hearing Aids in School Environments: Working toward Optimization

    Science.gov (United States)

    Ricketts, Todd A.; Picou, Erin M.; Galster, Jason

    2017-01-01

    Purpose: The hearing aid microphone setting (omnidirectional or directional) can be selected manually or automatically. This study examined the percentage of time the microphone setting selected using each method was judged to provide the best signalto-noise ratio (SNR) for the talkers of interest in school environments. Method: A total of 26…

  7. Electromagnetic Design and Optimization of Directivity of Stripline Beam Position Monitors for the High Luminosity Large Hadron Collider

    CERN Document Server

    Draskovic, Drasko; Jones, Owain Rhodri; Lefèvre, Thibaut; Wendt, Manfred

    2015-01-01

    This paper presents the preliminary electromagnetic design of a stripline Beam Position Monitor (BPM) for the High Luminosity program of the Large Hadron Collider (HL-LHC) at CERN. The design is fitted into a new octagonal shielded Beam Screen for the low-beta triplets and is optimized for high directivity. It also includes internal Tungsten absorbers, required to reduce the energy deposition in the superconducting magnets. The achieved broadband directivity in wakefield solver simulations presents significant improvement over the directivity of the current stripline BPMs installed in the LHC.

  8. Topology optimization using bi-directional evolutionary structural optimization based on the element-free Galerkin method

    Science.gov (United States)

    Shobeiri, Vahid

    2016-03-01

    In this article, the bi-directional evolutionary structural optimization (BESO) method based on the element-free Galerkin (EFG) method is presented for topology optimization of continuum structures. The mathematical formulation of the topology optimization is developed considering the nodal strain energy as the design variable and the minimization of compliance as the objective function. The EFG method is used to derive the shape functions using the moving least squares approximation. The essential boundary conditions are enforced by the method of Lagrange multipliers. Several topology optimization problems are presented to show the effectiveness of the proposed method. Many issues related to topology optimization of continuum structures, such as chequerboard patterns and mesh dependency, are studied in the examples.

  9. Optimization of hydrofoil for tidal current turbine based on particle swarm optimization and computational fluid dynamic method

    Directory of Open Access Journals (Sweden)

    Zhang De-Sheng

    2016-01-01

    Full Text Available Both efficiency and cavitation performance of the hydrofoil are the key technologies to design the tidal current turbine. In this paper, the hydrofoil efficiency and lift coefficient were improved based on particle swarm optimization method and XFoil codes. The cavitation performance of the optimized hydrofoil was also discussed by the computational fluid dynamic. Numerical results show the efficiency of the optimized hydrofoil was improved 11% ranging from the attack angle of 0-7° compared to the original NACA63-818 hydrofoil. The minimum pressure on leading edge of the optimized hydrofoil dropped above 15% at the high attack angle conditions of 10°, 15°, and 20°, respectively, which is benefit for the hydrofoil to avoiding the cavitation.

  10. Analysis and optimization of current sensing circuit for deep sub-micron SRAM

    Institute of Scientific and Technical Information of China (English)

    Wang Yiqi; Zhao Fazhan; Liu Mengxin; Lü Yinxue; Zhao Bohua; Han Zhensheng

    2011-01-01

    A quantitative yield analysis of a traditional current sensing circuit considering the random dopant fluctuation effect is presented.It investigates the impact of transistor size,falling time of control signal CS and threshold voltage of critical transistors on failure probability of current sensing circuit.On this basis,we present a final optimization to improve the reliability of current sense amplifier.Under 90 nm process,simulation shows that failure probability of current sensing circuit can be reduced by 80% after optimization compared with the normal situation and the delay time only increases marginally.

  11. Starship Sails Propelled by Cost-Optimized Directed Energy

    CERN Document Server

    Benford, James

    2011-01-01

    Microwave propelled sails are a new class of spacecraft using photon acceleration. It is the only method of interstellar flight that has no physics issues. Laboratory demonstrations of basic features of beam-driven propulsion, flight, stability ('beam-riding'), and induced spin, have been completed in the last decade, primarily in the microwave. It offers much lower cost probes after a substantial investment in the launcher. Engineering issues are being addressed by other applications: fusion (microwave, millimeter and laser sources) and astronomy (large aperture antennas). There are many candidate sail materials: carbon nanotubes and microtrusses, graphene, beryllium, etc. For acceleration of a sail, what is the cost-optimum high power system? Here the cost is used to constrain design parameters to estimate system power, aperture and elements of capital and operating cost. From general relations for cost-optimal transmitter aperture and power, system cost scales with kinetic energy and inversely with sail di...

  12. Path Partition in Directed Graph – Modeling and Optimization

    Directory of Open Access Journals (Sweden)

    Issam Abdel Kader

    2013-03-01

    Full Text Available The concept of graph theory is therefore perfectly suitable to structure a problem in its initial analysis phases since a graph is the most general mathematical object. At the structural level, the nodes represent the objects, the variables… and the arc forms the binary relation of influence among them. Many real problems can be modeled as path partition in directed graph that played particular role in the operation of arranging a set of nodes especially in case of directed acyclic graph (DAG. We encounter such graph in schedule problems, the analysis of language structure, the probability theory, the game theory, compilers…. Moreover managerial problem can be modeled as acyclic graphs, also the potential problem has a suitable solution if and only if the graph is acyclic.

  13. Optimal directional view angles for remote-sensing missions

    Science.gov (United States)

    Kimes, D. S.; Holben, B. N.; Tucker, C. J.; Newcomb, W. W.

    1984-01-01

    The present investigation is concerned with the directional, off-nadir viewing of terrestrial scenes using remote-sensing systems from aircraft and satellite platforms, taking into account advantages of such an approach over strictly nadir viewing systems. Directional reflectance data collected for bare soil and several different vegetation canopies in NOAA-7 AVHRR bands 1 and 2 were analyzed. Optimum view angles were recommended for two strategies. The first strategy views the utility of off-nadir measurements as extending spatial and temporal coverage of the target area. The second strategy views the utility of off-nadir measurements as providing additional information about the physical characteristics of the target. Conclusions regarding the two strategies are discussed.

  14. Direct electrochemical sensor for label-free DNA detection based on zero current potentiometry.

    Science.gov (United States)

    Wu, Nai-ying; Gao, Wei; He, Xu-lun; Chang, Zhu; Xu, Mao-tian

    2013-01-15

    A direct electrochemical DNA biosensor based on zero current potentiometry was fabricated by immobilization of ssDNA onto gold nanoparticles (AuNPs) coated pencil graphite electrode (PGE). One ssDNA/AuNPs/PGE was connected in series between clips of working and counter electrodes of a potentiostat, and then immersed into the solution together with a reference electrode, establishing a novel DNA biosensor for specific DNA detection. The variation of zero current potential difference (ΔE(zcp)) before and after hybridization of the self-assembled probe DNA with the target DNA was used as a signal to characterize and quantify the target DNA sequence. The whole DNA biosensor fabrication process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with the use of ferricyanide as an electrochemical redox indicator. Under the optimized conditions, ΔE(zcp) was linear with the concentrations of the complementary target DNA in the range from 10nM to 1μM, with a detection limit of 6.9nM. The DNA biosensor showed a good reproducibility and selectivity. Prepared DNA biosensor is facile and sensitive, and it eliminates the need of using exogenous reagents to monitor the oligonucleotides hybridization.

  15. Simulation of injury potential compensation by direct current stimulation in rat spinal cord.

    Science.gov (United States)

    Wang, Aihua; Zhang, Guanghao; Zhang, Cheng; Wu, Changzhe; Song, Tao; Huo, Xiaolin

    2014-01-01

    Injury potential, a significant index of spinal cord injury (SCI), is generated by the movement of extracellular ions. It can be compensated through applied direct current (DC) stimulation, which prevents the influx of the free calcium, and eventually reduces the development of secondary injury. Therefore, the compensation of injury potential is beneficial to the repairing of the function of spinal cord. The compensation effect can be evaluated by whether the magnitudes of longitudinal electric fields (EFs) are compensated to zero. However, there have been no established criteria to determine the distribution and shape of stimulating electrodes. In this study, in order to optimize the stimulating electrodes, a finite element model (FEM) of rat spinal cord was developed, and the EFs changes induced by electrodes of different sizes, shapes and locations after SCI were calculated. All the designed configurations of electrodes were able to compensate injury potential, but the resultant compensation effects vary. Pin and disc electrodes produced uneven EFs, while ring electrodes produced uniformly distributed EFs. Moreover, large ring electrodes can compensate the longitudinal EFs almost to zero with relatively low current density (0.55 μA/mm(2)) applied. These results provide a basis for the determination of electrical stimulation parameters in the compensation of injury potential.

  16. 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%.

  17. Numeric Investigation of Brain Tumor Influence on the Current Distributions During Transcranial Direct Current Stimulation.

    Science.gov (United States)

    Song, Bo; Wen, Peng; Ahfock, Tony; Li, Yan

    2016-01-01

    This study constructed a series of high-resolution realistic human-head models with brain tumors, and numerically investigated the influence of brain tumor's location and grade on the current distributions, under different electrode montages during tDCS. The threshold area and the peak current density were also derived and analyzed in the region of interest. The simulation result showed that it is safe to apply tDCS on the patients with brain tumors to treat their neuropsychiatric conditions and cancer pain caused by the tumor; although considerable changes of the current distributions are induced by the presence of a brain tumor. In addition, several observations on the global and local influences of tumor grade and possible edema have been made as well. These findings should be helpful for researchers and clinical doctors to treat patients with brain tumors. This study is also the first numerical study to fill in the gap of tDCS applications on the patients with brain tumors.

  18. Optimization of magnetically driven directional solidification of silicon using artificial neural networks and Gaussian process models

    Science.gov (United States)

    Dropka, Natasha; Holena, Martin

    2017-08-01

    In directional solidification of silicon, the solid-liquid interface shape plays a crucial role for the quality of crystals. The interface shape can be influenced by forced convection using travelling magnetic fields. Up to now, there is no general and explicit methodology to identify the relation and the optimum combination of magnetic and growth parameters e.g., frequency, phase shift, current magnitude and interface deflection in a buoyancy regime. In the present study, 2D CFD modeling was used to generate data for the design and training of artificial neural networks and for Gaussian process modeling. The aim was to quickly assess the complex nonlinear dependences among the parameters and to optimize them for the interface flattening. The first encouraging results are presented and the pros and cons of artificial neural networks and Gaussian process modeling discussed.

  19. Closed form of optimal current waveform for class-F PA up to fourth harmonic

    Indian Academy of Sciences (India)

    Anamarija Juhas; Ladislav A Novak

    2015-04-01

    In this paper, rigorous analytical derivation of the coefficients of optimal current waveform for class-F power amplifier (PA) up to fourth harmonic (dc, 1st, 2nd and 4th harmonic) is presented. The coefficients of the optimal current waveform along with related maximum attainable efficiency are provided in closed form. The results obtained are also of interest for the inverse class-F, in the case when optimal voltage waveform consists of dc, 1st, 2nd and 4th harmonic.

  20. A Streaming Potential/Current-Based Microfluidic Direct Current Generator for Self-Powered Nanosystems.

    Science.gov (United States)

    Zhang, Rui; Wang, Sihong; Yeh, Min-Hsin; Pan, Caofeng; Lin, Long; Yu, Ruomeng; Zhang, Yan; Zheng, Li; Jiao, Zongxia; Wang, Zhong Lin

    2015-11-01

    A simple but practical method to convert the hydroenergy of microfluids into continuous electrical output is reported. Based on the principle of streaming potential/current, a microfluidic generator (MFG) is demonstrated using patterned micropillar arrays as a quasi-porous flow channel. The continuous electrical output makes this MFG particularly suitable as a power source in self-powered systems. Using the proposed MFG to power a single nanowire-based pH sensor, a self-powered fluid sensor system is demonstrated.

  1. Multiday Transcranial Direct Current Stimulation Causes Clinically Insignificant Changes in Childhood Dystonia: A Pilot Study.

    Science.gov (United States)

    Bhanpuri, Nasir H; Bertucco, Matteo; Young, Scott J; Lee, Annie A; Sanger, Terence D

    2015-10-01

    Abnormal motor cortex activity is common in dystonia. Cathodal transcranial direct current stimulation may alter cortical activity by decreasing excitability while anodal stimulation may increase motor learning. Previous results showed that a single session of cathodal transcranial direct current stimulation can improve symptoms in childhood dystonia. Here we performed a 5-day, sham-controlled, double-blind, crossover study, where we measured tracking and muscle overflow in a myocontrol-based task. We applied cathodal and anodal transcranial direct current stimulation (2 mA, 9 minutes per day). For cathodal transcranial direct current stimulation (7 participants), 3 subjects showed improvements whereas 2 showed worsening in overflow or tracking error. The effect size was small (about 1% of maximum voluntary contraction) and not clinically meaningful. For anodal transcranial direct current stimulation (6 participants), none showed improvement, whereas 5 showed worsening. Thus, multiday cathodal transcranial direct current stimulation reduced symptoms in some children but not to a clinically meaningful extent, whereas anodal transcranial direct current stimulation worsened symptoms. Our results do not support transcranial direct current stimulation as clinically viable for treating childhood dystonia.

  2. Subcortical structures in humans can be facilitated by transcranial direct current stimulation

    NARCIS (Netherlands)

    Nonnekes, Jorik; Arrogi, Anass; Munneke, Moniek; Asseldonk, van Edwin; Oude Nijhuis, Lars; Geurts, Alexander; Weerdesteyn, Vivian

    2014-01-01

    BACKGROUND: Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that alters cortical excitability via application of a weak direct current. Interestingly, it was demonstrated in cats that tDCS can facilitate subcortical structures as well (Bolzonii et al., J P

  3. Modeling trans-spinal direct current stimulation for the modulation of the lumbar spinal motor pathways

    Science.gov (United States)

    Kuck, A.; Stegeman, D. F.; van Asseldonk, E. H. F.

    2017-10-01

    Objective. Trans-spinal direct current stimulation (tsDCS) is a potential new technique for the treatment of spinal cord injury (SCI). TsDCS aims to facilitate plastic changes in the neural pathways of the spinal cord with a positive effect on SCI recovery. To establish tsDCS as a possible treatment option for SCI, it is essential to gain a better understanding of its cause and effects. We seek to understand the acute effect of tsDCS, including the generated electric field (EF) and its polarization effect on the spinal circuits, to determine a cellular target. We further ask how these findings can be interpreted to explain published experimental results. Approach. We use a realistic full body finite element volume conductor model to calculate the EF of a 2.5 mA direct current for three different electrode configurations. We apply the calculated electric field to realistic motoneuron models to investigate static changes in membrane resting potential. The results are combined with existing knowledge about the theoretical effect on a neuronal level and implemented into an existing lumbar spinal network model to simulate the resulting changes on a network level. Main results. Across electrode configurations, the maximum EF inside the spinal cord ranged from 0.47 V m‑1 to 0.82 V m‑1. Axon terminal polarization was identified to be the dominant cellular target. Also, differences in electrode placement have a large influence on axon terminal polarization. Comparison between the simulated acute effects and the electrophysiological long-term changes observed in human tsDCS studies suggest an inverse relationship between the two. Significance. We provide methods and knowledge for better understanding the effects of tsDCS and serve as a basis for a more targeted and optimized application of tsDCS.

  4. Direct estimation of diffuse gaseous emissions from coal fires: current methods and future directions

    Science.gov (United States)

    Engle, Mark A.; Olea, Ricardo A.; O'Keefe, Jennifer M. K.; Hower, James C.; Geboy, Nicholas J.

    2013-01-01

    Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper. Here we take advantage of stochastic Gaussian simulation to interpolate CO2 fluxes measured using a dynamic closed chamber at the Ruth Mullins coal fire in Perry County, Kentucky. This approach allows for preparing a map of diffuse gas emissions, one of the two primary ways that gases emanate from coal fires, and establishing the reliability of the study both locally and for the entire fire. Future research directions include continuous and automated sampling to improve quantification of gaseous coal fire emissions.

  5. Optimized design of resonant controller for stator current harmonic compensation in DFIG wind turbine systems

    DEFF Research Database (Denmark)

    Liu, Changjin; Chen, Wenjie; Blaabjerg, Frede

    2012-01-01

    This paper presents an analytical method to optimize the parameters of resonant controller which is used in a Doubly-Fed Induction Generator (DFIG). In the DFIG control system, the fundamental current loop is controlled by PI-controllers, and the stator harmonic current loop is controlled by reso...... design procedure of the resonant controller parameters is presented. The maximum possible gain of the resonant controller can be directly evaluated from the procedure. Simulations and experiments are presented to validate the complete analysis....... by resonant controllers. The effects of the resonant controller on the system stability and the steady-state performance are discussed in details. The analysis shows that the resonant controller has an important impact on the system stability when the resonant frequency is close to the crossover frequency...... of the open loop gain. The gain of the resonant controller is mainly determined by the DFIG transient inductance, the proportional gain of the PI controller, and the required phase margin. Based on the analytical expression of the phase margin and the crossover frequency of the control system, a systematic...

  6. Propagation direction reversal of ionization zones in the transition between high and low current magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    School of Materials Science and Engineering, State Key Lab for Materials Processing and Die & Mold Technology, Huazhong University of Science and Technology, Wuhan 430074, China; Department of Physics, University of California Berkeley, Berkeley, California 94720, USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA; Yang, Yuchen; Liu, Jason; Liu, Lin; Anders, André

    2014-12-11

    Past research has revealed the propagation of dense, asymmetric ionization zones in both high and low current magnetron discharges. Here we report about the direction reversal of ionization zone propagation as observed with fast cameras. At high currents, zones move in the E B direction with velocities of 103 to 104 m/s. However at lower currents, ionization zones are observed to move in the opposite, the -E B direction, with velocities ~;; 103 m/s. It is proposed that the direction reversal is associated with the local balance of ionization and supply of neutrals in the ionization zone.

  7. An exact approach to direct aperture optimization in IMRT treatment planning

    Energy Technology Data Exchange (ETDEWEB)

    Men Chunhua [Department of Industrial and Systems Engineering, University of Florida, Gainesville, Florida 32611-6595 (United States); Romeijn, H Edwin [Department of Industrial and Systems Engineering, University of Florida, Gainesville, Florida 32611-6595 (United States); Taskin, Z Caner [Department of Industrial and Systems Engineering, University of Florida, Gainesville, Florida 32611-6595 (United States); Dempsey, James F [Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385 (United States)

    2007-12-21

    We consider the problem of intensity-modulated radiation therapy (IMRT) treatment planning using direct aperture optimization. While this problem has been relatively well studied in recent years, most approaches employ a heuristic approach to the generation of apertures. In contrast, we use an exact approach that explicitly formulates the fluence map optimization (FMO) problem as a convex optimization problem in terms of all multileaf collimator (MLC) deliverable apertures and their associated intensities. However, the number of deliverable apertures, and therefore the number of decision variables and constraints in the new problem formulation, is typically enormous. To overcome this, we use an iterative approach that employs a subproblem whose optimal solution either provides a suitable aperture to add to a given pool of allowable apertures or concludes that the current solution is optimal. We are able to handle standard consecutiveness, interdigitation and connectedness constraints that may be imposed by the particular MLC system used, as well as jaws-only delivery. Our approach has the additional advantage that it can explicitly account for transmission of dose through the part of an aperture that is blocked by the MLC system, yielding a more precise assessment of the treatment plan than what is possible using a traditional beamlet-based FMO problem. Finally, we develop and test two stopping rules that can be used to identify treatment plans of high clinical quality that are deliverable very efficiently. Tests on clinical head-and-neck cancer cases showed the efficacy of our approach, yielding treatment plans comparable in quality to plans obtained by the traditional method with a reduction of more than 75% in the number of apertures and a reduction of more than 50% in beam-on time, with only a modest increase in computational effort. The results also show that delivery efficiency is very insensitive to the addition of traditional MLC constraints; however, jaws

  8. Individual Differences and State-Dependent Responses in Transcranial Direct Current Stimulation.

    Science.gov (United States)

    Hsu, Tzu-Yu; Juan, Chi-Hung; Tseng, Philip

    2016-01-01

    Transcranial direct current stimulation (tDCS) has been extensively used to examine whether neural activities can be selectively increased or decreased with manipulations of current polarity. Recently, the field has reevaluated the traditional anodal-increase and cathodal-decrease assumption due to the growing number of mixed findings that report the effects of the opposite directions. Therefore, the directionality of tDCS polarities and how it affects each individual still remain unclear. In this study, we used a visual working memory (VWM) paradigm and systematically manipulated tDCS polarities, types of different independent baseline measures, and task difficulty to investigate how these factors interact to determine the outcome effect of tDCS. We observed that only low-performers, as defined by their no-tDCS corsi block tapping (CBT) performance, persistently showed a decrement in VWM performance after anodal stimulation, whereas no tDCS effect was found when participants were divided by their performance in digit span. In addition, only the optimal level of task difficulty revealed any significant tDCS effect. All these findings were consistent across different blocks, suggesting that the tDCS effect was stable across a short period of time. Lastly, there was a high degree of intra-individual consistency in one's responsiveness to tDCS, namely that participants who showed positive or negative effect to anodal stimulation are also more likely to show the same direction of effects for cathodal stimulation. Together, these findings imply that tDCS effect is interactive and state dependent: task difficulty and consistent individual differences modulate one's responsiveness to tDCS, while researchers' choices of independent behavioral baseline measures can also critically affect how the effect of tDCS is evaluated. These factors together are likely the key contributors to the wide range of "noises" in tDCS effects between individuals, between stimulation protocols

  9. Pseudospectral Collocation Methods for the Direct Transcription of Optimal Control Problems

    Science.gov (United States)

    2003-04-01

    solving optimal control problems for trajectory optimization, spacecraft attitude control, jet thruster control, missile guidance and many other... optimal control problems using a pseudospectral direct transcription method. These problems are stated here so that they may be referred to elsewhere...e.g., [7]. 2.3 Prototypical Examples Throughout this thesis two example problems are used to demonstrate various prop- erties associated with solving

  10. Investigation of In Vitro Bone Cell Adhesion and Proliferation on Ti Using Direct Current Stimulation.

    Science.gov (United States)

    Bodhak, Subhadip; Bose, Susmita; Kinsel, William C; Bandyopadhyay, Amit

    2012-12-01

    Our objective was to establish an in vitro cell culture protocol to improve bone cell attachment and proliferation on Ti substrate using direct current stimulation. For this purpose, a custom made electrical stimulator was developed and a varying range of direct currents, from 5 to 25 µA, were used to study the current stimulation effect on bone cells cultured on conducting Ti samples in vitro. Cell-materials interaction was studied for a maximum of 5 days by culturing with human fetal osteoblast cells (hFOB). The direct current was applied in every 8 h time interval and the duration of electrical stimulation was kept constant at 15 min for all cases. In vitro results showed that direct current stimulation significantly favored bone cell attachment and proliferation in comparison to nonstimulated Ti surface. Immunochemistry and confocal microscopy results confirmed that the cell adhesion was most pronounced on 25 µA direct current stimulated Ti surfaces as hFOB cells expressed higher vinculin protein with increasing amount of direct current. Furthermore, MTT assay results established that cells grew 30% higher in number under 25 µA electrical stimulation as compared to nonstimulated Ti surface after 5 days of culture period. In this work we have successfully established a simple and cost effective in vitro protocol offering easy and rapid analysis of bone cell-materials interaction which can be used in promotion of bone cell attachment and growth on Ti substrate using direct current electrical stimulation in an in vitro model.

  11. Methods of centers and methods of feasible directions for the solution of optimal control problems.

    Science.gov (United States)

    Polak, E.; Mukai, H.; Pironneau, O.

    1971-01-01

    Demonstration of the applicability of methods of centers and of methods of feasible directions to optimal control problems. Presented experimental results show that extensions of Frank-Wolfe (1956), Zoutendijk (1960), and Pironneau-Polak (1971) algorithms for nonlinear programming problems can be quite efficient in solving optimal control problems.

  12. Optimization Tool for Direct Water Cooling System of High Power IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Blaabjerg, Frede

    2016-01-01

    important issue for thermal design engineers. This paper aims to present a user friendly optimization tool for direct water cooling system of a high power module which enables the cooling system designer to identify the optimized solution depending on customer load profiles and available pump power. CFD...

  13. Comparison of Direct Multiobjective Optimization Methods for the Design of Electric Vehicles

    OpenAIRE

    2006-01-01

    International audience; "System design oriented methodologies" are discussed in this paper through the comparison of multiobjective optimization methods applied to heterogeneous devices in electrical engineering. Avoiding criteria function derivatives, direct optimization algorithms are used. In particular, deterministic geometric methods such as the Hooke & Jeeves heuristic approach are compared with stochastic evolutionary algorithms (Pareto genetic algorithms). Different issues relative to...

  14. Planning the Minimum Time and Optimal Survey Trajectory for Autonomous Underwater Vehicles in Uncertain Current

    Directory of Open Access Journals (Sweden)

    Michael A. Hurni

    2015-12-01

    Full Text Available The authors develop an approach to a “best” time path for Autonomous Underwater Vehicles conducting oceanographic measurements under uncertain current flows. The numerical optimization tool DIDO is used to compute hybrid minimum time and optimal survey paths for a sample of currents between ebb and flow. A simulated meta-experiment is performed where the vehicle traverses the resulting paths under different current strengths per run. The fastest elapsed time emerges from a payoff table. A multi-objective function is then used to weigh the time to complete a mission versus measurement inaccuracy due to deviation from the desired survey path.

  15. Hybrid Direct Carbon Fuel Cell Performance with Anode Current Collector Material

    DEFF Research Database (Denmark)

    Deleebeeck, Lisa; Kammer Hansen, Kent

    2015-01-01

    The influence of the current collector on the performance of a hybrid direct carbon fuel cell (HDCFC), consisting of solid oxide fuel cell (SOFC) with a molten carbonate-carbon slurry in contact with the anode, has been investigated using current-voltage curves. Four different anode current...... collectors were studied: Au, Ni, Ag, and Pt. It was shown that the performance of the direct carbon fuel cell (DCFC) is dependent on the current collector materials, Ni and Pt giving the best performance, due to their catalytic activity. Gold is suggested to be the best material as an inert current collector...

  16. Design and Optimization of Air-Doped 3-dB Terahertz Fiber Directional Couplers

    DEFF Research Database (Denmark)

    Bao, Hualong; Nielsen, Kristian; Rasmussen, Henrik K.;

    2014-01-01

    We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down- doped with a triangular array of air holes.......We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down- doped with a triangular array of air holes....

  17. Optimizing tooth form with direct posterior composite restorations.

    Science.gov (United States)

    Raghu, Ramya; Srinivasan, Raghu

    2011-10-01

    Advances in material sciences and technology have provided today's clinicians the strategies to transform the mechanistic approach of operative dentistry into a biologic philosophy. In the last three decades, composite resins have gone from being just an esthetically pleasing way of restoring Class III and Class IV cavities to become the universal material for both anterior and posterior situations as they closely mimic the natural esthetics while restoring the form of the human dentition. In order to enhance their success, clinicians have to rethink their protocol instead of applying the same restorative concepts and principles practiced with metallic restorations. Paralleling the evolution of posterior composite resin materials, cavity designs, restorative techniques and armamentarium have also developed rapidly to successfully employ composite resins in Class II situations. Most of the earlier problems with posterior composites such as poor wear resistance, polymerization shrinkage, postoperative sensitivity, predictable bonding to dentin, etc., have been overcome to a major extent. However, the clinically relevant aspect of achieving tight contacts in Class II situations has challenged clinicians the most. This paper reviews the evolution of techniques and recent developments in achieving predictable contacts with posterior composites. A Medline search was performed for articles on "direct posterior composite contacts." The keywords used were "contacts and contours of posterior composites." The reference list of each article was manually checked for additional articles of relevance.

  18. Optimizing tooth form with direct posterior composite restorations

    Directory of Open Access Journals (Sweden)

    Ramya Raghu

    2011-01-01

    Full Text Available Advances in material sciences and technology have provided today′s clinicians the strategies to transform the mechanistic approach of operative dentistry into a biologic philosophy. In the last three decades, composite resins have gone from being just an esthetically pleasing way of restoring Class III and Class IV cavities to become the universal material for both anterior and posterior situations as they closely mimic the natural esthetics while restoring the form of the human dentition. In order to enhance their success, clinicians have to rethink their protocol instead of applying the same restorative concepts and principles practiced with metallic restorations. Paralleling the evolution of posterior composite resin materials, cavity designs, restorative techniques and armamentarium have also developed rapidly to successfully employ composite resins in Class II situations. Most of the earlier problems with posterior composites such as poor wear resistance, polymerization shrinkage, postoperative sensitivity, predictable bonding to dentin, etc., have been overcome to a major extent. However, the clinically relevant aspect of achieving tight contacts in Class II situations has challenged clinicians the most. This paper reviews the evolution of techniques and recent developments in achieving predictable contacts with posterior composites. A Medline search was performed for articles on ′′direct posterior composite contacts.′′ The keywords used were ′′contacts and contours of posterior composites.′′ The reference list of each article was manually checked for additional articles of relevance.

  19. Optimal swimming speed in head currents and effects on distance movement of winter-migrating fish

    DEFF Research Database (Denmark)

    Brodersen, J.; Nilsson, P.A.; Ammitzbøl, J.

    2008-01-01

    ecologically and economically important. We here use passive and active telemetry to study how winter migrating roach regulate swimming speed and distance travelled per day in response to variations in head current velocity. Furthermore, we provide theoretical predictions on optimal swimming speeds in head...... currents and relate these to our empirical results. We show that fish migrate farther on days with low current velocity, but travel at a greater ground speed on days with high current velocity. The latter result agrees with our predictions on optimal swimming speed in head currents, but disagrees...... with previously reported predictions suggesting that fish ground speed should not change with head current velocity. We suggest that this difference is due to different assumptions on fish swimming energetics. We conclude that fish are able to adjust both swimming speed and timing of swimming activity during...

  20. Optimization of polymer electrolyte fuel cell cathode catalyst layers via direct numerical simulation modeling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guoqing; Mukherjee, Partha P.; Wang, Chao-Yang [Electrochemical Engine Center (ECEC), Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2007-06-30

    The cathode catalyst layer (CL), due to sluggish oxygen reduction reaction and several transport losses therein, plays an important role in the overall performance of polymer electrolyte fuel cells (PEFCs). The relative volume fractions of the constituent phases, i.e. the electronic, electrolyte and void phases, of the cathode CL need to be selected appropriately in order to achieve an optimal balance between oxygen diffusion and proton conduction. In this work, the influence of electrolyte and void phase fractions of the cathode CL on the cell performance is investigated based on a pore-level description of species and charge transport through a random CL microstructure via the direct numerical simulation (DNS) model. Additionally, the effects of inlet relative humidity and net water transport from the anode on the cathode performance have been studied which indicate the interdependence between the CL composition and the cell operating conditions. The results indicate that the low humidity operation benefits the performance by enhancing the oxygen transport especially under high current densities. Finally, the DNS model predicts the volume fractions of 0.4 and 0.26 for the void and electrolyte phases, respectively, as the optimal composition of the catalyst layer for the best performance. (author)

  1. 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

    2015-01-01

    Background: 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. Methods: 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. Results: 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. Conclusion: 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. PMID:25522422

  2. 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.

  3. Optimization of the collimation system for CSNS/RCS with the robust conjugate direction search algorithm

    CERN Document Server

    Ji, H F; Huang, M Y; Xu, S Y; Wang, N; Wang, S

    2016-01-01

    The Robust Conjugate Direction Search (RCDS) method is used to optimize the collimation system for Rapid Cycling Synchrotron (RCS) of the Chinese Spallation Neutron Source (CSNS). The parameters of secondary collimators are optimized for a better performance of the collimation system. To improve the efficiency of the optimization, the Objective Ring Beam Injection and Tracking (ORBIT) parallel module combined with MATLAB parallel computing is used, which can run multiple ORBIT instances simultaneously. This study presents a way to figure out an optimal parameter combination of the secondary collimators for a machine model in preparation for CSNS/RCS commissioning.

  4. Two dimensional simulation of direct methanol fuel cell : a new (embedded) type of current collectors

    OpenAIRE

    Kulikovsky, A. A.; Divisek, J.; Kornyshev, Yu. M.

    2000-01-01

    A two-dimensional numerical model of the direct methanol fuel cell with gas fuel is developed. Simulation of the cell with current collectors of conventional geometry reveal the formation of fuel-depleted, "shaded" regions in the cathode and anode catalyst layers. These regions are positioned in front of current collectors, farther from the gas channel windows. Another disadvantage of the conventional geometry is the concentration of electron current at the edges of current collectors. Based ...

  5. Cytotoxicity, Bactericidal, and Antioxidant Activity of Sodium Alginate Hydrosols Treated with Direct Electric Current

    Directory of Open Access Journals (Sweden)

    Żaneta Król

    2017-03-01

    Full Text Available The aim of the study was to investigate the effect of using direct electric current (DC of 0, 200, and 400 mA for five minutes on the physiochemical properties, cytotoxicity, antibacterial, and antioxidant activity of sodium alginate hydrosols with different sodium chloride concentrations. The pH, oxidation-reduction potential (ORP, electrical conductivity (EC, and available chlorine concentration (ACC were measured. The effect of sodium alginate hydrosols treated with DC on Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Micrococcus luteus, Escherichia coli, Salmonella enteritidis, Yersinia enterocolitica, Pseudomonas fluorescence, and RAW 264.7 and L929 cells was investigated. Subsequently, the antioxidant properties of hydrosols were evaluated by determining the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH and ferric reducing antioxidant power (FRAP. The results have shown that after applying 400 mA in hydrosol samples with 0.1% and 0.2% NaCl all tested bacteria were inactivated. The ACC concentration of C400 samples with NaCl was equal to 13.95 and 19.71 mg/L, respectively. The cytotoxicity analysis revealed that optimized electric field conditions and the addition of sodium chloride allow for the avoidance of toxicity effects on normal cells without disturbing the antibacterial effects. Due to the presence of oxidizing substances, the DPPH of variants treated with DC was lower than the DPPH of control samples.

  6. Cytotoxicity, Bactericidal, and Antioxidant Activity of Sodium Alginate Hydrosols Treated with Direct Electric Current.

    Science.gov (United States)

    Król, Żaneta; Marycz, Krzysztof; Kulig, Dominika; Marędziak, Monika; Jarmoluk, Andrzej

    2017-03-22

    The aim of the study was to investigate the effect of using direct electric current (DC) of 0, 200, and 400 mA for five minutes on the physiochemical properties, cytotoxicity, antibacterial, and antioxidant activity of sodium alginate hydrosols with different sodium chloride concentrations. The pH, oxidation-reduction potential (ORP), electrical conductivity (EC), and available chlorine concentration (ACC) were measured. The effect of sodium alginate hydrosols treated with DC on Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Micrococcus luteus, Escherichia coli, Salmonella enteritidis, Yersinia enterocolitica, Pseudomonas fluorescence, and RAW 264.7 and L929 cells was investigated. Subsequently, the antioxidant properties of hydrosols were evaluated by determining the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) and ferric reducing antioxidant power (FRAP). The results have shown that after applying 400 mA in hydrosol samples with 0.1% and 0.2% NaCl all tested bacteria were inactivated. The ACC concentration of C400 samples with NaCl was equal to 13.95 and 19.71 mg/L, respectively. The cytotoxicity analysis revealed that optimized electric field conditions and the addition of sodium chloride allow for the avoidance of toxicity effects on normal cells without disturbing the antibacterial effects. Due to the presence of oxidizing substances, the DPPH of variants treated with DC was lower than the DPPH of control samples.

  7. Transcranial direct current stimulation in Parkinson's disease: Neurophysiological mechanisms and behavioral effects.

    Science.gov (United States)

    Broeder, Sanne; Nackaerts, Evelien; Heremans, Elke; Vervoort, Griet; Meesen, Raf; Verheyden, Geert; Nieuwboer, Alice

    2015-10-01

    Recent research has highlighted the potential of transcranial direct current stimulation (tDCS) to complement rehabilitation effects in the elderly and in patients with neurological diseases, including Parkinson's disease (PD). TDCS can modulate cortical excitability and enhance neurophysiological mechanisms that compensate for impaired learning in PD. The objective of this systematic review is to provide an overview of the effects of tDCS on neurophysiological and behavioral outcome measures in PD patients, both as a stand-alone and as an adjunctive therapy. We systematically reviewed the literature published throughout the last 10 years. Ten studies were included, most of which were sham controlled. Results confirmed that tDCS applied to the motor cortex had significant results on motor function and to a lesser extent on cognitive tests. However, the physiological mechanism underlying the long-term effects of tDCS on cortical excitability in the PD brain are still unclear and need to be clarified in order to apply this technique optimally to a wider population in the different disease stages and with different medication profiles.

  8. Metabolic Investigation in Gluconacetobacter xylinus and Its Bacterial Cellulose Production under a Direct Current Electric Field.

    Science.gov (United States)

    Liu, Miao; Zhong, Cheng; Zhang, Yu Ming; Xu, Ze Ming; Qiao, Chang Sheng; Jia, Shi Ru

    2016-01-01

    The effects of a direct current (DC) electric field on the growth and metabolism of Gluconacetobacter xylinus were investigated in static culture. When a DC electric field at 10 mA was applied using platinum electrodes to the culture broth, bacterial cellulose (BC) production was promoted in 12 h but was inhibited in the last 12 h as compared to the control (without DC electric field). At the cathode, the presence of the hydrogen generated a strong reductive environment that is beneficial to cell growth. As compared to the control, the activities of glycolysis and tricarboxylic acid cycle, as well as BC productivity were observed to be slightly higher in the first 12 h. However, due to the absence of sufficient oxygen, lactic acid was accumulated from pyruvic acid at 18 h, which was not in favor of BC production. At the anode, DC inhibited cell growth in 6 h when compared to the control. The metabolic activity in G. xylinus was inhibited through the suppression of the tricarboxylic acid cycle and glycolysis. At 18-24 h, cell density was observed to decrease, which might be due to the electrolysis of water that significantly dropped the pH of cultural broth far beyond the optimal range. Meanwhile, metabolites for self-protection were accumulated, for instance proline, glutamic acid, gluconic acid, and fatty acids. Notably, the accumulation of gluconic acid and lactic acid made it a really tough acid stress to cells at the anode and finally led to depression of cell growth.

  9. Escherichia coli as a fatty acid and biodiesel factory: current challenges and future directions.

    Science.gov (United States)

    Rahman, Ziaur; Rashid, Naim; Nawab, Javed; Ilyas, Muhammad; Sung, Bong Hyun; Kim, Sun Chang

    2016-06-01

    Biodiesel has received widespread attention as a sustainable, environment-friendly, and alternative source of energy. It can be derived from plant, animal, and microbial organisms in the form of vegetable oil, fats, and lipids, respectively. However, biodiesel production from such sources is not economically feasible due to extensive downstream processes, such as trans-esterification and purification. To obtain cost-effective biodiesel, these bottlenecks need to be overcome. Escherichia coli, a model microorganism, has the potential to produce biodiesel directly from ligno-cellulosic sugars, bypassing trans-esterification. In this process, E. coli is engineered to produce biodiesel using metabolic engineering technology. The entire process of biodiesel production is carried out in a single microbial cell, bypassing the expensive downstream processing steps. This review focuses mainly on production of fatty acid and biodiesel in E. coli using metabolic engineering approaches. In the first part, we describe fatty acid biosynthesis in E. coli. In the second half, we discuss bottlenecks and strategies to enhance the production yield. A complete understanding of current developments in E. coli-based biodiesel production and pathway optimization strategies would reduce production costs for biofuels and plant-derived chemicals.

  10. Stem cell technology for tendon regeneration: current status, challenges, and future research directions

    Directory of Open Access Journals (Sweden)

    Lui PP

    2015-12-01

    Full Text Available Pauline Po Yee Lui Headquarter, Hospital Authority, Hong Kong SAR, People's Republic of China Abstract: Tendon injuries are a common cause of physical disability. They present a clinical challenge to orthopedic surgeons because injured tendons respond poorly to current treatments without tissue regeneration and the time required for rehabilitation is long. New treatment options are required. Stem cell-based therapies offer great potential to promote tendon regeneration due to their high proliferative, synthetic, and immunomodulatory activities as well as their potential to differentiate to the target cell types and undergo genetic modification. In this review, I first recapped the challenges of tendon repair by reviewing the anatomy of tendon. Next, I discussed the advantages and limitations of using different types of stem cells compared to terminally differentiated cells for tendon tissue engineering. The safety and efficacy of application of stem cells and their modified counterparts for tendon tissue engineering were then summarized after a systematic literature search in PubMed. The challenges and future research directions to enhance, optimize, and standardize stem cell-based therapies for augmenting tendon repair were then discussed. Keywords: stem cells, tendon repair, tendon tissue engineering, tendon injuries

  11. THE ASSESSMENT OF ENTREPRENEURIAL PERSONALITY: THE CURRENT SITUATION AND FUTURE DIRECTIONS

    Directory of Open Access Journals (Sweden)

    Javier Suárez-Álvarez

    2016-01-01

    Full Text Available Entrepreneurship is fundamental in modern society because it represents an important source of innovation, employment, productivity, and growth. While the first theoretical models arose from economic and sociological approaches, psychology provides models that integrate different aspects such as cognitions, attitudes and personality, which allow a more detailed study. The purpose of this paper is to show the main contributions of psychology to the assessment of the enterprising personality. For this purpose, the main models and instruments developed to date were reviewed. The results confirm that the enterprising personality has a multidimensional structure and eight personality traits can be highlighted: achievement motivation, risk-taking, autonomy, self-efficacy, stress tolerance, innovativeness, internal locus of control, and optimism. From a methodological point of view, Item Response Theory and Computerised Adaptive Tests represent the most advanced and modern methods for assessing enterprising personality. There are currently several measurement instruments available. Future areas of research should be directed at the construction of multidimensional models as well as providing alternatives that facilitate a reduction in social desirability and other biases inherent in self-reports.

  12. Using Feasible Direction to Find All Alternative Extreme Optimal Points for Linear Programming Problem

    Directory of Open Access Journals (Sweden)

    S. F. Tantawy

    2007-01-01

    Full Text Available We presented a feasible direction method to find all optimal extreme points for the linear programming problem. Our method depends on the conjugate gradient projection method starting with an initial point we generate a sequence of feasible directions towards all alternative extremes.

  13. Transcranial direct current stimulation modulates human color discrimination in a pathway specific manner.

    Directory of Open Access Journals (Sweden)

    Thiago Leiros eCosta

    2012-09-01

    Full Text Available Previous research showed that Transcranial Direct Current Stimulation (tDCS can modulate visual cortex excitability. However, there is no experiment on the effects of tDCS on color perception to date. The present study aimed to investigate the effects of tDCS on color discrimination tasks. 15 healthy subjects (mean age of 25.6 ± 4.4 years were tested with Cambridge Color Test 2.0 (Trivector and Ellipses protocols and a Forced-choice Spatial Color Contrast Sensitivity task (vertical red-green sinusoidal grating while receiving tDCS. Anodal, cathodal and sham tDCS were delivered at Oz for 22 minutes using two square electrodes (25cm2 with a current of 1.5mA in sessions separated by 7 days. Anodal tDCS significantly increased tritan sensitivity (p<0.01 and had no significant effect on protan, deutan or red-green grating discrimination. The effects on the tritan discrimination returned to baseline after 15 minutes (p<0.01. Cathodal tDCS reduced the sensitivity in the deutan axis and increased sensitivity in the tritan axis (p<0.05. The lack of anodal tDCS effects in the protan, deutan and red-green grating sensitivities could be explained by a ceiling effect since adults in this age range tend to have optimal color discrimination performance for these hues. The differential effects of cathodal tDCS on tritan and deutan sensitivities and the absence of the proposed ceiling effects for the tritan axes might be explained by Parvocellular (P and Koniocellular (K systems with regard to their functional, physiological and anatomical differences. The results also support the existence of a systematic segregation of P and K color-coding cells in V1. Future research and possible clinical implications are discussed.

  14. Sexuality education in North American medical schools: current status and future directions.

    Science.gov (United States)

    Shindel, Alan W; Parish, Sharon J

    2013-01-01

    Both the general public and individual patients expect healthcare providers to be knowledgeable and approachable regarding sexual health. Despite this expectation there are no universal standards or expectations regarding the sexuality education of medical students. To review the current state of the art in sexuality education for North American medical students and to articulate future directions for improvement. Evaluation of: (i) peer-reviewed literature on sexuality education (focusing on undergraduate medical students); and (ii) recommendations for sexuality education from national and international public health organizations. Current status and future innovations for sexual health education in North American medical schools. Although the importance of sexuality to patients is recognized, there is wide variation in both the quantity and quality of education on this topic in North American medical schools. Many sexual health education programs in medical schools are focused on prevention of unwanted pregnancy and sexually transmitted infection. Educational material on sexual function and dysfunction, female sexuality, abortion, and sexual minority groups is generally scant or absent. A number of novel interventions, many student initiated, have been implemented at various medical schools to improve the student's training in sexual health matters. There is a tremendous opportunity to mold the next generation of healthcare providers to view healthy sexuality as a relevant patient concern. A comprehensive and uniform curriculum on human sexuality at the medical school level may substantially enhance the capacity of tomorrow's physicians to provide optimal care for their patients irrespective of gender, sexual orientation, and individual sexual mores/beliefs. © 2013 International Society for Sexual Medicine.

  15. The solution of singular optimal control problems using direct collocation and nonlinear programming

    Science.gov (United States)

    Downey, James R.; Conway, Bruce A.

    1992-08-01

    This paper describes work on the determination of optimal rocket trajectories which may include singular arcs. In recent years direct collocation and nonlinear programming has proven to be a powerful method for solving optimal control problems. Difficulties in the application of this method can occur if the problem is singular. Techniques exist for solving singular problems indirectly using the associated adjoint formulation. Unfortunately, the adjoints are not a part of the direct formulation. It is shown how adjoint information can be obtained from the direct method to allow the solution of singular problems.

  16. Characterization of a direct methanol fuel cell using Hilbert curve fractal current collectors

    Energy Technology Data Exchange (ETDEWEB)

    Kuan, Yean-Der [Department of Refrigeration, Air-Conditioning and Energy Engineering, National Chun-Yi University of Technology, NO 35, Lane 215, Section 1, Chung-Shan Road, Taiping City, 411 Taichung County (China); Chang, Jing-Yi [Department of Mechanical and Electro-Mechanical Engineering, Tamkang University, Tamsui, 251 Taipei County (China); Lee, Shi-Min [Department of Aerospace Engineering, Tamkang University, Tamsui, 251 Taipei County (China); Lee, Shah-Rong [Department of Mechanical Engineering, Technology and Science Institute of Northern Taiwan, Peitou, 112 Taipei (China)

    2009-02-01

    The current collector or bi-polar plate is a key component in direct methanol fuel cells (DMFCs). Current collector geometric designs have significant influence on cell performance. This paper presents a continuous type fractal geometry using the Hilbert curve applied to current collector design in a direct methanol fuel cell. The Hilbert curve fractal geometry current collector is named HFCC (Hilbert curve fractal current collector). This research designs the current collector using a first, second and third order open carved HFCC shape. The cell performances of the different current collector geometries were measured and compared. Two important factors, the free open ratio and total perimeter length of the open carved design are discussed. The results show that both the larger free open ratio and longer carved open perimeter length present higher performance. (author)

  17. Characterization of a direct methanol fuel cell using Hilbert curve fractal current collectors

    Science.gov (United States)

    Kuan, Yean-Der; Chang, Jing-Yi; Lee, Shi-Min; Lee, Shah-Rong

    The current collector or bi-polar plate is a key component in direct methanol fuel cells (DMFCs). Current collector geometric designs have significant influence on cell performance. This paper presents a continuous type fractal geometry using the Hilbert curve applied to current collector design in a direct methanol fuel cell. The Hilbert curve fractal geometry current collector is named HFCC (Hilbert curve fractal current collector). This research designs the current collector using a first, second and third order open carved HFCC shape. The cell performances of the different current collector geometries were measured and compared. Two important factors, the free open ratio and total perimeter length of the open carved design are discussed. The results show that both the larger free open ratio and longer carved open perimeter length present higher performance.

  18. Effectiveness of transcranial direct current stimulation and visual illusion on neuropathic pain in spinal cord injury

    National Research Council Canada - National Science Library

    Soler, Maria Dolors; Kumru, Hatice; Pelayo, Raul; Vidal, Joan; Tormos, Josep Maria; Fregni, Felipe; Navarro, Xavier; Pascual-Leone, Alvaro

    2010-01-01

    ... with neuropathic pain following spinal cord injury. In a sham controlled, double-blind, parallel group design, 39 patients were randomized into four groups receiving transcranial direct current stimulation with walking visual illusion or with control...

  19. An Optimization System with Parallel Processing for Reducing Common-Mode Current on Electronic Control Unit

    Science.gov (United States)

    Okazaki, Yuji; Uno, Takanori; Asai, Hideki

    In this paper, we propose an optimization system with parallel processing for reducing electromagnetic interference (EMI) on electronic control unit (ECU). We adopt simulated annealing (SA), genetic algorithm (GA) and taboo search (TS) to seek optimal solutions, and a Spice-like circuit simulator to analyze common-mode current. Therefore, the proposed system can determine the adequate combinations of the parasitic inductance and capacitance values on printed circuit board (PCB) efficiently and practically, to reduce EMI caused by the common-mode current. Finally, we apply the proposed system to an example circuit to verify the validity and efficiency of the system.

  20. Jamming transition of a two-dimensional traffic dynamics with consideration of optimal current difference

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Arvind Kumar, E-mail: akgupta@iitrpr.ac.in; Redhu, Poonam

    2013-11-01

    A modified two-dimensional lattice hydrodynamic traffic flow model is proposed by incorporating the optimal current difference effect of leading vehicles. Phase transitions and critical phenomenon are investigated near the critical point both analytically and numerically. Based on the configuration of vehicles, it is shown that two distinct jamming transitions occur: conventional jamming transition to the kink jam and jamming transition to the chaotic jam. It is shown that consideration of optimal current difference effect stabilizes the traffic flow and suppresses the traffic jam efficiently for all possible configurations of vehicles on a square lattice.

  1. Task-driven optimization of CT tube current modulation and regularization in model-based iterative reconstruction

    Science.gov (United States)

    Gang, Grace J.; Siewerdsen, Jeffrey H.; Webster Stayman, J.

    2017-06-01

    Tube current modulation (TCM) is routinely adopted on diagnostic CT scanners for dose reduction. Conventional TCM strategies are generally designed for filtered-backprojection (FBP) reconstruction to satisfy simple image quality requirements based on noise. This work investigates TCM designs for model-based iterative reconstruction (MBIR) to achieve optimal imaging performance as determined by a task-based image quality metric. Additionally, regularization is an important aspect of MBIR that is jointly optimized with TCM, and includes both the regularization strength that controls overall smoothness as well as directional weights that permits control of the isotropy/anisotropy of the local noise and resolution properties. Initial investigations focus on a known imaging task at a single location in the image volume. The framework adopts Fourier and analytical approximations for fast estimation of the local noise power spectrum (NPS) and modulation transfer function (MTF)—each carrying dependencies on TCM and regularization. For the single location optimization, the local detectability index (d‧) of the specific task was directly adopted as the objective function. A covariance matrix adaptation evolution strategy (CMA-ES) algorithm was employed to identify the optimal combination of imaging parameters. Evaluations of both conventional and task-driven approaches were performed in an abdomen phantom for a mid-frequency discrimination task in the kidney. Among the conventional strategies, the TCM pattern optimal for FBP using a minimum variance criterion yielded a worse task-based performance compared to an unmodulated strategy when applied to MBIR. Moreover, task-driven TCM designs for MBIR were found to have the opposite behavior from conventional designs for FBP, with greater fluence assigned to the less attenuating views of the abdomen and less fluence to the more attenuating lateral views. Such TCM patterns exaggerate the intrinsic anisotropy of the MTF and NPS

  2. Dependence of critical current density on crystalline direction in thin YBCO films

    DEFF Research Database (Denmark)

    Paturi, P.; Peurla, M.; Raittila, J.

    2005-01-01

    The dependence of critical current density (J(c)) on the angle between the current direction and the (100) direction in the ab-plane of thin YBCO films deposited on (001)-SrTiO3 from natiocrystalline and microcrystalline targets is studied using magneto-optical microscopy. In the films made from ...... indicating that in addition to linear defects also the twin boundaries are very important flux pinning sites. (c) 2005 Elsevier B.V. All rights reserved....

  3. Outcomes in spasticity after repetitive transcranial magnetic and transcranial direct current stimulations

    OpenAIRE

    Gunduz, Aysegul; Kumru, Hatice; Pascual-Leone, Alvaro

    2014-01-01

    Non-invasive brain stimulations mainly consist of repetitive transcranial magnetic stimulation and transcranial direct current stimulation. Repetitive transcranial magnetic stimulation exhibits satisfactory outcomes in improving multiple sclerosis, stroke, spinal cord injury and cerebral palsy-induced spasticity. By contrast, transcranial direct current stimulation has only been studied in post-stroke spasticity. To better validate the efficacy of non-invasive brain stimulations in improving ...

  4. Pulsed Direct Current Electric Fields Enhance Osteogenesis in Adipose-Derived Stromal Cells

    OpenAIRE

    Hammerick, Kyle E.; James, Aaron W.; Huang, Zubin; Prinz, Fritz B.; Michael T. Longaker

    2009-01-01

    Adipose-derived stromal cells (ASCs) constitute a promising source of cells for regenerative medicine applications. Previous studies of osteogenic potential in ASCs have focused on chemicals, growth factors, and mechanical stimuli. Citing the demonstrated role electric fields play in enhancing healing in bone fractures and defects, we investigated the ability of pulsed direct current electric fields to drive osteogenic differentiation in mouse ASCs. Employing 50 Hz direct current electric fie...

  5. Direct-current resistivity data from 94 sites in northeastern Palm Beach County, Florida

    Science.gov (United States)

    Peterson, Cathleen J.

    1988-01-01

    Direct-current resistivity data were collected from 94 vertical electric sounding profiles in northeastern Palm Beach County, Florida. Direct-current resistivity data, which may be used to determine the location and thicknesses of shallow, semipermeable marls or locate zones of high chloride concentration, are presented in this report. The resistivity data consist of field data, smoothed data, layer resistivity from smoothed data, and Cartesian graphs of resistivity in relation to depth for 94 sites located in northeastern Palm Beach County. (USGS)

  6. Bursting and spiking due to additional direct and stochastic currents in neuron models

    Institute of Scientific and Technical Information of China (English)

    Yang Zhuo-Qin; Lu Qi-Shao

    2006-01-01

    Neurons at rest can exhibit diverse firing activities patterns in response to various external deterministic and random stimuli, especially additional currents. In this paper, neuronal firing patterns from bursting to spiking, induced by additional direct and stochastic currents, are explored in rest states Corresponding to two values of the parameter VK in the Chay neuron system. Three cases are considered by numerical simulation and fast/slow dynamic analysis, in which only the direct current or the stochastic current exists, or the direct and stochastic currents coexist. Meanwhile, several important bursting patterns in neuronal experiments, such as the period-1 "circle/homoclinic" bursting and the integer multiple "fold/homoclinic" bursting with one spike per burst, as well as the transition from integer multiple bursting to period-1 "circle/homoclinic" bursting and that from stochastic "Hopf/homoclinic" bursting to "Hopf/homoclinic" bursting, are investigated in detail.

  7. Improvement of Power Flow Calculation with Optimization Factor Based on Current Injection Method

    Directory of Open Access Journals (Sweden)

    Lei Wang

    2014-01-01

    Full Text Available This paper presents an improvement in power flow calculation based on current injection method by introducing optimization factor. In the method proposed by this paper, the PQ buses are represented by current mismatches while the PV buses are represented by power mismatches. It is different from the representations in conventional current injection power flow equations. By using the combined power and current injection mismatches method, the number of the equations required can be decreased to only one for each PV bus. The optimization factor is used to improve the iteration process and to ensure the effectiveness of the improved method proposed when the system is ill-conditioned. To verify the effectiveness of the method, the IEEE test systems are tested by conventional current injection method and the improved method proposed separately. Then the results are compared. The comparisons show that the optimization factor improves the convergence character effectively, especially that when the system is at high loading level and R/X ratio, the iteration number is one or two times less than the conventional current injection method. When the overloading condition of the system is serious, the iteration number in this paper appears 4 times less than the conventional current injection method.

  8. A column-generation-based method for multi-criteria direct aperture optimization.

    Science.gov (United States)

    Salari, Ehsan; Unkelbach, Jan

    2013-02-01

    Navigation-based multi-criteria optimization has been introduced to radiotherapy planning in order to allow the interactive exploration of trade-offs between conflicting clinical goals. However, this has been mainly applied to fluence map optimization. The subsequent leaf sequencing step may cause dose discrepancy, leading to human iteration loops in the treatment planning process that multi-criteria methods were meant to avoid. To circumvent this issue, this paper investigates the application of direct aperture optimization methods in the context of multi-criteria optimization. We develop a solution method to directly obtain a collection of apertures that can adequately span the entire Pareto surface. To that end, we extend the column generation method for direct aperture optimization to a multi-criteria setting in which apertures that can improve the entire Pareto surface are sequentially identified and added to the treatment plan. Our proposed solution method can be embedded in a navigation-based multi-criteria optimization framework, in which the treatment planner explores the trade-off between treatment objectives directly in the space of deliverable apertures. Our solution method is demonstrated for a paraspinal case where the trade-off between target coverage and spinal-cord sparing is studied. The computational results validate that our proposed method obtains a balanced approximation of the Pareto surface over a wide range of clinically relevant plans.

  9. Transcranial Direct-Current Stimulation Increases Extracellular Dopamine Levels in the Rat Striatum

    Directory of Open Access Journals (Sweden)

    Tomoko eTanaka

    2013-04-01

    Full Text Available Background: Transcranial direct-current stimulation is a non-invasive procedure that achieves polarity-dependent modulation of neuronal membrane potentials. It has recently been used as a functional intervention technique for the treatment of psychiatric and neurological diseases; however, its neuronal mechanisms have not been fully investigated in vivo. Objective/Hypothesis: To investigate whether the application of cathodal or anodal transcranial direct-current stimulation affects extracellular dopamine and serotonin levels in the rat striatum. Methods: Stimulation and in vivo microdialysis were carried out under urethane anesthesia, and microdialysis probes were slowly inserted into the striatum. After the collection of baseline fractions in the rat striatum, cathodal or anodal transcranial direct-current stimulation was applied continuously for 10 min with a current intensity of 800 µA from an electrode placed on the skin of the scalp. Dialysis samples were collected every 10 min until at least 400 min after the onset of stimulation.Results: Following the application of cathodal, but not anodal, transcranial direct-current stimulation for 10 min, extracellular dopamine levels increased for more than 400 min in the striatum. There were no significant changes in extracellular serotonin levels. Conclusion: These findings suggest that transcranial direct-current stimulation has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia.

  10. Direct-aperture optimization applied to selection of beam orientations in intensity-modulated radiation therapy

    Science.gov (United States)

    Bedford, J. L.; Webb, S.

    2007-01-01

    Direct-aperture optimization (DAO) was applied to iterative beam-orientation selection in intensity-modulated radiation therapy (IMRT), so as to ensure a realistic segmental treatment plan at each iteration. Nested optimization engines dealt separately with gantry angles, couch angles, collimator angles, segment shapes, segment weights and wedge angles. Each optimization engine performed a random search with successively narrowing step sizes. For optimization of segment shapes, the filtered backprojection (FBP) method was first used to determine desired fluence, the fluence map was segmented, and then constrained direct-aperture optimization was used thereafter. Segment shapes were fully optimized when a beam angle was perturbed, and minimally re-optimized otherwise. The algorithm was compared with a previously reported method using FBP alone at each orientation iteration. An example case consisting of a cylindrical phantom with a hemi-annular planning target volume (PTV) showed that for three-field plans, the method performed better than when using FBP alone, but for five or more fields, neither method provided much benefit over equally spaced beams. For a prostate case, improved bladder sparing was achieved through the use of the new algorithm. A plan for partial scalp treatment showed slightly improved PTV coverage and lower irradiated volume of brain with the new method compared to FBP alone. It is concluded that, although the method is computationally intensive and not suitable for searching large unconstrained regions of beam space, it can be used effectively in conjunction with prior class solutions to provide individually optimized IMRT treatment plans.

  11. Reduction of edge effect on disk electrodes by optimized current waveform.

    Science.gov (United States)

    Wang, Boshuo; Petrossians, Artin; Weiland, James D

    2014-08-01

    Rectangular pulses applied to disk electrodes result in high current density at the edges of the disk, which can lead to electrode corrosion and tissue damage. We explored a method for reducing current density and corrosion, by varying the leading edge of the current pulse. Finite-element modeling and mathematical analysis were used to predict an optimal waveform that reduces current density at the edge while also maintaining short pulse duration. An approximation of the optimized waveform was implemented experimentally and applied to platinum disk electrodes. Surface analysis using energy-dispersive spectroscopy showed significant reduction of corrosion on the periphery of these electrodes after pulsing, compared to those pulsed with the control rectangular waveform.

  12. Sequential Optimization of Paths in Directed Graphs Relative to Different Cost Functions

    KAUST Repository

    Mahayni, Malek A.

    2011-07-01

    Finding optimal paths in directed graphs is a wide area of research that has received much of attention in theoretical computer science due to its importance in many applications (e.g., computer networks and road maps). Many algorithms have been developed to solve the optimal paths problem with different kinds of graphs. An algorithm that solves the problem of paths’ optimization in directed graphs relative to different cost functions is described in [1]. It follows an approach extended from the dynamic programming approach as it solves the problem sequentially and works on directed graphs with positive weights and no loop edges. The aim of this thesis is to implement and evaluate that algorithm to find the optimal paths in directed graphs relative to two different cost functions ( , ). A possible interpretation of a directed graph is a network of roads so the weights for the function represent the length of roads, whereas the weights for the function represent a constraint of the width or weight of a vehicle. The optimization aim for those two functions is to minimize the cost relative to the function and maximize the constraint value associated with the function. This thesis also includes finding and proving the relation between the two different cost functions ( , ). When given a value of one function, we can find the best possible value for the other function. This relation is proven theoretically and also implemented and experimented using Matlab®[2].

  13. Optimizing energy management of fuel cell-direct storage-hybrid systems; Optimierendes Energiemanagement von Brennstoffzelle-Direktspeicher-Hybridsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Bocklisch, Thilo

    2010-03-29

    The dissertation presents a new optimizing energy management concept for fuel cell-direct storage-hybrid systems. Initially, the characteristics of specific energy time series are investigated on the basis of real measurement data. A new concept for the multi-scale analysis, modelling and prediction of fluctuating photovoltaic supply and electric load demand profiles is developed. The second part of the dissertation starts with a discussion of the benefits of and the basic coupling and control principles for fuel cell-direct storage-hybrid systems. The typical characteristics of a PEM-fuel cell, a metal hydride hydrogen storage, a lithium-ion battery and a supercap unit are presented. A new modular DC/DC-converter is described. Results from experimental and theoretical investigations of the individual components and the overall hybrid system are discussed. New practicable models for the voltage-current-curve, the state of charge behaviour and the conversion losses are presented. The third part of the dissertation explains the new energy management concept. The optimization of power flows is achieved by a control-oriented approach, employing a) the primary control of bus voltage and fuel cell current, b) the secondary control to limit fuel cell current gradient and operating range and to perform direct storage charge control, and c) the system control to optimally adjust secondary control parameters aiming for a reduction of dynamic fuel cell stress and hydrogen consumption. Results from simulations and experimental investigations demonstrate the benefits and high capabilities of the new optimizing energy management concept. Examples of stationary and portable applications conclude the dissertation. (orig.)

  14. Impact of transcranial direct current stimulation (tDCS) on neuronal functions

    NARCIS (Netherlands)

    Das, S. (Suman); P. Holland (Peter); M.A. Frens (Maarten); O. Donchin (Opher)

    2016-01-01

    textabstractTranscranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, modulates neuronal excitability by the application of a small electrical current. The low cost and ease of the technique has driven interest in potential clinical applications. However, outcomes a

  15. IMRT of prostate cancer. A comparison of fluence optimization with sequential segmentation and direct step-and-shoot optimization

    Energy Technology Data Exchange (ETDEWEB)

    Treutwein, Marius; Hipp, Matthias; Koelbl, Oliver; Bogner, Ludwig [Dept. of Radiation Oncology, Regensburg Univ. Medical Center (Germany)

    2009-06-15

    Background and purpose: intensity-modulated radiation therapy (IMRT) has shown its superiority to three-dimensional conformal radiotherapy in the treatment of prostate cancer. Different optimization algorithms are available: algorithms which first optimize the fluence followed by a sequencing (IM), and algorithms which involve the machine parameters directly in the optimization process (DSS). The aim of this treatment-planning study is to compare both of them regarding dose distribution and treatment time. Patients and methods: ten consecutive patients with localized prostate cancer were enrolled for the planning study. The planning target volume and the rectum volume, urinary bladder and femoral heads as organs at risk were delineated. Average doses, the target dose homogeneity H, D{sub 5}, D{sub 95}, monitor units per fraction, and the number of segments were evaluated. Results: while there is only a small difference in the mean doses at rectum and bladder, there is a significant advantage for the target dose homogeneity in the DSS-optimized plans compared to the IM-optimized ones. Differences in the monitor units (nearly 10% less for DSS) and the number of segments are also statistically significant and reduce the treatment time. Conclusion: particularly with regard to the tumor control probability, the better homogeneity of the DSS-optimized plans is more profitable. The shorter treatment time is an improvement regarding intrafractional organ motion. The DSS optimizer results in a higher target dose homogeneity and, simultaneously, in a lower number of monitor units. Therefore, it should be preferred for IMRT of prostate cancer. (orig.)

  16. Designing spectrum-splitting dichroic filters to optimize current-matched photovoltaics.

    Science.gov (United States)

    Miles, Alexander; Cocilovo, Byron; Wheelwright, Brian; Pan, Wei; Tweet, Doug; Norwood, Robert A

    2016-03-10

    We have developed an approach for designing a dichroic coating to optimize performance of current-matched multijunction photovoltaic cells while diverting unused light. By matching the spectral responses of the photovoltaic cells and current matching them, substantial improvement to system efficiencies is shown to be possible. A design for use in a concentrating hybrid solar collector was produced by this approach, and is presented. Materials selection, design methodology, and tilt behavior on a curved substrate are discussed.

  17. Optimization of a neural network based direct inverse control for controlling a quadrotor unmanned aerial vehicle

    Directory of Open Access Journals (Sweden)

    Heryanto M Ary

    2015-01-01

    Full Text Available UAVs are mostly used for surveillance, inspection and data acquisition. We have developed a Quadrotor UAV that is constructed based on a four motors with a lift-generating propeller at each motors. In this paper, we discuss the development of a quadrotor and its neural networks direct inverse control model using the actual flight data. To obtain a better performance of the control system of the UAV, we proposed an Optimized Direct Inverse controller based on re-training the neural networks with the new data generated from optimal maneuvers of the quadrotor. Through simulation of the quadrotor using the developed DIC and Optimized DIC model, results show that both models have the ability to stabilize the quadrotor with a good tracking performance. The optimized DIC model, however, has shown a better performance, especially in the settling time parameter.

  18. Multi-Step Amplitude Quantization for Ultralow Sidelobe Phased Arrays by Direct Optimization Synthesis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, a new amplitude quautization synthesis method for ultraiow sidelobe phased arrays is proposed,which is based on the constrained nonlinear optimization algorithm. By introducing a set of critical constraint conditionsinto the optimization model, we can directly quantize the amplitude distribution instead of replacing it with a continuousequivalent aperture antenne The mutual coupling and the element patterns are also considered in the quantizationsynthesis. Finally, some array simulation results are given to show the effectiveness of the method.

  19. The research on direct-drive wave energy conversion system and performance optimization

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhongxian; YU Haitao; HU Minqiang

    2014-01-01

    A direct-drive wave energy conversion system based on a three-phase permanent magnet tubular linear generator (PMTLG) and a heaving buoy is proposed to convert wave energy into electrical energy. Sufficient experimental methods are adopted to compare the computer simulations, the validity of which is verified by the experiment results from a wave tank laboratory. In the experiment, the motion curves of heaving buoy are with small fluctuations, mainly caused by the PMTLG’s detent force. For the reduction of these small fluctuations and a maximum operational efficiency of the direct-drive wave energy conversion system, the PMTLG’s detent force minimization technique and the heaving buoy optimization will be discussed. It is discovered that the operational efficiency of the direct-drive wave energy conversion system increases dra-matically after optimization. The experiment and optimization results will provide useful reference for the future research on ocean wave energy conversion system.

  20. Design of passive directional acoustic devices using Topology Optimization - from method to experimental validation

    DEFF Research Database (Denmark)

    Christiansen, Rasmus Ellebæk; Fernandez Grande, Efren

    2016-01-01

    The paper presents a topology optimization based method for designing acoustic focusing devices, capable of tailoring the sound emission pattern of one or several sources, across a chosen frequency band. The method is demonstrated numerically considering devices optimized for directional sound...... emission in two dimensions and is experimentally validated using three dimensional prints of the optimized designs. The emitted fields exhibit a level difference of at least 15 dB on axis relative to the off-axis directions, over frequency bands of approximately an octave. It is demonstrated to be possible...... to outperform the latter in terms of directivity and maximum side-lobe level over nearly an octave band. A set of frequencies are considered simultaneously in the design formulation and performance robustness toward uniform spatial production errors in the designed devices is assured by including perturbations...

  1. Current limiting characteristics of transformer type SFCL with coupled secondary windings according to its winding direction

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sung Hun [Dept. of Electrical Engineering, Soongsil University, Seoul (Korea, Republic of); Han, Tae Hee [Dept. of Aero Materials Engineering, Jungwon University, Goesan (Korea, Republic of)

    2017-06-15

    In this paper, the current limiting characteristics of the transformer type superconducting fault current limiter (SFCL) with the two coupled secondary windings due to its winding direction were analyzed. To analyze the dependence of transient fault current limiting characteristics on the winding direction of the additional secondary winding, the fault current limiting tests of the SFCL with an additional secondary winding, wound as subtractive polarity winding and additive polarity winding, were carried out. The time interval of quench occurrence between two superconducting elements comprising the transformer type SFCL with the additional secondary winding was confirmed to be affected by the winding direction of the additional secondary winding. In case of the subtractive polarity winding of the additional secondary winding, the time interval of the quench occurrence in two superconducting elements was shorter than the case of the additive polarity winding.

  2. Bi-directional evolutionary topology optimization of continuum structures with one or multiple materials

    Science.gov (United States)

    Huang, X.; Xie, Y. M.

    2009-02-01

    There are several well-established techniques for the generation of solid-void optimal topologies such as solid isotropic material with penalization (SIMP) method and evolutionary structural optimization (ESO) and its later version bi-directional ESO (BESO) methods. Utilizing the material interpolation scheme, a new BESO method with a penalization parameter is developed in this paper. A number of examples are presented to demonstrate the capabilities of the proposed method for achieving convergent optimal solutions for structures with one or multiple materials. The results show that the optimal designs from the present BESO method are independent on the degree of penalization. The resulted optimal topologies and values of the objective function compare well with those of SIMP method.

  3. Effectiveness of transcranial direct current stimulation and visual illusion on neuropathic pain in spinal cord injury.

    Science.gov (United States)

    Soler, Maria Dolors; Kumru, Hatice; Pelayo, Raul; Vidal, Joan; Tormos, Josep Maria; Fregni, Felipe; Navarro, Xavier; Pascual-Leone, Alvaro

    2010-09-01

    The aim of this study was to evaluate the analgesic effect of transcranial direct current stimulation of the motor cortex and techniques of visual illusion, applied isolated or combined, in patients with neuropathic pain following spinal cord injury. In a sham controlled, double-blind, parallel group design, 39 patients were randomized into four groups receiving transcranial direct current stimulation with walking visual illusion or with control illusion and sham stimulation with visual illusion or with control illusion. For transcranial direct current stimulation, the anode was placed over the primary motor cortex. Each patient received ten treatment sessions during two consecutive weeks. Clinical assessment was performed before, after the last day of treatment, after 2 and 4 weeks follow-up and after 12 weeks. Clinical assessment included overall pain intensity perception, Neuropathic Pain Symptom Inventory and Brief Pain Inventory. The combination of transcranial direct current stimulation and visual illusion reduced the intensity of neuropathic pain significantly more than any of the single interventions. Patients receiving transcranial direct current stimulation and visual illusion experienced a significant improvement in all pain subtypes, while patients in the transcranial direct current stimulation group showed improvement in continuous and paroxysmal pain, and those in the visual illusion group improved only in continuous pain and dysaesthesias. At 12 weeks after treatment, the combined treatment group still presented significant improvement on the overall pain intensity perception, whereas no improvements were reported in the other three groups. Our results demonstrate that transcranial direct current stimulation and visual illusion can be effective in the management of neuropathic pain following spinal cord injury, with minimal side effects and with good tolerability.

  4. Superoxide mediates direct current electric field-induced directional migration of glioma cells through the activation of AKT and ERK.

    Directory of Open Access Journals (Sweden)

    Fei Li

    Full Text Available Direct current electric fields (DCEFs can induce directional migration for many cell types through activation of intracellular signaling pathways. However, the mechanisms that bridge extracellular electrical stimulation with intracellular signaling remain largely unknown. In the current study, we found that a DCEF can induce the directional migration of U87, C6 and U251 glioma cells to the cathode and stimulate the production of hydrogen peroxide and superoxide. Subsequent studies demonstrated that the electrotaxis of glioma cells were abolished by the superoxide inhibitor N-acetyl-l-cysteine (NAC or overexpression of mitochondrial superoxide dismutase (MnSOD, but was not affected by inhibition of hydrogen peroxide through the overexpression of catalase. Furthermore, we found that the presence of NAC, as well as the overexpression of MnSOD, could almost completely abolish the activation of Akt, extracellular-signal-regulated kinase (Erk1/2, c-Jun N-terminal kinase (JNK, and p38, although only JNK and p38 were affected by overexpression of catalase. The presenting of specific inhibitors can decrease the activation of Erk1/2 or Akt as well as the directional migration of glioma cells. Collectively, our data demonstrate that superoxide may play a critical role in DCEF-induced directional migration of glioma cells through the regulation of Akt and Erk1/2 activation. This study provides novel evidence that the superoxide is at least one of the "bridges" coupling the extracellular electric stimulation to the intracellular signals during DCEF-mediated cell directional migration.

  5. Development of a Peltier Current Lead for the 200-m-Class Superconducting Direct Current Transmission and Distribution System

    Science.gov (United States)

    Kawahara, Toshio; Emoto, Masahiko; Watanabe, Hirofumi; Hamabe, Makoto; Yamaguchi, Sataro; Hikichi, Yasuo; Minowa, Masahiro

    2013-07-01

    Reducing cryogenic heat leaks is critical for superconducting applications. Reduction of heat leak at the terminals is essential for uses with short-length applications, where cryogenic losses at the terminals dominate. We are developing a 200-m-class superconducting direct current (DC) transmission and distribution system (CASER-2), and have used a Peltier current lead (PCL) for heat insulation at the terminals. The PCL consists of thermoelectric elements and copper leads, which enhance the performance of superconducting systems. As DC flows through the current lead, thermoelectric elements on opposite terminations of a superconducting line can be used to decrease the heat ingress to the cryogenic environment ( n-type on one end, p-type on the opposite end). During the current feeding and cooling test, a large temperature difference was observed across thermoelectric elements in the PCL. This demonstrates that we have successfully insulated the heat leak at the current lead. During the fourth cooling test, we established a new PCL design with p-type elements at terminal B, and then compared the performance of the terminals. Several improvements were implemented, including balancing the resistances of the PCL to enhance the stability of the superconducting systems.

  6. Optimization of multi-revolution low-thrust transfer based on modified direct method

    Institute of Scientific and Technical Information of China (English)

    CUI Ping-yuan; SHANG Hai-bin; REN Yuan; LUAN En-jie

    2008-01-01

    A modified direct optimization method is proposed to solve the optimal muhi-revolution transfer with low-thrust between Earth-orbits. First, through parametefizing the control steering angles by costate variables, the search space of free parameters has been decreased. Then, in order to obtain the global optimal solution ef-fectively and robustly, the simulated annealing and penalty function strategies were used to handle the con-straints, and a GA/SQP hybrid optimization algorithm was utilized to solve the parameter optimization problem, in which, a feasible suboptimal solution obtained by GA was submitted as an initial parameter set to SQP for re-finement. Comparing to the classical direct method, this novel method has fewer free parameters, needs not ini-tial guesses, and has higher computation precision. An optimal-fuel transfer problem from LEO to GEO was taken as an example to validate the proposed approach. The results of simulation indicate that our approach is a-vailable to solve the problem of optimal multi-revolution transfer between Earth-orbits.

  7. Metabolic investigation in Gluconacetobacter xylinus and its bacterial cellulose production under a direct current electric field

    Directory of Open Access Journals (Sweden)

    Miao eLiu

    2016-03-01

    Full Text Available The effects of a direct current (DC electric field on the growth and metabolism of Gluconacetobacter xylinus were investigated in static culture. When a DC electric field at 10 mA was applied using platinum electrodes to the culture broth, bacterial cellulose (BC production was promoted in 12 hours (h but was inhibited in the last 12 h as compared to the control (without DC electric field. At the cathode, the presence of the hydrogen generated a strong reductive environment that is beneficial to cell growth. As compared to the control, the activities of glycolysis and tricarboxylic acid cycle, as well as BC productivity were observed to be slightly higher in the first 12 h. However, due to the absence of sufficient oxygen, lactic acid was accumulated from pyruvic acid at 18 h, which was not in favor of BC production. At the anode, DC inhibited cell growth in 6 h when compared to the control. The metabolic activity in G. xylinus was inhibited through the suppression of the tricarboxylic acid cycle and glycolysis. At 18-24 h, cell density was observed to decrease, which might be due to the electrolysis of water that significantly dropped the pH of cultural broth far beyond the optimal range. Meanwhile, metabolites for self-protection were accumulated, for instance proline, glutamic acid, gluconic acid and fatty acids. Notably, the accumulation of gluconic acid and lactic acid made it a really tough acid stress to cells at the anode and finally led to depression of cell growth.

  8. Optimal Geometry of CMOS Voltage-Mode and Current-Mode Vertical Magnetic Hall Sensors

    OpenAIRE

    2015-01-01

    Four different geometries of a vertical Hall sensor\\ud are presented and studied in this paper. The current spinning\\ud technique compensates for the offset and the sensors, driven in\\ud current-mode, provide a differential signal current for a possible\\ud capacitive integration over a defined time-slot. The sensors have\\ud been fabricated using a 6-metal 0.18-μm CMOS technology and\\ud fully experimentally tested. The optimal solution will be further\\ud investigated for bendable electronics. ...

  9. Comparison of direct machine parameter optimization versus fluence optimization with sequential sequencing in IMRT of hypopharyngeal carcinoma

    Directory of Open Access Journals (Sweden)

    Bogner Ludwig

    2007-09-01

    Full Text Available Abstract Background To evaluate the effects of direct machine parameter optimization in the treatment planning of intensity-modulated radiation therapy (IMRT for hypopharyngeal cancer as compared to subsequent leaf sequencing in Oncentra Masterplan v1.5. Methods For 10 hypopharyngeal cancer patients IMRT plans were generated in Oncentra Masterplan v1.5 (Nucletron BV, Veenendal, the Netherlands for a Siemens Primus linear accelerator. For optimization the dose volume objectives (DVO for the planning target volume (PTV were set to 53 Gy minimum dose and 59 Gy maximum dose, in order to reach a dose of 56 Gy to the average of the PTV. For the parotids a median dose of 22 Gy was allowed and for the spinal cord a maximum dose of 35 Gy. The maximum DVO to the external contour of the patient was set to 59 Gy. The treatment plans were optimized with the direct machine parameter optimization ("Direct Step & Shoot", DSS, Raysearch Laboratories, Sweden newly implemented in Masterplan v1.5 and the fluence modulation technique ("Intensity Modulation", IM which was available in previous versions of Masterplan already. The two techniques were compared with regard to compliance to the DVO, plan quality, and number of monitor units (MU required per fraction dose. Results The plans optimized with the DSS technique met the DVO for the PTV significantly better than the plans optimized with IM (p = 0.007 for the min DVO and p 0.05. Plan quality, target coverage and dose homogeneity inside the PTV were superior for the plans optimized with DSS for similar dose to the spinal cord and lower dose to the normal tissue. The mean dose to the parotids was lower for the plans optimized with IM. Treatment plan efficiency was higher for the DSS plans with (901 ± 160 MU compared to (1151 ± 157 MU for IM (p-value Renormalization of the IM plans to the mean of the dose to 95% of the PTV (D95 of the DSS plans, resulted in similar target coverage and dose to the parotids for both

  10. Directed Current Without Dissipation: Reincarnation of a Maxwell-Loschmidt Demon

    Science.gov (United States)

    Goychuk, Igor; Haenggi, Peter

    We investigate whether for initially localized particles a directed current in rocked periodic structures is possible in absence of a dissipative mechanism. With a pure Hamiltonian dynamics the breaking of Time-Reversal-Invariante presents anecessary condition to find nonzero current values. Numerical studies are presented for the classical Hamiltonian dynamical case. These support the fact that indeed a finite current does occur when a time-reversal symmetry-breaking signal, such as a harmonic mixing signal, is acting. To gain analytical insight we consider the coherent driven quantum transport in a one-dimensional tight-binding lattice. Here, a finite coherent current is absent for initially localized preparations; it emerges, however, when the initial preparation (with zero initial current) possesses finite coherence. The presence of phase fluctuations will eventually kill any finite current, thereby rendering the nondissipative currents a transient phenomenon.

  11. Observation of the Field, Current and Force Distributions in an Optimized Superconducting Levitation with Translational Symmetry

    Science.gov (United States)

    Ye, Chang-Qing; Ma, Guang-Tong; Liu, Kun; Wang, Jia-Su

    2016-08-01

    The superconducting levitation realized by immersing the high-temperature superconductors (HTSs) into nonuniform magnetic field is deemed promising in a wide range of industrial applications such as maglev transportation and kinetic energy storage. Using a well-established electromagnetic model to mathematically describe the HTS, we have developed an efficient scheme that is capable of intelligently and globally optimizing the permanent magnet guideway (PMG) with single or multiple HTSs levitated above for the maglev transportation applications. With maximizing the levitation force as the principal objective, we optimized the dimensions of a Halbach-derived PMG to observe how the field, current and force distribute inside the HTSs when the optimized situation is achieved. Using a pristine PMG as a reference, we have analyzed the critical issues for enhancing the levitation force through comparing the field, current and force distributions between the optimized and pristine PMGs. It was also found that the optimized dimensions of the PMG are highly dependent upon the levitated HTS. Moreover, the guidance force is not always contradictory to the levitation force and may also be enhanced when the levitation force is prescribed to be the principle objective, depending on the configuration of levitation system and lateral displacement.

  12. Observation of the Field, Current and Force Distributions in an Optimized Superconducting Levitation with Translational Symmetry

    Science.gov (United States)

    Ye, Chang-Qing; Ma, Guang-Tong; Liu, Kun; Wang, Jia-Su

    2017-01-01

    The superconducting levitation realized by immersing the high-temperature superconductors (HTSs) into nonuniform magnetic field is deemed promising in a wide range of industrial applications such as maglev transportation and kinetic energy storage. Using a well-established electromagnetic model to mathematically describe the HTS, we have developed an efficient scheme that is capable of intelligently and globally optimizing the permanent magnet guideway (PMG) with single or multiple HTSs levitated above for the maglev transportation applications. With maximizing the levitation force as the principal objective, we optimized the dimensions of a Halbach-derived PMG to observe how the field, current and force distribute inside the HTSs when the optimized situation is achieved. Using a pristine PMG as a reference, we have analyzed the critical issues for enhancing the levitation force through comparing the field, current and force distributions between the optimized and pristine PMGs. It was also found that the optimized dimensions of the PMG are highly dependent upon the levitated HTS. Moreover, the guidance force is not always contradictory to the levitation force and may also be enhanced when the levitation force is prescribed to be the principle objective, depending on the configuration of levitation system and lateral displacement.

  13. Feasibility of transcranial direct current stimulation use in children aged 5 to 12 years.

    Science.gov (United States)

    Andrade, Agnes Carvalho; Magnavita, Guilherme Moreira; Allegro, Juleilda Valéria Brasil Nunes; Neto, Carlos Eduardo Borges Passos; Lucena, Rita de Cássia Saldanha; Fregni, Felipe

    2014-10-01

    Transcranial direct current stimulation is a noninvasive brain stimulation technique that has been studied for the treatment of neuropsychiatric disorders in adults, with minimal side effects. The objective of this study is to report the feasibility, tolerability, and the short-term adverse effects of transcranial direct current stimulation in children from 5 to 12 years of age. It is a naturalistic study of 14 children who underwent 10 sessions of transcranial direct current stimulation as an alternative, off-label, and open-label treatment for various languages disorders. Frequency, intensity, adverse effects, and perception of improvement reported by parents were collected. The main side effects detected were tingling (28.6%) and itching (28.6%), acute mood changes (42.9%), and irritability (35.7%). Transcranial direct current stimulation is a feasible and tolerable technique in children, although studies regarding plastic and cognitive changes in children are needed to confirm its safety. In conclusion, this is a naturalistic report in which we considered transcranial direct current stimulation as feasible in children.

  14. GPU-based ultra-fast direct aperture optimization for online adaptive radiation therapy

    CERN Document Server

    Men, Chunhua; Jiang, Steve B

    2010-01-01

    Online adaptive radiation therapy (ART) has great promise to significantly reduce normal tissue toxicity and/or improve tumor control through real-time treatment adaptations based on the current patient anatomy. However, the major technical obstacle for clinical realization of online ART, namely the inability to achieve real-time efficiency in treatment re-planning, has yet to be solved. To overcome this challenge, this paper presents our work on the implementation of an intensity modulated radiation therapy (IMRT) direct aperture optimization (DAO) algorithm on graphics processing unit (GPU) based on our previous work on CPU. We formulate the DAO problem as a large-scale convex programming problem, and use an exact method called column generation approach to deal with its extremely large dimensionality on GPU. Five 9-field prostate and five 5-field head-and-neck IMRT clinical cases with 5\\times5 mm2 beamlet size and 2.5\\times2.5\\times2.5 mm3 voxel size were used to evaluate our algorithm on GPU. It takes onl...

  15. Optimization of self-directed target coverage in wireless multimedia sensor network.

    Science.gov (United States)

    Yang, Yang; Wang, Yufei; Pi, Dechang; Wang, Ruchuan

    2014-01-01

    Video and image sensors in wireless multimedia sensor networks (WMSNs) have directed view and limited sensing angle. So the methods to solve target coverage problem for traditional sensor networks, which use circle sensing model, are not suitable for WMSNs. Based on the FoV (field of view) sensing model and FoV disk model proposed, how expected multimedia sensor covers the target is defined by the deflection angle between target and the sensor's current orientation and the distance between target and the sensor. Then target coverage optimization algorithms based on expected coverage value are presented for single-sensor single-target, multisensor single-target, and single-sensor multitargets problems distinguishingly. Selecting the orientation that sensor rotated to cover every target falling in the FoV disk of that sensor for candidate orientations and using genetic algorithm to multisensor multitargets problem, which has NP-complete complexity, then result in the approximated minimum subset of sensors which covers all the targets in networks. Simulation results show the algorithm's performance and the effect of number of targets on the resulting subset.

  16. Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuchen [State Key Lab for Materials Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Zhou, Xue [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150000 (China); Liu, Jason X. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Anders, André, E-mail: aanders@lbl.gov [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)

    2016-01-18

    We present evidence for breathing modes in magnetron sputtering plasmas: periodic axial variations of plasma parameters with characteristic frequencies between 10 and 100 kHz. A set of azimuthally distributed probes shows synchronous oscillations of the floating potential. They appear most clearly when considering the intermediate current regime in which the direction of azimuthal spoke motion changes. Breathing oscillations were found to be superimposed on azimuthal spoke motion. Depending on pressure and current, one can also find a regime of chaotic fluctuations and one of stable discharges, the latter at high current. A pressure-current phase diagram for the different situations is proposed.

  17. Influence of the intensity and loading time of direct current electric field on the directional migration of rat bone marrow mesenchymal stem cells.

    Science.gov (United States)

    Wang, Xiaoyu; Gao, Yuxuan; Shi, Haigang; Liu, Na; Zhang, Wei; Li, Hongbo

    2016-09-01

    Exogenic electric fields can effectively accelerate bone healing and remodeling through the enhanced migration of bone marrow mesenchymal stem cells (BMSCs) toward the injured area. This study aimed to determine the following: (1) the direction of rat BMSC (rBMSC) migration upon exposure to a direct current electric field (DCEF), (2) the optimal DCEF intensity and duration, and (3) the possible regulatory role of SDF-1/CXCR4 axis in rBMSC migration as induced by DCEF. Results showed that rBMSCs migrated to the positive electrode of the DCEF, and that the DCEF of 200 mV/mm for 4 h was found to be optimal in enhancing rBMSC migration. This DCEF strength and duration also upregulated the expression of osteoblastic genes, including ALP and OCN, and upregulated the expression of ALP and Runx2 proteins. Moreover, when CXCR4 was inhibited, rBMSC migration due to DCEF was partially blocked. These findings indicated that DCEF can effectively induce rBMSC migration. A DCEF of 200 mV/mm for 4 h was recommended because of its ability to promote rBMSC migration, proliferation, and osteogenic differentiation. The SDF-1/CXCR4 signaling pathway may play an important role in regulating the DCEF-induced migration of rBMSCs.

  18. Optimization of Key Parameters of Energy Management Strategy for Hybrid Electric Vehicle Using DIRECT Algorithm

    Directory of Open Access Journals (Sweden)

    Jingxian Hao

    2016-11-01

    Full Text Available The rule-based logic threshold control strategy has been frequently used in energy management strategies for hybrid electric vehicles (HEVs owing to its convenience in adjusting parameters, real-time performance, stability, and robustness. However, the logic threshold control parameters cannot usually ensure the best vehicle performance at different driving cycles and conditions. For this reason, the optimization of key parameters is important to improve the fuel economy, dynamic performance, and drivability. In principle, this is a multiparameter nonlinear optimization problem. The logic threshold energy management strategy for an all-wheel-drive HEV is comprehensively analyzed and developed in this study. Seven key parameters to be optimized are extracted. The optimization model of key parameters is proposed from the perspective of fuel economy. The global optimization method, DIRECT algorithm, which has good real-time performance, low computational burden, rapid convergence, is selected to optimize the extracted key parameters globally. The results show that with the optimized parameters, the engine operates more at the high efficiency range resulting into a fuel savings of 7% compared with non-optimized parameters. The proposed method can provide guidance for calibrating the parameters of the vehicle energy management strategy from the perspective of fuel economy.

  19. Effect of Modulated Alternating and Direct Current Iontophoresis on Transdermal Delivery of Lidocaine Hydrochloride

    Directory of Open Access Journals (Sweden)

    Gaurav Bhatia

    2014-01-01

    Full Text Available The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87±120.03 μg/sq·cm compared to 744.81±125.41 μg/sq·cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27±18.71 μg/sq·cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h.

  20. Effect of modulated alternating and direct current iontophoresis on transdermal delivery of lidocaine hydrochloride.

    Science.gov (United States)

    Bhatia, Gaurav; Banga, Ajay K

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 μ g/sq · cm compared to 744.81 ± 125.41 μ g/sq · cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 μ g/sq · cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h.

  1. Method and system for a gas tube-based current source high voltage direct current transmission system

    Energy Technology Data Exchange (ETDEWEB)

    She, Xu; Chokhawala, Rahul Shantilal; Bray, James William; Sommerer, Timothy John; Zhou, Rui; Zhang, Di

    2017-08-29

    A high-voltage direct-current (HVDC) transmission system includes an alternating current (AC) electrical source and a power converter channel that includes an AC-DC converter electrically coupled to the electrical source and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and the DC-AC inverter each include a plurality of legs that includes at least one switching device. The power converter channel further includes a commutating circuit communicatively coupled to one or more switching devices. The commutating circuit is configured to "switch on" one of the switching devices during a first portion of a cycle of the H-bridge switching circuits and "switch off" the switching device during a second portion of the cycle of the first and second H-bridge switching circuits.

  2. Analysis of modern optimal control theory applied to plasma position and current control in TFTR

    Energy Technology Data Exchange (ETDEWEB)

    Firestone, M.A.

    1981-09-01

    The strong compression TFTR discharge has been segmented into regions where linear dynamics can approximate the plasma's interaction with the OH and EF power supply systems. The dynamic equations for these regions are utilized within the linear optimal control theory framework to provide active feedback gains to control the plasma position and current. Methods are developed to analyze and quantitatively evaluate the quality of control in a nonlinear, more realistic simulation. Tests are made of optimal control theory's assumptions and requirements, and the feasibility of this method for TFTR is assessed.

  3. Multi-point design optimization of hydrofoil for marine current turbine

    Institute of Scientific and Technical Information of China (English)

    罗兴锜; 朱国俊; 冯建军

    2014-01-01

    The comprehensive performance of the marine current turbine is an important issue in the ocean energy development. Its key is the performance of the hydrofoil, which is used to form the turbine blade. A multi-point optimization method of the hydrofoil is proposed in this paper. In this method, the Bezier curve is used to parameterize the hydrofoil. The geometrical parameters are used as variables while the lift-drag ratio and the cavitation performance of the hydrofoil are used as the objective functions. The NSGA-II algorithm is chosen as the optimization algorithm. In order to resolve the difficulty of this high-dimensional multi-objective optimi- zation problem, the conception of the distance metric in the metric space is introduced to unify the lift-drag ratio and the cavitation performance under different working conditions. And then, the above optimization method is applied in the NACA63-815 hydro- foil’s optimal design under three typical conditions. Finally, the results from the performance comparison of the original and optimi- zed hydrofoils obtained by using the CFD simulation are analyzed in detail. It is indicated that the optimized hydrofoils enjoy a better hydrodynamic performance than the original ones under the three conditions. The feasibility and the theoretical validity of this optimization method are confirmed by the results.

  4. Optimization of the uniformity of light yield from scintillator tiles read out directly by silicon photomultipliers

    Energy Technology Data Exchange (ETDEWEB)

    Bobchenko, B.; Chadeeva, M. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Engineering Physics Institute, Moscow (Russian Federation); Danilov, M. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Engineering Physics Institute, Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation); Mironov, D., E-mail: dima.mironov@itep.ru [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Engineering Physics Institute, Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation); Rusinov, V.; Tarkovskiy, E. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Engineering Physics Institute, Moscow (Russian Federation)

    2015-07-01

    The scintillator tiles with direct readout by silicon photomultipliers (SiPM) have been studied. The SiPM is placed inside the dimple machined in the center of the big face of 30×30×3 mm{sup 3} tile. The different dimple geometries were studied. The tiles with the optimal dimple design show the uniformity of response comparable to the tiles with fiber readout. The direct-readout approach provides a reasonable way for the construction of supermultichannel calorimeters.

  5. From current status to optimization of HCV treatment: Recommendations from an expert panel.

    Science.gov (United States)

    Craxì, Antonio; Perno, Carlo Federico; Viganò, Mauro; Ceccherini-Silberstein, Francesca; Petta, Salvatore

    2016-09-01

    Chronic hepatitis C virus (HCV) infection is a major public health problem at a global level, causing an enormous burden of hepatic and extra-hepatic morbidity and mortality. Treatment of chronic HCV (CHC) has been revolutionized in the last few years by the introduction of highly effective and well tolerated direct acting antiviral agents (DAAs) able to achieve >90% rates of sustained virological response (SVR) in many groups of patients, including those previously excluded from interferon-based regimens. For such reason interferon-free regimens are now the treatments of choice for all patients. Successful anti-HCV treatment can stop liver disease progression and can solve the HCV-related extra hepatic manifestations, eventually reducing both liver-related and overall mortality. Together with the rapidly accumulating data about the evolution of treatment landscape, different guidelines from national and international Liver Scientific Societies have been published until today. However, these recommendations may not be applied worldwide as, due to high treatment costs, most of them identify as priority groups only patients with advanced liver disease. Moreover some types of patients pose clinical management problems for which even the guidelines do not always provide useful answers. With the aim of treatment optimization by filling some of the gaps of the current guidelines and addressing the remaining unmet needs in practice, a group of Italian experts, experienced on treatment of HCV infection, met in Stresa in February 2016. The summary of all the considerations arising from this two-day meeting and the final statements are reported in this position paper.

  6. Current direction, wind direction, temperature, and salinity data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 01 February 1981 - 01 February 1981 (NODC Accession 8100516)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, temperature, wind direction, and salinity data were collected using moored current meter casts in the Gulf of Mexico from February 1, 1981 to...

  7. Wind direction/velocity and current direction/velocity data from current meter casts in a world wide distribution from 1970-12-06 to 1991-10-01 (NODC Accession 9700218)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind direction/velocity and current direction/velocity data were collected using current meter casts in a world wide distribution from December 6, 1970 to October...

  8. Current direction, benthic organisms, temperature, and wind direction data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 22 September 1977 - 30 November 1978 (NODC Accession 7900110)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, benthic organisms, temperature, and wind direction data were collected using moored current meter casts in the Gulf of Mexico from September 22,...

  9. Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS).

    Science.gov (United States)

    Lefaucheur, Jean-Pascal; Antal, Andrea; Ayache, Samar S; Benninger, David H; Brunelin, Jérôme; Cogiamanian, Filippo; Cotelli, Maria; De Ridder, Dirk; Ferrucci, Roberta; Langguth, Berthold; Marangolo, Paola; Mylius, Veit; Nitsche, Michael A; Padberg, Frank; Palm, Ulrich; Poulet, Emmanuel; Priori, Alberto; Rossi, Simone; Schecklmann, Martin; Vanneste, Sven; Ziemann, Ulf; Garcia-Larrea, Luis; Paulus, Walter

    2017-01-01

    A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson's disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer's disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform t

  10. The Current Status and Future Directions of Heavy Charged Particle Therapy in Medicine

    Science.gov (United States)

    Levy, Richard P.; Blakely, Eleanor A.; Chu, William T.; Coutrakon, George B.; Hug, Eugen B.; Kraft, Gerhard; Tsujii, Hirohiko

    2009-03-01

    As aggressive, 3D-conformal treatment has become the clearly accepted goal of radiation oncology, heavy charged-particle treatment with protons and heavier ions has concurrently and relentlessly ascended to the forefront. Protons and helium nuclei, with relatively low linear-energy-transfer (LET) properties, have consistently been demonstrated to be beneficial for aggressive (high-dose) local treatment of many types of tumors. Protons have been applied to the majority of solid tumors, and have reached a high degree of general acceptance in radiation oncology after three decades and 55,000 patients treated. However, some 15% to 20% of tumor types have proven resistant to even the most aggressive low-LET irradiation. For these radio-resistant tumors, treatment with heavier ions (e.g., carbon) offers great potential benefit. These high-LET particles have increased relative biological effectiveness (RBE) that reaches its maximum in the Bragg peak. Irradiation with these heavier ions offers the unique combination of excellent 3D-dose distribution and increased RBE. We are presently witnessing several, important parallel developments in particle therapy. Protons will likely continue their exponential growth phase, and more compact design systems will make protons available to a larger patient population—thus becoming the "heavy charged particle of choice" for Cancer Centers with limited financial resources. In parallel, major academic efforts will further advance the field of heavier ion therapy, exploring all opportunities for particle treatment and continuing the search for the ideal particle(s) for specific tumors. The future of ion therapy will be best realized by clinical trials that have ready access to top-quality delivery of both protons and heavier ions that can be accurately shaped for treatment of a specific pathology, and which will permit direct randomized-trial comparison of the effectiveness of the various ions for different diseases. Optimal results

  11. A semi-analytical direct optimal control solution for strongly excited and dissipative Hamiltonian systems

    Science.gov (United States)

    Ying, Zu-guang; Luo, Yin-miao; Zhu, Wei-qiu; Ni, Yi-qing; Ko, Jan-ming

    2012-04-01

    A semi-analytical direct optimal control solution for strongly excited and dissipative Hamiltonian systems is proposed based on the extended Hamiltonian principle, the Hamilton-Jacobi-Bellman (HJB) equation and its variational integral equation, and the finite time element approximation. The differential extended Hamiltonian equations for structural vibration systems are replaced by the variational integral equation, which can preserve intrinsic system structure. The optimal control law dependent on the value function is determined by the HJB equation so as to satisfy the overall optimality principle. The partial differential equation for the value function is converted into the integral equation with variational weighting. Then the successive solution of optimal control with system state is designed. The two variational integral equations are applied to sequential time elements and transformed into the algebraic equations by using the finite time element approximation. The direct optimal control on each time element is obtained respectively by solving the algebraic equations, which is unconstrained by the system state observed. The proposed control algorithm is applicable to linear and nonlinear systems with the quadratic performance index, and takes into account the effects of external excitations measured on control. Numerical examples are given to illustrate the optimal control effectiveness.

  12. Optimization of current waveform tailoring for magnetically driven isentropic compression experiments

    Science.gov (United States)

    Waisman, E. M.; Reisman, D. B.; Stoltzfus, B. S.; Stygar, W. A.; Cuneo, M. E.; Haill, T. A.; Davis, J.-P.; Brown, J. L.; Seagle, C. T.; Spielman, R. B.

    2016-06-01

    The Thor pulsed power generator is being developed at Sandia National Laboratories. The design consists of up to 288 decoupled and transit time isolated capacitor-switch units, called "bricks," that can be individually triggered to achieve a high degree of pulse tailoring for magnetically driven isentropic compression experiments (ICE) [D. B. Reisman et al., Phys. Rev. Spec. Top.-Accel. Beams 18, 090401 (2015)]. The connecting transmission lines are impedance matched to the bricks, allowing the capacitor energy to be efficiently delivered to an ICE strip-line load with peak pressures of over 100 GPa. Thor will drive experiments to explore equation of state, material strength, and phase transition properties of a wide variety of materials. We present an optimization process for producing tailored current pulses, a requirement for many material studies, on the Thor generator. This technique, which is unique to the novel "current-adder" architecture used by Thor, entirely avoids the iterative use of complex circuit models to converge to the desired electrical pulse. We begin with magnetohydrodynamic simulations for a given material to determine its time dependent pressure and thus the desired strip-line load current and voltage. Because the bricks are connected to a central power flow section through transit-time isolated coaxial cables of constant impedance, the brick forward-going pulses are independent of each other. We observe that the desired equivalent forward-going current driving the pulse must be equal to the sum of the individual brick forward-going currents. We find a set of optimal brick delay times by requiring that the L2 norm of the difference between the brick-sum current and the desired forward-going current be a minimum. We describe the optimization procedure for the Thor design and show results for various materials of interest.

  13. Performance Prediction of Differential Fibers with a Bi-Directional Optimization Approach

    Directory of Open Access Journals (Sweden)

    Yi Wang

    2013-12-01

    Full Text Available This paper develops a bi-directional prediction approach to predict the production parameters and performance of differential fibers based on neural networks and a multi-objective evolutionary algorithm. The proposed method does not require accurate description and calculation for the multiple processes, different modes and complex conditions of fiber production. The bi-directional prediction approach includes the forward prediction and backward reasoning. Particle swam optimization algorithms with K-means algorithm are used to minimize the prediction error of the forward prediction results. Based on the forward prediction, backward reasoning uses the multi-objective evolutionary algorithm to find the reasoning results. Experiments with polyester filament parameters of differential production conditions indicate that the proposed approach obtains good prediction results. The results can be used to optimize fiber production and to design differential fibers. This study also has important value and widespread application prospects regarding the spinning of differential fiber optimization.

  14. Design Optimization and Site Matching of Direct-Drive Permanent Magnet Wind Generator Systems

    DEFF Research Database (Denmark)

    Li, H.; Chen, Zhe

    2009-01-01

    This paper investigates the possible site matching of the direct-drive wind turbine concepts based on the electromagnetic design optimization of permanent magnet (PM) generator systems. Firstly, the analytical models of a three-phase radial-flux PM generator with a back-to-back power converter...

  15. Strategies for Inclusion of Structural Mass Estimates in the Direct-Drive Generator Optimization Process

    DEFF Research Database (Denmark)

    Henriksen, Matthew Lee; Jensen, Bogi Bech

    2013-01-01

    Usage of a lookup table containing the structural mass and air gap deformation for direct-drive wind turbines of various dimensions is demonstrated. The development of the table is described in detail. Optimal generator designs while both neglecting and considering the structural mass are also...

  16. Non-Cyanide Electrodeposited Ag–PTFE Composite Coating Using Direct or Pulsed Current Deposition

    Directory of Open Access Journals (Sweden)

    Raymond Sieh

    2016-07-01

    Full Text Available The effects of FC-4 cationic surfactant on electrodeposited Ag–PTFE composite coating using direct or pulsed currents were studied using scanning electron microscope (SEM, energy dispersive X-ray (EDS, optical microscope, and a linear tribometer. FC-4:PTFE in various ratios were added to a non-cyanide succinimide silver complex bath. Direct or pulsed current method was used at a constant current density to enable comparison between both methods. A high incorporation rate of PTFE was successfully achieved, with pulsed current being highly useful in increasing the amount of PTFE in the composite coating. The study of coating wear under sliding showed that a large majority of the electrodeposited coatings still managed to adhere to the substrate, even after 10 wear cycles of sliding tests. Performance improvements were achieved on all the samples with a coefficient of friction (CoF between 0.06 and 0.12.

  17. Emission of excimer radiation from direct current, high-pressure hollow cathode discharges

    Science.gov (United States)

    El-Habachi, Ahmed; Schoenbach, Karl H.

    1998-01-01

    A novel, nonequilibrium, high-pressure, direct current discharge, the microhollow cathode discharge, has been found to be an intense source of xenon and argon excimer radiation peaking at wavelengths of 170 and 130 nm, respectively. In argon discharges with a 100 μm diam hollow cathode, the intensity of the excimer radiation increased by a factor of 5 over the pressure range from 100 to 800 mbar. In xenon discharges, the intensity at 170 nm increased by two orders of magnitude when the pressure was raised from 250 mbar to 1 bar. Sustaining voltages were 200 V for argon and 400 V for xenon discharges, at current levels on the order of mA. The resistive current-voltage characteristics of the microdischarges indicate the possibility to form arrays for direct current, flat panel excimer lamps.

  18. Safety of transcranial direct current stimulation in alcohol-induced psychotic disorder with comorbid psoriasis

    Directory of Open Access Journals (Sweden)

    Venkataram Shivakumar

    2016-01-01

    Full Text Available Transcranial Direct Current Stimulation (tDCS involves application of weak direct electric currents (up to 2mA using scalp electrodes with resultant neuroplasticity modulation by altering the cortical excitability. Though the side effect profile of tDCS is benign and less severe, the utility and safety of tDCS in dermatological conditions remains a concern. In this context, we report the safe administration of tDCS in a subject with substance induced psychosis and co-morbid psoriasis.

  19. Outcomes in spasticity after repetitive transcranial magnetic and transcranial direct current stimulations

    Institute of Scientific and Technical Information of China (English)

    Aysegul Gunduz; Hatice Kumru; Alvaro Pascual-Leone

    2014-01-01

    Non-invasive brain stimulations mainly consist of repetitive transcranial magnetic stimulation and transcranial direct current stimulation. Repetitive transcranial magnetic stimulation exhib-its satisfactory outcomes in improving multiple sclerosis, stroke, spinal cord injury and cerebral palsy-induced spasticity. By contrast, transcranial direct current stimulation has only been studied in post-stroke spasticity. To better validate the effcacy of non-invasive brain stimulations in im-proving the spasticity post-stroke, more prospective cohort studies involving large sample sizes are needed.

  20. Persistent Directional Current at Equilibrium in Nonreciprocal Many-Body Near Field Electromagnetic Heat Transfer

    Science.gov (United States)

    Zhu, Linxiao; Fan, Shanhui

    2016-09-01

    We consider the consequence of nonreciprocity in near-field heat transfer by studying systems consisting of magneto-optical nanoparticles. We demonstrate that, in thermal equilibrium, a nonreciprocal many-body system in heat transfer can support a persistent directional heat current, without violating the second law of thermodynamics. Such a persistent directional heat current cannot occur in reciprocal systems, and can only arise in many-body systems in heat transfer. The use of nonreciprocity therefore points to a new regime of near-field heat transfer for the control of heat flow in the nanoscale.

  1. Compulsory Checking of Nuclear Power Engineering Materials by Direct and Eddy Current

    Science.gov (United States)

    Larionov, V. V.; Lider, A. M.; Sednev, D. A.; Xu, Shupeng

    2016-08-01

    The testing technology of copper parts designed for dry storage of spent nuclear fuel with application of direct and eddy current has been developed. Measurements results of flaw quantity caused hydrogenation and oxidation processes are presented. Evolution of copper M 001 flaw structure during hydrogenation from gaseous medium is analyzed. It has been demonstrated that the dependence of copper p electrical resistance on number of flaws in its structure has dome shaped character and changes with eddy current frequency change. Number of flaws formed by hydrogen depends on direction (100) or (200) of the crystal structure of copper lattice.

  2. Transcranial direct-current stimulation induced in stroke patients with aphasia: a prospective experimental cohort study

    Directory of Open Access Journals (Sweden)

    Michele Devido Santos

    Full Text Available CONTEXT AND OBJECTIVE: Previous animal and human studies have shown that transcranial direct current stimulation can induce significant and lasting neuroplasticity and may improve language recovery in patients with aphasia. The objective of the study was to describe a cohort of patients with aphasia after stroke who were treated with transcranial direct current stimulation. DESIGN AND SETTING: Prospective cohort study developed in a public university hospital. METHODS: Nineteen patients with chronic aphasia received 10 transcranial direct current stimulation sessions lasting 20 minutes each on consecutive days, using a current of 2 mA. The anode was positioned over the supraorbital area and the cathode over the contralateral motor cortex. The following variables were analyzed before and after the 10 neuromodulation sessions: oral language comprehension, copying, dictation, reading, writing, naming and verbal fluency. RESULTS: There were no adverse effects in the study. We found statistically significant differences from before to after stimulation in relation to simple sentence comprehension (P = 0.034, naming (P = 0.041 and verbal fluency for names of animals (P = 0.038. Improved scores for performing these three tasks were seen after stimulation. CONCLUSIONS: We observed that excitability of the primary motor cortex through transcranial direct current stimulation was associated with effects on different aspects of language. This can contribute towards future testing in randomized controlled trials.

  3. A Direct Multiple Shooting Method for Missile Trajectory Optimization with The Terminal Bunt Manoeuvre

    Directory of Open Access Journals (Sweden)

    S. Subchan Subchan

    2011-08-01

    Full Text Available Numerical solution of constrained nonlinear optimal control problem is an important field in a wide range of applications in science and engineering. The real time solution for an optimal control problem is a challenge issue especially the state constrained handling. Missile trajectory shaping with terminal bunt manoeuvre with state constaints is addressed. The problem can be stated as an optimal control problem in which an objective function is minimised satisfying a series of constraints on the trajectory which includes state and control constraints. Numerical solution based on a direct multiple shooting is proposed. As an example the method has been implemented to a design of optimal trajectory for a missile where the missile must struck the target by vertical dive. The qualitative analysis and physical interpretation of the numerical solutions are given.

  4. Optimization of the collimation system for CSNS/RCS with the robust conjugate direction search algorithm

    Science.gov (United States)

    Ji, Hong-Fei; Jiao, Yi; Huang, Ming-Yang; Xu, Shou-Yan; Wang, Na; Wang, Sheng

    2016-09-01

    The Robust Conjugate Direction Search (RCDS) method is used to optimize the collimation system for the Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS). The parameters of secondary collimators are optimized for a better performance of the collimation system. To improve the efficiency of the optimization, the Objective Ring Beam Injection and Tracking (ORBIT) parallel module combined with MATLAB parallel computing is used, which can run multiple ORBIT instances simultaneously. This study presents a way to find an optimal parameter combination of the secondary collimators for a machine model in preparation for CSNS/RCS commissioning. Supported by National Natural Science Foundation of China (11475202, 11405187, 11205185) and Youth Innovation Promotion Association of Chinese Academy of Sciences (2015009)

  5. Direct leaf trajectory optimization for volumetric modulated arc therapy planning with sliding window delivery

    CERN Document Server

    Papp, Dávid

    2013-01-01

    We propose a novel optimization model for volumetric modulated arc therapy (VMAT) planning that directly optimizes deliverable leaf trajectories in the treatment plan optimization problem, and eliminates the need for a separate arc-sequencing step. In this model, a 360-degree arc is divided into a given number of arc segments in which the leaves move unidirectionally. This facilitates an algorithm that determines the optimal piecewise linear leaf trajectories for each arc segment, which are deliverable in a given treatment time. Multi-leaf collimator (MLC) constraints, including maximum leaf speed and interdigitation, are accounted for explicitly. The algorithm is customized to allow for VMAT delivery using constant gantry speed and dose rate, however, the algorithm generalizes to variable gantry speed if beneficial. We demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. For that purpose, we first obtain a reference plan for intensity modulated...

  6. Real time optimization of solar powered direct contact membrane distillation based on multivariable extremum seeking

    KAUST Repository

    Karam, Ayman M.

    2015-09-21

    This paper presents a real time optimization scheme for a solar powered direct contact membrane distillation (DCMD) water desalination system. The sun and weather conditions vary and are inconsistent throughout the day. Therefore, the solar powered DCMD feed inlet temperature is never constant, which influences the distilled water flux. The problem of DCMD process optimization has not been studied enough. In this work, the response of the process under various feed inlet temperatures is investigated, which demonstrates the need for an optimal controller. To address this issue, we propose a multivariable Newton-based extremum seeking controller which optimizes the inlet feed and permeate mass flow rates as the feed inlet temperature varies. Results are presented and discussed for a realistic temperature profile.

  7. Design of Optimal Sparse Feedback Gains via the Alternating Direction Method of Multipliers

    CERN Document Server

    Lin, Fu; Jovanović, Mihailo R

    2011-01-01

    We design sparse and block sparse feedback gains that minimize the $H_2$ norm of distributed systems. Our approach consists of two steps. First, we identify sparsity patterns of the feedback gains by incorporating sparsity-promoting penalty functions into the $H_2$ problem, where the added terms penalize the number of communication links in the distributed controller. Second, we optimize the state feedback gains subject to the structural constraints determined by the identified sparsity patterns. This polishing step improves the $H_2$ performance of the distributed controllers. In the first step, we identify sparsity structure of the feedback gains using the alternating direction method of multipliers, which is a powerful algorithm well-suited to large optimization problems. This method alternates between optimizing the sparsity and optimizing the closed-loop $H_2$ norm, which allows us to exploit the structure of the corresponding objective functions. In particular, we take advantage of the separability of t...

  8. PERFORMANCE OPTIMIZATION OF LINEAR INDUCTION MOTOR BY EDDY CURRENT AND FLUX DENSITY DISTRIBUTION ANALYSIS

    Directory of Open Access Journals (Sweden)

    M. S. MANNA

    2011-12-01

    Full Text Available The development of electromagnetic devices as machines, transformers, heating devices confronts the engineers with several problems. For the design of an optimized geometry and the prediction of the operational behaviour an accurate knowledge of the dependencies of the field quantities inside the magnetic circuits is necessary. This paper provides the eddy current and core flux density distribution analysis in linear induction motor. Magnetic flux in the air gap of the Linear Induction Motor (LIM is reduced to various losses such as end effects, fringes, effect, skin effects etc. The finite element based software package COMSOL Multiphysics Inc. USA is used to get the reliable and accurate computational results for optimization the performance of Linear Induction Motor (LIM. The geometrical characteristics of LIM are varied to find the optimal point of thrust and minimum flux leakage during static and dynamic conditions.

  9. Studying the Effects of Transcranial Direct-Current Stimulation in Stroke Recovery Using Magnetic Resonance Imaging

    OpenAIRE

    Stagg, Charlotte J; Johansen-Berg, Heidi

    2013-01-01

    Transcranial direct-current stimulation (tDCS) is showing increasing promise as an adjunct therapy in stroke rehabilitation. However questions still remain concerning its mechanisms of action, which currently limit its potential. Magnetic resonance (MR) techniques are increasingly being applied to understand the neural effects of tDCS. Here, we review the MR evidence supporting the use of tDCS to aid recovery after stroke and discuss the important open questions that remain.

  10. Effect of Direct Electric Current on the Cell Surface Properties of Phenol-Degrading Bacteria

    OpenAIRE

    Luo, Qishi; Wang, Hui; Zhang, Xihui; Qian, Yi

    2005-01-01

    The change in cell surface properties in the presence of electric currents is of critical concern when the potential to manipulate bacterial movement with electric fields is evaluated. In this study, the effects of different direct electric currents on the cell surface properties involved in bacterial adhesion were investigated by using a mixed phenol-degrading bacterial culture in the exponential growth phase. The traits investigated were surface hydrophobicity (measured by adherence to n-oc...

  11. Studying The Effects Of Transcranial Direct Current Stimulation In Stroke Recovery Using Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Charlotte J Stagg

    2013-12-01

    Full Text Available Transcranial direct current stimulation (tDCS is showing increasing promise as an adjunct therapy in stroke rehabilitation. However questions still remain concerning its mechanisms of action, which currently limit its potential. Magnetic Resonance (MR techniques are increasingly being applied to understand the neural effects of tDCS. Here, we review the MR evidence supporting the use of tDCS to aid recovery after stroke and discuss the important open questions that remain.

  12. Effects of Direct Torque Control Switching Strategies on Common Voltage and Bearing Current

    Directory of Open Access Journals (Sweden)

    Mohammad Taghi Sadeghzadeh

    2012-04-01

    Full Text Available Bearing current sininduction motorsare considered a sone of the most damaging factors. Induced shaft voltage through the parasitic capacitors cause this type of current. Inthispaper,given the increasing importance of direct torque control of induction motorin industry, various switching tables are assessed in order to ensure the lowest common voltage while maintaining the performance characteristics of the drive. Finally best switching table based on the minimum CMV, less torque rippleand better quality out put reference tracking is proposed.

  13. Assessment of flow and cure monitoring using direct current and alternating current sensing in vacuum-assisted resin transfer molding

    Science.gov (United States)

    Vaidya, Uday K.; Jadhav, Nitesh C.; Hosur, Mahesh V.; Gillespie, John W., Jr.; Fink, Bruce K.

    2000-12-01

    Vacuum-assisted resin transfer molding (VARTM) is an emerging manufacturing technique that holds promise as an affordable alternative to traditional autoclave molding and automated fiber placement for producing large-scale structural parts. In VARTM, the fibrous preform is laid on a single-sided tool, which is then bagged along with the infusion and vacuum lines. The resin is then infused through the preform, which causes simultaneous wetting in its in-plane and transverse directions. An effective sensing technique is essential so that comprehensive information pertaining to the wetting of the preform, arrival of resin at various locations, cure gradients associated with thickness and presence of dry spots may be monitored. In the current work, direct current (dc) and alternating current sensing/monitoring techniques were adopted for developing a systematic understanding of the resin position and cure on plain weave S2-glass preforms with Dow Derakane vinyl ester VE 411-350, Shell EPON RSL 2704/2705 and Si-AN epoxy as the matrix systems. A SMARTweave dc sensing system was utilized to conduct parametric studies: (a) to compare the flow and cure of resin through the stitched and non-stitched preforms; (b) to investigate the influence of sensor positioning, i.e. top, middle and bottom layers; and (c) to investigate the influence of positioning of the process accessories, i.e. resin infusion point and vacuum point on the composite panel. The SMARTweave system was found to be sensitive to all the parametric variations introduced in the study. Furthermore, the results obtained from the SMARTweave system were compared to the cure monitoring studies conducted by using embedded interdigitated (IDEX) dielectric sensors. The results indicate that SMARTweave sensing was a viable alternative to obtaining resin position and cure, and was more superior in terms of obtaining global information, in contrast to the localized dielectric sensing approach.

  14. Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation: A functional MRI study.

    Science.gov (United States)

    Kwon, Yong Hyun; Jang, Sung Ho

    2012-08-25

    We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.

  15. An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

    Energy Technology Data Exchange (ETDEWEB)

    Litzenberger, Wayne; Lava, Val

    1994-08-01

    References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

  16. Automatic detection of the optimal ejecting direction based on a discrete Gauss map

    Directory of Open Access Journals (Sweden)

    Masatomo Inui

    2014-01-01

    Full Text Available In this paper, the authors propose a system for assisting mold designers of plastic parts. With a CAD model of a part, the system automatically determines the optimal ejecting direction of the part with minimum undercuts. Since plastic parts are generally very thin, many rib features are placed on the inner side of the part to give sufficient structural strength. Our system extracts the rib features from the CAD model of the part, and determines the possible ejecting directions based on the geometric properties of the features. The system then selects the optimal direction with minimum undercuts. Possible ejecting directions are represented as discrete points on a Gauss map. Our new point distribution method for the Gauss map is based on the concept of the architectural geodesic dome. A hierarchical structure is also introduced in the point distribution, with a higher level “rough” Gauss map with rather sparse point distribution and another lower level “fine” Gauss map with much denser point distribution. A system is implemented and computational experiments are performed. Our system requires less than 10 seconds to determine the optimal ejecting direction of a CAD model with more than 1 million polygons.

  17. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    Directory of Open Access Journals (Sweden)

    Ju Feng

    2015-04-01

    Full Text Available Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data at Horns Rev and three different joint distributions are obtained, which all fit the measurement data quite well in terms of the coefficient of determination . Then, the best of these joint distributions is used in the layout optimization of the Horns Rev 1 wind farm and the choice of bin sizes for wind speed and wind direction is also investigated. It is found that the choice of bin size for wind direction is especially critical for layout optimization and the recommended choice of bin sizes for wind speed and wind direction is finally presented.

  18. Predicting the Direction of Stock Market Index Movement Using an Optimized Artificial Neural Network Model.

    Science.gov (United States)

    Qiu, Mingyue; Song, Yu

    2016-01-01

    In the business sector, it has always been a difficult task to predict the exact daily price of the stock market index; hence, there is a great deal of research being conducted regarding the prediction of the direction of stock price index movement. Many factors such as political events, general economic conditions, and traders' expectations may have an influence on the stock market index. There are numerous research studies that use similar indicators to forecast the direction of the stock market index. In this study, we compare two basic types of input variables to predict the direction of the daily stock market index. The main contribution of this study is the ability to predict the direction of the next day's price of the Japanese stock market index by using an optimized artificial neural network (ANN) model. To improve the prediction accuracy of the trend of the stock market index in the future, we optimize the ANN model using genetic algorithms (GA). We demonstrate and verify the predictability of stock price direction by using the hybrid GA-ANN model and then compare the performance with prior studies. Empirical results show that the Type 2 input variables can generate a higher forecast accuracy and that it is possible to enhance the performance of the optimized ANN model by selecting input variables appropriately.

  19. Process Parameter Optimization of the Pulsed Current Argon Tungsten Arc Welding of Titanium Alloy

    Institute of Scientific and Technical Information of China (English)

    M.Balasubramanian; V.Jayabalan; V.Balasubramanian

    2008-01-01

    The selection of process parameters for obtaining optimal tensile properties in the pulsed current gas tungsten arc welding is presented. The tensile properties include ultimate tensile strength, yield strength and notch tensile strength. All these characteristics are considered together in the selection of process parameters by modified taguchi method to analyse the effect of each welding process parameter on tensile properties. Experimental results are furnished to illustrate the approach.

  20. Eddy Current Analysis and Optimization for Superconducting Magnetic Bearing of Flywheel Energy Storage System

    Science.gov (United States)

    Arai, Yuuki; Yamashita, Tomohisa; Hasegawa, Hitoshi; Matsuoka, Taro; Kaimori, Hiroyuki; Ishihara, Terumasa

    Levitation and guidance force is electromagnetic generated between a superconducting coil and zero field cooled bulk superconductors used in our flywheel energy storage system (FESS). Because the magnetic field depends on the configuration of the coil and the bulks, the eccentricity and the vibration of a rotor cause fluctuation in the magnetic field which induces eddy current and consequent Joule heat on electric conductors such as cooling plates. Heat generation in the cryogenic region critically reduces the efficiency of the FESS. In this paper, we will report the result of the electromagnetic analysis of the SMB and propose an optimal divided cooling plate for reducing the eddy current and Joule heat.

  1. Realization and optimization of bus bar current transducers based on Hall effect sensors

    Science.gov (United States)

    Blagojević, Marjan; Jovanović, Uglješa; Jovanović, Igor; Mančić, Dragan; Popović, Radivoje S.

    2016-06-01

    In this paper the realization and optimization of two coreless open-loop bus bar current transducers based on a Hall effect sensor are presented. Two types of bus bar are evaluated: flat rectangular and rectangular with a restrictive region in the middle. Both realized transducers are capable of measuring AC and DC currents up to 300 A and 10 kHz frequency with nonlinearity less than 0.3% in the entire range. Several methods for resolving issues with the skin effect and stray magnetic fields are presented along with the experimental test results. Some of the presented methods are novel and have never been evaluated.

  2. Leakage Current Optimization Techniques During Test Based on Don't Care Bits Assignment

    Institute of Scientific and Technical Information of China (English)

    Wei Wang; Yu Hu; Yin-He Han; Xiao-Wei Li; You-Sheng Zhang

    2007-01-01

    It is a well-known fact that test power consumption may exceed that during functional operation. Leakage power dissipation caused by leakage current in Complementary Metal-Oxide-Semiconductor (CMOS) circuits during test has become a significant part of the total power dissipation. Hence, it is important to reduce leakage power to prolong battery life in portable systems which employ periodic self-test, to increase test reliability and to reduce test cost. This paper analyzes leakage current and presents a kind of leakage current simulator based on the transistor stacking effect.Using it, we propose techniques based on don't care bits (denoted by Xs) in test vectors to optimize leakage current in integrated circuit (IC) test by genetic algorithm. The techniques identify a set of don't care inputs in given test vectors and reassign specified logic values to the X inputs by the genetic algorithm to get minimum leakage vector (MLV).Experimental results indicate that the techniques can effectually optimize leakage current of combinational circuits and sequential circuits during test while maintaining high fault coverage.

  3. A self-discharge model of Lithium-Sulfur batteries based on direct shuttle current measurement

    DEFF Research Database (Denmark)

    Knap, Vaclav; Stroe, Daniel Loan; Swierczynski, Maciej Jozef

    2016-01-01

    . A simple but comprehensive mathematical model of the Li-S battery cell self-discharge based on the shuttle current was developed and is presented. The shuttle current values for the model parameterization were obtained from the direct shuttle current measurements. Furthermore, the battery cell depth......-of-discharge values were recomputed in order to account for the influence of the self-discharge and provide a higher accuracy of the model. Finally, the derived model was successfully validated against laboratory experiments at various conditions....

  4. Optimization of multifocal transcranial current stimulation for weighted cortical pattern targeting from realistic modeling of electric fields.

    Science.gov (United States)

    Ruffini, Giulio; Fox, Michael D; Ripolles, Oscar; Miranda, Pedro Cavaleiro; Pascual-Leone, Alvaro

    2014-04-01

    Recently, multifocal transcranial current stimulation (tCS) devices using several relatively small electrodes have been used to achieve more focal stimulation of specific cortical targets. However, it is becoming increasingly recognized that many behavioral manifestations of neurological and psychiatric disease are not solely the result of abnormality in one isolated brain region but represent alterations in brain networks. In this paper we describe a method for optimizing the configuration of multifocal tCS for stimulation of brain networks, represented by spatially extended cortical targets. We show how, based on fMRI, PET, EEG or other data specifying a target map on the cortical surface for excitatory, inhibitory or neutral stimulation and a constraint on the maximal number of electrodes, a solution can be produced with the optimal currents and locations of the electrodes. The method described here relies on a fast calculation of multifocal tCS electric fields (including components normal and tangential to the cortical boundaries) using a five layer finite element model of a realistic head. Based on the hypothesis that the effects of current stimulation are to first order due to the interaction of electric fields with populations of elongated cortical neurons, it is argued that the optimization problem for tCS stimulation can be defined in terms of the component of the electric field normal to the cortical surface. Solutions are found using constrained least squares to optimize current intensities, while electrode number and their locations are selected using a genetic algorithm. For direct current tCS (tDCS) applications, we provide some examples of this technique using an available tCS system providing 8 small Ag/AgCl stimulation electrodes. We demonstrate the approach both for localized and spatially extended targets defined using rs-fcMRI and PET data, with clinical applications in stroke and depression. Finally, we extend these ideas to more general

  5. Progress in American Superconductor's HTS wire and optimization for fault current limiting systems

    Science.gov (United States)

    Malozemoff, Alexis P.

    2016-11-01

    American Superconductor has developed composite coated conductor tape-shaped wires using high temperature superconductor (HTS) on a flexible substrate with laminated metal stabilizer. Such wires enable many applications, each requiring specific optimization. For example, coils for HTS rotating machinery require increased current density J at 25-50 K. A collaboration with Argonne, Brookhaven and Los Alamos National Laboratories and several universities has increased J using an optimized combination of precipitates and ion irradiation defects in the HTS. Major commercial opportunities also exist to enhance electric power grid resiliency by linking substations with distribution-voltage HTS power cables [10]. Such links provide alternative power sources if one substation's transmission-voltage power is compromised. But they must also limit fault currents which would otherwise be increased by such distribution-level links. This can be done in an HTS cable, exploiting the superconductor-to-resistive transition when current exceeds the wires' critical J. A key insight is that such transitions are usually nonuniform; so the wire must be designed to prevent localized hot spots from damaging the wire or even generating gas bubbles in the cable causing dielectric breakdown. Analysis shows that local heating can be minimized by increasing the composite tape's total thickness, decreasing its total resistance in the normal state and decreasing its critical J. This conflicts with other desirable wire characteristics. Optimization of these conflicting requirements is discussed.

  6. Experimental study on directional solidification of Al-Si alloys under the influence of electric currents

    Science.gov (United States)

    Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.

    2016-07-01

    The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al-Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.

  7. Current state and future directions of neurochemical biomarkers for Alzheimer's disease

    NARCIS (Netherlands)

    de Jong, Daniëlle; Kremer, Berry P H; Olde Rikkert, Marcel G M; Verbeek, Marcel M

    2007-01-01

    In this comprehensive review, we summarize the current state-of-the-art of neurochemical biomarkers for Alzheimer's disease. Predominantly, these biomarkers comprise cerebrospinal fluid biomarkers directly related to the pathophysiology of this disorder (such as amyloid beta protein, tau protein). W

  8. Current state and future directions of neurochemical biomarkers for Alzheimer's disease.

    NARCIS (Netherlands)

    Jong, D. de; Kremer, H.P.H.; Olde Rikkert, M.G.M.; Verbeek, M.M.

    2007-01-01

    In this comprehensive review, we summarize the current state-of-the-art of neurochemical biomarkers for Alzheimer's disease. Predominantly, these biomarkers comprise cerebrospinal fluid biomarkers directly related to the pathophysiology of this disorder (such as amyloid beta protein, tau protein).

  9. Counteracting fatigue in multiple sclerosis with right parietal anodal transcranial direct current stimulation

    NARCIS (Netherlands)

    Hanken, K.; Bosse, M.; Möhrke, K.; Eling, P.A.T.M.; Kastrup, A.; Antal, A.; Hildebrandt, H.

    2016-01-01

    Background: Fatigue in multiple sclerosis (MS) patients appears to correlate with vigilance decrement as reflected in an increase in reaction time and errors with prolonged time-on-task. Objectives: The aim of this study was to investigate whether anodal transcranial direct current stimulation (tDCS

  10. Simulating transcranial direct current stimulation with a detailed anisotropic human head model

    NARCIS (Netherlands)

    Rampersad, S.M.; Janssen, A.M.; Lucka, F.; Aydin, U.; Lanfer, B.; Lew, S.; Wolters, C.H.; Stegeman, D.F.; Oostendorp, T.F.

    2014-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique able to induce long-lasting changes in cortical excitability that can benefit cognitive functioning and clinical treatment. In order to both better understand the mechanisms behind tDCS and possibly improve t

  11. Effects of Transcranial Direct Current Stimulation (tDCS) on Behaviour and Electrophysiology of Language Production

    Science.gov (United States)

    Wirth, Miranka; Rahman, Rasha Abdel; Kuenecke, Janina; Koenig, Thomas; Horn, Helge; Sommer, Werner; Dierks, Thomas

    2011-01-01

    Excitatory anodal transcranial direct current stimulation (A-tDCS) over the left dorsal prefrontal cortex (DPFC) has been shown to improve language production. The present study examined neurophysiological underpinnings of this effect. In a single-blinded within-subject design, we traced effects of A-tDCS compared to sham stimulation over the left…

  12. Neuroprotective effect of cathodal transcranial direct current stimulation in a rat stroke model.

    Science.gov (United States)

    Notturno, Francesca; Pace, Marta; Zappasodi, Filippo; Cam, Etrugul; Bassetti, Claudio L; Uncini, Antonino

    2014-07-15

    Experimental focal brain ischemia generates in the penumbra recurrent depolarizations which spread across the injured cortex inducing infarct growth. Transcranial direct current stimulation can induce a lasting, polarity-specific, modulation of cortical excitability. To verify whether cathodal transcranial direct current stimulation could reduce the infarct size and the number of depolarizations, focal ischemia was induced in the rat by the 3 vessels occlusion technique. In the first experiment 12 ischemic rats received cathodal stimulation (alternating 15 min on and 15 min off) starting 45 min after middle cerebral artery occlusion and lasting 4 h. In the second experiment 12 ischemic rats received cathodal transcranial direct current stimulation with the same protocol but starting soon after middle cerebral artery occlusion and lasting 6 h. In both experiments controls were 12 ischemic rats not receiving stimulation. Cathodal stimulation reduced the infarct volume in the first experiment by 20% (p=0.002) and in the second by 30% (p=0.003). The area of cerebral infarction was smaller in animals receiving cathodal stimulation in both experiments (p=0.005). Cathodal stimulation reduced the number of depolarizations (p=0.023) and infarct volume correlated with the number of depolarizations (p=0.048). Our findings indicate that cathodal transcranial direct current stimulation exert a neuroprotective effect in the acute phase of stroke possibly decreasing the number of spreading depolarizations. These findings may have translational relevance and open a new avenue in neuroprotection of stroke in humans.

  13. Cathodal Transcranial Direct Current Stimulation of the Right Wernicke's Area Improves Comprehension in Subacute Stroke Patients

    Science.gov (United States)

    You, Dae Sang; Kim, Dae-Yul; Chun, Min Ho; Jung, Seung Eun; Park, Sung Jong

    2011-01-01

    Previous studies have shown the appearance of right-sided language-related brain activity in right-handed patients after a stroke. Non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) have been shown to modulate excitability in the brain. Moreover, rTMS and…

  14. Single-layer skull approximations perform well in transcranial direct current stimulation modeling

    NARCIS (Netherlands)

    Rampersad, S.M.; Stegeman, D.F.; Oostendorp, T.F.

    2013-01-01

    In modeling the effect of transcranial direct current stimulation, the representation of the skull is an important factor. In a spherical model, we compared a realistic skull modeling approach, in which the skull consisted of three isotropic layers, to anisotropic and isotropic single-layer approxim

  15. Transcranial direct current stimulation in refractory continuous spikes and waves during slow sleep: a controlled study

    DEFF Research Database (Denmark)

    Varga, Edina T; Terney, Daniella; Atkins, Mary D

    2011-01-01

    Cathodal transcranial direct current stimulation (tDCS) decreases cortical excitability. The purpose of the study was to investigate whether cathodal tDCS could interrupt the continuous epileptiform activity. Five patients with focal, refractory continuous spikes and waves during slow sleep were ...

  16. Subcortical structures in humans can be facilitated by transcranial direct current stimulation

    NARCIS (Netherlands)

    Nonnekes, J.H.; Arrogi, A.; Munneke, M.A.M; Asseldonk, E.H. van; Nijhuis, L.B.; Geurts, A.C.H.; Weerdesteyn, V.G.M.

    2014-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that alters cortical excitability. Interestingly, in recent animal studies facilitatory effects of tDCS have also been observed on subcortical structures. Here, we sought to provide evidence for the potential

  17. Subcortical Structures in Humans Can Be Facilitated by Transcranial Direct Current Stimulation

    NARCIS (Netherlands)

    Nonnekes, J.H.; Arrogi, A.; Munneke, M.A.M.; Asseldonk, van E.H.F.; Oude Nijhuis, L.B.; Geurts, A.C.; Weerdesteyn, V.

    2014-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that alters cortical excitability. Interestingly, in recent animal studies facilitatory effects of tDCS have also been observed on subcortical structures. Here, we sought to provide evidence for the potential

  18. Microwave testing of high-Tc based direct current to a single flux quantum converter

    DEFF Research Database (Denmark)

    Kaplunenko, V. K.; Fischer, Gerd Michael; Ivanov, Z. G.

    1994-01-01

    Design, simulation, and experimental investigations of a direct current to a single flux quantum converter loaded with a Josephson transmission line and driven by an external 70 GHz microwave oscillator are reported. The test circuit includes nine YBaCuO Josephson junctions aligned on the grain b...

  19. Current state and future directions of neurochemical biomarkers for Alzheimer's disease

    NARCIS (Netherlands)

    de Jong, Daniëlle; Kremer, Berry P H; Olde Rikkert, Marcel G M; Verbeek, Marcel M

    2007-01-01

    In this comprehensive review, we summarize the current state-of-the-art of neurochemical biomarkers for Alzheimer's disease. Predominantly, these biomarkers comprise cerebrospinal fluid biomarkers directly related to the pathophysiology of this disorder (such as amyloid beta protein, tau protein). W

  20. Pharmacologic versus direct-current electrical cardioversion of atrial flutter and fibrillation

    NARCIS (Netherlands)

    Van Gelder, IC; Tuinenburg, AE; Schoonderwoerd, BS; Tieleman, RG; Crijns, HJGM

    1999-01-01

    Conversion of atrial flutter and atrial fibrillation (AF) can be achieved by either pharmacologic or direct-current (DC) electrical cardioversion. DC electrical cardioversion is more effective and restores sinus rhythm instantaneously; however, general anesthesia is necessary, which can cause severe

  1. Safety and efficacy of transcranial direct current stimulation in acute experimental ischemic stroke.

    Science.gov (United States)

    Peruzzotti-Jametti, Luca; Cambiaghi, Marco; Bacigaluppi, Marco; Gallizioli, Mattia; Gaude, Edoardo; Mari, Silvia; Sandrone, Stefano; Cursi, Marco; Teneud, Luis; Comi, Giancarlo; Musco, Giovanna; Martino, Gianvito; Leocani, Letizia

    2013-11-01

    Transcranial direct current stimulation is emerging as a promising tool for the treatment of several neurological conditions, including cerebral ischemia. The therapeutic role of this noninvasive treatment is, however, limited to chronic phases of stroke. We thus ought to investigate whether different stimulation protocols could also be beneficial in the acute phase of experimental brain ischemia. The influence of both cathodal and anodal transcranial direct current stimulation in modifying brain metabolism of healthy mice was first tested by nuclear magnetic resonance spectroscopy. Then, mice undergoing transient proximal middle cerebral artery occlusion were randomized and treated acutely with anodal, cathodal, or sham transcranial direct current stimulation. Brain metabolism, functional outcomes, and ischemic lesion volume, as well as the inflammatory reaction and blood brain barrier functionality, were analyzed. Cathodal stimulation was able, if applied in the acute phase of stroke, to preserve cortical neurons from the ischemic damage, to reduce inflammation, and to promote a better clinical recovery compared with sham and anodal treatments. This finding was attributable to the significant decrease of cortical glutamate, as indicated by nuclear magnetic resonance spectroscopy. Conversely, anodal stimulation induced an increase in the postischemic lesion volume and augmented blood brain barrier derangement. Our data indicate that transcranial direct current stimulation exerts a measurable neuroprotective effect in the acute phase of stroke. However, its timing and polarity should be carefully identified on the base of the pathophysiological context to avoid potential harmful side effects.

  2. Early Childhood Inclusion in the United States: Goals, Current Status, and Future Directions

    Science.gov (United States)

    Guralnick, Michael J.; Bruder, Mary Beth

    2016-01-01

    The current status and future directions of early childhood inclusion in the United States are discussed from the perspective of 4 key goals: access, accommodations and feasibility, developmental progress, and social integration. Recommendations are put forward to promote inclusion goals emphasizing administrative structures, personnel…

  3. An optimal control method for maximizing the efficiency of direct drive ocean wave energy extraction system.

    Science.gov (United States)

    Chen, Zhongxian; Yu, Haitao; Wen, Cheng

    2014-01-01

    The goal of direct drive ocean wave energy extraction system is to convert ocean wave energy into electricity. The problem explored in this paper is the design and optimal control for the direct drive ocean wave energy extraction system. An optimal control method based on internal model proportion integration differentiation (IM-PID) is proposed in this paper though most of ocean wave energy extraction systems are optimized by the structure, weight, and material. With this control method, the heavy speed of outer heavy buoy of the energy extraction system is in resonance with incident wave, and the system efficiency is largely improved. Validity of the proposed optimal control method is verified in both regular and irregular ocean waves, and it is shown that IM-PID control method is optimal in that it maximizes the energy conversion efficiency. In addition, the anti-interference ability of IM-PID control method has been assessed, and the results show that the IM-PID control method has good robustness, high precision, and strong anti-interference ability.

  4. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    DEFF Research Database (Denmark)

    Feng, Ju; Shen, Wen Zhong

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distribu......Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint...... quite well in terms of the coefficient of determination R-2. Then, the best of these joint distributions is used in the layout optimization of the Horns Rev 1 wind farm and the choice of bin sizes for wind speed and wind direction is also investigated. It is found that the choice of bin size for wind...... direction is especially critical for layout optimization and the recommended choice of bin sizes for wind speed and wind direction is finally presented....

  5. Evaluation of Thermoelectric Properties of Bite Alloys for the Optimization of Gas-Cooled Peltier Current Lead

    Science.gov (United States)

    Fujii, T.; Fukuda, S.; Kawahara, T.; Emoto, M.; Sugino, M.; Sun, J.; Hamabe, M.; Watanabe, H.; Yamaguchi, S.

    2010-04-01

    A direct current superconducting power transmission (DC-SCPT) test facility with 20-meter power cable has been developed in Chubu University. Heat leakage through current leads dominates in case of short-distance DC-SCPT. To solve this problem, we have developed special Peltier current lead (PCL) with bismuth telluride (BiTe) alloy is used as a Peltier material, and have studied a gas-cooled PCL as a novel type current lead for higher reduction of the heat leakage. In order to achieve high efficiency, highest thermoelectric figure of merit material is important to be used especially at low temperature conditions. In our work we measured the thermoelectric properties of BiTe samples, and optimized geometry of PCL by the numerical calculations. It was fount that the heat leakages through PCL and gas-cooled PCL are reduced to 55% and to 36% of the conventional copper current lead (CCL) at the self-cooling condition, correspondingly. PCL can reduce the total electric power consumption of the whole system. We also discuss the heat exchange ratio for the gas-cooled PCL, and extend this approach for further reduction of the heat leakage.

  6. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design

    Science.gov (United States)

    Rifai, Damhuji; Abdalla, Ahmed N.; Razali, Ramdan; Ali, Kharudin; Faraj, Moneer A.

    2017-01-01

    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient. PMID:28335399

  7. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design.

    Science.gov (United States)

    Rifai, Damhuji; Abdalla, Ahmed N; Razali, Ramdan; Ali, Kharudin; Faraj, Moneer A

    2017-03-13

    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient.

  8. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design

    Directory of Open Access Journals (Sweden)

    Damhuji Rifai

    2017-03-01

    Full Text Available The use of the eddy current technique (ECT for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM. The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient.

  9. Direct-current piezoelectric nanogenerator based on p-Si/n-ZnO heterojunction

    Science.gov (United States)

    Shao, Zhengzheng; Li, Xiujian

    2016-03-01

    We have demonstrated a direct-current piezoelectric nanogenerator with a novel structure of p-Si/n-ZnO heterojunction. Low resistance p-type silicon chip, with a large number of nano-concaves on the surface, was utilized as a top electrode over the n-type ZnO nanorod arrays, forming a heterojunction nanogenerator. Piezoelectric current, with average singles about 1 nA, was generated from the heterojunction nanogenerator. Rectifying behavior of the p-Si/n-ZnO heterojunction in our piezoelectric nanogenerator was analyzed from the I-V curve and the energy band structure. Furthermore, output tests of reverse connection and two devices parallel connection clearly eliminate the effects from measurement system errors and confirms that the current is generated from the nanogenerator. Our research presents an approach to integrating a new type of nanogenerator using the silicon chip directly, without expensive Pt or Au coated on the electrode surfaces.

  10. A comparison between two optimized TFPM geometries for 5 MW direct-drive wind turbines

    DEFF Research Database (Denmark)

    Nica, Florin Valentin Traian; Ritchie, Ewen; Leban, Krisztina Monika

    2013-01-01

    for the industry. The approach presented in this paper focuses on a reduction in mass of active materials, which constitute the generator, because the price of the machine is in direct relation with the amount of materials used for the construction. This strategy is applied for two types of TFPM geometries...... in order to asses which behaves better when subjected to optimization and which provides the best result. In order to obtain the mass of active materials the entire analytical design has to be covered, making the analytical design to behave as a cost function for the optimization program. The innovation...

  11. Focal Hemodynamic Responses in the Stimulated Hemisphere During High-Definition Transcranial Direct Current Stimulation.

    Science.gov (United States)

    Muthalib, Makii; Besson, Pierre; Rothwell, John; Perrey, Stéphane

    2017-07-17

    High-definition transcranial direct current stimulation (HD-tDCS) using a 4 × 1 electrode montage has been previously shown using modeling and physiological studies to constrain the electric field within the spatial extent of the electrodes. The aim of this proof-of-concept study was to determine if functional near-infrared spectroscopy (fNIRS) neuroimaging can be used to determine a hemodynamic correlate of this 4 × 1 HD-tDCS electric field on the brain. In a three session cross-over study design, 13 healthy males received one sham (2 mA, 30 sec) and two real (HD-tDCS-1 and HD-tDCS-2, 2 mA, 10 min) anodal HD-tDCS targeting the left M1 via a 4 × 1 electrode montage (anode on C3 and 4 return electrodes 3.5 cm from anode). The two real HD-tDCS sessions afforded a within-subject replication of the findings. fNIRS was used to measure changes in brain hemodynamics (oxygenated hemoglobin integral-O2 Hbint ) during each 10 min session from two regions of interest (ROIs) in the stimulated left hemisphere that corresponded to "within" (Lin ) and "outside" (Lout ) the spatial extent of the 4 × 1 electrode montage, and two corresponding ROIs (Rin and Rout ) in the right hemisphere. The ANOVA showed that both real anodal HD-tDCS compared to sham induced a significantly greater O2 Hbint in the Lin than Lout ROIs of the stimulated left hemisphere; while there were no significant differences between the real and sham sessions for the right hemisphere ROIs. Intra-class correlation coefficients showed "fair-to-good" reproducibility for the left stimulated hemisphere ROIs. The greater O2 Hbint "within" than "outside" the spatial extent of the 4 × 1 electrode montage represents a hemodynamic correlate of the electrical field distribution, and thus provides a prospective reliable method to determine the dose of stimulation that is necessary to optimize HD-tDCS parameters in various applications. © 2017 International Neuromodulation Society.

  12. Evaluation of Direct Collocation Optimal Control Problem Formulations for Solving the Muscle Redundancy Problem.

    Science.gov (United States)

    De Groote, Friedl; Kinney, Allison L; Rao, Anil V; Fregly, Benjamin J

    2016-10-01

    Estimation of muscle forces during motion involves solving an indeterminate problem (more unknown muscle forces than joint moment constraints), frequently via optimization methods. When the dynamics of muscle activation and contraction are modeled for consistency with muscle physiology, the resulting optimization problem is dynamic and challenging to solve. This study sought to identify a robust and computationally efficient formulation for solving these dynamic optimization problems using direct collocation optimal control methods. Four problem formulations were investigated for walking based on both a two and three dimensional model. Formulations differed in the use of either an explicit or implicit representation of contraction dynamics with either muscle length or tendon force as a state variable. The implicit representations introduced additional controls defined as the time derivatives of the states, allowing the nonlinear equations describing contraction dynamics to be imposed as algebraic path constraints, simplifying their evaluation. Problem formulation affected computational speed and robustness to the initial guess. The formulation that used explicit contraction dynamics with muscle length as a state failed to converge in most cases. In contrast, the two formulations that used implicit contraction dynamics converged to an optimal solution in all cases for all initial guesses, with tendon force as a state generally being the fastest. Future work should focus on comparing the present approach to other approaches for computing muscle forces. The present approach lacks some of the major limitations of established methods such as static optimization and computed muscle control while remaining computationally efficient.

  13. Current direction and CTD data from moored current meter and CTD casts in the Delaware Bay from 01 January 1984 - 01 December 1984 (NODC Accession 8600001)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and CTD data were collected using moored current meter and CTD casts in the Delaware Bay from January 1, 1984 to December 1, 1985. Data were...

  14. Current direction and CTD data from moored current meter and CTD casts in the North Pacific Ocean from 05 February 1979 - 01 December 1980 (NODC Accession 8300042)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and CTD data were collected using moored current meter and CTD casts in the North Pacific Ocean from February 5, 1979 to December 1, 1980. Data...

  15. Current direction data from moored current meter casts in the North Pacific Ocean, 31 May 1983 - 01 October 1983 (NODC Accession 8400162)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction data were collected using moored current meter casts in the North Pacific Ocean from May 31, 1983 to October 1, 1983. Data were submitted by...

  16. Current direction and temperature data from moored current meter casts in the Atlantic Ocean from 29 August 1979 - 01 November 1979 (NODC Accession 8200153)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and temperature data were collected using moored current meter casts in the Atlantic Ocean from August 29, 1979 to November 1, 1979. Data were...

  17. Current direction data from moored current meter casts in the North Pacific Ocean from 30 June 1979 - 16 August 1979 (NODC Accession 8200104)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction data were collected using moored current meter casts in the North Pacific Ocean from June 30, 1979 to August 16, 1979. Data were submitted by...

  18. Current direction data from moored current meter casts in the Delaware Bay from 23 February 1976 - 23 September 1985 (NODC Accession 8600005)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction data were collected using moored current meter casts in the Delaware Bay from February 23, 1976 to September 23, 1985. Data were submitted by...

  19. Current direction data from moored current meter casts in the North Atlantic Ocean 09 July 1975 - 01 November 1976 (NODC Accession 8300078)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction data were collected using moored current meter casts in the North Atlantic Ocean from July 9, 1975 to November 1, 1976. Data were submitted by...

  20. Current direction, temperature, and conductivity data from moored current meter casts in the North Pacific Ocean from 29 April 1981 - 02 December 1981 (NODC Accession 8300030)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, temperature, and conductivity data were collected using moored current meter casts in the North Pacific Ocean from April 29, 1981 to December 2,...

  1. Current direction and CTD data from moored current meter and CTD casts in the Atlantic Ocean from 04 August 1980 - 14 August 1981 (NODC Accession 8200240)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and CTD data were collected using moored current meter and CTD casts in the Atlantic Ocean from August 4, 1980 to August 14, 1981. Data were...

  2. Current direction data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 16 July 1979 - 02 August 1979 (NODC Accession 8000501)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction data were collected using moored current meter casts in the Gulf of Mexico from July 16, 1979 to August 2, 1979. Data were submitted by Texas A...

  3. Current direction and temperature data from moored current meter casts in the Gulf of Mexico from 24 March 1980 - 16 June 1980 (NODC Accession 8200220)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and temperature data were collected using moored current meter casts in the Gulf of Mexico from March 24, 1980 to June 16, 1980. Data were...

  4. Direct SQP-methods for solving optimal control problems with delays

    Energy Technology Data Exchange (ETDEWEB)

    Goellmann, L.; Bueskens, C.; Maurer, H.

    1994-12-31

    The maximum principle for optimal control problems with delays leads to a boundary value problem (BVP) which is retarded in the state and advanced in the costate function. Based on shooting techniques, solution methods for this type of BVP have been proposed. In recent years, direct optimization methods have been favored for solving control problems without delays. Direct methods approximate the control and the state over a fixed mesh and solve the resulting NLP-problem with SQP-methods. These methods dispense with the costate function and have shown to be robust and efficient. In this paper, we propose a direct SQP-method for retarded control problems. In contrast to conventional direct methods, only the control variable is approximated by e.g. spline-functions. The state is computed via a high order Runge-Kutta type algorithm and does not enter explicitly the NLP-problem through an equation. This approach reduces the number of optimization variables considerably and is implementable even on a PC. Our method is illustrated by the numerical solution of retarded control problems with constraints. In particular, we consider the control of a continuous stirred tank reactor which has been solved by dynamic programming. This example illustrates the robustness and efficiency of the proposed method. Open questions concerning sufficient conditions and convergence of discretized NLP-problems are discussed.

  5. A Bi-directional Energy Splitable Model for Energy Optimization in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    A. Rajeswari

    2011-01-01

    Full Text Available Wireless Sensor Networks is a budding  prototype of networking and computing, where a node may be self powered and individual node have the capability to sense and compute and communicate. Wireless Sensor Networks have been proposed for variety of applications such as Industrial control and monitoring and home automation and consumer electronics and security andMilitary sensing, Asset tracking and supply chain management, Intelligent Agriculture, Missile directing, Fire alarming, Landslide Warning, Environmental monitoring and health monitoring and commercial applications. In Wireless Sensor Network large number of nodes are deployed randomly. Depends on the network architecture the application may be personalized such as Energy Efficiency, Routing and Power Management and data dissemination. Energy Optimization involves in minimizing an energy expenditure and maximizing the lifetime of the complete network. In the proposed work, the placement of nodes are directly involved with residual energy. Energy Optimization in sensor network is very difficult task to achieve it. The optimization of energy is performed through Bidirectional Energy Splitable Model. The data flow in both forward and backward directions are considered, In order to achieve the best QOS in transmission, some parameters such as load, delay and direction of individual nodes are considered. A mathematical model is developed to determine the data flow of  individual node based on the residual energy.

  6. A role for biological optimization within the current treatment planning paradigm

    Energy Technology Data Exchange (ETDEWEB)

    Das, Shiva [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710 (United States)

    2009-10-15

    /rectum EUDs were reduced (after DVO) by 5.0%/3.9%, and highest doses were reduced by 4.6%/7.8%. The optimization with purely biological OAR objectives achieved bladder/rectal EUDs that were 7.4%/3.1% lower than from DVO, but only reduced highest doses by 1.4%/0.7%. In the olfactory neuroblastoma case, the target was closely surrounded by the eyes, optic nerves, chiasm, and brainstem. In one of the scenarios studied, the eyes, optic nerves, and chiasm were targeted for EUD reduction after DVO. EUD to the left eye, right eye, left optic nerve, right optic nerve, and chiasm were reduced by 7.0%, 5.7%, 4.7%, 4.1%, and 0.6%, respectively, and highest doses were reduced by 16.5%, 11.0%, 5.1%, 3.8%, and 1.5%, respectively. The optimization with purely biological OAR objectives was less effective for the eyes and optics nerves. EUDs for the left eye/right eye/left optic nerve/right optic nerve/chiasm were lower than that from DVO by 0.4%/2.7%/4.0%/2.8%/15.6% and highest doses were lower by 4.6%/1.4%/2.4%/6.4%/7.1% (but purely biological optimization was better overall for the OARs not targeted for EUD reduction). Conclusions: Incorporating biological optimization after dose-volume constrained optimization can further reduce biological metrics, while preserving the important dose reductions achieved by dose-volume constrained optimization. Thus, biological optimization may be accommodated within the framework of current IMRT planning clinical expectations.

  7. Transspinal direct current stimulation modulates migration and proliferation of adult newly born spinal cells in mice.

    Science.gov (United States)

    Samaddar, Sreyashi; Vazquez, Kizzy; Ponkia, Dipen; Toruno, Pedro; Sahbani, Karim; Begum, Sultana; Abouelela, Ahmed; Mekhael, Wagdy; Ahmed, Zaghloul

    2017-02-01

    Direct current electrical fields have been shown to be a major factor in the regulation of cell proliferation, differentiation, migration, and survival, as well as in the maturation of dividing cells during development. During adulthood, spinal cord cells are continuously produced in both animals and humans, and they hold great potential for neural restoration following spinal cord injury. While the effects of direct current electrical fields on adult-born spinal cells cultured ex vivo have recently been reported, the effects of direct current electrical fields on adult-born spinal cells in vivo have not been characterized. Here, we provide convincing findings that a therapeutic form of transspinal direct current stimulation (tsDCS) affects the migration and proliferation of adult-born spinal cells in mice. Specifically, cathodal tsDCS attracted the adult-born spinal cells, while anodal tsDCS repulsed them. In addition, both tsDCS polarities caused a significant increase in cell number. Regarding the potential mechanisms involved, both cathodal and anodal tsDCS caused significant increases in expression of brain-derived neurotrophic factor, while expression of nerve growth factor increased and decreased, respectively. In the spinal cord, both anodal and cathodal tsDCS increased blood flow. Since blood flow and angiogenesis are associated with the proliferation of neural stem cells, increased blood flow may represent a major factor in the modulation of newly born spinal cells by tsDCS. Consequently, we propose that the method and novel findings presented in the current study have the potential to facilitate cellular, molecular, and/or bioengineering strategies to repair injured spinal cords.NEW & NOTEWORTHY Our results indicate that transspinal direct current stimulation (tsDCS) affects the migratory pattern and proliferation of adult newly born spinal cells, a cell population which has been implicated in learning and memory. In addition, our results suggest a

  8. Modelling the effect of electrode displacement on transcranial direct current stimulation (tDCS).

    Science.gov (United States)

    Ramaraju, Sriharsha; Roula, Mohammed Ali; McCarthy, Peter

    2017-09-19

    Transcranial Direct Current Stimulation (tDCS) is a neuromodulatory technique that delivers a low-intensity, direct current to cortical areas with the purpose of modulating underlying brain activity. Recent studies have reported inconsistencies in tDCS outcomes. The underlying assumption of many tDCS studies has been that replication of electrode montage equates to replicating stimulation conditions. It is possible however that anatomical difference between subjects, as well as inherent inaccuracies in montage placement, could affect current flow to targeted areas. The hypothesis that stimulation of a defined brain region will be stable under small displacements was tested. Approach: Initially, we compared the total simulated current flowing through ten specific brain areas for four commonly used tDCS montages: F3-Fp2, C3-Fp2, Fp1-F4, and P3-P4 using the software tool COMETS. The effect of a slight (~1cm in each of four directions) anode displacement on the simulated regional current density for each of the four tDCS montages was then determined. Current flow was calculated and compared through 10 segmented brain areas to determine the effect of montage type and displacement. The regional currents, as well as the localised current densities, were compared with the original electrode location, for each of these new positions. Results: Recommendations for montages that maximise stimulation current for the ten brain regions are considered. We noted that the extent to which stimulation is affected by electrode displacement varies depending on both area and montage type. The F3-Fp2 montage was found to be the least stable with up to 38% change in average current density in the left frontal lobe while the Fp1-F4 montage was found to the most stable exhibiting only 1% change when electrodes were displaced. Significance: These results indicate that even relatively small changes in stimulation electrode placement appear to result in surprisingly large changes in current

  9. Design technology co-optimization assessment for directed self-assembly-based lithography: design for directed self-assembly or directed self-assembly for design?

    Science.gov (United States)

    Lai, Kafai; Liu, Chi-Chun; Tsai, Hsinyu; Xu, Yongan; Chi, Cheng; Raghunathan, Ananthan; Dhagat, Parul; Hu, Lin; Park, Oseo; Jung, Sunggon; Cho, Wooyong; Morillo, Jaime; Pitera, Jed; Schmidt, Kristin; Guillorn, Mike; Brink, Markus; Sanders, Daniel; Felix, Nelson; Bailey, Todd; Colburn, Matthew

    2017-01-01

    We report a systematic study of the feasibility of using directed self-assembly (DSA) in real product design for 7-nm fin field effect transistor (FinFET) technology. We illustrate a design technology co-optimization (DTCO) methodology and two test cases applying both line/space type and via/cut type DSA processes. We cover the parts of DSA process flow and critical design constructs as well as a full chip capable computational lithography framework for DSA. By co-optimizing all process flow and product design constructs in a holistic way using a computational DTCO flow, we point out the feasibility of manufacturing using DSA in an advanced FinFET technology node and highlight the issues in the whole DSA ecosystem before we insert DSA into manufacturing.

  10. Directed Current Induced by an Symmetrically ac Force Coexisting with a Time-Delayed Feedback

    Institute of Scientific and Technical Information of China (English)

    易述婷; 宋晖; 欧志娥; 艾保全; 熊建文

    2012-01-01

    We study the transport of overdamped Brownian particles in a symmetricaJly periodic potential in the presence of an asymmetrically ac driving force and a time-delayed feedback. It is found that for low frequencies, the average velocity can be negative by changing the driving amplitude, for high frequencies, there exists an optimized driving amplitude at which the average velocity takes its maximum value. Additionally, there is a threshold value of driving amplitude below which no directed transport can be obtained for high frequencies. For the large value of the delay time, the average velocity is independent of the delay time.

  11. Optimization of solenoid based low energy beam transport line for high current H+ beams

    Science.gov (United States)

    Pande, R.; Singh, P.; Rao, S. V. L. S.; Roy, S.; Krishnagopal, S.

    2015-02-01

    A 20 MeV, 30 mA CW proton linac is being developed at BARC, Mumbai. This linac will consist of an ECR ion source followed by a Radio Frequency Quadrupole (RFQ) and Drift tube Linac (DTL). The low energy beam transport (LEBT) line is used to match the beam from the ion source to the RFQ with minimum beam loss and increase in emittance. The LEBT is also used to eliminate the unwanted ions like H2+ and H3+ from entering the RFQ. In addition, space charge compensation is required for transportation of such high beam currents. All this requires careful design and optimization. Detailed beam dynamics simulations have been done to optimize the design of the LEBT using the Particle-in-cell code TRACEWIN. We find that with careful optimization it is possible to transport a 30 mA CW proton beam through the LEBT with 100% transmission and minimal emittance blow up, while at the same time suppressing unwanted species H2+ and H3+ to less than 3.3% of the total beam current.

  12. Enhancing the accelerated beam current in the booster synchrotron by optimizing the transport line beam propagation

    Indian Academy of Sciences (India)

    Saini R S; Tyagi Y; Ghodke A D; Puntambekar T A

    2016-04-01

    In this paper, we present the results of transverse beam emittance and twiss parameter measurement of an electron beam, delivered by a 20 MeV microtron which is used as a pre-injector system for a booster synchrotron in the Indus Accelerator Facility at RRCAT Indore. Based on these measured beam parameters, beam optics of a transport line was optimized and its results are alsodiscussed in this paper. This beam transport line is used to transport the electron beam from the 20MeV microtron to the booster synchrotron. The booster synchrotron works as a main injector for Indus-1 and Indus-2 synchrotron radiation facilities. To optimize the beam optics of a transport linefor proper beam transmission through the line as well as to match the beam twiss parameters at the beam injection point of another accelerator, it is necessary to know the transverse beam emittance and twiss parameters of the beam coming from the first one. A MATLAB-based GUI program has been developed to calculate the beam emittance and twiss parameters, using quadrupole scanmethod. The measured parameters have been used for beam transport line optimization and twiss parameters matching at booster injection point. After this optimization, an enhancement of ∼50% beam current has been observed in the booster synchrotron.

  13. Recovery of spinal cord function induced by direct current stimulation of the injured rat spinal cord.

    Science.gov (United States)

    Wallace, M C; Tator, C H; Piper, I

    1987-06-01

    Direct current stimulation has been shown by others to enhance the regeneration of several types of tissues, including nervous tissue in some species. The purpose of the present experiment was to assess the value of direct current stimulation for enhancing the recovery of spinal cord function after clip compression injury of the rat spinal cord. Twenty Wistar rats underwent a 1-minute, 50-g clip compression injury at T-1, after which electrodes were placed epidurally with the anode proximal and the cathode distal to the injury site. These electrodes were attached to a stimulator implanted subcutaneously. Ten animals received stimulators that produced a constant current of 14 microA, and the remainder received stimulators with no electrical output and served as controls. Assignment of stimulators was random, and the treatment group was not identified until sacrifice. Neurological function was tested weekly for 15 weeks by the inclined plane technique, after which the animals were killed and the injured cords were examined for histological evidence of regeneration. The mean inclined plane result for the treatment group (39 +/- 5 degrees) was significantly better than that for the control group (31 +/- 6 degrees) (P less than 0.02), although there was no significant difference in histological findings between the two groups. Thus, direct current stimulation of the injured mammalian spinal cord produced improvement in neurological function and warrants further investigation.

  14. Anodal transcranial direct current stimulation over the supramarginal gyrus facilitates pitch memory.

    Science.gov (United States)

    Schaal, Nora K; Williamson, Victoria J; Banissy, Michael J

    2013-11-01

    Functional neuroimaging studies have shown activation of the supramarginal gyrus during pitch memory tasks. A previous transcranial direct current stimulation study using cathodal stimulation over the left supramarginal gyrus reported a detrimental effect on short-term pitch memory performance, indicating an important role of the supramarginal gyrus in pitch memory. The current study aimed to determine whether pitch memory could be improved following anodal stimulation of the left supramarginal gyrus. The performances of non-musicians on two pitch memory tasks (pitch recognition and recall) and a visual memory control task following anodal or sham transcranial direct current stimulation were compared. The results show that, post-stimulation, the anodal group but not the control group performed significantly better on both pitch memory tasks; performance did not differ on the face memory task. These findings provide strong support for the causal involvement of the left supramarginal gyrus in the pitch memory process, and highlight the potential efficacy of transcranial direct current stimulation as a tool to improve pitch memory. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  15. Optimization of a neural architecture for the direct control of a Boost converter

    Directory of Open Access Journals (Sweden)

    Fredy Hernán Martinez Sarmiento

    2012-06-01

    Full Text Available In research related to control of DC/DC converters, artificial intelligence techniques are a great improvement in the design and performance. However, some of these tools require the use of trial and error strategies in the design, making it difficult to obtain an optimal structure. In this paper, we propose a direct control based on artificial neural network, whose design has been optimized using bio-inspired searching strategies, with the idea of optimizing simultaneously two different but important aspects of the network: architecture and weights connections. The control was successfully applied to a boost type converter. The results obtained allow us to observe the dynamic performance of the scheme, in which the response time and variation in the output voltage can be concluded that the criteria used for the control loop design were appropriate.

  16. Plasma environment during hot cathode direct current discharge plasma chemical vapor deposition of diamond films

    Institute of Scientific and Technical Information of China (English)

    朱晓东; 詹如娟; 周海洋; 胡敏; 温晓辉; 周贵恩; 李凡庆

    1999-01-01

    The plasma characteristics have been investigated in situ by using optical emission spectroscopy (OES) and the Langmuir probe during hot cathode direct current discharge plasma chemical vapor deposition of diamond films. The changes of atomic H and CH radical in the ground state have been calculated quantitatively according to the results of OES and the Langmuir probe measurement as discharge current density varied. It is shown that atomic H and CH radicals both in the ground state and in the excited state increase with the enhancement of the discharge current density in the plasma. The electron density and CH emission intensity increase linearly with the enhancement of discharge current densities. The generation of different carbon-containing radicals is related to the elevation of electron temperature. Combining the growth process of diamond films and the diagnostic results, it is shown that atomic H in the excited state may improve the diamond growth efficiently, and the increase of electron temperat

  17. Electrochemical deposition and characterization of zinc–nickel alloys deposited by direct and reverse current

    Directory of Open Access Journals (Sweden)

    JELENA B. BAJAT

    2005-12-01

    Full Text Available Zn–Ni alloys electrochemically deposited on steel under various deposition conditions were investigated. The alloys were deposited on a rotating disc electrode and on a steel panel from chloride solutions by direct and reverse current. The influence of reverse plating variables (cathodic and anodic current densities and their time duration on the composition, phase structure and corrosion properties were investigated. The chemical content and phase composition affect the anticorrosive properties of Zn–Ni alloys during exposure to a corrosive agent (3 % NaCl solution. It was shown that the Zn–Ni alloy electrodeposited by reverse current with a full period T = 1 s and r = 0.2 exhibits the best corrosion properties of all the investigated alloys deposited by reverse current.

  18. Experimental Investigation of a Direct Methanol Fuel Cell with Hilbert Fractal Current Collectors

    Directory of Open Access Journals (Sweden)

    Jing-Yi Chang

    2014-01-01

    Full Text Available The Hilbert curve is a continuous type of fractal space-filling curve. This fractal curve visits every point in a square grid with a size of 2×2, 4×4, or any other power of two. This paper presents Hilbert fractal curve application to direct methanol fuel cell (DMFC current collectors. The current collectors are carved following first, second, and third order Hilbert fractal curves. These curves give the current collectors different free open ratios and opening perimeters. We conducted an experimental investigation into DMFC performance as a function of the free open ratio and opening perimeter on the bipolar plates. Nyquist plots of the bipolar plates are made and compared using electrochemical impedance spectroscopy (EIS experiments to understand the phenomena in depth. The results obtained in this paper could be a good reference for future current collector design.

  19. An Adaptive Particle Swarm Optimization Algorithm Based on Directed Weighted Complex Network

    Directory of Open Access Journals (Sweden)

    Ming Li

    2014-01-01

    Full Text Available The disadvantages of particle swarm optimization (PSO algorithm are that it is easy to fall into local optimum in high-dimensional space and has a low convergence rate in the iterative process. To deal with these problems, an adaptive particle swarm optimization algorithm based on directed weighted complex network (DWCNPSO is proposed. Particles can be scattered uniformly over the search space by using the topology of small-world network to initialize the particles position. At the same time, an evolutionary mechanism of the directed dynamic network is employed to make the particles evolve into the scale-free network when the in-degree obeys power-law distribution. In the proposed method, not only the diversity of the algorithm was improved, but also particles’ falling into local optimum was avoided. The simulation results indicate that the proposed algorithm can effectively avoid the premature convergence problem. Compared with other algorithms, the convergence rate is faster.

  20. Phage display-based strategies for cloning and optimization of monoclonal antibodies directed against human pathogens.

    Science.gov (United States)

    Clementi, Nicola; Mancini, Nicasio; Solforosi, Laura; Castelli, Matteo; Clementi, Massimo; Burioni, Roberto

    2012-01-01

    In the last two decades, several phage display-selected monoclonal antibodies (mAbs) have been described in the literature and a few of them have managed to reach the clinics. Among these, the anti-respiratory syncytial virus (RSV) Palivizumab, a phage-display optimized mAb, is the only marketed mAb directed against microbial pathogens. Palivizumab is a clear example of the importance of choosing the most appropriate strategy when selecting or optimizing an anti-infectious mAb. From this perspective, the extreme versatility of phage-display technology makes it a useful tool when setting up different strategies for the selection of mAbs directed against human pathogens, especially when their possible clinical use is considered. In this paper, we review the principal phage display strategies used to select anti-infectious mAbs, with particular attention focused on those used against hypervariable pathogens, such as HCV and influenza viruses.

  1. Global Inverse Optimal Tracking Control of Underactuated Omni-directional Intelligent Navigators (ODINs)

    Institute of Scientific and Technical Information of China (English)

    Khac Duc Do

    2015-01-01

    This paper presents a design of optimal controllers with respect to a meaningful cost function to force an underactuated omni-directional intelligent navigator (ODIN) under unknown constant environmental loads to track a reference trajectory in two-dimensional space. Motivated by the vehicle’s steering practice, the yaw angle regarded as a virtual control plus the surge thrust force are used to force the position of the vehicle to globally track its reference trajectory. The control design is based on several recent results developed for inverse optimal control and stability analysis of nonlinear systems, a new design of bounded disturbance observers, and backstepping and Lyapunov’s direct methods. Both state- and output-feedback control designs are addressed. Simulations are included to illustrate the effectiveness of the proposed results.

  2. Directed Bee Colony Optimization Algorithm to Solve the Nurse Rostering Problem

    Science.gov (United States)

    Amudhavel, J.; Pothula, Sujatha; Dhavachelvan, P.

    2017-01-01

    The Nurse Rostering Problem is an NP-hard combinatorial optimization, scheduling problem for assigning a set of nurses to shifts per day by considering both hard and soft constraints. A novel metaheuristic technique is required for solving Nurse Rostering Problem (NRP). This work proposes a metaheuristic technique called Directed Bee Colony Optimization Algorithm using the Modified Nelder-Mead Method for solving the NRP. To solve the NRP, the authors used a multiobjective mathematical programming model and proposed a methodology for the adaptation of a Multiobjective Directed Bee Colony Optimization (MODBCO). MODBCO is used successfully for solving the multiobjective problem of optimizing the scheduling problems. This MODBCO is an integration of deterministic local search, multiagent particle system environment, and honey bee decision-making process. The performance of the algorithm is assessed using the standard dataset INRC2010, and it reflects many real-world cases which vary in size and complexity. The experimental analysis uses statistical tools to show the uniqueness of the algorithm on assessment criteria. PMID:28473849

  3. Image-Guided Hydrodynamic Gene Delivery: Current Status and Future Directions

    Directory of Open Access Journals (Sweden)

    Kenya Kamimura

    2015-08-01

    Full Text Available Hydrodynamics-based delivery has been used as an experimental tool to express transgene in small animals. This in vivo gene transfer method is useful for functional analysis of genetic elements, therapeutic effect of oligonucleotides, and cancer cells to establish the metastatic cancer animal model for experimental research. Recent progress in the development of image-guided procedure for hydrodynamics-based gene delivery in large animals directly supports the clinical applicability of this technique. This review summarizes the current status and recent progress in the development of hydrodynamics-based gene delivery and discusses the future directions for its clinical application.

  4. Optimization of Superconducting Focusing Quadrupoles for the HighCurrent Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Sabbi, GianLuca; Gourlay, Steve; Gung, Chen-yu; Hafalia, Ray; Lietzke, Alan; Martovetski, Nicolai; Mattafirri, Sara; Meinke, Rainer; Minervini, Joseph; Schultz, Joel; Seidl, Peter

    2005-09-16

    The Heavy Ion Fusion (HIF) program is progressing through a series of physics and technology demonstrations leading to an inertial fusion power plant. The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is exploring the physics of intense beams with high line-charge density. Superconducting focusing quadrupoles have been developed for the HCX magnetic transport studies. A baseline design was selected following several pre-series models. Optimization of the baseline design led to the development of a first prototype that achieved a conductor-limited gradient of 132 T/m in a 70 mm bore, without training, with measured field errors at the 0.1% level. Based on these results, the magnet geometry and fabrication procedures were adjusted to improve the field quality. These modifications were implemented in a second prototype. In this paper, the optimized design is presented and comparisons between the design harmonics and magnetic measurements performed on the new prototype are discussed.

  5. Direct-current vertical electrical-resistivity soundings in the Lower Peninsula of Michigan

    Science.gov (United States)

    Westjohn, D.B.; Carter, P.J.

    1989-01-01

    Ninety-three direct-current vertical electrical-resistivity soundings were conducted in the Lower Peninsula of Michigan from June through October 1987. These soundings were made to assist in mapping the depth to brine in areas where borehole resistivity logs and water-quality data are sparse or lacking. The Schlumberger array for placement of current and potential electrodes was used for each sounding. Vertical electrical-resistivity sounding field data, shifted and smoothed sounding data, and electric layers calculated using inverse modeling techniques are presented. Also included is a summary of the near-surface conditions and depths to conductors and resistors for each sounding location.

  6. Development of a Direct Methanol Fuel Cell with Lightweight Disc Type Current Collectors

    Directory of Open Access Journals (Sweden)

    Yean-Der Kuan

    2014-05-01

    Full Text Available The direct methanol fuel cell (DMFC adopts methanol solution as a fuel suitable for low power portable applications. A miniature, lightweight, passive air-breathing design is therefore desired. This paper presents a novel planar disc-type DMFC with multiple cells containing a novel developed lightweight current collector at both the anode and cathode sides. The present lightweight current collector adopts FR4 Glass/Epoxy as the substrate with the current collecting areas located at the corresponding membrane electrolyte assembly (MEA areas. The current collecting areas are fabricated by sequentially coating a corrosion resistant layer and electrical conduction layer via the thermal evaporation technique. The anode current collector has carved flow channels for fuel transport and production. The cathode current collector has drilled holes for passive air breathing. In order to ensure feasibility in the present concept a 3-cell prototype DMFC module with lightweight disc type current collectors is designed and constructed. Experiments were conducted to measure the cell performance. The results show that the highest cell power output is 54.88 mW·cm−2 and successfully demonstrate the feasibility of this novel design.

  7. Limitations in direct and indirect methods for solving optimal control problems in growth theory

    Directory of Open Access Journals (Sweden)

    Ratković Kruna

    2016-01-01

    Full Text Available The focus of this paper is on a comprehensive analysis of different methods and mathematical techniques used for solving optimal control problems (OCP in growth theory. Most important methods for solving dynamic non-linear infinite-horizon growth models using optimal control theory are presented and a critical view of the limitations of different methods is given. The main problem is to determine the optimal rate of growth over time in a way that maximizes the welfare function over an infinite horizon. The welfare function depends on capital-labor ratio, the state variable, and the per-capita consumption, the control variable. Numerical methods for solving OCP are divided into two classes: direct and indirect approach. How the indirect approach can be used is given in the example of the neo-classical growth model. In order to present the indirect and the direct approach simultaneously, two endogenous growth models, one written by Romer and another by Lucas and Uzawa, are studied. Advantages and efficiency of these different approaches will be discussed. Although the indirect methods for solving OCP are still the most expanded in growth theory, it will be seen that using direct methods can also be very efficient and help to overcome problems that can occur by using the indirect approach.

  8. Optimization of controllability and robustness of complex networks by edge directionality

    Science.gov (United States)

    Liang, Man; Jin, Suoqin; Wang, Dingjie; Zou, Xiufen

    2016-09-01

    Recently, controllability of complex networks has attracted enormous attention in various fields of science and engineering. How to optimize structural controllability has also become a significant issue. Previous studies have shown that an appropriate directional assignment can improve structural controllability; however, the evolution of the structural controllability of complex networks under attacks and cascading has always been ignored. To address this problem, this study proposes a new edge orientation method (NEOM) based on residual degree that changes the link direction while conserving topology and directionality. By comparing the results with those of previous methods in two random graph models and several realistic networks, our proposed approach is demonstrated to be an effective and competitive method for improving the structural controllability of complex networks. Moreover, numerical simulations show that our method is near-optimal in optimizing structural controllability. Strikingly, compared to the original network, our method maintains the structural controllability of the network under attacks and cascading, indicating that the NEOM can also enhance the robustness of controllability of networks. These results alter the view of the nature of controllability in complex networks, change the understanding of structural controllability and affect the design of network models to control such networks.

  9. Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A., E-mail: jrogers@illinois.edu [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Wahab, Muhammad A.; Alam, Muhammad A. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Li, Yuhang [Institute of Solid Mechanics, Beihang University, Beijing 100191 (China); Tomic, Bojan [Department of Electrical Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Huang, Jiyuan [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Burns, Branden [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Song, Jizhou [Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027 (China); Huang, Yonggang [Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-04-07

    Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.

  10. Individualized treatment with transcranial direct current stimulation in patients with chronic non-fluent aphasia due to stroke.

    Science.gov (United States)

    Shah-Basak, Priyanka P; Norise, Catherine; Garcia, Gabriella; Torres, Jose; Faseyitan, Olufunsho; Hamilton, Roy H

    2015-01-01

    While evidence suggests that transcranial direct current stimulation (tDCS) may facilitate language recovery in chronic post-stroke aphasia, individual variability in patient response to different patterns of stimulation remains largely unexplored. We sought to characterize this variability among chronic aphasic individuals, and to explore whether repeated stimulation with an individualized optimal montage could lead to persistent reduction of aphasia severity. In a two-phase study, we first stimulated patients with four active montages (left hemispheric anode or cathode; right hemispheric anode or cathode) and one sham montage (Phase 1). We examined changes in picture naming ability to address (1) variability in response to different montages among our patients, and (2) whether individual patients responded optimally to at least one montage. During Phase 2, subjects who responded in Phase 1 were randomized to receive either real-tDCS or to receive sham stimulation (10 days); patients who were randomized to receive sham stimulation first were then crossed over to receive real-tDCS (10 days). In both phases, 2 mA tDCS was administered for 20 min per real-tDCS sessions and patients performed a picture naming task during stimulation. Patients' language ability was re-tested after 2-weeks and 2-months following real and sham tDCS in Phase 2. In Phase 1, despite considerable individual variability, the greatest average improvement was observed after left-cathodal stimulation. Seven out of 12 subjects responded optimally to at least one montage as demonstrated by transient improvement in picture-naming. In Phase 2, aphasia severity improved at 2-weeks and 2-months following real-tDCS but not sham. Despite individual variability with respect to optimal tDCS approach, certain montages result in consistent transient improvement in persons with chronic post-stroke aphasia. This preliminary study supports the notion that individualized tDCS treatment may enhance aphasia

  11. Current research and future directions in pattern identification: Results of an international symposium.

    Science.gov (United States)

    Lee, Myeong Soo; Lee, Ju Ah; Alraek, Terje; Bian, Zhao-Xiang; Birch, Stephen; Goto, Hirozo; Jung, Jeeyoun; Kao, Shung-Te; Moon, Sang-Kwan; Park, Bongki; Park, Kyung-Mo; You, Sooseong; Yun, Kyung-Jin; Zaslawski, Chris

    2016-12-01

    A symposium on pattern identification (PI) was held at the Korea Institute of Oriental Medicine (KIOM) on October 2, 2013, in Daejeon, South Korea. This symposium was convened to provide information on the current research in PI as well as suggest future research directions. The participants discussed the nature of PI, possible research questions, strategies and future international collaborations in pattern research. With eight presentations and an extensive panel discussion, the symposium allowed participants to discuss research methods in traditional medicine for PI. One speaker presented the topic, 'Clinical pattern differentiation and contemporary research in PI.' Two speakers presented current trends in research on blood stasis while the remaining five other delegates discussed the research methods and future directions of PI research. The participants engaged in in-depth discussions regarding the nature of PI, potential research questions, strategies and future international collaborations in pattern research.

  12. Spreading depolarizations have prolonged direct current shifts and are associated with poor outcome in brain trauma

    DEFF Research Database (Denmark)

    Hartings, Jed A; Watanabe, Tomas; Bullock, M Ross

    2011-01-01

    Cortical spreading depolarizations occur spontaneously after ischaemic, haemorrhagic and traumatic brain injury. Their effects vary spatially and temporally as graded phenomena, from infarction to complete recovery, and are reflected in the duration of depolarization measured by the negative direct...... current shift of electrocorticographic recordings. In the focal ischaemic penumbra, peri-infarct depolarizations have prolonged direct current shifts and cause progressive recruitment of the penumbra into the core infarct. In traumatic brain injury, the effects of spreading depolarizations are unknown......, although prolonged events have not been observed in animal models. To determine whether detrimental penumbral-type depolarizations occur in human brain trauma, we analysed electrocorticographic recordings obtained by subdural electrode-strip monitoring during intensive care. Of 53 patients studied, 10...

  13. Spatial and polarity precision of concentric high-definition transcranial direct current stimulation (HD-tDCS)

    Science.gov (United States)

    Alam, Mahtab; Truong, Dennis Q.; Khadka, Niranjan; Bikson, Marom

    2016-06-01

    Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that applies low amplitude current via electrodes placed on the scalp. Rather than directly eliciting a neuronal response, tDCS is believed to modulate excitability—enhancing or suppressing neuronal activity in regions of the brain depending on the polarity of stimulation. The specificity of tDCS to any therapeutic application derives in part from how electrode configuration determines the brain regions that are stimulated. Conventional tDCS uses two relatively large pads (>25 cm2) whereas high-definition tDCS (HD-tDCS) uses arrays of smaller electrodes to enhance brain targeting. The 4  ×  1 concentric ring HD-tDCS (one center electrode surrounded by four returns) has been explored in application where focal targeting of cortex is desired. Here, we considered optimization of concentric ring HD-tDCS for targeting: the role of electrodes in the ring and the ring’s diameter. Finite element models predicted cortical electric field generated during tDCS. High resolution MRIs were segmented into seven tissue/material masks of varying conductivities. Computer aided design (CAD) model of electrodes, gel, and sponge pads were incorporated into the segmentation. Volume meshes were generated and the Laplace equation (\

  14. Augmenting Visual Search Performance with Transcranial Direct Current Stimulation (tDCS)

    Science.gov (United States)

    2015-03-01

    withdrew. Of the 11 participants who completed the study, 6 were male and 5 were female. The age for the participants ranged from 24 to 42 years old (mean...significantly improves detection accuracy during the task compared to the sham condition. In addition,, a correlation was found in relation to...eye field, sustained attention , transcranial direct current stimulation, monotonous, vigilance, percent of eye closure 16. SECURITY CLASSIFICATION

  15. Is transcranial direct current stimulation a potential method for improving response inhibition?☆

    OpenAIRE

    Kwon, Yong Hyun; Kwon, Jung Won

    2013-01-01

    Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments. This study used a stop-signal task to determine whether transcranial direct-current stimulation over the pre-supplementary motor area alters the reaction time in motor inhibition. Forty healthy subjects were recruited for this study and were randomly assigned to either the tran...

  16. Transcranial direct current stimulation in patients with Alzheimer’s disease: Challenges and responses

    OpenAIRE

    Yuan, Hong; Tabarak, Serik; Yu, Jing; Lei, Xu

    2015-01-01

    The use of transcranial direct current stimulation (tDCS) as a noninvasive therapeutic approach for Alzheimer’s disease (AD) has gained increasing attention. Research regarding the utility of tDCS in AD is inconsistent. In this study, we reviewed the importance of individual diversity among AD patients, starting from the uninformative mean results. We also demonstrated variation among AD patients. Highly educated patients seem to benefit more; education also seems to modulate baseline measure...

  17. Adjuvant transcranial direct current stimulation for treating Alzheimer's disease: A case study

    OpenAIRE

    Suellen Marinho Andrade; Camila Teresa Ponce Leon de Mendonça; Thobias Cavalcanti Laurindo Pereira; Bernardino Fernandez-Calvo; Regina Coely Neves Araújo; Nelson Torro Alves

    2016-01-01

    ABSTRACT We report the case of a 73-year-old male patient with Alzheimer's disease who underwent 10-daily transcranial direct current stimulation (tDCS) sessions. tDCS was applied over the left dorsolateral prefrontal cortex as an adjuvant to the traditional treatment that the patient was receiving, which consisted of anticholinergic medication and cognitive training. The data were qualitatively analyzed and are presented in an analytic and structured form. The effects on cognitive performanc...

  18. Action Mechanisms of Transcranial Direct Current Stimulation in Alzheimer’s Disease and Memory Loss

    OpenAIRE

    Hansen, Niels

    2012-01-01

    The pharmacological treatment of Alzheimer’s disease (AD) is often limited and accompanied by drug side effects. Thus alternative therapeutic strategies such as non-invasive brain stimulation are needed. Few studies have demonstrated that transcranial direct current stimulation (tDCS), a method of neuromodulation with consecutive robust excitability changes within the stimulated cortex area, is beneficial in AD. There is also evidence that tDCS enhances memory function in cognitive rehabilita...

  19. Transcranial direct current stimulation in refractory continuous spikes and waves during slow sleep: a controlled study

    DEFF Research Database (Denmark)

    Varga, Edina T; Terney, Daniella; Atkins, Mary D;

    2011-01-01

    Cathodal transcranial direct current stimulation (tDCS) decreases cortical excitability. The purpose of the study was to investigate whether cathodal tDCS could interrupt the continuous epileptiform activity. Five patients with focal, refractory continuous spikes and waves during slow sleep were...... recruited. Cathodal tDCS and sham stimulation were applied to the epileptic focus, before sleep (1 mA; 20 min). Cathodal tDCS did not reduce the spike-index in any of the patients....

  20. Transcranial Direct Current Stimulation in Stroke Rehabilitation: A Review of Recent Advancements

    OpenAIRE

    Andrea Gomez Palacio Schjetnan; Jamshid Faraji; Metz, Gerlinde A.; Masami Tatsuno; Artur Luczak

    2013-01-01

    Transcranial direct current stimulation (tDCS) is a promising technique to treat a wide range of neurological conditions including stroke. The pathological processes following stroke may provide an exemplary system to investigate how tDCS promotes neuronal plasticity and functional recovery. Changes in synaptic function after stroke, such as reduced excitability, formation of aberrant connections, and deregulated plastic modifications, have been postulated to impede recovery from stroke. Howe...