WorldWideScience
 
 
1

An Injector for the Variable Specific Impulse Magnetoplasma Rocket  

Science.gov (United States)

We present a summary of progress on the development of a plasma injector for NASA's VASIMR (Variable Specific Impulse Magnetoplasma Rocket) engine. The plasma rocket constrains a flowing plasma in an asymmetric magnetic bottle and exhausts it through a magnetic nozzle to produce thrust. The injector is a plasma source located on the axis of symmetry, forward of the series of coils forming the constraining magnetic field. The injector is intended to produce a well-collimated jet of highly ionized plasma which will enter the central cell of the machine through its forward mirror. The prototype design is based on that of a Lorentz Force Accelerator developed as a thruster by the electric propulsion research group at Princeton. Our investigation focuses on the effects of the rocket's magnetic field on the operation of the injector, the effect of a local magnetic field on the discharge behavior, and the effectiveness of discharge initiation by glow discharge versus initiation by ECRH. We evaluate the performance of this prototype injector by comparing the characteristics of the plasma it inserts into the central cell of the engine with the characteristics called for in the design of the plasma rocket.

Glover, T. W.; Chang-Diaz, F. R.; Squire, J. P.; Chan, A. A.

1997-11-01

2

Monte-Carlo particle dynamics in a variable specific impulse magnetoplasma rocket  

Energy Technology Data Exchange (ETDEWEB)

The self-consistent mathematical model in a Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is examined. Of particular importance is the effect of a magnetic nozzle in enhancing the axial momentum of the exhaust. Also, different geometries and rocket symmetries are considered. The magnetic configuration is modeled with an adaptable mesh, which increases accuracy without compromising the speed of the simulation. The single particle trajectories are integrated with an adaptive time-scheme, which can quickly solve extensive Monte-Carlo simulations for systems of hundred thousands of particles in a reasonable time (1--2 hours) and without the need for a powerful supercomputer.

Ilin, A.V. [Lockheed Martin Space Mission Systems and Services, Houston, TX (United States); Diaz, F.R.C.; Squire, J.P. [JSC/NASA, Houston, TX (United States). Advanced Space Propulsion Lab.; Carter, M.D. [Oak Ridge National Lab., TN (United States)

1999-01-01

3

Design Analysis of a High Temperature Radiator for the Variable Specific Impulse Magnetoplasma Rocket (VASIMR)  

Science.gov (United States)

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR), currently under development by Ad Astra Rocket Company, is a unique propulsion system that can potentially change the way space propulsion is performed. VASIMR's efficiency, when compared to that of a conventional chemical rocket, reduce propellant needed for exploration missions by a factor of 10. Currently plans include flight tests of a 200 kW VASIMR system, titled VF-200, on the International Space Station. The VF-200 will consist of two 100 kW thruster units packaged together in one engine bus. Each thruster unit has a unique heat rejection requirement of about 27 kW over a firing time of 15 minutes. In order to control rocket core temperatures, peak operating temperatures of about 300 C are expected within the thermal control loop. Design of a high temperature radiator is a unique challenge for the vehicle design. This paper will discuss the path taken to develop a steady state and transient based radiator design. The paper will describe radiator design options for the VASIMR thermal control system for use on ISS as well as future exploration vehicles.

Sheth, Rubik B.; Ungar, Eugene K.; Chambliss, Joe P.; Cassady, Leonard D.

2011-01-01

4

Design of a High Temperature Radiator for the Variable Specific Impulse Magnetoplasma Rocket  

Science.gov (United States)

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR), currently under development by Ad Astra Rocket Company (Webster, TX), is a unique propulsion system that could change the way space propulsion is performed. VASIMR's efficiency, when compared to that of a conventional chemical rocket, reduces the propellant needed for exploration missions by a factor of 10. Currently plans include flight tests of a 200 kW VASIMR system, titled VF-200, on the International Space Station (ISS). The VF-200 will consist of two 100 kW thruster units packaged together in one engine bus. Each thruster core generates 27 kW of waste heat during its 15 minute firing time. The rocket core will be maintained between 283 and 573 K by a pumped thermal control loop. The design of a high temperature radiator is a unique challenge for the vehicle design. This paper will discuss the path taken to develop a steady state and transient-based radiator design. The paper will describe the radiator design option selected for the VASIMR thermal control system for use on ISS, and how the system relates to future exploration vehicles.

Sheth, Rubik B.; Ungar, Eugene K.; Chambliss, Joe P.

2012-01-01

5

Experimental evidence of parametric decay processes in the variable specific impulse magnetoplasma rocket (VASIMR) helicon plasma source  

Science.gov (United States)

Decay waves have been observed in the megahertz range in the helium plasma generated by the variable specific impulse magnetoplasma rocket magnetoplasma thruster. They are measured using one of the tips of a triple probe connected to a 50 ? input of a spectrum analyzer via a dc block (a small capacitor). The maximum amplitude of all waves is in the center of the plasma and does not appear correlated to the radial electron density or temperature profiles. The waves seem to be generated close to the helicon antenna that was 91 cm "upstream" from the measuring Langmuir probe. A possible explanation is parametric decay of the large amplitude helicon wave that also generates the plasma.

Boswell, R. W.; Sutherland, O.; Charles, C.; Squire, J. P.; Chang Díaz, F. R.; Glover, T. W.; Jacobson, V. T.; Chavers, D. G.; Bengtson, R. D.; Bering, E. A.; Goulding, R. H.; Light, M.

2004-11-01

6

Experimental evidence of parametric decay processes in the variable specific impulse magnetoplasma rocket (VASIMR) helicon plasma source  

International Nuclear Information System (INIS)

Decay waves have been observed in the megahertz range in the helium plasma generated by the variable specific impulse magnetoplasma rocket magnetoplasma thruster. They are measured using one of the tips of a triple probe connected to a 50 ? input of a spectrum analyzer via a dc block (a small capacitor). The maximum amplitude of all waves is in the center of the plasma and does not appear correlated to the radial electron density or temperature profiles. The waves seem to be generated close to the helicon antenna that was 91 cm 'upstream' from the measuring Langmuir probe. A possible explanation is parametric decay of the large amplitude helicon wave that also generates the plasma

7

Recombination processes in a flowing magnetized plasma: Application to ionization energy recovery in the variable specific impulse magnetoplasma rocket (VASIMR)  

Science.gov (United States)

Electric propulsion involves the acceleration of charged particles (ions and electrons) through electric and magnetic body forces. The collection of these charged particles, or plasma, cannot be stored but must be created in-situ. Therefore, energy must be supplied to a neutral gas to create the plasma that is accelerated by the body forces. The energy that is used to create the plasma, i.e., ionization energy, is typically lost, "frozen" in the exhaust of the thruster. When the kinetic energy in the plasma flow is much larger than the energy used to create the plasma, this frozen-flow loss is negligible. Conversely, if the frozen-flow loss is a major fraction of the total plasma energy, its recovery, even in a partial way, may improve the energy efficiency of the thruster while also providing a potential means for thrust augmentation. This dissertation investigates the underlying physics, which could enable the practical recovery of frozen-flow losses by processes such as surface and volume recombination. For surface recombination, the ions approach the surface of the metal and are neutralized by electrons from the metal via the Auger neutralization process. For volume recombination, the ions and electrons recombine, with energy released via line radiation or by transferring energy to a third body such as another electron. Since the total energy of the neutralized ion, an atom, is less than the total energy of the ion and electron pair before recombination, conservation of energy requires the release of energy as the ion and electron recombine. The measurements described in this dissertation were performed on the VX-10 experiment, a plasma device supporting the development of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept and located at the Advanced Space Propulsion Laboratory of the Johnson Space Center. Results suggest that the recombination energy can be recovered. The available energy and power recovered depends on the local plasma conditions at the axial location of interest, rather than on conditions at the plasma source. Also, experimental data with neutral gas injection indicates that the extracted power can be used for thrust augmentation, alas, at the expense of specific impulse. The neutralization of the exhaust jet can also be useful in producing efficient plasma detachment from the magnetic nozzle, thereby alleviating the concern for plasma detachment from the magnetic field for these operating regimes.

Chavers, Donald Gregory

8

Experimental validation of single pass ion cyclotron resonance absorption in a high speed flowing plasma applied to the variable specific impulse magnetoplasma rocket (VASIMR)  

Science.gov (United States)

The topic of this thesis is the experimental characterization and analysis of single pass ion cyclotron resonance heating as applied to acceleration of ions for electric propulsion. The experimental work was done on the VX-10 experiment of the VASIMR (Variable Specific Impulse Magnetoplasma Rocket) concept. In ion cyclotron resonance heating (ICRH) a RF wave is launched into a magnetized plasma where it then accelerates the ions by increasing their rotational speed around the magnetic field lines. The electric field vector of the right hand component of the wave will rotate around the field lines with a frequency oRF in the same direction as the ion's cyclotron motion about the field lines. Consequently, when oRF ? oci (where oci is the ion's cyclotron frequency) the force from the electric field of the wave on the ions will result in a continuous rotational energy gain. The perpendicular velocity of the ions generated by ICRH is then converted into axial velocity by the decreasing gradient of the axial magnetic field at the exhaust of the propulsion system from conservation of the magnet moment. This increase in axial velocity is predicted to cause a decrease in density due to conservation of current in the plasma. In order to characterize this density drop during ion cyclotron heating, a single channel interferometer system was developed and implemented on the VX-10. Interferometer density measurements were taken at three different locations on the VX-10 experiment upstream and downstream of the ion acceleration zone. Measurements were made of the density drop in both Helium and Deuterium plasma discharges during ICRH under a variety of operating conditions including magnetic field profile, gas flow rate and ICRH power pulse timing, and ICRH power. A clear measurement of a density drop was observed downstream of the ion resonance zone characteristic of ion acceleration and measurement of little change in density upstream of the resonance zone where no acceleration was expected. Good agreement between the measured and predicted power scaling of ion acceleration due to ICRH was found. And experimental evidence that the shape of the magnetic field profile will influence ICRH acceleration as predicted is also presented and analyzed.

Davis, Christopher Nelson

9

ICRF Development for the Variable Specific Impulse Magnetoplasma Rocket  

Science.gov (United States)

The feasibility of using magnetically vectored and rf-heated plasmas for space propulsion (F. R. Chang-Diaz, et al., Bull. Am. Phys. Soc., 41, 1541 (1996)) is being investigated experimentally on an asymmetric magnetic mirror device at the Advanced Space Propulsion Laboratory (ASPL), Johnson Space Center, NASA. Analysis of the antenna interaction with and the wave propagation through the dense plasma propulsion system is being studied at ORNL(Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy under contract number DE-AC05-96OR22464.), using antenna design codes developed for ICH systems and mirror codes developed for the EBT experiment at ORNL. The present modeling effort is directed toward the ASPL experimental device. Antenna optimization and performance, as well as the design considerations for space-qualified rf components and systems (minimizing weight while maximizing reliability) will be presented.

Ryan, P. M.; Baity, F. W.; Barber, G. C.; Carter, M. D.; Hoffman, D. J.; Jaeger, E. F.; Taylor, D. J.; Chang-Diaz, F. R.; Squire, J. P.; McCaskill, G.

1997-11-01

10

Ultrahigh Specific Impulse Nuclear Thermal Propulsion  

Energy Technology Data Exchange (ETDEWEB)

Research on nuclear thermal propulsion systems (NTP) have been in forefront of the space nuclear power and propulsion due to their design simplicity and their promise for providing very high thrust at reasonably high specific impulse. During NERVA-ROVER program in late 1950's till early 1970's, the United States developed and ground tested about 18 NTP systems without ever deploying them into space. The NERVA-ROVER program included development and testing of NTP systems with very high thrust (~250,000 lbf) and relatively high specific impulse (~850 s). High thrust to weight ratio in NTP systems is an indicator of high acceleration that could be achieved with these systems. The specific impulse in the lowest mass propellant, hydrogen, is a function of square root of absolute temperature in the NTP thrust chamber. Therefor optimizing design performance of NTP systems would require achieving the highest possible hydrogen temperature at reasonably high thrust to weight ratio. High hydrogen exit temperature produces high specific impulse that is a diret measure of propellant usage efficiency.

Anne Charmeau; Brandon Cunningham; Samim Anghaie

2009-02-09

11

Cognitive impulsivity in specific learning disabilities.  

Science.gov (United States)

Many studies on cognitive impulsivity in learning disabled children have been criticized for their methodological limitations, and they have not dealt with the different types of learning disability. The aim of this study was to overcome these limitations and to assess if there was a significant cognitive impulsivity in reading disorder and/or spelling disorder by using the 20-item Matching Familiar Figures Test (MFF20). A total of 110 children (second through eighth grades) were recruited from a cohort of children assessed for the first time in a National Health clinic specialized in the study of specific learning disabilities. In all, 30 dyslexic children and 25 children with spelling disorder (all children without an ADHD comorbidity) were compared with 55 children of a control group on the MMF20 (accuracy and time latency). Results showed that the children with reading disorder were less accurate than the children with spelling disability (pdyslexia were faster than both the other groups in response time (pADHD children, dyslexic children have impaired frontal/prefrontal functions. Clinical and treatment implications are discussed. PMID:15981139

Donfrancesco, Renato; Mugnaini, Daniele; Dell'Uomo, Andrea

2005-08-01

12

Study of the Helicon Source Operation in the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) Experiment  

Science.gov (United States)

During this research period the following models of the VASIMR helicon discharge have been further developed and applied to analyze the on-going VX- 10 ASPL experiment: A) 1D semi-analytical model for a mixed-collisional propellant flow B) OD power and balance model for the whole helicon discharge In this particular research period we have concentrated on the MW-level performance of the VASIMR helicon source. Favorable high-power scaling and reduced ionization costs were obtained, and presented at the VASIMR NASA review in the Fall '02. This Grant is continuation of the previous NAG9-1224 award. The research results are summarized in 14 publications; they were presented as 20+ talks at the major International Conferences and scientific seminars at the leading Academic and Research Institutions. The reported results allowed helicon discharge characterization, understanding of the several experimental observations, and helped to make predictions and propose structural modifications for the advanced VASIMR helicon source operation.

Molvig, Kim; Batishchev, Oleg

2003-01-01

13

The Simplest Model of the Relation Between the Specific Payload Cost and Specific Impulse  

Science.gov (United States)

The elementary relation between the specific cost of a payload and initial and final mass of a rocket and the formula by Tsiolkovsky are used to derive the relation between the cost of 1kg of payload and specific impulse of rocket propulsion. Investigations of the function obtained for it allows to find optimal values for the new cost criterion and the specific impulse. It is demonstrated that the highest possible specific impulse does not necessarily lead to the minimum payload cost.

Prisniakov, V. F.

14

Coaxial plasma thrusters for high specific impulse propulsion  

Science.gov (United States)

A fundamental basis for coaxial plasma thruster performance is presented and the steady-state, ideal MHD properties of a coaxial thruster using an annular magnetic nozzle are discussed. Formulas for power usage, thrust, mass flow rate, and specific impulse are acquired and employed to assess thruster performance. The performance estimates are compared with the observed properties of an unoptimized coaxial plasma gun. These comparisons support the hypothesis that ideal MHD has an important role in coaxial plasma thruster dynamics.

Schoenberg, Kurt F.; Gerwin, Richard A.; Barnes, Cris W.; Henins, Ivars; Mayo, Robert; Moses, Ronald, Jr.; Scarberry, Richard; Wurden, Glen

1991-01-01

15

Mission design for Human Outer Planet Exploration (HOPE) using a magnetoplasma spacecraft  

Science.gov (United States)

To send humans beyond Mars, a Human Outer Planet Exploration (HOPE) mission has been studied for new spacecraft concepts and technologies. In this paper, an interplanetary trajectory and a preliminary spacecraft design are presented for the HOPE visit to Callisto, one of Jupiter's moons. To design a round-trip trajectory for the mission, the characteristics of the spacecraft and its trajectories are analyzed. A detailed optimization approach is formulated to utilize a Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine with capabilities of variable specific impulse, variable engine efficiency, and engine on-off control. It is mainly illustrated that a 30 MW powered spacecraft can make the mission possible in a 5-year round trip constraint around the year 2045. Trajectories with different power and reactor options are also discussed. The results obtained in this study can be used for formulating an overall concept for the mission.

Park, Sang-Young; Seywald, Hans; Krizan, Shawn A.; Stillwagen, Frederic H.

2006-08-01

16

An Analytic Approximation to Very High Specific Impulse and Specific Power Interplanetary Space Mission Analysis  

Science.gov (United States)

A simple, analytic approximation is derived to calculate trip time and performance for propulsion systems of very high specific impulse (50,000 to 200,000 seconds) and very high specific power (10 to 1000 kW/kg) for human interplanetary space missions. The approach assumed field-free space, constant thrust/constant specific power, and near straight line (radial) trajectories between the planets. Closed form, one dimensional equations of motion for two-burn rendezvous and four-burn round trip missions are derived as a function of specific impulse, specific power, and propellant mass ratio. The equations are coupled to an optimizing parameter that maximizes performance and minimizes trip time. Data generated for hypothetical one-way and round trip human missions to Jupiter were found to be within 1% and 6% accuracy of integrated solutions respectively, verifying that for these systems, credible analysis does not require computationally intensive numerical techniques.

Williams, Craig Hamilton

1995-01-01

17

Variable thrust/specific-impulse of multiplexed electrospray microthrusters  

Science.gov (United States)

We report on the development of a single-propellant ElectroSpray (ES) microthruster able to: (a) cover a wide range of specific impulse (Isp) and thrust at high propulsion efficiency, and (b) provide macroscopic thrust via micro-fabricated emitter arrays. The electrospray is a mature technology for the emission of fast nanodroplets at a propulsive efficiency larger than 50% over the full Isp range. The size of the droplets depends on the propellant flow rate and the physical properties of the electrolyte, especially the electric conductivity. To achieve a useful thrust one needs to multiplex the ES by operating many in parallel, which we achieve via silicon microfabrication of arrays of multiple and identical nozzles. The Multiplexed Electrospray (MES) micro-thruster is composed mainly of two electrodes: a nozzle-array and an extractor electrode, between which the electric field needed to form the ES is established. We tested nozzle arrays with up to 37 capillaries, that are spaced 1mm apart, with ID/OD = 10/30? m. The capillaries are filled with 2.01? m silicon dioxide beads to increase the hydraulic impedance and ensure uniform flow rate through the different emitters. A third electrode (accelerator) is mounted downstream the extractor to accelerate the droplets, thereby increasing the microthruster performance. The system is packaged in an alumina casing for electrical insulation and propellant feed. Tests run in a vacuum chamber at a pressure ? 10-5 mbar demonstrated reliable operation for several hours with a relatively high beam energy of 7.56kV. The 37-nozzle MES device was tested with the ionic liquid ethylammonium nitrate (EAN), at estimated total flow rates between 1.2 and 14 ? L/h, emitted currents between 14.2 and 23.0 ? A, specific impulse ranging between 710 and 1930s, and thrust ranging between 7.5 and 33 ? N. EAN is well suited to cover a relatively broad range of charge/mass- at an average propulsion efficiency of 66%. With further scale-up to a 600-MES system, the device would be suitable for micro-satellites missions such as attitude control and station keeping.

Lenguito, G.; Fernandez de la Mora, J.; Gomez, A.

18

Mission maps for use in the choice of specific impulse for manned Mars missions  

Energy Technology Data Exchange (ETDEWEB)

The choice of engine concept for the initial manned missions to Mars should be driven by what can be feasibly built and flight qualified in the near term, and by the level of engine performance that is required for these missions. This paper addresses how mission requirements affect the choice of specific impulse, and consequently what values of the specific impulse best serve these missions. Broad mission surveys and sensitivity studies were performed to determine the specific impulse values that allow for fast transfer times and wide launch windows. We find that a specific impulse of around 1000 to 1200 sec is sufficient. Choosing an engine concept that has a higher specific impulse value is not justified for these missions because the modest reduction in propellant requirements and further widening of the launch windows does not compensate for the substantially greater technical risk. 3 refs., 8 figs.

Madsen, W.W.; Neuman, J.E.; Olson, T.S.; Siahpush, A.S.

1991-01-01

19

Nonreciprocal magnetoplasma sheath waves  

Science.gov (United States)

We present theoretical and experimental results relevant to azimuthal magnetoplasma sheath waves in the case of the magnetic field parallel to the axis of a thick conducting cylinder. For the theory, a planar geometry is used with the ambient magnetic field parallel to the conducting plane and propagation perpendicular to the magnetic field. The results show two low-frequency transverse magnetic (TM) modes propagating in opposite directions with different propagation constants and also different cutoff frequencies separated by the cyclotron frequency. At frequencies above the upper hybrid frequency, one unidirectional TM mode is found. No transverse electric (TE) modes have been found. The experimental setup consists of a metallic cylinder with two protruding radial monopole antennas separated by an angle of 90°, placed in an axially magnetized laboratory plasma. Measurements of the two-port S parameters clearly show nonreciprocity caused by the propagation of different wave modes in opposite directions.

Lüttgen, Andrea A. E.; Balmain, Keith G.

1996-11-01

20

HTS Magnets for Advanced Magnetoplasma Space Propulsion Applications  

Energy Technology Data Exchange (ETDEWEB)

Plasma rockets are being considered for both Earth-orbit and interplanetary missions because their extremely high exhaust velocity and ability to modulate thrust allow very efficient use of propellant mass. In such rockets, a hydrogen or helium plasma is RF-heated and confined by axial magnetic fields produced by coils around the plasma chamber. HTS coils cooled by the propellant are desirable to increase the energy efficiency of the system. We describe a set of prototype high-temperature superconducting (HTS) coils that are being considered for the VASIMR ( Variable Specific Impulse Magnetoplasma Rocket) thruster proposed for testing on the Radiation Technology Demonstration (RTD) satellite. Since this satellite will be launched by the Space Shuttle, for safety reasons liquid helium will be used as propellant and coolant. The coils must be designed to operate in the space environment at field levels of 1 T. This generates a unique set of requirements. Details of the overall winding geometry and current density, as well as the challenging thermal control aspects associated with a compact, minimum weight design will be discussed.

Carte, M.D.; Chang-Diaz, F.R. Squire, J.P.; Schwenterly, S.W.

1999-07-12

 
 
 
 
21

Alfvenic shock waves in a collisional magnetoplasma  

International Nuclear Information System (INIS)

Compressional Alfvenic shock waves in a cold collisional magnetoplasma are investigated. For this purpose, we use the hydrodynamic equations and Faraday's law to derive the governing nonlinear equations for the compressional Alfven waves. It is shown that the latter can appear in the form of Alfvenic shock waves. -- Highlights: ? We model Alfvenic shock waves in a cold collisional plasma. ? The shock waves appear as monotonic or oscillatory, depending on temporal and spatial scales. ? Can be responsible for cross-field proton acceleration.

22

Oscillonic Mach cones in a dusty magnetoplasma  

International Nuclear Information System (INIS)

The possibility for the formation of Mach cones in a dusty magnetoplasma containing elongated charged dust grains has been examined theoretically. It is predicted that the Mach cones can be formed by dipole oscillons (wave modes associated with the oscillations of dust dipoles around their mean positions) in a laboratory plasma containing elongated (rodlike) negatively charged dust grains. An experiment in radio-frequency dusty plasma discharges should be conducted for verifying the theoretical prediction that has been made here

23

Europa Sample Return Mission Utilizing High Specific Impulse Propulsion Refueled with Indigenous Resources  

Science.gov (United States)

We have conducted studies of a revolutionary new concept for conducting a Europa Sample Return Mission. Robotic spacecraft exploration of the Solar System has been severely constrained by the large energy requirements of interplanetary trajectories and the inherent delta V limitations of chemical rockets. Current missions use gravitational assists from intermediate planets to achieve these high-energy trajectories restricting payload size and increasing flight times. We propose a 6-year Europa Sample Return mission with very modest launch requirements enabled by MITEE. A new nuclear thermal propulsion engine design, termed MITEE (MIniature reacTor EnginE), has over twice the delta V capability of H2/O2 rockets (and much greater when refueled with H2 propellant from indigenous extraterrestrial resources) enabling unique missions that are not feasible with chemical propulsion. The MITEE engine is a compact, ultra-lightweight, thermal nuclear rocket that uses hydrogen as the propellant. MITEE, with its small size (50 cm O.D.), low mass (200 kg), and high specific impulse (~1000 sec), can provide a quantum leap in the capability for space science and exploration missions. The Robotic Europa Explorer (REE) spacecraft has a two-year outbound direct trajectory and lands on the satellite surface for an approximate 9 month stay. During this time, the vehicle is refueled with H2 propellant derived from Europa ice by the Autonomous Propellant Producer (APP), while collecting samples and searching for life. A small nuclear-heated submarine probe, the Autonomous Submarine Vehicle (ASV), based on MITEE technology, would melt through the ice and explore the undersea realm. The spacecraft has approximately a three year return to Earth after departure from Europa with samples onboard. Spacecraft payload is 430 kg at the start of the mission and can be launched with a single, conventional medium-sized Delta III booster. The spacecraft can bring back 25 kg of samples from Europa. Europa, in the Jovian system, is a high priority target for an outer Solar System exploration mission. More than a decade ago the Voyager spacecraft revealed Europa as a world swathed in ice and geologically young. NASA's Galileo spacecraft passed approximately 500 miles above the surface and provided detailed images of Europa's terrain marked by a dynamic topology that appeared to be remnants of ice volcanoes or geysers. The surface temperature averages a chilly -200° C. The pictures appear to show a relatively young surface of ice, possibly only 1 km thick in some places. Internal heating of Europa from Jupiter's tidal pull could form an ocean of liquid water beneath the surface. More recently, Ganymede and Callisto are believed to be ocean-bearing Jovian moons based on magnetometer measurements from the Galileo spacecraft. If liquid water exists, life may also. NASA plans to send an orbiting spacecraft to Europa to measure the thickness of the ice and to detect if an underlying liquid ocean exists. This mission would precede the proposed Europa Sample Return mission, which includes dispatching an autonomous submarine-like vehicle that could melt through the ice and explore the undersea realm. Because of the large energy requirements typical of these ambitious solar system science missions, use of chemical rockets results in interplanetary spacecraft that are prohibitive in terms of Initial Mass in Low- Earth Orbit (IMLEO) and cost. For example, using chemical rockets to return samples from Europa appears to be technically impractical, as it would require large delta V and launch vehicle capabilities. On the other hand, use of nuclear thermal rockets will significantly reduce IMLEO and, subsequently, costs. Moreover, nuclear thermal rockets can utilize extraterrestrial resources as propellants, an option not practical with chemical rockets. This "refueling" capability would enable nuclear rockets to carry out very high-energy missions, such as the return of large amounts of extraterrestrial material to Earth. The Europa missions considered in this pro

Paniagua, J.; Powell, J. R.; Maise, G.

2002-01-01

24

Tri polar vortices associated with toroidal ion temperature gradient modes in a magnetoplasma with sheared flows  

International Nuclear Information System (INIS)

A system of nonlinear equations for low-frequency toroidal ion-temperature-gradient modes in a nonuniform magnetoplasma with sheared plasma flow is presented. For some specific profiles of the equilibrium density, the ion temperature and sheared plasma flows, the nonlinear equations admit a tripolar vortex. The numerical results show a negative potential vortex core between the lobs of a dipole-like structure which has a positive value of the potential

25

Radiation Condition for a Magnetoplasma Medium-I.  

Science.gov (United States)

The paper is concerned with the radiation condition for an unbounded magnetoplasma which is both anisotropic and dispersive. The usual form of the celebrated Sommerfeld radiation condition pertains to an isotropic and nondispersive medium and is not appli...

S. R. Seshadri, T. T. Wu

1966-01-01

26

Sex differences in impulsive action and impulsive choice.  

Science.gov (United States)

Here, we review the evidence for sex differences in behavioral measures of impulsivity for both humans and laboratory animals. We focus on two specific components of impulsivity: impulsive action (i.e., difficulty inhibiting a prepotent response) and impulsive choice (i.e., difficulty delaying gratification). Sex differences appear to exist on these measures, but the direction and magnitude of the differences vary. In laboratory animals, impulsive action is typically greater in males than females, whereas impulsive choice is typically greater in females. In humans, women discount more steeply than men, but sex differences on measures of impulsive action depend on tasks and subject samples. We discuss implications of these findings as they relate to drug addiction. We also point out the major gaps in this research to date, including the lack of studies designed specifically to examine sex differences in behavioral impulsivity, and the lack of consideration of menstrual or estrous phase or sex hormone levels in the studies. PMID:24286704

Weafer, Jessica; de Wit, Harriet

2014-11-01

27

Impulsiveness in professional fighters.  

Science.gov (United States)

Sports involving repeated head trauma are associated with risk of neurodegenerative disorders such as chronic traumatic encephalopathy (CTE). Among the behavioral manifestations of CTE is increased impulsiveness. Here, the authors investigate the relationship between impulsiveness and exposure to head trauma in a large group of active professional fighters. Fighters tended to report less impulsiveness than did non-fighting control respondents. Overall, greater fight exposure was associated with higher levels of a specific form of impulsiveness, although there were differences between mixed martial arts fighters and boxers. Fight exposure was associated with reduction in volume of certain brain structures, and these changes were also associated with impulsiveness patterns. Longitudinal studies of professional fighters are important to understand the risk for neuropsychiatric problems. PMID:24515676

Banks, Sarah J; Mayer, Brittany; Obuchowski, Nancy; Shin, Wanyong; Lowe, Mark; Phillips, Michael; Modic, Michael; Bernick, Charles

2014-01-01

28

Impulsive action: Emotional impulses and their control  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a novel theoretical view on impulsive action, integrating thus far separate perspectives on nonreflective action, motivation, emotion regulation, and impulse control. We frame impulsive action in terms of directedness of the individual organism towards, away, or against other givens – towards future states and away from one's present state. First, appraisal of a perceived or thought-of event or object on occasion, rapidly and without premonition or conscious deliberation, triggers a motive to modify one's relation to that event or object. Situational specifics of the event as perceived and appraised motivate and guide selection of readiness for a particular kind of purposive action. Second, perception of complex situations can give rise to multiple appraisals, multiple motives, and multiple simultaneous changes in action readiness. Multiple states of action readiness may interact in generating action, by reinforcing or attenuating each other, thereby yielding impulse control. We show how emotion control can itself result from a motive state, or state of action readiness. Our view links impulsive action mechanistically to states of action readiness, which is the central feature of what distinguishes one kind of emotion from another. It thus provides a novel theoretical perspective to the somewhat fragmented literature on impulsive action.

K RichardRidderinkhof

2014-06-01

29

Rayleigh-Taylor/gravitational instability in dense magnetoplasmas  

International Nuclear Information System (INIS)

The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

30

Rayleigh-Taylor/gravitational instability in dense magnetoplasmas  

Energy Technology Data Exchange (ETDEWEB)

The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

Ali, S., E-mail: shahid.ali@ncp.edu.p [National Centre for Physics, Quaid-i-Azam University Campus, Islamabad (Pakistan); IPFN, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Ahmed, Z. [COMSATS Institute of Information Technology, Department of Physics, Wah Campus (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ahmad, I. [COMSATS Institute of Information Technology, Department of Physics, Islamabad Campus (Pakistan)

2009-08-10

31

Whistler waves guided by density depletion ducts in a magnetoplasma  

Science.gov (United States)

The guided propagation of whistler waves along cylindrical density depletion ducts in a magneto-plasma is studied. It is shown that, under certain conditions, such ducts can support volume and surface eigenmodes. The dispersion properties and field structure of whistler modes guided by density depletion ducts are analyzed. The effect of collisional losses in the plasma on the properties of modes is discussed.

Bakharev, P. V.; Zaboronkova, T. M.; Kudrin, A. V.; Krafft, C.

2010-11-01

32

Measurement of plasma parameters in the exhaust of a magnetoplasma rocket by gridded energy analyzer and emissive Langmuir probe  

Science.gov (United States)

The 10 kilowatt prototype of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine, abbreviated as VX-10, is designed to eject plasma at exhaust velocities of tens of kilometers per second. In this device, energy is imparted to the plasma ions by two mechanisms: ion cyclotron resonant heating (ICRH), and acceleration in an ambipolar electric field. Measurements from two different electrostatic probes are combined to determine how much each mechanism contributes to the total ion energy. The first probe is a gridded retarding potential analyzer (RPA) that incorporates a multi-channel collimator to obtain precise measurement of the ion and electron parallel energy distributions. The second is an emissive Langmuir probe that measures the DC and RF components of the plasma potential. The plasma potential obtained from the emitting probe allows calculation of the parallel velocity distribution once the parallel energy distribution is obtained from the energy analyzer data. Biasing the RPA housing is shown to minimize the plasma perturbation, as monitored by an auxiliary probe. When this minimization is done, the RPA measurements become compatible with the emissive probe's measurement of plasma potential. The collimated RPA and emissive probe have been used to examine the effects of a double dual half-turn (DDHT) antenna encircling the plasma. When power at the ion cyclotron frequency is applied, changes are seen in the saturation current and mean ion energy of the collimated RPA characteristic. The evolution of these changes as the RPA is moved downstream from the antenna is interpreted as firm evidence of ion cyclotron heating, albeit at absorbed energies of less than 1 electronvolt per ion. The emissive probe shows that, within experimental error, all of the increased ion energy is accounted for by an increase in the plasma potential that occurs when the ICRF power is applied. The combined RPA and emissive probe data also show that there is a jet of flowing plasma in the VX-10 when operated with the helicon source alone but that the signal from this jet is overwhelmed by a rapidly growing stationary plasma within the first second of the discharge.

Glover, Timothy Ward

2002-01-01

33

Dimensions of Impulsive Behavior in Adolescent Smokers and Nonsmokers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Robust associations have been identified between impulsive personality characteristics and cigarette smoking during adolescents, indicating that impulsive behavior may play an important role in the initiation of cigarette smoking. The present study extended this research by using laboratory behavioral assessments to explore relationships between three specific dimensions of impulsive behavior (impulsive decision-making, inattention and disinhibition) and adolescent cigarette smoking. Particip...

Fields, Sherecce; Collins, Christine; Leraas, Kristen; Reynolds, Brady

2009-01-01

34

Zonal winds and dipolar vortices in a rotating dusty magnetoplasma  

Energy Technology Data Exchange (ETDEWEB)

It is shown that the Rossby and dust-Alfven waves in a rotating dusty magnetoplasma are coupled due to the spatial nonuniformity of the angular rotation velocity of the dust fluid. The nonlinear wave interaction is governed by a pair of equations comprising the evolution of the dust fluid vorticity and the dust-Alfven wave magnetic field. These nonlinear equations are then used to investigate the generation of zonal winds and the formation of a dipolar vortex. The results are relevant for understanding the origin of the strong turbulence and large scale structures, which are often observed in the planetary magnetospheres.

Shukla, P K [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Dwivedi, P K [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Stenflo, L [Department of Plasma Physics, Umeaa University, SE-90187 Umeaa (Sweden)

2003-03-01

35

Zonal winds and dipolar vortices in a rotating dusty magnetoplasma  

International Nuclear Information System (INIS)

It is shown that the Rossby and dust-Alfven waves in a rotating dusty magnetoplasma are coupled due to the spatial nonuniformity of the angular rotation velocity of the dust fluid. The nonlinear wave interaction is governed by a pair of equations comprising the evolution of the dust fluid vorticity and the dust-Alfven wave magnetic field. These nonlinear equations are then used to investigate the generation of zonal winds and the formation of a dipolar vortex. The results are relevant for understanding the origin of the strong turbulence and large scale structures, which are often observed in the planetary magnetospheres

36

Impulsive control for fast nanopositioning.  

Science.gov (United States)

In this paper we present a non-linear control scheme for high-speed nanopositioning based on impulsive control. Unlike in the case of a linear feedback controller, the controller states are altered in a discontinuous manner at specific instances in time. Using this technique, it is possible to simultaneously achieve good tracking performance, disturbance rejection and tolerance to measurement noise. Impulsive control is demonstrated experimentally on an atomic force microscope. A significant improvement in tracking performance is demonstrated. PMID:21343639

Tuma, Tomas; Sebastian, Abu; Häberle, Walter; Lygeros, John; Pantazi, Angeliki

2011-04-01

37

Impulsive control for fast nanopositioning  

Energy Technology Data Exchange (ETDEWEB)

In this paper we present a non-linear control scheme for high-speed nanopositioning based on impulsive control. Unlike in the case of a linear feedback controller, the controller states are altered in a discontinuous manner at specific instances in time. Using this technique, it is possible to simultaneously achieve good tracking performance, disturbance rejection and tolerance to measurement noise. Impulsive control is demonstrated experimentally on an atomic force microscope. A significant improvement in tracking performance is demonstrated.

Tuma, Tomas; Sebastian, Abu; Haeberle, Walter; Pantazi, Angeliki [IBM Research-Zurich, Saeumerstrasse 4, 8803 Rueschlikon (Switzerland); Lygeros, John, E-mail: uma@zurich.ibm.com, E-mail: ase@zurich.ibm.com, E-mail: wha@zurich.ibm.com, E-mail: lygeros@control.ee.ethz.ch, E-mail: agp@zurich.ibm.com [Automatic Control Laboratory, Swiss Federal Institute of Technology, Physikstrasse 3, 8092 Zurich (Switzerland)

2011-04-01

38

Evolution of magnetic topology of an erupting arched laboratory magnetoplasma  

Science.gov (United States)

Arched magnetoplasma structures ubiquitously exist in the solar atmosphere and affect energetic phenomena such as flares and coronal mass ejections. Presence of an electrical current in such structures generates a twisted magnetic-field and the term arched magnetic flux rope (AMFR) is used for them. In the limit of low electrical current (compared to the current-threshold for the kink instability), the magnetic twist in an AMFR becomes small and it resembles the structure of an arched magnetic flux tube. However, the term arched magnetic flux rope can be used for arched magnetoplasma structures without any loss of generality. We report results on the evolution of the magnetic topology of an erupting laboratory AMFR during its eruption. The AMFR (plasma ? ? 10-3, Lundquist number ? 102-105, AMFR radius/ion-gyroradius ? 20, B ? 1000 Gauss at footpoints) is created using a lanthanum hexaboride (LaB6) plasma source and it evolves in an ambient magnetoplasma produced by another LaB6 source (See Ref. [2] for details of the experiment). The eruption is triggered by gradually increasing the electrical current in the AMFR and its evolution is captured by a fast-CCD camera. The relative magnitudes of the parameters of the AMFR and the ambient magnetoplasma can be varied to simulate a variety of conditions relevant to solar eruptions. The experiment runs continuously with a 0.5 Hz repetition rate. Hence, the plasma parameters of the AMFR are recorded with a good spatiotemporal resolution (spatial-resolution/AMFR-length ? 10-2 - 10-3, temporal-resolution/eruption-time ? 10-3) using computer-controlled movable probes. The three-dimensional magnetic-field of the AMFR is directly measured using a three-axis magnetic-loop probe. The pre-eruption phase of the AMFR remains quiescent for ? 100 Alfven transit times and the camera images evince a persistent appearance of the AMFR during this phase. In contrast, the post-eruption phase of the AMFR is associated with significant changes in its magnetic topology. Our measurements in the post-eruption phase have identified emergence of magnetic flux ropes from the leading edge of the AMFR and excitation of fast waves and global kink mode oscillations. The main focus of this presentation will be on demonstrating the dramatic changes in the connectivity of the magnetic-field lines of the AMFR during the eruption. Implication of the magnetic-field-line connectivity to the solar AMFR eruptions will also be discussed. References: (1) Tripathi and Gekelman, Phys. Rev. Lett. 105, 075005 (2010) (2) Tripathi and Gekelman, Solar Phys. 286, 479 (2013) (Work performed at Basic Plasma Science Facility, UCLA and supported by US DOE and NSF)

Tripathi, S.; Gekelman, W. N.

2013-12-01

39

Nonlinear electrostatic shock waves in inhomogeneous dense dusty magnetoplasmas  

Energy Technology Data Exchange (ETDEWEB)

The Linear and nonlinear propagation characteristics of drift dust acoustic waves were studied in an inhomogeneous electron-ion-dust (e-i-d) quantum magnetoplasma with neutrals in the background using the well-known quantum hydrodynamic (QHD) model. The Korteweg-de Vries-Burgers (KdVB) and Kadomtsev-Petviashvili-Burgers (KPB) equations are obtained. Furthermore, the solutions of the KdVB and KPB equations are presented using the tangent hyperbolic (tanh) method. The variation of the shock profile with the quantum Bohm potential, collision frequency, ratio of drift to shock velocity in the co-moving frame and effect of magnetic field is also investigated. The relevance of the present investigation to dense astrophysical environments is also highlighted.

Masood, W [TPPD, PINSTECH, PO Nilore, Islamabad (Pakistan); Karim, S; Shah, H A, E-mail: waqasmas@gmail.co [Department of Physics, GC University, 54000 Lahore (Pakistan)

2010-10-15

40

Electric field variability and classifications of Titan's magnetoplasma environment  

CERN Document Server

The atmosphere of Saturn's largest moon Titan is driven by photochemistry, charged particle precipitation from Saturn's upstream magnetosphere, and presumably by the diffusion of the magnetospheric field into the outer ionosphere, amongst other processes. Ion pickup, controlled by the upstream convection electric field, plays a role in the loss of this atmosphere. The interaction of Titan with Saturn's magnetosphere results in the formation of a flow-induced magnetosphere. The upstream magnetoplasma environment of Titan is a complex and highly variable system and significant quasi-periodic modulations of the plasma in this region of Saturn's magnetosphere have been reported. In this paper we quantitatively investigate the effect of these quasi-periodic modulations on the convection electric field at Titan. We show that the electric field can be significantly perturbed away from the nominal radial orientation inferred from Voyager 1 observations, and demonstrate that upstream categorisation schemes must be use...

Arridge, Chris; Guio, Patrick

2011-01-01

 
 
 
 
41

Impulsivity and Its Treatment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Identification, description and therapeutic management of impulsivity, which underlies the mechanism and coexistence of many neurological and psychiatric diseases, are considered to be very crucial. Treatment can be applied in two ways; either for the disorder that occurs with impulsivity or for the treatment of the impulsive behavior itself. Disorders associated with or accompanied by impulsivity can be classified as borderline and antisocial personality disorders, schizophrenia, bipolar dis...

P?nar Güzel Özdemir; Yavuz Selvi; Adem Ayd?n

2012-01-01

42

Laser pulse propagation in inhomogeneous magnetoplasma channels and wakefield acceleration  

Science.gov (United States)

Wakefield excitation in a preformed inhomogeneous parabolic plasma channel by an intense relativistic (?1019 W/cm2) circularly polarized Gaussian laser pulse is investigated analytically and numerically in the presence of an external longitudinal magnetic field. A three dimensional envelope equation for the evolution of the laser pulse is derived, which includes the effect of the nonparaxial and applied external magnetic field. A relation for the channel radius with the laser spot size is derived and examines numerically to see the external magnetic field effect. It is observed that the channel radius depends on the applied external magnetic field. An analytical expression for the wakefield is derived and validated with the help of a two dimensional particle in cell (2D PIC) simulation code. It is shown that the electromagnetic nature of the wakes in an inhomogeneous plasma channel makes their excitation nonlocal, which results in change of fields with time and external magnetic field due to phase mixing of the plasma oscillations with spatially varying frequencies. The magnetic field effect on perturbation of the plasma density and decreasing length is also analyzed numerically. In addition, it has been shown that the electron energy gain in the inhomogeneous parabolic magnetoplasma channel can be increased significantly compared with the homogeneous plasma channel.

Sharma, B. S.; Jain, Archana; Jaiman, N. K.; Gupta, D. N.; Jang, D. G.; Suk, H.; Kulagin, V. V.

2014-02-01

43

Laser pulse propagation in inhomogeneous magnetoplasma channels and wakefield acceleration  

International Nuclear Information System (INIS)

Wakefield excitation in a preformed inhomogeneous parabolic plasma channel by an intense relativistic (?1019?W/cm2) circularly polarized Gaussian laser pulse is investigated analytically and numerically in the presence of an external longitudinal magnetic field. A three dimensional envelope equation for the evolution of the laser pulse is derived, which includes the effect of the nonparaxial and applied external magnetic field. A relation for the channel radius with the laser spot size is derived and examines numerically to see the external magnetic field effect. It is observed that the channel radius depends on the applied external magnetic field. An analytical expression for the wakefield is derived and validated with the help of a two dimensional particle in cell (2D PIC) simulation code. It is shown that the electromagnetic nature of the wakes in an inhomogeneous plasma channel makes their excitation nonlocal, which results in change of fields with time and external magnetic field due to phase mixing of the plasma oscillations with spatially varying frequencies. The magnetic field effect on perturbation of the plasma density and decreasing length is also analyzed numerically. In addition, it has been shown that the electron energy gain in the inhomogeneous parabolic magnetoplasma channel can be increased significantly compared with the homogeneous plasma channel

44

Ion Acoustic Waves in an Alkali Magneto-Plasma  

International Nuclear Information System (INIS)

By a series of experiments on ion wave propagation in a magneto-plasma of caesium ionized by surface ionization, the authors studied the effects due to collisions between ions and neutral particles, the mean plasma velocity, the ratio ? = Te/Ti of electron and ion temperatures and the non-linear behaviour of a collisionless plasma. In a machine called OPS using direct injection of caesium illuminating one emitter the effect of collisions between neutrals and ions has been studied. The ratio ? = Te/Ti of the electron and ion temperatures which is an important parameter for the propagation and damping of the ion waves can be easily modified by injection of helium into the machine. The variations of phase velocity and damping as functions of the frequency for different pressures of injected neutral gas show a change in the ion temperature, the mean plasma velocity and a continuous transition from the Landau damping to the collisionnal damping. A separation of the two zones, the first one where the ions are cooled and the other where the wave is propagating, allows the study of the Landau damping and the measurement of the ratio ?. A non-linear damping of the ion wave has been observed and studied. The classical Landau damping is found for the lower frequency range but as the distance of propagation is of the order of or larger than half a wavelength, the measured damping becomes less than the Landau damping rate, and amplituan the Landau damping rate, and amplitude modulation is observed. The pseudo-wavelength and the modulation rate are bound by the period and amplitude of the wave as is foreseen by a non-linear theory. We observed that the wave behaviour is similar to the effect obtained in mixing the ion wave and a fast wave which has been found in the experiments. (author)

45

Ray trajectories and wave fronts of radiated electromagnetic modes in an inhomogeneous magnetoplasma  

International Nuclear Information System (INIS)

In an inhomogeneous magnetoplasma ray trajectories and wave fronts of electromagnetic modes radiated from a localized source are investigated numerically in a kinetic electromagnetic theory. Energy trajectories of electromagnetic modes in an inhomogeneous plasma are obtained for various plasma and magnetic parameters and various initial conditions. Wave fronts of those modes in such an inhomogeneous system are obtained. (Auth.)

46

Parametric instabilities of Langmuir waves in a non-uniform magnetoplasma  

International Nuclear Information System (INIS)

It is shown that an obliquely propagating electron plasma wave in a non-uniform magnetoplasma is unstable with respect to drift wave perturbations. The growth rates for the three-wave decay interaction as well as modulational instabilities are obtained. (orig.)

47

Characteristics of slow magnetoplasma waves on the surface of a semiconductor  

International Nuclear Information System (INIS)

It is demonstrated that it is possible to excite resonantly and detect magnetoplasma waves on the surface of a semiconductor; and the results of an investigation of the propagation of such waves at various angles relative to a magnetic field B are reported

48

Risk Factors and Impulsivity in Obesity  

Directory of Open Access Journals (Sweden)

Full Text Available In addition to genetic tendency, social, cultural, emotional and diet-related factors play important role in the development of obesity. Impulsivity is the possible predictor of relapse in obesity treatment. Impulsivity is also considered as a predicting factor among patients who quit the treatment. Research has shown that obese people are more impulsive than other people. Impulsive features are especially found to be higher with those who have binge eating disorder. Impulsive people appears to have no control over their behaviors on eating and they have more interest towards food with higher calories. Another issue that strengthens the assocaition between obesity and impulsivity is the obesity in children with attention deficit hyperactivity disorder. Dopaminergic deficiency in the reward centre of the brain can be a common pathway for both attention deficit and obesity. Several approaches have been searched and put forward to sustain the patients’ lost weights after diet. Specific cognitive behavioral approaches developed for the treatment of impulsive behavior could contribute much into obesity treatment . Obesity is a chronic disease that requires long term treatment and follow up.

Bilge Burcak Annagur

2010-12-01

49

A Weakly Nonlinear Analysis of Impulsively-Forced Faraday Waves  

CERN Document Server

Parametrically-excited surface waves, forced by a periodic sequence of delta-function impulses, are considered within the framework of the Zhang-Vi\\~nals model (J. Fluid Mech. 1997). The exact impulsive-forcing results, in the linear and weakly nonlinear regimes, are compared with numerical results for sinusoidal and multifrequency forcing. We find surprisingly good agreement between impulsive forcing results and those obtained using a two-term truncated Fourier series representation of the impulsive forcing function. As noted previously by Bechhoefer and Johnson (Am. J. Phys. 1996), in the case of two equally-spaced impulses per period there are only subharmonic modes of instability. The familiar situation of alternating subharmonic and harmonic resonance tongues emerges for unequally-spaced impulses. We extend the linear analysis for two impulses per period to the weakly nonlinear regime for one-dimensional waves. Specifically, we derive an analytic expression for the cubic Landau coefficient in the bifurca...

Catlla, A; Silber, M; Catlla, Anne; Porter, Jeff; Silber, Mary

2005-01-01

50

Impulsivity and Sensation Seeking in Alcohol Abusing Patients with Schizophrenia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objective: Some studies have found that high levels of impulsivity and sensation seeking, particularly disinhibition are associated with substance abuse in patients with schizophrenia, as in the general population. However, no study has assessed impulsivity and sensation seeking specifically in schizophrenia patients with alcohol abuse or dependence. Materials and methods: We compared impulsivity and sensation seeking in a group of schizophrenia patients (DSM-III-R criteria) with lifetime alc...

Dervaux, Alain; Laqueille, Xavier; Bourdel, Marie-chantal; Olie?, Jean-pierre; Krebs, Marie-odile

2010-01-01

51

Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma  

International Nuclear Information System (INIS)

We study the amplitude modulation of low-frequency, long-wavelength electrostatic drift-wave envelopes in a nonuniform quantum magnetoplasma consisting of cold ions and degenerate electrons. The effects of tunneling associated with the quantum Bohm potential and the Fermi pressure for nonrelativistic degenerate electrons, as well as the equilibrium density and magnetic field inhomogeneities are taken into account. Starting from a set of quantum magnetohydrodynamic equations, we derive a nonlinear Schrödinger equation (NLSE) that governs the dynamics of the modulated quantum drift-wave packets. The NLSE is used to study the modulational instability (MI) of a Stoke's wave train to a small plane wave perturbation. It is shown that the quantum tunneling effect as well as the scale length of inhomogeneity plays crucial roles for the MI of the drift-wave packets. Thus, the latter can propagate in the form of bright and dark envelope solitons or as drift-wave rogons in degenerate dense magnetoplasmas

52

Electron parallel velocity and temperature gradient driven electrostatic fluctuations in nonuniform magnetoplasmas  

International Nuclear Information System (INIS)

The combined effects of the electron-temperature (ET) and parallel electron velocity (PEV) gradients on electrostatic instabilities in a nonuniform magnetoplasma are investigated. For this purpose, a hybrid approach is used, in which the electrons are treated as a magnetized fluid, while the ions are described by means of a kinetic description. A new dispersion relation is derived, which shows how different plasma modes are linear coupled in the presence of the ET and PEV gradients. The dispersion relation is analyzed analytically (numerically) to demonstrate the instability of long- and short-wavelength electrostatic modes (to examine the combined effects of ET and PEV gradients) in nonuniform magnetoplasmas. The present results may be useful in understanding the salient features of nonthermal fluctuations and associated anomalous cross-field electron fluxes in forthcoming laboratory experiments

53

Modulation of the dephasing time for a magnetoplasma in a quantum well  

CERN Document Server

We investigate the femtosecond kinetics of optically excited 2D magneto-plasma. We calculate the femtosecond dephasing and relaxation kinetics of the laser pulse excited magneto-plasma due to bare Coulomb potential scattering, because screening is under these conditions of minor importance. By taking into account four Landau subbands in both the conduction band and the valence band, we are now able to extend our earlier study [Phys. Rev. B {\\bf 58}, 1998,in print (see also cond-mat/9808073] to lower magnetic fields. We can also fix the magnetic field and change the detuning to further investigate the carrier density-dependence of the dephasing time. For both cases, we predict strong modulation in the dephasing time.

Wu Ming Wei

1998-01-01

54

Non-linear wave interaction in a magnetoplasma column. I - Theory. II Experiment  

Science.gov (United States)

The paper presents an analysis of non-linear three-wave interaction for propagation along a cylindrical plasma column surrounded either by a metallic boundary, or by an infinite dielectric, and immersed in an infinite, static, axial magnetic field. An averaged Lagrangian method is used and the results are specialized to parametric amplification and mode conversion, assuming an undepleted pump wave. Computations are presented for a magneto-plasma column surrounded by free space, indicating that parametric growth rates of the order of a fraction of a decibel per centimeter should be obtainable for plausible laboratory plasma parameters. In addition, experiments on non-linear mode conversion in a cylindrical magnetoplasma column are described. The results are compared with the theoretical predictions and good qualitative agreement is demonstrated.

Larsen, J.-M.; Crawford, F. W.

1979-01-01

55

Electromagnetic wave propagation in a magneto-plasma filled coaxial structure. I - Theoretical. II - Experimental  

Science.gov (United States)

This study is concerned with the problem of electromagnetic wave propagation in a magneto-plasma filled coaxial structure. The problem is formulated using the classical boundary value problem approach. A numerical investigation shows the existence of propagating slow modes, backward modes, a quasi-TEM mode, and waveguide-type modes in a magneto-plasma filled coaxial structure. Dispersion curves for these different modes are presented. Measurements have been made of electromagnetic propagation in a coaxial electrode structure filled with longitudinally magnetized plasma. The annular plasma region had a 9.55 cm outer diameter, a 3.82 cm inner diameter and was approximately 60 cm long. A magnetic field of 300 gauss was employed. Electromagnetic wave frequencies were in the range .5 to 2.4 GHz. The plasma was generated by a continuous glow discharge. The resulting dispersion curves closely follow the predicted curves for the quasi-TEM mode.

Askins, H. W., Jr.; Miller, D. B.

1975-01-01

56

Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the amplitude modulation of low-frequency, long-wavelength electrostatic drift-wave envelopes in a nonuniform quantum magnetoplasma consisting of cold ions and degenerate electrons. The effects of tunneling associated with the quantum Bohm potential and the Fermi pressure for nonrelativistic degenerate electrons, as well as the equilibrium density and magnetic field inhomogeneities are taken into account. Starting from a set of quantum magnetohydrodynamic (QMHD) equ...

Misra, A. P.

2014-01-01

57

Magneto-plasma separation as a method for reprocessing of spent fuel and radioactive waste  

International Nuclear Information System (INIS)

A variant of a separating device based on the plasma-beam discharge is considered, including: processes of radioactive material (SF and RAW) ionization; evaluation of the mass-production capacity of the device with taking into account the atomic weight of the separated substance and the spatial-density characteristics of the plasma used and main power consumption. The consideration enables one to estimate more objectively the potentialities of magneto-plasma separating devices and to determine the method for controlling them

58

Investigation of Magneto-Plasma Compressor Operation Powered from a Helical Flux Compression Generator  

Science.gov (United States)

A mathematical model for a helical flux compression generator (FCG) with a plasma-dynamical load in the form of a magnetoplasma compressor (MFC) is presented. The problem of electrically matching the MPC with an FCG is solved analytically. The mathematical model enables one to calculate the output parameters of the FCG-MPC system for given initial conditions. A comparison is made between the calculated results and the experiment.

Golosov, S. N.; Vlasov, Yu. V.; Demidov, V. A.; Kazakov, S. A.

2004-11-01

59

Dimensions of Impulsive Behavior in Adolescent Smokers and Nonsmokers  

Science.gov (United States)

Robust associations have been identified between impulsive personality characteristics and cigarette smoking during adolescents, indicating that impulsive behavior may play an important role in the initiation of cigarette smoking. The present study extended this research by using laboratory behavioral assessments to explore relationships between three specific dimensions of impulsive behavior (impulsive decision-making, inattention and disinhibition) and adolescent cigarette smoking. Participants were male and female adolescent smokers (n = 50) and nonsmokers (n = 50). Adolescent smokers were more impulsive on a measure of decision-making; however, there were significant smoking status by gender interaction effects for impulsive inattention and disinhibition. Male smokers were most impulsive on the measure of inattention, but male smokers were least impulsive on the measure of disinhibition. Correlations between biomarkers of smoking and impulsive inattention and disinhibition were found for females but not males. The current findings, coupled with previous findings (Reynolds et al., 2007), indicate there may be robust gender difference in associations between certain types of impulsive behavior and cigarette smoking during adolescence. PMID:19803629

Fields, Sherecce; Collins, Christine; Leraas, Kristen; Reynolds, Brady

2011-01-01

60

Dimensions of impulsive behavior in adolescent smokers and nonsmokers.  

Science.gov (United States)

Robust associations have been identified between impulsive personality characteristics and cigarette smoking during adolescents, indicating that impulsive behavior may play an important role in the initiation of cigarette smoking. The present study extended this research by using laboratory behavioral assessments to explore relationships between three specific dimensions of impulsive behavior (impulsive decision-making, inattention, and disinhibition) and adolescent cigarette smoking. Participants were male and female adolescent smokers (n = 50) and nonsmokers (n = 50). Adolescent smokers were more impulsive on a measure of decision-making; however, there were significant smoking status by gender interaction effects for impulsive inattention and disinhibition. Male smokers were most impulsive on the measure of inattention, but male smokers were least impulsive on the measure of disinhibition. Correlations between biomarkers of smoking and impulsive inattention and disinhibition were found for females but not males. The current findings, coupled with previous findings (Reynolds et al., 2007), indicate there may be robust gender difference in associations between certain types of impulsive behavior and cigarette smoking during adolescence. PMID:19803629

Fields, Sherecce; Collins, Christine; Leraas, Kristen; Reynolds, Brady

2009-10-01

 
 
 
 
61

Optically measured explosive impulse  

Science.gov (United States)

An experimental technique is investigated to optically measure the explosive impulse produced by laboratory-scale spherical charges detonated in air. Explosive impulse has historically been calculated from temporal pressure measurements obtained via piezoelectric transducers. The presented technique instead combines schlieren flow visualization and high-speed digital imaging to optically measure explosive impulse. Prior to an explosive event, schlieren system calibration is performed using known light-ray refractions and resulting digital image intensities. Explosive charges are detonated in the test section of a schlieren system and imaged by a high-speed digital camera in pseudo-streak mode. Spatiotemporal schlieren intensity maps are converted using an Abel deconvolution, Rankine-Hugoniot jump equations, ideal gas law, triangular temperature decay profile, and Schardin's standard photometric technique to yield spatiotemporal pressure maps. Temporal integration of individual pixel pressure profiles over the positive pressure duration of the shock wave yields the explosive impulse generated for a given radial standoff. Calculated explosive impulses are shown to exhibit good agreement between optically derived values and pencil gage pressure transducers.

Biss, Matthew M.; McNesby, Kevin L.

2014-06-01

62

Reconsidering the link between impulsivity and suicidal behavior.  

Science.gov (United States)

It is widely accepted that suicidal behavior often occurs with little planning. We propose, however, that suicidal behavior is rarely if ever impulsive-that it is too frightening and physically distressing to engage in without forethought-and that suicidal behavior in impulsive individuals is accounted for by painful and fearsome behaviors capable of enhancing their capacity for suicide. We conducted a meta-analysis of the association between trait impulsivity and suicidal behavior and a critical review of research considering the impulsiveness of specific suicide attempts. Meta-analytic results suggest the relationship between trait impulsivity and suicidal behavior is small. Furthermore, studies examining a mediating role of painful and provocative behaviors have uniformly supported our model. Results from our review suggest that researchers have been unable to adequately measure impulsivity of attempts and that measures sensitive to episodic planning must be developed to further our understanding of this phenomenon. PMID:24969696

Anestis, Michael D; Soberay, Kelly A; Gutierrez, Peter M; Hernández, Theresa D; Joiner, Thomas E

2014-11-01

63

Ballistic impulse gauge  

Science.gov (United States)

A gauge for detecting the impulse generated in sample materials by X-rays or other impulse producing mechanisms utilizes a pair of flat annular springs to support a plunger relative to a housing which may itself be supported by a pair of flat annular springs in a second housing. The plunger has a mounting plate mounted on one end and at the other, a position or velocity transducer is mounted. The annular springs consist of an outer ring and an inner ring with at least three arcuate members connecting the outer ring with the inner ring.

Ault, Stanley K. (Antioch, CA)

1993-01-01

64

Impulse abstractors with memories  

International Nuclear Information System (INIS)

The abstractor described here uses several properties of bistable circuits simultaneously in order to store, delay and connect the impulses. After considering the principle of its operation, several actual applications and some possible further uses of the apparatus are described. (author)

65

Micropower impulse radar imaging  

Energy Technology Data Exchange (ETDEWEB)

From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

Hall, M.S.

1995-11-01

66

The possibility of boron carbide coating formation by using a coaxial magnetoplasma accelerator  

Science.gov (United States)

A coaxial magnetoplasma accelerator can generate a dense and high velocity plasma jet by applying a pulsed high-current arc-discharge. The results of the experiment investigations of plasmodynamic synthesis in the B-C system have been shown while hyper speed jet boron carbide electric-discharged plasma steams onto copper substrate. The boron carbide coatings were formed on the copper substrate without a binder material. The formation of the crystalline boron carbide coating on the copper substrate was analyzed through X-ray diffractometry, transmission electron microscopy and scanning electron microscopy.

Sivkov, A.; Rachmatullin, I.; Makarova, A.

2014-10-01

67

Electrostatic instabilities in current-carrying magnetoplasmas with equilibrium density and ion velocity gradients  

International Nuclear Information System (INIS)

Detailed studies of electrostatic wave instabilities in a current-carrying magnetoplasma with equilibrium density and ion velocity gradients are presented. For this purpose, a general dispersion relation is derived by using a non-Boltzmann electron response as well as an ion density perturbation, which includes the ion-neutral drag. Our dispersion relation contains previously known results as limiting cases, but it also includes some additional instabilities associated with the electron-wave resonant interaction. The present results can help to understand the origin of the nonthermal electrostatic waves in laboratory and space plasmas where there are free energy sources due to ion velocity gradients and streaming particle motions

68

Ion-acoustic solitons in warm magnetoplasmas with super-thermal electrons  

CERN Document Server

In this work, the phenomenon of formation of localised electrostatic waves (ESW) or soliton is considered in a warm magnetoplasma with the possibility of non-thermal electron distribution. The parameter regime considered here is relevant in case of magnetospheric plasmas. We show that deviation from a usual relaxed Maxwellian distribution of the electron population has a significant bearing in the allowed parameter regime, where these ESWs can be found. We further consider the presence of more than one electron temperature, which is inspired by recent space-based observations[key-2].

Choudhury, B; Das, G C; Bora, M P

2012-01-01

69

Three dimensional electrostatic solitary waves in a dense magnetoplasma with relativistically degenerate electrons  

Energy Technology Data Exchange (ETDEWEB)

In this paper, small but finite amplitude electrostatic solitary waves in a relativistic degenerate magnetoplasma, consisting of relativistically degenerate electrons and non-degenerate cold ions, are investigated. The Zakharov-Kuznetsov equation is derived employing the reductive perturbation technique and its solitary wave solution is analyzed. It is shown that only compressive electrostatic solitary structures can propagate in such a degenerate plasma system. The effects of plasma number density, ion cyclotron frequency, and direction cosines on the profiles of ion acoustic solitary waves are investigated and discussed at length. The relevance of the present investigation vis-a-vis pulsating white dwarfs is also pointed out.

Ata-ur-Rahman,; Qamar, A. [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan); National Centre for Physics, QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Masood, W. [National Centre for Physics, QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); COMSATS, Institute of Information Technology, Park Road, Chak Shahzad, Islamabad 44000 (Pakistan); Eliasson, B. [Physics Department, University of Strathclyde, Glasgow G4 0NG, Scotland (United Kingdom)

2013-09-15

70

The parametric decay of dust ion acoustic waves in non-uniform quantum dusty magnetoplasmas  

International Nuclear Information System (INIS)

The parametric decay instability of a dust ion acoustic wave into low-frequency electrostatic dust-lower-hybrid and electromagnetic shear Alfven waves has been investigated in detail in an inhomogeneous cold quantum dusty plasma in the presence of external/ambient uniform magnetic field. The quantum magnetohydrodynamic model of plasmas with quantum effect arising through the Bohm potential and Fermi degenerate pressure has been employed in order to find the linear and nonlinear responses of the plasma particles for three-wave nonlinear coupling in a dusty magnetoplasma. A relatively high frequency electrostatic dust ion acoustic wave has been taken as the pump wave. It couples with two other low-frequency internal possible modes of the dusty magnetoplasma, viz., the dust-lower-hybrid and shear Alfven waves. The nonlinear dispersion relation of the dust-lower-hybrid wave has been solved to obtain the growth rate of the parametric decay instability. The growth rate is at a maximum for a small value of the external magnetic field B0. It is noted that the growth rate is proportional to the unperturbed electron number density noe and is independent of inhomogeneity beyond Le=2 cm. An extraordinary growth rate is observed with the quantum effect.

71

Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma  

CERN Document Server

We study the amplitude modulation of low-frequency, long-wavelength electrostatic drift-wave envelopes in a nonuniform quantum magnetoplasma consisting of cold ions and degenerate electrons. The effects of tunneling associated with the quantum Bohm potential and the Fermi pressure for nonrelativistic degenerate electrons, as well as the equilibrium density and magnetic field inhomogeneities are taken into account. Starting from a set of quantum magnetohydrodynamic (QMHD) equations, we derive a nonlinear Schr\\"odinger equation (NLSE) that governs the dynamics of the modulated quantum drift-wave packets. The NLSE is used to study the modulational instability (MI) of a Stoke's wave train to a small plane wave perturbation. It is shown that the quantum tunneling effect as well as the scale length of inhomogeneity play crucial roles for the MI of the drift-wave packets. Thus, the latter can propagate in the form of bright and dark envelope solitons or as drift-wave rogons in degenerate dense magnetoplasmas.

Misra, A P

2014-01-01

72

Electrodynamics and dispersion properties of a magnetoplasma containing elongated and rotating dust grains  

International Nuclear Information System (INIS)

The electrodynamics and dispersion properties of a magnetized dusty plasma containing elongated and rotating charged dust grains are examined. Starting from an appropriate Lagrangian for dust grains, a kinetic equation for the dust grain and the corresponding equations of motion are derived. Expressions for the dust charge and dust current densities are obtained with the finite size (the dipole moment) of elongated and rotating dust grains taken into account. These charge and current densities are combined with the Maxwell-Vlasov system of equations to derive dispersion relations for the electromagnetic and electrostatic waves in a dusty magnetoplasma. The dispersion relations are analyzed to demonstrate that the dust grain rotation introduces new classes of instabilities involving various low-frequency waves in a dusty magnetoplasma. Examples of various unstable low-frequency waves include the electron whistler, the dust whistler, dust cyclotron waves, Alfven waves, electromagnetic ion-cyclotron waves, as well as lower-hybrid, electrostatic ion cyclotron, modified dust ion-acoustic waves, etc. Also found is a new type of unstable waves whose frequency is close to the dust grain rotation frequency. The present results should be useful in understanding the properties of low-frequency waves in cosmic and laboratory plasmas that are embedded in an external magnetic field and contain elongated and rotating charged dust grains

73

Investigating Impulse Loading Using Model Rocketry  

Science.gov (United States)

A project is presented that uses experimentally determined thrust data for a commercial model rocket engine to investigate impulse loading relations. Certain model rocket engines approach impulse loading; completely burning in a fraction of a second. Using a fixture instrumented with strain gages and a high-speed National Instruments data acquisition system, the students experimentally collect the thrust verses time response of several Estes model rocket engines. The students formulate two flight models for a rocket of known mass loaded with the specific engine being investigated. The first model uses the measured thrust data directly as input to the governing differential equation for the rocket. The students are challenged to formulate an appropriate drag model through a literature search and must justify their choice. A second flight model is formulated using an equivalent impulse, based on the experimental thrust data, as loading. The students calculate flight trajectories based on both nonlinear models using numerical methods and critically compare/contrast the results. The project has been found to engage students and to effectively provide hands-on insight in the value, and limitations, of impulse loading methods.

Newberry, Byron

2011-05-26

74

Sleep patterns and impulse control among Japanese junior high school students.  

Science.gov (United States)

Adolescents with decreased impulse control exhibit behavioral problems. Lifestyles are related to impulse control. However, the relations of sleep patterns and impulse control among adolescents are unknown. Thus we examined how sleep patterns were associated with impulse control among Japanese junior high school students. Surveys were completed by a nationwide sample of 1934 students. A significant association between decreased impulse control and bedtimes after midnight was revealed. Specific lifestyle factors related to bedtimes after midnight were older age, greater numbers of hours spent watching television, lack of participation in an extracurricular activity, greater use of convenience stores, and increased attendance at cram schools. This study revealed that going to sleep after midnight was significantly related to decreased impulse control among adolescents. Data about specific lifestyle factors related to going to sleep after midnight should be useful in preventing those behaviors demonstrated by school children that derive from decreased impulse control. PMID:20005566

Abe, Takeru; Hagihara, Akihito; Nobutomo, Koichi

2010-10-01

75

IMPULSE---an advanced, high performance nuclear thermal propulsion system  

International Nuclear Information System (INIS)

IMPULSE is an advanced nuclear propulsion engine for future space missions based on a novel conical fuel. Fuel assemblies are formed by stacking a series of truncated (U, Zr)C cones with non-fueled lips. Hydrogen flows radially inward between the cones to a central plenum connected to a high performance bell nozzle. The reference IMPULSE engine rated at 75,000 lb thrust and 1800 MWt weighs 1360 kg and is 3.65 meters in height and 81 cm in diameter. Specific impulse is estimated to be 1000 for a 15 minute life at full power. If longer life times are required, the operating temperature can be reduced with a concomitant decrease in specific impulse. Advantages of this concept include: well defined coolant paths without outlet flow restrictions; redundant orificing; very low thermal gradients and hence, thermal stresses, across the fuel elements; and reduced thermal stresses because of the truncated conical shape of the fuel elements

76

Role of ambient magnetic field in driving the eruption of an arched laboratory magnetoplasma  

Science.gov (United States)

Eruptions of arched magnetoplasma structures cover a wide spatiotemporal scale on the Sun and drive energetic phenomena such as coronal mass ejections. Due to presence of an electrical-current and associated twist in the magnetic-field, the term “arched magnetic flux rope” (AMFR) is used for these structures. Contemporary models of solar eruptions predict that solar AMFRs are confined for relatively long duration (days to weeks) by ambient magnetic fields (known as strapping field) before their sudden eruption. The structure of the ambient-magnetic-field plays an important role in the evolution of the confined and erupting solar AMFRs. In a laboratory plasma experiment, the interaction between an AMFR and its ambient magnetic field has been investigated. The AMFR (plasma ? ? 10-3, Lundquist number ?102-105, AMFR radius/ion-gyroradius ? 20, B ? 1000 G at footpoints) was produced using a LaB6 plasma source in an ambient magnetoplasma (B ? 0 - 100 G). The ambient magnetic field was oriented normal to the symmetry plane of the AMFR. The experiment runs continuously and generates reproducible AMFR eruptions with a period of 2 s. Hence, the plasma parameters were recorded with a good resolution (spatial-resolution/AMFR-length ? 10-2 - 10-3, temporal-resolution/eruption-time ? 10-3) using computer-controlled movable probes. A fast-CCD camera was utilized to capture the evolution of the AMFR. The pre-eruption phase of the AMFR remained quiescent for ? 100 Alfven transit times and the camera images evinced its persistent appearance. In contrast, the post-eruption phase of the AMFR was observed to be associated with significant changes in its magnetic topology. Our initial results suggest that linkage of the magnetic-field of the AMFR with the ambient magnetoplasma (which is ignored in the models of solar eruptions) plays the most important role in the ejection of a large flux rope from the leading edge of the AMFR. Implications of these results to actual solar eruptions will be discussed. References: (1) Tripathi and Gekelman, Phys. Rev. Lett. 105, 075005 (2010) (2) Tripathi and Gekelman, Solar Phys. 286, 479 (2013)(Work performed at the Basic Plasma Science Facility, UCLA and supported by US DOE and NSF)

Tripathi, Shreekrishna; Gekelman, Walter

2014-06-01

77

Portable High Voltage Impulse Generator  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a portable high voltage impulse generator which was designed and built with insulation up to 20 kV. This design was based on previous work in which simulation software for standard waves was developed. Commercial components and low-cost components were used in this work; however, these particular elements are not generally used for high voltage applications. The impulse generators used in industry and laboratories are usually expensive; they are built to withstand extra high voltage and they are big, making them impossible to transport. The proposed generator is portable, thereby allowing tests to be made on devices that cannot be moved from their location. The results obtained with the proposed impulse generator were satisfactory in terms of time and waveforms compared to other commercial impulse generators and the standard impulse wave simulator.

S. Gómez

2011-07-01

78

Phase matching for third-harmonic generation in collisional magnetoplasmas  

International Nuclear Information System (INIS)

This paper presents a derivation of the phase-matching conditions for generation of the third-harmonic (3?1) and combination frequencies (?1+2?2), by two fundamental electromagnetic waves of frequencies ?1 and ?2, propagating in the extraordinary mode along a magnetic field in a collisional plasma. Expressions for the corresponding optimum distance of propagation for maximum output and the associated values of the phase functions have been derived. In the case of the third-harmonic generation phase matching occurs when the gyrofrequency of the electrons is twice the wave frequency (for all values of plasma frequency). In the case of the combination frequencies, the phase-matching condition is represented by an expression for plasma frequency ?p in terms of the wave frequencies ?1, ?2 and the gyrofrequency ?c of electrons. Furthermore, it is seen that in the (?c/?1)-(?2/?1) plane, phase matching occurs in a narrow region; for every point in this region, there is a corresponding value of (?p/?1). The dependence of optimum distance of propagation and the corresponding value of the phase function on electron collision frequency ?av/?1 have been graphically illustrated for a specific case. An estimate of the maximum value of the third-harmonic conversion efficiency has also been made

79

The Causes of Impulse Buying Behavior among Iranian Shoppers  

Directory of Open Access Journals (Sweden)

Full Text Available The retailers have a tendency to involve in the procedure of buying and to produce an atmosphere to convincethe people for buying goods. The overall purpose of the paper is to gain insights into impulse buying behavioramong Iranian shoppers and to arrive at a better understanding on how situational, personal, and product relatedfactors influence impulse buying. The cross-sectional survey design is the specific survey method employed inthis research. The instrument for collecting data was a questionnaire and the samples were selected based on thecluster sampling method that includes 207 participants. Findings show that situational variables (storeenvironment have a positive influence on impulse buying through positive mood and the felt urge to buy has amediator role between impulse buying tendency and impulse buying. The study also found that demographicvariables (job status has not moderation role between the hedonic shopping and felt urge to buy impulsively.The findings of the research contribute to the knowledge, retailers and salesperson training. This studydemonstrates empirically which important factors influence on impulse buying behavior among Iranianconsumers.

Amir Foroughi

2014-10-01

80

Electron acoustic wave driven vortices with non-Maxwellian hot electrons in magnetoplasmas  

Science.gov (United States)

Linear dispersion characteristics of the Electron Acoustic Wave (EAW) and the corresponding vortex structures are investigated in a magnetoplasma in the presence of non-Maxwellian hot electrons. In this regard, kappa and Cairns distributed hot electrons are considered. It is noticed that the nonthermal distributions affect the phase velocity of the EAW. Further, it is found that the phase velocity of EAW increases for Cairns and decreases for kappa distributed hot electrons. Nonlinear solutions in the form of dipolar vortices are also obtained for both stationary and non-stationary ions in the presence of kappa distributed hot electrons and dynamic cold electrons. It is found that the amplitude of the nonlinear vortex structures also reduces with kappa factor like the electron acoustic solitons.

Haque, Q.; Mirza, Arshad M.; Zakir, U.

2014-07-01

 
 
 
 
81

Spin effect on parametric decay of oblique Langmuir wave in degenerate magneto-plasmas  

International Nuclear Information System (INIS)

The electron spin ?1/2 effects on the parametric decay instability of oblique Langmuir wave into low-frequency electromagnetic shear Alfven wave and Left-Handed Circularly Polarized wave (LHCP) has been investigated in detail, in an electron-ion quantum plasma immersed in the uniform external magnetic field. Incorporating the quantum effects due to electron spin, Fermi pressure and Bohm potential term, the quantum magneto-hydrodynamic (QMHD) model has been used to investigate the linear and nonlinear response of the plasma species for three-wave coupling interaction in a quantum magneto-plasmas. Nonlinear dispersion relations and growth rate of the problem have been derived analytically. It has been shown that the spin of electrons has considerable effect on the growth rate of parametric instability problem even when the external magnetic field B0 is below the quantum critical magnetic field strength BQ=4.4138×1013G

82

Modified screening potential in a high density inhomogeneous quantum dusty magnetoplasma  

International Nuclear Information System (INIS)

The effect of strong ambient static magnetic field on Shukla-Nambu-Salimullah (SNS) potential in a dusty quantum magnetoplasma has been investigated using quantum hydrodynamic model. The potential is significantly modified by quantum statistical effects, density inhomogeneity, and dust polarization drift effect. The effective length of the modified SNS potential is found to be a sensitive function of external static magnetic field, ExB0 drift, and the scale length of inhomogeneity. Here E is the electric polarization vector produced via density inhomogeneity, and B0 is the ambient static magnetic field. It is found that dust polarization drift effect predominates the ion polarization drift effect in high magnetic field environments. It attracts our attention to the careful study of the underlying physics of dusty plasma environment of neutron stars and magnetars.

83

Absorption of intense Gaussian electromagnetic radiation in a magnetoplasma via inverse bremsstrahlung  

International Nuclear Information System (INIS)

A self-focused Gaussian laser beam propagating in the direction of static magnetic field in a collisional magnetoplasma has been considered. The explicit expressions for the time averaged power absorbed for left and right handed circularly polarised waves have been obtained. The effect of magnetic field and focusing on the rate of power absorbed is studied in weak field regime (?sub(E) > ?sub(Th)). It is observed that the rate of absorption of right circularly polarised radiation decreases whereas for left circularly polarised radiation increases in weak field regime whereas reverse holds good in strong field regime. It is also observed that the increase in magnetic field decreases the focussing length for right circularly polarised wave whereas defocusses the left circularly polarised wave and power absorption for both the modes shows a typical behaviour due to coupling between them. (author)

84

Electrostatic drift-wave instability in a nonuniform quantum magnetoplasma with parallel velocity shear flows  

International Nuclear Information System (INIS)

The propagation of high and low frequency (in comparison with the cyclotron frequency) electrostatic drift-waves is investigated in a nonuniform, dense magnetoplasma (composed of electrons and ions), in the presence of parallel shear flow, by employing the quantum magnetohydrodynamic (QMHD) model. Using QMHD model, a new set of equations is presented in order to investigate linear properties of electrostatic drift-waves with sheared plasma flows for dense plasmas. In this regard, dispersion relations for coupled electron-thermal and drift-ion acoustic modes are derived and several interesting limiting cases are discussed. For instance, it is found that sheared ion flow parallel to the external magnetic field can drive the quantum drift-ion acoustic wave unstable, etc. The present investigation may have relevance in dense astrophysical environments where quantum effects are significant.

85

Magnetoplasma waves on the surface of semiconducting nanotube with a superlattice  

International Nuclear Information System (INIS)

The spectra of plasma waves in the electron gas on the surface of semiconducting nanotube with a superlattice are considered. The external magnetic field is directed along the axis of the nanotube and the superlattice. The analysis of the intraband and interband magnetoplasma waves in the degenerate electron gas is presented in quantum and quasiclassical limits. If a number of angular motion levels are filled up then the magnetoplasmon frequencies oscillate with variation of nanotube parameters similarly to the de Haas-van Alphen oscillations. The frequencies demonstrate also the Aharonov-Bohm oscillations on magnetic flux through the nanotube cross-section. The oscillation pattern is determined by the ratio of the Fermi energy to minizone width. If this ratio is sufficiently large the beats appear in the plot of magnetoplasmon frequency as a function of tube parameters.

86

Formation of the compression zone in a plasma flow generated by a magnetoplasma compressor  

Science.gov (United States)

Processes occurring in a plasma flow generated by a magnetoplasma compressor (MPC) during the formation of the compression zone are discussed. The paper presents results of measurements of the spatial distribution of the electric current in the plasma flow, the temporal and spatial (along the flow) distributions of the plasma density, and the profiles of the velocity of individual flow layers along the system axis. The spatial distribution of the electromagnetic force in the flow is analyzed. It is shown that the plasma flow is decelerated when approaching the compression zone and reaccelerated after passing it. In this case, the plasma flow velocity decreases from ? = (2-3) × 107 cm/s at the MPC output to ? MPC output. In some MPC operating modes, a displacement of the magnetic field from the compression zone and the formation of toroidal electric current vortices in the plasma flow after passing the compression zone were detected.

Solyakov, D. G.; Petrov, Yu. V.; Garkusha, I. E.; Chebotarev, V. V.; Ladygina, M. S.; Cherednichenko, T. N.; Morgal', Ya. I.; Kulik, N. V.; Stal'tsov, V. V.; Eliseev, D. V.

2013-12-01

87

Model for nonlinear evolution of localized ion ring beam in magnetoplasma  

Energy Technology Data Exchange (ETDEWEB)

An electrostatic hybrid model, which investigates the nonlinear evolution of a localized ion ring beam in a magnetoplasma, is described and applied to the generation and evolution of turbulence in the very low frequency (VLF) ({Omega}{sub ci}<{omega}<{Omega}{sub ce}) range, where {Omega}{sub ci(e)} is the ion (electron) gyro frequency. Electrons are treated as a fluid and the ions with the particle-in-cell method. Although the model is electrostatic, it includes the effects of energy loss by convection of electromagnetic VLF waves out of the instability region by utilizing a phenomenological model for effective collisions with the fluid electrons. In comparison with a more conventional electrostatic hybrid model, the new model shows much more efficient extraction of energy from the ion ring beam and reduced background plasma heating over a range of parameters.

Scales, W. A. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061-0111 (United States); Ganguli, G.; Mithaiwala, M. [Plasma Physics Division, Naval Research Laboratory, Washington D.C. 20375 (United States); Rudakov, L. [Icarus Research, Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780 (United States)

2012-06-15

88

Spin effect on parametric decay of oblique Langmuir wave in degenerate magneto-plasmas  

Energy Technology Data Exchange (ETDEWEB)

The electron spin ?1/2 effects on the parametric decay instability of oblique Langmuir wave into low-frequency electromagnetic shear Alfven wave and Left-Handed Circularly Polarized wave (LHCP) has been investigated in detail, in an electron-ion quantum plasma immersed in the uniform external magnetic field. Incorporating the quantum effects due to electron spin, Fermi pressure and Bohm potential term, the quantum magneto-hydrodynamic (QMHD) model has been used to investigate the linear and nonlinear response of the plasma species for three-wave coupling interaction in a quantum magneto-plasmas. Nonlinear dispersion relations and growth rate of the problem have been derived analytically. It has been shown that the spin of electrons has considerable effect on the growth rate of parametric instability problem even when the external magnetic field B{sub 0} is below the quantum critical magnetic field strength B{sub Q}=4.4138×10{sup 13}G.

Shahid, M. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan); Department of Physics, Government College University, Lahore-54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan)

2013-08-15

89

Model for nonlinear evolution of localized ion ring beam in magnetoplasma  

International Nuclear Information System (INIS)

An electrostatic hybrid model, which investigates the nonlinear evolution of a localized ion ring beam in a magnetoplasma, is described and applied to the generation and evolution of turbulence in the very low frequency (VLF) (?cice) range, where ?ci(e) is the ion (electron) gyro frequency. Electrons are treated as a fluid and the ions with the particle-in-cell method. Although the model is electrostatic, it includes the effects of energy loss by convection of electromagnetic VLF waves out of the instability region by utilizing a phenomenological model for effective collisions with the fluid electrons. In comparison with a more conventional electrostatic hybrid model, the new model shows much more efficient extraction of energy from the ion ring beam and reduced background plasma heating over a range of parameters.

90

Self-trapping and self-focusing of an elliptical laser beam in a collisionless magnetoplasma  

International Nuclear Information System (INIS)

The authors have studied the self-trapping and self-focusing-defocusing of an elliptically shaped laser beam in a magnetoplasma. The critical self-trapping power of the beam for the ordinary mode is twice the critical power for the extraordinary mode. On both sides of the critical power required for self-trapping, there are separate values of the critical power for the x-dimension as well as for the y-dimension of the beam. At and above the critical value for the x-dimension, the beam defocuses in both directions while at and below the critical value for the y-dimension, it self-focuses in both directions. Self-trapping is also observed in the case of the ordinary mode at a critical value of the external magnetic field for any power value. (author)

91

Impulsivity, gender, and the platelet serotonin transporter in healthy subjects  

Directory of Open Access Journals (Sweden)

Full Text Available Donatella Marazziti, Stefano Baroni, Irene Masala, Francesca Golia, Giorgio Consoli, Gabriele Massimetti, Michela Picchetti, Mario Catena Dell’Osso, Gino Giannaccini, Laura Betti, Antonio Lucacchini, Antonio CiapparelliDipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, University of Pisa, Pisa, ItalyAbstract: The present study explored the possible relationships between impulsivity, gender, and a peripheral serotonergic marker, the platelet serotonin (5-HT transporter (SERT, in a group of 32 healthy subjects. The impulsivity was measured by means of the Barratt Impulsivity Scale, version 11 (BIS-11, a widely used self-report questionnaire, and the platelet SERT was evaluated by means of the specific binding of 3H-paroxetine (3H-Par to platelet membranes, according to standardized protocols. The results showed that women had a higher BIS-11 total score than men, and also higher scores of two factors of the same scale: the motor impulsivity and the cognitive complexity. The analysis of the correlations revealed that the density of the SERT proteins, as measured by the maximum binding capacity (Bmax of 3H-Par, was significantly and positively related to the cognitive complexity factor, but only in men. Men showed also a significant and negative correlation with the dissociation constant, Kd, of (3H-Par binding, and the motor impulsivity factor. These findings suggest that women are generally more impulsive than men, but that the 5-HT system is more involved in the impulsivity of men than in that of women.Keywords: impulsivity, gender, serotonin transporter, Barratt Impulsivity Scale, platelets, 3H-paroxetine

Donatella Marazziti

2009-12-01

92

A comparison of parametric decay of oblique Langmuir wave in high and low density magneto-plasmas  

International Nuclear Information System (INIS)

The parametric decay instability of an obliquely propagating Langmuir wave into the low-frequency electromagnetic shear Alfven wave and the Left-Handed Circularly Polarized wave has been investigated in an electron-ion plasma, immersed in a uniform external magnetic field. Quantum magneto-hydrodynamic model has been used to find the linear and non-linear response of a high density quantum magneto-plasma. Going to the classical limit (??0) retrieves the results for low density classical plasma. Nonlinear dispersion relations and growth rates are derived with analytically and numerically. It is observed that growth rate in the high density degenerate magneto-plasma increases exponentially, while in the low density classical case it increases logarithmically

93

A comparison of parametric decay of oblique Langmuir wave in high and low density magneto-plasmas  

Energy Technology Data Exchange (ETDEWEB)

The parametric decay instability of an obliquely propagating Langmuir wave into the low-frequency electromagnetic shear Alfven wave and the Left-Handed Circularly Polarized wave has been investigated in an electron-ion plasma, immersed in a uniform external magnetic field. Quantum magneto-hydrodynamic model has been used to find the linear and non-linear response of a high density quantum magneto-plasma. Going to the classical limit (??0) retrieves the results for low density classical plasma. Nonlinear dispersion relations and growth rates are derived with analytically and numerically. It is observed that growth rate in the high density degenerate magneto-plasma increases exponentially, while in the low density classical case it increases logarithmically.

Shahid, M.; Hussain, A. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan); Department of Physics, Government College University, Lahore-54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan)

2013-09-15

94

Multi-dimensional instability of obliquely propagating ion acoustic solitary waves in electron-positron-ion superthermal magnetoplasmas  

Science.gov (United States)

The solitary structures of multi-dimensional ion-acoustic solitary waves (IASWs) have been considered in magnetoplasmas consisting of electron-positron-ion with high-energy (superthermal) electrons and positrons are investigated. Using a reductive perturbation method, a nonlinear Zakharov-Kuznetsov equation is derived. The multi-dimensional instability of obliquely propagating (with respect to the external magnetic field) IASWs has been studied by the small-k (long wavelength plane wave) expansion perturbation method. The instability condition and the growth rate of the instability have been derived. It is shown that the instability criterion and their growth rate depend on the parameter measuring the superthermality, the ion gyrofrequency, the unperturbed positrons-to-ions density ratio, the direction cosine, and the ion-to-electron temperature ratio. Clearly, the study of our model under consideration is helpful for explaining the propagation and the instability of IASWs in space observations of magnetoplasmas with superthermal electrons and positrons.

EL-Shamy, E. F.

2014-08-01

95

Distinctive features of ion-acoustic solitons in electron-positron-ion superdense magnetoplasmas with degenerate electrons and positrons  

Science.gov (United States)

Using the extended Poincaré-Lighthill-Kuo reductive perturbation method to study the small-amplitude ion acoustic solitary wave dynamics (propagation and interaction), it is shown that in the Thomas-Fermi magnetoplasma consisting of inertial-less degenerate electrons and positrons and isothermal ions, distinctive features emerge when the ultrarelativistic degeneracy pressure applies to electrons and positrons. Calculations show that ion-acoustic solitary waves may interact differently in such plasmas under ultrarelativistic degeneracy pressure.

Akbari-Moghanjoughi, M.

2010-09-01

96

Dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons  

Science.gov (United States)

The dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons has been investigated in the framework of perturbed and non-perturbed Kadomtsev-Petviashili (KP) equations. Applying the reductive perturbation technique, we have derived the KP equation in electron-positron-ion magnetoplasma with kappa distributed electrons and positrons. Bifurcations of ion acoustic traveling waves of the KP equation are presented. Using the bifurcation theory of planar dynamical systems, the existence of the solitary wave solutions and the periodic traveling wave solutions has been established. Two exact solutions of these waves have been derived depending on the system parameters. Then, using the Hirota's direct method, we have obtained two-soliton and three-soliton solutions of the KP equation. The effect of the spectral index ? on propagations of the two-soliton and the three-soliton has been shown. Considering an external periodic perturbation, we have presented the quasi periodic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas.

Saha, Asit; Pal, Nikhil; Chatterjee, Prasanta

2014-10-01

97

Strong stability of impulsive systems  

Energy Technology Data Exchange (ETDEWEB)

The strong stability of the zero solution of impulsive systems with impulses at fixed moments of time is investigated. It is proved that the existence of piecewise continuous functions with certain properties is a necessary and sufficient condition for the strong stability of the zero solution of such systems. By using differential inequalities for piecewise continuous functions, sufficient conditions for the strong stability of the zero solution are found.

Kulev, G.K.; Bainov, D.D.

1988-06-01

98

Strong stability of impulsive systems  

International Nuclear Information System (INIS)

The strong stability of the zero solution of impulsive systems with impulses at fixed moments of time is investigated. It is proved that the existence of piecewise continuous functions with certain properties is a necessary and sufficient condition for the strong stability of the zero solution of such systems. By using differential inequalities for piecewise continuous functions, sufficient conditions for the strong stability of the zero solution are found

99

Nucleus accumbens core and shell inactivation differentially affects impulsive behaviours in rats.  

Science.gov (United States)

Impulsivity is a multifactorial phenomenon, determined by deficits in decision-making (impulsive choice) and impulse control (impulsive action). Recent findings indicate that impulsive behaviour is not only top-down controlled by cortical areas, but also modulated at subcortical level. The nucleus accumbens (NAc) might be a key substrate in cortico-limbic-striatal circuits involved in impulsive behaviour. Dissociable effects of the NAc subregions in various behavioural paradigms point to a potential functional distinction between NAc core and shell concerning different types of impulsivity. The present study used reversible inactivation of the rats' NAc core and shell via bilateral microinfusion of the GABAA receptor agonist muscimol (0.05?g/0.3?l) and fluorophore-conjugated muscimol (FCM, 0.27?g/0.3?l) in order to study their contribution to different aspects of impulse control in a 5-choice serial reaction time task (5-CSRTT) and impulsive choice in a delay-based decision-making T-maze task. Acute inactivation of NAc core as well as shell by muscimol increased impulsive choice, with higher impairments of the rats' waiting capacity in the T-maze following core injections compared to shell. Intra-NAc shell infusion of muscimol also induced specific impulse control deficits in the 5-CSRTT, while deactivation of the core caused severe general impairments in task performance. FCM did not affect animal behaviour. Our findings reveal clear involvement of NAc shell in both forms of impulsivity. Both subareas play a key role in the regulation of impulsive decision-making, but show functional dichotomy regarding impulse control with the core being more implicated in motivational and motor aspects. PMID:24810333

Feja, Malte; Hayn, Linda; Koch, Michael

2014-10-01

100

Impulsivity, risk taking, and timing.  

Science.gov (United States)

This study examined the relations among measures of impulsivity and timing. Impulsivity was assessed using delay and probability discounting, and self-report impulsivity (as measured by the Barratt Impulsiveness Scale; BIS-11). Timing was assessed using temporal perception as measured on a temporal bisection task and time perspective (as measured by the Zimbardo Time Perspective Inventory). One hundred and forty three college students completed these measures in a computer laboratory. The degree of delay discounting was positively correlated with the mean and range of the temporal bisection procedure. The degree of delay and probability discounting were also positively correlated. Self-reported motor impulsiveness on the BIS-11 was positively correlated with present hedonism and negatively correlated with future orientation on the ZTPI. Self-reported non-planning on the BIS-11 was positively correlated with fatalism on the ZTPI. These results show that people who overestimate the passage of time (perceive time as passing more quickly) hold less value in delayed rewards. They also confirm previous results regarding the relation between delay and probability discounting, as well as highlight similarities in self-report measures of impulsivity and time perspective. PMID:22542458

Baumann, Ana A; Odum, Amy L

2012-07-01

 
 
 
 
101

Risk Factors and Impulsivity in Obesity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In addition to genetic tendency, social, cultural, emotional and diet-related factors play important role in the development of obesity. Impulsivity is the possible predictor of relapse in obesity treatment. Impulsivity is also considered as a predicting factor among patients who quit the treatment. Research has shown that obese people are more impulsive than other people. Impulsive features are especially found to be higher with those who have binge eating disorder. Impulsive people appears ...

Bilge Burcak Annagur

2010-01-01

102

Impulsivity and sensation seeking in alcohol abusing patients with schizophrenia  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: Some studies have found that high levels of impulsivity and sensation seeking, particularly disinhibition are associated with substance abuse in patients with schizophrenia, as in the general population. However, no study has assessed impulsivity and sensation seeking specifically in schizophrenia patients with alcohol abuse or dependence. Material and Methods: We compared impulsivity and sensation seeking in a group of schizophrenia patients (DSM-III-R criteria with lifetime alcohol abuse or dependence (n=34 and in a group without lifetime substance abuse or dependence (n=66. The patients were assessed using the Composite International Diagnostic Interview (CIDI for DSM-III-R disorders, the Positive and Negative Syndrome Scale, the Barratt Impulsivity Scale (BIS, the Zuckerman Seeking Sensation Scale (SSS, and the Physical Anhedonia Scale (PAS. Results: The mean scores for impulsivity and sensation seeking were higher in the group with lifetime alcohol abuse or dependence than in the group without substance abuse or dependence (BIS: 63.4 SD: 18,7 vs 51.3 SD: 14.2 respectively, ANOVA: F=11.12, p=0.001; SSS: 17.6 SD: 5.9 vs 13.5 SD: 6.7 respectively, ANOVA: F=7.45, p=0.008. There was no significant differences between the two groups on PAS score. Conclusion: Increased impulsivity or sensation seeking may be a link between schizophrenia and alcohol abuse or dependence.

AlainDervaux

2010-09-01

103

Impulsivity and physical aggression: examining the moderating role of anxiety.  

Science.gov (United States)

Individuals vary in their propensity to engage in aggressive behaviors, and recent research has sought to identify individual differences that contribute to a person's propensity for physical aggression. Previous research has shown that impulsivity and aggression have a consistent relational pattern among many different samples. However, not all impulsive people will engage in aggressive behavior, perhaps because of other factors such as level of physiological arousal from anxiety. Specifically, one factor, namely physiological symptoms of anxiety such as those often associated with panic, may help as a predictor variable to be used in risk assessments or subclassification systems of aggression. Participants included 689 college students who completed self-report questionnaires assessing impulsivity, physical aggression, and anxiety. Multivariate hierarchical regression analyses were conducted. Greater scores on the measure of impulsivity were associated with higher levels of reported physical aggression. The interaction (impulsivity x anxiety) was not statistically significant, suggesting that impulsivity has the same effect on physical aggression regardless of the level of anxiety. There was a main effect for anxiety, which was associated with higher levels of reported physical aggression. Our findings may help inform typologies for identifying predictor variables used in risk assessment and treatment planning. PMID:24934013

Hatfield, Joshua; Dula, Chris S

2014-01-01

104

Pharmacologic treatment of impulsive aggression with antiepileptic drugs.  

Science.gov (United States)

Aggressive behavior is a major concern in mental health and criminal justice settings. Although pharmacotherapy is often used in the treatment of the violent individual, no medication is presently approved by the US Food and Drug Administration specifically for such use. In recent years, antiepileptic drugs (AEDs) have become increasingly popular for the management of impulsive (reactive) aggressive behavior. The research literature has implicated several neurobiologic deficits associated with impulsive aggression, including reduced central serotonergic functioning, executive dysfunction, and prefrontal deficits. It has been suggested that the neurobiologic deficits specific to impulsive aggressive behavior may serve as indicators of an ineffective behavioral control system. A review of the literature finds that AEDs, particularly those that block sodium channels and/or have GABA-related mechanisms of action, are effective in reducing the frequency and intensity of impulsive aggressive outbursts both when used as the primary agent of treatment and as an adjunct to ongoing pharmacotherapy. Strong evidence for efficacy in impulsive aggression exists from randomized controlled trials for most of the common AEDs (phenytoin, carbamazepine, oxcarbazepine, lamotrigine, valproate/divalproex sodium, topiramate). Additional controlled studies are needed for tiagabine and gabapentin. Of the common AEDs, only levetiracetam has been shown to be ineffective in the treatment of impulsive aggression. It is important to note that the anti-aggressive effects seen with the AEDs appear to be specific to the impulsive form of aggression. Individuals who display premeditated aggression do not seem to benefit from this type of treatment. Clinically, we recommend phenytoin (initial dose 100 mg three times daily) as the AED of first choice for the treatment of impulsive aggressive outbursts. This recommendation is based on this drug's limited side effect profile (compared with the other AEDs) and the large amount of empiric data supporting its clinical efficacy in impulsive aggression. In the event that the impulsive aggressive individual does not respond to pharmacotherapy with phenytoin, carbamazepine (initial dose 150 mg three times daily) and valproate/divalproex sodium (initial dose 250 mg three times daily) have both proved to be effective secondary options. PMID:19744405

Stanford, Matthew S; Anderson, Nathaniel E; Lake, Sarah L; Baldridge, Robyn M

2009-09-01

105

Pre-attentive information processing and impulsivity in bipolar disorder.  

Science.gov (United States)

Early responses to stimuli can be measured by sensory evoked potentials (EP) using repeated identical stimuli, S1 and S2. Response to S1 may represent efficient stimulus detection, while suppression of response to S2 may represent inhibition. Early responses to stimuli may be related to impulsivity. We compared EP reflecting stimulus detection and inhibition in bipolar disorder and healthy controls, and investigated relationships to impulsivity. Subjects were 48 healthy controls without family histories of mood disorder and 48 with bipolar disorder. EP were measured as latencies and amplitudes for auditory P50 (pre-attentional), N100 (initial direction of attention) and P200 (initial conscious awareness), using a paired-click paradigm, with identical stimuli 0.5 s apart. Impulsivity was measured by questionnaire and by laboratory tests for inability to suppress responses to stimuli or to delay response for a reward. Analyses used general linear models. S1 amplitudes for P50, N100, and P200, and gating of N100 and P200, were lower in bipolar disorder than in controls. P50 S1 amplitude correlated with accurate laboratory-task responding, and S2 amplitude correlated with impulsive task performance and fast reaction times, in bipolar disorder. N100 and P200 EP did not correlate with impulsivity. These findings were independent of symptoms, treatment, or substance-use history. EPs were not related to questionnaire-measured or reward-based impulsivity. Bipolar I disorder is characterized by reduced pre-attentional and early attentional stimulus registration relative to controls. Within bipolar disorder, rapid-response impulsivity correlates with impaired pre-attentional response suppression. These results imply specific relationships between ERP-measured response inhibition and rapid-response impulsivity. PMID:24054520

Swann, Alan C; Lijffijt, Marijn; Lane, Scott D; Steinberg, Joel L; Acas, Michelle D; Cox, Blake; Moeller, F Gerard

2013-12-01

106

Dopamine agonists and the suppression of impulsive motor actions in Parkinson disease.  

Science.gov (United States)

The suppression of spontaneous motor impulses is an essential facet of cognitive control that is linked to frontal-BG circuitry. BG dysfunction caused by Parkinson disease (PD) disrupts the proficiency of action suppression, but how pharmacotherapy for PD impacts impulsive motor control is poorly understood. Dopamine agonists improve motor symptoms of PD but can also provoke impulsive-compulsive behaviors (ICB). We investigated whether dopamine agonist medication has a beneficial or detrimental effect on impulsive action control in 38 PD patients, half of whom had current ICB. Participants performed the Simon conflict task, which measures susceptibility to acting on spontaneous action impulses as well as the proficiency of suppressing these impulses. Compared with an off-agonist state, patients on their agonists were no more susceptible to reacting impulsively but were less proficient at suppressing the interference from the activation of impulsive actions. Importantly, agonist effects depended on baseline performance in the off-agonist state; more proficient suppressors off agonist experienced a reduction in suppression on agonist, whereas less-proficient suppressors off agonist showed improved suppression on agonist. Patients with active ICB were actually less susceptible to making fast, impulsive response errors than patients without ICB, suggesting that behavioral problems in this subset of patients may be less related to impulsivity in motor control. Our findings provide further evidence that dopamine agonist medication impacts specific cognitive control processes and that the direction of its effects depends on individual differences in performance off medication. PMID:22571461

Wylie, Scott A; Claassen, Daniel O; Huizenga, Hilde M; Schewel, Kerilyn D; Ridderinkhof, K Richard; Bashore, Theodore R; van den Wildenberg, Wery P M

2012-08-01

107

Dopamine Agonists and the Suppression of Impulsive Motor Actions in Parkinson's Disease  

Science.gov (United States)

The suppression of spontaneous motor impulses is an essential facet of cognitive control that is linked to frontal-basal ganglia circuitry. Basal ganglia dysfunction caused by Parkinson’s disease (PD) disrupts the proficiency of action suppression, but how pharmacotherapy for PD impacts impulsive motor control is poorly understood. Dopamine agonists improve motor symptoms of PD, but can also provoke impulsive-compulsive behaviors (ICB). We investigated whether dopamine agonist medication has a beneficial or detrimental effect on impulsive action control in thirty-eight PD patients, half of whom had current ICB. Participants performed the Simon conflict task, which measures susceptibility to acting on spontaneous action impulses as well as the proficiency of suppressing these impulses. Compared to an off agonist state, patients on their agonist were no more susceptible to reacting impulsively, but were less proficient at suppressing the interference from the activation of impulsive actions. Importantly, agonist effects depended on baseline performance in the off agonist state; more proficient suppressors off agonist experienced a reduction in suppression on agonist, whereas less proficient suppressors off agonist showed improved suppression on agonist. Patients with active ICB were actually less susceptible to making fast, impulsive response errors than patients without ICB, suggesting that behavioral problems in this subset of patients may be less related to impulsivity in motor control. Our findings provide further evidence that dopamine agonist medication impacts specific cognitive control processes and that the direction of its effects depends on individual differences in performance off medication. PMID:22571461

Wylie, S.A.; Claassen, D.O.; Huizenga, H.M.; Schewel, K.D.; Ridderinkhof, K.R.; Bashore, T.R.; van den Wildenberg, W.P.M.

2012-01-01

108

An introduction to impulse radar  

Science.gov (United States)

An impulse radar is one whose waveform is a single cycle sinewave. Its most distinctive characteristic is its very wide relative bandwidth. Much has been said and claimed for such a radar, as compared to conventional narrowband radar; but there is very little written about what it is, what it can and cannot do, and what is required to achieve such radars in practice. A description is presented of the spectrum of an impulse radar as compared to the more usual short pulse radar. The requirements, problems, and current technology of the various subsystem that make up an impulse radar (transmitters, receivers, and antennas) are discussed. All three of these major subsystems for an impulse radar are presently far from adequate for practical applications (other than for probing underground). A number of problem areas are reviewed, including electromagnetic compatibility, target scattering, the radar is discussed and the differences noted. Several potential applications are briefly reviewed, including target-to-clutter enhancement, target recognition, resolution of low altitude multipath, and target scattering enhancement, as well as its successful use for underground probing. Currently, the claims made for many of the proposed applications were justified, but the major differences between the impulse radar and conventional radar provide interesting technical challenges that would be worthy of fundamental investigation and understanding.

Skolnik, Merrill I.

1990-11-01

109

Modifying the risk associated with an impulsive temperament: a prospective study of drug dependence treatment.  

Science.gov (United States)

The evidence linking the personality trait of impulsivity and substance misuse is well established. Importantly, impulsivity not only predicts substance misuse problems but has an association with duration in treatment, likelihood of completing treatment and time to relapse. Treatment that focuses on increasing awareness and acceptance of thoughts and emotions may potentially address impulsive behaviour and in this respect improve treatment outcomes for substance misuse. The current paper investigated the relationship between the facet of impulsivity that taps into poor inhibitory control and treatment outcome. In addition, there was a specific focus on ascertaining the impact of an increase in awareness and attentional control measured in 144 adult substance users receiving treatment in a residential therapeutic community. Impulsivity predicted poorer treatment outcome (measured as drug use severity). Increases in awareness and acceptance of emotions and thoughts during treatment were related to better outcome although this was not associated with baseline levels of impulsivity. Clinical and theoretical implications are discussed. PMID:24924874

Staiger, Petra K; Dawe, Sharon; Richardson, Ben; Hall, Kate; Kambouropoulos, Nicolas

2014-11-01

110

Impulsive Neural Networks Algorithm Based on the Artificial Genome Model  

Directory of Open Access Journals (Sweden)

Full Text Available To describe gene regulatory networks, this article takes the framework of the artificial genome model and proposes impulsive neural networks algorithm based on the artificial genome model. Firstly, the gene expression and the cell division tree are applied to generate spiking neurons with specific attributes, neural network structure, connection weights and specific learning rules of each neuron. Next, the gene segment duplications and divergence model are applied to design the evolutionary algorithm of impulsive neural networks at the level of the artificial genome. The dynamic changes of developmental gene regulatory networks are controlled during the whole evolutionary process. Finally, the behavior of collecting food for autonomous intelligent agent is simulated, which is driven by nerves. Experimental results demonstrate that the algorithm in this article has the evolutionary ability on large-scale impulsive neural networks

Yuan Gao

2014-05-01

111

Impulsivity: four ways five factors are not basic to addiction.  

Science.gov (United States)

Several impulsivity-related models have been applied to understanding the vulnerability to addiction. While there is a growing consensus that impulsivity is multifaceted, debate continues as to the precise number of facets and, more critically, which are most relevant to explaining the addiction-risk profile. In many ways, the current debate mirrors that which took place in the personality literature in the early 1990s (e.g., Eysenck's 'Big Three' versus Costa and McCrae's 'Big Five'). Indeed, many elements of this debate are relevant to the current discussion of the role of impulsivity in addictive behavior. Specifically, 1) the use of factor analysis as an atheoretical 'truth-grinding machine'; 2) whether additional facets add explanatory power over fewer; 3) the delineation of specific neurocognitive pathways from each facet to addictive behaviors, and; 4) the relative merit of 'top-down' versus 'bottom-up' approaches to the understanding of impulsivity. Ultimately, the utility of any model of impulsivity and addiction lies in its heuristic value and ability to integrate evidence from different levels of analysis. Here, we make the case that theoretically-driven, bottom-up models proposing two factors deliver the optimal balance of explanatory power, parsimony, and integration of evidence. PMID:24576666

Gullo, Matthew J; Loxton, Natalie J; Dawe, Sharon

2014-11-01

112

Dynamic behavior of the quantum Zakharov-Kuznetsov equations in dense quantum magnetoplasmas  

International Nuclear Information System (INIS)

Quantum Zakharov-Kuznetsov (qZK) equation is found in a dense quantum magnetoplasma. Via the spectral analysis, we investigate the Hamiltonian and periodicity of the qZK equation. Using the Hirota method, we obtain the bilinear forms and N-soliton solutions. Asymptotic analysis on the two-soliton solutions shows that the soliton interaction is elastic. Figures are plotted to reveal the propagation characteristics and interaction between the two solitons. We find that the one soliton has a single peak and its amplitude is positively related to He, while the two solitons are parallel when He?e is proportional to the ratio of the strength of magnetic field to the electronic Fermi temperature. External periodic force on the qZK equation yields the chaotic motions. Through some phase projections, the process from a sequence of the quasi-period doubling to chaos can be observed. The chaotic behavior is observed since the power spectra are calculated, and the quasi-period doubling states of perturbed qZK equation are given. The final chaotic state of the perturbed qZK is obtained

113

Dust acoustic solitary and shock excitations in a Thomas-Fermi magnetoplasma  

Science.gov (United States)

The linear and nonlinear properties of dust-acoustic waves are investigated in a collisionless Thomas-Fermi magnetoplasma, whose constituents are electrons, ions, and negatively charged dust particles. At dust time scale, the electron and ion number densities follow the Thomas-Fermi distribution, whereas the dust component is described by the classical fluid equations. A linear dispersion relation is analyzed to show that the wave frequencies associated with the upper and lower modes are enhanced with the variation of dust concentration. The effect of the latter is seen more strongly on the upper mode as compared to the lower mode. For nonlinear analysis, we obtain magnetized Korteweg-de Vries (KdV) and Zakharov-Kuznetsov (ZK) equations involving the dust-acoustic solitary waves in the framework of reductive perturbation technique. Furthermore, the shock wave excitations are also studied by allowing dissipation effects in the model, leading to the Korteweg-de Vries-Burgers (KdVB) and ZKB equations. The analysis reveals that the dust-acoustic solitary and shock excitations in a Thomas-Fermi plasma are strongly influenced by the plasma parameters, e.g., dust concentration, dust temperature, obliqueness, magnetic field strength, and dust fluid viscosity. The present results should be important for understanding the solitary and shock excitations in the environments of white dwarfs or supernova, where dust particles can exist.

Rahim, Z.; Ali, S.; Qamar, A.

2014-07-01

114

Whistler wave excitation by a loop antenna in a bounded collisional magnetoplasma  

International Nuclear Information System (INIS)

Excitation of electromagnetic waves by spatially bounded given electric currents in the presence of an axially magnetized cylindrical plasma column surrounded by free space is studied. A rigorous solution for the total field comprising both the discrete and continuous parts of the spatial spectrum of the excited waves is found. Using the obtained field representation, an expression for the impedance of a loop antenna is derived and the contributions of guided and unguided modes of the column to the antenna impedance are determined for the whistler frequency range. Conditions have been revealed under which the real part of the antenna impedance is dominated by the contribution of guided waves. It is shown that when allowance for relatively small collisional losses in the plasma results in division of the guided whistler waves into weakly and strongly damped modes with significantly different field structures, appreciable redistribution of the antenna-launched power among the excited modes takes place. The results obtained are useful for clarification of the power-absorption mechanisms of whistler-range waves in a cylindrical magnetoplasma

115

Dynamics of the excitation of an upper hybrid wave by a rippled laser beam in magnetoplasma  

International Nuclear Information System (INIS)

This paper presents the effects of a laser spike (superimposed on an intense laser beam) and a static magnetic field on the excitation of the upper hybrid wave (UHW) in a hot collisionless magnetoplasma, taking into account the relativistic nonlinearity. The laser beam is propagating perpendicular to the static magnetic field and has its electric vector polarized along the direction of the static magnetic field (ordinary mode). Analytical expressions for the growth rate of the ripple, the beam width of the rippled laser beam, and the UHW have been obtained. It is found that the coupling among the main laser beam, ripple, and UHW is strong. The ripple gets focused when the initial power of the laser beam is greater than the critical power for focusing. It has been shown that the presence of a laser spike affects significantly the growth rate and the dynamics of the UHW. In addition, it has been seen that the effect of changing the strength of the static magnetic field on the nonlinear coupling and on the dynamics of the excitation of the UHW is significant. The results are presented for typical laser plasma parameters

116

Nongyrotropy in magnetoplasmas: simulation of wave excitation and phase-space diffusion  

Directory of Open Access Journals (Sweden)

Full Text Available Nongyrotropic (gyrophase bunched ion distributions in a magnetoplasma are studied by analytical methods and by two-dimensional hybrid code simulations. Nongyrotropy may not occur in a plasma being simultaneously homogeneous, stationary, and solenoidal in phase space. A detailed study is performed for a homogeneous and stationary plasma with sources and sinks in phase space. The analytical investigation cast in the framework of linearized Maxwell-Vlasov theory yields a coupling of low-frequency left-handed, right-handed, and longitudinal modes. Nongyrotropic ion distributions are unstable; they excite left-handed waves. The growth rate is comparable to that of the ion ring instability. The hybrid code simulation study confirms the expected propagation direction parallel to the background magnetic field. Three diffusion processes are studied: arc lengthening, arc broadening, and arc radius decreasing corresponding to particle energy diffusion. The characteristic diffusion time-scales are found to be of the order of 101 wave cycles.

U. Motschmann

117

Eruption of an arched magnetic flux rope in an ambient magnetoplasma  

Science.gov (United States)

Arched magnetic flux ropes (AMFRs) are arch-shaped, current-carrying, magnetized plasma structures that ubiquitously exist in the solar atmosphere. A laboratory plasma experiment [Tripathi and Gekelman, PRL 105, 075005 (2010)] has been built to study the eruption of AMFRs in two essential steps: (i) production of an AMFR (n˜ 10^19 m-3, Te˜14 eV, B˜1 kG, L˜0.5 m) with a persistent appearance lasting several Alfven transit times using a Lanthnum Hexaboride (LaB6) plasma source, and (ii) generation of controlled plasma flows from the foot-points of the AMFR using two laser beams (1064 nm, 1 J/pulse). An additional LaB6 source produces a large magnetoplasma in the background. The laser generated flows drive the eruption by injecting plasma and magnetic flux in the AMFR. The experiment is highly reproducible and runs continuously with a 0.5 Hz repetition rate, hence evolution of the AMFR is recorded using computer-controlled movable probes in 3D. High-speed imaging, Langmuir and 3-axis magnetic-loop probes are the main diagnostic tools. New results from this experiment on global kink-mode oscillations of the AMFR, excitation of fast waves, and ejection of a large magnetic flux rope from the apex of the AMFR will be presented.

Tripathi, Shreekrishna; Gekelman, Walter

2012-10-01

118

Electric field variability and classifications of Titan's magnetoplasma environment  

Directory of Open Access Journals (Sweden)

Full Text Available The atmosphere of Saturn's largest moon Titan is driven by photochemistry, charged particle precipitation from Saturn's upstream magnetosphere, and presumably by the diffusion of the magnetospheric field into the outer ionosphere, amongst other processes. Ion pickup, controlled by the upstream convection electric field, plays a role in the loss of this atmosphere. The interaction of Titan with Saturn's magnetosphere results in the formation of a flow-induced magnetosphere. The upstream magnetoplasma environment of Titan is a complex and highly variable system and significant quasi-periodic modulations of the plasma in this region of Saturn's magnetosphere have been reported. In this paper we quantitatively investigate the effect of these quasi-periodic modulations on the convection electric field at Titan. We show that the electric field can be significantly perturbed away from the nominal radial orientation inferred from Voyager 1 observations, and demonstrate that upstream categorisation schemes must be used with care when undertaking quantitative studies of Titan's magnetospheric interaction, particularly where assumptions regarding the orientation of the convection electric field are made.

C. S. Arridge

2011-07-01

119

Dust grain dynamics due to nonuniform and nonstationary high-frequency radiations in cold magnetoplasmas  

Directory of Open Access Journals (Sweden)

Full Text Available A general nonlinear theory for low-frequency electromagnetic field generation due to high-frequency nonuniform and nonstationary electromagnetic radiations in cold, uniform, multicomponent, dusty magnetoplasmas is developed. This theory permits us to consider the nonlinear action of all waves that can exist in such plasmas. The equations are derived for the dust grain velocities in the low-frequency nonlinear electric fields arising due to the presence of electromagnetic cyclotron waves travelling along the background magnetic field. The dust grains are considered to be magnetized as well as unmagnetized. Different regimes for the dust particle dynamics, depending on the spatio-temporal change of the wave amplitudes and plasma parameters, are discussed. It is shown that induced nonlinear electric fields can have both an electrostatic and electromagnetic nature. Conditions for maximum dust acceleration are found. The results obtained may be useful for understanding the possible mechanisms of dust grain dynamics in astrophysical, cosmic and laboratory plasmas under the action of nonuniform and nonstationary electromagnetic waves.

A. K. Nekrasov

2006-03-01

120

Impulsivity and Attention Deficit-Hyperactivity Disorder: Subtype Classification Using the UPPS Impulsive Behavior Scale  

Science.gov (United States)

This study examined the classification accuracy of the UPPS Impulsive Behavior Scale (UPPS) in discriminating several attention deficit/hyperactivity disorder (ADHD) subtypes, including predominantly inattentive type (ADHD/I), combined type (ADHD/C), and combined type with behavioral problems (ADHD/ODD), between each other and a non-ADHD control group using logistic regression analyses. The sample consisted of 88 children ranging in age from 9.0 years to 12.8 years, with a mean of 10.9 years. Children were predominantly male (74%) and Caucasian (86%) and in grades 3–7. Results indicated that the UPPS performed well in classifying ADHD subtypes relative to traditional diagnostic measures. In addition, analyses indicated that differences in symptoms between subtypes can be explained by specific pathways to impulsivity. Implications for the assessment of ADHD and conceptual issues are discussed. PMID:21765593

Derefinko, Karen J.; Lynam, Donald R.; Milich, Richard; Fillmore, Mark T.

2011-01-01

 
 
 
 
121

Teaching About Impulse and Momentum  

Science.gov (United States)

This AAPT/PTRA manual on Teaching about Impulse and Momentum contains background and activities to help students with this topic. Samples from the full print manual are available here. In the complete manual, a section on theory and applications is followed by laboratory, classroom, and computer activities. The printed manual includes a section on modern physics applications of the topic as well assessment questions. For additional information about AAPT/PTRA see http://www.aapt.org/PTRA and about Teaching about Impulse and Momentum manual see the AAPT Store.

Franklin, William

2005-12-15

122

Measurements of laser generated impulse  

Energy Technology Data Exchange (ETDEWEB)

The total impulse delivered by pulsed-laser illumination of planar targets in vacuum. Data are presented for several target materials (aluminum and some of its alloys, titanium, and kevlar/epoxy structural composite) as a function of incident fluence for laser wavelengths of 248 nm, 2.8 ..mu..m, and 10.6 ..mu..m. 4 tabs.

King, T.; Barrus, D.; Dingus, R.; Osborne, Z.; Phipps, C.

1986-01-01

123

Online Impulse Buying and Product Involvement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Do consumers behavior different on the Internet from other marketing channels? This study investigates impulse buying behaviors in both traditional store and online shopping contexts. The results show that impulsive buying tendency and involvement with clothing products is positively associated with impulse buying behavior of clothing in traditional store shopping, but not online. For computer peripherals, on the other hand, higher impulsive buying tendency and higher product involvement are ...

Tsai Chen

2008-01-01

124

Impulse sales cooler. Final report  

Energy Technology Data Exchange (ETDEWEB)

In the past years, the use of impulse coolers has increased considerably and it is estimated that at least 30.000 are installed in shops in Denmark. In addition, there are many small barrel-shaped can coolers. Most impulse coolers are open, which results in a large consumption of energy, and the refrigeration systems are often quite inefficient. A typical impulse cooler uses app. 5 - 8 kWh/day corresponding to a consumption of energy in the magnitude of 60 GWh/year. For several years, the Danish company Vestfrost A/S has produced an impulse sales cooler in the high-efficiency end and the energy consumption of the cooler is measured to be 4.15 kWh/day. The POS72 cooler formed the baseline of this project. At the start-up meeting in 2008, several ideas were discussed with the objective to reduce energy consumption and to use natural refrigerants. Among the ideas were better air curtains, removable lids, better condensers, use of R600a refrigeration system and better insulation. Three generations of prototypes were built and tested in a climate chamber at Danish Technological Institute and the third generation showed very good performance: the energy consumption was measured to 2.215 kWh/day, which is a 47% reduction compared to the baseline. That was achieved by: 1) Improving the cold air cycling system including the air curtain. 2) Using the natural refrigerant R600a (isobutane) and the Danfoss NLE9KTK compressor, which has better efficiency compared to the compressor in the baseline product. 3) Using a box type condenser without fins (preventing dust build-up) and with a relatively high surface area. 4) Improving the insulation value of the plastic cabinet by reducing turbulence in the air gap between the plastic walls and improving the insulation value of the EPS moulded insulation surrounding the refrigeration system at the bottom of the cooler. 5) Preventing short-circuit of warm air around the condenser. 6) The improvements are cost efficient and will not add much to the cost of the cooler. The development project has resulted in a unique impulse sales cooler using natural refrigerant and a refrigeration system, which consumes about half the amount of energy compared to the previous Vestfrost impulse cooler and less than half of the energy compared to other types of impulse sales coolers. (LN)

Pedersen, Per Henrik (DTI, Taastrup (Denmark))

2010-11-15

125

Baseline impulsive choice predicts the effects of nicotine and nicotine withdrawal on impulsivity in rats.  

Science.gov (United States)

Impulsive choice, a form of impulsivity, is associated with tobacco smoking in humans. Trait impulsivity may be a vulnerability factor for smoking, or smoking may lead to impulsive behaviors. We investigated the effects of 14-day nicotine exposure (6.32mg/kg/day base, subcutaneous minipumps) and spontaneous nicotine withdrawal on impulsive choice in low impulsive (LI) and high impulsive (HI) rats. Impulsive choice was measured in the delayed reward task in which rats choose between a small immediate reward and a large delayed reward. HI and LI rats were selected from the highest and lowest quartiles of the group before exposure to nicotine. In non-selected rats, nicotine or nicotine withdrawal had no effect on impulsive choice. In LI rats, chronic nicotine exposure decreased preference for the large reward with larger effects at longer delays, indicating increased impulsive choice. Impulsive choices for the smaller immediate rewards continued to increase during nicotine withdrawal in LI rats. In HI rats, nicotine exposure and nicotine withdrawal had no effect on impulsive choice, although there was a tendency for decreased preference for the large reward at short delays. These results indicate that nicotine- and nicotine withdrawal-induced increases in impulsive choice depend on trait impulsivity with more pronounced increases in impulsive choice in LI compared to HI subjects. Increased impulsivity during nicotine exposure may strengthen the addictive properties of nicotine and contribute to compulsive nicotine use. PMID:24060391

Kayir, Hakan; Semenova, Svetlana; Markou, Athina

2014-01-01

126

Targeting impulsivity in Parkinson's disease using atomoxetine.  

Science.gov (United States)

Noradrenergic dysfunction may play a significant role in cognition in Parkinson's disease due to the early degeneration of the locus coeruleus. Converging evidence from patient and animal studies points to the role of noradrenaline in dopaminergically insensitive aspects of the parkinsonian dysexecutive syndrome, yet the direct effects of noradrenergic enhancement have not to date been addressed. Our aim was to directly investigate these, focusing on impulsivity during response inhibition and decision making. To this end, we administered 40 mg atomoxetine, a selective noradrenaline re-uptake inhibitor to 25 patients with Parkinson's disease (12 female /13 male; 64.4 ± 6.9 years old) in a double blind, randomized, placebo controlled design. Patients completed an extensive battery of neuropsychological tests addressing response inhibition, decision-making, attention, planning and verbal short term memory. Atomoxetine improved stopping accuracy on the Stop Signal Task [F(1,19) = 4.51, P = 0.047] and reduced reflection impulsivity [F(1,9) = 7.86, P = 0.02] and risk taking [F(1,9) = 9.2, P = 0.01] in the context of gambling. The drug also conferred effects on performance as a function of its measured blood plasma concentration: it reduced reflection impulsivity during information sampling [adjusted R(2) = 0.23, F(1,16) = 5.83, P = 0.03] and improved problem solving on the One Touch Stockings of Cambridge [adjusted R(2) = 0.29, F(1,17) = 8.34, P = 0.01]. It also enhanced target sensitivity during sustained attention [F(1,9) = 5.33, P = 0.046]. The results of this exploratory study represent the basis of specific predictions in future investigations on the effects of atomoxetine in Parkinson's disease and support the hypothesis that targeting noradrenergic dysfunction may represent a new parallel avenue of therapy in some of the cognitive and behavioural deficits seen in the disorder. PMID:24893708

Kehagia, Angie A; Housden, Charlotte R; Regenthal, Ralf; Barker, Roger A; Müller, Ulrich; Rowe, James; Sahakian, Barbara J; Robbins, Trevor W

2014-07-01

127

Distinctive features of ion-acoustic solitons in EPI super-dense magneto-plasmas with degenerate electrons and positrons  

CERN Document Server

Using the extended Poincar\\'{e}-Lighthill-Kuo (PLK) reductive perturbation method to study the small-amplitude ion acoustic solitary wave (IASW) dynamics (propagation and interaction), it is shown that in Thomas-Fermi magneto-plasma consisting of inertial-less degenerate electrons and positrons and isothermal ions, distinctive features emerge when the ultra-relativistic degeneracy pressure applies to electrons and positrons. Calculations show that ion-acoustic solitary waves may interact differently in such plasmas under ultra-relativistic degeneracy pressure.

Akbari-Moghanjoughi, M

2010-01-01

128

Stroop test performance in impulsive and non impulsive patients with Parkinson's disease.  

Science.gov (United States)

Impulsive personalities are considered to have a general impairment in cognitive flexibility and cortical inhibition. To examine this hypothesis we used a trial by trial Stroop task in impulsive and non impulsive patients with Parkinson's disease (PD) and recorded errors and reaction times (RT). We tested 28 impulsive PD (PD+ICB) and 24 non impulsive PD (PD-ICB) patients prior to and after dopaminergic medication. These results were compared with 24 age matched normal controls. We found an increased error rate in all PD patients prior to their usual medication which resolved after medication. Furthermore patients on medication showed enhanced cognitive flexibility and shorter RT. There was no difference between non impulsive and impulsive PD patients. This suggests that the impulsive behaviours may not affect response inhibition tasks and the response inhibition required in the Stroop test does not engage the same processes that differentiate impulsive and non-impulsive PD patients, which likely involve mesolimbic dopamine. PMID:21247790

Djamshidian, Atbin; O'Sullivan, Sean S; Lees, Andrew; Averbeck, Bruno B

2011-03-01

129

Neuroanatomical and Neurochemical Basis of Impulsivity  

Directory of Open Access Journals (Sweden)

Full Text Available The term ‘impulsivity’ encompasses a multitude of behaviours that are poorly conceived, premature, inappropriate, and that frequently result in unwanted or deleterious outcomes. Impulsivity manifests as impatience carelessness, risk-taking, sensation-seeking and pleasure-seeking, an underestimated sense of harm, and extroversion. Impulsivity is a core symptom of a broad spectrum of psychiatric disorders. Through focusing on different aspects of impulsive behavior, it has proved possible to devise a variety of behavioral paradigms to measure impulsivity in both human and non-human subjects. These can be broadly divided into two categories: those measuring impulsive action or motoric impulsivity, and those measuring impulsive choice or impulsive decision-making. Impulsive action can be broadly defined as the inability to withhold from making a response. Within the framework of behavioral neuroscience and cognitive psychology, impulse control has been described as an active inhibitory mechanism which modulates the internally or externally driven pre-potent desire for primary reinforcers such as food, sex or other highly desirable rewards. This inhibitory control mechanism may provide the substrate by which rapid conditioned responses and reflexes are transiently suppressed, so that slower cognitive mechanisms can guide behavior. This process is referred to as response inhibition. Two of the most common tests used to study inhibitory processes are the go/no-go and stop-signal reaction time tasks. Impulsivity is also evident in the making of impulsive decisions or choices as well as in impulsive actions. Here, there is no “pre-potent” response that is primed and then forcibly inhibited, but a decision-making processes. Impulsive decision making or impulsive choice is defined as initiating actions without adequately considering other possible choices or consequences. Impulsive choice is typically measured in the delay discounting paradigm. In tis paradigm, the tendency to prefer small immediate rewards over larger, more delayed reinforcers is measured. ?mpulsive choice is defined by a greater tendency to value or choose smaller, more immediate reinforcers. Impulsivity is a multi-faceted behaviour. This behaviour may be studied by subdividing it into different processes neuroanatomically and neurochemically. Neuroanatomical data support the suggestion that behavioral disinhibition (impulsive action / motoric impulsivity and delay-discounting (impulsive choice / decision making differ in the degree to which various components of frontostriatal loops are implicated in their regulation. The dorsal prefrontal cortex does not appear to be involved in mediating impulsive choice, yet does have some role in regulating inhibitory processes. In contrast, there appears to be a pronounced role for the orbitofrontal cortex and basolateral amygdala in controlling impulsive choice. Other structures, however, such as the nucleus accumbens and subthalamic nucleus may be common to both circuits. From the neurochemical perspective, dopamine system and dopamine- 2 (D2 receptors in particular, seems to be closely involved in making impulsive choice. When the noradrenaline system does not function optimally, it might contribute to increased impulsivity. Serotonin might act upon prefrontal cortex to decrease impulsive choices. Interactions between the serotonin and the dopamine systems are important in the regulation of impulsive behaviour. It is possible that various receptor subtypes of the serotonin system may exert differing and even contrasting effects on impulsive behaviour. Although it is very informative to study neurotransmitter systems separately, it should be kept in mind that there are very intimate interactions between the neurotransmitter systems mentioned above. Based on the fact that impulsivity is regulated through multiple neurotransmitters and even more receptors, one may suggest that pharmacotherapy of impulsivity requires a drug acting on more than one receptor. In addition, when considering improving

Kemal Yazici

2010-08-01

130

Self-organization of local magnetoplasma structures in the upper layers of the solar convection zone  

International Nuclear Information System (INIS)

Self-organization and evolution of magnetoplasma structures in the upper layers of the solar convection zone are discussed as a process of diffuse aggregation of magnetic flux tubes. Equations describing the tube motion under the action of magnetic interaction forces, hydrodynamic forces, and random forces are written explicitly. The process of aggregation of magnetic flux tubes into magnetic flux clusters of different shapes and dimensions is simulated numerically. The obtained structures are compared with the observed morphological types of sunspot groups. The quantitative comparison with the observational data was performed by comparing the fractal dimensions of the photospheric magnetic structures observed in solar active regions with those of structures obtained in the numerical experiment. The model has the following free parameters: the numbers of magnetic flux tubes with opposite polarities on the considered area element (Nn and Ns), the average radius of the cross section of the magnetic flux tube (a), its effective length (l), the twist factor of the tube field (k), and the absolute value of the average velocity of chaotic tube displacements (d). Variations in these parameters in physically reasonable limits leads to the formation of structures (tube clusters of different morphological types) having different fractal dimensions. Using the NOAA 10488 active region, which appeared and developed into a complicated configuration near the central meridian, as an example, it is shown that good quantitative agreement between the fractal dimensions is achieved at the following parameters of the model: Nn = Ns = 250 ± 50; a = 150 ± 50 km; l ? 5000 km, and d = 80 ± 10 m/s. These results do not contradict the observational data and theoretical estimates obtained in the framework of the Parker “spaghetti” model and provide new information on the physical processes resulting in the origin and evolution of local magnetic plasma structures in the near-photospheric layers of the solar convection zone

131

Non-linear diffusion of charged particles in a turbulent magnetoplasma  

International Nuclear Information System (INIS)

A unified theory is presented which describes non-linear effects on relative and absolute diffusion of charged particles in a magnetoplasma, in analogy with analogous methods used for diffusion studies of pollutants in the environment. Explicit results are obtained for non-linear diffusion of test particles represented by their guiding centers in a turbulent energy spectrum in K-1 and K-3, which corresponds to recent measurements in the T.F.R. Tokamak. As expected, a BOHM scaling of the absolute diffusion coefficient is obtained for frozen turbulence. The growth of an initially small cloud of particles in an arbitrary turbulent medium corresponds to the process of relative diffusion. It is described by a generalization of the Brownian motion, including a first stage of very slow initial relative diffusion, followed by a stage of rapid expansion of the cloud up to the final stage in which particles become uncorrelated, and Brownian diffusion is reached asymptotically. The stage of exponential growth, observed in fluid turbulence corresponds to the clump effect in plasma turbulence. It is entirely due to the effect of trajectory correlations. The LJAPUNOV exponent of this exponential separation is obtained analytically. Numerical solutions of the diffusion equation are presented for the effective radius of the cloud as function of time in the case of a model spectrum of drift-wave turbulence. When compared with classical Brownian diffusion of uncorrelated particles, the effective ''diffusion coefficient'' for correlated particles is found to be reduced by orders of magnitude for rather long times. Practical implications for experimental situations are also discussed (Barium clouds released in the ionosphere, pellet injection in e.g. Tokamaks)

132

Online Impulse Buying and Product Involvement  

Directory of Open Access Journals (Sweden)

Full Text Available Do consumers behavior different on the Internet from other marketing channels? This study investigates impulse buying behaviors in both traditional store and online shopping contexts. The results show that impulsive buying tendency and involvement with clothing products is positively associated with impulse buying behavior of clothing in traditional store shopping, but not online. For computer peripherals, on the other hand, higher impulsive buying tendency and higher product involvement are positively associated with higher impulse buying online, but not in-store shopping.

Tsai Chen

2008-12-01

133

The relationship between temperament and impulsive behaviors in eating disordered subjects.  

Science.gov (United States)

To date, few studies have examined the personality characteristics and clinical predictors of impulsive behaviors in eating disorders (ED). The aim of this work was to study the prevalence of a wide range of impulsive behaviors in a sample of 554 ED subjects and to examine the predictors of these behaviors. Subjects were diagnosed according to DSM-IV criteria as having anorexia nervosa restricting type (ANR; n = 183), anorexia nervosa binge eating/purging type (ANBP; n = 65), bulimia nervosa purging type (BNP; n = 244), and bulimia nervosa nonpurging type (BNNP; n = 62). Nine different types of impulsive behaviors were assessed in these groups. About 55% of the whole sample reported at least one type of impulsive behavior, 35% more than one, and about 13% more than three. According to findings, impulsive and multi-impulsive subjects are characterized by the presence of purging behavior and by specific temperamental features such as high levels of novelty seeking and low persistence. The prediction of impulsive behavior is further improved by considering the presence of a history of childhood abuse, maternal psychiatric morbidity, and some specific psychological symptoms such as maturity fears, perfectionism, depression, and obsessive-compulsive symptoms. The presence of impulsive behavior appears to be associated with overall higher levels of psychiatric symptomatology and eating psychopathology, thus indicating that they are an important feature to be considered in the assessment and treatment of ED. PMID:16864331

Favaro, Angela; Zanetti, Tatiana; Tenconi, Elena; Degortes, Daniela; Ronzan, Andrea; Veronese, Angela; Santonastaso, Paolo

2005-01-01

134

Colliding Plane Impulsive Gravitational Waves  

Digital Repository Infrastructure Vision for European Research (DRIVER)

When two non-interacting plane impulsive gravitational waves undergo a head-on collision, the vacuum interaction region between the waves after the collision contains backscattered gravitational radiation from both waves. The two systems of backscattered waves have each got a family of rays (null geodesics) associated with them. We demonstrate that if it is assumed that a parameter exists along each of these families of rays such that the modulus of the complex shear of each...

Barrabe?s, C.; Bressange, G. F.; Hogan, P. A.

2000-01-01

135

Imaging impulse control disorders in Parkinson's disease and their relationship to addiction.  

Science.gov (United States)

Established substance addictions and impulse control disorders (ICDs) such as pathological gambling share similar underlying neurobiology, and recent data extends these commonalities to the risk factors that increase an individuals' susceptibility to develop such behaviours. In Parkinson's disease (PD), impulse control disorders (ICDs) are increasingly recognised to develop after patients begin dopamine (DA) restoration therapy, in particular DA agonists. In both the PD and non-PD population, more impulsive individuals are at increased risk for impulse control disorders. Here, we review the neuroimaging data confirming the connection between addiction and ICDs, and revealing how DA agonists might cause specific alterations of basal ganglia and cortical function that vary as a function of an individuals' propensity for impulsivity. PMID:23232664

Ray, Nicola J; Strafella, Antonio P

2013-04-01

136

Linking Impulsivity and Inhibitory Control Using Manual and Oculomotor Response Inhibition Tasks  

Science.gov (United States)

Separate cognitive processes govern the inhibitory control of manual and oculomotor movements. Despite this fundamental distinction, little is known about how these inhibitory control processes relate to more complex domains of behavioral functioning. This study sought to determine how these inhibitory control mechanisms relate to broadly defined domains of impulsive behavior. Thirty adults with attention-deficit/hyperactivity disorder (ADHD) and 28 comparison adults performed behavioral measures of inhibitory control and completed impulsivity inventories. Results suggest that oculomotor inhibitory control, but not manual inhibitory control, is related to specific domains of self-reported impulsivity. This finding was limited to the ADHD group; no significant relations between inhibitory control and impulsivity were found in comparison adults. These results highlight the heterogeneity of inhibitory control processes and their differential relations to different facets of impulsivity. PMID:21982865

Roberts, Walter; Fillmore, Mark T.; Milich, Richard

2011-01-01

137

A Review of Impulse Buying Behavior  

Directory of Open Access Journals (Sweden)

Full Text Available Researchers and Practitioners have been interested in the field of impulse buying for the past sixty years (Clover,1950; Stern, 1962; Rook, 1987; Peck and Childers, 2006; Chang et.al, 2011. The purpose of this paper is toprovide a detailed account of the impulse buying behavior by compiling the various research works literature inthe field of Retailing and Consumer Behavior. It gives a broad overview of the impulse buying construct and thevarious behavior related aspects. A wide range of journal databases and books were referred to review the worksof various researchers. The content analysis of the various research works led to the classification of literatureinto different factors influencing impulse buying and further development of research framework. The multipleaspects of the subject are categorized for future research works in the area of impulse buying with thesuggestions. The paper will be useful for marketing practitioners and researchers towards comprehensiveunderstanding of the consumer’s impulsiveness.  

G. Muruganantham

2013-04-01

138

Prueba de impulso cefálico Head impulse test  

Directory of Open Access Journals (Sweden)

Full Text Available Introducción: Dentro del estudio de la función del equilibrio, la prueba de impulso cefálico representa una herramienta rápida, sencilla y de fácil interpretación, que explora la indemnidad del reflejo óculo-vestibular. Este examen ha cobrado relevancia reciente como complemento a la prueba calórica en diversos contextos y no ha sido explorado en nuestro país. Objetivo: Explorar sensibilidad y especificidad de esta prueba en nuestro contexto local, junto con contribuir a la difusión de una herramienta de creciente relevancia en otoneurología. Material y método: Estudio prospectivo, ciego, de evaluación de test diagnóstico. En una muestra de pacientes consultando por vértigo agudo se realizó prueba de impulso cefálico al momento de la consulta inicial, y al momento de realizar prueba funcional de VIII par. Resultados: Se evaluaron 52 pacientes, 44% de ellos con disfunción vestibular según prueba calórica clásica como patrón de oro. La sensibilidad de la prueba de impulso cefálico fue de 47,6% y su especificidad de 83,9%, con un valor predictivo positivo y negativo de 66,7% y 70,3%. El acuerdo del examen entre dos evaluadores independientes fue alto (Kappa = 0,84. Discusiones: A pesar de una baja sensibilidad por sí sola, la prueba de impulso cuenta con una alta especificidad y un valor predictivo positivo razonable. Es además altamente reproducible, realizable en menos de un minuto y no genera náuseas u otros síntomas en el paciente. Consideramos este examen como un complemento al estudio de la función vestibular, con implicaciones prácticas en el inicio precoz de terapia y con importantes potencialidades en diversos ámbitos de la otoneurología.Introduction: In balance function evaluation, head impulse test is a fast, simple and easy to interpret test, which explores the vestibulo-ocular reflex. Having gained in the last decade growing importance as a complement to traditional caloric test, this test hasn't been explored in our context yet. Aim: To assess sensitivity and specificity of this test in our context, along with contributing to the spread of an increasingly important tool in otoneurology Material and method: A prospective, blinded, diagnostic test assessment. In a sample of patients consulting for acute vertigo, head impulse test was performed at the time of initial consultation, and at the time of VIII nerve functional testing. Results: We evaluated 52 patients, 44% with vestibular dysfunction as shown in caloric test results as gold standard. Sensitivity of the head impulse test was 47.6%, its specificity 83.9%, with positive and negative predictive value of 66.7% and 70.3% respectively. Agreement between two independent examiners was high (Kappa = 0.84. Discussion: Despite its low sensitivity, impulse test showed a high specificity and a reasonable positive predictive value. It was also highly reproductible, and generates no nausea or other symptoms in the patient. We consider this test as a complement to vestibular function evaluation, with clinical applicationssupportingearly onset of therapy. We believe this test to withhold significant potential in various otoneurological developing applications.

Hayo A Breinbauer K

2011-08-01

139

Impulsive differential inclusions a fixed point approach  

CERN Document Server

Impulsive differential equations have been developed in modeling impulsive problems in physics, population dynamics, ecology, biotechnology, industrial robotics, pharmacokinetics, optimal control, etc. The questions of existence and stability of solutions for different classes of initial values problems for impulsive differential equations and inclusions with fixed and variable moments are considered in detail. Attention is also given to boundary value problems and relative questions concerning differential equations. This monograph addresses a variety of side issues that arise from its simple

Ouahab, Abdelghani; Henderson, Johnny

2013-01-01

140

Hydrodynamic impulse in a compressible fluid  

International Nuclear Information System (INIS)

A suitable expression for hydrodynamic impulse in a compressible fluid is deduced. The development of appropriate impulse formulation for compressible Euler equations confirms the propriety of the hydrodynamic impulse expression for a compressible fluid given here. Implications of the application of this formulation to a compressible vortex ring are pointed out. Extension of Benjamin's variational characterization of a moving axisymmetric vortex system to a compressible fluid is explored.

 
 
 
 
141

Multiple Modes of Impulsivity in Parkinson's Disease  

Science.gov (United States)

Cognitive problems are a major factor determining quality of life of patients with Parkinson's disease. These include deficits in inhibitory control, ranging from subclinical alterations in decision-making to severe impulse control disorders. Based on preclinical studies, we proposed that Parkinson's disease does not cause a unified disorder of inhibitory control, but rather a set of impulsivity factors with distinct psychological profiles, anatomy and pharmacology. We assessed a broad set of measures of the cognitive, behavioural and temperamental/trait aspects of impulsivity. Sixty adults, including 30 idiopathic Parkinson's disease patients (Hoehn and Yahr stage I–III) and 30 healthy controls, completed a neuropsychological battery, objective behavioural measures and self-report questionnaires. Univariate analyses of variance confirmed group differences in nine out of eleven metrics. We then used factor analysis (principal components method) to identify the structure of impulsivity in Parkinson's disease. Four principal factors were identified, consistent with four different mechanisms of impulsivity, explaining 60% of variance. The factors were related to (1) tests of response conflict, interference and self assessment of impulsive behaviours on the Barrett Impulsivity Scale, (2) tests of motor inhibitory control, and the self-report behavioural approach system, (3) time estimation and delay aversion, and (4) reflection in hypothetical scenarios including temporal discounting. The different test profiles of these four factors were consistent with human and comparative studies of the pharmacology and functional anatomy of impulsivity. Relationships between each factor and clinical and demographic features were examined by regression against factor loadings. Levodopa dose equivalent was associated only with factors (2) and (3). The results confirm that impulsivity is common in Parkinson's disease, even in the absence of impulse control disorders, and that it is not a unitary phenomenon. A better understanding of the structure of impulsivity in Parkinson's disease will support more evidence-based and effective strategies to treat impulsivity. PMID:24465678

Nombela, Cristina; Rittman, Timothy; Robbins, Trevor W.; Rowe, James B.

2014-01-01

142

Design and Implementation of Impulse Distributed Waveform Generator – Time Interleaved Impulse Generator  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the design and implementation of impulse distributed waveform generator which generates UWB pulses with a bandwidth of 7GHz (1GHz to 8GHz.It utilizes time interleaved impulse generators to generate waveforms. Wide bandwidth is achieved by reducing the width of the impulses generated by time-interleaved impulse generators. Each of the impulse generators are triggered by the tunable delay unit which introduces the delay between the impulses generated. The Pulse shaping circuit shapes the impulses, by pulse amplitude tuning. The amplitude tuned impulses are combined together to obtain the waveform by using on-chip transmission line. Pulse width tuning and delay tuning makes this circuit reconfigurable. The pulse width can be tuned from 80ps to 1ns, and trigger delay can be varied from 30ps to 100ps.

S.Janaki

2013-06-01

143

Saturation of Richtmyer's impulsive model  

International Nuclear Information System (INIS)

In this Brief Communication, we use results from two-dimensional simulations to calculate for what product of perturbation wave number (k) and initial amplitude (a0) the Richtmyer impulsive model will fail in its prediction of shock wave driven instability growth as a function of initial shock Mach number. For ''large'' ka0, we suggest a formula which bounds the maximum value of the ratio of the amplitude growth rate over the interface speed by one minus the ratio of the interface speed and the transmitted shock speed. (c) 2000 American Institute of Physics

144

Impulsivity and the Sexes: Measurement and Structural Invariance of the UPPS-P Impulsive Behavior Scale  

Science.gov (United States)

Before it is possible to test whether men and women differ in impulsivity, it is necessary to evaluate whether impulsivity measures are invariant across sex. The UPPS-P Impulsive Behavior Scale (negative urgency, lack of premeditation, lack of perseverance, and sensation seeking, with added subscale of positive urgency) is one measure of five…

Cyders, Melissa A.

2013-01-01

145

Investigation of the properties of electrostatic IA solitary wave structures in negative ion magneto-plasmas with superthermal electrons  

Science.gov (United States)

A rigorous theoretical investigation is carried out in analyzing the excitation of electrostatic ion acoustic (IA) solitary wave (SW) structures in two dimensional negative ion magneto-plasmas with superthermal electrons (following ? type distribution). The Zakharov-Kuznetsov (ZK) equation is derived by employing the well known reductive perturbation method, and the analytical solution of ZK equation assists to find out the SW profiles along with their properties. The consequences of different plasma parameters (regarding our considered plasma system) variation on SW structures has been studied. It is found that magnetic field intensity, superthermal parameter ? and temperature of positive and negative ions as well as their densities significantly modify the basic characteristics (amplitude, width, etc.) of the SW waves. A comparison of the SW structures is also presented when the electrons are Maxwellian to when they are superthermal. The relevance of the findings of this work with astrophysical plasmas is briefly pointed out.

Hussain, S.; Ali Shan, S.; Akhtar, N.; Masud, M. M.

2014-08-01

146

EUV radiation from pinching discharges of magnetoplasma compressor type and its dependence on the dynamics of compression zone formation  

Science.gov (United States)

This paper is devoted to the investigation of plasma stream parameters and the intensity of extreme ultraviolet (EUV) radiation from the compression zone in various modes of operation of a magnetoplasma compressor (MPC). Two gases of different masses, either helium or argon, were used for the ignition of MPC discharge under the residual pressure. The plasma stream density along the axis and the EUV radiation energy were measured. It was shown that the compression zone position depends on the initial density of the residual gas. The EUV radiation energy was measured with a calibrated AXUV in the wavelength range of 12.2-15.8 nm. It was revealed that the radiation energy increased by 30-50% with decreasing initial gas pressure.

Garkusha, I. E.; Cherednychenko, T. N.; Ladygina, M. S.; Makhlay, V. A.; Petrov, Yu V.; Solyakov, D. G.; Staltsov, V. V.; Yelisyeyev, D. V.; Hassanein, A.

2014-05-01

147

VLF/ELF input impedance of an arbitrarily oriented loop antenna in a cold collisionless multicomponent magnetoplasma.  

Science.gov (United States)

A study is made of the input impedance Z of a small strip-loop antenna with arbitrary orientation in a cold collisionless uniform multicomponent magnetoplasma. Assuming a uniform current distribution, an integral expression for Z is derived which is valid for arbitrary values of driving frequency, plasma composition and density, loop orientation angle, and static magnetic field strength. The integral expression is evaluated numerically for the VLF/ELF range in a plasma modeled upon the inner magnetosphere. Approximate closed-form expressions for Z are also developed. It is found that the loop VLF/ELF input reactance is essentially identical to its free space self inductance. Also the loop radiation resistance is found to be a strong function of the loop orientation angle for frequencies near the lower-hybrid-resonance frequency or below the proton gyrofrequency.

Wang, T. N. C.; Bell, T. F.

1972-01-01

148

Food-related impulsivity in obesity and binge eating disorder--a systematic review.  

Science.gov (United States)

Impulsivity towards food has been recognized as a potential factor leading to increased food intake in obesity. Patients suffering from binge eating disorder (BED) form a specific subgroup of obese people that might be characterized by increased impulsivity. These assumptions, although, have yet to be verified. Therefore, this review evaluates evidence for food-related impulsivity in obese people with and without BED and examines possible differences between both populations. More precisely, evidence for the two components of impulsivity is analyzed separately: evidence for reward sensitivity, specifically, the urge for appetitive stimuli and evidence for rash-spontaneous behaviour such as acting disinhibited with no regard for the consequences. Our search resulted in 51 articles demonstrating generally increased food-related impulsivity. We found particular emphasis on increased reward sensitivity in obese people, which appeared to be more pronounced in people with BED. There was little and conflicting evidence, however, concerning increased rash-spontaneous behaviour in obese people without BED, but consistent evidence of an increase in obese people with BED. All in all, the evidence supports the view that BED represents a specific phenotype of obesity with increased food-related impulsivity. Taking these specific deficits into account can enhance the effectiveness of weight reduction programmes and psychotherapy. PMID:23331770

Schag, K; Schönleber, J; Teufel, M; Zipfel, S; Giel, K E

2013-06-01

149

Recreational drug use and impulsivity in a population of Canadian undergraduate drinkers  

Directory of Open Access Journals (Sweden)

Full Text Available The consumption of drugs during young adulthood may be particularly detrimental given important neurodevelopmental changes occurring during this period. As impulsivity may lead to substance use and substance use to the commission of seemingly impulsive acts, an improved understanding of the relationship between alcohol use, other substance use and impulsivity in young adults is important. We gathered information on self-reported impulsivity, recreational drug use, and drinking habits of 205 (105 female undergraduate students. Results showed that 64% of the students reported using marijuana at least once and these individuals were more likely to report binge drinking. Polydrug use, defined as using marijuana and at least one other illicit substance, was reported by 20% of students. These individuals reported more drinking occasions per month and had higher levels of trait impulsivity. Rates of recreational drug use were similar to those reported in recent national surveys, suggesting an increase in experimentation with specific illicit drugs. Given that a majority of undergraduate drinkers reported marijuana use and its association with binge drinking, future research should clarify the relationship between marijuana use and binge consumption of alcohol and prevention efforts should consider the conjoint targeting of marijuana and binge drinking. The associations between polydrug use, binge-level alcohol consumption and elevated self-reported impulsivity suggests that perceived trait impulsivity across multiple domains may predispose to excessive use of multiple substances. Longitudinal studies should examine the contribution of impulsivity to the initiation and experimentation with illicit drugs and the influence of specific substances on impulsivity.

IrisMBalodis

2010-10-01

150

Laser impulse generation required for space debris deorbiting  

Science.gov (United States)

Impulse generation using laser energy has advantages for aerospace propulsion; energy can be supplied from a remote device, thereby reducing a necessary mass on board and accompanied cost; the specific input energy is not limited by inherent energy of working fluid. After Kantrowitz proposed the concept of laser propulsion in 1972, impulse generation and launch performance either with single or multiple laser pulses has been experimentally studied. Possible application of this technique ranges even to space debris de-orbiting. As the example which actually launched a projectile, Yabe conducted an experiment that 0.1-gram paper airplane with an acryl overlay was launched at about 1.4 m/s using 0.6-J-class Nd:YAG laser. In Tanaka et al.'s experiment, 7 -microgram multi-layered flyer was accelerated to about 13 km/s using 20-J-class Nd:glass laser. Myrabo, using a 10-kW-class repetitive-pulse carbon dioxide laser, successfully launched a 51-gram 'lightcraft' at about 15 m/s up to altitude of 71 m. In these experiments, the values of impulse (i.e., momentum) and momentum coupling coefficient were estimated about 0.14 x 10-3 kg-m/s, 91x10-3 kg-m/s and 765x10-3 kg-m/s and about 240 N/MW, 4 N/MW and 50 N/MW, respectively. The objective of this study is to enhance a laser-driven impulse using a 300-J-class single pulsed laser owing to fluid-dynamic process. In this paper, we discuss a high-speed launch performance of a 1-gram projectile by enhanced impulse and achieved momentum coupling coefficient which are significantly improved using fluid-dynamic effect.

Watanabe, Keiko; Sasoh, Akihiro

2004-09-01

151

Electro-impulse Method of Surface Cleaning  

Directory of Open Access Journals (Sweden)

Full Text Available This article is focused on the qualitative assessment of the electro-impulse method of surface cleaning efficiency. Heat exchanger tubes are cleaned under the action of blast waves created by the high voltage discharge in the liquid. The article presents dependences of degree of surface purification on the impulse voltage at switching device and on spark rate

Bekbolat R. Nussupbekov

2013-01-01

152

Hyperkinetic Impulse Disorder in Children's Behavior Problems  

Science.gov (United States)

A very common cause of children's behavior disorder disturbance is an entity described as the hyperkinetic impulse disorder. This is characterized by hyperactivity, short attention span and poor powers of concentration, irritability, impulsiveness, variability, and poor schoolwork. The existence of this complexity may lead to many psychological…

Laufer, Maurice W.; Denhoff, Eric; Solomons, Gerald

2011-01-01

153

Oscillation criteria for impulsive dynamic equations on time scales  

Directory of Open Access Journals (Sweden)

Full Text Available Oscillation criteria for impulsive dynamic equations on time scales are obtained via impulsive inequality. An example is given to show that the impulses play a dominant part in the oscillations of dynamic equations on time scales.

Weizhen Feng

2007-12-01

154

Revisiting Impulsivity in Suicide: Implications for Civil Liability of Third Parties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Previous research and popular conceptualizations of suicide have posited that many suicides are the result of impulsive, “on a whim” decisions. However, recent research demonstrates that most suicides are not attempted impulsively, and in fact involve a plan. Legally, suicide has historically been considered to be a superseding intervening cause of death that exonerates other parties from liability, but currently there are two general exceptions to this view. Specifically, another party m...

Smith, April R.; Witte, Tracy K.; Teale, Nadia E.; King, Sarah L.; Bender, Ted W.; Joiner, Thomas E.

2008-01-01

155

Impulse-response functions of several detectors used in flow-injection analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A procedure for the determination of the impulse-response function of a detector is given. Its application to photometers, ion-sensitive field effect transistors, a potentiometric detector at constant current and a voltammetric detector shows that the impulse-response function can be used to obtain specific information about the performance of the detector in the manifold. This function clearly shows the contribution of the detector to the peak broadening and how the detector generates the fi...

Nugteren-osinga, I. C.; Hoogendam, E.; Bos, M.; Linden, W. E.

1990-01-01

156

Successful restrained eating and trait impulsiveness.  

Science.gov (United States)

Restrained eaters with high scores on the Perceived Self-Regulatory Success in Dieting Scale (PSRS) are more successful than low scorers in regulating their food intake. According to the theory of temptation-elicited goal activation (Fishbach, Friedman, & Kruglanski, 2003), they have become successful because, due to earlier repeated instances of successful self-control, they formed an associative link between temptations and thoughts of dieting. It is unclear, however, why they should have been more successful in earlier attempts at self-control than their unsuccessful counterparts. We examined whether trait impulsiveness plays a role by investigating the associations between dietary restraint, trait impulsiveness, and PSRS. Results showed that the interaction between dietary restraint and impulsiveness predicted dieting success: A lower level of impulsiveness was associated with greater dieting success among restrained eaters. These results suggest that restrained eaters who are less impulsive are more likely to become successful restrained eaters as identified with the PSRS. PMID:23017465

van Koningsbruggen, Guido M; Stroebe, Wolfgang; Aarts, Henk

2013-01-01

157

Time Devours Things: How Impulsivity and Time Affect Temporal Decisions in Pathological Gamblers  

Science.gov (United States)

Impulsivity is associated with several psychiatric disorders in which the loss of control of a specific behavior determines the syndrome itself. One particularly interesting population characterized by reported high impulsivity and problematic decision-making are those diagnosed with pathological gambling. However the association between impulsivity and decision making in pathological gambling has been only partially confirmed until now. We tested 23 normal controls and 23 diagnosed pathological gamblers in an intertemporal choice task, as well as other personality trait measurements. Results showed that gamblers scored higher on impulsivity questionnaires, and selected a higher percentage of impatient choices (higher percentage of smaller, sooner rewards), when compared to normal controls. Moreover, gamblers were faster in terms of reaction times at selecting the smaller, sooner options and discounted rewards more rapidly over time. Importantly, regression analyses clarified that self-reported measures of impulsivity played a significant role in biasing decisions towards small but more rapidly available rewards. In the present study we found evidence for impulsivity in personality traits and decisions in pathological gamblers relative to controls. We conclude by speculating on the need to incorporate impulsivity and decision biases in the conceptualization of pathological gambling for a better understanding and treatment of this pathology. PMID:25296184

Grecucci, Alessandro; Giorgetta, Cinzia; Rattin, Andrea; Guerreschi, Cesare; Sanfey, Alan G.; Bonini, Nicolao

2014-01-01

158

Time devours things: how impulsivity and time affect temporal decisions in pathological gamblers.  

Science.gov (United States)

Impulsivity is associated with several psychiatric disorders in which the loss of control of a specific behavior determines the syndrome itself. One particularly interesting population characterized by reported high impulsivity and problematic decision-making are those diagnosed with pathological gambling. However the association between impulsivity and decision making in pathological gambling has been only partially confirmed until now. We tested 23 normal controls and 23 diagnosed pathological gamblers in an intertemporal choice task, as well as other personality trait measurements. Results showed that gamblers scored higher on impulsivity questionnaires, and selected a higher percentage of impatient choices (higher percentage of smaller, sooner rewards), when compared to normal controls. Moreover, gamblers were faster in terms of reaction times at selecting the smaller, sooner options and discounted rewards more rapidly over time. Importantly, regression analyses clarified that self-reported measures of impulsivity played a significant role in biasing decisions towards small but more rapidly available rewards. In the present study we found evidence for impulsivity in personality traits and decisions in pathological gamblers relative to controls. We conclude by speculating on the need to incorporate impulsivity and decision biases in the conceptualization of pathological gambling for a better understanding and treatment of this pathology. PMID:25296184

Grecucci, Alessandro; Giorgetta, Cinzia; Rattin, Andrea; Guerreschi, Cesare; Sanfey, Alan G; Bonini, Nicolao

2014-01-01

159

Solar impulsive energetic electron events  

Science.gov (United States)

The Sun is capable of accelerating ions from ~ tens of keV up to tens of GeV and electrons from ~ tens of eV up to hundreds of MeVs in transient events such as flares and fast coronal mass ejections (CMEs). The energized particles escaping into the interplanetary medium are referred to as Solar Energetic Particle (SEP) events. The great majority of SEP events are impulsive SEP events that are dominated by ~1-100 keV electrons and ~MeV/nucleon ion emissions, with enhanced 3 He/ 4 He ratios up to 10 4 times the coronal values (also called electron/ 3 He-rich SEP events). This thesis is focused on solar impulsive energetic electron events, the electron part of impulsive SEP events, using electron observations from the 3-D Plasma and Energetic Particle instrument (3DP) on the WIND spacecraft near the Earth. First, I present the first comprehensive statistical study of solar energetic electron events over almost one solar cycle. I find that the occurrence rate of solar electron events shows a strong solar-cycle variation; after correction for the background effect, the estimated occurrence frequency exhibits a good power-law distribution, and the estimated occurrence rate near the Earth is ~1000/year at solar maximum and ~30/year at solar minimum for the instrumental sensitivity (~2.9×10^-4 (cm 2 s str eV) -1 for the 40 keV channel) of WIND/3DP, about one order of magnitude larger than the observed occurrence rate. Solar energetic electron events have a one-to-one association with type III radio bursts and a poor association with flares, but a close association with 3 He- rich ion emissions. These 3 He-rich electron events also have a poor association with flares but a close (~ 60%) association with west-limb CMEs. Then I present two case studies: one investigating the temporal relationship between solar impulsive electrons and type III radio emissions, and the second studying the temporal relationship between solar impulsive electrons and 3 He- rich ions. For both studies, I chose nearly scatter-free electron events and developed a forward-fitting method that assumes an isosceles triangular injection profile (equal rise and fall times) at the Sun. I find that in electron/3He-rich SEP events, the low-energy (~0.4 to 6-9 keV) electron injection starts ~9 min before the coronal release of the type III radio burst; the high-energy (~13 to ~300 keV) electron injection starts ~8 min after the type III burst; and the injection of ~MeV/nucleon, 3 He-rich ions begins ~1 hour later. I also find that the selected electron/ 3 He-rich SEP events have a remarkable one-to-one association with fast west-limb CMEs, and most of the associated CMEs are narrow. Finally, I present a case study to investigate the propagation of different energy electrons in solar impulsive electron events. I find that in the interplanetary medium, low-energy (~ 10-30 keV) electrons propagate differently, with more scattering at high energies. Such scattering appears to be caused by resonance with waves/turbulence at scale greater than ~ the thermal proton gyroradius in the solar wind. Although a transition to more scattering occurs at energies where the electron injection delays are detected, I show that the scattering is not enough to produce these delays. Based on the results of this thesis, a coherent picture of electron/ 3 He-rich SEP events can be built up. At the Sun, the low-energy (~0.4 to 6-9 keV) electrons may be accelerated in jets that are ejected upward from magnetic reconnection sites between closed and open field lines; these low-energy electrons generate the type III radio bursts. The jets may appear as CMEs high in the corona, and the high-energy (~13 to ~300 keV) electrons may then be accelerated at >~ 1 R S by CMEs, acting on the seed electrons provided by the low-energy injection. The ~MeV/nucleon, 3 He-rich ions may be accelerated by selective resonance with electron-beam generated waves and/or by fast, narrow CMEs. In the interplanetary medium, both low and high energy electrons often propagate ne

Wang, Linghua

160

Effects of multiple scatter on the propagation and absorption of electromagnetic waves in a field-aligned-striated cold magneto-plasma: implications for ionospheric modification experiments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found...

Robinson, T. R.

2002-01-01

 
 
 
 
161

Impulsive phase of solar flares: theory  

International Nuclear Information System (INIS)

The paper reviews the theoretical interpretation of impulsive phase phenomena in solar flares. The impulsive phase is defined to be that period of approx. 10 - 100s duration, during which the flare radiative output undergoes its most rapid, dramatic increase and decrease. The interpretation of the various impulsive phase radiation signatures are examined, including the i) hard x-ray emission, ii) radio emission, iii) UV, H? and white light emissions and iv) gamma-ray emission. The acceleration mechanisms are discussed with respect to candidate acceleration mechanisms, and the synthesis of the theory and observations. (UK)

162

Scanning capability analysis of laser impulse radar  

Science.gov (United States)

In this paper, we present our research about laser impulse radar-LIR. The overlap mode of laser impulse is analyzed for LIR. That the special scanning mode called Five-Points mode is used for the LIR. According to the scanning model, the best scanning times is given. And from the steps of azimuth and pitching scanning angles we are analyzed the model. To provide the theory guidelines of laser impulse radar scanning system design, the reflector scanning speeds in azimuth and pitching angles are derived and the relation between them is given. Finally, the scanning system errors caused by laser and machine system are analyzed and the solutions are presented.

Chen, Dapeng; Sun, Hongwei; Han, Yu

2014-03-01

163

Stability analysis of impulsive functional differential equations  

CERN Document Server

This book is devoted to impulsive functional differential equations which are a natural generalization of impulsive ordinary differential equations (without delay) and of functional differential equations (without impulses). At the present time the qualitative theory of such equationsis under rapid development. After a presentation of the fundamental theory of existence, uniqueness and continuability of solutions, a systematic development of stability theory for that class of problems is given which makes the book unique. It addresses to a wide audience such as mathematicians, applied research

Stamova, Ivanka

2009-01-01

164

Effects of Cannabis on Impulsivity: A Systematic Review of Neuroimaging Findings  

Science.gov (United States)

We conducted a systematic review to assess the evidence for specific effects of cannabis on impulsivity, disinhibition and motor control. The review had a specific focus on neuroimaging findings associated with acute and chronic use of the drug and covers literature published up until May 2012. Seventeen studies were identified, of which 13 met the inclusion criteria; three studies investigated acute effects of cannabis (1 fMRI, 2 PET), while six studies investigated non-acute functional effects (4 fMRI, 2 PET), and four studies investigated structural alterations. Functional imaging studies of impulsivity studies suggest that prefrontal blood flow is lower in chronic cannabis users than in controls. Studies of acute administration of THC or marijuana report increased brain metabolism in several brain regions during impulsivity tasks. Structural imaging studies of cannabis users found differences in reduced prefrontal volumes and white matter integrity that might mediate the abnormal impulsivity and mood observed in marijuana users. To address the question whether impulsivity as a trait precedes cannabis consumption or whether cannabis aggravates impulsivity and discontinuation of usage more longitudinal study designs are warranted. PMID:23829358

Wrege, Johannes; Schmidt, Andre; Walter, Anna; Smieskova, Renata; Bendfeldt, Kerstin; Radue, Ernst-Wilhelm; Lang, Undine E.; Borgwardt, Stefan

2014-01-01

165

Impulsively generated fast coronal pulsations  

Science.gov (United States)

Rapid oscillations in the corona are discussed from a theoretical standpoint, developing some previous work on ducted, fast magnetoacoustic waves in an inhomogeneous medium. In the theory, impulsively (e.g., flare) generated mhd (magnetohydrodynamic) waves are ducted by regions of low Alfven speed (high density) such as coronal loops. Wave propagation in such ducts is strongly dispersive and closely akin to the behavior of Love waves in seismology, Pekeris waves in oceanography and guided waves in fiber optics. Such flare-generated magnetoacoustic waves possess distinctive temporal signatures consisting of periodic, quasi-periodic and decay phases. The quasi-periodic phase possesses the strongest amplitudes and the shortest time scales. Time scales are typically of the order of a second for inhomogeneities (coronal loop width) of 1000 km and Alfven speeds of 1000/kms, and pulse duration times are of tens of seconds. Quasi-periodic signatures have been observed in radio wavelengths for over a decade and more recently by SMM. It is hoped that the theoretical ideas outlined may be successfully related to these observations and thus aid the interpretation of oscillatory signatures recorded by SMM. Such signatures may also provide a diagnostic of coronal conditions. New aspects of the ducted mhd waves, for example their behavior in smoothly varying as opposed to tube-like inhomogeneities, are currently under investigation. The theory is not restricted to loops but applied equally to open field regions.

Edwin, P. M.; Roberts, B.

1986-01-01

166

Impulsively generated fast coronal pulsations  

International Nuclear Information System (INIS)

Rapid oscillations in the corona are discussed from a theoretical standpoint, developing some previous work on ducted, fast magnetoacoustic waves in an inhomogeneous medium. In the theory, impulsively (e.g., flare) generated mhd (magnetohydrodynamic) waves are ducted by regions of low Alfven speed (high density) such as coronal loops. Wave propagation in such ducts is strongly dispersive and closely akin to the behavior of Love waves in seismology, Pekeris waves in oceanography and guided waves in fiber optics. Such flare-generated magnetoacoustic waves possess distinctive temporal signatures consisting of periodic, quasi-periodic and decay phases. The quasi-periodic phase possesses the strongest amplitudes and the shortest time scales. Time scales are typically of the order of a second for inhomogeneities (coronal loop width) of 1000 km and Alfven speeds of 1000/kms, and pulse duration times are of tens of seconds. Quasi-periodic signatures have been observed in radio wavelengths for over a decade and more recently by SMM. It is hoped that the theoretical ideas outlined may be successfully related to these observations and thus aid the interpretation of oscillatory signatures recorded by SMM. Such signatures may also provide a diagnostic of coronal conditions. New aspects of the ducted mhd waves, for example their behavior in smoothly varying as opposed to tube-like inhomogeneities, are currently under investigation. The theory is not restricted to loops but applied equally to open field regions

167

Dopaminergic network differences in human impulsivity.  

Science.gov (United States)

Dopamine (DA) has long been implicated in impulsivity, but the precise mechanisms linking human variability in DA signaling to differences in impulsive traits remain largely unknown. By using a dual-scan positron emission tomography approach in healthy human volunteers with amphetamine and the D2/D3 ligand [18F]fallypride, we found that higher levels of trait impulsivity were predicted by diminished midbrain D2/D3 autoreceptor binding and greater amphetamine-induced DA release in the striatum, which was in turn associated with stimulant craving. Path analysis confirmed that the impact of decreased midbrain D2/D3 autoreceptor availability on trait impulsivity is mediated in part through its effect on stimulated striatal DA release. PMID:20671181

Buckholtz, Joshua W; Treadway, Michael T; Cowan, Ronald L; Woodward, Neil D; Li, Rui; Ansari, M Sib; Baldwin, Ronald M; Schwartzman, Ashley N; Shelby, Evan S; Smith, Clarence E; Kessler, Robert M; Zald, David H

2010-07-30

168

Synchronization of impulsively coupled complex networks  

International Nuclear Information System (INIS)

We investigate the synchronization of complex networks, which are impulsively coupled only at discrete instants. Based on the comparison theory of impulsive differential systems, a distributed impulsive control scheme is proposed for complex dynamical networks to achieve synchronization. The proposed scheme not only takes into account the influence of all nodes to network synchronization, which depends on the weight of each node in the network, but also provides us with a flexible method to select the synchronized state of the network. In addition, it is unnecessary for the impulsive coupling matrix to be symmetrical. Finally, the proposed control scheme is applied to a chaotic Lorenz network and Chua's circuit network. Numerical simulations are used to illustrate the validity of this control scheme. (general)

169

Stochastic impulsive control for the stabilization of Lorenz system  

International Nuclear Information System (INIS)

This paper derives some sufficient conditions for the stabilization of Lorenz system with stochastic impulsive control. The estimate of the upper bound of impulse interval for asymptotically stable control is obtained. Some differences between the system with stochastic impulsive control and with deterministic impulsive control are presented. Computer simulation is given to show the effectiveness of the proposed method. (general)

170

Preliminary Study of Impulse-Momentum Diagrams  

Science.gov (United States)

In this paper we present a new representation to help students learn about momentum, impulse and conservation of momentum which we call an Impulse-Momentum Diagram. We include a description of this diagram as well as examples of how instructors can use them in the classroom. Next we present preliminary quantitative and qualitative data of a study we conducted where students used these representations. Our final analysis shows how students benefited from these representations.

Rosengrant, David; Mzoughi, Taha

2009-01-24

171

Stability of sets for impulsive systems  

Energy Technology Data Exchange (ETDEWEB)

Problems related to the stability and asymptotic stability of sets of sufficiently general type with respect to impulse systems are considered. The research is done by means of piecewise continuous auxiliary functions which are an analogue of the classical Lyapunov functions. It is proved that the existence of such functions with certain properties is a sufficient condition for various types of stability and asymptotic stability of sets with respect to impulsive systems.

Kulev, G.K.; Bainov, D.D. (Plovdiv Univ. (Bulgaria))

1989-02-01

172

Stability of sets for impulsive systems  

International Nuclear Information System (INIS)

Problems related to the stability and asymptotic stability of sets of sufficiently general type with respect to impulse systems are considered. The research is done by means of piecewise continuous auxiliary functions which are an analogue of the classical Lyapunov functions. It is proved that the existence of such functions with certain properties is a sufficient condition for various types of stability and asymptotic stability of sets with respect to impulsive systems

173

Hybrid impulsive control for closed quantum systems.  

Science.gov (United States)

The state transfer problem of a class of nonideal quantum systems is investigated. It is known that traditional Lyapunov methods may fail to guarantee convergence for the nonideal case. Hence, a hybrid impulsive control is proposed to accomplish a more accurate convergence. In particular, the largest invariant sets are explicitly characterized, and the convergence of quantum impulsive control systems is analyzed accordingly. Numerical simulation is also presented to demonstrate the improvement of the control performance. PMID:23781158

Zhao, Shouwei; Sun, Jitao; Lin, Hai

2013-01-01

174

Impulsive nature in collisional driven reconnection  

International Nuclear Information System (INIS)

Compressible magnetohydrodynamic simulation is carried out in order to investigate energy relaxation process of the driven magnetic reconnection in an open finite system through a long time calculation. It is found that a very impulsive energy release occurs in an intermittent fashion through magnetic reconnection for a continuous magnetic flux injection on the boundary. In the impulsive phase, the reconnection rate is remarkably enhanced up to more than ten times of the driving rate on the boundary. (author)

175

Clinical aspects of impulsive compulsive behaviours in Parkinson's disease.  

Science.gov (United States)

Impulsive-compulsive behaviours (ICBs) are an increasingly well-recognised adverse-effect of dopaminergic medications used to treat Parkinson's disease. ICBs include pathological gambling, compulsive sexual behaviour, compulsive buying, and binge eating, together with punding and the addiction-like compulsive use of dopamine replacement therapy, or dopamine dysregulation syndrome. The prevalence of ICBs was approximately 14% in a large study undertaken in specialist movement disorder clinics. Dopamine dysregulation syndrome is more associated with compulsive l-dopa use, whereas other ICBs are more linked with oral dopamine agonist use. Other mechanisms implicated in the development and perpetuation of ICBs in PD include aberrant learning from reward-related situations, including decreased learning from negative feedback, increased measures of impulsivity or sensation seeking, and strong preference for immediate over future rewards. Treatment options for impulsive-compulsive behaviours include pharmacological, surgical and psychological interventions. The early recognition and prevention of ICBs, coupled with awareness of clinical risk factors for the development of these behaviours is of paramount importance, given the lack of specific treatments for these sometimes debilitating behaviours. PMID:21839478

Djamshidian, Atbin; Averbeck, Bruno B; Lees, Andrew J; O'Sullivan, Sean S

2011-11-15

176

Impulsivity in sexual offenders – new ideas or back to basics?  

Directory of Open Access Journals (Sweden)

Full Text Available Despite the fact that the group of sexual offenders remains a population which is still difficult to study, the results of current research are considered novel and interesting. Surprisingly, the very old descriptions applying to paraphilia, which is considered to be one of the reasons of sexual offences, appear to be accurate, especially in the context of similarities between impulsivity and pathologic sexual behaviors. Notably, the nomenclature concerning impulsivity enables a specific and reasonable description of behaviors associated with sexual offences. Moreover, the results of research studies show that it is the lack of inhibition, not pathologic arousal, which is the most important factor in the pathogenesis of forbidden sexual behaviors. In addition, it has been shown that behavioral manifestations of impulsivity (substance abuse, suicide attempts appear commonly in sexual offenders.Mutual relationships between alcohol drinking, suicide attempts, history of child sexual abuse and sexual offences, in symptomatologic and etiologic aspect, raise a suggestion that all these phenomena may share a common background of poor inhibitory control.

Aleksandra Krasowska,

2013-07-01

177

Anger and Impulsivity in Adolescents Attempting Suicide  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: We aimed to evaluate anger and impulsivity in adolescent suicide attempters between the ages of 12 and 18, compared with control group; investigate the relation between hostility, impulsivity and suicide intent.Patients and Methods: Thirty-six adolescent patients between the ages of 12 and 18 referred to the Marmara University Hospital, Child and Adolescent Psychiatry Policlinic because of attempted suicide between June 2009 and May 2010, were included in the study. Thirty-four healthy subjects were selected as control group. Clinical assessment of participants was made with the Kiddie Schedule for Affective Disorders and Schizophrenia Present and Life Time Version. Adolescents were also evaluated with the Spielberg State Trait Anger Expression Inventory and Barratt's Impulsivity Scale. The seriousness of attempted suicide in adolescents was determined with the Suicide Intent Scale.Results: Average total and subscores (except anger control subscore of anger and impulsivity scales were found higher in adolescents attempting suicide than in control group (p0.05.Conclusion: Anger and impulsivity merit attention in adolescent attempted suicides. Additionally, our results reinforce the need for further studies investigating the relation between personality traits, psychiatric, familial and social factors for better understanding of the effect of anger and impulsivity in adolescent suicide behavior. (Marmara Medical Journal 2012;25:148-52

Elif AKIN

2012-01-01

178

Topological conjugation and asymptotic stability in impulsive semidynamical systems  

Science.gov (United States)

We prove several results concerning topological conjugation of two impulsive semidynamical systems. In particular, we prove that the homeomorphism which defines the topological conjugation takes impulsive points to impulsive points; it also preserves limit sets, prolongational limit sets and properties as the minimality of positive impulsive orbits as well as stability and invariance with respect to the impulsive system. We also present the concepts of attraction and asymptotic stability in this setting and prove some related results.

Bonotto, E. M.; Federson, M.

2007-02-01

179

Impulsivity and decision making in alcohol-addicted individuals [Impulsywno?? a podejmowanie decyzji u osób uzale?nionych od alkoholu  

Directory of Open Access Journals (Sweden)

Full Text Available Decision making processes are the research problem, that has been increasingly undertaken. Alcohol addiction is a disease associated with unfavorable decision making, in spite of its negative consequences. Impulsivity plays an important role in alcoholics’ decision making. It can be understood in terms of behavioral and/or cognitive flexibility disorders, that manifest in cognitive function disorders, making it difficult or even impossible to quickly and adequately assess the situation and to adjust behavior according to its requirements. Neurobiological and genetic research indicate the existing relationship between impulsivity and certain genetic predisposition. In alcohol addicts, impulsivity can be understood also in terms of specific personality traits, e.g. novelty seeking according to the theory of Cloninger. Although the concept of impulsivity itself has been the main topic of many studies, not many of them concern also decision making processes. In studies concerning alcoholics’ decision making, the relationship between this processes and behavioral impulsivity defined in many different ways, has been noticed. Some of these works define unfavorable decision making processes itself as a feature of impulsivity. Based on the results of theoretical works and research studies, it seems that it would be worth to define more precisely the concept of impulsivity, in order to determine its effect on decision making. The assessment of whether - and to what extent - the two variables (impulsivity and decision making can be considered as separate should also be taken into account.

Ka?wa, Agnieszka

2013-04-01

180

Inductance and near fields of a loop antenna in a cold magnetoplasma in the whistler frequency band  

Energy Technology Data Exchange (ETDEWEB)

The influence of a magnetoplasma on the inductance of a circular loop antenna oriented perpendicular to the ambient static magnetic field and operated in the whistler frequency band is studied. Based on a strict electrodynamic approach, the analytical treatment of the antenna reactance is performed for a uniform rf current distribution along the antenna wire. Calculations are made for plasma parameters and operating frequencies typical for active ionospheric experiments and laboratory rf (helicon) sources of dense magnetized plasmas. It is shown that the plasma influence on the inductance of the loop antenna remains relatively weak, even for antennas with dimensions close to half of the longitudinal whistler wavelength, when the rf field distribution in the antenna near zone is strongly different from that in vacuum. The theoretical predictions are confirmed by measurements performed on the large KROT plasma device. The results obtained are of crucial importance for the preparation of active ionospheric experiments and for the matching of loop antennas used in laboratory rf sources of dense magnetized plasmas.

Gushchin, M. E.; Korobkov, S. V.; Kostrov, A. V. [Institute of Applied Physics, 603950 Nizhny Novgorod (Russian Federation); Zaboronkova, T. M. [Department of Applied Physics, Technical University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Krafft, C. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau Cedex, Univ. Paris Sud, 91405 Orsay Cedex (France)

2012-09-15

 
 
 
 
181

Inductance and near fields of a loop antenna in a cold magnetoplasma in the whistler frequency band  

Science.gov (United States)

The influence of a magnetoplasma on the inductance of a circular loop antenna oriented perpendicular to the ambient static magnetic field and operated in the whistler frequency band is studied. Based on a strict electrodynamic approach, the analytical treatment of the antenna reactance is performed for a uniform rf current distribution along the antenna wire. Calculations are made for plasma parameters and operating frequencies typical for active ionospheric experiments and laboratory rf (helicon) sources of dense magnetized plasmas. It is shown that the plasma influence on the inductance of the loop antenna remains relatively weak, even for antennas with dimensions close to half of the longitudinal whistler wavelength, when the rf field distribution in the antenna near zone is strongly different from that in vacuum. The theoretical predictions are confirmed by measurements performed on the large KROT plasma device. The results obtained are of crucial importance for the preparation of active ionospheric experiments and for the matching of loop antennas used in laboratory rf sources of dense magnetized plasmas.

Gushchin, M. E.; Zaboronkova, T. M.; Krafft, C.; Korobkov, S. V.; Kostrov, A. V.

2012-09-01

182

Inductance and near fields of a loop antenna in a cold magnetoplasma in the whistler frequency band  

International Nuclear Information System (INIS)

The influence of a magnetoplasma on the inductance of a circular loop antenna oriented perpendicular to the ambient static magnetic field and operated in the whistler frequency band is studied. Based on a strict electrodynamic approach, the analytical treatment of the antenna reactance is performed for a uniform rf current distribution along the antenna wire. Calculations are made for plasma parameters and operating frequencies typical for active ionospheric experiments and laboratory rf (helicon) sources of dense magnetized plasmas. It is shown that the plasma influence on the inductance of the loop antenna remains relatively weak, even for antennas with dimensions close to half of the longitudinal whistler wavelength, when the rf field distribution in the antenna near zone is strongly different from that in vacuum. The theoretical predictions are confirmed by measurements performed on the large KROT plasma device. The results obtained are of crucial importance for the preparation of active ionospheric experiments and for the matching of loop antennas used in laboratory rf sources of dense magnetized plasmas.

183

Development and implementation of a new ultrafast imaging diagnostic for laboratory magnetoplasma: application in the plasma radial transport characterization  

International Nuclear Information System (INIS)

Non intrusive diagnostics have been developed in order to increase the precision in the data obtained from plasmas in a turbulent state. This thesis was carried on the development and the implementation of a new diagnostic for laboratory plasmas, i.e. an ultra-fast imaging system recording the spontaneous light emission, applied in turbulent plasmas of a magnetoplasma. The low resolution camera is composed of an array of photodetectors, their sensibility is centered on the main wavelength of the studied plasmas. Moreover, records can be longer than fifty milliseconds, even with a 100.000 frames per second recording frequency. This camera allows a precise study of both the spatial evolution of a phenomena and a statistical analysis of the recorded turbulent signal. Our prototype has been used to record different instable regimes of the laboratory magnetized plasma device. The main goal of this thesis was on the development and on the validation of this new diagnostic. Further studies will be devoted to the identification of the instabilities and underlying mechanisms. (author)

184

Cross-focusing of two co-axial Gaussian electromagnetic beams in a magnetoplasma and plasma wave generation  

International Nuclear Information System (INIS)

An investigation is presented of the cross-focusing of two Gaussian electromagnetic beams (two-dimensional) and consequent plasma wave generation at difference frequency ?? in a hot collisionless magneto-plasma. The two Gaussian EM beams are assumed to be propagating along the static magnetic field in the extraordinary mode. Because of Gaussian intensity distribution of the two EM beams ponderomotive force becomes finite and redistribution of the electrons occurs. If the initial powers of the two EM beams are more than the critical powers for self-focusing, the beams get self-focused. The fact that the ponderomotive force is dependent on the intensities of both the beams, leads to 'cross-focusing' i.e. focusing of one beam is affected by the other. Plasma wave generation at difference frequency which depends on the background electron density and effective intensity of the two beams gets accordingly modified. It is seen that the magnitude of the magnetic field considerably affects the plasma wave excitation. (author)

185

Differential associations between impulsivity and risk-taking and brain activations underlying working memory in adolescents.  

Science.gov (United States)

Increased impulsivity and risk-taking are common during adolescence and relate importantly to addictive behaviors. However, the extent to which impulsivity and risk-taking relate to brain activations that mediate cognitive processing is not well understood. Here we examined the relationships between impulsivity and risk-taking and the neural correlates of working memory. Neural activity was measured in 18 adolescents (13-18 years) while they engaged in a working memory task that included verbal and visuospatial components that each involved encoding, rehearsal and recognition stages. Risk-taking and impulsivity were assessed using the Balloon Analogue Risk Task (BART) and the adolescent version of the Barratt Impulsiveness Scale-11 (BIS-11A), respectively. We found overlapping as well as distinct regions subserving the different stages of verbal and visuospatial working memory. In terms of risk-taking, we found a positive correlation between BART scores and activity in subcortical regions (e.g., thalamus, dorsal striatum) recruited during verbal rehearsal, and an inverse correlation between BART scores and cortical regions (e.g., parietal and temporal regions) recruited during visuospatial rehearsal. The BIS-11A evidenced that motor impulsivity was associated with activity in regions recruited during all stages of working memory, while attention and non-planning impulsivity was only associated with activity in regions recruited during recognition. In considering working memory, impulsivity and risk-taking together, both impulsivity and risk-taking were associated with activity in regions recruited during rehearsal; however, during verbal rehearsal, differential correlations were found. Specifically, positive correlations were found between: (1) risk-taking and activity in subcortical regions, including the thalamus and dorsal striatum; and, (2) motor impulsivity and activity in the left inferior frontal gyrus, insula, and dorsolateral prefrontal cortex. Therefore these findings suggest that while there may be some overlap in the neural correlates of working memory and their relationship to impulsivity and risk-taking, there are also important differences in these constructs and their relationship to the stages of working memory during adolescence. PMID:24582821

Panwar, Karni; Rutherford, Helena J V; Mencl, W Einar; Lacadie, Cheryl M; Potenza, Marc N; Mayes, Linda C

2014-11-01

186

Neural substrates of time perception and impulsivity.  

Science.gov (United States)

Several studies provide empirical evidence for the association between impulsivity and time perception. However, little is known about the neural substrates underlying this function. This investigation examined the influence of impulsivity on neural activation patterns during the encoding and reproduction of intervals with durations of 3, 9 and 18s using event-related functional magnetic resonance imaging (fMRI). Twenty-seven subjects participated in this study, including 15 high impulsive subjects that were classified based on their self-rating. FMRI activation during the duration reproduction task was correlated with measures of two self-report questionnaires related to the concept of impulsivity (Barratt Impulsiveness Scale, BIS; Zimbardo Time Perspective Inventory, ZTPI). Behaviorally, those individuals who under-reproduced temporal intervals also showed lower scores on the ZTPI future perspective subscale and higher scores on the BIS. FMRI activation revealed an accumulating pattern of neural activity peaking at the end of the 9- and 18-s intervals within right posterior insula. Activations of brain regions during the reproduction phase of the timing task, such as those related to motor execution as well as to the 'core control network' - encompassing the inferior frontal and medial frontal cortices, the anterior insula as well as the inferior parietal cortex - were significantly correlated with reproduced duration, as well as with BIS and ZTPI subscales. In particular, the greater activation in these regions the shorter were the reproduced intervals, the more impulsive was an individual and the less pronounced the future perspective. Activation in the core control network, thus, may form a biological marker for cognitive time management and for impulsiveness. PMID:21763642

Wittmann, Marc; Simmons, Alan N; Flagan, Taru; Lane, Scott D; Wackermann, Ji?í; Paulus, Martin P

2011-08-11

187

Impulsive behavior in adults with attention deficit/ hyperactivity disorder: characterization of attentional, motor and cognitive impulsiveness.  

Science.gov (United States)

Attention-deficit/hyperactivity disorder (ADHD) is characterized by inattention and/or hyperactivity/impulsivity. Impulsivity persists in adults with ADHD and might be the basis of much of the impairment observed in the daily lives of such individuals. The objective of this study was to address the presence, and more importantly, the three dimensions of impulsivity: attentional, non-planning and motor, in how they may relate to neuropsychological mechanisms of impulse control. We studied a sample of 50 adults with ADHD and 51 healthy comparison controls using the Barratt Impulsivity Scale Version 11 (BIS), and neuropsychological tasks, namely the Continuous Performance Task (CPT-II) and the Iowa Gambling Task (IGT). The ADHD group showed more signs of impulsivity on the three dimensions of BIS, committed more errors of omission and commission on the CPT-II, and made more disadvantageous choices on the IGT. These results support the existence of deficits related to three components of impulsivity: motor, cognitive, and attentional among adults with ADHD. Most importantly, this study also highlights the complementary nature of self-report questionnaires and neuropsychological tasks in the assessment of impulsivity in ADHD adults. PMID:17521490

Malloy-Diniz, L; Fuentes, D; Leite, W Borges; Correa, H; Bechara, A

2007-07-01

188

Exponential stability analysis of impulsive stochastic functional differential systems with delayed impulses  

Science.gov (United States)

This paper is concerned with the exponential stability analysis of impulsive stochastic functional differential systems with delayed impulses. Although the stability of impulsive stochastic functional differential systems have received considerable attention. However, relatively few works are concerned with the stability of systems with delayed impulses and our aim here is mainly to close the gap. Based on the Lyapunov functions and Razumikhin techniques, some exponential stability criteria are derived, which show that the system will stable if the impulses' frequency and amplitude are suitably related to the increase or decrease of the continuous flows. The obtained results improve and complement ones from some recent works. Three examples are discussed to illustrate the effectiveness and the advantages of the results obtained.

Cheng, Pei; Deng, Feiqi; Yao, Fengqi

2014-06-01

189

Micropower impulse radar technology and applications  

Energy Technology Data Exchange (ETDEWEB)

The LLNL-developed Micropower Impulse Radar (MIR) technology has quickly gone from laboratory concept to embedded circuitry in numerous government and commercial systems in the last few years[l]. The main ideas behind MIR, invented by T. McEwan in the Laser Program, are the generation and detection systems for extremely low- power ultra-wideband pulses in the gigaHertz regime using low-cost components. These ideas, coupled with new antenna systems, timing and radio-frequency (RF) circuitry, computer interfaces, and signal processing, have provided the catalyst for a new generation of compact radar systems. Over the past several years we have concentrated on a number of applications of MIR which address a number of remote-sensing applications relevant to emerging programs in defense, transportation, medical, and environmental research. Some of the past commercial successes have been widely publicized [2] and are only now starting to become available for market. Over 30 patents have been filed and over 15 licenses have been signed on various aspects of the MIR technology. In addition, higher performance systems are under development for specific laboratory programs and government reimbursables. The MIR is an ultra- wideband, range-gated radar system that provides the enabling hardware technology used in the research areas mentioned above. It has numerous performance parameters that can be Selected by careful design to fit the requirements. We have improved the baseline, short- range, MIR system to demonstrate its effectiveness. The radar operates over the hand from approximately I to 4 GHz with pulse repetition frequencies up to 10 MHz. It provides a potential range resolution of I cm at ranges of greater than 20 m. We have developed a suite of algorithms for using MIR for image formation. These algorithms currently support Synthetic aperture and multistate array geometries. This baseline MIR radar imaging system has been used for several programmatic applications.

Mast, J., LLNL

1998-04-15

190

Underground scanning with an impulse radar  

International Nuclear Information System (INIS)

Impulse radar is being evaluated for possible applications at the Waste Isolation Pilot Project (WIPP) in southeastern New Mexico. Potential applications are (1) scanning salt to identify inclusions, structural discontinuities, and other anomalies before excavation; and (2) verifying the locations of stored radioactive-waste canisters. Four underground experiments were run. The extent and shape of dome-salt pillars and a langbeinite pillar were measured with the radar. Metal targets that simulated waste canisters were located to within a few centimetres after they had been buried for 18 months. If the material being scanned contains clay seams and other conductive inclusions, penetration by radar is limited. It is anticipated that clean bedded salt will be an excellent medium for scanning with an impulse radar. The impulse radar as it now exists can be used for WIPP applications

191

Almost periodic solutions of impulsive differential equations  

CERN Document Server

Impulsive differential equations are suitable for the mathematical simulation of evolutionary processes in which the parameters undergo relatively long periods of smooth variation followed by short-term rapid changes (that is, jumps) in their values. Processes of this type are often investigated in various fields of science and technology. The question of the existence and uniqueness of almost periodic solutions of differential equations is an age-old problem of great importance. The qualitative theory of impulsive differential equations is currently undergoing rapid development in relation to the investigation of various processes which are subject to impacts during their evolution, and many findings on the existence and uniqueness of almost periodic solutions of these equations are being made. This book systematically presents findings related to almost periodic solutions of impulsive differential equations and illustrates their potential applications.

Stamov, Gani T

2012-01-01

192

Impulsive synchronization of different hyperchaotic (chaotic) systems  

Energy Technology Data Exchange (ETDEWEB)

The impulsive synchronization has been employed to synchronize two different hyperchaotic (chaotic) systems. Conditions on impulse distances are given in order to obtain stable synchronization in the nominal case and robust stability in the case that we experience uncertainties in the systems dynamic and/or measurement noise. Under the given conditions, it is guaranteed that the error dynamics is asymptotically stable for the nominal case and convergent to a predetermined level for uncertain and/or noisy circumstances. Computer simulations are provided to assess results of the given theorems in the paper.

Haeri, Mohammad [Advance Control System Laboratory, Electrical Engineering Department, Sharif University of Technology, Tehran (Iran, Islamic Republic of)], E-mail: haeri@sina.sharif.edu; Dehghani, Mahsa [Advance Control System Laboratory, Electrical Engineering Department, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

2008-10-15

193

Impulse control disorders in Parkinson's disease  

Directory of Open Access Journals (Sweden)

Full Text Available Impulse control disorders (ICDs in Parkinson's disease (PD are common with a frequency of 13.61% , which are associated with impaired functioning and with depressive, anxiety and obsessive symptoms, novelty seeking and impulsivity. These behaviors have a bad influence on PD patients in the quality of life. Different behavioral subtypes suggest pathophysiological differences. Recent large scale studies and converging findings are beginning to provide an understanding of mechanisms underlying ICDs in PD which can guide the prevention of these behaviors and optimize therapeutic approaches. This paper will take a review on the recent advances in the epidemiology, risk factors, pathophysiology, diagnosis and therapy of ICDs in PD.

HAN Xun

2013-08-01

194

Spray deposition using impulse atomization technique  

International Nuclear Information System (INIS)

A novel technique, impulse atomization, has been used for spray deposition. This single fluid atomization technique leads to different spray characteristics and impact conditions of the droplets compared to gas atomization technique which is the common technique used for spray deposition. Deposition experiments with a Cu-6Sn alloy were conducted to evaluate the appropriateness of impulse atomization to produce dense material. Based on these experiments, a model has been developed to simulate the thermal history and the local solidification rates of the deposited material. A numerical study shows how different cooling conditions affect the solidification rate of the material

195

Cortical thickness of superior frontal cortex predicts impulsiveness and perceptual reasoning in adolescence.  

Science.gov (United States)

Impulsiveness is a pivotal personality trait representing a core domain in all major personality inventories. Recently, impulsiveness has been identified as an important modulator of cognitive processing, particularly in tasks that require the processing of large amounts of information. Although brain imaging studies have implicated the prefrontal cortex to be a common underlying representation of impulsiveness and related cognitive functioning, to date a fine-grain and detailed morphometric analysis has not been carried out. On the basis of ahigh-resolution magnetic resonance scans acquired in 1620 healthy adolescents (IMAGEN), the individual cortical thickness (CT) was estimated. Correlations between Cloninger's impulsiveness and CT were studied in an entire cortex analysis. The cluster identified was tested for associations with performance in perceptual reasoning tasks of the Wechsler Intelligence Scale for Children (WISC IV). We observed a significant inverse correlation between trait impulsiveness and CT of the left superior frontal cortex (SFC; Monte Carlo Simulation P<0.01). CT within this cluster correlated with perceptual reasoning scores (Bonferroni corrected) of the WISC IV. On the basis of a large sample of adolescents, we identified an extended area in the SFC as a correlate of impulsiveness, which appears to be in line with the trait character of this prominent personality facet. The association of SFC thickness with perceptual reasoning argues for a common neurobiological basis of personality and specific cognitive domains comprising attention, spatial reasoning and response selection. The results may facilitate the understanding of the role of impulsiveness in several psychiatric disorders associated with prefrontal dysfunctions and cognitive deficits. PMID:22665261

Schilling, C; Kühn, S; Paus, T; Romanowski, A; Banaschewski, T; Barbot, A; Barker, G J; Brühl, R; Büchel, C; Conrod, P J; Dalley, J W; Flor, H; Ittermann, B; Ivanov, N; Mann, K; Martinot, J-L; Nees, F; Rietschel, M; Robbins, T W; Smolka, M N; Ströhle, A; Kathmann, N; Garavan, H; Heinz, A; Schumann, G; Gallinat, J

2013-05-01

196

A Model-based Analysis of Impulsivity Using a Slot-Machine Gambling Paradigm  

Directory of Open Access Journals (Sweden)

Full Text Available Impulsivity plays a key role in decision-making under uncertainty. It is a significant contributor to problem and pathological gambling. Standard assessments of impulsivity by questionnaires, however, have various limitations, partly because impulsivity is a broad, multi-faceted concept. What remains unclear is which of these facets contribute to shaping gambling behavior. In the present study, we investigated impulsivity as expressed in a gambling setting by applying computational modeling to data from 47 healthy male volunteers who played a realistic, virtual slot-machine gambling task. Behaviorally, we found that impulsivity, as measured independently by the 11th revision of the Barratt Impulsiveness Scale (BIS-11, correlated significantly with an aggregate read-out of the following gambling responses: bet increases, machines switches, casino switches and double-ups. Using model comparison, we compared a set of hierarchical Bayesian belief-updating models, i.e. the Hierarchical Gaussian Filter (HGF and Rescorla-Wagner reinforcement learning models, with regard to how well they explained different aspects of the behavioral data. We then examined the construct validity of our winning models with multiple regression, relating subject-specific model parameter estimates to the individual BIS-11 total scores. In the most predictive model (a three-level HGF, the two free parameters encoded uncertainty-dependent mechanisms of belief updates and significantly explained BIS-11 variance across subjects. Furthermore, in this model, decision noise was a function of trial-wise uncertainty about winning probability. Collectively, our results provide a proof of concept that hierarchical Bayesian models can characterize the decision-making mechanisms linked to impulsivity. These novel indices of gambling mechanisms unmasked during actual play may be useful for online prevention measures for at-risk players and future assessments of pathological gambling.

Saee Paliwal

2014-07-01

197

Increased reflection impulsivity in patients with ephedrone induced Parkinsonism  

Science.gov (United States)

Aims To examine a syndrome of chronic manganism that occurs in drug addicts in Eastern Europe who use intravenous methcathinone (ephedrone) contaminated with potassium permanganate. The basal ganglia, especially the globus pallidus and the putamen, are damaged irreversibly in many cases. Routine neuropsychological assessment has revealed no cognitive deficits despite widespread abnormalities on brain imaging studies and severe extrapyramidal motor handicap on clinical examination. Design Case control study. Setting Ephedrone patients and patients with opioid dependence were recruited from Lviv, Ukraine. Participants We tested 15 patients with ephedrone induced toxicity, 13 opiate dependent patients, who were receiving opioid replacement therapy and 18 matched healthy volunteers. Measurements The ‘beads task’, an information gathering task to assess reflection impulsivity was used and feedback learning, working memory and risk taking were also assessed. Findings Opiate dependent patients differed from controls on three out of four tasks, whereas ephedrone patients differed from controls on only one task. More specifically both patient groups were more impulsive and made more irrational choices on the beads task than controls (p0.1) or risk taking (p>0.1) compared with controls. Opioid dependent patients had significantly worse working memory (p<0.001) and were significantly more risk prone than controls (p=0.002). Conclusions Ephedrone patients may have similar deficits in information gathering and decision making to opiate dependent patients, with preservation of working memory and risk taking. This may reflect specific damage to anterior cingulate- basal ganglia loops. PMID:23228208

Djamshidian, Atbin; Sanotsky, Yanosh; Matviyenko, Yuriy; O'Sullivan, Sean S.; Sharman, Stephen; Selikhova, Marianna; Fedoryshyn, Ludmyla; Filts, Yuriy; Bearn, Jenny; Lees, Andrew J.; Averbeck, Bruno B.

2012-01-01

198

A new Calculation Procedure for Spatial Impulse Responses in Ultrasound  

DEFF Research Database (Denmark)

A new procedure for the calculation of spatial impulse responses for linear sound fields is introduced. This calculation procedure uses the well known technique of calculating the spatial impulse response from the intersection of a circle emanating from the projected spherical wave with the boundary of the emitting aperture. This general result holds for all aperture boundaries for a flat transducer surface, and this is used in the procedure to yield the response for all types of flat transducers. An arbitrary apodization function over the aperture can be incorporated through a simple one-dimensional integration. The case of a soft baffle mounting of the aperture is also included. Specific solutions for transducer boundaries made from lines are given, so that any polygon transducer can be handled. Specific solutions for circles are also given. Finally, a solution for a general boundary is stated, and all these boundary elements can be combined to, e.g., handle annular arrays or semi-circle transducers. Results from an implementation of the approach are given and compared to previously developed solutions for a simple aperture, a complex aperture, and a Gaussian apodized circular transducer.

Jensen, JØrgen Arendt

1999-01-01

199

Neuropsychological and cognitive psychophysiological substrates of impulsive aggression.  

Science.gov (United States)

The purpose of this study was to test whether subjects who commit impulsive vs non-impulsive aggression differ on measurements of personality, neuropsychology, and cognitive psychophysiology, and whether these differences can yield information regarding the etiology of impulsive aggression. Subjects were two groups of prison inmates, distinguished by their committal of impulsive or nonimpulsive aggression, and matched noninmate controls. All inmates met DSM III-R criteria for an antisocial personality disorder but for no other disorder. Impulsiveness, anger, and peak P300 latencies did not differ between the inmate groups, but verbal symbol decoding and peak P300 amplitudes did. Impulsiveness and verbal skills were inversely correlated. Impulsiveness was inversely correlated with, and verbal skills positively correlated with P300 amplitudes. The results indicate that aggression is not homogenous, even among antisocial persons, and that impulsive aggression is related to neuropsychological and cognitive psychophysiological measures of information processing beyond those factors related to criminality alone. PMID:9129785

Barratt, E S; Stanford, M S; Kent, T A; Felthous, A

1997-05-15

200

Mean – Median Filtering For Impulsive Noise Removal  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this paper is a new Mean- Median filtering for denoising extremely corrupted images by impulsive noise. Whenever an image is converted from one form to another, some of degradation occurs at the output. Improvement in the quality of these degraded images can be achieved by the application of Restoration and /or Enhancement techniques. Noise removing is one of the categories of Enhancement. Removing noise from the original signal is still a challenging problem. Mean filtering fails to effectively remove heavy tailed noise & performance poorly in the presence of signal dependent noise. The successes of median filters are edge preservation and efficient attenuation of impulsive noise. An important shortcoming of the median filter is that the output is one of the samples in the input window. Based on this mixture distributions are proposed to effectively remove impulsive noise characteristics. Finally, the results of comparative analysis of mean-median algorithm with mean, median filters for impulsive noise removal show a high efficiency of this approach relatively to other ones.

N.Sakthivel

2014-04-01

 
 
 
 
201

The Hydraulic Ram (Or Impulse) Pump  

Science.gov (United States)

The hydraulic impulse pump utilizes a fraction of the momentum of a flowing stream to lift a small portion of that water to a higher level. There it may be accumulated in an elevated cistern to provide sufficient water for several families, for the pump works 24 h a day with no additional source of energy. The operation of the pump is described,…

Mills, Allan

2014-01-01

202

PERFORMANCE OF IMPULSE NOISE DETECTION METHODS IN REMOTE SENSING IMAGES  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Remote sensing (RS) images are affected by different types of noises like Gaussian noise, speckle noise and impulse noise. These noises are introduced into the RS images during acquisition or transmission process. The main challenge in impulse noise removal is to suppress the noise as well as to preserve the details (edges). Removal ofthe impulse noise is done by two stages: detection of noisy pixel and replacement of that pixel. Detecting and Removing or reducing impulse noise is a very acti...

Mrs.V.RADHIKA,; Padmavathi, Dr G.

2010-01-01

203

Hyperactive-Impulsive Symptoms Associated with Self-Reported Sleep Quality in Nonmedicated Adults with ADHD  

Science.gov (United States)

Objective: Individuals with ADHD often report sleep problems. Though most studies on ADHD and sleep examined children or nonclinically diagnosed adults, the present study specifically examines nonmedicated adults with ADHD to determine whether inattentive and hyperactive-impulsive symptoms are associated with sleep problems. Method: A total of 22…

Mahajan, Neha; Hong, Nuong; Wigal, Timothy L.; Gehricke, Jean-G.

2010-01-01

204

Interleukin-6 reflects trait impulsivity in suicide attempters  

Directory of Open Access Journals (Sweden)

Full Text Available Background : High cerebrospinal fluid (CSF and plasma interleukin-6 (IL-6 levels have been reported in suicide attempters. Features of the suicidal temperament include such personality traits as anger and aggression, impulsivity, anxiety proneness and low socialization. High levels of neuroticism and low levels of conscientiousness assessed with structured personality inventories have previously been associated to increased levels of IL-6, in population based samples. The aim of this study was to assess whether plasma levels of IL-6 were associated to specific personality traits in suicide attempters. Methods : Plasma concentration of IL-6 was measured in 58 suicide attempters with a high throughput automated biochip immunoassay system. Patients were evaluated using the Karolinska Scale of Personality (KSP. A standard multiple regression analysis was performed with IL-6 as the dependent variable and KSP factors Neuroticism, Nonconformity, Psychoticism and Extraversion as independent variables adjusted for age and gender. Results : The regression model was significant (R 2=0.40, F ratio?=?7.3, df?=?6, p<0.0001, and the results suggested that high scores on Extraversion were associated with high levels of IL-6 (t ratio?=?4.14, p<0.0001. IL-6 levels showed a significant positive correlation with trait impulsivity (r=0.39, p=0.003. Conclusions : In suicide attempters, IL-6 may be related to trait impulsivity, a key feature of the suicidal temperament. This study motivates further studies on cytokine activity and their involvement in behavioural development. The study adds further support on biological involvement in suicidal behaviour.

Jussi Jokinen

2012-09-01

205

ADHD-hyperactive/impulsive subtype in adults  

Directory of Open Access Journals (Sweden)

Full Text Available This is the first study to evaluate ADHD-hyperactive/impulsive subtype in a large clinical sample of adults with ADHD. The Quality of Life, Effectiveness, Safety and Tolerability (QuEST study included 725 adults who received clinician diagnoses of any ADHD subtype. Cross-sectional baseline data from 691 patients diagnosed with the hyperactive/impulsive (HI, inattentive (IA and combined subtypes were used to compare the groups on the clinician administered ADHD-RS, clinical features and health-related quality of life. A consistent pattern of differences was found between the ADHD-I and combined subtypes, with the combined subtype being more likely to be diagnosed in childhood, more severe symptom severity and lower HRQL. Twenty-three patients out of the total sample of 691 patients (3% received a clinician diagnosis of ADHD - hyperactive/impulsive subtype. Review of the ratings on the ADHD-RS-IV demonstrated, however, that this group had ratings of inattention comparable to the inattentive group. There were no significant differences found between the ADHD-HI and the other subtypes in symptom severity, functioning or quality of life. The hyperactive/impulsive subtype group identified by clinicians in this study was not significantly different from the rest of the sample. By contrast, significant differences were found between the inattentive and combined types. This suggests that in adults, hyperactivity declines and inattention remains significant, making the hyperactive/impulsive subtype as defined by childhood criteria a very rare condition and raising questions as to the validity of the HI subtype in adults.

Stephen V. Faraone

2010-01-01

206

Flare kernel in the impulsive phase  

International Nuclear Information System (INIS)

The impulsive phase of a flare is characterized by impulsive bursts of x-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area

207

H? Control of Fuzzy Impulsive Systems with Quantized Feedback  

Directory of Open Access Journals (Sweden)

Full Text Available This paper is concerned with the problem of H? control of fuzzy nonlinear impulsive systems with quantized feedback. New results on the H? feedback control are established for one class of fuzzy nonlinear uncertain impulsive systems and one class of fuzzy nonlinear impulsive systems with nonlinear uncertainties by choosing appropriately quantized strategies and applying Lyapunov function approach, respectively.

Yingqi Zhang

2009-07-01

208

Borderline personality disorder, impulsivity, and the orbitofrontal cortex.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVE: Orbitofrontal cortex lesions produce disinhibited or socially inappropriate behavior and emotional irregularities. Characteristics of borderline personality disorder include impulsivity and affective instability. The authors investigated whether aspects of borderline personality disorder, in particular impulsivity, are associated with orbitofrontal cortex dysfunction. METHOD: Measures of personality, emotion, impulsivity, time perception, sensitivity to reinforcers, and spatial wor...

Berlin, Ha; Rolls, Et; Iversen, Sd

2005-01-01

209

On Exact Controllability of First-Order Impulsive Differential Equations  

Directory of Open Access Journals (Sweden)

Full Text Available Many dynamical systems have an impulsive dynamical behavior due to abrupt changes at certain instants during the evolution process. The mathematical description of these phenomena leads to impulsive differential equations. In this work, we present some new results concerning the exact controllability of a nonlinear ordinary differential equation with impulses.

Tisdell ChristopherC

2010-01-01

210

Instability of solutions of impulsive systems of differential equations  

Energy Technology Data Exchange (ETDEWEB)

We consider instability of the zero solution of impulsive systems of differential equations with unfixed moments of the impulse effect. Piecewise continuous auxiliary functions are used which are analogues of the classical Lyapunov functions. An analogue of Chetaev`s theorem for systems of differential equations without impulses is proved and some corollaries are deduced.

Bainov, D.D. [Academy of Medicine, Sofia (Bulgaria); Kulev, G.K. [Plovdiv Univ. (Bulgaria); Stamova, I.M. [Technical Univ., Sliven (Bulgaria)

1996-08-01

211

Lewis rats have greater response impulsivity than Fischer rats.  

Science.gov (United States)

Impulsivity, a tendency toward immediate action without consideration of future consequences, is associated with a wide array of problematic behaviors. Response impulsivity, a type of behaviorally-assessed impulsivity characterized by behavioral disinhibition, is also associated with health risk behaviors. Response impulsivity is distinct from choice impulsivity, which is characterized by intolerance for delay. Lewis rats have higher levels of choice impulsivity than Fischer rats (Anderson & Woolverton, 2005; Madden et al., 2008; Stein et al., 2012). However, no studies have examined whether Lewis and Fischer rats have different levels of response impulsivity. The present research examined response impulsivity in the two rat strains. Subjects were 16 male Lewis and Fischer rats. Rats' response impulsivity was measured using the Five Choice Serial Reaction Time Task (5-CSRTT). In addition, their locomotor activity was measured in locomotor activity chambers. Lewis rats had more premature responses than Fischer rats during the 5-CSRTT assessment [F(1, 14)=5.34, prat strain groups [F(1, 14)=3.05, p=.10], suggesting that overall movement did not account for group differences in response impulsivity on the 5-CSRTT. It can be concluded from this research that Lewis rats have higher levels of response impulsivity than Fischer rats, and therefore provide a valid rat model of individual differences in impulsivity. PMID:24613059

Hamilton, Kristen R; Potenza, Marc N; Grunberg, Neil E

2014-11-01

212

Final report of LDRD project: Electromagnetic impulse radar for detection of underground structures  

Energy Technology Data Exchange (ETDEWEB)

This report provides a summary of the LDRD project titled: Electromagnetic impulse radar for the detection of underground structures. The project met all its milestones even with a tight two year schedule and total funding of $400 k. The goal of the LDRD was to develop and demonstrate a ground penetrating radar (GPR) that is based on high peak power, high repetition rate, and low center frequency impulses. The idea of this LDRD is that a high peak power, high average power radar based on the transmission of short impulses can be utilized effect can be utilized for ground penetrating radar. This direct time-domain system the authors are building seeks to increase penetration depth over conventional systems by using: (1) high peak power, high repetition rate operation that gives high average power, (2) low center frequencies that better penetrate the ground, and (3) short duration impulses that allow for the use of downward looking, low flying platforms that increase the power on target relative to a high flying platform. Specifically, chirped pulses that are a microsecond in duration require (because it is difficult to receive during transmit) platforms above 150 m (and typically 1 km) while this system, theoretically could be at 10 m above the ground. The power on target decays with distance squared so the ability to use low flying platforms is crucial to high penetration. Clutter is minimized by time gating the surface clutter return. Short impulses also allow gating (out) the coupling of the transmit and receive antennas.

Loubriel, G.; Aurand, J.; Buttram, M.; Zutavern, F.; Brown, D.; Helgeson, W.

1998-03-01

213

Improvement of impulse breakdown strength of an XLPE cable by modifing semiconducting layer  

Science.gov (United States)

A technique was investigated which reduces insulation thickness by improving breakdown strength of XLPE (cross-linked polyethylene) cables, using additives to improve interfaces of semiconducting layers, in order to restrain construction cost. Miniature model cables of 1mm insulation thick, 2mm diameter of inner semiconducting layer were manufactured. An additive was included in the semiconducting layer of each miniature cable to improve the interface with the insulating layer. The strength of dielectric breakdown was measured by testing of the impulsive pressure with lightning. The results of the impulse breakdown test show a rise in breakdown strength, indicating the effective function to make interface defects harmless. Based on the results of a previous report, a specific kind of additive which has an excellent function to improve both ac and impulse breakdown strength was selected. Additives used in this test are mainly nonionic surface active agents such as polyglyceric fatty acid esters.

Hozumi, N.; Okamoto, T.; Ishida, M.

1988-09-01

214

Self-reported impulsivity, rather than sociosexuality, predicts women's preferences for masculine features in male faces.  

Science.gov (United States)

Previous research has suggested that an individual's sociosexual orientation (i.e., their willingness to engage in sexual behavior outside of long-term relationships) may influence the qualities they find attractive in a potential mate. Results, however, have not been consistent and, moreover, studies have tended to draw from specific social groups. Here, we tested the relationship between sociosexuality and female's preferences for masculinity in male faces, using a diverse population. We furthermore investigated impulsivity alongside sociosexuality, as this trait has been suggested as a "root" cause of variation in sexual behavior (Cross, 2010) and thus may better explain variation in mate choice. Results showed a significant association between increases in both sociosexuality and two subcomponents of impulsivity and greater preferences for masculine male features. Regression analysis suggested that a subcomponent of impulsivity, namely lack of planning, was the primary determinant of preferences. We discuss the implications these results have for our understanding of female attraction to masculine features. PMID:24346865

Boothroyd, Lynda G; Brewer, Gayle

2014-07-01

215

The utility of rat models of impulsivity in developing pharmacotherapies for impulse control disorders.  

Science.gov (United States)

High levels of impulsive behaviours are a clinically significant symptom in a range of psychiatric disorders, such as attention deficit hyperactivity disorder, bipolar disorder, personality disorders, pathological gambling and substance abuse. Although often measured using questionnaire assessments, levels of different types of impulsivity can also be determined using behavioural tests. Rodent analogues of these paradigms have been developed, and similar neural circuitry has been implicated in their performance in both humans and rats. In the current review, the methodology underlying the measurement of different aspects of impulsive action and choice are considered from the viewpoint of drug development, with a focus on the continuous performance task (CPT), stop-signal task (SST), go/no-go and delay-discounting paradigms. Current issues impeding translation between animal and human studies are identified, and comparisons drawn between the acute effects of dopaminergic, noradrenergic and serotonergic compounds across species. Although the field could benefit from a more systematic determination of different pharmacological agents across paradigms, there are signs of strong concordance between the animal and human data. However, the type of impulsivity measured appears to play a significant role, with the SST and delay discounting providing more consistent effects for dopaminergic drugs, while the CPT and SST show better predictive validity so far for serotonergic and noradrenergic compounds. Based on the available data, it would appear that these impulsivity models could be used more widely to identify potential pharmacotherapies for impulse control disorders. Novel targets within the glutamatergic and serotonergic system are also suggested. PMID:21410459

Winstanley, Catharine A

2011-10-01

216

Oscillatory Activity in the Medial Prefrontal Cortex and Nucleus Accumbens Correlates with Impulsivity and Reward Outcome  

Science.gov (United States)

Actions expressed prematurely without regard for their consequences are considered impulsive. Such behaviour is governed by a network of brain regions including the prefrontal cortex (PFC) and nucleus accumbens (NAcb) and is prevalent in disorders including attention deficit hyperactivity disorder (ADHD) and drug addiction. However, little is known of the relationship between neural activity in these regions and specific forms of impulsive behaviour. In the present study we investigated local field potential (LFP) oscillations in distinct sub-regions of the PFC and NAcb on a 5-choice serial reaction time task (5-CSRTT), which measures sustained, spatially-divided visual attention and action restraint. The main findings show that power in gamma frequency (50–60 Hz) LFP oscillations transiently increases in the PFC and NAcb during both the anticipation of a cue signalling the spatial location of a nose-poke response and again following correct responses. Gamma oscillations were coupled to low-frequency delta oscillations in both regions; this coupling strengthened specifically when an error response was made. Theta (7–9 Hz) LFP power in the PFC and NAcb increased during the waiting period and was also related to response outcome. Additionally, both gamma and theta power were significantly affected by upcoming premature responses as rats waited for the visual cue to respond. In a subgroup of rats showing persistently high levels of impulsivity we found that impulsivity was associated with increased error signals following a nose-poke response, as well as reduced signals of previous trial outcome during the waiting period. Collectively, these in-vivo neurophysiological findings further implicate the PFC and NAcb in anticipatory impulsive responses and provide evidence that abnormalities in the encoding of rewarding outcomes may underlie trait-like impulsive behaviour. PMID:25333512

Rich, P. Dylan; Nevado-Holgado, Alejo J.; Fernando, Anushka B. P.; Van Dijck, Gert; Holzhammer, Tobias; Paul, Oliver; Ruther, Patrick; Paulsen, Ole; Robbins, Trevor W.; Dalley, Jeffrey W.

2014-01-01

217

Single-photon emission tomography imaging of monoamine transporters in impulsive violent behaviour  

International Nuclear Information System (INIS)

Several studies have shown that impulsive violent and suicidal behaviour is associated with a central serotonin deficit, but until now it has not been possible to use laboratory tests with high sensitivity and specificity to study this kind of deficit or to localize the sites of serotonergic abnormalities in the living human brain. The aim of this study was to test the hypothesis that monoamine transporter density in brain is decreased in subjects with impulsive violent behaviour. We studied serotonin (5-HT) and dopamine (DA) transporter specific binding in 52 subjects (21 impulsive violent offenders, 21 age- and sex-matched healthy controls, and ten non-violent alcoholic controls) with single-photon emission tomography (SPET) using iodine-123-labelled 2?-carbomethoxy-3?(4-iodophenyl)tropane ([123I]?-CIT) as the tracer. The blind quantitative analysis revealed that the 5-HT specific binding of [123I]?-CIT in the midbrain of violent offenders was lower than that in the healthy control subjects (P<0.005; t test) or the non-violent alcoholics (P<0.05). The results imply that habitual impulsive aggressive behaviour in man is associated with a decrease in the 5-HT transporter density. (orig.)

218

Behavioral Components of Impulsivity Predict Alcohol Consumption in Adults with ADHD and Healthy Controls  

Science.gov (United States)

Background The degree to which distinct behavioral components of impulsivity predict alcohol consumption is as yet not well-understood. Further, the possibility that this relation might be more pronounced in groups characterized by heightened impulsivity (i.e., individuals with ADHD) has not been tested. Methods The current study examined the degree to which three specific behavioral components of impulsivity (i.e., poor response inhibition, poor attentional inhibition, and increased risk-taking) were associated with quantity and frequency of alcohol consumption in a group of young adult social drinkers with ADHD (n = 33) and in a comparison control group (n = 21). Participants performed the delayed ocular return task (attentional inhibition), the cued go/no-go task (behavioral inhibition), and the Balloon Analogue Risk Task (risk-taking). Results Both poor behavioral inhibition and greater risk-taking were related to greater quantity of consumption in the entire sample, whereas poor attentional inhibition was related to greater quantity specifically among those with ADHD. By contrast, only risk-taking was associated with frequency of consumption, and this was found specifically in the control group. Conclusions These findings provide important information regarding the potential role of distinct behavioral components of impulsivity in drinking behavior, and highlight unique relevance of attentional impairments to drinking behavior in those with ADHD. PMID:20863628

Weafer, Jessica; Milich, Richard; Fillmore, Mark T.

2010-01-01

219

Stability and Stabilization of Impulsive Stochastic Delay Difference Equations  

Directory of Open Access Journals (Sweden)

Full Text Available When an impulsive control is adopted for a stochastic delay difference system (SDDS, there are at least two situations that should be contemplated. If the SDDS is stable, then what kind of impulse can the original system tolerate to keep stable? If the SDDS is unstable, then what kind of impulsive strategy should be taken to make the system stable? Using the Lyapunov-Razumikhin technique, we establish criteria for the stability of impulsive stochastic delay difference equations and these criteria answer those questions. As for applications, we consider a kind of impulsive stochastic delay difference equation and present some corollaries to our main results.

Liming Wang

2010-01-01

220

LMFBR core flowering response to an impulse load  

International Nuclear Information System (INIS)

Some incidental situations like MFCI (Meeting Fuel Coolant Incident) may induce a core flowering and lead to consider impulse loads applied to LMFBR core. These highly dynamic loads are very different considering their spatial repartition and their frequency content from the seismic loads which have been deeply studied. Recently, tests have been performed on the LMFBR core mock-up RAPSODIE in order to validate the calculation methods for centered impulse load. These tests consist in injecting water quickly in the mock-up through a specific device replacing the core central assembly. The influence of the injection pressure and the influence of the injection axial position have been investigated. During the tests, the top displacements of some assemblies have been measured. The aim of this paper is first to present the experimental device and the test results. Then a non linear numerical model is described; this model includes the impact between subassemblies and is based on an homogenization method allowing to take into account with accuracy the fluid structure interaction. The comparisons between calculation results and test results will finally be presented

 
 
 
 
221

The genetic correlation between impulsivity and sensation seeking traits.  

Science.gov (United States)

A number of studies have demonstrated associations between sensation seeking traits and measures of impulsivity. This study examined contributions to the observed correlations between imupulsivity and sensation seeking traits. Fifty-seven pairs of identical and 49 pairs of fraternal twins who were reared apart and 90 individuals who also participated in the Minnesota Study of Twins Reared Apart completed the Control scale of the Multidimensional Personality Questionnaire (MPQ; Tellegen, 1982) and the four subscales of the Sensation Seeking Scale (SSS; Zuckerman, 1979). Consistent with previous studies, the Control scale was significantly correlated with the SSS. A Cholesky decomposition of the data indicated that the phenotypic correlations between the Control scale and the four subscales of the SSS were mediated almost entirely by genetic factors. In the final reduced model the proportion of the genetic variance of the Control scale in common with the SSS was estimated as 55%, and the rest of the genetic variance (45%) was attributed to the genetic variance specific to the Control scale. The results emphasize the importance of common biological mechanisms underlying associations between impulsivity and sensation seeking traits. PMID:9336082

Hur, Y M; Bouchard, T J

1997-09-01

222

Tomographic reconstruction of the pulse-echo spatiotemporal impulse response  

Science.gov (United States)

Virtually every area of ultrasonic imaging research requires accurate estimation of the spatiotemporal impulse response of the instrument, and yet accurate measurements are difficult to achieve. The impulse response can also be difficult to predict numerically for a specific device because small unknown perturbations in array properties can generate significant changes in predicted pulse-echo field patterns. A typical measurement for a 1-D array transducer employs a line scatterer oriented perpendicular to the scan plane. Echoes from line scatterers located throughout the field of view constitute estimates of shift-varying line response functions. We propose an inverse-problem approach to the reconstruction of point-spread functions from line-spread functions. A collection of echoes recorded for a range of line-scatterer rotation angles are treated as projections of sound pressure onto the transducer array surface. Although the reconstruction is mathematically equivalent to filtered backprojection, it provides significant advantages with respect to interpolation that confound straightforward implementations. Field II predictions used to model measurements made on commercial systems suggest the reconstruction accuracy is with 0.32% for noiseless echo data. Application of the method to data acquired from a commercial system are evaluated from the perspective of deconvolution.

Nguyen, Nghia Q.; Abbey, Craig K.; Yapp, Rebecca D.; Insana, Michael F.

2010-03-01

223

Interactive effects of drinking history and impulsivity on college drinking  

Science.gov (United States)

The transition from adolescence into emerging adulthood is a critical developmental period for changes in alcohol use and drinking related problems. Prior research has identified a number of distinct developmental alcohol use trajectories, which appear to be differentially related to young adult drinking outcomes. Another correlate of alcohol use in early adulthood is impulsivity. The primary aim of this study was to examine the moderating role of impulsivity in the relation between patterns of past alcohol use and hazardous drinking during the first year of college. Participants (N=452; 49% male; mean age 18.5 years; 82% Caucasian) completed self-report measures during the first year of college, including retrospective alcohol use calendars, current alcohol use and drinking problems, and personality. Group-based trajectory modeling was used to identify groups with similar adolescent drinking history from retrospective, self-report. Four groups were identified: abstainers/very light users, late/moderate users, early/moderate users, and steep increase/heavy users. The abstainer/very light user group reported the lowest levels of alcohol use and problematic drinking in college; the steep increase/heavy use group reported the highest levels of alcohol use and problematic drinking. As predicted, the role of personality—specifically urgency, or emotion-based rash action—was strongest among moderate use groups. These findings may be helpful in guiding targeted prevention and intervention programs for alcohol use and abuse. PMID:24018231

Adams, Zachary W.; Milich, Richard; Lynam, Donald R.; Charnigo, Richard J.

2014-01-01

224

Development of metrics to identify military impulse noise  

Science.gov (United States)

Urban encroachment of military bases continues to be a serious problem, affecting training exercises and overall military readiness. The military currently performs noise monitoring around bases to ensure that environmental conditions are favorable for tests or exercises. Despite refinements, current monitoring systems still suffer from occasional false positives and rely heavily on human interpretation. The long range goal of this work is to create a more accurate and autonomous noise classifier. The specific aims of the work are to create a library of recorded military impulse noise sources and to develop, test, and refine the noise classifier algorithms. Representative, high quality field measurements of various noise sources (25 mm and larger) will be conducted at a few military bases under varying environmental conditions. Measurements of wind noise and thunder will also be recorded. The software will be developed in MATLAB and will employ several common impulse noise metrics used for hearing conservation, including rise, peak, and fall times, crest factor, A- and B-durations, Lpk and kurtosis, among others. A neural network will be trained to discern between the recorded military noise sources and naturally occuring noise based on these metrics. Preliminary results from the measurements and analysis will be presented. [Work supported by SERDP.

Vipperman, Jeffrey S.

2005-04-01

225

Morphometric correlation of impulsivity in medial prefrontal cortex.  

Science.gov (United States)

Impulsivity is a complex behaviour composed of different domains encompassing behavioural dis-inhibition, risky decision-making and delay discounting abnormalities. To investigate regional brain correlates between levels of individual impulsivity and grey matter volume, we performed voxel-based morphometric correlation analysis in 34 young, healthy subjects using impulsivity scores measured with Barratt Impulsivity Scale-11 and computerized Kirby's delay discounting task. The VBM analysis showed that impulsivity appears to be reliant on a network of cortical (medial prefrontal cortex and dorsolateral prefrontal cortex) and subcortical (ventral striatum) structures emphasizing the importance of brain networks associated with reward related decision-making in daily life as morphological biomarkers for impulsivity in a normal healthy population. While our results in healthy volunteers may not directly extend to pathological conditions, they provide an insight into the mechanisms of impulsive behaviour in patients with abnormalities in prefrontal/frontal-striatal connections, such as in drug abuse, pathological gambling, ADHD and Parkinson's disease. PMID:23274773

Cho, Sang Soo; Pellecchia, Giovanna; Aminian, Kelly; Ray, Nicola; Segura, Barbara; Obeso, Ignacio; Strafella, Antonio P

2013-07-01

226

Impulsive action and impulsive choice across substance and behavioral addictions: cause or consequence?  

Science.gov (United States)

Substance use disorders are prevalent and debilitating. Certain behavioral syndromes ('behavioral addictions') characterized by repetitive habits, such as gambling disorder, stealing, shopping, and compulsive internet use, may share clinical, co-morbid, and neurobiological parallels with substance addictions. This review considers overlap between substance and behavioral addictions with a particular focus on impulsive action (inability to inhibit motor responses), and impulsive choice (preference for immediate smaller rewards to the detriment of long-term outcomes). We find that acute consumption of drugs with abuse potential is capable of modulating impulsive choice and action, although magnitude and direction of effect appear contingent on baseline function. Many lines of evidence, including findings from meta-analyses, show an association between chronic drug use and elevated impulsive choice and action. In some instances, elevated impulsive choice and action have been found to predate the development of substance use disorders, perhaps signifying their candidacy as objective vulnerability markers. Research in behavioral addictions is preliminary, and has mostly focused on impulsive action, finding this to be elevated versus controls, similar to that seen in chronic substance use disorders. Only a handful of imaging studies has explored the neural correlates of impulsive action and choice across these disorders. Key areas for future research are highlighted along with potential implications in terms of neurobiological models and treatment. In particular, future work should further explore whether the cognitive deficits identified are state or trait in nature: i.e. are evident before addiction perhaps signaling risk; or are a consequence of repetitive engagement in habitual behavior; and effects of novel agents known to modulate these cognitive abilities on various addictive disorders. PMID:24864028

Grant, Jon E; Chamberlain, Samuel R

2014-11-01

227

Thin film eddy current impulse deicer  

Science.gov (United States)

Two new styles of electrical impulse deicers has been developed and tested in NASA's Icing Research Tunnel. With the Eddy Current Repulsion Deicing Boot (EDB), a thin and flexible spiral coil is encapsulated between two thicknesses of elastomer. The coil, made by an industrial printed circuit board manufacturer, is bonded to the aluminum aircraft leading edge. A capacitor bank is discharged through the coil. Induced eddy currents repel the coil from the aluminum aircraft structure and shed accumulated ice. A second configuration, the Eddy Current Repulsion Deicing-Strip (EDS) uses an outer metal erosion strip fastened over the coil. Opposite flowing eddy currents repel the strip and create the impulse deicing force. The outer strip serves as a surface for the collection and shedding of ice and does not require any structural properties. The EDS is suitable for composite aircraft structures. Both systems successfully dispelled over 95 percent of the accumulated ice from airfoils over the range of the FAA icing envelope.

Smith, Samuel O.; Zieve, Peter B.

1990-01-01

228

Pinning impulsive control algorithms for complex network  

International Nuclear Information System (INIS)

In this paper, we further investigate the synchronization of complex dynamical network via pinning control in which a selection of nodes are controlled at discrete times. Different from most existing work, the pinning control algorithms utilize only the impulsive signals at discrete time instants, which may greatly improve the communication channel efficiency and reduce control cost. Two classes of algorithms are designed, one for strongly connected complex network and another for non-strongly connected complex network. It is suggested that in the strongly connected network with suitable coupling strength, a single controller at any one of the network's nodes can always pin the network to its homogeneous solution. In the non-strongly connected case, the location and minimum number of nodes needed to pin the network are determined by the Frobenius normal form of the coupling matrix. In addition, the coupling matrix is not necessarily symmetric or irreducible. Illustrative examples are then given to validate the proposed pinning impulsive control algorithms

229

[Formation of impulses in an excitable medium].  

Science.gov (United States)

The paper deals with the evolution of initial perturbation in an active distributed system, described by non-linear equations of a diffusion type. Division of all movements into the less than slow greater than and less than fast greater than ones in time and space makes it possible to give a simple analytical description of all the stages. The following cases are possible: a) Initial distribution limited in space falls into two diverging impulses, each of them consists of two sharp fronts connected by slow movements. While propagating each impulse acquires a stationary form; b) Meeting fronts are formed in the wave, the result is that the initial perturbation disappears in a finite time; c) A sharp front with zero rate of propagation is initiated; its slow evolution may lead to an autooscillation process. The solutions obtained are applicable to the description of concentration waves in oscillatory chemical reactions. PMID:1138960

Ostrovski?, L A; Iakhno, V G

1975-01-01

230

FEM Analysis of Turgo Impulse Turbine Blade  

Directory of Open Access Journals (Sweden)

Full Text Available The present research work describes the development of Turgo turbine blades on the Solidworks software. Finite element simulation (Ansys V14 has been used for analysis of stress and total deformation produced inside the Turgo impulse turbine. Finite element simulation is effective when it is used to analyze the strain and stress distribution. It has been observed during analysis that the maximum stress occurs at the root of blade suction side.

Sourabh KHURANA

2013-07-01

231

Literature Survey on Impulse Noise Reduction  

Directory of Open Access Journals (Sweden)

Full Text Available In every image processing algorithm quality of image plays a very vital role because the output of thealgorithm depends on the quality of input image. Hence, several techniques are used for image qualityenhancement and image restoration. Some of them are common techniques applied to all the imageswithout having prior knowledge of noise and are called image enhancement algorithms. Some of the imageprocessing algorithms use the prior knowledge of the type of noise present in the image and are referred toas image restoration techniques. Image restoration techniques are also referred to as image de-noisingtechniques. In such cases, identified inverse degradation functions are used to restore images. In thissurvey, we review several impulse noise removal techniques reported in the literature and identify efficientimplementations. We analyse and compare the performance of different reported impulse noise reductiontechniques with Restored Mean Absolute Error (RMAE under different noise conditions. Also, we identifythe most efficient impulse noise removing filters. Marking the maximum and minimum performance offilters helps in designing and comparing the new filters which give better results than the existing filters

Manohar Koli

2013-10-01

232

Impulse approximation versus elementary particle method  

International Nuclear Information System (INIS)

Calculations are made for radiative muon capture in 3He, both in impulse approximation and with the elementary particle method, and results are compared. It is argued that a diagrammatic method which takes a selected set of Feynman diagrams into account only provides insufficient warrant that effects not included are small. Therefore low-energy theorems are employed, as first given by Adler and Dothan, to determine the amplitude up to and including all terms linear in photon momentum and momentum transfer at the weak vertex. This amplitude is applied to radiative muon capture with the elementary particle method (EPM). The various form factors needed are discussed. It is shown that the results are particularly sensitive to the ?-3He-3H coupling constant of which many contradictory determinations have been described in the literature. The classification of the nuclear wave function employed in the impulse approximation (IA) is summarized. The ?-decay of 3H and (radiative muon capture in 3He is treated and numerical results are given. Next, pion photoproduction and radiative pion capture are considered. IA and EPM for radiative muon capture are compared more closely. It is concluded that two-step processes are inherently difficult; the elementary particle method has convergence problems, and unknown parameters are present. In the impulse approximation, which is perhaps conceptually more difficult, the two-step interaction for the nucleon is considered as effectively point-like with small non-local corrections. (Auth.)

233

Development of the relativistic impulse approximation  

International Nuclear Information System (INIS)

This talk contains three parts. Part I reviews the developments which led to the relativistic impulse approximation for proton-nucleus scattering. In Part II, problems with the impulse approximation in its original form - principally the low energy problem - are discussed and traced to pionic contributions. Use of pseudovector covariants in place of pseudoscalar ones in the NN amplitude provides more satisfactory low energy results, however, the difference between pseudovector and pseudoscalar results is ambiguous in the sense that it is not controlled by NN data. Only with further theoretical input can the ambiguity be removed. Part III of the talk presents a new development of the relativistic impulse approximation which is the result of work done in the past year and a half in collaboration with J.A. Tjon. A complete NN amplitude representation is developed and a complete set of Lorentz invariant amplitudes are calculated based on a one-meson exchange model and appropriate integral equations. A meson theoretical basis for the important pair contributions to proton-nucleus scattering is established by the new developments. 28 references

234

A preliminary case study of androgen receptor gene polymorphism association with impulsivity in women with alcoholism  

Directory of Open Access Journals (Sweden)

Full Text Available Daniel J Mettman, Merlin G Butler, Albert B Poje, Elizabeth C Penick, Ann M Manzardo Departments of Psychiatry and Behavioral Sciences and Pediatrics, MS 4015, Kansas University Medical Center, Kansas City, KS, USA Objective: The androgen receptor (AR gene, located on the X chromosome, contains a common polymorphism involving cytosine-adenine-guanine (CAG repeats, which impacts disease and could contribute to the unequal sex ratio in alcoholism. CAG repeats in the AR gene are known to correlate with impulsivity in males. We report the first preliminary study examining the association between the number of CAG repeats and measures of impulsivity in females with chronic alcoholism. Methods: A total of 35 women and 85 men with chronic alcoholism were previously recruited for a nutritional clinical trial, and 26 well-characterized females (19 African–American and seven Caucasian with alcoholism agreed to participate for genetic testing. Genomic deoxyribonucleic acid (DNA was isolated from peripheral blood and CAG repeats determined by analyzing polymerase chain reaction (PCR-amplified products, using the polymorphic AR gene assay. CAG repeat length was correlated with raw scores from the Barratt Impulsivity Scale, version 11 and the Alcoholism Severity Scale. Results: CAG repeat lengths were significantly longer in Caucasian alcoholic women compared with African–Americans, and the average number of CAG repeats were significantly, positively correlated (P<0.05 with impulsivity scores. Women with average CAG repeat length (CAGave ?18, representing the upper quartile of the repeat range, showed significantly greater mean raw impulsivity scores. CAG repeat length appeared to have less effect in African–American compared with Caucasian women, possibly due to a shorter average repeat length. Conclusion: We found an association between the number of CAG repeats and impulsivity in females with chronic alcoholism, specifically in women with CAGave ?18, seen more commonly in Caucasian compared with African–American women. Keywords: AR gene, CAG repeat, African-American, Caucasian, behavior

Mettman DJ

2014-03-01

235

The integrated design of powder aligning and impulse magnetizing systems  

International Nuclear Information System (INIS)

This paper describes an integrated finite element based methodology for the design and analysis of powder aligning systems and impulse magnetizing fixtures for the manufacture of anisotropic bonded Nd Fe B permanent magnet components. The relationships between the final component properties and the magnitudes of the aligning field and subsequent magnetizing field are illustrated by extensive experimental characterization of a commercial grade of anisotropic Nd Fe B injection moulding compound (Compodic NDA502E). The modelling techniques employed are experimentally validated by a case study on a 4 pole self-shielding rotor, the mould and fixture parameters for which were specifically selected to produce only partial alignment and saturation. The utility of an automated design technique is illustrated by the optimization of a mould to achieve near full alignment and saturation of the 4 pole rotor. (author)

236

Anomalous electron transport in high power impulse magnetron sputtering  

International Nuclear Information System (INIS)

Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is charge perturbation-or so-called modified two-stream instabilities (MTSIs). It is known that MTSIs give rise to acceleration of the charged plasma species and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion using collisions to transport electrons has failed.

237

Anomalous electron transport in high power impulse magnetron sputtering  

Energy Technology Data Exchange (ETDEWEB)

Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is charge perturbation-or so-called modified two-stream instabilities (MTSIs). It is known that MTSIs give rise to acceleration of the charged plasma species and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion using collisions to transport electrons has failed.

Lundin, Daniel; Helmersson, Ulf [Plasma and Coatings Physics Division, IFM-Materials Physics, Linkoeping University, SE-581 83 Linkoeping (Sweden); Kirkpatrick, Scott; Rohde, Suzanne [Mechanical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0656 (United States); Brenning, Nils [Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm (Sweden)], E-mail: danlu@ifm.liu.se

2008-05-01

238

Stability Analysis and Design of Impulsive Control Lorenz Systems Family  

International Nuclear Information System (INIS)

Lorenz systems family unifying Lorenz system, Chen system and Lue system is a typical chaotic family. In this paper, we consider impulsive control Lorenz chaotic systems family with time-varying impulse intervals. By establishing an effective tool of a set of inequalities, we analyze the asymptotic stability of impulsive control Lorenz systems family and obtain some new less conservative conditions. Based on the stability analysis, we design a novel impulsive controller with time-varying impulse intervals. Illustrative examples are provided to show the feasibility and effectiveness of our method. The obtained results not only can be used to design impulsive control for Lorenz systems family, but also can be extended to other chaotic systems. (general)

239

Exponential Stability of Impulsive Discrete Systems with Multiple Delays  

Directory of Open Access Journals (Sweden)

Full Text Available The stability problem of impulsive discrete systems with multiple delays is studied. By means of the Lyapunov stability theory and discrete-time Halanay-type inequality technique, we develop sufficient conditions for the exponential stability for the impulsive discrete systems with multiple delays, which involves multiple delays not only at non-impulsive time instants but also at impulsive time instants. The results are extended to two special discrete systems: the delayed discrete systems with time delays at only impulsive time instants and the delayed discrete systems with time delays at only non-impulsive time instants. Finally, the validity of the obtained results is shown by a numerical example

Yuanqiang Chen

2013-11-01

240

The Relationship between Impulsive and Reflective Problem Solving Behavior  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Problem solving is an axial ability of educational promotion. Impulsive individual against reflectivity has fewer tendencies to involve in solving different problems. The purpose of present study was to evaluate the correlation between impulsivity, need for cognition and problem solving performance.Materials and Method: In this study, 72 individuals were randomly selected. Missionaries and cannibal's problem, Barrat Impulsivity Scale (BIS-11 and need for cognition scale were used for evaluation. Results: Findings show negative correlation between problem solving performance and impulsivity and positive correlation between problem solving and need for cognition. Duration of problem solving was not correlated with need for cognition and impulsivity.Conclusion: Pearson coefficient of correlation show that individuals with high level of need for cognition had better performance in problem solving accuracy but duration of problem solving is not related to impulsivity and need for cognition

Vahid Nejati

2012-03-01

 
 
 
 
241

Virtual Shopping and Impulse Purchasing Strengths and Weaknesses in Pakistan  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This research analyzed the perceptive of consumers doing online shopping and impulse purchasing. This study examined the behavior of thirty consumers who were asked to fill the questionnaire based on some close ended questions. The focus of this investigation was to discuss the strengths and Weaknesses of online shopping and impulse purchasing in developing country like Pakistan. Today consumers choose and buy things while sitting at home through internet and buy things impulsively. Do consum...

Muhammad Ali Hussain; Muhammad Zeeshan Anwar; Humna Mehboob; Ayesha Majeed; Tanzila Samin

2011-01-01

242

Impulsive synchronization of Chen's hyperchaotic system  

Energy Technology Data Exchange (ETDEWEB)

In this Letter the impulsive synchronization of the Chen's hyperchaotic systems is discussed. Some new and sufficient conditions on varying impulsive distance are established in order to guarantee the synchronizabillity of the systems using the synchronization method. In particular, some simple conditions are derived in synchronizing the systems by equal impulsive distances. Two illustrative examples are provided to show the feasibility and the effectiveness of the proposed method. The boundaries of the stable regions are also estimated.

Haeri, Mohammad [Advanced Control System Lab, Electrical Engineering Department, Sharif University of Technology, Tehran (Iran, Islamic Republic of)]. E-mail: haeri@sina.sharif.edu; Dehghani, Mahsa [Advanced Control System Lab, Electrical Engineering Department, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

2006-08-07

243

Lipschitz stability of impulsive systems of differential equations  

Energy Technology Data Exchange (ETDEWEB)

Notions of Lipschitz stability of the zero solution of impulsive systems of differential equations with fixed moments of impulse effect are introduced. Sufficient conditions for various types of uniform Lipschitz stability are obtained and the relations between these notions are investigated. The results obtained are used for the investigation of the uniform Lipschitz stability of the zero solution for linear impulsive systems of differential equations.

Kulev, G.K.; Bainov, D.D. (Plovdiv Univ., Plovdiv, (Bulgaria))

1991-05-01

244

Force and impulse from an Aharonov-Bohm flux line  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We calculate the force and impulse operators for a charged particle in the field of an Aharonov-Bohm flux line. The force operator is formally the Lorentz force, with the magnetic field operator modified to include quantum corrections due to anomolous commutation relations. Expectation values for stationary states are calculated. Nonstationary states are treated by integrating the force operator in time to obtain the impulse operator. Expectation values of the impulse are ca...

Keating, J. P.; Robbins, J. M.

2002-01-01

245

Effects of Pramipexole on Impulsive Choice in Male Wistar Rats  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Clinical reports, primarily with Parkinson's disease patients, note an association between the prescribed use of pramipexole (and other direct-acting dopamine agonist medications) and impulse control disorders, particularly pathological gambling. Two experiments examined the effects of acute pramipexole on rats' impulsive choices where impulsivity was defined as selecting a smaller–sooner over a larger–later food reward. In Experiment 1, pramipexole (0.1 to 0.3 mg/kg) significantly...

Madden, Gregory J.; Johnson, P.; Brewer, A.; Pinkston, J. W.; Fowler, S.

2010-01-01

246

Energetic electrons in impulsive solar flares  

International Nuclear Information System (INIS)

A new analysis was made of a thermal flare model proposed by Brown, Melrose, and Spicer (1979) and Smith and Lilliequist (1979). They assumed the source of impulsive hard X-rays to be a plasma at a temperature of order 10 to the 8th power K, initially located at the apex of a coronal arch, and confined by ion-acoustic turbulence in a collisionless conduction front. Such a source would expand at approximately the ion-sound speed, C sub S square root of (k T sub e/m sub i), until it filled the arch. Brown, Melrose, and Spicer and Smith and Brown (1980) argued that the source assumed in this model would not explain the simultaneous impulsive microwave emission. In contrast, the new results presented herein suggest that this model leads to the development of a quasi-Maxwellian distribution of electrons that explains both the hard X-ray and microwave emissions. This implies that the source sizes can be determined from observations of the optically-thick portions of microwave spectra and the temperatures obtained from associated hard X-ray observations. In this model, the burst emission would rise to a maximum in a time, t sub r, approximately equal to L/c sub s, where L is the half-length of the arch. New observations of these impulsive flare emissions were analyzed herein to test this prediction of the model. Observations made with the Solar Maximum Mission spacecraft and the Bern Radio Observatory are in good agreement with the modelodel

247

Energetic electrons in impulsive solar flares  

Science.gov (United States)

A new analysis was made of a thermal flare model proposed by Brown, Melrose, and Spicer (1979) and Smith and Lilliequist (1979). They assumed the source of impulsive hard X-rays to be a plasma at a temperature of order 10 to the 8th power K, initially located at the apex of a coronal arch, and confined by ion-acoustic turbulence in a collisionless conduction front. Such a source would expand at approximately the ion-sound speed, C sub S = square root of (k T sub e/m sub i), until it filled the arch. Brown, Melrose, and Spicer and Smith and Brown (1980) argued that the source assumed in this model would not explain the simultaneous impulsive microwave emission. In contrast, the new results presented herein suggest that this model leads to the development of a quasi-Maxwellian distribution of electrons that explains both the hard X-ray and microwave emissions. This implies that the source sizes can be determined from observations of the optically-thick portions of microwave spectra and the temperatures obtained from associated hard X-ray observations. In this model, the burst emission would rise to a maximum in a time, t sub r, approximately equal to L/c sub s, where L is the half-length of the arch. New observations of these impulsive flare emissions were analyzed herein to test this prediction of the model. Observations made with the Solar Maximum Mission spacecraft and the Bern Radio Observatory are in good agreement with the model.

Batchelor, D. A.

1984-01-01

248

Impulsive and Compulsive Behaviours in Parkinson's disease  

Science.gov (United States)

Impulsive compulsive behaviours (ICBs) in Parkinson’s disease (PD) are a common and devastating side effect of dopamine replacement therapy. In this review we describe the phenomenology, prevalence and risk factors of these patients. Results of behavioural studies assessing the neuropsychological profile emphasize that the ICBs, which are behavioural addictions, are not hedonically motivated. Rather, other factors such as the inability to cope with uncertainty may be triggering ICBs. New insights from functional imaging studies, strengthening the incentive salience hypothesis are discussed and therapeutic guidelines for the management of ICBs in PD are given. PMID:24313567

Averbeck, BB; O'Sullivan, SS; Djamshidian, A

2014-01-01

249

Impulsive and compulsive behaviors in Parkinson's disease.  

Science.gov (United States)

Impulsive-compulsive behaviors (ICBs) in Parkinson's disease (PD) are a common and devastating side effect of dopamine replacement therapy. In this review we describe the phenomenology, prevalence, and risk factors of patients with PD. Results of behavioral studies assessing the neuropsychological profile of patients with PD emphasize that the ICBs, which are behavioral addictions, are not hedonically motivated. Rather, other factors such as the inability to cope with uncertainty may be triggering ICBs. New insights from functional imaging studies, strengthening the incentive salience hypothesis, are discussed, and therapeutic guidelines for the management of ICBs in PD are given. PMID:24313567

Averbeck, B B; O'Sullivan, S S; Djamshidian, A

2014-01-01

250

Dynamical mechanical systems under random impulses  

CERN Document Server

The book presents the methods of analysis of dynamical mechanical systems subjected to stochastic excitations in form of random trains of impulses. This particular class of excitations is adequately characterized by stochastic point processes and behaviour of dynamical systems is governed by stochastic differential equations driven by point processes. Based on the methods of point processes the analytical techniques are devised to characterize the response of linear and nonlinear mechanical systems as the solutions of underlying stochastic differential equations. A number of example problems o

Iwankiewicz, R

1995-01-01

251

Tbe nonequilibrium statistical performances of impulse signals  

International Nuclear Information System (INIS)

It is shown theoretically and experimentally that impulse signals of various waveforms have the common behavior of the information entropy change depending on dispersion (form factor) and fractal dimension. Signal entropy of simple form raises proportionally to dispersion, normalized entropy of complicated signals with self-similar properties diminishes till the value that belongs to interval [I1, I2], where I1=0.567, I2=0.806 - are universal numbers, that were theoretically determined. Realization of the self-organized signals are obtained experimentally - using the generator with nonlinear inertial converter, and numerically - using the nonlinear equations of corresponding three-dimensional dynamic system. (author)

252

Antiepileptics for aggression and associated impulsivity  

Science.gov (United States)

Background Aggression is a major public health issue and is integral to several mental health disorders. Antiepileptic drugs may reduce aggression by acting on the central nervous system to reduce neuronal hyper-excitability associated with aggression. Objectives To evaluate the efficacy of antiepileptic drugs in reducing aggression and associated impulsivity. Search methods We searched CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, metaRegister of Controlled Trials (mRCT) and ClinicalTrials.gov to April 2009. We also searched Cochrane Schizophrenia Group’s register of trials on aggression, National Research Record and handsearched for studies. Selection criteria Prospective, placebo-controlled trials of antiepileptic drugs taken regularly by individuals with recurrent aggression to reduce the frequency or intensity of aggressive outbursts. Data collection and analysis Three authors independently selected studies and two authors independently extracted data. We calculated standardised mean differences (SMDs), with odds ratios (ORs) for dichotomous data. Main results Fourteen studies with data from 672 participants met the inclusion criteria. Five different antiepileptic drugs were examined. Sodium valproate/divalproex was superior to placebo for outpatient men with recurrent impulsive aggression, for impulsively aggressive adults with cluster B personality disorders, and for youths with conduct disorder, but not for children and adolescents with pervasive developmental disorder. Carbamazepine was superior to placebo in reducing acts of self-directed aggression in women with borderline personality disorder, but not in children with conduct disorder. Oxcarbazepine was superior to placebo for verbal aggression and aggression against objects in adult outpatients. Phenytoin was superior to placebo on the frequency of aggressive acts in male prisoners and in outpatient men including those with personality disorder, but not on the frequency of ‘behavioral incidents’ in delinquent boys. Authors’ conclusions The authors consider that the body of evidence summarised in this review is insufficient to allow any firm conclusion to be drawn about the use of antiepileptic medication in the treatment of aggression and associated impulsivity. Four antiepileptics (valproate/ divalproex, carbamazepine, oxcarbazepine and phenytoin) were effective, compared to placebo, in reducing aggression in at least one study, although for three drugs (valproate, carbamazepine and phenytoin) at least one other study showed no statistically significant difference between treatment and control conditions. Side effects were more commonly noted for the intervention group although adverse effects were not well reported. Absence of information does not necessarily mean that the treatment is safe, nor that the potential gains from the medication necessarily balance the risk of an adverse event occurring. Further research is needed. PMID:20166067

Huband, Nick; Ferriter, Michael; Nathan, Rajan; Jones, Hannah

2014-01-01

253

Transient Impulsive Giant Electronic Raman Redistribution  

CERN Document Server

Resonant Raman excitation by ultrafast vacuum ultraviolet laser pulses is a powerful means to study electron dynamics in molecules, but experiments must contend with linear background ionization: frequencies high enough to reach resonant core-valence transitions will usually ionize all occupied orbitals as well, and the ionization cross sections are usually dominant. Here we show that attosecond pulses can induce a new process, transient impulsive stimulated Raman scattering, which can overwhelm valence ionization. Calculations are performed for atomic sodium, but the principal is valid for many molecular systems. This approach opens the path for high fidelity multidimensional spectroscopy with attosecond pulses.

Miyabe, S

2014-01-01

254

PERFORMANCE OF IMPULSE NOISE DETECTION METHODS IN REMOTE SENSING IMAGES  

Directory of Open Access Journals (Sweden)

Full Text Available Remote sensing (RS images are affected by different types of noises like Gaussian noise, speckle noise and impulse noise. These noises are introduced into the RS images during acquisition or transmission process. The main challenge in impulse noise removal is to suppress the noise as well as to preserve the details (edges. Removal ofthe impulse noise is done by two stages: detection of noisy pixel and replacement of that pixel. Detecting and Removing or reducing impulse noise is a very active research area in image processing. In this paper three different existing detection methods are discussed with the intension of developing a new one.

Mrs.V.RADHIKA,

2010-09-01

255

Genetic association of impulsivity in young adults: a multivariate study.  

Science.gov (United States)

Impulsivity is a heritable, multifaceted construct with clinically relevant links to multiple psychopathologies. We assessed impulsivity in young adult (N~2100) participants in a longitudinal study, using self-report questionnaires and computer-based behavioral tasks. Analysis was restricted to the subset (N=426) who underwent genotyping. Multivariate association between impulsivity measures and single-nucleotide polymorphism data was implemented using parallel independent component analysis (Para-ICA). Pathways associated with multiple genes in components that correlated significantly with impulsivity phenotypes were then identified using a pathway enrichment analysis. Para-ICA revealed two significantly correlated genotype-phenotype component pairs. One impulsivity component included the reward responsiveness subscale and behavioral inhibition scale of the Behavioral-Inhibition System/Behavioral-Activation System scale, and the second impulsivity component included the non-planning subscale of the Barratt Impulsiveness Scale and the Experiential Discounting Task. Pathway analysis identified processes related to neurogenesis, nervous system signal generation/amplification, neurotransmission and immune response. We identified various genes and gene regulatory pathways associated with empirically derived impulsivity components. Our study suggests that gene networks implicated previously in brain development, neurotransmission and immune response are related to impulsive tendencies and behaviors. PMID:25268255

Khadka, S; Narayanan, B; Meda, S A; Gelernter, J; Han, S; Sawyer, B; Aslanzadeh, F; Stevens, M C; Hawkins, K A; Anticevic, A; Potenza, M N; Pearlson, G D

2014-01-01

256

Modified impulsive synchronization of fractional order hyperchaotic systems  

International Nuclear Information System (INIS)

In this paper, a modified impulsive control scheme is proposed to realize the complete synchronization of fractional order hyperchaotic systems. By constructing a suitable response system, an integral order synchronization error system is obtained. Based on the theory of Lyapunov stability and the impulsive differential equations, some effective sufficient conditions are derived to guarantee the asymptotical stability of the synchronization error system. In particular, some simpler and more convenient conditions are derived by taking the fixed impulsive distances and control gains. Compared with the existing results, the main results in this paper are practical and rigorous. Simulation results show the effectiveness and the feasibility of the proposed impulsive control method. (general)

257

Dissecting impulsivity and its relationships to drug addictions.  

Science.gov (United States)

Addictions are often characterized as forms of impulsive behavior. That said, it is often noted that impulsivity is a multidimensional construct, spanning several psychological domains. This review describes the relationship between varieties of impulsivity and addiction-related behaviors, the nature of the causal relationship between the two, and the underlying neurobiological mechanisms that promote impulsive behaviors. We conclude that the available data strongly support the notion that impulsivity is both a risk factor for, and a consequence of, drug and alcohol consumption. While the evidence indicating that subtypes of impulsive behavior are uniquely informative-either biologically or with respect to their relationships to addictions-is convincing, multiple lines of study link distinct subtypes of impulsivity to low dopamine D2 receptor function and perturbed serotonergic transmission, revealing shared mechanisms between the subtypes. Therefore, a common biological framework involving monoaminergic transmitters in key frontostriatal circuits may link multiple forms of impulsivity to drug self-administration and addiction-related behaviors. Further dissection of these relationships is needed before the next phase of genetic and genomic discovery will be able to reveal the biological sources of the vulnerability for addiction indexed by impulsivity. PMID:24654857

Jentsch, J David; Ashenhurst, James R; Cervantes, M Catalina; Groman, Stephanie M; James, Alexander S; Pennington, Zachary T

2014-10-01

258

Impulsive control of a financial model [rapid communication  

Science.gov (United States)

In this Letter, several new theorems on the stability of impulsive control systems are presented. These theorem are then used to find the conditions under which an advertising strategy can be asymptotically control to the equilibrium point by using impulsive control. Given the parameters of the financial model and the impulsive control law, an estimation of the upper bound of the impulse interval is given, i.e., number of advert can been decreased (i.e., can decrease cost) for to obtain the equivalent advertising effect.The result is illustrated to be efficient through a numerical example.

Sun, Jitao; Qiao, Fei; Wu, Qidi

2005-02-01

259

Correlations between the disintegration of melt and the measured impulses in steam explosions  

International Nuclear Information System (INIS)

To find our correlations in steam explosions (melt water interactions) between the measured impulses and the disintegration of the melt, experiments were performed in three configurations i.e. stratified, entrapment and jet experiments. Linear correlations were detected between the impulse and the total surface of the fragments. Theoretical considerations point out that a linear correlation assumes superheating of a water layer around the fragments of a constant thickness during the fragmentation process to a constant temperature (here the homogeneous nucleation temperature of water was assumed) and a constant expansion velocity of the steam in the main expansion time. The correlation constant does not depend on melt temperature and trigger pressure, but it depends on the configuration of the experiment or of a scenario of an accident. Further research is required concerning the correlation constant. For analysing steam explosion accidents the explosivity is introduced. The explosivity is a mass specific impulse. The explosivity is linear correlated with the degree of fragmentation. Knowing the degree of fragmentation with proper correlation constant the explosivity can be calculated and from the explosivity combined with the total mass of fragments the impulse is obtained which can be used to an estimation of the maximum force

260

Motor impulsivity during childhood and adolescence: A longitudinal biometric analysis of the go/no-go task in 9- to 18-year-old twins.  

Science.gov (United States)

In the present study, we investigated genetic and environmental effects on motor impulsivity from childhood to late adolescence using a longitudinal sample of twins from ages 9 to 18 years. Motor impulsivity was assessed using errors of commission (no-go errors) in a visual go/no-go task at 4 time points: ages 9-10, 11-13, 14-15, and 16-18 years. Significant genetic and nonshared environmental effects on motor impulsivity were found at each of the 4 waves of assessment with genetic factors explaining 22%-41% of the variance within each of the 4 waves. Phenotypically, children's average performance improved across age (i.e., fewer no-go errors during later assessments). Multivariate biometric analyses revealed that common genetic factors influenced 12%-40% of the variance in motor impulsivity across development, whereas nonshared environmental factors common to all time points contributed to 2%-52% of the variance. Nonshared environmental influences specific to each time point also significantly influenced motor impulsivity. Overall, results demonstrated that although genetic factors were critical to motor impulsivity across development, both common and specific nonshared environmental factors played a strong role in the development of motor impulsivity across age. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:25347305

Bezdjian, Serena; Tuvblad, Catherine; Wang, Pan; Raine, Adrian; Baker, Laura A

2014-11-01

 
 
 
 
261

Impulse Propagation in Disordered Hertzian Chains  

Science.gov (United States)

It was shown by Nesterenko [1] that an impulse initiated at an end of a chain of elastic grains in mutual contact, i.e., interacting via the nonlinear Hertz potential, travels as a soliton-like object. Recent theoretical [2], experimental [3] and numerical studies [4] have validated his findings. In the presentation we shall examine the propagation of an impulse in an imperfect system that is characterized by grains composed of different elastic materials, different sizes, shapes and velocity-dependent friction. Our study shows that even in the presence of considerable disorder, most of the energy still travels as a weakly dispersive bundle of energy. According to our calculations, the amplitude, position and geometry of the leading pulse are related to chain disorder via simple scaling laws. We shall comment upon the inverse problem of determining the material properties by studying the pulse propagation, with many potential applications. [1] V.F. Nesterenko, J Appl Mech Tech Phys 5, 733 (1983) [2] S. Sen and M. Manciu, Physica A 268, 644 (1999); A. Chatterjee, Phys Rev E 59, 5912 (1999) [3] C. Coste, E. Falcon and S. Fauve, Phys Rev E 56, 6104 (1997); E.J. Hinch and S. Saint-Jean, Proc R Soc A 455, 3201 (1999) [4] M. Manciu, V. Tehan and S. Sen, Chaos (in press)

Manciu, Marian; Sen, Surajit; Hurd, Alan J.

2000-03-01

262

Concrete structures under impact and impulsive loading  

International Nuclear Information System (INIS)

This book contains papers contributed to the RILEM/CEB/IABSE/IASS-Interassociation Symposium on 'Concrete Structures under Impact and Impulsive Loading'. The essential aim of this symposium is to provide an international forum for the exchange of information on existing and current research relating to impact problems as well as to identify areas to which further research activities should be directed. The subject of the symposium is far ranging. Fifty five papers were proposed and arranged in six technical sessions, a task which sometimes posed difficulties for the Organization Committee and the Advisory Group, because some of the papers touched several topics and were difficult to integrate. However, we are confident that these minor difficulties were solved to the satisfaction of everyone involved. Each session of the symposium is devoted to a major subject area and introduced by a distinguished Introductory Reporter. The large international attendance, some 21 countries are represented, and the large number of excellent papers will certainly produce a lively discussion after each session and thus help to further close the gaps in our knowledge about the behaviour of structures and materials under impact and impulsive loading. (orig./RW)

263

An improved radial impulse turbine for OWC  

Energy Technology Data Exchange (ETDEWEB)

Traditionally, wells turbines have been widely used in OWC plants. However, an alternative has been studied over recent years: a self-rectifying turbine known as an impulse turbine. We are interested in the radial version of the impulse turbine, which was initially proposed by M. McCormick. Previous research was carried out using CFD (FLUENT {sup registered}), which aimed to improve knowledge of the local flow behavior and the prediction of the performance for this kind of turbine. This previous work was developed with a geometry taken from the literature, but now our goal is to develop a new geometry design with a better performance. To achieve this, we have redesigned the blade and vane profiles and improved the interaction between them by means of a new relation between their setting angles. Under sinusoidal flow conditions the new design improves the turbine efficiency by up to 5% more than the geometry proposed by Professor Setoguchi, in 2002. In this paper, the design criteria we have used is described, and the flow behavior and the performance of this new design are compared with the previous one. (author)

Pereiras, Bruno; Castro, Francisco; Rodriguez, Miguel A. [Energy Engineering and Fluid Mechanics Department, University of Valladolid, Paseo del cauce 59, 47011, Valladolid (Spain); Marjani, Abdelatif el [Labo. de Turbomachines, Ecole Mohammadia d' Ingenieurs (EMI), University of Mohammed V Agdal. Av Ibn Sina, B.P. 765 Agdal Rabat (Morocco)

2011-05-15

264

Impulsive brightenings in quiescent solar prominences  

International Nuclear Information System (INIS)

At large spatial scales, quiescent solar prominences appear static in nature, but they are dynamic at smaller scales. This thesis reports on high resolution observations of quiescent prominences using the tunable, Universal Birefringent Filter and the echelle spectrograph on the Vacuum Tower Telescope at Sacramento Peak Observatory. More than 40 hours of wavelength scans of H alpha and HeD3 disclose a class of activity near the edges of quiescent prominences, characterized by enhancement of H alpha radiative power by as much as 4 x 1024 erg s-1 and enhanced line widths of up to 0.92 A, over areas 5 to 25 arcseconds across, for lifetimes of tens of minutes; we call this activity impulsive brightenings. The H alpha profile is centrally reversed by as much as 25% in some, while other contain significant line-of-sight velocities. Brightenings with H alpha reversal show correlations between depth of reversal and both line width and peak intensity. The correlation between line width and reversal depth is closest; as functions of time and position these quantities display similar behavior. Comparison of the reversed profiles with those from a surge suggest an opacity-related cause of the central reversals. The other activity displays doppler shifts corresponding to 2 to 50 km s-1 and the H alpha profiles indicate high opacities, but are not necessarily reversed. Three models for impulsive brightening are considered

265

Parameters Determination of Oscillatory Impulse Current Waveform  

Science.gov (United States)

This paper proposes numerical techniques to distil waveform parameters out of digitally measured data of oscillatory impulse current. The first method, to be used for liner circuit, based on a curve-fitting technique in which a smooth analytical curve is defined to fit the noise-superposed measured data. The waveform parameters are derived from the curve. The algorithm is examined its performance using a measured waveform data which is obtained from a circuit composed of linear elements only. It is not rare when impulse current is measured in a circuit with non-linear element, namely an arrester. After carefully observed behaviours of the circuit current when the non-linear element turns on and off, authors developed two algorithms capable to determine the parameters from the recorded data obtained from a circuit having a ZnO arrester. The developed algorithm processed the waveform data generated by TDG which is to be issued in 2009 as a part of IEC 61083-2. The details of the algorithm are to be demonstrated in the paper.

Sato, Shuji; Nishimura, Seisuke; Seki, Shingo

266

College drinking behaviors: mediational links between parenting styles, impulse control, and alcohol-related outcomes.  

Science.gov (United States)

Mediational links between parenting styles (authoritative, authoritarian, permissive), impulsiveness (general control), drinking control (specific control), and alcohol use and abuse were tested. A pattern-mixture approach (for modeling non-ignorable missing data) with multiple-group structural equation models with 421 (206 female, 215 male) college students was used. Gender was examined as a potential moderator of parenting styles on control processes related to drinking. Specifically, the parent-child gender match was found to have implications for increased levels of impulsiveness (a significant mediator of parenting effects on drinking control). These findings suggest that a parent with a permissive parenting style who is the same gender as the respondent can directly influence control processes and indirectly influence alcohol use and abuse. PMID:16784353

Patock-Peckham, Julie A; Morgan-Lopez, Antonio A

2006-06-01

267

PARTS: (Plasma Accelerated Reusable Transport System)  

Science.gov (United States)

The Plasma Accelerated Reusable Transport System (PARTS) is an unmanned cargo shuttle intended to ferry large payloads to and from Martian orbit using a highly efficient VAriable Specific Impulse Magnetoplasma Rocket (VASIMR). The design of PARTS focuses on balancing cost and minimizing transit time for a chosen payload consisting of vehicles, satellites, and other components provided by interested parties.

Aherne, Michael; Davis, Phil; England, Matt; Gustavsson, Jake; Pankow, Steve; Sampaio, Chere; Savella, Phil

2002-01-01

268

State Estimation for the VASIMR Plasma Engine  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents work on the application of virtual metrology techniques to the VAriable Specific Impulse Magnetoplasma Rocket (VASMIR) engine. The work concentrates on the estimation of internal temperatures of the rocket using state space models and Optical Emission Spectroscopy (OES). These estimations are useful as direct thermal measurements will not be available in the final system design.

Lynn, Shane; Ringwood, John; Del Valle Gamboa, Juan Ignacio

2008-01-01

269

Sex differences in the relationship between white matter microstructure and impulsivity in adolescents.  

Science.gov (United States)

Rapid maturational brain changes occur during adolescence--a time associated with risk-taking behaviors and improvements in cognition. The present study examined the relationship between white matter (WM) microstructure, impulsive behavior and response inhibition in female and male adolescents. Twenty-one healthy adolescents underwent diffusion tensor imaging using a 3.0-T magnetic resonance imaging system. Impulse control was assessed using the Bar-On Emotional Quotient Inventory, Youth Version. Response inhibition was assessed using the Stroop Color-Word Interference Test. Fractional anisotropy (FA), a measure of WM coherence, and trace, a measure of overall diffusivity, were determined from voxels manually placed in the midline and in the left and right forward-projecting arms of the genu and the splenium of the corpus callosum. Sex-specific differences were observed for the relationship between FA and impulsive behavior in the right anterior callosum for males and in the splenium for females. Males, compared to females, displayed significantly higher FA in the left WM region. Although trace was not associated with impulse control, trace in the genu (for females) and splenium (males and females) was associated with Stroop performance. Regional differences in trace also were evident, with lower values in the splenium observed than in all other regions. Although the latter significantly improved with age, no sex differences in impulse control or in Stroop performance were detected. The present findings provide supporting evidence for sex-related differences in the development of WM microstructure during adolescence. These data further suggest a neurobiological mechanism underlying some of the emotional and cognitive changes commonly observed in males versus females during the adolescent period. PMID:16916700

Silveri, Marisa M; Rohan, Michael L; Pimentel, Patricia J; Gruber, Staci A; Rosso, Isabelle M; Yurgelun-Todd, Deborah A

2006-09-01

270

Individual Differences in Impulsive Choice and Timing in Rats  

Science.gov (United States)

Individual differences in impulsive choice behavior have been linked to a variety of behavioral problems including substance abuse, smoking, gambling, and poor financial decision-making. Given the potential importance of individual differences in impulsive choice as a predictor of behavioral problems, the present study sought to measure the extent…

Galtress, Tiffany; Garcia, Ana; Kirkpatrick, Kimberly

2012-01-01

271

GENERAL: Impulsive Control for Fractional-Order Chaotic Systems  

Science.gov (United States)

We propose an impulsive control scheme for fractional-order chaotic systems. Based on the Takagi-Sugeno (T-S) fuzzy model and linear matrix inequalities (LMIs), some sufficient conditions are given to stabilize the fractional-order chaotic system via impulsive control. Numerical simulation shows the effectiveness of this approach.

Zhong, Qi-Shui; Bao, Jing-Fu; Yu, Yong-Bin; Liao, Xiao-Feng

2008-08-01

272

Impulsive Control for Fractional-Order Chaotic Systems  

International Nuclear Information System (INIS)

We propose an impulsive control scheme for fractional-order chaotic systems. Based on the Takagi–Sugeno (T-S) fuzzy model and linear matrix inequalities (LMIs), some sufficient conditions are given to stabilize the fractional-order chaotic system via impulsive control. Numerical simulation shows the effectiveness of this approach. (general)

273

Oscillation of solutions to impulsive dynamic equations on time scales  

Directory of Open Access Journals (Sweden)

Full Text Available In this article, we study the oscillation of second order impulsive dynamic equations on time scales. The effect of the moments of impulse are fixed. Using Riccati transformation techniques, we obtain some conditions for the oscillation of all solutions

Qiaoluan Li

2009-09-01

274

Impulsive integral equations in Banach spaces and applications  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we first use the fixed point theory to prove two existence theorems of positive solutions for the impulsive Fredholm integral Equations in Banach spaces. And then, we offer some applications to the two-point boundary value problems for the second order impulsive differential equations in Banach spaces.

Dajun Guo

1992-01-01

275

Asymptotic behavior of second-order impulsive differential equations  

Directory of Open Access Journals (Sweden)

Full Text Available In this article, we study the asymptotic behavior of all solutions of 2-th order nonlinear delay differential equation with impulses. Our main tools are impulsive differential inequalities and the Riccati transformation. We illustrate the results by an example.

Haifeng Liu

2011-02-01

276

Designing an electro-impulse de-icing system  

Science.gov (United States)

Basic principles and parameters for a system to deice aircraft with electromagnetic impulses are described. The physical basis for deicing by such impulses is explained, and the requirements involved in the electrodynamic design, structural dynamic design, and system design are discussed. Some manufacturing and testing problems and techniques are described.

Zumwalt, G. W.; Friedberg, R. A.

1986-01-01

277

A new nonlinear impulsive delay differential inequality and its applications  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract In this article, a new nonlinear impulsive delay differential inequality is established, which can be applied in the dynamical analysis of nonlinear systems to improve many extant results. Using the inequality, we obtain some sufficient conditions to guarantee the exponential stability of nonlinear impulsive functional differential equations. Two examples are given to illustrate the effectiveness and advantages of our results.

Wang Huali

2011-01-01

278

Virtual Shopping and Impulse Purchasing Strengths and Weaknesses in Pakistan  

Directory of Open Access Journals (Sweden)

Full Text Available This research analyzed the perceptive of consumers doing online shopping and impulse purchasing. This study examined the behavior of thirty consumers who were asked to fill the questionnaire based on some close ended questions. The focus of this investigation was to discuss the strengths and Weaknesses of online shopping and impulse purchasing in developing country like Pakistan. Today consumers choose and buy things while sitting at home through internet and buy things impulsively. Do consumer in Pakistan are using Internet for shopping online? Do they make more impulse purchase on the Internet? Does online shopping save time? Do online shopping is more attractive or consumer feels lack of trust? Impacts of advertising are also discussed. We covered the virtual shopping weakness and strengths in our VSIPSWP (Virtual Shopping and Impulse Purchasing Strengths and Weaknesses in Pakistan Models.

Muhammad Ali Hussain

2011-11-01

279

Impulse Testing of Corporate-Fed Patch Array Antennas  

Science.gov (United States)

This paper discusses a novel method for detecting faults in antenna arrays. The method, termed Impulse Testing, was developed for corporate-fed patch arrays where the element is fed by a probe and is shorted at its center. Impulse Testing was devised to supplement conventional microwave measurements in order to quickly verify antenna integrity. The technique relies on exciting each antenna element in turn with a fast pulse (or impulse) that propagates through the feed network to the output port of the antenna. The resulting impulse response is characteristic of the path through the feed network. Using an oscilloscope, a simple amplitude measurement can be made to detect faults. A circuit model of the antenna elements and feed network was constructed to assess various fault scenarios and determine fault-detection thresholds. The experimental setup and impulse measurements for two patch array antennas are presented. Advantages and limitations of the technique are discussed along with applications to other antenna array topologies

Chamberlain, Neil F.

2011-01-01

280

Chaotic attitude control of satellite using impulsive control  

International Nuclear Information System (INIS)

Nowadays, attitude control systems of satellites demand better performance, resulting in the application of new advanced nonlinear control theory. In this paper, impulsive control is applied to a six-dimensional system which describes the attitude dynamics of a satellite subjected to deterministic external perturbations which induce chaotic motion when no control is affected. Several theorems on the stability of impulsive control systems are presented. These theorems are then used to find the conditions under which the chaotic systems can be asymptotically controlled to the origin by using impulsive control. Given the parameters of the chaotic system and the impulsive control law, an estimation of the upper bound of the impulse interval is given. Finally, we give some simulations results to visualize the effectiveness and feasibility of the proposed method.

 
 
 
 
281

The functional anatomy of impulse control disorders.  

Science.gov (United States)

Impulsive-compulsive disorders such as pathological gambling, hypersexuality, compulsive eating, and shopping are side effects of the dopaminergic therapy for Parkinson's disease. With a lower prevalence, these disorders also appear in the general population. Research in the last few years has discovered that these pathological behaviors share features similar to those of substance use disorders (SUD), which has led to the term "behavioral addictions". As in SUDs, the behaviors are marked by a compulsive drive toward and impaired control over the behavior. Furthermore, animal and medication studies, research in the Parkinson's disease population, and neuroimaging findings indicate a common neurobiology of addictive behaviors. Changes associated with addictions are mainly seen in the dopaminergic system of a mesocorticolimbic circuit, the so-called reward system. Here we outline neurobiological findings regarding behavioral addictions with a focus on dopaminergic systems, relate them to SUD theories, and try to build a tentative concept integrating genetics, neuroimaging, and behavioral results. PMID:23963609

Probst, Catharina C; van Eimeren, Thilo

2013-10-01

282

On coating adhesion during impulse plasma deposition  

Science.gov (United States)

The impulse plasma deposition (IPD) technique is the only method of plasma surface engineering (among plasma-based technologies) that allows a synthesis of layers upon a cold unheated substrate and which ensures a good adhesion. This paper presents a study of plasma impacts upon a copper substrate surface during the IPD process. The substrate was exposed to pulsed N2/Al plasma streams during the synthesis of AlN layers. For plasma-material interaction diagnostics, the optical emission spectroscopy method was used. Our results show that interactions of plasma lead to sputtering of the substrate material. It seems that the obtained adhesion of the layers is the result of a complex surface mechanism combined with the effects of pulsed plasma energy impacts upon the unheated substrate. An example of such a result is the value of the critical load for the Al2O3 layer, which was measured by the scratch-test method to be above 40 N.

Nowakowska-Langier, Katarzyna; Zdunek, Krzysztof; Chodun, Rafal; Okrasa, Sebastian; Kwiatkowski, Roch; Malinowski, Karol; Sk?adnik-Sadowska, Elzbieta; Sadowski, Marek J.

2014-05-01

283

Investigation of gas discharge impulse image intensifiers  

CERN Document Server

The gas discharge impulse image intensifiers (GDIII) operated in the streamer mode are studied in this work. The GDIII has a resolution of 5-15 lines/cm and light amplification up to approx 10 sup 1 sup 0. The possibility to design a single-electron GDIII for RICH-detectors is considered. For this purpose the emission of photoelectrons in He, Ne, Ar, Xe, CO sub 2 , iC sub 4 H sub 1 sub 0 and their mixtures in the 50-760 Torr pressure range have been investigated. The best working gas for the GDIII is Ne+(approx 0.1%)iC sub 4 H sub 1 sub 0 mixture having an electron output factor up to 0.45.

Gushchin, E M; Timofeev, M K

1999-01-01

284

Optimal Stochastic Impulse Control with Delayed Reaction  

International Nuclear Information System (INIS)

We study impulse control problems of jump diffusions with delayed reaction. This means that there is a delay ?>0 between the time when a decision for intervention is taken and the time when the intervention is actually carried out. We show that under certain conditions this problem can be transformed into a sequence of iterated no-delay optimal stopping problems and there is an explicit relation between the solutions of these two problems. The results are illustrated by an example where the problem is to find the optimal times to increase the production capacity of a firm, assuming that there are transaction costs with each new order and the increase takes place ? time units after the (irreversible) order has been placed

285

Impulse oscillometry: interpretation and practical applications.  

Science.gov (United States)

Simple spirometry and body plethysmography have been routinely used in children aged > 5 years. New techniques based on physiologic concepts that were first described almost 50 years ago are emerging in research and in clinical practice for measuring pulmonary function in children. These techniques have led to an increased understanding of the pediatric lung and respiratory mechanics. Impulse oscillometry (IOS), a simple, noninvasive method using the forced oscillation technique, requires minimal patient cooperation and is suitable for use in both children and adults. This method can be used to assess obstruction in the large and small peripheral airways and has been used to measure bronchodilator response and bronchoprovocation testing. New data suggest that IOS may be useful in predicting loss of asthma control in the pediatric population. This article reviews the clinical applications of IOS, with an emphasis on the pediatric setting, and discusses appropriate coding practices for the clinician. PMID:25180727

Bickel, Scott; Popler, Jonathan; Lesnick, Burton; Eid, Nemr

2014-09-01

286

Impulsive electron acceleration by Gravitational Waves  

CERN Document Server

We investigate the non-linear interaction of a strong Gravitational Wave with the plasma during the collapse of a massive magnetized star to form a black hole, or during the merging of neutron star binaries (central engine). We found that under certain conditions this coupling may result in an efficient energy space diffusion of particles. We suggest that the atmosphere created around the central engine is filled with 3-D magnetic neutral sheets (magnetic nulls). We demonstrate that the passage of strong pulses of Gravitational Waves through the magnetic neutral sheets accelerates electrons to very high energies. Superposition of many such short lived accelerators, embedded inside a turbulent plasma, may be the source for the observed impulsive short lived bursts. We conclude that in several astrophysical events, gravitational pulses may accelerate the tail of the ambient plasma to very high energies and become the driver for many types of astrophysical bursts.

Vlahos, L; Papadopoulos, D B; Vlahos, Loukas; Voyatzis, George; Papadopoulos, Demetrios

2004-01-01

287

Energetic electrons in impulsive solar flares  

International Nuclear Information System (INIS)

Impulsive bursts of hard X rays and microwaves are observed during most solar flares, and both emissions can be attributed to a common distribution of source electrons with energies from approximately 10 keV to several hundred keV. A detailed account of the evolution of the electron distribution is crucial to a complete description of the energy release process in flares. In this dissertation, a new analysis is made of a thermal flare model proposed by Brown, Melrose, and Spicer (1979) and Smith and Lilliequist (1979). Brown, Melrose, and Spicer (1979) and Smith and Brown (1980) argued that the source assumed in this model would not explain the simultaneous impulsive microwave emission. In contrast, the new results presented here show that this model leads to the development of a quasi-Maxwellian distribution of electrons that explains both the hard x-ray and microwave emissions. This implies that the source sizes can be determined from observations of the optically-thick portions of microwave spectra and the temperatures obtained from associated hard x-ray observations. The x-ray observations were obtained with the Hard X-ray Burst Spectrometer on board the Solar Maximum Mission spacecraft, and the microwave observations were obtained from the Bern Radio Observatory in Switzerland. The results of this investigation are in good agreement with the model and are not explained by any other flare models which have been considered. A re-evaluation of contradictory reports regarding the visibility of individual starspots led to the conclusion that large spots would indeed be observable with equipment of high precision. A comprehensive physical and evolutional model for the cumulative spectroscopic and photometric behavior of AR Lac was constructed by augmentation of other models and incorporation of the results of the present investigation

288

Relations between trait impulsivity, behavioral impulsivity, physiological arousal, and risky sexual behavior among young men.  

Science.gov (United States)

The current study examined how impulsivity-related traits (negative urgency, sensation seeking, and positive urgency), behavioral measures of risk taking and reward seeking, and physiological reactivity related to three different risky sexual behaviors in sexually active undergraduate men (N = 135). Regression analyses indicated that sensation seeking and behavioral risk-taking predicted unique variance in number of sexual partners. These findings suggest that, for young men, acquisition of new partners is associated with need for excitement and reward and willingness to take risks to meet those needs. Sensation seeking, behavioral risk-taking, and skin conductance reactivity to arousing stimuli was related to ever having engaged in sex with a stranger, indicating that, for men, willingness to have sex with a stranger is related not only to the need for excitement and risk-taking but also with innate responsiveness to arousing environmental triggers. In contrast, regression analyses indicated that young men who were impulsive in the context of negative emotions were less likely to use condoms, suggesting that emotion-based impulsivity may be an important factor in negligent prophylactic use. This study adds to the current understanding of the divergence between the correlates of risky sexual behaviors and may lend utility to the development of individualized HIV prevention programming. PMID:24958252

Derefinko, Karen J; Peters, Jessica R; Eisenlohr-Moul, Tory A; Walsh, Erin C; Adams, Zachary W; Lynam, Donald R

2014-08-01

289

Impulsive and/or planned behaviour: can impulsivity contribute to the predictive utility of the theory of planned behaviour?  

Science.gov (United States)

This prospective study tested the prediction that impulsivity would contribute to the prediction of behaviour over and above key variables from an extended theory of planned behaviour (TPB) model. At Time 1, participants completed a questionnaire including measures of TPB constructs related to the avoidance of high-calorie snacks, in addition to measures of impulsivity and dietary restraint. At Time 2, participants (N=315) completed a questionnaire assessing their snacking behaviour over the previous 2 weeks. Results revealed that impulsivity significantly contributed to the prediction of behaviour over and above TPB constructs, with those higher in impulsivity being more likely to snack. This relationship was not moderated by behavioural intention. It is concluded that impulsivity might profitably be included alongside TPB variables when predicting behaviours that are not adequately characterized by careful, analytic, compensatory decision-making strategies. PMID:18282371

Churchill, Sue; Jessop, Donna; Sparks, Paul

2008-12-01

290

Group vs. single mindfulness meditation: exploring avoidance, impulsivity, and weight management in two separate mindfulness meditation settings.  

Science.gov (United States)

Recent research has identified that mindfulness meditation in group settings supports people who are trying to lose weight. The present research investigated mindfulness meditation in group and individual settings, and explored the potential impact on weight loss and other factors (i.e. mindfulness, impulsivity, and avoidance) that may assist or hinder weight loss. Specifically, the hypotheses tested were that the group setting assisted dieters more than the individual setting by reducing weight, cognitive-behavioral avoidance, and impulsivity and by increasing mindfulness. Participants (n?=?170) who were trying to lose weight were randomly assigned to practice meditation for 6 weeks within a group or independently. Measurements in mindfulness, cognitive-behavioral avoidance, impulsivity, and weight occurred twice (pre- and post-intervention). Results indicated that participants in the group setting lost weight and lowered their levels of cognitive-behavioral avoidance, while impulsivity and mindfulness remained stable. On the other hand, participants in the individual condition lost less weight, while there was an increase in cognitive-behavioral avoidance and mindfulness scores, but a decrease in impulsivity. Seeing that benefits and limitations observed in group settings are not replicated when people meditate alone, this study concluded that mindfulness meditation in individual settings needs to be used with caution, although there are some potential benefits that could aid future weight loss research. PMID:24585500

Mantzios, Michail; Giannou, Kyriaki

2014-07-01

291

Complex Dynamics of an Impulsive Control System in which Predator Species Share a Common Prey  

Science.gov (United States)

In an ecosystem, multiple predator species often share a common prey and the interactions between the predators are neutral. In view of this fact, we propose a three-species prey-predator system with the functional responses and impulsive controls to model the process of pest management. It is proved that the system has a locally stable pest-eradication periodic solution under the assumption that the impulsive period is less than some critical value. In particular, two single control strategies (biological control alone or chemical control alone) are proposed. Finally, we compare three pest control strategies and find that if we choose narrow-spectrum pesticides that are targeted to a specific pest’s life cycle to kill the pest, then the combined strategy is preferable. Numerical results show that our system has complex dynamics including period-doubling bifurcation, quasi-periodic oscillation, chaos, intermittency and crises.

Pei, Yongzhen; Liu, Shaoying; Li, Changguo

2009-06-01

292

A simplified approach to uncertainty quantification for orbits in impulsive deflection scenarios  

Science.gov (United States)

For the majority of near-Earth Asteroid (NEA) impact scenarios, optimal deflection strategies use a massive impactor or a nuclear explosive, either of which produce an impulsive change to the orbit of the object. However, uncertainties regarding the object composition and the efficiency of the deflection event lead to a non-negligible uncertainty in the deflection delta-velocity. Propagating this uncertainty through the resulting orbit will create a positional uncertainty envelope at the original impact epoch. We calculate a simplified analytic evolution for impulsively deflected NEAs and perform a full propagation of uncertainties that is nonlinear in the deflection delta-velocity vector. This provides an understanding of both the optimal deflection velocities needed for a given scenario, as well as the resulting positional uncertainty and corresponding residual impact probability. Confidence of a successful deflection attempt as a function of launch opportunities is also discussed for a specific case.

Howley, Kirsten; Wasem, Joseph

2014-11-01

293

Time Domain Modeling of Powerline Impulsive Noise at Its Source  

Directory of Open Access Journals (Sweden)

Full Text Available Noise characteristics of an indoor power line network strongly influence the link capability to achieve high data rates. The appliances shared with PLC modems in the same powerline network generate different types of noises, among them the impulsive noises are the main source of interference resulting in signal distortions and bit errors during data transmission. With regard to impulsive noise many models were proposed in the literature and shared the same impulsive noise definition: “unpredictable noises measured in the receiver side”. Authors are, consequently, confronted to model thousands of impulsive noises whose plurality would very likely come from the diversity of paths that the original impulsive noise took. In this paper, an innovative modelling approach is applied to impulsive noises which are studied here directly at their sources. Noise at receiver would be simply the noise model at source convolved by powerline channel block. In the new analytical model, the impulsive noise at source is described by a succession of short pulses, each modeled by a phase-shifted Gaussian. Noises at source are classified into 6 different classes [1], and a noise generator is established for each class.

Hassina Chaouche

2011-09-01

294

Relationship between Impulsivity, Snack Consumption and Children's Weight  

Science.gov (United States)

Background Childhood overweight is a public health problem associated with psychosocial and physical problems. Personality traits, such as impulsivity, may contribute to the development of overweight. Objective This study examines 1) the association between general impulsivity traits (reward sensitivity and disinhibition) and children's weight, 2) the association between impulsivity traits and unhealthy snack consumption, and 3) the potential mediating role of unhealthy snack consumption in the relationship between impulsivity traits and children's weight. Methods Included were 1,377 parent-child dyads participating in the IVO Nutrition and Physical Activity Child cohorT (INPACT). Children had a mean age of 10 years. Parents completed a questionnaire to measure children's unhealthy snack consumption. Children completed a door-opening task to assess reward sensitivity and completed a questionnaire to measure disinhibition. Children's height and weight were measured to calculate their BMI z-scores. Cross-sectional linear regression analyses were performed to test the associations. Results Disinhibition was positively associated with unhealthy snack consumption but not with BMI z-scores. Reward sensitivity was not related to unhealthy snack consumption or to BMI z-scores. Conclusions No evidence was found for a mediating effect of unhealthy snack consumption in the relation between impulsivity traits and children's weight. However, disinhibition appears to have a negative influence on children's unhealthy snack consumption. Future research focusing on food-related impulsivity in addition to general impulsivity will provide additional insight into factors that influence children's unhealthy snack consumption and weight. PMID:24586413

Scholten, Eline W. M.; Schrijvers, Carola T. M.; Nederkoorn, Chantal; Kremers, Stef P. J.; Rodenburg, Gerda

2014-01-01

295

Impulsivity moderates the association between physical activity and alcohol consumption.  

Science.gov (United States)

Mounting evidence indicates that physical activity and alcohol consumption are positively associated, but potential moderators of this relationship remain unclear. Both physical activity and alcohol drinking are potentially reinforcing and may be more strongly associated among individuals who tend to be higher in reward seeking and related processes governed by the prefrontal cortex. Thus, behaviors linked to the prefrontal cortex, such as impulsivity, may influence the association between physical activity and alcohol intake. The present study therefore evaluated dimensions of impulsivity as moderators of the association between physical activity and alcohol consumption. We surveyed 198 undergraduate students and obtained self-reports of their drinking habits, physical activity, and dimensions of impulsivity. We found that moderate but not vigorous physical activity was positively associated with drinking. Linear regression analyses were used to evaluate dimensions of impulsivity as moderators of the association between physical activity (vigorous or moderate) and drinks per week. Results revealed a consistent pattern of interactions between the positive urgency and sensation seeking dimensions of impulsivity and moderate physical activity on number of drinks per week. For both interactions, there was a significant positive association between moderate physical activity and drinking at higher but not lower levels of impulsivity. We conclude that impulsivity moderates the positive association between physical activity and alcohol consumption. These results have significant implications for the development of prevention and treatment programs for alcohol use disorders. PMID:24525252

Leasure, J Leigh; Neighbors, Clayton

2014-06-01

296

The effectiveness of EEG-feedback on attention, impulsivity and EEG: a sham feedback controlled study.  

Science.gov (United States)

EEG-feedback, also called neurofeedback, is a training procedure aimed at altering brain activity, and is used as a treatment for disorders like Attention Deficit/Hyperactivity Disorder (ADHD). Studies have reported positive effects of neurofeedback on attention and other dependent variables. However, double-blind studies including a sham neurofeedback control group are lacking. The inclusion of such group is crucial to control for unspecific effects. The current work presents a sham-controlled, double-blind evaluation. The hypothesis was that neurofeedback enhances attention and decreases impulsive behavior. Participants (n=27) were students selected on relatively high scores on impulsivity/inattention questionnaires (Barrat Impulsivity Scale and Broadbent CFQ). They were assigned to a neurofeedback treatment or a sham group. (sham)Neurofeedback training was planned for 15 weeks consisting of a total of 30 sessions, each lasting 22 min. Before and after 16 sessions (i.e., interim analyses), qEEG was recorded and impulsivity and inattention was assessed using a stop signal task and reversed continuous performance task and two questionnaires. Results of the interim analyses showed that participants were blind with respect to group inclusion, but no trend towards an effect of neurofeedback on behavioral measures was observed. Therefore in line with ethical guidelines the experiment was ceased. These results implicate a possible lack of effect of neurofeedback when one accounts for non-specific effects. However, the specific form of feedback and application of the sham-controlled double-blind design may have diminished the effect of neurofeedback. PMID:20478360

Logemann, H N Alexander; Lansbergen, Marieke M; Van Os, Titus W D P; Böcker, Koen B E; Kenemans, J Leon

2010-07-19

297

A musculoskeletal model of human locomotion driven by a low dimensional set of impulsive excitation primitives.  

Science.gov (United States)

Human locomotion has been described as being generated by an impulsive (burst-like) excitation of groups of musculotendon units, with timing dependent on the biomechanical goal of the task. Despite this view being supported by many experimental observations on specific locomotion tasks, it is still unknown if the same impulsive controller (i.e., a low-dimensional set of time-delayed excitastion primitives) can be used as input drive for large musculoskeletal models across different human locomotion tasks. For this purpose, we extracted, with non-negative matrix factorization, five non-negative factors from a large sample of muscle electromyograms in two healthy subjects during four motor tasks. These included walking, running, sidestepping, and crossover cutting maneuvers. The extracted non-negative factors were then averaged and parameterized to obtain task-generic Gaussian-shaped impulsive excitation curves or primitives. These were used to drive a subject-specific musculoskeletal model of the human lower extremity. Results showed that the same set of five impulsive excitation primitives could be used to predict the dynamics of 34 musculotendon units and the resulting hip, knee and ankle joint moments (i.e., NRMSE = 0.18 ± 0.08, and R (2) = 0.73 ± 0.22 across all tasks and subjects) without substantial loss of accuracy with respect to using experimental electromyograms (i.e., NRMSE = 0.16 ± 0.07, and R (2) = 0.78 ± 0.18 across all tasks and subjects). Results support the hypothesis that biomechanically different motor tasks might share similar neuromuscular control strategies. This might have implications in neurorehabilitation technologies such as human-machine interfaces for the torque-driven, proportional control of powered prostheses and orthoses. In this, device control commands (i.e., predicted joint torque) could be derived without direct experimental data but relying on simple parameterized Gaussian-shaped curves, thus decreasing the input drive complexity and the number of needed sensors. PMID:23805099

Sartori, Massimo; Gizzi, Leonardo; Lloyd, David G; Farina, Dario

2013-01-01

298

A musculoskeletal model of human locomotion driven by a low dimensional set of impulsive excitation primitives  

Directory of Open Access Journals (Sweden)

Full Text Available Human locomotion has been described as being generated by an impulsive (burst-like excitation of groups of musculotendon units, with timing dependent on the biomechanical goal of the task. Despite this view is supported by many experimental observations on specific locomotion tasks, it is still unknown if the same impulsive controller (i.e. a low-dimensional set of time-delayed excitation primitives can be used as input drive for large musculoskeletal models across different human locomotor tasks. For this purpose, we extracted, with non-negative matrix factorization, five non-negative factors from a large sample of muscle EMG signals in two healthy subjects during four motor tasks including walking, running, sidestepping, and crossover cutting maneuvers. The extracted non-negative factors were then averaged and parameterized to obtain task-generic Gaussian-shaped impulsive excitation curves or primitives. These were used to drive a subject-specific musculoskeletal model of the human lower extremity. Results showed that the same set of five impulsive excitation primitives could be used to predict the dynamics of 34 musculotendon units and the resulting hip, knee and ankle joint moments (i.e. NRMSE = 0.18±0.08, and R2 = 0.73±0.22 across all tasks and subjects without substantial loss of accuracy with respect to using experimental EMG recordings (i.e. NRMSE = 0.16±0.07, and R2 = 0.78±0.18 across all tasks and subjects. Results support the hypothesis that dynamically different motor tasks might share similar neuromuscular control strategies. This might have implications in neurorehabilitation technologies such as human-machine interfaces for the torque-driven, proportional control of powered prostheses and orthoses. In this, device control commands (i.e. predicted joint torque could be derived without direct experimental data but relying on simple parameterized Gaussian-shaped curves, thus decreasing the input drive complexity and the number of needed sensors.

MassimoSartori

2013-06-01

299

Chaos in three species food chain system with impulsive perturbations  

International Nuclear Information System (INIS)

In this paper, we investigate three species food chain system with periodic constant impulsive perturbations of mid-level predator. Conditions for extinction of lowest-level prey and top predator are given. By using the Floquet theory of impulsive equation and small amplitude perturbation skills, we consider the local stability of lowest-level prey and top predator eradication periodic solution. Further, influences of the impulsive perturbations on the inherent oscillation are studied numerically, which shows the rich dynamics (for example: period doubling, period halfing, non-unique dynamics) in the positive octant. The dynamics behavior is found to be very sensitive to the parameter values and initial value

300

Introduction to special section: ADHD, impulsivity, and alcohol abuse.  

Science.gov (United States)

The goal of this special section is to highlight progress made and primary research reports on the relation between Attention Deficit Hyperactivity Disorder (ADHD), impulsivity, and alcohol use disorders (AUDs) utilizing a diverse range of methods. The four papers examine various psychological processes underlying the broad construct of impulsivity that are related largely to impairments in inhibitory control. The section addresses the influences of reward sensitivity, working memory/attention control, and social functioning in the development and persistence of AUDs among individuals with ADHD. These papers are important because they approach the relation between ADHD and AUDs, and the role of impulsivity, from varied perspectives. PMID:24708145

Shirley, Mariela C; Sirocco, Karen Y

2014-04-01

 
 
 
 
301

Impulse control in Kalman-like filtering problems  

Directory of Open Access Journals (Sweden)

Full Text Available This paper develops the impulse control approach to the observation process in Kalman-like filtering problems, which is based on impulsive modeling of the transition matrix in an observation equation. The impulse control generates the jumps of the estimate variance from its current position down to zero and, as a result, enables us to obtain the filtering equations for the Kalman estimate with zero variance for all post-jump time moments. The filtering equations for the estimates with zero variances are obtained in the conventional linear filtering problem and in the case of scalar nonlinear state and nonlinear observation equations.

Michael V. Basin

1998-01-01

302

The reshapers of current impulses for the contact welding  

Directory of Open Access Journals (Sweden)

Full Text Available The analysis and generalization of principles of construction of current impulses reshapers for the contact welding is conducted, taking into account new decisions in this domain and its progress modern trends. Signs on which it is possible to classify such devices are selected, and on the basis of these signs their modern classification is made. With the use of the offered classification chart the most perspective principle of construction of impulses reshapers for microwelding is selected. That is accumulation energy type reshaper of impulses without transformer on the basis of transistor regulators, workings in the continuous mode.

Paerand Yu. E.

2008-06-01

303

Correlation Between Steady State and Impulse Earth Resistance Values  

Directory of Open Access Journals (Sweden)

Full Text Available This study presented experimental results of earthing systems under low-magnitude currents and under high impulse currents. The details of the measuring circuit involved for both types of testing were described. Three field sites were selected. At each site, three earth electrodes configurations were used. This makes up to nine earthing systems. From both low magnitude and impulse tests, the correlation between the steady state earth resistance value and the earth resistance under fast impulse currents can be observed. The relation between the calculated and measured steady state earth resistance is also shown in this study.

N. M. Nor

2009-01-01

304

Effects of multiple scatter on the propagation and absorption of electromagnetic waves in a field-aligned-striated cold magneto-plasma: implications for ionospheric modification experiments  

Directory of Open Access Journals (Sweden)

Full Text Available A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found that the interaction layer is much broader than the wavelength of the test wave. This is due to the combined electric fields of the scattered waves becoming localised on the contour of a fixed plasma density, which corresponds to a constant value for the local upper-hybrid resonance frequency over the whole interaction region. The results are applied to the calculation of the refractive index of an ordinary mode test wave during modification experiments in the ionospheric F-region. Although strong anomalous absorption arises, no new cutoffs occur at the upper-hybrid resonance, so that in contrast to the predictions of previous single scatter theories, no additional reflections occur there. These results are consistent with observations made during ionospheric modification experiments at Tromsø, Norway.

Key words. Ionosphere (active experiments; ionospheric irregularities Radio science (ionospheric propagation

T. R. Robinson

305

Neurobiologia dos transtornos do controle dos impulsos / The neurobiology of impulse control disorders  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Revisar os artigos sobre substratos neurobiológicos dos transtornos do controle dos impulsos. O jogo patológico é o foco central desta revisão na medida em que a maioria dos estudos biológicos dos formalmente classificados como transtornos do controle dos impulsos examinou este transtorno. [...] MÉTODO: Foi feita uma busca no banco de dados Medline de artigos publicados de 1966 até o presente para identificar aqueles relevantes para serem revisados neste artigo. DESFECHOS: Estudos pré-clínicos sugerem que a neuromodulação das monoaminas cerebrais está associada à tomada de decisões impulsivas e aos comportamentos de risco. Os estudos clínicos implicam diversos sistemas de neurotransmissores (serotoninérgico, dopaminérgico, adrenérgico e opióide) na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. Estudos de neuroimagem preliminares têm indicado o córtex pré-frontal ventromedial e o estriato ventral como atuantes na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. As contribuições genéticas para o jogo patológico parecem substanciais e os estudos iniciais têm relacionado esse transtorno a polimorfismos alélicos específicos, ainda que os achados de varredura genômica ainda tenham que ser publicados. CONCLUSÃO: Mesmo que tenham sido logrados avanços significativos em nossa compreensão sobre os transtornos do controle dos impulsos, mais pesquisas são necessárias para ampliar o conhecimento existente e traduzir esses achados em avanços clínicos. Abstract in english OBJECTIVE: To review the neurobiological substrates of impulse control disorders. Pathological gambling is a main focus of the review in that most biological studies of the formal impulse control disorders have examined this disorder. METHOD: The medical database Medline from 1966 to present was sea [...] rched to identify relevant articles that were subsequently reviewed to generate this manuscript. RESULTS: Preclinical studies suggest that differential brain monoamine neuromodulation is associated with impulsive decision-making and risk-taking behaviors. Clinical studies implicate multiple neurotransmitter systems (serotonergic, dopaminergic, adrenergic, and opioidergic) in the pathophysiology of pathological gambling and other impulse control disorders. Initial neuroimaging studies have implicated the ventromedial prefrontal cortex and ventral striatum in the pathophysiology of pathological gambling and other impulse control disorders. Genetic contributions to pathological gambling seem substantial and initial studies have implicated specific allelic polymorphisms, although genome-wide analyses have yet to be published. CONCLUSION: Although significant advances have been made in our understanding of the neurobiology of impulse control disorders, more research is needed to extend existing knowledge and translate these findings into clinical advances.

Wendol A, Williams; Marc N, Potenza.

306

Neurobiologia dos transtornos do controle dos impulsos The neurobiology of impulse control disorders  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Revisar os artigos sobre substratos neurobiológicos dos transtornos do controle dos impulsos. O jogo patológico é o foco central desta revisão na medida em que a maioria dos estudos biológicos dos formalmente classificados como transtornos do controle dos impulsos examinou este transtorno. MÉTODO: Foi feita uma busca no banco de dados Medline de artigos publicados de 1966 até o presente para identificar aqueles relevantes para serem revisados neste artigo. DESFECHOS: Estudos pré-clínicos sugerem que a neuromodulação das monoaminas cerebrais está associada à tomada de decisões impulsivas e aos comportamentos de risco. Os estudos clínicos implicam diversos sistemas de neurotransmissores (serotoninérgico, dopaminérgico, adrenérgico e opióide na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. Estudos de neuroimagem preliminares têm indicado o córtex pré-frontal ventromedial e o estriato ventral como atuantes na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. As contribuições genéticas para o jogo patológico parecem substanciais e os estudos iniciais têm relacionado esse transtorno a polimorfismos alélicos específicos, ainda que os achados de varredura genômica ainda tenham que ser publicados. CONCLUSÃO: Mesmo que tenham sido logrados avanços significativos em nossa compreensão sobre os transtornos do controle dos impulsos, mais pesquisas são necessárias para ampliar o conhecimento existente e traduzir esses achados em avanços clínicos.OBJECTIVE: To review the neurobiological substrates of impulse control disorders. Pathological gambling is a main focus of the review in that most biological studies of the formal impulse control disorders have examined this disorder. METHOD: The medical database Medline from 1966 to present was searched to identify relevant articles that were subsequently reviewed to generate this manuscript. RESULTS: Preclinical studies suggest that differential brain monoamine neuromodulation is associated with impulsive decision-making and risk-taking behaviors. Clinical studies implicate multiple neurotransmitter systems (serotonergic, dopaminergic, adrenergic, and opioidergic in the pathophysiology of pathological gambling and other impulse control disorders. Initial neuroimaging studies have implicated the ventromedial prefrontal cortex and ventral striatum in the pathophysiology of pathological gambling and other impulse control disorders. Genetic contributions to pathological gambling seem substantial and initial studies have implicated specific allelic polymorphisms, although genome-wide analyses have yet to be published. CONCLUSION: Although significant advances have been made in our understanding of the neurobiology of impulse control disorders, more research is needed to extend existing knowledge and translate these findings into clinical advances.

Wendol A Williams

2008-05-01

307

Neurobiologia dos transtornos do controle dos impulsos / The neurobiology of impulse control disorders  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Revisar os artigos sobre substratos neurobiológicos dos transtornos do controle dos impulsos. O jogo patológico é o foco central desta revisão na medida em que a maioria dos estudos biológicos dos formalmente classificados como transtornos do controle dos impulsos examinou este transtorno. [...] MÉTODO: Foi feita uma busca no banco de dados Medline de artigos publicados de 1966 até o presente para identificar aqueles relevantes para serem revisados neste artigo. DESFECHOS: Estudos pré-clínicos sugerem que a neuromodulação das monoaminas cerebrais está associada à tomada de decisões impulsivas e aos comportamentos de risco. Os estudos clínicos implicam diversos sistemas de neurotransmissores (serotoninérgico, dopaminérgico, adrenérgico e opióide) na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. Estudos de neuroimagem preliminares têm indicado o córtex pré-frontal ventromedial e o estriato ventral como atuantes na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. As contribuições genéticas para o jogo patológico parecem substanciais e os estudos iniciais têm relacionado esse transtorno a polimorfismos alélicos específicos, ainda que os achados de varredura genômica ainda tenham que ser publicados. CONCLUSÃO: Mesmo que tenham sido logrados avanços significativos em nossa compreensão sobre os transtornos do controle dos impulsos, mais pesquisas são necessárias para ampliar o conhecimento existente e traduzir esses achados em avanços clínicos. Abstract in english OBJECTIVE: To review the neurobiological substrates of impulse control disorders. Pathological gambling is a main focus of the review in that most biological studies of the formal impulse control disorders have examined this disorder. METHOD: The medical database Medline from 1966 to present was sea [...] rched to identify relevant articles that were subsequently reviewed to generate this manuscript. RESULTS: Preclinical studies suggest that differential brain monoamine neuromodulation is associated with impulsive decision-making and risk-taking behaviors. Clinical studies implicate multiple neurotransmitter systems (serotonergic, dopaminergic, adrenergic, and opioidergic) in the pathophysiology of pathological gambling and other impulse control disorders. Initial neuroimaging studies have implicated the ventromedial prefrontal cortex and ventral striatum in the pathophysiology of pathological gambling and other impulse control disorders. Genetic contributions to pathological gambling seem substantial and initial studies have implicated specific allelic polymorphisms, although genome-wide analyses have yet to be published. CONCLUSION: Although significant advances have been made in our understanding of the neurobiology of impulse control disorders, more research is needed to extend existing knowledge and translate these findings into clinical advances.

Wendol A, Williams; Marc N, Potenza.

2008-05-01

308

High power impulse magnetron sputtering discharge  

Energy Technology Data Exchange (ETDEWEB)

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique, which is easily scalable and has been successfully introduced into various industrial applications. The authors give an overview of the development of the HiPIMS discharge, and the underlying mechanisms that dictate the discharge properties. First, an introduction to the magnetron sputtering discharge and its various configurations and modifications is given. Then the development and properties of the high power pulsed power supply are discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Finally, some of the models that have been developed to gain understanding of the discharge processes are reviewed, including the phenomenological material pathway model, and the ionization region model.

Gudmundsson, J. T.; Brenning, N.; Lundin, D.; Helmersson, U. [University of Michigan--Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240 (China) and Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland); Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44, Stockholm (Sweden); Plasma and Coatings Division, IFM-Materials Physics, Linkoeping University, SE-581 83, Linkoeping (Sweden)

2012-05-15

309

Impulsive dynamic equations on a time scale  

Directory of Open Access Journals (Sweden)

Full Text Available Let $mathbb{T}$ be a time scale such that $0, t_i, T in mathbb{T}$, $i = 1, 2, dots, n$, and $0 < t_i < t_{i+1}$. Assume each $t_i$ is dense. Using a fixed point theorem due to Krasnosel'skii, we show that the impulsive dynamic equation $$displaylines{ y^{Delta}(t = -a(ty^{sigma}(t+ f ( t, y(t ,quad t in (0, T],cr y(0 = 0,cr y(t_i^+ = y(t_i^- + I (t_i, y(t_i , quad i = 1, 2, dots, n, }$$ where $y(t_i^pm = lim_{t o t_i^pm} y(t$, and $y^Delta$ is the $Delta$-derivative on $mathbb{T}$, has a solution. Under a slightly more stringent inequality we show that the solution is unique using the contraction mapping principle. Finally, with the aid of the contraction mapping principle we study the stability of the zero solution on an unbounded time scale.

Youssef N. Raffoul

2008-05-01

310

[Impulsive-compulsive syndrome in Parkinson's disease].  

Science.gov (United States)

Dopaminergic replacement therapy (DRT) is effective in treatment the motor symptoms of Parkinson's disease (PD) but can lead to impulse control disorders (ICD) in some patients. ICD include pathological gambling, hypersexuality, compulsive shopping, binge eating, punding, dopamine dysregulation syndrome (DDS). Authors studied the prevalence of ICD and its impact on the quality of life and daily activities of PD patients and their relatives. Among 246 patients studied, 55 patients (23%) (28 men, mean age 66.5±9.4 years) were diagnosed with ICD. DDS was noted in 36.4%, punding in 36.4%, binge eating in 23.6%, hypersexuality in 14.5%, compulsive shopping in 14.5% and pathological gambling in 1.8%. Of these 55 patients, 10 (18.1%) had symptoms of 2 of the ICDs: 3 (5.45%) had 3 of the ICDs and 2 (3.63%) patients had 5 of the ICDs. Quality of life ranged from 25% to 89%. Treatment approaches including the adjustment of doses of levodopa and dopamine receptor agonists in PD patients with ICD are presented. PMID:23994929

Nikitina, A V; Fedorova, N V

2013-01-01

311

Controllability of impulsive functional differential systems with nonlocal conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In this article, we study the controllability of impulsive functional differential equations with nonlocal conditions. We establish sufficient conditions for controllability, via the measure of noncompactness and Monch fixed point theorem.

Yansheng Liu

2013-08-01

312

On second order impulsive functional differential equations in Banach spaces  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a fixed point theorem due to Schaefer is used to investigate the existence of solutions for second order impulsive functional differential equations in Banach spaces.

M. Benchohra

2002-01-01

313

Impulse Cytophotometry as a Quantitative Method of Cytochemistry.  

Science.gov (United States)

The problems involved in histochemical quantification procedures are discussed using determination of the amounts of substances in the cell nucleus as an example. Uses of the impulse cytophotometer are compared with absorption photometry methods. Uses of ...

H. Krug

1975-01-01

314

On eventual stability of impulsive systems of differential equations  

Directory of Open Access Journals (Sweden)

Full Text Available The notions of Lipschitz stability of impulsive systems of differential equations are extended and the notions of eventual stability are introduced. New notions called eventual and eventual Lipschitz stability. We give some criteria and results.

A. A. Soliman

2001-11-01

315

First- and second-order dynamic equations with impulse  

Directory of Open Access Journals (Sweden)

Full Text Available We present existence results for discontinuous first- and continuous second-order dynamic equations on a time scale subject to fixed-time impulses and nonlinear boundary conditions.

Atici FM

2005-01-01

316

First- and second-order dynamic equations with impulse  

Directory of Open Access Journals (Sweden)

Full Text Available We present existence results for discontinuous first- and continuous second-order dynamic equations on a time scale subject to fixed-time impulses and nonlinear boundary conditions.

D. C. Biles

2005-05-01

317

Electro-impulse de-icing - A status report  

Science.gov (United States)

The advantages and disadvantages of the Electro-Impulse De-Icing (EIDI) system are examined. The design and operation of the EIDI are described. The effect of repeated impulsive loads on the structure and skin of the aircraft surface is investigated. It is observed that the wing skin directly over the coil receives the greatest stresses. Data from the testing of metal leading edges reveal that after 11,500 impulses cracks appear in the sheet brackets attaching the ribs to the coil beams. The composite leading edge was evaluated for fatigue, and after 20,000 impulses no cracks were detected. The advantages of the band-aid coil mount are discussed.

Zumwalt, G. W.

1988-01-01

318

Oscillation of high order linear functional differential equation with impulses  

Directory of Open Access Journals (Sweden)

Full Text Available We study the solutions to high-order linear functional differential equations with impulses. We improve previous results in the oscillation theory for ordinary differential equations and obtain new criteria on the oscillation of solutions.

Haihua Liang

2005-08-01

319

The hierarchical structure of self-reported impulsivity  

Science.gov (United States)

The hierarchical structure of 95 self-reported impulsivity items, along with delay-discount rates for money, was examined. A large sample of college students participated in the study (N = 407). Items represented every previously proposed dimension of self-reported impulsivity. Exploratory PCA yielded at least 7 interpretable components: Prepared/Careful, Impetuous, Divertible, Thrill and Risk Seeking, Happy-Go-Lucky, Impatiently Pleasure Seeking, and Reserved. Discount rates loaded on Impatiently Pleasure Seeking, and correlated with the impulsiveness and venturesomeness scales from the I7 (Eysenck, Pearson, Easting, & Allsopp, 1985). The hierarchical emergence of the components was explored, and we show how this hierarchical structure may help organize conflicting dimensions found in previous analyses. Finally, we argue that the discounting model (Ainslie, 1975) provides a qualitative framework for understanding the dimensions of impulsivity. PMID:20224803

Kirby, Kris N.; Finch, Julia C.

2010-01-01

320

Oscillation of nonlinear impulsive hyperbolic equations with several delays  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we study oscillatory properties of solutions to nonlinear impulsive hyperbolic equations with several delays. Sufficient conditions for oscillations of the solutions are established.

Anping Liu

2004-02-01

 
 
 
 
321

Variational Method to the Impulsive Equation with Neumann Boundary Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available We study the existence and multiplicity of classical solutions for second-order impulsive Sturm-Liouville equation with Neumann boundary conditions. By using the variational method and critical point theory, we give some new criteria to guarantee that the impulsive problem has at least one solution, two solutions, and infinitely many solutions under some different conditions, respectively. Some examples are also given in this paper to illustrate the main results.

Sun Juntao

2009-01-01

322

Impulse Control of a Diffusion with a Change Point  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper solves a Bayes sequential impulse control problem for a diffusion, whose drift has an unobservable parameter with a change point. The partially-observed problem is reformulated into one with full observations, via a change of probability measure which removes the drift. The optimal impulse controls can be expressed in terms of the solutions and the current values of a Markov process adapted to the observation filtration. We shall illustrate the application of our ...

Abbas-turki, Lokman A.; Karatzas, Ioannis; Li, Qinghua

2014-01-01

323

Asymptotic stability of a genetic network under impulsive control  

International Nuclear Information System (INIS)

The study of the stability of genetic network is an important motif for the understanding of the living organism at both molecular and cellular levels. In this Letter, we provide a theoretical method for analyzing the asymptotic stability of a genetic network under impulsive control. And the sufficient conditions of its asymptotic stability under impulsive control are obtained. Finally, an example is given to illustrate the effectiveness of the obtained method.

324

Manipulation of plasma grating by impulsive molecular alignment  

International Nuclear Information System (INIS)

We experimentally demonstrated that multiphoton-ionization-induced plasma grating in air could be precisely manipulated by impulsive molecular alignment. In the linear region, the impulsively aligned molecules modulated the diffraction efficiency of the plasma grating for a time-delayed femtosecond laser pulse. In the nonlinear region, the third harmonic generation from the plasma grating was either enhanced or suppressed by following the alignment of the molecules

325

Impulsive plasma waves observed by DE 1 in nightside magnetosphere  

International Nuclear Information System (INIS)

Impulsive plasma waves with a frequency range of 1-9 kHz were found in the wide-band electric field data (650 Hz to 10 kHz) from the DE 1 satellite received at the Kashima station in Japan. The impulsive plasma waves were often accompanied by a strong hiss band at about 1 kHz, but not by a chorus. The frequency-time spectra of these waves are very similar to those of electrostatic bursts associated with ELF chorus in the outer dayside magnetosphere, but these impulsive waves were observed at low geomagnetic latitudes in nightside magnetospheric regions much nearer the Earth for geomagnetic quiet and disturbed times. Local plasma densities (? 1 cm-3) obtained from the characteristic frequency of VLF emissions associated with the impulsive plasma waves agree with those observed simultaneously by the DE 1 retarding ion mass spectrometer. It is inferred from the local plasma density and the empirical relation of the plasmapause position with Kp that the impulsive plasma waves are occurring just outside the plasmapause. The impulsive plasma waves are discussed in terms of a resistive medium instability caused by Landau resonant trapping of thermal electrons by the associated hiss band at about 1 kHz, since this mechanism seems to be plausible from the available data and the frequency-time spectra are similar to electrostatic bursts identified previously. Some of the events do not seem to have a strong ELF hiss band accompanying the impulsive plasma waves. It ipanying the impulsive plasma waves. It is suggested that these events may be due to electrons bunched by an ELF hiss band in a nearby region or may be caused by space discharges in the vicinity of the long-wire antenna on the DE 1 spacecraft

326

Robust stability of impulsive systems: A functional-based approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An improved functional-based approach for the stability analysis of linear uncertain impulsive systems relying on Lyapunov looped-functionals is provided. Looped functionals are peculiar functionals that allow to encode discrete-time stability criteria into continuous-time conditions and to consider non-monotonic Lyapunov functions along the trajectories of the impulsive system. Unlike usual discrete-time stability conditions, the obtained ones are convex in the system matrices, an important ...

Briat, Corentin; Seuret, Alexandre

2012-01-01

327

From gene to brain to behavior: schizophrenia-associated variation in AMBRA1 alters impulsivity-related traits.  

Science.gov (United States)

Recently, genome-wide association between schizophrenia and an intronic variant in AMBRA1 (rs11819869) was reported. Additionally, in a reverse genetic approach in adult healthy subjects, risk allele carriers showed a higher medial prefrontal cortex blood oxygen level-dependent (BOLD) response during a flanker task examining motor inhibition as an aspect of impulsivity. To test whether this finding can be expanded to further aspects of impulsivity, we analysed the effects of the rs11819869 genotype on impulsivity-related traits on a behavioral, temperament and neural level in a large sample of healthy adolescents. We consider this reverse genetic approach specifically suited for use in a healthy adolescent sample, as these individuals comprise those who will eventually develop mental disorders in which impulsivity is implicated. Healthy adolescents from the IMAGEN study were included in the neuropsychological analysis (n = 848) and a functional magnetic resonance imaging (fMRI) task (n = 512). Various aspects of impulsivity were assessed using the Temperament and Character Inventory-Revised, the Substance Use Risk Profile Scale, the Cambridge Cognition Neuropsychological Test Automated Battery, and the Stop Signal Task (SST) in the fMRI paradigm. On a behavioral level, increased delay aversion was observed in risk allele carriers. Furthermore, risk allele carriers showed a higher BOLD response in an orbito-frontal target region during the SST, which declined to trend status after Family Wise Error correction. Our findings support the hypothesis that the schizophrenia-related risk variant of rs11819869 is involved in various aspects of impulsivity, and that this involvement occurs on a behavioral as well as an imaging genetics level. PMID:23551272

Heinrich, Angela; Nees, Frauke; Lourdusamy, Anbarasu; Tzschoppe, Jelka; Meier, Sandra; Vollstädt-Klein, Sabine; Fauth-Bühler, Mira; Steiner, Sabina; Bach, Christiane; Poustka, Luise; Banaschewski, Tobias; Barker, Gareth J; Büchel, Christian; Conrod, Patricia J; Garavan, Hugh; Gallinat, Jürgen; Heinz, Andreas; Ittermann, Bernd; Loth, Eva; Mann, Karl; Artiges, Eric; Paus, Tomáš; Lawrence, Claire; Pausova, Zdenka; Smolka, Michael N; Ströhle, Andreas; Struve, Maren; Witt, Stephanie H; Schumann, Gunter; Flor, Herta; Rietschel, Marcella

2013-09-01

328

Parental inconsistency, impulsive choice and neural value representations in healthy adolescents.  

Science.gov (United States)

A well-characterized potential marker for addiction is impulsive choice, stably measured by delay discounting (DD) paradigms. While genetic influences partly account for inter-individual variance in impulsivity, environmental factors such as parenting practices may have an important role. The present study investigates how inconsistent fulfillment of delayed reward promises impacts on DD. A combined correlational and experimental functional magnetic resonance imaging (fMRI) design was performed in a sample of 48 healthy adolescents (13-15 years). More specifically, neural activation during a DD task was investigated at two assessment points (T0 and T1). Adolescents' self-reports of parenting and substance use were assessed at T0. Between assessment points, we experimentally varied the reliability of delayed reward promises, measuring the impact of this intervention on DD and neural value processing at T1. In the correlational part, same-sex parent reward inconsistency was associated with steeper DD and an attenuated subjective value (SV) representation in the nucleus accumbens (NAcc) and ventromedial prefrontal cortex (vmPFC). Steeper DD was in turn associated with alcohol use during the past year. In the experimental part, the reward inconsistency manipulation resulted in an attenuation of the NAcc SV representation, similar to the parental inconsistency effect. Together, our correlational and experimental findings raise new light on how parents may influence their children's degree of impulsivity, making parenting a potential target in addiction prevention. PMID:24736798

Schneider, S; Peters, J; Peth, J M; Büchel, C

2014-01-01

329

[Impulsivity in sexual offenders--new ideas or back to basics?].  

Science.gov (United States)

Despite the fact that the group of sexual offenders remains a population which is still difficult to study, the results of current research are considered novel and interesting. Surprisingly, the very old descriptions applying to paraphilia, which is considered to be one of the reasons of sexual offences, appear to be accurate, especially in the context of similarities between impulsivity and pathologic sexual behaviors. Notably, the nomenclature concerning impulsivity enables a specific and reasonable description of behaviors associated with sexual offences. Moreover, the results of research studies show that it is the lack of inhibition, not pathologic arousal, which is the most important factor in the pathogenesis of forbidden sexual behaviors. In addition, it has been shown that behavioral manifestations of impulsivity (substance abuse, suicide attempts) appear commonly in sexual offenders. Mutual relationships between alcohol drinking, suicide attempts, history of child sexual abuse and sexual offences, both in symptomatologic and etiologic aspect, raise a suggestion that all these phenomena may share a common background of poor inhibitory control. PMID:24946478

Krasowska, Aleksandra; Jakubczyk, Andrzej; Czernikiewicz, Wies?aw Marek; Wojnar, Marcin; Nasierowski, Tadeusz

2013-01-01

330

The effects of vasopressin deficiency on aggression and impulsiveness in male and female rats.  

Science.gov (United States)

The role of vasopressin in aggression received much attention in recent years. However, vasopressin has complex roles on social behavior, which are affected by social experience, motivation and hormonal background, suggesting that its effects depend on the condition of subjects. This hypothesis was tested here by studying the impact of vasopressin deficiency on aggressiveness in reproductively naive and reproductively experienced males, as well as in lactating females, with special reference to the patterns and contexts of attack behavior. We also studied effects on impulsiveness, a behavioral feature strongly related to aggression. Vasopressin deficiency did not affect aggressiveness in reproductively experienced males, decreased the share of violent attacks in reproductively inexperienced males without affecting total attack counts, and suppressed maternal aggression in both early and late phases of lactation; violent forms of attack were decreased in the latter but not the former phase. Changes in aggression appeared unrelated to general changes in maternal behaviors. Impulsivity in the delay discounting task was markedly decreased by vasopressin deficiency in lactating females but not males. Taken together, our findings confirm that vasopressin has an impact on aggressiveness, but show that this impact depends on the condition of subjects, and suggest that the effects of vasopressin on maternal aggression develop in conjunction with impulsivity. Interestingly, overall effects on aggression and specific effects on violent attacks dissociated in both males and females, which hints to the possibility that vasopressin has distinct roles in the development of escalated forms of aggression. PMID:25001964

Fodor, Anna; Barsvari, Beata; Aliczki, Mano; Balogh, Zoltan; Zelena, Dora; Goldberg, Steven R; Haller, Jozsef

2014-09-01

331

Longitudinal trajectories of sensation seeking, risk taking propensity, and impulsivity across early to middle adolescence.  

Science.gov (United States)

Adolescent substance use and abuse show associations with increases in disinhibitory constructs, including sensation seeking, risk taking propensity, and impulsivity. However, the longitudinal trajectories of these constructs from early to middle adolescence remain largely unknown. Thus, the current study examined these developmental trajectories in 277 adolescents (Mage=11.00 at Wave 1), over five consecutive yearly waves. Controlling for age, Hierarchical Linear Modeling analyses showed that sensation seeking increased linearly, whereas risk taking propensity and impulsivity demonstrated curvilinear changes. Specifically, risk taking propensity increased in the first four waves of assessment but did not evidence changes at the last assessment wave. Impulsivity, on the other hand peaked at wave four before subsequently declining. A comparison between females and males and Black and White adolescents suggested that these groups' trajectories were similar. Black adolescents' sensation seeking trajectory differed from adolescents who belonged to the "Other" racial group (i.e., adolescents who neither self-identified as Black or White). Generally, the study findings replicate and extend earlier work indicating that these risk factors increase across early adolescence and begin to level-off during middle adolescence. The importance of understanding the natural course of these core constructs is of great importance for directing future relevant prevention and intervention work. PMID:24566195

Collado, Anahi; Felton, Julia W; MacPherson, Laura; Lejuez, C W

2014-11-01

332

STOP TALKING ! Inhibition of speech is affected by word frequency and dysfunctional impulsivity  

Directory of Open Access Journals (Sweden)

Full Text Available Speaking is a complex natural behavior that most people master very well. Nevertheless, systematic investigation of the factors that affect adaptive control over speech production is relatively scarce. The present experiments quantified and compared inhibitory control over manual and verbal responses using the stop-signal paradigm. In tasks with only two response alternatives, verbal expressions were slower than manual responses, but the stopping latencies of hand and verbal actions were comparable. When engaged in a standard picture-naming task using a large set of pictures, verbal stopping latencies were considerably prolonged. Interestingly, stopping was slower for naming words that are less frequently used compared to words that are used more frequently. These results indicate that adaptive action control over speech production is affected by lexical processing. This notion is compatible with current theories on speech self-monitoring. Finally, stopping latencies varied with individual differences in impulsivity, indicating that specifically dysfunctional impulsivity, and not functional impulsivity, is associated with slower verbal stopping.

WeryVan Den Wildenberg

2010-09-01

333

Determination of acoustical transfer functions using an impulse method  

Science.gov (United States)

The Transfer Function of a system may be defined as the relationship of the output response to the input of a system. Whilst recent advances in digital processing systems have enabled Impulse Transfer Functions to be determined by computation of the Fast Fourier Transform, there has been little work done in applying these techniques to room acoustics. Acoustical Transfer Functions have been determined for auditoria, using an impulse method. The technique is based on the computation of the Fast Fourier Transform (FFT) of a non-ideal impulsive source, both at the source and at the receiver point. The Impulse Transfer Function (ITF) is obtained by dividing the FFT at the receiver position by the FFT of the source. This quantity is presented both as linear frequency scale plots and also as synthesized one-third octave band data. The technique enables a considerable quantity of data to be obtained from a small number of impulsive signals recorded in the field, thereby minimizing the time and effort required on site. As the characteristics of the source are taken into account in the calculation, the choice of impulsive source is non-critical. The digital analysis equipment required for the analysis is readily available commercially.

MacPherson, J.

1985-02-01

334

Association of impulsivity and polymorphic microRNA-641 target sites in the SNAP-25 gene.  

Science.gov (United States)

Impulsivity is a personality trait of high impact and is connected with several types of maladaptive behavior and psychiatric diseases, such as attention deficit hyperactivity disorder, alcohol and drug abuse, as well as pathological gambling and mood disorders. Polymorphic variants of the SNAP-25 gene emerged as putative genetic components of impulsivity, as SNAP-25 protein plays an important role in the central nervous system, and its SNPs are associated with several psychiatric disorders. In this study we aimed to investigate if polymorphisms in the regulatory regions of the SNAP-25 gene are in association with normal variability of impulsivity. Genotypes and haplotypes of two polymorphisms in the promoter (rs6077690 and rs6039769) and two SNPs in the 3' UTR (rs3746544 and rs1051312) of the SNAP-25 gene were determined in a healthy Hungarian population (N = 901) using PCR-RFLP or real-time PCR in combination with sequence specific probes. Significant association was found between the T-T 3' UTR haplotype and impulsivity, whereas no association could be detected with genotypes or haplotypes of the promoter loci. According to sequence alignment, the polymorphisms in the 3' UTR of the gene alter the binding site of microRNA-641, which was analyzed by luciferase reporter system. It was observed that haplotypes altering one or two nucleotides in the binding site of the seed region of microRNA-641 significantly increased the amount of generated protein in vitro. These findings support the role of polymorphic SNAP-25 variants both at psychogenetic and molecular biological levels. PMID:24391914

Németh, Nóra; Kovács-Nagy, Réka; Székely, Anna; Sasvári-Székely, Mária; Rónai, Zsolt

2013-01-01

335

Analysis and design of set-stability for impulsive control systems  

International Nuclear Information System (INIS)

This Letter studies analysis and design of set-stability for impulsive control systems. A new comparison theorem of asymptotic set-stability for impulsive differential system is presented. Based on the new result, we derive some less conservative conditions for asymptotic set-stability of impulsive control systems with impulse at fixed times, and the results are used to design impulsive control laws of nonlinear systems for set-stability. A numerical example is used to verify the theoretical result

336

High power impulse magnetron sputtering discharge  

International Nuclear Information System (INIS)

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique, which is easily scalable and has been successfully introduced into various industrial applications. The authors give an overview of the development of the HiPIMS discharge, and the underlying mechanisms that dictate the discharge properties. First, an introduction to the magnetron sputtering discharge and its various configurations and modifications is given. Then the development and properties of the high power pulsed power supply are discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Finally, some of the models that have been developed to gain understandiat have been developed to gain understanding of the discharge processes are reviewed, including the phenomenological material pathway model, and the ionization region model.

337

Failure mechanisms in composite panels subjected to underwater impulsive loads  

Science.gov (United States)

This work examines the performance of composite panels when subjected to underwater impulsive loads. The scaled fluid-structure experimental methodology developed by Espinosa and co-workers was employed. Failure modes, damage mechanisms and their distributions were identified and quantified for composite monolithic and sandwich panels subjected to typical blast loadings. The temporal evolutions of panel deflection and center deflection histories were obtained from shadow Moiré fringes acquired in real time by means of high speed photography. A linear relationship of zero intercept between peak center deflections versus applied impulse per areal mass was obtained for composite monolithic panels. For composite sandwich panels, the relationship between maximum center deflection versus applied impulse per areal mass was found to be approximately bilinear but with a higher slope. Performance improvement of sandwich versus monolithic composite panels was, therefore, established specially at sufficiently high impulses per areal mass ( I0/ M¯>170 m s -1). Severe failure was observed in solid panels subjected to impulses per areal mass larger than 300 m s -1. Extensive fiber fracture occurred in the center of the panels, where cracks formed a cross pattern through the plate thickness and delamination was very extensive on the sample edges due to bending effects. Similar levels of damage were observed in sandwich panels but at much higher impulses per areal mass. The experimental work reported in this paper encompasses not only characterization of the dynamic performance of monolithic and sandwich panels but also post-mortem characterization by means of both non-destructive and microscopy techniques. The spatial distribution of delamination and matrix cracking were quantified, as a function of applied impulse, in both monolithic and sandwich panels. The extent of core crushing was also quantified in the case of sandwich panels. The quantified variables represent ideal metrics against which model predictive capabilities can be assessed.

Latourte, Félix; Grégoire, David; Zenkert, Dan; Wei, Xiaoding; Espinosa, Horacio D.

2011-08-01

338

Impulsividade e acidentes de trânsito / Impulsiveness and traffic accidents  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese CONTEXTO: As lesões por acidentes de trânsito são um problema de saúde pública e constituem uma das principais causa mortis de adultos jovens no mundo. OBJETIVO: Revisar resultados relevantes sobre a relação entre impulsividade e comportamentos de risco e acidentes de trânsito. MÉTODO: O levantament [...] o bibliográfico foi realizado nas bases MedLine, LILACS, Desastres, Cochrane Lybrary, no banco de teses da CAPES e PsycINFO, compreendendo o período de 1966 a 2006. RESULTADOS: Dos 11 estudos originais encontrados ("n" de 3806 indivíduos), seis abordaram a associação entre impulsividade e comportamento de risco no trânsito e cinco trataram da impulsividade e acidentes de trânsito. A associação entre impulsividade e correr por aventura foi observada em dois estudos e a correlação entre impulsividade e infrações em três. No desfecho acidentes, três autores mostraram associação e dois não. CONCLUSÕES: A impulsividade está associada ao comportamento de risco no trânsito, correr por aventura e infrações. A associação entre impulsividade e mais envolvimento em acidentes é controversa. Abstract in english BACKGROUND: Injuries due to road traffic accidents are a major public health problem as well as one of the main causes of death among young males aged 15 to 44 years. OBJECTIVES: This paper reviews the relation between impulsiveness and risk driving behavior and between impulsiveness and traffic acc [...] idents. METHODS: Bibliographic review. Sources: MedLine (1966 to 2006), Cochrane databases, LILACS, Desastres, PsycINFO and CAPES theses archive. RESULTS: In total, 11 original studies (n=3806). Association between impulsiveness and speeding for the thrill (02 articles), impulsiveness and driver violations (03 articles) and impulsiveness traffic road accidents (03 articles). CONCLUSIONS: The impulsiveness is associated to the risky driving behavior, "run for thrill" and "traffic violations". The association between impulsiveness and accident proness is controversal.

Marcus Maximilliano, Araújo; Leandro Fernandes, Malloy-Diniz; Fábio Lopes, Rocha.

339

Dopamine agonists and risk: impulse control disorders in Parkinson's disease.  

Science.gov (United States)

Impulse control disorders are common in Parkinson's disease, occurring in 13.6% of patients. Using a pharmacological manipulation and a novel risk taking task while performing functional magnetic resonance imaging, we investigated the relationship between dopamine agonists and risk taking in patients with Parkinson's disease with and without impulse control disorders. During functional magnetic resonance imaging, subjects chose between two choices of equal expected value: a 'Sure' choice and a 'Gamble' choice of moderate risk. To commence each trial, in the 'Gain' condition, individuals started at $0 and in the 'Loss' condition individuals started at -$50 below the 'Sure' amount. The difference between the maximum and minimum outcomes from each gamble (i.e. range) was used as an index of risk ('Gamble Risk'). Sixteen healthy volunteers were behaviourally tested. Fourteen impulse control disorder (problem gambling or compulsive shopping) and 14 matched Parkinson's disease controls were tested ON and OFF dopamine agonists. Patients with impulse control disorder made more risky choices in the 'Gain' relative to the 'Loss' condition along with decreased orbitofrontal cortex and anterior cingulate activity, with the opposite observed in Parkinson's disease controls. In patients with impulse control disorder, dopamine agonists were associated with enhanced sensitivity to risk along with decreased ventral striatal activity again with the opposite in Parkinson's disease controls. Patients with impulse control disorder appear to have a bias towards risky choices independent of the effect of loss aversion. Dopamine agonists enhance sensitivity to risk in patients with impulse control disorder possibly by impairing risk evaluation in the striatum. Our results provide a potential explanation of why dopamine agonists may lead to an unconscious bias towards risk in susceptible individuals. PMID:21596771

Voon, Valerie; Gao, Jennifer; Brezing, Christina; Symmonds, Mkael; Ekanayake, Vindhya; Fernandez, Hubert; Dolan, Raymond J; Hallett, Mark

2011-05-01

340

Dynamics of Dense Magnetized Plasma Streams and their Interaction with Material Surfaces: Comparative Studies with Magnetoplasma Compressor (MPC) and Quasi-Steady-State Plasma Accelerator QSPA Kh-50  

International Nuclear Information System (INIS)

The quasi-steady-state plasma accelerator QSPA Kh-50 and short-pulsed magnetoplasma compressor (MPC) have been used for comparative studies of plasma-surface interaction and materials erosion issues, development of recommendations for fusion reactor materials and in numerical models for validation of predictive codes. The main advantage of QSPA in simulation experiments is possibility of generation of long magnetized pulse plasma streams with the pulse duration of 0.2-0.3 ms, the ion impact energy of 0.9 keV, the heat loads up to 20 MJ/m2, and the plasma parameter betta up to 0.3, which combination is not achievable in other types of plasma sources. Using within the framework of one problem both short- (?1-3 ?s) and long pulsed (300 ?s) plasma devices permitted to investigate the plasma effects on materials surfaces in a wide range of plasma pulse duration with varied energy and particle loads to the exposed surfaces. Crack patterns (major- and micro-type) in tungsten targets and cracking thresholds (both threshold energy load for the cracking onset and threshold target temperature related to ductile-to-brittle transition) as well as residual stresses after repetitive plasma pulses have been studied for different tungsten grades and, in particular, for a deformed W material, which is considered as the ITER-reference grade. The thickness of major- and micro-cracks, the network distance as well as the penetration of cracks into the material depth are analyzed. Comparisons of the cracking failure of deformed tungsten with behaviour of sintered W samples are performed. Results of QSPA plasma exposures are compared with short pulse PSI experiments with pulsed plasma gun and dense plasma-focus facilities, aiming at features of surface damage and tungsten impurities behavior in near-surface plasma in front of the target. (author)

 
 
 
 
341

Modulating presence and impulsiveness by external stimulation of the brain  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background "The feeling of being there" is one possible way to describe the phenomenon of feeling present in a virtual environment and to act as if this environment is real. One brain area, which is hypothesized to be critically involved in modulating this feeling (also called presence is the dorso-lateral prefrontal cortex (dlPFC, an area also associated with the control of impulsive behavior. Methods In our experiment we applied transcranial direct current stimulation (tDCS to the right dlPFC in order to modulate the experience of presence while watching a virtual roller coaster ride. During the ride we also registered electro-dermal activity. Subjects also performed a test measuring impulsiveness and answered a questionnaire about their presence feeling while they were exposed to the virtual roller coaster scenario. Results Application of cathodal tDCS to the right dlPFC while subjects were exposed to a virtual roller coaster scenario modulates the electrodermal response to the virtual reality stimulus. In addition, measures reflecting impulsiveness were also modulated by application of cathodal tDCS to the right dlPFC. Conclusion Modulating the activation with the right dlPFC results in substantial changes in responses of the vegetative nervous system and changed impulsiveness. The effects can be explained by theories discussing the top-down influence of the right dlPFC on the "impulsive system".

Baumgartner Thomas

2008-08-01

342

Impulse Volt-Time Characteristics of Oil and OIP Insulation  

Directory of Open Access Journals (Sweden)

Full Text Available Estimation of insulation strength of transformer oil and Oil Impregnated Paper (OIP insulation, which constitutes major portion of insulation in power transformer, is an important task. Also, it is often necessary to evaluate the breakdown strength of oil and OIP under non-standard impulse voltages, since the oil and OIP insulation is subjected to non-standard waveshapes between inter-disc and inter-turn insulation. This necessitates for a generalized model to estimate the insulation strength of it. In this study impulse strength of transformer oil and OIP insulation have been extensively analysed for very small electrode gap distances ranging from 0.1 to 2.5 mm, which represents the inter-turn and inter-disc thickness of the insulation. The statistical mean volt-time characteristics for uniform and highly non-uniform electrode configurations are obtained experimentally for few gap distances. A Hyperbolic model is developed based on the Disruptive Effect (DE model parameters, namely onset voltage (Uo and Critical Disruptive Effect Area (DE * to predict the volt-time characteristics. The DE parameters are also utilised to predict the impulse breakdown characteristics of oil and OIP under non-standard impulse voltages of standard and unidirectional oscillatory impulse waveshapes for all the gap distances and the errors are found to be less than 10%.

S. Venkatesan

2005-01-01

343

IPD -The Use of Impulse Plasma in Surface Engineering  

Science.gov (United States)

It is evident that impulse plasma ensures both the highest level of nonequilibrity and highest level of vapour ionisation. These conditions seemed to be especially suitable for synthetizing the phases with high energetic barrier of nucleation process. In our methods, called by us as the Impulse Plasma Deposition (IPD) the impulse plasma is generated and accelerated in a coaxial accelerator. The only source of electric energy in the plasma process is condenser battery charged to the voltage of order of kVs. During the discharge of condensers individual plasmoids are being accelerated in the coaxial generator by the Ampere force to the speed of the order of 10^4 ms-1 and directed to the non-heated substrate. The most characteristic feature of the is that the synthesis proceeds in the impulse plasma itself, with the participation of ions. The crystallization on ions (ionization degree of the impulse plasma is equal to 100%) makes individual plasmoids to be strongly enriched rather in clusters or particles agglomerates with dimensions of order of single nms than the atoms. Because of the very short life time of plasmoids (approx. 10-4 sec each) the surface coalescence of particles delivered to the substrate has a limited character. As a consequence the material of the layer has nanocrystalline, globular morphology.

Zdunek, Krzysztof

2008-10-01

344

Vibration testing based on impulse response excited by laser ablation  

Science.gov (United States)

This paper proposes an innovative vibration testing method based on impulse response excited by laser ablation. In conventional vibration testing using an impulse hammer, high-frequency elements of over tens of kilohertz are barely present in the excitation force. A pulsed high-power YAG laser is used in this study for producing an ideal impulse force on a structural surface. Illuminating a point on a metal with the well-focused YAG laser, laser ablation is caused by generation of plasma on the metal. As a result, an ideal impulse excitation force generated by laser ablation is applied to the point on the structure. Therefore, it is possible to measure high-frequency FRFs due to the laser excitation. A water droplet overlay on the metal is used to adjust the force magnitude of laser excitation. An aluminum block that has nine natural frequencies below 40 kHz is employed as a test piece. The validity of the proposed method is verified by comparing the FRFs of the block obtained by the laser excitation, impulse hammer, and finite element analysis. Furthermore, the relationship between accuracy of FRF measurements and sensitivity of sensors is investigated.

Kajiwara, Itsuro; Hosoya, Naoki

2011-10-01

345

Cocaine Modulation of Frontostriatal Expression of Zif268, D2, and 5-HT2c Receptors in High and Low Impulsive Rats  

Science.gov (United States)

Impulsivity shares high comorbidity with substance abuse in humans, and high impulsivity (HI) in rats has been identified as a predictive factor for cocaine addiction-like behavior. Despite the evidence that high impulsivity is associated with altered function of corticostriatal networks, the specific neural substrates underlying the increased vulnerability of impulsive individuals to develop cocaine addiction remain unknown. We therefore investigated specific neural correlates of HI within the corticostriatal circuitry and determined how they interact with a protracted history of cocaine self-administration. We used in situ hybridization to map brain expression of two major genes implicated in impulsivity, encoding the dopamine D2 receptor (DA D2R) and the 5-HT2c receptor (5-HT2cR), and an immediate early gene associated with neuronal plasticity, zif268, in groups of rats selected for HI and low impulsivity (LI) on a 5-choice serial reaction time task (5-CSRTT) immediately after 5-CSRTT training, and following 10 or 50 days of cocaine self-administration. HI rats exhibited decreased DA D2R mRNA in the mesolimbic pathway, and increased 5-HT2cR mRNA in the orbitofrontal cortex compared with LI rats. HI rats also showed decreased zif268 mRNA in the ventral and dorsomedial striatum. Cocaine exposure decreased striatal D2R mRNA in both HI and LI rats, decreased 5-HT2cR mRNA differentially in striatal and prefrontal areas between HI and LI rats, and selectively decreased zif268 mRNA in the orbitofrontal and infralimbic cortices of HI animals. These findings implicate novel markers underlying the vulnerability of impulsive rats to cocaine addiction that localize to the OFC, infralimbic cortex, and striatum. PMID:23632436

Besson, Morgane; Pelloux, Yann; Dilleen, Ruth; Theobald, David EH; Lyon, Alan; Belin-Rauscent, Aude; Robbins, Trevor W; Dalley, Jeffrey W; Everitt, Barry J; Belin, David

2013-01-01

346

Biocontrol in an impulsive predator-prey model.  

Science.gov (United States)

We study a model for biological pest control (or "biocontrol") in which a pest population is controlled by a program of periodic releases of a fixed yield of predators that prey on the pest. Releases are represented as impulsive increases in the predator population. Between releases, predator-pest dynamics evolve according to a predator-prey model with some fairly general properties: the pest population grows logistically in the absence of predation; the predator functional response is either of Beddington-DeAngelis type or Holling type II; the predator per capita birth rate is bounded above by a constant multiple of the predator functional response; and the predator per capita death rate is allowed to be decreasing in the predator functional response and increasing in the predator population, though the special case in which it is constant is permitted too. We prove that, when the predator functional response is of Beddington-DeAngelis type and the predators are not sufficiently voracious, then the biocontrol program will fail to reduce the pest population below a particular economic threshold, regardless of the frequency or yield of the releases. We prove also that our model possesses a pest-eradication solution, which is both locally and globally stable provided that predators are sufficiently voracious and that releases occur sufficiently often. We establish, curiously, that the pest-eradication solution can be locally stable whilst not being globally stable, the upshot of which is that, if we delay a biocontrol response to a new pest invasion, then this can change the outcome of the response from pest eradication to pest persistence. Finally, we state a number of specific examples for our model, and, for one of these examples, we corroborate parts of our analysis by numerical simulations. PMID:25195089

Terry, Alan J

2014-10-01

347

Application of E^p-Stability to Impulsive Financial Model  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we consider an impulsive stochastic model for an investment with production and saving profiles. The conditions for financial growth for the investment are investigated under impulsive action and results are obtained using the quantitative and Ep stability methods. The impulsive stochastic differential equation considered is assumed to be driven by a process with jump and non-linear gestation properties. One of the results established shows that, in the long run, it is impossible for a financial investment to grow or dominates the prescribed average financial investment but has a threshold value for which the investment cannot grow beyond. It is also established that an $E^{p}-$ stable investment vector can be found which allows financial growth but this vector must be constrained to be in a given invariant set:It is advisable for the saving and depreciation to satisfy certain growth rates for proper income and investment growths.

Sam Olatunji Ale

2013-07-01

348

Nonlinear resonant interaction between acoustic impulse and electrons in superconductors  

International Nuclear Information System (INIS)

The problem of inelastic electron interaction in a perfectly pure superconductor with a longitudinal sound impulse is considered. It is shown that the problem reduces to the equivalent one of elastic scattering by the static potential, and the sound absorption is expressed in terms of the reflection coefficient of this scattering. The classical and quantum properties of the scattering are studied and the phase region in which new excitations are created is indicated. A formula is derived that expresses the density matrix of the excitations created in terms of the exact scattering matrix of an impulse. The quasiclassical creation of excitations by a smooth-shaped impulse is investigated with regard to both overbarrier and underbarrier processes

349

THz impulse radar for biomedical sensing: nonlinear system behavior  

Science.gov (United States)

The THz impulse radar is an "RF-inspired" sensor system that has performed remarkably well since its initial development nearly six years ago. It was developed for ex vivo skin-burn imaging, and has since shown great promise in the sensitive detection of hydration levels in soft tissues of several types, such as in vivo corneal and burn samples. An intriguing aspect of the impulse radar is its hybrid architecture which combines the high-peak-power of photoconductive switches with the high-responsivity and -bandwidth (RF and video) of Schottky-diode rectifiers. The result is a very sensitive sensor system in which the post-detection signal-to-noise ratio depends super-linearly on average signal power up to a point where the diode is "turned on" in the forward direction, and then behaves quasi-linearly beyond that point. This paper reports the first nonlinear systems analysis done on the impulse radar using MATLAB.

Brown, E. R.; Sung, Shijun; Grundfest, W. S.; Taylor, Z. D.

2014-03-01

350

Measuring long impulse responses with pseudorandom sequences and sweep signals  

DEFF Research Database (Denmark)

In architectural acoustics, background noise, loudspeaker nonlinearities, and time variances are the most common disturbances that can compromise a measurement. The effects of such disturbances on measurement of long impulse responses with pseudorandom sequences (maximum-length sequences (MLS) and inverse repeated sequences (IRS)) and with linear and logarithmic sweep signals have been examined. The results reveal that the sweep method can provide a significant reduction of the effect of distortion compared with MLS/IRS techniques but, unlike what is claimed in the literature, sweep signals cannot reject all distortion artifacts from the causal part of the estimated impulse response. In all cases, an improvement of 3 dB in signal-to-noise ratio can be achieved if the measurement time is doubled either by averaging over two excitations or by doubling the length of the excitation signal. The time-frequency selectivity performed by the sweep technique is found to yield higher immunity to impulsive noise and timevariances.

Torras Rosell, Antoni Technical University of Denmark,

2010-01-01

351

Behavior of viscoplastic circular plates under gaussian impulse  

International Nuclear Information System (INIS)

The dynamic plastic behavior of viscoplastic circular plates subjected to impulse loading is presented. The impulse is assumed to impart a transverse axisymmetric velocity with a spatial Gaussian distribution. The combined influence of membrane forces, bending moments and strain-rate sensitivity is considered in predicting the deformation. Numerical results are presented to show influence on the rate of growth of plastic regimes, the deflection configuration and the total time of response. It is concluded that the spatial distribution of impulse has a considerable effect on the deformation response of the plate, and relatively small effect on the total time of response; furthermore, the simple bending theory is inadequate to reliably predict the response. (orig.)

352

FLANN Detector Based Filtering of Images Corrupted by Impulse Noise  

Directory of Open Access Journals (Sweden)

Full Text Available We present a novel non-linear scheme for image restoration based on neuro-detector using Functional Link Artificial Neural Network (FLANN followed by an improved spatial filter. The method is applied to images corrupted by impulse noise with varying strengths and different noise probability. The neural detector is based on the concept of training or learning by examples. When trained properly, the detector used to detect impulse noise in any image degraded by impulse noise. Hence, the method is suitable for real time image restoration applications. The simulated results obtained from the proposed scheme outperforms existing approaches are highly satisfactory and it outperforms the earlier suggested methods in terms of residual NSR in restored images.

Banshidhar Majhi

2005-01-01

353

Impulsivity and the self-defeating behavior of narcissists.  

Science.gov (United States)

Currently prominent models of narcissism (e.g., Morf and Rhodewalt, 2001) primarily explain narcissists' self-defeating behaviors in terms of conscious cognitive and affective processes. We propose that the disposition of impulsivity may also play an important role. We offer 2 forms of evidence. First, we present a meta-analysis demonstrating a strong positive relationship between narcissism and impulsivity. Second, we review and reinterpret the literature on 3 hallmarks of narcissism: self-enhancement, aggression, and negative long-term outcomes. Our reinterpretation argues that impulsivity provides a more parsimonious explanation for at least some of narcissists' self-defeating behavior than do existing models. These 2 sources of evidence suggest that narcissists' quest for the status and recognition they so intensely desire is thwarted, in part, by their lack of the self-control necessary to achieve those goals. PMID:16768652

Vazire, Simine; Funder, David C

2006-01-01

354

Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging  

Science.gov (United States)

This dissertation investigates the feasibility of a real-time transthoracic Acoustic Radiation Force Impulse (ARFI) imaging system to measure myocardial function non-invasively in clinical setting. Heart failure is an important cardiovascular disease and contributes to the leading cause of death for developed countries. Patients exhibiting heart failure with a low left ventricular ejection fraction (LVEF) can often be identified by clinicians, but patients with preserved LVEF might be undetected if they do not exhibit other signs and symptoms of heart failure. These cases motivate development of transthoracic ARFI imaging to aid the early diagnosis of the structural and functional heart abnormalities leading to heart failure. M-Mode ARFI imaging utilizes ultrasonic radiation force to displace tissue several micrometers in the direction of wave propagation. Conventional ultrasound tracks the response of the tissue to the force. This measurement is repeated rapidly at a location through the cardiac cycle, measuring timing and relative changes in myocardial stiffness. ARFI imaging was previously shown capable of measuring myocardial properties and function via invasive open-chest and intracardiac approaches. The prototype imaging system described in this dissertation is capable of rapid acquisition, processing, and display of ARFI images and shear wave elasticity imaging (SWEI) movies. Also presented is a rigorous safety analysis, including finite element method (FEM) simulations of tissue heating, hydrophone intensity and mechanical index (MI) measurements, and thermocouple transducer face heating measurements. For the pulse sequences used in later animal and clinical studies, results from the safety analysis indicates that transthoracic ARFI imaging can be safely applied at rates and levels realizable on the prototype ARFI imaging system. Preliminary data are presented from in vivo trials studying changes in myocardial stiffness occurring under normal and abnormal heart function. Presented is the first use of transthoracic ARFI imaging in a serial study of heart failure in a porcine model. Results demonstrate the ability of transthoracic ARFI to image cyclically-varying stiffness changes in healthy and infarcted myocardium under good B-mode imaging conditions at depths in the range of 3-5 cm. Challenging imaging scenarios such as deep regions of interest, vigorous lateral motion and stable, reverberant clutter are analyzed and discussed. Results are then presented from the first study of clinical feasibility of transthoracic cardiac ARFI imaging. At the Duke University Medical Center, healthy volunteers and patients having magnetic resonance imaging-confirmed apical infarcts were enrolled for the study. The number of patients who met the inclusion criteria in this preliminary clinical trial was low, but results showed that the limitations seen in animal studies were not overcome by allowing transmit power levels to exceed the FDA mechanical index (MI) limit. The results suggested the primary source of image degradation was clutter rather than lack of radiation force. Additionally, the transthoracic method applied in its present form was not shown capable of tracking propagating ARFI-induced shear waves in the myocardium. Under current instrumentation and processing methods, results of these studies support feasibility for transthoracic ARFI in high-quality B-Mode imaging conditions. Transthoracic ARFI was not shown sensitive to infarct or to tracking heart failure in the presence of clutter and signal decorrelation. This work does provide evidence that transthoracic ARFI imaging is a safe non-invasive tool, but clinical efficacy as a diagnostic tool will need to be addressed by further development to overcome current challenges and increase robustness to sources of image degradation.

Bradway, David Pierson

355

Investigation of the impulse response of an image inversion interferometer  

Science.gov (United States)

Based on the proposal of Wicker and Heintzmann "Interferometric resolution improvement for confocal microscopes" [1] we demonstrate in principle the functionality of an image inversion interferometer (III) experimentally, which can be described by an appropriate frequency transfer function. Thereby, the FWHM of the impulse response narrows around 30% compared to the PSF of a classical system. The experimental data yield a FWHM of the impulse response of 0.83 ?m as compared to the theoretical value of 1.21 ?m at ?0=589 nm by a wide field detection (NA=0.25) without an interferometer.

Weigel, D.; Babovsky, H.; Kiessling, A.; Kowarschik, R.

2010-02-01

356

Impulsive Exponential Consensus of Multi-agent Nonlinear Fuzzy Systems  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we investigate the problem of impulsive exponential consensus of multi-agent systems, where each agent is represented by an identical T-S fuzzy model. Firstly, a fuzzy impulsive control protocol is designed for networks with fixed topology based on the local information of agents. Then sufficient conditions in terms of linear matrix equalities are given to guarantee the exponential consensus of the multi-agent fuzzy systems. Numerical simulations show the effectiveness of our theoretical results.

Liping Zhang

2013-01-01

357

Model Predictive Control based on Finite Impulse Response Models  

DEFF Research Database (Denmark)

We develop a regularized l2 finite impulse response (FIR) predictive controller with input and input-rate constraints. Feedback is based on a simple constant output disturbance filter. The performance of the predictive controller in the face of plant-model mismatch is investigated by simulations and related to the uncertainty of the impulse response coefficients. The simulations can be used to benchmark l2 MPC against FIR based robust MPC as well as to estimate the maximum performance improvements by robust MPC.

JØrgensen, John Bagterp

2008-01-01

358

Single-impulse magnetic focusing of launched cold atoms  

CERN Document Server

We have theoretically investigated the focusing of a launched cloud of cold atoms. Time-dependent spatially-varying magnetic fields are used to impart impulses leading to a three-dimensional focus of the launched cloud. We discuss possible coil arrangements for a new focusing regime: isotropic 3D focusing of atoms with a single-impulse magnetic lens. We investigate focusing aberrations and find that, for typical experimental parameters, the widely used assumption of a purely harmonic lens is often inaccurate. The baseball lens offers the best possibility for isotropically focusing a cloud of weak-field-seeking atoms in 3D.

Pritchard, M J; Smith, D A; Hughes, I G; Pritchard, Matthew J; Arnold, Aidan S; Smith, David A; Hughes, Ifan G

2004-01-01

359

Single-impulse magnetic focusing of launched cold atoms  

International Nuclear Information System (INIS)

We have theoretically investigated the focusing of a launched cloud of cold atoms. Time-dependent spatially-varying magnetic fields are used to impart impulses leading to a three-dimensional focus of the launched cloud. We discuss possible coil arrangements for a new focusing regime: isotropic 3D focusing of atoms with a single-impulse magnetic lens. We investigate focusing aberrations and find that, for typical experimental parameters, the widely used assumption of a purely harmonic lens is often inaccurate. The baseball lens offers the best possibility for isotropically focusing a cloud of weak-field-seeking atoms in 3D

360

Impulsive and hybrid dynamical systems stability, dissipativity, and control  

CERN Document Server

This book develops a general analysis and synthesis framework for impulsive and hybrid dynamical systems. Such a framework is imperative for modern complex engineering systems that involve interacting continuous-time and discrete-time dynamics with multiple modes of operation that place stringent demands on controller design and require implementation of increasing complexity--whether advanced high-performance tactical fighter aircraft and space vehicles, variable-cycle gas turbine engines, or air and ground transportation systems. Impulsive and Hybrid Dynamical Systems goes beyond similar

Haddad, Wassim M; Nersesov, Sergey G

2014-01-01

 
 
 
 
361

Reciprocity calibration of impulse responses of acoustic emission transducers.  

Science.gov (United States)

By means of reciprocity calibration in Rayleigh-wave and longitudinal-wave sound fields, frequency characteristics of amplitude and phase of absolute sensitivity of acoustic emission transducers were measured on the basis of the newly derived complex reciprocity parameters, and the impulse responses were obtained through inverse Fourier transform. Calibration results were confirmed with supplemental experiments in which the fracturing of a pencil lead was utilized for the source of elastic waves. Impulse responses of acoustic emission transducers to both the Rayleigh-wave and longitudinal-wave displacement velocities were determined by means of purely electrical measurements without the use of mechanical sound sources or reference transducers. PMID:18244283

Hatano, H; Chaya, T; Watanabe, S; Jinbo, K

1998-01-01

362

Lightning Impulse Waveform Parameters Abstraction Based on High Speed Filter  

Directory of Open Access Journals (Sweden)

Full Text Available A simple, shortcut and accurate algorithm is needed in lightning Impulse waveforms (include chopped wave parameters abstraction in embedded system. Algorithm is put forward which implements mountain shape template convolution by forming rectangle template convolution two times. This method greatly lower down the computational complexity and obtain the time and frequency localization at same time. The results of waveform parameters obtained by this method accord with the requirements of standard IEC1083-2 completely. And it was highly consistent with standard impulse calibration instrument. The computational complexity and the ability of frequency restraining of this algorithm was analyzed.

Xiaodong Zheng

2005-01-01

363

Impulsive electromagnetic response of thin plasmonic metal sheets  

Science.gov (United States)

The impulsive electromagnetic response of a thin metallic coating on a dielectric half-space is analytically investigated. Both TM- and TE-polarized electromagnetic fields in the configuration are excited by an impulsive line source. The problem is analytically solved with the help of the high-contrast thin-sheet boundary conditions and the extended Cagniard-DeHoop technique. Closed-form space-time expressions for electromagnetic fields are found, numerically evaluated, and discussed with regard to the pulsed excitation of surface plasmon phenomena.

Å tumpf, M.; Vandenbosch, Guy A. E.

2014-08-01

364

Development and implementation of a new ultrafast imaging diagnostic for laboratory magnetoplasma: application in the plasma radial transport characterization; Developpement et mise en oeuvre d'un diagnostic d'imagerie ultra-rapide en magnetoplasma de laboratoire: application a la caracterisation du transport radial du plasma  

Energy Technology Data Exchange (ETDEWEB)

Non intrusive diagnostics have been developed in order to increase the precision in the data obtained from plasmas in a turbulent state. This thesis was carried on the development and the implementation of a new diagnostic for laboratory plasmas, i.e. an ultra-fast imaging system recording the spontaneous light emission, applied in turbulent plasmas of a magnetoplasma. The low resolution camera is composed of an array of photodetectors, their sensibility is centered on the main wavelength of the studied plasmas. Moreover, records can be longer than fifty milliseconds, even with a 100.000 frames per second recording frequency. This camera allows a precise study of both the spatial evolution of a phenomena and a statistical analysis of the recorded turbulent signal. Our prototype has been used to record different instable regimes of the laboratory magnetized plasma device. The main goal of this thesis was on the development and on the validation of this new diagnostic. Further studies will be devoted to the identification of the instabilities and underlying mechanisms. (author)

Brault, C

2007-07-15

365

Interval oscillation criteria for second-order forced delay differential equations under impulse effects  

Directory of Open Access Journals (Sweden)

Full Text Available We establish some oscillation criteria for a forced second-order differential equation with impulses. These results extend some well-known results for forced second-order impulsive differential equations with delay.

Qiaoluan Li

2013-02-01

366

Laboratory and self-report assessments of impulsive behavior in adolescent daily smokers and nonsmokers.  

Science.gov (United States)

This research compared adolescent daily smokers (n=25) and nonsmokers (n=26) on different measures of impulsivity. Assessments included question-based measures of delay (DDQ) and probability (PDQ) discounting, a measure of behavioral disinhibition (go-stop task), and a self-report measure of impulsivity (Barratt Impulsiveness Scale-Adolescent). Adolescent smokers were more impulsive on the DDQ and Barratt Impulsiveness Scale--Adolescent but not on the PDQ or the go-stop task. However, there was a significant interaction between smoking status and gender on the go-stop task, with male smokers performing less impulsively on this measure than male nonsmokers--an effect not observed with the female adolescents. These findings indicate that adolescents who smoke cigarettes are more impulsive with respect to some, but not all, types of impulsivity than are adolescents who do not smoke. PMID:17563213

Reynolds, Brady; Patak, Michele; Shroff, Palak; Penfold, Robert B; Melanko, Shane; Duhig, Amy M

2007-06-01

367

The regularity of geodesics in impulsive pp-waves  

Science.gov (United States)

We consider the geodesic equation in impulsive pp-wave space-times in Rosen form, where the metric is of Lipschitz regularity. We prove that the geodesics (in the sense of Carathéodory) are actually continuously differentiable, thereby rigorously justifying the -matching procedure which has been used in the literature to explicitly derive the geodesics in space-times of this form.

Lecke, Alexander; Steinbauer, Roland; Švarc, Robert

2014-01-01

368

The Chaotification of Discrete Hopfield Neural Networks via Impulsive Control  

International Nuclear Information System (INIS)

The chaotification of discrete Hopfield neural networks is studied with impulsive control techniques. No matter whether the original systems are stable or not, chaotification theorems for discrete Hopfield neural networks are derived, respectively. Finally, the effectiveness of the theoretical results is illustrated by some numerical examples. (general)

369

Periodic components of hand acceleration/deceleration impulses during telemanipulation  

International Nuclear Information System (INIS)

Responsiveness is the ability of a telemanipulator to recreate user trajectories and impedance in time and space. For trajectory production, a key determinant of responsiveness is the ability of the system to accept user inputs, which are forces on the master handle generated by user hand acceleration/deceleration (a/d) impulses, and translate them into slave arm acceleration/deceleration. This paper presents observations of master controller a/d impulses during completion of a simple target acquisition task. Power spectral density functions (PSDF's) calculated from hand controller a/d impulses were used to assess impulse waveform. The relative contributions of frequency intervals ranging up to 25 Hz for three spatially different versions of the task were used to determine which frequencies were most important. The highest relative power was observed in frequencies between 1 Hz and 6 Hz. The key frequencies related to task difficulty were in the range from 2 Hz to 8 Hz. the results provide clues to the source of the performance inhibition

370

Impulsivity, gender, and the platelet serotonin transporter in healthy subjects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Donatella Marazziti, Stefano Baroni, Irene Masala, Francesca Golia, Giorgio Consoli, Gabriele Massimetti, Michela Picchetti, Mario Catena Dell’Osso, Gino Giannaccini, Laura Betti, Antonio Lucacchini, Antonio CiapparelliDipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, University of Pisa, Pisa, ItalyAbstract: The present study explored the possible relationships between impulsivity, gender, and a peripheral serotonergic marker, the platelet serotonin (5-HT) tr...

Donatella Marazziti; Stefano Baroni; Irene Masala; et al

2009-01-01

371

Future Orientation, Impulsivity, and Problem Behaviors: A Longitudinal Moderation Model  

Science.gov (United States)

In the current study, based on a sample of 1,873 adolescents between 11.4 and 20.9 years of age from the first 3 waves of the National Longitudinal Study of Adolescent Health, we investigated the longitudinal effects of future orientation on levels of and developmental changes in problem behaviors, while controlling for the effects by impulsivity;…

Chen, Pan; Vazsonyi, Alexander T.

2011-01-01

372

Multivalued impulsive neutral functional differential inclusions in Banach spaces  

Directory of Open Access Journals (Sweden)

Full Text Available In paper the existence of solutions for first and second order impulsive neutral functional differential inclusions in Banach spaces is investigated. The results are obtained by using a fixed point theorem for condensing multivalued maps due to Martelli and the semigroup theory.

M. Benchohra

2002-03-01

373

Dwell-time conditions for robust stability of impulsive systems  

CERN Document Server

We prove that impulsive systems, which possess an ISS Lyapunov function, are ISS for time sequences, which satisfy the fixed dwell-time condition. If the ISS Lyapunov function is the exponential one, we provide stronger result, which guarantees uniform ISS of the whole system over sequences, which satisfy the generalized average dwell-time condition.

Dashkovskiy, Sergey

2012-01-01

374

[Impulsiveness as a multidimensional construct: an analysis in alcoholic patients].  

Science.gov (United States)

Impulsiveness is multifactorial in nature; hence, to investigate its components diverse theoretical models supported by different measurement tools have been proposed. Attention has been particularly focused on the effects that impulsiveness can have in determining and/or maintaining a behaviour of dependence. In the present study a group of subjects with alcohol dependence in treatment (N = 20) were compared with a control group (N = 21); the two groups were administered three different instruments designed to investigate the dimension of impulsiveness. A significant difference was found concerning the performance on the Iowa Gambling Task. This is a test that simulates a gambling situation and so evaluates the capacity to discern, in a decisional task, advantageous vs. non-advantageous options, where the former permit an immediate modest gain but also a future modest loss while the latter carry a heavier penalty than they allow to gain, even if the gains are very big. The alcoholics persisted in making impulsive choices significantly more than the control group, preferrng thus the higher wins but risking also greater losses. This result, in line with what is reported by the present contributions on the decisional style of subjects characterized by drug abuse, may be important in understanding the factors that predispose to and maintain excessive drinking behaviour. PMID:18924298

Vicenzi, G; Giorgi, I; Pessa, E

2006-01-01

375

A Survey on Oscillation of Impulsive Ordinary Differential Equations  

Directory of Open Access Journals (Sweden)

Full Text Available This paper summarizes a series of results on the oscillation of impulsive ordinary differential equations. We consider linear, half-linear, super-half-linear, and nonlinear equations. Several oscillation criteria are given. The Sturmian comparison theory for linear and half linear equations is also included.

Zafer A?ac?k

2010-01-01

376

High energy nucleon incident optical potential by relativistic impulse approximation  

International Nuclear Information System (INIS)

The optical potentials by relativistic impulse approximation (RIA) are utilized for the high energy nucleon incidence. The nucleon-nucleon scattering amplitudes are derived from the phase shift and parametrized as a function of the incident nucleon energy. The optical potential by RIA reproduces the experimental data. (author)

377

Solar Flare Impulsive Phase Emission Observed with SDO/EVE  

CERN Document Server

Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T = 5.8 - 7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3 - 4 MK, and we use spatially-unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied the DEMs exhibited a two component distribution during the impulsive phase, a low temperature component with peak temperature of 1 - 2 MK, and a broad high temperature one from 7 - 30 MK. A bimodal high temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emissi...

Kennedy, Michael B; Mathioudakis, Mihalis; Keenan, Francis P

2013-01-01

378

Understanding Computation of Impulse Response in Microwave Software Tools  

Science.gov (United States)

In modern microwave engineering curricula, the introduction of the many new topics in microwave industrial development, or of software tools for design and simulation, sometimes results in students having an inadequate understanding of the fundamental theory. The terminology for and the explanation of algorithms for calculating impulse response in…

Potrebic, Milka M.; Tosic, Dejan V.; Pejovic, Predrag V.

2010-01-01

379

Dimensions of impulsive behavior and treatment outcomes for adolescent smokers.  

Science.gov (United States)

Adolescent cigarette smoking rates remain a significant public health concern, and as a result there is a continued need to understand factors that contribute to an adolescent's ability to reduce or quit smoking. Previous research suggests that impulsive behavior may be associated with treatment outcomes for smoking. The current research (N = 81) explored 3 dimensions of impulsive behavior as predictors of treatment response from a social-cognitive type program for adolescent smokers (i.e., Not On Tobacco; N-O-T). Measures included laboratory assessments of delay discounting, sustained attention, and behavioral disinhibition. A self-report measure of impulsivity was also included. Adolescent smokers who had better sustained attention were more likely to reduce or quit smoking by the end of treatment. No other measures of impulsivity were significantly associated with treatment response. From these findings, an adolescent smoker's ability to sustain attention appears to be an important behavioral attribute to consider when implementing smoking cessation programs such as N-O-T. PMID:24417209

Harris, Millie; Penfold, Robert B; Hawkins, Ariane; Maccombs, Jared; Wallace, Bryan; Reynolds, Brady

2014-02-01

380

Simplified transient model of the transformer during impulse test  

Energy Technology Data Exchange (ETDEWEB)

The challenge of accurately modelling transformers within a power system was discussed with particular reference to transformer windings. The difficulty lies in the fact that transformers have a large number of core designs and their many parameters are both nonlinear and frequency dependent. A complete model of a transformer would require that every turn be represented and that all mutual couplings, inductive and capacitive, be included with every other turn. Transformer windings are exposed to various short duration impulse voltages of high amplitude produced by lightning or switching transients, and by insulator flashover. As such, winding insulation is one of the most important constructional elements of a transformer. Any weakness in insulation may cause transformer failure. A sensitive standard impulse test was performed in this study in order to verify the integrity of transformer insulation. High frequency transformer models from the literature were reviewed, and a simplified transient model was then proposed for a transformer operating during an impulse test via full wave impulse. The model parameters were identified. The simulation results from the Electromagnetic Transients Program (EMTP) were found to be in approximate agreement with the 25 kVA distribution transformer experimental results. 32 refs., 8 figs.

Al-Ammar, E.; Karady, G.G. [Arizona State Univ., Tempe, AZ (United States). Dept. of Electrical Engineering

2007-07-01

 
 
 
 
381

Relationships among Impulsiveness, Locus of Control, Sex, and Music Practice  

Science.gov (United States)

This study is an investigation of relationships among impulsiveness, locus of control, sex, observed practice behaviors, practice effectiveness, and self-reported practice habits in a sample of 40 college brass players. Practice effectiveness was defined by the amount of change in pretest and posttest performance achievement scores over one…

Miksza, Peter

2006-01-01

382

33 CFR 183.586 - Pressure impulse test.  

Science.gov (United States)

...2010-07-01 2010-07-01 false Pressure impulse test. 183.586 Section 183.586...order: (a) Perform the static pressure test under § 183.580. (b) If...water. (g) Perform the static pressure test under §...

2010-07-01

383

Zonisamide in managing impulse control disorders in Parkinson's disease.  

Science.gov (United States)

Impulse control disorders (ICDs) are a set of behaviours that take place in a subgroup of patients with Parkinson's disease (PD). Although reduction or switch of dopamine agonists or decrease of levodopa are the common treatment, this does not always improve the compulsive behaviour. Zonisamide (ZNS) has proved effective for motor symptoms in PD and it may be also useful in the field of ICDs. The aim of our study is to evaluate the safety and efficacy of ZNS in PD patients with ICDs who did not improve following a reduction of either levodopa or dopamine agonists. Fifteen patients were initiated on 25 mg/day ZNS dosage, which was titrated to 200 mg/day, as tolerated. Severity of the behaviours was assessed by means of the Clinical Global Impression and the Barratt Impulsiveness Scale, while motor impairment was assessed by means of the Unified Parkinson's Disease Rating Scale (UPDRS). Demographic data, medication dose, treatment duration and adverse events were also collected and analyzed. There was a marked reduction in the severity of impulsive behaviours and global impulsiveness (mean change from baseline -5.8 to -4.8, respectively). UPDRS changed only marginally. ZNS was generally well tolerated. Our study suggests that ZNS may be effective for ICDs in PD. The lack of studies with other medications to treat these behaviours in PD and the potential beneficial effects of ZNS for motor complications make this drug important in the treatment of the disease. PMID:20509031

Bermejo, Pedro Emilio; Ruiz-Huete, Cristina; Anciones, Buenaventura

2010-10-01

384

Parents' Reactions to Youths' Hyperactivity, Impulsivity, and Attention Problems  

Science.gov (United States)

Hyperactivity, impulsivity, and attention problems (HIA) in children and adolescents are stressful for parents. In this study, we used theories of parents' perceived power and attributions for youths' behaviors to develop a model to understand parents' reactions to their youths' HIA. We followed 706 youths (376 boys and 330 girls, aged 10-12 years…

Glatz, Terese; Stattin, Hakan; Kerr, Margaret

2011-01-01

385

Radiative muon capture: impulse approximation and the continuity equation  

International Nuclear Information System (INIS)

A modified form of the impulse-approximation effective Hamiltonian of the nuclear radiative muon capture is developed. The electromagnetic-current continuity equation to minimise the meson-exchange-current corrections is used. The method is directly applicable to other radiative reactions with two currents, e. g., to the pion photoproduction process

386

What is Impulse Buying? An analytical network processing framework for prioritizing factors affecting impulse buying  

Directory of Open Access Journals (Sweden)

Full Text Available One of the most important issues affecting profitability is to determine the impact of different factors influencing purchasing activities. In this paper, we perform an extensive literature survey to detect different purchasing factors influencing customers' behavior. The factors are categorized in three different groups and they are ranked using analytical network process. The results of our survey indicate that three factors of personal, product and situational play important roles in purchasing impulse. The personal item includes different factors where demographic characteristic factors receive the highest ranking (35% followed by other factors are feelings, excitement and fun, self identify, education and novelty. There are also three sub-factors associated with demographic characteristics including gender, age and race and the weights are 0.46748, 0.42668 and 0.10584, respectively, which means gender is the most important factor followed by age and race. Finally, the other factor is associated with situational factors' group, which includes presence of others, culture, design of store, time available, local market condition, sales staff and self service with the relative importance of 0.04296, 0.08733, 0.12130, 0.22217, 0.05643, 0.15346 and 0.31635, respectively.

Javad Siahkali Moradi

2012-08-01

387

Nonoscillatory and Oscillatory Criteria for First Order Nonlinear Neutral Impulsive Differential Equations  

Directory of Open Access Journals (Sweden)

Full Text Available A survey of recent studies in neutral impulsive differential equations reveals that most of such works revolve around the quest for oscillatory conditions for linear impulsive differential equations.  The development of oscillatory and nonoscillatory criteria for nonlinear impulsive differential equations has so far attracted very little attention.  In this paper, we obtain sufficient conditions for the existence of oscillatory and nonoscillatory solutions for nonlinear first order neutral impulsive differential equations with constant delays.

I. O. Isaac

2011-05-01

388

Right ventromedial prefrontal cortex: a neuroanatomical correlate of impulse control in boys  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Emerging data on the neural mechanisms of impulse control highlight brain regions involved in emotion and decision making, including the ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC) and amygdala. Variation in the development of these regions may influence one's propensity for impulsivity and, by extension, one's vulnerability to disorders involving low impulse control (e.g. substance abuse). Here we test the hypothesis that lower impulse control is associated with s...

Boes, Aaron D.; Bechara, Antoine; Tranel, Daniel; Anderson, Steve W.; Richman, Lynn; Nopoulos, Peg

2009-01-01

389

Generating chaos for discrete time-delayed systems via impulsive control.  

Science.gov (United States)

Generating chaos for a class of discrete time-delayed systems via impulsive control is investigated in this paper. With the augmented matrix method, the time-delay impulsive systems can be transformed into a new class of linear discrete impulsive systems. Based on the largest Lyapunov exponent and the boundedness of the systems, some theoretical results about the chaotification for the discrete impulsive systems with time delay are derived and an example is given to visualize the satisfactory control performance. PMID:20370290

Guan, Zhi-Hong; Liu, Na

2010-03-01

390

Rated and measured impulsivity in children is associated with diminished cardiac reactions to acute psychological stress.  

Science.gov (United States)

This study examined the association between impulsivity and heart rate reactions to a brief psychological stress in pre-adolescent children. Impulsivity was assessed by two response inhibition tasks and maternal self-report. Heart rate was measured at rest and in response to a mental arithmetic challenge. Children high in impulsivity showed blunted cardiac stress reactions. This result resonates with previous findings that blunted stress reactivity is characteristic of a range of problematic behaviours often associated with impulsivity. PMID:25038303

Bennett, Carmel; Blissett, Jackie; Carroll, Douglas; Ginty, Annie T

2014-10-01

391

Impulse control and its application in portfolio and hedging with both fixed and proportional transaction costs  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we will state impulse control and its application in portfolio selection. For this purpose, we first introduce Quasi Variational Inequalities. Introducing impulse control, in stochastic stopping times we have jumps with stochastic size. Then by using approximative Markov chain, the optimal impulse control is obtained in portfolio, including European option. Finally, considering default parameters, the numerical results in optimal impulse control is obtained.

A. Delavarkhalafi

2014-05-01

392

Complexity of an SIR epidemic dynamics model with impulsive vaccination control  

Energy Technology Data Exchange (ETDEWEB)

This paper considered an IR epidemic model with impulsive vaccination, which may inherently oscillate. We studied the impulsive control and get the conditions on which epidemic-elimination solution is globally asymptotically and the conditions of boundedness of system. On the other hand if the epidemic is turn out to be endemic, we studied numerically the influences of impulsive vaccination on the periodic oscillation of the system which is without impulsion and found phenomenon of chaos in this case.

Zeng Guangzhao [Department of Applied Mathematics, Dalian University of Technology, DaLian, LiaoNing 116024 (China); Department of Mathematics, ShaoGuan University, ShaoGuan, GuangDong 512005 (China); E-mail: guangzhaoz@sgu.edu.cn; Chen Lansun [Department of Applied Mathematics, Dalian University of Technology, DaLian, LiaoNing 116024 (China); E-mail: lschen@math.ac.cn; Sun Lihua [Department of Applied Mathematics, Dalian University of Technology, DaLian, LiaoNing 116024 (China)

2005-10-01

393

Complexity of an SIR epidemic dynamics model with impulsive vaccination control  

International Nuclear Information System (INIS)

This paper considered an IR epidemic model with impulsive vaccination, which may inherently oscillate. We studied the impulsive control and get the conditions on which epidemic-elimination solution is globally asymptotically and the conditions of boundedness of system. On the other hand if the epidemic is turn out to be endemic, we studied numerically the influences of impulsive vaccination on the periodic oscillation of the system which is without impulsion and found phenomenon of chaos in this case

394

The influence of culture on students' impulsive buying behaviour in the Vaal Triangle area / Luzaan Hamilton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Impulse buying or unplanned purchases by consumers constitute a major proportion of purchases in certain product categories. Studies in the United States widely reported that impulse consumer buying behaviour accounts for up to 80% of all purchases in certain product categories, and it has been suggested that purchases of new products result more from impulse purchasing than from prior planning. South Africa is a nation of shoppers with increasing numbers defined as impulse buyers who respond...

Hamilton, Luzaan

2011-01-01

395

Recreational Drug Use and Impulsivity in a Population of Canadian Undergraduate Drinkers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The consumption of drugs during young adulthood may be particularly detrimental given important neurodevelopmental changes occurring during this period. As impulsivity may lead to substance use and substance use to the commission of seemingly impulsive acts, an improved understanding of the relationship between alcohol use, other substance use and impulsivity in young adults is important. We gathered information on self-reported impulsivity, recreational drug use, and drinking habits of 205 (...

Balodis, Iris M.; Potenza, Marc N.; Olmstead, Mary C.

2010-01-01

396

Carrion crows cannot overcome impulsive choice in a quantitative exchange task  

Directory of Open Access Journals (Sweden)

Full Text Available The ability to control an immediate impulse for a future, more preferred outcome has long been thought to be a uniquely human feature. However, studies on non-human primates revealed that some monkeys and apes are capable of enduring delays to get a more preferred food and/or more food of the same kind. Recently two corvid species, the common raven (Corvus corax and carrion crow (Corvus corone corone, exchanged food for a better quality reward, whereas they seemed to have difficulties to do so for a higher quantity. In the present study we specifically investigated carrion crows’ ability to overcome an impulsive choice in a quantitative exchange task. After a short delay, individuals were asked to give back an initial reward (cheese to the human experimenter in order to receive a higher amount of the same reward (2, 4 or 8 pieces. We successfully tested six captive crows. Three individuals never exchanged one piece of cheese against a higher quantity; the other three birds did exchange at very low rates. In order to rule out, that crows’ poor performance is due to the fact that they cannot discriminate between different quantities or that they do not attribute a higher value to higher quantities, we performed a preference test between one and more pieces of cheese. All birds chose the higher quantities significantly more often, indicating that they can discriminate between quantities and that higher quantities actually have a value for them. Taken together, these results suggest that, although crows may possess the cognitive abilities to judge quantities and to overcome an impulsive choice, they do so only in order to optimize the qualitative but not quantitative output in the exchange paradigm.

ThomasBugnyar

2012-04-01

397

Lag Synchronization of a Class of Time-delayed Chaotic Neural Networks by Impulsive Control  

Directory of Open Access Journals (Sweden)

Full Text Available The paper studies the exponential lag synchronization of a class of delayed chaotic neural networks with impulsive effects via the unidirectional linear coupling. Some sufficient conditions are derived by establishing impulsive differential delay inequality and using M-matrix theory. An illustrative example is also provided to show the effectiveness and feasibility of the impulsive control method.  

Jing Wan

2013-06-01

398

Dimensions of Impulsivity and Aggression Associated with Suicide Attempts Among Bipolar Patients: A Preliminary Study  

Science.gov (United States)

Impulsivity and hostility are often thought to be interrelated among depressed patients with suicidal behavior, but few studies have examined this relationship empirically. In this study, we assessed trait impulsivity and hostility among 52 DSM-IV bipolar subjects with and without histories of suicide attempts. Impulsivity and hostility were…

Michaelis, Benjamin H.; Goldberg, Joseph F.; Davis, Glen P.; Singer, Tara M.; Garno, Jessica L.; Wenze, Susan J.

2004-01-01

399

The geometrical analysis of a predator-prey model with two state impulses.  

Science.gov (United States)

Using successor functions and Poincaré-Bendixson theorem of impulsive differential equations, the existence of periodical solutions to a predator-prey model with two state impulses is investigated. By stability theorem of periodic solution to impulsive differential equations, the stability conditions of periodic solutions to the system are given. Some simulations are exerted to prove the results. PMID:22561587

Zhao, Lichun; Chen, Lansun; Zhang, Qingling

2012-08-01

400

Instructional and improvisational models of music therapy with adolescents who have attention deficit hyperactivity disorder (ADHD): a comparison of the effects on motor impulsivity.  

Science.gov (United States)

This study compared the impact of instructional and improvisational music therapy approaches on the level of motor impulsivity displayed by adolescent boys (n = 13) who have Attention Deficit Hyperactivity Disorder (ADHD). A combination of a multiple contrasting treatment and an experimental control group design was used. No statistical difference was found between the impact of the contrasting approaches as measured by a Synchronised Tapping Task (STT) (Humphrey, 2003) and the parent and teacher versions of Conners' Rating Scales (Conners, 1997) Restless-Impulsive (R-I) and Hyperactive-Impulsive (H-I) subscales. However, while no firm conclusions can be drawn, there are indications that the instructional approach may have contributed to a reduction of impulsive and restless behaviors in the classroom. Further, over the period of the study, both music therapy treatment groups significantly improved accuracy on the STT, and teachers reported a significant reduction in Conners' DSM-IV Total and Global Index subscale scores. These findings tentatively suggest that music therapy may contribute to a reduction in a range of ADHD symptoms in the classroom, and that increasing accuracy on the STT could be related to improvement in a range of developmental areas-not specifically motor impulsivity. PMID:16671837

Rickson, Daphne J

2006-01-01

 
 
 
 
401

Modulatory role of the brain-derived neurotrophic factor Val66Met polymorphism on the effects of serious life events on impulsive aggression in borderline personality disorder.  

Science.gov (United States)

Impulsive aggression belongs to the key features of borderline personality disorder (BPD). In the development of BPD, serious life events are known to play a major role. Acute and chronic stress has been suggested to inhibit hippocampal brain-derived neurotrophic factor (BDNF) synthesis and to mediate neural plasticity in response to adverse social experiences. Recently it has been reported that the frequency of violent suicide attempts is higher in adult suicide attempters reporting severe childhood sexual abuse and carrying the Val(66)Val genotype of the BDNF Val(66)Met polymorphism. In this study we analysed modulating effects of BDNF Val(66)Met polymorphism on the effects of physical maltreatment, rape and childhood sexual abuse on impulsive aggression. One hundred and fifty-nine BPD patients from Germany and of Caucasian descent were included. Impulsive aggression was assessed by the Buss-Durkee-Hostility Inventory (BDHI). Childhood sexual abuse accounted for 23.6% of the variance of BDHI sum score. Childhood sexual abuse decreased BDHI sum score in BDNF Val/Val carriers but not in Met carriers. In contrast to previous findings this study analysing a specific gene x environment interaction in BPD patients suggests a decreasing effect of childhood sexual abuse on impulsive aggression in BPD patients, particularly in BDNF Val/Val carriers. The interrelations between serious life events, impulsive aggression and the BDNF Val(66)Met polymorphism as well as their implication for BPD are far from understood and require further investigations. PMID:19817874

Wagner, S; Baskaya, O; Dahmen, N; Lieb, K; Tadi?, A

2010-02-01

402

The nature of impulsivity: visual exposure to natural environments decreases impulsive decision-making in a delay discounting task.  

Science.gov (United States)

The benefits of visual exposure to natural environments for human well-being in areas of stress reduction, mood improvement, and attention restoration are well documented, but the effects of natural environments on impulsive decision-making remain unknown. Impulsive decision-making in delay discounting offers generality, predictive validity, and insight into decision-making related to unhealthy behaviors. The present experiment evaluated differences in such decision-making in humans experiencing visual exposure to one of the following conditions: natural (e.g., mountains), built (e.g., buildings), or control (e.g., triangles) using a delay discounting task that required participants to choose between immediate and delayed hypothetical monetary outcomes. Participants viewed the images before and during the delay discounting task. Participants were less impulsive in the condition providing visual exposure to natural scenes compared to built and geometric scenes. Results suggest that exposure to natural environments results in decreased impulsive decision-making relative to built environments. PMID:24841421

Berry, Meredith S; Sweeney, Mary M; Morath, Justice; Odum, Amy L; Jordan, Kerry E

2014-01-01

403

Selective excitation of spin resonance in orthoferrite PrFeO3 with impulsive polarized terahertz radiation  

International Nuclear Information System (INIS)

Single cycle terahertz (THz) pulses were employed to excite coherent spin waves in (110)-oriented PrFeO3 single crystal. The free induction decay radiations at frequency of 0.34?THz (quasi-ferromagnetic mode, FM mode) and 0.41 THz (quasi-antiferromagnetic mode, AFM mode) were observed arising from the coupling of magnetic moment with the impulsive magnetic field of polarized terahertz radiation. These two spin modes in PrFeO3 can be excited and modulated by the magnetic field of THz pulse with a specific polarization with respect to the crystal axis. The extracted complex dielectric permittivity and magnetic permeability dispersion in THz range suggest a higher efficiency of energy transfer from the impulsive THz pulse into the AFM than the FM spin system

404

Selective excitation of spin resonance in orthoferrite PrFeO{sub 3} with impulsive polarized terahertz radiation  

Energy Technology Data Exchange (ETDEWEB)

Single cycle terahertz (THz) pulses were employed to excite coherent spin waves in (110)-oriented PrFeO{sub 3} single crystal. The free induction decay radiations at frequency of 0.34?THz (quasi-ferromagnetic mode, FM mode) and 0.41 THz (quasi-antiferromagnetic mode, AFM mode) were observed arising from the coupling of magnetic moment with the impulsive magnetic field of polarized terahertz radiation. These two spin modes in PrFeO{sub 3} can be excited and modulated by the magnetic field of THz pulse with a specific polarization with respect to the crystal axis. The extracted complex dielectric permittivity and magnetic permeability dispersion in THz range suggest a higher efficiency of energy transfer from the impulsive THz pulse into the AFM than the FM spin system.

Song, Gaibei; Jiang, Junjie; Wang, Xinyan; Jin, Zuanming; Lin, Xian; Ma, Guohong, E-mail: ghma@staff.shu.edu.cn, E-mail: sxcao@shu.edu.cn; Cao, Shixun, E-mail: ghma@staff.shu.edu.cn, E-mail: sxcao@shu.edu.cn [Department of Physics, Shanghai University, Shanghai 200444 (China)

2013-12-28

405

Electro-impulse de-icing of a turbofan engine inlet  

Science.gov (United States)

The application of electromagnetic impulse deicing (EIDI) systems to turbofan engine inlets on business aircraft has been investigated experimentally. The tests were performed in the Icing Research Tunnel at NASA's Lewis Research Center. The deicing system testbed was a Falcon Fanjet 20 engine nacelle. The effectiveness of various deicing coil configurations and mount designs were compared, and design parameters were developed specifically for EIDI systems in turbofan engines. Flight tests were also carried out at altitudes in the range 3000-6000 ft corresponding to a temperature range of -3 to -8 C. It is shown that the ice particles removed from the engine inlet by the deicing system were small enough for the engine to ingest. Tentative design specifications are given with respect to the optimum coil configuration, and operating power of a EIDI production candidate.

Zumwalt, G. W.

1985-01-01

406